Ultra-high temperature ceramic

2637:. To achieve densification at lower temperatures, several techniques can be employed: additives such as SiC can be used in order to form a liquid phase at the sintering temperature, the surface oxide layer can be removed, or the defect concentration can be increased. SiC can react with the surface oxide layer in order to provide diboride surfaces with higher energy: adding 5–30 vol% SiC has demonstrated improved densification and oxidation resistance of UHTCs. SiC can be added as a powder or a polymer to diboride UHTCs. The addition of SiC as a polymer has several advantages over the more traditional addition of SiC as a powder because SiC forms along the grain boundaries when added as a polymer, which increases measures of fracture toughness (by ~24%). In addition to improved mechanical properties, less SiC needs to be added when using this method, which limits the pathways for oxygen to diffuse into the material and react. Although addition of additives such as SiC can improve densification of UHTC materials, these additives lower the maximum temperature at which UHTCs can operate due to the formation of 2869:

for use in space nuclear power applications. While boron carbide is the most popular material for fast breeder reactors due to its lack of expense, extreme hardness comparable to diamond, and high cross-section, it completely disintegrates after a 5% burnup and is reactive when in contact with refractory metals. Hafnium diboride also suffers from high susceptibility to material degradation with boron transmutation, but its high melting point of 3,380 °C and the large thermal neutron capture cross section of hafnium of 113

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materials. However, the different methods of processing UHTCs can lead to great variation in hardness values. UHTCs exhibit high flexural strengths of > 200 MPa at 1,800 °C, and UHTCs with fine-grained particles exhibit higher flexural strengths than UHTCs with coarse grains. It has been shown that diboride ceramics synthesized as a composite with silicon carbide (SiC) exhibit increased fracture toughness (increase of 20% to 4.33 MPam) relative to the pure diborides. This is due to material

279: 2185:(SHS). This technique takes advantage of the high exothermic energy of the reaction to cause high temperature, fast combustion reactions. Advantages of SHS include higher purity of ceramic products, increased sinterability, and shorter processing times. However, the extremely rapid heating rates can result in incomplete reactions between Zr and B, the formation of stable oxides of Zr, and the retention of 66: 400:

them on modified nuclear ordnance Mk12A reentry vehicles and launching them on Minuteman III ICBMs. Sharp B-1 had a HfB2/SiC nosecone with a tip radius of 3.5 mm which experienced temperatures well above 2,815 °C during reentry, ablating away at an airspeed of 6.9 km/s as predicted; however, it was not recovered and its axially-symmetric cone shape did not provide

25: 2776:/20 vol%SiC can be prepared with 99% density at 2,000 °C in 5 min via spark plasma sintering. ZrB2-SiC composites have also been prepared by spark plasma sintering at 1,400 °C over a period of 9 min. Spark plasma sintering has proven to be a useful technique for the synthesis of UHTCs, especially for preparation of UHTCs with smaller grain sizes. 125: 2820:, and stoichiometric boron content. Boron acts as a "burnable" neutron absorber because its two isotopes, 10B and 11B, both transmute into stable nuclear reaction products upon neutron absorption (4He + 7Li and 12C, respectively) and therefore act as sacrificial materials which protect other components which become more 2755:/20 vol.% SiC by 25%. Sintered density has also been shown to increase with the addition of Fe (up to 10% w/w) and Ni (up to 50% w/w) to achieve densifications of up to 88% at 1,600 °C. More advances in pressureless sintering must be made before it can be considered a viable method for UHTC processing. 2657:

of UHTC pellets obtained from this method. In order to achieve >99% densification from hot pressing, temperatures of 1,800–2,000 °C and pressures of 30 MPa or greater are required. UHTC materials with 20 vol.% SiC and toughened with 5% carbon black as additives exhibit increased densification

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A significant enhancement in hardness (~30%) of (Hf-Ta-Zr-Nb)C material compared to the monolithic UHTCs (HfC, TaC, ZrC, NbC) and in comparison to the hardest monocarbide (HfC) and the binary (Hf-Ta)C was recorded. The mechanism behind this enhancement in hardness maybe because of bonding behavior or

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and HfN have similarly strong covalent bonds but their refractory nature makes them especially difficult to synthesize and process. The stoichiometric nitrogen content can be varied in these complexes based on the synthetic technique utilized; different nitrogen content will give different properties

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Due to the combination of refractory properties, high thermal conductivity, and the advantages of large stoichiometric boron content outlined in the above discussion of integral neutron absorbing fuel pellet cladding, refractory diborides have been used as control rod materials and have been studied

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is suppressed by rapid heating over the range 1,500–1,900 °C; this minimizes the time the material has to coarsen. Higher densities, cleaner grain boundaries, and elimination of surface impurities can all be achieved with spark plasma sintering. Spark plasma sintering also uses a pulsed current

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Hot pressing is a popular method for obtaining densified UHTC materials that relies upon both high temperatures and pressures to produce densified materials. Powder compacts are heated externally and pressure is applied hydraulitically. In order to improve densification during hot pressing, diboride

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by pressureless sintering is very difficult to obtain; Chamberlain et al. have only been able to obtain ~98% densification by heating at 2,150 °C for 9 h (Figure 3). Efforts to control grain size and improve densification have focused on adding third phases to the UHTCs, some examples of these

1613:

The UHTC composites show higher mechanical properties like Tensile strength, Young's modulus, hardness, flexural strength, and fracture toughness at high temperatures as compared to monolithic UHTCs. The high sintering temperature and pressure result in high residual stress in the composites, which

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with B. At temperatures higher than 1600 °C, pure diborides can be obtained from this method. Due to the loss of some boron as boron oxide, excess boron is needed during borothermic reduction. Mechanical milling can lower the reaction temperature required during borothermic reduction. This is

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UHTCs, specifically Hf and Zr based diboride, are being developed to handle the forces and temperatures experienced by leading vehicle edges in atmospheric reentry and sustained hypersonic flight. The surfaces of hypersonic vehicles experience extreme temperatures in excess of 2,500 °C while

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The Young's modulus for TiC-WC (3.5 wt%) - CNT(2 wt%) at 1,600 °C is 428 GPa vs 300 GPa for TiC and the flexural toughness of TiC-WC (3.5 wt%) - CNT (2 wt%) at the same temperature is 8.1 MPa m as compared to TiC which is 3.7 MPa m. For ZrC the fracture toughness at 1,900 °C is 4 MPa m

404:

data needed to evaluate the performance of UHTCs in linear leading edges. To improve the characterization of UHTC mechanical strength and better study their performance, SHARP-B2, was recovered and included four retractable, sharp wedge-like protrusions called "strakes" which each contained three

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In order to test real world performance of UHTC materials in reentry environments, NASA Ames conducted two flight experiments in 1997 and 2000. The slender Hypersonic Aero-thermodynamic Research Probes (SHARP B1 and B2) briefly exposed the UHTC materials to actual reentry environments by mounting

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is another method for the processing of UHTC materials. Spark plasma sintering often relies on slightly lower temperatures and significantly reduced processing times compared to hot pressing. During spark plasma sintering, a pulsed direct current passes through graphite punch rods and dies with

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has been used as a drained cathode in the electroreduction of molten Al(III). In drained-cathode processes, aluminum can be produced with an electrode gap of only 0.25 m with an accompanying reduction in required voltage. However, implementation of such technology still faces hurdles: with a

1602:

Table 3 lists UHTC carbides and borides mechanical properties. It is extremely important that UHTCs are able to retain high bending strength and hardness at high temperatures (above 2000 °C). UHTCs generally exhibit hardness above 20 GPa due to the strong covalent bonds present in these

455:, though significant work has continued in characterizing the nitrides, oxides, and carbides of the group four and five elements. In comparison to carbides and nitrides, the diborides tend to have higher thermal conductivity but lower melting points, a tradeoff which gives them good thermal 1617:

At 1,200 °C, the flexural strength of SiC is 170 MPa vs SiC-ZrC (10 wt%) is 350 MPa. At 2,000 °C, Titanium Carbide's flexural strength is 410 MPa vs TiC-WC (5% vol) is 491 MPa vs TiC-SiC (40% vol) is 543 MPa. Similarly the flexural strength for TaC-SiC (20% vol) is 715 MPa at

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resulting from bonding between boron 2p orbitals and metal d orbitals; before group (IV), the number of available electrons in a unit cell is insufficient to fill all bonding orbitals, and beyond it they begin to fill the antibonding orbitals. Both effects reduce the overall

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Titanium diboride is a popular material for handling molten aluminum due to its electrical conductivity, refractory properties, and its ability to wet with molten aluminum providing a superior electrical interface while not contaminating the aluminum with boron or titanium.

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at the end of a fuel cycle. In addition to this deleterious effect of integrating a neutron absorber on the surface of a fuel pellet, boron coatings have the effect of creating a power density bulge in the middle of a nuclear reactor fuel cycle through the superposition of

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powders can undergo milling by attrition to obtain powders of <2μm. Milling also allows for more uniform dispersion of the additive SiC. Hot pressing temperature, pressure, heating rate, reaction atmosphere, and holding times are all factors that affect the density and

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is only achieved at temperatures above 1800 °C once grain boundary diffusion mechanisms become active. Unfortunately, processing of UHTCs at these temperatures results in materials with larger grain sizes and poor mechanical properties including reduced toughness and

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also being exposed to high-temperature, high-flow-rate oxidizing plasma. The material design challenges associated with developing such surfaces have so far limited the design of orbital re-entry bodies and hypersonic air-breathing vehicles such as scramjets and DARPA's

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can lower densification temperatures and can react with surface oxides to promote densification. Hot pressing may result in improved densities for UHTCs, but it is an expensive technique that relies on high temperatures and pressures to provide useful materials.

2189:. Stoichiometric reactions have also been carried out by reaction of attrition milled (wearing materials by grinding) Zr and B powder (and then hot pressing at 600 °C for 6 h), and nanoscale particles have been obtained by reacting attrition milled Zr and B 2627:

Diboride-based UHTCs often require high-temperature and -pressure processing to produce dense, durable materials. The high melting points and strong covalent interactions present in UHTCs make it difficult to achieve uniform densification in these materials.

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Sharp edges dramatically reduce drag, but the current generation of thermal protection system materials are unable to withstand the considerably higher forces and temperatures experienced by sharp leading edges in reentry conditions. The relation between

1504:

In comparison with carbide and nitride-based ceramics, diboride-based UHTCs exhibit higher thermal conductivity (refer to Table 2, where we can see that hafnium diboride has thermal conductivity of 105, 75, 70 W/m*K at different temperature while

2805:, enhancing the fuel efficiency of sustained flight vehicles such as DARPA's HTV-3 and the landing cross-range and operational flexibility of reusable orbital spaceplane concepts being developed such as the Reaction Engines Skylon and Boeing X-33. 371: 2926:

single crystals to 212.96 MPa, with flexural strength highly correlated to the size of grains in the annealed ceramic material. Conductivity at 500 °C was found to be 0.005 Ω cm for the 40% SiC composite, versus 0.16 Ω cm in pure SiC.

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For applications based on combustion harsh environments and aerospace, Monolithic UHTCs are of concern because of their low fracture toughness and brittle behavior. UHTC composites are a potential approach to overcome these deficiencies.

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UHTCs can be prepared from solution-based synthesis methods as well, although few substantial studies have been conducted. Solution-based methods allow for low temperature synthesis of ultrafine UHTC powders. Yan et al. have synthesized

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Fattahi, M.; Asl, M.S.; Delbari, S.A.; Namini, A.S.; Ahmadi, Z.; Mohammadi, M. Role of nano-WC addition on microstructural, mechanical and thermal characteristics of TiC-SiCw composites. Int. J. Refract. Met. Hard Mater. 2020, 90,

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allows for its conductivity to decrease with increasing temperature, preventing uncontrollable electrical discharge while maintaining high operational upper bounds for operation. It was also found that through incorporation of 40%

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reduction in voltage, there is a concomitant reduction in heat generation and better insulation at the top of the reactor is required. In addition to improved insulation, the technology requires better bonding methods between TiB

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is another method for processing and densifying UHTCs. Pressureless sintering involves heating powdered materials in a mold in order to promote atomic diffusion and create a solid material. Compacts are prepared by uniaxial die

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fuel pellets in Westinghouse AP-1000 nuclear reactors. The high thermal neutron absorbance of boron also has the secondary effect of biasing the neutron spectrum to higher energies, so the fuel pellet retains more radioactive

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soon follows. The polymer must be stable, processable, and contain boron and carbon in order to be useful for the reaction. Dinitrile polymers formed from the condensation of dinitrile with decaborane satisfy these criteria.

2196:(10 nm in size). Unfortunately, all of the stoichiometric reaction methods for synthesizing UHTCs employ expensive charge materials, and therefore these methods are not useful for large-scale or industrial applications. 367:, with research at the center continuing to the present through funding from the NASA Fundamental Aeronautics Program. UHTCs also saw expanded use in varied environments, from nuclear engineering to aluminum production. 4770:

Guron, Marta M., Myung Jong Kim, and Larry G. Sneddon. (2008). "A Simple Polymeric Precursor Strategy for the Syntheses of Complex Zirconium and Hafnium‐Based Ultra High‐Temperature Silicon‐Carbide Composite Ceramics".

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phases have been formed using a plasma voltage and current of 50 V and 500 A, respectively. These coating materials exhibit uniform distribution of fine particles and porous microstructures, which increased hydrogen

463:

of many UHTCs are shown in Table 1. Despite the high melting points of pure UHTCs, they are unsuitable for many refractory applications because of their high susceptibility to oxidation at elevated temperatures.

1521:

sufficient for the failure of SiC; indeed, it was found that hollow cylinders could not be cracked by an applied radial thermal gradient without first being notched on the inner surface. UHTCs generally exhibit

2591:(PECVD) has also been used to prepare UHTC diborides. After plasma of the reacting gases is created (by radio frequency or direct current discharge between two electrodes) the reaction takes place, followed by 2128:

are greatly enhanced through the inclusion of 30% weight silicon carbide due to the formation of a protective glassy surface layer upon the application of temperatures in excess of 1,000 °C composed of

2133:. To determine the effect of SiC content on diboride oxidation, ManLabs conducted a series of furnace oxidation experiments, in which the oxidation scale thickness as a function of temperature for pure HfB 2541:

can be dispersed in boron carbide polymeric precursors prior to reaction. Heating the reaction mixture to 1,500 °C results in the in situ generation of boron carbide and carbon, and the reduction of

4141:

Liu, Han et al. "Microstructure and mechanical properties of the spark plasma sintered TaC/SiC composites: Effects of sintering temperatures". Journal of The European Ceramic Society 32 (2012): 3617-3625

435:

on the rear strakes was much higher than expected. The material failures were found to result from very large grain sizes in the composites and pure ceramics, with cracks following macroscopic crystal

2533:

at 1,500 °C. The synthesized powders exhibit 200 nm crystallite size and low oxygen content (~ 1.0 wt%). UHTC preparation from polymeric precursors has also been recently investigated. ZrO

2684:-SiC composites at 1800 °C. These additives react with impurities to form a transient liquid phase and promote sintering of the diboride composites. The addition of rare earth oxides such as Y 1256:(5–7.8 x 10 K) and improved oxidation resistance in comparison to other classes of UHTCs. Thermal expansion, thermal conductivity and other data are shown in Table 2. The crystal structures, 1551:

and therefore the enthalpy of formation and melting point. Experimental evidence shows that as one moves across the transition metal series in a given period, the enthalpy of formation of MB

4814:

Zhou, Shanbao; et al. (2010). "Microstructure, mechanical properties and thermal shock resistance of zirconium diboride containing silicon carbide ceramic toughened by carbon black".

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because the bow shock in front of a blunt body protects the underlying surface from the full thermal force of the onrushing plasma with a thick layer of relatively dense and cool plasma.

2275:

mixture yields increased conversion to the diboride, and particle sizes of 25–40 nm at 800 °C. After metallothermic reduction and DSHS reactions, MgO can be separated from ZrB

375: 378: 377: 373: 372: 4084:

Ni, Dewei; Cheng, Yuan; Zhang, Jiaping; Liu, Ji-Xuan; Zou, Ji; Chen, Bowen; Wu, Haoyang; Li, Hejun; Dong, Shaoming; Han, Jiecai; Zhang, Xinghong; Fu, Qiangang; Zhang, Guo-Jun (2022).

379: 2658:

above 1,500 °C, but these materials still require temperatures of 1,900 °C and a pressure of 30 MPa in order to obtain near theoretical densities. Other additives such as

419:

as shown in Figure 1. The vehicle was successfully recovered, despite the fact that it impacted the sea at three times the predicted velocity. The four rear strake segments (HfB

3427:

Cedillos-Barraza, Omar; Manara, Dario; Boboridis, K.; Watkins, Tyson; Grasso, Salvatore; Jayaseelan, Daniel D.; Konings, Rudy J. M.; Reece, Michael J.; Lee, William E. (2016).

3016:

Lawson, John W., Murray S. Daw, and Charles W. Bauschlicher (2011). "Lattice thermal conductivity of ultra high temperature ceramics ZrB2 and HfB2 from atomistic simulations".

2149:/20% SiC has the best oxidation resistance. Extreme heat treatment leads to greater oxidation resistance as well as improved mechanical properties such as fracture resistance. 2738:

that hinders densification occurs during sintering due to the low-intrinsic sinterability and the strong covalent bonds of Ti, Zr, and Hf diborides. Full densification of ZrB

1555:

ceramics increases and peaks at Ti, Zr, and Hf before decaying as the metal gets heavier. As a result, the enthalpies of formation of several important UHTCs are as follows:

143: 2595:. The deposition takes place at lower temperatures compared to traditional CVD because only the plasma needs to be heated to provide sufficient energy for the reaction. ZrB 207:

and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually

278: 2352:

and better sinterability. Boron carbide must be subjected to grinding prior to the boron carbide reduction in order to promote oxide reduction and diffusion processes.

4981: 4934: 4800: 4622: 4324: 3811: 3734: 3602: 3413: 3359: 3071: 2207:

to their respective diborides can also be achieved via metallothermic reduction. Inexpensive precursor materials are used and reacted according to the reaction below:

2359:

if a UHTC coating is desired. Precursor or powder particles react with plasma at high temperatures (6,000–15,000 °C) which greatly reduces the reaction time. ZrB

4074:

Vinci A, Zoli L, Sciti D, et al. Mechanical behaviour of carbon fibre reinforced TaC/SiC and ZrC/SiC composites up to 2100 °C. J Eur Ceram Soc 2019, 39: 780–787

3827: 2256:

via SHS often leads to incomplete conversion of reactants, and therefore double SHS (DSHS) has been employed by some researchers. A second SHS reaction with Mg and

376: 38: 2772:

that cleans surface oxides off of the powder. This enhances grain boundary diffusion and migration as well as densification of the material. The UHTC composite ZrB

1232:

to the material, such as how if x exceeds 1.2 in ZrNx, a new optically transparent and electrically insulating phase appears to form. Ceramic borides such as HfB

4463:

Zoli, Luca; Costa, Anna Luisa; Sciti, Diletta (December 2015). "Synthesis of nanosized zirconium diboride powder via oxide-borohydride solid-state reaction".

4233:

Tului, Mario; et al. (2008). "Effects of heat treatments on oxidation resistance and mechanical properties of ultra high temperature ceramic coatings".

3651:

Fahrenholtz, W. G.; et al. (2004). "Processing and characterization of ZrB 2-based ultra-high temperature monolithic and fibrous monolithic ceramics".

2182: 2909:/60%SiC composites have been used as novel conducting ceramic heaters which display high oxidation resistance and melting points, and do not display the 2588: 1629:

The high strength of the materials is obtained due to the high homogeneities of the microstructures and the solute dispersion in the microstructures.

447:

Most research conducted in the last two decades has focused on improving the performance of the two most promising compounds developed by Manlabs, ZrB

4127:

Min-Haga, Eungi and William D. Scott. "Sintering and mechanical properties of ZrC-ZrO2 composites". Journal of Materials Science 23 (1988): 2865-2870

1538:

structures with alternating hexagonal sheets of metal and boride atoms. In such structures, the principal frontier electronic states are bonding and

5187: 5132: 5079: 3864: 3862:

K. Sairam; J.K. Sonber; T.S.R.Ch. Murthy; C. Subramanian; R.K. Fotedar; R.C. Hubli. (2014). "Reaction spark plasma sintering of niobium diboride".

5046: 4907: 4849: 4773: 4525: 4297: 4268: 3264: 2898:

capital cost of the former and the design difficulty of the latter. Composite materials must have each component degrade at the same rate, or the

4150:

Stanley R. Levine and Elizabeth J. OpilaGlenn Research Center, Cleveland, Ohio. Characterization of an Ultra-High Temperature Ceramic Composite.

1263:

Table 2. Thermal expansion coefficients across selected temperature ranges and thermal conductivity at a fixed temperature for selected UHTCs.

4523:

Yan, Yongjie; et al. (2006). "New Route to Synthesize Ultra‐Fine Zirconium Diboride Powders Using Inorganic–Organic Hybrid Precursors".

4344: 3757: 2979: 374: 363:

such as the National Aerospace Plane, Venturestar/X-33, Boeing X-37, and the Air Force's Blackstar program. New research in UHTCs was led by

5044:

Venkateswaran, T.; et al. (2006). "Densification and properties of transition metal borides-based cermets via spark plasma sintering".

4673:

Reich, Silvia; et al. (1992). "Deposition of thin films of Zirconium and Hafnium Boride by plasma enhanced chemical vapor deposition".

3523:

Barraud, Elodie; et al. (2008). "Mechanically activated solid-state synthesis of hafnium carbide and hafnium nitride nanoparticles".

3243:

Bargeron, C. B.; et al. (1993). "Oxidation Mechanisms of Hafnium Carbide and Hafnium Diboride in the Temperature Range 1400 to 21C".

4381:

Karuna Purnapu Rupa, P.; et al. (2010). "Microstructure and Phase Composition of Composite Coatings Formed by Plasma Spraying of ZrO

408:

The SHARP-B2 test that followed permitted recovery of four segmented strakes which had three sections, each consisting of a different HfB

5334: 5147:

Sironen, Charlton (2012). "Neutronic characteristics of using zirconium diboride and gadolinium in a Westinghouse 17x17 fuel assembly".

4391: 44: 2843:

creates a gap between coating and fuel, and increases the fuel's centerline temperature; such cladding materials have been used on the

2794: 4015:"High-temperature Mechanical Properties and Their Influence Mechanisms of ZRC-Modified C-SiC Ceramic Matrix Composites up to 1600 °C" 439:. Since this test, NASA Ames has continued refining production techniques for UHTC synthesis and performing basic research on UHTCs. 306:

properties of binary ceramics, they discovered that the early transition metal borides, carbides, and nitrides had surprisingly high

4436: 1223:

carbides have high melting points due to covalent carbon networks although carbon vacancies often exist in these materials; indeed,

179: 161: 106: 52: 290:

Materials Laboratory to begin funding the development of a new class of materials that could withstand the environment of proposed

5130:

Xu, Liang; et al. (2012). "Study on in-situ synthesis of ZrB2 whiskers in ZrB2 ZrC matrix powder for ceramic cutting tools".

3753:"Ultrahigh temperature ceramics (UHTCs) based on ZrB2 and HfB2 systems: Powder synthesis, densification and mechanical properties" 2975:"Ultrahigh temperature ceramics (UHTCs) based on ZrB2 and HfB2 systems: Powder synthesis, densification and mechanical properties" 2177:

via stoichiometric reaction is thermodynamically favorable (ΔG=−279.6 kJ mol) and therefore, this route can be used to produce ZrB

2910: 3794:

Rhodes, W. H., Clougherty, E. V. and Kalish, D. (1970). "Research and Development of Refractory Oxidation Resistant Diborides".

3719:

Rhodes, W. H., Clougherty, E. V. and Kalish, D. (1968). "Research and Development of Refractory Oxidation Resistant Diborides".

4878: 4816: 4755:

Kaufman, Larry & Edward V. Clougherty. (1963). "Investigation of Boride Compounds for Very High-Temperature Applications".

3525: 3157: 2786: 76: 4905:

Chamberlain, Adam L., William G. Fahrenholtz, and Gregory E. Hilmas. (2005). "Pressureless sintering of zirconium diboride".

3382: 2902:

and thermal conductivity of the surface will be lost with active material still remaining deeper within the electrode plate.

4295:

Chamberlain, Adam L., William G. Fahrenholtz, and Gregory E. Hilmas. (2009). "Reactive hot pressing of zirconium diboride".

2229:

Mg is used as a reactant in order to allow for acid leaching of unwanted oxide products. Stoichiometric excesses of Mg and B

5246:

Cheminant-Coatanlem, P.; et al. (1998). "Microstructure and nanohardness of hafnium diboride after ion irradiations".

4214: 2400:

and B after milling. This method is also not very useful for industrial applications due to the loss of expensive boron as

5107: 4876:

Zhang, Xinghong; et al. (2008). "Effects of Y2O3 on microstructure and mechanical properties of ZrB2- SiC ceramics".

1523: 360: 291: 2944:

Wuchina, E.; et al. (2007). "UHTCs: ultra-high temperature ceramic materials for extreme environment applications".

5379: 5369: 5248: 3653: 3216: 431:/SiC/C) failed. The actual heat flux was 60% less than expected, actual temperatures were much lower than expected, and 4165:"Introduction to H2020 project C3HARME – next generation ceramic composites for combustion harsh environment and space" 2089:, which is rapidly lost at the elevated temperatures UHTCs are most useful at; boron, for example, readily oxidizes to 203:

that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high

4434:

Peshev, P. & G. Bliznakov. (1968). "On the borothermic preparation of titanium, zirconium and hafnium diborides".

3975:

Mao, Haobo; Shen, Fuqiang; Zhang, Yingyi; Wang, Jie; Cui, Kunkun; Wang, Hong; Lv, Tao; Fu, Tao; Tan, Tianbiao (2021).

2557:(CVD) of titanium and zirconium diborides is another method for preparing coatings of UHTCs. These techniques rely on 1614:

can be released at high temperatures. Therefore, the mechanical properties increase with the increase in temperature.

4235: 3214:

Shimada, Shiro. (2002). "A thermoanalytical study on the oxidation of ZrC and HfC powders with formation of carbon".

4948:

Wang, Xin-Gang, Wei-Ming Guo, and Guo-Jun Zhang. (2009). "Pressureless sintering mechanism and microstructure of ZrB

3977:"Microstructure and Mechanical Properties of Carbide Reinforced TiC-Based Ultra-High Temperature Ceramics: A Review" 5374: 3018: 2865:

cermets are being studied which would extend fuel lifetime by superimposing three simultaneous degradation curves.

2797:

and temperature in a leading edge is inversely proportional, i.e. as radius decreases temperature increases during

286:

Beginning in the early 1960s, demand for high-temperature materials by the nascent aerospace industry prompted the

5001: 4712: 2077:

While UHTCs have desirable thermal and mechanical properties, they are susceptible to oxidation at their elevated

270:. However, ongoing research is focused on improving the processing techniques and mechanical properties of UHTCs. 5330:"The Development of an Electroconductive SiC-ZrB Composite through Spark Plasma Sintering under Argon Atmosphere" 2554: 364: 259: 231: 3306:

Jenkins, R.; et al. (1988). "Powder Diffraction File: from the International Center for Diffraction Data".

3262:

Levine, Stanley R.; et al. (2002). "Evaluation of ultra-high temperature ceramics for aeropropulsion use".

2735: 2290:

reduction is one of the most popular methods for UHTC synthesis. The precursor materials for this reaction (ZrO

355:

spaceplane development. Three decades later, however, research interest was rekindled by a string of 1990s era

347:

UHTC research was largely abandoned after the pioneering mid-century Manlabs work due to the completion of the

3203:. 2nd Annual Conference on Composites, Materials and Structures, Cocoa Beach, FL, United States. Vol. 22. 2340:

has also been observed as a product from the reaction, but if the reaction is carried out with 20–25% excess B

2173:. This reaction provides for precise stoichiometric control of the materials. At 2,000 K, the formation of ZrB 1207:

are brittle due to the strong bonds that exist between carbon atoms. The largest class of carbides, including

4636:

Pierson, J. F.; et al. (2000). "Low temperature ZrB2 remote plasma enhanced chemical vapor deposition".

4151: 287: 5162:

Sinclair, John (1974). "Compatibility of Refractory Materials for Nuclear Reactor Poison Control Systems".

4492:"Synthesis of group IV and V metal diboride nanocrystals via borothermal reduction with sodium borohydride" 3796: 5115: 4554: 2726: 2592: 2583:

for coating on metal (and other material) surfaces. Mojima et al. have used CVD to prepare coatings of ZrB

2562: 1241: 255: 4995:

Khanra, A. K. & M. M. Godkhindi. (2005). "Effect of Ni additives on pressureless sintering of SHS ZrB

3342:

Schwetz, K. A., Reinmoth, K. and Lipp (1981). "A. Production and Industrial Uses of Refractory Borides".

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or applying composite coatings each present their own unique challenges, with the high cost and large TiB

2336:

This method requires a slight excess of boron, as some boron is oxidized during boron carbide reduction.

2100:

which becomes a liquid at 490 °C and vaporizes very rapidly above 1,100 °C; in addition, their

5219: 4975: 4928: 4794: 4616: 4318: 3805: 3728: 3596: 3407: 3353: 3315: 3065: 2604: 2599:

has been prepared via PECVD at temperatures lower than 600 °C as a coating on zircalloy. Zirconium

2280: 2190: 2078: 295: 2808:

Zirconium diboride is used in many boiling water reactor fuel assemblies due to its refractory nature,

3429:"Investigating the highest melting temperature materials: A laser melting study of the TaC-HFC system" 84: 5294: 5257: 5010: 4721: 4710:

Sonber, J. K. & A. K. Suri. (2011). "Synthesis and consolidation of zirconium diboride: review".

4684: 4647: 4596: 4400: 4353: 4176: 4026: 3924: 3836: 3766: 3701: 3662: 3440: 3398:

Pankratz, L. B., Stuve, J. M. and Gokcen, N. A. (1984). "Thermodynamic Data for Mineral Technology".

3344: 3126: 3099: 3027: 2988: 2809: 2769: 2712: 2113: 1539: 1200: 665: 510: 307: 204: 5214:

Ewing, Robert A. & Duane Neuman Sunderman. (1961). "Effects of Radiation Upon Hafnium Diboride".

4585:

coated on copper plate by chemical vapour deposition, and its corrosion and oxidation stabilities".

2833: 1610:

Table. 3 Flexural strength, hardness, and Young's Modulus at given temperatures for selected UHTCs.

3188:. 16th AIAA/DLR/DGLR International Space Planes and Hypersonic Systems and Technologies Conference. 3153:"Overview of United States space propulsion technology and associated space transportation systems" 3122: 2946: 2141:

20 v% SiC were compared. At temperatures greater than 2,100 K the oxide scale thickness on pure HfB

315: 1252:. Borides exhibit high thermal conductivity (on the order of 75–105 W/mK) and low coefficients of 5310: 5026: 4954: 4737: 4675: 4416: 4194: 4107: 3678: 3633: 3053: 2813: 2802: 2670: 1570: 1240:

benefit from very strong bonding between boron atoms as well as strong metal to boron bonds; the

416: 337: 323: 239: 200: 1244:

structure with alternating two-dimensional boron and metal sheets give these materials high but

282:

Figure 1. An UHTC strake composed of three different sections with different UHTC compositions.

4054: 3950: 3505: 3466: 3378: 2798: 2569: 2337: 2250: 2158: 1257: 1253: 1228: 1021: 925: 634: 405:

different UHTC compositions which were extended into the reentry flow at different altitudes.

401: 243: 4843:

Zhu, Tao; et al. (2009). "Densification, microstructure and mechanical properties of ZrB

4163:

Sciti, Diletta; Silvestroni, Laura; Monteverde, Frédéric; Vinci, Antonio; Zoli, Luca (2018).

5343: 5302: 5265: 5196: 5088: 5055: 5018: 4963: 4916: 4887: 4858: 4825: 4782: 4729: 4692: 4655: 4638: 4604: 4587: 4563: 4534: 4503: 4472: 4445: 4408: 4361: 4306: 4277: 4244: 4184: 4097: 4044: 4034: 3988: 3940: 3932: 3873: 3844: 3774: 3670: 3625: 3584: 3573:"Mechanical, Thermal and Oxidation Properties of Refractory Hafnium and Zirconium Compounds" 3534: 3497: 3456: 3448: 3273: 3225: 3166: 3043: 3035: 2996: 2955: 2825: 2369: 1584: 1556: 1544: 1518: 1179: 1155: 1055: 1011: 987: 894: 829: 798: 730: 572: 456: 384: 330: 224: 16:

Type of refractory ceramics that can withstand extremely high temperatures without degrading

5232: 3328: 2731: 2701: 2659: 2356: 2109: 1506: 1249: 1224: 1117: 1086: 956: 860: 764: 603: 541: 247: 5073:

Zhao, Yuan; et al. (2009). "Effect of holding time and pressure on properties of ZrB

4366: 4339: 3779: 3752: 3674: 3001: 2974: 2318:

is prepared at greater than 1,600 °C for at least 1 hour by the following reaction:

2237:

are often required during metallothermic reductions in order to consume all available ZrO

2165:

can be synthesized by stoichiometric reaction between constituent elements, in this case

5298: 5261: 5014: 4725: 4688: 4651: 4600: 4404: 4357: 4180: 4030: 3928: 3840: 3770: 3705: 3666: 3444: 3130: 3103: 3031: 2992: 2348:

remains. Lower synthesis temperatures (~1,600 °C) produce UHTCs that exhibit finer

5059: 4862: 4310: 4281: 4049: 4014: 3945: 3912: 3461: 3428: 3307: 2654: 2576: 2530: 2389: 2311: 2090: 696: 436: 5269: 4829: 4659: 4552:

Su, Kai & Larry G. Sneddon. (1993). "A polymer precursor route to metal borides".

4013:

Sha, Jianjun; Wang, Shouhao; Dai, Jixiang; Zu, Yufei; Li, Wenqiang; Sha, Ruyi (2020).

3911:

Castle, Elinor; Csanádi, Tamás; Grasso, Salvatore; Dusza, Ján; Reece, Michael (2018).

3588: 3571:

Opeka, M. M., Talmy, I. G., Wuchina, E. J., Zaykoski, J. A. and Causey, S. J. (1999).

3277: 3229: 5363: 5314: 5285: 5030: 4967: 4920: 4786: 4741: 4608: 4538: 4476: 4449: 4420: 4198: 4111: 3682: 3637: 3057: 2849: 2844: 2734:, and then the compacts are fired at chosen temperatures in a controlled atmosphere. 2629: 2393: 2303: 2287: 1604: 1196: 460: 348: 299: 5077:-SiC composite fabricated by the spark plasma sintering reactive synthesis method". 1618:

1,900 °C which is about 40% higher than TaC (500 MPa) at the same temperature.

4733: 4490:

Zoli, Luca; Galizia, Pietro; Silvestroni, Laura; Sciti, Diletta (23 January 2018).

4248: 3557: 2832:

must be enriched in 11B because the gaseous helium evolved by 10B strains the fuel

2764: 2558: 251: 5108:"Ultra High Temperature Ceramics: Densification, Properties and Thermal Stability" 4891: 4189: 4164: 3538: 2161:

and thus can be prepared by a wide variety of synthetic methods. UHTCs such as ZrB

2112:, the incorporation of fibers, and the addition of rare-earth hexaborides such as 1534:

UHTCs results from the occupancy of bonding and antibonding levels in hexagonal MB

1517:

was investigated by ManLabs and it was found that these materials did not fail at

5200: 5092: 3877: 2104:

makes them poor engineering materials. Current research targets increasing their

2899: 2854: 2821: 2817: 2600: 2401: 2193: 2101: 1245: 392: 388: 263: 3936: 3616:

Samsonov, G. V. & Serebryakova, T. I. (1978). "Classification of Borides".

3184:

S. M. Johnson; Matt Gasch; J. W. Lawson; M. I. Gusman; M. M. Stackpole (2009).

2877:

makes it an attractive control rod material when clad with a refractory metal.

2459:

using a molar ratio M:B of 1:4 at 700 °C for 30 minutes under argon flow.

5348: 5329: 5306: 4412: 4102: 4085: 3501: 2913:

resistance property of pure silicon carbide. The metal-like conductance of ZrB

2862: 2615:

can occur at temperatures in the range of 150–400 °C in order to prepare

2580: 2526: 2349: 2257: 2242: 1633:

some solid solution hardening effects arising from localized lattice strains.

467:

Table 1. Crystal structures, densities, and melting points of selected UHTCs.

319: 303: 235: 4696: 4262:Çamurlu, H. Erdem & Filippo Maglia. (2009). "Preparation of nano-size ZrB 4212:

Paul, A.; et al. (2012). "UHTC composites for hypersonic applications".

3993: 3976: 3509: 3201:

SHARP-B 2: Flight Test Objectives, Project Implementation and Initial Results

2375:

Another method for the synthesis of UHTCs is the borothermic reduction of ZrO

1509:

and nitride have values only around 20W/m*K). Thermal shock resistance of HfB

5022: 4340:"Preparation of ultrafine boride powders by metallothermic reduction method" 3485: 3048: 2870: 2759: 2616: 2166: 2105: 1548: 1212: 432: 352: 311: 267: 262:. Despite their advantages, UHTCs also have some limitations, such as their 4058: 3954: 3913:"Processing and Properties of High-Entropy Ultra-High Temperature Carbides" 3484:

Li, JinPing; Meng, SongHe; Han, JieCai; Zhang, XingHong (1 November 2008).

3470: 5283:

Welch, Barry J (1999). "Aluminum production paths in the new millennium".

1526:

in the range of 5.9–8.3 × 10 K.The structural and thermal stability of ZrB

4152:

https://ntrs.nasa.gov/api/citations/20040074335/downloads/20040074335.pdf

2874: 2638: 2634: 2186: 1260:, densities, and melting points of different UHTCs are shown in Table 1. 1220: 1216: 459:

and makes them ideal for many high-temperature thermal applications. The

423:) fractured between 14 and 19 seconds into reentry, two mid segments (ZrB 4567: 2579:. This synthesis route can be employed at low temperatures and produces 1227:

has one of the highest melting points of any material. Nitrides such as

4508: 4086:"Advances in ultra-high temperature ceramics, composites, and coatings" 4039: 3629: 2959: 2748: 2744: 1208: 1204: 216: 212: 5177:

Sonber, J. K.; et al. (2010). "Investigations on synthesis of HfB

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depletion and faster burning of 11B. To help level out this bulge, ZrB

250:

components. They can be fabricated through various methods, including

4581:

Motojima, Seiji, Kimie Funahashi, and Kazuyuki Kurosawa. (1990). "ZrB

3848: 2922:

flexural strength was reduced from 500 MPa and 359 MPa in SiC and ZrB

208: 4491: 3825:

Munro, R. G. (1997). "Material Properties of a Sintered alpha-SiC".

3572: 3170: 3152: 3186:

Recent Developments in Ultra High Temperature Ceramics at NASA Ames

302:

at Manlabs Incorporated. Through a systematic investigation of the

3293:

Ultra High Temperature Ceramics: Application, Issues and Prospects

2427:

were successfully synthesized by Zoli's Reaction, reduction of TiO

2245:

and can be used to produce the diborides by SHS. Production of ZrB

2170: 369: 220: 230:

UHTCs are used in various high-temperature applications, such as

2801:. Vehicles with "sharp" leading edges have significantly higher 1577: 1563: 356: 2890:

and the bulk graphite electrode substrate. Bonding tiles of TiB

2837: 2355:

Boron carbide reductions can also be carried out via reactive

341: 118: 59: 18: 5188:

International Journal of Refractory Metals and Hard Materials

5133:

International Journal of Refractory Metals and Hard Materials

5080:

International Journal of Refractory Metals and Hard Materials

3865:

International Journal of Refractory Metals and Hard Materials

2751:

in particular has shown an increase in the toughness of HfB

2407:

Nanocrystals of group IV and V metal diborides such as TiB

2120:). It has been found that the oxidative resistance of HfB 4266:

powder by self-propagating high-temperature synthesis".

3486:"Valence electron structure and properties of the ZrO2" 139: 88: 2108:

and oxidation resistance by exploring composites with

5286:

Journal of the Minerals, Metals and Materials Society

3721:

Part II, AFML-TR-68-190, ManLabs Inc., Cambridge, MA

3618:

Sov. Powder Metall. Met.Ceram. (English Translation)

2517:

powders using the inorganic-organic precursors ZrOCl

134:

may be too technical for most readers to understand

5335:Journal of Electrical Engineering & Technology 2873:and low reactivity with refractory metals such as 2763:uniaxial pressure exerted on the sample material. 2680:have also been used during the hot pressing of ZrB 2081:. The metal component oxidizes to a gas such as CO 3490:Science in China Series E: Technological Sciences 427:/SiC) fractured, and no fore strake segments (ZrB 3828:Journal of Physical and Chemical Reference Data 3552:Samsonov, G. V. & Vinitskii, I. M. (1980). 3295:. 2nd Ceramic Leadership Summit, Baltimore, MD. 1607:and a reduction in grain size upon processing. 3746: 3744: 2310:are less expensive than those required by the 359:programs aimed at developing a fully reusable 3146: 3144: 3142: 3140: 3089: 3087: 3085: 3083: 3081: 8: 5181:and development of a new composite with TiSi 4980:: CS1 maint: multiple names: authors list ( 4933:: CS1 maint: multiple names: authors list ( 4799:: CS1 maint: multiple names: authors list ( 4621:: CS1 maint: multiple names: authors list ( 4323:: CS1 maint: multiple names: authors list ( 3810:: CS1 maint: multiple names: authors list ( 3733:: CS1 maint: multiple names: authors list ( 3601:: CS1 maint: multiple names: authors list ( 3412:: CS1 maint: multiple names: authors list ( 3358:: CS1 maint: multiple names: authors list ( 3070:: CS1 maint: multiple names: authors list ( 3375:Ceramic Science for Materials Technologists 2623:Processing of UHTCs and the addition of SiC 2183:self-propagating high-temperature synthesis 53:Learn how and when to remove these messages 4338:Nishiyama, Katsuhiro; et al. (2009). 2603:can also be used as a precursor in PECVD. 5347: 4507: 4365: 4188: 4101: 4048: 4038: 3992: 3944: 3778: 3460: 3047: 3000: 2743:phases include the addition of boron and 2388:due to the increased particle mixing and 2344:C, the ZrC phase disappears, and only ZrB 2145:is thinner than that on pure SiC, and HfB 180:Learn how and when to remove this message 162:Learn how and when to remove this message 146:, without removing the technical details. 107:Learn how and when to remove this message 3377:. Chapman & Hall. pp. 330–343. 2153:Synthesis of diboride (Zr, Hf, Ti) UHTCs 1639: 1622:which increases to 5.8 MPa m for ZrC-ZrO 1265: 469: 277: 83:Relevant discussion may be found on the 5149:University of South California, 1509920 5047:Journal of the European Ceramic Society 4908:Journal of the American Ceramic Society 4850:Journal of the European Ceramic Society 4774:Journal of the American Ceramic Society 4526:Journal of the American Ceramic Society 4496:Journal of the American Ceramic Society 4298:Journal of the European Ceramic Society 4269:Journal of the European Ceramic Society 3265:Journal of the European Ceramic Society 2936: 2645:lowers the operating temperature of ZrB 2575:) in the gaseous phase and use H2 as a 5228: 5217: 4973: 4926: 4792: 4614: 4316: 3803: 3726: 3594: 3405: 3351: 3324: 3313: 3063: 344:were found to be the best performing. 4345:Journal of Physics: Conference Series 4215:The American Ceramic Society Bulletin 4137: 4135: 4133: 4123: 4121: 4070: 4068: 4008: 4006: 4004: 3970: 3968: 3966: 3964: 3906: 3904: 3893: 3891: 3889: 3887: 3758:Journal of Physics: Conference Series 2980:Journal of Physics: Conference Series 2947:The Electrochemical Society Interface 2649:from 3,245 °C to 2,270 °C. 2587:on Cu at 700–900 °C (Figure 2). 2561:and boron halide precursors (such as 144:make it understandable to non-experts 7: 3751:Zhang, Guo-Jun; et al. (2009). 2973:Zhang, Guo-Jun; et al. (2009). 395:technique. 0.41 mm nozzle, 4x speed. 351:missions and the elimination of the 340:containing approximately 20% volume 4392:Journal of Thermal Spray Technology 2641:liquids. The addition of SiC to ZrB 5106:J.F. Justin; A. Jankowiak (2011). 5060:10.1016/j.jeurceramsoc.2005.05.011 4863:10.1016/j.jeurceramsoc.2009.03.008 4311:10.1016/j.jeurceramsoc.2009.07.006 4282:10.1016/j.jeurceramsoc.2008.09.006 3675:10.1023/b:jmsc.0000041691.41116.bf 3400:Bulletin 677, U.S. Bureau of Mines 3245:Johns Hopkins APL Technical Digest 3199:Salute, Joan; et al. (2001). 14: 4952:–SiC ceramics doped with boron". 4830:10.1016/j.matchemphys.2010.03.028 4437:Journal of the Less Common Metals 3696:Bansal, Narottam P., ed. (2004). 3117:Bansal, Narottam P., ed. (2004). 3094:Bansal, Narottam P., ed. (2004). 87:. Please help Knowledge (XXG) by 34:This article has multiple issues. 4968:10.1016/j.scriptamat.2009.03.030 4921:10.1111/j.1551-2916.2005.00739.x 4787:10.1111/j.1551-2916.2007.02217.x 4539:10.1111/j.1551-2916.2006.01269.x 4477:10.1016/j.scriptamat.2015.07.029 3554:Handbook of Refractory Compounds 2911:negative temperature coefficient 2828:. However, the boron in ZrB2|ZrB 123: 64: 23: 4879:Journal of Alloys and Compounds 4817:Materials Chemistry and Physics 4236:Surface and Coatings Technology 3526:Journal of Alloys and Compounds 3158:Journal of Propulsion and Power 2267:as reactants along with the ZrB 193:Ultra-high-temperature ceramics 79:of non-free copyrighted sources 42:or discuss these issues on the 4757:ManLabs. Inc., Cambridge, Mass 4734:10.1179/1743676111y.0000000008 4367:10.1088/1742-6596/176/1/012043 4249:10.1016/j.surfcoat.2008.04.015 3780:10.1088/1742-6596/176/1/012041 3698:Handbook of Ceramic Composites 3119:Handbook of Ceramic Composites 3096:Handbook of Ceramic Composites 3002:10.1088/1742-6596/176/1/012041 2314:and borothermic reactions. ZrB 1524:thermal expansion coefficients 1: 5270:10.1016/s0022-3115(98)00059-2 4892:10.1016/j.jallcom.2007.10.137 4660:10.1016/s0040-6090(99)00721-x 4190:10.1080/17436753.2018.1509822 3589:10.1016/s0955-2219(99)00129-6 3539:10.1016/j.jallcom.2007.02.017 3278:10.1016/s0955-2219(02)00140-1 3230:10.1016/s0167-2738(02)00180-7 5249:Journal of Nuclear Materials 5201:10.1016/j.ijrmhm.2009.09.005 5093:10.1016/j.ijrmhm.2008.02.003 5002:Advances in Applied Ceramics 4713:Advances in Applied Ceramics 4609:10.1016/0040-6090(90)90028-c 4450:10.1016/0022-5088(68)90199-9 4169:Advances in Applied Ceramics 4090:Journal of Advanced Ceramics 3878:10.1016/j.ijrmhm.2013.12.011 3723:. IV: Mechanical Properties. 3654:Journal of Materials Science 3151:Sackheim, Robert L. (2006). 1203:at high temperatures. Metal 4847:–SiCw ceramic composites". 2392:that result from decreased 5396: 3937:10.1038/s41598-018-26827-1 3019:Journal of Applied Physics 5349:10.5370/jeet.2010.5.2.342 5307:10.1007/s11837-999-0036-4 4413:10.1007/s11666-010-9479-y 4103:10.1007/s40145-021-0550-6 3700:. Springer. p. 211. 3502:10.1007/s11431-008-0119-4 3098:. Springer. p. 192. 2555:Chemical vapor deposition 1195:UHTCs all exhibit strong 487: 484: 481: 478: 475: 472: 260:chemical vapor deposition 5328:Shin, Yong-Deok (2010). 4697:10.1002/adma.19920041005 3994:10.3390/coatings11121444 3291:Johnson, Sylvia (2011). 2736:Exaggerated grain growth 1500:Thermodynamic properties 1272:Thermal expansion (10/K) 5023:10.1179/174367606x69898 288:United States Air Force 5227:Cite journal requires 4555:Chemistry of Materials 3323:Cite journal requires 3026:(8): 083507–083507–4. 2727:Pressureless sintering 2286:Synthesis of UHTCs by 2241:. These reactions are 2079:operating temperatures 1652:Flexural Strength(MPa) 1242:hexagonal close-packed 482:Lattice parameters (Å) 396: 283: 256:spark plasma sintering 205:thermal conductivities 89:rewriting this article 3797:Mechanical Properties 3373:McColm, I.C. (1983). 2816:cross-section of 759 2605:Thermal decomposition 2404:during the reaction. 2157:UHTCs possess simple 1598:Mechanical properties 382: 361:hypersonic spaceplane 322:were used. Of these, 296:Boeing X-20 Dyna-Soar 281: 5116:Journal AerospaceLab 3583:(13–14): 2405–2414. 3272:(14–15): 2757–2767. 2810:corrosion resistance 2770:electrical discharge 2619:, conductive films. 2501:+ 4Na(g,l) + 2.5NaBO 2114:lanthanum hexaboride 1649:Young's Modulus(GPa) 1540:antibonding orbitals 1278:Thermal cond. (W/mK) 1201:structural stability 511:Hafnium carbonitride 308:thermal conductivity 91:with your own words. 5380:Composite materials 5370:Aerospace materials 5299:1999JOM....51e..24W 5262:1998JNuM..256..180C 5015:2005AdApC.104..273K 4726:2011AdApC.110..321S 4689:1992AdM.....4..650R 4652:2000TSF...359...68P 4601:1990TSF...189...73M 4568:10.1021/cm00035a013 4405:2010JTST...19..816K 4358:2009JPhCS.176a2043N 4181:2018AdApC.117S..70S 4031:2020Mate...13.1581S 3929:2018NatSR...8.8609C 3841:1997JPCRD..26.1195M 3800:. Part II, Vol. IV. 3771:2009JPhCS.176a2041Z 3706:2005hcc..book.....B 3667:2004JMatS..39.5951F 3445:2016NatSR...637962C 3131:2005hcc..book.....B 3104:2005hcc..book.....B 3032:2011JAP...110h3507L 2993:2009JPhCS.176a2041Z 2803:lift to drag ratios 2795:radius of curvature 2589:Plasma enhanced CVD 2482:(g) (M=Ti, Zr, Hf) 2073:Chemical properties 443:Physical properties 316:mechanical strength 292:hypersonic vehicles 244:hypersonic aircraft 201:refractory ceramics 4955:Scripta Materialia 4676:Advanced Materials 4509:10.1111/jace.15401 4465:Scripta Materialia 4040:10.3390/ma13071581 3917:Scientific Reports 3630:10.1007/bf00796340 3577:J. Eur. Ceram. Soc 3433:Scientific Reports 3217:Solid State Ionics 2960:10.1149/2.F04074IF 2814:neutron-absorption 2159:empirical formulas 1258:lattice parameters 397: 284: 266:and difficulty in 77:close paraphrasing 5375:Ceramic materials 5054:(13): 2431–2440. 4857:(13): 2893–2901. 4562:(11): 1659–1668. 4533:(11): 3585–3588. 4305:(16): 3401–3408. 4243:(18): 4394–4398. 3661:(19): 5951–5957. 3496:(11): 1858–1866. 3453:10.1038/srep37962 3040:10.1063/1.3647754 2824:with exposure to 2799:hypersonic flight 2474:+ 2Na(g,l) + NaBO 2070: 2069: 1519:thermal gradients 1497: 1496: 1281:Temperature (°C) 1254:thermal expansion 1199:which gives them 1188: 1187: 1022:Zirconium dioxide 926:Zirconium nitride 635:Zirconium carbide 479:Crystal structure 402:flexural strength 380: 314:, and reasonable 225:transition metals 190: 189: 182: 172: 171: 164: 117: 116: 109: 57: 5387: 5354: 5353: 5351: 5325: 5319: 5318: 5280: 5274: 5273: 5256:(2–3): 180–188. 5243: 5237: 5236: 5230: 5225: 5223: 5215: 5211: 5205: 5204: 5174: 5168: 5167: 5159: 5153: 5152: 5144: 5138: 5137: 5127: 5121: 5120: 5112: 5103: 5097: 5096: 5070: 5064: 5063: 5041: 5035: 5034: 4992: 4986: 4985: 4979: 4971: 4945: 4939: 4938: 4932: 4924: 4902: 4896: 4895: 4886:(1–2): 506–511. 4873: 4867: 4866: 4840: 4834: 4833: 4824:(2–3): 470–473. 4811: 4805: 4804: 4798: 4790: 4781:(5): 1412–1415. 4767: 4761: 4760: 4752: 4746: 4745: 4707: 4701: 4700: 4670: 4664: 4663: 4639:Thin Solid Films 4633: 4627: 4626: 4620: 4612: 4588:Thin Solid Films 4578: 4572: 4571: 4549: 4543: 4542: 4520: 4514: 4513: 4511: 4502:(6): 2627–2637. 4487: 4481: 4480: 4460: 4454: 4453: 4431: 4425: 4424: 4378: 4372: 4371: 4369: 4335: 4329: 4328: 4322: 4314: 4292: 4286: 4285: 4276:(8): 1501–1506. 4259: 4253: 4252: 4230: 4224: 4223: 4209: 4203: 4202: 4192: 4160: 4154: 4148: 4142: 4139: 4128: 4125: 4116: 4115: 4105: 4081: 4075: 4072: 4063: 4062: 4052: 4042: 4010: 3999: 3998: 3996: 3972: 3959: 3958: 3948: 3908: 3899: 3895: 3882: 3881: 3859: 3853: 3852: 3849:10.1063/1.556000 3835:(5): 1195–1203. 3822: 3816: 3815: 3809: 3801: 3791: 3785: 3784: 3782: 3748: 3739: 3738: 3732: 3724: 3716: 3710: 3709: 3693: 3687: 3686: 3648: 3642: 3641: 3613: 3607: 3606: 3600: 3592: 3568: 3562: 3561: 3549: 3543: 3542: 3533:(1–2): 224–233. 3520: 3514: 3513: 3481: 3475: 3474: 3464: 3424: 3418: 3417: 3411: 3403: 3395: 3389: 3388: 3370: 3364: 3363: 3357: 3349: 3339: 3333: 3332: 3326: 3321: 3319: 3311: 3303: 3297: 3296: 3288: 3282: 3281: 3259: 3253: 3252: 3240: 3234: 3233: 3224:(3–4): 319–326. 3211: 3205: 3204: 3196: 3190: 3189: 3181: 3175: 3174: 3148: 3135: 3134: 3114: 3108: 3107: 3091: 3076: 3075: 3069: 3061: 3051: 3049:2060/20110015597 3013: 3007: 3006: 3004: 2970: 2964: 2963: 2941: 2826:thermal neutrons 2199:Reduction of ZrO 1640: 1545:bonding strength 1275:Temp. range (°C) 1266: 1197:covalent bonding 1156:Vanadium nitride 1056:Tantalum nitride 988:Vanadium carbide 895:Titanium nitride 799:Titanium carbide 731:Zirconium boride 573:Tantalum carbide 470: 457:shock resistance 437:grain boundaries 387:set of fins via 385:hafnium diboride 383:Production of a 381: 310:, resistance to 199:) are a type of 185: 178: 167: 160: 156: 153: 147: 127: 126: 119: 112: 105: 101: 98: 92: 68: 67: 60: 49: 27: 26: 19: 5395: 5394: 5390: 5389: 5388: 5386: 5385: 5384: 5360: 5359: 5358: 5357: 5327: 5326: 5322: 5282: 5281: 5277: 5245: 5244: 5240: 5226: 5216: 5213: 5212: 5208: 5184: 5180: 5176: 5175: 5171: 5161: 5160: 5156: 5146: 5145: 5141: 5129: 5128: 5124: 5110: 5105: 5104: 5100: 5076: 5072: 5071: 5067: 5043: 5042: 5038: 4998: 4994: 4993: 4989: 4972: 4951: 4947: 4946: 4942: 4925: 4904: 4903: 4899: 4875: 4874: 4870: 4846: 4842: 4841: 4837: 4813: 4812: 4808: 4791: 4769: 4768: 4764: 4754: 4753: 4749: 4709: 4708: 4704: 4683:(10): 650–653. 4672: 4671: 4667: 4635: 4634: 4630: 4613: 4584: 4580: 4579: 4575: 4551: 4550: 4546: 4522: 4521: 4517: 4489: 4488: 4484: 4462: 4461: 4457: 4433: 4432: 4428: 4388: 4384: 4380: 4379: 4375: 4337: 4336: 4332: 4315: 4294: 4293: 4289: 4265: 4261: 4260: 4256: 4232: 4231: 4227: 4211: 4210: 4206: 4162: 4161: 4157: 4149: 4145: 4140: 4131: 4126: 4119: 4083: 4082: 4078: 4073: 4066: 4012: 4011: 4002: 3974: 3973: 3962: 3910: 3909: 3902: 3896: 3885: 3861: 3860: 3856: 3824: 3823: 3819: 3802: 3793: 3792: 3788: 3750: 3749: 3742: 3725: 3718: 3717: 3713: 3695: 3694: 3690: 3650: 3649: 3645: 3615: 3614: 3610: 3593: 3570: 3569: 3565: 3551: 3550: 3546: 3522: 3521: 3517: 3483: 3482: 3478: 3426: 3425: 3421: 3404: 3397: 3396: 3392: 3385: 3372: 3371: 3367: 3350: 3345:Radex Rundschau 3341: 3340: 3336: 3322: 3312: 3305: 3304: 3300: 3290: 3289: 3285: 3261: 3260: 3256: 3242: 3241: 3237: 3213: 3212: 3208: 3198: 3197: 3193: 3183: 3182: 3178: 3171:10.2514/1.23257 3150: 3149: 3138: 3125:. p. 198. 3116: 3115: 3111: 3093: 3092: 3079: 3062: 3015: 3014: 3010: 2972: 2971: 2967: 2943: 2942: 2938: 2933: 2925: 2921: 2916: 2908: 2897: 2893: 2889: 2884: 2860: 2841: 2831: 2782: 2775: 2768:to generate an 2754: 2741: 2720: 2716: 2709: 2705: 2699: 2695: 2691: 2687: 2683: 2678: 2674: 2667: 2663: 2648: 2644: 2625: 2614: 2610: 2598: 2586: 2573: 2566: 2549: 2545: 2540: 2536: 2524: 2520: 2516: 2508: 2504: 2500: 2496: 2492: 2488: 2481: 2477: 2473: 2469: 2465: 2458: 2454: 2450: 2446: 2442: 2438: 2434: 2430: 2426: 2422: 2418: 2414: 2410: 2399: 2390:lattice defects 2386: 2382: 2378: 2366: 2362: 2357:plasma spraying 2347: 2343: 2332: 2328: 2324: 2317: 2307: 2301: 2297: 2293: 2278: 2274: 2270: 2265: 2261: 2254: 2248: 2240: 2236: 2232: 2225: 2221: 2217: 2213: 2206: 2202: 2180: 2176: 2164: 2155: 2148: 2144: 2140: 2136: 2132: 2127: 2123: 2119: 2110:silicon carbide 2098: 2094: 2088: 2084: 2075: 1957: 1938: 1919: 1855: 1791: 1727: 1663: 1646:Temperature(°C) 1625: 1600: 1593: 1588: 1581: 1574: 1567: 1560: 1554: 1537: 1533: 1529: 1516: 1512: 1507:hafnium carbide 1502: 1419: 1401: 1383: 1363: 1308: 1289: 1250:single crystals 1239: 1235: 1193: 1180:unstable ? 1129: 1125: 1087:Niobium nitride 1029: 957:Silicon carbide 868: 861:Tantalum boride 837: 772: 765:Titanium boride 738: 704: 666:Hafnium nitride 604:Niobium carbide 542:Hafnium carbide 454: 450: 445: 430: 426: 422: 415: 411: 370: 334: 327: 276: 248:nuclear reactor 246:components and 186: 175: 174: 173: 168: 157: 151: 148: 140:help improve it 137: 128: 124: 113: 102: 96: 93: 82: 69: 65: 28: 24: 17: 12: 11: 5: 5393: 5391: 5383: 5382: 5377: 5372: 5362: 5361: 5356: 5355: 5342:(2): 342–351. 5320: 5275: 5238: 5229:|journal= 5206: 5195:(2): 201–210. 5182: 5178: 5169: 5164:NASA Tm X-2963 5154: 5139: 5122: 5098: 5074: 5065: 5036: 5009:(6): 273–276. 4996: 4987: 4962:(2): 177–180. 4949: 4940: 4915:(2): 450–456. 4897: 4868: 4844: 4835: 4806: 4762: 4747: 4720:(6): 321–334. 4702: 4665: 4628: 4582: 4573: 4544: 4515: 4482: 4455: 4426: 4399:(4): 816–823. 4386: 4382: 4373: 4330: 4287: 4263: 4254: 4225: 4204: 4155: 4143: 4129: 4117: 4076: 4064: 4000: 3960: 3900: 3883: 3854: 3817: 3786: 3740: 3711: 3688: 3643: 3624:(2): 116–120. 3608: 3563: 3544: 3515: 3476: 3419: 3390: 3383: 3365: 3334: 3325:|journal= 3308:Swarthmore, PA 3298: 3283: 3254: 3235: 3206: 3191: 3176: 3136: 3109: 3077: 3008: 2965: 2935: 2934: 2932: 2929: 2923: 2919: 2914: 2906: 2895: 2891: 2887: 2882: 2858: 2839: 2829: 2781: 2778: 2773: 2752: 2747:. Addition of 2739: 2718: 2714: 2707: 2703: 2697: 2693: 2689: 2685: 2681: 2676: 2672: 2665: 2661: 2655:microstructure 2646: 2642: 2624: 2621: 2612: 2608: 2596: 2584: 2577:reducing agent 2571: 2564: 2547: 2543: 2538: 2534: 2531:phenolic resin 2522: 2518: 2514: 2509:(g) (M=Nb,Ta) 2506: 2502: 2498: 2494: 2490: 2486: 2479: 2475: 2471: 2467: 2463: 2456: 2452: 2448: 2444: 2440: 2436: 2432: 2428: 2424: 2420: 2416: 2412: 2408: 2397: 2394:particle sizes 2384: 2380: 2376: 2364: 2360: 2345: 2341: 2330: 2326: 2322: 2315: 2312:stoichiometric 2305: 2299: 2295: 2291: 2276: 2272: 2268: 2263: 2259: 2252: 2246: 2238: 2234: 2230: 2223: 2219: 2215: 2211: 2204: 2200: 2178: 2174: 2162: 2154: 2151: 2146: 2142: 2138: 2134: 2130: 2125: 2121: 2117: 2096: 2092: 2086: 2082: 2074: 2071: 2068: 2067: 2064: 2061: 2058: 2055: 2052: 2051: 2048: 2045: 2042: 2039: 2035: 2034: 2031: 2029: 2026: 2023: 2019: 2018: 2015: 2013: 2010: 2007: 2003: 2002: 1999: 1997: 1994: 1991: 1987: 1986: 1983: 1981: 1978: 1975: 1971: 1970: 1967: 1964: 1961: 1958: 1955: 1951: 1950: 1947: 1945: 1942: 1939: 1936: 1932: 1931: 1928: 1926: 1923: 1920: 1917: 1913: 1912: 1910: 1907: 1905: 1902: 1899: 1898: 1896: 1893: 1890: 1887: 1884: 1883: 1881: 1878: 1875: 1872: 1869: 1868: 1866: 1863: 1860: 1857: 1853: 1849: 1848: 1846: 1843: 1841: 1838: 1835: 1834: 1832: 1829: 1826: 1823: 1820: 1819: 1817: 1814: 1811: 1808: 1805: 1804: 1801: 1798: 1795: 1792: 1789: 1785: 1784: 1782: 1779: 1777: 1774: 1771: 1770: 1768: 1765: 1762: 1759: 1756: 1755: 1753: 1750: 1747: 1744: 1741: 1740: 1738: 1735: 1732: 1729: 1725: 1721: 1720: 1718: 1715: 1713: 1710: 1707: 1706: 1704: 1701: 1698: 1695: 1692: 1691: 1689: 1686: 1683: 1680: 1677: 1676: 1673: 1670: 1667: 1664: 1661: 1657: 1656: 1655:Hardness(GPa) 1653: 1650: 1647: 1644: 1623: 1599: 1596: 1591: 1586: 1579: 1572: 1565: 1558: 1552: 1535: 1531: 1527: 1514: 1510: 1501: 1498: 1495: 1494: 1491: 1488: 1485: 1482: 1478: 1477: 1475: 1473: 1470: 1467: 1463: 1462: 1460: 1458: 1455: 1452: 1448: 1447: 1445: 1443: 1440: 1437: 1433: 1432: 1429: 1426: 1423: 1420: 1417: 1413: 1412: 1410: 1408: 1405: 1402: 1399: 1395: 1394: 1392: 1390: 1387: 1384: 1381: 1377: 1376: 1373: 1370: 1367: 1364: 1361: 1357: 1356: 1353: 1350: 1347: 1344: 1340: 1339: 1336: 1333: 1330: 1327: 1323: 1322: 1319: 1316: 1313: 1310: 1306: 1302: 1301: 1298: 1295: 1293: 1291: 1287: 1283: 1282: 1279: 1276: 1273: 1270: 1237: 1233: 1192: 1189: 1186: 1185: 1182: 1176: 1173: 1170: 1167: 1164: 1161: 1158: 1152: 1151: 1148: 1145: 1142: 1139: 1136: 1133: 1130: 1127: 1123: 1120: 1118:Aluminum oxide 1114: 1113: 1110: 1107: 1104: 1101: 1098: 1095: 1092: 1089: 1083: 1082: 1079: 1076: 1073: 1070: 1067: 1064: 1061: 1058: 1052: 1051: 1048: 1045: 1042: 1039: 1036: 1033: 1030: 1027: 1024: 1018: 1017: 1014: 1008: 1005: 1002: 999: 996: 993: 990: 984: 983: 980: 977: 974: 971: 968: 965: 962: 959: 953: 952: 949: 946: 943: 940: 937: 934: 931: 928: 922: 921: 918: 915: 912: 909: 906: 903: 900: 897: 891: 890: 887: 884: 881: 878: 875: 872: 869: 866: 863: 857: 856: 853: 850: 847: 844: 841: 838: 835: 832: 830:Niobium boride 826: 825: 822: 819: 816: 813: 810: 807: 804: 801: 795: 794: 791: 788: 785: 782: 779: 776: 773: 770: 767: 761: 760: 757: 754: 751: 748: 745: 742: 739: 736: 733: 727: 726: 723: 720: 717: 714: 711: 708: 705: 702: 699: 697:Hafnium boride 693: 692: 689: 686: 683: 680: 677: 674: 671: 668: 662: 661: 658: 655: 652: 649: 646: 643: 640: 637: 631: 630: 627: 624: 621: 618: 615: 612: 609: 606: 600: 599: 596: 593: 590: 587: 584: 581: 578: 575: 569: 568: 565: 562: 559: 556: 553: 550: 547: 544: 538: 537: 534: 531: 528: 525: 522: 519: 516: 513: 507: 506: 503: 500: 497: 494: 490: 489: 488:Melting point 486: 485:Density (g/cm) 483: 480: 477: 474: 461:melting points 452: 448: 444: 441: 428: 424: 420: 413: 409: 332: 325: 275: 272: 188: 187: 170: 169: 131: 129: 122: 115: 114: 72: 70: 63: 58: 32: 31: 29: 22: 15: 13: 10: 9: 6: 4: 3: 2: 5392: 5381: 5378: 5376: 5373: 5371: 5368: 5367: 5365: 5350: 5345: 5341: 5337: 5336: 5331: 5324: 5321: 5316: 5312: 5308: 5304: 5300: 5296: 5292: 5288: 5287: 5279: 5276: 5271: 5267: 5263: 5259: 5255: 5251: 5250: 5242: 5239: 5234: 5221: 5210: 5207: 5202: 5198: 5194: 5190: 5189: 5173: 5170: 5165: 5158: 5155: 5150: 5143: 5140: 5135: 5134: 5126: 5123: 5119:. 3, AL03-08. 5118: 5117: 5109: 5102: 5099: 5094: 5090: 5086: 5082: 5081: 5069: 5066: 5061: 5057: 5053: 5049: 5048: 5040: 5037: 5032: 5028: 5024: 5020: 5016: 5012: 5008: 5004: 5003: 4991: 4988: 4983: 4977: 4969: 4965: 4961: 4957: 4956: 4944: 4941: 4936: 4930: 4922: 4918: 4914: 4910: 4909: 4901: 4898: 4893: 4889: 4885: 4881: 4880: 4872: 4869: 4864: 4860: 4856: 4852: 4851: 4839: 4836: 4831: 4827: 4823: 4819: 4818: 4810: 4807: 4802: 4796: 4788: 4784: 4780: 4776: 4775: 4766: 4763: 4758: 4751: 4748: 4743: 4739: 4735: 4731: 4727: 4723: 4719: 4715: 4714: 4706: 4703: 4698: 4694: 4690: 4686: 4682: 4678: 4677: 4669: 4666: 4661: 4657: 4653: 4649: 4645: 4641: 4640: 4632: 4629: 4624: 4618: 4610: 4606: 4602: 4598: 4594: 4590: 4589: 4577: 4574: 4569: 4565: 4561: 4557: 4556: 4548: 4545: 4540: 4536: 4532: 4528: 4527: 4519: 4516: 4510: 4505: 4501: 4497: 4493: 4486: 4483: 4478: 4474: 4470: 4466: 4459: 4456: 4451: 4447: 4443: 4439: 4438: 4430: 4427: 4422: 4418: 4414: 4410: 4406: 4402: 4398: 4394: 4393: 4377: 4374: 4368: 4363: 4359: 4355: 4352:(1): 012043. 4351: 4347: 4346: 4341: 4334: 4331: 4326: 4320: 4312: 4308: 4304: 4300: 4299: 4291: 4288: 4283: 4279: 4275: 4271: 4270: 4258: 4255: 4250: 4246: 4242: 4238: 4237: 4229: 4226: 4221: 4217: 4216: 4208: 4205: 4200: 4196: 4191: 4186: 4182: 4178: 4174: 4170: 4166: 4159: 4156: 4153: 4147: 4144: 4138: 4136: 4134: 4130: 4124: 4122: 4118: 4113: 4109: 4104: 4099: 4095: 4091: 4087: 4080: 4077: 4071: 4069: 4065: 4060: 4056: 4051: 4046: 4041: 4036: 4032: 4028: 4024: 4020: 4016: 4009: 4007: 4005: 4001: 3995: 3990: 3986: 3982: 3978: 3971: 3969: 3967: 3965: 3961: 3956: 3952: 3947: 3942: 3938: 3934: 3930: 3926: 3922: 3918: 3914: 3907: 3905: 3901: 3894: 3892: 3890: 3888: 3884: 3879: 3875: 3871: 3867: 3866: 3858: 3855: 3850: 3846: 3842: 3838: 3834: 3830: 3829: 3821: 3818: 3813: 3807: 3799: 3798: 3790: 3787: 3781: 3776: 3772: 3768: 3765:(1): 012041. 3764: 3760: 3759: 3754: 3747: 3745: 3741: 3736: 3730: 3722: 3715: 3712: 3707: 3703: 3699: 3692: 3689: 3684: 3680: 3676: 3672: 3668: 3664: 3660: 3656: 3655: 3647: 3644: 3639: 3635: 3631: 3627: 3623: 3619: 3612: 3609: 3604: 3598: 3590: 3586: 3582: 3578: 3574: 3567: 3564: 3559: 3555: 3548: 3545: 3540: 3536: 3532: 3528: 3527: 3519: 3516: 3511: 3507: 3503: 3499: 3495: 3491: 3487: 3480: 3477: 3472: 3468: 3463: 3458: 3454: 3450: 3446: 3442: 3438: 3434: 3430: 3423: 3420: 3415: 3409: 3401: 3394: 3391: 3386: 3380: 3376: 3369: 3366: 3361: 3355: 3347: 3346: 3338: 3335: 3330: 3317: 3309: 3302: 3299: 3294: 3287: 3284: 3279: 3275: 3271: 3267: 3266: 3258: 3255: 3250: 3246: 3239: 3236: 3231: 3227: 3223: 3219: 3218: 3210: 3207: 3202: 3195: 3192: 3187: 3180: 3177: 3172: 3168: 3164: 3160: 3159: 3154: 3147: 3145: 3143: 3141: 3137: 3132: 3128: 3124: 3120: 3113: 3110: 3105: 3101: 3097: 3090: 3088: 3086: 3084: 3082: 3078: 3073: 3067: 3059: 3055: 3050: 3045: 3041: 3037: 3033: 3029: 3025: 3021: 3020: 3012: 3009: 3003: 2998: 2994: 2990: 2987:(1): 012041. 2986: 2982: 2981: 2976: 2969: 2966: 2961: 2957: 2953: 2949: 2948: 2940: 2937: 2930: 2928: 2912: 2903: 2901: 2878: 2876: 2872: 2866: 2864: 2856: 2851: 2846: 2845:uranium oxide 2842: 2835: 2827: 2823: 2819: 2815: 2811: 2806: 2804: 2800: 2796: 2790: 2788: 2779: 2777: 2771: 2766: 2761: 2758:Spark plasma 2756: 2750: 2746: 2737: 2733: 2728: 2724: 2721: 2710: 2679: 2668: 2656: 2650: 2640: 2636: 2631: 2630:Densification 2622: 2620: 2618: 2606: 2602: 2594: 2590: 2582: 2578: 2574: 2567: 2560: 2556: 2552: 2532: 2528: 2510: 2483: 2460: 2405: 2403: 2395: 2391: 2373: 2371: 2358: 2353: 2351: 2339: 2334: 2329:C + 3C → 2ZrB 2319: 2313: 2309: 2289: 2288:boron carbide 2284: 2282: 2281:acid leaching 2266: 2255: 2244: 2227: 2208: 2197: 2195: 2192: 2188: 2184: 2172: 2168: 2160: 2152: 2150: 2137:, SiC and HfB 2115: 2111: 2107: 2103: 2099: 2080: 2072: 2065: 2062: 2059: 2056: 2054: 2053: 2049: 2046: 2043: 2040: 2037: 2036: 2032: 2030: 2027: 2024: 2021: 2020: 2016: 2014: 2011: 2008: 2005: 2004: 2000: 1998: 1995: 1992: 1989: 1988: 1984: 1982: 1979: 1976: 1973: 1972: 1968: 1965: 1962: 1959: 1953: 1952: 1948: 1946: 1943: 1940: 1934: 1933: 1929: 1927: 1924: 1921: 1915: 1914: 1911: 1908: 1906: 1903: 1901: 1900: 1897: 1894: 1891: 1888: 1886: 1885: 1882: 1879: 1876: 1873: 1871: 1870: 1867: 1864: 1861: 1858: 1851: 1850: 1847: 1844: 1842: 1839: 1837: 1836: 1833: 1830: 1827: 1824: 1822: 1821: 1818: 1815: 1812: 1809: 1807: 1806: 1802: 1799: 1796: 1793: 1787: 1786: 1783: 1780: 1778: 1775: 1773: 1772: 1769: 1766: 1763: 1760: 1758: 1757: 1754: 1751: 1748: 1745: 1743: 1742: 1739: 1736: 1733: 1730: 1723: 1722: 1719: 1716: 1714: 1711: 1709: 1708: 1705: 1702: 1699: 1696: 1694: 1693: 1690: 1687: 1684: 1681: 1679: 1678: 1674: 1671: 1668: 1665: 1659: 1658: 1654: 1651: 1648: 1645: 1642: 1641: 1638: 1634: 1630: 1627: 1619: 1615: 1611: 1608: 1606: 1605:densification 1597: 1595: 1589: 1582: 1575: 1568: 1561: 1550: 1546: 1541: 1525: 1520: 1508: 1499: 1492: 1489: 1486: 1483: 1480: 1479: 1476: 1474: 1471: 1468: 1465: 1464: 1461: 1459: 1456: 1453: 1450: 1449: 1446: 1444: 1441: 1438: 1435: 1434: 1430: 1427: 1424: 1421: 1415: 1414: 1411: 1409: 1406: 1403: 1397: 1396: 1393: 1391: 1388: 1385: 1379: 1378: 1374: 1371: 1368: 1365: 1359: 1358: 1354: 1351: 1348: 1345: 1342: 1341: 1337: 1334: 1331: 1328: 1325: 1324: 1320: 1317: 1314: 1311: 1304: 1303: 1299: 1296: 1294: 1292: 1285: 1284: 1280: 1277: 1274: 1271: 1268: 1267: 1264: 1261: 1259: 1255: 1251: 1247: 1243: 1230: 1226: 1222: 1218: 1214: 1210: 1206: 1202: 1198: 1190: 1183: 1181: 1177: 1174: 1171: 1168: 1165: 1162: 1159: 1157: 1154: 1153: 1149: 1146: 1143: 1140: 1137: 1134: 1131: 1121: 1119: 1116: 1115: 1111: 1108: 1105: 1102: 1099: 1096: 1093: 1090: 1088: 1085: 1084: 1080: 1077: 1074: 1071: 1068: 1065: 1062: 1059: 1057: 1054: 1053: 1049: 1046: 1043: 1040: 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