This paper reviews the crystal chemistry, synthesis, densification, microstructure, mechanical properties, and oxidation behavior of zirconium diboride (ZrB2) hafnium (HfB2) ceramics. The refractory diborides exhibit partial or complete solid solution with other transition metal diborides, which allows compositional tailoring properties such as thermal expansion coefficient hardness. Carbothermal reduction is typical synthesis route, but reactive processes, methods, pre-ceramic polymers can...

Zirconium diboride (ZrB 2 ) and ZrB ceramics containing 10, 20, 30 vol% SiC particulates were prepared from commercially available powders by hot pressing. Four‐point bend strength, fracture toughness, elastic modulus, hardness measured. Modulus did not vary significantly with content. In contrast, strength toughness increased as content increased. Strength 565 MPa for to >1000 samples 20 or SiC. The increase in was attributed a decrease grain size the presence of WC.

Zirconium diboride (ZrB 2 ) was densified (>98% relative density) at temperatures as low 1850°C by pressureless sintering. Sintering activated removing oxide impurities (B O 3 and ZrO from particle surfaces. Boron had a high vapor pressure removed during heating under mild vacuum (∼150 mTorr). Zirconia more persistent to be chemical reaction. Both WC B 4 C were evaluated additives facilitate the removal of . Reactions proposed based on thermodynamic analysis then confirmed X‐ray...

Thermophysical properties were investigated for zirconium diboride (ZrB 2 ) and ZrB –30 vol% silicon carbide (SiC) ceramics. Thermal conductivities calculated from measured thermal diffusivities, heat capacities, densities. The conductivity of increased 56 W (m K) −1 at room temperature to 67 1675 K, whereas the –SiC decreased 62 over same range. Electron phonon contributions determined using electrical resistivity measurements used, along with grain size models, explain observed trends....

The oxidation behaviour of transition metal diboride ceramics is reviewed with emphasis on the performance zirconium and hafnium diboride. First, nominally pure diborides discussed, focusing to linear mass gain kinetics at temperatures above ∼1100°C. Next, use SiC other additives that produce silica based scales when oxidised reviewed. These improve protection due formation/stability outer layer borosilicate glass acts as a barrier diffusion oxygen substrate. However, elevated (>1650°C)...

Abstract Dense (Hf, Zr, Ti, Ta, Nb)C high‐entropy ceramics were produced by hot pressing (HP) of carbide powders synthesized carbothermal reduction (CTR). The relative density increased from 95% to 99.3% as the HP temperature 1750°C 1900°C. Nominally phase pure with rock salt structure had grain sizes ranging 0.6 µm 1.2 µm. mixed high‐energy ball milling (HEBM) followed CTR at 1600°C, which resulted in an average particle size ~100 nm and oxygen content 0.8 wt%. Low sintering temperature,...

Abstract The mechanical properties of single‐phase (Hf,Zr,Ti,Ta,Nb)C high‐entropy carbide (HEC) ceramics were investigated. Ceramics with relative density >99% and an average grain size 0.9 ± 0.3 µm produced by a two‐step process that involved carbothermal reduction at 1600°C hot pressing 1900°C. At room temperature, Vickers hardness was 25.0 1.0 GPa load 4.9 N, Young's modulus 450 GPa, chevron notch fracture toughness 3.5 MPa·m 1/2 , four‐point flexural strength 421 27 MPa. With...

Zirconium diboride (ZrB 2 ) ceramics were sintered to a relative density of ∼98% without applied external pressure. Densification studies performed in the temperature range 1900°–2150°C. Examination bulk as function revealed that shrinkage started at ∼2100°C, with significant densification occurring only 2150°C. At 2150°C, isothermal holds used determine effect time on and microstructure. For hold 540 min ZrB pellets reached an average 6.02±0.04 g/cm 3 (98% theoretical) grain size 9.0±5.6...

Zirconium diboride (ZrB 2 ) was densified by pressureless sintering using <4‐wt% boron carbide and/or carbon as aids. As‐received ZrB with an average particle size of ∼2 μm could be sintered to ∼100% density at 1900°C a combination and react remove the surface oxide impurities. Even though reduction increased oxygen content powders from ∼0.9 wt% for as‐received powder ∼2.0 wt%, in enhanced sinterability powder. Attrition‐milled <0.5 nearly full 1850°C either or boride carbon....

The synergistic roles of boron carbide and carbon additions in the enhanced densification zirconium diboride (ZrB 2 ) by pressureless sintering have been studied. ZrB was sintered to >99% relative density at 1900°C. combination wt% 1 promoted removing surface oxide impurities (ZrO B O 3 inhibiting grain growth. Four‐point bending strength (473±43 MPa), Vickers' microhardness (19.6±0.4 GPa), fracture toughness (3.5±0.6 MPa·m 1/2 ), Young's modulus (507 GPa) were measured. Thermal...

Densification of tantalum carbide (TaC) was studied by hot pressing at temperatures ranging from 1900° to 2400°C with and without sintering additives. Without additives, the relative density increased 75% 1900°C 96% 2400°C. A microstructural examination showed no observable grain growth up 2300°C. enhanced carbon (C) and/or B 4 C additions. TaC a 0.78 wt% addition achieved 97% Additions 0.36 or 0.43 0.13 98% 2200°C, accompanied rapid 2100°C higher temperatures.

A pressureless sintering process was developed for the densification of zirconium diboride ceramics containing 10–30 vol% silicon carbide particles. Initially, boron evaluated as a aid. However, formation borosilicate glass led to significant coarsening, which inhibited densification. Based on thermodynamic calculations, combination carbon and added, enabled (relative density >98%) by solid‐state at temperatures low 1950°C. Varying size starting particles allowed final particle morphology...

Bioactive glasses are promising materials for bone scaffolds due to their ability assist in tissue regeneration. When implanted vivo, bioactive can convert into hydroxyapatite, the main mineral constituent of human bone, and form a strong bond with surrounding tissues, thus providing an advantage over polymer scaffold materials. Bone fabrication using additive manufacturing techniques provide control pore interconnectivity during scaffold, which helps mimicking trabecular bone. 13-93 glass,...

A glass used to liquid‐phase sinter BaTiO 3 was developed and its properties were tested determine the feasibility of using this aid densification behavior. Glass added pure powder pressed into dimpled pellets with contents varying from 4 20 vol%. The breakdown strength measured compared two commercially available dielectric materials. Liquid‐phase sintering increased for all compositions tested. samples containing vol% additions by a factor 2.8 .