ZrC Powders Research Articles

Effect of heat treatment on the decomposition of TiC–ZrC solid solutions by spark plasma sintering

TiC–ZrC solid solutions at ZrC composition of 5–90mol% were consolidated by spark plasma sintering of TiC and ZrC powders. The phase decomposition behavior by heat-treatment at 1273–2273K was investigated. TiC–ZrC solid solutions with 10–70mol% ZrC decomposed into TiC- and ZrC-rich phases after heat treatment at 1473–2273K for 3.6ks. The decomposition resulted in the formation of nodular structures several tens to hundreds nanometers in length with coherent crystal orientation relationship of the TiC-rich phase {100} // ZrC-rich phase {100}. The Vickers hardness and fracture toughness increased with increasing heat-treatment temperature and reached maximum values of 26GPa and 3.0MPam1/2, respectively, for 80TiC–20ZrC heat treated at 1873K.

Low-temperature preparation of ZrC powders using a combined sol–gel and microwave carbothermal reduction method

Low-temperature preparation of ZrC powders using a combined sol–gel and microwave carbothermal reduction method

ZrB2–ZrCxN1−x Eutectic Composites Produced by Melt Solidification

Ceramic eutectics are naturally occurring in‐situ composites and can offer superior mechanical properties. Here, ZrB2–ZrCxN1−x quasi‐binary ceramic eutectic composites were produced by arc‐melting a mixture of ZrB2, ZrC, and ZrN powders in an N2 atmosphere. The arc‐melted ZrB2–ZrCxN1−x composites containing 50 mol% of ZrB2 (irrespective of the ZrC/ZrN ratio) showed rod‐like eutectic structures, where ZrCxN1−x single‐crystalline rods were dispersed in the ZrB2 single‐crystalline matrices. Multiple orientation relationships between the ZrCxN1−x rods and the ZrB2 matrices were observed, and one was determined as ZrB2 {} //ZrxN1−x {111} and ZrB2 < > //ZrCxN1−x < > . The rod‐like eutectic composites had higher hardness than the hypo‐ and hypereutectic composites and the 50ZrB2–40ZrC–10ZrN (mol%) eutectic composite showed the highest Vickers hardness (Hv) of 19 GPa.

Influence of Oxidation Behavior of Feedstock on Microstructure and Ablation Resistance of Plasma-Sprayed Zirconium Carbide Coating

Plasma spray is one of the suitable technologies to deposit carbide coatings with high melting point, such as ZrC. However, in the spray processes performed under atmosphere, oxidation of the carbide powder is inevitable. To investigate the influence of the oxidation behavior of feedstock on microstructure and ablation resistance of the deposited coating, ZrC coatings were prepared by atmospheric and vacuum plasma spray (APS and VPS) technologies, respectively. SiC-coated graphite was applied as the substrate. The obtained results showed that the oxidation of ZrC powder in APS process resulted in the formation of ZrO and Zr2O phases. Pores and cracks were more likely to be formed in the as-sprayed APS-ZrC coating. The VPS-ZrC coating without oxides possessed denser microstructure, higher thermal diffusivity, and lower coefficients of thermal expansion as compared with the APS-ZrC coating. A dense ZrO2 layer would be formed on the surface of the VPS-ZrC-coated sample during the ablation process and the substrate can be protected sufficiently after being ablated in high temperature plasma jet. However, the ZrO2 layer, formed by oxidation of the APS-ZrC coating having loose structure, was easy to be washed away by the shearing action of the plasma jet.

Synthesis of zirconium carbide nanoparticles by polymerised complex route

A polymerised complex route, based on polyesterification between tartaric acid–zirconium complex and ethylene glycol (EG), has been demonstrated to synthesise ZrC powders at a relatively low temperature (1300°C). The Fourier transform infrared results confirmed the coordination of tartaric acid to the zirconium ion. Furthermore, this complex reacted with EG through polyesterification to immobilise the metal ion in the rigid polymer. The intimate mixing of the reaction components has thus been achieved in ZrO2/carbon ‘coke” due to the suppression of segregation of the reaction components during pyrolysis. Finally, well crystallised ZrC nanoparticles (50–150 nm) were obtained through the carbothermal reduction of ZrO2/carbon ‘coke’, concerning the formation of the intermediate oxycarbide phase.

Spark plasma sintering of TiC–ZrC composites

TiC–ZrC composites were consolidated from TiC and ZrC powders by spark plasma sintering (SPS) at 1500–2200°C. For sintering temperatures above 1800°C, the sintered bodies with TiC compositions of 60–90mol% were densified to relative densities above 95%. For sintering temperatures below 1900°C, the sintered bodies were composed of Ti- and Zr-rich solid solutions, (Ti, Zr)C; at high temperatures above 2000°C, they formed a single-phase (Ti, Zr)C. Above 2000°C, the single-phase (Ti, Zr)C had a uniform morphology. The single-phase (Ti, Zr)C and the composites of Ti- and Zr-rich (Ti, Zr)C for TiC compositions greater than 80mol% exhibited values of Vickers hardness above 26GPa.

Direct electrochemical synthesis of zirconium carbide from zirconia/C precursors in molten calcium chloride

ZrC was successfully synthesized by direct electrolysis of non-sintering ZrO2/C mixture in molten CaCl2 electrolyte. The process of the electrochemical solid state reduction was investigated by characterizing the composition and microstructure of the products under different experimental conditions, in conjunction with analyzing the voltammetric features of initial powders in molten CaCl2. The results showed that the pure ZrC powder could be obtained by direct electrolysis of non-sintering ZrO2/C mixture in 1123K CaCl2 melt at 3.1V for 7h when carbon content in mixture was over stoichiometric ratio of ZrC. Besides the role of carbon source, carbon also promoted the electrochemical reduction of ZrO2. The reaction process involved the electrochemical reduction of ZrO2 in the presence of carbon to form ZrC with CaZrO3 as intermediate.

Synthesis of ZrC Nanoparticles in the ZrO2–Mg–C–Fe System Through Mechanically Activated Self-Propagating High-Temperature Synthesis

ZrC nanoparticles in the matrix of Fe were produced by the mechanically activated self-propagating high-temperature method using ZrO2/C/Mg/Fe powder mixtures. The effects of milling time, Fe content, and combustion temperature as well as the formation route for synthesizing ZrC powder particles were studied. The samples were characterized by XRD, SEM, TEM, and DTA. The XRD results revealed that, after 18 h of mechanical activation, ZrO2/ZC/Mg/Fe reacted with the self-propagating combustion (SHS) mode at 870 °C producing the ZrC–Fe nanocomposite. It was also found that both mechanical activation and Fe content played key roles in the ZrC synthesis temperature. With a Fe content of (5–40) wt%, the SHS reaction proceeded favorably and both the ZrC formation temperature and the adiabatic temperature (T ad) decreased. The MgO content was removed from the final products using a leaching test process by dissolving in hydrochloric and acetic acids.

Elaboration of ZrC-SiC composites by spark plasma sintering using polymer-derived ceramics

The combination of Polymer-Derived Ceramics (PDC) and Spark Plasma Sintering (SPS) was used in order to synthesize ZrC-SiC composites containing 10 to 40wt.% SiC. The whole process was studied: cross-linking of the SiC pre-ceramic polymer, mixing with commercial ZrC powders followed by pyrolysis and ball milling steps, and finally densification of the composite material using SPS. The optimized SPS conditions consist in the choice of an applied load of 50MPa under vacuum, and a soaking temperature of 2223K for 15min. High relative densities were reached under these conditions (94 to 100%). Furthermore, the addition of SiC gave an increase in the elastic moduli and hardness, which reached a maximum at 20wt.% SiC.

Synthesis of nanosized zirconium carbide powders by a combinational method of sol–gel and pulse current heating

Zirconium carbide nanopowders were synthesized by a novel method combining the advantages of sol–gel method and rapid synthesis using pulse current heating. The core-shelled structure of ZrO 2 /C mixture was obtained during the sol–gel process, and further heat treatment in SPS led to the fast formation of ZrC. The particle size of ZrO 2 played an important role in the synthesis of nanosized ZrC powders. In addition, the coalescence and grain growth of ZrC particles could be also limited due to the fast heating rate. As a result, the reactions were thoroughly completed at a relatively low temperature and ZrC nanopowders of 60–100 nm were obtained. The corresponding powders also had low oxygen content (∼0.64 wt%) and residual carbon content (∼0.27 wt%). Additive-free ZrC powders could be sintered to ∼99% relative density with an average grain size of 0.8 μm at low temperature of 1750 °C.

Preparation of highly dispersed ultra-fine ZrC by combination of carbothermal reduction of ball-milled ZrO2 and C mixture and bead milling

Ultra-fine zirconium carbide powder with particle size below 200nm was produced by the carbothermal reduction of ZrO2, graphite powder, and subsequent mechanical milling. After heat-treatment at 1400°C for 2h under vacuum, ZrC agglomerates (average size, 7.53μm) were obtained with crystallite sizes of ~200nm. Mechanical bead mill proved to be efficient in dispersing the ZrC powder agglomerates into separate ZrC particles with a narrow particle-size distribution. Only 10min of milling produced ultra-fine ZrC powder with an average particle size of 170nm. The synthesized ZrC was found to be compatible with W powder.

Low Temperature Synthesis of High Quality Zirconium Carbide Powder

Pure submicron-sized ZrC powder was successfully synthesized in KCl by using ZrO2, Mg and carbon black as the starting raw materials. KCl showed strong accelerating effect on the molten salt synthesis. As a result, the reaction temperature was reduced to as low as 800oC, which is much lower than the temperatures used by most of the other synthesis techniques reported so far. It is believed that both ZrO2 and carbon black had acted as the “templates” in the synthesis process. High quality ZrC powders prepared with the present technique could be used for making important ZrC based composites for various applications.

Reactive spark plasma sintering of ZrC and HfC ceramics with fine microstructures

Zirconium carbide and hafnium carbide ceramics were prepared by reactive spark plasma sintering, using oxides and carbon black as the raw materials. The phase and microstructure evolution during the sintering process was investigated. It was found that ZrC and HfC powder intermediates were formed at 1750 and 1800°C, respectively. Due to the high sinterability of the in situ formed carbide particles, samples with a fine microstructure could be densified at a relatively low temperature.

Spark plasma sintering of ZrC–SiC ceramics with LiYO2 additive

Abstract Spark plasma sintering (SPS) of ZrC–SiC composite powders in the presence of LiYO2 sintering additive was studied. The starting powders were obtained by a carbothermal reduction (CTR) of natural mineral zircon (ZrSiO4), which provided an intimate mixing of in-situ created ZrC and SiC powders. This composite powder and LiYO2 as additive were densified by spark plasma sintering. Microstructural features of the composite were investigated by XRD, SEM/EDS and AFM analysis. The sintered composite material possesses promising mechanical properties and excellent cavitation resistance which was observed with a cavitation erosion test. The values of Vickers microhardness and fracture toughness of the composite material are 20.7 GPa and 5.07 MPam1/2, respectively.

The change occurred in W/ZrC composite properties by using nano reactants

In this article the effect of using nano reactants in the properties of W–ZrC composite fabricated by hot-press and reaction sintering has been evaluated. At first the W and ZrC powders were hot-pressed to produce W/ZrC composite and then the WC/ZrO2 and the WC/ZrSiO4 mixture were reaction sintered. The starting powders were selected in nano size to see the difference. In the case of using nano reactants the amount of unreacted and unwanted phases reduced and the reaction progressed better. Also the evaluated properties including density, hardness and modulus of elasticity are better in W/ZrC composite made by nano reactants.

Carbothermal synthesis of ZrC powders using a combustion synthesis precursor

ZrC powders were synthesized by carbothermal reduction of a combustion synthesized precursor derived from zirconium nitrate, urea, and glucose mixed solution. The results showed that the obtained precursor was comprised of polyporous blocky particles. The precursor powders were subsequently calcined under argon at 1200–1600°C for 3h. The transformation of ZrO2 to ZrC, by adopting this route, occurred at 1300°C. The preparation of ZrC experienced an intermediate phase of ZrOxCy. ZrC powders synthesized at 1500°C are characterized by the spherical shape, small particle size (120–180nm in diameter), low oxygen content (1.4wt.%) and non-aggregated particles.

Radio‐Frequency Atmospheric‐Pressure Plasma Synthesis of Ultrafine ZrC Powders

A radio‐frequency atmospheric‐pressure plasma process has been applied to the synthesis of ultrafine ZrC powders using ZrCl4 and CH4 as precursors. Both thermodynamic analysis and experiments were conducted and the as‐prepared samples were characterized by X‐ray diffraction, electron microscopy, and laser scattering. Results showed that ZrC powders with particle size <100 nm and surface area of 36.56 M2/g could be obtained. The addition of excess H2 contributed to the increase in conversion rate. The conversion rate was about 65% when the carrier gas ratio (H2/CH4) was set at 4.0 and added axially through the injection probe.

Pressureless sintering of ZrC-based ceramics by enhancing powder sinterability

The sinterability of ZrC was enhanced by high-energy ball milling as well as introduction of graphite and SiC as sintering additives. Densification process and microstructure development were investigated for ZrC-based ceramics densified by pressureless sintering. As-received ZrC powder showed poor sinterability. After high-energy ball milling, ZrC powder can be sintered to 98.4% theoretical density at 2100 °C. The obtained ceramic had fine microstructure and fewer entrapped pores. Introduction of 2 wt.% graphite combined with high-energy ball milling lowered the densification temperature of ZrC. The relative density of obtained ceramic reached up to 95% at 1900 °C. Introduced SiC inhibited ZrC grain growth during sintering and consequently avoided the entrapped pores within the grains. The relative density of ZrC–SiC reached up to 96.7% at 2100 °C. ZrC–SiC composite formed an interesting intragranular structure and had high fracture strength at room temperature.

In situ fabrication of ZrC powder obtained by self-propagating high-temperature synthesis from Al–Zr–C elemental powders

The in situ synthesis of ZrC powder utilizing self-propagating high-temperature synthesis (SHS) reaction that occurred in the compact consisting of Al, Zr and C powders was investigated. The result shows when Al contents were 0–40 wt.% SHS reaction proceeded favorably. The as-products display a uniform distribution of ZrC particles with the sizes ranging from 8 μm at Al free to 50 nm at 40 wt.% Al. The temperature curve, coupled with the quenched treatment, indicates that the Al–Zr reaction to form ZrAl 3 initiated and then C reacted with ZrAl 3 to form the more stable ZrC phase. It also proves that the mechanism of reaction–precipitation should be responsible for the formation of ZrC in this system. Al has been playing an important role in determining the formation of ZrC, not only as a diluent to inhibit the ZrC grains from coarsening, but also as an intermediate reactant to participate in the total reaction.

From trimethylvinylsilane to ZrC–SiC hybrid materials

We describe a new route to synthesize hybrid ZrC–SiC materials in a one-pot procedure. Polycarbosilane was generated from trimethylvinylsilane in the presence of ZrC powder. A specific interaction between the polymer and the ceramic particles was evidenced. The conversion of precursor into composite was achieved by pyrolysis under argon up to 1100 °C. From thermogravimetric analyses, pyrolysis tests and SEM observations, it has been shown that these hybrid materials kept a stability above 850 °C, and their total mass loss remained lower than 20%.