41 results on '"Zhou, Yu"'
Search Results
2. Rapid synthesis of Ti alloy with B addition by spark plasma sintering
- Author
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Feng, Haibo, Zhou, Yu, Jia, Dechang, and Meng, Qingchang
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TITANIUM alloys , *SINTERING , *METALLIC composites , *TRANSMISSION electron microscopes - Abstract
Abstract: The in situ TiB/Ti–4.0Fe–7.3Mo composites were fabricated by plasma spark sintering (SPS) technique using mechanical alloying of Ti, Fe65Mo and B powder. The effects of sintering temperature on densification of the composites and microstructure of the in situ synthesized TiB were investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). A dense composite was obtained after sintering at 1000°C for 5min. Under proper ball milling and SPS conditions in situ TiB reinforced Ti–4.0Fe–7.3Mo composites have been prepared. The in situ TiB showed a typical needle shape grow along [010] direction. The transverse cross-section of TiB grain is a hexagonal shape with the planes of (100), (101) and . The stacking faults in the (100) plane were observed in the TiB needles. [Copyright &y& Elsevier]
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- 2005
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3. TEM observation of dynamic distortion in 2Y-PSZ/steel composites
- Author
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Guo, Yingkui, Zhou, Yu, Duan, Xiaoming, Li, Dongbo, and Lei, Tingquan
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STEEL , *SINTERING , *ISOSTATIC pressing , *MICROSTRUCTURE , *PHASE transitions - Abstract
2Y-PSZ/steel composites have been sintered by vacuum hot-pressing. The microstructure was studied by TEM after the composites were impacted at the average strain of 1.0×103 S-1 by split Hopkinson method. The results showed that the phase transformation from γ to α′ occurred in the matrix of TRIP steel under dynamic loading. Dynamic mechanical properties of 2Y-PSZ/steel composites were improved because of the transformation of distortion induced Martensite. The morphology of Martensite induced by distortion was mainly twins. The sub-structure of Martensite was mainly twins. But there was no mid-ridge and distortion twins comptetely expanded to the whole Martensite. Moreover, there was dislocation Martensite at the same sample. The inhomogeneous spread of stress wave in 2Y-PSZ/steel composites led to the different dimension of twins Martensite. When dynamic distortion was relatively efficient, Martensitic dimension and twins distance were increased and the second twins would occur. ZrO2 grains are finely distributed in matrix TRIP steel, which improved the dynamic flow stress of 2Y-PSZ/steel composites. Moreover, ZrO2 could undergo tetragonal→monoclinic phase transformation, which would improve the dynamic yield strength of the composites. But when the content of ZrO2 exceeded 20 vol.%, it would restrain the transformation of dynamic distortion induced Martensite in TRIP steel and led to the decrease of the dynamic mechanical properties of 2Y-PSZ/steel composites. [Copyright &y& Elsevier]
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- 2004
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4. B2O3‐modified geopolymer and its liquid‐phase sintered products for immobilization of strontium.
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Jia, Lingyu, He, Peigang, Jia, Dechang, Yuan, Jingkun, Cai, Delong, Li, Daxin, Duan, Xiaoming, Yang, Zhihua, and Zhou, Yu
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STRONTIUM , *RADIOISOTOPES , *SINTERING , *RADIOACTIVE wastes , *MICROSTRUCTURE , *LEACHING , *CERAMICS , *GEOSYNTHETICS , *CERAMIC-matrix composites - Abstract
Sr‐containing ceramic products produced from geopolymer, (Na, Sr)‐GP, have been reported as excellent candidate materials for the immobilization of radionuclide 90Sr, despite sintering temperature at 1200°C. In this work, the product possessing the best immobilization performance (leaching rate of 1.29% for Sr2+) can be produced at 1000°C in the method of liquid‐phase sintering via the addition of fluxing agent B2O3 at 2.0 wt% in the geopolymer precursor. The mechanical properties of the geopolymer precursor (Na, Sr)‐GP were also enhanced via the promotion role of B2O3 to geopolymerization. It was revealed that the overall anti‐leaching ability of the Sr‐containing ceramic product not only depends on the microstructure of the loading substrate but also can be affected by the chemical state of radioactive strontium retention in the loading matrix. [ABSTRACT FROM AUTHOR]
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- 2023
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5. Microstructure evolution, enhanced hardness and toughness in the solid-solution ceramic composite by reaction pressureless sintering of ZrB2 and TiC powders.
- Author
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Kong, Qingyi, Huo, Sijia, Chen, Lei, Wang, Yujin, Ouyang, Jiahu, and Zhou, Yu
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SOLUTION strengthening , *CERAMIC powders , *MICROSTRUCTURE , *SINTERING , *TITANIUM carbide , *HARDNESS - Abstract
Fully dense ZrB 2 –TiC composites were produced by reactive pressureless sintering using ZrB 2 and TiC as the starting reactants. The effect of TiC content on microstructure and mechanical properties of ZrB 2 –TiC composites was investigated. The densification and grain refinement were achieved due to the reaction and solid solution coupling effect. Besides, elongated (Ti, Zr)B 2 plate-like grains with a high aspect ratio were obtained for the first time by the reaction of ZrB 2 and TiC. The ZrB 2 -70 mol%TiC composite exhibited good comprehensive mechanical properties of high hardness of 29.0 GPa, flexural strength of 555 MPa, and fracture toughness of 5.4 MPa m1/2 due to grain-refinement and solid solution strengthening, and plate-like grains toughening effects. [ABSTRACT FROM AUTHOR]
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- 2022
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6. Influence of vanadium content on the microstructural evolution and mechanical properties of (TiZrHfVNbTa)C high-entropy carbides processed by pressureless sintering.
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Chen, Lei, Zhang, Wen, Tan, Yongqiang, Jia, Peng, Xu, Chenguang, Wang, Yujin, Zhang, Xinghong, Han, Jiecai, and Zhou, Yu
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CERAMICS , *VANADIUM , *SPECIFIC gravity , *SINTERING , *VICKERS hardness , *CARBIDES - Abstract
• The adding vanadium to (TiZrHfVNbTa)C favors eliminating Nb segregation and enhancing densification. • Excess adding vanadium reduces single-phase-forming ability of (TiZrHfVNbTa)C, due to the lattice distortion increment. • Mechanical properties of (TiZrHfVNbTa)C is optimized via adjusting vanadium content and sintering temperature. A series of (TiZrHfVNbTa)C high-entropy ceramics with different vanadium contents have been fabricated by pressureless sintering at 2300 °C–2500 °C for 1 h, utilizing self-synthesized carbide powders obtained by carbothermal reduction. The addition of vanadium is beneficial to promote densification process and refine grain, as well as facilitate the homogeneous distribution of metal elements. The distribution of pores is also modified, almost entirely existing at grain boundary, and the integral mechanical properties achieve optimization. However, excess adding vanadium does not favor forming a single-phase (TiZrHfVNbTa)C high-entropy ceramic. The optimal (TiZrHfVNbTa)C high-entropy ceramic sintered at 2300 °C possesses a high relative density of 97.5 % and homogeneous microstructure with small grain size of 1.2 μm. The flexural strength and Vickers hardness reach 473 MPa and 24.9 GPa, respectively. This work has established a cost-effective and convenient preparation of novel (TiZrHfVNbTa)C high-entropy carbide ceramics. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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7. Spark plasma sintering and improved fracture toughness of silicoboron carbonitride ceramics with the integration of 2D MXene.
- Author
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Liang, Bin, Liao, Xingqi, Zhu, Qishuai, Yu, Ming, Li, Jiacheng, Geng, Bo, Liu, Kangwei, Jia, Dechang, Yang, Zhihua, and Zhou, Yu
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FRACTURE toughness , *CERAMICS , *SILICON nitride , *SINTERING , *NANOSTRUCTURED materials , *MICROSTRUCTURE - Abstract
MXenes have good application prospects due to the attractive mechanical and physicochemical properties. Here, for the first time, silicoboron carbonitride (Si–B–C–N) ceramics with the integration of MXene(Ti 3 C 2 T x) nanosheets were developed, and the influences of MXene additives (1.0–3.0 wt%) on mechanical properties and microstructures were investigated. The ceramics containing 3.0 wt% MXene(Ti 3 C 2 T x) show better mechanical properties including fracture toughness of 7.6 MPa‧m1/2, 36% higher than ceramics without any additives. The toughening mechanisms consist of pull-out, delamination, crack bridging, and crack deflection. This work demonstrates that MXenes are good reinforcements for enhancing the fracture toughness of structural ceramics, and also paves the way for the investigation of high-temperature properties of MXene-containing ceramics. [ABSTRACT FROM AUTHOR]
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- 2021
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8. Microstructure and mechanical properties of the α-SiAlON/α-SiC composites: Effects of heat treatment
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Liu, Limeng, Ye, Feng, and Zhou, Yu
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MICROSTRUCTURE , *MECHANICAL properties of metals , *SILICON carbide , *METALLIC composites , *HEAT treatment of metals , *SINTERING , *FRACTURE mechanics , *CERAMIC materials - Abstract
Abstract: Self-toughening α-SiAlON/6H-SiC composites containing both α-SiAlON and α-SiC elongated grains in the microstructures were previously fabricated by spark plasma sintering (SPS). In this study, the α-SiAlON/6H-SiC composites were heat treated at 1850°C for 3h. The effects of the heat treatment on the phase compositions, microstructures, and mechanical properties were investigated. The results showed M′ phases formed from crystallization of the intergranular glassy films. No polytype transformation for the SiC phase was observed. Both α-SiAlON and α-SiC grains grow anisotropic in the heat treatment, rather than converted into the brittle equiaxed morphologies. The flexural strength and fracture toughness of the post heat-treated composites were further increased and the 40wt% SiC composition reached 907MPa and 8.5MPam1/2, respectively. [Copyright &y& Elsevier]
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- 2011
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9. Fast bonding α-SiAlON ceramics by spark plasma sintering
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Liu, Limeng, Ye, Feng, Zhou, Yu, Zhang, Zhiguo, and Hou, Qinglong
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CERAMIC materials , *CHEMICAL bonds , *SINTERING , *SILICON compounds , *PLASMA gases , *ELECTRIC spark , *MICROSTRUCTURE , *MECHANICAL behavior of materials - Abstract
Abstract: Yb- and Y-doped α-SiAlON ceramics were effectively bonded by spark plasma sintering in less than 20min without using any interlayer materials at 1650–1700°C. The microstructures and mechanical properties of the joints were investigated by means of SEM, STEM, EDX, and three-point bending tests. The results showed that α-SiAlON joint formation was accompanied by fundamental rare earth diffusion. The intergranular liquids in the α-SiAlON ceramics at the bonding temperatures provided the diffusion paths for the species. α-SiAlON grain growth across the joining interfaces modified the joint microstructures to secure high bonding strength. [Copyright &y& Elsevier]
- Published
- 2010
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10. Microstructure compatibility and its effect on the mechanical properties of the α-SiC/β-Si3N4 co-reinforced barium aluminosilicate glass ceramic matrix composites
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Liu, Limeng, Ye, Feng, Zhou, Yu, and Zhang, Zhiguo
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MICROSTRUCTURE , *GLASS-ceramics , *SILICON carbide , *SILICON nitride , *SINTERING , *ALUMINUM silicates , *COMPOSITE materials , *MECHANICAL behavior of materials - Abstract
Monolithic α-SiC particles and in situ β-Si3N4-reinforced barium aluminosilicate (BAS) glass ceramic matrix composites with good mechanical properties were obtained by spark plasma sintering. However, attempts at the synthesis of ternary phase composites in order to maximize the reinforcing effects by co-adding α-SiC and β-Si3N4 were only partly successful. β-Si3N4 grain growth was remarkably hindered by the coexistent α-SiC, thus the resultant composite suffered a loss of reinforcement efficiency. [Copyright &y& Elsevier]
- Published
- 2010
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11. Preparation and microstructural characterization of (Nd1−x Gd x )2(Ce1−x Zr x )2O7 solid solutions
- Author
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Liu, Zhan-Guo, Ouyang, Jia-Hu, Zhou, Yu, and Xia, Xiao-Liang
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MICROSTRUCTURE , *CERAMIC powders , *PARTICLE size determination , *SINTERING , *NEODYMIUM , *SCANNING electron microscopy , *X-ray diffraction - Abstract
Abstract: (Nd1−x Gd x )2(Ce1−x Zr x )2O7 (0≤ x ≤1.0) powders with an average particle size of 100nm were synthesized with chemical-coprecipitation and calcination method, and were characterized by X-ray diffractometry and scanning electron microscopy. The sintering behaviour of (Nd1−x Gd x )2(Ce1−x Zr x )2O7 powders was studied by pressureless sintering at 1600–1700°C for 10h in air. The relative densities of (Nd1−x Gd x )2(Ce1−x Zr x )2O7 solid solutions increase with increasing the sintering temperature, and gradually decrease with increasing the content of neodymium and cerium at identical temperature levels. (Nd1−x Gd x )2(Ce1−x Zr x )2O7 solid solutions have a single phase of defect fluorite-type structure among all the composition combinations studied. The lattice parameters of (Nd1−x Gd x )2(Ce1−x Zr x )2O7 solid solutions agree well with the Vegard''s rule. [Copyright &y& Elsevier]
- Published
- 2009
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12. Effect of heat treatment on microstructure and mechanical properties of ZrC particles reinforced tungsten-matrix composites
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Zhang, Taiquan, Wang, Yujin, Zhou, Yu, and Song, Guiming
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HEAT treatment of metals , *MICROSTRUCTURE , *MECHANICAL behavior of materials , *METALLIC composites , *TUNGSTEN , *SINTERING - Abstract
Abstract: A 20vol.% ZrCp/W composite is fabricated by hot-pressing, and its mechanical properties can be significantly improved by the addition of ZrC particles. On the other side, the residual pores within ZrC particles clustering regions which are some latent microcrack sources are mainly caused by the relative low sinterability of ZrC particles. In order to eliminate the pores within the particle clusters, the as-sintered composite is annealed at 2300°C for 1h. The microstructure of the annealed composite becomes more uniform and densified. Components of the as-sintered and annealed composites are composed of a dilute solid solution tungsten-matrix, (Zr, W)C solid solution particles and a new W2C phase, but the content of W2C phase in the annealed composite increases. After annealing, the strength properties of the composite decrease, but its plasticity increases. [Copyright &y& Elsevier]
- Published
- 2009
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13. Effect of temperature gradient in the disk during sintering on microstructure and mechanical properties of ZrCp/W composite
- Author
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Zhang, Taiquan, Wang, Yujin, Zhou, Yu, and Song, Guiming
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ZIRCONIUM carbide , *NANOSTRUCTURED materials , *TEMPERATURE effect , *SINTERING , *MECHANICAL behavior of materials , *METALLIC composites - Abstract
Abstract: A detailed microstructural and mechanical characterization of a PM processed 20vol.% ZrCp/W composite disk indicates that the composite from the edge to the center of the disk has different phase compositions and mechanical properties. The difference is caused by a temperature gradient in the disk during heating and cooling. [Copyright &y& Elsevier]
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- 2009
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14. Microstructures of short-carbon-fiber-reinforced SiC composites prepared by hot-pressing
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He, Xiulan, Guo, Yingkui, Zhou, Yu, and Jia, Dechang
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CARBON fibers , *SILICON carbide , *MICROSTRUCTURE , *FIBER-reinforced ceramics , *SINTERING , *SCANNING electron microscopy , *X-ray diffractometers - Abstract
Abstract: Microstructures of short-carbon-fiber-reinforced silicon carbide composites, prepared by hot-pressing with MgO–Al2O3–Y2O3 as sintering additives, were investigated by means of X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. The results showed that the composites could be densified at a relatively low temperature of 1800 °C via the liquid-phase-sintering mechanism. The amorphous interphase in the composites not only avoided the direct contact of the fibers with the matrix, but also improved the fiber/matrix bonding, so they could improve the densification of the composites and avoid the degeneration of the carbon fiber. The nano silicon carbide derived from polycarbosilane, could play a role of improving the relative density of the composites. [Copyright &y& Elsevier]
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- 2008
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15. Novel Method for Fabrication of Silicon Nitride/Silicon Oxynitride Composite Ceramic Foams Using Fly Ash Cenosphere as a Pore-Forming Agent.
- Author
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Shao, Yingfeng, Jia, Dechang, Zhou, Yu, and Liu, Boyang
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CERAMICS , *FOAM , *SILICON nitride , *FLY ash , *SINTERING , *MICROSTRUCTURE , *NITROGEN , *X-ray diffractometers - Abstract
Silicon nitride/silicon oxynitride (Si3N4/Si2N2O) ceramic foams with tailored microstructures were prepared by a gelcasting process using fly ash cenosphere (FAC) as a pore-forming agent. The slurry has a suitable viscosity so that the floating velocity of FAC in the slurry is slow enough to avoid delamination between the FAC and the matrix during consolidation. Experimental observation showed that a uniform distribution of FAC was achieved in the matrix. Sintering was carried out at 1500°, 1600°, and 1700°C, respectively, for 1 h under a nitrogen atmosphere. X-ray diffractometry analysis indicated that Si2N2O was formed via the reaction between FAC and Si3N4. Microstructural analysis revealed that spherical-shaped pores obtained from FAC were uniformly dispersed in the composite. Si3N4/Si2N2O composite ceramic foams with apparent porosities of 62.0%–67.4% and a bending strength of 21–39 MPa were obtained eventually. [ABSTRACT FROM AUTHOR]
- Published
- 2008
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16. Processing and characterization of SiB0.5C1.5N0.5 produced by mechanical alloying and subsequent spark plasma sintering
- Author
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Yang, Zhi-Hua, Jia, De-Chang, Zhou, Yu, and Zhang, Jiu-Xing
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MECHANICAL alloying , *SINTERING , *POWDER metallurgy , *SILICON carbide - Abstract
Abstract: SiB0.5C1.5N0.5 nanopowders were synthesized by mechanical alloying method, and a predominantly amorphous with a small volume fraction of nanocrystalline phase was formed in the powders. The results showed that the crystallites were SiC, and the polytype of SiC were 3C and 6H. SiB0.5C1.5N0.5 powders were consolidated by spark plasma sintering (SPS) technique at 1800°C under different sintering pressure. The grain boundaries of SiC and BCN phase could not be clearly distinguished for the ceramics sintered under 25MPa. When the pressure increased to 40MPa, SiC phase almost completely crystallized, and its grain size was less than 1μm. BCN phase were mainly distributed at boundary of SiC grain. Some amorphous structures were found in the sintered ceramics. Relative densities of the ceramics increased from 76.6% to 92.4%, and mechanical property values increased two or three times with the increase of sintering pressure. For the ceramics sintered under a pressure of 40MPa, flexural strength, fracture toughness, elastic modulus and Vickers’ hardness attained to 311.5MPa, 3.45MPam1/2, 133.0GPa and 3.68GPa, respectively. The mass of the SiBCN ceramics lose by several percent below 930°C in air, and then keep unchanged above 1100°C. [Copyright &y& Elsevier]
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- 2008
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17. Investigation on the microstructure of self-reinforced Nd-α-sialon ceramics
- Author
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Liu, Chunfeng, Ye, Feng, Zhou, Yu, and Meng, Qingchang
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SILICON compounds , *CERAMICS , *SINTERING , *CRYSTALLIZATION , *MICROSTRUCTURE , *DISLOCATIONS in crystals , *TRANSMISSION electron microscopy , *X-ray diffraction - Abstract
Abstract: α-Sialon ceramics doped with Nd2O3 were prepared by hot-pressing sintering at 1900°C holding for 1h with a heat preservation for 1h at 1500°C. Microscopic observations indicate that elongated α-sialon grains appear and are embedded in the fine equiaxed-grain matrix. A small amount of β-sialon phases and secondary crystallized phases M′ (Nd2Si3−x Al x O3+x N4−x ) also exist in the Nd-α-sialon ceramic. A core/shell structure can be found in the elongated α-sialon and β-sialon grains with a high aspect ratio, in which some misfit dislocations surround the core. The 21R AlN-polytype was observed by transmission electron microscopy (TEM), which could not be detected by X-ray diffraction (XRD) due to its trace amount. Different nucleation and growth modes of sialon grains were also discussed. [Copyright &y& Elsevier]
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- 2008
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18. Spark plasma sintering of functionally graded material in the Ti–TiB 2 –B system
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Feng, Haibo, Meng, Qingchang, Zhou, Yu, and Jia, Dechang
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SINTERING , *ISOSTATIC pressing , *POWDER metallurgy , *MICROMECHANICS - Abstract
Abstract: A six-layer functionally gradient material (FGM) of Ti–TiB–TiB2 was rapidly fabricated by spark plasma sintering (SPS) in vacuum. Both B and TiB2 were used and reacted with Ti to synthesize TiB. Adjusting the content ratio of B to TiB2 in individual layers could control the amount of synthesized TiB by two steps during sintering. The composition and microstructure of the layers in FGM were investigated by XRD, SEM and TEM. The synthesized TiB has needle-like, agglomerated and elongated morphologies. The content of agglomerated TiB increased and that of needle shape TiB decreased with increasing the target TiB volume fraction ranging from 20 to 60%. The elongated TiB was observed in the other two layers with higher target TiB volume fraction, which structure is similar to the agglomerated TiB. The FGM with Ti on one side to Ti–TiB–TiB2 on the other were fabricated at relative low sintering temperature and short dwelling time by spark plasma sintering. [Copyright &y& Elsevier]
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- 2005
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19. Effects of sintering temperature on the microstructure and properties of h-BN ceramics with MAS as liquid sintering aid.
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Niu, Bo, Cai, Delong, Yang, Zhihua, Duan, Xiaoming, Duan, Wenjiu, Qiu, Baofu, Li, Qian, He, Peigang, Jia, Dechang, and Zhou, Yu
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GLASS-ceramics , *MICROSTRUCTURE , *TEMPERATURE effect , *CERAMICS , *THERMAL conductivity , *SINTERING - Abstract
MgO-Al 2 O 3 -SiO 2 (MAS) glass ceramic was used as liquid sintering aid to densify h -BN ceramics, and effects of sintering temperature on the phase composition of MAS, texture behavior of h -BN grains and properties of the composite ceramics were studied. h -BN grains will react with MAS by forming N-M (Al3+ and Si4+) coordinate-covalent bonds and inhibit the crystallization of glass phase. The h -BN grains will rotate parallel to the pressure direction due to the joint action of the liquid sintering aid and the pressure. The sintering temperature will significantly affect the properties of the composite ceramics by effecting the texture behavior of h -BN grains. And higher sintering temperature of 1900 °C will result in the decline of mechanical properties and increase of thermal conductivity due to the decrease of texture degree caused by the grain growth of h -BN. [ABSTRACT FROM AUTHOR]
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- 2020
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20. Microstructure and Mechanical Properties of Spark Plasma Sintered TaC0.7 Ceramics.
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Liu Limeng, Ye Feng, Zhou Yu, and Zhang Zhiguo
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CERAMIC materials , *FUSION reactors , *METAL fractures , *MICROSTRUCTURE , *SINTERING , *SPECTRUM analysis ,TANTALUM isotopes - Abstract
The TaC0.7 composition was spark plasma sintered (SPS) at 1600°-1900°C using TaC and Ta as the starting powders. Densification process, phase evolution, microstructure development, and the mechanical properties of the composites were investigated. The results indicated that the TaC0.7 composition could be SPS to >95% of theoretical density in 5 min at 1600°C or above. The phase formation was associated with carbon diffusion from the starting particles TaC to Ta to form Ta2C and Ta6C5 as intermediate phases, and subsequently the equilibrium phases of TaC y and ζ-Ta4C3− x. The presence of lamellar ζ-Ta4C3− x regions enhanced the flexure strength (up to 972 MPa) and fracture toughness (up to 13.8 MPa·m1/2). [ABSTRACT FROM AUTHOR]
- Published
- 2010
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21. Effects of high pressure on the low-temperature sintering of dense amorphous SiBCN monoliths.
- Author
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Li, Daxin, Li, Qian, Yuan, Jingkun, Cai, Delong, Wang, Shengjin, Zhou, Yu, Yang, Zhihua, Jia, Dechang, Yu, Dongli, and Tian, Yongjun
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CERAMIC powders , *SINTERING , *MATERIALS at high pressures , *SILICON compounds , *LOW temperatures , *MICROSTRUCTURE , *MECHANICAL behavior of materials - Abstract
In this study, amorphous SiBCN powders were mechanical milled and consolidated by low-temperature sintering at different pressure to provide an insight into the densification and mechanical behavior of dense amorphous SiBCN monoliths. Results show that the mechanical properties undergo a gradual variation closely related to the microstructural evolution. The increased degree of densification with few defects and free volume results in significantly improving Young’s modulus and nano hardness in case of high pressure application. The consolidation at relatively low pressure (3 GPa) occurs by heavy deformation with the support of limited short-range diffusion, whereas the densification at higher pressure (5 GPa) is mostly diffusion controlled showing a classic sintering mechanism. At 1000 °C, higher pressure (5 GPa) suppresses crystallization leading to an effective solid-state reaction, while SiBCN monoliths consolidated by lower pressure (3–4 GPa) show a hybrid structure of dominant amorphous phases and few nanocrystals. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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22. Effect of magnetic CoFe2O4 component on sintering densification process of Bi3.15Nd0.85Ti3O12 ceramics.
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Zhang, Hongjun, Ke, Hua, Zhang, Liwei, Wang, Wen, Jia, Dechang, and Zhou, Yu
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IRON metallurgy , *SINTERING , *CONSTRUCTION materials , *ARCHITECTURAL glass , *MICROSTRUCTURE - Abstract
Sintering densification processes of the composite ceramics (Bi 3.15 Nd 0.85 Ti 3 O 12 (BNdT)/CoFe 2 O 4 (CFO)) have been investigated using dilatometric experiments combining with the TG-DTA, density measurements and microstructure studies. Microstructures analyses and quantitative calculations show that the composite ceramics achieve densification at low temperatures (<1150 °C). The formation of coherent-lattice interfaces between (200)/(020) BNdT and (310) CFO are considered to play an important role on such densification. The intrinsic preferred orientation of BNdT grains is suppressed by CFO phase because of this coherent relationship. Although the sintering activation energies of 0.8BNdT-0.2CFO are about 2.7 times larger than those of pure BNdT due to the pinning effect, the composite ceramic could still be densified, indicating the formation energy of coherent-lattices provided the extra sintering force. The even coercive electric fields of the resulting pure BNdT and 0.8BNdT-0.2CFO ceramic are approximately 89 and 97 kV/cm, respectively, at 250 kV/cm. The polarization of 0.8BNdT-0.2CFO reaches saturation around 430 kV/cm. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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23. Si-B-C-N monoliths with LaB6-induced well-developed BN(C) flakes.
- Author
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Liang, Bin, Yang, Zhihua, Miao, Yang, Zhu, Qishuai, Liao, Xingqi, Li, Quan, Tian, Zhuo, Jia, Dechang, and Zhou, Yu
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SILICON compounds , *MONOLITHIC reactors , *CERAMIC materials , *MECHANICAL alloying , *SINTERING , *METAL microstructure , *FRACTURE toughness - Abstract
Si-B-C-N ceramic monoliths with LaB 6 additive were prepared by mechanical alloying followed by spark plasma sintering. The microstructures and mechanical properties were investigated compared to LaB 6 -free Si-B-C-N counterparts. After sintered at 1900 °C/50 MPa, the La/Si-B-C-N monoliths provide well-developed BN(C) flakes (≤100 nm in thickness) and improved fracture toughness, while the BN(C) ones show no lamellar microstructures in Si-B-C-N systems. The solid-solution of La in BN(C) grains promotes ordered arrangement of BN(C) along the (0002) plane causing in situ growth of BN(C) thus leading to an increase in toughness by 40% (from 5.6 to 7.8 MPa m −1/2 ). [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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24. Effects of passing a direct current on densification of SiC ceramics with 10 wt.% Al2O3 – Y2O3 as an additive.
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Liu, Limeng, Zhong, Lianbing, Geng, Guihong, Ye, Feng, and Zhou, Yu
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SILICON carbide , *SOIL densification , *CERAMIC metals , *ALUMINUM oxide , *YTTRIUM oxides , *ADDITIVES , *DIRECT currents - Abstract
β – SiC powder mixed with 10 wt.% Al 2 O 3 and Y 2 O 3 powder in a molar ratio of 2: 3 was consolidated by spark plasma sintering (SPS) at 1700–1900 °C. Three SPS routes were designed to contrast the effects of passing a strong direct current (DC) on the densification behavior of the SiC materials. The wetting of the Y – Al – Si – O liquid to the SiC particles was increased by the DC, hence better densification. The resultant SiC ceramic had a finer uniform microstructure and high flexural strength. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
25. Effect of sintering pressure on the texture of hot-press sintered hexagonal boron nitride composite ceramics
- Author
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Duan, Xiaoming, Jia, Dechang, Wu, Zhilian, Tian, Zhuo, Yang, Zhihua, Wang, Shengjin, and Zhou, Yu
- Subjects
- *
SINTERING , *PRESSURE , *BORON nitride , *FIBER-reinforced ceramics , *MICROFABRICATION , *MICROSTRUCTURE , *X-ray diffraction - Abstract
Textured hexagonal boron nitride (BN) composite ceramics with mullite as sintered additive were fabricated by hot-press sintering under different pressures. The degrees of texture and the microstructures of these materials were evaluated using X-ray diffraction, pole figures and scanning electron microscopy. The results showed that the hexagonal BN composite ceramics have obvious directional orientation. The preferred orientation of the c-axis of hexagonal BN grains was along the direction of pressure, and the sintering pressure influences texture formation. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
26. Microstructure and mechanical properties of the spark plasma sintered TaC/SiC composites: Effects of sintering temperatures
- Author
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Liu, Han, Liu, Limeng, Ye, Feng, Zhang, Zhiguo, and Zhou, Yu
- Subjects
- *
MICROSTRUCTURE , *MECHANICAL properties of metals , *PLASMA gases , *SINTERING , *TANTALUM compounds , *SILICON carbide , *TEMPERATURE effect , *CRYSTAL grain boundaries , *COMPOSITE materials - Abstract
Abstract: TaC/SiC composites with 20vol.% SiC addition were densified by spark plasma sintering at 1600–1900°C for 5min under 40MPa. Effects of sintering temperatures on the densification, microstructures and mechanical properties of composites were investigated. The results showed the materials achieved >98% of theoretical density at a temperature as low as 1600°C. While the TaC grains grew slightly with the sintering temperature increasing, the SiC particles in materials decreased in size. Equiaxed to elongated grain morphology transformation was observed in the SiC phase in the 1900°C material to obtain a higher flexural strength and fracture toughness of 715MPa and 6.7MPam1/2, respectively. Lattice enlargement of the TaC phase in the 1900°C material suggested possible Si diffusion into TaC grains. Ta was also detected in SiC grains by energy dispersive spectroscopy. Glassy pockets present at multi-grain junctions explained the enhanced densification. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
27. Microstructure and mechanical properties of the spark plasma sintered Ta2C ceramics
- Author
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Liu, Limeng, Liu, Han, Ye, Feng, Zhang, Zhiguo, and Zhou, Yu
- Subjects
- *
METAL microstructure , *MECHANICAL properties of metals , *TANTALUM compounds , *CERAMIC metals , *SINTERING , *EFFECT of temperature on metals , *FRACTURE mechanics - Abstract
Abstract: Single phase hexagonal α-Ta2C ceramics were synthesized by spark plasma sintering and using TaC and Ta as the starting powders. Effects of sintering temperatures and holding times on the densification process, phase formation, microstructure development, and mechanical properties of the α-Ta2C ceramics were investigated. Densification occurred in the temperature range of 1520–1675°C in less than 2.5min. But completion of the Ta2C formation took about 40min at 1500°C, and 5min at 1900°C. The materials sintered at 1500°C consisted of fine equiaxed grains. The Ta2C grains grew anisotropic to form an elongated self-toughening microstructure at 1700°C. At 1900°C, the neighboring Ta2C individual crystals coalesced to form large Ta2C blocks to entrap the residual pores. Although higher flexural strength and fracture toughness were reached at 1700°C, the unstable microstructures of the Ta2C materials indicated limited applications at high temperatures. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
28. Electrical properties of the GdSmZr2O7 ceramic under different sintering conditions
- Author
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Liu, Zhan-Guo, Ouyang, Jia-Hu, Sun, Ke-Ning, and Zhou, Yu
- Subjects
- *
CERAMIC materials , *ELECTRIC properties , *GADOLINIUM compounds , *SINTERING , *SUPERIONIC conductors , *CRYSTAL structure , *MICROSTRUCTURE , *X-ray diffraction , *ARRHENIUS equation - Abstract
Abstract: The GdSmZr2O7 ceramic is prepared by pressureless-sintered method under different conditions as a possible solid electrolyte. The crystal structure, microstructure and electrical properties are characterized by the X-ray diffraction, field-emission scanning electron microscopy and ac impedance spectroscopy, respectively. The GdSmZr2O7 ceramic exhibits a single phase of the pyrochlore-type structure. The total conductivity of the GdSmZr2O7 ceramic obeys the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173K. The GdSmZr2O7 ceramic is an oxide-ion conductor in the oxygen partial pressure range of 1.0×10−4 to 1.0atm at all test temperature levels. According to the experimental results of the present work, the maximum value of the total conductivity for the GdSmZr2O7 ceramic is about 1.01×10−2 Scm−1 at 1173K. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
29. Microstructure and mechanical properties of the spark plasma sintered TaC/SiC composites
- Author
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Liu, Limeng, Ye, Feng, Zhang, Zhiguo, and Zhou, Yu
- Subjects
- *
TANTALUM alloys , *SILICON carbide , *COMPOSITE materials , *MICROSTRUCTURE , *MECHANICAL behavior of materials , *SINTERING , *POROSITY - Abstract
Abstract: TaC/SiC composites with 5–40vol.% 6H–SiC were fabricated by spark plasma sintering at 1800°C for 5min. Effects of SiC concentrations on the densification, microstructure, and mechanical properties of the materials were investigated. The results showed the densification process of the TaC/SiC composites was composed of six sequent stages. SiC addition was effective in eliminating the closed porosities in the final stage to yield fully dense TaC/SiC composites at 20vol.% SiC concentrations and above. TaC grain sizes decreased with SiC concentration increase. The 40vol.% SiC composition had the highest flexure strength and fracture toughness up to 703MPa and 6.8MPam1/2 due to the reinforcement of the SiC agent. The TaC/SiC composites with 20 and 40vol.% SiC showed good flexural strength at 1400°C. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
30. Synthesis of α-SiC/α-SiAlON composites by spark plasma sintering: Phase formation and microstructures development
- Author
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Liu, Limeng, Ye, Feng, He, Xiulan, and Zhou, Yu
- Subjects
- *
COMPOSITE materials , *ELECTRIC spark , *PLASMA gases , *SINTERING , *SILICON compounds , *MICROSTRUCTURE , *NITROGEN , *STRENGTH of materials - Abstract
Abstract: α-SiC/α-SiAlON composites with 80wt% α-SiC (6H phase) were fabricated by spark plasma sintering at 1800–2000°C in a 0.6atm nitrogen atmosphere. The effects of the temperatures on the phase development, microstructures and mechanical properties were investigated. The results showed the Si3N4, AlN, Al2O3, and Y2O3 particles were isolated by the 6H-SiC to prevent α-SiAlON formation at 1800°C. The Si3N4 decomposed at 1900°C and above, thus added Si in the phase compositions. The α-SiC grains grew anisotropic in the sintering liquids at 1800°C and 1900°C, forming the self-reinforcing microstructures, and accordingly increased the flexural strength and fracture toughness. In cooling down immediately after the temperature reached 2000°C, a transitory hold at 1700°C transformed the 6H-SiC into the 3C polytype in 30s. The electric current was suspected of activating this polytype transformation. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
31. Low temperature sintering of ZrC–SiC composite
- Author
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Zhao, Liyou, Jia, Dechang, Duan, Xiaoming, Yang, Zhihua, and Zhou, Yu
- Subjects
- *
CERAMICS , *METALLIC composites , *LOW temperatures , *SINTERING , *ZIRCONIUM carbide , *SILICON carbide , *MICROSTRUCTURE , *GRAPHITE - Abstract
Abstract: High-energy ball milling and spark plasma sintering were adopted to prepare ZrC–SiC composite. Zirconium carbide, silicon, and graphite powders were used as raw materials. ZrC–30vol.%SiC was sintered to a relative density of >96.1% at 1800°C. The composite showed a fine microstructure. The fracture strength reached up to 523.4MPa, Vickers’ hardness 18.8GPa, fracture toughness 4.0MPam1/2, and elastic modulus 390.5GPa. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
32. Effect of Preforming Process and Starting Fused SiO2 Particle Size on Microstructure and Mechanical Properties of Pressurelessly Sintered BNp/SiO2 Ceramic Composites.
- Author
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Jia, Dechang, Zhou, Lizhong, Yang, Zhihua, Duan, Xiaoming, and Zhou, Yu
- Subjects
- *
MECHANICAL behavior of materials , *SINTERING , *ISOSTATIC pressing , *MICROSTRUCTURE , *TRANSMISSION electron microscopes , *SCANNING electron microscopes , *CHEMICAL bonds - Abstract
Hexagonal BN particles (BNp) reinforced fused SiO2 matrix composite (BNp/SiO2) was regarded as a very important candidate material for potential applications on wave transparent thermal protection parts. In this study, pressurelessly sintered 15 vol% BNp/SiO2 composites were prepared by cold isostatic pressing (CIP) and gel-casting routes, respectively, using two kinds of fused silica powders with different particle sizes (5.82 and 3.24 μm in d50, respectively) as starting SiO2. It was demonstrated that the microstructure and mechanical properties of the composites were well dependent on the preforming techniques of green compacts. Gel-casting preforming route has an overwhelming superiority over CIP route on the thermal stability of fused SiO2 matrix against α-cristobalite crystallization, sinterability, and thus the mechanical properties. Using the finer fused silica (3.24 μm in d50) as the starting SiO2, the 15 vol% BNp/SiO2 composite sintered at 1375°C get a density of 2.05 g/cm3, the silica matrix primarily keep amorphous phase with uniformly dispersed nanosized α-cristobalite crystallites (<5 nm in diameter). The bending strength, fracture toughness and Young's modulus all reach the highest values, 101.5 ± 4.3 MPa, 1.57 ± 0.04 MPa·m1/2 and 61.3 ± 2.4 GPa, respectively. Microstructure characteristics, chemical bond information and mechanical properties of the as-prepared composites are correlated with their preforming routes, starting fused SiO2 particle size, sintering temperature, etc. based on X-ray diffractometry, scanning electron microscope, transmission electron microscope, high resolution transmission electron microscope, and FT-IR analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
33. Pressureless sintering of ZrC-based ceramics by enhancing powder sinterability
- Author
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Zhao, Liyou, Jia, Dechang, Duan, Xiaoming, Yang, Zhihua, and Zhou, Yu
- Subjects
- *
SINTERING , *CERAMIC materials , *ZIRCONIUM carbide , *MICROSTRUCTURE , *GRAPHITE , *MOLECULAR structure , *CRYSTAL growth , *BALL mills , *STRENGTH of materials - Abstract
Abstract: 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 2wt.% 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. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
34. Densification process of TaC/TaB2 composite in spark plasma sintering
- Author
-
Liu, Limeng, Ye, Feng, He, Xiulan, and Zhou, Yu
- Subjects
- *
COMPACTING , *METALLIC composites , *SINTERING , *MICROSTRUCTURE , *MECHANICAL properties of metals , *TANTALUM , *POWDER metallurgy , *CHEMICAL processes , *VAPOR pressure - Abstract
Abstract: A TaC composite with ∼11wt% in situ TaB2 was fabricated by spark plasma sintering at 1600–1900°C. The densification process was studied by analysis of the densifying shrinkage of the powder compacts. Three distinct stages for densification were determined. The starting powder mixture of TaC, B4C and Ta completed reaction to form the desired TaC and TaB2 at temperature <1583°C. At around ∼1750°C, the TaC/TaB2 material significantly improved relative density to ∼95% with rapid grain growth. The final densification took place very rapidly at 1900°C by releasing a high pressure vapor. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
35. Effect of Si/C ratio and their content on the microstructure and properties of Si–B–C–N Ceramics prepared by spark plasma sintering techniques
- Author
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Yang, Zhi-Hua, Jia, De-Chang, Duan, Xiao-Ming, Sun, Ke-Ning, and Zhou, Yu
- Subjects
- *
MICROSTRUCTURE , *CERAMICS , *SINTERING , *SILICON compounds , *MECHANICAL alloying , *MECHANICAL behavior of materials , *BORON nitride , *POWDERS - Abstract
Abstract: Nano-sized Si–B–C–N powders nearly amorphous with different mole ratio of Si/C were prepared by mechanical alloying (MA) technique using cubic silicon (c-Si), hexagonal boron nitride (h-BN) and graphite powder (Cp) as starting materials, then consolidated at 1800°C under a pressure of 40MPa for 3min by spark plasma sintering (SPS). Sub-micrometer sized β-SiC and nano-sized BCN phase were formed as the final components in the ceramics. The grain size of the β-SiC tend to be a little coarser with the increase of the Si/C ratio as well as their total content, but no changes are observed for the fine sub-micrometer structure characteristics of β-SiC and BCN grains. Mechanical properties of the Si–B–C–N ceramics were found remarkably increased with the increase of the mole ratio of Si/C and their total relative content. Thermal physical properties, including thermal diffusivity, heat capacity, thermal conductivity, as well as thermal expansion coefficient were also studied. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
36. Effect of cesium substitution on the thermal evolution and ceramics formation of potassium-based geopolymer
- Author
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He, Peigang, Jia, Dechang, Wang, Meirong, and Zhou, Yu
- Subjects
- *
CESIUM , *CERAMICS , *SYNTHETIC products , *POTASSIUM , *THERMAL expansion , *MICROSTRUCTURE , *HYDROXYL group , *SINTERING - Abstract
Abstract: The thermal evolution of cesium-substituted potassium-based geopolymer ((K1−x Cs x )2O·Al2O3·5SiO2·11H2O, x =0, 0.1, 0.2, 0.3, and 0.4) on heating is studied by a variety of techniques. Phase compositions and thermal expansion behaviors of the ceramics derived from the geopolymer are characterized. All of the geopolymer specimens with or without cesium substitution exhibit similar thermal evolution trends. Major weight losses before 600°C from all the geopolymer specimens are observed and are resulted from evaporation of free water and hydroxyl groups. Thermal shrinkage of these specimens can be divided into four stages, i.e. structural resilience, dehydration, dehydroxylation and sintering, according to the dilatometer results. For these specimens, significant difference is observed in the viscous sintering stage and the effect of cesium is to reduce the thermal shrinkage in this stage due to the increased matrix viscosity. In the ceramics derived from geopolymer, the amount of stabilized leucite increases with the amount of cesium and with 20% cesium substitution leucite is fully stabilized in cubic phase. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
37. Spark plasma sintering of cBN/β-SiAlON composites
- Author
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Ye, Feng, Hou, Zhaoping, Zhang, Haijiao, Liu, Limeng, and Zhou, Yu
- Subjects
- *
COMPOSITE materials , *SINTERING , *PLASMA gases , *ELECTRIC spark , *SILICON compounds , *MICROFABRICATION , *MECHANICAL behavior of materials , *MICROSTRUCTURE - Abstract
Abstract: cBN/β-SiAlON composites with different cBN contents were fabricated by spark plasma sintering (SPS) process. The densification, thermal stability of cBN, microstructure and mechanical properties of the resultant composites were investigated. The addition of cBN particles to β-SiAlON could increase the Vickers hardness, flexural strength and fracture toughness of β-SiAlON. It is attributed to the high density, no obvious cBN to hBN transformation and good interface bonding between cBN grains and β-SiAlON matrix. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
38. Study on microstructures and mechanical properties of short-carbon-fiber-reinforced SiC composites prepared by hot-pressing
- Author
-
He, Xiulan, Guo, Yingkui, Yu, Zemin, Zhou, Yu, and Jia, Dechang
- Subjects
- *
FIBROUS composites , *CARBON fibers , *SILICON carbide , *POWDERS , *MICROSTRUCTURE , *MECHANICAL behavior of materials , *HIGH pressure (Technology) , *SINTERING - Abstract
Abstract: Short-carbon-fiber-reinforced silicon carbide composites were prepared by hot-pressing with SiC powder, Polycarbosilane as precursor polymer and MgO–Al2O3–Y2O3 as sintering additives. The phase composition, microstructure and mechanical properties of the composites with different Polycarbosilane content were investigated. The results showed that, dense composites could be prepared at a relatively low temperature of 1800°C via the liquid-phase-sintering mechanism and the highest mechanical property was obtained for the composites with 20wt.% PCS and 8wt.% sintering additives. The amorphous interphase formed during sintering process in the composites not only contributed to the densification of the composites, but also improved the fiber–matrix bonding. The nano-silicon carbide derived from Polycarbosilane, could also play a role of improving the relative density of the composites. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
39. Rapid densification and reaction sequences in self-reinforced Y-α-SiAlON ceramics with barium aluminosilicate as an additive
- Author
-
Ye, Feng, Zhang, Lei, Zhang, Haijiao, Liu, Limeng, Liu, Chunfeng, and Zhou, Yu
- Subjects
- *
CERAMICS , *ALUMINUM silicates , *COMPACTING , *SINTERING , *CRYSTAL growth , *PHASE transitions , *MECHANICAL behavior of materials , *MICROSTRUCTURE , *CRYSTALLIZATION - Abstract
Abstract: Y-α-SiAlON (Y1/3Si10Al2ON15) ceramics with 5wt.%BaAl2Si2O8 (BAS) as an additive were synthesized by spark plasma sintering (SPS). The kinetic of densification, phase transformation sequences and grain growth during sintering process were investigated. Full densification could be achieved by 1600°C without holding and using a heating rate of 100°Cmin−1, but the transformation from α-Si3N4 to α-SiAlON is not completed simultaneously with the densification process. The equilibrium phase assemblage could be reached after SPS at 1800°C for 5min and the resultant material possesses self-reinforced microstructure with high hardness of 19.2GPa and fracture toughness of 6.8MPam1/2. The complete crystallization of BAS is beneficial to the high temperature mechanical properties. The obtained could maintain the room strength up to 1300°C. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
40. Improvement of grain size and crystallization degree of LPSed h-BN composite ceramics by amorphization/nanocrystallization of raw h-BN powders.
- Author
-
Zhang, Zhuo, Duan, Xiaoming, Qiu, Baofu, Chen, Lei, Cai, Delong, He, Peigang, Yang, Zhihua, Jia, Dechang, and Zhou, Yu
- Subjects
- *
GRAIN size , *AMORPHIZATION , *POWDERS , *SINTERING , *CERAMICS - Abstract
h-BN composite ceramics were prepared by hot-pressing using La 2 O 3 and Al 2 O 3 as additives to form liquid phases during sintering. The effect of the amorphization/nanocrystallization of raw h-BN powders by high-energy ball-milling on the microstructure evolution of h-BN composite ceramics was investigated. The amorphization/nanocrystallization of raw h-BN powders significantly promotes grain growth during liquid-phase sintering. The specimen prepared using ball-milled h-BN powders possesses a higher crystallization degree, larger grain size, higher texture degree and more significant anisotropic thermal conductivity than the specimen prepared using raw h-BN powders. Image 1 [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
41. Inhibiting Effect of Additives on Formation of ZrC Phase in ZrB2- BN Composites by Reactive Hot Pressing.
- Author
-
Chen, Lei, Wang, Yujin, Cui, Lei, Zhou, Yu, Song, Guiming, and Zhang, G.-J.
- Subjects
- *
COMPOSITE materials , *POWDERS , *ISOSTATIC pressing , *MICROSTRUCTURE , *SINTERING - Abstract
The ZrB2- BN composite without ZrC impurity was prepared successfully using reactive hot pressing via carbothermal reduction of ZrO2 with B4 C, C, and BN powders. The influences of additives and sintering temperature on the phase and microstructure of composites were investigated. The formation reaction of ZrC was inhibited by decreasing the evaporation of intermediate product B2 O3 due to forming a SiO2- B2 O3 eutectic system with the addition of SiO2 or SiO2 - CaF2. In comparison, SiO2- CaF2 exhibited better inhibition capacity of ZrC. ZrB2- BN composite without impure ZrC phase was achieved. In addition, the content of ZrO2 decreased with increasing sintering temperature, and finally disappeared when sintered at 1800°C. Moreover, the relative density of the ZrB2- BN composite reached 96.9%. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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