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1.
Cubic boron nitride (cBN) powder was coated with Ni nanoparticle and SiO2 nanolayer (abbreviated as cBN/Ni and cBN/SiO2, respectively) by rotary chemical vapor deposition (RCVD), and compacted with SiO2 powder by spark plasma sintering at 1473–1973 K for 0.6 ks. The effects of Ni and SiO2 coatings on the densification, phase transformation of cBN and hardness of SiO2–cBN composites were compared. The phase transformation of cBN to hBN was identified at 1973 K in SiO2–cBN/SiO2 composites, 300 K higher than that in SiO2–cBN/Ni composites, indicating that SiO2 retarded the transformation of cBN. The relative density of SiO2–cBN/SiO2 with 50 vol% cBN sintered at 1873 K was 99% with a hardness of 14.5 GPa. 相似文献
2.
《Journal of the European Ceramic Society》2014,34(2):197-203
TiN–TiB2 composites were fabricated by spark plasma sintering at 1773–2573 K. Effects of TiN and TiB2 content on relative density, microstructure, and mechanical properties were investigated. Above 2373 K, TiN–TiB2 composites exhibited relative densities over 95%. A high density of 99.7% was obtained at 2573 K with 20–30 vol% TiB2. Shrinkage of the TiN–70 vol% TiB2 composite was the highest at 1573–2473 K. For the TiN–70 vol% TiB2 composite prepared at 1973–2373 K, TiN grains were small, while at 2573 K, TiB2 became a continuous matrix, in which irregular-shaped TiN dispersed. hBN was formed in the TiN–TiB2 composite containing 50–60 vol% TiB2 above 2373 K. The maximum Vickers hardness and fracture toughness obtained for the TiN–80 vol% TiB2 composite sintered at 2473 K was 26.3 GPa and 4.5 MPa m1/2, respectively. 相似文献
3.
Electroconductive ZrO2–Al2O3–25 vol% TiN ceramic nanocomposites were prepared by spark plasma sintering at 1200 °C for 3 min. The electrical resistivity of the composites decreased from 4.5 × 10?4 Ω m to 3 × 10?5 Ω m as the Al2O3 content in the ZrO2–Al2O3 matrix increased from 0 to 100 vol%. SEM images graphically presented the microstructural evolution of the composites and a geometrical percolation model was applied to investigate the relationship between the electrical property and the microstructure. The results indicated that the addition of Al2O3 to ZrO2–TiN improved the electrical conductivity of the material by tailoring the structure from “nano–nano” type for ZrO2–TiN to “micro–nano” type for ZrO2–Al2O3–TiN. 相似文献
4.
Alicia Weibel Alain Peigney Geoffroy Chevallier Claude Estournès Christophe Laurent 《Ceramics International》2013,39(5):5513-5519
Carbon nanotube–iron–mullite nanocomposite powders were prepared by a direct method involving a reduction in H2–CH4 and without any mechanical mixing step. The carbon nanotubes are mostly double- and few-walled (3–6 walls). Some carbon nanofibers are also observed. The materials were consolidated by spark plasma sintering. Their electrical conductivity is 2.4 S/cm whereas pure mullite is insulating. There is no increase in fracture strength, but the SENB toughness is twice than the one for unreinforced mullite (3.3 vs. 1.6 MPa m1/2). The mechanisms of carbon nanotube bundle pullout and large-scale crack-bridging have been evidenced. 相似文献
5.
《Ceramics International》2016,42(3):3745-3750
The process of densification and development of the microstructure of mullite–ZrO2/Y2O3 ceramics from mixture of Al2O3, SiO2, ZrO2 and Y2O3 by gradually adding of α–β Si3N4 nanopowder from 1 to 5 wt% by traditional and spark plasma sintering were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and some ceramic and mechanical properties. The processes of DTA for all samples are characterised by a low-pitched endo-effect, when gradual mullite formation and noticeable densification at temperatures of 1200–1400 °C is started. It is testified by shrinkage and density both for traditionally and by SPS-sintered samples. The influence of the Si3N4 additive on the density characteristics is insignificant for both sintering cases. For SPS samples, the density reaches up to 3.33 g/cm3, while for traditionally sintered samples, the value is 2.55 g/cm3, and the compressive strength for SPS grows with Si3N4 additives, reaching 600 N/mm2. In the case of traditional sintering, it decreases to approximately 100 N/mm2. The basic microstructure of ceramic samples sintered in a traditional way and by SPS is created from mullite (or pseudo-mullite) crystalline formations with the incorporation of ZrO2 grains. The microstructure of ceramic samples sintered by SPS shows that mullite crystals are very densely arranged and they do not have the characteristic prismatic shape. The traditional sintering process causes the creation of voids in the microstructure, which, with an increasing amount of Si3N4 additive, are filled with mullite crystalline formations. 相似文献
6.
《Journal of the European Ceramic Society》1999,19(5):571-579
The relative wear resistance of αSiC–TiB2 composites prepared by reactive sintering was investigated on a pin on flat tribometer, in air and in presence of water. Experimental results show that the composite materials are less worn than monolithic SiC. The wear mechanisms in air and water are identified.In air, a protective oxidised debris layer is formed on the composites, whereas roller formation was observed with SiC. In water, the surface of the composites is polished, whereas SiC is worn by fragile ruptures (cleavages). 相似文献
7.
《Ceramics International》2017,43(2):1904-1910
High-performance B4C–SiC nanocomposites with intergranular/intragranular structure were fabricated through spark plasma sintering assisted by mechanochemistry with B4C, Si and graphite powders as raw materials. Given their unique densification behaviour, two sudden shrinkages in the densification curve were observed at two very narrow temperature ranges (1000–1040 °C and 1600–1700 °C). The first sudden shrinkage was attributed to the volume change in SiC resulting from disorder–order transformation of the SiC crystal structure. The other sudden shrinkage was attributed to the accelerated densification rate resulting from the disorder–order transformation of the crystal structure. The high sintering activity of the synthesised powders could be utilised sufficiently because of the high heating rate, so dense B4C–SiC nanocomposites were obtained at 1700 °C. In addition, the combination of high heating rate and the disordered feature of the synthesised powders prompted the formation of intergranular/intragranular structure (some SiC particles were homogeneously dispersed amongst B4C grains and some nanosized B4C and SiC particles were embedded into B4C grains), which could effectively improve the fracture toughness of the composites. The relative density, Vickers hardness and fracture toughness of the samples sintered at 1800 °C reached 99.2±0.4%, 35.8±0.9 GPa and 6.8±0.2 MPa m1/2, respectively. Spark plasma sintering assisted by mechanochemistry is a superior and reasonable route for preparing B4C–SiC composites. 相似文献
8.
《Journal of the European Ceramic Society》2003,23(13):2193-2202
For the development of a new wear resistant and chemically stable glass-ceramic glaze, the CaO–ZrO2–SiO2 system was studied. Compositions consisting of CaO, ZrO2, and SiO2 were used for frit, which formed a glass-ceramic under a single stage heat treatment in electric furnace. In the sintered glass-ceramic, wollastonite (CaSiO3) and calcium zirconium silicate (Ca2ZrSi4O12) were crystalline phases composed of surface and internal crystals in the microstructure. The internal crystal formed with nuclei having a composition of Ca1.2Si4.3Zr0.2O8. The CaO–ZrO2–SiO2 system showed good properties in wear and chemical resistance because the Ca2ZrSi4O12 crystals positively affected physical and mechanical properties. 相似文献
9.
Salim Benaissa Mohamed Hamidouche Mostafa Kolli Gilbert Fantozzi 《International Journal of Applied Ceramic Technology》2019,16(2):638-646
The aim of this work was the analysis of the experimental results of a transparent alumina (BMA15) ceramic which was fabricated by Spark Plasma Sintering (SPS) from nanopowder (BMA15, Baikowski Chimie, France), at different temperatures (1200°C, 1250°C, 1300°C). With the application of a maximum uniaxial pressure of 73 MPa during all the fabrication-cycle (more than 3 hours). We sought an optimal sintering temperature combining better optical and mechanical properties of our pellets. The sintered alumina (BMA15) has a crystalline and dense microstructure. The samples sintered at 1200°C exhibit the best optical properties, in particular: good real inline transmission (RIT) and an optical gap greater than those of the samples sintered at 1250°C and 1300°C. Due to their low density, the Young modulus of alumina sintered at 1200 °C, deduced by ultrasound, has a low value which is about 385 GPa. Similarly, its small grain size gives it a better Vickers hardness ~ 21 GPa. Therefore, the value of the coefficient of friction μ stabilizes around the mean value of 0.21. 相似文献
10.
《Journal of the European Ceramic Society》2021,41(14):6952-6961
B4C–TiB2 ceramic composites were fabricated by a two-step method. First, B4C–TiB2 composite powders were synthesized from TiC–B powder mixtures at 1400 ℃, then mixed with commercial B4C powders by ball milling and the B4C–TiB2 ceramic composites were prepared by hot pressing at 1950 ℃. This two-step method not only effectively refined TiB2 grains, but also allowed the composition of the composites to be freely designed. The microstructure and mechanical properties of the composites were investigated. The results showed that the B4C–TiB2 ceramic composite with a 10 wt% TiB2 content obtained the ideal comprehensive performance, with a volume density, Vickers hardness, bending strength, and fracture toughness of 2.61 g/cm3, 35.3 GPa, 708 MPa, and 5.82 MPa m1/2, respectively. The advantages of the in-situ reaction process were fully exerted by the two-step method, which made a remarkable contribution to the excellent properties of B4C–TiB2 ceramic composites. 相似文献
11.
《Ceramics International》2020,46(3):2923-2930
Densification and mechanical behavior of graphite-free and graphite-doped ZrB2–TiC composites were investigated. Spark plasma sintering was used to achieve near fully-dense composites. Microstructural and phase analysis were carried out via scanning electron microscopy and X-ray diffraction spectroscopy, to illustrate the sintering and toughening mechanisms in the fabricated samples. Results indicated that 1 wt% graphite nano-flakes can improve the hardness of the composite. However, 3% drop in relative density and ~6% decrease in indentation fracture toughness were observed. The formation of TiB2 and ZrC was verified in both TiC-contained composites, although B4C was recognized as the byproduct of reactive sintering in graphite-doped composite. Moreover, the microstructural analysis and the peak shifts in XRD pattern indicated the formation of a solid solution between the ZrB2 and TiB2 phases. Higher hardness of the graphite-doped sample was also attributed to the formation of B4C as a superhard interfacial phase. Toughening mechanisms as well as possible chemical reactions which result in the in-situ formed reinforcement phases were also discussed. 相似文献
12.
《Journal of the European Ceramic Society》2022,42(7):3192-3203
A Si3N4–ZrN wear-resistant self-healing composite material was developed. Si3N4–ZrN composite ultrafine powders were synthesized at a temperature of 1200 °С via solid-state reactions without milling and densified by spark plasma sintering at 1650 °C to a relative density of 97 ± 0.5%. Balls 13.494 mm in diameter for ball bearings manufactured by spark plasma sintering had a fine-grained structure with a grain size of 200–500 nm, Vickers hardness of 22.5 ± 1.8 GPa, and indentation fracture toughness of 6.2 ± 0.4 MPa. The tribological properties of the composite were investigated under static and dynamic loading. The self-healing capability of the Si3N4–ZrN composite was evaluated in the temperature range 500–550 °С. High-temperature three-point bending tests of notched specimens showed a bending strength of 383 ± 21 MPa at room temperature and 413 ± 30 MPa at 500 °С, which confirmed the self-healing of the composite. 相似文献
13.
《Ceramics International》2023,49(15):24989-25002
Multiphase ceramics have been highlighted due to the combination of different properties. This work proposes to obtain the multiphase composite of (Zr,Ti)B2–SiC based on the mixture of ZrB2, SiC, and TiO2 sintered without pressure. The effect of TiO2 addition on solid solution formation with ZrB2, densification, microstructure, and mechanical properties was investigated. For this, 2.0 wt% TiO2 was added to ZrB2–SiC composites with 10–30 vol% SiC and processed by reactive pressureless sintering at 2050 °C with a 2 h holding time. Sinterability, crystalline phases, microstructure, Vickers hardness, and indentation fracture toughness of these composites were analyzed and compared to the non-doped ZrB2–SiC samples. The XRD analysis and EDS elemental map images indicated the incorporation of Ti atoms into the ZrB2 crystalline structure with solid solution generation of (Zr,Ti)B2. The addition of TiO2 resulted in matrix grain size refinement and a predominant intergranular fracture mode. The relative densities were not significantly modified with the TiO2 addition, though a higher weight loss was detected after the sample sintering process. The composites doped with TiO2 showed an increase in fracture toughness but exhibited a slightly lower Vickers hardness compared to composites without TiO2 addition. 相似文献
14.
Mengwen Zhang Lutong Yang Zhaosheng Li Binyang Jiang 《International Journal of Applied Ceramic Technology》2023,20(1):527-533
Al2O3–cBN has received considerable attention in the field of ceramic cutting tools due to its high hardness, high wear resistance, and low cost, but poor interfacial bonding affects the performance of the composite. In this study, a novel hot-forging process was used to prepare high-performance Al2O3–cBN composites using Ti(C,N) as a binder. The evolution of the morphology, phase, and microstructure of the hot-forged Al2O3–Ti(C,N)–cBN composites was determined, and the mechanical properties were measured. The relative density of the composites increases significantly after hot forging, and the deformation of the composites increases with the hot-forging temperature. The highest performing Al2O3–Ti(C,N)–cBN composite was prepared by hot forging at 1600°C and has a hardness of 20 GPa, a bending strength of 647 MPa and a fracture toughness of 5.37 MPa m1/2, which are superior to those of a directly hot-pressed sintered composite. However, at hot-forging temperatures higher than 1700°C, Al5O6N and TiB2 are formed in the composite. In the composite hot forged at 1800°C, serrated grain boundaries promote the strength and toughness of the composite to 877 MPa and 6.76 MPa m1/2, respectively. Therefore, the novel hot-forging process is expected to enhance material properties. 相似文献
15.
Highly dense AlN–SiC composites with various SiC additions (0–50?wt-%) were fabricated at 1800°C by plasma activated sintering. The effect of SiC addition on structural, thermal and dielectric properties as well as microwave absorbing performance of the composites was investigated. The thermal conductivity decreases with increasing SiC addition, from 68.7 W (m?K)?1 for 0?wt-% SiC to 19.38?W (m?K)?1 for 50?wt-% SiC. On the contrary, the permittivity and dielectric loss increase gradually, from 7.6–8.5 to 22–26.7 and from 0.02–0.1 to 0.2–0.53, respectively. AlN–SiC composite with better thermal and dielectric properties in 30?wt-% SiC, whose thermal conductivity and dielectric loss are found to be 24.88?W (m?K)?1 and 0.15–0.74, respectively. Furthermore, the composite exhibits microwave absorbing performance with the minimum reflection loss (RL) of ?16.5 dB at 15.5 GHz and the frequency range of 2.6 GHz for RL below ?10 dB (90% absorption). 相似文献
16.
《Ceramics International》2016,42(6):7328-7335
Phase-pure BiFeO3 powders were synthesized by sol–gel technique. Based on these powders, high-density BiFeO3 ceramics were prepared by spark plasma sintering (SPS) at 700 °C along with annealing for 2 and 4 h, respectively, at 650 °C under atmospheres of air and oxygen. X-ray diffraction analysis revealed that the 4 h-oxygen-annealed sample contained a single rhombohedral perovskite phase while the samples annealed in the other conditions contained small quantities of impurity phases besides the rhombohedral perovskite phase. The relative density of the 4 h-oxygen-annealed sample was about 96%, being apparently higher than that of the other samples. In comparison with the 4 h-air-annealed sample, the dielectric constant of the 4 h-oxygen-annealed sample was relatively higher. The activation energy for electrical conduction was about 1.17 eV for the 4 h-oxygen-annealed sample while it was about 0.98 eV for the 4 h-air-annealed sample, showing that the former would have a lower room-temperature conductivity (~2.6×10−14 S cm−1) than the latter (~2.1×10−13 S cm−1). It is therefore anticipated that the oxygen-annealed sample could possess better ferroelectric properties as compared to the air-annealed sample. 相似文献
17.
Si3N4–TiN composites were successfully fabricated via planetary ball milling of 70 mass% Si3N4 and 30 mass% Ti powders, followed by spark plasma sintering (SPS) at 1250–1350 °C. The sintering mechanism for SPS was a hybrid of dissolution–reprecipitation and viscous flow. The electrical resistivity decreased with increasing sintering temperature up to a minimum at 1250 °C and then increased with the increasing sintering temperature. The composites prepared by SPS at 1250–1350 °C could be easily machined by electrical discharge machining. Composite prepared by SPS at 1300 °C showed a high hardness (17.78 GPa) and a good machinability. 相似文献
18.
《Diamond and Related Materials》1999,8(10):1838-1846
This paper summarizes theoretical and experimental studies of cBN–TiN and cBN–TiC of cBN:TiN/TiC molar ratio 1:1 and 2:1. Theoretical calculations show that, at temperatures between 1000 and 1400°C, TiN reacts with BN forming one new phase, TiB2, and that TiC reacts with cBN forming two new phases, TiB2 and TiC0.8N0.2.. Experimental cBN–TiC/TiN composites were prepared by high pressure hot pressing and the samples were subsequently heat treated.After heat treatment, sinters of cBN–TiN/TiC were characterized using transmission electron microscopy and X-ray diffraction. The samples exhibited a dense polycrystalline structure, and a thin layer of fine TiB2 was visible at the BN–binder interface. It was found that hardness decreased significantly after heat treatment. 相似文献
19.
Mengyang Liu Shuangshuang Wang Sifang Li Chengwei Liu Shuaiou Luo Deqiang Wang 《International Journal of Applied Ceramic Technology》2023,20(4):2261-2270
Uniformly dispersed nano-sized aluminum nitride powders were prepared by the sol–gel foaming method using aluminum nitrate as the aluminum source, sucrose as the carbon source, and ammonium chloride as the foaming agent. The effects of ammonium chloride content on the particle size and the sintering properties of aluminum nitride were investigated. The results showed that when the molar ratio of ammonium chloride to aluminum nitrate was .5, the colloidal foams were uniform, large, and fluffy, and amorphous alumina precursors with uniform particles could be prepared. Aluminum nitride powder with a particle size of 22–27 nm can be obtained by calcining these precursors in nitrogen atmosphere at 1400°C for 2 h. At the same time, aluminum nitride bulk material with a relative density of 95% can be obtained by sintering the compact samples in nitrogen atmosphere at 1700°C for 2 h. 相似文献
20.
Xixi Hu Shenglin Zhong Jing Geng Peicheng Mo Jiuyang Li Peixun Wang Luyu Yang Yi Wu 《International Journal of Applied Ceramic Technology》2023,20(4):2183-2193
Polycrystalline cubic boron nitride (PcBN) composites were synthesized in situ with TiB2, TiN, and Sialon as binders under ultrahigh temperature (1550°C) and high pressure (5.5 GPa). X-ray diffractometry, universal testing machine, field emission scanning electron microscopy, and transmission electron microscopy were used to study the effect of Sialon content (0%, 20%, 40%, 60%, and 80% by mass of binder) on the phase composition, microstructure, and mechanical properties of PcBN composites. The results show that the main phases in the system are lamellar TiN, needle-rodlike TiB2, and irregular long-rodlike Sialon. Some TiB2 grows along the (1 0 −1 0) face, and Sialon grows along the (0 0 0 1) face. The density and mechanical properties of the sintered product are significantly improved due to the formation of Sialon. When the content of Sialon is 60%, the binder is uniformly distributed, the cBN interface is well bonded, and the density is the highest. At this time, the strength reaches the maximum 34.57 GPa, the fracture toughness is 6.82 MPa m1/2, and the flexural strength reaches the maximum 870.79 MPa. On the whole, cBN composites have excellent prospects for future applications in cutting inserts due to their excellent mechanical properties. 相似文献