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立方氮化硼(cBN)是在碱金属、碱土金属及它们的氮化物、硼化物、硼氮化物等触媒参与,在高压高温条件下由六方氮化硼(hBN)转变而成的。文章就一些添加物,例如,Si、B2O3、AIN、VB族等价杂质、wBN、尿素、水等对hBN转变为cBN所产生的影响做一简要综述。 相似文献
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氮化硼对锆刚玉莫来石材料力学性能及显微结构的影响 总被引:1,自引:1,他引:1
研究了锆刚玉米莫来石-氮化硼复合材料的显微结构及力学性能,结果表明,在锆刚玉莫来基质引入氮化硼,降低材料的抗折强度,但可提高断裂韧性。这是氮化硼的微裂纹增韧作用所致。氮化硼的编织状结构可阻碍晶界的滑移,降低材料高温强度的衰减率。材料内生成的针状9Al2O3.2B2O3,在断裂过程生产拔出效应,有利于力学性能的提高。 相似文献
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通过采用不同添加物进行制样并在不同温度下进行烧结实验 ,测试样的收缩率、吸水率、体积密度、显气孔率、玻璃相含量等 ,研究了Cr2 O3、MgO、TiO2 三种添加物对硅线石精矿烧结性能的影响。结果表明 :这些添加物均可改善硅线石的烧结性能 ,其最佳加入量分别为 :TiO2 2 %、MgO 2 %、Cr2 O33% 相似文献
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以氮化硼为填充,聚丙烯为基体,采用熔融共混的方法制备聚丙烯/氮化硼复合材料。通过力学性能、流动性能以及导热性能等研究发现,随着氮化硼的加入,复合材料的冲击性能、弯曲性能、熔体流动性均有明显提升,拉伸强度、断裂伸长率、熔体流动速率有明显下降。氮化硼填充量为20%,复合材料的冲击强度为3.42 kJ/m2,弯曲强度为41.97 MPa,弯曲模量为2.78 GPa,拉伸强度为30.37 MPa,断裂伸长率为4.14%,熔体流动速率为2.89 g/(10 min),此时导热系数均为0.345 W/(m·K),比纯PP基体增加了50%。 相似文献
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Tianfeng Li Yongjun Chen Wei Li Jianbao Li Lijie Luo Tao Yang Longyang Liu Gaolong Wu 《Ceramics International》2018,44(6):6456-6460
In this study, silicon nitride (Si3N4) ceramics added with and without boron nitride nanotubes (BNNTs) were fabricated by hot-pressing method. The influence of sintering temperature and BNNTs content on the microstructures and mechanical properties of Si3N4 ceramics were investigated. It was found that both flexural strength and fracture toughness of Si3N4 were improved when sintering temperature increases. Moreover, α-Si3N4 phase could transform into β-Si3N4 phase completely when sintering temperature rises to 1800 °C and above. BNNTs can enhance the fracture toughness of Si3N4 dramatically, which increases from 7.2 MPa m1/2 (no BNNTs) to 10.4 MPa m1/2 (0.8 wt% BNNTs). However, excessive addition of BNNTs would reduce the fracture toughness of Si3N4. Meanwhile, the flexural strength and relative density of Si3N4 decreased slightly when BNNTs were added. The related toughening mechanism was also discussed. 相似文献
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Guandong Liang Guoxun Sun Jianqiang Bi Weili Wang Xiangning Yang Yonghan Li 《Ceramics International》2021,47(2):2058-2067
Uniformly dispersed boron nitride nanosheets (BNNSs) reinforced silicon nitride (Si3N4) composites were prepared by surface modification assisted flocculation combined with SPS sintering. In order to improve the dispersibility of the BNNSs in the composites, the liquid phase stripped BNNSs are surface functionalized by a two-step covalently modification. The amino-modified BNNSs (NH2-BNNSs) and Si3N4 powders have opposite surface potential, mixed evenly by electrostatic interaction during flocculation. The results showed that mechanical properties of Si3N4 composites were obviously enhanced by adding NH2-BNNSs. The fracture toughness and bending strength of Si3N4 composites added 0.75 wt% NH2-BNNSs were increased by 34% and 28%, respectively, compared with monolithic Si3N4. Toughening mechanisms are synergistic action of the torn, pull-out or bridging of BNNSs and crack deflection mechanisms with microstructural analyzes. The dielectric properties of the Si3N4 ceramics are also improved after the addition of NH2-BNNSs. 相似文献
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Xiangning Yang Jianqiang Bi Guandong Liang Yonghan Li Linjie Meng Chengge Wu Xiangyu Zhang 《International Journal of Applied Ceramic Technology》2022,19(5):2817-2825
The boron nitride nanosheets (BNNSs)/aluminum nitride (AlN) composites were prepared by hot press sintering at 1600°C. The microstructure, mechanical properties, and thermal conductivity of the samples were measured, and the effect of adding BNNSs to AlN ceramics on the properties was studied. It is found that the addition of BNNSs can effectively improve the mechanical properties of AlN. When the additional amount is 1 wt%, the bending strength of the sample reaches the maximum value of 456.6 MPa, which is 23.1% higher than that of the AlN sample without BNNSs. The fracture toughness of the sample is 4.47 MPa m1/2, a 68.7% improvement over the sample without BNNSs. The composites obtained in the experiment have brilliant mechanical properties. 相似文献
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《Ceramics International》2016,42(15):16655-16658
Nanocrystalline hexagonal boron nitride powders (h-BN) were synthesized from urea and boric acid followed by pirolysis and subsequent heat treatment in nitrogen atmosphere. Materials have been analyzed by means of X-ray diffraction, Photoluminescence and Field emission electron microscopy methods. Obtained results show that starting h-BN powder, synthesized at 750 °C, is composed of ~11 layer crystallites with average crystallite thickness and crystallite lateral size of 3.94 and 10.4 nm, respectively. A broad emission and intense luminescence intensity were observed due to the large atomic disorder. Higher annealing temperature increases crystallite size and turbostratic h-BN transforms to well crystallized h-BN at 1500 °C. 相似文献
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Using Si and BN powders as raw materials, silicon nitride/hexagonal boron nitride (Si3N4/BN) ceramic composites were fabricated at a relatively low temperature of 1450 °C by using the reaction bonding technology. The density and the nitridation rate, as well as the dimensional changes of the specimens before and after nitridation were discussed based on weight and dimension measurements. Phase analysis by X-ray diffraction (XRD) indicated that BN could promote the nitridation process of silicon powder. Morphologies of the fracture surfaces observed by scanning electron microscopy (SEM) revealed the fracture mode for Si3N4/BN ceramic composites to be intergranular. The flexural strength and Young's modulus decreased with the increasing BN content. The reaction-bonded Si3N4/BN ceramic composites showed better machinability compared with RBSN ceramics without BN addition. 相似文献
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《Ceramics International》2017,43(4):3569-3575
Spherical boron nitride nanoparticles have been successfully fabricated by temperature-controlled pyrolysis procedure in a N2 atmosphere, using boron acid and urea as the precursors. The carbon spheres were prepared from glucose (C6H12O6) by a hydrothermal method as a template to be used. Comprehensive scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier infrared spectrum (IR) characterizations all confirm that the obtained products are spherical boron nitride. The amount of C6H12O6 and reaction time were found to affect the morphology and structure of the as-prepared products. The average diameter of the spherical boron nitride nanoparticles synthesized with the addition of C6H12O6 is about 0.3–1 µm. The spherical boron nitride has a high surface area of 176.78 m2g−1 and ~3.5 nm pore size. The as-synthesized nanospheres also exhibit strong photoluminescence (PL) bands at 436, 454, 486, and 616 nm under 312 nm excitation, indicating that they could have potential application in novel optical devices. 相似文献
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Well-dispersed boron nitride nanosheets (BNNSs) reinforced fused silica composites were successfully fabricated by surface modification assisted flocculation method. Surface modification can enhance the performance of flocculation process. BNNSs were homogeneously mixed with fused silica through the electrostatic interaction between hydroxylated BNNSs with negative charge and amino-modified fused silica with positive charge. The BNNSs can act as excellent nanofillers for enhancing the mechanical properties of fused silica composites. Approximately 74% and 48% increases in flexure strength and fracture toughness can be achieved for the 1.5 wt% BNNSs/fused silica composite, respectively. The toughening mechanisms were analyzed by microstructural characterization, especially for pull-out mechanism. 相似文献
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《Journal of the European Ceramic Society》2017,37(9):3195-3202
In order to overcome intrinsic brittleness and poor mechanical properties of fused silica (FS), boron nitride nanosheets (BNNSs) as a novel reinforcement were employed for fabrication of BNNSs/fused silica composites. BNNSs with micron lateral size were homogeneously dispersed with FS powder using a surfactant-free flocculation method and then consolidated by hot pressing. The flexural strength and fracture toughness of the composite with the addition of only 0.5 wt.% BNNSs increased by 53% and 32%, respectively, compared with those of pure FS. However, for higher BNNSs contents the improvement in mechanical properties was limited. Microstructural analyzes have shown that the toughening mechanisms are combinations of the pull-out, crack bridging, and crack deflection mechanisms. 相似文献
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Heng Wang Weimin Wang Hao Wang Fan Zhang Yawei Li Zhengyi Fu 《Ceramics International》2018,44(11):12216-12224
Water pollution has become a serious global issue owing to the large amounts of contaminants generated from industrial and agricultural development. Recently, various boron nitride-based micro/nano-materials have exhibited efficient sorption capacity for contaminants from water. Herein, novel urchin-like boron nitride hierarchical structure assembled by free-growing boron nitride nanotubes and crapy boron nitride nanosheets is firstly fabricated via a sample two-step approach, including the synthesis of analogous "core-shell" structured boron-containing precursor and thermal catalytic chemical vapor deposition. A combined growth mechanism of vapor-liquid-solid and vapor-solid is proposed to control the formation of BN hierarchical structure. The unique structure exhibits superior removal capacity of 115.07?mg?g?1 and 92.85?mg?g?1 for Pb2+ and Cu2+ in water solution, respectively. The excellent adsorption performance of the product mainly derives from the vast lattice imperfections, the high-density edge active sites, the expanded interplanar spacing, as well as the unique structural characteristics. They are beneficial for structural stability and enough space for accommodating the adsorbed heavy metal ions. These results indicate that the urchin-like boron nitride hierarchical structure is a promising adsorption material for water treatment. 相似文献
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Murat Durandurdu 《Journal of the American Ceramic Society》2020,103(2):973-978
We generate a tetrahedrally coordinated amorphous boron nitride (BN) model by means of first principles molecular dynamics calculations and report its mechanical and electrical properties in detail. The amorphous configuration is almost free from chemical disorder and consists of about 20% coordination defects, similar to tetrahedral (diamond-like) amorphous carbon. Its theoretical band gap energy is about 2.0 eV, less than 4.85 eV estimated for cubic BN. The bulk modulus and Vickers hardness of tetrahedral amorphous BN are computed as 206 GPa and 28-35 GPa, respectively. Based on these findings, we propose that tetrahedral noncrystalline BN can serve as electronic and hard materials as well. 相似文献