共查询到19条相似文献,搜索用时 93 毫秒
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研究了在MgO-C耐火材料中添加单斜氧化锆或锆英石所形成的MgO-ZrO2-C材料的性能和显微结构.结果表明(1)加入单斜氧化锆和锆英石导致材料的高温抗折强度降低.(2)热震温度低于1000 ℃时,加入不同量的单斜氧化锆或锆英石对材料抗折强度损失率的影响较小;而热震温度为1200 ℃时,不同的添加量有较大的差别,当单斜氧化锆的添加量为5%~7%,锆英石的添加量为1.54%时,MgO-ZrO2-C材料的抗折强度损失率最小.(3)添加的单斜氧化锆在1200 ℃的热震温度下有部分ZrO2固溶到了镁砂颗粒的内部;而添加的锆英石在1200 ℃下变化轻微,但在1400 ℃下,材料中仅存在少量未分解或分解不完全的锆英石,MgO由基质向锆英石颗粒内部扩散,导致分解完全的锆英石颗粒转变为ZrO2、CMS和c- ZrO2小颗粒. 相似文献
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锆莫来石材料的反应烧结机制和显微结构特征 总被引:5,自引:0,他引:5
研究了用锆英石和工业氧化铝合成锆莫来石材料的反应烧结过程和显微结构。结果表明,添加适量MgCl2·6H2O可以促进反应烧结进程。锆英石大颗粒完全分解以后形成ZrO2聚集体,结构中出现封闭气孔可能与ZrO2聚集体有密切关系。加入MgCl2·6H2O后锆莫来石材料显微结构的主要特征:ZrO2有聚集体和均匀分布两种赋存形式;封闭气孔一般与ZrO2聚集体相邻。 相似文献
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以3Y-TZP粉体为基体、5%NH4HCO3为造孔剂,通过混合、压制成型后在不同温度进行微波烧结和1 250℃玻璃渗透制备ZrO2全瓷材料。结果表明:微波烧结后原3Y-TZP中的单斜相全部转变为四方相,并且通过渗透后物相不变。各个不同温度微波烧结后再渗透试样的密度和显微硬度比未渗透有一定程度提高,断裂韧性和抗弯强度显著提高,其中1 200℃微波烧结后再渗透的试样晶粒尺寸细小、均匀,其密度、显微硬度、断裂韧性和抗弯强度最高,达到5.88g/cm3、10.56GPa、12.01MPa·m1/2和522.37MPa,分别比未渗透提高了2.1%、0.6%、41.0%和55.1%。 相似文献
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本文研究了反应烧结含ZrO_2的刚玉-莫来石材料及其碳结合材料的相组成,显微结构和力学性能。结果表明,对刚玉-莫来石材料由于加入氧化锆引起的微裂纹,中、低温强度趋于下降;但在1300℃以上,强度和抗蠕变性能都有明显上升。这可能是因为微裂纹得到一定弥合,同时氧化锆和莫来石之间形成晶界固溶。对碳结合刚玉-莫来石-氧化锆材料,在所有试验温度下,强度都随石墨加入量增加而下降。强度-温度曲线呈现两个特征:(1)由600℃至800℃强度下降,而由800℃至1000℃强度均有回升;(2)由1300℃至1400℃强度略有回升。这与金属粉添加剂在不同温度下的行为有密切关系。形成针状或纤维状的碳化物有利于提高强度。 相似文献
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《Ceramics International》2021,47(2):2255-2260
This study firstly developed Hf1-xVxB2 (x = 0, 0.01, 0.02, 0.05) powders, which were derived from borothermal reduction of HfO2 and V2O5 with boron. The results revealed that significantly refined Hf1-xVxB2 powders (0.51 μm) could be obtained by solid solution of VB2, and x ≥ 0.05 was a premise. However, as the content of V-substitution for Hf increased, Hf1-xVxB2 ceramics sintered by spark plasma sintering at 2000 °C only displayed a slight densification improvement, which was attributed to the grain coarsening effect induced by the solid solution of VB2. By incorporating 20 vol% SiC, fully dense Hf1-xVxB2-SiC ceramics were successfully fabricated using the same sintering parameters. Compared with HfB2-SiC ceramics, Hf0.95V0.05B2-20 vol% SiC ceramics exhibited an elevated and comparable value of Vickers hardness (23.64 GPa), but lower fracture toughness (4.09 MPa m1/2). 相似文献
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《Journal of the European Ceramic Society》2017,37(5):1985-1992
Mg-doped sialon ceramics with the composition of M0.4Si10.2Al1.8O1N15 were fully densified by hot pressing at 1850 °C for 1 h, using 0.5 wt.% MgF2 or CaF2 as a sintering additive. Densification behavior, phase assemblage, microstructure, and mechanical and optical properties were investigated in detail. The addition of fluorides, especially MgF2, not only resulted in more high-temperature liquid by promoting the dissolution of more N and other constituents but also reduced the viscosity of liquid due to the terminal effect of fluorine. Consequently, the densification was effectively improved. Additionally, the fluoride addition facilitated the formation of a small amount of β-sialon. Both the samples possessed high hardness (∼20 GPa) and fracture toughness (∼4.2 MPa m1/2). The CaF2-added sample exhibited higher infrared transmittance than its counterpart due to less residual glass phase. The present work implies that fluorides are also very effective sintering additives for densifying α-sialon. 相似文献
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In this work, the effect of ZrB2 (0, 5, 10 and 20?vol%) ceramic reinforcement on densification, structure, and properties of mechanically alloyed Al was investigated. The milling of Al-ZrB2 powder compositions resulted in formation of agglomerates with varied size. In particular, the size of agglomerates was reduced considerably with increased addition of ZrB2 to Al. Interestingly, the densification of hot pressed Al increased from 96.06% to 99.22% with ZrB2 addition. The reduction of agglomerates size was attributed to the enhanced densification of Al-ZrB2 composites. Pure Al showed relatively low hardness (0.94?GPa) and it was improved to 1.78?GPa with the addition of 20?vol% ZrB2. The mechanical properties have significantly been improved for Al-ZrB2 composites. Especially Al - 20?vol% ZrB2 possessed a very high yield strength (529?MPa), compressive strength (630?MPa) and compressive strain of 19.25%. Realization of such a good combination of mechanical properties is the highest ever reported for Al composites so far in the literature. The coefficient of friction (COF) of Al-ZrB2 varied narrowly between 0.33 and 0.40 after dry sliding wear against steel disc. The wear rate of Al-ZrB2 composites was within mild wear regime and varied between 98.88?×?10?6 and 34.66?×?10?6 mm3/Nm. Among all the compositions, Al - 20?vol% ZrB2 composite exhibited the lowest wear rate and high wear rate was noted for pure Al. Mild abrasion, tribo-oxidation, third body wear (wear debris) and delamination were the major material removal mechanisms for Al-ZrB2 composites. Overall the hardness, strength and wear resistance of Al - 20?vol% ZrB2 composite was improved by 84.3%, 84.3% and 64.2%, respectively when compared to pure Al. 相似文献
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《Ceramics International》2020,46(8):12145-12155
Alumina-coated cubic boron nitride (c-BN) particles (c-BN@Al2O3) were prepared using a heterogeneous nucleation method. Then, they were added to a (Ti,W)C-based cermet tool material after synthesis via vacuum hot-press sintering. The microstructure and mechanical properties of the (Ti,W)C-based cermet tool material with varying c-BN@Al2O3 contents were recorded and analyzed. The results show that with increasing c-BN@Al2O3 concentration, the relative density, flexural strength, fracture toughness, and Vickers hardness all increase first and then decrease, and the average grain size first decreases and then increases. The introduction of Al2O3 into the c-BN particles used for surface modification can improve the wettability and interfacial bonding strength between the c-BN and matrix particles, restrain the grain growth of the matrix particles, and improve the flexural strength of cermet tool materials. The addition of c-BN@Al2O3 also alters the crack propagation mechanism of the cermet tool material and introduces multiple toughening mechanisms to improve the fracture toughness of the cermet tool material. The high hardness of c-BN and Al2O3 is the main reason for the increase in hardness; however, excessive addition of such material reduces the relative density, resulting in a decrease in hardness. 相似文献
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《Journal of the European Ceramic Society》2020,40(2):220-225
ZrC ceramics containing 30 vol% SiC-ZrB2 were produced by high-energy ball milling and reactive hot pressing. The effects of ZrB2 content on the densification, microstructure, and mechanical properties of ceramics were investigated. Fully dense ceramics were achieved as ZrB2 content increased to 10 and 15 vol%. The addition of ZrB2 suppressed grain growth and promoted dispersion of the SiC particles, resulting in fine and homogeneous microstructures. Vickers hardness increased from 23.0 ± 0.5 GPa to 23.9 ± 0.5 GPa and Young’s modulus increased from 430 ± 3 GPa to 455 ± 3 GPa as ZrB2 content increased from 0 to 15 vol%. The increases were attributed to a combination of the higher relative density of ceramics with higher ZrB2 content and the higher Young’s modulus and hardness of ZrB2 compared to ZrC. Indentation fracture toughness increased from 2.6 ± 0.2 MPa⋅m1/2 to 3.3 ± 0.1 MPa⋅m1/2 as ZrB2 content increased from 0 to 15 vol% due to the increase in crack deflection by the uniformly dispersed SiC particles. Compared to binary ZrC-SiC ceramics, ternary ZrC-SiC-ZrB2 ceramics with finer microstructure and higher relative densities were achieved by the addition of ZrB2 particles. 相似文献
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Zhuang Lu Limeng Liu Guihong Geng Alexander M. Laptev Zhaoping Hou Yujin Wang 《Ceramics International》2019,45(6):6712-6717
TaC ceramics with 0.03–0.60?wt% of boron additions were prepared by hot pressing at 2100?°C for 1?h under a pressure of 40?MPa. Effects of boron content on densification, phase composition, microstructure, mechanical properties and oxidation resistance of the TaC ceramics were investigated. When the boron content was 0.12?wt% and above, full density was obtained due to reactions between boron and oxygen impurity at presence of TaC. Minor phases of TaB2 and C were formed in the 0.24 and 0.60?wt% B compositions after gas-out of the oxygen impurity. Microstructure of the TaC ceramics was refined with increasing in boron content. The TaC ceramic with 0.24?wt% of boron showed the best mechanical properties with a Vickers hardness, flexural strength and fracture toughness of 17.7?GPa, 534?MPa and 4.6?MPa?m1/2, respectively. When more boron was added, interfacial bonding of the TaC grains was strengthened causing a decrease in fracture toughness. Oxidation resistance of the TaC ceramics increased with boron content. Particularly, the 0.60?wt% B composition showed a weight gain of 0.0018?g/cm2 after oxidization at 800?°C in air for 3?h. 相似文献