Effects of BN content on the mechanical properties of nanocrystalline 3Y-TZP/Al_2O_3/BN dental ceramics

3 Y-TZP/3 wt% Al_2O_3 powder was coated with varying amounts of BN using the urea and borate reaction sintering method, and then multiphase ceramics were prepared by hot pressing sintering. The micro-topography and the compositional analysis of synthesized ceramics were conducted through scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A mechanical tester was used to analyze the Vickers hardness, fracture toughness, and bending strength of the synthesized ceramics. The results showed that the ceramic with a BN content of 12 wt% showed the best processability, but had diminished mechanical properties(such as fracture toughness and bending strength). The ceramic with a BN content of 9 wt% showed better processability than those with 3 wt% and 6 wt% BN. However, the fracture toughness was affected by the addition of 9 wt% BN, making this ceramic only usable as a base material for a three-unit fixed bridge. In contrast, the ceramics with a BN content of 3 wt% or 6 wt% fulfilled the criteria for use in multi-unit restoration, but their low processability made them unsuitable for milling after sintering.     

Reinforcing effect of graphene on the mechanical properties of Al2O3/TiC ceramics

Multilayer graphene (MLG)-reinforced Al2O3/TiC ceramics were fabricated through hot pressing sintering, and the reinforcingef-fect of MLG on the microstructure and mechanical properties of the composites was investigated by experiment and simulation. The simula-tion of dynamic crack initiation and propagation was investigated based on the cohesive zone method. The results show that the composite added with 0.2wt% MLG has excellent flexural strength and high fracture toughness. The major reinforcing mechanisms are the synergistic effect by strong and weak bonding interfaces, MLG pull-out, and grain refinement resulting from the addition of MLG. In addition, the ag-gravating of crack deflection, branching, blunting, and bridging have indispensable contribution to the improvement of the as-designed mate-rials.     

Effects of metal binder on the microstructure and mechanical properties of Al2O3-based micro-nanocomposite ceramic tool material

The Al2O3?(W,Ti)C composites with Ni and Mo additions varying from 0vol% to 12vol% were prepared via hot pressing sintering under 30 MPa. The microstructure was investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). Mechanical properties such as flexural strength, fracture toughness, and Vickers hardness were also measured. Results show that the main phases A12O3 and (W,Ti)C were detected by XRD. Compound MoNi also existed in sintered nanocom-posites. The fracture modes of the nanocomposites were both intergranular and transgranular fractures. The plastic deformation of metal particles and crack bridging were the main toughening mechanisms. The maximum flexural strength and fracture toughness were obtained for 9vol% and 12vol% additions of Ni and Mo, respectively. The hardness of the composites reduced gradually with increasing content of metals Ni and Mo.     

低温烧结Al2O3/3Y-TZP复合材料的力学性能

采用可低温烧成的高活性Al2O3以及ZrO2(x(Y2O3)=3%)粉料制备了m(Al2O3)m(3Y-TZP)=8515的复合材料.经成型后的试样在常压、1 350～1 500℃温度下2 h烧成,在1 425℃的相对低温下烧成就可获得相对密度大于0.99的烧结体.利用X射线衍射仪和扫描电子显微镜分别对试样的相组成和显微结构进行分析,研究了相组成和显微结构对Al2O3/3Y-TZP复合材料的力学性能的影响.分析结果表明,在1425℃温度下烧成的复合材料具有了最佳的力学性能,其抗弯强度、断裂韧性和维氏硬度分别达到856 MPa,7.4MPa·m1/2和16.4GPa.     

Al2O3／TiC陶瓷材料的改性研究

研究了固体润滑剂CaF2和BN对Al2O3／TiC陶瓷材料的力学性能和显微结构的影响，实验表明，Al2O3／TiC／CaF2陶瓷材料的力学性能比Al2O3／TiC/BN陶瓷材料的力学性能好，XRD衍射结果和微观结构显示，Al2O3／TiC／BN材料中的BN与Al2O3反应生成AIN，产生大量裂纹，致使材料的强度和硬度都大幅下降，Al2O3／TiC／CaF2陶瓷材料中的CaF2在烧结过程中没发生化学反应；材料晶粒大小均匀，基体组织呈网状结构，有利于提高材料的强度和硬度。     

底材厚度对铝热反应熔化制备的块体纳米晶Fe3Al材料的组织和性能的影响

通过铝热反应熔化方法在厚度为5~15 mm的铜底材上制备块体纳米晶Fe3Al材料.通过X射线衍射(XRD)研究材料的晶粒尺寸,研究材料室温压缩下的力学性能和硬度.结果表明,所制备材料的晶粒尺寸均约为20nm,且晶粒尺寸随底材厚度的增加而增加.底材厚度为5 mm时纳米晶Fe3Al材料的屈服强度和硬度具有最大值,随着底材厚度的增加,屈服强度和硬度急剧减小,最后趋于稳定.5 mm时纳米晶Fe3Al材料的屈服强度约是10mm时的1.5倍.     

Al_2O_3／nano－SiC复相陶瓷力学性能及显微结构

研究了热压烧结Ａｌ２Ｏ３／ｎａｎｏ－ＳｉＣ复相陶瓷的力学性能及显微结构。研究表明,纳米ＳｉＣ的引入显著地改善了材料的力学性能,在ＳｉＣ添加体积分数为１０％时,Ａｌ２Ｏ３／ｎａｎｏ－ＳｉＣ复相陶瓷抗弯强度σｆ达峰值为８６９ＭＰａ,断裂韧性ＫＩｃ也达峰值为６．７ＭＰａ·ｍ０．５,比纯Ａｌ２Ｏ３基体材料分别提高１３８％和８１％。ＴＥＭ观察表明：纳米ＳｉＣ晶粒主要存在于Ａｌ２Ｏ３基体晶粒内部,形成独特的“晶内型”结构。当受外力作用时,既能因弥散的纳米颗粒诱发穿晶断裂,且穿晶断裂时,还能因晶内存在第二相颗粒而引起裂纹偏转,起到增强增韧作用。     

BN表面镀镍对Ni-Cr/BN减摩密封材料烧结性能的影响

为改善减摩密封材料Ni-Cr/BN的烧结性能,在碱性条件下以硫酸镍为主盐、水合联氨为还原剂,采用化学镀方法在BN粉表面生成镀镍层;采用粉末冶金方法制备Ni-Cr/BN复合材料,并研究BN粉表面镀镍对Ni-Cr/BN烧结性能的影响。研究结果表明:在1000℃烧结时,BN粉表面镀上连续均匀的镀镍层能显著提高BN粉与Ni-Cr合金基体的润湿性,使Ni-Cr/BN减摩材料的抗拉强度由9.16MPa提高到27.88MPa,抗弯强度由21.40MPa提高到49.12MPa;但当烧结温度达到1100℃时,BN粉表面的镀镍层发生球化并脱落,镀镍层对Ni-Cr/BN减摩密封材料烧结性能的改善效果降低。     

铅硼硅酸盐玻璃中Al2O3含量对复相玻璃陶瓷性能的影响

以低软化点的铅硼硅酸盐玻璃和Al2O3粉末为原料,制备Al2O3/玻璃低温共烧复合玻璃陶瓷材料。考察烧结温度和添加不同质量分数的Al2O3对复合玻璃陶瓷烧结机制和微波介电性能的影响,并探讨了作用机制。结果表明:Al2O3掺入PbO-B2O3-SiO2玻璃中改善了与Al2O3陶瓷的界面润湿,对烧结有一定的促进作用。在添加质量分数为4%Al2O3的复相玻璃陶瓷、烧成温度为850℃时性能最好,其密度为3.1 g/cm3,介电常数为8.46,介电损耗为0.001 1。     

Ni对铝热反应制备块体纳米晶Fe3Al材料力学性能的影响

通过铝热反应熔化方法制备Ni质量分数分别为5%、10%、15%的块体纳米晶Fe3Al材料,研究材料在室温压缩和弯曲下的力学性能及硬度.结果表明,所制备材料的平均晶粒尺寸均约为21 nm;随着合金元素Ni质量分数的增加,材料的硬度和屈服强度δ0.2逐渐增大;材料在弯曲实验中均表现为脆性断裂,弯曲强度随Ni含量的增加先增大后减小,w(Ni)=10%的材料弯曲强度最大,为328.7 MPa.     

二次烧成对CaO-B2O3-SiO2系微晶玻璃结构和性能的影响

研究一次和二次烧成对CaO-B2O3-SiO2(CBS)微晶玻璃的烧结性能与介电性能的影响。用X线衍射(XRD)、扫描电镜(SEM)等分析探讨二次烧成对CBS微晶玻璃的微观结构与介电性能的关系。结果表明:与一次烧成相比,二次烧成能够促进玻璃体中的小晶粒生长,试样的收缩率和体积密度有所增加,有利于介电常数提高和介质损耗的降低,且体系中没有出现新的晶相;875℃烧结的试样,X/Y轴收缩率均为14.33%,体积密度达到2.46 g/cm3,10MHz介电常数和损耗相应为6.21和3.5×10-3,热膨胀系数为11.86×10-6/℃,抗折强度为157.36MPa。     

烧结工艺对透明氧化铝陶瓷性能的影响

以Isobam600AF为分散剂,Isobam104为胶黏剂,采用注凝成型工艺和真空无压烧结技术,通过改进两步烧结法制备了透明氧化铝陶瓷,探究了不同烧结温度和保温时间对氧化铝陶瓷晶粒尺寸、致密度、光学性能和力学性能的影响.结果表明:该烧结工艺可有效控制晶粒尺寸长大和提高相对密度,进而提高其光学性能和力学性能.在烧结过程中,当温度升高到一定范围时,致密化过程开始,且致密化速率随着温度的升高和保温时间的延长先增加后降低,在两步烧结1 400 ℃保温3 h时致密化速率达到最快.因此,坯体的致密化过程是非线性的,且具有一个最高致密化速率温度和保温时间点.     

BN含量对注射成形AlN-BN复相陶瓷性能和组织的影响

采用粉末注射成形和无压烧结相结合的工艺制备AlN-BN复相陶瓷,讨论了AlN-BN混合料的流变性能以及BN含量对复相陶瓷热导率、硬度以及显微组织的影响.研究结果表明, AlN-BN混合料具有良好的流动性和较小的温度敏感性,适宜陶瓷注射成形.复相陶瓷的热导率、致密度以及硬度随着BN含量增加而降低,主要是由于BN本身具有较低的硬度和热导率以及在烧结过程中形成特殊的卡片房式结构阻碍了AlN烧结致密化造成的.综合考虑热导率和可加工性能的要求,最佳的BN质量分数在10%～15%之间,所制备的复相陶瓷的热导率大于120W·m-1·K-1,硬度低于HRA 80,致密度大于90%.     

Al2O3陶瓷材料高应变率下的动态力学性能

针对常规SHPB实验系统的不足对其进行改进,采用改进的SHPB实验方法对Al2O3陶瓷材料的动态力学性能进行了实验研究,表明改进的SHPB实验方法可以成功地进行高强度材料高应变率下的动态力学性能实验。实验得到了Al2O3陶瓷材料在不同应变率下的动态应力应变曲线,结果表明,Al2O3陶瓷为弹脆性材料,其动态应力应变呈非线性关系;在高应变率下,陶瓷材料的动态应力应变关系是应变率相关的,材料的初始弹性模量、破坏应力、破坏应变值随应变率的增大而增大。最后对Al2O3陶瓷高应变率下的变形机理进行了讨论。     

CeO_2对堇青石陶瓷的相组成和性能的影响

为了获得堇青石含量高且具有一定孔隙率的堇青石质耐火材料 ,用 X射线衍射仪、扫描电镜和热膨胀仪等手段研究了由氧化物粉末 (Mg O、Al2 O3 和 Si O2 )制备堇青石陶瓷时 ,添加 Ce O2 对堇青石陶瓷相组成和性能的影响 ,分析了 Ce O2 在烧结过程中的作用机理。试验表明 ,在 1370℃烧结 3h,该陶瓷由堇青石和孤立分布的玻璃相组成。随 Ce O2含量增加 ,陶瓷的致密度、弯曲强度和热膨胀系数逐渐升高。适量添加 Ce O2 (质量分数为 0 .0 2～ 0 .0 4) ,显著降低中间相(方石英、尖晶石 )的含量。Ce O2 的作用主要与改变 Si4+、Al3 +和 Mg2 +离子的扩散有关。这种工艺特别适用于制造窑具、高温气体过滤器等部件     

电致发热SiC多孔陶瓷Al2O3/SiO2复相绝缘涂层制备

以异丙醇铝为前驱物,水为溶剂,硝酸为胶溶剂,用分散法制得性能稳定的透明氧化铝溶胶,将多孔陶瓷置于氧化铝溶胶中反复浸渍,经低温和高温热处理后使其表面形成致密的Al2O3和SiO2陶瓷涂层。通过EDS能谱分析得到Al2O3的含量约54%,SiO2含量约46%,电阻较涂覆前显著增加,得出用溶胶-凝胶法涂覆陶瓷体表面后,再经热处理是一种切实可行的制备绝缘陶瓷涂层的方法。     

La2O3-Al2O3-SiO2 glass-infiltrated 3Y-TZP all-ceramic composite for the dental restorative application

The 3 mol％ yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) powder had three particle size distributions,while the fine one was lower than 100 nm.The 3Y-TZP compact was prepared by dry-press...     

铝热反应制备YAG/Al2O3复相陶瓷的组织和性能

利用铝热反应熔化法制备YAG/Al2O3复相陶瓷材料,研究配料中Y2O3含量对复相陶瓷显微组织和力学性能的影响.结果表明:复相陶瓷的相组成为YAG和Al2O3,合有少量的Fe相.随着Y2O3含量的增大,Al2O3颗粒分布越均匀,复相陶瓷的维氏硬度先减小后增加,而相对密度是增加的,在x=0.90时达到最大值分别10.9 ...     

CuCrW(Al2O3) nanocomposite: mechanical alloying,microstructure, and tribological properties

The effect of alumina nanoparticle addition on the microstructure and tribological properties of a CuCrW alloy was investigated in this work.Mechanical alloying was carried out in a satellite ball mill.The tribological properties of the samples were evaluated using pin-on-disk wear tests with different pins (alumina,tungsten carbide,and steel pins).The results indicated that the tungsten carbide pin had a lower coefficient of friction than the alumina and steel pins because of its high hardness and low surface roughness.In addition,when the sliding rate was decreased,the weight-loss rate increased.The existence of alumina nanoparticles in the nanocomposite led to a lower weight-loss rate and to a change in the wear mechanism from adhesive to abrasive.     

TiC/TiN/Al2O3复合陶瓷的研究进展

文章综述了TiC/TiN/Al2O3复合陶瓷的研究进展,介绍了复合陶瓷的制备工艺、组织与性能,探讨了材料成分对组织和力学性能的影响,总结了复合陶瓷的增韧机制及在刀具上的应用情况,指出纳米复合陶瓷是进一步改善强韧性的主要发展方向,为氧化铝陶瓷的广泛应用丰富了科学内涵.