溶胶-凝胶法对Al2O3陶瓷表面改性的研究

研究了八种不同陶瓷试样的抗弯强度和韦布尔模数。结果表明 ,试样的抗弯强度按线切割、粗磨、精磨、抛光、热处理、氧化铝一次涂层、氧化铝二次涂层、Al2 O3-SiO2 混合涂层的次序依次提高。而韦布尔模数以Al2 O3-SiO2 混合涂层最高 ,其次是热处理试样。理论分析可知 ,热处理过程可使裂纹钝化甚至弥合 ,减少了裂纹半径C ,因此提高了抗弯强度。涂层方法可以提高试样的抗弯强度 ,但可能使晶界与晶粒产生裂纹而导致韦布尔模数下降。由Al2 O3-SiO2 混合涂层试样的横截面SEM形貌图可知 ,该方法可使溶胶颗粒渗入基体更深 ,可以很好地弥合试样表层裂纹。     

溶胶—凝胶法对A12O3陶瓷表面改性的研究

研究了八种不同陶瓷试样的抗弯强度和韦布尔模数。结果表明，试样的抗弯强度按线切割、粗磨、精磨、抛光、热处理、氧化铝一次涂层、氧吕二次涂层、Ａ１２Ｏ３－ＳｉＯ２混合涂层的次序依次提高。而韦布尔模数以Ａ１２Ｏ３－ＳiＯ２混合涂层最高，其次是热处理试样。理论分析可知，热处理过程可使裂纹印化甚至弥合，减少了裂纹半径Ｃ，因此提高了抗弯强度。涂层方法可以提高试样的抗弯强度，但可能使晶界与晶料产生裂纹而导致韦布尔     

Al2TiO5／ZrO2纳米复相陶瓷的制备及性能研究

以氧氯化锆((ZrOCl2·8H2O)、硫酸铝(Al2(SO4)3·18H2O)、硫酸氧钛(TiOSO4·2H2O)为初始原料,以氨水为沉淀剂,将液相共沉淀法得到的Al2TiO5/ZrO2纳米复合粉体前驱体,经1000℃焙烧2h,制备了ZrO2含量(w)为2%、5%、8%的Al2TiO5/ZrO2纳米复合粉体;复合粉体经造粒后以100Mpa压力成型试样,试样尺寸为53mm×10mm×10mm,经1350、1400、1450、1500℃2h制备了Al2TiO5/ZrO2(缩写AT/Z)纳米复相陶瓷试样。研究了ZrO2含量、烧结温度对试样的烧结性能、热膨胀性能、抗热震性能的影响,并借助XRD、SEM分析了试样的物相组成、显微结构。结果表明:随着ZrO2含量的增加和烧结温度的提高,试样的显气孔率减小,抗弯强度增大。烧结温度为1500℃、ZrO2含量(w)为5%的ATZ-54试样,抗弯强度最大,为103.2MPa;在1250℃的热膨胀率仅为0.08%,其热膨胀系数α约为0.65×10-6℃-1;AT/Z纳米复相陶瓷试样具有细晶镶嵌结构;从室温到1100℃急冷急热冲击31次后,试样表面仍保持完整,抗热震性能明显高于其他...     

用溶胶-凝胶法制备Al_2O_3涂层工程陶瓷的表面改性研究

分析了溶胶 -凝胶法制备Al2 O3 溶胶的适宜工艺条件 ,在氧化铝基陶瓷基体上成功地制备了Al2 O3 涂层 ;利用X射线衍射分析和差热分析 (DTA)方法对Al2 O3 凝胶粉末的相变过程进行了研究 .通过分析精磨、热处理、Al2 O3 一次和二次溶胶涂层 4种试样的抗弯强度测量值对材料总体性能进行了估计 .结果表明 :Al2 O3 涂层工程陶瓷可以提高基体的抗弯强度而降低其分散性 ,效果好于单纯的热处理 .通过观察4种试样的表面SEM形貌和两种涂层试样的断面SEM形貌提出了溶胶涂层钝化或弥合表面微裂纹的理论模型     

氧化锆-莫来石复合材料的机械性能和热性能

以ZrO2和电熔莫来石为主要原料,制备出了氧化锆-莫来石复合材料.研究了不同温度下ZrO2添加量对莫来石陶瓷的抗弯强度(σ)、断裂韧性(KIC)和热膨胀系数(CTE)的影响.结果发现,ZrO2的加入促进了莫来石陶瓷的烧结.1550℃下添加20wt%ZrO2的试样的σ和KIC最高分别达到268.23MPa和4.05MPa·m1/2,针状莫来石晶体交错排布以及亚微米级ZrO2颗粒的钉扎作用是材料强度和韧性提高的主要原因.材料的线性热膨胀系数随着ZrO2添加量的增加而增大.     

氧化锆纤维对氮化物复合材料性能的影响

在Si3N4、BN陶瓷中加入涂层处理后的ZrO2纤维对其进行复合,研究ZrO2纤维对氮化物复合材料部分性能的影响.结果表明:ZrO2纤维的引入能降低材料的抗弯强度,但是加入适量的ZrO2纤维后材料的热学性能可得到较大的改善.     

Al_2O_3—SiO_2混合溶胶—凝胶涂层对工程陶瓷表面改性的研究

利用溶胶—凝胶法在SG4工程陶瓷基体上成功制备了Al2 O3—SiO2 混合涂层 ;通过X射线仪测定了Al2 O3—SiO2 凝胶粉末的晶相组成。对精磨、热处理、Al2 O3涂层和Al2 O3—SiO2 混合涂层四种试样抗弯强度的样本均值和样本标准离差进行了比较 ,并通过观察四种试样表面的SEM形貌和两种涂层试样断面的SEM形貌初步分析了表面改性的原因。分析结果表明 :溶胶涂层对基体表面微裂纹有一定的弥合作用 ,可以提高基体的抗弯强度而降低材料强度的分散性 ,其效果好于单纯的热处理 ,Al2 O3—SiO2 混合涂层试样的表面质量优于Al2 O3涂层试样 ;Al2 O3—SiO2 混合涂层渗入基体更深 ,可以更好地弥合基体表面微裂纹 ,有效提高基体的抗弯强度。     

Al2O3—SiO2混合溶胶—凝胶涂层对工程陶瓷表面改性的研究

利用溶胶－凝胶法在SG4工程陶瓷基体上成功制备了Al2O3-SiO2混合涂层;通过X射线仪测定了Al2O3-SiO2凝胶粉末的晶相组成。对精磨、热处理、Al2O3涂层和Al2O3-SiO2混合涂层四种试样抗弯强度的样本均值和样本标准离差进行了比较,并通过观察四种试样表面的SEM形貌和两种涂层试样断面的SEM形貌初步分析了表面改性的原因。分析结果表明：溶胶涂层对基体表面微裂纹有一定的弥合作用,可以提高基体的抗弯强度而降低材料强度的分散性,其效果好于单纯的热处理,Al2O3-SiO2混合涂层试样的表面质量优于Al2O3涂层试样;Al2O3-SiO2混合涂层渗入基体更深,可以更好地弥合基体表面微裂纹,有效提高基体的抗弯强度。     

用溶胶—凝胶法制备Al2O3涂层工程陶瓷的表面改性研究

分析了溶胶－凝胶法制备Al2O3溶胶的适宜工艺条件。在氧化铝基陶瓷基体上成功地制备了Al2O3涂层;利用X射线衍射分析和差热分析（DTA）方法对Al2O3凝胶粉末的相变过程进行了研究,通过分析精磨,热处理,Al2O3一次和二次溶胶涂层4种试样的抗弯强度测量值对材料总体性能进行了估计,结果表明：Al2O3涂层工程陶瓷可以提高基体的抗弯强度而降低其分散性,效果好于单纯的热处理,通过观察4种试样的表面SEM形貌和两种涂层试样的断面SEM形貌提出了溶胶涂层钝化或弥合表面微裂纹的理论模型。     

添加ZrO_2对Ta_2O_5陶瓷结构与性能的影响

以ZrO2和Ta2O5粉体为原料,采用固相反应法制备了ZrO2掺杂Ta2O5陶瓷。研究了ZrO2掺杂对Ta2O5陶瓷的相组成、微观结构、抗弯强度、热膨胀系数和抗热震性能的影响。结果表明:ZrO2掺杂可在烧成过程中抑制β-Ta2O5相向α-Ta2O5相的转变,5%(质量分数,下同)ZrO2掺杂Ta2O5陶瓷为β-Ta2O5单相固溶体。3%ZrO2掺杂,显著抑制了Ta2O5陶瓷高温烧结过程中的晶粒长大,避免了晶界开裂;掺杂量达到5%以上时,可显著促进Ta2O5陶瓷的烧结致密化。5%ZrO2掺杂的Ta2O5陶瓷表现出较高的抗弯强度(74.5MPa),低的热膨胀系数(1.96×10-6/℃)和良好的抗热震性能。     

Strength of additive manufactured alumina

The strength of 3D-printed alumina parts fabricated using the Lithography-based Ceramic Manufacturing (LCM) technology is investigated. The influence of the sintering parameters, printing direction, surface condition (i.e. machined or as-printed), and/or geometry on the strength distribution is studied under uniaxial and biaxial bending tests. Weibull parameters, i.e. characteristic strength and Weibull modulus, are determined and compared between the different samples. Experimental findings show that samples sintered at higher temperatures yield higher Weibull modulus, associated with a more homogeneous microstructure. Fractographic analyses reveal the influence of surface finish (as-printed or machined) on strength and show the importance of reporting testing configuration along with printing direction to assess the mechanical response of 3D-printed parts. Based on these results, manufacturing recommendations are given which shall advance the progress in optimization of alumina ceramics fabricated using the LCM technology.     

ZrO2对Al2TiO5-板状刚玉复合材料性能的影响

以α-Al2O3微粉、板状刚玉和TiO2为主要原料,添加不同含量的ZrO2,通过高温烧成以固相反应直接合成Al2TiO5-板状刚玉-ZrO2复合材料,研究了ZrO2含量对复合材料的烧结收缩率、显气孔率、强度等的影响。结果表明:添加ZrO2的复相材料的收缩率和体积密度明显增加。ZrO2含量为4%时,可以制备出高致密度高强度的Al2TiO5-板状刚玉-ZrO2复合材料,其显气孔率为9.31%,抗折强度为25.6MPa,抗压强度为225MPa。     

Preparation of Si3N4 ceramics with high strength and high reliability via a processing strategy

In this study, the preparation of Si₃N₄ ceramics with high mechanical reliability is investigated. The influences of several processing steps on the bending strength and the Weibull modulus are reported including: (i) coating of the Si₃N₄ powder with its sintering aids, (ii) oxidation of the coated powder, (iii) cold isostatic pressing, (iv) gelcasting of the green bodies and (v) gas pressure sintering. It was found that all the aforementioned steps contribute to improvements of strength and reliability of Si₃N₄ ceramics. Via an optimised processing strategy, Si₃N₄ ceramics with a bending strength and a Weibull modulus as high as 944.7±29.5 MPa and 33.9, respectively, could be prepared. Additionally, it was also found that surface modifications, i.e. coating and oxidation of Si₃N₄ powder, increased the rheological properties of the powder suspension in aqueous media, which is favourable for in situ colloidal forming such as gelcasting.     

Fracture Strength of Polycrystalline Silicon Wafers for the Photovoltaic Industry

The fracture strength of polycrystalline silicon wafers has been investigated by means of twist and four-point bending tests. Under a twisting configuration, which generates high tensile stresses within the middle of the wafers, a unimodal distribution in strength is obtained. The characteristic strength and Weibull modulus are 131.0 MPa, and 14.4, respectively. Under a four-point bending configuration, which generates high stresses both at the surface and at the edges, an additive bimodal distribution is obtained. The first mode of the distribution has a characteristic strength of 76.0 MPa and a Weibull modulus of 1.6; the second mode has a characteristic strength of 161.2 MPa and a Weibull modulus of 11.5. Fractographic observations confirm that the first mode (lower strength) corresponds to wafers which failed from large edge chips (sizes up to 90 μm). Weibull analysis suggests that the second mode (higher strength) corresponds to wafers which failed from smaller surface chips (sizes up to 50 μm). The results obtained point to large edge chips as the most dangerous defects degrading the fracture strength of the wafers. This is of great relevance for the photovoltaic industry, as fracture of silicon wafers limits both the performance and lifetime of the solar cells, and production yields.     

ZrO2增韧Al2O3—TiC系陶瓷复合材料的力学性能及其耐磨性能

本文通过对ＺｒＯ２增韧Ａｌ２Ｏ３－ＴｉＣ系复相陶瓷材料的制备工艺以及ＺｒＯ２含量的变化对材料断裂韧性、抗弯强度以及硬度的影响研究，采用Ｘ射线衍射法分析断口相变量随组成变化对多元系相陶瓷断裂韧性、抗弯强度的影响，同时分析在不同冲击工况下其耐冲蚀磨损特性与力学性能之间的关系。     

固相含量对氧化锆陶瓷注凝成型的影响

研究了超细ZrO2粉体注凝成型过程中固相含量对料浆粘度、生坯强度和烧结材料密度等的影响。在固相含量50vol%~54vol%的范围内,随着固相量的增加,料浆悬浮体的粘度明显提高,成型坯体的均匀性下降,生坯强度出现极值,烧结材料的密度逐渐降低,固相含量以50vol%~52vol%为宜。     

Size effect of carbon fiber-reinforced silicon carbide composites (C/C-SiC): Part 1 – bending load and statistical effects

This study analyzed the influence of the sample volume, number of tested specimen, and testing method on the flexural strength of fabric-reinforced ceramic matrix composites. For this purpose, seven different batches of C/C-SiC were prepared with four different sample thicknesses to determine the flexural strengths and Weibull moduli by three- and four-point flexural tests. The result showed that C/C-SiC exhibits a size effect of strength under bending load because a decrease of measured flexural strength with increased specimen size was observed. This size effect was discussed regarding the Weibull weakest link approach and the concept of quasi-brittle materials.The determined Weibull moduli were comparable for the same load condition but dissimilar for the identical material if the load condition were changed from three- to four-point bending. Hence, the Weibull modulus was found to be not an inherent material constant for C/C-SiC and the Weibull weakest link approach seems not appropriate.     

ZrO2对钼渣微晶陶瓷性能的影响

制备了以钼渣为主要原料，以ZrO2作品核剂的微晶陶瓷材料。研究了ZrO2含量变化对钼渣玻璃晶化行为和力学性能的影响。采用XRD、SEM、DTA等测试技术，对该体系的晶化机理进行了探讨。结果发现，当ZrO2的含量为1％时可发生整体析晶，析晶活化能为212．834kJ／mol，抗弯强度为66.9918MPa，显微硬度为6.95GPa。