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     

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     

溶胶-凝胶法Al2O3涂层工程陶瓷抗弯强度的数学解析

应用数学方法分析了Al2O3涂层工程陶瓷抗弯强度的实验结果。叙述了用有限个试样的实验结果估计工程陶瓷总体抗弯强度的原理和方法,对得出的分布特征参数的物理意义进行了探讨,发现置信边值强度μ左可以反映材料总体抗弯强度的大小,而均方差置信区间右边值σ右则可以表征材料性能的分散程度,使用这两个参数可以更可靠地评价工程陶瓷的强度水平,可作为材料强度性能的评价指标。并用该强度指标分析了溶胶一凝胶Al2O3涂层对工程陶瓷表面改性的效果。     

溶胶-凝胶工艺制备ZrO2涂层对工程陶瓷表面改性的研究

采用无机盐先驱体 ,溶胶 -凝胶工艺在氧化铝基工程陶瓷上成功制备了ZrO2 涂层。用差热分析(DTA)、扫描电子显微镜 (SEM)、X射线衍射 (XRD)等分析手段对ZrO2 涂层的物相组成、表面和断面形貌进行了表征。对精磨、热处理、ZrO2 涂层试样的抗弯强度和Weibull模数进行了比较。结果表明 :ZrO2 涂层可以明显改善陶瓷的表面质量 ;涂层与基体结合紧密 ,无明显的界面层 ;涂层试样的抗弯强度和Weibull模数均比未涂层试样有明显的提高。     

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。     

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。     

溶胶-凝胶法制备Al2O3纳米粉

以Al(NO3) 3和NH3·H2 O为原料制备AlOOH勃姆石溶胶 ,加入PVA作为分散剂 ,干燥后制成干凝胶。干凝胶经不同温度下煅烧得到不同晶型的Al2 O3纳米粉。X—射线衍射分析结果表明 ,勃姆石干凝胶在煅烧过程中的物相变化为AlOOH→ε-Al2 O3→ -Al2 O3→δ -Al2 O3→θ -Al2 O3→α-Al2 O3,采用电子显微镜和BET比表面积法测量出Al2 O3纳米粉的颗粒大小     

SiC晶须表面涂覆Al2O3的溶胶—凝胶工艺及机理

用异丙醇铝为先驱体通过溶胶-凝胶工艺成功地在SiC晶须表面涂覆了5—30nm的Al_2O_2涂层。认为SiC表面与Al(OC_2H_7)_2(OH)形成配位键并构成胶团是形成涂层的重要机制。研究了溶胶浓度、晶须预处理,晶须直径和反复涂层对涂层效果的影响。     

氧化铝泡沫陶瓷及其表面溶胶–凝胶涂层的制备

采用有机泡沫浸渍法制备了氧化铝泡沫陶瓷,考察了工艺参数对泡沫陶瓷结构和性能的影响,研究了溶胶–凝胶法在泡沫陶瓷表面形成凝胶涂层的制备工艺。结果表明：对有机泡沫进行15%NaOH水溶液处理及5%PVA水溶液活化处理,采用离心挂浆工艺,制备了3种规格的的泡沫陶瓷,其孔尺寸范围为0.8～1.2mm,孔筋尺寸为0.1～0.25mm。泡沫陶瓷的抗压强度随ppi值（每英寸模板孔数）的增大而提高;二次挂浆有利于抗压强度的提高。泡沫陶瓷的抗热震性能随ppi值的减小而增加。采用负压浸胶工艺,可较好地在泡沫陶瓷表面形成TiO2凝胶涂层。     

多孔Al2O3-ZrO2陶瓷的微观结构

以Al₂O₃、ZrO₂陶瓷粉体为溶质,以莰烯为溶剂,以Texaphor963作为添加剂,制备出低粘度高稳定性的陶瓷浆料,采用冷冻注模工艺制备出具有较高强度的陶瓷坯体,采用无压烧结工艺,得到了多孔Al₂O₃-ZrO₂陶瓷制品,并对其微观结构进行了研究。     

高密、高强Al2O3陶瓷离心成形的研究

采用平均粒度0.6μm99Al     

Characterization and tribological investigation of sol-gel Al2O3 and doped Al2O3 films

Thin films of Al₂O₃ and doped Al₂O₃ were prepared on a glass substrate by dip coating process from specially formulated ethanol sols. The morphologies of the unworn and worn surfaces of the films were observed with atomic force microscope (AFM) and scanning electron microscope (SEM). The chemical compositions of the obtained films were characterized by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of obtained thin films sliding against Si₃N₄ ball were evaluated and compared with glass slide on a one-way reciprocating friction tester. XPS results confirm that the target films were obtained successfully. The doped elements distribute in the film evenly and exist in different kinds of forms, such as oxide and silicate. AFM results show that the addition of the doped elements changes the structure of the Al₂O₃ films, i.e., a rougher and smoother surface is obtained. The wear mechanisms of the films are discussed based on SEM observation of the worn surface morphologies. As the results, the doped films exhibit better tribological properties due to the improved toughness. Sever brittle fracture is avoided in the doped films. The wear of glass is characteristic of brittle fracture and severe abrasion. The wear of Al₂O₃ is characteristic of brittle fracture and delamination. And the wear of doped Al₂O₃ is characteristic of micro-fracture, deformation and slight abrasive wear. The introduction of ZnO is recommended to improve the tribological property of Al₂O₃ film.     

Effect of Al2O3 on mechanical properties of Ti3SiC2/Al2O3 composite

The effect of Al₂O₃ on mechanical properties of Ti₃SiC₂/Al₂O₃ composite fabricated by SPS was studied systematically. The results show that the hardness of the Ti₃SiC₂/Al₂O₃ composite can reach 10.28 GPa, 50% higher than that of pure Ti₃SiC₂. However, slight decrease in the other mechanical properties was observed with Al₂O₃ addition higher than 5–10 vol.%, which is believed to be due to the agglomeration of Al₂O₃ in the composite.     

Al_2O_3–ZrO_2复相陶瓷的低温力学性能和热学性能

采用无压烧结法制备Al2O3–15%（质量分数）ZrO2（简称ZTA）复相陶瓷,研究了ZTA复相陶瓷在293～77K的力学性能以及300～5K的热学性能,分析了ZTA复相陶瓷在不同温度断裂时断面上ZrO2发生的相变量和相变区宽度。结果表明：ZTA复相陶瓷的抗弯强度、断裂韧性和Vickers硬度均随温度下降而逐渐提高;77K时抗弯强度、断裂韧性和Vickers硬度比293K时分别提高了10.8%、19.7%和10.4%;ZTA复相陶瓷的热导率随温度下降先增大,在97K时达到最大值,然后随温度下降而降低。低温环境增强了ZTA复相陶瓷中应力诱导t-ZrO2→m-ZrO2的相变增韧效应,提高了ZTA复相陶瓷的低温力学性能。ZTA复相陶瓷具有良好的低温力学性能和较小的低温热导率,是一种有广阔应用前景的低温结构陶瓷材料。     

Al2O3/Cu-O composites fabricated by pressureless infiltration of paper-derived Al2O3 porous preforms

Al₂O₃/Cu-O composites were fabricated from the paper-derived alumina matrix infiltrated with a Cu-3.2?wt% O alloy. Paper-derived alumina preforms with an open porosity ranging from ～ 14 to ～ 25?vol% were prepared by sintering of alumina-loaded preceramic papers at 1600?°C for 4?h. Pressureless infiltration at 1320?°C for 4?h of the preforms with Cu–O alloy resulted in the nearly dense materials with good mechanical and electrical properties, e.g. fracture toughness up to 6?MPa?m^0.5, four-point-bending strength up to 342?MPa, Young's modulus up to 281?GPa and electrical conductivity up to 2?MS/m depending on the volume fraction of copper alloy in the composites. The technological capability of this approach was demonstrated using prototypes in various engineering fields fabricated by lamination, corrugating and Laminated Object Manufacturing (LOM) methods.     

Fabrication and microstructure evolution of Al2O3/ZrBN-SiCN/Al2O3 high-temperature oxidation-resistant composite coating

The oxidation-resistance of thin film sensors, particularly at high temperatures, is critical for the lifetime and performance of the sensor. The preparation and oxidation-resistance of an Al₂O₃/ZrBN-SiCN/Al₂O₃ composite film with a sandwich-structure was performed using reactive magnetron sputtering. The microstructure evolution of the composite film is examined herein using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. Oxygen diffusion was significantly inhibited by the formation of crystalline Al₂SiO₅ and Zr-B-C amorphous phase inside the composite film. The Pt-13%Rh/Pt thin film thermocouple (TFTC) with the Al₂O₃/ZrBN-SiCN/Al₂O₃ composite film as a protective layer was fabricated and calibrated. Both the stability and lifetime of the TFTC was significantly enhanced for temperatures up to 1000?℃. The test error of the TFTC was reduced by half, compared with that of the TFTC with the Al₂O₃ protective layer, indicating an excellent oxidation-resistant performance of the composite film.     

Phase diagram of the Al2O3-HfO2-Y2O3 system

The phase diagram of the Al₂O₃-HfO₂-Y₂O₃ system was first constructed in the temperature range 1200-2800 °C. The phase transformations in the system are completed in eutectic reactions. No ternary compounds or regions of appreciable solid solution were found in the components or binaries in this system. Four new ternary and three new quasibinary eutectics were found. The minimum melting temperature is 1755 °C and it corresponds to the ternary eutectic Al₂O₃ + HfO₂ + Y₃Al₅O₁₂. The solidus surface projection, the schematic of the alloy crystallization path and the vertical sections present the complete phase diagram of the Al₂O₃-HfO₂-Y₂O₃ system.     

Effect of surface-modified Al2O3 on the thermomechanical properties of polybutylene succinate/Al2O3 composites

This study investigates the effect of the incorporation of alumina particles on the thermomechanical properties of polybutylene succinate (PBS)/Al₂O₃ composites. The alumina surface was modified with the carboxylic groups of maleic acid through simple acid-base and in situ polymerization reactions. Scanning electron microscope (SEM) results revealed the introduction of maleic acid treated alumina significantly affect the morphology of the PBS/Al₂O₃ composites as compared to the neat PBS. The thermal conductivity of the composite (0.411?W?m^?1 K^?1) was more than twice that of neat PBS. The composite containing polymerization-modified alumina showed a 50% increase in storage modulus compared with that of neat PBS. In addition, universal testing machine (UTM) and differential scanning calorimetry (DSC) measurements indicated an increase in the tensile strength and degree of crystallinity after the incorporation of modified alumina in the PBS/Al₂O₃ composite.