Wet-chemical coating of silicon carbide fibers with hexagonal boron nitride layers

Hexagonal BN fiber coatings and BN powders were prepared by pyrolysis of the raw materials boric acid and urea in an atmosphere consisting of hydrogen and nitrogen. The powders were used to determine the appropriate mixing ratio of the raw materials to produce BN with the desired composition and crystal structure. The pyrolysis of boric acid and urea in a molar mixing ratio of 1:2 resulted in a BN that was hexagonal and had a near-stoichiometric composition.To prepare a solution for the coating of fibers, boric acid and urea were dissolved in an ethanol-water mixture. The coating was then applied to SiC filaments using a continuous roll-to-roll dip-coating process. It could be shown by SEM/EDS that BN layers were applied to the fibers. No significant bridging in the fiber bundle was found. Furthermore, it could be demonstrated by grazing incidence x-ray diffraction that the layers were crystalline.     

精密铸造磷酸盐粘结自硬型芯的试验研究

介绍了一种新型专利———浇注成形自硬制芯材料及相应的制芯工艺。这种芯料采用水溶性磷酸盐为粘结剂、氧化镁为固化剂、高纯二氧化硅为耐火骨料。简要介绍了芯料的组成和固化机理。在不同条件下检测了该种型芯的一些重要工艺参数,如常温、高温强度和发气性,分析归纳了这些参数的影响因素,同时对某些应用性能,如浆料的工作时间和型芯的精度、表面粗糙度、抗热震性、溃散性、可化学清理性和对铸造合金液体的热化学稳定性等进行了评价和描述。     

激光重熔工艺对热喷涂陶瓷层微观结构的影响

研究了在１Ｃｒ１８ＮｉｏＴｉ基体上热喷涂Ａｌ２Ｏ３－１３％ＴｉＯ２陶瓷层，进行激光重熔对陶瓷微观结构的影响。激光重熔陶瓷层中，主要组成相为ａ－ＡＩ２Ｏ３及ＡＩ２ＴｉＯ５，在条件合适时，在ａ－ＡＩ２Ｏ３中还有一种超结构，即有序相析出；有序相的存在可阻碍表面裂纹的产生；激光重熔陶瓷层中，扫描速度增加，表面裂纹的宽度增加；激光输出功率增加，表面裂纹的宽度亦增加。     

新型连铸结晶器铜管的开发

将自蔓延高温合成技术与离心铸造技术结合，开发了陶瓷内衬复合铜管技术，可在铜管内表面涂敷耐磨性和耐蚀性优良的陶瓷涂层。为提高陶瓷涂层致密度、韧性和结合强度，研究了添加剂的影响，结果表明，在铝热剂中加入SiO2、CrO3可提高致密度，加入N2B4O7可提高结合强度，加入ZrO2可提高断裂韧性。陶瓷内衬复合铜管应用于管坯结晶器，可提高使用寿命，降低成本。     

借助差热分析研究镍基高温合金/陶瓷型壳界面反应

借助差热分析研究镍基高温合金/陶瓷型壳的界面反应,分别从热力学和动力学的角度分析出镍基高温合金叶片在生产过程中陶瓷型壳所需的最佳面层涂料是CoAl2O4.     

Al2O3/ZrO2快速凝固复合陶瓷显微结构与力学行为

通过在铝热剂中引入适量的ZrO2粉末,基于铝热氧化-还原反应、重力下陶瓷/金属液相分离,以大过冷条件下熔体共晶生长方式,制备出以ZrO2正方相纳微米纤维镶嵌于其上且长径比为8.0～12.0的蓝宝石棒晶及少量α- Al2O3片晶为基体的Al2O3/ZrO2自生复合陶瓷.通过材料力学性能测试与裂纹扩展路径观察,研究复合陶瓷显微结构与其力学行为之间的关系.结果表明,复合陶瓷的弯曲强度与断裂韧度分别达到1 256 MPa与13.2 MPa·m1/2;分布于蓝宝石棒晶上大量的面间距为纳微米尺度的Al2O3/ZrO2两相低能界面及残余压应力,使蓝宝石棒晶与陶瓷基体得以强化,迫使裂纹沿蓝宝石棒晶边界偏转;同时,因处于裂纹尖端尾部的蓝宝石棒晶桥接与拔出、α- Al2O3片晶桥接与摩擦互锁等效应,又使裂纹扩展呈现出强烈的稳定化倾向.     

Al_2O_3/SiC_w陶瓷材料中晶须的极限和最佳含量探讨

从Al2O3与SiC晶须热胀失配分析入手，分析了Al2O3／SiCw陶瓷材料中晶须的极限含量，得出了晶须的极限含量为43vol％。研究表明：晶须含量超过极限值时，Al2O3／SiCw强度大幅下降的主要原因有二个，即1．材料的致密度急剧降低，气孔率增大；2．由于热胀失配所产生的残余张应力导致基体材料的开裂。通过实验证明，当晶须含量为20～30vol％时，Al2O3／SiCw陶瓷材料能获得最佳增韧补强效果。     

泡沫陶瓷过滤片后添加下置包对提高砂型铸造中铝液充型能力的研究

以铝液的流动性试样为研究对象,研究砂型铸造泡沫陶瓷过滤片后安放一定尺寸的下置包对铝液流动性的影响.同时,将下置包运用于生产热裂圆环薄壁铸件,表明:在泡沫陶瓷过滤片后安放一定尺寸的下置包对金属液的充型能力有较大提高,并且下置包的设置和安放工艺简单.     

Effect of nozzle type on pulse-jet cleaning performance of ceramic filter tube

The dust-cleaning efficiency of the ceramic filter tube is the key factor to determine the long-term stable operation of the dust removal system, and the type of nozzle significantly influences the performance. In this study, four types of nozzles (injection hole, sudden enlargement nozzle, tubular nozzle, and induction nozzle) are used to conduct comparative experimental study on the dust-cleaning effect of the ceramic filter tube. Using the schlieren technique find that the tubular and induction nozzles can improve the deviation angle of pulse-jet airflow. The injection parameters were set as an injection pressure of 200 kPa, an injection distance of 120 mm and a pulse width of 80 ms in the experiment. Using the sidewall pressure measurement system indicates that the integrated pressure of the sudden enlargement nozzle is the largest, but the uniformity is poor. The comprehensive pressure of the sudden enlargement nozzle is increased by 64.86 %, and the non-uniformity is reduced by 28.62 % compared with those of the induction nozzle. Using the visualization filtration cycle test system implies that the degree of damage and stripping state of the dust layer are directly proportional to the sidewall pressure. Moreover, it is found that the residual pressure drop changes exponentially with the dust removal quality under different nozzle types. These conclusions can help explain the mechanism of dust stripping and provide a basis for the selection of nozzles.     

陶瓷刀具模糊可靠性及其与刀具材料力学性能的关系

基于模糊数学和可靠性数学的基本理论 ,阐述了刀具模糊可靠性的基本概念和评价方法 ,并进一步应用于陶瓷刀具研究领域 ,建立了陶瓷刀具模糊可靠性与刀具材料力学性能的关系 ,从而使得不做或少做切削实验就能评价陶瓷刀具可靠性的设想成为可能