多孔石英基体上CVD法沉积氮化硅涂层的工艺、结构与性能研究

以甲硅烷(20％甲硅烷+80％氢气)和氨气作为反应前驱体,选择孔隙率为20％左右的多孔石英陶瓷基体,采用CVD法在多孔石英基体表面制备了氮化硅涂层.研究了沉积反应温度、反应压力、反应气体配比以及沉积时间等工艺参数对附着力的影响,确定了CVD法制备氮化硅涂层的最佳工艺参数,通过对所得涂层及复合材料进行抗弯强度和介电性能的表征,探讨了氮化硅涂层对多孔石英基体力学性能和介电性能的影响.     

基于多孔Si_3N_4陶瓷基底BN涂层制备与表征

在多孔氮化硅陶瓷(Si_3N_4)表面制备氮化硼(BN)涂层,可以提高天线罩的多方面性能,其研究具有重要的工程应用价值。以硼酸(H_3BO_3)及碳黑为原料,利用两种方法制备BN涂层,一种方法是在氮化硅基体表面涂覆H_3BO_3与炭黑,然后在氮气气氛下烧结制备BN涂层(简称一步法);另一种方法采用H_3BO_3分解在多孔Si_3N_4基体表面制备B_2O_3涂层,然后利用碳热还原反应将B2O3涂层转变为BN涂层(简称两步法),通过X射线衍射分析(XRD)观察了涂层的物相组成,扫描电镜(SEM)观察涂层的形貌及涂层与基体的结合情况。研究结果表明:两种方法制备的涂层由BN组成,无残余B_2O_3,其中一步法制备的涂层表面粗糙,存在大量裂纹和气孔,涂层厚度较厚,大约17μm;两步法制备的涂层结构致密,表面光滑,涂层厚度约为2μm,且与基体结合良好。     

低介电高强度多孔氮化硅陶瓷的研制

以氮化硅为基体,通过加入一定量的特殊无机添加剂,控制好相关工艺参数成功地制备出低密高强低介电的多孔氮化硅材料。采用有机涂层对多孔氮化硅材料表面进行封孔处理,通过对封孔前后材料电性能的对比分析得出:涂层对封孔后表面致密的整体材料电性能影响微小。     

多孔氮化硅微观组织结构对力学性能的影响

通过添加造孔剂苯甲酸,利用气氛压力烧结技术制备出了不同气孔率(40%～70%)的多孔氮化硅陶瓷,研究了显微结构对材料力学性能的影响;通过分析发现发育较好的长柱状β-氮化硅晶粒保证了材料获得良好的室温力学性能;而材料密度低、晶粒发育不完全是多孔氮化硅陶瓷力学性能下降的主要原因。本文制备的多孔氮化硅断裂形式为沿晶和穿晶断裂模式,当陶瓷气孔率为52%时,弯曲强度为195MPa。     

多孔氮化硅陶瓷的制备及应用现状

综述了多孔氮化硅陶瓷目前的研究进展,介绍了添加造孔剂法,成型和烧结工艺中造孔法,干燥及其它工艺造孔法等方法制备多孔氮化硅陶瓷,最后展望了多孔氮化硅陶瓷在催化剂载体,气体过滤器以及航空透波材料等领域的应用。     

陶瓷隔热瓦耐高温高辐射率涂层的制备及表征

在短切莫来石纤维隔热瓦表面采用浆料喷涂法制备了短切莫来石纤维增韧Mo Si_2-Si C-B_2O_3-SiO_2/Mo Si_2-Si C-B_2O_3-SiO_2-SiB_6梯度涂层,并利用XRD、XPS、SEM和EDS对涂层的组成、结构及形貌进行了分析,探讨了涂层的形成机理。分析表明涂层主要由MoSi_2、硼硅玻璃及少量的Mo_(4.8)Si_3C_(0.6)组成。涂层表面及截面的SEM照片表明涂层表层致密,靠近基体部分疏松多孔,部分涂层深入多孔的基体,提高了涂层与基体的结合力。     

金属-多孔陶瓷复合型催化剂载体的研制

通过金属镍和堇青石多孔陶瓷制备了复合型催化剂载体,探索了多孔陶瓷涂层与金属基体之间的结合工艺,测量了涂层材料的相关性能.实验表明通过适当的过渡层处理,可以实现陶瓷与金属基体之间的牢固结合.     

氮化硅基多孔陶瓷的制备技术、孔隙结构及其相关性能

氮化硅多孔陶瓷是近年来得到广泛关注的一类新型的结构?功能一体化陶瓷材料,在航空航天、机械、化工、海洋工程等重要领域有着广阔的应用前景。本文介绍了氮化硅基多孔陶瓷的主要制备技术,回顾了氮化硅基多孔陶瓷力学性能和介电性能的研究进展。考虑到高孔隙率氮化硅基多孔陶瓷力学性能难以提高,磷酸盐结合氮化硅基多孔陶瓷已经逐渐成为新的研究热点,因此,本文进一步对磷酸盐结合氮化硅基多孔陶瓷的制备技术、力学性能、介电性能、热学性能进行了综合评述,并对氮化硅基多孔陶瓷的应用前景进行了展望。     

多孔氮化硅陶瓷透波材料研究进展

多孔氮化硅陶瓷透波材料具有优异的机械性能、耐热性能及介电性能,成为透波材料科学研究领域中的热点之一。本文介绍了多孔氮化硅陶瓷的主要制备技术,并对国内外多孔氮化硅陶瓷透波材料的应用研究进展进行了综述。     

多孔氮化硅陶瓷的研究进展

综述了多孔氮化硅陶瓷材料的国内外研究现状和进展,介绍了多孔氮化硅陶瓷的主要制备方法,分析了微观组织对多孔氮化硅陶瓷力学性能的影响,并与其他多孔陶瓷进行了性能比较,最后展望了多孔氮化硅陶瓷的发展前景.     

石英陶瓷天线罩封孔增强涂层的研究

对石英基体进行封孔和防潮处理,分析了密度、吸水率、气孔率、强度及介电性能的变化,封孔和防潮处理后基体强度明显增加,而对介电性能没有影响.     

Mechanical Properties of Oxidation-Resistant SiC/C Compositionally Graded Graphite Materials

Mechanical properties of oxidation-resistant SiC/C compositionally graded graphite materials composed of a CVD SiC coating layer, a SiC/C graded layer, and a graphite substrate were studied by bending, compressive, and hardness tests at room temperature. CVD SiC coated graphite and graphite with a SiC/C graded layer alone were also examined. The bending strengths of oxidation–resistant SiC/C compositionally graded graphite materials as well as CVD SiC coated graphite were about twice as much as that of graphite. The bending and compressive strengths of graphite with the SiC/C graded layer alone were almost the same as those of graphite. The higher strengths of graphite with the CVD SiC layer can be mainly due to the CVD SiC strength itself, and partly due to the smooth CVD surface. No effect of the SiC/C layer on the strengths was discussed in terms of porosity, surface morphology, and the strength of SiC.     

硅藻土基多孔陶瓷的制备及研究

到11.65 m2/g,孔容0.288 m3/g,孔径为6.26 nm.     

Effect of oxygen pressure on the microstructure and mechanical properties of Mo coating deposited on steel 42CD4 by thermal flame spraying

Abstract

Surface treatments and coatings are a practical approach used to extend the life of components and structures, especially the most stressed surfaces of the technical component under consideration. The objective of this work is to study the effect of oxygen pressure on the microstructure and the mechanical properties of the Mo coating deposited on 42CD4 steel by flame thermal spraying. The effect of the oxygen flow is controlled by the oxygen pressure. The coatings were characterized by scanning electron microscopy (SEM), energy dispersion spectrometry, X-ray diffraction, Vickers hardness measurement and four-point bending tests. The results show that oxygen pressure in the oxidant is a critical parameter, as our results revealed that increasing oxygen pressure has a positive effect on microstructure and on mechanical properties of the coating. The increase in oxygen pressure generates a better microstructure, with a denser, more compact coating and a low porosity.     

等离子喷涂工艺参数对B4C涂层性能的影响

本文研究了喷涂距离对大气等离子喷涂Ｂ４Ｃ涂层的沉积效率、气孔率、显微硬度和抗热震性能的影响,发现喷涂距离会严重影响Ｂ４Ｃ粉末在等离子体射流中的熔融状态,从而对这些性能产生显著影响。实验结果表明,通过优化工艺参数,尤其是选择适当的喷涂距离,可以在大气呀涂条件下制得同高压等离子喷涂相近所孔率和显微硬度的Ｂ４Ｃ涂层。     

Waste derived glass ceramic composites prepared by low temperature sintering/sinter-crystallisation

Glass-ceramics based on iron rich wastes were produced by direct sintering and by following an innovative approach, combining direct sintering and sinter-crystallisation processes. According to the second method, a layered tile was manufactured by single firing at 900°C using a selected combination of wastes for both the porous body and the dense coating layer. The coating layer (‘glaze’) results from the sinter-crystallisation of a waste derived glass mixed with zircon and recycled borosilicate glass. The glaze sealed the porosity of the body and enhanced both mechanical properties and chemical stability. The results show a near to zero water absorption rate, despite a low geometric density (～2?g?cm^??3), accompanied by a Young's modulus of ～40?GPa and a bending strength of ～30?MPa. The chemical stability of the glass-ceramics thus developed was assessed by the application of a toxicity control leaching procedure. Furthermore, cell culture tests were carried out to evaluate the potential cytotoxicity of the materials.     

化学镀Ni-P合金镀层孔隙率的影响因素

钕铁硼化学镀Ni-P合金层的孔隙率与镀层的耐蚀性有很大的关系。以铁氰化钾为指示剂采用贴滤纸法测定钕铁硼化学镀Ni-P合金层的孔隙率,研究了镀液pH、温度、主盐、还原剂及络合剂浓度对化学镀Ni-P合金层孔隙率的影响,并确定最佳的镀液参数,通过扫描电镜验证实验结果。结果表明:孔隙率随着镀液组成、pH及温度的增加而先减小后增加。     

Relationship between certain ceramic roofing tile characteristics and biodeterioration

This paper examines the relationship of certain red ceramic roofing tile properties to roofing tile biodeterioration. The following properties were studied: apparent porosity, roughness, and the presence or absence of two types of coatings.The effect of apparent porosity was studied by varying the peak firing temperature of a standard industrial red ceramic roofing tile composition and by preparing several clay mixtures, of different chemical and mineralogical composition, that were fired at various peak temperatures. The effect of roofing tile roughness was determined by either polishing or sanding fired standard red roofing tiles. A waterproof ceramic glaze coating and a photocatalytic coating were formulated to analyse the effect of the presence of different types of coatings. Roofing tile bioreceptivity was evaluated with a method developed in a previous study using the cyanobacteria Oscillatoria sp, which enabled roofing tile resistance to microbial colonization to be determined.As expected, bioreceptivity rose as apparent porosity (measured as water absorption) increased, enabling possible water retention, which favours biological growth. Similarly, greater roughness encouraged micro-organism adhesion and raised bioreceptivity. It was found that, after prolonged exposure periods (several months) under very favourable conditions for biological colonization, roofing tiles coated with the waterproof ceramic glaze were colonized. However, glazed standard red roofing tiles covered with a TiO₂ photocatalytic coating exhibited practically no biological growth under the test conditions used, even after long exposure times, owing to the chemical-physical effect of the TiO₂-based coating.     

β-TCP scaffold coated with PCL as biodegradable materials for dental applications

Requirements for an ideal scaffold include biocompatibility, biodegradability, mechanical strength and sufficient porosity and pore dimensions. Beta tricalcium phosphate (β-TCP) has competent biocompatibility and biodegradability, but has low mechanical strength because of its porous structure. Polycaprolactone (PCL) is a biodegradable polymer with elastic characteristics and good biocompatibility. In this study, β-TCP/PCL composites were prepared in different ratio and their morphology, phase content, mechanical properties, biodegradation and biocompatibility were investigated. After coating, surfaces of β-TCP scaffolds were covered with the PCL while some of the pores were partially clogged. The compression and bending strength of β-TCP scaffolds were significantly enhanced by PCL coating. The degradation rate of the scaffold in Tris buffer was reduced with higher content of the PCL coating. MTT and ALP assays showed that the osteoblast cells could proliferate and differentiate on PCL coated scaffolds as well as on bare β-TCP scaffolds. Based on the comprehensive analysis achieved in this study, it is concluded that the β-TCP/PCL composite scaffold fabricated with 40% β-TCP and 5% PCL exhibits optimum properties suitable for dental applications.     

脱硝催化剂用堇青石多孔陶瓷的制备与性能研究

以偏高岭土、氧化铝和滑石为原料,利用压制成型制备出堇青石多孔陶瓷并采用浸渍涂覆法制备锰基低温脱硝催化剂.通过气孔率、抗折强度、热膨胀系数、SEM、BET等测试探究了碳粉和淀粉两种造孔剂及添加量、不同酸处理时间等因素对堇青石性能的影响并考察了不同浸渍次数的催化剂在80~200 ℃间的脱硝性能.结果表明:造孔剂为碳粉且添加量为4%时,得到的堇青石具有良好的性能,此时气孔率达31.12%,热膨胀系数为3.10×10-6/K,抗折强度为21.41 MPa;适当的酸处理有助于堇青石表面孔结构的丰富且能大幅提升其比表面积,最佳处理时间为2 h;当浸渍次数为4次时,整体式催化剂的性能最佳,牢固度可达90.18%,140 ℃时的脱硝率可达74.5%以上.