Lu Shi
材料科学技术（英文）
This paper described a process for synthesizing a new multiphase TiC/Ti2AlC/TiAl3 composite, in which Ti, Al4C3 and graphite powders were utilized as raw materials, and in situ spark plasma sintering-reactive sintering (SPS-RS) methods were involved. The intermediate phases of Ti3Al and TiAl were found during the reactive sintering process and the reactions for the phase's formation were proposed. The microstructure and mechanical properties of the composites were investigated. The high-resolution transmission electron microscopy (HRTEM) image of the interface showed that no amorphous phases were detected along the grain boundary. The orientation relationships between the Ti2AlC and the TiC were shown to be (0001)Ti2AlCjj(111)TiC and
[1210]Ti2AlC||[110]TiC. The average hardness, fracture toughness, Young's modulus and bending strength of the composite were 15.1±0.8 GPa, 4.9±0.3 MPa?m1/2, 261±13 GPa and 776±18 MPa, respectively. The toughening mechanism was also discussed.
关键词:
Ceramic
Lu Shi
材料科学技术（英文）
This paper described a process for synthesizing a new multiphase TiC/Ti2AlC/TiAl3 composite, in which Ti, Al4C3 and graphite powders were utilized as raw materials, and in situ spark plasma sintering-reactive sintering (SPS-RS) methods were involved. The intermediate phases of Ti3Al and TiAl were found during the reactive sintering process and the reactions for the phase's formation were proposed. The microstructure and mechanical properties of the composites were investigated. The high-resolution transmission electron microscopy (HRTEM) image of the interface showed that no amorphous phases were detected along the grain boundary. The orientation relationships between the Ti2AlC and the TiC were shown to be (0001)Ti2AlCjj(111)TiC and
[1210]Ti2AlC||[110]TiC. The average hardness, fracture toughness, Young's modulus and bending strength of the composite were 15.1±0.8 GPa, 4.9±0.3 MPa?m1/2, 261±13 GPa and 776±18 MPa, respectively. The toughening mechanism was also discussed.
关键词:
Ceramic
Jianguo YANG
,
Jingwei WU
,
Hongyuan FANG
材料科学技术（英文）
In order to understand the rate-controlling process for the interfacial layer growth of brazing joints brazed with active composite filler materials, the thickness of brazing joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of A2O3 particulate was studied. The experimental results indicate although there are A2O3 particulates added into active filler metals, the time dependence of interfacial layer growth is t2 as described by Fickian law for the joints brazed with conventional active filler metal. It also shows that the key factor affecting the interfacial layer growth is the volume fraction of alumina in the composite filler material compared with the titanium weight fraction in the filler material.
关键词:
Composite filler material
,
null
,
null
,
null
A. Ibrahim
材料科学技术（英文）
Alumina specimens were joined together with thin aluminium interlayer at 750 and 900°C under different applied pressures and holding time in air. Flexural strength of the joints was then measured using a standard four-point bend test method. Characterization of the interface was carried out to correlate the increase in flexural strength with the applied pressure, holding temperature and time. The study showed that the strength of joint is affected by all three parameters, i.e., processing temperature, holding time as well as applied pressure.
关键词:
Pressure-assisted air brazing
A. Ibrahim
材料科学技术（英文）
Alumina specimens were joined together with thin aluminium interlayer at 750 and 900°C under different applied pressures and holding time in air. Flexural strength of the joints was then measured using a standard four-point bend test method. Characterization of the interface was carried out to correlate the increase in flexural strength with the applied pressure, holding temperature and time. The study showed that the strength of joint is affected by all three parameters, i.e., processing temperature, holding time as well as applied pressure.
关键词:
Pressure-assisted air brazing
Jianguo YANG
,
Hongyuan FANG
,
Xin WAN
材料科学技术（英文）
Al2O3/Al3O3 joints were brazed with a new kind of filler materials, which were formed by adding Al2O3 particulates into Ag-Cu-Ti active filler metal. The results showed that the material parameters (the Ti content, Al2O3 particulate volume fraction) of the composite filler materials affected the shear strength of brazed joints. When the Ti content was 2 wt pct in the filler metal, the shear strength of brazing joints decreased with the increasing the volume ratio of Al2O3 particulate. When the Ti content was 3 wt pct in the filler metal, the shear strength of joints increased from 93.75 MPa(Al2O3p 0 vol. pct) to 135.32 MPa(Al2O3p 15 vol. pct).
关键词:
Composite filler material
,
null
,
null
,
null
Wingkei Ho
催化学报
doi:10.1016/S1872-2067(15)61003-8
由于人们80%的时间呆在室内,室内空气的质量直接影响人类健康,因此近年来室内空气质量越来越受到人们的关注.室内污染物包括CO氮氧化物(NOx)和挥发性有机化合物(VOCs),它们给人体健康带来众多负面影响.更为重要的是,考虑到节能,现代建筑的空气密闭性大都较高,但这种减少吸入新鲜空气的设计直接导致室内各种污染物的累积.有些家用电器,如燃气灶和热水器,在使用的时候会涉及到煤、油和天然气的燃烧,特别是通风较差的情况下会成为室内主要的污染源.常规的治理技术,包括吸附和过滤,其成本相对较高,也不适用于低浓度污染物的治理.尤其是更换不及时的过滤器在排风系统中可能会成为VOCs的一个来源.因此,很有必要开发一种新型的技术以降低室内污染物的浓度和保持一个清洁的室内空气环境,从而保障人们的身体健康.光催化是去除室内空气污染物的有效方法.例如, TiO2、钛酸铋和钛酸锶等具有强氧化能力和稳定的光催化活性,因而是高效的光催化剂.一般而言,通常报道的TiO2光催化剂是高度分散的、或悬浮于液体介质中的细小颗粒或粉末.然而,粉末状的TiO2光催化剂不适宜于室内空气净化,因为它变得可吸入而对人体健康造成不利的影响.因此,人们尝试将TiO2颗粒作为薄膜固定在不同的刚性载体上,如玻璃、不锈钢和铝合金板.对基体进行涂覆可显著影响光催化时反应物的表面吸附行为.一般而言,光催化薄膜通常涂覆在平面上,如蜂窝空气过滤器.三维(3D)多孔的陶瓷泡沫对气体通过具有非常好的流体性质,因此本文以它作为涂覆的基体.这种陶瓷泡沫具有3D多孔结构,多种孔密度、比表面积和化学性质.3D多孔陶瓷泡沫空气过滤器的床层空隙率较高,因此使用时压降较低,且不像蜂窝空气过滤器,它具有复杂多变的孔结构,可增强流体的扰动和混合.另外,3D多孔陶瓷泡沫空气过滤器的开发多孔和网状的结构使得在催化体系具有非常好的气体动力学性质,催化剂表面和气体反应物有充分的接触.多孔材料在液相或气相催化反应中具有独特的优势,因此,陶瓷泡沫、多孔的氧化铝、多孔硅胶.分子筛和活性炭经常被用作催化剂载体.在固体基体上TiO2膜的形成可能使得TiO2光催化剂的有效比表面积降低,从而导致其光催化活性下降.然而,由于具有中孔结构的TiO2薄膜的比表面积大,其用于催化反应的活性位也更多,因此使用时仍然具有较高的活性.前期研究表明,涂覆在平面玻璃、不锈钢和氧化铝基体上的中孔TiO2薄膜用于环境净化时表现出增强的光催化效率.另外,室内环境中NO和NO2的浓度一般分别为几百个ppb之内和100 ppb以下.可见, NO是主要的室内空气污染物,对人体健康危害较大.基于此,本文首次采用反胶束法将中孔锐钛矿TiO2薄膜均匀一地涂覆在3D多孔高比表面积的泡沫过滤器上,采用X射线衍射、扫描电镜、X射线光电子能谱、N2吸附-脱附、紫外-可见光光谱和原子力显微镜对所制样品进行了表征,并将样品用于紫外光下催化降解NO,以揭示所制的中孔TiO2涂层具有高的比表面积和高的光催化活性,从而克服使用TiO2粉末所带来的不足.结果表明,由于中孔TiO2薄膜涂层具有较大的有效比表面积,其表面存在很多吸附活性位,用于吸附在反应过程中形成的水蒸汽、气相反应物和产物,因而具有更高的光催化活性,因此在陶瓷泡沫空气净化系统中可以高效地光催化NO降解：在所考察的不同孔密度的陶瓷泡沫过滤器涂覆的TiO2上400 ppb的NO单程转化率均在92.5%以上,高于涂覆在平面陶瓷砖上的TiO2.该陶瓷过滤器的3D多孔特性可增强流体的扰动和混合,使得气相反应物与光催化剂表面有着充分的接触；其大的孔密度也导致高的光催化速率.另外,本文所制样品在所有反应过程中均保持较高且稳定的NO降解速率,这表明其在NO降解反应中没有失活.
关键词:
二氧化钛
,
光催化
,
陶瓷
,
一氧化氮
,
涂覆
吴日民
,
居相文
,
程晓农
,
杨娟
材料科学与工程学报
doi:10.14136/j.cnki.issn 1673-2812.2015.06.031
ZrW2O8作为一类新型负热膨胀(NTE)材料,其可控热膨胀复合材料的研制一直受到广泛关注.本文综述了目前ZrW2O8复合材料的研究现状,着重介绍了ZrW2O8与纯金属(Cu和Al)、合金(Fe-Ni,TiNi)、陶瓷(ZrO2,SnO2)以及聚合物(聚酯纤维,环氧树脂,聚酰亚胺和酚醛树脂)复合材料的研究成果,并指出存在的问题和未来的研究方向.
关键词:
ZrW2O8
,
可控热膨胀
,
复合材料
,
TiNi合金
,
陶瓷
,
聚合物
杨金华
,
刘占军
,
王立勇
,
郭全贵
,
宋进仁
,
刘朗
新型炭材料
通过加热TiB2及 ZrB2粉末与等静压炭块至共熔点以上的方法制备出新型炭/陶复合材料涂层 TIB、ZRB-1与ZRB-2。结果表明,所制自生复合材料涂层的表层与内部结构明显不同,表层由B掺杂的高度有序石墨构成,内部由TiB2-C或ZrB2-ZrC-C合金组成。 TIB、ZRB-1与ZRB-2涂层中石墨的d002值分别为0.3359、0.3360与0.3354 nm,接近或等于单晶石墨的d002值(0.3354 nm),表明高度有序石墨结构的形成。3种涂层内部石墨的拉曼光谱中D峰、D'峰明显,2D峰强度低及G峰向高波数偏移,这些特征是由石墨碳网格结构中B掺杂所致。此外,ZrB2粒径小有利于涂层表层应力的释放。
关键词:
石墨
,
陶瓷
,
涂层
,
自生复合材料
