Chuncheng ZHU
,
Xinghong ZHANG
,
Xiaodong HE
,
Qiang XU
材料科学技术（英）
TiC-TiB2-Cu composites were produced by self-propagating high-temperature synthesis combined with pseudo hot isostatic pressing using Ti, B4C and Cu powders. The microstructure and mechanical properties of the composites were investigated. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the final products were only TiC, TiB2 and Cu phases. The clubbed TiB2 grains and spheroidal or irregular TiC grains were found in the microstructure of synthesized products. The reaction temperature and grain size of TiB2 and TiC particles decreased with increasing Cu content. The introduction of Cu into the composites resulted in a drastic increase in the relative density and flexual strength, and the maximum values were obtained with the addition of 20 wt pct, while the fracture toughness was the best when Cu content was 40 wt pct.
关键词:
Composite
,
null
,
null
,
null
Chen Bin
,
Yin Kai-Yang
,
Lu Tian-Feng
,
Sun Bing-Yi
,
Dong Qing
,
Zheng Jing-Xu
,
Lu Chen
,
Li Zhan-Chun
材料科学技术（英）
doi:10.1016/j.jmst.2016.06.010
AZ91/HA composite was prepared by AZ91 magnesium alloy and porous HA using squeeze casting method. The microstructure and mechanical property of the AZ91/HA composite were studied. The results show that the molten AZ91 alloy completely infiltrated the preform without destroying the porous structure of the HA preform. The compressive strength of AZ91/HA composite increased significantly compared with that of the porous HA. The immersion test indicated that AZ91 alloy shows a lower corrosion resistance and is easier to be corroded in comparison with HA.
关键词:
Biodegradable
,
Magnesium alloy
,
Porous HA
,
Composite
,
Squeeze casting
Hongyan Zhu Baochang Wu Dihong Li Dongxing Zhang Yuyong Chen
材料科学技术（英）
This paper aims at investigating the effect of voids on the tensile properties of [(±45)4/(0,90)/(±45)2]S and [(±45)/04/(±45)(0,90)]S composites. Specimens with void contents in the range of 0.4% to 9.0% were fabricated from carbon/epoxy fabric. The void content was determined by ultrasonic attenuation and optical image analysis, and microscopic inspection was also used to analyze the shape and size of the voids. The influence of voids on the tensile strength and modulus of both stacking sequence is compared in terms of the size and the shape of the voids. The effect of voids on the initiation and propagation of tensile failure of both stacking sequence composite was investigated.
关键词:
Composite
,
null
,
null
Hongyan Zhu Baochang Wu Dihong Li Dongxing Zhang Yuyong Chen
材料科学技术（英）
This paper aims at investigating the effect of voids on the tensile properties of [(±45)4/(0,90)/(±45)2]S and [(±45)/04/(±45)(0,90)]S composites. Specimens with void contents in the range of 0.4% to 9.0% were fabricated from carbon/epoxy fabric. The void content was determined by ultrasonic attenuation and optical image analysis, and microscopic inspection was also used to analyze the shape and size of the voids. The influence of voids on the tensile strength and modulus of both stacking sequence is compared in terms of the size and the shape of the voids. The effect of voids on the initiation and propagation of tensile failure of both stacking sequence composite was investigated.
关键词:
Composite
,
null
,
null
Guozheng KANG
,
Chuan YANG
,
Jixi ZHANG
材料科学技术（英）
Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of Al2O3 short fiber reinforced Al-Mg alloy matrix composite at elevated temperatures were researched. The interfacial microstructural characteristics and the fracture surfaces of the composite at different temperatures were observed by transmission electron microscope (TEM) and by scanning electron microscope (SEM), respectively. Then, from the results of microscopic observation, the fracture mechanisms of the composite at different temperatures are discussed. Finally, the tensile strengths of the composite at elevated temperatures were predicted by statistical integration average (SIA) method with the consideratio of various fracture mechanisms. It was shown that the strengths and fracture mechanisms of the composite at elevated temperature (300°C) were significantly different from those at room temperature due to the variations of interfacial bonding states. The tensile strengths predicted by the SIA method at elevated temperatures agreed well with the experimental results.
关键词:
Fracture
,
null
,
null
,
null
JunhHua WU
材料科学技术（英）
Microwave dielectric measurements over the broad bandwith of 10 MHz to 20 GHz were conducted on composites comprising bundles of single-walled carbon nanotubes (SWNT) embedded in an epoxy matrix, in comparison to the nano-graphite and MWNT. It is found that both relative real and imaginary permittivity of the nanocomposites are strong functions of the SWNT concentration, showing large, wide dielectric and electrical response. Distinct resonance around 1.5 GHz is observed at high SWNT concentrations, accompanied by the downshift of the resonance frequency with increasing concentration. Largely, the SWNT-epoxy composites share the behavior of the MWNT owing to structural similarity, much more effective than the nano-graphite. The remarkable, broadband dielectric and electrical properties of the nanotubes acquired in the work originate from their unique seamless graphene architectures, modeled by two major contributions, dielectric relaxation/resonance and electronic conduction, which is substantiated by the agreement between theoretical analysis and experimental results. The carbon nanotube composites are prospective for microwave applications and offer experimental evidence for fundamental studies in low-dimensional systems.
关键词:
Single-walled carbon nanotube
,
carbon
,
nanotube
,
Dielectric
Yanjun ZHENG
,
Lishan CU
,
IYan LI
,
Dazhi YANG
材料科学技术（英）
The reverse martensitic transformation of TiNi shape memory alloy fibers embedded in a pure aluminum matrix was studied in this paper. Results showed that the phase composition of the TiNi alloy fibers prior to prestraining at the room temperature had a significant influence on the differential scanning calorimetry (DSC) results of the composites. By a comparison to the high temperature X-ray diffraction (XRD) results, it was confirmed that the martensite was divided into two groups: the self-accommodating martensite (SAM) and the preferentially oriented martensite (POM). The evolving process of the separation of martensite was discussed.
关键词:
Shape memory alloy
,
null
,
null
,
null
Peng ZHANG
,
Yunhui DU
,
Hanwu LIU
,
Daben ZENG
,
Jianzhong CUI
,
Limin BA
材料科学技术（英）
The electromagnetic-mechanical stirring technology was used to prepare QTi3.5-15/graghite slurry. The distribution of graphite particles in QTi3.5-15/graghite slurry was studied using cold quenching method. The results show that solid fraction of QTi3.5-15/graphite slurry increases with the decreasing of stirring temperature. There is a linear relationship between solid fraction and stirring temperature. With the increasing of solid fraction, the distribution of graphite particles in slurry becomes uniform gradually. When the solid fraction is larger than 45%, the rising of graphite particles in slurry can be restricted, and QTi3.5-15/graghite slurry with uniform distribution of graphite particles can be prepared.
关键词:
null
,
null
,
null
Jinyong ZHANG
材料科学技术（英）
Titanium diboride based composites, good candidates for contact materials, have high hardness, Young's modulus, high temperature stability, and excellent electrical, thermal conductivity. However a good interface of TiB2/Cu is very difficult to achieve for oxidation of TiB2. To avoid this oxidation behavior, the in situ combusting synthesis technology, SHS, was used to prepare TiB2/Cu composite. The characters of Ti-B-xCu SHS were studied in detail, such as combustion temperature, products phases and grain size. Based on the experimental results a proper technology way of self-high temperature synthesis plus quick press (SHS/QP) was determined and compact TiB2/Cu composites with relative density over than 97 pct of the theoretical were fabricated by this method. The properties and microstructures of these TiB2 based composites were also investigated.
关键词:
Self-high temperature synthesis (SHS)
,
null
,
null
沈丽娟
,
梁若雯
,
吴棱
催化学报
doi:10.1016/S1872-2067(15)60984-6
环境污染和能源短缺是制约当今社会发展的重大问题。光催化技术可直接利用太阳能驱动一系列重要的化学反应,具有能耗低、反应条件温和、无二次污染等优点,是解决这一问题的有效途径。实现这个过程的关键在于寻找设计高效的光催化剂。目前,光催化材料主要由无机半导体组成,其结构的改造和修饰难度很大,难以根据实际需要来控制其大小、形状以及物理化学特性。而有机化合物具有优良的分子剪裁与修饰的功能,但它们却在坚固性与稳定性等方面具有明显的缺点。因此如果能发展既具有无机化合物的稳定性又具有有机化合物的可剪裁与修饰性的新型光催化材料,无疑将促进光催化的发展和应用。金属-有机骨架材料(Metal-Organic Frameworks, MOFs)正是这样一类结合了无机物的稳定性和有机物的可修饰性的杂化材料。 MOFs是一类以金属阳离子为节点、有机配体为连接体的多孔配位聚合物的总称。这类材料不仅拥有超高的比表面积、丰富的拓扑结构,而且其结构兼具可剪裁性、可设计性、易调变等特点,在气体吸附储存、分离、传感等领域都有广泛的应用。在催化领域MOFs也显示出巨大的应用前景：(1)比表面积大,有利于对反应底物的吸附,促进催化反应的进行；(2)组成多样,结构具可剪裁性、可设计性、易调变等特点,通过对其金属单元或者配体进行改变修饰,可以实现对MOFs结构和性能的调变；(3)MOFs中金属-氧单元之间由有机配体隔开,相当于分立的半导体量子点,在反应中不易发生团聚。并且各个分立的金属-氧单元之间可能存在协同效应,有利于保持催化剂的稳定性和产生高的催化活性。因此, MOFs材料是一类非常有潜力的异相催化剂。光催化是一类典型的多相催化技术,与传统半导体光催化材料相比, MOFs由于具有可在分子水平进行灵活调控的优点,在光催化领域的应用更有优势。此外, MOFs结构上的确定性为研究催化剂的界面电荷迁移和光催化机理提供了便利条件,通过对其构-效关系的研究和光催化反应机理的探索反过来有助于我们从微观尺度上进一步认识光催化的本质。 MOFs材料在光催化领域已经有了初步的研究。越来越多的MOFs材料被成功应用于光催化降解染料、选择性转化有机物、光解水制氢和CO2还原等反应。典型的有MOF-5、UiO-66和MIL-125系列等。近年来,已有少量的文献综述了MOFs这类材料在光催化领域的研究。这些文献主要围绕MOFs在光催化过程中所起到的作用,比如作为催化剂、助催化剂或载体来展开；或者是从MOFs的光催化应用领域,比如污染物降解、产氢、二氧化碳还原、有机物转化来分类展开。本文围绕如何设计合成高效的MOFs光催化剂,综述了近年来国内外关于提高MOFs的光催化性能而开展的相关研究工作,包括理论研究MOFs的能级结构及化学性质、在MOFs配体上修饰官能团调变其能带结构、染料或者金属化合物光敏化MOFs提高其光吸收性能、负载金属/碳材料及半导体复合提高光生载流子的分离效率等。最后,本文对MOFs光催化剂的未来发展趋势进行了展望,强调开发新型的MOFs光催化剂,并加强对MOFs光催化机制的研究,有助于指导现有MOFs催化剂的改良和设计新型光催化剂。
关键词:
金属-有机骨架材料
,
光催化
,
配体
,
功能化
,
光敏化
,
助催化剂
,
复合材料
