Morphology of ultra fine iron particles

Variation in morphology of the silica thin film coated ultra fine goethite particles(length:140 nm, aspect ratio:11/1, surface area:95 m²/g, SiO2/Fe:3.4 wt%) in the process of decomposition and subsequent reduction was examined by means of gas adsorption and electron microscopy. Microporous hematite particles, prepared by decomposition of the silica-coated ultra fine goethite particles at 250°C in vacuo, were subjected to heat-treatment at 700°C in air to form the nonporous hematite particles without degradation of the acicular shape. The highly acicular and nonporous ultra fine iron particles(length:110 nm, aspect ratio:10/1, surface area: 80 m²/g) were obtained as a result of shrinkage of the particles in the reduction process of the nonporous hematite particles at 400°C in hydrogen gas. Coercivity of the ultra fine iron particles was 1660 Oe.     

The effect of dispersed paint particles on the mechanical properties of rubber toughened polypropylene composites

The influence of dispersed paint particles on the mechanical properties of rubber toughened PP was investigated. The matrix was basically a hybrid of PP, rubber and talc. Model systems with spherical glass bead filled matrix were also studied to examine the effect of filler shape and size. Properties like tensile strength, strain at break, impact strength, and fracture toughness were influenced by the dispersed inclusions. Tensile strength at yield decreased linearly according to Piggott and Leinder's equation. Strain at break decreased more drastically with paint particles than glass beads, revealing that irregularly shaped particles offered greater stress concentrations. The tensile strength and strain at break were less influenced by the size of paint particles whereas a slight decrease in the modulus values was observed with decreasing particle size. Impact strength and fracture toughness also decreased with increasing filler fraction. Lack of stress transfer between filler and matrix aided in reduction of impact strength. Decrease in fracture toughness was influenced by volume replacement and constraints posed by fillers. The size of paint particles had little effect on the impact strength and fracture properties at the filler concentration levels used in this investigation.     

Studies on polypropylene composites filled with talc particles

Tensile and impact properties of talc-filled isotactic polypropylene composites are investigated at 0–60 wt% filler contents. Tensile modulus registered an increase whereas tensile yield strength and strain-at-break decreased with increasing filler content. Mechanical restraint imposed by the talc particles on the molecular mobility or deformability of polypropylene explained the increase in modulus and decrease in strain-at-break while decrease in tensile yield strength was attributed to decreased crystallinity and formation of stress concentration points around the filler particles. Izod impact strength decreased with increased talc content. Surface modification of talc with a titanate coupling agent LICA 38 enhanced the filler-polymer interaction, further modifying the composite properties consequent upon significant decrease in the stress concentration. Scanning electron microscopic studies revealed better dispersion of surface-modified filler particles in the polymer matrix.     

Effect of carbide particles on the ablation properties of tungsten composites

The high temperature ablation behavior of tungsten composites containing carbides produced by vacuum hot pressing is studied as a function of reinforcement chemistry (ZrC and TiC) and content using a self-made oxyacetylene ablation equipment. A dynamic responding multiwavelength pyrometer was employed to measure the temperature of the ablation surface, and a thermocouple was employed to measure the temperature of the back surface during the time that a specimen was being ablated. The mass and linear ablation rates are lower in composites containing ZrC, decreasing with increasing particle content in both composites system. The values of the mass and linear ablation rates were in the order from high to low: W>30TiC/W>40TiC/W>30ZrC/W>40ZrC/W (30TiC/W stands for 30 vol.% TiC particle content in the W matrix, the same below). The important temperature curves of the ablation surfaces of specimens were successfully detected online. Ablated surfaces and vertical sections of the specimens were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Thermochemical oxidation of tungsten, TiC, and ZrC was the main ablation mechanism of ZrC/W and TiC/W composites. These ablation behaviors are discussed based on the thermophysical and chemical properties of both the composite systems.     

Effect of annealing on the mechanical properties and structure of carbon-black polypropylene composites

We present the results of investigation of the behavior of mechanical and various physical characteristics of polypropylene with and without three types of fillers produced in Poland depending on the type of heat treatment. It is shown that if the content of the carbon-black filler is as high as 10%, then the composite behaves as a conductor. Thermal treatment improves all mechanical properties of materials except fracture toughness. This is also partially explained by changes in the crystal lattice. Technical University of Czestochowa, Institute of Metal Working and Plastics, Czestochowa, Poland. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 1, pp. 75–82, January–February, 1999.     

纳米蒙脱土对木粉/聚丙烯复合材料发泡性能的影响

采用高压釜间歇式发泡法,结合超临界CO2微孔发泡技术制备了发泡木粉-纳米蒙脱土(NMMT)/聚丙烯(PP)复合材料.通过对复合材料的结晶行为、流变性能、泡孔形貌及压缩性能进行分析,主要研究了NMMT对其微孔结构及力学性能的改善作用.结果 表明:NMMT的引入使木粉/PP复合材料中PP基体的结晶速率加快,结晶度减小,有利...     

碱处理对SF/PP木塑复合材料力学性能的影响

采用不同碱处理浓度、处理时间对剑麻纤维(SF)进行表面改性,通过与聚丙烯树脂(PP)混合、塑炼、模压成型制备SF/PP木塑复合材料。研究了剑麻纤维(SF)表面的碱处理方法、含量对SF/PP木塑复合材料力学性能的影响,借助光学显微镜和扫描电子显微镜对SF纤维和复合材料的冲击断面进行微观结构分析。结果表明:碱处理能够提高SF/PP木塑复合材料的力学性能。在碱浓度为10%时,处理时间为4h,SF含量为20%时,冲击强度为15.78kJ.m-2达到最大值,弯曲强度和弯曲模量随着SF含量的增加出现增大的趋势。     

超细CaCO3填充SBS的性能研究

采用双辊开炼机和平板高压制样的方法制备了超细CaCO2/SBS复合材料,采用SEM、DSC和TG对复合材料的断面形貌和热性能进行了分析,同时,对复合材料的力学性能进行了考察.结果表明,表面处理的超细CaCO3在SBS体系中与弹性体充分结合,断面产生了大量的网状结构,进一步提高了材料的拉伸强度、断裂伸长率和热稳定性,硬度增加幅度较小.     

功能化聚丙烯对纳米SiO2/聚丙烯复合材料性能的影响

以环氧功能化聚丙烯(PP-g-GMA)作为纳米SiO2/PP复合材料的增容剂,研究了PP-g-GMA对复合材料力学、结晶和流变性能的影响.研究结果表明,PP-g-GMA的加入使PP复合材料的拉伸强度、冲击强度提高;使PP的结晶峰温明显提高,使复合材料的储能模量和复合黏度均明显高于纯PP.     

Effect of crystalline properties on coercive force in iron acicular fine particles

Crystallographic properties and their size dependence in acicular fine particles of iron prepared by reduction from-FeOOH were investigated by transmission electron microscopy and compared with magnetic properties. Although both larger particles with an average needle length of 0.5m and smaller ones of 0.2m length have single domain configuration, the former are crystal lographicaIly polycrystalline while the latter are single crystal with a [100] axial orientation, an easy magnetization direction of iron. The coercive force, principally yielded by external shape anisotropy, is higher in smaller particles in spite of their inferior axial ratio. The intrinsic magnetocrystalline anisotropy is inferred to be the most responsible to give rise to this further increase of coercive force. The experimentally obtained values of magnetic properties are also compared with the theoretical estimation, which results semi-quantitatively in good accordance.     

Mechanical properties of trans-polyoctenylene grown epitaxially on oriented polypropylene films

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

三维编织复合材料弹性性能的表面胞体效应

在作者已有的内胞模型基础上, 结合陈利等的面胞纱线走向及Chou 等对表面纤维束截面形状的描述,建立了由面胞和内胞组合的有限元分析模型, 比较真实地模拟了三维四向编织复合材料的真实结构。通过有限元计算预测了其弹性性能, 并同实验结果进行了比较, 分析讨论了三维四向编织复合材料的面胞对整体弹性性能的影响。研究结果证明了面胞在三维四向编织复合材料弹性性能有限元预测中的重要性。      

Effect of transverse cracks on the elastic properties of high temperature angle-ply laminated composites

The development of transverse cracks can be detrimental to the stiffness and dimensional stability of composite laminates. In this investigation, a modified shear lag analysis, taking into account the concept of stress perturbation function, is employed to evaluate the effect of transverse cracks on the stiffness reduction in high temperature angle-ply laminated composites. The results present well the effect of high temperature and the fibre orientation of the outer layers on the degradation of mechanical properties of the angle-ply polymer composite laminates.     

Effects of hydrophobation treatments of wood particles with an amino alkylsiloxane co-oligomer on properties of the ensuing polypropylene composites

In this study an amino alkylsiloxane co-oligomer was used to treat the wood particles to weight percent gains of 1.5%, 4.5%, and 7.0%, respectively, and coupling effects on the properties of the ensuing wood polypropylene composites were determined. The n-propyl-trimethoxysilane (alkylsilane) and 3-amino-propyltriethoxysilane (aminosilane) were also used for comparison. Compared to composites filled with untreated particles, composites treated with co-oligomer exhibited greater reduction in both the rates of water uptake and dimensional swelling than those treated with the other two silanes. Both, the flexural- and Charpy impact strengths of the composites, were moderately reduced but the tensile strength increased up to 23% due to treatment with the co-oligomer. The different effects by the silanes were also evidenced by dynamic mechanical analysis and microscopy. These results show that use of the co-oligomer can create a highly hydrophobic composite and any improvement in the mechanical properties is comparable to that with aminosilane.     

Effect of compatibilization on mechanical and thermal properties of polypropylene–soy flour composites

A new biobased composite was developed by adding soy flour (SF) to polypropylene (PP). This composite shows an enhanced tensile strength and modulus but decrease in elongation at break. The compatibilizer (coupling agent) appears to have a synergistic effect on tensile strength. The presence of the compatibilizer improves the dispersion of SF in the PP matrix. The addition of glycerol plasticizer to the composite improves the processability resulting in improved performance, as compared to composites without glycerol plasticizer. The optimal compatibilizer content appears to be 6%.     

Effect of alumina particles loading on the mechanical properties of light-cured dental resin composites

The purpose of this study is to evaluate the effect of alumina (Al₂O₃) loading on the mechanical properties of dental resin composites (DRCs). The DRCs were prepared based on Al₂O₃ particles and bisphenol A-glycidyl methacrylate (Bis-GMA) was used as the base monomer. The silane-treated Al₂O₃ particles were mixed with the resin matrix in proportions of 40, 50, and 60 wt%, respectively. Resin matrix without filler was used as the control sample. The Vickers hardness (HV) and flexural modulus (FM) of the DRCs mixed with Al₂O₃ particles were found to be superior compared to the control sample; the values increased from 14.4 to 23.5 kg/mm² and 1.5 to 5.7 GPa, respectively. However, the flexural strength (FS) values of DRCs were slightly decreased as the filler loading increased i.e. from 84.5 to 74.2 MPa. The results also revealed statistically significant increases in the HV and FM. On the other hand, FS values showed significant decrease when filler loading was increased (P < 0.05).     

Effect of glass fiber hybridization on properties of sisal fiber–polypropylene composites

Natural fiber reinforced polymer composites became more attractive due to their light weight, high specific strength, and environmental concern. However, some limitations such as low modulus, poor moisture resistance were reported. This study aimed to investigate the effect of glass fiber hybridization on the physical properties of sisal–polypropylene composites. Polypropylene grafted with maleic anhydride (PP-g-MA) was used as a compatibilizer to enhance the compatibility between the fibers and polypropylene. Incorporating glass fiber into the sisal–polypropylene composites enhanced tensile, flexural, and impact strength without having significant effect on tensile and flexural moduli. In addition, adding glass fiber improved thermal properties and water resistance of the composites.     

Effect of nano-sized bioactive glass particles on the angiogenic properties of collagen based composites

Angiogenesis is essential for tissue regeneration and repair. A growing body of evidence shows that the use of bioactive glasses (BG) in biomaterial-based tissue engineering (TE) strategies may improve angiogenesis and induce increased vascularization in TE constructs. This work investigated the effect of adding nano-sized BG particles (n-BG) on the angiogenic properties of bovine type I collagen/n-BG composites. Nano-sized (20–30 nm) BG particles of nominally 45S5 Bioglass^® composition were used to prepare composite films, which were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The in vivo angiogenic response was evaluated using the quail chorioallantoic membrane (CAM) as an model of angiogenesis. At 24 h post-implantation, 10 wt% n-BG containing collagen films stimulated angiogenesis by increasing by 41 % the number of blood vessels branch points. In contrast, composite films containing 20 wt% n-BG were found to inhibit angiogenesis. This experimental study provides the first evidence that addition of a limited concentration of n-BG (10 wt%) to collagen films induces an early angiogenic response making selected collagen/n-BG composites attractive matrices for tissue engineering and regenerative medicine.