Mehdi Ebrahimian-Hosseinabadi Fakhredin Ashrafizadeh Mohammadreza Etemadifar Subbu S. Venkatraman
材料科学技术（英文）
In this paper, preparation of nano-biphasic calcium phosphate (nBCP), mechanical behavior and load-bearing of poly (lactide-co-glycolide) (PLGA) and PLGA/nBCP are presented. The nBCP with composition of 63/37 (w/w) HA/β-TCP (hydroxyapatite/β-tricalcium phosphate) was produced by heating of bovine bone at 700°C. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation (TIPS) at -60°C under 4 Pa (0.04 mbar) vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.
关键词:
Scaffold
王龙妹
,
杜挺
金属学报
用直接平衡法研究了1500,1550,1600℃Ni液中Y-S平衡关系,测定了钇的脱硫常数lgK_(YS)及Y,S的一阶活度相互作用系数e_S~Y与温度的关系,并进行了有关的热力学计算。由测得的数据算出Ni液中YS的标准生成自由能△G_((Y)S),钇的标准溶解自由能△G_((Y)(l)→[Y]Ni),活度系数γ_Y~o,以及钇的克原子分数自相互作用系数∑_Y~Y和百分浓度自相互作用系数e_Y~Y与温度的关系。 对于反应[Y]_(Ni)+[S]_(Ni)=YS_(s) △G_((Y)S)=-215000+95.53T(cal/mol)脱硫常数: lgK_(YS)=-47000/T+20.86 e_S~Y=-350200/T+179 △G_((Y)(l)→[Y]Ni)=126200-79.31T(cal/mol) lgγ_(Y)=27584/T-15.151 ∑_Y~Y=-127T05/T+69.79 e_Y~Y=-364.8/T+0.2018
关键词:
Journal of the European Ceramic Society
Y2SiO5 has potential applications as functional-structural ceramic and environmental/thermal barrier coating material. As an important grain-boundary phase in the sintered Si3N4, it also influences the mechanical and dielectric performances of the host material. In this paper, we present the mechanical properties of Y2SiO5 including elastic moduli, hardness, strength and fracture toughness, and try to understand the mechanical features from the viewpoint of crystal structure. Y2SiO5 has low shear modulus, low hardness, as well as high capacity for dispersing mechanical damage energy and for resisting crack penetration. Particularly, it can be machined by cemented carbides tools. The crystal structure characteristics of Y2SiO5 suggest the low-energy weakly bonded atomic planes crossed only by the easily breaking Y-O bonds as well as the rotatable rigid SiO4 tetrahedra are the origins of low shear deformation, good damage tolerance and good machinability of this material. TEM observations also demonstrate that the mechanical damage energy was dispersed in the form of the micro-cleavages, stacking faults and twins along these weakly bonded atomic planes. which allows the "microscale-plasticity" for Y2SiO5.
关键词:
Y2SiO5;mechanical properties;damage;strength;fracture;yttrium silicate;ceramics;system;si3n4-sio2-y2o3;coatings;monazite;strength;phases
LI Guodong
,
D U Ting
,
Central Iron and Steel Research Institute
,
Ministry of Metallurgical Industry
,
Beijing
,
China LI Guodong
,
Department No.16
,
Central Iron and Steel Research Institute
,
Ministry of Metallurgical Industry
,
Beijing
,
100081
,
China
金属学报(英文版)
The thermodynamic properties of Cu-Ce-S and Cu-Y-S liquid solutions were studied by the chemical equilibrium technique at 1200℃. The equilibrium constants and the standard free energies of formation of CeS and YS were determined for the reactions: CeS=[Ce]+[S] and YS = [Y]+[S] . For the solution of Ce_(1) and Y_(l) in pure Cu according to the reactions: Ce_(1)= [Ce] and Y_(1)= [Y] , the standard free energies of solutions were obtained. The first order and second order interaction coefficients between solute elements as well as the activity coefficients γ_(Ce)~0 and γ_Y~0 in liquid Cu were also determined.
关键词:
Cu-Ce-S system
,
null
,
null
D.Q. Wan
,
G.C. Yang
金属学报(英文版)
The microstructure formation and mechanical property involving icosahedral quasicrystal (I-phase) in the Y-rich Mg-Zn-Y alloy have been studied. The equilibrium formation of I-phase from the Y-rich Mg-Zn-Y melt is through a peritectic reaction between the Y-rich melt and the primary W-phase, which is discussed in detail. The independent nucleation and coupling growth mechanism between the W-phase and the I-phase, from the melt, are revealed, which is significant for understanding the peritectic reaction process involving icosahedral quasicrystal in the Mg-Zn-Y alloy. The mechanism of the quasicrystal phase strengthened magnesium alloys is also discussed here.
关键词:
Mg-Zn-Y
,
null
,
null
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element, composed of two layers of helically wound fiber, was suggested. To detect the structural characteristics of such a microstructure, four types of macro fiber specimens made of engineering composites were employed: axially aligned solid and hollow cylinders, and single- and double-helical hollow cylinders. These specimens were subjected to several possible loadings, and the experimental results reveal that only the double-helical structural unit possesses the optimum comprehensive mechanical properties. An interlaminar transition zone model imitating bamboo bast fiber was proposed and was verified by engineering composite materials. In our work, the transition zone can increase the interlaminar shear strength of the composite materials by about 15%. These biomimetic structural models can be applied in the design and manufacture of engineering composite materials.
关键词:
bamboo;bast fiber;biomimetics;engineering composites
Journal of Alloys and Compounds
In this work, the influence of element Y on the mechanical properties of the as-cast Mg-5.5Zn-xY-0.8Zr alloys (with element Y content of 0, 1.08, 1.97 and 3.08 wt.%) has been investigated and compared. The results showed that the alloy with Y content of 1.08 wt.% had the superior tensile strength, but its ductility was the lowest. When Y content reached 1.97 or 3.08 wt.%, the tensile strength of the alloys decreased obviously, but the ductility had a little improvement. X-ray phase analysis showed that when Y content was 1.08 wt.%, the alloy mainly contained I-phase and alpha-Mg matrix, whereas when Y content was 1.97 or 3.08 wt.%, besides I-phase and alpha-Mg matrix, W-phase would be formed. And the diffraction peak of W-phase intensified with the increase of element Y content. Based on fracture observations, the influence of I-phase and W-phase on the mechanical properties of the alloys has been explained, respectively. It revealed that I-phase was closely bonded with the Mg matrix and could effectively retard the basal slip, and then strengthened the alloy greatly. However, W-phase was easily cracked during the tensile process, which degraded the mechanical properties. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
As-cast Mg alloys;mechanical properties;I-phase and W-phase;Mg-Zn-Y-Zr alloy;behavior;phase
Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science
This work mainly investigated the microstructure and mechanical properties of Mg-Zn-Y-Zr alloys with Zn/Y ratios of 5 and 10. An X-ray diffraction (XRD) analysis indicated that the two alloys were mainly composed of an icosahedral phase (I-phase) and alpha-Mg matrix. For the alloy with a Zn/Y ratio of 10, however, the diffraction peaks of the I-phase were stronger. Microstructure observation showed that the I-phase preferentially existed in the form of I-phase/alpha-Mg matrix interdendritic eutectic pockets at grain boundaries. Moreover, when the Zn/Y ratio was increased 2 times, the volume fraction of the I-phase in the alpha-Mg matrix increased 1.5 times and a tiny Mg(7)Zn(3) phase formed. Energy-dispersive spectroscopy (EDS) mapping and electron probe microanalysis (EPMA) results suggested that the chemical composition of the I-phase was not a constant value. Computer-aided cooling curve analysis (CA-CCA) indicated that, for the alloy with a Zn/Y ratio of 5, formation of the I-phase relied on the W-phase transformation and the eutectic reaction of the residual melt. However, the I-phase formation for the alloy with a Zn/Y ratio of 10 depended on the eutectic reaction of the melt. Tensile tests indicated that the mechanical properties of the two as-cast alloys were poor. After hot extrusion processing, the mechanical properties of the alloy with a Zn/Y ratio of 10 were noticeably increased. The ultimate tensile strength (UTS) and elongation to failure reached 320 MPa and 13 pct, respectively.
关键词:
metal-matrix composites;quasi-crystalline particles;icosahedral phase;strengthening mechanisms;solidification;behavior;magnesium;fatigue;diagram;systems
