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Density of capillaries and the oxygen diffusion model in the porous silk fibroin film
BAI Lun, XU Jianmei, SUN Qilong, DI Chuanxia, ZUO Baoqi, GUAN Guoping, WU Zhenyu
Front. Mater. Sci.. 2007, 1 (3): 237-242.
https://doi.org/10.1007/s11706-007-0042-9
In order to obtain porous silk fibroin films (PSFFs) fit for the repair of different tissues and organs and design the configuration of the PSFFs more rationally, a model of the oxygen diffusing system of the capillary was built, and also the equations of the model were solved. Moreover, the relationships between the distribution of the oxygen concentration and each affecting factors were discussed, a method was developed to estimate the density of the capillaries in the tissue, and hereby discussed the characteristics of the oxygen diffusion in the tissues around the open capillaries.
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Study on the mechanical and biological property of PMMA bone cement modified with ultra-fine glass fibers and nano-hydroxyapatite
WU Qisheng, CHENG Futao, WEI Wuji
Front. Mater. Sci.. 2007, 1 (3): 247-251.
https://doi.org/10.1007/s11706-007-0044-7
In this study, polymethylmethacrylate (PMMA) bone cement (BC) was modified with ultra-fine glass fibers (UFGF) and nano-hydroxapatite (nano-HAP) synthesized by hydrothermal method. The results show that when the contents of both UFGF and nano-HAP powders are about 5%, the ultimate tensile strength (UTS), ultimate impact toughness (UIT), tensile strain (TS), and elastic modulus (EM) have been promoted a lot. The interface bond was improved by silicane treatment. Pre-grinding mixture of PMMA, UFGF, and nano-HAP can largely improve the mechanical property of PMMA. The PMMA modified with UFGF and HAP has better bioactivity than that modified with pure UFGF when they share the same content. Nano-HAP powder and modified PMMA were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).
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Fabrication and biocompatibility in vitro of potassium titanate biological thin film/titanium alloy biological composite
QI Yumin, CUI Chunxiang, LIU Shuangjin, WANG Huifen, HE Yun
Front. Mater. Sci.. 2007, 1 (3): 252-257.
https://doi.org/10.1007/s11706-007-0045-6
A potassium titanate biological thin film/titanium alloy biological composite was fabricated by way of bionic chemistry. The biocompatibility in vitro of Ti-15Mo-3Nb and the potassium titanate biological thin film/titanium alloy was studied using simulated body fluid cultivation, kinetic clotting of blood and osteoblast cell cultivation experiments in vitro. By comparing the biological properties of both materials, the following conclusions can be obtained: (1) The deposition of a calcium phosphate layer was not found on the surface of Ti-15Mo-3Nb, so it was bioinert. Because the network of potassium titanate biological thin film could induce the deposition of a calcium phosphate layer, this showed that it had excellent bioactivity. (2) According to the values of kinetic clotting, the blood coagulation time of the potassium titanate biological thin film was more than that of Ti-15Mo-3Nb. It was obvious that the potassium titanate biological thin film possessed good hemocompatibility. (3) The cell compatibility of both materials was very good. However, the growth trend and multiplication of osteoblast cells on the surface of potassium titanate biological thin film was better, which made for the concrescence of wounds during the earlier period. As a result, the potassium titanate biological thin film/titanium alloy showed better biocompatibility and bioactivity.
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Effects of pH and initial Ca2+-H2PO4- concentration on fibroin mineralization
REN Yongjuan, SUN Xiaodan, CUI Fuzhai, KONG Xiangdong
Front. Mater. Sci.. 2007, 1 (3): 258-262.
https://doi.org/10.1007/s11706-007-0046-5
In the present study, the effects of pH and initial Ca2+-H2PO4- (Ca-P) concentration on fibroin mineralization were studied. The crystal growth of calcium phosphates was regulated by regenerated silk fibroin for 8 h (at pH 4.0, 7.0 and 10.0, respectively). Meanwhile, different concentrations of Ca2+ were employed at a certain pH value, keeping the initial Ca-P molar ratio constant at 1.67, i.e., the stoichiometry of hydroxyapatite [Ca10(PO4)6(OH)2, HAP]. The products were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results demonstrated that, compared to pH 4.0 and 10.0, pH 7.0 promoted the transformation of brushite (CaHPO4°2H2O, DCPD) to HAP. In the composites of mineralized fibroin, DCPD is the main inorganic phase at both relatively low and high pH, while HAP is the main inorganic phase at pH 7.0. Additionally, the initial Ca-P concentration does not affect the kind of inorganic phase in the synthesized mineralized fibroin, but induce to different contents of inorganic mineral and different morphology of DCPD at pH 4.0 and pH 10.0.
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Inorganic replication of human hair and in situ synthesis of gold nanoparticles
LIU Shuxia, HE Junhui
Front. Mater. Sci.. 2007, 1 (3): 263-267.
https://doi.org/10.1007/s11706-007-0047-4
The structure of hair was replicated via a solgel process using human hair as a template. When using silicate and tetraethoxysilane (TEOS) as the precursor, the cell structure of the hair cuticle was not well replicated. When using Ti(OnBu)4 as the precursor, however, titania microtubes were obtained, with nanopores in their walls and nanoporous platelets on their outer surfaces, which were derived from cuticle cells on the hair surfaces. The nanopores in the microtubes acted as an effective nanoreactor for in situ synthesis of Au nanoparticles. The microchannels, nanopores and noble metal nanoparticles may provide a unique combination that would be attractive in applications such as catalysis, adsorption, and separation.
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Vision-based weld seam tracking in gas metal arc welding
GAO Jinqiang, WU Chuansong, LIU Xizhang, XIA Dianxiu
Front. Mater. Sci.. 2007, 1 (3): 268-273.
https://doi.org/10.1007/s11706-007-0048-3
A low-cost visual sensing system is developed to realize weld seam tracking in gas metal arc welding (GMAW). The system consists of a commercial CCD camera, narrow-band composite filter lens, an image capturing card, an industrial computer, a welding control unit, a GMAW power source, and a worktable. Images of root gap and its vicinity are captured in the GMAW welding process by the system. The captured images are processed by an algorithm on the basis of the analysis of gray characteristics of the root gap to get the offsetting information between torch and root gap centerline. The offsetting information is then used to realize weld seam tracking in the GMAW process. Welding seam tracking experiment is conducted by a simple proportional (P) controller. The results show that tracking error is basically less than ±0.5 mm.
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Effect of Mn on strain accumulation in Nb microalloying steels
ZHU Guohui, S. V. Subramanian
Front. Mater. Sci.. 2007, 1 (3): 274-279.
https://doi.org/10.1007/s11706-007-0049-2
High Mn is added in line pipe steels to strengthen them. Also, Mn lowers the phase transformation temperature, which is an advantage because it lowers the rolling temperature for grain size control. However, Mn retards the kinetics of precipitation of NbC in thermo-mechanical processing in Nb microalloying steels. In high-grade line pipe steels, the control of strain accumulation behavior is the key to the control of grain size. Strain accumulation can only be obtained when static recrystallization between passes could be suppressed. The effect of NbC precipitates on suppressing recrystallization has been widely investigated, mostly focusing on the Zener pinning of NbC on grain boundaries. However, it is applicable in large strain and long inter-pass time. In short inter-pass time, such as strip mill rolling, recrystallization behavior is controlled by the complicated interaction of precipitation with recovery and recrystallization. In this paper, the effect of Mn on strain accumulation during multi-pass strip mill rolling based on the interaction of precipitates with the activation energy of grain boundary migration and recovery, and the thermodynamics and kinetics of recrystallization are discussed systematically.
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Research on Au-Al bonding properties based on a thermal shock environment
ZHOU Jicheng, YAN Qinyun, JIANG Qinming, YANG Dan, HUANG Yun
Front. Mater. Sci.. 2007, 1 (3): 280-283.
https://doi.org/10.1007/s11706-007-0050-9
The thermal shock experiment of Au-Al bonding has been carried out. The mechanical characteristics, structure morphology and electrical characteristics degradation mechanism have also been researched. No cracks were observed in the bonding interface, and the bonding joints also showed good mechanical characteristics with pull stress of 3.0 to 12.0 g. Due to high temperature, the Au-Al intermetallic compound Au5Al2 with high resistibility was formed, which ultimately led to electrical failure. For the samples that were fabricated on the basis of the present technique, the bonding reliability has been evaluated. It has been found that the lifespan rule obeys the Weibull distribution, and at a high temperature of 150?C under 95% confidence level, the estimated results are η = 547 h, m = 3.83. In a room temperature environment, the Au-Al bonding samples lifespan has also been predicted on the basis of the rule of reliability evaluation. The result shows that the lifespan is about 20 years, while the reliability degree is 90%.
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Morphology and quantitative characteristics of ceramic phase in Ti-HA composites with ≤20vol% HA
ZHANG Long, CUI Zhenduo, WEI Qiang, YANG Xianjin
Front. Mater. Sci.. 2007, 1 (3): 288-292.
https://doi.org/10.1007/s11706-007-0052-7
This paper studied Ti-HA composites with low volume fractions of hydroxyapatite (HA), which are usually used as internal layers of functionally graded materials to withstand heavy load. Optical microscopy (OM), X-ray diffractometry (XRD), and scanning electron microscopy (SEM) were used to analyze the microstructure of cold-pressed composites after sintering at 1,100vH. Quantitative analysis of volume fractions and mean particle volumes of the ceramic phase was adopted to further discuss the reaction between Ti and HA. CaO and TixPy were produced in the Ti-HA reaction. With the increase of HA volume fraction, the Ti-HA reaction could be divided into three stages including stable initiation, stimulating term and re-stabilization according to the quantitative characteristics of the ceramic phase.
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