A novel wound dressing material — fibrin–chitosan–sodium alginate composite sheet

The present study describes preparation and characterization of fibrin–chitosan–sodium alginate composite (F–C–SA) in sheet form. F–C–SA composite was prepared and characterized for its physicochemical properties like water absorption capacity, surface morphology, FTIR spectra and mechanical properties. The optimum quantities of fibrin, chitosan and sodium alginate to get better mechanical properties to composite were determined. FTIR spectrum confirmed the interaction between amino groups of chitosan, fibrin and sodium alginate and SEM studies revealed composite nature of the material.     

Microstructure and microhardness of AA1050/TiC surface composite fabricated using friction stir processing

Friction stir processing (FSP) has been developed by several researchers to produce an upper surface modification of metallic materials. The fabrication of TiC particulate (~2? $\upmu $ m) reinforced aluminum matrix composite (AMC) using FSP is studied in this paper. The measured content of TiC powders were compacted into a groove of 0.5?mm × 5.5?mm. A single pass FSP was carried out using a tool rotational speed of 1600?rpm, processing speed of 60?mm/min and axial force of 10?kN. A tool made of HCHCr steel, oil hardened to 62 HRC, having a cylindrical profile was used in this study. The microstructure and microhardness of the fabricated AMC were analysed. Scanning Electron Microscope (SEM) micrographs revealed a uniform distribution of TiC particles which were well-bonded to the matrix alloy. The hardness of the AMC increased by 45% higher than that of the matrix alloy.     

异种搅拌摩擦焊AA5083-H111和AA6351-T6铝合金的力学和冶金性能(英文)

研究异种搅拌摩擦焊AA5083-H111和AA6351-T6铝合金的微观结构和力学性能。在3种不同的焊接速度(36、63、90 mm/min)下焊接AA5083-H111和AA6351-T6铝合金,分析焊接速度对接头力学和冶金性能的影响。结构表明,与其他焊接速度相比,焊接速度为63 mm/min时接头的力学性能和冶金性能较好。焊缝区由未混合区、机械混合区和混流区组成。所观察到的断裂模式为韧性纤维断裂。     

搅拌铸造AA6061-T6/AlNp复合材料的干滑动磨损行为

以AA6061为基体、AlN颗粒为增强体,采用搅拌铸造工艺得到AA6061-T6/AlNp复合材料,研究了AA6061-T6/AlNp复合材料的干滑动磨损行为。开发回归模型来预测复合材料的磨损率。采用四因素、五水平的正交实验进行优化。实验因素包括滑动速度、滑动距离、荷载、增强体AlN颗粒的质量分数。采用SYSTAT 12软件和统计工具,如方差分析（方差分析）和t实验,验证回归模型。结果表明,开发的回归模型可以有效预测复合材料的磨损率,置信度达95%。采用回归模型,并依据磨损表面形貌分析,预测实验因素对AA6061-T6/AlNp复合材料磨损率的影响。回归模型预测结果表明,复合材料的磨损率随着增强体AlN质量分数的增加而降低,随着滑动速度、滑动距离、荷载的增加而增加。     

Synthesis of nanosized barium titanate/epoxy resin composites and measurement of microwave absorption

Barium titanate/epoxy resin composites have been synthesized and tested for microwave absorption/transmission. Nanocrystalline barium titanate (BaTiO₃ or BT) was synthesized by the hydrothermal method and the composites of BT/epoxy resin were fabricated as thin solid slabs of four different weight ratios. BT was obtained in the cubic phase with an average particle size of 21 nm, deduced from the X-ray diffraction data. The reflection loss (RL) and transmission loss (TL) of the composite materials were measured by the reflection/transmission method using a vector network analyser R&S: ZVA40, in the frequency range 8·0–18·5 GHz (X and Ku-bands). The RL was found to be better than −10 dB over wide frequency bands. The higher RL for lower concentration of BT could be due to increase in impedance matching effects. Low TL values indicate that the absorption by BT is quite low. This could be due to formation of BT in the cubic paraelectric phase.     

AA6061/ZrB_2原位复合材料的干滑动磨损行为(英文)

通过往铝熔体中添加K2ZrF6和KBF4制备AA6061/ZrB2原位复合材料,并对该复合材料的干滑动磨损形为进行研究。构建了一数学模型来预测该复合材料的磨损速率。采用4因素5水平的中心复合旋转设计方法来减少实验工作量。考察滑动速度、滑动距离、载荷和ZrB2质量分数这4个因素对制备的复合材料的磨损速率的影响,通过观察磨损表面形貌分析这些因素的影响。结果表明,原位生成的ZrB2颗粒改善了复合材料的磨损性能。该复合材料的磨损速率随着滑动速度、滑动距离和载荷的增加而增加。     

Investigations into the effect of cathode material on temperature distribution during electrochemical machining

Electrochemical machining (ECM) is one of the most widely used unconventional manufacturing processes. Its capabilities have not been fully exploited mainly because of some inherent problems associated with tool design. Most of the models available for tool design in ECM ignore the effect of the heat transferred through the cathode and anode and its effects on the variation of different process parameters during ECM.

In the present paper, a simple thermal-resistance model of the ECM process is proposed. Using this model, the effects of the heat transferred through electrodes on temperature distribution, electrolyte conductivity, anode profile, metal removal rate (MRR), etc. have been studied. The experimental data have then been used to test the accuracy of the model.

The tests show that, for accurate determination of the anode profile, any model which takes no account of the heat transferred through the electrodes will yield erroneous results.     

搅拌速度对搅拌摩擦工艺制备的Cu/B4C表面复合材料显微组织和滑动磨损行为的影响（英文）

采用搅拌摩擦工艺合成Cu/B4C表面复合材料,并分析搅拌速度对该复合材料显微组织和滑动磨损行为的影响。搅拌速度以200 r/min从800变化至1200 r/min,横向速度、轴向力、沟槽宽度及搅拌头外形保持不变。采用光学和扫描电子显微镜对所制备表面复合材料的显微组织进行观察。采用销盘滑动磨损试验装置研究该表面复合材料的滑动磨损性能。结果表明:搅拌速度对表面材料的面积和B4C颗粒的分布具有显著影响。在较高的搅拌速度下此复合材料中B4C颗粒分布均匀;而在低搅拌速度下B4C颗粒分布均匀性较差。此外,本文报道搅拌速度对复合材料的颗粒尺寸、硬度、磨损率、磨损表面和磨屑的影响。     

Role of friction stir processing parameters on microstructure and microhardness of boron carbide particulate reinforced copper surface composites

Friction stir processing (FSP) was applied to fabricate boron carbide (B₄C) particulate reinforced copper surface composites. The effect of FSP parameters such as tool rotational speed, processing speed and groove width on microstructure and microhardness was investigated. A groove was contrived on the 6 mm thick copper plates and packed with B₄C particles. FSP was carried out using five various tool rotational speeds, processing speeds and groove widths. Optical and scanning electron microscopies were employed to study the microstructure of the fabricated surface composites. The results indicated that the selected FSP parameters significantly influenced the area of surface composite, distribution of B₄C particles and microhardness of the surface composites. Higher tool rotational speed and lower processing speed produced an excellent distribution of B₄C particles and higher area of surface composite due to higher frictional heat, increased stirring and material tranportation. The B₄C particles were bonded well to the copper matrix and refined the grains of copper due to the pinning effect of B₄C particles. B₄C particles retained the original size and morphology because of its small size and minimum sharp corners in the morphology.