New Technique for Making Composite Materials—Field Assisted Diffusion Bonding of Alumina to Aluminum

There are two ways to join ceramics to metals: brazing and bonding. However, brazing processes are time-comsuming and energy-comsuming and is limited by the low working temperature. Generally speaking, bonding, or specifically, Diffusion Bonding performs better than brazing. Besides diffusion bonding, a more specialized technique is Field Assisted Diffusion Bonding (FADB).

Research of Nanostructures Formation during Self-Propagating High-Temperature Synthesis of Boride-Containing Composite Materials

This paper considers the technique of obtaining boride-containing nanostructured composite materials by the method of self-propagating high-temperature synthesis (SHS). It is shown that the selection of regimes and conditions of reactions allows receiving materials on the basis of titanium and chromium borides as well as aluminum oxide with finely dispersed structure and high mechanical properties.

Development of a Composite Material Based on Wood Waste Stabilized with Recycled Expanded Polystyrene

Environmental pollution is a whole world concern. One of the causes of that pollution is the proliferation of plastic waste. Among these wastes there is expanded polystyrene (EPS), mainly from packaging. This study aims to valorize EPS waste by developing a composite material from EPS waste and wood waste. For this purpose, a resin made of EPS has been elaborated by dissolving EPS in acetone. That resin was used as a binder in volume proportions of 15%, 20%, 25% and 30% to stabilize the samples. Some of them were thermoformed. The method of elaboration was based on a device consisting of an extruder for mixing the constituents, and a manual press for shaping and compacting the samples. Analyses show that the drying time depends on the composition of the mixture. Increasing the resin content leads to reduce water absorption and porosity of the samples;it also contributes to homogenize the internal structure of the samples. However, for the same resin contents, the thermoformed samples are less porous;they have more homogeneous internal structure;and absorb less water than non-thermoformed samples.

Electrical resistivity of TiB_2/C composite cathode coating for aluminum electrolysis

The electrical resistivity of TiB2/C cathode composite coating at different temperatures was measured with the electrical conductivity test device; the effects of TiB2 content and kinds of carbonaceous fillers as well as their mean particle size on their electrical resistivities were investigated. The results show that electrical resistivity of the coating decreases with the increase of TiB2 content and the decrease of its mean particle size. When the mass fraction of TiB2 increases from 30% to 60%, the electrical resistivity of the coating at room temperature decreases from 31.2μΩ·m to 23.8μΩ·m. The electrical resistivity of the coating at 960℃ lowers from 76.1μΩ· m to 38.4μΩ·m with the decrease of TiB2 mean particle size from 12μm to 1μm. The kinds of carbonaceous fillers have great influence on the electrical resistivity of TiB2/C composite coating at 960℃, when the graphite, petroleum coke and anthracite are used as fillers, the electrical resistivities of the coating are 20.3μΩ·m, 53.7μΩ·m and 87.2μΩ·m, respectively. For the coating with petroleum coke filler, its electrical resistivity decreases with the increase of the mean particle size of petroleum coke filler. The electrical resistivity at 960℃ decreases from 56.2μΩ·m to 48.2μΩ·m with the mean particle size of petroleum coke increasing from 44μm to 1200μm. However, too big carbonaceous particle size has adverse influence on the abrasion resistance of coating. Its proper mean particle size is 420μm.

Effect of baking processes on properties of TiB_2/C composite cathode material

Pitch and TiB2/C green composite cathode material were respectively analyzed with simultaneous DSC-TGA, and effects of three baking processes of TiB2/C composite cathode material, i.e. K25, K5 and M5, on properties of TiB2/C composite cathode material were investigated. The results show that thermogravimetrie behavior of pitch and TiB2/C green composite cathode is similar, and appears the largest mass loss rate in the temperature range from 200 to 600 ℃. The bulk density variation of sample K5 before and after baking is the largest （11.9%）, that of sample K25 is the second, and that of sample M5 is the smallest （6.7%）. The crushing strength of sample M5 is the biggest （51.2 MPa）, that of sample K2.5 is the next, and that of sample K5 is the smallest （32.8 MPa）. But, the orders of the electrical resistivity and electrolysis expansion of samples are just opposite with the order of crushing strength. The heating rate has a great impact on the microstructure of sample. The faster the heating rate is, the bigger the pore size and porosity of sample are. Compared with the heating rate between 200 and 600℃ of samples K25 and K5, that of sample M5 is slower and suitable for baking process of TiB2/C composite cathode material.

Magnetic properties of NdFeB-coated rubberwood composites

Magnetic properties of composites prepared by coating lacquer containing neodymium iron boron （Nd-Fe-B） powders on rubberwood were characterized by vibrating sample magnetometry （VSM）, magnetic moment measurements, and attraction tests with an iron-core solenoid. The Nd-Fe-B powders were recycled from electronic wastes by the ball-milling technique. Varying the milling time from 20 to 300 min, the magnetic squareness and the coercive field of the Nd-Fe-B powders were at the minimum when the powders were milled for 130 rain. It followed that the coercive field of the magnetic wood composites was increased with the milling time increasing from 130 to 300 min. For the magnetic wood composites using Nd-Fe-B obtained from the same milling time, the magnetic squareness and the coercive field were rather insensitive to the variation of Nd-Fe-B concentration in coating lacquer from 0.43 to 1.00 g/cm3. By contrast, the magnetization and magnetic moment were increased with the Nd-Fe-B concentration increasing. Furthermore, the electrical current in the solenoid required for the attraction of the magnetic wood composites was exponentially reduced with the increase in the amount of Nd-Fe-B used in the coating.

Compressive failure of spruce wood rings reinforced with glass epoxy composite

We experimentally tested under radial compressive loads and statistically analyzed rings constructed from spruce wood and reinforced with glass fiber.We used the Weibull distribution in statistical analysis,and tested five types of rings including unreinforced and composite reinforced（CR） as wound around the ring,oriented as two layers at angles of 45°,60°,75° and 90° to the column axis.We calculated 95 % reliability of load carrying capacity of the rings by Weibull distribution.The highest load carrying capacity was obtained with CR rings at 60° to the axial axis of the ring.Load carrying capacities of rings at CR90,CR75,CR60 and CR45 were 137,192,215 and 126 %greater,respectively,than unreinforced rings.For unreinforced rings,failures resulted from catastrophic breaking of wood materials.None of the reinforced rings failed catastrophically because the outer surface of the rings was reinforced with glass–epoxy composite fiber.Cracks began at the core of the materials under the composite layer for all specimens and resulted in failure of the rings.

Study on the Physical and Mechanical Properties of Al-Powder Reinforced Bioactive Glass: Ceramic Composite Material

Glass-ceramic samples, having composition of SiO2-35, CaO-45, Na2O-10 and P2O5-10 in weight ratio were prepared through sintering route. Glass powder was reinforced by Al powder. The strength of glass-ceramic composite was found to be temperature dependent, and it varies with the addition of Al powder. Flexural strength increases with the increase of powder addition and sintering temperature, however, decreases with the increase of sintering time. There is an optimum temperature (>1100℃) above which flexural strength of all samples decreases. Bulk density changes to a higher value as the addition of Al-powder increases up to 3% by weight above which density decreases slowly. On the other hand, apparent porosity and water absorption decrease with the increase of percentage of Al powder added. Porosity and water absorption also showed a dependent characteristic on sintering time and sintering temperature.

Recent development and challenges in enhancing fire performance on wood and wood-based composites:A 10-year review from 2012 to 2021

Due to their durability,versatility,and aesthetic value,wood and wood-based composites are widely used as building materials.The fact that these materials are flammable,however,raises a major worry since they might cause fire hazards and significant loss of life and property.The article investigates the variables that affect fire performance as well as the various fire-retardant treatments and their mechanisms.The current developments and challenges in improving the fire performance of wood and wood-based composites treated with fire-retardant materials are summarized in this paper.Nanoparticles,organic chemicals,and densification are some recent developments in fire-retardant treatments that are also emphasized.Key points from the review are summarized,along with potential areas for further research and development.

Dielectric properties of spark plasma sintered AlN/SiC composite ceramics

In this study, we have investigated how the dielectric loss tangent and permittivity of AlN ceramics are affected by factors such as powder mixing methods, milling time, sintering temperature, and the addition of a second conductive phase. All ceramic samples were pre-pared by spark plasma sintering （SPS） under a pressure of 30 MPa. AlN composite ceramics sintered with 30wt%-40wt%SiC at 1600℃ for 5 min exhibited the best dielectric loss tangent, which is greater than 0.3. In addition to AlN and β-SiC, the samples also contained 2H-SiC and Fe5Si3, as detected by X-ray difraction （XRD）. The relative densities of the sintered ceramics were higher than 93%. Experimental results indicate that nano-SiC has a strong capability of absorbing electromagnetic waves. The dielectric constant and dielectric loss of AlN-SiC ce-ramics with the same content of SiC decreased as the frequency of electromagnetic waves increased from 1 kHz to 1 MHz.

Microstructural characterization of Cu/Al composites and effect of cooling rate at the Cu/Al interfacial region

Cu/Al composites are of vital importance in industrial applications because of their numerous advantages. The influence of bond-ing temperature and cooling rate on the microstructure and morphology of Cu/Al composites was investigated in this paper. The interfacial morphology and constituent phases at the Cu/Al interface were analyzed by optical microscopy and field-emission scanning electron mi-croscopy equipped with energy-dispersive X-ray spectroscopy. The results indicate that effective Cu-Al bonding requires a higher bonding temperature to facilitate interdiffusion between the two metals. The microstructural characteristics are associated with various bonding tem-peratures, which impact the driving force of interdiffusion. It is observed that cooling rate exerts a significant influence on the morphology and amount of the intermetallic compounds at the interfacial region. Meanwhile, microhardness measurements show that hardness varies with the bonding temperature and rate of cooling.

增强体表面改性在高导热金属基复合材料中的应用

随着电子技术的高速发展和电子器件的更新换代,电子封装材料的性能需求越来越高。金属基复合材料,尤其是铝基和铜基复合材料具有高导热、低膨胀、高稳定性等特点,是具有广阔应用前景的电子封装材料。然而,金刚石、石墨烯、硅等增强体与基体的润湿性差,或者在高温下与基体发生有害的界面反应,限制了此类高导热金属基复合材料的开发和应用。本文简述了金属基复合材料的界面研究进展,结合影响金属基复合材料界面结合的因素,提出了几种改善界面结合的方法。增强体表面改性是改善金属基复合材料界面的重要途径之一,常用工艺有磁控溅射法、化学气相沉积法、溶胶凝胶法、化学镀法等;最后,对增强体表面改性在高热导金属基复合材料中的应用进行分析和展望。

含氟高分子材料包覆铝核壳材料研究进展

金属铝(Al)具有高燃烧热值、高密度、低耗氧量等优异性能,是固体复合推进剂领域最受青睐的金属添加剂。为了提高固体复合推进剂的性能,有必要采取措施对Al进行包覆改性。近年来含氟高分子包覆Al因其优异的综合性能而受到广泛关注。介绍了不同种类的含氟高分子包覆金属Al核壳材料、不同包覆方法、Al核壳材料的性能以及含氟高分子与Al的作用机理,总结发现通过Al核壳结构设计、含氟高分子引入和Al颗粒表面的自活化策略等途径,含氟高分子与氧化铝层之间的表面发生剧烈的氧化过程,增强Al核壳材料点火和燃烧性能,显著改善推进剂的燃烧团聚和燃烧效率。但目前含氟高分子包覆Al核壳材料研究过程仍存在许多不足,如缺乏新型多元含氟高分子包覆Al的能量性能的研究;缺乏Al颗粒与包覆层在高升温速率下作用机理的认识;包覆效率和批量制备能力低,阻碍了其实际应用等。未来可从进一步增强朝着研发新型含氟聚合物、研究对反应历程中产物的实时捕捉和开发工业化生产制造技术等方向发展。

Carbon Materials Reinforced Aluminum Composites:A Review

Carbon materials, including carbon fibers, graphite, diamond, carbon foams, carbon nanotubes, and graphene, are attractive reinforcements for aluminum matrix composites due to their excellent mechanical and/or physical properties as well as light weight. Carbon materials reinforced aluminum （C/Al） composites are promising materials in many areas such as aerospace, thermal management, and automobile. However, there are still some challenging problems that need to be resolved, such as interfacial reactions, low wettability, and anisotropic properties. These problems have limited the use of these composites. This review mainly focuses on the categories, fabrication processes, existing problems and solutions, coatings and interfaces, challenges and opportunities of C/Al composites so as to provide a useful reference for future research.

石墨膜/铝复合材料制备工艺与性能研究

将石墨膜和铝箔以铺层的形式交替排布,采用真空热压烧结技术制备石墨膜/铝复合材料,研究真空热压烧结参数对复合材料微观组织和性能的影响。结果表明:石墨膜在复合材料中分布均匀,符合预期构型设计;真空热压烧结参数对复合材料微观组织影响显著,优化后的制备工艺参数为640℃/50 MPa/100 min,该条件下制备的复合材料界面结合良好,致密度高,没有检测到Al_(4)C_(3)相;随着石墨膜体积分数的增加,复合材料面内热导率呈现先增加后下降的趋势,石墨膜体积分数为30%时,复合材料面内热导率最大,为219.71 W/(m·K)。

非对称循环载荷下铝基复合材料的疲劳寿命预测

铝基复合材料由不同力学性能和疲劳行为的多种材料组成。在非对称循环载荷下,各组分间的相互作用和影响使其疲劳寿命预测变得复杂。为解决这一问题,研究一种非对称循环载荷下铝基复合材料疲劳寿命预测方法。用Na_(3)Al F_(6)和Ti O_(2)粉末强化铝合金基体,制备出复合材料样品。设计非对称循环载荷加载条件。用Walker裂纹扩展式结合Chaboche模型进行铝基复合材料疲劳寿命预测,Chaboche模型能较好地描述材料在循环加载下的非线性行为;通过引入应力比参数,Walker公式可更准确地预测裂纹在不同应力水平下的扩展行为。将两者结合能更全面地考虑材料在疲劳过程中的各种因素,从而提高疲劳寿命预测的准确性。结果表明:随着应力幅值的增加,试件裂缝长度随之上升,同时随着循环圈数的增加,试件应力随之上升,这使得铝基复合材料疲劳寿命下降,且该方法的预测结果与实测值更接近,说明预测结果可靠。

木塑复合材料在家具中的应用

木塑材料作为一种复合型材质具有较强的可塑性、较小的污染性,相较于塑料及实木材质优势明显,在家具制造领域的实用性逐渐增强。本文主要分析了木塑复合材料在家具中应用的原则与优势、设计方法以及应用实例,为木塑材料家具产品开发提供更多的思路与建议。

复材界面剪切强度对铝模板粘接性能的影响分析

为探究复合材料界面剪切强度对铝模板材料粘接的影响,运用线性弹性分析方法进行计算,反映出胶层抗剪强度,并提出剪切强度的计算公式。结合整个结点的平衡方程,导出了粘弹性体的应力-应变关系式,通过考虑节点全局平衡的弯矩系数,将剪切粘接性能变化与胶层厚度相结合,提出了粘接样品的制备流程。通过仿真实验分析进行了验证,发现在加载前、加载后,铝模板材料剪切力-位移曲线基本一致,当加载时,最大剪切力可达533.5 N,胶粘力随胶粘层厚度的增大而进一步下降。结果表明,所提研究方法有助于揭示粘接材料在受力时的真实响应,为设计和优化粘接结构提供了更可靠的参考。

矿物钢塑复合材料与木塑复合材料性能对比研究

对矿物钢塑复合材料板材与传统木塑复合材料进行系统表征,并对外观及微观结构、无机组成成分、热性能和力学性能等进行了对比分析研究。扫描电镜(SEM)结果表明,矿物钢塑复合材料板材的形状规则、无翘曲变形,样品断面较为密实,而木塑板材液氮脆断面存在界面剥离,易发生变形翘曲。红外光谱(FTIR)结果表明,三种板材的基体材料均为聚氯乙烯(PVC)树脂,其特征峰与PVC红外光谱类似。热重分析(TG和DTG)表明,木塑复合材料的热失重速率和质量损失率大于其余两种矿物钢塑,矿物钢塑的热稳定性较木塑复合材料得到了较大提升。随着铸造灰和钢渣的加入,复合材料的弯曲强度和模量均得到了提高,且经铸造灰填充的矿物钢塑力学性能为三者中最高,其弯曲强度和弯曲模量分别为33.0 MPa和4.72 GPa。矿物钢塑复合材料具有优异的热性能、力学性能,作为一种新型绿色环保材料,为我国大宗工业固废的高附加值回收提供一种新的解决方案。

锡铋合金/肉豆蔻酸制备具有金属外壳的储能木材

【目的】利用锡铋合金对肉豆蔻酸浸渍材进行热处理,在热的驱动下将锡铋合金引入木材内部,以解决木基相变储能材料面临的液体泄漏和导热性差问题。【方法】以浸渍了肉蔻豆酸的杨木为基材,通过高低温交替热处理将锡铋合金与基材结合,制备具有金属外壳的储能木材。利用扫描电镜、邵氏硬度计、万能力学试验机、导热系数仪、差式扫描量热仪对储能木材的微观形貌、端面硬度、顺纹抗压强度和热性能进行测试。【结果】在160~220℃热处理1~5 min下试样质量增长效果显著,力学性能与热性能随着热处理温度的上升与时间的延长而提升,顺纹抗压强度和端面硬度相较于未处理材分别提升了120.02%~149.59%、13.53%~46.93%,轴向、径向导热率分别提升了34.18%~165.67%、38.11%~80.70%。在190℃热处理5 min条件下锡铋合金的填充效果最佳,端面硬度、轴向、径向导热率达到最高值62.65 HD、0.5324和0.2987 W/(m·K)。木材内部肉豆蔻酸的留存率介于27.54%~63.68%之间,经过160℃热处理3 min后储能密度最高(59.38 J/cm3)。【结论】高低温交替热处理促使锡铋合金进入到木材的导管内,实现了不同程度的渗透。木材的三维孔隙结构与外层填充的锡铋合金解决了相变材料的液体泄漏及导热性差问题。制备的储能木材综合了木材、金属与相变材料的优势,具有更优异的端面硬度、顺纹抗压强度与热性能,有望应用于建筑墙体和储能地板等领域。