高强度碳化硅泡沫陶瓷的制备及其抗压强度研究

选用Al2O3、Y2O3作为烧结助剂,通过有机模板复制法及多次浸渍涂覆工艺制备出高强度碳化硅泡沫陶瓷材料。系统地研究了原料组成、烧结温度等工艺参数对制得的碳化硅泡沫陶瓷物相组成、宏观结构、微观结构的影响,同时对陶瓷的气孔率、力学性能等进行了测试。结果表明:通过选取不同PPI值的有机泡沫模板,泡沫陶瓷宏观孔径可控;随着涂覆次数的增加,陶瓷体孔径减小、孔棱直径增加;随着烧结温度的提高,孔棱致密度增加,抗压强度显著提高;在1700℃下获得了20PPI值,气孔率为77%,抗压强度达2.48MPa的碳化硅泡沫陶瓷。     

膨胀珍珠岩-泡沫铝复合材料层合管的力学性能研究

采用渗流法制备膨胀珍珠岩一泡沫铝复合材料,以其为芯,钢管为面板制备层合管,研究了静态压缩条件下泡沫铝及其层合金属管的变形行为和能量吸收性能.研究表明:由于泡沫铝的填充,钢管的变形方式发生改变,由不对称屈曲转变为轴对称屈曲;层合管的平台区比原来增高、增长,压缩屈服强度由29.61MPa增高至51.62MPa,其吸能性能也...     

Preparation of open-cell metal foams by investment cast

1. Introduction Metal foams are a new kind of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They are potential materials for lightweight structures, energy absorption, and thermal management applications. They can be divided into closed and open cell structures (sponges). For sponges, the typical applications of these open-cell materials so far are heat exchangers, filter elements, acoustic absorbers, stiffening elements, crash absorb…     

Texture evolution of extruded AZ31 magnesium alloy sheets

The evolution of texture during the annealing and hot rolling process of extruded AZ31 magnesium alloy sheets was studied. There are two kinds of texture components in the extruded AZ31 sheets. One is {0002}<1-010> and the other is {1-010}<1-120>. The {0002}<1-010>component predominates. After annealing at 723 K for 3 h, both {0002}<1-010> and {1-010}<1-120> components are strengthened moderately. This indicates that grains with both two components mentioned above grow faster than those with other orientations. The {1-010}<1-120> component disappears and the intensity of {0002}<1-010> component decreases significantly after hot rolling with a 30% reduction at 623 K. This is mainly attributed to rotational dynamic recrystallization (RDX) during the hot rolling.     

高密度石墨泡沫及其石蜡复合材料的热物理性能(英文)

以中间相沥青和添加中间相炭微球的沥青为原料,调整发泡压力和发泡温度制备沥青泡沫,经1273K炭化和2973K石墨化,制备了高密度石墨泡沫。为了进一步提高石墨泡沫的密度,采用573 K的沥青反复浸渍炭化未添加中间相炭微球的沥青在1273K下所制的泡沫炭,再经2973K石墨化获得增密度后的石墨泡沫。而后制备了相应石墨泡沫/石蜡复合材料。研究了石墨泡沫热物理性能的影响因素和石墨泡沫/石蜡复合材料的热行为。研究表明:沥青组分、发泡温度和发泡压力决定了石墨泡沫的结构和热物理性能,而石墨泡沫的热导率决定了复合材料的热行为。与石蜡相比,石墨泡沫/石蜡复合材料的热扩散系数提高了768至1588倍。石墨泡沫/石蜡复合材料的潜热与石蜡的质量分数成正比。该复合材料是快速响应电子散热材料的良好选择。     

XPS挤塑板薄抹灰外墙外保温系统工程质量控制措施

对XPS挤塑板薄抹灰外墙外保温系统在工程应用中出现的问题进行了分析,从系统材料、设计、施工技术、修补技术、检测验收等方面进行了针对性的工程质量控制,提出了改进方案和技术措施,以此促进外墙外保温技术的健康发展.     

套接扣压式薄壁钢导管(KBG)电线管路施工工法

本文介绍套接扣压式薄壁钢导管的施工技术,着重阐述了KBG管安装的特点、工艺原理,操作要点以及质量要求,对KBG管路的施工有借鉴意义。     

Young’s modulus and thermal conductivity of closed-cell,open-cell and inverse ceramic foams – model-based predictions,cross-property predictions and numerical calculations

Numerical calculations of relative Young’s modulus and thermal conductivity have been performed on computer-generated microstructures of wall-based (closed-cell) and strut-based (open-cell) cellular materials (foams) and inverse foams. The results are compared to rigorous upper bounds (Wiener-Paul, Hashin-Shtrikman), model-based predictions (power-law, exponential) and cross-property predictions (CPRs). It is shown that closed-cell foams exhibit higher property values than open-cell and inverse foams, Kelvin foams higher than random foams, and the difference between closed-cell and open-cell foams is larger than that between Kelvin and random foams. While the properties of closed-cell foams are higher than the power-law prediction, those of inverse and open-cell random foams are between the exponential and power-law predictions, and open-cell Kelvin foams follow the Gibson-Ashby power-law prediction for open-cell foams. The Pabst-Gregorová CPR is shown to predict Young’s modulus with accuracy better than ±0.02 relative property units (better than any model-based relation and any other CPR).     

Microstructure,thermal conductivity and simulation of elastic modulus of MAX-phase (Ti2AlC) gel-cast foams

MAX-phase (Ti₂AlC) gel-cast foams manufactured using agarose as gelling agent were investigated in terms of their microstructural, mechanical and thermal properties. The microstructural analysis of Ti₂AlC foams made using SEM were compared with those using X-ray micro tomography. The Young’s Modulus of Ti₂AlC foams was determined using the impulse excitation technique. This experimental data was correlated with the Gibson-Ashby, Spriggs and Cross-property relation models. The thermal conductivity measurements were carried out by Laser-Flash analysis correlating to the pore network in the Ti₂AlC foam structure derived from μCT measurement. FEM-simulations of the mechanical behaviour were carried out on real structure models to determine a strut wise stress distribution under load.     

聚氨酯制品的应用现状及发展趋势

说明了聚氨酯泡沫的种类,介绍了硬质泡沫、软质泡沫、弹性体泡沫及非泡沫制品在经济中的广泛应用;同时展示了我国聚氨酯的现状及其在未来的发展前景。