关键词： Metal-supported solid oxide fuel cell   NiO-8YSZ   Spray drying   Sintering  

摘要： The plasma spray method is widely used to produce NiO-8YSZ (composed of nickel oxide (NiO) and 8 mol% yttria-stabilized zirconia) anode layers in metal-supported solid oxide fuel cell (SOFC). Flowability control of microsized particles is important for achieving consistent performance of the SOFC anode layer. When microsized particles are fabricated via spray drying and sintering, the most significant factors that influence flowability are their sizes, distribution, and surface conditions. Thus, the aim of this study is to analyze the fabrication conditions for microsized NiO-8YSZ cermet particles made from a nanoscale, sinterable NiO-8YSZ dispersion solution by using an appropriate spray-drying and sintering process. The characteristics of the as sprayed and sintered NiO-8YSZ composite particles (such as size, distribution, roughness, and nanostructure) were analyzed via field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), particle size distribution (PSD), Brunauer-Emmett-Teller (BET) surface area, and atomic force microscopy (AFM). The as-sprayed microsized NiO-8YSZ particles became smaller and more uniformly distributed as the rotational speed used for spray drying increased. As a result of sintering, the extent of shrinkage of as-sprayed microsized NiO-8YSZ particles generated at high RPMs was lower than that of particles formed at low RPMs. No significant difference was observed in the distribution of the nanosized NiO and 8YSZ particles at different rotational speeds. Furthermore, the highest BET surface areas were observed for particles generated at 8000 RPM before sintering at 13.74 m(2)/g. After sintering, the highest BET surface area was 0.94 m(2)/g for particles generated at 16,000 RPM. Differences in nanostructure and surface roughness between as-sprayed and sintered microsized NiO-8YSZ particles were identified via AFM. This study is expected to provide important fundamental information useful for optimizing SOFC e

关键词： 废弃涤纶纺织品   回收聚对苯二甲酸乙二醇酯(r-PET)   高密度聚乙烯(HDPE)   同质复合   低温固相挤出  

摘要： 由低温固相挤出工艺制备了连续废弃涤纶纺织品/回收聚对苯二甲酸乙二醇酯(r-PET)/高密度聚乙烯(HDPE)同质复合材料。采用扫描电子显微镜(SEM)、动态热机械分析仪(DMA)、差示扫描量热仪(DSC)、热重分析仪(TGA)、毛细管流变仪及万能电子拉力机等对含有不同编织结构的废弃涤纶纺织品复合材料微观结构和性能进行了研究。研究结果表明,线圈结构的废弃涤纶纺织品(F2)对复合材料结构与性能影响最显著。F2明显改善了HDPE在r-PET中的分散性,提高了复合材料的表观黏度、刚性以及热稳定性,并使得复合材料的拉伸强度、弯曲强度和弯曲模量分别提高了13.3%、28%和24%。

关键词： 硅粉加入量   碳纤维复合铝碳耐火材料   显微结构   强度  

摘要： 以电熔白刚玉、石墨、硅粉和碳纤维为主要原料,通过固定刚玉细粉和硅粉总含量(29%),改变硅粉加入量(0~20%)制得了六组碳纤维增强铝碳耐火材料。采用XRD、SEM及EDS等研究了硅粉加入量对不同温度处理后材料物相组成、显微结构及强度的影响。结果表明:(1)220℃热处理后,硅粉含量低于8%时,抗折耐压强度变化不大;硅粉的含量高于8%时,抗折与耐压强度均降低。(2)1400℃热处理后,当硅粉含量从0增加到8%时,耐压强度与抗折强度均得到明显改善。而当硅粉量进一步增加时,试样出现裂纹,强度显著下降。(3)综合考虑,硅粉的最佳加入量为8%,此时经220℃、1400℃热处理后材料具有最好的抗折强度及耐压强度。

关键词： Ti2AlN   热压烧结   金属陶瓷   微观结构  

摘要： 以TiN,Ti和Al粉末为原料,按1∶1∶1.03的配比,经机械球磨混合后,采用热压烧结的方法制备Ti_2AlN块体陶瓷材料。采用X射线衍射(XRD)、场发射扫描电镜(SEM)和透射电镜(TEM)等手段,分析烧结产物的相组成和微观结构特征。研究表明:在烧结温度为1300℃、保温2.5 h下,可获得物相比较单一的Ti_2AlN陶瓷材料,所得Ti_2AlN为六方晶系层片状结构,组织呈现出各向异性,晶体中存在孪晶;烧结产物中残存少量的纳米级TiN颗粒。

关键词： 二硅化钼/氧化铝   复合材料   烧成气氛   显微结构   介电性能  

摘要： 采用固相烧结法制备MoSi_2/Al_2O_3复合材料,研究了空气、真空、Ar气氛对显微结构及介电性能的影响。结果表明:Ar气氛下试样烧结性能好于真空及空气气氛,MoSi_2颗粒被Al_2O_3包覆且分散均匀;3种气氛下烧成的试样均含MoSi_2、Al_2O_3和Mo_5Si_3相,而空气下发现有SiO_2,真空及Ar保护气氛有少量Mo;空气气氛下烧成的复合材料气孔率最大,断裂韧性与抗弯强度最低;Ar保护气氛烧成后试样的断裂韧性与抗弯强度分别达到9.70 MPa·m^(1/2)与179.5 MPa。随频率的增加,不同烧结气氛制备的MoSi_2/Al_2O_3复合材料的介电常数和介电损耗均降低;随着烧结气氛从空气、真空、Ar气的变化,复合材料介电常数的实部和虚部均增加。

关键词： Al2O3-Cr2O3耐火材料   铝铬固溶体   烧成气氛   烧成温度   显微结构  

摘要： 为探讨烧成气氛和温度对低铬Al_2O_3-Cr_2O_3耐火材料性能的影响,以w(Cr_2O_3)≤20%的Al_2O_3-Cr_2O_3耐火材料纯基质为研究对象,将质量分数为50%的电熔Al_2O_3细粉、10%的电熔Cr_2O_3细粉、10%的电熔Cr_2O_3微粉和30%的烧结α-Al_2O_3微粉,外加3%(w)的PVA水溶液为结合剂配料后压制成圆片试样,然后分别在空气气氛或埋炭气氛中于1 450、1 550和1 650℃保温3 h烧成,并研究烧成温度和气氛对烧后试样显气孔率、体积密度和显微结构的影响。结果表明:随着烧成温度的升高,试样的显气孔率下降,体积密度升高。显微结构分析发现,无论是空气气氛还是埋炭气氛,随着温度的升高,铝铬固溶体晶粒逐步发育长大,形成连续多孔的网络骨架结构;空气气氛下Cr^(3+)更易迁移扩散,固溶反应较为充分,烧成试样形成的铝铬固溶体晶粒更为粗大、结构连续性好。因而,空气气氛下1 650℃烧成更有利于改善Al_2O_3-Cr_2O_3材料的性能。

关键词： 自组装   多层复合膜   光催化氧化   耦合增强效应  

摘要： 以石英玻璃片为基底,利用自组装技术在TiCl_4-HCl体系中生长纳米TiO_2,与在Fe(NO_3)_3-HNO_3体系中生长纳米FeOOH制备负载型多层不同层序FeOOH-TiO_2纳米复合薄膜光催化材料。高分辨透射电镜(HRTEM)表征结果显示:复合膜由纳米锐钛矿和针铁矿构成。UV-Vis表征结果显示:TiO_2与FeOOH间的复合使TiO_2吸收带均发生一定程度的红移,其中FeOOH/TiO_2/FeOOH/TiO_2和FeOOH/TiO_2/FeOOH复合薄膜的吸收带分别为490nm和498 nm;在以罗丹明B溶液为模拟废水的光催化实验中发现:负载FeOOH/TiO_2/FeOOH/TiO_2和FeOOH/TiO_2/FeOOH的两种复合薄膜材料的光催化效果最佳;并且FeOOH膜在复合膜最外层比TiO_2膜在最外层时光解效率高。具有一定吸附能力的针铁矿薄膜与TiO_2薄膜的复合优化了复合膜内部微孔结构,促进两者间形成了积极地吸附-光催化耦合增强效应。

关键词： 金属玻璃基复合材料   颗粒   自由体积   Ramberg-Osgood模型   韧性  

摘要： 基于自由体积理论和Ramberg-Osgood模型,并利用ABAQUS软件,建立颗粒随机分布代表性体积单元模型,模拟了Ti_(64.5)Zr_(14.5)V_(18.5)Cu_(2.5)颗粒增韧Ti基金属玻璃基复合材料在单轴拉伸状态下的微结构效应,讨论了颗粒的体积分数、团聚数目、长径比、定位取向和界面对金属玻璃韧性的影响。结果表明:提高颗粒体积分数能显著提高复合材料的塑性,但部分牺牲了复合材料的强度;增大颗粒长径比能够增强复合材料的塑性和屈服强度;使颗粒的取向与荷载方向成90°或0°,不仅增强了复合材料的塑性,而且与其他排布相比也增强了复合材料的强度;减少团聚数目至2个以下,能明显减少金属玻璃基复合材料的塑性和强度的损失,使团聚中颗粒与荷载成90°,却能改善复合材料的塑性和强度;在颗粒增韧金属玻璃基复合材料中加入零厚度界面,能观察到在主剪切带上颗粒和基体在界面处脱粘,得到与实验现象更加吻合的结果。通过上述的研究能够很好地理解复合材料的微结构效应,并有利于材料的设计。

关键词： 木薯渣   纳米化   H2O2   绿色化  

摘要： 以NaOH、NaClO和H_2O_2为助剂,采用均质、球磨和超声3种机械力相结合的绿色方法对木薯渣(CDs)进行纳米化处理,得到纳米化的木薯渣(NCDs)。利用FT-IR、SEM、AFM、TG、DSC和粒径测试等手段对NCDs进行表征,研究不同助剂及不同工艺对CDs纳米化效果的影响。结果表明:加入15%质量分数的H_2O_2作为助剂,在均质、球磨和超声3种工艺手段共同处理的条件下,CDs纳米化效果最佳,NCDs最小粒径达到30nm,与CDs相比,其稳定性不仅得到提高,而且在悬浮液中的沉降速率变慢。

关键词： Composite   distribution   electron microscopy   homogeneity   image analysis   microstructure  

摘要： The physical properties of particle-reinforced composite materials are highly affected by the distribution of particles within a matrix material. In this study, a microstructural image analysis method with a new distribution index for quantifying the degree of distribution in composite materials was developed. The free-path spacing between particles was measured to calculate the distribution (D) index based on the coefficient of variation. The proposed method was applied to six digitally created reference patterns as representative binary composite microstructures and three actual ceramic-matrix composites, respectively. It is found that the D index increased from 0.00 to 0.67 depending on the degree of distribution or homogeneity level based on the reference patterns. The homogeneity levels for the binary composites are then classified from a perfect (maximum) to very low level (minimum) based on increasing D index values, where a high D index presents a poorer distribution. The results obtained for reference patterns and metal silicide-refractory oxide composite microstructures indicate that the proposed method is a useful tool to quantify the degree of distribution with high accuracy, and can be efficiently used for different types of composite microstructures.