真空脱气处理对网眼多孔陶瓷力学性能的改善

采用有机泡沫浸渍工艺制备了碳化硅基网眼多孔陶瓷,研究了真空脱气处理对浆料流变特性和烧结体的力学性能及显微结构的影响。结果表明：脱气处理改善了浆料的流变行性,使浆料在有机泡沫体上 的涂覆量增加和结构均匀性得到改善;压汞仪测试数据和SEM观察表明脱气处理明显地消除了孔筋内的孔径为100μm左右的大气孔;经脱气处理后,材料的抗弯强度从2.34MPa提高到3.18MPa。脱气处理对网眼陶瓷强度的改善主要来自两方面的贡献：一是相对密度的增加,二是孔筋中大气孔的消除,但后者是最主要的贡献,这个结果与目前建立的开孔陶瓷泡沫的力学模型吻合得很好。     

网眼多孔陶瓷浸渍成型工艺的研究

采用一种具有三维网状结构和连通气孔的氨酯海绵作为骨架来制备网眼多孔陶瓷。采用一种亲水憎水平衡值（HLB）＞12的表面活性剂溶液对海绵体孔筋表面进行改性处理,改善了海绵与水基浆料之间的粘附性,增加了浆料涂覆量。研究了浆料固含量、有机泡沫体网眼大小,对辊间距和挤压次数对浆量涂覆量及结构均匀性的影响。结果表明：浆料固含量和对辊间距是影响涂覆量及结构均匀性的最主要因素。还发现网眼烧结体的相对密度与相对对辊间距具有很好的线性关系,这为预测和优化材料的渗透率及机械强度提供了一定的依据。     

熔渗反应烧结泡沫SiC的组织及性能

采用有机泡沫浸渍结合熔渗反应烧结技术制备了一种高性能泡沫SiC,该种泡沫陶瓷由SiC陶瓷孔筋形成类似于泡沫的三维网络连通结构,平均孔径尺寸约2 mm,相对密度15%~42%(体积分数),具有高的可控性,其强度随密度增加而提高,压缩强度11~48 MPa,弯曲强度7~25 MPa。研究了材料受力时的变形行为,结果表明,该种泡沫SiC具有不同于常见报道中的泡沫陶瓷的形变机制,其应力应变曲线只有弹性变形阶段,原因在于材料整体均匀性高,陶瓷孔筋组织致密且晶粒细小,受力时表现出良好的整体协调性。材料具有优良的热导性能。同时该种材料还可以加工成复杂形状,可适应各种应用需求。     

碳化硅网眼多孔陶瓷的制备

本工作采用有机泡沫浸渍工艺制备了具有相互贯通气孔的碳化硅网眼多孔陶瓷,通过选择合适的流变剂获得了对海绵具有良好涂覆发育性能的浆料,探讨了粘结剂对网眼多孔亿性能的影响,结果表明：硅溶胶是一种比较理想的粘结剂．ＸＲＤ、ＳＥＭ研究了烧结制品的晶相组成及显微结构,同时还对烧结制品的孔筋、气孔率、力党性通行幸有征。本工作在１４５０℃下保温１ｈ获得了气孔率为７５％～８５％、抗弯强度达２．５ＭＰａ以上的碳化硅网     

双马来酰亚胺泡沫的微观形貌与结构控制研究

以偶氮二甲酰胺(AC)为发泡剂制备了改性双马来酰亚胺(BMI)泡沫,用扫描电镜(SEM)对泡沫的微观形貌进行观察,研究泡沫的发泡过程及不同条件下泡沫的泡孔结构,包括密度、孔径、单位体积的泡孔数目、发泡倍率等。结果表明:改性的BMI泡沫是一种闭孔结构泡沫,其构型为排泄型十二面体。可通过发泡体系的黏度、温度和发泡剂含量控制BMI泡沫的结构,随发泡体系黏度的增加,泡沫密度,成核密度N0和单位体积的泡孔数目Nf增加,泡孔直径减小,均匀性变好。泡沫密度随发泡剂AC含量提高而降低,当AC含量超过7%(质量分数)时,泡沫密度反而上升。随发泡温度提高,泡沫密度降低,孔径增大,泡沫成型稳定性变差。     

搅拌摩擦焊制备7075铝合金泡沫夹芯板塑性变形及发泡工艺研究

目的 研究搅拌摩擦焊(FSW)制备泡沫铝夹芯板(AFS)预制坯的成形规律和发泡过程中泡孔的演变规律。方法 采用搅拌摩擦焊工艺制备7075铝合金泡沫夹芯板。利用金相显微镜和扫描电子显微镜对不同焊接参数条件下AFS预制坯组织形貌进行分析，同时，利用单向拉伸和高温杯突试验对不同温度下AFS预制坯的成形性能进行研究，并且针对AFS预制坯发泡性能及不均匀热变形行为对发泡性能的影响进行分析。结果 在焊接转速为2 000 r/min、进给速度为50 mm/min情况下，可获得板粉混合均匀、无明显缺陷的接头;在450 ℃时，搅拌摩擦焊制备的预制体与轧制板材的成形性能相似，真应变达到0.55，伸长率高达73%。450 ℃下杯突试验样品再结晶比例从60.6%增加至82.7%。在680 ℃发泡温度下，保温225 s，能够制备孔径结构均匀、高质量的铝合金泡沫夹芯板。结论 搅拌摩擦焊工艺制备的预制坯经过塑性变形后进行发泡，可以获得具有均匀孔隙结构的泡沫夹芯板弯曲部件。     

有机泡沫法制备多孔羟基磷灰石生物支架

采用有机泡沫法制备了多孔羟基磷灰石(HA)支架,考察了水解预处理工艺、粘结剂聚乙烯醇(PVA)和固相HA的含量对孔隙率的影响,利用扫描电子显微镜(SEM)观察了支架的孔结构.研究结果表明,采用有机泡沫法可获得孔径均匀的多孔HA支架;有机泡沫(海绵)模板经过水解处理后,其挂浆量增加;支架的孔隙率随PVA含量的增加而增大;浆料中固相HA含量在70%左右为宜,此时材料的孔隙率最大.     

煤基炭泡沫孔结构调控

以肥煤镜质组富集物为前驱体,采用高压渗氮法制备煤基炭泡沫,研究了发泡温度、发泡压力和发泡时间对炭泡沫孔结构的影响。利用SEM观察炭泡沫的孔胞形貌,同时利用Nano Measurer分析软件统计SEM照片孔胞直径分布和孔喉直径分布以及平均孔径。结果表明:微孔塑料成核理论可以定性解释炭泡沫的孔结构变化趋势。发泡温度的升高导致成核密度增加,同时导致气体在胶质体的溶解度降低,不利于孔胞长大。发泡压力的增大导致炭泡沫的孔胞密度增加,临界成核半径降低,同时加剧了热聚合反应,导致胶质体的粘度增大,不利于孔胞长大。发泡时间的延长会使热聚合更加充分,影响胶质体粘度,进而影响孔结构。     

中间相沥青基炭泡沫体的制备、结构及性能

以合成中间相萘沥青为原料，采用加压发泡法制备孔径均匀的初生炭泡沫体，经700℃～1000℃和2300℃～2800℃热处理制备出炭化和石墨化炭泡沫体；以700℃炭化处理所得的炭泡沫体作为芯材制成夹芯复合材料。研究了原料性能、发泡以及热处理工艺参数对炭泡沫微观结构和力学性能的影响，考察了炭泡沫体夹芯复合材料的微波吸收性能。结果表明：发泡过程中保持均匀的温度场是制备孔径均匀的炭泡沫体的关键因素，压力是影响孔结构的主要因素。炭泡沫体的微晶结构、力学性能以及微波吸收性能沿xy和XZ面方向（分别表示垂直和平行于重力方向）具有各向异性。     

表面处理对碳化硅泡沫陶瓷挂浆性能的影响

采用有机泡沫浸渍法制备碳化硅泡沫陶瓷时，通过对聚氨脂泡沫进行不同改性剂的表面处理来改善其挂浆性能，利用一种更加合理的表征方法，即测量挂浆后泡沫陶瓷素坯孔筋尺寸和表征孔筋挂浆后形貌来衡量挂浆性能．试验结果表明，在所选用的四种改性剂中，羧甲基纤维素（CMC）的改性作用最好，其次是硅溶胶，而聚乙烯醇（PVA）效果最差．CMC的改性效果主要来源于pH值〉7条件下形成的疏水基团与有机泡沫结合而亲水基团与水基浆料结合的结构，这种结构可以显著改善有机泡沫与水基浆料的润湿性．     

An Innovative Approach fro Improving the Reliability of Reticulated Porous Cermaics

An innovative approach has been developed to fabricate reticulated porous ceramics(RPCs) with uniform macrostruc-ture by using the polymeric sponge as the templates.In this approach,the coating process comprises of two stages.In the first stage,the thicker slurry was used to coat uniformly the sponge substrate.The green body was preheated to produce a reticulated perform with enough handling strength after the sponge was burned out.In the second stage,the thinner slurry was used to coat uniformly the perform .The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process.A few filled cells and cell faces occur in the fabrication and the struts were thickened.A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively.The result shows that the mechanical reliability of RPCs is improved by the innovative approach.This innovative approach is very simple and controlled easily,and will open up new technological applications for RPCs.     

An Innovative Approach for Improving the Reliability of Reticulated Porous Ceramics

An innovative approach has been developed to fabricate reticulated porous ceramics (RPCs) with uniform macrostruc-ture by using the polymeric sponge as the templates. In this approach, the coating process comprises of two stages. In the first stage, the thicker slurry was used to coat: uniformly the sponge substrate. The green body was preheated to produce a reticulated preform with enough handling strength after the sponge was burned out. In the second stage, the thinner slurry was used to coat uniformly the preform. The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process. A few filled cells and cell faces occur in the fabrication and the struts were thickened. A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively. The result shows that the mechanical reliability of RPCs is improved by the innovative approach     

两次离心挂浆工艺制备网眼多孔陶瓷

以具有三维网状结构和贯通气孔的聚氨酯泡沫体为载体,采用两次离心挂浆工艺制备了高气孔率、无堵孔且结构均匀可控的氮化硅网眼多孔陶瓷.借助TG-DSC分析了泡沫体的热分解过程,确定了排胶工艺.借助流变测量和光学显微镜观察了挂浆工艺及浆料粘度对泡沫体挂浆量和多孔结构的影响,并对制品材料的微观结构和性能进行了表征.结果表明,与传统辊压工艺相比,采用两次离心挂浆工艺后,改善了多孔结构的均匀性,显著提高了材料强度,为高强度、结构可控、网眼多孔陶瓷的制备提供了一个有效途径.     

三维连通网络陶瓷电磁参数的改性

以水玻璃为溶胶、以SiO2气溶胶粉末和磁性γ-Fe2O3粉末为填料，通过浸渍挂浆、凝胶、无机化等步骤，对三维连通网络陶瓷的介电常数和磁导率进行了改性．结果表明，填加SiO2气溶胶粉末可以有效降低网络陶瓷的介电常数，控制SiO2气溶胶的填加量可以实现网络陶瓷介电常数的连续可调．填加磁性材料亦可以在一定范围内改变网络陶瓷的磁导率．在水玻璃溶胶浆料中加入不高于10％(质量分数)的SiO2气溶胶粉末，可使网络陶瓷的抗压性能显著提高；SiO2气溶胶粉末的填加量大于10％后，溶胶在网络陶瓷骨架表面及Si02颗粒之间难以形成连续结合而使网络陶瓷的抗压强度下降．     

Macroporous SiOC Ceramics with Dense Struts by Positive Sponge Replication Technique

Highly porous SiOC ceramics (≥90% open porosity) containing dense struts have been prepared following positive sponge replication technique using silsesquioxane based preceramic polymer. The morphological features including cell size, cell window size, and strut size of the macroporous SiOC ceramics have been analyzed using electron microscopy. Subtle variation in the crosslinking condition of the preceramic polymer infiltrated polyurethane template enables the formation of hollow as well as dense struts, which has a profound influence on compressive strength of the macroporous bodies. Synchrotron radiation micro computed tomography is used to construct the three dimensional images of the macroporous ceramics that indicate isotropy of the pores and excellent interconnectivity.

     

Sintering behavior of alumina rich cordierite porous ceramics

Porous ceramics are increasingly becoming important in particulate gas filtration. They are an effective alternative to the honeycombed structure in the case of diesel engines. Porous ceramics are made by infiltrating ceramic slurry into a polymeric sponge followed by drying and heating to burn out the polymeric sponge and obtain a ceramic sponge with large open porosity. In this paper we report optimized drying and sintering conditions for alumina cordierite porous ceramics. The microwave drying time ranging from 5–30 min depending on the power and the amount of loading. The shapes of the object was maintained in most of the structures. The sintering temperature was optimized around 1380°C. These results were analyzed using XRD data and SEM micrographs.     

Bioactive borosilicate glass scaffolds: improvement on the strength of glass-based scaffolds for tissue engineering

Three-dimensional macroporous scaffolds with the pore size of 200-500 mum were fabricated by replication method using bioactive borosilicate glass from Na(2)O-K(2)O-MgO-CaO-SiO(2)-P(2)O(5)-B(2)O(3) system. The effects of the strength of the strut in reticulated scaffold, as well as the geometrical parameter of the scaffold on the strength of reticulated scaffold were investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that the solidified glass struts in the reticulated scaffold could be obtained through a sufficient vicious flow of glass, during the fabrication. By increasing the solid content in slurries, from which the scaffold was made, the load-bearing units of the reticulated scaffold switch from struts to the walls between the pores, and the compressive strength dramatically climbs higher than the theoretical strength calculated by Gibson model. In particular, the compressive strength of the reticulated scaffold, as high as approximately 10 MPa with the porosity of approximately 70%, is close to the reported compressive values of human cancellous bone. This indicates the bioactive borosilicate glass-based scaffold is a promising candidate for bone tissue engineering.