Preparation and properties of low cost porous titanium by using rice husk as hold space

The present study demonstrates an effective low cost effective process for the production of porous titanium with 50-60 vol% porosity using 20 wt% rice husk(RH) with the hold spaces in the size ranges of 100-180,180-250,250-380,and 380-550 μm.The analysis of the samples revealed an interconnected pore microstructure consisting of a mixture of coarse channel pores,created during burnout of RH.The compressive strength of the developed samples was in the range of 17-70 MPa and depended strongly on their porosity and pore size.Large amounts of cleavage steps appeared on the brittle fracture surface after compression of the samples.The 3D morphology of porous titanium surface with rice husk sizes of 100-180μm and 380-550μm can be characterized by the micro-hole surface of pore size,and the size of the hole diameter and husk.The developed porous titanium is considered potentially useful in future medical or industrial application of biomass.     

多孔材料的孔结构对其力学性能及破裂机制的影响

针对多孔材料的孔结构对其宏观力学性能及其破裂机制与耐久性的影响,对两种不同孔结构的多孔材料进行了单轴压缩和冻融循环试验,建立了能反映材料内部孔隙结构的三维非均匀数值模型,对两种多孔材料在单轴压缩下的破裂机制进行了分析.实验结果表明:孔结构对于金尾矿多孔材料的力学性能有显著影响.较大的孔隙率除会显著降低材料的抗压强度外,吸能性能会显著增加;在±25℃范围内冻融循环10次条件下的试验结果表明,当金尾矿多孔材料的孔隙率较小且为闭孔结构时,孔洞因冻融造成的孔壁颗粒脱落填塞而造成材料的抗冻性能有所提高;孔隙率较小时,金尾矿多孔材料在单轴压缩下的裂纹扩展主要从试件两端向试件中部扩展贯通为一条连续主拉裂纹,次生裂纹较少;而孔隙率较大时,压缩过程会出现大量微裂纹,最终主裂纹附近会伴随大量次生裂纹.     

多孔钛植入体表层孔隙内TGF-β1缓释明胶微球涂层的工艺优化

采用正交试验法优化载转化生长因子β1(transforming growth factor-β1,TGF-β1)缓释明胶微球多孔钛植入体制备工艺,探讨多孔钛植入体孔隙内微球涂层的载药、释药特性.采用粉末注射成形(Metal Injection Molding, MIM)技术制备多孔钛植入体,选用明胶为TGF-β1缓释载体材料,乳化冷凝聚合交联法制备明胶微球,检测微球粒径与形貌以及载TGF-β1微球的包封率、载药率,采用渗涂法制备多孔钛表层孔隙内载TGF-β1明胶微球涂层,释放试验检测涂层的释药特性.实验结果表明,MIM技术制备的多孔钛植入体的孔隙度为(62.02±1.82)%,孔径为50～300 μm,抗压缩强度为(63.23±12.81) MPa,弹性模量为(0.95±0.61) GPa.明胶微球粒径随明胶浓度的减小、搅拌速度和交联时间的增加而减小,交联剂用量对微球粒径影响无显著性差异.制备的TGF-β1明胶微球为球形,平均粒径为(21.42±3.67) μm,载药量为(0.91±0.02) μg/g,包封率为(91.41±1.82)%.TGF-β1微球涂层体外14 d,时的TGF-β1释放率为(94.2±3.4)%;粒径为(21.42±3.67) μm的明胶微球的最佳工艺参数如下:明胶浓度为10%,搅拌速度为800 r/min,交联剂用量为0.1 mL,交联时间为2 h.多孔钛植入经5%(质量分数)明胶溶液预处理后用20 g/L微球渗涂可在表层孔隙内形成均匀微球涂层,且不阻塞表层孔隙,微球涂层TGF-β1释放时间为14 d.     

红外焦平面多孔硅绝热层制备及应用

采用电化学法及原电池法制备了多孔硅样品.通过在阳极氧化反应中HF溶液浓度、电流密度和反应时间的不同来控制多孔硅的孔隙率和膜厚.实验结果表明：不同电流密度下制备的多孔硅样品,孔隙度有相同的变化趋势,刚开始增加,然后减少;多孔硅的生长速度随电流密度的增加而升高.在多孔硅样品表面封装BST热释电敏感元件进行性能测试,结果表明...     

利用粉煤灰制备轻质多孔陶粒工艺研究

以粉煤灰为主要原料,高岭土、生石灰和玻璃粉为辅助原料,采用微波发泡法制备了水处理用多孔陶粒.研究了不同配方和不同烧结温度等对陶粒气孔率、强度等性能的影响,得到了制造高气孔率的多孔陶粒的最佳工艺条件.在最佳工艺条件下所制得的多孔陶粒的显气孔率为60%,闭气孔率为10%,抗压强度为9.5 MPa.     

Synthetic CaSiO_3 sol-gel powder and SPS ceramic derivatives: “In vivo” toxicity assessment

The paper presents template strategy using siloxane-acrylate latex and its modified form to prepare nanostructured calcium silicate(wollastonite) containing nanosized gold and regular porosity. Optimal conditions for the annealing of silicate xerogel were outlined leading to nanoporous wollastonite with minimal porous defects(pore size corresponds to latex particles 150–200 nm). The fabrication of nanostructured wollastonite ceramics was suggested to use spark plasma sintering(SPS). The formation of porous ceramic framework(compressive strength ～120 MPa) via SPS consolidation of silicate xerogel(xonotlite) contained latex template(poreformer),a feature of the method for wollastonite template synthesis. The ceramic wollastonite samples have been implanted into ICR/CD1 mice to test the toxicity of the material "in vivo". The results are of great interest for the preparation of high-quality biomaterials for modern medicine using simple technological approaches and available raw materials.     

Porous SiC ceramics fabricated by quick freeze casting and solid state sintering

Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid state sintering.Poly(vinyl alcohol)(PVA) was added as binder and pore morphology controller in this work.The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries.Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics.The solid content of slurries and PVA content varied from 60 to 67.5 wt%and 2-6 wt%,respectively.Besides,the grain morphology of ceramics was also tailored by changing the sintering temperature from 2050 to 2150 ℃.Porous SiC ceramics with an average porosity of 42.72%,flexural strength of 59.28 MPa were obtained at 2150 ℃ from 67.5 wt% slurries with 2 wt% PVA.     

Cryogenic induced phase separation of chitosan solution

The chitosan porous membrane was prepared by extending the principle of thermally induced phase separation (TIPS) for the polymer-diluent system to the polymer solution at arnbient temperature to carry out the cryogenic induced phase separation (CIPS). The porous membrane obtained was characterized by scanning electron microscopy (SEM) and gas permeability. It was found that a specific lacy pore structure morphology corresponding to the TIPS’ solicd-liquid phase separation was formed in the demixing process and the porosity could be more than 70%. The research of demixing mechanism and membrane-formation process showed that the membrane was stacked through porous lamella. The porosity of membrane increases and the pore diameter decreases with increasing solidtfying temperature. Both the porosity and pore diameter decrease with the chitosan concentration increase.     

Cryogenic induced phase separation of chitosan solution——A novel method for preparation of membrane with high porosity

The chitosan porous membrane was prepared by extending the principle of thermally induced phase separation (TIPS) for the polymer-diluent system to the polymer solution at ambient temperature to carry out the cryogenic induced phase separation (CIPS). The porous membrane obtained was characterized by scanning electron microscopy (SEM) and gas permeability. It was found that a specific lacy pore structure morphology corresponding to the TIPS' solid-liquid phase separation was formed in the demixing process and the porosity could be more than 70%. The research of demixing mechanism and membrane-formation process showed that the membrane was stacked through porous lamella. The porosity of membrane increases and the pore diameter decreases with increasing solidifying temperature. Both the porosity and pore diameter decrease with the chitosan concentration increase.     

铝用石墨阴极孔隙结构与石墨化程度关系研究

铝用石墨阴极孔隙结构的常规研究方法难以对不同石墨化程度材料进行快速量化和智能化分析。根据体视学原理在二维空间定义孔隙结构参数,采用图像分析技术对不同类型石墨阴极孔隙结构的孔隙率、孔径、形状因子、孔隙取向及连通率等进行分析表征。结果表明,所用图像分析方法可定量分析石墨阴极材料的孔隙结构特征,并显示其与材料石墨化程度的规律性关系,所获数据有助于评价阴极材料性能和优化阴极制备过程参数。     

孔径及孔隙率对火山岩强度特性影响的模拟

在对火山岩圆球形孔隙结构研究的基础上,运用岩石破裂过程分析系统模拟了火山岩单轴压缩过程,研究了孔径及孔隙率对火山岩岩石变形强度特性的影响.研究结果表明:孔径从0.1 mm增加到0.3 mm,极限应变的降低百分率随着孔隙率的增加保持在一定范围内波动;弹性模量的降低百分率随着孔隙率的增加逐渐增加,并且呈现明显的线性增加趋势.在恒定孔隙率下,孔径对其影响主要表现在随孔径的增大,破坏模式由剪切破坏逐渐向劈裂破坏过渡.     

多孔混凝土排水基层路用性能研究

多孔混凝土作为路面的基层,应具有良好的物理性质和力学性质。文中通过室内试验与理论分析,给出多孔混凝土有效空隙率与全空隙率、渗透系数与空隙率的关系。得出多孔混凝土强度随龄期的发展规律,弯拉强度、劈裂强度与抗压强度的相关关系,抗压强度与空隙率的关系以及2种形式下的双对数疲劳方程;多孔混凝土弯拉弹性模量与弯拉强度,以及抗压弹性模量与轴心抗压强度的关系;多孔混凝土的温缩系数和干缩系数。     

多孔混凝土排水基层路用性能研究

多孔混凝土作为路面的基层，应具有良好的物理性质和力学性质。文中通过室内试验与理论分析，给出多孔混凝土有效空隙率与全空隙率、渗透系数与空隙率的关系。得出多孔混凝土强度随龄期的发展规律，弯拉强度、劈裂强度与抗压强度的相关关系，抗压强度与空隙率的关系以及2种形式下的双对数疲劳方程；多孔混凝土弯拉弹性模量与弯拉强度，以及抗压弹性模量与轴心抗压强度的关系；多孔混凝土的温缩系数和干缩系数。     

炭泡沫中Si含量对碳化硅多孔陶瓷 组织和性能的影响

研究炭泡沫预制体中Si添加量的变化对碳化硅多孔陶瓷的组织及性能的影响. 以中间相沥青添加一定质量分数的Si粉为原料,经发泡工艺制备含Si的炭泡沫预制体并结合反应烧结工艺制得碳化硅多孔陶瓷. 对碳化硅多孔陶瓷的微观形貌、相组成、孔隙率、孔筋密度和抗弯强度进行分析与测试. 结果表明:随着炭泡沫预制体中Si量的增加,碳化硅多孔陶瓷的孔隙率下降,孔筋密度增加,抗弯强度提高. 当Si的质量分数为50%时,多孔陶瓷孔筋完全由SiC相组成,孔筋密度为3.14g/cm3,多孔陶瓷的抗弯强度达到23.9MPa,对应孔隙率为55%.     

Microwave sintering effects on the microstructure and mechanical properties of Ti-51at%Ni shape memory alloys

Ti-51at%Ni shape memory alloys (SMAs) were successfully produced via a powder metallurgy and microwave sintering technique. The influence of sintering parameters on porosity reduction, microstructure, phase transformation temperatures, and mechanical properties were investigated by optical microscopy, field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), compression tests, and microhardness tests. Varying the microwave temperature and holding time was found to strongly affect the density of porosity, presence of precipitates, transformation temperatures, and mechanical properties. The lowest density and smallest pore size were observed in the Ti-51at%Ni samples sintered at 900℃ for 5 min or at 900℃ for 30 min. The predominant martensite phases of β2 and β19' were observed in the microstructure of Ti-51at%Ni, and their existence varied in accordance with the sintering temperature and the holding time. In the DSC thermograms, multi-transformation peaks were observed during heating, whereas a single peak was observed during cooling; these peaks correspond to the presence of the β2, R, and β19' phases. The maximum strength and strain among the Ti-51at%Ni SMAs were 1376 MPa and 29%, respectively, for the sample sintered at 900℃ for 30 min because of this sample's minimal porosity.     

用渗流法制备多孔金属的孔结构及其控制

利用自行研制的填料粒子，采用独特的渗流法制备了多孔金属铝，提出了填料颗粒为球形时多孔金属孔隙率的计算模型，实验证明用此模型预测多孔金属的经是可行的，用该法制备的多孔金属具有理想的孔结构。     

多孔铜合金高温压缩蠕变行为的数值模拟

采用RDL05电子蠕变疲劳试验机,在不同温度（550,600,650,700℃）以及不同应变速率（10-4,10-3,10-2／s）条件下对多孔铜合金进行高温压缩实验,获得多孔铜合金真应力一应变曲线,计算并得到相应温度下的蠕变本构方程．采用ANSYS软件对多孔铜合金进行高温压缩蠕变模拟,研究了孔径、载荷、孔形等因素对多孔铜合金蠕变性能影响．研究结果表明,孔径越大,温度、载荷越高,多孔铜合金蠕变变形越大,蠕变速率更快,蠕变性能越不稳定;在蠕变过程中,内棱孔壁处容易引起应力集中;孔隙形貌对多孔铜合金结构影响很大,随着孔形边数的增加,多孔铜合金结构越不稳定;在相同载荷下,三角形孔压缩量最小,圆形孔压缩量最大．     

Preparation and characterization of porous ceramics prepared by kaolinite gangue and Al(OH)<Subscript>3</Subscript> with double addition of MgCO<Subscript>3</Subscript> and CaCO<Subscript>3</Subscript>

Porous ceramics were prepared from kaolinite gangue and Al(OH)₃ with double addition of MgCO₃ and CaCO₃ by the pore-forming in-situ technique. The characterizations of porous ceramics were investigated by X-ray diffractometry, scanning electron microscopy, and mercury porosimetry measurements, etc. It is found that although the decomposition of MgCO₃ and CaCO₃ has little contribution to the porosity, the double addition of MgCO₃ and CaCO₃ strongly affects the formation of liquid phase, and then changes the phase compositions, pore characterization, and strength. The appropriate mode is the sample containing 1.17wt% MgCO₃ and 1.17wt% CaCO₃, which has high apparent porosity (41.0%), high crushing strength (53.5 MPa), high mullite content (76wt%), and small average pore size (3.24 μm).     

水泥基复合材料氯离子扩散系数与孔隙率之间的关系

为了研究水泥基复合材料中孔隙率对氯离子扩散系数的影响,成型了不同水灰比,含骨料体积分数、粒径与级配不同的砂浆试样;采用稳态电加速法测试氯离子扩散系数、压汞技术测试孔结构参数、微焦点计算机断层扫描技术(X-CT)可视化孔结构分布,系统地研究了水泥基复合材料氯离子扩散系数与其骨料体积分数、总孔隙率、毛细孔隙率、连通孔径之间的关系。结果表明：骨料与基体之间的界面过渡区(界面区)显著地改变了水泥石中孔结构分布,水灰比越小,多孔的界面区对材料孔隙率的影响越显著;水泥基复合材料的氯离子扩散系数与其总孔隙、毛细孔隙率之间有很好的相关性,与其连通孔径几乎成线性关系,连通孔径越大,氯离子的扩散系数越大。     

氧化锆基NOx传感器扩散障研究

以Al2O3为主要原料,添加适量ZrO2和储氧剂,以超细炭粉作造孔剂,制备氧化锆基NOx传感器的多孔扩散障,对其附着状态、孔隙率、形貌和测试信号等进行分析。结果表明,随着扩散障造孔剂含量的增加,扩散障与基体附着下降,孔隙率增加;造孔剂含量为15%时,扩散障与基体附着良好,孔隙分布均匀,其传感器的测量泵对NO呈现出良好的极限电流趋势,测试灵敏度和精度高。