组织工程多孔支架材料和制备方法

制备组织工程多孔支架的材料有3大类天然材料、生物陶瓷、合成高分子材料。介绍了其中的一些常用物质,并以聚合物材料的应用为主介绍了含聚合物材料的多孔支架的制备方法纤维粘接法、静电纺丝法、相分离法、气体发泡法、溶液浇注-沥滤法、固体自由成型法、颗粒烧结法。     

Fabrication of Highly Porous Chromium Carbide with Multiple Pore Structure

A unique process, which consists of camphene‐based freeze‐casting and reactive sintering, has been developed to fabricate highly porous Cr₃C₂ ceramics, which were featured with a well‐defined multisize porous structure, consisting of large pore channels throughout the sample and small pores on the porous struts. The porous structure was found to be affected by the solid loading content and the casting temperature. Decreasing the solid loading content or increasing the freezing temperature increased the size of large pore channels. However, the size of small pore was not significantly influenced by the variation in the freeze‐casting parameters. Compared with other techniques reported for the fabrication of porous ceramics, high porosity can easily be achieved by this method. The sintering mechanism of the formation of the porous structure was also discussed in this study.     

Fabrication of Porous Nanocrystalline TiO2 Materials by SPS

A dense microcellular ceramic structure is fabricated using micron-sized Al₉₀Mn₉Ce₁ alloy powder clad with 8 wt% TiO₂ nanopowder by filling the ceramic with the Al₉₀Mn₉Ce₁ metal alloy composite and subjecting the mixture to a temperature of 520 °C. SEM imaging shows that the thickness of the ceramic cell wall is 1.0–2.0 μm; and, the inner dimension of the alloy is 15–40 μm. The ceramic filled with the metal alloy composite is subjected to deep corrosion with 10% hydrochloric acid solution; and, a porous nanocrystalline TiO₂ structure is obtained. Results show that this novel preparation procedure provides a pathway with which to produce porous nano-materials for a wide range of applications. Based on the experimental results, a transient interface sintering mechanism of the spark plasma sintering (SPS) nano/micro mixing powder is proposed.     

Porous Mullite Preforms via Fused Deposition

Nonrandom porous mullite ceramic preforms were fabricated by the indirect fused deposition process. MgO was added to commercial mullite powders as a sintering aid. The influence of porosity and the amount of MgO on the densification and mechanical properties was studied. The shrinkage and compressive strength of the porous samples were found to increase with increasing MgO content. At constant MgO concentration, shrinkage was found to decrease linearly as the volume fraction of porosity increased. The compressive strength of porous samples decreased with an increase in the volume fraction of porosity at constant MgO content.     

Preparation of Highly Pure Fine Mullite Powder

The preparation of high-purity mullite powders (3Al₂O₃· 2SiO₂) was examined using aluminum salts or boehmite and fumed silica. The combination of aluminum sulfate and fumed silica was found to have the highest quality for mullite powder. A slurry consisting of an aqueous solution of aluminum sulfate and fumed silica was dried and heated at 1350°C and was attrition-milled for 2 h. The mullite powder obtained was composed of submicrometer, uniform, and equiaxial particles with narrow size distribution. It was hot-pressed at 1600°C for 1 h under 10 MPa or was sintered at 1650°C for 3 h. The bulk densities of the products made by both processes were 3.16 and 3.09 g/cm³.     

Fabrication of Highly Porous Alumina Prepared by Gelation Freezing Route with Antifreeze Protein

Macroporous alumina ceramic monolith was fabricated by the novel gelation freezing method with antifreeze protein (AFP). The gelation freezing route with AFP is a simple and efficient way to produce macrocellular ceramics with tailored and uniform pore architecture as well as high porosity.     

颗粒涂层法制备莫来石瓷的研究

把吸附水分的α-Al_2O_3湿粉分散到含表面活性剂硬脂胺、Span-60的80Vol％环已烷-20Vol％正硅酸乙脂(TEOS)疏水溶剂中,经长时间的密封搅拌处理,制得了α-Al_2O_3颗粒表面有无定形SiO_2涂层的复合粉料。用透射电镜观察和ζ-电位测量相结合的方法证明在α-Al_2O_3颗粒表面得到了SiO_2涂层。对复合粉料进行了热分析和物相分析。复合粉料成型后,研究了坯体的烧结过程和烧结中的物相变化情况。试样在1600℃烧结得到接近致密、晶粒尺寸均匀、细小的莫来石瓷。根据实验现象对颗粒涂层过程和坯体的致密化过程进行了详细探讨。     

Fabrication and Properties of Low-Shrinkage Reaction-Bonded Mullite

Mullite ceramics were fabricated according to the recently developed reaction-bonded Al₂O₃ (RBAO) technology. Green compacts consisting of mechanically alloyed Al, SiC, and Al₂O₃ were heat-treated in two steps. During the first hold at 1200°C, Al and SiC were oxidized to form Al₂O₃ and SiO₂. On further heating, mullite was formed which then sintered during the second hold at 1550°C. All reactions involved in the process were associated with volume expansions that almost compensated for the shrinkage on sintering. Processing details and microstructure development are discussed. Reaction-bonded mullite ceramics exhibit high fracture strength, e.g., 290 MPa at a density of 97% of theoretical density.     

多孔陶瓷的制备及应用

根据成孔原理，多孔陶瓷成型工艺可分为七大类，对各种工艺进行了简要论述结合作者的工作对有机泡沫体浸渍工艺中的关键技术进行了较详细的探讨，并简要描述了两次离心挂浆工艺的过程及实验结果。最后，展望了多孔陶瓷的应用前景及尚待解决的问题。     

Fabrication of Highly Porous Silica Thermal Insulators Prepared by Gelation–Freezing Route

Highly porous silica thermal insulators were produced by gelation of a gelatin solution with dispersed silica particles, followed by freeze‐drying and heating at 800°C. The relationship between the ice‐template morphology and the parameters involved in gelation freezing was investigated, in addition to the effect of the microstructure on the thermal conductivity of the silica insulators. The porosity and thermal conductivity of the insulators ranged from 88 to 98 vol% and from 0.168 to 0.054 W (m·K)^?1, respectively, both of which could be controlled by changing the silica content in the gel stage. Gelation–freezing route was proved to be a feasible and promising route for the production of very highly porous, machinable insulators.     

Fabrication of Mullite Body Using Superplastic Transient Phase

Mullite, an extremely creep-resistant ceramic, has been fabricated using a novel processing/forming approach taking advantage of superplastic transitional phases. Starting with a mixture of alumina, silica, and a small amount of lithia additive (0.8 wt%), a processing window of about 50°C around 1350°C has been found within which the material can be densified and superplastically deformed with negligible mullitization. The lithia additive promotes a transient lithium aluminosilicate glassy phase that greatly enhances sintering and deformation. The superplastic premullite maintains a nearly constant grain size during deformation between 1250° and 1400°C, over a strain rate from 6 × 10⁻⁷ to 10⁻¹ s⁻¹, and has unusually high activation energy values in the range of 1150 to 2086 kJ/mol. An increase in the transient glassy phase content due to the increased matrix dissolution at higher temperatures contributes in part to this anomaly. The mullite work pieces thus shaped become creep resistant again after a postforming annealing/mullitization treatment which decreases the creep rate by 6 orders of magnitude. The mechanical properties (hardness, toughness, and strength) of the finished mullite are compared to those of conventionally processed mullite.     

Fabrication of Highly Porous Yttria-Stabilized Zirconia by Acid Leaching Nickel from a Nickel-Yttria-Stabilized Zirconia Cermet

Porous Y₂O₃-stabilized ZrO₂ (YSZ) samples were synthesized by preparing NiO/YSZ composites by tape casting and calcining at 1800 K, reducing the NiO to nickel in H₂ at 973 K, and finally leaching the nickel out of the structure with 2.2 M HNO₃ at 353 K. Porous YSZ was prepared from NiO/YSZ composites containing 0, 20, 40, and 50 wt% NiO. Complete removal of the nickel was demonstrated by XRD, weight changes, and porosity increases. Porosities >75% could be achieved without structural collapse of the YSZ phase. Finally, the method was applied to the fabrication of a solid oxide fuel cell with a copper-based anode operating on H₂ and n -butane.     

多孔莫来石陶瓷的近净尺寸制备及性能

以蓝晶石和Al₂O₃粉体为原料、PMMA微球为造孔剂、Isobam104为分散胶凝剂,结合凝胶注模工艺与造孔剂法,实现了收缩率可控的多孔莫来石陶瓷的近净尺寸制备。研究了烧结温度对相组成的影响以及固相含量对样品微观结构、相组成、收缩率、气孔率及抗压强度的影响。结果表明：随着固相含量的增加,样品在1 500℃烧结后收缩率先减小后增大,在固相含量为30%（体积分数）、造孔剂含量为30%（质量分数）时,样品的总收缩率接近于0,实现了多孔莫来石陶瓷的近净尺寸制备。多孔莫来石陶瓷呈现出较高的气孔率（60.4%）、较小的平均气孔尺寸（3.75μm）和较高的抗压强度（8.3 MPa）。利用制备过程中的体积膨胀效应,可以有效地控制多孔陶瓷制备过程中的收缩率,实现了多孔莫来石陶瓷的近净尺寸制备,对制备大尺寸复杂形状多孔陶瓷部件、降低加工成本具有重要参考价值。     

Fabrication of Highly Porous Samaria-Doped Ceria by Acid Leaching Magnesia from Magnesia–Samaria-Doped Ceria Ceramics

Highly porous Ce_0.8Sm_0.2O_1.9 (CSO) was prepared by acid leaching MgO from CSO–MgO (CSM) ceramics with acetic acid solution. The effects of leaching conditions and MgO content were studied. Using 60 vol% acetic acid at 85°C for 8.5 h, the MgO in CSM ceramics was effectively leached out but no CSO was dissolved; thus highly porous CSO with an open porosity of 68% was successfully prepared. The open porosity of sufficiently leached pellet increased with the MgO content, but when the vol% of MgO exceeded 60%, the flexural strength of the leached pellets decreased from 25 to 1 MPa. The leaching approach allows the fabrication of porous CSO with the vol% of MgO up to 60%.     

自生晶须强韧化莫来石材料的研究

采用溶胶－凝胶法制备Al2O3-SiO粉料,并通过二步加热处理工艺制备自生晶须莫来石材料。研究结果表明,凝胶胶化时间、干凝胶预烧温度和粉料粒度以及生坯密度对自生晶须有重要影响,自生晶须对莫来石材料有明显的强韧化作用。     

高初始含湿多孔介质喷雾干燥过程的热质耦合传递

多孔介质是大量干燥过程的主体,由于实际多孔介质干燥过程的复杂性,建立通用的干燥过程传热传质模型十分困难。通过分析喷雾干燥过程中高初始含湿多孔介质与干燥介质之间的传热传质机理以及各因素对传热传质的影响,根据马歇尔方程探讨了干燥介质与料雾之间的水蒸汽分压差在干燥过程中的变化情况,反映了多孔湿介质在喷雾干燥操作中的传热传质过程的几种特性,为确定实际生产中喷雾干燥器的操作条件指明了新的出路。     

Fabrication of a Highly Porous Bioactive Glass–Ceramic Scaffold with a High Surface Area and Strength

A bioactive glass–ceramic scaffold was fabricated, in which two interlaced three-dimensional (3-D) glass–ceramic walls could serve as active surfaces for the formation of a bond to bone. For its fabrication, a 3-D graphite network acting as a template was prepared using the rapid prototyping method, and then uniformly dip coated with a melt-derived glass slurry. The resultant sample was heat treated at 900° or 1000°C for 5 h to remove the graphite network and densify the glass–ceramic walls. The fabricated sample exhibited an ultra-high porosity (∼95%), high compressive strength (0.2±0.03 MPa), as well as a tightly controlled pore structure. In addition, this sample had a high surface area owing to its unique structure, which was expected to enhance the rate of bone growth.