蛋白发泡法制备泡沫陶瓷固化工艺研究

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殷刘彦, 周新贵, 余金山, 赵爽, 罗征, 杨备. 蛋白发泡法制备泡沫陶瓷固化工艺研究. 无机材料学报, 2012, 27(12): 1331-1335
YIN Liu-Yan, ZHOU Xin-Gui, YU Jin-Shan, ZHAO Shuang, LUO Zheng, YANG Bei. Study on the Consolidation Process of Protein Foaming in the Preparation of Ceramic Foams. Journal of Inorganic Materials, 2012, 27(12): 1331-1335 复制到剪切板

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蛋白发泡法制备泡沫陶瓷固化工艺研究

殷刘彦, 周新贵, 余金山, 赵爽, 罗征, 杨备

国防科学技术大学新型陶瓷纤维及其复合材料重点实验室, 长沙 410073

周新贵, 教授. E-mail:zhouxinguilmy@163.com

殷刘彦(1989-), 男, 硕士研究生. E-mail:hanqing421720@sina.com

基金:国家自然科学基金(E020301);

摘要

选用蛋清蛋白作为发泡剂, 采用蛋白发泡法制备了高孔隙率的泡沫氮化硅陶瓷. 设计了三种不同固化工艺: 常压固化、恒压固化和高压固化, 固化气压依次升高, 研究了固化气压对泡沫陶瓷开孔率、孔隙形貌和孔径分布的影响. 其中, 恒压固化制品的平均孔径和开孔率最高, 分别为210 μm和78.6%, 且孔径分布比较均匀, 常压固化次之, 高压固化制品开孔率和平均孔径最低. 常压和恒压固化制品为椭球形孔洞, 有一定的排列取向, 而高压固化制品多为规则的球形孔. 随着固化气压的升高, 制品孔壁厚度增加, 高压固化制品的孔壁厚度最高, 其压缩强度接近50 MPa.

关键词: 蛋白发泡; 泡沫陶瓷; 氮化硅; 固化工艺

中图分类号:TB332 文献标志码:A 文章编号:1000-324X(2012)12-1331-05

Study on the Consolidation Process of Protein Foaming in the Preparation of Ceramic Foams

YIN Liu-Yan, ZHOU Xin-Gui, YU Jin-Shan, ZHAO Shuang, LUO Zheng, YANG Bei

National Key Laboratory of Science and Technology on Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073, China

Fund:National Natural Science Foundation of China (E020301);

Abstract

High porosity Si₃N₄ ceramic foams were fabricated by protein foaming method using egg white protein as foam agents. Atmosphere-, constant- and high-pressure consolidation processes were tested to prepare ceramic foams. The effects of air pressure on cellular structure, open porosity and pore size distribution of the as-prepared ceramic foams were investigated. The results showed that ceramic foams with average pore size and porosity of 210 μm and 78.6% was obtained by constant-pressure consolidation, which are the highest values among all the three groups. Moreover, SEM reveals that ceramic foams with uniformly ellipsoidal pores are produced by atmosphere- and constant-pressure consolidation processes, while ceramic foams with regular sphere pores are produced by high-pressure consolidation. The walls’ thickness of the pores increase with the increase of air pressure during consolidation process. As a result, the high-pressure consolidation process yields the highest compressive strength (nearly 50 MPa) of ceramic foams.

Keyword: protein foaming; ceramic foams; Si₃N₄; consolidation

Show Figures

泡沫陶瓷由于具有低密度、低热导、比表面积大、耐高温、耐腐蚀等优点而被广泛用于污水净化, 熔融金属过滤, 催化剂载体, 生物功能材料, 隔音吸声以及隔热材料等领域^{[ 1, 2, 3, 4, 5, 6]}. 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[ 7, 8, 9, 10, 11]}、泡沫碳化硅^{[ 12]}、泡沫氮化硅^{[ 13]}等. 氮化硅因具有优异的力学性能, 良好的热震性能和耐高温性能^{[ 14, 15]}等而受到了广大研究者的重视.

目前常用的泡沫陶瓷制备方法^{[ 16]}主要有添加造孔剂法、有机泡沫浸渍法和发泡法. 添加造孔剂法可以通过控制造孔剂的添加量和粒径进而控制泡沫陶瓷孔隙率和孔径, 但制备三维连通的高孔隙率泡沫陶瓷工艺难度较大. 有机泡沫浸渍法能制备出孔隙率较高且为开孔的泡沫陶瓷, 但是制品的力学性能较差限制了其应用. 利用生物高分子如蛋白质、淀粉等发泡^{[ 7, 9, 10, 11]}, 不仅可以制备出力学性能优异的高孔隙率泡沫陶瓷, 而且还可以通过控制发泡和固化工艺进而调控泡沫陶瓷的孔隙率和孔径分布.

蛋白质是一种生物高分子材料, 在水溶液中表现出表面活性剂的一些特殊性质, 能吸附在气-液表面提高气泡在水溶液中稳定性从而获得泡沫浆料; 当泡沫浆料受热或者pH发生变化时, 蛋白质会发生不可逆变性, 形成三维网络, 从而固定泡沫浆料的孔隙结构^{[ 17, 18, 19]}. 蛋白发泡所使用的原料无毒、来源广泛、成本低且对环境的污染小, 是一种理想的泡沫陶瓷制备方法. 泡沫浆料固化工序是蛋白发泡制备泡沫陶瓷整个工艺中最关键部分, 它直接决定了坯体的成型性和制品的孔隙结构. 国外大量理论研究表明, 固化过程中气泡内外的气压差是气泡生长的主要驱动力, 控制着制品的孔隙结构^{[ 20, 21]}. 然而由于泡沫浆料的不稳定性, 外界气压会导致浆料中气泡的大小以及含量的变化, 使得制备工艺难度较大, 从而导致与此相关的具体实验研究较少. 本研究在充分理解蛋白质发泡固化原理的基础上, 模仿压力锅原理设计了一种特制模具, 泡沫浆料在模具中固化时, 可以通过调节模具上气压控制阀门达到控制泡沫浆料固化气压的目的, 并在此基础上研究了固化气压对制品孔隙率、孔径分布以及孔洞形貌的影响.

1 实验过程

1.1 原料

实验所用蛋白质粉是由吉林金翼蛋品有限公司提供的蛋清蛋白质粉, 主要成分为去除鸡蛋蛋清中水分和糖类的产物. 所用的氮化硅粉为富当特种耐火材料有限公司生产(平均粒径约为0.7 μm, α-Si₃N₄>92%), 烧结助剂为CeO₂(国药集团化学试剂有限公司, 纯度>99.99%)和Al₂O₃(国药集团化学试剂有限公司, 纯度>99.0%). 分散剂为罗门哈斯公司生产的DURAMAX-D3005 陶瓷浆料分散剂.

1.2 泡沫陶瓷的制备

在Si₃N₄粉中加入6wt%的CeO₂和2wt%的Al₂O₃混合于去离子水中, 加入适量的罗门哈斯公司产的DURAMAX-D3005分散剂调节浆料粘度. 固相含量控制在40vol%, 分散剂的量控制在浆料总质量的0.6wt%. 常温下以100 r/min的速度球磨浆料20~24 h后加入8wt%(相对于浆料总质量)的蛋白质粉, 蛋白质粉加入后以100 r/min的速度球磨2 h得到泡沫浆料. 将获得的泡沫浆料注入特制模具中后放置于恒温水浴中, 随水浴一起升温到80℃, 并保温1 h, 固化后的泡沫浆料随水浴炉冷却至室温. 随后在空气中静置24 h后脱模, 并在烘箱中60℃烘干. 烘干后的坯体经低温烧除蛋白, 在N₂保护下常压烧结成陶瓷, 烧结过程中炉内最大气压为 0.067 MPa. 具体烧结工艺如下: 60 min由室温升至1450℃, 保温1 h后利用30 min的时间升温至 1700℃并保温1 h.

1.3 测试表征

采用美国TA SDT Q600热重分析仪分析蛋清蛋白的DSC-TGA曲线, 并根据实验结果确定蛋白质的烧除温度. 采用上海精晖仪器设备有限公司产的NDJ-1旋转式粘度计测量浆料粘度. 采用日本JEOM产JSM-6700F型扫描电镜观察泡沫陶瓷的孔隙结构, 并结合图象分析软件获得试样孔孔径分布. 采用阿基米德排水法测量泡沫Si₃N₄陶瓷制品的孔隙率以及密度. 采用长春万能试验机厂产的WDW-100多传感电子万能试验机测试制品压缩强度. 用于压缩强度测试的试样尺寸为10 mm× 10 mm×10 mm, 加载速率为0.5 mm/min. 每组测试3~4个试样并取平均值.

2 结果与讨论

2.1 泡沫浆料固化工艺研究

泡沫陶瓷的孔隙结构很大程度上取决于泡沫浆料的固化成型工艺, 而泡沫浆料固化是一个非常复杂的过程, 这个过程中不仅有蛋白质的变性和空间网络骨架的形成, 还伴随着其气泡的长大和合并. 泡沫浆料中气泡生长过程中主要受到气泡内外的气体压力, 气泡表面张力以及浆料粘度的影响^{[ 22]}. 其中, 气泡内外的压力差是气泡生长的主要驱动力, 而浆料的粘度则阻碍着气泡长大. 制备出的陶瓷浆料粘度较低, 旋转式粘度计转速为60 r/min时, 浆料粘度为660 mPa·s.

图1为实验中用到的泡沫浆料固化模具原理示意图. 固化过程中, 模具内部气体压力主要利用模具顶部气嘴调节. 固化过程中当模具内气体压力超过一定值时, 模具顶部气嘴被顶开; 小于此临界值时, 气嘴在闭合, 从而保持模具内部气压恒定. 高压固化时, 气嘴一直保持密封, 模具内部气体压力随着固化温度升高而升高. 实验过程中, 泡沫浆料起始温度为室温20℃, 固化温度为80℃. 恒压固化时, 起始阶段随着温度升高模具内气压升高, 约在37℃时达到最大值, 此时气体压力理论计算值约为104.00 kPa, 随着温度的进一步升高模具内气压保持不变. 高压固化时模具内气压随着固化温度的升高而增加. 忽略固化过程中泡沫浆料内气泡体积以及气泡内部气体压力的变化, 当温度达到80℃时, 模具内气压最高, 理论计算值约为122.07 kPa.

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	图1 泡沫浆料固化模具原理示意图Fig. 1 Sketch map of the model designed for slurry foam consolidation under the condition of atmosphere-pressure (left) or constant-pressure when heated (right)

2.2 蛋白质烧除工艺制定

图2为空气中蛋白质DSC-TGA曲线. 当温度超过200℃时, 蛋白质出现明显失重, 随着温度的升高蛋白质的重量保留率急剧减少. 温度超过520℃时, 蛋白质的重量保留率小于2%, 随着温度的进一步升高, 蛋白质的重量保留率基本不再变化, 说明蛋白质已经完全烧除. 为了充分除去坯体中的蛋白质, 减小残余碳等对Si₃N₄烧结过程的不利影响,我们将蛋白质的烧除温度定在600℃, 并在600℃保温1 h. 同时, 为了防止泡沫坯体在蛋白质烧除过程中的开裂, 将升温速率控制在1 ℃/min.

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	图2 空气中蛋清蛋白的DSC-TGA曲线Fig. 2 DSC-TGA curve of egg white protein in air

2.3 制品性能表征

三种不同固化工艺制备出的泡沫陶瓷开孔率、相对密度以及平均孔径等参数如表1所示. 三种固化工艺得到的制品均具有较高的开孔率和较低密度, 其中恒压固化制备的制品开孔率达到78.6%, 密度为0.69 g/cm³, 平均孔径达到了210 μm, 明显高于其它两种固化工艺. 制品的压缩强度随着固化过程中气体压力的升高而升高, 其中高压固化制备出的泡沫氮化硅陶瓷压缩强度最高接近50 MPa.

表1 不同固化方式制备出的泡沫陶瓷开孔率、平均孔径和密度 Table 1 Open porosity, average pore size, density and compressive strength of Si₃N₄ ceramic foams

三种不同固化工艺制备出的泡沫陶瓷孔径分布(如图3所示). 常压固化得到的泡沫陶瓷孔径主要集中在120~260 μm之间, 而恒压固化制备出的泡沫陶瓷孔径主要集中在140~240 μm之间, 但孔径分布更加均匀. 泡沫浆料固化小气泡生长过程中需要克服的比表面张力大于大气泡, 即小气泡生长过程中对驱动力的依赖程度高于大气泡. 常压固化时, 由于外界气压相对较低, 驱动力较大, 因而小气泡和大气泡都能较好的生长, 导致制品中直径较小和较大的气泡都相对较多. 而与常压固化相比, 恒压固化时泡沫浆料中一部分直径较小的气泡可能会因为驱动力的减小而不能生长, 生长过程中还可能被大气泡吞并, 只有孔径较大的气泡才能长大, 最终导致孔径分布比较均匀. 高压固化制品的孔径分布规律与其它两种工艺制品差别较大, 其孔径主要集中在100~180 μm左右. 这是因为高压固化时, 泡沫浆料中的气泡生长的驱动力较小, 泡沫浆料固化过程中较大的气泡外界压力甚至成为气泡长大的阻力, 气泡生长受阻, 从而导致制品的孔径较小.

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	图3 三种不同工艺制备出的泡沫陶瓷孔径分布Fig 3 Pore size distribution of samples fabricated by three different consolidation processes

三种不同固化方式制备出的泡沫陶瓷的孔隙形貌如图4所示. 常压和恒压固化制备出的泡沫陶瓷孔洞呈椭球形, 有明显的取向. 这主要因为泡沫浆料在模具中固化时, 由于受到模具的限制, 浆料只能沿着模具轴向膨胀, 最终可能会导致气泡的取向排列; 而高压固化时, 这可能是由于泡沫沿各个方向膨胀都比较困难, 气泡不能充分生长, 甚至在固化过程中消失, 孔洞彼此之间被致密基体分开. 最终导致制品孔径较小且为规则的球形. 恒压固化制备出的泡沫陶瓷孔壁上缺陷明显少于常压固化制品. 产生这种现象的原因可能是: 常压固化时, 气泡内外气压差相对较大, 生长驱动力大, 气泡生长迅速, 导致部分气泡生长过程中可能开裂^{[ 23]}, 因而制品孔壁缺陷较多. 而高压固化制品孔洞彼此之间被致密基体隔开, 孔壁上缺陷较少.

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	图4 不同固化方式制备的泡沫Si₃N₄陶瓷形貌Fig. 4 Pore structure of Si₃N₄foams prepered by different consolidation processes(a) Atmosphere-pressure; (b) Constant-pressure; (c) High-pressure

对于泡沫陶瓷而言, 除孔隙率外, 其孔壁厚度也是决定其力学性能的重要指标之一. 如图5所示为三种不同固化工艺制备出的泡沫陶瓷孔壁形貌, 可以看出随着固化气压的升高, 泡沫陶瓷孔壁厚度逐渐增加. 如图5(c), 高压固化制备出的泡沫陶瓷孔壁较厚在30~40 μm之间, 明显大于常压固化和恒压固化, 这可能是制品的压缩强度较高的原因.常压固化制品孔壁厚度和孔隙率与恒压固化制品接近, 但是其压缩强度明显偏低, 这可能是因为其孔壁具有较多的缺陷所致.

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	图5 不同固化方式制备的泡沫Si₃N₄陶瓷孔壁形貌Fig. 5 Wall structure of Si₃N₄ foams prepared by different consolidation processes(a) Atmosphere-pressure; (b) Constant-pressure; (c)High-pressure

3 结论

1) 采用蛋白发泡法制备了Si₃N₄泡沫陶瓷, 其蛋白质烧除温度为600℃, 升温速率为1 ℃/min.

2) 借鉴压力锅原理, 所设计的模具用于泡沫浆料的固化, 其固化气压大小可调. 研究发现制品的孔径和开孔率并不随着固化气压的升高而单调降低, 其中恒压固化所制样品开孔率和孔径都明显高于其它两种固化工艺, 分别为78.6%和210 μm, 且孔径分布比较均匀. 常压和恒压固化制品的孔洞呈椭圆形, 而高压固化制品的孔洞为规则的球形.

3) 随着固化气压的升高, 泡沫陶瓷孔壁厚度增加, 其中高压固化制品的孔壁厚度最大, 约为30~40 μm, 制品的压缩强度接近50 MPa.

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[11]	He X, Su B, Zhou X G, et al. Gelcasting of alumina ceramic using an egg white protein binder system. Ceram. Silik. , 2011, 55(1): 1-7. [本文引用:2]
[12]	Fitzgerald T J, Michaud V J, Mortensen A. Processing of microcellular SiC foams. J. Mater. Sci. , 1995, 30(4): 1037-1045. [本文引用:1] [JCR: 2.163]
[13]	Yu J L, Yang J L, Li H X, et al. Study on particle-stabilized Si₃N₄ ceramic foams. J. Mater. Lett. , 2011, 65(12): 1801-1804. [本文引用:1] [JCR: 0.711]
[14]	Shao Y F, Jia D C, Liu B Y. Characterization of porous silicon nitride ceramics by pressureless sintering using ﬂy ash cenosphere as a pore-forming agent. J. Eur. Ceram. Soc. , 2009, 29(8): 1529-1534. [本文引用:1] [JCR: 2.36]
[15]	Riley F L. Silicon nitride and related materials. J. Am. Ceram. Soc. , 2000, 83(2): 245-265. [本文引用:1] [JCR: 2.107]
[16]	Studart A, Urs T, Gonzenbach E T, et al. Processing routes to macroporous ceramics: a review. J. Am. Ceram. Soc. , 2006, 89(6): 1771-1789. [本文引用:1] [JCR: 2.107]
[17]	Garrn I, Reetz C, Brand es N, et al. Clot-forming: the use of proteins as binders for producing ceramic foams. J. Eur. Ceram. Soc. , 2004, 24(3): 579-587. [本文引用:1] [JCR: 2.36]
[18]	Berthold A, Schubert H, Brand es N, et al. Behaviour of BSA and of BSA-derivatives at the air/water interface. J. Coll. Sur. A, 2007, 301(1/2): 16-22. [本文引用:1]
[19]	Bhattacharjee S, Besra L, Singh B P. Effect of additives on the micro- structure of porous alumina. J. Eur. Ceram. Soc. , 2007, 27(1): 47-52. [本文引用:1] [JCR: 2.36]
[20]	Arefmanesh A, Advani S G. Diffusion induced growth of a gas bubble in a viscoeleastic fluid. J. Rheol. Acta, 1991, 30(3): 274-283. [本文引用:1]
[21]	Fan J T, Mitchell J R, Blanshard J M V. A model for the oven rise of dough during baking. J. Food Eng. , 1999, 41(2): 69-77. [本文引用:1] [JCR: 0.558]
[22]	Santanu D, Parag B. Inﬂuence of slurry characteristics on porosity and mechanical properties of alumina foams. J. Appl. Ceram. Techno. , 2006, 3(5): 382-392. [本文引用:1]
[23]	Gan Z, Ellis P R, Schofield J D. Gas cell stabilization and gas retention in wheat bread dough. J. Cereal Sci. , 1995, 21(3): 215-230. [本文引用:1] [JCR: 2.088]

1988

2.36

0.0

... 泡沫陶瓷由于具有低密度、低热导、比表面积大、耐高温、耐腐蚀等优点而被广泛用于污水净化, 熔融金属过滤, 催化剂载体, 生物功能材料, 隔音吸声以及隔热材料等领域^{[1,2,3,4,5,6]} ...

2012

2.224

0.0

2012

1.789

0.0

2006

1.348

0.0

J. Porous. Mat.. 2006, 13(2):115-121 DOI:10.1007/s10934-006-7006-9

Preparation of phenolic resin derived 3-D ordered macroporous carbon

1.National University of Defense Technology Key Lab of Ceramic Fiber and Composites Changsha 410073 People’s Republic of China Changsha 410073 People’s Republic of China<br/>2.Chungnam National University Department of Fine Chemical Engineering and Chemistry Daejeon 305-764 South Korea Daejeon 305-764 South Korea<br/>

Three-dimensionally ordered long-range macroporous carbon structures were prepared using commercially available phenolic resin by utilizing sacrificial colloidal silica crystalline arrays as templates that were subsequently removed by HF etching after pyrolysis in an argon atmosphere. SEM, TEM, and BET were employed to characterize the morphology and the surface area of the porous carbon structures. The pore size (150–1000 nm) and BET surface area, which reflect pore volume (298.6 m²/g (1.32 cm³/g) ∼ 93.7 m²/g (0.12 cm³/g)), of the macroporous carbon structures produced were approximately proportional to the size (150–1000 nm) of the sacrificial silica sphere templates used (annealing temp. 550°C). The achieved 550 nm porous carbon structures were examined to function as potential catalyst carriers and were successfully impregnated with Ag or Pt-Ru on their inner walls after borohydride reduction at room temperature. In addition, porous carbon patterns were fabricated using the ‘micromolding in capillary’ technique, which has potential applications in the microreaction technology.

1997

2.107

0.0

2006

2.107

0.0

2009

2.224

0.0

... 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[7,8,9,10,11]}、泡沫碳化硅^[12]、泡沫氮化硅^[13]等 ...

... 利用生物高分子如蛋白质、淀粉等发泡^[7,9,10,11], 不仅可以制备出力学性能优异的高孔隙率泡沫陶瓷, 而且还可以通过控制发泡和固化工艺进而调控泡沫陶瓷的孔隙率和孔径分布 ...

2000

2.36

0.0

... 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[7,8,9,10,11]}、泡沫碳化硅^[12]、泡沫氮化硅^[13]等 ...

2009

2.143

0.0

Compos. Part B. 2009, 40(7):638-644 DOI:10.1016/j.compositesb.2009.04.016

Natural additives in protein coagulation casting process for improved microstructural controllability of cellular ceramics

Abstract

Aiming to improve the microstructural controllability of porous ceramic, starch was introduced as a natural additive into an environmental friendly process-protein coagulation casting. Results indicated that the viscosity of alumina/starch slurries was affected by the combined effect of the total solid loading and the water uptake of starch. Furthermore, as pore former and wet foam stabilizer, starch helped to increase the open porosity and obtain a more uniform distribution of microstructures in the fabricated alumina foams. A better microstructural controllability of the alumina foam prepared by the modified protein coagulation casting process was realised which is believed to be beneficial to the multifunctional application of these ceramic foams.

... 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[7,8,9,10,11]}、泡沫碳化硅^[12]、泡沫氮化硅^[13]等 ...

2010

2.36

0.0

J. Eur. Ceram. Soc.. 2010, 30(14):2871-2880 DOI:10.1016/j.jeurceramsoc.2010.03.020

Porous alumina ceramics prepared with wheat flour

Abstract

It is shown that wheat flour can be used as a pore-forming and body-forming agent in ceramic technology. In contrast to pure native starch, however, the pores do not result from the swelling starch granules alone but are mainly due to protein-assisted foaming. Therefore the porosity is significantly higher and the pore size larger than that resulting from the starch granules alone, and the wet milling time applied for homogenizing the ceramic suspensions becomes the most critical process parameter. Alumina suspensions with 70 wt.% alumina and 20–30 vol.% wheat flour with different initial particle size (fine grade and semolina, respectively) have been prepared using milling times of up to 8 h. Porosities of up to approx. 60% can be achieved with only 20 vol.% of flour or semolina after 8 h of milling time, with the cell sizes (diameters of pore cavities resulting from foam bubbles) being essentially independent of the milling time (median diameters of 120–240 μm). Effective pore throat sizes (i.e. diameters of cell windows or channels between cells), measured via mercury porosimetry, are 1–2 μm for short milling times (2–3 h), but for long milling times (8 h) they change by more than one order of magnitude to median sizes of 20–30 μm, closely corresponding to the median size of wheat starch granules (approx. 20 μm).

... 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[7,8,9,10,11]}、泡沫碳化硅^[12]、泡沫氮化硅^[13]等 ...

2011

0.0

... 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[7,8,9,10,11]}、泡沫碳化硅^[12]、泡沫氮化硅^[13]等 ...

1995

2.163

0.0

... 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[7,8,9,10,11]}、泡沫碳化硅^[12]、泡沫氮化硅^[13]等 ...

2011

0.711

0.0

... 目前研究较为热门的泡沫陶瓷主要泡沫氧化铝^{[7,8,9,10,11]}、泡沫碳化硅^[12]、泡沫氮化硅^[13]等 ...

2009

2.36

0.0

J. Eur. Ceram. Soc.. 2009, 29(8):1529-1534 DOI:10.1016/j.jeurceramsoc.2008.09.012

Characterization of porous silicon nitride ceramics by pressureless sintering using ﬂy ash cenosphere as a pore-forming agent

Abstract

A new method for fabricating porous silicon nitride ceramics has been developed by using fly ash cenosphere (FAC) with mean diameter of 87 μm as a pore-forming agent. Sintering was carried out at 1780 °C for 2 h under a nitrogen atmosphere. FAC can also act as a sintering aid besides a pore-forming agent. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that YSiO₂N forms instead of Y₂Si₃O₃N₄ when FAC is incorporated. Microstructural analysis revealed that large spherical cavities are scattered in a relative dense matrix. Porous Si₃N₄ ceramics with density of 2.17–2.30 g/cm³, Young’s modulus of 141–150 GPa and strength of 180–320 MPa were obtained by changing the FAC content.

... 氮化硅因具有优异的力学性能, 良好的热震性能和耐高温性能^[14,15]等而受到了广大研究者的重视 ...

2000

2.107

0.0

... 氮化硅因具有优异的力学性能, 良好的热震性能和耐高温性能^[14,15]等而受到了广大研究者的重视 ...

2006

2.107

0.0

... 目前常用的泡沫陶瓷制备方法^[16]主要有添加造孔剂法、有机泡沫浸渍法和发泡法 ...

2004

2.36

0.0

J. Eur. Ceram. Soc.. 2004, 24(3):579-587 DOI:10.1016/S0955-2219(03)00259-0

Clot-forming: the use of proteins as binders for producing ceramic foams

Abstract

This project uses the change of functional properties of proteins for ceramic and powder metallurgical shaping. Albumin (Bovine Serum Albumin, BSA) as a major constituent of blood was added as a model binder to an aqueous powder suspension, which then showed a sufficiently low viscosity for mould filling. The flow behaviour showed a structural viscosity being best described by a Herschel–Bulkley model. Temperatures higher than 66 °C lead to a significant increase of viscosity caused by irreversible changes in the spatial-structure of the protein molecule. Albumin, however, had a second effect in this process. Since albumin has amphiphilic properties its solutions are prone to foaming. A fine cellular foam structure of approximately 50–300 μm cell diameter was formed, probably due to a stable arrangement at the liquid gas interface. The combination of foaming and increase of stiffness lead to a stable protein-ceramic foam structure. After burn out and sintering final densities in the range from 8 to 20% t.d. were achieved. Fine cellular structures have more isolated pores while larger cells are typically interconnected. Typical applications would be high temperature insulation, catalyst carriers or scaffolds for cell technology.

... 当泡沫浆料受热或者pH发生变化时, 蛋白质会发生不可逆变性, 形成三维网络, 从而固定泡沫浆料的孔隙结构^[17,18,19] ...

2007

0.0

... 当泡沫浆料受热或者pH发生变化时, 蛋白质会发生不可逆变性, 形成三维网络, 从而固定泡沫浆料的孔隙结构^[17,18,19] ...

2007

2.36

0.0

J. Eur. Ceram. Soc.. 2007, 27(1):47-52 DOI:10.1016/j.jeurceramsoc.2006.01.023

Effect of additives on the micro- structure of porous alumina

Abstract

Protein forming, a direct consolidation technique for shaping of powders into a rigid body, use globular protein as gelling agent, which makes the process environment friendly. The present paper combines foaming and gelling capabilities of globular protein (albumin) along with starch to consolidate the ceramic bodies to develop porous structure based on alumina. The effect of albumin and starch on the gel strength, rheological properties of alumina slurry as well as the microstructure of final structure were studied in detail. It has been observed, that albumin which gels by forming strong polymer network dominates the gel properties, and thereby the strength of the consolidated green bodies, whereas starch, being insoluble in water at room temperature, increases the viscosity of slurry, but increases stability of foamed slurry. Also starch acts as pore former to introduce connectivity between pores and hence increases open porosity. Hence, by controlling albumin and starch ratio in the slurry one can control the microstructural developments in the cast body to obtain the desired micro-structure.

... 当泡沫浆料受热或者pH发生变化时, 蛋白质会发生不可逆变性, 形成三维网络, 从而固定泡沫浆料的孔隙结构^[17,18,19] ...

1991

0.0

... 国外大量理论研究表明, 固化过程中气泡内外的气压差是气泡生长的主要驱动力, 控制着制品的孔隙结构^[20,21] ...

1999

0.558

0.0

... 国外大量理论研究表明, 固化过程中气泡内外的气压差是气泡生长的主要驱动力, 控制着制品的孔隙结构^[20,21] ...

2006

0.0

... 泡沫浆料中气泡生长过程中主要受到气泡内外的气体压力, 气泡表面张力以及浆料粘度的影响^[22] ...

1995

2.088

0.0

... 产生这种现象的原因可能是: 常压固化时, 气泡内外气压差相对较大, 生长驱动力大, 气泡生长迅速, 导致部分气泡生长过程中可能开裂^[23], 因而制品孔壁缺陷较多 ...