堇青石蜂窝陶瓷热膨胀特性的研究

汽车尾气净化器用蜂窝陶瓷载体对材料的抗热冲击性能要求很高,要求材料具有特别低的热膨胀系数。本文通过对堇青石陶瓷的平均热膨胀系数及微观热膨胀系数的分析,研究了堇青石蜂窝陶瓷的热膨胀特性。     

超低膨胀系数堇青石蜂窝陶瓷材料的制备

利用XRD、SEM等测试技术对NGK和宜兴某厂的堇青石蜂窝陶瓷样品进行对比分析和研究,结果得出:由于NGK堇青石陶瓷在微观结构方面产生微裂纹导致NGK(0.2×10-6/℃)生产的堇青石蜂窝陶瓷热膨胀系数(1.2×10-6/℃)比宜兴产的小。由此提出了超低膨胀系数堇青石陶瓷的制备方案,即从浆料分散及烧成制度两个方面对宜兴蜂窝陶瓷微观结构进行优化从而有效降低其膨胀系数。     

堇青石蜂窝陶瓷的发展现状及应用

本文简要介绍了堇青石蜂窝陶瓷在国内外的发展现状、堇青石蜂窝陶瓷的制备工艺、影响堇青石蜂窝陶瓷热膨胀系数的因素,以及堇青石蜂窝陶瓷的应用方向。随着堇青石蜂窝陶瓷性能的提高,其应用也越来越广泛。     

堇青石蜂窝陶瓷板的热膨胀性能优化

堇青石材料具有低热膨胀系数和良好的红外辐射特性,其制成的蜂窝陶瓷燃烧板被广泛应用于节能灶具中。为了改善现有燃烧板在工作时容易掉渣的情况,本文以堇青石为主要原料,碳粉、锂辉石、高岭土、废片粉为辅助原料,并考察不同添加量对蜂窝陶瓷的热膨胀性能、掉渣情况的影响。以蜂窝陶瓷的掉渣情况与收缩率、抗折强度、吸水率的关系为目标设计正交试验,试验结果表明陶瓷掉渣情况与上述三个指标成正比,在造孔剂含量、锂辉石含量、高岭土含量都为10%、废片粉含量为25%时,所制备的堇青石质蜂窝陶瓷结构均匀,性能最优,在一定程度上改善了蜂窝陶瓷的掉渣情况。     

告别陶瓷传统工艺 开创纳米施釉新技——纳米釉堇青石日用耐热瓷简介

本文介绍了活跃在陶瓷材料工程领域的各类低热膨胀陶瓷材料,包括石英玻璃陶瓷、锂辉石质陶瓷、钛酸铝陶瓷、堇青石陶瓷等材料的缺点,重点分析了纳米釉堇青石质日用耐热瓷与其他陶瓷材料对比的优越性。     

酸处理对堇青石质蜂窝陶瓷性能的影响

用硝酸溶液对堇青石质蜂窝陶瓷样品进行处理。测定了酸处理时间不同的样品的热膨胀系数、气孔率和吸水率及抗压强度，研究了酸处理对堇青石质蜂窝陶瓷性能的影响规律，通过SEM分析了酸处理前后样品的断面形貌．并用ICP测定了酸处理液中的各种离子浓度，探讨了酸处理影响性能的机理。试验结果表明：酸处理能显著降低堇青石质蜂窝陶瓷的热膨胀系数，增加显气孔率和吸水率，但削弱了材料的机械强度。     

蜂窝堇青石陶瓷负载的CaZr_4P_6O_(24)涂层的制备及表征

采用溶胶-凝胶法制备了化学组成为CaZr4P6O24(CZP)的溶胶态前驱物,用其涂覆薄壁蜂窝堇青石陶瓷,经过700℃焙烧2h转化为具有低热膨胀特性的结晶态CZP涂层。用X射线衍射和BET(Brunauer-Emmett-Teller)氮吸附法表征了涂层的物相和孔结构,用扫描电镜观察了涂层表面及涂层与基体的界面结合处的形貌,用能量色散光谱仪分析了涂层中的元素分布及含量。结果表明:在蜂窝堇青石陶瓷基体上形成的涂层组成为CZP;表面沉积了19.5%(质量分数)CZP的蜂窝堇青石陶瓷的BET比表面积、孔体积和平均孔径分别为16.4m2/g,0.0225mL/g和2.74nm。CZP涂层与蜂窝堇青石基体的界面结合良好。发动机台架性能试验结果表明:"CZP-蜂窝堇青石"复合载体负载的单钯催化剂表现出与"γ-Al2O3-蜂窝堇青石"负载的单钯催化剂相近的三效转化活性。     

蜂窝陶瓷催化剂的开发及其应用

阐述了堇青石质蜂窝陶瓷及贵金属催化剂的工艺过程和特性，并探讨了蜂窝陶瓷催化剂的应用范围。     

堇青石质蜂窝陶瓷

堇青石蜂窝陶瓷主要用于汽车废气净化催化剂载体及内燃机废气粒子过滤器。本文简述了堇青石蜂窝陶瓷的性能要求．并概括总结了其制造方法以及降低其热膨胀系数的技术途径。     

堇青石质蜂窝陶瓷

堇青石蜂窝陶瓷主要用于汽车废气净化催化剂载体及内燃机废气粒子过滤器。本文简述了堇青石蜂窝陶瓷的性能要求，并概括总结了其制造方法以及降低其热膨胀系数的技术途径。     

蜂窝陶瓷蓄热材料的研究现状

蜂窝陶瓷蓄热材料应该具有热膨胀系数低、比热容大、比表面积大、导热性能好、抗热震性好等特性。本文详细介绍了几种多孔陶瓷材料的优缺点,指出堇青石质复相材料是目前研究最广泛的蜂窝陶瓷材料。堇青石与多种催化剂匹配性好,比表面积大、热膨胀系数小,但耐热性稍差,于是通过添加一些添加剂来提高堇青石作为蜂窝陶瓷蓄热体的性能。这些添加剂与堇青石结合形成复相材料,可以降低热膨胀系数、提高抗热震性等。     

堇青石峰窝状结构填料的制备和应用

本文研究了利用堇青石为主要原料制备蜂窝状结构填料的工艺过程,重点考察了增塑剂的组成和焙烧温度对填料性能的影响,测试了堇青石的稳定性和峰窝状结构填料的热膨胀系数,工业试验表明:该蜂窝状结构填料是一种有效的气体分布器,可以使催化剂铂的损失减少12.5%.     

降低蜂窝状堇青石陶瓷载体热膨胀的途径

详细叙述了降低蜂窝状堇青石陶瓷载体热膨胀的各种途径。主要包括设计适宜的化学组成 ,控制各种原料的种类、杂质含量、形貌、粒度以及对其进行必要的预处理 ,选用合适的添加剂 ,选择最佳烧成工艺 ,调节气孔率、孔径分布和烧成后陶瓷体的酸处理。     

Crystal Structures and Mechanism of Thermal Expansion of High Cordierite and Its Solid Solutions

The crystal structure of high cordierite and that of high cordierite solid solutions containing either Mn or Ga or Ge were refined. The structural changes caused by substitutions and the characteristic features of deformations of each T1O₄, T2O₄ tetrahedron and MO₆ octahedron were clarified. Thorough crystal chemical considerations led to a conclusion that the structure of Mn-bearing solid solution at room temperature may be regarded as a model structure of high cordierite at an elevated temperature. On the basis of the thermal expansion mechanism derived from this consideration, the thermal expansion behavior of the solid solutions is presented.     

Development of a Novel Design for Diesel Particulate Filter

A novel design for diesel particulate emission filter based on wall structure of pore channels of honeycomb filter is proposed. Our anticipation in this new design is that, if whiskers are coated on walls of the pore channels of honeycomb filter, the trapping efficiency of honeycomb filter will be improved and also the pressure drop will be substantially reduced. In present study, cordierite whiskers were coated on cordierite based honeycomb support (diameter 13 cm, and height 14.5 cm, 600 cells/inch²) by in-situ method. Whisker coating was carried out on walls of the pore channels of cordierite support from aqueous slurry containing a mixture of kaolin, talc, alumina and silica. Coating was performed by wash coat method. Firing was carried out at 1350C for 4 h under flowing air atmosphere. XRD measurements revealed us complete formation of cordierite phase. SEM analysis on the coating showed the formation of three-dimensional network of cordierite whiskers on cordierite support. In order to evaluate the particulates trapping efficiency of the newly developed honeycomb filter, smoke test was carried out with a 2L diesel engine for the both un-coated and coated cordierite honeycomb samples and the results were discussed with respect to their microstructures.     

元素掺杂对堇青石晶体结构及热膨胀系数的作用

堇青石陶瓷在抵抗热震和热膨胀方面具有独特的优点,特别适合用于象汽车尾气净化载体和集成电路基板等对热膨胀要求极为严格的场合,为了进一步降低堇青石陶瓷的热膨胀系数和改善晶体热膨胀的各向异性效应,目前大多采用掺杂元素的方法,如Ｇａ、Ｇｅ、Ｆｅ和Ｃａ,本文阐述了堇青石晶体的热膨胀机理,按照元素的性质详细叙述了各类元素的掺杂对堇青石的晶格常数格沿α堇青石两个晶轴ａ、ｃ方向热膨胀系数的影响。     

Effect of Microstructure on the Thermal Expansion Coefficient of Sintered Cordierite Prepared from Sol Mixtures

Dense cordierite ceramics were prepared from a sol mixture of alumina, silica, and magnesia, and the relationship between microstructure and thermal expansion was clarified for sinters with relative density greater than 97%. In the dense cordierite ceramics, submicrometer‐sized primary cordierite crystals aligned in the same crystal orientation and constituted the domain structure. We discovered that these domain structures could be easily observed by optical polarizing microscopy and quantified by digital image analysis of the photographs. The occurrence of microcracks between domains larger than 40 μm was induced by the thermal expansion anisotropy of the cordierite crystal axes. As a result, the mean thermal expansion coefficient of the cordierite ceramics decreased to 0.4 × 10^?6 K^?1 from the average value of the crystal axes of 1.7 × 10^?6 K^?1. This lower thermal expansion coefficient could be theoretically explained by partial microcracking.     

贵金属催化燃烧催化剂的研究

VOCs大多具有毒性,并伴有刺激性的恶臭,直接排放会威胁人类健康,并对环境造成严重污染。目前,催化燃烧技术是工艺较为成熟,同时也是应用较为广泛的VOCs的净化方法。实际过程使用的催化燃烧催化剂多为具有规整结构的蜂窝状催化剂,活性组分通常为Pt、Pd、Ru等贵金属。从整体式催化剂的角度出发,制备了Al_2O_3和TiO_2两种涂层的整体式催化剂用于催化燃烧消除苯的实验,未添加铈锆粉时的活性顺序:Pt/Al_2O_3/堇青石Pt/TiO_2/堇青石;添加铈锆粉后的活性顺序:Pt/CZ-Al_2O_3/堇青石Pt/CZ-TiO_2/堇青石,同时铈锆粉的添加还可以提高催化剂的热稳定性。     

Development of a high-temperature combustion catalyst system and prototype catalytic combustor turbine test results

A new combustion catalyst system for gas turbines composed of high-temperature durable ceramic catalysts made of fine manganese-substituted hexaaluminate particles and noble metal-carrying cordierite honeycomb catalysts has been developed. A 160 kW prototype catalytic combustor turbine rigged with a 220 mm in diameter catalyst system was constructed and tested including a continuous 215-hour operation and repeated sudden stops. The results showed practical combustion performance with ultra-low NO_x emissions less than 40 ppm (converted to 0% oxygen) and the feasibility of long term catalyst durability.