纳米复相陶瓷

本文简要介绍了纳米复相陶瓷、纳米复相陶瓷力学性能，着重分析了纳米Ｓｉ３Ｎ４－ＳｉＣ复相陶瓷显微结构特点，同时展望了今后纳米复相陶瓷的研究重点。     

纳米复相陶瓷研究进展

介绍了制备纳米复相陶瓷的方法。对纳米复相陶瓷的研究进展进行了综合评述。     

纳米复相陶瓷

纳米复相陶瓷以其优异的性能受到大家的关注，成为陶瓷研究领域的研究热点。本文在介绍纳米复相陶瓷分类、材料设计和制备的同时，着重阐述了纳米复相陶瓷中纳米颗粒对材料的显微结构和性能的影响。     

纳米陶瓷及其纳米复相陶瓷的研究现状

综述了纳米陶瓷和纳米复相陶瓷的的研究现状．探讨了纳米陶瓷的力学性能及其热喷涂纳米陶瓷涂层存在的问题．分析了纳米复相陶瓷的增韧机理，为纳米陶瓷的研究和应用提供了理论依据。     

纳米复相陶瓷研究动态

20世纪80年代中期发展起来的纳米复相陶瓷，对陶瓷材料的性能产生重大的影响，为材料的利用开拓了一个新的领域，已成为材料科学研究的热点之一。综述了纳米复相陶瓷新近的研究动态，介绍了其制备方法和性能。     

可加工BN/B_4C复相陶瓷的制备与其抗热震性能

采用热压烧结工艺制备了BN/B4C微米复相陶瓷和BN/B4C纳米复相陶瓷。由淬水法测试了单相B4C陶瓷,BN/B4C微米复相陶瓷和BN/B4C纳米复相陶瓷的抗热震性能,用三点弯曲法测试了热震后样品的抗弯强度。结果表明:BN/B4C微米复相陶瓷和BN/B4C纳米复相陶瓷的抗热震性能明显高于单相B4C陶瓷的抗热震性能,而且BN/B4C纳米复相陶瓷的抗热震性能明显高于BN/B4C微米复相陶瓷的抗热震性能。BN/B4C微米复相陶瓷和BN/B4C纳米复相陶瓷具有良好的抗热震性能主要是由于具有较高的抗弯强度和较低的弹性模量;同时BN/B4C复相陶瓷中的BN/B4C弱界面和层状结构的h-BN晶粒能够显著提高复相陶瓷的抗热震性能。     

可加工陶瓷研究进展

介绍了国内外可加工玻璃陶瓷、石墨系复相陶瓷、h-BN系纳米复相陶瓷、可加工层状复相陶瓷、可加工多孔陶瓷、稀土磷酸盐系复相陶瓷和Mn＋1AX。化合物等7种可加工陶瓷的制备机理的研究现状,并对该领域今后的发展方向进行了进一步探讨。     

纳米复相陶瓷的制备及性能研究进展综述

本文综述了纳米复相陶瓷的研究进展。介绍了纳米复相陶瓷的分类及制备技术,详细地阐述了纳米复相陶瓷的力学性能和微观结构,分析了提高其断裂强度、断裂韧性及抗蠕变性等性能的机理。     

水基纳米SiC复合料浆的流变性能和稳定性

引言 纳米复相碳化硅陶瓷是在多相复合碳化硅陶瓷基础上发展起来的-种新型碳化硅陶瓷材料,通过引人第二或第三纳米增强相来同时实现细晶结构、梯度残余应力场、裂纹桥联、自增韧等增强增韧机理,从而获得多强韧化机理协同强化碳化硅陶瓷,已成为碳化硅陶瓷的研究方向之一[1-4].其中,纳米增强相在碳化硅基体(包括料浆、复合粉体、陶瓷)中的分布是制备纳米复相碳化硅陶瓷的关键和前提之一[5].     

纳米复相陶瓷材料的烧结技术

纳米复相陶瓷的烧结与普通陶瓷的烧结不同，在纳米复相陶瓷的烧结过程中需要采取相应的措施尽可能地控制晶粒的长大。目前，国内外研究者主要是通过改进传统烧结技术或采用新型烧结技术烧结制备纳米复相陶瓷。文章综述了目前国内外用的比较多的几种制备纳米复相陶瓷的烧结技术，并对其特点和应用情况进行了总结。     

Scrap of magnesia parts,the reasons for it,and means of reducing it

Conclusions The most common and characteristic forms of scrap of magnesia parts differing in form, dimensions, and composition are shown. These include deviations of the dimensions from the nominal, breaking off of the corners and edges, nonuniformity, welding together, spots, voids, fire cracks, spalls, and cracks of different origin.The reasons for formation of scrap were determined. The primary of them are the reduced quality of the raw material (chromite, magnesite) with a larger quantity of impurities containing limited silicon and calcium oxides, sometimes insufficient density, grain size, and completeness of hydration of the magnesite powders, nonconformity of the bunker, proportioning, mixing, and pressing equipment to the requirements of modern production of progressive high-quality refractories, the insufficiently high binding capacity of lignosulfonates, deviations in the quality of assembly and finishing of press equipment and automatic ejectors, of the car floor lining, and in firing conditions, a high variation in density of the green parts, and nonuniform heating and cooling in the volume of the parts and of the whole charge during firing. More than 50% of the total scrap of all forms is due to firing scrap of parts.The primary means of reducing or eliminating scrap of parts and simultaneously increasing their quality based on the reasons for formation of different forms of it were noted. These above all else, are increasing the volumes and improving and introduction of new methods of concentration of magnesite and chromite, a successive increase in the share of chrome concentrates, chromium-containing broken parts, and powders by firing of magnesite and caustic dust in the production of magnesia refractory parts as the result of a decrease in the share of commercial natural chromite and magnesite, the use in the production of parts of high-quality type PMSP-93 powder produced in shaft kilns and used as the charge for production of fused materials, the use of the prospect of processes for production of dense periclase powders uniform in chemical analysis from recovered caustic dust, replacement of obsolete mixing and press equipment by more modern, increasing the strength of green parts by above all else improving the binding properties of LST and increasing pressing pressure, forming of the taper of parts by the side plates of the die, improving the quality of assembly and increasing the reliability of functioning of press equipment and automatic ejectors, improving car floor linings, introduction of new methods and increasing the volumes of production of progressive unfired refractories in place of certain forms of fired parts, observation of all production parameters, and a relationship of the wages of labor to the quantity of scrap and the quality of refractories.Introduction of the new management system and the active work of the quality groups created will open up and lead to the action of unutilized reserves for reduction of scrap.Translated from Ogneupory, No. 2, pp. 31–38, February, 1989.     

聚焦结构、界面与多尺度问题,开辟化学工程的新里程

20世纪90年代以来,随着计算机技术和测量仪器的迅速发展,化学工程的研究水平日益提升,由经验规则的判断逐渐提高到计算机模拟量化分析. 化学工程的研究范围也日益扩大,下至纳微尺度结构与界面的观察与量化,上至宏观尺度设备与工厂的系统集成. 化学工程的服务对象也由化学工业扩展到冶金、材料、能源、环境、生物等诸多进行物质转化的过程工业. 目前化工科技界正在呼吁寻求继第一里程单元操作、第二里程传递过程和化学反应工程之后的第三里程. 化学工程中以往惯用的忽视非均匀多尺度结构和界面存在的平均方法是造成预测偏差和调控、放大困难的主要原因. 必须关注结构、界面和多尺度问题,研究多尺度结构、界面的量化预测理论和优化调控方法,建立多尺度结构、界面与"三传一反"的关系模型,与当代先进的计算方法、计算流体力学和计算机模拟相结合,有望解决化工过程与设备的优化调控与放大的难题,成为化学工程发展的新里程.     

油气集输过程中含油污泥减量化

集输过程中的含油污泥具有成分复杂、含液率高、乳化胶结稳定等特性，占油田危险废物新增量的约60%，是污染防治的重点。近年来，学者们开展了大量“调质-固液分离”减量化技术降低其环境风险和处置成本，但仍存在需要针对含油污泥不同来源优选相匹配的减量化调质方法和装置的难题。为此，本文回顾了氧化、破乳、絮凝、干化/半干、超声波、微波等化学与物理调质方法，离心机、叠螺机、压滤机3种固液分离装置研究进展，通过分别对各种调质方法及装置的对比分析，重点阐述了其作用机理、优缺点、适用对象。其中化学调质方法中破乳氧化、加酸更适用于高含聚油泥；表面活性剂破乳需加热，可与超声波相结合；有机和无机絮凝剂配合可提高罐底泥中油回收效果；干化/半干化法受经济效益制约。在文献基础上，认为未来应加强生物表面活性剂、生物电化学系统、椭圆叠螺机、基于固液分离装置数值模型基础上的设计与优化软件、多学科相结合的减量化耦合技术研究。     

磷酸分解磷矿过程中金属元素的浸出规律研究

探究了以磷酸分解磷矿,关键酸解工艺参数对磷及Fe、Al、Mg、Pb、As浸出的影响规律,并从热力学角度进行了分析。结果表明,磷矿内磷及Fe、Al、Mg浸出率随磷酸质量分数、反应温度、反应时间和液固比的增大而增大,搅拌速度影响不明显;Pb浸出率随磷酸质量分数、反应温度和液固比的增大而增大,搅拌速度、反应时间影响不明显;As浸出率随反应温度升高呈先增大后减小趋势,随反应时间增加略有减小,磷酸质量分数、搅拌速度和液固比影响不明显。控制磷酸质量分数为30%（以P₂O₅计）、反应温度为80 ℃、搅拌速度为300 r/min、反应时间为150 min、液固质量比为10∶1,在此条件下,磷及Fe、Al、Mg、Pb、As的浸出率分别为98.65%、68.56%、48.54%、95.84%、32.85%和84.62%。通过热力学分析表明磷矿内Mg、As浸出率较高,Pb浸出率较低,而Fe、Al浸出率大小主要取决于磷矿中褐铁矿及高岭土含量。     

Federal regulations applicable to the fatty acid industry

Recent legislation including the Clean Air Act, the Clean Water Act, the Occupational Safety and Health Act, the Solid Waste Disposal Act, the Resource Conservation and Recovery Act, and, especially, the Toxic Substances Control Act, is having a great impact on chemical manufacturers. The burgeoning maze of rules, regulations, policy statements, implementing these acts imposes serious obligations on all those engaged in fatty acid manufacture, processing, distribution, and research and development. The Manufacturing and Processing Notices, Sec. 5, and Reporting and Retention of Information, Sec. 8, requirements of TSCA, require extensive recordkeeping and reporting, and will affect industry’s development of new products and significant new uses of products. The status of fatty chemicals on the inventory of existing chemicals and the SDA efforts in the listing of premanufacture notification are extremely important to all segments of the fatty acid and derivative industries.     

Chitin filaments from dibutyrylchitin precursor: Fine structure and physical and physicochemical properties

Chitin filaments obtained after alkaline hydrolysis of dibutyrylchitin (DBCH) precursor filaments were investigated. The morphological structure, fine structure, and selected physical and physicochemical properties were studied. The studies of morphological structure included the assessment of the cross-section profile, the length and developing index of the contour line of the cross sections, the appearance of spherolitical crystalline aggregations, and the existence of skin–core building. The appraisal of the fine structure comprised the recognition of the lattice crystal system and the parameters of the unit cell, the crystallinity degree and average lateral crystallite sizes, and the crystalline and amorphous orientation. The characterization of physical properties included the appraisal of density, mechanical, thermal, electrical, and optical properties. In the area of physicochemical properties, swelling and dyeability were examined. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 807-819 1997     

Synthesis of alumina-bonded polycrystalline diamond by detonation

In this study, nanodiamond, aluminum isopropoxide, and hexogen (RDX) were used as starting materials to synthesize alumina-bonded polycrystalline diamond materials under high-temperature and high-pressure conditions generated by the detonation of the explosive. During detonation, the surface of the nanodiamond is coated with boron, silicon, and chromium through vacuum diffusion. Carbides of boron, silicon, and chromium referred as “bridges” are formed at the diamond/metal interface during the carbonization reaction. The "bridge" formed between diamond and nanoalumina considerably reduced the possibility of oxidation of nanodiamond as well as its graphitization during the detonation reaction. The phase, morphology, microstructure, and elemental composition of the detonation products were characterized by X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The results revealed that the explosion causes alumina and diamond to bond tightly to form alumina-bonded polycrystalline diamond composites. The thermal stabilities of the nanodiamond particles coated with boron, silicon, and chromium were found to be markedly higher, and the diamond phase remained intact even after heating at elevated temperatures. Thus, boron, silicon, and chromium reduced the wetting angle of diamond and alumina and improved the degree of bonding between them. Furthermore, boron facilitated the bonding between nanodiamond and alumina. In contrast, the bond was weaker in the case of silicon. Chromium also aided the bonding of the nanodiamond and alumina but introduced a large amount of oxygen into the composite.     

Some gas phase reactions during the firing of magnesite-chromite refractories in a tunnel kiln

Conclusions A correlation is shown between the high-temperature, physicochemical processes in basic refractories, changes and reactions in the gaseous phase, and the nature of the wear of the roof of a tunnel kiln.As a result of dissociation, oxidation, and volatilization the waste gases are enriched with vapors of alkalis, CrO₃, sulfur trioxide, and oxides of iron and magnesium, and become corrosive with respect to the kiln lining. The reaction of the oxides vapors with each other and with the lining of the roof and their condensation determines the nature of the wear in the magnesite-chromite refractories, the chemical and mineral compositions of the resulting deposits and crusts. The main source of alkalis and sulfur trioxide is the sulfite yeast dregs (sulfite lye) present in the goods being fired.We determined the temperature relationship with the composition and amounts of deposits and crusts. Carcase and skeletal deposits and crusts formed on the firing section of the kiln, mainly periclase and spinel compositions; in the warming-up section the deposits were brittle, granulated, consisting of sulfates, chromates, chromium oxide, periclase, and spinels.It was found that the deposits on the walls of the pores in the MKhS refractories consist of sulfates and chromates, forming solid solutions.Translated from Ogneupory, No. 5, pp. 13–16, May, 1980.     

重组胶原蛋白的绿色生物制造及其应用

胶原蛋白存在于各个组织器官,与动物胶原蛋白相比,重组胶原蛋白组分单一、安全性高、生产过程可控。本篇综述简述了重组胶原蛋白不同表达体系的构建,包括动植物以及微生物表达体系,比较了不同体系的优缺点。着重介绍了微生物体系中影响产物表达的不同发酵参数的调控,产物的分离纯化工艺以及重组胶原蛋白在医学领域的应用。提出微生物发酵体系较动植物体系成本低,操作简单,易于扩大生产;温度、pH、溶解氧、葡萄糖、乙酸浓度等影响大肠杆菌发酵中的蛋白表达量;酵母发酵中,甲醇添加量、温度、pH和溶解氧是主要影响参数;微生物发酵体系均需通过不同的粗纯及精纯技术获得纯度较高的产物。同时,重组胶原蛋白在生物医学领域发挥着重要作用。