New refractory concretes and binding systems: Basic trends of development, production, and use of refractories in the 21st century. Part III. Spinel and cast (self-flowing) concretes

The state-of-the-art in the field of creation and use of spinel, spinel-forming, and corundum-spinel concretes in the world is analyzed. In contrast to foreign-made concretes of this calss produced using high-alumina cement Russian specialists have developed cementless spinel concretes of the type of ceramic castables. Achievements in the field of low-cement self-flowing (cast) concretes, which are often more effective than vibrocompacted ones, are considered. The factors that determine their quality are analyzed. Concretes of this class can be obtained on the base of ceramic binders (HCBS). Due to their diminished (compared to low-cement concretes) water demand the materials can possess a lower porosity. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 12‐18, April, 1998. Parts I and II have been published in Nos. 2 and 3, 1998. To be continued.     

New refractory concretes and binding systems: Basic trends of development, production, and use of refractories in the 21st century. Part II. Ceramic binders and castables

A brief review of recently obtained and studied ceramic binding systems and castables based on them is presented. It is shown that corundum ceramic castables (Al₂O₃>95%) and ceramic castables based on aluminomagnesia spinel can be produced in principle. New molding methods that employ static pressing, ramming (vibroramming), and centrifugal shaping are described. The centrifugal method was used to produce ceramic castables (d _max≤5 mm) with an initial porosity of 13–14%. The method of vibroramming from molding systems with a moisture content of 3.4–4.0% was used to produce mullite-corundum ceramic castables with an elevated density and strength. The high efficiency of use of ceramic castables in metallurgy is due to the superfine porous structure of their matrix (binding) phase. The predominant pore size in various binders is 0.01–1.0 μm. In service, materials with such a structure are not impregnated by slag or metal. A principle for increasing the endurance of refractories produced from conventional raw materials using a new technology is suggested. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 3, pp. 15–24, March, 1998. For the beginning of the article see No. 2, 1998.     

New refractory concretes and binding systems: Basic trends of development, production, and use of refractories in the XXIst century. Part I. Trends of development, binding systems

General trends in the development, production, and service of refractories are considered. The share of refractories used in ferrous metallurgy amounts to 60–70%, which means that the predominant trend is determined by the requirements imposed on the refractories used in the steel industry. The proportion of unshaped refractories in the total production will inevitably grow. The basic problem in this field is the improvement of their matrix (disperse) phase, i.e., the binding system. The main types of refractory binders, of which highly concentrated ceramic binding suspensions (HCBS) are the most interesting, are considered. In contrast to natural ceramic binders (clays) HCBS are artificial systems that can be obtained on the basis of many refractory materials. The priority aspect in the creation of new refractory concretes (castables) and binders is described. The first artificial ceramic binders and cement-free refractory concretes based on them were created and installed by the author at the end of the 60s, and in the 70s he suggested many types of ceramic castables, including superlow-cement ones. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 2, pp. 4–13, February, 1998.     

A study of components of the binding (matrix) system of new refractory concretes. Part I. components and general characteristics of binding systems

New refractory concretes (such as ceramic castables and super-low-cement concretes) are considered and analyzed as composite materials consisting of a highly disperse binding system (matrix) and a polydisperse refractory filler. The mineral and grain compositions of binding systems used in fabricating ceramic castables and low-cement concretes are characterized. HCBS are characterized by the presence of ultradisperse particles in their composition (a colloidal component < 0.1 (μm) which determine the binding properties. A pioneering definition of a binding system for new refractory concretes is suggested.     

Basic trends in development of production of refractory materials for the glass industry in Russia

The basic refractory plants in Russia that manufacture refractory products for glass companies and the materials made by them are presented. The basic trends in development of refractory production are examined.     

Cements in the 21st century: Challenges,perspectives, and opportunities

Since its widespread use in concrete began over 100 years ago, the chemical composition and physical properties of portland cement have changed only incrementally in response to various and competing pressures of constructability and cost. Instead, the construction demands have been met largely through the development and introduction of chemical admixtures that are added to the binder during mixing. These same demands persist into the 21^st Century and are just as important now as before, yet newer driving forces are simultaneously pushing the industry both toward more automated construction and toward more sustainable concrete materials that generate lower CO₂ and have longer service life. These new cement binder formulations and new construction technologies are expected to go well outside the bounds of traditional portland cement compositions and batching and placing practices. This study examines the origins of these new market demands and the influence they are having on the construction industry. Seven scientific or technological pathways are identified that will be critical for enabling the kinds of transformational changes in cement and concrete construction that the industry needs: (i) additive manufacturing, (ii) designer admixtures, (iii) curated materials data repositories, (iv) computationally designed composites, (v) big data and smart materials, (vi) alternative binder compositions, and (vii) next‐generation instrumentation.     

New cements for the 21st century: The pursuit of an alternative to Portland cement

Preparation of this article entailed authors analyzing the contents of quite a number of papers, although the main objective was never to review the state of the art of new cements. Rather authors intend to discuss why they believe alkaline activated cement can be positioned at the epicentre of a new and necessary transition from today's Portland cement to the new cements of the future. A brief history of alkaline cements serves as an introduction to the technology itself. The interest roused around calcium sulfoaluminate-based cements is also reviewed, albeit summarily. The greater part of the article focuses, however, on alkaline cements which are classified into five categories. The fundamental chemical and structural characteristics of aluminosilicate-based alkaline cements are also described, and the key advances made in the understanding of synthetic gels are discussed. The paper ultimately finds hybrid cements to be technologically viable materials for contemporary construction.     

Rheology in the technology of ceramics and refractories. Part 5. Dilatancy: Classification and types of dilatant systems

A great majority of high-density ceramic binding suspensions (HDBS) and the related molding systems, characterized by a volume fraction of the solid phaseC _v=0.80−0.85, exhibit a strongly pronounced dilatancy that is a source of difficulties for the production and use of these materials. The effect of dilatancy and the mechanism of dilatant flow are analyzed from the standpoint of thermodynamics and colloid chemistry. Original experimental results and published data are generalized and a classification of the main types of dilatancy is proposed. The effects of some important factors on the character of dilatant flow in high-density ceramic binding suspensions based on quartz glass, quartz sand, mullite, and titanium dioxide are considered. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 2, pp. 8–16, February, 1997. For the previous articles of this series see No. 3 (1994), No. 12 (1995), and Nos. 1 and 10 (1996).     

Rheology in the technology of ceramics and refractories. Part 6. Dilatant systems and factors determining their properties

The effects of various factors, including the characteristics of the solid phase, bulk concentration, stabilization, coagulation, temperature, and vibrations, on the dilatant properties of high-density ceramic binding suspensions are considered. The main factor controlling the dilatancy is the proximity of the actual bulk concentrationC _v to the critical valueC _{v cr}, corresponding to the concentration of shape formation (conversion of the suspension into a solid). Suspensions of quartz glass withC _{v cr}=0.91 possessed a Newtonian character of flow forC _v=0.75−0.78, while suspensions withC _{v cr}=0.70−0.75 exhibited a strong dilatancy even in the range ofC _v=0.60−0.64. The dilatancy of some highly disperse suspensions at much lower values ofC _v is caused by a high value of the effective bulk concentrationC _{v ef}, including a considerable volume of bound liquid. On the basis of results of original studies and generalization of published data, a mechanism is formulated according to which dilatancy is treated as due to the effect of constrained volume in disperse systems. Most suspensions are characterized by a bulk dilatancy according to Reynolds. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 2–14, April, 1997. For the previous articles of this series see Refractories and Industrial Ceremics No. 3 (1994), No. 12 (1995), Nos. 1 and 10 (1996), and No. 2 (1997).     

Catalytic conversion of methane to more useful chemicals and fuels: a challenge for the 21st century

The very large reserves of methane, which often are found in remote regions, could serve as a feedstock for the production of chemicals and as a source of energy well into the 21st century. Although methane currently is being used in such important applications as the heating of homes and the generation of hydrogen for ammonia synthesis, its potential for the production of ethylene or liquid hydrocarbon fuels has not been fully realized. A number of strategies are being explored at levels that range from fundamental science to engineering technology. These include: (a) stream and carbon dioxide reforming or partial oxidation of methane to form carbon monoxide and hydrogen, followed by Fischer–Tropsch chemistry, (b) the direct oxidation of methane to methanol and formaldehyde, (c) oxidative coupling of methane to ethylene, and (d) direct conversion to aromatics and hydrogen in the absence of oxygen. Each alternative has its own set of limitations; however, economical separation is common to all with the most important issues being the separation of oxygen from air and the separation of hydrogen or hydrocarbons from dilute product streams. Extensive utilization of methane for the production of fuels and chemicals appears to be near, but current economic uncertainties limit the amount of research activity and the implementation of emerging technologies.     

21世纪新型聚酯材料PTT的性能与应用

介绍了新型聚酯材料PTT的开发、性质、应用及市场前景;指出PTT集各种材料的优良性能于一身,必将成为流行的聚酯材料。     

从霍尼韦尔国内第一订单看工业清洗剂发展新趋势

为了保护自然环境和地下水,处于对人类生存和发展的需要,原有的具有破坏臭氧层物质(ODS)的清洗剂将会退出市场,行业召唤创新的清洗剂技术。本文从霍尼韦尔公司的内部采购案例开始,分析了行业的需求与挑战,通过对比霍尼韦尔氟化学品部的Solstice高性能溶剂(SolsticePF)与现有几种主要清洗剂的性能优劣,显示了Solstice高性能溶剂在环保、安全和清洁等方面的优异性能,从而说明创新的环保型绿色无污染的工业清洗剂将成为未来中国清洗剂工业市场发展的主流。     

Polymer fibre composites, basic types, principles of fabrication, and properties. Part 3. Basic types of polymer fibre composites, properties, and use

The basic types of polymer composite materials (PCMM) made from different kinds of reinforcing fibre fillers: short-cut fibres, paper, yarns, tow, sliver, fabrics, and nonwovens, and their properties and use are examined. Information on the fabrication and properties of the different kinds of composites are reported: extruded fibre plastics, getinaxes, textolites, unidirectional composites, honeycomb plastics, and others. New kinds of composites with ultrahigh mechanical and thermal characteristics are also examined. Some of the reported information was previously covered very sparely in the literature. Based on the examination, the features of polymer fibre composites are summarized in comparison to other materials, and they can be summarized as the following basic points: 1) combining different kinds of fibre fillers and matrices (binders) allows fabricating PCM with a wide range of properties by selecting the optimum indexes for articles with a broad spectrum of applications; 2) articles made of fibre PCM are not very materials-intensive and are technologically effective for processing in comparison to many traditional materials, metals and ceramics in particular; 3) with respect to the specific mass characteristics, fibre PCM can be many times superior to articles made of traditional materials—metals, etc., so that the mass (weight) characteristics of articles made of fibre composites can be significantly reduced, which is especially important for using them in vehicles, aircraft, rescue equipment, and sporting goods; 4) articles made of composites have high performance reliability, are almost immune to corrosion, and do not require special protection or periodic painting of the surface. Due to the features of the properties and use, fibre PCM have a great future in the most varied areas of application. See No. 4, 7–12 (2005) for Part 1; No. 5, 54–69 for Part 2. __________ Translated from Khimicheskie Volokna, No. 1, pp. 41–50, January–February, 2006.