THE THERMAL EXPANSION OF SOME REFRACTORY OXIDES1

The thermal expansion of crystals of alpha-alumina, magnesia, chromite, mullite, and zircon and of a mass of fused zirconia has been measured up to 1000°C. The results are exhibited in tables and in graphical form.     

THE REVERSIBLE THERMAL EXPANSION OF REFRACTORY MATERIALS

The reversible thermal expansion from 15–1000°C was measured for kaolin, siliceous and aluminous fire clays, quartzite, alumina, magnesia, and carborundum, after preliminary burnings at cones 06, 9, 14 and 20, and as well as for English commercial silica bricks before and after use in a coke oven and the roof of a steel furnace. Kaolin and bauxitic fire clay after calcination have a regular reversible thermal expansion which does not vary much with the temperature of calcination. Siliceous fire clays, after calcination at cone 06 (980°C) or cone 9 (1280°C) display irregularities (departures from uniformity) in their expansion. Between 500° and 600°C they show a large expansion due to contained quartz and on cooling the contraction in that region is larger than the corresponding expansion. Moreover, the expansion between 100° and 250°C after being fired to cone 9 (1280°C) exceeds the average. After calcination at higher temperatures, cone 14 (1410°C) or cone 20 (1530°C). these materials gradually lose these peculiarities until on incipient vitrification a linear expansion similar to that of kaolin is attained. This change is due to the destruction of quartz by its interaction with the clay material and fluxes; it takes place most easily in a fine-grained, rather friable clay such as ball clay. The previous thermal treatment necessary for a particular clay in order to obtain regular expansion in use can only be determined by trial. It can be stated with confidence that in such a piece of apparatus as a glass pot or crucible, a distinct gain will result from maintenance at a high temperature for some time before use, but that the red heat of an ordinary pot arch is useless for the purpose. An increase in the porosity of a fire clay was accompanied by a corresponding decrease in expansion between 15° and 1000°C until a porosity of 50% was attained. Further increase in porosity produced very little change in the expansion. No irregularities in expansion were shown by magnesia brick, carborundum, or alumina bonded with 10% of ball clay. Welsh quartzite with lime bond, either unfired or after burning at cone 06, had a large expansion to 550 °C and a much larger expansion from 550–600 °C due to the inversion of α to β quartz while from 600–1000°C a slight contraction took place. Firing to cone 9 converted part of the quartz into cristobalite, thus increasing the expansion from 200–250°C. This conversion was considerably increased on burning for two hours at cone 14, which greatly reduced the expansion from 550–600°C with a corresponding increase of that from 200–250°C. The conversion of the quartz into cristobalite was completed by a further heating for two hours at cone 20. Determinations of refractive indices and specific gravities confirmed these results. Flint inverted to cristobalite with greater ease than quartz. Commercial silica brick consisted chiefly of cristobalite and unconverted quartz and showed a large expansion up to 300°C, followed by a considerably smaller but regular expansion to 550°C. From 550° to 600°C the rate of expansion was considerably increased, but above 600°C the change in dimensions was small. The innermost exposed layer of a silica brick after use in a coke oven was an impure glass with a steady expansion, but only half as large as that of the layers of brick behind, which was made for shelling away. A silica brick after use in a steel furnace was divided into four layers. The layer exposed to the furnace heat was practically all cristobalite and silicates, the next layer the same, the third layer showed some α to β quartz expansion as well as the α to β cristobalite expansion, while the fourth (outermost) layer exposed to air was similar to the brick before use. In these bricks exposure to high temperature had evidently completed the change from quartz to cristobalite which had been largely effected in the kiln during manufacture. Little or no tridymite had formed. The reversible thermal expansion from 15–1000°C of the commercial silica brick examined was 1.1 to 1.3%, about double that of fire clay brick.     

THE PHYSICAL STRUCTURE OF REFRACTORY MATERIALS1

The relation of physical structure to the performance characteristics is pointed out. It is shown that chemical composition is of value principally as a means of control of raw materials, the value of the end product being determined largely by the crystallographic relationship existing between grain and bond.     

耐火纤维材料高温热导率的分形

引　言耐火纤维材料是一种具有复杂微空间结构的多孔介质性材料 .纤维的堆积是随机无序的 ,这种无规的几何结构导致其热物理特性的多样性 .对此类材料在低温下的热物性已进行了较深入的研究[1～ 3] ,但对其在高温条件下的研究报道甚少 .从传热机理来看 ,在高温条件下 ,耐火纤维材料内不仅有气体和纤维的热传导 ,热辐射也很重要 ,因此 ,材料的微空间结构和温度是影响其热性能的主要因素 .研究高温热辐射的方法有有限体积法[4 ] 、离散传递法[4 ] 、等效热阻法等 .本文运用分形理论[5～ 7] ,对新型高铝耐火纤维材料进行了分形描述 ,并结合等效…     

THE DETERMINATION OF THE BULK AND PORE VOLUMES OF REFRACTORY MATERIALS1

A new sand displacement method for the determination of the bulk volume and bulk specific gravity of refractory or other material is described. A gas porosimeter with a vertical U-tube manometer for the determination of pore volumes of materials is also described together with calculations of the possible errors. The porosities, bulk specific gravities, and calculated true specific gravities of 15 types of refractory bricks obtained by means of these two methods, and the usual water absorption method are tabulated for comparison.     

THE THERMAL CONDUCTIVITY OF SOME REFRACTORIES1

The problem of measuring the thermal conductivity of materials up to high temperatures has been studied, especially in regard to the sources of error. This investigation has shown that many of the previous determinations of thermal conductivity may have had little precision due to a lack of appreciation of the errors involved. The values of thermal conductivity for a number of refractories are given, as obtained by a new type of apparatus designed to eliminate to a considerable extent the errors of measurement. However, it is believed that these values may have an error as high as ± 25 % for the better heat conductors; so there is still much work to be done in developing a method for measuring thermal conductivity with the precision usual in other physical measurements.     

纳米流体热导率的测量

运用瞬态热线法测定了不同种类、不同体积份额配比的纳米流体的热导率,分析了纳米粒子属性、份额、尺度等因素对纳米流体热导率的影响.实验结果表明,在液体中添加纳米粒子显著增加了液体的热导率.通过对实验结果进行分析,提出了计算纳米流体热导率的关联式.     

THE CAPILLARY SUCTION OF SOME CERAMIC MATERIALS1

The forces which act when clay is mixed with water and when water is removed from wet clay by evaporation have received little study. For this reason, very little definite information regarding the internal mechanism of the drying of clayware is available. In this paper, the writer reviews the experiments and theories of Pukall, Terzaghi, Dixon, etc., lists some of the forces which may act when ware is drying, and defines an important force which he calls “capillary suction.” A simple experiment is described, by means of which this force can be readily demonstrated. The development and final form of an apparatus for measuring the capillary suction of ceramic materials is described and data obtained from measurements on a ball clay, a kaolin, flint, feldspar and mixtures of these substances are reported. Capillary suction decreases rapidly with increase in the flint and feldspar of a ceramic body. By utilizing the capillary suction produced by evaporation of water from a clay surface, water at atmospheric pressure has been made to enter a steel bomb in which the gas pressure was maintained at 200 lbs. per square inch.     

热循环对水泥基材料抗压强度的影响及机理研究

研究了硬化水泥基材料在20～180℃范围内热循环20次后强度的变化规律,经热循环试样强度较同龄期对比试样的强度有明显下降的结论.通过对水泥石和石英砂集料的线膨胀率的精确测定,对比两者线膨胀率的差异,找出热循环时导致水泥基材料内应力产生的原因,并解释硬化水泥基材料经热循环后强度性能降低的现象.     

THE PROPERTIES OF SOME CLAY-LIKE MATERIALS OF THE BENTONITE TYPE1

The evidence obtained in this work would indicate that bentonites are mixtures of two or more materials rather than one. The exact composition of these is not known but they are probably mixtures of colloidal silicates and fine-grained kaolinite in varying proportions. They are characterized by the following properties: Conchoidal fracture; an index of refraction between 1.48 and 1.54; high water of plasticity and volume drying, shrinkage varying from that of highly plastic clays to 114.61% and 195.9%, respectively; and a high alkali plus alkali earth content, usually above 5%. When added in small amounts to certain clays, some bentonites increase the dry strength to a remarkable extent. In firing they vitrify between 1000°C, soften at cones 1–14 and burn to a buff to brown color and therefore can only be used in small amounts in white ware. It is possible by adding finely ground quartz and small amounts of bentonite to certain fire clays to produce mixtures approaching the Arkansas and certain other glass pot clays in physical properties and in index of refraction. Adding too much bentonite to clays causes them to crack in drying.     

多孔固体催化剂的有效导热系数

建立了测定多孔固体催化剂骨架导热系数的实验装置和由此计算催化剂有效导热系数的简化方法，测定并计算了若干工业过程催化剂的有效导热系数，同时，计算了甲烷蒸汽转化催化剂的非等温效率因子。     

THE USE OF RADIATION PYROMETERS ON REFRACTORY KILNS1

The high cost of maintenance of platinum thermocouples has greatly discouraged the use of pyrometers on kilns firing silica and other high refractories. The method of using a combination recorder employing thermocouples for the lower ranges of temperatures and the radiation pyrometer for the higher ranges is described. The accuracy of the measurements is fully equal to those made with platinum thermocouples at a temperature for which the latter are durable, and the radiation pyrometer has the advantage of not deteriorating at high temperatures. Neither couple nor radiation tube is damaged by removal while hot, so that the tubes may be kept in constant service, thus making the cost of the complete installation very reasonable.     

STUDIES ON THERMAL BEHAVIOUR OF TETRAALKOXYSILANES

Tetraalkoxysilanes (Compounds A to O) were prepared by reacting SiCI4 with corresponding alcohols in the liquid phase in the presence of pyridine as acid acceptor in benzene solvent. Based on the experimental evidences and theoretical calculations tentative structures had been proposed. Properties such as density, refractive index, viscosity, surface tension, molecular weight, thermal expansion, specific heat, thermal conductivity, decomposition temperature and oxidation stability were determined. Prandtl number, Reynold's number and heat transfer coefficient for tetraalkoxysilanes were calculated and were compared with those of coolanols of Monsanto Chemicals, USA. Thermal stability of the compounds was studied by heating them at 200°C for 100 hours in the presence and in the absence of phenyl-a-naphthylamine and diphenylamine as stabilizers and redetermining some of the properties like density, refractive index, surface tension, viscosity and molecular weight

The variation of the properties due to heat treatment is less significant when they are heated in the presence of a stabilizer. The low variation of physical constants by heat treatment particularly in the presence of a stabilizer suggests that these compounds are thermally stable and can be used in heat transfer and other thermal applications with stabilizers     

SURVEY OF LITERATURE ON SLAG TESTS FOR REFRACTORY MATERIALS*

A survey of the literature for the period 1932 through 1940 on the subject of slag tests for refractory materials is presented. This survey supplements similar reviews of Ferguson and of Simpson. A classified index to methods of testing and means for evaluating slag attack on refractories is also presented. This key has been prepared from references which appear in the present survey and also in the two previous articles. All of the references cited are to be found in the appended Bibliography.     

RESEARCHES IN DRY-PRESS REFRACTORIES,III. THE EFFECT OF VACUUM ON THE UNFIRED PROPERTIES OF SOME DRY-PRESS REFRACTORY BATCHES1

A series of tests on several typical refractory bodies are presented. These include data showing the effect of varying the amount of vacuum, and its length of time of application on the green and dry properties. The limits of pressure attainable with a mechanical press are also discussed.     

某些物质对亚硫酸盐氧化的阻滞作用

通过除氧试验和空气氧化试验,了某些物质对亚硫酸盐氧化的阻滞作用,结果发现,下列三类物质够阻滞亚硫酸盐与氧的反应;第一类物质是自由基链反应终止剂,通过消除亚硫酸盐氧化过程中生成的自由基而抑制反应;第二类物质是螯合剂,通过螯合亚硫酸盐溶液中的过渡族金属元素催化剂杂质的而减缓反应速度;第三类物质是链反应引发剂,早于添加过量而由引发剂转变为终止剂,试验结果为亚硫酸直氧化的自由基机理提供了有力的证据,也为防     

新型陶瓷材料的动力学研究

本文采用法国Setaram TG一DTA92热分析仪对几种新型陶瓷材料——锰锌铁氧体和镍锌铁氧体进行了实验研究,并由热分析结果计算了它们的反应动力学参数,该工作对新型陶瓷材料的加工具有指导意义。     

SOME THERMAL CHARACTERISTICS OF CLAYS1

The literature pertaining to thermal reactions, specific heats, and thermal conductivities of clays is reviewed and discussed, particular attention being given to the heat required to fire various clays. All clays undergo an endothermic reaction between 100°C and 650°C amounting to from 30 to 150 calories per gram. An exothermic reaction takes place at about 950°C which evolves from 10 to 40 calories per gram. The specific heats of clays and shales are about. 45 over the interval 20°C to 1100°C.     

THE ATTACK OF ARSENIC COMPOUNDS ON FIRECLAY REFRACTORY MATERIAL1

McSwiney's statement regarding arsenic compounds being responsible for rapid corrosive action on tank blocks is discussed. It is pointed out that if arsenic compounds exert a marked corrosive action on fire clay, it should be demonstrated by an increased iron oxide or alumina content, or both, in the resulting glass. Data collected in experiments run is presented, which contradicts McSwiney's statement. Only when arsenic in excess of the amount used ordinarily is present in glasses melted at temperatures of 1450 and 1500°C, or above ordinary working temperatures, can corrosion due to arsenic be traced. A full discussion of corrosion of glass house refractories, effects of colors on the heat conductivity of glasses at high and low temperatures, and variations between the types of glasses referred to in Dr. Turner's paper and in McSwiney's, is presented by McSwiney.