EFFECT OF REDUCING GASES ON THE TRANSVERSE STRENGTH OF FIRECLAY BRICKS1

It was reported that fireclay brick, when heated in the presence of carbon monoxide, were disintegrated by the progressive deposition of finely divided carbon at the “iron spots” in the brick. The conditions necessary for the occurrence of this phenomenon were not definitely known, although the known reversibility of the catalytic reaction around 650°C and the outcome of small scale experiments indicated that disintegration would not occur above this temperature. To obtain more definite information on this score, the effect of city gas at 550°C and 1100°C on the transverse strength of three brands of fireclay brick was determined. No significant changes in strength occurred at 1100°C. At 550°C two of the brands suffered very significant decreases in strength, but the other brand was unaffected, although it had the highest iron content.     

ACTIVITIES OF THE SOCIETY

A study of phase equilibria in the condensed system SiO₂–ZnO by the quenching method shows the existence of (a) only one compound, Zn₂SiO₄, the mclting point of which is 1512°C; (b) a region of two immiscible liquid phases in equilibrium with cristobalite at 1695°C, extending from 2 to 35 mol. per cent ZnO; (c) a euiectic between tridymite and Zn₂SiO₄ at 1432°C and 49.1 mol. per cent ZnO; (d) a eutectic between ZnO and Zn2 SiO4 at 1507°C and 77.5 mol. per ceut ZnO. The mclting point of Zno is found to be 1975°± 25°C. An irdium vessel is described which can be used in an induction furnace to obtain constant temperatures up to 2300°C in an oxidizing atmosphere.     

Microstructure evolution of hydration products and strength change of hydratable alumina-bonded castables below 1250°C

There have been reports that strength of hydratable alumina (HA)-bonded castables without silica fume drops significantly at 600°C and decreases substantially again at 1000°C. But the strength variation of the HA-bonded castables during the intermediate temperature range has not been investigated and elaborated from the perspective of phase evolution and microstructural change in the castables. In this work, the relationship between the change in the strength of castables and the microstructural characteristics of the HA-bonded castables was investigated. The phase and microstructure evolution of HA-bonded castables between 110°C and 1250°C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). It has been found that strength drops of the HA-bonded castables during heating process do not mainly happen at the temperature at which HA hydrates decompose, but at the temperature at which the structure of dehydrated HA hydrates disintegrates.     

DIELECTRIC BEHAVIOR OF ANNEALED POLY(VINYLIDENE FLUORIDE)

This study deals with the effect of annealing temperature of Polyvinylidene Fluoride quenched from melt into ice-water on the dielectric behavior. Measurements were carried out in the temperature range 25°C to 130°C and in the frequency range 1 kHz to 10 MHz. It was found that the dielectric permittivity and dielectric strength decreases with increasing annealing temperature. This is a result of morphological changes including defects creation, recrystallization and additional crystallization at expense of the amorphous phases.     

Strength retention of self-reinforced,absorbable polyglycolide rods in hydrolytic environment

Absorbable polyglycolide suture fibers were sintered with the compression molding techniques to cylindrical rods at temperatures between 205°C and 232°C for 3–5 min with final pressures of 50–80 N/mm². The cylindrical rods had nominal diameters between 1.5–4.5 mm and a length of 50 mm. The initial bending moduli and the initial bending strengths of the rods were between 9–15 GPa and 220–430 MPa, respectively. The shear strengths of the rods were between 165–255 MPa. The hydrolytic loss of mechanical strength of the above self-reinforced, absorabable polyglycolide rods were studied in phosphate buffer at 37°C and 77°C. It was found that the rate of strength loss decreases with the increasing diameter of the rods. On the other hand, the rate of strength loss increases when the temperature of the buffer solution is raised. The strength, retention time at 37°C was between 7–10 weeks showing that the loss of mechanical strength of self-reinforced polyglycolide rods occurs more rapidly in vivo than in vitro.     

THE RELATIVE MAGNITUDE OF RADIATION AND CONVECTION HEATING IN A MUFFLE KILN1

Rates of Heating by Convection and by Radiation in a Muffle Kiln, 38°×18°× 36° high, were each determined for temperatures from 350° to 800°C from measurements with a steady flow water calorimeter whose surface was first gold plated and then covered with a mixture of platinum black and lamp black. Taking the reflecting powers as 91 and 4 per cent, respectively, for the two surfaces, the radiation heating increases approximately according to the Stefan-Boltzmann fourth power law, while the convection heating comes out proportional to the temperature difference between calorimeter and muffle; that is, C=γ(T-t) where γ= 2.34×10⁻⁴ gm. cal./cm.² sec. The ratio of convection to radiation decreases from about .40 at 350° to .10 at 800°C, so that for the higher temperatures the convection heating may be neglected in rough computations of the rate of heating in such a kiln.     

USE OF ALUMINUM METAL IN THE CERAMIC INDUSTRY I,PROPERTIES OF REFRACTORIES PRODUCED WITH MIXTURES OF ALUMINUM,FIRE CLAY,AND GROG*

The addition of aluminum metal powder to fire-clay-grog mixtures greatly increased the strength of the fired brick as a result of an aluminothermic reaction between the metal and the silica in the clay and grog. Because the reaction takes place at 930°C. and causes the temperature to rise rapidly, it is necessary to heat these refractories only to 930°C. to produce hard, well-fired brick. Such products have a high load-carrying capacity at furnace temperatures and also a fair spalling resistance.     

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.     

Properties of molded soy protein isolate plastics

Thermal property of soy protein isolates (SPI) was studied with differential scanning calorimetry and thermogravimetric analysis. The weight loss of pure SPI is about 300°C. The glass transition temperature (T_g) is above 200°C. The best molding temperature of glycerin plasticized SPI plastics were then given. It is between 125 and 140°C. Subsequently the special property of molded SPI plastics was investigated. Results show that the atmosphere humidity affects the mechanical property and thermal property of SPI plastics. With the increasing humidity, the tensile strength decreases. While the elongation at breakage and peak area of the differential scanning calorimetry curve increases. At high temperature even at 140°C the molding temperature SPI plastics still have tensile strength though it decreases with the increasing test temperature while elongation at breakage increases. Dynamic mechanic thermal analysis test show that the storage modulus decreases with the rising temperature. The mechanical loss peak appears at lower temperature with the increasing amount of glycerin content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

THE SOLUBILITY OF QUARTZ AND CLAY IN FELDSPAR1

The literature on the subject is completely reviewed. The method used involved the addition of increasing amounts of kaolin to fixed amounts of feldspar and the addition of increasing amounts of quartz to fixed amounts of feldspar. All compositions were examined microscopically and the presence of undissolved kaolin was shown by the appearance of mullite needles, while the presence of undissolved quartz was shown by the presence of cristobalite. Soda feldspar is a better solvent for both quartz and clay than potash feldspar. The solution of quartz in soda feldspar starts at about 1350°C and increases with the temperature until at 1425°C. 32 parts of quartz per 100 of feldspar are dissolved. The solution of quartz in high potash feldspar does not start until 1400°C and only 4 parts are soluble at 1425°C to every 100 parts of feldspar. The solution of clay in soda feldspar starts at 1225°C and increases with the temperature until at 1425°C thirty-six parts are soluble. The solution of clay in high potash feldspar starts at 1250°C and at 1425°C the solubility is 20.5 parts per 100 of feldspar. The solution of quartz in porcelain bodies starts at the same temperature as it does in the pure feldspar which the body contains. The amount of solution per unit of feldspar is much greater. The general trend of one of the boundary lines in the ternary system K₂O-A1₂O₃-SiO₂ has been found.     

A STUDY OF THE HEATING AND COOLING CURVES OF JAPANESE KAOLINITE

Effect of heating Japanese kaolinite at 100° to 1400° C for 3 to 4 hours.—Ignition loss of weight Was found to occur chiefly between 400° and 600°C, the rate of increase per degree reaching a maximum at about 460 °C. Changes of microstructure were observed at 600°, 900–1000°, 1250–1300° and at 1400 °C, when sillimanite began to develop. Heating and cooling curves for Japanese kaolinite, to 1400°C.—A differential method was used with quartz sand as the comparison substance. In addition to the known reactions: (1) an endothermic from 450° to 700°, and (2) an exothermic near 950°, (3) an exothermic change between 1200° and 1300° was discovered, and it was observed that the endothermic reaction seems to include two periods of heat absorption, (1a) 450° to 650° and (1b) 650° to 700°. In explanation , the author suggests that 1a is due to dehydration, 1b to dissociation of kaolinite into free alumina and free silica, 2 to a polymerization of the alumia and 3 to the formation of amorphous sillimanite. In the discussion, E. W. Washburn calls attention to the fact that the author has neglected the endothermic reaction of quartz at 575 °C and suggests that some of his conclusions are therefore erroneous. Heating and cooling curves for alumina obtained from the nitrate, hydroxide and sulfate by calcination are given in figure 6. Exothermic reactions which are ascribed by the author to polymerization of alumia occur at 800° to 900° and at 1100° to 1200° instead of at 950° and at 1250° as in the case of kaolinite.     

Effect of Temperature on the Joints Strength of an Automotive Polyurethane Adhesive

In this paper, the performance of an automotive polyurethane adhesive was studied through adhesive joints tests. Butt joints and single lap joints were fabricated and tested at seven temperature measuring points (TMPs). It is shown that both the tensile strength and lap shear strength decrease with the increasing of temperature. Quadratic polynomial expression obtained by the least square method can represent the tensile and lap shear strength as a function of temperature very well. ?40°C, 0°C, and 90°C were selected as the most ideal TMPs for this adhesive through the comparison of the residual sums of squares of 35 fitting curves with different combination of TMPs. Scarf joints with adhesive angles of 60° and 30° were fabricated and tested at ?40°C, 0°C, and 90°C. It also showed a decrease in joint strength with the increasing temperature. Joint strength as a function of adhesive angle is presented. It was found to closely follow a linear behaviour. A three-dimensional surface, consisting of temperature, adhesive angle, and joint strength, is presented finally to facilitate the design of automotive bonding structures.     

THE EFFECT OF STEAM ON THE TRANSVERSE STRENGTH OF FIRECLAY BRICKS1

In connection with an investigation of checker brick for carbureters of water-gas machines, it was considered desirable to find out whether or not fireclay brick suffered an appreciable decrease in transverse strength when exposed to the action of steam at a high temperature. Except for occasional references to the “destructive action” of steam, no information on this score was found in the literature. This paper describes experiments in which standard straight bricks at 11,00°C were subjected to the action of steam at the same temperature and the resulting change in transverse strength measured. No significant decrease in strength due to the action of steam alone was found.     

THE INFLUENCE OF CHEMICAL COMPOSITIONS ON THE PHYSICAL PROPERTIES OF SODA-LIME GLASSES1

Nineteen soda-lime glasses covering the commercial field were prepared, melted, and fined for 2 hours. The chemical composition of the raw materials was determined by usual analytical methods; the refractive index was determined by an Abbé refractometer; density, by the normal suspension method; and softening point, by the Littleton method with the furnace as specified in Jour. Amer. Ceram. Soc., 10 [4], 259-63 (1927). The data indicate the following points: (1) When the silica was kept constant by increasing the dolomitic lime at the expense of soda an increase in softening point of 11 to 12°C per 1% increase was obtained. Likewise the density increases 0.004 and the refractive index 0.0015 per 1% increase of lime. (2) When the soda was kept constant the softening point was practically constant. The density decreases 0.011 and the refractive index 0.0030 per 1% increase of silica at the expense of lime. (3) When the lime was kept constant the increase in softening point per 1% increase in silica varied as follows : 5% lime 21°C, 8% lime 17°C, 10% lime 15°C, and 12% lime 12°C. The density decreased 0.008 and the refractive index 0.0015 per 1% increase in silica at the expense of soda. (4) A thermo-chemical relation of the softening points and the chemical compositions (calculated) closely paralleling the “liquidus” surfaces of Feild and Roysters' system: CaO-Na₂O-SiO₂.     

RELATION OF CRUSHING STRENGTH OF SILICA BRICK AT VARIOUS TEMPERATURES TO OTHER PHYSICAL PROPERTIES*

The failure at elevated temperatures under constant load for silica brick is reported using the Iupuy load test apparatus. The crushing strength at 1500°F, 1800°F. 2100°F, and 2400°F is recorded, as well as the crushing strength at room temperature. The size of test piece utilized normally was 1 by 1 by 2′/2 inches. A definite relationship is shown to exist between the strength at room temperature and that at elevated temperatures. The effect of variation in lime content, bats content, and fluxes is also reported. Data were obtained on brick made from three different quartzites. Additional physical data are reported to give information concerning the properties of the brick tested.     

THE TRANSVERSE STRENGTH OF FIRE-CLAY TILES AT FURNACE TEMPERATURES1

Commercial fire-clay tiles, were tested at furnace temperatures, for transverse strength. This was supplemented by tests of tiles of known composition made in the laboratory. Moduli of rupture obtained varied from 245.5 pounds per square inch at 1275°C, to 28.9 pounds per square inch at 1350°C but the data collected do not warrant definite conclusions.     

OSCILLOGRAPH STUDY OF DIELECTRIC PROPERTIES OF BARIUM TITANATE

A disk of barium titanate was fired to 1350°C. for six hours in an electric furnace. Silvered electrodes were then fired on the disk at 650°C. A cathode-ray oscillograph measurement was made of the dielectric properties in order to analyze the whole charging and discharging cycle. The material showed saturation of the dielectric flux density or charge with increase of field strength or voltage and is therefore a new type of ferroelectric material. The dielectric properties of such a nonlinear circuit element was studied over a temperature range from –175° to +140°C. at field strengths of 59, 134,234, 580, and 4300 volts per cm. Peaks in the dielectric constant were observed near –70°, +10°, and 120°C. As the field strength was increased, the two lower peaks increased in magnitude and all peaks shifted slightly to lower temperature.     

PROGRESS REPORT ON INVESTIGATION OF FIRECLAY BRICK AND THE CLAYS USED IN THEIR PREPARATION1

This is a progress report of an extensive study of fire clays and fireclay brick. It includes the results of a preliminary study of clays representative of those used in the manufacture of refractories throughout the United States. Chemical analyses and a summary of physical tests are given of both fire clays and the brick manufactured from them. The thermal expansion behavior of the fire clays fired at 1400°C and those of the fire brick “as received” from the manufacturer and also after firing at 1400°C, 1500°C, and 1600°C were studied and the materials classified into groups having characteristic thermal expansions. The moduli of elasticity and rupture were determined at 20°C, 550°C, and 1000°C. The resistance of the brick to spalling in a water-quenching test is expressed in an empirical relation correlating the elasticity, strength, coefficient of expansion, and percentage of grog used in compounding the brick batches. Data are presented on individual bricks made by the same manufacturer showing probable reasons for great differences in the number of quenchings required to cause spalling in the water-dip test.     

Tensile properties of two-dimensional carbon fiber reinforced silicon carbide composites at temperatures up to 2300 °C

Carbon fiber reinforced silicon carbide (C/SiC) composites are of the few most promising materials for ultra-high-temperature structural applications. However, the existing studies are mainly conducted at room and moderate temperatures. In this work, the tensile properties of a two-dimensional plain-weave C/SiC composite are studied up to 2300 °C in inert atmosphere for the first time. The study shows that C/SiC composite firstly shows linear deformation behavior and then strong nonlinear characteristics at room temperature. The nonlinear deformation behavior rapidly reduces with temperature. The Young’s modulus increases up to 1000 °C and then decreases as temperature increases. The tensile strength increases up to 1000 °C firstly, followed by reduction to 1400 °C, then increases again to 1800 °C, and lastly decreases with increasing temperature. The failure mechanisms being responsible for the mechanical behavior are gained through macro and micro analysis. The results are useful for the applications of C/SiC composites in the thermal structure engineering.     

EFFECT OF TIME AND TEMPERATURE UPON THE CHLORINATION OF FLINT FIRE CLAY

An experiment is described in which flint fire clays were chlorinated at fixed temperature between 500°C and 950°C and for varying periods of times. A replaceable condensing system permitted the rate of formation of the volatile chlorides to be studied.