POROSITY: VII. THE DETERMINATION OF THE POROSITY OF HIGHLY VITRIFIED BODIES43

Design and Accuracy .—The accuracy limitations of the general laboratory research type of porosimeter are discussed and the principles of design indicated. McLeod-Gauge Type of Porosimeter .—A new type of porosimeter is described with which the pore volume of any test piece may be directly determined within 0.01–0.02 cc. Results with Electrical Porcelain .—Tests of eight pieces of electrical porcelain indicated a porosity of 0±0.01 per cent. This result was confirmed by dye penetration tests. An Apparatus for Measuring the Porosity of Full Size Brick .—A simple and rapid apparatus for measuring the porosity of full size brick by the “General Method”(Jour. Amer. Ceram. Soc., 5, 113–16 (1922)) is figured and described.     

EFFECTIVENESS OF DIFFERENT METHODS OF MAKING ABSORPTION DETERMINATIONS AS APPLIED TO HOLLOW BUILDING TILE1

The experimental work consisted primarily in selecting specimens from hollow tile from seventeen sources and saturating them for the absorption determination by (1) immersion in water at room temperature for various periods ranging from fifteen minutes to nine days, (2) boiling for various periods ranging from 1 hour to 5 hours and then cooling in water at room temperature for at least one hour, and (3) repeated vacuum treatments. The true porosity for some of the specimens was then obtained from the specific gravity and the per cent saturation reached by the various methods was calculated. The results show that the five-hour boiling treatment gives results 1.2 greater than 72 hours immersion in cold water for the shale tile, 1.35 greater for the fire clay tile, 1.20 greater for the surface clay tile, 1.25 greater for the mixed clay tile and 1.28 greater for an average of all tile. They also show that the cold water immersion treatment gives 73.5 per cent saturation, the boiling treatment 92.7 per cent saturation, and the vacuum treatment 97.0 per cent saturation. In general the paper shows that the most consistent and practical way of determining the absorption of hollow tile is by boiling for five hours and then cooling for at least one hour before the saturated weight is taken.     

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.     

Mass transfer and biochemical reaction in enzyme membrane reactor systems—II: Expanded analysis for single enzyme systems: effects of enzyme intermediates,denaturation and elution

A detailed study of the dynamics of a packed-bed reactor containing immobilized enzyme particles is presented. The analysis consists of (i) transient state behavior; (ii) models for interphase and interfacial mass transfer between fluid and solid phases and intraphase mass transfer for the solid phase; (iii) detailed reaction rate model for the Bodenstein intermediates; (iv) mass balances for substrates, Bodenstein intermediates, unoccupied enzyme active sites, and products; and (v) models for enzyme denaturation and elution. The general reactor model consists of a set of nonlinear, coupled, partial differential equations. Numerical solutions of the system equations were obtained, using the discrete-space, continuous-time method of lines and realistic parameter values. A generalized map of the range of validity of the Steady-State Hypothesis was established under conditions where multiple mass transfer gradients were present within the reactor.A detailed analysis of the computational errors was performed. It was conclusively shown that the computer simulation solutions obtained in the analyses were not disguised to any significant degree as a result of employing finite difference approximations to the spatial derivatives.It was shown that the level of “error” involved in invoking the Steady-State Hypothesis depends on the relative magnitude of the kinetic parameters and also on the level of “disturbance” at the reactor inlet (i.e. per cent change in substrate inlet concentration). The “error”, however, did appear to be strikingly insensitive to the magnitude of the resistances to mass transfer, as characterized by the Modified Sherwood Number. It was concluded that, given any complete set of kinetic parameters, a transient, heterogeneous, isothermal reactor model based on the Steady-State Hypothesis may be used for predicting time-varying concentration profiles for minor (i.e., less than 5 per cent change in substrate inlet concentration) “disturbances” at the reactor inlet. The corresponding “errors” would be at an acceptable level (i.e., less than 2 per cent in the concentration and less than 10 per cent in the time lag) under these conditions.Further, various mechanisms for enzyme denaturation and elution were incorporated in the general reactor model. Numerical solutions of the resulting system of partial differential equations were obtained, using hypothetical parameter values. Through extensive simulation research, it was shown that the loss in activity of immobilized enzyme reactors cannot be uniquely ascribed to any one particular set of mechanistic deactivation modes.     

金属铝粉和纳米Al2O3粉对陶瓷结合剂性能的影响

将金属铝粉、纳米Al₂O₃粉引入基础陶瓷结合剂,通过红外光谱分析陶瓷结合剂玻璃结构,X射线衍射表征其物相变化,并测试其耐火度,利用扫描电镜分析陶瓷结合剂立方氮化硼(CBN)复合材料的微观结构,并测试抗折强度,系统分析了金属铝粉、纳米Al₂O₃粉的单掺及复掺对陶瓷结合剂性能的影响。结果表明,金属铝粉使陶瓷结合剂耐火度升高,玻璃结构没有明显改变,部分铝粉转变为Al₂O₃,添加金属铝粉的陶瓷结合剂CBN复合材料抗折强度随烧结温度升高而提高。纳米Al₂O₃粉使陶瓷结合剂耐火度降低,呈玻璃相,但有少量Al₂SiO₅晶体和Li_xAl_xSi_3-xO₆晶体析出,添加纳米Al₂O₃粉的陶瓷结合剂CBN复合材料烧结温度720 ℃时出现较高抗折强度,达93.7 MPa。金属铝粉和纳米Al₂O₃粉的复掺有利于玻璃网络结构的键合,陶瓷结合剂以玻璃相为主,也有少量晶体析出,二者复掺对提高陶瓷结合剂CBN复合材料抗折强度更有优势,但烧结温度也相应升高,烧结温度740 ℃时抗折强度达最高值,为97.4 MPa。     

Problems of Foam Glass Production

Principles of producing foam glass rate considered. A correlation between structure and such properties as density, water absorption, strength, and thermal conductivity of materials obtained is demonstrated. The advantages, disadvantages, and prospects of a “cold” method for foam glass production are discussed.     

Lightweight glass–ceramic tiles from the sintering of mining tailings

Modern thermally-insulating building façades comprise lightweight structural panels, in turn mostly composed of porcelain stoneware with engineered porosity. Sintered glass–ceramics may represent a valid alternative, mainly considering layered articles, with a dense surface layer on a highly porous body that could be manufactured by double pressing. In this paper we present a low cost route to lightweight tiles, developed starting from mining tailings, such as waste from the mining of boron-rich minerals and basalt rock, and recycled glasses, such as common soda-lime glass and pharmaceutical borosilicate glass. A highly porous body was obtained by direct sintering of mixtures of mining tailings and soda-lime glass; despite the homogeneity of porosity and the formation of new crystal phases (at only 1000 °C), favorable to good mechanical properties, the water absorption remained far above the limits (>2 wt%). The water absorption was minimized by introduction of a dense glaze, associated to the firing of mixtures coated by a thin layer of recycled borosilicate glass powders; both color and shrinkage were optimized by the mixing of borosilicate glass with powders of zircon mineral and vitrified boron waste/basalt/soda-lime mixture.     

Investigation of the Adherence of Glass to Metals and Alloys

This investigation made use of the kinetic adherence test devised by Kapnicky¹ for testing the adherence of molten glass to heated metal samples. This testing apparatus attempts to simulate the conditions of the automatic forming machines of the glass-container industry. Several commercially pure metals and alloys plus a carbon-iron series were run for their adherence temperatures. It was found that as the per cent carbon in iron was increased the adherence temperature was decreased. Heat-treating of a modified brass sample decreased its adherence temperature. Persistence tests were run using tungsten, nickel, and Monel with clear and amber soda-lime glass. The persistence test consisted of holding the temperature of the metal constant below its adherence temperature and dropping molten glass beads on the heated metal surface until adherence occurred. The amber glass used gave higher persistance values than the clear soda-lime glass, although the adherence temperatures checked very closely. Monel metal heated to 900°F. gave a persistence of more than 800 molten glass contacts using amber glass at the rate of one glass contact per minute.     

A SIMPLE “SEALED-IN MERCURY ELECTRODE” APPARATUS FOR TESTING THE BREAKDOWN VOLTAGE OF HEAVY INSULATING MATERIALS1

A method has been developed whereby thick plates of insulating materials (of small area) may be electrically punctured under oil. The specimen is cemented between two hollow electrode holders by means of red sealing wax, as illustrated. One electrode holder, the elbow, may be made of ordinary cast-iron piping or glass. Mercury poured into both tubes gives the necessary contact. It is possible by these means to puncture a porcelain cylinder of diameter 1 ⅛ inches and 1 ⅛ inches thick at 142 kv., and with a porcelain cylinder 2 inches in diameter and 2 inches thick to reach 176 kv. without arcing. The “sealed-in mercury electrode” method has been compared with two other methods employing spheres and disks as electrodes, by puncturing cast polished plate glass specimens. The new method gives consistent results, the values being on the average 15 % higher than values obtained by the other two methods.     

SOLUBLE SALTS AND CLAY WARES*

A résumé of the present knowledge of the causes and the prevention of “Scum” and “Efflorescence.” It is proposed that the term “Efflorescence” be restricted to designate the surface deposits appearing because of the presence of soluble salts in the clays or burned wares and that the term “Scum” be used to describe the salts formed by the action of gases upon the wares during the drying or burning operations. Mention is made of the formation of a surface coating upon the ware soon after the kiln is opened, sometimes not appearing until some days after the ware is removed from the kiln. This scum is readily and permanently removed by the application of water. Such a residue was found to consist of sodium sulfate and sodium chloride. It is suggested that its formation was due to the presence of sodium chloride in the fuel and its subsequent deposition on the burned ware where it was changed in part to the sulfate by the action of the oxides of sulfur evolved from the fuel.     

Measurement of the elastic properties of polymer melts

A method and apparatus for measuring the elastic and other properties of polymers in the melt state is presented. The recoverable strain magnitude and the rate of strain recovery have been measured as a function of: applied shear rate, applied shear magnitude, temperature and molecular weight. The elastic properties indicate that there is an abrupt change or “transition” in the response of polystyrene melts at temperatures well above the glass transition. This abrupt change is found to be molecular weight dependent. The results are interpreted qualitatively in terms of molecular structure and practical processing operations. The possible relationship of this “transition” to T_u, is briefly discussed.     

碱金属氧化物Na2 O对陶瓷结合剂金刚石磨具性能的影响

通过调整陶瓷结合剂中碱金属氧化物Na₂O含量,来探究碱金属氧化物Na₂O对陶瓷结合剂金刚石磨具性能的影响。当n(Na₂O)/n(SiO₂)=0.1时,磨具试样的强度(57.7 MPa)和硬度(117 HRB)达到最大值。随着碱金属氧化物Na₂O添加量的增加,结合剂的耐火度随之显著降低,流动性显著增加。磨具试样断口SEM照片表明,适量的碱金属氧化物Na₂O能够使磨具断面空隙减少,孔隙度降低,结合剂与磨料分布更加均匀,结合剂与磨料结合界面更加紧密。XRD分析表明,磨具试样在720 ℃下烧结,结合剂中除了玻璃相还产生了一种晶相,结合剂中碱金属氧化物Na₂O的含量对烧结后产生的晶相种类无影响。     

Vitrification of a waste water flocculate from a petroleum catalyst manufacturer

Chemical and mineral compositions of a waste water flocculate generated in a manufacturer producing fluidized-bed catalytic cracking catalysts were analyzed. The flocculate was then calcined at 1200–1350 °C. X-ray diffraction analysis results indicate that the flocculate can be directly vitrified at 1350 °C without the addition of any other ingredients. The density and chemical durability of the directly vitrified product are comparable with commercial soda-lime-silicate glasses. However, the viscosity of directly vitrified glass melt was very high. Thus, the refining and shaping of the glass melt were difficult. With the addition of minerals such as limestone, dolomite and fluorite, workable glasses could be formed. The influence of MgO on the structure and properties of the obtained glasses is discussed. Results show that the density and hardness of the glass increase with the increase of MgO, whereas the chemical durability, transition and crystallization temperatures decrease. The present study provides a general way to utilize waste water flocculates in glass production.     

An application of the barcroft-warburg apparatus to the study of antioxidants in fats

Summary The results of the active oxygen method and those obtained with the Barcroft-Warburg apparatus at 70° C. are in good agreement with storage tests at room temperature on lard to which no anti-oxidant is added and on lard to which lecithin alone is added. With lard to which d-isoascorbyl palmitate or d-isoascorbyl monostearate, in concentrations between 0.01 and 0.10 per cent, is added the results with the Barcroft-Warburg apparatus are in much better agreement with storage tests than are those of the active oxygen method. The d-isoascorbyl esters in 0.01 to 0.10 per cent in lard usually behave as antioxidants with the active oxygen method and as pro- or antioxidants, depending on their concentration, with the Barcroft-Warburg apparatus and during storage at room temperature. This study demonstrates that in testing new compounds for antioxidant properties conclusions should not be drawn from results obtained when the experimental conditions of the test are very different from the conditions under which the antioxidant is to be used. It emphasizes the importance of correlating the results of accelerated tests with storage tests. Presented before the Division of Agricultural and Food Chemistry at the 105th Meeting of the American Chemical Society, Detroit, Michigan, April 13, 1943.     

ELECTRICALLY HEATED GLASS ANNEALING LEHR1

Time-temperature data relating to relaxation of stresses. —Existing time-temp, data covering the relaxation of stresses in annealing of glass has been assembled. Range, control, and distribution of temp. are important factors in annealing. The annealing time was reduced from 5 to 2.3 hours when temp. var. was reduced from 10° to 2.5°C, in the case of one glass whose annealing temp. was 476°. Electric heat secures perfect anneal in shortened time. —Electric heat with its automatic control holds temp. within +0.6 per cent in ranges required for annealing, as shown by tests, even when the temp. changes 23° per hour and when the annealing treatmat (as for optical glass) covers a month in time. Vertical Lehr superior to horizontal type. —Electrically heated lehrs of horizontal and vertical types are discussed. The vertical lehr offers many apparent advantages and a higher thermal efficiency. A particular lehr of 500–600 Ibs. ware capacity per hour, shows efficiencies in ratio of 6 to 10 in favor of electric lehr of vertical type. Tests made on an electrically heated vertical lehr annealing high grade ware showed a reduction in cost of manufactured part of 20 per cent, or more than 75 times total cost of electric power consumed.     

USE OF SEDIMENTARY KAOLINS OF GEORGIA IN WHITE-WARES1

Introduction.—From twenty-six different clays tested the eleven best suited to the white ware industries were washed and, after preliminary tests were run, were tried out in the different white ware industries. Laboratory Tests on Crude Clays.—Tables containing data on the physical properties of the green and burned clays are given. Laboratory Tests on Washed Clays.—Test bars and color pats were made from a typical white ware body. The usual physical tests on unburned and burned bodies are reported. Results obtained on the rate of casting and strength of the clays as compared to English and Florida clays are included in the data. Industrial Application.—Plant practice tests carried out at two floor tile and one wall tile plant are reported. Bodies containing eleven Georgia clays were tried out. Better results were obtained in the vitrified bodies than in the porous bodies. The smaller shapes gave better results than the larger. Tests on general ware and electrical porcelain art: in progress. The conclusion is reached that the Georgia sedimentary clays can be used to displace all the china clay in a vitrified tile body but less than half the china clay in plastic bodies. The color of a body is greatly improved by using washed clay: and can be further improved by the addition of cobalt stain.     

Heat assisted twin screw dry granulation

A new “assisted” dry granulation method has been devised for the twin‐screw granulator. The method may be beneficial to drug preparation as it limits heat exposure to only one barrel zone, much shorter than melt granulation. Its mechanism was investigated using four placebo formulations, each containing a polymer binder with a glass transition temperature lower than 130°C. Variables of study included screw configuration, screw speed, barrel zone temperature, and moisture content. Granulated samples were characterized for size and porosity while feed powders were examined for their thermal transitions, interparticle friction, cohesion, and sintering rate. Results indicated that granule coalescence relied on melting of polymer binder in the kneading blocks by a combination of heat conducted from barrel and generated from screw speed friction. Successful granulation was possible with minimal addition of water, although varying the moisture content showed the relevance of the polymer's glass transition temperature and sintering progress. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

A yttrium aluminosilicate glass fiber with graded refractive index fabricated by melt‐in‐tube method

A graded‐index fiber with yttrium aluminosilicate (YAS) glass core was fabricated by a “Melt‐in‐Tube” method. The refractive index and stress profiles of the fibers exhibit a highly symmetrical gradient tendency along the radial axis which is in accordance with the results of element migration. Based on the formation mechanism of YAS glass core, the relationships between the refractive index/stress profile and the spontaneous migration are discussed. A linear all‐fiber laser based on the obtained fiber shows a laser output threshold of 11.48 mW and slope efficiency of 8.3%. The near‐field beam intensity distribution of fiber laser with spectrum FWHM of 0.24 nm indicates the good laser beam quality. The facile “Melt‐in‐tube” method was proved to be reliable in designing graded‐index fiber through the dissolution and diffusion process, which is more advanced than commonly used “Rod‐in‐tube” method.     

THE STRENGTH OF GLASS AS AFFECTED BY CASING1

Considerable regarding the strengthening of glass by surface chilling has been written. Theoretically it has been shown that the modulus of rupture of slabs toughened glass may have a maximum of 3.4 times that of annealed glass. Complicated shapes and large surfaces cannot be satisfactorily treated by this method. Very similar results may be obtained by the method commonly called “casing,” wherein the article consists of three layers, the two outer ones being of glass having a lower coefficient of expansion than the inner layer. After annealing in the usual way the outer layers are left in compression and the central layer is in tension. By combining these initial stresses with those set up during a test to determine the modulus of rupture, a set of equations was derived. These equations were expressed in graph form, one of which gave the relation of case thickness expressed in tenths of the total thickness to the relative strength compared to flawless annealed glass. A number of curves were shown based upon the ratio of maximum internal tension to the maximum tension at the surface. These curves enabled the proper case thickness to be found in order to develop optimum strength for any assumed ratio of maximum internal tension to external tension. Another graph showed the corresponding initial tension and compression due to casing for the conditions outlined above. These curves showed that the case thickness could vary considerably without greatly affecting the strength and also that the initial stresses are smaller than those usually thought necessary. The maximum relative strength as developed by “casing” had a somewhat smaller value than that developed by “toughening.”