bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction and Fired‐Property Studies of Cordierite Compositions
Authors: LAMAR R. S. , WARNER M. F.
Published: June 2006

Ceramic bodies approaching the theoretical composition of cordierite were prepared from mixtures of talc and clay; talc, clay, and varying amounts of MgCO3; talc, clay, and alumina; and prochlorite and clay. Additions of BaCO3 and PbSiO, were made. Differential thermal analysis and X‐ray diffraction methods were used in reaction studies of each composition. Bodies had thermal expansions from 0.344 to 0.109% (25° to 900°C.). BaCO3 and PbSiO3 affected thermal expansion. Dielectric properties were improved by additions of BaCO3 and were markedly improved by additions of both BaCO3 and PbSiOl. Cordierite started to crystallize at about 1250°. Additions of PbSiO3 lowered this temperature about 50°C. With sufficient BaCO3, the Ba‐C phase, as described by Wisely, crystallized in place of cordierite. The crystallization temperature for the Ba‐C phase was about 1200°C. With insufficient BaCO3, both cordierite and Ba‐C formed. Additions of PbSiO3 reduced the crystallization temperature of the Ba‐C phase by 50°C. and increased the glassy phase. Several of the compositions should haw considerable practical value.
Abrasion Resistance of Some Dry‐Process Enamels
Authors: SPANGENBERG WILLIAM C.
Published: June 2006

The resistance to abrasion of some dry‐process cast‐iron enamels was investigated using the new weight‐loss method of testing abrasion resistance now under development by the Porcelain Enamel Institute. Some modifications of the test procedure based on preliminary studies, and which were accepted by the P.E.I. Quality Development Committee, were adopted for the investigation. The test differentiated between surface and subsurface abrasion resistance. Data obtained on eight commercial enamels showed the general superiority of acid‐resistant enamels compared with non‐acid‐resisting compositions. It was found that longer smelting times and small mill additions of tin oxide improved the abrasion resistance. Changes in firing treatment had little effect on this property.
Fundamental Studies of Talc: I, Constitution of TaIcs
Authors: PASK JOSEPH A. , WARNER MAURICE F.
Published: June 2006

Talcs exhibit considerable variation in texture and in chemical analyses. These variations are explored on the basis of phase, field, and atomic structure considerations with the aid of chemical, X‐ray, and dserential thermal analyses. It is proposed that this complexity is accounted for primarily on the basis of the existence of solid solutions of the layer or group type.
Additional Phase Equilibrium Data for the System CaO‐MgO‐SiO2
Authors: RICKER R. W. , OSBORN E. F.
Published: June 2006

Results of studies of phase equilibria in mixtures lying along the olivine join and in the low‐silica portion of the system CaO‐MgO‐SiO2 necessitate the making of certain changes in the published diagram for this system. At or near liquidus temperatures, solid solution between forsterite and monticellite is extensive, although not continuous. X‐ray diffraction, optical, and phase equilibrium data are presented for this olivine series. In the low‐silica region a field of tricalcium silicate has been outlined and approximate liquidus temperatures have been determined. A revised equilibrium diagram for the system is presented.
Fundamental Study and Equipment for Sintering and Testing of Cermet Bodies: VI, Fabrication, Testing, and Properties of 72 Chromium‐28 Alumina Cermets
Authors: SHEVLIN THOMAS S.
Published: June 2006

Physical properties, including firing shrinkage, density, modulus of rupture from 75° to 2400°F., stress‐rupture life in cross bending and in tension at 1800° and at 2000°F., modulus of elasticity, tensile strength from 75° to 2000°F., comparative impact resistance, oxidation resistance, thermal expansion, and thermal‐shock resistance, for the composition 28% alumina‐72% chromium combine to indicate the potential value of this material in high stress applications at elevated temperatures where severe thermal shock may be encountered. While the thermal‐shock resistance is much better than that possessed by the low‐chromium high‐alumina bodies discussed in Part V, the mechanical properties at elevated temperatures do not appear to suffer as a result of the highly continuous metal phase in the more recently developed body.
Stability of Refractories in Liquid Metals
Authors: REED E. L.
Published: June 2006

Present technological developments are making more extensive use of liquid metals as heat‐transfer agents. Their stable and relatively noncorrosive character makes them especially adaptable for high‐temperature applications. The compatibility of various liquid metals with refractories has been investigated in the past over a temperature range up to several hundred degrees centigrade. To extend this information to much higher temperatures, corrosion experiments were carried out at North American Aviation utilizing liquid sodium, tin, and bismuth. Tests were conducted in the range 800° to 1500°C. using molybdenum, tantalum, tungsten, graphite, alumina, zirconia, and other materials. The experimental apparatus and procedures employed in conducting both static and dynamic tests are described and significant results are summarized.
Solid Solution and Chromium Oxide Loss in Part of the System MgO‐Al2O3‐Cr2O3‐SiO2
Authors: WARSHAW I. , KEITH M. L.
Published: June 2006

Thermal and X‐ray studies show that there is complete solid solution between MgO.Cr2O3 and MgO.Al2O3 and that the spinel solid solutions are stable with no exsolution down to temperatures as low as 510°C. There is no solid solution of excess Cr2O3 in MgO.Cr2O3 nor of MgO.Cr2O3 in Cr2O3. The join MgO.Cr2O3–Al2O3 is found to be nonbinary; compositions along that join yield mixtures of a chromium oxide‐alumina solid solution and a spinel solid solution on firing to temperatures high enough to promote solid‐state reaction. Chromium oxide loss by volatilization increases at higher temperature. At a given temperature, chromium oxide loss is found to vary directly with the partial pressure of oxygen in the furnace atmosphere and with the ratio of MgO to SiO2 in the charges heated.
A Study of Hairlining
Authors: COX J. E. , ANDREWS A. I.
Published: June 2006

A test for the hairlining tendencies of enamels is presented. A curved 4‐ by 8‐in. piece of 18‐gauge enameling iron is used as a test piece in which a simulated service condition of strain is produced by a 2‐ by 2‐in. piece of 16‐gauge enameling iron placed on the top center of the test piece. Before enamel application the specimen is curved lengthwise in a mold of 1 1/2‐ft. radius of curvature with a resulting permanent distortion of approximately 1/8 in.; the strain condition is obtained by an unattached straining piece. These two conditions enable good reproducibility of the direction and magnitude of the distortion due to uneven heating during firing, and the resulting pattern of hairlines varies only as influenced by enameling variables. The stepwise process of hairline formation is described with the aid of photographs and photomicrographs of enamel surfaces and cross sections. The effects of ground‐coat and cover‐coat variables and the significance of proper firing schedules are presented and discussed.
Phosphate‐Bonded Talc: A Superior Block‐Talc Substitute
Authors: COMEFORO J. E. , BREEDLOVE J. G. , THURNAUER HANS
Published: June 2006

Phosphate‐bonded talc shows advantages over block talc, which indicates that it is a superior substitute for this strategically important raw material. A satisfactory product has been made using talc from domestic sources. It has been formed by various methods, such as dry pressing, hydrostatic pressing, or hot pressing. Some factors that control the properties of the end product have been investigated, and the mechanical and dielectric properties are compared with those of natural block talc.
Synthetic Mica Investigations: III, Precision‐Controlled Electric Furnaces for Temperatures to 1500°C
Authors: HUMPHREY R. A. , WORDEN E. C.
Published: June 2006

Three furnaces using silicon carbide heating elements are described, including (1) a utility furnace for melting and testing, (2) a precisioncontrolled (± 1/2°C.) crystallization furnace, and (3) a rectangular crystallization furnace. Schematic drawings of the furnaces and a simplified wiring diagram for the heating elements are included. One composite controller is described from a functional viewpoint, with a block‐diagram presentation. A complete circuit diagram of this controller also is incorporated. The use of saturable core reactors in regulating power to electric furnaces is advocated; reactors permit the control of electricity in a manner similar to adjustment of the flow of water by means of a valve.
Refractory Castables: II, Some Properties, and Effects of Heat‐Treatments
Authors: HEINDL R. A. , POST Z. A.
Published: June 2006

Differential thermal analyses were made and weight losses were determined up to 1000°C. for a domestic and an imported high‐alumina hydraulic cement after hydrating. Refractory castables were prepared in the laboratory with these two cements and fire‐clay brick and flintclay aggregates. Compressive, transverse, and tensile strengths of these castables were obtained after heating 4,8, and 12 months at 300°C. and at other temperatures up to 1350°C. for shorter periods of time. Sixteen commercial brands of castables were tested for sieve analysis, P.C.E., and flow, on the material “as received”. The three types of strengths of the sixteen castables also were determined after treatments at 95% relative humidity and after heating at temperatures up to 1350°C. Some information on porosity and structural and linear changes after the heat‐treatments was obtained.
Improved Method of Measuring Thermal Conductivity of Dense Ceramics
Authors: RUH EDWIN
Published: June 2006

An instrument has been developed to measure the thermal conductivity of dense ceramic materials over the temperature range 20° to 200°C. A cylindrical ceramic specimen 1/2 in. in m diameter by 1/2 in. long is used in the instrument. hessures lower than 1μ of mercury are used to reduce heat losses and to permit rapid attainment of steady‐state conditions.
Determination of Potassium in Glass with the Hydrogen Flame Photometer
Authors: CLOSE PAUL , WATSON M. T.
Published: June 2006

Use of the hydrogen flame attachment and the Beckman Model DU spectrophotometer to determine potassium in soda‐lime and boro‐silicate glasses in the order of 0.01 to 2.5% K2O is described. Data are presented showing the effect of varying concentrations of sodium, calcium, magnesium, barium, zinc, aluminum, and iron on the potassium flame emission. The potassium emission is relatively free from interference effects except from zinc and large amounts of barium. The method is rapid, precise, and accurate to 2% of the K2O present in the sample.
The System CaO‐ZnO‐SiO2
Authors: SEGNIT E. R.
Published: June 2006

Equilibrium relationships in this ternary system were determined by the quenching method. The only ternary compound occurring in the system was found to be Ca2ZnSi2O7, which corresponds to the natural mineral hardystonite. It has a congruent melting point (1425°C.) and a large primary‐phase field in the center of the system. Primary‐phase fields for cristobalite, tridymite, CaSiO3, Ca3Si2O7, Ca2SiO4, ZnO, and Zn2SiO4 were also determined in part or in full. The results of this work have some bearing on the minerals and reactions occurring in lead blastfurnace slags and in glazes containing zinc oxide.
High‐Temperature Zirconium Phosphates
Authors: HARRISON D. E. , McKINSTRY H. A. , HUMMEL F. A.
Published: June 2006

The existence of two zirconium phosphate compounds has been established. The “normal” phosphate, ZrP2O7, has a reversible inversion at 300 °C. and dissociates to the zirconyl compound, (ZrO)2P2O7, at 1550°C., with the simultaneous loss of P2O5 as vapor. The room‐temperature form of ZrP2O7 is cubic with refractive index 1.657 ± 0.003. The zirconyl compound has a stable existence to temperatures around 1600°C. and is characterized by a very low linear thermal‐expansion coefficient.
Effect of Ceramic Coatings on Fatigue Strength of Metal
Authors: PLANKENHORN W. J.
Published: June 2006

A series of tests was conducted to determine the effect of porcelain enamels and ceramic coatings on the endurance limit and the fatigue life of ingot iron components subjected to flexure. The specimens were of the Krouse cantilever beam type. They were designed to provide a uniform bending triangle with a uniform stress throughout the test area. A completely reversed stress was applied by repeated bending in a standard motor‐driven fatigue‐testing unit. The results were plotted as S‐N curves with the stress plotted as the ordinate and the number of cycles to failure as the abscissa. A comparison of the curves for the metal alone and for the coated metal showed that ceramic coatings noticeably improved the fatigue strength and also the fatigue life at stresses above the endurance limit.
Studies on Red‐Colored Silver Glass
Authors: BANERJEE BHUPATI KUMAR
Published: June 2006

X‐ray and spectroscopic investigations of a variety of red‐colored silver glasses have been undertaken and an attempt has been made to explain the cause of the coloration. The absorption spectra show the presence of a band around 5017 a.u. and 5025 a.u. in borate and in phosphate glass specimens, respectively, and the silver crystallites in both phosphate and borate specimens have been identified by the X‐ray diffraction method.
Plastic Deformation of Ceramic‐Oxide Single Crystals
Authors: WACHTMAN J. B. , MAXWELL I. H.
Published: June 2006

It was found that plastic deformation takes place in periclase above 1100°C., in rutile above 600°C., and in sapphire above 900°C. The mechanism is slip; in sapphire (0001) is the slip plane and [1120] is the slip directiog. All creep curves for sapphire in tension show the same qualitative features. Each consists of three stages: a stage of increasing creep rate (sometimes called an incubation period), a stage of large but decreasing creep rate (sometimes called first‐stage creep), and a stage of small and nearly constant creep rate (sometimes called second‐stage creep). The so‐called third‐stage creep, characteristic of metal behavior, has not been noted. Plastic deformation increases the electrical resistivity of sapphire at constant temperature.
Fluoride Model Systems: IV, The Systems LiF‐BeF2 and PbF2‐BeF2
Authors: ROY D. M. , ROY R. , OSBORN E. F.
Published: June 2006

Additional information on phase equilibria in the subsolidus region of the system LiF‐BeF2 was obtained and a study was made of the system PbF2–BeF2. In the system LiF‐BeF2 the compound LiBeF3 occurs; it decomposes below the solidus at 300° C. to yield Li2BeF4 and the quartz form of BeF2. An additional subsolidus compound having the probable composition LiBe2F5 forms below 275°C. No evidence was found for the existence of the alleged compound LiBe2F5. In the system PbF2‐BeF2 two compounds occur: 3PbF2.BeF2 and PbF2‐BeF2; the former melts congruently at 482°± 5°C. and the latter at 585°± 5°C. Extensive solid solution exists between PbF2.BeF2 and BeF2. The cristobalite form of BeF2 crystallizes from glasses of high BeF2 content at temperatures of 450°C. or lower but is converted to the quartz form by heating at higher temperatures or in the presence of liquid.
Synthetic Mica Investigations: IV, Dielectric Properties of Hot‐Pressed Synthetic Mica and Other Ceramics at Temperatures up to 400°C.
Authors: COMEFORO J. E. , HATCH R. A.
Published: June 2006

The dielectric properties of hot‐pressed synthetic mica were studied in comparison with those of other ceramic insulating materials with special attention to the variation of these properties with temperatures up to 400° C. Power‐factor and dielectric‐constant measurements were made at 1 mc., and the volume resistivity was determined on a d.‐c. resistance bridge with a voltage of 22.5. The comparison revealed the importance of evaluating the electrical properties of a dielectric material at the temperature at which the insulator is expected to operate. A plot of the power‐factor data against the reciprocal of the absolute temperature did not permit the results to be represonted by two intersecting straight lines, as has been previously reported.
Solid‐state Equilibrium Relations in the System MgO‐Al2O3‐SiO2‐ZrO2
Authors: HEROLD PAUL G. , SMOTHERS W. J.
Published: June 2006

Using techniques developed by Goldschmidt and lately utilized by Foster, solid‐state equilibria were studied in the system MgO‐Al2O3‐SiO2 ZrO2. The ternary systems MgO‐Al2OrSiO2 and MgO‐SiO2‐ZrO2 are the only faces of this four‐phase system that have beep studied extensively. Compositions in each of the four faces were heated to temperatures below their fusion point and, after they had been cooled, they were examined by X rays to identify the phases present. After solid‐state equilibria had been established or verified in the four faces of the system, quaternary compositions were studied to determine the Alkemade tetrahedra.
A High‐Temperature X‐Ray Camera
Authors: JOHNSON J. R.
Published: June 2006

A high‐temperature X‐ray camera capable of operating as high as 2200°C. is described. The specimen is heated by a simple tantalum resistance heater. Temperature control is maintained by a constant power input. A sliding film holder permits a number of successive pictures to be taken without disturbing the specimen or apparatus.
Role of Nickel Dip in Enameling of Sheet Steel
Authors: MOORE D. G. , PITTS J. W. , HARRISON W. N.
Published: June 2006

An investigation was made of the effects of (a) the firing time and (b) the weight of nickel deposited from the nickel‐dip solution on the adherence developed by a cobalt‐free and a cobalt‐bearing ground‐coat enamel on both enameling iron and a titanium‐bearing low‐carbon steel. At 1550°F. the nickel improved the measured adherence index the most during the 2‐minute firing. The effect of the nickel, however, decreased markedly with longer firing times. There was an optimum nickel deposit for maximum adherence, an optimum that varied from 50 to about 120 mg. per sq. ft., depending on the type of cleaning used and on the type of enamel applied. The nickel dip reduced the tendency to fish‐scale. Furthermore, there was an apparent relation between fish‐scaling resistance and good adherence; no specimen with an adherence index of 70 or above showed fish‐scaling tendencies. Metallographic studies of the interface of coated specimens showed that nickel dipping of the steel before enameling brought about a surface roughening during the firing operation. A relationship was noted between the degree of roughening and the measured adherence index. The roughening of the steel surface was ascribed to galvanic corrosion.
Density Phenomena in the Transformation Range of a Borosilicate Crown Glass
Authors: RITLAND HAROLD N.
Published: June 2006

The effect of heat‐treatment in the transformation range on the density of a borosilicate crown glass was studied by the method of quenched samples. An empirical equation is presented which satisfactorily represents the approach of the density to its equilibrium value at three temperatures. The density‐temperature relation in the special case of cooling at a constant rate is discussed theoretically and experimentally. It is shown that if the initial temperature is sufficiently high, the density‐temperature relations for different cooling rates are identical except for a displacement along the equilibrium density‐temperature line by an amount proportional to the logarithm of the cooling rate. The final density reached after cooling through the entire transformation range is also shown to depend linearly on the logarithm of the rate. The implications of these results are discussed.
Processing Studies on Pure Oxide Bodies
Authors: McCREIGHT LOUIS R.
Published: June 2006

The results of some studies on the effect of (1) ball‐milling time, (2) granulating by “slugging,” and (3) dry pressing of pure oxide ceramic bodies are presented. When the compressive strength of specimens of single‐component bodies was plotted against ball‐milling time (in revolutions), minima in the curves were found between 30,000 and 50,000 revolutions. For a multicomponent body of the porcelain type and one of the oxide porcelain type, when the same data were plotted, maxima in the curves were found between 30,000 and 40,000 revolutions. Granulating by slugging provided 30% greater compressive strength, 1.5% less shrinkage, and 1% less absorption in the specimens as compared with specimens formed from ungranulated material. High‐pressure forming, preferably by hydrostatic pressure, was desirable; however, there appeared to be an optimum pressure for the physical properties of each material.
Some Influences of Carbon in Enameling of Steel
Authors: CHU G. P. K. , MAGOR J. K. , DAVIS H. M.
Published: June 2006

Analyses of the gases produced by carbon‐bearing ferrous materials, fired in an oxidizing environment with or without enamel bisque, are correlated with the enameling properties and the microstructures of the materials. Total carbon content, or total volume of carbon oxides producible in designated circumstances, is not a reliable guide to enameling behavior form and distribution of the carbide phase are critically significant. A vacuum system for extraction and analysis of gases is described.
Synthetic Mica Investigations: V, A Low‐Shrinkage Machinable Ceramic of Phosphate‐Bonded Synthetic Mica
Authors: COMEFORO J. E.
Published: June 2006

By using phosphoric acid as the binding agent for powdered synthetic mica, it was possible to produce by dry‐pressing a glass‐free machinable low‐shrinkage dielectric whose properties were controllable by varying the mica com‐ position, the forming pressure, the firing temperature, and the phosphate content. The total shrinkage was easily maintained at less than 3%, with the transverse strength in excess of 6000 lb. per sq. in. A zero‐shrinkage composition was also developed and its properties are discussed. A dense, impervious ceramic was not produced by this method; the water absorption seldom was less than 4% with forming pressures of 10,000 lb. per sq. in. or less. The dielectric characteristics of this ceramic approached those reported for hot‐pressed phosphate‐free synthetic mica when it had similar porosity. The dielectric loss factor was of the order of 1 to 2% at room temperature and 4 to 8% at 300°c. and 1 mc. This material is suggested as a replace‐ ment for natural block talc.
High‐Temperature Testing Techniques for Brittle Refractory Materials
Authors: GANGLER JAMES J.
Published: June 2006

The evaluation of brittle refractory materials calls for special techniques that are different from those normally used for ductile materials. Techniques have been developed at the N.A.C.A. Lewis Flight Propulsion Laboratory to evaluate brittle materials as turbine blades in jet engines and in creep, stress rupture, and thermal shock. The type of equipment and the procedure for creep and stress‐rupture testing are described. A parameter is given by which the thermal‐shock resistance of brittle materials is related to their physical properties. A simple apparatus has been devised to verify experimentally conclusions given by this parameter. Another apparatus is described that simulates the thermal‐shock conditions encountered in a jet engine. The final testing of materials in a jet engine is described.
Magnetic Ceramics: IV, Development of a Complex Ferrite with a Rectangular Hysteresis‐Loop Characteristic
Authors: ECONOMOS GEORGE
Published: June 2006

A complex ferrite composition was investigated to ascertain how much the magnetic properties of the final product were affected by body preparation, forming pressure, firing temperature, and time at peak temperature. One reducing and three oxidizing atmospheres, in addition to a quenching cycle, were investigated. The magnetic parameters μi and Bm increased with density, whereas Hc decreased. The specimens fired at the maximum peak temperature, or quenched from above 800°C, gave markedly diminished BT values. The maximum loop rectangularity followed the same pattern.
Study of Efflorescence on Experimental Brickwork Piers
Authors: RITCHIE T.
Published: June 2006

Efflorescence on brickwork piers made of three types of brick and six mortars appeared to depend mainly on (a) the Portland cement content of the mortar, (b) the type of brick, and (c) the season of the year. Efflorescence formed in the cold part of the year and was absent in the summer. Portland cement substituted for lime in mortars contributed to efflorescence; however, the amount of efflorescence depended also on the type of brick (probably on the pore structure).
Study of Efflorescence Produced on Ceramic Wicks by Masonry Mortars
Authors: RITCHIE T.
Published: June 2006

Ceramic wicks (Efflorwicks) were partly embedded in cylinders of masonry mortars of various compositions, and the hardened mortars were alternately wetted and dried, which produced various amounts of efflorescence on the wicks. Portland cement in mortars contributed significantly to efflorescence. The alkaline material of the cementing substance of the mortars appeared to be an important source of the efflorescence.
Polarographic Analysis for Antimony in Glass
Authors: WILLIAMS J. P. , SCHWENKLER T. A.
Published: June 2006

Antimony, usually added as a fining agent in a concentration range of about 0.2 to 2.0% Sb2O3, can be determined readily in many types of glass with a polarograph. Interfering elements are seldom encountered in common glass compositions, so chemical separations are not necessary. The mean difference between chemical and polarographic analyses for twenty‐one glasses covering soda‐lime, borosilicate, lead, and barium compositions is about 0.02% Sb2O3.
Drying Rates in Infrared Drying of Clay
Authors: WOO DAVIS , SIMONS H. P. , JONES P. R.
Published: June 2006

Equations are presented showing the effect of (a) distance of lamp bank from drying surface, (b) thickness of material, (c) absorptivity of the material, (d) intensity of radiation, and (e) humidity on the drying rate of clay. The equations were developed by graphical methods and it was found that the drying rate was a linear function of intensity of radiation and absorptivity of clay and a power function of thickness and distance of lamps from the drying surface. Infrared drying was independent of humidity below an absolute humidity of 71%.
Phase Equilibria in the System BaTiO3‐SiO2
Authors: RASE D. E. , ROY RUSTUM
Published: June 2006

The system BaTiO3–SiO2 is characterized by two congruently melting compounds and a compound having a subsolidus stability maximum. A barium analogue of the mineral sphene, BaTiSiO5, was shown to melt congruently at 1400°C, and BaTiSi2O7 melted congruently at 1250°C. The gem mineral benitoite (BaTiSi3O9) was synthesized hydrothermally and was shown to decompose below the solidus to form BaTi‐So2O7 and SiO2 when heated above 965°C, hydrothermally or above 1050°C, dry. Three eutectics in the system were determined: at 1245°C. and 70 mole % SiO2, at 1246°C. and 63% SiO2, and at 1260°C. and about 29% SiO2. Glasses with high refractive indices were obtained over a limited range of compositions. The cubic‐hexagonal transition temperature in barium titanate was raised sharply by small additions of silica. The maximum inversion temperature observed was 1575°C. and must have been due to limited solid solution of SiO2 in BaTiO3.

Three intermediate compounds have been shown to exist in the system BaTiO3‐SiO2. The barium analogue of sphene, BaTiSiO5, melts congruently at 1400°C, and BaTiSi2O7 melts congruently at 1250°C. The compound BaTiSi3O9 (benitoite) was found to dissociate to form BaTiSi2O7 and SiO2 at 1050°C, under dry conditions and at 965°C, hydro‐thermally. This important gem mineral was synthesized from completely melted and quenched stoichiometric mixtures treated hydrothermally below 965°C, and at a water pressure of 5000 lb, per sq. in.

There are three simple eutectics in the system: one between BaTiSi2O7 and SiO2 at 1245°C, and 70 mole % SiO2; one between BaTiSi2O7 and BaTiSiO5 at 1246°C, and 63% SiO2; and one between BaTiSiO5 and BaTiO3 at 1260°C, and about 29% SiO2.

It was fairly easy to obtain glasses having refractive indices between 1.70 and 1.88 over a composition range of 50 to 75% Silica.

The data pertaining to the cubic‐hexagonal transition in barium titanate were best explained on the basis of limited solid solution. As a result of the solid solution, the cubic‐hexagonal transition temperature is raised sharply from 1460°C. for the pure barium titanate to about 1575°C. by small additions of silica. The limits of solid solubility are approximately 8 and 4% SiO2 for the cubic and hexagonal forms, respectively.
Magnetic Ceramics: V, Magnetic Properties of Square Loop Ferrites Within the System MgO‐MnO‐Fe2O3
Authors: ECONOMOS GEORGE
Published: June 2006

Thirteen compositions within the center of the system MgO‐MnO‐Fe2O3 were investigated because of their rectangular hysteresis‐loop characteristic. Initial permeabilities were measured, and Bm, BT, Hc, and R8m were obtained from quasi‐static hysteresis loops. High MgO content was found to be detrimental to the magnetic properties and to impair the loop rectangularity. The highest hysteresis‐loop squareness ratio, R, 8m, was found in a composition with high Fe2O3 content, and the lowest coercive force, Hc, was found in a composition with high MnO content.
Effect of Firing Cycle on Structure and Some Dielectric and Piezoelectric Properties of Barium Titanate Ceramics
Authors: EGERTON L. , KOONCE S. ELOISE
Published: June 2006

In the preparation of barium titanate ceramics for dielectric and piezoelectric applications, careful attention must be given to many factors which determine the ultimate performance of the ceramic. In this study structural differences were observed with the aid of electron micrographs as the time and temperature of firing were varied. At lower temperatures and shorter firing intervals crystals remained small, grain‐boundary areas were relatively large, and there were numerous voids where several crystals joined. As the time and/or temperature were increased, crystals became larger with an improved grain‐boundary condition that resulted in better structure. An optimum condition was soon reached beyond which rounding of edges at grain boundaries where several crystals joined became more pronounced. This caused an increase in the number of voids. Accompanying these changes, the 1‐kc. dielectric constant, the piezoelectric constants (thickness mode), and coupling coefficients first improved, reached optimum values, and then declined slightly, but the resistance to depoling continually decreased as the crystal size increased. An experimental technique of rapid heating and cooling was used to prepare dense specimens of chemically pure barium titanate with relatively small average crystal sizes. Dielectric constants as high as 3000 with Q values of 80 were obtained for these high‐density ceramics, accompanied by low effective piezoelectric constants and coupling coefficients.
Investigation of California Talc for Use in Wall Tile
Authors: LENNON J. W.
Published: June 2006

The suitability of various California talcs for use in a wall‐tile body was investigated. The nature of the talcs and their associated minerals was studied using the petrographic microscope, chemical and differential thermal analysis, and heavy liquid separation techniques. The characteristics of the various talc ores were related to some of the properties of the fired wall tile.
New Method of Preparing Clay Samples for Differential Thermal Analysis
Authors: WALTON J. D.
Published: June 2006

A method of preparing clay samples for differential thermal analysis which permits the analysis to be made with the test and reference samples freely exposed to the furnace atmosphere is described. The data obtained when samples were thus heated are presented, together with those obtained when an Inconel block was used to contain the clay. The sensitivity of the two methods is compared, with particular emphasis on the increased sensitivity in the low‐temperature range which resulted from the use of the new method.
Structural Behavior in the System (Ba, Ca, Sr) TiO3 and Its Relation to Certain Dielectric Characteristics
Authors: McQUARRIE MALCOLM
Published: June 2006

The effect of strontium additions on the immiscibility region between barium titanate and calcium titanate was studied and it was found that the two‐phase gap is closed by about 18% strontium titanate when the specimens are fired at 1430°C.; at lower firing temperatures the gap is greater and there is evidence of incomplete reaction. The effect of different firing temperatures on the dielectric properties of bodies in this region is discussed and the theoretical conclusions are supported by experimental data. The strontium titanate‐calcium titanate binary was studied and the phase boundaries (cubic‐tetragonal, tetragonal‐orthorhombic) were located with regard to changing composition and temperature.
A Tungsten Coil Furnace for High‐Temperature X‐Ray Diffraction Investigations
Authors: McKEAND I. J. , HURSH R. K.
Published: June 2006

A furnace with a tungsten coil as the heating element has been designed and built for use with the X‐ray diffraction spectrometer in the study of phase changes and equilibria at high temperatures. Tests indicate that temperatures up to 2000°C. can be reached and maintained for long periods of time in a neutral atmosphere. Materials which are not readily affected by the tungsten vapors that are present can be heated successfully in this type of furnace.

With this furnace, samples may be heated to and held at temperatures up to 2000° C. while X‐ray spectrometer data are obtained. Phase changes and equilibrium conditions existing at temperatures considerably above those obtainable with Pt alloy elements and at different time intervals at constant temperatures can thus be readily and positively determined. It should be noted, however, that materials which are readily reduced by tungsten vapors cannot be satisfactorily heat‐treated in this particular type of furnace.
Further Study of Sintering Phenomena
Authors: WILDER D. R. , FITZSIMMONS E. S.
Published: June 2006

The sintering mechanism of aluminum oxide was studied with attention to the influence of time, temperature, and particle size. Mechanisms proposed by other investigators are reviewed as they pertain to the information obtained from the study. Shrinkage, density, and grain growth are considered; they indicate that rate and degree of sintering increase with decreasing particle size. Loose powders are shown to exhibit sintering phenomena when the particle size is small.
Ceramic Coatings for Nuclear Reactors A Progress Report
Authors: RICHMOND JOSEPH C. , LEFORT HENRY G. , WILLIAMS CHARLES N. , HARRISON WILLIAM N.
Published: June 2006

Ceramic coatings were prepared from materials having low absorption coefficients for thermal neutrons. They were specifically designed for application to typical high‐temperature alloy parts for use in nuclear reactors. Best results were obtained with boron‐free coatings of the frit‐refractory type, in which a high‐barium frit containing small amounts of phosphate, beryllia, lime, zinc oxide, and titania was milled with additions of ceria or mixtures of chromic oxide and ceria. Coating compositions and test data are given.

Summary and Conclusions

A total of 85 new frits and more than 200 new coatings were prepared and tested in the development of ceramic coatings for the protection of high‐temperature alloys against oxidation in air at elevated temperatures. The coatings which were designed especially for use in nuclear reactors, where only materials of low absorption coefficients for thermal neutrons can be used, may be suitable for more conventional purposes. The development work is still in progress, but the results to date may be summarized as follows:

(1) Boron‐free frits have been developed and tested that have average neutron absorption coefficients in the range 0.15 to 0.50 barn, fritting temperatures of 2600°F. or below, and fiber‐deformation softening temperatures of 1450°F. or above.

(2) The best frits developed to date are of the barium silicate type and contain small amounts of BeO, CaO, ZnO, and P2O5. Some of them also contain TiO2.

(3) Coatings containing these frits, with admixtures of clay and various refractory oxides, have been developed and tested. The firing temperatures of the most promising of these coatings are in the range 1850° to 2250°F.

(4) Of the refractory oxides used as mill additions in the coatings, best results were obtained with Cr2O3 and CeO2 and mixtures of the two.

(5) The best ratio of frit to refractory oxide for all frits is 65 to 35 parts by weight.

(6) Coatings were applied and adhered well to all the following alloys: types 309, 310, and 321 stainless steel, Inconel, Nichrome V, Stellite 25, and S‐816.

(7) The protection given to the various coated alloy specimens varied with the composition of the alloys as well as with the composition of the coatings. Type 321 stainless steel was the most difficult to protect, and Nichrome V and Inconel were the easiest to protect. Type 310 stainless steel was relatively easy to protect.

(8) The best evaluation of the degree of oxidation of a coated specimen during long‐time heating in air was obtained by microscopic comparison of metallographic sections of tested and untested coated specimens and determinations of the depth of external oxidation, maximum depth of stringer penetration, and number of stringers per inch of specimen.

(9) The better coatings reduced greatly both the depth of stringer penetration and number of stringers per inch on type 310 stainless steel tested at 1900°F. for approximately 150 hours.
Electromotive Effects in Glass‐Salt Pairs
Authors: REED LEONARD
Published: June 2006

Liquid and solid metallic salts in contact with glass hare been found to produce a potential drop across the glass‐salt interface which decays with time. A qualitative explanation of this phenomenon is offered in terms of the glass structure with relation to the adsorption and polarizability of the salt ions at the interface.
Effects of Nuclear Reactor Exposure on Some Properties of Vitreous Silica and Quartz
Authors: PRIMAK W. , FUCHS L. H. , DAY P.
Published: June 2006

In a nuclear reactor, quartz alters gradually to an amorphous form. Some of the property changes observed are (a) decreases in density, refractive indices, rotatory power, and birefringence, (b) disappearance of the α‐β transition, and (c) changes in the absorption spectrum. The properties of vitreous silica also alter in a nuclear reactor, the density and refractive index increasing somewhat. On heating the irradiated solids the properties alter in a complex manner.
Thermal Expansion of Vitreous Silica
Authors: SMYTH HAROLD T.
Published: June 2006

The thermal expansion of vitreous silica is negative at low temperatures. This negative expansion can be explained as being caused by the transverse vibrations of the oxygen atoms. The frequency of such vibrations, because of the structure of vitreous silica, decreases as the structure shrinks, and this decrease results in negative thermal expansion.
Synthetic Mica Research in Japan
Authors: NODA TOKITI
Published: June 2006

Research on the synthesis of mica was started in Japan in 1938. As the first step, compositions which crystallize easily were investigated. The next step was the determination of the temperature of crystallization from melts and the rate of crystal growth. Experiments with growing of crystals were performed and these fundamental properties were determined. Various types of mica were synthesized. The results of (1) the determination of temperature of crystallization and rate of growth of fluor‐phlogopite from melts and (2) studies on the isomorphism in the various types of synthetic mica, e.g., chemical composition, crystal size, refractive index, electrical properties, heat of crystallization, and temperature of crystallization, are summarized. The practical uses of both synthetic mica and glass‐bonded synthetic mica ceramics are described.
Glass Fibers with Oriented Chain Molecules
Authors: GOLDSTEIN MARTIN , DAVIES T. H.
Published: June 2006

The concept of glass as a polymer of silicon, phosphorus, or other glassforming atoms connected by oxygen atoms suggests that fibers with oriented linear chains may be prepared. Previous attempts to demonstrate such orientation have failed, however, with glasses of the usual compositions. The composition in which linear chains seem most likely to occur is that of the “meta” salts in which each glassformer is bound, on the average, to two others through oxygen atoms. Under drawing conditions indicated by the theory of viscoelastic properties of high polymers, fibers of sodium metaphosphate glass have been prepared that show birefringence and give X‐ray diffraction patterns similar to those of organic fibers with oriented chain molecules. Under analogous treatment sodium metasilicate failed to give such effects.
Magnetic Ceramics: I, General Methods of Magnetic Ferrite Preparation
Authors: ECONOMOS GEORGE
Published: June 2006

Various methods of preparing the technically important ferrospinels are discussed; particular attention is given to the reactivity and homogeneity of the final mixture. The reactivity and intimacy of mixing of the initial components may be improved by the use of chemical methods of comminution and mixing, viz., thermal decomposition of the mixed chemicals, chemical precipitation of the components, or ignition of the components in a fine state of division. The use of controlled partial pressures of oxygen (CO2‐CO mixtures) for the preparation of magnetite and manganese ferrite is discussed. The feasibility of the application of these methods on a commercial scale is outlined.
Thermal Conductivity: XII, Temperature Dependence of Conductivity for Single‐Phase Ceramics
Authors: KINGERY W. D.
Published: June 2006

Theoretical relationships and experimental data concerning thermal conductivity for a number of oxide materials have been compared over a wide temperature range. Deviations from the basic proportionality between k and 1/T are caused by radiant‐energy transmission, a high Debye temperature, a low mean free path of the thermoelastic waves, porosity, and in a few cases electronic conductivity. Extrapolation of thermal conductivity data to high temperatures is not reliable.
Distribution of Crystals in Titania Enamels Fired Directly on Steel
Authors: LYNCH E. D. , FRIEDBERG A. L.
Published: June 2006

A new technique for studying the crystalline material in fired enamel is described. Using this technique, it was found that the main difference in the crystalline nature of enamel coatings is the presence of FeO crystals at the interface of good bond specimens and the absence of FeO at the interface of poor bond specimens. The effect of certain processing treatments on FeO formation is discussed briefly.
Apparatus for Measurement of Viscoelastic Properties of Glass
Authors: McCORMICK J. M.
Published: June 2006

An apparatus for the precision measurement of the motion of torsion pendulums having glass samples as their elastic elements is described. The temperatures used range from ‐90° to 1200°F.; the range of frequencies is 0.1 to 10 cycles per second. Both the decay of a simple pendulum and sustained oscillation of a driven pendulum are used. The basic observation used for all measurements is elapsed time, the least increment of which is 10 microseconds with the apparatus used. Examples of the data obtained for The American Ceramic Society standard sample of soda‐lime glass and for fused silica are given.
Magnetic Ceramics: II, Properties of Magnetite and Manganese Ferrite Fired in Various Atmospheres
Authors: ECONOMOS GEORGE
Published: June 2006

Magnetite and manganese ferrite, fired in various atmospheres, were tested for initial a.‐c. permeability, for quasi‐static hysteresis characteristics of Bm, Br, and Hc, and for resistivity. Optimum properties were obtained for magnetite made under exactly controlled oxygen pressures and for manganese ferrite fired in a CO2 atmosphere. These data are discussed with reference to the resistivity as affected by probable cation distribution.
Some Properties of the Oxides of Vanadium and Their Compounds
Authors: KING BURNHAM W. , SUBER LEON L.
Published: June 2006

Vanadium tetroxide and vanadium pentoxide were prepared and some of their physical properties were measured. A brief survey was then made of some of their binary oxide compounds. Various mixtures of V2O4 or V2O6 and BeO, MgO, CaO, SrO, BaO, Al2O3, SiO2, TiO2, CeO2, ZrO2, Nb2O6, and U3O8 were heated. When compounds were formed, some of their properties were determined. Refractoriness, thermal expansion, and optical properties were considered of special interest. Vanadium pentoxide was found to have a linear thermal expansion of only 0.63 × 10−6 per °C. from 30° to 450°C.
Physical Characteristics of Titanium Carbide Type Cermets at Elevated Temperatures
Authors: KNUDSEN F. P. , MORELAND R. E. , GELLER R. F.
Published: June 2006

The principal purpose of this investigation was to determine the creep behavior and strength at 1200° to 1850°F. of cermets which may be used in the high‐temperature areas of aircraft. Initially a series of bending tests was made on variations of Kennametal 150‐type Kentanium containing from 5 to 30% nickel binder. The 5, 15, and 20% compositions were the strongest and the most creep resistant. Because of the need for both thermal and mechanical shock resistance, tensile creep tests were then made on K150‐type Kentanium compositions containing 20, 25, and 30% nickel binder. A limited number of tests also were made on Kennametal composition K162B and on Firth Sterling composition FS‐27. The cermet K162B was the most creep resistant and the strongest. Linear thermal expansion determinations were made on Kennametal compositions K138A, K138, K151, and K151A. Their coefficients of expansion between room temperature and 1205°C. ranged from 8.1 × 10−6 to 8.6 × 10−6 per °C. Metallo‐graphic examinations were made of all the tensile‐tested specimens; in general, the test strains were too small to cause any noticeable deformation or changes in microstructure.
Magnetic Ceramics: III, Effects of Fabrication Techniques on Magnetic Properties of Magnesium Ferrite
Authors: ECONOMOS GEORGE
Published: June 2006

Magnesium ferrite specimens made of unreacted (mixed oxides) and reacted (ground ferrite) materials were prepared to determine the effects of forming pressure, firing temperature, time at peak temperature, firing atmosphere, and quenching treatment on their magnetic and electrical properties. High firing temperatures (1450°C.), long holding times (8 hours), and quenching from the highest temperature (1200°C.) produced the highest μi, and Bm, the lowest Hc, and a decrease in Br. These changes were related to the change in the void volume and particle size of the specimens brought about by the fabrication techniques and to the alterations in the degree of inversion in the spinel lattice during quenching. Oxygen loss or gain from the stoichiometric amount caused a loss of magnetic properties. X‐ray and microstructure studies aided in the interpretation of the experimental data.
Constitution of Bone China: III, High‐Temperature Phase Equilibrium Studies in the System Tricalcium PhosphateAnorthite‐Silica
Authors: PIERRE P. D. S. ST.
Published: June 2006

The primary‐phase fields of the system tricalcium phosphate‐anorthite‐silica are delineated, and the distribution of isotherms is related to the firing of bone china. The system is a true ternary with a eutectic at 11% tricalcium phosphate, 51% anorthite, 38% silica that melts at 1290°± 5°C.