bluuebunny/crossref_metadata_2025 huggingface dataset:
THEORY OF SPALLING*
Authors: PRESTON F. W.
Published: July 2010

This paper registers objection to the purely mathematical parts of F. H. Norton's The physical nature of the spalling process will be dealt with later.
TERRA COTTA SLIP COATINGS*
Authors: McDowrll Samuel J.
Published: July 2010

Compositions in the high clay area of the triaxial, feldspar, clay, Cornwall stone, were studied as slip coatings for a terra cotta body. Calcined English ball clay was used to introduce a portion of the clay content. The porosity, checking behavior, tendency to craze in the autoclave, and the relative compression of the slips are shown. A typical desirable slip was chosen and the effect of additions of various fluxes and coloring oxides was studied. Slips of this type seem to offer the terra cotta industry the possibility of vitreous slips with greater resistance to moisture crazing.
STRESS‐RESISTING MATERIAL*
Authors: Preston F. W.
Published: July 2010

A collection of notcs on the stresses set up in glassware of various sorts by various forces and treatments is presented, with some observations on how the stresses act to produce failure.
STRENGTH AND DURABILITY TESTS OF MORTAR‐MIX MORTAR*
Authors: Spangler M. G.
Published: July 2010

The continued use and development of finely ground raw clay, or mortar‐mix, as a plasticizer for cement‐sand mortars has led to further and more comprehensive physical tests of this product. This paper gives a brief description and the results of tension, compression, freezing and thawing, bond strength, and absorption tests recently conducted on samples of mortar‐mix from two clay products plants in Iowa. These tests are compared with similar tests of hydrated lime when used as a plasticizer. They confirm a previous conclusion that there is no substantial difference in the physical propcrtics of sand‐cement mortars whcn equal percentages of mortar‐mix or hydrated lime are used as the greasing agent.
POTASH‐SODA‐LIME FELDSPAR EUTECTIC STUDY*
Authors: Martz Joseph A.
Published: July 2010

An investigation was made of the fusion behavior of the potash feldspar, soda feldspar, and soda‐lime feldspar system, all materials being of commercial grade. The potash feldspar had a pyrometric cone equivalent of cone 9 1/2, the soda feldspar, cone 6 1/2, and the soda‐lime feldspar deformed at cone 11 l/2. Mixtures varying according to the triaxial diagram were made in the form of pyrometric cones. These were fired in groups along with standard Orton cones.

The 30% commercial potash fcldspar‐70% commercial soda feldspar mixture reached 6 o'clock deformation when standard Orton cone 6 showed 2 o'clock deformation.

The mixture of 62 l/2% commercial potash feldspar with 37 1/2% soda‐lime feldspar reached 6 o'clock deformation when cone 7 showed 1 o'clock deformation, the deformation of the cone 9 1/2 potash feldspar being reduced 3 cones by the addition of the proper percentage of the cone ll 1/2% soda‐lime feldspar.

There was an increase in deformation temperatures (no indication of eutectic) in the plagioclase series, soda feldspar to soda‐lime feldspar.

The mixture of 30% commercial potash feldspar, 60% commercial soda feldspar, 10% soda‐lime feldspar showed 6 o'clock deformation when cone 6 showed 1 o'clock deformation, this being the lowest temperature at which any member of the system showed 6 o'clock deformation.
SOME SHEET‐IRON GROUND‐COAT REBOIL AND BOND STUDIES USING SEVERAL ENAMELING STOCKS*
Authors: Ebrioht H. E , Clawson C. D. , Irwin J. T.
Published: July 2010

This paper presents results and observations obtained from a study of metals and some metallic oxides as mill additions to eliminate or reduce reboiling of ground‐coat enamels.
THE THERMAL EXPANSION OF SHEET‐IRON GROUND‐COAT ENAMELS*
Authors: Andrews Andrew I. , Smith Robert K.
Published: July 2010

The thermal expansions of sheet‐iron ground‐coat enamels were determined by use of the interferometer. The results showed that the calculated expansions based on the factors of Mayer and Havas were close to the actual expansions. It was also shown that variations of borax, feldspar, and quartz resulted in a fairly uniform change in the expansion. The softening of the enamels in the interferometer test proved to be a characteristic change depending 011 the fusibility of the enamel. These data showed promise as a test for fusibility.
RESISTANCE TO SUDDEN TEMPERATURE CHANGE OF SOME BODIES OF THE SYSTEM TALC‐CLAY‐MULLITE*
Authors: King R. M. , Evans C. L.
Published: July 2010

Several bodies capable of being processed by thc usual manufacturing methods, with varying talc, clay, and mullite content, were studied to determine their relative resistance to thermal shock. These bodies were fired a t various temperatures and submitted to quenching and transverse strength tests.
THE DETERMINATION BY X‐RAY METHODS OF CRYSTALLINE COMPOUNDS CAUSING OPACITY IN ENAMELS*
Authors: Andrews A. I. , Clark G. L. , Alexander H. W.
Published: July 2010

The crystalline compounds present in vitreous enamels were determined by X‐ray methods, particular reference being given to the opacifiers. It was shown that tin is present in enamels as crystalline tin oxide and antimony as the crystalline antimony pentoxide. Fluorspar added to the enamel contributes crystalline calcium fluoride. Cryolite and sodium silicofluoride contribute crystalline sodium fluoride. Other opacifiers and compounds such as zirconiuni oxide, zirconium silicatc, calcium phosphate, arsenic oxide, and zinc sulfide added to enamels were studied. With the exception of the zirconium opacity the compounds causing opacity in enamels were identified alone and in the presence of other opacifiers.
GASES IN GLASS*
Authors: Dalton R. H.
Published: July 2010

ARSTRACT

An apparatus is described for extracting the gas from glass at glass‐furnace temperature and determining its composition. Results are given for glasses of various compositions and various melting histories. All ordinary glasses were found to contain appreciable quantities of dissolved (or chemically combined) gas, the amount varying from a few hundredths to a few tenths per cent. Water is frequently the most abundant gas, the content being highest in borosilicate glasses. Carbon dioxide is also usually present, the amount depending on the basicity of the glass. Nitrogen, carbon monoxide, and hydrogen were never found present in appreciable quantities. All oxidized glasses contain some oxygen. Glasses containing arsenic give off a comparatively large volume of oxygen. The effect of this oxygen on fining is discussed. It has been found that remelting a glass has little effect on the gas content. The gas content is greatly influenced by the size of the melt, being the lowest in small experimental melts.
PROGRESS REPORT ON THE STUDY OF GASES IN ENAMELING IRON*
Authors: Baker Ralph W. , Joublance J. C.
Published: July 2010

Since all ferrous materials contain within their structure a varied assortment and quantity of gases, a discussion is presented of the effect of such factors as time, temperature, atmosphere, and deliberate methods used in the manufacture of enameling iron. A study of the important gaseous impurities in ferrous materials is given. Melting investigations were made to determine at high temperatures the absorptive capacity of specially prepared irons for air, nitrogen, hydrogen, and carbon monoxide, and the influence of carbon, manganese, silicon, and aluminum on the absorption and retentive capacities. Manganese in increasing amounts increased the absorption of all gases. A critical percentage content of 0.25% of manganese was found to exist, at which maximum absorption of nitrogen occurred; below and above this percentage content the absorption of nitrogen decreased.

Many grades of enameling iron were subjected to a similar investigation. Certain irregularities of various analyses of commercial irons were noted in that there were irregularities of absorption and retention of gases in a range of temperature which included the temperature at which porcelain enamels were fired. The enameling iron of low carbon and low manganese content, containing only the permissibly low phosphorus, sulfur, silicon, and alloying elements, should insure dependable performance during enameling operations.
EFFECT OF ORGANIC GRINDING MEDIA ON WATER‐SOLUBLE SILICA FRIT*
Authors: Blair Hrlen , Schwartzwalder Karl
Published: July 2010

The tendency of fine particles of a slightly water‐soluble silicate to agglomerate, thus preventing effective determination of grain‐size distribution in the dried material, may be overcome by wing organic liquids as the grinding media. An explanation is offered for the action of various liquids.
A Study of the Effect of Lubricants on the Adherence of Molten Glass to Heated Metals
Authors: DOWLING W. C. , FAIRBANKS H. V. , KOEHLER W. A.
Published: July 2010

An improved kinetic test was devised by which the adherence of molten glass to metal may be evaluated. The results were expressed as the highest metal temperature at which the molten glass beads do not adhere. The variables of the test investigated were temperature of molten bead, height of fall of the molten bead, and slope and surface roughness of metal sample. The cumulative effect of the variables on the precision of measurement of the adherence temperature was found to be ±33° F. Several types of glass mold lubricants were investigated as to their effects on the adherence temperature and as to their persistence on heated metal surfaces. Several silicone lubricants were found to have high critical adherence temperatures while the graphitized oil base lubricant gave the best persistence.
Relationship of Tensile Strength of Glass Fibers to Diameter
Authors: OTTO WILLIAM H.
Published: July 2010

The measured strength of a glass fiber is associated with the special circumstances attending its formation. Experimental evidence is presented which shows that, contrary to generally accepted belief, the strength of a fiber does not depend on fiber diameter. When fibers of different diameter are formed under controlled, nearly identical conditions, the breaking strengths are identical within the experimental limits and there is no significant effect of diameter as such.

(1) The properties of glass fibers, including strength, are associated with the special circumstances attending their formation.

(2) In the past, fibers of different diameters were inevitably made under different forming conditions; it was found necessary in hand drawing to heat the glass to higher temperatures and to pull faster to obtain fibers of small diameter.

(3) In the past, therefore, fibers of different diameters were reported as having different strengths (i.e., breaking stresses, not breaking loads), and this difference was ascribed to diameter as such without considering whether it might be due to different forming conditions.

(4) When fibers of different diameter are formed under controlled, nearly identical conditions, the breaking strengths are identical within the experimental limits and there is no significant effect of diameter as such.
An Efficient and Stable Algorithm for Calculating Fictive Temperatures
Authors: Markovsky Alex , Soules Thomas F. , Boyd D.C.
Published: July 2010

An algorithm is given for calculating the fictive temperature of glass based on the differential form of Narayanaswamy's equation. This algorithm is more convenient and much more efficient than direct solution of the integral equation and has been implemented in viscoelastic stress analysis using finite‐difference and finite‐element methods.
Study of Microstructural Effects in the Strength of Alumina Using Controlled Flaws
Authors: Lawn Brian R. , Freiman Stephen W. , Baker Theresa L. , Cobb Deborah D. , Gonzalez Armando C.
Published: July 2010

Strength characteristics were studied as a function ofVickers indentation Load for aluminas with two grain sizes. At low loads the strengths tend to well‐defined plateaus, the levels of which bear an inverse relation to grain size. These trends are consistent with a trunsition from indentation‐controlled to microstructure‐controlled behavior as flaw size diminishes. The conventional indentation fracture formalism was modified to account for this transition.
Nitrogen Coordination in Oxynitride Glasses
Authors: Brow RichardK. , Pantano CarloG. , Boyd D.C.
Published: July 2010

Soda‐silica and soda‐lime‐silica glasses were prepared with varying amounts of Si3N4, to produce oxynitride glasses with nitrogen contents up to 3.23 mol%. The glasses were analyzed by Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, and evidence for the formation of tricoordinated nitrogen groups in the glasses was obtained.
Effect of Age on Diffusion in Hydrated Alite Cement
Authors: PARROTT L.J. , PATEL R.G. , KILLOH D.C. , JENNINGS H. M.
Published: July 2010

Hydration of alite cement paste of 0.59 water/cement ratio caused the larger pores (>50 nm) to progressively fill with calcium hydroxide and a porous calcium silicate hydrate gel. At early stages of hydration, the larger pores were directly interconnected and diffusion rates were consequently rapid. At later times, the hydrate shells around the adjacent alite grains began to intergrow, continuity of the larger pores was reduced, and diffusion rates were reduced. Beyond 70% hydration, diffusion rates diminished very rapidly with only small amounts of additional hydration. The reduction in continuity of the larger pores was monitored directly by microscopic examination of resin replicas of the pores.
Determination of OH Extinction Coefficients in R2O‐B2O3‐SiO2 Glasses (R = Li, Na, K)
Authors: NIETO MARIA ISABEL , DURAN ALICIA , NAVARRO JOSE MARIA FERNANDEZ , MAZO JOSE LUIS OTEO
Published: July 2010

Infrared spectra of glasses of the system R2O‐B2O3‐SiO2 were investigated. The extinction coefficients of the hydroxyl absorption band (“free OH”) were calculated by a method proposed for alkali borate glasses. The results confirmed the applicability of this method to homogeneous and phase‐separated alkali borosilicate glasses. The variation of the hydroxyl absorption band position was interpreted according to the structural characteristics of the studied glasses.
Effect of Li2CO3 on Reaction Between CaO and CO2
Authors: BERUTO DARIO , KIM M. G. , BARCO LUIGI
Published: July 2010

Reaction between CaO powders and CO2(g) is often limited by slow diffusion of CO2 through the CaCO3 product. Additions of Li2CO3 are shown to increase the reaction rate. At temperatures around 940 K, near to the Li2CO3‐CaCO3 eutectic temperature, 935 K, complete reaction of the CaO with CO2 can be achieved when the heating rate and Li2CO3 content are optimized. At lower temperatures Li2CO3 causes lesser but measurable increases in reaction rates. SEM and surface area observations suggest different reaction paths when Li2CO3 is present, when Li2CO3 and eutectic are present, and when eutectic alone is present.
Faceted Grain Boundaries in Al2O3
Authors: MORRISSEY K. J. , CARTER C. B.
Published: July 2010

Different types of faceted grain boundaries in commercial poly‐crystalline Al2O3 were examined. Three distinct cases, namely the basal twin, the rhombohedral twin, and other special high‐angle grain boundaries, are discussed, comparing theoretical models and experimental observations. It is shown that the faceting of the boundaries can be associated with their migration. A mechanism for the separation of a σ= 13 grain houndary from a pinning void, small grain, or second‐phase particle is illustrated. It is also shown experimentally that faceting of high‐angle boundaries can occur on a scale of Σ 5 nm, and that, theoretically, faceting most likely also occurs on an atomistic scale. Throughout the theoretical analysis the basal plane is predicted to be a favored facet plane, which is confirmed by experimental observation.
Multiaxial Loading Fracture of Al2O3 Tubes: II, Weibull Theory and Analysis
Authors: PETROVIC J. J. , STOUT M. G.
Published: July 2010

The Weibull statistical fracture theory for multiaxial loading was developed for thick‐ and thin‐walled tube geometries subjected to multiaxial loading in tension‐internal pressure, compression‐internal pressure, and pure torsion. As compared to uniaxial tension, lower strengths are predicted for tension‐tension stress states and higher strengths for tension‐compression stress states. Comparison to experimental results for A1203 tubes indicates a reasonable agreement with Weibull theory predictions for tension‐internal pressure and compression‐internal pressure conditions, but an underestimation of stress state effects in pure torsion. Results indicate a weakening effect of in‐flaw‐plane tensile stresses, with no observed influence of in‐plane compressive stresses.
Interreaction Between Al2O3 and a CaO‐Al2O3 Melt
Authors: JONGHE LUTGARD C. DE , SCHMID HERBERT , CHANG MEI
Published: July 2010

Poly crystalline and single‐crystalline α‐alumina were reacted with a eutectic CaO‐Al2O3 melt at 1530°C. A reaction zone develops in which a strongly textured CA6 layer, as well as a CA2 layer, forms, with a remaining layer of unreacted CaO‐AI2O3 melt. Silica, an impurity in the α‐alumina, is rejected by the advancing CA6 phase and accumulates as calcium alumino‐silicates in channels that assist in the reaction as fast transport paths. Reaction mechanisms and welding are briefly discussed.
Geometrical Effects in Elastic/Plastic Indentation
Authors: MARSHALL DAVID B.
Published: July 2010

A general analysis of elastic/plastic indentation fracture for an arbitrary‐shaped indenter is presented. The analysis is based on the observation that the residual indentation stress field provides the driving force for crack formation. After establishing that the influences of indenter geometry and load on the residual field are completely characterized by the volume of the indentation, a relation between the extent of radial cracking, the indentation volume, and the material properties is derived. Predictions of the analysis are examined by comparing calculated load/crack‐length relations for two specific indenter geometries (Vickers pyramid and sphere) with experimental measurements in ZnS. For Vickers indentation the crack length is proportional to (load)2/3, whereas for spherical indenters the variation of crack length with load is nearly linear.
A Study of Silica‐Fume‐Modified Cements of Varied Fineness
Authors: KUMAR A. , ROY DELLA M.
Published: July 2010

Pastes and mortars of portland cements with varying fineness were studied. The effect of blending the cements with silica fume up to 10% is presented. Thermogravimetry, heat of hydration, X‐ray diffraction, scanning electron microscopy, compressive strengths, and microhardness measurements were used to evaluate the pastes and mortars. The study reveals that properties and strengths of existing portland cements may be enhanced through the addition of silica fume. Coarse cements are benefited greatly through the blending. Energy savings during grinding may be realized through this process.
Preparation of Pb(Zr,Ti)03 Through the Use of Cupferron
Authors: Kakegawa Kazuyuki , Mohri Jun‐Ichi , Shirasaki Shin‐Ichi , Takahashi Koichiro
Published: July 2010

An organic chelation reagent, cupferron, was used to coprecipitate Ti4+ andZr4+. After the materials were fired, they were mixed with PbO powder and fired again at high temperatures to obtain Pb(Zr,Ti)03 (PZT). It was confirmed that this method is useful for the preparation of homogeneous PZT having no compositional fluctuations. No coexistence range of the tetragonal and rhombohedral phases was observed in the PZT compositions near the morphotropic phase boundary.
Compatibility Relations of A1203 in the System Zr02‐Al203‐Si02‐CaO
Authors: Pena Pilar , Aza Salvador De
Published: July 2010

Compatibility relations of Al203 in the quaternary system Zr02‐Al203‐Si02‐CaO were studied by firing and quenching followed by microscopy and energy‐dispersive X‐ray examination. A projection of the boundary surface of the primary crystallization volume of Al203 was constructed in terms of the CaO, Si02, and Zr02 contents of the mixtures recalculated to 100 wt%. Two invariant points, where four solids coexist with a liquid phase, are defined, and the positions of the isotherms were established.
Preparation and Properties of Nitrogen‐Containing Na2O‐B2O3 Glasses
Authors: Frischat Günther H. , Krause Wolfgang , Hübenthal Horst
Published: July 2010

Up to 3.3 wt% nitrogen can be incorporated into Na2O‐B2O3 glass melts. The melting procedure is described, and structure models are given. In contrast to N‐containing silicate glasses, the borate glasses were transparent; however, micrographs of their fracture surfaces showed some crystallinity. Properties were determined as a function of the N and Na2O contents of the glasses. Compared with N‐containing silicate glasses, the properties of borate glasses are much less changed by the nitrogen introduced.
High‐Yield Synthesis of Si3N4/SiC Ceramic Materials by Pyrolysis of a Novel Polyorganosilazane
Authors: SEYFERTH DIETMAR , WISEMAN GARY H.
Published: July 2010

The action of basic catalysts such as KH on the ammonolysis products of CH3SiHCl2, (CH3SiHNH)n, results information of polysilazanes of intermediate molecular weight (600 to 1800). Pyrolysis of these polysilazanes gives ceramic materials, which appear to be mixtures of Si3N4, SiC, and C, in yields of 80 to 85%.
Thermal Expansion of ZrC From 120 to 300 K by an X‐Ray Powder Method
Authors: RAHIMZADEH EBRAHIM , JOSHI NARAYAN R. , SINGH SOHAN
Published: July 2010

Thermal expansion of ZrC, which has the NaCI type structure, was determined from, 120 to 300 K by a powder X‐ray diffraction method. The lattice parameter was measured precisely using a specially designed D‐shaped symmetrical back‐reflection‐focusing camera with the specimen hanging from a cryoflask in the vacuum chamber outside the camera on the Rowland circle. The average coefficient of linear thermal expansion of ZrC in this temperature range is 6.22 x 10‐6/K. The Zr/C ratio was 0.993.
Thermal Conductivity of Cr2O3 in the Vicinity of the Neel Transition
Authors: WILLIAMS ROBERT K. , GRAVES RONALD S. , MCELROY DAVID L.
Published: July 2010

Thermal conductivity (A) data for two dense Cr2O3 samples are reported. The results, which span the temperature range 270 to 360 K, show an inflection near the Neel transition temperature, 308 K. An analysis shows that the slope of the higher‐temperature portion of the λlD−1−T curve is about what would be expected for ordinary 3‐phonon U‐process scattering. Above TN the mean free path for phonon‐spin scattering is constant and equal to ∼10 nm.
Compositional Modification of Hot‐Pressed Silicon Nitride by High‐Temperature Electrolysis
Authors: CLARKE D. R.
Published: July 2010

Impurities and additives used in the liquid‐phase densifica‐tiondensification of silicon nitride ceramics are preferentially partitioned to the residual intergranular glass phase remaining in these materials. On the basis of a simple phenomenological ionic migration model, it is proposed and demonstrated that a high‐temperature electrolysis treatment may be used to modify the concentration of both the additive and impurities. The compositional modification has a number of consequences and, as an illustration, the improvement in high‐frequency dielectric loss produced as a result of the electrolysis treatment is presented.
Sodium Diffusion and Leaching of Simulated Nuclear Waste Glass
Authors: McGRAIL B. P. , KUMAR A. , DAY D. E.
Published: July 2010

Oxides such as CaO, ZnO, Fe20O3, and Zr0O2 were substituted for Si0O2 into a 14 Na20‐10 B20O3‐76 Si0O2 (wt%) glass in proportion to their weight percent in PNL‐7668 simulated nuclear waste glass. No correlation was found between the Na diffusion coefficient (DNa) in the bulk glass and sodium leaching in water for any of the iron‐containing borosilicate glasses. Effective diffusion coefficients calculated from the sodium leach rates in deionized water were 500 to 2000 times larger than DNa. The experimental leaching data agreed with a diffusion‐convection model where the convective term was a measured “phase‐boundary” velocity moving into the glass.
Strength of Hot‐Pressed Silicon Nitride After High‐Temperature Exposure
Authors: JAKUS K. , RITTER J.E. , ROGERS W.P.
Published: July 2010

Short‐term exposure of hot‐pressed silicon nitride to temperatures greater than 800°C in an oxidizing atmosphere causes an increase in the room‐temperature strength and eliminates the truncated strength distribution produced by room‐temperature proof‐testing. Acid‐etching the proof‐tested samples restores the original truncated distribution. These strength changes are shown to be related to the formation of a glassy phase on the surface that smooths out the preexisting machining flaws. More extensive, long‐term oxidation produces surface pits that lead to an irreversible change in strength
Electrolysis of Soda‐Lime Silicate Glass in Water
Authors: DOREMUS ROBERT H. , BABINEC ANN , D'ANGELO KATHLEEN , DOODY MICHAEL , LANFORD WILLIAM A. , BURMAN CHANDRA
Published: July 2010

Thin glass bulbs made of commercial soda‐lime glass were electrolyzed in aqueous solution. Ratios of mobilities of sodium and hydronium ions in the glass were calculated and compared to results of inter diffusion experiments with these ions. The results showed that a combination of electrolysis and ion exchange measurements can be used to test theories of the diffusion‐controlled step in the reaction of water with glass, and that an interionic diffusion mechanism with complete ionization of the ions from SiO groups in the glass is the preferred mechanism.
Electronically Conducting Doped Chromium Oxides
Authors: CROSBIE G. M. , TENNENHOUSE G. J. , TISCHER R. P. , WROBLOWA H. S.
Published: July 2010

Samples of polycrystalline chromium oxide doped with Li2O, MgO, NiO, and Ta2O5 were prepared by hot‐pressing to test for suitability as current collector materials of the sulfur electrode in the sodium‐sulfur cell. Density, grain size, dopant uniformity, and resistivity (to 350°C) were measured. X‐ray photoelectron spectroscopy (XPS) tends to support the established model of Ni2+ on Cr3+ sites to explain the compositional dependence of electrical resistivity after air anneal. A higher level of Cr2O3 powder purity was required to obtain the low resistivities with the Li2O dopant than with the MgO or NiO dopant. An observed increase in the bulk resistivity during several months of electrochemical cycling in sodium polysulfidelsulfur melts is attributed to loss of electronic carriers caused by equilibration of those carriers with the low oxygen partial pressure of the melt. Li2O‐ and (to a lesser extent) MgO‐doped Cr2O3 appear to be suitable as container coating materials.
Synthesis, Sintering, and Microstructure of Nasicons
Authors: KURIAKOSE A. K. , WHEAT T. A. , AHMAD A. , DIROCCO J.
Published: July 2010

The preparation and characterization of Hong and von Alpen types of Nasicons are described. When highly reactive gel‐processed powders are heated at about 1000°C, Nasicons are formed in a finely divided state. Sintering of compacts requires 1125° to 1325°C, depending on the composition. Observed sintering kinetics suggest a liquid‐phase mechanism; SEM reveals the Hong Nasicons to contain two (when zirconia‐free) or three phases. The von Alpen materials are zirconia‐free, but consist of two phases. A glass phase is common to both materials, and its presence is attributed to the liquid‐phase sintering mechanism.
Phase Relations in the System Na2O‐Li2O‐Al2O3
Authors: HODGE J. D.
Published: July 2010

A subsolidus phase diagram for the system Li2O‐Na2O‐Al2O3 at 1500°C is presented. Unlike the analogous system MgO‐Na2O‐Al2O3, β″ was the only ternary compound observed in the section of the lithia‐based system examined in this study. A fairly extensive region of β solid solution was found. In contrast, the range of compositions where β″ exists is small and does not extend into the Na2O‐Al2O3 binary.
Compaction Behavior of Spray‐Dried Alumina
Authors: FREY R.G. , HALLORAN J. W.
Published: July 2010

Compaction behavior and resultant porosity of spray‐dried alumina were examined over a range of pressures from 18 to 345 MPa. The variability in pressed density and pore size was measured as a function of spray‐dried granule size, binder concentration, and powder moisture content. An exponential behavior was found between pressed density and compaction pressure, density increasing with the logarithm of the compaction pressure. Pore size also displays an exponential behavior, pore diameter decreasing with the log of increasing pressure. The distribution width about the median pore size was noted to decrease approximately in a log‐log response to increasing compaction pressure. The behavior of the compaction and porosity curves is related to the degree to which the polymer binder is plasticized which, in turn, affects the pressure at which the spray‐dried granules begin to crush. This apparent yield pressure, although dependent on amount of binder and powder moisture, is intrinsically dependent on the water/binder ratio. Finally, by analogy to soil mechanics, an empirical equation relating compact density, yield pressure, and slope is presented.
Direct Observation of Crack Tip Geometry of SiO2 Glass by High‐Resolution Electron Microscopy
Authors: Bando Yoshio , Ito Setsuro , Tomozawa Minoru
Published: July 2010

Crack tips in thin SiO2 glass films were observed directly by high‐resolution/high‐voltage electron microscopy. An elliptical crack with radius of curvature ∼ 1.5 nm was observed. When the glass film with the crack was soaked in water at 90°C for 7 d, the crack tip became blunt by a process of dissolution and precipitation.
Rationalized Load and Lifetime of Brittle Materials
Authors: Menčík Jaroslav
Published: July 2010

The design and testing of structural parts from materials which exhibit subcritical crack growth can be improved by introducing auxiliary quantities into the classical concepts of fracture mechanics. The equivalent static stress, equivalent loading time, standardized loading time, and standardized lifetime, as well as the decrease in lifetime and residual lifetime, are defined, with examples of their application.
Thermogravimetry/Differential Thermal Analysis and Phase Identification of Cs2O·Al2O3·2TiO2 in the Ternary System Cs2O‐A12O3‐TiO2
Authors: Solomah Ahmad G. , Odoj Reinhard , Freiburg Christoph
Published: July 2010

Thermogravimetry and differential thermal analyses were conducted on the mixture 2CsNO3+A12O3+2TiO2 up to 1530 K. The resultant phase was identified as orthorhombic Cs2Al2Ti2O8 with lattice parameters aO=0.996, b0=0.898, and co=0.573 nm. Simultaneous TG/DTA was performed to quantify weight loss and volatilization of cesium and to monitor the development and/or stability of the phase as a function of temperature.
Mechanical Behavior of SiC(f)/SiC Composites and Correlation to in situ Fiber Strength at Room and Elevated Temperatures
Authors: Singh Dileep , Singh Jitendra P , Wheeler Michael J.
Published: July 2010

Mechanical properties of Nicalon‐fiber‐reinforced silicon carbide matrix composites were evaluated, in flexure, at various temperatures ranging from ambient to 1300°C. First matrix cracking stress ranged from 250 to 280 MPa and was relatively insensitive to test temperature. The measured ultimate strength showed a small increase from a room‐temperature value of 370 to 460 MPa at 800°C. Beyond 800°C, however, strength dropped to as low as 280 MPa at 1300°C. This decrease in ultimate strength at elevated temperatures is believed to be partly due to degradation of in situ Nicalon fiber strength. Scanning electron microscopy was employed to evaluate the in situ Nicalon fiber strengths via fracture mirror size measurements. Degradation of Nicalon fiber strength is attributed to thermal damage and to structural changes to the fiber at elevated temperatures. Measured values of ultimate strength of the composites were compared with predictions made on the basis of in situ fiber strength characteristics and an available analytical model.
Compositional Dependence of Absorption and Fluorescence of b3+ in Oxide Glasses
Authors: Takebe Hiromichi , Murata Takahiro , Morinaga Kenji
Published: July 2010

The integrated absorption cross section, the spontaneous emission probability, and the stimulated emission cross section of Yb3+ were determined in silicate, phosphate, borate, germanate, aluminate, gallate, and ZBLAN host glasses. The compositional dependence of the stimulated emission cross section of the 2F5/2→2F7/2 transition is determined mainly by the integrated absorption cross section in the glasses. A peak stimulated emission cross section above 1 pm2, which is the highest value in glasses, was obtained in a gallate glass with a composition of 40K2O·20Ta2O5. 40Ga2O3. The factors affecting the integrated absorption cross section are discussed using the Judd‐Ofelt parameters of Er3+ calculated in previous studies.
Corrosion of Zinc‐Containing Cabal Glasses by Various Leaching Solutions
Authors: Khedr Amal AbouBakr , ElBatal Hatem AbdelRahman
Published: July 2010

The corrosion behavior of some cabal glasses (CaO‐B2O3‐Al2O3) containing ZnO was evaluated both as a bulk specimen and as grain powder. Different leaching solutions were used including HCI, H2SO4, and NaOH for varying temperatures or periods of exposure. Zinc oxide replacing calcium oxide in cabal glasses of constant 40 mol% B2O3, 30 mol% Al2O3, caused a decrease in chemical durability in all leaching solutions used. The corrosion was found to be linear with time in the limit of investigation (1–4 h) but with different rates depending on the type of leaching solution or temperature.
Thermal Conductivity of Vapor‐Liquid‐Solid and Vapor‐Solid Silicon Carbide Whisker‐Reinforced Lithium Aluminosilicate Glass‐Ceramic Composites
Authors: Hasselman D. P. H. , Donaldson Kimberly Y. , Thomas J. R. , Brennan John J.
Published: July 2010

The thermal conductivities of two lithium aluminosilicate glass‐ceramic matrix composites reinforced with 30 vol% of either SiC VS (rice hull) whiskers or SiC VLS (vapor‐liquid‐solid) whiskers were determined from room temperature to 500°C. Because of the preferred alignment of the whiskers, the thermal conductivity values normal to the hot‐pressing direction were found to be significantly higher than those in the parallel direction. The composites with the VLS whiskers exhibited higher thermal conductivity values than those with the VS whiskers. An analysis of the room‐temperature data showed that the thermal conductivity values parallel to the hot‐pressing direction were higher than those predicted from theory, even for whiskers with infinite thermal conductivity and perfect interfacial thermal contact. This effect was attributed to a significant contribution of percolation to the total heat flow as a result of direct whisker‐to‐whisker contact. For both types of whiskers, the interfacial thermal conductance and thermal conductivity values (at ∼6.5 × 105 W/(m2‐K) and 200 W/(m·K), respectively) inferred from the composite thermal conductivity values perpendicular to the hot‐pressing direction were essentially the same. It was concluded that the order of magnitude difference in thickness for the two whisker types was primarily responsible for the differences in thermal conductivity measured for these two composites.
Diffusion of Degradation Products in Ceramic Moldings during Pyrolysis: Effect of Geometry
Authors: Matar Samir A. , Edirisinghe Mohan J. , Evans Julian R. G. , Twizell E. H.
Published: July 2010

A general equation applicable to a sphere, an infinite plate, and an infinite cylinder is used to calculate the transient diffusion of degradation product in a ceramic molding during pyrolysis. The solution includes the concentration‐dependent diffusion coefficient for diffusion of monomer in its parent polymer which forms the continuous phase in the ceramic in the as‐molded state. In the early stages of pyrolysis, before continuous porosity has developed, the model searches for the critical heating rate above which defects are produced. Reasonable agreement is obtained with experimentally measured critical heating rates for 3‐mm‐thick plates.
Piezoelectric Ceramics with Functional Gradients: A New Application in Material Design
Authors: Wu Carl C. M. , Kahn Manfred , Moy Walter
Published: July 2010

Internal strain amplification can be utilized in piezoelectric ceramics to obtain relatively large displacements. The monomorph described in the present work is a bending bar made from a single piece of material into which a smooth gradient of piezoelectric activity is introduced. The application of a voltage then causes the bar to bend due to the differential stresses that are induced. These are relatively uniformly distributed and do not peak in the center as in a conventional bimorph. Significantly increased life and reliability can then be achieved.
Calcium Phosphate Materials Prepared from Precipitates with Various Calcium:Phosphorus Molar Ratios
Authors: ŚAlósarczyk Anna , Stobierska Ewa , Paszkiewicz Zofia , Gawlicki Marek
Published: July 2010

Depending on the calcium:phosphorus molar ratio of the initial precipitates determined by precipitation conditions (calcium:phosphorus molar ratio of reactants and pH of reaction environment), after sintering at 1250°C, monophase, biphase, or triphase ceramics consisting of hydroxyapatite, β‐tricalcium phosphate, α‐tricalcium phosphate, and calcium oxide were obtained. The phase composition and properties—i.e., density, shrinkage, hardness, bending strength, and roughness—of the fractured surfaces of the isostatically re‐pressed sinters were determined.
Piezoelectric Moduli of Piezoelectric Ceramics
Authors: Nan Ce‐Wen , Clarke David R.
Published: July 2010

The effective piezoelectric moduli of polycrystalline piezoelectric ceramics are calculated using a straightforward averaging method (a Voigt average) and a more rigorous effective‐medium theory recently developed for piezocomposites. The effects of polarization orientation within each crystallographic domain and the shape of the domain on the effective piezoelectric moduli are presented. The effective‐medium theory, which includes full coupling of the elastic and dielectric interactions, gives results in reasonable agreement with experimental ones.
Structure Change in Strontium Oxide‐Doped Dicalcium Silicates
Authors: Fukuda Koichiro , Maki Iwao , Ito Suketoshi , Ikeda Susumu
Published: July 2010

A series of strontium‐bearing dicalcium silicate (Ca2Si04 solid solutions (C2S(ss)), (SrχCa1‐χ)2SiO4 with 0.02 ≤χ≤ 0.10, was prepared and examined by powder X‐ray diffrac‐tometry. These crystals, heated in the stable‐temperature region of the α phase and then quenched in water, were composed of the β phase, with χ≤ 0.08, and the α'L and β phases, with χ= 0.10. With increasing x, the unit‐cell axes of the β phase expanded and the β angle became small with eventual increase in the unit‐cell volume. The Rietveld analysis of the β‐C2S(ss) with χ= 0.08 showed that the Sr2+ ions preferentially occupied the seven‐coordinated site rather than the eight‐coordinated site. This site preference, which was originally established in the parent α‐phase structure, seemed to cause the systematic change in the cell dimensions.
Stress Analysis of Contact Deformation in Quasi‐Plastic Ceramics
Authors: Fischer‐Cripps Anthony C. , Lawn Brian R.
Published: July 2010

A stress analysis is made of Hertzian contact deformation in relatively tough ceramics with heterogeneous microstructures, where the response is essentially quasi‐plastic rather than ideally elastic‐brittle. Contact data for two such heterogeneous ceramics, a micaceous glass‐ceramic with modest hardness and a silicon nitride with high hardness, are presented as illustrative cases. Data from a soft steel serve as a comparative baseline. Two distinctive aspects of the deformation response are explored: indentation stress‐strain nonlinearity; and size and shape of the damage zone. For the harder ceramics, the stress‐strain nonlinearity is less pronounced, and the quasi‐plastic zone is more tightly confined beneath the contact, than in traditional ductile metals. As in metals, the deformation process in the ceramic structures is essentially shear driven, but has its origin in microstructurally localized interfacial sliding faults rather than in dislocation slip. Finite element modeling (FEM) is used to compute the shear stress distributions beneath the spherical indenters for selected experimental loading conditions. The underlying basis of the FEM calculations is an elastic‐plastic constitutive relation based on a critical shear condition for yield, but incorporating a strain‐hardening characteristic to allow for local elastic constraints on the sliding shear faults. The FEM calculations are able to simulate the main features of the stress‐strain curves and the evolving deformation zone geometries. In addition, the calculated tensile stress distributions are able to account, at least in part, for the suppression of conventional brittle fracture tendencies in tougher ceramics.
β‐Si3N4Whiskers Embedded in Oxynitride Glasses: Interfacial Microstructure
Authors: Sun Ellen Y. , Alexander Kathleen B. , Becher Paul F. , Hwang Shyh‐Lung
Published: July 2010

Interfacial microstructures in βP‐Si3N4(w)‐Si‐Al‐Y‐O‐N‐glass systems were investigated by systematically varying the nitrogen content and the Al:Y ratio of the glass matrix. High‐resolution and analytical transmission electron microscopy (HREM and AEM) studies revealed that the interfacial microstructure is a function of the glass composition. No interfacial phases were formed in glasses with low Al:Y ratios and in glasses with high Al:Y ratios and low nitrogen content, whereas epitaxial growth of an interfacial layer (100–200 μm thick) on the βP‐Si3N4(w) occurred in a glass matrix with high Al:Y ratio and high nitrogen content. The interfacial layer was identified to be a β'‐SiAION phase. Interfaces containing the SiAION layer exhibited high debonding energy compared to Si3N4(w)–glass interfaces. HREM studies indicated that the lattice‐mismatch strain in the SiAION layer was relieved by dislocation formation at the SiAION–Si3N4(w) interface. The difference in interfacial debonding energy was, hence, attributed to the local atomic structure and bonding between the glass‐β‐Si3N4 and the glass–β'‐SiAION phases. This observation was clear evidence of the strong influence of glass chemistry on the interfacial debonding behavior by altering the interfacial microstructure.
Phase Reaction and Sintering Behavior in the Pseudoternary System AlN‐Y2O3‐AI2O3
Authors: Kim Nam Heun , Fun Qian Duan , Komeya Katsutoshi , Meguro Takeshi
Published: July 2010

Phase reaction and sintering behavior in the ternary system AlN‐Y2O3(0‐10 wt%)‐Al2O3(0‐40 wt%) at temperatures ranging from 1600° to 2000°C were studied. The density of the sintered 100 wt% A1N specimens increased monotoni‐cally with firing temperature, but the maximum value was limited to 95%, even at 2000°C firing. All the specimens containing Y2O3, regardless of their Al2O3 content, achieved full density by sintering at 1800°C. However, at and above 1900°C, the densities decreased with increased Al2O3 content. This densification behavior appeared to be based on the grain morphology and decomposability of the existing compounds in the products. The phases present in the sintered A1N‐Al2O3 were composed of AlN, Al2O3, and γ‐AION below 1900°C, and 27R, 20H, and 16H at and above 1950°C. In the A1N‐Y2O3‐Al2O3 specimen, yttrium aluminum garnet (YAG) phase formed in the first stage at a temperature <1600°C, after which aluminum oxynitrides appeared. In the specimens sintered at 1950°C or higher, γ‐AION phase, with a higher Al2O3:A1N ratio, and 27R phase, with a lower Al2O3:A1N ratio, coexisted, and the contents were quantitatively low in comparison with the Y2O3‐free specimens, although Y2O3 trapped Al2O3 to produce YAG. This differed from the A1N‐Al2O3 phase diagram proposed by McCauley et al. The grain morphologies depended on the presence of the above phases. The grains based on A1N and γ‐AION were granular, and those based on 27R, 20H, and 16H poly‐typoids were platelike.
Pressureless Sintering of Dense Si3N4 and Si3N4/SiC Composites with Nitrate Additives
Authors: Kim Jae‐Yuk , Iseki Takayoshi , Yano Toyohiko
Published: July 2010

The effect of aluminum and yttrium nitrate additives on the densification of monolithic Si3N4 and a Si3N4/SiC composite by pressureless sintering was compared with that of oxide additives. The surfaces of Si3N4 particles milled with aluminum and yttrium nitrates, which were added as methanol solutions, were coated with a different layer containing Al and Y from that of Si3N4 particles milled with oxide additives. Monolithic Si3N4 could be sintered to 94% of theoretical density (TD) at 1500°C with nitrate additives. The sintering temperature was about 100°C lower than the case with oxide additives. After pressureless sintering at 1750°C for 2 h in N2, the bulk density of a Si3N4/20 wt% SiC composite reached 95% TD with nitrate additives.
High‐Temperature Chemical Stability of Plasma‐Sprayed Ca05Sr05Zr4P6O24 Coatings on Nicalon/SiC Ceramic Matrix Composite and Ni‐Based Superalloy Substrates
Authors: Lee Woo Y. , Cooley F Kevin M. , Berndt Christopher C. , Joslin Debra L. , Stinton David P.
Published: July 2010

The potential application of Ca05Sr05Zr4P6O24 (CS50) as a corrosion‐resistant coating material for Si‐based ceramics and as a thermal barrier coating material for Ni‐based superalloys was explored. A ∼200 (xm thick CS50 coating was prepared by air plasma spray with commercially available powder. A Nicalon/SiC ceramic matrix composite and a Ni‐based superalloy coated with a ∼200 (xm thick metallic bond coat layer were used as substrate materials. Both the powder and coating contained ZrP2O7 as an impurity phase, and the coating was highly porous as‐deposited. The coating deposited on the Nicalon/SiC substrate was chemically stable upon exposure to air and Na2SO4/O2 atmospheres at 1000°C for 100 h. In contrast, the coating sprayed onto the superalloy substrate significantly reacted with the bond coat surface after similar oxidation in air.
Thermal Diffusivity/Conductivity and Specific Heat of Mullite‐Zirconia‐Silicon Carbide Whisker Composites
Authors: Russell Laura M. , Donaldson Kimberly Y. , Hasselman D. P. H. , Ruh Robert , Adams Jane W.
Published: July 2010

The thermal diffusivity of mullite‐ZrO2‐SiCw materials was determined from 25° to 1000°C for composites in which the ZrO2 had different amounts of monoclinic and tetragonal phase, and varying SiCw content. At 25°C the thermal diffusivity of the matrix materials increased with increasing amounts of monoclinic phase, and little or no anisotropy was seen. Composites with SiCw additions showed significant increases in thermal diffusivity and anisotropy as compared with the matrix materials. With increasing temperature, thermal diffusivities of the matrices and their respective composites decreased, and at 1000°C differences were small. Specific heat was determined from 25° to 700°C and thermal conductivity values calculated. Specific heat increased with temperature and was not composition dependent, except for one sample. Thermal conductivity values as a function of temperature followed the same trends as the thermal diffusivity values.
Characterization and Low‐Temperature Sintering of Reactive Mn‐Zn Ferrite Powder
Authors: Aoyama Tatsuji , Hirota Ken , Yamaguchi Osamu , Aono Yasuyuki , Matsutani Nobuya
Published: July 2010

Highly sinterable Mn‐Zn ferrite powder consisting of sub‐micrometer‐size particles with structural distortion has been prepared by grinding a coprecipitated powder with a media agitation mill. Dense pure Mn‐Zn ferrites (>98% of theoretical) with an average grain size of 1.9 μm can be fabricated by heating at 900°C in a stream of N2. They show high permeability of 820 at 10 kHz through 1 MHz and an electric resistivity of 50 Ω cm at 1 kHz.