bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress Analysis of the Seal in a Sodium‐Sulfur Battery Cell
Authors: Trantina G. G.
Published: June 2006

A finite‐element stress analysis of the seal in a sodium‐sulfur battery cell was performed. Sealing stresses due to thermal expansion mismatch are relatively low but can be further reduced by modifying the counterbore. The effect of ovality can be treated as a seal thickness effect where the stresses increase with seal thickness. The effect of fracture strength, Weibull modulus, and strength degradation parameters on the probability of failure of beta alumina in the cell was demonstrated.
Surface and Bulk ‐OH Infrared Absorption in ZrF4‐ and HfF4‐Based Glasses
Authors: Gbogi E. O. , Chung K.‐H. , Moynihan C. T. , Drexhage M. G.
Published: June 2006

Infrared absorption at the 3400 cm−1 ‐OH peak has been measured as a function of thickness for several ZrF4‐BaF2‐LaF3 and HfF4‐BaF2LaF3 glasses to separate contributions from bulk and surface ‐OH. For glasses melted under CCl4 reactive atmosphere, the peak is due almost entirely to surface ‐OH. In ambient atmosphere the ‐OH peak exhibited no time dependence over a 30 d period, indicating a very small rate of surface attack by atmospheric H2O.
Solubility and Diffusion of Si in B4C
Authors: Hase T. , Suzuki Hiroshige
Published: June 2006

Diffusion couples of B4C/SiC single crystals were annealed at 1800° to 2100°C. Electron probe tnicroanalysis of the joined diffusion couple showed that the solubility limit and diffusion coefficient, D, for Si in B4C are 0.27 to 0.36% wt% and D = 0.165 exp(—101200/RT), respectively.
Thermochromism in Reduced Phosphate Glasses
Authors: ABE YOSHIHIRO , KAWASHIMA KOICHI , SUZUKI SUGURU
Published: June 2006

Coloring and bleaching of reduced phosphate glasses in the systems K2O‐B2Or Al2O3‐P2O5 and K2O‐Al2O3‐P2O5, containing no silver halide, were studied. The as‐cast glasses, which are colorless and transparent, become tinged with red when they are reheated at high temperatures for long times. The bleached specimens (PTC‐RP glass) are obtained by heating at >600°C, then quenching. The PTC‐RP glasses exhibit coloring phenomena by irradiation of light or by heating above 200°C; the colored glasses are again bleached thermally. Coloring of the glasses by heating is described in this paper in terms of phase change within the colloidal phosphorus formed in the glasses. The apparent activation energy for the thermocoloring is estimated to be ∼15×104 J/mol (35 kcal/mol).
Sodium Motion in Phase‐Separated Sodium Silicate Glasses
Authors: JANNEK H. D. , DAY D. E.
Published: June 2006

The thermally stimulated polarization and depolarization current (TSPC/TSDC) technique was used to study Naplus; ion motion in phase‐separated silicate glasses containing between 10.3 and 20 mol% Na2O. Generally, two TSDC peaks and a high‐temperature background (HTB) current were observed. The two TSDC peaks were attributed to different types of Naplus; motion, i.e. a short‐range reorientation process and a longer‐range translational motion. Changes in the microstructure affected only the size of the larger TSDC peak located at higher temperatures.
Electronic Conduction and Thermopower of Magnetite and Iron‐Aluminate Spinels
Authors: MASON T. O. , BOWEN H. K.
Published: June 2006

Electrical‐conductivity and thermoelectric‐power measurements of magnetite and iron‐aluminate spinels at high temperatures confirm a small‐polaron model of electronic conduction. Electrical properties corroborate the previously established cation distribution and defect model. Iron cations become randomly distributed between sublattices at the highest temperature. An n‐to‐p transition therefore occurs at the 50%Fe3O4‐50%FeAl2O4 composition. Cation distribution and defect equilibria appear to be independent of composition.
Superionic Conducting Glasses: Glass Formation and Conductivity in the System Ag2S‐AgPO3
Authors: BAUD G. , BESSE J. ‐P.
Published: June 2006

Glass phases showing high ionic conductivity at room temperature were prepared through a rapid quenching of molten mixtures of the system Ag2S‐AgPO3; the specimens obtained were homogeneous and transparent cylindrical blocks. Room‐temperature conductivity data show a monotonic increase with xag2s in the glass‐forming range. Linear fits of the Arrhenius plots of the bulk conductivity were obtained in the 290 K to Tg (glass‐transition temperature) range. The transport numbers of Ag ions in the glasses were measured by the emf method. The results show that all glasses in this system are practically pure ionic conductors due to the presence of Ag ions, so that they may be regarded as solid electrolytes.
Grain‐Oriented PbNb2O6 Ceramics
Authors: Granahan M. , Holmes M. , Schulze W. A. , Newnham R. E.
Published: June 2006

Grain‐oriented ceramics of ferroelectric lead metaniobate have been prepared by molten salt synthesis of anisotropic crystallites followed by doctor blade casting. The sintered ceramics have an orthorhombic texture with elongated c axis grains parallel to the casting direction. This allows efficient poling in directions perpendicular to the tape.
Coating of Small Alumina Crucibles with Magnesia using a Two‐Step Drain Casting Technique
Authors: Haroun N. A. , El‐Masry M. A. A.
Published: June 2006

A new technique of coating ceramic ware using two‐step drain casting is described in which small alumina crucibles are drain cast followed by drain casting a magnesia coat in the same mold. Cosintering at 1500°C resulted in ware defects unless heating schedules embodying arrests at lower temperatures were used.
A New Si3N4 Material: Phase Relations in the System Si‐Sc‐O‐N and Preliminary Property Studies
Authors: Morgan P. E. D. , Lange F. F. , Clarke D. R. , Davis B. I.
Published: June 2006

A new polyphase silicon nitride alloy has been developed using Sc2O3 as a densification aid. Subsolidus phase relations in the system Si‐Sc‐O‐N are reported together with preliminary oxidation and compressive creep results of a representative composition in the Si3N4‐Si2N2O‐Sc2Si2O7 phase field. Microstructural observations of the material are also presented.
Partition of Hydrogen in the Modified Chemical Vapor Deposition Process
Authors: WOOD D. L. , SHIRK JAMES S.
Published: June 2006

In the modified chemical vapor deposition (MCVD) process for making glass fibers, most of the hydrogen coming into the reaction from hydrogen‐bearing impurities in the starting materials is not incorporated in the glass. It is instead mostly converted to HCl, which is not absorbed by the newly formed silica particles, and passes out the exhaust stack. The residual partial pressure of H2O formed in equilibrium with HCl in the presence of O2 and Cl2 accounts quantitatively for the OH appearing in the glass when the known solubility of H2O in silica is considered. The H2O/HCl equilibrium is quenched at a temperature below that of the reaction zone at a value for which the rate of reaction approximates the transit time across the deposition zone. Quantitative agreement is obtained for published OH concentrations produced by SiHCl3 doping.
Boron Redistribution in Sintered α‐SiC During Thermal Oxidation
Authors: COSTELLO J. A. , TRESSLER R. E. , TSONG I. S. T.
Published: June 2006

The redistribution of the boron impurity in sintered α‐SiC during thermal oxidation was investigated over the temperature range 1200· to 1400,°C using sputter‐induced photon spectrometry (SIPS). The process was modeled with the Stanford University Processing Engineering Models Program (SUPREM) which permitted the estimation of diffusivities of boron in the growing oxide and the substrate. The process is characterized by segregation of the boron in the oxide near the interface and a corresponding depletion of boron in the substrate. The apparent diffusivities in the oxide were about three orders of magnitude higher than the published values for boron in pure SiO2, presumably because the film is much less pure than pure SiO2. The apparent diffusivities of the boron in the polycrystalline silicon carbide were almost five orders of magnitude higher than the published values for boron in single‐crystal silicon carbide. The diffusivities in the silicon carbide represent boron transport via the grain boundaries which were partially oxidized during the thermal treatment.
Grain‐Size Dependence of Fracture Energy in Ceramics: I, Experiment
Authors: RICE R. W. , FREIMAN S. W. , BECHER P. F.
Published: June 2006

Evaluation of literature data combined with new experimental measurements shows that crystal structure is a basic factor in the grain‐size dependence of the critical fracture energy of ceramics. Notch beam (NB), double cantilever beam (DCB), and work‐of‐fracture (WOF) tests of materials having a cubic crystal structure generally agree and show, at most, a limited variation of fracture energy with grain size. However, maxima of the order of 25% in γ at intermediate grain size and 25% decreases in γ at larger grain size may occur. Materials of noncubic crystal structure show broader variations in γ with G. Both DCB and WOF tests show γ passing through maxima that are typically 100 to >400% of values at fine or large grain size. Limited DT data are consistent with this trend but various results of NB tests are mixed. Some NB test data agree with the DCB and WOF trends, whereas others taken from the same materials show no change or only a limited continuous decrease of γ as G increases.
Oxygen Diffusion in Magnesium Aluminate Spinel
Authors: REDDY K. P. R. , COOPER A. R.
Published: June 2006

Oxygen self‐diffusion in MgAl2O4 single crystals was investigated by annealing the samples in 18O enriched gas at 98 kPa (1 atm) and measuring the tracer concentration profiles using a proton activation technique. The diffusion coefficients in the range 1625 to 1925 K for stoichiometric crystals are represented by:

Oxygen diffusivity in alumina‐rich nonstoichiometric samples is higher than in stoichiometric samples.
Preferential Dissolution of an Intergranular Amorphous Phase in a Nuclear Waste Ceramic
Authors: Clarke D. R.
Published: June 2006

A leaching experiment is conducted on thin transmission electron microscope samples of a tailored polyphase nuclear waste ceramic. The results demonstrate that the intergranular noncrystalline phase is preferentially dissolved, which calls attention to the possibly detrimental role of any intergranular glass in ceramics designed to immobilize nuclear waste.
Phase Relations in Crystalline Ceramic Nuclear Waste Forms: The System UO2+x‐CeO2‐ZrO2‐ThO2 at 1200°C in Air
Authors: PEPIN JOHN G. , MCCARTHY GREGORY J.
Published: June 2006

Steady‐state phase relations in the system UO2+x‐CeOz‐ZrO2‐ThO2 were determined for application to phase relations in high‐level crystalline ceramic nuclear waste forms. Samples were treated at 1200°C at an oxygen partial pressure of 21.3 kPa and a total pressure of 101.3 kPa. Phase assemblages were found to be comprised of cubic solid solutions of the fluorite‐structure type, solid solutions based on ZrO2, and orthorhombic solid solutions based on U3O8.
A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: I, Direct Crack Measurements
Authors: ANSTIS G.R. , CHANTIKUL P. , LAWN B.R. , MARSHALL D.B.
Published: June 2006

The application of indentation techniques to the evaluation of fracture toughness is examined critically, in two parts. In this first part, attention is focused on an approach which involves direct measurement of Vickers‐produced radial cracks as a function of indentation load. A theoretical basis for the method is first established, in terms of elastic/plastic indentation fracture mechanics. It is thereby asserted that the key to the radial crack response lies in the residual component of the contact field. This residual term has important implications concerning the crack evolution, including the possibility of post indentation slow growth under environment‐sensitive conditions. Fractographic observations of cracks in selected “reference” materials are used to determine the magnitude of this effect and to investigate other potential complications associated with departures from ideal indentation fracture behavior. The data from these observations provide a convenient calibration of the Indentation toughness equations for general application to other well‐behaved ceramics. The technique is uniquely simple in procedure and economic in its use of material.
A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: II, Strength Method
Authors: CHANTIKUL P. , ANSTIS G. R. , LAWN B. R. , MARSHALL D. B.
Published: June 2006

An examination is made of the sharp‐indentation technique of strength‐test precracking for toughness evaluation. The experimental approach follows that proposed by other workers but the theoretical analysis contains one vital new feature; the residual‐stress term discussed in Part I of this study is now introduced explicitly into the strength formulation. This modification overcomes a major systematic discrepancy evident in the previous models and at the same time, by virtue of attendant changes in the nature of the crack stability prior to attaining a failure configuration, eliminates the need for frac‐tographic measurements. Other advantages are also apparent, notably an insensitivity to postindentation radial crack extension. The main disadvantage is that only one result is obtained per specimen. Indentation/strength data from ceramics listed in Part I confirm the essential features of the theory and provide a suitable calibration factor. The method has special application to those materials which do not necessarily produce a well‐defined radial crack pattern, in which case an “effective”Kc appropriate to fracture properties at the flaw level is obtained.
Nonstoichiometry in Undoped BaTiO3
Authors: CHAN N.‐H. , SHARMA R.K. , SMYTH D.M.
Published: June 2006

Equilibrium electrical conductivity data for large‐grained, poly crystalline, undoped BaTiO3, as a function of temperature, 750° to 1000°C, and oxygen partial pressure, 10−20<PO2<10−1 MPa, were quantitatively fit to a defect model involving only doubly ionized oxygen vacancies, electrons, holes, and accidental acceptor impurities. The latter are invariably present in sufficient excess to control the defect concentrations through the compensating oxygen vacancies, except under the most severely reducing conditions. Singly ionized oxygen vacancies play no discernible role in the defect chemistry of BaTiO3 within this experimental range. The derived accidental acceptor content has a slight temperature dependence which may reflect some small amount of defect association. Deviation of the conductivity minima from the ideal shape yields a small PO2‐independent conductivity contribution, which is tentatively identified as oxygen vacancy conduction.
Intergranular Slow Crack Growth in MgF2
Authors: MECHOLSKY J. J.
Published: June 2006

Fractographic analysis of delayed failure of magnesium fluoride bars at room temperature showed that slow crack growth proceeds intergranularly, whereas rapid crack growth proceeds transgranularly. The size of the semielliptical demarcation between the intergranular and transgranular regions agreed well with the critical size predicted from a fracture mechanics equation. The ratio of the critical flaw size to fracture mirror (mirror‐mist, mist‐hackle, and crack branching) radii was shown to be constant, but the initial flaw size to fracture mirror radii were functions of the time to fracture. The observed time to fracture did not agree with that calculated.
Influence of Impurities on High‐Temperature Reactions of Kaolinite
Authors: JOHNSON SYLVIA M. , PASK JOSEPH A. , MOYA JOSE S.
Published: June 2006

When kaolinite is heated for differential thermal analysis (DTA) the second exothermic peak (∼1275°C) is due to growth of mullite crystals accelerated by formation of a liquid phase. The third exothermic peak (∼1460°C) is due to crystallization of cristobalite. Addition or presence of impurity oxides causes the second peak to shift in temperature and accelerates the formation of cristobalite so that the third peak may appear as low as the second exothermic peak temperature.
Migration of Small Pores in Potassium Chloride Due to a Temperature Gradient
Authors: LEMAIRE P. J. , BOWEN H. K.
Published: June 2006

Pore migration in KCl crystals subjected to a temperature gradient occurs by a vaporization‐condensation mechanism. The behavior of small (<100 μm) pores was observed using hot‐stage microscopy. A size‐dependent probability of pore motion was noted in which the fraction of mobile pores in a given size range steadily increased with size. Pores larger than =50 μm were always mobile. These observations are explained in terms of the probabilities of pore‐dislocation intersections. Screw‐type dislocations are found to be essential for providing molecular height surface ledges needed for vaporization and pore motion. The observation that some small pores moved and then stopped is explained by the fact that the vaporization rate becomes very low when the pore‐dislocation intersection occurs at the edge of a faceted pore.
Actinide Valences in Borosilicate Glass
Authors: KARRAKER D. G.
Published: June 2006

Optical and Mössbauer spectra show that actinide ions are incorporated in a borosilicate glass matrix as U(VI), Np(IV), P(IV), and Am(III). Uranium was reduced by graphite to U(V) and U(IV), but Pu(IV) remained unchanged. It is inferred from their valences that Np, Pu, and Am are part of the borosilicate network and U is probably a network‐modifier.
Influence of Interdiffusion on Solid Solution Formation and Sintering in the System BaTiO3‐SrTiO3
Authors: KOLAR D. , TRONTELJ M. , STADLER Z.
Published: June 2006

Formation of BaTiO3‐SrTiO3 solid solution during sintering of powder mixtures is characterized by preferential diffusion of Ba2+ ions. As a consequence, several nonequilibrium phases are temporarily formed; they were identified by X‐ray and microprobe analysis. Eutectic liquid appears below 1300°C, which may explain exaggerated grain growth during sintering of BaTiO3‐SrTiO3 mixtures. Disturbance in neck growth and Kirkendall‐type porosity hamper densification in the heterogeneous system as compared with the pure titanates.
Microstructural Analysis of Sintered High‐Conductivity Zirconia with Al203 Additions
Authors: BUTLER E.P. , DRENNAN J.
Published: June 2006

Transmission electron microscopy (at 100 and 1000 kV potential) and analytical scanning transmission electron microscopy were used to study α‐Al203 second‐phase particles and their interactions with grain boundaries in two high‐conductivity Y203/Yb203 stabilized zirconia ceramics containing deliberate additions of the alumina as a sintering aid. Most of the Al203 particles were intragranular and microanalysis showed that they contained inclusions rich in Zr or Si plus Zr. Al2O3 particles at grain boundaries were frequently associated with amorphous cusp areas rich in Si and Al. The results suggest that the Al203 acts as a scavenger for SiO2, removing it from grain‐boundary localities. A model is proposed whereby this process occurs as the boundaries meet the second‐phase particles, assisted by rapid grain‐boundary diffusion. Such an ZrO2‐Al2O3‐SiO2 interaction and partitioning is predicted thermodynamically and offers a possible explanation for the improvements in ionic conductivity brought about by Al2O3 additions, as reported in the literature.
Dissolution of a Stationary Bubble in a Glassmelt with a Reversible Chemical Reaction: Rapid Forward Reaction Rate Constant
Authors: WEINBERG MICHAEL C.
Published: June 2006

The effects of a reversible chemical reaction on the dissolution of a stationary gas bubble in a glassmelt are considered. The governing equations for a model system are presented and analyzed for a variety of the controlling parameters. Approximation methods are used to obtain analytical results for the bubble radius shrinkage rate. These results are compared to numerical solutions of the complete governing equations. A comparison is made between the influence of reversible and irreversible reactions on gas bubble dissolution behavior.
Considerations of Inhomogeneity Effects in Sintering
Authors: EVANS A. G.
Published: June 2006

Inhomogeneous regions of powder particle size or of particle packing result in nonuniform sintering rates. This nonuniformity induces stresses which may, in turn, create microstructural defects. A method for calculating these stresses is described and some aspects of defect development are discussed.
Reaction Products in the System MgCl2‐NaOH‐H2O
Authors: MAŽURANIĆ CARMEN , BILINSKI HALKA , MATKOVIĆ BORIS
Published: June 2006

The precipitation process of solid phases Mg3(OH)5CI‐4H2O (phase 5), Mg2(OH)3CI‐4H2O (phase 3), and Mg(OH)2 was followed by the addition of NaOH water solution in MgCl2 water solutions of different concentrations (0.001 to 4.8 mol dm−3) and characterized by chemical, potentiometric, coulometric, and X‐ray diffraction analyses. The concentration range in which the precipitation of solid phases occurs was determined. The phase distributions relative to the pH of solution and concentrations of magnesium and chloride were defined by the equilibrium diagram. The approximate solubility products of stable solid phases formed at different ionic strengths and at 293 K were determined.
A Simple Method for Determining Elastic‐Modulus–to‐Hardness Ratios using Knoop Indentation Measurements
Authors: Marshall D. B. , Noma Tatsuo , Evans A. G.
Published: June 2006

A simple indentation technique for measuring the hardness‐to‐modulus ratio of elastic/plastic materials was developed. The method, which is based on measurement of the elastic recovery of the in‐surface dimensions of a Knoop indentation, allows ready evaluation of the hardness‐to‐modulus ratio to an accuracy better than 10%.
Surface Oxidation of CaF2 in Air
Authors: Kumar Binod
Published: June 2006

Surface oxidation of fusion‐cast CaF2 in air was studied at 700°, 800°, and 900°C. Oxidation proceeds by a complex reaction mechanism involving creation of anion vacancies and formation of CaO, Ca(OH)2, and CaCO3. An equilibrium governed by the temperature and time of oxidation exists between formation and decomposition of CaCO3.
Structural Reliability:A Processing‐Dependent Phenomenon
Authors: EVANS A. G.
Published: June 2006

The principal sources of fracture in ceramic polycrystals have been identified; they include surface cracks produced during surface finishing and voids, inclusions, or large grains generated during processing. The dominance of a specific fracture source depends on the microstructure, test temperature, and stress distribution. The origins of processing‐induced defects have been examined and certain dominant processing variables identified. Connections between processing and structural reliability have thereby been established.
Fracture Behavior of Low‐Density Fibrous Ceramics
Authors: GREEN D. J. , RITTER J. E. , LANGE F. F.
Published: June 2006

It was established that subcritical crack growth occurs in the silica fiber‐based tiles that are currently in use as part of the thermal protection system (TPS) of the Space Shuttle. By measuring the tensile strength distribution and the subcritical crack‐growth parameters, it was possible to predict the material's behavior during proof‐testing. A similar time dependence of dynamic strength was also found for structural systems using this ceramic tile, suggesting that the ceramic is controlling their strength behavior. It was possible, therefore, to predict the influence of the proof testing currently in use for the Shuttle. These predictions were found to be in reasonable agreement with the experimentally determined strength distributions after proof‐testing. This study confirmed that proof‐testing and tile densification should lead to improved reliability of the TPS. The research further suggests that the subcritical crack‐growth behavior in these fibrous tiles is simiilar to that observed in bulk glass of similar composition and that failure occurs by the tensile fracture and fragmentation of individual fibers.
Mechanical Properties of Liquid‐Phase‐Bonded Copper‐Ceramic Substrates
Authors: WITTMER M. , BOER C. R. , GUDMUNDSON P. , CARLSSON J.
Published: June 2006

Liquid‐phase bonding of copper foils to ceramic substrates is a very attractive technique for the fabrication of metallized substrates for hybrid power electronics applications. The design and reliability considerations of such substrates necessitate the knowledge of their mechanical properties. Therefore, stresses and strains in the copper and in the ceramic of bonded substrates were investigated. Theoretical calculations are presented to support the experimental results and to find the influence of stresses and strains in the fabrication of copper ceramic substrates using the liquid‐phase‐bonding technique.
Determination of the Parameters of Native Disorder in α‐Al2O3
Authors: EL‐AIAT M. M. , KRóGER F. A.
Published: June 2006

Compensation of single‐crystal, acceptor‐dominated samples of α‐Al2O3 by hydrogen leads to samples showing conductivity by protons, electrons, holes, Al‴i, and V‴Al Values of the partial conductivities as a function of temperature are used to determine the parameters of native ionic and electronic disorder.
Temperature Dependence of Static Fatigue of Optical Fibers Coated with a Uv‐Curable Polyurethane Acrylate
Authors: CHANDAN H.C. , KALISH D.
Published: June 2006

The static fatigue of fused silica optical fibers coated with a uv‐curable polyurethane acrylate was measured, in water, from 40° to 90°C in 10° C intervals. The usual log (time‐to‐failure) vs log (applied stress) plotting of the data gives a bilinear fit at all test temperatures examined. By assuming exponential temperature dependence for static fatigue parameters, empirical static fatigue equations are generated for the two straight‐line segments. These equations are then used to generate a static fatigue design diagram at a given temperature. In view of the possible coating effects on static fatigue, these results should be cautiously applied to optical fibers coated with other polymers.
Measurement of Stress Due to Thermal Expansion Anisotropy in Al2O3
Authors: BLENDELL J. E. , COBLE R. L.
Published: June 2006

The stress due to thermal expansion anisotropy in polycrystalline Al2O3 was measured. The broadening of spectroscopic R lines (692 and 693 nm, due to Cr3+ impurities) was used to measure the stresses (at 77 K) in samples with grain sizes of 50 to 150 μm that had been cooled, from 2150 K, at constant rates from 0.1 to 100 K/min. The maximum stress was found to vary from 80 to 100 MPa, depending on the thermal history of the sample. The results are compared to the predictions of a model based on stress relaxation by diffusional creep and are in good agreement for the dependence on cooling rate. No effect due to grain‐size changes was observed due to the limited range of grain sizes accessible in this study.
Acid‐Enhanced Crack Initiation in Glass
Authors: Dabbs T. P. , Lawn B. R.
Published: June 2006

Silicate glass rods containing Vickers indentations in the subthreshold‐fracture region can show dramatic strength losses on brief immersion in acid solutions. The effect is most significant for “normal” glasses, notably soda‐lime glass, and for HF‐based acids. After extended immersion the strength begins to recover, ultimately surpassing the original (pre‐immersion) level, as glass dissolution processes become dominant. The weakening effect is interpreted in terms of chemically enhanced residual‐contact stress effects.
Spectroscopic Behavior of Iron(III) in Silicate Glass
Authors: Baiocchi E. , Bettinelli M. , Montenero A. , Di Sipio L.
Published: June 2006

The coordination of ferric iron was studied in lead silicate and lead‐sodium silicate glasses by optical spectroscopy in the region 11000 to 28500 cm−1.There is clear evidence from the spectra ofFe3+ octahedral and tetrahedral coordination, which is also supported by ligand field calculations.
X‐Ray Powder Diffraction Data for Two Hexagonal Aluminum Monoxycarbide Phases
Authors: Yokokawa Harumi , Dokiya Masayuki , Fujishige Masao , Kameyama Tetsuya , Ujiie Seiichi , Fukuda Kenzo
Published: June 2006

Aluminum monoxycarbide formed when Al2O3 is reduced by carbon in the presence of Si3N4 gives two X‐ray diffraction profiles. The high‐temperature phase exhibits the normal 2H wurtzite‐type pattern, whereas the low‐temperature phase produces three major lines in addition to the 2H profile. Interplanar spacings and lattice dimensions are reported, both phases can be regarded as solid solutions with AIN and / or SiC. It is suggested that the p‐Al4SiC4 reported by Barczak may have been a mixture of these monoxycarbides.
Surface Areas and Morphologies of CaO Produced by Decomposition of Large CaCO3 Crystals in Vacuum
Authors: Powell Elizabeth K. , Searcy Alan W.
Published: June 2006

The CaO formed by complete isothermal decomposition of calcite single crystals in vacuum has surface areas that range from 127.10 m2g at 650°C to 60 ± 20 m2/g at 900°C. Surface areas are not significantly reduced by annealing at 900°C in vacuum. SEM observations and other available data show that CaO particles, which are first formed in an aggregate with relatively uniform pores, rearrange when the CaO layer thickness exceeds =10 to 50 μm.
Separation of Cavitation‐Strain and Creep‐Strain During Deformation
Authors: Raj Rishi
Published: June 2006

A significant fraction of the strain in high‐temperature deformation may arise from cavitation. A methodology is described for separating the creep strain from the cavitation strain. Such a distinction is necessary because cavitation and creep are mechanistically different processes.
Interaction Between Superplasticizers and Calcium Aluminate Hydrates
Authors: MASSAZZA F. , COSTA U. , BARRILA A.
Published: June 2006

Sodium lignosulfonate and naphthalene and melamine sulfonate formaldehyde condensates, dissolved in lime water, are adsorbed on C4AH13 and C3AH6. When dissolved in dimethylsulfoxide the same admixtures are adsorbed on C4AH13 but, apparently, not on C3AH6. The adsorption isotherms of the two polycondensates are very similar but different from those of lignosulfonate. This fact can be attributed to the considerable structural difference between the synthetic admixtures and the lignine derivative. The particle zeta potential is modified by the presence of the admixtures, minimum additions of which are enough to bring the zeta potential to negative constant values. Nevertheless, the values of the potential cannot be correlated with the viscosity of the aluminate hydrate pastes, since the viscosity first increases and then decreases as the admixture increases. This behavior can be explained by a bridging effect among the particles, which overcomes the repulsive effect due to zeta potential.
Flexible Composite Transducers
Authors: SAFARI A. , HALLIYAL A. , BOWEN L.J. , NEWNHAM R.E.
Published: June 2006

Flexible piezoelectric composites made from PZT spheres and polymers with 1‐3 connectivity were fabricated using several types of polymers. The dielectric constants of the composites were 300 to 400 and the piezoelectric voltage coefficients g33 were 45 to 55×lO−3 V‐m/N. The high‐frequency properties of the composites were measured in both the thickness and radial mode of resonance. The frequency constants and the coupling coefficients of the composites for the thickness mode of resonance are comparable with the corresponding values for PZT. Possible applications of the composites are indicated.
Electronic Ceramics in High‐Temperature Environments
Authors: SEARCY ALAN W. , MESCHI DAVID J.
Published: June 2006

Simple thermodynamic means are described for understanding and predicting the influence of temperature changes, in various environments, on electronic properties of ceramics. Thermal gradients, thermal cycling, and vacuum annealing are discussed, as well as the variations of activities and solubilities with temperature.
Effect of Continuous‐Wave High‐Intensity Laser Radiation on the Strength of Silicon Nitride and Silicon Carbide
Authors: Veltri R. , Galasso F.
Published: June 2006

Laser interaction with silicon nitride and silicon carbide ceramics shows that hot‐pressed silicon nitride was less affected than reaction‐bonded silicon nitride at the same energy levels. Both of these showed greater thermal‐shock resistance than hot‐pressed silicon carbide.
Raman Spectra of Strontium Titanate
Authors: Balachandran U. , Eror N. G.
Published: June 2006

At room‐temperature the Raman spectrum was second‐order, in agreement with, the selection rules for the cubic perovskite structure. The second‐order spectrum originates largely from pairs of phonons with wave vectors near the Brillouin zone boundary. First‐order Raman‐active modes predicted in the tetragonal phase of SrTiO3 are observed on cooling to 120 K, where a new impurity‐related band is observed at 793 cm−1. The presence of impurities raised the cubic to tetragonal phase transition temperature to 120 K.
Integrated Intensities and Lattice Parameters for Mo5Si3
Authors: Naidu S.V.N. , Mays C. F. , Houska C.R.
Published: June 2006

An expanded listing of experimental and calculated X‐ray diffraction integrated intensities as well as “d” spacings is given for MosSi). The intensity data are found to be in excellent agreement with the space group 14/mem (x =0.075, y =0.224 for Mo positions and x ∼0.167 for Si). Mo5Si3 lattice parameters, corresponding to the tetragonal system, and a =0.96425 ± 0.00005, c =0.49096 ±0.00003 mm.
Quantitative Determination of the Hydroxyl Content of Vitreous Silica
Authors: Shelby J.E. , Vitko J. , Benner R.E.
Published: June 2006

The molar extinction coefficient for bound water in the form ofhydroxyl in vitreous silica has been determined by a thermogravimetric technique. The value obtained, 181 L/mol cm, is believed to be considerably more accurate than the values now used.
Preparation of High‐Density Ceria‐Yttria Ceramics
Authors: DRAGOO A.L. , DOMINGUES L. P.
Published: June 2006

Fine Ce‐Y oxide powders were prepared by coprecipitation of the carbonate, followed by calcination at 620°C. Hydrolysis of trichloroacetic acid was used to precipitate most of the material from a homogeneous solution; addition of ammonium bicarbonate and ripening of the precipitate were used to increase the yield to 68 to 70%. The precipitate apparently consisted of more than one phase and had an overall composition which suggested that it was a possible mixture of hydrated carbonate, hydroxycarbonate, and hydroxide. The calcined oxide powder was used to prepare an yttria‐doped ceria ceramic by hot‐pressing. The ceramic had the fluorite structure phase with a lattice constant of 0.541088 nm and a composition of Ce0.914Y0.086O1.957. The bulk density of the material was 6.96 g/cm3, or 99.4% of theoretical density. The ceramic had equiaxed grains, with an average dimension of 1 to 4 μm and with residual porosity mainly along the grain boundaries. Ac impedance properties of the chemically prepared oxide are compared with those of mechanically mixed and fired Y‐doped CeOZ.
The Systme Al‐Mg‐O‐N
Authors: And J. Weiss , Griel P. , Gauckler L. J.
Published: June 2006

Phase equilibria studies in the system Al‐Mg‐O‐N reveal a large homogenituy range of the magnesium‐aluminum‐oxynitride spinel with a constant anion sublattice nad idela or deficient cation sublattices. The compound 6AIN MgO has a hexagonal lattice with a = 0.2998 and c = 0.5328 am.
Electrical Conductivity of HF‐H2O‐ Impregnated Na2O.3SiO2 Glass
Authors: Nakanishi K. , Acocella J. , And J. Molinelli; , Tomozawa M.
Published: June 2006

Up to 5.75 WHO of concentrated (49 wt%) HF solution was placed in Nazo.3SiO2 glass under hydrothermal conditions. Electrical conductivity of the resulting glasses was primarily determined by the water content.
Measurement of the Crystallographically Transformed Zone Produced by Fracture in Ceramics Containing Tetragonal Zirconia
Authors: CLARKE D. R. , ADAR F.
Published: June 2006

During fracture of ceramics containing tetragonal zirconia particles, a volume of zirconia material on either side of the crack irreversibly transforms to the monoclinic crystal structure. Transformation zone sizes, measured using Raman microprobe spectroscopy, are presented for three sintered ceramics. In a single‐phase ZrO2−3.5 mol% Y2O3 material, an upper bound measurement of 5 μm is obtained for the zone size. In the Al2O3/ZrO2 composites studied, the zone size is deduced to correspond to ∼1 grain in diameter. On the basis of the monoclinic concentrations derived from the Raman spectra it is further concluded that only a fraction of the ZrO2 grains within the transformation zone transform, providing indirect evidence for the effect of particle size on the propensity for transformation.
Leaching of Polyphase Nuclear Waste Ceramics: Microstructural and Phase Characterization
Authors: JANTZEN C.M. , CLARKE D.R. , MORGAN P.E.D. , BARKER A.B.
Published: June 2006

The leaching of complex polyphase nuclear waste ceramics is described in the context of the geochemically established dissolution behavior of the constituent phases. Static leach tests conducted on ceramic monoliths in deionized water, in simulated silicate, and in brine groundwaters, conforming to Materials Characterization Center standards and an accelerated, microscopic leach test, were used to identify the processes. Dissolution and formation of surface passivation layers are discussed in terms of hydrolysis and the adsorption of the metal hydroxocomplexes onto the monolith surface. The factors observed to affect dissolution are pertinent to the leaching of other polyphase nuclear waste ceramics.
Thermomechanical Behavior of Refractory Concrete Linings
Authors: BUYUKOZTURK ORAL , TSENG TSI‐MING
Published: June 2006

A numerical analysis model was developed for predicting the behavior of dual‐component, refractory‐lined coal‐gasification vessels. The temperature‐dependent constitutive law, failure criteria, creep behavior, thermal expansion contraction behavior, and shrinkage characteristics of refractory concrete were formulated. To verify the proposed model, a three‐dimensional simulation analysis was made of an experimental gasifier vessel. The model was then used to study parameters on a circular, dual‐component, refractory concrete‐lined coal‐gasification vessel. The effects of shrinkage, creep, temperature distributions, vessel shell temperatures, bond barriers and anchor spacing, size, and shape on the performance of the gasifier vessel were studied. Design recommendations are made to aid in improving the mechanical reliability of refractory concrete‐lined coal‐gasification vessels.
Ion Beam Effects on Glass Surfaces
Authors: Smets B. M. J. , Lommen T. P. A.
Published: June 2006

X‐ray photoelectron spectroscopy has been used to show that 4 keV Ar + bombardment of glass results in a drastic alteration of the sample surface. Field‐induced migration of sodium ions and preferential sputtering account for these changes. The sputter yield is directly related to the binding energy of the ejected particles, in accordance with the linear collision cascade theory.
Origin of Preferential X‐Ray Line Broadening in Goethite‐Derived Fe2O3
Authors: Yamaguchi T. , Takahashi T.
Published: June 2006

The broadening of selected X‐ray diffraction peaks in goethite‐derived Fe2O3 was studied in terms of the structure factors of the oxygen and iron atoms. Calculation of the structure factors in the ideal corundum and Fe2O3 lattices showed that the intensities of the broad peaks result primarily from the iron atoms. Thus, preferential line broadening in goethite‐derived Fe2O3 is interpreted in terms of incomplete displacement of iron atoms during decomposition.
A Theoretical Estimate of Solution‐Precipitation Creep in MgO‐Fluxed Si3N4
Authors: Tsai R. L. , Raj R.
Published: June 2006

The creep rate in MgO‐fluxed hot‐pressed Si3N4 is calculated by means of a model which assumes a solution‐precipitation mechanism, and by using the kinetic data for the dissolution rate of β‐Si3N4 in an Mg‐Si‐O‐N glass (which was obtained in independent experiments). Despite simplifying assumptions, the predictions match quite favorably with experimental measurements of creep in hot‐pressed Si3N4.
Enhancement of Electrical Conduction in ZnO by CoO Doping
Authors: Koumoto Kunihito , Aoki Nouliaki , Kitaori Noriyuki , Yanaoida Hiroaki
Published: June 2006

Electrical conductivity of sintered ZnO was increased at high temperatures by CoO doping. Thermoelectric power measurements confirmed that ZnO doped with CoO was still an n‐type semiconductor. Temperature‐independent behavior of the carrier density was observed.
Modelling Annealing Lehrs for Flat Glass
Authors: GARDON ROBERT
Published: June 2006

Computer simulation of heat transfer in annealing lehrs for flat glass is combined with a method developed earlier for the calculation of stresses in glass. With this combined model one can predict stresses produced by annealing schedules that are readily realized in practice. Implications for the design, operation, and energy economy of lehrs are discussed.
Reaction of Silicate Glasses and Mullite with Hydrogen Gas
Authors: ISO STEPHEN T. , PASK JOSEPH A.
Published: June 2006

The increasing order of corrosion resistance to H2 gas flowing fast enough to ensure that the reaction is the slow step is fused silica, aluminosilicate glass, and mullite at T=1300° to 1500° C; the activation energies are 347.3, 358.6, and 389.1 kj/mol (83.0, 85.7, and 93.0 kcal/mol), respectively. No detectable reaction with a‐Al2O3 was observed. Addition of a small amount of CaO to the glass reduced its activation energy (283.7 kj/mol (67.8 kcal/mol)) and made its reactivity with H2 similar to that of mullite at high temperatures. The reaction product for the glasses consisted of a porous zone composed of an intermediate layer close to mullite in composition and an outer layer of a‐AI2O3. The reaction product for mullite consisted of a porous a‐Al2O3 residue layer.
Microhardness and Elastic Moduli of Si‐Y‐A1‐O‐N Glasses
Authors: Messier Donald R. , Broz Alfred
Published: June 2006

Glasses containing up to 15 at.% N were prepared and tested. The glasses were translucent to transparent, very hard, and had elastic moduli as high as 186 GPa.
Critical Load for Median Crack Initiation in Vickers Indentation of Glasses
Authors: Ishikawa H. , Shinkai N.
Published: June 2006

Critical load characteristics for the indentation‐induced median crack in ternary lead‐zinc‐borate and commercial silicate glasses were investigated. The critical load is directly proportional to the fracture toughness/Vickers microhardness term, supporting the Lawn‐Evans model; however, the magnitude of the load is considerably greater than that estiated from the model. The relation of critical load to deformation/fracture properties is discussed in terms of the stress field around the indent area and fractography.
Functional Form of the Arrhenius Equation for Electrical Conductivity of Glass
Authors: Syed R. , Gavin D. L. , Moynihan C. T.
Published: June 2006

Very precise electrical conductivity data on a series of six glasses (molar composition 25[xNa2O+(l−x)K2O]‐5Al2O3−70SiO2 with 0.95 ≤x≤l) have been obtained over a large temperature range (∼310°C). Analysis of these data suggests that the preexponential term in the Arrhenius conductivity equation is temperature independent.
Thermal‐Gradient‐Induced Migration of Bubbles in Molten Glass
Authors: MATTOX DOUGLAS M. , SMITH HARRY D. , WILCOX WILLIAM R. , SUBRAMANIAN R. SHANKAR
Published: June 2006

Buoyant fining of molten glasses does not occur in a weightless environment. One method suggested for fining is to apply a temperature gradient to cause bubbles to move because of the surface tension temperature dependency. Ground‐based experiments were conducted to demonstrate that thermal migration actually occurred in glassmelts and to estimate the magnitude of the effect. Thermal migration, consistent with theory, was found in borax melts, evidencing an approximately linear relation between bubble diameter and bubble velocity for a given temperature and gradient. Other effects, such as near‐bubble interaction, were also observed.
Investigation of the System CaO‐MgO‐V2O5: II, Crystalline Solutions and Crystal Chemistry
Authors: PARKER FRED J. , McCAULEY RONALD A.
Published: June 2006

The extent of the crystalline solutions in the system CaO‐MgO‐V2Os was studied quantitatively by the determination of lattice parameters. Metavanadate solutions existed along the length of the CV‐MV join, while the defect garnet solutions occurred at 29 to 32 mol% MgO on the orthovanadate join. The addition of solute ions created structural changes in the directions of the polyhedral layers (a‐ and c‐axis directions). Little change was reflected in the direction of polyhedral chains (b‐axis direction). The amount of solute allowed into the host lattices was structurally limited due to the significant differences in size between Mg2+ and Ca2+.
Neutron Diffraction Study of Structural Characteristics and Ionic Mobility of a‐Al2O3 at High Temperatures
Authors: ALDEBERT P. , TRAVERSE J. P.
Published: June 2006

The high‐temperature structure of a–Al2O3 was studied by powder neutron diffraction up to 2000° C. The changes in the structural parameters (unit cell and positional parameters and thermal B factors) with temperature give evidence of low aluminum and oxygen mobilities; Al ions are, however, always more mobile than oxygen. An enhancement with temperature of the structural anisotropy tends to weaken the weaker of the two distinct Al‐O bonds. This can be interpreted as an evolution toward the bonding expected in the liquid state.
Mechanochemical Polishing of Silicon Nitride
Authors: Vora H. , Orent T. W. , Stokes R. I
Published: June 2006

Two oxides of iron, Fe2O3 and Fe3O4, were identified as suitable soft abrasives for mechanochemical polishing of Si3N4. Removal rates up to 1.6 μ.m /h were observed when hot‐pressed Si3N4 samples were mechanochemically polished using these abrasives on a linen plastic lap. The polished surfaces were flat and scratch‐free, with a peak‐to‐valley roughness of <20 nm. Auger electron spectroscopy of these surfaces revealed a thin layer (≤10 nm) of a silicon oxynitride that contained carbon and ∼0.5 at.% iron.
Integral Antireflective Surface Production on Optical Glass
Authors: Cook Lee M. , Ciolek Sally , Mader Karl‐Heinz
Published: June 2006

Integral antireflective surfaces with extremely high laser‐damage thresholds were prepared on optical glasses by controlled corrosion in neutral solution. Properties of such surfaces are discussed and compared with gradient antireflective surfaces produced on phase‐separated borositicate glasses.
Effect of Homovalent Framework Cation Substitutions on the Sodium Ion Conductivity in Na3Zr2Si2PO12
Authors: Cava R. J. , Vogel Eva M. , Johnson David W.
Published: June 2006

The reported activation volume for sodium ion transport in the fast‐ion conductor Na3Zr2Si2PO12 is surprisingly large. Therefore, attempts were made to alter the size of the diffusion channels through partial substitution of As, Ge, Ti, Th, and Hffor the framework cations to decrease geometric structural hinderance of the diffusion process. Sodium ion conductivity is improved at temperatures below 200°C far the Hf substitutions. The existence and electrical properties of the apparently isostructural Na3Hf2Si2PO12, which has a room‐temperature conductivity of 1.0Ω10−3Ω cm−1, are reported.