bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of the Sodium Metasilicate‐Sand Reaction by an EMF Method
Authors: PAPADOPOULOS K.
Published: October 2006

A cell was set up consisting of a reference melt and a mixture of sodium metasilicate and sand at 1100°C. Since the liquid phase of the mixture continuously changed composition as the reaction proceeded, the emf also changed and provided a method of studying the rate of reaction. In the early stages of the reaction, the emf obeyed an equation derived from the assumption that the rate of attack on the sand particles was directly proportional to their surface area and to the chemical potential gradient of Na2O across a boundary layer.
Further Studies on Environment‐Sensitive Hardness and Machinability of Al2O3
Authors: SWAIN MICHAEL V. , LATANISION R. M. , WESTWOOD A. R. C.
Published: October 2006

Studies were continued on the effects of surface‐active environments on the hardness and the rates of drilling and abrasive wear of mono‐ and polycrystalline Al2O3. Changes in hardness induced by n‐alcohols and various aqueous environments were correlated with changes in ζ‐potential, hardness being maximum at the point of zero charge (pzc). Diamond‐core drilling rates exhibited a similar relation. Studies of the environment‐sensitive abrasive wear of both mono‐ and polycrystalline Al2O3 on a diamond‐impregnated metallographic wheel revealed more complicated behavior. The wear rate of Al2O3 under n‐alcohols is markedly dependent on the viscosity of the environment, with little or no correlation with ζ‐potential being evident. Studies using methanol‐water mixtures indicated, on the other hand, a slight viscosity dependence and the converse correlation with ζ‐potential to that observed in diamond‐core drilling, i.e. the rate of material removal was lowest at the pzc. Tests in aqueous solutions revealed no dependence on viscosity, but a strong inverse dependence on ζ‐potential, wear rate again being lowest at the pzc. These and other results are interpreted in terms of the various influences of adsorbed species on the near‐surface flow and fracture behavior of Al2O3.
Transformational Superplasticity in the Bi2O3‐Sm2O3 Eutectoid System
Authors: SMYTH J. R. , BRADT R. C. , HOKE J. H.
Published: October 2006

Transformational superplasticity associated with the eutectoid reaction in the Bi2O3‐Sm2O3 system was observed and characterized in hypoeutectoid and hypereutectoid compositions. Transformational strain varied linearly with applied stress and exhibited a stress‐axis intercept, or threshold stress, that is related to the proeutectoid microconstituent. Results are explained quantitatively using the analysis by Greenwood and Johnson and a creep mechanism.
Wetting of SiC, Si3N4, and Carbon by Si and Binary Si Alloys
Authors: WHALEN T. J. , ANDERSON ANTHONY T.
Published: October 2006

The wetting of several new materials for gas turbine engines, e.g. SiC, Si3N4, and C, by liquid Si and binary Si alloys containing Cu, Fe, and B was determined by the sessile drop method. All contact angles measured were < 90°. Hot‐pressed SiC, Si3N4, and Refel SiC are easily wet by Si; wetting is controlled by the balance of interfacial energies. Carbon is wet well by Si, but wetting is controlled by reaction and, in some carbons, by infiltration of Si into C. Additives to Si such as B and Fe can form compounds in reaction zones during wetting at interfacial areas.
Strength of Zirconium Diboride Ceramics After Cyclic Loading or Heating
Authors: STRAUSS ERIC L. , KIEFER TED F.
Published: October 2006

Strength losses in diboride ceramics resulting from load cycling near ultimate strength and from thermal cycling to 3000°F were investigated. Specimen configurations included notched and unnotched flexural specimens as well as specimens oriented in 3 orthogonal directions with respect to the billet pressing direction. Flexural fatigue testing for 2 to 8 million cycles produced no failures when stress levels were below 80% of flexural control strengths. Static loading of specimens that survived the fatigue test revealed no strength deterioration as a result of stress cycling. Thermal exposure produced an oxide coating; strength reductions caused by thermal cycling could be correlated with the thickness of this coating.
High‐Temperature Defect Structure of Cobalt‐Doped α‐Alumina
Authors: DUTT B. V. , HURRELL J. P. , KRÖGER F. A.
Published: October 2006

Room‐temperature optical absorption spectra, electron spin resonance spectra at 15° to 18°K, electrical conductivity, and emf measurements on concentration cells at 1620°C are analyzed and used to determine the defect structure of Codoped α‐Al2O3. The crystals are mixed ionic and electronic conductors at 1620°C: ionic conduction occurs at 10‐8 atm< p O2 < 10‐3 atm, with triply charged interstitial Al ions as the major charge carriers, and electronic conduction occurs at 10‐3 atm < p O2 < 1 atm, with holes as the major charge carriers. A defect model based on the charge compensation of divalent Co at Al sites by triply charged Al interstitials is proposed. The mobilities and activation energy of ions and holes, the oscillator strengths of Co2+ and Co3+ absorption bands, parameters for electron spin resonance spectra, level positions of substitutional Co2+ and an unknown donor, and equilibrium constants for defect formation reactions are determined.
Effect of Alumina Content on the Oxidation of Hot‐Pressed Silicon Carbide
Authors: SINGHAL S. C. , LANGE F. F.
Published: October 2006

The oxidation behavior at 1370°C of dense SiC, hot‐pressed with the aid of Al2O3, has been investigated as a function of Al2O3 content. Increasing amounts of the Al2O3 hot‐pressing aid increased the oxidation rate. Observations of the oxide surface show that a glassy phase (indicating formation of a liquid at the oxidation temperature) containing Si, Al, Fe, and K forms over the residual Al2O3 in the hot‐pressed material. It is suggested that the oxygen transport through an impure aluminosilicate liquid is faster than that through a pure SiO2 scale, thus causing an increased oxidation rate.
Theoretical Base and Experimental Techniques for Determination of Surface Energies of Ceramic Materials
Authors: RHEE S. K.
Published: October 2006

The surface energy of ceramic materials is described from a fundamental point of view, and methods for determining the surface energy are summarized. The influence of surface relaxation and surface adsorption on the surface energy is discussed.
Transport Processes in Composite Media
Authors: DAVIS H. T. , VALENCOURT L. R. , JOHNSON C. E.
Published: October 2006

Transport processes in two types of composite media were investigated. In one type, exemplified by hydrogen diffusion in steel with microvoids present, short‐lived trapping reactions result in a lowering of the effective or overall diffusion coefficient. The other type of composite consists of randomly mixed parts or phases having no interfacial resistance or trapping. The percolation properties of such systems are reviewed, and thermal conductivity, self‐diffusivity, and gas permeability in certain porous solids are analyzed in the light of percolation theory.
Composition Dependence of Elastic Moduli in Na2O‐TiO2‐SiO2 Glasses
Authors: JOHNSTON R. A. , BABCOCK C. L.
Published: October 2006

Measurements of the elastic moduli for Na2O‐TiO2‐SiO2, glasses located in 2 adjacent primary phase fields are quantitatively represented by equations in terms of linear mole fractions. Evaluation of the data showed that these linear relations are unique for each group of glasses studied.
Thermal Study of the Effect of Additives on the Hydration of Tricalcium Silicate
Authors: BEN‐DOR LINA , PEREZ DROR , SARIG SARA
Published: October 2006

The rate of paste hydration of 3CaO·SiO2(C3S) and the effects of additions of CaCl2, CdI2, and CrCl3, were studied by differential thermal analysis and thermogravimetry. X‐ray analyses were used to identify the synthesized C3S. The salts CaCl2, CdI2, and CrCl3, accelerated the hydration of C3S. The degree of hydration was estimated by the amount of Ca(OH)2, formed, as determined by TG.
Structural Approach to the Problem of Oxygen Content in Alpha Silicon Nitride
Authors: KATO KATSUO , INOUE ZENZABURO , KIJIMA KAZUNORI , KAWADA ISAO , TANAKA HIROKICHI , YAMANE TSUNEKO
Published: October 2006

The crystal structure of α‐Si3N4 was reinvestigated by an X‐ray method using a single‐crystal specimen prepared by chemical vapor deposition. The oxygen content of the specimen (0.05 ± 0.03%) was determined by 14 MeV neutron activation analysis. The α form crystallizes in the space group P31c with uniteell dimensions a=7.818 ± 0.003 Å and c= 5.591 ± 0.004 Å. The structure was refined by the full‐matrix least‐squares method using 1143 observed structure factors. The Si‐N distances determind ranged from 1.715 to 1.759 Å, and the final value of R was 0.041. Structural evidences indicated that the α form is essentially pure Si3N4.
Controlled Surface Flaws in Hot‐Pressed Si3N4
Authors: PETROVIC J. J. , JACOBSON L. A. , TALTY P. K. , VASUDEVAN A. K.
Published: October 2006

Surface flaws of controlled size and shape were produced in high‐strength hot‐pressed Si3N4with a Knoop microhardness indenter. Fracture was initiated at a single suitably oriented flaw on the tensile surface of a 4‐point‐bend specimen, with attendant reduction in the measured magnitude and scatter of the fracture strength. The stress required to propagate the controlled flaw was used to calculate the critical stress‐intensity factor,KIC, from standard fracture‐mechanics formulas for semielliptical surface flaws in bending. After the bend specimen had been annealed, the room‐temperatureKICvalues for HS‐130 Si3N4increased to a level consistent with values obtained from conventional fracture‐mechanics tests. It was postulated that annealing reduces the residual stresses produced by the microhardness indentation. The presence of residual stresses may account for the lowKIC, values. Elevated‐temperatureKICvalues for HS‐130 Si3N4were consistent with double‐torsion data. Controlled flaws in HS‐130 Si3N4exhibited slow crack growth at high temperatures.
Light‐Scattering Measurements of Structural Relaxation in Glass by Digital Correlation Spectroscopy
Authors: LAI CHING C. , MACEDO P. B. , MONTROSE C. J.
Published: October 2006

Digital clipped auto correlation spectroscopy was used to investigate the kinetic features of thermodynamic fluctuation processes which relax on time scales from 10−6 to 102 s. The autocorrelation function associated with structural relaxation in Na2O· K2/O·6SiO2, glass was determined in the annealing region. The results indicate a nonexponential correlation function that can be fitted with the decay function exp ‐ (t/τβ)β, where β and τβ are adjustable parameters. The parameter β which characterizes the deviation from a simple exponential, was essentially constant (β= 0.57 ± 0.02) from 468 ° to 550 ° C. The characteristic time constant, τβ ranged from 1.35 × 10−2 to 6.30 s. The computed average relaxation times were compared with shear viscosity data reported for a similar glass; both the temperature dependence and the magnitude agreed well with the predictions of viscoelastic theory.
High‐Temperature Creep of Y2O3‐Stabilized ZrO2
Authors: SELTZER M. S. , TALTY P. K.
Published: October 2006

The compression creep behavior of Y2O3‐stabilized ZrO2 (YSZ) was studied at temperatures to 2000 ° C. The function of Y2O3 content and grain size was tested in specimens with various impurity concentrations and porosity distributions. For relatively fine‐grained specimens, creep rates increased with the 1.5 power of the applied stress at low stresses and with the third power at high stresses. The results for coarse‐grained specimens can, in general, be fit by the cube dependence. The 1.5 power can be reduced to a linear dependence by correcting for an apparent threshold stress, which decreases with increasing temperature. Creep activation energies for YSZ are 128 ± 10 kcal/mol, independent of Y2O3 content, impurity level, grain size, and porosity distribution. In addition, over a broad range of temperatures and stresses the absolute values of the steady‐state creep rates are influenced only by grain size and O2 partial pressure.
SIMS Analysis of Aqueous Corrosion Profiles in Soda‐Lime‐Silica Glass
Authors: GOSSINK R. G. , de GREFTE H. A. M. , WERNER H. W.
Published: October 2006

In secondary ion mass spectrometry (SIMS) of glasses compensation of surface charging is necessary to avoid migration of mobile ions. A charge‐compensation method, involving a metal diaphragm placed on the sample surface and a rastered primary ion beam, was tested on aqueous corrosion profiles in 20Na2O·10CaO·700SiO2 (mol%) glass. The method was effective with both O− and O2+ primary ions.
Micromorphology of the Interfacial Zone Around Aggregates in Portland Cement Mortar
Authors: BARNES B. D. , DIAMOND SIDNEY , DOLCH W. L.
Published: October 2006

Scanning electron microscopy showed that micromorphological features of the interfacial zone, which occur next to glass slide “model aggregates” occur also in mortars made with standard Ottawa silica sand. These features included formation of a duplex film on the sand‐grain surfaces, development of large well‐formed Ca(OH)2 crystals at intervals near the interface with their c axes roughly parallel to it, development of stacked‐platelet secondary Ca(OH)2 in open spaces immediately adjacent the duplex film, and hydration leading to the presence of hollow‐shell hydration grains (Hadley grains) in the interfacial region.
Mechanical Properties of Hot‐Pressed Silicon Nitride with Different Grain Structures
Authors: HIMSOLT GUENTHER , KNOCH HEINRICH , HUEBNER HEINZ , KLEINLEIN FRIEDRICH WILHELM
Published: October 2006

During hot‐pressing of α‐Si3N4 powders, the equiaxed α micro‐structure gradually transforms into a β structure characterized by needle‐shaped prismatic grains which are closely entangled and linked together. With increasing amounts of the β fraction, the bend strength, fracture toughness, and work of fracture increase significantly, then decrease as grain growth occurs. The Klc, improves by a factor of >2 and the change in γF by a factor of >4. The crack resistance to achieve the same crack velocity in materials of different β contents shows a similar trend. The dependence of the mechanical properties on the microstructure is explained by linking and pullout of the β crystals and by grain coarsening.
KIcand Delayed Fracture Measurements on Hot‐Pressed SiC
Authors: HENSHALL J. L. , ROWCLIFFE D. J. , EDINGTON J. W.
Published: October 2006

The fracture resistance of hot‐pressed SiC between 300 and 1773 K was measured usingKIc, and notched‐beam delayed‐fracture tests. An analysis was developed which enables crack velocities as low as 10−11ms−1to be derived from the failure time.
The Defect Structure of Unintentionally Doped α‐Al2O3 Crystals
Authors: MOHAPATRA S. K. , TIKU S. K. , KRÖR F. A.
Published: October 2006

Electrical conductivity and the ionic and electronic transference numbers were determined for two types of unintentionally doped single crystalline sapphire for current directions perpendicular to the r plane (1102). One was acceptor dominated and the other was initially donor (Hix) dominated, changing to acceptor domination after a prolonged anneal at 1600°C. The positions of the electronic energy levels of dominant impurities and the constants regulating the oxidation‐reduction of these impurities and of pure Al2O3 are determined. The latter shows a discrepancy with an expression reported previously.
Erosive Damage Depth in Ceramics: A Study on Metastable, Tetragonal Zirconia
Authors: LANGE F. F. , EVANS A. G.
Published: October 2006

A novel method is described for measuring the depth of erosion damage on ceramics that exhibit a stress‐induced martensitic transformation. The technique is applied to metastable, tetragonal zirconia, eroded with silicon carbide particles. The damage depth data are compared with fracture depth predictions from single‐particle studies, on the premise that the surface transformation zone can be attributed to the presence of impact fractures. The reasonable correlation obtained adds credence to the suggestion that single‐particle tests are pertinent to erosion prediction in the plastic response regime
Strength Degradation of Glass Impacted with Sharp Particles: II, Tempered Surfaces
Authors: LAWN B. R. , MARSHALL D. B. , WIEDERHORN S. M.
Published: October 2006

The analysis of strength degradation in the preceding paper is here extended to tempered surfaces. Addition of a surface compression term to the indentation fracture equations leads to simply modified degradation relations. Impact energy is again identified as the important service variable in degradation. Comparative strength tests on thermally tempered and annealed glass disks after impaction with SiC particles confirm the predicted energy dependence of strength loss. The results indicate that surface‐strengthening processes can be just as effective in improving resistance to strength degradation as can increasing toughness. However, improvements in surface erosion resistance are relatively insignificant.
Quenched Metastable Glassy and Crystalline Phases in the System Lithium‐Sodium‐Potassium Metatantalate
Authors: NASSAU KURT , WANG CHRISTINE A. , GRASSO MICHAEL
Published: October 2006

A twin‐roller apparatus was used to quench 21 melts in the three pseudobinary systems and in the pseudoternary system composed of LiTaO3, NaTaO3, and KTaO3. Glasses were obtained in all but the high‐Na region. X‐ray diffraction and differential thermal analysis studies of the metastable compositions showed that there were two metastable crystalline phases when the materials crystallized; one phase was a defect pyrochlore structure centered at KTaO3 and the other appeared at Li0.8K0.2TaO3. The metastable phases subsequently transformed into the expected stable phases on heating. There is some evidence for a subsolidus two‐glass region in the system (K,Na)TaO3.
The Influence of Substructures on Tensile Creep of MgO Single Crystals
Authors: CLAUER A. H. , SELTZER M. S. , WILCOX B. A.
Published: October 2006

Tensile creep tests were performed at 1400°C and a stress of 44.1 MN/m2 on <110> oriented MgO single crystals which had been prestrained at 1800°C in tension to produce various dislocation substructures. Several substructures, ranging from blocky (somewhat diffuse) subgrains to random dislocation arrays, were developed by varying the tensile strain rate at 1800°C. Introducing substructure had no significant effect on the early stages of primary creep (to ∼1% strain), but increased the minimum creep rate compared to that in pristine (substructure‐free) material. A precreep substructure of blocky subgrains was more creep resistant than one consisting of random dislocation arrays.
Role of Physical Properties in the Resistance of Brittle Ceramics to Failure by Thermal Buckling
Authors: HASELMAN D. P. H.
Published: October 2006

An analysis is presented of the role of the physical properties which affect the thermal buckling behavior of ceramic materials for various geometric and thermal conditions. For a column with slight initial curvature or a curvature as the result of a transverse temperature gradient, expressions are derived for the maximum increase in temperature, ΔTmax or transverse temperature gradient, or heat flux to which the column can be subjected to avoid failure under the influence of the bending stresses. From the solutions obtained several “thermal buckling resistance parameters” are defined for comparing the relative thermal buckling resistance of brittle materials. Numerical examples indicate that thermal buckling of brittle materials of the proper geometry can occur relatively easily.
Crystallography and Microstructure of Directionally Solidified Oxide Eutectics
Authors: MINFORD W. J. , BRADT R. C. , STUBICAN V. S.
Published: October 2006

The crystallographic features of several directionally solidified binary oxide eutectics were examined by the Buerger precession X‐ray method and are discussed in terms of the lattice misfit and ionic charge compensation at the interface, particularly with regard to the oxygen sublattice. Fibrous and lamellar micro‐structures are classified and the resultant morphologies related to the phase volumes. The interphase spacing proportionality to the inverse square root of the solidification rate is examined.
Reaction of Beta‐Dicalcium Silicate and Tricalcium Silicate with Carbon Dioxide and Water Vapor
Authors: GOODBRAKE C. J. , YOUNG J. F. , BERGER R. L.
Published: October 2006

The carbonation‐reaction kinetics of beta‐dicalcium silicate (2CaO·SiO2 or β‐C2S) and tricalcium silicate (3CaO. SiO2 or C3S) powders were determined as a function of material parameters and reaction conditions and an equation was developed which predicted the degree of reaction. The effect of relative humidity, partial pressure of CO2, surface area, reaction temperature, and reaction time on the degree of reaction was determined. Carbonation followed a decreasing‐volume, diffusion‐controlled kinetic model. The activation energies for carbonation of β‐C2S and C3S were 16.9 and 9.8 kcal/mol, respectively. Aragonite was the principal carbonate formed during the reaction and the rate of carbonate formation was coincident with depletion of the calcium silicates; C‐S‐H gel formation was minimal.
Segregation of Aliovalent Solutes Adjacent Surfaces in MgO
Authors: BLACK JOHN R. H. , KINGERY W. DAVID
Published: October 2006

The segregation of ferrous iron, ferric iron, chromium, and scandium solutes adjacent {100} surfaces of MgO crystals in the single‐phase region was studied by ion microprobe mass spec‐troscopy. Excess concentration in a region near the surface was found for Fe3+, Cr3+, and Sc3+, but none for Fe2+. This segregation is the type predicted as necessary to balance the negative surface charge.
Strength‐Grain Size Relations in Polycrystalline Ceramics
Authors: SINGH J. P. , VIRKAR ANIL V. , SHETTY D. K. , GORDOW R. S.
Published: October 2006

A model is presented to explain the strength‐grain size behavior of ceramics exhibiting duplex microstructures and of ceramics with uniform coarse‐grained microstructures. Using an energy balance analysis, the model shows that in most ceramics an hitiipl flaw contained within a single large grain will initially propagate and then arrest after entering the region of increased fracture‐surface energy. The arrested flaw will subsequently propagate to failure at the value OF the critical stress intensity factor. Using the data in the literature, a strength‐(grain size)−1/2 plot for MgAl2O4 was generated.
Reaction and Diffusion in Silver‐Arsenic Chalcogenide Glass Systems
Authors: HOLMQUIST GLENN A. , PASK JOSEPH A.
Published: October 2006

The diffusion of Ag from the metal or Ag2Se in amorphous As2S3 and As2Se3 at 175°C is accompanied by the reduction of As from a valence of 3+ to 2+ or 2+ to 1 + to maintain charge neutrality in the glass. Only Ag+ diffuses at this temperature; all other ions are essentially immobile. An amorphous reaction‐product phase is formed in the diffusion zone with a composition range of 28.6 to 44.4 at % Ag. The lower limit corresponds to all As cations of 2+ valence (equivalent to amorphous Ag2As2S3); the upper limit, the maximum solubility of Ag in these glasses, corresponds to all As cations of 1 + valence (equivalent to amorphous Ag1As2S3). The diffusivity of Ag in these glasses at 175°C for concentrations of 10 to 35 at.% Ag is

Sulfide 4× 10−14 exp[(+0.23±0.01)(at.% Ag)]cm2/s

Selenide 2′ 10−11 exp[(+0.14±0.01)(at.% Ag)]cm2/s
High‐Temperature Deformation of Hypostoichiometric 239PuO2
Authors: PETROVIC J. J.
Published: October 2006

The high‐temperature deformation of hypostoichiometric 239PuO2 was investigated using constant‐displacement‐rate compression tests. Considerable ductility (10 to 25% true strain) was observed at 800° to 1500°C. Yield stresses decreased with increasing temperature and decreasing strain rate. Strain‐rate sensitivity values increased from 0.011 at 800° to 0.205 at 1500°C, whereas deformation activation energies were 121 to 157 kcal/mol. Deformed microstructures showed no evidence of grain‐boundary cracking, suggesting that dislocation motion is the dominant high‐temperature deformation mechanism.
Interface Between Chemically Vapor Deposited Titanium Carbide and Cemented Carbide Substrate
Authors: SHARMA N. K. , WILLIAMS WENDELL S.
Published: October 2006

The interface between a TiC coating deposited by CVD and a substrate of Co‐bonded multicarbide was studied by SEM, RHEED, and AES. The presence of an additional phase several micrometers thick at the interface is indicated by etching and SEM examination. Earlier supposition that it is an R) phase, W6Co6C, is confirmed by reflection high‐energy electron diffraction. This phase surrounds all the near‐surface WC grains but the cubic‐carbide grains are not contacted. It is suggested that, because of their capacity for nonstoichiometry, the cubic‐carbide grains act as carbon sources and prevent the local decarburization of the binder phase which leads to η formation.
Oxidation of Sintered Cobalt Oxide
Authors: OTT W. R. , RANKIN D. T.
Published: October 2006

The kinetics and mechanism of the oxidation of sintered pellets of CoO and Co0.5Mg0.5O in air at high temperatures were investigated to find stable heat sources containing 60Co. The initial stages of oxidation of both materials were nuclei‐growth‐controlled, i.e. In [1/(1‐X)] =ktm. The reaction rate constant for CoO decreased at 800° to 960°C, the temperature where the cobalt oxide spinel decomposed. The reaction‐rate constant for decomposition of the mixed oxide was maximum at 700°C and decreased at higher temperatures. This decrease confirmed the validity of the nuclei‐growth solid‐state reaction‐rate equations.
Hydration of Tricalcium Silicate in the Presence of Lignosulfonates, Glucose, and Sodium Gluconate
Authors: MILESTONE N. B.
Published: October 2006

Two commercial calcium lignosulfonates were separated into their main constituents, i.e. fractions high in salts of lignosulfonic acids and fractions high in sugars and sugar‐acid salts. Hydration of C3S in the presence of these fractions was studied. The fractions high in sugar acids caused a delay in hydration with a subsequent acceleration of hydration at additions of 0.1%. Fractions high in lignosulfonates caused little delay, whereas additions of 0.5% caused complete inhibition. Hydration was also studied in the presence of glucose and sodium gluconate. Adding 0.1 % glucose delayed hydration for about 11 days, whereas adding 0.1% sodium gluconate caused complete inhibition. The delay in hydration is discussed in terms of poisoning of nucleation sites.
Rayleigh Scattering Losses in Soda Borosilicate Glasses
Authors: TYNES A. R. , PEARSON A. DAVID , NORTHOVER W. R.
Published: October 2006

The present writers predicted that Rayleigh scattering losses in some soda borosilicate glasses would be less than in pure vitreous silica. The simple heuristic arguments that lead to this prediction and the scattering loss measurements which appear to confirm it are presented.
Contact‐Induced Failure of Prestressed Glass Plates
Authors: CHANTIKUL P. , LAWN B. R. , MARSHALL D. B.
Published: October 2006

An indentation fracture technique was used to determine critical contact conditions under which prestressed brittle surfaces are subject to catastrophic failure. A theoretical model based on the growth of a well‐developed, contact‐induced half‐penny crack leads to a simple inverse‐cube power relation between indentation load and tensile prestress. The analysis is developed in terms of fracture parameters which are readily calibrated in routine indentation/strength tests. Experiments on glass disks loaded simultaneously in biaxial flexure and Vickers indentation confirm the essential failure predictions of the theory; toughness is the key material parameter controlling resistance to failure. The results emphasize the danger of spurious tensile stresses in ceramic systems exposed to severe contact events.
Raman and Infrared Spectroscopic Studies of the Crystalline Phases in the System Pb2SiO4‐PbSiO3
Authors: FURUKAWA TOSHIHARU , BRAWER STEVEN A. , WHITE WILLIAM B.
Published: October 2006

The stable and metastable phase relations in the system Ph2SiO4‐PhSiO3, were reexamined using Raman and ir spectroscopy to characterize the phases. Three stable phases, H‐Ph2SiO4, M‐Ph2SiO4, and M‐Ph2SiO4 (alamosite) and four metastable phases, L‐Ph2SiO3, phase X, L‐PhSiO3 and hexagonal PhSiO3, occur in the portion of the system investigated. The Raman and ir spectra allow some conclusions to be drawn about the structures of silicate groups in the lead silicate crystalline phases.
Structural Properties of Calcium Silicate Pastes: I, Effect of the Hydrating Compound
Authors: BERGER R. L. , BENTUR ARNON , MILESTONE N. B. , KUNG J. H.
Published: October 2006

The chemical and physical properties of C3S, β‐C2S, a C3S/C2S blend, and portland cement pastes cured at 25°C were investigated. The H2O specific surface areas of the calcium silicate samples follow a common linear relation when plotted against a CIS ratio. The β‐C2S had higher capillary porosity and N2 surface area, resulting from increased mesopore volume at the expense of micropores. All calcium silicate pastes had similar polysilicate content vs time curves, indicating an aging process which is not sensitive to the starting composition of the hydrating calcium silicate. The polysilicate content of portland cement was much lower than that of the corresponding calcium silicate pastes. Strength‐capillary porosity relations for the various systems are discussed.
A Viscosity‐Temperature Relation for Glass
Authors: FONTANA E. H. , PLUMMER W. A.
Published: October 2006

A theory for the viscosity and structure of glass as a function of temperature and composition had been advanced, proposing that at a few critical temperatures silicate glasses undergo structural transformations. Between these transformation temperatures, the activation energy and lattice coefficient are constant. A series of special glasses were melted and viscosity was measured to test this theory. The results indicate that the viscosity‐temperature behavior of glass does not conform to the previously proposed model. The activation energy appears to vary continuously over the entire temperature range studied. However, a critical temperature does exist at which the temperature coefficient of the activation energy changes. This discovery represents a more subtle change than that previously envisaged.
Relation of Surface Structure of Glass to HF Acid Attack and Stress State
Authors: TOMOZAWA MINORU , TAKAMORI TAKESHI
Published: October 2006

The surfaces of commercial glasses (mainly borosilicate glasses) were investigated by HF etching and surface‐stress measurement. The HF etch rate was slow at the surface for some phase‐separated glasses, which was attributed to excess alumina in the surface layer produced during the glass manufacture. After heat treatment of the glass rods, either with or without the as‐Received surfaces, compressive (tangential) stresses were observed in all the glasses studied. These stresses were probably caused by evaporation of water from the surface during heat treatment.
Strength and Life Prediction for Hot‐Pressed Silicon Nitride
Authors: TRANTINA G. G.
Published: October 2006

The strength of hot‐pressed Si3N, was evaluated for constant stress rate, linear cyclic stress, and constant‐stress loading. A stress‐rupture rig was used to simultaneously test 10 samples under constant‐stress loading. Exponential crack‐growth‐rate expressions were numerically integrated for constant stress rate and cyclic‐stress loading and an approximate expression for the time‐to‐failure for these loading cases was developed. For either the power law or the exponential crack‐growth‐rate formulation, linear cyclic‐stress and constant‐stress‐rate loading can be treated with the same fracture stress‐time‐to‐failure representation. This correspondence was demonstrated for hot‐pressed Si3N4. The exponential crack‐growth formulation provided a consistent interpretation of the strength‐degradation results, whereas the power‐law formulation was inadequate.
Analysis of Field‐Assisted Binary Ion Exchange
Authors: ABOU‐EL‐LEIL MAHMOUD , COOPER A. R.
Published: October 2006

A differential equation was derived for ionic migration in a system with two mobile ions. Stationary solutions were obtained for the case where the slower ion follows the faster, which reduce to those obtained when diffusion is ignored. When the faster ion is “behind” the slower no stationary solutions are possible, but the diffusion term is not important for this case and appropriate solutions are readily obtained. However, by taking account of diffusion at the boundaries, where it is important, infinite gradients are avoided and concentration equilibrium is permitted at the glass‐salt interface. The concentration distributions predicted from this approach are compared with those measured on glass that has been ion exchanged with electric field assistance. Although the agreement is reasonable, there is some discrepancy, due in part to the assumption of concentration‐independent species mobility.
The Effects of Prehydration on the Liquid Hydration of 3CaO·Al2O3with CaSO4·2H2O
Authors: BREVAL ELSE
Published: October 2006

Liquid hydration and water‐vapor hydration of 3CaO·Al2O3, were studied. Variable parameters were hydration time, temperature, relative humidity, and amount of gypsum. The hydration products (gel, ettringite, hexagonal hydrates, and 3CaO·Al2O3·6H2O) were studied by electron microscopy, X‐ray diffractometry, and thermal analysis. A reaction scheme is proposed. The degree of water‐vapor hydration influenced the sequence of the subsequent liquid hydration which, however, was independent of the composition of the water‐vapor hydration products. Below a critical degree of water‐vapor hydration (≊3% combined water) the reaction with liquid water occurred as if no water‐vapor hydration had taken place. Above this value the reaction gave hydration products suggesting a change of the 3CaO·Al2O3reactivity. A possible correlation with the retardation of strength development of prehydrated cement is suggested.
Computation of Ternary Molten Salt Phase Diagrams
Authors: LIN P.‐L. , PELTON A. D. , BALE C. W.
Published: October 2006

The thermodynamic properties of all phases in the 15 binary systems formed among the salts LiCl, NaCl, KCI, MgCl2, CaCl2, and SrCl2, were obtained and expressed in mathematical form by a critical analysis of the measured binary phase diagrams and of published binary thermodynamic data. Interpolation procedures were then used to estimate the thermodynamic properties of the 20 ternary systems formed among the 6 salts and all 20 ternary phase diagrams were calculated using a computer program designed for the purpose. Agreement with the measured phase diagrams for the 8 ternary systems for which measured diagrams are available is good.
Depth Profile Measurement by Secondary Ion Mass Spectrometry for Determining the Tracer Diffusivity of Oxygen in Rutile
Authors: ARITA M. , HOSOYA M. , KOBAYASHI M. , SOMENO M.
Published: October 2006

Secondary ion mass spectrumètry has been applied for measuring the tracer diffusivity of oxygen in the c direction of single‐crystal rutile for a temperature range of 1150 to 1450 K at 6000 Pa pressure of oxygen gas. Specimens diffusion‐annealed in oxygen gas containing 18O were subsequently continuously sputtered and analyzed for 16O and 18O. The tracer diffusivity was determined from the depth profile of 18O, taking into account a surface exchange reaction of oxygen. The tracer diffusivity in Cr2O3‐doped rutile was 3 to 8 times larger than that in pure rutile. For pure rutile, the diffusivity is expressed by D(m2/s)=3.4×10−7, exp [‐251(kJ/mol)/RT], and for 0.08 mol% Cr2O3‐doped rutile, by D(m2/s)= 2.0×10−8 exp[‐204(KJ/mol)/RT]. The Cr2O3 doping had a catalytic effect on the rate constant of the surface exchange reaction on the c surface. The rate constant is represented, for pure rutile, by K(m/s)= 2.4×10−1 exp[‐246(KJ/mol)/RT], and for 0.08 mol% Cr2O3‐doped rutile, k(m/s)= 3.5×10−5 exp[‐131(KJ/mol)/RT].
Raman Study of the Reactions in a Glass‐Forming Mixture with Molar Composition:30K2CO3‐70SiO2‐1As2O3
Authors: VERWEIJ HENK
Published: October 2006

The results of a study of the reactions in a glass‐forming batch with molar composition 30K2CO3‐70SiO2‐lAs2O3 are given. Laser Raman spectroscopy was used for nondestructive identification of silicate, carbonate, arsenite (As3+), and arsenate (As5+) ions in the vitreous or crystalline state, occurring in quenched reaction mixtures. It is shown that in the first stage of melting a potassium‐rich liquid phase is formed, containing metasilicate chains (SiO2−3)x and carbonate ions, in which all arsenic is present in the pentavalent state as AsO13‐ ions. When this liquid phase reaches the final product glass composition the AsO13‐ ions condense to As2O4−7 (As5+) ions and AsO−2 (As3+) groups, during which process O2 is formed. The preliminary results of studies on crystalline and vitreous potassium arsenates and arsenites and of arsenic‐containing potassium silicate glasses are given for identifying arsenate and arsenite groups. It is argued that the reaction mechanism found describes the effectiveness of As2O3 as a fining agent. Contrary to the current view in the literature for the fining action of As2O3, which states that an O2 evolution which is triggered by a temperature increase causes fining, an important effect is found in the O2 evolution triggered by alkali oxide concentration variations during melting.
Phase Diagram for a Portion of the System Li2O‐Nd2O3‐P2O5
Authors: NAKANO JUN'ICHI , YAMADA TOMOAKI , MIYAZAWA SHINTARO
Published: October 2006

In the ternary system Li2O‐Nd2O3‐P205, part of the phase diagram relevant to the growth of single LindP4O12 (LNP) crystals was examined. LNP melts incongruently and decomposes into NdP3O9 and liquid at the peritectic temperature of 970°C. For the crystal growth, an Li2O‐P2O5 mixture should be used as a flux. The melt compositions from which LNP nucleates were clarified.
Self‐Diffusion of Er in Pure and HfO2‐Doped Polycrystalline Er2O3
Authors: SCHEIDECKER R. W. , BERARD M. F.
Published: October 2006

Using a tracer sectioning technique, the self‐diffusion of Er in pure and HfO2‐doped polycrystalline Er2O3 was measured at 1614° to 1900°C. Up to ≊ 10 mol% HfO2 dopant level, the Er self‐diffusion coefficients followed a relation based on cation vacancies as the principal mobile defects present and available for cation diffusion. Above 10 mol% HfO2, deviation from this relation occurred, apparently due to clustering of cation vacancies and oxygen interstitials around the dopant hafnium ions. The activation energy for the self‐diffusion of Er in pure Er2O3 was 82.2 kcal/mol and increased with the HfO2 dopant level present.
Reaction of Hydraulic Calcium Silicates with Carbon Dioxide and Water
Authors: GOODBRAKE C. J. , YOUNG J. F. , BERGER R. L.
Published: October 2006

The carbonation of wetted powders of beta‐dicalcium silicate (β·2CaO·SiO2=β‐C2S) and tricalcium silicate (3CaO·SiO2= C3S) was studied as a function of reaction conditions. The water/solids ratio is an important parameter and there is an optimum value for each silicate. Relative humidity and the partial pressure of CO2 also strongly affect the reaction. The rate of carbonation can be conveniently represented by plotting the degree of carbonation against the logarithm of time. C‐S‐H and calcite are the initial reaction products. Subsequently, carbonation of the C‐S‐H produces silica gel, whereas aragonite may form if the system is allowed to dry out.
Preparation and Properties of Yttrium‐Silicon‐Aluminum Oxynitride Glasses
Authors: LOEHMAN RONALD E.
Published: October 2006

Glasses containing up to 7 at.% nitrogen were prepared in the system Y‐Si‐Al‐O‐N. The glass transition temperature, hardness, and relative fracture toughness increase and the thermal expansion coefficient decreases with increasing nitrogen content. Weight losses after 350 h in 95°C distilled water are not simply related to nitrogen content, but for some compositions they are half that reported for fused silica. The electrical conductivity at 548°C and 10 kHz is 7.8×10−10 (Ω·cm)−1 for one composition. Fourier transform ir spectroscopic analysis indicates the presence of Si‐N bonds in the glasses. The data suggest that nitrogen substitutes for oxygen in the glass network to produce a more highly cross‐linked structure.
Hydrogen Permeability of Sintered Aluminum Oxide
Authors: ROBERTS RODNEY M. , ELLEMAN THOMAS S. , III HAYNE PALMOUR , VERGHESE KURUVILLA
Published: October 2006

Hydrogen permeability of high‐density, high‐purity sintered alumina tubes was measures is a function of temperature and pressure using tritium as a tracer. The permeability, ø, at 1200° to 1450°C and hydrogen partial pressure between 2 and 50 kPa is:

φ(H atoms cm cm−2 s−1 kPa−0.43) = exp(48.95±0.61)

exp[−318.2±18.8 kJ(g·atom)−1 (RT)−1]

Diffusion coefficients and solubility values deduced from the permeation experiments are consistent with earlier independent measurements. No accelerated permeation due to micro‐structural defects or changes during the experiments was observed. Comparison of hydrogen permeability of alumina with the values observed for metals shows that alumina may be a suitable coating material for use as a hydrogen permeation barrier.
Multibarrier Kinetics of Brittle Fracture: I, Stress Dependence of the Subcritical Crack Velocity
Authors: BROWN S. D.
Published: October 2006

A general equation for the subcritical crack velocity in brittle materials is derived using steady‐state, multibarrier kinetics. It provides a basis from which specialized expressions can be developed for the crack velocity in specific cases. One social equation for v=v(K) at constant temperature, derived from the general expression, has a mathematic form that fits data representative of a wide variety of specific cases. Examples are presented and the equation is discussed in terms of its physical foundations.
Photoperiod‐induced apoptosis in the male genital tract epithelia of the golden hamster
Authors: Carballada Rosa , Jara Marco , Esponda Pedro
Published: October 2006

The aim of this study was to identify some details of the changes induced by a short‐day light regime (8:16 light:dark) on the male genital tract and accessory sex glands of the golden hamster Mesocricetus auratus. We principally examined the presence of apoptotic cells in the epithelium from different regions of the epididymis, seminal vesicles, prostate and coagulating gland. We detected an increase in the percentage of apoptotic cells in situ using the TUNEL technique in animals that were maintained for 6, 8 or 12 weeks in a short photoperiod. That those cells were indeed undergoing apoptosis was confirmed by the immunodetection of the active fragment of caspase‐3. The apoptotic indices in the different tissues analysed were low, but were maintained for weeks, suggesting cell loss at a steady rate. We tried to correlate these changes with the testosterone levels in serum as well as with the oxidative stress in the tissue. On the other hand, the increase in size and number of lipofuscin granules indicated the possibility that a parallel increase in oxidative stress occurred in the tissues. The normalization in the number of apoptotic cells and lipofuscin granules in animals treated with testosterone suggests that both phenomena might be related to changes in the hormone levels.
Inducible 70 kDa heat shock protein does not protect spermatogenic cells from damage induced by cryptorchidism
Authors: Widlak Wieslawa , Winiarski Boleslaw , Krawczyk Aleksandra , Vydra Natalia , Malusecka Ewa , Krawczyk Zdzislaw
Published: October 2006

Accumulation of inducible heat shock proteins (e.g. Hsp70i) during cellular stress confers thermotolerance, reduces the consequences of damage and facilitates cellular recovery, while abrogation of Hsp70i expression renders sensitivity to apoptosis. Testis translocation into abdominal cavity, which results in temperature elevation, does not induce expression of the Hsp70i proteins. Despite constitutive expression of testis‐specific Hsp70 proteins, spermatocytes are very sensitive to damage at elevated temperatures. To test whether Hsp70i protein could protect testes from heat‐induced damage, we have engineered transgenic mice that over‐express this protein selectively in spermatocytes and spermatids. We demonstrate that the testes of cryptorchid transgenic mice, like those of wild‐type mice, exhibit reduced weight and smaller sizes of their seminiferous tubules, disorganization of their germinal epithelium structures, appearance of multinucleated giant cells, and reduced populations of germ cells. The data show that constitutive expression of Hsp70i does not protect the seminiferous epithelium against cryptorchidism‐induced damage.
Education needs for integrated care: a literature review
Authors: Howarth Michelle , Holland Karen , Grant Maria J.
Published: October 2006

Aim.  This paper reports a systematic review to identify the education needs of the workforce within primary care to promote the effective delivery of integrated health and social care services.

Background.  The need for different professionals to work more closely dominates global health policy. The drive to develop a workforce prepared for the future is crucial to the success of integrated services. However, some have argued that nurses are ill‐equipped to meet the challenges of integrated service provision. The ability to work interprofessionally is an important skill which needs to be developed to support integrated working.

Methods.  Structured searches were undertaken on organizational websites and the Caredata, CINAHL, Cochrane Library, MEDLINE, Sociofile databases between December 2002 and April 2004 to identify policy documents and primary research studies. The robustness of identified research studies were appraised using recognized appraisal tools.

Findings.  Six themes were identified which indicate essential elements needed for integrated care. The need for effective communication between professional groups within teams and an emphasis on role awareness are central to the success of integrated services. In addition, education about the importance of partnership working and the need for professionals to develop skills in relation to practice development and leadership through professional and personal development is needed to support integrated working.

Conclusion.  Education which embeds essential attributes to integrated working is needed to advance nursing practice for interprofessional working. Further research exploring this and its impact on integrated provision is essential to ensure that evidence‐based services are provided. The reinforcement of partnerships between higher education institutions and health and social care organizations should ensure that the workforce is educated to manage continuous change in service delivery. Innovative ways of teaching and learning which promote inter‐professional working need to be explored.