Showing papers in "Journal of the American Ceramic Society in 1967"
TL;DR: In this article, the double-cantilever cleavage technique was used to observe crack motion and to accurately measure crack velocities in glass, where the measured crack velocity is a complicated function of stress and of water vapor concentration in the environment.
Abstract: Results of a new experimental approach to static fatigue of glass are presented. Using the double-cantilever cleavage technique, it was possible to observe crack motion and to accurately measure crack velocities in glass. The measured crack velocity is a complicated function of stress and of water vapor concentration in the environment. Experimental results are discussed with reference to current theories of static fatigue.
1,010 citations
345 citations
TL;DR: In this paper, the solubility of boron in graphite was determined in the temperature interval of 1800° to 2500°C, and the maximum solubilities were 2.35 at.
Abstract: The solubility of boron in graphite was determined in the temperature interval of 1800° to 2500°C. The maximum solubility was 2.35 at. % at 2350°C; the solution was shown to be substitutional.
274 citations
TL;DR: In this paper, the kinetics of the reactions of various glasses with water and aqueous solutions with pH from 1 to 13 were studied and the rates of removal of various glass constituents under varied experimental conditions were reported and potential mechanisms for these reactions were discussed.
Abstract: The kinetics of the reactions of various glasses with water and aqueous solutions with pH from 1 to 13 was studied. Simple binary alkali oxide-silica glasses were examined as well as some ternary glasses derived from the binary compositions by substituting alkaline-earth oxides for silica. All components of the glass were determined in the extract; the glasses varied from those very easily decomposed by water to those having durability comparable to that of commercial glasses. The equilibrium conditions of the system glass-water are distinguished from the approach to that equilibrium normally observed in such experiments. The rates of removal of various glass constituents under varied experimental conditions are reported and potential mechanisms for these reactions are discussed.
264 citations
TL;DR: In this article, phase relations in the system ZrO2-MgO with emphasis on the range 1350° to 1600°C were derived from samples, using precision lattice parameters, X-ray diffraction line intensities, and petrographic observations.
Abstract: Phase relations were studied in the system ZrO2-MgO with emphasis on the range 1350° to 1600°C A phase relation was determined from samples, using precision lattice parameters, X-ray diffraction line intensities, and petrographic observations, and from dynamic observations of the phases present using high-temperature X-ray diffraction techniques Limits were established for the solubility of MgO in tetragonal ZrO2 and for the range of the cubic solid solution The phase relations below 1240°C were complicated by hysteresis in the monoclinic to tetragonal inversion of ZrO2
213 citations
TL;DR: Simultaneous decomposition of yttrium and zirconium alkozides was used to obtain an almost ideal mixture of powders of high surface activity as discussed by the authors.
Abstract: Simultaneous decomposition of yttrium and zirconium alkozides was used to obtain an almost ideal mixture of powders of high surface activity. From this powder a translucent body, “Zyttrite,” was made with a grain size of less than 1μ. The mixed oxide was consolidated into a stabilized body by firing at 1000°C for 30 min. This is indicative of a phenomenal increase in solid state reactivity. High-density fully stabilized cubic solid solutions of 6 mole % Y2O3-ZrO2 were obtained on sintering at 1450°C. A typical specimen had a density of 5.9 g/cm3, a coefficient of thermal expansion of 11 × 10−6 in./in.°C, and a grain size of 2 to 4μ. Test pieces withstood 2200°C firings in air for 262 hr with grain growth of 35 to 50μ and virtually no change in composition, density, or stabilization.
202 citations
201 citations
150 citations
TL;DR: In this article, phase equilibrium relations in the system PbO-TiO2-ZrO2 were studied by quenching in the range where the pbO content is 50 mole % and more.
Abstract: Phase equilibrium relations in the system PbO–TiO2–ZrO2 were studied by quenching in the range where the PbO content is 50 mole % and more. Isotherms were examined at 1100°, 1200°, and 1300°C and tie lines were determined between the liquid and solid solution in equilibrium. The incongruent melting point of PbZrO3 was 1570°C and the equilibrium between liquid, PbO-type solid, and PbZrO3 is peritectic. Pb(Zr,Ti)O3 solid solutions containing more than 14 mole % PbZrO3 decomposed to liquid, ZrO2, and Pb(Zr,Ti)O3 and the decomposition temperature rises from 1340° to 1570°C with increasing PbZrO3 content. The system PbTiO3–PbZrO3 should not be treated as a binary, but as a section of the ternary system.
140 citations
TL;DR: In this article, splat and other rapid quenching techniques were applied to a systematic study of simple oxides, and four new pure oxide glasses were obtained (V2O5, TeO2, MoO3, and WO2).
Abstract: Splat and other rapid quenching techniques were applied to a systematic study of simple oxides, and four new pure oxide glasses were obtained (V2O5, TeO2, MoO3, and WO2). The high-temperature tetragonal form of WO3 coexists with a metastable short-range-order-only phase. The structure of a new metastable high-temperature phase, δ-Ta2O6, resembles δ-Nb2O6. Predominant phases found in quenched Al2O3 belong to the γ-(spinel type) series.
130 citations
TL;DR: In this article, the β-quartz structure can be crystallized from most glasses in the system SiO2-Mg(AlO2)2-LiAlO 2 as well as from many containing the additional components Zn(Al O2), Li2ZnO2, and Li2BeO2 and internal nucleation is afforded by adding ZrO2 or TiO2.
Abstract: Metastable solid solutions with the β-quartz structure can be crystallized from most glasses in the system SiO2-Mg(AlO2)2-LiAlO2 as well as from many containing the additional components Zn(AlO2)2 Al(AlO2)3, Li2ZnO2, and Li2BeO2. Internal nucleation is afforded by additions of ZrO2 or TiO2. Either transparent or opaque crystalline materials can be formed from glasses containing about 70% SiO2. The transparency is due to a combination of low birefringence in the major stuffed β-quartz phase and minute crystal size. Thermal expansions vary from -20 to +50 × 10−7/°C. Thermal stability is highly variable. Breakdown products include spinel, cordierite, β-spodumene, willemite, mullite, and cristobalite. Magnesian compositions can be strengthened by a 2Li+⇌ Mg2+ ionexchange reaction. Abraded flexural strengths range from 30,000 to 160,000 psi.
TL;DR: The nucleation and crystallization of Li2O-Al2O3-SiO2 glasses containing TiO2 were investigated using transmission electron microscopy of thin sections produced from bulk samples as discussed by the authors.
Abstract: The nucleation and crystallization of Li2O-Al2O3-SiO2 glasses containing TiO2 were investigated using transmission electron microscopy of thin sections produced from bulk samples. Phase separation occurs during cooling from the melt, and on heating, a large number of titanium-aluminum crystals approximately 50 A in diameter are formed. These crystals are the heterogeneous nuclei for the crystallization of the remaining glass. Photomicrographs of various stages of crystallization show the development of the fine-grained glass-ceramic.
TL;DR: The transition from amorphous alumina to α-alumina was studied by X-ray diffraction, electron diffraction and DTA, TGA, and microscopic observation as mentioned in this paper.
Abstract: The transition of amorphous alumina to α-alumina was studied by X-ray diffraction, electron diffraction, DTA, TGA, and microscopic observation. The amorphous alumina was prepared by condensing vapor from evaporating molten alumina in vacuo onto the glass envelope of the vacuum chamber. The amorphous alumina was transformed to a poorly crystalline material by heating for 16 hr between 570° and 670°C. Between 670° and 1200°C, the poorly crystalline alumina was converted to α-alumina via two parallel series of transition aluminas. The principal series was γ-alumina to δ-alumina to α-alumina. A minor amount of θ-alumina developed from the initial crystallization and persisted throughout the duration of the principal series as a parallel path. Some conversion of δ- to θ-alumina was detected above 900°C. DTA produced an unexplained exothermic peak at 320°C and a second exothermic peak at 860°C which corresponded to formation of metastable aluminas.
TL;DR: In this article, phase relations for the systems ZrO2-WO2 and WO3 from 1000° to 1700° C were determined by the quenching technique using sealed sample containers.
Abstract: Phase relations for the systems ZrO2–WO2–WO3 and HfO2–WO2–WO3 from 1000° to 1700° C were determined by the quenching technique using sealed sample containers In the system ZrO2–WO3, 1:2 compound, ZrW2O8 forms, having a cubic structure with a= 9159 A The ZrW2O8 melts incongruently at 1257°± 3°C to ZrO2 and liquid and has a lower limit of stability at 1105°C, below which ZrO2 and WO3 coexist in equilibrium One eutectic and one peritectic were established: at 1231°± 3°C and 74 mole % WO3, and at 1257°± 3°C and 71 mole % WO3, respectively Along the join ZrO2–WO2, no compound formed Two invariant points were determined: ZrO2, WO2, W, and liquid are in equilibrium at 1430°± 5°C and 76 mole % WO2, whereas WO2, W18O49, W, and liquid coexist at 1530°± 5°C and 89 mole % WO2- Equilibrium relations in the system ZrO2–WO2–WO3 were investigated at four temperatures At 1200°C, a cubic phase with composition near W20O58 was found; it exists in equilibrium with ZrO2, W18O49, W20O58, and WO3 As the temperature increases, the liquid formed along the ZrO2–WO3 join extends into the ternary system, crosses the join ZrO2–W20O58 at 1300°C, and crosses the join ZrO2–W18O49 at 1400°C The cubic phase can take more zirconium into its solid solution at 1300° than at 1200°C At 1500°C, the system can no longer be treated as a simple ternary oxide system because of the presence of metallic tungsten, and equilibrium relations are presented on the basis of the system ZrO2–W–WO3 Phase equilibrium relations in the systems HfO2–WO3, HfO2–WO2, and HfO2–WO2–WO3 in the temperature ranges studied are much like those in the corresponding zirconium system
TL;DR: The addition of ThO2 to Y2O3 inhibits grain growth and allows the sintering process to proceed to theoretical density by maintaining a high diffusion flux of vacancies from the pores to the grain boundaries.
Abstract: The addition of ThO2 to Y2O3 inhibits grain growth during sintering and allows the sintering process to proceed to theoretical density by maintaining a high diffusion flux of vacancies from the pores to the grain boundaries. The inhibition of grain growth is accomplished by the segregation of ThO2 solute at the grain boundaries, causing a decrease in the grain-boundary mobility. The segregation of ThO2 at the grain boundaries can be inferred from the results of the microhardness and grain-growth studies presented. Further evidence for segregation is provided by quenching experiments and surface activity experiments.
TL;DR: In this article, the elastic constants and coefficients of thermal expansion of polycrystalline forsterite (Mg2SiO4) and steatite (mgSiO3) were determined from room temperature to 1000°K.
Abstract: The elastic constants and coefficients of thermal expansion of polycrystalline forsterite (Mg2SiO4) and steatite (MgSiO3) were determined from room temperature to 1000°K. Two elastic moduli, the adiabatic bulk modulus, Bs, and the shear modulus, G, decrease linearly with temperature above 500°K. The Gruneisen constant γ and a parameter δ, defined as — (dBs/dT)/αBs, calculated from the present data were virtually independent of temperature at the high-temperature range. Poisson's ratio, δ, rises linearly with temperature over the range of measurement; the slope is highest for materials with the lowest room-temperature value of σ.
TL;DR: In this paper, the phase boundaries for the metastable two-liquid regions in the Li2O and Na2O systems were estimated using stable phase diagrams and assumptions based on sub-regular solution behavior.
Abstract: Activities of alkali metal oxides and silica are calculated for regions of the Li2O-SiO2, Na2O-SiO2, and K2O-SiO2 phase diagrams where volatility, cell potential, and thermodynamic data are available. For the high-silica composition regions, activities are calculated from the stable phase diagrams and assumptions based on sub-regular solution behavior. These data permit estimates of the phase boundaries for the metastable two-liquid regions in the Li2O and Na2O systems which may be compared with experiment. An estimate is also made of the critical point for K2O-SiO2 to determine whether metastable phase separation in this system will be experimentally obtainable.
TL;DR: In this paper, the solubility of zirconium in monoclinic Zirconia was determined from 1200° to 2000°C, and the cubic-tetragonal inversion temperature of ZrO2 was shown to be lower to approximately 1490°C for samples containing α-Zr and oxide phase.
Abstract: The system Zr-O was studied in the composition range 50 to 66.7 at.% O by metallographic analysis, high-temperature X-ray analysis, and lattice parameter determinations at room temperature. The solubility of zirconium in zirconia was determined from 1200° to 2000°C, and the cubic-tetragonal inversion temperature of ZrO2 was shown to be lowered to approximately 1490°C for samples containing α-Zr and oxide phase. Alpha zirconium has greater solubility in the cubic phase than in the tetragonal phase, and the inversion is revealed, in samples quenched from the cubic field, by the exsolution of α-Zr, which is metallographically characterized as striations. At room temperature, the striations are oriented with the 111 and 11° planes of monoclinic zirconia.
TL;DR: In this article, the distribution of cations in different coordinations in the spinel structure as a function of equilibrium temperature was quantitatively determined for several phases and the relative X-ray intensities of various reflections of the quenched phases were measured and compared with intensities calculated for various models of cation distribution.
Abstract: The distribution of cations in different coordinations in the spinel structure as a function of equilibrium temperature was quantitatively determined for several phases. The spinels were synthesized and/or reacted at various temperatures and pressures. The relative X-ray intensities of various reflections of the quenched phases were measured and compared with intensities calculated for various models of cation distribution. In NiAl2O4 the cation arrangements at 600° and 1550°C are (Al1.0)IV(Ni1.0 Al1.0)VIO4 and (Ni0.25Al0.75)IV(Ni0.75Al1.25)VIO4, respectively. In Ni2GeO4, between 610° and 1400°C, the concentration of Ni2+ ions in tetrahedral sites increases from 0 to 23% and in octahedral sites it decreases from 100 to 77% of total nickel present. All these transitions were reversible under equilibrium conditions and can be classified as second-order “reconstructive transition of disorder.” Many spinels cannot be classified as normal or inverse but have a cation distribution which is an equilibrium function of the temperature.
TL;DR: In this article, the electrical conductivity of polycrystal and polycrystalline uranium dioxide was measured from room temperature to 3000°K and the best linear fit of the log σ versus T−1 curve above 1400°K is σ= 3.57 × 103e−(1.15 ev/KT).
Abstract: The electrical conductivity of nearly stoichiometric single-crystal and polycrystalline uranium dioxide was measured from room temperature to 3000°K. Below approximately 550°K, the curve of log σ versus T−1 is linear with a calculated activation energy of approximately 0.17 ev. Between 550° and 1250°K, however, the shape of the curve changes; this change varies from one specimen to another. The electrical conductivity increases rapidly with increasing temperature above 1250°K with a change from p-type to n-type conduction. The best linear fit of the log σ versus T−1 curve above 1400°K is σ= 3.57 × 103e−(1.15 ev/KT). Above 1900°K, the curve deviates slightly from linearity and is best fit by the equation σ= 2.10 × 10−2T1.4e−(0.916 ev/KT).
TL;DR: In this paper, the Young's and shear moduli for fully dense MgO were determined as 3070 and 1305 kbars, respectively, and the deviation between the experimental data and theory was explained on the shape of the included phases.
Abstract: : The Young's and shear moduli of MgO-porosity and MgO-porosity-Ni composites were measured at low concentrations of the included phases. The effect of the included phases was observed to be greater than that which would have been predicted from theory. The deviation between the experimental data and theory was explained on the basis of the shape of the included phases. The Young's and shear moduli for fully dense MgO were determined as 3070 and 1305 kbars, respectively. (Author)
TL;DR: In this article, the types of fractures in a whiteware body containing quartz vary as a function of quartz grain size, and the transition from one type of fracture to another is illustrated by strength, thermal expansion, and water absorption, as well as microstructural observations.
Abstract: The types of fractures in a whiteware body containing quartz vary as a function of quartz grain size. The transition from one type of fracture to another is illustrated by strength, thermal expansion, and water absorption, as well as microstructural observations. The thermal expansion behavior of compositions containing alumina does not vary as a function of grain size, thus showing the absence of fracture in white-ware bodies containing alumina.
TL;DR: In this article, the structure of the glass and the changes occurring during crystallization as a function of temperature and heating rate were examined by X-ray diffraction, transmission and replication electron microscopy, density, and other measurements.
Abstract: Transparent glass-ceramics, in which the major phase was NaNbO3, were obtained by heat treatment of glasses in the Na2O-Nb2O5-SiO2 system. The structure of the glass and the changes occurring during crystallization as a function of temperature and heating rate were examined by X-ray diffraction, transmission and replication electron microscopy, density, and other measurements. On heating, a rather abrupt formation of uniformly dispersed particles was observed. In the early stages of crystallization, these particles contained NaNbO3 as loose, radially grown dendrites of identical crystal orientation which became dense during later stages of crystallization. The particle sizes ranged from 200 to 10,000 A, depending on the SiO2 content of the glass. Transparency of the crystallized material was dependent on the particle size rather than on the amount of NaNbO3 formed. The temperature at which crystallization occurred increased with the heating rate whereas the viscosity at crystallization decreased. For a given value of the rate of crystal formation per °C of temperature increase, the product (viscosity)n× (heating rate) was constant. The nucleation and growth phenomena which occurred in these glasses was attributed to microheterogeneities of higher Nb2O5 content which formed part of the glass structure.
TL;DR: In this paper, the nucleation and growth of titania-nucleated nepheline in glass was studied using electron micrographic and X-ray diffraction techniques.
Abstract: Electron micrographic and X-ray diffraction techniques were used to study the nucleation and growth of titania-nucleated nepheline in glass. On heating, the glasses phase-separated as a prelude to the crystallization sequence. The first crystalline phase identified was the metastable phase, carnegieite. With time, the equilibrium phase, nepheline, crystallized and the titania crystallized to anatase. The resulting materials were nonporous and largely crystalline. These nepheline glass-ceramics were chemically strengthened by treatments in molten potassium salts. A K+→ Na+ exchange took place and effected transformation of nepheline to kalsilite. This transformation was a function not only of the exchange treatment, but of the composition of the initial nepheline crystals. Confining the kalsilite surface against a volume increase during the phase transformation created a surface compressive stress. Glass-ceramics containing nepheline crystals with an appropriate structure were chemically strengthened in this manner to yield bulk, abraded modulus of rupture values above 200,000 psi.
TL;DR: In this article, the effect of 3-1 octahedral site ordering on the initial permeability, dc resistivity, resonance Une width, geff factor, and saturation magnetization was discussed.
Abstract: Dense lithium ferrite ceramic bodies prepared by hot-pressing exhibited rectangular hysteresis loops. A number of physical properties of technical interest were evaluated and results given. These include initial permeability, dc resistivity, resonance Une width, geff factor, and saturation magnetization. The effect of 3–1 octahedral site ordering is discussed. Investigation was extended to the preparation of solid solutions of lithium ferrite and zinc ferrite (Lio.0.5Feo.0.5)1-xZnx-Fe2O4, where 0 ≤x≤ 0.7. Methods of separate control of remanent induction, Br, and coercive force, Hc, are described.
TL;DR: In this paper, the hot hardness of TiB2, W2B5, ZrB2 and W2C of <95% density was determined to temperatures approaching 1900°C.
Abstract: The hot hardness of TiB2, W2B5, ZrB2, HfB2, ZrO2, Al2O3, NbC, Tic, TaC1-x, HfG1+x, (Ta0.8Hf0.2)C1+x, W2C, and (W0.65Cr0.14Re0.14Ta0.07)2C of <95% density was determined to temperatures approaching 1900°C. In all cases, the hardness decreased rapidly with increasing temperature. The data are compared to those available in the literature.