Showing papers on "Atmospheric temperature range published in 1986"
TL;DR: In this article, the oxidation kinetics of several single-crystal and polvcrystalline silicon carbide materials and singlecrystal silicon in dry oxygen over the temperature range 1200° to 1500°C were fitted to the linear-parabolic model of Deal and Grove.
Abstract: The oxidation kinetics of several single-crystal and polvcrystalline silicon carbide materials and single-crystal silicon in dry oxygen over the temperature range 1200° to 1500°C were fitted to the linear-parabolic model of Deal and Grove. The lower oxidation rates of silicon carbide compared to silicon can be rationalized by additional consumption of oxidant in oxidizing carbon to carbon dioxide. The (000J) Si face of the silicon carbide platelets exhibited lower parabolic oxidation rates than the (0001) C face, by a factor of 10 at 1200°C. Apparent activation energies increased from a value of ∼120 kJ/mol below 1400°C to a value of ∼300 kJ/mol above this temperature. The (0001) Si face exhibited this high activation energy over the entire temperature range. The controlled nucleation thermally deposited material exhibited the highest oxidation rates of the polycrystalline materials followed by the hot-pressed and sintered α-silicon carbides. In general, the oxidation rates of the polycrystalline materials were bracketed by the oxidation rates of the basal planes of the single-crystal materials. Higher impurity concentrations and higher density of nucleation sites led to a greater susceptibility to crystallization of the scale which significantly complicated the oxidation behaviors observed. When crystallization of the oxide scale occurred in the form of a layer of spherulitic cristobalite crystals, a retardation of the oxidation rates was observed. An accelerated oxidation behavior was found when this coherent layer was superseded by the formation of fine mullite crystals.
323 citations
TL;DR: In this paper, the structural phase transitions in SnS and SnSe have been investigated by neutron diffraction in the temperature range 295-1000 K using a high temperature furnace, and accurate positional and thermal parameters have been obtained as a function of temperature both in the α- and β-phase (TlI-type, B33).
313 citations
TL;DR: In this article, the solubility constant of Henry's law has been experimentally determined in a tholeiitic basalt melt and the data permit calculation of the distribution of noble gases between a melt and coexisting vesicles.
265 citations
TL;DR: In this paper, the authors used the diffusion rates for oxygen as a function of temperature, the cooling rate of the rock, the mineral grain sizes, and the mode of a rock to estimate the apparent 18O16O temperature in a single sample of feldspars, quartz, and hornblende.
239 citations
TL;DR: In this paper, the local structural environments of Y/sup 3 +/ and Zr/sup 4 +/ in 18 wt% Y/sub 2/O/sub 3/-stabilized zirconia were studied using extended X-ray absorption fine structure spectroscopy over the temperature range.
Abstract: The local structural environments of Y/sup 3 +/ and Zr/sup 4 +/ in 18 wt% Y/sub 2/O/sub 3/-stabilized zirconia were studied using extended X-ray absorption fine structure spectroscopy over the temperature range - 120/sup 0/ to 770/sup 0/C. The measured cation-oxygen distances reflect those of the parent oxides, with the mean Zr-O distance 0.017 nm shorter than the mean Y-O distance. The spread in the Zr-nearest-neighbor and Zr-next-nearest-neighbor distances is considerably larger than observed for Y/sup 3 +/. This result is attributed to the anion vacancies being preferentially sited adjacent to the smaller Zr/sup 4 +/ cation which, with ensuing relaxations, permits a closer contact between Zr/sup 4 +/ and its oxygen neighbors. Thus, the structural environment of these Zr/sup 4 +/ ions resembles that of the 7-coordinated Zr/sup 4 +/ in monoclinic zirconia. Increasing the temperature of the sample results in the local structural environments of the two cations becoming more alike, suggesting that increased anionic mobility leads to an increasingly random distribution of anion vacancies.
216 citations
TL;DR: In this article, a review of recent developments in the expanding phenomenology of amorphous solid electrolytes is presented, and the authors emphasize the importance of studying the fast ion motions by mechanical response, in addition to electrical response measurements.
185 citations
TL;DR: In this article, the effect of metal halides (Co2+, Sn2+, and Hg2+) on the properties of polyimides was described, and the electrical conductivity was studied as a function of temperature and field.
Abstract: This paper describes the effect of metal halides (Co2+, Sn2+, and Hg2+) on the properties of polyimides. Low temperature, solution polycondensation reaction of pyromellitic dianhydride and 4,4′-diaminodiphenyl ether was used for preparation of a poly(amide-acid) solution in dimethylformamide ([η] = 2.0 dL/g). Films containing 1% (w/w) of cobalt (II) chloride, tin (II) chloride, and mercury (II) chloride were prepared by solution casting of poly(amide-acid) from the DMF solution. Cyclodehydration to polyimide was done by heating the films in nitrogen atmosphere for one hour each at 100°, 200°, and 250°C. The color of the films depended on the dopant and was yellow (HgCl2 or SnCl2) or green (CoCl2) Higher percentage weight loss was observed in doped films in nitrogen atmosphere in the temperature range of 250–400°C. No significant difference in thermal behavior of doped and undoped films was observed above 500°C. Doping reduced the tensile strength of polyimide films, maximum reduction was observed in CoCl2-doped film. The electrical conductivity of polyimide films as a function of temperature and field was studied. Undoped polyimide showed ohmic behavior up to 150°C. In doped films at lower voltages Poole-Frenkel mechanism was operative, while at high voltages Richardson-Schottky's mechanism was operative. Dielectric relaxation in polyimide films was also studied.
173 citations
TL;DR: In this article, the authors measured the thermal expansion of the cubic beta polytype of SiC from 20 to 1000° C by the X-ray diffraction technique and found that the coefficient of thermal expansion can be expressed as the second order polynominal: α11=3.19×10−6+ 3.60×10 −9T−1.2 (1/° C).
Abstract: Thermal expansion of the cubic beta or (3C) polytype of SiC was measured from 20 to 1000° C by the X-ray diffraction technique. Over that temperature range, the coefficient of thermal expansion can be expressed as the second order polynominal: α11=3.19×10−6+ 3.60×10−9
T−1.68×10−12
T
2 (1/° C). It increases continuously from about 3.2×10−6/° C at room temperature to 5.1×10−6/° C at 1000° C, with an average value of 4.45 × 10−6/° C between room temperature and 1000° C. This trend is compared with other published results and is discussed in terms of structural contributions to the thermal expansion.
163 citations
TL;DR: The mechanism of ethanol decomposition on the Ni(111) surface has been investigated between 155 and 500 K as mentioned in this paper, and the sequence of bond scission steps which occur as ethanol undergoes dissociative reactions on this surface was deduced using deuterium and 13 C isotopic labels.
158 citations
TL;DR: Two distinctly different steps precede rapid hydrolysis of dipalmitoylphosphatidylcholine small unilamellar vesicles by pancreatic phospholipase A2: a Ca2+-independent binding of the enzyme to the substrate vesicle, which for chemically pure bilayers occurs best in the gel phase, and at least one of these two steps appears to involve enzyme-enzyme interaction.
155 citations
TL;DR: In this paper, the force between two surfaces coated with pentaoxyethylene dodecyl ether, C12E5, and immersed in aqueous solution was measured as a function of surface separation in the temperature range 15-37 °C.
Abstract: The force between two surfaces coated with pentaoxyethylene dodecyl ether, C12E5, and immersed in aqueous solution has been measured as a function of surface separation in the temperature range 15–37 °C. The surfaces were prepared by allowing the non-ionic surfactant to adsorb on to hydrophobised mica from the solution. At 15 °C the interaction is repulsive at all separations, but above 20 °C an attractive minimum appears at separations below ca. 4 nm. The attraction increases rapidly with temperature and is identified with the interaction that gives rise to the phase separation (‘clouding’) in micellar solutions of many non-ionic surfactants as well as in the poly-(ethylene oxide)–water system.The net interaction is composed of two large parts, one entropic that is attractive and one enthalpic that is repulsive. The two parts nearly cancel, making the net interaction repulsive at low temperatures but attractive at high. They apparently originate mainly from the hydration interactions between the oxyethylene head groups on one surface with those on the other, and are of the same order of magnitude as in pure poly(ethylene oxide)–water solutions.The thickness of the non-ionic surfactant layers increases with temperature, implying a decrease in surface area per head group. This indicates that the intralayer head-group interaction also becomes more attractive (or less repulsive) with temperature.
TL;DR: In this paper, it was found that the ratio of magnetite to hematite in the surface oxide film appears to increase with increasing water vapor pressure, ascending temperature, and extending oxidation time.
Abstract: Laser Raman spectroscopy (LRS) has been applied for the detection and characterization of thin corrosion films formed on iron in air at a temperature range from 100 to 150 C. In situ ellipsometric measurements have also been conducted for quantitative estimations of the film growth kinetics. It is found that (1) the oxidation of iron in dry air leads to the formation of a surface oxide film composed primarily of magnetite and (2) the water vapor in air accelerates the formation of hematite. The ratio of magnetite to hematite in the surface oxide film appears to increase with (1) increasing water vapor pressure, (2) ascending temperature, and (3) extending oxidation time.
TL;DR: In this paper, the authors studied electrical conduction phenomena in polyimide (Kapton) films with particular attention devoted to the separation of interface and bulk phenomena, and the effective work function for aluminum-polyimide is estimated to be 1.7 eV in the temperature range between 100 and 270°C.
Abstract: Electrical conduction phenomena in polyimide (Kapton) films were studied with particular attention devoted to the separation of interface and bulk phenomena. The measurements were carried out with a variety of methods in the temperature range of 50 to 270 °C at electrical fields of 104 to 6×105 V/cm and at time intervals of up to 2×104 s after voltage application. Biased, two‐side metallized samples yield, after sufficiently long voltage application, interface‐controlled steady‐state currents described by Schottky injection, modified by space‐charge layers in the vicinity of the electrodes. The effective work function for aluminum‐polyimide is estimated to be 1.7 eV in the temperature range between 100 and 270 °C. A distinct dependence of these currents on electrode material is observed. Bulk phenomena were studied on one‐side metallized samples subject to positive‐corona charge injection. At temperatures below 200 °C, significantly larger currents than those for biased, two‐side metallized samples were observed. The current‐voltage characteristics are ohmic at low fields and space‐charge limited at high fields. From these data, trap modulated mobilities for positive carriers of 4×10−12 cm2/V s at 50 °C and 10−9 cm2/V s at 200 °C, ohmic bulk conductivities of 10−16 (Ω cm)−1 at 100 °C and 10−14 (Ω cm)−1 at 200 °C and an intrinsic carrier density of 5×1013 cm−3 independent of temperature are obtained. Activation energies for the mobility are between 0.2 and 0.8 eV for the temperature range between 50 and 200 °C.
TL;DR: In this paper, a moving boundary in the substrate, parallel to the oxide-metal interface, was associated with a specific oxygen level of 5.0 + or - 0.5 at. pct.
Abstract: The oxidation kinetics of commercial purity Ti-A55 exposed to laboratory air in the 593-760 C temperature range were continuously monitored by thermogravimetric analysis. The oxide thickness was measured by microscopy, and the substrate contamination was estimated from microhardness measurements. The microhardness depth profiles were converted to oxygen composition profiles using calibration depth. The oxygen diffusion coefficient in alpha-Ti appears to be approximately concentration-independent in the 1-10 at. pct oxygen range. Diffusion coefficient for oxygen in TiO2 has been estimated as a function of temperature and is found to be about 50 times the value in alpha-Ti. The metallographically prepared cross sections of the oxidized specimens revealed a 'moving boundary' in the substrate, parallel to the oxide-metal interface. This boundary was associated with a specific oxygen level of 5.0 + or - 0.5 at. pct. It occurred at a distance from the oxide-metal interface which was correlatable with temperature and time of exposure. The diffusion coefficient corresponding to the composition of this moving boundary is in excellent agreement with the effective diffusion coefficient for the substrate contamination.
TL;DR: In this paper, a thin, cirriform cloud that formed in the temperature range of −83° to −84°C and an altitude range at 16.2 to 16.7 km is presented.
Abstract: Mesurements obtained in a thin, cirriform cloud that formed in the temperature range of −83° to −84°C and an altitude range at 16.2 to 16.7 km are presented. Implications of the results for particle generation in polar stratospheric clouds developing with similar conditions are discussed.
TL;DR: In this article, detailed absorption measurements and the analysis of the absorption spectra of In1−xGaxAs lattice matched to InP are reported, and the lattice matching parameter Δa/a covered a range from +4×10−3 to −1× 10−3.
Abstract: Detailed absorption measurements and the analysis of the absorption spectra of In1−xGaxAs lattice matched to InP are reported. The lattice matching parameter Δa/a covered a range from +4×10−3 to −1×10−3. From the absorption data of material with small matching parameter we obtain the value of the interband matrix element ( P2=20.7 eV), the excitonic Rydberg (Ex =2.5 meV), and damping constant (Γ0=5.1 meV) in the temperature range from 1.5 to 340 K. From the temperature dependent band‐gap shrinkage and exciton damping constant Γ, information on the carrier‐phonon interaction is obtained. The effect of the biaxial stress in the epitaxial layers caused by the mismatch with the substrate is demonstrated by absorption spectra which directly reveal the valence band splitting due to stress. Absorption measurements on samples with and without substrate indicate that the strained expitaxial layers do not relax completely if the substrate is etched away. The remaining strain field is probably caused by misfit dislo...
TL;DR: Semiconducting vanadium-bismuth oxide glasses have been prepared in the composition range 80-95 mol% V2O5 and the DC conductivity of the annealed glasses has been measured in the temperature range 80 −480 K and compared with those of phosphate and tellurite glasses as discussed by the authors.
Abstract: Semiconducting vanadium-bismuth oxide glasses have been prepared in the composition range 80–95 mol% V2O5 The DC conductivity of the annealed glasses has been measured in the temperature range 80–480 K and compared with those of phosphate and tellurite glasses The conductivity is sensitive to microstructure The data have been analysed in the light of models of polaronic hopping conduction Hopping of the polaron is shown to be adiabatic in nature Mott's T 1 4 analysis is made at low temperature
TL;DR: In2Se3 thin films were grown with good stoichiometry at a substrate temperature around 460 K in the α phase and were shown to remain in the β phase above 480 K.
TL;DR: In this article, the adsorption and thermal decomposition of ammonia at a Ni(110) surface was studied by means of thermal desorption (TD) and high resolution electron energy loss (HREEL) spectroscopy in the temperature range 110-500 K.
01 Jan 1986
TL;DR: In this article, the density of solids and the lattice constants (for the latter see “Uranium” Suppl. Vol. C4, 1984, pp. 112/7) are directly interrelated.
Abstract: The density of solids and the lattice constants (for the latter see “Uranium” Suppl. Vol. C4, 1984, pp. 112/7) are directly interrelated. In general the X-ray density calculated from the lattice constants agrees very well with the density determined from pycnometric measurements. Except for a relatively narrow temperature range in the neighborhood of the melting point, the dilatometrically measured thermal expansion coefficient generally agrees well with the lattice constant changes determined via X-ray diffraction. In uranium dioxide, however, several additional difficulties arise, which make the measurements uncertain and the results less comparable.
TL;DR: In this paper, electrical conductivity and relaxation studies have been carried out on Parel 58 elastomer with a variety of lithium salts in vacuum over the temperature range 5-380 K and at pressures up to 0.65 GPa.
Abstract: Audio frequency electrical conductivity and relaxation studies have been carried out on Parel 58 elastomer and Parel 58 elastomer complexed with a variety of lithium salts. The measurements have been carried out in vacuum over the temperature range 5–380 K and at pressures up to 0.65 GPa over the temperature range 230–380 K. Both the electrical conductivity for the complexed material and the electrical relaxation time associated with the α relaxation in the uncomplexed material exhibit VTF or WLF behavior. From a VTF analysis for both the vacuum electrical relaxation time and electrical conductivity, Ea is found to be about 0.09 eV and T0 is found to be about 40 °C below the ‘‘central’’ glass transition temperature. In addition, it is found that the activation volumes for the electrical relaxation time and the electrical conductivity are the same when compared relative to T0. These results imply that the mechanism controlling ionic conductivity is the same as that for the α relaxation, namely large‐scale segmental motions of the polymer chain.
TL;DR: In this paper, a polybutadiene of narrow molecular weight distribution was modified using 4-phenyl-1, 2,4-triazoline-3,5-dione.
Abstract: Polybutadiene of narrow molecular weight distribution was modified using 4-phenyl-1, 2,4-triazoline-3,5-dione. The degree of modification was 1% and 2% with respect to the repeating units. Hydrogen bonding between the highly polar urazole groups thus incorporated into the polymer gives rise to the formation of a thermoreversible elastomeric network. Dynamic mechanical measurements in the temperature range between 220 and 330 K support the picture of the thermoreversible hydrogen bond interaction. The rubber elastic plateau is shifted to higher temperatures and lower frequencies. The increase in the plateau modulus cannot be attributed solely to the contribution of the network structure but is mainly a consequence of the broadening of the relaxation time spectrum in the modified samples. From the temperature dependence of the shift factors log(aT) it is concluded that the general WLF approach fails. The strong temperature dependence of the apparent activation energy of flow is a consequence of the temperature dependence of the hydrogen bond interaction.
TL;DR: In this paper, a binary alloy without boron was compared with an alloy containing 0.78 at.% B by tensile testing over the temperature range 300-640 K. Both alloys were processed by powder metallurgy.
TL;DR: In this paper, a semiclassical theory of infrared linewidths in the gas, previously developed for linear molecules, is extended to asymmetric top molecules, including a satisfactory treatment of the close collisions and is consequently adapted to describe the temperature dependence of the linwidths, in particular in the combustion temperature range.
Abstract: A semiclassical theory of infrared linewidths in the gas, previously developed for linear molecules, is extended to asymmetric top molecules. It includes a satisfactory treatment of the close collisions and is consequently adapted to describe the temperature dependence of the linewidths, in particular in the combustion temperature range. Numerical applications to the water vapor perturbed by nitrogen, oxygen, and argon show strong different behaviors following the nature of the perturber. For oxygen and argon perturbers, the contribution of close collisions is the predominant mechanism of line broadening. The consistency of the theoretical model is evidenced by comparison with precise measurements for H2O–N2, –O2, and Ar at 300 K. Moreover, the calculated temperature dependence of the linewidths is compared with recent experimental data for H2O–Ar between 1300 and 2300 K.
TL;DR: In this article, the morphology of poly(aryl-ether-etherketone) (PEEK) has been studied using optical microscopy (at room temperature and at elevated temperatures), small-angle light scattering (H v and V v ), transmission electron microscopy(bright field, dark field, and selected area electron diffraction), and wide and smallangle X-ray scattering.
TL;DR: The sticking coefficient for dissociative oxygen adsorption is 0.86 ± 0.03 at T > 160 K and 0.23 at T ≥ 0.48 as mentioned in this paper.
TL;DR: In this article, the frequency and temperature dependence of the elastic moduli of commercially available polymers has been studied in the temperature range of 0-35°C and for frequencies 102-106 Hz.
Abstract: The frequency and temperature dependence of the elastic moduli of a number of commercially available polymers has been studied in the temperature range of 0–35 °C and for frequencies 102–106 Hz. Away from transitions a significant new relationship has been obtained, i.e., the Young’s modulus of these polymers is proportional to log of frequency. Using this relationship, together with the low and high frequency data, transitions in some of the polymers were identified.
TL;DR: In this article, the principal axial coefficients of thermal expansion of hexagonal alpha SiC have been determined by X-ray diffraction measurements in the temperature range 20-1000 C. Alpha(11) was found to be larger than alpha(33) over the entire temperature range.
Abstract: The principal axial coefficients of thermal expansion, alpha(11) and alpha(33), of the (4H) polytype of hexagonal alpha SiC have been determined by X-ray diffraction measurements in the temperature range 20-1000 C. Alpha(11) and alpha(33), derived from the lattice parameter measurements, were expressed as the second-order polynomials in temperature. Alpha(11) was found to be larger than alpha(33) over the entire temperature range, with a thermal expansion anisotropy factor A increasing from 0.04 at room temperature to 0.11 at 1000 C. The thermal expansion results for the (4H) structure were compared with previously published results for the cubic (3C) and the hexagonal (6H) SiC polytypes.
TL;DR: In this article, the authors determined the free-volume hole sizes in amine-cured epoxy polymers by comparing the observed ortho-positronium lifetimes with the known lifetime-free volume correlation for low-molecular-weight systems.
Abstract: Positronium annihilation spectroscopy (PAS) has been used to study the microstructural properties of amine-cured epoxy polymers. We have determined the free-volume “hole” sizes in these polymers by comparing the observed ortho-positronium lifetimes with the known lifetime–free volume correlation for low-molecular-weight systems. The free volumes for four epoxies with different crosslink densities are found to vary significantly over the temperature range between −78° and 250°C. The free-volume holes for these polymers are found to range from 0.025 to 0.220 nm3. Two important transition temperatures were found: one corresponds to the glass transition temperature Tg determined by differential scanning calorimetry (DSC), and the other occurs about 80–130°C below Tg. The sub-Tg transition temperature is interpreted tentatively as being where hole size reaches dimensions adequate for positronium trapping or else the onset temperature for local mode or side-chain motions. These two transition temperatures plus two additional onset temperatures are found to be correlated with crosslink densities calculated from stoichiometry.
TL;DR: In this paper, the structure and crystal growth of undoped, asdeposited, and annealed silicon films prepared by chemical vapor deposition (CVD) and low-pressure chemical vapor injection (LPCVD) of silane have been studied with use of x-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM).
Abstract: Structure and crystal growth of undoped, as‐deposited, and annealed silicon films prepared by chemical vapor deposition (CVD) and low‐pressure chemical vapor deposition (LPCVD) of silane have been studied with use of x‐ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). The grain size and a complete texture analysis are performed on CVD films grown at atmospheric pressure and temperature range 600≤Td≤805 °C, LPCVD films grown in the pressure range 0.1≤Pd≤2 Torr and temperature range 500≤Td≤650 °C and annealed amorphous CVD and LPCVD films near Ta=600 °C. We obtain systematically amorphous, strong 〈220〉 polycrystalline, and inhomogeneous partially crystallized films 〈111〉 or 〈311〉 oriented depending on the deposition conditions. The presence of a given texture is explained by a model which takes into account the specific free surface energies of the starting equilibrium forms and the extinction of some crystalline planes by {111} slow growing facets. The appearance of the 〈220〉 tex...