Showing papers on "Atmospheric temperature range published in 1999"
TL;DR: In this article, the apparent molar enthalpies of solution atT =298.15 K were derived from these solubilities, and the resulting values are ΔsolHm(o-C9H8O4,m=0.0226 mol kg−1)=22.9 kJ mol−1.
1,105 citations
TL;DR: In this article, the thin layer drying characteristics of hazelnuts during roasting were described for a temperature range of 100-160°C, using five semi-theoretical and two empirical thin layer models.
445 citations
TL;DR: A large first-order magnetic phase transition in an organic radical, 1,3,5-trithia-2,4,6-triazapentalenyl, is described and may have applications in thermal sensors, switching units, and information storage media based on organic radical crystals.
Abstract: A large first-order magnetic phase transition in an organic radical, 1,3,5-trithia-2,4,6-triazapentalenyl, is described. The transition occurs with a wide thermal hysteresis loop over the temperature range 230 to 305 kelvin. The high-temperature phase is paramagnetic, and its structure consists of a uniform one-dimensional stacking of the radical. The low-temperature phase is diamagnetic because of strong dimerization along the stacking direction. The results may have applications in thermal sensors, switching units, and information storage media based on organic radical crystals.
439 citations
TL;DR: The thermal properties of polycrystalline Ti3SiC2 in the 25°C-1000°C temperature range determined by Rietveld refinement of high temperature neutron diffraction data, show that at all temperatures, the amplitudes of vibration of the Si atoms are higher than those of the Ti and C atoms as mentioned in this paper.
322 citations
TL;DR: The electrical conductivity of the system ZrO2-Ln2O3 (Ln=lanthanides) has been measured as a function of dopant concentration in a temperature range 350-1000°C.
321 citations
TL;DR: In this article, perovskite oxides of Ln0.4Sr0.6Co0.8Fe0.2O3−δ have been prepared by the solid state reaction of corresponding oxides.
303 citations
TL;DR: In this article, the translational self-diffusion coefficients of supercooled water at atmospheric pressure were examined using pulsed-gradient spin-echo NMR diffusion measurements down to 238 K.
Abstract: The translational self-diffusion coefficients of supercooled water at atmospheric pressure were examined using pulsed-gradient spin−echo NMR diffusion measurements down to 238 K. As the temperature decreased, the diffusion behavior became distinctly non-Arrhenius. It was found that the diffusion behavior when plotted in an Arrhenius form was well-described by a Vogel−Tamman−Fulcher-type relationship in the temperature range from 298 to about 242 K. However, a fractional power-law-type equation was found to provide a better fit that extended over the entire measured temperature range. Below this temperature range, the diffusion coefficient decreased rather steeply, and at 238 K, the diffusion coefficient was 1.58 × 10-10 m2 s-1, the lowest value of the water diffusion coefficient so far determined. At this temperature the activation energy for the diffusion was found to be of the order of 44.4 kJ mol-1. The data presented here should allow theoretical models of water to be more stringently tested.
297 citations
TL;DR: The structure of CaTiO3 has been studied at high temperatures by powder neutron diffraction methods as mentioned in this paper, and two phase transitions are evident, with an intermediate tetragonal (I/mcm) structure forming near 1500 K and a primitive cubic structure above 1580 K. Detailed Rietveld analyses of the data suggest there may also be a phase transition from the room temperature Pbnm structure to an orthorhombic Cmcm structure around 1380 K, which is a remarkable feature of the results.
Abstract: The structure of CaTiO3 has been studied at high temperatures by powder neutron diffraction methods. From inspection of the diffraction data two phase transitions are evident, with an intermediate tetragonal (I/mcm) structure forming near 1500 K and a primitive cubic structure above 1580 K. Detailed Rietveld analyses of the data suggest there may also be a phase transition from the room temperature Pbnm structure to an orthorhombic Cmcm structure around 1380 K. A remarkable feature of the results is the regular variation in the out-of-phase octahedral tilt angle over the entire temperature range.
277 citations
TL;DR: In this paper, single crystals doped with Er3+ have been grown by the flux top-seeded-solution growth method and the crystallographic structure of the lattice has been refined.
Abstract: )2 single crystals doped with Er3+ have been grown by the flux top-seeded-solution growth method. The crystallographic structure of the lattice has been refined, being the lattice constants a=10.652(4), b=10.374(6), c=7.582(2) A, β=130.80(2)°. The refractive index dispersion of the host has been measured in the 350–1500 nm range. The optical absorption and photoluminescence properties of Er3+ have been characterised in the 5–300 K temperature range. At 5 K, the absorption and emission bands show the (2J+1)/2 multiplet splittings expected for the C2 symmetry site of Er in the Gd site. The energy positions and halfwidths of the 72 sublevels observed have been tabulated as well as the cross sections of the different multiplets. Six emission band sets have been observed under excitation of the 4F7/2 multiplet. The Judd–Ofelt (JO) parameters of Er3+ in KGW have been calculated: Ω2=8.90×10-20 cm2, Ω4=0.96×10-20 cm2, Ω6=0.82×10-20 cm2. Lifetimes of the 4S3/2, 4F9/2, and 4I11/2 multiplets have been measured in the 5–300 K range of temperature and compared with those calculated from the JO theory. A reduction of the 4S3/2 and 4I11/2 measured lifetimes with increasing erbium concentration has been observed, moreover the presence of multiphonon non-radiative processes is inferred from the temperature dependence of the lifetimes.
237 citations
TL;DR: In this paper, the temperature dependence of the cation distribution in synthetic spinel (MgAl 2O4) was determined using in-situ time-of-flight neutron powder diffraction.
Abstract: The temperature dependence of the cation distribution in synthetic spinel (MgAl 2O4) was determined using in-situ time-of-flight neutron powder diffraction. Neutron diffraction patterns of stoichiometric MgAl2O4 and slightly non-stoichiometric Mg0.99Al2O4 samples were collected under vacuum on heating from room temperature to 1600 8C, and the cation distribution was determined directly from site occupancies obtained by Rietveld refinement. The equilibrium non-convergent ordering has been analyzed using both the O’Neill-Navrotsky and Landau thermodynamic models, both of which fit the observed behavior well over the temperature range of the measurements. Fitting the data between 560 8C and 1600 8C using the O’Neill and Navrotsky (1983) thermodynamic model yields a5 32.8 6 0.9 kJ/mol and b5 4.7 6 2.0 kJ/mol. The fit to the Landau expression for ordering gives values of Tc 5 445 6 109 K and c 95 1.62 6 0.21. This confirms suggestions that the sign of the b coefficient in FeAl 2O4 and MgAl2O4 is positive, and opposite to that found in other 2‐3 oxide spinels. Non-equilibrium order-disorder behavior below 600 8C has been analyzed using the Ginzburg-Landau model, and successfully explains the time-temperature dependent relaxation behavior observed in the inversion parameter. Changing the stoichiometry, even by as little as 1 mol% Mg-deficiency, significantly reduces the degree of order.
209 citations
TL;DR: In this article, different compositions of NiZn ferrites prepared by the citrate precursor method and sintered in the temperature range 1100-1400°C were reported for different compositions.
Abstract: Dielectric properties such as dielectric constant, ϵ′ , and dielectric loss factor, tan δ ∈ , are reported for different compositions of NiZn ferrites prepared by the citrate precursor method and sintered in the temperature range 1100–1400°C. It is observed that ϵ′ and tan δ ∈ for samples prepared in the present work are much lower than those normally obtained for NiZn ferrites prepared by the conventional ceramic method. The low values are attributed to better compositional stoichiometry, single-phase spinel structure and uniform microstructure of the samples. The low dielectric loss makes these samples especially attractive for use at high frequencies.
TL;DR: In this article, the temperature dependence of the thermo-optic coefficient for crystalline silicon was measured in the temperature range between room temperature and 550 K at the wavelength of 1523 nm by means of an interferometric technique.
Abstract: The temperature dependence of the thermo-optic coefficient for crystalline silicon has been measured in the temperature range between room temperature and 550 K at the wavelength of 1523 nm by means of an interferometric technique. This technique, which requires a very simple experimental setup, is based on the observation of the fringe pattern produced by temperature changes in a Fabry–Perot resonator. Measurement results indicate that the thermo-optic coefficient is independent on the sample doping and crystal plane orientation. The experimental data appear to be in agreement with the few values reported to date at this important wavelength. The temperature dependence of the excitonic band gap is also calculated by fitting these data with a recently introduced model of ∂n/∂T.
TL;DR: In this paper, gallium oxide thin films have promising properties for high-temperature-stable and n-type semiconducting properties at high temperatures above 600°C, and they have been used for detecting reducing gases as surface control-type sensors in the temperature range of 500°-850°C.
TL;DR: In this article, the donor nature of sulfur in diamond was obtained by introducing hydrogen sulfide into the microwave assisted plasma chemical vapor deposition process, which was successfully doped into homoepitaxial diamond (100) films, which exhibit n-type conduction by Hall-effect measurements in the temperature range of 250--550 K.
Abstract: Evidence for the donor nature of sulfur in diamond was obtained by introducing hydrogen sulfide into the microwave assisted plasma chemical vapor deposition process. The sulfur was successfully doped into homoepitaxial diamond (100) films, which exhibit n-type conduction by Hall-effect measurements in the temperature range of 250--550 K. The mobility of electrons at room temperature was 597 ${\mathrm{cm}}^{2}$ ${\mathrm{V}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. The ionization energy of 0.38 eV was determined by measuring the carrier concentration as a function of temperature.
TL;DR: In this paper, the authors reported the observation of visible cathodoluminescence of rare-earth Dy, Er, and Tm implanted in GaN, at atmospheric pressure to recover implantation damages and activated the rare earth ions.
Abstract: We reported the observation of visible cathodoluminescence of rare-earth Dy, Er, and Tm implanted in GaN. The implanted samples were given isochronal thermal annealing treatments at a temperature of 1100 °C in N2 or NH3, at atmospheric pressure to recover implantation damages and activated the rare-earth ions. The sharp characteristic emission lines corresponding to Dy3+, Er3+, and Tm3+ intra-4fn-shell transitions are resolved in the spectral range from 380 to 1000 nm, and observed over the temperature range of 8.5–411 K. The cathodoluminescence emission is only weakly temperature dependent. The results indicate that rare-earth-doped GaN epilayers are suitable as a material for visible optoelectronic devices.
TL;DR: In this paper, the resistivities of individual multiwalled pure and boron-doped carbon nanotubes have been measured in the temperature range from 25 to 300 degrees C. The connection patterns were formed by depositing two-terminal tungsten wires on a nanotube using focused-ion-beam lithography.
Abstract: The resistivities of individual multiwalled pure and boron-doped carbon nanotubes have been measured in the temperature range from 25 to 300 °C. The connection patterns were formed by depositing two-terminal tungsten wires on a nanotube using focused-ion-beam lithography. A decrease of the resistivity with increasing temperature, i.e., a semiconductor-like behavior, was found for both B-doped and pure carbon nanotubes. B-doped nanotubes have a reduced room-temperature resistivity (7.4×10−7–7.7×10−6 Ωm) as compared to pure nanotubes (5.3×10−6–1.9×10−5 Ωm), making the resistivity of the doped tubes comparable to those along the basal plane of graphite. The activation energy derived from the resistivity versus temperature Arrhenius plots was found to be smaller for the B-doped (55–70 meV) than for the pure multiwalled nanotubes (190–290 meV).
TL;DR: In this article, the bond properties of fiber reinforced polymer (FRP) reinforcing bars (rebars) at temperatures ranging from room temperature (20°C) to high temperatures of up to 250°C are discussed.
Abstract: The bond properties of fiber reinforced polymer (FRP) reinforcing bars (rebars) at temperatures ranging from room temperature (20°C) to high temperatures of up to 250°C are discussed in this paper. The bond properties in this temperature range were studied for a number of commercially produced rebars, where different bond “treatments” were applied to FRP rebars. Test results showed a reduction of between 80 and 90% in the bond strength as the temperature increased from 20 to 250°C. In comparison, ordinary deformed steel rebars showed a reduction of only 38% in the same temperature range. In addition, a reduction in the bond stiffness, which was determined from the slope of the ascending branch of the pullout load versus slip curve, was seen as the temperature increased. At elevated temperatures the postpeak bond decrease was gradual as compared with the instantaneous drop at room temperature. Greater sensitivity to high temperatures was seen in FRP rebars, in which the bond relies mainly on the polymer treatment at the surface of the rod.
TL;DR: In this article, the properties of high-surface-area La M 1− x Cu x O 3 (Mn or Co) perovskites prepared by the citrate method were studied by H 2 TPR and O 2 TPD techniques.
TL;DR: In this article, micro-Raman scattering from single crystal GaN films, both free-standing and attached to Al2O3 substrates, was performed over the temperature range from 78 to 800 K.
Abstract: Micro-Raman scattering from single crystal GaN films, both free-standing and attached to Al2O3 substrates, was performed over the temperature range from 78 to 800 K. These measurements reveal that the Raman phonon frequency decreases and the linewidth broadens with increasing temperature. This temperature dependence is well described by an empirical relationship which has proved to be effective for other semiconductors. The experiments also demonstrate that the strain from Al2O3 substrates compresses the epitaxial GaN in the c-axis direction.
TL;DR: In this article, the authors synthesized polycrystalline Ti3SiC2 by reactive HIPing of Ti, SiC and C powders, which was obtained when treated at 1500°C, 40 MPa for 30 min The density was 99% of the theoretical value.
Abstract: The dense polycrystalline Ti3SiC2 has been synthesized by reactive HIPing of Ti, SiC and C powders The bulk material with the highest Ti3SiC2 content about 97 vol % was obtained when treated at 1500°C, 40 MPa for 30 min The density was 99% of the theoretical value The Ti3SiC2 grains had the columnar and plate-like shapes The grains were well boned to form a network structure Many stacking faults were observed along the (001) plane of Ti3SiC2 The Vickers hardness, Young's modulus, flexural strength and fracture toughness were 4 GPa, 283 GPa, 410 MPa and 112 MPa m1/2, respectively The Ti3SiC2 was stable up to 1100°C in air The electrical resistivity was 27 × 10−7 Ω·m at room temperature The resistivity increased linearly with the increasing temperature It may be attributed to a second order phase transition The Seebeck coefficient was from 4 to 20 μV/K in the temperature range 300–1200 K It seems that Ti3SiC2 is semi-metallic with hole carriers from this small positive value
15 Mar 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors reported that the addition of as little as 1 wt.% boron improved the oxidation resistance of Mo5Si3 by as much as five orders of magnitude over a temperature range of 800-1500°C.
Abstract: The addition of as little as 1 wt.% (=3 at.%) boron improved the oxidation resistance of Mo5Si3 by as much as five orders of magnitude over a temperature range of 800–1500°C. The mechanism of oxidation protection is the formation of a borosilicate glass scale that flows to form a passivating layer over the base intermetallic. The compositional homogeneity range for T1 (Mo5Si3Bx) phase was determined to be much smaller than that reported previously by Nowotny. Compressive creep measurements show that materials based on the phase assemblage of T1-T2 (Mo5SiB2)–Mo3Si have high creep strengths similar to single phase Mo5Si3. Electrical resistivity of selected compositions was also measured and varied from ≈0.06 mΩ-cm at room temperature to 0.14 mΩ-cm at 1500°C. Temperature coefficient of resistivity (TCR) was estimated to be on the order of 1×10−4 C−1 for most compositions.
TL;DR: In this article, the authors studied lattice dynamic properties of thin films from 5 to 300 K using metal-oxide bilayer Raman scattering and found that the optical phonon lines and the asymmetry persist up to room temperature.
Abstract: We have studied lattice dynamic properties of ${\mathrm{SrTiO}}_{3}$ thin films from 5 to 300 K using metal-oxide bilayer Raman scattering. First-order zone-center optical phonons, symmetry forbidden in single crystals, have been observed in the thin films, indicating strain-induced lowering of symmetry. The asymmetric line shape of the ${\mathrm{TO}}_{2}$ phonon is interpreted as evidence for micropolar regions in the thin films, likely due to oxygen vacancies. The optical phonon lines and the asymmetry persist up to room temperature.
TL;DR: In this paper, a low-cost chemical deposition technique using sodium zincate bath was used to produce 0.05-0.50 µm size crystallites with preferred c-axis orientation.
Abstract: Zinc oxide (ZnO) thin films were prepared by a low cost chemical deposition technique using sodium zincate bath. Structural characterizations by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) indicate the formation of ZnO films, containing 0.05–0.50 μm size crystallites, with preferred c-axis orientation. The electrical conductance of the ZnO films became stable and reproducible in the 300–450 K temperature range after repeated thermal cyclings in air. Palladium sensitised ZnO films were exposed to toxic and combustible gases e.g., hydrogen (H2), liquid petroleum gas (LPG), methane (CH4) and hydrogen sulphide (H2S) at a minimum operating temperature of 150 °C; which was well below the normal operating temperature range of 200–400 °C, typically reported in literature for ceramic gas sensors. The response of the ZnO thin film sensors at 150 °C, was found to be significant, even for parts per million level concentrations of CH4 (50 ppm) and H2S (15 ppm).
TL;DR: This review describes the chemical kinetics and rate constant values k for the reaction 2NO + O2 = 2NO2 and points out that NO3, the intermediate of one of the two mechanisms, deserves serious attention in NO inhalation therapy.
TL;DR: In this article, the Boltzmann equation was used to calculate the charged impurity-scattering-limited low-temperature electronic resistivity of Si MOSFETs.
Abstract: We calculate within the Boltzmann equation approach the charged impurity-scattering-limited low-temperature electronic resistivity of low-density $n$-type inversion layers in Si MOSFET structures. We find a rather sharp quantum to classical crossover in the transport behavior in the $0--5\mathrm{K}$ temperature range, with the low-density, low-temperature mobility showing a strikingly strong nonmonotonic temperature dependence, which may qualitatively explain the recently observed anomalously strong temperature dependent resistivity in low-density, high-mobility MOSFETs.
TL;DR: In this paper, the changes in the surface structure of mechanically activated and mechanosynthesized zinc ferrite as a function of the mechanical treatment time and the relaxation of the mechanically induced inverse spinel structure by thermal treatment in the temperature range 800-1100 K have been studied using the ESCA method.
TL;DR: In this article, the experimental values of the thermal boundary resistance occurring at interfaces between two solids at sub-ambient temperatures are reviewed, and new data are presented in the temperature range from 4 K to 300 K for the thermal resistance between different metals (Cu, stainless steel), interlayered by various cryogenic bonding agents (Apiezon-N, Cryocon grease, In and InGa), or mechanically connected (dry) contacts.
Abstract: The experimental values of the thermal boundary resistance occurring at interfaces between two solids at sub-ambient temperatures are reviewed. New data are presented in the temperature range from 4 K to 300 K for the thermal resistance between different metals (Cu, stainless steel), interlayered by various cryogenic bonding agents (Apiezon-N, Cryocon grease, In and InGa), or mechanically connected (dry) contacts. Depending on the contact materials, the thermal conductance varies between and at room temperature, and decreases approximately linearly by one order of magnitude between 200 K and 20 K. Our experimental data agree well with the data reported in the literature for the temperature range below 4 K and measurements near room temperature.
TL;DR: In this article, the fundamental principles of the operation of a solid-state laser are presented for the case when the active element is a thin disk and an analytical model of this laser is developed.
Abstract: The fundamental principles of the operation of a solid-state laser are presented for the case when the active element is a thin disk. An analytical model of this laser is developed. The model is used to calculate the influence of the various parameters on the operational efficiency of the laser. A detailed model is also developed for calculations relating to a specific laser design and this model takes account of the geometry of the active medium, of the diode pump configuration, and of the operating conditions. Experiments yielded a cw output power up to 350 W and an optical pumping efficiency of ~ 50% (the corresponding values obtained in this single-mode regime were approximately 100 W and 440%). These results were obtained below 0 °C for eight passes of the pump radiation through the active medium. At room temperature and for 16 passes the same parameters were several tens of watts and an efficiency up to 58%. These experimental results were in good agreement with the predictions of the theoretical model.
TL;DR: In this paper, the effects of postdeposition annealing on the structural, electrical, and optical properties of Tantalum oxide (Ta2O5) thin films were analyzed.
Abstract: Tantalum oxide (Ta2O5) thin films were fabricated on Pt-coated Si, n+-Si, and poly-Si substrates by metalorganic solution deposition technique. The effects of postdeposition annealing on the structural, electrical, and optical properties were analyzed. The Ta2O5 films were amorphous up to 600 °C. A well-crystallized orthorhombic phase with strong a-axis orientation was obtained at an annealing temperature of 650 °C. The refractive index was found to increase with annealing temperature and a value of 2.08 (at 630 nm) was obtained for films annealed at 750 °C. The electrical measurements were conducted on metal–insulator–metal (MIM) and metal–insulator–semiconductor capacitors. The dielectric constant of amorphous Ta2O5 thin films was in the range 29.2–29.5 up to 600 °C, while crystalline thin films, annealed in the temperature range 650–750 °C, exhibited enhanced dielectric constant in the range 45.6–51.7. The high dielectric constant in crystalline thin films was attributed to orientation dependence of the dielectric permittivity. The dielectric loss factor did not show any appreciable dependence on the annealing temperature and was in the range 0.006–0.009. The frequency dispersion of the dielectric properties was also analyzed. The films exhibited high resistivities of the order of 1012–1015 Ω cm at an applied electric field of 1 MV/cm in the annealing temperature range of 500–750 °C. The measurement of current–voltage (I–V) characteristics in MIM capacitors indicated the conduction process to be bulk limited. The I–V characteristics were ohmic at low fields, and Poole–Frenkel effect dominated at high fields. The temperature coefficient of capacitance was in the range 52–114 ppm/°C for films annealed in the temperature range 500–750 °C. The bias stability of capacitance, measured at an applied electric field of 1 MV/cm, was better than 1.41% for Ta2O5 films annealed up to 750 °C. For a 0.15-μm-thick film, a unit area capacitance of 3.0 fF/μm2 and a charge storage density of 22.3 fC/μm2 were obtained at an applied electric field of 0.5 MV/cm.
TL;DR: In this paper, the hydraulic conductivities of water saturated Ca-bentonite with dry densities of 1.4, 1.6, and 1.8 Mg/m 3 were measured within the temperature range of 20 to 80°C.