Showing papers on "Atmospheric temperature range published in 1971"
TL;DR: In this paper, the infrared spectra of poly(acetylene), poly(d2), copoly(acety+acetylene-d2) and copoly (acetylene+acetane-d1+acetene-d 2) are reported over a wide temperature range (ca. −100 to 180°C) and a tentative assignment of the observed spectra is made on the basis of model structures in which infinite planar chains of all trans, all trans-cisoid, and all cis-transoid configurations are assumed.
Abstract: The infrared spectra of poly(acetylene), poly(acetylene-d2), copoly(acety+acetylene-d2), and copoly(acetylene+acetylene-d1+acetylene-d2) prepared by the Ti(OC4H9)4–Al(C2H5)3 system over a wide temperature range (ca. −100 to 180°C) are reported. A tentative assignment of the observed spectra is made on the basis of model structures in which infinite planar chains of all trans, all trans–cisoid, and all cis–transoid configurations are assumed. The spectral data are best interpreted on the basis of an all cis-transoid (or an all trans-cisoid) structure for the polymers prepared at temperatures lower than −78°C, and an all trans structure for the polymers prepared at temperatures higher than 150°C.Simplified calculations of the C-H and C-D out-of-plane deformation frequencies are made for various model chains. It has been concluded from a comparison of the observed and calculated frequencies that the cis-opening of the triple bond occurs in a polymerization reaction with the Ti(OC4H9)4–Al(C2H5)3 catalyst system at low temperatures.
550 citations
TL;DR: In this article, the elastic and plastic properties of filaments of non-crystalline Pd 20 a/o Si alloy and the changes that occur on crystallization during and after heating at various temperatures have been examined.
435 citations
01 Apr 1971
TL;DR: Stress relaxation tests have been made in the temperature range 200° to 400°C on two materials, the Mg-Al eutectic alloy and commercial purity zirconium.
Abstract: Stress relaxation tests have been made in the temperature range 200° to 400°C on two materials, the Mg-Al eutectic alloy and commercial purity zirconium. The materials represent respectively high and low homologous temperature regimes. The novel features of the tests are the use of high speed, high sensitivity digital measurement techniques and the direct reduction of the data to stress-strain rate curves. It was possible in this way to obtain phenomenological information on the material behavior over a very large range of strain rate with very few specimens. Comparison was made with results obtained by more conventional differential strain rate tests. The test lends itself well to establishing the phenomenology of mechanical behavior of metals.
172 citations
TL;DR: In this paper, the effects of temperature and hydrostatic pressure on the ferroelectric (FE) properties of PbTiO3 and on certain properties of Ba TiO3 which have not been treated or emphasized earlier were investigated.
Abstract: The effects of temperature and hydrostatic pressure on the ferroelectric (FE) properties of PbTiO3 and on certain properties of BaTiO3 which have not been treated or emphasized earlier were investigated. For PbTiO3, the FE-paraelectric (PE) transition is of first-order, and the transition temperature, Tc, decreases with pressure with an initial slope of -8.4 ± 0.3°K/kbar. It is estimated that the latent heat associated with the transition is 350 ± 45 cal/mole, with a corresponding entropy change of 0.46 ± 0.05 cal/mole°K. In the PE phase, the static dielectric constant, e, obeys the Curie-Weiss law e = C/(T- T0) over a wide temperature range. Both C and T0 decrease with pressure. At constant % e varies with pressure according to e = C*/(p-po), where p0 decreases strongly with increasing T while C* is very weakly T-dependent. The results can be explained in terms of an increase of the frequency of the soft FE mode with pressure, and the Gruneisen parameter and its Tdependence are determined for this mode. ...
166 citations
TL;DR: In this article, a thermogravimetric system is described for the determination of the total oxygen consumption, sample weight change, and vaporization rate during the oxidation of a single molecule.
Abstract: A thermogravimetric system is described for the determination of the total oxygen consumption, sample weight‐change, and vaporization rate during the oxidation of . The results show an increasing deviation from parabolic kinetics with increasing temperature at 250 mm oxygen pressure. The following equation is used to describe the total oxygen consumption in the temperature range of 800°–1500°C Because is oxidized stoichiometrically, this result can be converted to the recession of as follows
140 citations
TL;DR: In this article, the interaction of oxygen with a polycrystalline W filament has been studied in the temperature range 300-1200°K and for exposures between 10−7 and 1'torr·sec.
Abstract: The interaction of oxygen with a polycrystalline W filament has been studied in the temperature range 300–1200°K and for exposures between 10−7 and 1 torr·sec. Both sticking probabilities and desorption spectra have been measured. After low exposures (〈2×10−6 torr·sec) the adsorbate is all desorbed as O atoms with first order kinetics. With higher exposures, oxygen is removed as oxides: WO, WO2, WO3, W2O6. The desorption spectra for each of these species are complex, and nine distinct and reproducible oxide states are identified. Saturation coverages in each of these states are independent of adsorption temperature in the range 300–1200°K. At a total coverage of 8.5×1014 O2 molecules cm−2, 2.2×1014 O2 molecules cm−2 are desorbed as oxides; after exposures 〉 10−2 torr·sec at 300°K, the total uptake rises to 15×1014 O2 molecules cm−2. At temperatures between 500 and 1000°K and exposure up to 1 torr·sec, a multilayer oxide film is formed of unlimited thickness. The desorption product from this oxide film is ...
131 citations
01 Jan 1971-Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry
TL;DR: A technique is described for the high-speed measurement of heat capacity, electrical resistivity, hemispherical total and normal spectral emittances of electrical conductors at high temperatures (above 1900 K) with millisecond resolution.
Abstract: A technique is described for the high-speed measurement of heat capacity, electrical resistivity, hemispherical total and normal spectral emittances of electrical conductors at high temperatures (above 1900 K) with millisecond resolution. Duration of an individual experiment, in which the specimen is heated from room temperature to close to its melting point, is less than one second. Temperature measurements are made with a high-speed photoelectric pyrometer. Quantities are recorded by a high-speed digital data acquisition system which has a resolution of approximately one part in 8000. Time resolution of the entire system is 0.4 ms. Results on the above properties of molybdenum in the temperature range 1900 to 2800 K are reported and are compared with those in the literature. Estimated inaccuracy of measured properties in the above temperature range is: 2 to 3 percent for heat capacity, 0.5 percent for electrical resistivity, 3 percent for hemispherical total emittance and 2 percent for normal spectral emittance.
121 citations
TL;DR: In this paper, a defect structure which incorporates singly and doubly ionized nonstoichiometric oxygen vacancies and acceptor states was inferred from the agreement between the theoretically derived relation and the experimentally observed O2-partial pressure and temperature dependence of the conductivity.
Abstract: A defect structure which incorporates singly and doubly ionized nonstoichiometric oxygen vacancies and acceptor states, presumably associated with impurities, was inferred from the agreement between the theoretically derived relation
and the experimentally observed O2-partial-pressure and temperature dependence of the conductivity. This relation describes the behavior over the entire O2 pressure and temperature range investigated. A simplified defect model gave good agreement for the limiting case where n> >p but was shown to be in error compared with the more comprehensive relation above. The standard enthalpies of formation for singly and doubly ionized O vacancies in BaTiO3, are 4.3 and 5.7 eV, respectively. The difference between these values, 1.4 eV, corresponds to a donor energy level which lies near the middle of the band gap.
108 citations
TL;DR: In this article, the open circuit voltages of a cell were measured over a composition range of 6.9-50 a/o (atom per cent) alloy in the temperature range 282°-389°C.
Abstract: The open‐circuit voltages of the cell were measured over the composition range of 6.9–50 a/o (atom per cent) alloy in the temperature range 282°–389°C. The composition of the alloy was varied by coulometrically charging and discharging the cell. The emf values of the cell are independent of the composition up to 47 a/o lithium in the alloy and their temperature dependence follows the relationship , where is in millivolts, , and σ is the standard deviation. The constant potential exhibited by the alloy is ascribed to the formation of phase on the alloy surface. The standard free energies of formation for are estimated to be −7.49, −7.24, and − 7.09 kcal/mole at 300°, 350°, and 380°C, respectively. The standard enthalpy and entropy of formation are constant, −10.40 kcal/mole and −5.08 cal/mole deg, respectively, in this temperature range. Since the electrochemically prepared lithium‐aluminum alloy has a constant potential over a wide composition range and exhibits good electrochemical behavior, it can serve as a good reference electrode as well as a high energy density anode in molten salt systems containing lithium.
107 citations
TL;DR: In this article, the epitaxial relationship and electrical properties of silicon on sapphire were studied by growing films up to 20 μ thick using high-temperature sublimation in 10−10 Torr vacuum on the (1012), (1123), (0001), and (1120) substrate surfaces.
Abstract: Epitaxy of silicon on sapphire was studied by growing films up to 20 μ thick using high-temperature sublimation in 10−10 Torr vacuum on the (1012), (1123), (0001), and (1120) substrate surfaces. The surface structure and chemistry of both substrate and film could be monitored using LEED and Auger electron spectroscopy. The epitaxial relationships and the electrical properties were found to depend on deposit-substrate interactions, substrate temperature, and surface structure. A range of epitaxial temperatures could be defined for each substrate orientation within which the proper surface structure could be maintained during film growth. The behavior outside the epitaxial range was explored, revealing several causes for breakdown of optimum growth. The (1012) substrate was found to have the largest epitaxial temperature range. Silicon films of (100), (111), and, under special circumstances, the (110) orientations could be produced. Films thicker than 2 μ could be grown with essentially bulk values for carrier mobility (carrier concentration between 5×1015 and 8×1018/cm3). Film type (n or p), resistivity, and carrier concentration could be controlled by the choice of proper source material, and were reproducible within a factor of 2. Minority carrier lifetimes were about 10−9 sec; this short lifetime is probably due to the presence of defects, especially within the first micron of growth.
103 citations
TL;DR: In this paper, it was shown that the energy per electron hole pair for α-particles is 4.27 eV ± 0.05 at 300 K with a linear variation with band gap of 2.7 over the temperature range 87 K to 340 K.
TL;DR: In this article, the authors presented heat capacity data for the five LnAl 2 compounds, where Ln=La, Ce, Pr, Nd and Gd, in approximate agreement with R In (2 J + 1) except for GdAl 2 in which the discrepancy was about 25 percent.
TL;DR: In this article, electron spin resonance and nuclear magnetic resonance were used to study paramagnetic vanadium vanadium-phosphate and molybdenum phosphate glasses.
Abstract: Paramagnetic vanadium‐phosphate and molybdenum‐phosphate glasses have been studied using electron‐spin resonance and nuclear magnetic resonance. These glasses were nominally 80% MO:20% P2O5, where MO denotes the transition‐metal oxide. The electron‐spin‐resonance results showed a strongly exchanged, narrowed interaction with V4+/V5+ and Mo5+/Mo6+ ratios and line shapes which were independent of temperature over the range 77°–300°K. Since the conductivity is nonlinear in this temperature range, the result is direct evidence that the mobility is temperature dependent and that the average paramagnetic‐site is unchanged over this temperature range. The nuclear magnetic resonance of 51V and 31P in the glasses verifies the assumption of exchange narrowing. The 51V quadrupole coupling (1.5 MHz) and spin‐lattice relaxation time (T1<500 μsec) were temperature independent over the 77°–300°K range. The 31P resonances in each of the glasses also had temperature‐independent properties. For the molybdenum glass the lin...
TL;DR: The temperature dependence of elastic constants c 11 − c 12 and c 44 of Fe 2.05 Ti 0.95 O 4.00 is measured by the ultrasonic pulse echo method, using a small platelet with approximate dimension of 5×7×1.364mm, for the temperature range of 77°∼300°K as discussed by the authors.
Abstract: The temperature dependence of elastic constants c 11 – c 12 and c 44 of Fe 2.05 Ti 0.95 O 4.00 is measured by the ultrasonic pulse echo method, using a small (110) platelet with approximate dimension of 5×7×1.364mm, for the temperature range of 77°∼300°K. c 11 – c 12 decreases anomalously with decreasing temperature in the paramagnetic phase, whereas c 44 increases. An extraordinarily large attenuation is observed around the Curie temperature in the 1\bar10 shear mode which couples to c 11 – c 12 . The elastic constants obtained, c 11 - c 12 =0.265×10 12 dyne/cm 2 and c 44 =0.396×10 12 dyne/cm 2 at room temperature, are almost an order of magnitude smaller than those of magnetite and spinel, and provide a reasonable explanation for the giant magnetostriction observed in the crystal. The soft mode in the crystal is interpreted to be due to the Jahn-Teller relaxation effect of Fe 2+ ions in the tetrahedral site.
TL;DR: In this paper, it was shown that conduction in amorphous germanium sandwich layers is by hopping in the temperature range up to 300°K, where the carriers are supplied by a large density of acceptor states (1018-1019 cm-3) near to the localized valence band.
Abstract: The current-voltage behaviour of amorphous germanium sandwich layers has been investigated in the temperature range 2°K to 79°K. The results obtained, in conjunction with those of Walley (1968) for the range 77°K to 300°K, are discussed in terms of a model for conduction in amorphous germanium. It is also shown that similar processes must be responsible for conduction in amorphous silicon.Following the analyses of Mott (1969) and Hill (1970) it is concluded that conduction in amorphous germanium (and silicon) is by hopping in the temperature range up to 300°K. The carriers are supplied by a large density of acceptor states (1018-1019 cm-3) near to the localized valence band. At low temperatures the current limiting process is field assisted emission from acceptors and this gives rise to power law (I ∝ V8) and exponential (I ∝ exp V½) behaviour in the current-voltage characteristics. Transport between the acceptors is via states in the localized part of the valence band. At higher temperatures the limiting...
TL;DR: In this paper, the authors showed that very fine titanomagnetite particles are responsible for the observed behaviour of the basaltic basaltite nuclei in the presence of superparamagnetic particles.
Abstract: Hysteresis loops of basaltic rocks which usually have aggregates of magnetic particles have been studied in the temperature range 25° to −190°C. Some samples showed coercive forces as high as 930 oe at −190°C. Blocking temperature studies of the magnetic grains in these samples revealed that they contain particles, most of which are superparamagnetic at or around room temperature. The studies are consistent with the inference that very fine titanomagnetite particles are responsible for the observed behaviour of the samples.
TL;DR: Results suggest that the two processes of folding of acidified staphylococcal nuclease may correspond to a sequence involving nucleation of ordered structure followed by the formation of hydrophobic interactions.
TL;DR: In this paper, fine-grained Zirconium dioxide films were identified as nearly stoichiometric, monoclinic, using electron microprobe analysis, infrared absorption, and transmission electron microscopy.
Abstract: Zirconium dioxide films in the thickness range of 500–8000Aring; have been prepared by chemical vapor deposition in the temperature range of 800°a 1000° C. The films were identified as fine‐grained (∼325Aa), nearly stoichiometric, monoclinic , using electron microprobe analysis, infrared absorption, and transmission electron microscopy. The films exhibited remarkable resistance to most aqueous acids and bases, although slight etching occurred in hot (220°C) phosphoric acid. The deposits had an index of refraction of and an optical energy gap of 5.12 eV. deposited on silicon offered little resistance to Na diffusion at 600°C, while films deposited on thermal were a good barrier due to pile‐up of the Na near the interface. The current density, , depended on the field, , where was 6 for the metal biased negatively and 2.75 or 5, depending on the magnitude of the field, for the opposite polarity. The dielectric constant in the frequency range of was relatively independent of frequency near 300° K and equal to approximately 18, however some dispersion was noted near 573°K. The a‐c conductivity could be represented by where is the measuring frequency and β a temperature dependent parameter, decreasing from . The dielectric strength of the films varied between , independently of thickness and polarity. High frequency (1 MHz) C‐V measurements indicated the presence of negative surface charge, which varied between . The structures exhibited instability under negative bias, indicative of negative charge being injected into the insulator. C‐V measurements on the double dielectric system showed that the presence of caused a flatband voltage displacement . In addition, the flatband voltage shifted as a function of time under negative bias and was found to obey the relationship .
TL;DR: The thermal diffusivity of BN has been measured from 100 K-800 K using a 'flash' method; published specific heat data has been used to evaluate the thermal conductivity as discussed by the authors.
Abstract: The thermal diffusivity of BN has been measured from 100 K-800 K using a 'flash' method; published specific heat data has been used to evaluate the thermal conductivity. Over a limited temperature range the results have been confirmed by steady state measurements. The thermal conductivity parallel to the deposition plane has been found to have a maximum value of about 2.5 W cm-1 K-1 at 235 K, while perpendicular to it the thermal conductivity shows no maximum but decreases from about 2.5*10-2 W cm-1 K-1 at 100 K to 1.7*10-2 W cm-1 K-1 at 800 K. The conductivity parallel to the deposition plane has been analysed using a two dimensional mode in which the vibrations in and out of the plane are independent and the latter depend only upon the resistance of the layer to bending. Characteristic temperatures for the two modes of 2290 K and 1200 K respectively have been estimated. Above 200 K the conductivity can be explained in term of Umklapp processes and boundary scattering from crystallites estimated to have average diameters in the deposition plane of 580 AA and 290 AA for the two samples investigated.
TL;DR: The lifetime of fission gas at grain boundaries is controlled by resolution and atomic diffusion of gas atoms through the uranium dioxide lattice rather than by the migration of bubbles up the temperature gradient.
TL;DR: In this paper, the spectral line intensities and shapes of Raman lines in an oriented single l-alanine crystal were studied in detail at temperatures ranging from 120 to 300°K.
Abstract: Spectral line intensities and shapes of Raman lines in an oriented single l‐alanine crystal were studied in detail at temperatures ranging from 120 to 300°K. It has been found: (1) Although most of the vibrational modes are polar, the effects of long‐range electrical force on the internal vibration modes are not large. For the lattice modes, the electric dipolar interaction tends to induces coupling between modes of different symmetries; (2) the molecular configuration of an l‐alanine molecule in crystal remains unchanged in the 120–300°K temperature range although crystalline strain and ahnarmonic interaction between molecules significantly affect the Raman spectral lines; (3) for temperature above 220°K, the line shape of the −NH3+ torsional mode becomes a sensitive function of temperature. The linewidth study of this mode shows that the breaking of a second H bond is an important mechanism for broadening the torsional mode at T above 220°K.
TL;DR: In this paper, Anderson revived interest in a fundamental constant of a solid called δ, which was first introduced by Gruneisen and was used by Anderson to explain the temperature dependence of the bulk modulus of oxide compounds.
Abstract: There is very little data on the behavior of the bulk modulus of crystals over a wide temperature range. Recently, Anderson revived interest in a fundamental constant of a solid called δ, which was first introduced by Gruneisen. This parameter is similar in many respects to the well‐known Gruneisen parameter γ and was used by Anderson to explain the temperature dependence of the bulk modulus of oxide compounds. In the present paper, general expressions for δ have been derived in a simple manner correlating the thermodynamical and the interatomic potential approaches. The parameter δ has also been related to the Gruneisen parameter using the Slater and Dugdale‐MacDonald equations. The relative appropriateness of different expressions for δ has been discussed. The computed values of δ for NaCl‐ and CsCl‐type alkali halides based on the Born‐Mayer and the modified Born‐Mayer potential forms have been reported and are found to be consistent and in essential agreement with other determinations. These values have been used to calculate the adiabatic bulk modulus as a function of temperature for KCl and NaCl. A good agreement is found with the experimental data over most of the temperature range in the neighborhood of and above the room temperature. This general accord with the predictions of theory clearly indicates that in the temperature range where the experimental data is inadequate, it is possible to predict the temperature dependence of the bulk modulus of nonoxide compounds also, using Anderson's equation and the relationships for δ developed in the present paper.
TL;DR: The specific heat of DyVO 4 has been measured in the temperature range 1 − 20 K as discussed by the authors and two anomalies are observed; one at a temperature of 14.0 K corresponding to a crystallographic distortion and the second at 3.07 K attributable to antiferromagnetic ordering.
TL;DR: In this article, low-temperATURE conditions were found to be related to CLAY MINERAL and EXCHANGEABLE CATION types of clays, and the evolution of heat in this range is correlated with a phase change in the interfaceted water supply.
Abstract: LOW TEMPERATURE DIFFERENTIAL THERMAL ANALYSES OF SELECTED CLAY-WATER SYSTEMS WERE MADE TO LOCATE IMPORTANT PHASE CHANGE TEMPERATURES AND TO DEFINE FRUITFUL TEMPERATURE-PRESSURE FIELDS FOR PRECISE CALORIMETRIC INVESTIGATION. IN ADDITION TO AN EXOTHERM CORRESPONDING TO INITIAL FREEZING, ONE, TWO OR THREE EXOTHERMS WERE OBSERVED BETWEEN -35C AND -60C. THE LOW TEMPERATURE EXOTHERMS DO NOT DEPEND CRITICALLY UPON WATER CONTENT, BUT CLEARLY THEY ARE RELATED TO CLAY MINERAL AND EXCHANGEABLE CATION TYPE. THE EVOLUTION OF HEAT IN THIS TEMPERATURE RANGE PROBABLY CORRESPONDS TO A PHASE CHANGE IN THE INTERFACIAL WATER. /AUTHOR/
TL;DR: In this article, single crystals of the diamond-like tetragonal compounds ZnSiP2, CdSiP 2 and CdSnP2 were grown by vapor transport and by precipitation from liquid Sn.
TL;DR: In this paper, the authors investigated the kinetics of the vacuum sublimation of ice single crystals by a vacuum microbalance technique in the temperature range −90 to −40°C.
Abstract: The kinetics of the vacuum sublimation of ice single crystals has been investigated by a vacuum microbalance technique in the temperature range −90 to −40°C. The vaporization coefficient αv ≡ (observed vaporization rate) ÷ (theoretical maximum rate) and the activation enthalpy of sublimation, Δ Hs*, vary markedly with temperature in this range. At temperatures below about −85°C, α v=1 and Δ Hs* equals the thermodynamic enthalpy of sublimation Δ Hs°. Between about −85 and −60°C, αv decreases slowly with increasing temperature, Δ Hs*≲ΔHs°. Between about −60 and −40°C, αv decreases progressively more rapidly with increasing temperature and Δ Hs* decreases to a high‐temperature limiting value of ≃ 12 Δ Hs°. The effects of various experimental parameters such as crystal orientation, doping with impurities and adsorbed gases on the ice vaporization kinetics have also been investigated. Neither grain boundaries nor crystal orientation has a measurable effect on the rate. Ice doped with monovalent impurities was ...
TL;DR: In this article, the surface and bulk critical exponents of NiO were determined using the molecular field model and qualitative scaling arguments, and it was shown that the surface exchange interaction is weaker than the bulk exchange interaction.
TL;DR: In this paper, a synthetic polycrystalline sample of Ni(OH)2 was investigated by means of neutron diffraction in the temperature range 4.2 to 293 °K.
Abstract: A synthetic polycrystalline sample of Ni(OH)2 was investigated by means of neutron diffraction in the temperature range 4.2 to 293 °K. The crystallochemical structure of this compound is analogous to the structure of Ca(OH)2. At temperatures below 28 °K Ni(OH)2 is antiferromagnetic with magnetic moments directed parallel to the c0-axis.
TL;DR: In this article, the internal friction and Young's modulus of a hydrogen doped niobium single crystal were measured in the temperature range 20 to 370°K and the activation energy of the peak was found to be about 0·27 eV.