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1.
《Journal of membrane science》1987,33(2):221-240
We studied the effects of temperature on the sulfate permease of Penicillium chrysogenum (PC) (a mesophile with a growth temperature range of 4-35°C) and Penicillium duponti (PD) (a thermophile with a growth temperature range of 27-58°C). Arrhenius plots of sulfate permease activity from mycelia grown at 50°C (PD), 30°C (PD and PC) or 8°C (PC) indicate that at temperatures below the transition point there is little difference in the activation energy of sulfate permease in mycelia from PD grown at 50°C or 30°C or PC grown at 30°C or 8°C; however, the temperature of the transition point for the permease from each set of mycelia assayed reflects the optimum growth temperature of the fungal source. Transitions occur at 15 °C for mycelia from PC and 35 ° C for PD mycelia. Kinetic measurements indicate that the Km of sulfate permease in PC cells grown at a variety of temperatures is essentially the same at various temperatures. As an example, the Km of 8°C or 30°C grown PC is about 55 μM at 25°C and 45 μM at 8°C. Vmax measurements reflect growth conditions such as temperature and growth stage. p]Lipid composition of the mycelia dramatically reflect growth temperatures. Double bond index values vary from 1.94 for PC grown at 8°C to 0.81 for PD grown at 50°C. The percentage of total fatty acid represented by linolenic acid varies from 45% in 8°C grown PC to 4.2% or less in 30°C grown PC. No linolenic is found in mycelia from PD. 相似文献
2.
H. Ipser Prof. Dr. K. L. Komarek Helga Mikler 《Monatshefte für Chemie / Chemical Monthly》1974,105(6):1322-1334
The iron—tellurium phase diagram was investigated by thermal, X-ray, and isopiestic measurements up to 1,100°C. Tetragonal β(≈FeTe0.9) with a homogeneity range from 45.9 to 48.1 at % Te at 715°C is stable from room temperature to 844°C where it decomposes peritectoidally into Fe and rhombohedral high-temperature β′(≈FeTe0.9). β′ decomposes at 914°C peritectically into Fe and liquid, and at 800°C by a eutectoid reaction into β and γ(≈FeTe1.2). γ exists between 809° (γ→β′+δ) and 636°C (γ→β+δ). The monoclinically distorted NiAs-phase δ decomposes peritectically at 55.2 at % Te and 812°C into β′ and liquid and is stable down to the eutectoid δ?β+δ′ at 565±15°C and 58.8 at % Te. δ is separated from hexagonal NiAs-type δ′ by a narrow two-phase region. δ′ has a maximum range of homogeneity at 650°C from 59.2 to 65.1 at % Te and exists between the eutectoid δ′?β+ε at 519°C and the peritectic δ+L?δ′ at 766°C. Orthorhombic ε(≈FeTe2.0) is stable from room temperature to the peritectic δ′+L=ε at 649°C. ε and Te form a degenerate eutectic at 446°C. 相似文献
3.
Oxidefluorides of Niobium and Tantalum The reaction of NbF5 with SiO2 (silica glass ampules) at 310°C or with SiO2 (Aerosil) at 180°C always leads to NbO2F. To the contrary the reaction with laboratory glass (Jenaer Geräteglas) at 130°C leads to NbOF3. TaF5 reacts in silica glass ampules at 400°C by formation of TaO2F, however at 300°C or 260°C by formation of TaOF3. Silica glass did not react with NbF5 at 130°C, however Nb2O5 and NbF5 gave at 130°C in silica glass ampoules NbOF3. Similarly, TaF5 and Ta2O5 or TaO2F formed at 260°C in nickel ampoules TaOF3. The chemical and the thermochemical behaviour of oxidefluorides have been investigated. The compounds NbOF3 and TaOF3 are isomorphic. Lattice constants are mentioned. 相似文献
4.
E. Mendelovici A. Sagarzazu R. Villalba 《Journal of Thermal Analysis and Calorimetry》1993,40(3):1115-1122
Synthetic iron-manganese glycerates with compositions corresponding to different molar ratios of Fe: Mn, contain large amounts of H2O (up to 22%). Heating in air at ≈270°C produces a hydrated, disordered Mn-ferrite structure (jacobsite), as shown by XRD and IR spectroscopy. At this temperature no alkoxide groups are detected. TG curves show 45.6% to ≈54% weight losses at 290°C, with a sharp loss from 270° to 290°C for all samples, attributed mostly to the Curie transition of MnFe2O4. Further heating of each sample at ≈670°C results in a well-crystallized hematite and variable amounts of bixbyite. At this stage no H2O is left. Further calcination at ≈1050°C gives qualitatively the same products as at 670°C. Colour changes occur during the heating process. In admixtures of goethite with MnCO3 or pyrolusite the main difference from the counterpart alkoxide is shown after heating at 270°C, when the Fe?Mn mineral mixture produces mostly protohematite (disordered hematite) instead of disordered jacobsite resulting from the alkoxides. 相似文献
5.
When the anatase form of TiO2 was heated at a constant rate of 6°C/min to 450°C it crystallized from hydrated amorphous TiO2 gel at 170°C in pure water or at <150°C in NaOH solutions. The uptake of Na+ ions into crystallized anatase affected the reactions subsequent to this initial crystallization while only anatase crystals continued to grow with increasing temperature in pure water. Immediately after the nearly amorphous second stage at 325°C, conversion from colloidal anatase particles to square sheet-shaped bronze-type TiO2 crystals began at 350°C and was complete at 425°C in 0.5 M NaOH. This conversion was considered to proceed via crystallographic shear rather than via dissolution and precipitation since this also happened with thermal treatment to 700°C in air. 相似文献
6.
The temperature-composition phase diagram of the HgTe—HgI2 pseudobinary system was determined between 25 and 670°C using differential scanning calorimetry, differential thermal analysis, Debye-Scherrer powder X-ray diffraction techniques, and metallographic analysis methods. Solid solutions of HgTe and HgI2 with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7±0.8 Mol-% HgI2 in HgTe at 501±5°C. The monoclinic intermediate phase Hg3Te2I2 is formed by a peritectic reaction upon cooling at 501±5°C, with the peritectic point at approximately 37±4 Mol-% HgI2. The previously unknown cubic phase Hg3TeI4 (a = 6.240±0.003 Å) is formed by a eutectoid reaction at 238±3°C and is stable up to 273±3°C, where it melts by a peritectic reaction with the peritectic point at approximately 79±3 Mol-% HgI2. Between Hg3TeI4 and HgI2 is a eutectic point at 82±3 Mol-% HgI2 and 250±3°C. The α to β transition of HgI2 at 133±3°C is independent of sample composition between 33.3 and 100 Mol-% HgI2. 相似文献
7.
《Journal of solid state chemistry》1986,62(2):177-183
The phase relations in the 0–65 at% Hg portion of the condensed mercury-selenium system were determined from liquidus temperatures to 250°C by evacuated silica tube experiments in which vapor is always a phase. Stoichiometric HgSe melts at 795 ± 2°C whereas Hg0.51Se0.49 melts at 797 ± 2°C and Hg0.49Se0.51 melts at 793 ± 2°C. In the HgSeSe portion of the system a monotectic exists at 683 ± 3°C and 71.5 at% Se and a liquid immiscibility field at this temperature extends from 71.5 to 85.5 at% Se. The presence of HgSe depresses the melting temperature of Se by about 8°C. An eutectic exists between HgSe and Se at 208°C and a composition of more than 99.95 at% Se. In the HgHgSe portion of the system a monotectic exists at 708 ± 3°C and about 25 at% Se. The solubility of Hg in HgSe was found to exceed stoichiometry by 1.11 ± 0.25 at% at 650°C whereas the solubility of Se in HgSe exceeds stoichiometry by 0.75 ± 0.25 at% Se at the same temperature. All synthetic mercury selenides show the sphalerite type structure. The unit cell dimension of stoichiometric HgSe is a0 = 6.080 ± 0.001 Å. Mercury selenide synthesized in equilibrium with liquid Se gives a0 = 6.082 ± 0.001 Å and mercury selenide synthesized in equilibrium with Hg gives a0 = 6.078 ± 0.001 Å. 相似文献
8.
Ray L. Frost Sara J. Palmer János Kristóf Erzsébet Horváth 《Journal of Thermal Analysis and Calorimetry》2010,99(2):501-507
Three halotrichites namely halotrichite Fe2+SO4·Al2(SO4)3·22H2O, apjohnite Mn2+SO4·Al2(SO4)3·22H2O and dietrichite ZnSO4·Al2(SO4)3·22H2O, were analysed by both dynamic, controlled rate thermogravimetric and differential thermogravimetric analysis. Because of
the time limitation in the controlled rate experiment of 900 min, two experiments were undertaken (a) from ambient to 430 °C
and (b) from 430 to 980 °C. For halotrichite in the dynamic experiment mass losses due to dehydration were observed at 80,
102, 319 and 343 °C. Three higher temperature mass losses occurred at 621, 750 and 805 °C. In the controlled rate thermal
analysis experiment two isothermal dehydration steps are observed at 82 and 97 °C followed by a non-isothermal dehydration
step at 328 °C. For apjohnite in the dynamic experiment mass losses due to dehydration were observed at 99, 116, 256, 271
and 304 °C. Two higher temperature mass losses occurred at 781 and 922 °C. In the controlled rate thermal analysis experiment
three isothermal dehydration steps are observed at 57, 77 and 183 °C followed by a non-isothermal dehydration step at 294 °C.
For dietrichite in the dynamic experiment mass losses due to dehydration were observed at 115, 173, 251, 276 and 342 °C. One
higher temperature mass loss occurred at 746 °C. In the controlled rate thermal analysis experiment two isothermal dehydration
steps are observed at 78 and 102 °C followed by three non-isothermal dehydration steps at 228, 243 and 323 °C. In the CRTA
experiment a long isothermal step at 636 °C attributed to de-sulphation is observed. 相似文献
9.
Jitka Hreščak Barbara Malič Jena Cilenšek Andreja Benčan 《Journal of Thermal Analysis and Calorimetry》2017,127(1):129-136
The solid-state synthesis of undoped K0.5Na0.5NbO3 (KNN) and KNN doped with 1, 2 and 6 mol% Sr, from potassium, sodium and strontium carbonates with niobium pentoxide, was studied using thermal analysis and in situ high-temperature X-ray diffraction (HT-XRD). The thermogravimetry and the differential thermal analyses with evolved-gas analyses showed that the carbonates, which were previously reacted with the moisture in the air to form hydrogen carbonates, partly decomposed when heated to 200 °C. In the temperature interval where the reaction was observed, i.e., between 200 and 750 °C, all the samples exhibited the main mass loss in two steps. The first step starts at around 400 °C and finishes at 540 °C, and the second step has an onset at 540 °C and finishes with the end of the reaction between 630 and 675 °C, depending on the particle size distribution of the Nb2O5 precursor. According to the HT-XRD analysis, the perovskite phase is formed at 450 °C for all the samples, regardless of the Sr content. The formation of a polyniobate phase with a tetragonal tungsten bronze structure was detected by HT-XRD in the KNN with the largest amount of Sr dopant, i.e., 6 mol% of Sr, at 600 °C. 相似文献
10.
Dr. Thomas Hansen Dr. Xiaobo Sun Dr. Marco Dalla Tiezza Dr. Willem-Jan van Zeist Joost N. P. van Stralen Prof. Dr. Daan P. Geerke Dr. Lando P. Wolters Prof. Dr. Jordi Poater Dr. Trevor A. Hamlin Prof. Dr. F. Matthias Bickelhaupt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(44):e202201093
The C−X bond activation (X = H, C) of a series of substituted C(n°)−H and C(n°)−C(m°) bonds with C(n°) and C(m°) = H3C− (methyl, 0°), CH3H2C− (primary, 1°), (CH3)2HC− (secondary, 2°), (CH3)3C− (tertiary, 3°) by palladium were investigated using relativistic dispersion-corrected density functional theory at ZORA-BLYP-D3(BJ)/TZ2P. The effect of the stepwise introduction of substituents was pinpointed at the C−X bond on the bond activation process. The C(n°)−X bonds become substantially weaker going from C(0°)−X, to C(1°)−X, to C(2°)−X, to C(3°)−X because of the increasing steric repulsion between the C(n°)- and X-group. Interestingly, this often does not lead to a lower barrier for the C(n°)−X bond activation. The C−H activation barrier, for example, decreases from C(0°)−X, to C(1°)−X, to C(2°)−X and then increases again for the very crowded C(3°)−X bond. For the more congested C−C bond, in contrast, the activation barrier always increases as the degree of substitution is increased. Our activation strain and matching energy decomposition analyses reveal that these differences in C−H and C−C bond activation can be traced back to the opposing interplay between steric repulsion across the C−X bond versus that between the catalyst and substrate. 相似文献
11.
Four samples of Venezuelan lateritic bauxites were heated to 300, 600 and 1000°C and the thermal reactions were studied by X-ray diffraction (XED) and by chemical extractability of silica and alumina. Gibbsite was converted to boehmite at 300°C, to an amorphous phase at 600°C and partly to corundum at 1000°C, with isomorphic substitution of Fe for some of the Al in the corundum structure. Goethite was converted to protohematite at 600°C and the hematite at 1000°C, with isomorphic substitution for Al for some of the Fe in both α-Fe2O3 varieties. Ti contributed by ilmenite is also occluded by the hematites. The occlusion of Ti takes place at 1000°C during the decomposition of the ilmenite and concomitant recrystallization of α-Fe2O3. 相似文献
12.
The nanocrystalline cubic Phase of zirconia was found to be thermally stabilized by the addition of 2.56 to 17.65 mol % Y2O3 (5.0 to 30.0 mol % Y, 95.0 to 70.0 mol % Zr cation content). The cubic phase of yttria stabilized zirconia was prepared by thermal decomposition of the hydroxides at 400°C for 1 hr. 2.56 mol % Y2O3‐ZrO2 was stable up to 800°C in an argon atmosphere. The samples with 4.17 to 17.65 mol % Y2O3 were stable to 1200°C and higher. All samples at temperatures between 1450°C to 1700°C were cubic except the sample with 2.56 mol % Y2O3 which was tetragonal. The crystallite sizes observed for the cubic phase ranged from 50 to 150 Å at temperatures below 900°C and varied from 600 to 800 nm between 1450°C and 1700°C. Control of furnace atmosphere is the main factor for obtaining the cubic phase of Y‐SZ at higher temperature. Nanocrystalline cubic Fe‐SZ (Iron Stabilized Zirconia) with crystallite sizes from 70 to 137 Å was also prepared at 400°C. It transformed isothermally at temperatures above 800°C to the tetragonal Fe‐SZ and ultimately to the monoclinic phase at 900°C. The addition of up to 30 mol % Fe(III) thermally stabilized the cubic phase above 800°C in argon. Higher mol % resulted in a separation of Fe2O3. The nanocrystalline cubic Fe‐SZ containing a minimum 20 mol % Fe (III) was found to have the greatest thermal stability. The particle size was a primary factor in determining cubic or tetragonal formation. The oxidation state of Fe in zirconia remained Fe3+. Fe‐SZ lattice parameters and rate of particle growth were observed to decrease with higher iron content. The thermal stability of Fe‐SZ is comparable with that of Ca‐SZ, Mg‐SZ and Mn‐SZ prepared by this method. 相似文献
13.
(NH4)3[M2NCl10] (M = Nb, Ta): Synthesis, Crystal Structure, and Phase Transition The nitrido complexes (NH4)3[Nb2NCl10], and (NH4)3[Ta2NCl10] are obtained in form of moisture-sensitive, tetragonal crystals by the reaction of the corresponding pentachlorides with NH4Cl at 400 °C in sealed glass ampoules. Both compounds crystallize isotypically in two modifications, a low temperature form with the space group P4/mnc and a high temperature form with space group I4/mmm. In case of (NH4)3[Ta2NCl10] a continuous phase transition occurs between –70 °C and +60 °C. For the niobium compound this phase transition is not yet fully completed at 90 °C. The structure of (NH4)3[Nb2NCl10] was determined at several temperatures between –65 °C und +90 °C to carefully follow the continuous phase transition. For (NH4)3[Ta2NCl10] the structure of the low temperature form was determined at –70 °C, and of the high temperature form at +60 °C. The closely related crystal structures of the two modifications contain NH4+ cations and [M2NCl10]3– anions. The anions with the symmetry D4h are characterized by a symmetrical nitrido bridge M=N=M with distances Nb–N = 184.5(1) pm at –65 °C or 183.8(2) pm at 90 °C, and Ta–N = 184.86(5) pm at –70 °C or 184.57(5) pm at 60 °C. 相似文献
14.
The lanthanum-mercury system has been studied by thermal- and X-ray analysis in the range 0–70 at.% La. The following compounds were found: LaHg (1078 °C), LaHg2 (1043 °C), LaHg3 (920 °C), LaHg4 (780 °C), La2Hg9~ (660 °C) and LaHg6~ (288 °C). Only two phases (1:1 and 1:2) melt congruently. A eutectic occurs at 41.0 at.% La and 980 °C.Crystal data for all the phases are given, and the behaviour of La in the formation of intermetallics with Zn, Cd and Hg is examined. 相似文献
15.
A sample of covellite of particle size 45–90 μm was heated in air at 20°C min–1 in a simultaneous TG-DTA apparatus. The phase compositions of the products at various temperatures were determined quantitatively
by XRD and FTIR. By 500°C, 5.8% of Cu2 O had formed, and this increased to a maximum of 44.8% at 585°C after which it decreased to zero by 750°C. 10% of CuO had
formed by 680°C, and then steadily increased to 83.6% at 1000°C. 5.9% of CuO⋅CuSO4 was found at 610°C, and increased to a maximum value of 79% after which it decomposed completely by 820°C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
KNO2 III below ?13°C is monoclinic, space group P21 or P21/m, with a0, b0, c0 = 4.677, 9.650, 6.395 Å, β = 93.8° at ?35°C. There is a further phase transformation between ?35°C and ?100°C to a new phase KNO2 VII, which is also monoclinic, space group P21 or P21/m: with a0, b0, c0 = 8.397, 4.773, 7.644 Å, β = 112° at ?100°C. Both these phases appear to be ordered. 相似文献
17.
Nanocrystalline BaSnO3 with a primary particle size of 40–60 nm was prepared through hydrolysis of a barium tin isopropoxide and following crystallization.
The thermal decomposition, the crystallization and the microstructure of the obtained powders were investigated with the help
of TG-DTA, IR, XRD, HRSEM and HRTEM. The organic rest groups in the as-prepared powder decompose thermally at 350°C, which
is accompanied by the building of BaCO3 that disappear again at 600°C. The crystallization of BaSnO3 takes place at 500–600°C. Single-phase BaSnO3 powders have been obtained at a temperature as low as 600°C. The amorphous as-prepared powder shows a cluster structure.
Nucleation of BaSnO3 beginning at 350°C was observed under HRTEM, and the spherical nano-particles of BaSnO3 calcined at 760°C crystallize well and are strongly aggregated. The presented results indicate a heterogeneous nucleation
and growth mechanism by the formation of BaSnO3. 相似文献
18.
Sodium cyclo-octaphosphate heptahydrate, (NaPO3)8 · 7H2O, has been made by heating lead cyclo-tetraphosphate at 340°C, dissolving the thermal product in a 3% aqueous solution of tetrasodium ethylene-diaminetetraacetate, and then crystallizing it by addition of sodium chloride and acetone to the solution. When the cyclo-octaphosphate was heated up to 400°C, it decomposed to produce phosphates with both shorter and longer chain lengths. A main product at 300° to 350°C was sodium cyclo-triphosphate, and the thermal product melted at about 630°C. 相似文献
19.
A. M. Sarwaruddin Chowdhury Christina Schmidt Klaus Neuking Gunther Eggeler 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):707-712
An interesting comparative case study on thermomechanical cycles including programming, cooling, unloading and heating to trigger the 1WE was done using Veriflex® at 62°C (T < Tg close to and below 5°C of Tg) and also at 72°C (T > Tg, close to and above 5°C of Tg) for slightly low strains (?m = 70%) and the recovery time of 10 min. Accumulation of strain was estimated during the thermomechanical treatments for using both 70% strains at 62°C (T < Tg), as well as at 72°C (T > Tg). Recovery ratios for 70% strains at 62°C (T < Tg), as well as for 72°C (T > Tg) were also estimated. It turns out that programming, cooling, unloading and heating to trigger the 1WE causes an increase of irreversible strain and is associated with a corresponding decrease of the intensity of the 1WE, in particular, during the first thermomechanical cycles. A LSCM (Laser Scanning Confocal Microscopic) study shows very little change in surface structure which evolved during cycling up to 70% strains at 72°C (T > Tg). 相似文献
20.
The thermal decomposition of natural iowaite of formula Mg6Fe2(Cl,(CO3)0.5)(OH)16·4H2O was studied by using a combination of thermogravimetry and evolved gas mass spectrometry. Thermal decomposition occurs over
a number of mass loss steps at 60°C attributed to dehydration, 266 and 308°C assigned to dehydroxylation of ferric ions, at
551°C attributed to decarbonation and dehydroxylation, and 644, 703 and 761°C attributed to further dehydroxylation. The mass
spectrum of carbon dioxide exhibits a maximum at 523°C. The use of TG coupled to MS shows the complexity of the thermal decomposition
of iowaite.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献