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51.
The molar enthalpies of the solid–solid and solid–liquid phase transitions were determined by differential scanning calorimetry
for pure TbCl3 and KTb2Cl7, RbTb2Cl7, CsTb2Cl7, K3TbCl6, Rb3TbCl6 and Cs3TbCl6 compounds. Both types of compounds, i.e. M3TbCl6 and MTb2Cl7 (M=K, Rb, Cs) melt congruently and show additionally a solid–solid phase transition with a corresponding enthalpy Δtrs
H
0 of 6.1, 7.6 and 7.0 kJ mol–1 for potassium, rubidium and caesium M3TbCl6 compounds andΔtrs
H
0 of 17.1 (rubidium) and of 12.1 and 10.9 kJ mol–1 (caesium) for MTb2Cl7 compounds, respectively. The enthalpies of fusion were measured for all the above compounds with the exception of Rb3TbCl6 and Cs3TbCl6. The heat capacities of the solid and liquid compounds have been determined by differential scanning calorimetry (DSC) in
the temperature range 300–1100 K. The experimental heat capacity strongly increases in the vicinity of a phase transition,
but varies smoothly in the temperature ranges excluding these transformations. C
p data were fitted by an equation, which provided a satisfactory representation up to the temperatures of C
p discontinuity. The measured heat capacities were checked for consistency by calculating the enthalpy of formation of the
liquid phase, which had been previously measured. The results obtained agreed satisfactorily with these experimental data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
52.
Fabienne Poncin-Epaillard Barbara Pomepui Jean-Claude Brosse 《Journal of polymer science. Part A, Polymer chemistry》1993,31(11):2671-2680
Polyolefins and their model molecules, some n-alcanes, have been modified by a tetrafluoromethane microwave plasma. The chosen molecules are high-density polyethylene (HDPE) and hexatriacontane (HTC), low-density polyethylene (LDPE) and paraffin, and polycaprolactone (PCL) and octadecyl octadecanoate (ODO). It has been found, except for paraffin, that the model surfaces have the same behavior as the corresponding polymers. Plasma modification is described as the sum of two mechanisms: degradation and fluorination. These reactions seem to be competitive and parallel. Degradation and fluorination rates are dependent on treatment time and are practically independent on substrate position. A domain of fluorination exists near the edge of plasma, whatever the substrate in or outside plasma. © 1993 John Wiley & Sons, Inc. 相似文献
53.
The areas of the fusion and crystallization peaks of K3TaF8 and K3TaOF6 have been measured using the DSC mode of the high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities and the temperature dependence of the used calorimetric method sensitivity, the values of the enthalpy of fusion of K3TaF8 at temperature of fusion 1039 K: ΔfusHm(K3TaF8; 1039 K) = (52 ± 2) kJ mol−1 and of K3TaOF6 at temperature of fusion 1055 K: ΔfusHm(K3TaOF6; 1055 K) = (62 ± 3) kJ mol−1 have been determined. 相似文献
54.
Thermal decomposition of some hydrocarbon and chlorinated hydrocarbon compounds in metal capillary tubes used in an inlet system for high speed gas chromatography has been investigated. The metal tube is cooled to about ?75°C by a flow of cold nitrogen gas in order to focus a vapor sample cryogenically. A capacitive discharge power supply is then used to heat the metal tube resistively in order to revaporize the sample and introduce it to the separation column as a plug 5-10 ms wide. The effects of tube temperature, tube material, sample vapor residence time, and type of carrier gas on thermal cracking are described. Use of a copper-nickel alloy tube resulted in less cracking than either pure platinum or pure nickel. Cracking is more significant with hydrogen as carrier gas than with helium. Cracking also increases with increasing sample residence time in the hot tube. Quantitative sample injection with minimum decomposition can be obtained for a variety of aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon compounds. 相似文献
55.
Comment on papers by K. Shanahan that propose to explain anomalous heat generated by cold fusion 总被引:1,自引:0,他引:1
Edmund Storms 《Thermochimica Acta》2006,441(2):207-209
Dr. Shanahan has published two papers (Thermochim. Acta 428 (2005) 207, Thermochim. Acta 382 (2002) 95) in which he argues that excess heat claimed to be produced by cold fusion is actually caused by errors in heat measurement. In particular, he proposes that unrecognized changes in the calibration constant are produced by changes in the locations where heat is being generated within the electrolytic cell over the duration of the measurement. Because these papers may lend unwarranted support to rejection of cold fusion claims, these erroneous arguments used by Shanahan need to be answered. 相似文献
56.
Electron ionization (EI) mass spectra of 46 compounds from several different compound classes were measured. Their molecular ion abundances were compared as obtained with 70‐eV EI, with low eV EI (such as 14 eV), and with EI mass spectra of vibrationally cold molecules in supersonic molecular beams (Cold EI). We further compared these mass spectra in their National Institute of Standards and Technology (NIST) library identification probabilities. We found that
- Low eV EI is not a soft ionization method, and it has little or no influence on the molecular ion relative abundances for large molecules and those with weak or no molecular ions.
- Low eV EI for compounds with abundant or dominant molecular ions in their 70 eV mass spectra results in the reduction of low mass fragment ions abundances thereby reducing their NIST library identification probabilities thus rarely justifies its use in real‐world applications.
- Cold EI significantly enhances the relative abundance of the molecular ions particularly for large compounds; yet, it retains the low mass fragment ions; hence, Cold EI mass spectra can be effectively identified by the NIST library.
- Different standard EI ion sources provide different 70 eV EI mass spectra. Among the Agilent technologies ion sources, the “Extractor” exhibits relatively abundant molecular ions compared with the “Inert” ion source, while the “High efficiency source” (HES) provides mass spectra with depleted molecular ions compared with the “Inert” ion source or NIST library mass spectra.
57.
T.D. Klots P. Devlin W.B. Collier 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14):2445-2456
Infrared and Raman measurements for benzimidazole are presented and discussed, including its argon-matrix infrared spectrum. To assist in the assignment, benzimidazole's harmonic force fields for the 321G* and 631G* levels were scaled by scaled factors derived by fitting the respective computed force fields of other indene derivatives to previously reported experimental vibrational frequencies. Comparison to the best set of experimental wavenumbers, usually taken from the matrix, shows mean 321G* and 631G* deviations of 7.0 and 5.8 cm−1 for the planar modes, and 14.0 and 6.8 cm−1 for the nonplanar modes, respectively, with much of the error residing in imino-hydrogen group modes. Standard entropies are derived with the matrix wavenumbers and the methods of statistical mechanics. An attempt to determine standard entropies by calorimetric methods was unsuccessful. The triple-point temperature Ttp and enthalpy of fusion Δ1crHm only are reported. 相似文献
58.
In this paper, Co-60γ ray was used to irradiate the ointment cold cream at room temperature (25°C). We also used FTIR, GC and thin film chromatogram to analyse various irradiated samples. It was found that the ointment cold cream can be irradiated at dose of 5–35 kGy and at dose rate from 0.2 to 0.6 kGy/h at room temperature (25°C) without evident decomposition. At dose of 5–15 kGy, the number of bacteria can be reduced to hygienic standard value. The radiation sterilization is a safe method for killing the bacteria in the ointment cold cream. 相似文献
59.
Diantha R. Kelman Lisa F. Szczepura Karen I. Goldberg Werner Kaminsky Anne K. Hermetet Lily J. Ackerman John K. Swearingen Douglas X. West 《Journal of Molecular Structure》2002,610(1-3):143-150
N-2-(4-picolyl)-N′-2-chlorophenylthiourea, 4PicTu2Cl, monoclinic, P21/c, a=10.068(5), b=11.715(2),
β=96.88(4)°,
and Z=4; N-2-(6-picolyl)-N′-2-chlorophenylthiourea, 6PicTu2Cl, triclinic, P-1, a=7.4250(8), b=7.5690(16), c=12.664(3) Å, =105.706(17), β=103.181(13), γ=90.063(13)°, V=665.6(2) Å3 and Z=2 and N-2-(6-picolyl)-N′-2-bromophenylthiourea, 6PicTu2Br, triclinic, P-1, a=7.512(4), b=7.535(6), c=12.575(4) Å, a=103.14(3), β=105.67(3), γ=90.28(4)°, V=665.7(2) Å3 and Z=2. The intramolecular hydrogen bonding between N′H and the pyridine nitrogen and intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen, as well as the planarity of the molecules, are affected by the position of the methyl substituent on the pyridine ring. The enthalpies of fusion and melting points of these thioureas are also affected. 1H NMR studies in CDCl3 show the NH′ hydrogen resonance considerably downfield from other resonances in their spectra. 相似文献
60.
A general approach to information correction and fusion for belief functions is proposed, where not only may the information items be irrelevant, but sources may lie as well. We introduce a new correction scheme, which takes into account uncertain metaknowledge on the source’s relevance and truthfulness and that generalizes Shafer’s discounting operation. We then show how to reinterpret all connectives of Boolean logic in terms of source behavior assumptions with respect to relevance and truthfulness. We are led to generalize the unnormalized Dempster’s rule to all Boolean connectives, while taking into account the uncertainties pertaining to assumptions concerning the behavior of sources. Eventually, we further extend this approach to an even more general setting, where source behavior assumptions do not have to be restricted to relevance and truthfulness. We also establish the commutativity property between correction and fusion processes, when the behaviors of the sources are independent. 相似文献