2003 Vol. 16, No. 1

Letter
In the product of carbon made from tar oil by plasma pyrogenation, some nanowires, whose diameter is 9~20 nm and whose length is 300 nm were found. The result of X-ray Energy Dispersed Spectrum (EDS) indicated that it is a new compound K2Ti8O15, which has never been reported before. Compared with the corresponding stoichiometry compound K2Ti8O15, it is a non-stoichiometry compound in which two oxygen atoms are absent. It is due to the fact that the intensive deoxidization occured in the experimental process and the valence of titalium is alterable. Its microstructure in detail by high revolution electromicroscopy (HREM) and X-ray diffraction were studied.
Article
The multi-photon dissociative photoionization dynamics of CF3I has been studied with femtosecond two-color pump-probe time of flight mass spectra at a pump pulse of 265 nm and a probe pulse of 398 nm. The life constants of CF3I+ and its fragment ions CF3+ and I+ are obtained as (96±7), (198±130) and (167±6)fs, respectively. The multi-photon dynamics leading to these ions differ. CF3I+ corresponds to a (1+2′) transition with one-photon pump excitation to the A band of CF3I. CF3+ are mainly formed by a tow-photon probe excitation to the CF3+ with subsequent dissociation of parent ions. I+ are produced in (2+2′) combined with (1+1′+2′) process. The results provide information on the multi-photon pathways involved.
A pulsed laser photoacoustic (PA) instrument operating under visible and ultraviolet range was reported, which used a YAG pumped dye laser (width 8 ns, repetition rate 10 Hz) as the light source. Photoacoustic spectra of C2H2 overtone excitation and A1Au←X1Σ+g electronic transition were obtained using the instrument and the dependence of PA signal intensity on the sample pressure and the laser energy was measured. The application of pulsed PA to electronic transition was less reported before. Because of the simplification of its theoretical treatment and experimental operation, the pulsed PA instrument can replace resonant (or non-resonant) moderate cw PA instrument in almost all the cases except the ultra high-resolution spectroscopy. The difference between pulsed and cw moderate PA was also discussed in the text.
Employing the self-adaptive parameter adjustment scheme, the chaotic dynamical behaviors in the coupled Belousove-Zhabotinsky-CSTR chemical system were investigated numerically. The confirmation of synchronization is using the criteria of maximum transverse Lyapunov exponent. The results show that when all the variables are involved in the parameter adjustment rule, the chaos synchronization between the response and the target systems were obtain. However, as only some of the variables can be detected easily in the real experiment, there are difficulties in employing this scheme experimentally. Therefore, that scheme to investigate the role of single variable separately were modified. The results show that no chaos synchronization can be obtained when [Br-] and [HBrO2] are used separately, except when [Ce4+] and [BrMA] are used. However, there is no easy way to detect [BrMA] in the experiment, [Ce4+] becomes the unique feasible variable involved in the adjustment role. Besides, the synchronization efficiency of different combinations of stiff constant and damping constants has been studied by means of synchronization-arriving time.
The ionic polarizable ability parameter is definedasgi. The connectivity index of the polarizable abiltym G is introduced fromgiand based on the adjacency matrix of molecular topological graph. Because different ions should not have the same oxidation number or the same main quantum numbers, 0G、1G amongm G have good structural selection for inorganic molecules. The 0G and 1G of 64 alkali and alkaline-earth metal oxide halide, sulfide, selenide and telluride are calculated. The result shows: the 0G and 1G all have a positive correlation with the atomic number and size of molecules, but have a negative correlation with the atomic ploarizable ability in molecules. Since the standard entropy of compound increases with the atomic number of compounds an decreases with the atomic ploarizable ability, the standard entropies of compounds have a positive correlation with the 0G and 1G of compounds. The standard entropies of 64 alkali and alkaline-earth metal oxide, halide sulfide and selenide are correlated with the0Gand1Gof these compounds.
The parameters of strong detonation for Nitromethane (NM) were calculated with the two-phase Repellent-Translation Equation of State(two-phase R-T EOS).The results are quite consistent with the data of quasi-steady strong detonation experiment in NM that contain velocities, pressures and temperatures. This not only tested the calculation method, but also the ZND theory of detonation and the two-phase R-T EOS again. Furthermore, the experiment methods were supported. The strong detonation parameter calculation method with the constant-kequation of state was conditionally confirmed.
For the system without adiabatic walls, rigid walls or semi-permeable walls and without chemical reactions or without other restrictions except restrictions of phase equilibrium conditions, if the number of components of the system is k and the number of phases is φ, the degree of freedom of the system at equilibrium is f=k-φ+2. Because the degree of freedom is incapable of being negative, f=k-φ+2≥0, viz.φ≤k+2. For the heterogeneous equilibrium, the number of phases is at least 2, so φ=k+2-f≥2, viz. f≤k. Hence the range of change of φ and f is 2≤φ≤k+2,0≤f≤k, respectitvely. If φ=k+2, there are no independent variables in the system at equilibrium. If φ=k+1, there is one independent variable; if the temperature is selected as the independent variable, the other dependent variables can be expressed as the function of the temperature. If φ=k, there are two independent variables; if the temperature and pressure are selected as the independent variables, the other dependent variables can be expressed as the function of the temperature and pressure. If 2≤φ≤k-1, there are more than two independent variables; if the temperature, pressure and some concentrations are selected as independent variables, the other dependent variables can be expressed as the function of the temperature, pressure and these concentrations. The differential relationships of dependent variables and independent variables are educed out according to the principle of phase equilibriums for 2≤φ≤k-1. In any phase the number of the variables is(k+1), viz. temperature T, pressure p and (k-1) mole fractions x1, x2,…, xk-1. The temperature and pressure are common variables of every phase. The number of independent variables is at best k for the heterogeneous equilibriums of k components. The temperature, pressure and (k-2) concentrations are selected as independent variables. The independent concentration variables are selected entirely from the first phase and the concentration variables of the other phases all act as dependent variables. There is at least one dependent concentration variable in the first phase.
The composite film of nanometer AgO2/silane coupling reagent aminopropyltriethoxy-silane (CH3O)3Si(CH2)3NH2was prepared on single-crystal silicon by the self-assembly of silane on the hydroxylated substrate followed with the deposition of nanometer AgO2 on the silane SAMs from an aqueous Ag2O gel. The resultant composite film was characterized by means of X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The contact angles of distilled water on the silane SAMs and the composite film were measured to compare the surface states. The experiment shows that the nanometer Ag2O can be easily incorporated in the silane SAMs and lead to changed surface state of the composite film. Nanometer Ag2O crystallites in a size of about 20 nm distribute quite uniformly in the composite film. It was anticipated that the composite film might find application to the protection of single-crystal Si substrate in MEMS devices and also propose a novel single electron device structure based on nanoscale Ag2O colloidal particles.
MgFe layered double hydroxides (LDH) have been synthesized at high supersaturation using a new method, involving separate nucleation and aging steps. The influence of aging temperature and aging time on the selectivity of crystal growth in different directions and the particle size of MgFe-LDH have been systematically investigated. XRD analyses show that the arrangement of layered cation in MgFe-LDH becomes more complete with increasing Mg∶Fe molar ratio. It has been shown that with increasing aging time at the same temperature, the crystallinity of MgFe-LDH increased and the particle size became larger. The same effect was observed when samples were aged at an increasing temperature for a fixed period, but the particle size of MgFe-LDH increased dramatically with the increasing aging temperature. The rate of crystal growth inadirection [110] crystalline face was found to be greater than that incdirection [002] crystalline face and the size of the crystallites in the adirection was larger than that in thecdirection under all experimental conditions.
SnO2 nanospheres and rhombus SnO2 nanocrystallites have been prepared with SnCl4·5H2O raw materials using a solvothermal process. Two kinds of prepared products have been characterized by means of X-ray diffraction (XRD), selected area electron diffraction (SAED) and transmission electron microscope (TEM) and the formation mechanism about the two kinds of prepared products have been analyzed. Transmission electron microscope showed the prepared product in oleic acid contained 3.5 nm ultrafine particles. This structure tends to have a high specific surface area and favorable for the application in gas-sensitive.
The stability constants of the ternary mixed-ligand complexes of Pt(ArL)(NTP)n- (n=2 or 3) have been determined by potentiometric pH titration in aqueous solution (I=0.1 mol/L, KNO3; 25℃), where NTP refers to adenosine 5′-triphosphate (ATP) and uridine 5′-triphosphate (UTP); ArL refers to 1,10-phenanthroline (Phen), 2,2′-bipyridyl (Bpy), and L-tryptophane (Trp). The stability difference between the ternary complexes and the binary complexes has been compared and discussed. The increased stability in the ternary mixed-ligand complexes can be attributed to the cooperative effect of πA-πB and the intramolecular ligand-ligand aromatic-ring stacking interaction. The extent of the intramolecular aromatic-ring stacking interaction in the ternary platinum (Ⅱ) complexes has been calculated, which is in accord with the size of the aromatic rings forming the stack.
Electronic structures and properties of metallocene [(eat5-C5H4R)Mo(CO)3]2(R: SiMe3,Si2Me5) have been calculated by means of G98W package and taking Lanl2dz basis set. The stabilities of the complexes, some frontier molecular orbital energies, the populations of the atomic net charges in these complexes and the composition characteristics of some frontier mlecular orbitals have been investigated. The results show that the structure units of the title complexes are energetically stable and they may exist as building blocks. Some results obtained may be useful as references for the synthesis of metallocene complexes and the analysis of the molecular assembly.
Effect of oxygen on the thermal degradation of PMMA was studied by mass spectrometry and thermal analysis with TG and DTA. For radical polymeric PMMA, there were two main degradation models in N2: the end-chain scission model and the random chain-breaking model. The conversion rate at turning point was about 26%. Kinetic analysis results indicated the end-chain scission was controlled by diffusion process and the average activation energy E was 158.5 kJ/mol and lnA was 27.69. The random chain-breaking reaction was 1.5 order chemical reaction. The average activation energy E and lnA was 214.79 kJ/mol and 40.46, respectively. In air, there were also two stages of mass loss and the turning point conversion rate was about 70%. In the first stage, the decomposition of peroxy radicals has a notable effect on the overall degradation rate. The associated kinetic mechanism was first order chemical reaction and the average activation energy E was 130.32 kJ/mol and lnA was 24.81. In the second stage of mass loss, PMMA had already burnt and the reaction was also first order chemical reaction. The average activation energy and lnA were 78.25 kJ/mol and 13.97, respectively.
The chemical structure of O,O,O-tri-n-butyl phosphorothioate (TBSTP) and S,S,S-tri-n-butyl phosphorotetrathioate (TBTTP) synthesized in laboratory were analyzed by means of mass spectrometer(MS) and Bio-Red Win-IR spectrometer (FT-IR). The extreme-pressure, antiwear and friction-reducing properties of liquid paraffin with TBSTP and TBTTP as additives were examined with a four-ball machine. The worn surfaces of the steel ball were analyzed by means of X-ray photoelectron spectroscopy (XPS) and scanning electron micro-scopy (SEM). It has been found that the two compounds as additives in liquid paraffin are effective in improving the antiwear behavior and load-carrying capacity. But they can′t improve the friction-reducing behavior of liquid paraffin. The SEM morphologies and the XPS analytical results of the worn surfaces indicate that the additives absorbed in the surface by the physical or chemical process and tribochemical reactions were involved for steel-steel frictional pair, with the formation of a multiple boundary lubricating film composed of phosphorothioate and tribochemical reaction products of the lubricants.
The distribution of Ag+ in gelatin with respect to molecular weight was studied using gel exclusion chromatography? flame atomic absorption spectroscopy. Firstly, several gels used for isolating gelatin protein components were studied and the result indicated that dextran G-75 was favourable for the present study. The γ, β, α and other lower molecular weight components of gelatin could be isolated from each other by means of gel G-75. The results demonstrated that the Ag+ in gelatin was combined only with the α protein component and not with the γ or the β components.