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- Author or Editor: D. Wang x
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Abstract
Radioiodination of tri-n-butylstannyl-3-quinuclidinyl benzilate (TQNB) and N-succinimidyl-3-(tri-n-butylstannyl) benzoate (STB) was studied. STB was radiolabeled efficiently using iodogen to prepare radioactive N-succinimidyl-3- iodobenzoate (S125IB). TQNB was radioiodinated using Chloramine-T to obtain radioactive iodo-3-quinuclidinyl benzilate (125IQNB). Both S125IB and 125IQNB showed good stability at room temperature in the dark.
Abstract
Lead zirconate titanate (PZT) ceramic powder has been synthesized from metal nitrate solutions using the EDTA-gel method with different nitric acid/EDTA ratios. It was found that the thermal decomposition of the precursor was strongly affected by the nitric acid/EDTA ratio, the amount of sample, the atmosphere, and the heating rate. Crystallization of the perovskite PZT phase initiated at external temperatures as low as 250°C, as a result of the exothermic decomposition reaction of the nitrate-EDTA complexes. Possible reaction schemes are suggested and discussed to describe the thermal decomposition of PZT-EDTA precursors under different experimental conditions.
Abstract
A new compound cyclohexyl-t-butyldimethylammonium tetraphenylborate, [C6H11N(CH3)2(C(CH3)3)]BPh4 has been prepared, and its decomposition mechanism was studied by TG. The IR spectra of the products of thermal decomposition were examined at every stage. Kinetic analysis for the first stage of thermal decomposition process was obtained by TG and DTG curves, and kinetic parameters were obtained from the analysis of the TG-DTG curves with integral and differential equations. The most probable kinetic function was suggested by comparison of kinetic parameters.
Abstract
Raw chemicals such as metal nitrates and chlorides were found to affect the thermal decomposition behaviour of EDTA-gel precursors used for the production of ceramic powders. Fine, homogeneous ceramic powders were produced from nitrate solutions while chlorides gave segregated phases. In studies on the production of lead zirconate titanate (PZT) using chlorides, the segregation and loss of lead was observed and shown to be caused by the formation and evaporation of PbCl2. Thermal analysis (DTA/TG) quantitatively proved the suggested reaction mechanism for this phase segregation. Crystallization of the desired perovskite phase of lead zirconate titanate (PZT) and barium titanate (BT) initiated at temperatures as low as 250°C in the nitrate-EDTA precursors. Water of crystallization and formation of BaCO3 in the barium titanate precursor were suggested to account for differences in the observed decompositional behaviours of the BT and PZT precursors.
Abstract
In 1951, unsaturated prairie soil was contaminated with fission products and actinides. Fifty years later, in 2001, soil samples were collected from the contaminated site. This paper describes the techniques used to analyze these samples, including gamma-spectroscopy (GS) for 137Cs, neutron activation analysis (NAA/GS) for 238U, liquid scintillation counting (LSC) for 90Sr and inductively coupled plasma mass spectroscopy (ICP-MS) for 238U and 113mCd. As expected, ICP-MS was found to have the lowest detection level, while the techniques were ranked in order of increasing uncertainty as GS, NAA/GS, ICP-MS and LSC.
Abstract
The complex (C11H18NO)2CuCl4(s) was synthesized. Chemical analysis, elemental analysis, and X-ray crystallography were used to characterize the structure and composition of the complex. Low-temperature heat-capacities of the compound were measured by an adiabatic calorimeter in the temperature range from 77 to 400 K. A phase transition of the compound took place in the region of 297–368 K. Experimental molar heat-capacities were fitted to two polynomial equations of heat-capacities as a function of the reduced temperature by least square method. The peak temperature, molar enthalpy, and entropy of phase transition of the compound were calculated to be T trs = 354.214 ± 0.298 K, Δtrs H m = 76.327 ± 0.328 kJ mol−1, and Δtrs S m = 51.340 ± 0.164 J K−1 mol−1.
Summary
The sorption and desorption of radionuclide 90Sr2+were investigated on untreated calcareous soil and two treated soils to remove organic matter and calcium carbonate using batch technique. The experiments were carried out at ambient condition, pH 7.8±0.1 and in the presence of 0.001M NaCl. Effects of fulvic acid and ionic strength on the sorption of 90Sr2+on calcareous soil were also studied. It was found that the sorption isotherms are linear in the strontium concentration range used herein, and the sorption of 90Sr2+on the calcareous soil can be described as a reversible sorption process and the sorption mechanism is mainly ion-exchange. The sorption is dependent on ionic strength, and fulvic acid enhances the sorption of 90Sr2+on calcareous soil. Organic matter present in the calcareous soil is a significant trap of 90Sr2+and is responsible for the sorption.
Abstract
The aim of this study is to investigate the melting/freezing characteristics of paraffin by adding Cu nanoparticles. Cu/paraffin composite phase change materials (PCMs) were prepared by a two-step method. The effects of Cu nanoparticles on the thermal conductivity and the phase change heat transfer of PCMs were investigated by the Hot Disk thermal constants analyzer and infrared monitoring methods, respectively. The maximum thermal conductivity enhancements up to 14.2% in solid state and 18.1% in liquid state are observed at the 2 wt% Cu/paraffin. The photographs of infrared monitoring suggest that the melting and freezing rates of Cu/paraffin are enhanced. For 1 wt% Cu/paraffin, the melting and freezing times can be saved by about 33.3 and 31.6%, respectively. The results provide that adding nanoparticles is an efficient way to enhance the phase change heat transfer of PCMs.
Abstract
Adding a magnetic field gradient to the conventional TG system constructs the magnetic thermogravimetry analysis (TG(M) i.e. Faraday methods) and the magnetic derivative thermogravimetry (DTG(M)) techniques. We used the techniques to study the nanocrystalline processes of the FeCuNbSiB and FeCuNbCoSiB amorphous alloys. Some problems of their applications such as the characteristic temperature T min and T C are also discussed in detail.
Abstract
The combustion behavior of Shuangya Mountain (SYM) coal dust has been investigated by means of TG in this paper. The reaction fraction 
can be obtained from isothermal TG data. The regressions of g(), an integral function of
vs. t for different reaction mechanisms were performed. The mechanism of nucleation and nuclei growth is determined as the controlling step of the coal dust combustion reaction by the correlation coefficient of the regression, and the kinetic equation of the SYM coal dust combustion reaction has been established.
