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Abstract  

There is a thin layer of organic lubricant on commercial silver flake surfaces. This lubricant layer is a fatty acid salt formed between a fatty acid and silver flake surfaces. Thermal decomposition behavior of the silver flake lubricant is investigated in this study. The heat flow and mass loss of a silver flake are studied using differential scanning calorimetry (DSC) and thermogravimetry (TG), respectively. The silver flake is also oven heated to different isothermal temperatures (150,190, 250 and 300C) for one h. Then chemical nature of the lubricant of the heated silver flake sample are studied using diffuse reflectance infrared Fourier transfer spectroscopy (DRIFTS). Based on the results, a mechanism of thermal decomposition of the silver flake lubricant is proposed. It is found that decomposition of the lubricant - the fatty acid salt -includes the release of the fatty acid, formation of short chain acids by decomposition of hydrocarbon moiety of the fatty acid, and formation of alcohols through decarbonation of the short chain acids.

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Abstract  

There is a thin layer of organic lubricant on commercial silver (Ag) flakes that are widely used as the fillers in electrically conductive adhesives (ECAs). This lubricant layer highly affects the properties such as conductivity of the ECAs. Therefore, understanding the behavior of Ag flake lubricant layer is essential for developing high performance ECAs. This work is aimed at studying the chemical nature of the lubricant layer, interaction between the lubricant layer and Ag flakes, and thermal behavior of the lubricants during heating. A blank Ag powder is ball-milled into Ag flakes with five fatty acids that have different carbon–hydrogen chain length as lubricants. After lubrication, the Ag flakes are studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry (TG), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). It is found that (i) Ag flakes lubricated with fatty acids of different chain lengths have exothermic DSC peaks and mass losses at different temperatures, (ii) the lubricant layer on the lubricated Ag flake surfaces is a salt formed between the acid and Ag, and (iii) exothermic DSC peaks (in air) of a lubricated Ag flake is probably due to the oxidation of lubricant layer on the Ag flake surface.

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Abstract  

We study the L p -saturation for the linear combination of Bernstein-Kantorovich operators. As a result we obtain the saturation class by using K-functional as well as some modulus of smoothness.

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Summary  

A tail-made polymer matrix is proposed to remove strontium ions from aqueous solutions. The removal behavior of strontium ions on a crosslinked copolymer containing methacrylic acid as functional groups was investigated as a function of sorptive concentration, time, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solution. It is found that a maximum adsorption of Sr(II) ions can be obtained on the crosslinked copolymer after 30 minutes and at pH 8. The increase of Sr(II) ion concentration in the solution resulted in an increase in the amount of Sr(II) ions adsorbed on the crosslinked copolymer containing methacrylic acid as functional groups. However, after a maximum of Sr(II) concentration in the solution, the percentage of adsorbed Sr(II) ions decreased. The adsorption data are well represented by the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The adsorption capacity of the copolymer and the free energy change were calculated by using the D-R isotherm. For the adsorption of Sr(II) ions on the crosslinked copolymer the thermodynamic parameters (DH°,DS° andDG°) were calculated.

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Abstract  

The effect of excipients on the secondary structure of lyophilized proteins was studied through second-derivative Fourier transform infrared (FTIR) spectroscopic analysis. The glass transition temperature (T g), denaturation temperature (T d) and moisture content were determined by differential scanning calorimetry (DSC) and thermogravimetry (TG). T g, T d and the preservation of protein secondary structure were found to be dependent upon the type and amount of the excipient included in the formulation. Meanwhile, the lyophilized proteins easily adsorbed amounts of moisture during storage to reduce their T gs and stability.

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Abstract  

Temperature programmed combustions (TPC) of Yang-Quan anthracite, Liao-Cheng lean coal and Li-Yan bituminous coal in oxy-fuel atmosphere were conducted in a thermogravimetric analyzer and characteristic parameters were deduced from the TG-DTG curves. The results showed that combustion got harder to progress as the coalification degree increasing. Within range of 40%, effect of heightening O2 concentration favored the combustion process, but beyond this zone, the effect leveled off. The model-fitting mathematical approach was used to evaluated the kinetic triplet (f (α), E, A) through Coats–Redfern method. The calculation showed that D 3-Jander was the proper reaction model and the evaluations of E and A validated the experimental results.

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Summary  

Radionuclide (137Cs, 238U, 232Th and 40K) concentrations were determined in a sediment trap and bottom sediment samples collected from a station at the eastern Turkish coast of the Black Sea. The specific activity of the 137Cs radionuclide in the settling particles ranged from 0.04±0.01 to 0.10±0.02 Bq. g-1dry weight. The calculated flux rate of the 137Cs was between 0.37 and 2.59 Bq. m-2. d-1in the sampling periods of 2002 and 2003. The 137Cs concentration in the bottom sediment profile were between 0.039±0.013-9.083±0.017 Bq. g-1dry weight in the same station. The vertical profile of the radionuclides suggests that they have little mobility during the 17 years after the Chernobyl accident.

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Thermal decomposition of the carbon nanotube/SiO2precursor powders

Thermal analysis coupled with mass spectrometry

Journal of Thermal Analysis and Calorimetry
Authors:
H. Yu
,
C. Lu
,
T. Xi
,
L. Luo
,
J. Ning
, and
C. Xiang

Summary  

TG-DSC-MS (thermogravimetry-differential scanning calorimetry-mass spectrometry) coupling techniques were used to make a simultaneous characterizing study for the thermal decomposition process of the carbon nanotube (CNT)/SiO2precursor powders prepared by rapid sol-gel method. The thermal stability of the CNT and the SiO2pure gel were investigated by TG-DSC. The results showed that the oxidation of CNT began from 530 and combusted at about 678C at the heating rate of 10C min-1in air. Moreover, the faster the heating rate, the higher the temperature of CNT combustion. The appropriate calcinations temperature of the CNT/SiO2precursor powders should be held for 1 h at 500C.

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