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Two new types of reversed-phase sintered plate have been prepared used in planar electrochromatography (PEC). One was bonded with phenyl, instead of octadecyl, without end-capping or with different amounts of end-capping and the other was bonded with octadecyl and then end-capped with phenyl instead of methyl. Both worked well with mobile phases containing no buffer salts, and high potential could be used with low Joule heating. Four dyes were used as samples to examine the characteristics of these two types of plate in planar electrochromatography. The former was unsatisfactory but the latter gave satisfactory results. Our preliminary work revealed that suitable bonding of octadecyl was from 0.03 to 0.06 whereas suitable bonding of phenyl for end-capping was from 0.005 to 0.02, which was readily achieved.

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resulting mixture was compressed into pellet form by applying pressure around 498 MPa using a hydraulic press. These pellets were sintered at 1,050 °C for 2 h. The sintered pellets were coated with silver paint to act as electrodes for the electrical

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Summary The disposal of used automotive tires has caused many environmental and economical problems to most countries. We propose the use of rice husk as filler for increasing the value of recycled tire rubber. Thermal degradation of both components and their sintering mixtures is presented in this paper. Thermal decomposition of rice husk occurs in various steps in the temperature range between 150 and 550°C. This complex process is the result of the overlapping of thermal decomposition of the three major constituents common in all lignocellulosic materials, i.e., hemicellulose, lignin and cellulose. Hemicellulose is degraded at temperatures between 150 and 350°C, cellulose from 275 to 380°C and lignin from 250 to 550°C. The degradation process of major constituents of scrap tires or their composites is observed at temperatures between 150 and 550°C. For composites, the addition of rice husk (maximum 25%) produces an increase in the mass loss rate. This effect is higher as the amount of rice husk increases. However, the degradation initial temperature of elastomeric matrix is not affected with addition of rice husk. Apparent kinetic parameters were also studied by the isoconversional Friedman method. We observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed.

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A thermal strengthening process, which occurs during low-temperature heating of binder-free silicon nitride, has been investigated using simultaneous thermal analysis, dilatometry and FTIR and shown to occur in separate stages over clearly identifiable temperatures. Reactions which give the strengthening are the loss of physically and chemically combined water and the decomposition of ammonium carbonate and various hydrosilicates. Compacts have bend strengths of 8–10 MPa after strengthening at 500°C and 30–34 MPa after strengthening at 900°C. High-temperature dilatometry shows several stages of sintering. The maximum rate occurs at 1800°C with shrinkage commencing at 1450°C. Densities of 98.3% theoretical are obtained on heating to 1900°C.

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Summary The effect of sintering on the maximum capture efficiency of CO2 is studied, using a carbonation/calcination cycle for a series of samples with different stoichiometries of dolomite and calcite. For the materials that belong to the categories of limestone and dolomitic limestone, sintering decreases the extent of carbonation significantly at the two different highest temperatures studied. The extent of carbonation for the same maximum heating temperature depends mainly on the percentage of dolomite. Sintering is negligible in the dolomitic rocks, especially at the maximum heating temperature of 1005°C. The composition of the carrier gas does not seem to play a significant role. The reduction of the extent of carbonation at the second heating /cooling cycle in limestone, and the durability after enough successive cycles of calcination/carbonation in the dolomitic rocks, does not seem to be affected by the maximum temperatures of calcination that were used at the experiments.

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Based on an RP-18 sintered plate, a new type of plate, RP-18 sintered aluminum nitride ceramic plate, was manufactured, which was made from silica gel and glass powders sintered on an aluminum nitride ceramic plate by bonding octadecyl and methyl silanes in suitable proportion. The key step of making such a plate was to soak the ceramic plate in the solution of sodium hydroxide before coating; other steps were the same as those of conventional RP-18 sintered plates. Besides its high mechanical stability and regeneration ability, the plate could work perfectly without addition of any buffer salts to mobile phase in planar electrochromatography (PEC) and was superior in eliminating joule heating.In this work, we used only the conventional apparatus to study the superiority of the new plate in eliminating joule heating from one side of the thin layer. The new plate would exhibit more of its superiority if it were used on pressurized PEC (PPEC) to eliminate joule heating from two sides of the thin layer.

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A kinetic model for the reaction sintering of oxide ceramics in the system Al2O3–SiO2–ZrO2 using mixtures of intermetallic compounds is presented. A 2D finite-difference model is developed to describe the exothermic gas-solid reactions taking place during the firing of ZrAl3/ZrSi2 powder compacts. The model accounts for the oxidation kinetics of the powder particles, as well as the consumption and diffusion of gaseous oxygen through the porous matrix. Additionally, possible changes in the pore structure of the green body due to the oxidation reactions and sintering effects are incorporated in the model. The resulting differential equations are coupled with a two-dimensional Fourier heat balance equation leading to a system of nonlinear partial differential equations, which is solved by the numerical method of lines. The influence of different processing parameters like sample composition and heating cycle on the reaction sintering process is investigated and the model-predicted reaction behaviour is compared to experimental results.

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Feasibility of using fixed bed column of conventional ion exchangers/sorbent and chemical precipitation based processes have been examined for the effective removal of the very low levels of 106Ru activity from NH4NO3 effluent generated during wet processing of rejected sintered depleted uranium fuel pellets. Based on the results, a simple process involving precipitation of cobalt sulphide along with ferric hydroxide was selected and further optimization of process variables was carried out. The optimized process has been found to be highly efficient in reducing 106Ru activity down to extremely low levels.

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Noncontact dilatometry, compared to differential scanning calorimetry (DSC), was used together with scanning electron microscopy and densification behavior studies to investigate the parameters that govern the kinetics of transformation of kaolin to mullite during sintering. Three kaolinitc clays from Cameroon, with different SiO2/Al2O3 molar ratio, were examined. The temperatures of mullite nucleation were 973, 979, and 984 °C at 5 °C/min heating rate, respectively, for values of SiO2/Al2O3 molar ratio equal to 4.22, 2.22, and 2.08. At 20 °C/min heating rate, the temperatures are shifted to higher values, 992, 997, and 1,001 °C. The mullitization phenomenon, which includes a first step of nucleation and a second one of crystal growth, presented activation energy in the range of 650–730 kJ/mol, depending on the nature of the sample investigated. These values, obtained by noncontact dilatometer measurements, were comparable to those obtained by means of DSC and are in agreement with literature values. The difference in sintering kinetics for the three kaolinitic clays could explain the different morphologies obtained for the mullite grains.

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A non-destructive activation analytical method developed for the determination of the axial concentration distributions of Al, Si and K residual additives in sintered tungsten rods is briefly described. A 14 MeV neutron generator is used to produce the reactions27Al(n, p)27Mg,28Si(n, p)28Al and39K(n, 2n)38K and the activities are compared with standards. A weighted least-squares fitting program is used for peak area determination of the scintillation spectra. A scheme of the irradiating and measuring arrangement with a pneumatic sample-transfer system is presented. The system is applicable to large-scale routine analysis and lends itself well to automation. The results of preliminary measurements with this arrangement are given.

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