Isothermal characteristics of methane adsorption and changes in the pore structure before and after methane adsorption with high-rank coal

The pore structure is an essential factor that influences the isothermal characteristics of methane adsorption of coal, and the pore structure is altered after methane adsorption. In this study, a high-rank coal sample was investigated via methane adsorption isothermal measurement, and changes in the pore structure were studied using low-pressure N2 adsorption and low-pressure CO2 adsorption before and after the methane adsorption. The excess adsorption capacity exhibits a rapid increase at low pressure, reaching a maximum when the test pressure is approximately 8 MPa. Following that, the excess adsorption capacity of the high-rank coal tends to decrease. After the methane adsorption, the pore volume and specific surface area of the micro-, meso-, and macropores increase as compared to those before the methane adsorption, especially for micropores with apertures greater than 0.8 nm and mesopores with apertures below 10 nm. This is mainly caused by high pressure in the methane adsorption, indicating a pressure effect on the pore structure after the methane adsorption. After the methane adsorption, the ratio of pores with various sizes in the high-rank coal is enhanced, but the connectivity for meso- and macropores presents a slight decrease.

Isothermal measurement of current-voltage characteristics of Gunn diodes with reflection of their discontinuities and hysteresis

Requirements to the measuring setup are formulated, which make it possible obtaining isothermal current-voltage (I-V) characteristics of the Gunn diode with reflection of their discontinuities, region of negative differential resistance, and hysteresis. The influence of the inductance of the test pulses, source on the occurrence of self-excitation in the connecting transmission line is investigated. The maximum permissible values of the inductance of the test signal source are indicated. Operation of the measuring circuit without self-excitation was experimentally achieved in most of the region with negative differential resistance. The isothermal I-V characteristics of the Gunn diode were measured with a controlled systematic error due to the comparing the measurement result with the developed model of the I-V characteristic.

Thermal Decomposition Kinetic and Electrochemical Properties of KZn2(PO4)(HPO4)

Thermal decomposition kinetic reaction parameters of KZn2(PO4)(HPO4) was investigated by non-isothermal measurement used in a multivariate non-linear regression analysis. The anticorrosive performance of the phosphate extracts in different pH 3.5% NaCl was studied by polarization and open circuit potential measurements. Kinetics analysis shows that the decomposition of KZn2(PO4)(HPO4) acts as a double-step reaction of : a n order autocatalytic reaction (Cn) with n =1.0791, E1 = 365.06 kJ/ mol, A1 =8.69×1022s−1 is followed by a expended Prout-Tompkins reaction (Bna) with n=2.6548, E2 = 390.91 kJ /mol, A2 = 5.37×1024 s−1. In different pH 3.5% NaCl extracts, KZn2(PO4)(HPO4) functions as a cathodic inhibitor on steel and is even superior to other phosphates in efficiency. The inhibiting efficiency of the pigments on steel decrease in the order: KZn2(PO4)(HPO4) > aluminum zinc phosphate > zinc phosphate ≧ aluminum triphosphate

The Analysis of Space Charge Behavior in Nylon 11

A combined isothermal and non-isothermal measurement technique is described for analyzing space charge behavior in dielectric materials. The experimental conditions are chosen so that the dipolar effects are insignificant and the measured current is mainly due to space charge detrapping. For polyamide 11 four peaks have been identified above the poling temperature. As the difference between the peak temperature and the poling temperature increases, the apparent activation energies decrease suggesting that only the faster modes participate to the charging process. The charge associated to the apparent peak and the peak at 96 °C scales linearly with the polarization field. The injected space charge at 35 °C is very stable at 150 °C, an important fact with respect to technological applications of polyamide 11 as an electroactive material.