Interfacial adhesion between fiber and matrix has a strong influence on composite mechanical performance. To exploit the reinforcement potential of the fibers in advance composite, it is necessary to reach a deeper understanding on the relation between fiber surface treatment and interfacial adhesion. In this study, air plasma was applied to modify carbon fiber (CF) surface, and the capability of plasma grafting for improving the interfacial adhesion in CF/thermoplastic composite was discussed and also the mechanism for composite interfacial adhesion was analyzed. Results indicated that air plasma treatment was capable of increasing surface roughness as well as introducing surface polar groups onto CF; both chemical bonding and mechanical interaction were efficient in enhancements of interlaminate shear strength of CF/PPESK composite, while mechanical interaction has a dominant effect on composite interfacial adhesion than chemical bonding interaction.

No abstract

No abstract

Hydrogen chloride (HCl) contributes substantially to the atmospheric Cl; both species could affect the composition of Earth’s atmosphere and the fate of pollutants. Here, we present the kinetics study for syn-CH3CHOO reaction with HCl using experimental measurement and theoretical calculations. The experiment was conducted in a flow tube reactor at a pressure of 10 Torr and temperatures ranging from 283 to 318 K by using the OH laser-induced fluorescence (LIF) method. Transition-state theory and quantum chemistry calculations with QCISD­(T) were used to calculate the rate coefficients. Weak negative temperature dependence was observed with a measured activation energy of −(2.98 ± 0.12) kcal mol–1 and a calculated zero-point-corrected barrier energy of −3.29 kcal mol–1. At 298 K, the rate coefficient was measured to be (4.77 ± 0.95) × 10–11 cm3 s–1, which was in reasonable agreement with 2.2 × 10–11 cm3 s–1 from the theoretical calculation.

In inductively coupled plasma sources, discharge transitions from electrostatic mode (E mode) to electromagnetic mode (H mode) and from H mode to E mode occur. In previous studies, only a few works paid attention to the effects of the impedance matching network. Cunge et al. [Plasma Sources Sci. Technol. 8, 576 (1999)] investigated the E-H and H-E mode transitions under two different impedance matching situations, but no physical mechanism or interpretation was presented. This issue is remained to be systematically and quantitatively investigated, and the underlying mechanism to be unveiled. In this paper, the effects of the impedance matching network were experimentally studied in electropositive argon gas by varying the series capacitance in an inversely L-shaped matching network. The positive and negative feedback regions are established according to the effect of varying the series capacitance on the output power of the rf power supply. It was found that under the same experimental parameters, the discharge mode transitions are apt to be discontinuous and continuous in the positive and negative feedback regions, respectively. In addition, the critical coil rf current (or applied power) at the mode transition, the hysteretic loop width, and the difference in applied power during the discharge mode transition vary with the series capacitance. The critical coil rf current at the E-H mode transition is not always higher than that at the H-E mode transition.

No abstract

In a low-pressure radio-frequency (13.56 MHz), inductively coupled argon plasma generated by a normal cylindrical rf coil, electric field, current density, and absorbed power density is calculated from magnetic field measured with a phase-resolved magnetic probe. The anomalous skin effect (ASE) for the cylindrical rf coil is compared to those previously reported for the planar and re-entrant cylindrical rf coils. Physical reasons for our observed characteristics of ASE are presented. With the increasing discharge power, the size and the number of negative and positive power absorption regions evolve into several distinct patterns. For the low discharge power (at 156.9 W), there is one area of positive and one area of negative power absorption in the radial direction. For the medium discharge power (279 W–683.5 W), there are two areas of negative and two areas of positive power absorption. For the even higher discharge power (above 803.5 W), the number of areas is the same as that of the medium discharge power, but the size of the inner positive and negative power absorption areas is approximately doubled and halved, respectively, while the outer positive and negative power absorption areas slightly shrinks. The evolution of positive and negative power absorption regions is explained as a result of electron thermal diffusion and the energy conversion between rf current and electric field. The spatial decays of electric field and current density are also elucidated by linking them with the positive and negative power absorption pattern.

In a 2.45 GHz electron cyclotron resonance xenon ion source powered with circular plate-antenna, a rapid evolution of radial plasma-profile with discharge power in a region below 35 W and the abrupt jump of ion beam current accompanied by sudden radial-expansion of discharge glow were observed. Based on analyses about quantified glow images captured from the end-view of the discharge chamber and the ion beam current against the discharge power, the fast evolution of the radial plasma-profile is attributed to the counteraction of standing wave and the skin effect, the coincidence of enhanced microwave absorption in the electron plasma resonance layer, and the transverse magnetic confinement of electrons. The jump of ion beam current and the sudden radial-expansion of discharge glow are confirmed to be originated from the extraordinary-wave discharge at the electron cyclotron resonance layer beyond the plate antenna when the skin effect is dominant.