Microwave-enhanced critical current in superconducting aluminum strips

A study has been made of the enhancement of the critical current in superconducting aluminum microstrips by microwave radiation. The observed enhancement is compared to calculations based on the Eliashberg theory modified for application to critical current enhancement. Theory and experiment are in reasonable agreement if the strongly temperature-dependent microwave impedance is taken into account.     

Microwave-enhanced chemical vapor infiltration: a sharp interface model

A simple one-dimensional model for describing CVI into a fibrous preform is presented and analyzed. The derivation requires that the thermal and electrical properties of the preform and substrate are disparate. Mathematically the model takes the form of a moving-boundary problem, where the boundary is the interface between the preform and the substrate. Effects of heat loss and radiation at the boundaries and the nonlinear dependence of dielectric parameters on temperature are all taken into account, in addition to the spatial dependence on gas concentration. Processing times for different power levels and inlet concentrations for different initial substrate thicknesses are obtained, and the implications to processing strategies are discussed.     

Microwave-enhanced catalytic degradation of 4-chlorophenol over nickel oxides under low temperature

Microwave-enhance catalytic degradation (MECD) of 4-chlorophenol (4-CP) using nickel oxide was studied. A mix-valenced nickel oxide was obtained from nickel nitrate aqueous solution through a precipitation with sodium hydroxide and an oxidation by sodium hypochlorite (assigned as PO). Then, the as-prepared PO was irradiated under microwave irradiation to fabricate a high active mix-valenced nickel oxide (assigned as POM). Further, pure nanosized nickel oxide was obtained from the POM by calcination at 300, 400 and 500 degrees C (labeled as C300, C400 and C500, respectively). They were characterized by X-ray (XRD), infrared spectroscopy (IR) and temperature-programmed reduction (TPR). Their catalytic activities towards the degradation of 4-CP on the efficiency of the degradation were further investigated under continuous bubbling of air through the liquid-phase and quantitative evaluation by high pressure liquid chromatography (HPLC). Also, the effects of temperature, pH and kinds of catalysts on the efficiency of the degradation have been investigated. The results showed that the 4-CP was degraded completely by MECD method within 20 min under pH 7, T=40 degrees C and C=200 g dm(-3) over POM catalyst. The relative activity was affected significantly with the oxidation state of nickel.     

Microwave-enhanced synthesis of magnetic porous covalent triazine-based framework composites for fast separation of organic dye from aqueous solution

A novel type of magnetic porous carbonaceous polymeric material, CTF/Fe(2)O(3) composite (CTF = covalent triazine-based framework), has been synthesized by a facile microwave-enhanced high-temperature ionothermal method. By selecting ZnCl(2) as a reaction medium and the Lewis acid catalyst, and choosing FeCl(3)·6H(2)O as an iron oxide precursor, a series of CTF/Fe(2)O(3) composites with different γ-Fe(2)O(3) contents has been prepared in 60 min. The resulting samples were characterized by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibration sample magnetometer (VSM), and N(2) sorption-desorption isotherms. The obtained CTF/Fe(2)O(3) composites exhibit high surface areas (930-1149 m(2) g(-1)), and their saturation magnetizations at 300 K vary from 1.1 to 5.9 emu g(-1), depending respectively on different Fe(2)O(3) contents (6.43-12.43 wt%) in the CTF/Fe(2)O(3) composites. The CTF/Fe(2)O(3) composites were applied to remove organic dye from aqueous solution by selecting methyl orange as a model molecule, and both high adsorption capacity (291 mg g(-1), corresponding to 0.889 mmol g(-1)) and fast adsorption kinetics (k(ads) = 4.31 m(2) mg(-1) min(-1)) were observed.     

Grain boundary chemistry

Recent advances in experimental measurements of grain-boundary segregation are reviewed. It is now feasible to measure segregation and relate it to boundary structure at the atomic level. It is also possible to measure nanometre-level segregation at dozens of grain boundaries, so a better statistical picture of the distribution of segregant is available. There is strong experimental evidence emerging for an electronic explanation of the role of segregation in controlling bulk mechanical properties, such as temper embrittlement.