Effect of carbon surface oxidation on platinum supported carbon particles on the performance of gas diffusion electrodes for the oxygen reduction reaction

The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms, polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of a gas diffusion electrode for oxygen reduction reaction.     

Anodic oxidation of mecoprop herbicide at lead dioxide

The electrochemical oxidation of an aqueous solution containing mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) has been studied at PbO₂ anodes by cyclic voltammetry and bulk electrolysis. The influence of current density, hydrodynamic conditions, temperature and pH on the degradation rate and current efficiency is reported. The results obtained show that the use of PbO₂ leads to total mineralization of mecoprop due to the production of oxidant hydroxyl radical electrogenerated from water discharge. The current efficiency for the electro-oxidation of mecoprop is enhanced by low current density, high recycle flow-rates and high temperature. In contrast, the pH effect was not significant. It has also been observed that mecoprop decay kinetics follows a pseudo-first-order reaction and the rate constant increases with rising current density.     

Oxidation of some aliphatic polyols on anodically deposited MnO2

Galvanostatic steady state current potential measurements were carried out for oxidation of a series of aliphatic alcohols having varying number of hydroxyl groups. The anodically deposited layer of MnO₂ on platinum was used as the electrode material. The deposit was characterised by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and electrode potential measurements. The catalytic role of MnO₂ in the electro-oxidation of alcohols was indicated by the chronopotentiograms and the cyclic voltammograms. An analysis of the electrochemical data indicated a catalytic EC mechanism in which Mn (V) is generated electrochemically and consumed chemically in succession. Based on this and the hydrogen bonding interaction between alcoholic hydroxyl groups and MnO₂ layer, a mechanism was proposed which accounts for the variation in the observed electrochemical reaction orders. Tafel behaviour was found to be followed only approximately. Current efficiency of the electrochemical oxidation of polyols was studied. Replacement of platinum by carbon as current collector was found to leave the electrocatalytic activity of the MnO₂ deposit practically unaltered.     

Electrochemical behaviour of phenylethanolamine at gold in aqueous solution

The electrooxidation of phenylethanolamine (2-amino-1-phenylethanol) at a gold electrode in alkaline electrolyte has been studied. Measurement of the differential capacitance of the electric double layer versus the electrode potential has shown that the adsorption of phenylethanolamine at the gold-solution interface plays a significant role in the oxidation mechanism. The effect of amine concentration, electrolyte pH and potential scan rate on the electrooxidation is analysed.     

Mechanism of heat transport in nanofluids

We have calculated thermal conductivity of alumina nanofluids (with water and ethylene glycol as base fluids) using temperature as well as concentration-dependent viscosity, η. The temperature profile of η is obtained using Gaussian fit to the available experimental data. In the model, the interfacial resistance effects are incorporated through a phenomenological parameter α. The micro-convection of the alumina nanoparticle (diameter less than 100 nm) is included through Reynolds and Prandtl numbers. The model is further improved by explicitly incorporating the thermal conductivity of the nanolayer surrounding the nanoparticles. Using this improved model, thermal conductivity of copper nanofluid is calculated. These calculations capture the particle concentration-dependent thermal conductivity and predict the dependence of the thermal conductivity on the size of the nanoparticle. These studies are significant to understand the underlying processes of heat transport in nanofluids and are crucial to design superior coolants of next generation.     

燃气锅炉运行经济性探讨

文章在对国内现有燃气锅炉的设计参数及运行参数调查、分析的基础上，指出其效率不高的原因，提出了改进措施。     

Study on Preparation and Application of Ti／Si Complex Zeolite

A Ti/Si complex zeolite has been prepared. X-ray diffraction and infrared spectrometry study has shown that two structures, namely the ZSM-5 and MCM-41, exist in the sample. BET tests have revealed that the complex zeolite contains regular mesopores of 2.6 nm. Ultraviolet spectrometry analysis has shown that the Ti species exist in the zeolite skeleton in the form of tetra-coordinate valence. The Ti/Si complex zeolite (TS-1/Ti-MCM-41) has apparently improved catalytic activity with respect to the macromolecular organic compound oxidation as compared to individual components of either Ti or Si containing zeolites (TS-1 and Ti-MCM-41).     

碳铬镍含量对高铬铸铁测温保护管性能的影响

通过高温氧化和高温磨损实验,研究了C、Cr、Ni 3个主要元素对高铬铸铁在高温条件下抗氧化和抗磨损性能的影响。结果表明:Cr含量越高,抗氧化性能和抗磨损性能越好;提高碳含量,明显提高高铬铸铁的高温抗磨性能;当w(Cr)=16％时,加入Ni能提高高铬铸铁的高温抗氧化性能;w(Cr)=30％时,Ni对高铬铸铁的抗氧化性能和抗磨损性能影响不明显.在1100℃以下,选用w(C)=2.8％,w(Cr)=30％、不加Ni的高铬铸铁铸造高温抗磨热电偶保护管,既有较好的使用寿命,又可降低成本.     

Thermal Performance Analysis of Highly Reflective Coating on Residences in Hot and Arid Climates

A 1-D transient model (RESHEAT), developed by the writers, was used to study the thermal performance of a highly reflective paint applied sequentially to the outer walls and roof of a simulated residence in a hot and arid region of the southwestern United States. The model uses climatological inputs from a file that includes hourly data on ambient temperatures, insolation, cloud cover, and so on, at the particular location. The model focuses particularly on the potential cooling load reduction due to the reduced heat pickup from the inside attic surfaces to the outer surfaces of the supply duct. This simulation showed that a reduction of 33.6% (cooling load) on the average is achieved over the base case where no reflective paint is used when the outer surface of the roof and walls are painted. Alternatively, only a 11% reduction would be achieved if the reflective paint is applied only to the roof. Savings of $42 per month are conservatively estimated from calculations made when applying this technology to a typical residence (roof and walls) equipped with a 4 ton refrigeration unit in the Southwest.