Thermophysical properties of aqueous NaOH−H2O solutions at high concentrations

The working fluids, used in the majority of all mechanical heat pumps, are expected to be phased out within some few years due to their contribution to the stratospheric ozone depletion and global warming. Absorption heat pumps and transformers are receiving a new renaissance in the field of heating, refrigeration, air-conditioning, and heat recovery. Sodium hydroxide solutions are more propitious to the pulp and paper industry compared to other working pairs. Novel correlations have been developed to compute the vapor pressure, density, enthalpy, and viscosity of sodium hydroxide solutions. These correlations cover the most extensive range of validity ever proposed: 273–473 K for temperatures and 0.2–1 kg water per kg solution for concentrations.     

CO2 capture at high temperature using calcium-based sorbents

Calcium-based sorbents synthesized from CaO, CaCO₃, and Ca(OH)₂ precursors were demonstrated as high-temperature CO₂ capture materials. The effect on CO₂ capture capability of calcium-based sorbents receiving different activations was also investigated. After proper activation, the best carbon capturing material is CaO that captured 75% of available CO₂ in nine cyclic tests and captured 61% even after 40 cyclic experiments. The correlation of the structural difference in the three activated sorbents and CO₂ conversion has been discussed. The sintering effect is presumably a major cause for activity decline of calcium-based sorbents… after cyclic carbonation/decarbonation runs.     

Thermal transpiration of CO2 at high temperature

Thermal transpiration data for CO₂ in the range 50–545°C have been determined following the relative method. Among different equations suggested for the theoretical calculation of this effect, only the Kavtaradze equation agrees well with the experimental data.     

Corrosion behavior of 5Cr0.5Mo steel in sulfur‐bearing solution at high temperature

Corrosion behavior of 5Cr0.5Mo steel in sulfur‐bearing solutions as a function of temperature, test time, and sulfur content was investigated by weight loss measurements in this study. The results indicate that the corrosion rate of the steel increases with increasing test temperature. Besides, the corrosion rate increases during the initial test time and then decreases with longer test duration. Moreover, the corrosion rate rises with a higher amount of sulfur in the solution, and consequently a lower amount of sulfur leads to a decreased corrosion rate. In addition, the effect of Cr and Mo elements has been discussed.     

Deformation of Ni-Al at high temperature

Nickel-rich Ni-Al was deformed in the temperature range 720 K to 1200 K. The deformation mechanism was found to be independent of the composition. An anomalous behaviour of the activation volume is described in the stoichiometric compound and is attributed to the easy activation of [1 10] slip in the temperature range 850 K to 950 K.     

Fracture toughness of concretes at high temperature

The fracture toughness of ordinary and refractory concretes in the range of 20–1300C was investigated, and the stress intensity factor, K _Ic, on three-point bent specimens (according to ASTM E-399 recommendation) determined. With an increase in testing temperature, the stress intensity factor decreases for both concretes. The values of K _Ic at 20C for both concretes are comparable, being equal to 0.64 MNm^–3/2 for ordinary concrete, and 0.72 MNm^–3/2 for refractory concrete, respectively. At 1100C, K _Ic has a value of 0.043 MNm^–3/2 for ordinary concrete, and for the refractory concrete at 1300C, K _Ic=0.34 MNm^–3/2. The method presented for predicting the behaviour of concrete at high temperature may be used in engineering practice.     

Ultrasonic characterization of refractories at high temperature

A knowledge of the elastic constants of refractory materials is necessary for carrying out stress analysis of high temperature structural design. Together with internal friction such measurements can give useful NDT information. In developing new materials these parameters show well-defined discontinuities at their high temperature mechanical limits. Techniques for these measurements are also based mainly on disks but rods and rings are described. Observations on conventional materials such as silica, molybdenum and tungsten have been extended to graphite, graphite fabrics and the silicon nitrides. In general these materials have very stable thermophysical properties but show wide variations from batch to batch.     

Behaviour of Al-Mg alloys at high temperature

The behaviour of a few Al-Mg alloys (up to 7.1 wt% Mg) has been studied on heating in air at 500°C for 8 h or more. The precipitation of a spinel phase, MgAl₂O₄, is found to take place on the surface and along the transverse section (depth) of the specimen. The alloys seem to be resistant to internal oxidation below 4.5% Mg and thereafter prone to it. Beryllium modification does not suppress the progress of internal oxidation taking place in the Al-Mg alloys. The results have been interpreted on the basis of anodized photomicrographs and X-ray diffraction data.     

Decomposition of 2-naphthalenesulfonate in electroplating solution by ozonation with UV radiation

This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined with UV radiation in the electroplating solution. 2-NS is commonly used as a brightening and stabilization agent in the electroplating solution. Semibatch ozonation experiments were conducted under various reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS were analyzed at specified time intervals to elucidate the decomposition of 2-NS. Total organic carbon (TOC) is chosen as a mineralization index of the ozonation of 2-NS. In addition, values of pH and oxidation reduction potential were continuously measured in the course of experiments. As a result, the nearly complete mineralization of 2-NS via the ozonation treatment can be achieved. The mineralization of 2-NS is found accelerated by the introduction of UV radiation and has a distinct relationship with the consumption of applied ozone. These results can provide useful information for the proper removal of 2-NS in the electroplating solution by the ozonation with UV radiation.     

高温改性凹凸棒石对Cr(Ⅵ)的吸附研究

将凹凸棒石经低温煅烧改性,得到一种改性凹凸棒石材料,以提高凹凸棒石的吸附性能,通过BET(比表面积分析)和FT-IR(红外光谱仪)等实验技术及吸附含铬离子废水来袁征凹凸棒石的性能.实验结果表明高温改性可以提高凹凸棒石的比表面积及其吸附性能;当改性温度为350℃时,可以获得最大的比表面积为140.7m2/g.当凹凸棒石用量为10g/L、溶液pH为2,吸附时间为1h,去除率可以达到98％.     

纳米氧化铋基材料高温相变的研究

以分析纯Bi(NO3)3·5H2O和Y(NO3)·6H2O为原料制备纳米β-Bi2O3和Bi2O3-Y2O3(75%(摩尔分数)Bi2O3 25%(摩尔分数)Y2O3)粉体,平均粒度分别为40和30nm.经TG-DTA、高温XRD以及高温拉曼的研究结果表明,亚稳态的纳米β-Bi2O3粉体在升温过程中于420℃先向低温稳定的α-Bi2O3转变,在720℃时向δ-Bi2O3相转变,降温过程则是由δ→β→α.由于纳米Bi2O3具有很高的活性,使得相变温度比微米Bi2O3有所降低.纳米Bi2O3-Y2O3复合粉体升温过程中,Y2O3的固溶反应在较低温度(400℃)开始,500℃时β-Bi2O3完全转变为δ相,同时Y2O3完全固溶到δ-Bi2O3晶体中.Y2O3的掺杂使得Bi2O3的β→δ相转变温度大幅降低.     

高温下钙基吸收剂循环吸收CO2的研究进展

钙基吸收剂的循环煅烧/碳酸化反应是煤燃烧或气化过程中捕获CO2的有效途径.本文主要介绍了不同前体对CaO循环吸收CO2性能的影响,并介绍了解决石灰石经过多次循环后吸收CO2能力急剧衰减的方法.     

Interface-facilitated stable plasticity in ultra-fine layered FeAl/FeAl2 micro-pillar at high temperature

Fe-Al compounds possess a combination of high strength and corrosion resistance at high temperatures.However,increasing Al content to make them lighter results in embrittlement.Here,we investigate the high-temperature behavior of a novel,lightweight,ultra-fine-layered FeAl/FeAl2 material.We report a transition from unstable to stable plasticity at 450 ℃.Below 450 ℃,deformation is dominated by localized shear deformation within the soft FeAl layers,while above 450 ℃,it proceeds by co-deformation between FeAl and the brittle FeAl2 layers.We show that co-deformation is associated with the temperature at which the interface converts from sliding to sourcing dislocations for FeAl2.     

Rapid synthesis of CdSe nanocrystals in aqueous solution at room temperature

Water-soluble thioglycolic acid-capped CdSe nanocrystals (NCs) were prepared in aqueous solution at room temperature. We investigated the effects of pH values on the fluorescence intensity of the as-prepared CdSe NCs, and discussed the influence of the initial pH values on the fluorescence property. Their mean diameter was estimated to be 1.9 nm depending on the initial pH values in the preparation, the photoluminescence quantum yield could reach as high as 1.9%, almost comparable to the CdSe NCs prepared by an organometallic route. Finally, the products were characterized by Fourier transform infrared spectrometry (FTIR), atomic force microscope (AFM) and X-ray powder diffraction (XRD). AFM image showed that the NCs were ball-shaped with good dispersibility. XRD analysis disclosed that the CdSe NCs were of cubic zinc-blended structure.