Papers by Keyword: Low Temperature

Abstract: As the important device to perceive the operating state of grid, the condition monitoring device of electric equipment solves such problems as the high rate of false alarm and failure of device caused by the low temperature in winter of cold areas. This paper measures the thermal conductivity of such three kinds of materials as asbestos, rubber and nano porous aerogels in the temperature range of -55°C to +80°C by steady state method, and analyzes the influence of temperature on the thermal conductivity of three materials. According to the result of experiment, the thermal conductivity of nano porous aerogels is the lowest and is affected least by temperature among three kinds of materials. Nano porous aerogels apply to state monitoring device operated in cold areas; and rubber can also be used as thermal insulation material when the operating temperature is generally higher than -20°C.

Abstract: Epoxy resin insulating materials have been extensively applied to main power transmission and transformation equipment. As the use environment of power transmission and transformation equipment becomes increasingly harsh, the reliability requirement of power grids for equipment is becoming higher and higher. It’s very necessary to master electrical and mechanical properties of low-temperature epoxy resin insulating materials. Dielectric properties, power-frequency breakdown properties, power-frequency flashover properties and mechanical properties of epoxy resin insulating materials under low temperature were investigated in this paper. The study results indicate that as the temperature declines, dielectric properties of epoxy resin composite materials are slightly degraded. After the temperature drops to below -40°C, dielectric properties start being gradually recovered to the state under normal temperature; AC breakdown, AC flashover and tensile properties of the materials are gradually improved as the temperature decreases.

Abstract: For a closed working environment, the CO2 content in the air in a closed space will rise continuously due to personnel breathing and some equipment or electronic devices, and even exceed the allowable content in the normal working environment. In order to prevent the CO2 content from exceeding the standard in the closed working environment, the method of low temperature liquefaction is used to separate the CO2 in the air. Through simulation calculation and comparison of key parameters of the process of using cascade liquefaction and nitrogen expansion liquefaction to reduce CO2 concentration in air, it is concluded that it is feasible to use cryogenic liquefaction method to separate carbon dioxide from air to purify air and improve air quality in confined space.

Abstract: In this work, solution combustion processed titanium, zinc co-doped indium oxide high transparent semiconducting thin films were demonstrated at annealing temperatures of 300, 350 °C. In the process, low-temperature combustion at 123 °C was verified through thermogravimetric analysis; acetylacetone, 2-methoxyethanol served as fuel and solvent respectively in the redox reaction. Indium titanium zinc oxide (ITiZO) films were developed on glass substrates by spin coating followed by annealing at different temperatures. ITiZO films, powder exhibited high crystallinity exactly matching with indium oxide peaks without forming secondary phases. But, the presence of In, Ti, Zn, and O is clearly visible on film through energy dispersive spectroscopy. Films had transparency more than 85% in the visible range with optical band gap ranging 3.8-3.9 eV. These ITiZO films with smooth and low roughness ranging 0.46-0.5 nm, can have a potential application as an active layer in transparent thin film transistors and optoelectronic devices.

Abstract: The mechanical responses of Ti-5Al-2.5Sn alloy at low temperatures were investigated under quasi-static and dynamic tensile loads using MTS system and SHTB system, respectively. Tensile stress-strain curves were obtained over the temperature range of 153 to 298K and the rate range of 0.001 to 1050 s^-1. Experimental results indicate that the tensile behavior of Ti-5Al-2.5Sn alloy is dependent on strain rate and temperature. Yield stress and flow stress increase with increasing strain rate and decrease with increasing temperature. Results also indicate that strain hardening rate of Ti-5Al-2.5Sn alloy is lower at high strain rate, while strain hardening rate varies little with testing temperature. The Khan-Huang-Liang constitutive model was chosen to characterize the tensile responses of Ti-5Al-2.5Sn alloy at low temperatures and different strain rates. The model results coincide well with the experimental results within the tested temperature and rate ranges.

Abstract: A series of Mn-based spinels over TiO₂ catalysts have been prepared with the impregnation method. Catalysts were comprehensively characterized using XRD, FESEM, H₂-TPR, and the activity evaluation of NH₃-SCR, while long-time stability tests and the effect of H₂O on NH₃-SCR were also investigated. Meanwhile, K poisoning effect was studied by preparing K-doped catalysts (K-Mn/TiO₂, K-Cu-Mn/TiO₂, K-Mg-Mn/TiO₂ and K-Co-Mn/TiO₂). According to the characterizations, Cu-Mn/TiO₂, Mg-Mn/TiO₂ and Co-Mn/TiO₂ catalysts exhibited superior low-temperature SCR activity, stability, K resistance and H₂O resistance due to the formation of spinels (MgMn₂O₄, CoMn₂O₄, CuMn₂O₄).

Abstract: In this paper, a preliminary study in the wetting behavior and interface reaction between active Sn-Ag-4Ti solder alloy and C-plane sapphire was given. An in-situ observation of Sn-Ag-4Ti alloy on C-plane sapphire revealed a decrease in contact angles at temperature close to 550°C. Moreover, sapphire/sapphire and sapphire/copper sandwich joints were brazed using Sn-3.5Ag-4Ti alloy at 500 ^oC, 550°C and 600 °C to investigate the microstructure evolution and interface reaction. Microstructure characterization and element analysis indicated that the temperature affected the diffusion of active Ti element by modifying the formation of Sn-Ti intermetallics compounds in Sn-Ag-Ti solder alloy. The absorption of Ti together with the release of Al from sapphire suggested the interface reaction between Sn-Ag-Ti alloy and sapphire was triggered at 550°C.

Abstract: To study the low temperature effects of tensile mechanical properties on Hydroxyl-terminated polybutadiene (HTPB) propellant, a quasi-static mechanical experiment was conducted. The results show that tensile mechanical parameters are closely related to strain rate and low temperature. With the decrease of temperature and increase of strain rate, the modulus and tensile strength of HTPB propellant increase obviously. Based on the time-temperature equivalence principle (TTEP), the master curves of tensile strength and initial modulus for HTPB propellant were obtained, which can facilitate the structural integrity analysis of the propellant. The damage of propellant is matrix tearing and dewetting between the filled particles and matrix.

Abstract: Mg-Mo-V-Ti catalysts of low temperature denitrification were prepared by dipping method. In order to study the activity of selective catalytic reduction, the catalyst was placed in a fixed bed reactor. Industrial flue gas was simulated with cylinder gas. Results indicate that the 0.1wt% content of MgO catalyst has good performance on denitration activity and sulfur resistance. The effects of oxygen content, space velocity and reaction temperature on the activity of the 0.1MgO-6MoO₃-3V₂O₅-TiO₂ wt% catalyst were investigated. With the increase of oxygen concentration, the denitrification efficiency increases when the oxygen concentration is less than 8%. When the oxygen content is greater than 8%, the denitrification efficiency is almost the same. The denitrification efficiency decreases with the increase of space velocity. The removal efficiency of NO 0.1MgO-6MoO₃-3V₂O₅-TiO₂ wt% catalyst over increases first and then becomes stable with the increase of temperature, and the conversion efficiency of SO₂ is less than or equal to 2.2% at 120~240 °C.

Abstract: Mo-V-Ti catalysts of low temperature denitrification were prepared by dipping method. In order to study the activity of selective catalytic reduction, the catalyst was placed in a fixed bed reactor. Industrial flue gas was simulated with cylinder gas. The experimental condition is NO: 500ppm, NH₃:500ppm, O₂:8%, SO₂:100ppm, N₂: equilibrium gas, space velocity: 36000h^-1. Results indicate that the catalyst prepared by dipping method had good denitrification activity and sulfur resistance at low temperature. The optimum ratio of catalyst was 3V₂O₅-6MoO₃-91TiO₂ (wt %). The conversion efficiency of NO was 80~93%, and the conversion efficiency of SO₂ was less than 1% at 180~260 °C.