Crystallisation process of Al80Fe10Ti10 amorphous phase

Abstract

In the present study, crystallisation behaviours of the Al₈₀Fe₁₀Ti₁₀ amorphous phase (prepared by mechanical alloying) has been investigated using X-ray diffraction and differential thermal analysis techniques. It was found that Al₈₀Fe₁₀Ti₁₀ amorphous phase exhibits one-stage crystallisation on heating [amorphous to Al₁₃Fe₄, Al(Fe,Ti) and Al₅Fe₂ intermetallic phases]. The activation energies for crystallisation of Al₈₀Fe₁₀Ti₁₀ amorphous phase were determined as 326, 322, 351 and 301 kJ mol^?1 by means of the Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, Friedman and Afify equations respectively. Kinetic parameters such as Avarmi exponent or reaction order n and frequency factor K_o were also discussed. The reaction orders obtained for the crystallisation was ～2·03, suggesting that a diffusion controlled crystallisation process with a decreasing nucleation rate was the crystallisation mechanism. The deduced K_o value for crystallisation peak was calculated to be 6·75×10¹⁰ s^?1.     

硅藻土涂料在热模法离心铸造球铁管中的应用

采用硅藻土为骨料配制的悬浊液作为涂料涂覆于管模内壁生产球铁管,论述了涂料原材料选择、涂料配制、性能及合适的施涂方式。试验表明,膨润土浆持续搅拌2h,再静止10h后配制涂料;硅藻土是涂料热模法中最合适的骨料;对于小管径的管模涂料,膨润土含量高一些,硅藻土与膨润土的质量比为(8～15):1;对于大口径管模涂料,膨润土含量稍低,硅藻土与膨润土质量比为(12～20):1,另外,有气喷涂是最佳的喷涂方式。     

Thermal comfort of patients: Objective and subjective measurements in patient rooms of a Belgian healthcare facility

In healthcare facilities, the prediction of mean thermal comfort perception of patients and staff is necessary to formulate requirements for the architectural and building systems design and control, and for establishing guidelines for the use of clothing and bedding systems.     

Experimental tile with phase change materials (PCM) for building use

The use of phase change materials (PCM) and their possible architectural integration is a path in the search for optimizing energy efficiency in construction. As part of this path, a pavement has been designed which, in combination with the PCM, serves as a passive thermal conditioning system (new patent n°. ES2333092 A1) [1]. The prototype has been tested experimentally and the results proved that it is a viable constructive solution improving the energy performance of sunny locals.     

Study of the geometry of a voided clay brick using non-rectangular perforations to optimise its thermal properties

This study seeks to improve the geometrical distribution of bricks to optimise the equivalent thermal transmittance of a wall built of Termoarcilla^® ECO 29 voided clay bricks, using calculations according to Spanish UNE [1], AENOR [10], European EN [6], [7], [8] and [9] and international ISO [11] and [12] standards.The objective is to study improvements in the wall's thermal conductivity, always remembering the limitations imposed by the manufacturing process. Simulations are made using a finite elements application [14].It is concluded that, within the possibilities allowed by the manufacturing process, with non-rectangular voids the heat flux has to cross a higher number of voids, which improves its thermal properties. A rhomboid layout of voids with the longer diagonal at right angles to the heat flux is the best internal void layout. If the internal perforations are also extended to the end of the tongue and groove, the direct thermal bridge in this type of brick is broken.Finally, a 290 mm wide brick with 25 rows is obtained with the geometrical properties described above which shows an improvement of almost 16% over the original ECO 29 brick, performing well in all climatic areas of Spain, with a full-bed mortar joint 30 mm thick.     

Synthesis of zirconium tungstate–zirconia core–shell composite particles

In this work, ZrW₂O₈–ZrO₂ core–shell composite particles were synthesized. ZrW₂O₈ that was used in the core is a material with negative coefficient of thermal expansion, and it was synthesized from a high-pH precursor based on use of tungstic acid and zirconium acetate. Shell layer was composed of ZrO₂ nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. While volume of the shell was effectively controlled by the initial zirconium ion concentration in the solutions, the rate of precipitation was a function of the ratio of initial concentrations of urea to zirconium ions. It is hypothesized that isolation of the ZrW₂O₈ within a layer of ZrO₂, will be a key element in solving problems associated with reactivity of ZrW₂O₈ towards other components in sintering of ceramic–ceramic composites with tuned or zero thermal expansion coefficient.     

Thermal conductivity measurement of the epoxies and composite material for low temperature superconducting magnet design

The thermal conductivities of solid materials were measured by a G-M cryo-cooler based apparatus in the temperature range of 2.6–21.0 K. The performance of this apparatus was verified by measuring the thermal conductivity of 304-stainless steel, and good reproducibility as well as accuracy was shown when compared with the certified values. The thermal conductivities of EC1017 and Stycast2850FT and a composite material were measured. Similar behavior to amorphous materials was shown for EC1017 and Stycast2850FT in that there was an apparent plateau, which could be ascribed to a very lower crystallinity of epoxy. An equivalent model was proposed to predict the thermal conductivity of the composite material.     

Small-scale experiments of self-sustaining decomposition of NPK fertilizer and application to events aboard the Ostedijk in 2007

Small-scale experiments to investigate the self-sustaining decomposition (SSD) behaviour of NPK 16.16.16 fertilizer have been undertaken. These experiments show that this material will undergo self-sustaining decomposition and are used to give insight into the behaviour of the reaction. A three-step decomposition process is observed leading to a self-sustained reaction reaching temperatures of 200–350 °C. The measured heat of reaction is 0.73–1.8 MJ/kg. Measurements are applied to the events that occurred aboard the ship Ostedijk in 2007 in which a SSD reaction occurred. The mass loss rate from the cargo was calculated to range from 0.5 kg/s on the first day to 12 kg/s on the last day. From this measurement, the maximum fire size was estimated to be in the range 5.8–29 MW.     

Effects of repeated exposures to severely cold environments on thermal responses of humans

Abstract

This study was conducted to investigate the effects of different exposure rates on thermal responses with the total cold exposure time the same under each of the conditions. After resting in a warm room (25°C) for 10 minutes, six male students wearing standard cold protective clothing entered an adjoining cold room (— 25°C). Each 5-, 10- and 20-minute cold exposure was repeated 12, 6 and 3 times, respectively. Each cold exposure was followed by a similar duration of rest at 25°C. Total cold exposure time was the same under the three conditions. Rectal temperature, skin temperatures, blood pressure, 17-hydroxycoyticoids (OHCS), counting task and subjective responses were measured. At the end of the cold exposure skin temperatures in the shorter exposures were higher than those in the other conditions, except on the foot. Discomfort due to cold was less in the shorter exposures and manifestation of discomfort was delayed. However, there were no differences among the three conditions in the fall of rectal temperature and urinary excretion of 17-OHCS, which are good indices of cold stress, Moreover, increase in blood pressure and decrease in counting task due to cold were not different among the three conditions. Even though the cold exposure time for each stay was short, when cold exposures were repeated frequently, cold stress of the whole body and decrease in manual task performance were the same as in the longer cold exposure.