No abstract

No abstract

No abstract

Iron-based soft magnetic composites (SMCs) are promising substitutes for laminate steels in electromagnetic applications due to their excellent magnetic properties and productivity. However, the preparation process is a key factor in deciding the magnetic performance of SMCs. In this work, the Fe-based soft magnetic composites with improved soft magnetic properties were achieved by optimizing the compaction and the annealing process. Results showed that the core-shell structure of powders which would directly have an impact on the permeability and the core loss of the SMCs could be affected by the compaction and the annealing process. In addition, the magnetic properties were enhanced by tuning the microstructure. As a result, the optimal magnetic performance of the compact with high permeability and low total core loss was obtained. The real part of the permeability of the soft magnetic composites could reach a maximal value of 336.8 and a rather low core loss of 2.5 W Kg −1 (measured at 50 mT and 5 kHz). Therefore, soft magnetic composites with enhanced magnetic properties were obtained by optimizing the powder metallurgy (PM) process in this study.

In consideration of the important influence of the season change on the temperature difference, the poor thermal inertia of non-thermal insulation walls and the inflammableness of organic thermal insulation walls, it is designed to prepare the phase-change material into the phase-change mortar applied to the exterior of the building walls so as to improve the thermal inertia of the wall in summer. The phase-change material, taking the lowest eutectic mixture mainly formed with lauric acid and myristic acid, hereinafter referred to as 'fatty acid', as the main of phase-change material, and the expanded perlite as the inorganic carrier, is prepared into a phase-change aggregate by way of absorption, through encapsulating the aggregate, the optimal process parameters are then determined. The phase-change mortar with the phase-change perlite aggregate is prepared, and simulation test on the thermal performance of the temperature control is conducted. Laboratory results indicate that, the expanded perlite absorbs 200% fatty acid by way of vacuum absorption method, and is encapsulated by 67% polyurethane resin, and then becomes a stable phase-change perlite aggregate. Phase-change perlite-based mortar can achieve better temperature control effect, additionally, the increasing of the dosage of the fatty acid, the decreasing of the effective caloric value will become faster, and the longer the temperature delaying time as well as the greater the temperature dropping amplitude, meaning that the effect of controlling the temperature becomes more outstanding. IntroductionThe improvement on thermal inertia of buildings is an important task in the fields of construction and energy. At present, most studies are based on thermal energy storage material. However, there also exist a series of problems, such as high costs of sensible heat of stone, large size and temperature fluctuations during heat accumulation. Prevalent organic insulation wallboards are flammable; therefore, PCMs have been applied in the research and development of Latent Thermal Energy Storage. 1-3 Phase-change material has optimum phase-transition temperature, large phase-change latent heat and stable physico-chemical properties. 4-6 Solid-liquid phase change material has owned comparatively mature technology but the defect of flowing as well; so, in order to eliminate leaks, it should be encapsulated before combining with base materials in practical use 7 .Researchers have conducted studies on the thermal analysis of phase-change mortar and phase-change aggregate. Neeper 8 investigated the optimal parameters of phrase-change wallboards using a one-dimensional model and evaluated the benefit from heating and cooling system of construction products. But the results from this numerical analysis are not completely reliable by themselves. Sari et al. 9 prepared a phrasechange aggregate with good thermal stability from expanded perlite which absorbed 150% lauric acid. But its stability in alkali surroundings has seldom been studied, with domestic test standards fo...