Study On Thermal Insulation Properties Of Nanoporous Materials

At this stage, the fossil energy increasingly dried up and the environmental pollution caused in its using process has compelled the reasonable and efficient use of limited natural resources. The thermal insulation technology is an significant measure to realize the efficient utilization of the fossil energy. In recent years, with the significant improvement of nanotechnology accompanying by the new extension of its application fields, the materials with nanoporous has become a research hotspot in the field of high-performance thermal insulating material owing to its unique and excellent thermal insulating ability.In this study, firstly, two style aerogel were prepared by supercritical drying and azeotropic distillation drying process. By comparing their main properties including of the porous network structure, the thermal insulating property has been investigated outstandingly. Then, for the research on SBA-15, MCM-41 and SBA-16 molecular sieve materials, the crystal structure, microstructure and the porous characteristics have been studied for the further investigation of their thermal insulating ability. This part of the work would provide some experimental data for expanding the application field of molecular sieve materials. Last, the effects of nanoporous thermal insulating material on the temperature of molten steel and heat transfer of ladle layers using finite element analysis method have been studied deeply.The obtained results were as follows:1) The hydrophobic effect had been realized by azeotropic distillation drying process. Compared aerogel received by azeotropic distillation drying with the one received by supercritical drying, although the crystal structures were both amorphous and the nitrogen adsorption-desorpyion isotherms were both attributed to type IV, the former was attributed to the typical H2 type, which indicated that its mesoporous characteristics was imperfect. While the latter was preferred to be H1 type, which indicated that its mesoporous was relatively uniform and its distribution in the range of 2~40 nm. The differences resulting from microstructure made that the latter one had a lower thermal conductivity at room temperature or 200℃, which corresponding to 0.020/0.033 W·m-1·K-1, respectively.2) The longth of SBA-15 molecular sieve was about 1μm, and the width was0.5μm. Its morphology was like as short rod and its internal mesoporous channel had a very regular primary orientation and a secondary orientation. The morphology of MCM-41 molecular sieve was like irregular short rod or particle. The particle size of SBA-16 molecular sieves received by the EISA synthetic route was about 1μm like "crystal" polyhedron shape, showing orderly in the scale of mesoscopic. The nitrogen adsorption-desorpyion isotherms showed that pore size distribution of SBA-15 and MCM-41 molecular sieve were 8~12 nm and 2~4 nm, respectively, but channel of SBA-16 mesoporous molecular sieve materials with 3D body centered cubic structure was only about 4 nm. The average pore size of these molecular sieve materials were7.47, 3.53, and 3.53 nm, respectively. Among the three molecular sieve materials,MCM-41 owned a lowest thermal conductivity, only 0.043 W·m-1·K-1at room temperature.3) Using nanoporous thermal insulating material with 10 mm thick as heat insulating layer of ladle, comparing to the ladle without thermal insulation layer or with the conventional insulation materials, that could make the steel temperature increased by 6.82 oC or 3.12 oC, respectively, after the steel last standing for 15 min.And the temperature drop rate of the steel reduced to 0.1938oC·min-1. At the same time, the temperature of ladle shell gone down about 113 oC.