Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: The Linear Thermal Expansion of Bulk Nanocrystalline Ingot Iron from Liquid Nitrogen to 300 K | Nanoscale Res Lett 2010 5 48-54 DOI S11671-009-9441-4 NANO EXPRESS The Linear Thermal Expansion of Bulk Nanocrystalline Ingot Iron from Liquid Nitrogen to 300 K S. G. Wang Y. Mei K. Long Z. D. Zhang Received 7 August 2009 Accepted 9 September 2009 Published online 17 September 2009 to the authors 2009 Abstract The linear thermal expansions LTE of bulk nanocrystalline ingot iron BNII at six directions on rolling plane and conventional polycrystalline ingot iron CPII at one direction were measured from liquid nitrogen temperature to 300 K. Although the volume fraction of grain boundary and residual strain of BNII are larger than those of CPII LTE of BNII at the six measurement directions were less than those of CPII. This phenomenon could be explained with Morse potential function and the crystalline structure of metals. Our LTE results ruled out that the grain boundary and residual strain of BNII did much contribution to its thermal expansion. The higher interaction potential energy of atoms the less partial derivative of interaction potential energy with respect to temperature T and the porosity free at the grain boundary of BNII resulted in less LTE in comparison with CPII from liquid nitrogen temperature to 300 K. The higher LTE of many bulk nanocrystalline materials resulted from the porosity at their grain boundaries. However many authors attributed the higher LTE of many nanocrystalline metal materials to their higher volume fraction of grain boundaries. Keywords Linear thermal expansion Bulk nanocrystallined materials Severe rolling technique S. G. Wang El K. Long Z. D. Zhang Shenyang National Laboratory for Materials Science Institute of Metal Research and International Centre for Materials Physics Chinese Academy of Sciences Shenyang 110016 People s Republic of China e-mail sgwang@ Y. Mei Institute of Sciences Dalian Fisheries University Dalian 116023 People s Republic of China Introduction The thermal properties of materials are important
