11-01 :: December 2010 / January 2011
nanotimes News in Brief
temperature. The group of NIMTE has dedicated to the research and development of industrial techno- logy for high-performance neodymium magnet, and made a series technological progress at production process. For preparation of the excellent perfor- mance of NdFeB magnets, technologic processes of preparation, including strip casting, hydrogen decre- pitation, jet milling, etc., are optimized in details. Researchers make a systematic study on the me- chanism of grain growth, and obtain the developed strips with uniform columnar grain structure.
This technique progress has reached the internatio- nal advanced level. Furthermore, the effects of the residue hydrogen content on the magnetic proper- ties and corrosion resistance of Nd-Fe-B sintered magnets are studied. The sintering processes of magnets with different residue hydrogen contents are studied systematically, and it was found that high residual hydrogen contents can result in local HDDR and a decrease in magnetic properties of magnets.
Base on this research results, the improved HD technique is presented. In addition, the prepara- tions of low temperature coefficient magnets have a significant progress. The primary and secondary alloy were designed and blended with rational allo- cation by dual-alloy method and process optimiza- tion. The absolute value of temperature coefficient of coercivity reaches 0.53%/°C, much lower than that of magnets (0.64 %/°C) prepared by single alloy with same alloy composition.
http://english.nimte.cas.cn/
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Researchers at the R&D Center of Lubricating and Protecting Materials of the Lanzhou Institute of Chemical Physics (LICP), CAS, China, have develo- ped a facile approach for the fabrication of porous polyimide films with an ordered surface.
In this approach, the polyamic acid (PAA, precursor of polyimide)/DMF solution was blended with silica microspheres first and then dried under vacuum to obtain PAA/silica composite film with well-ordered surface. After thermal imidization and removal of si- lica, porous polyimide film with 2D ordered surface was obtained.
This method needs no complex preparation pro- cess of template-like colloid crystals, as previously reported. It relies on the in situ self-assembly of PAA/silica complex microspheres where PAA chains interact with silica microspheres via hy- drogen bonding during vacuum-drying. The study on the wettability behavior of the prepared porous polyimide films indicated that the ordered surface topography of the as-prepared polyimide films could change the wettability from hydrophilicity to hydrophobicity.
The approach is facile in that neither the prepara- tion of special template nor complex preparation process nor precise control over condition is neces- sary.
Furthermore, the method could be employed for mass production of ordered porous polyimide films, and by changing the content and size of silica microspheres, the pore size and porous structure of the porous polyimide films could be tunable. This technique presents a simple paradigm in the pre-
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