Switchable Dielectric Materials Based on 2-Methylimidazole

Two novel coordination polymers with molecular structures（2MI）＋[Zn（2MI）Cl3]-（1） and（2MI）＋NO3-（2） based on ligand 2-methylimidazole（2MI） were synthesized under solution method. Compound 1 crystallizes in the monoclinic system, space group Cc with a=7.489（2）, b=13.448（4）, c=13.983（4） , β=98.402（2）°, Z=4 and V=102.246（2） 3. Compound 2 crystallizes in the orthorhombic system, space group pnma with a=14.296（3）, b=6.3180（12）, c=7.3862（13） , β=90°, Z=4 and V=667.1（2） 3. Dielectric measurements show compounds 1 and 2 have reversible dielectric anomalous behaviors with variation frequencies at different temperature.

Experimental and Simulation Studies on Cold Welding Sealing Process of Heat Pipes

Sealing quality strongly affects heat pipe performance, but few studies focus on the process of heat pipe sealing. Cold welding sealing technology based on a stamping process is applied for heat pipe sealing. The bonding mechanism of the cold welding sealing process （CWSP） is investigated and compared with the experimental results obtained from the bonding interface analysis. An orthogonal experiment is conducted to observe the effects of various parameters, including the sealing gap, sealing length, sealing diameter, and sealing velocity on bonding strength. A method with the utilization of saturated vapor pressure inside a copper tube is proposed to evaluate bonding strength. A corresponding finite element model is developed to investigate the effects of sealing gap and sealing velocity on plastic deformation during the cold welding process. Effects of various parameters on the bonding strength are determined and it is found that the sealing gap is the most critical factor and that the sealing velocity contributes the least effect. The best parameter combination （AIB3CID3, with a 0.5 mm sealing gap, 6 mm sealing length, 3.8 mm sealing diameter, and 50 mm/s sealing velocity） is derived within the experimental parameters. Plastic deformation results derived from the finite element model are consistent with those from the experiment. The instruction for the CWSP of heat pipes and the design of sealing dies of heat pipes are provided.

Synthesis,Crystal Structure and Thermal Decomposition of a New Energetic Dipotassium 3,3'-Dinitro-5,5'-bis-1,2,4-triazole-1,1'-diolate

A new energetic dipotassium 3,3-dinitro-5,5-bis-1,2,4-triazole-1,1-diolate [K2（DNOBT）] was synthesized, and structurally characterized by elemental analysis, IR spectra, 13 C NMR and single-crystal X-ray diffraction. K2（DNOBT）·2H2O crystallizes in monoclinic system, space group P21/n with a=6.0446（10）, b=15.999（3）, c=6.4169（11） , β=99.421（2）°, V=612.21（18） 3, Z=4, Dc=2.009 g·cm（-3）, F（000）=372, μ=0.838 mm（-1）, S=1.012, the final R=0.0248 and w R（I 〉 2σ（I））=0.0604. Thermal decomposition of the title compound was studied by using DSC and TG-DTG, and there is primarily one exothermic decomposition process at 371.5 ℃.

Influence of Heat Treatment Temperature on Microstructure and Bonding of TiO2 Film Coated on Diamond Particles Surface

TiO_2 films were coated on the surface of diamond particles using a sol-gel method. The effects of heat treatment temperature on the morphology, phase composition and chemical bond of diamond particles coated with TiO2 films were investigated through SEM, TEM, X-ray diffraction analysis, Raman spectroscopy, FTIR, and XPS. The results showed that when being heat-treated at 600 ℃, the amorphous TiO_2 film transfered to the anatase film which bonded well with diamond substrate. Meanwhile, the Ti-O-C bond formed between TiO2 film and diamond substrate. When being heat-treated at 800 ℃, TiO2 film was still anatase, and partial diamond began to graphitize. The graphitizated carbon could also form the Ti-O-C bond with TiO_2 film, although TiO_2 film would tend to crack in this case.