Polyamide I1 （PAll） and its nanocomposites with different organoclay loadings were prepared by melt-compounding and subsequent pelletizing. The crystal phase transitions of PAl 1 and its clay nanocomposites were inv...Polyamide I1 （PAll） and its nanocomposites with different organoclay loadings were prepared by melt-compounding and subsequent pelletizing. The crystal phase transitions of PAl 1 and its clay nanocomposites were investigated by variable-temperature X-ray diffraction. It was found that the Brill transition of the nanocomposite was 20 K higher than that of the neat PAl 1 for both heating and cooling processes. The PAl 1 d-spacings of the nanocomposites were observed to be smaller than those of the neat PAl 1 for melt crystallization. The constraints imposed by the addition of layered clay, restricting the thermal expansion of the polymer chains, are probably responsible for such a reduction of the d-spacing.展开更多
The application of semiconductor materials was limited as electromagnetic absorption materials,due to the unstable absorption performance caused by the temperature sensitivity.In this work,a structurally controllable ...The application of semiconductor materials was limited as electromagnetic absorption materials,due to the unstable absorption performance caused by the temperature sensitivity.In this work,a structurally controllable ceramic heterojunction was developed by assembling structural units of SiC nanowires(SiCnws)and Ba_(0.75)Sr_(0.25)Al_(2)Si_(2)O_(8)(BSAS).Benefiting from the optimization of the energy gap and the construction of heterogeneous interfaces,the ceramic heterojunction can achieve stable electromagnetic absorption from room temperature to 600℃,the effective absorption bandwidth is almost unchanged.And the minimum reflection loss value reached-63.6 dB at 600℃.Meanwhile,the SiCnws/BSAS ceramic heterojunction shows stable electromagnetic absorption performance in various simulated outdoor environments,including acid rain,seawater,high temperature and water vapor corrosion.This result provides a fire-new idea to realize the environmental adaptability of electromagnetic absorption materials and largely broadens its application prospect.展开更多
The efficient synthesis of dimethylhexane-1,6-dicarbamate(HDC)from 1,6-hexanediamine(HDA)and methyl carbonate over a series of heterogeneous catalysts(e.g.,Mg O,Fe2O3,Mo2O3,and Ce O2)was investigated.The reaction path...The efficient synthesis of dimethylhexane-1,6-dicarbamate(HDC)from 1,6-hexanediamine(HDA)and methyl carbonate over a series of heterogeneous catalysts(e.g.,Mg O,Fe2O3,Mo2O3,and Ce O2)was investigated.The reaction pathway was confirmed as an alcoholysis reaction through a series of designed experiments.Under optimized conditions,100%HDA conversion with 83.1%HDCtotaland 16.9%polyurea was obtained using a onestep with high temperature procedure with Ce O2as the catalyst.A new two-step with variable temperature technology was developed based on the reaction pathway to reduce the polyurea yield.Using the proposed method,the HDCtotalyield reached 95.2%,whereas the polyurea yield decreased to 4.8%.The Ce O2catalyst showed high stability and did not exhibit any observable decrease in the HDC yield or any structural changes after four recycling periods.展开更多
<正> Two new binuclear copper（Ⅱ） complexes, [Cu（oxpn）CuL]（ClO4）2, have been synthesizedand characterized, where oxpn is N,N’ bis（3-aminopropyl）oxamido and L is 1,10-phenan-throline （phen） or 5-nitro-...<正> Two new binuclear copper（Ⅱ） complexes, [Cu（oxpn）CuL]（ClO4）2, have been synthesizedand characterized, where oxpn is N,N’ bis（3-aminopropyl）oxamido and L is 1,10-phenan-throline （phen） or 5-nitro-1,10-phenanthroline （NO2-phen）. The crystal structure and vari-able-temperature magnetic susceptibility （4- 300 K） of the Complex （L=phen） have beendetermined. Crystal data: orthorhombic system, space group Pnma, with a = 10.433（1）, b11.458（2）, c = 21.999（2）A, z = 4. Every copper（Ⅱ） ion is in a square pyramidal environment.The two copper（Ⅱ） ions are linked by μ-oxamido bridge and the separation of them is 5.208A. The singlet-triplet energy gap J was found equal to -452.92cm-1, indicating that astrongantiferromagnetic spin-exchange interaction operates between the copper（Ⅱ） ions.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51125011)Guangxi Small Highland Innovation Team of Talents in Colleges and UniversitiesGuangxi Funds for Specially-appointed Expert
文摘Polyamide I1 （PAll） and its nanocomposites with different organoclay loadings were prepared by melt-compounding and subsequent pelletizing. The crystal phase transitions of PAl 1 and its clay nanocomposites were investigated by variable-temperature X-ray diffraction. It was found that the Brill transition of the nanocomposite was 20 K higher than that of the neat PAl 1 for both heating and cooling processes. The PAl 1 d-spacings of the nanocomposites were observed to be smaller than those of the neat PAl 1 for melt crystallization. The constraints imposed by the addition of layered clay, restricting the thermal expansion of the polymer chains, are probably responsible for such a reduction of the d-spacing.
基金supported by the National Natural Science Foundation of China(Grant No.52072303 and 51821091)National Science and Technology Major Project(Grant No.J2019-VI-0014-0129)。
文摘The application of semiconductor materials was limited as electromagnetic absorption materials,due to the unstable absorption performance caused by the temperature sensitivity.In this work,a structurally controllable ceramic heterojunction was developed by assembling structural units of SiC nanowires(SiCnws)and Ba_(0.75)Sr_(0.25)Al_(2)Si_(2)O_(8)(BSAS).Benefiting from the optimization of the energy gap and the construction of heterogeneous interfaces,the ceramic heterojunction can achieve stable electromagnetic absorption from room temperature to 600℃,the effective absorption bandwidth is almost unchanged.And the minimum reflection loss value reached-63.6 dB at 600℃.Meanwhile,the SiCnws/BSAS ceramic heterojunction shows stable electromagnetic absorption performance in various simulated outdoor environments,including acid rain,seawater,high temperature and water vapor corrosion.This result provides a fire-new idea to realize the environmental adaptability of electromagnetic absorption materials and largely broadens its application prospect.
基金Supported by the Science and Technology Ministry of China(2013BAC11B03)National Nature Science Foundation of China(21476244,21206180,21406245)
文摘The efficient synthesis of dimethylhexane-1,6-dicarbamate(HDC)from 1,6-hexanediamine(HDA)and methyl carbonate over a series of heterogeneous catalysts(e.g.,Mg O,Fe2O3,Mo2O3,and Ce O2)was investigated.The reaction pathway was confirmed as an alcoholysis reaction through a series of designed experiments.Under optimized conditions,100%HDA conversion with 83.1%HDCtotaland 16.9%polyurea was obtained using a onestep with high temperature procedure with Ce O2as the catalyst.A new two-step with variable temperature technology was developed based on the reaction pathway to reduce the polyurea yield.Using the proposed method,the HDCtotalyield reached 95.2%,whereas the polyurea yield decreased to 4.8%.The Ce O2catalyst showed high stability and did not exhibit any observable decrease in the HDC yield or any structural changes after four recycling periods.
基金Project supported by the National Natural Science Foundation of China.
文摘<正> Two new binuclear copper（Ⅱ） complexes, [Cu（oxpn）CuL]（ClO4）2, have been synthesizedand characterized, where oxpn is N,N’ bis（3-aminopropyl）oxamido and L is 1,10-phenan-throline （phen） or 5-nitro-1,10-phenanthroline （NO2-phen）. The crystal structure and vari-able-temperature magnetic susceptibility （4- 300 K） of the Complex （L=phen） have beendetermined. Crystal data: orthorhombic system, space group Pnma, with a = 10.433（1）, b11.458（2）, c = 21.999（2）A, z = 4. Every copper（Ⅱ） ion is in a square pyramidal environment.The two copper（Ⅱ） ions are linked by μ-oxamido bridge and the separation of them is 5.208A. The singlet-triplet energy gap J was found equal to -452.92cm-1, indicating that astrongantiferromagnetic spin-exchange interaction operates between the copper（Ⅱ） ions.
