A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process ...A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process conditions, including infiltration temperature, infiltration time, and gas flux were investigated. The energy dispersion spectra （EDS） result showed that the main elements of this composite contained Si, N, and O. The X-ray diffraction （XRD） results indicated that phases of the composite before and after treatment at 1350℃ were all amorphous. A little fiber pull-out was observed on the cross section of the composite by scan electron microscope （SEM）. As a result, the composite exhibited good thermal stability, but an appropriate interface was necessary between the fiber and the matrix.展开更多
Novel red-emitting Eu3＋, Sm3＋ singly doped and co-doped Ca14Mg2（SiO4）8 phosphors were prepared by conventional solidstate reaction. Powder X-ray diffraction patterns were employed to confirm phase pttrity. Ca14Mg2...Novel red-emitting Eu3＋, Sm3＋ singly doped and co-doped Ca14Mg2（SiO4）8 phosphors were prepared by conventional solidstate reaction. Powder X-ray diffraction patterns were employed to confirm phase pttrity. Ca14Mg2（SiO4）8：Eu3＋ phosphors exhibited intense red emission under 394 nm excitation and Ca14Mg2（SiO4）8：Sm3＋ phosphors, excited at 405 nm, also showed strong red emitting at 602 nm. The concentration quenching mechanism of Cal4Mg2（SiOa）s：Eu3＋ was dipole-dipole interaction, while that of CalnMg2（SiOn）8：Sm3＋ was energy migration among nearest neighbor ions. The results indicated that Ca14Mg2（SiOn）8：Eu3＋ and Ca14Mg2（SiOn）s：Sm3＋ were promising red-emitting phosphors for WLEDs. Meanwhile, the effect of co-doping Sm3＋ ions on photoluminescence properties of CalaMg2（SiO4）s：Eu3＋ was studied and energy transfer from Sm3＋ to Eu3＋ was discovered in Eu3＋, Sm3＋ co-doped phosphors.展开更多
Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor（VDMOS） devices with composite SiO2-Si3N4 film gates are investigated.The relationships amon...Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor（VDMOS） devices with composite SiO2-Si3N4 film gates are investigated.The relationships among the important electrical parameters of the samples with different thickness SiO2-Si3N4 films,such as threshold voltage,breakdown voltage,and on-state resistance in accumulated dose,are discussed.The total dose experiment results show that the breakdown voltage and the on-state resistance barely change with the accumulated dose.However,the relationships between the threshold voltages of the samples and the accumulated dose are more complex,and not only positively drift,but also negatively drift.At the end of the total dose experiment,we select the group of samples which have the smaller threshold voltage shift to carry out the single event effect studies.We find that the samples with appropriate thickness ratio SiO2-Si3N4 films have a good radiation-hardening ability.This method may be useful in solving both the SEGR and the total dose problems with the composite SiO2-Si3N4 films.展开更多
基金This study was financially supported by the Key Foundation of National Science in China (No. 90405015), the National Elitist Youth Foundation of China (No. 50425208the Doctorate Foundation of Northwestern Polytechnical University (CX200505).
文摘A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process conditions, including infiltration temperature, infiltration time, and gas flux were investigated. The energy dispersion spectra （EDS） result showed that the main elements of this composite contained Si, N, and O. The X-ray diffraction （XRD） results indicated that phases of the composite before and after treatment at 1350℃ were all amorphous. A little fiber pull-out was observed on the cross section of the composite by scan electron microscope （SEM）. As a result, the composite exhibited good thermal stability, but an appropriate interface was necessary between the fiber and the matrix.
基金supported by the Hong Kong,Macao and Taiwan Science and Technology Cooperation Special Project of Ministry of Science and Technology of China(2014DFT10310)the National Basic Research Program of China(973 Program,2014CB643801)the National Natural Science Foundation of China(51402288,51102229,21401184)
文摘Novel red-emitting Eu3＋, Sm3＋ singly doped and co-doped Ca14Mg2（SiO4）8 phosphors were prepared by conventional solidstate reaction. Powder X-ray diffraction patterns were employed to confirm phase pttrity. Ca14Mg2（SiO4）8：Eu3＋ phosphors exhibited intense red emission under 394 nm excitation and Ca14Mg2（SiO4）8：Sm3＋ phosphors, excited at 405 nm, also showed strong red emitting at 602 nm. The concentration quenching mechanism of Cal4Mg2（SiOa）s：Eu3＋ was dipole-dipole interaction, while that of CalnMg2（SiOn）8：Sm3＋ was energy migration among nearest neighbor ions. The results indicated that Ca14Mg2（SiOn）8：Eu3＋ and Ca14Mg2（SiOn）s：Sm3＋ were promising red-emitting phosphors for WLEDs. Meanwhile, the effect of co-doping Sm3＋ ions on photoluminescence properties of CalaMg2（SiO4）s：Eu3＋ was studied and energy transfer from Sm3＋ to Eu3＋ was discovered in Eu3＋, Sm3＋ co-doped phosphors.
文摘Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor（VDMOS） devices with composite SiO2-Si3N4 film gates are investigated.The relationships among the important electrical parameters of the samples with different thickness SiO2-Si3N4 films,such as threshold voltage,breakdown voltage,and on-state resistance in accumulated dose,are discussed.The total dose experiment results show that the breakdown voltage and the on-state resistance barely change with the accumulated dose.However,the relationships between the threshold voltages of the samples and the accumulated dose are more complex,and not only positively drift,but also negatively drift.At the end of the total dose experiment,we select the group of samples which have the smaller threshold voltage shift to carry out the single event effect studies.We find that the samples with appropriate thickness ratio SiO2-Si3N4 films have a good radiation-hardening ability.This method may be useful in solving both the SEGR and the total dose problems with the composite SiO2-Si3N4 films.
