The instrumented applied rod casting apparatus （ARCA） was developed to investigate the effects of tensile forces in the hot tearing formation of cast AI-Si alloys. The obtained data of tensile forces/temperature was...The instrumented applied rod casting apparatus （ARCA） was developed to investigate the effects of tensile forces in the hot tearing formation of cast AI-Si alloys. The obtained data of tensile forces/temperature was used to identify hot tearing initiation and propagation and the fracture surface of samples was also investigated. The result shows that the applied tensile forces have a complex effect on load onset for the hot tearing initiation and propagation. During the casting solidification, the tensile forces are gradually increased with the increase of solid fraction. Under the action of tensile forces, there will appear hot tearing and crack propagation on the surface of the sample. When the tensile forces exceed the inherent strength of alloys, there will be fractures on the sample. As for the A356 alloy, the critical fracture stress is about 0.1 MPa. The hot tearing surface morphology shows that the remaining intergranular bridge and liquid films are thick enough to allow the formation of dendrite-tip bumps on the fracture surface.展开更多
The improvements of the design and the compatibility with silicon IC of RF MEMS switch are presented.The compatibility with silicon IC is realized by dielectric isolation technology,and the decrease of the pull voltag...The improvements of the design and the compatibility with silicon IC of RF MEMS switch are presented.The compatibility with silicon IC is realized by dielectric isolation technology,and the decrease of the pull voltage of the switch is done by etching some holes on the metal membrane.The preliminary test results are as follows: C off and C on are 0 32pF,6pF,respectively;the pull down voltage is about 25V.The package of the RF MEMS switch is done by micro stripline,and the isolation and the insertion loss are 35dB,2dB,respectively at 1 5GHz;the switching speed is about 3μs by oscilloscope.展开更多
Fe-doped amorphous FexCl~ granular films were prepared on n-Si （100） substrates by d.c. magnetron sputtering. The structur- al properties of FexC1-x films were investigated by X-ray diffraction （XRD）, atomic force...Fe-doped amorphous FexCl~ granular films were prepared on n-Si （100） substrates by d.c. magnetron sputtering. The structur- al properties of FexC1-x films were investigated by X-ray diffraction （XRD）, atomic force microscope （AFM） and Raman spec- troscopy. The results show that the iron and carbon of as-deposited films are in amorphous state, and the FexC1-x films are di- amond-like carbon （DLC） films. After doping iron into the DLC films, a smooth surface morphology of the FexC1-x films has been obtained with the surface roughness Ra of about 0.231 nm for x=18at%. The FexC1-x films have good soft magnetic prop- erties with the coercivity of approximately 20 Oe. A high positive magnetoresistance （MR） up to 93% with x=lat% was ob- served in a FexCl-x granular film at 300 K. The resistance characteristic of Fe-C films is changed at about 230 K and the positive MR effect can be understood by the p-n heterojunction theory.展开更多
基金Project(2011ZX04001-031)supported by National Science and Technology Major Project of"High-end CNC Machine Tools and Basic Manufacturing Equipment",ChinaProject(51371109)supported by the National Natural Science Foundation of China
文摘The instrumented applied rod casting apparatus （ARCA） was developed to investigate the effects of tensile forces in the hot tearing formation of cast AI-Si alloys. The obtained data of tensile forces/temperature was used to identify hot tearing initiation and propagation and the fracture surface of samples was also investigated. The result shows that the applied tensile forces have a complex effect on load onset for the hot tearing initiation and propagation. During the casting solidification, the tensile forces are gradually increased with the increase of solid fraction. Under the action of tensile forces, there will appear hot tearing and crack propagation on the surface of the sample. When the tensile forces exceed the inherent strength of alloys, there will be fractures on the sample. As for the A356 alloy, the critical fracture stress is about 0.1 MPa. The hot tearing surface morphology shows that the remaining intergranular bridge and liquid films are thick enough to allow the formation of dendrite-tip bumps on the fracture surface.
文摘The improvements of the design and the compatibility with silicon IC of RF MEMS switch are presented.The compatibility with silicon IC is realized by dielectric isolation technology,and the decrease of the pull voltage of the switch is done by etching some holes on the metal membrane.The preliminary test results are as follows: C off and C on are 0 32pF,6pF,respectively;the pull down voltage is about 25V.The package of the RF MEMS switch is done by micro stripline,and the isolation and the insertion loss are 35dB,2dB,respectively at 1 5GHz;the switching speed is about 3μs by oscilloscope.
基金supported by the National Natural Science Foundation of China (Grant No. U0734001)the Fundamental Research Funds for the Central Universities,SCUT (Grant Nos. 2009ZM0247 and 2012ZZ0015)
文摘Fe-doped amorphous FexCl~ granular films were prepared on n-Si （100） substrates by d.c. magnetron sputtering. The structur- al properties of FexC1-x films were investigated by X-ray diffraction （XRD）, atomic force microscope （AFM） and Raman spec- troscopy. The results show that the iron and carbon of as-deposited films are in amorphous state, and the FexC1-x films are di- amond-like carbon （DLC） films. After doping iron into the DLC films, a smooth surface morphology of the FexC1-x films has been obtained with the surface roughness Ra of about 0.231 nm for x=18at%. The FexC1-x films have good soft magnetic prop- erties with the coercivity of approximately 20 Oe. A high positive magnetoresistance （MR） up to 93% with x=lat% was ob- served in a FexCl-x granular film at 300 K. The resistance characteristic of Fe-C films is changed at about 230 K and the positive MR effect can be understood by the p-n heterojunction theory.
