Silicon thin-film solar cells are considered to be one of the most promising cells in the future for their potential advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollutio...Silicon thin-film solar cells are considered to be one of the most promising cells in the future for their potential advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollution. In this paper, latest progress on poly-crystalline silicon solar cells on ceramic substrates achieved by our group was reported. Rapid thermal chemical vapor deposition (RTCVD) was used to deposited poly-crystalline silicon thin films, and the grains of as-grown film were enlarged by Zone-melting Recrystallization (ZMR). As a great change in cell′s structure, traditional diffused pn homojunction was replaced by a-Si/c-Si heterojunction, which lead is to distinct improvement in cell′s efficiency. A conversion efficiency of 3.42% has been achieved on 1 cm2 a-Si/c-Si heterojunction solar cell (Isc=16.93 mA, Voc=310.9 mV, FF=0.6493, AM=1.5 G, 24 ℃), while the cell with diffused homojunction only got an efficiency of 0.6%. It indicates that a-Si emitter formed at low temperature might be more suitable for thin film cell on ceramics.展开更多
The fraction of TiN/Si3N4 in the cross section was observed with scanning electric microscope （SEM）, and residual stresses of TiN coated on the surface of Si3N4 ceramic were measured with X-ray diffraction （XRD）.T...The fraction of TiN/Si3N4 in the cross section was observed with scanning electric microscope （SEM）, and residual stresses of TiN coated on the surface of Si3N4 ceramic were measured with X-ray diffraction （XRD）.The hardness of TiN film was measured, and bonding strength of TiN film coated on Si3N4 substrate was measured by scratching method. The formed mechanism of residual stress and the failure mechanism of the bonding interface in the film were analyzed, and the adhesion mechanism of TiN film was investigated preliminarily. The results show that residual stresses of TiN film are all behaved as compressive stress, and TiN film is represented smoothly with brittle fracture, which is closely bonded with Si3N4 substrate. TiN film has high hardness and bonding strength of about 500 MPa, which could satisfy usage requests of the surface of cutting Si3N4 ceramic.展开更多
Fe/Al2O3 ceramic coating was made by spraying and sol-gel. The corrosion resistance between Fe/Al2O3 ceramic coating and steel 45# was studied. By microscope and X-ray diffraction, the binding and the composition of ...Fe/Al2O3 ceramic coating was made by spraying and sol-gel. The corrosion resistance between Fe/Al2O3 ceramic coating and steel 45# was studied. By microscope and X-ray diffraction, the binding and the composition of the interface were also analyzed. The results showed that Fe/Al2O3 ceramic coating had dense struc- ture, less porosity and better binding with the substrate which was effective to prevent erosive liquor immersing into the inside of ceramic coating. Some substances that distributed homogeneously in Fe/Al2O3 ceramic coating, such as α-Al2O3, FeAlO3 and Fe3Al, could improve the corrosion resistance of this material.展开更多
Glass-ceramics containing β-quartz as a main crystal phase based on the system of SiO2-Al2O3-Li2O-K2O-MgO-ZnO were investigated for the application to magnetic storage substrate for higher storage capacity. Parent gl...Glass-ceramics containing β-quartz as a main crystal phase based on the system of SiO2-Al2O3-Li2O-K2O-MgO-ZnO were investigated for the application to magnetic storage substrate for higher storage capacity. Parent glasses were prepared, then nucleated and crystallized at certain temperatures for 3-4 h. The crystallization kinetics of glass-ceramics was also studied. The grain size was estimated by Scherrer formula and image treatment of transmission electron microscopy （TEM）. The results showed that the Avrami exponent was determined to be 3.88, the activation energy 189.3＋7 k J/tool and the grain size 30-60 nm. A detailed microstructure of the glass-ceramics, including grain distribution and the morphology of nano-crystalline was characterized by TEM, X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, differential thermal analysis （DTA）. The relationship between microstructure and mechanical properties was also discussed.展开更多
High voltage power modules are used in numerous applications to build high power converters. Technically, these modules are made of different materials and among them, dielectric materials are organic and inorganic. O...High voltage power modules are used in numerous applications to build high power converters. Technically, these modules are made of different materials and among them, dielectric materials are organic and inorganic. Organic insulators (gels) are used to avoid corona discharges in the vicinity of connecting wires and high voltage dies (diodes and transistors) and to protect them from moisture and contaminants. Inorganic insulators (ceramic substrates) are used to insulate the high voltage which dies from the grounded elements and to transfer heat to the heat sink. Despite being used since the late 90s, there is a lack of fundamental knowledge about the electrical properties of these substrates. Consequently, manufacturers tend to assure the reliability by over sizing them. As there are no clear rules for how to do that, failures occur, leading to the converter shutdown. The aim of this study is to bring new information about the understanding of the dielectric strength of ceramic materials used in these modules. We have focused our work on the correlation between the mechanical and the dielectric properties of ceramics by using relevant experiments. We provide new information about the impact of existing cracks on the ceramic dielectric failure, according to the electromechanical breakdown model. Our conclusions bring crucial information about the precautions to be taken during manufacturing and implementation of these substrates in power modules to reduce the likelihood of the particular causes of failure.展开更多
The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY Y 2O 3 stabilized ZrO 2 transition layer and Y 2O 3 stabilized ZrO 2 ceramic layer are prepared on nickel alloy substrates using the plasma spray ...The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY Y 2O 3 stabilized ZrO 2 transition layer and Y 2O 3 stabilized ZrO 2 ceramic layer are prepared on nickel alloy substrates using the plasma spray technique. The relationship among the composition, structure and property of the coatings are investiga ted by means of optical microscope, scanning electronic microscope and the experiments of thermal shock resistance cycling and high temperature oxidation resistance. The results show that the structure design of introdu cing a transition layer between Ni alloy substrate and ZrO 2 ceramic coating guarantees the high quality and properties of the coatings; ZrO 2 coatings doped with a little SiO 2 possesses better thermal shock resistance and more excellent hot corrosion resistance as compared with ZrO 2 coating materials without SiO 2 ;the improvement in performance of ZrO 2 coating doped with SiO 2 is due to forming more dense coating structure by self closing effects of the flaws and pores in the ZrO 2 coatings.展开更多
文摘Silicon thin-film solar cells are considered to be one of the most promising cells in the future for their potential advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollution. In this paper, latest progress on poly-crystalline silicon solar cells on ceramic substrates achieved by our group was reported. Rapid thermal chemical vapor deposition (RTCVD) was used to deposited poly-crystalline silicon thin films, and the grains of as-grown film were enlarged by Zone-melting Recrystallization (ZMR). As a great change in cell′s structure, traditional diffused pn homojunction was replaced by a-Si/c-Si heterojunction, which lead is to distinct improvement in cell′s efficiency. A conversion efficiency of 3.42% has been achieved on 1 cm2 a-Si/c-Si heterojunction solar cell (Isc=16.93 mA, Voc=310.9 mV, FF=0.6493, AM=1.5 G, 24 ℃), while the cell with diffused homojunction only got an efficiency of 0.6%. It indicates that a-Si emitter formed at low temperature might be more suitable for thin film cell on ceramics.
文摘The fraction of TiN/Si3N4 in the cross section was observed with scanning electric microscope （SEM）, and residual stresses of TiN coated on the surface of Si3N4 ceramic were measured with X-ray diffraction （XRD）.The hardness of TiN film was measured, and bonding strength of TiN film coated on Si3N4 substrate was measured by scratching method. The formed mechanism of residual stress and the failure mechanism of the bonding interface in the film were analyzed, and the adhesion mechanism of TiN film was investigated preliminarily. The results show that residual stresses of TiN film are all behaved as compressive stress, and TiN film is represented smoothly with brittle fracture, which is closely bonded with Si3N4 substrate. TiN film has high hardness and bonding strength of about 500 MPa, which could satisfy usage requests of the surface of cutting Si3N4 ceramic.
文摘Fe/Al2O3 ceramic coating was made by spraying and sol-gel. The corrosion resistance between Fe/Al2O3 ceramic coating and steel 45# was studied. By microscope and X-ray diffraction, the binding and the composition of the interface were also analyzed. The results showed that Fe/Al2O3 ceramic coating had dense struc- ture, less porosity and better binding with the substrate which was effective to prevent erosive liquor immersing into the inside of ceramic coating. Some substances that distributed homogeneously in Fe/Al2O3 ceramic coating, such as α-Al2O3, FeAlO3 and Fe3Al, could improve the corrosion resistance of this material.
基金The work was supported by the National Natural Science Foundation of China(Grant No.90206017)the High Tech.Program of Ministry of Science and Technology of China(Grant No.2003BA301A21)+2 种基金the Science and Technology Development Foundation of University of Shanghai(Grant No.02AK26)the Applied Materials(AM)Foundation(Grant No.0208)the Key Subject Construction Project(Material Science)of Shanghai Educational Committee.
文摘Glass-ceramics containing β-quartz as a main crystal phase based on the system of SiO2-Al2O3-Li2O-K2O-MgO-ZnO were investigated for the application to magnetic storage substrate for higher storage capacity. Parent glasses were prepared, then nucleated and crystallized at certain temperatures for 3-4 h. The crystallization kinetics of glass-ceramics was also studied. The grain size was estimated by Scherrer formula and image treatment of transmission electron microscopy （TEM）. The results showed that the Avrami exponent was determined to be 3.88, the activation energy 189.3＋7 k J/tool and the grain size 30-60 nm. A detailed microstructure of the glass-ceramics, including grain distribution and the morphology of nano-crystalline was characterized by TEM, X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, differential thermal analysis （DTA）. The relationship between microstructure and mechanical properties was also discussed.
文摘High voltage power modules are used in numerous applications to build high power converters. Technically, these modules are made of different materials and among them, dielectric materials are organic and inorganic. Organic insulators (gels) are used to avoid corona discharges in the vicinity of connecting wires and high voltage dies (diodes and transistors) and to protect them from moisture and contaminants. Inorganic insulators (ceramic substrates) are used to insulate the high voltage which dies from the grounded elements and to transfer heat to the heat sink. Despite being used since the late 90s, there is a lack of fundamental knowledge about the electrical properties of these substrates. Consequently, manufacturers tend to assure the reliability by over sizing them. As there are no clear rules for how to do that, failures occur, leading to the converter shutdown. The aim of this study is to bring new information about the understanding of the dielectric strength of ceramic materials used in these modules. We have focused our work on the correlation between the mechanical and the dielectric properties of ceramics by using relevant experiments. We provide new information about the impact of existing cracks on the ceramic dielectric failure, according to the electromechanical breakdown model. Our conclusions bring crucial information about the precautions to be taken during manufacturing and implementation of these substrates in power modules to reduce the likelihood of the particular causes of failure.
文摘The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY Y 2O 3 stabilized ZrO 2 transition layer and Y 2O 3 stabilized ZrO 2 ceramic layer are prepared on nickel alloy substrates using the plasma spray technique. The relationship among the composition, structure and property of the coatings are investiga ted by means of optical microscope, scanning electronic microscope and the experiments of thermal shock resistance cycling and high temperature oxidation resistance. The results show that the structure design of introdu cing a transition layer between Ni alloy substrate and ZrO 2 ceramic coating guarantees the high quality and properties of the coatings; ZrO 2 coatings doped with a little SiO 2 possesses better thermal shock resistance and more excellent hot corrosion resistance as compared with ZrO 2 coating materials without SiO 2 ;the improvement in performance of ZrO 2 coating doped with SiO 2 is due to forming more dense coating structure by self closing effects of the flaws and pores in the ZrO 2 coatings.
