The formation of low-resistance Ohmic contacts in Ga_(2)O_(3) is crucial for high-performance electronic devices. Conventionally, a titanium/gold(Ti/Au) electrode is rapidly annealed to achieve Ohmic contacts, resulti...The formation of low-resistance Ohmic contacts in Ga_(2)O_(3) is crucial for high-performance electronic devices. Conventionally, a titanium/gold(Ti/Au) electrode is rapidly annealed to achieve Ohmic contacts, resulting in mutual diffusion of atoms at the interface. However, the specific role of diffusing elements in Ohmic contact formation remains unclear.In this work, we investigate the contribution of oxygen atom diffusion to the formation of Ohmic contacts in Ga_(2)O_(3). We prepare a Ti/Au electrode on a single crystal substrate and conduct a series of electrical and structural characterizations.Using density functional theory, we construct a model of the interface and calculate the charge density, partial density of states, planar electrostatic potential energy, and I–V characteristics. Our results demonstrate that the oxygen atom diffusion effectively reduces the interface barrier, leading to low-resistance Ohmic contacts in Ga_(2)O_(3). These findings provide valuable insights into the underlying mechanisms of Ohmic contact formation and highlight the importance of considering the oxygen atom diffusion in the design of Ga_(2)O_(3)-based electronic devices.展开更多
Ti3SiC2-reintbrced Ag-maJxix composites are expected to serve as eleclrical contacts. In this study, the wettability of Ag on a Ti3SiC2 subslxate was measured by the sessile drop melkod. The Ag-Ti3SiC2 composites were...Ti3SiC2-reintbrced Ag-maJxix composites are expected to serve as eleclrical contacts. In this study, the wettability of Ag on a Ti3SiC2 subslxate was measured by the sessile drop melkod. The Ag-Ti3SiC2 composites were prepared from Ag mad Ti3SiC2 powder mix- tures by pressureless sintering. The effects of compacting pressure （100-800 MPa）, sintering temperature （850-950~C）, mad soaking time （0.5-2 h） on the microslxucture mad properties of the Ag-Ti3SiC2 composites were investigated. The experimental results indicated that Ti3SiC2 paxticulates were uniformly distxibuted in flae Ag matrix, wiflaout reactions at the interthces between flae two phases. The prepared Ag-10wt%Ti3SiC2 had a relative density of 95% mad an electrical resistivity of 2.76 x 10 3 m~）＇cm when compacted at 800 MPa mad sintered at 950~C for 1 h. The incorporation of Ti3SiC2 into Ag was found to improve its hardness without substantially compromising its electrical conductivity; INs behavior was attxibuted to the combination of ceramic and metallic properties of the Ti3SiC2 reinforcement, suggesting its potential application in electrical contacts.展开更多
Wear and scuffing failures often occur in marine transmission gears due to high friction and flash temperature at the interface between the meshing-teeth.In this paper,a numerical solution procedure was developed for ...Wear and scuffing failures often occur in marine transmission gears due to high friction and flash temperature at the interface between the meshing-teeth.In this paper,a numerical solution procedure was developed for the predictions of transient friction and flash temperature in the marine timing gears during one meshing circle based on the 3D line contact mixed lubrication simulation,which had been verified by comparing the flash temperature with those from Blok’s theory.The effect of machined surface roughness on the mixed lubrication characteristics is studied.The obtained results for several typical gear pairs indicate that gear pair 4-6 exhibits the largest friction and the highest interfacial temperature increase due to severe rough surface asperity contacts,while the polished gear surfaces yield the smallest friction and the lowest interfacial temperature.In addition,the influences of the operating conditions and the gear design parameters on the friction-temperature behaviors are discussed.It is observed that the conditions of heavy load and low rotational velocity usually lead to significantly increased friction and temperature.In the meantime,by optimizing the gear design parameters,such as the modulus and the pressure angle,the performance of interfacial friction and temperature can be significantly improved.展开更多
A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)roughness.The essence of the degradation ...A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)roughness.The essence of the degradation of the maximum possible dilation angle is the degradation of the 3D average equivalent dip angle of the actual contact joint asperities.Firstly,models for calculating the maximum possible dilation angle at the initial and residual shear stress stages are proposed by analyzing the 3D joint morphology characteristics of the corresponding shear stages.Secondly,the variation law of the maximum possible dilation angle is quantified by studying the degradation law of the joint micro convex body.Based on the variation law of the maximum possible dilation angle,the maximum possible shear strength model is proposed.Furthermore,a method to calculate the shear stiffness degradation in the plastic stage is proposed.According to the maximum possible shear strength of rock joints,the shear stress-shear displacement prediction model of rock joints is obtained.The new model reveals that there is a close relationship between joint shear strength and actual contact joint roughness,and the degradation of shear strength after the peak is due to the degradation of actual contact joint roughness.展开更多
The 3C-SiC thin films used herein are grown on Si substrates by chemical vapor deposition. A1 contacts with differ- ent thickness values are deposited on the 3C-SiC/Si （100） structure by the magnetron sputtering met...The 3C-SiC thin films used herein are grown on Si substrates by chemical vapor deposition. A1 contacts with differ- ent thickness values are deposited on the 3C-SiC/Si （100） structure by the magnetron sputtering method and are annealed at different temperatures. We focus on the effects of the annealing temperature on the ohmic contact properties and mi- crostructure of A1/3C-SiC structure. The electrical properties of A1 contacts to n-type 3C-SiC are characterized by the transmission line method. The crystal structures and chemical phases of A1 contacts are examined by X-ray diffraction, Raman spectra, and transmission electron microscopy, respectively. It is found that the A1 contacts exhibit ohmic contact behaviors when the annealing temperature is below 550 ℃, and they become Schottky contacts when the annealing tem- perature is above 650 ℃. A minimum specific contact resistance of 1.8 × 10-4 Ω cm2 is obtained when the A1 contact is annealed at 250 ℃.展开更多
The solution of 3 D elastic-plastic frictional contact problems belongs to the un specified boundary problems where the interaction between two kinds of nonlinearities should occur. Considering the difficulties for th...The solution of 3 D elastic-plastic frictional contact problems belongs to the un specified boundary problems where the interaction between two kinds of nonlinearities should occur. Considering the difficulties for the solution of 3 D frictional contact problems, the key part is the determination of the tangential slip states at the contact points, and a great amount of computing work is needed for a high accuracy result. A new method based on a combination of programming and iteration methods, which are respectively known as two main kinds of methods for contact analysis, was put forward to deal with 3 D elastic-plastic contact problems. Numerical results demonstrate the efficiency of the algorithm illustrated here.展开更多
We consider a parametrized family of compact G2-calibrated solvmanifolds, and construct associative (so volume-minimizing submanifolds) 3-tori with respect to the closed G2-structure. We also study the Laplacian flow ...We consider a parametrized family of compact G2-calibrated solvmanifolds, and construct associative (so volume-minimizing submanifolds) 3-tori with respect to the closed G2-structure. We also study the Laplacian flow of this closed G2 form on the solvable Lie group underlying to each of these solvmanifolds, and show long time existence of the solution.展开更多
This study was conducted to do exposure assessment of the possible migration of antimony trioxide （Sb203） from Polyethylene terephthalate （PET） food contact materials （FCM）. Consumption Factor （CF） and Food-ty...This study was conducted to do exposure assessment of the possible migration of antimony trioxide （Sb203） from Polyethylene terephthalate （PET） food contact materials （FCM）. Consumption Factor （CF） and Food-type Distribution Factor （fT） were calculated from survey data with reference to the US FDA method. The most conservative migration conditions were obtained by testing Sb migration from PET FCM based on the Chinese national standard of GB/T 5009.101-2003[1].展开更多
系统研究了Ag Sn In Ni合金内氧化法制备Ag-Sn O_(2)-In_(2)O_(3)-Ni O电接触材料的微观组织演变机理及氧化物颗粒分布的调控。结果表明,退火工艺决定了Ag Sn In Ni的缺陷状态,随退火温度的升高,合金中缺陷密度降低,内氧化速度减慢。内...系统研究了Ag Sn In Ni合金内氧化法制备Ag-Sn O_(2)-In_(2)O_(3)-Ni O电接触材料的微观组织演变机理及氧化物颗粒分布的调控。结果表明,退火工艺决定了Ag Sn In Ni的缺陷状态,随退火温度的升高,合金中缺陷密度降低,内氧化速度减慢。内氧化过程中银合金同时发生回复与再结晶,但内氧化形成的Sn O_(2)和In_(2)O_(3)颗粒可钉扎位错、亚晶界等缺陷,抑制再结晶的发生。Ag-Sn O_(2)-In_(2)O_(3)-Ni O合金微观组织的差异是O原子沿着缺陷向样品内部扩散与Ag合金基体发生再结晶的相互竞争的结果,这导致了芯部组织为氧化物密度较低的颗粒状分布,而外侧组织为氧化物颗粒沿着缺陷墙呈现束装聚集分布。退火工艺为550℃/2 h、氧化工艺为700℃/0.3 MPa×26 h时,可获得氧化物尺寸和分布一致性高的Ag-Sn O_(2)-In_(2)O_(3)-Ni O材料。展开更多
基金Projects supported by the National Natural Science Foundation of China (Grant Nos.61874084,61974119,and U21A20501)。
文摘The formation of low-resistance Ohmic contacts in Ga_(2)O_(3) is crucial for high-performance electronic devices. Conventionally, a titanium/gold(Ti/Au) electrode is rapidly annealed to achieve Ohmic contacts, resulting in mutual diffusion of atoms at the interface. However, the specific role of diffusing elements in Ohmic contact formation remains unclear.In this work, we investigate the contribution of oxygen atom diffusion to the formation of Ohmic contacts in Ga_(2)O_(3). We prepare a Ti/Au electrode on a single crystal substrate and conduct a series of electrical and structural characterizations.Using density functional theory, we construct a model of the interface and calculate the charge density, partial density of states, planar electrostatic potential energy, and I–V characteristics. Our results demonstrate that the oxygen atom diffusion effectively reduces the interface barrier, leading to low-resistance Ohmic contacts in Ga_(2)O_(3). These findings provide valuable insights into the underlying mechanisms of Ohmic contact formation and highlight the importance of considering the oxygen atom diffusion in the design of Ga_(2)O_(3)-based electronic devices.
基金financially supported by the National Natural Science Foundation of China(Nos.51731004,51671054,and 51501038)“the Fundamental Research Funds for the Central Universities”in China
文摘Ti3SiC2-reintbrced Ag-maJxix composites are expected to serve as eleclrical contacts. In this study, the wettability of Ag on a Ti3SiC2 subslxate was measured by the sessile drop melkod. The Ag-Ti3SiC2 composites were prepared from Ag mad Ti3SiC2 powder mix- tures by pressureless sintering. The effects of compacting pressure （100-800 MPa）, sintering temperature （850-950~C）, mad soaking time （0.5-2 h） on the microslxucture mad properties of the Ag-Ti3SiC2 composites were investigated. The experimental results indicated that Ti3SiC2 paxticulates were uniformly distxibuted in flae Ag matrix, wiflaout reactions at the interthces between flae two phases. The prepared Ag-10wt%Ti3SiC2 had a relative density of 95% mad an electrical resistivity of 2.76 x 10 3 m~）＇cm when compacted at 800 MPa mad sintered at 950~C for 1 h. The incorporation of Ti3SiC2 into Ag was found to improve its hardness without substantially compromising its electrical conductivity; INs behavior was attxibuted to the combination of ceramic and metallic properties of the Ti3SiC2 reinforcement, suggesting its potential application in electrical contacts.
基金Project(51905118)supported by the National Natural Science Foundation of ChinaProject(3072020CF0306)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Wear and scuffing failures often occur in marine transmission gears due to high friction and flash temperature at the interface between the meshing-teeth.In this paper,a numerical solution procedure was developed for the predictions of transient friction and flash temperature in the marine timing gears during one meshing circle based on the 3D line contact mixed lubrication simulation,which had been verified by comparing the flash temperature with those from Blok’s theory.The effect of machined surface roughness on the mixed lubrication characteristics is studied.The obtained results for several typical gear pairs indicate that gear pair 4-6 exhibits the largest friction and the highest interfacial temperature increase due to severe rough surface asperity contacts,while the polished gear surfaces yield the smallest friction and the lowest interfacial temperature.In addition,the influences of the operating conditions and the gear design parameters on the friction-temperature behaviors are discussed.It is observed that the conditions of heavy load and low rotational velocity usually lead to significantly increased friction and temperature.In the meantime,by optimizing the gear design parameters,such as the modulus and the pressure angle,the performance of interfacial friction and temperature can be significantly improved.
基金National Natural Science Foundation of China(Nos.52208328 and 52104090)Innovation Fund Research Project of State Key Laboratory for GeoMechanics and Deep Underground Engineering(No.SKLGDUEK202201)Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering(No.Z020007).
文摘A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)roughness.The essence of the degradation of the maximum possible dilation angle is the degradation of the 3D average equivalent dip angle of the actual contact joint asperities.Firstly,models for calculating the maximum possible dilation angle at the initial and residual shear stress stages are proposed by analyzing the 3D joint morphology characteristics of the corresponding shear stages.Secondly,the variation law of the maximum possible dilation angle is quantified by studying the degradation law of the joint micro convex body.Based on the variation law of the maximum possible dilation angle,the maximum possible shear strength model is proposed.Furthermore,a method to calculate the shear stiffness degradation in the plastic stage is proposed.According to the maximum possible shear strength of rock joints,the shear stress-shear displacement prediction model of rock joints is obtained.The new model reveals that there is a close relationship between joint shear strength and actual contact joint roughness,and the degradation of shear strength after the peak is due to the degradation of actual contact joint roughness.
基金supported by the Shanghai Rising-Star Program,China(Grant No.13QA1403800)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.51002176)+2 种基金the Innovation Program of the Chinese Academy of Sciences(Grant No.KJCX2-EW-W10)the Industry–Academic Joint Technological Innovations Fund Project of Jiangsu Province,China(Grant No.BY2011119)the National High Technology Research and Development Program of China(Grant Nos.2013AA031603 and 2014AA032602)
文摘The 3C-SiC thin films used herein are grown on Si substrates by chemical vapor deposition. A1 contacts with differ- ent thickness values are deposited on the 3C-SiC/Si （100） structure by the magnetron sputtering method and are annealed at different temperatures. We focus on the effects of the annealing temperature on the ohmic contact properties and mi- crostructure of A1/3C-SiC structure. The electrical properties of A1 contacts to n-type 3C-SiC are characterized by the transmission line method. The crystal structures and chemical phases of A1 contacts are examined by X-ray diffraction, Raman spectra, and transmission electron microscopy, respectively. It is found that the A1 contacts exhibit ohmic contact behaviors when the annealing temperature is below 550 ℃, and they become Schottky contacts when the annealing tem- perature is above 650 ℃. A minimum specific contact resistance of 1.8 × 10-4 Ω cm2 is obtained when the A1 contact is annealed at 250 ℃.
基金theNationalKeyBasicResearchSpecialFoundation (G1 9990 3 2 80 5 ) the FoundationforUniversityKeyTeacherbytheMinistryofEducationo
文摘The solution of 3 D elastic-plastic frictional contact problems belongs to the un specified boundary problems where the interaction between two kinds of nonlinearities should occur. Considering the difficulties for the solution of 3 D frictional contact problems, the key part is the determination of the tangential slip states at the contact points, and a great amount of computing work is needed for a high accuracy result. A new method based on a combination of programming and iteration methods, which are respectively known as two main kinds of methods for contact analysis, was put forward to deal with 3 D elastic-plastic contact problems. Numerical results demonstrate the efficiency of the algorithm illustrated here.
文摘We consider a parametrized family of compact G2-calibrated solvmanifolds, and construct associative (so volume-minimizing submanifolds) 3-tori with respect to the closed G2-structure. We also study the Laplacian flow of this closed G2 form on the solvable Lie group underlying to each of these solvmanifolds, and show long time existence of the solution.
基金financially supported by the Beijing Natural Science Foundation-Sanyuan Joint FundingNo.15S00033
文摘This study was conducted to do exposure assessment of the possible migration of antimony trioxide （Sb203） from Polyethylene terephthalate （PET） food contact materials （FCM）. Consumption Factor （CF） and Food-type Distribution Factor （fT） were calculated from survey data with reference to the US FDA method. The most conservative migration conditions were obtained by testing Sb migration from PET FCM based on the Chinese national standard of GB/T 5009.101-2003[1].
文摘系统研究了Ag Sn In Ni合金内氧化法制备Ag-Sn O_(2)-In_(2)O_(3)-Ni O电接触材料的微观组织演变机理及氧化物颗粒分布的调控。结果表明,退火工艺决定了Ag Sn In Ni的缺陷状态,随退火温度的升高,合金中缺陷密度降低,内氧化速度减慢。内氧化过程中银合金同时发生回复与再结晶,但内氧化形成的Sn O_(2)和In_(2)O_(3)颗粒可钉扎位错、亚晶界等缺陷,抑制再结晶的发生。Ag-Sn O_(2)-In_(2)O_(3)-Ni O合金微观组织的差异是O原子沿着缺陷向样品内部扩散与Ag合金基体发生再结晶的相互竞争的结果,这导致了芯部组织为氧化物密度较低的颗粒状分布,而外侧组织为氧化物颗粒沿着缺陷墙呈现束装聚集分布。退火工艺为550℃/2 h、氧化工艺为700℃/0.3 MPa×26 h时,可获得氧化物尺寸和分布一致性高的Ag-Sn O_(2)-In_(2)O_(3)-Ni O材料。
