Efficient thermal management is critical to the reliability and performance of nanoscale electronic and photonic devices,particularly those incorporating multilayer structures.In this study,non-equilibrium molecular d...Efficient thermal management is critical to the reliability and performance of nanoscale electronic and photonic devices,particularly those incorporating multilayer structures.In this study,non-equilibrium molecular dynamics simulations were conducted to systematically investigate the effects of temperature,penetration depth,and Si layer thickness on the interfacial thermal resistance(ITR)in nanometer-scale Mo/Si multilayers,widely employed in extreme ultraviolet lithography.The results indicate that:(i)temperature variations exert a negligible influence on the ITR of amorphous Mo/Si interfaces,which remains stable across the range of 200-900 K;(ii)increasing penetration depth enhances the overlap of phonon density of states,thereby significantly reducing ITR;(iii)the ITR decreases with increasing Si thickness up to4.2 nm due to quasi-ballistic phonon transport,but rises again as phonon scattering becomes more pronounced at larger thicknesses.This study provides quantitative insights into heat transfer mechanisms at amorphous interfaces and also offers a feasible strategy for tailoring interfacial thermal transport through structural design.展开更多
In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prep...In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prepared by casting and annealing. The effects of adding Si on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated systematically. The results indicate that the as-cast and annealed alloys hold multiple structures, involving two major phases of （La, Mg）2Ni7 with a Ce2Ni7-type hexagonal structure and LaNi5 with a CaCu5-type hexagonal structure as well as one residual phase LaNi3. The addition of Si results in a decrease in （La, Mg）2Ni7 phase and an increase in LaNi5 phase without changing the phase structure of the alloys. What is more, it brings on an obvious effect on electrochemical hydrogen storage characteristics of the alloys. The discharge capacities of the as-cast and annealed alloys decline with the increase of Si content, but their cycle stabilities clearly grow under the same condition. Furthermore, the measurements of the high rate discharge ability, the limiting current density, hydrogen diffusion coefficient as well as electrochemical impedance spectra all indicate that the electrochemical kinetic properties of the electrode alloys first increase and then decrease with the rising of Si content.展开更多
Nano-structured photon management is currently an interesting topic since it can enhance the optical absorption and reduce the surface reflection which will improve the performance of many kinds of optoelectronic devi...Nano-structured photon management is currently an interesting topic since it can enhance the optical absorption and reduce the surface reflection which will improve the performance of many kinds of optoelectronic devices, such as Si-based solar cells and light emitting diodes. Here, we report the fabrication of periodically nano-patterned Si structures by using polystyrene nano-sphere lithography technique. By changing the diameter of nano-spheres and the dry etching parameters, such as etching time and etching power, the morphologies of formed Si nano-structures can be well controlled as revealed by atomic force microscopy.A good broadband antireflection property has been achieved for the formed periodically nano-patterned Si structures though they have the low aspect ratio(<0.53). The reflection can be significantly reduced compared with that of flat Si substrate in a wavelength range from 400 nm to 1200 nm. The weighted mean reflection under the AM1.5 solar spectrum irradiation can be as low as 3.92% and the corresponding optical absorption is significantly improved, which indicates that the present Si periodic nano-structures can be used in Si-based thin film solar cells.展开更多
The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and grow...The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration （Nd） is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.展开更多
Si coordination structures have been proven to greatly influence the ammonia-selective catalytic reduc-tion(NH_(3)-SCR)catalytic properties and the hydrothermal stability of Cu-based silicoaluminophosphate-form cataly...Si coordination structures have been proven to greatly influence the ammonia-selective catalytic reduc-tion(NH_(3)-SCR)catalytic properties and the hydrothermal stability of Cu-based silicoaluminophosphate-form catalysts.However,the role of various Si coordination structures in the NH_(3)-SCR reaction over Cu-SAPO-34 catalyst remains unknown.Herein,a batch of Cu-SAPO-34 samples with various Si contents was synthesized via a one-pot method to study the role of Si coordination structures in the NH_(3)-SCR catalytic properties and hydrothermal stability.Cu/34-2 with the highest proportion of Si(xOAl)(x=1~3)struc-tures exhibits remarkable durability with 90%NO reduction efficiency within 200~450℃ even after a hydrothermal aging treatment at 850℃.In contrast,Cu/34-1 and Cu/34-4 with the highest proportions of Si(4OAl)and Si(0OAl)structures,respectively,are significantly deactivated by the same hydrothermal treatment.To better understand this phenomenon,the relationship between the Si coordination struc-tures and SCR performance is established using characterization techniques and kinetics measurements.Results reveal that a high content of Si(4OAl)and Si(0OAl)is detrimental to the hydrothermal stability of Cu-SAPO-34 catalyst.However,Si(x OAl)(x=1~3)structures are conducive to the stabilization of isolated Cu^(2+),thus enhancing the stability to severe hydrothermal treatment.展开更多
A first-principles plane wave method with the ultrasoft pseudopotential scheme in the frame of the density functional theory （DFT） is performed to calculate the lattice parameters a and c, the bulk modulus B0 and it...A first-principles plane wave method with the ultrasoft pseudopotential scheme in the frame of the density functional theory （DFT） is performed to calculate the lattice parameters a and c, the bulk modulus B0 and its pressure derivative B0 of the zinc-blende GaAs （ZB-GaAs）, rocksalt GaAs （RS-GaAs）, CsCl-GaAs, NiAs- GaAs and wurtzite GaAs （WZ-GaAs）. Our results are consistent with the available experimental data and other theoretical results. We also calculate the phase transition pressures among these different phases. The results are satisfactory.展开更多
The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated....The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated. Lamellar structure consisted of Mo_5Si_3 (D8m) phaseand MoSi_2 (C11_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2 hypoeutectic alloy, thelamellar structure was found only after annealing and developed well with fine spacing on the orderof hundred nanometers after annealing at 1200℃ for 48 h. But when the annealing time was up to 96h, the well-developed lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, thelamellar structure was found both before and after annealing. However the volume fraction andspacing of the lamellar structure did not change significantly before and after annealing. Theeffects of the formation, development and destruction of lamellar structure on Vickers hardness ofalloys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48 h,the Vickers hardness was improved about 19% compared with that without annealing and formation oflamellar structure. The highest Vickers hardness of Mo5Si3-MoSi_2 hypereutectic was increasing about18% when annealing at 1200℃ for 48 h.展开更多
The dielectric properties of Au/Si3N4/n-Si （MIS） structures are studied using the admittance measurements （C–V and G/ω–V） each as a function of temperature in a range from 80 K to 400 K for two frequencies （10...The dielectric properties of Au/Si3N4/n-Si （MIS） structures are studied using the admittance measurements （C–V and G/ω–V） each as a function of temperature in a range from 80 K to 400 K for two frequencies （100 kHz and 1 MHz）. Experimental results show that both the dielectric constant （ε’） and the dielectric loss （ε＂） increase with temperature increasing and decrease with frequency increasing. The measurements also show that the ac conductivity （σac） increases with temperature and frequency increasing. The lnσac versus 1000/T plot shows two linear regions with different slopes which correspond to low （120 K–240 K） and high （280 K–400 K） temperature ranges for the two frequencies. It is found that activation energy increases with frequency and temperature increasing.展开更多
The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-...The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-Ga_2O_3 are in good agreement with experimental results. Si-and Sn-doped β-Ga_2O_3 tend to form under O-poor conditions, and the formation energy of Si-doped β-Ga_2O_3 is larger than that of Sn-doped β-Ga_2O_3 because of the large bond length variation between Ga–O and Si–O. Si-and Sn-doped β-Ga_2O_3 have wider optical gaps than β-Ga_2O_3, due to the Burstein–Moss effect and the bandgap renormalization effect. Si-doped β-Ga_2O_3 shows better electron conductivity and a higher optical absorption edge than Sn-doped β-Ga_2O_3, so Si is more suitable as a dopant of n-type β-Ga_2O_3, which can be applied in deep-UV photoelectric devices.展开更多
In this article, the quenched Nd_4.5Fe_75Co_1Si_l B_18.5 ribbons were prepared, and the structures and properties were investigated. The results show that the change of structures of Nd_4.5 Fe_75 Co_1 Si_1 B_18.5 qu...In this article, the quenched Nd_4.5Fe_75Co_1Si_l B_18.5 ribbons were prepared, and the structures and properties were investigated. The results show that the change of structures of Nd_4.5 Fe_75 Co_1 Si_1 B_18.5 quenched amorphous ribbons is Am→Am'+Fe_3B+Nd_2Fe_23B_3+Nd_2Fe_14B→Nd_2- Fe_14B when it is heated. The effect of crystallizing treatment temperature and time on the magnetic properties of the quenched alloy was studied. The magnetic properties of 16 m/s quenched ribbons for 710℃×1200 s crystallizing treatment reach _iH_c=238.6 hA/m, B_r=0.8987 T and (BH)max=51.39 kJ/m^3. The grain size is about DFe3=32 nm and DNd2Fe14B=22 nm.展开更多
Au/n-Si （MS） structures with a high dielectric interlayer （0.03 graphene-doped PVA） are fabricated to investigate the illumination and voltage effects on electrical and dielectric properties by using capacitance-v...Au/n-Si （MS） structures with a high dielectric interlayer （0.03 graphene-doped PVA） are fabricated to investigate the illumination and voltage effects on electrical and dielectric properties by using capacitance-voltage （C-V） and conductance-voltage （G/w-V） measurements at room temperature and at 1 MHz. Some of the main electrical parameters such as concentration of doping atoms （ND）, barrier height （ ФB（ C - V） ）, depletion layer width （WD） and series resistance （Rs） show fairly large illumination dispersion. The voltage-dependent profile of surface states （Nss） and resistance of the structure （Ri ） are also obtained by using the dark-illumination capacitance （Cdark- Cm） and Nicollian-Brews methods, respectively, For a clear observation of changes in electrical parameters with illumination, the values of ND, WD, ФB（O- V） and Rs are drawn as a function of illumination intensity. The values of ND and WD change almost linearly with illumination intensity. On the other hand, Rs decreases almost exponentially with increasing illumination intensity whereas ФB（C - V） increases. The experimental results suggest that the use of a high dielectric interlayer （0.03 graphene-doped PVA） considerably passivates or reduces the magnitude of the surface states. The large change or dispersion in main electrical parameters can be attributed to generation of electron-hole pairs in the junction under illumination and to a good light absorption. All of these experimental results confirm that the fabricated Au/0.03 graphene-doped PVA/n-Si structure can be used as a photodiode or a capacitor in optoelectronic applications.展开更多
The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance.In this study,dynamic carbonated water erosion was simulated t...The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance.In this study,dynamic carbonated water erosion was simulated to assess erosion depth,microstructure,phase migrations,and pore structure in various tunnel lining cement-based materials.Additionally,Ca^(2+)leaching was analyzed,and impact of Ca/Si molar ratio in hydration products on erosion resistance was discussed by thermodynamic calculations.The results indicate that carbonated water erosion caused rough and porous surface on specimens,with reduced portlandite and CaCO_(3) content,increased porosity,and an enlargement of pore size.The thermodynamic calculations indicate that the erosion is spontaneous,driven by physical dissolution and chemical reactions dominated by Gibbs free energy.And the erosion reactions proceed more spontaneously and extensively when Ca/Si molar ratio in hydration products was higher.Therefore,cement-based materials with higher portlandite content exhibit weaker erosion resistance.Model-building concrete,with C-S-H gel and portlandite as primary hydration products,has greater erosion susceptibility than shotcrete with ettringite as main hydration product.Moreover,adding silicon-rich mineral admixtures can enhance the erosion resistance.This research offers theory and tech insights to boost cement-based material resistance against carbonated water erosion in karst tunnel engineering.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52206092)the National Key R&D Program of China(Grant No.2024YFF0508900)+1 种基金the Big Data Computing Center of Southeast Universitythe Center for Fundamental and Interdisciplinary Sciences of Southeast University。
文摘Efficient thermal management is critical to the reliability and performance of nanoscale electronic and photonic devices,particularly those incorporating multilayer structures.In this study,non-equilibrium molecular dynamics simulations were conducted to systematically investigate the effects of temperature,penetration depth,and Si layer thickness on the interfacial thermal resistance(ITR)in nanometer-scale Mo/Si multilayers,widely employed in extreme ultraviolet lithography.The results indicate that:(i)temperature variations exert a negligible influence on the ITR of amorphous Mo/Si interfaces,which remains stable across the range of 200-900 K;(ii)increasing penetration depth enhances the overlap of phonon density of states,thereby significantly reducing ITR;(iii)the ITR decreases with increasing Si thickness up to4.2 nm due to quasi-ballistic phonon transport,but rises again as phonon scattering becomes more pronounced at larger thicknesses.This study provides quantitative insights into heat transfer mechanisms at amorphous interfaces and also offers a feasible strategy for tailoring interfacial thermal transport through structural design.
基金Projects(50961009,51161015)supported by the National Natural Science Foundation of ChinaProject(2011AA03A408)supported by the High-tech Research and Development Program of ChinaProjects(2011ZD10,2010ZD05)supported by the Natural Science Foundation of Inner Mongolia,China
文摘In order to ameliorate the electrochemical hydrogen storage performance of La-Mg-Ni system A2B7-type electrode alloys, a small amount of Si was added. The La0.8Mg0.2Ni3.3Co0.2Six （x=0-0.2） electrode alloys were prepared by casting and annealing. The effects of adding Si on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated systematically. The results indicate that the as-cast and annealed alloys hold multiple structures, involving two major phases of （La, Mg）2Ni7 with a Ce2Ni7-type hexagonal structure and LaNi5 with a CaCu5-type hexagonal structure as well as one residual phase LaNi3. The addition of Si results in a decrease in （La, Mg）2Ni7 phase and an increase in LaNi5 phase without changing the phase structure of the alloys. What is more, it brings on an obvious effect on electrochemical hydrogen storage characteristics of the alloys. The discharge capacities of the as-cast and annealed alloys decline with the increase of Si content, but their cycle stabilities clearly grow under the same condition. Furthermore, the measurements of the high rate discharge ability, the limiting current density, hydrogen diffusion coefficient as well as electrochemical impedance spectra all indicate that the electrochemical kinetic properties of the electrode alloys first increase and then decrease with the rising of Si content.
基金supported by NSFC(Nos.61036001and 11274155)"973"pro ject(2013CB632101)NSF of Jiangsu Province(BK2010010)and PAPD
文摘Nano-structured photon management is currently an interesting topic since it can enhance the optical absorption and reduce the surface reflection which will improve the performance of many kinds of optoelectronic devices, such as Si-based solar cells and light emitting diodes. Here, we report the fabrication of periodically nano-patterned Si structures by using polystyrene nano-sphere lithography technique. By changing the diameter of nano-spheres and the dry etching parameters, such as etching time and etching power, the morphologies of formed Si nano-structures can be well controlled as revealed by atomic force microscopy.A good broadband antireflection property has been achieved for the formed periodically nano-patterned Si structures though they have the low aspect ratio(<0.53). The reflection can be significantly reduced compared with that of flat Si substrate in a wavelength range from 400 nm to 1200 nm. The weighted mean reflection under the AM1.5 solar spectrum irradiation can be as low as 3.92% and the corresponding optical absorption is significantly improved, which indicates that the present Si periodic nano-structures can be used in Si-based thin film solar cells.
基金Supported by the National Natural Science Foundation of China under Grant No 61434006
文摘The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration （Nd） is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.
基金financial support from the National Natural Science Foundation of China (No.52000084)the China Postdoctoral Science Foundation (No.2019M662630)。
文摘Si coordination structures have been proven to greatly influence the ammonia-selective catalytic reduc-tion(NH_(3)-SCR)catalytic properties and the hydrothermal stability of Cu-based silicoaluminophosphate-form catalysts.However,the role of various Si coordination structures in the NH_(3)-SCR reaction over Cu-SAPO-34 catalyst remains unknown.Herein,a batch of Cu-SAPO-34 samples with various Si contents was synthesized via a one-pot method to study the role of Si coordination structures in the NH_(3)-SCR catalytic properties and hydrothermal stability.Cu/34-2 with the highest proportion of Si(xOAl)(x=1~3)struc-tures exhibits remarkable durability with 90%NO reduction efficiency within 200~450℃ even after a hydrothermal aging treatment at 850℃.In contrast,Cu/34-1 and Cu/34-4 with the highest proportions of Si(4OAl)and Si(0OAl)structures,respectively,are significantly deactivated by the same hydrothermal treatment.To better understand this phenomenon,the relationship between the Si coordination struc-tures and SCR performance is established using characterization techniques and kinetics measurements.Results reveal that a high content of Si(4OAl)and Si(0OAl)is detrimental to the hydrothermal stability of Cu-SAPO-34 catalyst.However,Si(x OAl)(x=1~3)structures are conducive to the stabilization of isolated Cu^(2+),thus enhancing the stability to severe hydrothermal treatment.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10776022, 10576020, and 60436010.
文摘A first-principles plane wave method with the ultrasoft pseudopotential scheme in the frame of the density functional theory （DFT） is performed to calculate the lattice parameters a and c, the bulk modulus B0 and its pressure derivative B0 of the zinc-blende GaAs （ZB-GaAs）, rocksalt GaAs （RS-GaAs）, CsCl-GaAs, NiAs- GaAs and wurtzite GaAs （WZ-GaAs）. Our results are consistent with the available experimental data and other theoretical results. We also calculate the phase transition pressures among these different phases. The results are satisfactory.
文摘The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated. Lamellar structure consisted of Mo_5Si_3 (D8m) phaseand MoSi_2 (C11_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2 hypoeutectic alloy, thelamellar structure was found only after annealing and developed well with fine spacing on the orderof hundred nanometers after annealing at 1200℃ for 48 h. But when the annealing time was up to 96h, the well-developed lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, thelamellar structure was found both before and after annealing. However the volume fraction andspacing of the lamellar structure did not change significantly before and after annealing. Theeffects of the formation, development and destruction of lamellar structure on Vickers hardness ofalloys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48 h,the Vickers hardness was improved about 19% compared with that without annealing and formation oflamellar structure. The highest Vickers hardness of Mo5Si3-MoSi_2 hypereutectic was increasing about18% when annealing at 1200℃ for 48 h.
基金Projected supported by Gazi University Scientific Research Project(BAP),FEF.05/2012-15
文摘The dielectric properties of Au/Si3N4/n-Si （MIS） structures are studied using the admittance measurements （C–V and G/ω–V） each as a function of temperature in a range from 80 K to 400 K for two frequencies （100 kHz and 1 MHz）. Experimental results show that both the dielectric constant （ε’） and the dielectric loss （ε＂） increase with temperature increasing and decrease with frequency increasing. The measurements also show that the ac conductivity （σac） increases with temperature and frequency increasing. The lnσac versus 1000/T plot shows two linear regions with different slopes which correspond to low （120 K–240 K） and high （280 K–400 K） temperature ranges for the two frequencies. It is found that activation energy increases with frequency and temperature increasing.
基金Project supported by the Science and Technology Program of Guangdong Province,China(Grant No.2015B010112002)the Science and Technology Project of Guangzhou City,China(Grant No.201607010250)
文摘The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-Ga_2O_3 are in good agreement with experimental results. Si-and Sn-doped β-Ga_2O_3 tend to form under O-poor conditions, and the formation energy of Si-doped β-Ga_2O_3 is larger than that of Sn-doped β-Ga_2O_3 because of the large bond length variation between Ga–O and Si–O. Si-and Sn-doped β-Ga_2O_3 have wider optical gaps than β-Ga_2O_3, due to the Burstein–Moss effect and the bandgap renormalization effect. Si-doped β-Ga_2O_3 shows better electron conductivity and a higher optical absorption edge than Sn-doped β-Ga_2O_3, so Si is more suitable as a dopant of n-type β-Ga_2O_3, which can be applied in deep-UV photoelectric devices.
基金Commission of Science and Technology of Province Liaoning !(No.962154).
文摘In this article, the quenched Nd_4.5Fe_75Co_1Si_l B_18.5 ribbons were prepared, and the structures and properties were investigated. The results show that the change of structures of Nd_4.5 Fe_75 Co_1 Si_1 B_18.5 quenched amorphous ribbons is Am→Am'+Fe_3B+Nd_2Fe_23B_3+Nd_2Fe_14B→Nd_2- Fe_14B when it is heated. The effect of crystallizing treatment temperature and time on the magnetic properties of the quenched alloy was studied. The magnetic properties of 16 m/s quenched ribbons for 710℃×1200 s crystallizing treatment reach _iH_c=238.6 hA/m, B_r=0.8987 T and (BH)max=51.39 kJ/m^3. The grain size is about DFe3=32 nm and DNd2Fe14B=22 nm.
文摘Au/n-Si （MS） structures with a high dielectric interlayer （0.03 graphene-doped PVA） are fabricated to investigate the illumination and voltage effects on electrical and dielectric properties by using capacitance-voltage （C-V） and conductance-voltage （G/w-V） measurements at room temperature and at 1 MHz. Some of the main electrical parameters such as concentration of doping atoms （ND）, barrier height （ ФB（ C - V） ）, depletion layer width （WD） and series resistance （Rs） show fairly large illumination dispersion. The voltage-dependent profile of surface states （Nss） and resistance of the structure （Ri ） are also obtained by using the dark-illumination capacitance （Cdark- Cm） and Nicollian-Brews methods, respectively, For a clear observation of changes in electrical parameters with illumination, the values of ND, WD, ФB（O- V） and Rs are drawn as a function of illumination intensity. The values of ND and WD change almost linearly with illumination intensity. On the other hand, Rs decreases almost exponentially with increasing illumination intensity whereas ФB（C - V） increases. The experimental results suggest that the use of a high dielectric interlayer （0.03 graphene-doped PVA） considerably passivates or reduces the magnitude of the surface states. The large change or dispersion in main electrical parameters can be attributed to generation of electron-hole pairs in the junction under illumination and to a good light absorption. All of these experimental results confirm that the fabricated Au/0.03 graphene-doped PVA/n-Si structure can be used as a photodiode or a capacitor in optoelectronic applications.
基金Project(2021YJ059)supported by the Research Project of China Academy of Railway Sciences。
文摘The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance.In this study,dynamic carbonated water erosion was simulated to assess erosion depth,microstructure,phase migrations,and pore structure in various tunnel lining cement-based materials.Additionally,Ca^(2+)leaching was analyzed,and impact of Ca/Si molar ratio in hydration products on erosion resistance was discussed by thermodynamic calculations.The results indicate that carbonated water erosion caused rough and porous surface on specimens,with reduced portlandite and CaCO_(3) content,increased porosity,and an enlargement of pore size.The thermodynamic calculations indicate that the erosion is spontaneous,driven by physical dissolution and chemical reactions dominated by Gibbs free energy.And the erosion reactions proceed more spontaneously and extensively when Ca/Si molar ratio in hydration products was higher.Therefore,cement-based materials with higher portlandite content exhibit weaker erosion resistance.Model-building concrete,with C-S-H gel and portlandite as primary hydration products,has greater erosion susceptibility than shotcrete with ettringite as main hydration product.Moreover,adding silicon-rich mineral admixtures can enhance the erosion resistance.This research offers theory and tech insights to boost cement-based material resistance against carbonated water erosion in karst tunnel engineering.
