In this paper, we report the modelling of quantum capacitance in both single-layer and bilayer graphene devices to investigate the temperature dependence. The model includes the existence of electron and hole puddles due to local fluctuations of the potential, which is taken into account with the possibility of finite lifetimes of electronic states to calculate the quantum capacitance using the Gaussian distribution. The results indicate that the simulations are in agreement with the experimental measurements, which proves the accuracy of the proposed model. On the other hand, temperature dependence around the charge neutrality point has been reported for both single and bilayer graphene.
{"title":"Modelling the Quantum Capacitance of Single-layer and Bilayer Graphene","authors":"Yousra Ammour, R. Remmouche, Rachid Fates","doi":"10.5755/j02.ms.34129","DOIUrl":"https://doi.org/10.5755/j02.ms.34129","url":null,"abstract":"In this paper, we report the modelling of quantum capacitance in both single-layer and bilayer graphene devices to investigate the temperature dependence. The model includes the existence of electron and hole puddles due to local fluctuations of the potential, which is taken into account with the possibility of finite lifetimes of electronic states to calculate the quantum capacitance using the Gaussian distribution. The results indicate that the simulations are in agreement with the experimental measurements, which proves the accuracy of the proposed model. On the other hand, temperature dependence around the charge neutrality point has been reported for both single and bilayer graphene.","PeriodicalId":18230,"journal":{"name":"Materials Science","volume":"64 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139242846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Dyakova, Gergi Stefanov, N. Marinkov, S. Gyurov, Y. Kostova
A new amorphous alloy (Al74Cu16Mg10)99,7Zr0.3 was prepared the applying a melt-spinning technique. Temperature dependence of viscosity of the alloy was determined using data from a PerkinElmer TMS2 thermo-mechanical analyzer processed according to a methodology based on the Free Volume Model (FVM). The strength of the alloy was calculated according to the Yang equation and the glass-forming ability was calculated according to the values of the Angell index mA. The activation energy of crystallization and the activation energy of the glass transition were computed using data from differential scanning calorimetry and thermomechanical experiments respectively. The activation energy of crystallization Еx = 168 ± 3.7 kJ/mol, was found to be higher than the activation energy of the glass transition Еg = 156 ± 1.4 kJ/mol, which means a dominant contribution of the atomic transport barrier, compared to the nucleation barrier. The relatively high temperature interval of the supercooled melt state Tx-Tg = 32 K and the low viscosity values in the same range ƞ(Тg) = 3.40E + 11 Pa.s and ƞ(Тx) = 1.87E + 10 Pa.s would allow thermomechanical treatment of the alloy in the temperature range of supercooled melt.
{"title":"Rheological Behavior of a New Amorphous Alloy (Al74Cu16Mg10)99,7Zr0.3","authors":"V. Dyakova, Gergi Stefanov, N. Marinkov, S. Gyurov, Y. Kostova","doi":"10.5755/j02.ms.34241","DOIUrl":"https://doi.org/10.5755/j02.ms.34241","url":null,"abstract":"A new amorphous alloy (Al74Cu16Mg10)99,7Zr0.3 was prepared the applying a melt-spinning technique. Temperature dependence of viscosity of the alloy was determined using data from a PerkinElmer TMS2 thermo-mechanical analyzer processed according to a methodology based on the Free Volume Model (FVM). The strength of the alloy was calculated according to the Yang equation and the glass-forming ability was calculated according to the values of the Angell index mA. The activation energy of crystallization and the activation energy of the glass transition were computed using data from differential scanning calorimetry and thermomechanical experiments respectively. The activation energy of crystallization Еx = 168 ± 3.7 kJ/mol, was found to be higher than the activation energy of the glass transition Еg = 156 ± 1.4 kJ/mol, which means a dominant contribution of the atomic transport barrier, compared to the nucleation barrier. The relatively high temperature interval of the supercooled melt state Tx-Tg = 32 K and the low viscosity values in the same range ƞ(Тg) = 3.40E + 11 Pa.s and ƞ(Тx) = 1.87E + 10 Pa.s would allow thermomechanical treatment of the alloy in the temperature range of supercooled melt.","PeriodicalId":18230,"journal":{"name":"Materials Science","volume":"135 ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139244849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Karthikeyan RAVI KUMAR, Rajkumar Subbiah, Ravi Balasundaram
Polymer composite materials play a vital role in many automotive and wind turbine industries because of their high mechanical properties. The present work emphasises the improvement of polymer composites used for different environmental conditions. The glass and basalt fibers with epoxy and vinyl ester matrix have been prepared individually with 3 % Ni(OH)2 filler. The mechanical and dielectric properties were investigated separately for each material. The mechanical properties of the glass fiber with vinyl ester and Ni(OH)2 filler showed better results. The dielectric strength of the glass fiber with vinyl ester and Ni(OH)2 filler material in a saline environment showed only a 38.16 % reduced dielectric value before saline treatment. The FE validation was also validated using Digimat- FE software for evaluating the void stress in the filler matrix. From the validation the glass fiber with epoxy resin and Ni(OH)2 filler showed the lowest von-Mises stress and shear stress values compared to the other materials. The overall results highlight the improvement of mechanical and electrical properties after the addition of Ni(OH)2 filler materials in offshore environment to meet the demands of the wind turbine industry.
{"title":"Studies on Mechanical and Dielectric Properties of the Ni(OH)2 Filler Reinforced Polymer Composite Materials for Structural Application","authors":"Karthikeyan RAVI KUMAR, Rajkumar Subbiah, Ravi Balasundaram","doi":"10.5755/j02.ms.34793","DOIUrl":"https://doi.org/10.5755/j02.ms.34793","url":null,"abstract":"Polymer composite materials play a vital role in many automotive and wind turbine industries because of their high mechanical properties. The present work emphasises the improvement of polymer composites used for different environmental conditions. The glass and basalt fibers with epoxy and vinyl ester matrix have been prepared individually with 3 % Ni(OH)2 filler. The mechanical and dielectric properties were investigated separately for each material. The mechanical properties of the glass fiber with vinyl ester and Ni(OH)2 filler showed better results. The dielectric strength of the glass fiber with vinyl ester and Ni(OH)2 filler material in a saline environment showed only a 38.16 % reduced dielectric value before saline treatment. The FE validation was also validated using Digimat- FE software for evaluating the void stress in the filler matrix. From the validation the glass fiber with epoxy resin and Ni(OH)2 filler showed the lowest von-Mises stress and shear stress values compared to the other materials. The overall results highlight the improvement of mechanical and electrical properties after the addition of Ni(OH)2 filler materials in offshore environment to meet the demands of the wind turbine industry.","PeriodicalId":18230,"journal":{"name":"Materials Science","volume":"14 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139268034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
2A12 hot-rolled aluminum alloy has high plasticity and toughness, and is widely used in the manufacturing of structural parts in aviation, aerospace, automobiles, and other fields. To explore the effect of friction stir welding process parameters on the welded joint properties of 2A12 hot-rolled aluminum alloy, experimental investigations were conducted. The surface appearance of the welded joints under different process parameters was observed, the microstructure, microhardness, tensile strength, yield strength, elongation and the fracture morphology of the welded joints were assessed. The findings suggested that when the rotation speed was 600 rpm and the forward speed was 250 mm/min, the tensile strength, yield strength and elongation of the welded joint were all maximum, which were 437.6 MPa, 381.6 MPa and 7.5 % respectively, reaching 85.5 %, 88.1 % and 35.7 % of the base material. Under the same forward speed, the tensile strength and elongation of the welded joint initially rose and subsequently declined with the increment of rotation speed. The microhardness distribution of the welded joint exhibited a W-shape pattern. The fracture morphology showed that the fracture type of the welded joint was a ductile fracture. Unlike the base material, the welded joints did not exhibit significant necking during the tensile testing. The research results can be utilized as a reference for the engineering application of friction stir welding of 2A12 hot-rolled aluminum alloy.
{"title":"Analysis of Friction Stir Welded Joint Properties of 2A12 Aluminum Alloy","authors":"X. Ge, Hongfeng Wang, Da Huang, Weiwei Song","doi":"10.5755/j02.ms.34723","DOIUrl":"https://doi.org/10.5755/j02.ms.34723","url":null,"abstract":"2A12 hot-rolled aluminum alloy has high plasticity and toughness, and is widely used in the manufacturing of structural parts in aviation, aerospace, automobiles, and other fields. To explore the effect of friction stir welding process parameters on the welded joint properties of 2A12 hot-rolled aluminum alloy, experimental investigations were conducted. The surface appearance of the welded joints under different process parameters was observed, the microstructure, microhardness, tensile strength, yield strength, elongation and the fracture morphology of the welded joints were assessed. The findings suggested that when the rotation speed was 600 rpm and the forward speed was 250 mm/min, the tensile strength, yield strength and elongation of the welded joint were all maximum, which were 437.6 MPa, 381.6 MPa and 7.5 % respectively, reaching 85.5 %, 88.1 % and 35.7 % of the base material. Under the same forward speed, the tensile strength and elongation of the welded joint initially rose and subsequently declined with the increment of rotation speed. The microhardness distribution of the welded joint exhibited a W-shape pattern. The fracture morphology showed that the fracture type of the welded joint was a ductile fracture. Unlike the base material, the welded joints did not exhibit significant necking during the tensile testing. The research results can be utilized as a reference for the engineering application of friction stir welding of 2A12 hot-rolled aluminum alloy.","PeriodicalId":18230,"journal":{"name":"Materials Science","volume":"67 12","pages":""},"PeriodicalIF":0.9,"publicationDate":"2023-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139275726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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