http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
( Rahul Ghosh ),( A. Venugopal ),( Pradeep P I ),( L. Rama Krishna ),( P. Ramesh Narayanan ),( Bhanu Pant ),( Roy M Cherian ) 한국부식방식학회(구 한국부식학회) 2018 Corrosion Science and Technology Vol.17 No.3
AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075 alloy owing to their high strength combined with better fracture toughness. It is necessary to improve the corrosion resistance and surface properties of the alloy by incorporating plasma electrolytic oxidation (PEO) method. AA7010-T7452 aluminum alloy has been processed through the forging route with multi-stage working operations, and was coated with 10μm thick Al<sub>2</sub>O<sub>3</sub> ceramic aluminina coating using the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC) and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strain rate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanical treatment during the forging process caused a fully recrystallized microstructure, which lead to the poor environmental cracking resistance of the alloy in 3.5% NaCl solution, despite the overaging treatment. Although the fabricated PEO coating improved general corrosion resistance, the brittle nature of the coating did not provide any improvement in SCC resistance of the alloy. However, the hardness and elastic modulus of the coating were significantly higher than the base alloy.
Rahul Ghosh,Hari K. Thota,R. Uma Rani 한국부식방식학회 2019 Corrosion Science and Technology Vol.18 No.5
A thin spray coating of inorganic black lithium polysilicate (IBLP) on black anodized AZ31B magnesiumalloy was fabricated for better corrosion resistance and thermo-optical properties for thermal control of spacecraftcomponents. The morphology of the specimens with and without IBLP-based spray coating was characterizedby SEM-EDS techniques. Impedance and potentiodynamic measurements on the specimens revealed bettercorrosion resistance for the specimen with a thin coating of lithium polysilicate. This was primarily dueto the presence of lithium polysilicate inside the micro-cracks of the black anodized specimen, restrictingthe diffusion paths for corrosive media. Environmental tests, namely, humidity, thermal cycling, thermovacuum performance, were used to evaluate the space-worthiness of the coating. The thermo-optical propertiesof the coating were measured before and after each environmental test to ascertain its stability. The specimenwith an IBLP-based spray coating showed enhanced thermo-optical properties, greater than ~0.90. Hence,the proposed coating demonstrated better handling, better corrosion resistance, and space-worthiness duringthe pre-launch phase owing to its improved thermo-optical properties.
Corrosion and Nanomechanical Behaviors of 16.3Cr-0.22N-0.43C-1.73Mo Martensitic Stainless Steel
( Rahul Ghosh ),( S. Chenna Krishna ),( A. Venugopal ),( P. Ramesh Narayanan ),( Abhay K. Jha ),( P. Ramkumar ),( P. V. Venkitakrishnan ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.6
The effect of nitrogen on the electrochemical corrosion and nanomechanical behaviors of martensitic stainless steel was examined using potentiodynamic polarization and nanoindentation test methods. The results indicate that partial replacement of carbon with nitrogen effectively improved the passivation and pitting corrosion resistance of conventional high-carbon and high- chromium martensitic steels. Post-test observation of the samples after a potentiodynamic test revealed a severe pitting attacks in conventional martensitic steel compared with nitrogen- containing martensitic stainless steel. This was shown to be due to (i) microstructural refinement results in retaining a high-chromium content in the matrix, and (ii) the presence of reversed austenite formed during the tempering process. Since nitrogen addition also resulted in the formation of a Cr<sub>2</sub>N phase as a process of secondary hardening, the hardness of the nitrogen- containing steel is slightly higher than the conventional martensitic stainless steel under tempered conditions, even though the carbon content is lowered. The added nitrogen also improved the wear resistance of the steel as the critical load (Lc2) is less, along with a lower scratch friction coefficient (SFC) when compared to conventional martensitic stainless steel such as AISI 440C.
Nalini Kanta Ghosh,Rahul R,Ashish Singh,Somanath Malage,Supriya Sharma,Ashok Kumar,Rajneesh Kumar Singh,Anu Behari,Ashok Kumar,Rajan Saxena 한국간담췌외과학회 2023 Annals of hepato-biliary-pancreatic surgery Vol.27 No.3
Backgrounds/Aims: Hemangiomas are the most common benign liver lesions; however, they are usually asymptomatic and seldom require surgery. Enucleation and resection are the most commonly performed surgical procedures for symptomatic lesions. This study aims to compare the outcomes of these two surgical techniques. Methods: A retrospective analysis of symptomatic hepatic hemangiomas (HH) operated upon between 2000 and 2021. Patients were categorized into the enucleation and resection groups. Demographic profile, intraoperative bleeding, and morbidity (Clavien-Dindo Grade) were compared. Independent t-test and chi-square tests were used for continuous and categorical variables respectively. p-value of < 0.05 was considered significant. Results: Sixteen symptomatic HH patients aged 30 to 66 years underwent surgery (enucleation = 8, resection = 8) and majority were females (n = 10 [62.5%]). Fifteen patients presented with abdominal pain, and one patient had an interval increase in the size of the lesion from 9 to 12 cm. The size of hemangiomas varied from 6 to 23 cm. The median blood loss (enucleation: 350 vs. resection: 600 mL), operative time (enucleation: 5.8 vs. resection: 7.5 hours), and postoperative hospital stay (enucleation: 6.5 vs. resection: 11 days) were greater in the resection group (statistically insignificant). In the resection group, morbidity was significantly higher (62.6% vs. 12.5%, p = 0.05), including one mortality. All patients remained asymptomatic during the follow-up. Conclusions: Enucleation was simpler with less morbidity as compared to resection in our series. However, considering the small number of patients, further studies are needed with comparable groups to confirm the superiority of enucleation over resection.
Ankush Bag,Rahul Kumar,Partha Mukhopadhyay,Mihir K. Mahata,Apurba Chakraborty,Saptarsi Ghosh,Sanjay K. Jana,Dhrubes Biswas 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4
In-situ RHEED and ex-situ AFM characterizations have been employed to investigate transformations of surface topography with the thickness of PAMBE grown AlGaN and InGaN on GaN. The ternary alloys have been grown with identical growth-front roughness as confirmed by XRR and RHEED observations. The spottier RHEED has been observed with increased thickness of the InGaN as opposed to streakier behavior of AlGaN. We have noticed incremental nature of RMS roughness, skewness and kurtosis of InGaN surface compared to GaN or AlGaN from AFM as evident by final spotty RHEED for InGaN. However, the analyzed fractal dimension is lower for InGaN as opposed to AlGaN ( ). From the kinetic roughening perspective of adatoms, the experimental evidences lead to the high correlation between binding energy of the cluster atoms ( ) and the modified DDA growth model with dissociation and evaporation to confirm the efficacy of the study. The initial streaky and spotty RHEED of InGaN and AlGaN, respectively, can be attributed to their Eb that causes smoothing and roughening of the GaN surface due to adatoms surface mobility behavior. Therefore, the fractal description reveals the fact during formation of nitride hetero-interface while other AFM results describe the top surface.
Reverse Bias Leakage Current Mechanism of AlGaN/InGaN/GaN Heterostructure
Apurba Chakraborty,Saptarsi Ghosh,Partha Mukhopadhyay,Sanjay K. Jana,Syed Mukulika Dinara,Ankush Bag,Mihir K. Mahata,Rahul Kumar,Subhashis Das,Palash Das,Dhrubes Biswas 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.2
The reverse bias leakage current mechanism of AlGaN/InGaN/GaNheterostructure is investigated by current-voltage measurement intemperature range from 298 K to 423 K. The Higher electric field acrossthe AlGaN barrier layer of AlGaN/InGaN/GaN double heterostructuredue to higher polarization charge is found to be responsible for strongFowler-Nordheim (FN) tunnelling in the electric field higher than3.66 MV/cm. For electric field less than 3.56 MV/cm, the reverse biasleakage current is also found to follow the trap assisted Frenkel-Poole(FP) emission in low negative bias region. Analysis of reverse FPemission yielded the barrier height of trap energy level of 0.34 eV withrespect to Fermi level.
Manish Debbarma,Subhendu Das,Bimal Debnath,Debankita Ghosh,Sayantika Chanda,Rahul Bhattacharjee,Surya Chattopadhyaya 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
Density functional calculations are carried out on elastic and thermal properties of zinc-blende specimens within HgxCd1−xS,HgxCd1−xSe and HgxCd1−xTe ternary systems. Elastic stiffness constants decrease almost linearly with increasing Hg-concentrationin each system. Each cubic sample is mechanically and dynamically stable, elastically anisotropic, compressibleagainst elastic deformation, ductile and fairly plastic. The hardness of specimens in each system reduces almost linearly withenhancement in Hg-composition. Mixed kind of bonding with dominancy of ionic bonding over covalent, central nature ofinteratomic forces and bond bending over stretching exist in all specimens. In each system, covalency, Debye temperature andfrequency, Debye temperature for acoustic phonon, thermal conductivity and melting temperature of specimens decreases,while Philip ionicity and Gruneisen parameter increases with increasing Hg-concentration.
Piyush Kumar,Reliance Jain,M. R. Rahul,Abhijit Ghosh,Sumanta Samal,Gandham Phanikumar 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9
The present study explores the high temperature deformation behavior of FeCoNiCrAlTi dual phase high entropy alloy(henceforth referred to as DP-HEA) in the temperature range of 900–1100 °C (1173–1373 K) and the strain rate varyingfrom 0.001 to 0.1 s−1. The as-cast sample has been characterized using scanning electron microscopy, X-ray diffraction,and differential scanning calorimetry, which reveals the presence of two phases, disordered γ and ordered γ′. A constitutiverelationship between the process parameters (stress temperature, strain, and strain rate) has been drawn using the Arrheniustypeequation to recognize the high temperature deformation behavior of the DP-HEA. The optimum thermomechanicalprocessing window of the DP-HEA has been determined by constructing multiple contour maps based on different parameterssuch as efficiency, strain rate sensitivity, etc. And the optimum processing domain has been found to lie approximately in thetemperature range of 1260–1300 K and SR = 10–2.3–10–2 s−1, 1325–1373 K and SR = 10–1.4–10–1 s−1 & 1173–1193 K andSR = 10–1.3–10–1.55 s−1. Finally, the stable and unstable regimes in the processing maps are correlated with the microstructureof hot deformed samples.
Manish Debbarma,Utpal Sarkar,Bimal Debnath,Sayantika Chanda,Debankita Ghosh,Rahul Bhattacharjee,Surya Chattopadhyaya 한국물리학회 2018 Current Applied Physics Vol.18 No.6
Influence of doping of mercury atom(s) on optoelectronic properties of binary cadmium chalcogenides have been investigated theoretically by designing the mercury doped cadmium chalcogenide ternary alloys in B3 phase at some specific Hg-concentrations and studying their optoelectronic properties using DFT based FP-LAPW methodology. The structural properties are computed using WC-GGA, while spin-orbit coupling included electronic and optical properties are computed using TB-mBJ, EV-GGA, B3LYP and WC-GGA exchange-correlation functionals. In addition, electronic properties of mercury chalcogenides are calculated precisely using the GGA+U functionals. The concentration dependence of lattice parameter and bulk modulus of each of the HgxCd1−xS, HgxCd1−xSe, HgxCd1−xTe alloy systems show almost linearity. For each of the alloy systems, band gap decreases almost linearly with increase in Hg-concentration in the unit cell and contribution from charge exchange to the band gap bowing is larger than that from for each of the volume deformation and structural relaxation. Also, covalent bonding exists between different constituent atoms in each compound. Optical properties of each specimen are computed from their spectra of dielectric function, refractive index, extinction coefficient, normal incidence reflectivity, optical conductivity, optical absorption coefficient and energy loss function. Several calculated results have been compared with available experimental and other theoretical data.