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Ashutosh Sharma,Hansung Lee,Byungmin Ahn 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9
In this study, equimolar AlCuSiFe-x (x = Cr, Mn, Zn, Sn) HEAs were fabricated by mechanical alloying (MA) and sparkplasma sintering methods (SPS). The MA was performed for 45 h followed by densification of powder compacts at 650 °C. The results revealed the formation of dual face-centered cubic (FCC) and body-centered cubic (BCC) structures in AlCuSiFex(x = Zn, Sn) while a single BCC solid solution was noticed in AlCuSiFe-x (x = Cr, Mn). After SPS treatment, AlCuSiFeSnalloy contained FCC with CuxSnywhile AlCuSiFe–Zn changed to FCC + BCC structure. Similarly, AlCuSiFeCr andAlCuSiFeMn showed the formation of BCC + FCC with additional σ- and μ-phases in the HEA matrix. The calculated thermodynamicparameters of HEAs also supported the formation of different solid-solution phases in each of the above HEAs. It was found that HEAs with the additive elements Sn and Zn tend to have major FCC phases, while those with Cr and Mngive rise to major BCC with brittle σ- and μ-phase, which further improves their mechanical strength.
Ashutosh Sharma,Ashok K. Srivastava,Kwan Lee,Byungmin Ahn 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
Lead-free Sn–58Bi– x CeO 2 ( x in wt% = 0, 0.3, 0.6 and 0.9) composite solder was prepared via mechanical blending andmelting route. The ceria nanoparticles (CeO 2 ) were prepared from chemical precipitation method. Further, the variationin microstructure and phase composition, melting point, wetting and mechanical properties were studied through scanningelectron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diff erential scanning calorimetry,spreading ratio, contact angle and tensile testing, respectively. It was shown that Sn–58Bi– x CeO 2 composite solders show16.66 and 32.05% increase in spread ratio and wetting angle, respectively, due to the enhanced melt fl uidity up to x = 0.6. The fraction of hard Bi-phase was also refi ned simultaneously. The tensile results showed a slight decrease in ultimatetensile strength and enhancement in ductility up to x = 0.3 and 0.6 except at x = 0.9. High temperature aging also demonstrateda reduced intermetallic compounds thickness when fraction of ceria nanoparticles in the matrix was up to x = 0.6. Itis suggested that for optimum set of soldering properties, the concentration of the nanoparticles should be at 0.6 wt% in themonolithic Sn–58Bi alloy.
Epoxy Polymer Solder Pastes for Micro-Electronic Packaging Applications
Ashutosh Sharma,정도현,Ju Seon Cheon,정재필 대한용접접합학회 2019 대한용접·접합학회지 Vol.37 No.2
Epoxy solder pastes are widely used in microelectronic packaging for joining die, interconnects, screen displays and as a heat dissipaters. Due to their simplicity and high reliability in chip or package bonding, epoxy solder pastes have been recently paid great attention as a competitive bonding material. The epoxy-based pastes are composed of conducting fillers (solder powder, metallic particles) mixed with epoxy polymer. The bonded joint is robust and has a higher strength after the curing of the epoxy polymer during joining. The inclusion of epoxy as a matrix also alleviate the problem of short-circuiting caused by metallic whisker formation. In view of these advantages, epoxy solder is highly attractive amongst electronic packages and in automotive cars. In this review, we have summarized the background and recent developments in the field of epoxybased solder pastes for electronic and automotive interconnection. Further improvements to improve this technology is also discussed in detail.
Photo Physical Studies of PVP Arrested ZnS Quantum Dots
Ashutosh Kumar Shahi,Bishnu Kumar Pandey,Bheeshma Pratap Singh,Bipin Kumar Gupta,Sukhvir Singh,Ram Gopal 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.2
Monodispersed polyvinylpyrrolidone (PVP) arrested ZnS quantumdots (QDs) having diameter in range ~2-5 nm are synthesized by acolloidal precipitation method using PVP as the stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM),high resolution transmission electron microscopy (HRTEM),selective area electron diffraction (SAED) and Fourier transforminfrared (FT-IR) spectroscopy are probed to investigate thestructural information. The optical properties are studied usingdiffuse UV-visible reflectance and photoluminescence (PL)spectroscopy techniques. TEM images as well as XRD reflectionpeak broadening indicate the nanometer size particles formationwith cubic (sphalerite) phase within the polymer matrix. Opticalabsorbance studies reveal an excitonic peak at around ~310 nmdictates the effect of quantum confinement effect in the ZnS QDs. PL emission spectra for ZnS QDs in PVP exhibit four emissionpeaks at ~382 nm, ~414 nm, ~480 nm and ~527 nm are observed. These excitonic emissions from ZnS QDs are caused by theinterstitial sulfur/Zn vacancies and surface states.
Fabrication and Shear Strength Analysis of Sn-3.5Ag/Cu-Filled TSV for 3D Microelectronic Packaging
Ashutosh Sharma,정도현,노명훈,정재필 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.6
In this study, lead free Sn-3.5Ag solder bumps have been depositedon Cu-filled through-silicon via (TSV) by electroplating method. Thesolder bumps are plated using an acidic solution composed of SnSO4,H2SO4, Ag2SO4, thiourea and an additive. The current density isvaried from −30 to −60 mA/cm2 to obtain the eutectic Sn-3.5Agsolder. The copper is electroplated in TSV using an acidic solution ofCuSO4·5H2O, H2SO4, HCl, and an inhibitor. The bottom-up Cufillingin TSV is achieved by a 3-step pulse periodic reverse (PPR)electroplating. It has been observed that the eutectic Sn-3.5Ag solderis achieved at a current density of −55 mA/cm2. The solder bumps arefurther reflowed onto TSV at 260 °C for 20 seconds, and shearstrength of the formed Sn-3.5Ag/Cu-filled TSV joint is investigated. The results indicate the formation of Cu6Sn5 and Ag3Sn intermetalliccompounds (IMCs) at the joint interface. It is found that with anincrease of shear speed from 0.5-10 mm/s, the shear stress initiallyincreases to a maximum, and then decreases beyond shear speed of10 mm/s through 500 mm/s. It is shown that the ductile fracture modegradually decreases beyond shear speed of 10 mm/s and disappearscompletely at 500 mm/s.
Effect of Mandibular Advancement Splint on Obstructive Sleep Apnea with Insulin Resistant Diabetes
Ashutosh Gupta,Arvind Tripathi,Praveen Rai,Piyush Sharma,Vijay Yadav,Dewanshu Kumar 대한수면연구학회 2020 Journal of sleep medicine Vol.17 No.1
Objectives: Obstructive Sleep apnea (OSA) is characterized by complete or partial obstruction of upper airflow despite the effort to breathe, leading to hypoxemia and hypercapnia. The resultant apnea causes sleep fragmentation, which in turn increases sympathetic activity, decreases insulin sensitivity and glucose uptake, and stimulates hepatic gluconeogenesis that ultimately leads to type 2 diabetes. Most studies exploring the effect of continuous positive airway pressure on insulin sensitivity have showed a positive effect. However, there is no evidence on the effect of mandibular advancement device on insulin resistance (IR). This study was aimed to evaluate the effect of mandibular advancement splint (MAS) on IR in patients with OSA. Methods: The present study was conducted at Department of Prosthodontics, Dental College Azamgarh, from June 2015 to July 2017. Sixty eight dentulous patients with type 2 diabetes and mild to moderate OSA and with stable diabetic regimen were included in the study. A MAS was fabricated and fixed at 70% of the maximum mandibular protrusion recorded. Patients that were comfortable with MAS after one month were assessed for apnea-hypopnea index, mean oxygen saturation, and IR at baseline, 6 months, and 1 year after wearing MAS. Results: An improvement in insulin sensitivity was observed at 6 months for mild OSA patients (p=0.001). For moderate OSA patients, no significant improvement was observed following MAS use (p>0.05). Conclusions: The finding suggested that MAS is effective in improving IR in mild OSA patients.
ZrO2 Nanoparticle Embedded Low Silver Lead Free Solder Alloy for Modern Electronic Devices
ASHUTOSH SHARMA,Hak Ki Yu,조인선,서형탁,안병민 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.1
In this article, the authors present the synthesis of Sn–1.0Ag–0.5Cu (SAC105) alloy embedded with zirconium oxide nanoparticlesusing simple mechanical blending and casting route. The cast samples were characterized in terms of microstructuralevolution, wetting, microhardness, and drop test reliability. The characterizations were performed by using a tabletopX-ray diff raction, fi eld emission scanning electron microscope, and the compositions were identifi ed by energy dispersivespectroscopy. The results showed that addition of ZrO 2 nanoparticles signifi cantly refi nes the grain size, Ag 3 Sn, and Cu 6 Sn 5intermetallic compounds thickness by 46, 14, and 26% respectively as compared to the single component SAC105 alloy. Theresults were also compared with those of standard Sn–3.0Ag–0.5Cu (SAC305) alloy. Although the spreading and microhardnessof SAC105 is found to be slightly poor or comparable to SAC305 yet drop test reliability can be improved signifi cantlyafter addition of ZrO 2 nanoparticles appreciably. This kind of refi nement results in a cheap alternative to SAC305 withcomparable mechanical strength and high solder joint reliability.
HZSM5 Assisted Upgradation of Kraft Lignin Derived Bio-oil
( Ashutosh Agarwal ),( Masud Rana ),( Seong-jae Park ),( Jeong-hun Park ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
Hierarchical and non-hierarchical mono and bimetallic Ni and/or Zn-HZSM5 catalysts were synthesized and compared for upgrading of Kraft lignin derived liquefaction bio-oil in a batch reactor at 300 ℃ for 1h under H2 atmosphere in supercritical ethanol. N<sub>2</sub> adsorption-desorption isotherms, FE-SEM, XPS, ICP-OES and XRD techniques were used to characterize the synthesized catalysts. HZSM5 crystalline structure was not significantly influenced by the incorporation of Ni and Zn. GC-MS and elemental analysis were used to analyze the upgraded bio-oils. After bio-oil upgrading, the amounts of 4-ethylguaiacol and 4- propylguaiacol increased considerably because of reduction in the amounts of unsubstituted guaiacol, 4-methylguaiacol, 4- propenylguaiacol and homovanillic acid. Hydrogenation, alkylation and deoxygenation were the prominent reaction mechanisms responsible for bio-oil upgrading. Highest HHV<sub>Boie</sub> (~29.93 MJ/Kg) was obtained for non-hierarchical 15Ni5Zn-HZSM5 and hierarchical 20Zn-HZSM5 catalysts. Hierarchical and non-hierarchical catalysts favored hydrogenation and deoxygenation, respectively.