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Rai, Alok Kumar,Gim, Jihyeon,Thi, Trang Vu,Ahn, Docheon,Cho, Sung June,Kim, Jaekook American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.21
<P>A facile and cost-effective urea-assisted autocombustion strategy has been designed for the fabrication of Co<SUB>3</SUB>O<SUB>4</SUB>/CoFe<SUB>2</SUB>O<SUB>4</SUB> nanocomposite and pure CoFe<SUB>2</SUB>O<SUB>4</SUB> anode materials followed by annealing at 700 and 900 °C for 6 h, respectively. To confirm the exact structure, Rietiveld analysis was performed on the Synchrotron XRD pattern of both the CoFe<SUB>2</SUB>O<SUB>4</SUB> samples annealed at 700 and 900 °C. The results clearly depicts the formation of two phases (Co<SUB>3</SUB>O<SUB>4</SUB>:CoFe<SUB>2</SUB>O<SUB>4</SUB>) with the ratio of [76.3(5):23.6(3)%] in the sample annealed at 700 °C sample, while single phase CoFe<SUB>2</SUB>O<SUB>4</SUB> formation was observed for the sample annealed at 900 °C. It has also been found that the designed nanocomposite sample is composed of small nanoparticles (50–100 nm), while the size of pure CoFe<SUB>2</SUB>O<SUB>4</SUB> particles is in the range from 600 nm to 1 μm. When applied as an anode material, the obtained Co<SUB>3</SUB>O<SUB>4</SUB>/CoFe<SUB>2</SUB>O<SUB>4</SUB> nanocomposite electrode exhibits high reversible capacity as well as excellent cycling stability and better rate capability in comparison to a pure CoFe<SUB>2</SUB>O<SUB>4</SUB> electrode. The enhanced electrochemical performance of the nanocomposite can be attributed to the intimate interconnection between Co<SUB>3</SUB>O<SUB>4</SUB> and CoFe<SUB>2</SUB>O<SUB>4</SUB>, along with the nanosize range of particles and high surface area, which not only favor fast kinetic properties facilitating electron transportation and Li<SUP>+</SUP> ion insertion/deinsertion but also relieve the stress caused by volume changes during the numerous charge/discharge cycles and suppress the degradation of the material.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-21/jp502004c/production/images/medium/jp-2014-02004c_0009.gif'></P>
Kumar Rai, Alok,Tuan Anh, Ly,Park, Chan-Jin,Kim, Jaekook Elsevier 2013 Ceramics international Vol.39 No.6
<P><B>Abstract</B></P> <P>Nickel oxide nanoparticles were synthesized via a simple and inexpensive microwave-assisted synthesis method within a fast reaction time of less than 20min. The calcination of as-prepared precursor at 600°C produces single phase nickel oxide. The lattice structure and morphology of the sample were investigated by X-ray diffraction, field-emission scanning electron microscopy and field-emission transmission electron microscopy. The particle size range of the nickel oxide nanoparticles varied from 50 to 60nm. Nickel oxide nanoparticles exhibited good electrochemical performances as an anode material for lithium-ion batteries. The prepared nickel oxide anode revealed a large initial discharge capacity of 1111.08mAhg<SUP>−1</SUP> at 0.03C rate and retained 80% of initial capacity (884.30mAhg<SUP>−1</SUP>) after 20 cycles. Furthermore, at elevated rate of 3.7C, the charge capacity of the nickel oxide electrode was as high as 253.1mAhg<SUP>−1</SUP>, which was 35% greater than that of commercial bulk nickel oxide (188mAhg<SUP>−1</SUP>). The enhancement of the electrochemical performance was attributed to the high specific surface area, good electric contact among the particles and easier lithium ion diffusion.</P>
Rai, Alok Kumar,Anh, Ly Tuan,Gim, Jihyeon,Mathew, Vinod,Kim, Jaekook American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.1
<P>A simple and low cost urea-assisted auto-combustion route was investigated for the synthesis of carbon coated CoO nanocomposite. CHN analysis determined the carbon content in CoO/C nanocomposite to be very low as 0.27 wt%. The results show that the CoO/C nanocomposite electrode displays marked lower charge transfer resistance, high lithium storage capacity, and much better rate capability than original CoO nanoparticles electrode.</P>
Alok Rai,Dushyant Chouhan,Sandeep Kumar Nema,Arkesh Madegowda,Rudra Narayan,Bikram K. Kar 대한견주관절학회 2024 대한견주관절의학회지 Vol.27 No.2
Background: Recurrent anterior shoulder dislocation (RASD) in cases of seizure disorders (SDs) total 50%–80% of all SD-associated shoulder instabilities. Based on the extent of bone loss, treatment options include bony and soft-tissue reconstructions, arthroplasty, and arthrodesis. The primary objective of this paper was to review the treatment options for RASD in SDs. Methods: Several bibliographic databases were searched for RASD treatment options in SD patients. The demographic outcome measures, the failure rate (defined as the relative risk of recurrence of dislocation postoperation), and the postoperative seizure recurrence rate were recorded. Results: We pooled 171 cases (187 shoulders) from 11 studies. Of these, one, five, two, two, and one reports studied Bankart's operation with remplissage (27 cases/29 shoulders), the Latarjet procedure (106/118), bone block operation (21/23), arthroplasty (11/11), and arthrodesis (6/6), respectively, in treating SD-associated RASD. The relative risk of failure between SD and non-SD patients was 3.76 (1.36–10.38) after the Latarjet operation. The failure rates were 17% and 13% for Bankart's operation with remplissage and the Latarjet procedure in SD patients, respectively, but 0% each for bone block operation, arthroplasty, and arthrodesis. The total rate of seizure recurrence after operation was 33% of the pooled cases. Conclusions: SD recurrence in the postoperative period, the size of the bone block, and the muscular attachments to a small coracoid autograft are the determinants of failure among various reconstructive operations in SD-associated RASD. Level of evidence: III
형정환,김길성,Alok Kumar Rai,Chan-Oh Jang,Chan-Yang Lee,Zagarzusem Khurelbaatar,Susant Kumar Acharya,이상권 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.1
One-dimensional (1D) single crystalline tellurium (Te) micro- and nanostructures were successfully prepared using thermal evaporation with a metallic Te powder. We found that the morphologies of the Te structures evolved from microrods to nanorods and finally tubular nanostructures with increasing growth temperatures of 500, 600, and 700 C. Our results strongly suggest that the growth temperature, which highly depends on the formation of a two-dimensional (2D) Te microcrystal layer on the substrate, plays an important role in determining the surface morphology and the crystal orientation of the Te micro- and nanostructures.
SINGHLAXMAN,U. S. Rai,Alok Kumar Rai,K. D. Mandal,이선영 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.1
CaCu2.90Zn0.10Ti4O12 ceramic was synthesized by a novel semi-wet route and calcined at 800°C in air for 8 h. The obtained powder was divided into three parts and sintered in air at 950°C for 6 h, 8 h, and 12 h,separately. XRD results confirmed the single phase formation of all the sintered samples with similar cubic structure of CaCu3Ti4O12 (CCTO). Scanning electron micrographs of the CaCu2.9Zn0.1Ti4O12 ceramic sintered for 6 h shows bimodal grain size distribution. Increasing the sintering time significantly promotes the grain growth and microstructural densification. The sintering duration was found to have tremendous influence on microstructure and dielectric properties of CaCu2.90Zn0.10Ti4O12 ceramic. The CaCu2.9Zn0.1Ti4O12 ceramic sintered for 12 h exhibited high dielectric constant εr ~ 5971 at 1 kHz and room temperature. It is found that εr is independent at high frequency and weakly dependent on temperature.
Anh, Ly Tuan,Rai, Alok Kumar,Thi, Trang Vu,Gim, Jihyeon,Kim, Sungjin,Shin, Eui-Chol,Lee, Jong-Sook,Kim, Jaekook Elsevier 2013 Journal of Power Sources Vol.243 No.-
<P><B>Abstract</B></P> <P>Undoped and 2 wt% vanadium (V<SUP>5+</SUP>) doped TiO<SUB>2</SUB> samples are prepared in polyol medium by low-temperature solvothermal method. The as-prepared samples are annealed at 400 °C for 5 h in an air atmosphere to increase the crystallinity. The XRD pattern shows that pure anatase TiO<SUB>2</SUB> is formed in both the doped and undoped samples. The maximum sizes of nanoparticles are found to be 300 nm and 15 nm with spherical shaped morphology for undoped TiO<SUB>2</SUB> and V<SUP>5+</SUP> doped TiO<SUB>2</SUB> samples respectively. In addition, 2 wt% V<SUP>5+</SUP> doped sample exhibits excellent electrochemical performance with high reversible specific capacity and excellent rate capability compared to the undoped case. This improvement can be attributed to the substitution of the Ti<SUP>4+</SUP> ions by V<SUP>5+</SUP> ions in the TiO<SUB>2</SUB> lattice and create more Ti<SUP>4+</SUP> vacancies in the lattice. This action may lead to the generation of apparently more number of free holes in the doped p-type semiconductor. Therefore, the increased hole concentration in the valence band can contribute to the electrical conductivity of the doped sample. Vanadium doping also influences the sample crystallinity and reduces the particle size, which provides a larger active surface area than that of undoped TiO<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A study on V<SUP>5+</SUP> doped TiO<SUB>2</SUB> as a high performance anode for lithium ion battery. </LI> <LI> V<SUP>5+</SUP> doping significantly influence the crystal structure and particle sizes. </LI> <LI> The electronic conductivity is largely improved through V<SUP>5+</SUP> doping. </LI> <LI> V<SUP>5+</SUP> doping greatly increased both the reversible capacity and cycling stability of TiO<SUB>2</SUB>. </LI> </UL> </P>
A Novel Additive Texturing of Stainless Steel 316 L Through Binder Jetting Additive Manufacturing
Suryank Dwivedi,Amit Rai Dixit,Alok Kumar Das,Akash Nag 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.6
The current study introduces the novel additive micro-texturing through the binder jetting additive manufacturing technique to fabricate circular micro-textured stainless steel 316L parts. The topographical analysis shows that the sample is manufactured with periodic feature sizes less than 250 μm and within an error limit of 7.62% with high metallographic purity. The wettability study indicates hydrophilic wetting behavior with contact angles in the ranges of 85.7°–82.5° for deionized water and 50.2°–36.7° for Hank’s balanced salt solution. The surface free energy for the textured part (53.484 mN/m) is improved by 72% compared to the untextured part (31.054 mN/m), leading to enhanced hydrophilicity. Further, in the scratch analysis, the textured sample shows better features intactness.
Kang, Jungwon,Baek, Sora,Mathew, Vinod,Gim, Jihyeon,Song, Jinju,Park, Hyosun,Chae, Eunji,Rai, Alok Kumar,Kim, Jaekook The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.39
<P>A Na<SUB>3</SUB>V<SUB>2</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>/C cathode synthesized by a polyol-assisted pyro-synthetic reaction and subsequent sintering delivered a discharge capacity of 235 mA h g<SUP>−1</SUP>, corresponding to an extraction of 4 Na per formula with steady capacity retention and impressive rate capabilities that maintain 56% of theoretical capacity at 2.67 C.</P> <P>Graphic Abstract</P><P>A carbon-coated Na<SUB>3</SUB>V<SUB>2</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>/C cathode was prepared by a pyro-synthetic process for sodium-ion batteries. The prepared cathode was aided by a carbon-network formed within the structure and possessed a high surface area of 159.4 m<SUP>2</SUP> g<SUP>−1</SUP> and dual porosity with pore-sizes in the mesopore range. The beneficial aspects contributed to enhance the rate performances. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm34451c'> </P>