Influence of metal powder shape on drag coefficient in a spray jet

S. Kumar,Hyuntaek Na,이창희,V. Selvarajan 한국물리학회 2009 Current Applied Physics Vol.9 No.3

In plasma spraying, particle shape, size, distribution and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. In the present work, nickel, iron and aluminium irregular powders in the size range from 50 to 63 lm were spheroidized using thermal plasma processing. The spheroidization experiments have been carried out at different gas flow rates and plasma torch power levels. The sphericity was analyzed using shape factor. Drag coefficients of the powders were estimated using Reynolds number and sphericity of the powders in plasma. For irregular particles, the drag coefficient is higher than that of the spherical because of its large area of contact with plasma. The temperature dependent on drag coefficient is also discussed. Increasing temperature increases the drag coefficient of the powder particles injected in to the plasma jet. Increasing plasma jet temperature changes the density and viscosity of the plasma which affects the particle’s drag coefficient in the plasma. The results are reported and discussed. In plasma spraying, particle shape, size, distribution and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. In the present work, nickel, iron and aluminium irregular powders in the size range from 50 to 63 lm were spheroidized using thermal plasma processing. The spheroidization experiments have been carried out at different gas flow rates and plasma torch power levels. The sphericity was analyzed using shape factor. Drag coefficients of the powders were estimated using Reynolds number and sphericity of the powders in plasma. For irregular particles, the drag coefficient is higher than that of the spherical because of its large area of contact with plasma. The temperature dependent on drag coefficient is also discussed. Increasing temperature increases the drag coefficient of the powder particles injected in to the plasma jet. Increasing plasma jet temperature changes the density and viscosity of the plasma which affects the particle’s drag coefficient in the plasma. The results are reported and discussed.

Fabrication of mesoporous BaTiO3/SnO2 nanorods with highly enhanced photocatalytic degradation of organic pollutants

S. Selvarajan,P. Malathy,A. Suganthi,M. Rajarajan 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-

Novel UV–vis-light-driven BaTiO3/SnO2 nanocomposites with three different molar ratios (1%, 3%, 5%) were synthesized by hydrothermal and precipitation deposition methods. The successfully characterized by UV-visible diffuse reflectance spectroscopy (DRS), FT-IR spectroscopy, X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), photoluminescence spectroscopy (PL), and Brunauer–Emmett–Teller surface area analysis (BET) techniques. The lmax of the prepared nanocomposite was highly red shifted from 220 nm to 410 nm compared to the bare metal oxides. The degradation of organic pollutants such as o-Chloroaniline (o-CLA) and methylene blue (MB) were studied using the prepared nanocomposite. The nanocomposite with molar ratio of 3% BaTiO3/SnO2 photocatalyst possesses excellent photocatalytic activity than the nanocomposite with molar ratio 1% BaTiO3/SnO2, 5% BaTiO3/SnO2, and the individual components BaTiO3, SnO2. The band edges of materials have been theoretically calculated on the basis of Mullikan electronegativity of atoms. The effect of operational parameters such as; pollutant concentration, pH, catalyst loading, OH radical trapping and COD (carbon oxygen demand) have been investigated in details. The kinetics of the photodegradation reactions were correlated with the pseudofirst- order model. The stability of nanocomposite was examined by recycling experiments.

Synthesis, growth and studies of undoped and sodium chloride-doped Zinc Tris-thiourea Sulphate (ZTS) single crystals

C. Krishnan,P. Selvarajan,S. Pari 한국물리학회 2010 Current Applied Physics Vol.10 No.2

Single crystals of undoped (pure) and sodium chloride (NaCl)-doped Zinc Tris-thiourea Sulphate (ZTS)were grown from aqueous solutions by slow evaporation technique. Morphological alterations have been observed when NaCl is doped into ZTS crystals. Density of the grown crystals was measured by floatation method. The values of unit cell parameters from single crystal X-ray diffraction (XRD) studies show that pure and sodium chloride-doped ZTS crystals are in orthorhombic structure. Impurity concentration in the doped crystals was estimated by using an atomic absorption spectrometer. Second Harmonic Generation (SHG) test for the undoped and NaCl-doped ZTS crystals was performed by the powder technique of Kurtz and Perry using a pulsed Nd:YAG laser. Microhardness studies show that hardness number (Hv)increases with load for all the grown crystals of this work. From the values of work hardening coefficients,it is concluded that pure and sodium chloride-doped ZTS crystals belong to the category of soft materials. UV–vis–NIR spectra show that the grown crystals have wide optical transparency in the entire visible region. Birefringence studies of the grown samples have been performed by channelled spectrum method. The thermal stability of the materials is found to be increasing with the doping concentration of sodium chloride (NaCl) in the lattice of ZTS crystals.

Glow discharge plasma-induced immobilization of heparin and insulin on polyethylene terephthalate film surfaces enhances anti-thrombogenic properties

Pandiyaraj, K.N.,Selvarajan, V.,Rhee, Y.H.,Kim, H.W.,Shah, S.I. Elsevier 2009 Materials science & engineering. C, Materials for Vol.29 No.3

Polyethylene terephthalate (PET) films were treated with DC glow discharge plasma followed by graft copolymerization with acrylic acid (AA) and polyethylene glycol (PEG). The obtained PET-PEG was coupled to heparin or insulin molecules. The surfaces were then characterized by contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The surface energies of the modified PET films were estimated using contact angle measurements, and the changes in crystallinity of the plasma-modified PET film surfaces were investigated by X-ray diffraction (XRD) analysis. The blood compatibilities of the surface-modified PETs were examined by in vitro thrombus formation, whole blood clotting time, platelet contact and protein adsorption experiments. The results revealed that the contact angle value decreased and that the interfacial tension between the modified PET films and blood protein was drastically diminished compared to unmodified PET film. The XPS results showed that the PET-AA surface containing carboxylic acid and the immobilized PET surface containing both carboxylic acid and amino groups exhibited a hydrophilic character, and AFM results showed marked morphological changes after grafting of AA, PEG and biomolecule immobilization. Heparin and insulin-coupled PET surfaces exhibited much less platelet adhesion and protein adsorption than the other surface-modified PET film surfaces.

A microcrystalline cellulose ingrained polydimethylsiloxane triboelectric nanogenerator as a self-powered locomotion detector

Chandrasekhar, A.,Alluri, N.,Saravanakumar, B.,Selvarajan, S.,Kim, S. J. Royal Society of Chemistry 2017 Journal of materials chemistry. C, Materials for o Vol.5 No.7

<P>Scavenging of ambient dissipated mechanical energy addresses the limitations of conventional batteries by providing an auxiliary voltaic power source, and thus has significant potential for self-powered and wearable electronics. Here, we demonstrate a cellulose/polydimethylsiloxane (PDMS) triboelectric nanogenerator (C-TENG) based on the contact and separation mode between a cellulose/PDMS composite film and an aluminium electrode. The device fabricated with a composite film of 5 wt% generates an open circuit voltage of 28 V and a short circuit current of 2.8 mu A with an instantaneous peak power of 576 mu W at a mechanical force of 32.16 N. The C-TENG was systematically studied and demonstrated to be a feasible power source that can commute instantaneous operation of LEDs and act as a self-powered locomotion detector for security applications. The C-TENG can also be used as a wearable power source with an in-built lithium ion battery charging circuit during a range of human motions.</P>

Extracellular RNAs and Extracellular Vesicles: Inception, Current Explorations, and Future Applications

Ayyappasamy Sudalaiyadum Perumal,Ramachandran Chelliah,Saptashwa Datta,Jayachandran Krishna,Melvin S. Samuel,Selvarajan Ethiraj,Chae Rin Park 한국식품위생안전성학회 2020 한국식품위생안전성학회지 Vol.35 No.6

유전적 조절, 유전자 발현 그리고 환경적 단서, 화학적 신호에 대응하는 표현형 변이에서 세포 RNA는 ubiquitous 역할 이외에도 세포 외 RNA(exRNA)라 하는 새로운 형태의 RNA는 추후 연구의 방향을 제시한다. exRNA는 membrane vesicles 또는 세포 외 소포체(EV)로 알려진 membrane blebs를 통해 세포 외부로 운반된다. EV의 형성은 원핵생물, 진핵생물, 고세균을 포함한 모든 미생물군에 우세하게 보존되어있다. 본 리뷰는 세균 유래 exRNA 에 관해 세가지 주제에 초점을 두었다. exRNA의 발견과 박테리아 유전자 배열에 대한 외부 RNA의 영향, b. exRNA 의 분비기작을 통한 방출, c. 다른 그람음성 및 그람양성균에 의해 분비되는 exRNA로 고안될 수 있는 응용 가능 분야이다. 본 리뷰에서 장내 미생물군의 probiotics 및 후 성유전학적 규제에서 본 exRNA와 exRNA마커와 같은 EV 파생 응용프로그램에 대한 의견을 제공할 것이다. In addition to the ubiquitous roles of cellular RNA in genetic regulations, gene expression and phenotypic variations in response to environmental cues and chemotactic signals, the regulatory roles of a new type of RNA called extracellular RNAs (exRNAs) are an up-and-coming area of research interest. exRNA is transported outside the cell through membrane blebs known as membrane vesicles or extracellular vesicles (EVs). EV formation is predominant and conserved among all microbial forms, including prokaryotes, eukaryotes, and archaea. This review will focus on the three major topics concerning bacterially derived exRNAs, i.e., 1) the discovery of exRNA and influence of extraneous RNA over bacterial gene regulations, 2) the known secretion mechanism for the release of exRNA, and 3) the possible applications that can be devised with these exRNA secreted by different gram-negative and gram-positive bacteria. Further, this review will also provide an opinion on exRNA- and EV-derived applications such as the species-specific exRNA markers for diagnostics and the possible roles of exRNA in probiotics and the epigenetic regulations of the gut microbiome.