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Post-annealing effect on the structural and mechanical properties of multiphase zirconia films deposited by a plasma focus device

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Chinese Physics B 2013年第12期22卷 442-450页

作者： I.A.Khan r.s.rawat r.Ahmad M.A.K.shahid Department of Physics Government College University National Institute of Education Nanyang Technological University Department of Physics GC University

Nanostructured multiphase zirconia films （MZFs） are deposited on Zr substrate by the irradiation of energetic oxygen ions emanated from a plasma focus device. The oxygen operating gas pressure of 1 mbar （1 bar=105 Pa） provides the most appropriate ion energy flux to deposit crystalline ZrO2 films. X-ray diffraction （XrD） patterns reveal the formation of polycrystalline ZrO2 films. The crystallite size （Cs）, crystal growth, and dislocation densities are attributed to increasing focus shots, sample axial distances, and working gas pressures. Phase and orientation transformations from t-ZrO2 to m-ZrO2 and c-ZrO2 are associated with increasing focus shots and continuous annealing. For lower （200 ℃） annealing temperature （AT）, full width at half maximum （FWHM） of diffraction peak, Cs, and dislocation density （δ） for （020） plane are found to be 0.494, 16.6 nm, and 3.63×10-3 nm-2 while for higher （400 ℃） AT, these parameters for （111） plane are found to be 0.388, 20.87 nm, and 2.29×10-3 nm-2, respectively. scanning electron microscope （sEM） results demonstrate the formation of rounded grains with uniform distribution. The estimated values of atomic ratio （O/Zr） in ZrO2 films deposited for different axial distances （6 cm, 9 cm, and 12 cm） are found to be 2.1, 2.2, and 2.3, respectively. Fourier transform infrared （FTIr） analysis reveals that the bands appearing at 441 cm-1 and 480 cm-1 belong to m-ZrO2 and t-ZrO2 phases, respectively. Maximum microhardness （8.65±0.45 GPa） of ZrO2 film is ～ 6.7 times higher than the microhardness of virgin Zr.

关键词： zrconia phase transformation XrD sEM Fourier transform infrared analysis

Dip Coating of Nano Hydroxyapatite on Titanium Alloy with Plasma Assistedγ-Alumina Buffer Layer:A Novel Coating Approach

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Journal of Materials science & Technology 2013年第6期29卷 557-564页

作者： M.Khalid M.Mujahid A.Nusair Khan r.s.rawat school of Chemical and Materials Engineering National University of Sciences and TechnologySector H-12IslamabadPakistan Institute of Industrial Control systems RawalpindiPakistan NssE National Institute of EducationNanyang Technological UniversitySingapore

This paper reported a novel coating approach to deposit a （HA） film on Ti6Al4V alloy with Al2O3 buffer layer for thin, crack free and nano-structured hydroxyapatite biomedical implants. The Al2O3 buffer layer was deposited by plasma spraying while the HA top layer was applied by dip coating technique. The X-ray diffraction （XrD） and raman reflections of alumina buffer layer showed α- to γ-Al2O3 phase transformation; and the fractographic analysis of the sample revealed the formation of columnar grains in well melted splats. The bonding strength between Al2O3 coating and Ti6Al4V substrate was estimated to be about 40 MPa. The presence of dip coated HA layer was confirmed using XrD, scanning electron microscopy （sEM） and energy dispersive X-ray spectroscopy （EDX） analysis. The sEM images exhibited that HA top layer enveloped homogenously the troughs and crests of the underneath rough （ra = 2.91 μm） Al2O3 surface. It is believed that the novel coating approach adopted might render the implant suitable for rapid cement-less fixation as well as biocompatible for longer periods.

关键词： Ti6Al4V alloy Biomaterials Buffer layer Ceramic coatings

Pulsed ion beam-assisted carburizing of titanium in methane discharge

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Chinese Physics B 2010年第1期19卷 247-256页

作者： M.shafiq M.Hassan K.shahzad A.Qayyum s.Ahmad r.s.rawat M.Zakaullah Department of Physics Quaid-i-Azam University Department of Physics GC University National Tokamak Fusion Program Natural sciences and science Education National Institute of EducationNanyang Technological University

The carburizing of titanium （Ti） is accomplished by utilizing energetic ion pulses of a 1.5 kJ Mather type dense plasma focus （DPF） device operated in methane discharge. X-ray diffraction （XrD） analysis confirms the deposition of polycrystalline titanium carbide （TIC）. The samples carburized at lower axial and angular positions show an improved texture for a typical （200）TIC plane. The Williamson-Hall method is employed to estimate average crystallite size and microstrains in the carburized Ti surface. Crystallite size is found to vary from - 50 to 100 nm, depending on the deposition parameters. Microstrains vary with the sample position and hence ion flux, and are converted from tensile to compressive by increasing the flux. The carburizing of Ti is confirmed by two major doublets extending from 300 to 390 cm^-1 and from 560 to 620 cm^-1 corresponding to acoustic and optical active modes in raman spectra, respectively. Analyses by scanning electron microscopy/energy dispersive x-ray spectroscopy （sEM/EDs） have provided qualitative and quantitative profiles of the carburized surface. The Vickers microhardness of Ti is significantly improved after carburizing.

关键词： carbide plasma focus microstructure surface morphology

structural, elemental, optical and magnetic study of Fe doped ZnO and impurity phase formation

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Progress in Natural science:Materials International 2014年第2期24卷 142-149页

作者： s.Karamat r.s.rawat P.Lee T.L.Tan r.V.ramanujan Natural science and science Education National Institute of Education Nanyang Technological University COMsATs Institute of Information Technology Department of Physics Middle East Technical University school of Material science and Engineering Nanyang Technological University Nanyang Avenue

We have prepared a series of(ZnO)1-x(Fe2O3)x≤0.10bulk samples with various concentrations of Fe dopant by ball milling and investigated their structural, compositional, optical and magnetic properties by means of X-ray diffraction(XrD), X-ray photoelectron spectroscopy(XPs),raman spectrometer and vibrating sample magnetometer(VsM), respectively. Information about different impurity phases was obtained through rietveld refinements of XrD data analysis. XPs results showed different valence states(Fe2+ tand Fe3+) supported by shaking satellite peaks in samples. With increasing Fe doping percentage, the crystal quality deteriorated and a shift of E2 low band(characteristic of ZnO) has been observed in raman spectra. Energy band gap estimated from reflectance UV–vis spectroscopy showed shift for all bulk samples. The magnetic behavior was examined using a vibrating sample magnetometer(VsM), indicating ferromagnetic behavior at room temperature(300 K). The effective magnetic moment per Fe atom decreases with increase in doping percentage which indicates that ferromagnetic behavior arises from the substitution of Fe ions in the ZnO lattice.

关键词： Fe doped ZnO Dilute magnetic semiconductor rietveld refinements X-ray spectroscopy Band gap Magnetic moment

role of Ion Beam Irradiation and Annealing Efect on the Deposition of AlON Nanolayers by Using Plasma Focus Device

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Plasma science and Technology 2013年第11期15卷 1127-1135页

作者： I.A.KHAN r.s.rawat r.VErMA G.MACHArAGA r.AHMAD Z.A.UMAr M.A.K.sHAHID Department of Physics Government College University38000 Faisalabad Pakistan National Institute of Education Nanyang Technological UniversitySingapore 637616Singapore Department of Physics GC University54000 Lahore Pakistan

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. samples are exposed to multiple （5, 10, 15, 20 and 25） focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6×10^19 m^- 3 to 1.3×10^19 m ^-3, respectively. Moreover, the effect of continuous annealing （473 K and 523 K） on an AlN surface layer synthesized with 25 focus shots is also examined. The main features of the X-ray diffraction （XrD） patterns with increasing focus shots are：（i） variation in the crystallinity of AlN along （111）, （200） and （311） planes, （ii） increasing average crystallite size of AlN （111） plane, and （iii） stress relaxation observed in AlN （111） and （200） planes. The crystallinity of AlN surface layer is comparatively better at 473 K annealing temperature. A broadened diffraction peak related to an aluminium oxide phase showing weak crystallinity is observed for 15 focus shots while non-bounded oxides are present in all other deposited layers. raman and Fourier transform infrared spectroscopy （FTIr） analysis confirm the presence of AlN and Al203 for the surface layer annealed at 473 K temperature. raman analysis shows that the overlapping of AlN and Al2Oa results in the development of residual stresses. scanning electron microscope （sEM） results demonstrate that the formation of rounded grains （range from 20 nm to 200 nm） and variations in their microstructures features depend on the increasing number of focus shots. Decomposition of larger clusters into smaller ones is observed.

关键词： characterization XrD focus shots X-ray diffraction nucleation surface layer

Mechanical properties of Al/a-C nanocomposite thin films synthesized using a plasma focus device

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Chinese Physics B 2014年第2期23卷 353-358页

作者： Z.A.Umar r.s.rawat r.Ahmad A.K.Kumar Y.Wang T.Hussain Z.Chen L.shen Z.Zhang NssE National Institute of EducationNanyang Technological University Department of Physics GC University Center for Advanced studies in Physics (CAsP) GC University school of Materials science and Engineering Nanyang Technological University Institute of Materials research and Engineering ASTAR (Agency for ScienceTechnology and Research)3 Research Link

The Al/a-C nanocomposite thin films are synthesized on si substrates using a dense plasma focus device with alu- minum fitted anode and operating with CH4/Ar admixture. X-ray diffractometer results confirm the formation of metallic crystalline Al phases using different numbers of focus shots. raman analyses show the formation of D and G peaks for all thin film samples, confirming the presence of a-C in the nanocomposite thin films. The formation of Al/a-C nanocomposite thin films is further confirmed using X-ray photoelectron spectroscopy analysis. The scanning electron microscope results show that the deposited thin films consist of nanoparticles and their agglomerates. The sizes of th agglomerates increase with increasing numbers of focus deposition shots. The nanoindentation results show the variations in hardness and elastic modulus values of nanocomposite thin film with increasing the number of focus shots. Maximum values of hardness and elastic modulus of the composite thin film prepared using 20 focus shots are found to be about 10.7 GPa and 189.2 GPa, respectively.

关键词： dense plasma focus X-ray photoelectron spectroscopy field emission scanning electron micro- scope elastic modulus

Comprehensive review on ethnomedicinal, phytochemistry and pharmacological profile of Ficus religiosa L.

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Journal of Traditional Chinese Medicine 2024年第5期44卷 1052-1057页

作者： rahul rawat Harish Kumar Neetu singh Aakash Deep Balasubramanian Narasimhan surender singh Yadav sanjiv Kumar Department of Pharmaceutical sciences Chaudhary Bansi Lal University Department of Botany Maharshi Dayanand University Faculty of Pharmaceutical sciences Maharshi Dayanand University

Ficus religiosa L.(F. religiosa) or sacred fig is a large perennial tree belonging to the family Moraceae or mulberry family. Though the tree has pan-tropical distribution but originally it is indigenous to the Indian subcontinent and Indochina region. Popularly the tree is named "Pepal or bodhi tree". Traditionally, it is practiced for the treatment of asthma, nose bleeding, heart disorders, diabetes, wound healing, ear problems, constipation, hyperlipidemia, gonorrhea, ulcers and infectious disorders. Chemical analysis demonstrated the presence of numerous bioactives including tannins, phenols, saponins, sugars, alkaloids, methionine, terpenoids, flavonoids, glycosides, proteins, separated amino acids, essential and volatile oils and steroids etc., which are probably responsible for its diverse pharmacological actions. The present work is an attempt to compile up-to-date comprehensive information on F. religiosa that covers its taxonomy, ethnomedicinal importance, phytochemistry, pharmacological attributes and clinical trials. Keeping in mind the various health attributes of F. religiosa, future research can be aimed at in-depth elucidation of the structure-function relationship and multifactorial signalings pathways.

关键词： Ficus religiosa clinical trials ethnomedicine health benefits pharmacology phytoconstituents

Tailored heterostructured Ni_(3)N-NiO nano-frameworks for boosting electrocatalytic oxygen evolution via surface-modulated plasma strategy

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Nano research 2024年第9期17卷 7909-7917页

作者： Bo Ouyang Haonan Qin Chao sun Yilin Deng Ang Li Jipeng Zhu Erjun Kan rajdeep singh rawat MIIT Key Laboratory of semiconductor Microstructure and Quantum sensing School of ScienceNanjing University of Science&TechnologyNanjing 210094China The Laboratory of road and Bridge Civil EngineeringSchool of ScienceNanjing University of Science&TechnologyNanjing 210094China Institute for Energy research Jiangsu UniversityZhenjiang 212013China Natural sciences and science Education National Institute of EducationNanyang Technological University637616Singapore

The facile reconfiguration of phases plays a pivotal role in enhancing the electrocatalytic production of H2 through heterostructure *** chemical methods have been explored extensively for this purpose,plasma-based techniques offer a promising avenue for achieving heterostructured ***,the conventional plasma approach introduces complexities,leading to a multi-step fabrication process and challenges in precisely controlling partial surface structure modulation due to the intricate interaction *** our pursuit of heterostructures with optimized oxygen evolution reaction(OEr)behavior,we have designed a facile auxiliary insulator-confined plasma system to directly attain a Ni_(3)N-NiO heterostructure(hNiNO).By meticulously controlling the surface heating process during plasma processing,such approach allows for the streamlined fabrication of hNiNO *** resulting nano-framework exhibits outstanding catalytic performance,as evidenced by its overpotential of 320 mV at a current density of 10 mA·cm^(-2),in an alkaline *** stands in stark contrast to the performance of NiO-covered Ni_(3)N fabricated using the conventional plasma method(sNiNO).Operando plasma diagnostics,coupled with numerical simulations,further substantiates the influence of surface heating due to auxiliary insulator confinement of the substrate on typical plasma parameters and the formation of the Ni_(3)N-NiO nanostructure,highlighting the pivotal role of controlled surface temperature in creating a high-performance heterostructured electrocatalyst.

关键词： structural modulation auxiliary insulator-confined plasma surface heating control heterostructure electrocatalytic O_(2) evolution

FEA-based Geometrical Modification of switched reluctance Motor for radial Force reduction

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Chinese Journal of Electrical Engineering 2024年第1期10卷 124-135页

作者： rani s Jayapragash r school of Electrical Engineering Vellore Institute of TechnologyChennai 600127India

switched reluctance motors(srMs)are becoming increasingly popular in the automotive sector owing to their robust ***,srMs are preferred particularly for EV applications owing to their fault tolerance,magnet-free structure,and high power/torque *** main concerns of srM compared to other machines include torque ripple and *** primary cause of vibration is the radial force created by the srM.A geometry-based modification of the srM to reduce the radial force without significantly changing the average torque produced is *** primary goal is to design a 4-phase,8/6 srM with a lower radial *** possible geometrical alterations are proposed:one with square windows and the other with circular holes on the rotor *** windows are sized and positioned to avoid flux *** criteria are developed for the optimal window size and *** element analysis(FEA)modelling of the srM is used to validate its *** FEA results are compared with the performance parameters obtained using the analytical *** the multiphysics design tool ANsYs to obtain the natural frequencies and associated deformations through modal *** to the conventional geometry,the radial force is significantly reduced by providing windows.

关键词： 8/6 srM radial force modal analysis FEA analysis natural frequencies srM with windows