Pulsed ion beam-assisted carburizing of titanium in methane discharge

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.

以反相位T1加权肝脏MR信号强度丢失和内脏脂肪测量为生物标记研究肝脏脂肪变性

目的探讨MRI反相位T1WI以及脂肪抑制T2WI上肝脏信号强度(SI)丢失和体质量指数(BMI)是否与非酒精性脂肪性肝病(NAFLD)或丙型肝炎病毒(HCV)

Glow Discharge Plasma Nitriding of AISI 304 Stainless Steel

Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction （XRD） to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase （TN） owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth （μm）. The results showed clear evidence of surface changes with substantial increase in surface hardness.

Copper Ion Beam Irradiation-Induced Effects on Structural,Morphological and Optical Properties of Tin Dioxide Nanowires

The 0.8 Me V copper （ Cu） ion beam irradiation-induced effects on structural, morphological and optical properties of tin dioxide nanowires （Sn02 NWs） are investigated. The samples are irradiated at three different doses 5 × 10^12 ions/cm2, 1 ×10^13 ions/cm2 and 5 × 10^13 ions/em2 at room temperature. The XRD analysis shows that the tetragonal phase of Sn02 NWs remains stable after Cu ion irradiation, but with increasing irradiation dose level the crystal size increases due to ion beam induced coalescence of NWs. The FTIR spectra of pristine Sn02 NWs exhibit the chemical composition of SnO2 while the Cn-O bond is also observed in the FTIR spectra after Cu ion beam irradiation. The presence of Cu impurity in SnO2 is further confirmed by calculating the stopping range of Cu ions by using TRM/SRIM code. Optical properties of SnO2 NWs are studied before and after Cu ion irradiation. Band gap analysis reveMs that the band gap of irradiated samples is found to decrease compared with the pristine sample. Therefore, ion beam irradiation is a promising technology for nanoengineering and band gap tailoring.

Surface-Induced Dissociation of Low Energy H_2^(+) Impact on a Carbon Surface: A Monte Carlo Simulation

A Monte Carlo simulation based on the classical binary collision approximation is performed to investigate the interaction of W2 ions with the carbon target. The incident H2^＋ ion is characterized by its translational energy, eigenenergy and population of the vibrational state, and orientation of the ion with respect to the target surface. It is shown that experimentally determined energy resolved mass spectrum of H＋ can be nicely reproduced with the help of the proposed model. These simulations predict that translational to vibrational （T → V） energy transfer efficiency increases nonlinearly with translational energy of the incident ion. T → V energy transfer efficiency along with the initial vibrational energy of the incident H＋ ion found to play an important role in dissociation. Our simulations also show that the fraction of absorbed, reflected, and dissociated ions depends on the translational energy. The average vibrational energy of reflected H＋ increases with its initial translational energy. Moreover, average number of collisions required for dissociation varies inversely with the initial translational energy of the H2^＋.

Ion-induced kinetic electron emission from ~6LiF,~7LiF and MgF_2 thin films

Secondary electron yields for Ar^＋ impact on 6LiF, 7LiF and MgF2 thin films grown on aluminum substrates are measured each as a function of target temperature and projectile energy. Remarkably different behaviours of the electron yields for LiF and MgF2 films are observed in a temperature range from 25 ℃ to 300 ℃. The electron yield of LiF is found to sharply increase with target temperature and to be saturated at about 175 ℃. But the target temperature has no effect on the electron yield of MgF2. It is also found that for the ion energies greater than 4 keV, the electron yield of 6LiF is consistently high as compared with that of 7LiF that may be due to the enhanced contribution of recoiling 6Li atoms to the secondary electron generation. A comparison between the electron yields of MgF2 and LiF reveales that above a certain ion energy the electron yield of MgF2 is considerably low as compared with that of LiF. We suggest that the short inelastic mean free path of electrons in MgF2 can be one of the reasons for its low electron yield.

Newtonian heating effects in three-dimensional flow of viscoelastic fluid

A mathematical model is constructed to investigate the three-dimensional flow of a non-Newtonian fluid. An in-compressible viscoelastic fluid is used in mathematical formulation. The conjugate convective process （in which heat the transfer rate from the bounding surface with a finite capacity is proportional to the local surface temperature） in three-dimensional flow of a differential type of non-Newtonian fluid is analyzed for the first time. Series solutions for the nonlinear differential system are computed. Plots are presented for the description of emerging parameters entering into the problem. It is observed that the conjugate heating phenomenon causes an appreciable increase in the temperature at the stretching wall.

Unsteady Squeezing Flow of Jeffery Fluid between Two Parallel Disks

We investigate an unsteady axisymmetric flow of a Jeffrey fluid between two parallel disks.The relevant partial differential equations are modeled and simplified by using appropriate transformations.The resulting ordinary differential system is solved and a series solution is obtained.Effects of various parameters of interest on the flow quantities are seen.It is found that the velocity profile increases when porosity and squeezing parameters are increased.

Three-dimensional mixed convection squeezing flow

The unsteady mixed convection squeezing flow of an incompressible Newtonian fluid between two vertical parallel planes is discussed. The fluid is electrically conducting. The governing equations are transformed into ordinary differential equations （ODEs） by appropriate transformations. The transformed equations are solved successfully by a modern and powerful technique. The effects of the emerging parameters on the flow and heat transfer characteristics are studied and examined. The values of the skin friction coefficient and the local Nusselt number are tabulated and analyzed.