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

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Communications in Theoretical Physics 2011年第2期55卷 315-320页

作者： Shakir Ullah A.H.Dogar a.qayyum Physics Division Pakistan Institute of Nuclear Science and Technology

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^＋.

关键词： ion-surface collisions surface-induced dissociation hydrogen molecular ions Monte Carlo simulation

Unsteady Squeezing Flow of Jeffery Fluid between Two Parallel Disks

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Chinese Physics Letters 2012年第3期29卷 135-138页

作者： a.qayyum M.Awais A.Alsaedi T.Hayat Department of Mathematics Quaid-I-Azam University 45320Islamabad 44000Pakistan Department of Mathematics Faculty of ScienceKing Abdulaziz UniversityP.O.Box 80257Jeddah 21589Saudi Arabia

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

关键词： ordinary unsteady flow

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

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Chinese Physics B 2010年第8期19卷 344-349页

作者： S.Ullah A.H.Dogar M.Ashraf a.qayyum Pakistan Institute of Engineering and Applied Sciences NiloreIslamabadPakistan Physics Division Pakistan Institute of Nuclear Science and TechnologyP.O.NiloreIslamabadPakistan Optics Laboratories P.O.Box 1021IslamabadPakistan

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.

关键词： ion-induced electron emission alkali halides electronic stopping electron mean free path

Newtonian heating effects in three-dimensional flow of viscoelastic fluid

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Chinese Physics B 2014年第5期23卷 373-379页

作者： a.qayyum T.Hayat M.S.Alhuthali H.M.Malaikah Department of Mathematics Quaid-i-Azam University 45320Islamabad 44000Pakistan Department of Mathematics Faculty of ScienceKing Abdulaziz University

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.

关键词： viscoelastic fluid three-dimensional flow Newtonian heating

Glow Discharge Plasma Nitriding of AISI 304 Stainless Steel

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Plasma Science and Technology 2007年第4期9卷 463-468页

作者： a.qayyum M.A.NAVEED S.ZEB G.MURTAZA M.ZAKAULLAH National Tokamak Fusion Program IslamabadPakistan Department of Physics Quaid-i-Azam University45320 IslamabadPakistan Salam Chair in Physics Government College University54000 LahorePakistan

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.

关键词： optical diagnostics plasma nitriding austenitic stainless steel

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

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

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Chinese Physics Letters 2016年第7期33卷 178-181页

作者： M.A.Khan a.qayyum I.Ahmed T.Iqbal A.A.Khan R.Waleed B.Mohuddin M.Malik Department of Physics University of Azad Jammu and Kashmir National Center of Physics Quaid-i-Azam University Campus UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology College of Graduate StudiesUniversity of South Africa Nanosciences African Network iThemba LABS-National Research Foundation

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.

关键词： of cm Copper Ion Beam Irradiation-Induced Effects on Structural,Morphological and Optical Properties of Tin Dioxide Nanowires in is that for been on

Insight into the dynamics of non-Newtonian Carreau fluid when viscous dissipation,entropy generation,convective heating and diffusion are significant

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Applied Mathematics(A Journal of Chinese Universities) 2024年第1期39卷 34-46页

作者： ZHOU Shuang-shuang Muhammad Ijaz Khan Sami Ullah Khan Sumaira.qayyum School of Science Hunan City UniversityYiyang 413000China Department of Mechanical Engineering Prince Mohammad Bin Fahd UniversityP.O.Box1664Al-Khobar 31952Kingdom of Saudi Arabia Department of Mathematics Namal UniversityMianwali 42250Pakistan Department of Mathematics Quaid-I-Azam University 45320Islamabad 44000Pakistan

The investigation endorsed the convective flow of Carreau nanofluid over a stretched surface in presence of entropy generation *** novel dynamic of viscous dissipation is utilized to analyze the thermal mechanism of magnetized *** convective boundary assumptions are directed in order to examine the heat and mass transportation of *** thermal concept of thermophoresis and Brownian movements has been re-called with the help of Buongiorno *** problem formulated in dimensionless form is solved by NDSolve *** graphical analysis for parameters governed by the problem is performed with physical *** affiliation of entropy generation and Bejan number for different parameters is inspected in *** numerical data for illustrating skin friction,heat and mass transfer rate is also *** motion of the fluid is highest for the viscosity ratio *** temperature of the fluid rises via thermal Biot *** generation rises for greater Brinkman number and diffusion parameter.

关键词： heat generation surface reaction CNTs based nano uid stretching/shrinking sheet thermal radiation

低速多电荷态离子在固体表面的电子发射产额(英文)

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IMP & HIRFL Annual Report 2006年 38-38页

作者：王瑜玉 a.qayyum Pakistan Institute of Nuclear Science and Technology P.O.Nilore Islamabad Pakistan.

Electron emission from solid surfaces by multi-charged ions is one of the most fundamental processes in ion-solid in- teractions and has received a great deal of attention recently. The total electron yieldγ,is usually defined as the number of electrons ejected per incident ions.γ,is commonly ascribed to the sum of the potential electron yieldγPEand the kinetic elec- tron yieldγ*** experimental studies on electron emission

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