排序方式: 共有18条查询结果,搜索用时 304 毫秒
1.
M. Abrar G.U. Farwa S. Naseer A. Saeed A.W. Khan Z. Iqbal S.T. Hussain M. Zakaullah 《Current Applied Physics》2013,13(3):567-575
Optical emission spectroscopy and Langmuir probe are used to investigate the low pressure inductively coupled Ar–N2 plasmas as function of rf power, filling pressure and Ar content in N2 discharge. It is observed that the active species generation, dissociation fraction and electron temperature significantly depends on discharge parameters and may be used to optimize the plasma reactor. Mixture of SWCNTs and MWCNTs are treated for different treatment time (0–120 min) at optimum discharge conditions. Changes induced in the elemental composition, surface morphology, crystallographic structure, and structural disorder in the plasma irradiated CNTs are analyzed by EDX, FTIR, SEM, XRD and Raman spectroscopy, respectively. Ar–N2 mixture plasma treatment of CNTs lead to a significant increase in the electrical conductivity, modify the microstructure and induce structural disorder and cause a transition of crystalline phase from well crystalline to an amorphous structure. 相似文献
2.
Zirconium aluminium oxynitride multiphase composite film is deposited on zirconium substrate using energetic nitrogen ions delivered from dense plasma Focus device. X-ray diffractometer (XRD) results show that five Focus shots are sufficient to initiate the nucleation of ZrN and Al2O3 whereas 10 Focus shots are sufficient to initiate the nucleation of AlN. XRD results reveal that crystal growth of nitrides/oxides increases by increasing Focus shots (up to 30 Focus shots) and resputtering of the previously deposited film is taken place by further increase in Focus shots (40 Focus shots). Scanning electron microscopic (SEM) results indicate the uniform distribution of spherical grains (∼35 nm). A smoother surface is observed for 20 Focus shots at 0° angular position. SEM results also show a net-type microstructure (thread like features) of the sample treated for 30 Focus shots whereas rough surface morphology is observed for 40 Focus shots. Energy dispersive spectroscopic profiles show the distribution of different elements present in the deposited composite films. A typical microhardness value of the deposited composite films is 5255 ± 10 MPa for 10 grams imposed load which is 3.3 times than the microhardness values of unexposed sample. The microhardness values of the exposed samples increases with increasing Focus shots (up to 30 Focus shots) and decreases for 40 Focus shots treatment due to resputtering of the previously deposited composite film. The microhardness values of the composite films decreases by increasing the sample's angular position. 相似文献
3.
Zakaullah M. Alamgir K. Rasool A. Shafiq M. Murtaza G. Waheed A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2001,29(1):62-68
Correlation of neutron emission with plasma electron temperature in a low-energy (2.3 kJ) plasma focus is investigated. To determine the plasma temperature by continuum X-ray analysis, cobalt is selected as the filter, which discriminates the line radiation from the background impurities like carbon, nitrogen, and oxygen, or the copper of which plasma focus electrodes are made. For a pressure range of high neutron emission (1-4 mbar), the neutron yield is found to correlate with the plasma temperature. The highest temperature recorded is 5 keV at 2.5 mbar, the filling pressure for the highest neutron emission in this device 相似文献
4.
A. Qayyum Shaista Zeb N.U. Rehman M. Zakaullah 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,107(3):361-371
Optical emission spectroscopy measurements are presented to characterize the different excitation and ionization processes of both atomic and molecular species in Ar-N2 mixture plasma under different discharge conditions. Particularly, the emission intensities of nitrogen (0-0) band of second positive system at 337.1 nm and (0-0) band of first negative systems at 391.4 nm are used to determine the dependence of their radiative states on argon fraction in the mixture. It is observed that the addition of argon gas influences the radiative states differently due to their different populating mechanisms. The results demonstrate that the addition of argon to nitrogen plasma remarkably enhance the population of N2(C3Πu) radiative state through Penning excitation involving argon metastable states. The electron temperature is determined from Ar-I spectral line intensities, using Boltzmann's plot method and is found to depend on argon fraction in the mixture. 相似文献
5.
6.
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. 相似文献
7.
Shaista Zeb A. Qayyum Mehboob Sadiq M. Shafiq A. Waheed M. Zakaullah 《Plasma Chemistry and Plasma Processing》2007,27(2):127-139
This paper reports the deposition of diamond-like carbon (DLC) films on Si <100>, using a low energy (1.45 kJ) dense plasma
focus assisted sputtering of graphite insert at the tip of the tapered anode. The substrates are placed in front of the anode
at different axial and angular positions and are exposed to multiple focus shots. The information regarding the DLC structure
is acquired by using Raman spectroscopy. The spectra are characterized by two broad bands known as “G-band” and “D-band”.
The results point towards the formation of DLC films with both sp3 (diamond like) and sp2 (graphite like) domains. In X-ray diffraction (XRD) pattern, no additional peak is observed except a peak at 2θ = 69° which corresponds to the silicon (Si) substrate. The intensity of Si peak is reduced after treatment indicating the
deposition of amorphous carbon. Scanning electron microscopy (SEM) results demonstrate that the smoothness of the film increases
with increasing the substrate angular positions with respect to the anode axis. Energy dispersive X-ray (EDX) analysis reveals
that the films deposited at lower axial and angular positions are thicker which is complemented by the cross-sectional views
of the films. 相似文献
8.
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. 相似文献
9.
M. Sharif S. Hussain M. Zakaullah A. Waheed 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):337-341
A 1.8 kJ Mather-type plasma focus (PF) for argon and hydrogen
filling is examined. Two anode configurations are used. One is tapered
towards the anode face, and the other is cylindrical but the face is cut at
different angles. At optimum conditions, the system is found to emit Cu–Kα
X-rays of about 1.6±0.1 J/sr in the side-on direction for argon
filling, which
is about 32% of the total X-ray emission. In 4π-geometry, maximum
total X-ray
yield and wall plug efficiency found are 26.4±1.3 J and 1.5±
0.1%
respectively. The modified geometry may help to use the PF as a radiation
source for X-ray diffraction. 相似文献
10.
M. Hassan R.S. Rawat P. Lee S.M. Hassan A. Qayyum R. Ahmad G. Murtaza M. Zakaullah 《Applied Physics A: Materials Science & Processing》2008,90(4):669-677
Nanocrystalline multiphase titanium oxycarbide (TiCxOy) thin films composed of TiC2, TiO0.325, Ti2O3 and graphitic carbon have been deposited on titanium substrates, using energetic carbon ions delivered by the UNU/ICTP and
the NX2 plasma focus devices operated at different repetition rates. X-ray diffraction (XRD) patterns of the nanocomposite
films reveal the relative transformation of various oxide and carbide phases accompanied by the suppression of the TiC2 phase when the energy flux of the ion beam and the repetition rate are increased. A field emission scanning electron microscope
(FESEM) with an energy dispersive X-ray spectroscopy (EDS) attachment reveals a non-porous microcrack-free nanocrystalline
granular surface morphology of the composite films with uniform carbon distribution. X-ray photoelectron spectroscopy (XPS)
confirms the formation of oxycarbides (TiCxOy) along with significant carbon adsorbate. Raman studies of the films also verify the relative phase transformation in the
TiCxOy nanocomposite by tuning the deposition parameters. The Vickers microhardness of the sample surface is improved more than
400%.
PACS 52.59.Hq; 52.77.Dq; 68.55.Jk; 81.15.-z; 81.65.Lp 相似文献