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Search Results: 1 - 10 of 400732 matches for " M. Zulfequar "
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Structural and Electrical Characterization of Sintered Silicon Nitride Ceramic  [PDF]
Imran Khan, M. Zulfequar
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.27102
Abstract: The electrical conduction phenomena, dielectric response and microstructure have been discussed in sintered silicon nitride ceramics at different temperature and frequencies. Microstructure and phase of the sintered samples was investigated by Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD). The electrical conductivity, dielectric constant and dielectric loss increases exponentially with temperature greater than 600 K. The dielectric constant and loss have been measured in the frequency range 100 Hz to 1 MHz. The a.c. conduction studies in the audio frequency range 500 Hz to 1 MHz indicates that the conduction may be due to the electronic hopping mechanism. Silicon Nitride ceramics became dense after sintering. The effect of grain size and role of phase on electrical and dielectric properties have been discussed. These types of samples can be used as a high temperature semi conducting materials for device packaging.
Estimation the Density of Localized State Glassy Se100–xZnx Thin Films by Using Space Charge Limited Conduction Measurement  [PDF]
Mohd. Nasir, M. Zulfequar
New Journal of Glass and Ceramics (NJGC) , 2012, DOI: 10.4236/njgc.2012.22013
Abstract: The dc conductivity in vacuum evaporated amorphous thin films of the glassy alloys Se100–xZnx(2 ≤ x ≤ 20) are meas-ured in the temperature range (308 - 388 K). The dc conductivity (σdc) is increases with increased of Zn concentration in the glassy alloys. The activation energy (ΔE) decreases with increase of Zn content. The conduction is explained on the basis of localized state in the mobility gap. To study the effect of electric field, a Current-Voltage characteristic has been measured at various fixed temperatures. The Current-Voltage data are fitted into the theory of space charge limited conduction in case of uniform distribution of traps in mobility gap at high electric fields (E ~104 V/cm) of these materials. The density of localized state (g0) are estimated by fitting in theory of space charge limited conduction (SCLC) at the temperature range of (352 - 372 K) in the glassy Se100–xZnx. The density of localized state (0) near the Fermi level are increases with increase of Zn concentration in the (Se100–xZnx) thin films and explain on the basis of increase of the Zn-Se bond.
DC Conductivity and Dielectric Behaviour of Glassy Se100–xZnx Alloy  [PDF]
Mohd. Nasir, M. Zulfequar
Open Journal of Inorganic Non-metallic Materials (OJINM) , 2012, DOI: 10.4236/ojinm.2012.22002
Abstract: The DC conductivity and dielectric properties of glassy Se100–xZnx 2 ≤ x ≤ 20 alloys have been investigated in the temperature range 303 - 487 K with frequency range 100 Hz – 1 MHz. It is observed that DC conductivity decreases and the activation energy increases with Zn content in Se-Zn system. Dielectric dispersion is observed when Zn incorporated in Se-Zn glassy system. The results are explained on the basis of DC conduction mechanism and dipolar-type dielectric dispersion.
DC Conductivity and Spectroscopic Characterization of Poly (o-toluidine) Doped with Binary Dopant ZrOCl2/AgI  [PDF]
Kiran Kumari, Vazid Ali, Gita Rani, Sushil Kumar, G.B.V.S. Lakshmi, M. Zulfequar
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.28142
Abstract: Aqueous binary dopant (ZrOCl2/AgI) is used in different ratio such as 1:1, 1:2 and 2:1 (w/w) for chemical doping to enhance the conductivity of synthesized Poly (o-toluidine) (POT). The doping of Poly (o-toluidine) is carried out using tetrahydrofuran as solvent. Doped samples are characterized using various techniques such as I-V characteristics, UV-Visible spectroscopy, X-ray diffractometry (XRD), FTIR and Photoluminescence (PL) studies. A significant enhancement in DC conductivity has been observed with the introduction of binary dopant. UV-Visible study shows that optical parameters change considerably after doping. Interestingly, both direct and indirect band gaps are observed in the doped samples. XRD patterns show the semi-crystalline nature of doped Poly (o-toluidine). FTIR study shows structural modifications in functional groups with doping in POT. A Photolyminescence spectrum exhibits the emission properties of the samples.
Synthesis, Electrical Conductivity, and Dielectric Behavior of Polyaniline/V2O5 Composites
Shama Islam,G. B. V. S. Lakshmi,Azher M. Siddiqui,M. Husain,M. Zulfequar
International Journal of Polymer Science , 2013, DOI: 10.1155/2013/307525
Abstract: Conducting polymer composites of polyaniline/vanadium pentaoxide PANI/V2O5 (with different initial weight percentage of V2O5) has been synthesized by in situ polymerization method. DC conductivity of compressed pellets has been analyzed in the temperature range 300–550?K and was found to increase with V2O5 doping. This increase in conductivity is mainly due to band conduction. It has also been observed that the dielectric constant and dielectric loss increase with the level of doping of V2O5 but remain independent of the frequency (50?KHz–1?MHz). X-ray diffraction pattern shows some order of crystallinity of composites due to interaction of polyaniline with V2O5. UV-visible spectroscopy shows an increase in the optical band gap with doping. 1. Introduction The conducting polymers have emerged as a new class of materials because of their unique electrical, optical, and chemical properties. By proper doping the conductivity of these materials can be varied from semiconducting to metallic regime, which offers new concept of charge transport mechanism. Among different conducting polymers, conductive polyaniline (PANI) has been studied extensively because of its ease of synthesis in aqueous media, its environmental stability, special electrical, and other properties. PANI and its derivatives have received much attention because of their various technological applications, reversible proton doping, high electrical conductivity, and ease of bulk synthesis. PANI is also a suitable candidate for a variety of technological applications such as solar cells, electromagnetic shielding, electrodes for rechargeable batteries, and sensors [1–11]. Many authors have studied the progress of chemical polymerization and doping of aniline and its derivatives. The effort was to correlate mechanisms of oxidation of anilines and properties of PANI such as electrical conductivity, molecular weight, and crystallinity. However, when they were taken in the composite form, their electrical as well as dielectric properties alter from those of basic materials. A number of groups had reported on the electrical conductivity and dielectric properties of composites of a variety of conducting polymers [12–15]. Recently heterogeneous conducting polymer composites, especially organic-inorganic composites, became the subject of extensive study. Among the base materials used, polyaniline (PANI) is one of the most extensively studied conducting polymer. Ever since its discovery in a pioneering work by Mc Diarmid et al. [16–21]. The DC conductivity of a conjugated polymer depends on the doping
Thermal Properties of Se100–xZnx Glassy System  [PDF]
Mohd Nasir, Mohd Abdul Majeed Khan, Mushahid Husain, Mohammad Zulfequar
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.25038
Abstract: The crystallization process in Se100–xZnx glassy system is investigated using differential scanning calorimeters (DSC). The samples are prepared by conventional melt-quenching technique in the composition range 2 ≤ x ≤ 20 (at%). Non-isothermal measurements are carried out for different heating rates .The value of the glass transition temperature Tg the crystallization temperature Tc and the crystallization peak temperature Tp, are found to be depending upon both heating rate as well as the composition from thermal analytical data. The investigation of crystallization kinetics indicates a single stage crystallization process. The glass transition energy Eg and the crystallization activation energy Ec are also evaluated from thermal analytical data. The analyzer has been used the most reliable non-isothermal kinetic methods. The value of kinetics parameters Eg, Ec and ‘n’ are calculated using non-isothermal kinetics methods. The analysis shows that the incorporation of Zinc content has a strong influence on the crystallization mechanism for the Se100–xZnx glassy system.
Optical and Structural Properties of ZnO Thin Films Fabricated by Sol-Gel Method  [PDF]
Ziaul Raza Khan, Mohd Shoeb Khan, Mohammad Zulfequar, Mohd Shahid Khan
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.25044
Abstract: Highly oriented and transparent ZnO thin films have been fabricated on ultrasonically cleaned quartz substrates by the sol-gel technique. X-ray diffraction, UV-VIS, FTIR, photoluminescence and SEM are used to characterize ZnO thin films. X-ray diffraction study show that all the films prepared in this work have hexagonal wurtzite structure, with lattice constants a = b = 3.260 Å, c = 5.214 Å. The optical band gap energy of the thin films is found to be direct allowed transition ~3.24 eV. The FTIR spectrum of the film has the characteristics ZnO absorption band at 482 cm?1. The photoluminescence spectrum of the samples has an UV emission peak centred at 383 nm with broad band visible emission centred in the range of 500 - 600 nm.
Enhancement of Field Emission Properties of Carbon Nanotubes by ECR-Plasma Treatment
Javid Ali,Avshish Kumar,Samina Husain,Shama Parveen,Renu Choithrani,Mohammad Zulfequar,Harsh,Mushahid Husain
Journal of Nanoscience , 2014, DOI: 10.1155/2014/437895
Abstract: We report a significant improvement in electron field emission property of carbon nanotubes film by using an electron cyclotron resonance plasma treatment. Our research results reveal that plasma treatment can modify the surface morphology and enhance the field emission characteristics of carbon nanotubes. Raman spectra indicate that plasma treated CNTs sample has lesser defects. Before plasma treatment, low current density of 6.5?mA/cm2 at 3.0?V/μm and at a high turn-on field of 2.4?V/μm was observed. ECR plasma treated CNTs showed a high current density of 20.0?mA/cm2 at 3.0?V/μm and at a low of 1.6?V/μm. The calculated enhancement factors are 694 and 8721 for ECR-plasma untreated and treated carbon nanotubes, respectively. We found an increase in the enhancement factor and emission current after the ECR-plasma treatment. This may be attributed to creation of geometrical features through the removal of amorphous carbon and catalyst particles. 1. Introduction Carbon nanotubes (CNTs) have great attention because of their unique morphologies, which make their uses in wide variety of applications. The different techniques for the synthesis of CNTs have been developed, such as arc discharge method, laser ablation method, and chemical vapor deposition (CVD) [1–4]. The most widely used method is CVD technique, in which the synthesis is achieved by putting a carbon source in the gas phase. One of the most promising applications of CNTs is in field emission (FE) devices [5–14]. High aspect ratio and atomically sharp radius of apex curvature of the CNTs enhance the local field and lower the threshold field for electron emission. The emission properties of CNTs are governed by the work function, crystalline structure, geometry of their tips, and so forth. In addition, the surrounding gases and impurities on the surface have also been known to strongly affect their FE characteristics. However, the effect of crystallinity of CNTs on the FE has not been much investigated till now. Schwoebel and Spindt [15] experimentally found that low-pressure hydrogen glow discharge can clean the surface contaminants in both microfabricated single molybdenum tips and arrays which resulted in a decrease of ~1?eV in the work function. Yu et al. [16] achieved a low-field electron emission in undoped nanostructure diamond by employing a hydrogen plasma heat treatment. Hydrogen plasma has been known to greatly enhance the field emission property of CNTs [17]. These references indicate that plasma treatment is an effective method to improve the field emission property of CNTs. In this
Study of Duct Characteristics Deduced from Low Latitude Ground Observations of Day-Time Whistler at Jammu  [PDF]
M. Altaf, M. M. Ahmad
International Journal of Astronomy and Astrophysics (IJAA) , 2013, DOI: 10.4236/ijaa.2013.33032
Abstract:

Propagation characteristics of low latitude whistler duct characteristics have been investigated based on day-time measurements at Jammu. The morphogical characteristics of low latitude whistlers are discussed and compared with characteristics of middle and high latitude whistlers. The Max. electron density (Nm) at the height of the ionosphere obtained from whistler dispersion comes out to be higher than that of the background which is in accordance with the characteristics of whistler duct. The equivalent width is found to be close to the satellite observations and the characteristics of whistler duct in low latitude ionosphere are similar to those in middle and high latitude ionosphere. The width of ducts estimated from the diffuseness of the whistler track observed during magnetic storm is found to lie in the range of 50 - 200 Km.

Review Article: Immobilized Molecules Using Biomaterials and Nanobiotechnology  [PDF]
Magdy M. M. Elnashar
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2010, DOI: 10.4236/jbnb.2010.11008
Abstract: Immobilized molecules using biomaterials and nanobiotechnology is a very interesting topic that touching almost all aspects of our life. It uses the sciences of biology, chemistry, physics, materials engineering and computer science to develop instruments and products that are at the cutting edge of some of today’s most promising scientific frontiers. In this review article, the author based on his experience in this arena has tried to focus on some of the supports for im-mobilization; the most important molecules to be immobilized such as DNA, cells, enzymes, metals, polysaccharides, etc and their applications in medicine, food, drug, water treatment, energy and even in aerospace. He specified a special section on what is new in the arena of supports and technologies used in enzyme immobilization and finally a recommendation by the author for future work with a special attention to up-to-date references.
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