The work presented in this thesis deals with the Cold Plasma, generated by a cost effective 50 Hz ac and 100 Hz pulsed dc electric power source. Characterization of nitrogen and argon-nitrogen plasma is carried out using different plasma diagnostics (Langmuir probe and optical emission spectroscopy) as well as various parameters, for the nitridation of materials such as AISI-4140 steel and aluminium alloy (Al-Mg 2 -Si). Surface changes induced in materials by nitrogen and argon-nitrogen plasma are described using different material’s surface diagnostic techniques. In the first experiment, Langmuir probe measurements are carried out to characterize 50 Hz ac generated nitrogen plasma as a function of filling pressure (2–5 mbar ) under constant power level. Plasma nitriding of AISI-4140 steel is executed for different time durations (2, 6, 10 and 14 h ) at filling pressures of 2 and 3 mbar , keeping the input power at 100 W and substrate temperature at 300 ο C . The plasma nitrided samples are characterized for their surface properties by using X-ray diffractometer (XRD) and Vickers microhardness tester. Results demonstrate the formation of nitrogen infused ferrite phase ( α N − Fe ) owing to the inclusion of nitrogen in the original iron lattice as interstitial solid solution. Significant increase in the surface hardness is observed when samples are treated for 14 h at a filling pressure of 2 mbar . The rapid decrease in the hardness value with increase in imposed load suggests the formation of the skinny modified layer. In the second experiment, 50 Hz ac abnormal glow discharge is characterized as a function of filling pressure (1–4 mbar ) using a Langmuir probe. It is found that electron temperature, electron density and electron energy distribution function decrease with the gas filling pressure. Nitriding of aluminum alloy (Al-Mg 2 -Si) is performed for various time durations (3, 6, 9 and 12 h ) and pressures (1 and 2 mbar ) by keeping the input power (100 W ) and substrate temperature (250 ο C ) constant. To explore the surface properties induced by plasma, X-ray diffractometer, optical micrography, atomic force microscopy and Vickers micro-hardness tester diagnostic techniques are used. Results exhibit the formation of cubic aluminum nitride (AlN). A significant increase in surface xivhardness is observed when samples are exposed at 1 mbar pressure for 12 h of processing time. A rapid decrease in surface hardness values with the imposed load suggests the formation of a thin modified surface layer. Langmuir probe diagnostic is used to determine the plasma parameters for argon mixing in nitrogen using ac generated plasma source. Results reveal that argon mixing in nitrogen plasma is an effective mode to increase electron density. Nitriding of aluminum alloy is performed in nitrogen-argon mixture (1:1) plasmas, to investigate the effect of argon mixing on surface properties. Samples are exposed for 3, 6, 9 and 12 h at a filling pressure of 2 mbar and an electrical input power of 100 W. The analysis is carried out by using x-ray diffractometer, scanning electron microscopy and Vickers micro hardness tester to investigate surface changes induced by plasma. X-ray diffractometer results exhibit the formation of cubic aluminum nitride (AlN) thin modified surface layer by reactive ac sputtering with argon as a sputtering gas and nitrogen as reactive gas. Moreover, significant increase in surface hardness is found for 12 h nitrided samples in nitrogen-argon mixture plasma. In this experiment, nitriding behavior of stainless steel is investigated using pulsed dc (100 Hz) plasma. Active species of nitrogen in plasma play key role in nitriding the substrate. Therefore, optical emission spectroscopy and Langmuir probe diagnostics are used to determine the plasma parameters. Measurements are carried out for different pressure (1, 1.5, 2 and 2.5 mbar) and power (25, 50, 75 and 100 W) to optimize the plasma nitriding process. Electron temperature and electron density are evaluated by using intensity ratio of two atomic nitrogen lines (746.8 nm and 869.1 nm) and full width at half maximum (FWHM) of a Stark broadened line (746.8 nm) respectively. Langmuir probe is also used for determination of electron temperature, density, flux and velocity in plasma. These parameters are found to be strongly affected by the pressure and power. However, more energetic electrons are produced at 1 mbar pressure and 100 W power, which are responsible for enhanced plasma-reaction with stainless steel. Nitriding is performed under this optimum condition for 4, 8 and 12 h of treatment time. Nitrided samples are characterized using x-ray diffraction (XRD), fourier transformation infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) in order to study the growth and structural properties of nitrided layer. XRD xvresults exhibit the formation of dominant ε − Fe 3 N phase which is also observed by FT- IR spectrum. SEM and AFM micrographs showed the modified surfaces of exposing samples.
The beauty of religion Islam is not only to provide the complete life style and charter for one to lead his life smoothly but it flourishes the human life with its eternal directions and commands full of hidden pleasures coupled with physical and spiritual care of human body. In fact, the everlasting religion comprised of such rulings that help individuals in every walk of life until and unless these rulings are implemented and executed in a proper way according to the prescribed codes of Almighty Allah and his Messenger, Prophet Muhammad PBUH. The thorough study of Shariah rulings reveals the fact that to protect the man’s life or even to make it in comfort and ease, the gradual and steady relaxation has been observed like the one unable to perform prayer in standing position, legitimate for him to sit or even through gestures according to the status of his illness and disease. Similarly, the fasting is important part of Worship, obligation upon Muslim to observe fasting during Ramadan with intentions to get Allah’s pleasure and piousness. This research study emphasis on highlighting the shariah rulings about the medication during fasting in order to know the extent of use, specification in drugs like injections and drips along with some relevant discussion about the spirit of medicine permission. The study will be the real addition to the knowledge and will be fine guidance for the Practiced Muslims.
This study aims to improve the teaching of writing narratives in an English language classroom. By using a qualitative method and a collaborative action research, the study was conducted in a private school in Karachi, Pakistan. In this study, the primary research participant was an English language teacher who was teaching English language at lower secondary level. There were five students who were the secondary research participants of the study. Their work was analyzed to see whether there was any improvement in their written narratives that was taught by both researcher and the research participant. In our English language classrooms, teaching of writing is done in a very traditional manner where teachers focus to product rather than the process of the writing. Teachers do not pay attention on writing and rewriting in order to improve the children's work. Mostly, the first draft of children's work is considered as final draft. Children encounter problems while writing because they are not provided with opportunities to develop their writing skills and they are often asked to write about topics which are not relevant to their lives. Thus, writing is best learnt in a natural setting with topics that are pertinent to their lives. Teachers need to provide a variety of experiences to children while teaching writing skills. The purpose of the study was to improve a teacher's teaching of writing narratives and to guide him/her to introduce above motioned strategy to make a shift from product to process of writing and thus, transform students into independent writers. For this study, reflective journal, observations and interviews were used to collect data. The teaching of writing narratives was found to be a useful activity as it builds practical and theoretical knowledge of the research participant. It was found that children best learnt to write when they are asked to write about topics that are relevant to their lives. Another observation was that the use of scenario to motivate children to write is less effective because it limits their creativity and they end up producing similar kind of texts. The use of writing frameworks and the steps of PA facilitate the teaching and learning of writing skills in an English language classroom. Furthermore, this study is significant for ELT in the context of Pakistan where writing, in English, is regarded as the most difficult skill among other teaching language skills. The finding of this study will