الأصوات العربية الفرعية في الدراسات الصوتية

يهدف هذا البحث إلى المساعدة على التعرف على كيفية تركيب الألفاظ العربية من حيث إتيان الحروف المجاورة في بنائها، وعند جمع أربعة أو أكثر في التلفظ بها. ويعين على تمييز الألفاظ الأعجمية التي لها ألفاظ عربية. واتبع الباحث المنهج الوصفي التحليلي في إجراء البحث. وفي ضوء ما تم تناوله تم التوصل إلى النتائج الآتية: 1- أن تصنيف الحروف الفرعية إلى مستحسن ومستقبح راجع عند القدماء لمبدأ الكثرة والقلة، فما كثر استعماله كان مستحسنا، وما قل استعماله وصف بالاستقباح. 2- تمثل الحروف الفرعية ألوانا من الآراء يعكس اختلاف القبائل العربية آدابها، وهي من صور الأداء المعروفة، مما جعل العلماء يقومون ببيان خواصها الصوتية. 3- جاءت هذه الحروف لإحداث نوع من التناسق والإنسجام في البنية الصوتية.

Synthesis, Characterization and Analytical Applications of Polypyrrole-Metal Oxide Composites

This thesis has been divided into four chapters. The first chapter is about the introduction of polypyrrole (PPy) and other conducting polymers (CPs). The importance and drawbacks of conducting polymers have been thoroughly discussed followed by the discussion about the need of composites of these polymers. The importance of CPs-metal oxide composites over individual components has been deliberated. The relevant literature and references have also been included. The second chapter is related to the synthesis, characterization and analytical applications of PPy-vanadium penta oxide (V2O5) composites. The materials were synthesized in aqueous medium by chemical oxidation polymerization method using FeCl3.6H2O as an oxidant followed by characterization using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), thermogravimetry analyzer (TGA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) technique, surface area and pore size analyzer, UV-visible spectrophotometry and LCR-meter. PPy was amorphous while the composites were crystalline in nature. The content of V2O5 improved the compactness, thermal stability, surface area and electrical conductivity of the composites. The band gap energy was found to be of the same value for all the composites. The gas sensing properties of the materials were checked for ammonia gas and some other organic liquid vapors. The composite PPy/8%V2O5 was of highest sensitivity and selectivity towards ammonia at room temperature. The limit of detection (LOD, response time and recovery time of this material was 1.4 ppm, 10.5 and 81.6 s, respectively. The performance of this composite has been compared with the reported data. In the third chapter, synthesis, characterization and analytical applications of PPy-MnO2 composites have been elaborated. The composites were synthesized and characterized by the same procedure as mentioned for Chapter-2. The content of MnO2 has almost same x effect on the properties of these composites as in case of PPy/V2O5 composites. However, the band gap energy was found to decrease continuously with increase in the percent amount of MnO2 in the composites. After studying the gas sensing characteristics, the composites PPy/10%MnO2 was found of unique properties with respect to its sensitivity, selectivity and limit of detection towards ammonia gas. The response of this material was far better than the already done work. The LOD was 0.4 ppm with response and recovery time 32.1 and 40 s, respectively. In the fourth chapter, unique PPy/V2O5-MnO2 hybrid composites has been synthesized, characterized and applied as gas sensor by the same methods as discussed for PPy/V2O5 composites. These materials were also applied as gas sensor. The composite PPy/4%V2O5-5%MnO2 (S3) was of better performance as compared to the reported hybrid composites regarding ammonia gas sensitivity. The LOD, response and recovery time of the material at room temperature was 5 ppm, 75 and 76 s, respectively.