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Synthesis and Characterizations of Magnetic Nanomaterials

Thesis Info

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Author

Nairan, Adeela

Program

PhD

Institute

University of the Punjab

City

Lahore

Province

Punjab

Country

Pakistan

Thesis Completing Year

2016

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2905/1/Adeela_Nairan_High_Energy_Physics_2016_HSR_UoP_Lahore_09.11.2016.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727468082

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The work presented in this PhD dissertation deals with the synthesis and characterizations of magnetic nanostructures using chemical methods. These nanostructures include nanoparticles, core/shell nanoparticles and core/shell nanowires which were synthesized via chemical coprecipitation method, solution evaporation method and sol-gel route followed by electrodeposition respectively. In this research, structural and magnetic properties of various ferrites (Spinel, Perovskite and Hexa-ferrites) with different dopant and chemical composition have been explored. Core/shell structure for nanoparticles and nanowires has also been studied in detail. Subsequently, the crystallinity and the phase purity of nanostructures were studied by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Surface morphology, grain size, and chemical composition was analyzed by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), High Resolution Transmission Electron Microscope (HRTEM) and Energy Dispersive X-ray Spectroscopy (EDX) techniques respectively. Vibrating sample magnetometer (VSM) was used for room temperature magnetic measurements, however, low temperature characterizations were performed with the help of physical property measurement system (PPMS). We have reported magnetic properties of La1-xCoxMnO3 nanostructures synthesized by hydrothermal route. The crystal structure has been characterized by X-ray diffraction (XRD) technique, which shows rhombohedral perovskite structure at room temperature. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) have been used to analyse morphology and chemical composition of prepared nanoparticles. Magnetic hysteresis loops of all the samples exhibit ferromagnetic behaviour at 10 K. Inverse susceptibility graphs as a function of temperature represent deviation from Curie Weiss law. The indication for short range ferromagnetic clusters well above Curie temperature is observed due to the Griffiths Phase (GP). It is proposed that the presence of GP arises from induced size effects of La and Co ions. BiFe1-xCoxO3 (0≤x≤0.1) nanoparticles prepared by using solution evaporation method endorsed the formation of rhombohedral Perovskite crystal structure with R3c space group. Structural parameters show decreasing behavior of lattice constants and increasing behavior of X-ray density by increase in doping (Co) content in BiFeO3. XRD vi and TEM claimed average particle size of 39 nm. Room temperature magnetic results shows increase in Hc and Ms of nanoparticles up to doping content of 7.5%. On the other hand, low temperature magnetic measurements showed increasing trend of magnetic parameters with decreasing temperature. Variation in coercivity with temperature was followed theoretically by using Kneller’s law while, saturation magnetization followed the modified Bloch’s law in temperature range of 5-300K. Thirdly, a series of hexaferrite nanoparticles, with general formula Ba2Co2-xMnxFe12O22 (0≤x≤1) was synthesized by chemical co-precipitation method. It was found that with increasing Mn concentration grain size of hexaferrite nanoparticles increased from few nanometers to micrometer range. Furthermore, magnetic analyzes revealed that with increasing Mn concentration at octahedral and tetrahedral sites, the coercivity and squareness were found to increase from 455Oe to 2550Oe, and 0.23 to 0.47, respectively. Theoretical approach was also used to calculate saturation magnetization of synthesized samples. Along with ferrite nanoparticles, core/shell nanoparticles of ferrite material were prepared. Bimagnetic monodisperse CoFe2O4/Fe3O4 core-shell nanoparticles were prepared by solution evaporation route. Preferential coating of iron oxide onto the surface of ferrite nanoparticles was confirmed from XRD and HRTEM analyzes. The average core size was about 18 nm with thickness of the shell 3 nm, which corroborates with TEM study. We have observed large coercivity 15.8kOe at T=5K, whereas maximum saturation magnetization (125 emu/g) is attained at T=100K for CoFe2O4/Fe3O4 core-shell nanoparticles. Saturation magnetization decreases due to structural distortions at the surface of shell below 100K. ZFC-FC plots show that synthesized nanoparticles are ferromagnetic up to room temperature and it has been noticed that core/shell sample possess high blocking temperature than Cobalt Ferrite. Presence of iron oxide shell significantly increases magnetic parameters as compared to the simple cobalt ferrite. A comprehensive study of magnetization properties for M-CoO (M=Co, Ni, Fe) core/shell nanowires has been presented. Ferromagnetic nanowires arrays layered with Cobalt oxide shell are fabricated by sol gel route followed by DC electrodeposition into AAO templates. Structure and morphology of fabricated nanowires reveals the formation of nanowires without existence of any impurity phase. Magnetic analysis briefly describes magnetization reversal mechanisms of nanowires by measurement of angular dependent coercivity for core and core-shell nanowires. It is found that two main vii mechanisms; curling and coherent rotation reversal modes describe the magnetization reversal mechanism at room temperature. Furthermore, angular dependence of squareness shows that easy axis of Co core and core shell nanowires lies along perpendicular to the wire axis whereas, for Ni and Fe nanowires easy axis is along parallel to the wire axis.
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مُلّا جان محمد

مُلاّ جان محمد
افسوس ہے گذشتہ مہینہ ہمارے دومخلص قومی کارکن ملاجان محمدکلکتہ اورمولانا محمد عاقل الٰہ آباد انتقال کرگئے۔ملا صاحب کااصل وطن پشاور تھالیکن عرصہ دراز سے کلکتہ میں آبسے تھے اوراب سچ مچ وہی ان کاوطن تھا۔نہایت پُرجوش،جری اوربیباک انسان تھے۔گذشتہ نصف صدی میں کوئی قومی اور ملی تحریک ایسی نہیں ہے جس میں انہوں نے بڑھ چڑھ کراورولولہ و عزم کے ساتھ حصہ نہ لیا ہو۔ ان کی علمی زندگی کاآغاز تحریک خلافت سے ہوا اوراختتام مجلس مشاورت پر۔کلکتہ میں شاید ہی کوئی مسلم ادارہ(یہاں تک کہ محمڈن اسپورٹنگ کلب بھی) ایسا ہوجس میں ملاصاحب نے نمایاں حصہ نہ لیاہو۔اسی وجہ سے وہ کلکتہ کے لوگوں میں بے حد مقبول تھے۔ بڑے بے غرض،بے لوث اورنہایت سادہ اورمخلص مسلمان تھے۔۱۹۵۰ء میں کلکتہ کے فساد میں لوگوں نے ان کو بچوں کی طرح چیختے اور روتے دیکھا ہے۔ عمر۸۵ سال کے قریب تھی۔ [نومبر ۱۹۷۲]

 

دراسة تحقيقية حول حياة الإمام نوح بن أبي مريم الجامع جرحا وتعديلا

Al-Imam Nooh Ibne Abi Maryam Aljam'a is one of the well known worldly personality among the International Scholars of Science of Hadith. Unluckily, his positive personality (Ta'deel) in the Science of chain of Narrators (Ilm-e-Asmaur Rijal wa See'r) had been hidden from the sights of worldly known scholars since centuries. This research contribution is based on manuscript of Al-Istighna fee Asma el Mashooreen Bilkuna by Hafiz Ibne Abdul Bar Al-Qurtubi Al-Maliki (death: 460 hijri) found from Mufti Ilahi Bakhsh Library Kandhala India، despite of the Jarah of other scholars. The manuscript is written by Al-Hafiz Abi Abdullah Muhammad bin Abil Fatah Al-Ba'li Alhanbali (Teacher and Mentor of Al-Hafiz Al-Zahabi) (death: 709 hijri). This contribution tries to explore the personality of the great scholar as well as shower a spot light on the critic of scholars and highlight the reality of this Imam.

Extraction of Bioethanol from Agricultural Wastes by Using Termites Gut Flora Through Fermentation

Pakistan utilizes huge amount of budget to import petroleum products from other countries because very limited resources of fossil fuels are available in country. However combustion of fossil fuel increases concentration level of greenhouse gases, those are destroying environment. There is a need of some alternate and cheaper resources of energy to overcome the deficiency of fuels. There are number of challenges for the marketable applications of the advanced technologies of fuel production which includes pretreatment methods and enzymes production. For the microbiologist and ecologist, termite gut represents an outstanding representative of highly structured micro environments and therefore also called as mini biorefineries. Because the decomposition of lignocelluloses is proficiently perform by these soil insects. A study was conducted to develop a method for the production of bioethanol from agricultural waste materials which includes corn stover, cotton stalk and rice straw by using cellulolytic bacteria from termite gut. Bacteria were isolated from termite gut and identified by 16S rRNA gene sequencing. The isolates were screened for CMCase and xylanase activity. Three isolates were selected among which two were bacillus sp. and the one was cellulomonas sp. Their avcilase CMCase and xylanase activities were studied on selected temperature and pH. It was found that all of the bacterial isolates have shown higher avicelase activity at 40 oC, CMCase and xylanase activity at 50 oC. Isolate 9x, 10 and 31 have shown higher avicelase activity at 7 pH, whereas CMCase activity was found to be optimum at pH 8. In case of xylanase activity isolate 9x and 10 showed higher activity at pH 6 and isolate 31 at pH 7. Biological and chemical pretreatments were compared for corn stover, cotton stalk and rice straw. Efficiency of enzymes of bacterial isolates for saccharification of agricultural substrates was assessed. It was observed that xylanase (isolate 9x) 1 2 released more sugar amount from corn stover as compared to other substrates. Direct saccharification and fermentation of corn stover and rice straw was carried out using all three bacterial isolates without using pretreatment methods. Ethanol concentration was analyzed by using High performance Liquid chromatography. It was observed that isolate 31 has produced higher amount of ethanol by using corn stover. Therefore it was found that these bacterial enzymes have the potential to hydrolyze not only pure substrates but can also degrade agricultural substrates. Bacterial isolates obtained from termite gut have potential to can convert different agricultural substrates into valuable bioproducts including various alcohols (ethanol) which may have new innovative source for producers.