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Synthesis and Characterization of Lithium- Manganese Rich Cathode Materials for Lithium Ion Batteries

Thesis Info

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Author

Iftekhar, Maryam

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2015

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2951/1/Maryam_Iftekhar_Chemistry_2016_QAU_07.03.2016.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727450421

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In this study 0.5LiMn 2 O 3 .0.5LiNi 1/3 Mn 1/3 Co 1/3 O 2 , a layered lithium-manganese rich nickel manganese cobalt (LMR-NMC) oxide, was a carefully selected composition for use as a cathode material in Li ion batteries. The effect of synthesis method and doping on this layered lithium-manganese rich, mixed metal oxides is presented. First part of this study deals with the effect of synthesis route on the electrochemical properties of the 0.5LiMn 2 O 3 .0.5LiNi 1/3 Mn 1/3 Co 1/3 O 2 material. A comparison between Co- precipitation, low temperature (90°C) sol-gel synthesised and high temperature (120°C) sol- gel synthesised LMR composite materials is presented. The study demonstrated that synthesis procedure and conditions strongly influence the electrochemical properties of the synthesized material. Co-precipitation and sol-gel synthesised LMR composites revealed obvious differences in capacity and cycle life, which give the impression from X-ray photoelectron spectra to be strongly related to the particles‘ surface reactivity. In the second part of study, the LMR-NMC materials were doped with varying amounts of aluminium. Small amounts of Al doping to the sol-gel material were shown to improve the rate capability and cyclability, in addition to decreasing voltage fade. The results were interpreted in terms of charge discharge studies and supported by differential capacity plots, impedance measurements and cyclic voltammetry data. The electrochemistry of an aluminium doped material was revealed to be highly dependent on the degree of aluminium doping – with the behaviour of 1% doped material giving a maximum capacity of 201 mAhg -1 at 150 mAg -1 and a capacity retention of 88% after 200 cycles. An attempt has been made to study the effect of Cr doping as well on the electrochemical properties of the LMR-NMC materials. It results in an increase in the initial charge/discharge capacity of the material while decreasing the capacity retention. However, the Cr as a dopant could not be assigned as an improvement in the LMR mixed metal oxide material. The study established the comparative role of co-precipitation and sol-gel methods on the improvement of electrochemical properties of the LMR-NMC oxides. Additionally, controlled Al doped samples substantially improved the discharge capacity while maintaining capacity retention event at very high C-rate.
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مرزا سلطان احمد

مرزا سلطان احمد
افسوس ہے کہ اعظم گڑھ کی ممتاز مقبول شخصیت مرزا سلطان احمد صاحب رٹائر ممبر بورڈ آف ریونیو نے طویل علالت کے بعد گزشتہ ۱۷؍ فروری کو انتقال کیا وہ پرانے علیگ اور اپنے زمانہ کے لائق ترین عہدہ داروں میں تھے، اپنی قابلیت سے ڈپٹی کلکٹری سے کلکٹری اور بورڈ کی ممبری تک ترقی کی اور جہاں رہے اپنی دیانتداری اور شرافت سے مقبول و نیک نام رہے، بڑے عہدہ داروں میں ایسے شریف اور خلیق انسان کم دیکھنے میں آئے ہیں، ان کا خمیر ہی اخلاق و شرافت سے گوندھا گیا تھا، ادنی و اعلیٰ ہر شخص کے ساتھ ان کا اخلاق یکساں تھا، ہر ملنے والے کے ساتھ کوئی نہ کوئی ایسی خصوصیت ضرور برتتے تھے جس سے اس کو یہ محسوس ہوتا کہ وہ اس کے ساتھ خاص تعلق رکھتے ہیں۔
بڑے وضعدار، فیاض اور مہمان نواز تھے جس سے جس قسم کے تعلقات تھے، اس کو عمر بھر نباہا، ملازمت کے زمانہ میں ان کا دستر خوان بڑا وسیع اور گھر مستقل مہمان خانہ تھا، ان کے اعزہ و احباب میں سے کوئی نہ کوئی ان کے یہاں مستقل مقیم رہتا تھا اور جس کو ضرورت ہوتی اس کی نقدی سے بھی مدد کرتے تھے، ہر حاجت مند کی مدد کے لیے ہر وقت تیار رہتے تھے اور اس کے لیے ایسے کام کر گزرتے تھے جس کی ہمت ہر شخص نہیں کرسکتا، وہ بڑے تنخواہ دار تھے لیکن جو کچھ کمایا سب صرف کردیا، اعظم گڑھ میں دو ہی ایسے شخص تھے جنھوں نے بہت پیدا کیا، مگر اپنے بعد کچھ نہیں چھوڑا، ایک مرزا صاحب، دوسرے اقبال سہیل مرحوم ملازمت سے ریٹائر ہونے کے بعد حکومت نے ان کے سامنے پبلک سروس کمیشن کی ممبری پیش کی، مگر انھوں نے وطن چھوڑنا پسند نہ کیا اور اعظم...

Development and Evaluation of an Audio System Trainer

Guided by the desire to contribute a little in the development of an innovative instructional technology for the teaching of electronics, this researcher constructed a prototype audio system trainer. Electronics teachers will find the instructional tool convenient and practical to use for visual instruction, laboratory activities and troubleshooting works in electronics. To support the functionality of the audio system trainer, the researcher developed a supplementary laboratory manual. The project whose production costs totaled fourteen thousand two hundred seventy two pesos and fifty centavos (Php 14,272.50) was finished in two weeks’ time. However, this amount is small if compared to the prices of commercially available instructional device developed for the same purpose. The completed project and the supplementary laboratory exercises were evaluated by selected technical faculty members of the College of Industrial Technology of the Bulacan State University, Bulacan Polytechnic College, University of Rizal System, and Lyceum of the Philippines University. Sampling technique as used in the study is both purposive and incidental. The prototype audio system trainer received an over-all mean rating of 4.62 which means that the project is highly acceptable on a set of criteria which includes – physical features, cost, function / operations, and durability. Furthermore, the supplementary laboratory exercises obtained a mean of 4.70 which could be interpreted that the respondents strongly agree on the validity of the manual.

Steady Flow of Fluids With Variable Viscosity

Nanofluids have wide range applications in processes involving heat transfer due to their proficient thermal conductivity. Such fluids exhibit substantial viscosity variation with temperature. This dissertation presents oblique stagnation point flow of variable viscosity nanofluid over a stretching surface. Porous medium, magnetic field, heat generation, thermal radiation and homogeneous-heterogeneous effects along with partial slip, thermal slip and convective surface are considered. Micro-rotation phenomenon is also fused with nanofluid flow comprising micropolar nanofluid. Nanofluid thermal conductivity is estimated by Maxwell-Garnett model, Hamilton Crosser thermal conductivity model is also employed when shape effects of nanoparticles are considered. Flow problems are first modeled and afterwards converted to non-linear system of ODEs via appropriate similarity transformations. Numerical solutions are obtained via stable and efficient Runge-Kutta-Fehlberg scheme with shooting quadrature and Keller-Box scheme. The impact of key emerging dimensionless parameters on non-dimensional normal, tangential velocity constituents, temperature, shear stress (at wall), heat flux along with streamlines distribution is visualized by graphs.