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Role of Carbon Nanotubes Reinforcement and Processing Parameters on Mechanical Properties of Alumina Based Nanocomposites

Thesis Info

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Author

Nabi Bakhsh

Program

PhD

Institute

Ghulam Ishaq Khan Institute of Engineering Sciences and Technology

City

Topi

Province

KPK

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1284

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727111369

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Along with other oxide ceramics, alumina is an important and widely used industrial material. Its applications include prostheses and dental implants used as bio-medical replacements, wear- resistant components and speedy cutting tools, thermal and electrical insulations and coatings for high temperature use. The effectiveness of alumina for such uses is credited to its excellent corrosion resistance, high hardness, good electrical and thermal insulating properties and high compressive strength. However, regardless of its excellent potentials and properties, its use for structural applications has significantly been limited due to its low-fracture toughness and low- fracture strength. The potential use of carbon nanotubes reinforced ceramic nanocomposites for various engineering applications has unlocked an interesting area of research. In the current work, two kinds of sintering routes, namely pressureless and spark plasma sintering are used for the synthesis of multiwalled carbon nanotube reinforced alumina matrix nanocomposites. The characterization of the resulted nanocomposites is carried out and their comparison with the sintering behavior of monolithic alumina is presented. Two types of composites were prepared by using pressureless and spark plasma sintering techniques both contained 1, 2 and 3 wt% of as-received and functionalized carbon nanotubes. The mixing and dispersion of carbon nanotubes in alumina was done by a novel technique of gas purging sonication. Varying percentages of carbon nanotubes in the composites were compacted using a uniaxial press followed by pressureless sintering at 1600°C in flowing argon with a dwell time of 15 minutes and spark plasma sintering at 1400°C under a pressure of 60 MPa for a holding time of 10 minutes. Pressureless sintered nanocomposites with 1 wt% carbon nanotubes gave 98.5% relative density with no degradation of carbon nanotubes. Moreover, it also resulted in an increase in fracture toughness from 8.1% and 9.4% and Young’s modulus by 5% and 7% when compared to as-received and functionalized carbon nanotube nanocomposites respectively with respect to pure alumina. This investigation has shown that the densification can be achieved without degradation of carbon nanotubes at elevated temperatures in the carbon nanotube-alumina nanocomposites sintered by conventional route. vWell-dispersed carbon nanotube-reinforced alumina nanocomposites have been synthesized successfully having a high density by spark plasma sintering. At 1 wt% functionalized carbon nanotubes addition in alumina, a near full density is achieved that contributes to the improvement in mechanical properties of the nanocomposites. On addition of 1wt% CNTs, fracture toughness values increased by approximately 18.6% and 14% for functionalized and as-received CNT-alumina nanocomposites respectively. However further addition of CNTs up to 3 wt % slightly decreased the hardness and the fracture toughness. Young’s modulus was improved by 6.5% for functionalized and 4% for as-received CNT-alumina nanocomposites over monolithic alumina. Average grain size of monolithic alumina is observed as 2.0 ± 0.5 μm while that of 1wt% CNT-alumina nanocomposite was less than 1 μm. The well-dispersed carbon nanotubes within the alumina matrix enhanced the pullout resistance, bridged the gaps between cracks and held up the crack propagation by using elasticity that lead to improved fracture toughness.
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۵۶۔ مجبور

مجبور

وقت کے نازک لمحوں میں

 ہم دونوںبہت قریب تھے

 پرایک دوجے کے دل سے بہت ہی دور

اس پر بھی بلا کی خاموشی طاری تھی

میں بھی بولنے سے عاری تھا

 دونوں اپنی اپنی انا کے ہاتھوں مجبورتھے

قیام امن میں مراکز تعلیم کا کردار تعلیمات نبویﷺ کی روشنی میں

One of the most important and fundamental elements of a civilized society is the presence of peace. In the absence of peace nothing can prosper and advance. In this age of science and technology, terrorist activities can become a cause of isolation from the rest of the world. That is why, every country gives extra attention to its peace and security. Many countries allocate huge sums of budget for this purpose. However, it is not only the responsibility of a government to establish peace, but, also of other institutions, especially, the educational institutions to play their role in this regard. In this article, the role of educational institutions for the promotion of peace has been discussed. Every person of society spends some time in these institutions. These institutions can teach and train their students to develop a peaceful conduct and tolerate the different behaviors and views. But there are some problems and difficulties for educational institutions to play their required role for peace. In the perspective of our country, we can say that if we solve these problems, our country can become more peaceful, will make progress by leaps and bounds and can become one of advanced countries of the world.

Willingness to pay for improved water supply services in Karachi

Karachi, Pakistan's largest cosmopolitan and home to over 21 million people, finds itself unable to fulfill the various public utility needs including basic amenities like water. Access to clean drinking water remains the greatest perceived need of the population (City District Government Karachi, 2007), a deficiency further hampered by the population size of the metropolis. Just three-fifths of the total number of households is connected to the Karachi Water & Sewerage Board (KWSB) supply line, and those connected received daily, only four hours of continuous water supply on average. In order to implement projects that increase water coverage and improve water supply services in a sustainable way, implementation of a cost recovery system is necessary, and for that it is important to examine willingness to pay of the beneficiaries of improved water supply. The objective of this study is to examine the determinants of the willingness to pay (WTP) of water consumers and to find out whether it is possible to increase tariffs. This study uses a contingent valuation method to estimate the mean willingness to pay using double bound dichotomous choice bidding. The total number of households surveyed through in-person interviews is 400. The households were randomly selected from Block 4 and Block 7 of Gulshan-e-Iqbal Town in Karachi. Estimation using interval data model reveal that sampled households expressed their WTP with a mean WTP of Rs. 2244 and Rs. 2080/ month for each model respectively. It also shows income affects the respondent's willingness to pay. The descriptive analysis result reveals that the mean WTP for improved water services is higher than the existing tariff