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Liquid Phase Exfoliation of Graphite to Graphene & its Applications in Polymeric Nanocomposites

Thesis Info

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Author

Nawaz, Khalid

Program

PhD

Institute

National University of Sciences & Technology

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2015

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/6685/1/Khalid_Nawaz_Materials_Engineering_2015_NUST_14.04.2016.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726590521

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Nanocomposites are superior to conventional one in terms of its mechanical performance. Pristine /functionalized graphene sheets (FGS) were incorporated into a range of model polymers. Solvent aided blending was adopted for better dispersion of FGS and graphene sheets in these polymers. Graphene was added to selected polymers like polyurethane (PU), poly (vinyl chloride) (PVC), poly (acrylonitrile) (PAN), poly (vinyl alcohol) (PVA) and poly (vinyl acetate) (PVAc) in order to improve the mechanical performance of these materials. Different forms of graphene nanosheets like pristine/FGS with different lateral dimensions were selected in order to study its effects on the mechanical performance of selected polymers in terms of young’s modulus, tensile strength and elongation at break. Graphene nanosheets were functionalized with octadecylamine and were incorporated in polyurethane and it was observed that 2.5 vol% is the mechanical percolation level for this polymer as above this loading there was improvement in the mechanical performance of polyurethane while at this loading the elongation at break was suffered slightly. Similarly in case of poly(vinyl chloride) a critical loading(1.5wt%) was observed at which there was improvement in mechanical properties of these polymers and almost no elongation at break was observed for this loading and the modulus determined in this case was superior to calculated from Halpin-Tsai equation. Two type of graphene nanosheets with different flake size (one and 3.5 micron) were incorporated in poly (acrylonitrile). Its comparative study was conducted it was observed the big flake improved the performance of polymers in terms of modulus and UTs while the response of small flake in terms of elongation at break was better than big flakes. Large area graphene oxide were synthesized and were introduced to poly(vinyl alcohol) and the role of these nano fillers were very pronounced in terms of modulus, UTS and elongation at break was not disturbed but slightly improved. Graphene flakes were studied through transmission electron microscopy(TEM) and Raman spectroscopy while dispersion of these flakes were in selected polymers was confirmed by scanning electron microscopy(SEM) and the mechanical performance of these nanocomposites were conducted on Zwick-Roell tensile tester. Graphene-based v polymer nanocomposites can be a new versatile soft material with numerous advantages. Graphite was exfoliated to graphene using NMP and water as solvent as well. 63mg/ml concentration was obtained during tip sonication in NMP while in case of water as media the maximum concentration obtained was 7mg/ml using sodium cholate as surfactant. The concentration of graphene nanosheets were studied through UV-visible spectroscopy while quality of flakes was studied through TEM and Raman spectroscopy.
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وہ جس میں اُسوہ کامل حلول ہوتا نہیں


وہ جس میں اُسوۂ کامل حلول ہوتا نہیں
’’قسم خدا کی محب رسولؐ ہوتا نہیں‘‘

حضورِ رب ازل ؛ مدعاے آدمؑ بھی
بغیر اسمِ محمدﷺ قبول ہوتا نہیں

بھٹکتا رہتا ہے وہ آندھیوں ، بگولوں میں
جو ذرّہ خاکِ مدینہ کی دُھول ہوتا نہیں

نبیؐ کے ذکرِ معطر میں جو بھی محو رہے
خزاں کے ہاتھوں وہ پامال پھول ہوتا نہیں

نبیؐ بھی ہم سے بشر ہیں تو پھر بتاؤ ہمیں
وحی کا ہم پہ بھلا کیوں نزول ہوتا نہیں

نظر میں جس کی رہے رحمتِ حبیبِ خداؐ
رہِ حیات میں ہرگز ملول ہوتا نہیں

خدا سے مانگو اگر صدقۂ رسولؐ خدا
قبولِ عرض میں عرفانؔ! طول ہوتا نہیں

Theological Foundations for Interfaith Dialogue in Islam

According to Qur’an, the difference of opinion among peoples of the world is natural and something that will always be there. However, in order to stop the difference from becoming a conflict, people should hold dialogue. The significance of dialogue in Islam is well understood by the fact that God chose to hold dialogue with angels concerning the creation of man. Furthermore, the Qur’an declares dialogue the greater jihad and arrangement of a successful dialogue is considered as a manifest victory In order to arrange a successful dialogue, Qur’an lays out a number of principles: 1- Dialogue should be held in such a nice way that it may lead the opponent to get a close friend. For this it is necessary to speak mildly and the dialogue must be based on wisdom and sincerity. 2- Dialogue should rest on the principle of mutual respect and should not contain any kind of abusive and taunting language. 3- Dialogue must not override the principle of justice and equality and must not be affected by the past experiences or personal grievances towards the opponent. 4- Dialogue should not address the issue of pulling everyone together, e.g. The opponent (for example a nation) should not be blamed for the evil deeds of few. 5- Dialogue should be held with an attitude that is characterized by patience and tolerance and efforts must be made to keep the vicious elements out from harming the process. 6- Both parties should openly acknowledge and recognize the mutually positive attributes. 7- Imposing one’s opinions upon the opponent must not be the objective of dialogue. 8- Both parties should, despite the inherent difference of opinion, pursue to find practical solutions by striving towards finding a common ground.

Endocrine Disruption, Genotoxicity and Biochemical Abnormalities in Human Population Exposed Chromium in Effluents of Tanneries in Pakistan

Chromium is one of the toxic heavy metals, which is extensively discharged from tanning industry to the environment. Chromium has binding potential to biomolecules in living systems and cause toxicity to biological life. Leather industry has been categorized as one of the highly polluting industry. Tanning industry is polluting the environment at a higher rate with huge amount of harmful material. These pollutants are also harmful for environment, humans and aquatic organisms. The aim of the present study was to investigate the effects of chromium on selected endocrine hormones, oxidative stress, DNA damage, biochemical and haematological parameters of tannery workers and environmental parameters. Two major cities, Peshawar and Sheikhupura, were selected for the sampling sites. Samples of effluents, ground water, soil and vegetables were collected from the neighboring vicinity of tanning industries. The background area and adjoining villages were considered as control areas. Seven trace metals (Cr, Cu, Ni, Cd, Pb, Fe, and Zn) were investigated in tannery effluents, ground water, soil and dietary vegetables (Spinacia oleracea, Solanum tuberusom and Solanum melongena) samples using Graphite Furnace Atomic Absorption Spectrophotometer. It was observed that both soil and groundwater of study area were badly affected by the toxic elements discharged by tanning industries. The maximum level of Cr in tannery effluents was 350.15 mg/l, while in the soil sample it approached to 31.13mg/l. The values of chromium, cobalt, cadmium, lead and iron in the tannery effluents from Sheikhupura and Peshawar were above the permissible limits set by WHO (World health organization) and FAO (Food and Agriculture organization). The concentration of chromium, cadmium, nickel and lead in study area ground water from Sheikhupura and Peshawar exceeded the standards of NSDWQ/Pak (National standard for drinking water quality). Vegetables irrigated with tannery effluents showed elevated level of Cr, Zn, Ni and Cd, which were above the permissible limits of WHO/FO. There was a significant positive correlation between all the trace metals in three media, tannery effluent, soil and ground water (p<0.001). The metal to metal association was supported by dendrograms using cluster analysis. A total of 240 smoking and nonsmoking individuals were registered in the study, including 120 chromium exposed tannery workers and 120 controls. The workers were selected from the tanneries of Sheikhupura and Peshawar, Pakistan. The average age of exposure group I was 20-35 years, exposure group II was 36-50 years and controls were 20-50 years. Hormonal parameters in the blood samples were determined by commercial kit, Chemiluminescent Microparticle Immunoassay (CMIA). Oxidative stress parameters were measured in the blood samples by spectrophotometric methods. DNA damage in lymphocytes was measured by comet assay (single-cell gel electrophoresis). Blood samples were collected from different age group subjects (chromium exposed tannery workers and controls). The results revealed that both smoking and nonsmoking exposed groups showed significantly higher chromium levels in blood and urine than those of unexposed groups. The levels of testosterone (326.238± 12), (306.636±13.8) and growth hormones (0.1030±0.03), (0.0734±0.01) were significantly decreased in both age groups of male tannery workers exposed to chromium. The level of progesterone (2.416 ± 1.1), estradiol (48.879 ± 40.1), luteinizing (1.9692± 0.82) and growth hormones of female tannery workers (0.7983±0.1) were significantly decreased while follicle stimulating hormone (9.2857 ± 0.7) was significantly increased as compared to unexposed population. Thyroid stimulating hormone, triiodothyronine and tetraiodothyronine hormones were not affected in tannery workers. The hormones in tannery workers in group II aged (36-50) were more affected due to long-term Cr exposure as compared to group 1 with short term chromium exposure and controls. This was further supported by correlation and regression analyses of the data. Pearson correlation showed that the levels of sex hormones (testosterone, progesterone, estradiol and luteinizing hormone) and growth hormone had negative correlation with blood chromium concentration in tannery workers. The present study revealed that occupational exposure to Cr (VI) and Cr (III) can lead to a detectable DNA damage in tannery workers. DNA damage (28.79± 2.154), (25.41± 7.199) in smoking and nonsmoking tannery workers were significantly higher than those of unexposed groups. In addition, DNA damage was significantly associated with concentration of chromium in blood. Malondialdehyde (MDA) levels (11.00 ± 0.7), (8.77± 2.3) and superoxide dismutase (SOD) concentrations (75.178± 2.3), (79.52±1.9) of smoking and nonsmoking exposed groups were significantly higher than those of unexposed groups. While glutathione (GSH) levels (59.926 ± 1.5), (55.702 ± 2.3) in smoking and nonsmoking exposed groups were significantly lower when compared with unexposed groups. Oxidative stress parameters and DNA damage in group II tannery workers aged (36- 50) with long-term Cr exposure were more affected as compared to tannery workers in group I with short term chromium exposure and controls. This investigation was further supported by correlation analysis. There was positive correlation between levels of blood chromium and DNA damage, MDA and SOD levels, while negative correlation was observed between blood chromium concentration and GSH levels in tannery workers. The results showed that duration of exposure and smoking has significant effect on DNA damage and oxidative stress parameters in tannery workers. The present study also described biochemical and haematological defects in tannery workers exposed to hexavalent chromium. From the findings, it is evident that white blood cells (WBC) (8.373±0.7), red blood cells (RBC) (4.12±0.5), haemoglobin (Hb) (10.02±1.14), mean corpuscular haemoglobin (MCH) (25.91±1.50), and packed cell volume (PCV) (42.62±2.0) were lower in exposed groups than that of controls. The values of liver function tests of tannery workers were found to be within the normal range in both the age groups except alkaline phosphatase (AP) activity (121.28±8.3), which was significantly increased in exposed groups. All other biochemical parameters were found to be within the normal range except the albumin (Alb) levels which was significantly decreased in exposed groups. The present study found that occupational exposure to chromium can lead to health hazards including hormonal abnormalities, oxidative stress, DNA damage and hematological and biochemical defects in tannery workers.