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Fabrication and Investigation of Organic and Nano Materials Based Sensors

Thesis Info

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Author

Saeed, Muhammad Tariq

Program

PhD

Institute

Ghulam Ishaq Khan Institute of Engineering Sciences and Technology

City

Topi

Province

KPK

Country

Pakistan

Thesis Completing Year

2012

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1691

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726188070

Similar


This work presents the fabrication and investigation of organic and nano materials based sensors for humidity, temperature and electromechanical applications. Polyaniline (PANI), orange dye (OD)-PANI composite and of cellulose- poly-N-epoxypropylcarbazole (PEPC) have been used for the fabrication of surface type humidity sensors. The sensors are fabricated by depositing films of various thicknesses on glass substrates between pre-deposited metallic electrodes. The sensing mechanism is based on the impedance and capacitance variations due to the absorption or desorption of water vapors. The consequences of annealing, measuring frequency and absorption-desorption behavior of the sensor have been discussed in detail. For all sensors impedance-humidity relationship shows more uniform change as compared to capacitance- humidity relationship in the given range humidity. The temperature sensors have been fabricated by using multiwalled carbon nanotubes (MWCNTs), V2O4-PEPC composite and CuPc on n-GaAs. The CNTs based sensors are fabricated by the deposition CNT nanopowder on a paper substrate and on adhesive elastic polymer tape. The nominal thickness of the CNT films on paper substrates is 30–40 μm while that of elastic substrate is ~ 300-430 μm. The DC resistance of the sensors decreases with increase in temperature. For both types‘ sensors, the resistance-temperature relationship shows wide range sensitivity. The V2O4-PEPC composite based temperature sensors are fabricated by drop-casting the blend of composite into the gap between preliminary deposited silver electrodes on glass substrates. The thickness of the V2O4-PEPC films is in the range of 20-40 μm. It is found that with increase in temperature the AC resistance of the samples decreases by 10-12 times. The response recovery time is also measure. The Ag/p-CuPc/n-GaAs/Ag cells are fabricated by the deposition of p-type copper phthalocyanine on n-type GaAs single-crystal semiconductor substrate. The temperature sensing and photoconductive behavior of the cells are investigated. The results reveal that with increase in temperature from 33-75 °C the resistance temperature coefficients (RTC) for the reverse and forward bias resistances are equal to -2.0 %/°C and -1.5 %/°C, respectively. Electromechanical sensors based on PANI, CNTs and CNTs-Cu2O composites have been fabricated and investigated. The 20-80 μm thick PANI films are deposited by drop-casting on Ag electrodes, which are preliminary deposited on glass substrates. The effect of displacement on the resistance and capacitance of film is investigated. It is observed that with increases in displacement the resistance decreases and the capacitance increases. For the fabrication of CNT–Cu2O composite based pressure sensors tablets of composite are made at a pressure of 353 MPa. The average diameter and the average thickness of the tablets are 10 mm and 4 mm, respectively, and both sides of the tablet are covered by silver paste. By varying pressure from 0-37 kN/m2, the change in DC resistance of the sensor is measured. The CNTs and CNTs–Cu2O composite based strain sensors have been fabricated by pressed tablets and elastic polymer beam. The 1 mm thick tablets of CNTs and CNTs–Cu2O composite are fabricated at a pressure of 200-300 MPa and 353MPa, respectively. The samples are installed on the polymer elastic beam by glue. The electric contacts to the samples are made by silver paste. The inter-electrodes distance (length) and diameter of the surface-type samples are in the range of 6–8 mm and 10 mm, respectively. It is found that DC resistance of the strain sensors increases under tension and decreases under compression, while the average strain sensitivities are in the range of 50-80 and 44–46 for CNTs and CNTs–Cu2O composite based sensors, respectively.
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سفر ہے شرط۔۔۔

سفر ہے شرط۔۔۔۔

                                                                                                ڈاکٹرعارف حسین عارفؔ

دنیا کی سیر کرنا ، آنکھوں سے دیکھنا اور لفظوں میں دکھانا سب مختلف ہنر ہیں۔ جو شخص دنیا کی سیر کا حوصلہ رکھتا ہے وہ اپنی آنکھیں اور دل کھلا رکھے اور قلم رواں رکھے تو اس کا سفر نہ صرف اپنا سفر رہ جاتا ہے بلکہ وہ اپنے ساتھ ساتھ دوسروں کو بھی ،جو کبھی قیدِ مقام سے نہیں گزرے، اپنے ساتھ ساتھ لیے پھرتا ہے۔ سفر نامہ نگار کی یہی خوبی ہوتی ہے کہ وہ ایک افسانوی فضا قائم کر تے ہوئے داستانوی ماحول بناتے ہوئے ، قاری کو اس طرح اپنی گرفت میں لیتا ہے کہ اُس کے ذہن کی سکرین پر وہ تمام مناظر اپنا عکس لیے ساتھ ساتھ چلتے جاتے ہیں۔

ڈاکٹر الطاف یوسف زئی کا سفر نامہ’’ نیل کے سنگ‘‘ اس لحاظ سے ایک منفرد سفر نامہ ہے کہ جس میں داستانوی عنصر بھی پایا جاتا ہے اور افسانے کا اختصار بھی۔ انھوں نے چند صفحات میں ہی مصر کی ایسی سیر کرادی ہے کہ جو آدمی ایک مہینہ میں بھی شاید نہ کر سکتا ہو۔ تاریخ کی بھاری بھرکم کتابوں کو ہاتھ لگانے سے ڈر لگتا ہے اور پھر ان کا اسلوب بھی اتنا دل خراش ہوتا ہے کہ ایک آدھ صفحے کے بعد کتاب کو طاق پہ سجا دینا ہی مناسب لگتا ہے مگر الطاف صاحب نے سفرنامے کو اس طرح خوبصورت اسلوب اور دل کش پیرائے سے مزین کیا ہے کہ قاری ساتھ ساتھ سفر کرتا چلا جاتا ہے۔ سب سے بڑھ کر ان کے اسلوب میں جو بر محل اشعار اور احادیث اور اسلامی روایات کا استعمال ہے وہ ان کی علمیت کی خبر بھی دیتا ہے اور ساتھ ہی قاری کو ایک اسلامی اور ادبی روایت سے بھی...

Educational Stratification and Nation Building Process in Pakistan

Abstract Pakistan has celebrated seven decades of independence but misfortunately the nation is still divided into several ideologies, believes, ethnicities, regionalism, provincialism, political and social classes. Throughout the world, education plays a significant role in nation building but the terrible upshot in Pakistan is the division of nation in the field of education and learning. There are numerous umbrellas under which our educational system is running. Therefore, current study objects to measure educational stratification and its effect on nation building process in Pakistan. In this regard, this research mainly focuses on four major prevailing educational systems such as; privately managed schools, public schools, army public schools and madarsa (religious educational institution). Data were collected through focus group discussions and analyzed by applying grounded approach theory. Four major themes emerged after data examination. These are uniformity of curricular, equal opportunities, political and bureaucratic involvement and lack of moral education. Study finds that education system is badly lacking in uniform ideology and moral learning. Furthermore, the poor system of education is negatively affecting nation building in Pakistan by enhancing public distrust, discrimination and regionalism. The results of the present study may be helpful in finding the way for uniform educational system which provide learning opportunities to every child without thinking of their caste, religion, language, economic class, political affiliation and ethnicity.

Impact of Negative Experiences on Academic Achievement of University Students: Cognitive Distortions As Mediating Factor

Negative experiences are part of life and being the part of life, negative experiences, can have potential effects on individuals‘ cognitive abilities which may further affect their academics. To explore this issue, prime efforts in this research were made to determine the impact of university students‘ negative experiences on their academic achievement as well as on the development of cognitive distortions among them. Furthermore, role of cognitive distortions as mediator between negative experiences and academic achievement was to be calculated also. Study objectives were followed by developing Questionnaire of Negative Experiences, and Scale of Cognitive Distortions along with self-reported GPA (Grade Point Average). Validity and reliability of developed tools was established by means of expert judgment and statistical procedures consequently. Research tools were administered to university students of Pakistan. Total 2213 students of final year were selected from 7 universities through cluster sampling technique. To reach the conclusion, frequency, percentage, and mean score were calculated for descriptive analysis. Moreover, Structure Equation Modeling (SEM) was adopted to calculate mediating role of cognitive distortions between negative experiences and academic achievement. Results revealed that departmental and friends‘ problems caused decline in academic achievement of university students. In contrast, financial issues, emotional experiences, and family problems became triggers of academic performance. Upon facing a number of stressful events, several cognitive distortions (i.e. ―Emotional Reasoning‖, ―Dichotomous Thinking‖, ―Fortune Telling‖, ―Labeling‖, ―Discounting Positive‖, ―Mental Filtering‖, ―Self-Blaming‖, and ―Mind Reading‖) were developed among university students. ―Fortune Telling‖, ―Discounting Positive‖, and ―Self Blaming‖ were clear source of decline in academic achievement. Whereas students‘ GPA was seem to be increased due to ―Emotional Reasoning‖, All-or-Nothing, ―Labeling‖, Mental Filter, ―Maximization‖, and ―Mind Reading‖. Only five of the focused cognitive distortions were found to mediate the impact of negative experiences on academic achievement of university students: ―All-or-Nothing‖, ―Discounting Positive‖, ―Fortune Telling‖, ‗Mental Filter‘, and ―Self-Blame‖. Structure Equation Model regarding mediation role of cognitive distortions between negative experiences and academic achievement was finalized by determining model fit indices calculated in SPSS Amos. Developed model is a significant contribution to existing knowledge, which would hopefully serve as assisting theoretical background for educationists, psychologists, teachers and students. It can lead them to identify particular cognitive biases in order to suggest measures for eradication of negative effects from university students.