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الخصائص الالكترونية للمفرق الهجين A - Ge/C - Si

Author name: اكرم نوري صادق الشديدي

General topic: Physics

Specific topic: Physics

University: University of Baghdad

University location: Baghdad

ترميم وازالة تشققات الصورة باستخدام طرق متعددة

Author name: رعد فالح حسن

General topic: Physics

Author name: عمر عدنان جاسم

Supervisor name: كريم علي جاسم | سوسن عبد الحسين مهدي

General topic: Physics

Specific topic: Solid State and Materials Physics

Degree: Master

University: University of Baghdad - Ibn Al-Haytham College Of Education For Pure Sciences - Physics Department

Language: English

University location: Baghdad

First pages:

Abstract: This study was carried out to prepare a porcelain samples of raw material 50 wt % kaolin dukhla, 25 wt % erzma sand glass and 25 wt% feldspar, boro silicate glass (Pyrex) used as a flux in the porcelain (ceramic) body, instead of feldspar, yielding a new material which has new properties with grain size equal to 53μ.Pyrex which was added to the porcelain to get the mixtures of sample. The all mixtures prepared and 10 wt % of distilled water was added, the resulting blends were die pressed of 25 MPa, to produce specimens with diameter of 25 mm and thickness of 5 mm, then they were dried and sintered for different temperatures (1200, 1250, and 1300) C° for 1 hour in an electric furnace. Physical properties measurements such as density, porosity, water absorption and length shrinkage percentage, were carried out, also mechanical properties (compression strength) and thermal properties. (Thermal conductivity and heat capacity) were measured The result of the physical properties measurement are found to be improved at increasing the ratio of Pyrex mixture, such as increase in density and shrinkage which a company with the decrease of porosity and water absorption, also the same changes were happened for these properties with increasing sintering temperature for all mixtures, and the highest increment in shrinkage have been shown at 1250 C°.The thermal conductivity and heat capacity have increased the ratio of Pyrex mixture, and there are small increment in these measurements, at increasing temperature for mixtures 3 and 4, but the increment is high for mixture no. (2).The results of mechanical properties measurements (diametrical strength) are found to be improved and increased at the increase of the ratio of Pyrex mixture and the mixture no. (3) have a highest strength. Also this improvement and increment in strength was continued for mixtures 2 and 3, with the increase of the sintering temperature whereas decreases for mixture (4) improvement in physical and mechanical properties for a new porcelain make suit usage in brick walls industry (porcelain tiles).

تاثير اضافة Al2O على الخصائص الكهربائية للفارستور من نوع ZnO == The Effect of (Al2O3) Additive on Electrical Properties of (ZnO) - Based Varistor

Author name: عباس فاضل شنون

Supervisor name: ايسر جمعة ابراهيم

General topic: Physics

Specific topic: Solid State and Materials Physics

Degree: Master

University: University of Baghdad - Ibn Al-Haytham College Of Education For Pure Sciences - Physics Department

Language: English

University location: Baghdad

First pages:

Abstract: ZnO based varistor samples having composition formela as shown below : - (X) is a variable take values (X = 0 , 0.1 , 0.5 , 1) % mol were prepared by a solid state reaction and sintered in air at a different sintering temperatures (1000,1100 and 1200)ᴼC for 2h by a heating rate of (5ᴼC. min - 1). The microstructure and electrical properties of sintered samples were investigated by using X - ray diffraction (XRD), energy dispersive spectroscopy (EDX), scanning electron microscopy (SEM), as well as electrical meas urements. XRD analyses showed that the crystallite size was decreased with the increase of Al2O3 concentration while it was increased with the increase of sintering temperature. Also from SEM images and by using linear intercept method we note that the grain size decreases with the increase of Al2O3 concentration while it increases with the increase of sintering temperature. Since the breakdown voltage is influenced by the size and the number of grains , so it was increased with the increase of Al2O3 concentration at certain sintering temperature to reach (2220V) at sample contains (1% of Al2O3) and sintered at 1000ᴼC for 2h, this is due to form a spinal phase (ZnAl2O4) which inhibits the grain growth.Also the breakdown voltage was decreased with the increase of sintering temperature at certain Al2O3 concentration to reach (255V) at sample sintered at 1200ᴼC for 2h and contains (0.1% l of Al2O3).By plotting the (J - E) curves of varistor samples we can notes that the adding of (0.1 and 0.5) % of Al2O3 dopants enhances the nonlinear behavior of ZnO varistor by increasing the nonlinear coefficient to reach its maximum values (46, 48) respectively which are sintered at 1000ᴼC for 2h, while the increase of Al2O3 concentration to(1% ) decreases the nonlinear coefficient to (29.2) which are sintered at 1000ᴼC for 2h .Compound ZnO Bi2O3 Sb2O3 CoO MnO2 Cr2O3 Al2O3 % mol 96.5 - X 0.7 1 0.8 0.5 0.5 X The increase of sintering temperature decreases the nonlinear coefficient to reach its minimum values (6.9, 8) at samples sintered at 1200ᴼC for 2h and contain a different amounts of Al2O3 concentration, this is due to the bad volatilization of bismuth that insured by (EDX) test.The leakage current was increased with the increase of both Al2O3 concentration and sintering temperature to reach its maximum value (0.33mA) at a sample which contains (1% ) of Al2O3 concentration and sintered at 1200ᴼC for 2h, that is because the Aluminum increases the free electrons (donor density ) at the conduction band.Deilectric constant decreases with the increase of the frequancy of the applied voltage for the samples which containe 0.1% of Al2O3 and sintered at (1000 and 1200)ᴼC for 2h and for the sample contain 1% of Al2O3 and sintered at 1000ᴼC, the deilectric constant decreases with the increase of sintering temperature while tangent factor increases with the increase of Al2O3 concentration, this is due to the increase of leakage current.

Author name: نصر عيسى نجم

Supervisor name: بشرى كاظم حسون الميالي

General topic: Physics

Specific topic: Thin Films

Degree: Master

University: University of Baghdad - Ibn Al-Haytham College Of Education For Pure Sciences - Physics Department

Language: Arabic

University location: Baghdad

First pages:

Abstract: حضرت اغشـيــة ( Bi2O3 ) على قواعد زجاجية بسمــك مختلـف( 450 , 350 , 250 ) nm وبـدقـة تصـل الـى ( ∓ 20 ) nm والمشـوب بمادة الالمنيـوم ( Al ) وبنسـب تشـويب مختلفة ( 3 , 2 , 1 ) % عنـد السمك ( 20 ∓ 450 ) nm والمحضرة بطريقـة التبخـر الحـراري في الفراغ وقد كان معدل ترسيب ( 1.20 nm / sec ) ,اضافة الى ذلك تم اكسدة اغشية البزموث ( Bi ) بدرجة حرارة ( 523 ) K وبزمن لا يزيد عن ساعة واحدة بوجود الهواء , وتـم دراسـة تاثيـر التلديـن علـى الخـواص التركيبيـة والبصـرية للاغشيـة النقيـة والمشـوبـة بـدرجات حــرارة ( 773 , 673 , 573 , R.T ) K ولمدة ساعة واحدة . استخـدمـت تقنية حيـود الاشعة لدراسـة الخصائص التركيبية للاغشية المحضرة واظهرت نتائج قياس حيود الاشعة السينية ( X - ray ) ان جميـع الاغشيـة المحضـرة النقيـة والمشوبـة تكون ذات تركيب متعـدد التبلـور ومـن النـوع الرباعـي والاتجاه السائد (201) لكل الاغشية المحضرة وزيادة معدل الحجم الحبيبي بزيادة سمك الغشاء , وهذا ما اشارت اليه قياسات مجهر القوة الذرية (AFM) كذلك يزداد معـدل الحجـم الحبيبي بزيادة نسب التشويب ما عدا النسبة ( 3 ) % . اظهرت الخصائص البصـرية ان النفاذية تتغير مع تغيـر كـل من سمك الغشاء ودرجة حرارة التلدين ونسب التشويب بالالمنيوم , وكذلـك تـم ايجاد فجـوة الطاقـة البصـرية للاغشيـة كافة فتبيـن انها مـن النـوع المباشـر المسموح لجميع الاغشية المحضرة وتزداد مع زيادة سمـك الغشاء, بينما تقـل مـع زيادة كـل من درجة حرارة التلدين ونسب التشويب عدا النسبة ( 3 % ) . اضافـة الى ذلـك تم حساب قيـم الثـوابـت البصريـة مثـل (معامل الامتصاص ومعامل الانكسار ومعامـل الخمـود وثابـت العـزل المعقد (الحقيقي والخيالي ) والتوصيلية الضـوئية ) كدالة الاطوال الموجية ( 1100 - 300 ) nm للاغشـية المحضرة . | This research includes studying the structural and optical properties of pure Bismuth Oxide ( Bi2O3 ) thin film at different thicknesses ( 250 , 350 and 450 ± 20 ) nm and doped by Aluminum ( Al ) of ( 450 ± 20 ) nm thickness with different doping ratios ( 1 , 2 , 3 ) % which is prepared by thermal evaporation method from depositing Bismuth film on glass substrates at R.T ( 300 ) K with deposition rate ( 1.20 nm / sec ) then oxidation Bismuth films at ( 523 ) K for one hour in air , Also it includes studing the effect of annealing temperature at ( R.T , 573 , 673 and 773 ) K for one hour on structural and optical properties for pure and doped films . The results of x - ray diffraction have been showed that pure and doped prepared films have polycrystalline structure with tetragonal phase with preferred orientation ( 201 ) for all prepared films the grain size increases with the increase of film thickness and this is in agreement with ( AFM ) measurements also it increases after doping except at ratio ( 3 % ) . This research also includes studing the optical properties of prepared pure and doped films . The transmission and absorption values changed with the changing of film thickness , annealing temperature and doping ratio with ( Al ) , the optical energy gap for allowed direct transition was evaluated and it increases with the increase of film thickness while it decreases with annealing temperature and doping percentage by ( Al ) except ratio ( 3 % ) . The optical properties results include calculating the optical constant (absorption coefficient , refractive index ,extinction coefficient, dielectric Constant with two parts real and imaginary and optical conductivity ) in the range of wave length ( 300 - 1100 ) nm for pure and doped films before and after annealing