دراسة لجودة الصورة للعين البشرية == A Study of the Image Quality for Human Eye
ميكانيكية الانتقال الالكترونية لثنائي شوتكي Al/c - Si/M == Electronic Transport mechanism of Al/c - Si/M Schottky Diodes
طريقة مطورة لتحديد السرعة النصف قطرية للطائرة باستخدام ازاحة دوبلر == An improved method for the determination of airplane radial velocity using Doppler shift
حسابات الامثلية لمنظومة مغاطيسية تتالف من حارف وعدسة == A Computational Optimization of Magnetic System Consists of Deflector and Lens
تطبيقات الانموذج العنقودي المزدوج في الانوية الخفيفة == APPLICATIONS OF COUPLED CLUSTER MODEL IN LIGHT NUCLEI
برنامج حسابي لحساب بعض خواص التراكيب البلورية == A Computational Program to Determine Some of Crystal Structure Specifications
ترميم الصور باستخدام تقنيات محورة غير خطية == Image Restoration Using Adaptive Nonlinear Techniques
استخدام تحويل الجيب تمام لتشفير حزمة التحويل المويجي التقريبية == Using Discrete Cosine Transform to Encode Approximation Wavelet Subband
محاكاة عامل التراكم لاشعة الكبح الناتجة من الامتصاص الكلي لاشعة بيتا == Simulation of Buildup Factor for Bremsstrahlung Produced by Complete Absorption of Beta Rays
تراكيز اليورانيوم في الدم البشري في بعض محافظات العراق باستخدام كاشف الاثر CR - 39 == DETERMINATION OF URANIUM CONCENTRATION IN HUMAN BLOOD SAMPLES IN SOME GOVERNORATES OF IRAQ BY USINGCR - 39 TRACE DETECTOR
تصميم حاسوبي لحزمة ايونية مركزة للمنظومة الليثوغرافية == Computer - Aided - Design Of Focused Ion Beam For a Lithography System
كشف اشعة كاما للنويدات المشعة في انسجة بشرية == GAMMA - RAYS DETECTION OF RADIONUCLIDES IN HUMAN TISSUES
تاثير اعادة الاعتيان والتكميم على ضغط البيانات الصوتية الرقمية == Effect of Resampling and Requantization on the Compression of Digital Audio Data
ترميم الصور الرقمية باستخدام خوارزمية المرشح التكراري == Restoration of Digital Images Using an Iterative Tikhonov - Miller Filter
دراسة الخصائص الطيفية لسلاسل نظائر نوى الهافنيوم والتنكستن باستخدام IBM وIBFM == Study of Spectroscopic Properties in Isotopic Chain of Hf and W Nuclei Using IBM and IBFM
تخمين الجرعة الاشعاعية للاشعة المؤينة وفوق البنفسجية باستخدام كواشف الاثر النووي == Radiation Dose Assessment for Ionizing and Ultraviolet Radiations Using CR - 39 , Lexan and LR - 115 Nuclear Track Detectors
تطور التركيب في نوى الباريوم الزوجية - الزوجية باستخدام نموذج البوزونات المتفاعلة == Structure Evolution in the even - even Ba nuclei with IBM
تحضير المركباث الجديدة Sn - 1223 وCu - 1223 الفائقت التوصيل العالي من Hg - 1223 == Preparation of Novel High Temperature Superconductor Compounds (Cu - 1223 and Sn - 1223) From Hg - 1223
تصميم وتصنيع غشاء رقيق من اكاسيد الزنك المضاد للانعكاس باستخدام تقنيات مختلفة == Design and Fabrication of Antireflection ZnO Thin Film by Using Different Techniques
بناء وتوصيف BNT - BKT - BT البيزوالكترك لخزن الطاقة == Construction and Characterization of BNT - BKT - BT Piezoelectrics for Energy Harvesting
Author name:
نذير بشير محمود
Supervisor name:
عماد خضير الشكرجي
Abstract:
Lead - free piezoelectrics are non - toxic, cheap and environmental friendlymaterials. Among them Bismuth Sodium Titanate (BNT) which has thechemical formula Bi0.5Na0.5TiO3 with a complex A - site perovskite structure. Inthis study, some modifications on BNT were used to help in applications byforming solid solution with Bi0.5K0.5TiO3 (BKT) and BaTiO3 (BT). The BNTbased(xBNT - yBKT - zBT) with x+y+z=1 ; were prepared via different methodsat the Morphotropic Phase Boundary (MPB) : 0.94BNT - 0.06BT , 0.93BNT - 0.07BT , 0.8BNT - 0.2BKT, 0.84BNT - 0.16BKT and 0.9BNT - 0.065BKT - 0.035BKT with their origin BNT , BKT and BT. Mini Database was proposeddepending on the results of international databases and some crystallographysoftware and plotted as phase diagrams. Several predictions were suggesteddepending on the built Mini Database and phase diagrams for the BNT - BKTBTsystem. The main prediction was : the physical properties either dependedon the changing of crystal structure ( polarization , dielectric constant ,piezoelectric coefficient ) or the properties had linearity with the composition (density, melting point , sintering temperature ). It has been focused on thestudying the crystal structure, dielectric measurements, hysteresis loopmeasurements and polarization fatigue analyses for ceramic samples.The samples were prepared by different methods : the hydrothermalmethod with spherical shape particles of 65nm - 600nm size; and by solid statereaction method. The powder were pressed in suitable template at 250MPa ,sintered according to database prediction "sintering temperature phase diagram", the resulted ceramic discs had relative density 90% - 96 %. These results agreed with the database predictions "sintering and density phase diagrams”.The crystal structure for the prepared samples were studied using X - ray diffraction (XRD) analysis, the XRD showed that the samples BNT - 6BT, BNT - 7BT, BNT - 20BKT, BNT - 16BKT and BNT - BKT - 35BT had the Morphtropic Phase Boundary (MPB) while BNT had the rhombohedral structure. BKT and BT had a tetragonal structure. These results agreed with the predictions "crystal structure phase diagram" The dielectric measurements showed that there were three regions for BNT - BKT - BT system; the first one was the samples with relaxor ferroelectric behaviors, the samples belonging to this region were BNT, BNT - 6BT, BNT - 7BT, BNT - 20BKT, BNT - 16BKT and BNT - BKT - 35BT (i.e. BNT and the MPB region). The second region was the samples with Normal ferroelectric behavior.The sample with this region was BT. The third region was the samples with relaxor - like ferroelectric behavior (weak ferroelectric) as in BKT. The Curie temperature for the samples within MPB was between 270℃ to 300℃, while for the origin : for BNT the Curie temperature was about 320℃; for BKT was about 370℃; and for BT was about 110℃. The depolarization temperature for samples within MPB region was below 100℃ (above room temperature) while for BNT was 250℃.The hysteresis loop measurements were studied both experimentally and theoretically. The study showed that the results for BNT were Ps=35μC/cm2, Ec=60kV/cm, for BKT was Ps=30μC/cm2, Ec=4.7kV/cm and for BT was Ps=26μC/cm2, Ec=9.8kV/cm, while for the samples within the MPB region the results were Ps=45μC/cm2, Ec ≈ 30kV/cm. The polarization had the largest value within MPB, which agreed with the first prediction by the proposed database (i.e. the polarization of BNT - BKT - BT system depends on crystal structure). The coercive electric (Ec) had a linear behavior with the composition. The value of Ec within MPB was in the range of 27kV/cm to 33kV/cm, which was half of the value for pure BNT. This result agreed with the second prediction by thedesigned database. The polarization fatigue analyses were performed depending on the fatigue model. The results showed that the polarization life cycle had the values of 1012 cycles for BNT, 1011 cycles for BT and 104 cycles for BKT, while within MPB region the polarization life had the largest value of about 1016 cycles which was much greater than in origin (BNT, BKT and BT). This result also agreed with the first prediction by the designed database (polarization life cycle had the largest value and depends on the crystal structure). The fatigue analyses predicted the value of applied electric field used in hysteresis loop measurements and the effect of cycle on the applied electric field.Finally, some of the problems were skipped and properties of BNT were enhanced by looking for the MPB region in the solid solution. The MPB showed the value for polarization to be larger than that in pure BNT, and it reduced the coercive electric field comparing to the original BNT. The polarization life cycle at MPB was much greater than in BNT. Therefore, this study could find some solutions for the drawbacks of BNT, and solve some problems for other piezoelectrics.
دراسة عامل تراكم الجرعة لاشعة كاما في الماء والكرافايت ضمن مدى الطاقة (10 - 4) م. ا. ف == A Study of Gamma Ray Dose Buildup Factors in Water and Graphite, in the Energy Range (4 - 10) MeV
تطوير واستخدام منظومه كشف المواد المتفجرة عن بعد == Development and Optimization of Stand off Explosive Material Detection System
السلوك التلبيدي والخواص العزلية للمتراكب MgAl204 - Al == Sintering behavior and thermal insulating properties of (MgAl204 - Al) spinel composite
Author name:
علي حسين صالح
Supervisor name:
قاصد عبد الستار صالح الجنابي
Abstract:
Spinel - Aluminum composites are drawing greater attention due to their low density, excellent physical, mechanical and refractory properties. This work aims to study the preparing one of the most current conventional technique and sintering behavior of Spinel - Al composite through characterization of the physical, mechanical properties as well as XRD and microstructure of the synthesis Spinel - Al composite specimens.Magnesia (MgO) and alumina (Al2O3) were used as starting materials to prepare stoichiometric magnesium aluminate spinel (MA) via single stage firing process (solid state reaction).Spinel (reinforced material) which prepared at sintering temperatures 12000C and 14000C for 2h soaking time was added in different weight percentage, i.e. 2,4,6,8 wt.% to the aluminum (matrix material) for synthesis Spinel - Al composites in a temperature range of 450 - 6500C via solid state reaction (SSR). The sintering parameters, XRD, microstructure, mechanical and thermal properties of the Spinel - Al composite products were investigated as well as the influence of each of the synthesized spinel contents and sintering temperature on sintering behavior of the composite products were also discussed. The results show that the better sintered density, water absorption, compressive strength, and thermal conductivity of the composite products obtained at low amount addition of spinel fired at 1200 and 14000C was 2wt.% and at 6500C.Also, studying of X - ray diffraction (XRD) for prepared spinel - aluminum composite specimens showed that the composites has many crystalline orientations (38.70, 44.970, 65.30 and 60.190), (390, 45.20, 65.620 and 60.330), (38.90, 45.150, 65.470, and 60.40) and (38.850, 45.260, 65.60 and 60.40) corresponding to (111), (200), (220) and (333) for 2,4,6,8wt% of spinel respectively.The studying of the morphology of spinel - aluminum composite specimens reveal that average grain size of reaches about 6.03, 6.17, 6.22, 6.3 (μm) for 2, 4, 6, 8 wt.% of MgAl2O4 fired at 12000C respectively, whereas their average grain size reaches about 7.18, 7.57, 7.9, 8.48 (μm) for the same spinel content fired at 14000C respectively.
تحضير ودراسة جسيمات الفضة النانوية وتاثيرها المضاد للبكتيريا == Preparing and Studying Nano Silver Particles and Their Anti Bacterial Effect
