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Home > Fabrication and Characterization of Terbium Substituted Ferrites

Fabrication and Characterization of Terbium Substituted Ferrites

Thesis Info

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Author

Khan, Muhammad Azhar

Program

PhD

Institute

Bahauddin Zakariya University

City

Multan

Province

KPK

Country

Pakistan

Thesis Completing Year

2011

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1879

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726185230

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This dissertation presents the effect of terbium substitution on the structural, magnetic, electrical and dielectric properties of ferrites of nominal compositions Ni1−xTbxFe2O4 and Mg1-xTbxFe2O4 (where x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18 and 0.20). The samples were initially sintered at 1000 °C and final sintering was performed at 1230 °C in order to prepare homogeneous ferrites. The said ferrites were characterized by X-ray Diffractometry, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Vibrating Sample Magnetometery and Ferromagnetic Resonance. Phase analysis from XRD patterns reveals that the samples have a cubic spinel structure along with a few traces of second phase recognized as orthorhombic phase (TbFeO3) and this phase becomes more conspicuous as the terbium (Tb) is substituted in Ni1−xTbxFe2O4 and Mg1- xTbxFe2O4 ferrites. The lattice parameter changes non-linearly as a function of Tb content in both series that was attributed to the differences in ionic radii of the cations involved and the solubility limit of terbium ions. A gradual increase in the bulk density was observed with the increase of terbium concentration in both series. FTIR absorption spectra of Ni1−xTbxFe2O4 and Mg1- xTbxFe2O4 ferrites exhibited two main absorption bands in the wave number range 370 cm-1 to 1500 cm-1, thereby confirming the spinel structure. The particle size measured from XRD analysis found to decrease with the increase of Tb substitution. The morphology of the samples indicates that samples are crack free along with a few agglomerates. The inclusion of Tb caused the magnetization index to drop which is due to redistribution of cations on the tetrahedral and octahedral sites. The coercivity is observed to decrease and this trend is deviated at higher concentrations of terbium ions in Ni1−xTbxFe2O4 and Mg1-xTbxFe2O4 ferrites. Ferromagnetic resonance linewidths are ≤ 1000 Oe for most of the samples. The nominal composition Ni.94Tb.06Fe2O4 have minimum linewidth, ΔH = 593 Oe, which is minimum of the reported linewidths for spinel ferrites. Hence these ferrites have potential in high frequency applications. The relative initial permeability generally decreases for all the Tb-substituted samples and these are attributed to the decrease in magnetization. The magnetic loss factor is damped with respect to frequency and has very low values in the high frequency region. The electrical resistivity increases and it is attributed to the hinderence in the hopping mechanism caused by the presence of Tb-ions in these ferrites which enhance hopping length between the cations involved in the conduction mechanism. The study on resistivity as a function of temperature shows that all the samples obey semiconducting behaviour. The drift mobility drops while the activation energy increases in a similar manner as that of resistivity. The samples NiFe2O4 and MgFe2O4 have high dielectric constant as compared to the substituted samples. Hence, introduction of Tb-ions in Ni1−xTbxFe2O4 and Mg1-xTbxFe2O4 decrease the dielectric constant. All the substituted samples indicate small values of dielectric loss. These features make these ferrites suitable for various applications.
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نظم

بے خبری کی آغوش ۔۔۔۔۔۔۔۔۔ ارشد معراج (اسسٹنٹ پروفیسر انٹر نیشنل یونیورسٹی اسلام آباد)

انہیں سردی نہیں لگتی

 

انہیں ذلت کی ساعت نے پرانے سیم نالوں کے کناروں پر گھسیٹا ہے

اور ان کے کالے ہونٹوں پر لگی ہے مہر صدیوں سے   

یہ کلر تھور دھرتی میں ہری خواہش کو بونے کی مشقت میں لگے ہیں

یہاں ”سابیریا“ سے آۓ پکھنو جب بھی کوندر میں مچلتے ہیں            

تو گارے سے بنیرے لیپ کرنے والیوں کے چولہے جلتے ہیں

کبھی چارے کی گھرلی میں پڑے شلجم ۔۔۔۔۔۔                        

ورگرنہ ساگ اور آدھی ادھوری روٹیاں

سوکھے بدن میں سوچ بھی لکنت زدہ ، سرگوشیاں ۔۔۔۔۔۔

” چاچا!

خدا دا شکر کر دے ہاں

جے اس ساڈے تے ایہہ ازمیش پاٸی ھیہ

جو او کردا ہمیشہ ٹھیک ای کردا

پر اے دسیں جو نمبردار مر سی

وت اے اوکھت گھٹ نہ ویسی “

کبھی خوابوں کی گھٹڑی کو اٹھانے سے سفر مشکل نہیں ہوتا

مگر سورج تو روزانہ ہی مشرق سے نکلتا ہے

اور آنکھوں کا حسیں عدسہ سکڑتا ہے

زوال آۓ تو مغرب میں وہ چھپتا ہے

ہمیشہ چندر اور مایا کٸی میلوں پہ بستے ہیں

انہیں بستی میں آنے کا کبھی رستہ نہیں ملتا

ہمیشہ پوہ رہتا ہے

پرالی کے سلگنے سے کہاں یہ ٹھنڈ جاتی ہے

 

 

Anatomy & Surgery: A love hate relationship

Introduction: Anatomy is still taught in medical schools as a basis for studying pathophysiology and surgery. Lack of integration of basic and clinical disciplines reduced teaching hours, and poor teaching methodologies have a significant effect on anatomical knowledge and medical education standards. Objectives: To evaluate the perspectives of undergraduate students of MBBS, fresh MBBS graduates, teaching faculty of anatomy, and consultants on the importance and reconstruction of the anatomy curriculum. Materials & Methods: A total of 600 subjects participated in this cross-sectional study. A feedback form was used to collect data regarding time allocation, clinical relevance, integration, and clear viewpoints in basic histology, embryology, and gross anatomy. The form included free text, binomial, and 5-point Likert scale replies. Results: Analysis of the results revealed that all stakeholders universally preferred integrated anatomy teaching throughout the academic years of medical school instead of demanding block during the early two years. According to the study, students experienced inadequacies in their anatomical knowledge when they started their clinical training. Conclusion: This study contributes further to the ongoing discussions in anatomical sciences education by revealing that new doctors believe that anatomical instruction should be prioritized regardless of their career goals.

Morphological and Molecular Characterization of Selected Macrofungi in Northern Areas of Khyber Pakhtunkhwa, Pakistan

Present study dealt with morphological and molecular characterization of macrofungi in northern parts of Khyber Pakhtunkhwa, Pakistan. This region represents floristically a rich part of Pakistan comprising well-known mountainous ranges of Himalaya and Hindu Kush, but a very few macrofungal surveys have been conducted so far. The present study was therefore endeavored to report some macrofungal species occurring in woodland and forest ecosystems of Northern parts of Khyber Pakhtunkhwa, Pakistan. Field surveys and collections of specimens were carried out at different sites of the study area during the years 2013‒2016. For collections, drying, preservation, micro-morphological and molecular characterization of the collected specimens, standard protocols were used. A total of 88 species belonging to 30 families and 57 genera are being reported and described in detail, of which 75 species belong to Basidiomycota and 11 to Ascomycota. Identity of 59 species was confirmed through molecular data inferred from nITS region. Out of the described species more than thirty percent showed their novelty. Albatrellus roseus, Amanita griseofusca, Clavariadelphus elongates, Descolea quercina, Gymnopilus swaticus and Phaeocollybia pakistanica have been published as new species and 25 other species are proposed as new to science including: Albatrellopsis flettiodes nom.prov., Amanita ahmadii nom.prov., A. cinerea nom.prov., Butyriboletus pakistanicus nom.prov., Caloboletus alpinus nom.prov., Cortinarius clavatus nom.prov., C. longistipes nom.prov., C. striatus nom.prov., Inocybe pallidorimosa nom.prov., I. salicetum nom.prov., Lactarius furcatilamellatus nom.prov., L. maireiodes nom.prov., Leucoagaricus campestris nom.prov., Lycoperdon microsporon nom.prov., Oudemansiella sparslamellata nom.prov., Phaeocollybia varicolor nom.prov., Pholiota microcarpa nom.prov., Pluteus iii populicola nom.prov., Pterula bisporitica nom.prov., Rhodocybe luteus nom.prov., Russula similis nom.prov., Tricholoma conicosulphureum nom.prov., Tricholomopsis robustus nom.prov., T. umbonatus nom.prov. and Veloporphyrellus purpureus nom.prov. Furthermore, 28 species are new records for Pakistani mycobiota viz., Agrocybe elatella, Amanita pallidorosea, Caloscypha fulgens, Coltricia abieticola, Coriolopsis gallica, Gymnopilus penetrans, Gymnopus dysodes, Hebeloma rostratum, Helvella leucopus, H. macropus, H. maculata, H. solitaria, Hericium cirrhatum, Inocybe putilla, Jahnoporus oreinus, Lactarius mediterraneensis, L. pterosporus, Lactifluus versiformis, L. volemus, Lanmaoa angustispora., Lepista panaeolus, Leucopaxillus giganteus, Russula kangchenjungae, R. olivacea, R. postiana, Verpa conica, Volvariella hypopithys and Volvopluteus earlei. Of these Amanita pallidorosea and lactifluus volemus have been published. Genera including Albatrellopsis, Albatrellus, Butyriboletus, Caloboletus, Caloscypha, Jahnoprus, Lanmaoa, Phaeocollybia, Pterula, Veloporphyrellus and Volvopluteus are addition to the fungi of Pakistan. The most abundant and diverse family was Russulaceae with 11 species distributed among 3 genera, followed by Agaricacea, Amanitaceae and Tricholomataceae with 7 species each. Boletaceae, Helvellaceae and Hymenogastraceae are represented by 6 species each. Results of the study reveals that northern parts of Khyber Pakhtunkhwa are rich in terms of macrofungi and there may be many other species awaiting documentation. This study therefore recommends further and in-depth surveys on exploration of macrofungi in woodland and forest ecosystems of the Northern parts of Khyber Pakhtunkhwa in particular iv and other parts of Pakistan in general. Published work form present PhD project is listed as annexure-A.