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Home > Fabrication and Characterization of Ytterbium and Transition Metal Cations Doped Bifeo3 Multiferroics

Fabrication and Characterization of Ytterbium and Transition Metal Cations Doped Bifeo3 Multiferroics

Thesis Info

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Author

Sajjad Ahmad

Program

PhD

Institute

The Islamia University of Bahawalpur

City

Bahawalpur

Province

Punjab

Country

Pakistan

Thesis Completing Year

2017

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/11168/1/Sajjad%20Ahmad_Chem_2017_IUB_PRR.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726185868

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This dissertation presents the effect of ytterbium (Yb), nickel (Ni) and cobalt (Co) doping on the structural, spectral, magnetic, electrical, dielectric and photocatalytic properties of BiFeO3 (BFO). The micro-emulsion synthesis route along with cetyl trimethyl ammonium bromide (CTAB) was used to synthesize BiFeO3 multiferroic. The doping was made to enhance various properties of BiFeO3. A pure phase sample of BFO was achieved with reaction conditions; a molar concentration ratio 1:1 between precursors and CTAB. The optimized annealing temperature was found at 900 ºC for 7 h. The crystallite size was found to be ~ 18 nm. The synthesized BFo has optical band gap ~ 2.6 eV and resistivity 1.005 x 109 Ωcm-1. In first series (BYCFO) (Bi1-xYbxCoyFe1-yO3) nanocrystalline ytterbium and cobalt were co-doped in BiFeO3. The doping concentrations were arranged in sequential increasing order as follows x = 0.00, 0.025, 0.05, 0.075, 0.1, 0.125 and y = 0.00, 0.05, 0.1, 0.15, 0.2, 0.25. Each series comprises on six samples. The X-ray diffraction (XRD) analysis indicated normal growth habitat Rhombohedral (R3c) phase. The inclusion of ytterbium and cobalt ions in BiFeO3 was observed by XRD. The incorporation of higher concentration of Yb3+ and Co3+ ions (x= 0.125, y= 0.25) revealed few extra peaks. The magnetic properties were measured by vibrating sample magnetometer (VSM). The inclusion of Yb and Co enhanced saturation magnetization (Ms) = 0.385 emu/g, remnant magnetization (Mr) = 0.13 emu/g and corecivity = 405 KOe which is higher as compared to the pure BiFeO3. The grain size was found in the range of 20- 24 nm. The dopants appreciably impeded the dielectric loss and dielectric parameters in the low frequency region and resonance peaks were appeared in the spectra at higher frequency (1.98 GHz) region. The optical band gap was found to be 1.5 eV which was lower than pure (2.15eV). The optimized photocatalytic performance of (Bi0.875Yb0.125Co0.25Fe0.75O3) was found 42 %. In second series (Bi1-xYbxNiyFe1-yO3), Yb and Ni were co-doped in BiFeO3. The XRD analysis indicated that the diffraction peak (006) at 2θ = 38.85° exhibited the normal Rhombohedral (R3c) structure. It was observed that diffraction peaks (204) and (110) at the diffraction angle (2θ) = 31.56 ° and 32.74 ° for concentrations of dopants x =0.10, y = 0.20. The spectra for further doping of dopants x=0.125 and y = 0.25 showed the disappearance of diffraction peak (006) and appearance of diffraction peak (111) at 2θ =27° which showed a phase transformation from Rhombohedral to orthorhombic phase. The measured grain size was 24 nm and UV/visible scan showed λmax = 400 nm with optical band gap of 1.25. The maximum resistivity was found ~ 1.4 x109 Ω- cm. The dielectric constant and dielectric loss disclosed a solid distribution at low frequencies and the leakage current density was suppressed with an increase in dopants cations. The photocatalytic performance of this series was higher as compared to the previous series (66 %) for 0.5 ppm of Congo red and time interval 51minutes. The band gap was enhanced to (1.25 eV). The ceramic was separated through a magnet bar and recycled after water washing. The comparison between two series was distinct. The particle size of BYCFO ranges from 20 to 24.37 nm but BYNFO series showed a particle size in a short range between 21 to 23.78 nm. The BYNFO series have maximum resistivity ranges 1.2x 109 Ω-cm. The BYCFO series resistivity 2.56 x 1010 Ωcm-1is 10 times higher than nickel doped series. The optical band gap showed a significant decrease for BYNFO series (1.25 eV) as compared to BYCFO (1.5 eV). The BYNFO nanocrystalline series showed a photo degradation efficiency of 66 % which was higher than the BYCFO nanocrystalline series. BYCFO showed maximum magnetization of 0.354 emu/g, corecivity 405 KOe, remanant magnetization ~ 0.115 emu/g for dopants concentration (x =0.125, y = 0.25).
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یہ عشق میں نہ سوچ تو کہ کیا نہیں ملا

یہ عشق میں نہ سوچ، تُجھے کیا نہیں ملا
ہے کر لیا، تو خاک میں اپنی جبیں ملا

ہم راہ دیکھتے ہی رہے جس کی عمر بھر
آیا وہ شہر میں بھی تو ہم سے نہیں ملا

بچپن میں دل کی بستی میں رہتے تھے کتنے لوگ
دیکھا شباب میں تو فقط اک مکیں ملا

اگلے جہاں کے عہد پہ ہم کو دیا ہے ٹال
کم بخت ہم کو وہ تو بلا کا ذہیں ملا

کہتے رہے تھے یار جسے ہم تمام عمر
اک دن عدو کی بزم میں وہ نازنیں ملا

گر یاں دیا نہ تُو نے تو نہ لوں گا حشر میں
یارب اسے اگر ہے ملانا، یہیں ملا

تطوّر العقيدة الإلحادية فى المجتمعات الإسلامية والغير الإسلامية وإنعكاساتها فى الجوانب المختلفة للحياة الإنسانية (دراسة تحليلية من المنظور الإسلامي)

The science of Islamic belief had been considered most valuable discipline among other disciplines of knowledge as it played an important, rather pivotal role in the practical life. Qualitative research technique was used for the collection, analysis, and demonstration of data. The research had addressed the four major dimensions of the topic which particularly include Meanings of Atheism and its essential elements, Development of Atheism in Islamic and Un-Islamic societies and response of Muslim scholars, Reflections of Atheism in various aspects of human life, and Analysis of Atheism in Islamic Perspective. The systematic review of literature disclosed that Atheism in Islamic perspective included the denial of God, Prophet Hood and hereafter or any of these elements. Atheism had equally affected the Muslim and Non-Muslim societies by blowing the materialism into social, economic and political system. In this connection, Muslim scholars were divided into four types in terms of their response to Atheism which was discussed in detail in paper. Moreover, Atheism had also affected the individual as well as collective life. The author had critically analyzed the Atheism in Islamic perspective and presented the conclusion and recommendations at the end.

Molecular Studies for Regulation and over Expression of Tylosin from Streptomyces Fradiae Nrrl-2702

Tylosin is a macrolide antibiotic used as veterinary drug and growth promoter. Attempts were made for over expression of tylosin through random mutagenesis of Streptomyces fradiae NRRL-2702 using ultraviolet (UV) and gamma (γ) irradiations. After 100 and 120 seconds exposure of UV (λ=300 nm), spore suspension of wild type strain exhibited 5% and 8% survival rate, respectively and these exposure times were found suitable to isolate the most potent mutant colonies. 300 colonies appeared on the agar plates at above mentioned exposure times including six morphologically altered colony types. Initially, all these colonies were screened for tylosin production using Bacillus subtilis bioassay and it was found that only morphologically altered colonies (UV-1, UV-2, UV-3, UV-4, UV-5 and UV-6) indicated tylosin production. Furthermore, HPLC analysis revealed an increase of 2.7 fold in tylosin yield (1500 mg/l) by one of the morphological mutants i.e., UV-2 in complex medium which was improved to 1750 mg/l as compared to the wild type strain (620 mg/l) by optimizing fermentation conditions in chemically defined media. The values of different kinetic parameters such as dry cell mass (21 g/l), maximum specific growth rate, μmax (0.052 h-1) and specific tylosin productivity qp (1.36 mg/g/h) were also higher in mutant UV-2 as compared to wild type strain. To further improve the stability and productivity of mutant UV-2, it was subjected to another round of mutagenesis by gamma irradiation using 60 Co source. As a result of this treatment, another morphologically altered mutant (γ-1) with an enhanced expression of tylosin up to 2500 mg/l in complex medium was obtained. Use of chemically defined media promoted tylosin production up to 3800 mg/l by this mutant γ-1 in the presence of glucose+lactose (45 g/l) and sodium glutamate (12.5 g/l) as carbon and nitrogen sources, respectively. In addition, much higher value of qp (3.34 mg/gh) was observed in case of mutant γ-1 as compared to wild strain (0.81 mg/gh). Moreover, UV irradiation associated changes were observed to be unstable with loss of tylosin expression whereas, mutant γ-1 displayed high stability on subsequent culturing even after 3 years of storage at -72°C. Furthermore, solid state fermentation system (SSF) was also developed for tylosin production with mutant γ-1 and wild type strains by using various economically cheaper and easily available agro-industrial wastes. Wheat bran as solid substrate gave highest production (2500 μg of tylosin/g substrate) by mutant γ-1 against wild type strain (300 μg tylosin/g substrate). The tylosin yield was further improved to 4500 μg/g substrate at optimized conditions of 70% moisture level, 10% inoculum (v/w), pH 9.2, temperature 30°C, supplemented with lactose and sodium glutamate on 9th day. Wild type strain displayed reduced production of tylosin (655 μg tylosin/g substrate) in SSF even after optimization of process parameters. This study has shown that solid state fermentation system significantly enhanced the tylosin yield by mutant γ-1. In this way, an overall increase of 6.87 fold in tylosin yield was achieved through a combination of UV and gamma irradiation mutagenesis and fermentation screening by mutant γ-1. Additionally, to acquire some more knowledge about enhanced expression of tylosin in mutant γ-1, molecular studies were attempted to explore any change in the regulatory genes (tylQ, tylP, tylS, tylR & tylT) of tyl cluster. Expression analysis by RT-PCR revealed that tylQ was switched off earlier in mutant γ-1 as compared to wild type strain, although there was no change in the sequence of tylQ gene from both the strains. On the other hand, the analysis of tylP indicated no change in expression pattern between wild type and mutant γ-1 strains but there was difference of a single base and a substitution mutation of T A was recorded at position 214 in 420bp product of tylP gene. Moreover, the deduced protein sequences of tylP gene from wild type and mutant γ-1 indicated that the point mutation resulted in the change of single amino acid i.e., serine to threonine (S T) at position 72. Furthermore, RT-PCR remained unsuccessful to detect the expression of three other regulatory genes i.e., tylS, tylR and tylT. So, routine PCR was used to amplify these genes, which revealed that there was no change in the nucleotide sequence of these genes either from mutant γ-1 or wild type strain. However, the sequences of these genes could be a valuable addition in databases because these were not available previously for this particular strain of Streptomyces fradiae NRRL-2702.