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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

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Showing 1 to 5 of 5 (0.048 seconds)

Spelling suggestions: "subject:"praseodymium"" "subject:"praseodimio""

1

Síntese e caracterização de precursores para catalisadores termicamente estáveis à base de lantanideos pelo método sol-gel

ROCHA, SORAYA M.R. da 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:50:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:43Z (GMT). No. of bitstreams: 1 10459.pdf: 5417083 bytes, checksum: ed654658e2629338a19dc7ae0a312583 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
RARE EARTH COMPOUNDS
ACETATES
SYNTHESIS
STRUCTURAL CHEMICAL ANALYSIS
PRECURSOR
PURIFICATION
CERIUM
SAMARIUM
NEODYMIUM
PRASEODIMIUM
CATALYSTS
ALUMINIUM OXIDES
sol-gel process
2

Estudo das correlacoes entre microestrutura propriedades magneticas e fator de quadratura em imas sinterizadas de PrFeB e NdFeB processados com hidrogenio / Relations microstructure - magnetic properties - squareness factor of PrFeB and NdFeB sintered magnets prepared with hydrogen

PERIGO, ELIO A. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:26:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:28Z (GMT). No. of bitstreams: 1 14042.pdf: 6705801 bytes, checksum: 3dbb089e18c9947629283f47af921286 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:05/04711-2
MAGNETIC PROPERTIES
PERMANENT MAGNETS
MAGNETS
MICROSTRUCTURE
MILLING
IRON ALLOYS
PRASEODIMIUM ALLOYS
BORON ALLOYS
CRYSTALLOGRAPHY
CRYSTALS
PHYSICAL PROPERTIES
SINTERING
GRAIN SIZE
3

Síntese e caracterização de precursores para catalisadores termicamente estáveis à base de lantanideos pelo método sol-gel

ROCHA, SORAYA M.R. da 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:50:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:43Z (GMT). No. of bitstreams: 1 10459.pdf: 5417083 bytes, checksum: ed654658e2629338a19dc7ae0a312583 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
rare earth compounds
acetates
synthesis
structural chemical analysis
precursor
purification
cerium
samarium
neodymium
praseodimium
catalysts
aluminium oxides
sol-gel process
4

Estudo das correlacoes entre microestrutura propriedades magneticas e fator de quadratura em imas sinterizadas de PrFeB e NdFeB processados com hidrogenio / Relations microstructure - magnetic properties - squareness factor of PrFeB and NdFeB sintered magnets prepared with hydrogen

PERIGO, ELIO A. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:26:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:28Z (GMT). No. of bitstreams: 1 14042.pdf: 6705801 bytes, checksum: 3dbb089e18c9947629283f47af921286 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho, avaliou-se inicialmente a preparação de ímãs sinterizados de Pr16Fe76B8 (% at.) por meio de moagem de alta energia em moinho tipo planetário, averiguando-se os efeitos do tempo de moagem bem como da velocidade rotacional do moinho. Encontraram-se as melhores propriedades magnéticas para um magneto preparado com a matéria-prima cominuída durante 75 minutos e velocidade rotacional de 200rpm [JR = (1,02 ± 0,02) T, 0JHc = (1,42 ± 0,03) T e (BH)max = (200 ± 4) kJm-3]. De forma a melhorar a remanência, reduziu-se o tempo de exposição da liga ao hidrogênio, de 60 minutos para 2 minutos, obtendo-se um ímã com JR = (1,14 ± 0,02) T, 0JHc = (1,44 ± 0,03) T e (BH)max = (250 ± 5) kJm-3, constatando-se que a causa para a reduzida remanência no primeiro caso decorria do baixo grau de orientação cristalográfica. Durante esta investigação, desenvolveu-se e validou-se uma nova metodologia para quantificação do parâmetro . Posteriormente, propôs-se uma correlação quantitativa inédita entre a microestrutura e o fator de quadratura em magnetos anisotrópicos de TR16Fe76B8 (TR = Nd ou Pr) sinterizados. A expressão apresentada utiliza o tamanho, a elongação e a circularidade médios dos grãos e seus respectivos desvios padrões. Melhora-se o fator de quadratura quando a microestrutura apresenta grãos arredondados e com estreita distribuição de tamanho. A homogeneidade de tamanho dos grãos apresenta uma influência maior sobre o fator de quadratura quando comparada à homogeneidade de forma dos grãos. Ademais, verificou-se que o tratamento térmico após a sinterização melhora a ix homogeneidade de forma ao passo que a moagem melhora a homogeneidade de tamanho dos grãos. Avaliou-se, adicionalmente, o efeito da temperatura sobre o fator de quadratura em magnetos sinterizados anisotrópicos, verificando-se que o mesmo é controlado principalmente por sua microestrutura e confirmando a expressão previamente proposta. Além disso, propôs-se uma correlação quantitativa entre o produto de energia máximo e o fator de quadratura. Compararam-se valores experimentais e calculados, utilizando a expressão apresentada, e a discrepância encontrada foi de 5%. Por fim, avaliou-se qual seria o valor mínimo do fator de quadratura em ímãs sinterizados, constatando-se que magnetos isotrópicos devem apresentar o menor valor para tal parâmetro em virtude do reduzido grau de alinhamento cristalográfico. Ademais, verificou-se que para este tipo de amostra, em geral, 0,20 FQ 0,30. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:05/04711-2
magnetic properties
permanent magnets
magnets
microstructure
milling
iron alloys
praseodimium alloys
boron alloys
crystallography
crystals
physical properties
sintering
grain size
5

Dobijanje nanofosfora na bazi fluorapatita dopirani Pr3+ jonima za bio-medicinske primene / Preparation of fluorapatite-based nanophosphorus doped with Pr3+ ions for bio-medical applications

Milojkov Dušan 08 October 2020 (has links)
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QFormat="true" Name="Subtle Reference"/> <w:LsdException Locked="false" Priority="32" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Intense Reference"/> <w:LsdException Locked="false" Priority="33" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Book Title"/> <w:LsdException Locked="false" Priority="37" Name="Bibliography"/> <w:LsdException Locked="false" Priority="39" QFormat="true" Name="TOC Heading"/> </w:LatentStyles></xml><![endif]--><!--[if gte mso 10]><style> /* Style Definitions */ table.MsoNormalTable{mso-style-name:"Table Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-parent:"";mso-padding-alt:0cm 5.4pt 0cm 5.4pt;mso-para-margin-top:0cm;mso-para-margin-right:0cm;mso-para-margin-bottom:8.0pt;mso-para-margin-left:0cm;line-height:107%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri","sans-serif";mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;}</style><![endif]--></p><p>Luminescentni nanokristali (nanofosfori) na bazi fluorapatita (FAP-a) dopirani elementima retkih zemalja idealni su kontrastni agenti za bio-medicinske primene, kao &scaron;to su detekcije, snimanja, praćenja i terapije ćelija kancera. Kancer je jedna od najče&scaron;ćih bolesti modernog doba čiji uspeh lečenja zavisi od rane dijagnostike i neinvazivnog tretmana. Luminescentne nanočestice mogu uneti inovativnu paradigmu u lečenje kancera kombinovanjem biosnimanja, dijagnostike i tretmana. Za studije fluorescentnih biosnimanja nanokristali fluorapatita dopirani retkim zemljama kao kontrastni agenti pružaju značajne prednosti u vidu velikih kontrasta i dugotrajnosti luminescencije, i &scaron;to je jo&scaron; važnije visoke biokompatibilnosti, netoksičnosti i bioaktivnosti. Glavni ciljevi ove doktorske disertacije su sinteza novih luminescentnih multifotonskih bionanomaterijala na bazi fluorapatita dopiranih jonima prazeodimijuma (Pr<sup>3+</sup>), njihova karakterizacija i evaluacija&nbsp; primene za fluorescentna biosnimanja kancera. Sintezom nanoprahova u umerenim uslovima metodom ko-precipitacije, a potom su&scaron;enjem na 110 <sup>o</sup>C i kalcinacijom na temperaturama od 700 i 1000 <sup>o</sup>C očekuje se pronalaženje najboljih uslova za dobijanje novih nanofosfora koji bi na&scaron;li i različite bio-medicinske primene u oblasti fluorescentnih biosnimanja. Proučavane su tri vrste PrFAP nanokristala, sa 0,1%, 0,5% i 1% atomskih procenta Pr<sup>3+</sup>, zajedno sa nedopiranim FAP kontrolnim uzorkom. Nivoi energije aktivator jona Pr<sup>3+</sup> sadrže metastabilna multipletna stanja koja nude mogućnosti efikasnih emisionih linija u vi&scaron;e boja u FAP nanokristalima, kao i u infracrvenoj i ultravioletnoj oblasti spektra. Metodom ko-precipitacije na sobnoj temperaturi (25 <sup>o</sup>C), a potom su&scaron;enjem na 110 <sup>o</sup>C, sintetisani su monofazni heksagonalni nanokristali PrFAPs nepravilnog sfernog oblika. Termičkom analizom sintetisanih uzoraka, na&nbsp;osnovu detektovanih temperaturnih opsega procesa dekarbonacije i dehidroksilacije, utvrđene su temperature kalcinacije od 700 i 1000 oC. Termička analiza i karakterizacija uzoraka su pokazale da Pr<sup>3+</sup> joni dovode do stabilizacije FAP strukture na vi&scaron;im temperaturama, &scaron;to je pripisano unosu lantanoidnih jona sa specifičnim magnetnim osobinama u sistem i stvaranju jačih privlačnih sila sa O<sup>2- </sup>anjonima. Nanokristali su&scaron;eni na 100 <sup>o</sup>C i kalcinisani na 1000 <sup>o</sup>C, zbog prisustva defekata kristalne re&scaron;etke koji zadržavaju emisiju Pr<sup>3+</sup> jona, nisu pokazali luminescentne karakteristike od značaja za primene u medicinskim fluorescentnim biosnimanjima. Kalcinacijom uzoraka na 700 <sup>o</sup>C izrađen je novi tip aktiviranih fluorapatitnih nanokristala dopira / <p>Luminescent nanocrystals (nanophosphorus) based on fluorapatite (FAP) doped with rare earth elements are ideal contrast agents for biomedical applications such as cancer cell detection, imaging, tracking and therapy. Cancer is one of the most common diseases of the modern times whose success of the cure depends on early diagnosis and non-invasive treatment. Luminescent nanoparticles can bring an innovative paradigm into the treatment of cancer by combining bioimaging, diagnostics and treatment. Rare earth doped fluorapatite nanocrystals as contrast agents for studies of fluorescence bioimaging, offer significant advantages in terms of high contrasts and long-term luminescence, and more importantly high biocompatibility, non-toxicity and bioactivity. The main objectives of this doctoral dissertation are the synthesis of novel luminescent multiphoton bionanomaterials based on fluorapatites doped with praseodymium ions (Pr<sup>3+</sup>), their characterization and evaluation of their application for cancer fluorescence bioimaging. Synthesis of nanopowders under moderate conditions by the co-precipitation method, followed by dried at 110 &deg;C and calcination at 700 and 1000 &deg;C, is expected to find the best conditions for obtaining new nanophosphors that would find different bio-<br />medical applications in the field of fluorescence bioimaging. Three types of PrFAP nanocrystals were studied, with 0,1%, 0,5%, and 1% atomic percentages of Pr<sup>3+</sup>, together with an undoped FAP control sample. Energy levels of the Pr<sup>3+</sup> ion activator contain metastable multiplet states that offer the possibility of efficient multi-color emission lines in FAP nanocrystals as well as in the infrared and ultraviolet regions of the spectrum. Single-phase hexagonal nanocrystals PrFAPs of irregular spherical shape were synthesized by the method of co-precipitation at room temperature (25 <sup>o</sup>C) and then drying at 110 <sup>o</sup>C. Thermal analysis of the synthesized samples, based on the detected temperature ranges of the decarbonation and dehydroxylation processes, determined calcination temperatures of 700 and 1000 <sup>o</sup>C. Thermal analysis with characterization showed that Pr<sup>3+</sup> ions lead to stabilization of the FAP structure at higher temperatures,&nbsp;which was attributed to the entry of lanthanoid ions with specific magnetic properties into the system and the creation of stronger attractive forces with O<sup>2-</sup> anions. Nanocrystals dried at 100 <sup>o</sup>C and calcined at 1000 <sup>o</sup>C, due to the presence of crystal lattice defects that quench the emission of Pr<sup>3+</sup> ions, did not show luminescent characteristics of significance for applications in medical fluorescence imaging. Calcination of the samples at 700 <sup>o</sup>C produced a new type of activated praseodymium doped fluorapatite nanocrystals (PrFAPa) with excitation-emission profiles in the visible part of the spectrum. Physicochemical characterization confirmed spherical crystals of hexagonal structure up to a nanometer size of about 20 nm. Quantum-chemical calculations predicted that Pr<sup>3+</sup> ions would be embedded in the crystal lattice of FAP nanocrystals at the Ca2 position (6h), which was followed by deformations of the F<sup>-</sup> ion position. The assumed substitution mechanism is one Pr3+ ion for one Ca<sup>2+</sup>, with partial substitution of F<sup>&ndash; </sup>anions with O<sup>2&ndash;</sup> and OH<sup>&ndash;</sup> and creation of vacancies due to achieving system neutrality. The results of in vitro biocompatibility and hemocompatibility showed that PrFAP nanocrystals were not toxic to living cells. In addition, the internalization of PrFAPa nanocrystals by skin (A431) and lung (A549) cancer cells was studied using fluorescence-based confocal microscopy and wide-field microscopy. The nanocrystals show characteristic green emission at 545 nm (<sup>3</sup>P<sub>0</sub>&rarr;<sup>3</sup>H<sub>5</sub> transition of Pr<sup>3+</sup> ion) and orange emission at 600 nm (<sup>1</sup>D<sub>2</sub>&rarr;<sup>3</sup>H<sub>4</sub>), which we use to discriminate from cell autofluorescence. Studies of the images obtained by confocal microscopy in the blue, green, and red channels revealed that nanocrystals could recognize the cell surface and adhere to it, but they did not confirm the entry of nanocrystals into the cells. The wide-field microscopy detected emission transitions in green and orange color, and confirmed that the luminescent signal was coming from inside the cells. Using resonant excitation of PrFAP nanocrystals at 488 nm and emission of 600 nm, confocal microscopy extracted the fluorescence signal from inside the cancer cells. Orthogonal projections across 3D confocal stacks show that the nanocrystals are able to enter the cells positioning themselves within the cytoplasm. Overall, the obtained PrFAPa nanocrystals are biocompatible and of the tested types, the 0,5% Pr<sup>3+</sup> doped nanocrystals show the highest promise as a tracking nanoparticle probe for bioimaging applications.</p>

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