Dissertations / Theses on the topic 'Hydroxyapatite'
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Lasgorceix, Marie. "Mise en forme par microstéréolithographie et frittage de céramiques macro-micro-poreuses en hydroxyapatite silicatée et évaluation biologique." Limoges, 2014. https://aurore.unilim.fr/theses/nxfile/default/9c91fe90-7df3-4e09-8fd9-809cb07dcf38/blobholder:0/2014LIMO4016.pdf.
Full textMacro-micro-porous bioceramics made of silicated hydroxyapatite (SiHA), with a controlled architecture, were shaped by microstereolithography and consolidated by sintering. For this purpose, slurries with SiHA particles, dispersed in organic photosensitive medium, were developed. Their rheological behaviour was studied according to the powder, organic diluent and dispersant amounts. A formulation, allowing a good compromise between rheological behaviour and reactivity of the suspension, definition and mechanical strength of the shaped macroporous parts, was chosen. After optimization of the process parameters, the study of the overcure, according to the dimensions and the geometry of the macropores, has led to a predictive sizing model of pores, used for the computer aided design of the parts. Model specimens, containing different pore sizes (> 300 μm) of several geometries, were then shaped. The influence of the sintering temperature and time, on the ceramic microstructure, was investigated. A controlled amount of open microporosity over a wide range (up to 37%) was obtained by adjusting these sintering parameters. Improving the osteointegration of osseous substitutes requires an optimization of their architecture. In this context, in order to assess the effect of the geometry of the macropores on the biological phenomena involved in osteogenesis, in vitro studies of bone cells proliferation and ex vivo studies of vascularization were performed on the SiHA porous substrates
Porter, Alexandra Elizabeth. "Ultrastructural comparison of hydroxyapatite and silicon-substituted hydroxyapatite for bone grafting applications." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620067.
Full textChappell, Helen Fiona. "Atomistic simulations of hydroxyapatite." Thesis, University of Cambridge, 2007. https://www.repository.cam.ac.uk/handle/1810/290022.
Full textDebbabi, M., M. Othmani, and A. Aissa. "Nanocrystalline Hydroxyapatite-Bisphosphonate Composites." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35199.
Full textWang, Haibo. "Hydroxyapatite degradation and biocompatibility." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1087238429.
Full textTitle from first page of PDF file. Document formatted into pages; contains xiv, 190 p.; also includes graphics. Includes bibliographical references (p. 166-190).
Shepherd, Jennifer Helen. "Hydroxyapatite and carbonate substituted hydroxyapatite suspensions produced by precipitation routes for scaffold applications." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611812.
Full textTang, Qian. "Production and characterisation of vacuum plasma sprayed (VPS) hydroxyapatite and silicon-substituted hydroxyapatite coatings." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609136.
Full textXu, Qingguo. "Hydroxyapatite coated drug delvery devices." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531796.
Full textDai, Xiaoshu. "Calcium phosphate scaffolds from electrospun PVA/inorganic sol precursors." Worcester, Mass. : Worcester Polytechnic Institute, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-042506-161758/.
Full textZhu, Xiaolong. "Nano hydroxyapatite collagen, nano hydroxyapatite and anodic oxides on titanium preparation, characterization and biological responses /." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97407215X.
Full textMonaco, Enzo. "pH Transients in Hydroxyapatite chromatography columns." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textLiu, Qing. "Hydroxyapatite/polymer composites for bone replacement." Enschede : University of Twente [Host], 1997. http://doc.utwente.nl/586.
Full textMerry, John. "Preparation and characterisation of carbonate hydroxyapatite." Thesis, Queen Mary, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392112.
Full textGotora, Duce. "Pre-cross-linked collagen-hydroxyapatite composites." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424838.
Full textEarl, Jonathan S. "Hydroxyapatite Nanoparticles and Dentine Tubule Infiltration." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486394.
Full textStephen, J. A. "Co-substitution in novel hydroxyapatite materials." Thesis, University of Aberdeen, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590972.
Full textSarqume, Mishu. "Phosphonatefunctionalized methacrylates with hydroxyapatite generating properties." Thesis, KTH, Skolan för kemivetenskap (CHE), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145940.
Full textShaw, John Hamish. "Preparation and characterisation of porous hydroxyapatite." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321661.
Full textBarralet, Jake Edward. "Processing and sintering of carbonate hydroxyapatite." Thesis, Queen Mary, University of London, 1995. http://qmro.qmul.ac.uk/xmlui/handle/123456789/52164.
Full textBoonphayak, Piyanan. "Substituted hydroxyapatite analysis of osteoblast response." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/substituted-hydroxyapatite-analysis-of-osteoblast-response(71ddb64d-03b9-4825-875e-61d68bd2d3e6).html.
Full textSantos, Catarina Ferreira dos. "Synthesis and functionalization of hydroxyapatite nanoparticles." Doctoral thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/11058.
Full textGraças aos desenvolvimentos na área da síntese de nanomaterais e às potentes técnicas de caracterização à nanoescala conseguimos hoje visualizar uma nanopartícula (NP) como um dispositivo de elevado potencial terapêutico. A melhoria da sua efectividade terapêutica requer no entanto o aprofundamento e sistematização de conhecimentos, ainda muito incipientes, sobre toxicidade, selectividade, efeitos colaterais e sua dependência das próprias características físico-químicas da NP em análise. O presente trabalho, elegendo como alvo de estudo uma substância considerada biocompatível e não tóxica, a hidroxiapatite (Hap), pretende dar um contributo para esta área do conhecimento. Definiram-se como metas orientadoras deste trabalho (i) estudar a síntese de nanoparticulas de Hap (Hap NP), e a modificação das características físico-químicas e morfológicas das mesmas através da manipulação das condições de síntese; (ii) estudar a funcionalização das Hap NP com nanoestruturas de ouro e com ácido fólico, para lhes conferir capacidades acrescidas de imagiologia e terapêuticas, particularmente interessantes em aplicações como o tratamento do cancro (iii) estudar a resposta celular a materiais nanométricos, com propriedades físico-químicas diversificadas. No que se refere à síntese de Hap NP, comparam-se dois métodos de síntese química distintos, a precipitação química a temperatura fisiológica (WCS) e a síntese hidrotérmica (HS), em meios aditivados com ião citrato. A síntese WCS originou partículas de tamanho nanométrico, com uma morfologia de agulha, pouco cristalinas e elevada área superficial especifica. A síntese HS à temperatura de 180ºC permitiu obter partículas de dimensões também nanométricas mas com área específica inferior, com morfologia de bastonete prismático com secção recta hexagonal e elevada cristalinidade. Com o objectivo de aprofundar o papel de algumas variáveis experimentais na definição das características finais das partículas de hidroxiapatite, designadamente o papel do ião citrato (Cit), variou-se a razão molar [Cit/Ca] da solução reagente e o tempo de síntese. Demonstrou-se que o ião citrato e outras espécies químicas resultantes da sua decomposição nas condições térmicas (180ºC) de síntese tem um papel preponderante na velocidade de nucleação e de crescimento dessas mesmas partículas e por conseguinte nas características físico-químicas das mesmas. Elevadas razões [Cit/Ca] originam partículas de dimensão micrométrica cuja morfologia é discutida no contexto do crescimento com agregação. Com o objectivo de avaliar a citotoxicidade in vitro das nanopartículas sintetizadas procedeu-se à esterilização das mesmas. O método de esterilização escolhido foi a autoclavagem a 121º C. Avaliou-se o impacto do processo de esterilização nas características das partículas, verificando-se contrariamente às partículas WCS, que as partículas HS não sofrem alterações significativas de morfologia, o que se coaduna com as condições de síntese das mesmas, que são mais severas do que as de esterilização. As partículas WCS sofrem processos de dissolução e recristalização que se reflectem em alterações significativas de morfologia. Este estudo demonstrou que a etapa de esterilização de nanopartículas para aplicações biomédicas, por autoclavagem, pode alterar substancialmente as propriedades das mesmas, sendo pois criticamente importante caracterizar os materiais após esterilização. Os estudos citotoxicológicos para dois tipos de partículas esterilizadas (HSster e WCSster) revelaram que ambas apresentam baixa toxicidade e possuem potencial para a modelação do comportamento de células osteoblásticas. Tendo em vista a funcionalização da superfície das Hap NP para multifunções de diagnóstico e terapia exploraram-se condições experimentais que viabilizassem o acoplamento de nanopartículas de ouro à superfície das nanopartículas de Hidroxiapatite (Hap-AuNP). Tirando partido da presença de grupos carboxílicos adsorvidos na superfície das nanopartículas de Hap foi possível precipitar partículas nanométricas de ouro (1,5 a 2,5 nm) na superfície das mesmas adaptando o método descrito por Turkevich. No presente trabalho as nanopartículas de Hap funcionaram assim como um template redutor do ouro iónico de solução, propiciando localmente, na superfície das próprias nanopartículas de Hap, a sua redução a ouro metálico. A nucleação do ouro é assim contextualizada pelo papel redutor das espécies químicas adsorvidas, designadamente os grupos carboxílicos derivados de grupos citratos que presidiram à síntese das próprias nanopartículas de Hap. Estudou-se também a funcionalização das Hap NP com ácido fólico (FA), uma molécula biologicamente interessante por ser de fácil reconhecimento pelos receptores existentes em células cancerígenas. Os resultados confirmaram a ligação do ácido fólico à superfície das diferentes partículas produzidas HS e Hap-AuNPs. Graças às propriedades ópticas do ouro nanométrico (efeito plasmão) avaliadas por espectroscopia vis-UV e às potencialidades de hipertermia local por conversão fototérmica, as nanoestruturas Hap-AuNPs produzidas apresentam-se com elevado interesse enquanto nanodispositivos capazes de integrar funções de quimio e terapia térmica do cancro e imagiologia. O estudo da resposta celular aos diversos materiais sintetizados no presente trabalho foi alvo de análise na tentativa de se caracterizar a toxicidade dos mesmos bem como avaliar o seu desempenho em aplicações terapêuticas. Demonstrou-se que as Hap NP não afectam a proliferação das células para concentrações até 500 g/ml, observando-se um aumento na expressão genética da BMP-2 e da fosfatase alcalina. Verificou-se também que as Hap NP são susceptíveis de internalização por células osteoblásticas MG63, apresentando uma velocidade de dissolução intracelular relativamente reduzida. A resposta celular às Hap-AuNP confirmou a não citotoxicidade destas partículas e revelou que a presença do ouro na superfície das Hap NP aumenta a taxa proliferação celular, bem como a expressão de parâmetros osteogénicos. No seu conjunto os resultados sugerem que os vários tipos de partículas sintetizadas no presente estudo apresentam também comportamentos interessantes para aplicações em engenharia de tecido ósseo.
Thanks to the last developments in the field of nanomaterials synthesis and to the powerful characterization techniques at the nanoscale, a nanoparticle (NP) can now be viewed as a device of high therapeutic potential. The improvement of its therapeutic effectiveness however still requires the deepening and systematization of important knowledge, still very incipient, on critical related issues including toxicity, selectivity, side effects and their own dependence on the physicochemical characteristics of the NP under analysis. The awareness of this need has framed the present work whose material target is a substance currently considered as biocompatible and nontoxic, hydroxyapatite (Hap), aiming to contribute to the referred pool of knowledge. The guiding goals of this work are here stated as: (i) to study the synthesis of nanoparticles Hap (Hap NP) for understanding the control of particle physico-chemical characteristics through the manipulation of its synthesis conditions, (ii) to study the functionalization of Hap NP with gold and with folic acid in order to impart both imaging and therapy abilities to the synthesized NP thus addressing their usefulness for particular applications related to the treatment of cancer, (iii) to examine the cellular response to nanosized materials having diverse physicochemical properties. For the study of Hap synthesis a hydrothermal synthesis (HS) technique assisted by citric acid additive was followed. The potential of citrate ion (Cit) for tailoring the synthesized particle morphology was exploited by varying the molar ratio [Cit:Ca] of the starting precursor solution. It was demonstrated that the citrate ion and/or other chemical species resulting from citrate decomposition at the used synthesis temperature (180°C) has a major role on nucleation and growth processes of the resulting Hap particles and on their final physico-chemical characteristics. Prismatic Hap particles with hexagonal cross section but with nanometric dimensions were obtained for a low [Cit:Ca] ratio while increasing ratios originated micrometer-sized particles composed by assembled fiber-like or sheet-like particles whose morphology may be discussed in the framework of an aggregation assisted growth. The evaluation of the biological performance of the produced nanometric Hap particles was the natural step in the present study. However, for the goal of comparing the impact of Hap NP morphology variations on cell response, a second chemical precipitation method (WCS) at physiological temperature and using the same additive was also adopted to produce thinner Hap NP. The physico-chemical characteristics of the two precipitated particles, i.e. HS and WCS Hap NP, were comparatively discussed, being found that thin needle-like particles of very high specific surface area (170 m2/g) are obtained from WCS as compared to the prismatic HS particles of lower specific surface area (55 m2/g) but of higher crystallinity. Moreover, as in vitro studies require sterilized materials, the particles were autoclaved at 121º C and the sterilization impact on the particles properties was evaluated as well. Contrarily to WCS particles no significant changes are observed on HS morphology, consistently with the high synthesis temperature conditions for HS NP that exceed largely autoclaving condition. WCS particles undergo dissolution and recrystallization processes which are reflected on significant changes of WCS NP morphology. These results demonstrate that autoclaving sterilization may substantially alter the properties of NP intended for biomedical applications being thus critically important to characterize the materials after sterilization. The in vitro cytotoxicity studies on both type of sterilised particles (HSster and WCSster) revealed that they present low toxicity and have potential for the modulation of the osteoblastic cell behaviour. The possibility of functionalizing Hap NP surface for multifunction purposes (diagnosis and therapy, for instance) was also exploited in the present work. Taking advantage from the presence of adsorbed carboxylic groups left by the synthesis process, HS NP surfaces could be used as a kind of template for gold precipitation, thus providing a new approach to Turkevich method for gold precipitation. Gold nanoparticles with an average diameter of 1.5 to 2.5 nm were effectively precipitated on HS nanoparticles facets as revealed by transmission electron microscopy (TEM). The reducing ability of the species adsorbed on HS surface including carboxylate compounds derived from citrate was thus confirmed as gold ions supplied by the neighbouring gold solution underwent a local reduction giving place to metallic gold spots and hence to nanostructured hydroxyapatite-gold nanoparticles (Hap-AuNPs). The functionalization of Hap NP with folic acid (FA), a molecule with high biological interest due to its easy recognition by the receptors on tumor cells, was also studied. The results confirmed the conjugation of FA to the surface of HS and Hap-AuNPs nanoparticles. Thanks to the optical properties of Hap-AuNPs imparted by the nanometric gold (plasmon effect) as confirmed by UV-vis spectroscopy and to the hyperthermia effect reported for metallic nanometric gold, the Hap-AuNPs here produced show a great potential as nanodevices able to integrate functions of chemical and thermal therapy for cancer and imaging. The cellular response to the various nanomaterials synthesized in this work was also analysed in an attempt to characterize their toxicity and to assess their biological performance aiming to identify potential therapeutic applications. It was demonstrated that Hap NP do not affect MG63 cell proliferation until concentrations up to 500 g/ml, as indicated by BMP-2 and alkaline phosphatase expression. It was also found that Hap NP undergo internalization by MG63 osteoblast cells, suffering a relatively low intracellular dissolution rate. The cellular response to Hap AuNPs confirmed their non-cytotoxicity while showing that the presence of gold at the surface of Hap NP increases the cell proliferation rate and the expression of osteogenic parameters. Altogether the in vitro results suggest that the behavior of the various types of particles synthesized in this study addresses a potential interest for applications in hard tissue engineering.
FERRI, MICHELE. "HYDROXYAPATITE-BASED MATERIALS FOR ENVIRONMENTAL PROCESSES." Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/815634.
Full textCoe, Samuel C. "The deposition, characterisation and biocompatibility of hydroxyapatite and silicon doped hydroxyapatite thin film coatings for orthopaedic applications." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/10984/.
Full textKim, Hyunbin. "Synthesis and control of microstructure, mechanical properties, and bioactivity in biphasic and preferentially oriented calcium phosphate bioceramics." Birmingham, Ala. : University of Alabama at Birmingham, 2007. http://www.mhsl.uab.edu/dt/2007p/kim.pdf.
Full textJohnson, Shevon. "Pulsed Laser Deposition of Hydroxyapatite Thin Films." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6839.
Full textWahl, Denys Adrien. "Collagen-hydroxyapatite scaffolds for bone tissue engineering." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491734.
Full textSwanprateeb, Jintamai. "Creep behaviour of hydroxyapatite reinforced polythylene composites." Thesis, Queen Mary, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307513.
Full textSavalani, Monica M. "Selective laser sintering of hydroxyapatite-polyamide composites." Thesis, Loughborough University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446487.
Full textBall, Michael David. "The optimisation of hydroxyapatite for osteoblast growth." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312229.
Full textEvans, Samuel Evans. "Adhesively bonded hydroxyapatite coatings for orthopaedic implants." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241146.
Full textHing, Karin Angela. "Assessment of porous hydroxyapatite for bone replacement." Thesis, Queen Mary, University of London, 1996. http://qmro.qmul.ac.uk/xmlui/handle/123456789/25123.
Full textConway, Jordan C. "Highly silicated hydroxyapatite : synthesis, characterisation and evaluation." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235581.
Full textShepherd, David Vincent. "Production and characterisation of zinc substituted hydroxyapatite." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609326.
Full textMarti, Patrick. "Zinc-containing hydroxyapatite coatings for orthopaedic applications." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611527.
Full textFriederichs, Robert John. "Co-substituted silicate hydroxyapatite for bone regeneration." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648822.
Full textWang, Ziqiu Wang. "THE ROLE OF BIOMOLECULES IN HYDROXYAPATITE BIOMINERALIZATION." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468445118.
Full textDenning, Paul Michael. "High power laser surface processing of hydroxyapatite." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399182.
Full textBilton, Matthew William. "Nanoparticulate hydroxyapatite and calcium-based CO2 sorbents." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3847/.
Full textWalsh, Dominic. "Morphological and architectural control of hydroxyapatite growth." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260198.
Full textLye, Peter. "Surface composition of hydroxyapatite in aqueous solutions." Thesis, Queensland University of Technology, 1985.
Find full textKočicová, Pavla. "Syntéza biokeramických materiálů na bázi hydroxyapatitu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230738.
Full textRočňáková, Ivana. "Vlastnosti a in vitro degradace kovových biodegradabilních materiálů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-263355.
Full textSaw, Eaden. "Syntheses of near-net shaped monolithic hydroxyapatite and hydroxyapatite-ASTM F75 composites by the oxidation of solid metal-bearing precursors /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488187049543288.
Full textValenová, Ludmila. "Optimalizace 3D tisku a post-processingu pokročilé keramiky na bázi kalcium fosfátu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442598.
Full textHoang, Quyen Quoc Yang Daniel. "Crystal structure and hydroxyapatite binding of porcine osteocalcin /." *McMaster only, 2003.
Find full textUn, Serhat Nusret. "Development Of Sol-gel Derived Hydroxyapatite-titania Coatings." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609449/index.pdf.
Full textC has been investigated. The coatings exhibit higher tendency for cracking when a high vapor pressure solvent, such as ethanol (C2H5OH) is used causing development of higher macroscopic stresses during evaporation of the sol. Titania sol formulations replacing the solvent with n-propanol (CH3(CH2)2OH) and acetly-acetone (C5H8O) combinations enhanced the microstructural integrity of the coating during evaporation and calcination treatments. Sol-gel processing parameters such as multilayer coating application and withdrawal rate can be employed to change the titania thickness in the range of 0.120 - 1.1 microns and to control the microstructure of HAp-titania hybrid coatings. Slower withdraw rates and multi-layer dip coating lead to coatings more vulnerable to cracking. A high calcination temperature in the range of 400 º
C-600 º
C lead to more cracking due to combined effect of densification originated stresses and thermal stresses upon cooling.
Aydin, Erkin. "Biodegradable Polymer - Hydroxyapatite Nanocomposites For Bone Plate Applications." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612252/index.pdf.
Full texts Modulus was observed. Although this increase was not high was not high probably due to the low fiber content in the final plates, this approach was found to be promising for the production of biodegradable polymeric bone plates with mechanical values closer to that of cortical bones. Biological compatibility of fibers was validated with in vitro testing. The osteoblasts attached and spread on the fibers indicating that bone fractures fixed with these could attract of bone forming osteoblasts into defect area and help speed up healing.
Bingol, Onur Rauf. "Hydrothermal-like Synthesis Of Hydroxyapatite From Calcium Sulfates." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612425/index.pdf.
Full text0.5H2O, PoP) and gypsum (CaSO4&bull
2H2O) has been performed. HAp synthesis was achieved by reacting 1 M of (NH4)2HPO4 (or 0.5 M of (NH4)2HPO4) solutions with solid calcium sulfate precursors under ambient pressure (1 atm) and hydrothermal-like (2 ±
0.2 atm, 120 °
C) conditions. Under ambient conditions, HAp formation kinetics was investigated at 25 °
C, 50 °
C and 90 °
C using 1 M of (NH4)2HPO4 solution. Conversion to HAp at such low temperature takes more than 21 days and it also promotes formation of additional calcium phosphate with HAp. At 25 °
C, HAp formation started after 7 days accompanied with formation of brushite (CaHPO4&bull
2H2O). At 50 °
C no significant conversion was observed after 6 h. However, at 90 °
C, phase pure HAp was formed after 2 h. On the other hand, under hydrothermal-like conditions, the HAp formation proceed much faster and it was also shown that HAp could be also synthesized from gypsum powders and bulk gypsum pellets. Using 1 M of (NH4)2HPO4 solution, HAp formation from PoP started 15 min and completed almost in 30 min, whereas 0.5 M of (NH4)2HPO4 reactant solution slowed down the conversion. The exact chemical identity of the HAp product of hydrothermal-like reaction was evaluated by post-synthesis calcinations and the thermal phase stability was related with the stoichiometry (Ca/P at ratio) of the HAp. The HAp phase was stable up to 600 °
C and above 600 °
C, &beta
-tricalcium phosphate (&beta
-Ca3(PO4)2, &beta
-TCP) was formed, suggesting that the resultant HAp was calcium-deficient. Mechanical testing by diametrical compression was performed to the HAp samples produced from bulk gypsum pellets. The strength was measured 1.2 MPa with highest solid to liquid (s:l) ratio 3.33 and decreased with s:l ratio. This change was found to be related with the porosity differences due to differences in s:l ratio. Additional mechanical tests were applied to the polycaprolactone (PCL) coated bulk HAp pellets for which the tensile strength was doubled. This study presents an easy and feasible method for production of HAp from a cheap and abundant calcium source &ndash
PoP. In addition, the findings provide a potential processing route for developing irregularly shaped bulk porous HAp structures.
Lindahl, Carl. "Biomimetic Deposition of Hydroxyapatite on Titanium Implant Materials." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183345.
Full textLahiri, Debrupa. "Hydroxyapatite-Nanotube Composites and Coatings for Orthopedic Applications." FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/444.
Full text