RESUMO A hidroxiapatita estequiométrica é um material bioreabsorvível e tem sido utilizada para reparação óssea e jateamento de implantes de titânio. Contudo, a hidroxiapatita estequiométrica não é estável acima de 1130 oC a 1200 oC limitando a temperatura de tratamento térmico realizado no biomaterial para aumentar a resistência mecânica dos aglomerados obtidos do processo de síntese a temperatura ambiente. Sendo assim, o objetivo deste trabalho foi a elaboração de fosfato de cálcio com razão molar Ca/P de 1,7. Com esta razão molar Ca/P é possível a formação de hidroxiapatita estável até aproximadamente 1360 oC, de acordo com o diagrama de equilíbrio CaO-P2O5. O fosfato de cálcio foi elaborado pelo método de síntese via úmida utilizando carbonato de cálcio e ácido fosfórico como matérias-primas. O material obtido da síntese é composto por partículas aglomeradas com tamanho entre 20 nm e 70 nm, sendo que o tamanho dos aglomerados varia de alguns µm até aproximadamente 200 µm. Os resultados da análise térmica e da difração de raios-X mostraram que a hidroxiapatita é estável entre 750 oC e 1350 oC. O tratamento térmico realizado a 1300 oC confirmou que não há transformação da hidroxiapatita em fosfato tricálcico acima de 1130 oC a 1200 oC como acontece com a hidroxiapatita estequiométrica. No tratamento térmico realizado a 1300 oC durante 1 hora obteve-se hidroxiapatita com 67 % de porosidade enquanto que no tratamento de 4 horas, a mesma temperatura, a porosidade foi de 17 %. A hidroxiapatita com alta porosidade tem aplicação na reparação óssea enquanto que a hidroxiapatita mais compacta pode ser utilizada no jateamento de implantes de titânio. Estas aplicações são discutidas no trabalho.

ABSTRACT Stoichiometric hydroxyapatite is a bioreabsorbable material and has been used for bone repair and shot blasting of titanium implants. However, the stoichiometric hydroxyapatite is not stable above 1130 oC to 1200 oC, limiting the heat treatment performed on the biomaterial to increase the mechanical strength of the granules obtained from the synthesis process at room temperature. Therefore, the aim of this work was the elaboration of calcium phosphate with Ca/P molar ratio of 1.7. With this Ca/P molar ratio, the formation of stable hydroxyapatite is possible up to approximately 1360 oC, according to the CaO-P2O5 equilibrium diagram. Calcium phosphate was prepared by the wet method of synthesis using calcium carbonate and phosphoric acid as raw materials. The material obtained from the synthesis consists of agglomerated particles with a size between 20 nm and 70 nm, while the size of the agglomerates varied from a few microns to approximately 200 µm. The results of the thermal analysis and X-ray diffraction showed that the hydroxyapatite is stable between 750 oC and 1350 oC. The heat treatment performed at 1300 oC confirmed that there is no transformation of hydroxyapatite into tricalcium phosphate above 1130 oC to 1200 oC as it happens for stoichiometric hydroxyapatite. In the heat treatment carried out at 1300 oC for 1 hour, hydroxyapatite was obtained with 67 % of porosity whereas in the treatment of 4 hours at the same temperature the porosity was 17 %. Hydroxyapatite with high porosity has applications in bone repair whereas the more compact hydroxyapatite can be used in the blasting of titanium implants. These applications are discussed in the work.

RESUMO As biocerâmicas bifásicas hidroxiapatita/fosfato tricálcico-beta (HA/TCP-β) microporosas são pesquisadas e se destacam em aplicações biomédicas como substitutos dos tecidos ósseos. Estes biomateriais são biocompatíveis e apresentam microestruturas microporosas interconectadas, que permitem sua utilização no reparo do tecido ósseo. Devido às suas características microestruturais, estes biomateriais vem sendo também avaliados para liberação controlada de fármacos. O presente trabalho teve como objetivo a incorporação do fármaco carboplatina no biomaterial granulado bifásico microporoso 60%HA/40%TCP-β pelo método de alto vácuo e caracterização do biomaterial carregado, nas concentrações de 1, 5, 10 e 20 mg/g de carboplatina no biomaterial. Os resultados apresentados envolvem a caracterização morfológica, microestrutural, cristalográfica e química do biomaterial granulado bifásico microporoso. A microscopia eletrônica de varredura (MEV) mostrou em suas micrografias a presença dos precipitados de carboplatina na microestrutura microporosa do biomaterial. O resultado da difratometria de raios X (DRX) permitiu a identificação dos picos representativos da fase cristalina da HA, TCP-β e da carboplatina depois do carregamento. A análise por espectroscopia na região do infravermelho (FTIR) evidenciou os modos vibracionais relativos aos fosfatos de cálcio, OH-e PO43-e também Pt-N e NH3 da molécula da carboplatina. Os resultados obtidos demonstraram que a microporosidade da biocerâmica e o método de alto vácuo possibilitaram o carregamento da carboplatina na microestrutura do biomaterial granulado.

ASBTRACT The hydroxyapatite/beta-tricalcium phosphate (HA/β-TCP) bioceramics, has been reported to be attractive for biomedical applications, used as bone tissue substitute materials. These biomaterials exhibited excellent biocompatibility and interconnected microporous microstructure that provides suitable environments for a controlled drug delivery system in bone treatments. The characterization study of the biphasic granular material 60% HA/40% β-TCP, was performed before and after loading the carboplatin using a high vacuum method. The drug was loaded at concentrations of 1 mg/g, 5 mg/g, 10 mg/g and 20 mg/g in a biphasic granular biomaterial. The morphological, microstructural, crystallographic and chemical characterization of the granulated biomaterial was investigated. SEM analysis showed structures identified as drugs precipitates on the structure of the biomaterial. The drug has been identified using X-ray technique, also. FTIR analysis indicated OH-and PO43-from calcium phosphates and Pt-N and NH3 vibrational bands from carboplatin molecules. The results showed that the high vacuum method was efficient for the incorporation of carboplatin in micropore structure of the granular biomaterial.

RESUMO Neste trabalho foram realizados estudos sobre a fabricação de um biocompósito à base de titânio para implantes dentários a partir da mistura de pó de hidreto de titânio (92%) com nitrato de cálcio (8% em volume). O pó de hidreto de titânio foi adicionado na solução aquosa de nitrato de cálcio, dissolvido por agitação mecânica, e em seguida os precursores foram misturados e dispersados/homogeneizados por ultrassom. Posteriormente, a mistura foi secada em evaporador rotativo, compactada com 600 MPa à temperatura ambiente, desmoldada e sinterizada em alto vácuo a 1200 oC durante 2 horas. Foi analisada a microestrutrura e fases formadas, as propriedades mecânicas, a rugosidade da superfície, a porosidade aberta, a molhabilidade da superfície e a citotoxicidade do biocompósito. As fases identificadas após a sinterização foram α-Ti e CaTiO3. O limite de resistência em compressão, o módulo de Young (E) e o ângulo de contato do biocompósito diminuíram significativamente com relação ao hidreto de titânio puro sinterizado nas mesmas condições. O limite médio de resistência em compressão do hidreto de titânio foi de 1794,67 MPa e do biocompósito foi de 481,36 MPa. O módulo de Young e o ângulo de contato do hidreto de titânio e do biocompósito foram de aproximadamente 112 GPa e 94 graus, e de 75 GPa e 83 graus, respectivamente. A rugosidade de superfície foi da mesma ordem de grandeza entre os materiais e ficou aproximadamente entre 1,4 e 1,5 µm (Ra) e 1,4 e 1,9 µm (Ra e Sa), medidas com rugosímetro de contato e com microscópio confocal a laser, respectivamente. A porosidade aberta do biocompósito sinterizado foi de aproximadamente três vezes maior do que aquela do hidreto de titânio sinterizado. Nos ensaios de citotoxicidade a porcentagem de células viáveis do biocompósito foi superior àquela do controle negativo e àquela do hidreto de titânio sinterizado.

ABSTRACT A titanium-based biocomposite was prepared from titanium hydrate powder and calcium nitrate for dental implant applications. The minor precursor was added in the major precursor of titanium hydrate in the concentration of 8% in volume. Titanium hydrate was added in the calcium nitrate solution, previously dissolved by mechanical agitation in distilled water, and then mixed/homogenized by ultrasound. The mixture was dried in a rotating evaporator, pressed at 600 MPa at room temperature and vacuum sintered at 1200 oC during 2 hours. It was analyzed the microstructure and phases formed, the mechanical properties, the surface roughness, the open porosity, the surface wetness and cytotoxicity of the materials. The phases formed in the biocomposite after sintering were α-Ti and CaTiO3. The compressive strength, Young modulus (E) and contact angle of the biocomposite significantly decreased compared to the sintered titanium hydrate. The average compressive strength of the titanium hydrate was 1794,67 MPa and of the biocomposite was 481,36 MPa. The Young modulus and contact angle of the titanium hydrate and of the biocomposite were approximately 112 GPa and 94 degree, and 75 GPa and 83 degree, respectively. The surface roughness was of the same order among the materials and found to be between 1.4 and 1.5 µm (Ra), and 1.4 and 1.9 µm (Ra and Sa), measured with a roughmeter and with a laser confocal microscope, respectively. The open porosity of the sintered biocomposite was approximately three times higher than that of sintered titanium hydrate. The viability cell percentage of the biocomposite was higher than that of negative control or sintered titanium hydrate.

Titanium-based composites with in-situ calcium and phosphor phases were prepared by powder metallurgy processing with titanium and hydroxyapatite (HA) powders. The mixtures were performed in a friction mill with alcohol for 5 hours, dried in a rotating evaporator, pressed at 600 MPa and sintered at 1200 ºC for 2 hours in argon atmosphere. Crystal phases of the as-fabricated composite are found to be, α-Ti, CaTiO3, Ca3(PO4)2 and Ti xPy phase(s). The analyses revealed that titanium particles were covered with a compact layer of Ti xPy and CaTiO3 phases, which resulted from the decomposition of HA into CaTiO3 and β-Ca3(PO4)2 at approximately 1025 ºC. Then the reactions were followed by the decomposition of β-Ca3(PO4)2, resulting in the growth of CaTiO3 layer and in the nucleation and growth of Ti xPy phase(s).

Thermal characterization of commercially pure titanium was carried out in dry air to investigate the oxidation kinetics, the oxide structures and their properties. Oxidation kinetics were performed by thermogravimetry in isothermal conditions between 300 and 750 °C for 48 hours and the oxide structures were studied by differential thermal analyses and X ray diffraction between room temperature and 1000 °C. The oxidation kinetic increases with temperature and is very fast in the initial period of oxidation, decreasing rapidly with time, especially up to 600 °C. Kinetic laws varied between the inverse logarithmic for the lower temperatures (300 and 400 °C) and the parabolic for the higher temperatures (650, 700 and 750 °C). Evidences from X ray diffraction and differential thermal analyses showed that crystallization of the passive oxide film, formed at room temperature, into anatase occurs at about 276 °C. The crystallized oxide structure is composed of anatase between 276 and 457 °C, anatase and rutile sublayers between 457 and 718 °C, and a pure layer of rutile after 718 °C. Rockwell-C adhesion tests reveled that the oxide films formed up to 600 °C have a good adhesion. Vickers indentations on the oxidized surfaces showed that the hardness of the oxide film, measured at 600 and 650 °C, is approximately 9500 MPa. At these temperatures the surface roughness varied between 0.90 and 1.30 mm.

Biocements formed from the composition Ca/P have been studied and developed since 1983. These biomaterials are promissing and have aroused great interest to biomedical surgery applications, fixation of prostheses and filling and reconstruction of bones. They can be employed as an element of load to fix implant and bone structure. In addition, biocements are easily shaped during surgical processes and favor early bone habitation, absorption, osseointegration, and osteoconduction of bone structure into the microstructure of the biocement thus favoring regeneration and reconstruction of bone tissue. This paper aims to develop biocements formed from calcium phosphate through the aqueous precipitation method by means of the dissolution-precipitation reaction, which involves solid/ liquid phase of CaO and phosphoric acid to form the calcium phosphate. The biocements investigated were synthesized when the molar ratios of Ca/P = 1.4, 1.5, 1.6, 1.7 and 1.8. The present results indicate that the aqueous precipitation method allowed nanostructured powder of calcium phosphate to form. Thermal treatment at 1300 °C for 2 hours provided biocements formed from calcium phosphate and hydroxyapatite. The study of hydration behaviour from 1 to 28 days in a solution, which contained 0.4% of sodium phosphate, emphasized phase modification and the presence of a microporous microstructure made of crystalline fibers. It was found that the shape and size of the crystalline fiber had a direct influence on the resulting mechanical properties. Investigating more carefully the behaviour of the specimens with a Ca/P molar ratio of 1.5, there was an increase in the strength value under compression as a function of time so that it reached the maximum value of strength ±45 MPa to specimens that had been hydrated for 28 days.

The goal of this work was to study the viability of burnt biomass residue from a pulp and paper plant applied as a raw material for mortar used in the construction industry. The waste - bottom ash - was incorporated into the mortar as a mineral addition to the Portland cement. The effect of the waste's grain size on the properties of mortars containing 10% in volume of waste was investigated, as well as the effect of the concentration of waste with grain size under 0.15 mm. The samples were evaluated after 28 days of aging by uniaxial compression, leaching test and scanning electron microscopy. These characterization techniques indicated that the properties of the mortars depend on the concentration, granulation and size distribution of the waste in the mortar's structure. Furthermore, some chemical elements may be present in stabilized and/or encapsulated form in the cement matrix.

The influence of the application of residues from the cellulose and paper industry in construction mortar was investigated. Mortars were prepared with CPI-S-32 or CPII-Z-32 Portland cements and sand in a 1:3 proportion. Four solids residues, i.e., Fiber, Dregs, Bottom Ash and Grit, were incorporated in the mortars in varying proportions. The bottom ash and dregs were used in place of cement, while fiber and grit were used to replace sand. The aging time of the samples was varied from 7 to 28 days. The results demonstrated that the type of cement and the aging time exerted a strong influence on the samples' microstructure and resistance to axial compression. The best values were obtained at 28 days of age with the CPI-S-32 cement. On the other hand, the type of residue and its concentration also affected microstructure and resistance to axial compression. The best results were obtained from bottom ash and grit.