José Brant de Campos

Porous Biphasic and Triphasic Bioceramics Scaffolds Produced by Gelcasting

The present work suggests a modified gel casting process, including polyethylene wax spheres addition to the suspension with the objective of creating uniform and interconnected pores in the body of samples. In the present study, apatite powders were synthesized at pH 10 and pH 12 in order to give rise to biphasic and triphasic bioceramics after sintering.

Bioactivity Assessment of Ag-HA

Cell culture medium has been used as an alternative to Kokubo’s solution in order to approach in vitro to in vivo bioactivity assessment. Moreover, the production of biomaterials with silver ions (Ag) has shown an antimicrobial effect and these are potential graft materials to prevent or reduce bacterial infection. In the present study, synthesis of hydroxyapatite (HA) and silverdoped hydroxyapatite (Ag-HA) with 0.13 mol% Ag (mol Ca:Ag) were performed and the bioactivity assessment was analyzed by scanning electron microscopy with field emission gun (FEG-SEM). The Ag-HA samples showed discrete bone-like apatite formation, indicating bioactivity behavior after in vitro incubation in McCoy cell culture medium after 7 days. Silver introduction into hydroxyapatite structure showed to be effective to produce a bioceramic with potential antibacterial effect and bioactivity.

Mg substituted apatite coating from alkali conversion of acidic calcium phosphate.

In this work, two solutions were developed: the first, rich in Ca2+, PO43- ions and the second, rich in Ca2+, PO43- and Mg2+, defined as Mg-modified precursor solution. For each Mg-modified precursor solution, the concentrations of Mg2+ ions were progressively increased by 5%, 10% and 15%wt. The aims of this research were to investigate the influence of magnesium ions substitution in calcium phosphate coatings on titanium surface and to evaluate these coatings by bioactivity assay in McCoy culture medium. The obtained coatings were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis, and the presence of Mg ions was confirmed by the inductively coupled plasma atomic emission spectroscopy (ICP) analysis. In vitro bioactivity assay in McCoy culture medium showed bioactivity after 14days in incubation for the HA and 10% Mg-monetite coatings. The high chemical stability of Mg-HA coatings was verified by the bioactivity assays, and no bone-like apatite deposition, characteristic of bioactivity, was observed for Mg-HA coatings, for the time period used in this study.

Síntese e caracterização do compósito Al2O3 -YAG e do Al2O3-YAG e Al2O3 aditivados com Nb2O5

The Al2O3-YAG composite exhibits high corrosion and creep resistance in aggressive environments, which provides quite glimpse attractive applications such as jet engine vanes and as gas turbines. This composite also shows high hardness and wear resistance allowing its use in ballistic armor. In this study, precursor powders of Al2O3, Y2O3 and Nb2O5 were homogeneously mixed in a planetary ball mill for 4 h, dried in an oven at 120 oC for 48 h, sieved and deagglomerated. The Al2O3-YAG composite was produced from mixtures of Al2O3-Y2O3 at 1300 oC for 2 h. Samples of Al2O3-YAG, Al2O3-YAG with Nb2O5 and Al2O3 with Nb2O5 were produced. Each powder composition was uniaxially pressed at 70 MPa. Sintering was performed at 1400 and 1450 oC. The powders as received and as processed were characterized for specific surface area and particle size. The sintered materials were characterized by apparent density and porosity by the Archimedes method and evaluated for shrinkage and loss of mass. The obtained results showed that further adjustments are needed in the sintering conditions of Al2O3-YAG composition with Nb2O5 in order to improve the densification and shrinkage, which were low, 60% and 3%, respectively. The Al2O3 with Nb2O5 addition, on the other hand, presented a satisfactory densification of 96% and shrinkage around 15%.

Síntese e caracterização de fosfatos de cálcio a partir da casca de ovo de galinha

Calcium phosphates are ceramic compounds employed nowadays in development of biomaterials used as bone substitutes in clinical orthopedic and odontologic areas. The aim of this work was explore chemical routes able to convert chicken eggshell, a rich material in CaCO3, in inorganic calcium phosphates, as beta tricalcium phosphate (β-Ca3(PO4)2) and hydroxyapatite (Ca10(PO4)6(OH)2), materials used as bone substitutes. A preliminary thermodynamic analysis has shown which acids were viable to chemical attack in chicken eggshell. Inorganic salts produced from chemical acid attack, using HCl, HNO3 and H3PO4, were converted in calcium phosphates in a second reaction step. Materials produced were heated in electrical furnace over 2 h at 900 oC. X-ray diffraction analyses have shown the presence of a mixture of different calcium phosphates phases and the formation of β-Ca3(PO4)2 single phase from different chemical routes and synthesis procedures that have been adopted.

Processamento e caracterização morfológica do compósito Al2O3-YAG aditivado com nióbia

The Al2O3-YAG composite has high mechanical strength at high temperatures which allows its use in air craft applications, since it increases the thermal efficiency of jet engines and helps the development of high performance gas turbines. This composite also exhibits some favorable properties toward military applications such as armor, due to its high hardness. In this study, Al2O3-YAG and Al2O3-YAG with 4wt.% Nb2O5 (niobia) samples were produced. The precursors powders were ground in a planetary ball mill for 4 h, dried in an oven at 120 oC during 48 h, deagglomerated and sieved. The powder mixtures were then uniaxially pressed at 70 MPa. Sintering was carried out at 1450 oC for 2, 3, and 4 h, with heating and cooling rates of 10 oC/min. The materials were characterized by scanning electron microscopy (SEM) in order to characterize the microstructure. X-ray diffraction with Rietveld refinement was performed to determine and quantify the structural phases, whereas density was measured by the Archimede´s method. The samples with niobia addition revealed approximately 5wt.% of yttrium niobate (YNbO4) phase. It is worth pointing out that there is no citation in the literature involving niobia addition to the Al2O3-YAG composite. On the other hand, the obtained results indicated that additional experiments regarding the sintering conditions are necessary to optimize density.

Modified Gelcasting Process to Prepare Porous Trifasic and Bifasic Hydroxyapatite scaffolds

In the present work, apatite powders were synthesized at pH 10, pH 11 and pH 12 in order to give rise to biphasic and triphasic bioceramics after sintering. A modified gelcasting process, including polyethylene wax spheres addition to the suspension, is proposed in comparison to the original gelcasting method. The aim of the addition is the creation of uniform, open and interconnected pores in the body of samples.

Influence of Alginate on Precipitation of Calcium Phosphates

Calcium phosphates are widely used in medicine and dentistry. However, synthesis of these substances through precipitation methods still presents problems regarding reproducibility. Alginate is a polymer extracted from brown algae, whose monomers are D-mannuronic and L-guluronic acids, and is suitable for biomedical applications. The aim of this paper is to investigate how the poly-ionic nature of alginate affects phase composition of calcium phosphate obtained through a precipitation method.

Al2O3-YAG Biphasic Composite Phase Determination Using Rietveld Method Measurements

TheAl2O3-YAG biphasic composite has been extensively studied since this system has important properties such as high resistance to corrosion and creep in harsh environments. This material system is potentially very attractive for high temperatures applications. In this work, the precursor powders of Al2O3 and Y2O3, were homogenized in planetary ball mill for 2h, dried in oven at 120oC for 48h, sieved and deagglomerated. It was performed a series of heat treatments over the powder for verification of the YAG phase formation, using1100, 1200, 1300°C and 1400 °C for 3.0 h time. The powders of the starting mixture after grinding and calcinations were characterized for phase quantification using the Rietveld method. The complete formation of the YAG phase in the composite was determined at1300°C after 3h.

Temperature Influence on the Calcium Phosphate Coatings by Chemical Method

The increasing interest in the use of brushite and monetite as resorbable calcium phosphate cements or graft materials is related to the fact of these phases being metastable under physiological environment, with higher solubility than hydroxyapatite phase. In this study, X-ray diffraction (XRD) and scanning electron microscopy with field emission gun (FEG-SEM) analyses were performed in order to assess the temperature influence on the production of calcium phosphate coatings by a chemical deposition method. Titanium substrates were successfully coated with brushite and monetite by a chemical deposition method and a brushite-monetite transformation was assessed with the increasing temperature. Brushite deposition was kinetically favored at low temperatures, whereas monetite was the major phase at higher temperatures.