Rubens Lincoln Santana Blazutti Marçal

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.

Slip Casting Used as a Forming Technique for Hydroxyapatite Processing

Ceramic materials have particular properties when compared to other classes of materials, exhibiting poor ductility as an example. Slip casting is a widely used ceramic forming technique, and already established in the literature and in the ceramic industry. This study aims to present slip casting as a processing route for producing hydroxyapatite (HA) struts, and show the thermal phase stability. The ceramic suspension was produced and stabilized with hydroxyapatite powder, deionized water and polyethylene glycol 400. The slip was poured into gypsum mold. The green bodies were heat treated at 900 and 1100°C. Hydroxyapatite was the only phase present in all samples, before and after heat treatments. Density measurements showed that the densification was higher for the ceramic bodies sintered at 1100°C, when compared to the ones calcined at 900°C.

Limit Speed Analysis and Absorbed Energy in Multilayer Armor with Epoxy Composite Reinforced with Mallow Fibers and Mallow and Jute Hybrid Fabric

Epoxy matrix composites reinforced with up to 10, 20 and 30 vol% of continuous and aligned natural mallow fibers and 30 vol% of mallow and jute hybrid fabric were for the first time ballistic tested as personal armor against class III 7.62 mm FMJ ammunition. The ballistic efficiency of these composites was assessed by measuring the dissipated energy and residual velocity after the bullet perforation. The results were compared with that in similar tests of aramid fabric (Kevlar™) commonly used in vests for personal protections. Visual inspection and scanning electron microscopy analysis of impact-fractured samples revealed failure mechanisms associated with fiber pullout, rupture and layers delamination. When compared to Kevlar™, the mallow fiber and hybrid fabric composite displayed practically the same ballistic efficiency. However, there is a reduction in both weight and cost, which makes both, mallow fiber and hybrid fabric composites, a promising material for personal ballistic protection.

Ballistic Performance in Multilayer Armor with Epoxy Composite Reinforced with Malva Fibers

A multilayer armoring system (MAS) is commonly formed by three layers. The initial layer is normally composed by a ceramic with high compressive strength, which absorbs most of the kinetic projectile energy. The subsequent composite layer was formed by epoxy matrix reinforced with natural malva fibers (Urena lobata, Linn), in the form of pure or hybrid fabric with jute fibers, in order to absorb part of the kinetic energy, and to retain ceramic and projectile shrapnel. A third layer formed by aluminum alloy, was included as a penetration restrictor for bullet and fragments by plastic deformation. The ballistic efficiency was evaluated by penetration of the 7.62 × 51 mm ammunition into a clay witness backing the armor. The results showed a great potential by epoxy composites reinforced with malva fabric as compared to other natural fibers and materials traditionally used in personal protection, such as Kevlar™ aramid.

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.

Synthesis of Ag-Hydroxyapatite

Silver-bioceramics have a great potential to optimize the bone grafts materials to avoid microorganism infections on patients. The present study synthesized and characterized hydroxyapatite doped with silver (Ag), by an acidic route of precipitation method, and the proposal of the Ag-HA synthesis is to promote the bioactivity and bactericidal ability with less toxicity for organism. The samples were analyzed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analysis. There was a pronounced grain growth after 1100°C HA and AgHA heat treatments for both HA and Ag-HA powders, observed by FEG-SEM analysis. XRD patterns of AgHA sintered at 1100°C showed HA as the main phase, but also a secondary whitlockite phase. However, 100% HA was observed for the Ag-HA samples heat treated at 700°C and 900°C. However, pure HA showed decomposition at 900°C. The acidic route of precipitation method showed to be effective for silver-doped hydroxyapatite production.

Bioactivity Assessment of Calcium Phosphate Coatings

Nowadays, bioactive coatings or modifications on titanium surface have been tested in vitro and in vivo. In this study, two types of calcium phosphate coatings were produced by a chemical deposition method and their bioactivity assay in cell culture medium were investigated. The calcium phosphate coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with field emission gun (FEG-SEM) analyses. Titanium substrate was successfully coated with brushite using chemical deposition method and, after a second step of conversion, the hydroxyapatite coating was obtained. The hydroxyapatite coating showed a bioactivity property after 14 days’ incubation in McCoy medium culture.

Apatite Coatings from Ostrich Eggshell and its Bioactivity Assessment

In this work a two-step thermochemical deposition of calcium phosphate from ostrich eggshell on titanium surface was performed. After the deposition, the coatings were immersed into 0,1M KOH solution in order to favoring HA precipitation. The coatings were characterized by scanning electron microscope with field emission gun (FEG-SEM), and X-ray diffraction (XRD) analysis. Bioactivity assessment was performed in cell culture media, McCoy 5A medium, for 14 days. XRD patterns showed brushite/monetite as the phases present at first deposition step; in the second deposition step XRD patterns indicated HA phase peaks on titanium surface. After 14 days on McCoy 5A medium, brushite/monetite coatings revealed bone-like apatite precipitation, showing bioactivity; hydroxyapatite coatings showed a surface modification but no significant bone-like apatite precipitation, thus lower bioactivity. The use of ostrich eggshells as an alternative source to obtain bioactive calcium phosphate coatings showed to be effective.

Synthesis and Characterization of CaO-SiO2-MgO Bioactive Glass Produced by Sol-Gel

Bioactive glasses have widely used in biomedical applications such as bone filler due to their excellent biocompatibility, bioactivity and osteoconduction characteristics. In this work, a silicate-rich glass was synthesized by the sol-gel method with 60% SiO2 – 30%CaO – 10% MgO composition where fumed silica acts as the silica precursor. This new method was hypothesized to reduce the gel formation time, due to the high surface area of the fumed silica. In addition, this would presumably increase the nanoporosity of the glass. For comparison purposes, we used a glass of the same composition, but with the conventional silica precursor, tetraethyl orthosilicate (TEOS), through the sol gel method. Both were heat treated at 450°C. FT-IR analysis before and after heat treatment at 450°C showed the presence of nitrate groups, especially in the TEOS samples. This is consistent with the more hygroscopic aspect of those samples. The fumed silica samples had significantly less pronounced peaks corresponding to the nitrate groups, consistent with the more porous structure and the less hygroscopic aspect. The fumed silica samples indeed had a lower gelling time and showed similar results obtained by XRD and FT-IR analyses, showing that the use of fumed silica is viable and advantageous in the glass synthesis by the sol-gel process

Production of Borosilicate Glasses from Residues of Ornamental Rocks

In this work, glasses with compositions, close to commercial borosilicate glasses, were developed. The main raw materials were residues of ornamental rock industries ( marbles and granites ). Beach sand was used in order to enrich the compositions with silica. Also, boron oxide was added to reach borosilicate glasses compositions. The obtained glasses were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), and hydrolytic resistance. The measured properties were compared to those of commercial glasses, available in the market, from two different brands. XRD results confirmed amorphous patterns of the produced glasses. The other tests revealed an excellent agreement between the obtained values and those from commercial glasses. Therefore, this study showed the possibility of using ornamental rocks residues as primary sources to produce borosilicate glasses. In addition, it became clear that an economic value could be aggregated to the residues, which otherwise would be discharged into nature causing pollution.