Materials Science Forum Vols. 727-728

Abstract: The Calcium Phosphate Cement (CPC) are bone substitutes with great potential for use in orthopedics, traumatology and dentistry due to its biocompatibility, bioactivity and osteoconductivity, and form a paste that can be easily shaped and placed into the surgical site. However, CPCs have low mechanical strength, which equals the maximum mechanical strength of trabecular bone. In order to assess the strength and time to handle a CPC composed primarily of alpha phase, were added sodium alginate (1%, 2% and 3% wt) and an accelerator in an aqueous solution. The cement powder was mixed with liquid of setting, shaped into specimens and evaluated for apparent density and porosity by Archimedes method, X-ray diffraction and compressive strength. A significant increase in compressive strength by adding sodium alginate was verified.

Abstract: The calcium phosphate cements (CPCs) based on α-tricalcium phosphate (α-TCP) are highly attractive for use in medicine and odontology, since they have similar chemical and phase composition of mineral phase of bones (calcium deficient hydroxyapatite (CDHA)). However, one of the biggest difficulties for use of this type of cement is its low mechanical strength due to the presence of undesirable phases, such as β-tricalcium phosphate. The route for obtaining α-TCP is at high temperature by solid state reaction, mixing calcium carbonate and calcium pyrophosphate. The aim of this work was to obtain calcium phosphate cements with improved strength, by studying the obtaining of α-TCP at temperatures of 1300, 1400 and 1500°C. The samples were analyzed by crystalline phases, pH, setting time, particle size, in vitro test (Simulated Body Fluid), porosity, density and compressive strength. The results show that the synthesis temperatures influence strongly the phases of powders obtained and the mechanical properties of cement, being unnecessary quenching for obtaining pure α-TCP.

Abstract: The present work reports on the preparation of Al₂O₃-TiO₂ ceramics by high-energy ball milling and sintering, varying the molar fraction in 1:1 and 3:1. The powder mixtures were processed in a planetary Fritsch P-5 ball mill using silicon nitride balls (10 mm diameter) and vials (225 mL), rotary speed of 250 rpm and a ball-to-powder weight ratio of 5:1. Samples were collected into the vial after different milling times. The milled powders were uniaxially compacted and sintered at 1300 and 1500°C for 4h. The milled and sintered materials were characterized by X-ray diffraction and electron scanning microscopy (SEM). Results indicated that the intensity of Al₂O₃ and TiO₂ peaks were reduced for longer milling times, suggesting that nanosized particles can be achieved. The densification of Al₂O₃-TiO₂ ceramics was higher than 98% over the relative density in samples sintered at 1500°C for 4h, which presented the formation of Al₂TiO₅.

Abstract: Titanium and their alloys have been used for biomedical applications due their excellent mechanical properties, corrosion resistance and biocompatibility. However, they are considered bioinerts materials because when they are inserted into the human body they are cannot form a chemical bond with bone. In several studies, the authors have attempted to modify their characteristic with treatments that changes the material surface. The purpose of this work was to evaluate obtaining of nanoapatite after growing of the nanotubes in surface of Ti-7.5Mo alloy. Alloy was obtained from c.p. titanium and molibdenium by using an arc-melting furnace. Ingots were submitted to heat treatment and they were cold worked by swaging. Nanotubes were processed using anodic oxidation of alloy in electrolyte solution. Surfaces were investigated using scanning electron microscope (SEM), FEG-SEM and thin-film x-ray diffraction. The results indicate that nanoapatite coating could form on surface of Ti-7.5Mo experimental alloy after nanotubes growth.

Abstract: The selective internal radiotherapy is an alternative to treat hepatocellular carcinoma. Glass microspheres containing a β^- emitter radionuclide are introduced in the liver, and they concentrate preferentially in the region where the cancer cells are located. The microspheres are trapped in the arterioles which feed the tumors, and the β^- particles annihilate the cancer cells. The glass particles must be spherical to avoid unnecessary bleeding, and the particle size must be restricted to a range which optimizes the blocking effect. Glass microspheres can be produced by heating glass particles using a flame or in a hot zone of a furnace. The particle size distribution is not easily predicted since it depends on the variation of the aspect ratio and the presence of agglomerates. In the present work, the spheronization process to obtain microspheres with diameters appropriate for radiotherapy treatment is evaluated. Samples were characterized by X-rays diffraction and Energy Dispersive X-rays Fluorescence Spectroscopy. The glass dissolution rate was determined in water at 90°C, and in Simulated Body Fluid (SBF) at 37°C. Glasses with dissolution rates close to 10^-8 g/(cm².d) were obtained, which make them suitable for the present application. Scanning Electron Microscopy was used to evaluate the surface of the microspheres before and after the dissolution tests.

Abstract: In this study the subcritical crack growth (SCG) behaviors of five dental bioceramics were evaluated in order to plot the crack growth velocity versus stress intensity factor (v-K) curves. Disc-shaped samples of two sintered porcelains, two glass-ceramics, and a glass-infiltrated ceramic composite were prepared and tested in artificial saliva using a biaxial flexure jig. The SCG parameters were evaluated by the dynamic fatigue test using five constant stress-rates and in an inert condition. Among the tested materials, the lithium disilicate glass-ceramic showed the highest susceptibility to strength degradation by SCG, whereas the glass infiltrated alumina composite showed the lowest susceptibility. The v-K curves showed that the SCG susceptibility significantly affects the crack growth velocity of the different bioceramics.

Abstract: This paper reports the preparation of ferrite Ni_0,5Zn0,5Fe₂O₄ by combustion reaction in a microwave oven, and its structural, morphological and magnetic characterization. The influence of microwave power and the fuel type was investigated. The samples were characterized by: XRD, BET, SEM and AGM. The results showed the formation of phase ferrite Ni_{0, 5}Zn_0,5Fe₂O₄ in all conditions evaluated. The presence of secondary phase hematite and nickel were observed only in samples with glycine. The microwave oven power and the fuel type altered the structure, morphology and magnetic behavior of the samples. In general, the samples synthesized with urea are promising for applications in catalysis, ferrofluids, magnetic sensors and the samples synthesized with glycine are promising for use as absorber electromagnetic radiation, due to the large particle size and good magnetic characteristics observed.

Abstract: The areas of research, synthesis and catalytic application of zeolites as molecular sieves are a field of great development and prominence in recent decades. Needs of the industries of petrochemical and fine chemicals have been encouraging specific studies for the application of molecular sieves looking for technological, commercial, and more recently sustainable developments. In this work molecular sieves type Al-MCM-41 and Al-SBA-15 has been synthesized using new synthesis routes by replacing the silica source conventionally used by rice husk. The molecular sieves obtained were confirmed by X-ray diffraction. Through the thermograms the decomposition of the driver at different temperatures was noticed. According to SEM micrographs can be observed that the material shows an aggregate of relatively uniform short particles.

Abstract: Research, synthesis and catalytic application of molecular sieves areas has been constituting a large field of development and prominence in recent decades, due to the large potential of these materials in respect of theirs catalytic properties. The need for costs reduction in the production of these structures, has encouraged the search for new sources of reactants which could provide an equal application of these sieves together with low costs. This work has the aim to obtain and to characterize molecular sieves type MCM-41 and Al-MCM-41 using new routes of synthesis. The molecular sieves MCM-41 and Al-MCM-41 were synthesized using the molar composition: 1 Si0₂: 0.04 Al0₃: 0.24 CTAB: 0.3 Na₂O: 150 H₂0. Through the thermal analysis it was possible to observe different peaks related to the presence of volatile materials and the structural director in the materials. Using techniques of characterization like XRD was possible to confirm the formation of the mesoporous structures using the amorphous silica derived from rice husk ash as a silica source.

Abstract: The preparation of ZSM-5 templates in the absence of organics is an area of high technological impact. These are responsible for the enhancement of the final products (zeolites). Therefore, the preparation of zeolites in the absence of template allows a compromise covering the low cost and environment. This study aimed to investigate the influence of synthesis time in the preparation of ZSM-5. This zeolite was prepared by hydrothermal synthesis, using as co-template (C₂H₅OH) and addition of seeds. The times of synthesis used were 3 to 5 days. The solids were characterized by XRD, BET and Spectroscopy in the infrared region. Through the results obtained with XRD, it was observed that all samples showed characteristic peaks of MFI structure of the group at intervals of 2θ = 7-9° and 23-25°, showing no presence of secondary phases. BET surface area showed a corresponding literature. The infrared showed bands characteristic of ZSM-5.