Materials Science Forum Vols. 775-776

Abstract: The present study reports obtaining biofuel by pyrolysis of plant oil and animal fat. This process consists in breaking of molecules at high temperatures, obtaining hydrocarbons, similar to oil, and oxygenates such as esters, carboxylic acids, aldehydes, etc. The research aimed to evaluate the thermal and kinetic behaviour and the heat of combustion of bio-oil and bio-oil mixtures / diesel oil. In this work, Thermogravimetric studies were performed (TG) at a heating rate of 10 ° C min^-1 under air atmosphere synthetic, Thermodynamic studies (ΔH, ΔS and ΔG) and about heat of combustion also were done. Thermal stability at 30°C was observed from thermogravimetric study. The kinetic calculations were performed in order to observe parameters such as activation energy (Ea) and Arrhenius factor.

Abstract: In this work suspensions containing natural amorphous silica fibers (NASF), amorphous silica gel and nanometric colloidal amorphous silica were prepared and rheologically analyzed. The suspensions were prepared by varying the volume percentage of solids between 22 and 32%, ammonium polyacrylate (APA), as dispersant, from 0 to 5% and polyvinyl alcohol (PVA), as binder, between 1 and 3.5%. The mixtures were obtained in a propeller mechanical mixer and formed by slip casting. The results of rheological characterization indicated that the suspensions with 30% solids, 4% dispersant and 3% binder were those that showed a stable rheological system and suitable for processing by slip casting.

Abstract: Porous glass-ceramics belonging to the Li₂O-ZrO₂-SiO₂-Al₂O₃ (LZSA) system were prepared by gelcasting. This processing technique associated to aeration of ceramic suspensions containing a foaming agent, allows the production of ceramics with high opened porosity (>90%), cell geometry tending to the spherical form, cellular interconnectivity and high green strength. In this work glass-ceramics foams were prepared by addition of different concentrations of foaming agents (Alkolan) and sintered at 750, 850 and 950oC for 30 min. The LZSA glass-ceramic foams were characterized by density, porosity, thermal shrinkage, microstructural analysis and mechanical strength. The morphological, physical and mechanical properties of the consolidated glass-ceramic foams indicated that the process of gelcasting may be a valid alternative to produce porous materials for applications at temperatures lower than 950°C.

Abstract: Ni-Ti-Nb system alloys show wide shape memory hysteresis, suitable for assembly applications. The microstructure is composed by NiTi matrix (with some dissolved Nb) and Nb dispersed particles (with some Ni and Ti content). These particles are to cause the hysteresis widening. This work evaluates the microstructure evolution during wire fabrication process of equiatomic Ni and Ti alloys with increasing Nb content (1.5, 3.0, 6.0 and 9,0%at.). It is shown that as-cast alloys with up to 9% at.Nb and near equiatomic Ni:Ti relation show three main microconstituents: NiTi matrix phase, interdendritic eutectic phase (NiTi + β-Nb) and Ti₃(Ni,Nb)₂ compound precipitates. It was observed that NiTi matrix phase and eutectic phase (NiTi + β-Nb) have ductile behavior while Ti₃(Ni,Nb)₂ compound have fragile behavior. There was not much hardness variation during hot swaging (200-300 HV) due to recovery and recrystallization processes. Mechanical hardening prevailed as the mechanism for increase hardness of cold worked samples from 200 to 450 HV.

Abstract: The incorporation of industrial residues into red clay ceramics has in past decades been used not only as a search for the alternative use of lower cost raw-materials but also an environmentally correct way of destination of polluting wastes. This work had as its objective to study the influence of incorporation of a quartzite stone residue on the mechanical strength of a red clay ceramic. Clay bodies were prepared with up to 40 wt% of the residue. These clay bodies were then uniaxially press-molded and sintered at 800 and 1050oC. The strength was evaluated by three points bend tests. The microstructural analysis was conducted by means of both optical and scanning electron microscopes. A tendency for decreasing the strength was found with the amount of incorporated residue. This was a consequence of the inert characteristic of the quartz, which is the predominant mineral in the quartzite stone, as well as the possible effect of cracks nucleated during the quartz allotropic transformation.

Abstract: For this workmixtureswere madewith three types ofPortland cement (CPII,CPIII, and CPIV), which were chosen because theyexhibit: good mechanical properties,lower heat ofhydrationgeneratedin the reaction, greater impermeability, greater resistance to environmentsaggressive.The objectwas to improve themechanical strengthofcementpasteswith the helpof experimental design. Ten different compositionswere prepared, which were tested forcompressivestrengthat 1 and14 days ofcuring. The results illustrated that the first day; the composition showed that the best result was composed of 50% of CP II and 50% of CP III. Already at 14 days, a paste made with 100% of CP III showed better results followed by composition made with 50%CP II and CP III 50%.

Abstract: In recent years the search for biodegradable polymers has excelled due to environmental issues. Among the biodegradable polymers from renewable sources, the poly (lactic acid) - PLA is one of the most widely used commercially, and several researches are being developed in order to improve their properties and thus increase its commercial applicability. Thus, this work aims to study the effects of incorporating polymer modifier (MBS Copolymer, Biostrength 150 - B150) and organoclay (Brasgel PA) in the properties of PLA. The study was conducted in two stages: with and without clay, and both with the B150. The concentrations used were 90/10 (PLA / modifier) and 3pcr (parts per hundred resin) of organoclay. The results showed that the mechanical properties of tensile and impact PLA significantly improved by using the polymeric modifier, indicating a gain in impact strength without a significant loss in modulus of elasticity.

Abstract: The development of biodegradable polymer composites is a promising alternative for obtaining environmentally friendly materials. The aim of this study was to develop polyhidroxybutyrate (PHB) composites with rice husk ashes and evaluate mechanical properties by tensile tests, determining stress and elongation at break and modulus of elasticity, flexural strength test and Izod impact tests, as well as density and hardness. The composites showed impact strength up to 25% greater than the polymeric material containing only PHB. Also for the testing of tensile strength in bending showed significant improvements in the composites up to 15%. The results indicate that the ash as filler in PHB is viable for applications in materials that already use the PHB in pure form, considering the technical aspects studied (processing and properties) and the environment, since in most tests there was a gain or maintenance of properties when compared to PHB.

Abstract: This work aimed to develop an alumina composite reinforced with polycrystalline alumina fibers to increase the mechanical properties of the product. A water-based processing was carried out, replacing the use of toxic and flammable organic solvents. The forming technique used was tape casting, which in addition to reliability and low cost, enables to make thin, flat tapes. The parameters for the tape casting process were: gap between the blades of 350 μm and casting speed of 12 cm/min. The process was optimized through a rheological study and alumina suspension with 50 wt.% solids was used. The slurry showed a pseudoplastic behavior and a high value of thixotropy. Several methods for separation and processing of the fibers were tested and a scattering using a specially designed support was the most efficient option. The tapes were thermopressed at 65°C and 30 MPa. The tensile test of green tapes showed a significant increase of the mechanical resistance for fiber-reinforced tapes, which was also dependent on fiber orientation.

Abstract: The increase amount of industrial wastes is becoming a serious worldwide environmental problem, which is aggravated by wastes containing toxic substances. This is the case of fluorescent lamps that use mercury vapor for light emission. At the end of their operational life these lamps should not be directly disposed to avoid the Hg toxic effects. Decontamination procedures take the Hg away but leave the other parts of the lamp as solid wastes. The mains part is the lamp glass, which finds many ways to be recycled. In the present work a fluorescent lamp glass waste was investigated as a possible material to be incorporated into a cement matrix as part of a civil construction concrete. Different amounts of waste up to 20 wt% were mixed with sand, gravel and cement to prepare concrete samples that were tested for the mechanical strength and water absorption in intervals of time until complete cure at 28 days. Although the waste failed to show pozzolanic activity, the incorporated concretes attended the required technical specifications.