Defect and Diffusion Forum Vol. 365

Abstract: The main purpose of this work is the energy saving by reducing friction and minimizing wear to avoid losses by raising the properties of nanomaterials on the surface layer. Therefore, we develop approaches for studying the tribological behavior phenomena concerning materials on surfaces of the layers to define the mechanical and tribological properties of materials to improve the surface layer materials of the treated parts. It was used for the vibratory grinding method of chemical mechanical processing surface using the technology of low-frequency vibration in the treatment of metal parts in the presence of chemical additives, which have a great influence on the improvement of mechanical and geometrical parameters (roughness, fatigue resistance, corrosion resistance, micro and macro hardness, structure) of mechanical parts. This method of vibratory grinding has great advantages such as the treatment of complex mechanical parts, the ability to process parts of different types and shapes at the same time. It is also known to be an environmentally friendly process. Thus this work consisted of a surface treatment by vibratory grinding of samples of different materials.

Abstract: Breakthrough curves (BTCs) obtained from column tests in heterogeneous soils are not satisfactorily simulated with the advection-dispersion equation (ADE) for some heavy tailed cases. Furthermore, the dispersion coefficient calculated with the ADE for heavy tailed BTCs are scale dependent when simulating columns of soil larger than the original test depth. In this paper we compare the usage of a fractional ADE (FADE) and the classical ADE to fit column tests BTCs made with Brazilian lateritic soils, discussing both contaminant transport theories and underlying stochastic models. The FADE can more accurately simulate heavy tailed BTCs, and when applying the adjusted FADE parameters to longer depths of soil, the FADE also predicts a more realistic scenario of contaminant transport through heterogeneous soil. The addition of fractional calculus in the advection-dispersion equation proves to improve contaminant transport predictions based on column tests over the classical ADE, with the use of a constant fractional dispersion coefficient that is scale independent.

Abstract: This paper discusses an application of neural network system on the performance of boride layer thickness. Boriding treatment was carried out in three different molten salts consisting of borax (Na₂B4O₇) added to boron carbide (B₄C), aluminum (Al) and silicon carbides (SiC). The substrate used in this study was XC38 steel. Borides layers involved in this work was obtained from a boriding treatment at the temperature range of 800-1050 °C with 50°C interval for 2, 4 and 6 h. A numerical experiment using normalized and binarized values was carried out, using a back-propagation algorithm in ANN. The modeling shows that for the three bath the depth of boride layer was predicted with good accuracy, with a highest performance of normalized values along experimental data range.

Abstract: The problem concerns the thermo-physical properties of the mould material to which the liquid metal is poured (foundry industry). In the foundry processes the sand mould fulfils an auxiliary role only as technological tool, but its physical and technological properties determine the quality of the casting. The study includes the iron plate casting experiments poured in multi-component porous sand mould. The temperature fields of casting and in different zones of the mould were recorded. The determining of the thermo-physical properties of mould sand in over-moisture zone using simulation tests in Procast system was the goal of our study. An originality of the related research is an attempt to take into account the effects of the global thermal phenomena occurring in the quartz sand bonded by bentonite-water binder, using the apparent thermal coefficients. The majority of foundry simulation systems are not capable to modeling the phase transformation of water into vapor, vapor transport and its condensation in porous media (mould). In these cases the application of apparent coefficients is an effective way.

Abstract: The macambira (Bromelia laciniosa) is a plant from the Bromeliaceae Family, Bromeliad genus, found in the Brazilian Northeast, highly resistant to dry climates. It has no commercial value. The aim of this study was to evaluate the potential of the macambira for ethanol production. For this, samples were collected in the rural area of Nova Floresta in the state of Paraíba, where the leaves were cut into small pieces, and then went through a process of drying in circulating air and went through a process of milling. The chemical characterization of the leaves was performed in order to determine the moisture, extracts, cellulose, hemicellulose, lignin and ash content. During the chemical characterization the following values were obtained; 8.14 ± 0.08% moisture, 7.49 ± 0.79% extracts, 28.49 ± 0.9% cellulose, 37.24 ± 0.9% hemicellulose, 5.42 ± 0.4% lignin 3.62 ± 0.1% ash. The pretreatment was performed with diluted acid to hydrolyze hemicellulose, and then acid hydrolysis was performed. Both were conducted in a stainless steel reactor with a capacity of 700 mL, with control of internal and external temperature. The concentration of sugars resulting from the acid hydrolysis was quantified using the technique of high performance liquid chromatography.

Abstract: Aiming at obtaining glucose, we studied the chemical pretreatment (NaOH + H₂SO₄) and the hydrolysis of sugarcane bagasse using as catalyst the acid-treated vermiculite clay. Samples of the bagasse before and after the treatment were characterized as to the fiber content and XRD. It has been found that the chemical pretreatment showed satisfactory results providing a decrease of 40% in the lignin content and of 43% in the hemicellulose content, regarding to the bagasse in natura. Catalytic tests in aqueous solution were performed at 200°C, to evaluate the use of vermiculite treated as a catalyst for the hydrolysis of sugarcane bagasse. The reaction product was filtered and the supernatant was analyzed by high performance liquid chromatography. A yield of 6.18% in glucose was achieved.

Abstract: Lignocellulosic wastes are the most abundant in the world and there is currently a global concern to harness them as biomass to produce cellulosic ethanol, being possible due to the materials being rich in cellulose. The main goal of this work is to produce the delignification from Sweet Sorghum waste free from extractives as well as the physico-chemical characterization in the natural state after being delignificated aiming to remove the lignin that acts as a barrier preventing access of the enzyme to the cellulose in the enzymatic hydrolysis processes. The following tests were performed: moisture, ash, cellulose, lignin, hemicelluloses, AR, extractives, XRD and SEM. Aftter the procedure of delignification, it was characterized as cellulose, lignin, XRD and SEM to check if there was removal of the lignin and if there was no change in crystallinity. The characterization showed that the Sweet Sorghum waste is a viable alternative for the production of bioethanol and proved to be an important source of cellulose presenting a content of glucose of 45.99 ± 0.63% and a lignin content of 14.63 ± 0.23%. The Sweet Sorghum waste was deslignificated by pulping with sodium hydroxide (NaOH) process, using as an experimental tool design type 2³ with 3 replications at the center point, to evaluate the effect of independent variables temperature, such as concentration of the NaOH solution and the time dependent variable in the delignification. The planning showed through the Pareto ́s diagram that the most influential variable in the process was the concentration which showed a response of 75.1258 and a greater interaction occurred on the variables temperature and concentration with a response of 1.653117. The regression model as well as being a statistically significant predictor, also presents a reason F calculated and F tabulated of 10.10 and achieving a maximum yield of 57.85% delignification. After delignification processes the waste showed a rate of 5.81 ± 0.18% lignin and 43.13 ± 0.53% cellulose , as well as an increase in crystallinity, verified by analysis of SEM and XRD .

Abstract: Different samples of pseudoboehmite were synthesized through the sol-gel process, using aluminum nitrate as precursor. The influence of variables on the product of the synthesis of pseudoboehmite was studied. The variables were the ageing temperature (25 and 130°C), addition or not of polyvinyl alcohol to the precursor solution and the ageing time of the PB. The pH adjustment of the precursor solution was made by using ammonium carbonate. The pseudoboehmites, which were obtained on different conditions, were then characterized by X-ray diffraction, thermal analysis (Differential Thermal Analysis and Thermo Gravimetric Analysis) and the desorption-absorption curves were obtained as well, in order to measure the pore volume of the samples and the specific surface area measurements through the BET method. Finally, the results were analyzed through an experimental factorial planning, which showed that high specific surface area pseudoboehmite was obtained.

Abstract: This paper presents the results of a defect structure investigation in commercially pure titanium alloy after hydrogen charging in a gaseous atmosphere at the temperature of 873 K up to the concentration of 5.1 at. %. Structure of samples was studied by positron lifetime, Doppler broadening and X-ray diffraction spectrometry. Several processes, corresponding to the different ranges of hydrogen concentrations were revealed. It was shown that hydrogen, penetrating in the material, expands its crystal lattice, initiates formation of vacancy-like defects of different dimensions and reacts with the last ones, forming the defect-hydrogen complexes.

Abstract: The mechanical and physical properties of epoxy-clay nanocomposites are known to be significantly affected by the dispersion and distribution of the clay particles in the epoxy matrix. The degree of dispersion of the clay particles in the epoxy matrix depends mainly on the processing parameters used to synthesize the nanocomposite.In this paper, the optimized high shear mixing parameters determined in an earlier work were used to disperse five different loadings of Nanomer I.30E nanoclay (1, 1.5, 2, 3 and 5 wt%) into DGEBA epoxy matrix. A systematic approach was adopted to optimize the degassing process of the mixture. X-Ray Diffraction (XRD) analyses showed that the optimum nanoclay dispersion was achieved for a degassing temperature of 120 °C. The flexural strength of the developed nanoclay/epoxy composite is found to increase by 15% for 1.5 wt% and due to the high stiffness of the clay, as compared with epoxy resin, the flexural modulus improved continuously with clay loading. The observed reduction in strength and fracture strain at high clay loadings is mainly attributable to the presence of clay agglomerations and voids formation. The diffusion of water molecules and maximum moisture uptake of epoxy are reduced considerably by the presence of nanoclay.