Daltro Garcia Pinatti

Wood Cellulignin as an Alternative Matrix for Enzyme Immobilization

The objective of this work was to select an efficient methodology for preparing active samples of Candida rugosa lipase immobilized in wood cellulignin, to be applied in hydrolysis and ester reactions. For this purpose, lipase was immobilized in the matrix by physical adsorption (pure cellulignin) and covalent binding (activated cellulignin with glutaraldeyde or carbonyldiimidazole [CDI]) in the presence or absence of polyethylene glycol (PEG) (Molecular mass of 1500 Daltons) as stabilizing agent. The activating agent and the presence of PEG-1500 in the immobilization procedure showed a strong influence on enzyme retention in the support. The values for enzyme retention ranged from 20 to 68%, and the highest yield was obtained when the enzyme was immobilized in cellulignin activated with CDI in the presence of PEG-1500. This immobilized derivative presented high hydrolytic (193.27 microM/[mg.min]) and synthetic (522.92 microM/[g.min]) activities when compared with those obtained by other techniques. The superiority of this immobilized system was confirmed by additional analyses, such as infrared spectroscopy and elemental analysis, which demonstrated an appropriate enzyme fixation and the highest level of protein incorporation in the support. Further information on the immobilized derivative was obtained by assessing the recycle potential in both aqueous and nonaqueous media.

Mechanical behaviour of copper 15% volume niobium microcomposite wires

Cu-Nb microcomposites are attractive in magnet pulsed field technology applications due to their anomalous mechanism of mechanical strength and high electrical conductivity. In this sense, recently it was conceived the use of Cu 15% vol. Nb wires to operate as a high tensile strength cable for a diamond cutting tool (diamond wires) for marble and granite slabbing. The multifilamentary Cu 15% vol. Nb composite was obtained using a new processing route, starting with niobium bars bundled into copper tubes, without arc melting. Cold working techniques, such as swaging and wire drawing, combined with heat treatments such as sintering and annealing, and tube restacking were employed. The tensile property of the composite was measured as a function of the niobium filaments dimensions and morphology into the copper matrix, in the several processing steps. An ultimate tensile strength (UTS) of 960 MPa was obtained for an areal reduction (R = Ao/A, with Ao-initial cross section area, and A-final cross section area) of 4x108 X, in which the niobium filaments reached thickness less than 20 nm. The anomalous mechanical strength increase is attributed to the fact that the niobium filaments acts as a barrier to copper dislocations.

Effect of the Particle Size of an Ash from Sugarcane Bagasse in the Properties of Red Ceramics

The influence of the particle size of an ash from sugarcane bagasse on the properties of incorporated red ceramics was investigated. Mixtures of kaolinitic clay from the municipal area of Campos of Goytacazes-RJ were prepared with additions of 0, 5 and 10% in weight of ashes from sugarcane bagasse. Ashes with different particle sizes lower than 149 μm (100 mesh), 75 μm (200 mesh) and 44 μm (325 mesh), were used in each incorporated composition. Specimens were 20 MPa uniaxially press-molded and sintered at 900 and 1050°C. The firing technological properties evaluated were diametrical shrinkage, water absorption and mechanical strength by diametrical compression. The results showed that the ash incorporation caused significant changes in the ceramic properties.

Processing of diamond composites for cutting tools by powder metallurgy and rotary forging

This paper shows the manufacture route of the bronze 4% weight diamond composite rope for direct application as diamond wires, and linear saws in the slabbing and cutting of dimension stones. This route consists of powder mix compaction, sintering and rotary forging techniques. Tensile tests were performed, reaching an ultimate tensile strength of 230MPa for the diameter of O=1.84mm. Scanning electron microscopy showed the diamond crystals distribution along the composite rope during its manufacture, as well as the diamond adhesion to the bronze matrix. Cutting tests were carried out with the external cutting rope, showing a probable performance 4 times higher than the diamond sawing discs, however its probable performance was about 5 to 8 times less than the conventional diamond wires (pearl system) due to the low abrasion resistance of the bronze matrix, low adhesion between the pair bronze-diamond due to the use of not metallized diamond single crystals.

Influence of the Granulometry of Organic Matter Ashes from Municipal Solid Waste on the Properties of Vitrified Ceramics

This work studies the influence of the granulometry of organic matter ashes from the municipal solid waste (MOL) on the mechanical properties of vitrified ceramics. Mixtures of clay with additions of the MOL ashes were prepared as vitrified ceramics. The degree of immobilization of the potentially toxic metals (PTM) contained in the ashes was then evaluated. Samples of a sedimentary clay with 13.5% of MOL ashes with granulometry, 35 and 200 mesh, were uniaxially pressed at 18 MPa and sintered at 1200°C. Results from 3- point flexural resistance and water absorption tests showed that the reduction in the particle size of the MOL ashes increased the mechanical resistance to 45 MPa while the water absorption reached 0.8%. These results and the high degree of immobilization of the PTM qualify the ceramic vitrification as an alternative to the final disposal of the MOL.

Lithium Disilicate Glass-Ceramic Obtained from Rice Husk-Based Silica

In this work lithium disilicate glass-ceramic and glasses based on the Li2O-SiO2 system have been investigated by replacing the high-purity SiO2 starting powder by silica obtained from rice husk. Glasses were developed at the stoichiometric composition of 66%.molSiO2:33%.molLiO2 using SiO2 obtained by thermochemical treatment of rice husk. The influence of rice husk-SiO2 on phase formation, microstructure, hardness and fracture toughness was determined and discussed. Investigations were carried out by means of differential thermal analysis, X-ray fluorescence, X-ray diffractometry and scanning electron microscopy. Amorphous and transparent glasses were obtained after melting. The glasses presented Tg near to 480 0C, crystallization peak at 660 0C in both glasses from different silica sources and Li2Si2O5 as the crystalline phase after heat treatment. The hardness (HV300gF) presented average values near to 430 HV for both high-purity and rice husk silica powders. Fracture toughness measurements present results near to 1.7 MP am1/2 for both compositions.

A new route to process diamond wires

We propose an original route to process diamond wires, denominated In Situ Technology, whose fabrication involves mechanical conformation processes, such as rotary forging, copper tubes restacking, and thermal treatments, such as sintering and recrystallisation of a bronze 4 wt.% diamond composite. Tensile tests were performed, reaching an ultimate tensile strength (UTS) of 230 MPa for the diameter of AE = 1.84 mm. Scanning electron microscopy showed the diamond crystals distribution along the composite rope during its manufacture, as well as the diamond adhesion to the bronze matrix. Cutting tests were carried out with the processed wire, showing a probable performance 4 times higher than the diamond sawing discs, however its probable performance was about 5 to 8 times less than the conventional diamond wires (pearl system) due to the low abrasion resistance of the bronze matrix, and low adhesion between the pair bronze-diamond due to the use of not metallised diamond single crystals.

Characterization of Granulometric Fractions of Ash from Boiler Burnt Sugarcane Bagasse

In the municipal area of Campos dos Goytacazes–RJ several ceramic industries are involved with a significant production of bricks and tiles. These ceramic products can serve as matrices for the incorporation of industrial residues such as the ash of sugarcane bagasse used as fuel in the boilers of the sugar and alcohol plants. The incorporation of ashes in ceramics is a solution that eventually can cause an improvement on the properties of the material. The objective of this work is to characterize granulometric fractions of sugarcane bagasse ash with particle sizes less than 149, 75 and 44 μm aiming at the ash incorporation into red ceramics. Chemical, mineralogical and microstructural characterization were carried out in the granulometric fractions. The results showed that the granulometric fractions present as main crystalline phase the cristobalite and that the ashes with smaller particle sizes can improve the densification of the ceramic body by the formation of more liquid phase during firing, due to the presence of less silica and more alkaline- and alkaline-earth oxides than the original ash.

Parabolic Solar Collector Coverage Made of High-Performance Concrete with Addition of Active Rice Husk Silica Integrated to a Biomass Thermoelectric Unit

Production of active rice husk silica (ARHS) in bubbling fluidized bed boiler of a thermoelectric unit (TEU) and its addition to high performance concrete (HPC) with a compression resistance of 90 MPa was developed in the last 10 years. A first factory in Brazil was established at Alegrete town, RS, and other factories are under planning. Data of ARHS production, specification and HPC trace are presented. Design of parabolic solar collector coverage (PSCC) for air heating for biomass drying in a special silo of the TEU is presented as well. Cost of HPC/ARHS is 10 times less than steel (USD 200/ton vs. USD 2000/ton, specific mass 2.5 vs. 7.6 g/cm3, respectively). Those characteristics allow simultaneous solution of four ecological problems: large span coverage, rain water collection, daily solar energy collection and storage, and drying of biomass. The integration of those characteristics results in decrease of biomass consumption maintaining the same UTE efficiency. Tracking parabolic solar collector can be avoided between Cancer and Capricorn Tropics, and it is sufficient its eastern-western orientation with inclination to the Equator by the latitude angle. Coverage of the area occupied by TEU is sufficient to dry its biomass consumption. Preheating of boiler water with solar energy is possible decreasing biomass consumption in sunny days; biomass is partially consummed at night and cloudy days. Coupling the above technologies with high pressure steam TEU and fast-growing short-rotation forest gives to the biomass electrical energy generation a competitive economical position with hydraulic, coal, natural gas, and aeolic energy generation.

Crystallization process of a biomaterial, the lithium disilicate, obtained from rice husk silica

In this work, the crystallization process of lithium disilicate glass-ceramic was investigated with SiO2 from rice husk silica replacing the high-purity SiO2 starting powder form commercial source. Glasses were developed at the stoichiometric composition of 66%.molSiO2:33%.molLiO2 using commercial SiO2 and the one obtained by thermochemical treatment of rice husk. To compare the SiO2 sources, the influence of the one from rice husk on crystallization process was measured using different granulometry, analyzing microstructure and the kinetic behavior. Investigations were carried out by means of differential thermal analysis (DTA), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Amorphous glasses were obtained after melting at 1550°C. The position of lithium disilicate glass-ceramic crystallization peaks (Tp) are between 550 to 660°C to different granulometry (<63mm, 63mm < × < 250mm and 1mm < × < 2mm) and DTA heat rates (5; 10; 15; and 20°C/min) in both glasses, and the relevant formed crystalline phase after DTA analysis (verified for XRD) was Li2Si2O5. SEM images showed the increase of glass substitution for crystalline phase to both glass-ceramics from different silica sources.