Felipe Amorim Berutti

Environmental and technical aspects of the utilisation of tannery sludge as a raw material for clay products

This paper is a report on the results of a feasibility study on the immobilisation of tannery sludge by producing a ceramic product. The main purpose of this work was to test the clays used in the manufacture of a ceramic that could incorporate tannery sludge. The raw materials, tannery sludge and clay, were mixed together in different proportions. The ceramic specimens were characterised with respect to water absorption, porosity, linear shrinkage and transverse rupture strength. Leaching tests, in accord with the Brazilian and German regulations, were done on ceramic bodies made with different additions of sludge. In order to evaluate the possibility of air contamination during the firing process, preliminary studies of air emissions were carried out The mechanical properties of the samples evaluated were similar to those specified for ceramic bricks. All the leaching tests have shown that the main sludge contaminant i.e. chromium, could be immobilised within a finished ceramic product. The studies of air emissions have shown that zinc and chlorine are mainly collected from gas emissions and hence are not immobilised by the ceramic system. The study shows that the properties of the ceramic materials produced are acceptable for applications such as bricks for the building industry.

Electrospun TiO2 Fiber Composite Photoelectrodes for Water Splitting

This work has focused on the development of electrospun TiO2 fiber composite photoelectrodes for hydrogen production by water splitting. For comparison, similar photoelectrodes were also developed using commercial TiO2 (Aeroxide P25) nanoparticles (NPs). Dispersions of either fibers or P25 NPs were used to make homogenous TiO2 films on fluorine-doped SnO2 (FTO) glass substrates by a doctor blade (DB) technique. Scanning electron microscopy (SEM) analysis revealed a much lower packing density of the DB fibers, with respect to DB-P25 TiO2 NPs; this was also directly reflected by the higher photocurrent measured for the NPs when irradiating the photoelectrodes at a light intensity of 1.5AM (1 sun, 1000 W/m(2)). For a better comparison of fibers vs. NPs, composite photoelectrodes by dip-coating (onto FTO) TiO2 sol-gel (SG) matrixes containing an equal amount (5 or 20 wt %) of either fibers or P25 NPs were also investigated. It emerged that the photoactivity of the fibers was significantly higher. For composites containing 5 wt % TiO2 fibers, a photocurrent of 0.5 mA/cm(2) (at 0.23 V vs Ag/AgCl) was measured, whereas 5 wt % P25 NPs only provided 0.2 mA/cm(2). When increasing to 20 wt % fibers or NPs, the photocurrent decreased, because of the formation of microcracks in the photoelectrodes, because of the shrinkage of the sol-gel. The high photoactivity of the fiber-based electrodes could be confirmed by incident photon to current efficiency (IPCE) measurements. Remarkably, the IPCE of composites containing 5 wt % fibers was between 35% and 40% in the region of 380-320 nm, and when accounting for transmission/reflection losses, the absorbed photon to current efficiency (APCE) was consistently over 60% between 380 nm and 320 nm. The superior photoactivity is attributed to the enhanced electron transport in the electrospun fibers, with respect to P25 NPs. According to this study, it is clear that the electronic connectivity ensured by the sol-gel also contributes positively to the enhanced photocurrent.

Synthesis of CeO2 and Y2O3-Doped CeO2 Composite Fibers by Electrospinning

Electrospinning was employed to produce homogeneous inorganic-organic composite fibers from alcohol solutions containing polyvinyl butyral (PVB) and precursor of yttrium and cerium ions. Upon heat treatment, ceria and yttria-doped ceria fibers were obtained. The fibers retained the original morphology observed in the as-spun composition. X-ray diffraction was used to identify the crystalline phases of the final products. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and BET analysis were employed to study the ceramic-phase formation and the morphological evolution of the fibers. Thus, uniform ceria and yttria-doped ceria fibers several micrometers long of high-phase purity were produced. The CeO2 and the CeO2 with Y2O3 fibers presented average diameters that ranged from 0.8 to 1.7 µm, and the distribution of specific surface ranged from 24 to 127 m2/g after heat treatment at 1000°C.

Application of titania fibers obtained by electrospinning in photocatalytic degradation of methyl orange

Composite fibers of polyvinylpirrolidone and titanium propoxide were prepared using the electrospinning technique. Titanium oxide fibers were obtained on heat treatment of this composite. These fibers were characterized by means of specific surface area, thermal analysis, X-ray diffraction and electronic microscopy processes. Evaluation of their photocatalytic activity was carried out in comparison with the nanometric powder TiO2 P25 from Degussa as reference. The photo-oxidative decomposition of methyl orange was followed by ultraviolet-visible spectroscopy to determine the acid- and basic pH values. The heat treatment of these fibers at higher temperatures led to a decrease in the anatase phase responsible for their photoactivity. The heat treatment, the phases of the material, the pH of the medium, and the surface area affected the physical-chemical and photocatalytic properties of the titania fibers.

Designing of TiO2/MWCNT Nanocomposites for Photocatalytic Degradation of Organic Dye

The nanocomposites were obtained from commercial multi-walled carbon nanotubes (MWCNTs) and with titanium tetra propoxide as TiO2 precursor, and heat treated at 400°C and 500°C to form crystalline phases of TiO2. The nanocomposites were investigated for their photocatalytic activity, employing them as catalysts in the degradation of organic methyl orange dye in an aqueous solution under UV radiation. The results were associated with the characteristics of the nanocomposite structure, using techniques such as x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Optical characterization was obtained by photoluminescence spectroscopy and diffuse reflectance spectroscopy. The highest photocatalytic efficiency was observed in the TiO2–MWCNT nanocomposites obtained in an acid medium and heat treated at 500°C. These results could be associated with the lower transition energy and level of defects in the TiO2 of these nanocomposites when compared to the other samples.

High-Energy Milling

Nanoparticles can be produced by mechanical attrition. Such nanoparticles are formed in a mill in which energy is used to transform course-grained materials into nanostructured powders. The particles themselves can have a size distribution of less than 100 nm, called a nanoparticle, or, as is common in materials milled using mechanical attrition, the product is highly crystalline, and the crystallite size after milling is between 1 and 10 nm in diameter, called nanocrystalline materials [1].

Electrospinning and characterisation of ceria doped yttria fibres

Abstract Homogeneous inorganic-organic composite fibres were produced using electrospinning technique from alcoholic solutions containing polyvinyl butyral and precursors of yttrium and cerium ions. Upon heat treatment, ceria and yttria doped ceria fibres retaining the original morphological features observed in the as spun composition were obtained. X-ray diffraction was used to identify the crystalline phases of the final products. Scanning electron microscopy, thermogravimetric analysis, differential thermal analysis and Brunauer-Emmett-Teller analysis were used to study the ceramic phase formation and the evolution of morphological features of the fibres. Thus, several micrometres long, uniform ceria and yttria doped ceria fibres of high phase purity were produced. The CeO2 and the CeO2 with Y2O3 fibres presented average diameter that ranged from 19 to 25 μm, and the distribution of specific surface ranged from 33 to 43 m2 g−1.

The Effects of pH on the Preparation of Alumina by Sol-Gel Process

ABSTRACT This article describes the effects of pH on the preparation and properties of aluminas (A l 2 O 3) produced by the sol-gel colloidal method. The precursor, hexahydrated aluminum chloride, was subjected to peptization reactions giving rise to a viscous gel with amorphous characteristics. Calcination at temperatures about 1000°C caused this gel to transform into alumina products with different morphologies, such as powders, fibers, or porous ceramic bodies, depending on the process parameters adopted, such as the pH and the drying conditions. These products were characterized according to their particle size distribution, thermogravimetry and differential thermal analysis (TG/DTA), and X-ray diffraction (XRD), and their morphologies were analyzed by scanning electron microscopy (SEM).

Effect of electrospun Phb and Hap-Phb composite scaffolds characteristics on mesenchymal stem cell growth viability

Repairing bone and tissue defects caused by trauma, cancer and neonatal disease is still a major challenge in medical and dental fields. Professionals in these areas are often faced with using a graft to aid the recovery of the affected areas. Grafts can be classified according to their origin as autogenous (autograft), allogeneic (from a donor of the same species) or alloplastic (biomaterials). The injured or missing tissues are typically filled with autogenous graft [1]. However, the removal of an autogenous graft often results in greater morbidity to the patient, local pain and infection, and the process prolongs surgical time and increases the cost of the procedure [2]. In contrast, allografts from tissue banks have been successfully used to repair tissue loss. However, using allografts is associated with limitations such as immunological compatibility, transmission of pathogens and the need for immunosuppressive drugs because of the risk of rejection [3]. In recent years, the field of tissue engineering has sustained significant progress due to the emergence of nanotechnology. Some studies have indicated that the use of nanostructured features on the surface of frameworks leads to increased tissue regeneration [4]. The pursuit of improving the properties of these frameworks via nanotechnology in conjunction with stem cells is a new frontier for bone and tissue regeneration. Among the different scaffolds types, the ones that has fibrous architecture resembling the fibrillar structure of the ECM showed better support for the cell attachment and proliferation In this context, the electrospinning technique is an effective way to obtain fibers and membranes suitable for a tissue engineering scaffold [5]. The electrospinning technique uses a high electrical potential applied to a polymer solution through a conductive capillary and a grounded collecting support. The increase in the voltage that suppress the surface tension of the solution causes an ejection of a charged jet that is stretched by the electric potential, the solvent is evaporated and fibers are deposited on the collector surface [6]. In an attempt to improve the properties of such frameworks, it is assumed that providing specific nanostructured cell binding sites promotes cell differentiation. Therefore, in order to obtain scaffolds that mimic tissue and bone ECM, it is essential to understand the effect of the parameters in the fiber manufacturing process of these frameworks when using the electrospinning technique. It is also necessary to correlate their microstructural features with the stem cells biocompatibility and the production of a mineralized matrix.

CCVD Synthesis of Carbon Nanotubes

Since their discovery in 1991 by Sumio Iijima [1], carbon nanotubes (CNTs) have generated enormous interest in the area of both fundamental and applied research, in view of their exceptional mechanical, thermal and electronic properties [2].