Semiconductors films have many applications, energy conversion is one of the main ones. Oxides are often the material used to fabricate these films. Electrophoresis technique can deposit oxides semiconductors at different voltages and time. Films of zinc oxide (ZnO) were electrodeposited on conductive glass, adding weight percentage of tin chloride to improve its photo catalytic properties. The films and cells were characterized by X-ray, UV-Vis and EIS. The characterization showed that higher voltage decreased the band gap value from 3.3 to 3.26 eV, below the average for pure zinc oxide, around 3.30. The films acted as photoanodes in solar cells, with maximum current density of 2.88 mA/cm2 and open circuit of 0.68 V. The synthesis method was efficient and can be used for further reseach into semiconductors’ films and be applied for membranes, photoanodes and other applications.

This paper presents a case study regarding the hard turning of tool steel specimens when some insidious surface patterns were observed beyond the usual parallel feed marks. An optical three-dimensional measuring device was used to characterize and compare common reference surfaces and textured profiles. Subsequently, these data were analyzed using an image processing computational tool, through which it was possible to infer that, indeed, the surface with an unusual appearance exhibited a very well-defined orientation texture. The vibration monitoring data during the turning process of the samples were then compared through spectral density analysis of the signal, from which a dominant frequency was observed in the range of 3100 to 3300 Hz for both, but with a considerably higher amplitude peak for the textured one, indicating an unstable cut, i.e., one subjected to excessive vibrations. Finally, the experimental modal analysis performed on the tool used identified a fundamental frequency of the same order of magnitude, which allows for establishing a potentially causal correlation between the occurrence of chatter and the obtaining of the textured surface. This technique may be a pleasant opportunity to improve the tribology performance of tools, as the potential of textures are well presented in recent studies.

Although biocomposite foams have been used as wound dressings, achieving accelerated healing with reduced complications requires precise control of exudate absorption and evaporation. This study evaluated the fluid handling capacity, water vapor transmission, and cytotoxicity of novel chitosan/bioactive glass composite foams. Prepared following a simple process, these foams have up to 60% porosity and interconnected pore networks. Cytotoxicity assays confirmed their non-toxicity to L-929 fibroblast cells. The foams demonstrated a liquid absorption capacity of up to 160%, with improved performance at higher levels of bioactive glass. Fluid handling tests showed effective moisture absorption and transfer, making these dressings suitable for the treatment of wounds such as burns and pressure ulcers. The water vapor transmission test confirmed the ability of the foams to promote high exudate removal rates, suggesting that chitosan/bioactive glass composites are promising for wound dressing applications.

Zirconia woodpile scaffolds (3Y-TZP/PL, n = 20), designed with null inter-filament spacing, were manufactured using the Direct Ink Writing (DIW), an extrusion 3D printing technique. A ceramic ink containing 40%v/v 3Y-TZP powder, 59%v/v PEG (Polyethylene glycol)/Laponite ink, and 1%v/v DBP (Dibutylphthalate) was used. For 3D printing, we used Ø 0.63 mm nozzles, a printing speed of 10 mm/s, a cross-layer deposition strategy, and no air gaps between filaments. The scaffolds were sintered at 1550 °C for 2 h. The mechanical characterization involved measurements of X-ray diffraction, scanning electron microscopy, Vickers microhardness, Vickers nanohardness, and modulus of elasticity and compressive strength. The sintered samples showed predominantly the ZrO2-tetragonal phase and a microstructure characterized by a bimodal distribution of grain sizes. The samples had a relative density of 90.1 ±1.5%, a Vickers microhardness of 1172 ±45 HV, a Vickers nanohardness of 1608 ±78 HV, a modulus of elasticity of 203 ±16 GPa, and a compressive strength of 192 ±54 MPa. The results showed that DIW processing followed by proper sintering is a promising method for making zirconia scaffolds for biomedical applications.

Over the last decades, high-entropy refractory alloys with shape memory (SM) effect have been increasingly studied. However, identifying the optimal composition among the vast array of potential systems remains a significant challenge for the scientific community. In this work, Ni-Ti alloys are studied via molecular dynamics simulations to determine the range of martensitic phase transformations, with the goal of developing in the future medium- (MEA) and high-entropy alloys (HEA) that exhibit SM behavior. Virtual samples with compositions of Ni(100-x)Tix (45 < x < 55) were created using the LAMMPS software, in a system consisting of 2000 atoms that interacted under the modified embedded atom method (MEAM) interatomic potential. In addition, simulations were also performed on systems with sizes of 4000 and 8000 atoms to assess the effect of system size on the phase transformation behavior. The structural evolution and phase transformations were analyzed by applying heating and cooling rates of 1 K/ps, controlled by the isothermal-isobaric (NPT) ensemble. The compositional range, in atom percent, for martensitic transformations was found to be 47.5 to 52.5% nickel. Martensitic transformations are complex, showing either direct or two-step transformations. At lower temperatures, the phases R and B19’ can be formed as a function of Ni content. In several cases, at intermediate temperatures, the Ni4Ti3 compound forms and influences the phase transformation process. Also, the larger the system size, the lower the phases transformation temperatures.

Homogeneous and stable ceramic suspensions with high solids loading and low viscosity pose a significant challenge in vat photopolymerization additive manufacturing, once solid particles tend to increase viscosity. Instead, organic materials can contribute to decrease viscosity and post-sintering shrinkage. A base suspension was formulated using PEGDA along with dispersant DISPERBYK-111 (3 wt.% of the monomer powder), zirconia powder (40 vol.%), n-methyl-2-pyrrolidone (10% vol.), and a photoinitiator (2 wt.% of the monomer). The introduction of 10 vol.% solvent resulted in a 22.6% reduction in the suspension viscosity. The average post-sintering shrinkage measured 26.11% across all three dimensions. Sintered components exhibited an average density of 5.95 g/cm3 and an average flexural strength of 256 ± 49 MPa. Additionally, the parts demonstrated anisotropic tribological behavior, low porosity and low surface roughness for polished (Ra 0.032) and untreated (Ra 0.33) surfaces. It was concluded that incorporating minimal amount of solvent into ceramic suspensions does not adversely affect their rheological and mechanical properties, while ensuring satisfactory surface quality of the sintered components.

In this research study, Aluminium-based alloy (AA6092) reinforced with 3 wt.% Boron Carbide (B4C) and 5 wt.% Zirconium dioxide (ZrO2) particulates was fabricated into Aluminium Metal Matrix Hybrid Composites (AMMHCs) via stir casting. These AMMHCs were subsequently friction-stir welded under various conditions to optimize the ultimate tensile strength (UTS) and weld nugget hardness (WNH) of the welded joints. This innovative AMMHC material is replacing the AA6061, and AA6082 composites for the applications like bulkhead partitions in ship hulls since this AMMHC has superior properties such as reduced weight, enhanced specific strength, and lower thermal expansion coefficient. To optimize the performance of friction stir welded butt joints in AA6092/3% B4C/5% ZrO2 composites, key Friction Stir Welding (FSW) process parameters including Tool Rotational Speed (TRS), Welding Speed (WS), Axial Load (AL) and Tool Tilt Angle (TTA) were examined. In this research work, empirical relationships were established between the most influential parameters (TRS, WS, and AL) and the resulting responses (UTS and WNH). A desirability function approach was employed to predict optimal values for UTS and WNH, leading to recommended process parameters of 1279.18 rpm for TRS, 53.54 mm/min for WS, and 4.9 kN for AL and TTA for 1.5°. The calculated UTS, and WNH values of 513.09 MPa and 194.92 HRB, respectively, were subsequently validated through experimental verification.

This study presents the results of constructing the master curve through dynamic mechanical analysis (DMA) of unidirectional composites made of glass fiber and epoxy resins of classes F and H to evaluate the thermal stability and durability of these materials. For this purpose, the viscoelastic behavior of the polymers and composites was evaluated using the time-temperature superposition (TTS) model, applying the empirical Sigmoidal equation and the Williams-Landel-Ferry (WLF) method to estimate the behavior at different temperatures. This approach allows the extension of experimentally accessible frequencies and the description of the entire relaxation behavior of the polymers. The time-temperature shift factor was determined from the DMA curves, generated from individual isotherms at different oscillation frequencies. It was observed that the viscoelastic behavior depends on both frequency and temperature, with a general equivalence between the behavior related to frequency and temperature during the transition processes. The composite materials manufactured by filament winding were also subjected to physical and thermal characterization through differential scanning calorimetry (DSC) and DMA, ensuring the consistent quality of high-performance structural composites. Once the time-temperature shift factors were described by the model, the master curve could be extrapolated to any desired temperature, reducing the need for extensive empirical testing.

P91 steels are widely used in power plants. They were developed in a context of increasing process temperatures to increase efficiency and reduce CO2 emissions into the atmosphere. In this sense, the energy industry aims to increase its efficiency and process control, for which temperature control is essential and welding thermocouples in P91 steel pipes may be necessary. In this context, this study aims to evaluate, in a preliminary way, the influence of welding thermocouples in P91 steel specimens subjected to fatigue testing. The results showed that in general there is a decrease in fatigue life, more prominent for 90 and 80% of the load. In addition, the insertion of defects such as welding points increases the probability of the initiation of fatigue cracks in the welded areas due to loss of properties. From 70% of the load onwards, infinite fatigue life was achieved for the welded and as suplied cases, and in both conditions the same fracture shape was obtained, observed macroscopically.

Tungsten carbide (WC) is a highly relevant material due to its exceptional catalytic properties and applications in composite materials and cutting tools. The production of nanocrystalline and ultrafine WC powders contributes to enhanced properties in these applications. Therefore, this study aims to obtain nanocrystalline WC powders with a high surface area from ammonium paratungstate (APT) derived from scheelite concentrate. To achieve this, a gas-solid reaction (carbothermal reduction) of APT was carried out at different temperatures under a mixed H2/CH4 atmosphere. The results showed that the WC powders obtained at 850°C present a higher purity with a crystallite size of 15.8 nm composed of agglomerates of ultrafine particles of 159 μm.

Metallic cobalt is valued for its thermal and corrosion resistance. In 2018, cobalt prices surged to 95,250 USD/t, fueled by the growing electric vehicle market. However, metallurgical challenges persist, including cost reduction and impurity control. Manganese, a frequent impurity in cobalt electrowinning from laterite and copper ores, can reach up to 560.6 mg·L−1 in leach solutions. Though solvent extraction removes ~90% of manganese, residual amounts impact current efficiency (CE), specific energy consumption (SEC), and deposit quality. Electrowinning tests at 200 A·m−2, 60°C, and pH 4 showed that 0.12 g·L−1 Mn2+ increased CE to 92.2% but raised SEC to 1.96 kWh·kg−1. Mn2+ altered deposit morphology, reducing microhardness and increasing brittleness. Thermogravimetric analysis revealed ~1.35% mass loss in deposits with Mn2+, while higher concentrations enhanced residual strain and enlarged crystallite sizes. Deposits exhibited primarily hexagonal close-packed (HCP) structures with occasional face-centered cubic (FCC) phases.

Polyhydroxybutyrate (PHB) is a crystalline and linear biopolymer that is biodegradable and biocompatible. However, due to its high crystallinity, PHB is rigid and brittle, limiting its applications. The brittleness of PHB can be reduced by incorporating reinforcing fillers. In this context, this study aimed to produce biodegradable composites based on a PHB matrix and mica, as a filler. Scanning electron microscopy (SEM) revealed the lamellar structure of mica within the PHB matrix. Fourier-transform infrared spectroscopy (FTIR) confirmed characteristic mica vibrations, while X-ray diffraction (XRD) identified crystalline phases from both PHB and the filler. Differential scanning calorimetry (DSC) demonstrated mica’s effect on crystallinity. Thermogravimetric analysis (TGA/DTG) showed increased thermal stability, with Tonset rising from 144 °C (pure PHB) to 212 °C (PHB/mica 12%) and Tmax from 207 °C to 260 °C. Tensile testing indicated reduced stiffness, from 413 MPa (pure PHB) to 333 MPa (PHB/mica 12%). These findings highlight mica’s role in modifying PHB’s structural, thermal, and mechanical properties, addressing gaps in the literature regarding this composite system.

This research examines the effect of thermal power plant desulfurization by-products on pipeline carbon steel alloy corrosion dynamics in soil aqueous solutions to improve soil properties and decrease carbon steel pipeline corrosion rates. Electrochemical tests such as chronopotentiometry, potentiostatic polarization, and electrochemical impedance spectroscopy (EIS) assessed corrosion behavior. Adding desulfurization by-products to soil solutions (DBS) created a transpassive layer during potentiostatic polarization, with a passive current density of about 10μA.cm-2. EIS measurements showed a substantial increase in polarization resistance, with the DBS exhibiting nearly 700 times higher resistance than the standard soil solution (SSS) at 0V (OCP). Raman spectroscopy identified lepidocrocite (γ−FeOOH) in the DBS-treated coupons, while maghemite and akaganeite were found in chloride-enriched conditions.AFM analysis indicated heightened surface roughness with DBS addition, especially with NaCl. XRF and FTIR spectroscopy of the waste products identified them as primarily composed of silica, aluminosilicates, and oxides of calcium, magnesium, and aluminum. The results elucidate DBS's impact on soil corrosion and suggest methods to mitigate corrosion in industrial and environmental contexts. This study enhances the understanding of buried pipeline corrosion mechanisms and presents a new use of thermal power plant waste for corrosion protection.

This work aims to deposit silica (SiO2) on polyamide 6,6 fabrics by hybrid corona-dielectric barrier discharge plasma at atmospheric pressure. The reactor used, developed at the Laboratory of Plasma and Processes of the Aeronautics Institute of Technology (LPP/ITA), allows the treatment of fabric surfaces by activation and plasma deposition processes, aiming, in this order, the alteration of wettability and the deposition of silica on its surface, using a silicic acid solution (Si(OH)4) as a silica precursor. The morphology of the deposited films was evaluated by scanning electron microscopy (SEM). To identify the chemical modifications generated by the plasma treatment, the untreated and treated samples were analyzed by Fourier transform infrared spectroscopy with attenuated reflectance (FTIR-ATR) and Energy Dispersive Spectroscopy (EDS). The thermal behavior of the treated and untreated samples was evaluated by Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Additionally, X-ray diffraction (XRD) was also used to identify crystalline phases in the film. The results showed that plasma processing proved to be an effective technique for modifying the surface characteristics of polyamide 6,6.

This study characterized wastes from scheelite and columbite-tantalite mining, as well as kaolin processing, to produce microfiltration membranes for wastewater treatment using a fast-sintered process. After characterization, the wastes were mixed with clays, pressed, and sintered at low temperatures of 1050 and 1100 °C. The resulting membranes exhibited pore size distributions ranging from 3 μm to 180 μm and flexural strengths exceeding 14 MPa. In a crossflow filtration system, permeate fluxes ranged from 177 L/h.m2 to 228 L/h.m2 at 2 bar, with permeabilities from 99 to 130 L/h.m2 bar depending on the waste content. Membranes with smaller pore sizes effectively removed 90% to 96% of turbidity from a water/clay suspension containing micrometric clay particles. This approach demonstrates that rapid sintering of ceramic membranes from mining waste can effectively reduce environmental impacts and energy costs, providing a sustainable solution for wastewater treatment.