The Effect of Surface Pretreatment of Aluminum Alloy 7075-T6 on the Subsequent Inhibition by Cerium(III) Acetate in Chloride-Containing Solution

The study aimed to investigate the effect of surface pretreatment on the corrosion protection of aluminum alloy 7075-T6 in sodium chloride solution using cerium acetate as a corrosion inhibitor. Different surface pretreatments were tested: (i) mechanical grinding, (ii) mechanical grinding and non-water diamond polishing, (iii) mechanical grinding, alkaline etching with NaOH and acid desmutting, and (iv) mechanical grinding, alkaline cleaning with a commercial SurTec cleaner and acid desmutting. Topography, composition, and morphology of inhibited surface during immersion were investigated using optical microscopy, 3-D profilometry, scanning electron microscopy/energy-dispersive X-ray analysis and Fourier transform infrared spectrometry. The corrosion properties were determined by potentiodynamic measurements and electrochemical impedance spectroscopy in sodium chloride solution without and with the addition of cerium acetate. A change in the composition and morphology of the inhibited surface was noticed as a function of surface pretreatment and immersion time. Appropriate surface treatment resulted in improved protection against localized corrosion even after long-term immersion up to 1 month. Among mechanical pretreatments, polishing gave better results than grinding. Among chemical pretreatments, alkaline cleaning in SurTec/HNO3 was more appropriate as a preceding step to acid desmutting than alkaline etching with NaOH.

Preparation of ZnO/Brucite Functional Composite Powder by the Mechanochemical Method

In this experiment, ZnO/brucite composite powder was prepared through the mechanochemical method; further, the properties, particle morphology, and structure of the composite powder were characterized. The results show that mechanical grinding action can promote the production of a large number of surface ions with unsaturated coordination number on the surface of brucite and ZnO particles, thereby promoting hydroxylation of the particle surfaces. The addition of NaOH to the composite system can also aid the further activation of the surface of the brucite and ZnO particles and the formation of more associated hydroxyl groups. Finally, a core–shell composite powder is formed with weak forces such as hydrogen bonds and van der Waals forces as the connecting bonds.

Contribution to Improvement of Fatigue Properties of Zr-4 Alloy: Gradient Nanostructured Surface Layer versus Compressive Residual Stress

The gradient nanostructured (GNS) layer forms beneath the surface of Zr-4 samples by the surface mechanical grinding treatment (SMGT) process, which increases the fatigue strength apparently due to the synergistic effect of the gradient nanostructured layer and compressive residual stress. The SMGTed Zr-4 samples are subjected to annealing to remove residual stress (A-SMGT) and the individual effect of the GNS layer and compressive residual stress can be clarified. The results show that the gradient nanostructure in the surface is stable after annealing at 400 °C for 2 h but residual stress is apparently removed. Both SMGTed and A-SMGTed Zr-4 samples exhibit higher fatigue strength than that of coarse-grained (CG) Zr-4 alloy. The fatigue fracture of Zr-4 alloy indicates that the hard GNS surface layer hinders fatigue cracks from approaching the surface and leads to a lower fatigue striation space than that of CG Zr-4 samples. The offset fatigue strength of 106 cycles is taken for SMRT-ed, A-SMRT-ed, and CG Zr-4 samples and the results indicate clearly that the GNS surface layer is a key factor for the improvement of fatigue strength of the Zr-4 alloy with surface mechanical grinding treatment.

De-protonation of Nickel Hydroxide by 200 kV Electron Irradiation

Previous studies of nickel hydroxide (Ni(OH)2) powders have shown that either heating or mechanical grinding can result in complete de-hydroxylation, leading to conversion to nickel oxide (NiO). In both cases, this process appears to occur in one stage, without evidence for any intermediate compounds being formed. During studies of Ni(OH)2 powders for applications in the positive electrodes of Ni metal hydride (NiMH) rechargeable batteries, using transmission electron microscopy (TEM), we have observed significant changes caused by exposure to the highly energetic electron beam used for imaging and analysis. It is shown here, using electron energy-loss spectroscopy (EELS), that de-hydroxylation under electron irradiation occurs in two stages, with nickel oxy-hydroxide (NiOOH) being formed at the intermediate stage.

Sustainable Ways and Methods of Recycling Epoxy Fiberglass Waste

This article presents two technological ways of recycling the wastes of the production and application of products made of highly oriented fiberglass bound by the epoxy matrix. The first technology is aimed at shredding the epoxy-based products obtained by pultrusion to create fine and ultrafine powders (up to 2-10 microns) used as fillers in various composites. The second technology offers a way to obtain coarse powders with a particle size of up to 100 microns, used in the composition of heat-insulating materials and fire-retardant intumescent coatings. Proposed is the mechanical grinding of fiberglass to a finely dispersed state with subsequent heating to a temperature of 400 °C in the presence of a foaming coke and liquid glass. This technology allows the full utilization of waste from the production and application of epoxy fiberglass, such as windmill blades and parts of molded products, leading to the creation of an environmentally friendly fire-resistant and heat-insulating material in the form of plates, blocks and other products with operation temperature up to 400C, as well as fire retardant coatings for building materials and structures. By varying the content of the foaming agent and soluble glass in the composition of the intumescent mixture, one can regulate the average density, thermal conductivity and strength of the material within significant limits, achieving characteristics that exceed those of traditional heat-insulating materials. The proposed material based on recycled epoxy fiberglass is inflammable and resistant to unfavorable environmental impacts; it has high biostability and provides heat and mass transfer during the operation in buildings and structures.

The Properties of OPEFB Cellulose Nanofibrils Produced by A Different Mode of Ultrafine Grinding

Cellulose Nanofibrils (CNFs) was resulted from deconstruction of the hierarchical structure of cellulose. CNFs are commonly obtained by mechanical fibrillation, such as ultrafine grinding processes and its variation. Nevertheless, the influence of different treatments on the properties of the resulting CNF especially from variety of ultrafine grinding mode has not been reported. This study investigates the properties of cellulose nanofibrils (CNF) produced from bleached pulp oil palm empty fruit bunch (OPEFB) Kraft pulp through an ultrafine grinder with two different treatments in the fibrillation process. These two treatments were: 1) ultrafine grinder with increasing gaps distances; -30, -50, -70, and -90 µm with five cycles in every gap, 2) ultrafine grinder on constant gaps (-30µm) with increasing grinding cycles: 5, 10, 15, 30, and 40 cycles through the grinder. The influence of the treatment was evaluated through particle size distribution, crystallinity index, and morphological properties. The result showed that the increasing gaps treatment efficiently improved the size uniformity of CNFs, length 147-139.5 nm, and scanning electron microscope micrograph confirmed that the diameter of CNF was smaller with the increasing grinding gaps than increasing grinding cycles. However, the increasing cycle’s treatment produced CNF with a higher crystallinity index. The crystallinity index (CrI) of the CNF decreased from 71.27 to 62.25% with increasing gaps, whereas the CrI of the CNF from increasing cycles was 69.35%. This study provides a valuable guideline for determining the appropriate process to produce CNF especially by mechanical grinding using ultrafine grinder from OPEFB according to the desired result.