Papers by Keyword: Immersion

Abstract: The use of out-of-furnace desulphurization of cast iron and various dispersed desulfurizing reagents is due to the desire to ensure the most complete removal of cast iron sulfur in the shortest period of time. The actual results of the industrial application of out-of-furnace desulfurization indicate that the practical results and application rates in a number of cases are not stable enough and are far from possible and expected. The studies were carried out on calculated and "cold" transparent physical models. Magnesium, lime, and calcium carbide were evaluated as desulfurizing reagents. Based on the actual results of physical modeling and subsequent calculations, an improved expression was formulated for determining the length of a gas jet in a liquid (L_str ) - the depth of the jet immersion, depending on the parameters of injection through a submerged lance. The processes of interaction between gas and solid phases in the near-lance zone during ladle desulphurization have been studied. It is shown that during the injection desulfurization of cast iron, the gas component of the flow stops its directional movement in the melt for up to 80 mm (practically 50–60 mm), solid particles continue to move in the bubble and hit the surface of this cavity. To assess the further movement of the particle through the "gas cavity-melt" boundary, the depth of penetration of particles into liquid iron was calculated. The motion of a particle in a melt can be described by an equation that is arranged for the conditions of vertical motion of a particle from top to bottom with a given initial velocity up to the complete stop of the particle. Nomograms are given to determine the specified parameters. Recommendations are given on the parameters of injection of magnesium and ground lime.

Abstract: This study investigates the corrosion resistance of Stainless Steel 201 through varying surface treatments and testing in a 3.5 wt% NaCl solution, mimicking seawater conditions. Given its prevalent use in industries like oil, Stainless Steel 201's resistance to pitting corrosion is crucial, primarily when used in pipes. The research employs electrochemical techniques, specifically Cyclic Voltammetry and Immersion, to treat the material's surface. The surface treatment using citrict acid (C₆H₈O₇) varying the concentration of 1, 1.5, and 2 M. Corrosion tests utilize open circuit potential, anodic polarization patterns, and characterization via optical microscopy and SEM-EDS. Results indicate that the material subjected to a Cyclic Voltammetry treatment with 2M citric acid exhibited the lowest corrosion rate at 0.001243 mmpy, with 21 instances of pitting corrosion. Conversely, untreated Stainless Steel 201 showed a higher corrosion rate of 0.006177 mmpy and 87 instances of pitting corrosion. This underscores the significant improvement in corrosion resistance achieved through the specified surface treatment, highlighting its potential value for enhancing Stainless Steel 201's longevity and performance in corrosive environments. Keywords: Stainless Steel 201, Cyclic Voltammetry, Immersion, Open Circuit Potential (OCP), Anodic polarization Patterns, Corrosion Rate, Pitting Corrosion.

Abstract: The water-resistance of cow-dung has made it a widely used stabiliser in traditional earthen structures in several Asian and African countries. Multiple studies have shown an improvement in water-resistance with the addition of cow-dung, but none provides insight into this behaviour. The present study investigates the water-resistance behaviour of cow-dung stabilised earthen blocks through an extensive experimental programme to identify and characterise the components of cow-dung responsible for its water-resistance. Fresh cow-dung was collected and separated into fibres (>63 μm), medium-sized microbial aggregates (1-63 μm) and small-sized microbial aggregates (0.5-7 μm). Each component was mixed with soil and samples were prepared at different water contents (optimum water content corresponding to the highest dry density and water content higher than optimum) and compacted with 2.5 MPa force to prepare compressed blocks. The water-resistance of these blocks was evaluated through the immersion and modified drip/rain test. It was found that the small-sized microbial aggregates are almost entirely responsible for water-resistance behaviour of cow-dung stabilised earthen blocks. Small-sized microbial aggregates were further characterised by gas chromatography, mercury intrusion porosimetry, N₂- BET surface area, zeta potential measurement and electron microscopy. The results indicate that the small-sized microbial aggregates are composed of clay-sized negatively charged particles that are rich in fatty acids. The hydrophobicity of these particles is hypothesised to be responsible for water-resistance behaviour. These insights are further used to produce stabilised blocks that performed at least 30 times better than the unstabilised blocks in both water-resistance tests. The study concludes with practical recommendations for the use of wet cow-dung over dry cow-dung and a reduction of fibre content to increase the water-resistance of earthen blocks.

Abstract: Currently, much consideration is given to earthen building materials regarding their highly sustainable properties. Numerous studies have highlighted their structural ability but their water sensitivity is still limiting a potentially more spread use. To limit this sensitivity several studies have recently brought out the positive effects of bio-stabilisers such as linseed oil or xanthan gum. These recent developments allow bio-stabilized earthen materials to be resistant to immersion in water. Also, a French experimental standard (XP P 13-901) for compressed earth blocks already asks for a minimal compressive strength after a two-hour immersion that is overly severe and is difficult to satisfy without the addition of high contents of hydraulic binders. In this paper, a critical study of this compressive test after immersion is conducted on bio-stabilized (linseed oil and xanthan gum) samples of different Breton earths. Some testing adjustments are suggested and the water-diffusion in the samples is followed and linked to previously obtained capillary absorption coefficients. It is shown that the effect of immersion on the mechanical strength depends on the sample size and that an equivalence between size and immersion time can be made based on an equivalent penetration depth. Linseed oil and xanthan gum help to significantly increase the compressive strength of the earthen materials after immersion and allow to avoid the addition of hydraulic binders in earthen blocks to obtained a strong water resistance. The water diffusion in the sample during the immersion can be linked to capillary absorption behaviour, thus a water content and a compressive strength after a given time of immersion could be easily predicted.

Abstract: The article provides a comparative analysis of changes in the PL spectra and infrared spectroscopy (IR) with reference and immersion samples of mesoporous silicon during long-term storage in air at room temperature. Immersion was carried out in an aqueous solution of iron nitrate (Fe (NO₃)₃) with a concentration of 0.2 M and 0.5 M with three times: 5, 10 and 20 minutes. An analysis of the FIR data for etalon and immersion samples showed a number of features found during long-term storage of mesoporous silicon: (1) a sharp decrease in the density of hydride bonds; (2) the polynomial nature of the growth of O₃-SiH and Si-OH bonds saturating dangling bonds; and (3) the polynomial growth of silicon dioxide with the formation of oxygen defects. It was found that after immersion in a solution of 0.5 M Fe (NO₃)₃ for 10 minutes, a more intense increase in the PL in mesoporous silicon is observed while maintaining its nanostructure after 200 days of storage compared with the etalon sample, for which a weak quantum size confinement (QSC) is observed. The main mechanism of photoluminescence increase in mesoporous silicon during long-term storage is radiative recombination from oxygen defect levels, not from a QSC effect.

Abstract: Studies are devoted to determining the effect of long-term storage (up to 200 days) of untreated and immersion-treated layers of mesoporous silicon in an aqueous lithium bromide solution obtained by anodizing with a current density of 10 mA/cm² in electrolyte HF: CH₃OH = 2: 1. It was found that an increase in the PL intensity and its saturation with a storage time of more than 100 days in all samples is observed. A detailed analysis of absorbance on bonds in m/por-Si showed that during storage, hydrogen bonds are destroyed, and the PL peak intensity is proportional to the increasing concentration of non-stoichiometric oxide, in which oxygen atoms forms radiative states. It was shown that in the treated samples, the PL intensity decreases with increasing immersion time, but the mechanism of photoluminescence through the quantum size confinement (QSC) effect in mesoporous silicon without and with immersion in an aqueous LiBr solution is not significant.

Abstract: Conversion coating in metal material was a method to control the corrosion. It applied in parts of car, aircraft, factory installation, and other appliances. There were three types of conversion coating: phosphate conversion coating, chromate conversion coating, and oxalate conversion coating. There were several aspects to consider in controlling the corrosion fully. This research used phosphate because phosphate conversion coating had a low corrosion rate, affordable production cost, and environmentally friendly. This research aimed to find out the corrosion resistance of ST37 carbon steel using phosphate conversion coating in various immersion durations. Therefore, the result was a breakthrough in using phosphate conversion coating for the industries. This research used the weight loss method to calculate the corrosion rate and macro photos to obtain the corrosion form during the test. This research used ST37 carbon steel with 100 mm x 30 mm x 10 mm as the specimen and phosphate with various coating durations (10, 20, and 30 minutes). Each variation had three specimens, so this research had nine specimens in total. This research calculated the daily corrosion rate for seven days using 5% NaCl as the corrosion solution. The average corrosion rate in specimens with 10 minutes duration was 1.9599 mpy, specimens with 20 minutes immersion was 1.7647 mpy, whereas specimens with 30 minutes duration were 1.3287 mpy. Thus, the longer immersion duration created a smaller corrosion rate. Also, the corrosion formed during the test was pitting and uniform corrosion.

Abstract: The experimatal alloys were aged at different temperatures of 180°C, 200°C, 220°C, and 240º C with calcium addition levels of (X=0.5, 1, 1.5, 2%) on Mg-6Al-1Zn-XCa alloy were investigated in 3.5% NaCl solution. All the experimatal alloys were immersed in 3.5% NaCl solutions and the resulted surface were analyzed to study the corrosion behaviour and its surface topography by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersed spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The result shows that corrosion attack occurred predominantly on ß phase and α phase exhibit relatively minor corrosion. In addition to that the increased aging temperature coarsens the intermetallic as well as α- Mg grains, which shows adverse effect to corrosion resistances and the best result were obtained at composition of 0.5wt.% Ca aged at 200°C.

Abstract: In the process of comparative studies of immersing layers of porous silicon (PS) in aqueous solutions of LiBr and Fe (NO₃)₃ with subsequent long-term storage up to 150 days, it is established that there exists: (1) the range of concentrations of LiBr (S/2 - S/4) and Fe (NO₃)₃ (0.2 M), which provide the maximum increase in the intensity of PL; (2) at low concentrations of both salts, a blue shift of the PL peaks and an increase in their intensity are observed during the long-term storage, which is associated with a decrease in the size of the NC in the PS and the influence of silicon bonds with lithium or iron ions; (3) full protection of the PS layer is observed in case of immersion in Fe (NO₃)₃ with a concentration of 0.7M - 0.8M.

Abstract: Polyethylene (PE) contributes largely to plastic wastes that exist in aquatic environments as a consequence of its widespread use. To address its low degradability, pro-oxidant fillers are incorporated into its polymer matrix, making it oxo-biodegradable. In this study, films from transparent oxo-biodegradable polyethylene plastic bags were immersed in deionized water at 50°C for 35 days. Indicators of water quality: pH, oxidation-reduction potential, turbidity, and total dissolved solids (TDS), were monitored every 7 days. It was observed that pH initially rises and then slowly decreases with time, oxidation-reduction potential decreases below the control, and turbidity and total dissolved solids both increase steadily with time. Moreover, films of smaller thickness lead to a dramatic increase in turbidity and TDS. The results imply that degrading oxo-biodegradable PE plastic bags result to significant reduction of water quality.