Recent developments in two-dimensional materials-based membranes for oil–water separation

The industrialization witnessed in the last century has resulted in an unprecedented increase in water pollution. In particular, the water pollution induced by oil contaminants from oil spill accidents, as well as discharges from pharmaceutical, oil/gas, and metal processing industries, have raised concerns due to their potential to pose irreversible threats to the ecosystems. Therefore, the effective treating of these large volumes of oily wastewater is an inevitable challenge to address. Separating oil–water mixtures by membranes has been an attractive technology due to the high oil removal efficiency and low energy consumption. However, conventional oil–water separation membranes may not meet the complex requirements for the sustainable treatment of wastewater due to their relatively shorter life cycle, lower chemical and thermal stability, and permeability/selectivity trade-off. Recent advancements in two-dimensional (2D) materials have provided opportunities to address these challenges. In this article, we provide a brief review of the most recent advancements in oil–water separation membranes modified with 2D materials, with a focus on MXenes, graphenes, metal–organic frameworks, and covalent organic frameworks. The review briefly covers the backgrounds, concepts, fabrication methods, and the most recent representative studies. Finally, the review concludes by describing the challenges and future research directions

Laser celaning process for the removal of surface contaminants, corrosion and paint

Laser cleaning is an ideal technology that replace conventional chemical technique for coating removal process. This unique technique can remove coating layer without defect the metal substrate surface. Laser cleaning process can be use in many industrial application such as Automotive industries and petrochemical industires. Archaeological sites of restoration possible with laser cleanin

Enhancement of laser absorptivity in metal by laser surface modification

An innovation which currently in 4th TRL aims to improve laser-material interaction by increasing absorption of laser energy through surface roughness using laser surface modificatio

Effect of laser frequency and focal length on copper surface temperature during laser heating

Laser heating is a process that uses laser as a heat source. In this paper, the copper surface temperature during the laser heating process was studied by controlling the laser frequency and focal length. The laser heating experiment was conducted using a fiber laser marking machine and irradiated with a constant 27 W laser power within a duration of 51 s. The laser frequency and focal length were varied from 100 to 300 kHz and −3 cm to +3 cm, respectively. Meanwhile, laser surface modification (LSM) was performed on the copper rod surface to enhance the laser energy absorption. Furthermore, the defocusing modes for laser heating were used to analyze the variation of temperature. The focus point of the focal length for this experiment was set up at 18.4 cm from the focal plane and denoted as 0. Laser frequency and focal length were found to play an important role in increasing the surface temperature during laser heating since it affects the heat input delivered to the materials. It was found that the surface temperature reaches a higher degree, 879.2 °C with the combination of 200 kHz laser frequency at focal length

Effect of electrokinetic treatment time on energy consumption and salt ions removal from clayey soils

Electrokinetics effectively removes contaminants, but its field-scale applications are limited mainly due to its high energy cost. In previous studies, the energy consumption was determined either by changing the soil’s specimens initial salt concentration while keeping the treatment time fixed or by changing the treatment time and keeping the same initial salt concentrations for all the specimens. Since both the initial salt concentration and treatment time are important parameters in determining reclamation cost, therefore, in this study, the soil specimens intentionally contaminated with different concentrations of sodium chloride (NaCl), i.e., varying from 3.7 to 15.5 g kg−1, were exposed to a constant DC electric field of 1 V cm−1 for different time durations, i.e., varying from 6 to 72 h. The results show that electroosmotic flow (EOF) was directed from the anode to the cathode and higher for specimens contaminated with relatively low salt concentration, i.e., up to 7.6 g kg−1. Therefore, for these specimens, due to the combined effect of electroosmosis and electromigration, the removal of Na+ was higher than the Cl−. However, for the specimen contaminated with a higher salt concentration, i.e., 15.5 g kg−1, the Cl− removal exceeded Na+ due to the marginalization of EOF. Regardless of initial salt concentration, the electroosmotic flow and salt ions removal rates decreased with increasing treatment time, which might be attributed to the development of acidic and alkaline environments in soil. The collision of acidic and alkaline fronts resulted in a large potential gradient in a narrow soil region of pH jump, diminishing it everywhere else. This nonlinearity in the electric potential distribution in soil reduced the EOF and electromigration of salt ions

Development of wear resistant metal matrix composite coatings based on laser surfacing engineering technique / Moinuddin Mohammed Quazi

Laser based additive manufacturing technology (LAM) comprising of Laser composite surfacing (LCS) technique has emerged as an alternative photon driven manufacturing technology for the fabrication of hybrid metal matrix composite coatings to enhance the mechanical and tribological properties of critical machinery components. To meet the application needs, instead of bulk material processing, surface coatings are rendered far more suitable and are often utilized in form of Hybrid metal matric composite coatings (HMMC). These coatings have great potential in the fabrication and regeneration of automotive, aerospace, defense and manufacturing components as protective hard facing self-lubricating wear resistant composite coating. Under the category of lightweight metals, self-lubricating coatings have eluded aluminium alloys and researchers have not realized the potential of optimization techniques for the laser processing parameters. This may dramatically increase the friction coefficient and wear rates of critical sliding components and the full potential of improvement in mechanical and surface properties are not realized. The present work explores the possibility to utilize several wear resistant metal matrixes composite (MMC) and hybrid (HMMC) coatings with the assimilation of various solid lubricants in these coatings blends to investigate their tribo-mechanical performance. In the first phase fabrication, characterization and optimization of Ni-WC based wear resistant MMC coatings was deposited on aluminium alloy AA5083. To achieve laser composite surfacing, an analysis on optimization of laser processing parameters was made, in order to improve the tribo-mechanical properties of aluminium alloy. To carry out the investigation, Taguchi optimization method using standard orthogonal array of L16 (34) was employed. Thereafter, the results were analyzed using signal to noise (S/N) ratio response analysis and Pareto analysis of variance (ANOVA). Finally, confirmation tests with the best parameter combinations obtained in the optimization process were made to demonstrate the progress made. Results showed that the surface hardness (953 Hv) and roughness (0.81m) of coated AA5083 samples were enhanced by 9.27%, and 13.14% respectively. Tribological behavior of LCS samples was investigated using ball-on-plate tribometer against a counter-body of hardened and tempered 440c bearing steel. It was revealed that the wear of the Ni-WC coated samples improved to around 2.5 times. For lower applied loads, coating exhibited abrasive wear mode and a reduction in plastic deformation. In the second phase, solid lubricant coating comprising of lamellar graphite and TiO2 was employed to fabricate Ni-WC based HMMC coatings on Al-Si hypereutectic piston alloy. The concentrations of both solid lubricants were varied in concentration of 5, 10, and 15 wt. % to identify their optimum concentration. Results indicated that the addition of graphite and TiO2 to fabricate HMMC was beneficial in reducing friction and wear of Ni-WC MMC coating. Furthermore, the hardness of both coatings was improved. The wear mechanism of MMC coating was transformed into mild abrasive and adhesive after the addition of both solid lubricants

Scratch adhesion and wear failure characteristics of PVD multilayer CrTi/CrTiN thin film ceramic coating deposited on AA7075-T6 aerospace alloy

This study highlights the scratch adhesion failure characterization and tribo-mechanical properties of physical vapor deposited (Cr, Ti) N coating on AA7075-T6 by using magnetron-sputtering technique. The surface morphology, microstructure and chemical composition of CrTi/CrTiN film were inspected by an optical microscope, scanning electron microscope (SEM) incorporated with energy dispersive X-ray spectroscopy (EDX) in addition to focused ion beam milling. The coating to substrate critical load of about 1261 mN was obtained, by employing coating deposition parameters of; DC power (300 W, RF power (200 W)), temperature (300 °C) and nitrogen flow rate (6%). Failure adhesion characteristics exhibited initial arc-tensile cracking followed by chipping and spallation that led to complete coating failure at Lc3. The tribo-mechanical aspects were evaluated by a pin-on-plate reciprocating testing unit, which showed a lower friction coefficient of 0.36 for CrTiN as compared with 0.43 for AA7075-T6. Subsequently, the wear depth was also reduced from 9.5 to 5.9 μm. It was revealed that the wear mechanism for AA7075-T6 was extensive deformation, abrasion and delamination, while the CrTiN exhibited slightly oxidative abrasive wear mode

Mechanical and tribological performance of a hybrid MMC coating deposited on Al–17Si piston alloy by laser composite surfacing technique

Laser composite surfacing (LCS) is a photon driven manufacturing technology that can be utilized for depositing hybrid metal matrix composite coatings (HMMC) on softer Ti/Al/Mg alloys to enhance their tribo-mechanical properties. LCS offers the advantages of higher directionality, localized microstructural refinement and higher metallurgical bonding between coating and substrate. The current research presents the tribo-mechanical evaluation and characterization of solid lubricant based Ni-WC coatings deposited by LCS on Al-Si piston alloy by varying the concentration of graphite between 5-to-15-weight percentage. The tribological behavior of LCS samples was investigated using a ball-on-plate tribometer. Results indicate that the surface hardness, wear rate and friction coefficient of the Al-Si hypereutectic piston alloy were improved after LCS of graphite based HMMC coatings. The maximum surface hardness of 781Hv was acquired for the Ni-WC coating containing 5 wt% graphite. The friction coefficient of Al-Si under dry sliding conditions was reduced from 0.47 to 0.21. The reduction in the friction coefficient was attributed to the formation of a shearable transfer layer, which prevented delamination and reduced adhesion, abrasion and fatigue cracking

Current research and development status of corrosion behavior of automotive materials in biofuels

The world’s need for energy is increasing with the passage of time and the substantial energy demand of the world is met by fossil fuels. Biodiesel has been considered as a replacement for fossil fuels in automotive engines. Biodiesels are advantageous because they provide energy security, they are nontoxic, renewable, economical, and biodegradable and clean sources of energy. However, there are certain disadvantages of biodiesels, including their corrosive, hygroscopic and oxidative natures. This paper provides a review of automotive materials when coming into contact with biodiesel blended fuel in terms of corrosion. Biodiesels have generally been proved to be corrosive, therefore it is important to understand the limits and extents of corrosion on different materials. Methods generally used to find and calculate corrosion have also been discussed in this paper. The reasons for the occurrence of corrosion and the subsequent problems because of corrosion have been presented. Biodiesel production can be carried out by different feedstocks and the studies which have been carried out on these biodiesels have been reviewed in this paper. A certain number of compounds form on the surface of materials because of corrosion and the mechanism behind the formation of these compounds along with the characterization techniques generally used is reviewed