Solid State Phenomena Vol. 377

Abstract: Corrosion is a pervasive degradation mechanism that arises when materials interact with their surrounding environment, especially in aggressive conditions like seawater. One effective corrosion countermeasure is the use of sacrificial anodes for cathodic protection, with aluminum anodes becoming increasingly popular for seawater applications. The electrochemical capacity of these sacrificial anodes is pivotal for efficient corrosion prevention. However, optimizing their composition and design to adhere to standards and prolong protection is challenging. This study introduces an Artificial Neural Network (ANN) as a tool to refine the elemental composition of sacrificial anode materials. We devised an ANN model that predicts the electrochemical capacity of aluminum-based sacrificial anodes with impressive accuracy. We also examined the impact of several elements (indium, cadmium, silicon, iron, and copper) on anode capacity using the ANN simulations. The designed ANN models (Al-10) showcased accuracy rates of 92%, endorsing the potential of the ANN approach. Notably, iron was observed to augment anode capacity, while silicon exhibited a negative influence. This research showcases a novel computational approach with ANN to predict and optimize the electrochemical capacity of aluminum-based sacrificial anodes, paving the way for enhanced corrosion prevention in harsh seawater conditions.

Abstract: The manufacturing industry has experienced tremendous growth in recent years. According to the Badan Pusat Statistik (BPS), the percentage of the manufacturing industry rise from 3.89% to 5.87%. This also applies to the pharmaceutical industry, where polishing of surface material is one of main factor in pharmaceutical industry. Electropolishing is one of the finishing stages that can be done to improve polishing of material surface. Electropolishing is an electrochemical polishing technique that incorporates an electrolytic-electric solution. This process works by dissolving a controlled anodic metal surface in an appropriate electrolyte. This makes it possible to increase the evenness of the metal surface. For the pharmaceutical equipmentded industry stipulates ASME BPE and ASME B46.1 standards for surface finish materials with an electropolish surface finish value is 0.38 µm. This study aims to determine the cathode-anode distance and time to electropolishing the surface of AISI 316L stainless steel material for pharmaceutical equipment with various suggested parameters. Metallographic and SEM (Scanning Electron Microscope) tests were also carried out to see the morphological results. The experimental results show that electropolishing with H₂SO₄ 98% (40% v) and H₃PO₄ 85% (60%v) solution, the distance and duration of the electropolishing process are correlated with each other; the closer and longer the process will give lower roughness results. The lowest roughness obtained is 0.141 µm with distance 5 cm and process duration of 10 minutes. For the corrosion rate is carried out using potentiodynamic polarization with a corrosion rate value obtained 0,001 mpy.

Abstract: Stainless steel 316L (SS316L) is widely used for applications that require corrosion resistance, especially in acidic environments. Despite its importance, the corrosion mechanism of SS316L in concentrated sulfuric acid at room temperature has not been sufficiently studied. In this research, the corrosion behavior of welded and bent SS316L specimens was investigated by varying the surface roughness, achieved by ground using 120-grit abrasive paper and polished until it mirror-like. The specimens were compared through immersion tests for three days at a temperature of 25°C. The chemical composition was analyzed using optical emission spectroscopy (OES), and the microstructure was observed using optical and scanning electron microscopy (SEM). Experimental tests and analysis showed that surface roughness increased the corrosion rate. Increasing the sulfuric acid concentration also increased the corrosion rate, but at a concentration of 50% wt, no corrosion occurred due to the stability of the passive layer.

Abstract: Surface cleanliness and smoothness are essential criteria for pharmaceutical components and they hold significant importance. Smooth surface minimizes bacterial accumulation and facilitates easier cleaning, promoting hygiene. In the pharmaceutical industry, equipment often employs electropolished tube pipes within machine components as conduits for processed medicinal solutions. Electropolishing is a widely-used electrochemical method involving a metal anode to achieve a smooth surface finish. This research is to investigate the impact of electropolishing temperature and time on the surface roughness of the inner surface of stainless steel 316L cylinders used in the pharmaceutical industry. Studying the influence of temperature and electropolishing time variations on the lowest surface roughness value inside a cylinder material, and identifying appropriate testing according to the ASME BPE surface roughness standard of less than 0.38 μm. Additionally, this study involves measuring the inner surface roughness, morphological characterization using metallurgical microscopy and SEM, as well as conducting potentiodynamic testing to assess the effectiveness of electropolishing. Based on the conducted experiments, it can be concluded that the lowest surface roughness value is found in samples subjected to a temperature variation of 60°C with a 7-minute EP duration, yielding an average surface roughness of 0.177 μm. Operational conditions that meet ASME BPE criteria (< Ra 3.8 μm) are achieved at electrolyte temperatures of 50°C and 60°C, with electropolishing process durations of 3-7 minutes. The lowest corrosion rate obtained was 0.00274 mpy with a surface roughness reduction of 70.50%, demonstrating the effectiveness of the electropolishing process.

Abstract: Thermally sprayed NiCrBSi alloys have attracted interest in various fields of protective coating applications due to their good properties, especially for wear and corrosion resistance. Titanium diboride (TiB₂) is an attractive additive particle because of its properties such as high hardness, high melting point, high chemical resistance, high elastic modulus and low density. In this work, the effect of TiB₂ on dry reciprocating wear behavior of NiCrBSi-TiB₂ coating was systematically studied. NiCrBSi alloy powder was mixed with 15, 20, and 25 wt.% TiB₂ powder. Subsequently, mixed powder was coated on the substrate of 316L stainless steel (∅20 mm and 5 mm thickness) by High Velocity Oxygen Fuel (HVOF) technique. The microstructure of the coating was investigated under an optical microscope and scanning electron microscope (SEM). The hardness of the coating was measured by microhardness. In addition, dry sliding friction and wear behavior of coating were performed on a reciprocating ball-on-flat wear tester machine. The high-chromium steel (AISI 52100) ball of 6 mm in diameter was used as the counterpart. The conditions of the tests were 8 mm in stroke, 1 and 2 Hz in testing frequency with 10 N load, and sliding distance of 100 m. The variation of friction coefficient was recorded during the tests. The results indicated that an increase in TiB₂ content within the coating led to the formation of dark gray phases, oxidation layers and porosities in the microstructure. Consequently, reduction in the coating's hardness and wear resistance were discovered. In addition, the addition of TiB₂ in the NiCrBSi coating resulted in the higher material loss on the counterface ball due to abrasive wear mechanism.

Abstract: Desalination plays a crucial role in addressing global water scarcity by providing a reliable source of freshwater from seawater and brackish water, supporting both human consumption and industrial needs. Feed spacers are an essential component of membrane systems, enhancing mixing and mass transfer. However, they also facilitate foulant deposition, with biofouling often initiating on the spacer surface before spreading to the membrane. Biofouling poses a significant challenge as it is difficult to remove once occurred. In response, extensive research has explored modifying feed spacer surfaces to mitigate fouling. Despite advancements, the use of hazardous chemical reagents in conventional spacer coatings raises serious environmental concerns, including contamination of the food chain and potential risks to human health. This review focuses on eco-friendly spacer coating strategies for biofouling resistance, emphasizing sustainable methods to address the environmental impacts of traditional approaches. Techniques such as plasma pretreatment, direct coating, oil-infused coatings, and candle-soot coatings have shown potential in reducing biofouling by modifying surface properties, including hydrophilicity, hydrophobicity, and biocidal characteristics. These methods have proven effective in mitigating membrane fouling, thereby improving the performance and lifespan of membrane systems. Finally, the paper outlines future research directions, including experimental and numerical approaches, to enhance spacer coatings for antifouling in membrane applications.

Abstract: The remediation of palm oil mill effluent (POME) presents a considerable hurdle for Malaysia’s palm oil mill, requiring fulfillment with the environmental regulations before discharge. This work demonstrated a semiconductor-mediated photocatalytic technology to treat POME and synchronously evaluated the biogas generation. X-ray diffraction findings indicated that the fabricated ZnO product possessed wurtzite as a major crystalline phase. Its band gap energy was measured to be 3.27 eV via a UV-vis diffuse reflectance spectroscopy technique. The hierarchical ZnO microsphere morphology assembled by lots of layered nanosheets was observed via field-emission scanning electron microscopy. Under UV irradiation, the as-fabricated ZnO product displayed an enhanced photoactivity in comparison to the commercially available TiO₂ in treating the POME. Moreover, the ZnO/Ce and ZnO/Eu were also fabricated and showed greater photocatalytic efficacy after doping the rare earth ion in ZnO. Remarkably, the evaluation of biogas generation depicted that the ZnO/Ce and ZnO/Eu photocatalysis produced a greater quantity of CH₄ and CO₂ after 360 min irradiation. The work offered an environmentally friendly and efficient photocatalytic technology via ZnO/RE in treating wastewater and synchronously generating renewable energy.

Abstract: This paper introduced a low-overpotential heterostructured NiCoFe-LDH@NiCo₂O₄ electrocatalyst for hydrogen evolution reaction (HER). The hecterostructure was synthesized by the hydrothermal method. The electrocatalyst was coated on a Nikel foam (NiCoFe-LDH@NCO/NF) to make the electrodes. The synergistic effects between NiCoFe-LDH and NiCo₂O₄, coupled with the unique structure and high electrochemically active surface area, resulted in high-performance HER electrocatalytic activity. The HER performance of NiCoFe-LDH@NCO/NF electrode exhibited a low overpotential of 147 mV at a current density of 50 mAcm⁻² and a Tafel slope of 83 mVdec⁻¹. The abundance and low cost of the constituent materials make NiCoFe-LDH@NCO/NF a promising candidate for practical applications in water splitting for sustainable hydrogen production.

Abstract: An asymmetric hybrid supercapacitor is designed using ternary nickel cobalt sulfide (TNCS) as cathode and a mixture of Cu-based metal-organic framework and reduced graphene oxide (MrGO) as anode with KCl as electrolyte. Various techniques including EIS, CV, and GCD are applied to evaluate the electrochemical properties. The EIS analysis shows total internal resistance is only 25 Ω. Taking advantages of the high conductivity and porosity nature of both electrode materials, the supercapacitor we built exhibit high specific capacitance (31 mF cm^-2 under 4 mA cm^-2). The supercapacitor also demonstrates high power density of 3.1 mW cm^-2 while charging within 5 s.