Development of Photocatalytic 3D-Printed Cementitious Mortars: Influence of the Curing, Spraying Time Gaps and TiO2 Coating Rates

This work evaluated the photocatalytic activity of 3D-printed cementitious mortar specimens functionalized with TiO2 nanoparticles to obtain a multifunctional and smart concrete. This research aims to assess the influence of different parameters related to the functionalization process such as adsorption, coating time gaps, and coating rates on the degradation efficiency of the functionalized cementitious specimens. Each specimen was evaluated under the degradation of Rhodamine B (RhB) in an aqueous solution using a sun-light simulation. The obtained results showed a decrease in adsorption (under dark condition) with increasing the sample curing age. The highest photocatalytic efficiency was observed for coated samples aged 7 days. By increasing the coating rates, the photocatalytic efficiency is enhanced. Nonetheless, regardless of the coating rates, all the specimens showed an increase in photocatalytic efficiency for longer time periods of light exposition, i.e., after 8 h of irradiation.

Biofilm inhibition and bactericidal activity of NiTi alloy coated with graphene oxide/silver nanoparticles via electrophoretic deposition

Biofilm formation on medical devices can induce complications. Graphene oxide/silver nanoparticles (GO/AgNPs) coated nickel-titanium (NiTi) alloy has been successfully produced. Therefore, the aim of this study was to determine the anti-bacterial and anti-biofilm effects of a GO/AgNPs coated NiTi alloy prepared by Electrophoretic deposition (EPD). GO/AgNPs were coated on NiTi alloy using various coating times. The surface characteristics of the coated NiTi alloy substrates were investigated and its anti-biofilm and anti-bacterial effect on Streptococcus mutans biofilm were determined by measuring the biofilm mass and the number of viable cells using a crystal violet assay and colony counting assay, respectively. The results showed that although the surface roughness increased in a coating time-dependent manner, there was no positive correlation between the surface roughness and the total biofilm mass. However, increased GO/AgNPs deposition produced by the increased coating time significantly reduced the number of viable bacteria in the biofilm (p < 0.05). Therefore, the GO/AgNPs on NiTi alloy have an antibacterial effect on the S. mutans biofilm. However, the increased surface roughness does not influence total biofilm mass formation (p = 0.993). Modifying the NiTi alloy surface using GO/AgNPs can be a promising coating to reduce the consequences of biofilm formation.

Effect of Current and Coating Time on the Layer Thickness and Corrosion Rate of Electroplated AISI 1045

Corrosion mostly occurs on carbon steel which is applied for automotive components and household needs. This natural phenomenon is impossible to be avoided. However, it can be set by escalating its corrosion initiation time. Electroplating is a method that can be used to give protection to slower the corrosion initiation time by forming a layer on the specimen surface, additionally, this method is simple and low cost. One of the most commonly used metals for electroplating is nickel, nickel electroplating is suitable for automotive component coating. For these reasons, this study is focused on analyzing the effect of current and coating time on the layer thickness and corrosion rate of AISI 1045 carbon steel with nickel electroplating. The current variations used were 0.5; 1.0; and 1.5 A and the coating time variations were 5, 10, and 15 minutes. AISI 1045 was used as the cathode, nickel was as the anode, and nickel chloride was the electrolyte solution. The specimen with a current of 1.5 A and a coating time of 15 minutes shows the thickest coating and the lowest corrosion rate, with values of 0.0205 mm and 0.94 mpy, respectively. This study indicates that the increase of the current and coating time enhances the layer thickness and declines the corrosion rate.

Fabrication of Polydimethysiloxane (PDMS) Dense Layer on Polyetherimide (PEI) Hollow Fiber Support for the Efficient CO2/N2 Separation Membranes

The development of thin layer on hollow-fiber substrate has drawn great attention in the gas-separation process. In this work, polydimethysiloxane (PDMS)/polyetherimide (PEI) hollow-fiber membranes were prepared by using the dip-coating method. The prepared membranes were characterized by Scanning Electron Microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and gas permeance measurements. The concentration of PDMS solution and coating time revealed an important influence on the gas permeance and the thickness of the PDMS layer. It was confirmed from the SEM and EDX results that the PDMS layer’s thickness and the atomic content of silicon in the selective layer increased with the growth in coating time and the concentration of PDMS solution. The composite hollow-fiber membrane prepared from 15 wt% PDMS solution at 10 min coating time showed the best gas-separation performance with CO2 permeance of 51 GPU and CO2/N2 ideal selectivity of 21.

Enhancing the Antibacterial Properties of PVDF Membrane by Hydrophilic Surface Modification Using Titanium Dioxide and Silver Nanoparticles

This work investigates polyvinylidene fluoride (PVDF) membrane modification to enhance its hydrophilicity and antibacterial properties. PVDF membranes were coated with nanoparticles of titanium dioxide (TiO2-NP) and silver (AgNP) at different concentrations and coating times and characterized for their porosity, morphology, chemical functional groups and composition changes. The results showed the successfully modified PVDF membranes containing TiO2-NP and AgNP on their surfaces. When the coating time was increased from 8 to 24 h, the compositions of Ti and Ag of the modified membranes were increased from 1.39 ± 0.13 to 4.29 ± 0.16 and from 1.03 ± 0.07 to 3.62 ± 0.08, respectively. The water contact angle of the membranes was decreased with increasing the coating time and TiO2-NP/AgNP ratio. The surface roughness and permeate fluxes of coated membranes were increased due to increased hydrophilicity. Antimicrobial and antifouling properties were investigated by the reduction of Escherichia coli cells and the inhibition of biofilm formation on the membrane surface, respectively. Compared with that of the original PVDF membrane, the modified membranes exhibited antibacterial efficiency up to 94% against E. coli cells and inhibition up to 65% of the biofilm mass reduction. The findings showed hydrophilic improvement and an antimicrobial property for possible wastewater treatment without facing the eminent problem of biofouling.

Electrophoretic Deposition Performance of Hydroxyapatite Coating on Titanium Alloys for Orthopedic Implant Application

Hydroxyapatite (HA) is potentially used as a coating material for titanium alloys to improve their bioactivity and then enhancing the osseointegration characteristic of metal implants for orthopedic application. Electrophoretic Deposition (EPD), one of the coating methods that is widely applied for coating metal because of its simplicity and relatively low cost, is chosen for coating metal implants. HA coating layer quality can be controlled by adjusting applied voltages and coating time of the EPD process. However, the optimum voltage and exposing time has not yet been known for new type titanium implant such as Ti-12Cr and TNTZ. This work is, therefore, focusing on the effect of applied voltage and coating time on the mass growth, HA coating thickness, and surface coverage that can be produced on the surfaces of both alloys, and also on the conventional titanium alloy, Ti6Al4V, for comparison. The result of this work showed that there is a significant influence of the titanium alloy type on the HA layer performances. However, it is necessary to choose a suitable voltage and to expose time for producing a sufficient coating layer that meets the standard of orthopedic implants.

A facile approach for obtaining NiFe­2O4/C nanocomposites and their magnetic properties assessment

NiFe2O4/C nanocomposites were prepared using the two-step process, including reverse microemulsion followed by thermochemical vapour deposition (TCVD). Micelles made in the first step worked well and NiFe2O4 nanoparticles owing sizes smaller than 10 nanometer with narrow size distribution were obtained. Acetylene gas was used as a carbon source for deposition on the surface of NiFe2O4 nanoparticles. Coating applied for 1 and 2 h at 700°C and resulted in an enhancement of NiFe2O4 nanoparticle size to a level of 30 nanometer. Powder X-ray diffraction (PXRD) patterns revealed the spiel formation for all samples; however, the crystallinity of them has been increased as much as temperature rose to a level of coating. Fourier transform infrared spectroscopy (FT-IR) verified the metal-oxygen bonding linked to the octahedral and tetrahedral vibrations. Micro-Raman spectra for the coated samples were recorded as well, and the results confirmed the existence of ordered and disordered carbon-based materials in nanocomposites. It is noteworthy to mention that, in the sample with 2 h coating time, the defect densities were lower than the sample with an hour coating time. The vibration sample magnetometer (VSM) was also used to investigate the magnetic properties. The as-prepared sample behaves like a superparamagnetic matter; however, the coated ones behave like ferromagnetic materials. The saturation magnetization and coercivity of coated samples were lower than their bulk counterparts which was due to their smaller size.

Improving Surface Properties of Inconel 600 Alloy by Electroless Ni-P Deposition

The use of electroless Ni-P plating (EN) coating has attracted a surprising interest in the most recent years. Many useful characteristics of the electroless-plating method have created many benefits in different industries such as oil, gas, electronic, automotive, aerospace, and chemical. Some of the highlighted properties of such a method are superior corrosion resistance, superior mechanical properties, and uniform thickness of the coating as well as good surface finish properties, good adhesion characteristics, and a wide range of thickness. In this paper, electroless plating has been applied in a (Ni-P) bath at two different times of 2 and 3 hr respectively. After the plating, a heat treatment at 400 °C for an hour under vacuum 10-4 torr has been done. The prepared samples were characterized by energy dispersive spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM). In addition, micro-hardness and corrosion rate following Tafel extrapolation in two acidic solutions (1M HCl and 1M H2SO4) were also determined. Vickers hardness values for specimens, coated by Ni -P at 2 and 3 hr have increased by 47 % and 32 % respectively. X-ray diffraction analysis for the coated surfaces showed two phases of Ni3P and NiP, presented before and after heat treatment. The SEM images of the cross sectional coated specimens revealed that the thickness of the coating is 68.43 and 92.71 µm for 2 and 3 hr coating time, respectively. Tafel analysis showed that the coated specimens had a lower corrosion current density compared to that for the bare specimens. The corrosion current density for the coated specimens in 1M H2SO4 increased by 57 % with 2 hr and 69 % at 3 hr coating time. While, the corrosion current density for the coated specimens in 1M HCl increased by 37 % and 83 % at 2 and 3 hr coating time respectively.