Anodic Alumina Membranes: From Electrochemical Growth to Use as Template for Fabrication of Nanostructured Electrodes

The great success of anodic alumina membranes is due to their morphological features coupled to both thermal and chemical stability. The electrochemical fabrication allows accurate control of the porous structure: in fact, the membrane morphological characteristics (pore length, pore diameter and cell density) can be controlled by adjusting the anodizing parameters (bath, temperature, voltage and time). This article deals with both the fabrication and use of anodic alumina membranes. In particular, we will show the specific role of the addition of aluminum ions to phosphoric acid-based anodizing solution in modifying the morphology of anodic alumina membranes. Anodic alumina membranes were obtained at −1 °C in aqueous solutions of 0.4 M H3PO4 added with different amounts of Al(OH)3. For sake of completeness, the formation of PAA in pure 0.4 M H3PO4 in otherwise identical conditions was also investigated. We found that the presence of Al(OH)3 in solution highly affects the morphology of the porous layer. In particular, at high Al(OH)3 concentration (close to saturation) more compact porous layers were formed with narrow pores separated by thick oxide. The increase in the electric charge from 20 to 160 C cm−2 also contributes to modifying the morphology of porous oxide. The obtained anodic alumina membranes were used as a template to fabricate a regular array of PdCo alloy nanowires that is a valid alternative to Pt for hydrogen evolution reaction. The PdCo alloy was obtained by electrodeposition and we found that the composition of the nanowires depends on the concentration of two metals in the deposition solution.

Examining Impacts of Acidic Bath Temperature on Nano-Synthesized Lead Selenide Thin Films for the Application of Solar Cells

The influence of bath temperature on nano-manufactured PbSe (lead selenide) films was successfully generated by utilizing CBD on the acid solution’s metal surface tool. Pb (NO3)2 was employed as a lead ion source as a precursor, while Na2O4Se was used as a selenide ion source. The XRD characterization revealed that the prepared samples are the property of crystalline structure (111), (101), (100), and (110) Miller indices. The scanning electron microscope indicated that the particles have a rock-like shape. There was a decrement of energy bandgap that is from 2.4 eV to 1.2 eV with increasing temperature 20°C–85°C. Thin films prepared at 85°C revealed the best polycrystal structure as well as homogeneously dispersed on the substrate at superior particle scales. The photoluminescence spectrophotometer witnessed that as the temperature of the solution bath increases from 20°C to 85°C, the average strength of PL emission of the film decreases. The maximum photoluminescence strength predominantly exists at high temperatures because of self-trapped exciton recombination, formed from O2 vacancy and particle size what we call defect centres, for the deposited thin films at 45°C and 85°C. Therefore, the finest solution temperature is 85°C.

Preparation of hydrophilic modified polyvinylidene fluoride (PVDF) ultrafiltration membranes by polymer/non-solvent co-induced phase separation: effect of coagulation bath temperature

Membrane separation technology is widely used in wastewater purification, but the issue of membrane fouling could not be ignored. Hydrophilic modification is an effective method to reduce membrane fouling. Therefore, in this work, a hydrophilic modified polyvinylidene fluoride (PVDF) ultrafiltration membrane was prepared by polymer/non-solvent co-induced phase separation, and the effect of coagulation bath temperature on the membrane structure and performance was systematically investigated based on the previous study. With the increased of the coagulation bath temperature, the phase separation process changed from delayed to instantaneous, and the membrane surface changed from porous to dense, while the macropore structures and sponge-like pores appeared on the cross-section. Meanwhile, the pure water flux decreased from 229.3 L/(m2·h) to 2.08 L/(m2·h), the protein rejection rate increased from 83.87% to 100%, and the surface water contact angle increased from 63° to 90°. Thus, excessively high coagulation bath temperature adversely affected the permeate and separation performance, as well as antifouling performance of the membrane. This study enriched the research for preparing separation membranes by polymer/non-solvent co-induced phase separation and provided a practical and theoretical reference for controlling the membrane structure and properties by changing the coagulation bath temperature.

ZnO nanowires growth direction and parameters affecting their surface morphology

ZnO nanowires (or nanorods) have been widely studied due to their unique material properties and remarkable performance in electronics, optics, and photonics. This chapter presents a review of the current research of ZnO nanowires (or nanorods) synthesized by hydrothermal method. We discussed the mechanism of its nucleation and growth taking the effect of different parameters on its growth direction and their final morphology into account. A mixture of zinc nitrate and hexamine as precursor is the most popular. We reported the effect of precursor type and concentration, pH of the growth solution, bath temperature, substrate type and seeded layer, and duration time.

Evaluation of Color Properties of Wool Fabrics Dyed with Calligonum comosum at Different Dye Conditions

In this search, the wool fabric was dyed with a natural dye Calligonum comosum (Callig. Co. dye); the dyeing process was applied under different conditions by changing dye bath temperature, time of dyeing, and pH of dye bath also using different mordants. Ultraviolet protection factor (UPF) was determined for each dyed wool sample. The role of these dying conditions on the via color strength analysis their effects on the reflectance spectra were investigated using the spectro-photometer tool, CIE tristimulus values, and the color parameters. The dye-ability strength and fastness to washing and perspiration properties of these wool samples dyed with (Callig. Co. dye) were carried out spectrophotometrically and evaluated the antimicrobial activity for blank and dyed wool fabrics via gram-positive and gram-negative was followed. The results showed that dyeing wool fabrics with (Callig. Co. dye) increased their protective abilities markedly, and they have effective protection against UV rays, also improving their antimicrobial activity. Moreover, Different conditions of the dye bath changed the optical properties noticeably. The present study will be useful for dermatologists advising patients regarding the UPF properties of clothes made from natural fabrics (wool) and dyed with natural colorants (Callig. Co. dye).

Properties Study of SILAR Deposited Cobalt Selenide Thin Films

Thin films are attractive materials to be used in laser, solar cells, sensors, phosphors, light emitting diodes, IR windows and flat panel displays. Several deposition methods have been employed to deposit thin films as reported by many researchers. In this report, the cobalt selenide thin films have been deposited onto microscope glass slide via successive ionic layer adsorption and reaction method. This deposition method is a simple method owing to the inexpensive technique and can produce films at a low bath temperature. All the samples were investigated by using XRD, FESEM and UV-visible spectrophotometer. The XRD pattern confirmed that cubic phase cobalt selenide thin films. The FESEM image exhibited that the obtained sample is dense, uniform, and smooth surface. Keywords: XRD, FESEM, Thin films, Cobalt selenide, SILAR technique, Semiconductor, Band gap.

Work fluctuations in the active Ornstein–Uhlenbeck particle model

We study the large deviations of the power injected by the active force for an active Ornstein–Uhlenbeck particle (AOUP), free or in a confining potential. For the free-particle case, we compute the rate function analytically in d-dimensions from a saddle-point expansion, and numerically in two dimensions by (a) direct sampling of the active work in numerical solutions of the AOUP equations and (b) Legendre–Fenchel transform of the scaled cumulant generating function obtained via a cloning algorithm. The rate function presents asymptotically linear branches on both sides and it is independent of the system’s dimensionality, apart from a multiplicative factor. For the confining potential case, we focus on two-dimensional systems and obtain the rate function numerically using both methods (a) and (b). We find a different scenario for harmonic and anharmonic potentials: in the former case, the phenomenology of fluctuations is analogous to that of a free particle, but the rate function might be non-analytic; in the latter case the rate functions are analytic, but fluctuations are realised by entirely different means, which rely strongly on the particle-potential interaction. Finally, we check the validity of a fluctuation relation for the active work distribution. In the free-particle case, the relation is satisfied with a slope proportional to the bath temperature. The same slope is found for the harmonic potential, regardless of activity, and for an anharmonic potential with low activity. In the anharmonic case with high activity, instead, we find a different slope which is equal to an effective temperature obtained from the fluctuation–dissipation theorem.

Effect of Current Density and Bath Temperature to The Corrosion and Wear Behaviour of Tungsten Carbide - Nickel Electrodeposition Coating

The composite (ceramic-metal) coating has become a desired coating due to its higher wear and corrosion behaviour compares to metal coating only. This study focuses on the effect of the deposition parameter which is the current density and bath temperature on the corrosion and wear behaviour of the coating. As the current density and temperature will affect the movement of the electron during deposition, it is important to evaluate its effect on the coating thickness and its wear and corrosion performance. The mild steel was used as the substrate and nickel-tungsten carbide (Ni-WC) as the coating. Watts’s bath was used as an electrolyte with the addition of 25 g/l WC. 0.2 A/cm2 and 0.5 A/cm2 has been chosen as the current density while 30 °C and 50 °C as their temperature. The coating was characterised using a scanning electron microscope (SEM) and x-ray diffractometer (XRD). Immersion test and weight loss test was used to evaluate the corrosion and wear behaviour respectively. The 3 g/l silicon carbide was used as abrasive materials in the wear testing. Vickers micro-hardness tester was used for hardness property evaluation. It is found that higher current density and higher bath temperature results in lower corrosion and wear rate which shows higher resistance.

A Wet-Spinning Process for Producing Carbon Nanotube/Polyvinylidene Fluoride Fibers Having Highly Consistent Electrical and Mechanical Properties

Studies of polymer/carbon nanotube (CNT) fibers typically focus on optimizing the overall properties, and the effects of structural variation on these properties are ignored. Thus, we investigated the longitudinal variation in the properties of CNT/polyvinylidene fluoride (CNT/PVDF) fibers prepared by wet spinning a solution of multi-walled nanotubes, PVDF, and dimethylacetamide. To this end, materials for the CNT/PVDF fiber were selected, and a dope solution was prepared using MWNT, PVDF, and dimethylacetamide (DMAc). To consider the process parameters that would affect the performance of the CNT/PVDF fiber during the wet-spinning process using the dope solution, the initial conditions for wet spinning were selected, including bath concentration, bath temperature, drying temperature, and elongation, and the CNT/PVDF fiber was spun under the corresponding conditions. Additionally, three performance stabilization processes were proposed to improve the initial conditions for wet spinning and manufacturing the fiber. Lastly, to confirm the reliability of the CNT/PVDF fiber in all sections, tensile strength, electrical conductivity, and cross-sectional images were analyzed for the 30 m, 60 m, and 90 m sections of the fiber, and the reliability of the wet-spinning process was verified.