Structural analysis of metal and semimetal adsorption on Cu{100} by low energy electron diffraction

The structures formed by growing a range of metals and semimetals on Cu{100} single crystal are investigated by quantitative low-energy electron-diffraction (LEED). Symmetrized Automated Tensor LEED (SATLEED) calculations are used to determine the structure of the surface alloys and overlayers formed. The Cu{100}/Pd system has been studied in the Pd coverage range 0.1-1.0 ML using SATLEED and Diffuse LEED (DLEED). Palladium atoms adsorb in the coverage range 0.1 < 0pd < 0.5 ML primarily by substitutional replacement of top layer copper atoms forming a two-dimensional CuxPd].x surface alloys leading to formation of an ordered Cu{100}-c(2x2)-Pd two-dimensional alloy at 0pa = 0.5 ML The kinetics and mechanism of an irreversible overlayer to underlayer transition in the Cu{100}-c(2x2)-Pd surface alloy (0pd = 0.5 ML) has been investigated. The activation energy for Pd site switching from the outermost layer to sub-surface (second layer) sites has been found to be 109±12 kJ mol'1 (1.13+0.12 eV). The structure of the underlayer alloy has been determined by SATLEED. Substitution of 0.5 ML of Pd into subsurface sites leads to significant expansion of the outermost two interlayer spacings Adzi2 = +3.3 ± 3.3 %, Adz23 = +6.6 ± 2.8 %. At monolayer coverage, Pd forms a double layer ordered c(2x2) CuPd alloy with p(2x2)-p2gg symmetry introduced into the outermost layer via clock rotation of the CuPd monolayer with the p(2x2) vertices centred over second layer Pd atoms. Lateral shifts of the top layer Cu and Pd atoms are determined to be 0.25+0.12A. The room temperature deposition of 0.5 ML Pt on Cu{100} followed by annealing to 525 K results an ordered c(2x2) Cu-Pt second layer capped with a pure Cu layer. The first and second interlayer spacings are found to be expanded by +5.1+1.7 % and +3.5+1.7%, respectively (relative to the bulk Cu interlayer spacing of 1.807 A) due to the insertion of the 8% larger Pt atoms into the second layer with Pt atoms rippled outwards towards the solid-vacuum interface by 0.08+0.06 A

Modification of Gold Surface with Gold Nanoparticles and Cyclohexyl Dithiocarbamate as a Selective Sensor for Cysteine

The self-assembly of cyclohexylamine dithiocarbamate (C6DTC) on gold (Au) and gold nanoparticles (AuNPs) was studied electrochemically using cyclic voltammetry (CV). Cyclic voltammetry was used to study the system Fe(CN)63-/Fe(CN)64- at the electrode surface of (C6DTC/Au) and (C6DTC/AuNPs). The application of the resulting chemically modified surface as a selective sensor for cysteine, among other amino acids, was investigated. Linear oxidative desorption technique was used to characterize the modified electrode that consists of the self-assembled monolayer of cyclohexylamine dithiocarbamate on gold nanoparticles deposited on Au electrode (C6DTC/AuNPs/Au). The results showed an enhancement in the oxidation peak of cysteine on the modified electrode and hence a greater sensitivity

Solid-State Mechanochemical Synthesis of Kaolinite-Urea Complexes for Application as Slow Release Fertilizer

This study investigated a mechanochemical (MC) process for synthesizing a slow-release urea fertilizer by cogrinding the starting materials of (NH2)2CO and amorphous kaolinite in a planetary ball mill. The tests with kaolinite contents ranging from 25 to 75 wt. %, milling time ranging from 1 (h) to 3 (h) and mill rotational speeds from 200 to 700 rpm were performed to evaluate the incorporation of (NH2)2CO and release of nitrogen into the solution. The analyses conducted using XRD, TGA, FT-IR and KNDU (Kjeldahl Nitrogen Determination Unit) indicated that the MC process was successfully applied to incorporate (NH2)2CO into the amorphous kaolinite structure. The release of nitrogen from the system (kaolinite-(NH2)2CO) when dispersed in water for 24 h reached up to 20% at 25% wt of kaolinite. Moreover, under the milling speed conditions for the system (kaolinite–(NH2)2CO), release of nitrogen reached between 25 and 40%. These results indicated that the MC process can be developed to allow amorphous kaolinite to act as a carrier of nitrogen nutrients to be released slowly for use as fertilizer

Mitigation of scale problem in the pumped Disi water to Amman, Jordan

Various methods are known to mitigate or prevent scale formation in pipes, rather by chemical addition, e.g., anti-scaling substances, or physically which includes ultrasonic or nanofiltration (NF). Nanofiltration membranes have a selectivity for the multivalent charged ions, so monovalent ions will pass the membrane partly and multivalent ions will be rejected completely. Chemical addition to prevent scale formation is based on justifying water parameters such as pH, alkalinity, and concentrations of ions that form the building units of scale crystal. In order to mitigate the scaling tendency in water pumped from the Disi aquifer to Amman city along its 345 km pipeline, different studies were conducted using simulated plumbing system. This part of the study is concerned with scale mitigation using nanofiltration and addition of chemicals. Nanofiltration was applied to reduce the hardness that causes scale deposition where it rejected around 70.5% of Ca2+, 71.98% Mg2+, 7.72% K+, 29.0% Na+, 66.63% Cl–, 86.51% NO3 – , 85.72% SO4 2–, and 69.85% CO2. Increasing the concentration of some ions such as Na+, K+ and Cl– keeping the allowable limit gave good results for scale mitigation

Mechanochemical Preparation of a Novel Slow-Release Fertilizer Based on K₂SO₄-kaolinite

In this study, a novel slow-release fertilizer (SRF) consisting of kaolinite and K2SO4 was prepared, employing the process of mechanochemical milling in a planetary ball mill. To obtain the optimum milling time and speed, several samples were made at fixed mass ratios of kaolinite: K2SO4 (3:1). The milling rotational speed ranged from 200 to 700 rpm for 120 min. Different milling times ranging from 60 to 180 min at fixed 600 rpm milling speed were also investigated to evaluate the incorporation of K2SO4 and to measure the liberation of K+ and SO42− ions into solution. The properties of the studied samples were analyzed by Fourier transformation infrared spectrometry (FTIR), thermal gravimetric analysis (TGA), and ion chromatography (IC). The mechanochemical process is a green chemistry procedure that is successfully applied to incorporate K2SO4 into the amorphous kaolinite structure. The slow-release performance was evaluated by determining the K+ and SO42− content in the aqueous solution upon leaching. The optimum released amount of K+ after 24 h was 32 mg L−1 for the milling conditions of 180 min and 700 rpm, indicating that K2SO4-kaolinite has good slow-release properties. The novel SRF is cost-effective, environmentally friendly, and improves the fertilizer’s efficiency in many agricultural applications

Study of the Microstructure, Corrosion and Optical Properties of Anodized Aluminum for Solar Heating Applications

Humans are increasingly required to harvest green solar energy in order to reduce energy bills and save the environment from the excessive use of fossil resources. In this article, the microstructures of both commercial non-colored anodized Al and commercial blackened anodized Al were studied using optical and scanning electron microscopy in order to interpret the results of their use as solar absorbing surfaces. Microscopic examination showed that the thickness of the anodization layers of the non-colored anodized Al and the blackened anodized Al were approximately 11 µm and 14 µm, respectively, and they were perfectly adhered to the mother Al. The corrosion rate of all studied Al surfaces was investigated using the potentiodynamic polarization technique in 3.5% NaCl as the corrosive medium. The blackened anodized Al surface exhibited the highest corrosion resistance, which made it the best surface for solar heating systems. Moreover, raw Al, matte black painted Al, and blackened anodized Al were tested as selective surfaces for solar radiation in different weather conditions. Our results demonstrated the superiority of the blackened anodized Al in terms of the ability to absorb solar radiation, in addition to its higher corrosion resistance properties. In experimental testing, temperature values higher than 90 °C were reached several times. A gain of an extra 5 °C was achieved when using a double-glazed cover in comparison with a single-glazed setup. In conclusion, we highly recommend using a commercial blackened anodized Al surface to manufacture solar absorbing heaters, owing to its similarity in solar radiation absorptivity with the commercial matte black painted Al, excellent corrosion resistance, superior endurance upon long-term exposure to solar radiation, light weight, low price, and availability. Additionally, the light reflectance % test demonstrated the characteristics of the used solar selective surfaces

Study of the Microstructure, Corrosion and Optical Properties of Anodized Aluminum for Solar Heating Applications

Humans are increasingly required to harvest green solar energy in order to reduce energy bills and save the environment from the excessive use of fossil resources. In this article, the microstructures of both commercial non-colored anodized Al and commercial blackened anodized Al were studied using optical and scanning electron microscopy in order to interpret the results of their use as solar absorbing surfaces. Microscopic examination showed that the thickness of the anodization layers of the non-colored anodized Al and the blackened anodized Al were approximately 11 &micro;m and 14 &micro;m, respectively, and they were perfectly adhered to the mother Al. The corrosion rate of all studied Al surfaces was investigated using the potentiodynamic polarization technique in 3.5% NaCl as the corrosive medium. The blackened anodized Al surface exhibited the highest corrosion resistance, which made it the best surface for solar heating systems. Moreover, raw Al, matte black painted Al, and blackened anodized Al were tested as selective surfaces for solar radiation in different weather conditions. Our results demonstrated the superiority of the blackened anodized Al in terms of the ability to absorb solar radiation, in addition to its higher corrosion resistance properties. In experimental testing, temperature values higher than 90 &deg;C were reached several times. A gain of an extra 5 &deg;C was achieved when using a double-glazed cover in comparison with a single-glazed setup. In conclusion, we highly recommend using a commercial blackened anodized Al surface to manufacture solar absorbing heaters, owing to its similarity in solar radiation absorptivity with the commercial matte black painted Al, excellent corrosion resistance, superior endurance upon long-term exposure to solar radiation, light weight, low price, and availability. Additionally, the light reflectance % test demonstrated the characteristics of the used solar selective surfaces

Inhibitory effect of Hydrex anti-scalant on calcium scale deposition from seawater under multiple-effect distillers' conditions

In this work, the inhibitory effect of a commercial anti-scalant (Veolia Hydrex® 9209) on the calcium minerals of carbonate, sulfate and hydrocalumite (Ca/Al) clay deposition from seawater has been investigated. Different concentration factors and anti-scalant doses were studied by analyzing the water hardness and turbidity. The inhibitory effect of the investigated anti-scalant was efficient even at lower concentrations. The percentage inhibition decreases with increasing the temperature and increases with increasing the dose/amount of the anti-scalant. The carbonate scale inhibition was >99% and 98–99% at 50 and 70 °C, respectively. The percentage inhibition of sulfate from hemihydrate was ranged from 80% to 87% for 2 and 8 ppm anti-scalant at 50 °C. The inhibition of Ca/Al hydrocalumite deposition increases from 70% to 90% upon increasing the dose from 3 to 5 ppm, respectively. A recommended useful dose of antiscalant for seawater is 5 ppm

Performance Comparison and Light Reflectance of Al, Cu, and Fe Metals in Direct Contact Flat Solar Heating Systems

The Sun is a huge and clean energy source that must be relied upon to reduce greenhouse gases and promote the renewable and sustainable energy transition. In this paper, the testing of Al, Cu, and Fe metals with different thicknesses, both bare and painted matte black, was investigated for solar water heating systems. The used technique was a direct contact flat solar heating system (DCFSHS). Many experiments were run to assess this system in terms of metals’ thicknesses and their thermal conductivities as well. Thicknesses of around 0.35 mm and 1 mm of Cu gave almost similar feedback. Maximum temperatures in the range of 93–97 °C were achieved during the autumn season in Amman, Jordan, while it was approximately 80 °C in winter. It has been confirmed that high water temperatures can be obtained in all used metals, regardless of their thermal conductivities. It was also found that a white color of the solar heater case inner wall leads to an increase in water temperature of approximately 4 °C in comparison to a black color. Furthermore, a light reflectance % test in the wavelength range of 240–840 nm for the studied metals, with both bare and black-painted surfaces, gave a superb result that was in line with the obtained results of the DCFSHS. Our innovative system design for solar water heating is due to improvements in many aspects, such as design, production costs, environment, and weight