Enhanced UV protection and water adsorption properties of transparent poly(methyl methacrylate) films through incorporation of amorphous magnesium carbonate nanoparticles

A simple solution casting approach was used to obtain transparent and flexible poly(methyl methacrylate) (PMMA) films incorporated with 1 – 4% by weight amorphous magnesium carbonate nanoparticles. Optical transparency was retained in visible wavelengths, while transmittance in the UV-B region was reduced by 22% at 310 nm and 58% at 256 nm with the addition of 4 wt. % nanoparticles. Furthermore, the incorporation of the nanoparticles was shown to provide protection for the films under UV-C irradiation (254 nm wavelength, 5 mW cm−2), with the amount of UV degradation decreasing with increasing concentration of nanoparticles. Films with incorporated nanoparticles were also shown to be able to retain adsorbed moisture much better than neat PMMA films; whereas neat PMMA films did not retain moisture, approximately 50% of the adsorbed moisture was retained in films containing 4 wt. % nanoparticles. These enhanced properties of PMMA are of great interest in applications such as flexible and transparent screens for personal electronic devices that require protection from both UV light and moisture.

Pozzolanic Reaction in Clayey Soils for Stabilization Purposes: A Classical Overview of Sustainable Transport Geotechnics

Problematic soil stabilization processes involve the application of binders to improve the engineering properties of the soil. This is done to change the undesirable properties of these soils to meet basic design standards. However, very little attention has been given to the reactive phase of soil stabilization. This phase is the most important in every stabilization protocol because it embodies the reactions that lead to the bonding of the dispersed particles of clayey soil. Hence, this reactive phase is reviewed. When clayey soils which make up the greatest fraction of expansive soil come in contact with moisture, they experience volume changes due to adsorbed moisture that forms films of double diffused layer on the particles. When this happens, the clayey particles disperse and float, increasing the pore spaces or voids that exist in the soil mass. Stabilizations of these soils are conducted to close the gaps between the dispersed clayey soil particles. This is achieved by mixing additives that will release calcium, aluminum, silicon, etc., in the presence of adsorbed moisture, and a hydration reaction occurs. This is followed by the displacement reaction based on the metallic order in the electrochemical series. This causes a calcination reaction, a process whereby calcium displaces the hydrogen ions of the dipole adsorbed moisture and displaces the sodium ion responsible for the swelling potential of clayey soils. These whole processes lead to a pozzolanic reaction, which finally forms calcium alumina-silica hydrate. This formation is responsible for soil stabilization.

Porosity in Aluminum Welds

Porosity constitutes the main defect in aluminium welds. It is generally assumed that the basic reason for its formation is the presence of hydrogen. Hydrogen can originate from a variety of sources. Major sources of hydrogen are surface contamination of both the parent and deposited metals in the form of hydroxides, hydrocarbons or oxides with adsorbed moisture. Another source of hydrogen can be impurity of the gas shield associated with either moisture or air sucked into the arc atmosphere if an incorrect welding procedure is adopted. It has been found that even 2 ppm of hydrogen in the molten metal, or 250 ppm of hydrogen in the gas shield can be sufficient to produce porosity in aluminium welds.

HIGROSCOPICITY OF CHARCOAL PRODUCED IN DIFFERENT TEMPERATURES

ABSTRACT This research aimed to evaluate hygroscopicity of charcoal produced under four different final carbonization temperatures. For evaluation of hygroscopicity charcoal samples were conditioned in environments with controlled temperature and relative humidity, using saturated salt solutions. The final carbonization temperature significantly influenced the products yields and the properties of charcoal. The charcoal produced in the final temperature of 750 °C showed the highest adsorption capacity of water, indicated by the moisture content after conditioning, in the higher relative humidity environment. Correlations were observed between adsorbed moisture and the porosity of charcoal produced.

Hydrogen Flammability Mitigation in a Containment Vessel Using a Recombiner

Plutonium oxide packaged in a 9975 Primary Containment Vessel (PCV) is evaluated in terms of preventing a flammable gas mixture due to hydrogen generation. Hydrogen is generated via radiolysis of adsorbed moisture on the plutonium oxide. A recombiner is placed in the PCV to recombine hydrogen and oxygen at concentrations to prevent hydrogen flammability. A detailed hydrogen diffusion analysis which evaluates expected and bounding conditions in order to demonstrate that hydrogen concentrations will remain below 5% by volume within PCV is presented.

Interface Reaction Behavior between Mn and SiO2 Formed by RF Sputter Deposition

The Present Work Investigated the Effects of Adsorbed Moisture in Substrates on the Growth of a Self-Forming Barrier Layer between Mn and SiO2. In Order to Control the Adsorbed Moisture, the Substrates of TEOS-SiO2/Si Were Pre-Annealed in Vacuum at Various Temperatures. Then, Mn Thin Films Were Deposited on the Substrate with or without Pre-Annealing. The Results of Interface Reaction after Additional Post-Annealing Indicated that an Interface Reaction Layer Becomes Thinner with Decreasing the Adsorbed Moisture in the SiO2Substrates.