Defect and Diffusion Forum Vol. 365

Abstract: SMC composites consist of chopped glass fiber as a reinforcements, polyester and mineral fillers. Among them, filler is one of the important factors for improving mechanical and thermal properties of composites, but it has not drawn much attention for SMC composites. In this study, the size effect of calcium carbonate as mineral filler on mechanical properties of SMC composites was discussed using five different sizes of commercial calcium carbonates without chopped fiber reinforcement, to focus on the size effect itself. The SMC process was modified to be suitable for a laboratory scale composed of three steps. The mean sizes of the calcium carbonates were 3 – 20 μm, and the specific surface areas were calculated to be 1 – 5 m²/g by BET. Small size of calcium carbonate having high surface area up to 4 m²/g showed high thermal resistance, and showed higher strength comparing to the large fillers because it affected to form a dense packed microstructure.

Abstract: One of the most promising absorber materials for thin-film solar modules are polycrystalline chalcopyrite thin-film solar cells based on Cu (In, Ga)Se₂ (CIGS). By having the direct band gap and high absorption coefficient, CIGS compounds have high solar to electricity conversion efficiency, reliability, and stability. The changes of physical properties of sol-gel derived CIGS thin-films were investigated after the beta irradiation. The effect of ionization radiation on the optical materials is promising in the radiation science and air and space science. The ionized radiation causes changes of physical and chemical properties by exciting the free carriers and forming electron-hole pairs. The irradiaton effect on the CIGS thin-films is evaluated by determining the optical band gap of the films exposed to the beta radiation source by using Sr-90 radioisotope. The variations in structural and optical properties were considered with respect to the absorbed dose level to investigate the characteristic properties of CIGS thin-films.

Abstract: Typically, biodiesel is produced via a chemical reaction called as transesterification of triglycerides obtained from oil crops and animal fat with some kinds of acidic or alkali catalyst and various kinds of alcohol such as methanol, ethanol and even butanol. In this work, some effects of the types of oil/alcohol and alcohol concentrations on the settling behaviour of glycerol, a byproduct obtained during biodiesel production is investigated. The reaction was performed using sodium hydroxide (NaOH) as a catalyst with a reaction temperature (60 oC) and 20 min for the reaction time. The biodiesel yield and the byproduct obtained from each experiment were separated and observed. An equal ratio of the biodiesel and the glycerol was again vigorously remixed. Hereafter, the settling behaviour of glycerol was observed. The results revealed that the settling time was reduced significantly as the alcohol concentration increased. In addition, when a mixture of two types of alcohol is applied, synergetic effect of the mixed alcohols reduced the settling time of the byproduct of glycerol.

Abstract: Work hardening is one of the most widely used methods in strengthening metals by increasing dislocation density, which can be achieved by raising plastic strain and/or suppressing dynamic recovery of the dislocations upon plastic deformation. Based on the analyses on the data reported in our previous work in cold-rolled Pd-H system (Scripta Materialia, Vol. 68 (2013), p. 743), we propose a new strategy in hardening Pd using hydrogen as a catalytic element. It is shown that since the introduction of hydrogen facilitates dislocation formation and increases the dislocation density in Pd upon plastic deformation, subjected to a same deformation level and subsequent removal of hydrogen, Pd can obtain a higher hardness compared to that without hydrogenation before deformation. It is further pointed out that the proposed strategy may, in addition, be applied to other metals, which can dissolve a relatively large amount of hydrogen, e.g. magnesium, nickel and niobium.

Abstract: In this study, a first-principles investigation of hydrogen storage in the FeTi intermetallic is carried out. The structural and electronic changes due to hydrogen insertion into the FeTi intermetallic are determined using DFT and pseudo-potential calculations through the code SIESTA (Spanish Initiative for Electronic Simulation of Thousand of Atoms). The pseudopotentials are constructed using Troullier and Martins parametrization which describes correctly the ion-electron interactions. To define the real-space grid, necessary for numerical calculations of the electron density, detailed tests were performed in order to choose the appropriate basis set, the energy cutoff and the k-grid cutoff. The exchange-correlation potential is treated with the generalized gradient approximation (GGA). Lattice data, bonding properties and the density of states provide an explanation for the role played by hydrogen in the chemical bond with the Ti and Fe constituents.

Abstract: In a global study of titanium alloys behavior in specific aqueous solution (embrittlement, corrosion and corrosion under stresses), the present work focuses on hydrogen diffusion into the metal and the consequences on its microstructure. Two ways of hydrogen charging were used to investigate this issue (gaseous and cathodic charging). The final aim is to determine a fitted method to create an identified microstructure and then to perform accelerated aging tests of titanium U-Bend samples into an autoclave with a specific environment. Hydrogen absorption and formation of titanium hydride have been studied by SEM analyses and by X-ray diffraction methods.

Abstract: Nitriding treatment is well known as one of the corrosion protection methods for steels as well as a way to prevent wear and fatigue. Initially, salt bath nitrocarburizing was popular, but recently, gas nitriding, gas nitrocarburizing, plasma nitriding and so on have come to be used more often because of their superior nitriding ability. In the case of nitriding, only nitrogen (N) diffuses into the steel, but in the case of nitrocarburizing, both nitrogen and carbon (C) diffuse into the steel. General speaking, nitriding includes all the treatments mentioned above. The corrosion behavior of nitride carbon steels has been understood mainly by salt bath or gas nitrocarburizing treatments^1)-4).However, recently, nitriding is mainly applied to parts for things such as automobiles which need protection from wear and fatigue, and is seldom used for parts which need corrosion resistance. The present paper is to remind researchers again that nitrided steels show good corrosion resistance.Therefore, the comparison of various thicknesses of nitride layers as well as the comparison between nitride layers on steel has been carried out in this examination, using the salt spray corrosion test method. The effect of oxidation treatment after nitriding was also investigated.

Abstract: This paper aims to present a mathematical model, based on the thermodynamics of irreversible processes to describe both the heat and mass transfer (liquid and vapor) during the drying of bodies with oblate spheroidal shape. The model was applied to describe drying of lentil grain, considering variables transport coefficients and convective boundary conditions at the surface of the solid. All equations were presented in oblate spheroidal coordinates and numerically solved by using the finite-volume method. Results of the average moisture content, average temperature, liquid flux, vapor flux, and moisture content and temperature distributions inside a lentil kernel during drying process (T=40 oC, RH=50% and v=0.3 m/s) were presented and analyzed.

Abstract: Characterized by excessive moisture at the base of a wall that slowly diminishes in the ascending direction of the wall, rising damp may contaminate building materials with hygroscopic salts. The selection of treatment methods for rising damp should be supported by an exhaustive evaluation and study of the conditioning factors to achieve a successful outcome of the treatment. Many intervention techniques exist for situations that present rising damp, varying in approach and application methods.Due to the information about treatment products and systems for rising damp being generally dispersed, this may cause the selection of treatments with inadequate approaches that hinder the effectiveness. Thus, a necessity exists to collect and systematize information on all treatment options for rising damp. HUMITECNIC files/catalogue allows the fulfilment of that objective.HUMITECNIC files/catalogue is prepared based on an extensive search of systems, products and treatments in the civil engineering marketplace, patented or not, accompanied when necessary by a suitable bibliography. In this way, the user is presented with different treatment options that communicate the intervention approach, the technology used, installation process, relevant properties, application and limitations. In a way to promote the information to users in a dynamic an interactive way, the catalogue is available from the purpose built HUMITECNIC website.

Abstract: In the present work, positron annihilation spectroscopy was employed for investigation of hydrogen-induced defects in Pd. Well annealed Pd samples were electrochemically charged with hydrogen and development of defects during hydrogen loading was investigated. At low concentrations (α-phase, x_H < 0.017 H/Pd) hydrogen loading introduced vacancies. When the hydrogen concentration exceeds 0.017 H/Pd, particles of hydrogen rich α’-phase are formed. This generates dislocations in the sample in order to accommodate the volume mismatch between the α and the α’-phase. Moreover, additional vacancies are introduced into the sample by crossing dislocations. Vickers hardness testing revealed that absorbed hydrogen causes hardening of the sample. In the α-phase region the hardness increases due to solid solution hardening caused by dissolved hydrogen. At higher hydrogen concentrations when dislocations were created hardness increases due to strain hardening caused by dislocations.