Surface pre-treatment and its influence on electric functionality and the formability of screen printed steel sheet

Industrial development focuses on multifunctional components due to rising requirements regarding e.g. light weight and security. A beneficial possibility to extend the functionality of structural components produced by metal forming is the usage of screen printed metal blanks. During the printing process insulating and electric inks are applied. The examined printed layer structure consists of three insulating full area layers and one conductive layer in the form of strain gauges. The two applied inks are solvent-based and printed with a half-automatic machine. To improve the adhesion and electric functionality, the impact of different mechanical and physical surface pre-treatments on the electrical characteristics is investigated in tensile tests. In particular, abrasive peening, ball peening, grinding and polishing (mechanical) and in addition plasma and corona technology (physical) were utilised. Contrary to expectations, the surface pre-treatment does not affect the adhesion to the steel sheet. The cracking of the printed strain gauges takes place prior to the delamination of the coating. Explanatory models are elaborated. They are based on the measurements of roughness, surface energy, edge sharpness and the electrical resistance of printed conductive structures before, during and after forming.     

Transparent Nanocrystalline Glass-Ceramic System for Organic Pollutants Degradation

Because of the superior photocatalytic activities of nanocrystalline TiO₂ and ZnO under UV irradiation, they were embedded into the glass system (SiO₂, TiO₂, ZnO, B₂O₃, Na₂O, K₂O, P₂O₅, Li₂O and BaO) to provide easy separation from the aqueous system. Different contents of TiO₂ and ZnO have been investigated. Conversion to glass-ceramic materials was carried out by heat treatment at 450 °C, which is the onset of the nucleation peak according to the differential thermal analysis (DTA) result, for different times. This heat treatment regime preserves the transparency of the prepared materials in the visible region and good absorption in the UV region. The high content of TiO₂ or ZnO caused an improvement of microhardness of the prepared materials, though the presence of the two oxides with the same ratio decreased the microhardness values. Photocatalytic activity of the prepared glass-ceramic materials was investigated according to their efficiency for the degradation of humic acid (HA), the major precursor of disinfection by-products (DBPs), from water. All samples were proved to be photoactive with different extents. Four hours heat treatment at 450 °C appears to be the best conditions for the development of TiO₂ and ZnO crystals leading to better photocatalytic activity.     

Efficient PL Emission from p-type Porous Silicon: A Comparative Study for Selection of Effective Anodization Parameters

The physical mechanism of highly efficient photoluminescence (PL) emission from p-type silicon is described by a comparative study of the effectiveness of the etching parameters in an electrochemical anodization technique. Two series of porous silicon samples were prepared in a combination of anodization current and time, to maintain the total amount of anodic charge transfer constant. Photoluminescence studies show that irrespective of the amount of charge transfer, the samples prepared with comparatively higher current density show an efficient PL as well as stronger blueshift in the emission energy vis-à-vis the samples prepared for longer durations. An overall decrease in crystallite size, as estimated by Raman spectral analysis, was observed for both series of samples with the progress of charge transfer. Comparative analysis shows a marginal difference in crystallite size for both series of samples in the initial state of charge transfer, whereas major differences arise at higher values. This is explained with the formation of silicon suboxide on the porous surface at higher current density, leading to initiation of side wall reaction, and higher reduction rate in crystallite size as well as strong luminescence due to the carrier quantum confinement effect.     

An Investigation of Mechanical Properties of Polyurethane Nanocomposites with Various Silicas: Experimental Study and Modeling of Finite Deformation Response

It is well-known that polymer nanocomposites can bring about superior mechanical, thermal, optical, physical, and chemical properties in comparison with pure polymers. In this study, different contents of unmodified silica nanoparticles (Si-Un), surface modified nano-silica by octylsilane (Si-OS), and surface modified nano-silica by polydimethylsiloxane (Si-PDMS) are added to the polyurethane (PU) matrix and their effects on the physical properties of the polymer examined. The experimental results indicate that most of the nanocomposites have a higher tensile strength and elongation. In addition, hyperelastic energy function models have been used to model the stress-strain relation of the nanocomposites. In this study, Mooney-Rivlin, neo-Hookean, Rivlin general polynomial, and Davies-De Thomas (DDT) models have been investigated, possessing respectively, two, one, eight, and three constants to be determined. The differential evolution (DE) optimization method, a strong heuristic optimization algorithm, has been used to find the constants; in which the absolute summation of the differences between the models’ predictions and experimental data is taken into account as the objective function and the models’ constants are considered as the decision variables. Moreover, equation constants are found by using regression, an indicator of DE optimization superiority. The results show that even though the Rivlin general polynomial model provides the most accurate prediction, the DDT model, consisting of three constants, can be considered as the most acceptable one.     

Segregation Behavior of Metal Impurities During Al-Si Melt Directional Solidification with an Open Ended Crucible

The distribution characteristic and segregation behavior of metal impurities during directional solidification of Al-20Si, Al-30Si and Al-40Si alloys have been investigated. The morphologies of the alloys and impurity phases were observed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The concentration profiles of representative metal impurities Al, Fe and Ti were measured by inductively coupled plasma optical emission spectrometry. The results indicate that the metal impurities segregate into the eutectic Al-Si melt during the growth of primary Si flakes and gradually segregate towards the top of each ingot during directional solidification. A concept of apparent segregation coefficient is proposed to characterize the segregation behavior of impurity elements. The apparent segregation coefficients of metal impurities decrease with increase in solidification temperature of the Al-Si alloys.     

Optimization of Preparation Conditions to Control Structural Characteristics of Silicon Dioxide Nanostructures Prepared by Magnetron Plasma Sputtering

In this work, highly-pure silicon oxide nanostructures were prepared by a closed-field unbalanced magnetron plasma sputtering technique. These nanostructures were characterized by Fourier-transform infrared spectroscopy, UV-visible spectroscopy, x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy and atomic force microscopy in order to determine the optimum preparation conditions. Minimum particle size of 20 nm was determined for the samples prepared at an inter-electrode distance of 4 cm, Ar:O₂ gas mixing ratio of 70:30, total gas pressure of 0.08 torr, discharge voltage of 2.5 kV, discharge current of 35 mA, anode temperature of 27 ^°C (room temperature) and cathode temperature of about 40 ^°C. These conditions are optimized to control the structural characteristics of such nanostructures and hence to satisfy certain requirements and purposes in spectroscopic and photonic applications of SiO₂ nanostructures.     

Appraisal of Agriglass in Promoting Maize Production Under Abiotic Stress Conditions

An agriglass composition containing different oxides acts as a slow release for macro and micro nutrients and was chosen to improve maize yield under most important abiotic stresses which affecting agriculture development; salinity and drought. A field experiment was performed in salt affected soil (EC =?7.5 dSm^??1) by using different water deficit rates (I1 = 100, I2 = 85 and I3 = 70% of maize water requirements). Irrigation levels were located in main plots. Every main-plot divided into six sub-plots contained glassy fertilizer treatments [F1 = 55 kg fed^?1 with 1/2 mm diameter of agriglass (fed. =?4200 m²), F2 = 55 kg fed^?1 with 1 mm diameter, F3 = 80 kg fed^?1 with 1/2 mm diameter, F4 = 80 kg fed^?1 with 1 mm diameter, F5 = Recommendations of Ministry of Agriculture and F6 = control]. The experimental results demonstrated that, ears, straw, grains and biological yields increased with increasing both water and agriglass rates. Application of agriglass as a slow release fertilizer improved yield more than mineral fertilizer. Some growth parameters, water use efficiency (IWUE), macronutrients concentration and their relations were included. Other studies on residual effect of agriglass and the annual application rates to withstand salinity and drought stress by strategic crops are required.     

One-Pot,Three-Component Synthesis of 2,3-Dihydro-4(1H)-Quinazolinones Catalyzed by Perchlorated Zirconia (HClO<Subscript>4</Subscript>/ZrO<Subscript>2</Subscript>) Nanoparticles as a Solid Acid Catalyst

Mono and disubstituted 2,3-dihydroquinazolin-4(1H)-ones were obtained in good yields via a one-pot, three component reaction of isatoic anhydride and aromatic aldehydes with ammonium acetate or primary amines in the presence of perchlorated zirconia (HClO₄/ZrO₂) nano particles as an efficient solid acid catalyst under solvent-free conditions. Simple workup and reusability of the catalyst are advantages of this method.     

Mini Review on the Structure and Properties (Photocatalysis), and Preparation Techniques of Graphitic Carbon Nitride Nano-Based Particle,and Its Applications

Graphite carbon nitride (g-C₃N₄) is well known as one of the most promising materials for photocatalytic activities, such as CO₂ reduction and water splitting, and environmental remediation through the removal of organic pollutants. On the other hand, carbon nitride also pose outstanding properties and extensive application forecasts in the aspect of field emission properties. In this mini review, the novel structure, synthesis and preparation techniques of full-bodied g-C₃N₄-based composite and films were revealed. This mini review discussed contemporary advancement in the structure, synthesis, and diverse methods used for preparing g-C₃N₄ nanostructured materials. The present study gives an account of full knowledge of the use of the exceptional structural and properties, and the preparation techniques of graphite carbon nitride (g-C₃N₄) and its applications.     

Numerical and experimental study of conjugate heat transfer in a horizontal air cavity

The demand for general reduction of the energy consumption in civil engineering leads to more frequent use of insulating materials with air gaps or cavities. Heat transfer through a constructional part can be decreased by adding an air gap and low emissivity reflective foils to the structure. In the first part of this paper, the impacts of cavity thickness and inner surface emissivity on combined conduction, convection and radiation heat transfer was experimentally explored in the case of constructional part with a horizontal cavity subjected to constant downward heat flux. The heat flow meter Netzsch HFM 436 Lambda was used for steady-state measurements. Results suggest that the studied parameters seriously affect the combined heat transfer in the composed structure. In the second part the paper reports the numerical study of two-dimensional conjugate heat transfer in closed horizontal cavity having air as the intervening medium. Numerical models validated by related experimental results were performed to further investigate the effect of radiation heat transfer. It was found that in general, the total heat flux through the composed structure decreases with increasing air cavity thickness, which is significant especially when low emissivity inner surfaces are taking into account. The direction of heat flow (downward or upward heat flow) has a significant impact on the convection heat transfer. An important contribution from the present work is the analysis of the optimal thickness of the cavity at different boundary conditions. The optimal thickness of the enclosure with low emissivity surfaces is 16 mm when subjected to upward heat flux.