Accelerated Optimization of Pure Metal and Ligand Compositions for Light-driven Hydrogen Production

Photocatalytic hydrogen production is a promising alternative to traditional hydrogen production. To implement photocatalytic hydrogen production the development of efficient, sustainable, and stable catalysts is necessary, and overcoming the current...

Effect of porosity and skew edges on transient response of functionally graded sandwich plates

This work for the first time presents the effect of porosity and skew edges on the transient response of functionally graded material (FGM) sandwich plates using a layerwise finite element formulation. Two configurations of FGM sandwich plates are considered. In the first configuration, the top and the bottom layers are made of the FGM and the core is made of pure metal, whereas in the second configuration, the bottom, core and the top layers are made of pure metal, FGM and pure ceramic, respectively. Four micromechanics models based on the rule of mixture are used to model porosity for these two configurations of FGM sandwich plates. A layerwise theory based on a first-order shear deformation theory for each layer that maintains the displacement continuity at the layer interface is used for the present investigation. An eight-noded isoparametric element with nine degrees of freedom per node is used to develop the finite element model (FEM). The governing equations for the present investigation are derived using Hamilton’s principle. A wide range of comparison studies are presented to establish the accuracy of the present FEM formulation. It has been shown here that the parameters like skew angle, porosity coefficient, volume fraction index, core to facesheet thickness ratio and boundary conditions have a significant effect on the transient response of FGM sandwich plates. Also, the present finite element formulation is simple and accurate.

Effect Of Suvarna Bhasma (Gold Calx) On Reproductive System Of Male Albino Rats

Suvarna Bhasma” (gold calx) (SB) prepared as per Ayurveda, a practicing medical system, is prescribed as a medicine in several ailments including conditions like oligozoospermia and asthenoszoospermia in male infertility. SB is prepared from pure metal gold by one of the processing methods detailed in Ayurveda classics. Gold along with other elements was reported in normal human seminal plasma. . In human pathological semen samples, the level of gold was less than normal. Gold may have a role in physiological activity of sperm as shown in case of other elements. The present study supports the hypothesis that the presence of gold is essential for sperm motility. Here we studied the effect of SB on male reproductive organs and semen from epididymis of rat. Present study was performed using Charles foster strain albino rats. Rats were divided into two groups of ten each namely, Group 1 (control) and Group 2 (study). Animals in study group were orally given a fixed amount of SB for 15 days. At the end of the study treated animals showed increase in body weight (<0.05) and testicular weight. In treated animals total sperm count (<0.05) and percentage of sperm motility were increased in epididymal fluid. Histological study showed increase in interstitial area of testes (<0.001), proliferation and branching of the epithelial layer of seminal vesicle. In the Study (gold treated) Group, the increased gold level in genital system may be responsible for the increase in sperm production and motility.

Vacuum wetting and contact interaction of some of the metallic melts with indium and tin oxides

Due to the unique combination of electric and optical properties such semiconductor oxides as tin and indium oxides are very perspective multifunctional materials for variety of microelectronic devices production. Experimental studies of these materials allow to define, for example energetic characteristics of the devices created and also to improve existing technologies of films formation, joining of electrocontacts to tin and indium oxides based materials by way of brazing which require additional wetting studies. It should be noted that data on wetting of mentioned oxides by metals are practically absent in literature. Thus a detailed study of the interfacial interaction, adhesion and wetting of ceramic SnO2 and In2O3 materials with some pure metal melts in vacuum was performed by the sessile drop method using foto- and video- fixing including concentration, temporal and temperature dependences of contact angles. It was found that most of the pure metals studied don't wet SnO2 ceramics. However rather intense chemical interaction took place in vacuum at high temperatures in contact of some metals (Sn, Ge, In) with surface of SnO2. It was also shown the effect of the experiment temperature and hold-up time on the values of contact angles. Wetting angles for powdery pressed specimens of In2O3 in the temperature range studied don't change noticeably and vary in a narrow range. For example, for Ga wetting angles vary from about 138 to 128 deg and for Sn  125119 deg, Wetting of SnO2 surface with AgCu melt with different copper content was shown to be insufficient to use it as a brazing alloy, yet this system can be used as a basis for creating a brazing composition. Keywords: indium oxide, tin dioxide, semiconductor, wetting, contact interaction, metal melt.

Hardness–Deformation Energy Relationship in Metals and Alloys: A Comparative Evaluation Based on Nanoindentation Testing and Thermodynamic Consideration

Nanoindentation testing using a Berkovich indenter was conducted to explore the relationships among indentation hardness (H), elastic work energy (We), plastic work energy (Wp), and total energy (Wt = We + Wp) for deformation among a wide range of pure metal and alloy samples with different hardness, including iron, steel, austenitic stainless steel (H ≈ 2600–9000 MPa), high purity copper, single-crystal tungsten, and 55Ni–45Ti (mass%) alloy. Similar to previous studies, We/Wt and Wp/Wt showed positive and negative linear relationships with elastic strain resistance (H/Er), respectively, where Er is the reduced Young’s modulus obtained by using the nanoindentation. It is typically considered that Wp has no relationship with We; however, we found that Wp/We correlated well with H/Er for all the studied materials. With increasing H/Er, the curve converged toward Wp/We = 1, because the Gibbs free energy should not become negative when indents remain after the indentation. Moreover, H/Er must be less than or equal to 0.08. Thermodynamic analyses emphasized the physical meaning of hardness obtained by nanoindentation; that is, when Er is identical, harder materials show smaller values of Wp/We than those of softer ones during nanoindentation under the same applied load. This fundamental knowledge will be useful for identifying and developing metallic materials with an adequate balance of elastic and plastic energies depending on the application (such as construction or medical equipment).

Thermal performance of roofs suitable for developing countries in tropical climate

Roof structures have been traditionally built from reed or straw in tropical climate locations. Now, traditional materials are often replaced by pure metal sheets. The roof construction is improved in terms of durability and cost effectiveness, but he roof built from pure metal sheets can cause excessive overheating of interior spaces. The aim of this paper is to compare dynamic thermal performance of different roof assemblies under real boundary conditions. For this purpose, a thermally insulated test box was built on the roof of the university. Six roof samples (0,9 m × 1,1 m) can be mounted on the roof. The roof covering made of pure steel sheet with Zn coating was the reference case. This assembly was then modified step-by-step either by change of colour, or by additional material layers of reed and earth boards, or by 2cm thick ventilated air cavity on the rear side of the sheet. In total, 18 different roof assemblies were tested in three consecutive test runs (approximately three-week periods between 07 – 09-2020). Ventilated air gap and white paint are the best adjustments to reduce heat flux. Dark colours of the metal sheet have the opposite effect. Influence of reed and earth boards was in many cases similar. One roof assembly was selected for use in real project.

Creation of complex composites from Metal-Organic Frameworks with pure metal nanoparticles under electronic irradiation

Metal-organic frameworks (MOFs) are unique materials with high porosity and flexibility utilized widely in chemistry and physics. However, they could be used as initial materials for creation new types of composites with nanoparticles. The creation of NPs inside MOFs crystals is related with different types of outer stimuli (temperature, light, and electron irradiation). Here we report about a new approach of the creation complex composites from MOFs’ crystals using the electron irradiation of the transmission electron microscope (TEM) as a highly precise method for the growing of different types of Ni and Cu nanoparticles and discuss about the dynamical process of NPs growth using the classical kinetic theory.

Review on bimetallic catalysts for electrocatalytic denitrification

Accelerated industrialization disrupts the global nitrogen cycle, resulting in alarmingly increased nitrate in groundwater and other water bodies. Electrocatalytic nitrate reduction (NO3RR) with high automation can effectively remove nitrate from polluted water, thus avoiding nitrate accumulation. However, the sluggish cathode reaction kinetics severely hampered the efficiency of NO3RR. Developing high-performance cathode catalysts is of great significance for boosting NO3RR. Compared with pure metal catalysts, bimetal catalysts can further improve the cathode activity and selectivity to nitrogen or ammonia in the electrocatalytic process, attracting extensive research interest. In this review, we discussed the background of denitrification requirements and the development status of bimetallic denitrification catalyst. Metallic cathode catalysts, such as noble-metal, 3d transition metal, main group metal, are described emphatically. Finally, present challenges and future outlook on bimetallic denitrification catalysts are depicted.