Ab initio Study of the Electronic and Optical Properties of Stable Boron Sheet

Utilizing first principles calculations within PW91 exchange-correlation method, we investigated a boron sheet that exhibits related electronic properties. The 2-dimensional boron sheet is flattened and has an atomic structure where the pair cores of every three ordered hexagons within the hexagonal network are loaded up by extra atoms, which saves the triangular lattice symmetry. The boron sheet takes possession of intrinsic metal properties and the electronic bands are comparable to the bands of the graphene that are close to the Fermi level. The real and imaginary parts of the dielectric function show a metallic or semiconductor behaviour, depending on the electric field direction.

The Seawater Heavy Metal Content of the Mining Port Close to the Residential Area in the Morowali District

Mining port operations are complex and can cause various forms of pollution. Analysis of seawater pollution from mining ports is required and complicated because of the various types of pollution, sources, effects, and different characteristics. This study examines the content of heavy metals in seawater in residential areas very close to mining ports. The method used sampling in three different places, examining seawater’s heavy metal properties. Secondary data of the quality of seawater was obtained from the results of data monitoring carried out by the company periodically since the port was built as a comparison material from the results of sample inspection. The results of this study indicate that the waters around the settlements contain heavy metals. The composition of Cd was 10%, Pb was125%, Cu was 625%, Ni was 760%, and Zn was 300% above the standard of seawater quality for the Port Area set by the Indonesian government, which did not match the yearly reports (secondary data). On the other hand, community activities also have a minor role as a source of pollution. Therefore, it is essential to do further research with a focus on finding sources of pollution.

Triclinic boron nanosheets high-efficient electrocatalysts for water splitting

Recently, two-dimensional (2D) boron nanosheets have been predicted to exhibit exceptional physical and chemical properties, which is expected to be widely used in advanced electronics, optoelectronic, energy storage and conversion devices. However, the experimental application of 2D boron nanosheets in hydrogen evolution reactiuon (HER) has not been reported. Here, we have grown ultrathin boron nanosheets on tungsten foils via chemical vapor deposition (CVD). The prepared triclinic boron nanosheets are highly crystalline, which perfectly match the structure in the previous theoretical calculations. Notably, the boron nanosheets show excellent HER performance. The Tafel slope is only 64 mV/dec-1 and the nanosheets can maintain good stability under long-time cycle in acidic solution. The improvement of performance is mainly due to the metal properties and a large number of exposed active sites on the boron nanosheets, which is confirmed by first-principle calculations.

Research of influence of heat treatment on metallophysical properties of metal of welded seams

Цель настоящего исследования - оценка влияния локальной термической обработки (нормализации и закалки с отпуском для продольных сварных соединений труб, сваренных контактной сваркой токами высокой частоты, а также высокотемпературного отпуска и термического отдыха для кольцевых стыков трубопроводов, сваренных дуговой сваркой) на показатели механических свойств и металлургического качества металла сварных соединений. Для проведения исследований в области продольных сварных соединений использовались трубы диаметром 530 мм с толщиной стенки 10 мм класса прочности К56, для оценки свойств металла кольцевых стыков были выбраны катушки длиной 500 мм с односторонней симметричной разделкой кромок с углом скоса 30°, изготовленные из труб диаметром 219-530 мм с толщиной стенки 8-15 мм из сталей класса прочности К42, К48, К56. В частности, показано, что высокий отпуск повышает пластичность, снижает уровень остаточных сварных напряжений (более чем на 30 %), твердость и прочность. Термический отдых сварных стыков способствует снижению уровня остаточного водорода в металле сварных соединений, что позволяет повысить свариваемость трубной стали при проведении ремонтных работ. В целом сделан вывод о том, что локальная термообработка позволяет оптимизировать показатели механических свойств металла сварных соединений и при необходимости получать требуемый уровень механических свойств. The purpose of this study is to assess the effect of local heat treatment (normalizing and quenching with tempering for longitudinal welded joints of pipes welded through contact welding with high frequency currents, and high-temperature tempering and cooling for arc welded circular joints of pipelines) on the mechanical properties and metallurgical quality of welded joint metal. To carry out research in the field of longitudinal welded joints, pipes with a diameter of 530 mm and a wall thickness of 10 mm with the K56 strength grade were used; to assess the metal properties of ring joints, 500 mm long spools with unilateral symmetrical beveling with a bevel angle of 30°, made of pipes with a diameter of 219-530 mm with wall thickness of 8-15 mm made from K42, K48, K56 strength grade steel, were used. In particular, it is shown that high tempering increases ductility, reduces the level of residual weld stresses (by more than 30 %), hardness and strength. Cooling of welded joints helps to reduce the level of residual hydrogen in the welded joint metal, which increases the weldability of pipe steel during repair works. In general, it is concluded that local heat treatment allows to optimize the indicators of mechanical properties of the welded joint metal and, if necessary, to obtain the required level of mechanical properties.

Improvement of Sheet Metal Properties by Inducing Residual Stresses into Sheet Metal Components by Embossing and Reforming

In sheet metal forming, combination of embossing and reforming allows the mechanical properties of sheet metal materials to be specifically improved. Here, local property modification is achieved by the residual stresses induced as a result of the one-sided embossing process followed by a reforming step. The residual stresses induced in this specific way can lead to a significantly increase in the fatigue strength of processed sheet metal components. However, in order to ensure this kind of component optimization in continuous operation, the induced stresses have to be homogeneous. In this respect, the main objective of the study reported about in this paper was to identify a forming strategy, consisting of the process steps embossing and reforming, that generates preferably homogeneous residual stress distributions into sheet metal blanks. For this, numerical and experimental investigations were carried out with samples of the stainless steel (X6Cr17) having a thickness of 1.5 mm. It was found that embossing and reforming, integrated into a conventional forming process, is a novel approach to specifically induce very localized homogeneous compressive residual stresses in sheet metal materials. This eliminates the need for costly post-processing by means of surface treatment.

Review on Manufacturing of Metal Foams

Metal foams possess excellent physical and mechanical properties. This paper reviews the common manufacturing process of metal foams. Various ways used to produce metal foams based on metal properties are described. The manufacturing process follows four primary routes: liquid state, solid state, ion or vapour processing. Liquid-state processing produces porosity to liquid or semi-liquid metals, and solid-state foaming produces metal foams with metal powder as starting material. For ion and vapour processing methods, metals are electro-deposited onto a polymer precursor. The polymer precursor is removed by chemical or heat treatment to produce metal foams. The advantages and limitations of each manufacturing process are also described.

Effect of Substrate Alloy Type on the Microstructure of the Substrate and Deposited Material Interface in Aluminium Wire Arc Additive Manufacturing

Wire + Arc Additive Manufacture is an Additive Manufacturing process that requires a substrate to initiate the deposition process. In order to reduce material waste, build and lead time, and improve process efficiency, it is desirable to include this substrate in the final part design. This approach is a valid option only if the interface between the substrate and the deposited metal properties conform to the design specifications. The effect of substrate type on the interface microstructure in an aluminium part was investigated. Microstructure and micro-hardness measurements show the effect of substrate alloy and temper on the interface between the substrate and deposited material. Microcracks in the as-deposited condition were only found in one substrate. The deposited material hardness is always lower than the substrate hardness. However, this difference can be minimised by heat treatment and even eliminated when the substrate and wire are made of the same alloy.

Code control for parametric models of induction heaters

In this paper, we describe our approach to building controllable models of induction heaters. Parameters of equivalent circuits of aluminum heating inductors include certain components tied to secondary elements. As long as metal properties are subject to change during the heating process, resistive and reactive parts of equivalent circuits should be taken into account. Adjustable resistive components have rarely been used in circuit models. To control equivalent resistive two-terminal parts, we offer pulse code control of impedance-changing switches. Controlling switching time in models with series, parallel, and mixed connection provides required softness of resistive conductivity change. Control characteristics of current and voltage were obtained with use of a simulator. As the result of our numerical experiment, the set of operating parameters for an induction device was determined.