Sort:
Show:
Page Size:
Topic review
Updated time: 10 Aug 2021
Submitted by: Jovan Tan
Definition: Since its discovery, magnesium has played an influential role in society. In its early days, military applications and wars fueled its growth. For example, magnesium was weaponized to construct incendiary bombs, flares, and ammunitions that were subsequently deployed in World War II, and it caused massive conflagrations and widespread devastations. Post-War, magnesium’s availability and unique blend of properties were explored and were found to be highly attractive for an extensive range of applications. Today, magnesium is used for engineering applications in automotive, aerospace, and consumer electronics. In addition, it has a role in organic chemistry and pharmaceuticals and is used to construct several general-purpose applications, such as sporting goods, household products, and office equipment.
Topic review
Updated time: 27 Aug 2021
Definition: The aim of this work is to explain the concepts of sustainability with respect to small artisanal gold mining. For this, a qualitative approach with a descriptive scope was used, for which the bibliographic review technique was conducted. In this sense, articles, theses, books and institutional documents, and any contribution related to the research topic were taken into consideration. Likewise, this documentation contributed to the delimiting aspects that allowed a contrast between the proposed definitions and small artisanal mining in the Northeast Antioquia region in Colombia. Based on the reviewed sources, different needs were recognized in artisanal small-scale gold mining in Northeast Antioquia that still need action. In conclusion, through the exposition of sustainability theories, three common factors were identified within the various positions that were raised—the environmental, economic, and sociocultural dimensions.
Topic review
Updated time: 16 Jul 2021
Submitted by: Ruitao Qu
Definition: Metallic glass (MG) is a class of metallic material fabricated by the fast-cooling during solidification. This alloy lacks the long-range order characteristic and the crystalline defects including grain boundaries and dislocations. The unique structural feature makes some mechanical properties of MG obviously superior than conventional crystalline alloys, such as strength, hardness, elastic limit, wear resistance, etc. It is estimated that ~90% of all mechanical failures in the structural materials are caused by fatigue. Thus, the fatigue property is an important evaluation index before a new structural material application. Without the dislocations and grain boundaries, the plastic deformation of MG occurs in the form of atomic clusters operation at room temperature, eventually leading to the generation of shear band. It is found that the fatigue damage and fracture of MGs were dominated by shear band. As a result, understanding how shear band evolution under cyclic loading is important for improving the fatigue performance of MGs.
Unfold
Topic review
Updated time: 23 Jun 2021
Submitted by: BEHZAD SADEGHI
Definition: Flake powder metallurgy (FPM) including different processing routes, conventional FPM (C-FPM), slurry blending (SB), shift-speed ball milling (SSBM), and high-shear pre-dispersion and SSBM (HSPD/SSBM). The name of FPM was derived from the use of flake metal powders obtained by low-speed ball milling (LSBM) from spherical powder. The uniformity of reinforcement distribution leads to increased strength and ductility. Powder is the basic unit in PM, especially advanced PM, and its control is key to various new PM technologies. The FPM is a typical method for finely controlling the powder shape through low-energy ball milling (LEBM) to realize the preparation of advanced material structures.
Unfold
Topic review
Updated time: 20 Apr 2021
Submitted by: Lawrence Cho
Definition: Recent research efforts to develop advanced–/ultrahigh–strength medium-Mn steels have led to the development of a variety of alloying concepts, thermo-mechanical processing routes, and microstructural variants for these steel grades. However, certain grades of advanced–/ultrahigh–strength steels (A/UHSS) are known to be highly susceptible to hydrogen embrittlement, due to their high strength levels. Hydrogen embrittlement characteristics of medium–Mn steels are less understood compared to other classes of A/UHSS, such as high Mn twinning–induced plasticity steel, because of the relatively short history of the development of this steel class and the complex nature of multiphase, fine-grained microstructures that are present in medium–Mn steels. The motivation of this paper is to review the current understanding of the hydrogen embrittlement characteristics of medium or intermediate Mn (4 to 15 wt pct) multiphase steels and to address various alloying and processing strategies that are available to enhance the hydrogen-resistance of these steel grades.
Unfold
Topic review
Updated time: 27 Apr 2021
Submitted by: Denzel Bridges
Definition: Nanojoining is the process of joining two surfaces together using nanomaterials as the primary filler metal. It includes, but is not limited to, nanosoldering, nanobrazing, and some forms of additive manufacturing. Note that, like with conventional soldering and brazing, only the filler metal undergoes melting, not the base material. Nanomaterials are materials in which at least one dimension 100 nm or less and include 0-D (e.g. nanoparticles, 1-D (e.g. nanowires and nanorods), 2-D (e.g. graphene), and 3-D (e.g. nanofoam) materials. Nanomaterials exhibit several notable properties that allow joining to occur at temperatures lower than the melting temperature of their bulk counterpart. For example, the melting temperature of Ag is 961.78 °C, but Ag nanomaterials begin to melt at a much lower temperature that is dependent depending on the size and shape. These properties include high surface area to volume ratio, the Gibbs-Thompson effect, and high surface energy. The low joining temperature of nanomaterials has been exploited numerous times for flexible electronics, printable electronics, and soldering applications; only within the last two decades have they been explored for high-temperature joining applications (>450 °C).
Unfold
Topic review
Updated time: 08 Jul 2021
Submitted by: MEHMET ALI RECAI ONAL
Definition: The ferromanganese (FeMn) alloy is produced through the smelting-reduction of manganese ores in submerged arc furnaces. This process generates large amounts of furnace dust that is environmentally problematic for storage. Due to its fineness and high volatile content, this furnace dust cannot be recirculated through the process, either. Conventional MnO2 production requires the pre-reduction of low-grade ores at around 900 °C to convert the manganese oxides present in the ore into their respective acid-soluble forms; however, the furnace dust is a partly reduced by-product. A hydrometallurgical route is proposed to valorize the waste dust for the production of battery-grade MnO2. By using dextrin, a cheap organic reductant, the direct and complete dissolution of the manganese in the furnace dust is possible without any need for high-temperature pre-reduction. The leachate is then purified through pH adjustment followed by direct electrowinning for electrolytic manganese dioxide (EMD) production. An overall manganese recovery rate of >90% is achieved.
Entry Collection : Environmental Sciences
Unfold
Topic review
Updated time: 03 Sep 2021
Submitted by: Haris Khan
Definition: The roll bonding (RB) process involves joining of two or more sheets of similar or dissimilar materials at various temperatures. The process requires rolling through a pair of rollers under adequate pressure resulting in the bonding of sheets. The process is categorized into three types, i.e., cold, hot, and warm roll bonding based on the ranges of the processing temperature which in turn is related to the recrystallization temperature.
Unfold
Videos
Updated time: 18 Sep 2021
Topic review
Updated time: 13 Sep 2021
Submitted by: Lingling Cao
Definition: Turbulent flow can be numerically resolved with different levels of accuracy. Many numerical approaches for solving turbulence have been proposed, such as the Reynolds-Averaged Navier–Stokes (RANS), the Large Eddy Simulation (LES), and Direct Numerical Simulation (DNS) approaches. Among these numerical methods, the RANS approach, specifically the Eddy Viscosity Model (EVM), is widely used for calculating turbulent flows thanks to its relatively high accuracy in predicting the mean flow features and its more limited computational demands. However, this approach suffers from several weaknesses, e.g., compromised accuracy and uncertainties due to assumptions in the model construction and insufficient incorporation of the fluid physics. In the LES approach, the whole eddy range is separated into two parts, namely, the large-scale eddy and subgrid-scale (SGS) eddy. The former can be directly resolved, while the latter is computed using the SGS model. As the computing power rapidly increases, this approach is extensively used to study turbulence physics and to resolve low-to-medium Reynolds number flows.
Unfold