Papers by Keyword: Structure

Abstract: Aluminum alloys are known for their wide application in the automotive, river and marine boat constructions, but also in hydraulic systems (radiators/oil coolers). Their use is made by manufacturing parts directly from the semi-finished state, with or without certain volumetric heat treatments and surface hardening, depending on the functional role and the physical-mechanical characteristics pursued. Some of these parts work in hydrodynamic conditions, where cavitation manifests itself through erosion, such as: propellers of boats and barges, pump rotors in water cooling systems of automobiles. Visual analyzes performed on sailboat and powerboat propellers, after identical durations and operating conditions, showed cavitation erosion damage, different depending on the type of aluminum alloy. As a result, the paper presents and analyzes the behavior and resistance to erosion by vibratory cavitation of 4 types of aluminum alloys in the state of rolled semi-finished products. To highlight the differences in the destruction of structures under the cyclic stresses of cavitational microjets, macro and microscopic images of the eroded structure are used, as well as the curves with the values of the parameters specific to cavitation, recommended by the ASTM G32 -2016 norms and used in the research laboratory's custom. The analysis of the results shows that the resistance of the structure to cavitation erosion is dependent on the type of alloy, the degree of brittle intermetallic compounds and the mechanical properties specific to toughness.

Abstract: East Kalimantan’s Coal has total humidity level at 18.21%, inherent humidity of 12.39%, fly ash content of 5.18%, volatile compounds of 38.22% and heat content of 6084 kcal/kg. However, chemical composition, functional group and crystallinity of raw and water rinsed Loa Janan bituminous coal have not been reported elsewhere. This research aims to investigate whether water rinsed treatment affects the structure of the coal or not. Coal size at 100 mesh-200 mesh is divided into 2, labeled as bituminous (a) stands for raw bituminous and bituminous (b) is for water rinsed-one. The bituminous (a) was analyzed using scanning electron miscroscopy (SEM)-energy dispersive xray (EDX), x-ray fluorescence (XRF), fourier transform infrared (FTIR) and powder x-ray diffraction (p-XRD) spectrophotometer. Meanwhile, bituminous (b) was heated at 40°C for 10 hours, cooled, rinsed using aquademin (1:5), stirred for 3 hours at 1500 rpm, and filtered. The bituminous (b) was heated at 40°C for another 10 hours and was characterized using the same technique as conducted to bituminous (a). Images revealed by SEM-EDX confirms the morphology ang topology of bituminous coal and the carbon content of them are 70.24% ± 0.87 (coal a) and 70.73% ± 0.08 (coal b). X-ray fluorescence analysis revealed that the bituminous (a) consisted of: Fe (46%), Si (21.5%), Al (5.4%) and bituminous (b): Fe (45%), Si (18.4%), Al (4.5%). There is a significant difference of their infrared spectra, both showed the peak at 1620 cm^-1 (C=C) for carbon aromatic vibration. The wide area of peak at 3423 cm^-1 is responsible for OH stretching vibration. Peaks intensity at 1620 cm^-1 and 3420 cm^-1 of bituminous (b) increased about 43.11% and 43.34%, respectively. The crystallinity degree of bituminous (b) (47.56%) is lower than that of bituminous (a) (69.72%). A sharp peak of XRD spectrum located at 2θ of 26.6^o (hkl = 002) was responsible for both quartz and graphite.

Abstract: Achieving dependable connections in open construction settings presents challenges or renders the use of stationary machines and equipment complicated, if not impossible. Therefore, there is a particular focus on the requirements for welding processes. Of particular interest is ensuring the strength and reliability of welded joints, especially through processes developed subsequent to the solidification of the weld at the weld zone. The extent of the thermal influence zone is contingent upon the welding conditions and the properties of the metal being welded. Hence, research into the impact of welding conditions on the formation of the structure of the welded zone and the thermal influence zone remains pertinent.

Abstract: Preparing of Sb₂S₃ precursor by sol gel method and the post selenization is a simple and low-cost method for preparing Sb₂(S, Se)₃. In the preparation process of this method, the number of spin-coating of Sb₂S₃ precursor determines the film thickness, structure, and S/Se ratio. In this work, the effects of different spin-coating times (1 to 5) on the structure, optical and electrical properties of the film were studied. The results showed that when the number of spin-coating increased from 1 to 5, the thickness of the film increased from 0.24 μm to 1.17 μm. When spin-coating twice, the strongest diffraction peak of the film changed from (120) to (230); as the spin-coating frequency continued to increase, the film gradually exhibited Sb₂S₃ characteristics, accompanied by a small amount of Sb₂O₃ impurities. In addition, excessive spin-coating cycles can cause large voids to appear on the surface of the film. From the UV-visible spectrum, it can be seen that as the thickness of the film increases, the light absorption also gradually improve, and the band gap increases from 1.34 eV to 1.66 eV. The Mott-Schottky test showed that the prepared thin films were all P-type semiconductor. When spin-coated twice, the carrier concentration of the thin film reached 5.8×10¹⁵cm^-3.

Abstract: The purpose of the present work is studying feature of structure and phase structure thermal processed high-strength pig-iron with spherical graphite. Re­search has been dictated by difficulty of differentiation of structural compo­nents in the normalized pig-iron, es­pecially perlite and top of bainite. It is explained, difficulties of differentiation in nickel pig-iron perlite (sor­bite, trostite) and top of bainite: a plenty austenite at the given way of heat treat­ment undergoes disintegration on evtektoide to the mechanism, and separate plates of bainite ferrite are very fine, as defines similarity of structures at etching in nit­ric acid and their super­vi­sion at small increases. Samples of the same alloy (about 2%Ni), but cooled with the big speed indus­trially, get structure needle of bainite. It is confirmed, that the quantity austenite increases with rise in temperature austenition. It is installed, that in the pig-iron, cast in the metal form trans­formation occurs to education of smaller quantity residual austenite. This effect is connected with smaller micro liquation che­mi­cal elements, first of all silicon. It is established, that in the pig-iron, cast in the metal form by virtue of specific distribution of chemical elements at crystallization and crushing evtekti­ke grains, manganese is kept in the places corresponding sites ledeburite, and on borders of grains, silicon is distributed in regular more intervals, than in the pig-iron, cast in the sandy form. All this predetermines more uniform and full course of process γ–α of transformation.

Abstract: The influence of the initial shape of graphite powder and Ni content on the structure and properties of the nickel-graphite powders and plasma-sprayed coatings is investigated. The irregularly and spherically shaped graphite powders were produced by mechanical crushing and mechanical crushing with rolling, respectively. It is shown, that spherically shaped graphite powder has advantages in flowability and better deposition of Ni layer. The nickel-graphite core-shell powders with 50 and 75 wt.% Ni content were used to deposit coatings by plasma spraying. The composition, structure, and hardness of the nickel-graphite coatings were studied.

Abstract: The structure and mechanical properties of a multicomponent high-entropy Al₄CoCrCuFeNi alloy in the as-cast and melt-quenched states were investigated. The alloy composition was analyzed based on the literature criteria for predicting the phase formation in high-entropy alloys, which considered the entropy and enthalpy of mixing, valence electron concentration as well as the atomic size difference of the components. The alloy films were synthesized by quenching from the melt using a splat-quenching technique. The cooling rate of the films was estimated to be ~ 10⁶ K/s based on the film thickness. The X-ray diffraction analysis revealed that both as-cast and melt-quenched Al₄CoCrCuFeNi alloy samples had an ordered B2 phase in their structure. The microhardness of the as-cast alloy was 6500 MPa, while the microhardness of the melt-quenched film was significantly higher and reached 9400 MPa.

Abstract: The purpose of this study is to compare binders of two different origins. The powders obtained from crushing pure C₃S and hydrated cement for 28 days with w/b=0.6 and 0.5, respectively, will be subjected to heat treatment at 800°C. This work used X-ray diffraction (XRD) as a technique to characterize. According to X-ray diffraction, heat treatment resulted in the synthesis of β-C₂S belite in the pure phase and two polymorphs α'-C₂S and β-C₂S in the cement phase. The binder regenerated from cement pastes generates C-S-H at an early stage, which can be attributed to the high reactivity of the α'-C₂S polymorph.

Abstract: The initial and final softening (melting) temperatures of redesigned iron ore agglomerates with basicities from 1.2 to 3.0, obtained under laboratory conditions, were investigated. The chemical and phase compositions of the laboratory agglomerates, their microstructures and local chemical compositions, the temperatures at the beginning and end of softening (melting), and the temperature interval of softening were studied. Dependencies of the influence of the basicity of iron ore agglomerates on their softening temperature interval, depending on the proportion of phase components, were obtained. It is shown that as the basicity and proportion of silicoferrite SFCA phases increase, the temperatures at the beginning and end of the softening increase and reach a maximum of 1200 and 1312 °С, respectively (at the basicity of the agglomerate of 1.8), after which the temperatures decrease. Simultaneously, the softening interval increased from 73 to 112 °C.

Abstract: This study reviewed the synthesis of Titania with different shapes in the presence of cetyltrimethylammonium chloride (CTAC) as the famous stabilizer for directly altering the morphology and dimensions. These CTAC stabilizers usually provide the synthesis of Titania with a narrow size distribution and mostly single-crystalline structures in high yields. Many papers on the synthesis of Titania are available. However, only a few articles focus on the synthesis of Titania using CTAC as the stabilizer. The general rule for the shape transformation of Titania by CTAC stabilizer can be easily summarized based on the literature during the last ten year from https://www.sciencedirect.com/ as the data source.