Papers by Keyword: Melting Point

Abstract: The melting parameters (melting point, specific heat of fusion) of copper samples with different volume structure (fine-grained, submicrocrystalline) and dispersivity (fine powder) were explored using differential thermal analysis. It was found that change in the metal structure from bulk coarse-grained to submicrocrystalline, and to submicron powders led to depression of melting point by ~18 °C and of specific heat of fusion by ~45 % relative to the standard values. It was shown that the high-energy impact on the starting coarse-grained metal used to obtain the samples with modified structure and dispersivity (severe plastic deformation, electric explosion of thin wires) caused changes in the composition of the material. An explanation for the observed influence of structure and dispersion factors on the melting parameters has been proposed on the basis of X-ray diffraction data, electron microscopy, and model calculations.

Abstract: Reducing the melting point, in creasing the thermal stability limit, and enhancing the specific heat capacity of molten salt are the research hotspots in the field of medium and high temperature energy storage in recent years. From the perspectives of the melting point, thermal stability limit, and specific heat capacity of nitrates, we summarize the melting point, thermal stability limit, and specific heat capacity enhancement of molten salts with different compositions and ratios. The melting points of molten salt with different compositions and ratios are compared. Furthermore, the enhancing effect of various nanomaterials on molten salt is elucidated. The application of nitrate molten salt is also summarized to provide a reference for the research and application of novel molten salts. Keywords: Nitrate Molten Salt; Melting Point; Thermal Stability Limit; Specific Heat Capacity; Application

Abstract: Using differential scanning calorimetry, phase transitions in polycarbonate-polytetramethylene oxide block copolymers were studied. It is shown that, depending on the ratio of rigid polycarbonate and flexible polytetramethylene oxide units, block copolymers can be two-phase or four-phase. It is shown that phase transitions in copolymers of a polyester-polyether depend on the ability to crystallize the components.

Abstract: Polypropylene (PP) is one of the biggest petro-polymers, which is used in very wide application nowadays. The environment problem due to materials such as plastics having very long time degradability, and critical petroleum sources have promoted some studies to empowerment of natural resources such as natural fibres for substituting or at least modifying petro-polymers. Because of biodegradability obtained from natural source, sorghum fibers are interesting to be used as filler in PP composites, despite of weak compatibility between them. Surface modification on the sorghum fibers through alkalinization prior to acetylation was aimed to improve the fiber compatibility to PP. The treatments were expected to substitute hydroxyl group in the sorghum fibers, into acetic ester group in order to increase their hydrophobicity as the fillers. Moreover, the treatments were able to unbundle single fibers into micro-fibrillated cellulose (MFC) fibres with increase in crystallinity index. Usage of this MFC fiber as filler in PP leads to improvement of the composite performances such as thermal properties. In this study, Fourier Transformation Infra-Red (FTIR) Spectroscopy, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Field-Emission Scanning Electron Microscope (FE-SEM) were used to evaluate the performances of the Sorghum fibers after the treatments and as the filler in the Sorghum fibers/PP composites. The experimental results showed the MFC fibers as the smallest sizes in 5.0 microns and the highest crystallinity index up to 79.1 %, obtained from alkalinization with 2.5 M NaOH prior to acetylation with 17.4 M CH3COOH and the glacial (CH3CO2)2. Compatibility study of the treated Sorghum fibers on PP shows an improvement indicated by a strong interaction between the fibers and PP on morphology observation, increase in melting point of PP from 163.4°C (using virgin Shorgum fibers) into 163.6°C (using treated Sorghum fibers) in DSC measurements.

Abstract: Gas-slag-forming systems of flux-cored wires for plasma building-up welding surveyed. Application of substances at overlaying welding boron triphtoride is considered, to provide the improvement of formation of the deposited bead, reduces vaporization. Systems of gas-slag-forming substances which are gating out boron triphtoride are proposed excreting boron triphtoride are investigated at overlaying welding.

Abstract: The attempt to produce various types of lead-free solder has been actively investigated around the world in order to substitute the harmful SnPb solders. The effects of Zn addition on the microstructure, melting point and microhardness of Sn-0.7Cu lead-free solder were investigated with 1 wt% and 5 wt% of Zn additions. Powder metallurgy (PM) method was used to fabricate these Sn-0.7Cu-Zn lead-free solders. The results revealed that the addition of Zn was able to improve the solder properties. The melting point of Sn-0.7Cu-Zn lead-free solder was decreased drastically as the increasing of Zn additions. The Zn particles were distributed homogenously along the grain boundaries and produced refined dendrite β-Sn, which also lead to a superior microhardness values of solders.

Abstract: The effect of Al addition on the microstructure, melting point and microhardness of SnCu-Al lead-free solder alloys were investigated with two different compositions of Al which were 1 wt% and 5 wt%. These solder alloys were fabricated through powder metallurgy (PM) method. The results showed that the melting point and the microhardness value of the SnCu-Al lead-free solder alloy were increased as the Al content increased from 1 wt% to 5 wt%. The grain growth of SnCu-Al lead-free solder alloy also tends to be retarded due to the homogenous distribution of Al at the grain boundaries.

Abstract: The current paper is devoted to technological improvements in high-precision plasma cutting of thin sheets on processing the steel St3 + aluminum A5M bimetallic composition. The composition obtained by explosion welding presents a compound of various materials which differ in such thermophysical characteristics as their melting point and their thermal conductivity. The principal difference in their thermophysical properties has predetermined the specific features of forming the cut edge of this bimetallic composition. Out of the variety of technologies for cutting this bimetallic composition, the Hi-Focus^plus technology intended for carbon steel processing and the Hi-Focus technology for aluminum alloys are chosen. It is established that when cutting the bimetallic composition on the side of steel grade St3, the undercut filled with the products of melted steel grade St3 is formed on the aluminum portion in using both technologies. Switching the direction of the cut from steel to aluminum results in forming a taper on the aluminum portion. In so doing, high precision and superior quality of cutting on the steel grade St3 portion are provided.

Abstract: This paper reports on the effect of activated carbon (AC) addition on the properties of Sn-Cu-Ni (SN100C) solder paste. The composite solder was prepared by mixing reinforcement particles (0, 0.25, 0.5, 0.75 and 1.0 wt. %) into SN100C solder paste. The melting temperature of composite solder was determined by using differential scanning calorimetry (DSC). Wettability of fabricated solder was studied through contact angles between solder and copper substrate interface. The intermetallic compound formation was studied after reflow soldering process.With increased carbon particles addition, the composite solder was found to have a slightly lower melting temperature compared to monolithic solder while the wettability of composite solder effectively had improved. The activated carbon particles in solder paste composite have significant effects on the formation of intermetallic compounds (IMCs) at the solder/Cu substrate interfaces by suppressing the IMCs thickness.

Abstract: This paper studies the melting of Cu-Pd bimetallic clusters with different Pd positions by using molecular dynamics simulation with a general embedded-atom method. The melting of clusters with 55 Pd atomic distributing different positions where the core-layer, second-layer, third-layer, fourth-layer and mixed. It is found that the changing of melting point is strongly related to the position of Pd atomic. The results indicate that the Pd atoms doped in the core layer and surface layer, below the melting point of the second layer and third layer. Meanwhile, this indicate that the Pd atomic doped in the second layer and third layer, the structure of cluster is relatively stable. The irregular phenomena of the melting were induced by the Pd position. This gives a new method to tune the melting point in bimetallic clusters.