Molten Stage Research Articles

Release Mechanism of Short- and Medium-Chain Chlorinated Paraffins from PVC Materials under Thermal Treatment.

Chlorinated paraffins (CPs) as plasticizers are massively added to polyvinyl chloride (PVC) products, during whose life cycle CPs can be continuously released especially under thermal stress. In this study, a PVC cable sheath was adopted as a representative kind of PVC material to investigate the release behaviors of short- and medium-chain CPs (SCCPs and MCCPs) under thermal treatment. Release percentages of CPs with increasing temperature followed a Gaussian-like curve. At the unmolten stage of 80 °C, heating for 10 min caused 0.051% of added SCCPs and 0.029% of added MCCPs to be released. At the molten stage of 270 °C, accumulative release rates of SCCPs and MCCPs within 10 min were up to 30 and 14%, respectively. The developed emission model indicated that material-gas partitioning and internal diffusion simultaneously governed the release of CPs. During thermal treatment, the release of CPs could be remarkably affected by the thermal expansion of the PVC material and the formation of breakage and micropores. Congener group profiles of released CPs indicated a slight fractionation effect for SCCPs during the release process. Furthermore, the release risk of CPs from the whole life cycle of PVC products was preliminarily evaluated.

Formation of Cu-Ni enriched phases during laser processing of non-equiatomic AlSiCrMnFeNiCu high entropy alloy nanoparticles

Al-rich non-equiatomic high entropy alloy nanoparticles (HEA NPs) were synthesized by ablating Al40(SiCrMnFeNiCu)60 (at%) target in deionized water using nanosecond Nd:YAG pulsed laser operating at a wavelength of 1064 nm and having 8 ns pulse duration. The synthesized NPs have retained the composition and structural phases (B2 type AlFe and Cr5Si3) of the target. The colloidal solution of these NPs was further processed with a 532 nm laser. Upon laser processing, compositional and structural changes in HEA NPs are systematically investigated by using electron microscopy and spectroscopic techniques. The cyclic reheating of NPs during laser processing triggers the formation of Cu-Ni nanoprecipitate over the processed NPs. Owing to their similar ionic sizes and having FCC structural phase, Cu-Ni segregated together during the molten stage and evolve as the precipitate upon solidification. Amongst all the binary combinations of elements present in the HEA NPs, Cu-Ni phases are thermodynamically favored. Based on our experimental results, a possible growth mechanism of Cu-Ni enriched nanoprecipitate is discussed.

IoT enabled temperature sensing system of molten metal in welding

• An automatic temperature sensing system is fulfilled through Internet of Things (IoT) based temperature sensing on molten metal in welding. • The temperature sensors, micro controller, LAN/Wireless communications and server are used to enhance the automatic temperature sensing on molten metal in welding process. • The experimentation is conducted on arc welding of mild steel. The quality characteristics and optimization studied through Taguchi method. The control of temperature in welding is essential to maintain the quality of metal joints. Due to current fluctuations and instrument errors, the quality of joint may be affected. The excess of temperature or molten stage may leads to change the effect of micro structure. An automatic temperature sensing system is needed to eliminate this problem. It is fulfilled through Internet of Things (IoT) based temperature sensing on molten metal in welding. The temperature sensors, micro controller, LAN/Wireless communications and server are used to enhance the automatic temperature sensing on molten metal in welding process. The experimentation is conducted on arc welding of mild steel. The quality characteristics and optimization studied through Taguchi method.

A review on Friction Stir Welding in Aluminium Alloys

Joining of aluminium alloys is always a challenging task due to its easily oxidising property in its molten stage. Although its application is huge in the building of aerospace structure, 2XXX and 7XXX series alloys are categorised as non-weldable aluminium alloys. Recent development in the application of friction stir welding process in the joining of these non-weldable alloys simplified the fabrication processes. In this review article, significance of friction stir welding comparing with other solid state metal joining process is addressed. Recent developments and application of this relatively new metal joining process in various industries are also discussed. Particular emphasis has been given to the mechanism responsible for the formation of this solid state joining technique. Apart from this, major process parameters that influence the formation of weld and weld defects caused by the improper selection of process parameters are also explained in detail.

Experimental Study on Use of Plastic Electronics Wastes in Pavement Blocks

Plastic waste is one of the topmost threats the world is facing today. Blanket ban one use of plastics to is quite difficult to implement considering the lifestyle of humanity. One of the novel ways of disposing of plastic e wastes, by using it constructively. To give a quick fix for plastic e-wastes, re-habitation method which investigated and enforced as a recovering product from Acrylonitrile-Butadiene-Styrene (ABS) as pavement block which is done by liquifying ABS material under safe surrounding with the addition of glass powder at molten stage increasing engraving it in pavement mould. After the process of plastering surface and rapid cooling of ABS results in pavement block. The compressive strength test and Chemical test conducted to find out the suitability of pavement blocks.

Quantifying frozen melt in crustal rocks: A new melt-o-meter based on zircon rim volumes

Quantifying the distribution of granitic melt at all scales in mid- to lower crustal migmatitic terranes is critical to understand crustal melting processes, chemical differentiation of the crust and its rheological behavior during deformation. We propose a new method to determine the fraction of frozen granitic melt on a hand specimen scale based on the relative volumes of newly precipitated to total zircon (FPZ = Fraction of newly Precipitated Zircon) as obtained by image analysis on dated zircon cores and rims. Using the calculated Zr-solubility [Zr]sat in the melt at the inferred melting temperature and the Zr concentration in the bulk sample [Zr]bulk, the fraction of melt Fmelt can be determined through Fmelt = FPZ × [Zr]bulk / [Zr]sat. The such obtained Fmelt corresponds to the melt fraction in the hand specimen at the time the system closed for melt mobility. Thermodynamic modelling further allows estimation of H2O-contents required to maintain the melt fraction obtained from the melt-o-meter in a molten stage. The applicability of this method has been tested on eight migmatitic samples with peak temperatures between 725 and 925 °C. Most of the lower temperature migmatites (<750 °C) retained Fmelt of 0.15–0.25 (±0.03–0.05), a melt fraction below or at the static melt escape threshold. In contrast, most of the higher-temperature migmatites (>800 °C) retained Fmelt of 0.35–0.50 (±0.07–0.10). At these melt fractions, melt extraction and melt migration from and within the source should be efficient. Consequently, these samples are likely open-system migmatites affected by melt accumulation or depletion processes. The melt-o-meter requires that the rock types under consideration produced a granitic melt that remained zircon-saturated and is therefore restricted to migmatitic meta-sediments and meta-granitoids. When applied carefully, this melt-o-meter offers a new and powerful tool to not only quantify melt distribution but also evaluate the extent of melt mobility in migmatites.

Evaluation of mechanical and tribological properties of hybrid AA6061 Al matrix composite

Aluminium matrix composite is that the effective and qualified material among the commercial domain. In this work, a trial has been created to make Aluminium Alloy 6061 metal bolstered with SiC and Al2O3 particles. The matrix metal aluminium has several distinctive properties like high strength, less weight and easy machinability. Silicon carbide has splendid hardness and wear resistance and aluminium oxide provides good compressive strength and wear resistance. Hence, they were chosen as the matrix and reinforcements. Four Samples are prepared by varying weight percentages of reinforcements. The reinforcements are taken equally for hybridization of each sample and varied as 2.5%, 5% and 7.5% and a monolithic aluminium sample also prepared for the comparison purposes. By using squeeze casting technique, the needful quantities of reinforcements mixed in the stirred molten stage of aluminium are solidified under high pressure. The purpose of the study is to judge the mechanical properties like hardness and compressive strength and tribological behaviour of the on top of invented AMC.

Recovery of metals from municipal solid waste incineration fly ash and red mud via a co-reduction process

Extraction of heavy metals is the preferred option for municipal solid waste incineration (MSWI) fly ash (FA) stabilization and reutilization. In this paper, a co-reduction process for FA and red mud (RM) was proposed. The complementary compositions of FA and RM were favorable for the volatilization of volatile heavy metals and the alloy formation of siderophile heavy metals in the co-reduction system. The molten stage temperature of co-reduction FA and RM can be decreased significantly to 1100 °C – 1300 °C, compared with the molten stage temperature of direct melting FA above 1400 °C. The wastes were converted into three products: iron alloy containing Fe, Cu, Ni, and Cr; secondary FA containing Pb, Zn, and Cd; and vitrified slag. In the optimized co-reduction process, 76.06 % Fe, 74.53 % Cu, 83.40 % Ni, and 58.44 % Cr can be recovered by iron alloy, and 98.95 % Cd, 98.21 % Pb, and 86.78 % Zn can be recovered by secondary FA. The contents of heavy metals in the vitrified slag are much lower than those in traditional direct melting slag. Consequently, this co-reduction process could be a more environmentally sound solution for beneficial reutilization of FA and RM.

Effect of Titanium Carbide Heat Exchanger Block and Retort on Oxygen Impurities in Mc-Silicon: Numerical Modelling

Primarily, mc-Silicon growth is undertaken by directional solidification (DS) process. Reduction of non-metallic impurities such as oxygen, carbon and nitrogen in DS produced mc-Si ingots is a challenging task and strong contaminations come from inner parts of the DS system. In conventional DS system heat exchanger block and retort are made of graphite. In our present work, we have used a heat exchanger block and retort made by titanium carbide (TiC). The simulation has been done for using both graphite and TiC as Heat exchanger block and retort. The simulation results were compared and analysed. The numerical simulation of oxygen impurity distributions in melt and crystal has been investigated. When we used TiC as Heat exchanger block and retort, it gives lower melt convection in the molten stage, more uniform temperature distribution in x- axis and lower temperature gradient in y-axis at the end of solidification. The lower melt convection can reduce the oxygen impurities and results in uniform oxygen distribution. So, TiC based DS system gives better results compared with the graphite-based system.

Comparative study on the pyrolysis of cellulose and its model compounds

In order to determine the cellulose pyrolysis mechanism, the difference of pyrolysis behavior among cellulose, cellobiose and glucose was investigated. The residue evolution of these three materials during pyrolysis process was originally explored. The morphology evolution shows that the color of all them changes from white to brown, and being black finally, and it is noteworthy that both the cellobiose and glucose evolve from initial powders to molten state and become puffy and porous char ultimately, while cellulose whether undergo the molten stage highly depends on the heating rate according to its residue evolution under different temperatures. Both the TG analysis of original samples and FTIR analysis of pyrolyzed residues reveal the different pyrolysis behavior of them, and the thermal stability follows the order: cellulose > cellobiose > glucose. Kinetic analysis shows that the glucose has the lowest global activation energy in pyrolysis. The products distribution results show that cellulose pyrolysis produces more non-condensable gases and less bio-oil than cellobiose and glucose. The GC–MS analysis of the bio-oil indicates that glucose bio-oil contains more 1,6-anhydro-β-d-glucofuranose than cellulose and cellobiose, while cellobiose bio-oil holds the highest content of furans compounds (furfural and 5-hydroxymethyl furfural), and cellulose bio-oil riches in levoglucosenone, cyclic ketones and low molecular weight compounds (acetic acid, hydroxyacetaldehyde, hydroxyacetone etc.). Finally, the cellulose model compounds based on the present and other work are discussed and the potential use of anhydro-oligosaccharides as a model compound in exploring the cellulose pyrolysis is suggested.

Condensate refractory inclusions from the CO3.00 chondrite Dominion Range 08006: Petrography, mineral chemistry, and isotopic compositions

We have found two refractory inclusions in the CO3.00 carbonaceous chondrite Dominion Range (DOM) 08006 that appear to be primary condensates from the early solar nebula. One, inclusion 56-1, contains the first four phases predicted to form by equilibrium gas-solid condensation: corundum; hibonite; grossite; and perovskite. The other, 31-2, contains nine predicted condensate phases: hibonite; grossite; perovskite; melilite; spinel; FeNi metal; diopside; forsterite; and enstatite. Except for melilite/spinel, the phases occur in the predicted sequence from core to rim of the inclusion, which has an irregular shape inconsistent with a molten stage. This inclusion preserves the most complete record of condensation in the early solar nebula that has yet been found. The physical evidence reported here supports equilibrium condensation calculations that predict the observed sequence as well as the assumptions upon which they are based, such as total pressure (∼10−3 atm), bulk system composition (solar), and COH proportions. All phases in both inclusions and the associated ferromagnesian silicates are 16O-rich, with Δ17O between −25 and −20‰, implying that this is the original composition of the vast majority of primary condensates and that 16O-poor compositions observed in many isotopically heterogeneous inclusions are largely due to subsequent isotopic exchange. While the nebula was well-mixed with respect to oxygen isotopic composition, clearly resolved anomalies in Ca and Ti isotopic compositions indicate that some isotopic heterogeneity existed early and was preserved during condensation. Inclusion 31-2 did not incorporate live 26Al and has nucleosynthetic anomalies in the heavy Ca and Ti isotopes (i.e., δ48Ca = 4.3 ± 1.9‰; δ50Ti = 8.8 ± 2.0‰). In contrast, inclusion 56-1 has radiogenic 26Mg excesses yielding a (26Al/27Al)0 ratio of (1.0 ± 0.1) × 10−5 and negative nucleosynthetic isotopic anomalies in Ca (δ48Ca = −10.3 ± 4.2‰) and Ti (δ50Ti = −4.3 ± 2.9‰). Thus, it represents a deviation from the mutual exclusivity relationship between 26Al incorporation and large nucleosynthetic anomalies. The reservoirs in which these inclusions formed had similar O-isotopic and different Al-, Ca– and Ti-isotopic compositions, suggesting that while the CAI-forming region was well-mixed with respect to oxygen isotopic composition, clearly resolved anomalies in Ca and Ti isotopic compositions indicate that some isotopic heterogeneity existed and was preserved during condensation.

Correlation between pulse 300 series SS wire parameters

A centralized and extensive relationship linking arc characteristics is presented to explain the metal transfer phenomenon, electrode melting rate, metal transport and weld-solidification during the Pulse gas metal arc welding. The study details interpretation of numerous arc, heat and mass transfer correlations during molten stage of the electrode, initiation of droplet, growth, detachment, transfer and impingement into the weld-pool. An interactive coupling between pulse process parameters, temperature distribution and weld pool dynamics has been discussed. This review elucidates conditions of the pulse metal transfer in the arc column and into the weld pool on the basis of current waveform, magnitude of peak, base and pulse current for 300stainless steel wire.

Effect of ternary nanoparticles fluid mixture in heat enhancement and heat storage

Nanofluid is a class of fluid that consists of metal nanoparticles such as aluminium oxide (Al2O3) and water solution. For effective heat removal, the concentration of these nanoparticles needs to be below 4%. It has been found that only if the concentration is below 4% that the heat removal is possible. The purpose of this paper is to enhance the heat removal effectiveness and the heat storage capacity of nanofluid with microencapsulated phase change material (MEPCM). When MEPCM particles are in the molten stage, it becomes favourable for heat removal and for storage. This paper demonstrates numerically the use of a ternary mixture of fluid containing MEPCM and Al2O3 nanoparticles. Both particles are at different concentrations, thus a set of different fluid/particles concentration is investigated. The fluid consists of Al2O3 nanoparticles and MEPCM particles in water. The effectiveness of these mixtures in heat storage is investigated for different concentrations of the two set of nanoparticles. Results reveal that this fluid can enhance the heat removal, and it has a good heat storage capability.

Evaluation of surface, microstructure and phase modifications on various tungsten grades induced by pulsed plasma loading

Progress in the field of nuclear fusion requires the development of a new generation of tungsten materials that are expected to meet specific property, lifetime and safety requirements. Pursuing this goal, the new materials must be properly tested in a wide range of conditions including cases where material is brought to the molten stage, such as with large fusion plasma instabilities. In this study, two prospective candidates from the family of dispersion strengthened (DS) tungsten materials, i.e., W-1%Y2O3 and W-2.5%TiC, were subjected to extreme heat loading exerted by the deuterium plasma generator PF6. The study focuses on the interaction of the tungsten matrix with the dispersed particles during material melting. The materials underwent significant changes in microstructure and phase content. Among the most serious was the loss of TiC particles and void formation in W-2.5%TiC and phase change of polymorphic Y2O3 particles in W-1% Y2O3.

Influence of cooling speed on the microstructure and wear behaviour of hypereutectic Fe–Cr–C hardfacings

The main focus of this work is to show influences of the cooling rate on the microstructure and wear performance of Fe–Cr–C hardfacings. The coatings were produced by welding. The weld overlays were cooled from the molten stage in selected variations: (i) standard cooling – cooling on air at the steel welding table; (ii) passive cooling – cooling of the base material during the hardfacing process with a water cooled cooper plate with 12°C; (iii) active cooling – cooling of the welding seam behind the main arc with CO2 gas at temperature of −80°C. For each cooling situation the temperature of the weld seam was measured in the melt pool with help of thermocouple. It was shown, that different cooling conditions can lead to the significant changes in the cooling-off time t8/5, dilution of the hardfacing with substrate and microstructural features of the hardfacings under investigation.Three different wear tests (three-body abrasion according to ASTM G65 standard, impact/abrasion and solid particle erosion) were performed to study the wear performances of Fe–Cr–C hardfacing. Testing results have shown that if the cooling-off time t8/5 is too short it influences the brittleness and increases the residual stresses of the Fe–Cr–C hardfacing, which lowers its impact resistance. The effect of the cooling rate is in good correlation with wear test results and gives promise for further microstructure and process optimisation for the improved tribological performance.

Thermal Decomposition Kinetics of RDX with Distributed Activation Energy Model

The thermal decomposition kinetics of RDX at different rates was studied by thermogravimetric analyzer(TG) and the activation energy of RDX was calculated by distributed activation energy model. It is shown that the thermal decomposition processes of RDX were divided into three stages according to the TG curves, they are molten stage, thermal decomposition stage and eng stage. The activation energies of RDX are all between 124.34 and 181.48KJ•mol-1 in the thermal decomposition stage of non-monotonously increasing. The activation energy of RDX is 139.98 KJ•mol-1 in the molten stage, and the thermal decomposition stage is167.24KJ•mol-1.

Free Energy of Mixing of the Binary Liquid Alloys of Sodium

Sodium is a highly reactive alkali metal. Within a binary liquid alloy it generally forms complexes. Due to formation of such complexes the thermodynamic properties of the binary alloys of sodium often show anomaly-deviating maximally from that of the ideal alloys. In the present work we have confined our investigation into the free energy of mixing (GM) of two binary alloys of sodium in liquid phase-Na-Pb and Na-Hg-near the melting point. For this purpose we have used Flory’s model and started with the activity of sodium in the sodium-lead liquid alloy and that of mercury in the sodium amalgam at molten stage. By the method of successive approximations we have ascertained the value of interchange energy for each alloy in the light of the experimental values of activity and finally computed GM for different concentrations of the constituent species. Our computation explains the observed symmetry and anomaly in the free energy of mixing of the Na-Pb and Na-Hg liquid alloys respectively.The Himalayan PhysicsVol. 3, No. 32012Page : 24-26

Electrical conductivity and Knight shift of liquid alkali metals

In the present work we have considered two alkali metals - sodium and potassium - at their molten stage near the melting point. For the purpose of this theoretical investigation we have used Harrison’s first principle (HFP) pseudopotential technique which is basically an orthogonalised plane wave method. The electrical resistivity has been computed through Ziman’s formula. Then the electrical conductivity of the present metals is found out just by taking the reciprocal of the values so obtained. Our computed results have been compared with the experimental data and a good agreement is obtained. A study of the existing literature reveals that the work with the magnetic property like Knight shift of metals is scarce. This has encouraged us to apply the said HFP technique to study the Knight shift of the present alkali metals. For this purpose we have used Knight’s formula. Our computed values of Knight shift are in reasonable agreement for the metals under investigation. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7181BIBECHANA 9 (2013) 92-95

Electrospun nanofibrous mats absorbed with fatty acid eutectics as an innovative type of form-stable phase change materials for storage and retrieval of thermal energy

The form-stable phase change materials (PCMs) with fatty acid eutectics absorbed in and/or supported by the overlaid mats of electrospun polyacrylonitrile (PAN) nanofibers or the derived carbon nanofibers were explored for storage and retrieval of thermal energy. The carbon mats were made from the PAN mats through stabilization in air followed by carbonization in nitrogen. Three fatty acid eutectics of capric acid–lauric acid, capric acid–palmitic acid, and capric acid–stearic acid were studied as model PCMs; for comparison, the individual fatty acid of capric acid was also studied. The results indicated that electrospun nanofibrous mats were highly porous and capable of absorbing a large amount of PCMs, and the maximum absorption capacities of PAN and carbon mats were ∼99wt% and ∼81wt%, respectively. The composite materials (i.e., the form-stable PCMs) could well-retain their overall shapes when the PCMs were in the molten stage; i.e., they would not flow/leak from the mats. The conversion of PAN mats into carbon mats increased the thermal energy storage/retrieval rates of the resulting composite PCMs; nonetheless, the thermal treatments of stabilization and carbonization also made the mats to be less fluffy, leading to the reduction of absorption amount. Morphological structures, as well as the properties of thermal energy storage, absorption capacity, and thermal energy storage/retrieval rates, of electrospun nanofibrous mats and the resulting composite PCMs were studied by scanning electron microscopy, differential scanning calorimetry, and measurement of melting/freezing times. The results indicated that the melting temperatures and enthalpies of the prepared composite PCMs were in the range of 19.8–31.4°C and 120.1–165.4kJ/kg for PAN mats, and 18.8–30.7°C and 92.1–128.0kJ/kg for carbon mats, respectively. In comparison with melting times of CA–PA/PAN and freezing times of CA–SA/PAN, the melting times of CA–PA/carbon and freezing times of CA–SA/carbon were shortened by about 49.5% and 41.0%, respectively. It is envisioned that this innovative type of form-stable PCMs could be utilized for potential applications in building energy conservation.

Top-seeded infiltration growth of Y–Ba–Cu–O bulk superconductors

A top-seeded melt-growth (TSMG) process is widely used to fabricate single domain YBa2Cu3Oy (Y–Ba–Cu–O) bulk superconductors. Pores are often found in the TSMG-processed Y–Ba–Cu–O samples due to the oxygen gas evolution during the molten stage. Recently developed liquid infiltration growth (LIG) process is known to be effective in suppressing the pore evolution and in refining the size of Y2BaCuO5 (Y211) particles dispersed in YBa2Cu3Oy matrix. The LIG process utilizes the liquid (Ba3Cu5O8) infiltration into a pre- sintered Y211 contact and slow cooling through a peritectic temperature. In this study, we fabricated bulk Y–Ba–Cu–O superconductors by the LIG process combined with top-seeding with SmBa2Cu3Oy seed and confirmed that a single-domain bulk can be produced. Trapped field measurements however showed that some distortion in the field distribution was observed in the region near the seed crystal, which was attributed to Y211 density and its relatively large size.