Solidification System Research Articles

Study on the characteristics of tungsten slag and its properties in the cement solidification system

Study on the characteristics of tungsten slag and its properties in the cement solidification system

Analyses of Distributions of Different Impurities for Growth of Polysilicon Ingots in Directional Solidification System

Analyses of Distributions of Different Impurities for Growth of Polysilicon Ingots in Directional Solidification System

Bactericidal Activity of Superabsorbent Polymer Granules for Their Applications in Respiratory Fluid Solidification Systems.

Disposal of respiratory secretions from patients having contagious diseases (e.g., COVID-19 and tuberculosis) poses a high risk of infection for healthcare workers. AcryloSorb canister liner bags are highly efficient for the safe handling of contagious respiratory secretions via solidification and disinfection processes. The canister liner bags are lined with disinfectant-impregnated superabsorbent polymer (DSAP) granules. The liner structure in the bag has a patented design that has upward progressive absorbent availability (Indian Patent application # 202041019872). AcryloSorb canister liner bags can decontaminate the fluid secretions absorbed in the bag and solidify within 10 min. The present study focused on the bactericidal effect of DSAP using Gram-negative bacteria, Klebsiella pneumoniae, and Gram-positive bacteria, methicillin-resistantStaphylococcus aureus (MRSA). Disinfectants such as peracetic acid (ethaneperoxic acid), sodium dichloroisocyanurate (sodium 3,5-dichloro-2,4,6-trioxo-1,3,5-triazinan-1-ide), rose bengal (disodium; 2,3,4,5-tetrachloro-6-(2,4,5,7-tetraiodo-3-oxido-6-oxoxanthen-9-yl) benzoate), and N,N-dimethyl-N-[3-(triethoxysilyl)propyl]octadecan-1-aminium chloride at different weight ratios were impregnated in superabsorbent polymer (SAP) granules. The bactericidal activities of DSAP were studied along with its solidification capacity. Disinfectants showed different bactericidal activities when impregnated with SAP granules. For example, peracetic acid-impregnated SAP granules (DSAP-P) showed 100% bactericidal activity for both Klebsiella pneumoniae and MRSA at 0.5 wt % peracetic acid. Sodium dichloroisocyanurate-impregnated SAP granules showed 100% bactericidal activity only at 5 wt % sodium dichloroisocyanurate (DSAP-S5). Even though peracetic acid was highly effective, SAP granules collapsed when impregnated with peracetic acid. The ease of handling, disinfection efficacy, and preserving the morphology of SAP granules make DSAP-S5, a suitable candidate for AcryloSorb canister liner bags.

Using ANSYS Fluent Finite Element Method to Simulate Effect of Opening Angle of Argon Inlet Channel in Polysilicon Directional Solidification System

Using ANSYS Fluent Finite Element Method to Simulate Effect of Opening Angle of Argon Inlet Channel in Polysilicon Directional Solidification System

Numerical research of gas-related defects for gray cast iron during sand casting

A novel simulation route included Arrhenius formula, mass conservation and Darcy’s law has been established, which can predict gas-related defects of gray cast iron. The effect of casting and solidification process on the thermal history, burning loss and pressure profile of the sand core was evaluated. Results showed that the pressure in surface region of the sand core was increased gradually, the binder in the sand core reached the decomposition temperature and sand core became thinner. The formation of these defects are highly dependent on the decomposition behavior inside the solidification system.

Numerical simulation approach to investigate the effect of gas tube design on the impurities distribution and thermal properties of multi-crystalline silicon ingot grown by directional solidification process

Multi-crystalline Silicon (mc-Si) grown by directional solidification (DS) system is considered as a crucial photovoltaic material due to its relatively low cost and high yield. The numerical modelling is very useful for understanding the impurities segregation during mc-Si growth process. In the present paper, numerical simulation is carried out to investigate the impact of Argon gas tube design as shower head. In this Argon gas tube modification act on the non-metallic impurities, melt-crystal interface, temperature distribution and stress levels in the silicon ingot during the different stages of solidification process. The proposed design resulted in remarkable reduction in the back transfer of CO from heater component of the DS furnace. The generated von misses stress is also discussed as the function of different stage of solidification. The results concluded that the stress level at the initial stage of solidification is lower but it is large at above 75 % solidification rate. Also, we found that the modified gas tube design gives better temperature distribution with melt-crystal interface (m-c) shape. The modified argon tube design will be helpful for enhancing the quality of silicon ingot by controlling the chemical reaction between silicon melt and impurity transport.

Influence of Recycled Fine Aggregate Content on Properties of Soft Soil Solidified by Industrial Waste Residue.

The influence of recycled fine aggregate content on the properties of soft soil solidified by industrial waste residue was systematically studied. First, the addition of recycled fine aggregate may provide skeleton support, which was conducive to improving the solidification properties. Comparing the addition of recycled fine aggregate content and a composite solidification agent separately, the compressive strength increased 48.01 times and 1.32 times, respectively. Second, the composition and quantity of the hydration products were analyzed by X-ray diffraction (XRD) and thermal gravity analysis (TG/DTG). In addition to silicon dioxide and aluminum oxide, a number of new minerals, including hydrated calcium silicate, calcium hydroxide and ettringite, were produced under different recycled fine aggregate contents. The diffraction peak of hydrated calcium hydroxide was weak, which indicated that the crystallinity and relative content was low. The main reason for this was that it was consumed as the activator of the secondary hydration reaction of blast furnace slag. With the increase in recycled fine aggregate content, the total weight loss (hydration products, crystal water, impurities) increased significantly, at rates of 6.9%, 7.0%, 7.2%, 8.8% and 9.7%. The addition of recycled fine aggregate does not change the composition and quantity of the hydration products, and the increased weight loss in this part might be caused by the cement paste attached to the surface of the recycled fine aggregate. Finally, their microstructure was analyzed by scanning electron microscopy (SEM). Larger and more pores appeared in the solidification system with the increase in recycled fine aggregate, and a large amount of ettringite was prepared. An excess in recycled fine aggregate caused more pores, and the negative impact of too many pores exceeded the lifting effect of the aggregate, resulting in the decline of its mechanical properties. Therefore, there was a suitable range for the use of recycled fine aggregate, which was not more than 40%. In conclusion, recycled fine aggregate not only acts as a skeleton to improve solidification strength, but could also realize the comprehensive utilization of waste, which provided a new scheme for solid waste utilization and soft soil solidification.

Development of Three-Dimensional LES Based Meshless Model of Continuous Casting of Steel

A large-eddy simulation (LES) based meshless model is developed for the three-dimensional (3D) problem of continuous casting (CC) of steel billet. The local collocation meshless method based on radial basis functions (RBF) is applied in 3D. The method applies scaled multiquadric (MQ) RBF with a shape parameter on seven nodded local sub-domains. The incompressible turbulent fluid flow is described using mass, energy, and momentum conservation equations and the LES turbulence model. The solidification system is solved with the mixture continuum model. The Boussinesq approximation for buoyancy and the Darcy approximation for porous media are used. Chorin’s fractional step method is used to couple velocity and pressure. The microscopic model is closed with the lever rule model. The LES model is compared to the two-equation Low Re k−ε turbulence Reynolds Averaged Navier–Stokes (RANS) model in terms of temperature, velocity and computational times. The LES model resolves transient character of vortices which RANS-type turbulence models are unable to tackle. The computational cost of LES models is considerably higher than in RANS. On the other hand, it results in a much lower computational cost than the direct numerical simulation (DNS). The paper demonstrates the ability of the method to solve realistic industrial 3D examples. Trivial adjustment of nodal densities, high accuracy, and low numerical diffusivity are the main advantages of this meshless method.

Impurity analysis of the effect of partial replacement of retort with an insulation material on mc-silicon grown in directional solidification furnace: Computational modeling

A transient global model has been created for modified directional solidification system. Since the efficiency of the solar cell mainly depends on the quality of the multi-crystalline silicon, it is important to modify the directional solidification system and to optimize the parameters. In multi-crystalline silicon solar cell, the concentration and segregation of impurities and precipitates plays a vital role in the conversion efficiency. Scalar parameters have been used to analyze the concentration and segregation of impurities in the grown mc-Si. The computation was developed to clarify the distributions of oxygen, carbon, nitrogen and silicon carbide. Five cases were discussed whereas except conventional case, all other cases show better results to grow good quality mc-Si ingot for solar cell applications.

Quality improvement of multi-crystalline silicon ingot by the Hot-Zone modification

Directional solidification process is the dominant method for the multi-crystalline silicon wafer production due to the lower production cost, simple operating process and mass production. Numerical simulation is the best tool to understand and enhance the multi-crystalline silicon ingot quality by using the directional solidification process for photovoltaic application. We improved the multi-crystalline silicon ingot quality by adding an additional graphite layer on the hot-zone of directional solidification furnace. We have simulated both modified and conventional directional solidification process and compared the temperature distribution, growth rate and stress distribution of both systems. The modified directional solidification system significantly increases the multi-crystalline silicon ingot quality compared to the conventional directional solidification process grown multi-crystalline silicon ingot. With the modified directional solidification system we have prevented the wall growth during the casting process.

Simulation of nucleation and evolution process of nuclei during solidification of Ti<sub>3</sub>Al alloy

The nucleation mechanism of Ti<sub>3</sub>Al alloy is simulated by the molecular dynamics method in this work. The atomic clusters on different spatial scales are identified in the solidification process by the cluster-type index method (CTIM), and the formation process and the growth process of critical nucleus are studied in depth. It is found that the solidification system contains ten thousands of different types of atomic cluster structures, but only 22 types play a key role in the nucleation process. In the nucleation and growth process of nuclei, the ICO-like cluster, the BCC-like cluster, and the defective FCC cluster and the defective HCP cluster respectively reach their saturation points at the characteristic temperature <i>T</i><sub>1</sub> (1110 K), <i>T</i><sub>2</sub> (1085 K) and <i>T</i><sub>3</sub> (1010 K). And the competition processes of these clusters are revealed according to the changes of their number and spatial distribution with temperature. By tracing the nucleation and growth process of the grain with parallel twin, it is found that the critical crystal nucleus is composed of single-phase FCC structures, and the preferent nucleation of metastable bcc structure is not observed. The twinned structure is formed by the layer-by-layer growth along the close-packed plane. It is also found that the CTIM is more accurate than other methods in revealing the microstructural characteristics during the solidification.

Influence of interface kinetics parameters on the overall fluctuation instability of the interface morphology of deep cell crystal

The effect of interface kinetics on the stability of deep cell morphology in directional solidification is studied. By using the multiple variable method and the matching asymptotic methodandby finding the mode solution of the system,the dispersion relation satisfied by the change rate of the disturbance amplitude of the cell-crystal interface is derived , and the quantization condition of the interface morphology is obtained. The results show that there are two global instability mechanisms in the directional solidification system with considering the growth of deep cell crystal with interfacial dynamic parameters : global oscillation instability mechanism and low-frequency instability. The stability analysis shows that the interface stability parameter <inline-formula><tex-math id="M4">\begin{document}$\mathrm{\varepsilon }$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220322_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220322_M4.png"/></alternatives></inline-formula>is related to the cell relative parameter <inline-formula><tex-math id="M5">\begin{document}$ {\mathrm{\lambda }}_{0} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220322_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220322_M5.png"/></alternatives></inline-formula>, and thatthe larger the interface dynamic parameter <inline-formula><tex-math id="M6">\begin{document}$ {M}_{\text{*}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220322_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220322_M6.png"/></alternatives></inline-formula>, the larger the stable region of the overall fluctuation instability of the dendrite structure in the overall oscillation modeis.

Microstructural Patterns, Microsegregation, Porosity, and Mechanical Properties of Hypoeutectic Al-Fe Alloy, and its Dependency with Solidification Thermal Parameters

Al-Fe alloys are usually used as packaging and structural materials, but in the recent years, there have been considered for possible applications in aerospace field. The solidification sequence in pure aluminum containing 1 wt.% Fe is described in term of the formation of macrostructure, microstructure, microsegregation, porosity and mechanical properties. This material was studied in the upward unidirectional solidification system under transient heat flow conditions. Differences in microstructure, microsegregation, porosity and mechanical properties such as ultimate tensile strength, elongation and microhardness, due to the thermal parameter effects were observed and discussed. Experimental growth laws relating cellular spacing to the cooling rate and solidification speed have been determined, indicating that the increase in thermal parameter have induced a refinement effect on cell morphology. Microsegregation profiles of Fe solute were experimentally determined from the central region of the cell to the intercellular region under different solidification speeds. The Fe microsegregation determined from central region of the cell (FS = 0) to the intercellular region (FS = 1) show a growing profile, in any case considered. However, the profiles move upward with the increase in solidification speed, which indicates that Fe solubility in solid, increases with the increase in solidification speed. The effect of the solidification thermal parameters and cellular spacing on the porosity content were experimentally investigated. The value of porosity content increased along the casting. These results have pointed out that porosity content is affected by solidification parameters and cellular patterns. Further, measurable effects of the thermal parameters, cellular spacing and porosity content on the mechanical properties were experimentally determined. It stands out among experimental results the influence of porosity on the mechanical properties of as-cast material. In any case analyzed, mechanical properties increase with decreasing porosity content.

Simulation of Effect of Ar Flow Rate on Silicon Ingot Growth in Directional Solidification System

Simulation of Effect of Ar Flow Rate on Silicon Ingot Growth in Directional Solidification System

Solidification Pattern of Si-Alloyed, Inoculated Ductile Cast Irons, Evaluated by Thermal Analysis

The solidification cooling curve itself as well as its first derivative, and related temperatures, reported to the calculated equilibrium temperatures in stable and metastable solidification systems, are used to predict the solidification characteristics of the cast iron. Silicon, as the most representative cast iron element, and inoculation, as graphitizing metallurgical treatment, have a major influence on the transition from the liquid to the solid state. Six experimental programs are performed, with Si content typically for non-alloyed (<3.0% Si), low (3.0–3.5% Si) and medium alloyed (4.5–5.5% Si) ductile cast irons, as Si-content increasing, and inoculation simultaneous effects. Silicon is an important influencing factor, but the base and minor elements also affect the equilibrium eutectic temperatures, much more in the Fe-C-Si-Xi stable system (15–20 °C) than in the metastable system (5–10 °C), comparing with their calculation based only on a Si effect (Fe-C-Si system). The highest positive effect of inoculation is visible in non-Si alloyed cast irons (2.5% Si): 9–15 °C for the eutectic reaction and 3 to 4 times increased at the end of solidification (37–47 °C). Increased Si content decreases inoculation power to 7–9 °C for low alloying grade (up to 3.5% Si), with the lowest contribution at more than 4.5% Si (0.3–2.0 °C). 2.5–3.5% Si ductile cast irons are more sensitive to high solidification undercooling, especially at the end of solidification (but with a higher efficiency of inoculation), compared to 4.5–5.5% Si ductile cast irons, at a lower undercooling level, and at lower inoculation contribution, as well.

Numerical Modelling of the Effect of Cooling Conditions and Mould Size during Solidification of Al-4.5%Cu Alloy in Static Casting Process

Mathematical developments and computer simulation have greatly aided the modern day study of solidification phenomena. This work presents a numerical modelling of the effect of cooling conditions and mould size during solidification of Al-Cu eutectic binary alloy in static casting process. The numerical method adopted for the current work is the finite volume method and the mathematical problem was formulated according to the classic continuum energy conservation equation for the transient solidification problems. The latent heat evolution was accounted for using the modified source-based method. The boundary conditions included all the modes of heat transfer between the solidifying system and its surrounding. Two cases were simulated to study the effect of cooling conditions and mould size on the solidification system. In case I, a Dirichlet boundary condition with a known temperature (373 K) value was imposed on the bottom of the mould surface. An adiabatic condition was imposed on the bottom of the mould in case II. It was observed that the different boundary conditions and mould sizes have significant influence on the rate and pattern of solidification. Cooling curve results and temperature contours from these models showed reasonable deviations due to various cooling conditions and mould sizes. Larger thermal and solid fraction layers were predicted for the case II with slower cooling rate. It was also observed that temperature distribution along the horizontal distance within the casting increases monotonically as mould size was increased.

Development of an Epoxy Solidification Method for Radioactive Spent Resins

An epoxy solidification method was developed and tested for volume reduction, homogeneity, and acceptance criteria such as leaching characteristics and compressive strength. It satisfied the acceptance criteria and confirmed excellent performance in terms of volume reduction and homogenization. An epoxy solidification system was developed to treat radioactive spent resins arising in nuclear power plants. The automated epoxy solidification system also minimizes the exposure of workers to radiation. And since it is solidified in a general drum size, it can be stably treated even with a general drum, thereby reducing the disposal cost to lower than a high-integrity container.

Phase change modelling with flexible source-based kinetics for non-equilibrium transitions

In this work, a modeling approach is developed to cope with the phase-change problems having deviations from equilibrium conditions. The mathematical model is based on continuity and enthalpy conservation equations. The core of the model is a source term of continuity which governs the rate of phase change. The formulation of the source term is originally proposed with an infinite series, i.e. an iterative rate-tuner, which accounts for both equilibrium and non-equilibrium phase changes. As the model tracks equilibrium transitions by the stand-alone rate-tuner, off-equilibrium paths are described by regulations of the rate-tuner. The model also resolves undercooling-superheating of phase change materials with a feature tackling nucleation-growth-transition using an interphase-detector-function. In order to evaluate the model, a computational program was developed from the equations discretized with finite volume method. The paper presents implementation of the code in three test problems; Test-case-I employs a typical Stefan problem, i.e. melting of an ice bar in equilibrium condition, which verifies the model with the exact solution. Test-case-II simulates the ice bar under periodic heating/cooling at its end, so that non-equilibrium melting/freezing arises at the end of the bar. Depths and fractions of the phase change are graphed versus the frequency of heating/cooling cycles and the rate-regulator parameter. A spectrum of kinetic behaviors is presented, depending on the rate-regulator parameter. Three kinetic behaviors are distinguished, namely; extremely fast (instantaneous equilibrium), intermediate (non-equilibrium) and extremely slow (bypassed, highly-restricted-rate). Finally, test-case-III deals with a non-equilibrium solidification in a real case (sodium-acetate-trihydrate) that exhibits undercooling and recalescence due to nucleation-growth kinetics. The model successfully predicted temperature history curves in comparison with experimental data. The model is a step toward enhancing our computational tools for non-equilibrium phase changes in advanced material processing like additive manufacturing, casting, welding, solidification and energy storage systems.

Mechanism of P-wave promoting the solidification feeding in the low-pressure casting of ZL205A alloy

ABSTRACT The effect of P/S-wave on the solidification feeding and the mechanism of vibration promoting the solidification feeding in the low-pressure casting are discussed in the paper. The casting defects were analysed by X-ray non-destructive testing and the buoyancy method. It can be found that the compactness of casting is greatly improved by vibration. In the solidification feeding, according to vibration theory, P-wave will play a decisive role. When the transmission direction of P-wave is perpendicular to the feeding direction, it will lead to the alternation of dense-sparse state in the solidification system. When feeding is blocked, in the sparse state, the diameter of the feeding channel will increase, so that the pressure loss of feeding decreases. At the feeding end, the feeding pressure will make the solidification feeding again. On the contrary, vibration can’t further promote the feeding in the dense state.

Influence of Additional Insulation Block on Melt-Crystal Interface Shape in Directional Solidification System for Growing High Quality mc-Silicon Ingot: a Simulation Investigation

We have carried out the numerical simulation for DS system for growing multi-crystalline silicon (mc-Si) ingot with different size additional insulation blocks. Thermal Stress, melt-crystal interface shape and dislocation density are the main factors that can determine the efficiency of solar cells. Thermal stress and dislocation density can be controlled by controlling the heat dissipation from the crucible. The simulation results revealed that the effective controll of melt-crystal interface shape has been obtained by the suitable additional insulation block in DS system. At particular size of insulation block (3 cm) the optimal melt-crystal interface shape, von Mises stress, Maximum shear stress and maximum principal stress have been established during the solidification process which can enhace the mc-Si ingot quality, for photovoltaic application.