Melting Characteristics Research Articles

Experimental study on the melting characteristics modulation of cubic ice cubes with different trace air contents under natural convection condition

Ice as a typical phase change material has the advantages of low cost, high latent heat and environmental friendliness, and the ice melting process under natural convective conditions is a fundamental study that has received wide attention. For the cubic ice cubes having different air contents, their melting characteristics becomes more complicated. The melting model of cubic ice under natural convection conditions was developed, which can accurately predict the time of the entire melting process. To validate the accuracy of the model, a series of melting experiments on cubic ice cubes are conducted and analyzed, with mass and air contents varied from 20 g to 50 g, and from 0 to 3.9 %, with a model error of less than ±20 %. Based on the maximum melt rate and the change in shape to a pyramid of cubic ice, the melting process can be divided into the initial melting, frustum-shaped, and pyramid-shaped stages. Varying the air content of the ice regulated the total melting time and the time proportion of the initial melting stage and the frustum-shaped stage of the ice. The proportion of time in the pyramid-shaped stage decreased from 64.3 % to 51.5 % for bubble ice with an air content of 3.9 % compared to clear ice. The proportion of time in the pyramid-shaped stage during the ice melting process is not significantly related to the air content and mass, and remains at approximately 27 %. Results of this study are meaningful for regulating the melting process and optimizing phase change energy storage technologies.

Technological Features of Filler Wire Melting for Arc Welding and Surfacing with the Introduction of SF6 into Protective Gas Atmosphere

On the basis of the results of experimental studies the paper establishes important patterns of dependence of the frequency of short circuits of the arc gap and the coefficient of loss of electrode metal due to spatter from the voltage on the arc and the feed rate of the filler wire during welding and surfacing with the introduction of gaseous SF6 into the Ar + CO2 protective mixture. It is proposed to introduce fluorine-containing components of SF6 directly into the protective gas mixture of 82 % Ar + 18 % CO2 in quantities not exceeding 2 %. The technology makes it possible to reduce the amount of diffusion hydrogen in the deposited metal, which is an urgent task when welding high-strength steels and materials sensitive to hydrogen embrittlement. Previously, we resolved a number of issues related to the obstacle to increasing the concentration of S in the deposited metal, which made it possible to determine the most effective concentrations of SF6 in the protective gas environment, limited to 1.5 % by volume of the total composition (Ar + CO2) + SF6. At the same time, modification of the protective gas atmosphere with the halide compound SF6 has a significant effect on the melting characteristics of the electrode wire and temperature indicators in the arc combustion zone. This is due to the high ionization potential of fluorine as a product of the high-temperature dissociation reaction of SF6. The results obtained have made it possible to determine the most effective relationships between the values of the mode parameters, as well as to study the specifics of melting the filler wire in a protective atmosphere modified with SF6. Important regularities have been established that reveal the technological features of welding and surfacing with modification of the protective atmosphere with halide compounds.

Heat transfer enhancement of PCM in the triple-pipe helical-coiled latent heat thermal energy storage unit and complete melting time correlation

Secondary flows induced in helical-coiled pipes significantly enhance the thermal storage performance of latent heat thermal energy storage units. This paper presents a three-dimensional model of a triple-pipe helical-coiled system to investigate the melting characteristics of phase change material within it. A correlation for the complete melting time was developed based on the simulation results. The findings indicate that the thermal-hydraulic fields of the heat transfer fluids and phase change material deflect from the vertical central axis at cross-sections. The secondary flows within the inner pipe are more effective in enhancing melting than those in the outer pipe. Melting performance improves with increasing inner pipe diameter, coil diameter (from 100 mm to 160 mm), inclination angle, or heat transfer fluid temperature, or decreasing helical pitch. The inner pipe diameter, helical pitch and heat transfer fluid temperature exhibit more pronounced influences. An inner pipe diameter of 30 mm, a coil diameter of 160 mm, a helical pitch of 80 mm, an inclination angle of 90°, a heat transfer fluid temperature of 360 K, and a heat transfer fluid Reynolds number of 2000, respectively produce a faster melting process. The developed correlation for the triple-pipe helical-coiled pipe thermal storage unit accurately predicts 96 % of the 45 data within ±11 %.

Структура та властивості багатошарового металу, наплавленого електродними порошковими дротами з осердям із порошків феросплавів та гранульованих твердосплавних матеріалів

Comparative studies of the possibility of using granulated hard alloy powders as a charge of flux-cored wires for electric arc surfacing have been carried out. In the studies, granulated powder of the PG-R6M5 brand with a fraction of 50...300 μm was used. As a standard, a flux-cored wire was used, in the core of which there was a composition of powders of different ferroalloys of the same fraction. The content of the charge components in the core of the standard wire was selected and calculated so as to obtain a similar chemical composition to the wire containing granulated hard alloy powder. The test samples were obtained by layer-by-layer electric arc surfacing under the flux layer with flux-cored wires on low-carbon steel plates. To obtain identical dependences, the flux-cored wires had the same diameter and filling factor and differed only in the content of the core. The test samples were deposited under the same conditions with strict adherence to the deposition regimes, which were monitored using a high-speed analog-to-digital converter. It was determined that the use of granulated hard alloy powder as a charge of flux-cored wire has a positive effect on the melting characteristics of the wire and the stability of the welding process in general in comparison with the standard reference wire, the charge of which contains ferroalloys. This effect can be explained by the greater chemical purity of the granulated powder and the uniformity of the physicochemical properties of its particles in comparison with the powders of various ferroalloys. The determined features of the melting of the wire with a charge with granulated hard alloy powder have a positive effect on the quality of the formation of the multilayer deposited metal and its structure, leading to an increase in its homogeneity, some grinding of the grain and a decrease in the number and size of microdefects, which should positively affect the operational properties of the deposited metal. Keywords: electric arc surfacing, multilayer deposited metal, tool steels, granular hard alloy powder, ferroalloy, metal structure.

Numerical simulation and analysis on melting characteristics of a solid-liquid phase change process based on hot air riveting

To improve welding efficiency, a hot air riveting technology applicable to simultaneous welding at multiple stations is proposed, with the challenge lying in clarifying the melting state of the weldment. A numerical simulation method is proposed to investigate the melting state of the tag, using the Audi airbag tag as an example. The effects of various process parameters, including the exhaust duct distance, hot air temperature, hot air velocity, and the diameter ratio β, on the melting state of the tag are discussed. The melting mass, internal contour plots of the weldment and the melting rates are compared among the different parameter settings. The results indicate that under a heating temperature of 240 °C, the increase in hot air velocity has the most significant promotional effect on the melting of the weldment. Moreover, regardless of the velocity level, an increase in hot air temperature consistently enhances the melting of the weldment. Concurrently, an increase in the exhaust duct distance has an adverse impact on melting, yet this effect diminishes as the heating temperature rises. Finally, it is observed that at lower temperatures (200 ℃), diameter ratio β = 2.0 is more conducive to melting, whereas at higher heating temperatures (240, 280 ℃), β = 2.5 is more favorable for the melting of the weldment. This method effectively grasps the melting behavior of the weldment, enabling the selection of appropriate process parameters for hot air welding in actual production based on specific requirements.

Effect of Press Cake-Based Particles on Quality and Stability of Plant Oil Emulsions.

Palm fat has uniquely optimal melting characteristics that are difficult to replace in products such as baked goods and chocolate-based items. This study investigates the efficacy of using Pickering emulsions derived from Swiss plant oils and their micromilled press cakes. Emulsification was carried out at both the lab and pilot scales using sunflower- and rapeseed-based recipes, with and without additional surfactants, for both oil-in-water and water-in-oil emulsions. The resulting emulsions were measured for viscosity and short- and long-term stability and linked to the properties of the raw materials. The results indicated that the contact angle, size, and macronutrient composition of the particles significantly impact emulsion quality, though differences in oil pressing methods might predominate these effects. The combination of particles and surfactants demonstrated a clear advantage with respect to interface stabilisation, with a suggested link between the wax content of the oil and particles and the resulting emulsion quality and stability.

Charging performance of a novel finned latent heat storage unit under sloshing

Latent heat storage (LHS) on ships using phase change materials (PCMs) is challenged by inefficient heat storage efficiency and susceptibility to sloshing conditions. To address this issue, this paper proposes a shell-and-tube LHS unit using innovative fins. The enthalpy-porosity approach is employed to study the melting characteristics of LHS units under sloshing, focusing on the effects of direction, frequency, and strength of sloshing conditions. An optimal fin configuration to enhance thermal storage performance under sloshing is proposed. The results indicate that the sloshing conditions effectively enhance the temperature uniformity and heat storage capacity of LHS units. Compared with the slosh-free condition, the full melting duration of PCMs in LHS units under roll and heave conditions is reduced by 20.9 % and 23.6 %, respectively. Moreover, the natural convection intensity and heat transfer uniformity under sloshing conditions increase significantly, improving the heat transport capacity in the late melting stage. Additionally, the heat storage capacity of LHS units improves with a decrease in sloshing frequency and an increase in sloshing strength; however, there is a limit to the performance enhancement gains. Interestingly, the arrangement of fins closest to the refractory zone effectively improves the heat transport in the later melting stage, resulting in a further 6.8% increase in the melting rate.

Features of Plasma-Thermal Melting of Ash and Slag from Incineration Plant1

Features of Plasma-Thermal Melting of Ash and Slag from Incineration Plant1

Melting properties of lunar regolith simulant for in-situ construction

Additive manufacturing using lunar regolith can significantly reduce reliance on Earth’s resources for future lunar surface construction. To enhance the quality of parts formed through additive manufacturing, a comprehensive understanding of the melting characteristics of lunar regolith is crucial. In this study, the melting temperature range, melt viscosity, workability range, and contact angels between melt and substrates of the CUG-1A lunar regolith simulant were determined. The complete melting temperature of CUG-1A is about 1320 °C, and the corresponding melt viscosity is 8.39 Pa⋅s. The five characteristic temperatures of CUG-1A under argon flow, including sintering point, softening point, half-sphere point, floating point, and fluid point, are 1081 °C, 1115 °C, 1149 °C, 1158 °C, and 1311 °C, respectively. These characteristic temperatures are about 35 °C–50 °C higher in vacuum. The melt demonstrates good wetting ability at the flow point temperature with contact angels of 29° and 21° on corundum and platinum. The bubble generation, growth and release processes were observed for the melts under vacuum conditions. These results would provide essential data for the development of in-situ construction technologies, such as energy beam focused melting lunar regolith.

Molybdenum isotope evidence for recycled oceanic crust in the mantle sources of continental intraplate mafic lavas, Emeishan Large Igneous Province

The chemical and lithological heterogeneities of Earth's mantle in oceanic settings have long been attributed to the presence of recycled materials such as subducted crust, oceanic or subcontinental lithosphere mantle and sediment, as evidenced by Mid-Ocean Ridge Basalts (MORB) and Ocean Island Basalts (OIB). However, the extent to which recycled materials contribute to mantle heterogeneity in continental settings remains uncertain. Here we present systematic Sr-Nd-Pb-Mo isotope data for the Pingchuan picritic porphyries and associated mafic rocks (basalts and gabbros) in the central Emeishan Large Igneous Province, southwestern China, to resolve this issue. In contrast to the gabbro samples that show continental crust contamination in variations of δ98/95Mo (relative to NIST SRM 3134, −0.35 ± 0.03 to 0.03 ± 0.02 ‰), the Pingchuan picritic porphyries and basalts show a large range of δ98/95Mo (−0.32 ± 0.01 to −0.15 ± 0.06 ‰) and broadly negative trend between δ98/95Mo and Ce/Mo ratios, which cannot be explained by post-magmatic alteration, crustal contamination, fractional crystallization, olivine accumulation, metasomatism or fluid-activity in the mantle source. They were most likely derived from incongruent melting of a heterogeneous mantle source, i.e., a deep mantle with chondritic-like δ98/95Mo (−0.15 ± 0.01 ‰) containing recycled oceanic crust (+ sediment) with light δ98/95Mo (< −0.32 ‰). The basalts display low δ98/95Mo (−0.32 ± 0.01 to −0.24 ± 0.04 ‰), high 87Sr/86Sri (0.7046 to 0.7059), TiO2, Sm/Yb, Dy/Yb and Ce/Mo, pointing to characteristics of melts produced by MORB-type eclogite (+ sediment) at relatively low degrees of partial melting. With increasing degrees of partial melting, melts produced by peridotite (87Sr/86Sri = 0.7035 to 0.7043, chondritic-like δ98/95Mo = −0.18 ± 0.03 to −0.15 ± 0.06 ‰) come to dominate, resulting in low TiO2, Sm/Yb, Dy/Yb and Ce/Mo of the Pingchuan picritic porphyries. From a global perspective, continental basalts also plot on the negative trend defined by the OIB datasets (δ98/95Mo vs. Ce/Mo). As such, Mo isotope may provide a robust tracer of recycled oceanic crust in shaping mantle heterogeneities that occur in both oceanic and continental settings.

Melting performance of PCM with MoS2 and Fe3O4 nanoparticles using leaf-based fins with different orientations in a shell and tube-based TES system

Phase change materials (PCMs) are frequently utilized in the thermal sector, especially for thermal energy storage (TES) applications. The purpose of this study was to analyze the thermal efficiency and melting characteristics of a leaf-vein-shaped fin in a triplex tube heat exchanger. The analysis focused on the use of pure molten salt PCM and a combination of molten salt PCM with MoS2 and Fe3O4 nanoparticles. The study utilized ANSYS Fluent software to conduct numerical simulations and analyze seven distinct fin arrangements. The simulations were employed to visualize and examine the liquid fraction, temperature, and fluid velocity. The findings indicated that the leaf-vein fin shape greatly improved the dispersion of liquid fraction, average temperature, and velocity in comparison to alternative fin designs. The addition of MoS2 and Fe3O4 nanoparticles significantly enhanced the melting and thermal characteristics of the PCM as a result of heightened thermal conductivity. This showcases the capability of the leaf-vein fin design and PCM nanocomposites to enhance the efficiency of thermal energy storage in triplex tube systems. About 2500 s PCM melt about 36% for case A, but melting rate enhance up-to 55% using nano particles. Melting rate enhance 91% in 1000 s in case of G using 8 fins as compare to case A having no fins.

Effect of rare earth elements scandium on Sn-0.7Cu brazing metal: First-principles calculation

In this paper, the effects of rare earth element Sc on the thermal and mechanical properties of precipitates (Cu6Sn5), (Cu3Sn) and Sn matrix in Sn-0.7Cu brazing metal, as well as the interface bonding strength between stable precipitates (Cu6Sn5) and Sn matrix were investigated based on first-principles calculations. The results show that the electronic structure of the precipitated phase and the matrix changes to a certain extent, the atomic bonding mode recombines, and the electron orbitals of the matrix atoms and the rare earth elements hybridize. In addition, rare earth elements improve the mechanical properties of precipitated phase and matrix, increase the plasticity of precipitated phase and enhance the strength of matrix. Rare-earth elements improve the thermodynamic properties of the matrix and precipitated phase to some extent, increase the heat capacity of the precipitated phase and the matrix, and reduce the melting point. At the same time, rare earth elements enhance the mechanical properties and thermodynamic stability of the interface between the precipitated phase and the matrix, and improve the oxidation resistance of the matrix. Transmission electron microscope (TEM) observation shows that there is a segregation of Cu atoms at the interface between precipitated phase and matrix. Other experimental results show that: Rare-earth element Sc has a positive effect on the mechanical properties, melting characteristics and oxidation resistance of the filler metal alloy. When the addition of Sc is 0.1 % (wt), the tensile strength and elongation of the alloy are significantly increased, the melting point is reduced, the surface oxidation resistance is increased, and the comprehensive properties of the alloy are the best.

A new steelmaking process using red mud as a fluorine-free flux: Promoting phosphorus removal and iron recovery

Bayer red mud, one of the most challenging solid wastes in the aluminum industry, is anticipated to be suitable for large-scale disposal in alignment with the specific requirements of the steelmaking process. This study determined the melting characteristics of various red mud-based fluxes using a high-temperature in-situ analysis system. Furthermore, the feasibility of large-scale application and the potential for substituting CaF2 in the iron and steelmaking process were investigated through a 10-kg induction furnace test and a 160-ton converter industrial test. The results indicate that the hot metal temperature during the pre-phosphorus removal stage ranged from 1254°C to 1430°C. Initial slag formation occurred within 2–4 minutes of oxygen blowing. The average slag basicity was between 1.5 and 2.1. Early dephosphorization and the average phosphorus distribution ratios were 41.4 %-63.4 % and 30, respectively. The mechanism of red mud-based fluxes in the early stage of steelmaking was further elucidated, and the application process was designed. The new process reduces the cost of slag materials, realizes the large-scale disposal of red mud, establishes the connection for the sustainable development of the steel and aluminum industries.

Experimental Study on Preparation of Inorganic Fibers from Circulating Fluidized Bed Boilers Ash.

The ash generated by Circulating Fluidized Bed (CFB) boilers is featured by its looseness and porosity, low content of glassy substances, and high contents of calcium (Ca) and sulfur (S), thus resulting in a low comprehensive utilization rate. Currently, the predominant treatment approach for CFB ash and slag is stacking, which may give rise to issues like environmental pollution. In this paper, CFB ash (with a CaO content of 7.64% and an SO3 content of 1.77%) was used as the main raw material. The high-temperature melting characteristics, viscosity-temperature characteristics, and initial crystallization temperature of samples with different acidity coefficients were investigated. The final drawing temperature range of the samples was determined, and mechanical property tests were conducted on the prepared inorganic fibers. The results show that the addition of dolomite powder has a significant reducing effect on the complete liquid phase temperature. The final drawing temperatures of the samples with different acidity coefficients range as follows: 1270-1318 °C; 1272-1351 °C; 1250-1372 °C; 1280-1380 °C; 1300-1382 °C; and 1310-1384 °C. The drawing temperature of this system is slightly lower than that of basalt fibers. Based on the test results of the mechanical properties of inorganic fibers, the Young's modulus of the inorganic fibers prepared through the experiment lies between 55 GPa and 74 GPa, which basically meets the performance requirements of inorganic fibers. Consequently, the method of preparing inorganic fibers by using CFB ash and dolomite powder is entirely feasible.

Analysis of the spatial heterogeneity of glacier melting in Tibet Autonomous Region and its influential factors using the K-means and XGBoost-SHAP algorithms

This study employed machine learning to comprehensively analyze glacier melting in Tibet Autonomous Region (TAR) and its vital influencing factors. Existing machine learning research often lacks detailed explanations, leading to generalized predictions without considering essential driving factors necessary for yielding an insightful understanding of glacier melting dynamics. To overcome these limitations and fulfill multi-level analysis requirements for comprehending glacier melting, this study identifies factors contributing to glacier melting heterogeneity and assesses distinct melting causes in three spatial melted glacier clusters. We utilized K-means unsupervised classification to cluster Tibet melted glaciers into three categories based on temperature, sunshine hours, evapotranspiration, precipitation, normalized vegetation index, and slope. XGBoost algorithm explores the nonlinear relationships of glacier melting with these features and Shapley values were used for model transparency, quantifying feature's influence on the melting process. Investigating geographical heterogeneity among clusters enhanced our understanding of the observed changes. High fitting accuracy (>0.98) enhanced the result reliability, as well. The results show that Tibetan glaciers melt significantly from 2010 to 2020, and the cluster analysis reveals its unique melting characteristics. Melting glaciers in the same cluster are not only similar in characteristics, but also in spatial and geographical distribution, with two of the clusters concentrating in the eastern part of TAR, and the third cluster scattered in the western part of the country. the XGBoost-SHAP analysis efficiently quantifies the contribution of each cluster feature to the glacier melting, revealing the different roles of different clustered features.

Simulation of melting characteristics of thermal washing of the wax layer in the pipeline based on lattice Boltzmann method

ABSTRACT The escalation of transportation costs and the obstruction of pipelines due to wax deposition significantly impact the secure and efficient production of oil fields. The thermal washing method, characterized by its simplicity and cost-effectiveness, is widely employed for dewaxing crude oil gathering pipelines. The investigation of the melting mechanism of the wax layer during thermal washing is extremely important. In this paper, the two-zone composite model of multiphase flow-porous medium in the mushy zone is introduced into the solid-liquid phase change lattice Boltzmann model based on the enthalpy method, and the problem of circumferential inhomogeneity in the melting of the wax layer and the important influence of flow and heat transfer in the mushy zone on the thermal washing are systematically investigated. The demarcation point (γ tr) between the high and low liquid fraction zones is measured to be 0.81 by microscopic experiment. The impacts of varying γ tr and Ste numbers on wax melting at different circumferential locations are analyzed in detail. The results show that the melting efficiency of wax exhibits a nonlinear enhancement from − 90° to 90°. The melting efficiency of wax decreases with increasing γ tr for wax layers between 90° and − 45°. The melting efficiency of wax increases with higher Ste numbers at all angles. The Ste number increases from 0.42 to 5.0, and the melting efficiency of the wax layer at angles ranging from 90° to − 90° increases by factors of 2.16, 2.16, 2.20, 2.61, and 3.33 respectively. The growth of the Ste number improves the warming rate and shortens the generation time of convection at the center point of the wax layer. The research findings serve as a fundamental reference for formulating a rational and efficient thermal washing scheme.

Effects of TiO2 and CaO/Al2O3 on Melting Characteristics, Surface Tension, and Structure Electroslag‐Remelting‐Type Low‐Fluorine Slag

The influence of TiO2 and CaO/Al2O3 on the surface tension of CaF2–CaO–Al2O3–SiO2–MgO–TiO2 low‐fluorine slag system is determined by pulling method, and the melting characteristics of the slag system are determined by differential scanning calorimetry . It is found that the surface tension decreases with the increase of temperature. With the increase of TiO2 from 7% to 16%, the surface tension decreases from 2.97 to 0.71 N m−1, the Tend decreases from 1683 to 1648 K, and the activation energy decreases gradually. When the CaO/Al2O3 increases from 0.9 to 1.8, both the surface tension and Tonset show a minimum value, the surface tension is 2.286 N m−1, the Tonset is 1498 K, and the crystallization phase is formed during the melting process. The main reason TiO2 affects the structure is the substitution of Ti4+ for Al3+ in the [AlO4]5− structure to form the Ti2O64− structure, which leads to depolymerization of the Q2 and Q3 polymerization degree and thus the slag system structure, while CaO/Al2O3 affects the slag polymerization degree by influencing the amount of bridging oxygen. Finally, the surface tension is characterized using each structure to derive a relationship between structure and surface tension.

Pressure-less melt infiltration characteristics of Mg melt into Ti powder preforms with various pore structures: Toward the application to the binder jetting additive manufacturing

Binder jetting (BJT) additive manufacturing enables the fabrication of complex-shaped metallic parts but requires sintering as post-processing to obtain dense parts. The sintering inevitably causes the shrinkage from green body to dense products, resulting in low dimensional accuracy. In contrast, pressure-less melt infiltration (PMI) fills pores in the green body with a liquid metal driven by capillary pressure and fabricates a dense metal matrix composite without severe shrinkage. To consider the applicability of pressure-less melt infiltration to the post-processing of binder jetting additive manufacturing, it is required to clarify the relationship between pressure-less melt infiltration process conditions and the relative density of the composites. In this study, the liquid Mg/solid Ti system was selected because of good wettability and absence of Mg-Ti intermetallic, and the conditions of Ti powder preforms (corresponding to the green body) were focused on. Ti powder preforms with various powder sizes (2300, 410, 140, and 20 μm) and different shapes (irregular and spherical) were cold-pressed at 76, 102, 127, 153, and 178 MPa to fabricate preforms with various relative densities, pore sizes, and pore morphologies to response the similar characteristics in BJT preforms. Mg melt infiltrated into the preforms under constant conditions to fabricate Mg/Ti composites. The structures of the preforms and composites were characterized by sample size measurement, optical and scanning electron microscopy, and X-ray computed tomography. It was revealed that the relative density of the composite increased with decreasing Ti powder size and using spherical Ti powder, whereas the compact pressure exhibited a slight effect. Furthermore, defect volume increased with increasing infiltration height but decreased around the top surface of the sample. Minute observations around defects in the composites revealed that defects were formed at larger pores, and Mg melt was infiltrated into pores above the defects. These results indicated that infiltration velocity varied depending on the flow channel structure, and gas was trapped at larger pores (far from the outside of the sample) where infiltration velocity was low. Using smaller Ti powder decreased the variation in pore size in the preform, resulting in improving the relative density of the composites by suppressing the gas trapping. This study provides a new insight into the pressure-less melt infiltration process as a post-processing of binder jetting additive manufacturing.

A Temperature-Transferable Coarse-Grained Model for Poly(lactic Acid) Melts.

We present a temperature-transferable coarse-grained (CG) model for poly(lactic acid) (PLA), specifically designed to replicate its volumetric properties and solubility parameter in the molten state. The CG-bonded potentials were derived by using the iterative Boltzmann inversion (IBI) optimization method to match structural properties from detailed atomistic models. A parametrization workflow was employed to determine nonbonded interaction parameters with temperature-dependent corrections that provide agreement with the target properties across the melting temperature range. The CG model successfully replicates key features of the PLA melt. It satisfactory reproduces the density and solubility parameter, maintains the dependence of chain conformation on molecular weight, and captures the dynamic behavior through agreement in scaled mean squared displacement and diffusion coefficients with the atomistic model. Additionally, the CG model offers much faster equilibration compared with the atomistic model. The proposed model is expected to be particularly useful for investigating the miscibility characteristics of PLA in various blends and composites that remain challenging to explore using fully atomistic simulations or experiments.

Antibacterial Food Packaging Containing Stably Dispersed Cu Nanoparticles Synthesized by Novel Physical Vapor Deposition Process

Polymeric materials were modified by nanoparticles on powder (NPP) facility in which metal nanoparticles (Cu, Cu/Zn alloy etc.) are formed on the surface of rotating carrier powder by using physical vapor deposition process untile the metal content reached 0.3wt.%. The polymer material with metal nanoparticles deposited on their surface through the NPP process was then added to the raw polymer material at a ratio of 1 to 9. The mixture of modified polymer powder and raw polymer powder were then processd into a film by conventional processes such as hot melting, extrusion, T-die, and antibacterial characteristics of the film were investigated. We ultimately manufactured antibacterial food package using the film and conducted preservation test for two weeks at room temperature. Since food package containing 0.03wt.% Cu nanoparticles showed over 99.9% bacteria reduction rate, it slowed down the progress of deterioration significantly compared to conventional packages. For safety evaluation, the amount of copper released out was analyzed and a cytotoxicity test was also conducted.