Stir Processing Research Articles

Effect of water on the excess properties of eutectic solvents

Three eutectic solvents were created utilizing a heating and stirring process. The solvents consist of tetrabutylammonium bromide and levulinic acid, as well as tetrabutylammonium chloride with either levulinic acid or lactic acid. The characterization of the samples was conducted using 1H NMR and IR techniques. The density and viscosity of three different low eutectic solvent and water binary mixture systems were determined within the temperature range of 293.15 to 333.15 K. The volume properties (excess molar volume, coefficient of expansion, coefficient of excess expansion) of the binary mixtures with different amounts of water were thoroughly investigated across the complete range of mole fraction. The study also investigated the impact of viscosity parameters, such as viscosity deviation and Excess activation Gibbs free energy of viscous flow. Furthermore, an analysis was conducted on the interaction between the eutectic solvent and the solvent molecules in the binary mixture. This analysis revealed the presence of hydrogen bonds between the eutectic solvent and water molecules. Moreover, it was confirmed that the excess properties could be fitted with the Redlich-Kister equation with r2 ≥ 0.99,demonstrating high suitability for binary mixes consisting of low eutectic solvents and water.

Facile Preparation of Three-Dimensional Cubic MnSe2/CNTs and Their Application in Aqueous Copper Ion Batteries.

Transition metal sulfide compounds with high theoretical specific capacity and excellent electronic conductivity that can be used as cathode materials for secondary batteries attract great research interest in the field of electrochemical energy storage. Among these materials, MnSe2 garners significant interest from researchers due to its unique three-dimensional cubic structure and inherent stability. However, according to the relevant literature, the performance and cycle life of MnSe2 are not yet satisfactory. To address this issue, we synthesize MnSe2/CNTs composites via a straightforward hydrothermal method. MnSO4·H2O, Se, and N2H4·H2O are used as reactants, and CNTs are incorporated during the stirring process. The experimental outcomes indicate that the fabricated electrode demonstrates an initial discharge specific capacity that reaches 621 mAh g-1 at a current density of 0.1 A g-1. Moreover, it exhibits excellent rate capability, delivering a discharge specific capacity of 476 mAh g-1 at 10 A g-1. The electrode is able to maintain a high discharge specific capacity of 545 mAh g-1 after cycling for 1000 times at a current density of 2 A g-1. The exceptional electrochemical performance of the MnSe2/CNTs composites can be ascribed to their three-dimensional cubic architecture and the 3D CNT network. This research aids in the progression of aqueous Cu-ion cathode materials with significant potential, offering a viable route for their advancement.

Exploring integrated heat and mass transfer in von-Kármán dynamics involving Reiner-Rivlin fluid with regression models

The rotating disk system is widely used in several important applications, including turbomachinery design, mixing and stirring processes, centrifugal blood pumps development, optimizing electronic component, cooling efficiency, and various others. Moreover, regression models offer comprehensive and reliable prediction for important parameters in flows developed by revolving disks. This article presents similarity solutions for coupled heat and mass transfer with viscous dissipation in an inelastic non-Newtonian fluid flow across a permeable revolving disk. The inclusion of diffusion terms due to Dufour and Soret effects establishes coupling between energy and concentration equations. Temperature and concentrations at disk surface are supposed to vary quadratically along the radial direction. The impacts of MHD, heat source/sink dynamics and Joule heating effects on thermal boundary layer are also scrutinized. MATLAB's bvp5c tool, based on collocation scheme, generates numerical results. Homotopy analysis method, a widely accepted analytical solution procedure, is then applied to produce the series solution. Selection of the optimal auxiliary parameter values featured in the series solution is also included. The impact of Reiner-Rivlin fluid assumption on the torque required by the disk is assessed. Furthermore, linear and quadratic regression models are developed for the skin friction factors, Nusselt number and Sherwood number.

Head-on collision of gravity currents of unequal strengths: Large-eddy simulations and laboratory experiments

The collision of two counterflowing gravity currents with unequal strengths was investigated through large-eddy simulations and laboratory experiments. The collisions were initiated by releasing currents from two partial-depth locks at identical heights but with different densities, characterized by the reduced gravity ratio, γg. By varying γg, we elucidate the transport processes of colliding gravity currents, spanning from comparable driving strengths (γg=1.0) to markedly disparate driving strengths (γg≪1). Three distinct regimes of colliding gravity currents were identified based on kinematic features derived from integrated measures. For γg≥0.92, the collisions are driven by counterflowing gravity currents with comparable driving strengths, leading to nearly symmetrical collisions with negligible impact on evolved flow patterns. In the intermediate regime when 0.4<γg<0.92, the collisions are weakly asymmetric, characterized by differing contact surface steepness and insensitive maximum vertical displacement of ascending motions to γg. For γg≤0.4, strongly asymmetric collisions dominate, featuring minimal vertical convective fluxes in the collision region rather than typical colliding currents. In this flow regime, the denser fluid mass intrudes beneath the less dense one, akin to the propagation of intrusive lock-exchange gravity currents. Additionally, mixing rates over the entire flow domain were quantified using background potential energy calculations. The results reveal that intense diapycnal mixing is predominantly driven by stirring processes before collision, with the mixing rate increasing as γg decreases. From the collision stage onward, currents with the gain of inertia converge within the collided region and move upward with the distinct opposite effect of negative buoyancy. Notably, the mixing rate stabilizes regardless of convective process variations and decreases consistently as the currents slump away from the collision region.

Direct Sonochemical Leaching of Li, Co, Ni, and Mn from Mixed Li-Ion Batteries with Organic Acids

Metals such as nickel, cobalt, lithium, and manganese are widely used in lithium-ion batteries (LIBs) in electronic devices and electric vehicles. It is forecast that there will be a strong increase in the number of electronic devices and electric vehicles in the coming years. (1) Background: In this paper, the application of ultrasound waves on improving Li, Co, Mn, and Ni leaching efficiency from mixed active cathode materials from different types of LIBs is presented. (2) Methods: Environmentally friendly, low-concentrated (0.75 M) organic acids (oxalic acid, citric acid) and, additionally, sulfuric acid, were used in sonochemical and chemical leaching (stirring process) at a temperature of 60 °C. (3) Results: The results showed significantly higher leaching efficiency of metals with ultrasound-assisted treatment, especially when using organic acids. An average of 50% better leaching results were obtained for Li in oxalic acid (99.6%) and for Co (93.1%) in citric acid during sonochemical leaching. (4) Conclusions: Based on the theory of hydrogen peroxide formation during ultrasound wave transition in solutions, the role of H2O2 as one of the most effective reductants used to enhance cobalt, manganese, and nickel leaching from LIBs is indicated.

Numerical study on the polydispersive effect of filler size distribution on the properties of thermal interface materials

Abstract Advanced thermal interface materials (TIMs) are indispensable for work reliability and lifespan assurance of high-power density electronic systems by facilitating timely and effective heat dissipation. A random algorithm consisting of diluting, dropping, and stirring processes is first proposed to simulate microstructures of TIMs with continuous particle size distribution, with an accessible maximum volume fraction of 55 vol%. Then the size polydispersity impact on the thermal performance and the fluidity of TIMs is numerically investigated. Simulation results reveal that as the particle size polydispersity increases, the thermal conductivity of TIMs improves, along with the improved fluidity. Therefore, it is necessary to consider the polydispersive impact of filler size distribution in actual production and optimize the material preparation process based on the actual distribution of particles. This work provides a deeper understanding of the influence of particle polydispersity on the co-optimization of the desired attributes of TIMs.

Electrolytic manganese residue pretreated by filter press-water washing and carbide slag: Manganese recycling, depth harmless and dispersion

Filter press-water washing and carbide slag (CS) were utilized for recycling manganese, ensuring depth harmless and dispersion of electrolytic manganese residue (EMR). Mn2+ recover profit, pH value, leaching concentration and particle sizes of treated water-washed EMR (TWEMR), as well as the microstructure and composition changes during disposal process was explored. Mn2+ recovery efficiency was 94.11 % with a profit of 10.56 $/(1 t EMR). CS primarily served as a dispersant and disposal agent, with a stepwise addition of CS (40 % + 60 %) and a change in stirring process (slow speed for 5 min and fast speed for 10 min) further enhancing the reaction process. Mn2+ and NH4+ leaching concentrations can be reduced to below the detection limits, while Mg2+ concentration reduced to 1.26 mg/L. Moreover, the dispersion of water-washed EMR (WEMR) was realized. Mn2+ and Mg2+ were solidified/stabilized in forms such as MnOOH, Mn3O4, Mn2O3, MnCO3, Mg(OH)2 and MgCO3. Furthermore, these ions could also be solidified/stabilized through the formation of ettringite, thaumasite, butlerite and calcium (aluminate) silicate hydrate (C-(A)-S-H) during the reaction process. This study provides a method for manganese recycling from EMR, ensuring depth harmless and dispersion of WEMR filter cake.

Mussel-inspired interface deposition strategy for mesoporous metal-phenolic nanospheres with superior antioxidative, photothermal and antibacterial performance

Metal-phenolic networks (MPNs) have emerged as a versatile and multifunctional platform applied in bioimaging, disease treatment, electrocatalysis, and water purification. The synthesis of MPNs with mesoporous frameworks and ultra-small diameters (<200 nm), crucial for post-modification, cargo loading, and mass transport, remains a formidable challenge. Inspired by mussel chemistry, mesoporous metal-phenolic nanospheres (MMPNs) are facilely prepared by direct deposition of the metal-polyphenol complex on the interface of oil nano-droplets composed of block copolymers/1,3,5-trimethylbenzene followed by a spontaneous template-removal process. Due to the penetrable and stable networks, the oil nano-droplets gradually leak from the networks driven by shear stress during the stirring process. As a result, MMPNs are obtained without additional template removal procedures such as solvent extraction or high-temperature calcination. The materials have a large pore size (∼12.1 nm), uniform spherical morphology with a small particle size (∼99 nm), and a large specific surface area (49.8 m2 g−1). Due to the abundant phenolic hydroxyl groups, the MMPNs show excellent antioxidative property. The MMPNs also have excellent photothermal property, whose photothermal conversion efficiency was 40.9 %. Moreover, the phenolic hydroxyl groups can reduce Ag+ in situ to prepare Ag nanoparticles loaded MMPNs composites, which have excellent inhibition performance of drug-resistant bacteria biofilm.

Mechanical stirring of bulk-stored maize in steel bins to suppress maize weevils and other beetle populations

This study investigates the effectiveness of periodic stirring as a non-chemical approach to suppress maize weevils, Sitophilus zeamais, and other beetle populations in large-scale grain storage bins. The research was conducted in a farm steel bin with a diameter of 9.8 m holding 127 Mg of maize, and a control bin of diameter 7.3 m holding 102 Mg of maize. Both bins were loaded with maize at 13% moisture and infested at a commercial tolerance rate of 2 weevils/kg of maize. Probe traps monitored beetle populations except for S. zeamais before stirring was initiated. Maize samples were collected at depths of 0, 0.9, 1.8 and 2.7 m with a vacuum-probe sampler prior to stirring and at 10, 20, 30 and 40 days of continuous stirring machine operation. Stirring achieved 100% control of live S. zeamais while the control bin experienced an increase in its S. zeamais population after 40 days. The stirring process also led to a significant reduction in dominant beetle populations such as hairy fungus beetles, Typhaea stercorea, and foreign grain beetles, Ahasuerus advena. Although the quality of maize in both bins changed at different depths and storage times, the treatment bin had higher bulk density (732.7 ± 3.98 kg/m3 to 768.9 ± 2.41 kg/m3), lower insect damage (0.02 ± 0.02% to 0.9 ± 0.28%), and higher allowable storage time (>249 days). Moisture content and molded kernels increased in the control bin, reaching 26.4 ± 1.29% and 3.2 ± 0.53%, respectively. The average percentage of broken corn and foreign material (BCFM) in the sweepings on the floor of the emptied treatment bin was 6.5 times higher than that in the control bin. Calculated packing factor values below 1.5 from the sweepings indicated that BCFM concentrations did not affect airflow. Stirring maize provides an alternative to the use of chemicals to control stored maize insect pests at a production scale.

Flow stirred by open turbine: A modal analysis of multiscale flow characteristics

AbstractThe turbulence observed in the stirred tank is a result of the superposition of flows at different scales, each exerting various influences on the operational processes. To understand the flow characteristics associated with stirring, this paper undertakes particle image velocimetry (PIV) experimental research on an unbaffled tank stirred by an open turbine featuring four distinct blade deflection angles. The flow field in the unbaffled tank manifests as a double‐circulation flow pattern; however, it is worth noting that the blade deflection angle exerts a significant impact on the stirring process. Specifically, when the blade deflection angle reached 90°, the flow discharge aligned closely with the radial direction, accompanied by pronounced fluctuations in the high‐velocity region. The Lagrangian coherent structures (LCS) formed were subsequently extracted and subjected to finite‐time Lyapunov exponent (FTLE) analysis. Notably, a more regular wake pattern emerged in proximity to the blade tip, while a larger scale flow structure persisted along the flow direction. To systematically analyze the flow field stirred by the open turbine, modal analysis was employed. By reconstructing the flow field based on the principle of 50% energy content, the decomposition of flows at different scales was achieved. The turbulent kinetic energy (TKE) generated by the various scale flows was subsequently calculated, revealing that the high TKE values primarily originate from the large‐scale flow structure. Conversely, the TKE generated by the small‐scale flow exhibits a uniform distribution across different regions. Notably, in regions characterized by higher velocities, the peak TKE associated with the small‐scale flow also manifests; however, it is significantly smaller in magnitude compared to that generated by the original flow or the large‐scale flow.

Impact of Injection Rate on Flow Mixing during the Refining Stage in an Electric Arc Furnace

During the refining stage of electric arc furnace (EAF) operation, molten steel is stirred to facilitate gas/steel/slag reactions and the removal of impurities, which determines the quality of the steel. The stirring process can be driven by the injection of oxygen, which is carried out by burners operating in lance mode. In this study, a computational fluid dynamics (CFD) platform is used to simulate the liquid steel flow dynamics in an industrial-scale scrap-based EAF. The CFD platform simulates the three-dimensional, transient, non-reacting flow of the liquid steel bath stirred by oxygen injection to analyze the mixing process. In particular, the CFD study simulates liquid steel flow in an industrial-scale EAF with three asymmetric coherent jets, which impacts the liquid steel mixing under different injection conditions. The liquid steel mixing is quantified by defining two variables: the mixing time and the standard deviation of the flow velocity. The results indicate that the mixing rate of the bath is determined by flow dynamics near the injection cavities and that the formation of very low-velocity regions or ‘dead zones’ at the center of the furnace and the balcony regions prevents flow mixing. This study includes a baseline case, where oxygen is injected at 1000 SCFM in all the burners. Two sets of cases are also included: The first set considers cases where oxygen is injected at a reduced and at an increased uniform flow rate, 750 and 1250 SCFM, respectively. The second set considers cases with non-uniform injection rates in each burner, which keep the same total flow rate of the baseline case, 3000 SCFM. Comparison between the two sets of simulations against the baseline case shows that by increasing the uniform flow rate from 1000 to 1250 SCFM, the mixing time is reduced by 10.9%. Moreover, all the non-uniform injection cases reduce the mixing time obtained in the baseline case. However, the reduction in mixing times in these cases is accompanied by an increase in the standard deviations of the flow field. Among the non-uniform injection cases, the largest reduction in mixing time compared to the baseline case is 10.2%, which is obtained when the largest flow rates are assigned to coherent jets located opposite each other across the furnace.

Computational heat transfer analysis of liquid food in a heat exchanger with varying stirrer settings in a nonclassical continuum framework

Rapid heat diffusion and stirring of food in channels and tanks for more desirable and safely regulated food delivery is of particular interest in food industry. In the present article, we investigate heat diffusion in a heat exchanger with varying stirrer settings in a nonclassical framework. Interestingly, the liquid food flows in all previous investigations are modeled using the classical continuous paradigm. Therefore, the purpose of this article is to offer a mathematical model that uses a nonclassical continuum framework to mimic the behavior of liquid food flows. This is influenced by the fact that during the stirring process, food particle microrotations affect the heat diffusion phenomenon, necessitating consideration of this in the modeling aspect of such studies. This non-Newtonian physical process is modeled based on the well-established theory of Cosserat continuum. The mathematical model presented here is taking into consideration a newly established constitutive relation by the author for the strain-based viscosity models in non-Newtonian mechanics. The applied constitutive relation incorporates the microrotational effects into the current rheology of rate-dependent viscosity model as a result of the kinematics at the macroscopic level. It offers a more practical method for examining the heat diffusion process in a heat exchanger. To the best of the author’s knowledge, this approach is first of its kind in analyzing heat diffusion process within non-Newtonian mechanics. The presented strain-based viscosity model is described in the form of PDEs along with prescribed boundary conditions. An in-house code is developed based on finite element method. The code is implemented using FreeFEM++. Liquid food flow in a heating process is analyzed numerically for heat transfer characteristics with varying Cosserat number and other physical aspects. Simulations are performed in a channel connecting a tank with different stirrer settings. Computed results are analyzed in a limiting case for accuracy and a strong agreement is achieved with the available solutions from the literature. Some interesting features of the liquid food flow and heat transfer are presented and discussed. It is observed that when liquid food particles rotate faster, the temperature difference between the walls also increases. The temperature difference between the top and bottom walls of the liquid food tank increases with faster speed of stirrers. Rise in the Cosserat number results in a dispersed vortices throughout the liquid food tank. The temperature differential between the liquid food tank’s top and bottom walls rises as a result of an increase in the microrotational motions of the food particles. Moreover, the microrotational motion of the liquid food particles rises with an increase in Cosserat number, enabling effective particle mixing.

Investigation of Al-7075/Al2O3/SiC by swirl casting and WEDM

The research, engineering, military, automotive, sports, and telecommunications industries are just a few of the many that make heavy use of aluminium metal matrix composites. The unique synergistic qualities of these composites, such as reduced weight density, improved performance, and thermal conductivity, make them highly desired. Because of its reputation for small but noticeable structural improvements, Al-7075 aluminium has seen extensive use in the aerospace industry. This research followed international criteria for evaluating specimens in terms of positional stiffness, deformation, impact resistance, and wear. It used the stir casting process to add SiC/Al2O3 to Al-7075 in percentages ranging from 2% to 8%. Hybrid Al-HMCs are the product of an aluminium metal matrix composite that was able to include 8% SiC/Al2O3via the stirring process. Because it combined aluminium oxide with silicon carbide, this Al-HMC showed improved mechanical qualities and stiffness. Aluminium metal composites with increasing amounts of Al2O3/ SiC showed reduced fatigue and frictional strengths. The effect on hardness remained small even when the MMC's SiC/Al2O3 proportions grew significantly. To further investigate the Wire Electrical Discharge Machining (WEDM) process, researchers used the L9 Arrays Design of Experiments (DOE) technique to incorporate new process variables. Our objective was to enhance the rate of material removal from Al-7075/SiC/Al2O3 while simultaneously improving the marginal surface roughness. Finding the best WEDM process parameters, including the ideal percentages of SiC/Al2O3, to achieve the desired surface roughness while minimising material removal rate was the goal of this investigation. To produce Al- 7075/SiC/Al2O3 composite materials with varying additive percentages in a production environment, this study will determine the best and most accurate WEDM process variables to use.

Regenerated Silica Gel for Isolation of Ethyl p-Methoxycinnamate from Kaempferia galanga rhizome

The main component from Kaempferia galanga rhizome extract is known as ethyl p-methoxycinnamate. Column chromatography using silica gel is one of the commonly used method for obtaining high purity of ethyl p-methoxycinnamate from K. galanga rhizome extract. In this study, the regeneration of silica gel then utilized for checking its reusability to undergo the isolation of ethyl p-methoxycinnamate. The silica gel was regenerated by utilizing two methods: (a) the direct furnace at 600 ⁰C; (b) the stirring process with aqueous solution of sulfuric acid which followed by furnace at 600 ⁰C. K. galanga rhizome extract was obtained under maceration by hexane. Regenerated silica gel was characterized by XRF and FTIR. The ethyl p-methoxycinnamate content was determined by UV-Vis spectrophotometry. The regenerated silica gel showed almost similar characteristic with the original commercial silica gel. The K. galanga rhizome extract after underwent column chromatography with regenerated silica gel showed high stability. This result ensured the utilization of regenerated silica gel can be considered for isolation of ethyl p-methoxycinnamate from K. galanga rhizome extract.

Penerapan Alat Bantu Pengaduk dan Manajemen Rantai Pasok untuk UMKM Pembuat Rendang

This community service program aims to solve the unstandardized production process and the high bargaining power from suppliers in rendang making for Small, Micro, and Medium Businesses (MSMEs). The appropriate technology and consultation training implementation are the applied method in achieving the goal. Therefore, the main problems to be solved are uniformity mixture between seasoning and meat during cooking process within 4-5 hours and low management skill to organize the supply chain components. The results are a uniform mixture of all ingredients and SMMB has basic supply chain management skills. The stirring process with constant speed and intermittent monitoring process during the entire cooking process produces the uniformity mixture. The SMMB is equipped with the skill to identify the supply chain components in the form of compact map. This community service program can blend technology and management implementation into interconnected activities to increase the MSMEs competitiveness, unlike similar community service program.

PENGECORAN ALUMINIUM MATRIKS KOMPOSIT BERPENGUAT CARBON NANOTUBE (CNT) DENGAN VARIASI PENAMBAHAN SERBUK MAGNESIUM

Aluminum matrix composite reinforced CNT have been developed to improve the mechanical properties of aluminum. In this study, the melting of Aluminum 1100 reinforced Carbon Nanotube (1 wt.% CNT) with variations in the addition of Magnesium powder was carried out by the slurry-based method. The casting of the specimens is carried out using a metal mold. CNT powder was first mixed with magnesium powder at 60°C. Then the aluminum is melted to a temperature of 700°C until it melts, then the temperature is lowered to 500°C or the texture has changed to be like mush (slurry based) and then mixed with CNT powder and Magnesium powder are added. After that the alloy was raised again at 720°C for 30 minutes and the stirring process was carried out, after that it was poured into a metal mold with a mold temperature of around 400°C. The samples were then analyzed for mechanical properties and microstructure observations. The results of the Vickers hardness test before the addition of Mg powder and CNT were 36.7 HV. While after the variation of adding 1wt.% Mg powder, the hardness of the specimen increased to 44.5 HV, the variation of adding 3% Mg powder was 45.3 HV, and the variation of adding 5% Mg powder reached a hardness value of 46 HV. The tensile test results on 3% Mg powder is 241.6 MPa. The wear test results show the wear rate value for the 1% Mg variation of 0.146 mg/s, the 3% Mg variation of 0.106 mg/s, and the 5% Mg variation with a wear rate value of 0.093 mg/s. The α-Al phase is the dominant phase formed, where the grain size and grain boundaries in the 3% Mg variation have a relatively small size and the spread of CNT is evenly distributed in the alloy, so the addition of Mg to the alloy can help spread CNT in Aluminum alloys.

Optimization of Arabinogalactan Sulfation in Process Scaling

To ensure the safety of the arabinogalactan sulfation process, the thermal effect of the reaction (148.26 kJ) was determined by the thermal flux balance method. The dependence of the dynamic viscosity of the reaction medium on the way of introducing the sulfating agent and on its particle size was studied by phase rheology. The stirring process was calculated to substantiate the optimum stirrer design and determine the quality parameters of stirring of the reaction medium. The data obtained allow optimization of the process for producing Agsular® substance in scaling of the production technology.

Structural improvement of propeller impellers of high-temperature and high-pressure reactor based on TRIZ theory

With the rapid development of science and technology, exploration and study of extreme environments have advanced significantly. Consequently, the demand for equipment designed to operate under these conditions has increased. This paper proposes an innovative design method for stirring impeller structures based on the Teoriya Resheniya Izobreatatelskikh Zadatch (TRIZ) theory. By analyzing the interaction between components during the stirring process, we establish a TRIZ conflict resolution-based model for the innovative design process of stirring impeller structures. Our innovative design process is model-led, based on the TRIZ conflict resolution theory. This process improves existing stirrer structures to design a new type of stirrer with an ultra-thin multi-cross-shaped hole structure. We compare our proposed structural model to an existing stirrer using Computational Fluid Dynamics (CFD) for numerical simulation. The effect of different thicknesses, numbers of holes, radii, and shapes of the frame stirrer on the flow field values was analyzed. The results indicate that reducing the stirrer thickness, increasing the number of holes, and perforating the stirring impeller can enhance its stirring capacity. Changing the opening radius and adding special-shaped holes to the stirring impeller can also modify its stirring capacity. Ultimately, the proposed frame stirrer with an ultra-thin multi-cross-shaped hole structure increases the maximum turbulence kinetic energy by 14.6% and the maximum speed by 32.9% compared to the existing stirrer. Studying the feasibility of this innovative model and design method can provide new ideas for designing high-temperature and high-pressure reactor impellers in extreme environments.

THE EFFECT OF AL2O3 AND STIRRING TIME ON DENSITY AND POROSITY OF ALUMINUM ADC12 FOAM

The instability of the foam forming during metallic foam manufacture commonly occurs, which will cause undesirable pores. The stability of the foam structure is one of the important factors. A stabilizer can maintain the foam cell during the melting process. In this study, the metal used is ADC12 with a 12 wt.% of Si element content, and the foaming agent is CaCO3. CaCO3 will produce gas to form bubbles in the melt during the solidification process and use a stabilizer to strengthen cell walls so that foam does not easily fall off or collapse. The stabilizer uses Al2O3 with the variation of Al2O3 are 1 to 3 wt.%. The stirring time is as variable as well. A stirring process is conducted to distribute foaming agents so that the foam distribution is more homogeny throughout the aluminum foam. The variation of the stirring time is carried out for 60, 120, and 180 seconds. The results show that as the time of stirring and the addition of stabilizer increases, the porosity will rise, but the density decrease. Compressive strength results show it has no significant relation with increasing the stabilizer and stirring time. The highest compressive strength is obtained in the sample with a stirring time of 120 seconds with an Al2O3 content of 1 wt.%.

Electrically charged behavior of the solution during the stirring process

In this study, the electrically charged behavior of solution in the flowing process was investigated. The results show that the electrically charged behavior gets affected by the flow speed of the solution and solution types. With the increase in flowing speed, the electric current and voltage generated by solution friction at different stirring speeds vary significantly because of the charge separation and the formation of double electric layers, which are generated because of the high-speed friction of objects with different work functions.