Low Melting Point Metal Alloy Research Articles

Analysis of experimental uncertainties in jet breakup length and jet diameter during molten fuel-coolant interaction

The jet breakup length is one of important phenomenological parameters to evaluate the corium debris bed coolability during the progress of severe accident in nuclear power plant, since the parameter is related to the determination of the liquid melt fraction in debris bed. Existing jet breakup length data reveal relatively large scattering and different trends, similar to the Saito or Epstein correlation, depending on cases. The scattering and separation of the data may be due to uncontrolled factors in the melt discharge condition and also inconsistent evaluation methods used for the jet breakup length.Through melt jet breakup experiments with low melting point metal alloy (Bi-Sn alloy), the influence of the estimation methods for the jet diameter (measured or calculated value) and the jet breakup length (position- or velocity-based value) was investigated. According to the comparison between the measured and calculated jet diameters, the experimental uncertainty was reduced by producing well-controlled melt jet. The concept of the jet breakup length was revisited in detail, emphasizing the shorter breakup length by the velocity-based method. The modification of the Saito correlation constant from 2.1 to 1.7 was suggested to fit the velocity-based breakup length. The importance of a well-defined data analysis process for non-dimensional jet breakup length was highlighted for the minimization of the experimental uncertainty.

Quantitative characterization of three-dimensional pore structure in hardened cement paste using X-ray microtomography combined with centrifuge driven metal alloy intrusion

In this paper, a centrifuge device is proposed to facilitate the intrusion of a low-melting point metal alloy into the pore space of hardened cement paste. X-ray microtomography is combined with metal centrifugation porosimetry (MCP) to quantitatively investigate 3D pore structure. The low-melting-point metal alloy is melted and introduced into pore space in pastes with water cement ratio of 0.5 and 1.0 at a temperature of 65 °C. 3D pore structure is quantitatively analyzed by X-ray microtomography after the molten metal alloy has been consolidated. A new threshold value segmentation method for pore space was proposed using conversion coefficient on region of interest (ROI). Porosity and pore size distribution are tested by MCP and compared with the results based on mercury intrusion porosimetry (MIP). The results show that the contrast between pore space and solid phase in the X-ray microtomography device image is improved. The total porosity obtained by MCP was found to be consistent with the results obtained by MIP.

Embedded electrical tracks in 3D printed objects by fused filament fabrication of highly conductive composites

The incorporation of electrical components into 3D printed products such as sensors or printing of circuits requires the use of 3D printable conductive materials. However, most conductive materials available for fused filament fabrication (FFF) have conductivities of less than 1000 S/m. Here, we describe the study of conductive thermoplastic composites comprising either nylon – 6 or polyethylene (PE) matrix. The fillers used were nickel and Sn95Ag4Cu1, a low melting point metal alloy. The combination of nickel metal particles and tin alloy allows for higher metal loading at lower melt viscosity, compared to composites of nickel metal particles alone. Conductivities of 31,000 S/m were achieved, and 30 vol. % metal loading was processable by a single screw extruder. Embedded conductive tracks of various geometries were easily printed via FFF. Electrical conductivity of embedded conductive track has been investigated as a function of geometrical variation, where conductive tracks printed along a horizontal axis show resistance of ≤ 1 Ω. Porosity of the printed track is shown to increase with prints along the vertical axis, leading to a reduction in electrical conductivity of more than two orders of magnitude.

A review of conductive polymer composites filled with low melting point metal alloys

Metal alloys with low melting temperatures may be blended into polymers to improve their electrical conductivity. We review the preparation, morphology, and electrical conductivity of polymer composites based on low melting point metal alloys, with or without additional filler particles. Since such alloys can be liquid under melt processing conditions, the composite morphology is determined by phenomena such as coalescence of liquid metal drops, orientation of the liquid metal phase, or selective wetting of a second filler by the liquid metal. None of these phenomena appear in conductive composites based on more common conductive fillers such as carbon black, carbon nanotubes, or metal particles. The published literature suggests that composites based on low melting metal alloys, with or without additional non‐melting filler particles, can have much higher percolation thresholds and much higher electrical conductivity (∼1,000 S/m) than those based on fillers such as carbon black or carbon nanotubes. Changes in other properties such as rheological or mechanical properties are also discussed. POLYM. ENG. SCI., 58:1010–1019, 2018. © 2017 Society of Plastics Engineers

Polymeric Sensor Fibers Based on a Piezoelectric Polymer and Metal Alloy/Carbon Nanotube/Polymer Composite for Structural Health Monitoring

Sensor fibers can be used for structural health monitoring in multiple environmental applications. Possible areas of applications are in geotextiles for monitoring the status of the reinforcement or in wind energy plants to monitor the load on wind blades. In this paper, a new type of sensor fiber based on a piezoelectric polymer (polyvinylidene fluoride) and a composite material made of a thermoplastic polymer, a low melting point metal alloy and carbon nanotubes (CNT) is presented. The piezoelectric polymer generates a signal when a load is applied if it is processed in the right way. Here, the formation of the piezoelectric crystalline structures will be presented. The conductive compound transmits the signal to measurement equipment. While CNT form a conductive network in the polymer, the metal alloy acts as a coating for the nanotubes and increases the electrical conductivity (100 S/m) by two orders of magnitude compared to pure CNT nanocomposites (approx. 1 S/m). The increased conductivity allows the transmission of the signals over larger distances, making the material favourable for large scale applications like wind blades.

Effect of nano-fillers on conductivity of polyethylene/low melting point metal alloy composites

A novel method for preparing conductive polyethylene (PE) composites has been developed. In the method, the powder of low melting point metal alloy (LMPA) is filled into the PE matrix by using twin screw extruder at a temperature below the melting point of the LMPA, and followed by a die drawing process at a temperature around the melting point of the metal alloy. It has been found that die drawing process, repeating the die drawing process and adding nano-fillers, such as montmorillonite (MMT) and multi-wall carbon nanotubes (MWCNTs), all help reduce the metal particle size in the PE matrix, thus improve the conductivity of the composite. The conductivity improvement is attributed to an increased number of the smaller metal particles. Therefore, conductive composites of polymer/metal alloy/nano-filler with high conductivity are possible to be prepared by using the new method.

English

Microwave modification converts wood into a highly porous material Torgvin with numerous cavities and dramatic changes to the physical and mechanical properties of wood including very high permeability. Impregnation of Torgvin with a low melting point metal alloy fills the voids with metal. Strength property values of the newly formed Vintorg-metal range between the property values of wood and Torgvin. Vintorg-metal has new properties compared to natural wood: high electro-conductivity, high thermo-conductivity, very high density, and other physical properties that require further study. New specific properties of the Vintorg-metal opens up new fields of potential application.

Preparation and Properties of Polymer Composites Filled with Low Melting Metal Alloys

Composites of polymers and low melting point metal alloys are little known classes of materials. In this work thermoplastic composites filled with differing contents of Wood's metal or Cerromatrix alloys have been studied in respect to their microstructure, mechanical, thermal, and electrical properties. It was found that the type of filler employed had significant influence only on the mechanical and thermal properties of composites. The results of volume resistivity show that all composites conduct electrical current well, even when metal loading is below 10vol.%. Low percolation threshold is caused by a unique interpenetrating network structure created by polymer and metal co-continuous phases.

A novel method to construct 3D electrodes at the sidewall of microfluidic channel

We report a simple, low-cost and novel method for constructing three-dimensional (3D) microelectrodes in microfluidic system by utilizing low melting point metal alloy. Three-dimensional electrodes have unique properties in application of cell lysis, electro-osmosis, electroporation and dielectrophoresis. The fabrication process involves conventional photolithography and sputtering techniques to fabricate planar electrodes, positioning bismuth (Bi) alloy microspheres at the sidewall of PDMS channel, plasma bonding and low temperature annealing to improve electrical connection between metal microspheres and planar electrodes. Compared to other fabrication methods for 3D electrodes, the presented one does not require rigorous experimental conditions, cumbersome processes and expensive equipments. Numerical analysis on electric field distribution with different electrode configurations was presented to verify the unique field distribution of arc-shaped electrodes. The application of 3D electrode configuration with high-conductive alloy microspheres was confirmed by particle manipulation based on dielectrophoresis. The proposed technique offers alternatives to construct 3D electrodes from 2D electrodes. More importantly, the simplicity of the fabrication process provides easy ways to fabricate electrodes fast with arc-shaped geometry at the sidewall of microchannel.

Experimental Modeling of the Continuous Casting Process of Steel Using Low Melting Point Metal Alloys—the LIMMCAST Program

This paper presents the new experimental facility LIMMCAST which was designed for modeling fluid flow and transport processes in the continuous casting of steel. The facility operates at temperatures of 200–400°C by using the low melting point alloy SnBi. The main parameters of the facility, including the dimensions of the test sections, will be given. The resultant possibilities with respect to flow investigations in the tundish, in the submerged entry nozzle, and in the mould will be discussed. Over the period of assembling and commissioning the LIMMCAST facility, the small-scale set-up Mini-LIMMCAST was employed which uses the alloy GaInSn that is liquid at room temperatures. At this precursory facility an experimental program was started which is focused on quantitative flow measurements in the mould and in the submerged entry nozzle (SEN). The Ultrasound Doppler Velocimetry (UDV) and the Contactless Inductive Flow Tomography (CIFT) were applied to determine the flow structure within the mould. First experimental results will be presented here for a single and a two-phase flow in which argon gas bubbles were injected at the inlet of the SEN. According to the concept of the electromagnetic brake the impact of a DC magnetic field on the emergent jet flow from the SEN has been studied.

A new rapid manufacturing process for multi-face high-speed machining

High-speed machining is known as one of the most effective rapid prototyping and/or manufacturing (RPM) processes that provides the various machining materials with excellent quality and dimensional accuracy. However, the high-speed machining process is not suitable for the rapid realization of 3D-shaped product because a considerable amount of time is required for the work piece fixturing process. High-speed rapid prototyping (HisRP), a new type of RPM technology, will be presented in this paper. The proposed HisRP has been developed using a combination of a multi-face high-speed machining process and a flexible fixturing technique. Low melting point metal alloys are used to hold the work piece during multi-face machining. An automatic set-up device, mounted and fixed to the work table, has also been developed to guarantee positional accuracy during a series of multi-face machining operations. This set-up device is expected to be beneficial for successive multi-face high-speed machining of working materials, for example for two-face or four-face machining. The proposed HisRP process has been shown to be a useful method for manufacturing 3D metal products with reduced lead time.

Development of rapid manufacturing process by high-speed machining with automatic fixturing

Rapid prototyping and manufacturing (RPM) technology has recently been used in many industries in order to shorten lead time and cost. During the last decade various kinds of RPM technologies were developed and commercialized. The high-speed machining process is one of the most effective RPM methods. Even though it offers some practical advantages (e.g., precision and versatility) over other RPM technologies, it still has several aspects that need to be improved. In particular, the method of workpiece fixturing is strongly required to be bettered because it greatly depends on the geometrical complexity of products. This paper describes a new RPM technology called high-speed rapid prototyping (HisRP). Basically HisRP is a high-speed machining process combined with a new automatic fixturing in which low melting point metal alloys are used to easily fix a complex workpiece. In addition, an automatic set-up device attachable to the table of the machine has been developed to ensure the quality of products during a series of machining operations. The designed automatic set-up device is expected to be beneficial for the four-step machining of a workpiece. It was mounted and fixed on the working table to guarantee the position accuracy. The proposed HisRP process has shown to be a useful method of manufacturing complex metal products with reduced lead time and cost.

98/02463 Optimization of sulfur impregnation protocol for fixed-bed application of activated carbon-based sorbents for gas-phase mercury removal : Liu, W. et al. Environ. Sci. Technol., 1998, 32, (4), 531–538

In this paper, a centrifuge device is proposed to facilitate the intrusion of a low-melting point metal alloy into the pore space of hardened cement paste. X-ray microtomography is combined with metal centrifugation porosimetry (MCP) to quantitatively investigate 3D pore structure. The low-melting-point metal alloy is melted and introduced into pore space in pastes with water cement ratio of 0.5 and 1.0 at a temperature of 65 °C. 3D pore structure is quantitatively analyzed by X-ray microtomography after the molten metal alloy has been consolidated. A new threshold value segmentation method for pore space was proposed using conversion coefficient on region of interest (ROI). Porosity and pore size distribution are tested by MCP and compared with the results based on mercury intrusion porosimetry (MIP). The results show that the contrast between pore space and solid phase in the X-ray microtomography device image is improved. The total porosity obtained by MCP was found to be consistent with the results obtained by MIP.

A transparent model of the human scala tympani cavity

A dimensionally accurate clear model of the human scala tympani has been produced to evaluate the insertion and position of clinically applied intracochlear electrodes for electrical stimulation. Replicates of the human scala tympani were made from low melting point metal alloy (LMA) and from polymethylmeth-acrylate (PMMA) resin. The LMA metal casts were embedded in blocks of epoxy and in clear silicone rubber. After removal of the metal alloy, a cavity was produced that accurately models the human scala tympani. Investment casting molds were made from the PMMA scala tympani casts to enable production of multiple LMA casts from which identical models were fabricated. Total dimensional distortion of the LMA casting process was less than 1% in length and 2% in diameter. The models have been successfully integrated into the design process for the iterative development of advanced intracochlear electrode arrays at UCSF. These fabrication techniques are applicable to a wide range of biomedical design problems that require modelling of visually obscured cavities.