Solid Metal Particles Research Articles

Thermal Performance and Reliability of Liquid Metal Pastes with Solid Metal Particles as Thermal Interface Materials for the Cooling of Computing Electronics

In recent years, we have developed a series of gallium-based liquid metal pastes containing low content solid metal particle additives (LMPMPs) to enhance thermal performance and control bondline thickness (BLT) of prepared liquid metal composites as thermal interface materials (TIMs). This new material is synthesized via in-situ by introducing gallium oxide into liquid metal alloys. In our recent research, we intensively investigated thermal properties of different primary liquid metal alloys containing small amounts of metal additives, and ran extensive reliability tests including power cycling, thermal cycling, and aging tests on the synthesized LMPMPs. In this paper, the thermal properties of the synthesized LMPMPs with different liquid metal alloys are studied with reliability tests that focus on power cycling by monitoring thermal resistance of LMPMPs over time using a custom power cycler. We have found power density, BLT, and different liquid metal alloys have a significant impact on thermal properties and reliability of LMPMPs. We also conducted thermal aging tests on Cu-LMPMPs-Cu sandwich specimens at 85°C in an ambient atmosphere to study the deterioration of thermal conductivity of LMPMPs over time, measured by laser flash analyzer using the layered structure method. Highly accelerated stress test (HAST) with a profile of 110°C, 85RH%, and 264 hours was used to study the decomposition of liquid metal alloys. Thermal cycling test with a profile of -40 to 125°C was employed to investigate the pump-out of LMPMPs. It has been proven that LMPMPs have much better thermal performances than polymer-based thermal grease.

Potential of Nanocarrier-Associated Approaches for Better Therapeutic Intervention in the Management of Glioblastoma.

Glioblastoma, commonly known as glioblastoma multiforme (GBM), is one of the deadliest and most invasive types of brain cancer. Two factors account for the majority of the treatment limitations for GBM. First, the presence of the blood-brain barrier (BBB) renders malignancy treatment ineffective, leading to recurrence without full recovery. Second, several adverse effects are associated with the drugs used in conventional GBM treatment. Recent studies have developed nanocarrier systems, such as liposomes, polymeric micelles, dendrimers, nanosuspensions, nanoemulsions, nanostructured lipid carriers, solid lipid nanocarriers, metal particles, and silica nanoparticles, which allow drug-loaded formulations to penetrate the BBB more effectively. This has opened up new possibilities for overcoming therapy issues. Extensive and methodical searches of databases such as PubMed, Science Direct, Google Scholar, and others were conducted to gather relevant literature for this work, using precise keyword combinations such as "GBM," "brain tumor," and "nanocarriers." This review provides deep insights into the administration of drugs using nanocarriers for the management of GBM and explores new advancements in nanotechnology. It also highlights how scientific developments can be explained in connection with hopeful findings about the potential of nanocarriers for the future successful management of GBM.

Elucidation of solid particle interfacial Phenomena in liquid sodium: Magnetic interactions on liquid metal and solid atoms at the solid interface

We were able to detect the nuclear magnetic resonance (NMR) signal of a liquid sodium clinging to the interface of solid metal particles for the first time. In this study, we confirmed the difference in the relaxation times due to the difference in the interactions between liquid sodium and metal particles suspended in the liquid sodium. It was found that the surface of the micro titanium particles and liquid metallic sodium interact physically, not chemically.

A Method for Measurement of Nonferrous Particles Sizes in Lubricant Oil Independent of Materials Using Inductive Sensor

Machine operating conditions can be obtained through lubrication oil detection; solid metal particles are the primary factor causing mechanical wear. The surface of the friction pair is usually specially treated with the nonferrous metal protective coating. Therefore, there are many kinds of nonferrous particles in the lubricating oil. In this paper, a method for measurement of nonferrous particles sizes independent of materials using the impedance signal of the inductive sensor is presented. Both the imaginary part and real part of the coil impedance signal are studied in this paper, which is different from traditional inductive sensor research only the imaginary part of impedance signal output is considered. Through theoretical analysis, it is found that the real and imaginary parts of coil impedance changes with different materials at the same size are corresponding to an elliptic function. Combining with the coil impedance measured in the experiment, the particle size can be obtained, which is independent of particle material.

Liquid Metals in Catalysis for Energy Applications

Summary To keep up with the fast-paced transitioning of the global energy sector, which is constantly thriving to enable reliable, economic, and sustainable energy production, catalysis research has been required to continuously evolve in response. The challenges in the existing systems are predominantly due to dependencies on heterogeneous solid catalysts that are susceptible to coking. In this respect, liquid-metal (LM) catalysts have been demonstrated to have a critical advantage over conventional catalysts. Recently, LMs acquired a place in catalysis, with a reputation often synonymous with interesting properties and a remarkable ability to break trade-offs between homogeneous and heterogeneous catalysis. This review bridges the fundamental principles of LM research and the recent advances in LM-based thermal and electrochemical catalysis for energy applications. Moreover, emerging approaches for the improved utilization of LMs are outlined, and the concepts requiring greater research attention that could enable the development of exciting energy solutions are highlighted.

Постановка нестаціонарної задачі фільтрування рідини у деформованому пористому середовищі

The regularities of the process of filtration of technological liquids through porous materials are investigated. At finishing operations of metalworking application of lubricating and cooling liquids are acquired. During operation, liquids are continuously and intensively contaminated with solid metal particles. To restore the original properties of process fluids are cleaned of mechanical impurities. The most widely used methods of purification of process fluids are by filtration. The use of filtration for the purification of process liquids is the most effective, because when filtering through a layer of porous materials, it is possible to achieve complete removal of solid particles from liquids. However, the peculiarities of the structure of the pores cause a number of specific phenomena that occur during the movement of liquids in the channels of the porous medium.The purpose of the research is to study and establish the pattern of the process of filtering process fluids through porous materials. When filtering process fluids through a layer of porous materials, the porous medium of the filter partition increases with the change of its porosity. The change in porosity occurs by reducing the pore volume of the porous space, because the solid particles together with the liquid penetrate into the pores of the channels of the porous space and hang up in them. The conducted researches allowed exposing and studying regularities of process of filtering and establishing the law of change of porosity of the porous environment. On the basis of the established regularities the differential equation is derived, which allows us to formulate the statement of the problem of liquid filtration through a layer of solid particles of the deformed porous medium of the filter partition under the given initial and boundary conditions.

Experimental study on convective heat transfer and entropy generation of carbon black nanofluid turbulent flow in a helical coiled heat exchanger

The convective heat transfer coefficient (CHTC) of a fluid is one of the most effective factors on the performance of a fluid in heat transfer equipment. Due to the higher conductivity of metals than that of liquids, solid metal particles can be mixed in a fluid to improve the CHTC of it. According to recent advances in nanotechnology, using nanofluids is one of the popular methods to increase heat transfer in heat exchangers. In this paper, the main influence factors on increasing the CHTC of the nanofluid, including flow rate and nanofluid concentration, were investigated. For this study, all tests were carried out in the Reynolds range of 10,000 to 31,500 which are definitely in turbulent regime. Furthermore, in order to reduce the number of tests, Design–Expert software using central composite method has been employed. The results indicate that increasing the Reynolds leads to an increase in the CHTC and a decrease in the friction factor. In addition, it was shown that at a constant Reynolds, carbon nanofluid with concentration of 0.21 mass% has about 40.7% higher CHTC than pure water. The variation of friction factor was investigated too and was found that this parameter is increased by increasing the nanofluid concentration and decreasing the Reynolds number. The entropy generation due to heat transfer and friction factor was assessed and finally showed that in 0.21 mass% where the maximum Nusselt is available, the entropy generation is the lowest. By calculating the Bejan number, the portions of heat and friction factors in generating entropy were determined.

ОСОБЛИВОСТІ ТЕРМОІМПУЛЬСНОГО ОЧИЩЕННЯ ПОВЕРХОНЬ І КРОМОК ДЕТАЛЕЙ ВІД ЗАБРУДНЕНЬ ПІСЛЯ МЕХАНІЧНОЇ ОБРОБКИ

The requirements for the quality of aviation technology are decisive in the creation of technological systems that ensure the industrial purity of products. But the cost component of the finishing and stripping technologies is also important, the value of which depends on the chosen method of removing liquids, for example, from hydraulic units of aircraft. Reliable and cost-effective manufacture of parts with specific geometric and technological properties is the main goal of industrial production. In a market economy, the production of competitive products is a necessity, and it is always the choice of a rational, stable price-quality ratio. The quality of engineering products is a multifactorial problem, depending on the complex of systemic organizational and technological measures. In the production of aircraft technology, quality assurance is associated with dependability and a guaranteed resource that is vital due to specific operating conditions. One of the most important measures to ensure the reliability and guaranteed life of aviation products is to ensure industrial cleanliness. Cleaning from microparticles, macro- and micro-hauler surfaces and edges of parts after mechanical types of processing is included in the complex of these measures. The most problematic is the cleaning of body parts with a complex configuration of external and internal surfaces. The need to remove liquids and other technological pollution is explained by functional, ergonomic and aesthetic reasons. If ergonomic and aesthetic factors do not affect the technical characteristics of products, then the functional ones are directly related to the operability of machines and mechanisms. Functional causes are the prevention of failures of hydraulic distribution and control devices, as well as the prevention of increased wear of critical parts occurring when friction pairs of solid metal particles enter the gaps, difficulties in assembling and positioning, reducing fatigue strength and so on. Burrs cause turbulence in the flow of gas or liquid, disrupting the flow uniformity. It is obvious that the mutually influencing processes occurring in the hydraulic systems of machines, in violation of working conditions, lead to an increase in negative phenomena. The peculiarity of the use of purification technologies is the need to remove liquids from 100% of the parts included in the autonomous system of mechanisms. If at least one detail is left untreated, then the working fluid, when in contact with contaminated surfaces, washes away these contaminants and spreads them throughout the system, while the most sensitive elements are damaged. The reasons for the need to clean the surface and edges of parts from technological contamination are given. A brief review of the results of modeling and research on the removal of burrs in the environment of detonating gas mixtures has been performed. The features of the thermopulse process are considered and the results of numerical and experimental studies are presented. A comparative analysis of the energy intensity of removing burrs of various metals is shown.

Heterogeneity in Heck Reactions with Heterogeneous Precatalysts

The Heck reaction is the most attractive C-C coupling way, which constitutes a universal approach of producing various classes of organic compounds for the development of new processes used in industry. A deeper understanding of the nature of true catalytic species starting with heterogeneous precatalysts will motivate potential breakthroughs in the rational design of future generations of homogeneous C-C coupling catalysts in nature. Heterogeneous catalyst systems are expected to achieve a high turnover number or good catalyst recycling with a minimal level of residual metal in the products via homogeneous catalysis. This review is focused on the investigation of heterogeneity towards Heck reactions with heterogeneous precatalysts, concisely summarizing the worldwide research published up to date with our appropriate discussion. The review includes the literature of heterogeneity studies involving various types of solid material-supported metal particles and various heterogenized metal complexes used as precatalysts. Either the cases where leached metal species from heterogeneous precatalysts were claimed to be true catalysts, or the cases where heterogenized metal species were asserted to contribute to catalysis are presented here. Meanwhile, some important experimentations and methods for assessing catalyst heterogeneity, which are linked with the design of effective homogeneous C-C coupling catalysts using heterogeneous precatalysts are briefly introduced to catalysis readers. Keywords: C-C coupling, heck, heterogeneity, heterogeneous, homogeneous, leaching, precatalysts.

Two-fluid, hydrodynamic model for spherical electrolyte systems

Spatial interaction effects between charge carriers in ionic systems play a sizable role beyond a classical Maxwellian description. We develop a nonlocal, two-fluid, hydrodynamic theory of charges and study ionic plasmon effects, i.e. collective charge oscillations in electrolytes. Ionic spatial dispersion arises from both positive and negative charge dynamics with an impact in the (far-)infrared. Despite highly classical parameters, nonlocal quenching of up to 90% is observed for particle sizes spanning orders of magnitude. Notably, the ionic system is widely tunable via ion concentration, mass and charge, in contrast to solid metal nanoparticles. A nonlocal soft plasmonic theory for ions is relevant for biological and chemical systems bridging hard and soft matter theory and allowing the investigation of non-classical effects in electrolytes in full analogy to solid metal particles. The presented semi-classical approach allows studying plasmonic photo-catalysis introducing nonlocal aspects into electrolyte-metal interactions.

Jumping liquid metal droplet in electrolyte triggered by solid metal particles

We report the electron discharge effect due to point contact between liquid metal and solid metal particles in electrolyte. Adding nickel particles induces drastic hydrogen generating and intermittent jumping of a sub-millimeter EGaIn droplet in NaOH solution. Observations from different orientations disclose that such jumping behavior is triggered by pressurized bubbles under the assistance of interfacial interactions. Hydrogen evolution around particles provides clear evidence that such electric instability originates from the varied electric potential and morphology between the two metallic materials. The point-contact-induced charge concentration significantly enhances the near-surface electric field intensity at the particle tips and thus causes electric breakdown of the electrolyte.

Field Application of a Newly Developed Personal Nanoparticle Sampler to Selected Metalworking Operations

A personal nanoparticle sampler (PENS) that simultaneously collects respirable particles (< 4 μm) and nanoparticles (< 0.1 μm) has recently been developed and calibrated in the laboratory. This study aims to evaluate the performance of the PENS in the workplace, and to determine the exposure characteristics during selected metalworking operations. Metal polishing/buffing, spot welding, and milling operations were selected to represent sources of solid metal particles, fume aggregates and metalworking fluid mists, respectively. In each operation, personal samples of a side-by-side PENS and SKC respirable dust aluminum cyclone were taken concurrently with ambient particle number size distribution measurements. The PENS-measured respirable particle mass concentrations (PM4) showed remarkable accuracy with respect to the reference SKC cyclone, regardless of particle type. The PENS-derived nanoparticle effective densities agreed reasonably well with the bulk densities expected for the substrate and materials in use. During the metalworking operations, the nanoparticle mass concentrations (PM0.1) were poorly associated with the PM4 but strongly correlated with the ambient nanoparticle number concentrations (PN0.1), due to the persistent, elevated levels of nanoparticles formed during the operations. Overall, these results suggest that the PENS is applicable for use in the workplace to assess respirable and nanoparticle personal exposure, and that metal polishing/buffing, welding and milling generate a considerable amount of nanoparticles.

입자 부상 제트에서 오리피스 길이가 입자 분포에 미치는 영향에 대한 연구

As a propellant of a high speed underwater vehicle, the hydro-reactive solid metal particles using seawater as a oxidizer maximizes its specific impulse when the solid metal particles and the seawater are uniformly mixed in the combustion chamber. The purpose of this study is to investigate the effects of injector geometry on the particle distribution of similarity point of view. For the purpose of this similarity of the mean velocity and particle number density along the radial direction was measured by Particle Image Velocimetry(PIV).

Reaction Regimes on the Synthesis of Hollow Particles by the Kirkendall Effect

The formation of hollow vs solid particles by means of the oxidation reaction of solid metal particles depends on the differential self-diffusivities of the reactants through the composite shell, the reaction probabilities at each interface, and the concentration and diffusivity of the element in solution. By means of a kinetic model of the oxidation process, we determine the phase diagrams for the geometry of the oxidized particles and propose four shell growth regimes. We experimentally illustrate the different growth scenarios by changing the conditions of oxidation of cadmium spherical crystals using different chalcogen precursors.

Metal-Based Nanoparticle Synthesis from the Rapid Expansion of Carbon Dioxide Solutions

Synthesis of 10 to 500 nm diameter Fe-based nanoparticles is described. Nanometer-sized droplets of iron carbonyl are generated by the rapid expansion of CO2-based supercritical fluid solutions and are photolyzed in-flight using a UV lamp to remove the carbonyl groups. Solid metal particles are collected electrostatically as coatings or loose particle aggregates on solid surfaces. Upon air oxidation, the iron particles react rapidly to produce an iron oxide phase. Mo-based nanoparticles were similarly produced using a Mo(Co)6 precursor. FTIR analysis of collected nanoparticles suggests that carbonyl groups are more readily photolyzed from the Fe precursor than from the Mo analog.

High Velocity Interparticle Collisions Driven by Ultrasound

Ultrasonic irradiation of slurries produces high velocity impacts between solid metal particles that are sufficient to cause interparticle melting. Sonication of 5 mum Zn powder as a slurry in alkanes, for example, produces dense agglomerates 50 mum in diameter consisting of approximately 1000 fused particles. Particle size was found to be the most influential parameter in inducing local melting during interparticle collisions. Ultrasonic irradiation of mixed powders resulted in formation of agglomerates with larger Zn particles "soldered" by the smaller ones. A simple kinematic model of the ultrasound-driven interparticle fusion predicts a melting criterion that is nonmonotonically dependent on particle size and is shown to be in agreement with experiment.

Pd-catalyzed Heck arylation of cycloalkenes—studies on selectivity comparing homogeneous and heterogeneous catalysts

Abstract Heck reactions of aryl bromides with cyclohexene and cyclopentene catalyzed by typical homogeneous as well as heterogeneous Pd catalysts (Pd/C, Pd/SiO 2 , Pd/MgO, Pd/Al 2 O 3 , and Pd(0), Pd(II) and [Pd(NH 3 ) 4 ] 2+ in zeolites Y or ZSM-5) have been studied in order to get detailed information on the reaction mechanism with regard to the catalyst. The focus of the present investigation was on correlations between selectivity (Heck products: double bond isomers of arylcycloalkenes, dehalogenation and double arylation products) and nature of the catalyst or active Pd species, respectively. The results indicate that dissolved molecular Pd species are responsible for the Heck coupling for both homogeneous and heterogeneous (solid) catalysts, whereas dehalogenation is due to a mechanism involving the surface of solid Pd metal particles and radical processes. The selectivity of the reactions can be controlled by the choice of catalyst and reaction conditions (base, solvent, temperature).

Observation of Aluminate Whiskers and Nanotubes in Dynamometer-Aged Three-Way Automotive Catalysts

Short nanotubes and whiskers of aluminates of different compositions, NixAl2O3+x, SrAl12O19 and (Nd,La)AlO3, with a noble metal particle attached to one end, are observed in dynamometer-aged automotive three-way catalysts (TWCs). The samples were from different production formulations for the US market that were aged for 120 h to simulate 100 000 miles of driving with a peak temperature of 1000-1050 °C in the middle of the catalyst monolith. NixAl2O3+x appears as nanotubes in both Pt/Rh- and Pd-based catalysts with NiO additions. The nanotubes suspend the precious metal catalyst particles in the gas stream. Solid whiskers of SrAl12O19 have been found in a Pd-based catalyst with SrO additions in both pores and within alumina agglomerates. (Nd,La)AlO3 whiskers have thus far been found only within alumina agglomerates in a Pd-based catalyst. The aspect ratio of the whiskers and nanotubes observed after aging is 4:1 or more. The solid noble metal particles are cuboctohedral in shape and average 90-150 nm in diameter, depending on the sample. Catalyst particle size controls the nanotube and whisker diameter, although some conical whiskers have also been observed.

Density gradients formed during compaction of bronze powders: the origins of part-to-part variation

The existence of density gradients in metal compacts has been recognized for over 50 years. However, previous attempts to quantify these gradients were limited by the difficulty of the technique involved and the ambiguity of the results. In this article, the utility of X-ray computer tomography (XRCT) in providing quantitative characterization of part-to-part variation in bronze compacts is demonstrated. Compaction behavior was also contrasted with previous work on porous spray-dried agglomerates. The density distribution patterns are qualitatively and quantitatively dissimilar. Different mechanisms appear to dominate the transmission of stress through assemblies of solid metal particles vs that of “softer,” spray-dried agglomerates. In addition, XRCT reveals that the structures found in the socalled “loose” powder (or “fill”) prior to compaction are both more complex than previously believed and capable of influencing final part-to-part variation.

Thermodynamic Analysis of Carbon Nucleation on a Metal Surface

AbstractA thermodynamic analysis of the carbon nucleation on the metal surface was performed. From the consideration of the catalytic mechanisms of carbon deposit formation on the metal surface we concluded that majority of these mechanisms include some common steps. The most important of them is the step of nucleation of carbon deposit on the metal surface. The master equation for the dependence of critical radius of the nucleus on reaction parameters was obtained. This equation demonstrates that a variation of the reaction parameters, such as the temperature, the nature of metal catalyst and the degree of supersaturation of the metal-carbon solution, can lead to the formation of different carbon deposits, such as filamentous carbon, multi-wall nanotubes (MWNT) or single-wall nanotubes (SWNT). The analysis performed allows us to conclude that for selective production of SWNT the nucleation must proceed at high temperature on the surface of liquid metal particles (Fe, Co, Ni). For solid metal particles (Mo) a high degree of supersaturation with carbon is also required.