Types Of Metallic Particles Research Articles

Effect of the solvent nature on the biological activity of gold-containing systems

Gold nanoparticles were prepared by metal-vapor synthesis using isopropanol, acetone or toluene as dispersion media. The electronic states of the metal and the nature of the sorbed layer on the surface of the nanoparticles were studied. The analysis of photoelectron spectra of the obtained nanoparticles showed that regardless of the synthesis conditions, gold in all samples is in the Au0, Au+ and Au3+ states and a carbon-containing shell is present on all types of metal particles. The study of anticancer activity of nanoparticles in vitro with human cell lines showed the dependence of biological activity on their interaction time of samples obtained in toluene dispersion medium. The metabolic activity of gold nanoparticles obtained in isopropanol or acetone medium decreased in the earliest period of testing.

Thermal Performance of Liquid Metal Pastes Containing low Content of Metal Particles for Thermal Interface Materials in IC Module Electronics

In recent years, considerable attention has been paid to gallium-based liquid metal alloys in their use as thermal interface materials for GPU, APU, and HPC in PC and super computers due to its considerably high thermal conductivity and low contact thermal resistance. Gallium-based Liquid metal paste containing low content of metal particles (LMP-MPs) to enhance thermal performance and controllable BLT of the prepared liquid metal composites for thermal interface materials (TIMs) prepared by in-situ introducing gallium oxide into the liquid metal alloys will be reported in our recent research. In this paper, we will report effect of the composition, particle size/types, and bond line thickness on thermal properties of the LMP-MPs. Thermal properties of the LMP-MPs were measured at 50o C using a thermal tester, TIMA5, based on ASTM-D5470 test methodology. It was found in the present study that the composition and types of metal particles, and BLT have significant influence on thermal conductivity, and the conductivity values increase with an increase of the content of metal particles and BLT. However, thermal resistance varies with the change of composition and BLT of LMP-MPs. Scanning electron microscope (SEM) was used to characterize microstructure of LMP-MPs with different metal particles and sizes. Micrographic morphology of the LMPs-MPs shows continuous frame structure observed with SEM, which could keep liquid metals from spreading out and stabilize the phase. We eventually found the LMP-MPs have the better wetting and adhesion properties on bare Cu, glass and bare Si surface than liquid metal alloys that endows good printability to the LMP-MPs. Continuous monitoring of thermal resistance of LMP-MPs at 45o C and 89o C using a house-made thermal tester shows stable thermal resistance after a few months, which indicates LMP-MPs have excellent thermal reliability in ambient atmosphere.

Impact of gold and silver nanoparticles in highly viscous flows with different body forces

ABSTRACT The present investigation is relevant to the multiphase flow of non-Newtonian fluid passing through the steep channel. Third-grade fluid is taken as the base liquid, while two different types of metallic particles are considered to form nano-suspensions. Two different plane flows are devised based on the development of rigid walls of the inclined channels. A comprehensive apprehension regarding the nonlinear flow dynamics is carried out with the help of a regular perturbation method, which is effectively less time-consuming and more analogous to analytic. Moreover, a comparative analysis depicts complete harmony with the existing literature. In addition, the current study reduces back to the customary nanofluid problem for the limiting case.

Lightning Impulse Breakdown Voltage RBDPO with the Presence of Metallic Particles Under a Uniform Electric Field

The performance of liquid insulation in power transformer is vulnerable to particles, especially the metallic particles. This paper presents the experimental study on the effect of metallic particles on the palm oil (PO) as dielectric insulating fluid under lightning impulse breakdown voltage. The type of PO used in this study is refined, bleached and deodorized Palm Oil (RBDPO) Olein. Two different types of metallic particles (copper and iron) with different concentrations (clean, low, medium, and high) were studied. The lightning impulse test has been carried out according to IEC 60897 standard and under the influence of a uniform electric field. For the comparative purpose, similar test has been carried out with mineral oil (MO). The presence of metallic particles reduces the average lightning impulse breakdown voltage of MO and PO but shows less significant effect to MO. This is because the streamers in the PO propagate faster and further than in the MO at the same voltage level. Hence, causing the breakdown voltage of PO lower than MO. Under negative lightning impulse, the breakdown voltage of MO is slightly higher than RBDPO. From the study, the increment of the number of particle level contamination will reduce the lightning impulse breakdown voltages of the PO.

Molecular dynamics simulations on formation of CO2 hydrate in the presence of metal particles

Understanding and controlling the growth of CO2 hydrates is critical for a variety of industrial applications, such as sequestration of greenhouse gases. Due to the excellent physical and chemical properties, metal nanoclusters are widely used as additives in hydrate experiments. However, little is known about the molecular mechanism of this process. In this study, molecular dynamics (MD) simulation was performed at 260 K and 30 MPa by adding different types of metal particles (Cu, Fe and Ag) and different mass fractions (0.2 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt% and 1.3 wt%) to study the growth kinetics of the CO2 hydrate system containing pre-placed hydrate crystal cells. Simulation results showed that the presence of these metal particles has a mixed effect on the growth kinetics, and the extent of the effect seems to varies with different additives and also with the concentration of the metal particles used. It was observed that Cu particles had the most obvious promoting effect on hydrate growth. When the mass fraction of Cu particles was between 0.2 wt% and 1.0 wt%, the rate of hydrate formation increased, especially at the mass fraction of 1.0 wt%. The growth rate of CO2 hydrate was almost 50% higher than that of pure water system at this concentration. In addition, Fe particles had a medium effect on promoting CO2 hydrate growth. Ag particles had no obvious effect on CO2 hydrate growth. Results show that the addition of metal particles with high specific surface areas greatly increases the mass and heat transfer among the gas, liquid and hydrate phases, which is conducive to the growth of CO2 hydrate.

Polyphenylene as an Active Support for Ru-Catalyzed Hydrogenolysis of 5-Hydroxymethylfurfural.

Selective transformation of biomass feedstocks to platform molecules is a key pursuit for sustainable chemical production. Compared to petrochemical processes, biomass transformation requires the defunctionalization of highly polar molecules at relatively low temperatures. As a result, catalysts based on functional organic polymers may play a prominent role. Targeting the hydrogenolysis of the platform chemical 5-hydroxymethylfurfural (5-HMF), here, we design a polyphenylene (PPhen) framework with purely sp2-hybridized carbons that can isolate 5-HMF via π-π stacking, preventing hemiacetal and humin formation. With good swellability, the PPhen framework here has successfully supported and dispersed seven types of metal particles via a newly developed swelling-impregnation method, including Ru, Pt, Au, Fe, Co, Ni, and Cu. Ru/PPhen is studied for 5-HMF hydrogenolysis, achieving a 92% yield of 2,5-dimethylfuran (DMF) under mild conditions, outperforming the state-of-the-art catalysts reported in the literature. In addition, PPhen helps perform a solventless reaction, achieving direct 5-HMF to DMF conversion in the absence of any liquid solvent or reagent. This approach in designing support-reactant/solvent/metal interactions will play an important role in surface catalysis.

Removal of Tetrachloroethene in Water with Nano Pd/Fe Bimetal Immobilized in Alginate Beads

In this study, nZVI, nPd/Fe and nPd/Fe-B particles were synthesized and used to remove PCE in solution to investigate the effects of several parameters such as the types of metal particles and their mass concentration. From the elemental mapping images of energy dispersive spectrometer (EDS), amorphous Fe and Pd were tightly integrated into the alginate matrix, which cannot be solely exfoliated from the whole composites. The results showed that the removal efficiency (r) and observed reaction rate constants (kobs) was the highest for nPd/Fe, followed by nPd/Fe-B and nZVI particles. Moreover, the larger the reductant dosage, the higher the r of PCE for nZVI, nPd/Fe, and nPd/Fe-B particles is. The pH in solution quickly raised from about 5-6 to 8-9 at the beginning of tests and then maintained at around 8-9 to the end of tests. The ORP in solutions descended to reductive state immediately at the beginning of tests and kept in the range between -730 and -770 mV to the end of tests indicating that the system maintained in a stable reductive state.

A non-sampling mixing index for multicomponent mixtures

Uniform mixing is crucial for different types of molecules, powders, and materials in several chemical, mineral, cement, and drug companies. However, there is no effective index to evaluate the uniformity of mixing of multiple components. This study proposes a non-sampling mixing index (SMI) that is applicable to both multiple mixtures with more than two components as well as binary mixtures. The proposed mixing index estimates a mixing state by using all subdomain mixing information for all particles without requiring sampling. In the study, the index was used to predict the mixing of different types of metallic particles in a screw blender. A discrete element based numerical technique was used to determine the transient location of particles in a screw blender at different rotation rates. The effectiveness of the SMI was demonstrated by comparing it with other representative mixing indices. The effectiveness was elucidated using a model of a binary system in which two groups of particles were mixed from 0% (no mixing) to 100% (perfect mixing). The SMI indicated a linear correlation from 0 to near 1 between test mixing conditions and the mixing indices in contrast to other conventional methods that over-predicted the mixing conditions. With respect to the DEM simulation, the SMI displayed values between SMI=0 at the initial stage and SMI=0.9–0.94 at a fully random mixed condition for the rpm ranges corresponding to 15, 30, 45 and 60. The results also indicated that the SMI value of zero occurred at the boundaries with the exception of the bottom and that a considerably lower mixing index was obtained at boundaries as opposed to inner subdomains with respect to the fully random mixed condition (t=20s and rpm=30).

Induced polarization response of porous media with metallic particles — Part 1: A theory for disseminated semiconductors

A model is proposed regarding the polarization of dispersed metallic conductors (e.g., pyrite and magnetite) in porous media free of redox-active ionic species in the pore water. We studied two cases corresponding to having a background material with or without chargeability. The model was based on the polarization mechanism of a single particle using well-established bounds for the reflection coefficient entering the definition of the dipole moment of the metallic grains. We used the Maxwell-Clausius-Mossotti mixing equation to obtain the complex conductivity of the mixture of dispersed metallic particles in the background porous material composed of the pore water and the insulating grains coated by an electric double-layer. This equation can be generalized to a mixture of various types of metallic particles (with their own properties) dispersed in the background porous material. Our model led to a very simple linear relationship between the chargeability and the volume content of metallic particles in the material. In addition, the chargeability depended weakly only on the shape of the spheroidal metallic particles as long as their orientation was random. The relaxation time defined from the phase peak frequency related to the diffusion coefficient of the [Formula: see text]- and [Formula: see text]-charge carriers in the metallic particles. This diffusion coefficient was consistent with the mobility of the charge carriers derived from theoretical considerations or electric conductivity measurements. In the presence of a polarizable background (e.g., a clayey matrix), we found that the total chargeability of the material can be determined from the chargeability of the metallic particles and the chargeability of the background material.

Modelling and measuring the thermal conductivity of multi-metallic Zn/Cu nanofluid

A metallic nanofluid is a suspension of metallic nanoparticles in a base fluid. Multi-metallic nanoparticles are a combination of two or more types of metallic particles. Such multi-metallic nanoparticles were suspended in water using an ultrasonic vibrator for different total volume fractions and different ratios of metallic/metallic nanoparticles. A transient hot wire setup was built to measure the thermal conductivity of the nanofluid at different temperatures. The experimental results were in good agreement with the results in the literature. Then, the experimental results were used as input data for an adaptive neural fuzzy inference system (ANFIS) to predict the thermal conductivity of the multi-metallic nanofluid. The maximum deviation between the ANFIS results and experimental measurements was 1 %. The predicted results and the experimental data were compared with other models. The ANFIS model was found to have good ability to predict the thermal conductivity of the multi-metallic nanofluid over the range of the experimental results.

Large-Scale Nanorods Nanomanufacturing by Electric-Field-Directed Assembly for Nanoscale Device Applications

A fast and highly scalable room-temperature nanomanufacturing process for fabricating metallic nanorods from nanoparticles for applications such as interconnects and sensors is presented. Metallic nanoparticles are precisely assembled into prefabricated vias by applying a controlled dynamic electric field between the electrodes at the bottom of the vias and a counter electrode placed far away from the vias. The nanoscale vias are fabricated employing conventional electron-beam nanolithography. The dimension of the fabricated nanorods is controlled by the size of the vias and assembly parameters such as the amplitude and frequency of the applied electric field. The mechanism of the assembly process is discussed by examining the effect of the applied voltages on the assembly process to provide a fundamental understanding for scaling down to nanoscale dimensions. This room-temperature aqueous fabrication process is environmentally friendly and can be used to make nanorods using different types of metallic particles.

Nonplasmonic Metal Particles as Excitation Energy Transfer Acceptors: an Unexpected Efficiency Revealed by Quantum Mechanics

We present a time-dependent density functional theory investigation of the excitation energy transfer (EET) between a typical chromophore (perylene diimide) and a small metal cluster (Au20). Two different physical descriptions are tested for the metal: the real (nonplasmonic) cluster and a hypothetical nanoparticle characterized by a bulk gold dielectric response (which thus sustains surface plasmons). By comparing the results obtained for the same EET process with the two types of metal particles, we show that, surprisingly, nonplasmonic small metal clusters can be as intrinsically effective as plasmonic particles in EET, a finding that is also relevant for applications in several field ranging from analytical chemistry to nanoscience.

Three-dimensional trapping of Mie metallic particles by the use of obstructed laser beams

In this article, we propose a method for three-dimensional optical trapping of metallic Mie particles using an obstructed laser beam. It is found from the ray-optics model that Mie gold, silver, and copper particles can be trapped against gravity in the focal region of a high numerical-aperture objective illuminated by a centrally obstructed Gaussian (TEM00-mode) beam. The axial trapping force of the three types of metallic particles is maximized in the near-infrared wavelength region. The maximum axial trapping efficiency increases with the size of the center obstruction and the aperture angle of an objective. Axial trapping force on Mie metallic particles is enhanced by a factor of two if an obstructed doughnut (TEM01*-mode) beam is employed. The experimental condition for achieving three-dimensional trapping is also discussed.

KrF excimer laser dry and steam cleaning of silicon surfaces with metallic particulate contaminants

KrF excimer laser-assisted dry and steam cleaning of single-crystal silicon wafers contaminated with three different types of metallic particles was studied. The laser fluence used was 0.3 J/cm2. In the dry process, for samples cleaned with 100 laser pulses the cleaning efficiency was 91, 71 and 59% for Au, Cu and W particles, respectively, whilst in steam cleaning the efficiency is about 100% after 5 laser pulses, independently of the type of contaminant. The effects of laser irradiation on the Si surface are investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Laser processing at 0.3 J/cm2 does not deteriorate the Si-wafer surface, either in dry or steam cleaning. However, the measured XPS intensity coming from the metallic component is greater on the cleaned surfaces than in the initial condition. Quantification of the XPS results, assuming a stratified overlayer model for the detected species and accounting for the presence of the metallic particles on the surface, showed that the obtained results can be explained by the formation of a fractional metallic monolayer on the cleaned surfaces, due to partial vaporisation of small particles initially present on the sample surface. This contamination of the substrate could be considered excessive for some applications and it shows that the process requires careful optimisation for the required efficiency to be achieved without degradation of the substrate.

Fermi level equilibration between colloidal lead and silver particles in aqueous solution

Colloidal solutions of lead and silver were mixed under the exclusion of air. The equilibration of the Fermi levels in the two different types of metal particles took place over a few days at room temperature. The equilibration took place by the transfer of lead atoms from lead to silver particles until the latter carried a lead mantle of one to two monolayers. This could be concluded from the observed changes in the optical spectrum of the silver particles. The results are discussed in terms of two mechanisms: (1) Pb atom transfer following heterocoagulation of the lead and silver particles and (2) electron transfer during Brownian encounters, followed by Pb{sup 2+} desorption from the lead particles and subsequent Pb{sup 2+} reductor on the silver particles carrying the transferred electrons. Traces of methylviologen, MV{sup 2+}, in the solution drastically increase the rate of equilibration; this is explained by a relay mechanism in which electrons in the lead particles are first picked up by MV{sup 2+} and are then transferred from MV{sup +} to the silver particles. 2 refs., 4 figs.

The formation of nickel-copper alloys in zeolite Y as studied by the ferromagnetic resonance method

Samples of zeolite Y with part of their Na + ions exchanged by Ni 2+ and Cu 2+ ions were dried and reduced by H 2. The resulting samples were investigated by the ferromagnetic resonance method, and by measuring their catalytic properties in n-hexane conversion. The results led to the conclusion that during reduction performed above 690 K part of the Ni 2+ and Cu 2+ ions form largesized metal particles at the outer surface of the zeolite crystals and that these are responsible for the magnetic behavior and the catalytic activity. In almost all bimetallic samples two types of metal particles are formed, namely, ferromagnetic particles with a high Ni content and paramagnetic particles with a high Cu content. The bulk composition of the ferromagnetic alloy particles was found to be nearly constant but the surface composition proved very sensitive to the reduction temperature. The formation of the NiCu alloy was found to influence the catalytic properties for n-hexane conversion. Compared with NiY, NiCuY was less active but more selective for the isomerization because of suppressing the hydrogenolysis reaction.