Macro Particles Research Articles

Comparative in vitro genotoxicity study of ZnO nanoparticles, ZnO macroparticles and ZnCl2 to MDCK kidney cells: Size matters

In the present study, we evaluated the roles that ZnO particle size and Zn ion release have on cyto- and genotoxicity in vitro. The Madin-Darby canine kidney (MDCK) cells were treated with ZnO nanoparticles (NPs), ZnO macroparticles (MPs), and ZnCl2 as a source of free Zn ions. We first tested cytotoxicity to define sub-cytotoxic exposure concentrations and afterwards we performed alkaline comet and cytokinesis-block micronucleus assays. Additionally, the activities of both catalase (CAT) and glutathione S-transferase (GST) were evaluated in order to examine the potential impairment of cellular stress-defence capacity. The amount of dissolved Zn ions from ZnO NPs in the cell culture medium was evaluated by an optimized voltammetric method. The results showed that all the tested zinc compounds induced similar concentration-dependent cytotoxicity, but only ZnO NPs significantly elevated DNA and chromosomal damage, which was accompanied by a reduction of GST and CAT activity. Although Zn ion release from ZnO NPs in cell culture medium was significant, our results show that this reason alone cannot explain the ZnO genotoxicity seen in this experiment. We discuss that genotoxicity of ZnO NPs depends on the particle size, which determines the physical principles of their dissolution and cellular internalisation.

Influence of negative bias voltage on microstructure and property of Al-Ti-N films deposited by multi-arc ion plating

In this study, we systematically investigated the effects of negative bias voltage on the composition, deposition efficiency, microstructure, and mechanical properties of multi-arc ion plated (MAIP) AlTiN films. The films were deposited on high-speed steel substrates by MAIP at various negative bias voltages. The results indicated that the Al content [Al/(Al+Ti) ratio] and the deposition efficiency were significantly altered by the application of negative bias voltages. X-ray photoelectron spectroscopy analysis showed that the AlTiN films were composed of Ti–N and Al–N bonds. The macroparticles (MPs) on the film surface decreased with increasing negative bias voltage. We also discussed the different types of MPs found on the films and their influence on the process of determining the hardness of the films. The microhardness of the films depends on the negative bias voltages. The films deposited at −250V exhibited a maximum hardness of ~45GPa. The adhesion and frictional tests revealed that the film deposited at −150V demonstrated the highest cracking resistance, the best adhesion under a critical load of 78 N, highest adhesion strength, and the lowest and stablest coefficient of friction at 0.23.

Application of nanochitosan and chitosan particles for adsorption of Zn(II) ions pollutant from aqueous solution to protect environment

Existence of heavy metals like zinc within water source is considered as one of the most important environmental problems. Accumulating within alive tissues, zinc raises various diseases and disorders. Chitosan is a hydrophilic polymer which is raised from acetyl groups of chitin from alkaline solution: it is employed widely as a well- known adsorbent for removing heavy metal ions. Present study aimed at optimizing the production of chitosan nano size particles by method of calvo and compared the adsorption of Zn (II) ions by chitosan macro and nano size particles. Adsorption experiments were conducted in a batch system and the effects of temperature, pH, contact time and initial concentration of metal ions on productivity of adsorption of zinc ions have been considered. Performing analysis DLS revealed that mean size of nano chitosan particles is 19.84 nm. Optimal adsorption by chitosan and nano chitosan has been done in pH 7 and about of 5. Efficiencies of both adsorbent were increased by increasing contact time. Both adsorbent had maximum efficiency at the temperature of 25 °C. At the concentration of 10 mg/L of zinc metal ions, maximum effective removal of chitosan macro and nano size particles were 90.80 and 99.10 %, respectively. Maximum capacity of adsorption by chitosan macro and nano size particle was 196.07 and 370.37 mg/g, respectively. Adsorption kinetics followed a pseudo second order model. Nanochitosan compared to chitosan particles had higher removal efficiency for Zinc metal ions due to nano size of particles, larger adsorption surfaces and more functional groups.

Transport of a Macroparticle in Vacuum Arc Sheath

The transport of a single macroparticle (MP) in the region adjacent to the negatively biased substrate immersed into vacuum arc produced plasma is investigated theoretically. The effect of potential electron emission from the deposition substrate due to bombardment of multiply charged ions on the MP dynamics is studied. It is shown that the substrate biasing can significantly restrict the MP content in films deposited by a titanium vacuum arc. It is obtained that the MPs with a size less than $1.1~\mu \text{m}$ cannot reach the substrate biased up to −300 V.

Output power fluctuations due to different weights of macro particles used in particle-in-cell simulations of Cerenkov devices

The output power fluctuations caused by weights of macro particles used in particle-in-cell (PIC) simulations of a backward wave oscillator and a travelling wave tube are statistically analyzed. It is found that the velocities of electrons passed a specific slow-wave structure form a specific electron velocity distribution. The electron velocity distribution obtained in PIC simulation with a relative small weight of macro particles is considered as an initial distribution. By analyzing this initial distribution with a statistical method, the estimations of the output power fluctuations caused by different weights of macro particles are obtained. The statistical method is verified by comparing the estimations with the simulation results. The fluctuations become stronger with increasing weight of macro particles, which can also be determined reversely from estimations of the output power fluctuations. With the weights of macro particles optimized by the statistical method, the output power fluctuations in PIC simulations are relatively small and acceptable.

Newtorites in bar detectors of gravitational wave

The detection of particles with only gravitational interactions (Newtorites) in gravitational bar detectors was studied in 1984 by Bernard, De Rujula and Lautrup. The negative results of dark matter searches suggest to look to exotic possibilities like Newtorites. The limits obtained with the Nautilus bar detector will be presented and the possible improvements will be discussed. Since the gravitational coupling is very weak, the possible limits are very far from what is needed for dark matter, but for large masses are the best limits obtained on the Earth. An update of limits for MACRO particles will be given.

Effect of Axial Magnetic Field on the Microstructure and Mechanical Properties of CrN Films Deposited by Arc Ion Plating

CrN films were deposited on the high-speed-steel substrates by arc ion plating. The effect of an axial magnetic field on the microstructure and mechanical properties was investigated. The chemical composition, microstructure, surface morphology, surface roughness, hardness and film/substrate adhesion of the film were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope (SEM), surface morphology analyzer, Vickers microhardness test and scratch test. The results showed that the magnetic field puts much effect on the microstructure, chemical composition, hardness and film/substrate adhesion of the CrN films. The N content increases and Cr content decreases when the magnetic flux density increases from 0 to 30 mT. All of the CrN films were found to be sub-stoichiometric. With an increase in the magnetic flux density, the film structures change in such way: Cr2N → Cr2N + CrN → CrN + Cr2N → CrN. The SEM results showed that the number of macroparticles (MPs) on the film surface is significantly reduced when the magnetic flux density increases to 10 mT or higher. The surface roughness decreases with the magnetic field, which is attributed to the fewer MPs and sputtered craters on the film surface. The hardness value increases from 2074 HV0.025 at 0 mT (without magnetic field) and reaches a maximum value of 2509 HV0.025 at 10 mT. The further increase in the magnetic flux density leads to a decrease in the film hardness. The critical load of film/substrate adhesion shows a monotonous increase with the increase in magnetic flux density.

Tangential cathode magnetic field and substrate bias influence on copper vacuum arc macroparticle content decreasing

Abstract The paper presents the results of an experimental study of accumulation of copper macroparticles (MP) on a negatively biased substrate immersed in DC vacuum arc plasma. The influence of normal and tangential magnetic fields and high-frequency short-pulsed negative bias was investigated. The joint application of a tangential magnetic field and high frequency short-pulsed negative bias provides an effect of MP multifold suppression. With a tangential magnetic field strength of 175 Gs and repetitively pulsed bias (7 μs, 105 p.p.s., − 2 kV), total suppression efficiency is 250-fold after 6 min of ion-plasma treatment. For macroparticles with the diameter of less or > 1 μm, the efficiency is 3000-fold or 70-fold, respectively. In comparison with an axisymmetric vacuum-arc plasma source, the application of a steered arc ensures a 10-fold reduction in MP density on a substrate immersed in copper vacuum-arc plasma. The possibility of ion implantation using low-energy high-frequency short-pulse plasma immersion by implementing DC vacuum arc plasma is discussed.

Plasma distribution properties of vacuum ribbon-like cathodic arc plasma fliter and Raman studies of diamond-like carbon films perpared by it

As is well known, most filtered cathodic vacuum arc deposition technology adopts filters with various geometries to remove macro particles in the last three decades, but almost all of them have a circular cross-section. Compared with the traditional toroidal duct filters, the rectangular graphite cathodic arc source can have a larger area which can be an arc source of a ribbon-like cathodic arc plasma filter, which has a higher coating efficiency due to its larger area arc source and may be more suitable for a larger scale industrial production. Thus, the research on the plasma distribution properties within the vacuum ribbon-like cathodic arc plasma filter is of great significance. In this paper, a rectangular graphite cathodic arc source is used to produce the ribbon-like cathodic arc plasma. Within the filter, a 90 curved magnetic duct with a rectangular cross-section is used as the arc filter. The ribbon-like cathodic arc plasma is transmitted from cathode to the deposition area along the magnetic line produced by external coils. A Faraday cup ion energy analyzer and a Langmuir probe are used to characterize the distribution properties of the filtered plasma at 15 places on the exit plane. Ion energies and ion density at these positions are obtained. For the special retrograde motion of the cathode spot on the rectangular target surface, the ion energies and ion density data are not stable. In order to obtain representative values, the net results are the average value of 3 measurements. Diamond-like carbon (DLC) films are deposited by the ribbon-like cathodic arc plasma filter at the same exit plane and their structures are characterized by Raman shift. To compare the distinctness of the 15 Raman spectrums, each Raman spectrum of the DLC films is normalized and shown in a figure. Meanwhile, the thicknesses of all the DLC films are measured by step profiler. Results show that the ion energies are of Maxwell distributions at all the 15 places on the exit plane. The ion energies vary from 0 to 60 eV, most being in the range from 20 to 30 eV. The arc voltage is 30 eV, which exactly coincides with the ion energies. While Raman spectra of the DLC films show an obvious correspondence relationship with the ion energies as well as the ion density and the DLC film thickness. The nano-hardness of the DLC films lies in a range of 25-43 GPa. Although the ion energies, ion density, DLC film thickness and nano-hardness are slightly different at different locations, they are not significant. Owing to the relatively evenly distributed properties of the ribbon-like arc plasma this may open great opportunities for a large area filtered arc deposition technique.

PENGARUH KOMPOSISI DAN UKURAN SERBUK KULIT KERANG DARAH (ANADORA GRANOSA) TERHADAP KEKUATAN TARIK DAN KEKUATAN BENTUR DARI KOMPOSIT EPOKSI-PSSERBUK KULIT KERANG DARAH

This study was aimed to investigate the effect of filler content and particle size of cockle-shell powder in tensile strength and impact strength of epoxy-PS composite. Epoxy resin was used as matrix, polyaminoamide as hardener, cockle-shell powder as reinforcement, polystyrene as toughening agent and chloroform as solvent. Filler content was varied from 10-50% and the macro particle was varied from 50-260 mesh. The composite was prepared by using compression moulding, then tensile test and flexural test were done. The results showed that addition of cockle-shell powder improved both tensile strength and impact strength of the composite. Addition of 30% (wt) reinforcement with 200 mesh particle size had given maximum tensile strength of 5,50 MPa and maximum impact strength of 30044,3 J/m2.

Investigation on Behavior of Macro-Particles in TiN Film by Arc Ion Plating.

Macroparticle contamination deteriorates the qualities and performances of protective coatings by arc ion plating, resulting in a limitation in their applications. In this work, the effects of transverse magnetic field (TMF), pulsed bias, gas pressure, and substrate position on behavior of the macro-particles (MPs) in TiN films are quantitatively investigated. It is demonstrated that the key factor of the deposition process on the MPs behavior is magnetic field, which controls the movement of arc spot significantly. At relatively low magnetic field intensity, the MPs behavior is greatly influenced by the other three process parameters. The sensibilities of the three parameters on MPs behavior are decreased with the increasing magnetic field intensity. At high magnetic field intensity, the MPs distribution keeps almost the same even when the other parameters are varied.

Analysis of particle behaviors using a region-dependent method in a jetting fluidized bed

The analysis of the flow hydrodynamics in jetting fluidized beds is of considerable significance as it is widely applied in pharmaceutical, food, chemical, and petrochemical industries. In this study, an improved sub grid scale (SGS) model in the large eddy simulation (LES) method has been used based on a discrete hard sphere particle model in a jetting fluidized bed. The comparison of simulation results with experimental data shows that the improved SGS method, with a mutative Smagorinsky constant SGS approach, results in a better agreement than when using an invariant constant. Furthermore the particle behavior was analyzed by a region-dependent analysis method to obtain the spatial relationship of the particle behavior. The tendency of macro particle behavior is quite different from that at the micro level, which means that the fluctuation in the bed is not related to the overall particle movement. The particle macro characteristics can be affected by multiple factors such as the type of gas in the jet, the type of particles and the bubbles in the bed. The granular temperature distribution, which is related to the micro turbulent movement, presents strong anisotropic features, and specific rules of bubble and particle behavior are deduced. The region-dependent analysis method is also discussed in this work.

Physical mechanisms of macroparticles number density decreasing on a substrate immersed in vacuum arc plasma at negative high-frequency short-pulsed biasing

The objective of this investigation was to study the physical mechanisms of macroparticles (MPs) number density decreasing on a substrate immersed in a vacuum arc plasma. It was found that negative repetitively pulsed biasing of the substrate significantly reduced the MPs content on surface. Several different physical mechanisms for the MPs decreasing have been identified. It was established that up to 10% of the MPs are repelled by the sheath electric field. Reduction of MPs density by almost 20% is attributable to ion sputtering after 2 min of processing. It was found that enhanced ion sputtering, MPs evaporation on substrate surface, and even evaporation of MPs in a sheath, can take place depending on the cathode material and the irradiation parameters.

CFD development for macro particle simulations

Numerous industrial operations involve fluid-particle systems, in which both phases display very complex behaviour. Some examples include fluidisation technology in catalytic reactors, pneumatic transportation of grain or powder materials, carbon nanotube alignment in the nano-devices and circuit integration and so on. In this paper, a macro particle method is developed to model the fluid-particle flows. The macro particle is formed by a collection of micro-sized particles so that the number of macro particles to be tracked is much less than the number of smaller particles. Unlike the calculations of instantaneous point variables of fluid phase with moving discrete boundaries of the smaller particles with direct numerical simulation, the boundary of each macro particle is just dealt with the blocked-off approach. On the other hand, the flow fields based on the present method is solved by original Navier–Stokes, rather than the modified ones based on the locally averaged theorem. The flow fields are solved on the length scale of computational cells, while the resolutions of solid particles are the size of macro particle, which is determined as needed in specific applications. The macro particle method is validated by several selected cases, which demonstrate that the macro particle method could accurately resolve fluid-particle systems in an efficient, robust and flexible fashion.

Reprint of: Physical mechanisms of macroparticles number density decreasing on a substrate immersed in vacuum arc plasma at negative high-frequency short-pulsed biasing

Abstract The objective of this investigation was to study the physical mechanisms of macroparticles (MPs) number density decreasing on a substrate immersed in a vacuum arc plasma. It was found that negative repetitively pulsed biasing of the substrate significantly reduced the MPs content on surface. Several different physical mechanisms for the MPs decreasing have been identified. It was established that up to 10% of the MPs are repelled by the sheath electric field. Reduction of MPs density by almost 20% is attributable to ion sputtering after 2 min of processing. It was found that enhanced ion sputtering, MPs evaporation on substrate surface, and even evaporation of MPs in a sheath, can take place depending on the cathode material and the irradiation parameters.

Titanium macroparticles density decreasing on the sample, immersed in plasma, at repetitively pulsed biasing

Abstract We have studied the features of the Ti macroparticles (MPs) accumulation on a substrate immersed in a DC vacuum arc plasma with a high frequency short pulse negative bias. The influence of several factors including processing time, the parameters of bias potential, and substrate characteristics was defined. It was found that the MP accumulation on a repetitively biased substrate was uneven over time. A deposition of MPs to substrate were significantly decreased after 1 min of processing at bias parameters f = 10 5 p.p.s., φ b = −2 kV and τ = 7 μs. It was experimentally shown that DC vacuum arc plasma without pre-filtering of MPs can be used for high frequency short pulse plasma immersion metal ion implantation.

Investigation of the possibility of unfiltered aluminium vacuum arc plasma application for high-frequency short-pulse plasma immersion ion implantation

Abstract This paper is devoted to the study of the possibilities of unfiltered aluminium vacuum arc plasma application for intermetallic layers formation using the high-frequency short-pulse plasma immersion ion implantation method. It is shown experimentally that the number density of aluminium macroparticles (MPs) on the substrate surface is decreased dramatically by 3 orders of magnitude when the ion-plasma substrate treatment time is increased from 30 s to 3 min at the bias potential −2 kV. It was shown that at high intensity low energy plasma immersion implantation of Al ions in Ti and Ni substrates a deep layer (several μm) of aluminium dopants with concentration in the range of (12–35) at% can be formed.

Application of high frequency short-pulsed negative biasing for the decreasing of macroparticle content on substrate immersed in vacuum arc plasma

Abstract The result of experimental study of macroparticles (MPs) accumulation on negatively biased substrate immersed in DC vacuum arc titanium plasma are presented. It was found that the negative high frequency short pulse biasing of substrate with respect to the adjacent plasma significantly reduces the MPs content on substrate surface. It was shown that the decreasing of MPs surface number density on a negatively biased substrate is determined by the pulse duration, pulse amplitude and processing time. The surface density of MPs with the size

AN EXPERIMENTAL STUDY ON THE HEAT ENHANCEMENT AND THE BIO-HEAT TRANSFER USING GOLD MACRO ROD AND ULTRASOUND: A POTENTIAL ALTERNATIVE TO KILL CANCER CELLS

We have previously proposed a method of treating so lid tumors with a combination of gold macro-rods irradiated with ultrasound. Macro particle sized ro ds offer a greater circumferential treatment area o ver nanoparticle options. Experimental studies were con ducted to investigate the heat enhancement and the bio-heat transfer to breast chicken using gold macr o rod and ultrasound. An ultrasound, other than a focused ultrasound, may produce heat enough to coo k a chicken breast up to about 1 cm diameter if a single gold rod is placed on the superficial tissue . Simulations and experimental results will provide the means to evaluate the treatment, to better desi gn a patient-specific therapy to achieve maximum destruction of tumor and injury minimization of hea lthy tissue by controlling size, shape and location of gold seeds and ultrasound parameters.

Sn thin film deposition using a vacuum arc plasma source with a refractory anode

A hot refractory anode vacuum arc (HRAVA) starts as a cathodic arc, which heats and deposits cathodic material on the anode. When the anode is hot, all the deposited cathode material is re-evaporated from the anode, forming a radially expanding plasma with reduced macroparticle (MP) contamination. This paper reports on the deposition of Sn films using this radially expanding arc plasma. The HRAVA current was I=60–175 A and the duration was up to 180s. Two electrode pairs were used. (1) A water-cooled Sn cathode with a diameter of D=60mm was used with a W anode having a thickness of d=10mm, diameter D=60mm and separated from the cathode by gaps of h=10 and 15mm. (2) A water-cooled Sn cathode with D=30mm was used with either of two graphite anodes, with d=9 or 15mm, D=32mm and h=10mm. The cathodes were recessed behind a boron nitride shield. A mechanical shutter controlled the deposition onset and exposure duration (15s) on glass substrates. The distance from the arc axis to the substrate (L) was 80, 110, or 125mm. Film thickness was measured with a profilometer. MPs on the coating surface were examined by optical microscopy.With D=60mm cathodes, L=125mm, and I=175 A, the deposition rate Vdep monotonically increased with time from 0.5 initially to 3.0μm/min after 120s. With the D=30mm cathode, L=110mm, I=175 A and d=9mm, Vdep increased with time to a peak of 0.84μm/min at 20s, and then decreased to a steady state of 0.69μm/min at 45s. The peak was due to re-evaporation from the hot anode of cathodic material, including MPs, which were deposited initially on the cold anode. The MP flux density decreased with I from 2.5 at I=80 A to about 1mm−2s−1 at I=175 A in case of D=30mm, L=110mm, d=9mm.