Macro Particles Research Articles

Modelling and Simulation of Mechanical Wear of Carburized Cutting Tool

The sporadic increase in demand for higher machining efficiency brought about various researches aimed at improving the condition of cutting tools against wear, which may lead to poor dimensional accuracy, damages to the tool and work piece, and also degrades the surface condition of the work piece. This study involved modeling and simulation of carburized cutting tool developed from recycled steel with palm kernel shell as carbon additive.Performance evaluation through experimental test and validation with model by using MATLAB to obtain optimal cutting parameters for the best performance was considered. The modelling involved transfer of macro particles consisting process of abrasion and adhesion commonly known as mechanical wear. Under this condition of mechanical wear, “deterministic” model was set up to handle abraso-adhesion processes but having some difficulties and therefore resulted to modelling the processes using stochastic process. This approach is used in creating equation for flank wear growth. Wear land and rates which were simulated with graphical representation also confirmed better performances over the imported control sample.

Diagnosis of the power frequency vacuum arc shape based on 2D-PIV

Abstract Vacuumcircuit breaker (VCB) is one of the important elements in the power grid that can control and protect the system. The diagnosis of the vacuum arc images in VCBs is helpful to the study on their breaking performance. But up to now, there are few reports on the macro-particle motion trajectories in the arc. As the macro-particles in the arc are flowing, the particle image velocimetry (PIV) can be grafted into the vacuum arc image processing. In this paper, the power frequency vacuum arc (peak is 6.9kA) was used as the treatment object, geometric characteristics of the vacuum arc shape using digital image processing technology were extracted, and the two dimensional motion trajectory and velocity distribution of the arc macro particles in different arc combustion stages were obtained based on 2D-PIV technology. Three stages were analyzed. In the rapid diffusion stage, the collision of the macro-particles is very intense in the anode region, and they spray along the anode surface. In the stable combustion stage, the velocity of the particles near the anode is small, and there is a smaller shrink. And finally in the extinction stage, their motion trajectories are in a state of rotation, near the anode and cathode are in a state of contraction.

Photo-Stabilisation and UV Blocking Efficacy of Coated Macro and Nano-Rutile Titanium Dioxide Particles in Paints and Coatings

Surface treated macro and nanoparticle TiO2 samples have been prepared, characterised and their efficiency as UV blockers evaluated in clear coatings and paints. The particle size of the ‘base’ TiO2 has been optimised to block UV radiation and the surface treatment developed to deactivate the photocatalytic activity of the surface of the TiO2 particles. The resultant UV blockers have been evaluated in both solvent and water-based clear coatings. Nanoparticle TiO2 has been prepared from ‘seed’ and the particle size was controlled by calcination. It was found that the choice of particle size is a compromise between UVA absorption, UVB absorption, visible transmission and photoactivity. It has been demonstrated that TiO2 with a crystallite size of 25 nm yields a product with the optimum properties. A range of dispersants was successfully used to disperse and mill the TiO2. Both organic and inorganic dispersants were used; 2-amino-2-methyl-1-propanol and 1-amino-2-propanol (MIPA) and P2O5 and Na2SiO3 respectively. The surface of the nano-TiO2 was coated with mixed oxides of silicon, aluminium, zirconium and phosphorous. Addition of the resultant coated nano-rutiles to an Isocyanate Acrylic clear coating prolonged the lifetime of that coating compared to the blank. Generally, a surface treatment based on SiO2, Al2O3 and P2O5 was more successful than one based on ZrO2, Al2O3 and P2O5. Higher addition levels of the surface treatment were beneficial for protecting the polymeric coating. The UV blocker products were also evaluated in a water-based acrylic, first a water-based dispersion of the UV blocker was prepared before addition to the acrylic. The dispersions and resultant acrylic thin films were evaluated using UV/Vis spectroscopy and durability assessed. The ratio of absorbance at 300:500 nm for the water-based dispersion was shown to be a good predictor of both the transparency of the resultant acrylic thin film and the durability of that film, in terms of weight loss. Macro grade titanium dioxide pigments were also prepared and coated with treatments of silica, alumina and siloxane and their photo-stabilising activity in alkyd paint film assessed and found to be directly related to the electron–hole pair mobility and trapping as determined by micro-wave spectroscopy.

Synthesis and Characterization of Nano Bioglass for the Application of Bone Tissue Engineering

In this paper, we are addressing the development of new composition (60%SiO2-30%CaO-10%P2O5) of biodegradable and biocompatible bioglass (nBG) nanoparticles. The bioglass nanoparticles have been fabricated by sol-gel method. To get functionalized bioglass nanoparticles, they were treated with lysozyme (1 mg/mL) for 48 h. Morphology of nanoparticles, such as structure, particle size, and surface topography were studied by TEM. Bioglass nanoparticles generate hydroxyapatite layer when nanoparticles treated with simulated body fluid (SBF) for 7 days. The presence of bioglass and hydroxyapatite phases confirmed by XRD. TEM images revealed irregular shaped with slightly agglomeration of nanoparticles in nanometer range (200 to 500 nm). The in-vitro biodegradation of nanoparticles was confirmed by weight loss in the presence of SBF. The cytotoxicity effects and cell proliferation of respective sample were investigated through MTT assay. BET results revealed average surface area (10.4 m2/g) of nanoparticles. The nano range of particles will provide better surface to volume ratio over micro or macro particles which makes them more effective so they are often able to react rapidly.

Modeling of interaction between arc and macroparticle in vacuum trigatron

This work investigates the interaction between high current vacuum arc (HCVA) and the macroparticle (MP) generated from the cathode spots in the small-size vacuum trigatron. Magnetohydrodynamic (MHD) model is used to describe the arc column. MPs are added into the MHD model, which are described by discrete phase model. The control equations of MPs include charging equation, motion equation, and heat transfer equation, in which the evaporation of MPs is also considered. Based on the above model, the effects of the diameter and initial velocity of MPs on the characteristics of them are studied. Simulation results show that MPs leave the interelectrode gap with a deflection angle larger than the initial angle under the influence of plasma. The motion of MPs is similar to that of projectiles. MPs with smaller diameter or slower velocity are influenced by the arc plasma more significantly. MPs can act as a source of the plasma, but these influences are not obvious in HCVA. What may be more harmful to the trigatron is the charging process of MPs during post-arc process.

The corrosion protection ability of TiAlN coatings produced with CA-PVD under superimposed pulse bias

In this study we have investigated the contribution of superimposing high voltage pulse on DC bias on the corrosion protection ability of TiAlN coatings deposited with cathodic arc physical vapor deposition (CA-PVD). Superimposing high voltage on DC bias resulted in the decrease of the number of attached macroparticles (MP) and also densified the columnar structure. These differences significantly improved the corrosion protection ability of the coatings that were determined by electrochemical impedance spectroscopy (EIS) in 0.1 N HCl solutions. An approximately 6 fold increase in the polarization resistance for the samples deposited by using −1000 V superimposed pulse voltage on 40 V DC bias when compared to the ones deposited only by DC bias. For further elaborating these results, the distribution, size and morphology of the corrosion sites were determined with ferroxyl test, scanning electron microscopy (SEM) and 3D optical profilometry. Results of the ferroxyl tests indicated a dramatic decrease of corrosion sites by superimposing −1000 V on DC bias. Closer investigation of these sites showed that corrosion of the substrate is first initiated at the bottom of the defects extending through the coating and then expanded below the coating. The depths and diameters of the corroding sites, revealed by removing their caps with ultrasonication were substantially lower for the samples produced with superimposed bias. Results of the study indicated the necessity of combining electrochemical corrosion test results with the morphology and distribution of corrosion sites for a proper understanding of the corrosion protection ability of hard coatings.

The application of the large particles method of numerical modeling of the process of carbonic nanostructures synthesis in plasma

The article deals with the numerical solution of the mathematical model of the particles motion and interaction in multicomponent plasma by the example of electric arc synthesis of carbon nanostructures. The high order of the particles and the number of their interactions requires a significant input of machine resources and time for calculations. Application of the large particles method makes it possible to reduce the amount of computation and the requirements for hardware resources without affecting the accuracy of numerical calculations. The use of technology of GPGPU parallel computing using the Nvidia CUDA technology allows organizing all General purpose computation on the basis of the graphical processor graphics card. The comparative analysis of different approaches to parallelization of computations to speed up calculations with the choice of the algorithm in which to calculate the accuracy of the solution shared memory is used. Numerical study of the influence of particles density in the macro particle on the motion parameters and the total number of particle collisions in the plasma for different modes of synthesis has been carried out. The rational range of the coherence coefficient of particle in the macro particle is computed.

The role of superimposing pulse bias voltage on DC bias on the macroparticle attachment and structure of TiAlN coatings produced with CA-PVD

Our attempts for cathodic arc physical vapor deposition (CA-PVD) of TiAlN coatings with high voltage pulse bias in order to tune their structural properties were not successful. Resulted coatings had an unacceptable rough surface with a large number of macroparticles (MPs). For solving this problem and benefiting from high voltage pulse bias-induced effects on the coatings structure we superimposed high voltage pulse on DC bias. For this purpose, Ti0.5Al0.5N coatings were deposited on HSS substrates using a DC bias voltage of 40 V and superimposed pulse bias voltages of 500, 1000 and 1500 V with a duty cycle of 14%. Structure, chemistry, morphology and mechanical properties of the coatings were determined in order to investigate the differences induced by the application of superimposed bias. Additionally, corrosion protection properties of the coatings were also investigated. According to the obtained results, this mode of application not only produced coatings with a denser and finer columnar structure but also resulted in a substantial reduction in the number of MPs. A decrease (maximum 3 at.%) in the Al content of the coatings was observed with increasing pulse bias magnitude when compared to their DC bias deposited counterpart. Substrate temperature also increased with increasing pulse bias magnitude, however, it did not increase above 460 °C. As a result of the decrease of MP attachment and denser structure of the coatings the corrosion protection properties of the coatings substantially improved. This effect became more pronounced with increasing superimposed voltage magnitude.

Impact of removal of micro and nano sized particles on the phenolic content and antioxidant activity: Study on aqueous and methanolic leaves extracts of Phlomis crinita

Due to the excellent ethnopharmacological properties of Phlomis crinita, it is widely used as natural remedy in the Mediterranean region. This study inspects the effect of micro and nano sized particles, contained in aqueous and hydromethanolic leaves extracts, on the antioxidant activities, phenolic and flavonoid contents. The macro particles were removed from extracts via filtration whereas the micro and nano particles were isolated through speed centrifugation. Antioxidant activities were screened in vitro by β-carotene-linoleic acid and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assays.The results showed that removal of microparticles don’t affect the properties of extracts, whereas the nanoparticles contributed much in the content of total phenolics and antioxidant potencies of both extracts. The highest impact of nanoparticles removal on antioxidant activity was observed in methanolic extract losing 72% of β-carotene bleaching inhibition and four-doubled its IC50 index. These findings suggest that nano sized particles are the nature’s store of bioactive constituents in herbal extracts, therefore their retention is highly recommended to preserve the totality of antioxidant capacities.

Synergetic effect for improved deposition of titanium nitride films

It is known that cathodic arc deposition (CAD) has been widely used in industry for high quality thin film coatings. An extremely high current density (~1012 A/m2) was created to evaporate and ionize the target material rapidly. However, the CAD also produces macroparticles or droplets along with the deposition process leading to the degradation of the film properties. Magnetic filters with different designs were therefore adopted to reduce the macro particles or droplets. However, the macroparticles still cannot be fully eliminated. Lately, a newly developed PVD process known as high power impulse magnetron sputtering (HiPIMS) was found to have the capability of yielding highly ionized flux of both gas and sputtered materials by applying a high power in short pulses to the target. High plasma density in the order of 1017 to 1019 m−3, which is three orders of magnitude higher than that of the conventional dc magnetron sputter (dcMS), can therefore be achieved from the large fluxes of energetic ions in a HiPIMS process. As a result, a smoother and denser thin film with better adhesion to the substrate can be obtained, leading to enhanced mechanical, electrical, and optical properties. However, it was also found the deposition rate of the HiPIMS process was much slower than that of the conventional dcMS and CAD process. Therefore, a hybridized deposition system combining CAD and HiPIMS was studied in this paper. Titanium nitride (TiN) films were deposited to investigate their microstructures, physical, chemical, and mechanical properties. The macroparticles were reduced in the HiPIMS system while thin films with enhanced hardness was obtained in the CAD system.

Influence of a Scanning Radial Magnetic Field on Macroparticle Reduction of Arc Ion-Plated Films

Cathode spot motion influences the physical characteristics of arc plasma and the related macroparticles (MPs) in resultant films; these MPs limit the application of arc ion plating (AIP). In this paper, a scanning radial magnetic field (SRMF) was applied to the cathode surface to control the cathode spot motion and reduce the MP contamination in the deposited films. It was shown that film surface morphologies prepared using SRMF were better than those using a static radial magnetic field (RMF). The improvement was greater with increased scanning range and frequency. Using SRMF, cathode spot motion was confined to a spiral trajectory on the cathode surface and the spots moved over a large area and at a fast-moving velocity. Both the large moving area and the fast velocity decreased the temperature on the cathode surface and thus reduced the emission of the MPs.

A Brief Study on Starch Based Bio-Plastics Produced From Staple Food Items

Increasing amounts of plastic contamination in the oceans leads to their ingestion by various organisms, causing suffocation by macro particles and bioaccumulation of micro-particles in smaller to larger organisms in the food chain, human beings at the very end of it (Racusin, Jacob Deva., and Ace McArleton, 2012, The Natural Building Companion: a Comprehensive Guide to Integrative Design and Construction. Chelsea Green Publishing). Hence, our food eats our own garbage. Bio-plastics have been a recent development, and are being considered for usage in medical and pharmaceutical industry too, apart from being the substitute to plastic which we normally use. In this paper we propose methods to produce bio-plastics from starch based, staple food items, which can not only biodegrade, but are also edible. We make a comparative study of bio-plastics produced from sources such as banana peel, corn and potato, amongst each other and against synthetic plastic, discuss their properties along with biodegradability from soil microbes, concluding the most apt bio-plastic to substitute the commonly used plastics.

Studies on the inward spherical solidification of a phase change material dispersed with macro particles

This paper investigates numerically the solidification of a phase change material (PCM) dispersed with high conductivity macro particles inside a spherical container. The formulation takes into account the addition of particles invoking an effective thermal conductivity model. A case study has been made comparing the experimental results available in the open literature for the solidification of a pure PCM case (without particles) to investigate the influence of particles. The results show that the addition of particles between 10 and 50% by volume, enhances the heat transfer rate by about 13.5 and 59% respectively. Parametric studies have been carried out to investigate the influence of relevant dimensionless numbers such as Biot number (Bi) and Stefan number (Ste) on the solidification characteristics of the PCM for different particle fractions. The role of particles was found to be significant at lower Ste compared to Bi. It has been concluded that the effect of particle fraction on the solidification is more compared to that of particle-PCM thermal conductivity ratio. It was found that there is no restriction on the choice of particle material for a given PCM, as long as the particle-PCM thermal conductivity ratio considered remain larger than 5.

Uptake, tissue distribution, and toxicity of polystyrene nanoparticles in developing zebrafish (Danio rerio)

Plastic pollution is a critical environmental concern and comprises the majority of anthropogenic debris in the ocean, including macro, micro, and likely nanoscale (less than 100nm in at least one dimension) plastic particles. While the toxicity of macroplastics and microplastics is relatively well studied, the toxicity of nanoplastics is largely uncharacterized. Here, fluorescent polystyrene nanoparticles (PS NPs) were used to investigate the potential toxicity of nanoplastics in developing zebrafish (Danio rerio), as well as to characterize the uptake and distribution of the particles within embryos and larvae. Zebrafish embryos at 6h post-fertilization (hpf) were exposed to PS NPs (0.1, 1, or 10ppm) until 120 hpf. Our results demonstrate that PS NPs accumulated in the yolk sac as early as 24 hpf and migrated to the gastrointestinal tract, gallbladder, liver, pancreas, heart, and brain throughout development (48–120 hpf). Accumulation of PS NPs decreased during the depuration phase (120–168 hpf) in all organs, but at a slower rate in the pancreas and gastrointestinal tract. Notably, exposure to PS NPs did not induce significant mortality, deformities, or changes to mitochondrial bioenergetics, but did decrease the heart rate. Lastly, exposure to PS NPs altered larval behavior as evidenced by swimming hypoactivity in exposed larvae. Taken together, these data suggest that at least some nanoplastics can penetrate the chorion of developing zebrafish, accumulate in the tissues, and affect physiology and behavior, potentially affecting organismal fitness in contaminated aquatic ecosystems.

Arc evaporated W-alloyed Ti-Al-N coatings for improved thermal stability, mechanical, and tribological properties

The protection of various tools and components through wear resistant coatings is imperative in highly efficient and precise industrial manufacturing processes. Especially, physical vapor deposited Ti1−xAlxN and Cr1−xAlxN coatings have been commonly used as hard protective coatings due to their outstanding thermal stability and mechanical strength. However, to increase the applicable working temperatures by simultaneously enhancing the wear performance (e.g., to allow for higher cutting speeds) further improvements are required.Therefore, we studied in detail the impact of tungsten (W)—in combination with the substrate bias potential (Ubias)—on the thermo-mechanical properties and wear performance of arc evaporated Ti1–x−yAlxWyN thin films. With increasing W content, the quality of our coatings significantly increases due to pronounced reduction of growth defects (quantity of macro particles). All coatings studied crystallize in a supersaturated, single-phased face-centered cubic Ti1−x−yAlxWyN structure and their hardness (H) increases whereas the indentation modulus (E) decreases with increasing W content. This results in increased H3/E2 values, with a maximum of 0.19GPa for Ti0.50Al0.41W0.09N prepared with Ubias=−120V (H≈35GPa, E≈483GPa). All W-alloyed coatings exhibit wear rates below 4∙10−5mm3/Nm during our dry sliding pin-on-disk tests against alumina balls at room temperature, with a tendency for reduced values if more droplets are present. The highest thermal stability, with respect to the decomposition of the supersaturated Ti1–x−yAlxWyN phase towards the stable constituents (at high temperature) TiN, AlN, and W, is obtained for Ti0.53Al0.42W0.05N prepared with Ubias=−80V. Here, the formation of the wurtzite-structured AlN can be delayed to 1000°C after 60min lasting isothermal annealings in vacuum.

Research into protective properties of electromagnetic screens based on the metal-containing nanostructures

We developed and examined protective properties of the metal polymeric electromagnetic screens. We used metal-containing particles of nano dimensions as a filler in the polymeric matrix. It was established that this provides shielding coefficient of 10 dB at the content of a metal substance of 11–12 %. In this case, reflection coefficients are 0.27–0.30. This is not attainable for the materials based on macro particles. It was found that increasing the dispersion of particles by 2–4 times reduces reflection coefficient by 0.15–0.20. We studied dependence of the electrical-physical properties of material on the content of a metal substance. This allowed us to calculate shielding coefficients and the contribution of protection to them due to the reflection of electromagnetic waves. Micro structural research revealed the uniformity of distribution of metal particles in the body of a polymer matrix. This has provided a possibility to calculate at their low concentrations the required coefficients using the relations for regular metal structures. We have demonstrated experimentally the possibility of fabricating electromagnetic screens of the gradient type in a single layer matrix.

Influence of Open Porosity, Hydration Products and Extent of Hydration on the Strength of Desilicated Lime Fly Ash Composites

The prediction of strength of lime ash composites is critical for quality control, material performance monitoring and material serviceability limit state. A study was conducted to investigate the influence of open porosity (an index of micro grain alignment and macro particle parking), sum of hydration products and extent of hydration of desilicated fly ash (DFA) on the unconfined compressive strength (UCS) of DFA lime composites. A comparison with as received fly ash (FA) was also done. The wet and dry cycle durability of DFA and as received FA composites was also investigated. The DFA and FA composites were found to have a UCS of 8.6 MPa and 7.9 MPa respectively. The FA composite was found to be more durable than the DFA composite as after 10 wet and dry cycles the composites had a UCS of 3.5 and 1.8 MPa respectively. Statistical correlation between UCS and open porosity, extent of FA/DFA hydration and sum of hydration products was implemented by Multivariate analysis. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of FA/DFA hydration and sum of hydration products) had the greatest influence on the UCS than individually. This study shows that no single parameter on its own can adequately be used to predict UCS of FA/DFA lime composites. Correlation coefficients above 0.98 were found to describe the relationship between the three parameters and UCS for each composite. Thus could account for differences in durability or soaked strength of materials with equal initial dry strength.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.14915

Release behavior and bioefficacy of imazethapyr formulations based on biopolymeric hydrogels

ABSTRACTControlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t1/2) ranged between 0.06 and 4.8 days in case of GG-NHG and 4.4 and 12.6 days for the GG-HG formulations. Weed control index (WCI) of GG-HG and GG-NHG formulations was similar to that of the commercial formulation and the herbicidal effect was observed for relatively longer period. Guar gum-based biopolymeric hydrogels in both macro and nano particle size range can serve as potential carriers in developing slow release herbicide formulations.

Comparative Investigation of Mechanical Properties of Epoxy Composites Reinforced with Short Fibers, Macro Particles, and Micro Particles

The present investigation reports the mechanical properties of banana short fiber, macro particle, and micro particle reinforced epoxy composites. Mechanical properties, such as tensile, flexural, and impact strength, of three different composites were studied and compared based on the three different fiber contents (25 wt%, 30 wt%, and 35 wt%). The composites were prepared by a compression moulding method for which the mixture containing the reinforcing agents and resin matrix was prepare dusing a mechanical stirrer. The scanning electron microscopy (SEM) analysis revealed the failure mechanism and the resulting damage that occurred in the composites. The short fiber composite with 35 wt% content showed the highest tensile strength (35.59 MPa), whereas the macro particle composite with 35 wt% content showed the highest flexural strength (67.16 MPa). In the case of the impact strength, both the short fiber and macro particle composites showed the highest impact strength (0.32 J). The mechanical properties of epoxy composites increased substantially with increase of content of reinforcing agents (short fiber, macro particle, and micro particle).

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.