Particles In Different States Research Articles

Hardness fluctuations caused by annealing in Zr-based bulk metallic glasses via nanoindentation

The micromechanical response of a Zr-based bulk metallic glass (BMG) annealed in air below and above its glass transition temperature was studied. Nano-sized particles in different states at different annealing temperatures were found on the surface of the samples, which were identified by energy-dispersive spectroscopy (EDS) as being CuNi elemental composition. The surface microhardness and nanoindentation creep behavior of the BMGs after annealed exhibited interesting results, at low annealing temperatures, the microhardness of the samples showed softening accompanied by poor creep resistance, while at high annealing temperatures, the hardness of the samples shows hardening and creep resistance was enhanced. The consequences of such a temperature-dependent dichotomy were intricately linked to element segregation, which led to microstructural fluctuations. A competing mechanism between the hardening effect of zirconia at the surface and the softening effect of elemental segregation in the formation of microporous structures inside the samples is proposed to account for the divergent mechanical properties due to the annealing temperature. This work presents helpful insights into microstructural changes and micromechanical properties of BMGs during annealing, as well as an experimental support for structural and property modulation of BMGs.

ИЗУЧЕНИЕ АЭРОДИНАМИЧЕСКИХ ХАРАКТЕРИСТИК МАКРОТЕХА И ОЦЕНКА ВОЗМОЖНОСТЕЙ ЕГО ИСПОЛЬЗОВАНИЯ ДЛЯ ДИНАМИЧЕСКОЙ АЭРОЗОЛЬНОЙ СЦИНТИГРАФИИ

Introduction: The leading protective mechanism of the lungs is the processes of deposition of inhaled substances and mucociliary clearance (MCC), the optimal method for studying which is dynamic radioaerosol scintigraphy. are not available on the market. The applicant in this regard for a number of characteristics is the radiopharmaceutical from albumin, produced in the Russian Federation under the brand name Macrotech (M). It is used for perfusion scintigraphy to verify primarily pulmonary embolism and its ability to study deposition of inhalants and MCC has not been studied. Purpose: To study the aerodynamic properties of M dispersion and to determine the possibilities of its use for dynamic radioaerosol scintigraphy of the lungs in order to assess the processes of deposition of inhaled substances and MCC. Material and methods: To study the aerodynamic properties of M, on which the assessment of the deposition of inhaled substances and MCC significantly depends, we studied the dispersion of its particles in different states, and studied them in shape and morphology. An ultrasonic inhaler TuR USI-50 (Germany) generated an aerosol from a suspension of M in distilled water. To study the dispersion in air, laser spectrometry was used using the Spraytec Malvern Instruments system (Great Britain). The protein content in the initial suspension and dispersible aerosol, collected in the form of a condensate, was determined using an Immulite 2000 XPi immunochemical analyzer (Siemens, USA).The shape and morphology of the particles were studied using scanning electron microscopy using. Results: The study of the aerodynamic properties of the dispersion of M indicated that its particles are involved in the dynamics of the movement of the airflow and the flight of water particles generated by the inhaler. The dispersity of the aerosol generated from the suspension M averaged about 5 μm and did not significantly depend on the concentration of the radiopharmaceutical and did not depend on the studied dispersion intensity and airflow rate set using an inhaler. The morphology of M particles was characterized by a complex shape and roughness. Conclusion: The aerodynamic characteristics of M are not optimal for studying the processes of deposition and MCC. However, a final verdict requires a direct assessment of the deposition of the inhaled radioaerosol generated from this preparation.

Influence of heat exchange on the motion characteristics and mechanical behavior of fine particles in an electrostatic precipitator

An experimental platform was established in order to study the motion characteristics and mechanical behavior of fine particles in an electrostatic precipitator utilizing a heat exchange mechanism. The concentration of fine particles in different states was tested. The force behavior model of particles was established in order to analyze their motion characteristics. The results show that the thermophoretic effect led to a reduction in the size range of the entrained particles and the size range of particles settling efficiently expanded. As compared to the dry state, the removal efficiency of particles in the heat exchange state, smaller than 0.3 μm, greatly improved and that of 0.01 μm particles improved by 30%. The re-entrainment depended on the magnitude of Fm + Fi and Fv + FJ, the heat exchange effect led to an increase in the in-layer force due to an electric field, Fm, van der Waals force, Fv, the electrostatic attraction force, FJ, and the repulsion forces, Fi. It was observed that the size of Fm + Fi and Fv + FJ was not much different.

Canonical ensemble ground state and correlation entropy of Bose–Einstein condensate

Constraint of a fixed total number of particles yields a correlation between the fluctuation of particles in different states in the canonical ensemble. Here we show that, below the temperature of Bose–Einstein condensation (BEC), the correlation part of the entropy of an ideal Bose gas is cancelled by the ground-state contribution. Thus, in the BEC region, the thermodynamic properties of the gas in the canonical ensemble can be described accurately in a simplified model which excludes the ground state and assumes no correlation between excited levels.

The use of water-extractable Cu, Mo, Zn, As, Pb concentrations and automated mineral analysis of flue dust particles as tools for impact studies in topsoils exposed to past emissions of a Cu-smelter

An exploratory study has been conducted to test the utility of automated mineral analysis observations to identify flue dust particles in topsoils exposed for several decades to emissions of a copper smelter. The methods used are readily available in mining countries. To identify the most impacted sites, the Cu, Zn, Pb, Mo and As levels in water and diluted sulphuric acid extractions of four topsoil size fractions (833–495μm, 246–148μm; 74–38μm; <38μm) were analysed. X-ray diffraction analyses were used to demonstrate the mineralogical degradation of smectite phases when approaching the smelter. Flue dust particles in different states of conservation in topsoils were directly observed by scanning electron microscopy (SEM) aided by energy dispersive detection of X-rays. Qemscan® scanning of dispersed topsoil preparations (10,000 particles) pinpoints smelter particles by their density; flue dust pearls can be tracked by sorting particles according to their sphericity, clearly identifying them as pyrometallurgical products. When sorting soil particles by mineral groups (e.g. sulphides), an increase in this phase group can be observed when approaching the smelter. SEM resolution limits observations to particles larger than 2–3μm. Smaller particles can be observed by transmission electron microscopy, although observer experience and the availability of equipment time are essential as is the case for SEM.

Deposition of WC-Co Coatings by a Novel High Pressure HVOF

WC-Co coatings are primarily deposited using the high velocity oxy-fuel (HVOF) spray process. However, the decomposition and decarburization of carbides during spraying affects the wear performance and fracture toughness of the coatings. In this paper, a novel high pressure HVOF was developed to achieve lower particle temperature and higher particle velocity. It enables combustion chamber pressures up to 3.0 MPa. The influence of combustion chamber pressure and oxygen/fuel ratio on WC-Co particle velocity and temperature levels were analyzed by numerical simulation. The experimental results show that the combustion chamber pressure and the oxygen/fuel ratio have a significant influence on particle velocity and melting degree, as well as on the microstructure and microhardness of the coating. High velocity WC-Co particles in different states, i.e., molten, semi-molten, and non-molten can be readily obtained by changing the spraying conditions. A comparison to the conventional JP-5000 was also performed.

Modeling of particle removal processes in brush scrubber cleaning

Abstract A new model describing the particle removal behaviour in brush scrubber cleaning is presented. The topology and roughness asperities of brush surface are considered. There are four situations of the particles relative to the brush roughness asperities. The forces on the particles in different states are analyzed and the particle removal criteria are listed. The particles are rolling away by the combined effects of hydrodynamic drag force and elastic force in contact area or only by the hydrodynamic drag force when in the concave area between the brush nodule asperities. When the particles are embedded in the brush asperities, the particle will be removed by friction between the bush and the particle. The cleaning results are coincident with the actual process and can be used as reference for designing a higher level cleaning process.

Effect of gas environment on properties of particles prepared by spray pyrolysis of metal nitrates

Particles in different states of oxidation were prepared by spray pyrolyses of aqueous solutions of silver and copper nitrates under different gas environments: air, nitrogen or mixture gas of 10 vol%H2-N2, respectively. Silver nitrate was converted to phase-pure silver at temperatures below 500 o C whose densification and crystallization were completed around 500

DOOSIM—A NEW SIMULATION MODEL FOR OIL SPILL MANAGEMENT

ABSTRACT A new oil spill simulation model has been developed as a part of the research program Dispersion of Oil On Sea (DOOS). The model includes features such as simulation of drift and fate of oil on the surface and in the water column, as well as effects of cleanup measures (mechanical recovery, application of chemical dispersants). The model utilizes the particle-in-fluid concept, where the oil spill is represented by a large number of particles in different states, i.e., on the surface, entrained in the water column, or evaporated. The near surface current shear is taken into account in the wind induced component of the drift, in terms of a two layer approach (reduced wind drift factor for entrained oil). In the design of the model, major efforts have been made to obtain a system which is easy to operate. This has led to a system consisting of three modules: one for entry of user-specified inputs, one for simulating an actual spill, and one for graphical presentation.