scholarly journals Milling Dynamics and Propagation of Mechanically Activated Self-Sustaining Reactions

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Alberto Cincotti ◽  
Gabriele Traversari ◽  
Giorgio Pia ◽  
Francesco Delogu
Keyword(s):  
Reaction Rate ◽  
Equations Of Motion ◽  
Analytical Description ◽  
Chemical Conversion ◽  
Mechanical Processing ◽  
Ball Mills ◽  
Operational Conditions ◽  
Powder Particles ◽  
Milling Dynamics ◽  
Individual Particles

This work focuses on the propagation of mechanically activated self-sustaining reactions during the mechanical processing of powder in ball mills. We use a numerical model to reconstruct the dynamics of a single ball and powder particles inside the reactor of a SPEX Mixer/Mill 8000 under operational conditions. Taking advantage of the analytical description of the reactor swing, the equations of motion of ball and powder particles are solved numerically. The discrete element method is used to describe contacts. Reaction is ignited in an individual particle randomly selected among those compressed during an impact between ball and reactor. A simple kinetic law and a set of rules involving degree of chemical conversion and distance between particles are used to obtain a phenomenological description of the reaction propagation. We show that the propagation is significantly affected by reaction rate in individual particles, with other factors being less influential. We observe a strong coupling between the dynamics of powder particles and the reaction propagation.

Liquid supercoolings and droplet cooling rates of remelted argon-atomized Fe–30Ni powder particles

1988 ◽  
Vol 3 (3) ◽  
pp. 441-452 ◽  
Author(s):  
Matthew R. Libera ◽  
Pedro P. Bolsaitis ◽  
R. Erik Spjut ◽  
John B. VanderSande
Keyword(s):  
Standard Deviation ◽  
Cooling Rate ◽  
Metal Droplet ◽  
Liquid Droplets ◽  
Interfacial Velocity ◽  
Gas Atmosphere ◽  
History Of ◽  
Powder Particles ◽  
The Difference ◽  
Individual Particles

Individual particles of argon-atomized Fe-30Ni powder are electrodynamically levitated and remelted by a CO2 laser pulse. The thermal history of each droplet during remelting and solidification is monitored by single-color radiation pyrometry at each of three wavelengths (850, 750, and 550 nm). Experiments are done in an atmosphere of either air or nitrogen. The average supercooling of six experiments performed in nitrogen is 298 K with a standard deviation of 14 K. This value is of the same order as several others reported in the literature using bulk levitation and emulsification techniques. The average supercooling of seven experiments performed in air is 163 K with a standard deviation of 20 K. The difference suggests that oxides are forming in the air-remelting experiments and catalyzing nucleation at relatively low supercoolings. The average cooling rate of the liquid droplets prior to solidification in nitrogen is 1.5 × 105 K/s. This measured cooling rate is somewhat higher than that predicted by Newtonian heat flow modeling, and the difference is attributed to radiative losses not considered in the Newtonian model. The measured cooling rate is used to estimate the total heat transfer coefficient characterizing cooling of a small metal droplet in a quiescent gas atmosphere. A lower bound of 1.5 × 106 K/s on the droplet heating rate during recalescence and a minimum average liquid/solid interfacial velocity during recalescence of 0.1 m/s are estimated.

Characteristics of the equations of motion of a reacting gas

1958 ◽  
Vol 4 (3) ◽  
pp. 276-282 ◽  
Author(s):  
L. J. F. Broer
Keyword(s):  
Heat Conduction ◽  
High Frequency ◽  
Sound Speed ◽  
Reaction Rate ◽  
Equations Of Motion ◽  
Sound Waves ◽  
Velocity Of Sound ◽  
Frequency Limit ◽  
Chemically Reacting ◽  
Set Up

The equations of motion for a chemically reacting gas in the absence of viscosity and heat conduction are set up. It is shown that the characteristic speed defined by this set of equations is the high-frequency limit of the phase velocity of sound waves as long as the reaction rate is finite. At infinite reaction rate (chemical equilibrium) the characteristics suddenly change to the lowfrequency sound speed. The nature of this transition is discussed in connection with a recent paper of Resler (1957).

scholarly journals The Effect of Powder Particle Biencapsulation with Ni-P Layer on Local Corrosion of Bonded Nd-(Fe,Co)-B Magnetic Material

2015 ◽  
Vol 60 (1) ◽  
pp. 153-157 ◽  
Author(s):  
D. Klimecka-Tatar ◽  
G. Pawłowska ◽  
M. Sozańska
Keyword(s):  
Magnetic Material ◽  
Epoxy Resin ◽  
Magnetic Materials ◽  
Powder Particle ◽  
Single Phase ◽  
Corrosion Behaviour ◽  
Powder Surface ◽  
Powder Particles ◽  
Individual Particles ◽  
Thermosetting Epoxy

Abstract Effect of the Nd-(Fe,Co)-B powder particle biencapsulation with Ni-P layer on bonded magnetic materials corrosion behaviour has been investigated. Bonded magnets were prepared from single-phase, nanocrystalline magnetic Nd11Fe77Co5B6 powder. Powder particles before consolidation were preliminary etched and then coated with bilayer (powder biencapsulation). The powder surface was coated as a first with autocatalytic applied Ni-P layer during 5, 15 and 30 minutes in Ni(II) containing bath and the second layer was thermosetting epoxy-resin. Impact of the used biencapsulation process was rated on the basis of polarization curves recorded in phosphate environment with addition of chloric ions. It has been established that the used biencapsulation method satisfactorily isolate individual particles of the powder and consequently, significantly inhibits corrosion processes of the final material, especially in passivating environment containing Cl-.

scholarly journals PARTICLE MOTION ON THE SPHERICAL SEGMENT WITH VERTICALS RADIALLY INSTALLED BLADES

2021 ◽  
Vol 3 (1) ◽  
pp. 27-36
Author(s):  
T. Volina ◽  
◽  
S. Pylypaka ◽  
A. Nesvidomin ◽  
◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Angular Velocity ◽  
Relative Motion ◽  
Particle Motion ◽  
Equations Of Motion ◽  
Analytical Description ◽  
Vertical Axis ◽  
Disk Surface ◽  
Spherical Segment ◽  
Technological Parameters

The relative motion of a particle on the inner surface of a horizontal spherical disk along a vertical blade mounted in the radial direction is considered in the article. The disk rotates around a vertical axis with a given angular velocity. A system of differential equations of motion of a particle is compiled and solved by numerical methods. The kinematic characteristics of the motion are found, the regularities of the relative motion of the particle on the surface of the cylinder are clarified. Graphs characterizing the motion of a particle at certain given parameters are constructed, namely: graph of angle change, which sets the position of the particle on the surface of the sphere in the direction of the meridian, graphs of absolute and relative velocities, graphs of change of forces of the reaction of the spherical disk and blade. Numerical integration of the obtained differential equation showed that in half a second the particle rises to the height of the hemisphere, and then begins to fall. In this case, the descent alternates with the rise to a complete stop of the particle at a certain height, i.e. the particle “sticks” and then rotates with the hemisphere. The angle of “sticking” can be found analytically. In addition, numerical calculation methods have shown that at zero value of the friction coefficient of the particle on the disk surface, i.e. at its absolutely smooth surface, and at the non-zero value of the friction coefficient of the blade surface, and at an unlimited increase of the disk angular velocity the particle “sticks” at the height of the center of the sphere. If both surfaces are absolutely smooth, then the damping oscillations of the angle that determines the position of the particle on the surface of the sphere in the direction of the meridian, occur indefinitely. The working surface of the disk of the centrifugal apparatus, which is made in the form of a spherical segment, provides the beginning of the flight of the particle at the time of ascent from the disk at a given angle to the horizontal plane, increasing the scattering area of the technological material. The analytical description of the particle motion obtained in the article makes it possible to investigate its acceleration along with the blades of the disk and to find the relative and absolute velocities at the moment of particle ascent from the disk. The found analytical dependencies allow determining the influence of constructive and technological parameters on the process of particle acceleration.

scholarly journals Dechlorination of Hexachloroethane in Water Using Iron Shavings and Amended Iron Shavings: Kinetics and Pathways

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
D. L. Wu ◽  
Y. X. Liu ◽  
Z. G. Liu ◽  
L. M. Ma
Keyword(s):  
Reductive Dechlorination ◽  
Reaction Rate ◽  
Reaction Pathway ◽  
Mechanical Processing ◽  
Contamination Control ◽  
First Order ◽  
Product Distributions ◽  
Processing Plants ◽  
Low Costs ◽  
Control Technologies

In contrast to previous studies which employed zero-valent iron powder, this paper investigated reductive dechlorination of hexachloroethane (HCA) using iron shavings and bimetallic iron shavings modified with Cu, Ag, or Pd. Results clearly show that iron shavings offer superior reductive dechlorination of HCA. In addition, surface-normalized pseudo first-order dechlorination rates of 0.0073 L·m−2·h−1, 0.0136 L·m−2·h−1, 0.0189 L·m−2·h−1, and 0.0084 L·m−2·h−1were observed in the presence of iron shavings (Fe0) and the bimetallic iron shavings Cu/Fe, Ag/Fe, and Pd/Fe, respectively. Bimetallic iron shavings consisting of Cu/Fe and Ag/Fe could greatly enhance the reductive reaction rate; Pd/Fe was used to achieve complete dechlorination of HCA within 5 hours. The additives of Ag and Pd shifted product distributions, and the reductive dechlorination of HCA occurred viaβreductive elimination and sequential hydrogenolysis in the presence of all iron shavings. This study consequently designed a reaction pathway diagram which reflected the reaction pathway and most prevalent dechlorination products. Iron shavings are a common byproduct of mechanical processing plants. While the purity of such Fe metals may be low, these shavings are readily available at low costs and could potentially be used in engineering applications such as contamination control technologies.

Reaction Engineering Studies of Homogeneous Rhodium-Catalyzed Methanol Carbonylation in a Laboratory Semi-Batch Reactor

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Reza Golhosseini ◽  
Abas Naderifar ◽  
Alireza Mohammadrezaei ◽  
Mohamadreza Jafari Nasr
Keyword(s):  
Reaction Rate ◽  
Methyl Acetate ◽  
Batch Reactor ◽  
Equilibrium Constants ◽  
Reaction Engineering ◽  
Ab Initio Method ◽  
Operational Conditions ◽  
Partial Pressures ◽  
Thermodynamic Restrictions ◽  
Good Agreement

Thermodynamic restrictions and simultaneous effects of operational conditions on the homogeneous rhodium-catalyzed carbonylation of methanol are studied in this line of research. It is shown that the general NRTL-Virial model can be appropriated to study thermodynamics of the carbonylation. It is obtained that the reaction is kinetically and thermodynamically reasonable at temperatures above 420K and below 520K, respectively. Moreover, at carbon monoxide partial pressures above 10 bar, the reaction rate is independent of the partial pressure. These results are in full accord with those reported in the literature. In addition, PCO > 2 bar is necessary for initializing the reaction. The parameters involved in the rate expression, equilibrium constants, CO solubility, and rate constant, are determined. The equilibrium constants are calculated with B3LYP/SDD ab initio method, and the value of Henry’s coefficient for CO (HCO) is determined as a function of temperature and methyl acetate conversion. The results predicted by this function agree well with those proposed by the general NRTL-Virial model with the errors below 11%. The Variation of CO solubility with acetic acid and methyl acetate concentrations is in good agreement with that obtained by others. It is found that the determined parameters give satisfactory predictions in modeling and simulation of the reaction.

An Integrated Mathematical Model of the Plasma Spraying Process

1998 ◽  
Author(s):  
J.W. Mckelliget ◽  
G. Trapaga ◽  
E. Gutierrez-Miravete ◽  
M. Cybulski
Keyword(s):  
Mathematical Model ◽  
Plasma Spraying ◽  
Thermal History ◽  
Plasma Plume ◽  
Equations Of Motion ◽  
Atmospheric Pressure Plasma ◽  
Spray Process ◽  
History Of ◽  
Powder Particles ◽  
Transient Thermal

Abstract This paper describes an integrated mathematical model of the atmospheric pressure plasma spray process and presents a comparison between computed results and experimental measurements. The model describes fluid flow and heat transfer in the plasma plume; heating, melting and vaporization of injected powder particles; deposition and freezing of the molten particles; and the transient thermal history of the substrate. The plasma plume calculations are based on the solution of the two-dimensional turbulent equations of motion. A dynamic and thermal balance permits the calculation of the particle temperatures and velocities. The thermal history of the growing coating is calculated under typical cyclic spraying conditions. The computed results are compared against existing experimental data obtained from commercial plasma spraying torches.

Mechanical Processing of Carbon Blacks. Resultant Effects in GR-S Compounds

1947 ◽  
Vol 20 (2) ◽  
pp. 537-545
Author(s):  
R. E. Dobbin ◽  
R. P. Rossman
Keyword(s):  
Electrical Conductivity ◽  
Carbon Black ◽  
Mechanical Work ◽  
Structure Theory ◽  
Mechanical Processing ◽  
High Modulus ◽  
Carbon Blacks ◽  
Liquid Retention ◽  
Black Surface ◽  
Individual Particles

Abstract It was suggested that carbon blacks owe some of their characteristic properties to a tendency for individual particles to cluster into chainlike groupings or secondary aggregates. Results of mechanical processing experiments show that application of mechanical work altered or destroyed secondary aggregates. This conclusion was made since resistance to compression had been permanently overcome. Analytical measurements confirmed the supposition that secondary aggregates had been altered or destroyed, since oil absorption and liquid retention values markedly decreased with mechanical work. Finally, properties of compounded GR-S stocks were seriously altered—namely, smoothness of milled stock, high modulus, and enhanced electrical conductivity. It is concluded that these properties were originally caused by the presence of secondary aggregates or structure units. Alternative interpretations of these data are possible—namely, it might be concluded that it was not possible to disperse the densified material to the same extent as the original carbon black. However, this hypothesis contends that a large particle size material is being dispersed. Therefore, a decrease in tensile strength should have been noted. There is also some meager evidence suggesting that the chemical nature or activity of the carbon black surface was altered, so that its contribution to modulus was limited. It is believed, however, that most of the evidence offered by the data presented here preponderantly supports the structure theory of high modulus blacks. The authors consider these results as preliminary in the study of the structure properties of carbon blacks. They appear to be of sufficient interest to be brought to the attention of those studying reinforcement. Data available at present do not permit an interpretation of the contribution of structure to properties of “smooth-out” modulus and electrical conductivity of compounded rubber stocks.

Minimization of the Local Rates of Entropy Production in the Design of Air-Cooled Gas Turbine Blades

1999 ◽  
Vol 121 (3) ◽  
pp. 466-475 ◽  
Author(s):  
G. Natalini ◽  
E. Sciubba
Keyword(s):  
Gas Turbine ◽  
Entropy Generation ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Equations Of Motion ◽  
Turbine Blades ◽  
Temperature Fields ◽  
Entropy Generation Rate ◽  
Two Dimensional ◽  
Operational Conditions

The paper presents the results of a numerical configuration study made on a two dimensional model of an internally cooled gas turbine vane. The analysis applies to a two-dimensional cascade at medium Reynolds number, subsonic Mach number, and steady state. The full Navier-Stokes equations of motion for turbulent viscous flow, together with the appropriate energy equation, are solved via a standard finite-element code with a k-ε closure, to obtain complete velocity and temperature fields. These fields are then used to compute the entropy generation rates corresponding to the viscous (sv) and thermal (st) dissipation. The thermo-fluid dynamic efficiency of difference versions of the same base configuration is assessed comparing the global (or integral) entropy generation rate in the passage. The procedure is general, can be extended to different configurations and different operational conditions, and provides the designer with a rational and effective tool to assess the actual losses in the fixed and rotating turbomachinery cascades.

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