scholarly journals Effect of tungsten nanoparticles on sintering of the Sn-Cu-Co-W powder material

2021 ◽  
Vol 2094 (4) ◽  
pp. 042088
Author(s):  
A V Ozolin ◽  
E G Sokolov
Keyword(s):  
Powder Material ◽  
Tungsten Powder ◽  
Liquid Phase Sintering ◽  
Scanning Electronic Microscopy ◽  
Noticeable Effect ◽  
Centrifugal Mill ◽  
Powder Particles ◽  
Kinetics Of ◽  
Static Pressing ◽  
Tungsten Nanoparticles

Abstract The effect of tungsten nanoparticles on the kinetics of sintering of the Sn-Cu-Co-W powder material used as a binder in diamond tools was studied. The W16,5 grade tungsten powder was mechanically activated in the AGO-2U planetary centrifugal mill for 60 minutes at the carrier rotation frequencies of 800 RPM. The mixture of tungsten, tin, copper, and cobalt powders was compacted by static pressing in press dies and then sintered in vacuum at the temperature of 820°C. The morphology and sizes of powder particles, as well as the structure of the sintered samples, were studied by the methods of scanning electronic microscopy. It has been demonstrated that tungsten nanoparticles have a noticeable effect on the process of dissolution-reprecipitation of cobalt in liquid-phase sintering.

The Effect of Tungsten Nanoparticles on the Hardness of Sintered Sn-Cu-Co-W Alloys

2020 ◽  
Vol 992 ◽  
pp. 511-516
Author(s):  
Evgeniy Georgiyevich Sokolov ◽  
Alexander Vitalyevich Ozolin ◽  
Svetlana Alexandrovna Arefieva
Keyword(s):  
Tungsten Powder ◽  
Dispersion Hardening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Centrifugal Mill ◽  
Size Of Particles ◽  
Tungsten Nanoparticles ◽  
Sintered Materials ◽  
Scanning Electron ◽  
Main Factor

The effect of tungsten nanoparticles and microparticles on the structure and hardness of sintered Sn–Cu–Co–W alloys has been studied. Tungsten powder of 19–24 μm sized particles was milled in a planetary-centrifugal mill, after which the size of particles was 25 nm to 20 μm. The milled and non-milled tungsten was then mixed with powders of tin, copper and cobalt. The specimens were compacted in moulds and sintered in vacuum at 820°C for 20 minutes. The structure of sintered materials was studied using X-ray diffraction analysis and scanning electron microscopy. Microhardness (HV0.01) of structural constituents and hardness of the materials were measured. It has been determined that it is alloys containing mechanically milled tungsten that have the highest hardness. The main factor influencing the rise of hardness is dispersion hardening with nanoparticles. A further factor is work hardening of tungsten microparticles during ball milling. The highest hardness of 109–111 HRB has been obtained in the Sn–Cu–Co–W alloy containing 23% wt. of milled tungsten, with the proportion of tin, copper and cobalt being 1/2.6/1.6.

scholarly journals Drying kinetics of baru flours as function of temperature

2018 ◽  
Vol 22 (10) ◽  
pp. 713-719 ◽  
Author(s):  
Douglas R. Reis ◽  
Fabrício B. Brum ◽  
Eduardo J. O. Soares ◽  
Jessiana R. Magalhães ◽  
Fabrício S. Silva ◽  
...  
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Food Industry ◽  
Nutritional Value ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Statistical Parameters ◽  
Noticeable Effect ◽  
Different Temperatures ◽  
Kinetics Of

ABSTRACT Several types of seeds have been initially used in the food industry due to the great potential that vegetable proteins have. Baru is a fruit commonly found in the Cerrado biome, having a high nutritional value. This paper aimed to determine and analyze the drying kinetics of whole and defatted baru almond flours at different temperatures. The flour resulting from almond milling was defatted using petroleum ether. The drying processes were performed at temperatures of 40, 50 and 60 ºC. The mathematical models of Page, Henderson and Pabis, Midilli & Kucuk, Thompson and Approximation of Diffusion were fitted to the experimental data. The results showed a noticeable effect of air temperature on the drying kinetics of whole and defatted baru almond flours. According to the statistical parameters of analysis, the models Midilli & Kucuk and Page were the ones with the best fits to the experimental data. The effective diffusivity values found ranged from 8.02 × 10–10 to 19.90 × 10–10 m2 s-1 and for the activation energy were 22.39 and 39.37 KJ mol-1 for whole and defatted almonds, respectively.

Effect of chloride ions on the kinetics of nitrobenzene reduction by powdered iron

2006 ◽  
Vol 60 (5) ◽  
Author(s):  
M. Heželová ◽  
L’. Pikna ◽  
D. Kladeková ◽  
L. Lux
Keyword(s):  
Specific Surface ◽  
Reaction System ◽  
Particulate Material ◽  
Surface Reactivity ◽  
Chloride Ions ◽  
Free Medium ◽  
Iron Particles ◽  
Nitrobenzene Reduction ◽  
Powder Particles ◽  
Kinetics Of

AbstractThe effect of different chloride ions concentrations on the reactivity of iron particles was studied using chronopotentiometry. It was found that the increase of Cl− ions concentration accelerated anodic dissolution of iron, thus enhancing its surface reactivity. This fact was confirmed also by the rate of nitrobenzene reduction by iron particles. The reactivity of powder particles of various sizes, hence of different specific surface, was investigated in chloride-free and chloride-containing acetate buffer electrolytes. Experimental results indicated that the rate of nitrobenzene reduction in the presence of chloride ions in the reaction system is faster in comparison with the rate in chloride-free medium for each studied grain fraction of particulate material.

scholarly journals Microstructure Characteristics of Ce-ZTA Ceramic Composites Obtained by Liquid Phase Sintering

2006 ◽  
Vol 530-531 ◽  
pp. 421-424
Author(s):  
Haine Beck ◽  
Maria do Carmo de Andrade Nono ◽  
Francisco Piorino Neto
Keyword(s):  
Ceramic Composite ◽  
Glassy Phase ◽  
Volume Fraction ◽  
Tetragonal Zirconia ◽  
Ceramic Composites ◽  
Liquid Phase Sintering ◽  
Scanning Electronic Microscopy ◽  
Powder Samples ◽  
Zirconia Toughened Alumina ◽  
Crystalline Matrix

Zirconia-toughened alumina (ZTA) ceramics with Ce-TZP (tetragonal zirconia polycrystalline doped with ceria) volume fraction on 33% were prepared with the addition.. The influence of glass infiltrated method was investigated. Coprecipitated Zr and Ce hydroxide mixture was obtained from ZrOCl2.8H2O and CeCl3. 7H2O aqueous solution. CeO2-ZrO2 calcinated powder was compacted and the compacted samples were sintered at 1180°C. Powder samples were characterized by scanning electronic microscopy (SEM), The volume fraction of each phase, the grains size and shapes, and the porosity were investigated with SEM. The relative density and shrinkage was investigate too. The results showed that the crystalline matrix was composed by SiO2 -B2O3-La2O3-Al2O3-Ce-TZP and revealed the important role played the glassy phase in the densification of this ceramic composite.

The Influence of Calcium Additive in the Structural Formation of Tungsten via Reduction Reaction

2015 ◽  
Vol 1088 ◽  
pp. 159-163
Author(s):  
Xin Yang ◽  
Dun Qiang Tan ◽  
Ya Lei Li ◽  
Wen He ◽  
Hong Bo Zhu ◽  
...  
Keyword(s):  
Hydrogen Reduction ◽  
Raw Materials ◽  
Tungsten Powder ◽  
Reduction Process ◽  
Reduction Reaction ◽  
Structural Formation ◽  
Powder Particles ◽  
Micro Morphology ◽  
Existing Form ◽  
Solution Doping

With the processes of solution doping and hydrogen reduction process, the raw materials APT powder was converted into the tungsten with calcium additive. Micro-morphology, micro-structure, the existing form of element calcium and their distribution were examined by SEM, HRTEM and EDS. The results show that Element calcium is mainly in the form of CaWO4in tungsten oxide powder and has two calcium tungstate forms which are CaWO4and Ca4.26W10O30in reducing tungsten powder. The Ca-W-O particles are embedding in the tungsten powder particles; the rest distribute between the tungsten powder particles.

scholarly journals Modeling of the mechanism of heterogeneous inhibition of the active flame centers of a jet burning system by fire extinguishing powder particles

2021 ◽  
Vol 66 (2) ◽  
pp. 250-256
Author(s):  
A. I. Kitsak
Keyword(s):  
Convective Motion ◽  
Combustion Products ◽  
Convective Transport ◽  
Fire Extinguishing ◽  
Hazardous Chemical ◽  
Active Particles ◽  
Molecular Transfer ◽  
Flame Suppression ◽  
Powder Particles ◽  
Kinetics Of

The relevance of the work is due to the lack of a physical interpretation of the process of extinguishing jet burning systems with fire extinguishing powders, which is important for ensuring effective fire extinguishing at gas and oil complexes and hazardous chemical industries. A mathematical model of the reaction kinetics of heterogeneous inhibition of active flame centers of a jet burning system by fire extinguishing powder particles in an unsteady mode is considered in the approximation of a purely molecular transfer of matter in the reaction zone. The regularities of the mechanism of heterogeneous inhibition of the active flame centers by the particles of the extinguishing powder under conditions when the active particles of the combustion products participate not only in diffuse, but also in convective transport are established. It is shown, that the convective motion of the active flame centers increases the reaction rate of heterogeneous inhibition of their particles of the extinguishing agent. The results obtained allow us to optimize the conditions for the supply of fire extinguishing powder to the jet burning medium for effective flame suppression.

Mechanical and Microstructural Properties of Selective Laser Melted 17-4 PH Stainless Steel

2015 ◽  
Author(s):  
Aref Yadollahi ◽  
Nima Shamsaei ◽  
Scott M. Thompson ◽  
Alaa Elwany ◽  
Linkan Bian
Keyword(s):  
Stainless Steel ◽  
Precipitation Hardening ◽  
Solution Annealing ◽  
Microstructural Characteristics ◽  
Noticeable Effect ◽  
Lack Of Fusion ◽  
Elongation To Failure ◽  
Powder Particles ◽  
Lower Elongation ◽  
Mechanical And Microstructural Properties

The present article focuses on the mechanical properties and microstructural features of Selective Laser Melted (SLM) 17-4 precipitation hardening (PH) stainless steel (SS) as well as their comparison to conventionally built materials. The topics investigated are the effects of different building orientations and post-fabrication heat treatment (solution annealing and aging) on the mechanical and microstructural characteristics of samples fabricated by SLM. Yield and ultimate tensile strengths of SLM-produced 17-4 PH SS were found to be lower than those of wrought materials (H900 condition). In addition, building orientations showed a noticeable effect on tensile properties. Presence of defects, such as pores resulting from entrapped gas, un-melted regions, and powder particles resulting from lack of fusion were the main reasons for lower elongation to failure of SLM-produced 17-4PH SS in this study.

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