Circulation instability of steady falling of a flat layer of fine dispersed particles

Smith has shown by dark-field electron microscopy of extracted ThO2 particles from TD-nickel (2% ThO2) that they possess single crystal characteristics. It is generally assumed that these particle dispersions are incoherent. However, some diffraction effects associated with the particle images appeared to be similar to coherency strain fields. The present work will demonstrate conclusively that ThO2 dispersed particles in TD-nickel (2% ThO2) and TD-NiCr (2% ThO2, 20% Cr, Ni) are single crystals. Moreover, the diffraction contrast effects are extinction fringes. That is, these effects arise because of the particle orientation with respect to the electron beam and the extinction conditions for various operating reflections The particles are in fact incoherent.

Download Full-text

Surface treatment with silver particles isles on Titanium cp: study of antimicrobial activity

Research Society and Development ◽

10.33448/rsd-v9i4.2662 ◽

2020 ◽

Vol 9 (4) ◽

pp. e27942662

Author(s):

Patrícia Capellato ◽

Cláudia Eliana Bruno Marino ◽

Gilbert Silva ◽

Lucas Victor Benjamim Vasconcelos ◽

Rodrigo Perito Cardoso ◽

...

Keyword(s):

Antimicrobial Activity ◽

Surface Treatment ◽

Titanium Surface ◽

Silver Clusters ◽

Silver Particles ◽

Silver Deposition ◽

Dispersed Particles ◽

Significant Difference ◽

Diffusion Assay ◽

Antibacterial Potential

During the last decades, researchers have been growing the interest in surface treatment with an antimicrobial agent. Silver nanoparticles (AgNPs) are widely used in biomedical fields due to their potent antimicrobial activity. So, in this study was investigated silver particles (isles) coated on titanium surface for dental and orthopedic application. Silver particles coating process on titanium surface were performed via sputtering that is a plasma-assisted deposition technique with and titanium without treatment was applied as comparing standard. Plasma treatment parameters were optimized so that the result was not a thin film of Ag but dispersed particles of Ag on the Ti-cp surface. The alloy surfaces were investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). In order to investigate antibacterial potential Staphylococcus aureus and Escherichia coli have been used at Agar diffusion assay. The results were analyzed by analysis of variance (ANOVA) in order to verify significant difference antimicrobial activity between samples that have shown no difference between the surfaces studied treatments. For silver deposition scattered particles (isles) over titanium surface for a 10-minute treatment, EDS revealed by silver clusters that the particles were not properly scattered onto surface, hence, the low effectiveness in antibacterial activity.

Download Full-text

Study of the structural degradation of steel 15Kh5M upon continuous duty

Industrial laboratory Diagnostics of materials ◽

10.26896/1028-6861-2020-86-1-38-43 ◽

2020 ◽

Vol 86 (1) ◽

pp. 38-43

Author(s):

Vladimir A. Kim ◽

Valeriya V. Lysenko ◽

Anna A. Afanaseva ◽

Khasan I. Turkmenov

Keyword(s):

Grain Boundaries ◽

Structural Changes ◽

Structural Transformations ◽

Structural Degradation ◽

Structural Arrangement ◽

Dispersed Particles ◽

Complex Process ◽

Multifractal Spectra ◽

Steel 15Kh5m ◽

Complex Indicators

Structural degradation of the material upon long-term thermal and force impacts is a complex process which includes migration of the grain boundaries, diffusion of the active elements of the external and technological environment, hydrogen embrittlement, aging, grain boundary corrosion and other mechanisms. Application of the fractal and multifractal formalism to the description of microstructures opens up wide opportunities for quantitative assessment of the structural arrangement of the material, clarifies and reveals new aspects of the known mechanisms of structural transformations. Multifractal parameterization allows us to study the processes of structural degradation from the images of microstructures and identify structural changes that are hardly distinguishable visually. Any quantitative structural indicator can be used to calculate the multifractal spectra of the microstructure, but the most preferable is that provides the maximum range of variation in the numerical values of the multifractal components. The results of studying structural degradation of steel 15Kh5M upon continuous duty are presented. It is shown that structural degradation of steel during operation under high temperatures and stresses is accompanied by enlargement of the microstructural objects, broadening of the grain boundaries and allocation of the dispersed particles which are represented as point objects in the images. The processes of structural degradation lead to an increase in the range of changes in the components of the multifractal spectra. High values of complex indicators of structural arrangement indicate to an increase in heterogeneity and randomness at the micro-scale level, but at the same time, to manifestation of the ordered combinations of individual submicrostructures. Those structural transformations adapt the material to external impacts and provide the highest reliability and fracture resistance of the material.

Download Full-text

Investigation of the microstructure evolution in TP347HFG austenitic steel at 700°C and its characterization method

High Temperature Materials and Processes ◽

10.1515/htmp-2021-0013 ◽

2021 ◽

Vol 40 (1) ◽

pp. 12-22

Author(s):

Yuetao Zhang ◽

Tingbi Yuan ◽

Yawei Shao ◽

Xiao Wang

Keyword(s):

Austenitic Steel ◽

Aging Time ◽

Microstructure Evolution ◽

Precipitate Phase ◽

Dispersion Strengthening ◽

Micro Hardness ◽

Dispersed Particles ◽

Nonlinear Ultrasonic ◽

The Matrix ◽

Solution Strengthening

Abstract This article reports the microstructure evolution in TP347HFG austenitic steel during the aging process. The experiments were carried out at 700°C with different aging time from 500 to 3,650 h. The metallographic results show that the coherent twin and incoherent twin are existed in the original TP347HFG grains, while they gradually vanished with the increase of the aging time. After aging for 500 h, a lot of fine, dispersed particles precipitated from the matrix, but they disappeared after aging for 1,500 h. When the aging time extend to 3,650 h, the precipitates appeared apparently coarse in TP347HFG steel, which include the M23C6 and σ phase; besides, the micro-hardness of TP347HFG also changes during the aging, which was closely related to the effect of dispersion strengthening and solution strengthening. The results of the nonlinear ultrasonic measurement reveal that the β′ of TP347HFG steel was also changed with the aging time. It first increased at 0–500 h, then reduced later, and increased finally at 1,500–3,650 h. The variation of β′ in TP347HFG was influenced by a combined effect of the twin microstructure and the precipitate phase, which indicate that the nonlinear ultrasonic technique can be utilized to characterize the microstructure evolution in TP347HFG.

Download Full-text