scholarly journals PHYSICO-CHEMICAL BASES OF ELECTROLYTIC SYNTHESIS OF CARBON NANOMATERIALS FROM MOLTEN SALTS. Part 1

2019 ◽  
Vol 85 (2) ◽  
pp. 69-79
Author(s):  
Inessa Novoselova ◽  
Serhii Kuleshov
Keyword(s):  
Solid Solution ◽  
Alkali Metal ◽  
High Speed ◽  
Carbon Nanomaterials ◽  
Carbon Deposition ◽  
Carbide Phases ◽  
Physico Chemical ◽  
Graphite Deposition ◽  
Predominant Process ◽  
Oxide Ions

An analysis of the decomposition potentials of lithium, sodium, potassium, calcium, barium, and magnesium carbonates with different versions of cathode products (elemental carbon, carbon monoxide, metal and carbide) in the range of 300-1900 K showed that for K2CO3 deposition of alkali metal on the cathode is most energetically profitable process at all temperatures. For Na2CO3 it is possible to obtain carbon at T < 1000 K. With temperature increase, the predominant process is the reduction of alkali metal. For Li2CO3, CaCO3, BaCO3, MgCO3 at T < 950 °C carbon deposition will be more advantageous, at higher temperatures reduction up to CO will be more advantageous. The decomposition of CO2 flows at more positive potentials compared with carbonate systems. However, low activity of CO2 in carbonate-containing melts will prevent the significant contribution of this reaction to the electrode process. Thermodynamic calculations of the dependence of the carbon deposition potentials from carbonate anion on the acidity of the melt (concentration of oxide ions) show the possibility of displacing this potential up to 0.8 V by changing the acid-base properties of the melt. On the basis of the analysis of binary phase diagrams, Me–C and MeC–C, criteria for selecting the cathode material for generation of the tubular structure of graphite are established. The diagrams should contain: (1) – solid solutions of C–Me at a temperature of 700–900 °C and sufficient solubility of carbon (up to ~ 1 at.%) in the metal should be observed; (2) – after saturation of the solid solution with carbon, the precipitation (precipitation) of graphite from the metal should occur without the formation of intermediate carbide phases; (3) – in the case of the formation of carbides, the diffusion of carbon in the solid solution С–Ме and in the carbide phase MeС should flow with high speed and quickly reach the concentration of carbon saturation for graphite deposition.

Metallographic analysis of M2 high speed steel granules

2019 ◽  
pp. 78-85
Author(s):  
L. E. Afanasieva
Keyword(s):  
Solid Solution ◽  
Cellular Structure ◽  
High Speed ◽  
Solution Structure ◽  
Supersaturated Solid Solution ◽  
High Speed Steel ◽  
Metallographic Analysis ◽  
M2 High Speed Steel ◽  
Melt Composition

The article is devoted to the metallographic analysis of the M2 high-speed steel granules. The study is based on the investigation of the microstructure of the M2 high-speed steel granules obtained by melt atomization. It is demonstrated that granules of similar size can harden both by chemically separating and chemically non-separating mechanism. These last ones have supersaturated solid solution structure of the liquid melt composition, a dispersed dendritic-cellular structure and an increased microhardness HV = 10267±201 MPa.

scholarly journals Physico-Chemical Bases Cultivation Variable-gap Semiconductor Solid Solution Si1−xGex from the Liquid Phase

2020 ◽  
Vol 6 (9) ◽  
pp. 10-17
Author(s):  
A. Razzakov ◽  
A. Matnazarov ◽  
M. Latipova ◽  
A. Japakov
Keyword(s):  
Solid Solution ◽  
Liquid Phase ◽  
Growth Direction ◽  
Si Substrates ◽  
Growth Modes ◽  
Physico Chemical ◽  
Technological Growth ◽  
Crystal Films ◽  
Semiconductor Solid Solution ◽  
Film Interface

Abstract. Single-crystal films of a graded-gap solid solution Si1-xGex (0 <x <1) was grown on Si substrates from limited tin, gallium solution-melt. Accordingly, liquid phase epitaxy method was applied in the process. The formation of dislocations, grown under various technological conditions, at the substrate-film interface along the growth direction of the Si1-xGex solid solution was studied. Optimal technological growth modes for obtaining crystalline perfect epitaxial layers and structures are given.

scholarly journals Microstructure and mechanical properties of high-manganese-containing high-speed twin-roll cast Al-Mn-Si alloy strips and their cold-rolled sheets

2020 ◽  
Vol 326 ◽  
pp. 06004
Author(s):  
T.Ha Nguyen ◽  
Ram Song ◽  
Yohei Harada ◽  
Shinji Muraishi ◽  
Shinji Kumai ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
High Speed ◽  
Solid Solution Hardening ◽  
Columnar Dendrite ◽  
Dispersion Hardening ◽  
High Manganese ◽  
Solution Hardening ◽  
Cold Rolled ◽  
Twin Roll

Al-Mn based alloys with high-manganese content are expected to have improved mechanical properties due to solid solution hardening and/or dispersion hardening. However, the increase of Mn solubility of the alloy is difficult by using the conventional DC casting. In order to solve this problem, in the present study, we focused on the twin-roll casting method which is characterized by high cooling rates. Several kinds of high Mn-containing Al-Mn-Si alloy strips were fabricated by using a vertical-type high-speed twin-roll caster equipped with a pair of water-cooled copper rolls. Direct temperature measurement of the liquid melt during the casting was also performed. The alloy strips of various compositions containing up to 4 Mn and 2 Si (wt%) were successfully obtained. By observing the microstructure of the cross section of the strip, we found the characteristic solidified structure. The solidified structure consisted of three layers. Two solidified shells with a columnar dendrite structure grew from the roll surfaces toward the strip center. In the mid-thickness region, the band structure consisting of equiaxed dendrites and globular grains was observed between the solidified shells. Very fine primary particles were observed in the matrix near the strip surface, while, relatively coarse particles with blocky and needle-like shape were observed in the central band of the as-cast strip. The electric conductivity measurement was performed for the as-cast strips. Mn solubility in Al matrix was estimated from the obtained values. The estimated Mn solubility in the Al-2Mn-xSi strips was between 1.5 ~ 1.8wt% Mn. It was over 1.43wt%Mn for the Al-4Mn-xSi strips. We found that the Mn solubility of the as-cast strips was considerably high. The strips were cold-rolled to the sheets and then annealed at various conditions. They were subjected to the tensile tests, and the effects of solid solution hardening and dispersion hardening are discussed.

scholarly journals Controllable synthesis of pomelo peel-based aerogel and its application in adsorption of oil/organic pollutants

2019 ◽  
Vol 6 (2) ◽  
pp. 181823 ◽  
Author(s):  
Guangyu Shi ◽  
Yizhu Qian ◽  
Fengzhi Tan ◽  
Weijie Cai ◽  
Yuan Li ◽  
...  
Keyword(s):  
High Speed ◽  
Chemical Properties ◽  
Absorption Capacity ◽  
High Porosity ◽  
X Ray Diffraction ◽  
Water Separation ◽  
Physico Chemical ◽  
Wide Range ◽  
Oil Water Separation ◽  
Oil Water

Oil/water separation is a field of high significance as it might efficiently resolve the contamination of industrial oily wastewater and other oil/water pollution. In this paper, an environmentally-friendly hydrophobic aerogel with high porosity and low density was successfully synthesized with renewable pomelo peels (PPs) as precursors. Typically, a series of sponge aerogels (HPSA-0, HPSA-1 and HPSA-2) were facilely prepared via high-speed dispersion, freeze-drying and silanization with methyltrimethoxysilane. Indeed, the physical properties of aerogel such as density and pore diameter could be tailored by different additives (filter paper fibre and polyvinyl alcohol). Hence, their physico-chemical properties including internal morphology and chemical structure were characterized in detail by Fourier transform infrared, Brunauer–Emmett–Teller, X-ray diffraction, scanning electron microscope, Thermal gravimetric analyzer (TG) etc. Moreover, the adsorption capacity was further determined and the results revealed that the PP-based aerogels presented excellent adsorption performance for a wide range of oil products and/or organic solvents (crude oil 49.8 g g −1 , soya bean oil 62.3 g g −1 , chloroform 71.3 g g −1 etc.). The corresponding cyclic tests showed the absorption capacity decreased slightly from 94.66% to 93.82% after 10 consecutive cycles, indicating a high recyclability.

scholarly journals Influence of Dispersing Method on the Quality of Nano-Admixtures Homogenization in Cement Matrix

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4865
Author(s):  
Elżbieta Horszczaruk ◽  
Paweł Łukowski ◽  
Cyprian Seul
Keyword(s):  
High Speed ◽  
Mechanical Performance ◽  
Chemical Properties ◽  
Cement Composite ◽  
Cement Matrix ◽  
Cement Composites ◽  
Nano Sio2 ◽  
Mechanical Stirring ◽  
Physico Chemical ◽  
Nano Fe3o4

In recent years, a nano-modification of the cement composites allowed to develop a number of new materials. The use of even small amount of nano-admixture makes possible not only to improve the physico-mechanical properties of the cement materials, but also to obtain the composite with high usability, optimised for the given application. The basic problem of nano-modification of the cement composites remains the effectiveness of dispersing the nanomaterials inside the cement matrix. This paper deals with the effect of the type and size of the nanoparticles on the tendency to their agglomeration in the cement matrix. The main techniques and methods of dispersing the nanomaterials are presented. It has been demonstrated, on the basis of the results of testing of three nanomodifiers of 0D type (nano-SiO2, nano-Fe3O4 and nano-Pb3O4), how the structure and properties of the nanomaterial affect the behaviour of the particles when dissolving in the mixing water and applying a superplasticiser. The nanoparticles had similar size of about 100 nm but different physico-chemical properties. The methods of dispersing covered the use of high-speed mechanical stirring and ultrasonication. The influence of the method of nano-modifier dispersing on the mechanical performance of the cement composite has been presented on the basis of the results of testing the cement mortars modified with 3% admixture of nano-SiO2.

scholarly journals Self-Assembling Peptides and Carbon Nanomaterials Join Forces for Innovative Biomedical Applications

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4084
Author(s):  
Petr Rozhin ◽  
Costas Charitidis ◽  
Silvia Marchesan
Keyword(s):  
Carbon Nanostructures ◽  
Biomedical Applications ◽  
Carbon Nanomaterials ◽  
Chemical Properties ◽  
Building Blocks ◽  
Research Areas ◽  
Self Assembling ◽  
Concise Review ◽  
Physico Chemical ◽  
Great Progress

Self-assembling peptides and carbon nanomaterials have attracted great interest for their respective potential to bring innovation in the biomedical field. Combination of these two types of building blocks is not trivial in light of their very different physico-chemical properties, yet great progress has been made over the years at the interface between these two research areas. This concise review will analyze the latest developments at the forefront of research that combines self-assembling peptides with carbon nanostructures for biological use. Applications span from tissue regeneration, to biosensing and imaging, and bioelectronics.

Influence of thermal cycling modes on VK8 hard alloy mechanical and tribological properties

2020 ◽  
pp. 55-65
Author(s):  
S. I. Bogodukhov ◽  
E. S. Kozik ◽  
E. V. Svidenko
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Wear Resistance ◽  
Thermal Cycling ◽  
Hard Alloy ◽  
Tribological Properties ◽  
High Speed ◽  
Metal Cutting ◽  
Hard Alloys ◽  
Mechanical And Tribological Properties

Hard alloys are popular materials widely used in the toolmaking industry. Refractory carbides included in their composition make carbide tools very hard (80 to 92 HRA) and heat-resistant (800 to 1000 °С) so as they can be used at cutting speeds several times higher than those used for high-speed steels. However, hard alloys differ from the latter by lower strength (1000 to 1500 MPa) and the absence of impact strength, and this constitutes an urgent problem. We studied the influence of thermal cycling modes on the mechanical and tribological properties of VK8 (WC–8Co) hard alloy used in the manufacture of cutters and cutting inserts for metal working on metal-cutting machines. As the object of study, we selected 5×5×35 mm billets made of VK8 (WC–8Co) alloy manufactured by powder metallurgy methods at Dimitrovgrad Tool Plant. The following criteria were selected for heat treatment mode evaluation: Vickers hardness, flexural strength, and mass wear resistance (as compared to the wear of asreceived samples that were not heat treated). Plates in the initial state and after heat treatment were subjected to abrasion tests. Wear results were evaluated by the change in the mass of plates. Regularities of the influence of various time and temperature conditions of heat treatment on the tribological properties of products made of VK group tungsten hard alloys were determined. An increase in the number of thermal cycling cycles improved such mechanical properties of the VK8 hard alloy as strength and hardness. When repeating the cycles five times, an increase in abrasive wear resistance was obtained compared to the initial nonheat-treated sample. The elemental composition of the VK8 hard alloy changed insignificantly after thermal cycling, only a slight increase in oxygen was observed on the surface of plates. The grain size after thermal cycling increased in comparison with the initial VK8 hard alloy. It was found that VK8 hard alloy thermocyclic treatment leads to a change in the phase composition. X-ray phase analysis showed the presence of a large amount of α-Co with an hcp-type lattice on the surface of a hard alloy and a solid solution of WC in α-Co. A change in the cobalt modification ratio causes a decrease in microstresses. An analysis of the carbide phase structure state showed that the size of crystallites and microstresses changed after thermal cycling. The lattice constant of the cobalt cubic solid solution decreased, which may indicate a decrease in the amount of tungsten carbide and carbon dissolved in it. Statistical processing of experimental results included the calculation of the average value of the mechanical property, its dispersion and standard deviation in the selected confidence interval.

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