The effect of titanium-carbon mixture mechanical activation on SHS pressing parameters and consolidated titanium carbide microstructure

2021 ◽  
pp. 38-46
Author(s):  
Yu. V. Bogatov ◽  
V. A. Shcherbakov ◽  
I. D. Kovalev
Keyword(s):  
Titanium Carbide ◽  
Mechanical Activation ◽  
Relative Density ◽  
Burning Rate ◽  
Ball Mill ◽  
Combustion Process ◽  
Refractory Product ◽  
Stoichiometric Mixture ◽  
Anomalous Increase ◽  
Average Size

The paper studies the effect of mechanical activation (MA) modes when stirring a stoichiometric mixture of titanium and soot powders in a ball mill on the properties of mixtures, combustion parameters, relative density, and the microstructure of consolidated titanium carbide samples obtained by SHS. MA conditions for Ti + C reaction mixtures in a ball mill were determined. An increase in the mass of grinding bodies activates the MA mechanism. It was shown that the greatest effect from MA was obtained with a two-stage preparation of mixtures: firstly, the titanium powder was activated separately, then the components were mixed together, and this process included not only their mixing, but also soot powder activation. It was found that combustion behavior is affected by the activation of not only titanium, but also soot. After MA of both components, an anomalous increase in the burning rate (more than 100 cm/s) was found on pressed samples. At the bulk density, there was no effect of MA on the mixture combustion process, since in this case the burning rate of all mixtures was in the range of 1.5–2.5 cm/s. It was revealed that MA of reagents for pressed samples leads to an increase in the combustion temperature, an increase in the relative density of the consolidated refractory product to 93–95 %, and a decrease in the average size of TiC grains. A decrease in the residual porosity of consolidated TiC is due to an increase in the hot pressing temperature and plasticity of the product synthesized during the reaction mixture combustion after MA. The main reason is an increase in the exothermic interaction rate. It was shown that MA when mixing reagents makes it possible to control combustion parameters, the microstructure of consolidated products and opens up new opportunities for obtaining refractory materials featuring a unique structure and properties by SHS pressing.

scholarly journals Supercritical Antisolvent Processing of Nitrocellulose: Downscaling to Nanosize, Reducing Friction Sensitivity and Introducing Burning Rate Catalyst

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1386 ◽  
Author(s):  
Oleg Dobrynin ◽  
Mikhail Zharkov ◽  
Ilya Kuchurov ◽  
Igor Fomenkov ◽  
Sergey Zlotin ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Burning Rate ◽  
High Speed ◽  
Combustion Process ◽  
Supercritical Antisolvent ◽  
Supercritical Fluid Technology ◽  
Improved Performance ◽  
Average Size ◽  
Friction Sensitivity ◽  
Nanosized Iron

A supercritical antisolvent process has been applied to obtain the nitrocellulose nanoparticles with an average size of 190 nm from the nitrocellulose fibers of 20 μm in diameter. Compared to the micron-sized powder, nano-nitrocellulose is characterized with a slightly lower decomposition onset, however, the friction sensitivity has been improved substantially along with the burning rate increasing from 3.8 to 4.7 mm·s−1 at 2 MPa. Also, the proposed approach allows the production of stable nitrocellulose composites. Thus, the addition of 1 wt.% carbon nanotubes further improves the sensitivity of the nano-nitrocellulose up to the friction-insensitive level. Moreover, the simultaneous introduction of carbon nanotubes and nanosized iron oxide catalyzes the combustion process evidenced by a high-speed filming and resulting in the 20% burning rate increasing at 12 MPa. The presented approach to the processing of energetic nanomaterials based on the supercritical fluid technology opens the way to the production of nitrocellulose-based nanopowders with improved performance.

scholarly journals Hydrogen application in internal combustion engines

2020 ◽  
Vol 21 (1) ◽  
pp. 14-19
Author(s):  
Arthur R. Asoyan ◽  
Igor K. Danilov ◽  
Igor A. Asoyan ◽  
Georgy M. Polishchuk
Keyword(s):  
Burning Rate ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Hydrocarbon Fuel ◽  
Internal Combustion ◽  
Technical Solution ◽  
Combustion Engines ◽  
Environmental Friendliness ◽  
Petroleum Origin ◽  
Order Of Magnitude

A technical solution has been proposed to reduce the consumption of basic hydrocarbon fuel, to improve the technical, economic and environmental performance of internal combustion engines by affecting the combustion process of the fuel-air mixture with a minimum effective mass fraction of hydrogen additive in the fuel-air mixture. The burning rate of hydrogen-air mixtures is an order of magnitude greater than the burning rate of similar mixtures based on gasoline or diesel fuel, compared with the former, they are favorably distinguished by their greater detonation stability. With minimal additions of hydrogen to the fuel-air charge, its combustion time is significantly reduced, since hydrogen, having previously mixed with a portion of the air entering the cylinder and burning itself, effectively ignites the mixture in its entirety. Issues related to the accumulation of hydrogen on board the car, its storage, explosion safety, etc., significantly inhibit the development of mass production of cars using hydrogen fuel. The described technical solution allows the generation of hydrogen on board the car and without accumulation to use it as an additive to the main fuel in internal combustion engines. The technical result is to reduce the consumption of hydrocarbon fuels (of petroleum origin) and increase the environmental friendliness of the car due to the reduction of the emission of harmful substances in exhaust gases.

Comparison of Novel Conductive Open- and Closed-Porous PPy-PLA Composites

2009 ◽  
Author(s):  
Christine Chan ◽  
Ellen Chan ◽  
Weijia Zhang ◽  
Hani E. Naguib
Keyword(s):  
Relative Density ◽  
In Situ Polymerization ◽  
Compression Molding ◽  
Salt Leaching ◽  
Conductive Composites ◽  
Order Of Magnitude ◽  
Density Values ◽  
Average Size ◽  
Porous Composites

This study compared the fabrication techniques and characterization of novel open- and closed-porous structures in PPy-PLA conductive composites. For the open-porous composites, PLA samples were fabricated using compression molding and salt leaching with varying salt-to-polymer mass ratios, which were subsequently coated with PPy by in situ polymerization of pyrrole and iron (III) chloride. For the closed-porous composites, a patterned structure of PPy within PLA was created using compression molding of PPy-coated PLA pellets, followed by gas saturation and foaming techniques in order to create the closed pores. Characterization of both porous composites included their physical, mechanical, and electrical properties. Results showed that the modulus increased with increasing relative density and decreasing open porosity. The open-porous composites had lower relative density values but higher open porosities compared to the closed-porous composites. The average size of the closed pores was approximately an order of magnitude larger than the open pores. Lastly, the open-porous composites had higher conductivity values than the closed-porous composites due to the greater surface area of the continuous conductive pathway. The comparisons between open- and closed-porous composites established their characteristic properties for their future development in applications.

Synthesis and Characterization of Nanometer Copper Ferrite by Auto-Combustion

2011 ◽  
Vol 347-353 ◽  
pp. 3472-3476
Author(s):  
Guang Xiu Cao ◽  
Tian Liu ◽  
Qing Hong Zhang ◽  
Hong Zhi Wang
Keyword(s):  
Raw Materials ◽  
Combustion Process ◽  
Copper Nitrate ◽  
Copper Ferrite ◽  
X Ray Diffraction ◽  
Uniform Size ◽  
Simple Method ◽  
Transmission Electron ◽  
Auto Combustion ◽  
Average Size

A simple method for preparing nanoscale copper ferrite particles with narrow distribution and uniform size was developed by auto-combusting the precursor using copper nitrate, iron nitrate, and malic acid as raw materials. The constituents and the thermal decomposition process of the precursor were studied by Fourier transform infrared (FT-IR), thermogravimetry-differental thermal analysis (TG-DTA) and X-ray diffraction (XRD). The results showed that the carboxyl and nitrate ion take part in the reaction during the auto-combustion process. The precursor decomposed completely at about 199 °C, to yield single phase product. Transmission electron microscopy (TEM) indicated that the average size of the as-burnt sample was about 90 nm.

Combustion synthesis of mechanically activated powders in the Nb–Si system

2002 ◽  
Vol 17 (8) ◽  
pp. 1992-1999 ◽  
Author(s):  
Filippo Maglia ◽  
Chiara Milanese ◽  
Umberto Anselmi-Tamburini ◽  
Stefania Doppiu ◽  
Giorgio Cocco
Keyword(s):  
Mechanical Activation ◽  
Single Phase ◽  
Milling Time ◽  
Combustion Process ◽  
Temperature Wave ◽  
The Self ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Niobium Silicides ◽  
Reactant Powder

The effect of the mechanical activation of the reactants on the self-propagating high-temperature synthesis (SHS) of niobium silicides was investigated. SHS experiments were performed on reactant powder blends of composition Nb:Si = 1:2 and Nb:Si = 5:3 pretreated for selected milling times. A self-sustaining reaction could be initiated when a sufficiently long milling time was employed. At short milling times, the reactions self-extinguished or propagated in an unsteady mode. Combustion peak temperature, wave velocity, and product composition were markedly influenced by the length of the milling treatment. Single-phase products could be obtained for sufficiently long milling times. Observation of microstructural evolution in quenched reactions together with isothermal experiments allowed clarification of the mechanism of the combustion process and the role played by the mechanical activation of the reactants.

Microstructure and properties of pure and composite metal powders after mechanical activation in planetary ball mill

2014 ◽  
Author(s):  
Michail A. Korchagin ◽  
Ivan A. Ditenberg ◽  
Konstantin I. Denisov ◽  
Alexander N. Tyumentsev
Keyword(s):  
Mechanical Activation ◽  
Ball Mill ◽  
Planetary Ball Mill ◽  
Metal Powders ◽  
Microstructure And Properties

An Experimental Investigation on the Combustion Process of a Simulated Turbocharged Spark Ignition Natural Gas Engine Operated on Stoichiometric Mixture

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Hailin Li ◽  
Timothy Gatts ◽  
Shiyu Liu ◽  
Scott Wayne ◽  
Nigel Clark ◽  
...  
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Combustion Process ◽  
Propagation Speed ◽  
Spark Ignition ◽  
Boost Pressure ◽  
Stoichiometric Mixture ◽  
Process Data ◽  
Intake Pressure ◽  
Flame Propagation Speed

This research investigated the combustion process of an AVL Model LEF/Volvo 5312 single cylinder engine configured to simulate the operation of a heavy-duty spark ignition (SI) natural gas (NG) engine operated on stoichiometric mixture. The factors affecting the combustion process that were examined include intake pressure, spark timing (ST), and the addition of diluents including nitrogen (N2) and carbon dioxide (CO2) to the NG to simulate low British thermal unit (BTU) gases. The mixing of diluents with NG is able to slow down the flame propagation speed, suppress the onset of knock, and allow the engine to operate on higher boost pressure for higher power output. The addition of CO2 was more effective than N2 in suppressing the onset of knock and slowing down the flame propagation speed due to its high heat capacity. Boosting intake pressure significantly increased the heat release rate (HRR) evaluated on J/°CA basis which represents the rate of mass of fuel burning. However, its impact on the normalized HRR evaluated on %/°CA basis, representing the flame propagation rate, was relatively mild. Boosting the intake pressure from 1.0 to 1.8 bar without adding diluents increased the peak HRR to 1.96 times of that observed at 1.0 bar. The increase was due to the burning of more fuel (about 1.8 times), and the 12.9% increase in the normalized HRR. The latter was due to the shortened combustion duration from 23.6 to 18.2 °CA, a 22.9% reduction. The presence of 40% CO2 or N2 in their mixture with NG increased the peak cylinder pressure (PCP) limited brake mean effective pressure (BMEP) from 17.2 to about 20.2 bar. The combustion process of a turbocharged SI NG engine can be approximated by referring to the HRR measured under a naturally aspirated condition. This makes it convenient for researchers to numerically simulate the combustion process and the onset of knock of turbocharged SI NG engines using combustion process data measured under naturally aspirated conditions as a reference.

scholarly journals The influence of mechanical activation on sintering process of BaCO3-SrCO3-TiO2 system

2012 ◽  
Vol 44 (3) ◽  
pp. 271-280 ◽  
Author(s):  
Darko Kosanovic ◽  
N. Obradovic ◽  
J. Zivojinovic ◽  
A. Maricic ◽  
V.P. Pavlovic ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Mechanical Activation ◽  
Ball Mill ◽  
Sintering Process ◽  
Electrical Measurements ◽  
Air Atmosphere ◽  
Titanate Ceramics ◽  
Scanning Electron

In this article the influence of mechanical activation on sintering process of bariumstrontium-titanate ceramics has been investigated. Both non-activated and mixtures treated in a planetary ball mill for 5, 10, 20, 40, 80 and 120 minutes were sintered at 1100-1400?C for 2 hours in presence of air atmosphere. The influence of mechanical activation on phase composition and crystal structure has been analyzed by XRD, while the effect of activation and sintering process on microstructure was investigated by scanning electron microscopy. It has been established that temperature of 1100?C was too low to induce final sintering stage for this system. Electrical measurements have been conducted for the densest ceramics sintered at 1400?C for 2 hours.

scholarly journals THE PHYSIOLOGICAL AND HYGIENIC EVALUATION OF THE OPERATOR’S WORKING CONDITIONS IN THE SYNTHESIS OF CHROMIUM DISILICIDE NANOCRYSTALLINE POWDERS BY HIGH-ENERGETICAL MECHANOACTIVATION METHOD

2017 ◽  
pp. 89-95
Author(s):  
A. P. Yavorovskiy ◽  
N. V. Solokha ◽  
O. V. Demetskaya ◽  
I. M. Andrusishina
Keyword(s):  
Mechanical Activation ◽  
Technological Process ◽  
Working Conditions ◽  
Ball Mill ◽  
High Energy ◽  
Working Environment ◽  
Planetary Ball Mill ◽  
Emission Spectrometry ◽  
Activation Process ◽  
Plant Design

Objective: to carry out the physiological and hygienic evaluation of the working conditions of operators producing chromium disilicide nanopowders by high-energetical mechanoactivation method and to develop the preventive recommendations. Material and methods. The object of research was the technological process of producing nanocrystalline chromium disilicide powder within a planetary ball mill. The hygienic assessment of the technological process, technological equipment and psycho-physiologic evaluation of the working environment of the operators were carried out using the generally accepted psychophysiological, hygienic, and chronometer methods of study. The concentration of nanoparticles in the working area was measured using the diffusion aerosol spectrometer DAS-2702 («Aeronanoteh», Russia), the nanopowder particle size was measured by the device Analysette 12 DynaSizer («Fritsch», Germany), the chemical composition of air samples was determined by atomic emission spectrometry with inductively coupled plasma (ICP-AES) using the device «Ortima 2100 DV» («Perkin-Elmer», USA). Results. It was found out for the first time that the mechanical activation process was accompanied by emission of nano-sized chromium into the air of the working area, which had not been detected before the beginning of the work. The total concentration of nanoparticles in the main room was 1.6-1.9 times higher than that in the working area of the planetary ball mill and exceeded the test levels recommended for nanomaterials in European countries. Conclusion. The basic adverse factors in case of producing nanopowder of chromium disilicide by mechanoactivation method are presence of nanoparticles of metals in the workplace air and intensity of work. We have proposed hygienic recommendations which are aimed at improving the plant design for the high-energy mechanical activation in the direction of ensuring tightness, reduction of manual work operations, audible and visual signaling during the technological process.

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