scholarly journals Effect of Mechanical Activation on Ti3AlC2 Max Phase Formation under Self-Propagating High-Temperature Synthesis

2015 ◽  
Vol 17 (3) ◽  
pp. 233 ◽  
Author(s):  
A.Yu. Potanin ◽  
P.A. Loginov ◽  
E.A. Levashov ◽  
Yu.S. Pogozhev ◽  
E.I. Patsera ◽  
...  
Keyword(s):  
Mechanical Activation ◽  
Front Propagation ◽  
Max Phase ◽  
Structural Defects ◽  
Powder Mixtures ◽  
Maximum Heat ◽  
High Temperature Synthesis ◽  
Maximum Heat Release ◽  
Kinetics Of ◽  
Pressing Technology

<p>In this study, we have investigated the effect of various mechanical activation (MA) modes on phase and structure formation in powder mixtures made up to produce Ti<sub>3</sub>AlC<sub>2</sub> MAX phase. The optimal MA duration has been established which results in the maximum heat release under SHS due to accumulation of structural defects leading to the growth of internal energy. The effect of MA on the character and kinetics of combustion front propagation has been investigated. It was shown that following pretreatment of a powder mixture in a planetary ball mill, the combustion mode changes from stationary to a pulsating combustion and, consequently, the combustion rate decreases. The burning-out of the sample is partial and with interruptions (depressions). Force SHS-pressing technology was used for obtaining of compacted samples with homogeneous structure based on Ti<sub>3</sub>AlC<sub>2</sub>.</p>

scholarly journals Development of Pore-Free Ti-Si-C MAX/Al-Si Composite Materials Manufactured by Squeeze Casting Infiltration

2019 ◽  
Vol 28 (10) ◽  
pp. 6248-6257 ◽  
Author(s):  
Anna Dmitruk ◽  
Krzysztof Naplocha ◽  
Andrzej Żak ◽  
Agata Strojny-Nędza ◽  
Hajo Dieringa ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Composite Materials ◽  
Squeeze Casting ◽  
Reference Sample ◽  
Xrd Analysis ◽  
Max Phase ◽  
Structural Defects ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
High Flowability

Abstract Open-porous MAX phase skeletons from Ti3SiC2 were manufactured by Microwave-Assisted Self-propagating High-temperature Synthesis (MASHS) and subsequently subjected to squeeze casting infiltration with an Al-Si lightweight casting alloy (EN AC-44200). This alloy was chosen due to its high flowability, corrosion resistance and good machinability. The manufactured composites, together with a reference sample of the original alloy, underwent testing of thermal properties, including thermal conductivity and diffusivity, specific heat and thermal expansion in the temperature range 50-500 °C, which corresponds to the expected working temperatures of the material. The fabricated AlSi/Ti3SiC2 composites have significantly increased thermal stability, with coefficients of thermal expansion (approximately 10-11 × 10−6 °C−1) half that of the original alloy. As regards mechanical properties, the instrumental Young’s modulus and Vickers hardness of the composite materials are 170.8 and 8.5 GPa, respectively. Moreover, the microstructure and phase composition, structural defects and potential impacts between constituents of the manufactured composites were characterized using SEM, TEM and STEM microscopy and EDS and XRD analysis.

scholarly journals Risk Analysis of Road Tunnels: A Computational Fluid Dynamic Model for Assessing the Effects of Natural Ventilation

2020 ◽  
Vol 11 (1) ◽  
pp. 32
Author(s):  
Ciro Caliendo ◽  
Gianluca Genovese ◽  
Isidoro Russo
Keyword(s):  
Natural Ventilation ◽  
Fluid Dynamic ◽  
Movement Time ◽  
Radiant Heat ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Road Tunnels ◽  
Maximum Heat Release ◽  
Computational Fluid Dynamics Cfd ◽  
Time Required

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels.

Extending the SHS combustion concentration limits in Ti + C + Fe powder mixtures by preliminary mechanical activation

2020 ◽  
Vol 25 ◽  
pp. 458-460
Author(s):  
A.V. Baranovskiy ◽  
G.A. Pribytkov ◽  
M.G. Krinitcyn ◽  
V.V. Homyakov ◽  
G.O. Dankovcev
Keyword(s):  
Mechanical Activation ◽  
Powder Mixtures ◽  
Preliminary Mechanical Activation ◽  
Concentration Limits

Effect of mechanical activation on the leaching kinetics of niobium-bearing mineralisation in KOH hydrothermal system

2018 ◽  
Vol 181 ◽  
pp. 123-129 ◽  
Author(s):  
Xiaohui Wang ◽  
Yujuan Jia ◽  
Shuhua Ma ◽  
Shili Zheng ◽  
Qing Sun
Keyword(s):  
Mechanical Activation ◽  
Hydrothermal System ◽  
Leaching Kinetics ◽  
Kinetics Of
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