scholarly journals Self-Consolidation Mechanism of Nanostructured Ti5Si3Compact Induced by Electrical Discharge

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
W. H. Lee ◽  
Y. W. Cheon ◽  
Y. H. Jo ◽  
J. G. Seong ◽  
Y. J. Jo ◽  
...  
Keyword(s):  
Electrical Discharge ◽  
Single Phase ◽  
External Pressure ◽  
Surface Oxide ◽  
Complete Conversion ◽  
Rapid Cooling ◽  
Pinch Force ◽  
Powder Particles ◽  
Solid Bulk ◽  
Solid Liquid

Electrical discharge using a capacitance of 450 μF at 7.0 and 8.0 kJ input energies was applied to mechanical alloyed Ti5Si3powder without applying any external pressure. A solid bulk of nanostructured Ti5Si3with no compositional deviation was obtained in times as short as 159 μsec by the discharge. During an electrical discharge, the heat generated is the required parameter possibly to melt the Ti5Si3particles and the pinch force can pressurize the melted powder without allowing the formation of pores. Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3compact. Three stepped processes during an electrical discharge for the formation of nanostructured Ti5Si3compact are proposed: (a) a physical breakdown of the surface oxide of Ti5Si3powder particles, (b) melting and condensation of Ti5Si3powder by the heat and pinch pressure, respectively, and (c) rapid cooling for the preservation of nanostructure. Complete conversion yielding a single phase Ti5Si3is primarily dominated by the solid-liquid mechanism.

scholarly journals Self-Consolidation and Surface Modification of Mechanical Alloyed Ti-25.0 at.% Al Powder Mixture by Using an Electro-Discharge Technique

2017 ◽  
Vol 62 (2) ◽  
pp. 1293-1297 ◽  
Author(s):  
S.Y. Chang ◽  
H.S. Jang ◽  
Y.H. Yoon ◽  
Y.H. Kim ◽  
J.Y. Kim ◽  
...  
Keyword(s):  
Surface Modification ◽  
Diffusion Process ◽  
Powder Mixture ◽  
Electrical Discharge ◽  
External Pressure ◽  
Solid Core ◽  
Input Energy ◽  
Electrical Discharges ◽  
Al Powder ◽  
Solid Bulk

AbstractElectrical discharges using a capacitance of 450 μF at 0.5, 1.0, and 1.5 kJ input energies were applied in a N2atmosphere to obtain the mechanical alloyed Ti3Al powder without applying any external pressure. A solid bulk of nanostructured Ti3Al was obtained as short as 160 μsec by the Electrical discharge. At the same time, the surface has been modified into the form of Ti and Al nitrides due to the diffusion process of nitrogen to the surface. The input energy was found to be the most important parameter to affect the formation of a solid core and surface chemistry of the compact.

scholarly journals Self-Consolidation Mechanism of Ti5Si3 Compact Obtained by Electro-Discharge-Sintering Directly from Physically Blended Ti-37.5 at.% Si Powder Mixture

2017 ◽  
Vol 62 (2) ◽  
pp. 1299-1302 ◽  
Author(s):  
S.Y. Chang ◽  
Y.W. Cheon ◽  
Y.H. Yoon ◽  
Y.H. Kim ◽  
J.Y. Kim ◽  
...  
Keyword(s):  
Oxide Film ◽  
Powder Mixture ◽  
External Pressure ◽  
The Self ◽  
Input Energy ◽  
Discharge Time ◽  
Powder Particles ◽  
Solid Bulk ◽  
Diffusion Of Impurities

AbstractCharacteristics of electro-discharge-sintering of the Ti-37.5at.% Si powder mixture was investigated as a function of the input energy, capacitance, and discharge time without applying any external pressure. A solid bulk of Ti5Si3was obtained only after in less than 129 μsec by the EDS process. During a discharge, the heat is generated to liquefy and alloy the particles, and which enhances the pinch pressure can condensate them without allowing a formation of pores. Three step processes for the self-consolidation mechanism during EDS are proposed; (a) a physical breakdown of oxide film on elemental as-received powder particles, (b) alloying and densifying the consolidation of powder particles by the pinch pressure, and (c) diffusion of impurities into the consolidated surface.

The Effect of Microwave Sintering Time to PM Aluminum Alloys

2015 ◽  
Vol 754-755 ◽  
pp. 240-244
Author(s):  
M.N. Derman ◽  
Syaza Nabilla Mohd Suhaimi ◽  
Zuraidawani Che Daud
Keyword(s):  
Microwave Sintering ◽  
Microwave Oven ◽  
Solid Particles ◽  
Binding Reaction ◽  
Aluminium Powder ◽  
Sintering Time ◽  
Conventional Sintering ◽  
Rapid Sintering ◽  
Powder Particles ◽  
Solid Liquid

Microwave sintering is new sintering technology method to produce Al alloys. The advantages of this method because of very short sintering time and less production cost compare to conventional sintering. However, the main problems in microwave sintering are required to be controlled sintering time due to rapid sintering mechanism. Therefore the effect of microwave sintering time to PM Aluminium will be studied. The compacted and sintered aluminium powder is placed in a microwave oven at a different period of 5 minutes, 10 minutes, 15 minutes and 20 minutes. Compression of 150 MPa is applied on aluminium powder to form pellets. Palette is shaped to 1cm in diameter and weighs 1g. SiC is placed together with aluminium samples in the microwave for the purpose of absorbing electromagnetic energy and is converted to heat. Results of different period sintering of aluminium pallet production altered physical properties of each sample. For a rapid sintering time, aluminium pallet does not show any binding reaction between powder particles. Whereas, for long microwave sintering period, solid particles phase change into solid-liquid phase caused by the movement and the formation of bonds between particles. Hence, this will be affecting the mechanical properties of the sample material.

Nano scale dynamics of bubble nucleation in confined liquid subjected to rapid cooling: Effect of solid-liquid interfacial wettability

2017 ◽  
Author(s):  
Mohammad Nasim Hasan ◽  
Kazi Fazle Rabbi ◽  
K. M. Mukut ◽  
Saiful Islam Tamim ◽  
A. H. M. Faisal
Keyword(s):  
Bubble Nucleation ◽  
Cooling Effect ◽  
Rapid Cooling ◽  
Nano Scale ◽  
Solid Liquid

scholarly journals Crystal Memory near Discontinuous Triacylglycerol Phase Transitions: Models, Metastable Regimes, and Critical Points

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5631
Author(s):  
David A. Pink ◽  
Marjorie Ladd-Parada ◽  
Alejandro G. Marangoni ◽  
Gianfranco Mazzanti
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Single Phase ◽  
Hydrocarbon Chain ◽  
Temperature Data ◽  
Recent Time ◽  
Recent Experimental Data ◽  
Hydrocarbon Chain Length ◽  
Discontinuous Phase ◽  
Solid Liquid

It is proposed that “crystal memory”, observed in a discontinuous solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystalline phases and a liquid TAG phase, in a superheated metastable regime. Such a coexistence has been detected. Solid crystals can act as heterogeneous nuclei onto which molecules can condense as the temperature is lowered. We outlined a mathematical model, with a single phase transition, that shows how the time-temperature observations can be explained, makes predictions, and relates them to recent experimental data. A modified Vogel-Fulcher-Tammann (VFT) equation is used to predict time-temperature relations for the observation of “crystal memory” and to show boundaries beyond which “crystal memory” is not observed. A plot of the lifetime of a metastable state versus temperature, using the modified VFT equation, agrees with recent time-temperature data. The model can be falsified through its predictions: the model possesses a critical point and we outline a procedure describing how it could be observed by changing the hydrocarbon chain length. We make predictions about how thermodynamic functions will change as the critical point is reached and as the system enters a crossover regime. The model predicts that the phenomenon of “crystal memory” will not be observed unless the system is cooled from a superheated metastable regime associated with a discontinuous phase transition.

Low-temperature synthesis and sintering of γ-Y2Si2O7

2006 ◽  
Vol 21 (6) ◽  
pp. 1443-1450 ◽  
Author(s):  
Ziqi Sun ◽  
Yanchun Zhou ◽  
Meishuan Li
Keyword(s):  
Single Phase ◽  
Synthesis Temperature ◽  
Densification Rate ◽  
Calcination Time ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Liquid Reaction ◽  
The Stability ◽  
Yttrium Disilicate ◽  
Solid Liquid

In this article, a novel pressureless solid-liquid reaction method is presented for preparation of yttrium disilicate (γ-Y2Si2O7). Single-phase γ-Y2Si2O7 powder was synthesized by calcination of SiO2 and Y2O3 powders with the addition of LiYO2 at 1400 °C for 4 h. The addition of LiYO2 significantly decreased the synthesis temperature, shortened the calcination time, and enhanced the stability of γ-Y2Si2O7. The sintering of these powders in air and O2 was studied by means of thermal mechanical analyzer. It is shown that the γ-Y2Si2O7 sintered in oxygen had a faster densification rate and a higher density than that sintered in air. Furthermore, single-phase γ-Y2Si2O7 with a density of 4.0 g/cm3 (99% of the theoretical density) was obtained by pressureless sintering at 1400 °C for 2 h in oxygen. Microstructures of the sintered samples are studied by scanning electron microscope.

Oxidation of PB-SN and PB-SN-in Alloys: Bulk VS. Grain boundary regions

1989 ◽  
Vol 167 ◽  
Author(s):  
D. A. Sluzewski ◽  
Y. A. Chang ◽  
V. C. Marcotte
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Tin Oxide ◽  
Single Phase ◽  
Surface Oxide ◽  
Scanning Auger Microscopy ◽  
Bulk Surface ◽  
Indium Oxides ◽  
Auger Microscopy ◽  
Argon Ion

AbstractAir oxidized Pb-Sn and Pb-Sn-In single phase alloys have been studied with scanning Auger microscopy. Line scans across grain boundaries combined with argon ion sputter etching revealed grain boundary oxidation. In the Pb-Sn samples, tin is preferentially oxidized with the grain boundary regions having a much higher percentage of tin oxide than the bulk surface oxide. In the Pb-Sn-In alloys, both tin and indium are preferentially oxidized with the grain boundary regions being enriched with tin and indium oxides.

Problems In Realistic Modelling Of Interfacial Reactions

1985 ◽  
Vol 54 ◽  
Author(s):  
Charles W. Allen ◽  
Gordon A Sargent
Keyword(s):  
Single Phase ◽  
Driving Forces ◽  
Thermodynamic Description ◽  
Nucleation Theory ◽  
Initial Reaction ◽  
Thermodynamic Prediction ◽  
Multiple Product ◽  
Solid Liquid ◽  
Reaction Processes ◽  
Reaction Problem

ABSTRACTFor modelling the reaction of chemically distinct materials in which intermediate alloy phases are formed a simple thermodynamic description is not adequate. Despite thermodynamic prediction of multiple product phases, a single phase generally forms first which is not necessarily that of greatest thermodynamic stability or of simplest structure. Such initial reaction processes may be modelled as metastable perltectoid (solid-solid) or perltectlc (solid-liquid) reactions, characterized by large thermodynamic driving forces with superimposed kinetic and morphological constraints. The interfacial reaction problem is reviewed in light of heterogeneous nucleation theory with emphasis on non-classical aspects.

Thermoelectric Performance of Half-Heusler TiNiSn Alloys Fabricated by Solid-Liquid Reaction Sintering

2010 ◽  
Vol 654-656 ◽  
pp. 2795-2798 ◽  
Author(s):  
Yoshisato Kimura ◽  
Chihiro Asami ◽  
Yaw Wang Chai ◽  
Yoshinao Mishima
Keyword(s):  
Figure Of Merit ◽  
Single Phase ◽  
Electrical Power ◽  
Reaction Sintering ◽  
Sintering Process ◽  
Liquid Reaction ◽  
Dimensionless Figure Of Merit ◽  
Maximum Value ◽  
Gas Atmosphere ◽  
Solid Liquid

A new fabrication process was proposed for half-Heusler type TiNiSn thermoelectric alloys. Based on the result that the TiNiSn phase can be formed easily at the Sn(Liquid)/TiNi(Solid) interface, the liquid-solid reaction-sintering process was developed using TiNi and Sn powders. The TiNi compound powders were prepared by the atomization method using argon gas atmosphere. We have fabrictaed nearly single-phase TiNiSn alloys and evaluated their thermoelectrical properties; the presnt TiNiSn alloys have large electrical power factor of about 3.5 mWm-1K-2, and the maximum value of dimensionless figure of merit, ZT = 0.67, can be achieved at around 700 K even without tuning of the carrier concentration through alloying elements.

Sign in / Sign up

Export Citation Format

Share Document