Analysis of Infiltration, Solidification, and Remelting of a Pure Metal in Subcooled Porous Preform

2010 ◽  
Vol 31 (7) ◽  
pp. 555-563 ◽  
Author(s):  
Yuwen Zhang ◽  
Piyasak Damronglerd ◽  
Mo Yang
Keyword(s):  
Pure Metal ◽  
Porous Preform

Infiltration and Solidification/Remelting of a Pure Metal in a Two-Dimensional Porous Preform

1996 ◽  
Vol 118 (1) ◽  
pp. 173-180 ◽  
Author(s):  
X. Tong ◽  
J. A. Khan
Keyword(s):  
Transfer Problem ◽  
Applied Pressure ◽  
Pure Metal ◽  
Matrix Composites ◽  
Two Dimensional ◽  
Porous Preform ◽  
Operating Variables ◽  
Aspect Ratios ◽  
Infiltration Front ◽  
Energy Equations

Infiltration and solidification/remelting of a pure metal in a two-dimensional porous preform are modeled numerically. It is assumed that under the action of constant applied pressure, the flow of liquid metal through the preform is within the range of the validity of Darcy’s Law. The distinguishing feature of this flow and heat transfer problem is the existence of two moving fronts: the infiltration front and the remelting front. The governing momentum and energy equations are nondimensionalized and cast into a Body-Fitted Coordinates (BFC) systems to deal with the transient and irregular physical domains. The dimensionless groups that govern the infiltration and remelting processes are: the dimensionless pressure difference, the dimensionless melting temperature, the preform permeability ratio, porosity, and the geometric parameters (inlet gate size, and the preform aspect ratio). A computational code has been developed to solve the problem and is verified by using the available published results. The key parameters describing the physical phenomena, i.e., the infiltration front and remelting front evolution, the total infiltration time, and the remelting region size, are presented as a function of the operating variables for two different aspect ratios. The results can be used to optimize the infiltration processing of Metal–Matrix Composites and other related manufacturing processes.

Microstructure of sputter deposited Ni-Sb ohmic contacts on GaAs

1989 ◽  
Vol 47 ◽  
pp. 450-451
Author(s):  
S. Yegnasubramanian ◽  
V.C. Kannan ◽  
R. Dutto ◽  
P.J. Sakach
Keyword(s):  
High Performance ◽  
Ohmic Contacts ◽  
Surface Defects ◽  
Pure Metal ◽  
Device Fabrication ◽  
Native Oxide ◽  
Metal Thin Films ◽  
Recent Developments ◽  
Different Temperatures ◽  
Sputter Deposited

Recent developments in the fabrication of high performance GaAs devices impose crucial requirements of low resistance ohmic contacts with excellent contact properties such as, thermal stability, contact resistivity, contact depth, Schottky barrier height etc. The nature of the interface plays an important role in the stability of the contacts due to problems associated with interdiffusion and compound formation at the interface during device fabrication. Contacts of pure metal thin films on GaAs are not desirable due to the presence of the native oxide and surface defects at the interface. Nickel has been used as a contact metal on GaAs and has been found to be reactive at low temperatures. Formation Of Ni2 GaAs at 200 - 350C is reported and is found to grow epitaxially on (001) and on (111) GaAs, but is shown to be unstable at 450C. This paper reports the investigations carried out to understand the microstructure, nature of the interface and composition of sputter deposited and annealed (at different temperatures) Ni-Sb ohmic contacts on GaAs by TEM. Attempts were made to correlate the electrical properties of the films such as the sheet resistance and contact resistance, with the microstructure. The observations are corroborated by Scanning Auger Microprobe (SAM) investigations.

scholarly journals Phosphate Buffer Solubility and Oxidative Potential of Single Metals or Multielement Particles of Welding Fumes

Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 30
Author(s):  
Manuella Ghanem ◽  
Esperanza Perdrix ◽  
Laurent Yves Alleman ◽  
Davy Rousset ◽  
Patrice Coddeville
Keyword(s):  
Transition Metals ◽  
Phosphate Buffer ◽  
Soluble Fraction ◽  
Certified Reference Materials ◽  
Health Effect ◽  
Oxidative Capacity ◽  
Pure Metal ◽  
Welding Fumes ◽  
Oxidative Potential ◽  
Potential Health

To evaluate the chemical behavior and the health impact of welding fumes (WF), a complex and heterogeneous mixture of particulate metal oxides, two certified reference materials (CRMs) were tested: mild steel WF (MSWF-1) and stainless steel WF (SSWF-1). We determined their total chemical composition, their solubility, and their oxidative potential in a phosphate buffer (PB) solution under physiological conditions (pH 7.4 and 37 °C). The oxidative potential (OPDTT) of WF CRMs was evaluated using an acellular method by following the dithiothreitol (DTT) consumption rate (µmol DTT L−1 min−1). Pure metal salts present in the PB soluble fraction of the WF CRMs were tested individually at equivalent molarity to estimate their specific contribution to the total OPDTT. The metal composition of MSWF-1 consisted mainly of Fe, Zn, Mn, and Cu and the SSWF-1 composition consisted mainly of Fe, Mn, Cr, Ni, Cu, and Zn, in diminishing order. The metal PB solubility decreased from Cu (11%) to Fe (approximately 0.2%) for MSWF-1 and from Mn (9%) to Fe (<1%) for SSWF-1. The total OPDTT of SSWF-1 is 2.2 times the OPDTT of MSWF-1 due to the difference in oxidative capacity of soluble transition metals. Cu (II) and Mn (II) are the most sensitive towards DTT while Cr (VI), Fe (III), and Zn (II) are barely reactive, even at higher concentrations. The OPDTT measured for both WF CRMs extracts compare well with simulated extracts containing the main metals at their respective PB-soluble concentrations. The most soluble transition metals in the simulated extract, Mn (II) and Cu (II), were the main contributors to OPDTT in WF CRMs extracts. Mn (II), Cu (II), and Ni (II) might enhance the DTT oxidation by a redox catalytic reaction. However, summing the main individual soluble metal DTT response induces a large overestimation probably linked to modifications in the speciation of various metals when mixed. The complexation of metals with different ligands present in solution and the interaction between metals in the PB-soluble fraction are important phenomena that can influence OPDTT depletion and therefore the potential health effect of inhaled WF.

Pure Metal Chelate Solutions by Ion Exchange

2008 ◽  
Vol 47 (4) ◽  
pp. 1277-1282
Author(s):  
George M. St. George ◽  
Chen-Chou Chiang ◽  
David A. Wilson
Keyword(s):  
Ion Exchange ◽  
Metal Chelate ◽  
Pure Metal

Dynamic Indentation of Copper and an Aluminium Alloy with a Conical Projectile at Elevated Temperatures

1965 ◽  
Vol 180 (1) ◽  
pp. 285-294 ◽  
Author(s):  
F. U. Mahtab ◽  
W. Johnson ◽  
R. A. C. Slater
Keyword(s):  
Strain Rate ◽  
Aluminium Alloy ◽  
Temperature Coefficient ◽  
Elevated Temperatures ◽  
Dynamic Pressure ◽  
Pure Metal ◽  
Dynamic Indentation ◽  
Strain Rate Effects ◽  
Dynamic Temperature ◽  
Temperature Range

The dynamic indentation of copper (B.S. 1433) and an aluminium alloy (B.S. 1476 HE 10) has been investigated, using cylindro-conical projectiles fired from an air-actuated gun. The experiments were performed with impact velocities varying between 1000 and 2500 in/s and at elevated temperatures up to 600°C for the copper and 550°C for the aluminium alloy. The magnitude of the corresponding range of mean strain rate was then 103-104/s, depending upon the material; impact velocity and temperature (see Appendix I). For the range of impact velocities investigated no consequential transition temperature † was encountered. The dynamic temperature coefficient† thus remained constant throughout the test temperature range for each material. This dynamic temperature coefficient was found to be equal to the static temperature coefficient corresponding to the sub-transitional temperature range for the respective materials. The mean effective dynamic indentation pressure is shown to decrease with temperature but the ratio of this dynamic pressure to the static indentation pressure increases with temperature. Strain rate effects for both materials were negligible for sub-transitional temperatures but become important at super-transitional temperatures. It was observed that the parameters on which the strain rate effect depends are in some way related to the absolute melting point of a pure metal.

Sign in / Sign up

Export Citation Format

Share Document