Electrical conductivity, self-diffusion, and volume expansion of alkali halides at the melting point

1988 ◽  
Vol 9 (5) ◽  
pp. 825-838 ◽  
Author(s):  
B. H. Armstrong
Keyword(s):  
Electrical Conductivity ◽  
Melting Point ◽  
Volume Expansion ◽  
Alkali Halides ◽  
Self Diffusion

scholarly journals Development of Antibacterial and Antifungal Triazole Chromium(III) and Cobalt(II) Complexes: Synthesis and Biological Activity Evaluations

Molecules ◽  
2018 ◽  
Vol 23 (8) ◽  
pp. 2013 ◽  
Author(s):  
Ricardo Murcia ◽  
Sandra Leal ◽  
Martha Roa ◽  
Edgar Nagles ◽  
Alvaro Muñoz-Castro ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Biological Activity ◽  
Melting Point ◽  
Inhibitory Concentration ◽  
Vero Cells ◽  
Visible Spectroscopy ◽  
Antifungal Activities ◽  
Antibacterial And Antifungal Activities ◽  
Antibacterial And Antifungal ◽  
New Compounds

In this work, six complexes (2–7) of Cr(III) and Co(II) transition metals with triazole ligands were synthesized and characterized. In addition, a new ligand, 3,5-bis(1,2,4-triazol-1-ylmethyl)toluene (1), was synthesized and full characterized. The complexes were obtained as air-stable solids and characterized by melting point, electrical conductivity, thermogravimetric analysis, and Raman, infrared and ultraviolet/visible spectroscopy. The analyses and spectral data showed that complexes 3–7 had 1:1 (M:L) stoichiometries and octahedral geometries, while 2 had a 1:2 (M:L) ratio, which was supported by DFT calculations. The complexes and their respective ligands were evaluated against bacterial and fungal strains with clinical relevance. All the complexes showed higher antibacterial and antifungal activities than the free ligands. The complexes were more active against fungi than against bacteria. The activities of the chromium complexes against Candida tropicalis are of great interest, as they showed minimum inhibitory concentration 50 (MIC50) values between 7.8 and 15.6 μg mL−1. Complexes 5 and 6 showed little effect on Vero cells, indicating that they are not cytotoxic. These results can provide an important platform for the design of new compounds with antibacterial and antifungal activities.

Studies on the freezing of pure liquids I. Critical supercooling in molten alkali halides

1960 ◽  
Vol 259 (1298) ◽  
pp. 325-340 ◽  
Keyword(s):  
High Temperature ◽  
Critical Temperature ◽  
Melting Point ◽  
Alkali Halide ◽  
Alkali Halides ◽  
Solid Particles ◽  
High Supersaturation ◽  
Chamber Temperature ◽  
Reduced Temperature ◽  
Heater Coil

A high-temperature cloud chamber is described in which a bead of alkali halide is supported on a heater coil mounted in the roof. By passing the current through the coil the temperature of the bead may be momentarily raised by several hundred degrees, producing salt vapour at high supersaturation. Condensation ensues in the presence of the inert supporting gas, and clouds of droplets or solid particles appear depending on the chamber temperature. Light scattered from the clouds under strong illumination is examined with a telescope, and the presence of crystalline particles is detected by their capacity to scintillate, or ‘twinkle’. It is found that twinkling in clouds of alkali halides appears sharply as the temperature is lowered below the melting point, defining a critical temperature of solidification for each salt. Reasons are given for regarding this temperature as the freezing threshold of molten salt droplets, for which supercoolings of about 150 °C are indicated. A reduced temperature, given by the ratio of the freezing threshold to the melting point, has the value of approximately 0.8 for all the alkali halides examined.

scholarly journals Influence of Work and Tool Materials on Parameters of Electrical Discharge Machining (Edm)

1970 ◽  
Vol 3 (1) ◽  
Author(s):  
A.K.M.N. Amin A.K.M.N. Amin ◽  
A.K. Sarder
Keyword(s):  
Electrical Conductivity ◽  
Melting Point ◽  
Recast Layer ◽  
Point Of View ◽  
Machined Surface ◽  
Tool Materials ◽  
Copper Electrodes ◽  
Wear Ratio ◽  
Tool Wear Ratio ◽  
The Given

Influence of the properties of work and tool materials on material removal rate (MRR), tool wear ratio (TWR), thickness of the recast layer, surface roughness and accuracy of machining in EDM process has been investigated. Copper brass, stainless steel, mild steel and grey cast irou have been used in various combinations as work and tool materials. From the experimental results it is found that MRR slows down with machining time. Apart from that it has been found that MRR and TWR are inversely proportional to the melting points of the work and tool materials respectively. Electrical conductivity of the tool material also has appreciable influence on tool wear ratio. Wear ratio was found to be minimum in the case of the copper electrode having maximum electrical conductivity.  It has been also observed that for all combinations of work and tool materials, a recast layer is formed on the machined surface. It has been observed that the micro cavities formed in the cases of lower melting point electrode materials like copper and brass having higher electrical conductivity are comparatively smaller in size (2-3 ?m) as compared to the sizes of the micro cavities (8-20 ?m) formed in the cases of high melting pointer electrodes having also lower electrical conductivity. Consequenty the machined surface roughness produced in the latter cases is higher.  It has been also observed that the debris concentration increases due to side sparking of the electrode. The tendency of debris concentration is the maximum at the middle of the tool-job interface resulting in high bottom surface inaccuracy, specially when high melting point work materials are machined with electrodes like brass having low melting point and relatively lower electrical conductivity. From the point of view of MRR, brass electrodes have been found to be the most suitable tool, but from the point of view of machining accuracy and surface finish copper electrodes were found to yield the best result for the given set of job materials. So it was concluded that brass electrodes should be recommended for rough machining and copper electrodes for finish machining of the given work materials.

The physical properties of anomalous water

1971 ◽  
Vol 24 (4) ◽  
pp. 675 ◽  
Author(s):  
WW Mansfield
Keyword(s):  
Electrical Conductivity ◽  
Surface Tension ◽  
Melting Point ◽  
Aqueous Solutions ◽  
Physical Properties ◽  
Vapour Pressure ◽  
Column Length ◽  
Anomalous Water

The properties of anomalous aqueous condensates, prepared in the manner described by Deryagin,1 vary with aqueous vapour pressure. The changes of column length and of melting point are similar to those of ordinary aqueous solutions. There is no sound evidence that the condensate exhibits abnormal viscosity, density, electrical conductivity, or surface tension.

Effect of Transition Metal Silicides on Microstructure and Mechanical Properties of Ultra-High Temperature Ceramics

2013 ◽  
pp. 125-179 ◽  
Author(s):  
Laura Silvestroni ◽  
Diletta Sciti
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Melting Point ◽  
Leading Edge ◽  
High Melting ◽  
High Melting Point ◽  
Ultra High Temperature Ceramics ◽  
Sintering Additives ◽  
Self Diffusion ◽  
Ultra High Temperature

The IV and V group transition metals borides, carbides, and nitrides are widely known as ultra-high temperature ceramics (UHTCs), owing to their high melting point above 2500°C. These ceramics possess outstanding physical and engineering properties, such as high hardness and strength, low electrical resistivity and good chemical inertness which make them suitable structural materials for applications under high heat fluxes. Potential applications include aerospace manufacturing; for example sharp leading edge parts on hypersonic atmospheric re-entry vehicles, rocket nozzles, and scramjet components, where operating temperatures can exceed 3000°C. The extremely high melting point and the low self-diffusion coefficient make these ceramics very difficult to sinter to full density: temperatures above 2000°C and the application of pressure are necessary conditions. However these processing parameters lead to coarse microstructures, with mean grain size of the order of 20 µm and trapped porosity, all features which prevent the achievement of the full potential of the thermo-mechanical properties of UHTCs. Several activities have been performed in order to decrease the severity of the processing conditions of UHTCs introducing sintering additives, such as metals, nitrides, carbides or silicides. In general the addition of such secondary phases does decrease the sintering temperature, but some additives have some drawbacks, especially during use at high temperature, owing to their softening and the following loss of integrity of the material. In this chapter, composites based on borides and carbides of Zr, Hf and Ta were produced with addition of MoSi2 or TaSi2. These silicides were selected as sintering aids owing to their high melting point (>2100°C), their ductility above 1000°C and their capability to increase the oxidation resistance. The microstructure of fully dense hot pressed UHTCs containing 15 vol% of MoSi2 or TaSi2, was characterized by x-ray diffraction, scanning, and transmission electron microscopy. Based on microstructural features detected by TEM, thermodynamical calculations, and the available phase diagrams, a densification mechanism for these composites is proposed. The mechanical properties, namely hardness, fracture toughness, Young’s modulus and flexural strength at room and high temperature, were measured and compared to the properties of other ultra-high temperature ceramics produced with other sintering additives. Further, the microstructural findings were used to furnish possible explanations for the excellent high temperature performances of these composites.

Self-Diffusion of Tl+ in Molten Thalium Nitrate

1977 ◽  
Vol 32 (12) ◽  
pp. 1433-1434
Author(s):  
S. Zuca ◽  
M. Constantinescu
Keyword(s):  
Diffusion Coefficient ◽  
Melting Point ◽  
The Self ◽  
Ionic Interactions ◽  
Temperature Range ◽  
Self Diffusion ◽  
Capillary Method ◽  
Self Diffusion Coefficient

Abstract The self-diffusion coefficient of Tl+ in molten TlNO3 in a temperature range of about 100° above the melting point was measured by the "diffusion-into-the capillary" method. The obtained results are discussed in terms of ionic interactions occuring in TlNO3 melt.

Selbstdiffusion in geschmolzenem LiCl / Self-Diffussion in Molten LiCl

1973 ◽  
Vol 28 (6) ◽  
pp. 881-884 ◽  
Author(s):  
R. Lenke ◽  
W. Uebelhack ◽  
A. Klemm
Keyword(s):  
Alkali Halides ◽  
The Other ◽  
Temperature Range ◽  
Self Diffusion ◽  
The Difference

Self-diffusion measurements on molten LiCl in the temperature range 610 °C ≦ ϑ ≦ 760 °C, obtained with a capillary-reservoir technique, result in the expressions D+ = [10.6 + 0.0307 ϑ - 610) ±0.81 × 10-5cm2/s,D_ = [ 5.8 + 0.0117 ϑ - 610) ±0.3] × 10-5cm2/s. These results fit well into the pattern of the other alkali halides. As with these, it is observed that (D + /R T) + (D_/R T) - (Λ/F2) >0, the difference increasing with rising temperature.

Isotopic Effect on the Melting Point of Lithium Nitrate

1970 ◽  
Vol 25 (5) ◽  
pp. 697-699 ◽  
Author(s):  
Bert Jansson ◽  
Arnold Lundén
Keyword(s):  
Melting Point ◽  
Isotope Effects ◽  
Zone Melting ◽  
Isotopic Effect ◽  
Lithium Nitrate ◽  
Lithium Metal ◽  
Self Diffusion ◽  
Fee Structure ◽  
The Difference ◽  
Self Diffusion Coefficient

The techniques of segregation during normal freezing and of zone melting have been used to establish that the melting point of 6LiNO3 is higher than that of 7LiNO3. The difference is of the order of 0.03 °C. The isotope shift of the melting point is in the opposite direction of the isotope effects found previously for phase transitions in solid lithium metal and lithium sulfate. For the latter salt a recalculation based on a more accurate value for the self-diffusion coefficient shows that the temperature of transition at about 575 °C to a fee structure is about 0.08 degr. lower for 6Li2SO4 than for 7Li2SO4.

Improved Electrical Conducting Wires for SOFCs

2008 ◽  
Vol 55-57 ◽  
pp. 797-800
Author(s):  
M. Masomtob ◽  
K. Wongtida ◽  
J. Charoensuk ◽  
S. Charojrochkul
Keyword(s):  
Electrical Conductivity ◽  
Melting Point ◽  
Alternative Energy ◽  
High Electrical Conductivity ◽  
Energy Devices ◽  
Temperature Range ◽  
Electrical Conducting ◽  
Alternative Choice ◽  
Gold Wires ◽  
The Cost

Solid Oxide Fuel Cells (SOFCs) have attracted a number of researchers due to their efficiency as alternative energy devices. Studies have been conducted to investigate different components of the SOFCs to improve the performances. Current collecting wires are the components which have affected the overall performance. Since SOFCs are normally operated in the temperature range of 700-1000 °C in dual atmospheres, the wiring material must be able to function at this condition. Currently, the material used to make the wires is platinum because of its high electrical conductivity, high melting point and oxidation resistant. However, platinum is expensive, especially for the practical operation of SOFCs. Silver could be an alternative choice due to its very high electrical conductivity. Nevertheless, the melting point of silver is rather low (900-960 °C). In our study, a modified silver current collecting wire has been used in the temperature range of 100-1000 °C. Their conductivity curves have demonstrated higher performances in comparison with the systems employing Pt and gold wires. In addition, the cost is reduced approximately 800-1000 times from that of the traditional material used.

Sign in / Sign up

Export Citation Format

Share Document