Improving the heat transfer of nanofluids and nanolubricants with carbon nanotubes

Low thermal conductivity is a primary limitation in the development of energyefficient heat transfer fluids required in many industrial and commercial applications. To overcome this limitation, a new class of heat transfer fluids was developed by suspending nanoparticles and carbon nanotubes in these fluids. The resulting heat transfer nanofluids and nanolubricants possess significantly higher thermal conductivity compared to unfilled liquids. Three types of heat transfer nanofluids and nanolubricants, each containing controlled fractions of single-wall carbon nanotubes, multiwall carbon nanotubes, vapor grown carbon fibers, and amorphous carbon have been developed for multifunctional applications, based on their enhanced heat transfer and lubricity properties. For more information, contact F.D.S. Marquis, South Dakota School of Mines and Technology, Department of Materials and Metallurgical Engineering, Rapid City, SD 57701; (605) 394-1283; fax (605) 394-3369; e-mail fernand.marquis@sdsmt.edu.     

High temperature oxidation of CoMn alloys

The oxidation of cobalt-manganese alloys in the range 0–45 wt%Mn corresponding to the stability of the α-phase of cobalt has been studied in the range 750–950°C as an example of binary alloys producing solid solution scales. The alloys oxidize according to a parabolic rate law with a rate constant intermediate between those of the pure metals. The scales were formed mainly by a CoOMnO solid solution with a spinel phase present either as dispersed particles or a continuous layer in the cubic oxide, particularly for the Mn-rich alloys: some degree of internal oxidation has also been observed. The scale properties show a time dependence at constant temperature which is unusual in these systems and is probably related to the presence of the spinel phase. The internal oxidation and the structure and composition of the external scale are discussed with reference to the phase diagram for this system and to the recent theories for the growth of solid solution scales.     

Structural and phase transformations,thermal stability,and magnetic and corrosive properties of nanocrystalline iron-based alloys obtained by mechanoactivation in organic media

A review of works on the investigations of structural and phase transformations that occur in iron during its mechanical disintegration in the presence of liquid organic media. It is shown that the mechanoactivation of metals in the presence of organic media leads to the formation of a nanocrystalline structure of complex phase composition which is determined by the chemical nature of the milling medium and can include (in different proportions) α-Fe, amorphous phases, carbides, oxides, etc. By varying the composition of the medium, the duration of milling, and the temperature of a subsequent heat treatment, it is possible to obtain nanocrystalline systems with different structural and phase composition, dispersity, and thermal, magnetic and corrosive properties. It has been shown that for the investigation of processes that take place in nanocrystalline materials, it is necessary to use, apart from methods of analysis of the composition and structure of substances at the mesoscopic level (electron microscopy, X-ray diffraction, etc.), also methods which give information at the level of local atomic environment. In this work, Mössbauer spectroscopy was used for the systems on the basis of iron.     

Low Manganese Steels For Nuclear Applications

When the radioactive isotope of manganese is not wanted, low manganese steels of 0.10 to 0.15 pet Mn have been made by the basic open hearth process and rolled into plate, bars, and seamless tubing. The low manganese steels are interchangeable with standard grades of carbon steels for many uses. They are superior to standard grades of carbon steels in terms of freedom from strain aging, improved high temperature strength and ductility, and absence of certain disadvantageous nuclear or chemical properties.     

Optimum composition of blast furnace slag as deduced from liquidus data for the quaternary system CaO-MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>

On the basis of liquidus measurements in the system CaO-MgO-Al₂O₃-SiO₂ and previously published data, diagrams have been constructed at 5 pct Al₂O₃ intervals from 5 to 35 pct Al₂O₃. Liquidus temperatures and primary phase fields are shown. The optimum composition of a blast furnace slag for a given alumina content is indicated. At the optimum point, ordinary slags will be entirely liquid and will have maximum desulphurization potential and minimum viscosity. The relation of optimum composition of slags to the “plateau region” of the liquidus surface, and the application of these data on synthetic quaternary slags to actual slag compositions are discussed. Index of refraction of glasses is given as well as composition, temperature, and phase data for each mixture.     

Influence of Reinforcement Content and Matrix Composition on the Oxidation Resistance of Aluminum-Matrix Composites (A3xx.x/SiCp)

A study was made on the influence of the SiCp proportion and the matrix concentration of four composites (A360/SiC/10p, A360/SiC/20p, A380/SiC/10p, A380/SiC/20p) on their oxidation behavior. Gravimetric tests were used in a kinetics study of the corrosion process at different temperatures (350, 400, 450, and 500°C). The influence of corrosion on mechanical properties was evaluated by hardness measurements. The nature of corrosion products and the influence of the microstructure on the morphology and growth of the oxidation layer were analyzed by SEM and low-angle XRD. The extent of the damage due to oxidation for Al/SiCp composites increases with the SiCp concentration due to the increase of nucleation sites. One of these nucleation sites is in the interface region between the matrix and the particles. Oxidation was influenced more by the percentage of alloy elements in the matrix than by the proportion of SiCp reinforcement. The presence of Cu and Ni in the matrix favors the oxidation process through the formation of different intermetallic compounds.     

Friction and the development of hard alloy surface microstructures during wear

Investigations of wear in sliding friction of WC-Hadfield steel hard alloy against cast tool steel have been carried out in a broad range of velocities and pressure values. Structural and phase composition variations have been revealed. Friction-affected zone was found to be 450 μm in depth. Structural γ → α, γ → transformation regions are located within 100 μm of the surface. These transformations contributed to the total solid solution deformation hardening.     

The Cd−Sm (Cadmium-Samarium) system

This program was supported by the Department of Energy through the Joint Program on Critical Compilation of Physical and Chemical Data coordinated through the Office of Standard Reference Data, National Bureau of Standards. Additional support was contributed by: Molycorp, Inc., Union Oil Co. of California, Los Angeles, CA; Reactive Metals and Alloys Corp., West Pittsburg, PA; Ronson Metals Corp., Newark, NJ; and Santoku Metal Industry Co., Ltd., Kobe, Japan. Literature searched through 1984. Professor Gschneidner is the ASM/NBS Data Program Category Editor for binary rare-earth alloys.     

A model for generation of directed graphs of information by the directed graph of metainformation for a two-level model of information units with a complex structure

A model for generation of directed graphs of information by the directed graph of metainformation for a two-level connected directed graph model of information units is described. It can be used as a basis in computer tools for editing information with a complex structure with different levels of abstraction and invariance to technological spaces (subject domains) in a common conceptual framework for carriers of this information, making it unnecessary to organize specialized training for these carriers or to involve professional intermediaries.