Search results

This paper aims to investigate the efficiency of a laminated composite for shielding applications. The solution has to be efficient not only for the shield against static magnetic fields but also “for low-frequency ones, in order to be well-suited for applications with electromagnetic perturbations in the frequency range DC to 100 kHz.”

The composite constituted of a steel sheet taken in a sandwich between two aluminum (Al) sheets is produced by cold roll bonding. A good adherence between Al and steel sheets, ensuring a good mechanical resistance, is obtained with a specific process. A previous study has shown that the optimal trade-off between adherence and magnetic shielding effectiveness (SE_H) is obtained with a 230 µm composite produced with an initial thickness of Al and steel sheets, respectively, of 250 and 100 µm. In this paper, the 230 µm Al/steel/Al composite is used in three applications modelized by two-dimensional numerical simulations. To obtain reasonable computation time for the simulations, a homogenization method is applied to the composite. Studied applications are a cylindrical box containing a coil, a square box under an external magnetic field and a high voltage cable.

In each application, SE_H is calculated at low frequency and different materials (Al/steel/Al, Al, steel and copper) are compared. It is observed that, in each application, the composite presents higher SE_H at equal mass, especially for frequencies between 5 and 100 kHz.

The proposed approach, from the material point of view to the system consideration, shows that the thin bimetallic composite is an innovative and promising solution for magnetic shielding in the case of applications with both DC and low-frequency perturbations.

The purpose of this paper is to synthesize a novel kind of crown‐type phosphate ionic liquids with better tribological properties for steel/Al system. The anions of crown‐type phosphate ionic liquids contain no F element, which are non‐corrosive to metal.

To improve the tribological properties of ionic liquid lubricants for the extremely difficult system of the steel‐against‐aluminum metal couple, novel crown‐type phosphate ionic liquids were prepared. The tribological properties of the crown‐type phosphate ionic liquids were evaluated at different loads and frequencies on an Optical SRV oscillating friction and wear tester. The morphology and chemical compounds of the wear scars were investigated by scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS).

Compared with conventional ionic liquids, the novel crown‐type phosphate ionic liquids prepared in the present work exhibit a more excellent anti‐wear ability for steel/Al2024 contact at different loads and frequencies. By the morphological analysis with SEM, less debris was observed in the worn surface lubricated with crown‐type phosphate ionic liquids, though more debris was observed when lubricated with LB106 and LP106. By the XPS analysis, boundary lubrication film composed of aluminum (III) oxide, organometallic compounds, and silicon aluminum phosphate were found in the worn surface. Namely, the tribological behaviors of the crown‐type phosphate ionic liquids could be attributed to their stronger adsorption and tribochemical interactions with the Al alloys.

Because of the higher mean friction coefficients of crown‐type phosphate ionic liquids in the research, researchers are encouraged to modify their structure for better tribological properties.

The crown‐type phosphate ionic liquid exhibited better anti‐wear performance for steel/aluminum contact than the conventional ionic liquids containing F element. This will expand the application of high strength aluminum alloys.

The phosphate ionic liquid is a non‐corrosive liquid and would not cause metal corrosion. Also, the tribological properties of crown‐type phosphate ionic liquid with steel/aluminum contact are better than that of conventional ionic liquids. By the designing of molecular structure, new phosphate ionic liquids will exhibit excellent tribological properties: lower wear volume and lower friction coefficient.

Like aqueous corrosion of metals, atmospheric corrosion of metallic articles has also been a matter of great anxiety due to the individual and joint action of oxygen, humidity and various types of pollution gases and ions in the atmospheres. As there is no limit of oxygen availability in the open atmosphere, this type of corrosion of metals is mainly controlled by humidity. In industrial mines and marine environments, however, metal attack is controlled by aggressive gases, ions and chloride ions respectively.

KEK Ltd., Hurdsfield Industrial Estate, Macclesfield, Cheshire SK10 2ND, announce an extension to their cryogenic grinding facility with the installation of a 2000 litre nitrogen tank (approximately 3 times the size of the previous facility).

Lubricating system protection. Corrosion of the bearing surfaces of a lubricated mechanism is reduced or prevented by adding an aqueous solution of sodium nitrite to the water‐immiscible lubricant in the lubricating system so that the solution is dispersed, but not permanently emulsified or dissolved, in the lubricant. The process may be applied to machinery having a closed or forced system of lubrication, particularly where the possibility of water having access to the working parts exists. Thus the process may be applied to marine turbine installations where leakage of sea water into the oil system may occur. The lubricant employed may be a straight mineral oil and the pH of the dispersion is preferably maintained between 6.5 and 9. A wetting agent, such as sodium petroleum sulphonate or a sulphated secondary alcohol, may be added to facilitate the separation of the aqueous phase from the dispersion whenever it is desired to remove the aqueous phase, for example by means of a centrifugal separator. According to the Provisional Specification, corrosion inhibitors other than sodium nitrite may be employed.—Brit. Pat. 681,248, S. E. Bowrey.

Introduction Visual inspection or observation at low magnification with an optical microscope has been of great help in analysing fracture surfaces. Optical microscopy, however, has distinct limitations, such as low resolution and small depth of field. The transmission electron microscope does not have these limitations.

Expansion of the Hoechst UK Ltd plant at Holliwell Green, Halifax has involved the manufacture and installation of four huge stainless steel mixing vessels.

THE steels to which reference is made in this article are primarily what are known as “alloy constructional steels.” The special steels which are being used to some extent in the construction of aeroplane frames and bodies are not included in this category. Alloy constructional steels are those developed by modern metallurgical research for use in engine parts, propeller shafting, and so forth.

Precision cleaning with solvent systems based on n‐propyl bromide (nPB) has become an important component of the circuit board fabrication process. The nPB‐based cleaners have proved themselves valuable alternatives to the once popular chlorocarbons and hydrochlorocarbons. These latter solvents have been largely banned or restricted because of toxicological and/or environmental considerations. n‐propyl bromide has nearly identical physical and cleaning properties to 1,1,1‐trichloroethane (1,1,1‐T or TCA), but it has a low Ozone Depletion Potential (ODP) and a low Global Warming Potential (GWP). A growing body of evidence shows that nPB‐based solvents are safe, effective and cost‐efficient alternatives for precision cleaning applications. New formulations have now been developed specifically for the electronics industry. The first challenge is the efficient removal of ionic residues left by certain types of solder flux. The second challenge is the prevention of tarnish on silver leads used on some circuit boards. Case histories and a discussion of relevant toxicological, environmental and regulatory considerations will be included.

Comparative investigations of the corrosion resistance of different coated sheet steels in various fuel mixtures were carried out. Corrosion resistance has been studied on the following materials: Neuratern (electrolytically deposited terne‐coated steel, Thyssen Stahl AG, Germany); Ternesheet (hot‐dip terne‐coated steel, Nippon Steel, Japan); hot‐dip terne‐coated steel (Dnepropetrovsk, Ukraine); Neuralyt (Zn‐Ni electrolytically deposited steel, Thyssen Stahl AG, Germany); fal‐D (hot‐dip aluminized steel, Thyssen Stahl AG, Germany); hot‐dip aluminized steel (Cherepovets), Russia); Galvalume (hot‐dip Zn‐55 per cent Al steel, Cherepovets, Russia). Investigations were carried out in the following environments: commercial petrol without special additives + water; commercial petrol, 10 per cent ethylated spirit + water; commercial petrol, 15 per cent methylated spirit + water. Corrosion resistance was evaluated in terms of ratings and weight loss. To compare the behaviour of the different types of samples and various fuel mixtures over the test period rating curves were plotted as a function of the test time.