Bright Layer Research Articles

The Effect of Deformation on the Corrosion Resistance of Nickel + Chromium Coatings: A Metallographic Study

SummaryA study has been made of the incidence of cracking in deformed nickel + chromium plated panels and of the relation to cracking corrosion behaviour. After very severe deformation, only semi-bright nickel remained completely free from cracking. Bright nickel cracked readily, and in heavily deformed regions the cracks tended to propagate, by notch effect, through ductile semi-bright nickel or copper undercoats. In specimens less severely deformed, cracking terminated at the semi-bright nickel/bright nickel or the copper/bright nickel interface. Thick, initially crack-free chromium coatings cracked over a wider area and induced many more cracks in bright nickel substrates than did chromium of conventional thickness, whereas over similar substrates thick microcracked chromium coatings induced fewer cracks than conventional chromium. In all test environments, wide cracks which terminated at an active substrate such as steel or zinc usually showed corrosion, of the substrate only, but in stationary and mobile exposure tests corrosion of both the bright nickel and the active substrate tended to occur in narrow cracks. In acetic-acid/salt spray, however, corrosion in even the narrowest cracks was confined to the active substrate. With increasing nobility of substrate, in the order brass, copper, semi-bright nickel, the proportion of corrosion occurring in the substrate decreased and attack was confined to the bright nickel layer.

Comparative anatomy of the bands of Schreger.

This is a comparative anatomical study of the bands of Sch re g e r in mammalian enamel. The observation was made on meridional ground section of the crown. The ground surface was stained with hematoxy lin.Through the investigation it was established that the mentioned structure of the enamel has a characteristic feature specific to each kind of animal. The pattern of the bands of S chr eger can therefore be useful as one of the taxonomic criteria.The zonial patterns can be classified into following main categories:1) Carnivora type: The bands are conspicuous because the diazoniae consisting of cross sections of the enamel rods are bounded clearly against the parazoniae which are cut mostly in longitudinal direction and oriented parallel to the course of the bands. They stand verticalupon the dentine surface and describe rather a streight course. me indifferent bright layer under the enamel surface is relatively thin.2) Primate type: The bands are relatively broad and each of them consists of 5-15 rods in its width. They stand oblique to the dentoenamel junction and run in more or less curved course. Leaving a thin indifferent layer above the dentine they vanish into a thicker bright layer under the enamel surface. The parazoniae are also composed with curved, oblique sections of the enamel rods so that the boundary of the dia- against the parazoniae is rather transitional.3) Ungulate type: The bands are considerably long and the indifferent zones are broad in accordance with the thick enamel of the order. They stand oblique to the dento. enamel junction and are more or less curved. The boundary between para- and diazoniae is still more obscure than that in the Primate type. Even in the parazoniae a parallel arrangement of the longitudinally cut rods is scarcely to encounter. The rods in the diazoniae are arranged in rows.4) Rodent type: The para- and diazoniae are in most Rodents bounded sharply against each other and no transition of the rods from a band to the adjacent one can be seen. They are straight and consist of rather small number of enamel rods, mostly of a single row of them. The Leporidae and Caviidae have, however, their own patterns of the bands of Schrege r. In general the molar teeth of the Rodents show zonial structures more or less modified from those found in the incisors.

Studies of Bright Gold Layers with The Electron Microscope

AbstractThe microscopic examination of bright gold layers reveals only to a very limited extent and only entirely empirically the structure and the essential technical properties of such layers. This limitation is due to the fact that the resolving power, which we are able to determine with the optical microscope, is not sufficient for resolving these layers of unusually fine particles. In order to obtain information about the optimum burning conditions, on the one side, and about the appropriate structure of such bright metal solutions on the other side, studies were conducted on such layers with the electron microscope. During these studies the method of impression was applied on the one hand which, as it is well known, can merely reveal the geometrical constitution of the surfaces of such specimens. On the other hand, commercial bright gold solutions were burnt upon extremely thin quarts foils, whereupon these foils were examined by irradiation.The electron microscopical studies of the burnt—in bright ...

The structure of the walls of parenchyma in avena coleoptiles

The structure of the primary wall and its relation to that of the secondary wall has long been a subject of controversy. In recent years evidence collected from various sources has led to somewhat divergent views. Thus consideration of the development of the conifer tracheid, for instance, has led to the suggestion that the molecular chains of cellulose, in the wall of the cambial initial, are initial rather steeply to the longi­tudinal axis, so that they form a spiral round the cell (Jaccard and Frey 1928; Preston 1934). On the other hand, a different idea may be derived from consideration of transverse sections of tracheids, as made by Bailey and Kerr (1935) and by Freudenberg and Dürr (1932) under the polarizing microscope. Observed in this way the tracheid wall clearly consists of at least three layers—an outer, and an inner, bright layer and a central dark layer. On the basis of such observations, Bailey and Kerr and Freudenberg have concluded that the direction of the cellulose micelles varies from point to point in the wall thickness. In the outer and inner layers they are said to run transversely and in the ventral layer longitudinally. This would confirm the earlier Work of Scarth, Gibbs and Spier (1929). While the validity of this interpretation is open to question (as will be pointed out elsewhere) it would possibly imply that since the outer lasers of the secondary wall lie nearest to the primary wall, the micelles in the latter would be oriented in the transverse plane rather than in a spiral. Certain suggestions concerning the relation between wall deposition and growth have, in fact, been made in terms of this transverse orientation in primary walls. Consideration of these hypotheses has been made elsewhere (Preston and Astbury 1937); the present paper is concerned more with a discussion of some evidence which has been quoted in their support (Castle 1937).

VII.— The Banded Constituents of Coal

1. The Physical Characteristics of the Banded Constituents. In the course of this paper it is proposed to describe what have become known to us within recent years as the banded constituents of bituminous coal. Prior to the year 1919, investigators into the constitution of coal were content to describe its appearance as bright or dull according to the predominance of the bright or dull layers in the specimens under examination. There were, however, in addition to these hard, bright and dull bands, varying lenticles of soft, black, charcoal-like substance to which specific names such as “mineral charcoal” and “mother of coal” had been applied. Another distinctive material forming part of some coal seams is cannel or “parrot” coal. This type of coal differs from the ordinary banded variety in its uniformity of texture, its satiny lustre and its marked conchoidal fracture. Its occurrence in coal seams is very uncertain and it is usually present in varying sized lenticular bands. In some publications it may be referred to as “boghead” coal owing to its similarity in appearance to the famous Torbanehill mineral. If a close inspection is made of a lump of ordinary bituminous coal, it will generally be found to consist of layers of materials whose power to reflect light varies considerably. There may be bands of bright, black, glassy lustre; bands of bright material which show minute striations; bands of dull, granular material; and, finally, lenticles of the soft, charcoal-like substance to which reference has already been made. It This 250-word extract was created in the absence of an abstract

On the origin of bright laminae in coal, and a suggestion arising out of their distribution

Although the vegetable origin of coal is universally accepted, there are points presented by coal seams which still await investigation. This is particularly true in regard to the manner in which the vegetable matter accumulated. The fact that two theories have been brought forward to explain the precise mode of origin of coal shows that divergent views exist among geologists on this question. The difference of opinion, however, may be more imaginary than real, for a small experience of the occurrence of coals throughout a single coalfield convinces one that both the growth in situ and drift origins have obtained, and one may find that while in one place a coal seam has unquestionably resulted from an accumulation of vegetable matter which grew on the spot where it now rests, in the same district equally indisputable evidence may be found to show that another bed of coal was entirely derived from drifted vegetation. In the present paper, I propose to discuss the nature and origin of certain bright laminae which are a characteristic feature in all bituminous coals, and to suggest that from their distribution in a coal seam, evidence can be obtained to show that many beds of coal have originated by a combination of both the growth in situ and drift modes of origin. A piece of ordinary bituminous coal is made up of a series of bright and dull layers. The surfaces of the latter, if closely examined, usually show that they are almost entirely made up