Critical aspects on the behavior of material from the mechanical tool-workpiece interaction in single point diamond turning

Some material aspects such as grain size, purity and anisotropy exert an important influence on surface quality, especially in single point diamond turning. The aim of this paper is to present and discuss some critical factors that can limit the accuracy of ultraprecision machining of non-ferrous metals and to identify the effects of them on the cutting mechanism with single point diamond tools. This will be carried out through observations of machined surfaces and chips produced using optical and scanning electron microscopy. Solutions to reduce the influence of some of these limiting factors related with the mechanism of generation of mirror-like surfaces will be discussed.

Investigation on diamond turning of silicon crystal - generation mechanism of surface cut with worn tool

This paper discusses the effect of tool wear on surface finish in single-point diamond turning of single crystal silicon. The morphology and topography of the machined surface clearly show the type of cutting edge wear reproduced onto the cutting grooves. Scanning electron microscopy is used in order to correlate the cutting edge damage and microtopography features observed through atomic force microscopy. The possible wear mechanisms affecting tool performance and surface generation during cutting are also discussed. The zero degree rake angle single point diamond tool presented small nicks on the cutting edge. The negative rake angle tools presented more a type of crater wear on the rake face. No wear was detected on flank face of the diamond tools.

Régates de Henley, [Jack] Beresford [vainqueur du Diamond Challenge Sculls] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 59930

Receipt from Tiffany and Co., New York for a diamond lace pin

Receipt from Tiffany and Co., New York for a diamond lace pin, Nov. 3, 1884.

Comparación de la actividad hemolítica y fosfolipásica A2 de Trichomonas vaginalis cultivada en presencia y ausencia de vitaminas 107 diamond.

Tesis (Maestría en Ciencias con acentuación en Microbiología) UANL, 2014.

Fabrication of diamond nanostructures and investigation of the imbedded NV centers

Diamant ist ein Material mit vielen außerordentlichen Eigenschaften, die ihn zu einem äußerst vielversprechenden Kandidaten für Anwendungen in Wissen-schaft und Technik machen. In den letzten Jahren wurde Diamant häufig als einzigartige Plattform für neue Anwendungen beispielsweise in der Quanteninformationstechnologie (QIT) oder in der Magnetometrie im Nanometermaßstab eingesetzt, wobei einer der wichtigsten lumineszierenden Gitterdefekte im Diamantgitter eingesetzt wird. Dabei handelt es sich um die sogenannten Stickstoff/Fehlenstellen-Farbzentren (NV-Zentren), die im sichtbaren Bereich mit einer absoluten Photostabilität bei Raumtemperatur emittieren. In dieser Arbeit wurden NV-Zentren in Diamantnanokristalliten und –nanosäulen untersucht, die während des Wachstumsprozesses erzeugt wurden. Einzelne Diamantnanokristallite und nanokristalline Diamantschichten (NCD), aus denen Nanosäulen geätzt wurden, wurden mithilfe der Hot Filament Chemical Vapour Deposition (HFCVD) abgeschieden. Zu Vergleichszwecken wurden auch ultrananokristalline Diamantschichten (UNCD) mittels Mikrowellen-CVD (MWCVD) hergestellt. Die Filme wurden sorgfältig in Bezug auf ihre Morphologie, kristallinen Eigenschaften und Zusammensetzung untersucht. Um die Möglichkeit einer Integration dieser Diamantschichten mit temperaturempfindlichen Materialien wie III/V-Halbleitern, Metallen mit niedrigem Schmelzpunkt oder Polymeren zu untersuchen, wurde der Einfluss der Substrattemperatur ermittelt. Eindimensionale NCD- und UNCD-Diamantnanostrukturen wurden mithilfe der Elektronenstrahllithographie (EBL) und reaktivem Ionenätzen in einem induktiv gekoppelten O2-Plasma (ICP-RIE) hergestellt. Zur Vorbereitung wurden zunächst die Ätzraten in Abhängigkeit von den vier wichtigsten Parametern ermittelt. Weitere Erkenntnisse über die Ätzmechanismen wurden durch Ätzexperiment mit unstrukturierten NCD- und UNCD-Schichten erhalten Mittels der EBL konnten mithilfe von Gold-Ätzmasken Nanosäulen mit Durchmessern von 50 nm bis zu 1 μm hergestellt werden.Eine optische Charakterisierung der NCD- und UNCD-Nanosäulen erfolgte mithilfe von Fluorenzenz-Mapping und Photomumineszenz-Spektroskopie. Diese Messungen ergaben, dass in beiden Arten von Säulen NV-Zentren vorhanden sind. Allerdings wurden nur in NCD-Säulen die gewünschten NV--Zentren gefunden, in UNCD-Säulen hingegen nur NV0-Zentren.

Diamond skin disease in a pig

Photograph showing diamond skin disease in a pig.

Synthesis, structural analysis, and magnetic behaviour of three fumarate bridged coordination polymers: five-fold interpenetrated diamond-like net of Ni-II, sheets of Ni-II and Co-II

The hydrothermal reactions of Ni(NO3)(2).6H(2)O, disodium fumarate (fum) and 1,2-bis(4-pyridyl)ethane (bpe)/1,3-bis(4-pyridyl) propane (bpp) in aqueous-methanol medium yield one 3-D and one 2-D metal-organic hybrid material, [Ni(fum)(bpe)] (1) and [Ni(fum)(bpp)(H2O)] (2), respectively. Complex 1 possesses a novel unprecedented structure, the first example of an "unusual mode" of a five-fold distorted interpenetrated network with metal-ligand linkages where the four six-membered windows in each adamantane-type cage are different. The structural characterization of complex 2 evidences a buckled sheet where nickel ions are in a distorted octahedral geometry, with two carboxylic groups, one acting as a bis-chelate, the other as a bis-monodentate ligand. The metal ion completes the coordination sphere through one water molecule and two bpp nitrogens in cis position. Variable-temperature magnetic measurements of complexes 1 and 2 reveal the existence of very weak antiferromagnetic intramolecular interactions and/or the presence of single-ion zero field splitting (D) of isolated Ni-II ions in both the compounds. Experimentally, both the J parameters are close, comparable and very small. Considering zero-field splitting of Ni-II, the calculated D values are in agreement with values reported in the literature for Ni-II ions. Complex 3, [{Co(phen)}(2)(fum)(2)] (phen=1,10-phenanthroline) is obtained by diffusing methanolic solution of 1,10-phenanthroline on an aqueous layer of disodium fumarate and Co(NO3)(2).6H(2)O. It consists of dimeric Co-II(phen) units, doubly bridged by carboxylate groups in a distorted syn-syn fashion. These fumarate anions act as bis-chelates to form corrugated sheets. The 2D layer has a (4,4) topology, with the nodes represented by the centres of the dimers. The magnetic data were fitted ignoring the very weak coupling through the fumarate pathway and using a dimer model.

A 'Kimberley protest': diamond mining, export sanctions, and poverty in Awatia, Ghana

The temporary suspension of diamond exports in Ghana in 2006 and 2007 is arguably the most significant move to address mounting criticisms of the Kimberley Process Certification Scheme (KPCS), an international initiative aimed at stemming the flow of rough diamonds used to finance wars. The ban, which took effect in November 2006, was much praised, particularly in civil society circles, where it continues to be seen as a genuine effort to prevent the smuggling of ‘conflict diamonds’. At the time, Ghana was accused of harbouring stones originating from rebel-held territories in neighbouring Côte d’Ivoire. No evidence was found in support of the case that it was a repository for ‘conflict diamonds’, however, and exports resumed early in March 2007. This article examines the context for the accusations of Ghana’s implication in the smuggling of illicit diamonds, and draws on recent fieldwork to explain how the suspension has affected Akwatia, the country’s main diamondiferous area. The actions taken raise important questions about how suspected violators – particularly smaller diamond-producing nations – of the KPCS should be handled, and underscore how global compacts can have a host of negative repercussions at the village level.

Poverty and livelihood diversification in rural Liberia: exploring the linkages between artisanal diamond mining and smallholder rice production

This paper provides an account of the changing livelihood dynamics unfolding in diamond-rich territories of rural Liberia. In these areas, many farm families are using the rice harvested on their plots to attract and feed labourers recruited specifically to mine for diamonds. The monies accrued from the sales of all recovered stones are divided evenly between the family and hired hands, an arrangement which, for thousands of people, has proved to be an effective short-term buffer against poverty. A deepened knowledge of these dynamics could be an important step towards facilitating lasting development in Liberia’s highly-impoverished rural areas.

Diamond mining, rice farming, and a ‘Maggi cube’: a viable survivial strategy in rural Liberia?

Since the conclusion of its 14-year civil war in 2003, Liberia has struggled economically. Jobs are in short supply and operational infrastructural services, such as electricity and running water, are virtually nonexistent. The situation has proved especially challenging for the scores of people who fled the country in the 1990s to escape the violence and who have since returned to re-enter their lives. With few economic prospects on hand, many have elected to enter the artisanal diamond mining sector, which has earned notoriety for perpetuating the country's civil war. This article critically reflects on the fate of these Liberians, many of whom, because of a lack of government support, finances, manpower and technological resources, have forged deals with hired labourers to work artisanal diamond fields. Specifically, in exchange for meals containing locally grown rice and a Maggi (soup) cube, hired hands mine diamondiferous territories, splitting the revenues accrued from the sales of recovered stones amongst themselves and the individual ‘claimholder’ who hired them. Although this cycle—referred to here as ‘diamond mining, rice farming and a Maggi cube’—helps to buffer against poverty, few of the parties involved will ever progress beyond a subsistence level