Processing Of Al-Cu-Fe Quasicrystalline Single Grains

1998 ◽  
Vol 553 ◽  
Author(s):  
T. A. Lograsso ◽  
A. R. Ross
Keyword(s):  
Hot Isostatic Pressing ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
Second Phase ◽  
Slow Cooling ◽  
History Of ◽  
Single Grain ◽  
A Minor ◽  
High Degree ◽  
Minor Quantity

AbstractThe phase equilibria of the Al-Cu-Fe quasicrystalline phase (y phase) is complex and conventional crystal growth techniques like the Bridgman and Czochralski methods are not applicable in preparation of large crystals. Large single grains of the y phase been have prepared by either slow cooling or isothermal anneals. In the later technique, arc melted ingots were subjected to either single or multiple heat treatments between 825 and 840°C to encourage grain growth. Following heat treatment, grains of the icosahedral phase are found either as isolated pentagonal-faceted crystals within the ingot or within clusters of intergrown grains. The growth of the large grains is independent of the sample processing history of the sample, is facilitated by the presence of liquid at the growth temperatures and is constrained by the physical dimension of the ingot. The microstructure of both grain types is similar containing a minor quantity (on the order of 5–10 %) of a second phase and a high degree of porosity in the as-grown state. The second phase is usually present as a thin layer between adjacent grains or associated with a pore within a single grain. The grain porosity is distributed throughout the ingot. These defects can be removed through post-growth hot isostatic pressing and anneal treatments.

scholarly journals Local Order in Single Grain Cd-Yb Icosahedral Phase

2003 ◽  
Vol 805 ◽  
Author(s):  
Y. Q. Wu ◽  
M. J. Kramer ◽  
T. A. Lograsso
Keyword(s):  
Cluster Structure ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
Local Order ◽  
Local Cluster ◽  
Transmission Electron Microcopy ◽  
Transmission Electron ◽  
Single Grain ◽  
Matching Rules ◽  
D Model

ABSTRACTSingle grains of icosahedral Cd84Yb16 quasicrystalline phase were characterized using high resolution transmission electron microcopy (HRTEM) technique. Image reconstruction of the obtained multiple through-focal series for both the two and five-fold axes are consistent with the local cluster structure of concentric polyhedra consisting of Cd tetrahedron (1/3 occupied icosahedron), Cd dodecahedron, Yb icosahedron and a Cd icosidodecahedron. Edge-sharing of the clusters can result in complete tiling of the 2-D projections. Simple matching rules are being investigated to construct a 3-D model.

Evidence for a new quasicrystalline transition state in Al65Cu20Fe15 alloy

1990 ◽  
Vol 48 (4) ◽  
pp. 134-135
Author(s):  
Z. Zhang ◽  
N.C. Li ◽  
K. Urban
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Icosahedral Phase ◽  
Electron Microscopy Study ◽  
Quasicrystalline Phase ◽  
Slow Cooling ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Icosahedral Quasicrystals

In Al65Cu20Fe15 alloy icosahedral quasicrystals are formed of extraordinary perfection. On the other hand, there are indications that the quasicrystalline phase is only stable at temperatures above about 800°C. Here we report on a transmission electron microscopy study of a new phase which represents a transition stage between the icosahedral quasicrystalline (IQ) phase and a crystalline phase. It can be described by a modulation of the IQ phase along one of the five-fold axes (A5) of the original IQ phase.The icosahedral phase in Al65Cu20Fe15 was obtained by arc melting the high purity elements and subsequent slow cooling. The material was then heat treated at 700°C for 24 hours and again slowly cooled to room temperature. During this treatment the regular IQ phase transformed into a phase characterized by the occurence of translation periodicity along one of the five-fold axes of the original IQ phase. This is demonstrated by a commensurate arrangement of electron diffraction spots only along one of the original A5 (Fig. 1). High-resolution electron microscopy (HREM) corroborates this observation (Fig. 2).

Phase Diagrams And Approximants

1998 ◽  
Vol 553 ◽  
Author(s):  
M. Quiquandon ◽  
Y. Calvayrac ◽  
A. Quivy ◽  
F. Faudot ◽  
D. Gratias
Keyword(s):  
Phase Diagram ◽  
Orthorhombic Phase ◽  
Ternary Systems ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
Quaternary Phase ◽  
Cubic Phases ◽  
Single Grain ◽  
Si Content ◽  
P Type

AbstractThe controled growth of large single grain of quasicrystalline phase in metallic alloys is a difficult task that requires a detailled knowledge of the corresponding phase diagram. We discuss the metallurgical specificities of the ternary systems AlCuFe and AlPdMn with respect to single icosahedral grain elaboration. We show that adding a few percents of Silicon in the AlCuFe system leads to stabilize two low order cubic approximants one, α, based on Bergman clusters with a parent F-type icosahedral phase and the other, α', based on Mackay clusters with a parent P-type icosahedral phase. A section of this quaternary phase diagram at constant Si content shows that these cubic phases have no common stability region but are located on opposite sides of an orthorhombic phase that is expected to be a complex synthetic structure mixing both Mackay and Bergman type atomic clusters.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

THE R.J. CHAMBERS COLLECTION: AN “ARCHIVIST'S” REVELATIONS OF 20th CENTURY ACCOUNTING THOUGHT AND PRACTICE

2006 ◽  
Vol 33 (1) ◽  
pp. 145-166 ◽  
Author(s):  
Graeme W. Dean ◽  
Peter W. Wolnizer ◽  
Frank L. Clarke
Keyword(s):  
Prima Facie ◽  
Accounting Education ◽  
Hard Copy ◽  
Accounting History ◽  
Research Areas ◽  
Archival Source ◽  
Inflation Accounting ◽  
History Of ◽  
High Degree ◽  
Accounting Standard Setting

A major, unique accounting archival source, the R.J. Chambers Collection comprises both hard copy and, utilizing cutting-edge search technology, internet accessible materials. From his academic beginnings, Chambers was an orderly person, an archivist of the extensive and varied evidence that underpinned his proposals for accounting reform. Opening research areas for accounting biography, the development of accounting thought, the history of accounting institutions, prosopography, public sector accounting history, and comparative international accounting history are foremost amongst the myriad justifications for seeking to unravel the accounting history “lodes” in archives such as the Goldberg, Chambers, and Briloff Collections [Potter, 2003]. The archiving of the meticulously kept Chambers papers from 1947–1999 provides an opportunity for unfolding the background to events previously withheld from accounting history scholars. Professional episodes in relation to inflation accounting, standard setting, proposals to reform accounting education, and the like that appeared prima facie to be worth investigating are now open to scrutiny from a different angle, with a different type of evidence available in this Collection. This Collection provides a high degree of archival provenance. In particular, it represents an orderly retention of past documentation of what Chambers wrote, and perhaps uniquely for accounting historians, received; thus, providing an extensive window from which to examine the disorderly present environment of acounting.

scholarly journals Euglycemic Diabetic Ketoacidosis after a Single Dose of Empagliflozin in a Patient with Pancreatitis

2021 ◽  
Vol 11 (2) ◽  
pp. 216-218
Author(s):  
Marta Brandão Calçada ◽  
Luís Fernandes ◽  
Rita Soares Costa ◽  
Sara Montezinho ◽  
Filipa Martins Duarte ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Diabetic Ketoacidosis ◽  
Drug Class ◽  
Clinical Suspicion ◽  
Laboratory Findings ◽  
Sodium Glucose Cotransporter ◽  
History Of ◽  
High Degree ◽  
Euglycemic Diabetic Ketoacidosis

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are the most recently approved drug class for the treatment of type 2 diabetes mellitus (T2D). Although they are largely well-tolerated, their intake has been associated with euglycemic diabetic ketoacidosis (DKA) in some rare cases. We report the case of a 70-year-old male with type 2 diabetes and no history of DKA, who started therapy with empagliflozin one day before presenting with acute pancreatitis and laboratory findings consistent with euglycemic DKA. SGLT2i can induce euglycemic DKA from the first dose. Given the atypical presentation, a high degree of clinical suspicion is required to recognize this complication.

929 Not Another Abscess - A Case of Streptococcal Myositis Misdiagnosed as a Right Axillary Abscess

2021 ◽  
Vol 108 (Supplement_2) ◽  
Author(s):  
O Oyende ◽  
J Jackman
Keyword(s):  
White Cell Count ◽  
General Surgeon ◽  
High Dose ◽  
General Anaesthetic ◽  
Microbiological Analysis ◽  
Reactive Protein ◽  
Affected Tissue ◽  
Life Threatening ◽  
History Of ◽  
High Degree

Abstract Introduction Streptococcal myositis is a rare form of infectious myositis caused by Lansfield A beta-haemolytic streptococci. It is characterised by rapidly spreading inflammation that can result in severe systemic toxicity and necrosis of the affected tissue if not diagnosed and aggressively treated. Presentation We report a case of a 42-year-old male who presented with a one-week history of worsening right axillary swelling that progressed to painful swelling of his arm. Inflammatory markers were significantly elevated with a white cell count of 17 ×109/L and C-reactive protein of 212 mg/L. On examination, a fluctuant axillary swelling was appreciated, and a decision was made for incision and drainage under general anaesthetic. Intraoperative aspiration of his arm revealed copious purulent fluid prompting intraoperative orthopaedic consult and exploration of the anterior compartment in which there was extensive involvement of the biceps muscle. The microbiological analysis revealed gram-positive cocci in chains, and microbiology advice sought for tailoring of antibiotic regimen. He has recovered well. Discussion Though uncommon, the emergency general surgeon should have a high degree of suspicion when evaluating soft tissue infections to avert potentially disastrous outcomes. Conclusion Early diagnosis, aggressive management with high-dose intravenous antibiotics, and surgical debridement are principles to treat this rare, life-threatening infection.

scholarly journals The Return of National Self-Sufficiency? Excavating Autarkic Thought in a De-Globalizing Era

2021 ◽  
Author(s):  
Eric Helleiner
Keyword(s):  
Intellectual History ◽  
International Political Economy ◽  
Economic Thought ◽  
John Maynard Keynes ◽  
New Politics ◽  
Self Sufficiency ◽  
National Economic ◽  
History Of ◽  
High Degree ◽  
Rich History

Abstract As the global crisis triggered by the COVID-19 virus unfolded, The Economist magazine published a cover in May 2020 titled “Goodbye globalization: the dangerous lure of self-sufficiency.” The title summed up well the new political interest in the ideology of national economic self-sufficiency in the pandemic context. Unfortunately, contemporary textbooks in the field of international political economy (IPE) say little about this kind of “autarkic” thought. No survey of the history of autarkic thought exists even within specialist IPE literature or in the fields of intellectual history and the history of economic thought. Filling this gap in existing scholarship, this article highlights a rich history of autarkic thought that includes the ideas of famous thinkers such as Jean-Jacques Rousseau, Johann Fichte, Mohandas Gandhi, and John Maynard Keynes. Three core rationales for a high degree of national self-sufficiency have been advanced in the past: (1) insulation from foreign economic influence, (2) insulation from foreign political and/or cultural influence, and (3) the promotion of international peace. At the same time, considerable disagreements have existed among autarkists about some of these rationales and their relative importance, as well as about the precise meaning of national self-sufficiency. These disagreements stemmed not just from differences in their specific goals but also from the different conditions across time and space in which autarkic thought was developed. In addition to improving understanding of the autarkic ideological tradition, this article contributes to emerging scholarship attempting to overcome Western-centrism in IPE scholarship as well as literature exploring the new politics of de-globalization in the current era.

scholarly journals Multi-Locus Selection and the Structure of Variation at the white Gene of Drosophila melanogaster

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 635-645 ◽  
Author(s):  
David A Kirby ◽  
Wolfgang Stephan
Keyword(s):  
Drosophila Melanogaster ◽  
White Gene ◽  
Transcriptional Unit ◽  
North American Population ◽  
Evolutionary Mechanisms ◽  
Locus Selection ◽  
Neutral Equilibrium ◽  
History Of ◽  
High Degree ◽  
Very High

Abstract We surveyed sequence variation and divergence for the entire 5972-bp transcriptional unit of the white gene in 15 lines of Drosophila melanogaster and one line of D. simulans. We found a very high degree of haplotypic structuring for the polymorphisms in the 3′ half of the gene, as opposed to the polymorphisms in the 5′ half. To determine the evolutionary mechanisms responsible for this pattern, we sequenced a 1612-bp segment of the white gene from an additional 33 lines of D. melanogaster from a European and a North American population. This 1612-bp segment encompasses an 834bp region of the white gene in which the polymorphisms form high frequency haplotypes that cannot be explained by a neutral equilibrium model of molecular evolution. The small number of recombinants in the 834bp region suggests epistatic selection as the cause of the haplotypic structuring, while an investigation of nucleotide diversity supports a directional selection hypothesis. A multi-locus selection model that combines features from both-hypotheses and takes the recent history of D. melanogaster into account may be the best explanation for these data.

scholarly journals Tuberculosis presenting as dacryoadenitis in the USA

2019 ◽  
Vol 12 (11) ◽  
pp. e231694 ◽  
Author(s):  
Harry Ross Powers ◽  
Mark Anthony Diaz ◽  
Julio C Mendez
Keyword(s):  
Correct Diagnosis ◽  
Developed Countries ◽  
Histopathological Analysis ◽  
Orbital Mass ◽  
Antituberculosis Therapy ◽  
The Usa ◽  
History Of ◽  
Patient’S History ◽  
High Degree ◽  
Filipino Woman

A 25-year-old Filipino woman living in the USA was evaluated for a 5-month history of left eye pain and a subsequent orbital mass. Histopathological analysis of the lacrimal mass showed a mixed inflammatory process with necrotising granulomas and positive cultures for Mycobacterium tuberculosis. She was treated with antituberculosis therapy, with resolution of symptoms. Tuberculosis dacryoadenitis is extremely rare in the USA and other developed countries. It requires a high degree of clinical suspicion with special attention to the patient’s history to make the correct diagnosis. It can be treated successfully with antituberculosis therapy.

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