A Theoretical and Empirical Perspective of SiC Bulk Growth

1998 ◽  
Vol 512 ◽  
Author(s):  
V. F. Tsvetkov ◽  
D. N. Henshall ◽  
M. F. Brady ◽  
R. C. Glass ◽  
C. H. Carter
Keyword(s):  
Defect Formation ◽  
Current Knowledge ◽  
Large Diameter ◽  
Thermoelastic Stress ◽  
Full Potential ◽  
Bulk Growth ◽  
Sublimation Method ◽  
Analytical Review ◽  
Empirical Perspective ◽  
Kinetics Of

ABSTRACTThe production of large diameter, high quality boules of SiC is essential to realize the full potential of this important semiconductor material. The objective of this paper is to provide a state-of-the-art analysis of the key directions for SiC bulk growth research, as well as presenting our most recent empirical results. Based on an analytical review of current knowledge, the following topics concerning growth of large 6H and 4H-SiC bulk crystals are discussed: 1) thermodynamics of the vapor phase including the efficiency of crystal growth, 2) kinetics of growth including mass transport in the boundary layer and 3) defect formation processes including thermoelastic stress. In addition, results of growth modeling are summarized and direction for further work suggested. Results on growth of semi-insulating and 50–75 mm diameter 4H-SiC wafers are presented. A discussion on micropipes, which are currently the most harmful defect in SiC wafers is presented. Although several mechanisms, or combinations of mechanisms, cause micropipes in SiC boules grown by the seeded sublimation method, we have reduced micropipe densities by orders of magnitude over the last few years. This continual reduction and the production of wafers with micropipe densities of less than 1 cm-2 (with >1 cm2 areas void of micropipes), indicate that micropipes will be reduced to a level that makes high current devices viable and that they may soon be totally eliminated.

scholarly journals Bioactivities of Lipid Extracts and Complex Lipids from Seaweeds: Current Knowledge and Future Prospects

Marine Drugs ◽  
2021 ◽  
Vol 19 (12) ◽  
pp. 686
Author(s):  
Diana Lopes ◽  
Felisa Rey ◽  
Miguel C. Leal ◽  
Ana I. Lillebø ◽  
Ricardo Calado ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Value Added ◽  
Chemical Diversity ◽  
Full Potential ◽  
Health And Wellness ◽  
Scientific Publications ◽  
Organic Extracts ◽  
Food And Feed ◽  
Pharmaceutical Industries ◽  
Complex Lipids

While complex lipids of seaweeds are known to display important phytochemical properties, their full potential is yet to be explored. This review summarizes the findings of a systematic survey of scientific publications spanning over the years 2000 to January 2021 retrieved from Web of Science (WoS) and Scopus databases to map the state of the art and identify knowledge gaps on the relationship between the complex lipids of seaweeds and their reported bioactivities. Eligible publications (270 in total) were classified in five categories according to the type of studies using seaweeds as raw biomass (category 1); studies using organic extracts (category 2); studies using organic extracts with identified complex lipids (category 3); studies of extracts enriched in isolated groups or classes of complex lipids (category 4); and studies of isolated complex lipids molecular species (category 5), organized by seaweed phyla and reported bioactivities. Studies that identified the molecular composition of these bioactive compounds in detail (29 in total) were selected and described according to their bioactivities (antitumor, anti-inflammatory, antimicrobial, and others). Overall, to date, the value for seaweeds in terms of health and wellness effects were found to be mostly based on empirical knowledge. Although lipids from seaweeds are little explored, the published work showed the potential of lipid extracts, fractions, and complex lipids from seaweeds as functional ingredients for the food and feed, cosmeceutical, and pharmaceutical industries. This knowledge will boost the use of the chemical diversity of seaweeds for innovative value-added products and new biotechnological applications.

Composition and Potential Health Benefits of Pomegranate: A Review

2019 ◽  
Vol 25 (16) ◽  
pp. 1817-1827 ◽  
Author(s):  
Vesna Vučić ◽  
Milkica Grabež ◽  
Armen Trchounian ◽  
Aleksandra Arsić
Keyword(s):  
Current Knowledge ◽  
Health Benefits ◽  
Punica Granatum ◽  
In Vivo Studies ◽  
Full Potential ◽  
Fruit Peel ◽  
Potential Health ◽  
Comprehensive Search

Background:: Pomegranate (Punica granatum L.) fruits are widely consumed and used as preventive and therapeutic agents since ancient times. Pomegranate is a rich source of a variety of phytochemicals, which are responsible for its strong antioxidative and anti-inflammatory potential. Objective:: The aim of this review is to provide an up-to-date overview of the current knowledge of chemical structure and potential health benefits of pomegranate. Method: : A comprehensive search of available literature. Results:: The review of the literature confirms that juice and extracts obtained from different parts of this plant, including fruit peel, seeds, and leaves exert health benefits in both in vitro and in vivo studies. The antidiabetic, antihypertensive, antimicrobial and anti-tumour effects of pomegranate fruit are of particular scientific and clinical interest. Conclusion:: Further investigations are required to clarify the mechanism of action of the bioactive ingredients and to reveal full potential of pomegranate as both preventive and therapeutic agent.

scholarly journals Wood Moisture-Induced Swelling at the Cellular Scale—Ab Intra

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 996 ◽  
Author(s):  
Xavier Arzola-Villegas ◽  
Roderic Lakes ◽  
Nayomi Z. Plaza ◽  
Joseph E. Jakes
Keyword(s):  
Cell Wall ◽  
Current Knowledge ◽  
Scale Up ◽  
Wall Layer ◽  
Future Research ◽  
Full Potential ◽  
Wood Moisture ◽  
Length Scales ◽  
Elementary Fibril ◽  
Swelling And Shrinking

Wood, a complex hierarchical material, continues to be widely used as a resource to meet humankind’s material needs, in addition to providing inspiration for the development of new biomimetic materials. However, for wood to meet its full potential, researchers must overcome the challenge of understanding its fundamental moisture-related properties across its many levels of hierarchy spanning from the molecular scale up to the bulk wood level. In this perspective, a review of recent research on wood moisture-induced swelling and shrinking is presented from the molecular level to the cellular scale. Numerous aspects of swelling and shrinking in wood remain poorly understood, sub-cellular phenomena in particular, because it can be difficult to study them experimentally. Here, we discuss recent research endeavors at each of the relevant length scales, including the molecular, cellulose elementary fibril, secondary cell wall layer nanostructure, cell wall, cell, and cellular levels. At each length scale, we provide a discussion on the current knowledge and suggestions for future research. The potential impacts of moisture-induced swelling pressures on experimental observations of swelling and shrinking in wood at different length scales are also recognized and discussed.

Native Point Defect Densities and Dark Line Defects in ZnSe

1995 ◽  
Vol 408 ◽  
Author(s):  
M. A. Berding ◽  
A. Sher ◽  
M. Van Schilfgaarde
Keyword(s):  
Free Energy ◽  
Point Defect ◽  
Defect Formation ◽  
Local Density ◽  
Full Potential ◽  
Nonradiative Recombination ◽  
Dark Line ◽  
Frenkel Defect ◽  
Native Point Defect ◽  
Defect Densities

AbstractNative point defect densities (including vacancies, antisites and interstitials) in ZnSe are calculated using a quasichemical formalism, including both vibrational and electronic contributions to the defect free energy. The electronic contribution to the defect formation free energy is calculated using the self-consistent first-principles full-potential linearized muffin-tin orbital (FP-LMTO) method and the local-density approximation (LDA). Gradient corrections are included so that absolute reference to zinc atoms in the vapor phase can be made. We find that the Frenkel defect formation energy is ∼0.3 eV lower at a stacking fault than in the bulk lattice. Nonradiative-recombination-induced Frenkel defect generation at stacking faults is proposed as a mechanism responsible for the limited device lifetimes.

Pipeline Stability: State of the Art

2008 ◽  
Author(s):  
Hammam O. Zeitoun ◽  
Knut To̸rnes ◽  
Gary Cumming ◽  
Masˇa Brankovic´
Keyword(s):  
Current Knowledge ◽  
Large Diameter ◽  
Research Work ◽  
Careful Consideration ◽  
Cost Driver ◽  
Engineering Practice ◽  
Design Codes ◽  
Limit States ◽  
Acceptance Criteria ◽  
Hydrodynamic Loads

Ensuring subsea pipeline stability on the seabed is one of the fundamental aspects of pipeline design. A comprehensive on-bottom stability design will include a detailed assessment of the hydrodynamic loads acting on the pipeline, the pipe-soil interaction, the structural response and a careful consideration of the acceptance criteria. Pipeline stabilisation is a major cost driver in some locations around the world, where the designer is faced with extreme design challenges including severe metocean conditions, shallow waters, large diameter lines, and uncertain or difficult geotechnical conditions. These may all contribute to complex stabilisation solutions resulting in costly construction techniques. The current knowledge and engineering practice applied in pipeline stability design is mostly based on the work performed during the 80s by the Pipeline Stability Design Project (PIPESTAB) and on the research conducted by the American Gas Association (AGA) in another Joint Industry project (JIP). At the time, these studies were aimed at gaining an understanding of the physics governing pipeline stability, in particular hydrodynamic loads on pipelines and soil resistance. These two aspects were investigated independently from each other. Understanding pipeline stability has evolved over the last decade due to the application of this knowledge, findings from further research work, the introduction and requirements of new pipeline codes, and advances in the understanding of pipe-soil interaction. Recently gained understanding has raised the question whether alternatives to the present design approaches and acceptance criteria, as specified in the design codes, could be developed. The areas of debate include the approach used for addressing pipe soil interaction, the hydrodynamic coefficients to be applied, the design kinematics to be considered, the design methodologies, the acceptance criteria, and compliance with design codes limit states. This paper presents an overview of the current available knowledge for addressing pipeline stability. The aim is to briefly summarise the key aspects of the pipeline stability design process and to include some historical perspective. The paper discusses the advantage and shortfalls of the different approaches with a view to consolidate understanding, rather than to provide a ready-made solution to a complex design problem.

Synergistic Influence of the Addition of Al, Ni and Pb to a Zinc Bath upon Growth Kinetics and Structure of Coatings

2013 ◽  
Vol 212 ◽  
pp. 115-120 ◽  
Author(s):  
Henryk Kania ◽  
Piotr Liberski
Keyword(s):  
Chemical Composition ◽  
Growth Kinetics ◽  
Current Knowledge ◽  
Silicon Steel ◽  
Optimum Concentration ◽  
Zinc Bath ◽  
Structure Of Coatings ◽  
Product Surface ◽  
Kinetics Of

In this paper the current knowledge about the influence of alloy additions used in galvanizing baths has been analysed. The optimum concentration of Al, Ni and Pb addition has been established. Tests have been conducted to determine the synergistic influence of the addition of AlNiPb in a zinc bath upon the structure and growth kinetics of coatings. The structure and the chemical composition of coatings obtained on steel with low silicon contents and on Sandelin steel have been developed. It has been determined that the synergistic influence of the AlNiPb addition effectively lowers the reactivity of Sandelin steel and it improves zincs flowing off the product surface which results in decreased zinc consumption and better appearance of the coating. The structure of coatings obtained in a Zn-AlNiPb bath on Sandelin steel is similar to the structure of coatings obtained on low-silicon steel.

Reduction of Dislocations in the Bulk Growth of SiC Crystals

2006 ◽  
Vol 527-529 ◽  
pp. 3-8 ◽  
Author(s):  
Daisuke Nakamura
Keyword(s):  
Dislocation Density ◽  
Growth Process ◽  
Large Diameter ◽  
Device Performance ◽  
Etch Pit Density ◽  
Bulk Growth ◽  
Etch Pit ◽  
Low Dislocation Density ◽  
The Impact

Recent reports on the impact of elementary dislocations on device performance and reliability suggest not only micropipe defects but also dislocations should be reduced or eliminated perfectly. This paper presents bulk growth process for reduction of the dislocations, and quality of the crystals grown by the process. Etch pit density of the best crystals grown by the process was lower by three orders of magnitude than that of conventional crystals. Moreover, large diameter crystals (>2”) with low dislocation density were successfully grown by the process.

Defect formation in Si-crystals grown on large diameter bulk seeds by a modified FZ-method

2018 ◽  
Vol 500 ◽  
pp. 5-10 ◽  
Author(s):  
H.-J. Rost ◽  
R. Menzel ◽  
D. Siche ◽  
U. Juda ◽  
S. Kayser ◽  
...  
Keyword(s):  
Defect Formation ◽  
Large Diameter
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