scholarly journals Greenockite Whiskers from the Bytom Burned Coal Dump, Upper Silesia, Poland

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 470
Author(s):  
Katarzyna Nowak ◽  
Irina Galuskina ◽  
Evgeny Galuskin
Keyword(s):  
Electron Beam ◽  
Crystal Growth ◽  
Substrate Surface ◽  
Drop Diameter ◽  
Large Excess ◽  
Vapor Liquid Solid ◽  
Upper Silesia ◽  
Vapor Liquid Solid Mechanism ◽  
Burning Coal ◽  
Fiber Thickness

Orange greenockite (CdS) aggregates were found in a small fumarole at a burned coal dump near Bytom, Upper Silesia, Poland and were studied using a variety of techniques in order to determine their chemistry, morphology, and most importantly, the mechanism of crystal growth. Greenockite rods, wires, and whiskers with bismuth drops on crystal tops are predominant in these aggregates. Greenockite rods oriented sub-perpendicular to the substrate surface. The rod thickness reaches 5–6 μm and about 10 μm in length. The catalyst bismuth drop has a diameter comparable to the rod thickness. Fiber forms (wires and whiskers) are sub-parallel to the substrate surface. The thickness of these forms is usually less than 2 μm, and the length can be close to 1 mm. The bismuth drop diameter can show a large excess over the fiber thickness. Catalyst drops on the tops of whiskers began to change their form dynamically and exploded, spraying bismuth under the electron beam effect. Rods grow along the [01–10] direction, and whiskers and wires (axial forms) along the [0001] direction. Greenockite rod crystals, carrying on top a relatively homogenous bismuth catalyst drop, were formed on the heated substrate according to the VLS (vapor–liquid–solid) mechanism at temperatures not lower than 270 °C. Greenockite whiskers and wires grew just above of the substrate surface according to the VQS (vapor–quasiliquid–solid) mechanism at temperatures lower than 200 °C. These mechanisms of growth have very rarely been recorded to occur in nature and even less so in burning coal dumps. The cooperative growth effects of the fiber greenockite crystals were also described.

Exploring SiC Growth Limitation of Vapor-Liquid-Solid Mechanism when Using Two Different Carbon Precursors

2013 ◽  
Vol 740-742 ◽  
pp. 323-326
Author(s):  
Kassem Alassaad ◽  
François Cauwet ◽  
Davy Carole ◽  
Véronique Soulière ◽  
Gabriel Ferro
Keyword(s):  
Growth Rate ◽  
High Growth ◽  
High Growth Rate ◽  
Carbon Precursor ◽  
Growth Limitation ◽  
Vapor Liquid Solid ◽  
Partial Pressures ◽  
Vapor Liquid Solid Mechanism ◽  
Vls Growth ◽  
Vapor Liquid

Abstract. In this paper, conditions for obtaining high growth rate during epitaxial growth of SiC by vapor-liquid-solid mechanism are investigated. The alloys studied were Ge-Si, Al-Si and Al-Ge-Si with various compositions. Temperature was varied between 1100 and 1300°C and the carbon precursor was either propane or methane. The variation of layers thickness was studied at low and high precursor partial pressure. It was found that growth rates obtained with both methane and propane are rather similar at low precursor partial pressures. However, when using Ge based melts, the use of high propane flux leads to the formation of a SiC crust on top of the liquid, which limits the growth by VLS. But when methane is used, even at extremely high flux (up to 100 sccm), no crust could be detected on top of the liquid while the deposit thickness was still rather small (between 1.12 μm and 1.30 μm). When using Al-Si alloys, no crust was also observed under 100 sccm methane but the thickness was as high as 11.5 µm after 30 min growth. It is proposed that the upper limitation of VLS growth rate depends mainly on C solubility of the liquid phase.

Biocompatible Ceramic-Biopolymer Coatings Obtained by Electrophoretic Deposition on Electron Beam Structured Titanium Alloy Surfaces

2016 ◽  
Vol 879 ◽  
pp. 1552-1557
Author(s):  
C. Ramskogler ◽  
L. Cordero ◽  
Fernando Warchomicka ◽  
A.R. Boccaccini ◽  
Christof Sommitsch
Keyword(s):  
Titanium Alloy ◽  
Surface Modification ◽  
Electron Beam ◽  
Electrophoretic Deposition ◽  
Composite Coatings ◽  
Substrate Surface ◽  
3D Structure ◽  
Titania Nanoparticles ◽  
Structured Surfaces ◽  
Major Interest

An area of major interest in biomedical engineering is currently the development of improved materials for medical implants. Research efforts are being focused on the investigation of surface modification methods for metallic prostheses due to the fundamental bioinert character of these materials and the possible ion release from their surfaces, which could potentially induce the interfacial loosening of devices after implantation. Electron beam (EB) structuring is a novel technique to control the surface topography in metals. Electrophoretic deposition (EPD) offers the feasibility to deposit at room temperature a variety of materials on conductive substrates from colloidal suspensions under electric fields. In this work single layers of chitosan composite coatings containing titania nanoparticles (n-TiO2) were deposit by EPD on electron beam (EB) structured Ti6Al4V titanium alloy. Surface structures were designed following different criteria in order to develop specific topography on the Ti6Al4V substrate. n-TiO2 particles were used as a model particle in order to demonstrate the versatility of the proposed technique for achieving homogenous chitosan based coatings on structured surfaces. A linear relation between EPD time and deposition yield on different patterned Ti6Al4V surfaces was determined under constant voltage conditions, obtaining homogeneous EPD coatings which replicate the 3D structure (pattern) of the substrate surface. The present results show that a combination of both techniques can be considered a promising surface modification approach for metallic implants, which should lead to improved interaction between the implant surface and the biological environment for orthopaedic applications.

scholarly journals Vapor-Liquid-Solid Growth and Properties of One Dimensional PbO and PbO/SnO2 Nanowires

2022 ◽  
Author(s):  
Nikolaos Kelaidis ◽  
Matthew Zervos ◽  
Nektarios Lathiotakis ◽  
Alexander Chroneos ◽  
Eugenia Tanasă ◽  
...  
Keyword(s):  
Vapor Liquid Solid ◽  
One Dimensional ◽  
Sno2 Nanowires ◽  
Vapor Liquid Solid Mechanism ◽  
Vapor Liquid Solid Growth ◽  
Vapor Liquid

PbO nanowires have been obtained via a self-catalyzed, vapor-liquid-solid mechanism and the reaction of Pb with O2 between 200°C and 300°C at 10 Pa. These had the form of tapes...

scholarly journals PULSE GROWTH OF THE GAAS NANOWIRES

2021 ◽  
Author(s):  
Alla Nastovjak ◽  
David Shterental ◽  
Nataliya Shwartz
Keyword(s):  
Vapor Liquid Solid ◽  
Gaas Nanowires ◽  
Vapor Liquid Solid Mechanism ◽  
Gaas Nanowire ◽  
Vapor Liquid

The results of the simulation of the GaAs nanowire self-catalyzed growth via vapor-liquid-solid mechanism using various pulse modes are presented in this work.

Synthesis of Aluminum Nitride Whiskers Via a Vapor-Liquid-Solid Process

1998 ◽  
Vol 547 ◽  
Author(s):  
Ying Dai ◽  
Ce-Wen Nan
Keyword(s):  
Carbon Black ◽  
Aluminum Nitride ◽  
Aluminum Powder ◽  
Nitrogen Atmosphere ◽  
Processing Conditions ◽  
Vapor Liquid Solid ◽  
Aluminum Powders ◽  
Sem And Tem ◽  
Vapor Liquid Solid Mechanism ◽  
Vapor Liquid

AbstractAluminum nitride whiskers were synthesized by nitridation of commercial aluminum powder at 1623K in a nitrogen atmosphere. The starting materials consisted of aluminum and carbon black. The carbon acted as a barrier between aluminum powders during nitridation and was removed by heating in air at 923K. The whiskers were about 0.5-1μm in diameter and 10-20μm in length. The droplets at the whisker tips showed that the whiskers grew via a vapor-liquid-solid mechanism. The morphologies of the whiskers were studied by means of SEM and TEM. The formation of the whiskers depended on the processing conditions.

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