Structural Instability of the Ceramic Coating in a Metal-Ceramic Composite Induced Through Control of Chemistry of the Bonding Atmosphere

1992 ◽  
Vol 280 ◽  
Author(s):  
Abhijit Ray
Keyword(s):  
Amorphous Phase ◽  
Bonding Temperature ◽  
Structural Instability ◽  
Processing Technique ◽  
High Concentration ◽  
Ceramic Phase ◽  
Enhanced Diffusion ◽  
Transmission Electron ◽  
Metal Ceramic ◽  
Novel Processing

ABSTRACTA novel processing technique has been developed to coat Al2O3 on Nb in an argon atmosphere with very low O2 content. It has been proposed1 that the low O2 content helped to increase the defect concentration in the ceramic phase resulting in an enhanced diffusion of Nb into Al2O3 at the metal-ceramic interface at a relatively low bonding temperature. A mathematical model has been developed1 to understand the effect of purified bonding atmosphere on interfacial diffusion. While diffraction studies in the transmission electron microscope revealed1 extensive amorphization at the metal-ceramic interface, EDX analysis showed1 that the interfacial amorphous phase has a very high concentration of O. Additionally, this phase is found to contain Al and Nb. The interfacial phase is formed due to the diffusion of Nb into the ceramic phase. The paradoxical phenomenon of O enrichment of the interfacial amorphous phase in a low O2 containing bonding atmosphere is due to the loss of gaseous oxides of Al from this phase. These oxides have relatively less proportion of O compared to Al2O3. Continuous loss of such oxides from the amorphous phase to the gaseous phase will, therefore, result in an O to Al ratio (in the amorphous phase) far exceeding that in Al2O3 (3:2).

Amorphization at the Metal-Ceramic Interface in Nb – Al2O3 Composite Through Extensive Interphase Diffusion

1992 ◽  
Vol 271 ◽  
Author(s):  
Abhijit Ray ◽  
Shyam K. Samanta
Keyword(s):  
Electron Microscopy ◽  
Amorphous Phase ◽  
Impurity Content ◽  
Interfacial Region ◽  
Oxygen Impurity ◽  
High Concentration ◽  
Electron Microscopic ◽  
Ceramic Phase ◽  
Ceramic Particles ◽  
Metal Ceramic

ABSTRACTA novel, low temperature and pressureless bonding technique has been developed to fabricate Al2O3 coated Nb composite. The nature of the interface bond has been characterized by extensive electron microscopic investigation, and a phenomenological model has been developed to explain the mechanism of bond formation. In the present technique a suspension (in distilled water) of fine Al2O3 powder (mean particle size of 0.2μm) was applied on polished and cleaned Nb blocks. The coatings were air dried and the coated metals were heat treated at 1100°C to achieve bonding between the ceramic and the metal. The process was carried out in an argon atmosphere. To reduce the oxygen impurity content in argon, the gas was passed over Mg turnings at 300°C before its entry into the bonding apparatus. Control of oxygen impurity in the bonding atmosphere in conjunction with the use of fine ceramic particles led to enhancement of interfacial diffusion. Scanning electron microscopy of the bonded specimens showed a consolidated layer in the ceramic phase close to the metal-ceramic interface. Transmission electron microscopy of the metal-ceramic interfacial region rOevealed a distribution of Al2O3 particles in an amorphous phase containing varying amount of Al, Nb, and 0. Prior treatment with Mg was to reduce the oxygen impurity content below the equlibrium oxygen partial pressure (at 1100°C) of Al2O3. This would result in loss of oxygen from the surface of the ceramic particles. Thus a region, with high concentration of 0= vacancy would form along the surfaces of the particles. As a result of excessive oxygen depletion, further continuation of this process would lead to degeneration of the crystal structure of the regions along the surfaces of the Al2O3 particles. These regions along the Al2O3 particle surfaces may then act as easy diffusion paths for Nb. Extensive diffusion of the metal into the ceramic phase along these paths would lead to the formation of an amorphous phase along the ceramic particle surfaces. Eventually, this phase will occupy the voids in between the ceramic particles, that are close to the metal-ceramic interface, and thus bond them together with the metal.

Processing and Crystal Microstructure of Porous High Pressure Crystallized Nanodiamond/UHMWPE Biomedical Nanocomposite

2011 ◽  
Vol 328-330 ◽  
pp. 857-860 ◽  
Author(s):  
Chau Chang Chou ◽  
Jyun Hao You ◽  
Cheng Lun Wu
Keyword(s):  
High Pressure ◽  
Porous Structure ◽  
Biomedical Application ◽  
Processing Technique ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Bulk Hardness ◽  
Novel Processing ◽  
Pressure Crystallization ◽  
Ultra High Molecular Weight

A novel processing technique using a series of mixing/refluxing procedures and high-pressure crystallization (HPC) to fabricate nanodiamond/ultra high molecular weight polyethylene (ND/UHMWPE) nanocomposites for biomedical application was examined. For better mimetic lubrication, a porous structure was implemented in this study. Vitamin E as an anti-oxidation additive was also incorporated in selected porous specimens. The morphology of the specimens was investigated by transmission electron microscopy. The phase and crystal characteristics were revealed by Raman spectroscopy and X-ray diffraction. Shore D hardness was used to study the effect of the material’s porous structure and particle-induced crystallization on the bulk mechanical property. The dispersion of NDs in the UHMWPE matrix can significantly promote the crystallinity of the HPC specimens, even with a porous structure. However, the bulk hardness does not reveal this improvement in crystal microstructure.

Effects of Concurrent Co or Ti Silicidation on Transient Diffusion and End-of-Range Damage in Phosphorus Implanted Silicon

1992 ◽  
Vol 262 ◽  
Author(s):  
J.W. Honeycutt ◽  
J. Ravi ◽  
G. A. Rozgonyi
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Complete Removal ◽  
Dislocation Loops ◽  
Enhanced Diffusion ◽  
Depth Profiles ◽  
Enhanced Dissolution ◽  
Implantation Damage ◽  
Transmission Electron ◽  
Defect Behavior ◽  
Secondary Ion

ABSTRACTThe effects of Ti and Co silicidation on P+ ion implantation damage in Si have been investigated. After silicidation of unannealed 40 keV, 2×1015 cm-2 P+ implanted junctions by rapid thermal annealing at 900°C for 10–300 seconds, secondary ion mass spectrometry depth profiles of phosphorus in suicided and non-silicided junctions were compared. While non-silicided and TiSi2 suicided junctions exhibited equal amounts of transient enhanced diffusion behavior, the junction depths under COSi2 were significantly shallower. End-of-range interstitial dislocation loops in the same suicided and non-silicided junctions were studied by planview transmission electron microscopy. The loops were found to be stable after 900°C, 5 minute annealing in non-silicided material, and their formation was only slightly effected by TiSi2 or COSi2 silicidation. However, enhanced dissolution of the loops was observed under both TiSi2 and COSi2, with essentially complete removal of the defects under COSi2 after 5 minutes at 900°C. The observed diffusion and defect behavior strongly suggest that implantation damage induced excess interstitial concentrations are significantly reduced by the formation and presence of COSi2, and to a lesser extent by TiSi2. The observed time-dependent defect removal under the suicide films suggests that vacancy injection and/or interstitial absorption by the suicide film continues long after the suicide chemical reaction is complete.

scholarly journals High-Tribological-Performance Polymer Nanocomposites: An Approach Based on the Superlubricity State of the Graphene Oxide Agglomerates

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2237
Author(s):  
Eder H. C. Ferreira ◽  
Angela Aparecida Vieira ◽  
Lúcia Vieira ◽  
Guilhermino J. M. Fechine
Keyword(s):  
Graphene Oxide ◽  
High Viscosity ◽  
Tribological Performance ◽  
Multilayer Graphene ◽  
High Concentration ◽  
Scanning Calorimetry ◽  
Mechanical Reinforcement ◽  
Transmission Electron ◽  
Twin Screw ◽  
Mechanical Tensile

Here, nanocomposites of high-molecular-weight polyethylene (HMWPE) and HMWPE-UHMWPE (80/20 wt.%) containing a low amount of multilayer graphene oxide (mGO) (≤0.1 wt.%) were produced via twin-screw extrusion to produce materials with a higher tribological performance than UHMWPE. Due to the high viscosity of both polymers, the nanocomposites presented a significant concentration of agglomerates. However, the mechanical (tensile) and tribological (volumetric loss) performances of the nanocomposites were superior to those of UHMWPE. The morphology of the nanocomposites was investigated using differential scanning calorimetry (DSC), microtomography, and transmission electron microscopy (TEM). The explanation for these results is based on the superlubricity phenomenon of mGO agglomerates. It was also shown that the well-exfoliated mGO also contained in the nanocomposite was of fundamental importance as a mechanical reinforcement for the polymer. Even with a high concentration of agglomerates, the nanocomposites displayed tribological properties superior to UHMWPE’s (wear resistance up to 27% higher and friction coefficient up to 57% lower). Therefore, this manuscript brings a new exception to the rule, showing that agglomerates can act in a beneficial way to the mechanical properties of polymers, as long as the superlubricity phenomenon is present in the agglomerates contained in the polymer.

ARCHITECTURE OF FLOWER-LIKE rGO/CNTs-LOADED CuxO NANOPARTICLES AND ITS PHOTOCATALYTIC PROPERTIES

NANO ◽  
2013 ◽  
Vol 08 (05) ◽  
pp. 1350052 ◽  
Author(s):  
BIN ZENG ◽  
XIAOHUA CHEN ◽  
XUTAO NING ◽  
CHUANSHENG CHEN ◽  
HUI LONG
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Performance ◽  
Degradation Process ◽  
Photocatalytic Properties ◽  
High Concentration ◽  
Graphene Oxides ◽  
Transmission Electron ◽  
Time Scanning ◽  
Reduced Graphene ◽  
First Time

Novel flower-like composite architecture was successfully synthesized by spray drying and post-calcinating method for the first time. Scanning electron microscopy and transmission electron microscopy observations confirmed that reduced graphene oxides/carbon nanotubes hybrid (rGO/CNTs) formed a flower-like micrometer structure and Cu2O , CuO ( Cu x O , x = 1 or 2) nanoparticles were decorated inside them. The photocatalytic properties were further investigated by evaluating the photodegradation of a pollutant methyl orange (MO). The experimental results indicated that this novel architecture enhanced photocatalytic performance with 96.2% decomposition of MO after 25 min in the presence of H 2 O 2 under visible light irradiation, which was much higher than that of Cu x O powders (33.2%). This could be attributed to the more efficient adsorption of MO molecules on flower-like rGO/CNTs and provide a high concentration of MO near to the Cu x O nanoparticles, thus promoting the photocatalytic degradation process.

Silicon-Sapphire Interface: A High Resolution Electron Microscopy Study

1980 ◽  
Vol 2 ◽  
Author(s):  
Fernando A. Ponce
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Silicon Layer ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Resolution Limit ◽  
High Concentration ◽  
Transmission Electron ◽  
Resolution Electron

ABSTRACTThe structure of the silicon-sapphire interface of CVD silicon on a (1102) sapphire substrate has been studied in crøss section by high resolution transmission electron microscopy. Multibeam images of the interface region have been obtained where both the silicon and sapphire lattices are directly resolved. The interface is observed to be planar and abrupt to the instrument resolution limit of 3 Å. No interfacial phase is evident. Defects are inhomogeneously distributed at the interface: relatively defect-free regions are observed in the silicon layer in addition to regions with high concentration of defects.

scholarly journals Syntheses of Colloidal F:In2O3 Cubes: Fluorine-Induced Faceting and Infrared Plasmonic Response

2018 ◽  
Author(s):  
Shin Hum Cho ◽  
Sandeep Ghosh ◽  
Zachariah J. Berkson ◽  
Jordan A. Hachtel ◽  
Jianjian Shi ◽  
...  
Keyword(s):  
Density Functional ◽  
Spectral Response ◽  
Visible Region ◽  
Scanning Transmission Electron Microscope ◽  
Colloidal Synthesis ◽  
Localized Surface Plasmon ◽  
High Concentration ◽  
Surface Binding ◽  
Transmission Electron ◽  
Scanning Transmission

Cube-shaped nanocrystals (NCs) of conventional metals like gold and silver generally exhibit localized surface plasmon resonance (LSPR) in the visible region with spectral modes determined by their faceted shapes. However, faceted NCs exhibiting LSPR response in the infrared (IR) region are relatively rare. Here, we describe the colloidal synthesis of nanoscale fluorine-doped indium oxide (F:In<sub>2</sub>O<sub>3</sub>) cubes with LSPR response in the IR region, wherein fluorine was found to both direct the cubic morphology and act as an aliovalent dopant. Single crystalline 160 nm F:In<sub>2</sub>O<sub>3</sub> cubes terminated by (100) facets and concave cubes were synthesized using a colloidal heat-up method. The presence of fluorine was found to impart higher stabilization to the (100) facets through density functional theory (DFT) calculations that evaluated the energetics of F-substitution at surface oxygen sites. These calculations suggest that the cubic morphology results from surface binding of F-atoms. In addition, fluorine acts as an anionic aliovalent dopant in the cubic bixbyite lattice of In<sub>2</sub>O<sub>3</sub>, introducing a high concentration of free electrons leading to LSPR. We confirmed the presence of lattice fluorine dopants in these cubes using solid-state <sup>19</sup>F and <sup>115</sup>In nuclear magnetic resonance (NMR) spectroscopy. The cubes exhibit narrow, shape-dependent multimodal LSPR extinction peaks due to corner- and edge-centered modes. The spatial origin of these different contributions to the spectral response are directly visualized by electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM).

scholarly journals A novel processing technique for fabrication of flexible YBa2Cu3O7−xwire

1989 ◽  
Vol 66 (9) ◽  
pp. 4532-4534 ◽  
Author(s):  
Shyam K. Samanta ◽  
S. Samajdar ◽  
W. Durrant ◽  
M. Gupta
Keyword(s):  
Processing Technique ◽  
Novel Processing

Electrochemical Testing and Structural Characterisation of Nickel Based Catalytic Coatings Produced by Direct Spraying

1998 ◽  
Vol 549 ◽  
Author(s):  
S.M.A. Sillitto ◽  
N.J.E. Adkins ◽  
D.R. Hodgson ◽  
E. Paul ◽  
R.M. Ormerod
Keyword(s):  
Raney Nickel ◽  
Phase Distribution ◽  
Pilot Scale ◽  
Processing Technique ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
Structural Characterisation ◽  
Beneficial Effects ◽  
Electrochemical Testing ◽  
Novel Processing

AbstractIn this paper a novel processing technique has been used to produce a range of low overpotential nickel based electrocatalytic coatings for use in the Chlor-alkali industry. These coatings include pure nickel as well as Raney nickel alloys, with particular focus upon the beneficial effects of molybdenum additions to Raney nickel.Structural characterisation of all coatings has been carried out using X-ray diffraction for quantitative phase identification, backed up by optical and electron microscopy for analysis of phase distribution. Measurement of the coatings' electrochemical properties has been performed in fully functioning micro-pilot scale electrolysis cells.

Recovery of niobium during comprehensive processing of pyrochlore-monazite-goethite ores

2021 ◽  
pp. 71-77
Author(s):  
N. A. Permyakova ◽  
M. V. Tsygankova ◽  
E. I. Lysakova
Keyword(s):  
Organic Phase ◽  
Tributyl Phosphate ◽  
Weight Ratio ◽  
Acid Leaching ◽  
Processing Technique ◽  
Pressure Leaching ◽  
High Concentration ◽  
Heat Treatment Mode ◽  
Efficient Processing ◽  
Comprehensive Processing

This paper looks at the pyrochlore-monazite-goethite ores of the Chuktukonsk deposit (0.98wt.% Nb2O5) and their processing with the help of acidbased (HNO3, H2SO4) and sulphatization techniques. Nitric-acid pressure leaching was found to be an efficient processing technique for this type of ore: ore size –0.074 mm; CHNO3 = 25%; CH2O2 = 5%; τ = 2 h; solid-to-liquid = 1:9; heat treatment mode: 1 h at 160 oC followed by 1 h at 230 oC. As a result, rare earth metals and manganese are leached to the solution while all of the contained niobium remains in the cake. Two different techniques were tested to recover niobium from the cake. One is based on the use of alkali (NaOH sintering), the other is an extractive leaching technique that combines acid leaching with liquid-liquid extraction of tributyl phosphate in one stage. It was established that niobium mi nerals can be efficiently decomposed when using a mixture of hydro fluoric and sulphuric acids with the concentrations of 4.08 and 8.46 mol/L, correspon dingly, as a leaching agent. At the weight ratio of 1:2:1 of the solid to aqueous to organic phase and after the slurry has been stirred intensively for 5 minutes, niobium fluorides, which form as a result of interaction between hydrofluoric acid and the cake components, can be recovered with a 50% solution of tributyl phosphate in octane. After that they transfer to an organic phase while impurities get accumulated in the solid residue. As niobium-containing cake has a high concentration of silicon, it is recommended to first remove silicon from the cake using a strong alkaline solution.

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