scholarly journals Atomistic Simulations of Surface Relaxations in Ni, Al, and Their Ordered Alloys

1986 ◽  
Vol 82 ◽  
Author(s):  
S. P. Chen ◽  
A. F. Voter ◽  
D. J. Srolovitz
Keyword(s):  
Surface Layer ◽  
Atomistic Simulations ◽  
Atomic Diameter ◽  
Ordered Alloys ◽  
Pure Metals

ABSTRACTWe have performed a series of simulations to examine the atomistic nature of surface relaxations in pure metals and ordered alloys. The surface relaxations (∆dn, n+1) are shown to be oscillatory and to decay rapidly into the bulk. The period and form of the oscillation may be determined by simple geometrical arguments. The oscillation wavelength is always of the order of an atomic diameter. In pure metals, the surface layer of atoms always displaces inward. However, in the ordered alloys the larger atom may displace outward. On planes composed of more than one atom types, rippling occurs.

scholarly journals Increasing the wear and corrosion resistance of steel parts by methods of complex boronikeling and borovolframing

2021 ◽  
pp. 50-54
Author(s):  
Б.Д. Лыгденов ◽  
М.А. Гурьев ◽  
С.Г. Иванов ◽  
Ц. Чжэн ◽  
А.М. Гурьев
Keyword(s):  
Corrosion Resistance ◽  
Surface Layer ◽  
Thermal Treatment ◽  
Boron Carbide ◽  
Structure And Properties ◽  
Multiphase Structure ◽  
Wear And Corrosion ◽  
Pure Metals ◽  
Wear And Corrosion Resistance ◽  
And Tungsten

The paper presents ways to increase the wear and corrosion resistance of steel parts by chemical and thermal treatment methods. Comprehensive studies of the structure and properties of St3 steel samples were carried out after simultaneous complex saturation with boron and nickel, boron and tungsten from saturating coatings based on boron carbide. Both compounds of these elements (oxides, carbides, borides) and pure metals were used as suppliers of nickel and tungsten. Studies have shown that multicomponent saturation processes make it possible to form a multiphase structure of a surface layer with a complex of useful properties. Moreover, by chemical-thermal treatment it is possible to obtain such a combination of properties of the hardened product, which cannot be obtained by other methods.

Epitaxial Island Growth and the Stranski-Krastanow Transition

2001 ◽  
Vol 696 ◽  
Author(s):  
A.G. Cullis ◽  
D.J. Norris ◽  
T. Walther ◽  
M.A. Migliorato ◽  
M. Hopkinson
Keyword(s):  
Surface Layer ◽  
Driving Force ◽  
Strain Energy ◽  
Atomistic Simulations ◽  
Wetting Layer ◽  
Island Growth ◽  
Critical Wetting ◽  
Elemental Segregation ◽  
Good Agreement ◽  
The Way

AbstractThe way in which the Stranski-Krastanow epitaxial islanding transition can be controlled by strain due to elemental segregation within the initially-formed flat ‘wetting’ layer is examined in detail. Experimentally measured critical ‘wetting’ layer thicknesses for the InxGa1−xAs/GaAs system (x = 0.25 - 1) are demonstrated to show good agreement with values calculated using a segregation model. The strain energy associated with the segregated surface layer is determined for the complete range of deposited In concentrations using atomistic simulations. The segregation-mediated driving force for the Stranski-Krastanow transition is considered to be important also for all other epitaxial systems exhibiting the transition.

scholarly journals NANOSTRUCTURES IN THE THIN LAYER OF COAL SUBSTANCE

2020 ◽  
pp. 746-757
Author(s):  
Виктор Михайлович Юров ◽  
Канат Мэтович Маханов ◽  
Василий Сергеевич Портнов
Keyword(s):  
Surface Layer ◽  
Thin Layer ◽  
Supramolecular Structure ◽  
Explosion Hazard ◽  
Physical Processes ◽  
Pure Metals ◽  
Bulk Structure ◽  
Structure Lead

В представленной работе рассмотрен поверхностный слой угольного вещества, структура и характеристики которого отличны от структуры объема. Этот слой имеет два уровня: d(I) равный 151,5 нм и d(II)≈10 ⋅ d равный 1515 нм для антрацита. Для чистых металлов d(I) равно 1 - 6 нм, что на 2 порядка меньше поверхностного слоя угольного вещества. Толщина этого слоя имеет порядок толщин высших фуллеренов С, равного 135 нм. Все эти особенности угольного вещества, имеющего углеродную основу и представляющего собой полимер с надмолекулярной структурой, приводят к тому, что именно поверхностный слой определяет физические процессы в нем, связанные с протеканием газов и жидкости, а также с явлениями взрывоопасности. In the present work, the surface layer of a coal substance is considered, the structure and characteristics of which are different from the bulk structure. This layer has two levels: d (I) equal to 151,5 nm and d(II) ≈ 10 ⋅ d equal to 1515 nm for anthracite. For pure metals d(I) is equal 1 - 6 nm, that is 2 orders of magnitude lesser than the surface layer of the coal substance. The thickness of this layer is of the order of 135 nm for the higher C fullerenes. All these features of a coal substance, which has a carbon base and is a polymer with a supramolecular structure, lead to the fact that it is the surface layer that determines the physical processes in it associated with the flow of gases and liquids, as well as with the phenomena of the explosion hazard.

scholarly journals Characterization and corrosion properties of electrodeposited Ni-W alloys

2001 ◽  
Vol 66 (11-12) ◽  
pp. 899-912 ◽  
Author(s):  
M. Obradovic ◽  
J. Stevanovic ◽  
A. Despic ◽  
R. Stevanovic ◽  
J. Stoch
Keyword(s):  
Solid Solution ◽  
Surface Layer ◽  
Complex Structure ◽  
Deposition Process ◽  
Corrosion Process ◽  
Cathodic Deposition ◽  
Corrosion Properties ◽  
Corrosion Rates ◽  
Pure Metals ◽  
Preferential Dissolution

Ni-W alloys electrodeposited from citrate solution consist of three different phases, which are all present in high W-content alloys: a solid solution of W in a Ni matrix; an intermetallic compound Ni4W, as well as another solid solution of Win Ni with a W content higher than 20 mol.%. XPS analysis revealed that the alloys were covered with a surface layer of complex structure containing the pure metals Ni and W, Ni(OH)2 andWO3, on the very surface as well as some partially reduced oxideWO2.72 (most probably a solid solution of WO2.72 in Ni) and tungsten carbide in the layer underneath. It is highly likely that some of the oxide species in the layer act as intermediates in the cathodic deposition process. Identifying these species should be the clue to a more detailed understanding of the mechanism of induced deposition of W than has been achieved so far. Corrosion of Ni-W alloys in sulfuric acid solution at OCP, occurs by the preferential dissolution of nickel from the surface layer. The longer the corrosion process lasts, the more the surface behaves like pure W. The lowest initial corrosion rates were recorded with alloys rich in W, but after aging at OCP the lowest corrosion c.d. was found for the Ni-W alloy with the most homogenous phase structure, consisting of the solid solution only.

The oxidation of Inconel alloy MA754 at low oxidation potential

1983 ◽  
Vol 41 ◽  
pp. 218-219
Author(s):  
D. N. Braski ◽  
P. D. Goodell ◽  
J. V. Cathcart ◽  
R. H. Kane
Keyword(s):  
Surface Layer ◽  
Oxidation Potential ◽  
Metal Interface ◽  
Elevated Temperature Strength ◽  
Surface Conditions ◽  
Inconel Alloy ◽  
Inco Alloy ◽  
Resistance To Oxidation ◽  
Oxide Particles ◽  
Cold Worked

It has been known for some time that the addition of small oxide particles to an 80 Ni—20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid enhances the oxidation resistance is being studied collaboratively by ORNL and INCO Alloy Products Company.Initial experiments were performed using INCONEL alloy MA754, which is nominally: 78 Ni, 20 Cr, 0.05 C, 0.3 Al, 0.5 Ti, 1.0 Fe, and 0.6 Y2O3 (wt %).Small disks (3 mm diam × 0.38 mm thick) were cut from MA754 plate stock and prepared with two different surface conditions. The first was prepared by mechanically polishing one side of a disk through 0.5 μm diamond on a syntron polisher while the second used an additional sulfuric acid-methanol electropolishing treatment to remove the cold-worked surface layer. Disks having both surface treatments were oxidized in a radiantly heated furnace for 30 s at 1000°C. Three different environments were investigated: hydrogen with nominal dew points of 0°C, —25°C, and —55°C. The oxide particles and films were examined in TEM by using extraction replicas (carbon) and by backpolishing to the oxide/metal interface. The particles were analyzed by EDS and SAD.

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 738-739
Author(s):  
W. H. Wu ◽  
R. M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Analysis ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Surface Layer Protein ◽  
Morphological Unit ◽  
Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

Electron-Mirror Microscopic Aspects of Ferroelectric Domains of BaTiO3 And Ca2Sr (C2H5CO2)6

1970 ◽  
Vol 28 ◽  
pp. 478-479
Author(s):  
Teruo Someya ◽  
Jinzo Kobayashi
Keyword(s):  
Surface Layer ◽  
Electric Fields ◽  
Quantitative Study ◽  
Recent Progress ◽  
Ferroelectric Domain ◽  
Resolving Power ◽  
Surface Pattern ◽  
Crystal Surfaces ◽  
One Dimensional ◽  
Ferroelectric Domains

Recent progress in the electron-mirror microscopy (EMM), e.g., an improvement of its resolving power together with an increase of the magnification makes it useful for investigating the ferroelectric domain physics. English has recently observed the domain texture in the surface layer of BaTiO3. The present authors ) have developed a theory by which one can evaluate small one-dimensional electric fields and/or topographic step heights in the crystal surfaces from their EMM pictures. This theory was applied to a quantitative study of the surface pattern of BaTiO3).

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

Microstructure of Electro-Eroded Cemented Carbide Surfaces

1968 ◽  
Vol 26 ◽  
pp. 284-285
Author(s):  
V. N. Filimonenko ◽  
M. H. Richman ◽  
J. Gurland
Keyword(s):  
Surface Layer ◽  
Cobalt Content ◽  
Cemented Carbides ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Metallographic Examination ◽  
Standard Procedures ◽  
Face Centered ◽  
Diamond Paste ◽  
Plastic Carbon

The high temperatures and pressures that are found in a spark gap during electrical discharging lead to a sharp phase transition and structural transformation in the surface layer of cemented carbides containing WC and cobalt. By means of X-ray diffraction both W2C and a high-temperature monocarbide of tungsten (face-centered cubic) were detected after electro-erosion. The W2C forms as a result of the peritectic reaction, WC → W2C+C. The existence and amount of the phases depend on both the energy of the electro-spark discharge and the cobalt content. In the case of a low-energy discharge (i.e. C=0.01μF, V = 300v), WC(f.c.c.) is generally formed in the surface layer. However, at high energies, (e.g. C=30μF, V = 300v), W2C is formed at the surface in preference to the monocarbide. The phase transformations in the surface layer are retarded by the presence of larger percentages of cobalt.Metallographic examination of the electro-eroded surfaces of cemented carbides was carried out on samples with 5-30% cobalt content. The specimens were first metallographically polished using diamond paste and standard procedures and then subjected to various electrical discharges on a Servomet spark machining device. The samples were then repolished and etched in a 3% NH4OH electrolyte at -0.5 amp/cm2. Two stage plastic-carbon replicas were then made and shadowed with chromium at 27°.

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