Design of a molecular-beam reflector yielding a uniform distribution of condensate over the plane of its cross section

1974 ◽  
Vol 17 (7) ◽  
pp. 930-933
Author(s):  
L. S. Palatnik ◽  
Yu. I. Grishchenko
Keyword(s):  
Uniform Distribution ◽  
Cross Section ◽  
Molecular Beam

Near-Surface Aggregation of Sn In Heavily Sn-Doped GaAs Films Grown By Molecular Beam Epitaxy

1985 ◽  
Vol 43 ◽  
pp. 368-369
Author(s):  
S. H. Chen
Keyword(s):  
Molecular Beam Epitaxy ◽  
Cross Section ◽  
Electron Spectroscopy ◽  
Molecular Beam ◽  
Surface Segregation ◽  
Secondary Ion Mass Spectrometry ◽  
Specimen Preparation ◽  
Near Surface ◽  
Gaas Films ◽  
Secondary Ion

Sn has been used extensively as an n-type dopant in GaAs grown by molecular-beam epitaxy (MBE). The surface accumulation of Sn during the growth of Sn-doped GaAs has been observed by several investigators. It is still not clear whether the accumulation of Sn is a kinetically hindered process, as proposed first by Wood and Joyce, or surface segregation due to thermodynamic factors. The proposed donor-incorporation mechanisms were based on experimental results from such techniques as secondary ion mass spectrometry, Auger electron spectroscopy, and C-V measurements. In the present study, electron microscopy was used in combination with cross-section specimen preparation. The information on the morphology and microstructure of the surface accumulation can be obtained in a fine scale and may confirm several suggestions from indirect experimental evidence in the previous studies.

Tanning Performance of a Novel Chrome-Free Complex Tanning Agent: Penetration and Distribution

2021 ◽  
Vol 116 (8) ◽  
Author(s):  
Zhen Wang ◽  
Ya-nan Wang ◽  
Yue Yu ◽  
Bi Shi
Keyword(s):  
Metal Complexes ◽  
Uniform Distribution ◽  
Charge State ◽  
Magnesium Oxide ◽  
Cross Section ◽  
Masking Effect ◽  
Pretreatment Method ◽  
Oxidized Starch ◽  
Novel Complex ◽  
The Cross

Penetration of tanning agent in leather plays an important role in tanning performance and properties of finished leather. A novel complex tanning agent composed of Al–Zr salts and highly-oxidized starch ligand, named TWLZ, was used for chrome-free tanning. The masking effect of highly-oxidized starch reduced the electropositivity of metal complexes, which should help penetration of TWLZ and moderate its fixation during tanning. The effects of tanning agent dosage, basification method and pretreatment method on the distribution of TWLZ in leather were investigated. Using 8% TWLZ and basifying with magnesium oxide benefited the penetration and distribution of TWLZ throughout the cross-section of leather. Pretreatment with an amphoteric organic tanning agent could regulate the charge state of the hide, balance the penetration and fixation of TWLZ, and thus show uniform distribution and satisfactory tanning performance. This work will guide the establishment of TWLZ chrome-free tanning system.

Effect of Pipe Inclination on Solids Distribution in Partially Stratified Slurry Flow

2019 ◽  
Author(s):  
Václav Matoušek ◽  
Jan Krupička ◽  
Jiří Konfršt ◽  
Pavel Vlasák
Keyword(s):  
Uniform Distribution ◽  
Cross Section ◽  
Inclination Angle ◽  
Concentration Profile ◽  
Stratified Flow ◽  
Concentration Profiles ◽  
Horizontal Pipe ◽  
Pipe Cross Section ◽  
Test Loop ◽  
Pipe Inclination

Abstract Partially stratified flows like flows of sand-water slurries exhibit non-uniform distribution of solids (expressed as a vertical profile of local volumetric concentration) in a pipe cross section. The solids distribution in such flows is sensitive to pipe inclination. The more stratified the flow is the more sensitive its concentration profile is to the pipe slope. In general, the distribution tends to become more uniform (less stratified) if the inclination angle increases from zero (horizontal pipe) to positive values (ascending pipe) up to 90 degree (vertical pipe). In a pipe inclined to negative angles (descending pipe) the development is different. The flow tends to stratify more if it changes from horizontal flow to descending flow down to the angle of about −35 degree. If the angle further decreases towards −90 degree, then the flow becomes less stratified reaching uniform distribution at the vertical position. This also means that the same flow exhibits a very different degree of stratification in ascending and descending pipes inclined to the same (mild) slope say between ±10 and ±40 degree. The rather complex development of the solids distribution with the variation of the inclination of pipe is insufficiently documented experimentally and described theoretically in predictive models for a concentration profile in partially stratified flow. In order to extend the existing limited data set with experimental data for partially stratified flow of medium sand slurry, we have carried out a laboratory experiment with the slurry of narrow graded fraction of sand with the mean grain size of 0.55 mm in our test loop with an invert U-tube inclinable to arbitrary angle between 0 and 90 degree. A pipe of the loop has an internal diameter of 100 mm. Both legs of the U-tube have a measuring section over which differential pressures are measured. Radiometric devices mounted to both measuring sections sense concentration profiles across a pipe cross section. Furthermore, the discharge of slurry is measured in the test loop. In the paper, experimental results are presented for various inclination angles with a small step between 0 and ±45 degree and a development in the shape of the concentration profiles with the changing inclination angle is analyzed. For the analysis, it is critical to distinguish between suspended load and contact load in the flow as the two loads tend to react differently to the flow inclination. The measured concentration profiles and pressure drops are compared with predictions by the layered model adapted for taking the flow inclination into account.

Tem Studies of GaAs/AlGaAs Heterostructures Grown on Patterned Substrates

1987 ◽  
Vol 102 ◽  
Author(s):  
D. M. Hwang ◽  
E. Kapon ◽  
M. C. Tamargo ◽  
J. P. Harbison ◽  
R. Bhat ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Chemical Etching ◽  
Molecular Beam ◽  
Patterned Substrates ◽  
Lateral Direction ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Device Applications ◽  
Substrate Surfaces

ABSTRACTEpitaxical growth rates depend strongly on the crystalline orientations of substrate surfaces. Multilayer growth on pre-patterned substrates with various crystal facets exposed results in a large variation of layer thicknesses in the lateral direction. This lateral definition can be used in device applications. Alternating layers of GaAs and AIGaAs were grown by molecular beam epitaxy on (100) GaAs substrates patterned with grooves and ridges along the [01T] and [011] directions by chemical etching. The results were analyzed with transmission electron microscopy using vertical cross-section techniques. Examples of using this method to fabricate ridges with tips of atomic sharpness and quantum-well lasers are presented.

Sign in / Sign up

Export Citation Format

Share Document