scholarly journals Faceted-rough surface with disassembling of macrosteps in nucleation-limited crystal growth

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Noriko Akutsu
Keyword(s):  
Crystal Growth ◽  
Rough Surface ◽  
Crystal Surface ◽  
Point Contact ◽  
Surface Model ◽  
Crossover Point ◽  
Growth Changes ◽  
Step Step ◽  
Surface Crystal ◽  
Nucleation Growth

AbstractTo clarify whether a surface can be rough with faceted macrosteps that maintain their shape on the surface, crystal surface roughness is studied by a Monte Carlo method for a nucleation-limited crystal-growth process. As a surface model, the restricted solid-on-solid (RSOS) model with point-contact-type step–step attraction (p-RSOS model) is adopted. At equilibrium and at sufficiently low temperatures, the vicinal surface of the p-RSOS model consists of faceted macrosteps with (111) side surfaces and smooth terraces with (001) surfaces (the step-faceting zone). We found that a surface with faceted macrosteps has an approximately self-affine-rough structure on a ‘faceted-rough surface’; the surface width is strongly divergent at the step-disassembling point, which is a characteristic driving force for crystal growth. A ‘faceted-rough surface’ is realized in the region between the step-disassembling point and a crossover point where the single nucleation growth changes to poly-nucleation growth.

Framboid Microcrystal Growth

2021 ◽  
pp. 235-261
Author(s):  
David Rickard
Keyword(s):  
Crystal Growth ◽  
Crystal Surface ◽  
Normal Growth ◽  
Hydrothermal Systems ◽  
Hydrothermal Conditions ◽  
Sedimentary Environments ◽  
Surface Nucleation ◽  
Growth Modes ◽  
Cubic Forms ◽  
Nucleation Growth

Framboid microcrystals grow through surface reaction of S2(-II) or H2S with =FeS moieties at defect sites on the pyrite crystal surface. The surface energies of pyrite vary from the most stable cubic through octahedral to pyritohedral and dodecahedral surfaces. Microcrystals commonly develop as truncated octahedra as the supersaturation decreases during crystal growth in sedimentary environments, although cubic forms may be favored under hydrothermal conditions. Screw dislocation growth followed by surface nucleation growth are the normal growth modes in sediments, whereas surface nucleation growth is likely to dominate in hydrothermal systems. The rate of crystal growth of framboids is unknown but appears to be very fast and normally diffusion-limited. Linear approximations to the diffusion equations show that average 6 μ‎m diameter framboids form in five days in sediments, and formation times increase exponentially from a few hours for ca. 2 μ‎m framboids to three years for the largest 250 μ‎m framboids.

scholarly journals Crystal growth of the core and rotated epitaxial shell of a heterometallic metal-organic framework revealed with atomic force microscopy

2021 ◽  
Author(s):  
Fajar Inggit Pambudi ◽  
Michael William Anderson ◽  
Martin Attfield
Keyword(s):  
Atomic Force Microscopy ◽  
Crystal Growth ◽  
Metal Organic Framework ◽  
Metal Organic Frameworks ◽  
Force Microscopy ◽  
The Core ◽  
Atomic Force ◽  
Metal Organic ◽  
Surface Crystal ◽  
Organic Framework

Atomic force microscopy has been used to determine the surface crystal growth of two isostructural metal-organic frameworks, [Zn2(ndc)2(dabco)] (ndc = 1,4-naphthalene dicarboxylate, dabco = 4-diazabicyclo[2.2.2]octane) (1) and [Cu2(ndc)2(dabco)] (2) from...

scholarly journals Coverage dependent adsorption sites in the K/Cu(100) system: A crystal truncation rod analysis

1993 ◽  
Vol 208 (1) ◽  
Author(s):  
H. L. Meyerheim ◽  
I. K. Robinson ◽  
V. Jahns ◽  
P. J. Eng ◽  
W. Moritz
Keyword(s):  
Crystal Surface ◽  
High Coverage ◽  
Adsorption Sites ◽  
System A ◽  
Crystal Truncation Rod ◽  
Surface Crystal

AbstractThe analysis of the intensity along the diffraction rods normal to the crystal surface (crystal truncation rods) has been used to analyse the adsorption sites of potassium atoms adsorbed atAt high coverage (

Design Optimization of Ultra-Low Flying Head-Disk Interfaces Using an Improved Elastic-Plastic Rough Surface Model

2006 ◽  
Vol 128 (4) ◽  
pp. 801-810 ◽  
Author(s):  
Allison Y. Suh ◽  
Sung-Chang Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Rough Surface ◽  
Contact Pressure ◽  
Surface Model ◽  
Successful Implementation ◽  
Contact Conditions ◽  
Friction Forces ◽  
Interfacial Forces ◽  
Elastic Plastic ◽  
The Mean ◽  
Improved Model

Sub-5nm flying head-disk interfaces (HDIs) designed to attain extremely high areal recording densities of the order of Tbit∕in2 are susceptible to strong adhesive forces, which can lead to subsequent contact, bouncing vibration, and high friction. Accurate prediction of the relevant interfacial forces can help ensure successful implementation of ultra-low flying HDIs. In this study, an improved rough surface model is developed to estimate the adhesive, contact, and friction forces as well as the mean contact pressure relevant to sub-5nm HDIs. The improved model was applied to four different HDIs of varying roughness and contact conditions, and was compared to the sub-boundary lubrication rough surface model. It was found that the interfacial forces in HDIs undergoing primarily elastic-plastic and plastic contact are more accurately predicted with the improved model, while under predominantly elastic contact conditions, the two models give similar results. The improved model was then used to systematically investigate the effect of roughness parameters on the interfacial forces and mean contact pressure (response). The trends in the responses were investigated via a series of regression models using a full 33 factorial design. It was found that the adhesive and net normal interfacial forces increase with increasing mean radius R of asperities when the mean separation is small (≈0.5nm), i.e., pseudo-contacting interface, but it increases primarily with increasing root-mean-square (rms) surface height roughness between 2 and 4nm, i.e., pseudo-flying interface. Also, increasing rms roughness and decreasing R, increases the contact force and mean contact pressure, while the same design decreases the friction force. As the directions of optimization for minimizing the individual interfacial forces are not the same, simultaneous optimization is required for a successful ultra-low flying HDI design.

Bubble-induced fast crystal growth of indomethacin polymorphs in a supercooled liquid

2021 ◽  
Vol 54 (5) ◽  
Author(s):  
Qin Shi ◽  
Fang Li ◽  
Jia Xu ◽  
Lingling Wu ◽  
Junbo Xin ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Physical Stability ◽  
Pharmaceutical Formulations ◽  
Supercooled Liquid ◽  
Pharmaceutical Solids ◽  
Liquid Bubble ◽  
Different Temperatures ◽  
Surface Crystal

Physical stability is one of the main challenges when developing robust amorphous pharmaceutical formulations. This article reports fast crystal growth behaviors of the γ and α forms of indomethacin (IMC) initiated by bubbles in the interior of a supercooled liquid. Bubble-induced crystal growth of γ-IMC exhibits approximately the same kinetics as its surface crystal growth, supporting the view that bubble-induced crystal growth is a surface-facilitated process. In contrast, the rates of bubble-induced crystal growth of α-IMC are much faster than those of its surface crystal growth. These results indicate that the bubble-induced crystal growth not only depends on the interface created by the bubble but also strongly correlates with the true cavitation of the bubble. Moreover, bubble-induced fast crystal growth of γ- and α-IMC can be terminated at different temperatures by cooling. These outcomes are meaningful for the in-depth understanding of physical stability and pre-formulation study of amorphous pharmaceutical solids showing surface-facilitated crystal growth.

A Simple Method for Estimating the Extent of Surface Crystal Development on Colored Cheddar Cheese

1986 ◽  
Vol 49 (6) ◽  
pp. 421-422 ◽  
Author(s):  
STEPHEN T. DYBING ◽  
STEVEN A. BRUDVIG ◽  
JAMES A. WIEGAND ◽  
EMIL A. HUANG
Keyword(s):  
Crystal Growth ◽  
Shelf Life ◽  
Environmental Conditions ◽  
Cheddar Cheese ◽  
Simple Method ◽  
Flat Surfaces ◽  
White Cheese ◽  
Shelf Life Studies ◽  
Non Destructive ◽  
Surface Crystal

A simple, non-destructive method for estimating the extent of crystal development as white specks on the surface of colored Cheddar cheese is described. This method involves photocopying the surface of the cheese with a photocopier set at an exposure calibrated to clearly show the crystals. The photocopies of the cheese surface are then compared to a series of photocopies showing designated increases in crystal growth. Crystal development was rated as follows: 0 = no crystals, 1= light, 2 = medium, 3 = heavy, and 4 = very heavy to encrusted crystal development. The method does not disrupt or destroy the environmental conditions existing in the cheese package, allowing extended shelf life studies to be done on the same piece of cheese. However, the photocopy technique may not work as well with white cheese or cheeses without flat surfaces.

Transient Method for Convective Heat Transfer Measurement With Lateral Conduction—Part I: Application to a Deposit-Roughened Gas Turbine Surface

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
J. Bons
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Rough Surface ◽  
Convective Heat ◽  
3D Model ◽  
Temperature History ◽  
Surface Model ◽  
Transient Method ◽  
Transfer Measurement ◽  
1D Model

The effect of lateral conduction on convective heat transfer measurements using a transient infrared technique over a rough surface is evaluated. The rough surface is a scaled model of gas turbine surface deposits. Comparisons are made between a full 3D finite volume analysis and a simpler 1D transient conduction model. The surface temperature history was measured with a high resolution infrared camera during an impulsively started hot gas flow over the rough test plate at a flow Reynolds number of 750,000. The boundary layer was turbulent with the peak roughness elements protruding just above the boundary layer momentum thickness. The 1D model underestimates the peak to valley variations in surface heat flux by up to a factor of 5 compared with the 3D model with lateral conduction. For the area-averaged surface heat flux, the 1D model predicts higher values than a 3D model for the same surface temperature history. This is due to the larger surface area of the roughness peaks and valleys in the 3D model, which produces a larger initial input of energy at the beginning of the transient. For engineering purposes, where the net heat load into the solid is desired, this lower 3D model result must be multiplied by the wetted-to-planform surface area ratio of the roughness panel. For the roughness model in this study, applying this correction results in a 25% increase in the area-averaged roughness-induced Stanton number augmentation for the 3D rough surface model compared with a flat 1D surface model at the same Reynolds number. Other shortcomings of the transient method for rough surface convective heat transfer measurement are identified.

Effect of Phosphate and Silica on the Rate of Crystallization of Sucrose

2005 ◽  
Vol 1 (5) ◽  
Author(s):  
Ms. Aamarpali Ratna Puri ◽  
S. Kaur
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Mother Liquor ◽  
Crystal Surface ◽  
Mass Transfer Process ◽  
Sugar Solution ◽  
Local Conditions ◽  
Concentration Difference ◽  
Different Temperatures ◽  
Sucrose Crystals

Sucrose Crystallization is a mass transfer process. Sucrose molecule's migration from solution to crystal is driven by concentration difference between the mother liquor and the crystal surface; the coefficient of super saturation is the most important parameter for the process. Supersaturation of sugar solution depends on the purity and brix of the mother liquor. It has large influence on product's quantity and quality (crystal yield, crystal size and size distribution) and on the cost of production i.e output/hour and energy consumption. However there is still no generally applicable theory, which permits an accurate prediction of the effects of all the factors that govern the industrial processes of crystallization from solution. The crystal growth depends on the viscosity, which further depends on the nature and amount of impurities. If the local conditions are favourable, localized layers of molecules of impurity can statistically remain on the surface for a period of time. On the other hand, if the interaction between the impurity and the layer is weak, then there will be competition between impurity and sucrose molecules thus affecting the sucrose crystal growth rate. In the present study, the growth rate of sugar crystals was studied, using two-litre automatic laboratory vacuum pan, under controlled conditions in the presence of impurities. The effect of phosphate and silica (adding one at time) on the growth rate of sugar crystals was studied at two different temperatures 328 and 338K and with two different seed sizes of sucrose (850 and 600µm). The growth rate was studied at two degrees of supersaturation (1.10 and 1.15). The growth rate of sucrose crystals (with or without added impurities) showed significant increase with the 10°C rise in temperature. The growth rate of sucrose crystals increased with the increase in the level of phosphate but decreased with the increase in the level of silica in sugar solution.

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