Science topic

# Surface Science - Science topic

For everyone interested in physical and chemical phenomena that occur at the interface of two phases
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It is known that the surface/interfacial tension tension can be measured by pendant drop method and the following equation: IFT=deltaro*g*de^2/H. 1/H is function of ds/de (1/H=f(ds/de)). I used this function for 1/H and it is okay for gas/liquid systems. When I used this this function for liquid-liquid mixtures, such as water-hexane (T=298.15 K and P=1 bar), it does not answer. Is 1/H different for liquid-liquid mixtures?
I recommend the article published in the Journal of Petroleum Science and Engineering (JPSE) for measuring the H parameter based on various S (S = ds/de) values. Please read Table 3 in the article.
"Developing a novel procedure in utilizing pendant drop method for determination of ultra-low interfacial tension and surface tension in near-miscibility conditions"
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I am currently working on cosmetic formulations.
I transferred the samples of emulsion into 50 ml bottles.
They were then held for a week at either room temperature (23 ±1 °C) or -15 ±1 °C before being heated to 23±1 °C.
However, when I measured the viscosity of samples, it appears that the cold sample is more viscous after thawing.
Does anyone have any ideas on the cause of the increase?
When you cool your emulsion, it turns into a jelly. If the jelly was stored for a long time, irreversible changes occurred in it under the influence of bacteria and time. After heating, these changes remain and change the viscosity. Compare the IR spectrum of the jelly immediately and after storage and you will see the difference in the spectrum.
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Having a background in health science I am aware that the term "interphase" is a biological one which describes a stage of cell division. Specifically it is defined as the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis.
This may be compared to a materials science definition for "interface" as the region formed when two phases (systems) are in contact through which the intensive properties of one phase transfer to the other.
When I would read "SEI" defined as solid electrolyte interphase in papers within my current field, I would always have a quiet giggle to myself and wonder how it gets past the editors, even in high impact publications. But I recently found myself forced to reassess my position, after digging around in foundational work on the SEI thing by Peled et al (1979). This paper has "interphase" in its title, and I believe there are peers who consider this to be the original work defining SEI. An excerpt from the paper:
It acts as an interphase between the metal and the solution and has the properties of solid electrolyte, through which electrons are not allowed to pass. Therefore, it is called "Solid Electrolyte Interphase (SEI)."
So the discussion is this, if these authors coined the term SEI, shouldn't it be acceptable for us as materials scientists to misappropriate "interphase" for our own purposes, and to hold our ground on it? On the other hand, what is science without clarity in our terminology? And how is "interphase" in a materials context saying anything more or less than the previously defined term "interface"?
The one thing I feel confident about is that we shouldn't be reading interchangeable definitions for the same thing, just depending on the source. Let alone seeing it arbitrarily interchanged within a single source - yes I have read individual papers where SEI is both "interphase" and "interface"...
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it means that, if want generate active sites onto latex glove waste via chemical modification. what is procedure and chemical that can be use. your response is highly needed. thank you
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I'm starting to work with DDSCAT (http://www.astro.princeton.edu/~draine/DDSCAT.html). In the examples there structures standards. But still do not understand how I can create new structures and what software to use it. I need to create a cluster of nanoparticles.
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If so, why? And what is the mechanism of inhibition?
Dear faysal,
In general case, it is not possible inhibit. But hydrocarbon (oil) water ratio along with application of water chemistry indicates scaling level which can prevent exposure to corrosive agents. Generated dry carbon dioxide gas(high temperature evolution) can itself behave as inhibitor inside the pipeline.
Ashish
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Most of the reported mixed metal oxides are prepared from their precursor materials. I want to prepare mixed metal oxides from already prepared metal oxide materials. For example, CaO and Fe2O3 are available commercially, I want to combine them together via a suitable chemical method like making a core-shell structure, or CaO coating on Fe2O3 surface. Please give me an idea on how to make mixed metal oxides from prepared metal oxide and send me any reference articles.
as per phase diagram of CaO-Fe2O3, mixed and heat in muffle furnace as indicated temperature
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Is it possible to estimate the polar and dispersive surface energy components from MD simulation?
I'm not sure what are polar and dispersive components but you can calculate the surface energy of a solvent or a laminar solid (such as graphene) with MD. Although it's not as accurate as first principle calculations still gives you a reasonable estimate. If polar simply means the electrostatic interactions and dispersive refers to the vdW interactions, then they can be easily distinguished and calculated separately using GROMACS or LAMMPS.
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The materials that are in contact with food are supposed to be classified as not only environmentally friendly but also potentially non-toxic to humans. Nowadays, some researchers suggest that organic and bio-based waxes could be good choices for lowering the surface energy and thus fabricating super-liquid-repellent surfaces. What else besides waxes do you recommend to be used for fabricating superhydrophobic and/or superomniphobic surfaces?
I would go towards silicones instead of waxes if you're looking for repellency beyond water. We just published work on how to repel oils using silicone brush chemistries: https://www.nature.com/articles/s41893-020-0591-9
You of course still need re-entrant structure and sufficient capillary resistance to support the composite interface, but a non-zero oil intrinsic contact angle is your first step.
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I have used FTIR to measure both the gas phase CO and surface adsorbed CO (on Ni powder catalyst with Al2O3 and SiO2 as substrate, DRIFTS mode). The Ni-C bond should lower the strength of the C-O bond (backdonation theory, etc), thus lower its vibrational frequency, but we have consistently observed the opposite: the surface CO has higher wavenumber than the gas phase CO. I am wondering how could this be possible?
I have attached a graph which compare the two spectra.
I agree with what Yuri Mirgorod has said. But, this is not quite unusual. In the case of OC:BH3 adduct also nCO goes from free CO value of 2143 to 2165 cm-1. In metal carbonyls M(dxy, dyz or dxz)-->pi*(CO) is responsible for decreasing the value. But CO bond polarization is equally responsible for nCO shifts. Please read the article: Chem. Sci., 2016, 7, 1174-1184 by Giovanni Bistoni et al. In fact, in Ni(CO)4, it is the pi-bonds (dNi-->pi*CO) are solely responsible for the existence of Ni(CO)4 molecule and not OC-->Ni sigma bonds.
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I am going to order 300nm oxide SiO2/Si wafers as a substrate for MoS2 growth by CVD and I am confused with the characteristics of these wafers. I have got quotations for dry thermal oxides with TTV<2um and I am not sure what parameter shows the best surface for the growth.
I appreciate your time and response to this question.
The choice, apart from cost, depends on the role that substrate must play in your experiments or devices.
If the substrate has to be fully isolated from the surface structures, I suggest you a Si wafer pre-coated with a thick (several hundreds nanometres) WET oxide. DRY oxide layers THERMALLY grown on Si have thickness in the far submicron range due to the very, very slow oxide growrh rate in pure O2 or O2/N2 furnace processes. Apart from thickness, they have a better electrical quality compared to wet oxides of the same thickness: the presence of steam in the growth process (in oven) used to grow WET layers causes the formation of a relevant density of local chemical defects (eg Si-O...H-O-Si) in the whole body of the film and at the interface with Si. Such defects often are electrically active and allows a leakage electron current transit across the oxide film (for film thickness lower than 100 nm or the like). To reduce such defectivity, post-growth thermal annealing processes, properly tailored, should be applied, so increasing yje cost again.
There is a chance to deposit insted than growing the oxide film on the Si wafer, by using a CVD process, such as Plasma-Enhanced CVD or Atmospheric Pressure CVD... But t morphological characteristics like th uniformity are generally worse than for grown films, and a final thermal annealing in N2 or N2/O2 environment is needed to recover a better density of the oxide and hence improve its chemical ruggedness..
Summarising:
1) If you merely need a mechanical substrate, that must not electrically interacts with your surface devices, just ask for WET growth of a, say, 1 um thickness. You may also ask for an additive post-growth thermal annealing in N2/O2 tailored to improve the oxide top selvedge chemistry (removing residual water-related radicals)
2) If a direct electric (currents) or dielectric (E field polarisation) interaction between your surface devices and the Si substrate are envisaged, just ask for a DRY oxide with thickness lower than 100 nm... however, if such an interaction is planned, you'd possibly need to choose of a precise thickness !
3) I would never ask for CVD layers, unless they are properly densified and a good uniformity, comparable with the thermal layers of same thickness, is assured.
I wrote so a long reply just to allow you to make a reasoned choice in ordering your substrates, with an eye to to cost and the other to the role of those substrates in your objectives.
Hope having helped you
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other than Möbius, Klein, Henneberg, Meeks, Roman (Steiner's), Boy, cross cap,
real projective plane.
A connected sum of any of those.
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The problem I have is that the film is not uniform. It is CVD grown on 270 nm SiO2 on Si substrate. I have tried using Tauc-Lorentz model according to a paper. But, in my opinion the problem comes from the fact that I have voids and thus the fitted data didn't follow the paper's prediction. Any suggestion is greatly appreciated. Thanks!
I agree with Christian Röling
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I am trying to model a surface by using software
Dear Seyed Razavi,
FLOW-3D CFD can be used.
Optimizing coating processes can be difficult to model due to small scale of fluid motion and the influence of effects such as wall adhesion and surface tension. This provides a convenient way to analyze these processes without having to resort to costly laboratory experiments. FLOW-3D‘s models can simulate surface tension gradients due to temperature variations, heat transfer, vaporization, condensation, solute transport and density-driven flows.
This FLOW-3D simulation of a forward roll coating process captures a ribbing defect due to a high capillary number. The model incorporates the effects of surface tension and viscosity as the backing rollers draw the fluid through a 400 micron nip. The accurate prediction of the onset of ribbing allows for researchers to identify optimal process parameters to avoid defects.
Hope this is helpful for you.
Ashish
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I try to find a solution to the navigation problem. There is a navigation system consists of three navigation positions, forming two bases (one position belongs two bases) and emitting three different signals. It provides us the opportunity to get two navigation parameters - two Time Differences of Arrival. So we have two surfaces - hyperboloids. But I need to complement my system with another navigation parameter, like Time of Arrival to find the 3d coordinates of my position.
What should I use as the third parameter to get the simplest equations, expressing my coordinates?
It could be Time of Arrival only from one position; Time of Arrival between two positions. But it could be two Times of Arrival which provide me the opportunity of having more information.
How can I find the equations, expressing my 3d coordinates in this navigation system?
I have a system of equations:
x1 = a*cosh(m1)*cos(n1)
y1 = a*sinh(m1)*sin(n1)
x2 = b*cosh(m2)*cos(n2)
y2 = b*sinh(m2)*sin(n2)
alpha - the angle between the bases.
I can suppose that the bases are equivalent and m1=m2. Then I obtain the problem of intersection of tho circles. It is the right way?
I will show you how to obtain the equations:
x₁ = acosh(m₁)cos(n₁)
y₁ = asinh(m₁)sin(n₁)
For m₁ = constant →
(x₁/acosh(m₁)) = cos(n₁)
(y₁/asinh(m₁)) = sin(n₁)
(cos(n₁))² + (sin(n₁))² = 1
(x₁/acosh(m₁))² + (y₁/asinh(m₁))² = 1.
Also, for n₁ = constant →
(x₁/acos(n₁)) = cosh(m₁)
(y₁/asin(n₁)) = sinh(m₁)
(cosh(m₁))² - (sinh(m₁))² = 1
(x₁/acos(n₁))² - (y₁/asin(n₁))² = 1.
We do the same argument for (x₂, y₂).
We assume non of cosh(m₁), cos(n₁), sinh(m₁) and sin(n₁)
is zero.
It is not clear what is the rule of alpha!
Best regards
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I know helium is the most commonly used gas in the discharge lamps used in UPS, and that you can also use Neon or Argon. But I can't seem to find any information on why helium is the go to choice?
Is it because of the higher photon energy or higher intensity or something else entirely?
Thanks in advance for any responses.
Dear Dr. Fabian Fogarty,
helium gas-discharge lamp is the most used in UPS because of the high ionization energy of helium resulting in a high photon energy (He(I)=21.22 eV and He(II)=40.81 eV) of the emitted radiation which is needed for photoemission. A thin Al foil can also be used to filter any He(I) from the He(II) radiation.
On the contrary, the wavelengths produced from discarge lamps containing neon or argon consisting of closely spaced multiplets.
Best regards, Pierluigi Traverso.
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Hi all,
I'm trying to analyze a thin film using a rotational sample holder. I hope azimuthal rotation would help to reduce the effect of induced surface roughness. How fast should I rotate the sample to improve the surface sensitivity?
Sam
Not sure if I got your point - you want to rotate during data acquisition? The conventional use of azimuthal rotation in XPS is to minimize the surface roughness during sputter-etching with Ar+ ion beam (so-called Zalar rotation). This is good for poly-crystalline samples as differently oriented crystallites etch more evenly than with the stationary sample. If used for depth profiling the depth resolution is greatly improved.
I never heard of anyone rotating the sample during data acquisition.
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I have scanned some of my experimental surfaces using Zeta and Alicona optical profilometers. Is there any opensource software to perform measurement of areal texture parameters on the output files of these instruments.
PS: I have take readings of major areal texture parameters from these instruments. I am expecting that such software will allow me to analyse more areal texture parameters than those given in the interface of the above mentioned profilometers.
I converted .al3d to .sdf using Gwyddion and then opened the file in Vision (see attached). Is there any particular areal parameter you are interested in?
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Hello,
I have grafted a layer of epoxysilane on a thermoset silane-crosslinked polyethylene. The thickness of the grafted layer is below 30 nm and the thickness of the crosslinked polyethylene substrate is 2 mm. A reviewer has asked me to perform 1HNMR and 13C-NMR analysis, in addition to ATR-FTIR and XPS, to characterize the functionalities in the nanometric layer. I should add that both the epoxy-silane layer and substrate are crosslinked and not soluble. I was wondering if you could guide me on how can I perform NMR analysis in order to detect the variations only in the nanometric layer on the surface (i.e., a surface-specific NMR).
Dear
Curtis Guild
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Suppose avg. grain size, crystal structure, young's Modulus, fracture strength, velocity of sound and surface roughness of both the crushed crystals (before and after crushing ) and the crushing surfaces, as well as load on grinding surface, static/dynamic friction coefficients are known. Then, is it possible to estimate the crushing sound of the crystals?
Conversely, if crushing sound of the crystals are analyzed, is it possible to find any mathematical relation between the variables outlined?
I am asking the questions since crushing minerals and recording-analyzing the sound require no sophisticated instrument at all.
Dear Sumit,
Sound of cracking crystals between two hard surface depends on couple of important metallurgical as well as mechanics factors such as increasing strains, grain distribution reaches log normal packing, coarsening of crystal grains, mis orientation angles, level of temperature distribution due to fraction between two surface with grain misalignment effect , critical grain size micro-cracking and thermal enhancement, cohesion crack nucleation, defects, cavities etc.
In general, If the size of the crystal grains is closed to the wavelength of the supersonic ray, the part will not be transparent to ultrasound, in this case the there will be no ultrasound bottom of signal. it is also seen that size of the crystal grain increases the intensity of supersonic wave decreases.
Sound products can be listen at high extrusion speeds.
Atomistic modeling is highly applicable in easy understanding of crack sound between hard metal.
Ashish
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I applied epoxy coating over hot rolled mild steel substrate using film applicator. After a while some of the areas are devoid of any resin or there are empty spaces wherein I can clearly feel the substrate ? They are not air bubbles, but what could be reason for this and how to prevent it ? Refer the attached image
Dear Muralishwara Kakunje,
Before the resin thickens and cures it needs to prepare bubble out by prepared torch. Use a heat gun on its low heat levels and aim the gun parallel to the bubbled surface, make sure you are not aiming directly straight down on the bubbles, the heat gun should always be at an angle so that empty spaces can be avoided. If impurities in the substrate and proper polishing not done properly secondary cause empty space cannot be ignored.
Hope it work out.
Ashish
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I have a gold nanoparticle which is functionalized with a tetraethylene glycol trimethylammonium ligand and I'm looking to deposit it on a surface. Thus far I've had a difficult time finding similar systems so reaching out to the scientific community to see if anyone knows of any literature which has done something similar.
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I want to adsorb C7H7NO2 (PABA) on ZnO surface. I know POSCAR file for ZnO surfaces 1 1 0, 1 0 0 etc.
How to give PABA positions in POSCAR file of ZnO. How does know PABA molecular positions ?
Shilendra
Hello, You can use 'structure manager' within CINEMAS(https://www.ikst.res.in/cinemas.php). There is a GUI based interactive surface builder utility.
A video tutorial on how to use 'structure manager' within CINEMAS: https://www.youtube.com/watch?v=GcWaBmAIXYA
CINEMAS is an integrated GUI based cross-OS(Windows/Ubuntu/Fedora) platform, where one can prepare calculations(GUI workflows), establish remote connections, execute calculations and post-process output data through integrated structure visualizer, numeric data plotter and even an in-built drawer to prepare figures for publication purpose. All in one place!
Thanks!
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Dear all,
I would like to know how the increase/decrease of the pH or ionic strength of the environment in which two negatively charged bodies are immersed will affect the "thickness" of the electrostatic double layer (EDL)? I have heuristically witnessed that low pH (e.g. 2) makes two negatively charged particles agglomerate, but I have not conducted experiments with high pH, and I have not played with solutions of different ionic strength. Some references would be helpful.
If the groups on the surface of the particles are pH-sensitive you can expect changes in the EDL. In general an increase in ionic strength will decrease the magnitude of the associated zeta potential.
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In my setup, I am intending to evaporate gold on mica substrate. After that, I intend to clean the gold surface and smooth it using nitrogen plasma (as we have some problems related to the vacuum if we use hydrogen). I looked up at the literature and found no article about that (they investigated hydrogen, argon, and oxygen so far). What could be the drawbacks or precautions that I need to put in mind? Any advice?
Surface treatment of metals using an atmospheric pressure plasma jet and their surface characteristic, September 2003, Surface and Coatings Technology 174(175):839-844, DOI: 10.1016/S0257-8972(03)00560-7
The above article is very nice. please go through this article. It might be useful for you.
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Contact angles are usually determined by goniometry. However, more often than not, this method reveals apparent contact angle (which reflects the net effect of surface chemistry and surface topography), rather than the intrinsic contact angle (or Young's contact angle, which reflects the contact angle of a liquid on an ideal surface - a nanosmooth, chemically homogeneous surface). Is there a way to predict the intrinsic contact angles (or surface energy) of an ideal surface using the chemical composition and/or molecular structure (e.g. through molecular dynamics)?
Dear Yifan Zhang,
This small paper may be of help:
Best regards.
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Hi,
I am using the isotherm obtained by the BET technique to calculate the pore size of some materials; I obtained an average pore size of approximately 10 nm in all my samples (I think that means that I have mesopores in my material), but I am not sure if these results are correct since the standard pressure used in BET may won't be enough (mesopores require greater pressures (>0.3) to be calculated than micropores). Should I use a different technique?
The average pore diameter is not enough to determine the porous nature of your material. I recommend that you do a pore size distribution, normally this is done using the BJH method, however if you have microporosity it is better to use a DFT method. Another thing that I can recommend is that the analysis is carried out with Ar and not with N2. When you make the measurement of microporous materials with N2 you can have erroneous readings, due to the N2's quadrupole moment, which leads to specific interactions with functional groups or exposed ions on material surfaces.
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I am an undergraduate who is trying to synthesize mesoporous particles by mixing several compounds.
Something is wrong with the experiment, I need advice.
Briefly, there is a problem in changing the composition of the dispersed phase in the emulsion.
I use a total of five compounds, A, B, C, D and surfactant(Pluronic).
A mixture of A and B is a dispersed phase(oil), and C, D and a surfactant are continuous phases(water).
Only A and C participate in the reaction, D is the catalyst, and B affects the morphology of the particles.
Prior to the experiment, the adviser was given the molar ratio of the reactants.(A : B : suf : C : D = 1 : x : y : z : w)
I dripped the dispersed phase in the continuous phase of stirring.
At this molar ratio, the reaction took place very well.
I now have to change the mole ratio of A and B in the dispersed phase.
For example, I need to change A : B from 1 : x to 1 : 2x etc.
(I thought I could just change it to 1 : x : y : z : w → 1 : 2x : y : z : w etc.)
My advisor said you shouldn't just stretch B into simple arithmetic.
What is the relationship between the spreading coefficient and the composition of the dispersed phase?
What is the relationship between the spreading coefficient and the amount of dispersed phase?
Dear Sang-Ho,
I have difficulties to figure out what is actually meant, so first here what I assume to be the case.
Continuous phase is water containing reactant C, catalyst D and a surfactant. For reaction you add a mixture of 2 oils (one reacts the other is inert) dropwise. If one assumes that compounds dissolved in water do not partition into the oil phase than changing composition of dispersed phase is only possible by changing the ratio of A to B. Important to consider whether A and B are fully miscible or only in limits.
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Hello Everyone,
I am currently optimizing the production process for the battery packs.
I would like to know how the great the increase in contact resistance with an aluminium oxide layer on the battery terminals?
I am going to use laser welding to bind the terminals together. If I file the terminal just before the welding to remove the top layer, will it make any difference? how quick is the passivation of aluminium?
Any literature would be very helpful. Is it possible to find out experimentally using the Impedance spectroscopy?
Aluminum oxid (Al2O3) represents an insulator with high value of electrical resistance 1x1014 Ω·cm. Al2O3 is created in very fine (a few nanometers) layer due to chemical reaction of aluminium with air oxygen. The battery terminal (e.g.in cars) should be protected against aluminum oxide ocurence with special grease. Al2O3 presence leads to a high resistance contact at the terminal reducing the performance of the battery.
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We wish to create an APTES monolayer within a channel. We are currently using 10% APTES in Ethanol, for 10 minutes incubation followed by washing. We have also tried 2% APTES for 1 hour. Both have given inconsistent results.
Could you suggest what would be a good method to achieve more repeatable performance?
P.S. before APTES we are activating the surface using H2O2 with HCL & H2O to generate reactive OH group on surface.
Rohan, the exact mechanism is not self-evident, but the effect was shown experimentally almost 30 years ago - water solution gives the finest APTES monolayer:
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Hello everyone! If an oxygen vacancy is the lack of an oxygen in a site in the lattice, what is a possible explanation for the ability to probe the presence/quantity of oxygen vacancies in an oxide film such as SnO2 and SiO2 by deconvoluting the O-1s XPS spectrum into various components, of which one is assigned to oxygen vacancies?
Especially since no O-1s XPS signals can be emitted if there is no oxygen at that vacancy.
This paper attempts to do just this on SiO2.
Thank you so much!
The vacant oxygen is NOT an "O-specie" with an oxidation state of (-1), the vacant oxygen is a vacant position in the lattice created due to the absence of an oxygen ion, thus, there is NO XPS-signal for the vacant oxygen, that is the core of the present question.
Please note that the oxygen ion with an oxidation state of (-1), present in peroxides, for example, have O 1s in the range (531.1 - 532.0) which is out of the range of the O 1s in the article attached by Helen Par .
For more details regarding the XPS of oxygen in its different states, please refer to:
DOI: 10.1039/a908800h
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I need to study the surface of nylon-6 blank fibres with a thickness of nearly 40 micrometre, I work in optics lab with many optical components such as beam splitters, lenses, mirrors ... etc, can I build a system to study the topology of this fibre?
Optical Scatterometry is already in use to study the surface topology of materials.
Please find the attached file regarding the principle of this method.
For more details, please refer to the ENCYCLOPEDIA OF MATERIALS CHARACTERIZATION by C. Richard Brundle and Charles A. Evans.
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Also, how do these hydrodynamic interparticle forces compare against hydration/depletion solvation-type interparticle forces? Are they all of the same nature?
It seems to me that liquid bridging interparticle forces are mainly relevant for humid gas-particle systems. It also seems to me that hydration forces between particles with hydrophilic surfaces are of the same origin as interparticle lubrication forces. However, I am not entirely certain about any of these statements.
In a more general sense, for liquid-particle colloidal suspensions (e.g., solid micro- and/or nano-particles in water), what interparticle forces of hydrodynamic nature are in play?
My limited understanding of lubrication forces based on the papers I have been able to access is that the theoretical analyses ignore colloidal forces (as per DLVO etc) and so I would suggest caution in applying the concepts of lubrication forces to colloidal systems. I say this looking at your question as a colloid scientist and not a not someone expert in fluid mechanics so I may be incorrect.
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If the answer is yes, then does the charge acquisition mechanism change with respect to metallic, metal oxide, and carbon-based nanoparticles?
And would it also change between totally pure water and tap water?
Assume no coatings, surfactants, or any stabilizing agents, and pH = 7.
Carbon based nanoparticles may become oxidized by e.g. air at imperfections and in this way surface groups may be formed that in aquous solutions dissociate. As indicated by Lehtinen the actual charge density will depend on the pK of the groups and the ionic strength.
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As a founder of silicoflask.com and as a scientist I wondering in what kind of molecular systems (or topic) you are interested in?
The SilicoFlask.com is a platform for molecular systems cloud computing. We use the Scheutjens-Fleer Self Consistent Field (SF-SCF) method to predict or confirm experimentally determined behaviour of the molecules. Our aim is to provide super-fast computer approach with a coarse-grained detailing level to help the scientists and pharmacy industry get the solid answer on their questions as soon as possible.
We recently added the list of topics we can deal with and it will be good if you may find them useful.
I will be very thankful if you can write below your favorite system from the list. The results will be taking into account for future tutorials.
Wish you a very good day!
-Boris.
Hello Boris Okrugin,
My name is Darrell Robinson and I am a Biomedical Engineering PhD student studying and conducting research in Systems Biology and Bioinformatics regarding Gene Expression of the Immune System.
I was contacted by an associate of yours named Veronica Bazunova, the Product Lead, regarding your software web platform called Silico Flask. She was looking for beta testers and gave me some information about it such as how to register.
I am very interested in beta testing the software and learning more about it, but when I tried to register or go to the home website the link did not work. If the project and/or the testing is still on-going and you are looking for some more people to test the software, please feel free to let me know by either email or by phone. I would be more than happy to get involved further.
If I contacted you in error, please let me know and I apologize in advance. Thank you and I look forward to hearing from you.
Best Regards,
Darrell Robinson
Binghamton University SUNY
Department of Biomedical Engineering
Systems Biology & Bioinformatics
PhD Student
Phone: 512-960-9838
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We got 0.2 m2/g-1 as the pore size in a BET study for Nitrogen adsorption.
Is this data is reliable enough for include in a research paper or are there any conclusions can be made why we got this value?
Dear Yasashri, The reliability of your determination depends on the amount of sample that you were using. Recently, I carried out nitrogen and krypton adsorption on a sample with a very low specific surface. With nitrogen, I obtained 0.33, 0.34 and 0.35 m2/g in three consecutive measurements. With krypton, I obtained 0.32, 0.33 and 0.32 m2/g in three consecutive measurements. If I agree with Dr Parra that krypton is more precise than nitrogen, I was agreeably surprised by the precision obtained with nitrogen adsorption. The key of this precision was the amount of sample that I used, nearly 10g. I measured the cold and warm volumes with helium after the measurements although given the very low surface area you could do that before, no helium entrapment is foreseen because I do not think that your sample has very narrow porosity.
I hope this helped you, best wishes, Vanessa
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Hi,
We grow thin film material A on top the substrate with other material B. In some situations, grown material is the same as the material of the substrate. Briefly, for epitaxial growth , they are 'hetero-epitaxial' and 'homo-epitaxial' growth respectively.
So, how can I measure (experimentally) or calculate (theoretically) the interface energy of the A-B interface?
Regards,
Anjan
There's a multitude of methods to determine interface binding energies although not all of them can be applied for every system, especially if the bond between film and substrate is extremely rigid:
-the most popular, recently, is probably the AFM shearing method. In this method the upper layer is picked up by an AFM tip and moved around; the force required to do so can be recalculated to your energy by modelling (see e.g. W. Wang, S. Dai, X. Li, J. Yang, D. J. Srolovitz, und Q. Zheng, Nature Comm.
6, 7853 (2015).), but be careful: the modelling is rather sensitive.
-if your film is sublimeable, you can try temperature programmed desorption spectroscopy (see A. de Jong und J. Niemantsverdriet, Surf. Sci. 233, 355 (1990). for a review of procedures)
-there's the whole field of microcalorimetry but I have no expertise in that field
-if there is an equilibrium of adsorption and desorption, you can of course measure the adsorption isotherm and get binding energies from that (see e.g. M. Desjonqueres und D. Spanjaard, Concepts in Surface Physics, 2. Ed. (Springer,
Berlin/Heidelberg, 1998).)
For the calculation of interface energies I would recommend the VASP program package. However, VASP is not straightforward and if you want to go there I strongly recommend you find a proper theoretician to to the calculations for you.
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I am investigating the COF of Aluminium surface before and after a surface finishing process. Before surface finishing the Ra is 15 um and after surface finishing assume Ra becomes <1um. COF increases with decrease in surface roughness. I expected the Vice versa. How to explain this?
However, the starting COF is Zero for Ra< 1 um. Is COF value 0 possible at start?
My test frequency is 5 Hz, Humidity - 65%. steel ball on aluminium sample.
I guess the misunderstanding that the COF should increase with surface roughness stems from the misleading colloquial usage of the term "rough". In general the COF doesn't correlate too much (at least not consistently) with surface roughness. However, if you have a very smooth surface, you might have adhesive components to the normal force in contact, which will result in an increase of the macroscopic apparent COF.
Note that one parameter is not sufficient to characterize roughness. And "zero" is just "smaller than measurement accuracy" :)
Best regards
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in order to bind catalytic active (CuO-precursor-doped) zeolith onto the surface of ceramic fibers, the impragnated fibers were calcinated at 500°C. However the ceramic fibers become brittle after the sintering process. The Zeolith particles were not firmly bound to the surface of the fiber. After washing in destilled water for 4 hours the zeolith particles were almost completely washed away.
From the abovementioned test it was concluded that the temperature required for a successful sintering is higher than 500°C but it will alter the internal structure of the ceramic fibers and make it brittle.
Is there a way to optimise the sintering process so that the zeolith particles can be bound firmly to the fiber surface without damaging the fiber itself? Is there an alternative to sintering to bind the zeolith particles onto ceramic fibers?
Functionalization of ceramic fibers by attaching the functional groups may improve upon the adhesive tendency of the surface of the fibers and zeolite particles May remain in place by chemisorption for longer duration of time even after washing with water or so.
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I have a cluster of water molecules. I want to model amorphous ice from that cluster. But for that I need to find out (best possible) minimum energy structure of that system. I tried Avogadro (https://avogadro.cc/) to search global minima but problem is I need to specify the rotational bonds. A cluster of water molecules do not have any rotational bond. Also I give interatomic distance as rotational bond then program wont work. I am attaching a starting structure of my ice model (CH4+nH2O+OH-) from which I want to start calculations. Please help me in this regard. I am using Gaussian 09 for my ab initio calculations.
Looking for the global energy minimum is hard since there are many possibilities (local minimum). Thus, this problem could be solved if you run a molecular dynamic simulation in your system and submit some of the screenshots to an ab initio energy's optimization.
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"near anhydrous conditions" is really an interesting statement.
I strongly recommend to read the mentioned article in which the Kinetik of different methoxy and ethoxy silanes are measured and compared.
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Hello,
Is it possible to have different particle structure at different deposition powers under the same background gas pressure?
I am depositing Ni-cermet thin films of about 250nm on avg. thickness via RF sputtering at various sputtering powers of 50W-200W. Regardless of the background reactive gas pressure, the micro-structure for 50W Ni-cermet is rice like, for 100W it changes to granular, for 150 one can see a mix of granular and circular while for 200W the structure of the Ni-cermet is completely circular.
Can anyone please explain what is causing this phenomenon.
Much Appreciated
Also, the gas pressure and the RF power both determine the sputtered particle energy (when it arrives on the substrate surface). And if the substrate is heated up, it could be another energy source. To get the particle structure, maybe you need to carefully balance these. Most of case, it's a combination of all these
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I prefer a silane with low boiling point as I am going to deposit it in the vapor phase (chemical vapor deposition).
I have tried TMS (Chlorotrimethylsilane) using CVD on Si wafer and I got water contact angle of ~55 which is not suitable for my purpose. I need something less hydrophobic (30-40 degree).
Dear colleagues,
we normally use Serva-Silicone solution in propanol.
The best results we have is after heating-up for one hour. The angle I never check.
However, a picture I have taken from a short movie...
(I have the impression, that the angle is different when only drying in air).
Regards
Alex
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I am in the process of building a new setup and have a discussion with my colleague on the subject.
We will measure several monolayers on a flat reflective surface inside a vacuum chamber with ~1 wavenumber resolution. The two 38mm windows will be placed at ~300 mm distance from the surface. The angle of incidence is 75 degrees. The window ports are normal to the IR beam axis. The beam is focused at the sample surface with a parabollic mirror placed before the entrance window.
As far as I understand, when the interference fringes are highly reproducible, background subtraction deals with them just fine. In my case of measurements in vacuum, the only irregularities I can think of are thermal expansion due to lab T variations, a slight misalignment of the reflective sample surface, and T variations at a liquid nitrogen cooled MCT detector assembly depending on the Dewar fill level, I guess. The room T variations can affect the distance between the KBr windows, and between the exit window and the external MCT detector. But these distances are so large that interferences do not survive at 1 cm-1 resolution. The fringes created via multiple reflections inside individual KBr windows will be highly reproducible, in my view. I cannot do much to improve the detector assembly.
Do I miss something and wedge/tilt in KBr windows could be useful?
If you want to avoid fringes - the cross-sectionof your film should have a wedge shape
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how to bring metallized spheres at the surface of the formulation. what I am facing is that metal coated glass spheres are sinking in resin system so it could not get the light reflection that I want. Is there any ways that - plausible in solid compositions-
that I can use to bring glass spheres on top ?
I was thinking to create surface tension difference which might lead to phase separation but since there is NO solvent\water , I could not accomplish.
it is a nanocoatings so we can not flip any sides.@MohammadRezaZamaniKouhpanji
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I'm not familiar with microscope types, features etc. and our R&D group wants to purchase a new microscope to characterize our sensors, materials, etc.
Can anyone recommend a good type or brand? Pros & Cons of various types? Stereoscope, Upright Brightfield, Inverted, Digital?
I hear that some new microscopes even offer profilometry analysis. Any suggestions would be greatly appreciated. Thanks!
Hello Fine microscopes for your research can be found in these sats. My recommendation is for Upright and Inverted Light Microscopes:
or Laser Scanning Microscopes
I wish you success with your choice. Regards Emil Yankov
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Hi everyone, I want to learn how simulate heterogeneous catalytic process, does anyone know any book, review or something where i could start?
Thanks and sorry for the inconvenience
Hello, Please elaborate you need of simulation a bit more. Both MM and QM and Hybrid QM/MM simulations are possible for any kind of catalysis.
Below is a link and reference to a book for catalytic computation:
Book by RSC
Hope this helps,
Regards
Ajay Khanna
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Hello!
I seek a method to hydrophilization of channels surface in assembled (bonded) pmma chip. I tried to use for this purpose UV/ozone treatment of pmma surface before bonding. However thermal bonding of pmma chip led to decrease of surface hydrophilicity (contact angle increase after thermal bonding).
Perhaps anybody know what kind of chemical reagents allow the surface of channels to be hydrophilized by pumping them through the pmma chip.
Thank you Jan!
I will try to treat the pmma by nitric acid.
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After plasma treatment of some polymer, both functionality and surface roughness is obtained. Total surface energy is increased. which component of surface energy includes the contribution from surface roughness ?
In my understanding surface roughness does influence the contact angle but energetic aspects should be considered separately assuming smooth interface. On the other hand, however, it is well known that the free energy of bodies depends on the curvature, so in this respect the average surface energy may depend on the roughness.
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Hello,
Our institution is buying a new XPS machine. Now we have to make a decision between Kratos Axis supra and Thermo Scientific Escalab Xi+. For this reason I would like to know about the experience from user's side. So maybe there is some users who has one of those machnes? If so, is there some issues with the equipment which could not be forseen before purchasing?
How often you had repairs (excluding replacement of consumables) Is service was fluent?
Is the Autimatics reliable in Axis supra?
The instruments are similar so it depends on your needs mostly. We have the Thermo 250 Xi and a PHI Quantum 2000. Technically, the Thermo is excellent - the spectra are superb and the acquisition rate is very fast. The Ar cluster gun is also a dream come true. The software can be a bit buggy though and the plots aren't as good as that produced by MultiPak for example. The sample holder is smaller than the Kratos and much smaller than the PHI. Keep that in mind if you analyse industrial samples. In terms of reliability, I'd rate the PHI higher than the Thermo, but Thermo has better support.
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What happens to the substrate kept in high vacuum and a high temperature of 773K (500oC) and above inside the Vacuum Chamber for a long time?
a) Will the contamination on the substrate removed at high vacuum? b) Any change in the surface of the substrate?
c) Will the surface get oxidized?
d) Destruction of the substrate
There really is too little information to offer a detailed answer, nevertheless:
a) Assuming that the contaminants are not covalently bound with the substrate, are present on the surface of the substrate rather than being enclosed in its structure and are "volatile" in such conditions (e.g. non-polymeric / low molecular weight organic compounds), they will be gradually desorbed from the surface of the substrate. Similarly, the temperature may be sufficient to decompose many organic compounds (and some inorganic species), with the products of such decomposition being potentially more volatile and also being removed in these conditions.
b) This will be dependent on the material of your substrate. If the substrate does not melt or undergo any polymorphic transitions, there should be no such changes, assuming that it is not "volatile" itself under your conditions.
c) No. Assuming the vacuum chamber is operating without faults and was purged with inert gas prior to applying your vacuum source, the traces of oxygen should not be able to oxidise your substrate, at least not to a noticeable extent.
d) Again, this is dependent on the material of the substrate and particularly its melting point and vapour pressure at the temperature you are using. For example, silicon, with a melting point of roughly 1700K and vapor pressure of roughly 0.5Pa at this temperature would be largely unaffected, unless you are using *extremely* high vacuum.
e) Possible solid phase reactions between the substrate and contaminants within that substrate.
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Hi,
Does anyone have any experiences with bioadhesive and biocompatible materials (except dopa/dopamine), which can be used for surface coating and improving biofilm growth on them??
Cheers
also there is a doctoral thesis on this subject under the supervision of Dr Taha AL-Taha
regards
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I am performing pool boiling experiment using water as the working fluid. To avoid any type of solid deposition on the boiling surface (copper in my case), which type of water should be preferred- distilled, deionized or millipore?
Does not matter (I am talking about good DI water system, they could be very different)
In terms of purity/resistivity the best is millipore. DI water could be both better and worse than distilled water, depending on a system; theoretically DI water should be better.
Generally for boiling distilled water is the worst one, but if DI system is a suspicious one then distilled water should be preferred.
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Historically we've studied organic molecules on metal samples mounted using tantalum clips to the sample plate. We are interested in performing experiments on HOPG but are unsure of the best way to mount. Metal clips block off part of the crystal, and so make clean cleaving of the crystal more difficult. However I am unsure if any UHV compatible adhesive can manage temperatures down to 77 K, while also surviving a several hundred degree annealing step.
Will it be possible to repeatedly study different organic monolayers on HOPG without repeatedly cleaving, i.e. only cleaning by annealing? In this case metal clips would be best.
Or would a low -T contact adhesive be best, and simply cleave the HOPG everytime a new molecule is studied, with no annealing?
Or is there some other mounting option that combines the best of both methods?
HOPG is a fairly cheap material as far as single crystals go, we always cleave a fresh surface for each experiment.
I have always mounted HOPG with clips, though it is true that HOPG surface is easily damaged since you are using STM it will be easy to avoid the damaged area.
It may be possible to avoid taking the sample in and out of vacuum to cleave by annealing, just make sure that that the surface is clean by LEEDS, XPS, or many STM spots no matter the method you use.
The debate about annealing HOPG is not new, some argue that air pockets can be trapped between the layers of the sample, but XPS tends to not show these pockets. In the end try a few things and stick with a method that works.
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There are many kinds of communition present in industry (as well as) during processing of some (kind of) operation. Particle size reduction can be achieved by applying force externally or by internal mass transfer during processing of some operation in reactive or non-reactive environment. Can any modification be proposed for reactive environment to the existing laws, Bond's etc., for size reduction?
Mass can't be reduced in a chemical reaction.
Do not reduce the mass it can be extremely dangerous (e=m*c^2).
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Can the concept of the N-face or the Ga-face exist when the GaN film is not a single crystal anymore but a polycrystalline film? Can there be something like a net polarity in poly films?
Of course, you can not determine the polarity by XPS.
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i am working with PTFE suspension, using dip-coating approach i am making superhydrophobic surface. as we all know at certain temperature heating PTFE shows certain change in property and make surface hydrophilic to hydrophobic. why after heating that PTFE np coated surface changes it properties? what can be the possible changes are there, which help PTFE surface change its behaviour at 250 degree c.?
What can be the explanation if before heating that Teflon coated surface was showing water contact angle 24 degree, and after heating at curing temperature the contact angle changes and shows 142 degree.
The hydrophílic coating is destroyed by the heating. You should confirm it by XPS.
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Using calcite and kaolinite as seeding materials, how does the BET surface of these seeds affect the precipitation of calcium carbonate in supersaturated medium.
Dear Prof. Towe,
Calcite, rhombohedral as shown in the figure attached (IB2). These are calcite powder purchase from sigma-aldrich. Kaolinite are standards from a mine in the US. Cheers!
Chin Yik
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To determine capacitance or charge build up of some material can one use material coated onto graphite electrode as the working electrode?
What I mean is let`s say we have a material (some polymer carbon nanotube composite) now we coat it onto graphite electrode and perform cyclovoltammetry. My doubt here is that when we will use graphite electrode, it will have some charge build up of its own i.e. capacitance of its own, so we will not be calculating the capacitance of our material rather we will end up measuring cyclovoltammetry of the combined system.
If we cannot use, what is so special about glassy carbon electrode?
As Artur Braun. However, I propose to use the EIS as a technique for your C , alongside the parameter value of :
VDC ~Vhigh, (Vhigh~Vmax, defended from the Voltammetry)
1)before and
2)after coating.
This Ccoat (EIS produced, Ccoat-modeled) should be more satisfactory for your task.
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It is argued that corrosion starts at grain boundaries or other imperfections because of (amongst other things) the higher energy level compared to the bulk material. Also in grain boundary engineering the lower susceptibility to corrosion of low sigma grain boundaries is adressed to the low energy levels of this special grain boundaries. But the energy of a free surface of stainless steel is up to two to three times higher compared to the energy of grain boundaries.
Can one imagine a grain boundary at the surface of a metall as a combination of free surface and grain boundary?
It is clear that the energy level is just a small aspect of corrosion and there are many different aspects that play a role. One important aspect seems to be the potential differences between the material inside the grain and the grain boundary. Does that meen the grain boundary alsways acts as the more anodic part? Becaus dissolution of Fe is the anodic reation. And if so why?
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I need to correlate the ionic state of Fe with the magnetic properties of Fe doped ferroelectric material. My way of synthesis is solid state reaction method.can I correlate the reason for magnetic properties of that ferroelectric material by taking core level spectra of Fe 2p and parent material site Ti? through XPS we do only surface characterization so is it useful or not? Can we confirm the incorporation of Fe ion in the parent Ti site through shifting of Ti corresponding BE peaks?
XPS is used to look at the surface composition and oxidation state of species present in the top 5 - 10 atomic layers. For a multi-compoennt system the surface composition can never, ever be the same as the bulk composition. You'll find that the major part of this surface is oxide and carbon. You would need to argon ion etch (or split a crystal as suggested above) to expose the bulk. Are you considerig XPS simply because you have such a unt in your facility? Your magnetic properties and their characterization is the real problem to focus on.
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I did annealing of polyethylene of 200um(size 2x2 mm) on Silicon at 300 °C for 10 min. After the annealing process i saw the thickness of polyethylene increased to 500um approx!!!!!!
Can anyone explain why there is increase in the thickness of 200um to 500um of polyethylene????.
Why would you have heated the polyethylene to 300 Celcius?? It has melted.
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A reviewer comment is:
Keeping on the quantum chemistry aspect, a single Fe atom cannot represent entirely a carbon-steel surface and this is was already debated on the computer simulations on surface science literature. In other words, it is clear that a single Fe atom would easily transfer electrons to the inhibitor due to an absence of the C neighborhood. However, does this behavior will still be kept in a metallic surface? The authors must adapt the text being clear that it was a model and also discuss the limitations for this approximation. Another important test might be a calculation with a carbon steel cluster instead of a single Fe atom.
Hi Ayman,
You could study the Fe-C surface using a slab model, fully relax the top few atomic layers and study the electron density using the Bader charge analysis. At the same time you need to study the structure of the inhibitor separately and its charge density. Finally, you study the adsorption of the inhibitor on the Fe-C surface and perform another Bader charge analysis. By comparing the results of the charge analysis calculation for the adsorption case to the clean surface and isolated inhibitor you should be able to observe the transfer of electrons.
I hope this explanation helps.
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I want to calculate surafce stress in Si (001) surface after reconstruction by using software quantum espresso. As in the output it is displaying stress matrix ..my z - component (sigma zz) of stress is not zero, but I have taken a enough vaccum , no external force acts on the surafce and therfore it should be zero .So I am not understanding why it is giving z - component (sigma zz) of stress ?
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I am studying pool boiling of water on copper surface at saturated temperature and atmospheric pressure. After the experiment I observe some sort of deposition (I am attaching an image) on the boiling surface. I clean each and every part of the setup with acetone before the experiment. I use millipore water. I polish the boiling surface with 600 grit size emery paper before the experiment. I am not sure whether there is actually deposition happening on the surface or not. So, I request the experts to observe the image and comment on it. Also, any suggestions related to this are highly appreciated.
Sir, the boiling chamber is open to atmosphere through few vents. I am interested in calculating the critical heat flux and heat transfer coefficient in the nucleate zone. I shall be modifying the surface once the test rig is validated with the literature values. The CHF values which I have observed during my experiments are in good agreement with the literature.
The reason behind not selecting steel is its lower thermal conductivity which will lead to higher operating temperatures. The contact angle observed on the surface after boiling was smaller (50 deg-60 deg) as compared to before boiling (82 deg to 88 deg). And also the triple contact line gets disturbed at the bright spots. So, I am not able to understand whether there is any impurity getting deposited on the surface or its just the oxidization of copper to one of its oxide.
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Do you believe that there is a correlation between rubber tack & viscosity of the compound?
Yes. Same polymer compound used. At different level of Mooney viscosity (ML) above results obtained.
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Hello ,
Optical bandgap (Eg) of bulk anatase TiO2 is known to 3.2 eV .
However, some references report that
the Eg of TiO2 can be around 3.8 eV when the film is deposited by
e-beam evaporation method.
Applied Surface Science 254 (2008) 2685–2689
Semicond. Sci. Technol. 31 (2016) 125012 (9pp)
What's the reason that makes the change of Eg depending on the
deposition method of TiO2?
The optical band gap energy of TiO2 may be depends on grain size of it's layers. It has been reported that Eg decreases as number of deposited layer increase which relates with the change in grain size. Please have a look at the below link.
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Questions: Is it true that the maximum spread factor(the ratio of the maximum spread diameter to the original droplet diameter) during droplet impaction on a substrate target should be always larger than one?
Could anyone who is familiar with this area help with this? Many thanks.
The degree of wetting is quantitatively characterized by the dimensionless cosine of the contact angle (wetting angle). The quartz has a contact angle of zero degrees. Teflon is -108 degrees. The 90 degree cosine is zero.
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For preparation of reconstructed Si(hkl) substrates, we generally employ direct current (DC) heating method in ultra-high vacuum (UHV) condition. In this case, initially we degas the Si(hkl) substrates at ~ 600 0C for 12-15 hours. Thereafter, we perform repetitive 'flash heating' at ~ 1200 0C for 30 sec. It consequences formation of very large ( 1μm × 1μm), well-ordered and atomically smooth reconstructed template.
Can we use such methods (inside the molecular beam epitaxy (MBE) chamber) for preparation of reconstructed Ge(001), Ge(111) substrates ?
Dear Anjan,
This will be difficult in my opinion. I would recommend few cycles of Ar+ ion sputtering at 0.75 keV at a partial pressure of Ar of 1 10-5 mbar followed by annealing at 970 K at UHV by direct heating method after degas.
As an alternative way is wet etching using aggressive chemistry: see e.g. here: http://iopscience.iop.org/article/10.1088/0957-4484/22/14/145604/meta, however it was not worked properly in my case.
Best wishes
Wojtek
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My enquiry is about any chemical/electrochemical species maybe ions or gas, etc. that adsorbs on Pb surface exposed to that species.
BET method is preferred choice for higher relative surface areas like porous materials, activated carbon ,quantum dots materials,graphene and nanosized metal oxides.I thinck the Lanqmuir model is compatible with metals which have low relative surface areas.
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Various methods as finding capacitance have already been discussed in some papers but it seems that reliable figures and data is not available. BET is out of question as metal catalyst is carbon supported. Is there any other method that could be used to determine the electroactive surface area of non-noble metals.
Hi Kumawat,
Go through the following articles. Very informative.
REAL SURFACE AREA MEASUREMENTS
IN ELECTROCHEMISTRY by S TRASATTI and  O. A. PETRII
Also, one of my colleagues has published a paper recently.
Electrochemical estimation of the active site density on metal-free nitrogen-doped carbon using catechol as an adsorbate by Arup Chakraborty
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After printing on glass with UV curable inks, delamination is seen around the printed areas. Does anyone know of any techniques/methods that can improve lamination on the printed sections?
Thank you.
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I have attached file with 2 sorption isotherms for cobalt ferrites. I want to know how to classify these them among standard IUPAC isotherms (Type I to Type VI). Is it necessary it has to go to one of these? How to exactly go for the analysis?
Figure 1 is a Type IV isotherm. A plateau is reached at a relative pressure of about 0.9. After this there is further condensation leading to another upswing in the isotherm. You would be advised to take the pore volumen micro + meso from the amount adsorbed on the desorption branch at a relative pressure of 0.96. The PSD from the desorption branch will probably show a bimodal distribution with a well defined peak at a diameter of about 3.7 nm due to the sudden closure of the hystersis loop. This pore width is an artefact and only points to the presence of narrower mesopores. For this reason some workers prefer to use the adsorption branch.
In Figure 2 the isotherm is also of Type IV due to the mesoporous nature, however, the plateau is not so well defined, leading to a further upswing at high relative pressure due to the presence of wider mesopores and macropores. In this case the peak at 3.7 nm from the PSD curve of the desorption branch will be even more evident since the sudden closure at a relative pressure close to 0.42 is even more pronounced.
Best regards,
Malcolm
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