Questions tagged [surface-chemistry]

Surface chemistry is roughly defined as the study of chemical reactions at interfaces between 2 or more phases.

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2answers
9k views

What is the difference between BET and Langmuir model for calculating the specific surface area?

Brunauer–Emmett–Teller (BET) surface area is measured by specific surface area of the adsorbent. BET surface area is measured by using non-corrosive gases like $\ce{N2}$, $\ce{CO2}$, $\ce{Ar}$ etc. ...
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100 views

Can negative adsorption be considered equal to sorption?

In my book it was written sorption is basically when the substance gets uniformly distributed into the bulk of the solid but at the same time its concentration is higher at the surface then in the ...
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1answer
443 views

What, if any, are the differences between hemiwicking and wicking?

I'm encountering these two terms, but their uses seem to be different, and there's little documentation out there defining the terms. Here is an example definition I've found of Wicking: Wicking ...
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1answer
2k views

What is the definition of porous materials?

Is there a consensus on scientific definition of porous materials? There are many definitions out there which do not seem accurate enough: from wikipedia (accessed July 2017): A porous medium or a ...
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1answer
496 views

How can I measure a droplets contact angle without a setup?

I have to use a phone camera to replicate the Sessile drop analyzer, but there doesn't seem to be a standard to different parameters, such as how far away should my camera be from the droplet or how ...
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55 views

Functionalizing CTAC stabilized nanoparticles

I am working on functionalizing silver-gold bimetallic nanoparticles. My nanoparticles are stabilized by CTAC(cetyltrimethylammonium chloride).The most articles which I found, are about the ...
3
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1answer
524 views

Substances comprised of large molecules are liquids at room temperature?

I am looking for compounds that are liquid at normal temperatures and are physically very large, to be used in an ellipsometer adsorption experiment. I am currently working with decane. The candidates ...
4
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1answer
168 views

How does water freeze and crystallize on a cold superhydrophobic surface?

Superhydrophobic surfaces are nano-structured to "repel" liquid water and there has been a lot of work done to understand the microscopics of wetting of these nanostructures. What I currently am ...
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178 views

Conductive hydrophobic material

I was looking for a conductive hydrophobic material if there is one? If not why? I was researching and I found some material about laser etching on metals that causes superhydrophobicity but that I ...
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1answer
71 views

Crystallisation and crystal surface

It is my understanding that if you put table salt (as an example of polar compound) in water, the Na+ and Cl- ions will freely move through the solution. They will make the solution conductive and ...
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2answers
337 views

Mixing water and oil in microgravity outside of a container

What would happen if I where to mix water and oil in a vacuum in microgravity where the temperatures were low enough so that the oil and water remain liquids also, the mixture is not inside of a ...
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2answers
133 views

How does physical adsorption of mixed gas occur on solid? (eg I mean how the gas molecules of compete each other for a slot on solid surface)

I am working on sorption phenomenon of gases (including inert gas) on coal seam surface. For a mixture of 2 gases at a certain pressure, carbon dioxide and methane, for instance, $\ce{CO2}$ is ...
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170 views

Very fast brass oxidation

I work for a company that manufactures pyrotechnics for the oil and gas industry, and we have been having an odd phenomenon occur. One part, a brass tube with a copper clip filled with black powder, ...
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2answers
1k views

How fast a surface oxide layer is formed on bulk chromium?

If a chromium piece is cut in half, how long would it take for an oxide layer to form on the new surface (room temperature)? i.e. is it a matter of seconds/minutes/hours/days/weeks? The closest study ...
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1answer
260 views

Transition state optimisation on the surface of periclase

I want to model a reaction catalysed by periclase ($\ce{MgO}$) using DFT. I have a good guess on the transition state (TS) of the reaction that goes in gas phase/solvent (produced using MOPAC). The ...
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1answer
239 views

What is a typical monolayer formation time for liquid phase adsorbate on a solid surface?

Let's say a solid is submerged in a solution of species with functional groups and a self-assembled monolayer is forming. What are the typical time scales for the formation of a continuous monolayer? (...
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0answers
220 views

What is the surfactant's role in the non-coalescence of water droplets?

I have recently seen many videos that talk about the noncoalescence of water droplets; however, I do not understand the purpose of adding surfactants into the water. From my knowledge (high school), ...
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0answers
779 views

Why non polar liquids wet non polar surfaces better than polar surfaces?

In semiconductor industry adhesion promoters (such as HMDS) are applied on various surfaces to improve adhesion between the surface and the photoresist: On SiO2 and many metals surfaces, the air ...
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1answer
3k views

Surface Tension and Evaporation

Why does acetone evaporate faster than ethanol yet still has a higher surface tension? I would expect it to have a lower surface tension... I got the data from surface-tension.de.
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1answer
2k views

What is the chemical structure of ceramic nonstick coating on pans?

There are lots of pans nowadays that have a ceramic nonstick coating instead of a PTFE coating. However I can not find anything online describing what kind of ceramic such nonstick coatings are. Does ...
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2answers
308 views

Overall equilibrium expression for competitive equilibria

I have a case where I have two reactions that depend on a common reactant. The reactions can be written as: I) $\ce{A + B <=> AB}$ II) $\ce{A + C <=> AC}$ We can thus write equilibrium ...
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1answer
7k views

Effect of pressure on adsorption of a gas

I am currently studying about the basic terms of surface chemistry, and am facing some conceptual doubt regarding the following: What effect does pressure have on the adsorption of a gas (adsorbate) ...
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2answers
406 views

Why does the BET equation take into consideration a multimolecular-layer, even though it deals with chemisorption?

I came across the Brunauer-Emmet-Teller (BET) equation recently, and one thing that I found strange was an implicit reference to the formation of molecular multi-layer. In the BET equation $$ \begin{...
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0answers
145 views

A surface with variable roughness

As you may know, wettability is a characteristic of each surface which determines what the contact angle would be when a droplet is put on the surface (see here for more info). Surface roughness has a ...
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1answer
1k views

Reaction mechanism in fluoride adsorption to aluminum oxide

Despite a fair amount of research (excluding non-open access journals, to which I have not got access), I cannot seem to find an explanation of the process that takes place when $\ce{F^-}$ adsorbs to ...
4
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1answer
457 views

Counterions in adsorption of ions

When an ion is adsorbed from an aqueous solution onto a solid, what happens to its counterion? Obviously, the solution does not become charged - does this mean that it too is adsorbed? (Example: $ \...
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6answers
11k views

Why does chemisorption increase with rise in temperature, even though it is an exothermic process?

Chemisorption is exothermic process, but still it increases with increase in temperature. Why? I know that there needs to be a minimum activation energy to be achieved in order to initiate ...
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Why do we have surface charges on a polymer sheet immerged in water ?

I am working with a conductive polymer sheet where I have dropped off a drop of water (with ions). I have plugged the polymer with a conductive wire and an other wire is on the drop. With a voltmeter ...
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1answer
56 views

Formation of a bubble which is not a sphere

Recently a friend of mine received a project from her college which was like - "Bring a bubble which isn't spherical in class. ". Could anyone please suggest how to prepare such a bubble ...
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1answer
220 views

Do bond energies differ for surface and bulk atoms in nanoparticles?

In nano-particles, surface atoms have fewer neighboring atoms in compare to bulk atoms. Is there any difference between bond energy of surface atoms and bulk atoms?
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1answer
260 views

Explain why alumina-containing zeolites possess chemically active surfaces

I think zeolites possess acid sites that are catalytically active in many hydrocarbon reactions. The pore system only allows molecules that are small enough to enter, hence it affects the selectivity ...
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1answer
1k views

Chromatography: Why does the insoluble compound get pulled along?

In paper chromatography, we see that a paper with an ink spot on it get dissolved in the liquid and travels up with water due to capillary action. Then the compounds with more affinity to the paper ...
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1answer
498 views

Does glass adsorb methanol to an exceptional extent?

Does (borosilicate) glass adsorb methanol to an exceptional extent? We are doing vapor density measurements of organic solvents using a microbalance and a sealed glass sphere. Other polar molecules ...
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1answer
2k views

Why does a silanized glass surface become hydrophobic?

What is the physical reason that a glass surface becomes hydrophobic by silanization? (e.g. is it due to increase in surface roughness due to the long chains which is created on the glass surface? or ....
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2answers
6k views

Why even the most volatile solvents leave a residue after evaporating?

After a solvent evaporates off of a surface there's always some residue left in the form of a strain. Why it is the case even for highly volatile solvents such as acetone, toluene etc?
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58 views

Wetting properties of FTO coated glass

I am trying to spin coat a layer of polymer+Quantum Dots on an FTO coated glass slide. My material is forming agglomerates at the edges of my slide. My polymer is PVK which has a conc of$\approx 4.5mg/...
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0answers
70 views

Could we bond hydrogen to the edges of covalent network structures like diamond?

I know that diamond is just carbon atoms structured in a way that differs from graphite and charcoal. The carbon atoms on the edges do not have full valence shells. Would it be possible to attach ...
12
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1answer
8k views

Is adsorption exothermic, and if so, why?

Why is adsorption exothermic? The explanation given in my textbook is: For a process to be spontaneous, the thermodynamic requirement is that, at constant temperature and pressure, $\Delta G &...
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1answer
761 views

Where does the charge on an electrode, responsible for the formation of a double layer once submerged in an electrolyte, come from?

I've started exploring electrical double layers and electrode-tissue interfaces whilst dealing with deep brain stimulation and stimulus artefact. I've heard many times that what causes the double ...
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1answer
91 views

Poly(3-hexyltiophene-2,5-diyl) (P3HT) reactions with inorganic salts in aqueous solution

I would need for my research at least as a starting point to know what kind of reactions occur at the interface of P3HT and an electrolyte. The electrolyte is simple $\ce{KCl}$ solution, maybe with $\...
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0answers
73 views

Surface stability in crystal growth

What is the meaning of "more thermodynamically stable surface" when we speak of crystallographic facet formation? For example in wurtzite crystals, the formation of (10-11) surfaces are more favorable ...
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0answers
75 views

Why is contact angle higher when I let the glass to be dried in silan solution?

I've read in literature that the silanization reaction is completed in a second. However, I realized an interesting thing; after one hour that my cleaned glass beads are deep coated in a silan bottle ...
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1answer
194 views

How to finish silanization process correctly?

I have some 2mm glass beads and I'm doing silanization on them. For doing that, I have a small bottle that I fill 1/3 with glass beads and then pour silan solution on them and shake well. However, ...
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4answers
3k views

How does polydimethylsiloxane stick to glass?

Polydimethylsiloxane (PDMS) is the main ingredient in Rain-X, a treatment that adheres to windshields. How does PDMS adhere to class? It can't form covalent Si-O bonds with glass, according to one ...
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1answer
420 views

How to disperse salicylic acid in sodium lauryl sulfate solution? [closed]

Anti-dandruff shampoo contains salicylic acid as an active ingredient, but when salicylic acid powder comes in contact with a base solution such as sodium laurylsulfate and water (1:3 wt/wt) caking of ...
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1answer
307 views

How durable is a silanized surface?

I have two questions regarding silanization: 1) How durable is a silanized glass surface? (i.e. How long a silanized surface can be kept without any change in its wettability or contact angle?) 2) ...
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0answers
54 views

What is the best material for my particles?

I'm investigating collision of a particle and a water droplet ($v_\mathrm{drop}=1~\mathrm{m/s}$, $v_\mathrm{particle} \approx 8\ \mathrm{m/s}$, $D_\mathrm{d}=2.8\ \mathrm{mm}$, $D_\mathrm{p}=2.0\ \...
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0answers
302 views

In silanization, how to clean kerosene from glass surface completely?

I'm doing some silanization experiments using kerosene to dilute the silan solution. For instance I use a mixture of 10% silan in kerosene. However, after several tests I realized that I cannot ...
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1answer
139 views

Why did I get these inconsistent experimental results in silanization?

I used a 50% wt mixture of Tetraethylorthosilicate + Kerosene for silanization of some glass plates with different treatment times (from 1 sec to 35 sec). However, the contact angle(CA) that I got ...
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0answers
120 views

How to do pre-treatment on surface and how to clean the glass surface after silanization?

By Silanization, I want to treat surface of some spherical glass beads. Each bead is supposed to be shot in a particle launcher (like a bullet from a gun). I have some detailed question for the ...