Surface Science - Science topic

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"

Zhi Zhao

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.

dear Michael Horn please find out the following link

Go through the bio-degradable items.

You may also take a look at options available for ADDA (another DDA code) since the shape formats are compatible. See https://github.com/adda-team/adda/wiki/FAQ#how-to-simulate-light-scattering-by-a-particle-which-shape-can-not-be-described-by-any-of-the-adda-predefined-shapes

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.

Refer this article:

Ashish

as per phase diagram of CaO-Fe2O3, mixed and heat in muffle furnace as indicated temperature

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.

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.

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.

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

A connected sum of any of those.

I agree with Christian Röling

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

Dear Victor Legkostup

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

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.

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.

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?

Dear

I appreciate your comprehensive and helpful answer.

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

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

See

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!

More tutorials: https://www.youtube.com/channel/UCi3u3VAMUqfcdyNDQbSzSHw

Thanks!

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.

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.

Dear Yifan Zhang,

This small paper may be of help:

http://www.photon.t.u-tokyo.ac.jp/~maruyama/papers/02/US-J_contact.pdf

Best regards.

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.

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.

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.

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:

Dear Anish Bhattacharya ,

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

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.

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.

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.

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

Email 1: drobin21@binghamton.edu

Email 2: drobinson289@gmail.com

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

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.

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

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.

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.

"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.

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

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

If you want to avoid fringes - the cross-sectionof your film should have a wedge shape

it is a nanocoatings so we can not flip any sides.@MohammadRezaZamaniKouhpanji

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

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

Thank you Jan!

I will try to treat the pmma by nitric acid.

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.

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.

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.

this link is useful

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4222227/

also there is a doctoral thesis on this subject under the supervision of Dr Taha AL-Taha

regards

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.

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.

Mass can't be reduced in a chemical reaction.

Do not reduce the mass it can be extremely dangerous (e=m*c^2).

Of course, you can not determine the polarity by XPS.

The hydrophílic coating is destroyed by the heating. You should confirm it by XPS.

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

As Artur Braun. However, I propose to use the EIS as a technique for your C , alongside the parameter value of :

V_DC ~V_high, (V_high~V_max, defended from the Voltammetry)

1)before and

2)after coating.

This C_coat (EIS produced, C_coat-modeled) should be more satisfactory for your task.

Thank you all for your answers.

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?

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.

Why would you have heated the polyethylene to 300 Celcius?? It has melted.

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.

Thanks for answering my doubts.

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.

Yes. Same polymer compound used. At different level of Mooney viscosity (ML) above results obtained.

The optical band gap energy of TiO₂ may be depends on grain size of it's layers. It has been reported that E_g decreases as number of deposited layer increase which relates with the change in grain size. Please have a look at the below link.

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.

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

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.

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

maybe try a primer

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