Science topic

Porous Materials - Science topic

A porous medium (or a porous material) is a material containing pores (voids). The skeletal portion of the material is often called the "matrix" or "frame". The pores are typically filled with a fluid (liquid or gas). The skeletal material is usually a solid, but structures like foams are often also usefully analyzed using concept of porous media.
Questions related to Porous Materials
  • asked a question related to Porous Materials
Question
3 answers
I am working on drug-loading into porous material and trying to quantify the loaded amount of drug into the material through UV-Vis. But every time I disperse the drug-loaded particles in a solvent the drug comes out of the material. Could anyone please suggest what else can be done to quantify the loaded amount of drug?
Relevant answer
Answer
1. Plot a maximum absorbance/amount of drug calibration plot.
2. Weigh a sample of the porous material with the drug.
3. Dissolve the porous material with the drug in the solvent as you do this.
4. take a spectrum of this solution
5. Use the calibration plot to determine the drug content.
  • asked a question related to Porous Materials
Question
1 answer
I would like to create a porous geometry. I am looking for your suggestions on any open-source software which can help me to create the geometry. It would be idle if I can control or define the porosity of my created geometry.
Relevant answer
Answer
Dear Ketaki,
OpenFOAM I believe, is useful for creating porous media.
  • asked a question related to Porous Materials
Question
5 answers
In Comsol software, we use the two physics "Heat Transfer in Porous Media" and "Heat Transfer in Solids and Fluids" to study the heat transfer from a porous part to solid and fluid areas. The problem is that the interface between the porous and fluid or solid areas in both physics is defined as thermal insulation. How do we define these common areas boundary conditions to establish the heat transfer between the porous and solid or fluid areas? In some numerical studies, they used the heat flux boundary conditions for the common areas of the porous and fluid sections. Still, I do not think this boundary condition is appropriate.
Relevant answer
Answer
Bonjour, I think you should activate the extra dimension that is available when you use a porous medium in COMSOL. Coupling of "Heat Transfer in Porous Media" and "Heat Transfer in Solids and Fluids" at boundary conditions.
  • asked a question related to Porous Materials
Question
6 answers
Hi
I am trying to model a poro-hyperelastic material, but the problem is, this kind of physics is not present in any of the FEM software including COMSOL or ABAQUS,the comsol have a module only for poro-linear elasticity, but there are few papers on its modelling and they are using subroutine for that.
please help
Relevant answer
Answer
Seyed Shayan Sajjadinia Okay Sir, Thanks alot
  • asked a question related to Porous Materials
Question
8 answers
Dear Researchers,
I need a 3D photo of a porous material such as attached one only to show the porosity, not for analyzing porous materials.
Can any one help me?
Regards
Foroogh
Relevant answer
Answer
Just came across this publication regarding the 3D pore reconstruction for my research using Amira. It still seems like the license is pretty pricey. I would like to kindly ask for help to have access to Amira. Could I kindly contact you privately?
Sincerely,
Douglas
  • asked a question related to Porous Materials
Question
5 answers
Experimental results of the Sound absorption coefficient of material have mostly been found to be in good terms with the Theoretical models. But the calculations look confusing. With imaginary terms and differential equations.
Are there any simplified calculations and methods for theoretical modeling in acoustics?
Relevant answer
Answer
Regarding your question on the Nocke paper, Equation 6 is derived from the previous 5 equations. The numerical value of Equation 6 depends on the values chosen for the parameters b, d, t and D. If the system is linear, the impedance should not be dependent on sound pressure, so I am guessing that the p in the denominator should not be there.
  • asked a question related to Porous Materials
Question
5 answers
Hi all,
The case I want to simulate includes a porous media baffle, with water on the left side and no water on the right. I want to simulate the process that water on the left flows into the porous media and then flows into the right side.
In my simulatioin, the seepage velocity (from the soil to the fluid domain) at the interface is calculated by solid part. Then, there should be more water at the interface in fluid domain. I’ve managed to couple the seepage velocity at the interface in OF, but how could I add the water due to the seepage according to the velocity at the interface? Could anyone please give me any hints?
Relevant answer
Answer
I refer you to two discussions which bear on the two problems of Eulerian two-fluid models closures: Turbulence and momentum interfacial transfer:
(6) Turbulence Closure for Two-Fluid RANS Modeling (researchgate.net)
(6) Interfacial Transfer Closure for Two-Fluid RANS Modeling (researchgate.net)
Look forward to exchanges on these topics
  • asked a question related to Porous Materials
Question
6 answers
Hi all,
The adsorption isotherm for a meso porous material like activated carbon shows an hysteresis loop at P/P0 around 0.4. Can anybody from this platform can explain what could be the reason?
Relevant answer
Answer
thanks for this importing question
  • asked a question related to Porous Materials
Question
6 answers
I am trying to simulate a problem, where I need R1, R2, H1, H2 and concentrated flux on the absorber. The nomenclatures are shown in the attached figure.
I will be thankful if someone helps me in getting the aforementioned data for a power plant.
Thank you
------
Manoj Kumar Sharma
Relevant answer
Answer
  • asked a question related to Porous Materials
Question
5 answers
I would like to get the pore size distribution (0.5nm~1.5nm) from the CO2 isotherm using a DFT model (CO2 @ 273 on Carbon, Slit Pores) and have some questions about the procedure.
1 - Which p/p0 range should I use and how many points should I get?
2 - Should I ask the ASAP to measure p0 or should I enter a fixed value myself? p0 = 26142 mmHg is the correct value?
3- After performing the procedure, do I need to purge the ASAP lines to perform an n2 isotherm?
Thank you for your attention.
Relevant answer
Answer
2) p0 of CO2 at 273K is indeed 26142 torr, so the ASAP will not be able to measure it. You can enter a fixed value of 26412, but if you do, don't ask for p/p0 values above ~0.03. A very convenient way to do this would be to enter a value of 760 torr (1 standard atmosphere and select point in the usual way starting as low as you like up to 0.995). THEN, once the isotherm has been measured, change p0 to 26142 in the software before calculating pore size. I'm assuming the s/w has a p0 "overwrite" function.
  • asked a question related to Porous Materials
Question
1 answer
I am trying to simulate the adsorption isothermal of Nacl in a porous materials via molceular simulation. How can I do it by GCMC method? I apply GCMC to get adsorption isothermal of gas in materials successfully.
Relevant answer
Answer
Hi, I recommend you to have a look at the following work: DOI: 10.1021/jp7097153, the system is water in silicalite at 300 K, (GCMC) simulation method
  • asked a question related to Porous Materials
Question
8 answers
Which porous materials (Micro/Meso/Macroporous) are very suitable for the electrocatalysis application (ORR, OER and HER)
Relevant answer
Sincerely,
Microporous with dimensions less than 2 nm are suitable for adsorption applications, but for electrocatalysis, mesoporous is more suitable to facilitate ion transfer. In general, among all these structures, a hierarchical structure with a variety of porosity dimensions is the best choice for your purpose. Of course, to choose the right type of structure, the ratio of mesopores to macro and microporosity must be at least double. Increasing the pyrolysis temperature in the furnace up to 900 ° C helps to achieve the mesoporosity structure. In addition, the use of steam-assisted physical activation helps to form more mesopores.
  • asked a question related to Porous Materials
Question
3 answers
I am trying to simulate the heat transfer and fluid flow in a volumetric (porous) solar receiver in COMSOL Multiphysics. I know the material porosity, PPI and thermo-physical properties, however, the exact structural properties, i.e., pore size, solid wall thickness, pore shape, etc., are unknown.
Will it be correct to simulate the computational model as a single domain with given porosity instead of considering the detailed internal structure of the material?
If there is any research article where a similar procedure is adopted, kindly share it with me. I will be thankful to you.
Thanking you
------
Manoj Kumar Sharma
  • asked a question related to Porous Materials
Question
4 answers
I am trying to simulate the heat transfer and fluid flow in a volumetric (porous) solar receiver in COMSOL Multiphysics. I know the material porosity, PPI and thermo-physical properties, however, the exact structural properties, i.e., pore size, solid wall thickness, pore shape, etc., are unknown.
Will it be correct to simulate the computational model as a single domain with given porosity instead of considering the detailed internal structure of the material?
If there is any research article where a similar procedure is adopted, kindly share it with me. I will be thankful to you.
Thanking you
------
Manoj Kumar Sharma
Relevant answer
Answer
Dear Manoj, I would suggest rereading Section 2.2.1 in the following review paper where it compared the continuum model versus the discrete model:
  • asked a question related to Porous Materials
Question
4 answers
I'm currently doing simulations related with contact against porous materials (Tissues) in ABAQUS. As long as I use Pore Pressure=0 as Boundary Condition everything works fine and I'm able to obtain results. The issue is that in the contact area it will be fluid flow out of the material(exudation) due to the compression imposed. The fluid flow is in both contacting zones wich violates the continuity equation.
I've worked with the FLOW subroutine in order to control the boundary conditions in the contact area, and I also have tried the *Contact permeability keyword. I even tried to impose Pore Pressure=0 as an INITIAL boundary conditions.
I have also altered the parameters used to control the solutions (As the maximum number of cutbaks) .
I've read in many places in the ABAQUS MANUAL that by default ABAQUS imposed a sealed boundary condition. I guess this might be true for free contact surfaces but in my case it the program won't run if this BC are not imposed.
Nothing of what I've tried works, the program stops without calculating the very first time increment in all previous cases. Only if I forced the Pore pressure = 0 during the whole simulation, the problem works.
Any advice?
Thanks!
Relevant answer
Answer
Hi, anyone has solved this problem? Amin Komeili
thanks!
  • asked a question related to Porous Materials
Question
8 answers
Metallic foams are considered emerging smart materials because of their low density, high heat dissipation, and high energy absorbing capacity. There are various techniques used for the fabrication of metallic foams. Powder metallurgy and casting are the most commonly used techniques. Which is the best technique for the fabrication of metallic foams, casting or powder metallurgy?
Relevant answer
Answer
Well , its depend on your final application but powder technology is easy and cheap besides good mechanical properties
  • asked a question related to Porous Materials
Question
1 answer
Join Date: Aug 2021
Location: Banglore
Posts: 3
Rep Power: 2
Ramanan CJ is on a distinguished road
Dear Scholars
I am trying to simulate molecular filtration of fluid like Reverse osmosis of water. I am new to Ansys and I am in need to succeed it.
Is it possible to do filtration by pore size of porous material and fluid molecules size?
If yes, kindly share with me. I will be thankful to you.
Kindly provide the email id for further communication.
Relevant answer
Answer
CFD Simulation
  • asked a question related to Porous Materials
Question
2 answers
Hi everyone,
I am currently trying to simulate the RTM process (Resin Transfer Molding) with StarCCM+. The medium is a porous material and the flow is a mixture of air+resin (taken as Newtonian). I know how to do it with Fluent but I fail with Star CCM+. Has anyone succeeded in implenting both the porous and VOF models together in Star CCM+ ?
Thank You for your feedback
S. C.
Relevant answer
Answer
Hello Stéphane Champmartin,
I am working on the simulation of drying a porous media (sand+binder) by hot air. I am using STARCCM + to represent the case. Can you please help me, if you have succeeded in implementing both the multiphase flow model and the porous media model in STARCCM+?
Thanks in advance
  • asked a question related to Porous Materials
Question
5 answers
Dear all,
we are trying to impregnate a porous ceramic body with furfuryl alcohol to get as much carbon as possible upon pyrolysis
Any suggestion on how to handle the procedure? I mean crosslinking agent, mixing, thermal treatment and so forth
Thanks a lot
Alberto
Relevant answer
Answer
Dear Alberto Ortona that's a very interesting question. I think a more or less direct answer to your question is provided in the following potentially useful article:
The effect of crosslinking on the formation of glasslike carbons from thermosetting resins
Unfortunately the paper has not been posted on RG as public full text. Perhaps you can access it through your institution.
Also of interest could be the following article:
Preparation, characterization and pyrolysis of poly(furfuryl alcohol)/porous silica glass nanocomposites: Novel route to carbon template
In this case all three authors have RG profiles. Thus there is a good chance that you can request the full text directly from one of the authors.
I hope this helps. I wish you good luck with your experiments!
  • asked a question related to Porous Materials
Question
8 answers
In general if we want to increase the specific capacitance or charge storage capacity in electrochemical energy storage devices we should have the pore size of the electrode material is slightly higher then the solvated ion size of the electrolyte for easily charging and discharging. If we have the pore size less then the solvated ions of the electrolytes. Can we enhance the parameter if yes How?
Relevant answer
Answer
The electric double layer formation of supercapacitors is governed by ion electrosorption at the electrode surface. The double layer is formed, when a charged electrode is placed in an electrolyte, which causes the electrolyte ions to migrate towards the charged surface in order to balance the applied potential.
It is a matter of debate whether pores provide the same contribution to the capacitance regardless of the size, or if subnanometer pores lead to an anomalous increase of capacitance[1].
1. Insights into the influence of the pore size and surface area...capacitor model https://pubs.rsc.org/en/content/articlelanding/2019/cp/c8cp06443a#!divAbstract
  • asked a question related to Porous Materials
Question
7 answers
What is the proper mechanism of biomass activation to prepare activated carbon?
Different activation agents are using for activated carbon preparation from biomass. How different biomass and/or different activating agents produce activated carbon of different properties.
Relevant answer
Answer
Pyrolyse sous azote
  • asked a question related to Porous Materials
Question
7 answers
I am currently using the asymptotic homogenization method to predict the elastic properties of a porous structure. The software I've been using only supports homogenization of an RVE with an isotropic base material, but in reality the base material will be transversely isotropic (the elastic constants of this material are known). Is there any way to take the compliance matrix resulting from the homogenization with an isotropic material and transform it to account for the transverse isotropy of the base material? For instance, if I know the Zener ratio of the base material, can that somehow be used to transform the structure properties?
  • asked a question related to Porous Materials
Question
4 answers
I am working on porous g-C3N4 synthesis using the acidification/sonication method, based on the following paper:
I followed the procedure mentioned in the paper, but the test results do not show a nanosheet porous material (SEM & FESEM). I want to know which parameters in this method (acidification/sonication) lead to nanosheet porous material?
I will be appreciated if you share your experiences.
Thank you so much in advance
Relevant answer
Answer
Dear Masoud Khalili many thanks for your very interesting technical question. Although I'm an inorganic chemist I would not claim to be a proven expert in this field. In fact, we never worked with C3N4 in any form. Thus all I can do when trying to answer your question is recommend to you some potentially useful references. For example, please have a look at the following useful research article entitled:
Template-free synthesis of 2D porous ultrathin nonmetal-doped g-C3N4 nanosheets with highly efficient photocatalytic H2 evolution from water under visible light
This paper is freely available as public full text.
Also please see:
Role of Acetaldehyde on Synthesizing Large Surface Area Porous g-C3N4 Nanosheets with Enhanced Photocatalytic Performance by Using Acetaldehyde–Melamine
I also strongly suggest that you use the "Search" function of RG to find and access other relevant articles on this topic. Just search e.g. for "C3N4 nanosheets" and then click on "Publications". This will provide you with a long list of interesting papers in this field, some of which have even been posted as public full texts:
  • asked a question related to Porous Materials
Question
3 answers
Hi, did anybody know how to measure the shape (e.g. size or bending angle) of molecule (e.g. long-chain alkanes) under confinement (inside porous materials) by experiment ?
Many thanks and best wishes,
Zhiqiang
Relevant answer
Answer
The molecular dynamical study can help to understand the molecular shape under confinement. you can check this paper.
  • asked a question related to Porous Materials
Question
7 answers
Nowadays, I'm working on sound absorption of porous materials. Experimentally I have found that by increasing thickness of porous materials the frequency, which maximum absorption occurs, decreases.
I mean that, in lower frequency maximum absorption occurs. I want to know what is the reason of this behavior?
Relevant answer
Answer
The relation of frequency and thickness of porous absorber is a rectangular hyperbola, which would be expressed in a generic form as follows.
f * t^m=b; where, m is the power term of thickness, and b is constant.
Thus with an increase of thickness the magnitude of the frequency of the sound wave tackled by the porous absorber decreases. In another way, we can say that the thicker the material better is the noise control performance.
  • asked a question related to Porous Materials
Question
3 answers
I am using FAU type zeolite Y (commercial names:CBV100 and CBV780, Si/Al:2.5 and 40, nominal cation: Na) and I am looking for the thermal conductivity and the specific heat as a function of temperature.
I have found a paper [Int J Thermophys (2013) 34:1197–1213 (DOI:10.1007/s10765-013-1467-2)] which has nearly the whole framework of zeolite but it has just one value, 1.09W/(mK).
What about specific heat value? I have been using the of 13X zeolite 840J(kgK). I found one paper about that (DOI: 10.1127/0935-1221/2010/0022-2026) but I am confused a little bit which function that i have to use.
Relevant answer
Answer
I am also looking for these data. I found the same article for heat capacity. I also found a dissertation by Liyan Qiu from 2000.
It gives 0.86 J/K/g for NaX. Water content is likely a significant variable.
  • asked a question related to Porous Materials
Question
14 answers
Why isn't the surface of porous TiO2 I synthesized porous?
I used TALH(Titanium(IV) bis(ammonium lactato) dihydroxide solution) as the precursor, and polystyrene spheres as the templates. Mixing them together and freeze drying the mixture. After that, I did calcination to remove the templates. But from SEM images, the materials are porous inside, but the surface is not porous. Do you have any idea about why the surface is not porous and how to make the surface also porous.
Besides, can a porous surface significantly affect the BET surface area of the products?
Relevant answer
Answer
Hi
It could possibly because of the higher concentration of TiO2 precursors, which initially are attached to polystyrene but after that, the content of polystyrene is not available to serve as a template. You can try with a higher concentration of polystyrene and a lower concentration of TiO2... Also, CTAB and other polymeric surfactants are better than polystyrene to make porous structure. Or you can consider adding some content of CTAB... you can see our recent work on silica, where we used CTAB to make coral reef structured silica.
Best Regards
  • asked a question related to Porous Materials
Question
15 answers
Does anyone know how I can find out parametric values of "Parameter Settings" of isotherms (Freundlich, Langmuir, Dubinin-Radushkevich and Temkin) in OriginLab or MATLAB? E.g. - link (2: 19 min).
Relevant answer
Answer
How to apply Freundlich adsorption isotherm. A complete guidance
  • asked a question related to Porous Materials
Question
2 answers
While sintering the Ti green sheets (1mm thick) having functionally graded aligned pores, in a vacuum furnace I am facing the issue of very low mechanical strength and high curvature in the sintered samples. Even the sample breaks easily by hand. Is there any possible way to avoid this curvature issue? I have already tried varying the heating rates from 2-10C/min but the curvature remains there in the samples. In my understanding, the curvature is due to pore-gradient across the thickness but I'm unable to find any solution in the literature to avoid this issue.
  • One point to note is that I am forming the sheets with the freeze-casting technique which means that powder is not under high compaction at any stage of sintering.
Your suggestions will be appreciated.
Thanks in advance!
Relevant answer
Answer
Thanks for the answer, Dr Yuri Mirgorod. I second your opinion and I believe the same as our Ti porous sheets are intentionally made with the gradient in porosity along the cross-section. So the wide pore size distribution is integral to our study. I was looking for some way to sinter these sheets by, somehow, countering the differential stresses arising from wider pore-size distribution. Still looking for the directions though.
  • asked a question related to Porous Materials
Question
2 answers
Goal: Deadline for manuscript submissions: 28 February 2021 Dear Colleagues, Metal–organic frameworks (MOFs) have attracted a significant amount of interest from researchers in a broad range of scientific disciplines. Their compositional and structural diversity and porous character, with a large surface area to mass ratio and volume, enable them to be used in many applications, including gas storage, catalysis, biomedical, sensing, and energy-related applications. MOF-derived structures at the nanometre scale (NMOFs) can be synthesized by choosing appropriate organic ligands and metal ions and have been shown to enhance the performance of drug nanocarriers and provide gas sensors with high sensitivity. Progress has been made in designing tailored NMOF structures and tuning their morphologies. However, the shaping and engineering of these porous materials remain major challenges and we still need to improve our understanding of the relationship between their performance and morphology. This Special Issue aims to present an overview of new advances in the preparation and surface engineering of size-controlled nanoscale MOFs. In addition to synthetic aspects, the scope of this Special Issue covers a broad range of applications, including nanomedicine, catalysis, gas storage, and sensors. Contributions in the form of original research articles, review papers, and short communications are welcome. Prof. Dr. Antonio Vargas-Berenguel Dr. Juan M. Casas-Solvas Guest Editors https://www.mdpi.com/journal/nanomaterials/special_issues/MetalOrganic_frame Keywords - Metal Organic Frameworks - Sensors - Nanocarriers - Catalysis - Nanoreactors - Drug Delivery - Gas storage - Functionalized MOFs - Nanoparticles - Storage - Porous materials - Removal
Relevant answer
Answer
Following
  • asked a question related to Porous Materials
Question
4 answers
Adsorbed water and gases can affect the weight of the porous carbon. Some times 6-7% weight loss can occur during the degassing of the sample. Will this weight loss affect the calculation of C, H,N and S ?
Relevant answer
Answer
Of course yes, if you are analysing for instance an activated carbon, a char obtained from biomass gasification etc. The CHNS analysis will be affected by adsorbed gases and moisture: for instance, adsorbtion of H2O and CO2 from lab atmosphere will affect the result of H and C, respectively. This would not appen only if you are analysing a spent, already saturated carbon. My recommendation is that you should identify a reproducible protocol (to eventually pre-treat and) to store your samples before CHNS analyses (see for instance
  • asked a question related to Porous Materials
Question
4 answers
TiO2 foam is generally highly porous in nature, but for my sample it is showing very less around 600 micromoles for 2.5 hours. Can you give some suggestions about this comment?
Relevant answer
Answer
If you are using TiO2 foam in a photoelectrochemical system as photoanode, the thickness of the electrode is very important. The thickness of the electrode (thin film) should be less than the electron diffusion length. Larger the thickness may lead to efficient recombination of photogenerated charge carriers.
  • asked a question related to Porous Materials
Question
22 answers
I just worried if this technique is not a standard pore size measurement method and can be argued.
Relevant answer
Answer
The pore size obtained from SEM analysis is higher than that of BET analysis due to a particular small area was selected for the SEM analysis. Otherwise, the BET surface analysis technique based on N2 adsorption-desorption isotherm analysis provides complete details on the specific surface area and porosity of the overall samples. Usually, SEM analysis is not a suitable choice for the pore size distribution analysis. For the precise determination of the porosity of the sample, BET analysis was carried out in this manuscript. Thus the pore size distribution obtained from the BET analysis is acceptable.
  • asked a question related to Porous Materials
Question
3 answers
I am advising a researcher on using abaqus to run a mechanobiology simulation which requires the calculation of the interstitial fluid flow.  The calculation is based on an equation from Prendergasts work in mechanoregulation such that the stimuli on stem cells may be used to calculate their differentiation.  
The stimuli S is determined by empirical constants, the octahedral shear strain, and the interstitial fluid flow v in the extracellular environment of cells (see attached paper).  We are unable to find a setting in abaqus to output the interstitial fluid flow as a field output variable.  
We are using Abaqus/CAE 6.14, performing the FEA on a porous elastic material, and using pressure elements (C3D4P) for the meshing phase.  
In summary, we are asking for help in finding the interstitial fluid flow values as an output for a porous elastic material subject to a loading condition in abaqus, when a model consists of a scaffold structure and a poroelastic material representative of a granulation tissue where cells may differentiate according to the aforementioned stimuli.
Relevant answer
Answer
Hi Paul, I think I have the same problem as you. I want to know which variable should be used as fluid flow (FLVEL or CFF) in Abaqus?@Paul F Egan
  • asked a question related to Porous Materials
Question
9 answers
I need to analyze the cross-section surface of highly porous granules with the SEM but I don't know how to prepare the samples. Is there anybody who have an idea of how to flatten porous and fragile granules so that I can use electronic microscopy ?
Relevant answer
Answer
Dear Dr. Louis Gaspard,
the granules culd be embedded in resin and kindly polished (e.g. with fine emery papers applied to suitables polishing systems) to smoothen fractures for further analysis. After ultrasonic cleaning and drying, the sample can glued on the sample holder and then sent into the coater for film coating.
If the granules are nonconductive in a vacuum chamber, no clear image could be obtained with no coating. Two kinds of coating apparatus can be used in sample preparation, namely, a gold coater and a carbon coater. When we want to observe the surface morphology of the particles, the surfaces of the sample can be coated with gold film. The obtained particle surface image result clear owing to the strong conductive property of gold film. Moreover, gold film does not affect surface morphology. When surface elements of the particles needed to be analysed by EDX probe, the samples can be coated with carbon film. The atomic number of gold is high, which means that the coverage of gold film is strong, which can interfere with detection of other elements. By contrast, carbon film meets the requirements of conductivity and does not affect detection of elements other than carbon.
Good work and best regards, Pierluigi Traverso.
  • asked a question related to Porous Materials
Question
6 answers
I coated a stone surface with K-siilcate. Apparently, it does noe seal the surface since the water penetrae the stone easily and the absorption coefficient does not change too much. However, the BET measurements show a very small specific surface area of just 1.4 m2 per g. What's wrong?
Relevant answer
Answer
Yuri Mirgorod Sorry, but I did not heat the coating films. They are formed at RT and remained alway at RM.
  • asked a question related to Porous Materials
Question
5 answers
I want to find the analytical solution of a radial diffusion system (1D cylindrical coordinates). Here what is considered is pressure diffusion. The conditions are simple and similar to the following.
Initial P = P0
P(r=infinite) = P0
P (r= 0) = P1 when t > 0
I need the solution of P at any r_i and t.
The flow rate term is unknown.
Could anyone give any suggestion? Thank you.
Relevant answer
Answer
see
Radial symmetry of solutions to diffusion equations with discontinuous nonlinearities
Joaquim SerraJournal:Journal of Differential EquationsYear:2013
best luck
  • asked a question related to Porous Materials
Question
18 answers
Porous media is not absorbing heat by radiation and density remain constant of overall control volume.
We are trying to formulate flow through "solar chimney with porous media as energy storage ".
In fluent we used :
1) k epsilon model
2) DO model for radiation
3) Pressure based model
4) Porous media
For elaborate details of problem refer document attached below .
Relevant answer
Answer
You must solve continuity equation, Darcy or modified Darcy equation and Energy Equation
  • asked a question related to Porous Materials
Question
8 answers
Hello everyone
I would like to ask a way to evaluate a precise, reliable and accurate surface area of a material.
I used a nitrogen adsorption-desorption analysis on my material, a nanocarbon, the isotherm was found to be type 3 were at low pressure the amount adsorbed is slowly increasing but at high pressure the amount adsorbed increases fast.
Generally, BET equation used for surface area calculation for a non-porous material that has a certain point of pressure where the monolayer adsorption can be distinguished from multilayer adsorption. The monolayer capacity is needed for BET calculation to find a surface area.
However, in type 3 isotherm, there was no "knee" on the isotherm because of their surface and adsorbate interactions, so BET equation is not suitable to find a surface area.
Another idea is using Krypton adsorption which is believed to be more suitable for very low surface area adsorbent and it might be get more information at very low pressure.
So, I would like to ask for a suggestion how to deal with this kind of material to get an accurate surface area with reliable value.
Thank you for any advice
Relevant answer
Answer
Whilst the BET equation can be applied computationally to any data set, the derived value has no physical meaning as the type 3 isotherm is indicating that a complete monolayer does not form across the surface. Type III (3) are extremely rare when using e.g. N2/77K and Ar/87K but are not unusual when making water vapor sorption measurements on chemically hydrophobic surfaces like pure activate carbons (graphitic or graphenic surfaces with no hydrophilic surface functional groups). Krypton's advantage only refers to measuring low surface areas, and not avoiding type III. Indeed, krypton on polymers might also generated a type III because of extremely weak gas-solid interactions.
The only solution, using adsorption, is to find an adsorbate (gas/vapor/liquid) which will "wet" to the surface (and form a complete monolayer before patchy multilayer adsorption accumulates).Regarding carbons, iodine and certain dyes have been used in this way (but from solution rather than from the vapor phase).
Some type II (2) isotherms can masquerade as type III when the surface related adsorption is very small compared to the rise at higher p/p0, and not enough data points at low p/p0 have been measured to show the knee. It's easy enough to find out by applying the BET equation and looking at the c-constant.
Hope that helps.
  • asked a question related to Porous Materials
Question
4 answers
hello everyone,
I need your help. I was meshing a porous media geometry with ICEM, and after meshing, I wanted to transfer the data to #fluent, I encountered this error "WARNING: Mesh has uncovered edges. ANSYS Fluent needs a complete boundary (lines in 2D) or it will give a variety of errors and not read in the mesh! If this was 2D Hexa, perhaps your edges are not associated with perimeter curves".
What should I do, please help me?
P.S. in the attachment I'll upload an image of the geometry.
Relevant answer
Adib Amini be welcome, I hope you fix the problems!
  • asked a question related to Porous Materials
Question
4 answers
Hello,
I need to impregnate the pores of a MOF with cu(acac)2, which I will then reduce under vacuum to copper nanoparticles. I plan on using the incipient wetness approach to do so. However, my MOF will not be in a powder form, but rather a self supported, fibrous mat form ( ). According to my current research, the solid support catalyst (MOF) is typically stirred as the metal precursor solution in chloroform (or other solvent) is added to it, yielding a paste. However, I cannot stir my fibrous mat. Will simple immersion of my mat in the metal precursor solution be sufficient to impregnate the pores of the MOF with the precursor? Or would a drop-wise method of adding my solution work without stirring the MOF? Is there another way around this issue?
Thank you for any answers!
Relevant answer
Answer
Claire Boyer I think that simply soaking the fibrous mat in a solution of Cu(acac)2 in dichloromethane over night will be sufficient to impregnate the pores of the MOF with the copper precursor. As suggested earlier, use dichloromethane instead of chloroform to dissolve you Cu(acac)2.
P.S. When other RG members help you by answering your questions, it is polite and a good practice on RG to recommend their answers.... 😎
  • asked a question related to Porous Materials
Question
4 answers
Filtration
Relevant answer
Answer
Il est préférable d'utiliser un mélange poreux de différents matériaux bien choisi.
  • asked a question related to Porous Materials
Question
5 answers
If I simulate the Electrical Double Layer of a cementatious material and then simulate the Piezoelectric property of the same material,which platform should I use to combine these two results?
If there are multiple ways to do so, which one is the best method?
Relevant answer
Answer
Thank you all for your answers. I was looking for more specific suggestions: which workbench to use and whether is it possible to do these simulations in the same software or not. I know that, multiphysics software will let me simulate the EDL, but it doesn't allow to design piezoelectric materials which are not traditional (in this case cement or cementatious materials).
  • asked a question related to Porous Materials
Question
8 answers
I have been trying to model the electrical double layer for geopolymer. But, I could not get any equations or simulation pathways that would help me calculate charge available at the surface of the materials.
Can you help me on this?
Relevant answer
Answer
An electrical double layer is being studied to modify cement for various applications. Cement is a complex mixture of oxides that hydrate differently depending on the composition of the cement and their concentration in the solution. It is impossible to mathematically simulate a double layer. You can take one oxide and work with it to simulate a double layer experiment.
  • asked a question related to Porous Materials
Question
6 answers
Hi, I'm trying a procedure to synthesis nano ZIF-90 in water for specific application, but there is some problem. pxrd pattern for as-synthesized MOF is not completely compatible with charactristic XRD pattern of ZIF-90, in terms of tetha. on the other side, as article indicated, i choose 1 to 40 ratio of zinc acetate to 2-imidazole carboxaldehyde to obtain particles with the scale of 100 nm, but led to really low yield, there is not another way to reach nanosize ZIF-90? I appreciate if anyone has the same experience and could help me.
Relevant answer
Answer
Naeimeh Hassanzadeh Goji Anytime. I did not also find the hydrate structure. Maybe it hasn't been reported, yet. You can give it a trial. Good Luck!
  • asked a question related to Porous Materials
Question
4 answers
Regardless of the specific application, I am searching for manuscripts studying heterogeneous properties such as solid matrix Poisson ratio and porosity. It can be from poroelastography etc.
Relevant answer
Answer
Thanks! In fact, I am the first author of the article you mentioned in which we assume uniform porosity and solid matrix Poisson’s ratio. Soon, I will add another publication in which those parameters are spatially dependent.
  • asked a question related to Porous Materials
Question
9 answers
To check CD and UV-Vis spectra for porous polymers.
Relevant answer
Answer
Dear Narmadha Manoranjan,
If you want to quickly check the CD properties of your polymers, there is a commercial CD spectrophotometer to use. You may find such tool in the Biology Department in your institue easily. Alternatively if you know the absorption spectra of your polymers, your can build up your own testing kits at certain wavelengths using circular polariser and two pair of linear polarisers, light source and detectors.
  • asked a question related to Porous Materials
Question
4 answers
Hi,
I have a graphite coating (50 um thick) on copper foil (10 um thick) and would like to do BET/BJH measurements. Do I need to scrap the graphite samples from copper foil to do BET/BJH analysis? I performed experiments without scraping the graphite (by cutting Cu foil/graphite in to small pieces) and got negative surface area. What is the right way to analyze the surface area and pore size distribution?
Any help will be much appreciated.
Thank you
Relevant answer
Answer
Guru,
Are you still getting negative surface area or C constants from the BET after the out-gassing treatment and checking for leaks? If so realize that the BET does not really measure the surface area or the adsorption energy, it is only a comparison measurement between chemically identical samples.
The BET has been proven to yield internal anomalies and all other "Henry's" law adsorption isotherms have also be disproved. So, it's not surprising that you are getting confusing answers.
If you are still working on this type of project, let me know and I can give you more advise.
  • asked a question related to Porous Materials
Question
4 answers
I have two 3D CT images, one is a sub-volume of the other. I want to measure to what extent the sub-volume is similar or representative to the bigger one. The CT images are binary; containing pores and solids and I need to correlate only pores in the 2 volumes, their distribution, sizes and connectivity. Any help?
Relevant answer
Answer
Thank you all for your reply. I really appreciate it.
  • asked a question related to Porous Materials
Question
3 answers
i want to synthesize monodispersd silver nanoparticles composite.
i have used HCP-B(porous polymer) that have so many -OH groups and benzene rings.
utill now , process is as follow.
1.polymer(surporting materi al) was dispersed in Distilled water.
2.silver nitrate was put in solution. After then stirring
3.sodium brohydride was added in solution(by using syringe pump)
4.addly reaction was stirred 2h.
i wonder mole ratio of nabh4/agno3 and during reducing , would i use ice bath?(for cotroll ),and dropwise rate is drop per second ?
Relevant answer
Answer
The porous material will adsorb silver ions. They will be in the pores and it will be difficult for the borohydride to contact these ions. Therefore, it is desirable to determine the amount of adsorption of ions on the pores. Reduction is carried out at about zero degrees with a six-fold molar excess of borohydride. Reduction occurs in solution instantly. In pores, it can be slower.
  • asked a question related to Porous Materials
Question
2 answers
How can I include the effect of wavelength and temperature on the absorptivity and refractivity of material or for example for a sphere in baked bed?
Thanks
Relevant answer
Answer
Farnoush Salehtash Thank you. are those experimental methods?
My work is just theoretical research.
  • asked a question related to Porous Materials
Question
4 answers
For a 3D single phase turbulent Air flow inside a partially filled channel with porous material, what kind of interface treatment does ANSYS Fluent use for the interface between a porous and a fluid zone by default?
I know there are different interface conditions such as The Ene, Levy and Sanchez-Palencia interface, The Beavers-Joseph interface, but i want to know which interface conditions does ANSYS Fluent use.
For the porous zone Forchheimer extended Darcy’s equation and the thermal equilibrium model have been employed and the flow has been considered as laminar flow, but for the fluid cell zone the flow is turbulent and RNG k-Epsilon turbulence modeling has been utilized.
Relevant answer
Answer
Yeah, of course.
No one answered this question here, so i asked this question on CFD-Online's forum. A user named LuckyTran gave me this answer:
"I don't think there is any special interface treatment.
When you select the laminar zone option, Fluent sets the turbulent production in that zone to zero. The variables (k, epsilon, etc.) are still transported through the laminar zone.
There is another option (accessed using TUI commands) that allows you to also set the turbulent viscosity to zero in the laminar zone. But again, they are simply transported.
The pressure drop due to the porous media is handled by adding an extra volumetric momentum sink. If you need a reference, refer to the user manual section on Porous Media Conditions (see 7.2.1-3).
There is only one momentum equation. Refer to my previous post for why there is only one momentum equation when you use a laminar zone option. Interface treatment is needed in general when you actually have two separate sets of governing equations. But that is not the case."
(the link for this discussion on CFD-Online's forum:
I wrote my understanding from this statements for the reviewer, fortunately, he/she accepted it and here is our published paper:
Best regards.
  • asked a question related to Porous Materials
Question
4 answers
Dear Sirs! I need your help. I will have to work with PIM-1 polymer. In order to plan my experiment properly, I am curious in which types of solvents the PIM-1 is soluble except DCM?
Relevant answer
Answer
Hello everyone,
Hlib Repich you can use THF or chloroform as a solvent.
Regards
  • asked a question related to Porous Materials
Question
4 answers
I would like to predict Stiffness of composite porous material by understanding the stiffness of each particles .To do so, Is there any methods or software?
Relevant answer
Answer
@ Pascale Royer
I will try it as well, Thank you
  • asked a question related to Porous Materials
Question
5 answers
I have an unknown sample to characterize using different techniques (mainly pore size distribution):
-X-ray computed tomography
-Mercury intrusion porosimetry
-Gas porosimetry
-BET tests for the surface area.
how would you proceed to make a perfect analysis (taking into consideration the time/money/precision factor)?
Any explanation, recommendation and/or articles for comparative studies would be a perfect help. Thank you in advance.
Moustafa
Relevant answer
Answer
For unknown materials, a BET surface area analysis (by gas adsorption) is a good place to start... this at least will reveal how much gas accessible surface there is and one can make certain inferences about the extent of meso and microporosity by combing the BET calculation with the t-plot method. A complete description of (gas accessible) micropore space requires low relative pressure gas adsorption isotherms and appropriate mathematical models (DFT, not BJH for micropores). Remember that gas molecular/atomic size plays a role in accessing the smallest of micropores; CO2 at 273K can access smaller pores than can N2 at 77K for example. Mesopore and small macropore size distribution can be done by gas adsorption up to a few hundred nm pore diameter. Gas adsorption isotherm hysteresis can reveal something about the connectivity of pores. Larger macropores are quickly evaluated using mercury intrusion porosimetry... up to ~1mm in diameter. The value of these fluid-based methods (gas adsorption and mercury intrusion) is that pore volume can be known directly, unlike diffraction and microscopy techniques. They still have a role to play of course to understand the underlying solid structure that is giving rise to the porosity. CAT scans can be useful in the meso/macro scale but cannot easily give quantitative values and of course rely on good X-ray contrast. Small angle scattering techniques really come into their own for amorphous and soft materials.
  • asked a question related to Porous Materials
Question
4 answers
I have observed that the absorbance is increasing at long irradiation time during photocatalytic experiment for a perovskite material .Even I completely separate the catalyst particles with the centrifuge.
I have used a porous perovskite as a photocatalyst which has been prepared by a sol-gel combustion method , You can see images of the scanning electron microscope and the absorption curve of rhodamine B in the presence of this catalyst.
Relevant answer
Answer
Absorbance or optical density is logarithmic ratio of intensity of incident to transmitted radiation. If the former is increased absorbance is bound to increase otherwise it can increase with conc. but that possibility is ruled out in your case. Longer irradiation May energize molecules to promote to higher levels to a greater extent.
  • asked a question related to Porous Materials
Question
2 answers
I'm trying to model porous media with anisotropic thermal conductivity in Ansys Fluent. However, there seems to be no method to directly input the the values of thermal conductivity in x, y and z direction. Kindly suggest methods to solve this issue.
Thank you in advance.
Relevant answer
Answer
Thank you sir
  • asked a question related to Porous Materials
Question
18 answers
I need to simulate the transition of Flow through Coarse Porous Media such as Rock-fill dams, to investigation of Water level profile in each distance from up-stream and determination of discharge of fluid seepage from the body of these media. Notice, I want to simulate a Single-Phase Flow.
How can I simulate this project? Please suggest and introduce a useful software for this issue to me...
What is your idea about Flow 3D, Fluent, ABAQUS,...
Relevant answer
Answer
Dear Dr. Majid Heydari ,
It would be appreciated if you explain more about the method you used to simulate the POROUS MEDIA for your Ph.D. thesis.
Best regards,
Mehdi
  • asked a question related to Porous Materials
Question
5 answers
I am running simulation for porous components and since the yield strength for porous materials changes relative to the thickness of the component, is there any way that i could set a limit of stress for particular thickness of the component?
Relevant answer
Answer
Suraj Bhatta I think ANSYS can't display your results exactly however, I believe I answered your concern in my previous answer. You have to analyse after extracting your results from ANSYS.
  • asked a question related to Porous Materials
Question
7 answers
Hi,
I need to calculate the inertial and viscous resistance for porous material in Fluent.
After checking the Fluent manual, I picked the Ergun equation.
My question is how to find the values for 3-directions? If I used the same value, I'm assuming that my material is isotropic.
Is there any other ways to calculate these values by equations not experimental?
Relevant answer
Answer
We all know that porous media are modeled by the addition of a momentum source term to the standard fluid flow equations. The source term is composed of two parts: a viscous loss term (Darcy, the first term on the right-hand side of Equation (i)), and an inertial loss term (the second term on the right-hand side of Equation (i)).
where, Si is the source term for the i th (x, y, or z ) momentum equation, lvl is the magnitude of the velocity and D and C are prescribed matrices. This momentum sink contributes to the pressure gradient in the porous cell, creating a pressure drop that is proportional to the fluid velocity (or velocity squared) in the cell.
For homogeneous porous media Equation (i) can be simplified as Equation (ii).
Where, "alpha" is the permeability and C2 is the inertial resistance factor. (1/alpha) and C2 is known as viscous and inertial resistances in porous media.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - -
How to calculate viscous and inertial resistances in porous media:
1. viscous resistance (1/alpha)
To calculate "alpha" or permeability in terms of the geometrical parameters, at least for the case of simple geometry, a great deal of effort has been spent on this endeavor, and the results are well presented by Dullien (1992). In the case of beds of particles or fibers, one can introduce an effective average particle or fiber diameter Dp and use the hydraulic radius theory of Carman–Kozeny (equation (iii)).
h(Dp) in Equation (iii) is the density function for the distribution of diameters Dp. The Carman–Kozeny equation gives satisfactory results for media that consist of
particles of approximately spherical shape and whose diameters fall within a
narrow range. The equation is often not valid in the cases of particles that deviate
strongly from the spherical shape, broad particle-size distributions, and consolidated media. Nevertheless, it is widely used since it seems to be the best
simple expression available.
2. inertial resistance (C2)
inertial resistance is calculated by following equation:
C2=2Cf/(alpha^1/2)
where Cf is a dimensionless form-drag constant. Ward (1964) thought that Cf might be a universal constant, with a value of approximately 0.55, but later it was found that Cf does vary with the nature of the porous medium, and can be as small as 0.1 in the case of foam metal fibers. Beavers et al. (1973) showed that the bounding walls could have a substantial effect on the value of Cf, and found that their data correlated fairly well with the expression
Cf=0.55(1-5.5(Dp/Dh))
where Dp is the diameter of their spheres and Dh is the equivalent diameter of the bed (hydraulic diameter).
Good luck.
  • asked a question related to Porous Materials
Question
8 answers
Any recommendations about this topic are highly appreciated!
Thanks!
Relevant answer
Answer
Do you consider the grain shape relevant within your model? I suppose subtracting repulsing surface area would be rather irrelevant, maybe the shape matters more than the area exposed depending on roughness?
Regards,
Orana Paullus
  • asked a question related to Porous Materials
Question
15 answers
Hi,
I need to set a porous zone (as radiator) in fluent. But I dont know any about the inputs like viscous resistance or velocity resistance coefficients. For a panel radiator for example, how can I determine these factors. cooling air will go through the small sections(ducts) between the radiator panels.
Relevant answer
Answer
Separate the domain(s) that you want it to be as a porous media in your problem by selecting "add frozen" option in "Geometry" section. Then choose a certain name for your porous media domain in order to be distinguished from other domains. Next, go to "setup" section and select "cell zone conditions". Then, double click on porous media zone determined in previous step. Now, you can check "porous zone" and insert your porous media details such as porosity and permeability.
  • asked a question related to Porous Materials
Question
4 answers
Dear all,
I've just followed the typical BET measurement and carried out some AC samples.
I don't know why the curve isn't similar to 6 types of the isotherm. I think the desorption process is not carried out in my measurement.
I really appreciate if you can share your experience in this regard.
Thank you !
Relevant answer
Answer
Thank you for all supports. I will check again as you mentioned
  • asked a question related to Porous Materials
Question
4 answers
I have obtained nitrogen adsorption desorption isotherms for a mesoporous sample. From these isotherms and BJH size distribution, I have calculated surface area, pore volume and average pore diameter. But, when I am asked "what is the pore volume fraction of meso and micropores?", what do I need to calculate and how?
Relevant answer
Answer
First of all, BJH is not the best model for micropores, use the DFT calculation instead. From the graphs, take total pore volume (PV), micropore volumes (<2 nm) µPV and mesopore volumes mPV (2-50 nm). Calculate the individual fractions as % or PV (µPV/PV*100, mPV/PV*100), check that you get 100% in total.
  • asked a question related to Porous Materials
Question
2 answers
It is well known from the scientific literature that the impedance response showed by porous electrodes exhibiting supercapacitive properties is typically characterized by a straight line displaying a phase angle close to -90 degrees (e.g., low-frequency domain), which is followed by a curved region in the complex-plane plot that connects to another straight line showing a phase angle close to -45 degrees (e.g., high frequency domain). Although there are several studies demonstrating that the high-frequency impedance response is the result of the porous electrode behavior, as was first explained by Robert De Levie in 1963, many authors still insist on the adoption of an erroneous theoretical treatment using equivalent circuits containing resistor and capacitor elements (or constant-phase elements) in connection with the Warburg diffusional impedance, which is characterized by a phase angle of -45 degrees. The problem here is that a stationary diffusional layer is very unlikely to be formed given that in the vast majority of cases the inert electrolyte is at a concentration of approximately 1.0 M, i.e., there is no chance that the behavior of the electrode characterized by a phase angle of -45 degrees in the high-frequency domain is due to a diffusion process of the inert ions established during the charge-discharge processes. In contrast, this behavior may be simply due to electrode porosity (e.g., geometric effects), as was extensively explained by Juan Bisquert.
Relevant answer
Answer
Both ways might be worth to go (test) in such a crossway(s), generally.
So, it is, more, interesting to note a specific case.
  • asked a question related to Porous Materials
Question
9 answers
I am presently working on the synthesis of Aluminium fumarate MOF and I would like to carry out computational analysis on it. I have checked the COD database for the .cif structure but did not find any.
I will greatly appreciate if you can help me get it.
I look forward to your kind assistance.
Thanks.
Shed.
Relevant answer
Answer
𝐒𝐀𝐌𝐄𝐄 𝐔𝐋𝐋𝐀𝐇 Can you get me the .cif of "1BNA".
  • asked a question related to Porous Materials
Question
2 answers
I have started working on computer based simulation using COMSOL Multiphysics ver 4.4. I want to see how a powder metallurgical steel part (compressed Fe compact) is heated up to 1000 oC. However, I need help in some points:
1. I select the Temperature-dependant solvation, but how can i put heating rate (K/min)?
2. Specific heat ratio of iron is needed? (Which value should i enter?)
Relevant answer
Answer
Rafael Barea , I have a similar challenge. Which function did you use? Can you refer me to a paper I can look at?
Thank you in advance.
  • asked a question related to Porous Materials
Question
5 answers
I have sections of porous material which is cut along the axis diametrically. How can we calculate tortuosity using the images of these cut sections? The size of the pores, pore distribution in these cut sections have been determined. 
Relevant answer
Answer
Of course, you are likely ultimately interested in the 3-D tortuosity from the 2-D images. If they are serial sections, you can stack them to form a 3-D image and then compute tortuosity using image analysis packages or by computing the 3-D microstructure's conductivity (formation factor). If the microstructure is isotropic, you could reconstruct representative 3-D microstructures by measuring the autocorrelation of the porosity and using Quiblier's technique to produce a 3-D microstrucure with a similar (same) autocorrelation. Software for doing this in the context of computing 3-D permeability of a pore structure can be found at: ftp://ftp.nist.gov/pub/bfrl/bentz/permsolver/.
Keep in mind that Alain's excellent comments concerning adequate resolution, etc. are very valid in general and to this reconstruction method in particular. Good luck.
  • asked a question related to Porous Materials
Question
5 answers
such as concrete
Relevant answer
Answer
Yes, I agree. For different materials, there should be different relations.
  • asked a question related to Porous Materials
Question
19 answers
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?
Thanks for all your help!
Relevant answer
Answer
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.
  • asked a question related to Porous Materials
Question
3 answers
Can we calculate the pore size and shape of a porous material or only it can be measured for single crystal using SAXS?
I we can calculate the pore size and shape then how it can be calculated?
Relevant answer
You can always apply the SAXS technique for obtaining pore size distributions if you have a two-phase system with quite a nice electron density differences. SAXS procedure determines the volume-weighted particle (or pore) size distribution Dv(R) from the scattering curve of an ensemble of spherical particles (or pores) having a homogeneous inner electron density distribution, and not showing interparticle interaction effects. The Dv(R) function refers to the volume-weighted particle size distribution ('volume distribution'). It may be seen as a histogram of the radii R of the particles that are present in the sample. The height of the Dv(R) function is proportional to the volume (not to the number) of particles that can be found within a given size interval when Dv(R) is normalized. then Dv(R)dR is the probability (by particle volume) of particles having a radius within an (infinitely small) interval dR. For spherical particles, the volume-weighted size distribution Dv(R) is related to the number-weighted size distribution Dn(R) by: Dv(R) ~ 4π/3 R3 Dn(R) The number-average of the particle size is always smaller than its volume-averaged value. The difference increases with increasing size polydispersity. Note that with electron microscopic techniques normally number distributions are determined.
  • asked a question related to Porous Materials
Question
14 answers
I am working on metal organic polyhedra topic to synthesize new metal-organic cages or other based frameworks. I want to conduct postsynthetic modification for one cage, but the solubility is very poor in most solvents, only methanol can dissolve but it needs large volume.
My question for who in the field of MOFs, COFs, MOPs, and other related chemistries, how can I deal with the problem of insolubility of synthesized materials to conduct postsynthetic reactions? what are the proposed strategies and methods to attain the target modified compound?
Relevant answer
Answer
Reactions can be of different types: addition, substitution (nucleophilic or electrophilic), acid-base reactions [adduct formation, coordination complexes], metathesis, transmetallation etc., One should examine the nature of the compound and what interactions with solvent will enable the compound (solute) to dissolve in it.
Some time reactions can be carried out in solid state by using finely divided particles (grind well in a mixer or using pestle-mortar to increase the surface area) using ball milling (popularly known as mechanochemical method).
Also one can use a solvent in which the reactants are insoluble but still reaction can happen.
If needed use more solvent and generate suspension and reaction can occur.
If it is sparingly soluble in methanol, still reaction can be carried out.
If it is ionic complex, try to substitute the anionic species with a better anion and that should help. If the complex is an anionic species, try to encapsulate the cation using polyethers, cryptands etc. to make it soluble in polar organic solvents.
  • asked a question related to Porous Materials
Question
1 answer
I am trying to do an adsorption work. I like to use Monte-Carlo simulation in fixed pressure process. I am using a porous material to adsorb H2 gas. In the stings tab after the selection of the Fixed Pressure Task, I couldn't see the Monte Carlo method in Method drop-down Menu. I just only see the Metropolis and Configurational Bias. But Tutorial says, I can select the Monte-Carlo method from here. Is there any suggestion? or am I not in the correct direction? Please help me.
Relevant answer
Answer
Metropolis and configurational bias are both Monte Carlo methods.
  • asked a question related to Porous Materials
Question
4 answers
What should be pore size to prevent water to go inside gas tube? Is there any relation between pore size and pressure of gas, or hydrophobic coating can help to prevent water to go inside tube.
For details please check figure.
Relevant answer
Answer
This depends a lot of the wetting conditions of water in your porous medium. It should be treated hydrophobic in order to avoid spontaneous imbibition. Capillary pressure Pc = 4*S*cos(theta)/Dp has to be compared to Pg - Ph, where Ph is hydrostatic pressure Ph = rho*g*h, and Pg being the pressure of your gas pushing on the top of the tube.
S : surface tension of water with ambient atmosphere
theta : contact angle for water with the material from which the tube is made, including the effect of a surface coating
Dp : pore diameter
rho : density of water
h : depth of water in contact with the porous
g : gravity constant
Your condition for the tube to remain tight impies : Pc + Ph < Pg
Hence hoosing theta > 90° (with appropriate coating) allows to have Pc negative, and the above condition is fullfilled if Pg is large enough or if Dp is small enough.
If you cannot coat the tube surface and Pc >0, then you will have to push very strong so that Pg > Pc + Ph, and you will have to choose Dp large, which will imply that your injecting gas will bubble in your water.
  • asked a question related to Porous Materials
Question
6 answers
Hi guys,
I have been searching throughout the internet for scholar articles but I couldn't find any articles regarding fabricating porous alumina sheet that is thicker than 0.5mm, is there any extra procedure/precautions that I should take?
I'm trying to make an aluminum tile (3mm thick) with the top surface being porous. (see image below)
Or is it possible for me to get a very thin PAO sheets and attach it to a larger aluminum body?
Here are the procedure that I've summarized from the scholar articles regarding fabricating porous alumina,
1. cleaning up the aluminum sheets
2. electrochemically polish it in a mixture of acid and alcohol, then dried.
3. Coat the rest of the body (shaded area) with acid resistant lacquer and leave one surface exposed for the acid penetration.
4. Anodize it in controlled temperature and voltage settings.
5. Acid etching
6. Anodizing it again which is similar to the previous setup at (4)
7. Cleaned and annealed.
Relevant answer
Answer
On the step 3 don't forget about backside contact fabrication to the sample prior the pasivation with the epoxy.
Regards