Science topic

# Advanced Materials - Science topic

Question
I am trying to optimize a molecular crystal using CRYSTAL17 software. I am getting error that the basis set I am using is linearly dependent. How can I solve such issue.
I tried changing my basis set but get same error. I tried changing k points and DFT integration grid but get same error.
Please help me solve this issue or tell me what I should do to avoid this in future.
thank you Anwesh Pandey . I will try that
Question
Nbc-Ni Cermets samples are sintered in a vacuum sintering furnace at @1450 degrees. The Samples were placed in the Alumina Piece as shown in the attached pictures. after sintering the color of the alumina piece changes to blue as shown in the picture. what can be the reason behind it? Thanks
Dear Abdul,
I never worked with these materials but they are high melting point-based, so I believe the influence will be minor. I recommend you'll measure Al content prior to and after the heat treatment of your samples.
Good luck.
Question
I have installed the DAMASK successfully with the help of the Internet. However, there is no specific tutorials about how to carry out a simulation. I have read all the Documentation from the website(https://damask.mpie.de/), but still do not know the complete and specific analysis procedures. If there is any step-by-step simulation tutorials, that will help me a lot. Thanks a lot!
Question
Hello,
I would like to review recent developments in high-strength alloy systems for applications at 1200 oC. As far as I know, Ni-based superalloys lose their strength over 1000 oC due to the dissolution of Ni3Al precipitates. Therefore I am wondering about what alloys systems (preferably non-refractory) are used for very high temperature (1200 oC) applications? Any recent developments in Ni-based superalloys that permit high temperature usage? Kindly provide some references.
Thank you.
After Vadim Verlotski , I recommend for you to start with the recent review by P.Tsakiropoulos, as its present the trends for developing Nb-silicide based alloys as feasible alloys for application at ultra-high temperatures for their density, oxidation and mechanical properties.
Best regards
Also in RG on:
Question
Hello Everyone,
In many materials we can observe linear band crossing even above or below the fermi level. So what is the importance of having DIrac points somewhat away from fermi level (lets say around 2eV) ?
Can any crossing of bands which is linear leads to a DIrac point ?
The Fermi level is the energy characteristic of the statistics
and separating occupied states of the valence band from the conduction band at T=0 Kelvin. It controls the occupation of any energy state by a given particle: an electron or a hole (fermion particles)in semiconductors. The position of the Fermi level depends on the number of free electrons holes, the effective masses of electrons and holes, and temperature.The Fermi level in an intrinsic semiconductor at the middle of the energy bandgap at T=0 Kelvin while the Fermi level has to move away from the midgap position in an extrinsic semiconductor.
Question
We need to characterize a few ceramic composite materials using chemisorption to find out the percentage of active metal surface area.
We are also looking for other methods that would help us find the active metal content reliably. It would be of great help to know if there are other techniques that could help us understand our catalyst better.
Thanks
As I understand...you need to do BET analysis. Any group working on polymeric sensors will be capable of such studies. In my knowledge, IIT Delhi and DRDE, Gwalior should be capable of this.
Question
I am looking for detailed ebooks on architectural materials and finishes that includes the whole list of pros and cons of using that particular material. Can someone suggest me some ebooks/magazines you came across?
Dear Lizny Jaufer,
The architecture of the Present
Contemporary architecture is the architecture of the twenty-first century, constantly changing and encompassing a variety of styles ranging from high-tech design and open spaces to forms that reflect movement, some resembling massive sculptures. Contemporary architectural styles share characteristics such as the use of modern building materials and computer-aided design, which encourage taller, lighter buildings of organic design. The "Birds Nest" sports complex in Beijing and the Disney Concert Hall in Los Angeles, both of which demonstrate the free-flowing forms possible with 3-D modeling software, are notable examples of contemporary architecture. The Kauffman Performing Arts Center in Kansas City is a local example, with its naturalistic metal forms and structural curtain wall of glass.
As a result of industrialization, modern architecture developed in response to new industrialized materials and technologies, resulting in-plane and sleek facades shunting ornamentation and rejecting earlier traditional styles, materials, and construction techniques. The material contributes to the physical form of a design. The only factor that is tangible in nature is building materiality. And this tangible component provides a variety of intangible emotions and feelings that can be controlled by choosing the appropriate material.
1. Concrete In Modern Architecture
2. Brick In Modern Architecture
3. Steel In Modern Architecture
4. Glass In Modern Architecture
5. Aluminum In Modern Architecture
6. Natural Stone In Modern Architecture
7. Wood In Modern Architecture
Question
Dear researchers,
I am working on Mg composites fabricated by powder metallurgy. I have investigated the wear behavior of Mg-based composites with variation in temperature. I observed that wear rate increased with an increase in the wear temperature. Can anyone explain me in detail, why is it happening? What is the mechanism? I am looking for your responses.
Thank you so much.
Thank you, sir. But I don't understand your language.
Question
Hello,
One of my colleagues is working with piezoelectric components and couldn't find the shock response spectrum for various piezoelectric components. Can anyone please share your idea to deal with the calculation process of shock response spectrum (srs) of piezoelectric components? However, any informative links that contain useful resources or details will be very helpful.
Thank you for your time and guidance.
Best wishes,
Faishal Rahaman
I have a RG write-up for the impulse excitation of a piezoelectric shock sensor (PSS), which you may find of interest for your current problem, see, . I just uploaded this Method today, 3/2/2022. I hope this helps.
Regards,
Thomas Cuff
Question
Dear Researchers :
Hope this discussion seems interesting for some of you
Is it correct to say :
"All Dielectric Materials are Electrical Insulators, but not all Electrical Insulators are Dielectric Materials" ?
I have this doubt, hopefully someone can provide a correct answer, and: Why not, or Why is it
Best Regards !
Yes very interesting question:
We can make the comparison simple as follows:
1. An insulator is a material with no free carrier concentrations (electrons) able to conduct electricity meaning here Sigma=0.
2. A dielectric is a material where the carriers are all tightly bound to the crystal atoms i.e. they are not free to move.
- This is similar to the insulator case, but this is true only under static electric field conditions (zero frequency or DC electric field).
- Under High frequency AC electric fields, a dielectric can contribute to the conduction through polarization, which is a type of conduction dominant in dielectrics at high frequencies)
- A simple insulator cannot do the same.
Question
Ansys Granta is not a free programme. Is there any other materials selection software that you would recommend, and what is the name of it? ( https://www.ansys.com/en-in/products/materials/granta-selector )
Hi, If you mind take a look at tables of the following paper (all links and licenses are mentioned):
Question
As every keyword have certain experts associated with it, based on their area of expertise. Can we initiate a devoted section for research collaboration, especially for the calls requiring bilateral or multinational collaborator?
Presently, My group is looking for a German collaborator in the area of " High performance based C-C composites" on following call "http://www.dst.gov.in/sites/default/files/DST-DFG-JointCall-10AUG2018.pdf"
Finding it difficult to have a relevant and interested group from Germany. kindly text me if anyone finds this call interesting.
Please share how I should proceed to search for interested researchers from Germany, My present approach is searching research papers on said area and mailing to the researcher if find relevant.
Prof. Ajitanshu Vedrtnam: In my opinion, the projects are more than enough instead of your suggested section.
Question
If I were to make a half dome as an umbrella to protect a city from rain and sun how would I proceed. Are there special materials or do you have an idea on how to make this? What do you say about an energy shield ?
Dear all, I think the easiest way is an underground city. Shullters are built for similar protection purposes. My Regards
Question
Limitations of carbon dot or carbon dot based products for commercialization.
We have tried to address a few things in this direction in our latest review article.
Question
Dear colleagues,
Could you please suggest me some rapid publication ISI journal list in nanotechnology, thinfilm (namely composite material, compound semiconductor thinfilm) with impact factor range from 1.5 to 4.0 (rapid publication)? I know some journals such as Journal of Material (Hindawi), Journal of Materials Science (Springer), JNN, Journal of Alloys and Compounds, Thin solid film and two lists:
However, I still can not find the suitable journal in these lists.
List of major Nanotechnology and related journals
1. Nature Nanotechnology
2. Nano Letters
4. Nano Today
5. ACS Nano
7. Journal of Physical Chemistry Letters
8. Biomaterials
9. Small
10. Nano Research
11. Scripta Materialia
12. Nanoscale
13. Lab on a Chip - Miniaturisation for Chemistry and Biology
14. Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
15. ACS Applied Materials and Interfaces
16. Biosensors and Bioelectronics
17. Journal of Physical Chemistry C
18. Nanomedicine: Nanotechnology, Biology, and Medicine
19. Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology
20. Nanotoxicology
21. Precision Engineering
22. Nanomedicine
23. Nanotechnology
24. Microporous and Mesoporous Materials
25. International Journal of Nanomedicine
26. Beilstein Journal of Nanotechnology
27. Journal of Bionanoscience
28. Nanotechnology, Science and Applications
29. Journal of Nanobiotechnology
30. Plasmonics
31. Biomedical Microdevices
32. Biomicrofluidics
33. IEEE Transactions on Nanotechnology
34. Microfluidics and Nanofluidics
35. Journal of Micromechanics and Microengineering
36. IEEE Transactions on Nanobioscience
37. Journal of Biomedical Nanotechnology
38. Photonics and Nanostructures - Fundamentals and Applications
39. Physica E: Low-Dimensional Systems and Nanostructures
40. Nanoscale Research Letters
41. Microelectronics and Reliability
42. Journal of Nanoparticle Research
44. Microscale Thermophysical Engineering
45. Microelectronic Engineering
46. Nano Biomedicine and Engineering
47. Nano-Micro Letters
48. ACM Journal on Emerging Technologies in Computing Systems
50. Journal of Nanophotonics
Question
This is more of a question, but put under discussion as it may lead to a discussion.
Large crack lengths in the range from 0.5mm to 100mm, can DAMASK simulate these cracks for materials like steels, Haynes, etc.?
I think the Damage model is still unavailable in damask.
Question
I have prepared magnesium green compacts from powders of different particle sizes. I observed that the green strength of compacts produced from fine powder was very low. Green compact splitted in two parts in the vertical plane during removal of green compact from the powder compaction dies. I repeated the experiment so many times and observed the same behavior. What can be the possible reason? Please explain.
Green compacts of any powder compacts have low strength because no bonding is there between particles. The green compacts possess whatever strength is because of compaction force. The compaction force removes the empty spaces and facilitates mechanical interlocking of particles. Only after sintering strength is developed. So, change the design of the die for easy removal of green compacts.
Question
rare-earth free Fe-based metallic glass, >10 mm critical casting diameter ?
any Al-based metallic glass, >10 mm diameter?
precious-metal free Ni-based metallic glass, >10 mm diameter?
rare-earth and precious-metal free Cu-based metallic glass, >30 mm diameter?
any metallic glass that is truly ultrastable and virtually never crystallizes?
I would say that the next major development in metallic glasses and bulk metallic glasses is to facilitate the production and use of these metals for various applications. Any progress that can overcome various limitations, such as the need for high-purity raw materials, expensive facilities and equipment, low ductility, critical diameter and so on, will be significant. Changes that enable the commercialization of these alloys.
Question
Need to do strain controlled fatigue test on ASTM E606 specimen. What I have referred from a research literature they have given strain ratio R, of 0.5 and a frequency of 0.2 Hz and strain levels of 0.7%–3.0%, 70% decline of peak load could anyone tell me how to decide this values ? From where they used the values there is no reference paper they have used in that particular research article.
Hi Dinesh
Strain controlled fatigue testing is important to study the behaviour of components undergoing either mechanically or thermally induced cyclic plastic strains that cause failure within fewer cycles (<10^5) than high cycle fatigue (>10^5-10^6 cycles).
The testing conditions are usually determined by the specific application you are considering. Doing this preliminary investigation will allow you to get more meaningful and useful results from the strain controlled tests.
So I would recommend to try to collect some initial indicative data to better plan the test conditions (temperature, R, frequency, strain levels). If the components (or an older version of the components) are already in service you can get some good indications by applying some strain gauges and thermocouples to the parts to understand what sort of strains they undergo and at what temperatures. If the components are still in the design phase then you will need to carry out some hand calculations or run some FEA analyses to get a feeling of what strain the parts will experience once in service.
Having said this, in terms of strain levels you can consider that you enter within the high cycle fatigue range when the part undergo loads that generate stresses below half of the yield strength of the material i.e. 0.2% so you want to stay above this value. In general you could run tests at strain level within 0.2% and 20-40%. It depends also by the material and test temperature. Then with the Coffin-Manson equation you can relate cycles to plastic strains.
To determine the values of temperature, frequency and R for your tests, as previously mentioned, it would be better if you use values close to your actual application to collect more reliable and useful data.
Question
Given data: Viscosity of the oil at 40 degrees is 416 cSt and viscosity of the oil at 100 degrees is 32 degree.
Question
Asbestos is considered the best brake friction material because of its high thermal stability, low wear rate, low cost, etc. But, due to its carcinogenic effects, asbestos has been phased out. Now, asbestos-free braking materials are being developed. Today, non-asbestos organic (NAO) brake pads are being used widely. But, NAO brake pads have low thermal stability. So, the NAO type of brake pads is not suitable for heavy-duty applications. So, which materials are ideal for heavy-duty braking applications? Metal matrix composites? Carbon-carbon composites? Ceramic composites? or any other?
Dear Sir,
Ceramic-Graphene, Kevlar- Graphene/CNT etc. are perfect materials for the heavy duty brake as per recent scientific outputs. However, it's commercial version still under review..
Question
What are the quantum materials? Quantum phenomenon takes place in every material at atomic level. then how to define quantum materials? is Iron (magnetic materials) quantum material as it shows magnetism which is the quantum phenomenon? if not then what are quantum materials?
Quantum materials are I believe are those materials that exhibit wave behavior, or equivalently particle-wave duality.
Question
Dear all,
I am working on the development of magnesium alloy AZ91 composites by powder metallurgy route. During the sintering of pure alloy samples, there is a decrease in density. Generally, density increases after sintering. What can be the possible reason for this anomalous behaviour? I have read in some papers that this can be due to foaming. Also, please tell me how I can avoid this?
The sintering process of a compact particle found to continue within two decoupled stage , particles shrinkage by densification and growth by coarsening behavior at higher temperature. At densification stage the loss of unstable materials will permit the internal pores formation of certain volumes and shapes. The small pores and\or concave surface morphology are able to shrink as mass transfer by inward atomic diffusion from the bulk of the particle towards the pore surface and fill the pore space. On the other hand large pores and\or a convex surface morphology is not able to shrink as mass transfer by outward atomic diffusion from the pore surface towards the bulk of the particle is dominated and, enlarge the pore space and leading to what you called process of foaming that responsible for lowering the density.
Now, owing to the higher surface to volume ratio of the particles of nano-size (less than@100nm) compared to that of sub-micron and micro-size, the outward mass diffusion of trapped material is faster. This could leave larger pores that are thermodynamically stable and not able to shrink, so the coarser particles permit shrinkage at a higher rate than those at lower sizes. Please any feedback is welcome to frame the discussion picture.
Best regards.
Question
Are BPDs (Basal Plane Dislocations) and Misfit dislocations different or same? If different, what's the difference between the two?
I believe they are different
Question
Generally, lattice constant increases if the doping atom has larger radius. But sometimes reverse phenomenon happens, that is lattice constant increases when doping atom has smaller radius. What are the probable reasons behind it?
The lattice constant, or lattice parameter, refers to the physical dimension of unit cells in a crystal lattice. Lattices in three dimensions generally have three lattice constants, referred to as a, b, and c. When a heteroatom with a smaller or larger radius was doped in a lattice structure e.g., C is getting doped in AB2O4 in place of B the lattice parameters of the doped material will change as compared to AB2O4. Thus, the crystallite size along with the unit cell volume will also change. So, by finding the correlation between the crystallite size and cell volume the reason can be explained from system to system. The above I can say from my side.
Regards
Question
Impact of negligent behaviour in medical practitioners to patients
Question
Hello everyone,
I hope you are doing well in this pandemic.
Currently, I am doing PhD in powder metallurgy. I am in the stage of submission, so looking for a postdoc. But, I am a little bit confused about the selection of the topic. I have worked on metal matrix composites, polymer matrix composites, and nanoparticles synthesis during my M.Tech and PhD. I have published papers in all three areas. Can anyone suggest which topic will be better for me (in terms of future scope, novelty)? I am looking for your valuable suggestions.
Thank you
Thank you, sir.
Question
In other to achieve the environmentally, friendly, biodegradable, sustainable and machinability of difficult- to- cut metals such as Inconel 718 at minimum quantity lubrications MQL in manufacturing processes.
Dear Paul Nnarotam Onyishi
The literature may be useful are,
Question
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?
Well , its depend on your final application but powder technology is easy and cheap besides good mechanical properties
Question
In powder metallurgy, energy is consumed in powder production, ball milling, powder compaction, and sintering. Whereas in casting, the energy is consumed only in melting the ingot. In some of the papers, I have read that energy consumption is lower in powder metallurgy. How? Can anyone explain, please?
Powder metallurgy process is a net forming process, more energy saving from the point of view of saving materials
Question
With the increasing demand, the consumption of metallic materials is increasing. But the primary sources of these materials (ores) are limited. So, there is an urgent need for an efficient recycling technique to meet the increasing demand. There are mainly two techniques, powder metallurgy and casting, used for recycling metallic materials. Which is the better technique, powder metallurgy or casting?
Just came across this question. Slightly unrelated but aligned to re-cycling in the foundry environment.
Please see my paper on recycling waste foundry sand:
The paper also looks at alternative methods of recycling waste foundry sand.
Hope this might be of some use to your overall topic.
Best Regards
Martin
Question
I am working on the development of metal matrix composites by powder metallurgy technique. Currently, I am using conventional sintering. Microwave sintering and plasma sintering are advanced sintering techniques. What are the differences between traditional sintering, microwave sintering, and plasma sintering? What are their advantages and disadvantages? Which one is better for the sintering of AZ91 magnesium alloy?
Using SPS, you'll get dense samples with less sintering time, providing less interfacial reactions between the matrix and the reinforcing phase. If you're using particle reinforcement type, you'll have better particle distribution. However, it is not impossible to get nearly full dense samples when using your method, especially if you have some low melting point phases that could provide a liquid media reducing porosity. In your case, you'll have to worry about, porosity since higher insertion of renforing phase will certainly increase porosity amount, higher sintering time will reduce porosity but will increase interfacial reactions between Mg matrix and the reinforcing phase. These interfacial reactions could be detrimental or beneficial it depends on the interfacial phases created and the property target. Particle distribution will be nice in your case if the temperature and time is well controlled. You'll probably find also precipitation of MgxAly at near areas around the reinforcing phases due to the creation high density areas of dislocations, favorite site of precipitates nucleation. I hope my answer will help you. Best regards.
Question
I am looking for the latest approaches to find the band-gap of Phononic / Periodic materials. In this regard, if anyone knows a reference (in detail) for Finite Difference Time Domain (FDTD) theory along with the Bloch method, please share.
For arbitrary unit cells, your best bet is an eigenmode simulation. Sweep the Bloch phase shifts across the various axes from 0 to pi and solve for the eigenfrequencies. The regions in which there are no found eigenfrequencies are your band gaps.
Question
I wanted to know recent additions of ICDD (JCPDS) files of Zinc oxide. I have ICDD files which were addded before 2003. If anyone knows the recent ICDD files or atleast PDF numbers it will be most helpful to compare my data.
You can easily get any XRD Reference or JCPDS file here,
Question
I want to buy MXenes any recommendations
Dear Muhammad Chhattal, the following RG thread may brings some help. My Regards
Question
If we evaporate Sulphur in a closed chamber along with the MoO3 films, will it convert MoO3 to MoS2?
Dear Karthik, thank you for asking this very interesting technical question. Yes, the conversion of MO3 thin films into MoS2 films by sulfurization with elemental sulfur is indeed possible. This process has for example been reported in the article entitled "Direct Transformation of Crystalline MoO3 into Few-
Layers MoS2" (Materials 2020, 13, 2293) which can be freely downloaded as pdf file from the general internet. It was pointed out that this process could be carried out at moderate temperatures using simple instrumentation. Elemental sulfur powder was used as sulfurization agent.
Question
HEA fabrication
In most cases high entropy alloys are prepared by melting the constituents together at high temperature. Since the entropy goes into the Gibbs free energy always as -TS, the role of entropy is higher at high temperatures. Many systems (but not all) therefore can be single phase liquid. The fast diffusion at high temperature and in liquid state distributes the atoms homogeneously in a short time. If the high entropy alloy is single phase at room temperature, too, the cooling can be made at medium rate. Attention is needed to prevent segregation of elements during solidification. Some tempering at temperatures just below the solidus temperature may be necessary to homogenise the alloy by solid state diffusion. If the solid state is not single phase a rapid solidification can produce single phase homogeneous alloy.
Another approach is to use powder metallurgy and homogenise the alloy by diffusion of elements during sintering. Homogenbeous distribution can be reached also by atomising the liquid alloy and sintering the powder particles.
A powder approach is also the mechanical alloying of mixed powders. Here the solid state diffusion enhanced by high defect densities can produce homogeneous alloy. However mechanical alloying in most case is connected with impurity pick-up from the milling system or from the atmosphere (oxygen).
Question
I am a novice student doing a research project on water absorption in polymer composites with sodium silicate coating.
I want to ask about how to determine the result of the percentage of water absorption which is the sum of the percentage gain in body weight and the percentage of dissolved matter lost
for example, the conditioned weight is 9.76 grams then the wet weight at the time of immersion for 24 hours is 7.05 grams. Because there was a reduction in weight, my specimen was reconditioned with the result that the reconditioned weight was 6.83 grams.
Is it true that the percentage increase in weight was -27.77% and the percentage of dissolved matter lost was 30.02%? Then to determine the percentage of water absorption, just add (-27.77%) + (30.02%)?
Is there something wrong with my calculations?
Dear all, it looks correct what you have done according to ASTM standard norm. However, it is quiet wise to use different analysis techniques to confirm your results, mainly dielectric one. Please see attached files. My Regards
Question
I am looking for studies related to austenization soaking times and ways to reduce the time to achieve full dissolution of carbides as well as not to obtain austenite grain growth. Grain growth will take place with increasing soaking time. I am looking for any studies that discuss about ways to reduce the soaking time to obtain full carbide dissolution as well as stay in the optimum austenite grain size range. The steels cast have carbon in the hyper-eutectoid range. i.e. greater than 0.78% C, in about 0.88% C. I would highly appreciate feedback from experts.
You should calculate dissolution temperatures of the predicted carbides in your steel based on the solubility products given by certain equations, (PHMN3) database. The dissolution temperatures of carbides are related to the carbon content and the carbide former element.
We have two equations of two carbies in our paper:
Question
Dear Researchers/Professors,
Could you please explain the Merits and Demerits of journal publications under the special issue?
Thank you.
Agree with Rifat Bhat
Question
What is the mechanism and method of making the steel fibers used in reinforcing concrete and what are the residues or wastes or losses caused from the manufacturing stage ?
Are there detailed industry instructions that can be obtained ?
Dear Ahmed Mousa,
Steel fibers are short discontinues strips of specially manufactured steel. Generally, their inclusion in the concrete improves the mechanical properties of concrete significantly. As the most common matrix, which is now mostly use in construction industry is Reinforced Cement Concrete. Main Reinforcement purpose is to resist bending due to applied load.
Ashish
Question
If I have a sample that consists of 2 substances with the same chemical composition but different crystal structure (one cubic and the other orthorhombic), how can I figure out what percentage of the sample consists of the cubic crystal structure and what percentage of the sample consists of the orthorhombic structure?
Hi dear Wei Ying Lieu
The Topic that you said " calculation phase percentage", they call it quantitative analysis. but first of all, you must find your exact phases (Qualitative Analysis).
For example, In steel, you found two phases:
1- Ferrite (BCC crystal structure)
2- Austenite (FCC crystal structure)
You can find them with XRD analysis software like X'pert highscore plus, Xpowder, Match, etc (Qualitative Analysis).
After a good qualitative analysis, you will download your phases "cif file". Then you can calculate your phase fraction with software (like X'pert highscore , Maud, etc)
I prefer to use X'pert highscore for Qualitative analysis & Maud for Quantitative analysis.
Good luck
Question
Hello Researchers..
I have created the vacancy in the supercell ? i want to find charge density Contour. can i use VESTA for this ? I have little idea of using Xcrystden. Will it be necessary to use Wien2K or please guide me with any other way ? thanks in advance.
#simulations #QUANTUMESPRESSO #modulation#VESTA#BURAI #metaloxides #vacancy
Question
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Question
dear all
can anyone explain to me or give me a reference how they find that the expression of the Zn-O bond length in the wurtzite structure is given by [1] :
$l=\sqrt{(\frac{a^2}{3}+(\frac{1}{2})-u)^2 c^2}$
where u is the positional parameter
$u=\frac{a^2}{3c^2}+1/4$
[1] Wang XS, Wu ZC, Webb JF, Liu ZG (2003) Appl Phys A 77:561
In the Wurtzite structure type you have four atoms per unit cell:
Zn 1/3, 2/3, 0
Zn 2/3, 1/3, 1/2
O 1/3, 2/3, u
O 2/3, 1/3, u + 1/2
(You can interchange Zn and O it makes no difference)
In a general triclinic structure the length of any vector squared is
EQ. 1:
d^2 = (u, v, z) G (u, v, z)^T (The second vector is a column matrix)
G is the metric tensor, whose 3x3 elements are the scalar products of the lattice vectors. in a hexagonal system you have a=b, alpha=beta=90 gamma=120 and thus
EQ. 2
( a^2 -1/2 a^2 0 )
G = ( -1/2 a^2 a^2 0 )
( 0 0 c^2)
In the Wurtzite type structure you have two vectors Zn-O:
[ 0 0 u ] and
[ -1/3 1/3 1/2-u ]
Plug these two vectors into the EQ. 1 you need to calculate
EQ. 3
( a^2 -1/2 a^2 0 ) [ 0 ]
d^2 = [ 0 0 u] ( -1/2 a^2 a^2 0 ) [ 0 ]
( 0 0 c^2 ) [ u]
and
EQ 4.
( a^2 -1/2 a^2 0 ) [ -1/3 ]
d^2 = [ -1/3 1/3 1/2-u] ( -1/2 a^2 a^2 0 ) [ 1/3 ]
( 0 0 c^2 ) [ 1/2-u]
(standard matrix algebra)
These are symmetrically NOT equivalent and NEED NOT have the same length!
The paper implicitly makes the (far fetched) assumption that the two distances are equal. If you force these two vectors to have the same length you obtain the relationship between u and the a/c ratio in eq. 1 in the paper.
And eq. 2 in the paper is simply the reslut of EQ. 4 written down in full.
You will find these type of calculations explained in any basic crystallographic text book! For example Giacovazzo et al. "Fundamental crystallography"), D.E.Sands "Vectors and tensors in Crystallography"
Question
A file of two images has been attached to this question.
This is a ferrite composition that has been prepared adopting auto-combustion method. The SEM of this sample has exhibited a peculiar grain structure. It seems, a lot of tiny grains have enclosed a large grain.
Why does this happen?
Best way to figure this out is to so do elemental mapping using EDS attachment to SEM.
Question
Is there a way to dope or combine the FeSe alloy onto a MXene (Ti3C2Tx) which can be used as a electrode for energy applications?
Dear Lokesh Murali thank you for this interesting technical question. I only found a references in which the combination of nickel selenide with Ti3C2Tx has been reported:
Ultrathin Ti3C2Tx (MXene) Nanosheet-Wrapped NiSe2 Octahedral Crystal for Enhanced Supercapacitor Performance and Synergetic Electrocatalytic Water Splitting
This paper is freely available as public full text on ResearchGate.
Question
Please suggest what are different types of polymorphic transformations and best available literature decoding the same. For example, I am not clear if:
1. Different polytypes of SiC are due to reconstructive/ displacive or any other transformation?
2. Is existence of C as diamond or graphite due to order-disorder transformation?
3. Is the energetic material like CL-20 having 4-5 polymorphs due to displacive transformation?
Dear,
In mineralogy, only topologically different structures of the same composition are usually considered to be polymorphs. Crystal structures formed of segments that can be stacked with different orientations are called polytypes. There is a symbolism of polytypes, based on the number of repeating segments and symmetry. Other options today do not differ in nomenclature rather (ordering-disordering -OD structures, polytypoids, etc.).
SiC is considered strongly polytypic, where Identical layers are shifted or rotated. Stacking in an identical position is not possible. It is good to draw the structure of one of the SiC polytypes in some program (Vesta, XTALDRAW etc.)
Graphite and diamond are completely different structures with different bonding characteristics. So the transition from graphite to diamond is completely reconstructive. However, graphite itself is polytypic (graphite-2H, -3R and disordered graphite) and probably also polymorphic (chaoite is high-pressure graphite). Diamond is polymorphic (diamond, lonsdaleyite).
I don't know anything about the CL-20 explosive.
Question
Hello everyone:
I am looking for a simple software program to model chemical bonds. The purpose is to generate a high-quality graphical abstract for a top leading journal in the field of chemistry. I am not interested in professional programs like Photoshop as I don't have enough time to learn. Any suggestion?
Question
Dear Researchers,
Please, which sites, tools, or programs you recommend to use in the design and selection of materials topic?
Regards,
Akram
Hey Akram, thank you for this interesting question. Attached you can find a list of the most appropriate material selection tools used in engineering design.
If you do have any further questions, do not hesitate to ask me.
All the best, Jerome
Question
I have seen Iranians publishing their works in this journal, however they are usually doing their research outside of Iran.
In science, all depends on the quality of research. If your work is unique and and well presented and has the significancy to the developement of science, it worth publishing. No matter country, race, origin, religion etc. In my field a lot of researchers are from Iran. Everybody will recognise you because of your work. Besides weley, you can also try on Elsevier, Springer, Sage, MDPI etc. Here is the link to search the suitable journal of these groups.
Almost all of the journal have basically two options: subcribe base and open access. Go for subscribe base option so that you don't need to pay at all.
Thank you.
Question
I am looking for ways to give orientation to micro-scaled silicon chips and I am thinking of using a 'life jacket' strategy to keep one side always floating and facing upwards. Are there any materials or surface modification techniques (like maybe if we make it super hydrophobic) to achieve this goal?
Trimesoyl 1,3,5‐tridimethyl malonate (TTDMM), trimesoyl 1,3,5‐tridiethyl malonate (TTDEM), trimesoyl 1,3,5‐tridipropyl malonate (TTDPM), trimesoyl 1,3,5‐tridibutyl malonate (TTDBM), and trimesoyl 1,3,5‐tridihexyl malonate (TTDHM) first‐generation dendrimers. TTDHM acts as superhydrophobe greater than polydimethylsiloxane (PDMS) compounds.
Question
Is there any way to construct different initial filler shapes like triangle, square, rectangle, pillar, and tube in any simulation software.
Thank you @Wojciech Kopec.
Question
I am looking for a scientific explanation for the anomalous values of Avrami exponents. Regrading the literature, the typical values of Avrami exponent have to be between 1 and 4. Different Avrami values demonstrate the different mechanisms of crystallization (Phase Transformation), including nucleation rate, growth rate, and dimensionality of the growth. Meanwhile, we obtained some anomalous values of Avrami exponents around 5, we appreciate any contribution in finding meaningful explanations.
I appreciate your explanations very much and congratulate you on your nice published paper. In addition to your accurate interpretations, we have provided some additional information in the following paper:
Question
So I know some metal-insulators (ex VO2) have thermochromic infrared-reflective properties, but most of these are insulators at low temperatures and conductive at high temperatures. Some perovskites conduct at low temperatures and insulate at high temperatures, but I haven't found any that show significant thermochromic properties and have a transition around 10C. Does anyone know of materials that satisfy these criteria? The temperature range doesn't need to be exact.
Dear Ethan,
There is a similar question which were posted in the research gate forum. This could answer your question. Please see the following link
Best wishes
Xuhua
Question
As shear strength of AA2024-T4 alloy is inversely proportional to the temperature. is there any equation to predict shear strength of AA2024-T4 with respect to temperature?
I believe you can hardly find any literature which correlates shear strength/yield strength with temperature for a specific alloy. That said, you will find an interesting article here ( ), which might be of some help.
I am also enclosing our recent paper ( ), which correlates different work-hardening parameters and processing temperature during plane strain compression of Aluminium 6016 T4 alloy. I look forward to seeing similar research correlating shear strength and processing temperature of AA2024-T4 alloy in the near future.
Question
1. In a Low-velocity impact test, I have got Force vs Time response. There were two peaks in cross-ply and angle-ply orientation. In cross-ply, its peak to peak distance is lesser when compared to angle-ply. What is its significance?
2. Another was, steep rise in the cross-ply but the linear increment in angle -ply. What might be the reason?
higher stiffness
Question
Hello, Everyone!
I am working on TiO2 composites and our prepared materials solution has a pH of 13 which is totally basic, and the process of pH value decrement is too slow could any please suggest the method of how to decrease the pH value of the solution fastly without changing the properties of the solution.
You can try buffers
Question
SERIES#9 (Monday, 2nd of November 2020 at 1-3 PM Jakarta)
#Speakers#
Rifan Hardian, MIL, MSc, MSc, PhD King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering Department-Saudi Arabia/ Metal-Organic-Frameworks (MOFs), Polymer Membrane and Machine Learning
Hasfi Fajrian Nurly,S.T., M.Eng*University of Science and Technology of China/*4D printed hydrogels
SERIES#10 (Monday, 9th of November 2020 at 1-3 PM Jakarta)
#Speakers#
Yus Rama Denny,PhD Department of Physic Education, Sultan Ageng Tirtayasa University*Transparent Conducting Oxide : History and Challenge for advance material applications*
Fatwa Firdaus Abdi,PhD Institute Solar Fuels Helmholtz-Zentrum Berlin-Germany* Semiconductor and photoelectrochemistry for water splitting and solar fuels*
SERIES#11 (Wednesday, 18th of November 2020 at 8:30-11:30 PM Jakarta)
#Speakers#
Dr. Chander Prakash Department of Mechanical Engineering, Lovely Professional University, Punjab-India Surface functionalization of biomaterials
*Prof. Dr. A Ali Alhamidi, S.T.,M.T*Department of Metallurgy Engineering, Sultan Ageng Tirtayasa University *Severe Plastic Deformation *
Nandang Mufti, PhD Department of Physics, Universitas Negeri Malang Advanced materials for renewable energy
FML WEBINAR SERIES#3 (Wednesday, 18th of November 2020 at 2-5 PM Jakarta)
#Speakers#
Dr. Enzo Liotti Senior Fellow of Departmental Lecturer in Processing of Advanced Materials,Department of Materials/Oxford University-UK Synchrotron X-Ray Techniques for Understanding Metal Alloys Structures and Its Evolution
Michal Rejdak, PhD * Laboratory of Cokemaking Technologies, Institute for Chemical Processing of Coal, Poland *Cokemaking Technologies
SERIES#12 (Monday, 23th of November 2020 at 2-5 PM Jakarta)
#Speakers#
Prof. Paula Maria Vilarinho Department of Materials and Ceramic Engineering (DEMaC), University of Aveiro-Portugal *Electrical Polarization Phenomena and Advanced Nano and Microelectronics Devices *
Bobby Aditya Darmawan,S.T.,M.Eng Department of Mechanical Engineering , Chonnam National University, Korea and Korea Institute of Medical Microrobotics The future prospects of microrobots in biomedical applications
SERIES#13 (Monday, 30th of November 2020 at 2-5 PM Jakarta)
#Speakers#
Dr. Ir. Hermawan Judawisastra, M.Eng Department of Material Engineering, Bandung Institute of Technology-Indonesia *Polymer Composites *
Sampo Tuukkanen, PhD Tampere University of Technology-Finland Nanocellulose piezo-sensors
@abdella. No, it's free. You will receive e-certificate and the slides.
Question
How to determine the structure of crystals (SC, FCC, BCC) using electron beam diffraction by tilting the samples? Thanks!
Hi Pistach,
You can use Electron Backscatter Diffraction (EBSD), this technique allows to obtain crystallographic and microstructural information. IIn the experimental setup, the sample is tilted 70 °. I don't know if that answers your question.
Best regards.
Question
I am working with h-BN and need to find out the strain due to in-plane lattice constant. The famous Williamson-Hall method may not be applicable here as it analyzes XRD for calculation of strain due to out-of plane which is not applicable for 2D.
The strain due to out of plane (i.e. c-axis) can be calculated by using the equation 6 of the attached file. Looking for same but due to in-plane lattice constant (a axis)
Question
I'm currently working on MXenes as Counter electrode (CE) for Dye sensitized solar cell (DSSC) application. I would like to know about the research work being done in this area.
Dear Lokesh Murali, I would like you to check all what was discussed on the subject at RG (see link below). If not satistied, I can add more data. My Regards
Question
What is the difference between the energetic disorder and structural disorder in organic materials? Thanks!
Dear Pistach Nyo please see this useful article which could answer your question. The paper is available as full text on RG:
Question
Any close value will also work.
Dear Abhishek Mukherjee,
The optical absorption coefficient can be obtained by using the equation [2] which can be used in a non-conducting dispersive medium. Here w is photon frequency, μo is the permeability of free space, ε1 and ε2 are frequency-dependent real and imaginary parts of dielectric permittivity from the VASP output of the first-principle calculation.
2. D. J. Griffiths . Introduction to Electrodynamics. 4th Edition, Pearson Education (2013).
Ashish
Question
I need references articles that explain the drawings for the following materials, which illustrate the diagram between DR UV-Vis spectrums of the following materials blank sample as expressed in Kubleka-Munk function versus
the measured wavelength and the materials are ZnO, CuO, Fe2O3, and Co3O4.
Question
I have a liquid that glows when UV light is shined. However, when I use my phone camera I can't see the glow, I just see a violet hue. What is the best way of capturing the fluorescence-glow from our samples? DO I need to use a filter for my camera?
it depends on the sensitivity of the camera with respect to the different wavelengths. I expect that a mobile phone camera is a standard Si detector, hence the sensitivity at low wavelengths is very poor. For sure the use of some filters can help you to obtain better resuts, but first of all you need to know the spectrum of the emitted fluorescence (in principle you can know it if you know the dyes in your system).
Question
Batteries
Energy
Please any one send me CIF file for NMC811 cathode material? my email adress: 3077667118@qq.com@@
Question
I would like to know the various transition metal chalcogenides or dichalcogenides (Se or S based), it would be most appreciated if their synthesis is also shared.
Dear Lokesh,
Selenides should have the better conductivity due to the narrower electronic band gap. As a rule of the thumb the band gap decreases with increasing polarizibility of the anions. As an example we can consider the Cd chalcogenides:
CdS 2.42 eV yellow body colour
CdSe 1.74 eV red body colour
CdTe 1.56 eV black body colour
However, this only concerns the intrinsic conductivity, while p- or n-type dopants can enhance the conductivity tremendously. Many TM chalcogenides can be made by precipitation from solution, as e.g. ZnS, CdS, HgS by the addition of S2- anions.
All the best,
Thomas
Question
Shift in PL emission peaks of SL- WS2 and SL-MoS2 is observed individually under applied strain but due to inter-layer coupling WS2/MoS2 hetero-structure does not show Excitonic behaviour corresponding to both mono-layers rather it shows the PL peaks corresponding to WS2 only in the PL spectra obtained for the hetero-structure. Why?
Huo, Nengjie, Zhongming Wei, Xiuqing Meng, Joongoo Kang, Fengmin Wu, Shu-Shen Li, Su-Huai Wei, and Jingbo Li. "Interlayer coupling and optoelectronic properties of ultrathin two-dimensional heterostructures based on graphene, MoS 2 and WS 2." Journal of Materials Chemistry C 3, no. 21 (2015): 5467-5473.
Question
The following link is related to the "Civil Engineering Publication Reviewers Registration Form". If you are interested to review the Research Articles, Book Chapters, Conference Papers related to Civil Engineering and register in the following link. Thank you in advance.
All the best,
Alonso
Question
The lifespan of the coronavirus outside the human body depends on several factors, such as the nature of the material on which it is deposited and its physico-chemical properties. For example, The duration seems longer for metals than for plastics or wood.
1) What are the reasons?
2) How to exploit this behavior by imagining more adequate coatings for our work plans and tables in laboratories and classrooms?
3) Do you have any ideas or suggestions?
Dear Darcherif Abdel Moumen
Any material with good anti- viral or anti-microbial activity can be an excellent choice. So far, there has been no practical or experimental use of any material in this regard. However, some of the nanomaterials like carbon nanotubes(CNTs), Boron nitride nanotubes (BNNTs) or Titanium dioxide may possibly be tested for this purpose in the near future.
Question
I have ferroelectric materials in powder form, in solid pellets form and as thin films . How to use Ultraviolet photoelectron spectroscopy (UPS) measurement for band gap calculation in ferroelectric thin films / bulk materials (capacitor) ?
Will it provide right information for Ag/FE/Ag , Where FE is in pellet form ?
Will it provide right information for Ag/FE thin film/FTO ?
Coupling UPS with LEIPS spectroscopies together you should be able to measure the band gap, ionization energy, and electron affinity. This is a low energy inverse photoemission process that bombards your sample with low energy electrons. Electrons fill unoccupied conduction band states and emit photons which you then detect.
UPS will give you a cutoff at the Fermi energy, which I‘d guess you can extrapolate to find the bandgap if you’re confident in the slope. Personally, I wouldn’t use it for anything but the valence band minimum. If you have an Auger system you can also use REELS to do a more accurate approximation.
Question
As a requirment in my project, I have to synthesize Formamidinium bromide (FABr). According to the protocols which are mentioned in the articles, I've synthesized this material but I think there is an error in my work?
Does anyone has the experience of this synthesis?
Because in the articles, the authors don't express all the steps, I want to know if there is any critical strategy during the synthesis of FABr and specially in the purification stage of this process.
I would appreciate if you point out a reliable article which has mentioned all the stages of this synthesis with it's details.
Have you tried the way I propose to go ahead for the same? Just try it.Somebody has done and successfully got some very interesting synthesis results.
Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH2)2PbX3 (FAPbX3) has been considered to be a better optoelectronic material than conventional CH3NH3PbX3 (MAPbX3). The FAPbBr3 photodetector’s responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W−1, which is four orders of magnitude higher than that of its MAPbBr3 counterparts. Materials such as Formamidine acetate, lead bromide (PbBr2, > 98%) and hydrobromic acid (48 wt% in water), Gamma-butyrolactone (GBL) and N,N-dimethylformamide (DMF) may required for synthesis.
Formamidinium iodide (FAI) and formamidinium bromide (FABr) can be synthesised by dissolving formamidinium acetate powder in a 2x molar excess of 57%w/w hydroiodic acid (for FAI) or 48%w/w hydrobromic acid (for FABr). FABr can be synthesized by slowly dropping 10 mL hydrobromic acid into 50 mmol (5.205 g) formamidine acetate in a flask, accompanied by continuous stirring at 0 °C for 2 h under argon atmosphere. The product FABr was formed once the solvent was removed using a rotary evaporator at 70 °C. The crude white powder was dissolved in ethanol and subsequently reprecipitated in diethyl ether. Then, the filtered product was dried at 60 °C in a vacuum oven for 24 h for further use.
Ashish
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