Ahmed Elsheikh

South Valley University · Department of Mechanical Engineering

Dear All,

I would like to ask about the best way to digest NiFe/C powdered samples by acid for atomic absorption spectroscopy?

Is HNO3 or HCL alone sufficient?

Or is it better to mix them and prepare aqua regia?

Any special notes in this particular context?

The sample digestion procedure?

Thank you for your kind attention!

Hello,

What are the the best methods (in terms of time and complexity) to exfoliate graphite to synthesize graphene?

I have tried to do it using DMF as a solvent aplplying sonication followed by washing and filteration. As the XRDs of both reactant and product are typical, it did not work out well. I probably did the mistake of taking all the solid product inc graphite preciptate at the bottom while I only should have used the suspended graphene layers. I am not sure if this interpetation is accuarte enough.

Any thoughts or ideas are appreciated!!

In the course of preparing bimetallic and trimetallic nanoparticles, there are three outcomes in terms of the XRD patterns: 1. They present single peaks that are intermediate between the peaks of the respective metals in which case a conclusion that a fully alloyed structure has been produced, 2. Sperate peaks representative of each metal which implies there is a bulk metal separation, 3. Overlapping peaks that are vaguely explained in the literature (some would explain the alloying degree is not very strong). It is, yet, very confusing since it is not appropriate to assume there is bulk metal separation which requires separate XRD peaks representing each metal individually at each diffraction phase. Moreover that a homogenous alloyed structure result would not be supported in the absence of single XRD peaks at different phase diffraction angles and while there is definite peak overlapping.

In this context, how could I best understand the peak overlapping and alloy formation potential?

Thank you for your insightful guidance.

Dear All,

I have prepared trimetallic PdAgNi nanoparticles supported on carbon in addition to their monometallic Pd/C and Ag/C counterparts. I am having some issues with the XRD pattern with the Ag/C pattern shown in the attached figure. There is a double-peak at 44 degrees, At this diffraction angle the Ag (200) is expected. I can not comprehend having two peaks around this facet while the other three facets (111), (220), and (311) have only one peak each.

Each of these was prepared by the borohydride co-reduction method while using KBr as a capping agent. The reaction was undertaken at room temperature for 30 min.

An idea why there are two peaks on the Ag pattern around 44 degrees?

Also, any idea about the intense and broader peaks on the trimetallic sample? The intense ones seem to represent Ag while the broader ones are probably due to Pd. Any idea about the potential of nanoalloy formulation by investigating this XRD patterns?

Thanks for your attention,

Ahmed

Dear All,

Could you, please, help me explain the different concentrations that were detected by ICP-OES? I used the same powder of hybrid C-Pd-Au-Ni nanocomposite. The samples were first digested in HNO3 (2 %). Then it was 10-fold diluted in aqua-regia (8%).

In the attached image, you can see that Powder 1, Powder 2, Powder 3 contain different concentrations of Pd, Au, and Ni even though the 3 samples are taken from the same powder batch.

Thanks for your help!

Dear All,

As researchers, we always make some hypotheses to resolve some problem based on reviewing the relevant literature. For example, someone could prepare two materials (A and B) and hypothesize that material A would work better than material B for a certain application C. Then, we design an experimental program to pursue and validate our hypotheses. The experimental results are then reproduced (maybe more than once) to remove any device-related error and ensure the results reflect the actual work of the prepared materials or device. When we get “positive” results meaning that our hypothesis is valid, then that’s a big success. However, sometimes the experimental results prove our hypothesis is actually completely wrong which makes us feel disappointment. In that sense, those results could be described as “negative”.

Of course, we are more than happy to publish the “positive” results. But how about the negative ones? I’ve read some articles that we should still go ahead and publish them to save the time and effort of other researchers who are considering similar hypotheses. However, some academics may not agree with that and shy away from publishing some results that prove they were WRONG.

Also, there is the journal’s angle. I am not sure if an editor would welcome publishing an article with negative results in the same way if the article presents positive ones.

The business owners/managers might also have their own views in this regard.

Those questions keep coming back and forth in my mind so I decided to ask other researchers on a wide platform such as RG.

Look forward to knowing your thoughts.

Best wishes,

Ahmed

Dear Fellows,

I synthesize intermetallic nanoparticles by chemical reduction and disperse them on carbon support. The TEM equipment I use is unable to highly magnify above 40kx. Beyond that the whole focusing and alignment work is lost due to lower voltage (100 kV) and conventional LaB6 filament. I am attaching some micrograph examples.

I was wondering if it is OK to estimate the particle size distribution of <5-nm particles at such low magnification? Or it would give misleading values?

Cheers,

Ahmed