| Author | Message | ||
     Art Springsteen (artspring) Senior Member Username: artspring Post Number: 36 Registered: 2-2003 |
Hello Carlos and Dave, David is correct- one of the big challenges of finding a 'good' carbon black with which to make standards is finding one that is spectrally 'neutral'. Some are, some aren't, depending on how they are made, residual hydrocarbons, etc. Graphite is a different matter- because of its laminar structure it is more specular at longer wavelengths and the reflectance increases with wavelength, making it pretty much useless for what we do. All that being said, it's difficult to pick out any structure in either graphite or carbon black unless it is highly diluted, or at least that's what we've seen, with PTFE or barium sulfate. It's my experience that most of the absorptions we see are in The C-H regions, both aromatic and aliphatic. | ||
| David W. Hopkins (dhopkins) Senior Member Username: dhopkins Post Number: 184 Registered: 10-2002 |
Hi Carlos, Welcome to the Discussion Group. I think you have chosen a difficult material to research using NIR. This region of the spectrum is primarily sensitive to compounds containing H bonded to heavier atoms such as C, N, S and O. What do you want to measure in graphite? You may be able to measure some contaminants, if you are careful to select good measurement conditions. I have measured various lots of Carbon Black. The material has been of interest in highly absorbing samples, Mixtures of CB in PTFE are available as absorbance standards. I can recommend the website of Art Springsteen's company, http://www.aviantechnologies.com/, but the emphasis there is particularly to select CB with no features. I think mixtures of graphite in PTFE, which is also available from Art, might enable you to get good measurements of fine details in your samples, if you select a suitable reference standard. I can well imagine that you would find conflicting information, because for many published spectra, the only features that would be observed would be noise. You will have to be cautious in your measurements to avoid measurements beyond the range of the spectrometer's capability. Best regards, Dave | ||
| Carlos Speglich (carlos) New member Username: carlos Post Number: 1 Registered: 8-2010 |
Hello all. I'm working with graphite, and one of the methods that must use is NIR, but I did not found a reliable source of information on that matter. A lot of curves have conflicting information, so I would like to know with you could point me some data base. Thanks a lot Carlos Speglich |