XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
264
T3: P–10
Comparison of photoacoustic, diffuse reflectance, attenuated total
reflectance and transmission infrared spectroscopy
for the study of biochars
Sylwia Pasieczna-Patkowska
1
, and Jarosław Madej
2
1
Department
of
Chemical
Technology,
Faculty
of
Chemistry,
Maria
Curie
Skłodowska
University,
3
Maria
Curie-Skłodowska Square, 20-031 Lublin, Poland, e-mail: sylwia.pasieczna@poczta.umcs.lublin.pl
2
Department of Geotechnical Engineering, Faculty of Civil Engineering and Architecture, Lublin
University of Technology, Nadbystrzycka 40, 20-618 Lublin, Poland
Among many physicochemical methods of biochars examination, infrared spectroscopy has
been one of the most frequently used instrumental analysis methods and it is a powerful
technique for investigating molecular chemistry of biochars. A range of different infrared
techniques, including photoacoustic spectroscopy (PAS), attenuated total reflectance (ATR),
diffuse reflectance spectroscopy (DRS) and transmission spectroscopy (TS), can be utilized to
characterize biochars. However, all aforementioned techniques have some disadvantages and
limitations. Analysis of biochars and other carbon materials with a very high carbon content, by
transmission IR spectroscopy is extremely difficult due to the fact that such materials, being
optically opaque, almost completely absorb incident IR radiation. Grinding and dilution in
potassium bromide may cause the destruction of their structure. For this reason, analysis of these
materials is performed mainly by using ATR, DRS and PAS techniques.
Traditional transmission technique, the oldest and most commonly used, is useful only to
study a sample bulk, and the major problem is the interference of the water present in potassium
bromide used for the pellets preparation. Moreover, removing water from already made pellets
may introduce chemical changes in the carbon material sample. DRS, PAS and, to some extent,
ATR are free from interference caused by the presence of water. PAS and ATR are so-called
surface techniques which allow to distinguish the bulk of the sample from its surface [1]. TS
allows to see the bulk of the biochar. Additionally, DRS can analyze both bulk and surface,
depending on the method of sample preparation (grinding with potassium bromide or analyzing
the sample as is, respectively).
This study shows the effectiveness and usefulness of four different FT-IR spectroscopic
techniques in rapid and, in the case of PAS, ATR and DRS, non-destructive direct measurement
of the biochars formation in different pyrolysis temperatures. The comparison of the spectra
obtained by the four FT-IR techniques allows to conclude that although some differences are
observed between the corresponding spectra, any of these techniques can be used as efficient
tool to control biochar’s surface functional groups quality. Nevertheless, PAS and ATR seem to
be the best techniques of the four, since they require hardly any sample preparation,
simultaneously providing good quality spectra of biochars. Due to the differences in the position
and intensity of the bands in the spectra obtained using four different IR spectroscopy
techniques (PAS, DRS, TS, ATR), in order to acquire precise and accurate spectroscopic data,
one selected spectroscopic technique should be used consequently. This will prevent
inaccuracies while comparing the spectra of biochars made in different conditions.
Keywords: biochar; surface analysis; infrared spectroscopy
Acknowledgment
This study was supported by the grant from Switzerland through the Swiss Contribution to the enlarged
European Union.
References
[1] C.Q. Yang, J.R. Simms, Fuel 74 (1995) 543.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
265
T3: P–11
Study of thin layers obtained from polymer ceramic precursors on steel
substrates
Anna Nyczyk-Malinowska
1
, Wiktor Niemiec
1
, Grzegorz Smoła
1
,
and Zbigniew Grzesik
1
1
Faculty of Materials Science and Ceramics, AGH University of Science and Technology,
Al. Mickiewicza 30, 30-059 Kraków, Poland, e-mail: nyczyk@agh.edu.pl
Polymer ceramic precursors are an interesting alternative to the raw materials applied in
conventional ceramic technologies. The main advantages of these materials are low cost, easy
processing, outstanding versatility of obtainable shapes and wide application range. One of the
most notable features of polymeric ceramic precursors is their ability to form low-dimensional
ceramic structures, such as thin layers and films.
During this study, thin layers of polysiloxane networks have been applied on steel substrates
and pyrolysed at different temperatures to obtain ceramic coatings. These polysiloxane networks
have been synthesised by the hydrosilylation reaction of commercial Polymethylhydrosiloxane
(PMHS) and 2,4,6,8-Tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4
Vi
) at different Si-H to
Si-Vi molar ratios. Coatings obtained at different temperatures were characterized by FTIR
spectroscopy to examine the transformation process of cross-linked polysiloxane to ceramic
layers. Scanning Electron Microscopy (SEM) allowed for investigating the possible presence of
cracks and pores in a given coating, as well as its adhesion to the substrate. The topography of
the layers and mechanical properties were evaluated using Atomic Force Microscope (AFM). In
addition, X-ray diffraction (XRD) was used to characterize the phase composition of ceramic
material. Based on the results of these experiments, the material with the best properties was
chosen for further studies.
The high-temperature corrosion resistance of Si-C-O coatings obtained at 900°C with molar
ratios Si-H to Si-Vi 1:1 was investigated. The product layers that formed on the samples during
high temperature oxidation studies carried out under isothermal conditions were studied by
means of SEM, AFM and XRD techniques. The anti-corrosion test along with additional
investigations show the high level of oxidation protection that Si–C–O coated steels possess
compared to the same uncoated materials.
Keywords: layers; ceramic precursors; corrosion resistance
Acknowledgments
This work is financially supported by the Polish National Science Centre (NCN) – Grant No.
2016/21/D/ST8/01688.
Dostları ilə paylaş: |