Publication detail

Characterization of Plasmachemical Treatment of Archaeological Artifacts

RAŠKOVÁ, Z., KRČMA, F., KLÍMA, M., KOUSAL, J.

Original Title

Characterization of Plasmachemical Treatment of Archaeological Artifacts

English Title

Characterization of Plasmachemical Treatment of Archaeological Artifacts

Type

journal article - other

Language

en

Original Abstract

Plasmachemical treatment of archaeological artifacts is a relatively new technique. Up to now, it has been used more or less intuitively in practice, but for a widespread application an exact characterization of the process is necessary. The process is based on using low-pressure hydrogen plasma in which the artifacts (in this case silver coins and some pieces of iron) are treated for several hours, usually in more steps. The problem is how long period of the plasmatic treatment is optimal and how to characterize its efficiency. From the kinetic point of view, the oxide and chloride molecules reduction is the main process. Significant, but not very intense radiation of the $\cdot $OH radical was observed in the optical emission spectra. Due to the fact that in pure hydrogen plasma the $\cdot $OH emission spectra is not overlapped by any radiation, we use its integral intensity in the range of 300 - 330 nm as an indicator of the oxides reduction effectiveness. The OH radiation shows specific dependence on time. Initially a fast increase, later a slower non-exponential decrease. The duration of the OH integral intensity decrease to the value of 10% of its maximum can be taken as the end of the reduction. It was found out that during the first two hours the reduction is completed. Besides, during the plasmachemical treatment of artifacts in ammonia-water vapour the intensities of the spectral lines of atomic hydrogen H(alpha) and H(beta) were measured as a function of plasmachemical treatment time. But in this case the end of reduction processes was difficult to estimate. The measuring device used for our experiments could be used in practice for plasmachemical treatment monitoring.

English abstract

Plasmachemical treatment of archaeological artifacts is a relatively new technique. Up to now, it has been used more or less intuitively in practice, but for a widespread application an exact characterization of the process is necessary. The process is based on using low-pressure hydrogen plasma in which the artifacts (in this case silver coins and some pieces of iron) are treated for several hours, usually in more steps. The problem is how long period of the plasmatic treatment is optimal and how to characterize its efficiency. From the kinetic point of view, the oxide and chloride molecules reduction is the main process. Significant, but not very intense radiation of the $\cdot $OH radical was observed in the optical emission spectra. Due to the fact that in pure hydrogen plasma the $\cdot $OH emission spectra is not overlapped by any radiation, we use its integral intensity in the range of 300 - 330 nm as an indicator of the oxides reduction effectiveness. The OH radiation shows specific dependence on time. Initially a fast increase, later a slower non-exponential decrease. The duration of the OH integral intensity decrease to the value of 10% of its maximum can be taken as the end of the reduction. It was found out that during the first two hours the reduction is completed. Besides, during the plasmachemical treatment of artifacts in ammonia-water vapour the intensities of the spectral lines of atomic hydrogen H(alpha) and H(beta) were measured as a function of plasmachemical treatment time. But in this case the end of reduction processes was difficult to estimate. The measuring device used for our experiments could be used in practice for plasmachemical treatment monitoring.

Keywords

optical spectroscopy, archaelogy, plasmachemical reduction, ancient metal conservation

RIV year

2002

Released

01.06.2002

Publisher

AV ČR

Pages from

D927

Pages count

6

BibTex


@article{BUT41209,
  author="Zuzana {Rašková} and František {Krčma} and Miloš {Klíma} and Jaroslav {Kousal}",
  title="Characterization of Plasmachemical Treatment of Archaeological Artifacts",
  annote="Plasmachemical treatment
of archaeological artifacts is a relatively new technique. Up to now, it
has been used more or less intuitively in practice, but for a widespread
application an exact characterization of the process is necessary. The
process is based on using low-pressure hydrogen plasma in which the
artifacts (in this case silver coins and some pieces of iron) are
treated for several hours, usually in more steps. The problem is how long
period of the plasmatic treatment is optimal and how to characterize its
efficiency. From the kinetic point of view, the oxide and chloride
molecules reduction is the main process. Significant, but not very intense
radiation of the $\cdot $OH radical was observed in the optical emission spectra.
Due to the fact that in pure hydrogen plasma the $\cdot $OH emission spectra is
not overlapped by any radiation, we use its integral intensity in the
range of 300 - 330 nm as an indicator of the oxides reduction effectiveness.
The OH radiation shows specific dependence on time. Initially a fast
increase, later a slower non-exponential decrease. The duration of the OH
integral intensity decrease to the value of 10% of its maximum can be taken
as the end of the reduction. It was found out that during the first two hours
the reduction is completed. Besides, during the plasmachemical treatment of
artifacts in ammonia-water vapour the intensities of the spectral lines of
atomic hydrogen H(alpha) and H(beta) were measured as a
function of  plasmachemical treatment time. But in this case the end of
reduction processes was difficult to estimate. The measuring device used
for our experiments could be used in practice for plasmachemical treatment
monitoring.
",
  address="AV ČR",
  chapter="41209",
  edition="NEUVEDENA",
  institution="AV ČR",
  journal="Czechoslovak Journal of Physics",
  number="D",
  volume="52",
  year="2002",
  month="june",
  pages="D927",
  publisher="AV ČR",
  type="journal article - other"
}