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Study of plasmachemical reduction of corrosive layers on bronze
Zemánek, Nikola ; Selucká, Alena (referee) ; Krčma, František (advisor)
The application of low-pressure low-temperature hydrogen plasma on artificial corrosion layers on bronze has been studied. For this purpose, three sets of bronze corroded samples were prepared. The first step of the model sample preparation was grinding of the bronze surface by using emery with 60, then 280 and finally by 600 grains density, in order to achieve the defined surface roughness. The next step of the work were optical and scanning electron microscopy observations with energy dispersive X-ray micro analysis (SEM-EDX) of the prepared bronze sample for purpose of surface structure characterization and element composition determination. Bronze samples with defined surface structure were corroded in different corrosion atmospheres. Three different model corrosion layers were formed by acidic atmospheres of hydrochloric acid, nitric acid and sulphuric acid. The element composition and structure of corrosion layer was determined by SEM-EDX again. The different amounts of oxygen, nitrogen, chlorine, sulfur, copper, tin and lead in the corrosion layer according to different types of corrosion atmospheres were determined. The next and also main part of the work was a plasma chemical reduction of corroded samples. The plasma reactor used the RF discharge (13.56 MHz) created in quartz tube with outer electrodes. The generation of capacitively coupled plasma in continuous or pulse mode by different supplied power was carried out. The plasma radiation emitted from the RF discharge during the sample treatment was measured by optical emission spectroscopy. The quantity of OH radical created in an active discharge by reactions of atomic hydrogen with the corrosion layer is a significant indicator of a reduction process. Therefore the OH radical band integral intensities observed as a function of the treatment time were used as a monitor for plasma chemical reduction process. The OH emission showed different behavior depending on corrosion layer composition during the plasma treatment. The transformations of the corrosion layer due to the plasma effect were investigated by means of SEM-EDX once again. Changes in the element composition of corrosion (or surface) layers in consequence of plasma chemical treatment are given. Generally, the element composition after the plasma chemical treatment showed explicitly that oxygen and chlorine content in the corrosion layer decreased, nitrogen was removed totally. Metal deposition on the reactor wall was observed occasionally. The SEM-EDX analyzes also showed that in some cases the tin content in sample surface layers was significantly decreased. For that reason, in case of bronze sample (artifacts) treatment, the sample and plasma temperature seem to be very important parameters for the process optimization. The acceptable conditions for plasma chemical treatment has been found in case of corrosion layer formed by nitric acid, only. The other corrosions will be a subject of further studies.
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Study of plasmachemical reduction of corrosive layers on bronze
Miková, Petra ; Selucká, Alena (referee) ; Krčma, František (advisor)
One of the important stages of the human history is certainly Bronze Age, on our territory dated 1900 - 800 BC. At that times, it was produced many objects of bronze, such as swords, spears, daggers, ornaments, jewelry. These artifacts are now found by archaeologists in excavations around the whole world. During the years there was an exposure to various types of substances and the environment and result in extensive corrosion of the used materials. To better understand the culture and traditions of our ancestors, it is necessary to carefully eliminate the corrosion and thorough inspection of these subjects. In this work, we consider the model corrosion layers removal by reduction in low-temperature hydrogen plasma. Plasma chemical reduction method was developed during the eighties years of last century and currently is further rapidly improved. Unfortunately, the process mechanism is not yet precisely known. Preparation of model corrosion layers were as follows: bronze blocks (weight approximately 80 g) were sharpend by electrical grinding machine (used paper 280 and then 600). Thus treated samples were rinsed in ethanol, dryed by hot dryer and stored in plastic bags. A Petri dish was placed at the bottom of the desiccator and it was poured by 20 ml of concentrated hydrochloric acid. Above the bowl has punched ceramic grid, on which the samples were placed. Closed desiccator was placed in darkness at the ambient laboratory temperature. To accelerate the samples corrosion process in a desiccator, the samples were sprinkled with acid. Plasma chemical treatment was carried out in a cylindrical reactor of quartz glass with outer copper electrodes. The RF (13.54 MHz) capacitivelly coupled plasma was used for the samples treatment. For each sample have been selected specific conditions: power (50 - 300 W), pulse (duty cycle of 10 – 25 %) or continuous mode. The optical emission spectroscopy monitored dependence of OH- intensity during the reduction. The decrease to the 1/10 of the maximum value leads to end the experiment. Based on this criterion, the treatment time of samples was in the range of 30 - 80 minutes. Corrosion has been removed from 7 samples. All the samples were covered by corrosion deep green color with a clearly visible crystalline structure before their inserting into the reactor. After the treatment, the color was dark black, and after leaving the air began to surface green, in some samples was observed in white and yellow tint. Surface top layer was removed on samples 1 and 5, where spontaneous dropout was reached. The pulse mode with duty cycle of 10 % and the powers of 200 and 300 W were applied for these two samples. The surface layer of samples treated with pulsed mode of 25 % was easily removable by spatula. The work demonstrated the applicability of hydrogen RF plasma in pulsed mode for the corrosion removal from bronze samples. The further work will be focused on the optimal treatment conditions search.
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Reduction of bronze corrosion layers using hydrogen plasma
Miková, Petra ; Selucká, Alena (referee) ; Krčma, František (advisor)
This diploma thesis is focused to the plasma chemical reduction of model corrosion layers prepared on bronze samples. Bronze was the main material for production of the subjects in Bronze Age. First, it was very rare, and therefore was used only for making jewellery and other decorative subjects. Later, the objects of daily use and weapons were produced of bronze. These objects are found and it is necessary to restore him and preserve the cultural heritage for future generations. The research and the optimalization of plasmochemical reduction of model corrosion layers on bronze samples contributes to this. A metallographic grinder was used to create a defined surface, first with the sandpaper P 280 and then after sample 90 degree rotation with the sandpaper P 600. This ensured uniform surface at all bronze samples that is necessary to provide the same corrosion conditions. The grinded samples were washed by ethanol and dried by hot air stream. To prevent contact with the surrounding atmosphere and successive initiation of corrosion, the samples were stored in lockable polyethylene bags. This step was followed by the preparation of model corrosion layers. Hydrochloric and sulfuric acids were chosen as corrosive environments. Petri dish containing 20 ml of the selected acid was placed at the bottom of the desiccator. Samples were placed to the ceramic grate, over the dish, and they were corroded (in vapours of hydrochloric acid for 34 days and in vapours of sulfuric acid for 27 days). The corroded samples were treated using low-pressure hydrogen plasma excited by RF generator. Treatment of samples was carried out in quartz cylindrical reactor (length of 90 cm, inner diameter 9.5 cm) with copper electrodes placed outside. The pressure in the reactor was ranged around 160 Pa at hydrogen flow rate of 50 sccm during the experiments. The continuous and pulse modes (duty cycle of 25%, 50% or 75%) at peak power of 50–300 watts were used for the treatment of 90 minutes duration. The plasma treatment was monitored by optical emission spectroscopy of OH radical using compact Ocean Optics HR4000 spectrometer. Its integral intensity is proportional to the corrosion layer removal. The rotational temperatures of plasma were calculated using selected OH rotational lines, too. The sample temperature during the treatment was measured by thermocouple installed inside the additional non-corroded samples. The reduction of corrosion layer is successful when the maximum of relative intensity of OH radicals is produced and follow gradual decline. The samples which corroded in vapours of sulphuric acid and were treated in pulse modes with duty cycle of 25 % or with delivered power of 50 W has produced no maximum. To the remain samples the maximum although were observed, but reduced corrosion products on the surface were very cohesive. The maximum of relative intensity of OH radicals was observed at all samples corroded in vapours of hydrochloric acid. But there is problem with temperature of sample during experiment. The samples which layer of corrosion product was after experiment incoherent produced the layer of deposit tin. This effect formation at a higher temperature of sample during experiment and therefore with greater deliver energy.
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Artistic casting, theory and practice
Palčíková, Zuzana ; Záděra, Antonín (referee) ; Šenberger, Jaroslav (advisor)
This work deals with the history of the production of art objects by investment pattern. The first part describes the method of casting used in the past and present. Casting technology is described in terms of, mold manufacturing, production lost model used materials. First described in the technology currently used in the production of shell molds. Then is described a technology used since antiquity with the lost production model into plaster molds and then making clay molds. In the practical part of this work is studied the production of cast bull Bull rocks present methods and the method used in ancient times. The first method is the production of cast bull by shell casting. The second method is casting a clay mold and reconstruction of its original form. Finally, are compared castings produced by these two methods.
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Plasma chemical removal of bronze corrosion layers
Miková, Petra ; Slavíček, Pavel (referee) ; Tiňo, Jozef (referee) ; Krčma, František (advisor)
The thesis deal with applying low-pressure low-temperature plasma to corrosion products layers on bronze. Layers of corrosion products on samples were artificially prepared. As a result, they had the same composition and could be irreversibly destroyed during experiments, which would not be possible with real archeological artifacts. Bronze, copper and tin alloy, samples were cut with respect to the size of the plasma-chemical device. XRF was used to determine the bronze composition. Before being corroded by the active medium, each sample was washed with ethanol and dried with a hot air stream. Until now, the procedure was the same for all samples. During formation of corrosion products layers, two factors have to be taken into account: the time consumption and the corrosiveness of the active environment. By focusing on one or the other factor, several groups of samples with differently degraded surfaces were created. The fastest way was to place samples in a corrosion chamber where sodium chloride solution was applied at the elevated temperature. The samples were corroded within a few days there. Longer, but in terms of corrosion products layers compactness better way proved procedure where the samples were sealed in the desiccator. At the desiccator bottom the Petri dish with an inorganic acid was placed, in our case, with hydrochloric acid inside. This method corroded the samples within one month. The longest but the most closed to the real live method was the burial of samples into soil or compost. However, this method corroded the samples within two years. Final step after the samples were removed from any corrosive environment, were dried under low pressure and were placed in a barrier film made bag together with moisture and oxygen absorbers. So prepared samples with layers of corrosion products have been treated in a low-pressure low-temperature plasma. Treatment was carried out in the apparatus which is based on the reactor: cylinder of quartz glass having a diameter of 100 mm and a length of 900 mm. The reactor was supplied with a working gas or a mixture of working gases with a total flow rate of 50 sccm. In our case, one is pure hydrogen or a combination with argon. A rotary oil pump was used to provide vacuum. The reactor base pressure was 10 Pa before treatment, while during the treatment it was 150 Pa. High-frequency generator (13.54 MHz) was used for supply the system with energy through two copper electrodes located outside the reactor. According to the energy delivery method, the treatment was carried out in a continuous or pulse mode. The sample temperature was monitored during the experiment and were evaluated the emission spectra from OES. The sample temperature was one of the key factors. The measurement was first done with a thermocouple, later switched to a thermocouple with optical data transmission. A safe temperature was set and then the whole process was controlled through it. In addition, the effect of the energy delivery method, value of the delivered power, sample size, presence of incrusted layers and composition of working gas were studied. After application of plasma, samples were analyzed by SEM – EDX and XRD. After the evaluation of the acquired knowledge and experience, a real artifact - a bronze chisel from the site of Boskovice - was treated. This documentation lacked the artifact, so it could be used to verify the lessons learned about plasma chemical reduction.
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Verification of the original technologies used for art castings
Hřebíček, Lukáš ; Mrázek, Martin (referee) ; Horáček, Milan (advisor)
This diploma thesis is describing making of the same art casting by using different foundry technologies/ moulds (ceramic shell mould, several types of plaster moulds including anhydride gypsum and also natural sand mould). In this thesis there is also description of casting the famous piece of bull from “Byci skala” (Bull Rock). The bull was cast into traditional clay mould which is believed to be the original technology. Also the original shape of the bull casting was reconstructed, i.e. a copy of the original bull casting made. As the main achievement of this work is an overview and comparison of several technologies suitable for making art castings.
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Plasma chemical removal of bronze corrosion layers
Miková, Petra ; Slavíček, Pavel (referee) ; Tiňo, Jozef (referee) ; Krčma, František (advisor)
The thesis deal with applying low-pressure low-temperature plasma to corrosion products layers on bronze. Layers of corrosion products on samples were artificially prepared. As a result, they had the same composition and could be irreversibly destroyed during experiments, which would not be possible with real archeological artifacts. Bronze, copper and tin alloy, samples were cut with respect to the size of the plasma-chemical device. XRF was used to determine the bronze composition. Before being corroded by the active medium, each sample was washed with ethanol and dried with a hot air stream. Until now, the procedure was the same for all samples. During formation of corrosion products layers, two factors have to be taken into account: the time consumption and the corrosiveness of the active environment. By focusing on one or the other factor, several groups of samples with differently degraded surfaces were created. The fastest way was to place samples in a corrosion chamber where sodium chloride solution was applied at the elevated temperature. The samples were corroded within a few days there. Longer, but in terms of corrosion products layers compactness better way proved procedure where the samples were sealed in the desiccator. At the desiccator bottom the Petri dish with an inorganic acid was placed, in our case, with hydrochloric acid inside. This method corroded the samples within one month. The longest but the most closed to the real live method was the burial of samples into soil or compost. However, this method corroded the samples within two years. Final step after the samples were removed from any corrosive environment, were dried under low pressure and were placed in a barrier film made bag together with moisture and oxygen absorbers. So prepared samples with layers of corrosion products have been treated in a low-pressure low-temperature plasma. Treatment was carried out in the apparatus which is based on the reactor: cylinder of quartz glass having a diameter of 100 mm and a length of 900 mm. The reactor was supplied with a working gas or a mixture of working gases with a total flow rate of 50 sccm. In our case, one is pure hydrogen or a combination with argon. A rotary oil pump was used to provide vacuum. The reactor base pressure was 10 Pa before treatment, while during the treatment it was 150 Pa. High-frequency generator (13.54 MHz) was used for supply the system with energy through two copper electrodes located outside the reactor. According to the energy delivery method, the treatment was carried out in a continuous or pulse mode. The sample temperature was monitored during the experiment and were evaluated the emission spectra from OES. The sample temperature was one of the key factors. The measurement was first done with a thermocouple, later switched to a thermocouple with optical data transmission. A safe temperature was set and then the whole process was controlled through it. In addition, the effect of the energy delivery method, value of the delivered power, sample size, presence of incrusted layers and composition of working gas were studied. After application of plasma, samples were analyzed by SEM – EDX and XRD. After the evaluation of the acquired knowledge and experience, a real artifact - a bronze chisel from the site of Boskovice - was treated. This documentation lacked the artifact, so it could be used to verify the lessons learned about plasma chemical reduction.
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Settlement of Bohemian Paradise in the Period of Lusatian Urn Fields
Žilincová, Lucia ; Chvojka, Ondřej (advisor) ; Juchelka, Jiří (referee) ; Novák, Miroslav (referee)
Charles University in Prague, Faculty of arts Institute of Prehistory and Early History Lucia Žilincová SETTLEMENT OF BOHEMIAN PARADISE IN THE PERIOD OF LUSATIAN URN FIELDS Dissertation thesis Summary: The main aim of my dissertation thesis is to contribute to better understanding of the Bohemian Paradise settlement in the Lusatian urn fields period and its relation and contacts to the neighbouring areas. The basic source is archaeological material from seven cemeteries (Sovenice /bez. Mladá Boleslav/, Sovenice /bez. Nymburk/, Svijany, Svijanský Újezd, Koryta, Březina, Příšovice) and two settlements of the Lusatian culture (Turnov-Maškovy zahrady, Svijany). Its analysis is basis for enrichement knowledge of Lusatian material culture and its clue for completing of missing elements in chronological development. Inevitable part of this work is substitution of these localities to the Bomemian Paradise frame and classification in the wider space of this culture widespreading. On the base of acquired knowledge I will try to solve the question of possibility for comparation of the settlement and burial material of Lusatian culture. 2016
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Analysis of chemical composition of prehistoric artifacts of copper and copper alloys in Czech lands
Kmošek, Matěj ; Bláhová, Zuzana (advisor) ; Fikrle, Marek (referee)
This work deals with chemical composition analysis of prehistoric artifacts of copper and copper alloys in Czech lands. It purvey listing of individual methods of natural sciences research together with their capabilities and limitations. Development and current state of chemical compostition analysis is described in this work. Focus of this work is a database of results of chemical composition analysis from Czech and foreign laboratories. Data file in the database is evaluated in terms of geography, chronology and type of artifacts.
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Verification of the original technologies used for art castings
Hřebíček, Lukáš ; Mrázek, Martin (referee) ; Horáček, Milan (advisor)
This diploma thesis is describing making of the same art casting by using different foundry technologies/ moulds (ceramic shell mould, several types of plaster moulds including anhydride gypsum and also natural sand mould). In this thesis there is also description of casting the famous piece of bull from “Byci skala” (Bull Rock). The bull was cast into traditional clay mould which is believed to be the original technology. Also the original shape of the bull casting was reconstructed, i.e. a copy of the original bull casting made. As the main achievement of this work is an overview and comparison of several technologies suitable for making art castings.
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