High Temperature Surface Conductivity of Hydrogenated Diamond Films Exposed to Humid Air

Surface conductivity of thin diamond films was measured as a function of temperature up to 450°C. Hydrogenated diamond was synthesized by chemical vapor deposition in hydrogen/carbon plasma. Low values of charge carrier activation energy ( ≈ 10 meV) were observed, when hydrogenated diamond films were exposed to the ambient humid air. However, the activation energy increased by two orders of magnitude as film temperature exceeded 300°C. We have attributed this behavior to the desorption of the $H_2O$ adlayer. The jump of the activation energy did not occur, when experiment was performed in vacuum. We have also shown that donor doping leads to the up-shift of the Fermi level much above the acceptor-like band gap levels induced by surface C-H bonds, which cannot be compensated by transfer of electrons from diamond to the double $H-H_2O$ layer

High Temperature Surface Conductivity of Hydrogenated Diamond Films Exposed to Humid Air

Surface conductivity of thin diamond films was measured as a function of temperature up to 450°C. Hydrogenated diamond was synthesized by chemical vapor deposition in hydrogen/carbon plasma. Low values of charge carrier activation energy ( ≈ 10 meV) were observed, when hydrogenated diamond films were exposed to the ambient humid air. However, the activation energy increased by two orders of magnitude as film temperature exceeded 300°C. We have attributed this behavior to the desorption of the $H_2O$ adlayer. The jump of the activation energy did not occur, when experiment was performed in vacuum. We have also shown that donor doping leads to the up-shift of the Fermi level much above the acceptor-like band gap levels induced by surface C-H bonds, which cannot be compensated by transfer of electrons from diamond to the double $H-H_2O$ layer

Application of novel nondestructive techniques to investigations of historical plasters: a case study of sgraffito decoration in Bożnów

Skuteczność konsolidacji rozwarstwionych i osłabionych strukturalnie tynków zabytkowych wymaga zarówno doboru odpowiednich środków konserwatorskich jak i znajomości zakresu występującej destrukcji. W czasie prac konserwatorskich przy dekoracji sgraffitowej w Bożnowie (Polska), w celu określenia zakresu występujących zniszczeń tynków, po raz pierwszy wykorzystano równocześnie technikę termowizyjną i radarową. Badania nieniszczące zostały uzupełnione analizami pobranych próbek metodami petrograficznymi, mikrochemicznymi oraz spektroskopowymi. Badania termowizyjne i radarowe powtórzono po zakończeniu prac konserwatorskich, co pozwoliło na ocenę skuteczności wykonanych zabiegów.The efficiency of consolidation of exfoliated and weakened historical plasters not only requires the choice of appropriate materials and careful examination of the range of destruction. In order to evaluate the deterioration of plasters of the sgraffito decoration in Bożnów (Poland) both thermovision and ground penetrating radar (GPR) techniques were applied jointly for the first time ever. Nondestructive testing was preceded by analysis of samples with petrographic, micro-chemical and spectroscopic methods. Thermovision and radar examination was repeated after the completion of restoration works, which allowed evaluating the efficiency of treatment performed. Sgraffito ornamentation on the northern wall of the western tower of the church in Bożnów was completed by Christoph Rutsch and his two assistants in 1609. The two-color technique was applied. Ornaments were scratched in moist, white lime paint applied on fresh lime plaster colored grey with charcoal. A collective character of the work is visible due to diversified workout of figures, ornaments and inscriptions. In the 19th century the sgraffito must have already been deteriorated and looked unattractive so it was punched with a hammer and covered with a layer of plaster. In 1931 the decoration was discovered by German scholars but it was plastered up again due to a poor state of preservation. It was uncovered again in 1972 and subjected to restoration treatment. For over 30 years the object was exposed to rainwater from the tower roof, which washed out lime paint and yield delamination and plaster losses. Except rainwater also capillary water was responsible for the deterioration of the ornament, as well as changing temperature and humidity conditions characteristic of outdoor exposure

The Importance of Structural Factors for the Electrochemical Performance of Graphene/Carbon Nanotube/Melamine Powders towards the Catalytic Activity of Oxygen Reduction Reaction

In this paper, we show the carbonization of binary composites consisting of graphene nanoplatelets and melamine (GNP/MM), multi-walled carbon nanotubes and melamine (CNT/MM) and trinary composites containing GNP, CNT, and MM. Additionally, the manuscript presents results on the influence of structural factors for the electrochemical performance of carbon composites on their catalytic activity. This study contributes to the wide search and design of novel hybrid carbon composites for electrochemical applications. We demonstrate that intensive nitrogen atom insertion is not the governing factor since hybrid system modifications and porous structure sometimes play a more crucial role in the tailoring of electrochemical properties of the carbon hybrids seen as a noble metal-free alternative to traditional electrode materials. Additionally, HRTEM and Raman spectra study allowed for the evaluation of the quality of the obtained hybrid materials

Luminescence from β-Irradiated Graphene Layers

We found that β-irradiated samples of crystallite graphite and multi-walled carbon nanotubes emit light during heating above room temperature. This behaviour is rather surprising for semimetals. Due to the lack of deep enough energy gap, this optical emission cannot be associated with interband transitions, as it is usually assumed in a thermally stimulated luminescence model. We suppose that the reported accumulated luminescence is the result of thermally stimulated relaxation of some kind of defects created in graphene structures by ionising radiation and therefore we offer to name it the relaxoluminescence. We anticipate the relaxoluminescence to be a starting point for developing a new spectroscopic method for nanotechnology. It can also throw a new light on the nature of defects, which are suspected of being responsible for strange magnetic effects in carbon