Papers by Author: Marina Davydova

Abstract: Synthetic diamond has remarkable properties comparable with natural diamond and hence is a very promising material for many various applications (sensors, heat sink, optical mirrors, cold cathode, tissue engineering, etc.). Nowadays, deposition of diamond films is normally employed in chemical vapor deposition (CVD) usually at high temperatures (800900 °C), what limit its application to high melting substrates. Gravimetric (mass) sensors belong to the major categories of chemical sensors and the most common type of mass sensor is the bulk acoustic quartz crystal microbalance (QCM). This contribution deals with a nanocrystalline diamond (NCD) growth from the H₂/CH₄/CO₂ gas mixture at low temperature (400 °C) by pulsed linear antenna microwave plasma system on 10 MHz circular AT-cut quartz resonators substrate. Gas sensor based on the NCD-coated QCM was developed for detection of ammonia (NH₃) at room temperature. Measurements not only confirmed the functionality of this first published NCD-coated QCM sensor, but in addition its sensitivity was twofold to a virgin QCM sensor with a gold active layer.

Abstract: Nanofibers are very promising new type of material with a broad range of possible applications. The new NANOSPIDER technology opens a possibility to produce nanofabrics in an amount large enough for them to start being interesting as a construction material. There are many so-called passive applications of nanotextiles (including different types of filters and protective layers), and active applications, when the active chemical agent is incorporated in their structure. In the present paper, however, the new possible application of nanofabrics is proposed: as a base material on which technically interesting nanoclusters are heterogeneously nucleated. The basic thermodynamics of heterogeneous nucleation on nanofibers is considered. The extreme curvature of nanofibers manifests itself in an energetic barrier of nucleation, which is quite different from a case of nucleation on a flat surface. The expression for Gibbs energy of cluster formation is derived, taking into account the elastic strain resulting from a volume (or shape) changes during nucleation.

Abstract: In the present work, the statistics of fragmentation is being studied in experiments with thin glass plates under uniformly distributed quasi-static loads. For this purpose the original pneumatic setup was manufactured. The glass plate is placed into a "sandwich" in order to fix the fragmentation pattern after unloading and to photograph it by a digital camera. A photoimaging and computer processing technique are used to assess the fragment areas and the total crack length.