Robert Pietrasik

Single and Multilayer Growth of Graphene from the Liquid Phase

The preparation of poly crystalline graphene from the liquid phase has been discussed.The mechanism of graphene growth from the liquid phaseon the Cu-Ni alloy and the type of atmosphere, used inthe graphene fabrication-acetylene, ethylene, hydrogen has been presented. Stages of nucleation and poly crystalline growth of graphene were identified. The paper presents theresults of a single-and multi-layered graphene growth phase.It is assumed the final result will mean the optimization of the industrial-scale production of low-cost poly crystalline graphene.

Properties of Surface Layers Processed by a New, High-Temperature Vacuum Carburizing Technology with Prenitriding - PreNitLPC®

The variety of vacuum carburizing with prenitriding (PreNitLPC® technology) consists in metering ammonia in the stage of charge heating for carburizing to reduce grain growth in the surface layer of carburized steel. This paper presents the effect of nitrogen interaction on the reduction of austenite grain growth during vacuum carburizing and on the mechanical properties (fatigue strength, impact resistance) of the layer treated in this way in relation to conventional carburizing methods.

The effect of hydrogen in lubricated frictional couples

The tribological experiments under circumstances of hydrodynamic and elastohydrodynamic lubrication, the immersion test in lubricating oil as well as the exposure test to the environment have been performed to elucidate the effect of hydrogen on soft and hardened surface layers. The occurrence of the effect of hydrogen tribosorption in lubricated frictional nodes has been confirmed. This effect proceeds at a different rate and in a different way for nitrided surface layers (and homologous layers), on the one hand, and for other soft or hardened surface layers on the other. The most probable mechanisms of the tribosorption for both the cases mentioned above have been presented and the significance of that phenomenon for the theory as well as for practical operation has been discussed.

The Precipitation and Dissolution of Alloy Iron Carbides in Vacuum Carburization Processes for Automotive and Aircraft Applications - Part II

The article is dedicated to the experiments and tests on the phenomena of precipitation and dissolution of alloy iron carbides in vacuum carburization processes. Special attention has been paid to the possibility of using artificial neural networks to predict the speed of the processes examined. In the section below, we are presenting the precipitation phenomena taking place in vacuum carburization processes and the experiments that were conducted. Moreover, a qualitative and metallographic analysis of carbide phenomena was described together with the method of numerical modelling and predicting the processes with the use of artificial neural networks.

Resistance-temperature characteristics of CVD and high strength metallurgical graphene

Gas sorption conditions on the graphene surface, as well as their influence on graphene properties, play a significant role when applications are considered. The influence of temperature and pressure on electric properties of graphene were investigated and discussed within this work, which was conducted in order to determine the border values for the sorption and desorption process of hydrogen on the graphene surface. The temperature was changed within the range of 243-373 K. Two types of graphene were used for comparison: one of graphene synthesised by our own method using chemical vapour deposition (CVD) and one of high strength metallurgical graphene (HSMG) in both conducting (cHSMG) and semiconducting (scHSMG) varieties. The characteristics were determined under hydrogen atmosphere in a fitted apparatus under pressure. The overall target material relies on the hydrogen storage of a designed graphene-based composite.