The aim of this research, part of a wider program called SPOFIC, is to investigate how the casting procedure affects the concentration of hydrogen and nitrogen gases in Compacted Graphite Iron used for the production of truck cylinder blocks. Hydris equipment was used for the Hydrogen measurements and the Optical Emission Spectroscopy and combustion analysis methods were used for the nitrogen measurements. The experiment was performed in one of the cooperating foundries. It was found that Hydrogen content is increased during pouring of the melt into the mold but nitrogen content does not seem to be effected by the process. In both cases the gas content never exceeded the solubility limit. The results are comparable with results from similar researches regarding Gray Cast Iron. / SPOFIC

Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1980 / Includes bibliographcial references. / by Farhad Hakimi. / M.S. / M.S. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

The purpose of this master thesis was to evaluate variations in solidification and cooling rate in compacted graphite iron prototype cylinder blocks and for each position relate this to the microstructure and also relate the microstructure to mechanical properties. This has been done to increase the knowledge to predict mechanical properties in cast iron components. There were three sample categories; reference-, tensile test- and thermocouple samples. The investigation included analysis of cooling curves, SinterCast parameters, image analysis, measured hardness and tensile strength. Thermocouples of type N were used at interesting positions for observation of the cooling behaviour and the image analysis was carried out by the software Axio Vision SE64 by Carl Zeiss GmbH. The hardness was measured according to Brinell HBW 5/750 and tensile testing was performed according to standard SS-EN ISO 6892-1:2009. It is concluded that the microstructure depend on many parameters, one of them is the position in the cylinder block. A relation between solidification time and the microstructure features; secondary dendrite arm spacing and eutectic cell size was observed. Because of dissimilarity in microstructure between the tensile test samples and thermocouple samples it is believed that the thermocouples have contributed with a cooling and/or nucleation effect. Considering the mechanical properties there is not solely the nodularity, eutectic cell size or secondary dendrite arm spacing that are the controlling microstructure feature, more research needs to be made.

Compacted Graphite Iron offers mechanical properties in between of gray cast iron and ductile iron. Thus,the material is seen as a hopeful alternative for engine cylinder blocks and heads satisfying environmentaland performance objectives. Nevertheless, CGI is more difficult to machine than conventional gray castiron due to the presence of MnS and thin wall section of probing high strength. This problem of CGI thenled to the initiation of large Optima Sweden project to study machinability and optimization of related toCGI.The thesis is centered on a study of tool life, cutting force and MRR with regards to machining parametersmainly feed rate and cutting speed for CGI milling. Tool life is measured; flank-wear is observed andcompared between several combinations of cutting parameters.Similarly cutting forces were measured using LMS software for full factorial design experiments. Extensivemachining experiments were carried out. Machining tests was done based on Design of Experiment (DoE)for high cutting data and lower data are performed separately. Comparison is made for tool life and cuttingforces. After data collection, analysis of tool life and force has been followed. Once the data is analyzedand checked its consistency. An approximate model is developed using MODDE software. Further, multiobjective optimization of tool life and Material removal rate (MRR) using cutting parameters mainly feedrate and cutting speed are investigated. Working on optimal parameters will allow for CGI is to becompetitive in manufacturing with gray CI, aluminum alloy, magnesium.Keywords: Compacted Graphite Iron (CGI), face milling, tool life, MRR, optimization, cutting force

We studied the effect of low energy (30 keV) ionic implantation of Ga+ in the direction parallel to the graphene planes (perpendicular to the c-axis) in oriented graphite ribbons with widths around 500 nm. Our experiments have reproducibly shown a reduction of electrical resistance upon implantation consistent with the occurrence of ionic channeling in our devices. Our results allow for new approaches in the modulation of the charge carrier concentration in mesoscopic graphite.

The existence of superconductivity in graphite has been under discussion since the 1960s when it was found in intercalated graphitic compounds, such as C8K, C8Rb and C8Cs. However, it was only about 40 years ago when the existence of superconductivity in pure graphite came up. In this work we directly investigate the interfaces highly oriented pyrolytic graphite (HOPG) has in its inner structure, since they play a major role in the electronic properties. The results obtained after studying the electrical transport provide clear evidence on granular superconductivity localized at the interfaces of graphite samples. Zero resistance states, strong current dependence and magnetic field effect on the superconducting phase support this statement. Additionally, an abrupt reduction in the measured voltage at temperatures from 3 to 175 K has been observed. However, the upper value of this transition temperature seems to not have been reached yet. A possible method to enhance it is to increase the carrier density of graphite samples. In order to preserve to quasi-two-dimensional structure of highly oriented pyrolytic graphite, chemical doping has been dismissed in the frame of this work. We used an external electric field to move the Fermi level and, hence, try to trigger superconductivity in multi layer graphene samples. A drop on the resistance at around 17 K has been measured for a large enough electric field applied perpendicular to the graphene planes. This transition is strongly affected by magnetic field and only appeared at low temperatures. As a result of the studies included in this work, it appears clear that graphite has a superconducting phase located at certain interfaces with a very high transition temperature.

Asymmetries in physisorbed systems give rise to interesting phases and phase transitions in two-dimensional (2D) monolayer and multilayer systems. The effects of asymmetric adsorbate and substrate interactions in monolayers of dipolar molecules on ionic substrates and N2 on graphite are studied. In the case of dipolar molecules on ionic substrates, 2D dielectric phase transitions using a modified Blume-Emery-Griffiths (BEG) model are determined theoretically. A dipole adsorbed vertically above a metal ion lattice site, and pointing up (down), is assigned a spin s=+1 (s=-1). An empty lattice site is assigned a spin S=0. Analytic solutions for both ferroelectrically and antiferroelectrically ordered systems are found. The model is applied to CO adsorbed on MgO and NaCl, and preliminary results for the phase diagram of CH3F on NaCl, are presented. Multilayer phase transitions for N2 on graphite are studied experimentally using synchrotron x-ray diffraction. The system is measured to undergo layering transitions, where the number of layers increases as the temperature of the system increases. A new multilayer phase diagram based on our results and the combined results published by other researchers is presented. The effects of capillary condensation on this multilayer system are quantified, and it is determined that its primary effect is to broaden the discrete layering transitions. The results for both studies are put into context with other adsorption systems with asymmetric interactions.

No description available.

Interference effects of co-generated hydrides of arsenic, antimony, bismuth and selenium on trapping behavior of selenium or antimony hydrides (analytes) within iridium modified, transversely heated graphite tube atomizer (THGA) was investigated. A twin-channel hydride generation system was used for independent separate generation and introduction of analyte and interferent hydrides, i.e. in simultaneous and/or sequential analyte-interferent and interferent-analyte mode of operation. Influence of the analyte and modifier mass, interferent amount, trapping temperature and composition of the gaseous phase was studied. A simple approach for elimination of mutual interference effects by modification of the gaseous phase with oxygen in substoichiometric ratio to chemically generated hydrogen is proposed and suppression of these interference effects is demonstrated. A hypothesis on mechanism of trapping and mutual interference effects is drawn.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20000号 / 工博第4244号 / 新制||工||1657(附属図書館) / 33096 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM