In this work, the metal and slag phase mixing in three steps of a ladle refining operation of steel melts and for an oxygen balance during cooling of cast iron melts have been studied at two Swedish steel plants and at two Swedish cast iron foundries, respectively. In order to predict the oxygen activity in the steel bulk in equilibrium with the top slag as well as in metal droplets in the top slag in equilibrium with the top slag, three slag models were used. In addition, the assumptions of a sulphur-oxygen equilibrium between steel and slag and the dilute solution model for the liquid steel phase were utilized in the calculations. Measured oxygen activities in steel bulk, which varied between 3.5-6 ppm, were compared to predicted oxygen activities. The differences between the predicted and measured oxygen activities were found to be significant (0-500%) and the reasons for the differences are discussed in the thesis. Slag samples have been evaluated to determine the distribution of the metal droplets. The results show that the relatively largest numbers of metal droplets are present in the slag samples taken before vacuum degassing. Also, the projected interfacial area between steel bulk and top slag has been compared to the interfacial area between the metal droplets and slag. The results show that the droplet-slag interfacial area is 3 to 14 times larger than the flat projected interfacial area between the steel and top slag. Furthermore, the effect of the reactions between top slag and steel and the slag viscosity on the metal droplet formation is discussed. The results show significant differences between the steel bulk and steel droplet compositions and the reasons for the differences are discussed in the thesis. The oxygen activity in different cast irons was studied. Plant trials were performed at three occasions for lamellar, compacted and nodular iron melts. The results show that at temperatures close to the liquidus temperature the oxygen activities were 0.03-0.1 ppm for LGI, around 0.02 ppm for CGI, and 0.001ppm for SGI. In addition, it was found that as the oxygen activities increased with time after an Mg treatment, the ability to form a compact graphite or a nodular graphite in Mg-treated iron melts was decreased. Also, extrapolated oxygen activity differences up to 0.07 ppm were found for different hypoeutectic iron compositions for lamellar graphite iron at the liquidus temperature. Overall, the observed differences in the dissolved oxygen levels were believed to influence how graphite particles are incorporated into the austenite matrix and how the graphite morphology will be in the cast product. / <p>QC 20160518</p>

The entry part introduce into the problematic of rework processes by molding injection tools for thermoplastic. Aim is necessity of change current rework process usage by electro discharge machining (EDM) technology.The theoretical part of the thesis describes the physical essence of EDM technology, the system of production of cutting electrodes and related issues. The practical part of work compare the process of production of copper and graphite electrodes with focus on production time and costs. The production parameters of the EDM process were analyzed and the wear of copper and graphite electrodes during the production process was compared. Main result of the thesis is an evaluation of the research activity, interpretation of the results of this activity and a proposal of measures to shorten the production time of the cutting electrodes and the time of the EDM machining by these electrodes.

The aim of this thesis is to elaborate a strategic analysis of the company KOH-I-NOOR Grafit, s.r.o., on this basis set vision and conceive a strategy suggestion. Principal methods of external analysis are PEST analysis and Porter's 5-forces model, in internal analysis are used analysis of internal sources and financial analysis. The next method is SWOT analysis, which sums up and interconnects the most important findings of previous analyses; on this ground is set a strategy of a chosen company and suggest a strategy.

I kommersiella litiumjonbatterier används ofta grafit i anodmaterialet, främst på grund av att det reversibelt kan placeras litiumjoner mellan dess lager. Grafit har dock en begränsad energitäthet och forskning bedrivs därför för att finna metoder som kan öka energitätheten hos anodmaterialet. Kisel, som har en betydigt högre energitäthet, kan interkalleras i grafiten för att öka energitätheten. För att undvika en förstörande volymexpansion som sker under litieringen när kisel tillämpas måste interkalleringen göras med kiselnanopartiklar. En skalbar metod för att framställa kiselnanopartiklar på nanografitflak har tagits fram och presenterats i en artikel av Phadatare et al. Syftet bakom det här arbetet har varit att lägga grund för en storskalig produktion av kiselbaserade anoder avsedda att användas i litiumjonbatterier för att ge dem en ökad kapacitet. Målet med arbetet var att genom laborativa undersökningar presentera hurvida metoden presenterad i artikeln är repeterbar samt hur olika parametrar påverkar resultatet inför en uppskalning. Resultaten bekräftade att metoden presenterad i artikeln är repeterbar och att den tillhörande ugnsprocessen bör utföras i en rörugn. Resultaten visade också att temperaturen för ugnsprocessen inte bör sänkas till så lågt som 600 °C, men att potential finns för att kunna sänka temperaturen från nuvarande 800 °C. Vid nuvarande temperatur bör andelen kisel inte ökas till ≥ 47 %, men bedöms ha potential att kunna ökas från nuvarande 33 %. Resultaten visade endast en liten bildning av kiselnanopartiklar då ett kiselpulver av annan kvalitet än det beskrivet i artikeln användes och visade på att valet av utgångsmaterialet är av stor vikt. Resultaten visade vidare att dispergeringsmedlet polyvinylakohol, PVA, inte kan uteslutas. Resultaten tydde på att det finns potential för att kunna minska andelen PVA, men att det inte bör reduceras till motsvarande en halverad koncerntration av vad som presenterats i artikeln. Resultaten visade också att processen måste utföras i en syrefattig miljö för att inte orsaka oxidaton av nanografiten. Däremot tydde resultaten på att mekanismen för bildningen av kiselnanopartiklar inte är syrekänslig och att mekanismen inte tycks vara beroende av att just PVA utgör den, om teorin stämmer, nödvändiga vätekällan. / In commercial lithium ion batteries graphite is often used in the anode material, mainly because it can reversibly contain lithium ions between the layers. However, graphite has a limited energy density and research is therefore being performed to find methods that will increase the energy density of the anode material. Silicon, which has a significantly higher energy density, can be intercalated in the graphite to increase the energy density. However, in order to avoid a destructive volume expansion that occurs during the lithiation, the intercalation must be performed with silicon nanoparticles. A scalable method for producing silicon nanoparticles on nanographite flakes has been developed and presented in an article by Phadatare et al. The purpose behind this work has been to lay the foundation for large-scale production of silicon- based anodes intended to be used in lithium-ion batteries to provide them with increased capacity. The aim of the work was to present whether the method is repeatable and how different parameters affect the results for an upscaling, which was done through laboratory investigations. The results confirmed that the method presented in the article is repeatable and that the process should be carried out using a tube furnace. The results also showed that the temperature of the oven process should not be lowered to 600 °C, but that there is potential to lower it from the current 800 °C. At the current temperature, the percentage of silicon should not be increased to ≥ 47 %, but is considered to have the potential to be increased from the current 33 %. Only a small proportion of silicon nanoparticles was formed when a silicon powder of a different quality than that described in the article was used and showed that the choice of the silicon starting material is of great importance. The results further revealed that the dispersant polyvinyl alcohol, PVA, cannot be excluded. The results showed that there is potential to reduce the proportion of PVA, but that it should not be reduced to as much as half the concentration that is presented in the article. The results showed that the process must be carried out in an oxygen-poor environment in order not to cause oxidation of the nanographite. However, the results also indicated that the mechanism for the formation of silicon nanoparticles is not oxygen sensitive and that the mechanism, if the existing theory is correct, does not appear to be dependent on PVA beeing the source of hydrogen.

This diploma thesis deals with an issue of lithium-ion batteries, primarily with negative (anode) electrode materials. Natural graphite in two forms, namely flake and expanded graphite, is used in the thesis as active electrode material. It is concerned with study of their capacity and output characteristics depending on the pressing pressure and discharging current. The first part of thesis consists of theory and describes basic principles and the composition of lithium-ion batteries. Materials, their characteristics used in production and theoretical description of measurement techniques are presented then. The second part of the thesis is focused on production, assembling and measurement of the characteristics of the produced electrodes. The aim of the thesis is finding the effects of changes of pressing pressure on the capacity, stability during cycling and stability at higher loads.

This thesis deals with the detection of gases. Based on the research, the theoretical part is devoted to the principles and construction of chemical gas sensors, especially the chemoresistive gas sensors, mainly with the active layer consisting of metal oxides and carbon nanotubes. In the second half of the theoretical part the carbon nanostructures, their properties and the methodology of preparation are reviewed. The experimental part deals with the type of support structure, preparation of the active layer and the method of its deposition and he principle of detection. In the results and discussion, the thesis focuses on the detailed processing of the results and the evaluation of the response ammonia, the impact of the modifications and procedures. In the end, the results obtained are compared, both with each other and with the relevant literature.

Tato práce je zaměřena na zlepšení tepelného managementu mikroelektroniky implementací materiálů na bázi uhlíku, přesněji grafitových fólií, do tepelné architektury mikroelektroniky. Práce začíná vysvětlením současných metod chlazení a výzev v oblasti mikroelektroniky. Poté přechází k běžně používaným materiálům - hliníku a mědi a přidává do výběru i uhlíkové alotropie. Ve druhé části tato práce obsahuje několik příkladů použití pyrolytické grafitové fólie v tepelném managementu mikroelektroniky, prokazuje jeho použitelnost a analyzuje přínosy pro šíření tepla, tepelnou vodivost při dodržení elektrické izolace a možné využití ve flexibilní elektronice.

Raman spectroscopy is an irreplaceable method for chemical and structural characterization of many substances. This is especially true for carbonaceous matter. It is non-destructive and capable of determining the crystallinity of the studied carbonaceous phase, and subsequently, with the aid of empirical relations, also the temperature of formation of the rock under study. Until very recently, the most of the Raman spectroscopy measurements was conducted only single point-wise on grains chosen on purpose, e.g., in an optical microscope. Alongside with the evolution and affordability of the Raman spectroscopic technique it is now very appealing to utilize the possibility of Raman mapping coupled to the automated analysis of large quantities of acquired spectra. The aim of this study was to critically evaluate the pros and cons of such an approach on selected rocks with varying carbon content and crystallinity of the carbonaceous phase. The samples range from graphite, Karelian shungite, elemental carbon-rich carbonates, alpine schist to eclogite. In general, we can rate the large area mapping as suitable in many cases, however, there are certain issues associated with the method, especially concerning the sample preparation and automated analysis. Several actions are proposed to limit the pitfalls...

Demand for high-quality graphite is expected to experience an extraordinary growth rate, in large part due to its wide range of industrial applications such as adsorbents, lubricants, electrodes, etc. This thesis developed a novel sustainable approach to produce green-graphite materials by applying biochar, acarbon-rich valuable by-product obtained from biomass, as a carbon precursor. Meanwhile, iron-based catalysts are applied to enable the graphitization at a relatively lower temperature. This study focuses on the different parameters which could affect the evolution of carbon structure. The samples were mixed with catalyst in two ways, dry mixing and wet impregnation. Aside from the addition method, several parameters including temperature, heating duration, and iron loading amount were varied from 800 to 1300 ℃, 1 to 6 hours, and 0 to 33.6% respectively, to figure out an optimum graphitization process. The samples were characterized by X-ray diffraction, Raman scattering, SEM and particle size distribution analysis. Based on the characterization results, it was confirmed that with the increase of the graphitization temperature, duration and amount of iron loading, synthetic graphite performs a better graphitization and a higher conversion rate. Meanwhile, a detailed dissolution-precipitation mechanism was introduced and discussed in the context of iron-carbon equilibrium phase diagram to explain this catalytic process. / Efterfrågan på högkvalitativ grafit förväntas uppleva en extraordinär tillväxttakt, till stor del på grund av dess breda utbud av industriella applikationer som adsorbenter, smörjmedel, elektroder etc.  Denna avhandling utvecklar ett nytt hållbart tillvägagångssätt för att producera grön-grafit genom att använda biokol, en kolrik värdefull biprodukt erhållen från biomassa, som en kolprekursor. Även järnbaserade katalysatorer används för att möjliggöra grafitisering vid relativt lägre temperaturer. Denna  studie fokuserar på  de olika  parametrar  som  kan  påverka  bildandet  av kolstrukturen. Proverna blandades med katalysatormaterialet på två sätt, torrblandning och våtimpregnering. Förutom tillsatsmetoden justeras flera andra parametrar, inklusive temperatur, uppvärmningstid och mängd järnbelastning för  att  få  en optimal  grafitiseringsprocess.  Proverna karakteriserades därefter genom röntgendiffraktion, Ramanspridning, SEM och  partikelstorleksfördelningsanalys. Baserat på karakteriseringsresultaten bekräftades det att med en ökande grafitiseringstemperatur, varaktighet och mängd av järnbelastning, får syntetisk grafit en bättre grafitisering och en högre omvandlingsgrad. Även en detaljerad upplösnings-utfällningsmekanism introducerades och diskuterades i sammanhanget av järn-kol jämviktsfasdiagrammet  för  att förklara den katalytiska processen.

Mikrovågsuppvärmning är en viktig process som används i många industriella tillämpningar. Användningen av mikrovågsuppvärmning inom industri är dock inte lika utbredd som den har potential till att vara på grund av orsaker som säkerhet, strålning och brist på kunskap. Arbetets mål är att få ökad förståelse för hur materialegenskaper som permittivitet, termisk ledningsförmåga och elektrisk ledningsförmåga påverkar upphettning i mikrovågsugn. För att åstadkomma detta utförs simuleringar samt experiment på grafit som undersöks under mikrovågsuppvärmning i kiln anpassad för mikrovågsugn. Resultaten jämförs med liknande simulationer av det dielektriska materialet regolit. Händelsen simuleras först i COMSOL Multiphysics varefter korresponderande laboration utförs i verkligheten. För att åstadkomma fungerande simulation i COMSOL kalibreras den med hjälp av en tidigare utförd simulation av kiln i mikrovågsugn samt med COMSOLs egna Microwave Heating-tutorial. Under arbetets gång läggs mycket energi på att optimera simuleringen utefter diverse problem, exempelvis att simulationen är väldigt krävande. Slutligen uppnås fungerande simuleringar som relaterade väl till det riktiga experimentet.