In fusion environment, large amount of helium (He) atoms are produced by transmutation along with structural damage in the structural materials, causing materials swelling and degrading of physical properties. In this thesis, using first-principles method, I examined the microscopic mechanism of He trapping in vacancies and voids in structural materials (vanadium solid and 6H–SiC composites). In vanadium, a single He atom located in the tetrahedral interstitial site (TIS) turned out to be more stable than that in the octahedral interstitial site (OIS). Helium atoms were placed one by one into the vacancy defects (monovacancy and void) from the remote TISs, and we calculated the trapping energies as a function of the number of He atoms inside the vacancy defects. We found that, the monovacancy and void (about 0.6 mn in diameter) can host up 18 and 66 He atoms, respectively, in vanadium solid. The induced internal pressure by He bubbles in monovacancy and small void increased up to 7.5 GPa and 19.3 GPa, respectively. In vacancy defect, the He–He equilibrium distances decreased with the amount of He atoms incorporated in monovacancy and small void, and the host lattice expanded dramatically. The atomic structures of selected He clusters trapped in vacancies were compared with the gas-phase clusters. In complex 6H–SiC, there are ten kinds of interstitial sites for a single He atom. According to the calculated formation energy, the most stable site is the. R site. [1], where R site alternates with hexagonal interstitial sites. We explored the interactions between an interstital He atom and HenVam (Va stands for vacancy) clusters (n, m = 1 – 4). We found that the binding energy between He and the HenVam clusters increases with the number of vacancies (e.g., the binding energy is 1.3 eV for He2Va3, and 1.7 eV for He2Va4, respectively). The small void (about 0.55 nm in diameter) in 6H–SiC can accommodate up to 14 He atoms and the corresponding internal pressure is estimated to be 2.5 GPa. The maximum density of He atoms in a small He bubble is about 50 atoms/nm3, which is of the same magnitude as the experimental value 10 atoms/nm 3. Compared to vanadium, a small nanosized void in the 6H–SiC host lattice has a weak tendency for trapping He. When trapped seventy He atoms in small void in vanadium, the nearest vanadium bond expands 22–28 %, and the volume of the void expands by 80%. At the same time, with fourteen atoms encapsulated in a small void in 6H–SiC, the local Si–C bonds explans 1–5%, and the volume of the small void expands about 7%. We suggest that the differences in the cohesive energies in these two systems are responsible for the different He trapping behavior. / <p>QC 20150126</p>

Nanotechnology, one of the most interesting sciences today will no doubt have an enourmous impact on tomorrow's society and industry. One of the most interesting nanomaterial that has been discovered is the semiconductor quantum dot (QD). This material shows interesting novel properties such as a size-dependent band gap, which is an effect caused by the quantum confinement effect in all three dimensions. Due to this phenomenon the absorption spectrum can be tuned to the desired value by adjusting the size of the QD. This thesis aims to investigate how the solvent ratio of H2O/Ethanol affects the optical and structural properties of copper sulfide QDs manufactured in a chemical synthesis way using modern microwave heating. The process of manufacturing QDs using chemical synthesis often involve a capping-agent to prevent the QDs from agglomerate into bigger structures. In this case one of the most common amino acids will be used and briefly investigated. Due to the small size the characteristics of nanomaterials must be investigated with sophisticated instruments and the QD is not an exception. In this work, the transmission electron microscope (TEM), powder X-ray diffraction (XRD) and ultraviolet-visible (UV-vis) spectroscope are utilized to determine the size and stoichiometrics of the particles made in the synthesis.

This project treats the W-C-Co-Cr quaternary system at low carbon contents. The main goals with this project were to find a four phase equilibrium between WC, Co-binder phase, η-phase (M6C) and a fourth unknown phase, to discover which the fourth phase is and to establish whether or not WC dissolves any chromium. In order to answer these questions a number of alloys were prepared, the compositions were chosen using thermodynamic calculations and observations from previous alloys. The samples were prepared using a powder metallurgical route and they were sintered at 1410oC. The samples were prepared for analysis via grinding and polishing and then analyzed using LOM, SEM, EDS, WDS and XRD. The results showed that no four phase equilibrium could be found in the analyzed spectra and therefore neither could the fourth phase. However other interesting phenomena were found. The η-phase showed a much higher solubility of chromium than previously thought. According to the current Sandvik-Seco database the η-phase should dissolve a maximum of 0.21 wt% and the maximum value detected using WDS was 8.42 wt%. The solubility of chromium in WC was found to be approximately 5 wt%. The most important conclusion that could be drawn from this project was that the Sandvik-Seco database for the W-C-Co-Cr system still needs to be improved, especially concerning the solubility of chromium in the η-phase.

hot peening is a surface treatment used to increase the fatigue strength of metallic components, for example gears, and it is of great interest to be able to model and simulate the effect of this treatment in order to save time and money. An important parameter that has to be considered when modeling the peening situation is the strain rate dependence of the target material.  In this work the strain rate dependence of SS2506 case hardened gear steel was investigated experimentally by making single impacts with spherical carbide balls on test plates of the steel and measuring depth, diameter and material pile-up of the formed indents. The results were then used to verify an FE-model for single impacts, which includes a model for strain rate dependence. The aim was to find the model, with corresponding material parameters, that represents the strain rate dependence the best. As a complement, experiments and simulations were also performed on an Almen strip (SAE 1070 cold rolled spring steel) to compare with the results of the SS2506 steel. Single impacts were also made with shot peening media used in the industry on the SS2506 test plates, in order to see how these indents differ from the ones made with spherical carbide balls. No strain rate dependence model was found that fit the experimental results for the SS2506 steel, while for the Almen plate, the Johnson-Cook model showed to fit the experimental results the best. The reason for this behavior of the SS2506 steel could be the transformation of retained austenite in the steel. The impacts made with shot peening media on the SS2506 steel showed that the roughness of the media has a great influence on the shape of the indents.

Carbon dioxide is one of the green house gases that cause climate changes. Both the European Union and the Swedish government have the goal to reduce the emission of green house gases. The first aim of this project was to calculate the amount of the total emissions when producing Sponge Iron powder at Höganäs for both upstream and process. The calculations showed an emission of 234, 2 k ton per year. The second aim was to calculate the carbon dioxide emissions when using biomass compared to natural gas in the belt furnace. The results showed that there could be made a 4% decrease in emission rates when using biomass. The third aim was to calculate the economical difference between biomass and natural gas as a fuel. After 10 years the using a biomass mix (30% is fiber sludge and the rest 70 % is wood residues) the payback time was reached, considering reduced need of emission allowances (124. 5 €/ton CO2 equivalents), an upfront investment of 13 MSEK, and a 5% depreciation each year .Using the same calculation, but with a higher cost for emission allowances, the payback time was reduced to 2-3 years depending on raw biomass. The fourth aim was to look at emission of other polluting substances and compare the difference between using natural gas versus biomass. Although carbon dioxide levels could be cut by 4% per year other substances emission levels will be higher because of the gasification process, especially NOx and mercury. Further investigation has to be done in order to understand how to manage a increased amount of other substances. / Koldioxid är en av de gaser som orsakar klimatförändringar genom växthuseffekten. Både Europeiska Unionen och Sverige har som mål att minska utsläppen av växthusgaser. Projektets syfte var att beräkna de totala koldioxidutsläppen vid framställning av järnpulver ifrån järnsvamp hos Höganäs för både upstream- (utsläpp vid tillverknings och transport) och processutsläppen. Beräkningar visade ett totalt utsläpp på 234, 2 kton per år. Det andra målet var att beräkna koldioxidutsläppen vid användning av biomassa kontra naturgas i bandugnen. Resultaten visade att utsläppen kan minskas med 4 % per år om man använder biomassa istället för naturgas. Det tredje målet var att beräkna den ekonomiska skillnaden mellan biomassa och naturgas. Efter 10 år kommer en anläggning som producerar bränsle ifrån en mixad biomassa nå lönsamhet gentemot fortsatt användning av naturgas. Om priset på utsläppsrätter ökar kan tiden till lönsamheten sänkas. Den fjärde mål var att titta på andra utsläpper som inte är koldioxid och jämföra skillnaden mellan användning av biomassbränsle kontra naturgas. Resultaten visar att utsläpp av NOx och kvicksilver kommer att få en betydande ökning om biomassa används. Dock är dessa utsläpp binder till kondenserat vatten. Ytterligare utredningar om hur detta ska tas om hand bör göras och om man kan ta hand om utsläppen på liknande sätt som det görs idag.

Firms have had difficulties in dealing with the risks that occur when providing fixed price contracts (FP) for both small – scale and large – scale projects to involved customers. This is general for the most companies surveying customers with the development for a product or service in the IT – industry. Research has paid minimum attention on how firms can imple-ment scientific proven agile methods to reduce the risks with FP contracts to increase profit margin. In FP contracts, the risks lie on the supplier providing the contract, where research has shown that companies have issues in determining the project scope in the planning pro-cess and how they can find certain approaches for increasing the dialogue in a buyer and seller arrangement. Therefore, firms are more comfortable in going into Time and Material (T&amp;M) arrangements where customers pay for the time and resources spent under a project process. This study also makes investigations on how firms can make accurate estimations of the development durations that occurs when providing this contracting form and how firms can identify risks into profitable pricing engagements. The study took ground in Lund, Swe-den at a company named Sigma Connectivity which is a firm developing services and prod-ucts based on wireless communication and the phenomenon called Internet Of Things (IoT).The delimitations that were made for this study was related to the marketing mix concept which conducts of seven strategies for business management of these seven strategies the choice was made to exclude exclude sustainable aspects, physical evidence, internal market-ing related to promotion, and location factors. Internal qualitative directive and semi – struc-tured interviews were methods used for determining variables and key issue with FP contracts that was included in the survey based approach to customers. Agile methods such as Feature Driven Development (FDD) and Work Breakdown Structure (WBS) were implemented in or-der to tackle the challenges of visualising a clear project scope description with clear specifi-cation on what is included in a FP contracts in small – scale and large – scale projects.The results conducted from this study shows that integrating scientific proven methods such as FDD and WBS in a firm, will help them to divide project processes into smaller mecha-nisms, which will provide sufficient access for an increased project scope allocation forcing the involved parties in a buyer and seller arrangement to hold both internal and external re-views which will enable the possibility of making pricing approaches during the project pro-cess. Results also shows that customers find FP contracts to be the most valuable but the diffi-culties that they have felt in this arrangement is to incorporate new ideas for a project scope change during a project process. The use of the FDD framework and WBS provided results that are vital for firms going into FP arrangements where clearer project scope definitions, key role identifications, increased pricing opportunities and communication channels were founded.Keywords: Fixed price contracts (FP), project scope, Work Breakdown Structure (WBS), Feature Driven development (FDD).

Cemented carbides are used in rock tool applications by reason of their beneficial mechanical properties, i.e. a combination of high toughness, wear resistance and hardness. The cemented carbides commonly receive their hardness from tungsten carbides (WC) whereas cobalt (Co) is the dominating binder material. To obtain a beneficial balance of these desired properties, the binder phase can be strengthened by post-sintering treatment to minimize the risk of catastrophic failure. Previous work has shown that the face centered cubic (FCC) cobalt phase is stabilized by a higher degree of dissolved tungsten in the binder. The residual stresses have been related to both further stabilization of the FCC and local transformation to a hexagonal close packed (HCP) phase. By exposing the inserts to mechanical deformation, i.e. inducing stress, the Co-binder material could theoretically transform from FCC to HCP. In this master thesis, five cemented carbides with three different binder phase compositions have been investigated. Additionally, the influence of the carbon content and addition of an alloying element was evaluated. This was done by electron backscatter diffraction (EBSD) analysis of the microstructure of each sample in as-sintered state and after post-treatment to gain better understanding on how the phase stability of the binder is affected by a post-sintering process. In addition, magnetic measurements, hardness-testing and mechanical tests were performed on the materials to evaluate the effect of using different binder compositions. It was found that a low carbon content provides smaller and more rounded WC grains and binder phase dominated by FCC-Co compared to an equivalent material with a high carbon content. A low carbon content furthermore resulted in a more wear resistant material. The addition of alloy MA presented a greater increase in surface hardness after post-treatment and made the materials even more wear resistant compared to the non-alloyed. The non-alloyed material performed better in a test measuring the fracture energy. A material with an Fe-based binder showed the least increase in surface hardness and the highest increase and overall fracture energy. All materials experienced a WC grain size refinement and an increase in their surface hardness after post-treatment. Only one material gave an indication on FCC to HCP phase transformation, no conclusions could be drawn from the other samples. / Hårdmetaller används i bergborrstift på grund av materialets fördelaktiga mekaniska egenskaper vilket innefattar en kombination av hög seghet, hårdhet och bra nötningsmotstånd. Hårdheten uppnås vanligen av volfram karbider (WC) medan segheten ges av en bindefas som oftast är baserad på cobolt (Co). För att få ett material med en bra balans mellan seghet och hårdhet så kan bindefasen stärkas genom en ytbehandling efter sintringen för att minimera risken för att borrstiftet går sönder under användning. I tidigare studier har det framkommit att ytcentrerad kubiskt tätpackad (FCC) cobolt stabiliseras av volfram som lösts i bindefasen. Spänningar som uppkommer på grund av detta har relaterats till vidare stabilisering av FCC-fasen, men även lokal omvandling till hexagonalt tätpackad (HCP) cobolt. Genom att utsätta borrstiften för mekanisk deformation, i.e. inducera spänningar, kan bindematerialet teoretiskt sett omvandlas från FCC till HCP. I detta examensarbete har fem bergborrstift med tre olika bindefassammansättningar undersökts. Därutöver har även inverkan av kolhalten och tillägget av ett legeringsämne utvärderats. Den primära metoden för att genomföra undersöka mikrostrukturen hos de sintrade och efterbehandlade stiften var bakåtspridd elektrondiffraktion (EBSD). Syftet med undersökningen var att öka förståelsen kring bindefasens fasstabilitet då den utsatts för en efterbehandlingsprocess. Även magnetisk mätning, hårdhetstestning och mekanisk prövning utfördes på materialen för att kunna jämföra de olika bindefassammansättningarna mot varandra. Resultaten visade att en låg kolhalt gav ett material med mindre och mer rundade WC korn samt att bindefasen dominerades av FCC-Co jämfört mot ett material med samma bas och hög kolhalt. Därtill uppvisade materialen med låg kolhalt bättre nötningsmotstånd. Legeringen av bindefasmaterialet visade en ökning i ythårdhet efter efterbehandling och gjorde materialen mer nötningsbeständiga än de icke-legerade materialen. De icke-legerade materialen visade däremot på högre krosstyrka. Materialet med en järn-baserad bindefas påvisade minst ökning av ythårdheten och högst ökning samt högsta värde på krosstrykan. Samtliga material visade en förfining av WC kornen och en ökning av ythårdheten efter efterbehandlingen. Endast ett material indikerade omvandling från FCC till HCP, inga slutsatser kunde dras från de övriga proverna.

This thesis has investigated the possibility of optimizing curing time by changing the energy source from a conventional oven to infrared radiation (IR) and if it is possible to achieve similar results as the company's current production of glass fiber composite tubes.   Many different parameters (time, temperature, heating rate, and rotation speed) might influence a cured composite tube's properties. Reduced factorial experiments were conducted to test all these parameters cost-efficient where each parameter was tested at a high and low level. However, every possible combination was not investigated.   Temperature measurements during the curing cycles, energy calculations, three-point bending, and differential scanning calorimetry analysis were conducted to compare the two different curing methods, hot air and IR curing. The current production flexural strength and glass transition temperature (Tg) have acted as benchmark values that the tubes cured with IR would have to reach to be considered a reliable manufacturing method. Differential scanning calorimetry (DSC) analyses were conducted to measure the Tg and three-point bending to determine the flexural strength. Due to that no standard exist for three-point bending of composite tubes, an in-house method was created and verified with a finite element simulation in Abaqus, to measure the flexural strength. The simulated reaction force was circa 76.9% of the measured force at the same displacement during the three-point bending test of the tubes. The simulation found that the stress concentration did occur at the same locations as the fracture occurred in the three-point bending test.     The temperature difference between the top of the laminate and the core was close to zero degrees for the current production by hot air in a thermal oven. A more significant temperature difference between the core and top of the laminate was found during curing with IR. However, a higher rotation speed was found to create a more evenly temperature distribution in the composite.    No clear correlation between the Tg and the flexural strength was found, as the literature suggests while comparing each test cured with IR. Nevertheless, by comparing every test cured with IR with the current production of the tube, it was determined that a lower Tg could cause a lower flexural strength. However, the lower flexural strength for the tubes cured by IR could also be explained by the temperature difference found between the core temperature and the top of the laminate during the curing process.       The reduced factorial experiments showed that it was possible to reach similar properties by curing with IR and reducing the curing time by 69.3%. Time and the combination of time and temperature were found to affect the result when it comes to the glass transition temperature. Regarding flexural strength, no parameters were found to impact the outcome. By investigating the time and temperature further, the curing time could be reduced to 71.3% compared with the current production and still achieve similar properties. Nevertheless, the energy use for curing with IR was found to require 8.3 times more than the current production.

The assignment handed out by Cementa in Skövde is to investigate why crack formation and propagation emerge in the fixed attachment clamps and propose solutions against it. The fixed attachments are part of the cooling element suspension, used in the cement production to cool the material coming out of the oven. There is also an attachment clamp for the cooling elements with a clearance around the cooling elements which allows some movement in all directions. Since Cementa has not performed any former research for this case, a thorough literature study is conducted. Material properties, manufacturing, fracture types and fracture mechanisms are subjects examined in the literature study. Hypotheses are formed using the gathered information and are tested by calculations and analyses. The two main hypotheses formed are: Stresses greater than the tensile strength for the steel causes crack formation. Fatigue causes crack formation. The methods used to investigate the hypotheses are calculations by hand and FE-analysis. The results from calculations and analyses shows that the clearance in the movable attachment had great influence on the stresses obtained in the fixed attachment and is the probable cause for crack formation and propagation. The most likely fracture mechanism is fatigue and corrosion, bad welds and thermal tension could be contributing factors for crack formation.

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