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  • 5201.
    Zhou, Xiaobin
    et al.
    Institute of Ferrous Metallurgy, Northeastern University, Shenyang, China.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhong, L.
    Yu, J.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical and physical simulation of a top blown converter2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 2, p. 273-281Article in journal (Refereed)
    Abstract [en]

    A mathematical model of a top blown converter, which was based on a physical model of a 30 t vessel, was developed in this study. A simplified model consisting of the converter was used in the mathematical simulation. With the simplified model, it is possible to run a large number of tracer calculations within a short time, compared to solving for the entire flow evolution each time. A cavity depth and radius comparison has been done between the physical model and the mathematical model, which showed a good relative difference of 2.5% and 6.1% for the cavity depth and radius, respectively. The velocity change in the bath of the converter was monitored by setting several monitoring points in the physical model. A fully developed flow field was assumed to occur when the fluctuations in these points were small or periodic. It took approximately 25 s to get a developed flow field. In addition, the predicted mixing time showed a good relative difference of 2.8% in comparison to the experimental data. A simplified model consisting of the converter has been used in the mathematical simulation. The comparison between the physical model and the mathematical model shows that the simplified top blown model can successfully be used to calculate long-time simulations, and the mixing time calculations in frozen field can save a large amount of time compared to the simulation time using a transient flow field.

  • 5202.
    Zhou, Xiaobin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. University Shenyang, China.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhong, Liangcai
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Numerical and Physical Simulations of a Combined Top-Bottom-Side Blown Converter2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 11, p. 1328-1338Article in journal (Refereed)
    Abstract [en]

    In this study, a side tuyere was introduced to investigate how it is possible to lower the mixing time and to avoid problems of a reduced stirring when using the application of slag splashing process in the combined top and bottom blown converter. Both physical and mathematical models were applied to study the flow in the bath. Specifically, the effects of a side-blowing gas jet on the bath stirring intensity was studied. The results indicate that the mixing time for a side blown converter is decreased profoundly compared to a conventional combined top and bottom blown converter. Overall, the mathematical model showed similar trends and a good agreement with that of the physical modeling data. Furthermore, the shear stress at the wall in the top-bottom-side (TBS) converter was considered, since the furnace lining is important when side blowing is used in the converter. It was found that the side wall shear stress is increased by introducing side blowing, especially in the region near the side blowing plume. Three side tuyeres with different locations in the same level did not show any obvious effects on the mixing of the bath, but showed apparent differences in the shear stress and the oscillation of the bath. Overall, the results showed that the mathematical model can be used to design the configuration of the metallurgical vessels when it is necessary to consider the oscillation and the shear stress of the bath.

  • 5203.
    Zhou, Xiaobin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. Northeastern University Shenyang, China.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhong, Liangcai
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Numerical Simulations of the Kinetic Energy Transferin the Bath of a BOF Converter2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 1, p. 434-445Article in journal (Refereed)
    Abstract [en]

    The paper focuses on the fundamental aspects of the kinetic energy transfer from a top andbottom gas injection to the bath of the basic oxygen furnace (BOF) by applying a mathematicalmodel. The analyses revealed that the energy transfer is less efficient when top lance height islowered or the flowrate is increased in the top blowing operations. However, an inverse trendwas found that the kinetic energy transfer is increased when the bottom flowrate is increased forthe current bottom blowing operation conditions. The kinetic energy transfer index resultsindicated that the energy transfer for the bottom blowing is much more efficient than that of thetop blowing operations. To understand the effects of the upper buoyant phase on the energydissipation of the bulk liquid in the bath, different mass and physical properties of slag and foamwere considered in the bottom blowing simulations. The slag on top of the bath is found todissipate by 6.6, 9.4, and 11.2 pct for slag mass values of 5, 9, and 15 t compared to the casewithout slag atop the surface of the bath, respectively. The results showed that the kinetic energytransfer is not largely influenced by the viscosity of the upper slag or the foaming phases.

  • 5204.
    Zhou, Xiaobin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. University Shenyang, China.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhong, Liangcai
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Optimization of Combined Blown Converter Process2014In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 10, p. 2255-2262Article in journal (Refereed)
    Abstract [en]

    A 1/6th scaled down physical model was used to study and optimize the stirring condition of a 30 t converter. A number of parameters were studied and their effects on the mixing time were recorded. A new bottom tuyere scheme with an asymmetrical configuration was found to be one of the best cases with respect to a decreased mixing time in the bath. Mathematical modeling was employed to study the flow field characteristics caused by the new tuyere scheme. In the mathematical model, a comparison between the existing and the new tuyere setups was made with regards to the mixing time and turbulence in the bath. In addition, a new volumetric method for calculating the mixing time was applied. The results showed that, on average, a 23.1% longer mixing time resulted from the volumetric method compared to the standard method where discrete point are used to track the mixing time. Furthermore, an industrial investigation was performed to check the effects of the new tuyere scheme in a converter by analyzing the [O], [C] and [P] contents in the bath. The results showed that the application effects of the new tuyere scheme yield a better stirring condition in the bath compared to the original case.

  • 5205.
    Zhu, Bin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Hubei University, China.
    Fan, L.
    Deng, H.
    He, Y.
    Afzal, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Dong, W.
    Yaqub, A.
    Janjua, N. K.
    LiNiFe-based layered structure oxide and composite for advanced single layer fuel cells2016In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 316, p. 37-43Article in journal (Refereed)
    Abstract [en]

    A layered structure metal oxide, LiNi0.1Fe0.90O2-δ (LNF), is explored for the advanced single layer fuel cells (SLFCs). The temperature dependent impedance profiles and concentration cells (hydrogen concentration, oxygen concentration, and H2/air atmospheres) tests prove LNF to be an intrinsically electronic conductor in air while mixed electronic and proton conductor in H2/air environment. SLFCs constructed by pure LNF materials show significant short circuiting reflected by a low device OCV and power output (175 mW cm-2 at 500°C) due to high intrinsic electronic conduction. The power output is improved up to 640 and 760 mW cm-2, respectively at 500 and 550°C by compositing LNF with ion conducting material, e.g., samarium doped ceria (SDC), to balance the electronic and ionic conductivity; both reached at 0.1 S cm-1 level. Such an SLFC gives super-performance and simplicity over the conventional 3-layer (anode, electrolyte and cathode) FCs, suggesting strong scientific and commercial impacts.

  • 5206.
    Zhu, Bin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. Haerbin University of Engineering, China.
    Liu, XiangRong
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Cheng, Y.
    Zhang, M.
    Novel catalytic electrodes for high performance solid oxide fuel cells operated at intermediate temperatures2007In: High-Performance Ceramics IV, Pts 1-3, Trans Tech Publications Inc., 2007, p. 428-433Conference paper (Refereed)
    Abstract [en]

    The all-ceria-composite ITSOFCs have demonstrated extraordinary fuel cell performances since the ceria-composite electrodes are very catalytic and conductive, and the ceria-composite electrolytes are highly conductive and also electrolytic, in addition to excellent compatibility between the electrolyte and electrodes based on the same ceria-based composite materials. The power density outputs from 200 to 800 mWcm -2, were obtained for temperatures between 400 and 700°C. The maximum power density 0.72 Wcm -2 (1500 mAcm -2) at 600°C and 0.82 Wcm -2 (1800 mAcm -2) at 700°C were achieved, respectively. These highly catalytic electrodes functioned extensively for many different fuels, such as hydrogen and hydrocarbon fuels, e.g., natural gas, coal gas, methanol and ethanol etc. In some special cases, the ITSOFCs with the ceria-composite electrodes could also work at as low as 200°C. All these good performances are based on the novel catalyst function of the ceria-composite electrodes and internal reforming mechanism.

  • 5207.
    Zhu, Bin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Liu, Xiangrong
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sun, J.
    Fuel cell studies using the CeO2-La2O3 based electrolytes2007In: High-Performance Ceramics IV, Pts 1-3, Trans Tech Publications Inc., 2007, p. 490-493Conference paper (Refereed)
    Abstract [en]

    The ceria oxide and lanthanum oxide are almost insulators, but the binary CeO2 and La2O3 system created a new type of the electrolyte with high ionic conductivity. The FC studies were carried out by using the CeO2-La2O3 and relevant composites as the electrolytes. The binary CeO2-La2O3 electrolytes showed a fuel cell performance 300 to 650 mWcm-2 at temperatures between 480 and 630°C, and their composites with the carbonates demonstrated the higher performance, 300 to 720 mWcm-2 for temperatures from 390 to 630°C.

  • 5208. Zhu, Feng
    et al.
    Li, Cuiping
    Ha, Minh Ngoc
    Liu, Zhifu
    Guo, Qiangsheng
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Shanghai Inst Technology, China.
    Molten-salt synthesis of Cu-SrTiO3/TiO2 nanotube heterostructures for photocatalytic water splitting2016In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 51, no 9, p. 4639-4649Article in journal (Refereed)
    Abstract [en]

    A series of Cu-loaded SrTiO3/TiO2 nanotube heterostructures were synthesized by a facile molten salts method and an impregnation-calcination method. Through adjusting the molar ratio of Sr/Ti, the photocatalytic performance of the samples changed regularly. When Sr/Ti = 0.2, the catalyst showed the highest performance in water splitting and the H-2 generation amount was 0.597 mmol under UV irradiation for 8 h. The enhanced performance of Cu-loaded SrTiO3/TiO2 nanotubes could be attributed to the heterostructures, the small crystallite size, and the reduced band gap inside them.

  • 5209.
    Zhu, Hongli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Areskogh, Dimitri
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Helander, Mikaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    A preliminary investigation on enzymatic oxidative polymerization of lignin2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry: Proceedings, ISWFPC, 2011, p. 238-241Conference paper (Refereed)
    Abstract [en]

    Enzyme catalyzed oxidative polymerization of technical bagasse lignin and low-molecular-weight ultra-filtered kraft pulp lignin (UFL) were studied in methanol-water solution. Lignin was dissolved in methanol-water solution at pH 13 in steam heated autoclave at 130°C for 2h. The polymerization reaction was conducted at 40°C with a commercial laccase under oxygen saturation. The weight-average molecular weight (Mw) of original macromonomer and polymerized lignin were characterized with alkaline size exclusion Chromatograph (SEC) system. Enzyme treatment increased the molecular weight of both technical bagasse lignin and ultra-filtered lignin up to 20 times. The reaction time and the enzyme dosage were studied to obtain the maximal molecular weight.

  • 5210.
    Zhu, Hongli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Areskogh, Dimitri
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Helander, Mikaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Investigation on enzymatic oxidative polymerization of technical soda lignin2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Article in journal (Other academic)
  • 5211.
    Zhu, Jinchao
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Khurshid, Mansoor
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Cargotec Sweden AB Bromma Conquip, Kronborgsgrand 23, S-16446 Kista, Sweden..
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Chalmers Univ Technol, Chalmersplatsen 4, S-41296 Gothenburg, Sweden..
    Accuracy of computational welding mechanics methods for estimation of angular distortion and residual stresses2019In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 5, p. 1391-1405Article in journal (Refereed)
    Abstract [en]

    This study estimates the angular distortion and residual stresses due to welding using the following methodologies: thermo-elastic-plastic, inherent strain (local-global), and substructuring on two types of welded joints (T-type fillet weld and butt weld). The numerical results are compared with the experimental measurements and these methodologies are evaluated in terms of accuracy and computational time. In addition, the influence of welding sequence on distortion and transverse residual stresses has been studied numerically by implementing the thermo-elastic-plastic and inherent strain (local-global) methods on the T-type fillet weld. For the T-type fillet weld, the estimated angular distortion from these methods is much the same and in good agreement with the experimental measurements. For the butt weld, the angular distortion calculated by the inherent strain (local-global) method is largely underestimated. In order to gain a better understanding of where the underestimation of angular distortion in the inherent strain (local-global) method comes from, the study discusses the influence of block length and welding speed on angular distortion. It is found that for long weld length or slow welding speed, activating the plastic strain gradually by dividing the weld bead into an appropriate number of blocks can reduce the level of underestimation of angular distortion.

  • 5212. Zhu, L.
    et al.
    Ang, C. Y.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Nguyen, K. T.
    Tan, S. Y.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhao, Y.
    Luminescent color conversion on cyanostilbene-functionalized quantum dots via in-situ photo-tuning2012In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 24, no 29, p. 4020-4024Article in journal (Refereed)
    Abstract [en]

    Photo-responsive CdSe quantum dots functionalized with the cyanostilbene unit are synthesized. The as-prepared quantum dot hybrid reveals a photo-tunable dual fluorescent characteristic. White light emission can be generated in situ from the hybrid through photoirradiation to adjust the relative intensities of the two complementary emissions. Luminescent color conversion through yellow, white, and blue can be realized by varying the photoirradiation time.

  • 5213. Zhu, M-Y
    et al.
    Jones, T
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Modelling study of slag foaming by chemical reactio2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, p. 51-56Article in journal (Refereed)
  • 5214.
    Zhu, Ning
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Song, Jun
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Etched diffraction grating demultiplexers based on amorphous silicon nanowire platform2008In: 2008 Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, AOE 2008, 2008Conference paper (Refereed)
    Abstract [en]

    We present some theoretical and experimental results of Etched Diffraction Grating demultiplexer based on amorphous silicon nanowire platform, including issues with polarization sensitivity, diffraction efficiency and an application to triplexer.

  • 5215. Zhu, Weizhen
    et al.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers, Sweden.
    Precipitation of Lignin from Softwood Black Liquor: An Investigation of the Equilibrium and Molecular Properties of Lignin2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 1, p. 1696-1714Article, review/survey (Refereed)
    Abstract [en]

    Extracting lignin from black liquor is an attractive option in modern pulp mills as a unit process for a combined biorefinery. The lignin obtained can be utilized as solid fuel or other high-value added products. The precipitation equilibrium of kraft lignin from softwood black liquor was studied in this work. It was found that with decreasing pH and temperature, or increasing ion strength, the solid yield increases. Moreover, precipitated softwood kraft lignin has a higher molecular weight and contains lower amounts of carbohydrates and phenolic groups than lignin precipitated from mixed hardwood/softwood black liquor. The content of methoxyl groups in softwood kraft lignin was found to decrease with increasing precipitation yield. An empirical model for estimating the precipitation yield of lignin was proposed and evaluated.

  • 5216.
    Zhu, Weizhen
    et al.
    Chalmers, Sweden.
    Westman, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers, Sweden.
    Lignin separation from kraft black liquor by combined ultrafiltration and precipitation: a study of solubility of lignin with different molecular properties2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 2, p. 270-278Article in journal (Refereed)
    Abstract [en]

    Lignin from wood is by far the largest source of bio-based aromatic raw material. Today a vast amount of lignin is processes and incinerated in kraft pulp mills around the world. One possible option to utilize the energy surplus in a modern kraft pulp mill is to extract lignin from black liquor. Precipitation of lignin is one important step in an extraction process. This study investigates how the molecular size and functional groups of lignin influenced the precipitation yield. Cross-flow filtration was applied to fractionate lignin with different molecular weights from a black liquor, precipitation studies was made on the different fractions. The precipitated lignin was characterized by GPC, HPAEC-PAD and NMR analysis. The results show that it was possible to obtain a more homogenous lignin by fractionation using cross-flow filtration. It was found that the molecular properties of kraft lignin, i.e. molecular weight and functional groups, influenced the yield of lignin precipitation: at the same precipitation condition, lignin fraction with higher molecular weight has higher precipitation yield. Lignin fraction with lower molecular weight contains less amount of carbohydrates and methoxyl groups but higher amount of phenolic groups.

  • 5217. Zhu, Z.
    et al.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Larsson, H.
    Reed, R. C.
    Isolation of optimal compositions of single crystal superalloys by mapping of a material's genome2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 90, p. 330-343Article in journal (Refereed)
    Abstract [en]

    The multicomponent composition space pertinent to the single crystal nickel-based superalloys is mapped and searched, using computational modelling. A resolution of 0.1 wt.% for the alloying elements is assumed, consistent with manufacturing practice. Databases are constructed of alloy compositions which are predicted to be of promising microstructural architecture: e.g. equal fractions of the γ and γ′ phases. These may be regarded as maps - one might term them genomes - of this class of structural alloy. By combining the databases with additional composition-dependent property models, it is demonstrated that compositions can be identified which - subject to the accuracy and limitations of the sub-models - are likely to prove optimal, e.g. on the basis of their creep resistance, density and cost. The methods circumvent the need for the traditional empirically-driven approaches to alloy design.

  • 5218. Zimmermann, Kristian
    et al.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Siemetzki, M.
    Testing and analysis of ultra thick composites2010In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 41, no 4, p. 326-336Article in journal (Refereed)
    Abstract [en]

    For the development of a composite main landing gear fitting in carbon fiber reinforced plastics the behavior and performance of Ultra Thick Laminate components is investigated. Material thicknesses exceeds 60 mm. For the purpose of validation a test program is arranged using T-cross sections subjected to multiple load cases. The components are manufactured entirely with non crimped fabrics (NCF) using an adapted open mould manufacturing process. In addition to these T-Sections large full scale subcomponents of the entire fitting are manufactured and tested. As main topic of this paper standard FE methods are investigated and validated for thick structures using the generated test results. Due to the presence of transverse shear and normal stresses a 3D modeling approach is chosen. Transverse shear and normal stresses are indentified as main failure cause and failure is mainly initiated in the curved regions. Solid composite brick elements offer an efficient way to model thick structures. These are incapable of calculating accurate shear stresses on a ply level; usable results are however achieved by discretisation of the component with multiple elements over thickness. In addition stress gradients in the failure region are small; stress variations on a ply level are minimal. Out of plane material properties are not available and initial assumptions are made. Material correction factors (degradation) are introduced and discussed.

  • 5219.
    Zimmermann, Uwe
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Domeij, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hallén, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Comparison between implanted and epitaxial pin-diodes on 4H-silicon carbide2004In: SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2 / [ed] Madar, R; Camassel, J, ZURICH-UETIKON: TRANS TECH PUBLICATIONS LTD , 2004, Vol. 457-460, p. 1037-1040Conference paper (Other academic)
    Abstract [en]

    Two sets of pin-diodes with epitaxially grown anode regions and implanted anode regions, respectively, were processed on the same low-doped n-type epitaxial layer. The designed breakdown voltage for the epitaxial layer was 5 kV with punch-through at about 2 kV. The almost ideal forward voltage drop of less than 3.5 V at current densities of 100 A cm(-2) of the epitaxial diodes indicates high-level carrier injection into the low-doped epitaxial layer, which is also supported by the results of reverse recovery measurements. At current densities above 10 A cm(-2) the forward voltage drop of the implanted pin-diodes is significantly higher than that of the epitaxial diodes.

  • 5220. Zinkevich, M.
    et al.
    Aldinger, F.
    Sundman, Bo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    The Ringberg workshop 2005 on thermodynamic modeling and first-principles calculations2007In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 31, no 1, p. 2-3Article in journal (Other academic)
  • 5221. Zuazo, I.
    et al.
    Hallstedt, B.
    Lindahl, Bonnie
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Soler, M.
    Etienne, A.
    Perlade, A.
    Hasenpouth, D.
    Massardier-Jourdan, V.
    Cazottes, S.
    Kleber, X.
    Low-Density Steels: Complex Metallurgy for Automotive Applications2014In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 66, no 9, p. 1747-1758Article in journal (Refereed)
    Abstract [en]

    The current aim in the development of third-generation steels for lightweighting automotive applications is to increase strength keeping at least the same formability as current steel concepts. In this philosophy, an optimal concept would be one that brings, in addition, a lower density. For this purpose, low-density steels have been designed with important aluminum additions obtaining density reductions of 8-10% or higher in comparison with low-carbon steels. At the levels required for lightweighting, aluminum introduces complex phenomena in steels. Here, some of the effects of aluminum in phase stability, CALPHAD-type modeling, and microstructure development are described, the latter in relation with mechanical properties. Finally, the potential of two families of lightweight steels for automotive applications is assessed by comparison with a steel currently present in automotive structures.

  • 5222.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    QPM Devices in KTA and RKTP2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Even though KTiOPO4 (KTP) is considered to be one of the best nonlinear materials for quasi phase matched (QPM) frequency conversion in the visible and the near-infrared spectral regions, its use is often limited by poor material homogeneity, high ionic conductivity, a considerable linear absorption and photochromatic damage. On the other hand, the improved material homogeneity and the lower ionic conductivity of bulk Rb-doped KTP (RKTP) make this material an ideal alternative for fabrication of fine-pitch QPM gratings, while the arsenate isomorph KTiOAsO4 (KTA) promises a better performance in the green spectral region and adds the advantage of a wider transparency window in the infrared. Unfortunately, the available studies on these materials are limited and unable to answer the question whether RKTP and KTA are feasible alternatives to KTP in terms of periodic poling and optical performance. The optical performance of the QPM devices depends on the periodic poling quality, therefore, a detailed comprehension of domain-grating formation in the KTP isomorphs is highly desired. The goals of this thesis were to gain a better understanding of the periodic poling process in the KTP isomorphs, in order to study the specifics of ferroelectric domain engineering in KTA and RKTP, and to evaluate the optical performance of these isomorphs. Fine-pitch periodically poled structures were engineered both in KTA and RKTP crystals. It was demonstrated that QPM gratings with excellent quality and with periods as short as 8.49 μm can be fabricated in KTA crystals. Comparative transmission studies have shown that periodically poled KTA (PPKTA) crystals can be superior to KTP for QPM second harmonic generation in the visible spectral region due to lower linear absorption. It was also demonstrated that RKTP is a superior alternative to KTP for high-quality QPM grating fabrication. A consistent room-temperature periodic poling of 5 mm thick RKTP crystals with a period of 38.86 μm has been achieved. The obtained large aperture periodically poled RKTP (PPRKTP) crystals showed an outstanding QPM grating uniformity and excellent optical performance in optical parametric oscillator (OPO) applications. Moreover, it was shown that RKTP is less susceptible to blue-induced infrared absorption than KTP. Finally, a novel and a relatively simple method for self-assembling quasi-periodic sub-μm scale ferroelectric domain structure in RKTP crystals has been presented. It was shown that, after treatment in aqueous KOH/KNO3 solution, periodic poling of RKTP with planar electrodes resulted in one-dimensional ferroelectric domain structure with an average periodicity of 650±200 nm, extending over the whole 1 mm thick crystal. Such self-assembled structures in RKTP were used to demonstrate 5th order non-collinear QPM backward second harmonic generation.

  • 5223.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Bulk Self-assembled Ferroelectric Domain Structures in RKTP2016Conference paper (Refereed)
  • 5224.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Quasi-periodic self-assembled sub-micrometer ferroelectric bulk domain gratings in Rb-doped KTiOPO42013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 25, p. 252905-Article in journal (Refereed)
    Abstract [en]

    We present a simple technique for fabricating quasi-periodic bulk sub-μm ferroelectric domain gratings in Rb-doped KTiOPO4 (RKTP) based on self-organized ferroelectric domain formation. One-dimensional ferroelectric domain structures, with an average periodicity of 650 ± 200 nm and extending throughout 1 mm thick crystals, are obtained by etching and subsequent electric field poling using planar electrodes. The sub-μm structures in RKTP were used to demonstrate 5th order non-collinear quasi-phase matched backward second harmonic generation.

  • 5225.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Safinas, Maratas
    Ekspla Ltd..
    Michailovas, Andrejus
    Ekspla Ltd..
    High-Performance Periodically Poled Rb-doped KTP For Frequency Conversion In Blue/Green Region2010In: Conference digest, 2010Conference paper (Refereed)
  • 5226.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Fokine, Michael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Fabrication of submicrometer quasi-phase-matched devices in KTP and RKTP [Invited]2011In: Optical Materials Express, ISSN 2159-3930, Vol. 1, no 7, p. 1319-1325Article in journal (Refereed)
    Abstract [en]

    We review the techniques used for fabrication of bulk submicrometer ferroelectric domain gratings in KTiOPO4 (KTP) and demonstrate that bulk Rb-doped KTiOPO4 (RKTP) is an excellent candidate for implementation of dense domain gratings. Compared to KTP, RKTP presents predominant domain propagation along the polar c-direction, substantially reduced lateral domain broadening, and higher poling yield. As a result we obtain homogeneous sub-μm periodic poling of RKTP with a period of 690 nm in 1 mm thick samples.

  • 5227.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    5 mm thick periodically poled Rb-doped KTP for high energy optical parametric frequency conversion2011In: Optical Materials Express, ISSN 2159-3930, Vol. 1, no 2, p. 201-206Article in journal (Refereed)
    Abstract [en]

    A 5 mm thick periodically poled bulk Rb-doped KTiOPO4 (KTP) crystal with a period of 38.86 μm was fabricated by electric field poling. Chemical etching and optical evaluation show a high quality of the periodic ferroelectric domain structure through the whole crystal aperture. The fabricated quasi-phase matching (QPM) device was used in an optical parametric oscillator pumped at 1064 nm with 12 ns pulses at 100 Hz repetition rate to generate 60 mJ parametric radiation with a conversion efficiency of 50%.

  • 5228.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    5 mm Thick Periodically Poled Rb:KTiOPO4 for High Power Optical Frequency Conversion2011In: Advanced Solid State Photonics 2011, 2011Conference paper (Refereed)
    Abstract [en]

    A periodically poled bulk Rb-doped KTiOPO 4crystal with 5 mm aperture was fabricated at room temperature. The ferroelectric domain structure is shown to be homogeneous across the whole aperture with a deffof 11 pm/V.

  • 5229.
    Zukauskas, Andrius
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Thilmann, Nicky
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Periodically Poled KTiOAsO4 For Mid-Infrared Light Generation2010In: Advanced Solid-State Photonics 2010, 2010Conference paper (Refereed)
    Abstract [en]

    A periodically poled KTiOAsO4crystal was fabricated at room temperature. The poled crystal shows a deffof 10.1 pm/V and gives a parametric conversion efficiency of 45%.

  • 5230.
    Zurauskaite, Laura
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Hellström, Per-Erik
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    The impact of atomic layer depositions on high quality Ge/GeO2 interfaces fabricated by rapid thermal annealing in O-2 ambient2017In: 2017 IEEE Electron Devices Technology and Manufacturing Conference, EDTM 2017 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 164-166, article id 7947553Conference paper (Refereed)
    Abstract [en]

    This work demonstrates high quality Ge/GeO2 interfaces fabricated by O-2 RTA that are degraded by a good quality SiO2 layer deposited by ALD. However, neither O-3 and H2O precursors commonly used during subsequent high-k ALDs nor Si precursor AP-LTO-330 do not degrade the interface. Thus Dit increase after SiO2 deposition is likely due to intermixing. Therefore, the effect of subsequent ALDs on the interface quality has to be considered while designing Ge-based gate stacks.

  • 5231.
    Zurauskaite, Laura
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Jones, L.
    Dhanak, V. R.
    Mitrovic, I. Z.
    Hellström, Per-Erik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Östling, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Investigation of Tm2Oj as a gate dielectric for Ge MOS devices2018In: ECS Transactions, Electrochemical Society, 2018, Vol. 86, no 7, p. 67-73Conference paper (Refereed)
    Abstract [en]

    In this work atomic layer deposited TnOj has been investigated as a high-k dielectric for Ge-based gate stacks. It is shown that when Tm203 is deposited on high-quality Ge/Ge02 gates, the interface state density of the gate stack is degraded. A series of post-deposition anneals are studied in order to improve the interface state density of Ge/GeO/TmjOs gates, and it is demonstrated that a rapid thermal anneal in O2 ambient can effectively reduce the interface state density to below 5-10" cmeV1 without increasing the equivalent oxide thickness. Fixed charge density in Ge/GeOx/Tm20j gates has also been investigated, and it is shown that while O2 post-deposition anneal improves the interface state density, the fixed charge density is degraded.

  • 5232. Zurauskiene, N.
    et al.
    Asmontas, S.S.
    Dargys, A.
    Kundrotas, J.
    Janssen, G.
    Goovaerts, E.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Koenraad, P.M.
    Wolter, J.H.
    Leon, R.
    Semiconductor nanostructures for infrared applications2004In: Functional Nanomaterials For Optoelectronics And Other Applications / [ed] Lojkowski, W; Blizzard, JR, Trans Tech Publications Inc., 2004, Vol. 99-100, p. 99-108Conference paper (Refereed)
    Abstract [en]

    The results of time-resolved photo luminescence (TRPL) and optically detected microwave resonance (ODMR) spectroscopy investigations of semiconductor quantum dots and quantum wells are presented. The ODMR spectra of InAs/GaAs QDs were detected via modulation of the total intensity of the QDs emission induced by 95 GHz microwave excitation and the exciton fine structure was studied. Very long life times (up to 10 ns) of photoexcited carriers were observed in this system using TRPL at low temperatures and excitation intensities promising higher responsitivity of such QDs for infrared photodetector development. The effects of proton and alpha particles irradiation on carrier dynamics were investigated on different InGaAs/GaAs, InAlAs/AlGaAs and GaAs/AlGaAs QD and QW systems. The results showed that carrier lifetimes in QDs are much less affected by proton irradiation than that in QWs. A strong influence of irradiation on PL intensity was observed in multiple QWs after high-energy alpha particles irradiation.

  • 5233. Åberg, J.
    et al.
    Vynnycky, M.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Heat-flux measurements of industrial on-site continuous copper casting and their use as boundary conditions for numerical simulations2009In: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 62, no 4-5, p. 443-446Article in journal (Refereed)
    Abstract [en]

    An embedded sensor, designed for rapid and accurate response times and using wireless data transmission, has been developed for the on-site measurement of temperatures in industrial continuous casting moulds. The sensor has been used to measure the temperature at several points in the mould during production in a Southwire copper casting process. The measured data has been used to calculate the temperature gradient in the mould to estimate the heat flux through it; this is then used as a boundary condition for numerical simulations of solidification. For these, we employ a method that tracks the solidification front explicitly; this has an advantage over fixed-grid methods in simulations for materials having a short solidification interval, since the release of latent heat at the solidification front can be resolved without resorting to a very fine mesh. The special considerations required for setting the initial condition for the numerical scheme and the time taken for the superheated melt to form a solid shell are also discussed.

  • 5234.
    Åberg, Jonas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    On the Experimental Determination of Damping of Metals and Calculation of Thermal Stresses in Solidifying Shells2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis explores experimentally and theoretically two different aspects of the properties and behaviour of metals: their ability to damp noise and their susceptibility to crack when solidifying.

    The first part concerns intrinsic material damping, and is motivated by increased demands from society for reductions in noise emissions. It is a material’s inherent ability to reduce its vibration level, and hence noise emission, and transform its kinetic energy into a temperature increase. To design new materials with increased intrinsic material damping, we need to be able to measure it. In this thesis, different methods for measurement of the intrinsic damping have been considered: one using Fourier analysis has been experimentally evaluated, and another using a specimen in uniaxial tension to measure the phase-lag between stress and strain has been improved. Finally, after discarding these methods, a new method has been developed. The new method measures the damping properties during compression using differential calorimetry. A specimen is subjected to a cyclic uniaxial stress to give a prescribed energy input. The difference in temperature between a specimen under stress and a non-stressed reference sample is measured. The experiments are performed in an insulated vacuum container to reduce convective losses. The rate of temperature change, together with the energy input, is used as a measure of the intrinsic material damping in the specimen. The results show a difference in intrinsic material damping, and the way in which it is influenced by the internal structure is discussed.

    The second part of the thesis examines hot cracks in solidifying shells. Most metals have a brittle region starting in the two-phase temperature range during solidification and for some alloys this region extends as far as hundreds of degrees below the solidus temperature. To calculate the risk of hot cracking, one needs, besides knowledge of the solidifying material’s ability to withstand stress, knowledge of the casting process to be able to calculate the thermal history of the solidification, and from this calculate the stress. In this work, experimental methods to measure and evaluate the energy transfer from the solidifying melt have been developed. The evaluated data has been used as a boundary condition to numerically calculate the solidification process and the evolving stress in the solidifying shell. A solidification model has been implemented using a fixed-domain methodology in a commercial finite element code, Comsol Multiphysics. A new solidification model using an arbitrary Lagrange Eulerian (ALE) formulation has also been implemented to solve the solidification problem for pure metals. This new model explicitly tracks the movement of the liquid/solid interface and is much more effective than the first model.

  • 5235.
    Åberg, Jonas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    An On-site Industrial Experimental Heat Flux Study during Solidification of Pure Copper in the Southwire Process2007In: T INDIAN I METALS, ISSN 0972-2815, Vol. 60, no 2-3, p. 191-196Article in journal (Refereed)
    Abstract [en]

    To study the production of pure copper and copper alloys in the Southwire process the temperature in the mould has been measured on-site in the production process in a number of positions. To increase the accuracy and robustness of measurements a new type of thermocouple based temperature sensor has been developed and tested. The test system includes wireless transmission of measured data from the moving mould. The results from the measurements are then used to calculate the energy transfer rate from the solidifying shell as a function of time. An initial in-situ measurement campaign has been performed and the results are very promising.

  • 5236.
    Åberg, Jonas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Vynnycky, Michael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nassar, Hani
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Bergström, Thomas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    An on-site experimental heat flux study and its interpretation in a FEMLAB finite element simulation of continuous casting of copper in the South-Wire process2005In: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 58, no 4, p. 509-515Article in journal (Refereed)
    Abstract [en]

    The South-Wire process, a development of the Properzi process, to continuously cast copper has been studied both experimentally and by finite element computer simulation. The experimental work has been performed on site to get temperature data as a function of time at several locations within the mould. These experimental data have been used to evaluate boundary conditions for the heat transfer from the strand-mould interface and through the mould. A simulation model of the casting process has been developed in the program FEMLAB. In this program temperature varying material data and time varying boundary conditions have been used. The simulation model has been verified by comparing with an analytical solution, and then applied to the real physical process.

  • 5237.
    Åberg, Jonas
    et al.
    KTH, Superseded Departments, Materials Processing.
    Widell, Björn
    KTH, Superseded Departments, Casting of Metals.
    Uniaxial material damping measurements using a fiber optic lattice: a discussion of its performance envelope2004In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 44, no 1, p. 33-36Article in journal (Refereed)
    Abstract [en]

    Damping is the internal transfer of kinetic energy to other forms of energy. Today, most methods use either bending or torsional vibration to measure damping. This means that the strain field in the specimen is nonhomogeneous. If the damping of the tested material is linear, strain-independent, the values acquired with these traditional methods will be equal to the intrinsic material damping of the material. If, however, the damping is strain-dependent, nonlinear, the measured value will be an average of the damping of the specimen, and not equal to its intrinsic material damping. To address this problem, a method is required to experimentally determine the damping in uniaxial tension in order to produce the same strain level in all parts of the test specimen and hence obtain a measurement of the intrinsic material damping. Using such a method, it is possible to view the material damping as the phase angle between the stress and the strain in a harmonic oscillation. In this paper, a method is suggested for measuring this phase shift in uniaxial tension to determine the material damping properties. It uses a tensile test machine, an optical fiber Bragg grating technique and a lock-in amplifier. Measurements with the phase shift technique have been suggested previously, but its performance envelope has been overestimated. In this paper, the performance envelope is discussed and restricted. It is shown that the envelope depends on the specimen length, loss factor and test frequency. An optical strain measurement method is also believed to help avoid many electrical measurement problems seen with the originally proposed method.

  • 5238.
    Åberg, Jonas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Widell, Björn
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Larsson, Petra
    Investigation of the Damping in Twelve Metallic Plates Using Frequency Response2006Report (Other academic)
  • 5239.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Diffusion in multicomponent phases2008In: The SGTE Casebook: Thermodynamics At Work, Elsevier, 2008, 2, p. 347-350Chapter in book (Refereed)
  • 5240.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Multicomponent diffusion in compound steel2008In: The SGTE Casebook: Thermodynamics At Work, Elsevier Ltd , 2008, 2, p. 386-391Chapter in book (Other academic)
  • 5241.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Thermodynamics and Diffusion Coupling in Alloys-Application-Driven Science2012In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 43A, no 10, p. 3453-3461Article in journal (Refereed)
    Abstract [en]

    As emphasized by Stokes (1997), the common assumption of a linear progression from basic research (science), via applied research, to technological innovations (engineering) should be questioned. In fact, society would gain much by supporting long-term research that stems from practical problems and has usefulness as a key word. Such research may be fundamental, and often, it cannot be distinguished from "basic" research if it were not for its different motivation. The development of the Calphad method and the more recent development of accompanying kinetic approaches for diffusion serve as excellent examples and are the themes of this symposium. The drivers are, e.g., the development of new materials, processes, and lifetime predictions. Many challenges of the utmost practical importance require long-term fundamental research. This presentation will address some of them, e.g., the effect of various ordering phenomena on activation barriers, and the strength and practical importance of correlation effects.

  • 5242.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Thermodynamics of phase transformations in steels2012In: Phase Transformations in Steels, Elsevier, 2012, Vol. 1, p. 56-93Chapter in book (Refereed)
    Abstract [en]

    The basics of thermodynamics are reviewed with special attention to phase transformations. The distinction between internal and external variables is emphasized and the general equilibrium conditions are derived from the combined first and second law. The concepts of entropy production and driving force as well as stability are discussed. The calculation of thermodynamic properties and phase equilibria is considered and the Calphad method is briefly reviewed, including modeling of substitutional and interstitial disorder. The thermodynamic bases of phase diagrams are examined, and finally, the effect of interfaces, fluctuations and thermodynamics of nucleation are reviewed.

  • 5243.
    Ågren, John
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Brechet, YvesHutchinson, ChristopherPhilibert, JeanPurdy, Gary
    Thermodyanmics and phase transformations: The selected works of Mats Hillert2006Collection (editor) (Other academic)
  • 5244.
    Ågren, John
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Gray, George T. (Rusty), III
    Los Alamos Natl Lab, Los Alamos, NM USA..
    Hwang, Jennie S.
    H Technol Grp, Cleveland, OH USA..
    Matlock, David K.
    Colorado Sch Mines, Golden, CO 80401 USA..
    TODAY'S TECHNOLOGY TRENDS: SHAPING THE FUTURE OF ADVANCED MATERIALS2018In: Advanced Materials and Processes, ISSN 0882-7958, E-ISSN 2161-9425, Vol. 176, no 5, p. 14-17Article in journal (Refereed)
  • 5245.
    Ågren, John
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Schmid-Fetzer, Rainer
    True Phase Diagrams2014In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 45A, no 11, p. 4766-4769Article in journal (Refereed)
    Abstract [en]

    With the use of today's computer softwares, phase diagrams can readily be plotted with a wide choice of variables on the axes. Hillert defined a true phase diagram as a diagram where each point uniquely defines the stable phases. He also showed that not all choices of axis variables give true phase diagrams. In this note we will demonstrate that although the rules stated by Hillert are necessary they are not sufficient to have true phase diagrams.

  • 5246.
    Åhman, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Undersökning av bindningsmekanismer vid pressning av metallaminat: Investigation of bondning mechanisms at the pressing of metal laminates2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Increased understanding of the mechanisms that operate in conjunction with the welding of metal surfaces may help to improve existing manufacturing processes, and to enable new products and combinations of materials. The purpose of the project has therefore been to acquire a deeper understanding of what is happening in the bond for steel and for the factors that form the basis for a bond to develop between metals in the production of laminates by pressing. The merge has been done by pressing and the surfaces after the experiments have been studied in detail in the scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and with interferenceprofilometry in Wyko, to provide a greater understanding of the mechanisms that influence the bonding in the interface between metals.

     

    The project was limited to contain the materials Docol 1000, HyTens 1200, Aluminum AA3003 and a commercial steel. The parameters varied in the experiments to study their influence closer are temperature, pressure, heat treatment and pretreatment. This has been implemented by pressing with varying temperature and pressure. The materials have been pressed at room temperature or heated in an oven at 300 or 600 degrees and pressed immediately after the levying. Pretreatment was done by cleaning in acetone followed by either brushing or sandblasting alternatively no pretreatment have been done at all.

    The result was that the increased pressure and increased temperature increases the chance of joining by pressing. Pressing at slightly elevated temperature (about 100-250 degrees, depending on the material) makes bonding possible for metals which are not joined together at room temperature. Pretreatment by sandblasting gives a rougher and more riddled surface than brushing. At the cracking in the oxide layer at the pressing, wells new clean metal into between the oxides to the surface. When the new material reaches the surface, a joint can be made with the opposite clean material. The clean metal that wells up, then flows in a pattern which presses down the oxide in the material, away from the surface. This is done so more clean material can come to the surface and a finer binding can be obtained.

  • 5247.
    Åkerlind, Kristina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jefimova, Zenja
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Possible reasons for flaking appearance during cold rolling on an austenitic stainless steel2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The research describes possible reasons why the flaking tendency during cold rolling can vary between different austenitic stainless steels. The flaking phenomenon was observed after a rolling process in Granlund Tools AB’s roll reducing mill “KOR-8”. A literature review was conducted with the purpose of finding a connection between rolling process, austenitic stainless steels and flaking. The laboratory work aimed at revealing possible differences between the flaked material and materials that is known to be cold rolled with high surface finish in the particular machine. In order to come to a conclusion regarding the flaking appearance, scanning electron microscopy (SEM), Vickers hardness test and light optical microscopy (LOM) were performed. The literature review along with the laboratory results made it possible to determine the two major factors affecting the flaking behavior. Two independent analyses revealed what came to be the most important discovery in this study. LOM showed the appearance of a thick oxide scale on the surface of the flaked steel which was further confirmed by SEM-Energy-Dispersive X-ray Spectroscopy that indicated the existence of oxides on the steel’s surface. These observations along with the knowledge that oxide scales grow only during high-temperature processing led to the conclusion that the steel is not appropriate for the cold rolling process due to the earlier steel manufacturing.

  • 5248.
    Åkermo, Malin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Thermoforming of closed cell polymer foam and its residual compressive mechanical properties2008In: 8th International Conference on Sandwich Structures, FEUP edições (Faculdade de Engenharia da Universidade do Porto Edicoes), 2008Conference paper (Refereed)
  • 5249.
    Åkermo, Malin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Larberg, Ylva
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Sjölander, Jens
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Hallnader, Per
    Saab.
    Influence of interply friction on the forming of stacked prepreg2013In: Proceedings of 19th International Conference on Composite Materials (ICCM19), Curran Associates, Inc., 2013, p. 919-928Conference paper (Refereed)
  • 5250.
    Åkesson, Krister
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Floc behaviour in a twin-wire blade pressure pulse2004Licentiate thesis, comprehensive summary (Other scientific)
102103104105106 5201 - 5250 of 5300
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