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  • 1.
    Abadei, S
    et al.
    Chalmers University of Technology.
    Gevorgian, S
    Chalmers University of Technology.
    Cho, C.-R
    Royal Institute of Technology.
    Grishin, A.
    Royal Institute of Technology.
    Andreasson, Johanna
    Lindbäck, Ture
    DC field dependent properties of Na0.5K0.5NbO₃/SiO₂/Si structures at millimeter-wave frequencies2001Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, nr 13, 1900-1902 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dielectric properties of laser-ablated 0.5-μm-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Ω cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-μm-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 μm. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices

  • 2.
    Abadei, S.
    et al.
    Chalmers University of Technology, Department of Microelectronics.
    Gevorgian, S.
    Chalmers University of Technology, Department of Microelectronics.
    Kugler, V.
    Department of Physics, Linköping University.
    Helmersson, U.
    Department of Physics, Linköping University.
    Andreasson, Johanna
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Microwave properties of tunable capacitors basee on magnetron sputtered ferroelectric Na0.5K0.5NbO3 film on low and high resistivity silicon substrates2001Inngår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 39, nr 1-4, 359-366 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, small signal DC voltage dependent dielectric permittivity, loss tangent, and tuneability of magnetron sputtered epitaxial Na0.5K0.5NO3 films are studied experimentally. (100)-oriented Na0.5K0.5NbO3 films are deposited onto SiO2-buffered CMOS grade low resistivity (p = 10-20 cm) and high resistivity (p = 15-45 kcm) silicon substrates. Planar capacitors with 2 or 4 m gaps between electrodes have been fabricated on top of ferroelectric films. These devices have been characterized in the frequency range 1.0 MHz to 50 GHz at temperatures 30 - 300K. Na0.5K0.5NbO3/SiO2/Si structures on high resistivity silicon substrate exhibit C-V performances typical for Metal-Insulator- Semiconductor (MIS) capacitors. At low frequencies, f 1.0 GHz, the large tuneability and large losses are associated with the MIS structure, while at higher microwave frequencies the tuneability is mainly associated with the ferroelectric, film. At 1.0 MHz and room temperature, the tuneability of Na0.5K0.5NbO3/SiO2/Si structures more than 90%, reducing to 10-15 % at 50 GHz. The losses decrease with increasing the DC bias and frequency. A Q-factor more than 15 at 50 GHz is observed. The dielectric permittivity of the Na0.5K0.5NbO3 film is in the range 50-150 at frequencies 0.045-50 GHz. On low resistivity substrate the performance of Na0.5K0.5NbO3 films is completely screened by the high losses in silicon, and the tuneability is negligible

  • 3.
    Abbasi, Saeed
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Characterisation of airborne particles from rail traffic2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Since the investigation of wear particles in rail transport started in late-1910s, the high mass concentration of these particles has raised worries among researchers concerned with air quality. However, effective action has yet to be taken because of lack of relevant knowledge. This thesis provides applicable information for the airborne wear particles in rail transport. Some aspects of their characteristics such as diameter size, mass concentration, number concentration, and morphology of particles were investigated in field tests and laboratory tests.The effects on particle characterisations from different operational conditions in the field tests, and applying different braking materials, conducting tests in different applied loads or sliding velocities in the laboratory tests were studied. The main advantage of conducting laboratory tests was to focus on studying particles from one source. The possibility of repetition, using high sensitive instruments and conducting tests at low costs are the other advantages of laboratory studies. Paper A describes how a pin-on-disc machine was used to reproduce similar real operational conditions during mechanical braking in a train. The results were validated by comparing the field tests results with the laboratory studies. The particles morphology and size distribution were also studied.Paper B presents a summary of field tests results. The effects of curve negotiating and applying braking in different real conditions were investigated with an on-board measurement.The element composition of the particles and their potential sources were also investigated outside of the particles morphologies.Paper C presents comprehensive results from laboratory studies on airborne particles from different braking materials. The differences in the particle characteristics in similar test conditions were attributable to different material compositions and dominant wear mechanisms. A new index was introduced in this paper and is suggested to be used as a qualitative factor with regard to the airborne wear particle emission rate.Paper D is a review of the recent studies of exhaust emission and non-exhaust emission from rail vehicles. A summary of results, measurements, adverse health effects, and proposed or applied solutions are reviewed in this paper.

  • 4.
    Abdollahifakhr, Hamon
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Datorstödd konstruktion.
    Sengul, Ceyhun
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Datorstödd konstruktion.
    AUTOMATIC DESIGN OF WIRING PATTERN FOR CAR SEAT HEATERS2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This projects aims to develop design automation in product development. Design automation causes increase in producibility and decrease in product cost and manufacturing lead time.

    The study at hand is proposed to provide a new method and to introduce procedure to the design of wiring pattern for a car seat heater for Kongsberg Automotive, KA. KA is a Norwegian company and a global provider of engineering, design, and manufacture for seat comfort, driver and motion control systems, fluid assemblies, and industrial driver interface products. The method that currently is used in the company to create a wiring pattern is neither sufficient enough nor automated.

    In order to design the wiring pattern, at first procedure is handled by the designer. Secondly, car seat heater 2D layout is imported and then, the dimensions of the elements are defined as constraints. Then VBA codes are opened and the program is run. The result will be a wiring pattern in different 2D layouts. To make the design process easier, we have modeled five different layouts; wiring pattern of one element, two elements, three elements, five elements (with two back sides) and one element trapezoidal 2D layout.

    The algorithm written in VBA (Visual basic for application) creates the pattern according to the dimensions of the elements which are used as inputs to define constrained parameters. The created macros are simple to use and easy to modify, independent from the programming knowledge. The user is only responsible with parameter input and running the program. The solution gives wiring pattern for a car seat heater.

  • 5.
    Abiri, Olufunminiyi
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-local models in manufacturing simulations2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ductile fracture presents challenges with respect to material modelling andnumerical simulations of localization. The strain and damage localization maybe unwanted as it indicates a failure in the process or, as in the case ofmachining and cutting, a wanted phenomenon to be controlled. The latterrequires a higher accuracy regarding the modelling of the underlying coupledplastic and fracturing/damage behaviour of the material, metal in the currentcontext as well as the stability and robustness of the simulation procedure.This aim of this work is to develop, evaluate and implement formulations thatcan efficiently and reliably handle localization problems in machiningsimulations. The focus is on non-local models. The non-local models extendthe standard continuum mechanics theory by using non-local continuumtheory in order to achieve mesh independent results when simulating fractureor shear localization.The non-local damage model is implemented and various formulations areevaluated in a Matlab™ based finite element code. The chosen algorithm wasthen implemented in commercial software. The implementations remedy themesh sensitivity problem and gives convergent solution for metal cuttingsimulations with reasonable cost. The length scale associated with the nonlocalmodels are in the current context considered as a numericalregularization parameter. The model has been applied in machiningsimulations and compared with measurements from industry.Keywords: Finite element simulation; Non-local damage; Plasticity; Machining

  • 6.
    Abiri, Olufunminiyi
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simplifications of non-local damage models2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ductile fracture presents challenges with respect to material modelling and numerical simulations of localization. The strain and damage localization may be unwanted as it indicates a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying coupled plastic and fracturing/damage behaviour of the material, metal in the current context as well as the robustness of the simulation procedure. The focus of this thesis is on efficient and reliable finite element solution of the localization problem through the non-local damage model. The non-local damage model extends the standard continuum mechanics theory by using non-local continuum theory in order to achieve mesh independent results when simulating fracture or shear localization. In this work, the non-local damage model and its various simplifications are evaluated in an in-house finite element code developed using Matlab™. The accuracy, robustness, efficiency and costs of the models are investigated and also compared to a general multi-length scale finite element formulation. A numerical study versus published data is used to demonstrate the validity of the model. The explicit non-local damage variant will be implemented in a commercial finite element code for use in machining simulation

  • 7.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-local damage models in manufacturing simulations2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Localisation of deformation is a problem in several manufacturing processes. Machining is an exception where it is a wanted feature. However, it is always a problem in finite element modelling of these processes due to mesh sensitivity of the computed results. The remedy is to incorporate a length scale into the numerical formulations in order to achieve convergent solutions. Different simplifications in the implementation of a non-local damage model are evaluated with respect to temporal and spatial discretisation to show the effect of different approximations on accuracy and convergence.

  • 8.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-local damage models in manufacturing simulations2015Inngår i: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 49, 548-560 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Localisation of deformation is a problem in several manufacturing processes. Machining is an exception where it is a wanted feature. However, it is always a problem in finite element modelling of these processes due to mesh sensitivity of the computed results. The remedy is to incorporate a length scale into the numerical formulations in order to achieve convergent solutions. Different simplifications in the implementation of a non-local damage model are evaluated with respect to temporal and spatial discretisation to show the effect of different approximations on accuracy and convergence.

  • 9.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Qin, Hao
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Comparison of Multiresolution Continuum Theory and Nonlocal Dame model for use in Simulation of Manufacutring Processes2016Inngår i: International Journal for Multiscale Computational Engineering, ISSN 1543-1649, Vol. 14, nr 1, 81-94 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modelling and simulation of manufacturing processes may require the capability to account for localization behavior, often associated with damage/fracture. It may be unwanted localization indicating a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying physics, as well as the robustness of the simulation procedure. Two different approaches for achieving mesh-independent solutions are compared in this paper. They are the multiresolution continuum theory (MRCT) and nonlocal damage model. The MRCT theory is a general multilength-scale finite element formulation, while the nonlocal damage model is a specialized method using a weighted averaging of softening internal variables over a spatial neighborhood of the material point. Both approaches result in a converged finite element solution of the localization problem upon mesh refinement. This study compares the accuracy and robustness of their numerical schemes in implicit finite element codes for the plane strain shear deformation test case. Final remarks concerning ease of implementation of the methods in commercial finite element packages are also given.

  • 10.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. University of Johannesburg, South Africa.
    Svoboda, Ales
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Wedberg, Dan
    Controlling Thermal Softening Using Non-Local Temperature Field in Modelling2016Inngår i: Journal of Machining and Forming Technologies, ISSN 1947-4369, Vol. 8, nr 1-2, 13-28 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the aims of this work is to show that thermal softening due to the reduced flow strength of a material with increasing temperature may cause chip serrations to form during machining. The other purpose, the main focus of the paper, is to demonstrate that a non-local temperature field can be used to control these serrations. The non-local temperature is a weighted average of the temperature field in the region surrounding an integration point. Its size is determined by a length scale. This length scale may be based on the physics of the process but is taken here as a regularization parameter.

  • 11.
    Abiri, Olufunminiyi
    et al.
    Institute of Intelligent Systems, University of Johannesburg.
    Wedberg, Dan
    AB Sandvik Coromant.
    Svoboda, Ales
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-Local Modelling of Strain Softening in Machining Simulations2017Inngår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 225, 012053Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Non-local damage model for strain softening in a machining simulation is presented in this paper. The coupled damage-plasticity model consists of a physically based dislocation density model and a damage model driven by plastic straining in combination with the stress state. The predicted chip serration is highly consistent with the measurement results. 

  • 12.
    Adamopoulos, Stergios
    TEI Thessaly, Greece.
    Recovery and utilization of wood and rubber at the end of their lifespan to produce innovative products2014Inngår i: Development and Business Prospects in Thessaly by Symbiotic Utilization of Agricultural and Industrial Solid Waste to Produce Materials and Energy, November 24, Larissa, Greece, 2014Konferansepaper (Annet vitenskapelig)
  • 13.
    Adekunle, Kayode
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Skrifvars, Mikael
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Synthesis of reactive soybean oils for use as thermoset resins in composites.2007Konferansepaper (Fagfellevurdert)
  • 14.
    Adolfi, Sofia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Slag inclusion formation during solidification of steel alloys and in cast iron2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis explores the formation of segregation and inclusions during solidification of steel and cast iron. A better understanding of the formation mechanism should result in decreasing fraction of defects during solidification of ingot and strand material.

    Density driven macrosegregation was studied both experimentally and theoretically to see the effect of channel segregation on the total segregation. Formation of these pencil-like segregations is due to natural convection in the solidifying metal caused by liquid enrichment of elements with lower density compared to the bulk. It is suggested to change the composition to compensate for this density difference.

    Inclusion precipitation can be finite by limitations in segregation. Saturated liquid is found in the last solidified areas, often between dendrites. Here the enrichment of the liquid is possible due to microsegregation. Meanwhile crystals form and solidify the elements with low solubility in the solid is pushed out in the remaining liquid. Soon the liquid is saturated to the level where spontaneous formation of inclusions occurs. Microstructure studies by aid of SEM and micro-probe measurements are analysed to find at what point during solidification process the inclusions start to form. In steel making this formation has a detrimental effect on the mechanical properties in contrary to the production of nodular cast iron where the inclusions have a beneficial effect on the graphite formation.

    Inoculation of cast iron aims at reaching higher number density of graphite nodules, nodule morphology modification and control of nodule distribution during solidification. Late precipitation of nucleation sites has shown to have a positive impact on preventing chill. To find the most potent inoculation agent different additives were tested. Special effort has been made to analyse the effect of oxides and sulphides as nucleation sites.

  • 15.
    Adolfsson, Robin
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Jönsson, Caroline
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Är SundaHus materialklassning kompatibel med Miljöbyggnads, BREEAMs och LEEDs materialkrav?: En studie om SundaHus miljöklassningar.2015Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Vi lever i ett samhälle där det är brist på bostäder och kraven på nya och hållbara byggnader är allt större. De hus som byggs idag har fokus på att vara energisnåla för att spara på resurser. Något som glöms bort är valet av material till huskonstruktionerna. Material kan påverka natur och människor från vagga till graven genom till exempel materialets farliga ingående ämnen. Certifieringssystemen Miljöbyggnad, BREEAM och LEED har kontrollerats och deras materialkriterier har tagits fram. Genom ett urval av konstruktionsmaterial tagna ur SundaHus har en granskning gjorts på dessa material gentemot certifieringssystemens kriterier på material för att se om de är kompatibla. Minoriteten av kriterier var granskningsbara mot separata material och gick att kontrollera i SundaHus. Nästan alla material klarade kriterierna som kunde användas från Miljöbyggnad och BREEAM oavsett klassning i SundaHus. Inga av LEEDs kriterier var kompatibla med SundaHus för separata material. Det faktum att de sämre klassningarna i SundaHus kunde klara kriterierna som granskades tyder på att kraven i miljöcertifieringssystemen är för låga. Högre och fler krav borde ställas gällande enskilda material och farliga ämnen i dem.  

  • 16.
    Agde Tjernlund, Jessica
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Length-scale effects in yielding and damage development in polymer materials2005Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 17.
    Agde Tjernlund, Jessica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Gamstedt, Kristofer
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Gudmundson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Length-scale effects on damage development in tensile loading of glass-sphere filled epoxy2006Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 43, nr 24, 7337-7357 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Particle-reinforced polymers are widely used in load-carrying applications. The effect of particle size on damage development in the polymer is still relatively unexplored. In this study, the effect of glass-sphere size on the damage development in tensile loaded epoxy has been investigated. The diameter of the glass spheres ranged from approximately 0.5-50 mu m. The first type of damage observed was debonding at the sphere poles, which subsequently grew along the interface between the glass spheres and epoxy matrix. These cracks were observed to kink out into the matrix in the radial direction perpendicular to the applied load. The debonding stresses increased with decreasing sphere diameter, whereas the length to diameter ratio of the resulting matrix cracks increased with increasing sphere diameter. These effects could not be explained by elastic stress analysis and linear-elastic fracture mechanics. Possible explanations are that a thin interphase shell may form in the epoxy close to the glass spheres, and that there is a length-scale effect in the yield process which depends on the strain gradients. Cohesive fracture processes can contribute to the influence of sphere size on matrix-crack length. Better knowledge on these underlying size-dependent mechanisms that control damage development in polymers and polymer composites is useful in development of stronger materials. From a methodology point of view, the glass-sphere composite test can be used as an alternative technique (although still in a qualitative way) to hardness vs. indentation depth to quantify length-scale effects in inelastic deformation of polymers.

  • 18.
    Agde Tjernlund, Jessica
    et al.
    KTH, Tidigare Institutioner, Hållfasthetslära.
    Gamstedt, Kristofer
    KTH, Tidigare Institutioner, Hållfasthetslära.
    Xu, Zhi-Hui
    KTH, Tidigare Institutioner, Materialvetenskap.
    Influence of molecular weight on strain-gradient yielding in polystyrene2004Inngår i: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 44, nr 10, 1987-1997 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental observations have indicated that the presence of strain gradients has an influence on the inelastic behavior of polymers as well as in other materials such as ceramics and metals. The present study has experimentally quantified length-scale effects in inelastic deformations of the polymer material polystyrene (PS) with respect to the molecular length. The experimental technique that has been used is nano-indentation to various depths with a Berkovich indenter. The hardness has been calculated with the method by Oliver and Pharr, and also by direct measurements of the area from atomic force microscopy. The experiments showed that the length-scale effects in inelastic deformations exist in polystyrene at ambient conditions. The direct method gave a smaller hardness than the Oliver-Pharr method. It was also shown that the length-scale parameter according to Nix and Gao increases with increasing molecular weight. For high molecular weights above a critical value of entanglement, there was no pertinent increase in the length-scale parameter. The length-scale parameter for strain-gradient plasticity has a size of around 0.1 μm for polystyrene.

  • 19.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Hansson, Lars
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood2013Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, nr 3, 499-513 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170 °C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.

  • 20.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Sweden.
    Morén, Tom
    Luleå University of Technology, Sweden.
    Moisture properties of heat-treated Scots pine and Norway spruce sapwood impregnated with wood preservatives2012Inngår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 44, nr 1, 85-93 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experiment was conducted on commercially heat-treated (HT) Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) sapwood collected from Ht Wood AB, Arvidsjaur, Sweden. Secondary treatment on HT wood was performed in laboratory scale by impregnating with water-repellent preservatives (a commercial one and pine tar) to evaluate their retention and different moisture-related properties. Preservative solutions were impregnated using a simple and effective method. Wood samples were heated at 170°C in a dry oven and were immediately immersed in preservative solutions. Considerable retention was observed in HT wood, particularly in pine. Moisture adsorption properties were measured after conditioning in a high-humidity environmental chamber (4°C and 84% RH). Experimental results showed that secondary treatment enhanced moisture excluding efficiencies by decreasing equilibrium moisture content, suggesting better hydrophobicity. Soaking test in water showed that antiswelling and water repellence efficiencies improved, especially in tar-treated wood. In addition, this type of treatment significantly decreased water absorption. It was also possible to decrease volumetric swellings. Thus, secondary treatment of HT wood with preservative, in particular with tar, improved dimensional stability and water repellency.

  • 21.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Hansson, Lars
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy2013Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 59, nr 1, 57-66 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.

  • 22.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Karlsson, Olov
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine: Impact of wood structure and resin allocation2012Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, nr 2, 251-258 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in un-even distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

  • 23.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Yang, Qian
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Accelerated Mold Test on Dried Pine Sapwood Boards: Impact of Contact Heat Treatment2013Inngår i: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, nr 3, 174-187 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ''sapwood out'' and ''sapwood in'' positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). An accelerated mold test was performed in a climate chamber where naturally mold-infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides that accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth were 170°C for 10 min. However, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.

  • 24.
    Aid, Graham
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Ragn-sells, Sweden.
    Kihl, Anders
    Ragn Sells AB.
    Driving forces and inhibitors of secondary stock extraction2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Even though it’s well known to mankind that our common resources are limited and that recycling is a key for a sustainable future; in reality we see few examples of true recycling where virgin raw material is substituted by waste. There are endless number of examples where waste is utilized to some extent without solving the core issue: reducing the need of extracting virgin raw materials. This article analyses some of the driving forces and inhibitors that explains why it’s so difficult establish secondary stock extraction although technology is available. The authors discuss and suggest possible ways for reducing the some of the main barriers.

  • 25.
    Aijaz, Asim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Kubart, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Ion induced stress relaxation in dense sputter-deposited DLC thin films2017Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 111, nr 5, 051902Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Deposition of high-density and low-stress hydrogen-free diamond like carbon (DLC) thin films is demonstrated using a pulsed ionized sputtering process. This process is based on high power impulse magnetron sputtering, and high C ionization is achieved using Ne as the sputtering gas. The intrinsic compressive stress and its evolution with respect to ion energy and ion flux are explained in terms of the compressive stress based subplantation model for DLC growth by Davis. The highest mass density was similar to 2.7 g/cm(3), and the compressive stresses did not exceed similar to 2.5 GPa. The resulting film stresses are substantially lower than those achieved for the films exhibiting similar mass densities grown by filtered cathodic vacuum arc and pulsed laser deposition methods. This unique combination of high mass density and low compressive stress is attributed to the ion induced stress relaxation during the pulse-off time which corresponds to the post thermal spike relaxation timescales. We therefore propose that the temporal ion flux variations determine the magnitude of the compressive stress observed in our films. Published by AIP Publishing.

  • 26. Ajay, A.
    et al.
    Raja, V. S.
    Sivakumar, G.
    Joshi, Shrikant V.
    Hot corrosion behavior of solution precursor and atmospheric plasma sprayed thermal barrier coatings2015Inngår i: Corrosion Science, Vol. 98, 271-279 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hot corrosion behavior of solution precursor plasma spray (SPPS) thermal barrier coating (TBC) in molten salt mixtures of 90wt.% Na<inf>2</inf>SO<inf>4</inf>+5wt.% V<inf>2</inf>O<inf>5</inf>+5wt.% NaCl and 50wt.% Na<inf>2</inf>SO<inf>4</inf>+50wt.% V<inf>2</inf>O<inf>5</inf> at 900°C is compared vis-à-vis atmospheric plasma spray (APS) coating. APS TBCs show better hot corrosion resistance than SPPS TBCs in both the salt mixtures. The vertical cracks in SPPS coatings, meant for strain tolerance and high thermal cycling life, serve as channels for transporting salts across the coating to bond coat/top coat interface and accelerate failure. © 2015 Elsevier Ltd.

  • 27.
    Akbarnejad, Shahin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Investigation on static strength of welded joints2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Although high strength steels represent yield strength up to 1300 MPa, welded structures reveal lowerstrength values. The strongest commercially available electrode provides the yield strength of about900 MPa. Therefore, in welded steels with strength above this type of filler metal, achieving anacceptable global strength is a crucial issue.

    In this master thesis, affects of different welding procedures on static strength of welded jointsof Weldox 960 and Weldox 1100 steels, were studied. These steels are produced by SSAB inOxelösund. Meanwhile, finite element method analyses were applied in order to investigatethe static strength behavior of such weldments under uniaxial tension.

    The welding parameters which were selected as variables are:

    •  Heat input
    • Weld joint geometry
    • Filler metal

    When weld metal is undermatching in strength levels than the base material, by applyingtension the soft weld metal begins to deform before parent metal. At that point thedeformation of resulted soft zone, including the weld metal and the heat affected zone, ishindered by high strength parent metal. Thus, uniaxial stress caused by uniaxial load isconverted to multiaxial stress. This conversion in tension results in increase in the staticstrength of weldment. The increase in strength is emphasized by increase in the width of thewelded joint while the thickness of the plate is kept as constant.

    After experiments and performing FEM studies, it was revealed that the static strength ofWeldox 960 welded joints approaches towards the tensile strength of parent metal by increasein the width of the weldment. In Weldox 1100 joints; a slight increase in tensile properties ofthe weldments, when the width of the sample increases, was observed.

  • 28.
    Akhtar, Farid
    Institute of Powder Metallurgy, University of Science & Technology, Beijing.
    A new method to process high strength TiCN stainless steel matrix composites2007Inngår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 50, nr 3, 250-254 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Layered composites of Ti(C, N) reinforcements and stainless steel have been prepared successfully by powder technology. The layer composite consisted of two layers. The upper layer consisted of TiCN reinforcements and stainless steel as binder material. The lower layer was entirely of binder material (stainless steel). The micro structural study revealed that the upper layer (TiCN/465 stainless steel) showed core–rim microstructure of conventional cermets and the lower layer showed the structure of sintered steel. An intermediate layer was formed due to diffusion reaction of upper and lower layers. This intermediate layer showed a gradient microstructure. The bending strength of the layered material measured was remarkably higher. Ninety per cent increase in the bending strength in the case of 50 wt-% reinforcement in the upper layer was found. The fracture morphologies of upper, lower and intermediate layers are also reported

  • 29.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    An investigation on the solid state sintering of mechanically alloyed nano-structured 90W--Ni--Fe tungsten heavy alloy2008Inngår i: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 26, nr 3, 145-151 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, 90W–7Ni–3Fe heavy alloy was investigated for its microstructure development, mechanical properties and fracture behavior after solid state sintering. The nano-sized powders were synthesized by mechanical alloying (MA). The microstructure of solid state sintered heavy alloys consisted of tungsten matrix. The average tungsten grain size in the range of 1.7–3.0 μm was obtained. It was found that the grain size largely affected the mechanical properties. Tensile strength more than 1200 MPa was achieved at a sintering temperature of 1350 °C. Fracture mechanisms based on microscopical observations on the fracture surfaces were studied. Matrix failure, tungsten-intergranular cleavage and tungsten–matrix interfacial separation were found to be the possible failure mechanisms.

  • 30.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Carbide reinforced steel matrix composites2009Inngår i: Recent Research Developments in Materials Science, Research Signpost, 2009Kapittel i bok, del av antologi (Fagfellevurdert)
  • 31.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ceramic reinforced high modulus steel composites: processing, microstructure and properties2014Inngår i: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 53, nr 3, 253-263 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ceramic reinforced steel matrix composites are materials for automotive, aerospace, wear and cutting applications. Such metal matrix composites (MMCs) combine attractive physical, mechanical and wear properties with ease of fabrication and low cost. The review focuses on the current state of the art of producing these metal matrix composites, ceramics reinforcements, composition of steel matrix, microstructure evolution and parameters influencing the mechanical and wear properties. Processing methods to fabricate ceramic reinforced steel matrix composites are discussed to produce these composites with low number of defects, homogeneous microstructure and high mechanical and wear performance. The influence of chemical nature of ceramic reinforcements and composition of steel matrix on the microstructure, mechanical and wear properties is presented. The strengthening mechanisms and parameters controlling wear performance of steel MMCs are described as a function of the content of ceramic reinforcements, microstructural design and structure of the steel matrix. Keeping in view the stability of ceramics in steels, suitable ceramic reinforcements and steel matrix materials are discussed. Moreover, the importance of microstructure and interface between ceramic reinforcement and steel matrix in controlling the mechanical properties of steel MMCs is highlighted. The review identifies area of research for development to fully appreciate and tailor the properties of these industrially important composites.

  • 32.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Effect of additive Cu-10Sn alloy on sintering Behavior of elemental powders in composition of 465 stainless steel2007Inngår i: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 14, nr 4, 61-74 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The addition of Cu-10Sn alloy for developing the high strength 465 maraging stainless steel from elemental powders was studied. The sintering parameters investigated include the sintering temperature, the sintering time, and the mass percent of Cu-10Sn. For vacuum sintering, effective sintering occurs at temperature between 1250°C and 1300°C. The maximum sintered density was achieved at 1300°C for 60 min with 3% (in mass percent) Cu-10Sn alloy. More than 3% (in mass percent) Cu-10Sn content and temperature above 1300°C caused slumping of the samples. A maximum density of 7.4 g/cm3 was achieved with 3% (in mass percent) Cu-10Sn content at a sintering temperature of 1300°C for 60 min. A maximum ultimate tensile strength (UTS) of 517 MPa was achieved with 3% (in mass percent) Cu-10Sn content. With content higher than 2% (in mass percent) Cu-10Sn, a maximum increase in the density was observed. The fracture morphologies of the sintered samples are also reported.

  • 33.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Effect of Microstructural Parameters on the Wear Properties of High Volume Ceramic Reinforced Metal Matrix Composites2009Inngår i: Powder Metallurgy Research Trends, New York: Nova Science Publishers, Incorporated , 2009Kapittel i bok, del av antologi (Fagfellevurdert)
  • 34.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hierarchical zeolites for carbon capture2014Patent (Annet (populærvitenskap, debatt, mm))
  • 35.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    High volume fraction carbide reinforced copper matrix composites for sliding contact applications2007Inngår i: PRICM 6: selected, peer reviewed papers from the Sixth Pacific Rim International Conference on Advanced Materials and Processing, November 5 - 9, 2007, ICC Jeju, Jeju Island, Korea / [ed] Young Won Chang; Nack J. Kim; Chong Soo Lee, Stafa-Zurich: Trans Tech Publications Inc., 2007, 627-630 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study deals with the processing, microstructure and properties of the carbide reinforced copper matrix composites. Powder technology was used to successfully fabricate the composites. NbC particulates were used as reinforcements for copper matrix. The microstructure of the composite was characterized by scanning electron microscopy. The microstructural study revealed that the NbC particles were distributed uniformly in the matrix phase. No interface debonding and micro- cracks were observed in the composite. NbC particles were found in round shape in copper matrix composite. The composite hardness of 78 HRA was found with 60vol% NbC content. Electrical conductivity as high as 7%IACS was achieved. The wear performance and conductivity value predicts that NbC reinforced copper matrix composites can be used as sliding contact applications.

  • 36.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Microstructure evolution and wear properties of in situ synthesized TiB 2 and TiC reinforced steel matrix composites2008Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 459, nr 1-2, 491-497 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Steel matrix composite reinforced with TiB2 and TiC reinforcements (30 to 70wt%) have been produced through the synthesis reaction from Ti, C and FeB. The sintered composites were characterized by X-ray diffraction and scanning electron microscopy. TiB2, TiC and steel were detected by X-ray diffraction analysis. The scanning electron micrographs revealed the morphology and distribution of the reinforcements. TiB2 and TiC were thermally stable in the steel matrix. The results showed that different mechanisms of evolution of reinforcements in steel matrix were operative. TiB2 grew in hexagonal prismatic or rectangular shape and TiC in spherical shape. The reciprocating sliding wear test was conducted on the composite. The results of sliding wear showed that the wear loss decreased with increase in the reinforcement content. The wear mechanisms were polishing wear and microploughing for the composites containing high volume fraction of the reinforcements, whereas microploughing and grooving were the dominant wear mechanisms for the composites containing low volume fraction of the reinforcements.

  • 37.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    On the microstructure and properties of tungsten heavy alloys2007Inngår i: Advanced materials and processing: selected, peer reviewed papers from the Sixth Pacific Rim International Conference on Advanced Materials and Processing, November 5-9, 2007, ICC Jeju, Jeju Island, Korea, PRICM 6 / [ed] Young Won Chang; Nack J. Kim; Chong Soo Lee, Stafa-Zurich: Trans Tech Publications Inc., 2007, Vol. 26-28, 1055-1058 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this research, the effect of microstructure on the mechanical properties of tungsten heavy alloys is discussed. The tensile properties of tungsten heavy alloys are found to be dependent on volume fraction of W, contiguity and grain size of W particle. The ductility is found to be influenced by contiguity and connectivity. The volume fraction of matrix increases sharply with the increase in rare metal oxide impurity, which adversely affects the mechanical properties of tungsten heavy alloys.

  • 38.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Processing, microstructure, properties and wear behavior of in situ synthesized TiB 2 and TiC thick films on steel substrates2007Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 201, nr 24, 9603-9609 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    TiB2 and TiC reinforced Fe matrix thick films (2 mm thickness) were produced through the synthesis reaction from Ti, C and FeB powders with varying porosity on the steel substrates. Powder technology was used as a processing method. The films and the substrates were sintered in a single step. TiB2, TiC and Fe were detected in the films by X-ray diffraction analysis. The fact that no other reaction product was detected revealed the thermal stability of TiB2 and TiC. The formation of secondary reaction products was inhibited during the reactive sintering. The films showed maximum strength of 163–466 MPa when sintered separately at 1350 °C. The strength of the films varied with their porosity. The films showed considerable bonding strength with the steel substrates. The delamination of the films from the steel substrates was observed at stress values from 454–781 MPa. The microstructure, fracture and delaminated surface morphologies were studied. The wear resistance against hardened high speed steel was studied in reciprocating sliding tests. The wear mechanisms were discussed by means of microscopical observation on the worn surfaces

  • 39.
    Akhtar, Farid
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Pulse current processing of hierarchically porous monoliths from macro and microporous powders2009Konferansepaper (Annet vitenskapelig)
  • 40.
    Akhtar, Farid
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Sintering behavior of elemental powders with FeB addition in the composition of martensitic stainless steel2007Inngår i: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 16, nr 6, 726-729 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of sintering additive for the development of high-strength martensitic stainless steel from elemental powders was studied. The sintering parameters investigated were: sintering temperature, sintering time, and wt.% of FeB. In vacuum sintering, effective sintering took place between 1300 and 1350 °C with 1-1.5 wt.% FeB addition. The maximum sintered density and ultimate tensile strength (UTS) were achieved after sintering at 1350°C for 60 min with 1 wt.% FeB. Secondary pores were observed in samples containing more than 1.5 wt.% FeB sintered at 1350 °C for 60 min. More than 1.5 wt.% FeB content and temperature above 1350°C caused slumping of the specimens. Maximum UTS of 505 MPa was achieved with 1 wt.% FeB content. Above 0.5 wt.% FeB content, maximum increase in density was observed. Fracture morphologies of the sintered samples are reported.

  • 41.
    Akhtar, Farid
    Stockholm University.
    Stainless Steel Polymer Composites2012Inngår i: Wiley Encyclopedia of Composites, John Wiley & Sons, 2012Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    In electronic, automotive, medical, and aerospace industries, electrostatic discharge (ESD) control and electromagnetic interference (EMI) shielding are important design considerations. Conductive polymer composites are well researched and commercially available materials for ESD control and EMI shielding. Several kinds of conductive fillers are incorporated in the form of particulates and fibers in polymer matrix. A comparison between various conductive fillers in polymer matrix is presented. Stainless steel fibers as conductive filler for polymer matrix offer several advantages. Polymer composites show resistivities in the range of 103−106 Ω/sq at a volume fraction as low as 0.75 vol% of stainless steel fibers. The effect of filler size, shape of the filler, critical volume fraction, and effect of polymer matrix on the ESD control/EMI shielding properties of the stainless steel-reinforced conductive polymer composite is discussed. Important parameters are described to obtain effective ESD control and EMI shielding using stainless fiber polymer matrix composites. Several reported stainless steel-reinforced polymer composites are summarized and their effectiveness for ESD control and EMI shielding is compared

  • 42.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Structured adsorbents with High CO2 over N2 selectivity and CO2 uptake capacity2012Inngår i: 2012 AIChE annual meeting: David L. Lawrence Convention Center, Pittsburgh, PA, October 28-November 2, 2012 : conference proceedings., New York: American Institute of Chemical Engineers, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Structured adsorbents with high CO2 adsorption capacity, CO2 over N2 selectivity and rapid adsorption and desorption kinetics are ideal for CO2 capture from power-plant flue gas at a low cost. We report here binder-free zeolite monoliths with high CO2 over N2 selectivity (> 500) and uptake capacity (4mmolg-1) at 298 K and 101 kPa. Binder-free zeolite monoliths were consolidated by a rapid and facile processing approach called pulse current processing (PCP) from partially K exchanged NaA powders. The pore widow size of NaA was optimized by partially exchanging Na with K cations to achieve a high CO2 over N2 selectivity while maintaining a high CO2 uptake capacity. The CO2 uptake from binary mixtures of 0.10CO2-0.90N2 was obtained from the single component CO2 and N2 adsorption isotherms by applying Ideal adsorption solution (IAS) and Fast IAS theories. The binder-free adsorbents with an optimum degree of ion exchange display extraordinarily high CO2 over N2 selectivity and high CO2 uptake, together with a rapid CO2 adsorption and desorption kinetics and high mechanical stability. The performance of the new adsorbent has been compared with other potential candidates for efficient swing adsorption processes by a figure of merit. Key words: CO2 Capture; Zeolite monoliths; Pulse current processing; Selectivity; Adsorption; Ideal adsorbed solution (IAS) theory

  • 43.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring gas adsorbents by processing of porous powders2014Konferansepaper (Fagfellevurdert)
  • 44.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring of Aluminophosphates Monoliths for Carbon Capture2015Konferansepaper (Fagfellevurdert)
  • 45.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring of Nanoporous Powders into Hierarchically Porous Nanostructured Adsorbents for Clean Energy2016Konferansepaper (Fagfellevurdert)
  • 46.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring of nanoporous powders into hierarchically porous nanostructured adsorbents for decarbunization2015Konferansepaper (Fagfellevurdert)
  • 47.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Structuring of porous powders for gas separation applications2013Konferansepaper (Annet vitenskapelig)
  • 48.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Structuring of porous powders into hierarchically porous adsorbents2013Konferansepaper (Fagfellevurdert)
  • 49.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Synthesis, microstructure and mechanical properties of Al 2 O 3 reinforced Ni 3 Al matrix composite2009Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 499, nr 1-2, 415-420 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method to synthesize alumina reinforced Ni3Al intermetallic matrix composites has been described. The powder mixture of nickel and aluminium was mechanically alloyed. The powder mixture was excessively heated during mechanical alloying and then exposed to atmosphere for oxidation. The oxidized powder mixture was transformed into alumina reinforced nickel aluminide matrix composite on subsequent pulse current processing. Alumina reinforcements were generated in the nickel aluminide matrix by in situ precipitation. The microstructure of the composite showed that the alumina reinforcements were 50–150 nm in size. The fine alumina reinforcements were homogeneously distributed in the matrix phase. The mechanical properties of the alumina reinforced nickel aluminide matrix composite fairly exceeded the nickel aluminide alloys. This novel synthesis approach allowed the rapid and facile production of high strength alumina reinforced Ni3Al matrix composites.

  • 50.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Zeolite adsorbents for gas separation applications2013Konferansepaper (Fagfellevurdert)
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