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Linder, D., Hou, Z., Xie, R., Hedström, P., Ström, V., Holmström, E. & Borgenstam, A. (2019). A comparative study of microstructure and magnetic properties of a Ni–Fe cemented carbide: Influence of carbon content. International Journal of Refractory Metals and Hard Materials, 80, 181-187
Open this publication in new window or tab >>A comparative study of microstructure and magnetic properties of a Ni–Fe cemented carbide: Influence of carbon content
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2019 (English)In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 80, p. 181-187Article in journal (Refereed) Published
Abstract [en]

Due to the renewed interest in alternative binders for cemented carbides it is important to understand how the binder composition influences not only mechanical properties but also the microstructure and related measurements for quality control. Microstructure and chemical composition of WC-Co is often evaluated by magnetic measurements. However, when the binder composition deviates significantly from conventional Co-based binders it should not be assumed that the standard measurements can be used to directly evaluate the same parameters. In this paper we investigate the influence of relative C-content on the microstructure and magnetic properties of an alternative binder cemented carbide. It is shown that the saturation magnetization is related to the relative C-content and the magnetic coercivity is related to the microstructure, more specifically to the binder phase distribution, but could not be directly linked to the carbide grain size in the same manner as for standard WC-Co. Furthermore, a direct correlation between Curie temperature and saturation magnetization is observed for this system which means that the Curie temperature potentially could be used for calibration of empirical relations or as a method to accurately determine the binder volume fraction.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Alternative binder, Cemented carbide, Cermet, Cobalt substitution, Magnetic properties, Metal-matrix composite, Microstructure
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-246465 (URN)10.1016/j.ijrmhm.2019.01.014 (DOI)000460992100018 ()2-s2.0-85060087544 (Scopus ID)
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-08-27Bibliographically approved
Hou, Z., Linder, D., Hedström, P., Forsberg, A., Holmström, E. & Ström, V. (2019). Effect of carbon content on the Curie temperature of WC-NiFe cemented carbides. International Journal of Refractory Metals and Hard Materials, 78, 27-31
Open this publication in new window or tab >>Effect of carbon content on the Curie temperature of WC-NiFe cemented carbides
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2019 (English)In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 78, p. 27-31Article in journal (Refereed) Published
Abstract [en]

We have investigated the effect of the carbon content on the Curie temperature of a cemented carbide composite material with a Ni-Fe alloy as the binder phase and WC as the hard phase. In the carbon concentration range from 5.72 to 5.83 wt% carbon, which covers the interval where WC coexists with fcc Ni-Fe without other phases (the ‘carbon window’), the Curie temperature rises from 200 to 527 °C. This result indicates the possibility to use the Curie temperature to determine the carbon balance in the system. With thermodynamic calculations and kinetic simulations we can quantitatively establish the correlation between the carbon and tungsten content of the binder phase and the Curie temperature. This strong compositional effect on the Curie temperature is quantitatively very different from the conventional Co-based cemented carbides, with Curie temperatures of about 950–1050 °C.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Alternative binder, Carbon window, Cemented carbide, Curie temperature, Hard metals, Binary alloys, Binders, Carbide tools, Carbides, Cobalt compounds, Iron alloys, Nickel alloys, Carbon concentrations, Cemented carbide composites, Cemented carbides, Compositional effects, Effect of carbons, Kinetic simulation, Thermodynamic calculations, Temperature
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-236334 (URN)10.1016/j.ijrmhm.2018.08.010 (DOI)000451489300003 ()2-s2.0-85052282006 (Scopus ID)
Note

QC 20181109

Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2018-12-11Bibliographically approved
Hou, Z., Linder, D., Hedström, P., Ström, V., Holmström, E. & Borgenstam, A. (2019). Evaluating magnetic properties of composites from model alloys – Application to alternative binder cemented carbides. Scripta Materialia, 168, 96-99
Open this publication in new window or tab >>Evaluating magnetic properties of composites from model alloys – Application to alternative binder cemented carbides
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2019 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 168, p. 96-99Article in journal (Refereed) Published
Abstract [en]

The magnetic properties of 85Ni-15Fe model alloys containing Co, W and C have been studied with the intent to isolate the influence of alloy chemistry on quality control measurements of alternative binder cemented carbides. The results show a strong influence of dissolved W on the Curie temperature and the saturation magnetization. The amount of dissolved C, and the presence of WC precipitates, on the other hand, is shown to have negligible effect. Furthermore, the magnetic coercivity is indicated to be entirely dominated by the microstructural features and quite insensitive to composition.

Place, publisher, year, edition, pages
Acta Materialia Inc, 2019
Keywords
Alternative binder, Cemented carbide, Magnetic properties, Metal-ceramic composite, Ni-Fe model alloy, Binary alloys, Binders, Carbide tools, Carbides, Cobalt alloys, Nickel alloys, Saturation magnetization, Alloy chemistry, Cemented carbides, FE model, Magnetic coercivities, Metal-ceramic composites, Microstructural features, Properties of composites, Quality control measurement, Iron alloys
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-252472 (URN)10.1016/j.scriptamat.2019.04.033 (DOI)000470798400021 ()2-s2.0-85064921201 (Scopus ID)
Note

QC 20190715

Available from: 2019-07-15 Created: 2019-07-15 Last updated: 2019-07-15Bibliographically approved
Masood, A., Baghbaderani, H. A., Ström, V., Stamenov, P., McCloskey, P., Mathúna, C. Ó. & Kulkarni, S. (2019). Fabrication and soft magnetic properties of rapidly quenched Co-Fe-B-Si-Nb ultra-thin amorphous ribbons. Journal of Magnetism and Magnetic Materials, 483, 54-58
Open this publication in new window or tab >>Fabrication and soft magnetic properties of rapidly quenched Co-Fe-B-Si-Nb ultra-thin amorphous ribbons
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2019 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 483, p. 54-58Article in journal (Refereed) Published
Abstract [en]

Ultra-thin soft magnetic amorphous ribbons of Co-Fe-B-Si-Nb alloy were synthesised by a single step rapid-quenching approach to acquire advantage of improved material performance and lower costs over commercial amorphous alloys. The amorphous ribbons of approximately 5.5 µm thicknesses were quenched by a single roller melt spinner in a single-step production process and characterised for their structural and magnetic properties. The disordered atomic structure of amorphous ribbons was confirmed by the X-ray diffraction. A surface morphology study revealed the continuity of ultra-thin ribbons without pores over a large scale. The amorphous alloy showed the ultra-soft magnetic properties in the as-quenched state. The observed thickness dependency of the magnetic properties was attributed to the increased surface roughness and possibly due to a lack of densely packed atomic structure resulting from the extremely high cooling rates experienced by ultra-thin ribbons. We propose that in-situ thinning process of amorphous ribbons significantly reduces the basic material cost and eliminates the need for post-processing steps; hence it provides the opportunity for mass production of high-performance soft magnetic amorphous ribbons at relatively lower costs.

Place, publisher, year, edition, pages
Elsevier B.V., 2019
Keywords
Amorphous metals, High-frequency applications, Soft-magnetic properties, Ultra-thin ribbons, Amorphous alloys, Crystal atomic structure, In situ processing, Iron alloys, Magnetic properties, Magnetism, Niobium alloys, Silicon alloys, Surface roughness, High cooling rates, Material performance, Production process, Soft magnetic properties, Structural and magnetic properties, Ultra-thin, Amorphous silicon
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-252492 (URN)10.1016/j.jmmm.2019.03.079 (DOI)000471858100009 ()2-s2.0-85063231036 (Scopus ID)
Note

QC 20190711

Available from: 2019-07-11 Created: 2019-07-11 Last updated: 2019-07-29Bibliographically approved
Pourrahimi, A. M., Andersson, R. ., Tjus, K., Ström, V., Björk, A. & Olsson, R. T. (2019). Making an ultralow platinum content bimetallic catalyst on carbon fibres for electro-oxidation of ammonia in wastewater. Sustainable Energy and Fuels, 3(8), 2111-2124
Open this publication in new window or tab >>Making an ultralow platinum content bimetallic catalyst on carbon fibres for electro-oxidation of ammonia in wastewater
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2019 (English)In: Sustainable Energy and Fuels, ISSN 2398-4902, Vol. 3, no 8, p. 2111-2124Article in journal (Refereed) Published
Abstract [en]

Electrocatalysis of wastewater containing ammonia is a promising alternative to chemical and biological water purification for several reasons, one being that energy-rich hydrogen gas is generated as a by-product while the reaction can be strictly controlled to meet demands. An objective has been to reduce the loading of expensive platinum (Pt) in the catalyst electrodes, and to reduce the poisoning of the metal surface during the electrolysis. Herein, the co-deposition of a copper-platinum (Cu-Pt) bimetallic alloy onto carbon filaments, stripped from their polymeric coating, is shown to give an electrocatalytic performance superior to that of pure Pt at a content of less than 3 wt% Pt. The key to the enhanced performance was to take advantage of micrometer-sized carbon filaments to distribute a very large bimetallic alloy surface uniformly over the filaments. The Cu-Pt-alloy-coated filaments also suffer less electrode poisoning than pure Pt, and are bonded more strongly to the carbon fibre due to better mechanical interlocking between the bimetallic alloy and the carbon filaments. High-resolution electron microscopy studies combined with a tuned electro-deposition process made it possible to tailor the catalyst micro/nano morphology to reach a uniform coverage, surrounding the entire carbon filaments. The results are promising steps towards large-scale wastewater treatment, combined with clean energy production from regenerated hydrogen.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Other Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-255760 (URN)10.1039/c9se00161a (DOI)000476912900020 ()2-s2.0-85069762947 (Scopus ID)
Note

QC 20190809

Available from: 2019-08-09 Created: 2019-08-09 Last updated: 2019-08-09Bibliographically approved
Antonio, C., Andersson, R. ., Ström, V., Wu, Q., Sacchi, B., Farris, S., . . . Olsson, R. T. (2019). Preparation and Comparison of Reduced Graphene Oxide and Carbon Nanotubes as Fillers in Conductive Natural Rubber for Flexible Electronics. Omega, 4(2)
Open this publication in new window or tab >>Preparation and Comparison of Reduced Graphene Oxide and Carbon Nanotubes as Fillers in Conductive Natural Rubber for Flexible Electronics
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2019 (English)In: Omega, ISSN 0030-2228, E-ISSN 1541-3764, Vol. 4, no 2Article in journal (Refereed) Published
Abstract [en]

Conductive natural rubber (NR) nanocomposites were prepared by solvent-casting suspensions of reduced graphene oxide(rGO) or carbon nanotubes (CNTs), followed by vulcanization of the rubber composites. Both rGO and CNT were compatible as fillers in the NR as well as having sufficient intrinsic electrical conductivity for functional applications. Physical (thermal) and chemical reduction of GO were investigated, and the results of the reductions were monitored by X-ray photoelectron spectroscopy for establishing a reduction protocol that was useful for the rGO nanocomposite preparation. Field-emission scanning electron microscopy showed that both nanofillers were adequately dispersed in the main NR phase. The CNT composite displays a marked mechanical hysteresis and higher elongation at break, in comparison to the rGO composites for an equal fraction of the carbon phase. Moreover, the composite conductivity was always ca. 3-4 orders of magnitude higher for the CNT composite than for the rGO composites, the former reaching a maximum conductivity of ca. 10.5 S/m, which was explained by the more favorable geometry of the CNT versus the rGO sheets. For low current density applications though, both composites achieved the necessary percolation and showed the electrical conductivity needed for being applied as flexible conductors for a light-emitting diode. 

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-246150 (URN)10.1021/acsomega.8b03630 (DOI)000460237300107 ()2-s2.0-85061903645 (Scopus ID)
Note

QC 20190318

Available from: 2019-03-14 Created: 2019-03-14 Last updated: 2019-05-22Bibliographically approved
Xie, R., Lizárraga, R., Linder, D., Hou, Z., Ström, V., Lattemann, M., . . . Vitos, L. (2019). Quantum mechanics basis of quality control in hard metals. Acta Materialia, 169, 1-8
Open this publication in new window or tab >>Quantum mechanics basis of quality control in hard metals
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2019 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 169, p. 1-8Article in journal (Refereed) Published
Abstract [en]

Non-destructive and reliable quality control methods are a key aspect to designing, developing and manufacturing new materials for industrial applications and new technologies. The measurement of the magnetic saturation is one of such methods and it is conventionally employed in the cemented carbides industry. We present a general quantum mechanics based relation between the magnetic saturation and the components of the binder phase of cemented carbides, which can be directly employed as a quality control. To illustrate our results, we calculate the magnetic saturation of a binder phase, 85Ni15Fe binary alloy, using ab-initio methods and compare the theoretical predictions to the magnetic saturation measurements. We also analyse interface and segregation effects on the magnetic saturation by studying the electronic structure of the binder phase. The excellent agreement between calculations and measurements demonstrates the applicability of our method to any binder phase. Since the magnetic saturation is employed to ensure the quality of cemented carbides, the present method allows us to explore new materials for alternative binder phases efficiently.

Place, publisher, year, edition, pages
Acta Materialia Inc, 2019
Keywords
Ab-initio calculations, Binder phase, Hard metal, Magnetic saturation
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-246425 (URN)10.1016/j.actamat.2019.02.036 (DOI)2-s2.0-85062451846 (Scopus ID)
Note

QC 20190401

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-06-11Bibliographically approved
Nordenström, M., Riazanova, A., Järn, M., Paulraj, T., Turner, C., Ström, V., . . . Svagan, A. (2018). Superamphiphobic coatings based on liquid-core microcapsules with engineered capsule walls and functionality. Scientific Reports, 8, Article ID 3647.
Open this publication in new window or tab >>Superamphiphobic coatings based on liquid-core microcapsules with engineered capsule walls and functionality
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 3647Article in journal (Refereed) Published
Abstract [en]

Microcapsules with specific functional properties, related to the capsule wall and core, are highly desired in a number of applications. In this study, hybrid cellulose microcapsules (1.2 +/- 0.4 mu m in diameter) were prepared by nanoengineering the outer walls of precursor capsules. Depending on the preparation route, capsules with different surface roughness (raspberry or broccoli-like), and thereby different wetting properties, could be obtained. The tunable surface roughness was achieved as a result of the chemical and structural properties of the outer wall of a precursor capsule, which combined with a new processing route allowed in-situ formation of silica nanoparticles (30-40 nm or 70 nm in diameter). By coating glass slides with "broccoli-like" microcapsules (30-40 nm silica nanoparticles), static contact angles above 150 degrees and roll-off angles below 6 degrees were obtained for both water and low surface-tension oil (hexadecane), rendering the substrate superamphiphobic. As a comparison, coatings from raspberry-like capsules were only strongly oleophobic and hydrophobic. The liquid-core of the capsules opens great opportunities to incorporate different functionalities and here hydrophobic superparamagnetic nanoparticles (SPIONs) were encapsulated. As a result, magnetic broccoli-like microcapsules formed an excellent superamphiphobic coating-layer on a curved geometry by simply applying an external magnetic field.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-225297 (URN)10.1038/s41598-018-21957-y (DOI)000426045700068 ()29483613 (PubMedID)2-s2.0-85042684065 (Scopus ID)
Note

QC 20180405

Available from: 2018-04-05 Created: 2018-04-05 Last updated: 2018-04-05Bibliographically approved
Karlsson, M. E., Mamie, Y. C., Calamida, A., Gardner, J. M., Ström, V., Pourrahimi, A. M. & Olsson, R. (2018). Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment. Langmuir, 34(17), 5079-5087
Open this publication in new window or tab >>Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment
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2018 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 17, p. 5079-5087Article in journal (Refereed) Published
Abstract [en]

A protocol for the aqueous synthesis of ca. 1-mu m-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 degrees C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 degrees C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 degrees C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 degrees C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 degrees C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 degrees C.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-228274 (URN)10.1021/acs.langmuir.8b01101 (DOI)000431463500016 ()29630844 (PubMedID)2-s2.0-85046301419 (Scopus ID)
Note

QC 20180521

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2018-05-21Bibliographically approved
Andersson, R., Cabedo, L., Hedenqvist, M., Olsson, R. & Ström, V. (2016). Superparamagnetic [sic] nanofibers by electrospinning. RSC Advances, 6(26), 21413-21422
Open this publication in new window or tab >>Superparamagnetic [sic] nanofibers by electrospinning
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2016 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 26, p. 21413-21422Article in journal (Refereed) Published
Abstract [en]

The preparation of superparamagnetic thin fibers by electrospinning dispersions of nanosized magnetite (Fe3O4, SPIO/USPIO) in a PMMA/PEO polymer solution is reported. The saturation magnetization and coercivity were not affected by the concentration (0, 1, 10, 20 wt%) or fiber orientation, showing hysteresis loops with high magnetization (64 A m(2) kg(-1) @ 500 kA m(-1)) and record low coercivity (20 A m(-1)). AC susceptibility measurements vs. temperature at frequencies from 60 to 2 kHz confirmed superparamagnetism. The mechanical properties were only slightly dependent on the particle concentration because the nanoparticles were separately encapsulated by the polymer. A uniform fibre fracture cross section was found at all the investigated particle contents, which suggests a strong interaction at the polymer/particle interface. A theoretical value of the magnetic low field susceptibility was calculated from the Langevin function and compared with measured values. The results show a distinct but concentration-independent anisotropy, favoring magnetization along the fiber orientation with no sign of exchange interaction, explained by complete nanoparticle separation. Superparamagnetism cannot be inferred from particle size alone, so a relevant interpretation and criterion for superparamagnetism is presented, in accordance with Neel's original definition. From the measurements, it can be concluded that magnetic characterization can be used to elucidate the material morphology beyond the resolution of available microscopy techniques (TEM and SEM).

National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-184563 (URN)10.1039/c5ra27791d (DOI)000371535200016 ()2-s2.0-84959386416 (Scopus ID)
Note

QC 20160405

Available from: 2016-04-05 Created: 2016-04-01 Last updated: 2017-11-30Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2170-0076

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