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Enqvist, Evelina
Publications (10 of 12) Show all publications
Enqvist, E., Ramanenka, D., Grácio, J., Marques, P. & Emami, N. (2016). The effect of ball milling time and rotational speed on ultra high molecular weight polyethylene reinforced with multiwalled carbon nanotubes (ed.). Polymer Composites, 37(4), 1128-1136
Open this publication in new window or tab >>The effect of ball milling time and rotational speed on ultra high molecular weight polyethylene reinforced with multiwalled carbon nanotubes
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2016 (English)In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 37, no 4, p. 1128-1136Article in journal (Refereed) Published
Abstract [en]

Ultra high molecular weight polyethylene (UHMWPE) composites reinforced with multiwalled carbon nanotubes (MWCNT) were produced using planetary ball milling. The aim was to develop a more wear resistant composite with increased mechanical properties to be used in stress bearing joints. The manufacturing technique, using ball-milling to incorporate MWCNT into UHMWPE matrix was investigated. The effect of manufacturing parameters such as effect of ball milling time and rotational speed on final composite was analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), particle size distribution and contact angle measurements. Ball milling as mixing technique for UHMWPE based composites is not a new approach but yet, the effect of time, rotational speed, loading of milling jar and type of ball mill has not been reported properly for UHMWPE. 0.5 and 1 wt% UHMWPE/MWCNTs were manufactured at different rotational speed and mixing time. The results indicate that rotational speed rather than mixing time is important for dispersing MWCNTs

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Applied Mechanics
Research subject
Machine Elements; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-6157 (URN)10.1002/pc.23275 (DOI)000372977000019 ()2-s2.0-84961692400 (Scopus ID)45c9af2b-6ba1-4cfd-9b4b-fcefebe70a97 (Local ID)45c9af2b-6ba1-4cfd-9b4b-fcefebe70a97 (Archive number)45c9af2b-6ba1-4cfd-9b4b-fcefebe70a97 (OAI)
Note

Validerad; 2016; Nivå 2

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Enqvist, E. & Emami, N. (2014). Nanodiamond reinforced ultra high molecular weight polyethylene for orthopaedic applications: Dry versus wet ball milling manufacturing method (ed.). Tribology - Materials, Surfaces & Interfaces, 8(1), 42564
Open this publication in new window or tab >>Nanodiamond reinforced ultra high molecular weight polyethylene for orthopaedic applications: Dry versus wet ball milling manufacturing method
2014 (English)In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 8, no 1, p. 42564-Article in journal (Refereed) Published
Abstract [en]

Nanodiamonds (NDs) were investigated as reinforcement for ultra high molecularweight polyethylene (UHMWPE). Dry and wet mixing with planetary ball milling was compared and analysed by scanning electron microscopy (SEM), differential scanning calorimerty (DSC), X-ray diffraction (XRD) and contact angle measurements. The composites were mixed from one to four hours to study the dispersion of the nanoparticles. It was concluded that wet mixing is more effective at distributing nanodiamonds in comparison to dry mixing. It could also be concluded that dry mixing increases the temperature by 20°C more than wet mixing which resulted in a more distinct welding process of the UHMWPE powder.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-30495 (URN)10.1179/1751584X13Y.0000000059 (DOI)455193ee-9371-4867-b758-ee1afefd8048 (Local ID)455193ee-9371-4867-b758-ee1afefd8048 (Archive number)455193ee-9371-4867-b758-ee1afefd8048 (OAI)
Note

Godkänd;2014;20131014 (emami);Konferensartikel i tidskrift;Bibliografisk uppgift: This paper is part of a special issue on 3rd International Tribology Symposium of IFToMM: Part I

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-04-20Bibliographically approved
Enqvist, E. (2013). Carbon nanofiller reinforced UHMWPE for orthopaedic applications: optimization of manufacturing parameters (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Carbon nanofiller reinforced UHMWPE for orthopaedic applications: optimization of manufacturing parameters
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Polymer composites research designed for orthopaedic applications are commonly focused on Ultra high molecular weight polyethylene (UHMWPE) reinforced by a variety of different nanoparticles. However, the high melt viscosity of UHMWPE renders conventional melt mixing techniques impossible for composite manufacturing. Either solvents that are often difficult to extract from the finished composite or addition of high density polyethylene is necessary in order to use conventional melt mixing techniques. Therefore, solid state mixing is convenient option for manufacturing of UHMWPE based nanocomposites.The aim of this work is to optimize manufacturing parameters (rotational speed and mixing time) for CNT and ND reinforced UHMWPE prepared by planetary ball milling. Many reports have previously been presented, where UHMWPE has been reinforced by CNTs through ball milling, but typically, only mixing time is presented as the crucial variable in ball milling and the movement of the vials, size of the balls, ball-to-powder mass ratio, mixing media and even rotational speed are often overlooked.During this work, both multi walled carbon nanotubes (MWCNTs) and nanodiamonds (NDs) as reinforcement in UHMWPE have been studied. Beginning with the optimal speed in a planetary ball mill for CNT reinforcement and continuing to time and mixing media for NDs. Scanning electron microscopy (SEM) has been used to study the dispersion of nanoparticles using an extreme high resolution SEM (XHR-SEM). Differential scanning calorimetry (DSC) was used to study the thermal properties of the nanocomposite and X-ray diffraction (XRD) was used to complement the crystallinity measurements obtained by DSC. The water contact angles were measured using the sessile drop method. The results showed changes in morphology on UHMWPE powder due to ball milling, such as flattening, welding of powder and changes in powder particle size. The ball milling procedure also negatively affected the crystallinity of the powder, however the crystallinity of the sintered material did not show this negative trend for all composites. Furthermore, thermal analysis did not show any changes in melting temperatures, which indicates that any thermal effects on the powder due to ball milling is only temporary. SEM analysis also showed that a higher speed and longer mixing times more effectively distribute and break down nanoparticle clusters, but at the expense of flattening of the powder and reduced powder crystallinity. It was also shown that wet mixing with ethanol was more efficient and less detrimental to powder morphology compared to dry mixing. Water contact angles were overall increased for composites compared to UHMWPE.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013. p. 49
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-18154 (URN)729602ff-1986-47dc-80f6-90f61ba7363a (Local ID)978-91-7439-556-3 (ISBN)729602ff-1986-47dc-80f6-90f61ba7363a (Archive number)729602ff-1986-47dc-80f6-90f61ba7363a (OAI)
Note
Godkänd; 2013; 20130204 (eveenq); Tillkännagivande licentiatseminarium Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Evelina Enqvist Ämne: Maskinelement/Machine Elements Uppsats: Carbon Nanofiller Reinforced UHMWPE for Orthopaedic Applications Optimization of Manufacturing Parameters Examinator: Bitr professor Nazanin Emami, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Professor Mats Johansson, Fiber och polymerteknik, KTH Tid: Fredag den 8 mars 2013 kl 09.00 Plats: Studion E632, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-01-10Bibliographically approved
Ramanenka, D., Enqvist, E. & Emami, N. (2013). Mechanical and thermal characterisation of novel UHMWPE-nano composite: A copmarrative study against virgin UHMWPE (ed.). Paper presented at EEIGM International Conference on Advanced materials research : 21/03/2013 - 22/03/2013. Paper presented at EEIGM International Conference on Advanced materials research : 21/03/2013 - 22/03/2013.
Open this publication in new window or tab >>Mechanical and thermal characterisation of novel UHMWPE-nano composite: A copmarrative study against virgin UHMWPE
2013 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Applied Mechanics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Solid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-28401 (URN)23030c58-1cc8-4a81-8e6a-f48f36f3d2ac (Local ID)23030c58-1cc8-4a81-8e6a-f48f36f3d2ac (Archive number)23030c58-1cc8-4a81-8e6a-f48f36f3d2ac (OAI)
Conference
EEIGM International Conference on Advanced materials research : 21/03/2013 - 22/03/2013
Note
Godkänd; 2013; 20130923 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-08Bibliographically approved
Enqvist, E. (2013). Nanodiamond reinforced Ultra high molecular weigt polyethylene through dry or wet ball milling (ed.). Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013. Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013.
Open this publication in new window or tab >>Nanodiamond reinforced Ultra high molecular weigt polyethylene through dry or wet ball milling
2013 (English)Conference paper, Oral presentation only (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-38661 (URN)d1ca6fa9-cff9-4f72-a753-6ea9ebf1df0e (Local ID)d1ca6fa9-cff9-4f72-a753-6ea9ebf1df0e (Archive number)d1ca6fa9-cff9-4f72-a753-6ea9ebf1df0e (OAI)
Conference
International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013
Note
Godkänd; 2013; 20130521 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-01-14Bibliographically approved
Emami, N., Ramanenka, D. & Enqvist, E. (2012). Mechanical and thermal characterisation of novel UHMWPE-nano composite: A copmarrative study against virgin UHMWPE (ed.). Paper presented at World Biomaterials Congress : 01/06/2012 - 05/06/2012. Paper presented at World Biomaterials Congress : 01/06/2012 - 05/06/2012.
Open this publication in new window or tab >>Mechanical and thermal characterisation of novel UHMWPE-nano composite: A copmarrative study against virgin UHMWPE
2012 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Applied Mechanics
Research subject
Machine Elements; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-39623 (URN)e73b4d0a-3b65-4bd6-9234-b85a84c4b0bf (Local ID)e73b4d0a-3b65-4bd6-9234-b85a84c4b0bf (Archive number)e73b4d0a-3b65-4bd6-9234-b85a84c4b0bf (OAI)
Conference
World Biomaterials Congress : 01/06/2012 - 05/06/2012
Note
Godkänd; 2012; 20130301 (emami)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-03-08Bibliographically approved
Enqvist, E., Marques, P., Grásio, J. & Emami, N. (2012). Nanoparticle reinforced UHMWPE for orthopaedic applications: Parameters affecting the manufacturing process (ed.). Paper presented at World Biomaterials Congress : 01/06/2012 - 05/06/2012. Paper presented at World Biomaterials Congress : 01/06/2012 - 05/06/2012.
Open this publication in new window or tab >>Nanoparticle reinforced UHMWPE for orthopaedic applications: Parameters affecting the manufacturing process
2012 (English)Conference paper, Oral presentation only (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-27534 (URN)10633c35-7de3-4496-82d3-9bcd3f775a87 (Local ID)10633c35-7de3-4496-82d3-9bcd3f775a87 (Archive number)10633c35-7de3-4496-82d3-9bcd3f775a87 (OAI)
Conference
World Biomaterials Congress : 01/06/2012 - 05/06/2012
Note
Godkänd; 2012; 20130301 (emami)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-08Bibliographically approved
Gopalakrishnan, P., Enqvist, E., Wallström, L., Gatlin, R. & Saiter, J. M. (2010). A new green thermoplastic polymer with improved hydrophobic character (ed.). Paper presented at . Macromolecular Symposia, 290(1), 25-29
Open this publication in new window or tab >>A new green thermoplastic polymer with improved hydrophobic character
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2010 (English)In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 290, no 1, p. 25-29Article in journal (Refereed) Published
Abstract [en]

A green thermoplastic polymer based on wheat flour was modified by the addition of a natural crosslinker genipin. Films of the polymer modified with different composition of genipin were prepared by extrusion. Free surface energy using contact angle method, moisture absorption test and hardness test were used to characterize the products. From moisture absorption and contact angle measurements, it was seen that for genipin amounts higher than 0.2% w/w, a hydrophobic character is achieved. Results obtained indicate enhancement in hydrophobic properties of the films.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Composite Science and Engineering
Research subject
Machine Elements; Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-8056 (URN)10.1002/masy.201050403 (DOI)000277250000004 ()2-s2.0-77950321252 (Scopus ID)67fa6290-4d27-11df-a0f4-000ea68e967b (Local ID)67fa6290-4d27-11df-a0f4-000ea68e967b (Archive number)67fa6290-4d27-11df-a0f4-000ea68e967b (OAI)
Note
Validerad; 2010; 20100421 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Emami, N., Enqvist, E., Grácio, J., Gonçalves, G. & Marques, P. (2010). Biotribolological behaviour of reinforced UHMWPE (ed.). Paper presented at International conference on Advanced Nano Materials : 12/09/2010 - 15/09/2010. Paper presented at International conference on Advanced Nano Materials : 12/09/2010 - 15/09/2010.
Open this publication in new window or tab >>Biotribolological behaviour of reinforced UHMWPE
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2010 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

Carbon nanoforms exhibit exceptional physical and chemical properties due to their nano-scale dimensions. They also have very high aspect ratio which makes them an excellent reinforcement material for polymer composites. Hydroxyapatite (HA) is the prime constituent of bone generation because of its ability to bond chemically with living bone tissues and positively affect the osteoblasts; this is due to its similar chemical composition and crystal structure to apatite in the human skeletal system. Ultra high molecular weight polyethylene (UHMWPE) is already used as implant material in high stress bearing areas such as hip and knee prosthesis. Wear debris of ultra high molecular weight polyethylene cause osteolysis which is a major reason of long-term failure of total hip replacements. In this study carbon nanoforms together with hydroxyapatite (HA) nanoparticles were used as reinforcement in UHMWPE matrix in order to produce high strength and wear resistant biocomposite with better bioactivity character. Solvent casting and melt blending methods were used during the preparation of this bio-nano composite. The manufacturing process was studied using different characterization methods such as diferencial scanning calorimetry (DSC), scanning electron microscopy (SEM) and Raman-spectroscopy. The tribological behaviour of the manufactured bio-nano composite was studied using pin-on-plate method. Wear and friction of the produced novel composite were studied in different biological lubrications. Different lubrication affected the friction rate and wear, though the results were not statistically different. The reinforced UHMWPE showed superior tribology behaviour in comparison to pure UHMWPE (p>0.05).

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-32398 (URN)6e5adc50-aebb-11df-a707-000ea68e967b (Local ID)6e5adc50-aebb-11df-a707-000ea68e967b (Archive number)6e5adc50-aebb-11df-a707-000ea68e967b (OAI)
Conference
International conference on Advanced Nano Materials : 12/09/2010 - 15/09/2010
Note
Godkänd; 2010; Bibliografisk uppgift: (invited speaker); 20100823 (emami)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-08Bibliographically approved
Emami, N., Enqvist, E., Larsson, R., Gracio, J. & Kumar, S. (2010). Friction, wear and surface characterization of metal-on-metal implant in protein rich lubrications (ed.). In: (Ed.), (Ed.), 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010. Paper presented at Nordic Symposium on Tribology : 08/06/2010 - 11/06/2010. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Friction, wear and surface characterization of metal-on-metal implant in protein rich lubrications
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2010 (English)In: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Conference paper, Published paper (Refereed)
Abstract [en]

Although various surface and interface characterization methods have been applied to study the physical wear, corrosion and implant surface interactions with biological environments, presently - in metal on metal (MOM) hip implant- the local and systematic effects of interaction between metal surfaces and protein rich lubrication in body are poorly understood. Materials and Methods: Cobalt-chromium-molybdenium (CoCrMo) alloys have been used in MOM implants extensively. In the present study the samples were immersed in four different biological lubricants (Human serum, synovial fluid, MEM and distill water) for 10 min, 1 hr, and 5 days of immersion and then studied by X-ray Photoelectron Spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). XPS determined the chemistry of elements located whit in the top few nanometers of materials. Friction and wear behavior of CoCrMo substrate in different biological lubricatin were also studied. Results and discussion: Spectra from P2p3/2, O1s, Ca2p3/2, C1s and N1s were collected. Metallic substrates behaved differently when immersed in the same lubricant for different time intervals. The four lubricants reacted differently with metallic surfaces. Larger calcium deposits occurred in supersaturated physiological solutions. Deposition of calcium phosphate was different on CoCrMo alloys depending on the lubricant and the immersion period. Specimens immersed in synovial fluid gave thinner oxide layers and lower calcium phosphate deposits. For all specimens, water immersion resulted in thicker oxide layer. Synovial fluid gave lowest coefficient of friction when distill water gave the highest value. Generally wear was higher for disc in comparison to the pin (in the pin on plate test).

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2010
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-36986 (URN)ad967ce0-834f-11df-ab16-000ea68e967b (Local ID)978-91-7439-124-4 (ISBN)ad967ce0-834f-11df-ab16-000ea68e967b (Archive number)ad967ce0-834f-11df-ab16-000ea68e967b (OAI)
Conference
Nordic Symposium on Tribology : 08/06/2010 - 11/06/2010
Note
Godkänd; 2010; Bibliografisk uppgift: CD-ROM; 20100629 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-03-08Bibliographically approved
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