| 1. |
- Coelho, Margarida, et al.
(författare)
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Nanotechnology in automotive industry : research strategy and trends for the future – small objects, big impacts
- 2012
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Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 12:8, s. 6621-6630
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this paper is to emphasize and present briefly the nanotechnology science and its potential impact on the automotive industry in order to improve the production of recent models with an optimization of the safety performance and a reduction in the environmental impacts. Nanomaterials can be applied in car bodies as light weight constructions without compromising the stiffness and crashwortiness, which means less material and less fuel consumption. This paper outlines the progress of nanotechnology applications into the safety features of more recent vehicle models and fuel efficiency, but also emphasis the importance of sustainable development on the application of these technologies and life cycle analysis of the considered materials, in order to meet the society trends and customers demands to improve ecology, safety and comfort.
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| 2. |
- Emami, Nazanin, et al.
(författare)
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Biotribolological behaviour of reinforced UHMWPE
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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).
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| 3. |
- Emami, Nazanin, et al.
(författare)
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Friction, wear and surface characterization of metal-on-metal implant in protein rich lubrications
- 2010
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Ingår i: 14th Nordic Symposium on Tribology. - Luleå : Luleå tekniska universitet. - 9789174391244
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Konferensbidrag (refereegranskat)abstract
- 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).
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| 4. |
- Emami, Nazanin, et al.
(författare)
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Novel bio nano-composite for biomedical application
- 2010
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Ingår i: 14th Nordic Symposium on Tribology. - Luleå : Luleå tekniska universitet. - 9789174391244
-
Konferensbidrag (refereegranskat)abstract
- 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 biocomposites with better bioactivity character. Solvent casting and melt blending methods was used during the preparation of this bio-nano composite. The phase compositions and the surface morphology of the nanocomposite material have been studied using X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), and micro-Raman spectroscopy. Nanoindentation technique was used to determine the elastic modulus and hardness of the nanocomposites with different weight% of HA and carbonnanoforms concentrations. The tribologic behaviour of this nano composite was studied using pin-on-plate method. Wear and friction of the produced nano-composites were studied in different biological lubrications.
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| 5. |
- Enqvist, Evelina, et al.
(författare)
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Optimisation of manufacturing process of UHMWPE/nanoHA/MWCNTs
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Hip- and knee replacements are amongst the most common performed surgical operations performed today. Ultra high molecular weight polyethylene (UHMWPE) is frequently used for joint-replacements due to its excellent properties such as high impact strength, toughness and low friction. Wear debris produced when UHMWPE is sliding against a metal counter face is one of the major causes of total failure of implant as an effect of wear debris induced osteolysis. The nano scale dimensions of Carbon nanotubes (CNTs) give them unique physical and chemical properties. Their high aspect ratio makes them perfect as reinforcement in composite materials. Hydroxyapatite (HA) is similar in chemical composition and structure to apatite naturally occurring in human bone tissue and is thus positively affecting bone integration. However the brittleness and poor strength of HA limits the use of HA in load-bearing areas. This work focuses on the manufacturing of a new CNT and HA reinforced UHMWPE bio nanocomposite, using solvent casting and a melt-mixing method. Hot press was used to fabricate the final sample. The produced bio-nanocomposite was characterized by use of differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and micro-Raman spectroscopy. Nanoindentation was used to study the hardness and elastic modulus of samples containing CNTs and different HA loading.
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| 6. |
- Enqvist, Evelina, et al.
(författare)
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The effect of ball milling time and rotational speed on ultra high molecular weight polyethylene reinforced with multiwalled carbon nanotubes
- 2016
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Ingår i: Polymer Composites. - : Wiley. - 0272-8397 .- 1548-0569. ; 37:4, s. 1128-1136
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 7. |
- Gonçalves, Gil, et al.
(författare)
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Breakdown into nanoscale of graphene oxide : Confined hot spot atomic reduction and fragmentation
- 2014
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedical applications due to its small size, intrinsic optical properties, large specific surface area, and easy to functionalize. To fully exploit nano-GO properties, a reproducible method for its production is of utmost importance. Herein we report, the study of the sequential fracture of GO sheets onto nano-GO with controllable lateral width, by a simple, and reproducible method based on a mechanism that we describe as a confined hot spot atomic fragmentation/reduction of GO promoted by ultrasonication. The chemical and structural changes on GO structure during the breakage were monitored by XPS, FTIR, Raman and HRTEM. We found that GO sheets starts breaking from the defects region and in a second phase through the disruption of carbon bonds while still maintaining crystalline carbon domains. The breaking of GO is accompanied by its own reduction, essentially by the elimination of carboxylic and carbonyl functional groups. Photoluminescence and photothermal studies using this nano-GO are also presented highlighting the potential of this nanomaterial as a unique imaging/therapy platform
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| 8. |
- Goncalves, Gil, et al.
(författare)
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Graphene oxide modified with PMMA via ATRP as a reinforcement filler
- 2010
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 40:44, s. 9927-9934
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Tidskriftsartikel (refereegranskat)abstract
- Graphene is a two-dimensional new allotrope of carbon, which is stimulating great curiosity due to its superior mechanical, electrical, thermal and optical properties. Particularly attractive is the availability of bulk quantities of graphene (G) which can be easily processed by chemical exfoliation, yielding graphene oxide (GO). The resultant oxygenated graphene sheets covered with hydroxyl, epoxy and carboxyl groups offer tremendous opportunities for further functionalization opening plenty of opportunities for the preparation of advanced composite materials. In this work poly(methyl methacrylate) (PMMA) chains have been grafted from the GO surface via atom transfer radical polymerization (ATRP), yielding a nanocomposite which was soluble in chloroform. The surface of the PMMA grafted GO (GPMMA) was characterized by AFM, HRTEM, Raman, FTIR and contact angle. The interest of these novel nanocomposites lies in their potential to be homogenously dispersed in polymeric dense matrices and to promote good interfacial adhesion, of particular relevance in stress transfer to the fillers. PMMA composite films were prepared using different percentages of GPMMA and pristine GO. Mechanical analysis of the resulting films showed that loadings as low as 1% (w/w) of GPMMA are effective reinforcing agents, yielding tougher films than pure PMMA films and even than composite films of PMMA prepared with GO. In fact, addition of 1% (w/w) of GPMMA fillers led to a significant improvement of the elongation at break, yielding a much more ductile and therefore tougher material. Thermal analysis showed an increase of the thermal stability properties of these films providing evidence that strong interfacial interactions between PMMA and GPMMA are achieved. In addition, AFM analysis, in friction force mode, is demonstrated to be an effective tool to analyse the surface filler distribution on polymer matrices
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