| 1. |
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| 2. |
- Anghel, Clara, et al.
(författare)
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A gas phase analysis technique applied to in-situ studies of gas-solid interactions
- 2007
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 47:10, s. 3440-3453
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Tidskriftsartikel (refereegranskat)abstract
- An ultrahigh vacuum technique using mass spectrometry for in-situ investigations of gas-solid interactions is described in this paper. Examples of chemical reactions (oxidation, hydration) between solids and gas mixtures, dissociation of gases on solid surfaces, outgassing of solid materials and permeation of gases through membranes are discussed where the experimental arrangement is explained in detail. This Gas Phase Analysis (GPA) technique can be used at temperatures from room temperature to 1200 degrees C and at pressures up to 1 atm. Aspects related to sample preparation, isotopic gas mixture selection, data acquisition, calibration and interpretation of the experimental data are also addressed.
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| 3. |
- Bagampadde, Umaru, et al.
(författare)
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Laboratory studies on stripping at bitumen/substrate interfaces using FTIR-ATR
- 2007
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 42:9, s. 3197-3206
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Tidskriftsartikel (refereegranskat)abstract
- A technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used to study movement of water into bitumen/substrate interfaces, as well as to characterize stripping. Bitumens from different sources were used and applied on various substrates (silicon, germanium and zinc selenide) as thin films. The influence of bitumen type, substrate type, temperature, film thickness and modification with amines, on water damage was studied. The technique gave information on water flow into interfaces and how stripping possibly occurs. It distinguished between stripping and non-stripping bitumens. At least one of three processes occurred, namely water diffusion, film fracture, and bitumen displacement by water, respectively. The diffusion of water did not obey Fick's law. Stripping was influenced by bitumen source when silicon and germanium substrates were used. Notching the films made the process of water entry almost occur immediately. Additives significantly reduced stripping in the moisture-sensitive bitumen on silicon and germanium substrates, even after film notching. Although, good agreement was observed between tests for the bitumens that did not strip, the tests on stripping bitumens showed poor agreement.
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| 4. |
- Björnström, Joakim, 1976, et al.
(författare)
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Antagonistic effect of superplasticizer and colloidal nano-silica in the hydration of Alite and Belite pastes
- 2007
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 42:11, s. 3901-3907
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Tidskriftsartikel (refereegranskat)abstract
- The dependence on the hydration rate for Alite and Belite clinker phases in the presence of a polycarboxylate superplasticizer PC SP upon addition of colloidal nano-silica CNS were monitored by means of Diffuse Reflectance Infrared spectroscopy DR-FTIR. Spectral signatures of clinker dissolution and product formation were acquired for both materials. The rates for the build-up of product vibrational band intensities were found to depend sensitively on addition of CNS. The hydration product was proposed to be calcium-silicate-hydrate C-S-H. Details in the spectral signatures were found to differ. Quantum chemical calculations were employed and found to be consistent with the interpretation that small clusters dominate the Alite C-S-H spectrum, whereas the Belite C-S-H spectrum results from extended polymers.
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| 5. |
- De Vrieze, S., et al.
(författare)
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The effect of temperature and humidity on electrospinning
- 2009
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 44:5, s. 1357-1362
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Tidskriftsartikel (refereegranskat)abstract
- Electrospinning is a process that generates nanofibres. Temperature and humidity affect this process. In this article the influence of humidity and temperature on the formation and the properties of nanofibres are studied using cellulose acetate (CA) and poly(vinylpyrrolidone) (PVP) as target materials. The experiments indicate that two major parameters are dependent of temperature and have their influence on the average fibre diameter. A first parameter is the solvent evaporation rate that increases with increasing temperature. The second parameter is the viscosity of the polymer solution that decreases with increasing temperature. The trend in variation of the average nanofibre diameter as a function of humidity is different for CA and PVP, which can be explained by variations in chemical and molecular interaction and its influence on the solvent evaporation rate. As the humidity increases, the average fibre diameter of the CA nanofibres increases, whilst for PVP the average diameter decreases. The average diameter of nanofibres made by electrospinning change significantly through variation of temperature and humidity. © 2008 Springer Science+Business Media, LLC.
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| 6. |
- Huang, Fang, et al.
(författare)
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Measurement of interfiber friction force for pulp fibers by atomic force microscopy
- 2009
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 44:14, s. 3770-3776
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Tidskriftsartikel (refereegranskat)abstract
- Interfiber friction in paper exists in fiber suspensions, fiber flocs, and fiber networks. The interfiber friction force is, therefore, important both in papermaking and in the use of paper. The objective of this research is to develop a methodology using atomic force microscopy (AFM) for the direct measurement of the friction force between pulp fibers. Different factors such as AFM scanning velocity, contact area, and fiber surface roughness were investigated. The results show that AFM is an effective tool for measuring micro-scale interfiber friction forces. Both AFM scanning velocity and fiber surface roughness affect the measured results. The coefficient of friction increases, but the initial adhesion force decreases, with increasing fiber surface roughness.
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| 7. |
- Joffe, Roberts, et al.
(författare)
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Interfacial shear strength of flax fiber/thermoset polymers estimated by fiber fragmentation tests
- 2005
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 40:9-10, s. 2721-2722
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Tidskriftsartikel (refereegranskat)abstract
- We study flax/thermoset polymer ISS [interfacial shear strength] for most common types of thermosets: vinylester, polyester, and epoxy. The effect of fiber surface treatment on ISS in such systems reinforced with flax fibers is investigated. Apparent ISS is evaluated from SFF tests by the Kelly-Tyson approach utilizing fiber strength at the critical length. Fiber strength at such small lengths is hardly accessible to direct testing, therefore it is usually extrapolated from test results at larger gauge lengths. We present ISS of flax fibers subjected to different treatments and thermoset polymers, derived from SFF tests using comprehensive fiber strength data.
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| 8. |
- Kapilashrami, Era, et al.
(författare)
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Wetting characteristics of oxygen-containing iron melts on refractory oxides
- 2005
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 40:9-10, s. 2371-2375
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Tidskriftsartikel (refereegranskat)abstract
- As part of refractory erosion studies, the wetting behaviour of molten iron containing varying amounts of oxygen on refractory oxides was investigated by the sessile drop method. The oxides investigated in the present work were alumina, silica and mullite. The reactions were followed in static as well as dynamic modes, under isothermal conditions, through contact angle measurements. Other parameters investigated in the present study were temperature and oxygen partial pressure. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen at constant partial pressure, came into contact with the surface of the drop. At a critical level of oxygen in the metal drop, a reaction product started forming at the drop/substrate interface and at this stage the contact angle dropped suddenly. In all cases there was a tendency for the contact angle to increase after this minimum. In the alumina case, the iron drop moved away from the reaction site, once the product layer had been formed at the interface, probably due to the imbalance in the surface forces. In the case Of SiO2 and mullite, liquid slags were formed. The substrates were analysed through SEM and EDS. The reaction products identified were in agreement with thermodynamic predictions. In the case Of SiO2, deep erosions were formed along the periphery of the drops, probably due to Marangoni flow. The possible mechanisms of the reactions and their impact on refractory erosion are discussed in the light of the present experimental results.
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| 9. |
- Karlsson, Robert, et al.
(författare)
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Rheological characterisation of bitumen diffusion
- 2007
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 42:1, s. 101-108
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion is considered important in the process of mixing old and new binders during asphalt recycling. The degree of mixing is presumed to greatly influence the final properties of recycled asphalt concrete. Previously, studies have been undertaken to investigate diffusion using FTIR-ATR (Fourier Transform Infrared Spectroscopy using Attenuated Total Reflectance). A need was identified to verify, if the rates of diffusion detected using FTIR-ATR were accompanied by changes in rheological properties. In this paper, a dynamic shear rheometer (DSR) with parallel plates is used for monitoring diffusion. Diffusion coefficients obtained at 60, 80 and 100 degrees C from tests of a soft bitumen (rejuvenator) diffusing into a stiff one are presented. The diffusion coefficients determined are compared with the corresponding diffusion coefficients obtained using FTIR-ATR. The comparison shows that the rates of diffusion detected by the DSR are of the same magnitude, but somewhat higher than the ones detected by FTIR-ATR.
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| 10. |
- Kuhl, Ellen, et al.
(författare)
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A continuum model for remodeling in living structures
- 2007
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 42:21, s. 8811-8823
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Tidskriftsartikel (refereegranskat)abstract
- A new remodeling theory accounting for mechanically driven collagen fiber reorientation in cardiovascular tissues is proposed. The constitutive equations for the living tissues are motivated by phenomenologically based microstructural considerations on the collagen fiber level. Homogenization from this molecular microscale to the macroscale of the cardiovascular tissue is performed via the concept of chain network models. In contrast to purely invariant-based macroscopic approaches, the present approach is thus governed by a limited set of physically motivated material parameters. Its particular feature is the underlying orthotropic unit cell which inherently incorporates transverse isotropy and standard isotropy as special cases. To account for mechanically induced remodeling, the unit cell dimensions are postulated to change gradually in response to mechanical loading. From an algorithmic point of view, rather than updating vector-valued microstructural directions, as in previously suggested models, we update the scalar-valued dimensions of this orthotropic unit cell with respect to the positive eigenvalues of a tensorial driving force. This update is straightforward, experiences no singularities and leads to a stable and robust remodeling algorithm. Embedded in a finite element framework, the algorithm is applied to simulate the uniaxial loading of a cylindrical tendon and the complex multiaxial loading situation in a model artery. After investigating different material and spatial stress and strain measures as potential driving forces, we conclude that the Cauchy stress, i.e., the true stress acting on the deformed configuration, seems to be a reasonable candidate to drive the remodeling process.
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