| 1. |
- Guldris Leon, Lorena, 1983, et al.
(författare)
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Understanding Mineral Liberation during Crushing Using Grade-by-Size Analysis - A Case Study of the Penuota Sn-Ta Mineralization, Spain
- 2020
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Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Coarse comminution test-work and modeling are powerful tools in the design and optimization of mineral processing plants and provide information on energy consumption. Additional information on mineral liberation characteristics can be used for assessing the potential of pre-concentration stages or screens in the plant design. In ores of high-value metals (e.g., Ta, W), standard techniques-such as the mineralogical quantification of grain mounts by quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) or chemical analysis by X-ray fluorescence (XRF) can be challenging, due to the low relative abundance of such valuable minerals. The cost of QEMSCAN is also a limiting factor, especially considering the large number of samples required for the optimization of coarse comminution. In this study, we present an extended analytical protocol to a well-established mechanical test of interparticle breakage to improve the assessment of coarse mineral liberation characteristics. The liberation of ore minerals is a function of the rock texture and the difference in size and mechanical properties of the valuable minerals relative to gangue minerals and they may fraction in certain grain sizes if they behave differently during comminution. By analyzing the bulk-chemistry of the different grain size fractions produced after compressional testing, and by generating element by size diagrams, it is possible to understand the liberation characteristics of an ore. We show, based on a case study performed on a tantalum ore deposit, that element distribution can be used to study the influence of mechanical parameters on mineral liberation. This information can direct further mineralogical investigation and test work.
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| 4. |
- Townsend, Philip, 1991, et al.
(författare)
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Tessellation-based stochastic modelling of 3D coating structures imaged with FIB-SEM tomography
- 2021
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Ingår i: Computational Materials Science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- To facilitate printing, coatings are typically applied to paperboard used for packaging to provide a good surface for application. To optimise the performance of the coating, it is important to understand the relationship between the microstructure of the material and its mass transport properties. In this work, three samples of paperboard coating are imaged using combined focused ion beam and scanning electron microscope (FIB-SEM) tomography data appropriately segmented to characterise the internal microstructure. These images are used to inform a parametric, tessellation-based stochastic three-dimensional model intended to mimic the irregular geometry of the particles that can be seen in the coating. Parameters for the model are estimated from the FIBSEM image data, and we demonstrate good agreement between the real and virtual structures both in terms of geometrical measures and mass transport properties. The development of this model facilitates exploration of the relationship between the structure and its properties.
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| 5. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Proton conduction in Perovskite Oxide BaZr0.5Yb0.5O3-δ Prepared by Wet Chemical Route
- 2008
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 155:11, s. 97-102
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Tidskriftsartikel (refereegranskat)abstract
- A wet chemical route has been used to synthesize the oxygen deficient perovskite Ba Zr0.5 Yb0.5 O3-δ. Analysis of X-ray powder diffraction data showed that both dried and hydrated samples adopt cubic crystal structures of space group Pm 3- m. Dynamic thermogravimetric analysis showed a significant mass loss for the hydrated sample compared to the dried sample, indicating that ∼28% of the oxygen vacancies are filled by protonic defects. The strong O-H stretch band, 2500-3500 cm-1, in the IR absorbance spectrum also clearly manifests the presence of significant levels of protons in the hydrated material. Proton conductivity was investigated on prehydrated (under dry Ar) and as-prepared (under wet Ar) samples. The heating cycle of the prehydrated sample showed higher proton conductivity compared to the cooling cycle, especially in the intermediate temperature range (150-550°C). Finally, comparison with data for Ba Zr0.9 Yb0.1 O3-δ revealed that the more heavily doped sample showed higher proton conductivity compared to the more lightly doped sample. © 2008 The Electrochemical Society.
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| 6. |
- Babaahmadi, Arezou, 1985, et al.
(författare)
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Development of an electro-chemical accelerated ageing method for leaching of calcium from cementitious materials
- 2016
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 49:1-2, s. 705-718
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Tidskriftsartikel (refereegranskat)abstract
- To facilitate the long term durability predictions of nuclear waste repositories, acceleration methods enhancing calcium leaching process from cementitious materials are needed, even though mechanisms not necessarily comparable to those predominant in a natural leaching process may be developed. In the previously published acceleration methods the samples are very small, which limits further physical or mechanical tests. In this paper, a new acceleration method based on electro-chemical migration is presented. The method although not driven with the same kinetics as in natural leaching, was designed in such a way that unnecessarily destructive by-effects could be minimized while promoting a higher leaching rate for a sample size suitable for further testing the mechanical and physical properties. It is shown that approximately 1x10^6 C of electrical charge per paste specimen of size Ø50 x 75 mm (approximately 230 g) is required to leach out the total amount of Portlandite. The chemical and mineralogical properties of leached samples are characterized by various techniques. It is concluded that aged samples are comparable to those leached in a natural leaching process as both are characterized by a layered system comprising an unaltered core delineated by total dissolution of Portlandite followed by a progressive decalcification of the calcium silicate hydrate gel.
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| 7. |
- Källbom, Arja, 1969, et al.
(författare)
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Multianalytical Assessment of Armour Paints-The Ageing Characteristics of Historic Drying Oil Varnish Paints for Protection of Steel and Iron Surfaces in Sweden
- 2021
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Ingår i: Heritage. - : MDPI AG. - 2571-9408. ; 4:3, s. 1141-1164
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of armour paints, historically used to protect ferrous industrial heritage, are explored. Amour paints contain lamellar and highly reflexive pigments of micaceous iron oxide (MIO) and metallic, leafing aluminium, bound in linseed oil and linseed oil-tung oil mixtures, on an inhibitive and soap-forming linseed oil primer (red lead). It is the first study of the binding media used for historical armour paints and investigates the chemical and physical ageing of armour paints using a multianalytical approach. Naturally aged examples are compared to accelerated aged replica armour paint, and to historical paints. The ageing and degradation reactions are assessed by complementary GC-MS and FTIR, together with measurements of wettability, hardness and surface colour. The historical paint formulations include linseed oils and alkyd binders. The results confirm that the leafing effect of aluminium pigments results in only a small concentration of binder at the surface: the paints studied reflect light and form a strong chemical and physical barrier. Linseed oils and tung oil mixtures have been proven to be suitable for the production of armour paints, but the evaluation of ageing and assessment of physical changes will require further investigation.
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| 8. |
- Larsson, Carl Fredrik, 1980, et al.
(författare)
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Overcurrent Abuse of Primary Prismatic Zinc–Air Battery Cells Studying Air Supply Effects on Performance and Safety Shut-Down
- 2017
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Ingår i: Batteries. - : MDPI AG. - 2313-0105. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Overcurrent abuse has been performed on commercial 48 Ah primary prismatic zinc (Zn)–Air battery cells with full air supply as well as with shut-off air supply. Compared to other battery technologies, e.g., lithium-ion batteries, metal–air batteries offer the possibility to physically stop the battery operation by stopping its air supply, thus offering an additional protection against severe battery damage in the case of, e.g., an accidental short circuit. This method may also reduce the electrical hazard in a larger battery system since, by stopping the air supply, the voltage can be brought to zero while maintaining the energy capacity of the battery. Measurements of overdischarge currents and current cut-off by suffocation have been performed to assess the safety of this type of Zn–air battery. The time to get to zero battery voltage is shown to mainly be determined by the volume of air trapped in the cell.
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| 9. |
- Kuzmenko, Volodymyr, 1987, et al.
(författare)
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Sustainable carbon nanofibers/nanotubes composites from cellulose as electrodes for supercapacitors
- 2015
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 90:2, s. 1490-1496
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Tidskriftsartikel (refereegranskat)abstract
- Supercapacitors are efficient energy storage devices with long lifetime and safe service. Their effectiveness,to a big extent, is dependent on electrode materials used for accumulation of energy in form ofelectrostatic charges. Over the last decades, variety of carbonaceous electrode materials has been used insupercapacitors. Mostly the production of such electrodes is still oriented on unsustainable fossil fuels asprecursors instead of sustainable renewable resources. In this study, freestanding carbonaceous electrodematerials for supercapacitors were derived from cellulose, the most abundant renewable resource. Theywere synthesized via carbonization of fibrillar cellulose impregnated with CNTs (carbon nanotubes). Theensuing composite materials consisted of a CNF (carbon nanofiber) scaffold (fiber diameter in the rangeof 50-250 nm) covered with layers of CNTs (tube diameter in the range of 1-20 nm). Moreover, thesecomposites were tested as electrode materials for supercapacitors. Incorporation of the CNTs into theCNFs improved electrical conductivity and also increased the surface area of the produced compositematerials, which led to high specific capacitance values (up to 241 F/g), cyclic stability, and powerdensity of these materials in electrochemical measurements. These results suggest that cellulose-derivedoriginal CNF/CNT composites are sustainable and efficient carbonaceous electrodes for supercapacitors.
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| 10. |
- Insulander Björk, Klara, 1982, et al.
(författare)
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Effect of the thorium oxide content on the leaching of a mixed thorium-uranium oxide fuel
- 2022
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 331, s. 2849-2857
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Tidskriftsartikel (refereegranskat)abstract
- Leaching of uranium from uranium oxide fuel in contact with water can be a radiation hazard problem in the case of fuel cladding failure, either during nuclear reactor operation or in an interim storage, as well as in a final repository. One way to mitigate this is to reduce the solubility of the fuel matrix by the mixing uranium oxide with a compound which is less soluble but otherwise of similar properties. In this paper, the effect of thorium oxide content on the leaching of the uranium oxide matrix is investigated. The method was to study the leaching of the uranium oxide fuel matrix as a function of a varying content of thorium oxide, using materials manufactured by powder co-milling. It was found that the substitution of more than 25% UO2 with ThO2 reduces the matrix leaching by more than one order of magnitude in most of the different leaching solutions investigated. The substitution of 7% UO2 with ThO2 results in a reduction of matrix leaching by 10–90%, depending on the concentration of borate and dissolved oxygen in the leaching solution.
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