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  • Journal article
    Diaz OG, Marquardt K, Harris S, Gale L, Vandeperre L, Saiz E, Giuliani Fet al., 2020,

    Degradation mechanisms of SiC/BN/SiC after low temperature humidity exposure

    , Journal of the European Ceramic Society, Vol: 40, Pages: 3863-3874, ISSN: 0955-2219

    The environmental degradation of SiC/BN/SiC CMCs under low temperature water exposure is still an unexplored field. This work shows how the effect of low temperature humid environments can be detrimental for turbostratic BN interphases, leading to a drop in mechanical properties. Furthermore, initial low-temperature humid environments can induce a faster degradation during subsequent thermal exposure. In order to understand how low temperature water exposure affects the CMC and how these changes affect the material response to subsequent exposures, intermediate temperature (800 °C) exposures have been studied before and after the low temperature humidity tests. The main challenge of this work consists of understanding how different constituents of the CMC structure (e.g. fibres and interphases) are degrading and consequently affecting the overall bulk mechanical performance and failure modes of the material. For this, linking the change in morphology and chemistry of the interphases with the micromechanical properties each constituent has been crucial.

  • Journal article
    McGilvery C, Jiang J, Rounthwaite N, Williams R, Giuliani F, Britton Tet al., 2020,

    Characterisation of carbonaceous deposits on diesel injector nozzles

    , Fuel: the science and technology of fuel and energy, Vol: 274, Pages: 1-9, ISSN: 0016-2361

    Diesel injector nozzles are highly engineered components designed to optimise delivery of fuel into the combustion chamber of modern engines. These components contain narrow channels to enhance spray formation and penetration, hence mixing and combustion. Over time, these injectors can become clogged due to fouling by carbonaceous deposits which may affect the long-term performance of a diesel engine. In this paper we explore the chemical composition and structure of deposits formed within the nozzle at the nanometre scale using electron microscopy. We focus on comparing deposits generated using a chassis dynamometer-based test with Zn fouled fuel with a DW10B dirty up test. We have developed and applied a method to precisely section the deposits for ‘top view’ scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis of the morphology and relative accumulation of deposits formed during chassis dynamometer and engine based dirty-up tests. We extend this analysis to finer length scales through lift-out of ~70 nm thick electron transparent cross section foils, including both the metal substrate and deposit, using focussed ion beam (FIB) machining. These foils are analysed using scanning transmission electron microscopy (STEM) and STEM-EDS. These thin foils reveal thin-film growth and chemical stratification of Zn, C, O and other elements in the organic deposit layers developed during growth on the steel substrate during industry standard fouling tests.

  • Journal article
    Jones LD, Vandeperre LJ, Haynes TA, Wenman MRet al., 2020,

    Theory and application of Weibull distributions to 1D peridynamics for brittle solids

    , Computer Methods in Applied Mechanics and Engineering, Vol: 363, Pages: 1-11, ISSN: 0045-7825

    Peridynamics is a continuum mechanics modelling method, which is emerging as a solution for – in particular – the modelling of brittle fracture. The inherent variability of brittle fracture is captured well by the Weibull distribution, which describes the probability of fracture of a given material at a given stress. Recreating a Weibull distribution in peridynamics involves adjusting for the fact that the body is made up of a large number of bonds, and the distribution of strengths associated with these bonds must be different to the distribution of strengths associated with the peridynamic body. In the local case, where the horizon ratio, m=1 is used, Weibull’s original simple size scaling gives exact results, but the overlapping nature of non-local bonds that occurs in higher m cases, typically used in the peridynamics literature (such as m=3), causes a significant distortion of Weibull distributions. The cause of these distortions is spurious toughening and partial component failures as a result of the reduced localisation associated with larger horizon ratios. In order to remove these distortions, appropriate size scaling is used for the bonds, and a methodology that is capable of reflecting the heterogeneity of the material in the model, is proposed. The methodology described means Weibull parameters measured at specimen or component level can be reproduced for higher values of m.

  • Journal article
    Zhou T, Wu C, Wang Y, Tomsia AP, Li M, Saiz E, Fang S, Baughman RH, Jiang L, Cheng Qet al., 2020,

    Super-tough MXene-functionalized graphene sheets

    , Nature Communications, Vol: 11, ISSN: 2041-1723

    Flexible reduced graphene oxide (rGO) sheets are being considered for applications in portable electrical devices and flexible energy storage systems. However, the poor mechanical properties and electrical conductivities of rGO sheets are limiting factors for the development of such devices. Here we use MXene (M) nanosheets to functionalize graphene oxide platelets through Ti-O-C covalent bonding to obtain MrGO sheets. A MrGO sheet was crosslinked by a conjugated molecule (1-aminopyrene-disuccinimidyl suberate, AD). The incorporation of MXene nanosheets and AD molecules reduces the voids within the graphene sheet and improves the alignment of graphene platelets, resulting in much higher compactness and high toughness. In situ Raman spectroscopy and molecular dynamics simulations reveal the synergistic interfacial interaction mechanisms of Ti-O-C covalent bonding, sliding of MXene nanosheets, and π-π bridging. Furthermore, a supercapacitor based on our super-tough MXene-functionalized graphene sheets provides a combination of energy and power densities that are high for flexible supercapacitors.

  • Journal article
    Haug M, Bouville F, Ruiz-Agudo C, Avaro J, Gebauer D, Studart ARet al., 2020,

    Cold densification and sintering of nanovaterite by pressing with water

    , JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 40, Pages: 893-900, ISSN: 0955-2219
  • Journal article
    Bhowmik A, Lee J, Adande S, Wang-Koh M, Jun T-S, Sernicola G, Ben Britton T, Rae CMF, Balint D, Giuliani Fet al., 2020,

    Investigating spatio-temporal deformation in single crystal Ni-based superalloys using in-situ diffraction experiments and modelling

    , Materialia, Vol: 9, Pages: 1-14, ISSN: 2589-1529

    In this study, we perform a detailed analysis of room temperature deformation of a [100]–orientated singlecrystal Ni-based superalloy, CMSX-4 micropillar, using a combinatorial and complimentary characterisation approach of micro-Laue diffraction coupled with post-deformation microscopy and crystal plasticity modelling.Time-resolved micro-Laue data indicated that deformation was initiated by activation of multiple slip (after 5%engineering strain) which led to the generation of a plastic strain accumulation accompanied by a two-foldincrease in the dislocation density within the micropillar. Subsequent to that, slip occurred primarily on two systems (11̄1)[101] and (111)[1̄01] with the highest Schmid factor in the single crystal micropillar thereby resultingin little accumulation of unpaired GNDs during a major part of the loading cycle, upto 20% strain in this case.Finite element crystal plasticity modelling also showed good agreement with the experimental analyses, wherebysignificant strains were found to develop in the above slip systems with a localisation near the centre of themicropillar. Post-deformation transmission electron microscopy study confirmed that deformation was mediatedthrough a/2<110> dislocations on {111} planes in the 𝛾-phase, while high stress levels led to shearing of the 𝛾′precipitates by a/2<110> partials bounding an anti-phase boundary free to glide on the {111} planes. Duringthe deformation of the single crystal micropillar, independent rotations of the 𝛾 and 𝛾′ phases were quantified byspatially resolved post-deformation micro-Laue patterns. The degree of lattice rotation in the 𝛾-phase was higherthan that in the 𝛾′-phase.

  • Journal article
    Elizarova I, Vandeperre L, Saiz Gutierrez E, 2020,

    Conformable green bodies: plastic forming of robocasted advanced ceramics

    , Journal of the European Ceramic Society, Vol: 40, Pages: 552-557, ISSN: 0955-2219

    Robocasting, or the additive manufacturing of ceramics by continuous extrusion of a ceramic paste, has limited capabilities when printing complex unsupported structures such as overhangs or free standing thin artefacts. In this paper we address this limitation using a new type of paste, which allows for shaping of the green bodies after printing. To illustrate the flexibility of the paste, it was used to produce both alumina and silicon carbide parts. The paste consists of a solution of phenolic resin in methyl ethyl ketone and ceramic powders. Fabricated parts can be cut, bent, folded and draped over various objects. Once dry and fully solid, the parts become rigid and can be processed further by slow pyrolysis and sintering. Sintered samples exhibit flexural strength comparable to both conventionally produced and robocasted ceramics and shaping of the green bodies after printing does not affect the mechanical strength of the sintered parts.

  • Journal article
    Peng J, Huang C, Cao C, Saiz E, Du Y, Dou S, Tomsia AP, Wagner HD, Jiang L, Cheng Qet al., 2020,

    Inverse Nacre-like Epoxy-Graphene Layered Nanocomposites with Integration of High Toughness and Self-Monitoring

    , MATTER, Vol: 2, Pages: 220-232, ISSN: 2590-2393
  • Journal article
    Pelissari PIBGB, Pandolfelli VC, Carnelli D, Bouville Fet al., 2020,

    Refractory interphase and its role on the mechanical properties of boron containing nacre-like ceramic

    , JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 40, Pages: 165-172, ISSN: 0955-2219
  • Journal article
    Wang S, Kalácska S, Maeder X, Michler J, Giuliani F, Britton Tet al., 2019,

    The effect of δ-hydride on the micromechanical deformation of Zircaloy-4 studied by in situ high angular resolution electron backscatter diffraction

    , Scripta Materialia, Vol: 173, Pages: 101-105, ISSN: 1359-6462

    Zircaloy-4(Zr-1.5%Sn-0.2%Fe-0.1%Cr wt%)is usedas nuclear fuel cladding materials and hydride embrittlementis amajor failure mechanism. To explore the effect of δ-hydrideon plastic deformation and performance of Zircaloy-4, in situhigh angular resolution electron backscatter diffraction(HR-EBSD)was used to quantify stress andgeometrically necessarydislocation(GND)density during bending tests of hydride-free and hydride-containingsingle crystalZircaloy-4 microcantilevers. Results suggest that while the stress applied was accommodated by plastic slip in the hydride-free cantilever,the hydride-containing cantilever showedprecipitation-induced GND pile-up at hydride-matrix interfacepre-deformation, andconsiderable locally-increasing GNDdensity under tensile stressupon plastic deformation.

  • Journal article
    Giuliani F, Ciurea C, Bhakhri V, Werchota M, Vandeperre LJ, Mayrhofer PHet al., 2019,

    Deformation behaviour of TiN and Ti–Al–N coatings at 295 to 573 K

    , Thin Solid Films, Vol: 688, ISSN: 0040-6090

    Temperature-dependent nanoindentation testing was employed to investigate the deformation behaviour of magnetron sputtered (100) TiN and Ti1-xAlxN (x = 0.34, 0.52, 0.62) coatings in the temperature range from 295 to 573 K. The maximum temperature is sufficiently below the deposition temperature of 773 K to guarantee for stable microstructure and stress state during testing. The TiN coating displayed the same hardness as bulk single crystal (SC) TiNbulk. The addition of aluminium to TiN (to form single-phase face centred cubic structured Ti1-xAlxN coatings) increased the room temperature hardness due to increased bond strength, lattice strain and higher activation energy for the dislocation slip. For coatings with a low aluminium content, Ti0.66Al0.34N, the decrease in hardness with temperature was similar to the TiN coating and SC-TiNbulk. In contrast, the hardness of coatings with moderate, Ti0.48Al0.52N, and high, Ti0.38Al0.62N, aluminium contents varied little up to 573 K. Thus, the Ti1-xAlxN matrix is mechanically more stable at elevated temperatures than its TiN relative, by providing a lower decrease in lattice resistance to the dislocation flow with increasing temperature. The findings suggest that the addition of Al to TiN (to form Ti1-xAlxN solid solutions) not only improves the hardness but also leads to stable hardness with temperature, and emphasizes the importance of bonding states and chemical fluctuations, next to structure and morphology of the coatings that develop with changing the chemistry.

  • Journal article
    Feilden E, Glymond D, Saiz E, Vandeperre Let al., 2019,

    High temperature strength of an ultra high temperature ceramic produced by additive manufacturing

    , Ceramics International, Vol: 45, Pages: 18210-18214, ISSN: 0272-8842

    In this study hafnium diboride was fabricated using the additive manufacturing technique robocasting. Parts have been successfully produced with complex shapes and internal structures not possible via conventional manufacturing techniques. Following pressureless sintering, the monolithic parts reach densities of 94–97% theoretical. These parts exhibit bending strength of 364 ± 31 MPa at room temperature, and maintain strengths of 196 ± 5 MPa up to 1950 °C, which is comparable to UHTC parts produced by traditional means. These are the highest temperature mechanical tests that a 3D printed part has ever undergone. The successful printing of the high density HfB2 demonstrates the versatile range materials that can be produced via robocasting using Pluronic pastes.

  • Journal article
    Del Carro L, Zinn AA, Ruch P, Bouville F, Studart AR, Brunschwiler Tet al., 2019,

    Oxide-Free Copper Pastes for the Attachment of Large-Area Power Devices

    , Journal of Electronic Materials, Vol: 48, Pages: 6823-6834, ISSN: 0361-5235
  • Journal article
    Wat A, Ferraro C, Deng X, Sweet A, Tomsia AP, Saiz E, Ritchie ROet al., 2019,

    Bioinspired nacre-like alumina with a metallic nickel compliant phase fabricated by spark-plasma sintering

    , Small, Vol: 15, ISSN: 1613-6810

    Many natural materials present an ideal "recipe" for the development of future damage-tolerant lightweight structural materials. One notable example is the brick-and-mortar structure of nacre, found in mollusk shells, which produces high-toughness, bioinspired ceramics using polymeric mortars as a compliant phase. Theoretical modeling has predicted that use of metallic mortars could lead to even higher damage-tolerance in these materials, although it is difficult to melt-infiltrate metals into ceramic scaffolds as they cannot readily wet ceramics. To avoid this problem, an alternative ("bottom-up") approach to synthesize "nacre-like" ceramics containing a small fraction of nickel mortar is developed. These materials are fabricated using nickel-coated alumina platelets that are aligned using slip-casting and rapidly sintered using spark-plasma sintering. Dewetting of the nickel mortar during sintering is prevented by using NiO-coated as well as Ni-coated platelets. As a result, a "nacre-like" alumina ceramic displaying a resistance-curve toughness up to ≈16 MPa m½ with a flexural strength of ≈300 MPa is produced.

  • Journal article
    Magrini T, Bouville F, Lauria A, Le Ferrand H, Niebel TP, Studart ARet al., 2019,

    Transparent and tough bulk composites inspired by nacre

    , NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
  • Journal article
    Le Ferrand H, Bouville F, 2019,

    Processing of dense bioinspired ceramics with deliberate microstructure

  • Journal article
    D'Elia E, Ahmed HS, Feilden E, Saiz Eet al., 2019,

    Electrically-responsive graphene-based shape-memory composites

    , Applied Materials Today, Vol: 15, Pages: 185-191, ISSN: 2352-9407

    Shape memory materials can open new design opportunities in fields as diverse as healthcare, transportation or energy generation. In this respect, shape memory polymers (SMPs) have attracted much attention due to their advantages over metals in terms of weight and reliability. However, they are still marred by slow reaction times and poor mechanical performance. In this work we show how, by integrating a graphene network in a SMP matrix, it is possible to create composites with very low carbon contents (below 1 wt%) able to change shapes in short times (10 s of seconds) in response to low electric voltages (<10 V). This is possible because the conductive network is highly interconnected at the microscopic scale, acting as a very efficient Joule heater. The composites exhibit excellent shape fixity (>0.95 ± 0.03) and shape recovery ratios (>0.98 ± 0.03). Due to the 2D nature of graphene, this network directs crack propagation during fracture resulting in materials that retain bending strengths close to 100 MPa and exhibit significant extrinsic toughening (with toughness that reach values up to 3 times the initiation value). Furthermore, changes in conductivity can be used to follow the formation and growth of damage in the material before catastrophic failure, allowing the use of this material as a damage sensor. These results provide practical guidelines for the design of reliable shape memory composites for structural and sensing applications.

  • Journal article
    Boughton O, Ma S, Cai X, Yan L, Peralta L, Laugier P, Marrow J, Giuliani F, Hansen U, Abel R, Grimal Q, Cobb Jet al., 2019,

    Computed tomography porosity and spherical indentation for determining cortical bone millimetre-scale mechanical properties

    , Scientific Reports, Vol: 9, ISSN: 2045-2322

    The cortex of the femoral neck is a key structural element of the human body, yet there is not a reliable metric for predicting the mechanical properties of the bone in this critical region. This study explored the use of a range of non-destructive metrics to measure femoral neck cortical bone stiffness at the millimetre length scale. A range of testing methods and imaging techniques were assessed for their ability to measure or predict the mechanical properties of cortical bone samples obtained from the femoral neck of hip replacement patients. Techniques that can potentially be applied in vivo to measure bone stiffness, including computed tomography (CT), bulk wave ultrasound (BWUS) and indentation, were compared against in vitro techniques, including compression testing, density measurements and resonant ultrasound spectroscopy. Porosity, as measured by micro-CT, correlated with femoral neck cortical bone’s elastic modulus and ultimate compressive strength at the millimetre length scale. Large-tip spherical indentation also correlated with bone mechanical properties at this length scale but to a lesser extent. As the elastic mechanical properties of cortical bone correlated with porosity, we would recommend further development of technologies that can safely measure cortical porosity in vivo.Introduction

  • Journal article
    Wang S, Giuliani F, Britton TB, 2019,

    Microstructure and formation mechanisms of δ-hydrides in variable grain size Zircaloy-4 studied by electron backscatter diffraction

    , Acta Materialia, Vol: 169, Pages: 76-87, ISSN: 1359-6454

    Microstructure and crystallography of δ phase hydrides in as-received fine grain and ‘blocky alpha’ large grain Zircaloy-4 (average grain size ∼11 μm and >200 μm, respectively) were examined using electron backscatter diffraction (EBSD). Results suggest that the matrix-hydride orientation relationship is {0001} α ||{111} δ ;<112¯0> α ||<110> δ for all the cases studied. The habit plane of intragranular hydrides and some intergranular hydrides has been found to be {101¯7} of the surrounding matrix. The morphology of intergranular hydrides can vary depending upon the angle between the grain boundary and the hydride habit plane. The misfit strain between α-Zr and δ-hydride is accommodated mainly by high density of dislocations and twin structures in the hydrides, and a mechanism of twin formation in the hydrides has been proposed. The growth of hydrides across grain boundaries is achieved through an auto-catalytic manner similar to the growth pattern of intragranular hydrides. Easy collective shear along <11¯00> makes it possible for hydride nucleation at any grain boundaries, while the process seems to favour grain boundaries with low (<40°) and high (>80°) c-axis misorientation angles. Moreover, the angle between the grain boundary and the adjacent basal planes does not influence the propensity for hydride nucleation.

  • Journal article
    Le Ferrand H, Bouville F, Studart AR, 2019,

    Design of textured multi-layered structures via magnetically assisted slip casting.

    , Soft Matter

    Multi-layered composites in nature often show functional properties that are determined by the specific orientation of inorganic building blocks within each layer. The shell of bivalve molluscs and the exoskeleton of crustaceans constitute prominent examples. An effective approach to artificially produce textured microstructures inspired by such complex composites is magnetically assisted slip casting (MASC). MASC is a colloidal process in which anisotropic particles are magnetically oriented at arbitrarily defined angles and collected at the surface of a porous mould to grow the material in an additive manner. Whereas a number of proof-of-concept studies have established the potential of the technique, the full design space available for MASC-fabricated structures, and the limits of the approach, have so far not been explored systematically. To fill this gap, we have studied both theoretically and experimentally the various torques that act on the particles at the different stages of the assembly process. We define the boundary conditions of the MASC process for magnetically responsive alumina platelets suspended in a low-viscosity aqueous suspension, considering the composition of the colloidal suspension and the dynamics of the particle alignment process under a rotating magnetic field. These findings lead to design guidelines for the fabrication of bio-inspired composites with customized multi-scale structures for a broad range of applications.

  • Journal article
    Wang S, Giuliani F, Britton T, 2019,

    Variable temperature micropillar compression to reveal <a> basal slip properties of Zircaloy-4

    , Scripta Materialia, Vol: 162, Pages: 451-455, ISSN: 1359-6462

    Zircaloy-4 is widely used as nuclear fuel cladding materials, where it is important to understand the mechanical properties between room temperature and reactor operating temperatures (around 623 K). To aid in this understanding, we have performed compression tests on micropillars aligned to activate <a> basal slip across this temperature range. Engineering analysis of the results indicates that the plastic yield follows a thermally activated constitutive law. We also observe the nature of the slip bands formed on the side surface of our pillars and see characteristic ‘bulging’ that tends to localise as temperature increases.

  • Journal article
    Grossman M, Pivovarov D, Bouville F, Dransfeld C, Masania K, Studart ARet al., 2019,

    Hierarchical Toughening of Nacre-Like Composites

  • Journal article
    Jun T-S, Maeder X, Bhowmik A, Guillonneau G, Michler J, Giuliani F, Britton TBet al., 2019,

    The role of β-titanium ligaments in the deformation of dual phase titanium alloys

    , Materials Science and Engineering: A, Vol: 746, Pages: 394-405, ISSN: 0921-5093

    Multiphase titanium alloys are critical materials in high value engineeringcomponents, for instance in aero engines. Microstructural complexity isexploited through interface engineering during mechanical processing to realisesignificant improvements in fatigue and fracture resistance and strength. Inthis work, we explore the role of select interfaces using in-situmicromechanical testing with concurrent observations from high angularresolution electron backscatter diffraction (HR-EBSD). Our results aresupported with post mortem transmission electron microscopy (TEM). Usingmicro-pillar compression, we performed in-depth analysis of the role of select{\beta}-titanium (body centred cubic) ligaments which separate neighbouring{\alpha}-titanium (hexagonal close packed) regions and inhibit the dislocationmotion and impact strength during mechanical deformation. These results shedlight on the strengthening mechanisms and those that can lead to strainlocalisation during fatigue and failure.

  • Journal article
    Alison L, Menasce S, Bouville F, Tervoort E, Mattich I, Ofner A, Studart ARet al., 2019,

    3D printing of sacrificial templates into hierarchical porous materials

    , SCIENTIFIC REPORTS, Vol: 9, ISSN: 2045-2322
  • Journal article
    Caballero SSR, Saiz E, Montembault A, Tadier S, Maire E, David L, Delair T, Gremillard Let al., 2019,

    3-D printing of chitosan-calcium phosphate inks: rheology, interactions and characterization

    , Journal of Materials Science: Materials in Medicine, Vol: 30, ISSN: 0957-4530

    Bone substitute fabrication is of interest to meet the worldwide incidence of bone disorders. Physical chitosan hydrogels with intertwined apatite particles were chosen to meet the bio-physical and mechanical properties required by a potential bone substitute. A set up for 3-D printing by robocasting was found adequate to fabricate scaffolds. Inks consisted of suspensions of calcium phosphate particles in chitosan acidic aqueous solution. The inks are shear-thinning and consist of a suspension of dispersed platelet aggregates of dicalcium phosphate dihydrate in a continuous chitosan phase. The rheological properties of the inks were studied, including their shear-thinning characteristics and yield stress. Scaffolds were printed in basic water/ethanol baths to induce transformation of chitosan-calcium phosphates suspension into physical hydrogel of chitosan mineralized with apatite. Scaffolds consisted of a chitosan polymeric matrix intertwined with poorly crystalline apatite particles. Results indicate that ink rheological properties could be tuned by controlling ink composition: in particular, more printable inks are obtained with higher chitosan concentration (0.19 mol·L−1).

  • Conference paper
    Rocher ME, Hermann T, McGilvray M, Ifti HS, Hufgard F, Eberhart M, Meindl A, Löhle S, Giovannini T, Vandeperre Let al., 2019,

    Testing a transpiration cooled zirconium-di-boride sample in the plasma tunnel at irs

    Transpiration cooling is an active thermal protection system (TPS), in which a coolant gas is fed through a porous material. This requires a material that stays structurally stable at high temperatures, while having the desired permeability. This paper explores transpiration cooling of Ultra-High-Temperature-Ceramics (UHTCs). A stagnation probe with transpiration cooled ZrB2 was tested in a plasma wind tunnel at a null point heat flux of 3.59 MW/m2 in steady state and transiently at 2 MW/m2. The aim is to understand whether transpiration cooling can increase the UHTC operating temperature by shielding it from oxygen and reducing the heating from surface re-combination. Several diagnostics are applied, including an Echelle spectrograph that explores outgassing of oxidation products from the surface. Infrared thermography is employed to track the surface temperature at the front and the back surface temperature is measured by a pyrometer. Furthermore, the Planck radiation background of the emission spectra is used to assess the front surface temperature. The testing included a variation in the injectant species and mass flux. While the uncooled sample fully oxidised at a surface temperature of 2150 K, 20.25 g/m2 s of helium and 620.11 g/m2 s of nitrogen prevented oxidation of the transpiration cooled samples. At a blowing parameter of 0.1094, the helium cooled probe reached a front surface temperature of 1428 K and reduced the incident heat flux by 77% compared to the uncooled sample. The nitrogen cooled sample had a maximum front surface temperature of 1128 K with a blowing parameter of 1.958 and an 83.3% lower incident heat flux than the uncooled sample.

  • Journal article
    Minas C, Rechberger F, Tervoort E, Bargardi FL, Billaud J, Niederberger M, Bouville F, Studart ARet al., 2018,

    Freezing of Gelled Suspensions: a Facile Route toward Mesoporous TiO2 Particles for High-Capacity Lithium-Ion Electrodes

    , ACS APPLIED NANO MATERIALS, Vol: 1, Pages: 6622-6629, ISSN: 2574-0970
  • Journal article
    Grossman M, Bouville F, Masania K, Studart ARet al., 2018,

    Quantifying the role of mineral bridges on the fracture resistance of nacre-like composites

  • Journal article
    Wang X, Peng J, Zhang Y, Li M, Saiz E, Tomsia AP, Cheng Qet al., 2018,

    Ultratough Bioinspired Graphene Fiber via Sequential Toughening of Hydrogen and Ionic Bonding

    , ACS NANO, Vol: 12, Pages: 12638-12645, ISSN: 1936-0851
  • Journal article
    Glymond D, Vandeperre LJM, 2018,

    Robocasting of MgO-doped alumina using alginic acid slurries

    , Journal of the American Ceramic Society, Vol: 101, Pages: 3309-3316, ISSN: 0002-7820

    The benefits of MgO doping of alumina for maintaining a homogeneous grain structure have long been established. Therefore in this work a bespoke ink for Robocasting of alumina is developed based on the gelation of alginic acid using magnesium ions, thereby ensuring homogeneous MgO doping of the alumina green body. The shear thinning behavior of alginic acid based solutions was paired with the rheological properties of a partially coagulated colloidal suspension to allow high solid loading inks (up to 50 vol%) with good extrusion behavior. Shear thinning coefficients of n ~ 0.2 were recorded, with yield stresses of 250 Pa and stiffness values in the range 100-1000 kPa. The printed alumina bars reached densities of >98% and unpolished strengths reached up to 326 ± 16 MPa after sintering at 0.4 mol/L magnesium chloride and 45 vol% alumina.

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