Publications
211 results found
Cai Q, Meille S, Chevalier J, et al., 2023, 3D-Printing of ceramic filaments with ductile metallic cores, Materials & Design, Vol: 225, ISSN: 0261-3069
The additive manufacturing of composite structures can open possibilities in the design and fabrication of devices but also demands new approaches. In this work, we use thermally reversible pastes to fabricate ceramic matrix (Al2O3) composites reinforced with continuous metallic fibres (steel). The approach is based on the micro-extrusion of ceramic–metal filaments with core–shell and layered arrangements. These filaments are employed in the additive manufacturing of dense and light-weight cellular structures that combine the stiffness and strength of the ceramic shell with the fracture resistance and energy absorption capabilities provided by the metal core. The approach can be used to extrude filaments with thin porous interlayers separating the core and the shells to create a weak fibre/matrix interphase. The cellular structures fabricated with these filaments exhibit higher compressive strengths and energy absorption capabilities than those fabricated from pure ceramics. The works of fracture of the dense composites are one to two orders of magnitude above those of the ceramic matrix (103 J/m2) while the bending strengths remain comparable to those of 3D printed alumina (200–350 MPa). The technique could be easily extended to other material combinations opening new opportunities in the additive manufacturing of multi-material parts and devices.
Li M, Zhou S, Guan Q, et al., 2022, Robust underwater oil-repellent biomimetic ceramic surfaces: combining the stability and reproducibility of functional structures, ACS Applied Materials and Interfaces, Vol: 14, Pages: 46077-46085, ISSN: 1944-8244
Robust underwater oil-repellent materials combining high mechanical strength and durability with superwettability and low oil adhesion are needed to build oil-repellent devices able to work in water, to manipulate droplet behavior, etc. However, combining all of these properties within a single, durable material remains a challenge. Herein, we fabricate a robust underwater oil-resistant material (Al2O3) with all of the above properties by gel casting. The micro/nanoceramic particles distributed on the surface endow the material with excellent underwater superoleophobicity (∼160°) and low oil adhesion (<4 μN). In addition, the substrate exhibits typical ceramic characteristics such as good antiacid/alkali properties, high salt resistance, and high load tolerance. These excellent properties make the material not only applicable to various liquid environments but also resistant to the impact of particles and other physical damage. More importantly, the substrate could still exhibit underwater superoleophobicity after being worn under specific conditions, as wear will create new surfaces with similar particle size distribution. This approach is easily scalable for mass production, which could open a pathway for the fabrication of practical underwater long-lasting functional interfacial materials.
Delage J, Saiz E, Al Nasiri N, 2022, Fracture behaviour of SiC/SiC ceramic matrix composite at room temperature, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 42, Pages: 3156-3167, ISSN: 0955-2219
Rauch N, Saiz E, Tomsia AP, 2022, Spreading of liquid Ag and Ag-Mo alloys on molybdenum substrates, INTERNATIONAL JOURNAL OF MATERIALS RESEARCH, Vol: 94, Pages: 233-237, ISSN: 1862-5282
Gremillard L, Saiz E, Chevalier J, et al., 2021, Wetting and strength in the tin - silver - titanium/sapphire system, INTERNATIONAL JOURNAL OF MATERIALS RESEARCH, Vol: 95, Pages: 261-265, ISSN: 1862-5282
Li M, Li W, Guan Q, et al., 2021, A tough reversible biomimetic transparent adhesive tape with pressure-sensitive and wet-cleaning properties, ACS NANO, Vol: 15, Pages: 19194-19201, ISSN: 1936-0851
Dry adhesives that combine strong adhesion, high transparency, and reusability are needed to support developments in emerging fields such as medical electrodes and the bonding of electronic optical devices. However, achieving all of these features in a single material remains challenging. Herein, we propose a pressure-responsive polyurethane (PU) adhesive inspired by the octopus sucker. This adhesive not only showcases reversible adhesion to both solid materials and biological tissues but also exhibits robust stability and high transparency (>90%). As the adhesive strength of the PU adhesive corresponds to the application force, adhesion could be adjusted by the preloading force and/or pressure. The adhesive exhibits high static adhesion (∼120 kPa) and 180° peeling force (∼500 N/m), which is far stronger than those of most existing artificial dry adhesives. Moreover, the adhesion strength is effectively maintained even after 100 bonding–peeling cycles. Because the adhesive tape relies on the combination of negative pressure and intermolecular forces, it overcomes the underlying problems caused by glue residue like that left by traditional glue tapes after removal. In addition, the PU adhesive also shows wet-cleaning performance; the contaminated tape can recover 90–95% of the lost adhesion strength after being cleaned with water. The results show that an adhesive with a microstructure designed to increase the contribution of negative pressure can combine high reversible adhesion and long fatigue life.
Li M, Li C, Blackman BRK, et al., 2021, Energy conversion based on bio-inspired superwetting interfaces, Matter, Vol: 4, Pages: 3400-3414, ISSN: 2590-2385
Bio-inspired superwetting interfaces can realize rapid transfer of liquid mass or momentum due to their unique surface structure and wetting characteristics. Combined with a suitably electrified material, these special interfaces can further promote the generation or transmission of electrons. Herein, we summarize the latest developments in water-energy collection technologies based on these interfaces, such as piezoelectric/triboelectric/pyroelectric nanogenerators. When it comes to harvesting energy generated by salinity gradients, reverse electrodialysis based on ion channels is now being widely investigated. We review the concept of “quantum-confined superfluids” on superwetting interfaces, and the conditions required to form a superfluid in molecular and ion channels. The applications of the superfluids in energy conversion are discussed, including the charging and discharging process of lithium batteries and harvesting salinity-gradient energy. This perspective identifies advantages, current challenges, and future directions in the development of energy-conversion devices using superwetting interfaces that could open the door to their broader application.
Li M, Li C, Blackman BRK, et al., 2021, Mimicking nature to control bio-material surface wetting and adhesion, International Materials Reviews, Vol: 67, Pages: 1-24, ISSN: 0950-6608
Nature has developed unique strategies to refine and optimise structural performance. Using surfaces designed at multiple length scales, from micro to nano levels, combined with complex chemistries, different natural organisms can exhibit similar wetting but different adhesion to liquids under specific environments. These biological surfaces have inspired researchers to develop new approaches to control surface wetting and liquid behaviour via surface adhesion. Here we review natural strategies to control the interaction of liquids with solid surfaces and the efforts to implement these strategies in synthetic materials designed to work in either atmospheric or underwater environment. Particular attention is paid to droplet behaviour on the special-adhesion surfaces in nature and artificial smart surfaces. We highlight recent progress, identify the common threads, and discuss the fundamental differences in a way that can help formulate rational approaches towards surface engineering, and identify current challenges as well as future directions for the field.
Gavalda-Diaz O, Manno R, Melro A, et al., 2021, Mode I and Mode II interfacial fracture energy of SiC/BN/SiC CMCs, Acta Materialia, Vol: 215, Pages: 1-11, ISSN: 1359-6454
Quantifying the mixed mode fracture toughness of interfaces in ceramic matrix composites (CMCs) is crucial for understanding their failure. In this work we use in situ micromechanical testing in the scanning electron microscope to achieve stable interfacial crack propagation in Mode I (Double Cantilever Beam) and Mode II (Push out) and measure the corresponding fracture resistances. We use this approach to measure the interfacial fracture resistance in SiC/BN/SiC CMCs and compare it to the fracture energy of the fibres. During in-situ testing, fracture paths can be observed while data is acquired simultaneously. We clearly observe debonding at the BN-fibre interface (i.e. inside adhesive debonding). The critical energy release rate of the BN-fibre interface for Mode I and II (GIc ≈ 2.1 ± 1.0 J/m2 and GIIc ≈ 1.2 ± 0.5 J/m2) are equivalent and is lower than that measured for the fibre using microscopic DCB tests (GIc ≈ 6.0 ± 2.0 J/m2). These results explain the generalized fibre debonding and pull out observed in the fracture of these CMCs. By enabling direct observation of crack paths and quantifying the corresponding fracture energies, we highlight possible routes for the optimisation and modelling of the new generation of CMC interphases.
Cao C, Lin Z, Liu X, et al., 2021, Strong Reduced Graphene Oxide Coated Bombyx mori Silk, ADVANCED FUNCTIONAL MATERIALS, Vol: 31, ISSN: 1616-301X
Li C, Li M, Ni Z, et al., 2021, Stimuli-responsive surfaces for switchable wettability and adhesion, Journal of the Royal Society Interface, Vol: 18, ISSN: 1742-5662
Diverse unique surfaces exist in nature, e.g. lotus leaf, rose petal and rice leaf. They show similar contact angles but different adhesion properties. According to the different wettability and adhesion characteristics, this review reclassifies different contact states of droplets on surfaces. Inspired by the biological surfaces, smart artificial surfaces have been developed which respond to external stimuli and consequently switch between different states. Responsive surfaces driven by various stimuli, e.g. stretching, magnetic, photo, electric, temperature, humidity and pH, are discussed. Studies reporting on either atmospheric or underwater environments are discussed. The application of tailoring surface wettability and adhesion includes microfluidics/droplet manipulation, liquid transport and harvesting, water energy harvesting and flexible smart devices. Particular attention is placed on the horizontal comparison of smart surfaces with the same stimuli. Finally, the current challenges and future prospects in this field are also identified.
De Meyere RMG, Song K, Gale L, et al., 2021, A novel trench fibre push-out method to evaluate interfacial failure in long fibre composites, Journal of Materials Research, Vol: 36, Pages: 2305-2314, ISSN: 0884-2914
Traditional fibre push-outs for the evaluation of interfacial properties in long fibre ceramic matrix composites present their limitations—solutions for which are addressed in this work by introducing the novel trench push-out test. The trench push-out makes use of a FIB milling system and an SEM in-situ nanoindenter to probe a fibre pushed into a trench underneath, allowing in-situ observations to be directly correlated with micromechanical events. SiCf/BN/SiC composites—candidate material for turbine engines—were used as model materials in this work. Different fibre types (Hi-Nicalon and Tyranno type SA3) were coated with BN interphases, presenting mean interfacial shear stresses of 14 ± 7 MPa and 20 ± 2 MPa, respectively, during fibre sliding. The micromechanical technique enabled visualisation of how defects in the interphase (voids, inclusions & milled notches) or in the fibre (surface asperities, non-uniform coatings) affected the variability of interfacial property measurement.
Gavalda-Diaz O, Lyons J, Wang S, et al., 2021, Basal plane delamination energy measurement in a Ti3SiC2 MAX phase, JOM, Vol: 73, Pages: 1582-1588, ISSN: 1047-4838
The {0001} basal plane delamination dominating the crack-wake bridging in MAX phases at a bulk scale has been investigated by studying the small-scale fracture of a Ti3SiC2. In situ micro-double cantilever beam (DCB) tests in a scanning electron microscope were used to grow a stable crack along the basal plane, measure the fracture energy, and study the crack propagation mechanism at the nanoscale. The results show that the fracture energy (10–50 J/m2) depends on small misorientations angles (e.g., 5°) of the basal plane to the stress field. This induces permanent deformation which can be observed once the DCB has been unloaded. The nanoscale study of the crack shows that the plasticity at the crack tip is small, but a number of pairs of dislocations are forming at each side of the crack. Hence, this study helps to explain the enhanced fracture energy values and possible sources of energy dissipation in basal plane delamination, which is the one of the main toughening mechanisms in the bulk fracture of MAX phases.
Leung CLA, Elizarova I, Isaacs M, et al., 2021, Enhanced near-infrared absorption for laser powder bed fusion using reduced graphene oxide, Applied Materials Today, Vol: 23, Pages: 1-10, ISSN: 2352-9407
Laser powder bed fusion (LPBF) is a revolutionary manufacturing technology that fabricates parts with unparalleled complexity, layer-by-layer. However, there are limited choices of commercial powders for LPBF, constrained partly by the laser absorbance, an area that is not well investigated. Carbon additives are commonly used to promote near infra-red (NIR) absorbance of the powders but their efficiency is limited. Here, we combine operando synchrotron X-ray imaging with chemical characterisation techniques to elucidate the role of additives on NIR absorption, melt track and defect evolution mechanisms during LPBF. We employ a reduced graphene oxide (rGO) additive to enable LPBF of low NIR absorbance powder, SiO2, under systematic build conditions. This work successfully manufactured glass tracks with a high relative density (99.6%) and overhang features (> 5 mm long) without pre/post heat treatment. Compared to conventional carbon additives, the rGO increases the powder's NIR absorbance by ca. 3 times and decreases the warpage and porosity in LPBF glass tracks. Our approach will dramatically widen the palette of materials for laser processing and enable existing LPBF machines to process low absorbance powder, such as SiO2, using a NIR beam.
Azcune I, Huegun A, Ruiz de Luzuriaga A, et al., 2021, The effect of matrix on shape properties of aromatic disulfide based epoxy vitrimers, European Polymer Journal, Vol: 148, Pages: 1-10, ISSN: 0014-3057
Aromatic disulfide based vitrimers show elasticity driven shape-memory and plastic reprocessability via associative rearrangement of dynamic covalent crosslinks. Those processess represent the two sides of a coin: the storage and relaxation of the strain energy caused by a deformation load. The key temperatures that trigger the underlying mechanisms, i.e. phase transition and disulfide exchange reaction, are extremely sensitive to the molecular structure of the polymer and under certain condition overlap. To gain insight on the relationship between the structure, dynamic and shape-changing properties, five aromatic disulfide-based epoxy networks with a range of Tg values (32–142 °C), molecular structure and crosslink densities (2252–462 mol m−3) were synthesized. The epoxy matrices were formulated combining different ratios of rigid bisphenol A diglycidyl ether (DGEBA) and flexible poly(propylene glycol) diglycidic ether (DGEPPG) epoxy monomers crosslinked by 4-aminophenyldisulfide hardener.
Aldegaither N, Sernicola G, Mesgarnejad A, et al., 2021, Fracture toughness of bone at the microscale, Acta Biomaterialia, Vol: 121, Pages: 475-483, ISSN: 1742-7061
Bone's hierarchical arrangement of collagen and mineral generates a confluence of toughening mechanisms acting at every length scale from the molecular to the macroscopic level. Molecular defects, disease, and age alter bone structure at different levels and diminish its fracture resistance. However, the inability to isolate and quantify the influence of specific features hampers our understanding and the development of new therapies. Here, we combine in situ micromechanical testing, transmission electron microscopy and phase-field modelling to quantify intrinsic deformation and toughening at the fibrillar level and unveil the critical role of fibril orientation on crack deflection. At this level dry bone is highly anisotropic, with fracture energies ranging between 5 and 30 J/m2 depending on the direction of crack propagation. These values are lower than previously calculated for dehydrated samples from large-scale tests. However, they still suggest a significant amount of energy dissipation. This approach provides a new tool to uncouple and quantify, from the bottom up, the roles played by the structural features and constituents of bone on fracture and how can they be affected by different pathologies. The methodology can be extended to support the rational development of new structural composites.
Cao C, Peng J, Liang X, et al., 2021, Strong, conductive aramid fiber functionalized by graphene, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING, Vol: 140, ISSN: 1359-835X
Petrova NL, Cai Q, Petrov PK, et al., 2020, Can novel bone substitutes withstand the enhanced resorbing activity of Charcot osteoclasts?, Publisher: WILEY, Pages: 48-48, ISSN: 0742-3071
Diaz OG, Marquardt K, Harris S, et 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.
Rocha VG, Saiz E, Tirichenko IS, et al., 2020, Direct ink writing advances in multi-material structures for a sustainable future, Journal of Materials Chemistry A, Vol: 8, Pages: 15646-15657, ISSN: 2050-7488
Novel manufacturing techniques such as additive manufacturing (AM, also referred to as 3D printing) will play a critical role in building a sustainable future. AM will reduce waste, energy consumption and production time by eliminating the need to assemble components. It will also enable the mass customization of complex devices. To reach their full potential, additive manufacturing technologies should be able to combine different materials in a single processing step. Although the development of multi-material printing is in its infancy, it could have a massive impact in fields as diverse as energy storage and generation, electronic devices, healthcare or structural composites to name a few. Here we provide a critical perspective on the advances and potential of multi-material printing using direct extrusion-based printing, also known as direct ink writing (DIW) or robocasting. We will show examples of devices and structures combining a wide range of materials from ceramics to metals, polymers and carbon with particular focus on three promising applications: energy storage, lightweight composites and sensors. The goals are to assess the progress made so far, to point out specific challenges and areas for further development and to provide guidelines to those interested in multi-material DIW.
Zhou T, Wu C, Wang Y, et 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.
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.
Peng J, Huang C, Cao C, et 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
Feilden E, Glymond D, Saiz E, et 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.
Wat A, Ferraro C, Deng X, et 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.
D'Elia E, Ahmed HS, Feilden E, et 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.
Caballero SSR, Saiz E, Montembault A, et 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).
Wang X, Peng J, Zhang Y, et al., 2018, Ultratough Bioinspired Graphene Fiber via Sequential Toughening of Hydrogen and Ionic Bonding, ACS NANO, Vol: 12, Pages: 12638-12645, ISSN: 1936-0851
Zhang Y, Peng J, Li M, et al., 2018, Bioinspired supertough graphene fiber through sequential interfacial interactions., ACS Nano, Vol: 12, Pages: 8901-8908, ISSN: 1936-0851
Natural nacre exhibits extraordinary functional and structural diversity, combining high strength and toughness. The mechanical properties of nacre are attributed to (i) a highly arranged hierarchical layered structure of inorganic minerals (95 vol %) containing a small amount only of organic materials (5 vol %), (ii) abundant synergistic interfacial interactions, and (iii) formation under ambient temperature. Herein, inspired by these three design principles originating from natural nacre, the supertough bioinspired graphene-based nanocomposite fibers (BGNFs) are prepared under room temperature via sequential interfacial interactions of ionic bonding and π-π interactions. The resultant synergistic effect leads to a super toughness of 18.7 MJ m-3 as well as a high tensile strength of 740.1 MPa. In addition, the electrical conductivity of these supertough BGNFs is as high as 384.3 S cm-1. They can retain almost 80% of this conductivity even after 1000 cycles of loading-unloading testing, which makes these BGNFs promising candidates for application in flexible and stable electrical devices, such as strain sensors and actuators.
Pelissari PIBGB, Bouville F, Pandolfelli VC, et al., 2018, Nacre-like ceramic refractories for high temperature applications, Journal of the European Ceramic Society, Vol: 38, Pages: 2186-2193, ISSN: 0955-2219
High-temperature ceramics, so-called refractories, are widely used for the manufacturing of metals, for energy generation and aerospace applications. Refractories are usually strong and stiff but fragile due to the lack of plastic deformation and other intrinsic toughening mechanisms. This inherent brittleness limits their use in applications where catastrophic failure is not tolerated. The present work reports the design and fabrication of refractories with a bio inspired nacre-like microstructure comprising aligned alumina platelets, separated by an aluminium borate interphase, obtained through transient liquid phase sintering. The bioinspired composites exhibit high strength, 672 MPa, toughness, 7.4 MPa m1/2, and stable crack propagation at high temperatures, above 600 °C, due to the aluminium borate interlayer. This makes nacre-like ceramic refractories sintered with a transient liquid phase good candidate for high temperature applications, competing favourably with ceramic matrix composites and following a simpler and cheaper processing route.
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