Hard Inorganic Materials Research Articles

Flexible thin film optical solar reflectors with Ta2O5-based multimaterial coatings for space radiative cooling

Optical Solar Reflectors (OSRs) combine low solar radiation absorption (α) and high broadband infrared emissivity (ε) and are applied to the external surface of spacecraft for its thermal management. Bulk glass OSR tiles are the incumbent, but ultra-lightweight and thin-film flexible OSR coatings are raising considerable interest for both space and terrestrial radiative cooling applications. In this work, a genetic algorithm combined with a transfer matrix method is used for the design and optimization of multimaterial thin-film OSRs for broadband radiative cooling. The algorithm simultaneously optimizes the spectral performance of the OSR at two parts of the wavelength spectrum, solar (0.3–2.5 μm) and thermal infrared (2.5–30 μm). The designed optimized OSR structure consists of 18 alternating layers of three materials, SiN, SiO2, and Ta2O5, on top of an Al mirror backreflector, with a total thickness of only 2.088 μm. The optimized multilayer stack contributes distributed Bragg reflections that reduce the residual solar absorption below that of an uncoated Al mirror. The optimized OSR is demonstrated experimentally on a 150 mm (6 in.) Si wafer and on a flexible polyimide substrate using a production level reactive sputtering tool. The fabricated thin film OSR shows good thermal-optical property with α = 0.11 and ε = 0.75 and achieves a net cooling power of 150.1 W/m2 under conditions of one sun total solar irradiance in space. The ultrathin coating fabricated using hard inorganic materials facilitates its integration onto flexible foils and enables large-scale manufacture of low-cost OSRs for broadband radiative cooling applications.

Nanoimprint Lithography Processing of Inorganic-Based Materials

We review past and recent progress in Nano-Imprint Lithography (NIL) methods to (nano-) structure inorganic materials from sol-gel liquid formulations and colloidal suspensions onto a surface. This technique, first inspired by embossing techniques, was developed for soft polymer processing, as final or intermediate materials, but is today fully adapted to hard inorganic materials with high dielectric constant, such as metal oxides, with countless chemical compositions provided by the sol-gel chemistry. Consequently, NIL has become a versatile, high throughput, and highly precise microfabrication method that is mature for lab developments and scaling up. We first describe the state-of-the-art in nanofabrication methods and the plethora of approaches developed in the last decades to imprint metal oxides from inorganic solutions. These are discussed and compared in terms of performances, issues, and ease of implementation. The final part is devoted to relevant applications in domains of interest.

Bio-Inspired Toughening of Composites in 3D-Printing.

Natural materials achieve exceptional mechanical properties by relying on hierarchically structuring their internal architecture. In several marine species, layers of stiff and hard inorganic material are separated by thin compliant organic layers, giving their skeleton both stiffness and toughness. This phenomenon is fundamentally based on the periodical variation of Young’s modulus within the structure. In this study, alteration of mechanical properties is achieved through a layer-wise build-up of two different materials. A hybrid 3D-printing device combining stereolithography and inkjet printing is used for the manufacturing process. Both components used in this system, the ink for jetting and the resin for structuring by stereolithography (SLA), are acrylate-based and photo-curable. Layers of resin and ink are solidified separately using two different light sources (λ1 = 375 nm, λ2 = 455 nm). Three composite sample groups (i.e., one hybrid material, two control groups) are built. Measurements reveal an increase in fracture toughness and elongation at break of 70% and 22%, respectively, for the hybrid material compared to the control groups. Moreover, the comparison of the two control groups shows that the effect is essentially dependent on different materials being well contained within separated layers. This bio-inspired building approach increases fracture toughness of an inherently brittle matrix material.

Dynamic metal-polymer interaction for the design of chemoselective and long-lived hydrogenation catalysts.

Metal catalysts are generally supported on hard inorganic materials because of their high thermochemical stabilities. Here, we support Pd catalysts on a thermochemically stable but "soft" engineering plastic, polyphenylene sulfide (PPS), for acetylene partial hydrogenation. Near the glass transition temperature (~353 K), the mobile PPS chains cover the entire surface of Pd particles via strong metal-polymer interactions. The Pd-PPS interface enables H2 activation only in the presence of acetylene that has a strong binding affinity to Pd and thus can disturb the Pd-PPS interface. Once acetylene is hydrogenated to weakly binding ethylene, re-adsorption of PPS on the Pd surface repels ethylene before it is further hydrogenated to ethane. The Pd-PPS interaction enables selective partial hydrogenation of acetylene to ethylene even in an ethylene-rich stream and suppresses catalyst deactivation due to coke formation. The results manifest the unique possibility of harnessing dynamic metal-polymer interaction for designing chemoselective and long-lived catalysts.

Hybrid Perovskites Depth Profiling with Variable-Size Argon Clusters and Monatomic Ions Beams.

Ion beam depth profiling is increasingly used to investigate layers and interfaces in complex multilayered devices, including solar cells. This approach is particularly challenging on hybrid perovskite layers and perovskite solar cells because of the presence of organic/inorganic interfaces requiring the fine optimization of the sputtering beam conditions. The ion beam sputtering must ensure a viable sputtering rate on hard inorganic materials while limiting the chemical (fragmentation), compositional (preferential sputtering) or topographical (roughening and intermixing) modifications on soft organic layers. In this work, model (Csx(MA0.17FA0.83)100−xPb(I0.83Br0.17)3/cTiO2/Glass) samples and full mesoscopic perovskite solar cells are profiled using low-energy (500 and 1000 eV) monatomic beams (Ar+ and Cs+) and variable-size argon clusters (Arn+, 75 < n < 4000) with energy up to 20 keV. The ion beam conditions are optimized by systematically comparing the sputtering rates and the surface modifications associated with each sputtering beam. X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and in-situ scanning probe microscopy are combined to characterize the interfaces and evidence sputtering-related artifacts. Within monatomic beams, 500 eV Cs+ results in the most intense and stable ToF-SIMS molecular profiles, almost material-independent sputtering rates and sharp interfaces. Large argon clusters (n > 500) with insufficient energy (E < 10 keV) result in the preferential sputtering of organic molecules and are highly ineffective to sputter small metal clusters (Pb and Au), which tend to artificially accumulate during the depth profile. This is not the case for the optimized cluster ions having a few hundred argon atoms (300 < n < 500) and an energy-per-atom value of at least 20 eV. In these conditions, we obtain (i) the low fragmentation of organic molecules, (ii) convenient erosion rates on soft and hard layers (but still different), and (iii) constant molecular profiles in the perovskite layer, i.e., no accumulation of damages.

Three-dimensional mesostructures as high-temperature growth templates, electronic cellular scaffolds, and self-propelled microrobots

Recent work demonstrates that processes of stress release in prestrained elastomeric substrates can guide the assembly of sophisticated 3D micro/nanostructures in advanced materials. Reported application examples include soft electronic components, tunable electromagnetic and optical devices, vibrational metrology platforms, and other unusual technologies, each enabled by uniquely engineered 3D architectures. A significant disadvantage of these systems is that the elastomeric substrates, while essential to the assembly process, can impose significant engineering constraints in terms of operating temperatures and levels of dimensional stability; they also prevent the realization of 3D structures in freestanding forms. Here, we introduce concepts in interfacial photopolymerization, nonlinear mechanics, and physical transfer that bypass these limitations. The results enable 3D mesostructures in fully or partially freestanding forms, with additional capabilities in integration onto nearly any class of substrate, from planar, hard inorganic materials to textured, soft biological tissues, all via mechanisms quantitatively described by theoretical modeling. Illustrations of these ideas include their use in 3D structures as frameworks for templated growth of organized lamellae from AgCl-KCl eutectics and of atomic layers of WSe2 from vapor-phase precursors, as open-architecture electronic scaffolds for formation of dorsal root ganglion (DRG) neural networks, and as catalyst supports for propulsive systems in 3D microswimmers with geometrically controlled dynamics. Taken together, these methodologies establish a set of enabling options in 3D micro/nanomanufacturing that lie outside of the scope of existing alternatives.

Generic Role of Polymer Supports in the Fine Adjustment of Interfacial Interactions between Solid Substrates and Model Cell Membranes.

To understand the generic role of soft, hydrated biopolymers in adjusting interfacial interactions at biological interfaces, we designed a defined model of the cell-extracellular matrix contacts based on planar lipid membranes deposited on polymer supports (polymer-supported membranes). Highly uniform polymer supports made out of regenerated cellulose allow for the control of film thickness without changing the surface roughness and without osmotic dehydration. The complementary combination of specular neutron reflectivity and high-energy specular X-ray reflectivity yields the equilibrium membrane-substrate distances, which can quantitatively be modeled by computing the interplay of van der Waals interaction, hydration repulsion, and repulsion caused by the thermal undulation of membranes. The obtained results help to understand the role of a biopolymer in the interfacial interactions of cell membranes from a physical point of view and also open a large potential to generally bridge soft, biological matter and hard inorganic materials.

Native supported membranes on planar polymer supports and micro-particle supports

To bridge soft biological materials and hard inorganic materials is an interdisciplinary scientific challenge. Despite of experimental difficulties, the deposition of native biological membranes on supports is a straightforward strategy. This review provides an overview of advances in the fabrication and characterization of native biological membranes on planar polymer supports and micro-particles.

Copper CMP with Composite Polymer Core–Silica Shell Abrasives: A Defectivity Study

The results of copper chemical mechanical planarization (CMP) experiments with a model slurry chemistry based on the combination of glycine–water–benzotriazole , and different types of composite A (silane coupling agents between the polymer core and the silica shell) and B (electrostatic attraction between the polymer core and the silica shell) abrasives, are presented. While the presence of BTA allows a 10-fold reduction in the static etch rate from , combining an oxidizer and complexing agent leads to removal rates higher than . Different surface morphology and root-mean-square (rms) roughness are observed after polishing with composite abrasives combined with different peroxide concentrations. Oxidizer concentrations as low as lead to a high nonuniformity and defectivity values. In particular, at pH , composite B performs better than pure colloidal silica during copper CMP using the IC-1000 pad, giving a comparable material removal rate (MRR), but a better surface finish due to the contribution of the elasticity of the polymer in gently transferring the applied load to the wafer surface. Cu CMP with pure polymer particles is a promising alternative to the hard inorganic material, especially if combined with suitable surfactants that act from both particle stabilization and friction reduction/lubrication improvement perspectives. The use of a medium/high-hardness pad IC-1000 is compared to the use of a soft Politex pad. In the former case, differences in terms of MRR, rms roughness, and total defects are observed between the composite abrasives A and B; in the latter case, the behavior of the two composites is similar. In the case of a soft pad in combination with composite abrasives, there is a remarkable improvement in the defectivity without any loss in MRR.

Copper CMP with Composite Polymer Core - Silica Shell Abrasives: A Defectivity Study

ABSTRACTThe results of copper Chemical Mechanical Planarization (CMP) experiments with a model slurry chemistry based on the combination of Glycine-water-Benzotriazole (Gly-H2O2-BTA), and different types of composite A (silane coupling agents between the polymer core and the silica shell) and B (electrostatic attraction between the polymer core and the silica shell) abrasives, are presented. While the presence of BTA allows a ten-fold reduction in the static etch rate from 95 nm/min. to 10 nm/min., combining oxidizer and complexing agent leads to removal rates higher than 400 nm/min. Different surface morphology and RMS roughness are observed after polishing with composite abrasives and different peroxide concentrations. Oxidizer concentrations as low as 0.1 vol.% lead to high non-uniformity and defectivity values. In particular, composite B performs better than pure colloidal/fumed silica during copper CMP using the IC-1000 pad, giving comparable Material Removal Rate (MRR), but a better surface finish due to the contribution of the elasticity of the polymer in gently transferring the applied load to the wafer surface. Cu CMP with pure polymer particles is a promising alternative to the hard inorganic material especially if combined with suitable surfactants that act from both particle stabilization and friction reduction / lubrication improvement perspectives.The use of the medium/high-hardness pad IC-1000 is compared to the use of a soft Politex pad. In the former case, differences in terms of MRR, MRS roughness, and total defects are observed between the composite abrasives A and B; in the latter case, the behaviour of the two composites is similar. In the case of a soft pad in combination with composite abrasives, there is a remarkable improvement in the defectivity without any loss in MRR.As revealed by SEM inspection of the composite particles collected in the slurry drain after CMP, for all the composites, the silica shell coverage is not disrupted by the shear forces and chemistry during the 1 min. polishing. Consequently, the stability and agglomeration properties of the particles in the complex Cu CMP chemistry can be helpful in explaining the experimental results in terms of MRR and surface finishing.

The Sandfish's Skin: Morphology, Chemistry and Reconstruction

The sandfish is a lizard having the remarkable ability to move in desert sand in a swimming-like fashion. The most outstanding adaptations to this mode of life are the low friction behaviour and the extensive abrasion resistance of the sandfish skin against sand, outperforming even steel. We investigated the topography, the composition and the mechanical properties of sandfish scales. These consist of glycosylated keratins with high amount of sulphur but no hard inorganic material, such as silicates or lime. Remarkably, atomic force microscopy shows an almost complete absence of attractive forces between the scale surface and a silicon tip, suggesting that this is responsible for the unusual tribological properties. The unusual glycosylation of the keratins was found to be absolutely necessary for the described phenomenon. The scales were dissolved and reconstituted on a polymer surface resulting in properties similar to the original scale. Thus, we provide a pathway towards exploitation of the reconstituted scale material for future engineering applications.

Polymer-Supported Membranes: Physical Models of Cell Surfaces

The functional modification of solid surfaces with plasma membrane models has been drawing increasing attention as a straightforward strategy to bridge soft biological materials and hard inorganic materials. Planar model membranes can be deposited either directly on solid substrates (solid-supported membranes), or on ultrathin polymer supports (polymer-supported membranes) that mimic the generic role of the extracellular matrix and the cell surface. The first part of this review provides an overview of advances in the fabrication of polymer-supported membranes. The middle section describes how such thin polymer interlayers can physically modulate the membrane–substrate contact. The last section introduces several methods to localize membranes and membrane proteins. Finally, some ideas are presented on combining supported membrane concepts with semiconductor technology toward applications in materials science.

SEM examination of human erythrocytes in uncoated bloodstains on stone: use of conventional as environmental‐like SEM in a soft biological tissue (and hard inorganic material)

Although nowadays the so-called environmental scanning electron microscopes (ESEMs) allow the observation of the samples without metal or carbon coating, many conventional scanning electron microscopes (SEMs) are still in use. On the other hand, the presence of erythrocytes (red blood cells, RBCs) in a smear is considered a blood confirmation. Such a presence has been previously reported even in Lower Stone Age implements. In previous works, I have reported several studies dealing with cytomorphology of RBCs in bloodstains using scanning electron microscopy with standard specimen preparation procedures, i.e. via coating the samples before SEM analysis. In order to explore the potential of conventional SEM as environmental-like SEM in haemotaphonomical studies, two alkaline (limestone) and two acid (flint) rock fragments were smeared with human blood from a male and a female. The bloodstains obtained in this way were then air dried indoors and stored into a non-hermetic plastic box. Afterwards, the smears and their rock substrates were examined directly without coating, via secondary electrons, using a JEOL JSM-6400 scanning electron microscope. Satisfactory results reveal the capability of a conventional SEM to work in secondary-electron mode as an environmental-like SEM on these kinds of biological and inorganic materials, and probably in many other biological and non-biological samples.

褐炭液化反応時に生成するスケールと沈降物 豪州５０ｔ／ｄパイロットプラント運転結果

The wall scales and reactor sediments formed during the liquefaction of Victorian brown coal with a 50 ton (dry coal) / day pilot plant were analyzed to clarify the mechanisms of their formation and the relationship between their amount and the operation time of the pilot plant, because they are very troublesome for long-term operation of a coal liquefaction plant.The scales on the preheater and the connecting pipe between the preheater and the first reactor consisted of NaCl (50-60 wt%) and Fe1-xS (30-40 wt%) originating from the used catalyst (Fe2O3 and S) and coal. The wall scales on the reactors mainly consisted of carbonates of Ca, Mg and Na which originated from ion exchangeable cations in the coal.Their main components were CaCO3, CaMg (CO3) 2 and Na6Mg2 Cl2 (CO3) 4 and changed in order from the first reactor to the fourth reactor. All scales were confirmed to be hard inorganic materials which had a layered structure.The total amount of the scale formed during the operation of the pilot plant was correlated with IEC / Ash (CLB) ×COT ((kg/kg) ·Eh), where ICE and Ash (CLB) were the amount of the ion exchangeable cations (Ca, Mg and Na) in the coal and catalyst, and that of the ash in the heavy liquid product (coal liquid bottom, CLB) used as a part of the solvent, respectively. This result suggested that unreactive solid particles (ash) in the feed slurry suppressed the scale formation during the liquefaction. In addition, an increase in pressure drop observed during the operation was also found to be mainly caused by the preheater scale.The sediments of the particles found in the reactor bottom were spheres of 0.5-1.0 mm and consisted of similar components to those of the wall scales. Their accumulation was prevented by withdrawing a small amount of the slurry from the first reactor bottom.

Tribo-electricity and friction. IV.—Electricity due to air-blown particles

Electric charges due to mutual impact of dust or other particles arise in various ways: ( a ) electric dust- or sand-storms in the Tropics; ( b ) electric snow storms in the Antarctic; ( c ) electric flashes seen in the ejectamenta from volcanoes; and ( d ) electric charges, and possibly sparking, brought about by the raising of organic powders in certain industrial processes. In this group of effects, charges are produced by the impact of a multitude of like particles. Now, frictional- and impact-charges have ever been regarded as resulting from the shock of two unlike substances. Until recently there was no principle by which charges from "like” substances could be interpreted; but experiments made by the writer throw light on the subject by showing that identical solid surfaces can charge one another by friction or impact, and, further, that this property of the surfaces changes as rubbing continues. It was there shown that such organic insulators as ebonite and celluloid yield considerable charges, whereas hard inorganic materials such as quartz, calcite and glass, produce smaller effects. When the “like” solids meet in violent impact, not rubbing, the combined net charge is not nil, as might be expected according to Faraday’s law of equal and opposite frictional charges, but finite, generally negative; so that the air surrounding the surfaces must attain an equal positive charge.