[This corrects the article DOI: 10.1021/acsomega.5c04483.].

Gallium oxynitride thin films were deposited by reactive RF sputtering from a liquid Ga target in a working gas mixture of argon, oxygen and nitrogen, with changing oxygen proportion. A combinatorial deposition method was applied that resulted in Ga-O-N samples of varying composition and enabled the characterization of material properties with high throughput over a wide composition range. The optical properties of the films were determined by spectroscopic ellipsometry, while X-ray diffraction and transmission electron microscopy were applied for structural characterization. The composition (measured by energy dispersive spectroscopy and elastic recoil detection analysis), structure and morphology of the films depended on the deposition conditions, especially the actual oxygen flow rate. The dependence of the refractive index and the optical gap on the elemental composition was determined and their values were plotted in ternary Ga-O-N composition diagrams. The same optical properties can occur for different compositions. It was shown that by varying the composition, the optical properties of gallium oxynitride films can be tuned.

In this study, a thorough mechanical and structural characterization of the entire Al-Cu binary thin film system has been carried out. Our novel combinatorial approach to facilitate complex studies of the entire layer system ensured both an efficient fabrication and characterisation. Using dual DC magnetron sputtering, fifteen Al100-xCux layers of varying compositions (0 <= x <= 100) were deposited in adjacent strips on a single, native oxide covered Si substrate. Microstructure and mechanical properties of the layers were comprehensively investigated by transmission electron microscopy (TEM) and nanoindentation. Experimental results show that at the near equiatomic compositions, the microstructure of the layers is a mixture of different hard, non-equilibrium phase (-Al2Cu, -Al4Cu9) components, resulting in exceptional strength with a maximum hardness up to similar to 16 GPa. Due to the hard matrix, the layers in the range of 40-70 at% Cu can be characterized by brittle deformation, strong indentation size effect (ISE) and plastic instability. In contrast, Al layers with low Cu content or Cu layers with low Al content deform plastically, mainly by grain boundary sliding, and as a result, no ISE occurs in these layers. Based on the revealed mechanical behaviour and microstructural properties, deformation mechanisms operating at different stages of the whole compositional range have been proposed.

During the experimental formation of sol-gel coatings, the colloid dispersions go through a drying process, and the structure of the coatings is formed as a result of complex chemical, colloidal, and capillary interactions. While computer simulations provide guidelines to tune and even design the nanomaterials synthesis, simulations of coating structure formation are hitherto unknown in the literature. Based on real experiments, we establish here a ReaxFF reactive force field-based molecular dynamics simulation protocol in order to investigate and determine the role of the experimental conditions on the pore structure formation in the coatings. Anatase TiO2 sol-gel coatings with a thickness of 50 nm, 7% open porosity, and a 2.4 nm pore radius were prepared on solid substrates using the dip-coating method. In the computational synthesis of porous TiO2 layers, the attractive capillary forces present during the drying step were accounted for by applying an external pressure, and their effect on the coatings' pore structure was investigated. It was found that the TiO2 layer structure corresponding to an external pressure of 10,000 atm in the simulations exhibited a porosity comparable to that determined by experimental methods. This demonstrates the impact of immersion capillary forces on sol-gel layer formation. The created computer model accurately describes the layer structure using real parameters, making it suitable for designing the coating structure through computer simulation.

Graded-thickness gold layers were deposited on fused silica by combinatorial magnetron sputtering and annealing to form nanoparticles with a laterally changing structure. The optical properties and sensing characteristics were determined as a function of the amount of sputtered material by scanning optical spectroscopies. The formation and sensing performance of Au nanoparticles were modeled and interpreted by finite element electromagnetic calculations. The most sensitive regions for the optical detection of ethanol, water, and Raman reporter molecules on the heat-treated surfaces were determined as a function of the deposited amount of Au. For all three analytes applied, we observed the best sensing performance for an effective deposited gold thickness of 2-3 nm. These results can be interpreted by considering the graded gold film's actual geometry and near-field optical properties.

After being an indispensable intermediate in the oxidative exfoliation route towards graphene, graphene oxide has gained its deserved value in materials science for numerous applications, from catalysis, through energy storage and conversion, to sensor use. In this work, three graphene oxides of tuned morphology and chemistry are used as a simplified model for porous carbon materials in hydrogen storage and as a Li-ion battery anode. The BET surface areas were, respectively, 9, 13, and 535 m2/g, while the corresponding O/C values from the X-ray photoelectron spectroscopy were 0.51, 0.17, and 0.12. Additionally, the samples were thoroughly characterized using scanning and transmission electron imaging, powder X-ray diffraction, thermal stability, and Raman and Fourier transform infrared spectroscopic methods. Hydrogen adsorption isotherms (−196 °C) and their comparison with nitrogen uptake revealed that pore accessibility, porous confinement, and surface chemistry, i.e., both morphology and surface chemistry, contribute to efficient adsorption. In the anode application, by contrast, surface chemistry was the single most defining factor for performance.

Studying the Ni-Si system, we confirmed the only known Ni31Si12 (S12) structure and in addition several new gamma modifications were also observed. Our TEM/STEM studies of gamma Ni-silicides revealed crystal structures with different atomic arrangements and even varying c cell parameters (similar to 6 & Aring;, similar to 12 & Aring;, similar to 18 & Aring;, similar to 36 & Aring;). Three of them were determined and named S6a, S6b and S18. The nomenclature of S6, S12 and S18 refers to their c cell parameters which are multiples of similar to 6 & Aring;. Nanoscale variability was also observed in the gamma Ni-silicides, where nanoscale variability was the outcome of stacking, inversion, twinning and intimate (001) intergrowths of the different modifications.

In this study, SiO2 thin films were sputtered from a Si target using reactive HiPIMS (high-power impulse magnetron sputtering) in an argon–oxygen process gas. In order to understand the behavior of HiPIMS, the deposition process was studied by systematically varying the sputtering parameters and monitoring the current waveforms. A decaying transient was observed at the leading edge of the pulse, caused by the L-C term of the HiPIMS generator, the cable, and the target. To investigate the periodic transient, we used, to the best of our knowledge, for the first time, a standing wave ratio meter (SWR). In order to be able to deposit films with the desired properties, the target voltage and its associated current characteristics were also investigated. The formation of a distinct step-like shape in the current–voltage characteristics is observed during reactive sputtering. A simple physical model was used to determine the position and length of the plateau. The appearance of hysteresis, which is typical of reactive sputtering, was also observed. These findings may help us to better understand the mechanism of reactive HiPIMS deposition of SiO2.

Sn-doped TiO2-carbon composites were identified as promising multifunctional supports for Pt electrocatalysts, in which the oxide component enhances resistance against corrosion and strong metal-support interactions at the Pt-oxide boundary ensure high stability for the Pt nanoparticles. This work is devoted to the study of the influence of preliminary functionalization of the carbon on the properties of Pt/Ti0.9Sn0.1O2-C catalysts. The structural, compositional and morphological differences between the samples prepared using functionalized or unmodified carbon, as well as the effect of carbon pre-modification on the electrocatalytic behavior of the synthesized Pt catalysts, were investigated using TEM, XRD, XPS, nitrogen adsorption and electrochemical measurements. The presence of oxygen-containing functional groups on carbon treated with HNO3 and glucose leads to the formation of a homogeneous coating of the carbon with dispersed crystallites of mixed oxide. Elemental mapping revealed the proximity of Sn species with highly dispersed (2-3 nm) Pt particles. Notably, the electrochemical results indicated enhanced activity in CO electrooxidation for both functionalized and unmodified carbon-containing catalysts. An improvement in the 10,000-cycle long-term stability of the catalyst prepared using functionalized carbon was evident compared to the catalyst with untreated carbon or reference Pt/C.

The decomposition of methane in an inert atmosphere, in other words, methane pyrolysis results in CO2-free "turquoise" hydrogen and solid carbon. MgO-supported bimetallic molybdenum-nickel (MoNi) catalyst shows a promising synergistic effect in the reaction. Our objective was to efficiently investigate how changes in the Mo/ Ni ratio influence the catalytic performance, with a particular focus on carbon deposition. A novel micro-combinatorial TEM technique has been successfully applied to generate, by magnetron sputtering, a continuous composition gradient of Mo-Ni nanoparticles on a SiOx-coated Au TEM grid, which is believed to be stable at high temperatures. The post-treatment of this model catalyst sample at 800 degrees C in diluted hydrogen yielded particles of uniform but variable composition. Attempts to induce carbon growth through methane exposure revealed a significant limitation: the Au and SiOx components of the grid interfered at high temperatures, causing Mo and Ni partial segregation and oxidation, which inhibited carbon formation. The model MoNi sample sputtered on an Au grid with a MgO-coated C membrane showed similar gold-induced effects, forming mixed metal oxides and no carbon after methane feed exposure. Interestingly, when a MoNi/MgO powder catalyst was deposited onto the Au grid, no carbon was formed either, while in the absence of the Au grid, carbon nanotubes were obtained, as expected. These results highlight the critical influence of the grid material on catalytic behavior and suggest that gold can actively inhibit coking, which may prove valuable in reactions where suppression of coking is desirable.

The well-known indentation size effect (ISE) is reviewed with special emphasis on the effect of grain size in the polycrystalline matrix. It is demonstrated that there is a close connection between the Hall-Petch relationship and the characteristics of the ISE phenomenon such that the ISE phenomenon may disappear in an ultrafine-grained (UFG) matrix. This finding is significant in any attempts to interpret nanoindentation measurements performed on UFG materials.

This study reports the structural rearrangement of TiO2 sol-gel coatings via aqueous ammonia vapor-induced pseudomorphic transformation. The coatings were applied to glass, silica-coated glass, and silica-coated silicon substrates. The transformation was initiated by aging the freshly deposited coatingsstill containing the molecular template Pluronic P123in an aqueous ammonia vapor atmosphere, resulting in significant reorganization of the primarily formed structure. Compared to aqueous vapor treatment for 4 days, the ammonia-based approach was more effective in enhancing optical transmittance, yielding a 1.25% higher average increase after just 4 h. The transformation led to notable changes in material properties: the monolayer coatings exhibited increased open porosity (from 38% to 55%), higher thickness (from 130 to 205 nm), and a reduced specific surface area (from 713 m2/cm3 to 392 m2/cm3). Additionally, a slight increase in pore radius (from 5.6 to 6.6 nm) was observed. While the photocatalytic activity decreased under both UV and visible light due to reduced surface area, the improved optical performance highlights the potential of aqueous ammonia vapor treatment as a powerful tool for tailoring the structure and functionality of mesoporous TiO2 coatings.

Development of strong metal-support interaction (SMSI) and its influence on the catalytic performance of the Pt/Ti0.8Mo0.2O2-C system, a representative of the mixed oxide-carbon composite supported Pt electrocatalyst family, were investigated. Structural, surface chemical and electrochemical properties of the as-prepared Pt/Ti0.8Mo0.2O2-C catalyst and its counterparts reduced in the 150-450 degrees C temperature range were compared. TEM elemental mapping confirmed the widespread formation of Pt-oxide-C triple junctions in all catalysts. XPS revealed electronic interaction between the Pt particles and the oxide both in the as-prepared and the reduced catalysts, moreover, demonstrated that transport of Mo to the surface of Pt is initiated by reduction in the 150-250 degrees C range. Electrochemical measurements pointed out the durability of these Pt-bound Mo species, which also enhance the oxygen reduction activity of the catalyst. Based on the results of 10,000-cycle stability tests, reductive pretreatment between 250-350 degrees C is recommended for enhancing the properties of Pt/Ti0.8Mo0.2O2-C catalysts by SMSI.

LaF3:1-6 mol%Yb3+,0.1 mol%Tm3+ nanoparticles with upconversion properties were synthesised by the co-precipitation method. Particles were characterized by transmission electron microscopy coupled with energy-dispersive spectrometry, inductively coupled plasma optical emission spectrometry, X-ray diffraction, and simultaneous thermogravimetry and differential thermal analysis. Upconversion properties were investigated by fluorescence spectroscopy, using 980 nm laser light excitation. The results show that the particles had a hexagonal LaF3 crystal structure. Crystallite and particle sizes decreased with increasing Yb3+ content and the average crystallite size changed between 18 and 36 nm, while the average particle diameter was 25-52 nm. The highest upconversion emission intensity at the 480 nm emission peak could be reached with an optimal Yb3+ content of 3 mol% and an Yb/Tm ratio of similar to 75. These upconverting nanoparticles, prepared using a cheap and environmentally friendly co-precipitation method and containing relatively low dopant ion concentrations, will be helpful in a variety of promising fields, such as sensing, solar cells and security applications.

As a perspective catalyst composition for methane non-oxidative decomposition/methane pyrolysis (CH4⇌C+2H2) yielding clean hydrogen and only solid carbon, the combination of nickel and molybdenum on MgO support was investigated. With deliberately low Ni content and strong metal-support interaction, 7%Ni4%Mo/MgO and 7%Ni12%Mo/MgO catalysts and the monometallic references were prepared. Structural analysis was performed using TPR, XRD, TEM, XPS and Raman spectroscopy in reduced state and after methane decomposition test. Catalytic performance was investigated i) in a highly diluted CH4 flow in a fixed bed reactor under temperature ramp and ii) in 50% CH4/Ar using a horizontal reactor at 800 °C. Synergetic interaction of Mo and Ni was observed under both conditions. The results revealed that the deactivation was coupled with alloy segregation for the low Mo loading, while the more stable, non-segregating Mo/Ni~1 composition of the individual metal particles in 7%Ni12%Mo/MgO sample resulted in good activity and high carbon nanotube yield.

This article investigates the spatial disposition and mobility of water molecules adsorbed at room temperature in a commercial activated amorphous carbon. Previous wide-angle X-ray scattering measurements are re-examined, together with new observations, in particular by high-resolution transmission electron microscopy, high field solid-state nuclear magnetic resonance, and pulsed field gradient nuclear magnetic resonance. The dry samples are composed largely of deformed turbostratic oxidized graphitic sheets, yielding an array of slit-pores with an average spacing of more than 0.4 nm. All the adsorbed water remains close to the aromatic substrate, and the landscape of adsorption sites is extremely heterogeneous. The water molecules are mobile. Water is initially adsorbed in small confined sites. With increasing relative humidity these develop into clusters that are spatially correlated, which spread and merge, on both sides of the graphitic sheets.

Design of composite support materials based on Sn-doped TiO2 and carbon is one of the strategies to develop corrosion-resistant and CO-tolerant Pt electrocatalysts for polymer electrolyte membrane (PEM) fuel cells. As the synthesis methodology may have crucial influence on the structural and functional properties of the composites, different preparation routes for the novel support materials are explored and compared. Ti(1-x)SnxO2–C (x: 0.1-0.3) composites with different mixed oxide/carbon ratios were prepared by two sol-gel-based synthesis routes, namely (i) the introduction of a Sn precursor after the formation of the TiO2-rutile nuclei on the carbon backbone (route A), and (ii) simultaneous introduction of Ti and Sn precursors, resulting in good mixing of the Sn- and Ti-sol before the addition of the carbon (route B). The bulk and surface microstructure of the composites and the electrocatalysts obtained by their Pt-loading were investigated in detail. The incorporation of tin into the TiO2-rutile unit cell was confirmed by X-ray powder diffraction and Raman spectroscopy; the results indicated doping levels in good accordance with the amount of tin precursor. The advantages of composites and Pt electrocatalysts obtained via synthesis route B were that they do not contain segregated Sn0 or SnO2 phases, have a more homogeneous/uniform mixed oxide distribution over the carbon backbone, and the electrochemically active surface area values (~60-80 m2/gPt) are twice as high as those of catalysts with similar compositions synthesized by method A. A common feature of the composites prepared by routes A and B was the presence of a tin oxide-rich overlayer identified by X-ray photoelectron spectroscopy. As a consequence, the electrocatalytic behavior of the catalysts was not influenced by the Ti/Sn ratio and was mainly dependent on the synthesis method used in the preparation of composite support materials. Elemental maps confirmed the formation of areas where Pt and the Sn doping element were in atomic proximity to each other, which means a favorable interaction either for the bifunctional mechanism or the electronic ligand effect. An increase in carbon content in composite materials led to an increase in both catalytic activity and long-term stability. The results of electrochemical studies showed that Sn-containing Pt catalysts with a high carbon content (75wt.%) are the most promising for potential use both as an anode and a cathode for PEM fuel cells.

High-throughput methods are extremely important in today’s materials science, especially in the case of thin film characterization. The micro-combinatorial method enables the deposition and characterization of entire multicomponent thin film systems within a single sample. In this paper, we report the application of this method for the comprehensive TEM characterization of the Y-Ti-O layer system. Variable composition samples (YxTi1−xOy) were prepared by dual DC magnetron sputtering, covering the entire (0 ≤ x ≤ 1) concentration range. The structure and morphology of phases formed in both as-deposited and annealed samples at 600, 700, and 800 °C were revealed as a function of Y-Ti composition (x). A comprehensive map showing the appropriate amorphous and crystalline phases, and their occurrence regions of the whole Y-Ti-O layer system, was revealed. Thanks to the applied method, it was shown with ease that at the given experimental conditions, the Y2Ti2O7 phase with a pyrochlore structure forms already at 700 °C without the TiO2 and Y2O3 by-phases, which is remarkably lower than the required temperature for most physical preparation methods, demonstrating the importance and benefits of creating phase maps in materials science and technology.