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.

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 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.

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.

A homogenized, supersaturated AlZnMgZr alloy was processed via severe plastic deformation (SPD) using a high-pressure torsion (HPT) technique for different revolutions at room temperature to obtain an ultrafine-grained (UFG) microstructure. The microstructure and mechanical properties of the UFG samples were then studied using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and tensile and hardness measurements. The main purpose was to study the effect of shear strain on the evolution of the microstructure of the investigated alloy. We found a very interesting evolution of the decomposed microstructure in a wide range of shear strains imposed by HPT. While the global properties, such as the average grain size (~200 nm) and hardness (~2200 MPa) appeared unchanged, the local microstructure was continuously transformed. After 1 turn of HPT, the decomposed UFG structure contained relatively large precipitates inside grains. In the sample processed by five turns in HPT, the segregation of Zn atoms into grain boundaries (GBs) was also observed. After 10 turns, more Zn atoms were segregated into GBs and only smaller-sized precipitates were observed inside grains. The intensive solute segregations into GBs may significantly affect the ductility of the material, leading to its ultralow-temperature superplasticity. Our findings pave the way for achieving advanced microstructural and mechanical properties in nanostructured metals and alloys by engineering their precipitation and segregation by means of applying different HPT regimes.

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.

In the last three decades, several severe plastic deformation (SPD) procedures have been developed and applied in materials science to create bulk, ultrafine-grained (UFG) structures. As a consequence of the SPD, not only submicron and even nanometer grain sizes can be obtained, but also new grain boundaries with non-equilibrium structures in a material may be formed. Therefore, both the strength and ductility of the UFG materials can change significantly compared to the coarse-grained counterparts. This review is focused on unusual mechanical behaviors of UFG Al and Al alloys, associated with grain boundary structure and segregations which are responsible for the modification of the Hall-Petch relationship and the so-called size-effect for UFG structure. Unusually high strain rate sensitivity, intensive grain boundary sliding and superplasticity at low temperature are described and surveyed. In addition, innovation potential of these phenomena is also briefly considered.

The composites of transition metal-doped titania and carbon have emerged as promising supports for Pt electrocatalysts in PEM fuel cells. In these multifunctional supports, the oxide component stabilizes the Pt particles, while the dopant provides a co-catalytic function. Among other elements, Sn is a valuable additive. Stong metal-support interaction (SMSI), i.e., the migration of a partially reduced oxide species from the support to the surface of Pt during reductive treatment is a general feature of TiO2-supported Pt catalysts. In order to explore the influence of SMSI on the stability and performance of Pt/Ti0.8Sn0.2O2-C catalysts, the structural and catalytic properties of the as prepared samples measured using XRD, TEM, XPS and electrochemical investigations were compared to those obtained from catalysts reduced in hydrogen at elevated temperatures. According to the observations, the uniform oxide coverage of the carbon backbone facilitated the formation of Pt-oxide-C triple junctions at a high density. The electrocatalytic behavior of the as prepared catalysts was determined by the atomic closeness of Sn to Pt, while even a low temperature reductive treatment resulted in Sn-Pt alloying. The segregation of tin oxide on the surface of the alloy particles, a characteristic material transport process in Sn-Pt alloys after oxygen exposure, contributed to a better stability of the reduced catalysts.

The novel, single-sample concept combinatorial method, the so-called micro-combinatory technique, has been shown to be suitable for the high-throughput and complex characterization of multicomponent thin films over an entire composition range. This review focuses on recent results regarding the characteristics of different binary and ternary films prepared by direct current (DC) and radiofrequency (RF) sputtering using the micro-combinatorial technique. In addition to the 3 mm diameter TEM grid used for microstructural analysis, by scaling up the substrate size to 10 × 25 mm, this novel approach has allowed for a comprehensive study of the properties of the materials as a function of their composition, which has been determined via transmission electron microscopy (TEM), scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), X-ray diffraction analysis (XRD), atomic force microscopy (AFM), spectroscopic ellipsometry, and nanoindentation studies. Thanks to the micro-combinatory technique, the characterization of multicomponent layers can be studied in greater detail and efficiency than before, which is beneficial for both research and practical applications. In addition to new scientific advances, we will briefly explore the potential for innovation with respect to this new high-throughput concept, including the creation of two- and three-component thin film databases.

A supersaturated Al-4.8%Zn-1.2%Mg-0.14%Zr (wt%) alloy was processed by the equal-channel angular pressing (ECAP) technique at room temperature in order to obtain an ultrafine-grained (UFG) microstructure having an average grain size of about 260 nm. The hardness and microstructural characteristics, such as the phase composition and precipitations of this UFG microstructure were studied using depth-sensing indentation (DSI), transmission electron microscopy (TEM), as well as non-isothermal scanning of differential scanning calorimetry (DSC), and compared to the properties of the un-deformed sample. Emphasis was placed on the effect of the UFG microstructure on the subsequent thermal processes in DSC measurements. It has been shown that the ECAP process resulted in not only an ultrafine-grained but also a strongly precipitated microstructure, leading to a hardness (2115 MPa) two and a half times higher than the initial hardness of the freshly quenched sample. Because of the significant changes in microstructure, ECAP has also a strong effect on the dissolution (endothermic) and precipitation (exothermic) processes during DSC measurements, where the dissolution and precipitation processes were quantitatively characterized by using experimentally determined specific enthalpies, ΔH and activation energies, Q.

Experimental data show that the conventional Hall-Petch relationship cannot be maintained in its original form for metals having submicrometer structures. We now propose a dislocation model which modifies the Hall-Patch relationship to provide a uniform description of the grain size strengthening of submicron-structured face -centered cubic (f.c.c.) metals and solid solution alloys.

Dual DC magnetron sputtered AlCu thin films representing the whole composition range were investigated by depth-sensing indentation (DSI), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Experimental results show exceptionally high hardness of -16 GPa in the middle concentration range of -40-70 at% Cu. Indentation tests also revealed phenomena related to indentation size-effect. At Al or Cu contents below 20 at%, the well-known size effect was not observed, which can be interpreted by the grain boundary sliding deformation mechanism of fine-grained films. In the middle range of the composition, the size effect can be clearly observed even against the fine grain structure. This is a consequence of the highly precipitated microstructure of these films, which leads to the indentation processes taking place in a manner more characteristic of amorphous materials.

In a single process run, an amorphous silicon oxynitride layer was grown, which includes the entire transition from oxide to nitride. The variation of the optical properties and the thickness of the layer was characterized by Spectroscopic Ellipsometry (SE) measurements, while the elemental composition was investigated by Energy Dispersive Spectroscopy (EDS). It was revealed that the refractive index of the layer at 632.8 nm is tunable in the 1.48–1.89 range by varying the oxygen partial pressure in the chamber. From the data of the composition of the layer, the typical physical parameters of the process were determined by applying the Berg model valid for reactive sputtering. In our modelling, a new approach was introduced, where the metallic Si target sputtered with a uniform nitrogen and variable oxygen gas flow was considered as an oxygen gas-sputtered SiN target. The layer growth method used in the present work and the revealed correlations between sputtering parameters, layer composition and refractive index, enable both the achievement of the desired optical properties of silicon oxynitride layers and the production of thin films with gradient refractive index for technology applications.

The depth-sensing indentation method has been applied for almost 30 years. In this review, a survey of several extended applications developed during the last three decades is provided. In depth-sensing indentation measurements, the load and penetration depth data are detected as a function of time, in most cases at controlled loading rates. Therefore, beside the determination of hardness and Young's modulus, different deformation mechanisms and many other dynamic characteristics and phenomena, such as the dynamic elastic modulus, load-induced phase transition, strain rate sensitivity, etc. can be studied. These extended applications of depth-sensing indentation measurements are briefly described and reviewed.