Understanding crystallization is crucial to enable improved design approaches for inorganic materials. Despite this importance, a deepened understanding of the mechanisms controlling this phase transition is still lacking. Herein, we employ in situ heating in a transmission electron microscope (TEM) to unravel crystallization phenomena in an Al-Ti-O system. Specifically, annealing of amorphous chemical vapor deposited (CVD) Al2TiO5-based coatings has been carried out in the temperature interval 700-900 degrees C. Crystallization typically occurs through a two-step process, where numerous smaller (<10 nm) crystals are initially formed, followed by rapid crystal growth. Examinations of the initial crystallization stages indicate that the amorphous-to-crystalline transformation is polymorphic and that several phases may nucleate simultaneously, including Al6Ti2O13 and Al16Ti5O34. A transient (time-dependent) nucleation rate is discovered based on the displayed nucleation behavior. Subsequent evaluations of the growth stages also reveal a preferential growth into larger crystals, and the coherent findings of this study indicate that crystallization occurs through a diffusionless (displacive) mechanism.

Oxygen is a commonly overlooked element influencing the properties of many metal oxides. By combining several analytical in situ techniques and theoretical calculations, we demonstrate that oxygen plays a vital part in the phase formation and crystallization of Al2TiO5-based chemical vapor-deposited coatings. Rutherford backscattering spectrometry (RBS) corroborates a polymorphic transformation during crystallization. Subsequent hard X-ray photoelectron spectroscopy (HAXPES) shows that crystallization occurs through a displacive (diffusionless) mechanism. Coupled with theoretical calculations, the crystallization and co-formation of Al2TiO5, Al6Ti2O13, and Al16Ti5O34 are suggested to be driven by the migration of oxygen ions and their corresponding vacancies.

In this work chemical vapour deposited (CVD) coatings of (Tix,W1-x)Ny from TiCl4, WF6, NH3 and Ar were investigated. This coating material has previously been deposited using other vacuum techniques but no publication has so far demonstrated CVD of (Tix,W1-x)Ny. The studied (Tix,W1-x)Ny coatings had a metallic molar ratio (Ti:W) close to 2:1 and 1:1, and were slightly over-stoichiometric with regard to N. The coatings appeared homogeneous and crystallised in a rock salt structure on an alpha-Al2O3 substrate. The cell parameter varied between 4.16 and 4.23 angstrom as a function of the deposition conditions, ranging from a pure TiNx to a pure WNx coating. The texture in the normal direction was (100) for the TiNx and (Tix,W1-x)Ny coatings and (111) for WNx. Electron backscattered diffraction (EBSD) results showed that a strong correlation to the substrate existed but random inplane orientation was also present. The microstructure showed columnar grains with well defined facets growing. Adding a mixture of TiCl4 and WF6 to produce (Tix,W1-x)Ny did increase the grain size significantly when compared to the case when only one metal precursor was present. The down-stream thickness profile, using only WF6 and NH3, displayed mass transport control behaviour, with the coating thickness converging to zero within the deposition zone. Using only TiCl4 on the other hand showed a uniform deposition profile, the signs of a surface kinetics controlled process.

Nucleation is a fundamental part in most syntheses of ceramic materials. Yet, few techniques enable control of this step, which would offer possibilities to attain full-scale kinetic selectivity of the syntheses to reach novel compounds with unique properties. Herein, we present a nucleationcontrolled crystallization pathway to synthesize coatings of aluminum titanate (Al2TiO5)-renowned for its low-to-negative thermal expansion-at significantly reduced temperatures than conventional solid-state techniques. Based on a kinetic study using in situ X-ray diffraction, detailed mechanistic insights into the crystallization process and phase evolutions within the Al- Ti-O system are obtained. The lowest activation energies for crystallization are given when the Al-Ti ratio is close-to-stoichiometric or Ti-enriched. Along with these compositions' similar kinetics at the earliest stages of the transformation, a joint nucleation behavior is discovered, revealing the elemental role of titanium in nucleating the main Al2TiO5 phase. Based on classical nucleation theory, we deduce the significant influence of the configurational entropy (Sconfig) when crystallization occurs in the nucleation-controlled domain. Finally, peculiar transition features are observed in the Al-enriched regime during annealing at intermediate temperatures, whose causes are ascribed to the presence of secondary nucleation events and possibilities of structural relaxations in the amorphous matrixes when crystallizing.

Tungsten carbonitride [W(C,N)] was deposited on cemented carbide substrates by chemical vapor deposition (CVD) in a hot-wall reactor using tungsten hexafluoride (WF6), acetonitrile (CH3CN), and hydrogen (H2) as precursors. Tungsten carbides and nitrides with a hexagonal δ-WC type structure are generally difficult to obtain by CVD. Here, it was found that the combination of WF6 and CH3CN precursors enabled the deposition of W(C,N) coatings with a δ-WC type structure and columnar grains. A process window as a function of the deposition temperature and precursor partial pressures was determined to establish the conditions for the deposition of such coatings. Scanning electron microscopy, x-ray diffraction, electron backscatter diffraction, and elastic recoil detection analysis were used for the investigation of the coating thickness, microstructure, texture, and composition. From the investigation of the kinetics, it was concluded that the growth was mainly controlled by surface kinetics with an apparent activation energy of 77 kJ/mol, yielding an excellent step coverage. The partial reaction orders of the reactants together with their influence on the microstructure and coating composition was further used to gain a deeper understanding of the growth mechanism. Within the process window, the microstructure and the texture of the W(C,N) coatings could be tailored by the process parameters, enabling microstructural engineering with tuning of the mechanical properties of the W(C,N) coatings. The nanoindentation hardness (36.6–45.7 GPa) and elastic modulus (564–761 GPa) were found to be closely related to the microstructure.

In this work, the hardness (H), the Young’s modulus (E) and the fracture toughness (KC) as well as the tribological behaviour during scratch testing of cubic CVD-TiWN films were determined and compared to a cubic CVD-WNx coating. Using nano-indentation it was shown that the hardness of the films were statistically similar (17.5 to 20.0 GPa), but the TiWN films had a slightly higher Young’s modulus (300 GPa) compared to the WNx reference (270 GPa). The fracture toughness was measured by cube corner indentation and showed that the WNx film possessed the highest fracture toughness (KC = 0.8 to 1.0 MPa×m½), while much lower values were obtained for the TiWN films due to long intergranular cracking. Through scratch testing, using three different tip radii, it was determined that the adhesion for the WNx film was the poorest. The TiWN coatings showed better over-all adhesion but spalling was observed when using the smallest stylus size. Instead, the major contributions to wear was attributed to plastic deformation of the asperities, forming debris on the stylus which eventually loosened and agglomerated to the surface. Using a 50 μm stylus, the critical load of fracture determined by acoustic emission (FC,AE) was recorded. Fc,AE of WNx was significantly lower (3.1(±0.4) N) than that of the lowest critical load for the TiWN films (4.6 (±1.8) N). Using a stylus radius of 500 μm, the Ti-rich sample, (Ti0.29,W0.14)N0.47, showed no visual cracking during the first two repeated passes. WNx showed short cracks in conjunction with surface defects. The (Ti0.20,W0.19)N0.49 sample showed longer cracks were longer but much less wide. Over-all, the main types of failure were determined to be interfacial fracture as well as crack formation linked to surface defects.

Al2TiO5-based coatings made from aluminium- and titanium-isopropoxide co-deposition using MOCVD, offering reduced temperatures and timescales for its synthesis without binary phase formation.

Tungsten nitride (WNx) is a hard refractory material with low electrical resistance that can be deposited using multiple methods. This study focuses on the microstructrual development of low pressure chemical vapor deposition grown WNx coatings. Also, the growth kinetics is studied and discussed in terms of the resulting microstructures. Samples of WNx were deposited using WF6, NH3, and Ar at 592–887 K in a hot-wall reactor with variable gas mixture compositions (NH3:WF6 = 0.5–25). The coatings were nitrogen-rich (x ∼ 1.65) and oxygen-free as determined by time-of-flight-elastic recoil detection analysis. X-ray diffraction showed that the coatings transformed from being amorphous to crystallizing as β-W2N at 641–690 K. The morphologies changed with deposition temperature. Being very fine grained and nodular at deposition temperatures 740 K and below, increasing the deposition temperature to 789 K while employing a NH3:WF6 molar ratio of 1, large disc-shaped protrusions were formed. When increasing the NH3:WF6 molar ratio to 25, striped facets became increasingly dominant. Investigating the latter by transmission electron microscopy, a microstructure of smaller ridges formed by twinning, oriented as <211> in the out-of-plane direction, was revealed across the facet surfaces. Transmission Kikuchi diffraction confirmed that <211> was the texture of these coatings. The partial reaction order of WF6 and NH3 at 740 K was determined to be close to 1/6 and 1/2, respectively. The apparent activation energy ranged from 82 to 12 kJ/mol corresponding to deposition temperatures from 592 to 887 K.

The reactivity of a quaternary multi-principal element alloy (MPEA), CoCrFeNi, as a substrate in thermal halide chemical vapor deposition (CVD) processes for titanium nitride (TiN) coatings was studied. The coatings were deposited at 850 degrees C-950 degrees C using TiCl4, H-2 and N-2 precursors. The coating microstructures were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM) with energy dispersive X-ray spectroscopy (EDS). Thermodynamic calculations of substrate and coating stability for a gas phase environment of N-2 and H-2 within a temperature range relevant for the experiments showed that Cr is expected to form hexagonal Cr2N and cubic (Ti1-epsilon 1 Cr epsilon 1)N or (Cr1-epsilon 2 Ti epsilon 2)N phases. These phases could however not be discerned in the samples by XRD after the depositions. Cr was detected at the grain boundaries and the top surface by EDS for a sample synthesized at 950 degrees C. Grain boundary and surface diffusion, respectively, were the suggested mechanisms for Cr transport into the coating and onto the top surface. Although thermodynamic calculations indicated that Cr is the most easily etched component of the CoCrFeNi alloy to form gaseous chlorides in similar concentrations to that of the residual Ti-chlorides, no sign of etching were found according to the imaging of the sample cross-sections using SEM and TEM. Cross-section and top surface images further confirmed that the choice of substrate had no significant detrimental influence on the film growth or microstructure.

The corrosion behaviour of Titanium carbonitride (Ti(C,N)) films grown by chemical vapour deposition was analysed in artificial sea water environment. From potentiodynamic polarisation curves, two passivation zones were detected, which originated from an initial oxidation of TiC and TiN to TiO2 followed by growth of the TiO2 layer upon increased polarisation. X-ray photoelectron spectroscopy analyses verified the mechanism by detecting a gradual decrease in Ti(C,N) peaks accompanied by a gradual increase of oxidised Ti (e.g. TiO2). It was likewise found that carbon in TiC mainly decomposes into carbonate species while the nitrogen in TiN remains elemental and likely escapes as nitrogen gas. Accordingly, Ti(C,N) behaves like a superposition of TiC and TiN with their individual oxidation behaviour, resulting in a highly corrosion resistant material.

Mass spectrometry-based proteomics benefits from efficient digestion of protein samples. In this study, trypsin was immobilized on nanoporous anodized alumina membranes to create an enzyme reactor suitable for peptide mass fingerprinting. The membranes were derivatized with 3-aminopropyltriethoxysilane and the amino groups were activated with carbonyldiimidazole to allow coupling of porcine trypsin via c-amino groups. The function was assessed using the artificial substrate Na-Benzoyl-L-arginine 4-nitroanilide hydrochloride, bovine ribonuclease A and a human plasma sample. A 10-membrane flow-through reactor was used for fragmentation and MS analysis after a single pass of substrate both by collection of product and subsequent off-line analysis, and by coupling on-line to the instrument. The peptide pattem allowed correct identification of the single target protein in both cases, and of > 70 plasma proteins in single pass mode followed by LC-MS analysis. The reactor retained 76% of the initial activity after 14 days of storage and repeated use at room temperature. Significance: This manuscript describes the design of a stable enzyme reactor that allows efficient and fast digestion with negligible leakage of enzyme and enzyme fragments. The high stability facilitates the use in an online-setup with MS detection since it allows the processing of multiple samples within an extended period of time without replacement.

Copper exposed to pure, O-2-free water for several months in glass- and metal-contained, well-controlled systems shows no evidence of corrosion, either through hydrogen evolution or through the occurrence of oxidized copper. The results contradict the interpretation of recent experiments where it has been claimed that copper corrodes in pure, O-2-free water far above the very limited extent predicted by established thermodynamic data. Reasons for the different experimental outcomes are discussed. Experimental and theoretical efforts to identify hitherto unknown, potentially corrosion driving species of the Cu-O-H system and studies of copper/water surface reactions are reviewed as background for the present study.

Significant capacity losses are generally seen for batteries containing high-capacity lithium alloy forming anode materials such as silicon, tin and aluminium. These losses are generally ascribed to a combination of volume expansion effects and irreversible electrolyte reduction reactions. Here, it is shown, based on e.g. elemental analyses of cycled electrodes, that the capacity losses for tin nanorod and silicon composite electrodes in fact involve diffusion controlled trapping of lithium in the electrodes. While an analogous effect is also demonstrated for copper, nickel and titanium current collectors, boron-doped diamond is shown to function as an effective lithium diffusion barrier. The present findings indicate that the durability of lithium based batteries can be improved significantly via proper electrode design or regeneration of the used electrodes.

Thermochromic films of VO2 were prepared by a two-step procedure: Sputtering was first used to deposit metallic vanadium, and such layers were subsequently oxidized in SO2 at a temperature in the 600–650 °C range. X-ray diffraction, Raman spectroscopy, measurements of temperature-dependent electrical resistance, and spectrophotometric transmittance data at different temperatures were employed to demonstrate that the films consisted of polycrystalline VO2 with good thermochromism, especially when oxidized at the highest temperature. Oxidation in SO2 is able to produce VO2 without the stringent process control that can be an obstacle for making VO2 by oxidation in O2.

Nanostructured iron oxides, and especially hematite, are interesting for a wide range of applications ranging from gas sensors to renewable solar hydrogen production. A promising method for deposition of low-dimensional films is atomic layer deposition (ALD). Although a potent technique, ALD of ultrathin films is critically sensitive to the substrate and temperature conditions where initial formation of islands and crystallites influences the properties of the films. In this work, deposition at the border of the ALD window forming a hybrid ALD/pulsed CVD (pCVD) deposition is utilized to obtain a deposition less sensitive to the substrate. A thorough analysis of iron oxide phases formation on two different substrates, Si(100) and SiO2, was performed. Films between 3 and 50 nm were deposited and analyzed with diffraction techniques, high-resolution Raman spectroscopy, and optical spectroscopy. Below 10 nm nominal film thickness, island formation and phase dependent particle crystallization impose constraints for deposition of phase pure iron oxides on non-lattice-matching substrates. Films between 10 and 20 nm thickness on SiO2 could effectively be recrystallized into hematite whereas for the corresponding films on Si(100), no recrystallization occurred. For films thicker than 20 nm, phase pure hematite can be formed directly with ALD/pCVD with very low influence of the substrate on either Si or SiO2. For more lattice matched substrates such as SnO2:F, Raman spectroscopy indicated formation of the hematite phase already for films with 3 nm nominal thickness and clearly for 6 nm films. Analysis of the optical properties corroborated the analysis and showed a quantum confined blue-shift of the absorption edge for the thinnest films.

The presence of O during the chemical vapour deposition (CVD) of B‐doped diamond results in the suppression of B incorporation into the diamond film. In this study, we demonstrate that the amount of residual O within the chamber is higher at the beginning of the diamond growth due to the O‐contaminated chamber walls, and is decreased after a certain time period. This leads to a gradual increase of the B incorporation by more than one order of magnitude during the early growth phases of nanocrystalline diamond (NCD). We further show that this suppression of B incorporation at the early growth phases of B‐doped diamond is influenced by the growth rate of the film. This is attributed to the constant time period whereby most of the residual O interacts with the B‐precursors in the gas phase by forming stable B–O species, which are flushed out from the chamber exhaust. Furthermore, the constant B profile of an NCD film grown in a loadlock hot‐filament CVD (HFCVD) system reveals that the amount of residual O is constant and minimal during the growth process. Therefore, our work proves that the use of a loadlock overcomes the B‐suppression problem at the early growth phases of diamond, making it the optimal solution for the growth of highly conductive thin diamond films.