Phase transition issues in the field of foods and drugs have significantly influenced these industries and consequently attracted the attention of scientists and engineers. The study of thermodynamic parameters such as the glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), enthalpy (H), and heat capacity (Cp) may provide important information that can be used in the development of new products and improvement of those already in the market. The techniques most commonly employed for characterizing phase transitions are thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), and differential scanning calorimetry (DSC). Among these techniques, DSC is preferred because it allows the detection of transitions in a wide range of temperatures (−90 to 550 °C) and ease in the quantitative and qualitative analysis of the transitions. However, the standard DSC still presents some limitations that may reduce the accuracy and precision of measurements. The modulated differential scanning calorimetry (MDSC) has overcome some of these issues by employing sinusoidally modulated heating rates, which are used to determine the heat capacity. Another variant of the MDSC is the supercooling MDSC (SMDSC). SMDSC allows the detection of more complex thermal events such as solid–solid (Ts-s) transitions, liquid–liquid (Tl-l) transitions, and vitrification and devitrification temperatures (Tv and Tdv, respectively), which are typically found at the supercooling temperatures (Tco). The main advantage of MDSC relies on the accurate detection of complex transitions and the possibility of distinguishing reversible events (dependent on the heat capacity) from non-reversible events (dependent on kinetics).

A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells. PACS 61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

A novel growth technique, called atomic partial layer deposition (APLD), has been proposed to expand the applications of, and the research in, atomic layer deposition (ALD). This technique allows the possibility for the fabrication of well-controlled alloys on a single atomic layer scale. To demonstrate the capabilities of this technique, samples of HfO₂ and TiO₂ were prepared as conventional ALD nanolaminates through the repeated exposure of the separated metal-precursor and reactant. Subsequently, HfO₂-TiO₂ APLD growth mode samples were obtained by varying the precursor doses and exposure times to obtain a fractional coverage in the monolayer of Hf and Ti. The thickness and structure of the samples were studied by X-ray reflectivity. The surface topography was studied using atomic force microscopy along with Kelvin probe force microscopy for surface potential mapping. Clear differences on the surface, compared with the conventional HfO₂/TiO₂ ALD nanolaminates, were observed, which confirmed the HfO₂-TiO₂ APLD growth. The films were analyzed using X-ray photoelectron spectroscopy (XPS) depth profile scans and angle resolved XPS, where well-defined HfO₂ and TiO₂ contributions were found for both the conventional and APLD mode samples, and an additional contribution, assigned to a ternary phase Hf-Ti-O, in the APLD grown films was observed. This result confirms that Hf and Ti form an alloy in a monolayer by APLD mode growth.

Al₂O₃ layers with thicknesses in the 25–120 nm range were deposited by plasma enhanced atomic layer deposition at 70 °C. Trimethylaluminum was used as organometallic precursor, O₂ and H₂O as oxidant agents and Ar as a purge gas. The deposition cycle consisted of 50 ms TMA pulse/10 s purge time/6 s of plasma oxidation at 200 W/10 s purge time. The optical constants and thicknesses of the grown layers were determined by spectroscopic ellipsometry, while the roughness was measured by atomic force microscopy, giving RMS values in the 0.29–0.32 nm range for films deposited under different conditions and having different thicknesses. High transmittance, ~90%, was measured by UV–Vis spectroscopy. X-ray photoelectron spectroscopy revealed that, with both types of oxidants, the obtained films are close to stoichiometric composition and, with high purity, no carbon was detected. Electrical characterization showed good insulating properties of both types of films, though the H₂O oxidant leads to better I-V characteristics.

The present paper describes the results of the study of solid solutions of Bi₂Mo_xW_(1−x)O₆, which were prepared by the route of solid-state reaction and tested for catalytic activity in the oxidation of CO into CO₂. X-Ray photoelectron spectroscopy (XPS) was conducted to obtain information on the chemical composition, and with the use of Bi₂MoO₆ and Bi₂WO₆ synthesized standards, quantitative measures were obtained. Catalytic studies of the samples show that they possess high activity, as a change in the temperature of activation as a function of the sintering temperature with the Mo/W ratio was detected. Bi–Mo mixed oxides have synergistic effects on the oxidation of CO, making possible the full conversion at lower temperatures than compounds that contain only single phases. The work described here demonstrates that a solid solution can be more efficient in oxidation, compared with single oxides studied separately.

Thermal atomic layer deposition (TALD) and plasma atomic layer deposition (PALD) were used for producing thin NiO _x films from nickel(II) acetylacetonate Ni(acac)₂, employing different oxidizing agents (deionized water H₂O, ozone O₃, and molecular oxygen O₂). The films were deposited at 300 °C (TALD) and 220 °C (PALD) over glass substrates; their physical and chemical properties were considerably influenced by the choice of oxidizing agents. In particular, ALD(H₂O) samples had a low growth per cycle (GPC) and a high concentration of defects. The best NiO _x parameters were achieved with PALD(O₂), featuring high GPC (0.07 nm/cycle), high optical transparency in the visible region, electrical resistivity (1.18 × 10⁴ Ω·cm), good carrier concentration (8.82 × 10¹³ cm^-3), and common mobility (5.98 cm²/V·s). The resulting NiO _x films are polycrystalline and homogeneous in thickness and composition. According to ultraviolet photoelectron spectroscopy (UPS), work function φ and the valence band maximum E _V can be tuned by the choice of the coreactant employed, with variations of up to ∼1 eV between TALD and PALD synthesis. Our results suggest that PALD permits one to achieve a better energy band alignment of NiO _x and CsFAMAPbBrI perovskite, which is promising for solar cell applications.