Characterization and tests of planar Co3O4 model catalysts prepared by chemical vapor deposition

The chemical vapor deposition method was used to deposit thin films of cobalt oxide starting with cobalt (II) acetylacetonate and oxygen. The deposition process was investigated and the obtained films were identified as a cubic spinel-type polycrystalline Co₃O₄ with a crystallite size of 30–40 nm. The coating was carbon-free and the surface oxygen concentration was measured to be 66 at.% with AES analysis. Smooth and highly uniform thin films were deposited on planar stainless steel substrates and subjected to TPR and catalysis tests that show positive correlation. The apparent activation energy of Co₃O₄ reduction to CoO was measured to be (33±5) kJ/mol. The catalytic activity of Co₃O₄ was investigated toward the conversion of both propane and ethanol to carbon dioxide. Though the catalytic action was registered at the same temperature, the deactivation process was seen to be different. The catalytic conversion of ethanol induces a fast deactivation process, which was linked to its high ability to reduce Co₃O₄.     

Synthesis, structure and catalytic properties of Fe-substituted barium hexaaluminates

A sol–gel method using Ba and Al isopropylates and iron nitrate has been used to synthesise barium hexaaluminate partially substituted with iron. After calcination under oxygen at 1200°C the -alumina structure was obtained. Formation of the mixed BaFe_xAl_12-xO₁₉ phase occurred for x=1–4. XRD measurements showed a good crystallinity of the structure and expansion of unit cell parameters due to the presence of larger Fe³⁺ ions substituting Al³⁺ ones in octahedral sites only. Mössbauer spectroscopy revealed that Fe³⁺ ions are present in four different octahedral sites slightly distorted. Catalytic activity in methane combustion showed that an optimum was obtained for solid containing 2 Fe ions per unit cell: the increase of the amount of introduced iron was counterbalanced by the decrease of specific surface area. Intrinsic activities have been calculated for the four solids in both the fresh and aged states. It is observed that increasing iron content increases relative activities in the same ratio as the populations of iron located in two sites as deduced from Mössbauer spectroscopy. It is then tentatively assumed that activity is attributed to octahedrally coordinated Fe³⁺ ions in some specific sites.     

Nonhypothesis Analysis of a Mutagenic Soybean (Glycine max [L.]) Population for Protein and Fatty‐Acid Composition

Soybean is a major source of oil for food, feed, and biofuel production. Mutagenesis is a tool for creating unique traits useful in breeding programs. The aim of this study is to use nonhypothesis statistical testing methods to make decisions about a mutagenic population. To this end, a total of 1037 mutation lines and 28 wild‐type lines were analyzed for fatty‐acid composition and protein content. Principal component analysis (PCA) was used to analyze the fatty acid profile, multivariate analysis of variance (MANOVA) to build a selection model for seed weight per plant and weight per 10 seeds, and clustering in conjunction with power analysis to determine the minimum number of individuals needed to create a MANOVA selection model for the oil to protein content. Five of the 35 possible entries were identified by PCA analysis for stearic acid and four of 16 possible entries for oleic acid. Interestingly, most of the selected mutants were validated genetically. In fact, selected mutants with high seed stearic acid or high seed oleic acid contents were verified to carry mutations on GmFAD2‐1A, GmFAD2‐1B, and GmSACPD‐C genes. This shows a promising method of identifying smaller portion of the population to screen for desired mutations.     

Application of Bu2Sn(acac)2 for the deposition of nanocrystallite SnO2 films: Nucleation, growth and physical properties

High-quality uniform SnO₂ thin films were successfully prepared by pulsed-spray evaporation chemical vapor deposition (PSE-CVD) method, using a cost-efficient precursor of ⁿBu₂Sn(acac)₂. The volatility and stability of ⁿBu₂Sn(acac)₂ were studied through thermogravimetric-differential thermal (TG-DTA) analysis and mass spectrometry, indicating the good adaptability for the CVD process. Deposition of SnO₂ films was made in the range of 250-450 °C to investigate the effect of substrate temperature on their structural and physical properties. The film growth activation energy changes from 66.5 kJ/mol in the range of 250-330 °C to 0 kJ/mol at 330-450 °C, suggesting the change of the rate-limiting step from surface kinetics to diffusion control. All films possess the rutile-type tetragonal structure, while a change of preferred orientation from (1 1 0) to (1 0 1) plane is observed upon the increase of the deposition temperature. The different variation of the nucleation and growth rates with the deposition temperature is proposed to explain the observed unusual change of crystallite size. A significant deterioration of the electrical conductivity was observed upon the increase of the deposition temperature, which was tentatively attributed to the non-specific decomposition of the precursor at high temperature leading to carbon contamination. Optical measurements show transparencies above 80% in the visible spectral range for all films, while band gap energy increases from 4.02 eV to 4.08 eV when the deposition temperature was raised from 250 °C to 450 °C.     

Effect of Moisture on the High-Temperature Stability of Unidirectionally Solidified Al2O3/YAG Eutectic Composites

The corrosion resistance of a unidirectionally solidified alumina/yttrium aluminum garnet (Al₂O₃/YAG) eutectic mixture was investigated at high temperature. Samples were exposed to high temperature (1200°–1800°C) in different atmospheres, which included argon, argon/water vapor, air, and air/water vapor. The most important microstructural changes occurred at the interface between the YAG and the Al₂O₃. Those changes consisted of localized thermal grooving, especially when the corrosive atmosphere contained water vapor. The samples exhibited significant weight loss at high temperature (1800°C) after 20 h of exposure. The calculated volume gain that was induced by the increased surface relief was low and limited, except when the corrosive atmosphere contained air, which indicated that the presence of air (particularly oxygen) induced a more-active corrosion process. On the other hand, no change in the flexural strength was observed, even after 100 h at 1800°C in a humid atmosphere, because of the cross-linked structure of the composite, which limited propagation of the groove.     

New Sol–Gel Route for the Preparation of Pure α-Alumina at 950°C

An anhydrous alumina (Al₂O₃) sol was prepared from aluminum isopropoxide and an organic solvent, using an acetic acid stabilizer. The complete conversion of the dried sol to α-Al₂O₃ was accomplished at a temperature of 950°C by a single transition via γ-Al₂O₃. Al₂O₃ that was deposited via dip coating resulted in amorphous films, even after annealing at 1100°C, because of the silicon diffusion from the substrate. This phenomenon was avoided using a rapid thermal treatment in a flame after dip coating, which resulted in uniform thin films that are converted to α-Al₂O₃ via heat treatment.     

Enabling Full Conversion Reaction with High Reversibility to Approach Theoretical Capacity for Sodium Storage

Conversion‐type electrode materials are emerging as promising candidates for high‐energy rechargeable batteries, owing to their substantially higher theoretical capacity relative to intercalation‐based materials. Nevertheless, the full benefit from conversion‐type electrode materials remains out of reach in sodium‐ion batteries, due to the inadequate conversion reaction toward sodium and the poor reversibility during desodiation. Here, a full conversion reaction with high reversibility is demonstrated through promoting the initial sodium intercalation and subsequent reconversion kinetics by transition metal doping. The doping‐induced lowering of the sodium intercalation energy in thermodynamics effectively drives the full conversion reaction, while the metal transition of the doped element enhances reconversion kinetics in achieving high reversibility. The obtained results open a new avenue for the development of high‐performance conversion‐type electrodes and provide a novel understanding of the conversion reaction mechanism.     

Self-catalyzed chemical vapor deposition method for the growth of device-quality metal thin films

Deposition of metals and alloys was demonstrated using thermal chemical vapor deposition starting from commercially available precursors in the absence of molecular hydrogen. The adopted chemical strategy relies solely on the selective reactivity of alcohols with metal complexes at deposition temperature. In this report, particular interest was given to the growth of nickel and silver. This process allows the optimization of the growth of single hcp and fcc phases of nickel starting from Ni(acac)₂, whereas several silver precursors allow the deposition of the fcc crystalline structure of silver. Steady growth kinetics, without incubation time, was noticed for all investigated precursors. The electrical conductivity of hcp-Ni, fcc-Ni and fcc-Ag shows the typical decay to the bulk value with increased film thickness, and the temperature resistivity coefficients are similar to the corresponding bulk material.     

CO and ethanol oxidation over LaCoO3 planar model catalysts: Effect of the thickness

The catalytic performance of the LaCoO₃ thin films toward CO and ethanol oxidation was studied in a reactor designed for the investigation of model planar catalysts. The effect of the thickness on the catalytic efficiency and the surface oxygen vacancies offers a straightforward method to identify or discriminate the oxygen species involved in the catalytic reaction. The weight-normalized reaction rate is demonstrated to be an intrinsic parameter and thus confirms the participation of the bulk lattice-oxygen in the studied catalytic reactions. Compared to other perovskite oxide powder catalysts, thin film catalysts show a remarkably higher activity toward ethanol and CO oxidation.     

Ultrasound applications in poultry meat processing: A systematic review

Ultrasound (US) is classified as a nonthermal treatment and it is used in food processing at a frequency range between 20 kHz and 1 MHz. Cavitation bubbles occur when the US strength is high enough to generate rarefaction that exceeds the intermolecular attraction forces in the medium. Currently, US is widely used in meat industries to enhance procedures, such as meat tenderization, emulsification mass transfer, marination, freezing, homogenization, crystallization, drying, and microorganism inactivation. In addition, combining ultrasonic energy with a sanitizing agent has a synergistic effect on microbial reduction. When poultry meat is treated using US, the expected quality is often better than the traditional methods, such as sanitization and freezing. US can be considered as a novel green technology for tenderizing and decontamination of poultry meat since both Escherichia coli and Salmonella are sensible to US. US improves the physical and chemical properties of meat proteins and can lead to a decrease in the α-helix in intramuscular protease complex in addition to a reduction in the viscosity coefficients. Therefore, ultrasonic treatment can be applied to enhance the textural properties of chicken meat. US can also be used to improve the drying rate when used under vacuum, compared with other traditional techniques. This review focuses on the potential of US applications in the management of poultry industries as the demand for good quality meat proteins is increasing worldwide.