Influence of the presence of titanium oxide on the formation of pyrochlore phase in ferroelectric strontium bismuth tantalate ceramics

The effects of addition of TiO₂ on the formation of pyrochlore phase and dielectric properties of ferroelectric SrBi₂Ta₂O₉ have been investigated. When the content of Ti02 is less than 10 mol%, no secondary phases are produced, and SrBi₂Ta₂O₉-TiO₂ solid solutions are formed. However, with TiO₂ content ≥20 mol%, a pyrochlore phase is produced. Raising the content of TiO₂ in starting materials significantly increases the amounts of pyrochlore phase, and reduces the initial temperature for the formation of pyrochlore phase. The existence of TiO₂ also decreases the thermal stability of SrBi₂Ta₂O₉, causing the decomposition of SrBi₂Ta₂O₉to take place at lower temperatures. Furthermore, the presence of TiO₂ reduces the dielectric constants as well as remnant polarization of formed ceramics.     

Reduction of NOx over Fe/ZSM-5 catalysts: mechanistic causes of activity differences between alkanes

Fe/ZSM-5 catalysts prepared by sublimation of FeCl₃ onto H/ZSM-5 catalyze the selective reduction of NO_x by hydrocarbons to N₂. The order of the relative rates and N₂ yields obtained with different alkanes reveals a non-trivial chemistry. The maximum yield is lower for propane than for n-butane but about the same for n- and iso-butane. However, at temperatures below this maximum, the N₂ yield is higher for propane and n-butane than for iso-butane. Deposits are formed on the catalyst that contain N atoms in a low-oxidation state which are able to react with NO₂ to form N₂. TPO and FTIR results show that the amount and also the character of the deposits depend on the nature of alkanes. The change of the oxidation state of nitrogen from a high value in NO or NO₂ to a lower value in nitrile and amino groups of the deposit is rationalized by applying mechanistic concepts of organic chemistry, including the Beckmann rearrangement and fragmentation. FTIR spectra and the observed oxygen- and nitrogen-containing compounds by GC-MS are potential clues to the reaction mechanism.     

Texture Development, Microstructure Evolution, and Crystallization of Chemically Derived PZT Thin Films

Two solution-based methods, metallo-organic decomposition and sol—gel processes, were used to study the effects of precursor solution type on the microstructure evolution and texture development of oriented PZT films. Microstructure development and perovskite content are strongly dependent on the heating rate. Fast heating rate forms a dense fine-grained microstructure with (111) orientation. Intermediate-temperature pyrolysis followed by a fast heating rate forms clustered or island structures of submicrometer grains with (100) orientation. Intermediate-temperature pyrolysis followed by a very slow heating rate forms larger spherical rosettes with random orientations. Pt_5–7Pb is a (111) textured transient intermetallic phase that nucleates PZT(111) texture. PbO is a (001) textured layer compound that nucleates PZT(100) texture. The texture selection of PZT films is independent of precursor systems but sensitive to the film thickness especially when sol—gel precursors and oxidizing atmosphere are used. Correlation and comparison of oriented sol—gel and MOD PZT films with electrical properties are also made.     

Low-Pressure Flame Deposition of Nanostructured Oxide Films

The influence of electroless nickel plating on lead-based relaxor ferroelectric multilayer ceramic capacitors (MLCs) was studied by a comparison experiment. It was found that the influence is related to reactions in the electroless plating. It is proposed that adsorbed hydrogen atoms generated in electroless plating can diffuse into the ceramic bodies of MLCs and undergo some reduction reaction with them, resulting in the failure of electroless nickel plating. The implications for the negative influence of electroplating on MLCs and for the degradation in MLCs are also included, in which much attention is paid to the reduction reaction of hydrogen atoms generated by electrolysis of water.     

Effects of ionic impurities on crystallization of cobalamin

In this paper, the influence of two typical ionic impurities (Na⁺ and Mg²⁺) is investigated with the focused beam reflectance measurement (FBRM) technique. In this system, the on-line FBRM is used as a tool for monitoring the crystallization process of cobalamin by measuring the chord length distribution of particles and the particle counts. It is noted that impurity Mg²⁺ has a more significant effect than Na²⁺ in crystal growth of the whole crystallization process. From the microscopic observation of crystals, Mg²⁺ has an obvious effect on the crystal habit, while Na²⁺ has little effect. In addition, the crystal habit changes can be monitored by particle vision measurement (PVM). Understanding these effects is helpful to aid optimization and improve process control.     

Growth of large-sized graphene thin-films by liquid precursor-based chemical vapor deposition under atmospheric pressure

Large-sized thin-films composed of single- and few-layered graphene have been synthesized by chemical vapor deposition (CVD) on copper foils under atmospheric pressure using ethanol or pentane as the precursor. Confocal Raman measurements, transmission electron microscopy and scanning tunneling microscopy show that the majority part of the obtained films exhibit hexagonal graphene lattice. Optical microscopy and electrical measurements confirm the continuity of these films. It is also found that the CVD-grown graphene films with ethanol as the precursor exhibit lower defect density, higher electrical conductivity, and higher hall mobility than those grown with pentane as the precursor. This liquid-precursor-based atmospheric pressure CVD synthesis provides a new route for simple, inexpensive and safe growth of graphene thin-films.     

Non-plasma ignition of lead styphnate by a semiconductor bridge and its comparison with plasma ignition

The process of non-plasma ignition of lead styphnate by a silicon-based semiconductor bridge is studied. Discharge characteristics with plasma and non-plasma ignition are analyzed. It is demonstrated that non-plasma ignition is characterized by a low energy and can be applied in cases with fine-grain energy materials.