The development of microstructural and electrical characteristics in some thick-film resistors during firing

The development of microstructural and electrical characteristics (sheet resistivities, TCRs, and noise indices) in some thick-film resistors during the firing process has been evaluated. Three 1 kohm/sq. resistor pastes (Du Pont), based on RuO₂, ruthenate or a mixture of both conductive phases, were fired at temperatures from 500°C to 950°C. The cell parameters of the RuO₂ in the 8031 and the 2031 resistors, the bismuth ruthenate in the 8029 resistors and the lead ruthenate in the 2031 resistors, were calculated from X-ray data. Microstructures were analyzed by SEM and EDS microanalysis. The absolute values of the cold and hot TCRs first decreased to a minimum at 850°C and then increased again with increasing firing temperature. The noise indices of the resistors generally decrease with increasing firing temperature.     

Optimization of a Fabric Softener Formulation with an Electrochemical Sensor and Streaming Potential Measurements

An electrochemical, cationic, surfactant-selective sensor based on multiwalled carbon nanotubes (MWCNT) functionalized with a sulfate group and the cetylpyridinium ion (MWCNT–OSO₃⁻CP⁺) as a sensing material was used for optimization of the formulation of a fabric softener. Potentiometric titrations were performed and response measurements were obtained using four cationic surfactants (CS) of technical grade and four CS of analytical grade. The slope closest to Nernstian was obtained for di-(tallow carboxyethyl) hydroxyethyl methylammonium methosulfate (MAS) (59.5 ± 1.1 mV/decade of activity in water and 57.5 ± 1.3 mV/decade of activity in CaCl₂). When using CS as analytes in potentiometric titrations, the best accuracy (99.8%) was obtained when using MAS; therefore, it was chosen as the CS for the fabric softener formulation. Due to the better properties of fabric softeners with silicone in their formulations, four silicones at several concentration levels were used as potential additives. Based on the stability and viscosity of the system, the diquaternary polydimethylsiloxane (DPS) (w = 0.19%) was chosen for the fabric softener formulation. The pH did not significantly influence the potential when in the range of 3–8 or the recovery of potentiometric titrations when in the range of 3–7. The application profile of the CS was assessed through streaming potential measurements of reference fabrics in an electrokinetic analyzer. The obtained electrokinetic parameters indicated on lag in adsorption of model fabric softener (MFS) based on MAS (w = 9%), with the addition of silicone DPS (MFS 3), on cotton and polyester fabrics, but advantage in stability when compared with other MFS investigated.     

Effects of extrusion with CO<Subscript>2</Subscript> injection on physical and antioxidant properties of cornmeal-based extrudates with carrot powder

Carrot powder and cornmeal were extruded at ratios of 0:100, 10:90, and 20:80 with and without CO₂ injection at die temperatures of 80, 100, and 120 °C. The effects of the composition of the extrudate, die temperature, and CO₂ injection on physicochemical and antioxidant properties of extruded products were studied. The results showed that die temperature had a significant effect on expansion ratio (ER), specific length, piece density, color, water absorption index (WAI), and water solubility index (WSI) (p < 0.05). The injection of CO₂ significantly affected the ER, WAI, WSI, lightness, redness, microstructure, total phenolic content, and the 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity of extrudates (p < 0.05). Increasing the proportion of carrot powder in extrudates resulted in better antioxidant properties and higher levels of crude ash, crude fat, crude protein, and redness; however, it resulted in lower WAI, lightness, and yellowness (p < 0.05). The study demonstrated that extrusion with CO₂ injection and addition of carrot powder may improve the nutritional quality and structure-forming ability of extrudates.     

Growth of Transparent and Conductive Polycrystalline (0001)‐ZnO Films on Glass Substrates Under Low‐Temperature Hydrothermal Conditions

Flat panel display technology seems to be an ever‐expanding field developing into a multibillion dollar market. A set of technical solutions involve a transparent conducting film (TCF) that is today still dominated by indium‐tin‐oxide (ITO). In a race to find alternatives that would avoid the indium pitfalls, mainly due to its increasing price and limited natural availablity, replacement materials have been extensively investigated. This work demonstrates that by exploiting basic principles of crystal growth in geometrically constrained conditions, zinc oxide (ZnO) could easily be utilized for this purpose. ZnO layers were grown on inexpensive glass substrates via low‐temperature citrate‐assisted hydrothermal (HT) method. It was shown that in the nucleation stage the crystal growth can be efficiently controlled by spatially confined oriented growth (SCOG) mechanism to produce smooth and dense (0001) oriented polycrystalline ZnO films with superb optical properties. Our products show optical transparency of 82% and surprisingly low sheet resistance for undoped ZnO, only in the order of few 100 Ω sq^?1. We believe that a very high degree of self‐organization between the ZnO crystals in our polycrystalline films grown under controlled SCOG conditions is main reason for the highest so far reported transparency to conductivity ratio for undoped ZnO thin film ceramics.     

Twinning and charge compensation in Nb2O5–doped SnO2–CoO ceramics exhibiting promising varistor characteristics

We investigated the effects of dual doping of SnO₂ varistor ceramics with 1 mol% CoO and different amounts of Nb₂O₅ (0.1–2 mol%) on the formation of twin boundaries, microstructure development and electrical properties. Nb₂O₅ addition shifts densification to higher temperatures (up to 1430 °C), producing microstructures composed of twinned SnO₂ grains. Already 0.1 mol% Nb₂O₅ triggers a three-fold increase in growth rate via the diffusion induced grain boundary mobility (DIGM). At 0.5 mol% of Nb₂O₅ chemical equilibrium is achieved and SnO₂ grains undergo normal grain growth. Electron back-scatter diffraction (EBSD) has shown that the prevailing type of twins is {101}. Cyclic twins are common. High-angle annular dark-filed scanning transmission electron microscopy (HAADF-STEM) image analysis revealed non-uniform segregation of Nb along the twin boundaries, indicating that they are not directly triggered by Nb₂O₅, but are a result of yet unexplained sequence of topotaxial replacement reactions. Energy dispersive spectroscopy (EDS) has shown that by dual doping of SnO₂ with CoO and Nb₂O₅ the amount of Co dissolved in SnO₂ grains is always ~4x lower compared to the amount of incorporated Nb and propose the following mechanism of tin out-diffusion: $6Sn{\left(IV\right)}_{Sn(IV)}^{\times }?Sn{\left(II\right)}_{Sn(IV)}^{\text{'}\text{'}}+Co{\left(II\right)}_{Sn(IV)}^{\text{'}\text{'}}+4Nb{\left(V\right)}_{Sn(IV)}^{?}$. Optimal electrical properties were achieved at 1 mol% Nb₂O₅ addition displaying high nonlinearity (α=50), moderate break-down voltage (571±12 V/mm) and low leakage current (I_L = 4.2 µA). The addition of 2 mol% of Nb₂O₅ has an inhibiting effect on densification and SnO₂ grain growth, resulting in a collapse of nonlinearity and increase of leakage current.     

Structural and electronic properties of the highly concentrated UxY1−xRu2Si2 alloy system

We report on the resistivity and thermopower measurements together with the microstructural investigations of two highly concentrated alloys of the U_xY_1−xRu₂Si₂ alloy system, for x = 0.5 and x = 0.67, nominally. Microstructural analysis shows the existence of two different crystalline phases at the room temperature: the solid solution U_cY_1−cRu₂Si₂ (c < x) phase and the phase which can be represented by chemical formula URu₂Si. We show that the uranium single ions dissolved in the YRu₂Si₂ matrix exhibit the ordinary or single-channel Kondo effect described by the Coqblin-Schrieffer Hamiltonian. In the light of the obtained results, the URu₂Si₂ compound is discussed.     

Structural peculiarities of 0.67 Pb(Mg1/3Nb2/3)O3–0.33 PbTiO3 thin films grown directly on SrTiO3 substrates

Growth of Pb(Mg_1/3Nb_2/3)O₃–33PbTiO₃ thin films by pulsed-laser deposition directly on non-conductive SrTiO₃ substrates for d₃₃-mode energy harvesters (EHs) was studied, as they offer a higher figure-of-merit than d₃₁-mode EHs. It was found that a high defect density, present in the film grown at 0.13?mbar, is manifested in the form of splitting of the (00l) peaks in X-ray diffraction, which was avoided by raising the process pressure to 0.27?mbar. Nevertheless, both films grow in a combined 2D and 3D manner, and form out-of-phase boundaries (OPBs) with a PbO rock-salt structure between the as-grown islands. It was found that the overall composition of the sample with optimized structural and functional properties was Pb_1.07Mg_0.19Nb_0.44Ti_0.32O₃, which is close to stoichiometric. The surplus of Pb is compensated by the formation of OPBs and Mg deficit maintains macroscopic electroneutrality. In-plane and out-of-plane relative permittivities of 1900 and 980, respectively, imply macroscopic out-of-plane polarization.