Rod-like Grains Research Articles

Porous Si3N4 Ceramics Prepared by TBA-based Gel-casting

In this work, the effects of ratio of monomer to cross-linker (AM/MBAM) and solid loading on the microstructure and mechanical properties of porous Si3N4 ceramics prepared by tert-butyl alcohol (TBA)-based gel-casting process were investigated. It was found that, when the ratio of monomer to cross-linker was 8, and the solid loading was 50 wt%, the mechanical properties of sintered samples were the most excellent, which resulted from the uniform pore size distribution and well-grown rod-like β-Si3N4 grains. In that case, the porosity and flexural strength of sintered samples were 50% and 125 MPa, respectively.

Ferroelectric Properties and Microstructures of Bi4-xDyxTi3O12 Thin Films

Dy-doped Bi4Ti3O12 thin films were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition technique, and the structures and electrical properties of the films were investigated. XRD results indicated that all of Bi4-xDyxTi3O12 films consisted of single phase of a bismuth-layered structure with well-developed rod-like grains. The remanent polarization ( Pr ) and coercive field (Ec) of the Bi4-xDyxTi3O12 Film with x=0.75 were 25μC/cm2 and 85KV/cm , respectively.

Electrical Characterization and Microstructures of Bi<sub>4-</sub><sub>x</sub>Gd<sub>x</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films

Gd2O3-doped bismuth titanate (Bi4-xGdxTi3O12: BGT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Gd-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Gd doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BGT film with x=0.75 were 28 μC/cm2 and 65 kV/cm, respectively.

Electrical Characteristics and Microstructures of Pr<sub>2</sub>O<sub>3</sub>-Doped Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films

Pr2O3-doped bismuth titanate (Bi4-xPrxTi3O12: BPT) thin films with random oriention were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique, and the structures and ferroelectric properties of the films were investigated. XRD studies indicated that all of BPT films consisted of single phase of a bismuth-layered structure with well-developed rod-like grains. For samples with x=0..0 , 0.25, 1.0 and 1.25, I-E characteristics exhibited negative differential resistance behaviors and their ferroelectric hysteresis loops were characterized by large leakage current, whereas for samples with x=0.5 and 0.75, I-E characteristics were simple ohmic behaviors and their ferroelectric hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BPT Film with x=0.75 were above 30μC/cm2 and 75KV/cm , respectively.

Reactive hot-pressing of platelet-like ZrB2–ZrC–Zr cermets: Processing and microstructure

In this study, two methods of powder reactions and reactive hot-pressing were used for the reaction of Zr+B4C powder mixtures. The powder reactions were performed at various temperatures, between 600°C and 1100°C, to examine the reaction behaviour occurring during the synthesis. To fabricate a cermet composed of platelet-like ZrB2 grains and equiaxed ZrCx grains, with intergranular Zr phase, reactive hot-pressing was conduced within temperature range of 1100–1900°C. The effects of temperature on the reactions, densification behaviour and microstructure of the samples were assessed. For samples sintered at 900°C or above, the Zr+B4C mixture was converted into ZrB2 and ZrCx; the conversion was completed at ~1100°C. Densification resulted from volume contraction due to the conversion of Zr+B4C mixture into ZrB2 and ZrCx, and the shrinkage due to grain boundary diffusion and grain boundary migration. For Zr+B4C mixtures sintered at or above 1400°C, relative densities exceeding 97% were obtained. When sintered at or below 1400°C, the resulting ZrB2–ZrCx–Zr cermet consisted of rod-like ZrB2 grains, equiaxed ZrCx grains and residual Zr. Highly-developed platelet-like ZrB2–ZrCx–Zr cermet was obtained only at sintering temperature of 1600°C or greater.

Facile solution-based fabrication of ZnIn2S4 nanocrystalline thin films and their photoelectrochemical properties

Hexagonal phase ZnIn2S4 nanocrystalline thin films are deposited by spin-coating method using an air-stable precursor solution. In the process, metal oxide and hydroxide are used as Zn and In sources to avoid the introduction of any anion impurity in ZnIn2S4 thin films. The rod-like nanocrystalline grains with width and length about 13 ± 3 nm and 26 ± 5 nm grow along c-axis after annealing in sulfur vapor at 500 °C for 2 h. Smooth and compact thin films with different In/Zn ratios are fabricated by controlling the ratio of two metal sources in precursor solution. The flat-band potentials of these n-type ZnIn2S4 thin films are in the range of −0.55 to −0.45 V vs. normal hydrogen electrode. The photoelectrochemical measurement demonstrates the excellent visible light response of ZnIn2S4 thin films. The light current under visible light illumination occupies almost 60% of the light current under full spectrum illumination. The facile solution-based method provides a novel thought to fabricate high-quality thin films of multi metal chalcogenides with excellent photoelectric properties via solving the other metal oxide and hydroxide in the solution.

Magnetic and magnetotransport properties of half-metallic CrO2-SnO2 composites

Half-metallic (CrO2)1−x-(SnO2)x composites were prepared under high temperature and high pressure conditions. The composites are composed of large rod-like CrO2 grains and small SnO2 nanoparticles. The CrO2 in the composites is very pure and its saturation magnetization is very close to the theoretical value. The composition dependence of magnetic and magnetotransport properties of the composites was studied. The coercive force (Hc) and remanence ratio (Mr/Ms) of the composites increase dramatically with increasing SnO2 content x for x > 0.6. This should be due to that the CrO2 grains have been well separated by SnO2 nanoparticles and the magnetic interactions among CrO2 grains become weak when x > 0.6. The resistivity and magnetoresistance at 5 K of the composites increase with increasing x, and the increase quickens up at x = 0.5. When x ≥ 0.5, the (CrO2)1−x-(SnO2)x composites show insulator behavior, and the temperature dependence of the resistivity can be well described by fluctuation-induced tunneling model. But when x ≤ 0.4, the (CrO2)1−x-(SnO2)x composites show insulator-metal transitions, and the transition temperature increases with increasing SnO2 concentration. Below the transition temperature, their resistivity can also be explained by fluctuation-induced tunneling model. The (CrO2)1−x-(SnO2)x composites show greater magnetoresistance than pure CrO2 at low temperature, which is attributed to enhancement of tunneling magnetoresistance by adding of SnO2.

Ferroelectric Properties and Microstructures of Bi<sub>4-x</sub> Lu<sub>x</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films

Lu2O3-doped bismuth titanate (Bi4-xLuxTi3O12: BLT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Lu-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Lu doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BLT film with x=0.75 were 28 μC/cm2 and 65 kV/cm, respectively.

Large Remanent Polarization of Pm<sub>2</sub>O<sub>3</sub>-Doped Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> Films

Pm-doped bismuth titanate (Pm4-xLaxTi3O12: BPT) and pure Bi4Ti3O12(BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. For the samples with x=0.25, 1.0, and 1.25, the current-voltage characteristics exhibited negative differential resistance behaviors and their P-V hysteresis loops were characterized by large leakage current, whereas for the samples with x=0.5 and 0.75, the current-voltage characteristics showed simple ohmic behaviors and their P-V hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BPT Fims with x=0.75 were above 40μC/cm2 and 60KV/cm , respectively.

Electrical Characterization and Microstructures of Ce-Doped Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films

Ce-doped bismuth titanate (Bi4-xCexTi3O12: BCT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. The experimental results indicated that Ce doping into BIT result in a remarkable improvement in ferroelectric propertis. The Pr and the Ec values of the BCT film with x=0.75 were 23 μC/cm2 and 80 kV/cm, respectively.

Large Remanent Polarization of Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> Films by Ho<sup>3+</sup> Substitution

Ho-doped bismuth titanate (Bi4-xHoxTi3O12: BHT) and pure Bi4Ti3O12(BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. For the samples with x=0.25, 1.0, and 1.25, the current-voltage characteristics exhibited negative differential resistance behaviors and their P-V hysteresis loops were characterized by large leakage current, whereas for the samples with x=0.5 and 0.75, the current-voltage characteristics showed simple ohmic behaviors and their P-E hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BHT Fims with x=0.75 were above 30μC/cm2 and 60KV/cm , respectively.

Electrical Characterization and Microstructures of Y<sub>2</sub>O<sub>3</sub>-Doped Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films

Y2O3-doped bismuth titanate (Bi4-xYxTi3O12: BYT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Y-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Y doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BYT film with x=0.75 were 28 μC/cm2 and 65 kV/cm, respectively.

Electrical Characterization and Microstructures of Bi<sub>4-x</sub> Sc<sub>x</sub> Ti<sub>3</sub>O<sub>12</sub> Thin Films Grown by Pulsed Laser Deposition Technique

Sc-doped bismuth titanate (Bi4-xScxTi3O12: BST) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. The experimental results indicated that Sc doping into BIT result in a remarkable improvement in ferroelectric properties. The Pr and the Ec values of the BST film with x=0.75 were 25 μC/cm2 and 65 kV/cm, respectively.

Preparation and Ferroelectric Properties of Bi<sub>4-x</sub>Tm<sub>x</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films

Tm2O3-doped bismuth titanate (Bi4-xTmxTi3O12, BTT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. The experimental results indicated that Tm doping into BIT results in remarkable improvement in ferroelectric properties. The Pr and the Ec values of the BTT film with x=0.75 were 28 μC/cm2 and 80 kV/cm, respectively.

Organic thin-film transistors based on thieno[3,4-c]pyrrole-4,6-dione conjugated polymer via oxidative polymerization

Thieno[3,4-c]pyrrole-4,6-dione (TPD)-based polymer (PDTTPD) with head-to-head (H-H) linkage of 3-dodecylthiophene unit was synthesized by ferric chloride oxidative polymerization. The polymer was characterized by chemical analysis as well as thermal analysis, optical spectroscopy and cyclic voltammeter. PDTTPD polymer showed excellent thermal stability, had significantly red-shifted of absorption edge by its solid film compared to its solution and a deep highest occupied molecular orbital (HOMO) energy level of −5.82eV. Polymer thin-film microstructures and morphologies were also investigated through atomic force microscope (AFM) and grazing-incidence X-ray diffraction (GIXD) which showed that the PDTTPD film is composed of rod-like crystalline grains and ordered structures. Organic thin-film transistors (OTFT) with common architectures were fabricated to evaluate OTFT performance and exhibited the preliminary hole mobility of 0.019cm−2V−1s−1.

Geometry dependence of the clogging transition in tilted hoppers

We report the effects of system geometry on the clogging of granular material flowing out of flat-bottomed hoppers with variable aperture size D and with variable angle θ of tilt of the hopper away from horizontal. In general, larger tilt angles make the system more susceptible to clogging. To quantify this effect for a given θ, we measure the distribution of mass discharged between clogging events as a function of aperture size and extrapolate to the critical size at which the average mass diverges. By repeating for different angles, we map out a clogging phase diagram as a function of D and θ that demarcates the regimes of free flow (large D, small θ) and clogging (small D, large θ). We do this for both circular holes and long rectangular slits. Additionally, we measure four types of grain: smooth spheres (glass beads), compact angular grains (beach sand), disklike grains (lentils), and rodlike grains (rice). For circular apertures, the clogging phase diagram is found to be the same for all grain types. For narrow slit apertures and compact grains, the shape is also the same as for circular holes when expressed in terms of projected area of the aperture against the average flow direction. For lentils and rice discharged from slits, the behavior differs and may be due to alignment between grain and slit axes.

Fabrication of Porous Silicon Nitride with High Porosity by Carbothermal Reduction-reaction Bonding

By using cheaper Si, SiO2 and carbon black as starting material, the porous silicon nitride ceramics with high porosity and uniform pore structure were prepared by carbothermal reduction-reaction bonding method. The influences of Si content on the microstructure and mechanical properties of the samples were investigated. Micro- structures and mechanical properties of porous silicon nitride ceramics were studied by XRD, SEM and three-point bending measurement. XRD analysis showed that only β-Si3N4 phase, minor of -Si3N4 phase and glass phase Y3Si3O3N4 were detected in the samples. SEM analysis showed that porous silicon nitride ceramics obtained were composed of rod-like β-Si3N4 grains and uniform pores. Porous silicon nitride ceramics with different porosities and

Morphology optimization for achieving air stable and high performance organic field effect transistors

To develop an all organic active matrix light emitting display required for large area thin display, electronic paper and electronic paints, Si-based thin film transistor has to be replaced with organic thin film transistor (OTFT). The most important issues in OTFT are the low charge carrier mobility and poor stability under ambient conditions, which critically depend on how organic thin films are grown on different substrates. Here we show that both these issues are correlated and can be overcome by certain surface morphology which can only be achieved through anisotropic growth. Careful control of different growth parameters can lead to unprecedented control on thin film morphology which has been shown to be engineered reversibly and reproducibly. High temperature and low evaporation rate increase the diffusive mobility of molecules, which are responsible for the stacking of molecules to higher length scales. By carefully choosing a temperature and evaporation rate, elongated rod-like grains were grown for achieving high performance and stable thin film transistors.

TiO2 nanotube arrays induced deposition of hydroxyapatite coating by hydrothermal treatment

In recent years, the bioactivity TiO2 nanotube arrays fabricated by anodization of Titanium has attracted wide attention. TiO2 nanotube arrays in the saturated Ca(OH)2 and 0.01 mol L−1 Na2HPO4 solution induced deposition of hydroxyapatite (HAp) coating were studied in this paper. The effect of the cooling time after hydrothermal treatment, hydrothermal temperature, Na2HPO4 solution concentration on the morphology of HAp coating induced by TiO2 nanotube arrays was investigated. The results show that the formed HAp coating is in a special two-layer structure at suitable hydrothermal temperature and Na2HPO4 solution concentration: the bottom layer is weakly crystallized HAp which is short rod-like in “criss-cross” spread, while the upper layer is HAp of high-degree crystallinity which is long rod-like in scattering spread. With the increase of cooling time after hydrothermal treatment, HAp coating coverage is increased with evener distribution and the long rod-like HAp crystal grains on the upper layer grow significantly. The increase in Na2HPO4 concentration makes the boundary between the two layers of the HAP coating unclear and gradually disappears. Too low hydrothermal temperature results in failure to form “cross” structured coating on the bottom layer.

Dielectric and Ferroelectric Properties of Er<sub>2</sub>O<sub>3</sub>-Doped Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films

Er2O3-doped bismuth titanate (Bi4-xErxTi3O12, BET) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Er-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675°C to lower temperature and a improvement in dielectric property. The experimental results indicated that Er doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BET film with x=0.75 were 21 μC/cm2 and 80 kV/cm, respectively.