Narrow Grain Research Articles

OsWOX3A is involved in negative feedback regulation of the gibberellic acid biosynthetic pathway in rice (Oryza sativa)

The plant-specific WUSCHEL-related homeobox (WOX) nuclear proteins have important roles in the transcriptional regulation of many developmental processes. Among the rice (Oryza sativa) WOX proteins, a loss of OsWOX3A function in narrow leaf2 (nal2) nal3 double mutants (termed nal2/3) causes pleiotropic effects, such as narrow and curly leaves, opened spikelets, narrow grains, more tillers, and fewer lateral roots, but almost normal plant height. To examine OsWOX3A function in more detail, transgenic rice overexpressing OsWOX3A (OsWOX3A-OX) were generated; unexpectedly, all of them consistently exhibited severe dwarfism with very short and wide leaves, a phenotype that resembles that of gibberellic acid (GA)-deficient or GA-insensitive mutants. Exogenous GA3 treatment fully rescued the developmental defects of OsWOX3A-OX plants, suggesting that constitutive overexpression of OsWOX3A downregulates GA biosynthesis. Quantitative analysis of GA intermediates revealed significantly reduced levels of GA20 and bioactive GA1 in OsWOX3A-OX, possibly due to downregulation of the expression of KAO, which encodes ent-kaurenoic acid oxidase, a GA biosynthetic enzyme. Yeast one-hybrid and electrophoretic mobility shift assays revealed that OsWOX3A directly interacts with the KAO promoter. OsWOX3A expression is drastically and temporarily upregulated by GA3 and downregulated by paclobutrazol, a blocker of GA biosynthesis. These data indicate that OsWOX3A is a GA-responsive gene and functions in the negative feedback regulation of the GA biosynthetic pathway for GA homeostasis to maintain the threshold levels of endogenous GA intermediates throughout development.

Dielectric Properties of Zr substituted Barium Strontium Titanate

The correlation between the dielectric properties and the structural characteristics of Zr substituted Ba0.6Sr0.4TiO3 (Barium Strontium Titanate) ceramics were investigated under different sintering conditions in this work. (Ba0.60Sr0.40ZryTi1−yO3) (y=0.1, 0.15 and 0.2) nanosized powders is synthesized by conventional solid state reaction method. The formation of (Ba0.60Sr0.40ZryTi1−yO3) was confirmed by XRD. The X-ray analysis reveals that all synthesized Ba0.60Sr0.40ZryTi1−yO3powders have a cubic perovskite structure. The influence of Zr content doping on the grain size and dielectric properties of BST, including dielectric constant and loss tangent were investigated. FE- SEM images show that, the average particle size is reduced with increasing Zr content and the average grain size is in the range 100–200 nm and the well dispersed nano powders have narrow grain size distribution. Dielectric characteristics were measured using Impedance Analyser over a range of frequencies (1kHz to 1MHz). The results show that, the dielectric constant has enhanced with doping of Zr whereas the loss tangent decreases. The particular composition is an excellent candidate for supercapacitor applications. The reduction in loss for Zr doped samples may be due to reduction in vacancy concentration and fine grain size of BST ceramic resulting in its excellent dielectric properties.

Identification of QTLs for grain size and characterization of the beneficial alleles of grain size genes in large grain rice variety BL129

Grain size is one of the most important agronomic components of grain yield. Grain length, width and thickness are controlled by multiple quantitative trait loci (QTLs). To understand genetic basis of large grain shape and explore the beneficial alleles for grain size improvement, we perform QTL analysis using an F2 population derived from a cross between the japonica variety Beilu 129 (BL129, wide and thick grain) and the elite indica variety Huazhan (HZ, narrow and long grain). A total number of eight major QTLs are detected on three different chromosomes. QTLs for grain width (qGW), grain thickness (qGT), brown grain width (qBGW), and brown grain thickness (qBGT) explained 77.67, 36.24, 89.63, and 39.41% of total phenotypic variation, respectively. The large grain rice variety BL129 possesses the beneficial alleles of GW2 and qSW5/GW5, which have been known to control grain width and weight, indicating that the accumulation of the beneficial alleles causes large grain shape in BL129. Further results reveal that the rare gw2 allele from BL129 increases grain width, thickness and weight of the elite indica variety Huazhan, which is used as a parental line in hybrid rice breeding. Thus, our findings will help breeders to carry out molecular design breeding on rice grain size and shape.

Ion-Assisted Plasma Etch Modeling of L1<sub>0</sub> Phase FePt Magnetic Media Fabrication With Embedded Mask Patterning Method

Embedded Mask Patterning (EMP) method uses a plasma etching process to form ultra-small but thermally stable isolated L10-FePt magnetic grains with embedded Ru hardmask1,2. It has been demonstrated as a promising and highly cost effective solution to fabricate the ultra-high density magnetic media for the next generation hard-disk drive technology, such as heat-assisted magnetic recording (HAMR). EMP process can produce recording media with extremely small and tunable grain size with narrow grain boundary thickness1. For example, at 10 Tbit/in2 recording density the required aspect ratio of vertically etched L1 0 -FePt bit is estimated as high as 4:1 with bit diameter ∼4–5nm and grain boundary ∼2–3nm. In this simulation study, we investigated manufacturability of formation of these nanometer size features in a CH 3 OH/Ar plasma etch process which is used to etch FePt through narrow Ru mask opening and to form volatile Fe-carbonyl product. With addition of Ar gas the etch selectivity of hard mask and magnetic material can be significantly improved3. In order to account for re-deposition of etch product, based on the ion-neutral synergy model4,5,6 we have formed a new chemical-physical etch rate model that also includes the effect of re-deposited etch product by calculating the re-deposition flux distribution in addition to neutral and ion flux coverage over the etch surface. Our simulation shows that the re-deposition rate can increase as etch progresses deeper into the substrate. It significantly reduces the etch rate more inside the higher aspect ratio (AR) features and produces non-uniform etched patterns across the grain boundary distribution, which may degrade media magnetic properties. The etch rate model is combined with a developed 2-D level set computational program to track the moving etch front at different etch time interval with the real-time etch rate distribution calculation. As the result, the simulation allow us to gain insights into the etch process characteristics and to help find optimal etch parameters using the EMP process to fabricate high density recording media.

Selective Formation of Zigzag Edges in Graphene Cracks.

We report the thermally induced unconventional cracking of graphene to generate zigzag edges. This crystallography-selective cracking was observed for as-grown graphene films immediately following the cooling process subsequent to chemical vapor deposition (CVD) on Cu foil. Results from Raman spectroscopy show that the crack-derived edges have smoother zigzag edges than the chemically formed grain edges of CVD graphene. Using these cracks as nanogaps, we were also able to demonstrate the carrier tuning of graphene through the electric field effect. Statistical analysis of visual observations indicated that the crack formation results from uniaxial tension imparted by the Cu substrates together with the stress concentration at notches in the polycrystalline graphene films. On the basis of simulation results using a simplified thermal shrinkage model, we propose that the cooling-induced tension is derived from the transient lattice expansion of narrow Cu grains imparted by the thermal shrinkage of adjacent Cu grains.

Infrared‐Transparent Y2O3–MgO Nanocomposites Fabricated by the Glucose Sol–Gel Combustion and Hot‐Pressing Technique

A glucose sol–gel combustion method has been developed to synthesize composite nanopowders with equal volume fractions of Y2O3 and MgO. The synthesis involves the generation of precursor foam containing Y3+ and Mg2+ cations via the chemical and thermal degradation of glucose molecules in aqueous solutions. Subsequent calcination of the foam gave the composite nanopowders uniform composition and surface areas of 44–62 m2/g depending on the relative amount of glucose. Then the nanopowder with an average particle size of 19 nm was consolidated by the hot‐pressing technique with different sintering temperatures. The fabricated nanocomposite is mid‐infrared transparent as the result of fine grains, narrow grain size distribution, and uniform phase domains. The transmittance increases with increase in the sintering temperature and reaches 83.5% at 3–5 μm mid‐infrared wave range once the temperature reaches 1350°C, which is close to the theoretical value of 85%. And it is noteworthy that the cutoff wavelength reaches 9.6 μm, which is superior to those of spinel, AlON, and sapphire. And the Vickers hardness of the sample reaches 10.0 ± 0.1 GPa, which is significantly higher than those of the coarse grained single‐phase MgO and Y2O3. The results indicate that the glucose sol–gel combustion and hot‐pressing technique is an effective method to fabricate infrared transparent Y2O3–MgO nanocomposites.

End Closure Joining of Ferritic-Martensitic and Oxide-Dispersion Strengthened Steel Cladding Tubes by Magnetic Pulse Welding

The magnetic pulse welding (MPW) technique was employed for the end closure joining of fuel pin cladding tubes made of ferritic-martensitic (FM) steel and oxide-dispersion strengthened (ODS) steel. The technique is a solid-state impact joining process based on the electromagnetic force, similar to explosive welding. For a given set of optimal process parameters, e.g., the end-plug geometry, the rigid metallurgical bonding between the tube and end plug was obtained by high-velocity impact collision accompanied with surface jetting. The joint region showed a typical wavy morphology with a narrow grain boundary-like bonding interface. There was no evidence of even local melting, and only the limited grain refinement was observed in the vicinity of the bonding interface without destructing the original reinforcement microstructure of the FM-ODS steel, i.e., a fine grain structure with oxide dispersion. No leaks were detected during helium leakage test, and moreover, the rupture occurred in the cladding tube section without leaving any joint damage during internal pressure burst test. All of the results proved the integrity and durability of the MPWed joints and signified the great potential of this method of end closure joining for advanced fast reactor fuel pin fabrication.

Microwave dielectric properties of (Ba1−xSrx)(Mg0.5W0.5)O3 ceramics

The densification, microstructural evolution and microwave dielectric properties of (Ba1−xSrx)(Mg0.5W0.5)O3 ceramics with x=0, 0.25, 0.5 and 0.75 are investigated in this study. The sintering temperature of the (Ba1−xSrx)(Mg0.5W0.5)O3 is significantly reduced from 1575°C to 1400°C as the x value increases from 0 to 0.25 and 0.50; this result is accompanied by the formation of the (Ba1−ySry)WO4 phase and a small quantity of second phase surrounding the grains. The grain size of the (Ba1−xSrx)(Mg0.5W0.5)O3 ceramics is increased by raising the Sr2+ content, which significantly lowers the sintering temperature. The microstructure of the (Ba0.75Sr0.25)(Mg0.5W0.5)O3 ceramic displays the smallest average grain size of approximately 0.8μm, with a narrow grain size distribution. Without long annealing time, very high Q×f values are obtained for the (Ba1−xSrx)(Mg0.5W0.5)O3 ceramics sintered at 1400–1575°C for a duration of only 2h. The (Ba0.75Sr0.25)(Mg0.5W0.5)O3 ceramic sintered at 1400°C results in the best microwave dielectric properties, including εr of 20.6, Q×f of 152,600GHz and τf of +24.0ppm/°C.

Influence of the textural parameters of resorcinol–formaldehyde dry polymers and carbon xerogels on particle sizes upon mechanical milling

Abstract Porous carbons find various applications in catalysis, electrochemical storage or sorption. Prior to use, their particle sizes need however to be controlled according to the targeted application. In this study, the grinding behavior of materials prepared from aqueous resorcinol–formaldehyde mixtures and displaying different pore textures was studied in detail. Both dry polymer gels and pyrolyzed carbon xerogels were compared in terms of particle size distributions after planetary ball-milling. The results show that the pore texture and the qualitative hardness of the materials have a strong influence on the grinding behavior, especially if carbon xerogels pyrolyzed before grinding are considered. On the other hand, it appears that the milling of polymer gels, followed by a pyrolysis step, is the most efficient way to obtain homogeneous particle size distributions, for all of the investigated mesopore textures. In this case, carbon particles displaying a narrow grain size distribution centered on a mode value near 10 μm are successfully obtained after similar grinding durations, with retention of the mesopore texture of the starting materials. This work also demonstrates the possibility of using mercury intrusion porosimetry as an interesting tool to assess simultaneously the mesopore dimensions and the particle sizes of porous powders.

Friction Stir Processing of Al-TiB2 In Situ Composite: Effect on Particle Distribution, Microstructure and Properties

Aluminum-based in situ composites suffer from the age-old issue of particle segregation along the grain boundaries after casting. In the present study, friction stir processing (FSP) was employed as a secondary process to improve the distribution of in situ formed TiB2 particles in Al-based composite. All the agglomerates of TiB2 were broken, and uniform distribution of particles was achieved after double-pass FSP. Also, FSP removed the casting defects and caused significant grain refinement of the Al matrix. The microstructure was characterized by equiaxed fine grains with average size of 3 µm and narrow grain size distribution. The microstructural refinements and homogenization after FSP not only enhanced the strength but also improved the ductility of the as-cast composite.

高純度3.3%Si鋼での二次再結晶発現

Possibility of the occurrence of secondary recrystallization in high purity material without containing inhibitor elements was investigated experimentally. Only in the sample with primary recrystallization annealing performed at 900°C, onset of secondary recrystallization was observed. The orientation of secondary recrystallized grains proved to be {110} <001> (Goss) orientation. It was also shown that normal grain growth was suppressed in the sample in which secondary recrystallization occurred. Narrow grain size distribution and strong texture accumulation were considered to help the stabilization of the matrix grains. Texture development during secondary recrystallization in the absence of inhibitors was discussed based on proposed growth models. It was shown from Grain Boundary Character Distribution (GBCD) analysis that the High Energy (HE) boundary model was applicable to secondary recrystallization and the Solid State Wetting (SSW) model was applicable to normal grain growth. The HE boundary was related theoretically to high mobility through high grain boundary diffusion coefficient. It was considered that reducing impurity elements exerted inherent high mobility of the HE boundary and hence led to the onset of the secondary recrystallization.

Effect of Process Parameters and Tool Geometry on Fabrication of Ni Particles Reinforced 5083 Al Composite by Friction Stir Processing

In the present study Ni particles were incorporated in 5083 Al alloy by friction stir processing (FSP) to fabricate metal particle reinforced composite. A conventional cylindrical tool was first used for FSP and several processing parameters (rotational and traverse speeds) were exploredto get a defect free stir zone and uniform distribution of the particles. The effect of tool geometry was also studied by using another tool having special features on the pin and the shoulder.A tool rotation speed of 1200rpm and traverse speed of 0.4mm/s were found to be optimum for obtaining a defect free stir zone. However, the distribution of Ni particles was inhomogeneous for all the parameters used with the plain cylindrical tool irrespective of defective or a sound stir zone.The tool with the special features, threads on the pin and spiral grooves on the shoulder, was found to be very effective in both producing a sound stir zone and dispersing the Ni particles. It was also found that ball milled fine particles were dispersed more uniformly in the stir zone compared to the as-received coarse particles. FSP also refined the grain size of the aluminium matrix from 25μm to 3μm. The microstructure was characterised by equiaxed fine grains with a high fraction of high angle grain boundaries and a narrow grain size distribution. The effect of the particle incorporation on the mechanical properties of the alloy was also investigated. The strength increased significantly compared to the base alloy and more importantly a high amount of ductility was also achieved in the composite.

Structural impact on the Hall–Petch relationship in an Al–5Mg alloy processed by high-pressure torsion

The evolution of microstructure and microhardness was studied in a commercial 5483 Al–5Mg alloy processed by high-pressure torsion (HPT) under a pressure of 6.0GPa up to 10 turns. Significant grain size refinement was observed even after 1/4 turn, and additional processing led to a further grain size reduction and a shift in the distribution of grain boundary misorientation angles towards higher values. An essentially fully homogeneous microstructure was reached after 10 turns with a final grain size of ~70nm, a saturation Vickers microhardness of Hv≈240 which was attained at and above equivalent strains of ~150, a relatively narrow grain size distribution and a fraction of ~80% of high-angle grain boundaries. Analysis shows the Hall–Petch plot deviates from the conventional linear relationship for samples processed through small numbers of turns, but after 3 or more turns there is a direct correlation between the results obtained in HPT processing and coarse-grained samples.

Fabrication and properties of TiB2-based cermets by spark plasma sintering with CoCrFeNiTiAl high-entropy alloy as sintering aid

Abstract Equiatomic CoCrFeNiTiAl high-entropy alloy (HEA) fabricated by mechanical alloying (MA) was used as sintering aid for the densification of TiB 2 by spark plasma sintering (SPS). The wettability between HEA and TiB 2 , the phases, microstructures and mechanical properties of the cermets were investigated. In the wetting analysis, excellent properties with a contact angle of 16.73° at 1420 °C was confirmed via sessile drop method. For the TiB 2 -based ceramics, no brittle phases can be detected in the XRD patterns. TEM observation revealed that there existed a narrow grain boundary between TiB 2 and the HEA. A typical structure of HEA can be observed in the liquid phase. An optimized sintering temperature of 1600 °C was determined for the preparation of the TiB 2 -5 wt.% HEA ceramics with the combination of mechanical properties, including the relative density of 99.12%, the Vickers hardness of 2356 HV5 and the flexural strength of 800.2 MPa.

Spark plasma sintering of Y2O3–MgO composite nanopowder synthesized by the esterification sol–gel route

The esterification sol–gel processed Y2O3–MgO composite nanopowder with an average grain size of 13nm was consolidated by spark plasma sintering. The fabricated nanocomposite ceramic is mid-infrared transparent as the result of fine grains, narrow grain size distribution and uniform phase domains. The grain size increased dramatically with the increase of sintering temperature. For the Y2O3–MgO nanocomposite ceramic sintered at 1100°C, the optical transmittance was greatly improved after the annealing process because of the relief of residual stress, carbides and oxygen vacancies.

Comparison of unsaturated flow and solute transport through waste rock at two experimental scales using temporal moments and numerical modeling

This study analyzed and compared unsaturated flow response and tracer breakthrough curves from a 10-m high constructed pile experiment (CPE) in the field (Antamina, Peru) and two 0.8m high laboratory-based columns. Similar materials were used at both experimental scales, with the exception of a narrower grain size distribution range for the smaller column tests. Observed results indicate that flow and solute transport regimes between experimental scales were comparable and dominated by flow and solute migration through granular matrix materials. These results are supported by analogous breakthrough curves (normalized to cross-sectional area and flow path length) that suggest observation- or smaller-scale heterogeneities within the porous media have been homogenized or smoothed at the transport-scale, long breakthrough tails, and similar recovered tracer mass fractions (i.e., 0.72–0.80) at the end of the experiment. CPE breakthrough curves do indicate a portion of the fluid flow follows rapid flow paths (open void or film flow); however, this portion accounts for a minor (i.e., ~0.1%) component of the overall flow and transport regime. Flow-corrected temporal moment analysis was used to estimate flow and transport parameter values; however large temporal variations in flow indicate that this method is better suited for conceptualizing transport regimes. In addition, a dual-porosity mobile–immobile (MIM), rate-limited mass-transfer approach was able to simulate tracer breakthrough and the dominant transport regimes from both scales. Dispersivity values used in model simulations reflect a scale-dependency, whereby column values were approximately 2× smaller than those values applied in CPE simulations. The mass-transfer coefficient, for solute transport between mobile and immobile regions, was considered as a model calibration factor. Column experiments are characterized by a larger “mobile to immobile” porosity ratio and a shorter experimental duration and flow path, which supports larger mass-transfer coefficient values (relative to the CPE). These results demonstrate that laboratory-based experiments may be able to mimic flow regimes observed in the field; however, the requirement of scale-dependent dispersivities and mass-transfer coefficients indicates that these tests may be more limited in understanding larger-scale solute transport between regions of different mobility. Nevertheless, the results of this study suggest that the reasonably simplistic modeling approaches utilized in this study may be applied at other field sites to estimate parameters and conceptualize dominant transport processes through highly heterogeneous, unsaturated material.

The Nb3Sn layers formation at diffusion annealing of Ti-doped multifilamentary Nb/Cu–Sn composites

The structure and morphology of superconducting Nb3Sn layers in multifilamentary Nb–Ti/Cu–Sn and Nb/Cu–Sn–Ti composite wires after various regimes of the diffusion annealing have been studied by transmission and scanning electron microscopy. The effect of the doping mode and Ti concentration on the thickness, structure and morphology of Nb3Sn layers is pronounced even after the first (low-temperature) stage of the diffusion annealing. After various regimes of the annealing the wires with doped bronze matrix (Nb/Cu–Sn–0.24Ti) demonstrate wider zones of fine equiaxed Nb3Sn grains with narrow grain size distributions compared to those with Ti-doped Nb filaments, which is of great importance for an attainment of the highest critical current densities Jc.

Development of fine-grain size titanium 6Al–4V alloy sheet material for low temperature superplastic forming

Fine-grained titanium 6Al–4V alloy, which typically has a grain size of about 1–2μm, can be made to superplastic form at around 800°C with special processing. The normal temperature for superplastic forming (SPF) with conventional titanium 6Al–4V sheet material is 900°C. The lower temperature performance is of interest to the Boeing Company because it can be exploited to achieve significant cost savings in processing by reducing the high-temperature oxidation of the SPF dies, improving the heater rod life for the hot presses, increasing operator safety and replacing the chemical milling operation to remove alpha case contamination with a less intensive nitric hydrofluoric acid etchant (pickle). In this report, room temperature tensile tests and elevated temperature constant strain rate tensile tests of fine-grained Ti–6Al–4V sheets provided by the Baoti Company of Xi׳an, China, were conducted according to the test method standards of ASTM-E8 and ASTM-E2448. The relationships among the processing parameters, microstructure and superplastic behavior have been analyzed. The results show that two of the samples produced met the Boeing minimum requirements for low-temperature superplasticity. The successful material was heat-treated at 800°C subsequent to hot rolling above the beta transus temperature, Tβ-(150–250°C). It was found that the sheet metal microstructure has a significant influence on superplastic formability of the Ti–6Al–4V alloy. Specifically, fine grains, a narrow grain size distribution, low grain aspect ratio and moderate β phase volume fraction can contribute to higher superplastic elongations.

Enhanced Coercivity of CaLaCo‐Doped SrM Hexaferrites by Microwave‐Calcination Technique

The effects of microwave calcination (MC) and conventional muffle furnace calcination (CC) on the microstructure and magnetic properties of M‐type hexagonal ferrite Ca0.15La0.39Sr0.46Fe11.7Co0.3O19 were investigated. The phase composition, microstructure, and magnetic properties of calcined materials were examined using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry. Experiments indicated that the MC method can achieve both pure phase, and fine and uniform grains for both calcined and sintered M‐type hexaferrites. MC treatments resulted in a magnetization at 15 kOe of 67 emu/g and an increase in coercivity by 12% over the CC technique. The improved magnetic properties resulting from microwave‐assisted calcination were attributed to the formation of a fine‐grained morphology, which yielded a narrow grain size distribution. The microwave calcinating technique was shown here to possess unique potential for fabrication of high‐performance ferrites and possibly other ceramics.

Development of uniaxial magnetocrystalline anisotropy in SrFe12−x(DyGd)xO19 thin film synthesized by incorporation of high coercivity nanoparticles in sol–gel method

SrFe12−x(DyGd)xO19 thin films with x=0–2.5 were synthesized by a sol–gel method on thermally oxidized silicon wafer (Si/SiO2). XRD patterns and FE-SEM micrographs demonstrated that single phase c-axis hexagonal ferrite films with rather narrow grain size distribution were obtained. It was found that the grain size is decreased from about 110nm (for the film with no substitution) to 35nm (for the film with the highest amount of substitution cations). AFM micrographs exhibited that the surface roughness decreases with an increase in substitution content. It was found from the VSM graphs that with an increase in substitution contents coercivity and saturation of magnetization increase. The maximum saturation of magnetization and coercivity at perpendicular direction were 250emu/g and 5.5kOe, respectively.