Slow Grain Research Articles

In situ growth and crystallization behavior of PP crystals induced by CF under supercritical N2

High-performance carbon fiber reinforced polypropylene (PP/CF) composite foams were successfully prepared using supercritical N2 as a physical blowing agent, significantly reducing raw material usage. However, the incorporation of supercritical N2 complicates the crystallization behavior of PP/CF, subsequently affects their property. Herein, this study proposes to prepare PP/CF films by solution method and observe in situ growth and crystallization behavior of PP crystals induced by CF under supercritical N2 for the first time. Numerous nucleation sites are formed in CF under supercritical N2, facilitating transcrystalline formation at the interface and confirming CF's potent heterogeneous nucleation capability. The surface tension effect of CF was visualized for the first time, noting the transformation of spherulites into dendritic structures. This transformation, becoming more pronounced with successive isothermal crystallizations, is attributed to changes in the rheological behavior of the PP melt. Furthermore, the research elucidates the mechanism behind CF-induced transcrystalline formation and the periodic growth of the crystal front under supercritical N2. A 20%CF addition reduced grain size by 41.2 % and increased grain density by 2.7 times at 130 °C. However, a higher CF content raises the interfacial free energy required for nucleation, leading to a slower grain growth rate. This work not only addresses the gap in understanding fiber-induced crystallization under supercritical gases but also lays a theoretical foundation for the crystallization behavior of other fibers under similar conditions. It provides critical insights for developing fiber-reinforced composite microcellular plastics with superior properties.

Exceptional stability of spinel Ni–MgAl2O4 catalyst with ordered mesoporous structure for dry reforming of methane

The dry reforming of methane reaction holds significant importance for the comprehensive utilization of CO2 and CH4, contributing to carbon neutrality. However, due to the high reaction temperatures, catalyst deactivation due to carbon deposition and sintering remains a challenge. In this study, a one-pot method was employed to improve the solvent evaporation self-assembly process for the preparation of Ni–MgAl2O4 catalysts. The impact of calcination temperature (600 °C, 800 °C, and 1000 °C) on the ordered mesoporous structure of the catalyst was investigated. Catalysts without an ordered mesoporous structure, such as Ni–MgAl2O4-1000, suffered deactivation due to carbon deposition caused by the large size of Ni grains, while Ni–MgAl2O4-600 deactivated due to sintering caused by the lack of confinement effect of the support on Ni. Conversely, Ni–MgAl2O4 catalysts with an ordered mesoporous structure exhibited confinement effects on Ni metal, resulting in excellent resistance to carbon deposition and sintering. Further investigation into the effect of different loading methods of Ni on methane dry reforming was conducted. A comparison was made between Ni–MgAl2O4 (800 °C) prepared by the one-pot method and Ni/MgAl2O4 (800 °C) prepared by the impregnation method. It was observed that Ni–MgAl2O4 catalysts, with Ni incorporated into the support, exhibited strong interaction between Ni and the support. During a 500-h long-term reaction, both CO2 and CH4 conversion rates remained at 90% for Ni–MgAl2O4 catalysts, with less carbon deposition and slower grain growth rate, demonstrating excellent reaction activity and stability. In contrast, the performance of Ni/MgAl2O4 catalysts gradually declined after 260 h. Ni–MgAl2O4 catalysts with ordered mesopores and strong interaction between Ni and the support displayed superior resistance to carbon deposition and sintering.

Grain growth kinetics, phase evolution during annealing and strain rate sensitivity of TRIP-assisted, dual-phase, non-equiatomic high entropy alloy

Transformation-induced plasticity-assisted dual-phase high-entropy alloys (TRIP-DP-HEAs) belong to a recently developed class of HEAs. TRIP-DP-HEAs have been reported to exhibit superior strength-ductility combination at room temperature as well as at high temperatures. Small amounts of carbon additions to TRIP-DP-HEAs are known to further improve the strength as a result of interstitial solid solution and nanoprecipitate strengthening effects. Current investigation compares the grain growth kinetics in a metastable, dual-phase (FCC and HCP), Fe49.5Mn30Co10Cr10C0.5, carbon-containing high entropy alloy (C-DP-HEA) with that in the corresponding carbon-free variant, Fe50Mn30Co10Cr10 HEA (DP-HEA). The alloys after being subjected to cold rolling, were annealed at 900 °C, 1000 °C and 1100 °C for 3, 30, 60 and 120 min, followed by water quenching. Slower grain growth kinetics was observed in C-DP-HEA due to Zener pinning by carbide particles. The activation energy for grain growth in C-DP-HEA was determined to be 339.71 kJ/mol, which is larger than that of DP-HEA (282.68 kJ/mol). The microstructures of the C-DP-HEA samples, after annealing at 900 °C for different durations of times and quenching, were investigated. The HCP phase fraction in the microstructure initially decreased with increase in annealing time/grain size and later increased with further increase in annealing time/grain size. This is explained based on the counteracting effect of grain boundary density and back stresses acting in samples having increased grain size. Strain rate sensitivity (SRS) parameter, ‘m’, was evaluated for both C-DP-HEA and DP-HEA. The strain rate jump tests were conducted at two quasi-static strain rates, 1 × 10−3 s−1 and 5 × 10−3 s−1, and at room temperature as well as at higher temperatures, 900 °C, 1000 °C and 1100 °C. The ‘m’ value was found to depend on the grain size, test temperature, and the presence of carbon in the alloy.

Facile synthesis, characterization, and mechanical properties of spinel-structured high-entropy oxides: Lattice distortion and sluggish diffusion effects induced by aluminum cation

For the first time, we adopted the in-situ formed alumina, which resulted from the thermal decomposition of cheap and accessible potassium alum, as the source of aluminum cation to synthesize (Co1/6Mn1/6Fe1/6Cr1/6Ni1/6Al1/6)3O4 spinel-structured high-entropy oxide powder after the solid state reaction process, showing the advantages of lower synthesis temperature and scalable fabrication. To investigate the effect of aluminum cation insertion on the mechanical properties of (Co1/6Mn1/6Fe1/6Cr1/6Ni1/6Al1/6)3O4, the (Co1/6Mn1/6Fe1/6Cr1/6Ni1/6Al1/6)3O4 and (Co1/5Mn1/5Fe1/5Cr1/5Ni1/5)3O4 ceramics were first fabricated and reported. Owing to significant lattice distortion induced by the aluminum cation, the (Co1/6Mn1/6Fe1/6Cr1/6Ni1/6Al1/6)3O4 possessed higher compressive strength, hardness, and elastic modulus, which were 139.3 MPa, 11.3 GPa, and 167.5 GPa, respectively. Moreover, the average grain size of (Co1/6Mn1/6Fe1/6Cr1/6Ni1/6Al1/6)3O4 only increased from 2.63 µm to 10.11 µm, while that of (Co1/5Mn1/5Fe1/5Cr1/5Ni1/5)3O4 increased from 1.77 µm to 15.61 µm. The slower grain growth rate of (Co1/6Mn1/6Fe1/6Cr1/6Ni1/6Al1/6)3O4 after aluminum cation insertion was attributed to the sluggish diffusion effect.

Flexible dual‐phase rare‐earth zirconate high‐entropy ceramic nanofibrous membranes for superior thermal insulation

AbstractCeramic fibers are potential lightweight materials for high‐temperature insulation due to their excellent high‐temperature stability and low thermal conductivity. However, the grain growth at high temperatures leads to the loss of flexibility and decreases in the thermal insulation performances of the ceramic fibers. Herein, we prepared flexible (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 (LNSGY) high‐entropy ceramic nanofibrous membranes using polyacetylacetone rare‐earth zirconium precursors by electrospinning method. According to the XRD and TEM analyses, the LNSGY nanofibrous membranes exhibited dual phases of defective fluorite and ordered pyrochlore structures. The grain size of the LNSGY fibers increased from 15.4 to 40.8 nm at heat treatments increasing from 800 to 1200°C; the slow grain growth in high‐entropy ceramic nanofibrous membranes contributed to the good flexibility. The fiber morphology was continuous and well distributed with diameters less than 500 nm. The thermal conductivity at room temperature was 0.0339 W/(m K). In addition, the high‐entropy ceramic nanofibrous membranes exhibited tensile strength and thermal stability at high temperatures. These performances provide further applications for high‐entropy ceramic nanofibrous membranes as high‐temperature insulation materials.

Relation between rheological properties and the stress state in subducting slabs

The distribution of different stress states in the subducting slab indicated by centroid moment tensor solutions for intra-slab earthquakes can help constrain the rheological properties of the slabs. A comparison of slabs in the western and eastern Pacific realms shows contrasting patterns in the stress states down to depths of ~ 350 km. The majority of slabs in the western Pacific show a pair of down-dip compression (DC) and down-dip tension (DT) domains in the upper and lower parts of the slab reflecting the effects of the slab unbending during progressive subduction. In contrast, slabs in the eastern Pacific show predominantly in-plane DT stress irrespective of slab geometry. Two-dimensional numerical simulations assuming constant slab thickness and viscosity indicate that the development of slabs with in-plane DT stress at depths of 100–300 km requires the slabs to be thin and have a low viscosity (1023 Pa s). Weak slabs bend easily and tend to fold when they encounter increased resistance to downward movement at the 660-km boundary. The associated DC stresses are not transmitted up the slab so negative buoyancy of the slab and DT stress dominates at intermediate depths for this type of slab. Most experimentally derived rheological parameters predict a high viscosity (> 1024 Pa s) for such slabs. However, two-dimensional numerical simulations using temperature- and pressure-dependent viscosity show that a relatively low activation energy (~ 110 kJ/mol) for diffusion creep is a possible explanation for the observed distribution of stresses in the slabs. Such low activation energies are compatible with recent experimental work on diffusion creep of polyphase mantle materials in which a low effective activation energy for creep results from a slow grain growth due to pinning effect of the secondary phase. The simulations provide a mechanical explanation for the observed dominantly DT stress state at 100–300 km depths for young slabs and paired DT and DC stress states at the same depth range for old slabs.Graphical

Sintering behavior and mechanism of Bi‐Zn‐Nb‐O microwave dielectric ceramics

AbstractBi‐Zn‐Nb‐O‐based microwave dielectric ceramics are promising candidates for wireless communication. Investigations have concentrated on their fabrication methods and doping modification. In this work, the densification mechanism and grain growth kinetics of the Bi‐Zn‐Nb‐O‐based microwave dielectric ceramics were explored. A significantly wide sintering temperature window (800–1000°C) of the monoclinic Bi2Zn2/3Nb4/3O7 (BZN) was found. High‐density stacking faults were observed in BZN grains at the initial stage of sintering, which could act as paths for mass transport, thus remarkably accelerating the densification process and decreasing the densification temperature. On the other hand, BZN possesses a high grain growth exponent and activation energy, which indicates a slow grain growth rate and a high threshold for abnormal grain growth, corresponding to the wide sintering temperature window. Moreover, the BZN ceramics display good microwave dielectric properties stability over a wide temperature range (25–450°C).

High strength Y2O3-stabilized zirconia continuous fibers up to 1500°C: Crystalline phase and microstructure evolution as well as grain growth kinetics

For zirconia continuous fibers, tensile strength is a very important performance parameter, which is affected by the crystal phase, its stability, grain size, processing temperatures, and so on. In this paper, the crystalline phases were adjusted through the Y2O3 contents and heat treatment temperatures in the range of 1000–1500°C. We found that interfacial segregation of Y3+ at high temperatures led to crystal phase instability, which was observed near the grain boundaries of the 13.8YSZ fibers. At high temperatures, the grain growth of different fibers occurred to different degrees. The regularities between the tensile strength, the strength retention and temperature, Y2O3 contents were discussed in detail. According to the highest tensile strength of a single fiber and Weibull modulus m, we found that the 5.4YSZ fibers were the most stable with the highest tensile strength and slow grain growth rate. The average strength was 1.6 GPa after heat-treating at 1500°C and the strength retention rate was about 54% under 1500°C for 60 min. Finally, the twistable 5.4YSZ continuous fibers with high strength were obtained by dry spinning technology. These results can provide reliable theoretical support and data sources for its high-temperature applications.

Phenomenon of anti-driving force during grain boundary migration

Grain boundary motion is a crucial process in the evolution of microstructure in materials. It is essential to comprehend the intricate behaviors associated with grain boundary migration. In this study, findings from atomistic simulations indicating that an increase in the driving force may result in slower grain boundary movement were presented. Additionally, switches in the mode of grain boundary shear coupling migration were observed. Notably, there were discernible differences in stress levels of the system and average atom energy of the grain boundary before and after the transition point. The occurrence of shear coupling behavior led to a reduction in stress. Consequently, it can be inferred that shear coupling is an effective mechanism for alleviating stress in materials. These findings provide valuable insights into the complex behaviors of grain boundary migration, as well as the potential use of shear coupling for stress relaxation and microstructure manipulation in materials.

Preparation of dense ThO2-based ceramics by Sc doping and simple sintering method

The Th1-xScxO2-x/2 (0 ≤ x ≤ 0.1) ceramic system with high density was originally prepared via a co-precipitation route and simple sintering method. XRD analysis indicates that the Th1-xScxO2-x/2 ceramics exhibited a single cubic fluorite structure and a slight increase of cell parameters. SEM images show that Sc doping contributed a decreasing pores and more uniform grain distribution. The calculated relative densities could reach up to a value higher than 99.0% for x = 0.01 during the isothermal process while the maximum actual relative density was only about 77.4% during the non-isothermal sintering process. And the analysis of grain growth kinetics demonstrates that Th1-xScxO2-x/2 was a solid solution with a high solubility of Sc for x = 0.01 and a low solubility of Sc for both x = 0.05 and x = 0.1, which resulted in a strongly slow grain growth for x = 0.1 due to the solute drag effect. The sintering mechanism investigation also illustrates that low amount (x = 0.01) of Sc doping could significantly enhance the densification sintering of ThO2-based ceramics and reduce the sintering temperature by nearly 150 °C. Such strategy has issued the bottleneck problem existed in the densification sintering of ThO2-based ceramics at a lower temperature without any other special sintering atmosphere, which even could be applicable for other ceramics difficult to sinter.

Grain boundary microstructure-property relationships in the cast & wrought Ni-based superalloy René 41 with boron and carbon additions

Cast & wrought Ni-based superalloys are required for manufacturing high-performance components in gas turbine engines. Their excellent high-temperature properties and corrosion resistance are brought about by their complex microstructure of a γ-matrix, intra- and intergranular γ' precipitates, carbides, and borides. The most highly-alloyed superalloy grades provide the high-temperature strength required for the design of next generation gas turbine engines but their processability remains challenging due to grain boundary (GB) cracking. A common mitigation approach is the addition of B and C to improve GB cohesion and strength. However, their detailed roles in GB segregation and precipitation and the link to GB properties during processing remains largely unexplored.We provide a systematic study on decorated GBs in the cast & wrought Ni-based superalloy René 41 with B and C additions. Tensile testing reveals that B additions reduce its ductility due to GB cracking but slow down grain growth during heat treatments more effectively, than C additions. GB-M2B, M6C, M23C6, and GB-γ' precipitates decorating GBs are sequentially precipitated. Their structures and compositions are shown to be unaffected by B and C additions. However, significant differences in the interfacial segregation of solutes are revealed. B is captured by GB-M2B and therefore unavailable to improve GB cohesion. C depletion and enrichment of solutes at interphase boundaries are identified as origin for the reduced ductility and thus, GB cracking. The findings are summarized as microstructural model and advance the detailed understanding of the processing – microstructure – properties relationships of cast & wrought Ni-based superalloys.

Heat stress in wheat: a global challenge to feed billions in the current era of the changing climate

Crop failure is largely caused by various climate hazards, and among them, heat stress is the primary factor hindering crop production. The significant global loss of crop yield is primarily due to heat-related damage during the reproductive phase. Terminal heat stress has been well documented in wheat, causing morphophysiological alterations, biochemical disruptions, and reduction of genetic potential. The formation of shoots and roots, the effect on the double ridge stage, and early biomass in the vegetative stage are also impacted by heat stress. The final negative outcomes of heat stress include reduced grain number and weight, slower grain filling rate, reduced grain quality, and shorter grain filling duration. Plants have developed mechanisms to adapt to heat stress through modifications in their morphological or growth responses, physiological and biochemical pathways, and changes in enzyme reactions. Numerous heat tolerance genes have been identified in wheat, but the more extensive study is needed to increase heat tolerance in crops to satisfy the food demands of the world’s growing population. The global food policy needs to prioritize and promote additional joint research and the development of heat-tolerant wheat breeding to ensure the world’s food security.

Formation of nanocrystalline AZ31B Mg alloys via cryogenic rotary swaging

A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study. The obtained alloy shows finer grains, higher strength, and a negligible tension-compression yield asymmetry, compared with that prepared via room-temperature rotary swaging. Transmission electron microscopy investigations showed that at the initial stage, multiple twins, mostly tension twins, were activated and intersected with each other, thereby refining the coarse grains into a fine lamellar structure. Then, two types of nanoscale subgrains were generated with increasing swaging strain. The first type of nanoscale subgrain contained twin boundaries and low-angle grain boundaries. This type of subgrain appeared at the twin-twin intersections and was mainly driven by high local stress. The second type of nanoscale subgrain was formed within the twin lamellae. The boundaries of this type of subgrain did not contain twin boundaries and were transformed from massive dislocation arrays. Finally, randomly oriented nanograins were obtained via dynamic recrystallization, under the combined function of deformation heat and increased stored energy. Compared with room-temperature rotary swaging, cryogenic rotary swaging exhibits a slower grain refinement process but a remarkably enhanced grain refinement effect after the same five-pass swaging.

An Integrated Bayesian Risk Model for Coastal Flow Slides Using 3-D Hydrodynamic Transport and Monte Carlo Simulation

The literature suggests two forms of flow slides: breaching and liquefaction. Both forms of failure have comparable ultimate circumstances, but the progression and sand movement mechanisms of breaching failure diverge from those of liquefaction. The first type, breaching, occurs in densely packed sand and is characterized by slow sand grain discharge throughout the dilation of the failing soil particles and negative excess pore pressures. The latter form, known as liquefaction, is the process by which a mass of soil abruptly begins to behave like a flowing liquid, and as a result, it can flow out across overly mild slopes. The process begins in compacted sand and is linked to positive surplus pore water pressures that are caused by the compaction of the sand. Despite the available literature on flow slide failures, our understanding of the mechanisms involved remains limited. Since flow slides often begin below the water surface, they can go undetected until the collapse reaches the bank above ground. The complexity of flow slides requires the use of cutting-edge technological instruments, diving equipment, advanced risk assessment, and a variety of noteworthy probabilistic and sensitivity analyses. Hence, we developed a new sensitivity index to identify the risk of breach failure and vulnerable coastal areas to this risk. In addition, we developed a sophisticated hybrid model that allows for all possibilities of flow slides in sync with random variables used in this new sensitivity index. In this new hybrid model, three distinctive models exist. The 3D Hydrodynamic Model addresses waves, wind, current, climate change, and sediment transport. The Monte Carlo Simulation is responsible for sensitivity analysis, and the Bayesian Network focuses on joint probabilities of coastal flow slide parameters of this new index that incorporates all environmental parameters, including climate change. With the assistance of these three models, researchers aim to: (a) expand the application scope by presenting a method on coastal flow slides; (b) consider different particle diameters corresponding to critical angle slope failure; (c) analyze variables that can play a pivotal role in the flow slides; and (d) present a methodology for coupling coastal flow slide projections with reliable outcomes. The hybrid model incorporates random variables of retrogressive breach failures, and the new risk index considers their ranges to control the simulation. The use of such a hybrid model and risk index offers a robust and computationally efficient approach to evaluating coastal flow slides.

Influence of ferrite-austenite distribution in 2205 duplex stainless steel on high-temperature solution nitriding behaviour

Duplex stainless steel 2205 was subjected to annealing treatments in the range of 1000–1200 °C to adjust the phase fractions of ferrite and austenite. Annealed steels were subsequently subjected to high-temperature solution nitriding, which transformed the surface-adjacent region into austenite under the influence of nitrogen ingress. Microstructural characterization of the pre-annealed state and the solution-nitrided cases were performed with X-ray diffractometry, light-optical microscopy, electron back-scatter diffraction and hardness indentation. The phase fractions of austenite and ferrite have a significant influence on the nitriding kinetics. A relatively high ferrite phase fraction results in finer grains in the nitrogen-stabilized austenite case. The developing austenite case and the evolution of the microstructure during solution nitriding are discussed in a computational thermodynamics and kinetics context. Slower grain growth in the austenite cases for higher ferrite phase fractions can be understood in terms of phase distribution, alloying element partitioning, and possibly, pinning effect by M2N nitrides.

Investigation on microstructures and properties of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy during isothermal heat treatment process

The Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy with globular microstructure was fabricated by isothermal heat treatment. The effects of isothermal temperatures and holding times on the semi-solid microstructure evolution were investigated. The results indicate that, with increase of the isothermal temperature, the average grain size increases and the spheroidization time shortens. With prolongation of holding time, the shape factor increases firstly and then decreases, and the average grain size decreases at first and then increases when the isothermal temperature is below 520 °C, however it increases gradually at 540 °C. The optimal semi-solid microstructure is obtained at 520 °C for 30 min, whose shape factor and average grain size are 0.90 and 56.4 µm, respectively. Compared with as-cast Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy, the compressive strength and plasticity of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy are increased by 36% and 108%, respectively. The formation of semi-solid microstructures includes three stages: melting separation, spheroidization, and coarsening growth. The sluggish diffusion effect of Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy leads to a low coarsening rate, resulting in slow grain growth.

Effect of oxide dispersoids on precipitation-strengthened Al-1.7Zr (wt %) alloys produced by laser powder-bed fusion

Binary Al-1.7 wt % Zr (Al-0.5 at % Zr) alloys, with and without 1 wt % (0.7 vol %) Al2O3 nanoparticle additions (80–100 nm), are fabricated by laser powder-bed fusion (L-PBF) from blends of Al, Zr, and Al2O3 powders. Elemental Zr, which is ~80 % dissolved in the melt pool, forms primary L12-Al3Zr precipitates upon solidification and is also retained in a supersaturated solid solution in the Al matrix. The primary L12-Al3Zr phase takes three forms: (i) discrete, micron-sized precipitates that nucleate fine Al matrix grains, (ii) elongated “strings” of submicron precipitates forming in highly enriched Zr regions, and (iii) < 100 nm precipitates within fine Al-grains. The Al2O3 nanodispersoid additions are either lost to slag or entrapped within Al-grains as oxide dispersoids, resulting in an oxide concentration of 0.46 wt % for the modified ODS alloy. Al2O3 nanoscale dispersoids (0.28 wt %) are also observed in the unmodified alloy, and are assumed to originate from (i) native oxides from the surface of the Al powder particles, and/or (ii) reaction with trace amounts of oxygen in the processing environment. The hardness upon aging at 400 °C reaches a peak value of ~750–850 MPa after 1.5 h, consistent with precipitation of secondary L12-Al3Zr nanoprecipitates. Upon overaging, hardness slowly decreases to 500 MPa (the as-processed value) after 1,500 h at 400 °C, with no difference observed between the Al-Zr and Al-Zr-Al2O3 alloys. Strengthening mechanisms combines Hall-Petch strengthening from micron-sized grains, Zr solid-solution strengthening, and secondary L12-Al3Zr precipitate strengthening, with slow precipitate coarsening and effective grain pinning by Al3Zr precipitates and oxide dispersoids located at grain boundaries. Creep resistance is comparable for both alloys, which show threshold stresses of ~15 and 6 MPa, at 300 and 400 °C respectively. Oxygen content analysis is recommended for all Al-based alloys fabricated via L-PBF due to the potential for non-reproducible nanoscale oxide inclusions (from native oxide on Al powders and from reaction with residual oxygen), which may affect the mechanical properties of the alloys, but are difficult to observe via SEM or TEM analysis.

Coordinating maize source and sink relationship to achieve yield potential of 22.5 Mg ha-1

Coordination between source and sink is vital for the final maize grain yield planted under high density. To clarify the source and sink characteristics of high yield potential (22.5 Mg ha-1), a four-year field experiment was conducted at Qitai Farm in Xinjiang, China. At silking, the maximum leaf area indexes were 5.8, 7.5, and 6.2 for cultivars of high yield level-1 (H1), high yield level-2 (H2), and high yield level-3 (H3) with yield increase of H1 < H2 < H3, which were 2.2, 4.6, and 3.9 at maturity, respectively. The H3 biomass was significantly higher than those of H1 and H2 during post-silking, and the H2 and H3 total kernel numbers were significantly higher than H1’s, although H2 had a significantly higher harvest ear number. While H3’s kernel size was not the largest of the three levels, H3 had a significantly higher thousand kernel weight. The grain filling analysis showed that H1 and H3 had shorter lag period durations (D1) than H2, and H3 had a longer maturation drying period duration (D3) than the other groups did. However, H1 and H3 had significantly higher grain filling rates than H2 in the lag period (D1), and H3’s was the lowest in the maturation drying period (D3). Also, H3’s maximum grain filling rate was significantly higher than H2’s, and H3 had significantly higher biomass/kernel number and kernel weight/leaf area ratios than H1 and H2 did. Based on our findings, three high yield levels were classified into three source-sink types: (1) H1: small source and weak productivity, small sink and short maturation drying period duration (D3); (2) H2: large source but weak productivity, large sink but slow grain filling start, and low maximum grain filling rate; (3) H3: small source but strong productivity, large sink, fast grain filling start, long maturation drying period duration (D3), and high maximum grain filling rate. We achieved an actual high yield of 22.4 Mg ha-1 for H3, which was also the highest yield in China. Therefore, hybrids with H3-type source and sink characteristics should be selected in the future for high-yield cultivation under dense planting.

How fluid infiltrates dry crustal rocks during progressive eclogitization and shear zone formation: insights from H2O contents in nominally anhydrous minerals

Granulites from Holsnøy (Bergen Arcs, Norway) maintained a metastable state until fluid infiltration triggered the kinetically delayed eclogitization. Interconnected hydrous eclogite-facies shear zones are surrounded by unreacted granulites. Macroscopically, the granulite–eclogite interface is sharp and there are no significant compositional changes in the bulk chemistry, indicating the fluid composition was quickly rock buffered. To better understand the link between deformation, fluid influx, and fluid–rock interaction one cm-wide shear zone at incipient eclogitization is studied here. Granulite and eclogite consist of garnet, pyroxene, and plagioclase. These nominally anhydrous minerals (NAMs) can incorporate H2O in the form of OH groups. H2O contents increase from granulite to eclogite, as documented in garnet from ~ 10 to ~ 50 µg/g H2O, pyroxene from ~ 50 to ~ 310 µg/g H2O, and granulitic plagioclase from ~ 10 to ~ 140 µg/g H2O. Bowl-shape profiles are characteristic for garnet and pyroxene with lower H2O contents in grain cores and higher at the rims, which suggest a prograde water influx into the NAMs. Omphacite displays a H2O content range from ~ 150 to 425 µg/g depending on the amount of hydrous phases surrounding the grain. The granulitic plagioclase first separates into a hydrous, more albite-rich plagioclase and isolated clinozoisite before being replaced by new fine-grained phases like clinozoisite, kyanite and quartz during ongoing fluid infiltration. Results indicate a twofold fluid influx with different mechanisms to act simultaneously at different scales and rates. Fast and more pervasive proton diffusion is recorded by NAMs that retain the major element composition of the granulite-facies equilibration where hydrogen decorates pre-existing defects in the crystal lattice and leads to OH increase. Contemporaneously, slower grain boundary-assisted aqueous fluid influx enables element transfer and results in progressive formation of new minerals, e.g., hydrous phases. Both mechanisms lead to bulk H2O increase from ~ 450 to ~ 2500 µg/g H2O towards the shear zone and convert the system from rigid to weak. The incorporation of OH groups reduces the activation energy for creep, promotes formation of smaller grain sizes (phase separation of plagioclase), and synkinematic metamorphic mineral reactions. These processes are part of the transient weakening, which enhance the sensitivity of the rock to deform.

Delayed Sowing Date Improves Rice Cooking and Taste Quality by Regulating the Quantity and Quality of Grains Located on Secondary Branches

Grains located on different positions of the panicle differed in grain weight and quality performance, however, the comprehensive effect of sowing dates on physiological and quantitative characteristics of grains located on different positions still remains unclear. In this study, a field experiment was conducted with two japonica rice cultivars, Nanjing 9108 and Ningjing 7, under 3 sowing dates (S1, 30th April; S2, 30th May; S3, 30th June). Delayed sowing treatments increased before-heading mean temperature (Tmean), day temperature (Tday), night temperature (Tnight) and mean solar radiation (Smean) for 0.94 °C, 0.99 °C, 1.23 °C, and 1.04 MJ, respectively, while decreased growth duration (GD) for 13.4 days, with 30 days delaying sowing date. Elevated before heading thermal resources and shortened GD contributed to enlarged panicle size via enhancing number of grains on secondary branches (SG) and led to higher ratio of SG per unit area (SG%). Meanwhile, delayed sowing decreased after heading Tmean, Tday, Tnight and Smean by 0.84 °C, 1.23 °C, 1.13 °C, and 2.12 MJ, respectively, with 30 days delaying sowing, and further enhanced rice stickiness (ST), peak viscosity (PKV) and breakdown (BD), but suppressed hardness (HD), amylose content (AC), cold pasting viscosity (CPV), hot pasting viscosity (HPV) and setback (SB) of SG, whilst grains on primary branches (PG) di no significant differences. Elevated taste and cooking quality of SG under delayed sowing was regulated by slower grain filling rate, which is largely regulated by AGPase and GBSS. Compared to PG, SG has better physiochemical, texture properties and RVA profiles due to its slower starch biosynthesis. The above results suggested that physiological (starch biosynthesis of SG) and quantitative parameters (amount of SG) of the rice population should be referred simultaneously to improve rice cooking and taste quality.