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Densification behavior, grain growth kinetics, mechanical and thermal properties of pressurelessly sintered zirconium diboride–silicon carbide (ZrB2–SiC) fabricated by extrusion of high solids loading pastes have been studied. The effects of sintering temperature (1600–2300°C), heating rate during constant heating rate sintering (10–50°C/min), and time during isothermal sintering (3–24 h) on density and grain size were examined. The apparent activation energy for densification was determined to be 940 ± 90 kJ/mol, suggesting lattice diffusion as the dominant sintering mechanism. Grain growth of both ZrB2 and SiC followed a normal grain growth power law with grain growth exponent n = 2 indicating diffusion‐controlled coarsening. The activation energies for grain growth were 267 ± 10 kJ/mol for ZrB2 and 264 ± 15 kJ/mol for SiC. Sintered microstructures were homogeneous with relative densities of 95%–99% depending on heat treatment schedules. Flexural strength (270 ± 40 MPa) was lower than hot‐pressed materials of equivalent composition by a factor of two or more due to the presence of pores originating from paste inhomogeneities. Young's modulus (482 ± 20 GPa) and Vicker's microhardness (22 ± 5 MPa HV0.2), as well as thermal diffusivity and thermal conductivity up to 1800°C were found to be comparable to hot‐pressed materials. [ABSTRACT FROM AUTHOR]

In the present article, the abnormal grain growth behavior of 20MnCr5 hot‐rolled bars with microalloying of 0.0198 wt% niobium low‐Nb steel (LNb) and 0.0241 wt% niobium high‐Nb steel (HNb) are investigated after heat treatment at 960 °C for 4 h. The radius of the hot‐rolled bars is 22.5 mm and the results show that the mixed grain region in LNb hot‐rolled bar is with a radius ranging from 9.5 to 22.5 mm, while the mixed grain region in HNb hot‐rolled bar is with a radius of 20 to 22.5 mm. The main precipitates are AlN and NbC, particles, and their composite precipitates. In LNb and HNb, the precipitates in outer region 1 are larger than those in inner region 3, and the number density is less. In the same region, the particle size of precipitates in LNb is larger than that in HNb, and the number density is much lower. Therefore, the mixed grains appear near the outer region of the experimental steels, and the mixed grain phenomenon of LNb is more serious than that of HNb. [ABSTRACT FROM AUTHOR]

This study investigates the influence of thermal history on grain boundary (GB) energy and the grain growth behavior of SrTiO3 at 1425°C. Two thermal profiles were explored: (1) a single‐step sintering at 1425°C for 1 h and (2) a two‐step profile with sintering completed at 1425°C for 1 h with an additional 10 h at 1350°C. Electron backscattered diffraction and atomic force microscopy were utilized to measure the grain size and GB energy distributions, respectively, for the samples before and after grain growth at 1425°C for 10 h. The two‐step profile exhibits fewer abnormal grains and a slower growth rate at 1425°C than the single‐step profile. Additionally, the two‐step sample comprises few high‐energy GBs and a narrow GB energy distribution, which suggests that it had a lower driving force for subsequent grain growth. The thermal profile was able to sufficiently change the growth rate such that the two‐step sample results in a finer grain size than observed for the single‐step sample after 10 h at 1425°C despite being exposed to elevated temperatures for almost twice as long. These results suggest that GB energy engineering through thermal profile modification can be used to control the grain growth rate and abnormal grain growth likelihood. [ABSTRACT FROM AUTHOR]

This study investigates the influence of thermal history on grain boundary (GB) energy and the grain growth behavior of SrTiO3 at 1425°C. Two thermal profiles were explored: (1) a single‐step sintering at 1425°C for 1 h and (2) a two‐step profile with sintering completed at 1425°C for 1 h with an additional 10 h at 1350°C. Electron backscattered diffraction and atomic force microscopy were utilized to measure the grain size and GB energy distributions, respectively, for the samples before and after grain growth at 1425°C for 10 h. The two‐step profile exhibits fewer abnormal grains and a slower growth rate at 1425°C than the single‐step profile. Additionally, the two‐step sample comprises few high‐energy GBs and a narrow GB energy distribution, which suggests that it had a lower driving force for subsequent grain growth. The thermal profile was able to sufficiently change the growth rate such that the two‐step sample results in a finer grain size than observed for the single‐step sample after 10 h at 1425°C despite being exposed to elevated temperatures for almost twice as long. These results suggest that GB energy engineering through thermal profile modification can be used to control the grain growth rate and abnormal grain growth likelihood. [ABSTRACT FROM AUTHOR]

In this study, a high-energy-density electrode was fabricated by combining cobalt-free layered oxide (NM) with olivine LiFePO4 (LFP) nanoparticles. The resulting mixed all-cobalt-free cathode electrode effectively minimized electrode porosity by filling the interstitial spaces between the micron-sized layered-oxide particles with nanoscale LFP particles, significantly improving electrode density, and exhibiting excellent electrode conductivity. Furthermore, the composite electrode composed of NM and LFP achieved a volumetric capacity exceeding 600 mAh/cm− 3, comparable to that of typical layered oxide cathode materials, while also demonstrating enhanced cycle-life performance relative to electrodes composed solely of layered oxide or LFP. The enhanced electrochemical performance is attributed to the efficient lithium-ion and electron conduction facilitated by the intimate contact between NM and LFP particles, the suppression of NM particle degradation due to the relatively stable LFP particles on the NM surface, and the reduced particle fracture during roll-pressing. These improvements have been confirmed through electrochemical analyses and electrode observations. [ABSTRACT FROM AUTHOR]

High pressure sintering shows great superiority in promoting the densification of the hard‐to‐densify refractory ceramics, and the underlying mechanisms are thus of great interest. In the present work, the densification process of tantalum carbide (TaC) ceramics affected by pressure was discussed through comparing the microstructural characteristics and sintering kinetics. The TaC ceramics sintered at 30–250 MPa show dense and uniform microstructure without oxide impurities and high‐density dislocations. With the increase of sintering pressure, particle rearrangement becomes prominent at initial stage, whereas grain boundary diffusion rather than lattice diffusion dominants the final stage mechanism. Grain growth is enhanced under high pressure through the plastic deformation process. Our work should facilitate to understand the mass transport mechanisms during the high pressure sintering or deformation process of carbide ceramics. [ABSTRACT FROM AUTHOR]

The effect of the flash event on grain growth behavior was examined in 8 mol% yttria-stabilized cubic zirconia (8Y-CSZ) polycrystals under direct and alternating electric fields/currents. Even at the same specimen temperature, the rate of the grain growth is accelerated in the flash event than in the heat treatment without electric field/current (0 V), suggesting that the non-thermal effect caused additionally under the flash event contributes to the acceleration of the grain growth. Although the grain growth behavior can be characterized by the empirical equation (d t n – d 0 n = kt) with the same grain growth exponent of n = 3 irrespective of the electric field/current, the activation energy for the grain growth is lowered under the flash event. This suggests that the non-thermal effect caused by the flash event does not affect the mechanism of the grain growth, but would accelerate the rate-controlling process of the grain growth. The non-thermal effects can be further accelerated in fine-grained specimens under the alternating current flash and/or by increasing the input power density. Since the grain growth is rate-controlled by the grain boundary cation diffusivity, the non-thermal effect under the flash event would accelerate the grain boundary cation diffusivities through the formation of excess oxygen vacancies depending on the polarity and the power density. [ABSTRACT FROM AUTHOR]

Large silicon nitride (Si3N4) grain can enhance thermal conductivity and fracture toughness in the Si3N4 ceramics. In this study, in order to use pores as a grain growth trigger and to achieve final densification, a limited amount of pores were introduced into the green compact. The pores were introduced by using four types of pore formers with diameters of 2, 20, 30, and 100 µm, and the pore volume was in the range of 3–18 vol%. The presence of pores promoted grain growth regardless of their diameter and volume, because no collisions occurred among the grains in the pores, and larger pores formed larger elongated grains. However, their large volume and diameter inhibited densification. Based on this tradeoff, the pore formers with a diameter of 30 µm exhibited superior properties, and fracture toughness and thermal conductivity increased to 10.2 MPa·m1/2 and 118.2 W/(m·K), respectively, as the pore volume increased to 5 vol%. These results revealed that the pores in the compacts before sintering could improve the thermal conductivity and fracture toughness if they promoted grain growth during the sintering procedure and finally disappeared. [ABSTRACT FROM AUTHOR]

The precipitate dissolution and grain growth during the solution treatment of a newly developed Ce‐containing 15Cr–22Ni–1Nb steel are investigated. The dissolution of eutectic NbC is the result of the elements diffusion along the concentration gradients, and honeycomb (Fe,Cr,Ni,Si)2(Nb,Mo) Laves phase transforms into a more stable Mo2C‐type M2C carbide. As the cerium content is increased from 0 to 0.0630 mass%, the area fraction of eutectic precipitates in forged and solution‐treated 15Cr–22Ni steel is decreased first and then increased. For the steel with 0.0055 mass% cerium content, the substantial reduction in the area fraction of precipitates during hot forging and solution treatment is ascribed to the severe abnormal grain growth. In the case of 15Cr–22Ni steel with 0.0019 and 0.0630 mass% cerium content, the average size of austenite grains after solution treatment is reduced, the multipeak development of grain size distribution is restrained, the range of grain size distribution is narrowed, and the variation coefficient of grain growth, the critical size of abnormally grown grain, and the proportion of abnormally grown grain are all decreased. The variation coefficient of grain growth and the critical size of abnormally grown grain in the steel are increased as the solution time is extended, whereas the proportion of abnormally grown grain presents a general trend of reduction. The established mathematical model of grain growth in the paper can be well applied to predict and control the average size of austenite grains in 15Cr–22Ni steel after solution treatment. [ABSTRACT FROM AUTHOR]

Skorohod and Olevsky's constitutive relation for viscous sintering (SOVS) is employed to simulate the shrinkage and relative density evolution of ceramics during the sintering process. While this model effectively simulates shrinkage and density evolution, the original formulation of the SOVS model does not explicitly incorporate grain growth or microstructural evolution. This paper introduces an enhanced version of the SOVS model, incorporating a novel calibration method to obtain the temperature dependence of the viscosity parameter. It considers grain growth as well as the evolution of the microstructure by adding new parameters. Simulations were conducted using Code_Aster, an open-source finite element software, in conjunction with MFront, a tool for formulating material behaviour equations. Dilatometer tests were performed with probes of porcelain stoneware composition to calibrate the model. The predictions of dimensional shrinkage and relative density evolution showed a high accuracy of the model (> 95%), enabling its use in the manufacturing process. [ABSTRACT FROM AUTHOR]

The densification of boron carbide based powder mixtures under flash pressure sintering was modeled. The computer model developed for this purpose was based on the Skorokhod–Olevsky–Shtern porous material densification theory and takes into account the grain growth kinetics under sintering. The model parameters were determined from the results of laboratory and computational experiments. Model adequacy was confirmed by comparison with available experimental data. [ABSTRACT FROM AUTHOR]

The influence of co--deposited hydrogen on microstructure of electrodeposited platinum (Pt) films was investigated using thermal desorption spectroscopy, X--ray diffraction and transmission electron microscopy. The Pt films were potentiostatically electrodeposited on a gold foil from a tetrachloroplatinate(II) solution at 0.1 - -0.3V vs. Ag/AgCl. From the thermal desorption spectra of hydrogen, a broad desorption peak at around 650K was observed in the Pt films deposited at 0.1 - -0.2V vs. Ag/AgCl, and a pronounced desorption peak at around 500K was observed in the Pt films deposited at -0.3V vs. Ag/AgCl. As the deposition potential was more negative, the current efficiency of Pt deposition was lower and the hydrogen concentration of Pt films was higher. These electrodeposited Pt films were consisted of fine grains of 9--17 nm, and the lattice parameter decreased with increasing hydrogen concentration. After heat treatment at 500 K, reduction of lattice contraction and increase in grain size were observed in the Pt films with higher hydrogen concentrations. The increase in grain size by the heat treatment was larger as the hydrogen concentration of Pt films was higher. Thus, it is clear that such grain growth observed in the electrodeposited Pt films was enhanced by hydrogen--induced superabundant vacancies. [ABSTRACT FROM AUTHOR]

Large‐area graphene is typically synthesized on rolled‐annealed copper foils, which require transferring to other substrates for applications. This study examines large‐area graphene growth on electrodeposited (ED) copper foils—used in lithium‐ion batteries and printed circuit boards—via plasma‐enhanced chemical vapor deposition (PECVD). It reveals that, for a set plasma power, a minimum growth time ensures full graphene coverage, leading to monolayer and then multilayer graphene, showing PECVD growth on ED copper is not self‐limited. The process also beneficially modifies the ED copper substrate, like removing the surface zinc layer and changing copper grain size and orientation, thus improving graphene growth. Additionally, the study includes high‐frequency scattering parameter (S‐parameter) measurements in a coplanar waveguide (CPW) system. This involves graphene on a sapphire substrate with a silver electrode. The S‐parameter data indicate that the CPW with graphene shows reduced insertion losses in high‐frequency circuits compared to those without graphene. This underscores graphene's role in reducing insertion losses between metallic and dielectric layers in high‐frequency settings, offering valuable insights for industrial and technological applications. [ABSTRACT FROM AUTHOR]

A new sintering technique as a combination of ultra-fast spark plasma sintering and high-pressure sintering was employed to densify UO 2 fuel pellets. UO 2 pellets with a relative density of 97.5 % and inhibited grain growth were fabricated at 1000 °C under 150 MPa within only 4.5 min. Both short sintering time and high pressure might explain the inhibited grain growth and hence finer microstructures. UO 2 fuel pellets prepared in this work exhibit excellent mechanical properties. [ABSTRACT FROM AUTHOR]

The crystalline quality and degree of c‐axis orientation of hexagonal AlN thin films correlate directly with their functional properties. Therefore, achieving AlN thin films of high crystalline quality and texture is of extraordinary importance for many applications, but particularly in electronic devices. This systematic study reveals, that the growth of c‐axis‐orientated AlN thin films can be governed by a chemical stabilization effect in addition to the conventionally known structural, strain‐induced, stabilization mechanism. The promotion of in‐plane growth of AlN grains with c‐axis out‐of‐plane orientation is demonstrated on Y, W, or Al seed layers with different thicknesses and crystallinity preliminary exposed to N2 at room temperature. It is established that the stabilization mechanism is chemical in nature: the formation of an N‐rich surface layer on the metal seed layers upon exposure to N2 pre‐determines the polarity of AlN islands at the initial stages of thin film growth while the low energy barrier for the subsequent coalescence of islands of the same polarity contributes to grain growth. These results suggest that the growth of c‐axis oriented AlN thin films can be optimized and controlled chemically, thus opening more pathways for energy‐efficient and controllable AlN thin film growth processes. [ABSTRACT FROM AUTHOR]

The challenge of producing dense fine-grained high-entropy ceramics is hereby addressed by a combined cold and conventional pressureless sintering method for the first time. It provides nearly fully dense high-entropy pyrochlores with better microstructural homogeneity, and only half the grain size of conventional pressurelessly sintered samples with identical density. Both the finer and more homogeneous microstructures benefit better mechanical properties in hardness and reduced Young's modulus. The kinetics and activation energies of both densification and grain growth were quantified and discussed to understand how cold sintering affects the microstructural evolution during the following pressureless sintering. More importantly, cathodoluminescence analysis suggested that cold sintering could cause more defects on the surface of the original particles, which could promote the grain boundary diffusion and have drag effects on grain boundary motion. The lessons learned here offer scientific understanding and technological guidance towards pressureless sintering of dense bulk high-entropy ceramics. [ABSTRACT FROM AUTHOR]

Inhibition mechanism of grain growth by metal carbide addition for WC-Co based ultrafine-grained cemented carbide was studied to develop 100 nm-grained cemented carbide. Two hypotheses of inhibition mechanism, a) inhibition by adsorption atoms at steps/kinks on WC crystal surface and b) inhibition by segregation layers on WC basal plane, were proposed. To judge which hypothesis is based on the inhibition mechanism, observation of TEM microstructure and analysis of segregation amount on WC/Co and WC/WC interfaces in WC-Co based cemented carbides including metal carbide additives were performed. Determining the presence or absence of segregation layer on WC crystal surface during liquid phase sintering was the judgement point of inhibition mechanism. The judgement was considered comparison between predictive phenomena on each hypothesis and experiment results. The experimental results supported that grain growth inhibited by adsorption atoms at steps/kinks on WC crystal surface during liquid phase sintering and segregation layer formed by precipitation during cooling after liquid phase sintering. Segregation mechanism of grain growth inhibitor was proposed based on the composition, solubility limit in liquid Co and that in solid Co of the inhibitor. Developments of 100 nm-grained WC-Co based cemented carbides with cobalt content of 4 and 10% were succeeded based on the resolution of inhibition mechanism. The hardness and transvers rupture strength of developed cemented carbides were 2300 HV and 4.7 GPa for 10%Co, 2600 HV and 3.0 GPa for 4%Co, respectively. Using the technique, 0.2 µm-grained cemented carbides were commercialized. [ABSTRACT FROM AUTHOR]

Ultrafine-grained binderless cemented carbides using 0.4 µm WC particles were prepared by adding Cr3C2, VC, TaC, βt and various sizes of Ti(C,N) particles. SEM observations of the polished and fractured surfaces revealed that the WC grains became finer after the addition of the carbides or carbonitrides. In the Ti(C,N)-added binderless cemented carbides, the WC grains became finer with decreasing Ti(C,N) particle size and increasing Ti(C,N) content. The grain size of WC in the binderless cemented carbide containing 0.1 μm Ti(C,N) was comparable to that of the Cr3C2-containing binderless cemented carbide, although not as fine as that of the VC-containing binderless cemented carbide. The binderless cemented carbides containing fine Ti(C,N) grains were harder and had higher strengths than the other carbides. The combined addition of fine Ti(C,N) and Cr3C2 resulted in more homogeneous WC grains. These results indicate that the grain growth inhibition of binderless cemented carbides varies depending on the type and grain size of the added carbonitrides. These findings will contribute to the future development of binderless cemented carbides. [ABSTRACT FROM AUTHOR]

Cemented carbide is a composite material of hard WC and soft Co, and has been widely used as a tool material because of its excellent balance of hardness and toughness. Among them, superfine cemented carbide with WC grain size of less than 1 μm is widely used as a base material for cutting tools and wear-resistant tools because it can achieve both high hardness and high strength. When using superfine cemented carbide as a cutting tool, it is essential to adopt the finer WC particles with higher Co dispersibility, in addition to the appropriate addition of grain growth inhibitors. If the WC particles can be finer, the hardness and transverse rupture strength of the alloy can be expected to improve. In addition, if Co particles, which are softer than WC particles, can be distributed more finely and homogeneously in the mixed powder, the mechanical properties of the alloy may be further improved. In this paper, we report on the improvement of Co dispersibility and the development of new ultra-fine WC, and introduce the cutting performance of the developed practical tools using above the WC powder. [ABSTRACT FROM AUTHOR]

Electrodeposited -oriented nanotwinned Cu (NT-Cu) films consist of micron-scale columnar grains and they are thermally stable up to 400 °C. By adding nanoscale equiaxed Cu grains at the bottom of the NT-Cu films, anisotropic large grain growth could be triggered below 200 °C. The grains grew over 50 μm in bonded Cu–Cu films with 5.7 μm thick. Two main factors are identified for the low thermal stability and large grain growth behavior. The grain refining and transition layer thickening are effective to lower the thermal stability of the NT-Cu and reduce the required temperature for recrystallization and grain growth in the NT-Cu film. By increasing the fine-grained layer and refining the grain size of the columnar twinned grains, anisotropic grain growth can occur at 150 °C. The low thermal stability NT-Cu can be employed to completely eliminate the bonding interface at low temperatures in Cu–Cu joints. However, when the fine-grained layer is thicker than a threshold value, normal grain takes place and the bonding interface remains. The mechanism of anisotropic large grain growth was also proposed.

The high-density Fe-6.5 wt% Si soft magnetic alloy samples were prepared using selective laser melting (SLM) technology. Annealing treatments with different temperatures were employed to promote grain growth. The microstructure, texture and magnetic hysteresis loops were characterized, aiming to investigate the relationship between microstructure and magnetic properties. The as-printed Fe-6.5 wt% Si alloy had weak texture and low density of ordered phases, and was featured by coarse grains in the top-view section and columnar grains in the side-view section. After annealing at 800 °C–1000 °C, the textures were slightly weakened, while the grain growth was not significant. Increasing the annealing temperature to 1100 °C led to abnormal grain growth behaviors. The grains of the as-printed Fe-6.5 wt% Si alloy showed randomly abnormal growth behaviors rather than oriented growth, which may be related to the low stored energy and initial size advantage before annealing. After annealed at 1100 °C for 1 h, the abnormal grain growth and the formation of large Goss ({110}) and Cube ({100}) grains resulted in microstructure coarsening and texture optimization. Thus, the corresponding ring-shaped sample exhibited excellent magnetic performance. The magnetic induction B8 is 1.21 T, the maximum relative permeability is 14.71 × 103 and the core loss P10/50 is 11.69 W/kg.

Ferroelectric ceramic capacitors have potential advantages in energy storage performance, such as high energy storage density and fast discharge speed, making them widely applicable in different energy storage devices. During heat treatment, ferroelectric ceramics undergo an evolution of grain growth leading to changes in dielectric properties. Optimizing the energy storage properties of ferroelectric ceramics during heat treatment is a crucial issue. In this work, a phase field modeling for dielectric breakdown coupled with a grain growth model is developed to give a fundamental understanding of the effect of grain growth on dielectric breakdown. In addition, this work proposes a breakdown detection method to shorten the computational time of the model. The results indicate the existence of a local maximum of the breakdown field strength during grain growth, leading to a local maximum of the energy storage density. It is found that the dielectric breakdown strength and the pattern of the final breakdown path are significantly influenced by the grain size and distribution. The model is also applicable to various dielectrics and provides guidance for the design of high-energy storage dielectrics. [ABSTRACT FROM AUTHOR]

Oxide ceramic matrix composites (Ox‐CMCs) are composed of porous matrices reinforced by dense fibers to achieve high damage tolerance. It is generally assumed that their mechanical properties are fiber dominant. However, fiber strength can also be influenced by the surrounding matrix as it can affect fiber grain growth. Fiber–matrix interactions are studied in this work regarding fiber microstructural evolution and composite strength. Minicomposites containing Nextel 610 fibers and different matrix compositions (alumina, alumina–zirconia, and mullite–alumina) are evaluated after sintering and after additional heat treatment at 1200°C for 100 h. Fiber grain growth during sintering is faster in alumina matrix and slower in mullite–alumina matrix. Scanning transmission electron microscope–energy‐dispersive X‐ray spectroscopy (STEM–EDX) measurements show that Si diffuses between fiber and matrix grain boundaries. This outward or inward diffusion of SiO2 leads to the respectively different grain growth kinetics. Grain growth inhibition in alumina–zirconia matrix is only observed after the longer heat treatment, suggesting that ZrO2 diffusion is slower than SiO2. The resultant composite strength depends not only on fiber properties, but also on matrix densification. Minicomposite with alumina–zirconia matrix showed higher strength, while mullite–alumina composites showed higher thermal stability. In summary, the properties of Ox‐CMCs can be tailored by adjusting the matrix composition with the used fibers. [ABSTRACT FROM AUTHOR]

The current research aimed to determine the contribution of dry matter (DM) stored in different plant parts to grain growth and the ability of this dry matter to compensate for the effects of the decrease in grain yield under water restrictions that occur during the post-anthesis period. This research was carried out under field conditions for 2 years in the Hatay province of Türkiye (36° 15ʹ N, 36° 13ʹ E). These cultivars were sown on 27 November in the first year and 10 December in the second year. Cultivars were sown into 6.0 × 1.2 m subplots with a row spacing of 0.20 m. The seeding density was 450 seeds m−2 in both experiments. Experiments were conducted in a randomized complete block with a split-plot arrangement with four replicates of treatments as the main plots and cultivars as the subplots. Six durum wheat cultivars were evaluated under two irrigation regimes: irrigation until physiological maturity (I1) and irrigation until anthesis (I2). Remobilization of total DM was significantly greater under I2 (1374 mg main stem−1) than that under I1 (1124 mg main stem−1). The largest share of DM remobilization in both irrigation regimes belonged to the pre-anthesis reserves. The compensatory effect of pre-anthesis DM reserves was also different in varieties. The highest value was found in the Zenit and the lowest in the Harran-95 and Amanos-97 cultivars. Because of the significant differences between the genotypes in terms of compensatory effects, it should be necessary to consider the ability to compensate for such ecological conditions and this can be an important selection feature in inbreeding. [ABSTRACT FROM AUTHOR]

Abstract The orientation and shape of ceramics grains was always neglected, resulting in a lot of information during sintering has not been excavated. In this study, a modified phase-field model in order to express the anisotropy of grain boundary energy is developed. The effects of the anisotropy of grain boundary energy on the grain orientation and shape evolution are investigated in detail. The ferroelectric ceramic thick films are prepared by tape casting. The comparison of experiment and simulation results shows that the anisotropy of grain boundary energy results in uneven grain orientation and bimodal grain size distribution. The quantitative analysis of grain microstructures helps to establish a relationship with the degree of anisotropy of grain boundary energy. Our findings provide a new way to judge the degree of anisotropy by calculating the relevant parameters in the SEM images of ceramics materials.

The challenge of preparing dense ultrafine-grained high-entropy ceramics through conventional pressureless sintering is hereby addressed by a simple two-step sintering method. Ultrafine-grained (Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2) 2 Zr 2 O 7 high-entropy zirconate with 99.2 % theoretical density and 135 nm grain size has been fabricated by pressureless two-step sintering for the first time. Compared to the conventional sintering, two-step sintering provides finer grain sizes and better microstructural uniformity, which yield excellent comprehensive mechanical properties with high hardness of 16.0 GPa, large elastic modulus of 262 GPa and high fracture toughness of 2.8 MPa·m1/2. It is believe that pressureless two-step sintering can be utilized to prepare other high-entropy ceramics with fine grain size and high quality. [ABSTRACT FROM AUTHOR]

The world race in scientific research in the fields of petroleum and how petroleum is transported to another place has inspired our scientific curiosity to research the welding bead of petroleum pipelines. This paper is an experimental examination of the response to the effect of heat treatments on the mechanical and microstructure properties of welded API X70 steel. Our study investigates how heat treatments altered the microstructure and mechanical properties of the fusion zone (FZ) in welded pipe steel of grade API X70. It shows microstructures achieved after one heat treatment at 550℃ for 1h, 2h, 3h, 4h and 5h. A metallographic test by the optical microscope and the scanning electron microscope (SEM) as well as the analysis of the samples by X-ray diffraction (XRD) and the measurement of the hardness test was applied to all the samples prepared. The results revealed that the isothermal heat treatment caused grain growth and coarsening reactions in the weld zone and the hardness of weld joints decreased were the main transformations after increasing the temperature of the heat treatment. [ABSTRACT FROM AUTHOR]

The phase transformation and nucleation growth behavior of niobium mineral phase in Bayan Obo mine under high temperature melting state were studied. The effects of different temperature mechanism, basicity (CaO/SiO2) and slag modifiers such as NaF, CaF2 and P2 Os on phase transformation and nucleation growth were emphatically investigated. The results show that the melting temperature above 1 400 °C and the crystallization temperature below 1 300 °C are the key to the phase conversion of high grade niobium ore. Control alkalinity between 1. 0 and 1. 3 is beneficial to the formation of single high grade niobium phase and the growth of grain. The addition of about 2% NaF or 2% 一 5 % CaF2 can improve the grade of Nb2O5 and grain coarsening of niobium rich phase. Although P2O5 is conducive to the transformation of niobium into a single high grade niobium mineral phase, excessive P2O5 will lead to sharp refinement of niobium phase grains. [ABSTRACT FROM AUTHOR]

Notwithstanding the impressive phase stability and low thermal conductivity exhibited by lanthanum zirconate (LZ), its low coefficient of thermal expansion is deemed a paramount limitation. In the present study, (La 1-x Y x) 2 Zr 2 O 7 with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, as new TBCs, were synthesized by reverse co-precipitation and calcination method. The XRD and Raman analyses elucidated that the substitution of Y3+ ions occurred exclusively at the La3+ positions. In addition, in accordance with FESEM and DTA findings, the incorporation of Y 2 O 3 has induced a reduction in particle size and an enhancement in crystallization resistance. The evaluation of the coefficient of thermal expansion (CTE) demonstrated a notable improvement following the introduction of Y 2 O 3. Specifically, the CTE of LZ increased from 9.34 × 10−6 °C-1 to 10.5 × 10−6 °C-1 in the case of (La 0.5 Y 0.5) 2 Zr 2 O 7 at 1100oC. Investigations of phase stability following a 50 h heat treatment at 1300oC indicated that Y 2 O 3 had no impact on phase stability. All compounds, similar to LZ, exhibited excellent phase stability. Furthermore, the addition of Y 2 O 3 significantly amplified the grain boundary diffusion mechanism during heat treatment, leading to an accelerated grain growth rate. The grain growth rate increased from 1.7 nm/h at LZ to 2.2 nm/h in the case of (La 0.6 Y 0.4) 2 Zr 2 O 7. [ABSTRACT FROM AUTHOR]

Uranium silicide (U3Si2) is regarded as a viable fuel option for improving the safety of nuclear power plants. In the present work, phase-field simulations were employed to investigate grain growth phenomena, encompassing both isotropic and anisotropic grain growth. In simulations of isotropic grain growth, it is commonly assumed that the energy and mobility of the grain boundaries (GBs) remain constant, represented by average values. The calculated grain growth kinetic rate constant, K, exhibits a close correspondence with the experimental measurements, indicating a strong agreement between the two. In simulations of anisotropic grain growth, the values of GB energy and mobility are correlated with the angular disparity between GBs. The simulation results demonstrated that the growth rate of U3Si2 can be influenced by both the energy anisotropy and mobility anisotropy of GBs. Furthermore, the anisotropy in mobility results in a greater prevalence of low-angle GB distribution in comparison to high-angle GBs. However, the energy anisotropy of GBs does not impact the frequency distribution of the angle difference between GBs. [ABSTRACT FROM AUTHOR]

The orientation and shape of ceramics grains was always neglected, resulting in a lot of information during sintering has not been excavated. In this study, a modified phase-field model in order to express the anisotropy of grain boundary energy is developed. The effects of the anisotropy of grain boundary energy on the grain orientation and shape evolution are investigated in detail. The ferroelectric ceramic thick films are prepared by tape casting. The comparison of experiment and simulation results shows that the anisotropy of grain boundary energy results in uneven grain orientation and bimodal grain size distribution. The quantitative analysis of grain microstructures helps to establish a relationship with the degree of anisotropy of grain boundary energy. Our findings provide a new way to judge the degree of anisotropy by calculating the relevant parameters in the SEM images of ceramics materials. [ABSTRACT FROM AUTHOR]

Cu–Cu joints have been adopted for ultra-high density of packaging for high-end devices. However, the processing temperature must be kept relatively low, preferably below 300 °C. In this study, a novel surface modification technique, quenching treatment, was applied to achieve Cu-to-Cu direct bonding using (111)-oriented nanotwinned Cu. The quenching treatment enabled grain growth across the Cu–Cu bonding interface at 275 °C. During quenching treatment, strain energy was induced in the Cu film, resulting in a wrinkled surface morphology. To analyze the strain energy, we utilized an electron backscattered diffraction system to obtain crystallographic information and confirmed it using kernel average misorientation analysis. [ABSTRACT FROM AUTHOR]

Core-rim structure has distinct advantage to improve the performances of KNN-based piezoceramics. Whereas the state of the core-rim structure is difficult to control during sintering. Here, the core-rim structured 0.96(K 0.51 Na 0.47 Li 0.02)(Nb 0.8 Ta 0.2)O 3 -0.04CaZrO 3 (KNLNT) ceramics were both obtained by conventional sintering (CS) and rapid sintering (RS). KNLNT ceramics prepared by rapid sintering exhibit more outstanding controllability on grain growth and core-rim structure and can hold the core/rim size ratio in a stable and favorable level due to extended effective range of grain boundary diffusion in densification. Benefiting from the controllable microstructure, the RS method prepared samples show excellent performance. The unipolar strain value of RS-1240 (S max =0.252%) is 2.07 times as much as CS-1110 (S max =0.122%). Large strain, low hysteresis and low dielectric permittivity features make the core-rim structured KNLNT ceramics a potential material for pulse drive applications and demonstrate that the manual precise control of core-rim structure could create many possibilities on materials design. [Display omitted] [ABSTRACT FROM AUTHOR]

Grain growth for various texture components in silicon steel was investigated via experiments and modeling. It was found that the clustered spatial arrangement of grains with specific orientations significantly altered the local environment for grain growth and consequently resulted in texture-differentiated grain size distribution (GSD) evolution. A novel local-field model was proposed to describe grain growth driven by continuous changing orientation and size distribution of adjacent grains. The modelling results show that the texture-differentiated grain growth in microstructure with grain clusters can produce a GSD with increased proportion in small-sized range and large-sized range by more than two-times, accompanied with an evident change in area fractions of various texture components. The effect of clustered spatial arrangement on grain growth can be precisely predicted, which is valuable to design and control the texture-differentiated GSD as well as the global GSD. [ABSTRACT FROM AUTHOR]

The ability to control the particle size of titanium dioxide nanoparticles (TNPs) is crucial for their practical use. This study presents a method for preparing monodisperse amorphous and anatase TNPs with high surface areas and tunable grain sizes. The method combines a sol-gel process with a hydrothermal process, using benzoic acid (BA) as a structure-directing agent. By adjusting the hydrolysis and condensation rates of the titanium alkoxide, we can synthesize monodisperse amorphous TNPs with a controllable size range of 200–800 nm. Additionally, the amorphous TNPs synthesized through this method serve as raw material, enabling the morphology of anatase TNPs to be inherited from amorphous TNPs with a hydrothermal reaction time of 1 h. When the hydrothermal reaction time is extended to 10 h, the closely linked primary titanium dioxide is fully separated and replaced by ultra-fine anatase TNPs. This optimal scheme show promise for self-assembly and large-scale synthesis of monodisperse amorphous and anatase TNPs. [ABSTRACT FROM AUTHOR]

Two strategies have been extensively employed to develop advanced accident tolerant fuels (ATF): improving thermal conductivity and producing large grain sized pellets. However, there are few reports on the simultaneous utilization of both strategies. In this work, we fabricated Mo–Cr alloy reinforced UO 2 (UMC) composite pellet with both high thermal conductivity and large grain size by a simple in-situ alloying method for the first time. The average grain size of UO 2 increased from 6 μm to 113 μm. Thermal conductivity of the UMC pellet (with 2 vol% Mo) at 1200 °C increased by 36.46% compared with pure UO 2. The increase rate of thermal conductivity per 1 vol% dopant reached about 18%. The Mo–Cr alloy formed continuous micro-cell layer around UO 2 particles. Such continuous micro-cell Mo–Cr alloy layer and increase of UO 2 grain size both helped improve the thermal conductivity of UMC composite pellets. Thermal expansion coefficient of the UMC under the operating temperature decreased by 11.90% compared with pure UO 2. The oxidation resistance of the UMC pellet under high temperature steam was also improved. This work provides a new strategy towards fabricating ATF with both high thermal conductivity and large grain size. [ABSTRACT FROM AUTHOR]

The effect of continuous heating after cold deformation on the microstructural evolutions and corrosion behavior of SUS 304L metastable austenitic stainless steel was investigated. After cold rolling with the reduction in thickness of 80%, a microstructure consisting of elongated grains was obtained, in which the X-ray diffraction (XRD) analysis revealed the formation of 96 vol.% strain-induced martensite. The subsequent continuous heating up to 750 °C led to full reversion/recrystallization and the development of an ultrafine grained (UFG) microstructure with an average grain size of 0.45 µm. Continuous heating up to higher temperatures resulted in a significant grain growth, where the average grain size of samples that heated up to 850, 900, 950, and 1100 °C were obtained as 2.5 µm, 5.5 µm, 14 µm, and 45 µm, respectively. The Hall-Patch relationship of H = 155 + 106/√D was developed for the dependence of hardness on the average grain size (D). By grain refinement, corrosion current density (iCorr) increased leading to the worsening of uniform corrosion resistance. However, breakdown potential (EBr) increased by grain refinement, indicating the improved pitting resistance. The Hall-patch-type equations of iCorr = 0.0147 + 0.4458/√D and EBr = 0.1964 + 0.0695/√D were proposed for correlating the corrosion parameters to D. [ABSTRACT FROM AUTHOR]

Abstract The crystalline quality and degree of c‐axis orientation of hexagonal AlN thin films correlate directly with their functional properties. Therefore, achieving AlN thin films of high crystalline quality and texture is of extraordinary importance for many applications, but particularly in electronic devices. This systematic study reveals, that the growth of c‐axis‐orientated AlN thin films can be governed by a chemical stabilization effect in addition to the conventionally known structural, strain‐induced, stabilization mechanism. The promotion of in‐plane growth of AlN grains with c‐axis out‐of‐plane orientation is demonstrated on Y, W, or Al seed layers with different thicknesses and crystallinity preliminary exposed to N2 at room temperature. It is established that the stabilization mechanism is chemical in nature: the formation of an N‐rich surface layer on the metal seed layers upon exposure to N2 pre‐determines the polarity of AlN islands at the initial stages of thin film growth while the low energy barrier for the subsequent coalescence of islands of the same polarity contributes to grain growth. These results suggest that the growth of c‐axis oriented AlN thin films can be optimized and controlled chemically, thus opening more pathways for energy‐efficient and controllable AlN thin film growth processes.

Abstract Large‐area graphene is typically synthesized on rolled‐annealed copper foils, which require transferring to other substrates for applications. This study examines large‐area graphene growth on electrodeposited (ED) copper foils—used in lithium‐ion batteries and printed circuit boards—via plasma‐enhanced chemical vapor deposition (PECVD). It reveals that, for a set plasma power, a minimum growth time ensures full graphene coverage, leading to monolayer and then multilayer graphene, showing PECVD growth on ED copper is not self‐limited. The process also beneficially modifies the ED copper substrate, like removing the surface zinc layer and changing copper grain size and orientation, thus improving graphene growth. Additionally, the study includes high‐frequency scattering parameter (S‐parameter) measurements in a coplanar waveguide (CPW) system. This involves graphene on a sapphire substrate with a silver electrode. The S‐parameter data indicate that the CPW with graphene shows reduced insertion losses in high‐frequency circuits compared to those without graphene. This underscores graphene's role in reducing insertion losses between metallic and dielectric layers in high‐frequency settings, offering valuable insights for industrial and technological applications.

The present study illustrates the mechanical and wear behaviour of Al-MWCNT composites by varying MWCNTs concentration (0 %,0.25 %, 0.50 % & 1 %) by weight in composites. These composites were synthesized through sintering in the muffle furnace after mechanical alloying which involved flattening and welding particles to form flake-shaped lamellar particles. The presence of MWCNT lamellas restricted grain growth, creating a 2D aluminium layer between the MWCNTs during sintering. Increasing the MWCNT content in aluminum refined the interlayer thickness of the composites. The compressive strength of Al is increased exponentially with the addition of CNTs. By adding CNTs to aluminium, the maximum strength was reached at 460 MPa in 1% samples, and the compression strength of the aluminium increased by 84 % as well. The sintered composites exhibited higher hardness and its value increased significantly when CNTs were added to the Al composite. The wear resistance of aluminium is substantially increased when CNTs are added, and the maximum wear resistance is achieved when CNTs are added at 0.5 wt%. The addition of CNTs reduced wear resistance, which could be attributed to the decrease in interface adhesion and agglomeration effects of CNTs.

Spark plasma sintering (SPS) is the most straightforward way to rapidly sinter nanoceramics, but the applied pressure prevents sintering of additively manufactured ceramics. Therefore, fast firing techniques such as “pressureless” SPS and ultra-fast high-temperature sintering, based on intense thermal radiation, are gaining interest. Here we compare pressure/current-assisted and pressureless SPS techniques for the rapid heating (∼300 °C/min, 5 min) of nanocrystalline zirconia with high sintering activity. The applied pressure and current indeed contributed to the lowestr temperatures needed for full densification of nanocrystalline zirconia, retaining very fine grain size, but also induced tetragonal phase transformations in the final sintering stages. When the radiative heat transfer was “decoupled” (pressureless SPS), a pronounced temperature difference between graphite crucible wall and simulated specimen temperature along with non-steady-state conditions during dwell were observed. Nevertheless, high heating rates facilitated fine and dense microstructures even in the absence of pressure/current.

This study investigates the microstructural evolution and growth behavior of intermetallic compound (IMC) layers in the Cu/(Sn-yAg, y = 0.29–2.00 wt%) system during isothermal aging within the temperature range of 433–473 K. Through systematic variations in Ag content, aging temperature, and time, the fundamental mechanisms governing IMC formation and growth in Cu/(Sn–Ag) solder joints are elucidated. The results demonstrate that IMC growth kinetics follow a power-law relationship, with IMC layer thickness increasing systematically with annealing time. The addition of Ag significantly influences IMC nucleation and growth, with higher Ag content correlating with faster growth rates. Furthermore, the temperature dependence of IMC growth rates is investigated, revealing higher temperatures leading to increased growth rates, indicative of boundary diffusion-controlled growth. By calculating activation enthalpies, values of 36.4 kJ/mol for Sn-2.00Ag and 30.2 kJ/mol for Sn-0.50Ag were obtained, providing quantitative insights into the faster growth rate of intermetallic compound thickness in the Cu/(Sn-2.00Ag) diffusion couple within the experimental temperature range. These findings offer valuable insights into factors affecting the reliability and performance of solder joints in electronic packaging applications.

The orientation (including the c axis orientation and crystal direction parallel to rolling direction) evolution of grown recrystallization grains during annealing at 250 °C for 45–180 min in Mg–Zn-Gd alloy was characterized by quasi-in-situ electron backscatter diffraction method. An unusual grain orientation rotation during the process of static recrystallization grain growth, rather than common plastic deformation or recrystallization nucleation process, was observed. Due to the higher storage energy, the growth size in the early stage of annealing (1.41 μm) is larger than that in the late stage of annealing (0.73 μm) for most (∼76%) grains, and corresponding average c-axis rotation angles are 3.65° and 1.39°, respectively, indicating that the larger the increase in grain size, the greater the changing degree in grain orientation. It is speculated that the orientation rotation during grain growth process is mediated by the interaction between dislocations and grain boundaries. The results reported in the current paper can provide a new insight into the study on the relationship between preferential grain growth and non-basal texture formation in rare earth contained Mg alloys.

Mechanical stability of freeze-casted porous alumina can be achieved by the stimulation of densification with control of the grain growth during sintering. To tailor the porous microstructure beneficially, in this study TiO2 was added and its segregation effect on the densification and its grain growth behaviors were investigated. As a result, abnormal grain growth was observed with faceted interfaces and explained by grain boundary structure dependent grain growth theory. In terms of densification, a higher bulk density was obtained with the addition of 1.5 wt% TiO2 (41.76 %TD) compared to that without doping (36.02 %TD). The benefit was evident at 1400 °C, whereas the bulk density decreased even with an addition of TiO2 above 1500 °C. This temperature dependence could be understood by a change in the dominant densification mechanism at 1500 °C, solving the puzzle of the enhanced densification only at low temperature.

It has been a common method to improve the mechanical properties of metals by manipulating their microstructures via static recrystallization, i.e., through heat treatment. Therefore, the knowledge of recrystallization and grain growth is critical to the success of the technique. In the present work, by using in-situ high temperature EBSD, the mechanisms that control recrystallization and grain growth of an extruded pure Mg were studied. The experimental results revealed that the grains of priority for dynamic recrystallization exhibit fading competitiveness under static recrystallization. It is also found that grain boundary movement or grain growth is likely to show an inverse energy gradient effect, i.e., low energy grains tend to swallow or grow into high energy grains, and grain boundaries of close to 30° exhibit superior growth advantage to others. Another finding is that {10–12} tensile twin boundaries are sites of hardly observed for recrystallization, and are finally swallowed by adjacent recrystallized grains. The above findings may give comprehensive insights of static recrystallization and grain growth of Mg, and may guide the design of advanced materials processing in microstructural engineering.

Abstract Ceramic composites based on Ce-TZP/Al2O3/H6A were sintered in order to promote grain growth and to study the effects of ZrO2 grain size on the properties of this material. A mixture of ZrO2-CeO2-Al2O3 powders was sintered at 1450 °C-2 h, following the manufacturer’s recommendations. Then, the samples were further treated at 1500 or 1600 °C, for 0, 2, 8, or 24 h. The sintered specimens were characterized by X-ray diffraction, relative density, and grain size distribution. Vickers nanohardness, Young’s modulus (E), and fracture toughness were measured. The materials showed complete densification for all sintering conditions studied. t-ZrO2, α-Al2O3, and cerium hexaluminate (H6A) were observed. The alumina and hexaluminate grains had average grain sizes of 0.7 and 4.5 μm (AR>3), respectively, without significant variations during the additional heat treatments. However, significant growth took place for the ZrO2 grains with increasing temperature and holding time, increasing the average grain size from 0.6~1.4 μm, when sintered at 1500 °C-2 h to 1600 °C-24 h, respectively. The materials exhibited Vickers nanohardness of 1800 HV and E=241±15 GPa. On the other hand, the considerable grain growth of the ZrO2 grains as a function of holding time reflected in a reduction of the fracture toughness, which decreased from 8.5 to 5.7 MPa.m1/2 for samples sintered at 1500 °C-2 h to 1600 °C-24 h, respectively.

To investigate the interconnected effects of manufacturing processes on microstructure evolution during hot-rolling, a through process model is required. A novel numerical implementation of the mean-field approach was introduced to efficiently describe the grain growth of larger systems and extended durations. In this approach, each grain is embedded within an average medium and interacts with the average medium, thus avoiding the complexities of individual grain interactions. The proposed upsampling approach dynamically adjusts the simulation grain ensemble, ensuring efficiency and accuracy regardless of the initial number of grains present. This adaptation prevents undersampling artifacts during grain growth. The accuracy of the model is verified against analytical solutions and experimental data, demonstrating high agreement. Moreover, the effects of different initial conditions are successfully investigated, demonstrating the model's versatility. Due to its simplicity and efficiency, the model can be seamlessly integrated into other microstructure evolution models. [ABSTRACT FROM AUTHOR]