Similar Microstructure Research Articles

Influence of powder layer thickness on microstructure and T5 heat treatability of F357 alloy fabricated by laser powder bed fusion process

Laser powder bed fusion (LPBF) is one of the most widely used additive manufacturing (AM) methods to produce metal parts with new functionalities, but it still suffers from a low built rate. Increasing the powder layer thickness is an efficient way to augment LPBF productivity. The objective of this study is to investigate the influence of the powder layer thickness during the LPBF of F357 alloy on the microstructure and age-hardening response during T5 heat treatment. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show that microstructure differences are negligible between samples printed at 30 µm and 50 µm layer thicknesses in the as-built condition. Samples built with both layer thicknesses and subjected to T5 heat treatments at 150 °C, 160 °C, and 170 °C also show similar microstructures and their α-Al cells contain large Si precipitates and small Si clusters and no β’’-Mg2Si precipitates. Therefore, β’’-Mg2Si precipitation hardening is not the dominant mechanism, and strengthening appears to be mainly due to the small Si clusters. With the help of the Johnson-Mehl-Avrami (JMA) model, the activation energy of the precipitation process of the samples built at 30 and 50 µm layer thicknesses is calculated to be 142 kJ/mol and 139 kJ/mol, respectively. These comparable values suggest a similar evolution of the precipitation hardening for both layer thicknesses, which is consistent with the observed microstructures. Consequently, the production efficiency of LPBF-printed F357 alloys can be enhanced by using higher layer thickness and the T5 heat treatment.

Microstructure and Mechanical Properties of an Ultrahigh-strength Titanium alloy Ti-4.5Al-5Mo-5V-6Cr-1Nb Prepared Using Laser Directed Energy Deposition and Forging: A Comparative Study

The application of titanium alloys in aerospace put forward the requirement for higher strength. Additive manufacturing is a promising method for the efficient and economical processing of titanium alloys. However, research on the additive manufacturing of ultrahigh-strength titanium alloys is still limited. The mechanisms of microsegregation for high alloying elements and poor plasticity are still not clear. In this study, an ultrahigh-strength titanium alloy Ti–4.5Al–5Mo–5V–6Cr–1Nb (TB18) was prepared using two methods: laser direct energy deposition (LDED) and forging. The LDEDed alloy contains three zones with similar grain morphologies but different microstructure. The microsegregation of the alloy is limited due to the rapid solidification and almost eliminated after the thermal cycle and solution treatment. With stress relief treatment, the LDEDed alloy exhibits anisotropic mechanical properties. After solution and aging treatments, its ultimate strength is enhanced; however, its plasticity is relatively lower than that of the wrought alloy with equally high strength. The excellent balance of the strength and plasticity of the wrought alloy can be ascribed to the formation of αWGB and multiscale α laths, which provides enlightenment for optimizing the properties of the LDEDed alloy.

In-situ nitrided pulsed-laser-deposited SrTiO3 films

We demonstrate in-situ nitrogen doping of archetypal ABO3 perovskite oxide, SrTiO3. In contrast to ordinary diffusion-based high-temperature nitriding, we employ pulsed laser deposition of thin films, whereto nitrogen is introduced in-situ during the growth. The nitrided polycrystalline films on commercial silicon substrates were obtained by deposition using nitrogen gas atmosphere. The nitrogen incorporation into the films was evidenced by x-ray photoelectron spectroscopy and proven by ultra-violet spectroscopic ellipsometry. By comparing the nitrided and regular films possessing similar microstructures, effects of nitrogen substitution on the optical and electrical behavior were identified. The nitrogen doping produced noticeable changes in the optical bandgap, static dielectric permittivity, and electrical conductivity. The revealed effects are critical for applications in capacitors, varactors, resistive switching, and catalysis and deserve further studies.

Upcycling of phosphogypsum as anhydrite plaster: The positive effect of soluble phosphorus impurities

The utilization of phosphogypsum (PG) to prepare anhydrite could massively consume its stockpiling and obtain stable and excellent gypsum materials. In order to effectively recycle and reuse PG, the influence mechanism of varying forms of soluble phosphorus impurities on the properties of anhydrite should be evaluated. In this paper, original PG respectively containing H3PO4 and Ca(H2PO4)2·H2O were proposed to prepare anhydrite, and their hydration, mechanical strength, volume stability, microstructure, and pore structure were investigated. Further, the mechanism behind soluble phosphorus impurities from the insight of crystal defects was discussed. The results show that H3PO4 and Ca(H2PO4)2·H2O could accelerate the anhydrite dissolution and dihydrate gypsum nucleation due to the increased crystal defects and the formation of the nucleation site. The early mechanical strength of anhydrite significantly increased due to its high hydration degree, compact microstructure, and fine pore size. H3PO4 and Ca(H2PO4)2·H2O possessed a similar beneficial effect regardless of the content. Remarkably, H3PO4 and Ca(H2PO4)2·H2O had slight effect on the late properties of anhydrite, and all the samples presented similar mechanical strength, hydration degree, microstructure, and pore structure. This work indicates that preparing anhydrite from PG is a feasible solution to recycle PG with high efficiency and high added value without considering its unstable and diverse phosphorus impurities.

Rheological and microstructural characterisation of lotus seed milks and their glucono-δ-lactone induced acid-set milk gels: 1. Effect of protein content

The physicochemical and acid gelation properties of lotus seed milks (LSMs), total solid concentrations varying from 5 to 20 wt%, were investigated in comparison with bovine skim milk (10 wt%). LSM was prepared by soaking, blending and milling, filtering followed by α-amylose treatment to hydrolyse the starch in order to reduce its viscosity. The particle size of LSM revealed a multimodal distribution with two main size distributions, a smaller one (∼0.06 and ∼1.5 μm) from protein aggregates as a result of the heat treatment and a larger one (∼1.5 μm and ∼250 μm) likely due to the presence of undissolved protein and cellular materials. A slight shift toward higher sizes, due to further protein denaturation, can be observed after heating at 80 °C for 30 min. As expected, the viscosity of LSM depended on the total solid concentration, and was found to be similar to that of the skim milk when the LSM concentration was around 5 wt%. Addition of glucono-δ-lactone resulted in the formation of LSM gels, and the gelation of LSM occurred when the pH decreased to ∼6 while that of skim milk occurred at pH 5.2. Small deformation rheological measurements showed that it is possible to obtain a LSM acid-gels similar in viscoelastic behaviour (complex modulus G*≈300 Pa after 5 h acidification) to 10 wt% skim milk gel when the concentration of LSM is about 11.1 wt% (same dietary energy as skim milk). Confocal laser scanning microscopy showed that a similar microstructure to skim milk gel is observed for 5 wt% LSM gel, while a denser protein network with voids were observed at high LSM concentrations. The colour of these milk gels appeared white under the naked eye and their syneresis decreased sharply with the increase in concentration with a syneresis similar to that of skim milk when LSM concentration was ≥15 wt%. This study suggested for the first time the potential of LSM to be a strong alternative for the manufacture of non-animal acid milk gels.

Development of Neovasculature in Axially Vascularized Calcium Phosphate Cement Scaffolds

Augmenting the vascular supply to generate new tissues, a crucial aspect in regenerative medicine, has been challenging. Recently, our group showed that calcium phosphate can induce the formation of a functional neo-angiosome without the need for microsurgical arterial anastomosis. This was a preclinical proof of concept for biomaterial-induced luminal sprouting of large-diameter vessels. In this study, we investigated if sprouting was a general response to surgical injury or placement of an inorganic construct around the vessel. Cylindrical biocement scaffolds of differing chemistries were placed around the femoral vein. A contrast agent was used to visualize vessel ingrowth into the scaffolds. Cell populations in the scaffold were mapped using immunohistochemistry. Calcium phosphate scaffolds induced 2.7-3 times greater volume of blood vessels than calcium sulphate or magnesium phosphate scaffolds. Macrophage and vSMC populations were identified that changed spatially and temporally within the scaffold during implantation. NLRP3 inflammasome activation peaked at weeks 2 and 4 and then declined; however, IL-1β expression was sustained over the course of the experiment. IL-8, a promoter of angiogenesis, was also detected, and together, these responses suggest a role of sterile inflammation. Unexpectedly, the effect was distinct from an injury response as a result of surgical placement and also was not simply a foreign body reaction as a result of placing a rigid bioceramic next to a vein, since, while the materials tested had similar microstructures, only the calcium phosphates tested elicited an angiogenic response. This finding then reveals a potential path towards a new strategy for creating better pro-regenerative biomaterials.

Change of the frozen storage quality of concentrated Mongolian milk curd under the synergistic action of ultra-high pressure and electric field

Based on the response surface method, the curd was frozen with a low voltage electrostatic field (LVEF) at −40 °C for 30 days after being treated by 286 MPa for 19 min. Compared with natural frozen samples, LVEF can effectively reduce freezing time and thawing loss of curd by 19.1 and 5.2%, respectively. LVEF reduced the size and rounded edges of ice crystals, maintaining color and hardness. The ultra-high-pressure-assisted (HPP) not only greatly accelerates the freezing rate and reduces thawing loss, but also delays proteolysis, and reduces loss of aroma. Also, HPP increases the β-fold and decreases random curl, leading stable secondary structure of the protein. However, the HPP yellowed the curd and increased its viscoelasticity. Both HPP and LVEF greatly decreased the Total Viable Count and Lactic Acid Bacteria count in curd. The HPP-LVEF-treated curd showed 50% decrease in freezing time, and a similar microstructure to fresh curd, suggesting that HPP before freezing and a combination of LVEF during freezing could improve the quality of frozen curd.

Effect of powder recycling on inclusion content and distribution in AISI 316L produced by L-PBF technique

AISI 316 L stainless steel is widely used as material to produce components by means of additive manufacturing. To increase the circular economy, the powders are collected and re-used after the printing process, thus the effect of powder recycling on microstructure and properties of printed components is of the utmost importance. This work focused the attention on non-metallic inclusions by examining virgin and recycled powders, and products printed by using both types of powders in a laser powder bed fusion (L-PBF) process.Recycled powders exhibit an irregular shape due to fragmentation, spatters and satellites and, compared to the virgin ones, have a higher gas (O, H and C) content. Both powders contain non-metallic inclusions with a larger quantity in the recycled ones.The printed samples have a similar microstructure, however those produced by using recycled powders exhibit voids of larger size and a little greater amount of inclusions. XRD and EDS examinations of inclusions extracted from the metallic matrix showed that they consist of a mix of amorphous and crystalline silica. Large part of these particles are already present in virgin powders and only a minor part forms during repeated printing operations. Accordingly, the quality of virgin powders is the factor that mainly affects the inclusion content of printed products indicating that the powder production process is the most critical stage of the whole manufacturing process.

Optimization of process parameters and mechanism of strengthening and toughening of Nb-W alloy prepared by chemical vapor deposition based on orthogonal test

In this paper, the chemical vapor deposition (CVD) method was used to prepare Nb-W binary alloys on Mo substrates for the first time. The influences of the process parameters on the composition, average deposition rate, and average deposition efficiency of the Nb-W alloys were studied by orthogonal experiments. Nb-W alloys with W contents ranging from 0.33% to 50.48% were successfully prepared. The mechanical properties and fracture morphologies of the Nb-W alloys prepared by the CVD method (CVDNb-W alloys) were tested by metallographic microscopy, scanning electron microscopy, electron probe analysis, and in situ tensile tests. The results showed that the Nb-W alloy prepared by the CVD method had uneven macroscopic distributions of Nb and W.The substrate temperature had the greatest influence on the lateral composition gradient, and the H2 flow had the least influence. The influence of the Cl2 flow through the Nb and W on the average deposition rate was also examined. The chlorination temperature of W had the least effect on the average deposition rate, and the average deposition efficiency decreased with the increase in the gaseous chloride ratio of W. The effects of other factors on the average deposition efficiency showed different degrees of wave dynamics. The metallographic observation of 16 samples showed that except for samples 3# and 4# (in which the mass percentages of W were less than 1%), the microstructures of the other samples (in which the mass percentages of W were all more than 1%) showed similar microstructures with layered structural features. Comprehensive analysis of the sample and inverse pole figures revealed that the (101) textural component mainly existed in the CVDNb-W alloys.With the increase in the mass percentage of W, the tensile strength of the CVDNb-W alloy increased correspondingly. The maximum strength of the alloy containing 9.68% W by mass reached 475 MPa, which exceeds the room-temperature tensile strength of Nb521, but the elongation at break was related to the alloy composition. Thus, the relationship did not show a discernible trend.

Compared microstructure and properties of an AlZnMgCu alloy processed by high pressure sliding and high-pressure torsion

Achieving high yield strength via submicrometer grain size and nanoscaled precipitation has been reached in 7### aluminum alloys thanks to severe plastic deformation (SPD) by High Pressure Torsion (HPT) process. Unfortunately, this technique has inherently strong limitations since only small parts can be processed and the plastic strain is not homogeneous. These limitations prevent large scale production of Ultra Fine Grain (UFG) materials for potential applications. A recent severe plastic deformation process, High Pressure Sliding (HPS) developed by Fujioka and Horita, allows to homogeneously deform large scale sheets by shear at higher speed. In this work, the competition between precipitation, grain growth and recrystallization during heat treatments after SPD was studied in depth for an AlZnMgCu alloys deformed by HPS with two deformation levels (γ ≈ 15 and γ ≈ 20) in order to investigate if the high mechanical properties obtained by HPT can be reached by HPS. Microstructures analyses after deformation and ageing were carried out by transmission electron microscopy and in situ small angle X ray scattering and then related to the mechanical behavior evaluated by tensile tests. Experimental data show very similar microstructures after HPS and HPT, with a good thermal stability thanks to the competition between precipitation, recrystallization and recovery. The obtained microstructural features lead to exceptional yield strength (>800 MPa) as compared to the classical aluminum alloys. This study is therefore very promising towards the aim of obtaining very high yield strength aluminum alloys suitable for applications.

Application of nickel plating by galvanization on steel surface of brazed cemented carbide-maraging steel joints

Recently, the integration of a maraging steel heat treatment into a vacuum brazing has been conducted successfully to manufacture high-strength and sound cemented carbide-steel joints with elevated mechanical properties of the steel component. Besides the use of low-melting silver-based active filler alloys and cost-intensive palladium-containing filler alloys, the application of a nickel layer on the maraging steel surface by an arc-PVD process is an adequate approach to overcome the low wettability of those steels, which is caused by high fractions of elements with a high oxygen affinity like titanium and molybdenum. Though nickel plating by arc-PVD is an elaborate and time-consuming coating process, it is not suitable for industrial applications since a high vacuum is required in the specimen chamber and only a small number of specimens can be processed at the same time.Therefore, this publication evaluates the application of nickel galvanization by chemical plating and electroplating as an alternative nickel-coating method to manufacture a brazed joint between a cemented carbide and maraging steel (1.2709) component by using the copper filler metal Cu 110 (TM = 1085 °C). The electroplated and PVD-coated reference specimens featured a sound joint from a minimum nickel layer thickness of 7.0 µm with a similar microstructure consisting mainly of a copper-based fillet and a nickel-rich phase band at the maraging steel-fillet interface. The chemical-plated specimens showed excessive diffusion between the joining partners due to the presence of melting point depressant phosphor between 10.5 and 12.0 wt.-% in the applied characteristic nickel-phosphorus layer. Consequently, titanium migration occurred from the maraging steel surface to the cemented carbide-fillet interface, and columnar iron-cobalt phases formed originating from the cemented carbide into the copper-rich fillet. Except for the specimens coated with no nickel and a 2.5-µm PVD layer, all brazed joints featured a shear strength of at least 150.0 MPa. The maximum shear strength of 344.8 MPa was achieved by electroplating the maraging steel joining surface with a 20.0-µm-thick nickel layer. Moreover, the steel heat treatment was carried out successfully since an elevated and homogenous hardness of at least 648 HV1 was measured in all steel specimens after brazing.

Towards a Better Understanding of the Interaction of Fe66Cr10Nb5B19 Metallic Glass with Aluminum: Growth of Intermetallics and Formation of Kirkendall Porosity during Sintering

Metallic-glass-reinforced metal matrix composites are a novel class of composite materials, in which particles of alloys with an amorphous structure play the role of reinforcement. During the fabrication of these composites, a crystalline metal is in contact with a multicomponent alloy of an amorphous structure. In the present work, the morphological features of the reaction products formed upon the interaction of Fe66Cr10Nb5B19 metallic glass particles with aluminum were studied. The composites were processed via spark plasma sintering (SPS), hot pressing or a combination of SPS and furnace annealing. The reaction products in composites with different concentrations of the metallic glass and different transformation degrees were examined. The products of the interaction of the Fe66Cr10Nb5B19 metallic glass with Al were observed as dense layers covering the residual alloy cores, needles of FeAl3 protruding from the dense shells as well as needles and platelets of FeAl3 distributed in the residual Al matrix. The possible role of the liquid phase in the structure formation of the reaction products is discussed. The formation of needle- and platelet-shaped particles presumably occurred via crystallization from the Al-Fe-based melt, which formed locally due to the occurrence of the exothermic reactions between aluminum and iron. At the same time, aluminum atoms diffused into the solid Fe-based alloy particles, forming an intermetallic layer, which could grow until the alloy was fully transformed. When aluminum melted throughout the volume of the composite during heating of the sample above 660 °C, a similar microstructure developed. In both Al–Fe66Cr10Nb5B19 and Al–Fe systems, upon the reactive transformation, pores persistently formed in locations occupied by aluminum owing to the occurrence of the Kirkendall effect.

Fibrous or Prismatic? A Comparison of the Lamello-Fibrillar Nacre in Early Cambrian and Modern Lophotrochozoans.

The Precambrian-Cambrian interval saw the first appearance of disparate modern metazoan phyla equipped with a wide array of mineralized exo- and endo-skeletons. However, the current knowledge of this remarkable metazoan skeletonization bio-event and its environmental interactions is limited because uncertainties have persisted in determining the mineralogy, microstructure, and hierarchical complexity of these earliest animal skeletons. This study characterizes in detail a previously poorly understood fibrous microstructure-the lamello-fibrillar (LF) nacre-in early Cambrian mollusk and hyolith shells and compares it with shell microstructures in modern counterparts (coleoid cuttlebones and serpulid tubes). This comparative study highlights key differences in the LF nacre amongst different lophotrochozoan groups in terms of mineralogical compositions and architectural organization of crystals. The results demonstrate that the LF nacre is a microstructural motif confined to the Mollusca. This study demonstrates that similar fibrous microstructure in Cambrian mollusks and hyoliths actually represent a primitive type of prismatic microstructure constituted of calcitic prisms. Revision of these fibrous microstructures in Cambrian fossils demonstrates that calcitic shells are prevalent in the so-called aragonite sea of the earliest Cambrian. This has important implications for understanding the relationship between seawater chemistry and skeletal mineralogy at the time when skeletons were first acquired by early lophotrochozoan biomineralizers.

Cost‐effective suspension formulation for flexible TiB2 tapes

AbstractThe manufacturing of ultra‐high temperature ceramic materials has significantly advanced over recent years, allowing for the development of new microstructures, architectures, shapes, and geometries to explore new properties and applications for these materials beyond aerospace. For example, titanium diboride (TiB2) exhibits high electrical and thermal conductivity that could satisfy the needs of battery applications by tailoring its geometry, microstructure, and architecture. In this work, aqueous tape casting of TiB2 has been investigated. Zeta potential measurements and suspension rheology were used to understand the role of dispersant, binder, and plasticizer in the suspension and their interaction with the surface chemistry of the TiB2 particles to develop a stable, homogenous suspension, with minimum additive amounts (0%–2 wt%). Homogeneous, flexible, and strong TiB2 tapes were prepared using suspensions with 30 vol% solids and characterized to compare different compositions, mixing methods, and thicknesses. The characterization shows the tailoring of the properties as a function of the controlled suspension formulation with a minimum amount of additives. Green tapes with 2 wt% dispersants, 1 wt% binder, and 2 wt% plasticizers had similar microstructure to those with half the plasticizer but quintuple Young's modulus (1.96 GPa). The effect on other relevant properties is also discussed.

Effective grain size dependence of crack propagation resistance in low carbon steel

Unlike numerous studies focused on the crack initiation occurred in steel materials, the influence of effective grain size on crack propagation resistance does not receive enough attention and the intrinsic mechanism is not elucidated. In this work, comparable matrix microstructures with varying effective grain sizes were designed using different weld thermal simulations. Instrumented Charpy impact tests were conducted on these specimens to document the variation of fracture behaviors. The results showed that the impact toughness changes notably regardless of their similar matrix microstructure. By sub-dividing the total impact absorbed energy into two parts based on the maximum load, we find a new inverse proportional relation between the effective grain size and energy dissipation at the crack propagation stage. This new function, which is akin in form to the classical RKR model, may have board applications for optimizing the fracture behavior because it explicitly displays the effect of metallurgical factors on crack propagation resistance. This relation further implies that the crack propagation resistance is more strongly dependent on the grain size compared to the crack initiation resistance. With focus on the brittle crack propagation stage, a sharp decrease in brittle cracking speed for fine-grained specimens is attributed to the mechanism that numerous tear-ridges and side ligaments formed by local plastic deformation exert a closure stress at the wake of crack tip.

Structure evolutions of the polymer derived medium-/high-entropy metal carbides

Ceramic powders with low oxygen content are highly demanded in monolithic ceramics. In this work, a series of medium-/high-entropy ceramic (HEC) particles, including (Zr0.25Ta0.25Nb0.25Ti0.25)C, (Zr0.2Ta0.2Nb0.2Ti0.2W0.2)C, (Zr1/6Ta1/6Nb1/6Ti1/6W1/6Hf1/6)C (Zr1/7Ta1/7Nb1/7Ti1/7W1/7Hf1/7V1/7)C, and (Zr1/8Ta1/8Nb1/8Ti1/8W1/8Hf1/8V1/8Mo1/8)C, were successfully fabricated by the polymer-derived ceramic (PDC) route. The structure evolutions of the precursor demonstrated that HEC particles obtained at 1800 °C possessed a single phase and rock-salt structure. All the samples had the similar microstructures (hillock structure) and a low oxygen impurity content (less than 2.00 wt%). The results also demonstrated that the as-obtained HEC particles had a disordered distribution of elements from nanoscale to microscale. This work proved a new method to fabricate the HEC powders with low oxygen impurity content and the HEC precursors for further obtaining the nanofibers or ceramic matrix composites.

Layered transition metal oxides prepared by plasma-enhanced sintering technique as environmentally stable cathode for potassium-ion batteries

Layered transition metal oxides are deemed the most promising cathode materials for potassium-ion batteries owing to their high energy density and scalable design. However, their inherent moisture sensitivity thwarts their potential commercial realization. Herein, we show the efficacy of plasma-enhanced sintering technique in enhancing the environmental stability of K0.6Ni0.2Co0.3Mn0.5O2 layered oxide. The attained K0.6Ni0.2Co0.3Mn0.5O2 microspheres manifest a potassium-deficient surface layer that significantly suppresses surface hygroscopicity. Consequently, K0.6Ni0.2Co0.3Mn0.5O2 can be kept and handled in ambient air condition, while yet achieve competitive potassium-ion storage performance compared with other reported layered cathode materials with similar composition and microstructures. Overall, this work accentuates plasma-enhanced sintering techniques as an effective strategy to circumvent the moisture sensitivity of potassium-containing layered metal oxides, leverageable to hygroscopic layered metal oxides for other energy storage systems.

Effects of pH and incubation temperature on properties of konjac glucomannan and zein composites with or without freeze-thaw treatment

This work investigated the effect of pH and incubation temperature on the morphology and properties of konjac glucomannan (KGM)-zein composites with or without freeze-thaw treatment. When the incubation temperature was 90 °C, the composites prepared in the pH range of 10.5–11.5 were concentrated polymer solutions, while the composites prepared in the pH range of 12.0–13.0 were gels. The pH of 12.5 was found to form the composites with the most dense microstructure, the highest storage modulus and crystallinity, and the greatest ability to resist plastic deformation during compression. The composites tended to form gels with the increase of incubation temperature from 40 °C to 90 °C at pH = 12.5. The temperature of 90 °C was found to form the composites with the most dense microstructure, the greatest ability to resist plastic deformation during compression, and the highest crystallinity and frequency stability. The composite prepared at an incubation temperature of 70 °C and a pH = 12.5 had similar microstructure, rheological properties, and texture properties to that prepared at an incubation temperature of 80 °C and a pH = 12.0. The freeze-thaw treatment caused a slight increase in storage modulus (G′) and crystallinity when the composites were concentrated polymer solutions. When the composites were gels, the freeze-thaw treatment caused a rough and inhomogeneous microstructure, increased the G′ and the ability to resist plastic deformation during compression, decreased the springiness, and altered the internal water mobility. pH and incubation temperature play important roles in the morphology and properties of KGM-zein composites. • The composites were concentrated polymer solutions prepared at 80 °C and pH ≤ 11.5. • The composites were gels prepared at 40 °C–80 °C and pH = 12.5. • 70 °C and pH = 12.5 endowed the composite with similar properties to 80 °C and pH = 12.0. • Freeze-thaw treatment had different effects on gel and concentrated polymer solution.

The Effects of the Particle Size Ratio on the Behaviors of Binary Granular Materials

The particle size ratio (PSR) is an important parameter for binary granular materials, which may affect the microstructure and macro behaviors of granular materials. However, the effect of particle ratio on granular assemblies with different arrangements is still unclear. To explore and further clarify the effect of PSR in different packing structures, three types of numerical samples with regular, layered, and random packing are designed. Numerical results show that PSR has significant effects on binary granular samples with regular packing. The larger the PSR, the stronger the strength, the larger the modulus, and the smaller the angle between the shear band and the load direction. And a theoretical solution of the peak stress ratio vs. PSR is obtained for regular packing, and the results by DEM are in good agreement with the theoretical solution. Under layered packing, PSR has little effect on peak stress ratio due to similar microstructure obtained with the changing of PSR. The modulus slightly increased with the increase of PSR. Under random packing with small grain content of 50%, PSR has little effect in the range of 0.5–0.9, but in a larger range, larger PSR leads to greater modulus.

Electrocatalytic CO 2 Reduction over Bimetallic Bi-Based Catalysts: A Review

Electrocatalytic CO ₂ Reduction over Bimetallic Bi-Based Catalysts: A Review