Sintering,microstructure and mechanical properties of commercial Y-TZPs

The sintering behaviour of Y-TZP ceramics, their resulting microstructures and properties are influenced not only by the characteristics of the raw materials but also were found to be dependent on the thermal history during the fabrication process. It is generally understood that fracture toughness increases as grain size increases up to a certain limit but in the present investigation, the results obtained challenge this view. The work is concerned with grain size dependence on the mechanical properties, in particular on the fracture toughness. Two commercially available powders based on two different processing techniques (i.e. coated and co-precipitated) were studied. It has been found that both materials exhibited different fracture toughness trends. Smaller grains of coated Y-TZP resulted in high fracture toughness >12 MPa m^1/2 while the opposite effect was seen in the co-precipitated material which showed enhanced fracture toughness with increasing grain size above a certain lower limit from a nonconventional heat treatment.     

Ultrafast Sodium Full Batteries Derived from X?Fe (X = Co,Ni, Mn) Prussian Blue Analogs

Exploring high‐rate electrode materials with excellent kinetic properties is imperative for advanced sodium‐storage systems. Herein, novel cubic‐like X? Fe (X = Co, Ni, Mn) Prussian blue analogs (PBAs), as cathodes materials, are obtained through as‐tuned ionic bonding, delivering improved crystallinity and homogeneous particles size. As expected, Ni‐Fe PBAs show a capacity of 81 mAh g^?1 at 1.0 A g^?1, mainly resulting from their physical–chemical stability, fast kinetics, and “zero‐strain” insertion characteristics. Considering that the combination of elements incorporated with carbon may increase the rate of ion transfer and improve the lifetime of cycling stability, they are expected to derive binary metal‐selenide/nitrogen‐doped carbon as anodes. Among them, binary Ni_0.67Fe_0.33Se₂ coming from Ni‐Fe PBAs shows obvious core–shell structure in a dual‐carbon matrix, leading to enhanced electron interactions, electrochemical activity, and “metal‐like” conductivity, which could retain an ultralong‐term stability of 375 mAh g^?1 after 10 000 loops even at 10.0 A g^?1. The corresponding full‐cell Ni‐Fe PBAs versus Ni_0.67Fe_0.33Se₂ deliver a remarkable Na‐storage capacity of 302.2 mAh g^?1 at 1.0 A g^?1. The rational strategy is anticipated to offer more possibilities for designing advanced electrode materials used in high‐performance sodium‐ion batteries.     

Influence of texture on the mechanical properties of commercially pure magnesium prepared by powder metallurgy

In the present work the influence of texture on the mechanical properties up to 500 °C of commercially pure magnesium prepared by PM was determined. Extrusion of magnesium powders was carried out between 250 and 450 °C. All extruded materials exhibited an intense fibre texture with the basal planes parallel to the extrusion direction whose intensity increased in line with the extrusion temperature. The microstructure consisted of highly elongated magnesium powder particles. All the materials presented a heterogeneous grain size resulting from the size distribution of the original magnesium powder particles. In addition, small MgO particles were found mainly decorating the original powder boundaries. The best mechanical properties corresponded to the materials extruded at 400 and 450 °C. This behaviour was associated particularly with the intense fibre texture of these materials.     

Strain rate-dependant mechanical properties of OFHC copper

The mechanical properties of high purity copper have been extensively studied in the literature, with yield and flow stresses measured as a function of strain rate, grain size, and temperature. This paper presents a comprehensive study of the strain rate and grain size dependence of the mechanical properties of OFHC copper, including an investigation of the previously observed upturn in rate dependence of flow stress at high rates of strain (≥500 s^?1). As well as a comprehensive review of the literature, an experimental study is presented investigating the mechanical properties of OFHC copper across a range of strain rates from 10^?3 to 10⁵ s^?1, in which the copper samples were designed to minimize the effects of inertia in the testing. The experimental data from this study are compared with multiple sources from the literature varying strain rate and grain size to understand the differences between experimental results on nominally the same material. It is observed that the OFHC copper in this study showed a similar increase in flow stress with strain rate seen by other researchers at high strain rates. The major contribution to the variation between experimental results from different studies is most likely the starting internal structure for the materials, which is dependent on cold working, annealing temperature, and annealing time. In addition, the experimental variation within a particular study at a given strain rate may be due to small variations in the internal structure and the strain rate history.     

Analysis of the Solidification and Microstructure of Two Aluminium Alloys Reinforced with TiB2 Particles

Two aluminium alloys with 6 wt% TiB₂ particles are studied for applications where increased wear resistance and mechanical strength at high temperature are required. The incorporation of hard ceramic particles has a strong influence on the microstructure and properties of the alloys. TiB₂ particles play an important role in the nucleation of the different phases of the alloys during solidification, and in the reduction of grain size and porosity. The solidification patterns of Al‐Si₇Mg_0.3 + TiB₂ (6 wt%) and Al‐Cu₅MgTi + TiB₂ (6 wt%) materials are compared to their corresponding non‐reinforced alloys, and the microstructures are analyzed.     

Evaluating the microstructure and mechanical properties of friction stir processed Al–Si alloy

In this study, mechanical behaviour and microstructural evolution in friction stir processing (FSP) of casting hypereutectic A390 aluminium alloy have been investigated. The mechanical behaviour of FSP samples was investigated by measuring the strain rate sensitivity using shear punch testing. The room-temperature shear punch tests were conducted at shear strain rates in the range of 10^?4–10^?1?s^?1. The results indicate that the strain rate sensitivity index increases from about 0.015 to 0.120 for as-cast A390 after third FSP pass and then experiences a further growth in FSP passes. The increase in the grain size and CuAl₂ intermetallic particle size result in a reduction in strain sensitivity index as well as shear strength after third FSP pass.     

Damascene Light‐Weight Metals

Besides widely investigated severely plastically deformed materials that are available in laboratory scale and size only, there is a high demand for semi‐finished products such as sheets and wires with similar mechanical properties. A damascene‐like technology applying swaging and bundling/swaging allows to deform Ti? Nb? Al composites up to a log. deformation strain of 8.4. Here, Al and Ti are used because of their low density, while Nb acts as diffusion barrier to prevent the formation of hardly deformable intermetallic phases. The obtained wires show an ufg microstructure with grain sizes of Ti and Al between 100 and 200 nm. In the cold‐worked condition the wires with a density of 4.0 g cm^?3 reveal an ultimate tensile strength of 790 MPa.     

Synthesis and mechanical behavior of nanostructured materials via cryomilling

Cryomilling, the mechanical attrition of powders within a cryogenic medium, is a method of strengthening materials through grain size refinement and the dispersion of fine, nanometer-scale particles. The technique was developed as a means to decrease both the size of these particles and their spacing within a metallic matrix to increase threshold creep stress and intermediate temperature performance. More recent work has been concerned with increasing the strength of lightweight structural materials. In this overview paper, the available literature is reviewed that covers the microstructural evolution during cryomilling, consolidation and processing, the thermal stability of the microstructure, and mechanical properties of consolidated materials. The properties of cryomilled materials are compared to those results for powders and consolidated materials generated by mechanical alloying, milling at ambient temperatures and other means to produce fine grained materials.     

Ultrafast Acoustofluidic Exfoliation of Stratified Crystals

While the remarkable properties of 2D crystalline materials offer tremendous opportunities for their use in optics, electronics, energy systems, biotechnology, and catalysis, their practical implementation largely depends critically on the ability to exfoliate them from a 3D stratified bulk state. This goal nevertheless remains elusive, particularly in terms of a rapid processing method that facilitates high yield and dimension control. An ultrafast multiscale exfoliation method is reported which exploits the piezoelectricity of stratified materials that are noncentrosymmetric in nature to trigger electrically‐induced mechanical failure across weak grain boundaries associated with their crystal domain planes. In particular, it is demonstrated that microfluidic nebulization using high frequency acoustic waves exposes bulk 3D piezoelectric crystals such as molybdenum disulphide (MoS₂) and tungsten disulphide (WS₂) to a combination of extraordinarily large mechanical acceleration (≈10⁸ m s^?2) and electric field (≈10⁷ V m^?1). This results in the layered bulk material being rapidly cleaved into pristine quasi‐2D‐nanosheets that predominantly comprise single layers, thus constituting a rapid and high throughput chip‐scale method that opens new possibilities for scalable production and spray coating deposition.     

Coupling Mechanical and Electrical Properties in Spin Crossover Polymer Composites

Spin crossover particles of formula [Fe{(Htrz)₂(trz)}_0.9(NH₂‐trz)_0.3](BF₄)_1.1 and average size of 20 nm ± 8 nm are homogeneously dispersed in poly(vinylidene fluoride‐co‐trifluoro‐ethylene), P(VDF‐TrFE), and poly(vinylidene fluoride) (PVDF) matrices to form macroscopic (cm‐scale), freestanding, and flexible nanocomposite materials. The composites exhibit concomitant thermal expansion and discharge current peaks on cycling around the spin transition temperatures, i.e., new “product properties” resulting from the synergy between the particles and the matrix. Poling the P(VDF‐TrFE) (70–30 mol%) samples loaded with 25 wt% of particles in 18 MV m^?1 electric field results in a piezoelectric coefficient d₃₃ = ?3.3 pC N^?1. The poled samples display substantially amplified discharges and altered spin transition properties. Analysis of mechanical and dielectric properties reveals that both strain (1%) and permittivity (40%) changes in the composite accompany the spin transition in the particles, giving direct evidence for strong electromechanical couplings between the components. These results provide a novel route for the deployment of molecular spin crossover materials as actuators in artificial muscles and generators in thermal energy harvesting devices.     

Zum Korrosions‐ und Verschleißverhalten von Nickeldispersionsschichten mit Nanopartikeln

Corrosion and Wear Behaviour of Nickel Dispersion Coatings with Nano Particles The present study describes the results of the electrochemical deposition of Nickel dispersion coatings from a Watts electrolyte with nano‐scaled particles. Subsequently, the incorporated particles lead to different microstructures and have impact on the mechanical properties. The corrosion and wear behaviour of these layers are of high interest regarding their applications. By means of potentiodynamic measurements and optical characterisation, the corrosion behaviour can by evaluated in correlation to the applied particles and additives. Unfortunately, an improvement of corrosion protection could not be measured. From investigations by means of oscillation tribometer, it can be shown that the incorporated particles improve the wear behaviour.     

Improvement of Low‐Temperature zT in a Mg3Sb2–Mg3Bi2 Solid Solution via Mg‐Vapor Annealing

Materials with high zT over a wide temperature range are essential for thermoelectric applications. n‐Type Mg₃Sb₂‐based compounds have been shown to achieve high zT at 700 K, but their performance at low temperatures (<500 K) is compromised due to their highly resistive grain boundaries. Syntheses and optimization processes to mitigate this grain‐boundary effect has been limited due to loss of Mg, which hinders a sample's n‐type dopability. A Mg‐vapor anneal processing step that grows a sample's grain size and preserves its n‐type carrier concentration during annealing is demonstrated. The electrical conductivity and mobility of the samples with large grain size follows a phonon‐scattering‐dominated T^?3/2 trend over a large temperature range, further supporting the conclusion that the temperature‐activated mobility in Mg₃Sb₂‐based materials is caused by resistive grain boundaries. The measured Hall mobility of electrons reaches 170 cm² V^?1 s^?1 in annealed 800 °C sintered Mg_{3 + δ}Sb_1.49Bi_0.5Te_0.01, the highest ever reported for Mg₃Sb₂‐based thermoelectric materials. In particular, a sample with grain size >30 mm has a zT 0.8 at 300 K, which is comparable to commercial thermoelectric materials used at room temperature (n‐type Bi₂Te₃) while reaching zT 1.4 at 700 K, allowing applications over a wider temperature scale.     

Microstructure and mechanical properties in nano and microscale SiC-included dissimilar friction stir welding of AA6061-AA2024

This work investigates the effect of SiC particles on the microstructure and mechanical properties of dissimilar friction stir welding between AA6061-T6 and AA2024-T351. Two variations in the size of SiC particles, along the joint line, various groove width, and tool offset, were used for the welding. It was found that the joints made by rotational speed of 800?rev?min^?1, travelling speed of 31.5?mm?min^?1, groove width of 0.3?mm, and tool offset of 0.5?mm exhibited the most uniform distribution of particles for both micro- and nano-scale SiC particles. Additionally, the smaller and rounded equiaxed particles result in easier material flow, a more uniform metal matrix composite, the smallest grain size in the stir zone and the highest tensile strength.     

Oriented Arrangement: The Origin of Versatility for Porous Graphene Materials

Macroscopic porous graphene materials composed of graphene sheets have demonstrated their advantageous aspects in diverse application areas. It is essential to maximize their excellent performances by rationally controlling the sheet arrangement and pore structure. Bulk porous graphene materials with oriented pore structure and arrangement of graphene sheets are prepared by marrying electrolyte‐assisted self‐assembly and shear‐force‐induced alignment of graphene oxide sheets, and the super elasticity and anisotropic mechanical, electrical, and thermal properties induced by this unique structure are systematically investigated. Its application in pressure sensing exhibits ultrahigh sensitivity of 313.23 kPa^?1 for detecting ultralow pressure variation below 0.5 kPa, and it shows high retention rate for continuously intercepting dye molecules with a high flux of ≈18.7 L m^?2 h^?1 bar^?1 and a dynamic removal rate of 510 mg m^?2 h^?1.     

Enhancing the Sequential Conversion‐Alloying Reaction of Mixed Sn–S Hybrid Anode for Efficient Sodium Storage by a Carbon Healed Graphene Oxide

To date, the possible depletion of lithium resources has become relevant, giving rise to the interest in Na‐ion batteries (NIBs) as promising alternatives to Li‐ion batteries. While extensive investigations have examined various transition metal oxides and chalcogenides as anode materials for NIBs, few of these have been able to utilize their high specific capacity in sodium‐based systems because of their irreversibility in a charge/discharge process. Here, the mixed Sn–S nanocomposites uniformly distributed on reduced graphene oxide are prepared via a facile hydrothermal synthesis and a unique carbothermal reduction process, producing ultrafine nanoparticle with the size of 2 nm. These nanocomposites are experimentally confirmed to overcome the intrinsic drawbacks of tin sulfides such as large volume change and sluggish diffusion kinetics, demonstrating an outstanding electrochemical performance: an excellent specific capacity of 1230 mAh g^?1, and an impressive rate capability (445 mAh g^?1 at 5000 mA g^?1). The electrochemical behavior of a sequential conversion‐alloying reaction for the anode materials is investigated, revealing both the structural transition and the chemical state in the discharge/charge process. Comprehension of the reaction mechanism for the mixed Sn–S/rGO hybrid nanocomposites makes it a promising electrode material and provides a new approach for the Na‐ion battery anodes.     

Phase‐Tunable Synthesis of Ultrathin Layered Tetragonal CoSe and Nonlayered Hexagonal CoSe Nanoplates

Multiple structural phases in transition metal dichalcogenides have attracted considerable recent interest for their tunable chemical and electronic properties. Herein, a chemical vapor deposition route to ultrathin CoSe nanoplates with tunable structure phases is reported. By precisely tailoring the growth temperature, ultrathin 2D layered tetragonal CoSe nanoplates and nonlayered hexagonal CoSe nanoplates can be selectively prepared as square or hexagonal geometries, with thickness as thin as 2.3 and 3.7 nm, respectively. X‐ray diffraction, transmission electron microscopy, and selected area electron diffraction studies show that both types of nanoplates are high‐quality single crystals. Electrical transport studies reveal that both the tetragonal and hexagonal CoSe nanoplates show strong thickness‐tunable electrical properties and excellent breakdown current density. The 2D hexagonal CoSe nanoplates display metallic behavior with an excellent conductivity up to 6.6 × 10⁵ S m^?1 and an extraordinary breakdown current density up to 3.9 × 10⁷ A cm^?2, while the square tetragonal nanoplates show considerably lower conductivity up to 8.2 × 10⁴ S m^?1 with angle‐dependent magnetoresistance and weak antilocalization effect at lower field. This study offers a tunable material system for exploring multiphase 2D materials and their potential applications for electronic and magnetoelectronic devices.     

Effect of Ni and Co nanoparticle-doped flux on microstructure of SAC305 solder matrix

Microstructure of the eutectic region and β-Sn grain of the solder matrix play an important role in the properties of the Sn-based solder joint. In the present study, Ni and Co nanoparticle (NP)-doped flux were added into the SAC305 solder matrix to observe their effect on the microstructure of the eutectic region and β-Sn grain during the reflow process. Results reveal that after the addition of Ni and Co NP-doped flux, the size of β-Sn grain and the size of IMC particles present in the eutectic region significantly reduced. The area of the eutectic region also increased. Reduction in size of β-Sn grain and IMC particles improves the mechanical and structural properties of the solder joint.

     

Exploring the Nickel–Graphene Nanocomposite Coatings for Superior Corrosion Resistance: Manipulating the Effect of Deposition Current Density on its Morphology,Mechanical Properties,and Erosion‐Corrosion Performance

The use of graphene‐based composite as anti‐corrosion and protective coatings for metallic materials is still a provocative topic worthy of debate. Nickel–graphene nanocomposite coatings have been successfully fabricated onto the mild steel by electrochemical co‐deposition technique. This research demonstrates the properties of nickel–graphene composite coatings influenced by different electrodeposition current densities. The effect of deposition current density on the; surface morphologies, composition, microstructures, grain sizes, mechanical, and electrochemical properties of the composite coatings are executed. The coarseness of deposited coatings increases with the increasing of deposition current density. The carbon content in the composite coatings increases first and then decreases by further increasing of current density. The improved mechanical properties and superior anti‐corrosion performance of composite coatings are obtained at the peak value of current density of 9 A dm^?2. The incorporation of graphene sheets into nickel metal matrix lead to enhance the micro hardness, surface roughness, and adhesion strength of produced composite coatings. Furthermore, the presence of graphene in composite coating exhibits the reduced grain sizes and the enhanced erosion–corrosion resistance properties.

     

Influence of powder characteristics and powder processing routes on microstructure and properties of hot pressed silicon nitride materials

Four different commercial Si₃N₄ powders were hot pressed with the addition of La₂O₃ and Y₂O₃ as sintering aids. Two powder processing routes were set up: addition of sintering aid powders by ultrasonic dispersion, addition of nanodispersed amorphous additive species by chemical coprecipitation. The following aspects were analyzed: characteristics of starting powders and powder mixtures, with reference to surface modification (electrokinetic behaviour and surface properties) induced by the powder treatment; sintering behaviour of the powder mixtures; influence of raw powders characteristics and processing route on microstructure and properties of dense materials. The microstructural characteristics of hot pressed materials (grain size, aspect ratio, grain boundary phases) were found to be dependent on powder characteristics and its process history. Significant variation of the mechanical properties (Young modulus, hardness, toughness and strength) were related to microstructural features. Strength, for example, ranges from 600 to 1200 MPa at room temperature and from 400 to 1000 MPa at 1200°C; toughness ranges from about 4 to about 6 MPam^1/2.     

Mechanical Properties,Fatigue Life,and Electrical Conductivity of Cu–Cr–Hf Alloy after Equal Channel Angular Pressing

Structure, mechanical, and service properties of a Cu–Cr–Hf alloy after quenching, equal‐channel angular pressing (ECAP), and subsequent aging have been studied. The positive effects of ultrafine‐grained structure formation (grain/subgrain size of ≈200 nm) during ECAP and strengthening particles precipitation upon subsequent aging at 450 °C on the mechanical and fatigue properties of the alloy are shown. Ultrafine‐grained Cu–Cr–Hf alloy after aging shows increasing in the fatigue limit on the basis of 10⁷ cycles from 185 to 375 MPa relative to that of the initial coarse‐grained state. The alloy after ECAP and aging also exhibits sufficient elongation to failure (11.4%) and good electrical conductivity (78%IACS).