Low Mechanical Stability Research Articles

Simulation and analysis of suspension based single axis mems capacitive accelerometer

This paper reports a comparison of different types of springs used in MEMS based capacitive accelerometers. In this work MEMS based Single-axis accelerometers are designed using different Suspension systems. Analysis of the structure is done for resonant frequency of 2kHz. Analytical modeling of the different suspensions is presented for the specified frequency. Stress, displacement and capacitive analysis of the accelerometer is done. The sensitivity of the accelerometer with parallel beam suspension is 70nm/g, 50nm/g for folded beam suspension and 35nm/g for serpentine beam suspension. Hence parallel beam suspension has 0.7 times improved sensitivity than folded beam and 2 times better than serpentine suspension accelerometer. Whereas the stress obtained for folded beam is better than the other two. Hence Parallel beam suspension is preferred for higher sensitivity and accuracy whereas Folded beam suspension is preferred for greater structural stability By comparing these devices, it is concluded that a compromise on certain parameters is required in order meet the requirements. If there is higher displacement sensitivity then there is lower mechanical stability and vice versa. The simulations are carried out using COMSOL Multiphysics.

Effects of electrospraying parameters on deposition of La0.3Sr0.7Fe0.7Cr0.3O3−δ cathode layer on GDC

High performance in intermediate temperature solid oxide fuel cells requires improvements especially in the microstructure of the cathode layer. New cobalt-free cathode materials are used because cobalt-containing cathodes have higher thermal expansion coefficients, poor long-term chemical stability, and lower mechanical stability. Recently cobalt-free cathodes have been proposed to solve these issues by using deposition methods other than electrospray deposition (ESD). In this study, ESD method is used to develop a cobalt-free cathode layer. The electrolyte layer is gadolinium-doped ceria that is deposited with La0.3Sr0.7Fe0.7 Cr0.3O3−δ (LSFCr) prepared by 2-butoxyethanol and ethylene glycol solvents as opposed to conventional solvents. Experimental ESD parameters are tested at different levels and combinations by applying statistical experimental design methods to optimize the microstructure. Coating deposited as such demonstrated higher electrochemical performance than similar electrodes fabricated by other methods.

Enabling Durable Ultralow-k Capacitors with Enhanced Breakdown Strength in Density-Variant Nanolattices.

Ultralow-k materials used in high voltage devices require mechanical resilience and electrical and dielectric stability even when subjected to mechanical loads. Existing devices with organic polymers suffer from low thermal and mechanical stability while those with inorganic porous structures struggle with poor mechanical integrity. Recently, 3D hollow-beam nanolattices have emerged as promising candidates that satisfy these requirements. However, their properties are maintained for only five stress cycles at strains below 25%. Here,wedemonstrate that alumina nanolattices with different relative density distributions across their height elicit a deterministic mechanical response concomitant with a 1.5-3.3 times higher electrical breakdown strength than nanolattices with uniform density. These density-variant nanolattices exhibit an ultralow-k of ≈1.2, accompanied by complete electric and dielectric stability and mechanical recoverability over 100 cyclic compressions to 62.5% strain.Weexplain the enhanced insulation and long-term cyclical stability by the bi-phase deformation where the lower-density region protects the higher-density region as it is compressed before the higher-density region, allowing to simultaneously possess high strength and ductility like composites. This study highlights the superior electrical performance of the bi-phase nanolattice with a single interface in providing stable conduction and maximum breakdown strength.

Direct Ink Writing of 3D Zn Structures as High‐Capacity Anodes for Rechargeable Alkaline Batteries

The relationship between structure and performance in alkaline Zn batteries is undeniable, where anode utilization, dendrite formation, shape change, and passivation issues are all addressable through anode morphology. While tailoring 3D hosts can improve the electrode performance, these practices are inherently limited by scaffolds that increase the mass or volume. Herein, a direct write strategy for producing template‐free metallic 3D Zn electrode architectures is discussed. Concentrated inks are customized to build designs with low electrical resistivity (5 × 10−4 Ω cm), submillimeter sizes (200 μm filaments), and high mechanical stability (Young's modulus of 0.1–0.5 GPa at relative densities of 0.28–0.46). A printed Zn lattice anode versus NiOOH cathode with an alkaline polymer gel electrolyte is then demonstrated. This Zn||NiOOH cell operates for over 650 cycles at high rates of 25 mA cm−2 with an average areal capacity of 11.89 mAh cm−2, a cumulative capacity of 7.8 Ah cm−2, and a volumetric capacity of 23.78 mAh cm−3. A thicker Zn anode achieves an ultrahigh areal capacity of 85.45 mAh cm−2 and a volumetric capacity of 81.45 mAh cm−3 without significant microstructural changes after 50 cycles.

Preparation of Aerogel-like Silica Foam with the Hollow-Sphere-Based 3D Network Skeleton by the Cast-in Situ Method and Ambient Pressure Drying.

Silica aerogels have incomparable advantages among thermal insulation materials because of their ultralow density and thermal conductivity, but cumbersome production processes, high cost, and low mechanical stability limit their practical application. In this study, a novel aqueous process to prepare lightweight aerogel-like silica foams (ASFoams) through the cast-in situ method and ambient pressure drying was proposed with multiblock polyurethane surfactant as the vesicle template. ASFoams possess a unique loose stacking morphology of the silica hollow sphere with a 3D network structure as the skeleton, which endues ASFoams with a low density of 0.059 g/cm3, low thermal conductivity of 36.1 mW·k-1·m-1, and pretty good mechanical properties. These properties make ASFoams a promising option for thermal insulation in industrial, aerospace, and other extreme environmental conditions. In addition, the micromorphology of ASFoams can be adjusted by changing the reaction conditions, which may provide a facile method for the preparation of a silica aerogel-like foam with adjustable microstructure.

A Review on Photocatalytic Glass Ceramics: Fundamentals, Preparation, Performance Enhancement and Future Development

Photocatalytic technology is considered as one of the most attractive and promising technologies to directly harvest, convert and store renewable solar energy for generating sustainable and green energy and a broad range of environmental applications. However, the use of a photocatalyst in powder or coating forms restricts its applications due to its disadvantages, such as difficulty in recovery of nano-powder, secondary pollution, low adhesion between photocatalytic coating and substrate material, short service life of photocatalytic film and so on. The investigation and application of photocatalytic glass-ceramics (PGCs) in water purification, bacterial disinfection, self-cleaning and hydrogen evolution have received extensive attention due to their inherent advantages of low cost, easy fabrication, transparency, chemical and mechanical stability. Real-time solutions to energy shortage and environmental pollution faced by the development of human society can be provided by rationally designing the chemical composition and preparation methods of glass ceramics (GCs). This review introduces the concept and crystallization mechanism of PGCs and expounds on the basic mechanism of photocatalysis. Then, the key point difficulties of GCs’ design are discussed, mainly including the methods of obtaining transparency and controlling crystallization technologies. Different modification strategies to achieve better photocatalytic activity are highlighted. Finally, we look forward to further in-depth exploration and research on more efficient PGCs suitable for various applications.

Dynamic Anion Delocalization of Single-Ion Conducting Polymer Electrolyte for High-Performance of Solid-State Lithium Metal Batteries

Lithium metal batteries (LMBs) have been considered as next-generation energy storages due to their extremely high theoretical specific capacity (3860 mAh g-1). However, current LMBs, using conventional liquid electrolytes, still could not fulfill the demand of soaring expansion of energy era, such as electrical vehicles, because of their safety issues, originated by uncontrollable electrolytic side reaction on the lithium, resulting unstable solid-electrolyte interphase (SEI) and vicious lithium dendritic growth [1]. Also, carbonate-based liquid electrolytes have an intrinsic flammability, and the lithium dendrite, which short-circuits a cell, can lead to severe safety hazard with the unfavorable flammability of current liquid system when they are ignited. Therefore, solid-state electrolytes have been spotlighted recently for a pathway for safe, and high energy and power LMBs, due to their superior thermal stability and low vapor pressure, while maintaining suitable electrolytic performances.In this study, solid-state single-ion conducting polymer electrolytes (SICPEs), utilizing dynamic anion delocalization (DAD), realizing high ionic conductivity and dimensional stability for high-performance LMB, are studied. The SICPEs enable superior lithium transference number, resulting in highly reduced concentration gradient of lithium cation along the electrolyte to suppress the undesirable lithium dendritic growth. However, SICPEs have prominently lower ionic conductivity than dual-ion conducting polymer electrolyte (DICPEs), which is a critical issue to make a slower charge/discharge for SICPEs [2]. Although an approach utilizing gel polymer electrolyte (GPE), using a liquid solvent as a plasticizer, has been exploited to increase the ionic conductivity of SICPEs, GPEs have struggled with lower mechanical stability, compared to solid state, and still existing flammability issue with the plasticizer. The novel plasticizer, which is described here, can interact with bulky anionic polymer matrix, so that the negative charge can be dispersed onto the whole complex by DAD. Once the bulky complex is formed by DAD, the dissociation of lithium cation from anionic matrix can be easier with the decreased activation energy and higher ionic conduction. While increasing the ionic conductivity with DAD, the nature of polymeric plasticizer will highly suppress flammability. DAD allows the membrane endure more tensile strength due to the dynamic structural change in crosslinking state, so that the polymer electrolyte can tolerate dendritic growth of lithium by morphological change on an electrode surface.The obvious advantages of DAD-induced solid polymer electrolytes in this study for a high energy and power, and ultra-safe LMB can present a novel approach of polymer electrolyte design to the astronomical demand of energy storages.[1] F. Ahmed, I. Choi, M.M. Rahman, H. Jang, T. Ryu, S. Yoon, L. Jin, Y. Jin, W. Kim, ACS Appl. Mater. Interfaces 2019, 11, 34930-34938.[2] D.-M. Shin, J.E. Bachman, M.K. Taylor, J. Kamcev, J.G. Park, M.E. Ziebel, E. Velasquez, N.N. Jarenwattananon, G.K. Sethi, Y. Cui, J.R. Long, Adv. Mater. 2020, 32, 1905771.

(Invited) Structure-Property Relationships in Highly Permeable Dioxolane-Based Perfluorinated Ionomers

Ion conducting polymers used as membranes and catalyst binders in membrane electrode assemblies (MEAs) have driven continuous improvements in fuel cell performance. Commercially available membrane materials (e.g., Nafion®) impart low gas permeability, high chemical and mechanical stability thanks to their semi-crystalline polytetrafluoroethylene (PTFE) matrix. This dense matrix also slows permeation of gases through the polymer, introducing significant mass-transport losses in the catalyst layers and limits fuel cell performance. In this presentation, I will discuss a new family of perfluorinated ionomers that incorporates an amorphous matrix based on a perfluoro(2-methylene 4-methyl-1,3-dioxolane) (PFMMD) backbone. The introduction of a PFMMD backbone disrupts the crystallinity of the matrix, increases the matrix free volume, and significantly improves its gas permeability.1 The dioxolane backbone also increases the glass transition temperature of the matrix, impacting its mobility, limiting the ionomer domain swelling and reducing its proton conductivity. I will describe a flexible synthesis method for PFMMD-based ionomers which allowed us to study ionomers with tunable sulfonic acid content and derive structure-property relationships through a combination of transport measurements (i.e., water uptake, proton conductivity, and permeability) and morphological characterization through Small- and Wide-angle X-ray scattering. We will show how the incorporation of dioxolane monomers with bulky, asymmetric side-chains results in a stiff ionomer matrix with distinct chemical and mechanical properties. By varying the dioxolane matrix mass fraction, we gained fundamental insights into the role of the matrix chemical structure on the dynamics of structural and transport processes in ion-conducting polymers.2 Through in situ water uptake measurements, we elucidated the impact of the mass fraction and matrix chemical structure on water sorption rates. The mass-transport swelling rate of Nafion was around 50% higher than in dioxolane-containing ionomers and was independent of the matrix mass fraction. Non-Fickian polymer relaxation rate was sensitive to both type and fraction of the matrix, increasing by 22% across the range of dioxolane fractions studied and by another 100% in Nafion. These effects are attributed to reduction of segmental mobility of the hydrophobic matrix upon incorporation of dioxolane groups. The polymer relaxation is shown to correlate to changes in ionomer conductivity and nanostructure, reveled through in situ Grazing-Incidence Small Angle X-ray Scattering (GISAXS) measurements, showing two distinct physical processes that enable (i) rapid water sorption and ionomer domain swelling and (ii) polymer relaxation and ordering of ionomer domain structure. Lastly, I will discuss the implication and potential utilization of these new materials for improved fuel cell performance. The results presented here underscore the significance of tailoring materials chemistry to specific requirements of fuel cell or electrolysis MEAs.

One-Step Hydrothermal Reaction Induced Nitrogen-Doped MoS2/MXene Composites with Superior Lithium-Ion Storage

MoS2, a typical transition metal dichalcogenide (TMDs), inheriting high theoretical capacity, open framework and unique electrochemical properties, is regarded as a promising electrode material. However, the low electronic conductivity and slow chemical kinetics of two-dimensional (2D) MoS2 lamellars, along with the large volume expansion during cycling hinder their application in Li-ion batteries. MXene inherits the strengths of excellent metallic conductivity, a low lithium-ion diffusion potential barrier and superior mechanical stability; however, its low reversible capacity and self-stacking problems as anode still need to be solved. Herein, the MXene Ti3C2Tx compound with MoS2 through a simple one-step hydrothermal reaction is introduced. The introduction of nitrogen-doped Ti3C2Tx can effectively restrain the volume change of MoS2 and ameliorate the electronic conductivity of the whole electrode, while MoS2 can alleviate the self-stacking of Ti3C2Tx during cycling. The as-prepared MoS2/MXene electrode delivers an initial discharge capacity of 1087 mA h g−1 with an initial Coulombic efficiency (ICE) of 81.6% at 100 mA g−1, and a specific discharge capacity of 731 mA h g−1 can be retained after 100 cycles. The excellent electrochemical performance demonstrates that nitrogen-doped MoS2/MXene can be a potential electrode material for Li-ion batteries.

Robust PANI-entangled CNTs Electro-responsive membranes for enhanced In-situ generation of H2O2 and effective separation of charged contaminants

Electro-responsive membranes provide a promising strategy to overcome the trade-off between water recovery and water quality in membrane-based wastewater treatment. However, the successful deployment of these membranes is restricted by their low mechanical stability and poor electrochemical reactivity. Herein, we strived to overcome these challenges by constructing a polyaniline-entangled oxidized CNTs (PANI@O-CNTs) cathodic membrane via a sequential laminating technique. The effective in-situ polymerization of the PANI network on the CNTs skeleton and the superior conductivity of the PANI@O-CNTs membrane was demonstrated by extensive characterizations. Durability test results showed the excellent mechanical and electrochemical stability of the robust PANI@O-CNTs membranes. Cyclic voltammetry (CV) analysis confirmed that the modification of nitrogen-rich PANI on CNTs boosted their reactivity for electro-generation of H2O2. By applying an external voltage of −2.0 V, the PANI@CNTs membrane displayed an enhanced rejection from 35.2 % to 77.4 % for negatively charged methyl orange (MO) dye and from 41.5 % to 79.8 % for positively charged methylene blue (MB) dye at 50 min operation time. Moreover, the rejection efficiencies further increased to 89.7 % for MO and 93.4 % for MB through the synergistic effect of electrostatic interactions and H2O2 oxidation. Additionally, antifouling experiments performed with oppositely charged dyes indicated that H2O2 oxidation played a critical role in flux recovery and fouling alleviation. Our results raise the prospect of utilizing electro-responsive membranes to remove specific organic matter from wastewater.

Experimental evaluation of the stability of chitosan based biocomposites under various environmental conditions

Chitosan is naturally derived polysaccharide and has various engineering applications. However, chitosanin its original form is not suitable for practical use due to its sensitivity to wide range of pH and has poormorphological properties and low mechanical stability. The properties and performance of chitosan couldbe improved by crosslinking and formation of composites using appropriate additives. In this study, aneco-friendly chitosan based crosslinked organic-inorganichybrid biocomposites, such as chitosan/Bentonite (ChBT), chitosan/titanium oxide (ChTi), and chitosan/alumina (ChAl); were prepared and thestabilities of the prepared biocomposites were evaluated under acidic and aqueous environments. Thestabilities of the prepared biocomposites were evaluated under acidic and aqueous environments. Stabilityof ChBT, ChTi, and ChAl in acidic solution increased with increase in crosslinker and inorganic doses.Similarly, the stability of the prepared biocomposites increased in aqueous environment. ChAl has shownthe highest stability in both conditions.

Effect of ultra-fast heating on microstructure and mechanical properties of cold-rolled low-carbon low-alloy Q&P steels with different austenitizing temperature

We performed ultra-fast heating (150 °C/s) quenching and partitioning (Q&P) processes to a cold-rolled low-carbon low-alloy steel. Adjusting the annealing temperature, we obtained two types of ferrite-containing Q&P steels with different matrix structure, i.e., martensitic matrix and ferritic matrix. The effect of ultra-fast heating on microstructure evolution and mechanical properties was analyzed, compared with the samples treated with conventional heating rate (10 °C/s). We also investigated the strain partition and fracture behaviors, basing on in-situ tensile tests under SEM. Results show that ultra-fast heating can significantly increase the A c1 and A c3 temperatures, and extend the temperature span of intercritical zone. It can also delay the complete recrystallization of deformed ferrite and promote the austenite nucleation, which leads to the structure refinement of the sample with martensitic matrix, improving both the strength and ductility. The increase of austenite nucleation rate and the incomplete recrystallization of deformed ferrite jointly promote the austenite transformation, which results in a distinct increase of martensite islands fraction in the sample with ferritic matrix, leading to its obvious increase of tensile strength and decrease of ductility. Strain partition is an important factor affecting the TRIP effect in ferrite-containing Q&P steels. For the sample with a martensitic matrix, retained austenite mainly possesses a film-like morphology and exists between martensite laths. The relatively high mechanical stability of retained austenite films and low local strain in martensitic regions result in the weak TRIP effect. The retained austenite in the sample with a ferritic matrix mainly distributes among ferrite grains and exhibits a blocky morphology. The relatively low mechanical stability of blocky retained austenite and high local strain in ferrite jointly enhance the TRIP effect. • Ultra-fast heating delays ferrite recrystallization. • Ultra-fast heating restrains martensite tempering. • Ultra-fast heating results in grain refinement of martensitic matrix. • Strain partition is a crucial factor controlling TRIP effect. • Main ductility origin is compatible deformation of matrix structures.

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Composite TiO2 films modified by CeO2 and SiO2 for the photocatalytic removal of water pollutants.

TiO2 particles of high photocatalytic activity immobilised on various substrates usually suffer from low mechanical stability. This can be overcome by the utilisation of an inorganic binder and/or incorporation in a robust hydrophobic matrix based on rare-earth metal oxides (REOs). Furthermore, intrinsic hydrophobicity of REOs may result in an increased affinity of TiO2-REOs composites to non-polar aqueous pollutants. Therefore, in the present work, three methods were used for the fabrication of composite TiO2/CeO2 films for photocatalytic removal of dye Acid Orange 7 and the herbicide monuron, as representing polar and non-polar pollutants, respectively. In the first method, the composition of a paste containing photoactive TiO2 particles and CeCl3 or Ce(NO3)3 as CeO2 precursors was optimised. This paste was deposited on glass by doctor blading. The second method consisted of the deposition of thin layers of CeO2 by spray coating over a particulate TiO2 photocatalyst layer (prepared by drop casting or electrophoresis). Both approaches lead to composite films of similar photoactivity that of the pure TiO2 layer, nevertheless films made by the first approach revealed better mechanical stability. The third method comprised of modifying a particulate TiO2 film by an overlayer based on colloidal SiO2 and tetraethoxysilane serving as binders, TiO2 particles and cerium oxide precursors at varying concentrations. It was found that such an overlayer significantly improved the mechanical properties of the resulting coating. The use of cerium acetylacetonate as a CeO2 precursor showed only a small increase in photocatalytic activity. On the other hand, deposition of SiO2/TiO2 dispersions containing CeO2 nanoparticles resulted in significant improvement in the rate of photocatalytic removal of the herbicide monuron.

High-strength, tough, and anti-swelling Schiff base hydrogels with fluorescent encryption writing, solvent response and double shape memory functions

The preparation of high-strength and tough hydrogels by hydrophobic association strategy is one of the research hotspots, but now the emerging applications put forward requirements in terms of the function and the water stability of the hydrogel in addition to mechanical properties. In order to meet these requirements, we reported anti-swelling fluorescent hydrogels with high strength and toughness, showing antibacterial properties as well as fluorescence encryption writing, underwater storage, fluorescence solvent response and double shape memory functions. The hydrophobic monomer (Z)-N-(4-(2-(quinoline-2-methylene)hydrazine-1-carbonyl) phenyl) methyl acrylamide (QHPMA) containing quinoline Schiff base was successfully introduced into the hydrogel system by solvent exchange method, and P(MAA-QHPMA) hydrogel based on hydrophobic association was prepared. The mechanical properties could be controlled by QHPMA content and Zn2+ concentration. The maximum tensile fracture stress and strain were 1.39 MPa and 162%, respectively. The maximum toughness was 1.21 MJ/m3. Hydrogels had a low swelling rate (201%) and mechanical property stability after soaking for 14 days. In addition, the hydrogel was used as an “off-on” fluorescence sensor. When the concentration of Zn2+ was 0.1 M, the fluorescence intensity was 1851% of that before complexing. The Zn2+-P(MAA-QHPMA) hydrogel had good antibacterial effect due to Zn2+ ions-quinoline Schiff bases coordination. Finally, the fluorescence encryption writing, underwater storage, fluorescence solvent response and double shape memory functions of P(MAA-QHPMA) hydrogel were designed and studied. This high-strength, tough, and anti-swelling fluorescent hydrogel is expected to be used in underwater sensors, solvent detection, shape memory materials and other fields.

Soft and Tough Microcapsules with Double‐Network Hydrogel Shells

AbstractHydrogel‐shelled microcapsules allow communication with the surrounding through molecule‐selective exchanges, serving as microcarriers for cells, drugs, catalysts, and nanoparticle sensors. However, the low mechanical stability of hydrogels has restricted their use in strong shear flows or compressive fields. Here, microcapsules are designed composed of water core and double‐network (DN) hydrogel shell using water‐in‐oil‐in‐water‐in‐oil triple‐emulsion templates to secure high mechanical stability as well as molecular size‐selective permeation. Monodisperse triple‐emulsion droplets are prepared using microfluidic devices. The core water contains divalent ions and the outer water layer contains poly(ethylene glycol)diacrylate (PEGDA) and sodium alginate. The PEGDA is first photocrosslinked by ultraviolet irradiation and the alginate is second ionically crosslinked with an infusion of divalent ions from the core by rupturing the middle oil layer. The resulting DN shells show excellent mechanical stability in comparison with single‐network (SN) shells made of PEGDA only. Enhanced elasticity of the DN enables the microcapsules to elastically deform and fully recover the original state for wide ranges of strain and strain rate. Moreover, the DN shells show a threshold force for the shell rupture almost one order of magnitude larger than the SN and maintain their integrity under violent shear flows.

Rationalization of brittleness and anisotropic mechanical properties of H13 steel fabricated by selective laser melting

This work revealed the causes of embrittlement and anisotropy in the mechanical properties of H13 steel fabricated by selective laser melting (SLM). It was found that the low mechanical stability of the carbon-enriched retained γ (austenite) films amongst martensite blocks transferred to high carbon twin martensite through stress-induced martensitic transformation upon plastic deformation, leading to a high susceptibility to cracking. Moreover, owing to the directional solidification nature in SLM, the majority of these retained γ films was aligned with the building direction (i.e. longitudinal direction). This significantly impaired the ductility of the steel when the load was perpendicular to these γ films (i.e. transverse loading condition).

Preparation of Stable Superhydrophobic Coatings on Complex‐Shaped Substrates

AbstractSuperhydrophobic surfaces have potential applications in many fields, but are seriously hindered by their complicated preparation methods and low mechanical stability. Thus, novel strategies for efficient preparation of robust superhydrophobic surfaces on various substrates are highly desired. Here, the preparation of stable superhydrophobic coatings on complex‐shaped substrates by the combination of phase separation and dip‐coating is reported. The coatings show excellent superhydrophobicity for both water and other frequently used liquids, superior impalement resistance, and high stability. Moreover, this strategy can make diverse complex‐shaped substrates superhydrophobic, outperforming the conventional methods. The strategy also has many other merits such as simple, fast (<1 min), scalable (50 kg stock solution per batch and large superhydrophobic samples), and low cost (7.8 CNY m−2 or 1.2 UDS m−2). The superhydrophobic coatings may find applications in many fields including anticorrosion and antiicing, and the findings here will inspire straightforward preparation of robust superhydrophobic coatings on diverse substrates.

Microstructure characterization and mechanical behaviour of laser additive manufactured ultrahigh-strength M54 steel

Ultra high-strength M54 steel blocks were fabricated by laser metal deposition. The microstructure and mechanical behavior of the material were investigated systematically. The microstructure of the as-deposited M54 steel is anisotropic; the cross-section (XOY plane) has a cellular structure, whereas the longitudinal section (XOZ and YOZ planes) shows a mixture of alternating cellular and columnar forms. Compositional segregation is present at the cell walls (interdendritic regions) in the as-deposited state, resulting in retained austenite at the cell walls. The cross-sectional XOY plane contains 10.08% austenite, whereas the XOZ and YOZ planes contain 24.59% and 22.4% austenite, respectively. The retained austenite at the cell wall (interdendritic region) has low thermal and mechanical stability and disappears after the cryogenic treatment or is transformed into martensite during a tensile test. The as-deposited samples show anisotropic mechanical properties. The transverse samples exhibit stronger transformation-induced plasticity (TRIP) and work hardenability with a lower yield strength of 662 MPa and higher ultimate strength of 1982 MPa, corresponding to a higher amount of retained austenite in this direction. The longitudinal ultimate strength and yield strength are 1832 MPa and 997 MPa, respectively. The ductility and toughness are also largely anisotropic, and their reduction in the transverse direction is only 1/3 of that in the longitudinal direction. The Vickers hardness of the microstructure increases slightly from the bottom to the middle and upper part of the sample due to less thermal cycling in the upper part.

Recent Advancements in Polyphenylsulfone Membrane Modification Methods for Separation Applications.

Polyphenylsulfone (PPSU) membranes are of fundamental importance for many applications such as water treatment, gas separation, energy, electronics, and biomedicine, due to their low cost, controlled crystallinity, chemical, thermal, and mechanical stability. Numerous research studies have shown that modifying surface properties of PPSU membranes influences their stability and functionality. Therefore, the modification of the PPSU membrane surface is a pressing issue for both research and industrial communities. In this review, various surface modification methods and processes along with their mechanisms and performance are considered starting from 2002. There are three main approaches to the modification of PPSU membranes. The first one is bulk modifications, and it includes functional groups inclusion via sulfonation, amination, and chloromethylation. The second is blending with polymer (for instance, blending nanomaterials and biopolymers). Finally, the third one deals with physical and chemical surface modifications. Obviously, each method has its own limitations and advantages that are outlined below. Generally speaking, modified PPSU membranes demonstrate improved physical and chemical properties and enhanced performance. The advancements in PPSU modification have opened the door for the advance of membrane technology and multiple prospective applications.