The mitigation of CMAS (calcium–magnesium–aluminum–silicon oxide) infiltration is a major requirement for the stability of thermal barrier coatings. In this study, yttria-stabilized zirconia (YSZ)–Al2O3–SiC, YSZ–Al2O3–Ta2O5, and YSZ–Al2O3–Nb2O5 self-healing composites produced by uniaxially pressing powders were investigated as an alternative to YSZ. CMAS infiltration in these materials was tested at 1250 °C for 10 h. Comparing the depth of CMAS infiltration using scanning electron microscope (SEM) in tandem with electron-dispersive X-ray spectroscopy (EDS), all self-healing materials were found to perform better than the reference materials. While standard YSZ shows massive CMAS infiltration, SEM micrographs and EDS maps revealed a 33-fold improvement in CMAS resistance for the YSZ–Al2O3–Nb2O5 system, which exhibited the best performance among the selected self-repairing materials. X-ray diffraction and high-resolution SEM micrographs taken 10 μm below the surface revealed that CMAS only infiltrated pores in the topmost region of the samples. Both YSZ–Al2O3–Ta2O5 and YSZ–Al2O3–Nb2O5 systems showed no signs of chemical reaction with CMAS.

Dissolution of oxides in aqueous solutions is fundamentally important for a range of applications and a critical process that determines the chemical durability of industrial ceramics, the performance of nuclear waste forms, and the chemical weathering of minerals. The thermodynamic equilibrium and kinetics of dissolution reactions are key to determining the rate at which oxides dissolve. The increase in collaborative research across disciplines in materials research necessitates a common background to tackle shared scientific problems across different fields. This review selectively examines the fundamentals of dissolution theories that have been developed in chemistry, geochemistry, and materials science, and assembles them into a single collective document for the broader materials science community. Applications of the theories are highlighted using examples from specific areas, but can be similarly applied to other areas. Challenges and future research needs for a predictive-level understanding are discussed in light of the current literature.

The disruptive potential of additive manufacturing (AM) relies on its ability to make customized products with considerable weight savings through geometries that are difficult or impossible to produce by conventional methods. Despite its versatility, applications of AM have been restricted due to the formation of columnar grains, resulting in solidification defects and anisotropy in properties. To achieve fine equiaxed grains in AM, alloy design and solidification conditions have been optimized in various alloy systems. In this review paper, the microstructure of high-entropy alloy (HEA) parts produced by selective laser melting and powder-based directed energy deposition is investigated. Solidification maps based on laser process parameters (as opposed to most commonly used solidification velocity and temperature gradient) are constructed by compiling available literature for single-phase face-centered cubic, body-centered cubic, and multiphase HEAs. These maps could guide printing of HEAs and provide an insight into the design of novel HEAs for AM.

Two different processing routes of mechanical alloying followed by the spark plasma sintering (powder metallurgy) and vacuum arc melting (casting route) were employed to understand the role of processing routes on the phase and microstructural evolution in an equiatomic CrMoNbTiW refractory high-entropy alloy. Besides a major BCC solid solution, a small fraction of carbide, σ phase, nitride, and oxide phases were observed in the alloys prepared by the powder metallurgy route in contrast to a single-phase BCC solid solution in the casting route. The milling atmosphere (dry milling in air and Ar) has significantly influenced the phase and microstructural evolution, illustrating the substantial role of contaminants. Good thermal stability of microstructure at high homologous temperatures was shown based on the long-term heat treatment at 1300 °C for 240 h. The phase evolution predictions via Calphad studies were found to be in reasonable agreement with the experimental observations, albeit with some limitations.

In the alloy materials, their mechanical properties mightly rely on the compositions and concentrations of chemical elements. Therefore, looking for the optimum elemental concentration and composition is still a critical issue to design high-performance alloy materials. Traditional alloy designing method via “trial and error” or domain experts’ experiences is barely possible to solve the issue. Here, we propose a “composition-oriented” method combined machine learning to design the Cu–Zn alloys with the high strengths, high ductility, and low friction coefficient. The method of separate training for each attribute label is used to study the effects of elemental concentrations on the mechanical properties of Cu–Zn alloys. Moreover, the elemental concentrations of new Cu–Zn alloys with the good mechanical properties are predicted by machine learning. The current results reveal the vital importance of the “composition-oriented” design method via machine learning for the development of high-performance alloys in a broad range of elemental compositions.

Growing zinc oxide (ZnO) nanowires (NWs) on yarns promotes smart sensing and creates opportunities for new applications. ZnO NWs sensing performance is influenced by its dimensions, which can be tailored by controlling the growth parameters. In this study, we investigated the effect of the growth parameters (time, temperature, and precursor concentration ratio) on the NWs’ morphology, dimensions, and piezoelectric performance. Our results showed that ZnO NWs produced with 6 and 9 h had long nanowires; however, they mainly got tangled with the nanowires on the adjacent fibers and peeled-off the fiber surface. Growth at a 1:1 precursor concentration ratio for 9 h produced the same nanowires’ length (~3 μm) as growth at a 3:1 precursor concentration ratio for 3 h. Among all of the studied growth conditions, ZnO NWs produced with a 3:1 precursor concentration ratio at 90 °C for 3 h showed uniform dimensions and stable electrical charge output.

The γ″ phase (hexagonal structure with space group ${ P\bar{6}}2{ m}$) plays an important role in the strengthening of Mg–Gd–Y–Ag–Zr alloy. In this study, Cs-corrected high-angle annular dark-field scanning transmission electron microscopy was applied to characterize the Mg–Gd–Y–Ag–Zr alloy in different conditions (as-cast, solution-treated, and isothermally aged at 200 °C). The nucleation, growing process, and transformation behavior of the plate-shaped γ″ phase were systematically investigated on the atomic scale. We found that the nucleation sites of the γ″ phase were separated by close-packed planes of the Mg matrix and the γ″ phase developed in two perpendicular directions of $\langle 10\bar{1}0 \rangle$ and ⟨0001⟩. The growing process of the γ″ phase on the atomic scale was captured. The γ″ phase was thermodynamically stable at room temperature, and no transformation behavior of the γ″ phase was observed up to 200 h during isothermal aging at 200 °C.

We fabricated a van der Waals heterostructure of WS2–ReSe2 and studied its charge-transfer properties. Monolayers of WS2 and ReSe2 were obtained by mechanical exfoliation and chemical vapor deposition, respectively. The heterostructure sample was fabricated by transferring the WS2 monolayer on top of ReSe2 by a dry transfer process. Photoluminescence quenching was observed in the heterostructure, indicating efficient interlayer charge transfer. Transient absorption measurements show that holes can efficiently transfer from WS2 to ReSe2 on an ultrafast timescale. Meanwhile, electron transfer from ReSe2 to WS2 was also observed. The charge-transfer properties show that monolayers of ReSe2 and WS2 form a type-II band alignment, instead of type-I as predicted by theory. The type-II alignment is further confirmed by the observation of extended photocarrier lifetimes in the heterostructure. These results provide useful information for developing van der Waals heterostructure involving ReSe2 for novel electronic and optoelectronic applications and introduce ReSe2 to the family of two-dimensional materials to construct van der Waals heterostructures.

This article reports findings when using a molybdenum–tungsten (MoW) interlayer for diamond thin film deposition on steel substrates. The main focus was on the postdeposition stress within the diamond films and its impact on the coating's tribological properties. The effect of MoW interlayer thickness and the effect of chemical vapor deposition (CVD) process temperature have been investigated. Nanocrystalline diamond films were deposited on steel substrates with MoW interlayers (thickness of 1.1, 4.5, and 8.3 μm) at two different deposition temperatures (650 and 875 °C). It was found that when depositing good quality diamond films on steel substrates, increasing interlayer thickness and decreasing CVD process temperature have to be jointly considered to obtain the optimal result. The diamond-coated steel substrates with the 8.3 μm interlayer deposited at the lower CVD processing temperature exhibited the least residual stress combined with excellent mechanical properties.

Cellprene™ is a recently developed polymeric blend based on poly(lactide-co-glycolide) (PLGA)/polyisoprene (PI) with good biological performance for biomedical applications. However, its potential as fiber scaffold in tissue engineering is still unknown, and the influence of processing parameters is yet to be understood. In this study, several compositions based on PLGA/PI blend mixed with hydroxyapatite (HAp) and polyethylene glycol (PEG) were prepared by solvent casting. Then, the membranes were used to produce micro/nanofibers by centrifugal spinning (CS) and electrospinning (ES). The viscosity's effect was studied to find an ideal viscosity value to produce homogeneous micro/nanofibers. The in vitro bioactivity test was also performed. Rheological results showed that the best viscosity range was (0.105 Pa s > η > 0.138 Pa s) for CS; larger fibers of ES were produced with lower viscosities. The sample with the lowest HAp concentration exhibited thinner and more homogeneous non-beaded fibers and proved its bioactivity response.

In this work, PbS and PbS/CdS core–shell quantum dots (QDs) were synthesized by a new photochemical approach. Prepared QDs were characterized by means of x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDAX), UV–Vis, and Z-scan analyses. Synthesized QDs were in a cubic phase with a spherical morphology, and the crystallite sizes are estimated using the strain–size method. A uniform shift of Bragg diffraction peaks and quenching (200) Bragg plane are interpreted as the growth of the CdS shell. Linear optical properties were investigated using Urbach analysis and Tauc formula. It was found that the density of states of QD conduction and valence bands are three dimensional. The estimated sizes of PbS QDs and PbS/CdS using exciton absorption peaks at room temperature are 1.8 and 2.7 nm, respectively, which are in good agreement with the strain–size plot analysis. The growth of the CdS shell resulted in a considerable decrease in the nonlinearity refractive index and a significant increase in the nonlinear absorption.

The effects of stress-free and stress-assisted pretreatments at a relatively high temperature on the creep properties of [001] and [011] oriented Ni-based single-crystal superalloys are investigated in this article. The results show that the creep life of the pretreated samples is shorter than that of the original samples. The variation of the γ/γ′ morphology during the creep process is characterized by the microstructure period. Based on the interaction between the dislocations in the γ matrix channel and the γ′ phase, the difference in creep properties of the two oriented alloys after pretreatment is analyzed. Combined with the crystal plasticity theory and the number of activated slip systems observed in the experiments, it can be concluded that the two oriented alloys after pretreatment show obvious creep anisotropy and that the creep life increases with the number of activated slip system.

The quality of the polymer raw material used in plastic processing methods is an important characteristic because it is one of the main factors in producing quality products. Therefore, the characterization of polymeric pellets in the polymer processing industry is very important to avoid using inferior materials. In general, differences in the interiors of polymeric pellets reflect differences in their densities. In this study, a high-sensitivity magnetic levitation method was used to characterize the polymeric pellets in four different occasions. The device used has a high sensitivity that can distinguish minute differences as small as of 0.0041 g/cm3 in density between different samples. In addition, the method can obtain a sample's density without knowing the weight and volume of the sample. This method can be used to characterize materials by testing only a single pellet, which is very useful for polymeric pellet characterization.

In this paper, the atomic resolution high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) was used as the main research method. Using HAADF-STEM, two types of long-period stacking ordered structure (LPSO)—14H and 18R-LPSO—were observed in Mg96Gd2Y1Ni1 alloy, and the precipitates at various stages of aging were observed. Moreover, a type of rectangular β precipitates were found, and the atomic models of β precipitates along the [0001]Mg and ${\tf="TeXGyrePagella-Bold (TrueType)"\char9001} 11\bar 20\hbox{]}_{{\rm{Mg}}}$ directions were identified. At the aging peak stage, a three-dimensional network structure composed of LPSO/γ′ precipitates and β′ precipitates and β precipitates was observed. The hardness of the unaged homogenized Mg96Gd2Y1Ni1 alloy was only 87 HV and the hardness value of aging peak was 128.4 HV. Compared with the unaged alloy, the hardness of the peak-aged alloy increased by 47.59%. The composite strengthening of the three types of precipitates induced a significant strengthening to the alloy.

As for the efficient dye-sensitized solar cells (DSSCs), one of the important goals is to increase the light harvesting efficiency to further improve the photoelectric conversion efficiency (PCE). The excellent photoanode materials should possess a uniform porous structure, a large surface area, high crystallinity, and good stability. Herein, the porous TiO2 electrode (named as S-1.5) with the above merits had been prepared by the simple template-assisted method with camphene as the pore-forming reagent. The surface area of the porous TiO2 electrode can be tailored by introducing the amount of camphene. The porous TiO2 layer with the optimal surface area directly adhered on the top of the ultra-thin P25 dense layer had been constructed and this unique electrode with a “double layers structure”, which named as S-1.5/P25. When DSSCs assembled with this photoanode, a desirable PCE of 8.31% had been achieved, which was obviously higher than that of the commercial P25 (7.62%) in parallel. The improved PCE can be attributed to the improved utilization of sunlight, the facilitated photo-generated electron transfer, and the reduced interface resistance. Meanwhile, the related characterization including electrochemical impedance spectroscopy, intensity-modulated photovoltage spectroscopy, and intensity-modulated photocurrent spectroscopy was characterized to explore the possible mechanism.

A novel Ag/AgBr/Nb2O5 heterojunction photocatalyst was successfully developed via a facile solvothermal method combined with deposition–precipitation. The morphology and composition of the Ag/AgBr/Nb2O5 photocatalyst were investigated by transmission electron microscopy and X-ray energy-dispersive spectrometry, respectively. The results showed that metallic Ag was formed on the surface of the AgBr by an in situ photoreaction. The low crystalline Nb2O5 (L-Nb2O5) substrate provides the photocatalyst with a high specific area and numerous active sites for catalysis, while the combination of the Ag/AgBr with L-Nb2O5 effectively facilitates the separation of photo-generated charge carriers. The photocatalytic activities of the samples were measured using the degradation of an aqueous solution of rhodamine B under different LEDs with UV (365 nm), yellow (595 nm), and white (400 nm ≤ λ ≤ 800 nm) light. The Ag/AgBr/L-Nb2O5 photocatalyst displayed a much higher photocatalytic activity than bare L-Nb2O5 under UV and visible-light irradiation.

Nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 suffers from severe structural instability and irreversible capacity loss during cycling due to cation disorder of Li+ and Ni2+. To solve this problem, the precursor Ni0.8Co0.1Mn0.1(OH)2 and well-ordered LiNi0.8Co0.1Mn0.1O2 cathode materials were successfully synthesized via controlled crystallization and high-temperature solid-state methods. The structure, morphology, and electrochemical performance of the precursor and LiNi0.8Co0.1Mn0.1O2 powders were investigated. The results show that the precursor Ni0.8Co0.1Mn0.1(OH)2 is made of sphere-like particles composed of needle-like primary crystal and LiNi0.8Co0.1Mn0.1O2 possesses a perfect layered structure with low Li/Ni disorder. Electrochemical data demonstrate that the material rate capabilities are 203.3, 187.7, 170.4, and 163 mA h/g from 0.1C to 10C, respectively. The capacity retention is 87.9% after 100 cycles at 1C, even the cut-off voltage was increased to 4.5 V. The high discharge capacity and outstanding cycling life can be attributed to the merits of a perfect crystal lattice with low Li/Ni disorder, fast lithium ion transport, and relatively low charge transfer resistance.

The advantage of alcohol–calcium method on the formation and the stability of vaterite against ethanol–water binary solvents (EWBS) method was studied through comparative experiment. The polymorphs and morphologies of CaCO3 were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results show that vaterite slowly decreases from 90.4 to 82.5% as increasing aging time from 0 to 1320 min in alcohol–calcium system, while quickly decreases from 46.5% to 0% at the same aging time in EWBS system. The similar variation as reaction temperature was found in both systems. SEM images indicate that calcite presents its typical rhombohedral morphology in both systems, while the morphologies of vaterite particles in two systems are different. In alcohol–calcium system, small vaterite nanoparticles aggregate into spherical microparticles, and these microparticles become porous, loose, and irregular, even incomplete, as increasing aging time and reaction temperature, while in EWBS system, vaterite nanoparticles aggregate into irregular microparticles. The advantage of alcohol–calcium method was discussed from the formation of the complex compound CaCl2·n(C2H5OH) in alcohol and its decomplexation in aqueous medium.

A simple and effective strategy is proposed for fabricating honeycomb-patterned ethyl cellulose (EC) films via a combination of the dip-coating and breath figure methods under a wide humidity range (40–90%). A mixture of toluene and methanol as a volatile solvent/nonsolvent pair was used to effectively control the surface morphology. Additionally, honeycomb patterns were successfully formed via dip-coating under a low humidity (relative humidity less than 40%), when water was directly added into the mixed solution. The important factors that influenced the morphology of EC honeycomb-patterned films were investigated, such as the humidity, solution concentration, and the withdrawal speed during dip-coating. The pore sizes could be controlled by changing the film-formation conditions. Water contact angle enables a transition from hydrophilic to hydrophobic. The possible mechanisms of honeycomb pattern formation are discussed. The fabrication of an ordered honeycomb-patterned film in a cost-effective and convenient manner will have broad application potential in the future.

Iron foams are potential materials for the production, purification, and recuperation of hydrogen through redox systems. They are inexpensive, recyclable, and environmentally friendly. Nevertheless, iron foams cannot be employed repeatedly for redox cycling at high temperatures because the structure suffers morphological changes and a decrease in the effective porosity. In this work, two different pore structures of Fe-foams fabricated by freeze-casting have been produced: constant (CP) and gradient (GP) pore size. CP Fe-foams were obtained by employing a double-sided cooling technique to minimize gradients in pore width that result when using one-sided, constant cooling solidification techniques. GP Fe-foams were manufactured using a fixed-temperature cold plate. Optical microscopy and X-ray tomography were employed to characterize the pore structure and, for GP Fe-foams, to investigate the effect of redox cycling. After redox cycling, GP Fe-foams exhibited significant pore degradation.