Crystals, Volume 12, Issue 3 (March 2022) – 135 articles

The scientific discussion about classical and nonclassical nucleation theories has lasted for two decades so far. Recently, multiple nucleation pathways and the occurrence and role of metastable intermediates in crystallization processes have attracted increasing attention, following the discovery of functional phase separation, which is now under investigation in different fields of cellular life sciences, providing interesting and novel aspects for conventional crystallization experiments. In this context, more systematic investigations need to be carried out to extend the current knowledge about nucleation processes. In terms of the data we present, a well-studied model protein, glucose isomerase (GI), was employed first to investigate systematically the early stages of the crystallization process, covering condensing and prenucleation ordering of protein molecules in diverse scenarios, including varying ionic and crowding agent conditions, as well as the application of a pulsed electric field (pEF). The main method used to characterize the early events of nucleation was synchronized polarized and depolarized dynamic light scattering (DLS/DDLS), which is capable of collecting the polarized and depolarized component of scattered light from a sample suspension in parallel, thus monitoring the time-resolved evolution of the condensation and geometrical ordering of proteins at the early stages of nucleation. A diffusion interaction parameter, K_D, of GI under varying salt conditions was evaluated to discuss how the proportion of specific and non-specific protein–protein interactions affects the nucleation process. The effect of mesoscopic ordered clusters (MOCs) on protein crystallization was explored further by adding different ratios of MOCs induced by a pEF to fresh GI droplets in solution with different PEG concentrations. To emphasize and complement the data and results obtained with GI, a recombinant pyridoxal 5-phosphate (vitamin B6) synthase (Pdx) complex of Staphylococcus aureus assembled from twelve monomers of Pdx1 and twelve monomers of Pdx2 was employed to validate the ability of the pEF influencing the nucleation of complex macromolecules and the effect of MOCs on adjusting the crystallization pathway. In summary, our data revealed multiple nucleation pathways by tuning the proportion of specific and non-specific protein interactions, or by utilizing a pEF which turned out to be efficient to accelerate the nucleation process. Finally, a novel and reproducible experimental strategy, which can adjust and facilitate a crystallization process by pEF-induced MOCs, was summarized and reported for the first time. Full article

Ternary compound YAlSi crystallizes with orthorhombic Cmcm symmetry. This structure contains Y–Si pairs of atoms, creating honeycomb-like sublattices. In this paper, we investigate the dynamical properties of the system, focusing on the chiral modes. These modes are associated with the circular motion of the atoms. We show that the chiral modes can be realized in the YAlSi compound, and it makes this compound suitable for further experimental study of the chiral phonons. Full article

This study reports the characteristics of water in channels of blue-green beryl and its effect on color. An industrial camera was used to measure color in the CIELAB color space. X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), ultraviolet-visible (UV–vis) spectroscopy, and silicate rock chemical analysis method were used for analysis. The peaks at 5105 cm⁻¹ and 5269 cm⁻¹ were the combination tone of type II water, which were negatively correlated with b*, and positively correlated with the peak area at 3162 cm⁻¹ (Na–H) and cell parameter a₀. The peaks at 7097 cm⁻¹ and 7142 cm⁻¹ were related to the metal ions types in the channels. Part of the water in the channel combined with Fe³⁺ to form [Fe₂(OH)₄]²⁺ and cause a yellow tone, and when the yellow tone combined with the blue tone caused by Fe²⁺, the beryl has a blue-green colour. Full article

New 6-CF₃-1H-pyrazolo[3,4-b]quinolines with a methyl and/or phenyl group attached to the pyrazole core (Molx (x = 1, 2, 3, 4)) were synthesized and characterized in terms of their optoelectronic applications: photovoltaic and electroluminescence. The fluorescence emissions of the investigated phenyl-decorated pyrazoloquinolines is caused by the photoinduced charge transfer p process occurring between the phenyl substituent and the pyrazoloquinoline core, while 1,3-dimethyl-6-CF₃-1H-pyrazolo[3,4-b]quinoline exhibits an π,π*-type emission. The number of phenyls and their substitution positions modulate both emission properties and HOMO energy levels. Next, the bulk heterojunction BHJ solar cells based on 1H-pyrazolo[3,4-b] quinoline derivatives with architecture ITO/PEDOT:PSS/PDT + Molx/Al were fabricated. The organic active layer was a blend of Molx and poly(3-decylthiophene-2,5-diyl). The complex refractive index and the layer thickness of the organic solar cells were determined using a spectroscopic ellipsometer Woollam M2000 (J.A. Woollam Co., Inc., Lincoln, NE, USA) and CompleteEASE software. For solar devices with the best value of power efficiency of approximately 0.38%, the thickness of the active layer (Mol3 + PDT) was 111 nm, with a short-circuit current density of J_SC = 32.81 μA/cm² and an open–circuit voltage of V_OC = 0.78 V. Finally, we demonstrated double-layer light-emitting diodes with an organic active layer (Molx + PVK) and an electron transporting material layer, ETM (2-[3,5-bis(4-phenyl-2-quinolyl)phenyl]-4-phenylquinoline (Tris-Q). Bright bluish-green light originating from the active layer was observed in the double-layer device, ITO/PEDOT:PSS/active layer/ETM/Ca/A. The active layer was a mixture of PV-doped 1H-pyrazolo[3, 4-b]quinoline dyes. An OLED device was constructed by employing Molx as an emitter, which gave a deep bluish-green emission with the spectra range of 481–506 nm. The best value of the maximum brightness at approximately 1436.0 cd/m2 was achieved for a diode based on Mol3 (1-phenyl-3-phenyl-6-CF₃-1H-pyrazolo[3,4-b]quinoline) and [R¹ = Ph, R³ = Ph and R⁶ = CF₃]. The current efficiency was up to 1.26 cd/A at 506 nm with a CIE of 0.007, 0.692. Full article

The CuCrSe₂ shows attractive physical properties, such as thermoelectric and multiferroic properties, but pure-phase CuCrSe₂ crystal is still quite challenging to obtain because CuCr₂Se₄ can be easily precipitated from a CuCrSe₂ matrix. Here, taking the advantage of this precipitation reaction, we grew a series of CuCrSe₂-CuCr₂Se₄ hetero-composites by adjusting growth parameters and explored their thermal conductivity property. Determined by electron-diffraction, the orientation relationship between these two compounds is [001] (100) CuCrSe₂‖[111] (220) CuCr₂Se₄. The out-of-plane thermal conductivity κ of these hetero-composites was measured by a time-domain thermo-reflectance method. Fitting experimental κ by the Boltzmann-Callaway model, we verify that interface scattering plays significant role to κ in CuCrSe₂-CuCr₂Se₄ hetero-composites, while in a CuCrSe₂-dominated hetero-composite, both interface scattering and anharmonic three-phonon interaction lead to the lowest κ therein. Our results reveal the thermal conductivity evolution in CuCr₂Se₄-CuCrSe₂ hetero-composites. Full article

The enhancement of the crystallization process through high pressures was studied by using ribavirin (RVB) as a model compound. The effects of high pressure on crystallization thermodynamics, nucleation kinetics, and process yield were evaluated and discussed. The solubility of ribavirin in three pure solvents was measured at different pressures from 283.15 to 323.15 K. The results indicate that the solubility data of ribavirin decreased slightly when pressure was increased. The induction time of the cooling crystallization of ribavirin under different pressures was measured. The results show that high pressure could significantly reduce the nucleation induction period. Furthermore, the nucleation kinetic parameters under different pressures were calculated according to the classical nucleation theory. The effect of high pressure on the anti-solvent crystallization of ribavirin was also studied. Full article

Concrete mixtures can be developed to deliver a broad spectrum of mechanical and durability properties to satisfy the configuration conditions of construction. One technique for evaluating the compressive strength of concrete is to suppose that it pursues a probabilistic model from which it is reliability estimated. In this paper, a new technique to generate probability distributions is considered and a new three-parameter exponential distribution as a new member of the new family is presented in detail. The proposed distribution is able to model the compressive strength of high-performance concrete rather than some other competitive models. The new distribution delivers decreasing, increasing, upside-down bathtub and bathtub-shaped hazard rates. The maximum likelihood estimation approach is used to estimate model parameters as well as the reliability function. The approximate confidence intervals of these quantities are also obtained. To assess the performance of the point and interval estimations, a simulation study was conducted. We demonstrate the performance of the offered new distribution by investigating one high-performance concrete compressive strength dataset. The numerical outcomes showed that the maximum likelihood method provides consistent and asymptotically unbiased estimators. The estimates of the unknown parameters as well as the reliability function perform well as sample size increases in terms of minimum mean square error. The confidence interval of the reliability function has an appropriate length utilizing the delta method. Moreover, the real data analysis indicated that the new distribution is more suitable when compared to some well-known and some recently proposed distributions to evaluate the reliability of concrete mixtures. Full article

It is shown that in auxetic materials (materials with negative Poisson’s ratio), supersonic Stoneley waves travelling without attenuation with a velocity equal to or exceeding maximum bulk wave velocity, may exist. Analytical expressions for the relation between negative Poisson’s ratio and Young’s moduli of the contacting isotropic media ensuring the condition of propagation for supersonic Stoneley waves, are derived by solving a secular equation for Stoneley waves. Full article

In this paper, the effects of oxygen vacancy and gallium vacancy on the optical and scintillation properties of undoped β-Ga₂O₃ crystal and 2.5 mol % Al doped gallium oxide were investigated. For the undoped β-Ga₂O₃, the transmittance is improved after annealing in oxygen or nitrogen atmosphere. After the introduction of Al element, the absorption cutoff appears slightly blue shift, and the band gap increases. For the undoped as-grown β-Ga₂O₃ single crystals, the decay time consists of a fast component (τ₁) of the order of nanoseconds, and two slow components (τ₂, τ₃) of tens to hundreds of nanoseconds. The contribution of the fast decay time component in the decay times is 2.78%. While for Al-doped β-Ga₂O₃, the faster (τ₁) time is 2.33 ns for the as-grown one, and the contribution is 68.02%. However, the pulse height spectrum shows that the introduction of 2.5 mol % Al will reduce the light yield of the β-Ga₂O₃ crystal. Full article

In order to study the effects of recycled aggregate with different particle gradations and different contents on the mechanical properties of cement soil modified by nano-MgO, unconfined compressive strength and scanning electron microscope (SEM) tests were carried out. The cement content was fixed at 15% and the nano-MgO content was 1.5%. The effects of two ages, three recycled aggregate contents, and three recycled aggregate particle gradations were considered. The test results show that the unconfined compressive strength of natural graded (RA), recycled coarse aggregate (SRA), and recycled fine aggregate (TRA) reached the maximum when the content of recycled aggregate was 20%, and the unconfined compressive strength of SRA was higher than that of TRA and RA. The residual strength of RA and SRA samples first increased and then decreased with the increase in recycled aggregate content, and the residual strength of TRA samples increased gradually with the increase in recycled aggregate content. The variation law of peak strain and peak strength of the three particle graded samples was consistent, and the variation law of brittle failure degree was highly consistent with that of residual strength. When the recycled aggregate content of RA, SRA, and TRA samples was 20%, the deformation resistance and stiffness of the samples were the best. In addition, SRA samples showed the best deformation resistance, followed by TRA samples and, finally, RA samples. The smaller the porosity of the sample, the tighter the sample structure and the stronger the bearing capacity of SRA. The unconfined compressive strength of the WPRA sample was represented by an exponentially negative power function of the porosity. Full article

Eu³⁺-doped Y_xLu_1−xNbO₄ (x = 0, 0.25, 0.5, 0.75, 1) were prepared by the solid-state reaction method. YNbO₄:Eu³⁺ and LuNbO₄:Eu³⁺ crystallize as beta-Fergusonite (SG no. 15) in 1–10 μm diameter particles. Photoluminescence emission spectra show a slight linear variation of emission energies and intensities with the solid-solution composition in terms of Y/Lu content. The energy difference between Stark sublevels of ⁵D₀→⁷F₁ emission increases, while the asymmetry ratio decreases with the composition. From the dispersion relations of pure YNbO₄ and LuNbO₄, the refractive index values for each concentration and emission wavelength are estimated. The Ω₂ Judd–Ofelt parameter shows a linear increase from 6.75 to 7.48 × 10⁻²⁰ cm² from x = 0 to 1, respectively, and Ω₄ from 2.69 to 2.95 × 10⁻²⁰ cm². The lowest non-radiative deexcitation rate was observed with x = 1, and thus LuNbO₄:Eu³⁺ is more efficient phosphor than YNbO₄:Eu³⁺. Full article

In this paper, the microstructural damage evolution of a steel with a ferrite–pearlite microstructure (C45E) was investigated during the process of cold upsetting. The development and the accumulation of microstructural damage were analyzed in different areas of samples that were deformed at different strain levels. The scanning electron microscopy (SEM) results showed that various mechanisms of nucleation of microcavities occurred during the upsetting process. In quantitative terms, microcavities were predominantly generated in pearlite colonies due to the fracture of cementite lamellae. In addition, the mechanism of decohesion had a significant influence on the development of a macroscopic crack, since a high level of microcracks, especially at higher degrees of deformation, was observed at the ferrite/pearlite or ferrite/ferrite interfaces. It was found that the distribution of microcavities along the equatorial plane of the sample was not uniform, as the density of microcavities increased with increasing strain level. The influence of stress state, i.e., stress triaxiality, on the nucleation and distribution of microcracks, was also analyzed. Full article

Recently, a two-dimensional (2D) heterostructure has been widely investigated as a photocatalyst to decompose water using the extraordinary type-II band structure. In this work, the MoTe₂/PtS₂ van der Waals heterostructure (vdWH) is constructed with different stacking structures. Based on density functional calculations, the stacking-dependent electronic characteristic is explored, so that the MoTe₂/PtS₂ vdWH possesses type-I and type-II band structures for the light-emitting device and photocatalyst, respectively, with decent stacking configurations. The band alignment of the MoTe₂/PtS₂ vdWH is also addressed to obtain suitable band edge positions for water-splitting at pH 0. Furthermore, the potential drop is investigated, resulting from charge transfer between the MoTe₂ and PtS₂, which is another critical promotion to prevent the recombination of the photogenerated charges. Additionally, the MoTe₂/PtS₂ vdWH also demonstrates a novel and excellent optical absorption capacity in the visible wavelength range. Our work suggests a theoretical guide to designing and tuning the 2D heterostructure using photocatalytic and photovoltaic devices. Full article

Diclofenac (DCF) is among the most effective non-steroidal anti-inflammatory drugs (NSAIDs) and at the same time one of the most consumed drugs worldwide. Since the ever-increasing use of diclofenac poses serious threats to ecosystems, its substantial removal is crucial. To address this issue, a variety of sorbents have been employed. Herein we present the diclofenac removal properties of two metal organic frameworks, namely [Zr₆O₄(OH)₄(NH₂BDC)₆]·xH₂O (MOR-1) and H₁₆[Zr₆O₁₆(H₂PATP)₄]·xH₂O (MOR-2). Batch studies revealed fast sorption kinetics for removal of DCF⁻ from water as well as particularly high selectivity for the drug vs. common competitive species. Moreover, the composite MOR-1-alginic acid material was utilized in a sorption column, displaying remarkable removal efficiency towards DCF⁻ anions. Significantly, this is the first time that column sorption data for removal of NSAIDs using MOF-based materials is reported. Full article

The processing parameters’ impact such as temperature (Temp.), feed rate (F.R.), and speed (S.) at three distinct grades of the same color was explored in this study. To investigate the effect of the characteristics on color formulations, they were each adjusted to five different levels. For these grades, which were all associated with the same color, an intermeshing twin-screw extruder (TSE) was used. The compounded materials were molded into flat coupons then evaluated with a spectrophotometer for their CIE (L*, a*, b*, and dE*) values. A spectrophotometer was used to determine the color of a compounded plastic batch, which measured three numbers indicating the tristimulus values (CIE L*a*b*). The lightness axis, which ranged from 0 (black) to 100 (white), is known as the L*-axis (white). Redness-greenness and yellowness-blueness were represented by the other two coordinates, a* and b*, respectively. The color difference deviation (Delta E*) from a target was dimensionless, when dE* approached zero. However, the most excellent favorable color difference value occurred and different processing impact factors on polycarbonate grade were investigated. Using the response service design (RSD) software of Stat-Ease Design-Expert^® (Minneapolis, MN, USA), historical data were gathered and evaluated. To reduce the value of dE*, the impacts of these processing factors were investigated with the three processing parameters. The whole tristimulus color value could be simulated. Parameters were adjusted on 45 different treatments, using a five-level controlled response method to investigate their impact on color and detect non-optimal responses. The ANOVA for each grade was used to build the predicted regression models. The significant processing parameters were subjected to experimental running to simulate the regression models and achieve the best color, reducing waste. Full article

The new 30-substituted triazole derivative of 3,28-O,O′-diacetylbetulin was obtained in the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC). The title compound was characterized by NMR, IR, HR-MS, and X-ray diffraction techniques. The X-ray diffraction study showed that the 1,2,3-triazole derivative crystallizes in the orthorhombic space group P2₁2₁2₁, Z = 4, and unit cell parameters are as follows a = 9.4860(10) Å, b = 13.9440(2) Å, and c = 30.2347(4) Å. The molecular packing is stabilized by intermolecular hydrogen interactions C-H…O. The Hirshfeld surface analysis showed the presence of the O…H interactions with a percentage of the 16.5% in the total Hirshfeld area. The MEP analysis showed that the nucleophilic regions are located near the oxygen atoms of the acyl and carbonyl groups of betulin moiety and the sulfur atom in the triazole linker. The HOMO and LUMO orbitals are located near the triazole moiety. The obtained results indicated that this new betulin derivative is more reactive with electrophilic than nucleophilic molecules. Full article

In this work, graphite intercalation compounds (GICs) were synthesized using three different oxidizers: (NH₄)₂S₂O₈, K₂S₂O₈, and CrO₃ with and without P₂O₅ as a water-binding agent. Furthermore, the samples obtained were heat-treated at 800 °C. Specimens were characterized by optical microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The correlation between different characteristic parameters of the Raman analysis has shown that the use of CrO₃ results in a much higher structural disorder compared to the products obtained using persulfate oxidizers. Narrowing the correlation set revealed that minimal defect concentration can be reached by using K₂S₂O₈, while the use of (NH₄)₂S₂O₈ causes a slightly higher concentration of defects. It was also established that the additional use of P₂O₅ can help to achieve more effective intercalation and has a positive effect on the formation of the stage I GIC phase. After heat treatment, the intercalated products mostly return to a graphite-like structure; however, the samples obtained with CrO₃ stand out with the most significant changes in their surface morphology. Therefore, analysis suggests that GICs obtained using persulfate oxidizers and P₂O₅ could be a candidate to produce high-quality graphene or graphene oxide. Full article

Plant extract-based green synthesis of metal nanoparticles (NPs) has become a popular approach in the field of nanotechnology. In this present investigation, silver nanoparticles were prepared by an efficient and facile approach using Juniperus procera extract as a bioreducing and stabilizing agent. The as-synthesized silver nanoparticles (JP-AgNPs) were characterized by several characterization techniques such as UV–Vis, XRD, FT-IR, HR-TEM, and EDX analysis. The XRD analysis evidently confirms that the as-synthesized Ag nanoparticles (NPs) from Juniperus procera plant extract (JP-AgNPs) are crystalline in nature. FT-IR analysis confirms that the plant extract plays a dual role as a bioreducing and capping agent, while HR-TEM revealed the spherical morphology of as-synthesized JP-AgNPs with the size of ~23 nm. Furthermore, the synthesized JP-AgNPs were evaluated for antibacterial properties against several bacterial and fungal strains such as Staphylococcus aureus (ATCC 12228), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Proteus mirabilis (ATCC 4753), Cryptococcus neoformans (ATCC 16620), and Candida albicans (ATCC 885-653). The JP-AgNPs displayed an efficient mean zone of inhibition (MZI) at 50.00 µL for bacterial associated with fungal pathogens than the plant extract. Mainly, MZI values against microbial pathogens were as follows; E. coli (17.17 ± 0.72 mm), P. mirabilis (14.80 ± 0.17 mm), and C. albicans (14.30 ± 0.60 mm), whereas JP-AgNPs showed moderate activity against P. aeruginosa (11.50 ± 0.29 mm) and C. neoformans (9.83 ± 0.44 mm). Notably, the tested JP-AgNPs have displayed almost similar antimicrobial activities with that of standard antimicrobial drugs, such as streptomycin and nystatin. The enhanced antimicrobial activity of JP-AgNPs can be ascribed to the quality of resultant NPs including, uniform size, shape, and aqueous colloidal stability of nanoparticles. Full article

Perovskite–like vanadate–molybdates are interesting from the point of view of their metal–like conductivity, which combines the correlated and free electron nature. A series of CaV_1–xMo_xO_3–δ solid solutions was considered near the Mo concentration x = 0.4, where a difficult–to–perceive structural transition was previously detected. High-resolution transmission electron microscopy revealed the phase separation of CaV_0.6Mo_0.4O_3–δ into nanoscale regions with different ratios of V and Mo concentrations, despite X–ray diffraction analysis exhibiting a homogeneous perovskite structure. The rest of the compositions from the CaV_1–xMo_xO_3–δ series do not show phase separation. The nonmonotonic behavior of the conductivity and linear expansion of CaV_1–xMo_xO_3±δ was shown when the oxygen activity in the N₂-H₂-H₂O gas mixture was varied, which is mainly determined by the partial decomposition of the perovskite phase. Against this background, the behavior of the electrical properties of the CaV_1–xMo_xO_3±δ individual phase remains unclear. Full article

The improved efficiency of perovskite-related photovoltaic devices, such as light-emitting diodes (LEDs), is related to film uniformity, the compactness of each layer, and thickness. Herein, we improved the traditional single-solvent, solution-processed method and developed a co-solvent method to prepare a two-dimensional (2D) (C₄H₉NH₃)₂PbBr₄ perovskite film for blue photoluminescence (PL) emissions. A poor film-forming uniformity was observed for the use of the single-solvent, dimethylformamide (DMF) method. In adding 1,2-dichlorobenzene (ODCB) of a smaller polarity to DMF, the co-solvent engineering dramatically changed the film-forming properties. Optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffractometer (XRD), and time-resolved PL (TR-PL) spectroscopy analyses confirmed that the perovskite film prepared by the co-solvent system had a good crystallinity, fewer defects, and a longer carrier lifetime. These experimental results show a simple, scalable (1.23 × 1.23 cm²), and stable reproducibility method for preparing 2D perovskite of 415 nm wavelength PL emissions that might be beneficial for the development of ultraviolet (UV) photodetectors, blue LEDs, and high-resolution displays. Full article

The nearly lattice-matched In_xGa_1−xN/In_yAl_1−yN epi-layers were grown on a GaN template by plasma-assisted molecular beam epitaxy with a metal modulation technique. The band-gap energy of In_xGa_1−xN QW in photoluminescence measurement was estimated to be 2.89 eV and the indium concentration (x) was 14.8%. In X-ray photoelectric spectroscopy, we obtained an indium concentration (y) in the In_yAl_1−yN barrier of 25.9% and the band-offset was estimated to be 4.31 eV. From the atomic layer measurements from high-resolution transmission electron microscopy, the lattice misfit between the In_xGa_1−xN QW and In_yAl_1−yN barrier was 0.71%. The lattice-matched In_xGa_1−xN/In_yAl_1−yN QWs can therefore be evaluated from the band profiles of III-nitrides for engineering of full-visible-light emitting diode in optoelectronic application. Full article

Three alloys based on nickel, rich in chromium due to their oxidation resistance at high temperature and containing ZrC carbides for their mechanical reinforcing against creep, were elaborated by foundry. After control of their as-cast microstructures, these alloys were subjected at 1100 °C to flexural creep and to oxidation in air. Script-like ZrC carbides were obtained in the interdendritic spaces, forming a eutectic compound with a part of the matrix. One of the alloys additionally contained Cr₇C₃ eutectic carbides. By comparison with a Ni–Cr–C reference alloy with similar contents in Cr and C, the three alloys demonstrated a much better creep resistance for the same conditions of stress and temperature. However, their oxidation rates were much greater than for the reference alloy. In contrast with the chromia-forming reference alloy, several kinds of oxides formed in the case of the three alloys, as NiCr₂O₄ spinel and oxides involving zirconium. A significant inward interdendritic oxidation progression was noticed for the three studied alloys. To benefit from the interesting creep resistance of these alloys for long sustainability in service, it appears necessary to significantly improve their oxidation behavior. Full article

Single crystals of Ho₂O₃-doped Y₂O₃ stabilized ZrO₂ (YSZ) with different Y₂O₃ and Ho₂O₃ contents were grown by the optical floating zone method. XRD and Raman spectra were measured and showed that crystal samples all had tetragonal structures. Measurements of positron annihilation lifetime spectra indicated that the increase in Y₂O₃ concentration led to the increases of defects and mean positron lifetime, which enhanced the scattering of light and reduced the luminous intensity and the quantum yield (QY) of the crystal. Under the excitation at 446 nm, photoluminescence (PL) spectra of Ho₂O_3-doped YSZ crystals showed emission peaks at 540, 551, 670, and 757 nm corresponding to Ho³⁺ transitions from ⁵S₂, ⁵F₄, ⁵F₅, and ⁵I₄ excited states to the ⁵I₈ ground state, respectively. At low Ho₂O₃-doped concentrations (0.10–0.50 mol%), the overall emission intensity increased with Ho₂O₃ contents, reached the maximum value at 0.50 mol%, then decreased with higher Ho₂O₃ contents, probably as a result of increased non-radiative relaxation caused by increased interactions between Ho³⁺ ions. Quenching of the PL occurred at Ho₂O₃ concentrations > 0.5 mol% and due to the electric dipole–dipole interaction. The calculated chromaticity coordinates (CIE) were approximately (0.307, 0.683) and the color purity achieved 99.6%. The results showed that Ho₂O₃: YSZ crystals were suitable for green light-emitting devices. Full article

During the solidification of hypoeutectic Al–7% Si alloy, density differences develop in the melt due to variations in concentration and temperature. On Earth, melt flow can occur due to gravity, which then affects the solidification process. The microgravity environment strongly eliminates convection in the melt and allows investigation of the solidification process in purely diffusive circumstances. In this study, four solidification experiments were performed on grain-refined and non-grain-refined Al–7 wt% Si alloy on-board the International Space Station (ISS) in the Materials Science Lab (MSL) to study the effect of solidification parameters (solid/liquid front velocity (v) and temperature gradient (G)) on the grain structure and dendritic microstructure. The grain structure has been analyzed in detail in some earlier studies. The aim of this work was to carry out detailed analysis of the macrosegregation caused by the diffusion of Si from the initial mushy zone during the homogenization step and the subsequent solidification phase of the experiments as well as the correlated distribution of eutectic along the solidification direction. The secondary dendrite arm spacing (SDAS) for different process conditions was also studied. For these two issues, microgravity experimental results were compared to simulation results. The macrosegregation was calculated by the finite difference method. Because the steady-state solidification conditions were never reached, the solidification process was characterized by the average front velocity and temperature gradient. Considering the actual liquidus temperature (T_L) caused by macrosegregation, the SDAS was calculated as a function of the average processing parameters and the actual liquidus temperature with the classical Kirkwood’s equation. As a result, good agreement was obtained between the calculated and measured SDAS. Full article

Five types of ductile cast irons (DCIs) were fabricated by crystallizers with different inner diameters, as well as five different austempered ductile cast irons (ADIs) after the same isothermal quenching process. The effects of amount, diameter, and morphology of graphite on the mechanical properties of DCI and ADI and the effect of the original as-cast microstructure on the microstructure after austempering were studied. The microstructures were characterized by optical microscopy, scanning electron microscopy, and X-ray diffraction. Their mechanical properties were examined by tensile, U-shaped impact, and hardness tests. As the diameter of the crystallizer increases from 60 mm to 150 mm, the diameter of the nodular graphite increases from ~10 to ~50 μm, and the nodularity rate decreases from 100 to 70%. The average ultimate tensile strength increases from ~500 MPa in the as-cast state to 1100 MPa in the austempered state and the hardness increases from ~180 HB to 400 HB. The elongation in cast state decreases from 11 to 4.6% and the elongation in ADI state decreases from 7 to 4.5%. Through the research in this paper, it can be seen that ADIs with different matrix microstructures can be obtained from different original as-cast microstructures through the same isothermal quenching process, and different casting crystallizers can be selected according to different performance requirements, which can reduce the nitrite pollution and reduce cost. Full article

This work is focused on the complex interplay of geometry of I⋯X halogen bonds (HaB) and intermolecular interaction energy in two isomorphic cocrystals [CpFe(CO)₂X] (C₂I₄) (X = Cl (1), Br (2)). Their IR-spectroscopic measurements in solid state and solution demonstrate the blue-shift of CO vibration bands, resulting from I⋯X HaB. The reluctance of their iodide congener [CpFe(CO)₂I] to form the expected cocrystal [CpFe(CO)₂I] (C₂I₄) is discussed in terms of different molecular electrostatic potential (MEP) of the surface of iodide ligands, as compared with chloride and bromide, which dictate a different angular geometry of HaB around the metal-I and metal-Br/Cl HaB acceptors. This study also suggests C₂I₄ as a reliable HaB donor coformer for metal-halide HaB acceptors in the crystal engineering of hybrid metal–organic systems. Full article

This work discusses the development of an analysis routine for evaluating the nanoparticle distribution in nanocomposite thin films. YBa₂Cu₃O_7−δ (YBCO) nanocomposite films were synthesized via a chemical solution deposition approach starting from colloidal YBCO solutions with preformed nanoparticles. The distribution of the nanoparticles and interlayer diffusion are evaluated with X-ray photoelectron spectroscopy (XPS) depth profiling and compared with cross-sectional transmission electron microscopy (TEM) images. It is shown that the combination of both techniques deliver valuable information on the film properties as nanoparticle distribution, film thickness and interlayer diffusion. Full article

In this work, the spectral properties of distributed Bragg reflector-based photonic crystal (DBR-PhC) structures were studied for the near-infrared (NIR) range. Different structural properties were varied to study their effect on the quality of the stopband and the appearance of the resonant dips in the reflection spectra of the DBR-PhC structure. The investigated structural features included the depth of PhC holes, hole radius, and number of PhC elements in the DBR structure. The 11-layered DBR structure was designed with a 2.4/1.4 refractive index contrast of alternating layers. The study aimed to achieve optical filtering properties in the DBR-PhC structure, to simplify the structural complexity of Fabry-Pérot filters by eliminating the FP cavity and upper-DBR mirror. The proposed DBR-PhC device can be used in different optical filtering and sensing applications. Full article

Additively manufactured Ni-Ti lattice structures have controllable bio/mechanical properties, as well as excellent large deformation and damping properties similar to those of natural bone. They have broad application prospects in the field of bone implantation. Triply Periodic Minimal Surface (TPMS) structures are believed to be the most potential and ideal bionic bone structures. In this work, Ni-Ti Gyroid-type TPMS lattice structures were fabricated by selective laser melting (SLM) and their manufacturing fidelity and compression properties were evaluated. By changing the maximum strain value, the hyperelastic recovery performance under cyclic stress was investigated. The results showed that the Ni-Ti Gyroid lattice structures fabricated by SLM had excellent manufacturability (relative density can reach 98.93%) and mechanical properties (elastic modulus is about 130.8 MPa, ultimate strength is about 2.7 MPa). The hyperelastic cycle testing showed that the elastic modulus, yield strength and ultimate strength of the lattice structures tended to stablilize gradually with increasing numbers of cycles. The residual strain increased with the number of cycles, and as the maximum strain increased from 4% to 8%, the residual strain also increased from 1% to 4%. Full article