Crystals

Ospinsk is an area in Russia well-known for mining the highest quality green nephrite in the world. However, the chatoyant green nephrite found here has not been studied to date. This study explores the mineralogy, geochemistry, and petrogenesis of chatoyant green nephrite collected from Ospinsk using polarizing microscope back-scattered electron images, scanning electron microscopy, Fourier transform infrared spectrometry, laser Raman spectroscopy, electron microprobe analysis, and laser ablation inductively coupled plasma mass spectrometry, and compares them with S-type green nephrite from other regions of the world. Tremolite is the main mineral constituent, and chromite, chlorite, graphite, and magnetite are accessory minerals in the samples. The chatoyant green nephrite from Ospinsk is serpentinite-related green nephrite. The Ti content of the chatoyant green nephrite from Ospinsk is significantly higher than that of green nephrite from other places. The chatoyant green nephrite deposit in Ospinsk is a contact metasomatic deposit related to ultramafic rocks. The ultramafic rocks first altered to serpentinite and later converted to tremolite after repeated thermal contact-based metasomatism. During the metasomatism of serpentinite into green nephrite, unilateral, compressive, and shear stresses caused by obduction forced directional growth of tremolite, resulting in chatoyancy. Full article

The magnetic and electronic properties of zigzag-triangular WS₂ and MoS₂ quantum dots are investigated using density functional theory calculations. The pristine WS₂ and MoS₂ nanodots hold permanent spin on their edges which originates from the unpaired electrons of the transition metals at the edges. The ferromagnetic spin ordering in zigzag-triangular WS₂ and MoS₂ can be transformed to antiferromagnetic ordering with S = 0 and to nonmagnetic, respectively, by edge passivation with 2H. The calculations of the Curie Temperature indicate that these magnetic states are stable and withstand room temperature. The paramagnetic susceptibility of these structures significantly decreases by edge sulfuration. Moreover, it can be converted to diamagnetic susceptibility by edge passivation with 2H as found in WS₂ nanodots. These structures are semiconductors with energy gaps of ~3.3 eV that decrease unexpectedly by edge passivation due to the existence of lone pairs from S atoms that give a high contribution to the low-energy molecular orbitals. With these preferable magnetic properties and controlled electronic ones, WS₂ and MoS₂ quantum dots are potential candidates for spintronic applications. Full article

Non-equilibrium molecular dynamics simulations have been used to investigate strain-rate dependence of plasticity and phase transition in [001]-oriented single-crystal iron under ramp compression. Here, plasticity is governed by deformation twinning, in which kinetics is tightly correlated with the loading rate. Over the investigated range of strain rates, a hardening-like effect is found to shift the onset of the structural bcc-to-hcp phase transformation to a high, almost constant stress during the ramp compression regime. However, when the ramp evolves into a shock wave, the bcc–hcp transition is triggered whenever the strain rate associated with the plastic deformation reaches some critical value, which depends on the loading rate, leading to a constitutive functional dependence of the transition onset stress on the plastic deformation rate, which is in overall consistence with the experimental data under laser compression. Full article

Interest in the deformation behavior and phase transformations of rare earth orthophosphates (REPO₄s) spans several fields of science—from geological impact analysis to ceramic matrix composite engineering. In this study, the phase behavior of polycrystalline, xenotime DyPO₄ is studied up to 21.5(16) GPa at ambient temperature using in situ diamond anvil cell synchrotron X-ray diffraction. This experiment reveals a large xenotime–monazite phase coexistence pressure range of 7.6(15) GPa and evidence for the onset of a post-monazite transformation at 13.9(10) GPa to scheelite. The identification of scheelite as the post-monazite phase of DyPO₄, though not definitive, is consistent with REPO₄ phase transformation pathways reported in both the experimental and the computational literature. Full article

Ambient humidity is an important factor to consider when maintaining dielectric films’ component performance. Herein, humidity-influenced experiments were conducted on complex spectral dielectric films based on SiO₂ and K9 substrates. Firstly, complex spectral dielectric films’ spectral and surface stresses in different humidity environments were measured. Subsequently, laser-induced damage threshold measurements were carried out on these components. The experimental results indicate that the environmental humidity will induce the evolution of the internal structure of the dielectric films on the mirror, resulting in the deformation of the coating surface and a slight shift of the reflection spectrum. At the same time, the environmental humidity also greatly influences the anti-laser damage performance of the dielectric film mirror. Dielectric films based on SiO₂ have excellent damage resistance in high-humidity environments. Conversely, K9-based dielectric films have better damage resistance in low-humidity environments. Full article

This report presents ‘giant’ and long-range premelting effects appearing in dielectric properties for the temperature and pressure paths of studies, with an explicit critical-like portrayal. The result was obtained for the ‘classic’ low molecular weight compound: nitrobenzene, tested in the solid and liquid phases. Dielectric studies enable the ‘extraction’ of the response from liquid layers between crystalline grains. Compressing increased the premelting effects, probably due to the ‘crushing’ of crystalline grains by isotropic squeezing and increasing the liquid layers between grains. This report indicates the significance of considering the melting/freezing phenomenon from the point of view of the ‘solid crystalline grains and critical-type liquid layers in synergic interactions’ concept. Full article

In this paper, the improvement of the characteristics of different steels that are subjected to extreme operating conditions, including the steels used in the manufacture of various military components, the AISI 52100, the manufacture of bearings, and other types of parts that are also subjected to severe operating conditions were analyzed regarding cold spraying, which uses different types of powders to increase the performance of the materials. The cold, thermal spraying technology “Cold Spray” is a method of processing particles in a solid state. Thermal spraying, based on the dynamic increase in gas acceleration up to supersonic speeds, leads to the obtainment of high kinetic energies, and the accelerated particles are deposited at values that are below their melting point. Research conducted through cold spray technology has seen a significant improvement in material properties; when processing the particles in a solid state, they adhere to the surface instead of eroding it. Cold spraying has proven to be an effective technique for improving material properties, as confirmed by its integration into different fields and industries, becoming competitive by being the only method for depositing particles below their melting point. Full article

A von Mises criterion for compatible deformation states that five independent slip systems must operate for polycrystals to deform uniformly and without failure at the grain boundaries, which is supported by the Taylor–Bishop–Hill theory or simply the Taylor model, defining the laws of plastic deformation of polycrystalline aggregates and being one of the key cornerstones of crystal plasticity theory. However, the criterion has fundamental flaws as it is based on an unfounded correlation between phenomenological material flow behaviour in continuum mechanics and crystal structure dependent dislocation slip, and there has been no experimental evidence to show simultaneous operation of five independent slip systems. In this paper, the Von Mises criterion and the Taylor model are revisited and examined critically, and the fundamental issues related to the requirement of independent slip systems for compatible deformation and the selection of the active slip systems are addressed. Detailed analysis is performed of the stress state that eliminates the possibility of the simultaneous operation of five independent slip systems, and of the relative displacement vector due to the dislocation slip which defines the quantity of the strain that can be expressed by a strain tensor, instead of individual strain components. Discussions are made to demonstrate that although three linearly independent slip systems are essentially sufficient for compatible deformation, one slip system, being selected according to Schmidt law, dominates at a time in a characteristic domain as deformation accommodation occurs between grains or characteristic domains rather than at each point. Full article

In order to investigate the effect of phase separation (PS) on the super duplex stainless steel SAF 2507, the evolution of the nanostructure, mechanical properties, and corrosion resistance of the alloy was studied after aging at 500 °C for 1, 10, 100, and 1000 h. The nanostructure of PS was quantitatively characterized by small-angle neutron scattering. The hardness, impact toughness, and pitting corrosion resistance were measured for different conditions. The results show that the early stage of PS had a more significant impact on the nanostructure and properties of SAF 2507. The fracture behavior of the alloy was likely determined by the mechanical properties of ferrite for aged conditions. The pitting corrosion resistance of SAF 2507 aged at 500 °C was closely related to the Cr depletion caused by PS, and the resistance became weaker with the progression of PS. The evolution of the passivation region with aging time correlated well with that of mechanical properties and characteristic parameters of PS, indicating that it is possible to develop a new nondestructive electrochemical method to quantify the evolution of PS in SAF 2507. Full article

Low-temperature solid fuel cells (LT-SOFCs) hold remarkable promise for the cooperative corporation of small- and large-scale applications. However, the meager oxygen-reduction retort of cathode materials mires the low operating temperature conditions of SOFCs. Herein, we have developed a perovskite structured LaFeO₃ by the co-doping of Gd and Ce ions, and their electrochemical properties have been studied. The developed LaFe_0.8Gd_0.1Ce_0.1O_3-δ cathode exhibits very small-area-specific-resistance and good oxygen-reduction reaction (ORR) activity at low operating temperatures of 450–500 °C. We have demonstrated a high-power density of 0.419 W-cm⁻² with a LaFe_0.8Gd_0.1Ce_0.1O_3-δ cathode operating at 550 °C with H₂ and atmospheric air as fuels. Moreover, LaFe_0.8Gd_0.1Ce_0.1O_3-δ exhibits high activation energy as compared to individual LaFeO_3, which helps to promote ORR activity. Various spectroscopic measurements such as X-ray diffraction, SEM, EIS, UV-visible, TGA, Ramana, and photoelectron spectroscopy were employed to understand the improved ORR electrocatalytic activity of Gd and Ce co-doped LaFeO₃ cathode. The results can further help to develop functional cobalt-free electro-catalysts for LT-SOFCs. Full article

This paper presents a zero-optical-distance mini-LED backlight with cone-shaped light coupling microstructures to achieve an ultra-thin backlight architecture (~0.1 mm thickness) by combining the characteristics of direct-lit and edge-lit backlights. There is no gap between the light guide plate (LGP) and the reflector, as well as between the LGP and the mini-LED embedded in the reflector. The illuminance uniformity and light extraction efficiency (LEE) of the whole structure reach 91.47% and 77.09%, respectively. Nine sub-modules are spliced together to realize 2D local dimming with 0.29% crosstalk. The structure shows high optical performance while reducing the thickness of the backlight module, which is of great significance for the development of mini-LED backlights. Full article

Thermodynamic properties of MgAl₂O₄ spinel are significant in understanding the phase relations of the Earth’s crust and upper mantle, but available values from experimental measurements are limited at ambient pressure conditions to date. Based on an iterative numerical approach and experimental data from the literature, we determined the self-consistent unit-cell volume, elastic moduli, and, particularly, thermodynamic properties, including thermal expansion, heat capacity, entropy, and the Grüneisen parameter of MgAl₂O₄ spinel over a wide temperature and pressure range. The obtained thermal expansion, heat capacity, entropy, and Grüneisen parameter of MgAl₂O₄ spinel show nonlinearly and are negatively correlated with pressure. Most importantly, we found that the pressure effects on thermal expansion and entropy increase with temperature, whereas the pressure effect on the heat capacity and the Grüneisen parameter decreases to a minimum at ~400 K and ~700 K, respectively, then increases or remains almost constant above this temperature, respectively. Full article

Weathering rind retains the greatest extent of the mineralogical and chemical composition information of the original mineral. Recently, we found some brownish-yellow or khaki serpentine jade weathering rinds with a thickness of 0.2–0.6 cm in Ji’an. The purpose of this paper is to explore differences in structural characteristics and chemical composition between weathering rinds and unweathered cores and summarize the formation of weathering rinds. In terms of structural characteristics, weathering rinds have smaller a₀, b₀, β values than unweathered cores; the specific surface area is 13.3987 m²/g; the pore volume is 0.0314 cm³/g; and the pore size distribution is characterized as more mesoporous (2–10 nm). The weathering rind shows partial dissolution of serpentine grains, increased porosity, and loosening structure. In terms of chemical composition, the weathering rind is characterized by the decrease of some serpentine major elements (Si, Mg, and Fe) and the increase of some impurity elements (Al, Ca, K, Na, and Cl). The weathering rind is the result of further alteration of serpentine jade, accompanied by the reduction of the Fe³⁺/Fe²⁺ ratio and the generation of the clay mineral (chlorite). In addition, it was also found that Ji’an serpentine jade belongs to Mg-bearing carbonate rock genesis, which are derived from marine deposits. Full article

This work describes the synthesis of a novel zinc(II) porphyrin complex, namely [Meso-4α-tetra-(1,2,3-triazolyl)phenylporphyrinato]zinc(II) symbolized by 4α-[Zn(TAzPP)] (4), using the click chemistry approach in the presence of copper iodide. All of the synthetic porphyrin species reported herein were fully characterized by elemental analysis, infrared spectroscopy, proton nuclear magnetic resonance, UV-visible spectroscopy, and fluorescence. To synthesize the 4α-[Zn(TAzPP)] complex (4), we produced 4α-Meso-tetra-o-nitrophenylporphyrin (H₂T_NO2PP) and 4α-meso-tetra-o-aminophenylporphyrin (4α-H₂TNH₂PP) (1) using known classic literature methods. This 4α atropisomer was converted to 4α-meso-tetra-o-azidophenylporphyrin (4α-H₂TN₃PP) (3) by reaction with sodium nitrite and sodium azide, and then it was metalated by Zn(II), leading to [4α-meso-tetra(2-azidophenyl)porphyrinate]zinc(II) (4α-[Zn(TN₃PP)]) (3). The click chemistry synthetic method was finally used to prepare 4α-[Zn(TAzPP)] (4). This new tetracoordinated zinc(II) porphyrin complex was prepared and characterized in order to: (i) produce a receptor for anion recognition and sensing application for Cl⁻ and Br⁻; (ii) study the catalytic decomposition of rhodamine B (RhB) and methyl orange (MO) dyes; and (iii) determine the electronic characteristics as a photovoltaic device. Complex (4) formed 1:1 complex stoichiometric species with chloride and bromide halides and the average association constants of the 1:1 addicts were ~ 10³. The photodecomposition of RhB and MO dyes in the presence of complex (4) as a catalyst and molecular oxygen showed that complex (4) presented a photodegradation yield of approximately 70% and could be reused for five successive cycles without any obvious change in its catalytic activity. The current-voltage characteristics and impedance spectroscopy measurements of complex (4) confirmed that our zinc(II) metalloporphyrin could be used as a photovoltaic device. Full article

High-energy materials genome (HEMG) is an analytical and calculation tool that contains relationships between variables of the object, which allows researchers to calculate the values of one part of the variables through others, solve direct and inverse tasks, predict the characteristics of non-experimental objects, predict parameters to obtain an object with desired characteristics and execute virtual experiments for conditions which cannot be organized or have difficultly being organized. HEMG is based on experimental data on the burning rate of various high-energy materials (HEMs) under various conditions, on the metadata on the quantum and physicochemical characteristics of HEMs components as well as on thermodynamic characteristics of HEMs as a whole. The history and current status of the emergence of HEMG are presented herein. The fundamental basis of the artificial neural networks (ANN) as a methodological HEMG base, as well as some examples of HEMG conception used to create multifactor computational models (MCM) of solid rocket propellants (SRP) combustion, is presented. Full article

The microstructure morphology and evolution of mechanical properties are investigated in this study. The results show that the phases displayed no clear change after thermal exposure at 250 °C for 200 h. The tensile strength of the as-cast alloy showed a downward trend in different degrees with the increase in the tensile temperature, while the influence of elongation was opposite to the tensile strength. In addition, the tensile strength tended to be stable after thermal exposure at 250 °C for 100 h. The main creep mechanism of the as-cast alloy at a low temperature and low stress (T ≤ 250 °C; σ ≤ 40 MPa) is grain-boundary creep. The Monkman–Grant empirical formula was used to fit the relationship between the creep life and the minimum creep rate, and the fitting results are:$t_r·{\dot{\epsilon }}_{min}^{0.95}=0.207$. Full article

In this work, the thin wall components of TC4 titanium alloy were produced by using external magnetic field hybrid gas metal welding (EM-GMAW). The effect of the external magnetic field on the forming, microstructure, and property of wire arc additively manufactured TC4 titanium alloy was studied in detail. The results showed that the height of the average deposition layer of EM-GMAW was less than that of GMAW and decreased with the increase of magnetic excitation current, and the width of the average deposition layer of EM-GMAW was greater than that of GMAW. The microstructure of the deposition layer consisted of fine α phase and coarse β grains. Compared with the traditional GMAW, the coarse β grain size in the EM-GMAW was reduced obviously. The maximum size of β grain was decreased by 100μm when the magnetic excitation current of 3A was used. In addition, the EM-GMAW tensile strength in the transverse and horizontal was increased by around 20 MPa and 100 MPa, respectively, compared with that of GMAW. Full article

High temperature oxidation is considered to play an essential role in the thickness debit effect on the creep rupture life of Ni-based single crystal (SC) superalloys. In order to clarify thickness effects, thin-walled specimens of different thickness (t = 0.1, 0.3, 1.0 mm) were prepared. Cyclic and isothermal oxidation tests of a high-Al Ni-based SC superalloy IC21 were carried out at 900 °C and 1100 °C in order to study the thickness effects on the oxidation behavior and consequent microstructural degradation. Thin-walled specimens of S01-N exhibited a good oxidation resistance when the protective scale-forming elements were enough in the matrix. Specimen thickness tuned the oxidation kinetics by changing the spallation behavior but had few influences on the thermodynamics. The easier stress relief via creep deformation in thin specimens is the main reason behind this phenomenon. Moreover, the obvious temperature effects on the multilayer oxide scales caused the different thickness-related spallation behaviors. Weaker microstructural degradation appeared and was further mitigated by reduced specimen thickness. Sufficient Al content is considered to be indispensable for the formation of protective α-Al₂O₃ scale with less degradation of matrix during the high temperature oxidation of thin-walled Ni-based SC superalloy castings. Full article