Crystal Zone Research Articles

Phase Equilibria for the Aqueous Quinary System Li+, Na+, K+, Mg2+//Cl––H2O Saturated with NaCl·2H2O at 258.15 K

The phase diagram can guide the comprehensive utilization of salt lake brine, particularly lithium extraction. In this paper, the study on phase equilibria of the quinary system Li+, Na+, K+, Mg2+//Cl––H2O saturated with NaCl·2H2O and its subsystem Li+, Na+, Mg2+//Cl––H2O at 258.15 K were carried out using the isothermal dissolution equilibrium method. Based on the experimental data, equilibrium diagrams for stable phases were plotted. For the equilibrium diagram of the quaternary system Li+, Na+, Mg2+//Cl––H2O at 258.15 K, there are two invariant points, five univariant curves, and four crystallization fields. The quinary system Li+, Na+, K+, Mg2+//Cl––H2O saturated with NaCl·2H2O at 258.15 K contains three invariant points, seven univariant curves, and five crystallization fields. Comparing the phase diagram of the system at 258.15 K to that at 298.15 K reveals that, except KCl, all crystallization zones have decreased, and LiCl·MgCl2·7H2O has the smallest crystallization zone compared to the other salts in the systems. This fundamental research could be valuable for promoting comprehensive utilization of the lithium-containing salt lake brine.

The Umm Matierah gold prospect: Mineralogical and geochemical characteristics of a potential low-sulfidation epithermal gold deposits, southeastern Arabian Shield, Saudi Arabia

The Umm Matierah gold prospect is located in the southeastern part of the Arabian Shield, at the northernmost tip of the Jabal Ishmas-Wadi Tathlith gold belt. Detailed mineralogical and geochemical investigations indicated that the studied metavolcanics show lithological varieties of meta-alkali basalt, meta-andesite, meta-trachyandesite, and meta-dacite. These rocks are foliated and hydrothermally altered (bleached), indicating a low-temperature propylitic alteration, affected by breccia veins and veinlets, and irregular stockwork. The Umm Matierah gold deposit is characterized by quartz-adularia-sericite-chlorite-carbonate alteration assemblage. The ore minerals of the Umm Matierah gold prospect are dominated by pyrite and arsenopyrite, with minor amounts of sphalerite. The sulfides have no preferred host rock; however, they are mainly present within the veins and veinlets and at the contacts with host rocks; they are also associated with the quartz-rich breccias. Minute gold grains are traced at the contact between the inner pitted and the outer clear zones of large pyrite crystals. Gold and sulfide enrichment do not exceed 10 vol% of the whole rock and are correlated with the thickness of extensive alteration zones that also show an ultimate association of chlorite with sulfide minerals. Compositionally, the studied rocks show 6.47 ppm average gold, are relatively rich in K, Ag, As, Sb, and W, and are relatively poor in Al, Na, Cu, Cr, Ni, Nb, Y, and Rb. The host rocks range in composition from ultrapotassic, shoshonitic, high-K calk-alkaline, to calk-alkaline end member, with transitional environmental signature from intraplate to oceanic island arc. These compositional features suggest that these rocks may have been derived from island source and subsequently slightly fractionated and contaminated during ascent and/or slightly affected by hydrothermal alteration. The host rocks display strong positive Eu, and negative Th, Nb, and Sr anomalies in keeping with the upper continental crustal pattern. There is a general enrichment of the LILEs and the LREEs relative to the MREEs. Collectively, our data, suggest that gold mineralization at Umm Matierah gold prospect, is a possible candidate for a low-sulfidation epithermal style of mineralization, spatially associated with the distal intrusion.

Partial crystallization in a Zr-based bulk metallic glass in selective laser melting

Metals and alloys in amorphous state are promising for the use as structural and functional materials due to their superior properties related to the absence of such defects as grain boundaries and dislocations. Obtaining the amorphous state requires quenching from liquid state with a high cooling rate. In conventional technologies, this is the reason for a considerable size limitation hindering application of amorphous alloys. Additive manufacturing (AM) is free of the size limitation. The so-called bulk metallic glass (BMG) alloys have extremely low critical cooling rates and can be used in AM. Recent studies on AM from Zr-based BMGs by selective laser melting (SLM) has proved the possibility of attaining the amorphous state and revealed partial crystallization to be the principal drawback of this process. The present work aims to analyze the conditions for partial crystallization and attempts to control it by optimizing the process parameters. A comprehensive parametric analysis is accomplished in single-track SLM experiments with Zr-based BMG alloy Vit 106. The observed microstructures are related to the temperature fields and thermal cycles estimated by an analytic heat-transfer model in the laser-impact zone. In the cross section of a laser track, a central bright domain is identified as the remelted zone. An annular darker crystallization zone encircles the remelted zone. The model fits the experimentally obtained dependencies of the remelted zone size versus laser power and scanning speed and indicates that 43 ± 2% of the incident laser energy is transferred into the substrate thermal energy. The principal energy losses are reflection of the incident laser radiation and material evaporation. Primary crystalline inclusions existing in the substrate before laser processing dissolve at the laser melting. The mean cooling rate in the remelted zone is up to 4 orders of magnitude greater than the critical cooling rate. Therefore, homogeneous nucleation is not expected. Nevertheless, the theoretically estimated crystallization times are sufficient for a considerable crystal growth in the heat-affected zone where primary crystalline inclusions and nuclei are not completely dissolved.

Phase equilibria in the quaternary NaBr–MgBr2–Na2SO4–MgSO4–H2O system at (323.15 and 348.15) K and their application

To explore the process of extracting bromide salts directly from concentrated bittern, the phase equilibria in the quaternary NaBr–MgBr2–Na2SO4–MgSO4–H2O system at (323.15 and 348.15) K were investigated using the isothermal dissolution equilibrium method. The corresponding equilibrium phase diagrams and water content diagrams were depicted. The phase diagram at 323.15 K consists of eight invariant points, fifteen univariant curves and nine crystallization zones. The phase diagram at 348.15 K has four invariant points, nine univariant curves and six crystallization regions. Double salts were formed in both cases, and either belongs to complex type. The solubility products of the double salts 6Na2SO4·7MgSO4·15H2O and 3Na2SO4·MgSO4 were fitted by adopting the multilinear regression method. The predicted phase diagrams established with the solubilities calculated based on the Pitzer model show good agreement with the measured ones. A new circulation process was proposed to extract NaBr from the concentrated bittern, which provided a theoretical basis for the separation of bromide salts from bittern straightly.

Tracking the Transition From a Gondwana LIP to the South Atlantic Ocean With Geochronological and Geochemical Indicators

AbstractEvidence of early oceanization during transition from large igneous provinces (LIPs) to new ocean crust is mostly missing in the geological record. Mafic dykes geochemically akin to mid‐ocean ridge basalts (MORBs) occur in late stages of LIPs, but their tectonic role during margin evolution remains poorly constrained. Here we use whole‐rock and high‐resolution clinopyroxene chemistry of two distinct types of mafic dykes from the southeastern Brazilian margin to show that a MORB‐like plumbing system became magmatically active in the central South Atlantic ∼2 Ma after the volcanic peak of the Paraná‐Etendeka Magmatic Province. The LIP basaltic dyke compositions resulted from the mixing between a highly metasomatized lithospheric mantle comprising enriched DMM and Archean contributions. The lack of elemental oscillatory zoning in clinopyroxene crystals suggests that they were produced by a single magma pulse, consistent with the strong magma fluxes in LIPs. In contrast, the MORB‐like dykes, which exhibit strong similarities with South Atlantic MORBs, are interpreted to represent early stages of oceanization deriving from the mixing of enriched asthenospheric melts either with ancient SCLM contributions or small crustal assimilation. The MORB‐like intrusions ascended and cooled rapidly along faults and were fed by numerous magma injections that suggest episodic decompression of the asthenospheric source ∼20 Ma before the birth of central South Atlantic. The combination of subduction‐influenced and MORB‐like dykes is recurrent in ancient and modern rifts globally, suggesting that thinned lithospheric blocks affected by ancient subduction events may become more susceptible to early oceanization in rifted margins.

Titanite Petrochronology Records Secular Temperature and Fluid Evolution During Ductile Deformation: An Example From Late Cretaceous Shear Zones in the Eastern Transverse Ranges

AbstractQuantifying the timing and conditions of ductile deformation is essential for quantitative models of lithospheric deformation. Yet, directly constraining these variables and documenting how they change during a single deformation event remain difficult. We present titanite microstructural, zoning, trace‐element, and U‐Pb data from <m‐scale mylonitic shear zones in the Eastern Transverse Ranges, CA (Joshua Tree National Park) that record (a) the timing and conditions of ductile deformation and (b) the evolution of deformation conditions within a single, punctuated ductile deformation event. Titanite grains in sheared plutonic rocks yield a bimodal distribution of dates (∼151 and ∼75 Ma) interpreted as the independently constrained pluton crystallization and shear zone deformation ages, respectively. Synkinematic titanite neocrystallization at ∼75 Ma documents early deformation at ∼640–710°C under hydrous fluid conditions. Recrystallized titanite rims with ∼75 Ma dates indistinguishable from the neocrystallized titanite record Zr‐in‐titanite temperatures of 600–610°C and higher F contents, suggesting that the fluid became a more halogen‐rich brine as deformation progressed and the system cooled. Chemical zoning related to fluid‐driven recrystallization occurs in tandem with lattice misorientations and partially to fully reset U‐Pb dates in bent titanite, implying that reactive fluid flow is the ultimate mechanism by which dates are reset in titanite deformed by dislocation creep. These data document a punctuated (e.g., ∼1–3 Myr) phase of high‐temperature deformation that accompanied local pluton emplacement and demonstrate that titanite petrochronology can capture multiple, discrete reactions associated with crustal weakening and variables that affect the rheological evolution of ductile shear zones.

Real-time structural characterization of isotactic polypropylene during cast film extrusion

Understanding the crystallization behavior of semi-crystalline polymers during processing is key to achieve the desired material performances. Isotactic polypropylene characteristics are highly tunable and easy to adjust by changing the processing conditions thanks to its structural versatility and polymorphic behavior. Hereby, we performed for the first time ever a challenging real-time X-ray characterization of isotactic polypropylene during the cast film extrusion process by interfacing a compact cast film extruder machine with a synchrotron line.We report data of excellent quality recorded from the contact point between the just extruded polymer melt and the water-refrigerated cooling roll further down to the cooling roll line by using a grazing incidence scattering geometry. The explored cooling roll temperatures (from 70 °C to 15 °C) allowed to produce iPP films with defined structural composition, from α to mesophase.Evolution of the phase crystallinity as a function of the contact time between the polymer melt and the cooling roll clearly shows the presence of three crystallization zones: 1) an amorphous zone, 2) a frostline zone and lastly 3) a high-crystallinity zone. In the end, the experimental data have been matched with simulated data using a simple crystallization kinetics model, finding a good agreement in terms of crystalline development over the investigated time scale.As a closing remark, we hope that our effort will spark new interest in the real-time characterization of semi-crystalline materials and that will ultimately be utilized as a starting point to optimize and expand the characterization of these extremely important materials.

The Lifetime Prediction and Insulation Failure Mechanism of XLPE for High-Voltage Cable

The performance parameters and service life of the insulation layer of high-voltage cables are the key to ensure safe cable operation. Through extracting the mechanical parameters of high voltage cable insulation layer under different thermal aging temperatures, a normal linear regression model is established to predict the service life of high voltage cables. Meanwhile, the physicochemical characteristics such as microscopic morphology and molecular structure changes of the cable insulation layer are analyzed, the dielectric properties and breakdown field strength under ac condition are tested and the macroscopic electrical properties of the insulation layer are studied, and the insulation failure mechanism is further analyzed. The experimental results show that the elongation at break retention rate of cross-linked polyethylene (XLPE) increases slowly with the aging time, and then decreases rapidly when it reaches 50% of the initial elongation at break retention rate. The normal linear regression prediction model is established based on the Arrhenius formula, and it can be obtained the life endpoint of XLPE high voltage cable about 65 years at an operating temperature of 70 °C. Further analysis, under the action of heat and oxygen, the crystal zone structure of cable insulation is seriously damaged, and the carbonyl index is significantly increased. Accordingly, when the aging failure point is reached, the dielectric permittivity and dielectric loss of insulation are significantly increased, and the breakdown performance is significantly decreased. The work has an important guiding significance for insulation condition assessment and life prediction of high voltage cable.

Processes and timescales of magmatic rejuvenation and residence prior to post-caldera rhyolitic eruptions: Ōkataina Volcanic Centre, Aotearoa New Zealand

Understanding the timescales and processes through which magma bodies form and develop in the crust prior to eruption is vital for volcanic monitoring and interpreting future unrest signals, particularly at caldera volcanoes. Here we present the results of a case study on Ōkataina Volcanic Centre, New Zealand, into the timescales of pre-eruptive processes operating during young intra-caldera eruptions, using Fe-Mg interdiffusion profiles in orthopyroxene. Three eruptions covering the three different vent regions, the 15.6 ka Rotorua episode from the Ōkareka Embayment, the 14.0 ka Waiohau episode from Tarawera, and the 5.5 ka Whakatāne episode from Haroharo have broadly similar rhyolitic compositions but show distinctions in their mineralogy and crystal zoning profiles. Back-scattered electron imaging coupled with major-element analyses of orthopyroxene cores and rims imply that open-system mixing and disequilibrium is a common process in the early stages of magma assembly at Ōkataina. Through interpreting mineral chemistry and zoning patterns, we infer that melt segregation, magma body assembly from the source mush and residence in the upper crust takes place on the order of decades up to several centuries, or (if prematurely triggered) as short as months. Priming events such as heating by basaltic injection (common in the Ōkataina rhyolite eruptions) occur over decades prior to eruption. Our findings highlight that multiple processes can dictate the assembly, residence and eruption of melt bodies from the crust and that most magmatic processes occur over timescales that are short enough to be directly relevant to geophysical imaging of magma reservoirs and monitoring initiatives.

Study of Phase Evolution Behavior of Ti6Al4V/Inconel 718 by Pulsed Laser Melting Deposition

In this study, a pulsed laser was used as the heat source for the additive work. The Ti6Al4V/Inconel 718 alloy wire was deposited on the substrate by melting using a pulsed laser. Using the above method, single-layer and double-layer samples were printed. The sample material printed in this way is highly utilized. Compared to the complicated pre-preparation work of metal powder pre-mixing, this printing method is simple to prepare and only requires changing the wire feeding speed. The study of this paper provides a theoretical guide for the subsequent fusion deposition of heterogeneous wire materials. The samples were analyzed after molding using SEM, EDS and XRD to characterize the microstructure of the samples. The samples can be divided into three zones depending on the microstructure, the bottom columnar crystal zone, the middle mixed phase zone, and the bottom equiaxed crystal zone. From the bottom to the top of the sample, the phase microstructure changes as γ + Laves → α + β + Ti2Ni + TiNi + Ni3Ti → α + β. The hardness data show that the highest value in the transition zone is 951.4 HV. The hardness of the top part is second only to the transition zone due to a large number of equiaxed crystals. The bottom region is dominated by columnar crystals and is the softest of the three regions with the lowest hardness value of 701.4 HV.

Experimental and calculated solubility isotherms of the quaternary NaBr–MgBr2–Na2SO4–MgSO4–H2O system and its ternary subsystem at 298.15 K

To further complete the phase equilibrium data of bittern system and prepare for the extraction of bromine resources from bittern, the solubility isotherms of the quaternary NaBr–MgBr2–Na2SO4–MgSO4–H2O system and its ternary subsystem MgBr2–MgSO4–H2O at 298.15 K were determined using the isothermal dissolution method. In the phase diagram of the ternary subsystem, there are five invariant points and five single salt crystallization zones corresponding to MgSO4·nH2O (n = 7, 6, 5, 1) and MgBr2·6H2O, where MgSO4·5H2O is a metastable phase. This report supplements and revises the previous data. The phase diagram of the quaternary system belongs to complex type, which comprises nine invariant points and ten crystallization zones including a double salt Na2SO4·MgSO4·4H2O and a metastable phase MgSO4·5H2O. Based on the Pitzer model, the interaction parameter ψ of Mg, Br and SO4 was obtained by fitting. The solubilities of the two systems were calculated, and the results show good agreement with the experimental values.

Fluid Components in Cordierite from the Rocks of Epidote-Amphibole Facies of the Muzkol Metamorphic Complex, Tajikistan: Pyrolysis-Free GC-MS Data

The composition of volatile components of cordierite from the Muzkol metamorphic complex was studied using shock destruction with pyrolysis-free gas chromatography-mass spectrometry (GC-MS) with simultaneous IR and Raman spectroscopy. Applying the GC-MS procedure, the component relative concentrations (rel.%) and composition of different zones of cordierite crystals were determined. It was found that the substantially magnesian cordierite was formed with a predominantly aqueous-carbonic acid fluid (from 57.06 to 67.88 rel.% H2O, from 24.29 to 32.95 rel.% CO2). From the center towards the crystal periphery, the molar fraction of carbon dioxide (CO2/(H2O + CO2)) decreases from 0.36 to 0.26, whereas the alkane/alkene ratio increases from 0.80 to 0.88. At least 11 homologous series of organic compounds among the identified volatile components, in addition to water and carbon dioxide, were determined, including oxygen-free aliphatic and cyclic hydrocarbons (paraffins, olefins, cyclic alkanes and alkenes, arenes, polycyclic aromatic hydrocarbons (PAHs)), as well as oxygen-containing (alcohols, esters, aldehydes, ketones, carboxylic acids) and heterocyclic (furans, dioxanes) organic compounds.

Investigation on microstructure and mechanical properties of Fe-based amorphous coatings prepared via laser cladding assisted with ultrasonic vibration

Fe-based amorphous coatings were deposited on 20# mild steel using laser cladding assisted with ultrasonic vibration under different ultrasonic powers from 0 W to 1000 W. When the ultrasound is introduced into the molten pool, it can increase the maximum temperature and life cycle and promote the solute exchange at the bottom of the molten pool. While it has little effect on the molten pool top's temperature field and element distribution. With increasing ultrasonic power, the gradient crystallization structure between the substrate and the amorphous coating increases from 46 μm to 81 μm and appears as a changed wave. The cracking trend of the coating decreases with increasing crystallization zone, which is similar to a spring, with an energy storage function that can release internal stress and reduce coating cracking. Interestingly, the amorphous phase still dominates the top zone of the Fe-based amorphous coating without influencing its function.

Chemical Structure and Microscopic Morphology Changes of Dyed Wood Holocellulose Exposed to UV Irradiation.

Dyed wood is prone to photoaging when exposed to UV irradiation which decreases its decorative effect and service life. Holocellulose, as the main component of dyed wood, has a photodegradation behavior which is still unclear. To investigate the effect of UV irradiation on chemical structure and microscopic morphology changes of dyed wood holocellulose, Maple birch (Betulacostata Trautv) dyed wood and holocellulose were exposed to UV accelerated aging treatment; the photoresponsivity includes crystallization, chemical structure, thermal stability, and microstructure were studied. Results showed that UV radiation has no significant effect on the lattice structure of dyed wood fibers. The wood crystal zone diffraction 2θ and layer spacing was basically unchanged. With the UV radiation time extension, the relative crystallinity of dyed wood and holocellulose showed a trend of increasing first and then decreasing, but the overall change was not significant. The relative crystallinity change range of the dyed wood was not more than 3%, and the dyed holocellulose was not more than 5%. UV radiation caused the molecular chain chemical bond in the non-crystalline region of dyed holocellulose to break, the fiber underwent photooxidation degradation, and the surface photoetching feature was prominent. Wood fiber morphology was damaged and destroyed, finally leading to the degradation and corrosion of the dyed wood. Studying the photodegradation of holocellulose is helpful to understand the photochromic mechanism of dyed wood, and, further, to improve its weather resistance.

Trace element geochemistry of spodumene megacrystals: A combined portable-XRF and micro-XRF study

Formation mechanisms of spodumene (LiAlSi2O6) megacrystals, such as those historically mined in the Black Hills of South Dakota or recently discovered in the Plumbago North deposit, Newry, Maine, remain puzzling, despite decades of observations and speculations. In-situ trace element geochemistry and zoning patterns in spodumene could provide insights into the primary growth mechanisms and optimize the extraction of lithium, but the size of these giant crystals greatly exceeds the chamber size of conventional compositional-mapping techniques. Here we propose a novel two-step approach for documenting the distribution of trace elements in sliced crystals, several decimeters in size, using 2D compositional mapping via 1) portable X-ray Fluorescence (pXRF) collected across a square grid with a step size of 0.5 to 1 cm and 2) benchtop micro-X-ray Fluorescence (μXRF) at step-size ≥ 25 μm using crystals or portions of crystals that were pre-screened via pXRF. Mineral-specific analytical optimization included specific filters and/or detector settings in order to avoid the Bragg peaks interfering with the Ka lines of Mn, Fe, Ge, Ga, ± Sn in spodumene when using a Bruker TRACER 5i pXRF unit, an M4 TORNADO μXRF instrument, or an M4 TORNADOPlus instrument.Two subhedral spodumene samples analyzed along crystallographically-oriented sections have a relatively homogenous, several decimeter-wide core (Zone 1) postdated by a strongly zoned, several centimeter-thin rim (Zone 2). With the increase in spatial resolution by three orders of magnitude, extraordinary oscillatory ± sector growth zoning, 0.1 mm to >1 cm wide, was revealed using μXRF in selected areas of Zone 2, that were pre-screened by pXRF. Typically, both Zones 1 and 2 are characterized by coupling of Fe with Ga ± Ti and decoupling from Mn, Sn, and Ge. An exception is Sn that decouples from Mn and couples with Fe,Ti, and Ga in Zone 2. This consistent zoning in crystals from distinct localities suggests two distinct growth episodes, marked by a sudden change in the crystallization mechanism, possibly from an undersaturated magma to fluid-saturated system. This integrated pXRF-μXRF method may assist with compositional and alteration characterization of lithium ore to optimize the processing and extraction methods. Additionally, the integrated techniques open a new venue of investigation of chemical heterogeneities and zoning patterns within coarse to megacrystic minerals and may serve as an excellent sample pre-screening prior to other microanalytical techniques.

Calcium ion regulation of sodium alginate in pure buckwheat noodles shown by in vitro simulated digestion.

The effects of calcium sodium alginate on quality and starch digestion of pure buckwheat noodles were investigated. The incorporation of calcium ions into noodles containing sodium alginate was found to reduce water absorption by the noodles during cooking, together with an increase of the turbidity. Calcium addition improved the noodle texture, as shown by the measurement of hardness, elasticity, adhesion, and chewability. In vitro simulations of digestion showed that calcium ion cross-linking with sodium alginate reduced glucose formation by approximately 23.3 mg/g. X-ray diffraction and Fourier transform infrared spectroscopy showed alterations in the crystal zone of the noodles induced by an alginate gel network, although no new chemical substances were generated. Noodles prepared by this exogenous method may be useful as functional foods for patients with diabetes.

Stable Phase Equilibria of the Quaternary Water-Salt System Li+, Rb+, Mg2+//SO4 2--H2O at T = 273.2 K.

The phase equilibria for the quaternary system Li+, Rb+, Mg2+//SO4 2- - H2O at 273.2 K were studied by the isothermal dissolution equilibrium method. Based on the measured data, the space diagram, stable phase diagram, water content diagram, and the diagram of density vs composition are plotted. The stable phase diagram in the system consists of four quaternary invariant points, nine univariate curves, and six crystallization zones. For the invariant points, E1 and E4 belong to the commensurate type, and E2 and E3 belong to the incommensurate type. The order of the crystallization area is Rb2SO4·MgSO4·6H2O > 3Li2SO4·Rb2SO4·2H2O > Li2SO4·Rb2SO4 > MgSO4·7H2O > Li2SO4·H2O > Rb2SO4. The density of the equilibrium liquid changed regularly with the content of Rb2SO4 in the solution. By comparing the stable phase diagram of the partial ternary subsystems at T = 273.2 K and T = 298.2 K, it is found that the crystallization regions of Rb2SO4 increases with the decrease in temperature, which indicates that cooling is conducive to the crystallization of Rb2SO4. By comparing the stable phase diagram of the system at T = 273.2 K and T = 308.2 K, it was found that the system was composed of four invariant points, nine univariate curves, and six crystal regions. The double salt 3Li2SO4·Rb2SO4·2H2O is converted to 3Li2SO4·Rb2SO4. The crystallization region of single salt MgSO4·7H2O, Rb2SO4 and double salt Li2SO4·Rb2SO4 decreased obviously.

Plasticity of Porous NiTi Alloys Obtained by Self-propagating High-temperature Synthesis in Closed and Open Gas Flow Reactors

ABSTRACT Porous NiTi alloys were obtained by self-propagating high-temperature synthesis (SHS) using layer-by-layer combustion in closed and open gas flow reactors under a protective argon atmosphere. The maximum compressive strain of porous NiTi alloys synthesized in the closed reactor was 34% compared to 7% in the open gas flow reactor. X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, energy dispersive spectroscopy, and optical microscopy showed that the reaction products in the two-phase gas zone of peritectic crystallization are in the form of isolated Ti2Ni crystalline clusters in the TiNi matrix. The ductility and strength of the recrystallized Ti2Ni phase hard dendrites increase the effective stiffness of porous NiTi alloys and decrease the maximum compressive strain. A highly porous NiTi alloy with improved mechanical properties was obtained by the SHS method in a closed reactor.

Liquid crystal spiral Dammann zone plates based on photoalignment technology

Liquid crystal spiral Dammann zone plates based on photoalignment technology

Novel strategy for space group determination in real space

Traditional space group determination methods are all in reciprocal space, which involves ambiguous identification on some space groups which have glide plane and screw axes. The novel strategy herein for space group determination in real space is based on the atom resolution high angle annular dark field (HAADF) technology. Three HAADF images in three specific crystal zone axes are needed at most. The proposed strategy for space group determination is easy and effective.