Acicular Shape Research Articles

The magma evolutional constrains on the genesis of proximal Zn skarn mineralization: A case study from the Yaojialing deposit in Tongling district, eastern China

The major factors especially the roles of the magma evolution controlling the Zn/Cu mineralization in skarn deposits are still controversial. Yaojialing is a large-sized skarn Zn polymetallic deposit (1.74 Mt Zn at 3.6 %, 30.4 t Au at 4.2 g/t and 24.8 t Cu at 0.83 %) located in the Tongling district of the Middle–Lower Yangtze belt (MLYB), both the proximal and distal areas of the deposit exhibit high Zn/Cu mineralization. The intrusions in Yaojialing primarily consist of quartz monzonite porphyry (QMP) and granodiorite porphyry (GDP), and the QMP is related to skarn mineralization. Both the QMP and GDP display relatively high (87Sr/86Sr)i values (0.707907 to 0.709390), low εNd(t) values (−9.05 to −8.17) and negative εHf(t) values (−8.51 to −11.72), suggesting that they originated from a mixed source of enriched mantle and lower crust. Both the QMP and GDP contain type I and type II amphiboles, while type III amphibole exists only in QMP. Type I amphibole is acicular crystals shape, type II amphibole is euhedral in shape and relatively large in size (0.6–2.0 mm), while type III amphibole crystallized around the margin of type II amphibole. The type I amphibole from QMP and GDP show similar calculated temperatures (948–1010 ℃), pressures (2.9–6.5 kbar, corresponding depths at 11.0 to 24.4 km), fO2 (ΔFMQ = 0.2–1.9) and H2O content (4.2–6.8 wt%). Type II amphibole crystallized at 815–941 ℃, 1.2–2.9 kbar (corresponding to depth of 4.6–11.1 km), ΔFMQ = 0.7–2.1, and 4.4–5.7 wt% H2O. Type III amphibole have a lower temperature (679–795 ℃), pressure (<0.5 kbar) and water content (2.5–4.3 wt%) but higher fO2 value (ΔFMQ = 3.1–3.8) compared to type I and type II amphiboles. Reverse zoning of plagioclase and higher Mg# (74 to 89) of type III amphibole in QMP are resulted from injection of mafic magma at shallow depths, which provide sufficient metal and favorable conditions for the formation of QMP parental magma. Modeling of magma H2O solubility indicates that QMP begins to exsolve fluid at depth of 6.2–11.1 km. Initial low oxygen fugacity and ore-forming element differential release during fluid exsolution process resulted in the high Zn/Cu mineralization at Yaojialing.

Geochemistry of hydrothermal and stream sedimentary rutile in the Tiegelongnan porphyry-epithermal Cu (Au) deposit, Tibet: A tool for exploration

Rutile is a common and stable mineral in porphyry Cu deposits, and morphology and geochemistry of rutile are recognized as a potential indicator mineral for exploration. In this study, we investigate physical features and chemical composition of hydrothermal rutile in the Tiegelongnan porphyry-epithermal system, as well as rutile in stream sediments nearby to establish a method to apply rutile as an exploration proxy. Four stages of hydrothermal rutile have been identified. Potassic alteration stage rutile (Rt1) is associated with biotite, with elongated and acicular shape and small grain size (20–50 μm). Rutile from lower temperature phyllic alteration (Rt2), quartz veins (Rt3), and advanced argillic alteration (Rt4), has characteristic sector zoning and larger grain size (50–150 μm). The sector zoning is more commonly present in Rt2, Rt3, Rt4, that are associated with high-grade Cu mineralization, and is associated with incorporation of W, Fe, V, Sn, and Zr. The earlier rutile (Rt1) also has a geochemical signature different from the other three types of rutile, characterized by significantly lower Al, Cu, Zr, Nb, Sn, Hf, and higher Sc and Fe contents. Low-temperature hydrothermal alteration stage rutile (Rt2, 3, 4) share many geochemical similarities, but Rt3 has higher Nb and Ta contents (median = 3371.0 and 176.0 ppm, respectively), whereas Rt4 has higher Sb content (median = 24.3 ppm).Rutile trace element data from this study and literature are integrated to develop a Partial Least Square-Discriminant Analysis (PLS-DA) multivariate statistics plots that can discriminate porphyry Cu deposit rutile from orogenic gold and VHMS deposits, as well as rutile from different alteration stages. The PLS-DA plots predict that stream sedimentary gold-bearing rutile (RtSAu) adjacent to the Tiegelongnan deposit are derived from the deposit, and mainly from low-temperature phyllic and advanced argillic alteration stages. This is consistent with geochemical similarity between the RtSAu and the Tiegelongnan low-temperature hydrothermal rutile (Rt2 + Rt4). This is further confirmed by a U-Pb age of 125.3 ± 4.7 Ma (n = 24, 2σ) for RtSAu, which is consistent with the main porphyry mineralization age of ∼ 120 Ma in the Tiegelongnan deposit. We infer that the RtSAu may have formed during the ∼120 Ma epithermal system at Tiegelongnan, which has already largely eroded. In general, our findings prove the capability of using rutile, by combing the texture, geochemical compositions, geochronology, PLS-DA tools, and their spatial distribution, as a proxy mineral for the exploration of porphyry Cu deposits.

Enhancing the Photocatalytic Activity and Luminescent Properties of Rare-Earth-Doped CeO2 Nanoparticles

Our study is focused on the structural and morphological characteristics, optical behaviour and photocatalytic properties of undoped and 5 at% Eu3+-, Gd3+- and Y3+-doped CeO2 nanoparticles prepared by a green hybrid sol-gel combustion method. Several techniques such as X-ray diffraction powder (XRD), Transmission Electron Microscopy (TEM), UV-Vis spectroscopy, Photoluminescence spectroscopy (PL) and Electron Paramagnetic Resonance (EPR) have been used to investigate the obtained samples. Moreover, the correlation between the characteristics and properties has been studied. The nanoparticles observed by TEM exhibit a pseudo-spherical shape, except for Y3+-doped CeO2, which presents an acicular shape. The average size of undoped and rare-earth-doped CeO2 nanoparticles is below 10 nm, in good agreement with the calculations performed based on XRD analyses. From UV-Vis analyses it has been deduced that with doping the band gap energy decreases, which shows that additional levels are introduced by doping into the CeO2 band gap. The EPR spectra evidence similar behaviour for all doped samples. The photocatalytic activity was evaluated by the degradation of rhodamine B (RhB) under UV light irradiation. The photodegradation mechanism has been studied in depth based on the formation of electron-hole pairs, and to evidence the reactive oxygen species, ESR coupled with spin-trapping experiments was performed. In the case of Y-doped CeO2 nanoparticles, the generation of both •OOH and •O2− radicals involved in RhB photodegradation was highlighted.

The Effect of Thermal Annealing on the Electrophysical Properties of Samples n-Si&lt;Ni,Сu&gt;

This paper presents the results of studies of the effect of isothermal annealing at temperatures T = 673¸1473 K in the time interval 5¸60 minutes on the electrical properties of silicon, simultaneously alloyed with nickel and copper. Samples of n-Si&lt;Ni,Cu&gt; were obtained on the basis of the starting material - single-crystal silicon, grown by the Czochralski method with the initial resistivity r = 0.3 Ohm×cm. Diffusion was carried out at a temperature of 1523 K for 2 hours. After that, the samples were cooled at a rate of 0.1 K/s. The morphological parameters of impurity nickel and copper atom clusters formed in the bulk of silicon were measured by electron probe microanalysis on a modern Superprobe JXA-8800R setup. As it turned out, in the volume of n-Si&lt;Ni,Cu&gt; samples, clusters of impurity atoms with different geometric shapes are formed, the sizes of which reach up to 500 nm. The electrical properties of the samples were studied by the Hall effect method using an Ecopia HMS-7000 instrument. It was revealed that under the influence of thermal annealing (TA) at T≥1273 K, impurity clusters decompose, which leads to an increase in the resistivity of n‑Si&lt;Ni,Cu&gt; samples. After exposure to TA at Т=1273 K for 15 minutes, the density of impurity nanoaccumulations of acicular and lenticular shapes sharply decreases in the sample volume. Under the influence of TA at T = 1473 K for 10 minutes in the volume of the sample, the decay of impurity nanoclusters with a spherical shape is observed. Also presented are the results of changes in the density of impurity clusters, as well as structural analyzes of the samples before and after exposure to thermal annealing.

The influence of calcium formate on the hydration of calcium sulfate hemihydrate

In this study, the influence of calcium formate (CF) on the hydration of a synthesized calcium sulfate hemihydrate (HH) powder was investigated. Isothermal calorimetry measurements showed that CF retards the hydration reaction of HH. This was confirmed by XRD of stored samples and pore solution analysis. Two retardation mechanisms were identified. The combination of pore solution and laser granulometric experiments revealed that firstly, the initial dissolution of hemihydrate decelerates because of high Ca2+ ion concentrations, donated by the faster dissolving CF. Secondly, the HCOO− species of CF adsorb on surfaces of the gypsum crystals, as further pore solution measurements showed. This impedes their formation kinetic. The gypsum crystals exhibited anisotropic peak narrowing in XRD measurements when CF was added. This was caused by a morphology change, which could be verified using the anisotropic domain size morphology approach during Rietveld refinement analysis and SEM images. Gypsum crystals exhibit a blockier shape with CF addition compared to the usual acicular shape in pure water.

Porous acicular mullite ceramics produced from well and poorly crystallized kaolinite

This work studies how the crystallinity of a raw kaolinite clay affects the properties of mullite ceramics produced from it. To this purpose, two well and poorly crystallized kaolinite samples from the repository of the Clay Mineral Society were assessed. Also, other two samples were produced in which the growth of mullite acicular grains were promoted by addition of a MoO3 precursor. The role of the kaolinite crystallinity and the MoO3 precursor on the properties of the final ceramics was studied. For each sample, the microstructure and the textural, crystalline, and mechanical properties were analyzed.The poorly crystallized kaolinite is more reactive than the well crystallized one and promotes better mullitization. In addition, when the MoO3 precursor is used, the formation of grains with acicular shape inhibits the ceramic shrinkage and promotes higher porosities. On the other hand, the flexural strength is slightly lower for the mullite produced from poorly crystallized kaolinite. Nevertheless, when this property is extrapolated to the case of zero porosity it is found that in such cases the ceramic solid fraction presents higher flexural strength, indicating that the porous mullite with the acicular grain morphology is a reinforced lightweight ceramic. The obtained results show that the crystallinity of the starting clay should be considered in the ceramic fabrication process due to its effects on the properties of the final product.

Microstructural and mechanical property evolution of a nuclear zirconium-4 alloy fabricated via laser powder bed fusion and annealing heat treatment

ABSTRACT Zirconium (Zr) alloys are widely used in nuclear energy because of their excellent mechanical properties and low thermal neutron absorption cross-section. This work investigated the printability, microstructure, and mechanical properties of Zr-4 alloy additively manufactured by laser powder bed fusion (LPBF) for the first time. The effect of annealing temperature on the microstructural and the mechanical property evolution of the printed Zr-4 alloy was studied. The results exhibited that the Zr-4 alloy with a high relative density of 99.77% was obtained using optimised printing parameters. With an increase in the annealing temperature, the formed α phase of the Zr-4 alloy changed from an acicular shape to a coarse-twisted shape, and finally to an equiaxed shape. Such microstructure change endowed the alloy with a high compressive strength of 2130 MPa and compressive strain of 36%. When the annealing temperature exceeded 700°C, Zr x (Fe2Cr) compounds were precipitated, strengthening the alloy by pinning effect. These findings provide valuable guidance for the manufacture of geometrically complex Zr alloy parts for nuclear power applications.

Synthesis and Analyses of Acicular Spinel Iron Oxide Particles with Core-Shell Structure Containing Manganese Ferrite and Magnetite

Acicular spinel iron oxide particles with a core-shell structure containing manganese ferrite (MnFe2O4) and magnetite (Fe3O4) were synthesized by uniformly crystallizing MnFe2O4 on the surface of the magnetite particles in an alkaline dispersion. Crystallizing 50 wt% of MnFe2O4 on Fe3O4 led to an increase in the apparent lattice constant from 0.839 nm to 0.841 nm. Transmission electron microscopy (TEM) observations of the particle shape and lattice images showed that MnFe2O4 was uniformly crystallized on the surface of the magnetite particles and their acicular shape was maintained. The coercive force and saturation magnetization were almost constant at 29.5 kA/m and 80-81 Am2/kg, respectively, when the crystallized MnFe2O4 content ranged from 0 to 30 wt%. When the MnFe2O4 content was increased to 50 wt%, the coercive force and saturation magnetization slightly decreased to approximately 28.0 kA/m and 74.1 Am2/kg, respectively, reflecting the lower magnetization of MnFe2O4 compared to that of Fe3O4.

Seed germination and post-seminal development of Victoria amazonica (Poepp.) J. C. Sowerby (Nymphaeaceae) in Central Amazon

The Amazon floodplains are specific ecosystems with high biodiversity and endemism, divided in varzeas, white fertile waters, and Igapos with poor and acid waters, black or clear, and mixed waters between the two typologies. The main purpose of this investigation was to characterize the seed germination and post-seminal development of Victoria amazonica (Poepp.) J.C. Sowerby, one of the few hydrophytes occurring in varzea and mixed waters in the region. In addition, it was evaluated the influence of environmental characteristics on the growth of the plants. Germination was monitored in seeds with and without scarification, in control and treatments with water low oxygen and in the dark. The plant development was monitored in field and laboratory; material from juvenile and adult plants was collected at six sampling sites near Manaus. Germination is favored in the dark, in hypoxic conditions, in water and seed coat shaved. The seedling has two cotyledons, one inside the seed and the other with an acicular shape, eophyll deltoid-hastate, abortive primary root and adventitious roots. New eophylls and the first metaphyll appear in twenty-day-old plants. The stem is rhizomatous. The mixed water environment was not very different from the varzea which is reflected in a similar chemical composition of the plants of both systems. The rhizomes of the varzea environment have caloric value three times higher than that of mixed water. This condition and the presence of larger leaves suggest the varzea floodplain to be more favorable environment for growth of Victoria amazonica.

Characterization of Fe3O4 Nanoparticles for Applications in Catalytic Activity in the Adsorption/Degradation of Methylene Blue and Esterification.

The aim of this study is to evaluate the applicability of the catalytic activity (CA) of the Fe3O4 magnetic system in the adsorption/degradation of methylene blue and esterification. The thermal decomposition method allowed the preparation of Fe3O4 nanoparticles. The crystallites of the Fe3O4 structural phase present an acicular form confirmed by X-ray diffraction. Transmission electron microscopy results identified the acicular shape and agglomeration of the nanoparticles. Mössbauer spectroscopy showed that the spectrum is composed of five components at room temperature, a hyperfine magnetic field distribution (HMFD), two sextets, a doublet, and a singlet. The presence of the HMFD means that a particle size distribution is present. Fluorescence spectroscopy studied the CA of the nanoparticles with methylene blue and found adsorption/degradation properties of the dye. The catalytic activity of the nanoparticles was evaluated in the esterification reaction by comparing the results in the presence and absence of catalyst for the reaction with isobutanol and octanol, where it is observed that the selectivity for the products MIBP and MNOP is favored in the first three hours of reaction.

Healing of concrete cracks by in-situ synthesis of ettringite induced by electric field

Cracking is inevitable in concrete and can seriously threaten the durability of the structures. This paper proposed electric-induced in-situ synthesis of ettringite as a crack healing strategy for concrete structure. Composite solutions of aluminum sulfate and calcium acetate with four different molar ratios of Ca to Al (1, 3, 5, 7) were used as electrolyte solutions. The effectiveness of healing was evaluated by crack closure ratio, permeability, and coverage ratio of the crack section, while the composition and microstructure of products were also investigated. From the results, when the Ca-Al ratio is 3 or 5, the crack closure time shortened to 1 day, and the permeability coefficient reduced by nearly 4 orders of magnitude compared to the unrepaired specimen after healing for 7 days. Of all the groups, the products penetrated the entire crack, and the coverage ratio of crack section can reach more than 60 % when the Ca-Al ratio is 5. Additionally, ettringite was detected as the main phase of products by X-ray diffraction and thermogravimetric analysis (TGA). Needle-shaped ettringite can be observed during the whole healing period through scanning electron microscopy (SEM). In-situ synthesized ettringite crystals evolved from small and short prismatic shapes to long and acicular shapes. These crystals overlapped with each other and formed a dense network structure.

Effect of rotating magnetic field (RMF) on the microstructure and mechanical properties of Al–2%Fe eutectic alloy

The effect of rotating magnetic field (RMF) on the solidification of microstructures and mechanical properties of Al–2%Fe (wt.%) eutectic alloy are studied in this manuscript. SEM, EDS and TEM techniques are adopted to analyze the evolution of Al3Fe intermetallics morphology in Al–2%Fe eutectic alloy. Without RMF, the length of Al3Fe intermetallics with large plate-like and long acicular shape are about 173 μm and 189 μm, respectively. With the RMF, the Fe-rich intermetallics is refined due to collision and shear action by the Lorentz force. When the intensity of the RMF reaches to 80 V, the average length of acicular Al3Fe intermetallics is 17 μm, and the average diameter of plate-like Al3Fe is 40 μm. However, when the intensity reaches to 100 V, the Al3Fe intermetallics coarsens. With the introduction of RMF, the tensile strength and elongation of the Al–2%Fe alloy increase accordingly. When the intensity of the RMF is 80V, the maximum tensile strength and elongation are 94.24 MPa and 13.37%, respectively. The influential mechanism of RMF is also discussed in this manuscript.

Microstructural analysis and mechanical property optimization for TP347HFG steel/6082 aluminum alloy electron beam welded joint

In view of the failure in direct joining between TP347HFG steel and 6082 aluminum alloy, electron beam welding with beam offset to 6082 is conducted to hinder the formation of Al–Fe intermetallic compounds. TP347HFG and 6082 are successfully joined, corresponding to the increased tensile strength and the maximum value up to 103.6 MPa (56% of 6082 base metal) when beam offset reaches 0.5 mm. θ-Al3Fe with various morphologies like acicular, petaloid, and actinomorphic shape was the main precipitate inside the weld. In view of the increased Fe content inside the weld, the morphology of θ-Al3Fe transforms from petaloid-like shape to coarse aciculiform and then to fine acicular clusters as the observed position moves from 6082 side to TP347HFG side. As the beam deviated to 6082 side, the volume of θ-Al3Fe was decreased, indicating the decreased microhardness of the weld. The continuously distributed reaction layer consisting of brittle η-Al2Fe5 is detected at the fusion line of TP347HFG side, which is detrimental to the mechanical properties of the joint. The thickness of the reaction layer is decreased due to beam offset. O content inside the weld was not more than 90 ppm, demonstrating the superiority of electron beam welding.

Microstructure of Ultrafine Acicular Bainite and Mechanical Properties of 3Cr2MnNiMo Mold Steel during Austempering

Herein, the effect of austempering treatment on martensite/bainite multiphase microstructure evolution and mechanical properties of 3Cr2MnNiMo mold steel are investigated, and the mechanical properties are compared with the conventional quenching and tempering (QT) treatment. It indicated that the morphology of martensite/bainite can be effectively tailored by changing the austempering temperature. With the increase of temperature from 280 to 360 °C, the microstructure changes from tempered martensite + bainite + blocky retained austenite (RA) to martensite + coarse bainite plate + blocky RA and irregular martensite/austenite (M/A) island. When the temperature reaches 420 °C, the martensite content reaches the maximum. The bainite morphology is surprisingly transformed from coarse bainite plate to ultrafine acicular shape owing to the reduction of the bainitic driving force and the sharp increase of carbon diffusion coefficient. Moreover, blocky RA and M/A islands disappear and are replaced by nanoscale filmy RA. The alternating distribution of variants has a refinement effect on the microstructure and the effective grain size reaches a minimum value. Compared with the conventional QT treatment, the tensile strength of austempering at 420 °C increased by 702 MPa, but the toughness and ductility levels are almost the same.

An experimental approach to a cementitious lightweight composite mortar using synthetic wollastonite

Synthetic wollastonite (SW) has been produced with a special green route being made up of three steps by using industrial marble and quartz wastes. Due to the acicular and fibrous shape, SW has been tried to improve engineering characteristics of cementitious lightweight composite mortar (CLCM). In this experimental study, ecofriendly CLCM was developed with SW as a cement replacement material. Physical and chemical properties of SW were specified with XRF, XRD and SEM analysis. The cement replacement levels were evaluated as 0, 0.5, 1, 2, 5, 10 and 20 %. Setting time, normal consistency, and mineralogical investigation with XRD analysis were investigated on cementitious pastes. Flowability, unit weight, water absorption, flexural and compressive strength, ultrasonic pulse velocity (UPV), and thermal conductivity analysis were carried out on CLCMs. Morphological observations reveal that SW grains were quite finer than cement particles, fibrous and acicular in shape, have a high aspect ratio, and have rough surfaces. Depending on the physical properties of SW, the water requirement of the cementitious paste increased and the setting times were delayed. Similarly, the workability of CLCMs decreased slightly, but a significant improvement was observed in the mechanical properties of the mortars at 2 % and 5 % replacement levels. Also, thermal conductivity of the mortars decreased as the SW replacement level increased. This research verifies the technical feasibility of SW application as a cement replacement in CLCM and may further promote the utilization of waste materials in production of SW.

Identification of twin and nanoscale Te precipitations in CdZnTe crystals grown by vertical gradient method with HRTEM

CdZnTe (CZT) has attracted much attention in nuclear detection field attribute to its high detection efficiency, high energy resolution and room-temperature operation. In this work, the CdZnTe samples were prepared by Vertical gradient method. High-resolution transmission electron microscopy (HRTEM) was used to investigate the nanoscale defects in CZT crystals. It is found that the twins are symmetric about the {111} plane, and the dislocations and stacking faults locate around the twin boundary. Te precipitations with hexagonal crystal structure is coherent with the CZT matrix. Te precipitated phases have three shapes of hexagon, polygon and irregularity, which determined by the interface energy between precipitations and matrix. The ordered phase with acicular shapes was found along [011] zone axis. The two variants of the ordered phase is corresponding to 1/211¯1 and 1/31¯11 ultrasound lattice, respectively. Besides the small angle grain boundaries with semi-coherent interface are observed. It is important to explore the behavior of nanoscale defects in the growth of CZT crystals in order to enlighten a path to regulate the nanoscale defects. The stability of the temperature interface is crucial to the preparation of high quality CZT crystals.

The Structure and Properties of Hardening Coatings of Low-Chromium Hard Alloys for Agricultural Machine Parts

A new surfacing material consisting of the Fe-Si-Cr-Cu-C-B system sparingly alloyed with chromium is proposed for agricultural machine parts hardening by induction surfacing method capable to replace the currently widely used materials like Sormite No. 1, 2, PG-US25/27 and those similar to them. The chromium content in the new material is 4.3 %, which is 3-8 times less than that in analogs. The new material was obtained metallurgically, its phase, chemical composition and properties were investigated. The main phase of the alloy is Ferrosilide FeSin, along the grain boundaries of which a carbide phase is precipitated represented by small particles of Cr2C3, Cr7C3 carbides of regular and acicular shapes, as well as large particles of special chromium carbides (Cr,Fe)7C3, (Cr,Fe)23C6. In terms of the relative content, the carbides present in the new material can be conventionally arranged in the following series: (Cr,Fe)23C6 &gt; (Cr,Fe)7C3 &gt; Cr7C3 &gt; Cr2C3.

Dachiardit-Ca, ferrierit-Mg a sprievodná zeolitová mineralizácia v dutinách chalcedónov na lokalitách Byšta, Brezina a Kuzmice (Slanské vrchy, Slovenská republika)

An interesting zeolite association has been identified at the localities Byšta, Brezina and Kuzmice, consisting of mordenite, clinoptilolite-Ca, dachiardite-Ca and ferrierite-Mg. Dachiardite-Ca (from Byšta and Brezina) and ferrierite-Mg (from Brezina) represent first recorded occurrences in the Slovak Republic. Zeolite mineralization occurs as white to gray crystalline fillings in small chalcedony cavities and crusts, developed in strongly altered Miocene rhyolites (Byšta and Brezina) or silicified andesites (Kuzmice). Crystals of dachiardite-Ca have acicular shapes, and are grouped into the radial, spherical and sheaf-like aggregates. Their average size ranges about 1 - 3 mm. Dachiardite-Ca from Byšta and Brezina is monoclinic, space group C2/m with following unit-cell parameters refined from X-ray powder diffraction data: a 18.618(8), b 7.498(3), c 10.284(4) Å, β 108.36(3)o, V 1362.4(1.3) Å3 and a 18.616(12), b 7.492(5), c 10.271(6) Å, β 108.27(5)o, V 1360.2(2.0) Å3, respectively. Chemical analysis is corresponding to the average empirical formula (Ca1.12K0.78Na0.16)Σ3.52(Al3.52Si20.56O48)·13H2O for dachiardite-Ca from Byšta and (Ca1.37Na0.48K0.25Ba0.02Mg0.02)Σ3.65(Al3.65Si20.37O48)·13H2O for dachiardite-Ca from Brezina. Ferrierite-Mg from Brezina forms acicular crystals and spherical aggregates of average size up to 1 mm. It is orthorhombic, space group Immm with following unit-cell parameters refined from X-ray powder difraction data: a 19.084(4), b 14.151(2), c 7.4932(16) Å, V 2023.7(1) Å3. Chemical analysis of ferrierite-Mg is corresponding to the following average empirical formula: (Mg1.14Ca0.48Ba0.40K0.28Na0.16Fe0.01)Σ2.47(Al5.09 Si31.06O72)·20H2O. PXRD as well as quantitative chemical data for clinoptilolite-Ca and mordenite are also provided in this paper. The formation of studied zeolites is associated with post-magmatic fluids significantly enriched in Si, which likely circulated during the younger stages of Miocene volcanic activity in the Slanské vrchy Mts. Hydrothermal fluids were probably generated from Si-rich rocks, represented predominantly by rhyolites under low temperature conditions (120 - 250 °C).

Fatigue Properties of Carbon Steel S45C and Die-cast Aluminum Alloy

The butt dissimilar joints of die-cast aluminum alloy and carbon steel by means of friction stir welding were prepared for investigating fatigue properties of the joints. The FSW tool used in this study has cemented carbide thread probe and a shoulder with scroll groove made of alloy tool steel. Fatigue tests were carried out under a load-controlled condition with a stress ratio R=-1 and R=0.1 in air at room temperature. From the experimental results, it was found that fatigue strength of the joint at 107 cycles were 117 MPa under R=-1 and 72 MPa under R=0.1, respectively. The fatigue fracture was initiated from the location approximately 6-7 mm distant from the welding interface. This site was thought to be the border between the stir zone and base metal. In the base metal region, a lot of silicon particles were distributed as acicular shape. On the other hand, in the stir zone, silicon particles were distributed as fine grain shape.

Microstructural characterization and mechanical properties of additively manufactured 17–4PH stainless steel

The aim of the present study is to carry out a comprehensive microstructural characterization on the Selective Laser Melting (SLM) printed 17–4PH stainless steel and to compare the results with commercial 17–4PH wrought alloy (in H1150 condition). It was found out that the middle region of as-printed SLM had less microporosities as compared to bottom and top regions which was attributed to the lower cooling rate in the middle-area and greater extent of fusion during manufacturing. The as-printed samples mainly consist of ά-martensite and retained austenite (γ). The electron back scatter diffraction (EBSD) results showed that the middle region had less retained austenite as compared to top and bottom ones. The fraction of high angle grain boundaries (HAGB) and twin boundaries (TB) in martensite in wrought alloy was found to be greater than the as-built samples. In contrast, a high fraction of HAGBs and low fraction of TBs were observed in austenite in as-printed samples. The SEM-TKD revealed that the fraction of phase boundaries close to Kurdjumov–Sachs (KS) orientation relationship (OR), i.e., x < 10°, was 93.3% and 91.73% for the wrought alloy and SLM printed, respectively. The average Vickers hardness of as-printed sample was ≈ 25% less than the commercial wrought alloy (in H1150 condition) which can be attributed to more retained austenite, larger grain size, and more microporosities in the matrix. Monotonic uniaxial tensile test and in-situ tensile deformation with the aid of EBSD were used to examine the mechanical strength of wrought and SLM samples and microstructural evolution during plastic deformation. The ultimate tensile strength (UTS) of the as-printed sample (≈1118 ± 4 MPa) was quite comparable to commercial alloy (1017 ± 2 MPa) but the uniform elongation was considerably higher in as-printed sample (21.8% ± 0.3 in as-printed versus 9.00% ± 0.56 in wrought alloy). EBSD analysis during the in-situ tensile test showed transformation induced by plasticity (TRIP effect) of γ → ά. The area fraction of retained austenite in SLMed sample decreased from 26.2% in stage I (zero strain) to 0.49% in stage IV (failure). Lath and acicular shape retained austenite transformed faster to martensite than the blocky shape austenite.