Needle-like Form Research Articles

Enhanced thermal stability and excellent electrochemical and photocatalytic performance of needle-like form of zinc-phthalocyanine

Enhanced thermal stability and excellent electrochemical and photocatalytic performance of needle-like form of zinc-phthalocyanine

A Comprehensive Investigation of Methanol Electrooxidation on Copper Anodes: Spectroelectrochemical Insights and Energy Conversion in Microfluidic Fuel Cells.

Here, we comprehensively investigated methanol electrooxidation on Cu-based catalysts, allowing us to build the first microfluidic fuel cell (μFC) equipped with a Cu anode and a metal-free cathode that converts energy from methanol. We applied a simple, fast, small-scale, and surfactant-free strategy for synthesizing Cu-based nanoparticles at room temperature in steady state (ST), under mechanical stirring (MS), or under ultrasonication (US). The morphology evaluation of the Cu-based samples reveals that they have the same nanoparticle (NP) needle-like form. The elemental mapping composition spectra revealed that pure Cu or Cu oxides were obtained for all synthesized materials. In addition to having more Cu2O on the surface, sample US had more Cu(OH)2 than the others, according to X-ray diffractograms and X-ray photoelectron spectroscopy. The sample US is less carbon-contaminated because of the local heating of the sonic bath, which also enhances the cleanliness of the Cu surface. The activity of the Cu NPs was investigated for methanol electrooxidation in an alkaline medium through electrochemical and spectroelectrochemical measurements. The potentiodynamic and potentiostatic experiments showed higher current densities for the NPs synthesized in the US. In situ FTIR experiments revealed that the three synthesized NP materials eletcrooxidize methanol completely to carbonate through formate. Most importantly, all pathways were led without detectable CO, a poisoning molecule not found at high overpotentials. The reaction path using the US electrode experienced an additional round of formate formation and conversion into carbonate (or CO2 in the thin layer) after 1.0 V (vs. Ag/Ag/Cl), suggesting improved catalysis. The high activity of NPs synthesized in the US is attributed to effective dissociative adsorption of the fuel due to the site's availability and the presence of hydroxyl groups that may fasten the oxidation of adsorbates from the surface. After understanding the surface reaction, we built a mixed-media μFC fed by methanol in alkaline medium and sodium persulfate in acidic medium. The μFC was equipped with Cu NPs synthesized in ultrasonic-bath-modified carbon paper as the anode and metal-free carbon paper as the cathode. Since the onset potential for methanol electrooxidation was 0.45 V and the reduction reaction revealed 0.90 V, the theoretical OCV is 0.45 V, which provides a spontaneous coupled redox reaction to produce power. The μFC displayed 0.56 mA cm-2 of maximum current density and 26 μW cm-2 of peak power density at 100 μL min-1. This membraneless system optimizes each half-cell individually, making it possible to build fuel cells with noble metal-free anodes and metal-free cathodes.

The precipitation behavior of η phase with lamellar morphology in a newly designed K439B nickel-based superalloy

The microstructure of nickel-based superalloys significantly influences their mechanical properties and performance. The precipitation behavior of η phase during heat treatment of a newly designed K439B superalloy was studied. The results demonstrate that the precipitation temperature of η phase in this alloy varies from 1040 to 1070 °C. A detailed analysis of the microstructure indicates that the η phase exhibits a ∼10 nm lamellar structure, unlike the needle-like form reported in previous research. The γ' phase is distributed on both sides of the η phase, and the Ti content in the η phase is higher than that in the γ' phase, although the content of Al and Ti in the η and γ' phases are higher than that in the matrix γ phase. Moreover, the γ′ phase demonstrates an orientation relationship of {111}γ||{0001}η and [110]γ/γ′||[11—20]η with the η phase. This study can be used as reference for heat treatment process design and optimization.

Study on the Effect of Nanoporous Copper Particle Size on Copper-Based Azide.

Preparing copper-based azide by in situ reaction is well-suited for MEMS processing technology and holds promising prospects in the field of MEMS micro-initiators. This study involved the preparation of porous copper with particle sizes of approximately 30 nm, 60 nm and 100 nm through powder sintering. These were used as precursors for a gas-solid in situ azide reaction to produce copper-based azide with varying morphologies and compositions. Copper-based azide micro-initiators were designed, and their output performance was evaluated using CL-20 and HNS-IV explosives. Analytical results revealed that the product from the reaction of the 100 nm precursor exhibited a lumpy and uneven structure with a conversion rate of 90.36%. The product from the 60 nm precursor reaction had a dense surface with a conversion rate of 94.56%, while the 30 nm precursor resulted in a needle-like form with a conversion rate of 92.82%. Detonation experiments demonstrated that the copper-based azide micro-initiators prepared with 100 nm of a porous copper precursor exhibited unstable output performance, requiring a 1.6 mg charge to successfully detonate CL-20 explosives. On the other hand, copper-based azide micro-initiators prepared from 60 nm and 30 nm of porous copper precursors exhibited stable output performance. A charge of 0.8 mg was adequate for reliably and consistently detonating CL-20 and HNS-IV explosives. The reduced particle size of the precursor enhanced the output performance of the copper-based azide micro-initiators, providing increased energy redundancy during detonation and improving overall usage reliability.

Ni50.8Ti49.2 alloy prepared by double-wire + arc additive manufacturing with a substrate heating temperature of 600 °C

In this study, a Ni50.8Ti49.2 single-walled component was prepared in-situ using double-wire + arc additive manufacturing using a substrate heated to 600 °C and TA1 and ER-Ni wires used as raw materials. The microstructure and properties of the component were thoroughly investigated. The results revealed that Ni4Ti3 precipitated mainly in spherical and needle-like forms, contributing to improved component strength through coherent strain strengthening and lattice distortion, respectively. The maximum hardness value reached an impressive 531 HV0.2. DSC curves showed distinct transformation temperatures: As = −24.8 °C, Af = 11.7 °C, Ms = 12.5 °C, and Mf = −28.1 °C. The presence of the precipitated phase altered the Ni content of the matrix, leading to overlapping peaks during the phase transformation process. After 15 cycles of compression, the component exhibited an unrecoverable strain approaching 1.75 %, demonstrating a certain degree of superelasticity.

Effect of Biosynthesized Nanoselenium on Controlling Tomato Root-Knot Nematode Meloidogyne incognita

Tomato is a globally important fruit crop, which is easily susceptible to infection by plant-parasitic nematodes during growth. In this study, selenium nanoparticles were biosynthesized through the selenite reduction pathway in a wild-type Pseudomonas stutzeri BB19 and were characterized by uniform nanostructured needle-like forms with an average size of 95.2 nm. The nematicidal effect of biosynthesized selenium nanoparticles (BioSeNPs) at different concentrations (2, 6, and 10 ppm) during the pre- or post-infection of tomato root-knot nematode (RKN), Meloidogyne incognita, was assessed under greenhouse conditions. The BioSeNPs were applied as a foliar spray or a soil drench, compared to ethoprophos nematicide (100 mL/pot). The results showed that the ethoprophos nematicide significantly reduced the number of galls, egg mass, and eggs/egg mass of M. incognita by 94.2, 92.8, and 49.8%, respectively. BioSeNPs, as foliar sprays, significantly reduced the number of galls in post-treated infected tomato plants at 10 ppm and in pre-treated infected tomato plants at 2 ppm by 91.9 and 91.4%, respectively. Concerning the egg mass, BioSeNPs significantly reduced it in pre-treated infected tomato plants at 2 ppm as a foliar spray by 90.9%. Moreover, BioSeNPs significantly reduced the eggs/egg mass in pre-treated infected tomato plants at 2 ppm as a soil drench by 43.3%. On the other hand, the BioSeNPs considerably improved tomato growth, chlorophyll a and b, carotenoid content, and enzymes (i.e., catalase and peroxidase) activity compared to untreated infected tomato plants (negative control). Hence, the BioSeNPs show a significant application potential as a cost-effective and environmentally friendly biocontrol agent for RKN management in tomato plants.

Revealing the role of polymer in the robust preparation of the 2,4-dichlorophenoxyacetic acid metastable crystal form by AI-based image analysis

The selective preparation of pure polymorphs is of great significance in the pharmaceutical industry. This work aims to prepare the pure metastable Form II of the 2,4-dichlorophenoxyacetic acid (2,4-D) and investigate the effects of polymer on the solution-mediated phase transformation (SMPT) with the assistance of AI-based image analysis. Firstly, a convolutional neural network model was built to segment and classify crystal Form II (needle) and crystal Form I (bulk). Then, the polymorphic transition kinetics based on the changes in the area of the two 2,4-D crystal forms over time was precisely and efficiently analyzed. The results revealed that the polymer additives mainly inhibited the dissolution of crystal Form II and the nucleation of crystal Form I, thereby obtaining pure metastable Form II of 2,4-D. The AI-based image analysis of the process evolution strategy offers insightful guidance on the manufacture of pure metastable crystal forms in the pharmaceutical and chemical industry. Metastable needle-like Form II of 2,4-D could be robustly prepared with polymer additive assistance. A convolutional neural network model, Crys-form CNN, was built to visualize and quantify the additives' effects on the crystal transformation process and determine the rate-controlling steps. • Pure metastable of the 2,4-D was robustly prepared with the assistance of polymer. • An AI-based image analysis model, Crys-form CNN, was built. • The SMPT of 2,4-D in the cuvette was in-situ monitored and visualized. • The effects of polymers on the SMPT were quantified by Crys-form CNN.

Křídové pískovce u Ždírce nad Doubravou (Českomoravská vrchovina): materiál pro gotické sakrální stavby v širokém okolí

The narrow, 40 km long belt of the Cretaceous sediments called „The Dlouhá mez“ has been preserved along the NW-SE-striking Železné hory fault within crystalline rocks in the Eastern Bohemia (Fig. 1). The youngest relic of this belt corresponds to the middle part of Jizera Fm. of middle Turonian age. In the southeastern part of the „Dlouhá mez“ belt, these deposits have fine-grained, glauconitic sandstone nature. Near the town of Ždírec nad Doubravou, the sandstone had been exploited for a long time in several presently abandoned quarries and used as a building material. The old quarry at the margin of Ždírec nad Doubravou was founded in the end of the 13th century, and it was replaced by new quarries between Ždírec nad Doubravou and the village of Nový Studenec in the second half of the 19th century. This sandstone was discovered in four gothic buildings in the wide surroundings of these quarries within the course of the macroscopic investigation by the author. To confirm this discovery, the author carried out microscopic investigation of ten sandstone samples taken both in the quarries and in the gothic buildings. Petrographic features of the sandstone were also specified. Microscopic study confirmed the identical character of all studied samples. The identity of sandstone exploited in the quarries and sandstones used in gothic buildings was also demonstrated by the analysis of total SiO2 content. The sandstone is fine-grained, with matrix-supported texture, variable content of glauconite grains and fragments of silicisponge spicules and rare foraminifera tests. Muscovite and feldspars occur in accessory amounts. The sandstone is silicified and exhibits a porosity from 6–8 to 20 %. The pores with very elongated, needle-like form originated by diagenetic dissolution of silicisponge spicules while the diagenetic quartz penetrated the original clayey and possibly also calcareous matrix. The foraminifera tests were also silicified during this process. Within subordinate thin layers in sandstone, the content of terrigenous quartz grains drops below 25 % (20–22 %) while the content of silicisponges fragments increases to 10–12 %. These layers can be classified as spiculitic, sandy silicite. The sandstone from Ždírec nad Doubravou was documented in two village churches (Krucemburk, Havlíčkova Borová), in a big church in the town of Havlíčkův Brod and in the chapel in the Lipnice Castle in the town of Lipnice nad Sázavou. These buildings originated in the last quarter of the 13th and in the 14th century. These localities are from 4 to 32 km away from the quarries near the town of Ždírec nad Doubravou (Fig. 1). The sandstones were used as ashlar masonry, window jambs and tracery, vault ribs and also in sculptures (figural corbels). A further investigation can probably reveal the Ždírec nad Doubravou sandstone in a higher number of medieval buildings.

Needle-like forms with a few tens of nanometer in diameter and more than a few tens of micrometer length, and specific oxygen state during In-flight glass melting

Needle-like forms with a few tens of nanometer in diameter and more than a few tens of micrometer length, and specific oxygen state during In-flight glass melting

A Model for the Deposition of Scale Crystals on the Surface of Clay Particles

Deposition and aggregation of scale on microbial surface leads to poor stabilization of the treatment of oilfield high-scale oily wastewater. To study the deposition characteristics of scale on the surface of microbial particles, we perform the deposition and aggregation of calcium sulfate on the surface of clay particles as simulators of microbes and establish the deposition-aggregation process model. According to the theory of crystal growth, the diffuse electric double layer theory for clay, and the charged colloid theory, the scale deposition model can be divided into induction period, formative period of scale crystal nucleation, and crystal growth period. When calcium sulfate crystals deposit and aggregate on the surface of clay particles, the zeta potential and the average particle size on the surface of the clay particles increase continuously over time and tend to increase and decrease in cycles. The scale crystals are wrapped divergently around the surface of the clay particles in a needle-like form, such that the clay suspension is in a state of high aggregation. Logarithmic value of the conductivity in the formation of scale crystal has a good linear relationship with time, which conforms to the first-order rate equation. Conductivity curves can better reflect the deposition course of scale crystal on the surface of clay particles, which is divided into the induction period (6 min), transition period (1.5 min), formative period of scale crystal nucleation (10.75 min), rapid growth period of scale crystal (8.5 min), slow growth period of scale crystal (14.75 min), and stationary phase (4.75 min), and with the formation of the scale crystal, the deposition rate constant decreases gradually from 0.00945 min−1 to 0.0001 min−1. The results uncovered that Deposition and aggregation rules of scale on the surface of clay particles and the basis for further studying on microbial surface.

Continuous Protein Crystallization in Mixed-Suspension Mixed-Product-Removal Crystallizers

The metastable needlelike form of lysozyme can be obtained from continuous crystallization in mixed-suspension mixed-product-removal (MSMPR) crystallizers for conditions at which the stable tetragonal form is obtained from batch crystallization. A 3D-printed airlift crystallizer and stirred tank crystallizer are used, which both approximate an MSMPR crystallizer well. The influence of residence time, precipitant concentration, and agitation mechanism on the attainable solid-state form is presented. The needlelike crystals appear after nucleation of the tetragonal form. An earlier transition from the tetragonal form to the needlelike form is observed in an airlift crystallizer compared to a conventional stirred crystallizer, which is possibly caused by reduced attrition and the presence of a gas–liquid interface in the airlift crystallizer. Furthermore, a long residence time and high precipitant concentration favor the formation of the needlelike crystals. This work demonstrates how the mode of operation of well-mixed crystallizers affects the attainable solid-state form of a model protein. The results generally show the importance of obtaining a quantitative understanding of the dynamic interplay between stochastic primary nucleation processes and deterministic growth and secondary nucleation processes so that future continuous MSMPR crystallizers can be designed and operated robustly to produce protein crystals of a desired solid-state form.

Composition of the nanosized orthorhombic O′ phase and its direct transformation to fine α during ageing in metastable β-Ti alloys

The structure and chemistry of the orthorhombic O′ phase after quenching of a Ti-23 at.%Nb-2 at.%O was measured using aberration-corrected transmission electron microscopy and atom probe tomography. The nanosized O′ phase, formed in the vicinity of ω, is enriched with oxygen and slightly depleted in Nb. Upon annealing, ω dissolves and the O′ phase develops in β up to 350 °C, above which temperature it transforms to colonies of fine α phase. Another needle-like form of α with lower Nb content is thought to nucleate from Nb-lean regions related to spinodal decomposition of β.

Influence of a high magnetic field on the solidification structures of ternary Al–Fe–Zr alloy

Abstract

Thermal Analysis for Detection of Zr-Rich Phases in Al–Si–Cu–Mg 354-Type Alloys

The principal aim of the present research study was to investigate the effects of minor additions of zirconium on phase precipitation in 354 alloys under very slow solidification rates. The results showed that reactions corresponding to precipitation of Cu-containing phases are also observed in the 354 alloy at temperatures below 500 °C. Zirconium reacts only with Ti, Si, and Al. The Zr-rich intermetallic phases observed in this study appear in two different forms: the phase (Al,Si)2(Zr,Ti) containing high levels of silicon which is block-like in form, and the phase (Al,Si)3(Zr,Ti) containing high levels of aluminum, which appears in needle-like form. There is no observable poisoning effect on the refinement of grain size after the addition of Zr to the alloys investigated, as was observed from the macrostructures of the thermal analysis samples obtained at high solidification rates, for the alloys containing Zr and Ti. In thermal analysis experiments carried out at the higher solidification rate, namely 4 °C s−1, there is an observable reaction within the temperature range of 667–671 °C which appears to be related to the precipitation of Zr-rich phases; it was not possible to observe this reaction at the lower solidification rate of 0.35 °C s−1 generally used in thermal analysis.

Effects of Cooling Rate on the Microstructure and Morphology of Sn-3.0Ag-0.5Cu Solder

This study explored the effect of the cooling rate on the microstructure and morphology of Sn-3.0Ag-0.5Cu (SAC305) lead-free solder. In the experiments, rapid cooling (P1: 63.17°C/s) of SAC305 solder resulted in high tensile strength (60.8 MPa) with no significant loss in ductility (strain >40%) due to the formation of fine-grained primary β-Sn (average size ∼14 μm) surrounded by a network-like fine eutectic structure consisting of β-Sn and particle-like Ag3Sn compound. As the cooling rate was reduced, the morphology of the Ag3Sn compound evolved progressively from a particle- to a needle-like form and finally to a leaf- or plate-like form. The cooling rate significantly affected the β-Sn grain size and the morphology of the Ag3Sn compound. Water cooling (at the fastest cooling rate of 100°C/s) of a solder sample resulted in a microstructure consisting of the finest structure of Ag3Sn and β-Sn with no Cu6Sn5, consequently exhibiting the highest hardness of the various specimens. By contrast, after cooling at the slowest rate of 0.008°C/s, the sample exhibited a coarse eutectic structure consisting of large plate-like Ag3Sn compound and isolated long rod-like Cu6Sn5 precipitates. This coarse structure resulted in both lower hardness and poorer tensile strength.

Qualitative discrimination between organic and biodynamic Sangiovese red wines for authenticity

In this study the ability of the droplet evaporation method (DEM) to discriminate between organic and biodynamic Sangiovese red wines was studied for the first time. The relationship between the sizing-parameters and shape-descriptors of the crystal structures and the chemical parameters of wines was evaluated, and the most significant correlations were found between the intensity of red color of wines with circularity (r = 0.90) and solidity (r = 0.94). Moreover the shape-descriptors allowed a discrimination between the organic and biodynamic Sangiovese red wines based on two kinds of structures: (i) needle-like and (ii) flower-like forms.

Synthesis and enhanced hydrogen desorption kinetics of magnesium hydride using hydriding chemical vapor synthesis

This paper describes the hydriding chemical vapor synthesis (HCVS) of the hydrogen storage alloy MgH2 in a hydrogen atmosphere and the product's hydrogenation properties. Mg powder was used as a starting material to produce submicron MgH2 and uniformly heated to a temperature of 600°C for Mg vaporization. The effects of deposited positions in HCVS reactor on the morphology and the composition of the obtained products were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analyses. It is clearly seen that after the HCVS process, the particle size of synthesized MgH2 was drastically reduced to the sub-micron or micrometer-scale and these showed different shapes (needle-like nanofibers and angulated plate) depending on the deposited position. The hydrogen desorption temperatures of HCVS–MgH2 were measured using a differential scanning calorimeter (DSC). It was found that after the HCVS process, the desorption temperature of HCVS–MgH2 decreased from 430 to 385°C and, simultaneously, the smallest particle size and the highest specific surface area were obtained. These observations indicate that the minimum hydrogen desorption temperature of HCVS–MgH2 powder with needle-like form can be obtained, and that this temperature is dependent on the particle size and the specific surface area of the products. The thermogravimetric analysis (TGA) for HCVS–MgH2 with needle-like and angulated plate morphologies showed that hydrogen started to be released at 340 and 375°C, respectively, when the temperature was increased at a heating rate of 5°C/min up to 400°C under an argon flow. The enhanced hydrogen storage performance was also achieved during subsequent hydrding–dehydriding cycles.

Characterization of rapidly solidified Ni–Si and Co–Al eutectic alloys in drop tube

Containerless solidifications of Ni–Si and Co–Al eutectic alloys were carried out using an 8 m drop tube. Molten alloy ejected into a drop tube was rapidly cooled and solidified during free fall. The microstructures of the rapid solidified alloys were evaluated. It was seen that the microstructures of Ni–Si and Co–Al eutectics change from the lamellar and plate-like eutectic to the anomalous eutectic and needle-like forms with decreasing the sample size, respectively. The values of the enthalpy of fusion and specific heat were determined by means of differential scanning calorimetry (DSC) during the transformation from liquid to the solid state. The microhardness of rapid solidified alloys was measured by using a microhardness test device. According to the present measurements, the values of microhardness (HV) for rapid solidified Ni–Si and Co–Al eutectics alloys increase with decreasing the eutectic spacing.

Unmasking a third polymorph of a benchmark crystal-structure-prediction compound.

Unmasking a third polymorph of a benchmark crystal-structure-prediction compound.

A comparative study of the SSC resistance of a novel welding process IEA with SAW and MIG

The Stress Sulphide Cracking resistance of X65 weldments produced by Indirect Electric Arc, Submerged Arc Welding (SAW) and Metal Inert Gas (MIG) processes were evaluated in a NACE solution saturated with H 2S at 25 °C, 37 °C and 50 °C using Slow Strain Rate Tests (SSRT) and electrochemical measurements. Weldments produced by the Indirect Electric Arc presented the best Stress Sulphide Cracking resistance at 25 °C. This behavior is attributed to the microstructural modification of the weld bead from ferrite in a needlelike form to a fine grain microstructure, which was not observed at 37 °C and 50 °C. In addition, the hydrogen permeation flux increased with the temperature, this result is associated with the ferrite phase. The electrochemical results show a decrease of the trapping sites for the atomic hydrogen on this weldment. This behavior has not been observed for the other welding processes due to their microstructure (a typical columnar growth of coarse grain).