Amorphous Samples Research Articles

Hydrophilic-amorphous versus hydrophobic-crystalline Sb2S3: The battle for higher photocatalytic efficiency

The dependence of crystallinity and hydrophilicity of the material on its photocatalytic activity is rarely explored and understood. In this work, the influence of crystallinity and surface wettability is demonstrated through the photocatalytic activity of Sb2S3 thin films. Amorphous and crystalline thin films of Sb2S3 having bandgaps of 2.36 and 1.89 eV respectively are prepared using thermal evaporation. Photocatalytic activity of both the films are evaluated in the degradation of methylene blue dye under visible light. Amorphous sample degraded 88 % of dye in 180 min of irradiation, with a reaction rate constant of 0.01/min. The crystalline sample removed only 64 % of the dye under the same condition. The analysis of the surface nature of the film using contact angle measurement revealed that, amorphous sample is hydrophilic and crystalline sample hydrophobic with water contact angles of 68° and 92° respectively. The role of surface wettability on photocatalysis is also analysed by modifying the film surface with the help of plasma treatment. The treatment reduced the hydrophilicity of the amorphous surface and at the same time transformed the crystalline surface from hydrophobic to hydrophilic. The change in the surface morphology such as formation of micro/nanostructures and variation in roughness, which contribute to the hydrophobicity is observed through AFM. The surface changes are reflected in the dye degradation efficiencies as well. The dye degradation efficiency reduced to 79 % in the amorphous sample and increased to 72 % in the crystalline sample. The study unveils the exciting efficiency of the hydrophilic, amorphous Sb2S3 films without any thermal or surface treatments as photocatalyst.

Orientation dependence of the nanocrystallization and magnetic behavior during annealing of the FINEMET alloy

The microscopic strain evolution and microstructural of FeCuNbSiB amorphous alloy samples were studied under both free and tensile stress annealing conditions using in-situ synchrotron X-ray diffraction (XRD) and transmission electron microscopy (TEM). An amorphous-nanocrystalline structure was developed in both samples after annealing at 813 K, as the microstrains increased and decreased along the parallel and perpendicular stress directions respectively. The applied stress during annealing imposed limitations on the size of nanocrystals along the tensile and perpendicular stress directions, resulting in smaller sizes compared to those obtained under free annealing conditions, due to the reduction in Gibbs free energy by the applied stress and the subsequent enhancement of nucleation rates. The nanocrystalline size perpendicular to the stress direction was slightly larger than that along the parallel stress direction because the suppression of atomic diffusion perpendicular to the stress direction during crystallization could be favorable for local atomic rearrangement.

Morphology and Crystallinity Effects of Nanochanneled Niobium Oxide Electrodes for Na-Ion Batteries.

Niobium pentoxide (Nb2O5) is a promising negative electrode for sodium ion batteries (SIBs). By engineering the morphology and crystallinity of nanochanneled niobium oxides (NCNOs), the kinetic behavior and charge storage mechanism of Nb2O5 electrodes were investigated. Amorphous and crystalline NCNO samples were made by modulating anodization conditions (20-40 V and 140-180 °C) to synthesize nanostructures of varying pore sizes and wall thicknesses with identical chemical composition. The electrochemical energy storage properties of the NCNOs were studied, with the amorphous samples showing better overall rate performance than the crystalline samples. The enhanced rate performance of the amorphous samples is attributed to the higher capacitive contributions and Na-ion diffusivity analyzed from cyclic voltammetry (CV) and the galvanostatic intermittent titration technique (GITT). It was found that the amorphous samples with smaller wall thicknesses facilitated improved kinetics. Among samples with similar pore size and wall thickness, the difference in their power performance stems from the crystallinity effect, which plays a more significant role in the resulting kinetics of the materials for Na-ion batteries.

Dynamics of Cu–Zr metallic glass devitrification under ultrafast laser excitation revealed by atomistic modeling

The physics of metallic glass local devitrification employing ultrafast laser irradiation is the cradle of complex phenomena that are still not understood despite its applicative potential in material processing for nanotechnology. This paper reports a theoretical simulation combining the two temperature model and classical molecular dynamics simulations to unravel the mechanisms that lead to the localized phase transition in Cu–Zr metallic glass. According to observations, the initial composition of amorphous samples plays an essential role, in addition to nonequilibrium thermodynamic processes caused by the laser energy deposition that alters the atomic environment. We further demonstrate that specific compositions devitrify despite its high glass-forming ability. The thermodynamic conditions fostering the emergence of a stable nanocrystalline phase are clearly established. The compressive pressure wave and the rapid heating process caused by ultrafast laser energy deposition synergistically contribute to disrupt the microstructure of the glass significantly, thereby initiating the devitrification process. Results are discussed using additional classical MD simulations that provide valuable insights for interpreting the distinct contributions of temperature and pressure to the phase transformation. Finally, the impact of the formed nanocrystals on the phononic thermal conductivity of the alloy is presented confirming the potential application of the laser-induced devitrification process for the development of a new generation of nanoarchitectured materials.

Effects of Stress on Loss and Magnetic Properties of Fe80Co3Si3B10P1C3 Amorphous Iron Cores

The research on how to reduce energy consumption and improve the efficiency of amorphous motors has extensive coverage. This study systematically investigates the influence of internal stress induced by impregnation curing and interference fit on the soft magnetic properties and loss characteristics of Fe80Co3Si3B10P1C3 (CAF4) amorphous alloy iron cores. The amorphous iron core samples undergo analysis through differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X-ray diffraction (XRD), magnetic performance testing equipment, flexible pressure sensors, and magnetostriction testers. The CAF4 amorphous iron core after impregnation curing (AIC) exhibits the lowest loss of P1.2T,1.5 kHz = 22.8 W/kg when annealed at 260 °C, representing a 21% increase compared to the pre-impregnation curing (BIC) state. Within the commonly utilized interference fit range, the loss growth rate of CAF4 amorphous iron cores is lower than that of Fe80Si9B11 (1K101). Likewise, at a frequency of 50 Hz and an excitation of 1000 A/m, the magnetostriction coefficient of CAF4 is smaller than that of 1K101. Within the typical interference fit range, the magnetization performance of CAF4 amorphous iron cores surpasses that of 1K101, favoring lightweight and compact motor designs and reducing copper losses. Consequently, CAF4 amorphous iron cores exhibit significant advantages when employed in motors.

A machine learning approach for the automated classification of bulk sp2 and sp3 carbon materials

AbstractPrincipal component analysis (PCA) and linear discriminant analysis (LDA) were used to classify different types of carbon material based on their Raman spectra. The selected reference materials were highly oriented pyrolytic graphite (HOPG), diamond‐like carbon (DLC), glassy carbon (GC), hydrogenated graphite‐like carbon (GLCH), and hydrogenated polymer‐like carbon (PLCH). These materials vary in crystallinity, predominant carbon hybridization, and hydrogen content. The training dataset was Raman spectra collected from commercial samples (HOPG, DLC, GC) and samples synthesized in our laboratory (GLCH, PLCH). The Raman spectra were collected using 532 nm laser excitation. The classification model revealed that the first principal component (PC1) was the determinant source of information to separate the crystalline from the amorphous carbon samples. PC2 allowed the separation of amorphous material with different levels of hybridization (sp2 and sp3). Finally, both PC2 and PC3 contributed to separate materials with different levels of hydrogenation. The classification model was tested using a library of Raman spectra of carbon materials reported in the literature, and the results showed a high accuracy prediction (97%). The model presented here provides an avenue for automated classification of carbon materials using Raman spectroscopy and machine learning.

A High Crystalline Perylene-Based Hydrogen-Bonded Organic Framework for Enhanced Photocatalytic H2O2 Evolution.

Hydrogen-bonded organic frameworks (HOFs) are a kind of crystalline porous material that have shown great potential for photocatalysis on account of their mild synthesis conditions and high crystallinity. Perylene-based photocatalysts have great potential for photocatalytic H2O2 production due to their excellent photochemical stability and broad spectral absorption. In this work, we designed and synthesized a high crystalline perylene-based HOF (PTBA) and an amorphous analog sample PTPA for photocatalytic H2O2 evolution. Under visible light irradiation, PTBA shows a higher photocatalytic H2O2 production rate of 2699 μmol g-1 h-1 than PTPA (2176 μmol g-1 h-1) and an apparent quantum yield (AQY) of 2.96% at 500 nm. The enhanced photocatalytic performance of PTBA is attributed to the promotion of the separation and transfer of photocarriers due to its high crystallinity. This work provides a precedent for the application of HOFs in the field of photocatalytic H2O2 generation.

Mesoporous Matrices as a Promising New Generation of Carriers for Multipolymorphic Active Pharmaceutical Ingredient Aripiprazole.

The enhancement of the properties (i.e., poor solubility and low bioavailability) of currently available active pharmaceutical ingredients (APIs) is one of the major goals of modern pharmaceutical sciences. Among different strategies, a novel and innovative route to reach this milestone seems to be the application of nanotechnology, especially the incorporation of APIs into porous membranes composed of pores of nanometric size and made of nontoxic materials. Therefore, in this work, taking the antipsychotic API aripiprazole (APZ) infiltrated into various types of mesoporous matrices (anodic aluminum oxide, native, and silanized silica) characterized by similar pore diameters (d = 8-10 nm) as an example, we showed the advantage of incorporated systems in comparison to the bulk substance considering the crystallization kinetics, molecular dynamics, and physical stability. Calorimetric investigations supported by the temperature-dependent X-ray diffraction measurements revealed that in the bulk system the recrystallization of polymorph III, which next is converted to the mixture of forms IV and I, is visible, while in the case of confined samples polymorphic forms I and III of APZ are produced upon heating of the molten API with different rates. Importantly, the two-step crystallization observed in thermograms obtained for the API infiltrated into native silica templates may suggest crystal formation by the interfacial and core molecules. Furthermore, dielectric studies enabled us to conclude that there is no trace of crystallization of spatially restricted API during one month of storage at T = 298 K. Finally, we found that in contrast to the crystalline and amorphous bulk samples, all examined confined systems show a logarithmic increase in API dissolution over time (very close to a prolonged release effect) without any sign of precipitation. Our data demonstrated that mesoporous matrices appear to be interesting candidates as carriers for unstable amorphous APIs, like APZ. In addition to protecting them against crystallization, they can provide the desired prolonged release effect, which may increase the drug concentration in the blood (resulting in higher bioavailability). We believe that the "nanostructirization" in terms of the application of porous membranes as a novel generation of drug carriers might open unique perspectives in the further development of drugs characterized by prolonged release.

Photovoltaic Wafering Silicon Kerf Loss as Raw Material: Example of Negative Electrode for Lithium‐Ion Battery**

AbstractSilicon powder kerf loss from diamond wire sawing in the photovoltaic wafering industry is a highly appealing source material for use in lithium‐ion battery negative electrodes. Here, it is demonstrated for the first time that the kerf particles from three independent sources contain ~50 % amorphous silicon. The crystalline phase is in the shape of nano‐scale crystalline inclusions in an amorphous matrix. From literature on wafering technology looking at wafer quality, the origin and mechanisms responsible for the amorphous content in the kerf loss powder are explained. In order to better understand for which applications the material could be a valuable raw material, the amorphicity and other relevant features are thoroughly investigated by a large amount of experimental methods. Furthermore, the kerf powder was crystallized and compared to the partly amorphous sample by operando X‐ray powder diffraction experiments during battery cycling, demonstrating that the powders are relevant for further investigation and development for battery applications.

Kinetics of the Oxygen Evolution Reaction (OER) on Amorphous and Crystalline Iridium Oxide Surfaces in Acidic Medium.

Amorphous and crystalline IrO2 catalysts are synthesized by the Adams method and characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The oxygen evolution reaction (OER) is investigated on both the catalyst surfaces in 0.5 M H2SO4 electrolyte. The Tafel slope estimated in the temperature range of 293-333 K on the two surfaces indicates a change in the rate-limiting steps. The data are also analyzed in terms of the Eyring equation to estimate the activation enthalpy (ΔH#) and pre-exponential factor (Af) as a function of overpotential and therefore the charge-transfer coefficient (α). The estimated α values suggest strong electrocatalysis on both the surfaces. While the ΔH# plays a decisive role in the electrocatalysis on the amorphous sample, the trend of Af indicates that an increase in the entropy on the crystalline surface is pivotal in reducing the reaction barrier.

Atomic-level structure determination of amorphous molecular solids by NMR

Structure determination of amorphous materials remains challenging, owing to the disorder inherent to these materials. Nuclear magnetic resonance (NMR) powder crystallography is a powerful method to determine the structure of molecular solids, but disorder leads to a high degree of overlap between measured signals, and prevents the unambiguous identification of a single modeled periodic structure as representative of the whole material. Here, we determine the atomic-level ensemble structure of the amorphous form of the drug AZD4625 by combining solid-state NMR experiments with molecular dynamics (MD) simulations and machine-learned chemical shifts. By considering the combined shifts of all 1H and 13C atomic sites in the molecule, we determine the structure of the amorphous form by identifying an ensemble of local molecular environments that are in agreement with experiment. We then extract and analyze preferred conformations and intermolecular interactions in the amorphous sample in terms of the stabilization of the amorphous form of the drug.

Synthesis and Hydrogenation of the Ti45−xVxZr38Ni17 (5 ≤ x ≤ 40) Mechanically Alloyed Materials

The mechanically alloyed amorphous alloys of the Ti45Zr38Ni17 composition are known for their ability to form a quasicrystalline state after thermal treatment. It is also known that the amorphous and quasicrystal alloys belonging to the Ti45Zr38Ni17 family are able to store hydrogen and yield gravimetric densities above 2 wt.%. In this contribution, we report the results of research on the Ti45Zr38Ni17 system with vanadium doped instead of titanium. We found that the amorphous samples with moderate doping (x < 20) show the ability to absorb hydrogen while maintaining the amorphous state and they transform into the novel glassy-quasicrystal phase during annealing. Those materials with higher vanadium concentrations do not form entirely amorphous structures. However, they still can absorb hydrogen easily. It was also confirmed that the in situ hydrogenation of the amorphous alloys is a straightforward process without decomposition of the alloy. In this process, hydrogen does not attach to any particular constituent of the alloy, which would lead to the formation of simple hydrides or nanoclusters. Therefore, we were able to confirm the fully amorphous nature of the deuterides/hydrides of the Ti45−xVxZr38Ni17 with moderate V doping.

Photovoltaic Characteristics of the a-C/a-C:B Homojunction from Palmyra Sugar with Nano-Spray Method

The a-C/a-C:B homojunction of palmyra sugar has been successfully fabricated using the nanospray method. Palmyra sugar was chosen as the main source of carbon because it is cheap, renewable, abundant and available around the clock. nanospray is used as a deposition method on glass ITO substrates because of several advantages, namely cheap, easy, portable, low power consumption, the deposited layer is more evenly distributed and thinner. Junction samples when in bright conditions [emitted light] showed an increase in current and voltage values ​​compared to dark conditions. Testing the current and voltage of the junction sample shows the characteristics of a rectifier diode. This confirms the results of the test using PES as a doping process with amorphous carbon with boron capable of changing the conduction type from a-C from an intrinsic semiconductor to a p-type semiconductor. Testing the junction sample when irradiated with visible light using a lamp shows symptoms of the photovoltaic effect. Tests directly on the sun when conditions AM 1.5 samples showed symptoms of the photovoltaic effect. This indicates that the a-C/a-C:B amorphous carbon homojunction junction sample functions as a solar cell.

High-Throughput Synthesis and Characterization Screening of Mg-Cu-Y Metallic Glass

Bulk metallic glasses can exhibit novel material properties for engineering scale components, but the experimental discovery of new alloy compositions is time intensive and thwarts the rate of discovery. This study presents an experimental, high-throughput methodology to increase the speed of discovery for potential bulk metallic glass alloys. A well-documented system, Mg-Cu-Y, was used as a model system. A laser additive manufacturing technique, directed energy deposition, was used for the in situ alloying of elemental powders to synthesize discrete compositions in the ternary system. The laser processing technique can supply the necessary cooling rates of 103–104 Ks−1 for bulk metallic glass formation. The in situ alloying enables the rapid synthesis of compositional libraries with larger sample sizes and discrete compositions than are provided by combinatorial thin films. Approximately 1000 discrete compositions can be synthesized in a day. Surface smoothness, as discerned by optical reflectivity, can suggest glass-forming alloys. X-ray diffraction coupled with energy dispersive X-ray spectroscopy can further refine amorphous alloy signatures and compositions. Transmission electron microscopy confirms amorphous samples. The tiered rate of amorphous alloy synthesis and characterization can survey a large compositional space and permits a glass-forming range to be identified within one week, making the process at least three orders of magnitude faster than other discrete composition techniques such as arc-melting or melt-spinning.

In situ monitoring of the hydration of calcium silicate minerals in cement with a remote fiber-optic Raman probe

This study utilized a novel in situ fiber-optic Raman probe to continuously monitor the hydration progress of tricalcium silicate (C3S) and dicalcium silicate (C2S) without the need for sampling, from early hydration stage to later stages, and from fresh to hardened states of paste samples. By virtue of the remarkable ability of this technique in characterizing either dry or wet and crystalline or amorphous samples, the hydration processes of C3S and C2S pastes with different water-to-solid (w/s) ratios could be monitored from the start of the hydration reaction. The main hydration products, calcium silicate hydrate (C–S–H) and portlandite/calcium hydroxide (CH), have been successfully identified and continuously monitored for variations in their respective amounts in situ. The effect of w/s ratio on the hydration processes of C3S and C2S pastes was also considered. Meanwhile, the x-ray diffraction (XRD) and thermogravimetric analysis (TGA) results showed a great correlation with the in situ Raman test results about hydration products, which demonstrated the reliability of this technology. Moreover, the signal-to-noise ratio (SNR) of this Raman probe is significantly superior to existing technologies for in situ fiber-optic Raman spectroscopy. This remote fiber-optic Raman probe enables the use of Raman spectroscopy in future construction projects for on-site monitoring and evaluation of health conditions and performance of concrete structures.

Crystalline S-doped TiO2 photoanodes from amorphous titanium oxysulfide (TiOxSy) for photo-oxidation reactions

S-doped TiO2 films were prepared by oxidation annealing of amorphous titanium oxysulfide (TiOxSy) at different temperatures. According to the X-ray diffraction patterns, the films calcined at temperatures of 300–600 °C showed only anatase phase, while the uncalcined sample was amorphous. The chemical composition of synthesized TiOxSy was estimated by X-ray photoelectron spectroscopy (XPS). High-resolution S 2p spectra showed S−2 bonds at 163.47 eV for the amorphous sample. The intensity of this signal decreased after heat treatment. Raman spectroscopy indicated an organization of the material structure with heat treatment of the material. Furthermore, optical characterization revealed that sulfur as dopant into the anatase TiO2 structure, shifted light absorption from ultraviolet to the visible region. Photoeletrochemical studies developed under polychromatic irradiation revealed superior photocurrents for samples calcined at 600 °C, with n-type behavior, adequate for photo-oxidation reactions.

Composition and morphology of biomass-based soot from updraft gasifier system

Soot is an aerosol formed by incomplete combustion of carbonaceous materials, and its formation in biomass gasification is inevitable. It is crucial to know the properties of the soot produced in the exhaust of gasification reactors in order to appreciate both its advantages and disadvantages. In this study, a variety of analytical techniques were used to examine the content and morphology of biomass soot produced by a top-lit updraft gasifier. The results of the experiment revealed that carbon and oxygen make up the majority of the soot, with minor amounts of other components. Both aromatic and aliphatic groups with significant oxygen concentrations can be seen in the soot based on the distribution of functional groups. The morphology revealed an uneven, stratified, amorphous sample. Meanwhile, the sample had a surface area of 193.8 m2/g and a pore diameter of 2.68 nm. These porous qualities point to a potential use of the soot sample as an adsorbent in water filtration after activation.

Mechanochemical Synthesis of Amorphous Silicates with an Enstatite and Forsterite Composition

The presence of amorphous silicate particles in interstellar and circumstellar space has been suggested based on the observation of 9.7 and 18 μm emission bands. We have successfully synthesized amorphous silicate samples of an enstatite and forsterite composition by the mechanical milling of mixed powder consisting of SiO2–MgO and SiO2–Mg(OH)2 reagent-grade particles under different rotation frequencies and milling times. These two types of starting materials are prepared to study the effect of the OH bond on synthesis and crystallization. The amorphous samples were characterized by X-ray diffraction and infrared spectroscopy. Amorphous samples with enstatite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2 at 300 rpm and for 300 hr. Amorphous samples with forsterite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2. The samples from SiO2–Mg(OH)2 require 400 rpm and a long milling time of 1600 hr. After crystallization, amorphous samples with an enstatite composition synthesized from SiO2–Mg(OH)2 mainly transform into forsterite with small amounts of amorphous silica SiO2 and enstatite depending on the rotation frequencies and milling time, while those from SiO2–MgO become enstatite. The amorphous samples with a forsterite composition are crystallized to forsterite from both starting materials. The presence of H2O or OH bonds significantly affects the final products after the crystallization of amorphous silicates of enstatite composition.

Amorphization versus cocrystallization of celecoxib-tramadol hydrochloride using CO2-assisted nano-spray drying

The manipulation of both solid-state form and particle size is a versatile means by which physicochemical properties of pharmaceutical drugs may be improved/fine-tuned. The work presented herein describes the solid-state and particle size control of the most recently FDA-approved pharmaceutical cocrystal, composed of two APIs, Celecoxib-Tramadol hydrochloride (Seglentis®), using a continuous atomization technique, namely supercritical CO2-assisted nano-spray drying. Using a three-factorial design of experiments, both (co)amorphous and cocrystalline samples were generated, depending on processing conditions. Mean particle sizes ranged from 120 nm to 1160 nm, with solution flow rate showing the most significant effect due to its impact on atomized droplet sizes. While all (co)amorphous samples displayed a similar morphology, one set of conditions produced a (co)amorphous sample with a larger degree of intermolecular interactions, comparable with the hydrogen bonding network observed in the cocrystalline samples. Tabletting of four formulations was carried out to investigate the impact of particle size and solid-state on tabletability, compactability and compressibility. While all formulations performed adequately in these critical quality attributes, the formulations which contained cocrystalline particles underperformed regarding tabletability and compactability due to their irregular shape and larger size. However, due to the increased prevalence of intermolecular interactions, the cocrystalline and (co)amorphous samples with a larger degree of hydrogen bonding led to improved compressibility.

Weak dehydration enhances the adsorption capacity of boehmite for anionic dyes

Various works have been conducted for enhancing anionic dye removal onto boehmite. However, the influence of the water content in boehmite on its adsorption performance has not been investigated to date. Therefore, we explored the impact of the level of dehydration of boehmite on its structural water content and anionic dye removal. Adsorbents were prepared via sol-gel method, followed by heat treatment under temperature range of 70–200 °C, covering weak and strong dehydration, and were tested for adsorption of methyl orange and Congo red. Surface properties of adsorbents including functional groups, crystallinity, surface area, porosity, and zeta potential were investigated. Strong dehydration yielded crystalline structures with high surface area (110–140 m2/g) and low water content, ineffective for anionic dye removal. Meanwhile, weakly dehydrated samples holding a low surface area (nonporous – 5.05 m2/g) and high water content exhibited excellent adsorption of the tested anionic dyes. The amorphous boehmite prepared at 100 °C showed the highest adsorption capacity of methyl orange (320 mg/m2, 900 mg/g), while the nonporous amorphous sample prepared at 200 °C demonstrated the highest adsorption capability for Congo red (527 mg/g). Through analyzing the adsorption results, chemical structure of the dyes, and surface characteristics of the adsorbents, we identified that the adsorption mechanism is influenced by electrostatic forces or hydrogen bonding. These findings present a promising application of weak dehydration and its resulting boehmite for effective adsorption of organic dyes in water.