Crystalline Phase Composition Research Articles

Low detection based on Pd Pt /In2O3 nanospheres for rapid hydrogen detection

Semiconductor gas sensors still have limitations in realizing rapid hydrogen measurement in lower hydrogen concentration environments. Therefore, in this paper, In2O3 cloud-like spherical hydrogen detection sensing materials with different Pd and Pt ratio loading were successfully prepared using the water bath method. The In2O3 sensing materials modified with noble metals Pd and Pt were designed for the rapid detection of hydrogen at 400 ppb with good selectivity under mixed gas components. The crystalline phase, morphology, and chemical composition of the prepared Pd and Pt-loaded In2O3 samples were analyzed using characterization techniques. The gas-sensing results showed that the In2O3 gas-sensing sensor with a Pd and Pt ratio loading of 1–2 had stronger H2 sensing performance at the optimum operating temperature (350°C). The response time and recovery time of In2O3 loaded with the opinion ratio at 350℃ and 400 ppb were 1 s and 15 s. The low detection limit was 400 ppb, with good repeatability and long-term stability. Finally, the enhanced gas sensitization mechanism of the In2O3 gas sensor loaded with Pd and Pt for H2 was discussed.

Sintering of Si3N4–SiC–MoSi2 composites additively manufactured by Multi Material Jetting

Sintering of Si₃N₄–SiC–MoSi₂ composites additively manufactured by Multi Material Jetting

Waste to shield: Tailoring cordierite/mullite/zircon composites for radiation protection through controlled sintering and Y2O3 modification

In this study, investment casting shell waste successfully utilized to produce cordierite/mullite/zircon composites. Green pellets, consisting of investment casting shell waste, alumina, and magnesia, were prepared and sintered at temperatures between 1250 and 1350 °C. The influence of the sintering temperature on the crystalline phase composition, densification behavior, flexural strength, microstructure, and radiation shielding properties of the cordierite/mullite/zircon composites is investigated. Phase analysis showed that characteristic cordierite peaks appear at 1250 °C, but the complete conversation of silica from investment casting shell waste into cordierite requires a sintering temperature of at least 1300 °C. Notably, the cordierite/mullite/zircon composite sintered at 1350 °C exhibited a sixfold increase in flexural strength compared to the ceramic composite directly fabricated from investment casting shell waste at the same sintering temperature. Furthermore, the effect of Y2O3 addition on composites' radiation shielding properties is investigated. The results show that the Y2O3 addition improved densification behavior, enhancing the shielding capabilities of the composites against fast neutron and gamma radiation. Our findings suggest that the developed ceramic composites show significant potential for gamma-ray and neutron shielding applications.

Biogenic Synthesis of Copper Nanoparticles from flower extract and their Cell Cytotoxic Potential

In order to overcome the negative potential risks of conventional nanoparticles and achieve the goal of human therapeutic uses, sustainable nanoparticles must be synthesized. In this paper, we have created a simple method for producing copper nanoparticles using green chemistry. With the use of Cassia auriculata's floral aqueous extract, copper nanoparticles (CuNPs) were effectively produced. In a UV-Visible Spectrophotometer, sythesized CuNPs detect absorbance at 276 nm, a hallmark of copper nanoparticles. The relevant functional groups involved in lowering and stabilizing CuNPs were found using Fourier Transform Infrared Spectroscopy. CuNPs shape, crystalline phase, and elemental composition were seen using scanning and transmission electron microscopy, energy dispersive analysis spectroscopy, and other techniques. Moreover, CuNPs' antibacterial and antifungal properties produced good inhibitory action against the pathogens that were put to the test. Furthermore, at low doses, CuNPs had no effect on the cytotoxicity of the cell lines MDCK and Caco-2. CuNPs may thus be turned into nano-drugs for the treatment of infectious diseases and tumour research.

In-situ synchrotron X-ray diffraction of hydroxyapatite-zirconia composite during conventional and flash sintering

We conducted in-situ X-ray diffraction to study the crystalline phase evolution in hydroxyapatite-zirconia composites during both conventional and flash sintering processes. Additionally, we examined the thermal history and microstructure of the composite under these sintering conditions. Despite both sintering methods reaching similar average temperatures, they yielded distinct results in terms of crystalline phase composition and microstructure. In the flash sintered samples, we observed a complete transformation of hydroxyapatite into α- tricalcium phosphate and a complete tetragonal to cubic phase transition in zirconia. Conversely, the conventionally sintered samples remained practically stable. Notably, the flash sintered samples exhibited needle-like microstructures, which were absent in their conventionally sintered counterparts. This divergence suggests that the application of an electric field plays a role in generating athermal effects during the sintering of hydroxyapatite-zirconia composites.

Composition, time, temperature, and annealing-process dependences of crystalline and amorphous phases in ductile semiconductors Ag2S1−xTex with x = 0.3–0.6

We investigate composition, time, temperature, and annealing-process dependences of crystalline and amorphous phases in ductile semiconductors Ag2S1−xTex with x = 0.3–0.6. We reveal that a metastable amorphous phase containing no secondary phases is obtainable at x = 0.6 even with furnace cooling and possesses ductility in the same manner as the end compound of Ag2S, while the high-temperature phase (HTP) of Ag2S precipitates in the amorphous phase at x = 0.3–0.5 by keeping the good ductility. During the crystallization process of the amorphous phase by annealing a sample at 373–503 K for 4–14 days and cooling it down slowly to room temperature, HTP of Ag2S disappears and the low-temperature phase (LTP) of Ag2S and the Ag5−dTe3 phase appear, while the amorphous phase remains. The ductility is observed for the samples containing the LTP of Ag2S but not for those containing the Ag5−dTe3 phase. Based on the obtained results, the possible phase diagram of Ag2S1−xTex with x = 0.3–0.6 is proposed, and the origin of the ductility in the LTP and HTP of Ag2S and amorphous phase is discussed. We believe that our study is helpful for properly predicting mechanical and transport properties of this material and developing this material as a component of bendable/wearable electronic devices for long-term use.

Fabrication and characterization of polyvinyl alcohol/TiO2 membrane immersed in simulated body fluid for biomedical application

AbstractIn this study, we synthesized hydroxyapatite (HA) on polyvinyl alcohol/TiO2 (PVA/TiO2) in which TiO2 was prepared by the sol‐gel method. HA was formed by immersing the membrane in the simulated body fluid (SBF) solution. We improved the mechanical strength of the membranes by adding glutaraldehyde (GA) combining with heat treatment to cross‐link the polymer network. In addition, the composition of TiO2 crystalline phase, TiO2 content in each membrane, and the duration of membrane immersion in SBF solution were investigated. The morphological structures of hydroxyapatite/polyvinyl alcohol/TiO2 (HA/PVA/TiO2) membranes were characterized by IR, SEM, and XRD. We confirmed that the HA formation depended on the TiO2 content and phase composition (rutile or anatase). Membranes containing TiO2 rutile‐phase showed more pronounced HA formation than membranes containing TiO2 anatase‐phase. The appearance of HA also depended on SBF immersion duration. Membranes soaked for 3 weeks showed significantly more HA formation than membranes soaked for 1 and 2 weeks. Furthermore, the number of cells in membranes soaked for 3 weeks was clearly higher than in other membranes. Finally, HA/PVA/TiO2 membranes containing 25 wt.% of TiO2 rutile‐phase are biocompatible based on the number of viable cells and thus have the potential for biomedical application.

Photoactive TiO2 ceramic coatings obtained by laser-assisted plasma electrolytic oxidation on commercial pure titanium

To address the challenges of controlling the morphology and crystalline phase composition of photoactive TiO2 ceramic coatings produced by existing plasma electrolytic oxidation (PEO) technology, a novel laser-assisted PEO method is proposed in this study. The analysis has revealed that the TiO2 coatings prepared by the laser-assisted PEO method had a more intricate 3D multi-porosity architecture. Furthermore, the ratio of TiO2 crystalline phases (anatase to rutile) in the coating can be controlled by adjusting the laser energy during the laser-assisted irradiation process. The fundamental reason for the change in the morphology and composition of the crystalline phases of the coatings is the induction and enhancement of the plasma discharge by laser-assisted irradiation. The photoelectrochemical behavior of the samples was evaluated by employing linear sweep voltammetry under continuous UV irradiation, and the photoresponse current density was measured under intermittent UV irradiation. The laser-assisted PEO coatings prepared with 80 W laser energy under laser-assisted irradiation exhibited the most favorable photoelectrochemical activity. Furthermore, further analysis showed that the enhanced photoelectrochemical activity of the photoactive titanium dioxide coatings was essentially due to a larger specific surface area, lower impedance, higher wettability, and a more suitable crystalline phase ratio.

Utilization of investment casting shell waste in the production of cordierite-mullite-zircon composites for radiation shielding: The influence of La2O3 additive

Cordierite-mullite-zircon ceramic composites were produced via reaction sintering of investment casting shell waste, Al2O3, and MgO at 1350 °C. The influence of La2O3 addition on the crystalline phase composition, microstructure, densification behavior, mechanical strength, and radiation shielding capabilities of the cordierite-mullite-zircon composites has been investigated. The X-ray diffraction (XRD) analysis confirmed the successful synthesis of cordierite-mullite-zircon composites with up to 5 wt% La2O3 additive content. However, a higher La2O3 content, exceeding 7 wt% resulted in cordierite decomposition. Furthermore, the addition of La2O3 significantly enhanced the densification behavior and microstructural development, leading to improved flexural strength and enhanced shielding against fast neutron and gamma radiation. This research suggests the potential of the fabricated ceramic composites derived from investment casting shell waste for applications in radiation shielding.

Zn Doping Improves the Anticancer Efficacy of SnO2 Nanoparticles

Tin dioxide (SnO2) nanoparticles (NPs) can be applied in several ways due to their low cost, high surface-to-volume ratio, facile synthesis, and chemical stability. There is limited research on the biomedical application of SnO2-based nanostructures. This study aimed to investigate the role of Zn doping in relation to the anticancer potential of SnO2 NPs and to enhance the anticancer potential of SnO2 NPs through Z doping. Pure SnO2 and Zn-doped SnO2 NPs (1% and 5%) were prepared using a modified sol–gel route. XRD, TEM, SEM, EDX, UV-Vis, FTIR, and PL techniques were used to characterize the physicochemical properties of produced NPs. XRD analysis revealed that the crystalline size and phase composition of pure SnO2 increased after the addition of Zn. The spherical shape and homogenous distribution of these NPs were confirmed using TEM and SEM techniques. EDX analysis confirmed the Sn, Zn, and O elements in Zn-SnO2 NPs without impurities. Zn doping decreased the band gap energy of SnO2 NPs. The PL study indicated a reduction in the recombination rate of charges (electrons/holes) in SnO2 NPs after Zn doping. In vitro studies showed that the anticancer efficacy of SnO2 NPs increased with increasing levels of Zn doping in breast cancer MCF-7 cells. Moreover, pure and Zn-doped SnO2 NPs showed good cytocompatibility in HUVECs. This study emphasizes the need for additional investigation into the anticancer properties of Zn-SnO2 nanoparticles in various cancer cell lines and appropriate animal models.

Characteristic microstructural phase evolution and the compressive strength development mechanisms of tricalcium silicate pastes under various initial carbonation curing environments

The effects of various initial carbonation curing environments on the phase evolution and resulting mechanical characteristics of tricalcium silicate paste were studied. For the analyses of the reaction products and microstructure, synchrotron X-ray diffraction, thermogravimetry, Fourier transform-infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy and high-resolution X-ray computed tomography were utilized. C3S cured under carbonation environment pressurized by 0.1 MPa showed excellent mechanical properties owing to the highest degree of reaction and homogeneous generation of CaCO3 with low-Ca/Si calcium silicate hydrates, resulting in a dense matrix with refined pore structure. C3S paste treated under other carbonation conditions underwent deteriorative microstructural phase transitions, including void evolution by decalcification of C–S–H and an inhomogeneous composition of crystalline phases, resulting in inferior properties.

A correlative experimental and theoretical investigation of phase formation and thermal stability of a quaternary Cr0.69Ta0.20B0.11N coating

In recent years, CrTa(B)N coatings deposited by physical vapor deposition have gained increasing interest due to their high hardness and good wear resistance. However, a detailed investigation of the microstructure of quaternary CrTaBN coatings both at ambient conditions and at elevated temperature is lacking in literature. Therefore, the present study provides an overview of the temperature-dependent phase formation and microstructure of a Cr0.69Ta0.20B0.11N coating grown by cathodic arc deposition. The face-centered cubic Cr1-x-yTaxByN solid solution was found to be the only crystalline phase present in the as-deposited coating, with the B atoms exclusively forming B-N bonds. Both, atom probe tomography and transmission electron microscopy suggest that the B concentration is increased at the grain boundaries compared to within the grain. Annealing CrTaBN at 1000 °C provokes no change in the crystalline phase composition, but results in a reduction of the B content due to the formation of volatile B-containing compounds. In addition, B-metal bonds form upon annealing as a consequence of the CrN→Cr2N+N decomposition. The here reported formation of B-N bonds in the as-deposited state and the annealing induced formation of B-metal bonds are consistent with density functional theory calculations of relaxed corresponding configurations as the energy differences between them are minute. The obtained findings provide a detailed insight into the phase formation of the given complex material system.

Hydrogen Production via Methanol Steam Reforming over CuO/ZnO/Al2O3 Catalysts Prepared via Oxalate-Precursor Synthesis

CuO/ZnO/Al2O3 catalysts are commonly used for the methanol steam reforming reaction. The oxalate precursor of CuO/ZnO/Al2O3 catalysts were prepared via the co-precipitation method using oxalic acid as the precipitator, deionized water and ethanol as the solvent, and microwave radiation and water baths as aging heating methods, respectively. This suggests that ethanol selects the crystalline phase composition of oxalate precursors and limits their growth. Microwave irradiation prompted the isomorphous substitution between Cu2+ of CuC2O4 and Zn2+ of ZnC2O4 in the mother liquid; Zn2+ in ZnC2O4·xH2O was substituted with Cu2+ in CuC2O4, forming the master phase (Cu,Zn)C2O4 in the precursor. Moreover, the solid solution Cu-O-Zn formed after calcination, which exhibited nano-fibriform morphology. It has the characteristics of small CuO grains, a large surface area, and strong synergistic effects between CuO and ZnO, which is conducive to improving the catalytic performance of methanol steam reforming. The conversion rate of methanol reached 91.2%, the space time yield of H2 reached 516.7 mL·g−1·h−1, and the selectivity of CO was only 0.29%.

Synthesis and in situ oxidation of copper micro- and nanoparticles by arc discharge plasma in liquid

This work presents a one-step controlled method for the synthesis of copper oxide nanoparticles using an arc discharge in deionized water without subsequent thermal annealing. The synthesis conditions were varied by changing the arc discharge current from 2 to 4 A. Scanning electron microscopy images of samples synthesized at discharge current of 2 A revealed the formation of tenorite (CuO) nanopetals with an average length of 550 nm and a width of 100 nm, which had a large surface area. Arc discharge synthesis at 3 and 4 A current modes provides the formation of a combination of CuO nanopetals with spherical cuprite (Cu2O) nanoparticles with sizes ranging from 30 to 80 nm. The crystalline phase and elemental composition of the synthesized particles were identified by X-ray diffraction analysis, Raman spectroscopy and Energy dispersive analysis. As the arc discharge current was raised from 2 to 4 A, two notable changes occurred in the synthesized particles: the Cu/O ratio increased, and the particle sizes decreased. At 4 A, the synthesized particles were from 30 to 80 nm in size and had a spherical shape, indicating an increase in the amount of cuprite (Cu2O) phase. The optical band gap of the aqueous solutions of copper oxide particles also increased from 2 to 2.34 eV with increasing synthesis current from 2 to 4 A, respectively. This suggests that the proposed synthesis method can be used to tune the band gap of the final material by controlling the Cu/O ratio through the current of arc discharge. Overall, this work demonstrates a novel approach to the synthesis of copper oxide nanoparticles with controllable CuO/Cu2O/Cu ratios, which has the potential to be useful in a variety of applications, particularly due to the significant enhancement of photocatalytic abilities and widen the working spectral range.

Electroconductive silicon nitride-titanium nitride ceramic substrates for CVD diamond electrode deposition

The present investigation was carried out to develop dense ceramics of silicon nitride-titanium nitride (Si3N4–TiN) with low electrical resistivity and excellent mechanical properties. The objective was to employ these ceramics as substrates of conductive diamond electrodes produced by chemical vapor deposition (CVD) for electrochemical applications. TiN powder was added to a Si3N4 matrix powder composition at varying volume fractions (21–30%). Disc-shaped samples were fabricated by mixing and pressing the powders, followed by pressureless sintering. The crystalline phase composition and microstructure were analyzed using X-ray diffraction and scanning electron microscopy, while the electrical resistivity was measured with a four-point probe configuration. The composites transitioned from insulating to conductive behavior between 23 and 27%vol TiN. The developed compositions displayed superior hardness, fracture toughness, elastic modulus, and thermal conductivity compared to the Si3N4 matrix. Notably, the composition containing 30%vol TiN displayed noteworthy properties, including a hardness value of 16.1 GPa, fracture toughness of 7.0 MPa m1/2, and electrical resistivity of 8.9 × 10−1 Ω cm. Finally, the proof-of-concept experiment demonstrated the potential of Si3N4–TiN composites as robust and electroconductive substrates for depositing conductive diamond electrodes. This was achieved by successfully depositing conductive diamond films on Si3N4–TiN substrates using the Hot Filament Chemical Vapor Deposition (HFCVD) technique.

Crystalline and amorphous microstructure evolution of Zr-Cu-Al ternary alloys solidified in drop tube

High undercooling rapid solidification process has a significant impact on the solidified microstructure and mechanical properties of materials. In this study, particles with a diameter range between 100 and 1100 µm of ternary Zr50Cu40Al10 and Zr49Cu46Al5 alloys were prepared by a drop tube. The evolution process of particle-solidified microstructure with decreasing particle diameter was analyzed using XRD, SEM, and TEM. For Zr50Cu40Al10 alloy, the solidified microstructure in the particle diameter ranges of 200–1100 µm is composed of an amorphous phase and a primary B2-ZrCu high-temperature metastable phase. As the particle diameter reduces, the retained crystalline phase in the solidified microstructure decreases progressively, and the dendrite grain length gradually becomes finer. When the particle diameter is reduced to below 200 µm, the crystalline phase has completely disappeared, and the solidified microstructure evolves into a completely amorphous structure. For Zr49Cu46Al5 alloy, in the particle diameter range of 400–1100 µm, the solidified microstructure consists of primary B19'-ZrCu phase, a small amount of Cu10Zr7 phase and Zr14Cu51 phase. As the particle diameter reduces, a grain refinement phenomenon also occurs in the solidified microstructure and the dendritic morphology changes from equiaxed grain to rod-shaped dendrite. The amorphous phase appears when the particle diameter is lowered to 470 µm and solidified microstructure evolves into a completely amorphous structure as the particle diameter is reduced to 146 µm. The nanoindentation results show that the micromechanical properties of amorphous composite microstructures are superior to the single component composition of crystalline or amorphous phase for Zr50Cu40Al10 and Zr49Cu46Al5 alloys. The reinforcement effect on the amorphous phase is related to the content of the second crystalline phase. Moreover, under similar particle diameters, the mechanical properties of Zr50Cu40Al10 particles are always better than those of Zr49Cu46Al5 particles.

Phase-Engineering of Layered Nickel Hydroxide for Synthesizing High-Quality NiOx Nanocrystals for Efficient Inverted Flexible Perovskite Solar Cells.

Nickel oxide (NiOx) nanocrystals have been widely used in inverted (p-i-n) flexible perovskite solar cells (fPSCs) due to their remarkable advantages of low cost and outstanding stability. However, anion and cation impurities such as NO3- widely exist in the NiOx nanocrystals obtained from calcinated nickel hydroxide (Ni(OH)2). The impurities impair the photovoltaic performance of fPSCs. In this work, we report a facile but effective way to reduce the impurities within the NiOx nanocrystals by regulating the Ni(OH)2 crystal phase. We add different alkalis, such as organic ammonium hydroxide and alkali metal hydroxides, to nickel nitrate solutions to precipitate layered Ni(OH)2 with different crystalline phase compositions (α and β mixtures). Especially, Ni(OH)2 with a high β-phase content (such as from KOH) has a narrower crystal plane spacing, resulting in fewer residual impurity ions. Thus, the NiOx nanocrystals, by calcinating the Ni(OH)x with excess β phase from KOH, show improved performance in inverted fPSCs. A champion power conversion efficiency (PCE) of 20.42% has been achieved, which is among the state-of-art inverted fPSCs based on the NiOx hole transport material. Moreover, the reduced impurities are beneficial for enhancing the fPSCs' stability. This work provides an essential but facile strategy for developing high-performance inverted fPSCs.

Ultrasensitive ethanol sensor based on Ce-modified SnO2 nanoflowers at low temperature

The improvement of ethanol gas-sensitive properties of SnO2 gas sensors is significant for the practical applications. The structures of pure SnO2 and Ce-modified SnO2 nanoflowers with different Ce contents (1 at%, 3 at% and 5 at%) were successfully prepared by a facile and environment friendly hydrothermal method with catalysis by CTAB and calcination in the air. The crystalline phase, morphology and chemical composition of the obtained SnO2 nanomaterials were analyzed, indicating that all four materials are flower-like structures assembled by nanosheets. The gas sensing behaviors of the fabricated sensors were systematically investigated. The results showed that Ce doping can significantly improve the sensing performance of the SnO2 gas sensors. The sensor based on 5 at% Ce-SnO2 nanoflowers exhibited not only high response (55), quick response/recovery time (7 s/9 s), excellent selectivity, but also long-time stability for 200 ppm ethanol at a lower operating temperature (125 °C). Furthermore, the gas sensing mechanism was also discussed in detail.

Optimizing fluidity and tensile strength of magnetically driven epoxy-cement repair materials based on response surface

Underwater crack repair is challenging due to drainage and exhaust, slurry retention at fixed points, and other issues. Magnetically driven epoxy resin cement slurry was developed, which can perform directional movement and fixed-point retention of slurry under the effect of an applied magnetic field. This paper focuses on slurry fluidity and tensile properties. Firstly, in the preliminary pre-study, the main influencing factors of the ratios were determined. Then, the optimum range of each factor is determined by a single-factor experiment. Furthermore, the response surface method (RSM) is applied to obtain an optimal ratio. Finally, the slurry is characterized by micro. Results showed that the evaluation index F proposed in this paper can well evaluate the interaction between fluidity (X) and tensile strength (Y). The 2FI regression model and the quadratic regression model are developed with fluidity and tensile strength as the response values and Epoxy Resin (ER) content, water-cement ratio, Fe3O4 content and sulphoaluminate cement (SAC) content as the influencing factors, and have reasonable fit and reliability. The relationship between the degree of influence of the influencing factors on the response value X and the response value Y in ascending order was: ER content > water-cement ratio > SAC content > Fe3O4 content. The magnetically driven slurry made by the optimal ratio can reach a fluidity rate of 223.31 mm and a tensile strength of 2.47 MPa. This is with relative errors of 0.36% and 1.65% from the model predicted values. Microscopic analysis showed that the magnetically driven epoxy resin cement slurry had a favorable crystalline phase, surface morphology, and structural composition.

TiO2 aerogel composite high-efficiency photocatalysts for environmental treatment and hydrogen energy production

Abstract Photocatalysis is a new type of renewable energy technology used in environmental treatment and hydrogen energy production. In this regard, a new class of photocatalysts, TiO2 aerogels, are attractive for having the chemical characteristics of TiO2 nanomaterials such as high catalytic activity, good stability, non-toxic, and non-polluting, and the structural characteristics of aerogels such as large specific surface area, high porosity, the 3-dimensional interconnected network structure composed of relatively uniform nanoparticles, and high light transmittance. Here we review the recent progress in TiO2 aerogels for photocatalysis, focusing on preparation techniques, the crystalline phases’ influence on photocatalytic properties, the modification of photocatalytic properties, and the analysis and discussion of future development. In particular, we first summarize various preparation techniques, including sol–gel method, nanoparticles self-assembly synthesis, and high-temperature aerosol technique, then detail the structure and composition of TiO2 crystalline phases that affect the photocatalytic properties. Subsequently, we discuss strategies to further enhance the photocatalytic properties of TiO2 aerogels by the composite of SiO2 aerogel semiconductors, the doping of metal dopants, and the doping or composite of non-metallic substances, and elaborate the modification mechanism and the modification effect achieved. Finally, combined with the research status of TiO2 aerogels and the development experience of other aerogels, we conduct a reasonable analysis and discussion on their further research directions and industrialization roads.