Small Crystal Grains Research Articles

Luminescence, XPS and Raman of crystalline quartz affected to high pressure by detonation

The Raman spectra, x-ray photoelectron spectroscopy (XPS), and x-ray excited luminescence spectra of crystalline quartz samples subjected to different pressure levels through detonation were compared with the spectra of the original samples. In the samples under study, the luminescence of a self-trapped exciton (STE) was analyzed, which, when excited by x-rays, has a high energy yield (∼20%) in crystalline α-quartz not treated by detonation. The deviations of the luminescence spectrum are small in the pressure range from 9 to 27 GPa relative to untreated samples, which means the presence of crystalline quartz grains. A sharp change in the spectrum occurs for the sample subjected to a pressure of 34 GPa. The STE band practically disappeared and a band appeared at 350 nm. This band appears in thermally stimulated luminescence (in contrast to the STE band, which is not observed at all in thermally stimulated luminescence) and, therefore, can be attributed to some defects arising due to high pressure. This luminescence is not similar to the luminescence of a stishovite single crystal, but analysis of the XPS spectra suggests the formation of non-crystalline stishovite in detonated samples. In the Raman scattering spectra, a single sharp line at 465 cm−1, characteristic of α-quartz, was observed in the samples after detonation pressure for the remaining small crystal grains. This line decreased greatly for the sample subjected to a pressure of 34 GPa. Against the structureless background of exposed samples of ‘poor’ optical quality, other Raman bands did not appear. It can be assumed that there are very broad bands of Raman scattering caused by the amorphization of stishovite under high detonation pressure. Amorphization explains the absence of luminescence, similar to the stishovite crystal.

Influence of liquid properties of colloidal crystals to thermal stability of colloidal crystals on different substrate surfaces through heterogeneous nucleation

The effects of liquid properties, such as pH and conductivity, on the thermal stability of electrostatically interacting colloidal silica crystals generated from heterogeneous nuclei were investigated mainly by measuring relative reflection spectra. The melting behavior of the colloidal crystals was also investigated. The melting points of both negatively and positively charged 3-aminopropyltriethoxysilane (APS)-treated substrates with different surface charges increased or decreased with increasing or decreasing pH. For both substrates, pH 5.5 was the modulation point of the crystal melting, and the melting point increased with increasing pH. For the negatively charged substrate, the melting point increased slowly as the pH decreased from pH 5.5. Meanwhile, the melting point of the APS-treated substrate increased more with decreasing pH from 5.5 than that of the negatively charged substrate. The cationisation of the substrate increased with decreasing pH, resulting in stronger electrostatic interactions with the negatively charged colloidal crystals and enhanced thermal stability. Next, we investigated the size of colloidal crystal grains in sample bottles for different liquid properties, and the results show that at the higher pH, the smaller crystal grains, indicating that pH affects both the substrates and crystals. Moreover, the binding effect of the APS-treated substrate on the crystals became stronger at lower pH, thereby enhancing the thermal stability of the crystals.Graphical

Suppressing the Photoinduced Halide Segregation in Wide‐Bandgap Perovskite Solar Cells by Strain Relaxation

AbstractEfficient and stable wide bandgap (WBG) perovskite solar cells (PSCs) are imperative for fabricating superior tandem devices. However, small crystal grains and light‐induced phase segregation of WBG perovskite result in large open‐circuit voltage (VOC) deficits, critically impeding the development of the related devices. Herein, the effective functional groups of Lewis‐base trans‐Ferulic acid (t‐FA) are employed to release the residual microstrain in the perovskite lattice. Larger perovskite crystals are formed by strengthening the interaction between the perovskite solute and solution. The lattice structure is stabilized to suppress light‐induced halide segregation. Finally, the power conversion efficiency (PCE) of the optimized device with a bandgap of ≈1.77 eV is increased from 17.33% to 19.31% with the enhancement of VOC. Moreover, replacing a mixture of MeO‐2PACZ and Me‐4PACZ as the hole transporting layer (HTL), the PCE further lifts to 19.9% and VOC is 1.32 V, one of the highest performances reported for WBG PSCs, especially for devices prepared entirely by solution spin‐coating. Therefore, this study provides a practicable alternative for realizing efficient WBG PSCs, which can contribute to the growth of perovskite‐based tandem devices.

Energy-efficient electrochemical degradation of ciprofloxacin by a Ti-foam/PbO2-GN composite electrode: Electrode characteristics, parameter optimization, and reaction mechanism

Reducing energy comsuption is crucial to commercialize electrochemical oxidation technologies. In this study, a novel PbO2 composite electrode (Ti-foam/PbO2-GN) was successfully fabricated based on a porous titanium (Ti) foam substrate and a β-PbO2 active layer embedded with multiple graphene (GN) interlayers, and applied as an anode for energy-efficient pulse electrochemical oxidation of ciprofloxacin (CIP). In contrast to PbO2 and Ti-foam/PbO2 electrodes, the Ti-foam/PbO2-GN electrode surface exhibited a more compact structure, smaller crystal grain size, and greater electrochemical active surface area. CIP removal of 89.7% was obtained with a low energy consumption (EE/O) of 6.17 kWh m−3 under pulse electrolysis conditions with a current density of 25.00 mA cm−2, pulse frequency of 5000 Hz, and pulse duty cycle of 50.0%. Up to 70.7% of the energy was saved in the pulse current mode compared to the direct current mode. Narrowing the electrode spacing to 2 cm facilitated the mass transfer process and enhanced oxidation efficiency. According to the intermediates identified, the pulse electrolysis of CIP primarily involved hydroxylation of the quinolone ring, breaking of the piperazine ring, defluorination, and decarboxylation processes, and a possible degradation mechanism of CIP was proposed. The continuous oxidation performance of CIP and the relatively low leaching of Pb2+ suggested that the Ti-foam/PbO2-GN electrode exhibited excellent stability, repeatability, and safety. The degradation results of CIP in real water also exhibits the great potential of environmental application. As a result, pulse electrochemical oxidation using a Ti-foam/PbO2-GN electrode has proven to be an energy-efficient and promising alternative for antibiotic wastewater treatment.

The influence of different complexing agents on the properties of tin dioxide (SnO2) deposited thin films through chemical bath approach

The present study explores the effect of disodium ethylenediamine tetraacetic acid and triethanolamine as alternative complexing agents to synthesize SnO2 thin films by employing simplistic chemical bath deposition method. The as-deposited tin dioxide thin films have been characterized by various analytical techniques particularly X-rays diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive x-ray analysis (EDX), and Raman spectroscopy. The XRD and Raman spectroscopy reveal the crystalline nature pertaining small crystal grains of the as-deposited SnO2 thin films with a tetragonal rutile structure. The SEM analysis unfolds that as-synthesized thin films using disodium ethylenediamine tetraacetic acid and triethanolamine, the grains of the films exhibit different shapes. The bandgap energies of the films have been estimated from the absorbance spectra through Tauc plot and the respective optical band gap of SnO2-EDTA and SnO2 -TEA exhibits the values as ∼4.2 eV and ∼3.8 eV, respectively. These findings suggest as-deposited tin dioxide thin films to be pertinent for use in solar radiation absorption applications.

Spray-coated nanocrystalline CsPbBr3 perovskite thin-films for large area and efficient rigid and flexible light emitting diodes

Large area and efficient CsPbBr 3 perovskite light emitting diodes (PeLEDs) were demonstrated by readily commercializable spray-coating method. The PeLEDs with controlled crystal grain size exhibited maximum electroluminescence peak position of ~534 nm, emission spectrum of ~18 nm of full width at half maximum, maximum luminance of 20388 cd/m 2 , maximum current efficiency of 51.0 cd/A, and maximum external quantum efficiency of 11.19%. The large area glass substrate-based rigid PeLED and polymer substrate-based flexible PeLED were also successfully demonstrated. In addition, the PeLEDs with controlled crystal grain size could generate electric power in a daytime like solar cells, which gained power conversion efficiency of 0.43–1.03% at 1 sun condition (AM 1.5 G 100 mW/cm 2 ). • Nanocrystalline CsPbBr 3 perovskite uniform thin-film is prepared by spray-coating. • The smaller crystal grain size is obtained by optimizing the solvent composition. • Large-area and flexible PeLEDs are fabricated by a scaleable spray-coating process. • The PeLEDs can be used as power generator in day time and as display in night time.

Semiflow Microwave Heating Reactor with Resonator Moving Mechanism Applied to Zeolite Synthesis.

A semiflow microwave (MW) heating reactor similar to a flow reactor system was developed. Slurry raw materials in the reaction tube were heated continuously and cooled rapidly by moving a thin MW resonator instead of flowing slurry raw materials. From highly viscous mother slurries, Linde-type A (LTA) and faujasite (FAU)-type zeolite nanoparticles of small crystal grains were synthesized quickly. Results show that this heating system can synthesize hydroxy-sodalite (SOD)-type zeolite from coal fly ash particles including those larger than 50 μm. Numerical calculations using the COMSOL Multiphysics program revealed the thermal distribution of liquids of various viscosities using the semiflow MW heating reactor.

Microrecycled Co3O4 from waste lithium-ion battery: Synthesis, characterisation and implication in environmental application

Microrecycling based techniques are developed to synthesise phase pure porous Co3O4 using thermal isolation and controlled recycling pathways to achieve environmental outcomes that could manufacture and recycle hazardous spent Lithium-ion batteries (LIBs). The existing synthesising strategies for high surface area and small crystal grains of Co3O4 rely on raw materials, complex chemicals and experimental conditions. Herein the proposed facile technique produces Co3O4 with nanosized crystal grains and a large specific surface area of 79.2 m2 g−1 by utilising the cathode and anode material (CAM) of spent LIBs. The controllable synthesis of the Co3O4 also offers value added co-product of Lithium in the form of Li2CO3. Further utilisation of synthesised Co3O4 as a catalyst for toxic dye degradation offers an excellent opportunity to deliver benefits for society by creating a resource from waste that could treat other waste in our environment.

Crystal growth and fluorescence of downconversion films in confined space with ingoing channels

Ultraviolet (UV) imaging technology plays an essential role in deep space exploration, fingerprint imaging, aerospace and other fields. To overcome the shortcomings of current detection technology arising from the limited detection band and low quantum efficiency, we propose to combine UV-responsive fluorescent film with visible light imaging technology to realize the UV imaging process through light conversion. The present work focuses on the preparation of UV-responsive light conversion thin films and their properties. A hydrothermally assisted in situ growth method is utilized to prepare downconversion (DC) NaYF4 thin films. The effects of reaction time on fluorescence and morphologies are investigated, followed by the creation of ingoing channels to achieve uniform light emission. The results show that the reflection fluorescence is enhanced by increasing reaction time from 8 to 24 h while fluorescence uniformity decreases, i.e., different locations on the DC films presented significant fluctuation in fluorescence intensity and morphologies. The reason is that sufficient time is allowed for crystal growth and Ostwald-ripening, which increases fluorescence intensity but resulting in various crystal structures. The use of 4 × 4 to 12 × 12 ingoing channels increases precursor concentrations in confined space, achieving uniform fluorescence. However, the crystal nucleation stage dominated by high precursor concentrations plays a crucial role in generation of small crystal grains, which reduces fluorescence intensity. Our work is beneficial for further optimization of reaction conditions for obtaining large-scale DC films with uniform and high fluorescence.

The stability of poly (3, 4-ethylenedioxythiophene) based on electrochemical polymerization and photoelectro-corrosion conditions

The stability of poly (3, 4-ethylenedioxythiophene) (PEDOT) was studied based on the photoelectro-corrosion. The type of electrolyte can affect morphology, crystallinity, crystal grain size, and hydrophilicity of PEDOT. The polymerization time was shortened and the crystal grain size of PEDOT was increased, and the corresponding PEDOT dissolution was increased under photoelectro-corrosion, along with the order of in the electrolyte containing Cl−, SO42−, PO43−, and ClO4−. The improved stability was attributed to increased crystallinity, small crystal grain size, and decreased hydrophilicity of PEDOT. The peroxidation of PEDOT caused partial deformation and more dissolution. The increase of applied potential and photoelectro-corrosion temperature led to the increase of PEDOT dissolution. Twenty kinds of dissolution products were detected under photoelectro-corrosion of PEDOT. Some dissolution products with corresponding m/z of 262, 284, 325, 561, 645, 704, and 713 were found to have some toxicology concerns. This means it is important to consider such degradation products in terms of their generation, potential release, and possible biological contact.

Identifying microstructural changes responsible for retarded grain growth during tungsten recrystallization after helium plasma exposure

Helium plasma is known to affect recrystallization in tungsten , with lower temperatures during plasma exposure leading to slower crystal grain growth. To understand why this occurs, tungsten samples were first exposed to helium plasma at surface temperatures between 300°C and 800°C, before annealing at temperatures between 1100°C and 1400°C. Annealing after helium exposure at 300°C was confirmed to lead to smaller crystal grains than annealing after exposure to helium at 500°C. Small 1-2 nm radius nanobubbles formed readily in tungsten after helium plasma exposure, but disappear after annealing at temperatures of 1100°C and above. The formation of cracks and open volumes beneath the surface was observed exclusively in tungsten exposed to helium-plasma at 300°C, with extensive surface cracks visible after annealing. These cracks were not observed for higher temperature helium exposure and likely form due to the strong tendency of bubbles to cluster along grain boundaries for helium exposure at 300°C. Despite this, nano-mechanical testing revealed a similar influence of annealing conditions on tungsten hardness for all plasma exposure conditions studied. The crack formation is likely caused by interactions between solute helium and residual defects from surface polishing.

Evaluating the Protective Effects of Calcium Carbonate Coating on Sandstone Cultural Heritage

The purpose of this work was to use different surfactants to deposit different crystalline calcium carbonate films on the surface of sandstone through a simple double displacement reaction. This was done to test the protective effects of calcium carbonate coatings based on water absorption, moisture permeability and weather resistance. Experimental results showed that the air permeability of the stone treated with vaterite calcium carbonate was reduced, but that this did not affect water vapor’s access into and out of the stone. Compared with untreated stone, the water absorption rate was reduced 0.5 times, and the weather resistance increased by 4 times due to small crystal grains, high solubility, and deep penetration hindering the erosion of water and soluble salts. These findings are expected to provide useful suggestions for the protection of stone cultural heritage.

Catalytic ozonation of thymol with a novel CoCe-MMO catalyst: Kinetics and mechanism

In this study, a novel ozonation catalyst CoCe mixed metal oxide (CoCe-MMO) was prepared for the degradation of organic wastewater containing thymol. The results showed that the addition of CoCe-MMO could effectively enhance the effect of thymol degradation, and the thymol could be completely removed after 40 min of reaction. The reaction kinetics was calculated. It accords with the quasi-first order reaction kinetics, and the reaction rate constant is about 0.1357 min −1 . The enhancement mechanism was discussed and the CoCe-MMO could react with ozone to produce strong oxidizing free radicals-hydroxyl radicals (•OH). The catalyst was characterized by XRD, SEM, and XPS. The results showed that the catalyst continued the lamellar laminated structure of its precursor, and present a higher crystallinity and smaller crystal grain size (about 58-70 nm), which would promote the production of •OH. The •OH and O 3 could attack the ortho-position of thymol for peacekeeping, making it gradually converted into small molecule acids, and finally completely degraded into CO 2 and H 2 O. The stability and reusability of the catalyst were also studied and the CoCe-MMO catalyst could maintain high activity after three cycles. And the metal ion leaching rates of Co and Ce are 0.39 mg/L and 0.03 mg/L respectively, which is lower than the emission standard. This paper showed that the catalyst has good application prospect and could provide technical support for pharmaceutical wastewater pollution control with catalytic ozonation.

A comparative investigation of gelatinized and regenerated starch composites reinforced by microfibrillated cellulose

This research demonstrated a novel and ecofriendly method for producing regenerated starch (RS)/microfibrillated cellulose (MFC) composite films with a nearly 1.4-fold improvement in tensile strength than traditional gelatinized starch (GS) films. Pure starch was dissolved in 14 wt% urea/4 wt% sodium hydroxide (NaOH) solution at 0 °C. Then, RS films and their biocomposite films containing MFC were prepared by dialyzing and solution-casting method. Results showed that the tensile strength and elongation at break of RS increased by 44.8% and 82.4%, compared with that of GS film, respectively. Owing to the adequate dispersion, lower viscosity-average molecular weight, higher amylose content, lower crystallinity and smaller crystal grain size, RS/MFC composite films exhibited significantly improved mechanical properties. The novel strategy used in this study will be helpful in preparing regenerated starch materials with excellent mechanical properties and biodegradability as alternatives to petrochemical plastics for the development of sustainable materials.

Ruthenium doped Ge2Sb2Te5 nanomaterial as fast speed phase-change materials with good thermal stability

Ge2Sb2Te5 (GST) as phase-change material has the advantage of good thermal stability and long cycle life, however large power consumption and lower phase change speed partly limit large-scale application for phase-change materials (PCM). In this paper, a comprehensive research is investigated on Ru doped GST phase-change material, from properties to performances for PCM application. Ru doping can efficiently improve the thermal stability of GST alloy and the thickness change of Ru0.05(GST)0.95 film is 3.3%. In addition, high 10-year data retention temperature (∼151 °C) and small crystal grain reflect the advantages of data retention and low power consumption for Ru0.05(GST)0.95 film. Furthermore, the structure characteristics show the stable face-centred cubic structure at crystalline state after annealing. As for electrical properties, Ru0.05(GST)0.95-based PCM cell shows excellent reversible SET-RESET properties with a suitable operation window and good endurance up to 106 electrical cycles with a resistance ratio of about 10. And also, it has a dramatically lower power consumption of 1.46 × 10-11 J compared with GST-based cell (4.76 × 10-10 J), making it a promising material for the Internet of Things (IOT) field applications.

Preparation of Li2CO3 powder nanoparticles by vacuum freeze drying

Decreasing the particle size of Li2CO3 powder is beneficial for advancing its applications in the manufacturing of different materials and drug delivery. Therefore, in this study, a novel bottom-up process based on freezing is proposed for the production of nanoparticles. Herein, two methods of explosive nucleation were used: addition of an anti-solvent and rapid freezing. Explosive nucleation of Li2CO3 occurred during the initial stage of anti-solvent addition; in contrast, in the freezing method, it occurred at a stage when the solute, which had not migrated, was extruded to the solid–liquid interface. Li2CO3 concentration had an effect on both the crystal grain and particle size. The controlled preparation of Li2CO3 nanoparticles was achieved within a certain range of A/B ratio; when the ratio decreased from 10/0 to 10/20 v/v, the controlled synthesis of Li2CO3 nanoparticles was achieved. A lower concentration of Li2CO3 decreased the size of the crystal grain and increased the size of the particles, as observed via transmission electron microscopy and dynamic light scattering. When the A/B ratio (where A is saturated Li2CO3 solution and B is deionised water) was decreased below 10/20 v/v, the crystal grain size of Li2CO3 did not reduce significantly. To further understand the nucleation, freezing was carried out at two temperatures, i.e. 223 ± 2 K and 267 ± 2 K. The lower freezing temperature resulted in a smaller crystal grain size and more concentrated distribution.

Grain size influence on the flexibility and luminous intensity of inorganic CaTiO3:Pr3+ crystal nanofibers

Traditional inorganic materials exhibit rigidity owing to the lack of polymer chains in polymer materials or atom slipping in metals. However, nanometerization has been recently proposed for the conversion of inorganic oxide materials into flexible materials. Herein, the flexible inorganic luminescent material, CaTiO3:0.2%Pr3+, was synthesized through electrospinning, and the macroscopic flexibility of pure inorganic CaTiO3:0.2%Pr3+ was achieved. The flexible membrane was characterized via X-ray diffraction, thermogravimetry, scanning electron microscopy (SEM), and photoluminescence analyses. The grain size was analyzed at various calcination temperatures via SEM, and the results suggested that the increase in the calcination temperature resulted in the growth of crystal grains. Studies have reported that the growth of crystal grains is beneficial for improving the luminescence performance; however, to obtain better flexibility, smaller crystal grains are required. This study provides an important reference for the design of flexible inorganic materials.

Enhancing the Phase Stability of Formamidinium Lead Triiodide by Addition of Calcium Chloride

Formamidinium lead triiodide (FAPbI3) with stable black perovskite phase and without significantly changing its bandgap is demonstrated by the incorporation of CaCl2. More incorporated CaCl2 in FAPbI3 creates a desirable crystal structure, satisfying the Goldschmidt tolerance factor, and thereby stabilizing black perovskite phase under ambient conditions. However, more incorporated CaCl2 in FAPbI3 is likely to degrade the perovskite due to its hygroscopic characteristics. In addition, the incorporated CaCl2 in FAPbI3 solution reduces solubility, causing the formation of smaller crystal grains and pinholes due to quick precipitation during the non-solvent dripping crystallization process. Accordingly, 5 % CaCl2 incorporated FAPbI3 films have the best phase stability and solar cell performance with 18.0 % of power conversion efficiency at 1 sun condition.

Correction to: Structural and optical analysis of Ag nanoparticle-assisted and vertically aligned TiO2 nanowires for potential DSSCs application

In this work, vertically aligned TiO2 nanowires (TiO2-NWs) and Ag nanoparticle (Ag-NP)-assisted and vertically aligned TiO2 nanowires (TAT-NWs) were deposited on glass and flexible polyethylene terephthalate (PET) substrates using the glancing angle deposition (GLAD) technique. The morphology and structural analysis of the samples manifest successful deposition of vertically aligned TiO2-NWs and TAT-NWs. The high-resolution transmission electron microscopy (HR-TEM) image of TiO2-NWs shows the polycrystalline nature. Further, the X-ray diffraction (XRD) result confirms the polycrystalline nature of both the TiO2-NW and TAT-NW samples. Besides, HR-TEM image confirms the presence of small crystal grains of Ag-NPs at the mid of the annealed TAT-NWs. It is evident from the selected area electron diffraction (SAED) analysis of TiO2-NWs and annealed TAT-NWs that the crystallinity of TiO2 present in the annealed TAT-NWs improves after annealing. The absorption spectrum analysis of TAT-NWs deposited on glass substrate shows enhances absorption peak in the visible region with a maximum peak at ~ 450 nm wavelength compared to the TiO2-NWs, which may be attributed to the surface plasmon resonance (SPR) effect of Ag-NPs. Further, it is interesting to observe that the TAT-NWs deposited on PET substrate show further absorption enhancement in the UV and visible regions. In addition, the photoluminescence (PL) analysis reveals that the band gap of TiO2-NWs is ~ 3.12 eV. Therefore, the proposed method of fabricating TAT-NWs on glass and flexible ITO-coated PET substrates using the GLAD technique may be applicable for developing novel photoanode for dye-sensitized solar cells (DSSCs) and other optoelectronic applications.

Highly Efficient Electro‐reforming of 5‐Hydroxymethylfurfural on Vertically Oriented Nickel Nanosheet/Carbon Hybrid Catalysts: Structure–Function Relationships

AbstractNi‐promoted electrocatalytic biomass reforming has shown promising prospect in enabling high value‐added product synthesis. Here, we developed a novel hybrid catalyst with Ni nanosheet forests anchored on carbon paper. The hybrid catalyst exhibits high efficiency in electrooxidation of HMF to FDCA coupling with H2 production in high purity. The Ni nanosheets have small crystal grain sizes with abundant edges, which is able to deliver an efficient HMF oxidation to FDCA (selectivity >99 %) at low potential of 1.36 VRHE with high stability. The post‐reaction structure analysis reveals the Ni nanosheets would transfer electrons to carbon and readily turn into NiOx and Ni(OH)x during the reaction. DFT results suggest high valence Ni species would facilitate the chemical adsorption (activation) of HMF revealing the reaction pathway. This work emphasizes the importance of the precise control of Ni activity via atomic structure engineering.