Spectroscopy Transmission Electron Research Articles

Fabrication and characterization of rubidium ferrites by the solution‐based combustion method using diverse organic fuels

Fabrication and characterization of rubidium ferrites by the solution‐based combustion method using diverse organic fuels

Amine-rich cyclotriphosphazene (P3N3) nano-cages for enhanced and selective Au(III) and Pd(II) recovery and hydrogen generation: Waste-to-resource tactics

Designing a new material for precious metals (PMs) recovery is of ultimate significance in the quest to explore highly efficient, selective, and stable adsorbents for a sustainable economy and green environment. Herein, novel amine-rich cyclotriphosphazene poly(tetrakis(4-aminophenyl)methane-co-cylotriphosphazene)- porous nano-cages (PTC-PNC) and microspheres (PTC-MS) were synthesized for adsorption and selective recovery of Au(III) and Pd(II) in aqueous solution. A combination of the abundant amine groups and the cage-like porous morphology of PTC-PNC makes it an ideal absorbent for recovery of the Au(III) (1592 mg g−1, pH 1.0, 60 oC) and Pd(II) (1372 mg g−1, pH 1.0, 60 oC) with high selectivity which was slightly decreased up to 8-11% even in the presence of 13 co-existing metals ions while an ultra-high recovery of 99% was obtained. The unique cage-like morphology of the PTC-PNC guarantees a fast adsorption equilibrium while the adsorption isotherm specifies a pseudo-second-order kinetic behavior and Langmuir isotherm. Amine groups were the most energetically favorable sites for the capturing and chelating of Au(III) and Pd(II) ions followed by their partial reduction to Au0 and Pd0. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron spectroscopy (HRTEM) analysis were employed to explore interactions and reduction mechanisms during the adsorption process. Adopting the waste-to-resource approach, after Au(III) and Pd(II) recovery, these adsorbents were applied for catalytic hydrogen generation from ammonia borane (AB) hydrolysis. Due to its favorable electronic structure, the PTC-PNC@Pd exhibited a higher hydrogen generation than PTC-PNC@Au. The as-synthesized PTC-PNC could be employed as a promising material for other MPs' selective recovery and green energy generation applications.

Co3O4 derived ZnO: An effective electrocatalyst for oxygen evolution reaction in alkaline media

The growing accessibility of hydrogen and renewable energy sources has led to a rising significance of cobalt oxide (Co3O4)-based electrocatalysts in the context of effective electrochemical water splitting. Among two-half cell reactions, oxygen evolution reaction (OER) is more complicated and sluggish in behaviour. We present a composite material based on cobalt oxide-derived zinc oxide (Co3O4@ZnO) prepared through a wet chemical technique to overcome this challenge. The as-prepared materials are analyzed for crystallinity, morphology, and chemical bonding through X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), high resolution transmission electron spectroscopy (HRTEM), and Fourier transform infrared (FTIR) spectroscopy, respectively. The optimized electrocatalyst reveals higher electrochemical performance for OER with an overpotential value of 262 mV at 10 mA/cm2 current density, Tafel slope value of 59 mV/dec, and charge transfer resistance (Rct) of 72 Ω. Moreover, the electrochemical active surface area (ECSA) is calculated as 320 cm2. Notably, the desired electrocatalyst shows the stability of 50 h at 10 and 20 mA/cm2 current densities. The as-prepared catalyst (Co3O4@ZnO) with effective electrochemical features can be a potential candidate for energy conversion applications toward a sustainable society.

Tuning grain boundary cation segregation with oxygen deficiency and atomic structure in a perovskite compositionally complex oxide thin film

Compositionally complex oxides (CCOs) are an emerging class of materials encompassing high entropy and entropy stabilized oxides. These promising advanced materials leverage tunable chemical bond structure, lattice distortion, and chemical disorder for unprecedented properties. Grain boundary (GB) and point defect segregation to GBs are relatively understudied in CCOs even though they can govern macroscopic material properties. For example, GB segregation can govern local chemical (dis)order and point defect distribution, playing a critical role in electrochemical reaction kinetics, and charge and mass transport in solid electrolytes. However, compared with conventional oxides, GBs in multi-cation CCO systems are expected to exhibit more complex segregation phenomena and, thus, prove more difficult to tune through GB design strategies. Here, GB segregation was studied in a model perovskite CCO LaFe0.7Ni0.1Co0.1Cu0.05Pd0.05O3−x textured thin film by (sub-)atomic-resolution scanning transmission electron microscopy imaging and spectroscopy. It is found that GB segregation is correlated with cation reducibility—predicted by an Ellingham diagram—as Pd and Cu segregate to GBs rich in oxygen vacancies (VO··). Furthermore, Pd and Cu segregation is highly sensitive to the concentration and spatial distribution of VO·· along the GB plane, as well as fluctuations in atomic structure and elastic strain induced by GB local disorder, such as dislocations. This work offers a perspective of controlling segregation concentration of CCO cations to GBs by tuning reducibility of CCO cations and oxygen deficiency, which is expected to guide GB design in CCOs.

Nanocrystalline Fe(Co)ZrMoBCu soft magnetic alloys: A transmission electron microscopy study of the microstructures

Nanocrystalline Fe81Zr7Mo2B9Cu1 and Fe40.5Co40.5Zr7Mo2B9Cu1 alloy ribbons were prepared by annealing the as-quenched amorphous alloys at their first exothermic peak temperature. The primary crystallization phases of Fe81Zr7Mo2B9Cu1 and Fe40.5Co40.5Zr7Mo2B9Cu1 consisted of nanoscale body-centered cubic α-Fe and α-FeCo grains, respectively. The microstructures and compositions were analyzed via transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), and area maps were obtained through energy-dispersive spectroscopy (EDS). The addition of Co decreased the mean grain size (D) and broadened the grain-size distribution (σ). The effect of the addition of Co on the Cu clusters and element distribution was studied in detail. Scanning transmission electron spectroscopy combined with energy-dispersive spectroscopy revealed that both alloys contained Cu clusters; the Fe40.5Co40.5Zr7Mo2B9Cu1 alloy exhibited a Cu-cluster density similar to that of the Fe81Zr7Mo2B9Cu1 alloy. Both alloys contained relatively less Fe in their residual amorphous phases than in their nanocrystals, with the nanocrystals in Fe40.5Co40.5Zr7Mo2B9Cu1 containing less Co than in the residual amorphous phase. Fe40.5Co40.5Zr7Mo2B9Cu1 exhibited higher specific saturation magnetization (Ms), specific remanent magnetization (Mr) and larger coercivity (Hc) than Fe81Zr7Mo2B9Cu1.

MOP-18-Derived CuO Fiber for Hybrid Supercapacitor Electrodes.

This study explores a simple method of fabricating hybrid supercapacitor electrodes, which could potentially broaden the application of this technology. The method involves electrospinning a uniform solution of Matrimid/Metal-Organic Polyhedra 18 (MOP-18) followed by carbonization at a relatively low temperature of 700 °C in air, rather than in an inert atmosphere, to create free-standing, redox-active hybrid supercapacitor electrodes. Additionally, the synthesis procedure requires no stabilization or activation steps, which enhances the cost effectiveness of the synthesized electrode materials. The resulting C/CuO composite was used as the working electrode, with a polyacrylonitrile (PAN)/Poly(methyl methacrylate) (PMMA) carbon nanofiber (CNF) electrode as the counter and 6 M KOH as the electrolyte in a T-cell configuration. The cell performance and redox activity were evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycling stability tests. Additionally, the physical and chemical structures of the electrode materials were assessed using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), X-ray diffractometry (PXRD), surface area analysis and other characterization techniques. The electrode material demonstrated a specific capacitance of up to 206 F/g. Supercapacitors utilizing this material display an energy density of 10.3 Wh/kg (active material) at a current density of 1 A/g in electrochemical testing.

Electrocatalysis of ammonia on NiCu nanoclusters with higher activity and stability synthesized by a simplified polyol technique

This work focuses on a simplified polyol process by which to synthesize five different NiCu/C nanoclusters (NCs) electrocatalysts with the variation of mass and atomic ratio. NCs are characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy, transmission electron spectroscopy (TEM), and scanning electron microscopy with energy-dispersive spectroscopy (EDS) for their crystallite and electronic structures, morphological studies, and elemental composition. The high-angle annular dark-field scanning TEM coupled with EDS elemental mapping has confirmed that nanoparticles (NPs) are formed with Ni and Cu, and NPs are subsequently noted to conform into NCs in such a fashion that NiCu NPs are interconnected to each other rather than overlapping considered a unique distribution of NiCu NCs on the carbon support observed in STEM. NPs arrangement in the conformation of NCs has largely increased in the coverage of NiCu-oxyhydroxides working as active sites for ammonia electrocatalysis evidenced in cyclic voltammograms and XPS investigation. NCs were employed for the oxidation of NH4OH, NH4Cl, NH4NO3, and (NH4)2SO4 of which NiCu/C-2 has shown the highest performance over other NiCu/C samples and their individuals. NiCu/C-2 is also found to have higher stability than other mono/bi-metallic electrocatalysts on the stability test preformed in an electrochemical environment. In addition, the sharp drops of the current in the chronoamperometric curves have been investigated during the stability test.

Nanoscale cathodoluminescence spectroscopy probing the nitride quantum wells in an electron microscope

To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level, cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In0.15Ga0.85N five-period multiquantum wells. The lattice–composition–energy relationship was established with the help of energy-dispersive x-ray spectroscopy, and the bandgaps of In0.15Ga0.85N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra. The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed. Our study establishing the direct relationship between the atomic structure of In x Ga1−x N multiquantum wells and photoelectric properties provides useful information for nitride applications.

Calculation of positron annihilation lifetime in diamond doped with B, Cr, Mo, Ti, W, Zr

Metal-matrix diamond composites have been extensively used and studied, but vacancies, doping, and other defects caused by the pretreatment of the diamond surface significantly affect the interface property between the metal base and diamond. Although techniques like transmission electron microscopy and spectroscopy analysis have been used to detect defects, they present certain limitations. Calculating the positron annihilation lifetime in diamond provides an accurate assessment of interface defect in the diamond. This study uses first-principles calculation methods and adopts various positron annihilation algorithms and enhancement factors, to compute the positron annihilation lifetimes in ideal diamond crystals, single vacancies, and diamond crystals doped with B, Cr, Mo, Ti, W, and Zr. The results, obtained by using local density functional in combination with Boronski & Nieminen algorithms and random-phase approximation restriction as annihilation enhancement factors, indicate that the computed positron annihilation lifetime of diamond is 119.87 ps, which is consistent closely with the experimental result in the literature. Furthermore, after B, Cr, Mo, Ti, W, and Zr atoms are doped into diamond (doping atomic concentration of 1.6%), the positron annihilation lifetimes change from a single vacancy 119.87 ps to 148.57, 156.82, 119.05, 116.5, 117.62, and 115.74 ps respectively. This implies that the defects due to doped atoms in diamond change their positron annihilation lifetimes, with the influence varying according to the different atoms doped. Based on the calculated electron density in diamond vacancies and doped atom areas, it is discovered that doping atoms do not cause severe distortion in the diamond lattice. However, after B and Cr atoms are doped, the positron annihilation lifetime increases significantly. The primary reason is that the relatively low positron affinity of B and Cr atoms results in an extended positron residence time in the vacancy, thereby increasing the annihilation lifetime. Overall, vacancies and doped atom defects in diamond will cause its positron annihilation lifetime to change. The above conclusions provide crucial theoretical references for detecting and identifying interface defects caused by doping treatment on the diamond surface during the preparation of metal-matrix diamond composites.

Integrating 1D/2D nanostructure based on Ni–Co-oxalate for energy storage applications

The performance of an electrochemical energy storage device highly depends on the electrode material. Currently, metal oxalates are evolving as low-cost and stable electrode materials for batteries and supercapacitors. Herein, mixed metal oxalate (NixCo1-xC2O4/NF) based binder-free electrode was fabricated. The nickel foam contributed not only as a substrate but also as a nickel source. The NixCo1-xC2O4/NF confirmed the crystalline phase through X-ray diffraction spectroscopy (XRD). Scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) confirmed the integrated 1D/2D-like morphology of NixCo1-xC2O4/NF. The electrochemical results reveled the NixCo1-xC2O4/NF electrode exhibit battery behavior with capacity retention of 86.58 % and possessed the highest specific capacity of 470.012 C g−1 at 1 A g-1. Hence, the nickel inclusion during the synthesis has further enhanced the overall properties and performance of the NixCo1-xC2O4/NF electrode.

Tailoring Breathing Behaviour of Solid Electrolyte Interphases (SEIs) Unraveled by Cryo-TEM

The cycling stability of batteries is closely related to the dynamic evolution of solid electrolyte interphases (SEIs) in response to the discharging/charging processes. Here we utilize the state-of-the-art cryogenic transmission electron microscopy (cryo-TEM) and spectroscopy to probe the SEI breathing behaviour induced by discharging/charging on the conversion-type anode made of Fe2O3 quasi-cubes. The incorporation of the identical-location strategy allows us to track the evolution of same SEIs at different charge states, which unequivocally unravels SEI breathing featured by swelling (contracting) upon lithiation (de-lithiation), and the associated compositional change. Bare Fe2O3 anode develops an unstable SEI layer due to the intermixing with the lithiation product Li2O, which exhibits a large thickness variation upon breathing as well as excessive growth, causing substantial capacity fading within 100 cycles. A transition from organic to inorganic-type SEI is also identified upon cycling, which gives rise to significantly increased SEI resistance. To tailor the SEI behaviour, we apply N-doped carbon coating on Fe2O3 (Fe2O3@CN), which can effectively separate the lithiation product from SEI. A thinner and chemically more stable SEI layer develops on Fe2O3@CN, resulting in remarkably enhanced cycling stability compared to bare Fe2O3. Our work demonstrates the importance of understanding and optimizing the dynamic behaviour of SEIs to achieve better battery performance.

The Impact of Titanium Nanotubes (TNTs) Incorporated into a Sodium Alginate-Based Nanocomposite Membrane on the Adsorption of Cationic Dye from Aqueous Solutions

In this study, we synthesized a composite membrane of molecularly imprinted TiO2 nanotubes (TNTs) embedded in a Sodium Alginate (SA) supporting matrix. The TNTs were synthesized using a simple hydrothermal technique, resulting in an average length of 20 nm. To improve their recyclability and photoactivity, these nanotubes were immobilized within the SA membrane. The casting solution was applied onto a glass plate using a glass rod to control the film thickness. Subsequently, the TNTs/SA nanocomposite membrane was obtained by drying at room temperature and crosslinking with glutaraldehyde and HCl to improve mechanical strength, chemical resistance and stability of the membrane. The as-prepared TNTs and composite films were characterized using various methods, including X-ray diffraction (XRD), Dynamic light scattering (DLS), Scanning electron microscopy (SEM), and Transmission electron spectroscopy (TEM). Scanning electron microscopy revealed the porous nature of the prepared TNTs/SA composite membrane. Further, these composite membranes were utilized for the adsorption of the cationic dye methylene blue (MB) from aqueous solutions. A 50 mg TNTs/SA nanocomposite membrane achieved an approximate degradation ratio of 85% for a 10 ppm MB concentration under room conditions within 180 min. Additionally, the effects of adsorbent dosage, dye concentration, and temperature were also investigated.

Enhanced piezoelectric energy harvesting using hybrid composites of MWCNTs and partially-reduced GO in RTV-SR for stable voltage generation

Recent studies have explored the use of flexible devices for piezoelectric energy harvesting, which can generate energy at a few volts on a laboratory scale. In this context, multiwall carbon nanotubes (MWCNTs), partially-reduced GO (p-rGO), and their hybrid composites based on room temperature vulcanized silicone rubber (RTV-SR) have emerged as innovative and novel approaches for energy production. The composites were prepared by mixing an RTV-SR solution with MWCNTs and p-rGO powder as fillers, resulting in improved mechanical properties and reinforcement of the RTV-SR matrix. The p-rGO was synthesized from graphite nanoplatelets (GNP) using the modified Hummers' method, followed by chemical and thermal reduction. The MWCNTs were used as received from the supplier. Characterization techniques such as scanning electron microscopy, x-ray diffraction, transmission electron spectroscopy, and atomic force microscopy revealed that the p-rGO consisted of less than five layers stacked in a crystalline domain. Static mechanical property analysis demonstrated that MWCNTs exhibited exceptional filler characteristics compared to other fillers studied. Piezoelectric energy harvesting measurements were performed, and the results indicated higher voltage generation for MWCNTs; however, it exhibited instability and a decline in performance after a few cycles due to electrode cracking. In contrast, the hybrid composite demonstrated stable voltage generation. Moreover, walking and running activities may generate renewable, simple, and sufficient voltage to power light-emitting diodes (LEDs).

Treatment of gastric cancer by green mediated silver nanoparticles using Pistacia atlantica bark aqueous extract

Abstract We herein demonstrate a novel green mediated silver nanoparticles (AgNPs) using Pistacia atlantica bark aqueous extract for the treatment of gastric cancer under in vitro conditions. Physicochemical and structural features of the nanocomposite biomaterial were assessed by several techniques like UV-Vis spectrum, transmission electron spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma-optical emission spectroscopy. The Ag NPs showed high antioxidant activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH). The IC50 of Ag NPs and Butylated hydroxytoluene against DPPH were 132 and 77 µg/mL, respectively. In the oncological part of this research, the status of normal and gastric cancer AGS and KATO III cell lines was determined. The IC50 of AgNPs was 193 and 250 µg/mL against AGS and KATO III. It seems that the prepared NP have stopped the growth of gastric cancer cells and the recent cancer cells have been removed with high concentration of NPs.

Graphene-Oxide-Coated CoP2@C Anode Enables High Capacity of Lithium-Ion Batteries

Cobalt diphosphides (CoP2) show a high theoretical capacity and hold great promise as anode materials for lithium-ion batteries (LIBs). However, the large variation in the volume and structure of CoP2 caused during lithium-ion insertion and extraction results in electrode fragmentation and a compromised solid electrolyte interface, ultimately leading to poor cycling performance. Herein, a composite of CoP2 nanoparticles encapsulated in carbon matrix has been successfully synthesized by carbonization of Co-MOF-based zeolitic imidazolate frameworks (ZIF-67) and sequential phosphorization and further wrapped in graphene oxide (CoP2@C@GO). The formation of CoP2 was confirmed by X-ray diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The morphology of CoP2@C with and without GO wrapping was examined by scanning electron microscopy and transmission electron spectroscopy. It was demonstrated that the decoration of GO significantly reduces the polarization of CoP2@C electrodes, enhancing their charge capacity and cycling stability as an anode material for LIBs. After 200 cycles, they deliver a capacity of 450 mAh·g−1.

Zinc-Intercalated Halloysite Nanotubes as Potential Nanocomposite Fertilizers with Targeted Delivery of Micronutrients.

This study reports on the development of nanocomposites utilizing a mineral inhibitor and a micronutrient filler. The objective was to produce a slow release fertilizer, with zinc sulfate as the filler and halloysite nanotubes as the inhibitor. The study seeks to chemically activate the intercalation of zinc into the macro-, meso-, and micropores of the halloysite nanotubes to enhance their performance. As a result, we obtained three nanocomposites in zinc sulfate solution with concentrations of 2%, 20%, and 40%, respectively, which we named Hly-7Å-Zn2, Hly-7Å-Zn20, and Hly-7Å-Zn40. We investigated the encapsulation of zinc sulfate in halloysite nanotubes using X-ray diffraction analysis, transmission electron spectroscopy, infrared spectroscopy (FTIR), and scanning electron microscopy with an energy-dispersive spectrometer. No significant changes were observed in the initial mineral parameters when exposed to a zinc solution with a concentration of 2 mol%. It was proven that zinc was weakly intercalated in the micropore space of the halloysite through the increase in its interlayer distance from 7.2 to 7.4. With an increase in the concentration of the reacted solution, the average diameter of the nanotubes increased from 96 nm to 129 nm, indicating that the macropore space of the nanotubes, also known as the "site", was filled. The activated nanocomposites exhibit a maximum fixed content of adsorbed zinc on the nanotube surface of 1.4 wt%. The TEM images reveal an opaque appearance in the middle section of the nanotubes. S SEM images revealed strong adhesion of halloysite nanotubes to plant tissues. This property guarantees prolonged retention of the fertilizer on the plant surface and its resistance to leaching through irrigation or rainwater. Surface spraying of halloysite nanotubes offers accurate delivery of zinc to plants and prevents soil and groundwater contamination, rendering this fertilizer ecologically sound. The suggested approach of activating halloysite with a zinc solution appears to be a possible route forward, with potential for the production of tailored fertilizers in the days ahead.

Exotic Electronic Properties of 2D Nanosheets Isolated from Liquid Phase Exfoliated Phyllosilicate Minerals.

Spectrally inactive, electrically insulating, and chemically inert are adjectives broadly used to describe phyllosilicate minerals like mica and chlorite. Here, the above is disproved by demonstrating aqueous suspensions of liquid exfoliated nanosheets from five bulk mica types and chlorite schist. Nanosheet quality is confirmed via transmission electron and X-ray photoelectron spectroscopies, as well as electron diffraction. Through Raman spectroscopy, a previously unreported size- and layer-dependent spectral fingerprint is observed. When analyzing the high-yield suspensions (≈1mgmL-1 ) through UV-vis spectroscopy, all phyllosilicates present bandgap (Eg ) narrowing from ≈7eV in the bulk to ≈4eV for monolayers. Unusually, the bandgap is inversely proportional to the areal size (A) of the nanosheets, measured via atomic force microscopy. Due to an unrecorded quantum confinement effect, nanosheet electronic properties scale toward semiconducting behavior (bandgap ≈3eV) as nanosheet area increases. Furthermore, modeling X-ray diffraction spectra shows that the root cause of the initial bandgap narrowing is lattice relaxation. Finally, with their broad range of isomorphically substituted ions, phyllosilicate nanosheets show remarkable catalytic properties for hydrogen production.

Broadband and ultrafast photodetector based on PtSe2 synthesized on hBN using molecular beam epitaxy

Two-dimensional (2D) van der Waals materials are potential candidates for high-performance optoelectrical devices owing to the bandgap modulation, high on/off ratio, and ultra-stability. However, the challenge of synthesizing large-area, uniform, and high-quality 2D van der Waals materials should be addressed to manufacture large-scale and uniform optoelectrical devices using these materials. Although several previous studies investigated synthesis methods using chemical vapor deposition and molecular beam epitaxy (MBE), there are certain limitations such as the non-uniformity, lots of grain boundaries, and low carrier mobility. Here, by studying a method for synthesizing PtSe2 on hBN buffer layer using MBE, we fabricated a PtSe2-based broadband photodetector. The high-quality PtSe2 synthesized on hBN was evaluated using Raman spectroscopy and scanning transmission electron spectroscopy. These revealed that the synthesized PtSe2 had a high quality and small grain boundary compared with PtSe2 synthesized on SiO2. Owing to the reduction in the carrier scattering and carrier recombination because of the high-quality and small grain boundaries, the photodetector using PtSe2 synthesized on hBN displayed optoelectrical properties that were significantly better than those of PtSe2 synthesized on SiO2. Therefore, using hBN as a buffer layer for PtSe2 growth, a remarkable performance of complex optoelectrical devices could be achieved.

Stable Ta2O5 nanotubes decorated by PbS by the SILAR method for photocatalytic dye degradation

Tantalum oxide Ta2O5 nanotubes (NTs) were prepared by electrochemical anodization and were decorated with lead sulfide nanoparticles PbS (NPs) by Successive Ionic Layer Adsorption and Reaction commonly known as the SILAR method. The PbS NPs/Ta2O5 NTs were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDX), Transmission Electron Spectroscopy (TEM), Photoluminescence (PL), and Diffuse Reflectance Spectroscopy (DRS). An increasing number of SILAR cycles applied on this substrate were shown to induce a variation in the optical properties and the bandgap of PbS NPs/Ta2O5 NTs. The bandgap went from 3.83 eV for bare Ta2O5 to 3.4 eV for Ta2O5 NTs decorated with 10 PbS SILAR cycles. Ten SILAR cycles were seen to correspond to 2.7 wt% and 1.4 M percentage of the decorated Ta2O5 NTs. Ten SILAR cycles were required to drive the fastest degradation kinetics of the Black Amido mediating Ta2O5 (NTs)-PbS NPs under light irradiation. However, longer SILAR cycles were not seen to faster the degradation kinetics due to light screening. The prepared nanotubes exhibited high stability over 5 photocatalytic reuse cycles.

Time-Dependent Passivation Performance of Plasma Sprayed FeCrMoCBY Amorphous Coating

The relationship between passive film growth behavior and passivation time for plasma-sprayed Fe48Cr15Mo14C15B6Y2 amorphous coating in borate buffer solution has been thoroughly studied. The morphological characteristic and structural feature of as-spayed amorphous coating were estimated by scanning electron spectroscopy (SEM), X-ray diffraction (XRD) and transmission electron spectroscopy (TEM). The influence of passivation time on the film evolution properties was measured by electrochemical impedance spectra (EIS), Mott–Schottky curves, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The results revealed that both corrosion resistance and self-repairing capacity of passive film greatly increased with time based on high electric field assumption. Reductions in donor density and flat band potential were accountable for a lower conductivity of passive film. An increment in Cr2O3 oxide as the inner barrier layer derived from the dehydration reaction of Cr(OH)3 contributed to the gradually densified structure of passive film. The extracted passive film thickness d increment with passivation time t conformed to the logarithm law on the basis of effective capacitance hypothesis: d=0.43lnt+52.06−2.18 (nm). Passivation mechanism within 600 s was ascribed to the adsorption of mechanical mixtures between metal ions and electrolytes, possibly leading to mechanical stress and rupture of passive film in the later growth procedure. The cation vacancy condensation process at the interface of coating/film was propitious in stabilizing the growth rate of passive film.