Crystal Surface Research Articles

Lattice-guided assembly of optoelectronically active π-conjugated peptides on 1D van der Waals single crystals.

The deployment of organic molecules in high-performance devices strongly relies on the formation of well-ordered domains, which is often complicated by the dynamic and sensitive nature of supramolecular interactions. Here, we engineered the assembly of water-processable, optoelectronic π-conjugated peptides into well-defined organic-inorganic heterointerfaced assemblies by leveraging the long-range anisotropic ordering of 1D van der Waals (vdW) crystals composed of subnanometer-thick transition metal sulfide chains (MS3; M = Nb, Ta) as assembly templates. We found that the monomers can readily form 1D supramolecular assemblies onto the underlying crystal surface, owing to the structural correspondence between the π-π interactions of the quaterthiophene (4T)-based peptide units (DDD-4T) and sulfur atom ordering along the NbS3 (100) surface. The heterointerfaced assemblies exhibited substantially red-shifted photoluminescence and enhanced visible-range photocurrent generation compared to solution-assembled films. Our results underscore the role of lattice matching in forming ordered supramolecular assemblies, offering an emergent approach to assembling organic building blocks endowed with improved physical properties.

The Effects of Different Zn Forms on Sintering Basic Characteristics of Iron Ore.

The micro-sintering method was used to determine the sintering basic characteristics of iron ore with Zn contents from 0 to 4%, the influence mechanism of Zn on sintering basic characteristics of iron ore was clarified by means of thermodynamic analysis and first-principles calculations. The results showed that (1) increasing the ZnO and ZnFe2O4 content increased the lowest assimilation temperature (LAT) but decreased the index of liquid phase fluidity (ILF) of iron ore. The addition of ZnS had no obvious effect on LAT but increased the LIF of iron ore. (2) ZnO and ZnFe2O4 reacted with Fe2O3 and CaO, respectively, during sintering, which inhibited the formation of silico-ferrite of calcium and aluminum (SFCA). The addition of ZnS accelerated the decomposition of Fe2O3 in the N2 atmosphere; however, the high decomposition temperature limited the oxidation of ZnS, so the presence of ZnS had a slight inhibitory effect on the formation of SFCA. (3) The Zn concentrated in hematite or silicate and less distributed in SFCA and magnetite in the form of solid solution; meanwhile, the microhardness of the mineral phase decreased with the increase in Zn-containing solid solution content. As the adsorption of Zn on the SFCA crystal surface was more stable, the microhardness of SFCA decreased more. The decrease in microhardness and content of the SFCA bonding phase resulted in a decrease in the compressive strength of the sinter.

Origins of authigenic gypsums and carbonate minerals in sediments at a cold seep site in the Sea of Marmara

In the Western High of the Sea of Marmara, where pervasive gas hydrate and hydrocarbon gas seepage occurs, late Pleistocene-Holocene sediments are composed of a lower lacustrine and an upper marine unit. The sedimentary evolution, gypsum formation and carbonate anomaly, under the complex sedimentary environment at cold seep sites on the Western High, have not been systematically well explained. The transition from the lacustrine to marine unit occurs at around 7.5 m below the sea floor (mbsf), with a sulfidization front present in the lacustrine sediments just below it, and the marine unit includes a sapropel layer between 5.20 and 7.20 mbsf. The sedimentary sequence is characterized by authigenic minerals including pyrite, carbonates, and gypsum in the upper 0.50 mbsf, corresponding to the present-day sulfate-methane transition zone (SMTZ) near the seafloor. Mineralogical, chemical and isotopic compositions (13C, 18O, 34S, 26Mg) of the sediments in the core studied show their close relationship with intensive sulfate-driven anaerobic oxidation of methane (AOM) and other hydrocarbons. The dissolution of carbonate, related to the gas and oil migration, and organic matter enrichment might be the main cause of carbonate deficiency in the sapropel unit. Heavy carbon isotopic composition (δ13CCarb = 6.98‰) of carbonate at 4.30 mbsf implies that the carbon might be the residual by-product of subsurface biodegradation of seeping petroleum. The formation of secondary gypsum and partial dissolution of carbonate in the Sea of Marmara is commonly considered of being associated with the aerobic oxidation of pyrite. However, the euhedral authigenic gypsum studied might be with different origins, possibly including anaerobic oxidation of Fe-sulfides, carbonate deficiency in the sapropel unit and AOM. Gypsums below SMTZ are with the size of hundreds of microns. Linear pits and grooves are developed on these gypsum surfaces, probably due to corrosion by the methane-rich fluid of latest hydrocarbon seepage. Platy hexagonal gypsum in SMTZ, without any corrosion on crystal surface, might be associated with the changing flux of the acidic composition (e.g. CO2) in the seepage. Depleted-26Mg by about 1‰ in the SMTZ might be caused by the upward seepage of hydrocarbons. Magnesium isotope of authigenic carbonate could be a valid proxy for the recognition of SMTZ in a hydrate geo-system.

Highly efficient and selective hydrogenation of furfural to furfuryl alcohol and cyclopentanone over Cu-Ni bimetallic Catalysts: The crucial role of CuNi alloys and Cu+ species

The selective hydrogenation of furfural derived from biomass is of significant importance in the synthesis of valuable chemical compounds. In this work, Cu-Ni bimetallic catalysts with varying metal ratios were effectively synthesized using the urea deposition method and employed in catalytic hydrogenation of furfural (FA) to furfuryl alcohol (FOL) and cyclopentanone (CPO) in different solvents. The study revealed that the synergistic interaction between Cu and Ni favors the formation of CuNi alloys, thereby facilitating the reduction of CuO and NiO and resulting in larger amount of metallic species (Cu0/+ and Ni0), and promoting the formation of highly dispersed nanoparticles. Moreover, the formed Cu+ species can serve as Lewis acid sites and improve the adsorption of polarized C = O, thus significantly enhancing the selectivity to FOL. More importantly, the cooperation between Cu+ species and water can promote the aqueous-phase hydrogenation-rearrangement (AP-HR) of FA to CPO. Also, in-situ/on-line DRIFTS shows that Cu3Ni1/SiO2 preferentially adsorbs and activates C = O and prefers to form 4-hydroxy-2-cyclopentenone (HCP), which is the key intermediate to form CPO. DFT calculations agree with the in-situ/on-line DRIFTS, showing that Cu3Ni1 (111) crystal surface with the lowest d-band center and the strongest electronic effects presents the highest adsorption energies of H2, H2O, and FA, the lowest adsorption energies of H*, FOL, and CPO, and the lowest energy barriers of Piancatelli rearrangement of FOL to HCP. Under the optimum conditions, Cu3Ni1/SiO2 gives 99.9 % yield to FOL at 333 K in isopropanol and 96.7 % yield to CPO at 413 K in water. The low cost and high activity of Cu3Ni1/SiO2 make it a potential catalyst for the green production of FOL and CPO in industry.

The types of metal M and crystal surface in the PtM (M = Co, Ni, Zn) IMCs catalysts to regulate catalytic performance of ethane direct dehydrogenation

PtM IMCs have improved catalytic performance of ethane dehydrogenation (EDH), however, identifying the functions of the types of metal M and crystal surface for the PtM IMCs catalysts in regulating EDH catalytic performance are still a challenge in experiment. This work fully investigated catalytic performance of EDH over three crystal surfaces (110), (111) and (200) of PtM IMCs (M = Co, Ni, Zn) by using density functional theory (DFT) calculations and kinetic Monte Carlo (kMC) simulations. The results show that the catalytic performance of EDH over PtM IMCs strongly depend on the types of metal M and crystal surfaces, the PtZn(111) catalyst is screened out as the most promising in EDH reaction with the optimal reaction temperature of 773.15 K. The geometrically isolated Pt site in the [PtM3] assembly of PtZn(111) could catalyze the CH cleavage, and C2H4* exhibits weak π-adsorption model at the individual Pt sites, promoting C2H4* desorption. Compared to (110) and (200) surfaces, the (111) surface with moderate Bader charge transfer showed the highest C2H4(g) production activity, and Zn atoms transferred more electrons to Pt atoms, which greatly weakened the charge transfer between C2H4* and the catalyst surface, favoring C2H4* desorption to inhibit C2H4* deep dehydrogenation. Moreover, the catalytic performance of PtZn(111) catalyst is superior to the industrially used PtSn catalyst. This work provides valuable structure clue for the design of high-performance catalyst in alkane direct dehydrogenation.

Exploring surface properties and premelting in crystals.

Crystal surfaces play a pivotal role in governing various significant processes, such as adsorption, nucleation, wetting, friction, and wear. A fundamental property that influences these processes is the surface free energy, γ. We have directly calculated γ(T) for low-index faces of Lennard-Jones (LJ), germanium, and silicon crystals along their sublimation lines using the computational cleavage technique. Our calculations agree well with experimental values for Si(111) and Ge(111), highlighting the accuracy of the method and models used. For LJ crystals, we identified a premelting onset at Tpm = 0.75Tm, marked by a sharp increase in atom mobility within the second outermost surface layer. Notably, Tpm closely aligned with the endpoint of the LJ melting line at negative pressures, Tend = 0.76Tm. We hypothesize that the emergence and coexistence of a liquid film atop the LJ crystal at Tpm < T < Tm correspond to the metastable melting line under negative pressures experienced by stretched crystal surfaces. Furthermore, our study of thin LJ crystal slabs reveals that premelting-induced failure leads to recrystallization below the homogeneous freezing limit, offering a promising avenue to explore crystal nucleation and growth at extremely deep supercoolings. Finally, no evidence of premelting was detected in the model crystals of Ge and Si, which is consistent with the experimental observations. Overall, our findings offer valuable insights into crystal surface phenomena at the atomic scale.

New insights into chitosan-induced biomimetic mineralization of hierarchical spherical nesquehonite: Characterization, DFT calculations and construction mechanism

Recently, CO2 mineralization with magnesium salts is a cost-effective method for CO2 utilization and sequestration. The obtained hydrated magnesium carbonate can serve as high-value added functional materials. Inspired by biomineralization, nesquehonite (NSQ) was prepared via chitosan-induced mineralization of MgCl2-(NH4)2CO3, achieving indirect mineralization of CO2. The effects of chitosan (CTS) addition, reaction temperature, and reaction time on the phase composition and micromorphology of the products were systematically investigated. When the chitosan addition was 2%, the reaction temperature was 60℃, and the reaction time was 300 min, the obtained product was hierarchical spherical NSQ with an average diameter of 10 μm. The construction mechanism of the hierarchical spherical NSQ was elucidated. Zeta potential and 1H NMR analyses indicated the interaction of CTS with Mg2+, binding Mg2+ through –OH and –NH2 groups, thereby prolonging the nucleation and growth process of NSQ. FT-IR, XPS, TEM, and AFM analyses revealed that CTS induced directional growth of nanosheets by chemisorption on the crystal surface. Ultimately, through CTS bridging, the nanosheets aggregated and assembled into NSQ sphere. DFT calculations further indicated that CTS forms Mg-O and Mg-N bonds with Mg2+ and that there are Mg-O, Mg-N bonds and hydrogen bonding interactions between CTS and NSQ. This work provides new insights into the preparation of hierarchical NSQ via a biomimetic mineralization mechanism. Additionally, NSQ with a multiscale hierarchical structure has a promising future in the fields of adsorbents, templating agents, and drug carriers.

Rhodium-decorated palladium nanocubes supported on Ni(OH)2 nanosheets/C for enhanced ethanol oxidation

This study investigates the improvement of Palladium (Pd)-based nanocatalysts for ethanol oxidation in alkaline solutions, a process often hindered by the poisoning of the catalyst’s surface. We synthesise Pd nanocubes and Rhodium (Rh)-decorated Pd nanocubes, both supported by a composite of nickel hydroxide nanosheets and carbon (Ni(OH)2/C). The developed Pd nanocatalysts possess a nanocubic morphology with smaller sizes compared to Pd/C, alongside additional nanostructures like nanorods X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses suggest that Rh decoration on Pd nanocubes prevents Pd oxidation, with Rh itself being oxidised. The electrocatalytic performance of the Rh/Pd/Ni(OH)2/C hybrid catalyst displays a notable enhancement, attributed to the combined effects of the exposed Pd (100) crystal surfaces, the addition of oxygenated species through the Ni(OH)2 component, and the deliberate addition of Rh. Comparative assessments reveal that this composite surpasses Pd/C and Pd/C nanocubes, achieving specific activities that are approximately 11.6 and 3.5 times greater, respectively. Electrochemical Impedance Spectroscopy data and chronoamperometric studies confirm superior ethanol oxidation efficiency and improved catalytic stability. These findings highlight the utility of Rh/Pd/Ni(OH)2/C nanocubes in direct ethanol fuel cells, providing promising pathways for enhancing fuel cell technologies.

Annealing Process on Metal–Oxide–Semiconductor Channel Properties for Quasivertical GaN‐on‐Sapphire Trench Metal–Oxide–Semiconductor Field‐Effect Transistor

Quasivertical gallium nitride trench‐gate metal–oxide–semiconductor field‐effect transistors with different etch radio frequency power and the impact of the order of annealing process in tetramethylammonium hydroxide wet treatment have been fabricated and studied. The high‐power device has a threshold voltage of 5.3 V and a maximum saturation current density of 552 A cm−2, whereas the low‐power device has a threshold voltage of 4.5 V and a maximum saturation current density of 650 A cm−2. However, the low‐power device has more severe off‐state leakage due to more fixed charges and defects on the device surface. Furthermore, the annealing process serves as an additional step before wet treatment. Scanning electron mircoscope image indicates that annealing at high temperatures prior to etching can eliminate surface oxide and redistribute surface imperfections, resulting in a smoother sidewall morphology. The relationship between temperature and mobility confirms the impact of the crystal surface feature on device performance.

Advanced electrocatalysts for fuel cells: Evolution of active sites and synergistic properties of catalysts and carrier materials

AbstractProton exchange‐membrane fuel cell (PEMFC) is a clean and efficient type of energy storage device. However, the sluggish reaction rate of the cathode oxygen reduction reaction (ORR) has been a significant problem in its development. This review reports the recent progress of advanced electrocatalysts focusing on the interface/surface electronic structure and exploring the synergistic relationship of precious‐based and non‐precious metal‐based catalysts and support materials. The support materials contain non‐metal (C/N/Si, etc.) and metal‐based structures, which have demonstrated a crucial role in the synergistic enhancement of electrocatalytic properties, especially for high‐temperature fuel cell systems. To improve the strong interaction, some exciting synergistic strategies by doping and coating heterogeneous elements or connecting polymeric ligands containing carbon and nitrogen were also shown herein. Besides the typical role of the crystal surface, phase structure, lattice strain, etc., the evolution of structure‐performance relations was also highlighted in real‐time tests. The advanced in situ characterization techniques were also reviewed to emphasize the accurate structure‐performance relations. Finally, the challenge and prospect for developing the ORR electrocatalysts were concluded for commercial applications in low‐ and high‐temperature fuel cell systems.

Influence of ZrO2 on non-isothermal crystallization kinetics, structure and optical properties of calcium borosilicate glasses

The objective of the present work is to study the effect of ZrO2 on the structure, crystallization behavior and optical properties of 30SiO2-30B2O3-10Y2O3-(30-x)CaO-xZrO2 glasses using Raman, DSC and UV–visible spectroscopy, respectively prepared by melt and quench method. The optical gap is decreased with ZrO2 content except BSZ-7.5. The refractive index, optical basicity, and oxide ion polarizability are exhibited increasing trend with increasing ZrO2 content due to the conversion of bridging oxygens into non-bridging oxygens. The FTIR spectra revealed that Q1 unit of glasses increases instead of Q2 with increasing ZrO2 content. Lasocka, Kissinger and Augis-Bennette approaches are employed to study the crystallization behavior of the glasses. Various thermal parameters such as Avrami’s constant, thermal stability and fragility index are also studied to find out their possible application. In the present study, ZrO2 acts as a modifier up to 5.0 mol% and enhance bulk crystallization whereas at higher concentration (beyond 5.0 mol%), it behaves as a former and enhance surface crystallization.

Application of halloysite nanotubes for batteries and supercapacitors

The advancement of novel materials for energy storage devices is a crucial conceptualization to address the limitation in the application of energy storage devices. Layered nano clay and its derivatives exhibit diverse crystal structures and surface functionalities, which can be modified through chemical, electrochemical, or physical means to yield innovative materials. Halloysite nanotubes (HNTs), a widely available aluminosilicate layered nano clay, possess a range of distinctive properties including a core-shell structure, high specific surface area, and different surface charged properties. Consequently, HNTs exhibit immense potential for utilization in energy storage equipment, such as batteries and supercapacitors. This paper initially presents the composite mechanism of HNTs based on their structural characteristics. It subsequently provides an overview of the research advancements in HNTs-related composite materials, focusing on electrode materials, electrolytes, and separators. The paper further summarizes the knowledge of HNTs-derived carbon materials, transition-metal materials, and polymer composite electrodes. Additionally, it analyzes the challenges encountered by HNTs in lithium-ion batteries (LIBs) and supercapacitors (SCs). The ultimate objective is to facilitate the progress of HNTs in the realm of electrochemical energy storage.

A novel aptasensor platform for the detection of carcinoembryonic antigen using quartz crystal microbalance

In this study, a quartz crystal microbalance (QCM) aptasensor for carcinoembryonic antigen (CEA), a well-known biomarker for various cancer types, was reported, utilizing two different aptamers. To achieve this, a nanofilm of 4-mercaptophenyl was electrochemically attached to gold-coated QCM crystal surfaces via the reduction of 4-mercaptobenzenediazonium salt (4 MB-DAT) using cyclic voltammetry. Subsequently, gold nanoparticles (AuNP) were affixed to this structure, and then aptamers (antiCEA1 and antiCEA2) modified with SH-functional ends bound to AuNPs completed the modification. The analytical performance of the CEA sensor was evaluated through simultaneous QCM measurements employing CEA solutions ranging from 0.1 ng/mL to 25 ng/mL. The detection limit (LOD) for CEA was determined to be 102 pg/mL for antiCEA1 and 108 pg/mL for antiCEA2 aptamers. Interday and intraday precision and accuracy tests yielded maximum results of 4.3 and + 3.8, respectively, for both aptasensors, as measured by relative standard deviation (RSD%) and relative error (RE%). The kinetic data of the aptasensors resulted in affinity values (KD) of 0.43 ± 0.14 nM for antiCEA1 and 0.75 ± 0.42 nM for antiCEA2. These values were lower than the reported values of 3.9 nM and 37.8 nM for both aptamers, respectively. The selectivity of the aptasensor was evaluated by measuring the signal changes caused by alpha-fetoprotein (AFP), cancer antigen (CA-125), and vascular endothelial growth factor (VEGF-165) individually and together at a concentration of 500 ng/mL, resulting in a maximum 4.1 % change, which was comparable to precision and accuracy values reported in the literature. After confirming the selectivity of the aptamers, recovery experiments were conducted using spiked commercial serum samples to simulate real samples, and the lowest recovery value obtained was 95.4 %. It was determined that two different aptasensors could be successfully used for the QCM-based detection of CEA in this study.

Etching Rate Analysis Model Based on Quartz Bond Angle Characteristics

This paper proposes a method for classifying crystal planes based on the bond angle characteristics of quartz unit cells and constructs an etch rate model for quartz crystal planes at both macro and micro scales. By omitting oxygen atoms from the quartz cell structure, a method based on bond angle characteristics was established to partition the atomic arrangement of the crystal surface. This approach was used to analyze the etching processes of typical quartz crystal planes (R, r, m, and (0001)), approximating the etching process of crystals as a cyclic removal of certain bond angle characteristics on the crystal planes. This led to the development of an etch rate model based on micro-geometric parameters of crystal planes. Additionally, using the proposed bond angle classification method, the common characteristics of atomic configurations on the crystal plane surfaces within the X_cut type were extracted and classified into seven regions, further expanding and applying the etch rate model. The computational results of this model showed good agreement with experimental data, indicating the rationality and feasibility of the proposed method. These also provide a theoretical basis for understanding the microstructural changes during quartz-based MEMS etching processes.

Peroxymonosulfate-activated photocatalytic degradation of norfloxacin via a dual Z-scheme g-C3N5/BiVO4/CoFe − LDH heterojunction: Operation and mechanistic insights

The design of novel dual Z-scheme heterojunction plays a significant path in eradicating organic contaminants via enriched charge carrier separation. Herein, a wet chemical method was used to synthesize ternary g-C3N5/BiVO4/CoFe–LDH (CBCF) nanocomposites, and their corresponding abilities were characterized as follows: crystal phases, optical properties, surface morphologies, and compositions. The g-C3N5/BiVO4/CoFe–LDH-30% (CBCF-3) sample optimized the removal efficiency of norfloxacin (NOR) by up to 95.3% through peroxymonosulfate (PMS) activation in a visible light medium. The combined effects from the Vis/PMS/CBCF-3 catalytic system led to 7-times higher degradation efficiency than visible light only system. This improved performance was attributed to the generation of reactive radical species because of higher PMS utilization and an effective Z-charge transfer process from well-oriented band structures. Moreover, scavenging tests and electron spin resonance analysis revealed the production of active radical and non-radical species, namely •OH, SO4•−, •O2−, and 1O2. Based on the appropriate experimental analysis, the expected NOR degradation mechanism and possible pathways were proposed. Then, the toxicity evaluation results revealed that the intermediate products may not have an adverse effect on the aquatic ecosystems. This research study provides a positive outcome for wastewater remediation using enriched dual Z-scheme mechanism.

Interface Engineering Induced Multi-Scale Self-Assembly NiFe-LDH Heterostructures for High-Performance Water Electrolysis.

Confronted with the pressing issue of energy scarcity, the development of an economical and potent bifunctional catalyst is of paramount importance. We adopt an interface engineering strategy to modify the surface of NiFe-LDH nanoplates with O2 plasma treatment. This process enhances the local electric field of NiFe-LDH, resulting in the formation of a self-assembled polycrystalline nanowire array on the nanoplate surface. After O2 plasma treatment for 30 min, the NiFe-LDH-P30 not only formed a heterostructure with rough surface, but also regulated the exposure of crystal surfaces. Due to the strong interface coupling between the self-assembled 3D nanoflowers, 2D nanoplates and 1D nanowires, the NiFe-LDH-P30 exhibits an excellent structural stability. Moreover, it demonstrated exceptional HER and OER activities in alkaline condition, achieving a low overpotentials of 154 mV and 242 mV at 10 mA cm-2, respectively. Furthermore, NiFe-LDH-P30 as the dual-electrode material for the cathode and anode in the process of water splitting results in a low voltage of 1.63 V at a current density of 10 mA cm-2. Through the strategic application of interface engineering, this work has pioneered a novel approach to the creation of transition metal-based electrocatalysts, which is benefit to a range of practical energy applications.

Antifungal and visible light driven photocatalytic degradation of Brilliant green dye by Ceria–Zirconia Nanocomposites

Green synthesis is a simple, eco-friendly and emerging approach of synthesizing CeriaZirconia nanocomposites (CZ NCs) and evaluates its performance for the photocatalytic treatment of industrial waste water. Ceria-Zirconia NCs were synthesized using leaf extracts of Jatropha gossypiifolia L. for the application towards photocatalytic degradation of Brilliant Green (BG) dye under visible light irradiation. The Ceria-Zirconia NCs were characterized by Fourier Transform Infrared (FT-IR) spectrometer, UV-Visible spectrophotometer, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDX). FT-IR spectra indicate the presence of amino, carboxyl and hydroxyl functional groups on the crystal surface of the nanocomposites. In UV-Visible spectra, the nanocomposites exhibit the highest absorbance at about 252 and 340 nm. From XRD, the average crystallite size of the CeriaZirconia NCs were found to be 80.36nm, while SEM images showed the spherical clusters of agglomerated nanocomposites. The elemental composition and the purity of the nanocomposites were confirmed by Energy Dispersive X-ray Spectroscopy. The superior antifungal activity was investigated against with the fungal strains Candida albicans, Aspergillus niger and penicillium.

Surface and interface chemistry of bromine–methanol‐etched Cd0.9Zn0.1Te crystals

Chemical polishing or chemo‐mechanical polishing is crucial as a last step of surface preparation to remove the damaged layer and contaminants from the surface of CdZnTe crystals. The bromine–methanol solution is widely used for this purpose. However, bromine–methanol solution enriches the surface with Te and results in poor performance of CdZnTe crystals. In this study, the effect of the chemical polishing with 5% bromine–methanol solution on the surface and at the interface is investigated and it is demonstrated that etching duration strongly influences surface stoichiometry and interface contaminants. The evolution of the surface topography with etching and chemical changes are presented. It is shown that after 90 s etching/polishing, subsurface damage is removed and Te enrichment is minimum. Moreover, interface layer thickness is the smallest for 90 s etching duration. It is presented that further increase in the etching duration disturbs the surface stoichiometry and interface depth. It also calculated that 90 s of etching shows low interface barrier and symmetrical current–voltage curve.

Adsorption structure and properties of Ni/Fe electrodeposition interface: a DFT study

The density functional theory calculations of the adsorption model of NiCl2, Ni, and Cl on the Fe surface, as well as interface electronic properties, provide theoretical guidance for improving the Ni electrodeposition process. The adsorption properties of these three species on the Fe (100) crystal surface at different coverages, and the adsorption properties of the single Ni on three different crystal surfaces of Fe (100), Fe (110), and Fe (111), were studied through calculations of adsorption energy, charge density, charge occupancy, and DOS. The results indicate that the H sites are the most favorable for the adsorption of Ni and Cl on the Fe (100) surface. T sites, B sites, and H sites are all potential adsorption sites for NiCl2. The order of adsorption strength is Ni > Cl > NiCl2. In response to changes in charge, the adsorption effect exhibits a negative correlation with surface coverage. In addition, the hybridization of Ni’s 3d orbitals, Cl’s 3p orbitals, and Fe’s 3d orbitals changes the distribution of the interface charge, resulting in an increase of the charge in the Fe surface. Ni exhibits better adsorption performance on Fe (100) surface, driven by the lattice structure, surface electron configuration, and Ni–Fe atomic interactions.

Phosphate/Silicate Ratio Allows for Fine-Tuning of Bioactive Glass Crystallisation and Glass-Ceramic Microstructure

A combination of XRD, solid-state NMR and state-of-the-art imaging techniques were used to investigate how the calcium orthophosphate/calcium silicate ratio affects the crystallisation of bioactive glasses in the system SiO2-P2O5-CaO-CaF2. In the phosphate-free glass, xonotlite, wollastonite and cuspidine crystallised. From 2.4 mol% P2O5, fluorapatite also formed, while the amount of wollastonite decreased. Crystallisation tendency was low for low phosphate contents, while above 3 mol% P2O5 it increased. The phosphate-free glass showed a volume crystallisation mechanism with constant activation energy. By contrast, the glass with the largest phosphate to silicate ratio showed both volume and surface crystallisation, causing a pronounced decrease in activation energy with crystallisation degree. This work shows that by changing the phosphate/silicate ratio we can determine which crystal phases form, obtaining for example fluorapatite-free or wollastonite-free glass-ceramics, depending on the desired application and properties such as mechanical strength or activity in contact with physiological solutions.