Boost the Crystal Installation and Magnetic Features of Cobalt Ferrite/M-Type Strontium Ferrite Nanocomposites Double Substituted by La3+ and Sm3+ Ions (2CoFe2O4/SrFe12−2xSmxLaxO19)

Spinel cobalt ferrite/hexagonal strontium hexaferrite (2CoFe₂O₄/SrFe_12−2xSm_xLa_xO₁₉; x = 0.2, 0.5, 1.0, 1.5) nanocomposites were fabricated using the tartaric acid precursor pathway, and the effects of La³⁺–Sm³⁺ double substitution on the formation, structure, and magnetic properties of CoFe₂O₄/SrFe_12−2xSm_xLa_xO₁₉ nanocomposite at different annealing temperatures were assayed through X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. A pure 2CoFe₂O₄/SrFe₁₂O₁₉ nanocomposite was obtained from the tartrate precursor complex annealed at 1100 °C for 2 h. The substitution of Fe³⁺ ion by Sm³–⁺La³⁺ions promoted the formation of pure 2CoFe₂O₄/SrFe₁₂O₁₉ nanocomposite at 1100 °C. The positions and intensities of the strongest peaks of hexagonal ferrite changed after Sm³⁺–La³⁺ substitution at ≤1100 °C. In addition, samples with an Sm³⁺–La³⁺ ratio of ≥1.0 annealed at 1200 °C for 2 h showed diffraction peaks for lanthanum cobalt oxide (La₃Co₃O₈; dominant phase) and samarium ferrite (SmFeO₃). The crystallite size range at all constituent phases was in the nanocrystalline range, from 39.4 nm to 122.4 nm. The average crystallite size of SrFe₁₂O₁₉ phase increased with the number of Sm³⁺–La³⁺ substitutions, whereas that of CoFe₂O₄ phase decreased with an x of up to 0.5. La–Sm co-doped ion substitution increased the saturation magnetization (Ms) value and the subrogated ratio to 0.2, and the Ms value decreased with the increasing number of double substitutions. A high saturation magnetization value (Ms = 69.6 emu/g) was obtained using a La³⁺–Sm³⁺ co-doped ratio of 0.2 at 1200 for 2 h, and a high coercive force value (Hc = 1192.0 Oe) was acquired using the same ratio at 1000 °C.     

Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing

A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated that: (1) more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrO_x; (2) the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N₂ ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 10¹² cm⁻² for as-deposited sample to 4.55 × 10¹² cm⁻² for the 800 °C annealed one. In addition, the leakage current density increase from about 10⁻⁶ A/cm² at V_g = +0.5 V for the as-deposited sample to 10⁻³ A/cm² at V_g = +0.5 V for the 900 °C annealed one.     

The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

The surface structure and adjacent interior of commercially available silicon nanopowder (np-Si) was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (“crystalline”) silicon atoms, each bound tetrahedrally to four other silicon atoms. From a combination of ¹H, ²⁹Si and ²H magic-angle-spinning (MAS) NMR results and quantum mechanical ²⁹Si chemical shift calculations, silicon atoms on the surface of “as-received” np-Si were found to exist in a variety of chemical structures, with apparent populations in the order (a) (Si–O–)₃Si–H > (b) (Si–O–)₃SiOH > (c) (HO–)_nSi(Si)_m(–OSi)_4−m−n ≈ (d) (Si–O–)₂Si(H)OH > (e) (Si–O–)₂Si(–OH)₂ > (f) (Si–O–)₄Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si–Si bond or a Si–O–Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O₂ gas at elevated temperature. A deliberately oxidized sample displays an increased population of (Si–O–)₃Si–H, as well as (Si–O–)₃SiOH sites. Considerable heterogeneity of some surface structures was observed. A combination of ¹H and ²H MAS experiments provide evidence for a substantial population of silanol (Si–OH) moieties, some of which are not readily H-exchangeable, along with the dominant Si–H sites, on the surface of “as-received” np-Si; the silanol moieties are enhanced by deliberate oxidation. An extension of the DEPTH background suppression method is also demonstrated that permits measurement of the T₂ relaxation parameter simultaneously with background suppression.     

Structural Properties of Zinc Oxide Nanorods Grown on Al-Doped Zinc Oxide Seed Layer and Their Applications in Dye-Sensitized Solar Cells

We fabricated zinc oxide (ZnO) nanorods (NRs) with Al-doped ZnO (AZO) seed layers and dye-sensitized solar cells (DSSCs) employed the ZnO NRs between a TiO₂ photoelectrode and a fluorine-doped SnO₂ (FTO) electrode. The growth rate of the NRs was strongly dependent on the seed layer conditions, i.e., thickness, Al dopant and annealing temperature. Attaining a large particle size with a high crystallinity of the seed layer was vital to the well-aligned growth of the NRs. However, the growth was less related to the substrate material (glass and FTO coated glass). With optimized ZnO NRs, the DSSCs exhibited remarkably enhanced photovoltaic performance, because of the increase of dye absorption and fast carrier transfer, which, in turn, led to improved efficiency. The cell with the ZnO NRs grown on an AZO seed layer annealed at 350 °C showed a short-circuit current density (J_SC) of 12.56 mA/cm², an open-circuit voltage (V_OC) of 0.70 V, a fill factor (FF) of 0.59 and a power conversion efficiency (PCE, η) of 5.20% under air mass 1.5 global (AM 1.5G) illumination of 100 mW/cm².     

Influence of Cu Content on Structure,Thermal Stability and Magnetic Properties in Fe72−xNi8Nb4CuxSi2B14 Alloys

The effect of substitution of Fe by Cu on the crystal structure and magnetic properties of Fe_72−xNi₈Nb₄Cu_xSi₂B₁₄ alloys (x = 0.6, 1.1, 1.6 at.%) in the form of ribbons was investigated. The chemical composition of the materials was established on the basis of the calculated minima of thermodynamic parameters: Gibbs free energy of amorphous phase formation ΔG^amorph (minimum at 0.6 at.% of Cu) and Gibbs free energy of mixing ΔG^mix (minimum at 1.6 at.% of Cu). The characteristic crystallization temperatures T_x1onset and T_x1 of the alpha-iron phase together with the activation energy E_a for the as-spun samples were determined by differential scanning calorimetry (DSC) with a heating rate of 10–100 °C/min. In order to determine the optimal soft magnetic properties, the wound cores were subjected to a controlled isothermal annealing process in the temperature range of 340–640 °C for 20 min. Coercivity Hc, saturation induction Bs and core power losses at B = 1 T and frequency f = 50 Hz P_10/50 were determined for all samples. Moreover, for the samples with the lowest Hc and P_10/50, the magnetic losses were determined in a wider frequency range 50 Hz–400 kHz. The real and imaginary parts of the magnetic permeability µ′, µ″ along with the cut-off frequency were determined for the samples annealed at 360, 460, and 560 °C. The best soft magnetic properties (i.e., the lowest value of Hc and P_10/50) were observed for samples annealed at 460 °C, with Hc = 4.88–5.69 A/m, Bs = 1.18–1.24 T, P_10/50 = 0.072–0.084 W/kg, µ′ = 8350–10,630 and cutoff frequency at 8–9.3 × 10⁴ Hz. The structural study of as-spun and annealed ribbons was carried out using X-ray diffraction (XRD) and a transmission electron microscope (TEM).     

Annealing Effect on the Structural and Optical Properties of Sputter-Grown Bismuth Titanium Oxide Thin Films

The aim of this work is to assess the evolution of the structural and optical properties of Bi_xTi_yO_z films grown by rf magnetron sputtering upon post-deposition annealing treatments in order to obtain good quality films with large grain size, low defect density and high refractive index similar to that of single crystals. Films with thickness in the range of 220–250 nm have been successfully grown. After annealing treatment at 600 °C the films show excellent transparency and full crystallization. It is shown that to achieve larger crystallite sizes, up to 17 nm, it is better to carry the annealing under dry air than under oxygen atmosphere, probably because the nucleation rate is reduced. The refractive index of the films is similar under both atmospheres and it is very high (n =2.5 at 589 nm). However it is still slightly lower than that of the single crystal value due to the polycrystalline morphology of the thin films.     

Polar and Non-Polar Zn1−xMgxO:Sb Grown by MBE

The article presents a systematic study of Sb-doped Zn_1−xMg_xO layers, with various concentrations of Mg, that were successfully grown by plasma-assisted MBE on polar a- and c-oriented and non-polar r-oriented sapphire substrates. X-ray diffraction confirmed the polar c-orientation of alloys grown on c-and a-oriented sapphire and non-polar structures grown on r-oriented substrates. A uniform depth distribution of the Sb dopant at level of 2 × 10²⁰ cm⁻³ was determined by SIMS measurements. Raman spectroscopy revealed the presence of Sb-related modes in all samples. It also showed that Mg alloying reduces the compressive strain associated with Sb doping in ZnO. XPS analysis indicates that the chemical state of Sb atoms in ZnMgO is 3+, suggesting a substitutional position of Sb_Zn, probably associated with two V_Zn vacancies. Luminescence and transmission spectra were measured to determine the band gaps of the Zn_1−xMg_xO layers. The band gap energies extracted from the transmittance measurements differ slightly for the a, c, and r substrate orientations, and the differences increase with increasing Mg content, despite identical growth conditions. The differences between the energy gaps, determined from transmission and PL peaks, are closely correlated with the Stokes shift and increase with the Mg content in the analyzed series of ZnMgO layers.     

On Structural Rearrangements during the Vitrification of Molten Copper

We utilise displacement analysis of Cu-atoms between the chemical bond-centred Voronoi polyhedrons to reveal structural changes at the glass transition. We confirm that the disordered congruent bond lattice of Cu loses its rigidity above the glass transition temperature (T_g) in line with Kantor–Webman theorem due to percolation via configurons (broken Cu-Cu chemical bonds). We reveal that the amorphous Cu has the T_g = 794 ± 10 K at the cooling rate q = 1 × 10¹³ K/s and that the determination of T_g based on analysis of first sharp diffraction minimum (FDSM) is sharper compared with classical Wendt–Abraham empirical criterion.     

The Effects of Zr Doping on the Optical,Electrical and Microstructural Properties of Thin ZnO Films Deposited by Atomic Layer Deposition

Transparent conducting oxides (TCOs), with high optical transparency (≥85%) and low electrical resistivity (10⁻⁴ Ω·cm) are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant materials. In the current study, we dope Zr into thin ZnO films grown by atomic layer deposition (ALD) to target properties of an efficient TCO. The effects of doping (0–10 at.% Zr) were investigated for ~100 nm thick films and the effect of thickness on the properties was investigated for 50–250 nm thick films. The addition of Zr⁴⁺ ions acting as electron donors showed reduced resistivity (1.44 × 10⁻³ Ω·cm), increased carrier density (3.81 × 10²⁰ cm⁻³), and increased optical gap (3.5 eV) with 4.8 at.% doping. The increase of film thickness to 250 nm reduced the electron carrier/photon scattering leading to a further reduction of resistivity to 7.5 × 10⁻⁴ Ω·cm and an average optical transparency in the visible/near infrared (IR) range up to 91%. The improved n-type properties of ZnO: Zr films are promising for TCO applications after reaching the targets for high carrier density (>10²⁰ cm⁻³), low resistivity in the order of 10⁻⁴ Ω·cm and high optical transparency (≥85%).     

Microstructures of HfOx Films Prepared via Atomic Layer Deposition Using La(NO3)3·6H2O Oxidants

Hafnium oxide (HfO_x) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfO_x films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO₃)₃·6H₂O solution (LNS) as an oxidant was investigated. The atomic layer deposition (ALD) conditions were optimized, and the chemical state, surface morphology, and microstructure of the prepared films were characterized. Furthermore, to better understand the effects of LNS on the deposition process, HfO_x films deposited using a conventional oxidant (H₂O) were also prepared. The ALD process using LNS was observed to be self-limiting, with an ALD temperature window of 200–350 °C and a growth rate of 1.6 Å per cycle, two times faster than that with H₂O. HfO_x films deposited using the LNS oxidant had smaller crystallites than those deposited using H₂O, as well as more suboxides or defects because of the higher number of grain boundaries. In addition, there was a difference in the preferred orientations of the HfO_x films deposited using LNS and H₂O, and consequently, a difference in surface energy. Finally, a film growth model based on the surface energy difference was proposed to explain the observed growth rate and crystallite size trends.     

Drop–Dry Deposition of Ni(OH)2 Precursors for Fabrication of NiO Thin Films

Drop–dry deposition (DDD) is a method of depositing thin films by heating and drying the deposition solution dropped on a substrate. We prepared Ni(OH)₂ precursor thin films by DDD and annealed them in air to prepare NiO thin films. The appropriate deposition conditions were found by changing the number of drop–dry cycles and the concentrations of chemicals in the solution, and the Ni(OH)₂ precursor film with a thickness of 0.3 μm and optical transmittance of more than 95% was successfully deposited. Raman and X-ray diffraction measurements were performed, and it was found that the NiO film was successfully fabricated after annealing at 400 °C. The p-type conductivity of the annealed film was confirmed by photoelectrochemical measurements. In addition, we prepared n-type ZnO by electrochemical deposition on NiO thin films. The current–voltage measurement results show that the ZnO/NiO heterojunction had rectification properties.     

Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films

Reactively sputtered nickel oxide (NiO_x) films provide transparent, antireflective, electrically conductive, chemically stable coatings that also are highly active electrocatalysts for the oxidation of water to O₂(g). These NiO_x coatings provide protective layers on a variety of technologically important semiconducting photoanodes, including textured crystalline Si passivated by amorphous silicon, crystalline n-type cadmium telluride, and hydrogenated amorphous silicon. Under anodic operation in 1.0 M aqueous potassium hydroxide (pH 14) in the presence of simulated sunlight, the NiO_x films stabilized all of these self-passivating, high-efficiency semiconducting photoelectrodes for >100 h of sustained, quantitative solar-driven oxidation of water to O₂(g).The oxidation of water to O₂(g) is a critical process for the sustainable solar-driven generation of fuels, including the generation of carbon-based fuels by the solar-driven reduction of carbon dioxide as well as the generation of H₂(g) by solar-driven water splitting (1, 2). Many technologically important semiconductors, including silicon (Si), Group III–V materials such as gallium arsenide (GaAs), and Group II–VI materials such as cadmium telluride (CdTe), have optimal band gaps for use in an integrated, dual light-absorber, solar-fuels generator (3). However, these materials are generally unstable and corrode or passivate rapidly when operated under photoanodic conditions in aqueous electrolytes. Furthermore, the efficient operation of a passive and intrinsically safe water-splitting system requires the use of either strongly alkaline or acidic electrolytes, presenting additional constraints on the stability of the photoanodes and electrocatalysts (4–6).The search for new, stable compound semiconductors or molecular systems for water oxidation has thus far yielded materials with low efficiencies and/or limited stability (7, 8). An alternative strategy for addressing the lack of materials known to be stable under the conditions needed for the efficient oxidation of water is to protect high-efficiency, technologically important semiconductors to enable their use in integrated solar-fuels generators by using buried semiconductor junctions to form a photovoltaic (PV)-biased electrosynthetic cell (9). In this approach, the surface of the otherwise unstable semiconducting light absorber is covered by a layer of a stable and partially transparent conductive oxide or metal, which serves either as a Schottky barrier or as a transparent conductive contact to a photoelectrode that contains a buried junction to provide the requisite charge separation. Metallized contacts to radial p-n junctions in Si microspheres have been used to effect the unassisted solar-driven splitting of HI(aq) and HBr(aq) (10), and metallized contacts have been used in conjunction with triple-junction–based hydrogenated amorphous Si (a-Si:H) photovoltaics for PV-biased electrosynthetic water splitting (11–13). The protective layers used in an integrated photoanode generally require a separate electrocatalyst for the oxidation of water on the electrode surface. Further, the entire assembly must be chemically compatible with and stable in the electrolytes and at the electrode potentials associated with photoelectrochemical water oxidation (14). Metals, metal alloys, semiconductors, degenerately doped transparent conducting oxides, catalytic transition-metal compounds, organic polymers, and surface functionalization methods have all been explored for this purpose, with only limited stability, limited electrical properties at junctions, and/or limited activity for water oxidation observed to date (14).Sputtered nickel oxide (NiO_x) films have been recently shown to be optically transparent, antireflective, conductive, stable, and highly catalytically active while protecting n-Si and np⁺-Si photoanodes in contact with aqueous 1.0-M KOH for the photoelectrochemical oxidation of water (15, 16). For np⁺-Si photoanodes, such an approach allowed for the stable production of O₂(g) for >1,200 h of continuous operation under 1-Sun simulated solar illumination, with a photocurrent-onset potential of −180 mV relative to the equilibrium water-oxidation potential and current densities in excess of 29 mA⋅cm⁻² at the equilibrium water-oxidation potential. We demonstrate herein that this protection strategy can be extended to semiconducting materials used in commercial photovoltaic solar cells and in high-efficiency devices, specifically textured crystalline Si passivated with a layer of amorphous Si, known as a heterojunction Si (HTJ-Si) device with a typical structure of (p⁺-a-Si|i-a-Si|n-c-Si|i-a-Si|n⁺-a-Si); n-i hydrogenated amorphous Si (a-Si:H) structures; and single-crystalline n-type CdTe light absorbers. All of these materials have band gaps appropriate (1–2 eV) for use in integrated solar fuel-generation devices, and this work demonstrates that the NiO_x protection strategy is effective on both single-crystalline and noncrystalline semiconductors.     

A Research on Delayed Thermal Depolarization,Electric Properties,and Stress in (Bi0.5Na0.5)TiO3-Based Ceramic Composites

Depolarization behavior is one of the main shortcomings of (Bi_0.5Na_0.5)TiO₃-based ceramics. Considering the undesirable efficiency of traditional modification methods, in this paper a series of 0–3 type ceramic composites 0.85(Bi_0.5Na_0.5)TiO₃-0.11(Bi_0.5K_0.5)TiO₃-0.04BaTiO₃-x mol% ZnO (BNKT-BT-xZnO)) were synthesized by introducing ZnO nanoparticles. The results of the X-ray diffraction pattern (XRD) and energy dispersive spectroscopy (EDS) demonstrate that the majority of ZnO nanoparticles grow together to form enrichment regions, and the other Zn²⁺ ions diffuse into the matrix after sintering. With ZnO incorporated, the ferroelectric–ergodic relaxor transition temperature, T_F-R, and depolarization temperature, T_d, increase to above 120 °C and 110 °C, respectively. The research on temperature-dependent P–E loops verifies an attenuated ergodic degree induced by ZnO incorporation. For this reason, piezoelectric properties can be well-maintained below 110 °C. The electron backscatter diffraction (EBSD) was employed to investigate the stress effect. Orientation maps reveal the random orientation of all grains, excluding the impact of texture on depolarization. The local misorientation image shows that more pronounced strain appears near the boundaries, implying stress is more concentrated there. This phenomenon supports the hypothesis that potential stress suppresses depolarization. These results demonstrate that the depolarization behavior is significantly improved by the introduction of ZnO. The composites BNKT-BT-xZnO are promising candidates of lead-free ceramics for practical application in the future.     

Effect of Cooling Rate on the Microstructure Evolution and Mechanical Properties of Iron-Rich Al–Si Alloy

The mechanical properties of iron-rich Al–Si alloy is limited by the existence of plenty of the iron-rich phase (β-Al₅FeSi), whose unfavorable morphology not only splits the matrix but also causes both stress concentration and interface mismatch with the Al matrix. The effect of the cooling rate on the tensile properties of Fe-rich Al–Si alloy was studied by the melt spinning method at different rotating speeds. At the traditional casting cooling rate of ~10 K/s, the size of the needle-like β-Al₅FeSi phase is about 80 μm. In contrast, the size of the β-Al₅FeSi phase is reduced to 500 nm and the morphology changes to a granular morphology with the high cooling rate of ~10⁴ K/s. With the increase of the cooling rate, the morphology of the β-Al₅FeSi phase is optimized, meanwhile the tensile properties of Fe-rich Al–Si alloy are greatly improved. The improved tensile properties of the Fe-rich Al-Si alloy is attributed to the combination of Fe-rich reinforced particles and the granular silicon phase provided by the high cooling rate of the melt spinning method.     

Ti-doped ZnO Thin Films Prepared at Different Ambient Conditions: Electronic Structures and Magnetic Properties

We present a comprehensive study on Ti-doped ZnO thin films using X-ray Absorption Fine Structure (XAFS) spectroscopy. Ti K edge XAFS spectra were measured to study the electronic and chemical properties of Ti ions in the thin films grown under different ambient atmospheres. A strong dependence of Ti speciation, composition, and local structures upon the ambient conditions was observed. The XAFS results suggest a major tetrahedral coordination and a 4+ valence state. The sample grown in a mixture of 80% Ar and 20% O₂ shows a portion of precipitates with higher coordination. A large distortion was observed by the Ti substitution in the ZnO lattice. Interestingly, the film prepared in 80% Ar, 20% O₂ shows the largest saturation magnetic moment of 0.827 ± 0.013 µ_B/Ti.     

Electrical Properties and Interfacial Studies of HfxTi1–xO2 High Permittivity Gate Insulators Deposited on Germanium Substrates

In this research, the hafnium titanate oxide thin films, Ti_xHf_1–xO₂, with titanium contents of x = 0, 0.25, 0.9, and 1 were deposited on germanium substrates by atomic layer deposition (ALD) at 300 °C. The approximate deposition rates of 0.2 Å and 0.17 Å per cycle were obtained for titanium oxide and hafnium oxide, respectively. X-ray Photoelectron Spectroscopy (XPS) indicates the formation of GeO_x and germanate at the interface. X-ray diffraction (XRD) indicates that all the thin films remain amorphous for this deposition condition. The surface roughness was analyzed using an atomic force microscope (AFM) for each sample. The electrical characterization shows very low hysteresis between ramp up and ramp down of the Capacitance-Voltage (CV) and the curves are indicative of low trap densities. A relatively large leakage current is observed and the lowest leakage current among the four samples is about 1 mA/cm² at a bias of 0.5 V for a Ti_0.9Hf_0.1O₂ sample. The large leakage current is partially attributed to the deterioration of the interface between Ge and Ti_xHf_1–xO₂ caused by the oxidation source from HfO₂. Consideration of the energy band diagrams for the different materials systems also provides a possible explanation for the observed leakage current behavior.     

Enhanced Corrosion Resistance of Layered Double Hydroxide Films on Mg Alloy: The Key Role of Cationic Surfactant

In this study, dense anticorrosion magnesium–aluminum layered double hydroxide (MgAl-LDH) films were prepared for the first time by introducing a cationic surfactant tetradecyltrimethyl ammonium bromide (TTAB) in the process of in situ hydrothermal synthesis of Mg-Al LDH films on an AZ31 magnesium alloy. Results of XRD, FTIR, and SEM confirmed that TTAB forms the MgAl-LDH-TTAB, although TTAB cannot enter into LDH layers, and MgAl-LDH-TTAB powders are much smaller and more homogenous than MgAl-CO₃²⁻-LDH powders. Results of SEM, EDS, mapping, and XPS confirmed that TTAB forms the MgAl-LDH-TTAB films and endows LDH films with denser structure, which provides films with better shielding efficiency. Results of potentiodynamic polarization curves (PDP) and electrochemical impedance spectroscopy (EIS) confirmed that MgAl-LDH-TTAB_{x g} films have better corrosion resistance than an MgAl-CO₃²⁻-LDH film. The corrosion current density (i_corr) of the MgAl-LDH-TTAB_{0.35 g} film in 3.5 wt.% NaCl solution was reduced to 1.09 × 10⁻⁸ A.cm⁻² and the |Z|_{f = 0.05 Hz} value was increased to 4.48 × 10⁵ Ω·cm². Moreover, the increasing concentration of TTAB in MgAl-LDH-TTAB_{x g} (x = 0.025, 0.05, 0.1, 0.2 and 0.35) provided denser outer layer LDH films and thereby increased the corrosion resistance of the AZ31 Mg alloy. Additionally, the |Z|_{f = 0.05 Hz} values of the MgAl-LDH-TTAB_{0.35 g} film still remained at 10⁵ Ω·cm² after being immersed in 3.5 wt.% NaCl solution for 168 h, implying the good long-term corrosion resistance of MgAl-LDH-TTAB_{x g} films. Therefore, introducing cationic surfactant in the process of in situ hydrothermal synthesis can be seen as a novel approach to creating efficient anticorrosion LDH films for Mg alloys.     

Synthesis and Characterization of Al- and SnO2-Doped ZnO Thermoelectric Thin Films

The effect of SnO₂ addition (0, 1, 2, 4 wt.%) on thermoelectric properties of c-axis oriented Al-doped ZnO thin films (AZO) fabricated by pulsed laser deposition on silica and Al₂O₃ substrates was investigated. The best thermoelectric performance was obtained on the AZO + 2% SnO₂ thin film grown on silica, with a power factor (PF) of 211.8 μW/m·K² at 573 K and a room-temperature (300 K) thermal conductivity of 8.56 W/m·K. PF was of the same order of magnitude as the value reported for typical AZO bulk material at the same measurement conditions (340 μW/m·K²) while thermal conductivity κ was reduced about four times.     

Challenges and Strategies in the Synthesis of Mesoporous Alumina Powders and Hierarchical Alumina Monoliths

A new rapid, very simple and one-step sol-gel strategy for the large-scale preparation of highly porous γ-Al₂O₃ is presented. The resulting mesoporous alumina materials feature high surface areas (400 m² g⁻¹), large pore volumes (0.8 mL g⁻¹) and the γ-Al₂O₃ phase is obtained at low temperature (500 °C). The main advantages and drawbacks of different preparations of mesoporous alumina materials exhibiting high specific surface areas and large pore volumes such as surfactant-nanostructured alumina, sol-gel methods and hierarchically macro-/mesoporous alumina monoliths have been analyzed and compared. The most reproducible synthesis of mesoporous alumina are given. Evaporation-Induced Self-Assembly (EISA) is the sole method to lead to nanostructured mesoporous alumina by direct templating, but it is a difficult method to scale-up. Alumina featuring macro- and mesoporosity in monolithic shape is a very promising material for in flow applications; an optimized synthesis is described.     

Design of Refining Slag Based on Structural Modifications Associated with the Boron Removal for SoG-Si

Solar grade silicon (SoG-Si) is the core material of solar cells. The removal of boron (B) has always been a challenge in the preparation of high purity Si. Slag refining has always been considered as one of the effective methods to remove B, but the design of refined slag has been limited by the cognition of the relationship between slag structure and impurity removal, and can only rely on the apparent basicity and oxygen potential adjustment of slag based on a large number of conditional experiments. In order to clarify the B removal mechanism of slag refining from Si, nuclear magnetic resonance (NMR) and Raman vibrational spectroscopy were used to investigate in detail the behavior and state of B and aluminum (Al) in the SiO₂–CaO–Al₂O₃–B₂O₃ slag. The role of the degree of B–Si cross linking on the B activity in slag was highlighted by comparing the partition ratio (L_B) between slag and Si. Q² structural unit of slag is an important site for capturing B. BO₄ (1B, 3Si) species is the main form of connection between B and silicate networks, which determines the activity of B in the slag. The addition of Al₂O₃ into SiO₂–CaO slag can change the relative fraction of Q² and BO₄ (1B, 3Si). Increasing Al₂O₃ content from 0 to about 20 wt% can lead to the overall increase of Q² population, and a tendency to decrease first and then increase of BO₄ (1B, 3Si) fraction under both basicity conditions (0.6 and 1.1). When Al₂O₃ content is less than 10 ± 1 wt%, the decrease of BO₄ (1B, 3Si) population plays a major role in deteriorating the connectivity between B and aluminosilicate network, which leads to a higher activity of B. When the Al₂O₃ content is greater than 10 ± 1 wt%, B is incorporated into the silicate network more easily due to the formation of more Q² and BO₄ (1B, 3Si), which contributes to a rapid decline in activity of B in slag.