Comparison between microwave and conventional calcination techniques in regard to reactivity and morphology of co-precipitated BaTiO3 powder,and the electrical and energy storage properties of the sintered samples

Barium titanate (BaTiO₃) nanopowders were synthesized by an aqueous co-precipitation method followed by calcination. Either 2.45 GHz microwaves or conventional heating was used in order to investigate the impact of these techniques on the synthesis time, microstructure, and electrical properties of the materials. The heating temperatures ranged from 620 °C to 810 °C. X-ray diffraction (XRD) revealed pure BaTiO₃ formation by microwave heating in a noticeably shorter time (five minutes) compared to conventional heating (3 h). Field emission scanning electron microscopy (FESEM) results confirmed that the microwave process led to nanocube formation, whereas in the conventional procedure, the particles tended to form spherical shapes. To evaluate the electrical properties, the samples heated at 620 °C were conventionally sintered at 1280 °C, 1330 °C, and 1380 °C. Higher dielectric, piezoelectric, and ferroelectric properties and more energy-saving efficiency (ε_r=1012, tan δ=0.035 d₃₃=85 pC/N, p_r=6.2 µC/cm² and η=48% respectively) were achieved in the microwave-heated BaTiO₃ sintered at 1380 °C compared to the conventionally heated BaTiO₃ (ε_r=824, tan δ=0.030 d₃₃=75 pC/N, p_r=5 µC/cm² and η=27%) demonstrating that microwave calcination substantially affects the final electrical properties.     

Synthesis and thermal performance of polymer precursor for ZrC ceramic

A novel ZrC preceramic precursor (PZC) was compounded via liquid phase chemical reaction without any organic solvent choosing ZrOCl₂·8H₂O and polyvinyl alcohol as Zr source and C source, respectively. The composition and structure of ZrC precursor were analysed through XRD, FT-IR, XPS and SEM. The results showed both Zr-O-C bonds and Zr-O bonds existed in the precursor. The results observed by SEM showed that many irregular particles were generated, whose particle sizes were mainly in the range of 0.2–3 μm. In addition, particle aggregation can be easily observed. Besides, the thermal property and pyrolysis process of PZC were studied. In accordance with XRD, the initial temperature of the earliest detection of ZrC in pyrolysis products of PZC was 1300 °C. Monoclinic ZrO₂ and tetragonal ZrO₂ can be observed at this temperature as well. Ulteriorly, when the pyrolysis temperature was risen up to 1500 °C, only ZrC ceramic can be found.     

Monodisperse hexagonal SrFe12O19 nanoflake with enchanced magnetic properties

Monodisperse SrFe₁₂O₁₉ (SrM) nanoflakes were successfully fabricated via a modified hydrothermal method. The effects of Fe³⁺/Sr²⁺ (R_F/S) and OH⁻/NO₃⁻ (R_O/N) molar ratio on phase, structure and morphology of the products were investigated by XRD, FT-IR, FESEM, and TEM. Meanwhile, the magnetic properties of the product were investigated via vibrating sample magnetisem (VSM). Results demonstrated that when the R_F/S=5 and R_O/N=2, the single phase SrFe₁₂O₁₉ particles were obtained. The as-obtained SrFe₁₂O₁₉ particles had monodisperse nanoflake structure and nano-micro scale in vertical and horizontal direction of SrM ferrite particle. The magnetic property results showed that such structure SrM ferrite particle had prospective saturation magnetization and coercivity, the largest values of Ms and Hc were 62.96 emu/g and 94.83 kA/m, respectively, which make it have a potential application as magnetic recording media and magneto-optical devices material.     

Chromium substituted copper ferrites via gluconate precursor route

CuFe_2−xCr_xO₄ spinel (0≤x≤2) powders were synthesized by a soft chemistry method—the gluconate multimetallic complex precursor route. The complex precursors were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, thermal analysis and Mössbauer spectroscopy. The oxide powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, Raman and Mössbauer spectroscopy. It was shown that the structure, morphology and magnetic properties of the obtained spinel powders depend on the concentration of Cr³⁺ ion. The XRD of the chromium substituted copper ferrite powders calcined at 700 °C/1 h indicated the formation of a cubic spinel type structure for x=0.5, 1.0 and a tetragonal structure for x=0, 0.2, 2. The crystallite size ranged from 19 nm to 39 nm. The Mössbauer spectroscopy revealed the site occupancy of iron ions, relative abundance and internal hyperfine magnetic fields in both tetrahedral and cubic CuFe_2−xCr_xO₄ spinels.     

Local Structure Investigation in Multiferroic BiFeO3–BaTiO3 Ceramics by XAS Technique and Their Relevant Properties

The (1?x)BiFeO₃‐xBaTiO₃ (with x = 0.1, 0.2, 0.3, and 0.4) ceramics were fabricated successfully by solid‐state reaction method. Single‐phase perovskite was obtained in all ceramics, as confirmed by XRD technique. It was observed that 0.7BiFeO₃–0.3BaTiO₃ was the morphotropic phase boundary (MPB) between rhombohedral and cubic phases, as also revealed from ferroelectric and magnetic properties. The simulated and experimental X‐Ray Absorption Spectroscopy (XAS) study revealed that BT in 0.75BF‐0.25BT is possibly taken a rhombohedral structure. Furthermore, the rounded ferroelectric hysteresis loops observed for 0.9BiFeO₃–0.1BaTiO₃ and 0.8BiFeO₃–0.2BaTiO₃ compositions could be attributed to their microstructure and surface charge effects and electron transfer between Fe³⁺ and Fe²⁺ ions. It was also found that high dielectric constant of 0.9BiFeO₃–0.1BaTiO₃ composition was a result of grain and grain‐boundary effects, as observed in SEM micrographs. In addition, a strong signature of dielectric relaxation behavior was observed in this ceramic system with the activation energy 0.467 eV obtained from the Arrhenius' law. Finally, the local structure investigation with XAS technique provided additional information to better understand the electric and magnetic properties in the BF‐BT ceramic system.     

Sintering of ferrite-BaTiO3 bulk particulate composites

Particulate magnetoelectric ceramic composites (PMCC) have received much attention since the last decade. These composites have many technological applications and are usually composed by magnetostrictive and piezoelectric phases. Cobalt-based spinel ferrites are among the most studied magnetostrictive phases for ferrite-based PMCCs and BaTiO₃ is an interesting choice for the piezoelectric phase because it is a lead-free ceramic, unlike the traditional PZT. In this work, cobalt ferrite (FCO) and Ni–Co ferrite (FNICO) were produced by the ceramic method and mixed to BaTiO₃ (TB) in order to further obtain sintered ferrite-BaTiO₃ particulate ceramic composites with a composition of 15 mol% ferrite – 85 mol% BaTiO₃. The ferrites, the BaTiO₃, and the ferrite-BaTiO₃ mixtures were analyzed by dilatometry, thermogravimetry (TG), and calorimetry (DSC) in temperatures up to 1300–1400 °C, with the aim to analyze the sintering behavior and the interactions between both ferrites and the BaTiO₃ during sintering. Sintered TB-FNICO and TB-FCO composite samples were also produced and they were analyzed by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The dilatometry results evidenced that the densification of the ferrite-BaTiO₃ samples is impaired, when compared to the pure ferrite and BaTiO₃ samples. The DSC/TG results evidenced the occurrence of reactions between the ferrites and the BaTiO₃ when they are co-sintered in air or argon atmospheres. The XRD patterns of the sintered composite samples did not exhibit diffraction peaks attributed to a third phase, whilst the punctual EDS analysis showed evidence of diffusion between the ferrite and BaTiO₃ particles.     

Long-sized rods of Al2O3–SiC–TiB2 ceramic composite material obtained by SHS-extrusion: Microstructure,X-ray analysis and properties

Long-sized rods of Al₂O₃–SiC–TiB₂ ceramic composite material were obtained by SHS-extrusion. The material was synthesized by self-propagating high-temperature synthesis (SHS) followed by high-temperature shear deformation. Ceramic samples app up to 465 mm in length and 5 mm in diameter were obtained. According to the results of XRD and SEM the obtained rods have a composite structure. The matrix is Al₂O₃ with distributed titanium diboride and silicon carbide particles. A uniform phase distribution was observed along the entire length of the rod. The microhardness of the matrix was 25–26 GPa, that of the dispersion-strengthening phases - 32–34 GPa. Heat resistance tests showed that during heat treatment at T = 1000 °C for 21 h, the sample specific weight gain and its real rate were 8.3 g/m² and 1 g/(m²∙h), respectively. The density, hardness and electrical resistivity of the samples obtained in this work were 3.27 g/cm³, 19.5 GPa, 3.1∙10⁻⁵ Ohm∙m, respectively.     

Microstructure and electrical properties of BaTiO3/Cu ceramic composite sintered in nitrogen atmosphere

BaTiO₃/xCu composite ceramics with x = 0–30 wt.% were fabricated by the traditional mixing oxide method and their microstructure, relative density, electric conductivity, permittivity and dielectric loss were measured as a function of the Cu mass fraction. The X-ray diffraction (XRD) patterns indicated that the dense composite has no chemical reaction between BaTiO₃ and Cu during sintering, and the relative diffraction intensity of Cu increased with the increase of Cu. The electric properties showed that the percolation threshold of BaTiO₃/Cu composites was x = 0.25 and its conductivity increased as the Cu content increased after that. With increasing Cu content up to 30 wt.%, the permittivity (?_r) markedly increased from ～3000 for monolithic BaTiO₃ to ～8000 at 1 kHz. Additionally, the temperature coefficient of this system was less than 5% in the temperature range of 25–115°C.     

Percolative BaTiO3–Ni composite nanopowders from alkoxide-mediated synthesis

BaTiO₃–Ni nanopowders have been synthesized via an alkoxide-mediated synthesis route through the hydrolysis and condensation of barium hydroxide octahydrate and titanium (IV) isopropoxide in the presence of submicron sized, spherical Ni particles originating from a commercial Ni paste, that was introduced during the preparation procedure. X-ray diffraction (XRD) patterns indicate that nanocomposite powders of the phases BaTiO₃ and Ni could be successfully prepared and tailor-made composition control was confirmed. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the synthesized BaTiO₃ nanoparticles were aggregates of nanosized primary particles as small as 40 nm in diameter. The average Ni particle size was estimated to be about 200 nm. Dilatometric measurements on green compacts of these powders revealed that the shrinkage of BaTiO₃–Ni composites is retarded compared to both, pure BaTiO₃ and Ni. Thermogravimetric analysis (TGA) shows weight losses due to the decomposition of organic binder from Ni paste, the release of water from the surface and of hydroxyl ions from inside the lattice of the BaTiO₃ nanoparticles. With the addition of nickel, the dielectric constant increased slightly due to the percolation effect.     

Dielectric properties and electrocaloric effect of yttrium-modified BaTiO3 ceramics

The electrocaloric effect (ECE) is a promising candidate to replace the vapor-compression cooling technology, which has reached its end of improving the energy utilization efficiency. In the present work, the Y-modified BaTiO₃ ceramics with nominal compositions of Ba(Ti_1-xY_x)O₃ (abbreviated as BT-100xY, where x = 0.0125, 0.025, 0.0375, 0.050 and 0.0625) have been prepared through the conventional solid-state reaction sintering method. The dielectric properties and electrocaloric effect of BT-100xY ceramics have been investigated in detail. The XRD patterns indicate that all the BT-100xY ceramics possess pure perovskite structure without secondary phases. The temperature dependence of dielectric permittivity reveals that the BT-1.25Y, 2.5Y, 3.75Y and 5.0Y are normal ferroelectrics, and the BT-6.25Y is a relaxor ferroelectric. The ECE is calculated through the indirect equation based on Maxwell relation. The BT-2.5Y exhibits the largest ΔT = 1.26 K and the largest ΔS = 1.68 J/kg · K among all the BT-100xY ceramics, and the BT-2.5Y also exhibits the largest ΔT/ΔE = 0.296 × 10^?6 K · m/V and the largest ΔS/ΔE = 0.394 × 10^?6 J · m/kg · K?V. The ECE in our work is comparable with or even larger than that of BaTiO₃-based ceramics previously reported, which indicates that the BT-100xY ceramics are promising ECE materials.     

Enhancement on electric responses of BaTiO3 particles with polymer‐coating

To enhance electric response by polymer coating, BaTiO₃/polymer shell–core composite particles were prepared by emulsion polymerization with polyimide, chitosan, polystyrene, polyacrylic acid, and polyacrylamide. Their micro structure was characterized by transmission electron microscopy, Fourier transform infrared, and automatic X‐ray diffraction, their properties were investigated using optical contact angle and dielectric constant, and their electric responses were studied indirectly by dynamic viscoelasticity analyzer. The results showed that BaTiO₃ cores remained in cubic, the surface hydrophilic of the particles changed as follows: BaTiO₃ > BaTiO₃/PI > BaTiO₃/PAM > BaTiO₃/Chitosan > BaTiO₃/PAA > BaTiO₃/PS, and the dielectric constants of the particles varied with the order of that BaTiO₃ > BaTiO₃/PI > BaTiO₃/PAM > BaTiO₃/Chitosan > BaTiO₃/PAA > BaTiO₃/PS. Eventually, the particles' electric response activities exhibited the order of BaTiO₃/PI > BaTiO₃/PAM > BaTiO₃/Chitosan > BaTiO₃/PAA > BaTiO₃/PS > BaTiO₃. Furthermore, the electric response of the particles showed a chief dependence on polymer‐coating, surface hydrophilic, and dielectric constant. As a result, BaTiO₃ particles' electric response was much enhanced by polymer‐coating, and their compatibility to aqueous continuous phase was ameliorated. For the BaTiO₃/polymer particles, fine surface hydrophile and high dielectric constant dominated the strong response to electric field. Ultimately, BaTiO₃/PI and BaTiO₃/PAM particles possessed the strongest electric response in the five composite particles. The conclusion suggests an effective approach to prepare excellent hydrous electrorheological elastomers. POLYM. COMPOS., 34:897–903, 2013. © 2013 Society of Plastics Engineers     

Microstructure and electrical properties of Er-doped 0.67 Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 ceramics with BaTiO3 templates

In this study, [001]-oriented Er-doped 0.67 Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (0.67PMN-0.33 PT) textured ceramics with different BaTiO₃ (BT) template concentrations were explored. The samples were prepared by tape-casting. Er³⁺ was added to modify the electrical properties of the polycrystalline ceramics, and the BT template was used to improve the texture of polycrystalline ceramics. The 0.67PMN-0.33 PT textured ceramics contained coexisting rhombohedral and tetragonal phases. The ceramics became increasingly textured as the sintering temperature increased up to 1250 °C. The piezoelectric coefficient of 0.67PMN-0.33 PT with 5 wt% BT was 634 pC/N, which is 1.2 times than that of randomly oriented 0.67PMN-0.33 PT. The strain of the ceramic with 5 wt% BT increased by 12.5% relative to a random control specimen. Analysis of the electrical properties and microstructure suggested that the enhancement of the piezoelectric coefficient and strain may be caused by the addition of Er³⁺ and the BT template. First, the directional growth of grains along the template affected the change-of-phase distribution of the system and formed a more adaptive phase. Second, Er³⁺ was substitutionally doped on the A-site of the perovskite to form local heterostructures. Finally, the relaxation components of the templates and Er³⁺ changed in the solid solution with the matrix. The solid solution of the BT templates and Er-doped-matrix powder changed the relaxation degree, which affected the interactions at the polar nanoregions and increased the piezoelectric coefficient of the ceramics.     

Synthesis and surface modification of submicron BaTiO3 powders via a facile surfactant-assisted method

Due to their unique properties, well-dispersed barium titanate (BaTiO₃) ultrafine powders can be used in wide-ranging fields. In the present work, by using barium hydroxide octahydrate (Ba(OH)₂·8H₂O) and α titanic acid (H₄TiO₄) as raw materials, uniform submicron BaTiO₃ powders with tetragonal structure and high degree of crystallinity were prepared via a solid-state reaction method at relatively low temperatures. Moreover, by simply using the stearic acid (St) as the modifier to modify the surface of the aggregated BaTiO₃ powders, well-dispersed BaTiO₃ particles could be obtained, which were then examined by complementary characterizations such as XRD, TEM, HRTEM, SEM, Raman, FT-IR, XPS and EDS. The results indicated that the tetragonal BaTiO₃ particles with submicron-size, good uniformity, and high crystallinity could be prepared at 800 °C for 1 h. Moreover, the addition of St for surface modification proved to be an effective way to avoid the agglomeration of the BaTiO₃ particles to get well-dispersed products, where 1 wt % of St was found to be the optimum concentration. The demonstrated surfactant-assisted surface modification method is expected to be applicable for other ultrafine powders to get well-dispersed particles.     

Dielectric properties and related ferroelectric domain configurations in multiferroic BiFeO3–BaTiO3 solid solutions

Dielectric properties and ferroelectric domain configurations of multiferroic xBaTiO₃–(1 ? x)BiFeO₃ (x = 0.10–0.33) solid solutions synthesized by conventional solid-state reaction, were reported. A structural transition from rhombohedral to pseudo-cubic structures appeared around x = 0.33, and the formation of impurity phase of Bi₂Fe₄O₉ was effectively depressed by doping BaTiO₃. Dielectric constants of xBaTiO₃–(1 ? x)BiFeO₃ solid solutions decreased with increasing the frequency, and the degree of decrease was related to the doping content of BaTiO₃. Transmission electron microscopy images revealed that the ferroelectric domain configurations in the multiferroic BiFeO₃–BaTiO₃ solid solutions with rhombohedral symmetry, exhibited a wavy character whereas a predominant intricate domain structure with fluctuating mottled contrast was observed in the multiferroic BiFeO₃–BaTiO₃ solid solution with pseudo-cubic phase structure. The presence of 1/2{1 1 1} superlattice spots in the selected area electron diffraction patterns taken from the multiferroic BiFeO₃–BaTiO₃ solid solutions with rhombohedral symmetry indicated that the ordered regions have a doubled perovskite unit cell.     

Hydrothermal synthesis and formation mechanism of tetragonal barium titanate in a highly concentrated alkaline solution

Tetragonal cube-shaped barium titanate (BaTiO₃) was produced by the hydrothermal treatment of a peroxo-hydroxide precursor, a single-source amorphous barium titanate precursor, in a highly concentrated sodium hydroxide solution. Phase pure barium titanate with cube-shaped morphology and particle-sizes in the 0.2–0.5 µm range were formed at temperatures above 80 °C. Also, the cube-shaped morphology of the BaTiO₃ product was preceded by spherical- and plate-like morphologies with, respectively, a Ti-excess and Ba-excess. Coinciding with these morphological observations, changes in the reaction product were also observed. The formation of crystalline BaTiO₃ proceeded alongside secondary BaTi₂O₅ and Ba₂TiO₄ phases. These secondary phases disappeared as the reaction time was increased leaving only BaTiO₃ as the sole reaction product. Kinetic analysis of the formation of hydrothermal BaTiO₃ crystallization by the Johnson-Mehl-Avrami method showed that BaTiO₃ crystallization is a homogeneous dissolution-precipitation reaction. The mechanism is governed by nucleation and growth in the beginning of the reaction and dissolution-precipitation dominating throughout the hydrothermal reaction process.     

Micro-mesoporous TiO2/SiO2 nanocomposites: Sol-gel synthesis,characterization, and enhanced photodegradation of quinoline

Micro-mesoporous TiO₂/SiO₂ nanocomposite powders have been successfully synthesized by the sol-gel process with different TiO₂/SiO₂ molar ratios and were applied in the UV-photodegradation of quinoline (λ = 254 nm). The structural, morphological, and textural characterization of the powders showed a homogeneous distribution of TiO2 nanoparticles within a porous amorphous SiO2 matrix. Due to the micro-mesoporous character of the materials, their textural characteristics were evaluated by the N2 adsorption method, by comparing BET, DR, Langmuir, and DFT theories. Si₆₀Ti₄₀ powders (60%SiO₂/40%TiO₂) presented the highest specific surface area (SSA) obtained from BET (SSA = 363 m²g^-1), DR (SSA = 482 m²g^-1), and Langmuir (SSA = 492 m²g^-1) due to the adequate particle size of TiO₂ and its high dispersion in the porous matrix. A higher degradation of quinoline in the presence of H₂O₂ (66%) was achieved using Si₈₀Ti₂₀ powders (80%SiO₂/20%TiO₂), as compared to pure sol-gel TiO₂ powders, (51%) under the same reaction conditions (1 UVC lamp - 250W, t = 180 min). The better performance of the Si₈₀Ti₂₀ nanocomposite could be attributed to the small TiO₂ anatase crystallite size (<5.7 nm), high dispersion of these crystallites in the SiO₂ matrix, great specific surface area (DR SSA = 342 m² g^?1), and the formation of Ti–O–Si bond, which is associated with new catalytic sites in TiO₂/SiO₂ composite.     

Structure and magnetic properties of Co3O4/SiO2 nanocomposite synthesized using combustion assisted sol-gel method

This paper reports on novel cobalt oxide nanoparticles (NPs) embedded in an amorphous silica (SiO₂) matrix, synthesized using a modified sol-gel method. SEM and TEM images show as-synthesized particles to aggregate in the shape of spheres and less than 5 nm in size, while XRD and SAED analysis both point to well crystallized cubic spinel cobalt oxide phase with an average crystallite size of about 4.6 nm. Raman analysis confirms the formation of cobalt (III) oxide (Co₃O₄) NPs. As-synthesized Co₃O₄ single-nanocrystallite has magnetic properties that correlate with finite size effects and uncompensated surface spins. Temperature dependence of ZFC-FC magnetization curves reveals a sharp peak around 10 K which corresponds to the blocking temperature. A Curie-Weiss behavior of magnetization above 25 K shows lower Néel temperature of the sample compared with its bulk counterpart T_N=40 K (possibly due to crystal defects and nano-dimensionality of the particles). The magnetic measurements exhibit high magnetization at low temperatures (M_S=54.3 emu/g) which can be associated with random canting of the particles’ surface spins and uncompensated spins in the core which tends to interact ferromagnetically at low temperatures. The initial magnetization curve falls out from the hysteresis loop at 5 K, which could be also the effect of surface spins.     

Electrospinning fabrication of partially crystalline bisphenol A polycarbonate nanofibers: The effects of molecular motion and conformation in solutions

Partially crystalline bisphenol A polycarbonate (BPAPC) nanofibers were successfully fabricated using a combination of a centrifugal field (1800 rpm) and an electrostatic field (25 kV). The BPAPC solution properties are key factors for adequately electrospinning the partially crystalline BPAPC nanofibers. The correlation times (τ_c) of methyl (τ_c = 9.3 ns) and of benzene-ring (τ_c = 15.3 and 15.8 ns) motions in the 14 wt.% BPAPC/THF solution were longer than in CH₂Cl₂ and CHCl₃, as determined by NMR. The distribution-peak maximum of the hydrodynamic radius of BPAPC in the 14 wt.% THF solution (R_h = 15 Å) was higher than in CH₂Cl₂ (R_h = 9.2 Å) and CHCl₃ (R_h = 7.9 Å), as evidenced by DLS data. We conclude that the BPAPC assumed a denser, more worm-like chain conformation in THF solvation.     

Influence of polarity of polymer on inorganic particle dispersion in dielectric particle/polymer composite systems

The influence of the polarity of polymers on the degree of dispersion of BaTiO₃ particles in BaTiO₃/polymer composite systems was investigated. The BaTiO₃ polymer composite systems were prepared from BaTiO₃ particles and low-density polyethylene (LDPE) or ethylene vinyl acetate copolymer (EVA) with 7 and 15 wt % vinyl acetate. Scanning electron microscopy observation showed that BaTiO₃ particles aggregated in the polymer matrices and dispersed more readily into the EVA matrix than into LDPE. The shift of the β-peak temperature by ca. +5°C in the temperature dispersion of the loss modulus was observed for EVA–BaTiO₃ composite systems in dynamic mechanical property measurement. On the other hand, the β-peak temperature of the polymers filled with graphite particles, which have hydrophobic surfaces, was almost constant in a volume fraction region of 0–0.3. The ellipsoidal axes' ratios given by comparison of experimental dielectric constant values and theoretical ones using the Maxwell equation were 4.2, 3.6, and 3.1 for LDPE/BaTiO₃, EVA(7%)/BaTiO₃, and EVA(15%)/BaTiO₃ composite systems, respectively. The axes' ratio decreased by the introduction of polar vinyl acetate groups into nonpolar LDPE. The results confirmed that the polarity of the polymers was one of the key factors governing the dispersibility of BaTiO₃ particles in the polymer matrix. © 1995 John Wiley & Sons, Inc.     

Characterization of core@shell-structured ZnO@Sb2S3 particles for effective hydrogen production from water photo spitting

In this study, Sb₂S₃-photosensitized ZnO photocatalysts (ZnO@Sb₂S₃) are used to enhance the production of hydrogen from water by photo-splitting. Various loadings of Sb₂S₃ are added to the surface of rod-shaped ZnO nanoparticles (100–150 nm) as a photosensitizer to absorb visible light. The obtained particles show core@shell structures in transmission electron microscopy images. The physicochemical characteristics of the Sb₂S₃, ZnO, and core@shell structured ZnO@Sb₂S₃ particles are confirmed using X-ray diffraction, UV–visible spectroscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. H₂ evolution from water photo-splitting is enhanced for the core@shell structured ZnO@Sb₂S₃ in a liquid system compared to that for pure ZnO and Sb₂S₃. Hydrogen gas is produced at a rate of 77.5 μmol/g after 10 h using the ZnO@Sb₂S₃ photocatalyst with a 7.0 mol% Sb₂S₃ loading. Based on cyclic voltammetry results, the high photoactivity of ZnO@Sb₂S₃ is attributed to both the fast excitation of electrons by increased absorption of visible light and the suppression of electron-hole (e^--h⁺) recombination, which results from the appropriate energy gap between the Sb₂S₃ and ZnO particles.