Paramagnetic Ho2O3 nanowires,nano-square sheets,and nanoplates

The morphology control of holmium oxide (Ho₂O₃) nanostructures has rarely been reported. In the present study, uniform Ho₂O₃ nanowires, nano-square sheets, and nanoplates were synthesized via the hydrothermal method and were characterized using scanning electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, ultraviolet–visible–near-infrared absorption, and X-ray photoelectron spectroscopy. The morphology was observed to be composed of different crystal phases and Ho complexes, but it changed to the same cubic Ho₂O₃ crystal phase upon high-temperature thermal treatment. Paramagnetic properties were obtained and discussed for the three different morphologies mentioned above. The newly reported morphologies and the physicochemical properties reported herein will widen the application scope of Ho oxide materials.     

Synthesis of Al2O3 nanowires by heat-treating Al4O4C in a carbon-containing environment

A novel route was developed for the synthesis of Al₂O₃ nanowires by heat-treating Al₄O₄C via Si atom doping in a furnace with a carbon heater. The nanowires had dimensions of 20–60 nm in diameter and a few hundred microns in length, and were tunable by adjusting the heating temperature. Al₂O₃ nanowires exhibited a curved, or twisted, structure and the interface of the bending part had a defective microstructure. The study of their growth mechanism indicates that the Al₂O₃ nanowires grew by a vapour–liquid–solid (VLS) growth process.     

Yb2O3 and Y2O3 co-doped zirconia ceramics

A suspension stabilizer-coating technique was employed to prepare x mol% Yb₂O₃ (x = 1.0, 2.0, 3.0 and 4.0) and 1.0 mol% Y₂O₃ co-doped ZrO₂ powder. A systematic study was conducted on the sintering behaviour, phase assemblage, microstructural development and mechanical properties of Yb₂O₃ and Y₂O₃ co-doped zirconia ceramics. Fully dense ZrO₂ ceramics were obtained by means of pressureless sintering in air for 1 h at 1450 °C. The phase composition of the ceramics could be controlled by tuning the Yb₂O₃ content and the sintering parameters. Polycrystalline tetragonal ZrO₂ (TZP) and fully stabilised cubic ZrO₂ (FSZ) were achieved in the 1.0 mol% Y₂O₃ stabilised ceramic, co-doped with 1.0 mol% Yb₂O₃ and 4.0 mol% Yb₂O₃, respectively. The amount of stabilizer needed to form cubic ZrO₂ phase in the Yb₂O₃ and Y₂O₃ co-doped ZrO₂ ceramics was lower than that of single phase Y₂O₃-doped materials. The indentation fracture toughness could be tailored up to 8.5 MPa m^1/2 in combination with a hardness of 12 GPa by sintering a 1.0 mol% Yb₂O₃ and 1.0 mol% Y₂O₃ ceramic at 1450 °C for 1 h.     

A hydrothermal reaction to synthesize CuFeS2 nanorods

A hydrothermal reaction route has been developed to prepare chalcopyrite phase CuFeS₂ nanorods at 200–250°C. X-ray powder diffraction and transmission electron microscopy results reveal that the CuFeS₂ synthesized displays nanorods with diameters of 20–40 nm and lengths of up to several micrometers. Elemental analysis gives the atomic ratio of Cu:Fe:S of 1:1.04:2.11. The ⁵⁷Fe Mössbauer spectrum exhibits a six-peak hyperfine magnetic spectrum and a like-splitted line non-magnetic peak. The factors influencing the formation of the CuFeS₂ nanorods were discussed.     

Synthesis and characterization of Er2O3 nanorods and nanosheets

It is very important to develop a new synthetic route for lanthanide metal oxides with novel morphologies and having different fundamental properties and application performances. Here, we report Er₂O₃ nanorods and nanosheets prepared by a facile hydrothermal method followed by post-thermal annealing treatment. Thermal treatment of Er₄O₂(OH)₈(HNO₃) and Er₂O₅H₄ was carried out to form the nanorods and nanosheets, respectively. Their physicochemical properties were evaluated by field-emission scanning electron microscopy, X-ray diffraction crystallography, high-resolution transmission electron microscopy, Fourier transform infrared (IR) spectroscopy, Ultraviolet-visible-near IR absorption spectroscopy, and X-ray photoelectron spectroscopy. The synthesis method and novel fundamental properties provide valuable information for the development of Er complexes and oxides.     

Yb2O3 and Gd2O3 doped strontium zirconate for thermal barrier coatings

Yb₂O₃ (10 mol%) and Gd₂O₃ (20 mol%) doped SrZrO₃ was investigated as a material for thermal barrier coating (TBC) applications. The thermal expansion coefficients (TECs) of sintered bulk Sr(Zr_0.9Yb_0.1)O_2.95 and Sr(Zr_0.8Gd_0.2)O_2.9 were recorded by a high-temperature dilatometer and revealed a positive influence on phase transformations of SrZrO₃ by doping Yb₂O₃ or Gd₂O₃. The results for the thermal conductivities of Sr(Zr_0.9Yb_0.1)O_2.95 and Sr(Zr_0.8Gd_0.2)O_2.9 indicated that both dopants can reduce the thermal conductivity of SrZrO₃. Mechanical properties (Young's modulus, hardness, and fracture toughness) of dense Sr(Zr_0.9Yb_0.1)O_2.95 and Sr(Zr_0.8Gd_0.2)O_2.9 showed lower Young's modulus, hardness and comparable fracture toughness with respect to YSZ. The cycling lifetimes of Sr(Zr_0.9Yb_0.1)O_2.95/YSZ and Sr(Zr_0.8Gd_0.2)O_2.9/YSZ double layer coatings (DLC), which were prepared by plasma spraying, were comparable to that of YSZ at operating temperatures <1300 °C. However, the cycling lifetime of Sr(Zr_0.9Yb_0.1)O_2.95/YSZ DLC was 25% longer, whereas Sr(Zr_0.8Gd_0.2)O_2.9/YSZ DLC had a shorter lifetime compared to the optimized YSZ coating at operating temperatures >1300 °C.     

The role of Eu2O3 and CeO2 on the phase formation,infrared emission and magnetic properties of Co0.6Zn0.4Fe2O4 ceramics by a solvothermal method

Nanosized Eu₂O₃ and CeO₂ co-addition CoZn ceramics have been achieved via a hydrothermal method by adjusting the mol ratios of Eu and Ce. The as-prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transform infrared (FTIR), Vibrating sample magnetometer (VSM) and Infrared emission measurement (IRE-2). The particle morphologies of the as-prepared samples evolve from spherical, to self-assembled nanoparticles, and irregular nanoparticles when the mol ratios (x) of Eu and Ce was changed from 0:10 to 10:0. Correspondingly, the main phases of the as-prepared samples change from both cubic spinel CoFe₂O₄ and CeO₂, pure cubic cerianite CeO₂, to amorphous. Meanwhile, the as-prepared samples appear transformed from a ferromagnetic behavior with a saturation magnetization 66.4 emu/g to a paramagnetic behavior with a saturation magnetization of 0.55 emu/g at turning point x=3.5:6.5. While the infrared emissivity is increasing as the x from 0:10 to 3.5:6.5, reach the maximum at 3.6:6.4, and then remain stable when further increasing x till 10:0. Those may be due to the amorphous tendency rising and the particle sizes gradual decreasing with x increasing from 0:10 to 10:0. What is more important is that the solvothermal method is proved to be an efficient way to prepare CoZn nano-ceramics in this study which may open new pathways to magnetic and far infrared therapy.     

Microwave-assisted rapid fabrication of Co3O4 nanorods and application to the degradation of phenol

A novel microwave-assisted hydrothermal route for preparation of Co₃O₄ nanorods had been developed. The process contained two steps: first, nanorods of cobalt hydroxide carbonate were obtained from a mixed solution of 50 ml of 0.6 M Co(NO₃)₂·6H₂O and 2.4 g of urea under 500 W microwave irradiated for 3 min. Then, the cobalt hydroxide carbonate nanorods were calcined at 400 °C to fabricate pure cobaltic oxide (Co₃O₄) nanorods. Both nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), infrared (IR) and temperature-programmed reduction (TPR). The catalytic activity towards the degradation of phenol over Co₃O₄ nanorods was further studied under continuous bubbling of air through the liquid phase. The results showed that phenol was degraded into harmless products (CO₂ and malonic acid). The mechanism of phenol degradation was also discussed.     

Improved formaldehyde sensor of Zn2SnO4/SnO2 microcubes by compositional evolution and Y2O3 decoration

Zn₂SnO₄/SnO₂(ZTO/SnO₂) and Y doped Zn₂SnO₄/SnO₂(ZTO/SnO₂) microcubes were synthesized by a hydrothermal route at 130?°C and subsequently used for obtaining gas sensors. To evaluate the structure, morphology, chemical state and optical bandgap, our sensors were characterized by XRD, SEM, XPS and UV–vis analysis. Compared with sensors based on ZTO/SnO₂ microcubes, the Y doped ZTO/SnO₂ microcubes had an optimum sensing performance to 100?ppm formaldehyde (HCHO), for instance lower working temperature (210?°C) and better response (46.07). In addition, the enhanced sensing mechanism of Y doped ZTO/SnO₂ microcubes was discussed in detail.     

Preparation and characterization of Bi2Se3 nanowires by electrodeposition

The electrodeposition of Bi₂Se₃ nanowires on an anodic aluminum oxide template was investigated by cyclic voltammetry in a tartaric acid aqueous solution. The electrochemical behavior of the Bi₂Se₃ nanowires in the electrolytic solution was also investigated using cyclic voltammetry, and the underpotential deposition mechanism of the Bi₂Se₃ nanowires was determined. According to the cyclic voltammetric curves, −0.20 V vs. SCE (saturated calomel electrode) was chosen as the deposition potential of the Bi₂Se₃ nanowires. The ratio of Bi to Se is nearly 2:3, verified by energy-dispersive X-ray spectroscopy and with the addition of surfactant. X-ray diffraction, scanning electron microscopy, selected-area electron diffraction and high-resolution transmission electron microscopy indicate that annealing can improve the crystallinity and chemical composition of Bi₂Se₃ nanowires. Surfactant can also improve the surface morphology and composition of the Bi₂Se₃ nanowires.     

Synthesis of single-crystal SnO2 nanowires for NOx gas sensors application

Single-crystal SnO₂ nanowires (NWs) were successfully synthesized and characterized as sensing materials for long-term NO_x stability detection in environmental monitoring. Reproducible and selective growths of the SnO₂ NWs on a patterned, 5 nm-thick gold catalyst coated on a SiO₂/Si wafer as substrate were conducted by evaporating SnO powder source at 960 °C in a mixture of argon/oxygen ambient gas (Ar: 50 sccm/O₂: 0.5 sccm). The as-obtained products were characterized by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman scattering, and photoluminescence (PL). The SEM and HRTEM images revealed that the products are single-crystal SnO₂ NWs with diameter and length ranges of 70 nm–150 nm and 10 μm–100 μm, respectively. The three observed Raman peaks at 476, 633, and 774 cm⁻¹ indicated the typical rutile phase, which is in agreement with the XRD results. The NWs showed stable PL with an emission peak centered at around 620 nm at room-temperature, indicating the existence of oxygen vacancies in the NW samples. The electrical properties of synthesized SnO₂ NWs sensor were also investigated and it exhibited a negative temperature coefficient of resistance in the measured range (300–525 K). The calculated activation energy E_c of SnO₂ NWs was 0.186 eV. Moreover, the SnO₂ NW sensors exhibited good response to NO_x gas. The response of the sensors to 5 ppm NO_x reached 105% at an operating temperature of 200 °C.     

Synthesis and characterization of Eu3+-doped C12H18Ca3O18 phosphor

A series of Eu³⁺-doped C₁₂H₁₈Ca₃O₁₈ phosphors were synthesized through a facile hydrothermal method and the properties of as-prepared phosphors were explored by X-ray diffractometer (XRD), scanning electron microscope (SEM), and photoluminescence (PL) spectrometer. The exploration results indicated that the C₁₂H₁₈Ca₃O_18:Eu³⁺ had been successfully synthesized. The morphology of C₁₂H₁₈Ca₃O_18:Eu³⁺ was a strip with the size of 100–4000 nm × 50–400 nm × 50–200 nm and the ratio of length to width of 2–80. The strongest emission peak of C₁₂H₁₈Ca₃O_18:Eu³⁺ around 620 nm was ascribed to ⁵D_o→⁷F₂ transition of Eu³⁺, and the peaks centered at 590, 653 and 694 nm respectively corresponded to ⁵D_o →⁷F₁, ⁷F₃, and ⁷F₄ transitions. C₁₂H₁₈Ca₃O_18: Eu³⁺ gave the red light emission, as indicated by color coordinate analysis. The photoluminescence intensity of the phosphors prepared under the Eu³⁺ concentration of 6% was the highest. The crystal structure of C₁₂H₁₈Ca₃O_18:Eu³⁺ was changed after europium ions occupied the lattice position of calcium ions. Europium ion could displace calcium arbitrarily. As a new kind of matrix, calcium citrate possesses the properties of both organic and inorganic compounds and the luminescent C₁₂H₁₈Ca₃O₁₈: x Eu³⁺ particles may be applied in biological fluorescent tags and luminescent materials.     

Effects of HCl concentration on the growth and negative thermal expansion property of the ZrW2O8 nanorods

A kind of negative thermal expansion ZrW₂O₈ nanorods were synthesized using a hydrothermal method, followed with a post-annealing at 570 °C for 2 h. Effects of HCl concentration on the microstructure, morphology and negative thermal expansion property in resulting ZrW₂O₈ powders were investigated by X-ray diffraction (XRD) and transmission electron microscope (TEM). Results indicate that the formation of the precursor ZrW₂O₇(OH)₂(H₂O)₂ significantly depends on the HCl concentration, and the precursors ZrW₂O₇(OH)₂(H₂O)₂ can form in the 2-8 mol/L HCl solution. With increasing the concentration of the HCl solutions from 2 to 8 mol/L, the rod-like ZrW₂O₈ particles become more homogeneous, and the average dimension change from 10 μm × 0.5 μm to 700 nm × 50 nm. All the ZrW₂O₈ powders obtained in different conditions exhibit negative thermal expansion property, and the average negative thermal expansion coefficients from 15 °C to 600 °C decrease gradually with the increasing HCl concentration.     

Novel chemical method for synthesis of LiV3O8 nanorods as cathode materials for lithium ion batteries

A novel method which is based on the hydrothermal reaction was employed to synthesize LiV₃O₈. First, the mixture solution of LiOH, V₂O₅, and NH₄OH was subjected to the hydrothermal reaction. The hydrothermal treatment yielded a clear, homogeneous solution. The evaporation of this solution led to the formation of a precursor gel. The gel was then heated at different temperatures in the range of 300-600 °C. The characterization by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) indicated that LiV₃O₈ nanorods have been obtained by this novel synthesis method. The electrochemical performance of the LiV₃O₈ nanorods have been investigated, which indicates that the highest discharge specific capacity of 302 mAh/g in the range of 1.8-4.0 V was obtained for the sample heated at 300 °C, and its capacity remained 278 mAh/g after 30 cycles.     

Hydrothermal synthesis of precursors for Y-TZP/α-Al2O3 composite

A coprecipitated xerogel having the composition of 90 vol.% zirconia (3 mol% Y₂O₃) and remaining 10 vol.% alumina was crystallized under hydrothermal conditions by adopting conventional (110 °C for 7 days) or microwave (250 °C for 2 h) routes. The hydrothermal treatments of crystallization were performed in the presence of (KOH+K₂CO₃) (K), (CH₃)₄NOH (TMA), or (C₂H₅)₄NOH (TEA) mineralizer solutions at different concentrations.The role of the two different hydrothermal routes, of the nature and the concentration of the mineralizer solution on the thermal behaviour of the resulting powders are discussed.     

Corrosion mechanisms of Al2O3/MgAl2O4 by V2O5, NiO, Fe2O3 and vanadium slag

The effects of V₂O₅, NiO, Fe₂O₃ and vanadium slag on the corrosion of Al₂O₃ and MgAl₂O₄ have been investigated. The specimens of Al₂O₃ and MgAl₂O₄ with the respective oxides above mentioned were heated at 10 °C/min from room temperature up to three different temperatures: 1400, 1450 and 1500 °C. The corrosion mechanisms of each system were followed by XRD and SEM analyses. The results obtained showed that Al₂O₃ was less affected by the studied oxides than MgAl₂O₄. Alumina was only attacked by NiO forming NiAl₂O₄ spinel, while the MgAl₂O₄ spinel was attacked by V₂O₅ forming MgV₂O₆. It was also observed that Fe₂O₃ and Mg, Ni, V and Fe present in the vanadium slag diffused into Al₂O₃. On the other hand, the Fe₂O₃ and Ca, S, Si, Na, Mg, V and Fe diffused into the MgAl₂O₄ structure. Finally, the results obtained were compared with those predicted by the FactSage software.     

Hydrothermal mass production of MgBO2(OH) nanowhiskers and subsequent thermal conversion to Mg2B2O5 nanorods for biaxially oriented polypropylene resins reinforcement

Mass production of one-dimensional (1D) nanomaterials has emerged as one of the most significant challenges in powder technology. In this contribution, MgBO₂(OH) nanowhiskers were hydrothermally produced at a kilogram scale in a 150 L stainless steel autoclave at 200 °C for 12.0 h by using MgCl₂·6H₂O, H₃BO₃ and NaOH as the raw materials. The subsequent thermal conversion of the MgBO₂(OH) nanowhiskers at 700 °C for 6 h led to 3.75 kg of high crystallinity monoclinic Mg₂B₂O₅ nanorods, with a length of 0.47-1.3 µm, a diameter of 55-160 nm, and an aspect ratio of 3-15. After the nanorods have been surface modified with the silane coupling agent KH-550, the reinforcing and toughening effects of the Mg₂B₂O₅ nanorods on the biaxially oriented polypropylene resins (BOPP-D1) were evaluated. The filling of the Mg₂B₂O₅ nanorods into the resins resulted in the increase in the tensile strength, the impact strength, and the melt flow index of the BOPP-D1 composites. The appropriate ratio of coupling agent to fillers (Mg₂B₂O₅ nanorods) and the ratio of fillers to resins were determined within the range of 0.6-1.2 wt.% and 8-15 wt.%, respectively. The optimal ratio of fillers to resins was ca. 10 wt.%. The present mass production of MgBO₂(OH) nanowhiskers and Mg₂B₂O₅ nanorods is believed to be helpful for enlarging and propelling the applications of the 1D magnesium borate nanostructures in the near future.     

Planar ultracapacitors of miniature interdigital electrode loaded with hydrous RuO2 and RuO2 nanorods

Planar ultracapacitors of miniature interdigital electrode are prepared, using the standard technologies of photolithography and reactive sputtering. The ultracapacitor is denoted by its deposition sequence, for example, hRuO₂NRGT indicates pseudocapacitive hydrous RuO₂ (hRuO₂) and RuO₂ nanorods (NR) are grown on an interdigital stack layer of gold (G) and titania (T). The connection between structure and performance is studied through contrasting the hRuO₂NRGT capacitor with other capacitors built on a less conducting stack layer or without hydrous RuO₂ filling the gaps between the nanorods. The stack layer can be a major source of cell resistance. For instance, a buffer layer of titania could be utilized between the capacitive RuO₂ and the Au current collector to overcome the delamination problem. But the less conductive titania also makes its cyclic voltammograms (CV) elliptical and tilted, and causes a pronounced IR drop during the cell discharging. In contrast, CV of the hRuO₂NRGT capacitor on a conductive stack layer takes the shape of horizontal rectangle, and its discharge curve shows no sign of IR drop. Filling hydrous RuO₂ into the gap reduces the cell resistance between nanorods, improves the discharge performance as well. The power output of hRuO₂NRGT, with the two resistances minimized, is 30.6 μW at 75 μA and 1.23 μW at 5 μA.     

The effect of co-doping with MgO and Yb2O3 on the structure and electrical conductivity of the Sm2Zr2O7 pyrochlore

SmYb_1−xMg_xZr₂O_7−x/2 (0 ≤ x ≤ 0.15) ceramics are pressureless-sintered at 1973 K for 10 h in air. The structure and electrical conductivity of SmYb_1−xMg_xZr₂O_7−x/2 ceramics are investigated by the X-ray diffraction, scanning electron microscopy and impedance spectroscopy measurements. SmYb_1−xMg_xZr₂O_7−x/2 ceramics exhibit a defect fluorite-type structure. The measured electrical conductivities of SmYb_1−xMg_xZr₂O_7−x/2 ceramics obey the Arrhenius relation, and electrical conductivity of each composition increases with increasing temperature from 673 to 1173 K. At identical temperature levels, the electrical conductivity of SmYb_1−xMg_xZr₂O_7−x/2 ceramics gradually increases with increasing magnesia content. SmYb_1−xMg_xZr₂O_7−x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10⁻⁴ to 1.0 atm at all test temperature levels. The electrical conductivity obtained in SmYb_1−xMg_xZr₂O_7−x/2 ceramics reaches the highest value of 2.72 × 10⁻³ S cm⁻¹ at 1173 K for the SmYb_0.85Mg_0.15Zr₂O_6.925 ceramic.     

Hydrothermal fabrication and analysis of piezotronic-related properties of BiFeO3 nanorods

This paper reports the fabrication of vertically oriented BiFeO₃ (BFO) nanorods on indium tin oxide/glass substrates through hydrothermal synthesis. Further, their piezotronic, piezophototronic, and piezophotocatalytic properties were analyzed. Various synthesis parameters were examined to modulate the morphology and alignment of BFO nanorods, including the ratios of precursors, the pH values, types of complex agents, and reaction times and temperatures. Transmission electron microscopy results demonstrated single crystallinity of the BFO nanorods. A band gap of approximately 2.3?eV was determined. The piezotronic and piezophototronic properties were observed through facile current–voltage measurement. The extended application of piezophotocatalysis under alternating external stress and visible-light irradiation, to decompose methylene blue solutions, was also ascertained. The piezophotocatalytic efficiency was improved by approximately 30% over photocatalysis in the first 30?min. Both O₂^?□and□·OH radicals were crucial for these activities.