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Supercapacitors (SCs) are promising for powering mobile devices, electric vehicles and smart power grids due to their fast charge/discharge rate, high power capability and robust cycle stability. Nitrogen-doped porous carbons are great alternatives because they provide pseudocapacitance without losing their power rate. Nanoporous carbon derived from metal organic frameworks (MOFs) is an ideal precursor for preparing heteroatom-doped carbons due to their abundant nitrogen contents and incredible specific surface areas. However, severe aggregations and the leakage of nitrogen can occur during harsh carbonization. In this study, we used CoAl-LDH (cobalt aluminum layered double hydroxide) as an in-situ growth substrate, allowing Co-based MOF to uniformly grow onto the CoAl-LDH to form a sandwiched MOF/LDH/MOF structure. After acid etching, we obtained waffle-like nanoporous carbons (WNPC). WNPC exhibited high nitrogen and oxygen retention (7.5 wt% and 9.1 wt%) and a broad mesopores distribution with specific surface areas of 594 m2g&minus, 1, which promoted a sieving effect. This renders a specific capacitance of 300.7 F&middot, g&minus, 1 at 1 A&middot, 1 and the high retention (72%) of capacitance at 20 A&middot, 1, ensuring its use at high-rate supercapacitor electrodes. Finally, the WNPC symmetric supercapacitor reaches a superior specific energy of 27 W&middot, h&middot, kg&minus, 1 at a power of 500 W&middot, 1, and a good cycle stability (85% capacitance retention after 10,000 cycles).

In this paper, we propose mixed metal ions in the node of the zeolitic imidazolate framework (ZIF) structure. The hybrid metal ZIF is formed for the gas separation of hydrogen and carbon dioxide. In the first stage, the nanoparticles were prepared as a coating on a substrate, and acting as secondary growing nuclei. The hybrid metal ZIF structures were characterized by X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). N2 adsorption&ndash, desorption isotherms determined surface area, and scanning electron microscopy (SEM) was used to observe the microstructure and surface morphology. The hybrid metal ZIF-8-67 powder had the largest surface area (1260.40 m2 g&minus, 1), and the nanoparticles (100 nm) could be fully dense-coated on the substrate to benefit the subsequent membrane growth. In the second stage, we prepared the hybrid metal ZIF-8-67 membrane on the pre-seeding substrate with mixed metal nanoparticles of cobalt and zinc, by the microwave hydrothermal method. Cobalt ions were identified in the tetrahedral coordination through UV&ndash, Vis, and the membrane structure and morphology were determined by XRD and SEM. Finally, a gas permeation analyzer (GPA) was used to determine the gas separation performance of the hybrid metal ZIF-8-67 membrane. We successfully introduced zinc ions and cobalt ions into the ZIF structure, where cobalt had a strong interaction with CO2. Therefore, GPA analysis showed an excellent H2/CO2 separation factor due to lower CO2 permeability. The CO2 permeance was ~0.65 &times, 10&minus, 8 mol m&minus, 2 s&minus, 1 Pa&minus, 1, and the separation factors for H2/CO2 and H2/N2 were 9.2 and 2.9, respectively. Our results demonstrate that the hybrid metal ZIF-8-67 membrane has a superior H2/CO2 separation factor, which can be attributed to its very high specific surface area and structure. Based on the above, hybrid metal ZIF-8-67 membranes are expected to be applied in hydrogen or carbon dioxide gas separation and purification.

Limestone is a relatively abundant and low-cost material used for producing calcium oxide as a CO2 adsorbent. However, the CO2 capture capacity of limestone decreases rapidly after multiple carbonation/calcination cycles. To improve the CO2 capture performance, we developed a process using limestone to transform the material into a rod Ca-based metal&ndash, organic framework (Ca-MOF) via a hydrothermal process with the assistance of acetic acid and terephthalic acid (H2BDC). The structural formation of rod Ca-MOF may result from the (200) face-oriented attachment growth of Ca-MOF sheets. Upon heat treatment, a highly stable porous rod network with a calcined Ca-MOF-O structure was generated with a pore distribution of 50&ndash, 100 nm, which allowed the rapid diffusion of CO2 into the interior of the sorbent and enhanced the CO2 capture capacity with high multiple carbonation&ndash, calcination cycle stability compared to limestone alone at the intermediate temperature of 450 &deg, C. The CO2 capture capacity of the calcined porous Ca-MOF-O network reached 52 wt% with a CO2 capture stability of 80% after 10 cycles. The above results demonstrated that rod Ca-MOF can be synthesized from a limestone precursor to form a porous network structure as a CO2 capture sorbent to improve CO2 capture performance at an intermediate temperature, thus suggesting its potential in environmental applications.

In this study, Ca-based multi-metals metal-organic framework (CaMgAl-MOF) has been designed as precursor material for carbon dioxide (CO2) capture to enhance the CO2 capture capacity and stability during multiple carbonation-calcination cycles. The CaMgAl-MOFs were constructed from self-assembly of metal ions and organic ligands through hydrothermal process to make metal ions uniformly distributed through the whole structure. Upon heat treatment at 600 &deg, C, the Ca-based multi-metals CaMgAl-MOF would gradually transform to CaO and MgO nanoparticles along with the amorphous aluminum oxide distributed in the CaO matrix. XRD, Fourier transform infrared (FTIR), and SEM were used to identify the structure and characterize the morphology. The CO2 capture capacity and multiple carbonation-calcination cyclic tests of calcined Ca-based metal-organic framework (MOF) (attached with O and indicated as Ca-MOF-O) were performed by thermal gravimetric analysis (TGA). The single metal component calcined Ca-MOF sorbent have the highest CO2 capture capacity up to 72 wt.%, but a lower stability of 61% due to severe particle aggregation. In contrast, a higher Ca-rich MOF oxide sorbent with tailoring the Mg/Al ratios, Ca0.97Mg0.025Al0.005-MOF-O, showed the best performance, not only having the high stability of ~97%, but also maintaining the highest capacity of 71 wt.%. The concept of using Ca-based MOF materials combined with mixed-metal ions for CO2 capture showed a potential route for achieving efficient multiple carbonation-calcination CO2 cycles.

In this study, amorphous MoO x films and Ag metal films were deposited on soda-lime glass via a sputtering system at room temperature. The experimental results indicate that MoO x films prepared with a 6% O 2 /Ar flow rate exhibit an amorphous phase with high transparency and an optical band gap of 2.7 eV. In-situ O 2 /Ar plasma was adopted to further modify the surface of the Ag mid-layer after deposition. This approach can enhance the visible transmittance of MoO x and Ag-based multilayers with the same sheet resistance. The polygrains oriented along the (111) and (200) directions in the inserted Ag thin films were adopted to supply carriers into the MoO x film and decrease the sheet resistance of the MoO x and Ag-based multilayer. The multilayer structure exhibited a sufficiently large Ag thickness (>10 nm), low resistance, and visible transmittance to serve as a transparent conductive electrode. The dependence of the Ag thickness, MoO x thickness, and plasma treatment time on the optical and electrical properties of Ag/MoO x and symmetric MoO x /Ag/MoO x were also explored. A figure of merit (FOM) of 5.3×10 −2 (Ω −1 ) was achieved at the visible wavelength of 550 nm for a MoO x /Ag/MoO x stacked layer with a 10-nm-thick Ag layer and a 30-nm-thick MoO 3 layer. Such a MoO x /Ag/MoO x stacked structure might be a promising electrode in potential applications of transparent conductive oxides.

Amorphous TiOx, WO3 and Ag mid-layer films were deposited on polyethersulfone (PES) and soda-lime glass via electron beam evaporation at room temperature. The crystallinity, microstructure and surface morphology of asymmetric TiOx/Ag/WO3 multilayers (TAW) and symmetric WO3/Ag/WO3 (WAW) multilayers were investigated. The polygrains oriented along the (111) planes in the inserted Ag thin films were adopted to supply carriers into both of the dielectric layers and reduce the sheet resistance of the multilayer. The TAW multilayer with a sufficiently large Ag thickness (>15 nm) exhibited low resistance, and highly visible transmittance, low infra-red transmittance, to serve as a transparent conductive electrode and a good heat mirror. The dependence of the Ag and TiOx thickness on the optical and electrical properties of TAW multilayers was also explored. A figure of merit (FOM) was used to find an optimal layer structure for a TAW multilayer with superior conductivity and highly visible transparency. A high FOM of 1.2 × 10−1 (Ω−1) was achieved at the visible wavelength of 550 nm for a asymmetric TAW stacked layer on PES with a 15-nm-thick Ag layer, a 40-nm-thick TiOx and a 40 nm-thick WO3 layer. The moisture resistances of the TAW stacking layer showed more robustness than that of the WAW sample after damp heat exposure.

A rapid, simple, and inexpensive process combining a microwave-assisted technique and a solvothermal method has been developed using graphene sheets and FeCl 3 ·6H 2 O as the reactant to prepare graphene/Fe 3 O 4 nanoparticle hybrids, which can be applied as an electromagnetic radiation absorbent. The experimental factors (i.e., composition ratio, microwave power, and irradiation time) on the products’ characteristics were examined. Under optimal conditions, the morphological analysis revealed that the graphene sheet was homogeneously covered with Fe 3 O 4 nanoparticles (∼50 nm). The electromagnetic parameters of the composites made from 20 wt% Fe 3 O 4 /graphene–epoxy were measured by a vector network analyzer. It was found that the 4- and 5 mm-thick composites could attain a reflection loss below −20 dB in the dual-ranges of 4–8 and 12–18 GHz.

The microwave absorbing properties of lithium aluminum silicate (LAS) and LAS–SiC double layer composite absorbers were investigated within the frequency range of 8.2–12.4 GHz at 300–500 °C. The composite absorbers for use as high-temperature radar wave-absorbing materials were developed by hot-pressing LAS glass–ceramic and LAS–SiC composite, which were used as the impedance transformer layer and the low-impedance resonator layer, respectively. Nanometer-size β-SiC powders were fabricated at the relatively low sintering temperature of 1450 °C in argon atmosphere. The structure and morphology of the SiC powders were characterized using thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The electromagnetic absorbing properties of the double layer at different temperatures and SiC contents were measured at normal temperature (27 °C) and high temperature by a vector network analyzer. The results indicate that the contents of nanometer-size β-SiC can increase the relative permittivity and dielectric loss of the double layer microwave absorbers. At high temperatures, the microwave absorber consisting of a 2-mm-thick layer of LAS ceramic and a 2-mm-thick layer of LAS–SiC composite with 10 wt% SiC content exhibited excellent performance with a minimum absorption at −42.8 dB at 10.5 GHz and the absorption bandwidth (reflection loss less than −10 dB) of 3.5 GHz in the X-band. The minimum reflection loss measured at 300–500 °C was less than −24 dB.

Amorphous TiOx films and Ag layer were deposited by electron-beam evaporation on soda-lime glass at room temperature. The details regarding the structure, surface morphology, and optical properties of the as-prepared TiOx films were examined by X-ray diffraction, scanning electron microscopy, and ultra-violet (UV) -visible-near-infrared (NIR) spectrometry. The TiOx films exhibit amorphous phase with an optical band gap of 3.35 eV. The polygrains oriented along the (111) and (200) directions in the Ag films were adopted to supply carriers into the TiOx film and lower the sheet resistance of the stacked layer. The multilayer exhibited a sufficiently large Ag thickness (>15 nm), low resistance, high UV transmittance, visible transmittance, and high NIR reflection. Dependence of Ag thickness, TiOx bottom-layer, and TiOx overlayer on the optical and electrical properties of TiOx/Ag/TiOx were explored. A figure of merit (FOM) was used to find an optimal structure for a multilayer with superior conductivity and visible transparency. An FOM of 9.8 × 10−2 (Ω−1) at the visible wavelength of 550 nm for a TiOx/Ag/TiOx stacked layer with an 18-nm-thick Ag and a 20-nm-thick TiOx was achieved. The TiOx/Ag/TiOx sample annealed at 500 °C 10 min also shows a good thermal stability.

In this study, a novel method was proposed to synthesize high quality Zn-doped CuInS2nanocrystals under high frequency magnetic field at ambient conditions. The magnetic Zn-doping gave superparamagnetic heating of the resulting nanocrystals via magnetic induction, causing an accelerating growth rate of the doped CuInS2under ambient conditions faster than conventional autoclave synthesis. Shape evolution of the Zn-doped CuInS2nanocrystals from initially spherical to pyramidal, to cubic, and finally to a bar geometry was detected as a function of time of exposure to magnetic induction. These colloidal solvents with different shaped nanocrystals were further used as “nanoink” to fabricate a simple thin film solar device; the best efficiency we obtained of these crystals was 1.01% with a 1.012 μm thickness absorber layer (bar geometry). The efficiency could be promoted to 1.44% after the absorber was thickened to 2.132 μm.

ZnO/Ag/ZnO (ZAZ) and ZnO/Cu/ZnO (ZCZ) were prepared. The dependence of crystalline, electrical, and optical properties for the multilayer on the postdeposition annealing (PDA) was studied. After PDA of 300°C for 20 min, the diffusion of Cu in ZnO occurs; this result is responsible for the increasing resistance of the annealed ZCZ. Ag with a thickness of 10 nm was deposited upon ZnO. The interface of ZnO and Ag is clearly revealed by high resolution transmission electron microscopy. The crystalline of ZnO and Ag films in the ZAZ with a sheet resistance (Rs) down to 4.17 Ω/sq. The ZAZ layer shows a better thermal stability (up to 400°C) than that of the ZCZ ones. The PDA degraded slightly the optical transmittance and increases the conductivity of ZAZ layer. The figure of merit (FOM) is applied to analysis of the ZAZ layer. The PDA can enhance the FOM of the ZAZ with Ag thickness >8 nm. The resultingRsand the transmittance ZAZ layers were analyzed by the Taguchi method to obtain the appropriate parameters. The optimized ZAZ has been verified with aRsof 2.3 Ω/sq, a high transmittance (71%), and the optimal FOM of 1.41 × 10−2 Ω−1.

A self-propagating high-temperature synthesis (SHS) method, which features a 2-step heating process carried out in a closed chamber, was developed to prepare multipod ZnO whiskers (mZnOw). A compacted Zn powder was first heated at 370 °C in air to form a refractory layer of ZnO on the surface of Zn particles. Next, the SHS reaction was ignited by rapidly heating to ∼750 °C under different oxygen gauge pressures ( P O 2 ) to obtain a loose white product mainly composed of mZnOw. It was found that the P O 2 strongly affected the reaction conversion and morphological features, along with the Zn-to-O ratio, of the as-synthesized products, which, in turn, might influence their photoluminescence and microwave absorption properties. A possible explanation for the effects of P O 2 on these characteristics was also proposed.

Heterojunction photovoltaic devices consisting of hybrid p-type organic Cu-phthalocyanine and inorganic n-type Al2O3 nanoparticle-coated aligned ZnO nanorods were fabricated. With microwave treatment, an interaction occurred between the Al2O3 and ZnO, as evidenced from TEM image. This interaction shifts the absorption peak of the aligned nanorods from the UV region to visible light and subsequently causes more charge generation. For 5 mol% Al2O3 nanoparticle-coated aligned ZnO nanorods treated with microwaves of 600 W for 300 sec, the maximum incident photon to electron conversion and energy conversion efficiencies under simulated sunlight of AM1.5G (10 mW/cm2) are 0.036 mA and 1.32%, respectively.

Photoelectronic characteristics are investigated in well-aligned MgO-coated ZnO nanorods (MgO/ZnO nanocables) grown on Si substrates buffered with ZnO film at a low temperature by solution techniques. Transmission electron microscopy shows that a rough surface was observed for the MgO-coated ZnO nanorods due to deposition of MgO nanoparticles on the surface of the ZnO nanorods. However, after annealed at high temperatures, the surface of the MgO-coated ZnO nanorods was flattened to form Mg-doped ZnO nanorods. Photoluminescence spectra of Mg-doped ZnO nanorods displayed a blue shift of the near-band-edge emission with increasing annealing temperature indicative of an increase in the band gap of the MgZnO alloy due to diffusion of the Mg atoms into the ZnO nanorods. In contrast, no blue shift was detected for the samples annealed in H2/N2 (5%/95%) reduction atmosphere but a blue emission was detected at 800 degrees C, indicating that MgO diffusion process may produce a new luminescent center to emit the blue emission in H2/N2 reduction atmosphere.

A two-step wet chemical process with economic and practical advantages was developed to prepare arrayed ZnO nanorods on glass substrates using zinc acetate dihydrate (Zn(CH3COO)2·2H2O, ZnAc2) and monoethanolamine (NH2CH2CH2OH, MEA) as raw materials. The proposed method includes the pre-deposition of a thin ZnO seed layer using the sol–gel technique and the subsequent hydrothermal growth of ZnO nanorods at 130 °C for 2 or 4 h. The synthesis process was monitored using X-ray diffraction (XRD), Fourier transformation infrared (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ZnO nanorods exhibited a diameter of 25–75 nm with an aspect ratio ranging from 10 to 50 after growing for 4 h. Each ZnO nanorod was confirmed to be a single crystal with a wurtzite structure and grow along the [0 0 0 2] direction during the hydrothermal process. Photoluminescence (PL) measurements confirmed that the ZnO nanorods exhibited a near-UV emission at ∼380nm together with a green emission that was centered at ∼500 nm. We note that the PL properties may be affected by the hydrothermal time.

Nanocrystalline ZnO particles were synthesized from an aqueous solution composed of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and urea (H2NCONH2). A precipitating precursor, basic zinc carbonate (Zn5(CO3)2(OH)6), was first formed by hydrothermally treating the solution at 120 °C for 2–4 h. Nanocrystalline ZnO particles were then obtained by calcining the precursors at 350–650 °C for 0.5–2 h. The synthesis products were characterized using thermogravimetry–differential scanning calorimetry–mass spectrometry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. Based on the experimental results, a possible reaction mechanism for the ZnO formation was proposed. The effects of experimental parameters (namely, the hydrothermal treatment time, the calcination time, and the calcination temperature) on the characteristics of the resulting ZnO products (i.e., the crystalline size and the photoluminescence properties) were analyzed by the Taguchi method to attain the optimum synthesis conditions. By using the appropriate parameters derived from this method, we verified that the optimized synthesis provided a yield of ~70% and that the resulting ZnO particles possessed the characteristics of a ~25 nm crystalline size and a satisfactory photoluminescence property.

A self-propagating high-temperature synthesis (SHS) method has been developed for synthesis of ZnO powder. Powders of Zn and an appropriate amount of NH 4 NO 3 were mixed and pressed into a compact place in a closed chamber with air atmosphere. The combustion reaction was ignited by heating the reactant compact directly using nichrome coil, and then as-synthesized products mainly composed of tetrapod whiskers could be obtained. Both the reaction phenomenon and the product yield were affected by the reactant composition and the stacking density, which might be explained by a proposed reaction mechanism.

Resveratrol is a natural polyphenol and possesses many biological functions such as anti-inflammatory activity and protection against atherosclerosis and myocardial infraction. Parkinson's disease is a common progressive neurodegenerative disease. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is the most useful neurotoxin to induce Parkinsonism. The present study was carried out to elucidate the neuroprotective effect and possible mechanism of resveratrol on MPTP-induced striatal neuron loss. Sixty adult Balb/c mice were divided into four groups: sham operation, MPTP treatment (30 mg/kg, i.p.), MPTP combined with resveratrol administration (20 mg/kg, i.v.), and resveratrol treatment alone. Microdialysis and high-performance liquid chromatography were used to analyze dihydroxybenzoic acid (DHBA) that reflected the hydroxyl radical level. In the present study, we found MPTP chronic administration significantly induced motor coordination impairment in mice. After MPTP administration, the hydroxyl radical levels in substantia nigra were also significantly elevated and animals displayed severe neuronal loss. Resveratrol administration significantly protected mice from MPTP-induced motor coordination impairment, hydroxyl radical overloading, and neuronal loss. Our results demonstrated that resveratrol could elicit neuroprotective effects on MPTP-induced Parkinsonism through free radical scavenging.

This study presents a successful preparation of fine powders of strontium ferrite, SrFe12O19, with different contents of SrTiO3 additive (i.e., SrFe12O19 + xSrTiO3, x = 0.00, 0.05, 0.10, 0.15 and 0.20) through a quasi-dry combustion synthesis route using Sr(NO3)2, Fe(NO3)·9H2O, glycine (NH2CH2COOH), and Ti powder as reactants. The synthesis route included mixing and dehydration procedures to produce a flammable, homogenous dried reactant mixture with its subsequent combustion at room temperature to form a voluminous loose product. The as-synthesized powder was calcined at various temperatures to study the effects of temperature on phase development and products’ properties. Characterizations of the products were evaluated based on the X-ray diffraction, morphology observations, and magnetic properties studied using various instrumental analyses. Nearly Pure, single magnetic domain SrFe12O19 powder with crystalline size ranging from 55 to 75 nm was produced when x = 0.00 at 1050 °C. It had a maximum intrinsic coercivity (iHc) of 4.92 kOe, a magnetization value (Mmax) of 60.13 emu/g, and a remanence magnetization (Mr) of 34.75 emu/g. Calcination at 1200 °C was found to increase the Mmax to 64.52 emu/g but to decrease the iHc. Experimental results suggested a possible mechanism for the formation of SrFe12O19. The as-synthesized powders and the calcined ones with different x values were introduced into thermal polyurethane (TPU) matrix to prepare a composite. The relative complex permittivity (ɛr = ɛ′ − jɛ″) and permeability (μr = μ′ − jμ″) of the composite specimens were measured within a frequency range of 1–12 GHz using a network analyzer. Adding SrTiO3 to SrFe12O19 was demonstrated not only to improve the ɛr but also to modify the μr. This similar effect was observed when adjusting the calcination temperature.

ZnO films were pre-treated with nitrogen implantation in the range from 5×1012 to 5×1015 cm−2. Effect of nitrogen concentration on structural crystallinity and photoluminescence properties of nitrogen-implanted ZnO films under different atmospheres and annealing treatments was investigated. It was found that there exists a solubility issue of nitrogen in ZnO films at 850 °C via secondary ion mass spectrometry (SIMS). It was found that the peak intensity of near band-edge (NBE) emission remarkably decreases with the increase of concentration of implanted nitrogen if annealed in nitrogen atmosphere due to the increased oxygen vacancies. However, when the ZnO was implanted with 5×1012 cm−2 and annealed in oxygen atmosphere, the optical properties are improved probably because the effective incorporation of O atom diminishes those donor levels (oxygen vacancies) and the crystallinity is also improved due to implanted nitrogen. However, excess nitrogen would reduce the crystallinity and promote the formation of the deep-level emission due to high amount of intrinsic and structure defects.

Ni0.5Zn0.5Fe2O4 ferrite powders were synthesized by a hydrothermal method. The nanoparticles of these materials were mixed with a thermal-plastic polyurethane (TPU)polymer in order to form a suitable composite for electromagnetic wave absorber in a frequency range from 2.0 to 15.0 GHz. The effect of particle size on the reflection loss was investigated by comparing nanosized and microsized powders. The reflection loss as a function of frequency ( f ), thickness of the absorber(d), the real and imaginary part of permittivity (ε’ /ε”) and the real and imaginary part of permeability (μ’/μ”) were obtained by calculation using the Bruggeman effective medium theory. The effect of Co2+, Cu2+, and Mg2+ on the reflection loss was also studied.

NiZn ferrite with the chemical formula Ni0.5−xZn0.5−xM2xFe2O4 (M = Co, Cu, or Mg, and x = 0 or 0.05) was synthesized by a combustion synthesis method using metal nitrates and urea ((NH2)2CO) as reactants. The nanocrystallite of these materials were mixed with a thermal-plastic polyurethane (TPU) elastomer to be converted into a microwave-absorbing composite. The complex relative permittivity (ɛr = ɛ′−jɛ″) and permeability (μr = μ′−jμ″) of the absorber were measured in a frequency range of 2–12 GHz. The reflection loss (R.L.), matching frequency (fm) and matching thickness (dm) were calculated using the theory of the absorbing wall. Effects of both the particle size of ferrite and the dopant presented in the ferrite on the electromagnetic properties and microwave-absorbing characteristics were investigated. It was found that nanoparticles around 40 nm exhibit higher reflection loss than both those obtained from micro-sized powders and those with size less than 25 nm. Also, it was shown that the Co-doped, Mg-doped, and Cu-doped NiZn ferrite-TPU composites could be designed to be more negative than −20 dB, in a frequency range of 2–12 GHz, to become promising materials for microwave-absorbing application. These doped ferrite-containing composites have more effective microwave-absorbing characteristics compared to undoped one.

In this study, Ni 0.5 Zn 0.5 Fe 2 O 4 powder was synthesized via an exothermic reaction between nitrates [Ni(NO 3 ) 2 ·6H 2 O, Zn(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O, and NH 4 NO 3 ] and glycine [NH 2 CH 2 COOH]. By adjusting the glycine-to-nitrates ratio, the oxygen balance (OB) values of the reactant mixtures can be varied in which the combustion phenomena is altered and thereby the as-synthesized products with different characteristics are obtained. An interpretation based on the measurement of maximum combustion temperature ( T c ) and the amounts of gas evolved during reaction for various OB values has been proposed regarding the nature of combustion and its correlation with the characteristics of as-synthesized products. After instrumental analyses, it is shown that the as-synthesized powders are nanoscale crystallites with a large specific surface area and they inherit a superparamagnetic behavior.

Silver nanoparticles coated with Ni 0.5 Zn 0.5 Fe 2 O 4 spinel ferrites, forming a core–shell structure, were synthesized by utilizing hydrothermal method at different ferrite/silver ratio (ferrite/silver=6/1, 4/1, 2/1, 1/1, 1/6) and introduced into polyurethane matrix to be a microwave absorber. The complex permittivity ( e ' , e ' ' ) and permeability ( μ ' , μ ' ' ) of absorbing composite materials consisted of ferrite/silver core–shell nanopowders and polyurethane were measured in the frequency range of 2–15 GHz. The reflection loss and matching frequency were calculated from measured data using theory of the absorbing wall for different ferrite/silver ratios. It was found that the matching frequency for reflection loss exceeded a satisfactory −25 dB at 9.0 GHz for using NiZn ferrite as a filler shifts to higher frequencies (10.9–13.7 GHz) as the ferrite/silver ratio of core–shell nano-filler decreased from 6/1 to 2/1. The present result demonstrates that microwave absorbers using ferrite/silver core-shell filler can be fabricated for the applications over 9 GHz, with reflection loss more than−25 dB for specific frequencies, by controlling the ferrite/silver ratio of the core–shell nano-fillers in the composites.

Since the discovery of YBa2Cu3O7−x (Y123) by Wu et al. in 1987 [1, 2], the applications of high-Tc ceramic superconductors in scientific and engineering fields have been increasing continuously [3–5]. The conventional method of preparing Y123 powders is by the solid-state reaction of oxides and carbonates [1, 2, 6]. These starting materials are stoichiometrically mixed, and then calcined in air or oxygen at atmospheric pressure and a temperature of 900–980 ◦C for 20–50 hr. Intermittent grinding is required to obtain phase-pure and homogeneous Y123 powders. Although the method is relatively simple, and alternative processes exist which decrease the total reaction time [7], all of the conventional solid reaction processes are, in general, timeconsuming and energy-intensive. Recently, a variety of wet-chemical synthesis methods have also been reported to be effective in generating ultrafine and more homogeneous powders of ceramic oxides [8–10]. Relatively complex schedules and low production rates are the common problems of the wet-chemical methods. Fortunately, the drawbacks of these methods as mentioned above could be partially eliminated by the combustion synthesis method, which has been applied to the synthesis of various high performance materials including ceramics, intermetallics, and composites [11, 12]. Among its many advantages are low processing cost, and high energy efficiency and production rates [13]. However, the lack of homogeneity and relatively lower purity of the synthesized product are two potential disadvantages. Recently, several researchers have used a sol–gel combustion method to synthesize ferrite and perovskite powders [14–16]. This is a novel and unique technique that combines the chemical sol–gel process and the combustion synthesis process. The advantages of this technique include inexpensive precursors, simple preparation process, and a resulting submicron-sized powder with high homogeneity. Although there have

Ni-ferrite (NiFe 2 O 4 ) powder was synthesized by a self-propagating high-temperature synthesis (SHS) process using Fe, Fe 2 O 3 and various Ni-containing species (Ni-CSs) as reactants. The reactants were thoroughly mixed and pressed into a cylindrical compact. The compact was ignited by electrical heating under oxygen partial pressures varying between 0.02 and 1.5 MPa. The effects of the type of Ni-containing species, the reactant composition, the oxygen pressure on the combustion temperature, and the product conversion were investigated. X-ray diffraction (XRD) analysis showed that oxygen pressure promoted product conversion. Among several Ni-containing species tested, Ni 2 O 3 was found to give the highest conversion. The product conversion increased with increasing iron content and then decreased with further increase in iron content. Scanning electron microscope (SEM) observations showed that the product synthesized is mostly in the form of agglomerated fine particles with submicron size (0.1–0.5 μm). Hysteresis behavior analysis showed that the product as synthesized possessed better soft magnetic properties when compared with commercial Ni-ferrite prepared by the solid reaction method.

A single-bath electrodeposition method was developed to integrate multilayer Ag/Co nanowires with a commercial anodic alumina oxide (AAO) template with a pore diameter of 100–200 nm. An electrolyte system containing silver nitride and cobalt sulfide was studied using cyclic voltammetry, and the electrodeposition rate was varied to optimize the electrodeposition conditions. A constant stepwise potential and a variable cation ratio of [Co2+]/[Ag+] were used during electrodeposition. After the dissolution of the template in aqueous NaOH solution, multilayered Ag/Co nanowires were obtained with a composition of [Co]/[Ag80Co20], as identified by XRD and TEM, when [Co2+]/[Ag+] = 150. By annealing at 200°C for 1 h, uniformly structured (Co99.57/Ag100) nanowires were obtained. Compared with pure Co nanowires, the magnetic hysteresis loops showed a greater magnetic anisotropy for (Co99.57/Ag100) nanowires than for pure Co nanowires, corresponding to a change in the easy axis upon magnetization.

Strong blue photoluminescence emission at 450 nm from alumina films prepared from an alumina precursor was observed. Photoluminescence measurements indicate that the peak intensity of the blue emission changes with the pH value of the peptizing solution, the annealing temperature and the atmosphere. The blue emission appears at a low temperature of 50 °C and reaches a maximum strength at 400 °C in an oxygen atmosphere and 600 °C in a nitrogen atmosphere. HRTEM images show that the alumina films are composed of nanoparticles with a diameter of ≦10 nm. It is believed that the observed strong photoluminescence is associated with inherent defect centers in the material, where these are related to the structure transition and transformation from the boehmite phase to the γ-alumina phase and bond cleavage.

The effect of H2 plasma treatment of a seed layer on the synthesis and characterization of zinc oxide (ZnO) nanorods is determined. Using an Al-doped ZnO (AZO) thin film as a seed layer, well-aligned ZnO nanorods are rapidly grown on an indium tin oxide (ITO)-coated glass substrate using a microwave hydrothermal method. The deposited AZO substrate was previously treated with H2 plasma. The effect of H2 plasma treatment of the seed layer on the alignment, growth rate, and crystallinity of the ZnO nanorods is determined. It is shown that the alignment and growth rate of the ZnO nanorods depend on the characteristics and roughness of the seed layer, which are improved by H2 plasma treatment. Various characterization methods such as X-ray diffraction (XRD), cathodoluminescence (CL), transmission electron microscopy (TEM), and X-ray photoemission spectroscopy (XPS) are used to determine the characteristic quality of the ZnO nanorods. A fundamental model of the effect of H2 plasma treatment on the seed layer and ZnO growth using a microwave hydrothermal process is also presented.

The CdS nanocrystals with different aspect ratios (ARs) can be synthesized directly in the presence of conjugated polymer poly(3hexylthiophene-2,5-diyl) (P3HT). The UV-vis spectra of the composite films show a blue shift of the p-p* transition band with an increasing aspect ratio (AR) of the CdS nanocrystals, which was attributed to the destruction of the ordered structure of polymer chains as supported by PL measurements. Atomic force microscope measurements on P3HT/CdS film also demonstrate the aggregation of CdS nanocrystal in the P3HT matrix is more apparent for the CdS nanocrystals of AR ¼4 than that of AR ¼16, indicating a stronger interaction between P3HT and CdS for a larger AR (16), which is favorable for the network structure and formation of percolation paths to increase the transport properties of the P3HT/CdS solar cells. Therefore, a higher power conversion efficiencies (PCE) up to 2.95% can be obtained for the in-situ-grown P3HT/CdS with AR ¼16 upon annealing treatment at 160 � C for 60 min.

Highly arrayed ZnO nanorods were fabricated on the Si substrate buffered with patterned ZnO film (ZnOf∕Si) via wet-chemical process. The growth behavior and morphology of single-crystal ZnO nanorods (ZNs) were investigated in terms of the annealing temperatures of the sputtered ZnO film. We found that the growth morphology of ZnO nanorods is strongly dominated by the grain size of the ZnO film on the Si substrate. The ZnOf∕Si substrate was annealed at above a critical temperature to promote the crystallization of ZnO phase, and high-resolution transmission electron microscopy demonstrated that both ZNs and ZnOf on Si substrate are coherent. Furthermore, the ZNs seem to nucleate from the concave tip near the grain boundary between two ZnO grains in the ZnO film because of higher surface energy. However, a higher annealing temperature may lead to the formation of a larger ZnO crystal due to the coplanar coalescence behavior of several individual ZnO nanorods.