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Monodisperse iron oxide nanoparticle-reduced graphene oxide composites were prepared by self-assembly in aqueous phase. Pre-synthesized iron oxide nanoparticles were transferred to aqueous phase and then mixed with graphene oxide dispersion. The iron oxide nanoparticles, with a diameter of around 10 nm, were self-assembled on the reduced graphene oxide sheets through electrostatic attraction during the reduction of graphene oxide. The magnetization curves indicated that all samples exhibited ferromagnetic behavior at room temperature with small coercivity. The values of specific saturated magnetization of composites with different densities of iron oxide nanoparticles are 38.3, 19.5, and 7.7 emu/g. Permittivity and permeability of composites exhibit obvious fluctuations, which are ascribed to the multiple magnetic resonances. The multiple resonances involve exchange resonances (the consequence of small size effect, surface effect, and spin wave excitations) and natural resonance.

Core–shell structural Fe 3 C@graphite-like carbon hollow spheres have been fabricated during carbonization of an environment-friendly precursor (alumina fibers coating with humic acid and Fe 3 + ions prepared by layer by layer self-assembly method). The diameter of the as-prepared hollow spheres ranges from 50 to 200 nm, while the thickness of the carbon shells is 20 nm (about 60 graphene layers). TEM results show that more than 95% hollow carbon spheres contain one Fe 3 C particle. Magnetic hysteresis measurement demonstrates the ferromagnetic property at room temperature, implying the potential application of the prepared composite as a support material in drug delivery area. A possible formation mechanism of the nanocomposite is suggested. This is a template-free method to produce the core–shell structural Fe 3 C@ graphite-like carbon hollow spheres.

Multilayer films consisting of negatively charged humic acid and positively charged polyelectrolyte have been fabricated on various substrates using the layer-by-layer self-assembly technique. The thickness (linearly increasing with the square root of NaCl concentration) and refractive index of the films determined by ellipsometry can be regulated by ionic strength through adjusting the coiling of the polyelectrolyte chains for assembly. The cone-shaped features on surface obtained by atomic force microscope are derived from the negatively charged colloidal humic acid binding with polyelectrolyte cation. The smooth features are corresponding to the dissociated humic acid with carboxylate ion (―COO−) electrostatically attracted on polyelectrolyte cation. These results are verified by Fourier transform infrared spectra. The linear dependence of the peak current on the square root of the scan rate revealed by the cyclic voltammetry indicates that the redox process at the electrode surface is diffusion-limited and the charge transport does not involve the film itself.

Simultaneous Al–Fe coatings on copper were prepared by pack cementation to investigate the microstructure and corrosion resistance. The cross-section of prepared specimen was analyzed by scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). Then the cross-section of specimen corroded by solution of ferric chloride in ethanol was evaluated using SEM and X-ray diffraction (XRD). The coating consists of an intermetallic layer and an interdiffusion layer, and the thickness of coating layer increases parabolically with holding temperatures from 730 °C to 900 °C. The aluminum content in the coating varies between 7.65 and 4.0% from the surface to the inside layer while the iron content varies between 2 and 0.5%. The coating layer is composed of а-Cu/Al solid solution with a small amount of iron. Alumina formed on the surface of the coating layer during corrosion provides very good protection for the coating layer in the corrosive atmosphere and enhances the corrosion resistance of the coating.

Hydrogen rich fuel gas production by gasification of wet biomass accompanied by CO 2 absorption is proposed. The paper addressed this topic, and experiments were conducted to investigate the effects of the moisture content ( M ), the molar ratio of Ca(OH) 2 to carbon in the biomass ([Ca]/[C]) and the reactor temperature ( T ) on hydrogen production and CO 2 absorption by CaO. Measurement of the calcium compounds in solid residues was carried out with XRD and SEM. The results show that directly gasifying of wet biomass not only favors hydrogen production but also promotes CO 2 absorption by CaO. For the experiment with wet biomass ( M = 0.90), the H 2 yield is increased by 51.5% while the CO 2 content is decreased by 28.4% than that for experiments with dry biomass ( M = 0.09). CaO plays the dual role of catalyst and sorbent. It is noteworthy that CaO reveals a stronger effect on the water gas shift reaction than on the steam reforming of methane. The increase of the reactor temperature contributes to produce more H 2 , but goes against CO 2 absorption by CaO. XRD spectrum and SEM image of the solid residues further confirmed that high temperature is unfavorable to CO 2 absorption by CaO. For the new method, the optimal operating temperature is in the 923–973 K range.

Hydrogen-rich gas production from pyrolysis of biomass in an autogenerated steam atmosphere was proposed. The scheme aims to utilize steam autogenerated from biomass moisture as a reactant to react with the intermediate products of pyrolysis to produce additional hydrogen. In the present Article, the effect of reactor temperature, moisture content, heating rate, and sweeping gas flow rate on the process was investigated experimentally. Measurement of the atomic structures of chars produced from pyrolysis of wet/predried biomass was carried out with XRD. The results show that heating rate is a key role in the process. Under fast-heating conditions, drying and pyrolysis occurred in a relatively shorter time, which enhances the interactions between the autogenerated steam and the intermediate products and hence produces more hydrogen. Under slow-heating conditions, however, the autogenerated steam from moisture will be partially purged away from the reaction zone, leading to a weakened effect on the subseque...

Aimed at the hydrogen production by gasification of wet biomass coupled CO 2 absorption, the microstructures of chars produced from gasification of wet/pre-dried biomass and several possible stages of absorbent were studied with N 2 adsorption, XRD and SEM. The results show that all the chars examined have essentially microporous structures of pore size less than 2 nm, and the char obtained from gasification of wet biomass at 923 K exhibits larger surface area ( A BET ) of 430.87 m 2 g −1 and total pore volume ( V pore ) of 0.188 m 3 g −1 than those (368.15 m 2 g −1 and 0.157 m 3 g −1 ) from pre-dried biomass at the same temperature. The great change of microstructures in the absorbents was observed in the gasification process. The CaO generated from the dehydration of Ca(OH) 2 has larger A BET and V pore , than its former Ca(OH) 2 , and the increase of pore mainly belongs to mesopores ranges (pore size between 2 nm and 50 nm). However, the generated CaO suffers from a jam of mesopores with the formation of CaCO 3 which will cause incomplete utilization. Although the burning of SR sample can realize CaO generation, the regenerated CaO with a totally deteriorated pore networks suggests poor reactivity. With the increase of temperature the CO 2 absorption by CaO is weakened gradually except in low temperature range of less than 973 K, meaning that the maximum temperature of the process should not exceed the decomposition temperature of CaCO 3 .

A modified rotating cone reactor (MRCR) was developed for the pyrolysis of coal with solid heat carrier. The experiments were performed to study the effects of cone rotational frequency, mass ratio of coal-to-sand, coal particle size and pyrolysis temperature on the pyrolysis of coal with solid heat carrier in the reactor. A real-time observation system was used to record the granular flow and mixing process in the rotating cone. The results show that the existence of bed behavior as one passive and one active layer is definitive for the granular flow in MRCR without stirrers. The rotating vessel with a stirrer is helpful to enhance the granular fluidity and mixing rate. The fine particles of coal and solid heat carrier in MRCR would be well mixed by a flat-bladed stirrer within 3–5 s. The particle discharge rate from the reactor tends to increase with the increasing of the cone rotational frequency, coal particle size or mass ratio of coal-to-heat carrier. Under the pyrolysis conditions, the weight loss of coal particles, sensitive to coal particle size, also depends on the pyrolysis temperature, the cone rotational frequency or the mass ratio of coal-to-heat carrier.

A novel annular spouted bed was developed and studied experimentally. The experiments were performed to examine the effects of feeding mode, air velocity and static bed height as well as particle size on particle mixing for different conditions in this device. The results show that feeding by a rotating cone greatly improves particle mixing by homogeneously projecting the particles into the annular bed. For feeding by a rotating cone, the time required to get uniform mixing laterally is shorten almost 10 times less than that for feeding at a fixed point. With increasing air velocity, the axial mixing speed increases more significantly than the lateral mixing speed. The static bed height has important effects on the uniformity of the final admixtures. With increasing static bed height, the degree of mixing of the final mixture (FDM) axially first decreases, then increases, but laterally, the FDM is monotone decreasing. The particles of small size are helpful to raise the mixing speed. In addition, the dead zone in the annular spouted bed was analyzed.

A homemade 7 × 2 inch MOCVD system is presented. With this system, high quality GaN epitaxial layers, InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown. The non-uniformity of undoped GaN epitaxial layers is as low as 2.86%. Using the LED structural epitaxial layers, blue LED chips with area of 350 × 350 μm2 were fabricated. Under 20 mA injection current, the optical output power of the blue LED is 8.62 mW.