Chemical Oxygen Demand of Seawater Determined with a Microwave Heating Method

This paper investigates a microwave heating method for the determination of chemical oxygen demand (COD) in seawater. The influences of microwave-power, heating time and standard substances on the results are studied. Using the proposed method, we analyzed the glucose standard solution, the coefficient of variation being less than 2%. Compared with the traditional electric stove heating method, the results of F-test and T-test showed that there was no significant difference between the two methods, but the microwave method had slightly higher precision and reproducibility than the electric stove method. With the microwave heating method, several seawater samples from Jiaozhou Bay and the South Yellow Sea were also analyzed. The recovery was between 97.5% and 104.3%. This new method has the advantages of shortening the heating time, improving the working efficiency and having simple operation and therefore can be used to analyze the COD in seawater.

STUDIES ON THE SYNTHESIS OF Ti_3O_5 BY MICROWAVE INDUCED PLASMA METHOD

Using a low power microwave generator and a surfatron discharge cavity, Ti3O5 was synthesized via the hydrogenation of TiO2 in surface wave induced microwave plasma. Besides, the chemical behavior of hydrogen in the plasma and its influence on the formation of Ti3O5 were preliminarily studied.

Influence of carbon coating prepared by microwave pyrolysis on properties of LiNi_(1/3) Mn_(1/3) Co_(1/3) O_2

A novel synthesis method of carbon-coated LiNil/3Mnl/3COl/302 cathode material for lithium-ion battery was reported. The carbon coating was produced from a precursor, glucose, by microwave-pyrolysis method. The prepared powders were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, X-ray fluorescence （XRF） and charge/discharge tests. XRD results indicate that the carbon coating does not change the phase structure of LiNil/3Mnl/3C01/302 material. SEM results show that the surface of spherical carbon-coated material becomes rough. Electrochemical performance results show that the carbon coating can improve the cycling performance of LiNii/3Mnl/3C01/302. The specific discharge capacity retention of the carbon-coated LiNi1/3Mnt/3Col/30z reached 85.0%-96.0% at the 50th cycle at 0.2C rate, and the specific discharge capacity retention is improved at a high rate.

Structural and spectroscopic characterization of HgS nanoparticles prepared via simple microwave approach in presence of novel sulfuring agent

Mercury sulfide (HgS) crystals with different morphologies and particle sizes, were obtained via a simple microwave reaction by a new precursor complex, [bis ((2-suphanylphenyl)imino]methylphenol) Hg(II)] ([Hg(C13H11NSO)2]2+). The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible (UV?Vis) spectroscopy. Mercury sulfide nanostructures with different sizes were prepared. The effects of precursor concentration, type of solvent, microwave time, and power on the particle size and morphology were investigated. The results show that the type of solvent and microwave power play key roles in the final size of HgS. Ethylene glycol is the best solvent for the synthesis of very fine particles of HgS, and the best power for the preparation of HgS nanoparticles with uniform size distribution is 900 W. The band gap for HgS nanoparticles calculated by UV–Vis spectrum was 3.2 eV which had about 1.2 eV blue shift in comparison with the band gap of 2 eV for bulk sample.

An AMSR-E Data Unmixing Method for Monitoring Flood and Waterlogging Disaster

Spectral remote sensing technique is usually used to monitor flood and waterlogging disaster.Although spectral remote sensing data have many advantages for ground information observation,such as real time and high spatial resolution,they are often interfered by clouds,haze and rain.As a result,it is very difficult to retrieve ground information from spectral remote sensing data under those conditions.Compared with spectral remote sensing tech-nique,passive microwave remote sensing technique has obvious superiority in most weather conditions.However,the main drawback of passive microwave remote sensing is the extreme low spatial resolution.Considering the wide ap-plication of the Advanced Microwave Scanning Radiometer-Earth Observing System(AMSR-E) data,an AMSR-E data unmixing method was proposed in this paper based on Bellerby's algorithm.By utilizing the surface type classifi-cation results with high spatial resolution,the proposed unmixing method can obtain the component brightness tem-perature and corresponding spatial position distribution,which effectively improve the spatial resolution of passive microwave remote sensing data.Through researching the AMSR-E unmixed data of Yongji County,Jilin Provinc,Northeast China after the worst flood and waterlogging disaster occurred on July 28,2010,the experimental results demonstrated that the AMSR-E unmixed data could effectively evaluate the flood and waterlogging disaster.

Structure and electrochemical properties of LiCoO_2 synthesized by microwave heating

Microwave synthesis method was applied to the fast preparation of LiCoO2. The structure of the synthesized oxides was analyzed by using X-ray diffraction. Only single-phase LiCoO2 was obtained. Electrochemical behaviors of LiCoO2 were investigated by charge-discharge cycling properties in the voltage range of 3.004.35 V（（vs Li）.） The results show that the prepared LiCoO2 powders calcinated at 900 ℃ for 120 min exhibit an initial charge and discharge capacity of 168 and 162 mA·h·g-1 at 0.1C current rate, respectively, as compared to 159 and 154 (mA·h·g-1) of LiCoO2 synthesized by conventional means. In addition, more than 95% of the capacity is retained （even） after 10 cycles. But with the increase of calcinating time, its electrochemical properties deteriorate. Compared with the conventional method, the microwave heating method is simple, fast, and with high energy efficiency.

RETRIEVAL OF CLEAR SKY MOISTURE PROFILES IN THE PACIFIC USING MEASUREMENTS OF MICROWAVE HUMIDITY SOUNDER FROM FY-3A SATELLITE

An improved Smith iterative method, which generally applies to microwave bands, is described. The moisture profiles retrieved from the brightness temperature data of microwave humidity sounder onboard FY-3A satellite, pertaining to clear sky, are shown over western North Pacific by using a vector-discrete ordination radiative transfer model. The retrieved profiles are compared with those from MODIS products, and the results of single point show that they are in good agreement with the results for lower layers. The distribution of retrieved humidity at 500 hPa is basically consistent with the actual situation, and the values are lower than that of the MODIS products. Compared with MODIS products, RMS is within 5.76g/kg at every single level separately.

Microwave absorption properties of Ag naowires/carbon black composites

The composite that can absorb the high-performance electromagnetic（EM） wave is constructed into a sandwiched structure composed of carbon black（CB）/ethylene-vinyl acetate（EVA） and Ag naowires（Ag NWs）. The Ag NWs sandwiched between two CB/EVA layers are used to improve the absorption properties of composite. The effects of EVA-to-CB weight ratio, concentration and diameter of Ag NWs with a thickness of 0.4 mm on microwave absorption are investigated.The results indicate that for an EVA-to-CB weight ratio of 1：3, Ag NW concentration of 1.0 mg/100 m L, and average diameter of 56 nm, the reflection loss（RL） of the composite is below-10 d B in a frequency range of 9.3 Ghz–18.0 GHz, with the minimum values of-40.0 d B and-25.6 d B at 13.5 GHz and 15.3 GHz, respectively. A finite element method（FEM）is used for calculating the RL of the composite. The calculated results are in agreement with the experimental data.

Data processing and error analysis for the CE-1 Lunar microwave radiometer

The microwave radiometer （MRM） onboard the Chang＇ E-1 （CE-I） lu- nar orbiter is a 4-frequency microwave radiometer, and it is mainly used to obtain the brightness temperature （TB） of the lunar surface, from which the thickness, temperature, dielectric constant and other related properties of the lunar regolith can be derived. The working mode of the CE-1 MRM, the ground calibration （including the official calibration coefficients）, as well as the acquisition and processing of the raw data are introduced. Our data analysis shows that TB increases with increasing frequency, decreases towards the lunar poles and is significantly affected by solar illumination. Our analysis also reveals that the main uncertainty in TB comes from ground calibration.

Synthesis of Fluorescent Carbon Quantum Dots and Their Application in the Plant Cell Imaging

Carbon quantum dots(CQDs) exhibit tremendous advantages for plant growth study due to its strong fluorescence and good biocompatibility. The fluorescent CQDs were synthesized by the onestep microwave method with the raw materials of citric acid(CA) and urea(UR), and expressed a unique green fluorescence with the optimal excitation wavelength of over 400 nm through adjusting the doping of N elements. It is demonstrated that CQDs can act as deliver media in plant and fluorescent probes for plant cell imaging through directly cultivated in the seedlings of melon and wheat, respectively. Based on the effects of the fluorescent CQDs on plants growth, we can further study the mechanisms of the ions transport in plants.

Cycloaddition of CO_2 and propylene oxide by using M(HBTC)(4,4'-bipy)·3DMF(M=Ni,Co,Zn) metal-organic frameworks

Three pillar-layered metal-organic frameworks（MOFs） based on M（HBTC）（4,4＇-bipy）.3DMF（M =Ni, Co, and Zn; HBTC = 1,3,5-benzenetricarboxylic acid, 4,4＇-bipy = 4,4′-bipyridine） were synthesized using a solvothermal method. Zn（HBTC）（4,4＇-bipy）.3DMF was synthesized for the first time using both a solvothermal and microwave method, and subsequently characterized by various physicochemical methods. The structure of M（HBTC）（4,4＇-bipy）.3DMF consisted of honeycomb grid layers of M2＋ ions and BTC units, which were further linked by the 4,4＇-bipy pillars to form a three-dimensional highly porous framework. All the MOFs displayed excellent synergistic catalytic properties with alkyl ammonium halides（TBAX） in the solventless fixation of CO_2 with epoxides to produce cyclic carbonates. The catalytic activities of these MOFs followed the trend Zn Co Ni,which was explained by the acid-base bifunctional properties. The microwave-synthesized Zn（HBTC）（4,4＇-bipy）.3DMF material exhibited physical, chemical, and catalytic properties that were similar to those of the catalyst obtained using a conventional solvothermal synthesis. The scope of various parameters, including recyclability, was studied, and a plausible reaction mechanism was suggested.

Preparation of Monodisperse Spherical SiO_2 by Microwave Hydrothermal Method and Kinetics of Dehydrated Hydroxyl

Monodisperse spherical SiO2 particles were successfully synthesized in 2-propanol-H2O-NH3 system by the microwave hydrothermal method using ammonia as catalyst. To investigate the influences on the size of spherical SiO2 particles, factors such as ammonia concentration, reaction temperature, stirring intensity and reactants mol ratio have been studied. The orthogonal experiments were carried out. The as-prepared SiO2 particles were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, Fourier transform infrared spectroscopy （FTIR） and differential thermal analysis （DTA）. The results indicated that the size of SiO2 particles increased greatly with the increase in ammonia concentration, temperature and reactants mol ratio, but increased slightly with the increase in stirring intensity. Monodisperse spherical Si02 particles were amorphous with perfect sphere and uniform size. Hydroxyl was detected in SiO2. Kinetic parameters were calculated, and finally the reaction rate equation of dehydrated hydroxyl was obtained.

First-principles study on anatase TiO_2 codoped with nitrogen and praseodymium

The crystal structures, electronic structures and optical properties of nitrogen or/and praseodymium doped anatase TiO2 were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on density functional theory. Highly efficient visible-light-induced nitrogen or/and praseodymium doped anatase TiO2 nanocrystal photocatalyst were synthesized by a microwave chemical method. The calculated results show that the photocatalytic activity of TiO2 can be enhanced by N doping or Pr doping, and can be further enhanced by N＋Pr codoping. The band gap change of the codoping TiO2 is more obvious than that of the single ion doping, which results in the red shift of the optical absorption edges. The results are of great significance for the understanding and further development of visible-light response high activity modified TiO2 photocatalyst. The photocatalytic activity of the samples for methyl blue degradation was investigated under the irradiation of fluorescent light. The experimental results show that the codoping TiO2 photocatalytic activity is obviously higher than that of the single ion doping. The experimental results accord with the calculated results.

Tunable Luminescence Properties and Elucidating the Electronic Structures of Single-Phase Spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)Phosphors for Warm-White-Lighting

A series of uniform single-phase spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors were prepared via a microwave hydrothermal method by using trisodium citrate dehydrate as surfactant.The phase structure,morphology and photoluminescence properties were measured by powder X-ray diffraction,scanning electron microscope and fluorescence spectrometer,respectively.The results show that uniform spherical microcrystals with diameters in the range of 2–4μm are obtained.And the phase and morphology of samples are not significantly changed by doping rare earth(RE^(3+))ions.Under the excitation wavelength of 356 and 365 nm,the samples BaWO 4:0.03Dy^(3+),yTm^(3+)can emit cold white light.In order to lower the correlated color temperature(CCT)to get a warm white light,the Eu^(3+)ions were doped into BaWO 4:0.03Dy^(3+),0.01Tm^(3+).Especially,under the excitation of 365 nm,BaWO 4:0.03Dy^(3+),0.01Tm^(3+),0.03Eu^(3+)phosphor shew a bright warm white light with color coordi-nate of(0.4013,0.3629)and CCT of 3288 K.Moreover,in the BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors,the energy transfer mechanism among Dy^(3+),Tm^(3+)and Eu^(3+)ions have been discussed and the change of electron structures have been calculated by first-principles calculations.The results shew that the uniform single-phase spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors could be favorable candidates in warm white LEDs.

Nano-engineered catalysts for high-performance oxygen reduction reaction

The efficient energy conversion of fuel cells is greatly constrained by the slow oxygen reduction reac tion(ORR)kinetics,which necessitates the use of highly active metal catalysts such as platinum(Pt).The critical challenge limiting large-scale usage of Pt is the capital cost that can be addressed through a pro totypical approach by embedding metal nanoparticles(NPs),e.g.,Pt NPs,in the conductive framework However,previously reported embedding approaches are sophisticated and suffer from limited yields leading to higher chemical process costs and remaining distant from commercial viability.Here,we re port a facile,cost-effective and time-efficient structural tuning approach to synthesizing ultrafine Pt NP impregnated within a conductive and highly porous carbon framework via a microwave-assisted polyo reduction method.Pt NPs with a uniform size of~2.27 nm can be successfully integrated within the pore of the carbon framework,enabling homogeneous dispersion.Benefiting from these highly dispersed and ultrafine Pt NPs,the electrochemical surface area(ECSA)is improved to 142.98 m^(2)/gPt,2.25 times highe than that of the commercial counterpart(63.52 m^(2)/gPt).Furthermore,our structurally optimized catalys composite features a remarkably catalytic activity with a high half-wave potential(E_(1/2))of 0.895 V and an improved mass activity(MA)of 0.2289 A/mgPt,2.39-fold improvement compared to the commercia counterpart.In addition,orthogonal experiments were designed to identify the key process parameter for fabricating Pt/C catalysts,offering insights for scaled-up and industrial production.

Microwave-assisted hydrothermal synthesis of Pt/SnO2 gas sensor for CO detection

In this paper,the Pt/SnO2 nanostructures were prepared via a facile one-step microwave assisted hydrothermal route.The structure of the introduced Pt/SnO2 and its gas-sensing properties toward CO were investigated.The results from the TEM test reveal that Pt grows on the SnO2 nanostructure,which was not found for bulk in this situ method,constructing Pt/SnO2.The results indicated that the sensor using 3.0 wt%Pt/SnO2 to 100 ppm carbon monoxide performed a superior sensing properties compared to 1.5 wt%and 4.5 wt%Pt/SnO2 at 225℃.The response time of 3.0 wt%sensor is 16 s to 100 ppm CO at225℃.Such enhanced gas sensing performances could be attributed to the chemical and electrical factors.In view of chemical factors,the presence of Pt facilitates the surface reaction,which will improve the gas sensing properties.With respect to the electrical factors,the Pt/SnO2 plays roles in increasing the sensor’s response due to its characteristic configuration.In addition,the one-step in situ microwave assisted process provides a promising and versatile choice for the preparation of gas sensing materials.

Fabrication and characterization of YVO_4:Eu^(3+) nanomaterials by the microwave technique

Fabrication and characterization of YVO4：Eu^3＋ nanophosphors prepared by microwave （MW） irradiation assisted soft template synthesis were reported. The effects of synthesis conditions such as different powers of MW irradiation, pH values and concentration of reac- tion materials on properties of nanophosphor were also investigated to obtain the controllable size, morphology and high luminescence efficiency. Morphology, crystalline structure, and optical properties were characterized by field emission scanning electron microscopy （FE-SEM）, X-ray diffraction （XRD） and fluorescence spectroscopy, respectively. The results showed that YVOa：Eu^3＋ nanophosphors were obtained by using diethyleneglycol （DEG） as soft template, with pH values in the range of 4 to 12, upon microwave irradiation from 300 to 900 W, at temperature of 80 ℃. The high fluorescent YVOa：Eu^3＋ nanocrystals obtained with size from 15 nm down to 8 nm are more effective to develop an ultrahigh sensitive fluorescent label for biomolecule, cell and tissue.

Comparative study of Co_(3)O_(4)-ZSM-5 catalysts synthesized by different hydrothermal methods for the catalytic oxidation of dichloromethane

In this work,various Co_(3)O_(4)-ZSM-5 catalysts were prepared by the microwave hydrothermal method(MH-Co_(3)O_(4)@ZSM-5),dynamic hydrothermal method(DH-Co_(3)O_(4)@ZSM-5),and conventio nal hydrothermal method(CH-Co_(3)O_(4)/ZSM-5).Their catalytic oxidation of dichloromethane(DCM)was analyzed.Detailed characterizations such as X-ray diffractometer(XRD),scanning microscopy(SEM),X-ray photoelectron spectroscopy(XPS),Brunauer-Emmett-Teller(BET),H2 temperature-programmed reduction(H2-TPR),temperature-programmed desorption of O_(2)(O_(2)-TPD),temperature-programmed desorption of NH_(3)(NH_(3)-TPD),diffuse reflectance infrared Fourier-transform spectra with NH_(3)molecules(NH_(3)-DRIFT),and temperature-programmed surface reaction(TPSR)were performed.Results showed that with the assistance of microwave,MH-Co_(3)O_(4)@ZSM-5 formed a uniform core-shell structure,while the other two samples did not.MH-Co_(3)O_(4)@ZSM-5 possessed rich surface adsorbed oxygen species,higher ratio of Co^(3+)/Co^(2+),strong acidity,high reducibility,and oxygen mobility among the three Co_(3)O_(4)-ZSM-5 catalysts,which was beneficial for the improvement of DCM oxidation.In the oxidation of dichloromethane,MH-Co_(3)O_(4)@ZSM-5 presented the best activity and mineralization,which was consistent with the characterizations results.Meanwhile,according to the TPSR test,HCl or Cl_(2)removal from the catalyst surface was also promoted in MH-Co_(3)O_(4)@ZSM-5 by their abundant Bronsted acid sites and the promotion of Deacon reaction by Co_(3)O_(4)or the synergistic effect of Co_(3)O_(4)and ZSM-5.According to the results of in situ DRIFT studies,a possible reaction pathway of DCM oxidation was proposed over the MH-Co_(3)O_(4)@ZSM-5 catalysts.

A micro-wave strategy for synthesizing room temperature phosphorescent materials

Room temperature phosphorescent(RTP)materials have a variety of applications ranging from bioimaging,optoelectronic devices to information security protection.However,the preparation procedures for these materials are always tedious and time-consuming.Here,we report a micro-wave approach to prepare RTP carbon dots(CDs)in only 8 min.The micro-wave promoted the carbon and boron bond formation using natural compounds glucose and boric acids.This result has been confirmed using TEM,FTIR,XPS and XRD measurements.The C-B hetero atomized material presented a long afterglow property.With the irradiation with UV light,we observed an eight-second RTP by naked eyes after the lamp was turned off,and the phosphorescence lifetime was 487 ms.This excellent performance was mainly due to the formation of B-C bonds that promoted the intersystem crossings(ISC)and non-radiation transition of triplet states.Moreover,the glass state of the materials also helped to stabilize the triplet states of B-CDs and made its non-irradiation inactivated,which resulted in the characteristics of yellow green RTP.These results have demonstrated that micro-wave is a convenient and effective strategy to make hetero atomized RTP material,providing new possibilities for their industrial productions.

Rapid synthesis and properties of color-tunable phosphors SrMoO4：Eu^3＋,Tb^3＋

Color-tunable phosphors Sr0.94MoO4：xEu^3＋, （0.06 - x）Tb^3＋ were synthesized rapidly by microwave ra- diation method with active carbon particle as microwave absorbent. The synthesized phosphors were investigated by X-ray powder diffraction （XRD） and fluorescence spec- trophotometer. The effects of the ratio of Eu^3＋ and Tb^3＋ on the phase structure and luminescent properties of the phos- phors were discussed. The results show that Eu^3＋,Tb^3＋-doped samples can be well indexed to the pure tetragonal scheelite- type SrMoO4, indicating that Eu^3＋ and Tb^3＋ are effectively doped into the SrMoO4 host lattices. The as-synthesized Sro.94MoO4：xEu^3＋,（0.06 - x）Tb^3＋ phosphors have two luminescent centers （Eu^3＋ and Tb^3＋）, which can show red and green emissions under ultraviolet light excitation, respec- tively. Doping concentration of Eu^3＋ and Tb^3＋ has great effect on the intensity of emission peaks and the chromaticity of the samples, and the full color between green and red light can be achieved by adjusting the relative concentration of Eu^3＋ and Tb^3＋.