Gravimetric analysis for PM_(2.5) mass concentration based on year-round monitoring at an urban site in Beijing

Daily PM_（2.5）（particulate matter with an aerodynamic diameter of below 2.5 μm） mass concentrations were measured by gravimetric analysis in Chinese Research Academy of Environmental Sciences（CRAES）, in the northern part of the Beijing urban area, from December 2013 to April 2015. Two pairs of Teflon（T1/T2） and Quartz（Q1/Q2） samples were obtained, for a total number of 1352 valid filters. Results showed elevated pollution in Beijing,with an annual mean PM_（2.5）mass concentration of 102 μg/m^3. According to the calculated PM_（2.5）mass concentration, 50% of our sampling days were acceptable（PM_（2.5）〈 75 μg/m^3）, 30% had slight/medium pollution（75–150 μg/m^3）, and 7% had severe pollution（〉 250 μg/m^3）. Sampling interruption occurred frequently for the Teflon filter group（75%） in severe pollution periods,resulting in important data being missing. Further analysis showed that high PM_（2.5）combined with high relative humidity（RH） gave rise to the interruptions. The seasonal variation of PM_（2.5）was presented, with higher monthly average mass concentrations in winter（peak value in February, 422 μg/m^3）, and lower in summer（7 μg/m^3 in June）. From May to August, the typical summer period, least severe pollution events were observed, with high precipitation levels accelerating the process of wet deposition to remove PM_（2.5）. The case of February presented the most serious pollution, with monthly averaged PM_（2.5）of 181 μg/m^3 and 32% of days with severe pollution. The abundance of PM_（2.5）in winter could be related to increased coal consumption for heating needs.

Catalytic performances of Ni/mesoporous SiO_2 catalysts for dry reforming of methane to hydrogen

Several mesoporous silicas with different morphologies were controllably prepared by sol-gel method with adjustable ratio of dual template, and they were further impregnated with aqueous solution of nickel nitrate, followed by calcination in air. The synthesized silica supports and supported nickel samples were characterized using N2-adsorption/desorption, X-ray diffraction (XRD), H2temperature-programmed reduction (H2-TPR), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and thermo-gravimetric analysis (TGA-DTG) techniques. The Ni nanoparticles supported on shell-like silica are highly dispersed and yielded much narrower nickel particle-size than those on other mesoporous silica. The methane reforming with dioxide carbon reaction results showed that Ni nanoparticles supported on shell-like silica carrier exhibited the better catalytic performance and catalytic stability than those of nickel catalyst supported on other silica carrier. The thermo-gravimetric analysis on used nickel catalysts uncovered that catalyst deactivation depends on the type and nature of the coke deposited. The heterogeneous nature of the deposited coke was observed on nickel nanoparticles supported on spherical and peanut-like silica. Much narrower and lower TGA derivative peak was founded on Ni catalyst supported on the shell-like silica. ? 2016 Science Press

Effect of Calcium Leaching on the Properties of Cement-based Composites

Leaching is one of the major factors that alter the mechanical properties of cement-based composites.This study is aimed to investigate the effect of leaching on the properties of cement-based composites.Specimens with two water/cementitious ratios and two mineral admixtures were tested.An electrical potential was applied to accelerate the leaching process.Compressive strength test,scanning electronic microscopy,thermogravimetric analysis and X-ray diffraction analysis were conducted.Test results demonstrated that the calcium leaching reduced compressive strengths of concrete specimens,and such effect was prominent on the specimens without mineral admixtures.The leaching resistance increased with a decrease in water/cementitious ratio and an increase in amount of mineral admixtures.The mineral admixtures would reduce the amount of calcium hydroxide and refine the pore structure through pozzolanic reactions.A fair relationship was found between the calcium leaching and the compressive strength.

Effects of processing technology on essential oil and pharmacological action of frankincense

Background:According to the traditional Chinese medicine theory,the common processing methods for Ruxiang(frankincense)include stir-frying processing and vinegar processing.Methods:With network pharmacology and thermal analysis methods,we selected and identified the main and irritating ingredients,established the pyrolysis characteristic parameters for identifying frankincense quality,quantified the starting and optimum temperature limits for processing frankincense,and analyzed the influences of processing adjuvants(vinegar)on combustion pyrolysis characteristics of frankincense.By applying Fourier transformation infrared spectrometry,high performance liquid chromatography,gas chromatography and UV-visible spectrometry,we evaluated the processing technology developed in our study of frankincense and its processed products.Results:Based on network pharmacology,we can find that the classical compounds of essential oil are the main pharmacodynamics components of frankincense possessing the anti-inflammatory,analgesia,anti-tumor,anti-ulcer and ant-inflammatory bowel disease effects.The pyrolysis combustion rate peaks of frankincense at 285.27±7.05℃and 476.99±13.46℃were the characteristic peaks used to identify frankincense quality.The specific temperature of slow-fire processing,including the vinegar processing and stir-frying processing,was 148.72±5.09℃.Heating for 5.67±0.98 min after reaching processing temperature was needed for processing frankincense with vinegar.The kinetics analysis showed that both frankincense and its vinegar mixture exhibited good linear relationships.The feasibility and practicability for our processing technology were verified through the determination of medicinal compounds by Fourier transformation infrared spectrometry,high performance liquid chromatography,gas chromatography and UV.Conclusion:Frankincense essential oils were the main active components of frankincense,which also can be taken as the internal chemical control indexes to judge the quality control and to optimize the processing technology of frankincense.The pyrolysis combustion rate peaks of frankincense at 285.27±7.05℃and 476.99±13.46℃were the characteristic peaks that can be used to identify frankincense quality.The optimum processing conditions of vinegar-processed frankincense with were as follows:with vinegar,20%;heating temperature,148.72±5.09℃;and heating time,5.67±0.98 min.Under these conditions,frankincense essential oil could cause a moderate effect on combustion pyrolysis characteristics to exert its corresponding pharmacological effects.

Diffusion Characteristics and Removal of Cyclohexane in Polyolefin Elastomer Melt

The diffusion coefficient of volatiles in polymer solutions is a crucial parameter to describe the mass transfer efficiency and ability of volatiles.In this research,polyolefin elastomer(POE)was used as a polymer,and cyclohexane was used as a volatile.A gravimetric analysis was applied to measure the diffusion coefficient of cyclohexane in POE.The devolatilization rate of the POE-cyclohexane system under different conditions was measured.The effects of temperature,film sample thickness,and initial concentration of volatiles on the devolatilization rate were discussed.Based on the devolatilization rate data,the average diffusion coefficient of cyclohexane in POE was obtained by fitting with a mathematical model.The experimental results indicate that the devolatilization rate increased with increasing temperature and initial concentration of volatiles,but it decreased with increasing sample thickness.As the thickness increased,the overall diffusion resistance increased.As the temperature increased,the molecular movement increased,resulting in the increase of average diffusion coefficient.The relationship between the diffusion coefficient of the POE-cyclohexane system and temperature follows the Arrhenius law.The diffusion activation energy E=6201.73 J/mol,and the pre-exponential factor of the diffusion coefficient D0=2.64×10^(-10) m^(2)/s.This work can provide basic data for exploring the devolatilization of POE polymers and serves as a useful reference for enhancing the effect of devolatilization.

Complexes of Rare Earth Picrates with 1,10-Phenanthroline-N-Oxide

Rare earth picrate complexes with the ligand PhenNO, RE(PhenNO)2(pic)3(RE = La, Pr, Nd, Sm to approximately Tb, Er, Y), have been prepared in non-aqueous medium. The complexes were characterized by elementary analysis, molar conductance, IR, Raman, electronic, fluorescence and 1H NMR spectra and TG-DTA techniques.

Synthesis, Growth and Characterization of Nonlinear Optical Single Crystal of Serine Succinate

Nonlinear optical single crystal of Serine Succinate (SSA) was grown from a mixed solvent of water, ethanol and methanol. Since amino acid exhibits nonlinear optical property, it is of interest to dope them in serine. The overwhelming success of molecular engineering in controlling nonlinear optical properties in last decade has prompted better initiative in crystal engineering. In the present study single crystals of serine doped with succinic acid in different ratios have been grown by slow evaporation solution growth method. Grown serine succinate crystals were subjected to various characterization techniques. The cell parameters of the grown crystals were characterized by X-ray diffraction analysis. FT-Raman spectral studies were carried out on the SAA grown material to confirm the synthesized compound and the functional groups of serine succinate single crystal were identified from FTIR analysis. The optical transparency and upper cut off value of UV transmission spectrum of SSA crystal were recorded. Fluorescence study was also carried out for the grown materials. The mechanical hardness was estimated by Vickers’s micro hardness tester. The second harmonic generation (SHG) of the grown crystal was confirmed by Kurtz powder technique. Thermal properties of serine succinate crystal were evaluated with thermogravimetric, differential thermal and differential scanning calorimetric analyses. The SEM studies were also reported.

Thermal Kinetics and Decomposition Mechanism of 1-Amino-1,2,3-triazolium Nitrate

The thermal decomposition kinetics of 1-amino-l,2,3-triazolium nitrate（ATZ-NO3） was investigated by non-isothermal TG-DTG at various heating rates（2,5,10,15 and 20 ℃/min）.The results show that the thermal decomposition of ATZ-NO3 consists of two stages corresponding to the losing of nitrate anion,substituent group and the splitting of triazole ring respectively.The kinetic triplets of the two stages were described by a three-step method.First,the differential Kissinger and intergral Ozawa methods were used to calculate the apparent activation energies（E） and pre-exponential factors（A） of the two decomposition stages.Second,two calculation methods（intergral （S）atava-（S）esták and differential Achar methods） were used to obtain several probable decomposition mechanism functions.Third,three judgment methods（average,double-extrapolation and Popescu methods） were used to confirm the most probable decomposition mechanism functions.Both reaction models of the two stages were randominto-nucleation and random-growth mechanisms with n=3/2 for the first stage and n=1/3,m=3 for the second stage.The kinetic equations for the two decomposition stages of ATZ-NO3 may be expressed as da/dt=1013.60·e-128970/RT（1-α）[-1n（1-α）]-1/2 and da/dt=1011.41·e-117370/RT（1-α）[-1n（1-α）]-2/3.The thermodynamic parameters including Gibbs free energy of activation（△G≠）,entropy of activation（△S≠） and enthalpy of activation（△H≠）,for the thermal decomposition reaction were also derived.

Synthesis and characterization of sodium-lithium niobate ceramic structures and their composites with biopolymers

Ceramic powders of Na_(1−x)Li_(x)NbO_(3)(LNN)have been synthesized by an aqueous sol-gel route.These solid solutions were prepared from Na-Li-Nb precursor gel.The precursor was synthesized from Na-EDTA,Li-EDTA and Nb-citrate complexes and they acted as the source of Na,Li and Nb,respectively.Citric acid and ethylenediaminetetraacetic acid(EDTA)were used as the chelating agents for Na,Li and Nb.The precursor gel was calcinated on a muffle furnace at 750℃for one hour and this provided the ceramic structures.Composites of LNN-biopolymers were prepared by the encapsulation of the ceramic structures into the biopolymeric scaffolds.The ceramic structures and composites were characterized by FTIR,NMR,TG and SEM analysis.

Influence of oxygen non-stoichiometry on physical properties of NdSr_2Mn_2O_(7±δ)

Nd Sr2Mn2O7＋δ compounds were synthesized by ceramic method under three different cooling conditions. The Nd Sr2Mn2O7＋δ samples were characterized by powder X-ray diffraction（XRD）. Oxygen non-stoichiometry data for the studied powders were determined by using gravimetric and X-ray photoelectron spectroscopy（XPS） methods. The correlation of cooling method and oxygen as non-stoichiometry was established. The electroconductivity in samples was studied by using four-point probe method, and the strong correlation with non-stoichiometry was found out. Magnetization measurements were carried out. It was found that the magnetic and transport properties of the samples were also influenced by oxygen non-stoichiometry. The evolution of the magnetic properties could be explained by the formation of magnetic clusters in the vicinity of oxygen vacancies（OV） and strong competition between the superexchange and double exchange interactions.