Preparation and Characterization of Cerium Doped Ti/SnO_2-Mn_2O_3/PbO_2 Electrode

The acid-proof anode Ti/SnO2+Mn2O3/PbO2 doped with Ce was prepared by thermal decomposition and electrodeposition combination technology, the effect of Ce on the morphology and structure of anode was also studied in this paper. The results obtained by cyclic voltammetry (CV), electrochemical impedance spectroscopic (EIS), X-ray Diffraction (XRD) and scanning electron microscopy (SEM) indicated that PbO2 crystal grains presented honeycomb structure were formed on the electrode surface by doping with Ce. The specific surface areas and catalytic active sites of the Ce-PbO2 doped electrode were increased and the catalytic activity was evidently greater than the undoped one. However, when Ce was doped into the intermediate layer (SnO2+Mn2O3), a more cracked surface structure formed, thus leading electrode deactivation by passivation of the Ti-substrate. So the anodic stability was decreased according to the accelerated life tests.

Structural and microwave absorption properties of CoFe_(2)O_(4)/residual carbon composites

Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.

Effect of Replacement of Headspace Gas on N_2O and CO_2Emissions in Anaerobic Incubation of Soil

To study effect of C2H2 and change of headspace gas on N2O emission, denitrification, as well as CO2emission, slumes of an agricultural soil were anaerobically incubated for 7 da3’s at 25 ℃. Both N2O reduction and CO2 emissions were inhibited by the addition of 100 mL L-1 of C2H2. However, the inhibition to CO2 emission was alleviated by the replacement of headspace gas, and the N2O emission was enhanced by the replacement. Acetylene disappeared evidently from the soil slumes during the incubation. Consequently results obtained from the traditional C2H2 blocking technique for determination of denitrification rate, especially in a long-time incubation, should be explained with care because of its side effect existing in the incubation environments without change of headspace gas. To reduce the possible side effect on the processes other than denitrification, it is suggested that headspace gas should be replaced several times during a long-time incubation.

Effect of CeO_2 on Crystal Structures and Catalytic Properties of the Mn_2O_3 Catalysts

The manganese-cerium complex oxide catalysts were prepared by coprecipitation.The crystal structures,the desorption properties of surface oxygen and reducibility of these catalysts were investigated by means of X-ray diffraction analysis (XRD),temperature-programmed desopotion-mass spectrography (TPD-MS) and temperature-programmed reduction (TPR).The crystal structure of Mn-O and Mn-Ce-O catalysts are bixbyite-Mn2O3 and γ-Mn2O3 respectively.The presence of CeO2 can not change the position of the feature peaks of Mn2O3 on the TPD or profiles,but can increase evidently the amount of the adsorbed surface oxygen,which are correlated with the catalytic activity for methanol oxidation.The activity of the catalyst is optimum when Mn/Ce atom ratio is 4:1.The presence of CeO2 brings a change of the reducibility,which reveals that there is an interaction between Mn2O3 and CeO2.

凋落茶叶对华中地区酸化茶园土壤N_2O与CO_2排放的影响

采用室内培养试验方法,研究了凋落茶叶添加(0、5、10 g·kg-1和20 g·kg^(-1))对酸化茶园土壤N_2O和CO_2排放特征的影响。结果表明:4种添加水平下,N_2O和CO_2排放通量分别为0.24~3.92μg·kg^(-1)·h^(-1)和0.33~1.84 mg·kg^(-1)·h^(-1);凋落茶叶的添加显著促进了酸化茶园土壤N_2O和CO_2排放(P<0.05),且两种气体的排放通量随着凋落茶叶添加量的增加而增加;凋落茶叶显著提高了酸化土壤pH值(P<0.05),且添加量越多,pH值变幅越大,其一定程度上改善了茶园土壤酸化现象。茶园土壤铵态氮与N_2O排放通量呈极显著相关,而硝态氮与N_2O排放通量未呈显著相关性。土壤可溶性有机碳含量与N_2O和CO_2排放通量均呈极显著相关关系。茶园土壤N_2O排放通量和CO_2排放通量呈极显著正相关。研究结果有助于阐明凋落茶叶对茶园土壤温室气体排放的作用规律,且对了解茶园生态系统碳氮循环有一定的理论意义。

Factors controlling N_2O and CH_4 fluxes in mixed broad-leaved/Korean pine forest of Changbai Mountain, China

Using the closed chamber technique, the in situ measurements of N2O and CH4 fluxes was conducted in a broad-leaved Korean pine mixed forest ecosystem in Changbai Mountain, China. from June 1994 to october 1995. The relationships between fluxes (N2O and CH4) and some major environmental factors (temperature, soil water content and soil availabIe nitrogen) were studied. A significant positive correlation between Nzo emission and air/soil temperature was observed, but no significant correIation was found between N2O emission and soil water content (SWC). This result showed that temperature was an important controlling factor of N2O flux. There was a significant correlation between CH4 uptake and SWC, but no significant correlation was found between CH4 uptake and temperature. This suggested SWC was an important factor controlling CH4 uptake. The very significant negative correlation between logarithmic N2O flux and soil nitrate concentration, significant negative correlation between CH4 flux and soil ammonium content were also found.

N_2O emissions from agricultural soils in the North China Plain: the effect of chemical nitrogen fertilizer and organic manure

An enclosed chamber technique was used to measure N 2O emissions from intensively agricultural soils of the North China Plain during the periods of 1995—1996 and 1997—1998, to reflect distinct components of winter wheat and summer maize growing seasons. The results showed that the continuous application of fertilizer in agricultural soils increased N\-2O emissions by a factor of 24.1—28.1, the calculated annual chemical N fertilizer\|transformed N\-2O\|N emissions was 0.67%. Our results indicated that the application of organic manure also had a significant influence on soil N 2O emissions, which combined with the use of chemical N increased about 20% in a year. It was calculated that there were about 0.11% N of organic manure transformed as N 2O N. Annual mean N 2O emission from our study area of fertilized soils was estimated to be 57.1 μgN 2O/(m 2·h). A weak correlation was also found between N 2O emissions and soil available nitrogen content NH + 4.

EFFECT OF SnO_2 ADDITION ON THE SERVICE LIFE AND ELECTROCHEMICAL PROPERTIES OF Ti/IrO_2,+Ta_2O_5 ANODES IN PHENOLSULFONIC ACID SOLUTION

Service life of two different oxide anodes in phenolsulfonic acid (PSA) solution was investigated by accelerated electrolysis. The durability of Ti/IrO_2+Ta_2 O_5 anode increased by the addition of SnO_2 in the mixed oxides. The degradation mechanisms of Ti/IrO_2+ Ta_2 O_5 and Ti/IrO_2 +Ta_2 O_5 +SnO+2 anodes were different. It was shown from the observation of scanning electron microscopy (SEM) and the electrochcmical measurement that, the deactivation of Ti/IrO_2 + Ta_2 O_5 anode was due to the build-up of an organic film on surface. The growth of the covered film on surface was restricted by addition of SnO_2, which resulted in increasing of the service life of anodes. The over-potential for oxygen evolution on Ti/IrO_2 +Ta_2 O_5 electrode increased after doping SnO_2, and the intermediate products of PSA building-up on the surface was much more rapidly oxidized. Meanwhile, a certain part of the surface oxide deposit entered into the solution leading to loss of oxides, which resulted in degradation of Ti/IroO_2 + Ta_2 O_5 anode containing SnO_2 component.

Effects of Different Synthetic Parameters on Structure and Performance of LiMn_2O_4 by Adipic Acid-Assisted Sol-Gel Method

The spinel lithium manganese oxide cathode materials were prepared by adipic acid-assisted sol-gel method at 350～900 ℃ in air. The effects of water content of solution, molar ratio between metal ion and adipic acid, cooling rate, synthesis temperature and particle sizes on structure and electrochemical performance of LiMn_2O_4 are investigated by X-ray diffraction (XRD), and cyclic voltammetry (CV). The result shows that the structure and electrochemical performance of LiMn_2O_4 are greatly affected by synthesis condition, and the optimal synthesis condition is determined. Charge-discharge test reveals that the particle size and cooling rate have significant effects on the electrochemical performance of LiMn_2O_4 cathode materials.

增温和秸秆还田对黑土农田土壤氮素有效性和N_2O通量的影响

土壤氮转化速率决定着土壤供氮能力,除受到温度的影响,还受到底物有效性的影响。然而,在农田生态系统中,关于土壤氮素有效性和N_2O通量对气候变暖和秸秆还田耦合的响应研究仍不足。本研究在东北黑土区进行增温和秸秆还田试验,采用离子交换树脂膜和静态暗箱法,原位监测0~20 cm土层土壤铵态氮、硝态氮有效性和氧化亚氮(N_2O)通量,探究增温和秸秆还田对农田黑土氮转化的影响。结果表明:增温、秸秆还田没有显著影响土壤氮有效性,但其在不同时期存在显著差异。秸秆还田显著增加了N_2O通量,且7月增温和秸秆还田处理对N_2O通量具有显著交互作用。在不增温条件下,秸秆还田使N_2O显著提升了109%;在增温条件下,秸秆还田使N_2O显著下降了2%。增温、秸秆还田和取样月份对N_2O通量也具有显著交互作用。研究结果有利于评估全球气候变暖背景下秸秆还田对农田生态系统氮周转的调控作用,对研究黑土氮循环过程具有重要参考价值。

CO_2/N_2开关微乳液及其油污洗涤和分离性能

采用等摩尔的十二烷基苯磺酸钠与N-十二烷基-N,N-二甲基叔胺为主乳化剂,正丁醇为助乳化剂,正庚烷为油相,制得O/W型微乳液。在CO_2/N_2交替作用下,可实现微乳液-相分离-微乳液的可逆转换;原始微乳液与复原微乳液半径分别为(10.89±0.21)和(11.50±0.47)nm。该微乳液对多孔固体和织物表面烃类矿物油的洗油率分别为99.13%±0.32%和98.30%±0.28%,对油砂表面原油的洗油率为54.52%±0.25%。活性物质量分数相等时,微乳稀释液对织物表面油性记号笔渍的去污力是市售洗衣粉的1.90倍;而微乳原液的去污力是市售洗衣粉的2.02倍。洗后含油废液通入CO_2可迅速实现油水分层,分离油相后的残余水相经阴、阳离子交换树脂和活性炭常规处理,COD和TOC分别为40.62和17.51 mg/L,符合GB 18918-2002中一级水排放标准(COD≤100 mg/L,TOC≤20 mg/L)。

Effects of ultrasonic impregnation combined with calcination in N_2 atmosphere on the property of Co_3O_4/CeO_2 composites for catalytic methane combustion

CoO/CeOcomposites with high surface areas and ultrafine crystalline sizes for catalytic combustion of methane were firstly prepared by a new sol-gel method which combined ultrasonic impregnation treatment and calcination in Natmosphere. The samples were characterized by various means such as nitrogen adsorption/desorption, X-ray diffraction(XRD), Htemperature-programmed reduction(H-TPR),X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). Results showed that the modified catalyst had the mesoporous structure, comparatively higher amount of surface oxygen and larger oxygen vacancies than others. As a result of the structure and surface composition merits, a high methane combustion conversion(50%) could be obtained at a low temperature of 262 °C for the modified CoO/CeOcomposites catalysts. The experimental results demonstrated that ultrasonic impregnation treatment combined with the Nthermal treatment prior to calcination in air had a promising application for preparation of CoO/CeOcomposites catalysts for low-temperature catalytic combustion of methane.

EFFECTS OF In_2O_3 DOPING AND SINTERING TEMPERATURE ON THE ELECTRICAL PROPERTIES OF ZnO VARISTORS

ZnO varistors are prepared using the 0.1-0.3mm ZnO powders. The effects of the sintering temperature, contents of In2O3 doping on the non-linear properties of ZnO varistors have been investigated. Theresults show that this kind of ZnO powder has a high sintering activity. It is suitable for making the low voltage varistors. The Vc decreases with the increase of sintered temperature, when the In2O3 content is fixed(0. 98 %, mass fraction), and increases with the increase of In2O3 contents when the temperature is steady.

Agglomeration Control of Ultrafine Y_2O_3-ZrO_2 and (MgO, Y_2O_3)-ZrO_2 Powders Synthesized by Coprecipitation Process

Chemical coprecipitation was used to produce ultrafine and easily sinterable Y2O3-stabilized and （Y2O3,MgO）-stabilized ZrO2 powders. Six precipitation processes for preparation of ZrO2-based ultrafine powders were designed separately, meanwhile different techniques used to control the agglomeration formation were proposed. By means of TEM, SEM, Raman spectroscopy and IR spectroscopy, the mechanisms of agglomeration control in the precipitation processes and post-precipitation and drying process were investigated. The experimental results show that adding appropriate anion surface active agents （such as PAA1460） or polymer （PEG1540 matching with PEG200） in aqueous solution systems during precipitation processes could reinforce charge effect and location effect for gel particles interface. Adding wetting agents to wet gels washing with distilled water during drying process could change interface structure of gel particles and decrease surface tension between gel particles. The agglomeration control in the precipitation, post-precipitation and drying processes had remarkable influence on the characteristics of powders. By adding various macromolecules in the processes, the agglomeration state could be controlled efficiently, and the characteristics of powders were improved.

Optimum Preparation Conditions of LiNi_(0.8)Co_(0.2)O_2 and LiNi_(0.95)Ce_(0.05)O_2 as Lithium-Ion Battery Cathode Materials

The preparation of LiNi_(0.8)Co_(0.2)O_2 was discussed by the multiply sintering method for solid reaction, in which the sintered material was smashed, ground and pelletted between two successive sintering steps. The optimum technological condition was obtained through orthogonal experiments by L_9(3~4) and DTA analysis. The result indicates that the factors of effecting the electrochemical properties of synthesized LiNi_(0.8)Co_(0.2)O_2 are molar ratio of Li/Ni/Co, oxygen pressure, homothermal time, the final sintering temperature in turn according to its importance. The oxygen pressure is reviewed independently and the technological condition is further optimized. With the same method, rare earth element Ce was studied as substitute element of Co and the cathode material of LiNi_(0.95)Ce_(0.05)O_2 with excellent electrochemical properties was prepared. The electrochemical testing results of LiNi_(0.8)Co_(0.2)O_2 and LiNi_(0.95)Ce_(0.05)O_2 experimental batteries show that discharge capacities of them reach 165 and 148 mAh·g^(-1) respectively and the persistence is more than 9 h at 3.7 V.

Effects of soil moisture and temperature on CH_4 oxidation and N_2O emission of forest soil

Soil samples were taken from depth of 0-12cm in the virgin broad- leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L-1 and 200 μL·L-1 CH4 and N2O concentration were supplied for analysis. Laboratory study on CH4 oxidation and N2O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N2O. Air-dried soil sample could not oxidize atmospheric methane, but could produCt N2O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L-1. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N2O emissions within 2 hours. There were curvilinear correlations between N2O emission and temperature (r2=0.706, p <0.05), and between N2O emission andtwater content (r2=0.2968. p <0.05). These suggested temperature and water content were important factors controlling N2O emission. The correlation between CH4 oxidization and temperature was also found while CH4 was supplied 200 μL·L-1 (r2 =0.3573, p<0.05). Temperature was an important f8Ctor controlling CH4 oxidation. However, when 20 μL·L-1 CH4 was supplied, there was no correlation among CH4 oxidization, N2O emission, temperature and water content.

FT-IR Spectroscopic Investigation of Co-adsorption of Acetonitrile and CO on Fresh Mo_2C/Al_2O_3 Catalyst

The adsorption of acetonitrile and its co-adsorption with CO on fresh Mo_2C/Al_2O_3 catalyst have been studied by insitu FT-IR spectroscopy.Linearly adsorbed CH_3CN and CH_3CH_2NH_2 were formed after CH_3CN adsorption on the Mo_2C/ Al_2O_3 catalyst.The appearance of a strong band at 1578 cm^(-1) indicates that CH_3CN was reactive with hydrogen on the Mo_2C/Al_2O_3 catalyst.

Sol-Gel Derived SiO_2-Y_2O_3∶Eu^(3+) Nanocomposites and Their PL Properties

An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various europium ions doping concentrations were carried out. XRD patterns indicate that the samples show an amorphous matrix structure, and the SEM patterns show that the samples present a multi-hole loosen structure, and a rod structure after high-temperature annealling treatment (800 ℃) for 3 h. Raman spectra demonstrate that Y3+ and Eu3+ ions were incorporated into the composites successfully through the sol-gel and post-anneal process. Under the excitation of 387 nm (7F0→5G2) violet light (but not 394 nm (7F0→5L6)), the strongest emission spectrum, the red light, was observed at around 616 nm (5D0→7F2) when the samples were re-treated by annealing at high temperature after 3 months laying aside. Without annealing treatment, the optimized doping mole ratio of Eu ions is about 9%, which is much higher than that doped in SiOglass with the concentration of 3.5%, and it then becomes 5% when the samples are treated by high temperature annealing. In addition, the excitation of 532 nm (7F0→5D1) light can also arouse a comparatively strong emission.

Effects of cultivation on N_2O emission and seasonal quantitative variations of related microbes in a temperate grassland soil

Laboratory and in situ experiments were done to investigate the influences of cultivation on temperate semi arid grassland (for 17 years spring wheat planted once every two years without fertilization) on soil N 2O emission and quantitative variations of related soil microbes. In the laboratory (25℃ and soil moisture 18%), cultivation increased soil transformations of fertilizer nitrogen (100 μg N/g as NaNO 3, urea, or as urea with dicyandiamide 1 μg N/g). The N 2O emissions from the cultivated and uncultivated soils with or without nitrogen additions were relatively low, and mainly originated from the nitrification. The soil N 2O emission due to cultivation decreased somewhat upon no fertilization or NaNO 3 addition, but significantly upon urea addition. The role of dicyandiamide as nitrification inhibitor was only considerable in the cultivated soil, and had small influence on decreasing N 2O emission in the two soils. The influence of cultivation on soil N 2O emission was also reflected by the number variations of microbes related with soil nitrogen transformation in the two soils. Compared to the uncultivated grassland, in situ ammonifiers and denitrifiers in the cultivated grassland quantitatively averagely increased, and aerobic no symbiotic azotobacters were quantitatively similar, leading to the continued decrease of organic matter content and the decrease of N 2O emission from the cultivated grassland soil.

Preparation and Characterization of Ce_x Th_(1-x)O_2 Solid Solutions Prepared by Sol-Gel Method

The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x = 0.2, 0.5, 0.8) Ce_xTh_(1-x)O_2. Raman spectrum showsthat Ce-Th complex oxides can promote the formation of oxygen vacancies. Two reduction peaks appearin the TPR profiles of Ce_xTh_(1-x)O_2 solid solution. The a peak is attributed to the reduction ofCe^(4+) on the surface, and the β peak is attributed to the reduction of bulk CeO_2. Theincorporation of Th atom into CeO_2 improves the reduction of CeO_2. Ce_xTh_(1-x)O_2 mixed oxidesare promising materials for oxygen vacancies produced, as well as catalysts for many reactionsinvolved oxygen, such as the catalysts for three-way reactions for reducing the releasing pollutantsor combustion of VOCs.