Z型g-C3N4/WO3·H2O的制备及其光催化CO2还原性能

以石墨相氮化碳(g-C₃N₄)和二水合钨酸钠为原料,采用水热合成法制备了复合材料g-C₃N₄/WO₃·H₂O(CNW-1),通过XRD、XPS、SEM、TEM对其进行了表征,探究了298 K、0.1 MPa条件下其对CO₂的可见光催化还原性能,并提出了可能的反应机理。通过调控WO₃结晶水含量可以实现CO和CH₄的产率调节,在反应10 h后,CNW-1具有最高的CH₄产率(0.33μmol/g),而g-C₃N₄/WO₃(CNW)具有最高的CO产率(0.67μmol/g)。该研究为CO₂选择性还原为C1化合物提供了一种有效策略,同时突出了以g-C₃N₄作为半导体构建Z型光催化体系在催化领域的应用潜力。     

Crystallization behavior and properties of K2O–CaO–Al2O3–SiO2 glass-ceramics

In order to obtain high-strength anorthite glass-ceramics, K₂O–CaO–Al₂O₃–SiO₂ quaternary glass and relevant glass-ceramics were prepared and investigated. The results show that anorthite along with kalsilite or leucite was precipitated from the parent glass. Kalsilite crystals were formed firstly and then converted into leucite through reacting with SiO₂ in the glass phase. The morphology of the crystals was dependent on the heat-treatment temperature. Column crystals were transformed into fine granular grains when the sintering temperature changed from 900 °C to 1100 °C. The activation energy (E_α) and avrami constant (n) were also calculated as 463.81 KJ/mol and 3.74 respectively, indicating that bulk nucleation and three-dimensional crystal growth were the dominating mechanisms in the temperature range 1000–1100 °C. The maximum value of the flexural strength for the glass-ceramics containing leucite was 248 MPa and the coefficient of thermal expansion (CTE) was in the range 5.69~11.94×10⁻⁶ K⁻¹. The leucite is the main reason for the high CTEs and high flexural strength of glass-ceramics.     

Z型g-C3N4/WO3·H2O的制备与光催化二氧化碳还原性能

利用可见光将CO₂转化为CO和CH₄有望同时解决温室效应和能源危机。Z型光催化体系能够最大限度降低光生电子-空穴对的复合,提高光催化效率。本文采用水热合成法制备了g-C₃N₄/WO₃·H₂O (CNW-1)复合材料,通过X射线衍射、X射线光电子能谱、电镜等方法进行结构表征,探究了298 K、0.1 MPa条件下其对CO₂的可见光催化还原性能,并提出了可能的反应机理。通过调控三氧化钨结晶水含量可以实现CO和CH₄的产量调节,在反应10 h后,CNW-1具有最高的CH₄产率(0.33 μmolg^_-1),而CNW具有最高的CO产率(0.67 μmolg_-1⁾。这项研究为CO₂选择性还原为C1化合物提供了一种有效策略,同时也突出了以g-C₃N₄作为半导体构建Z型光催化体系在催化领域的应用潜力。     

The influence of In2O3 on electrical characteristics of iron mixed Li2O–PbO–B2O3–SiO2–Bi2O3 multi-component glass system

Glasses of the composition 19Li₂O–20PbO–20B₂O₃–30SiO₂–(10−x) Bi₂O₃–1Fe₂O₃: xIn₂O₃ with six values of x (0 to 5.0) were synthesized. Dielectric properties viz., dielectric constant, ε′(ω), loss, tan δ, ac conductivity, σ_ac, electric modulus, M(ω) over wide ranges of frequency and temperature and also dielectric break down strength have been studied as a function of In₂O₃ concentration. The temperature dispersion of real part of dielectric constant, ε′(ω) has been analyzed using space charge polarization model. The dielectric loss (and also the electric moduli) variation with frequency and temperature exhibited relaxation effects and these effects were attributed to the divalent iron ion complexes. The ac conductivity exhibited maximal effect, whereas the activation energy for the conductivity demonstrated minimal magnitude at about 1.0 mol% of In₂O₃. The conductivity mechanism is understood due to the polaronic transfer between Fe²⁺ and Fe³⁺ ions. The low temperature ac conductivity mechanism is explained following the quantum mechanical tunneling model. Spectroscopic studies viz., optical absorption and ESR spectra have revealed that the redox ratio (Fe²⁺/Fe³⁺) is maximal when the concentration of In₂O₃ is ~1.0 mol%. The higher values of dielectric parameters observed at 1.0 mol% of In₂O₃ are attributed to the presence of iron ions largely in divalent state and act as modifiers. The analysis of these results together with spectroscopic studies has indicated that when In₂O₃ is present in the glass matrix in higher concentrations (more than 1.0 mol%) iron ions predominantly exist in trivalent state, occupy substitutional positions and make the glass more rigid. Such enhanced rigidity of the network is causing the decrease of dielectric parameters with the concentration of In₂O₃. Finally it is concluded that In₂O₃ mostly participate in the glass network in octahedral positions and make act as reducing agent (for iron ions) in the studied glass matrix when its concentration is ≤1.0 mol%.     

Determination of the eutectic solubility lines of the ternary system NaHCO3–Na2CO3–H2O

A crystallizer was built and a procedure developed to accurately measure the eutectic solubility lines where ice and salt coexist in equilibrium with the solution, for potential application of Eutectic Freeze Crystallization. The eutectic solubility lines of the ternary system NaHCO₃–Na₂CO₃–H₂O were determined experimentally and calculated with the extended UNIQUAC model. The extended UNIQUAC model describes the experimental data quite well. Anhydrous NaHCO₃ and Na₂CO₃·10H₂O were the only two types of crystals present in equilibrium with ice crystals in the ternary system. At the quadruple point NaHCO₃ and Na₂CO₃·10H₂O are in equilibrium with a solution of about 4.34 wt% of Na₂CO₃ and 4.77 wt% of NaHCO₃ at −3.32 °C. The anhydrous NaHCO₃ crystals were needle shaped with lengths between 5 and 10 μm, that were agglomerated into particles of about 100–300 μm, while the Na₂CO₃·10H₂O crystals were hexagonally shaped with sizes between 100 and 500 μm.     

Effect of different nucleation catalysts on the crystallization of Li2O–ZnO–MgO–Al2O3–SiO2 glasses

Based on local raw materials, a range of LiZnMg aluminosilicate glasses were prepared to investigate the influence of TiO₂, Cr₂O_3, and ZrO₂ on the crystallization behaviour and thermal expansion characteristics. Differential thermal analysis showed that the crystallization propensity increases in the order TiO₂ > Cr₂O₃ > ZrO₂. Virgilite, β-spodumene ss, gahnite, enstatite and cristobalite were formed in the prepared glass-ceramics. The microstructure of glass-ceramic samples showed growths of rounded and subrounded grains in the base sample, whereas, somewhat rod-like and accumulated growths appeared in samples containing ZrO₂. However, a rather homogeneous texture of accumulated growths was developed in glass-ceramics containing TiO₂ and Cr₂O₃. The coefficient of thermal expansion of parent glasses was sensitive to the type of nucleating agent added (Cr₂O₃ > TiO₂ > ZrO₂) varying from 24.8 × 10⁻⁷ to 65.1 × 10⁻⁷ °C⁻¹ being almost unchanged with the heat-treatment. The microhardness values of glass-ceramic samples were in the 763–779 kg/mm² range.     

Ag2O/WO3-SiO2气凝胶的制备及光催化性能研究

为扩大WO₃-SiO₂气凝胶的可见光吸收范围,改善其光催化效果,先以溶胶-凝胶法制备了WO₃-SiO₂气凝胶,再采用浸渍法制备了不同Ag₂O负载量的Ag₂O/WO₃-SiO₂复合气凝胶光催化剂。通过扫描电镜(SEM)、X射线衍射分析仪(XRD)、X射线光电子能谱仪(XPS)、紫外-可见光谱仪(UV-vis)、荧光分光光度计(PL)对样品进行了表征分析,并在464 nm波长光源下考察了样品光催化降解亚甲基蓝(MB)的性能。表征结果表明,负载的Ag₂O与WO₃-SiO₂气凝胶中的WO₃存在电子转移相互作用,形成了Ag₂O/WO₃异质结;Ag₂O/WO₃异质结使催化剂的带隙宽度变窄,有利于光生电子-空穴的激发,同时抑制了电子-空穴对的复合。结合光...     

Bi2O3对K2O–B2O3–SrO–Al2O3–Nb2O5–SiO2玻璃陶瓷介电储能性能的影响

随着电力电子系统的不断发展,高功率脉冲电容器的需求增多。电介质电容器因具有放电功率大、充放电速度快及性能稳定等优点,在电力系统、电子器件、脉冲电源等方面发挥着重要作用,广泛应用于民用领域及军事领域。通过熔融压延制备玻璃基体,采用可控结晶工艺研究了不同含量的Bi₂O₃ (x=0.0%、1.0%、2.0%、4.0%,摩尔分数)对K₂O–B₂O₃–Sr O–Al₂O₃–Nb₂O₅–SiO₂玻璃陶瓷物相演化、微观结构、介电和储能性能的影响。在该玻璃陶瓷中,KSr₂Nb₅O₁₅为主要析出晶相,当Bi₂O₃的加入量为x=2.0%(摩尔分数)时,热处理温度为950℃时,玻璃陶瓷样品的储能密度最大可达到1.27 J/cm³,室温下介电常数可达342,是热处...     

Structural and magnetic properties of Li2O–Fe2O3 ceramic nanostructures

xLi₂O–(1−x)α-Fe₂O₃ (x=0.1, 0.3, 0.5, and 0.7) nanoparticle systems were successfully synthesized by mechanochemical activation of Li₂O and α-Fe₂O₃ mixtures for 0–12 h of ball milling time. The study aims at exploring the formation of magnetic oxide semiconductors at the nanoscale, which is of crucial importance for catalysis, sensing and electrochemical applications. X-ray powder diffraction (XRD), Mössbauer spectroscopy and magnetic measurements were used to study the phase evolution of xLi₂O–(1−x)α-Fe₂O₃ nanoparticle systems under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the particle size as function of composition and milling times and indicated the presence of Li-substituted hematite and tetra lithium iron oxide LiFeO₂, along with the formation of multiple phases for large x values and long milling times. The Mössbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextets and a doublet upon duration of the milling process with lithium oxide. Magnetic measurements recorded at 5 K to room temperature (RT) in an applied magnetic field of 50,000 Oe showed that the magnetization of the milled samples is larger at low temperatures than at RT and increases with decreasing particle size. Zero field cooling measurements made possible the determination of the blocking temperatures of the specimens as function of ball milling time and evidenced the occurrence of superparamagnetism in the studied samples. This result correlates well with the observed presence of a quadrupole-split doublet in the Mössbauer spectra.     

Effect of ZnO–WO3 additives on sintering behavior and microwave dielectric properties of 0.95MgTiO3–0.05CaTiO3 ceramics

The effect of WO₃ addition on the phase formation, the microstructures and the microwave dielectric properties of 1 wt% ZnO doped 0.95MgTiO₃–0.05CaTiO₃ ceramics system were investigated. Formation of second phase MgTi₂O₅ could be effectively restrained through the addition of WO₃, but should be in right amount. WO₃ as additives could not only effectively lower the sintering temperature of the ceramics to 1310 °C, but also promote the densification. A dielectric constant ε_r of 20.02, a Q×f value of 62,000 (at 7 GHz), and a τ_f value of −5.1 ppm/°C were obtained for 1 wt% ZnO doped 0.95MgTiO₃–0.05CaTiO₃ ceramics with 0.5 wt% WO₃ addition sintered at 1310 °C.     

Study of AC electrical properties of V2O5–P2O5–B2O3–Dy2O3 glasses

The AC conductivity of glass samples of composition 60V₂O₅–5P₂O₅–(35−x)B₂O₃–xDy₂O₃, 0.4≤x≤1.2 has been analyzed. The samples were prepared by the usual melt-quench technique. The prepared compounds were analyzed by X-ray diffraction (XRD) and thermo gravimetric–differential thermal analysis (TG/DTA). The activation energies were evaluated using glass transition temperature (T_g) and peak temperature of crystallization (T_c) from TG/DTA. The dependence of activation energy on composition was discussed. The electrical conductance and capacitance were measured over a frequency range of 20 Hz to 1 MHz and a temperature range of 303–473 K; these reveal semiconducting features based predominantly on an ionic mechanism. The dielectric and complex-impedance response of the sample is discussed. The relaxation time was found to increase with increasing temperature. Jonscher's universal power law is applied to discuss the conductivity. The electrode polarization was found to be negligible and confirmed from electrical modulus.     

AlCl3·6H2O在FeCl3、CaCl2、KCl及KCl–FeCl3溶液中溶解度的实验及预测

如何将AlCl₃·6H₂O从众多组分中选择性地结晶分离是从煤矸石中提Al的关键,而AlCl₃·6H₂O在煤矸石酸浸体系中的热力学平衡数据对于结晶过程的控制至关重要。在25～85℃的温度范围内,测定了不同温度和溶液浓度下AlCl₃·6H₂O在FeCl₃、CaCl₂、KCl及KCl-FeCl₃溶液中的溶解度。实验发现温度对AlCl₃·6H₂O在所有溶液体系中溶解度的影响均不明显,溶解度只随温度的升高略有增加;溶液浓度是影响溶解度的主要因素,AlCl₃·6H₂O在所有溶液体系中的溶解度均随溶液浓度的升高而明显下降,分析其原因是由于溶液浓度的增大使得Cl^–同离子效应增强。为了提高OLI软件预测结果的准确性,对其嵌入Bromley-Zemaitis模型中“Al³⁺–Cl<...     

Effect of some nucleating agents on crystallizing phases and microstructure in Li2O–BaO–Al2O3–SiO2 system

Different concentrations of LiF and Cr₂O₃ were incorporated in Li, Ba aluminosilicate glass to establish their effects on the crystallization process. The kinetics of phase transformations, the final crystalline phase assemblages and the microstructures formed were found to be dependent on the types and concentration of the nucleant involved. Cr₂O₃ was found to increase the melting temperature and favor crystallization of β-spodumene ss hexacelsian and traces of monoclinic celsian. It also favors volume crystallization of finer grained microstructure. LiF was found to decrease the melting temperature and favor crystallization of β-spodumene ss and monoclinic celsian. LiF in low concentrations greatly facilitates the crystallization process, the β-eucryptite ss/β-spodumene ss transformation and hexacelsian/monoclinic celsian transformation. It also stimulates surface crystallization with holocrystalline coarse non-uniform textures. The effects of various Cr₂O₃ concentrations were discussed on the basis of the increased viscosity and separation of Cr₂O₃ and/or chromium spinel phases. The role of LiF was attributed to the role of fluorine ions in reducing the viscosity of the glasses, consequently facilitating crystallization of the structurally more complex silicate in addition to favoring reaching thermodynamic equilibrium.     

南通市大气中O3与NO2浓度特征分析

利用全国城市空气质量实时发布平台的数据,分析了2013.10~2014.3南通市O3、NO2浓度的变化规律。结果表明:南通市O3浓度日变化呈单峰型分布,日最大值出现在15点前后,日最小值出现在早晨8点前后;南通市NO2浓度日变化呈双峰型分布,上午9点左右与下午19点左右出现峰值。O3周末浓度高于工作日,而周末NO2浓度低于工作日,呈现明显的"周末效应"。南通市O3的形成可能处于VOCs控制区,减少VOCs的排放可以有效地控制低层大气中O3的浓度。     

Composite wasteform based on SiO2–PbO–CaO–ZrO2–TiO2–(B2O3–K2O) parent glass with zircon as the second component

Many different types of glass and ceramic wasteforms have been investigated for nuclear waste immobilization. This study deals with synthesizing composite wasteforms based on a parent glass belonging to the SiO₂–PbO–CaO–ZrO₂–TiO₂–(B₂O₃–K₂O) system with the use of zircon as a second component. The fabrication involves powder mixing, pressing and pressureless sintering. The processing conditions were investigated so as to achieve the highest density and the best sintering temperature for different amounts of zircon, i.e. 5, 10 and 15 wt%. The sintered products were studied by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM); as well as ICP-MAS for leaching experiments. The most promising composite containing zirkelite and titanite crystals in a lead-rich glassy matrix was obtained at 700 °C for 10 wt% zircon.     

铅纳米晶掺杂Na2O–B2O3–SiO2玻璃的三阶光学非线性

采用溶胶–凝胶法制备了铅纳米晶掺杂的Na2O–B2O3–SiO2玻璃。利用X射线衍射仪、透射电子显微镜、选区电子衍射结合X射线能谱对纳米晶的微结构、尺寸大小及组成进行分析。用紫外–可见–近红外分光光度法和Z-扫描技术分析了该玻璃的线性和非线性光学性质。结果表明:铅纳米晶在玻璃中呈球形,结晶性较好并表现出良好的分散性,属于立方晶系,颗粒尺寸大小基本分布在10~31nm范围内;在整个测试波长范围内没有明显的吸收峰,光学透过率高;Z-扫描测试结果表明,样品的非线性光学性能优良,其中三阶非线性性能参数为:γ=1.67×10–16m2/W,β=7.02×10–11m/W,χ(3)=2.61×10–17m2/W2。     

WO3/TiO2催化剂活性组分W对SO2的氧化特性

采用超声浸渍法制备了不同W负载量的WO₃/TiO₂催化剂,研究了W负载量、温度及SO₂浓度对催化剂表面SO₂氧化过程的影响。结果表明,催化剂表面SO₂氧化率随W负载量及温度的升高而增大,当W负载量由1%增至7%时,SO₂氧化率由0.034%升高至0.210%;而当温度由280℃升高至400℃时,SO₂氧化率由0.043%升高至0.240%。通过N₂吸附、XRD、Raman、NH₃-TPD、H₂-TPR及XPS等方法对催化剂样品进行表征。结果表明,活性组分W的增加会导致WO_x增加,该结构能够减弱催化剂表面Br?nsted酸性位点强度,增强SO₂在催化剂表面的吸附,同时导致催化剂表面吸附氧(O_α)增多,促进SO₂氧化;针对W负载量5%的催化剂原位红外试验结果表明,通入SO₂     

脱硝催化剂载体WO3/TiO2的制备及表征

以工业偏钛酸为原料,采用一步法和后嫁接法成功制备了选择性催化脱硝(SCR)催化剂载体材料钛钨(WO3/TiO2)粉。采用XRD、FTIR、NH3-TPD、BET等检测手段对样品进行表征。结果表明,两种方法制备的钛钨粉中钨物种主要以非晶态存在;一步法制备的钛钨粉与后嫁接法制备的钛钨粉相比,前者钨物种分散比较均匀,表面酸性较强,比表面积较大。可以认为,一步法制备的钛钨粉更适合作为脱硝催化剂的载体材料。     

含锌锰硼海藻酸体系Ca(NO3)2-Mg(NO3)2-H2O相图绘制及其在水溶肥料制备中的应用

采用等温溶解平衡法研究定量海藻酸、Zn(NO₃)₂、Mn(NO₃)₂、H₃BO₃体系中Ca(NO₃)₂-Mg(NO₃)₂-H₂O的相平衡关系,绘制0℃、10℃、20℃下的水盐体系相图,并根据相图制备了多种配方的液体水溶肥料产品。浸种实验表明,Ca、Mg、Zn、Mn、B、海藻酸质量浓度分别为71.00、36.20、16.15、8.09、2.02、0.106 1 g/L的配方水溶肥料400倍稀释液浸种效果最好。     

Electrical properties of Pr6O11-doped WO3 capacitor–varistor ceramics

The microstructure and electrical properties of Pr₆O₁₁-doped WO₃ ceramics were investigated. Results showed that the breakdown voltage of doped samples was lower than that of the undoped. The dielectric constant of doped samples was higher than that of the undoped, and the high dielectric constant made Pr₆O₁₁-doped WO₃ ceramics to be applicable as a kind of capacitor–varistor materials. A small content of Pr₆O₁₁ could significantly improve nonlinear properties of the samples. The WO₃–0.03 mol% Pr₆O₁₁ obtained a large nonlinear coefficient of 3.8, a low breakdown voltage of 8.8 V/mm, and a high dielectric constant of 7.69 × 10⁴ at 1 kHz. The defects theory was introduced to explain the nonlinear electrical behavior of Pr₆O₁₁-doped WO₃ ceramics.