介电失配度对沸石电流变液界面极化的影响

利用介电谱方法研究了NaA沸石/硅油和NaA沸石/煤油两种电流变液的介电行为, 测量发现两体系在10⁵ Hz处均出现明显的弛豫现象. 采用单弛豫Cole-Cole函数拟合各体系的介电参数, 结果表明在相同体积分数条件下硅油体系具有较大的介电增量(?ε), 且两体系的介电增量与体积分数(φ)均服从?ε＝4ε_mφ的函数关系. 通过计算和分析粒子与介质间介电失配程度, 阐明了油介质的介电常数(ε_m)对于沸石电流变液界面极化强度的贡献. 此外研究了吸附水对沸石电流变液界面极化的影响, 结果发现水的吸附对于体系的?ε值没有影响, 但明显降低了弛豫时间, 证明吸附水对沸石电流变液的界面极化率具有增强作用.     

钛酸铅/聚[偏氟乙烯(70)-三氟乙烯(30)]复合物的非线性介电性质

用自建的非线性介电测试装置研究了陶瓷相被极化 (B1 )以及陶瓷相和共聚物相都被极化 (B2 )的钛酸铅 /聚 [偏氟乙烯 ( 70 ) 三氟乙烯 ( 3 0 ) ](PT/P[VDF( 70 ) TrFE( 3 0 ) ]) 0 3型铁电复合物厚片在不同测试场强下的非线性介电系数 .对于PT含量 >0 3的复合物 ,介电系数ε1随场强的升高明显增大 .在 <0 1时 ,可用Maxwell Garnett方程拟合实验结果 .Bruggeman方程适合于低电场 ( <1MV/m)下复合物介电系数的预测 .通过Lz 的变化 ,用Yamada模型可拟合不同场强下复合物介电系数随的变化关系 .二阶非线性介电系数ε2 随的升高而增大 ,B2的ε2 大于B1 ,说明B2具有较高的剩余极化 .三阶非线性介电系数ε3 随场强的升高而减小 ,且高值的复合物具有较大的ε3 .两相都被极化试样的ε3 小于仅陶瓷相被极化的试样 .     

基于芯片介电电泳的细胞特性分析及种类判断

基于微流控芯片介电电泳( Dielectrophoresis,DEP)原理和技术,在自行设计制作的抛物线电极结构的微流控介电电泳芯片上,采用芯片介电泳临界频率测定法,选择缓冲液电导率为200～1000 μS/cm,激发电压为5V,分别对红细胞(RBC)、白细胞(WBC)和死活HepG2肝癌细胞的临界频率进行了测试,检测...     

阴离子表面活性剂SDBS胶束溶液的介电弛豫行为

用射频介电谱方法研究了0.1-80 mmol·L-1浓度的十二烷基苯磺酸钠(SDBS)水溶液体系的介质弛豫行为. 测量发现频率接近107 Hz时, 在临界胶束浓度(CMC)附近出现显著的介电弛豫现象. 采用Cole-Cole函数拟合SDBS体系介电数据, 其拟合参数具有明显变化规律: 介电增量(△ε)随SDBS摩尔浓度(cs)的增加而增大, 表现为两种线性关系, 并在cs=36 mmol·L-1附近出现拐点; 特征弛豫时间(τ0)却在cs=45 mmol·L-1出现极小值. 利用胶束电模型分析了介电弛豫机制, 认为束缚Na+对离子数量和胶束体积变化是引起介电增量和特征弛豫时间变化的两个重要原因.     

不同方法制备的介孔Ni/MgO催化剂上水蒸气重整苯酚制氢

利用浸渍法和水热共沉淀法两种方法,制备了介孔Ni/MgO催化剂,用于水蒸气重整生物质油模型物苯酚制取氢气;利用XRD、N2吸附/脱附、H2-TPR、TEM以及TG等手段对催化剂进行了表征。结果表明,以介孔MgO为载体,采用浸渍法制备的介孔NiO/MgO固溶体,具有较高的比表面积(60.6m2/g)以及较大的孔径(10.1nm)。与水热共沉淀法制备的催化剂相比,浸渍法制备的NiO/MgO前驱体经还原后的所得到介孔Ni/MgO催化剂Ni颗粒较小(5.0-6.0nm),分布均匀,具有较高的分散度(19.44%)。较大的比表面积能有效地促进活性金属颗粒的分散,而介孔有利于反应物和产物在催化剂孔道中的扩散。因此,该Ni/MgO催化剂在水蒸气重整苯酚制氢反应中具有较高的催化活性、稳定性和优异的抗积炭能力。     

PS-PBA粒子分散系的介电弛豫谱解析——同、反离子对弛豫的影响及表界面电参数的计算

制备了近纳米级的聚苯乙烯-丙烯酸丁酯(PS-PBA)复合微球粒子,并在40Hz～110×106Hz的宽频范围测量了该粒子分散在9种电解质中时的介电弛豫谱,发现了与PS微球粒子分散系不同的特异介电弛豫:低频弛豫对反离子种类具有敏感性而高频弛豫则与电解质种类几乎无关;根据Shilov-Dukhin模型和M-W-O模型分别分析了高、低频率的弛豫机制,并通过对介电谱的Cole-Cole拟合获得了各体系的介电参数.进一步利用Hanai方法由介电参数计算获得了所有体系的相参数;详细分析了体系的内部参数受PS-PBA微球自身结构以及电解质种类影响的原因;讨论了离子扩散系数对介电参数的影响,从而得出了低、高频的弛豫特征时间分别由同离子的扩散系数和反离子的扩散系数所决定之结论.最后,结合Grosse宽频介电理论计算了粒子表面的以及双电层的主要电参数,并分析了电解质种类差异对这些电参数的影响.     

沸石及核壳结构聚合物粒子分散系的介电解析── 粒子排列模式对体积分数的解释

在40 Hz～110 MHz频率范围对NaA沸石堆积体系和聚苯乙烯-聚吡咯悬浮液进行了介电测量. 两类体系分别在105和107 Hz表现出因界面极化产生的弛豫. 利用Hanai理论解析两类体系的介电谱, 发现解析体积分数与实测体积分数之间存在与体系的浓度相关的明显差异. 通过分析Wagner原始模型阐明了差异的原因, 指出了分散相粒子相互作用力与差异程度间的内在联系, 从介电角度为胶体分散系中粒子统计排列方式的确定提供了判定依据: 当分散系浓度高于临界值时, 其最可取粒子统计排列模式为六方最密型; 低于临界值后, 排列模式随浓度的降低逐渐向简单立方型转变.     

生物质在流化床中的空气-水蒸气气化研究

以流化床为反应器，对生物质的空气-水蒸气气化特性进行了研究。考察了一些主要参变量，如温度 (700 ℃～900 ℃)、水蒸气/生物质比(0～4.04)、空气当量比(0.19～0.27)以及生物质粒度(0.2 mm～0.9 mm)等对气化结果的影响。在实验研究的条件范围内，生物质产气率在1.43 m3/kg～2.57 m3/kg范围内变化，产气的低热值在6 741 kJ/m3～9 143 kJ/m3范围内变化。实验结果表明：较高的气化温度有利于氢的产生；但气化温度过高会使气体热值下降；与常规的空气气化相比，水蒸气的加入使生物质气化产气率显著提高，但水蒸气加入量过多使气化温度下降，产气率和产气热值降低；生物质颗粒粒度的大小对产气组分的分布和产气率均有影响，较小颗粒的生物质会产生较多的CH4、CO和较少的CO2。     

浓差极化的介电模型——复合膜/溶液体系的数值模拟

提出了具有电导率和介电常数线性分布的介质的介电模型, 并导出了其内部电的和结构性质的参数与宏观测量的电容和电导之间定量关系的理论表达式, 以模拟复合膜中的多孔层部分的介电弛豫行为. 大量的模拟计算描述并解释了多孔层介电谱随介电常数分布、厚度等性质而变化的规律. 进一步对具有层状构造的复合膜以及复合膜和溶液相组成的多层体系的弛豫行为进行了数值模拟, 比较了三个体系(多孔层、复合膜、复合膜/液相层状体系)的介电谱, 结果揭示了介电谱对各层性质的依赖关系. 所提出的电导率和介电常数线性分布的多孔层的介电模型, 也可用于具有其他电导率、介电常数分布规律的体系.     

类钙钛矿新铌酸盐Ba5LaTi2Nb3O18的合成、结构与介电特性

为满足现代通信技术小型化、集成化与高可靠性的迫切要求,探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理和电子科学等领域科学工作者的广泛关注,并已开发出复合钙钛矿结构的Ba(Mg1/3Ta2/3)O3、Ba(Zn1/3Ta2/3)O3和钨青铜结构的Ba6-3xLn8+2x·Ti18O54及Ba2Ti9O20等实用化的高性能材料[1～7].这类材料均由氧八面体共顶连接,而且氧八面体内(B位)、外(A位)阳离子比例等于或略大于1,由此,我们推测在B位与A位阳离子比例略小于1的类钙钛矿结构中也极有可能存在具有优良介电性能的新材料,因此对通式为AnBn-1O3n(n=5,6,7,8)的系列新化合物进行了系统的合成、结构与介电性能研究[8,9].本文报道在BaO-La2O3-TiO2-Nb2O5体系中合成的具有5层类钙钛矿结构的新铌酸盐Ba5LaTi2Nb3O18,发现该材料具有较好的介电性能.     

A comparative study of the metastable equilibrium solubility behavior of high-crystallinity and low-crystallinity carbonated apatites using pH and solution strontium as independent variables

Using solution strontium and pH as independent variables, the metastable equilibrium solubility (MES) behavior of two carbonated apatite (CAP) samples has been examined, a high-crystallinity CAP (properties expected to be similar to dental enamel) and a low-crystallinity CAP (properties expected to be similar to bone mineral). CAP samples were prepared by precipitation/digestion: (CAP A: high-crystallinity, 1.3 wt% CO3, synthesized at 85 degrees C; CAP B: low-crystallinity, 6.4 wt% CO3, synthesized at 50 degrees C). Baseline MES distributions were determined in a series of 0.1 M acetate buffers containing only calcium and phosphate (no strontium) over a broad range of solution conditions. To assess the influence of strontium, MES profiles were determined in a similar fashion with 20, 40, 60, and 80% of the solution calcium being replaced on an equal molar basis by solution strontium. To determine the correct function governing CAP dissolution, ion activity products (IAPs) were calculated from the compositions of buffer solutions based on the hydroxyapatite template (Ca(10-n)Sr(n)(PO4)6(OH)2 (n = 0-10)) and the calcium/hydroxide deficient hydroxyapatite template (Ca(9-n)Sr(n)(HPO4)(PO4)5OH (n = 0-9)). Findings: (a) for CAP A, at high solution strontium/calcium ratios, the MES profiles were essentially superimposable when the solution IAPs were calculated using the stoichiometry of Ca6Sr4(PO4)6(OH)2 and for CAP B by a stoichiometry of Ca7Sr2(HPO4)(PO4)5OH; (b) for CAP A, at low strontium/calcium ratios, the stoichiometry yielding MES data superpositioning was found to be that of hydroxyapatite and for CAP B, that of calcium/hydroxide deficient hydroxyapatite. When other stoichiometries were assumed, good superpositioning of the data was not possible.     

Electrochemical Catalytic Properties of Pt/FeSnO(OH)_5 towards Methanol Oxidation

The Pt/FeSnO(OH)_5 catalyst has been prepared by depositing Pt nanoparticles on the synthesized FeSnO(OH)_5 nanoboxes and demonstrates excellent performance towards methanol oxidation reaction(MOR) in direct methanol fuel cells(DMFCs).The Pt/FeSnO(OH)_5 catalyst exhibits a higher mass activity(1182.35 mA/mgPt) compared with Pt/C(594.57 mA/mgPt) catalysts.The X-ray powder diffraction,field emission scanning electron microscope,field emission transmission electron microscopy,X-ray photoelectron spectroscopy and electrochemical experiments have been employed to explore the relationships between the crystal structure and electrochemical properties.The increased activity and resistance of CO poisoning for Pt/FeSnO(OH)_5 catalyst can be attributed to the strong interaction between the transition metal in the hydroxide and Pt and the bifunctional effect.The higher relative concentration of Pt~0 in Pt/FeSnO(OH)_5 also contributes to the MOR activity.Moreover,the charge transfer resistance of Pt/FeSnO(OH)_5 is lower than that of Pt/C.Therefore,Pt/FeSnO(OH)_5 has great application prospect as a high-performance electrocatalyst in DMFCs.     

Reactivity of fly ash in cement paste studied by means of thermogravimetry and isothermal calorimetry

Four paste mixtures with varying replacement level of the cement content by fly ash have been studied. Due to fly ash, the acceleration period decreased and a third hydration peak was noticed with isothermal calorimetry. The total heat after 7 days increased with increasing fly ash content. From 1 to 7 days, thermogravimetry showed a higher chemically bound water and Ca(OH)₂-content for the pastes with fly ash. Between 7 and 14 days the calcium hydroxide started to be depleted due to the pozzolanic reaction. A unique relation was found between calcium hydroxide and total heat development.     

稀土氧化物对二次锌电极性能的影响

应用阴极极化法在锌电极上覆盖一层稀土氢氧化物膜La(OH)3或Ce(OH)3,并用循环伏安、动电位极化、定电位阴极极化实验研究其电化学性能.结果表明,La(OH)3或Ce(OH)3膜能抑制锌酸根离子的迁移,提高析氢过电位,降低腐蚀电流密度并能抑制枝晶生长.SEM观测显示,稀土氧化物La2O3或CeO2改变了锌沉积形态,进而提高了锌酸钙电极的充放电循环性能.     

Untersuchungen zur Physisorption und Chemisorption von Wasser auf Zinkoxid-Oberflächen

The investigation of different zinc oxide samples by means of thermogravimetry and infrared spectroscopy has shown that the surface of the samples is covered by an approximately monoatomic layer of hydroxide groups. Furthermore, varying amounts of carbonate groups are found which are due to the presence of zinc hydroxide carbonate II [Zn₅(OH)₆(CO₃)₂]. Below relative water vapour pressures of p/p₀ = 0.2 (25°C), two hydrogen bridges connect one physisorbed water molecule with two chemisorbed surface hydroxide groups. In addition, about the same amount of water is physically adsorbed between vapour pressures of p/p₀ 0.2 and 0.8. At still higher relative humidity, a multimolecular layer is built up which reaches a thickness of about 200 water molecules at p/p₀ = 1.0. All samples show in the v-OH region of the IR. spectrum a broad absorption with four bands, A, B, C, and D. The position of the bands and the change of their intensities when rising the temperature of the samples up to 600°C indicate that both bands of longer wave lengths, C and D, arise from physically adsorbed water molecules, while the bands A and B are due to hydroxide groups located on the crystallographic faces (0001) and (0001 ), respectively.     

电石制备过程中不同含钙化合物与焦炭的反应行为研究

针对粉状原料-氧热法电石生产新工艺的需求,通过程序升温法研究了多种粉状含钙原料与粉状焦炭直接反应制备电石的过程。结果表明,升温过程中CaCO3释放的CO2、Ca(OH)2和电石渣释放的H2O对焦炭的量和质的影响很小,CaCO3、Ca(OH)2和电石渣均可直接用于电石生产,电石生成反应自1 450℃开始,1 740℃左右达到峰值。CaSO4与焦炭在920℃左右反应形成CaS,在研究的温度范围内CaS不与焦炭反应。     

Selective production of benzene and naphthalene from poly(butylene terephthalate) and poly(ethylene naphthalene-2,6-dicarboxylate) by pyrolysis in the presence of calcium hydroxide

Poly(butylene terephthalate) (PBT) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) were pyrolysed in a fixed bed reactor in the presence of calcium hydroxide (Ca(OH)₂) in order to obtain benzene and naphthalene, respectively. In these experiments different ratios of polymer and Ca(OH)₂ were used. Also the temperature was varied in a range between 600 °C and 800 °C. It was found that the highest yield of benzene (67%) was obtained at a temperature of 700 °C and a molar Ca(OH)₂/PBT ratio of 10. The amount of carbon, fixed in the reactor residue after the experiment, was reduced from 56% for pure PBT to 38% under these conditions. Aromatic byproducts were reduced, as well, while the amount of 1,3-butadiene increased. Tetrahydrofuran was just formed under the influence of Ca(OH)₂.For PEN, the optimal conditions were found at a temperature of 600 °C and a molar Ca(OH)₂/PEN ratio of 5. A naphthalene yield of 80% from PEN was obtained. The rise of the naphthalene yield was caused by a more effective decomposition of the polyester by Ca(OH)₂, which led to the reduction of carbon in the reactor residue after the experiment from 59% for pure PEN to 10% under optimised conditions. The part of aromatic byproducts changed just slightly.     

羟基磷灰石中氢键的XPS考察

Several calcium orthophosphates (tricalcium phosphate, monocalcium dihydropho-sphate, dicalcium hydrophosphate, and hydroxyapatite) are characterized by XPS and IR method. The P2p electron binding energies follow the order Ca(H_2PO_4)_2>CaHPO_4>Ca_(10)(OH)_2(PO_4)_6>Ca_3(PO_4)_2. It is expounded that there is hydrogen bonding of (OH...OPO_3) between the OH~- ion and the neighbour oxygen of the phosphate in hydroxyapatite.     

Measurement and modelling of solubility for calcium sulfate dihydrate and calcium hydroxide in NaOH/KOH solutions

The solubility of calcium sulfate dihydrate (CaSO₄·2H₂O) and calcium hydroxide (Ca(OH)₂) in alkali solutions is essential to understand their desilication behavior from Bayer liquor. In this work, solubilities of calcium sulfate dihydrate and calcium hydroxide for the ternary systems of CaSO₄·2H₂O–NaOH–H₂O, CaSO₄·2H₂O–KOH–H₂O, and Ca(OH)₂–NaOH–H₂O were measured by using the classic isothermal dissolution method over the temperature range of 25–75 °C. The Pitzer model embedded in Aspen Plus platform was used to model the experimental solubility data for these systems. The experimental solubility data was employed to obtain the new binary interaction parameters for Ca(OH)⁺–OH⁻, Ca(OH)⁺–Ca²⁺ and Ca(OH)⁺–K⁺, suggesting that the species Ca(OH)⁺ is a dominant species in simulated solubility for alkali systems. Validation of the parameters was performed by predicting the solubility for the ternary systems of Ca(OH)₂–NaOH–H₂O, CaSO₄·2H₂O–NaOH–H₂O and CaSO₄·2H₂O–KOH–H₂O with the overall average relatively deviation (ARD) of 2.12%, 0.75% and 1.63%, respectively.     

Interactions of metal ions with water: ab initio molecular orbital studies of structure, vibrational frequencies, charge distributions, bonding enthalpies, and deprotonation enthalpies. 2. Monohydroxides

The formation and properties of a wide range of metal ion monohydroxides, M(n)(+)[OH(-)], where n = 1 and 2, have been studied by ab initio molecular orbital calculations at the MP2(FULL)/6-311++G**//MP2(FULL)/6-311++G** and CCSD(T)(FULL)/6-311++G**//MP2(FULL)/6-311++G** computational levels. The ions M(n)()(+) are from groups 1A, 2A, 3A, and 4A in the second, third, and fourth periods of the Periodic Table and from the first transition series. Geometrical parameters, vibrational frequencies, atomic charge distributions, orbital occupancies, and bonding enthalpies are reported. The M(n)(+)-O distances are shorter in the hydroxides than in the corresponding hydrates (published previously as Part 1, Inorg. Chem. 1998, 37, 4421-4431) due to a greater electrostatic interaction in the hydroxides. The natural bond orbitals for most of the first-row transition metal ion hydroxides do not contain a formal metal-oxygen bonding orbital; nevertheless the atomic charge distributions show that for both n = 1 and 2 a significant amount of electron density is consistently transferred from the hydroxide ion to the bound metal ion. Deprotonation enthalpies for the hydrates have been evaluated according to the simple dissociation process, M(n)(+)[OH(2)] --> M(n)(+)[OH(-)] + H(+), and also via proton transfer to another water molecule, M(n)(+)[OH(2)] + H(2)O --> M(n)(+)[OH(-)] + H(3)O(+). The drastic reduction in these deprotonation enthalpies as H(2)O molecules are sequentially bonded in the first coordination shell of the metal ion (amounting to 71, 64, 85, and 91 kcal/mol for the bonding of six water molecules to Mg(2+), Ca(2+), Mn(2+), and Zn(2+), respectively) is found to be due to the greater decrease in the bonding enthalpies for the hydroxides relative to the hydrates. Proton transfer to bases other than water, for example side chain groups of certain amino acids, could more than offset the decrease in deprotonation energy due to the filling of the first coordination shell. Linear relationships have been found between the pK(a) values for ionization of the Mg(2+), Ca(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+) aquo ions, and Delta for the bonding of the first water molecule, for the bonding of the hydroxide ion, and for proton dissociation from the monohydrate. Similar relationships have also been found between the pK(a) values and the reciprocal of the M-O bond lengths in both the monohydrates and hydroxides. Thus the ionization of metal hydrates in water echoes the properties of the monomeric species M(n)(+)[OH(2)].