Dielectric and pyroelectric characteristics of the infrared sensitive (Pb1?xSrx)TiO3 ceramics

PST ferroelectric ceramics were fabricated successfully by a two-step method, i e first, PbTiO₃ and SrTiO₃ were sintered respectively, then mixed and sintered together. The process and characteristics of PST ferroelectric ceramics were introduced and researched. Their dielectric and pyroelectric characteristics are as follows dielectric constant 10⁴ order, low dielectric loss (lower than 3.0% in the working frequency range of 1–1 000 kHz), saturation polarization intensity 10⁻¹ C/m² order, and pyroelectric coefficient 10⁻³ C/m²·K order.     

Synthesis and photoluminescence property of red phosphors LiEu1?xYx(WO4)0.5(MoO4)1.5 for white LED

A series of novel red phosphors LiEu_1−x Y _x (WO₄)_0.5(MoO₄)_1.5 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) were synthesized by conventional solid state reaction method with the starting materials: WO₃, MoO₃, Eu₂O₃, Li₂CO₃ and Y₂O₃. The spectrum and the crystal structure of the phosphors were characterized by F-4500 and XRD respectively. Meanwhile the effects of flux and Y³⁺ concentration on the crystal structure and luminescent properties of the phosphors were investigated. The results showed that the optimal content of flux () was 1 wt% and the optimal doping concentration of Y³⁺ was 0.5 mol. The emission spectrum showed the most intense peak was located at 615 nm, which corresponds to the ⁵ D ₀→⁷ F ₂ transition of Eu³⁺ and that Eu³⁺ occupied the lattice site of noncentrosymmetric environment in the scheelite phases. The excitation spectrum displayed that these phosphors could be effectively excited by ultraviolet (UV) (396 nm) and blue (466 nm) light, nicely in correspondence with the widely applied output wavelengths of ultraviolet or blue LED chips. The influence of flux on the luminescent properties of LiEu_0.5Y_0.5(WO₄)_0.5(MoO₄)_1.5 phosphor was analyzed. The XRD spectra indicated that the flux could help to crystallize the phosphor, and no other phases were formed except the tetragonal. When adding flux, the relative intensity of LiEu_0.5Y_0.5(WO₄)_0.5(MoO₄)_1.5 became much stronger and the average particle size of the phosphor decreased. Supported by the Key Programs for Science and Technology Development of Hubei Province (Grant No. 2005AA105A05)     

CeO2 的加入对(ZrO2)0.86(MgO)0.14陶瓷电导率的影响

对(ZrO     

制备方法对CeO2及CoOx/CeO2催化燃烧甲苯的影响

挥发性有机物(VOCs)是形成雾霾和臭氧的主要前驱物,控制其污染排放十分必要。论文研究采用热分解法、化学沉淀法和水热法制备CeO₂,并通过浸渍-焙烧将15 wt%的CoO_x负载在不同方法制备的CeO₂上,以甲苯为目标污染物研究了不同制备方法对CeO₂及CoO_x/CeO₂催化性能影响,并通过XRD、BET、SEM、H₂-TPR和Raman对催化剂进行表征。结果表明：在甲苯浓度为1,000 ppm,空速为20,000 h^_-1测试条件下,化学沉淀法制备的CeO₂具有最好的催化活性,在375℃达到80%的甲苯去除率;将其与Co物种复合后,Co/CeO₂-P能在255℃达到90%的去除率。300 ℃下,经过78 h的长周期实验,Co/CeO₂-P依然保持100%甲苯去除率。BET和H₂-TPR结果表明：不同方法制备的CeO₂拥有不同有比表面积和表面氧化还原性能,这是影响其催化活性的主要因素。     

Fe2(SO4)3对活性污泥微生物活性的影响

为了解Fe₂(SO₄)₃作为絮凝剂对活性污泥中微生物活性的影响,向活性污泥系统中投加质量浓度为20、40、60、80,100 mg·L-1的Fe₂(SO₄)₃,反应4 h后测定活性污泥的脱氢酶活性、比耗氧速率(R_SOU)、胞外聚合物(EPS)及各组分含量,同时测定系统出水的COD等各项指标．结果表明:Fe₂(SO₄)₃质量浓度在20～60 mg·L-1时对活性污泥的脱氢酶活性、R_SOUEPS及各组分含量影响均不大,此时污水中COD、TP、UV₂₅₄等污染物随Fe₂(SO₄)₃质量浓度增加而有较大幅度去除．Fe₂(SO₄)₃质量浓度为80 mg·L-1时,污泥的脱氢酶活性、R_SOU、总EPS含量均明显下降．当Fe₂(SO₄)₃质量浓度增加到100 mg·L-1时,污泥的脱氢酶活性、R_SOU进一步受到抑制,而总EPS含量则大幅度提升．此时污水中COD、TP、UV₂₅₄等污染物去除率增加幅度变缓,SCOD及NH₃-N去除作用有所下降．     

Thermal expansion properties and hygroscopicity of Y2?xSmxW3O12 (x = 0.0–0.4) compounds

A novel class of solid solutions of Y_2−x Sm _x W₃O₁₂ (x = 0.0−0.4) were synthesized and studied by means of powder X-ray diffraction. All samples crystallize in an orthorhombic space group Pnca. The lattice parameters a, b and c of Y_2−x Sm _x W₃O₁₂ increase with increasing Sm content. Since the compounds of this series hydrate at room temperature, thermogravimetric (TG) analysis was carried out. The result shows that the compound stores less water with increasing Sm content. The thermal expansion properties of Y_2−x Sm _x W₃O₁₂ (x = 0.1, 0.3 and 0.4) were investigated with high temperature X-ray diffraction. Negative thermal expansion coefficient α _I becomes less negative from −6.644×10⁻⁶ to −6.211×10⁻⁶°C⁻¹ when x changes from 0.1 to 0.4.     

Synthesis and luminescence properties of Pr3+ doped CaxBa1?xTiO3 (0.3?x<1) fine particles

Ca _x Ba_1−x TiO₃ (CBT) fine particles doped with red luminescence center of Pr³⁺ ions (Pr: CBT) were successfully synthesized by salt assisted spray pyrolysis (SASP) process. Scanning electronic microscope (SEM) and laser scattering analysis demonstrate that salt can be removed from the surface of particles by washing with Milli-Q water and the particles can be further separated by ball-milling to get well-dispersed Pr³⁺ ions doped CBT fine particles. The luminescence properties, such as photoluminescence (PL) and mechanoluminescence (ML), of as-synthesized Pr: CBT particles were investigated. For Pr: CBT fine particles with different Ca molar ratios, all the samples show one emission at 612 nm, with increasing Ca molar ratio, PL intensity of Pr: CBT fine particles become stronger and stronger. When pressure was loaded on the Pr: CBT pellet, mechanoluminescence(ML) emission was measured. The results show that the ML intensity is proportional to the applied pressure.     

空间L2(R2;e-x2-y2)中的函数逼近

利用L2(R2;e-x2-y2)的一个平移算子Fh定义了差分Δhk(f)和广义连续模Ωk(f;δ),根据Hermite多项式的性质引入了一个二阶微分算子D,由此来定义函数类Wφ(r,k)(D)和KH(α).借助于参考文献中的一些结论及研究方法可以得到f∈Wt(r,kv)(D)的充分必要条件,同时得到关于f∈KH(α),α>2的Fourier-Hermite系数cij(f)的级数∑i=0 to ∞∑j=0 to ∞cij(f)一定绝对收敛的结论.     

固态电解质LiZr2(PO4)3的掺杂及其在电极中的应用

NASICON型固态电解质磷酸锆锂(LZP)具有优异的结构稳定性和性能可靠性，但其在室温下的锂离子电导率较低，限制锂离子的传输。针对上述问题，采用溶胶凝胶法对磷酸锆锂电解质材料进行阳离子掺杂，提高材料的电导率，进而提升锂离子在材料中的输运能力。同时，将掺杂的磷酸锆锂电解质对电极进行修饰，提升电极本身的锂离子输运性能。探究了离子掺杂电解质对电极的锂离子扩散动力学性能的影响机理。实验结果表明，LiTi_0.25Zr_1.75(PO₄)₃对电极的锂离子扩散动力学性能提高最为显著，锂离子扩散系数达到3.25×10^-14cm²·S^-1,是未修饰电极的2.95倍，同时在5C倍率下，LiTi_0.25Zr_1.75(PO₄)₃修饰的电极比未修饰电极比容量提高了25.48 mAh·g^-1。     

水蒸汽对ZTM15(Y2O3)材料低温时效现象的影响

通过对ZrO2增韧莫来石陶瓷(ZTM)低温时效现象的研究,发现试样表面及内部存在的微裂纹是导致材料在100～200℃时效处理后强度下降的重要原因.当莫来石基体中四方氧化锆(t-ZrO2)晶粒为1.8μm时,ZTM15(2.0mol%Y2O3)材料在水蒸汽环境下经较短时间热处理,强度严重下降.水蒸汽可加速ZTM材料中四方氧化锆的相变．     

Cex(Tb0.27Dy0.73)1-xFe2合金的结构与磁致伸缩

采用X射线、金相和应变测试技术研究了Cex(Tb0.27Dy 0.73)1-xFe2合金的显微结构、晶格常数及磁致伸缩,结果表明未退火合金的主相为MgCu2型立方结构的1∶2相,第二相为1∶3相,且随着Ce含量的增加,第二相的含量也逐渐增加.经过700 ℃,72 h退火后,第二相的含量明显减少.合金的晶格常数和磁致伸缩随Ce含量的增加而减小.     

Mg70(A0.25Ni0.75)30合金结构及储氢性能

为研究稀土元素Ce、Y对非晶储氢合金催化及其性能的影响,采用快淬法制备Mg70(A0.25Ni0.75)30(A=Ce,Y)合金,使用Sievert’s气体吸附技术和差示热扫描技术研究其储氢性能和热力学稳定性。XRD衍射分析显示,快淬制备的合金为非晶合金,但在573K、2MPa的氢压下,氢化后的Mg70(Y0.25Ni0.75)30会产生MgH2、Mg2NiH4和2相,Mg70(Ce0.25Ni0.75)30会产生Mg2NiH4、CeNi5和MgH2相。不同温度的动力学测试结果表明,快淬法制备的Mg70-(Ce0.25Ni0.75)30和Mg70(Y0.25Ni0.75)30合金分别获得的最大吸氢量为质量分数4.42%和3.09%,Mg70(Ce0.25Ni0.75)30和Mg70(Y0.25Ni0.75)30合金前100s吸氢量分别达到各自最大吸氢量的97%和87%。通过对DSC曲线的分析发现,Mg70(A0.25Ni0.75)30的脱氢活化能较低,分别为111.025±2.790kJ/mol(A=Ce)、84.843±2.057kJ/mol(A=Y)和152.207±6.764kJ/mol(A=Y)。实验结果表明,Y元素对Mg70(A0.25Ni0.75)30合金催化及储氢性能的改善要优于Ce元素。     

α-Fe2O3(001)及其掺杂表面吸附As2O3机制的密度泛函理论

为提高催化剂抗砷能力,采用密度泛函理论（DFT）方法研究As₂O₃在α-Fe₂O₃（001）表面的吸附行为以及掺杂Mo、Mn、Ni对α-Fe₂O₃（001）表面As₂O₃吸附行为的影响。建立As₂O₃在α-Fe₂O₃（001）表面吸附模型和Mo、Mn、Ni掺杂的吸附模型,计算As₂O₃在催化剂表面的吸附能,分析成键态密度以及掺杂前后的As₂O₃在α-Fe₂O₃（001）表面的电荷布局。结果表明：这4种体系均发生电子转移,Mo掺杂活化了As₂O₃分子,使得As₂O₃倾向于吸附在Mo活性位点上,保护了Fe活性位点,...     

Influence of coexisting substances on the photodegradation behaviors of 17α-ethinylestradiol （EE2） in the UV/H2O2 process

The batch photodegradation reactor was used to investigate the influence of the common coexisting substances in wastewater,such as H+,anions (HCO3-,Cl-and NO3-) and organic compounds (methanol and bisphenol A),on the photodegradation behaviors of EE2 in the UV/H2O2 process.The results indicated that the addition of coexisting substances can influence the photodegradation behaviors of EE2 and it also follows the first-order kinetics.The acidic (pH 2-4) and alkaline (pH 10-12) medium benefit the photodegradation of EE2,but the photodegradation rate constant of EE2 keeps almost constant in the pH value of 4-10.The addition of anions,such as HCO3-,Cl-and NO3-,can inhibit the photodegradation of EE2,and the rate constant has a negative linear relationship with the concentration of the anions.However,the reduction degrees vary with the anions kinds,and the inhibition effect of the three anions is in the order of HCO3->NO3->Cl-.Addition of 5 mg/L methanol and bisphenol A can reduce the photodegradation rate constant of EE2by 84.31% and 72%,respectively.By comparison,the retardant effect of methanol is much more evident.In the studied concentrations range,the photodegradation rate constant of EE2 is the unary quadratic function of the organic compounds concentrations.     

负载型催化剂MnOx-CeO2/TiO2去除甲苯

为了考察铈掺杂对金属氧化物催化剂催化燃烧处理有机废气的影响,采用蜂窝状TiO2丝网作为催化燃烧催化剂的载体,以MnOx、CeO2作为活性组分,用浸渍法负载制备出催化燃烧催化剂,考察了活性组分负载量及配比、焙烧温度、焙烧时间对催化剂降解甲苯的影响.实验确定了催化剂的最佳制备工艺:Mn的负载量(质量分数)约为15%,Mn与Ce物质的量比为3∶1,催化剂的焙烧温度为500℃,焙烧时间为5h.结果表明:与催化剂MnOx/TiO2相比,掺杂Ce后的催化剂MnOx-CeO2/TiO2对甲苯催化燃烧的起燃温度和完全转化温度均有明显降低,催化剂表面燃烧物颗粒的粒径有所减小,分散均匀,更有利于甲苯的降解处理.     

N2与CH4对CO2非混相驱油效果的影响

在矿场应用中,注入CO2中混有的杂质气体会影响其驱油效果.为制定更加合理有效的开发方案,有必要研究杂质气体对CO2驱的影响.利用油藏数值模拟方法,在纯CO2气体注入参数优化的基础上,研究了N2与CH4两种杂质气体对CO2非混相驱体积波及系数、驱油效率、油井见气时间和采收率的影响;以尽量提高原油采收率为目标,确定了注入气中杂质气体的临界含量.结果表明,杂质气体的存在会导致CO2非混相驱体积波及系数增大,驱油效率降低,油井见气时间缩短;注入的CO2中N2的摩尔分数最高不应超过5%,CH4的摩尔分数最高不应超过14%.     

煤对N2/CH4/CO2混合气体竞争吸附特征与机理研究

为研究煤对N₂,CH₄及CO₂混合气体的竞争吸附特征及其机理,通过混合气体吸附/解吸装置,结合穿透曲线法,对大柳塔(DLT)、硫磺沟(LHG)、瑞能(RN)、山阳(SY)和屯宝(TB)5种煤样,开展了温度为20℃、注气压力为0.25 MPa条件下N₂,CH₄和CO₂等比例混合气体的竞争吸附试验,得到了不同煤样对混合气体竞争吸附的规律;通过低温氮气吸附法,分析了5种煤样的孔隙结构,研究了孔隙对混合气体竞争吸附的影响.结果表明：DLT,LHG和RN煤样中N₂和CH₄先达到吸附平衡,一段时间后这2种气体在装置出口端的体积分数均超过其初始体积分数,而SY和TB煤样中只有N₂的出口端体积分数超过了其初始体积分数.试验结果与Yoon-Nelson模型拟合结果较好,线性相关系数R²基本可达0.9以上;各煤样传质速率常数均有k(N₂)>k(CH_4<...     

Bi2O3和Fe2O3掺杂对BaTiO3陶瓷显微结构的影响

利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线能量色散谱(EDAX)等结构分析技术,研究了施主(Bi     

SO42-/ZrO2-Nd2O3固体酸的制备及其催化活性

以皮胶原纤维为模板剂,硫酸锆为锆源,掺杂稀土Nd元素制备SO42-/ZrO2-Nd2O3固体酸。通过TG、XRD、FT-IR、SEM以及N2吸附脱附分析等表征了制备条件对SO42-/ZrO2-Nd2O3固体酸结构的影响。结果表明,SO42-/ZrO2-Nd2O3固体酸较好地保持了模板的纤维结构,添加稀土Nd元素能有效抑制晶粒增长,ZrO2-Nd2O3晶粒尺寸为5.1~11.6 nm,比表面积为63.96 m2/g;以乙酸和正丁醇的酯化反应为模型反应考察SO42-/ZrO2-Nd2O3固体酸的催化活性,催化剂活性较高,重复使用5次,乙酸的转化率仍可达到85%,表现出较好的重复使用性,具有一定的工业应用前景。