共查询到20条相似文献，搜索用时 312 毫秒
1.
This work investigated the microwave dielectric properties of A-site substitution by rare earth La3+in(Pb0.5Ca0.5)(Fe0.5Ta0.5)O3(PCFT) system.A single perovskite phase was obtained only when the doping content was 2%.Suitable La3+ doping improved microwave dielectric performances.Excessive La3+doping caused the formation of secondary phase,which resulted in the decreasing of permittivity εrand quality factor Qfvalues.Especially,when the doping content is 2%-5%,permittivity εrwas above 75 and Qfvalues were 6... 相似文献
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The influences of the PbO-B2O3-CuV2O6 （PBC） additives on the microwave dielectric properties of （Pb0.5Ca0.5） （Fe0.5Nb0.5）O3 （PCFN） ceramics were investigated as a function of sintering temperature from 950 ℃ to 1 100 ℃. The sintering temperature of the specimens with the glass could be lowered from 1125 ℃ to 1 025℃ without the degradation of microwave dielectric properties. The microwave results showed that the dielectric constant cr was not significantly different while Qf values decreased with the increase of CuV206 content of PBC glass. For the specimens doped with PB-CV0.1 glass （81% PbO-9% B203-10% CuV2O6） and sintered at 1 025 ℃ for 3 h, the microwave dielectric properties of Qf=4 823 GHz, Cr=107.1 with TCF=＋15.03 ×10^-6/℃ were obtained. 相似文献
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Long Jiang Hanrui Du Le Li Xiangjiu Guan Yihao Zhang Liwei Li Xiaoxu Liu Lei Li Yingcheng Tian Li Zhang Shuai Wang Jie Chen Shaohua Shen 《天津大学学报(英文版)》2023,(6):462-472
The high exciton binding energy and lack of a positive oxidation band potential restrict the photocatalytic CO2 reduction efficiency of lead-free Bi-based halide perovskites Cs3Bi2X9(X=Br,I).In this study,a sequential growth method is presented to prepare a visible-light-driven(λ> 420 nm) Z-scheme heterojunction photocatalyst composed of BiVO4 nanocrystals decorated on a Cs3Bi2I9 nanosheet for photocatalyt... 相似文献
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采用溶胶-凝胶法制备了二氧化硅负载硅钨钼酸催化剂.以其为催化剂,对以丁酮和乙二醇为原料合成丁酮乙二醇缩酮的反应条件进行了研究,较系统地研究了酮醇物质的量比、催化剂用量、带水剂环己烷,反应时间对收率的影响.实验表明,二氧化硅负载硅钨钼酸催化剂是合成丁酮乙二醇缩酮的良好催化剂,在n（丁酮）∶n（乙二醇）=1∶1.4,催化剂用量为原料总质量的0.6%,环己烷作带水剂10 mL,反应时间75min的优化条件下,丁酮乙二醇缩酮的收率可达96.77%. 相似文献
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以二氧化硅负载磷钼钨酸H3PW6Mo6O40/SiO2为催化剂,苯甲醛和1,2-丙二醇为原料合成苯甲醛1,2-丙二醇缩醛.探讨H3PW6Mo6O40/SiO2对缩醛反应的催化活性,较系统地研究了醛醇物质的量比、催化剂用量、带水剂用量、反应时间等因素对产品收率的影响.实验表明:H3PW6Mo6O40/SiO2是合成苯甲醛1,2-丙二醇缩醛的良好催化剂,在n(苯甲醛)∶n(1,2丙二醇)=1∶1.5,催化剂用量为占总反应物质量的1.0%,带水剂环己烷用量10 mL,反应时间45 min的最佳条件下,苯甲醛1,2-丙二醇缩醛的收率可达83.3%. 相似文献
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采用溶胶-凝胶法,以硝酸铜、二氯化锡和钛酸四丁酯为原料,加入十六烷基三甲基溴化铵(CTAB)作软模板,制备CuO/SnO2/TiO2纳米复合物。分别用SEM、XRD、IR、UV-vis等对产物进行表征分析,CuO/SnO2/TiO2晶粒由锐钛矿相的TiO2、金红石相的SnO2和单斜晶系的CuO组成。以甲基橙为模拟污染物,研究其催化活性,结果表明CuO/SnO2/TiO2纳米复合物具有较好的光催化活性。 相似文献
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(K0.47Na0.47Li0.06)NbO3 (KNLN) lead-free ceramics were prepared by molten salt synthesis (MSS) method using k2CO3-Na2CO3 eutectic mixtures as the flux. The microstructure and piezoelectric properties when sintered at 980-1 030 ℃ were investigated. The calcined powders were examined by X-ray diffraction. The microstructure of the calcined powders and sintered bodies was observed using a scanning electron microscope (SEM).The piezoelectric constant d33 was measured using a quasi-static piezoelectric d33 meter. The planar coupling coefficient Kp was calculated by resonance-antiresonance method. The experimental data for each sample's performance indicators were the average values of 8 specimens. The relative densities of sintered specimens are above 97%, and the dielectric loss is below 0.03. It was found that (K0.47Na0.47Li0.06)NbO3 prepared by MSS is compact and lead-free. The piezoelectric constant d33 is 216 pC·N-1 and the planar electromechanical coupling factor Kp is 0.352. 相似文献
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The hot hardness behavior of Zr52.5Al10Ni10Cu15Be12.5 bulk metallic glass is studied from ambient temperature to the temperature over Tx （the onset crystallization temperature） using a hot macro-hardness tester and scanning electron microscopy （SEM）. The results show that the hot hardness behavior of Zr52.5Al10Ni10Cu15Be12.5 bulk metallic glass can be classified into 4 zones： the glassy zone in which the hardness almost linearly decreases with the increase of temperature, the viscoelastic zone in which the hardness is nearly unchanged, the viscous flow zone in which the hardness quickly tends towards near zero with temperature, and the crystallization zone in which the hardness sharply increases. The high temperature deformation behavior and the easy processable deformation region for bulk metallic glasses are also discussed on the basis of the hot marco-hardness. 相似文献
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由PM2.5和PM10引起的区域性大气污染日趋严重,对环境安全、动植物和人体健康造成了严重危害。本文通过对金口河区三年内新增企业情况、主要原辅料年用量及产品硅的年产生量、固体颗粒物年产生量与年排放量及空气中PM2.5和PM10含量的监测数据统计分析,评价出PM2.5和PM10的污染状况,进而提出可行的对策与建议。 相似文献
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采用超声波分散法制备了SiC-Al2O3-Y2O3体系陶瓷料浆,利用Zeta电位分析仪、粘度计、pH测试仪等设备对料浆的物理性能进行了测试,讨论分析了Zeta电位、pH值、粘度、固含量、素坯强度、沉降速率对陶瓷料浆性能的影响规律,结果表明:pH值为9.5,固含量为58%,加入0.8%阿拉伯树胶作为分散剂时SiC-Al2O3-Y2O3体系陶瓷料浆流动性好、固含量高、不易沉降。 相似文献
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Ba0.6Sr0.4TiO3 （BST） thin films with and without HfO 2 buffer layer were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Dependences of HfO 2 thickness on the dielectric property and leakage current of BST thin films were focused. The dielectric constant of BST thin films increased and then decreased with the increase of HfO 2 thickness, while the dielectric relaxation was gradually improved. The loss tangent and leakage current under positive bias decreased with the HfO 2 thickness increasing. The leakage current analysis based on the Schottky emission indicated an improvement of the BST/Pt interface with HfO 2 buffer layer. The loss tangent, tunability and figure of merit of optimized HfO 2 buffered BST thin film achieved 0.009 8, 21.91% （E max = 200 kV/cm）, 22.40 at 10 6 Hz, respectively. 相似文献
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焦更生 《渭南师范学院学报》2012,(2):57-60
为了提高C/C复合材料的高温抗氧化性能,设计了网状的SiC填充高性能的MoSi2和微量的TiSi2涂层,对制备涂层的化学形成机理进行了热力学分析.结果表明,在选择的实验条件下,制备设计的涂层是完全可行的,实验制备的涂层在1773K有氧环境下具有良好的抗氧化性能. 相似文献
16.
可见光光催化剂Bi2WO6制备研究进展 总被引：1，自引：0，他引：1
赵红丽 《唐山师范学院学报》2012,(2):11-15
综述了可见光光催化剂Bi2WO6制备研究进展,包括固相反应法、熔盐制备法、液相反应法、非晶态配合物法、水热法、微乳液-水热法、溶剂热法等。在这些制备方法中,水热法由于能够通过引入各种模板剂而方便地得到多种结构和形貌的Bi2WO6而被广泛采用,其它方法也各有其优点而有特定的使用场合。 相似文献
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以硅胶负载硅钨酸为催化剂,通过丁醛与1,2-丙二醇反应合成了丁醛1,2-丙二醇缩醛.较系统地研究了醛醇量比、催化剂用量、带水剂用量及反应时间等条件对收率的影响.结果表明:在丁醛用量为0.20 mol,n(丁醛)∶n(1,2-丙二醇)=1∶1.3,催化剂用量为0.1 g,环己烷为带水剂用量为4 mL,反应时间30 min的优化条件下,丁醛1,2-丙二醇缩醛的收率可达82.6%. 相似文献
18.
Gas chromatography （GC） analysis of sulfer dioxide is challenging because SO2 is a highly mobile and chemically active molecule. For the conventional GC method with flame photometric detector （FPD） and direct-injection, it is often ineffective particularly when the SO2 level is as low as on the trace level. In this paper, a modified GC system integrated with an adsorption-desorption device was developed to detect the trace SO2 impurity in H2 fuel. Adsorbent GDX-502 is used in the adsorber to adsorb/collect SO2 from the sample gas and desorb/release it in a concentrated flow so that the conventional GC at downstream could detect it with an acceptable accuracy. 相似文献
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In order to obtain anatase TiO2/expanded graphite with high expansion volume, titania gel was introduced to expandable graphite surface by sol-gel process, and then the composite was expanded and calcined at high temperature. The samples were analysed by using scanning electron microscope (SEM), X-ray diffraction(XRD), energy disperse spectroscopy(EDS), and differential scanning calorimetry(DSC). The optimal conditions for preparation are as follows: the molar ratio of tetrabutyl orthotitanate to triethanolamine is 1∶0.4, and the calcination and expansion temperature is in the range of 650-750 °C. Under such conditions, the expansion volume of composites could reach 98 mL/g, and the mass loss ratio is less than 5%. The analysis shows that lower temperature and smaller particle size of graphite are helpful to the formation of anatase-type of TiO2, but larger particle size will lead to lower mass loss ratio, and higher temperature and larger particle size will lead to higher expansion volume. 相似文献
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首先采用基于密度泛函理论(DFT)框架下广义梯度近似平面波超软赝势法(包括PBE、PBESOL、PW91、RPBE、WC)对尖晶石型ZnGa2O4的结构进行了优化,得到和实验值最接近晶格常数a0=0.8378 nm;然后在结构优化的基础上采用GGA-WC计算ZnGa2O4的电子结构和光学性质.结果表明,ZnGa2O4为间接带隙复合氧化物,带隙宽为2.335 eV; ZnGa2O4的静态介电常数为3.45,静态折射率为1.85,介电函数吸收边位于4.0 eV附近;ZnGa2O4的反射系数在19.3 eV附近取得最大值,吸收系数在11.0 eV～17.5eV间取值均较大,电子能量损失谱的共振峰在20.5 eV处,并与此能量时反射系数R(ω)的陡降相对应. 相似文献