共查询到19条相似文献,搜索用时 78 毫秒
1.
钨酸铋(Bi2WO6),结构最简单的Aurivillius相化合物,是近期受到研究者关注的新型光催化材料。然而,光催化剂粉末在反应介质中难被回收,工业化应用成本较高。本文用三步方法合成了可回收的Fe3O4/SiO2/Bi2WO6磁性复合光催化剂,通过溶剂热法合成具有磁性的Fe3O4,用溶胶凝胶法在Fe3O4表面覆盖SiO2层,后将磁性颗粒与Bi2WO6纳米片相结合。光催化剂的形貌结构及性能通过XRD、SEM、PL、UV-vis进行表征测试。结果表明,直径约500 nm的Fe3O4微球附着在边长约500 nm的Bi2WO6纳米片的表面,SiO2在两者之间起到了粘连作用。光催化剂Fe3O4/SiO2/Bi2WO6对于罗丹明B的光降解活性较好,且有一定磁性,可以通过外加磁场将其从溶液中分离,有较大的应用潜力。 相似文献
2.
采用凝胶注模成型工艺制备了SiC_w/Si_3N_4复合陶瓷,由扫描电镜(SEM)可以看出,随热处理温度升高,碳化硅晶须的长径比逐渐减小;随烧结温度升高,复合陶瓷开孔率降低,密度随晶须含量的增加而增加。研究表明,SiC_w/Si_3N_4复合陶瓷的介电常数实部和虚部随碳化硅晶须含量的增加而升高,当烧结温度为1600℃,晶须含量从5%增加到15%时,8 GHz时介电常数实部从13.4增加到22.8,虚部从0.67增加到4.86;当烧结温度为1750℃时,8 GHz时介电常数实部从9.2增加到21.7,虚部从0.51增加到3.02。由反射率曲线可以看出,烧结温度为1750℃比1600℃时反射衰减随晶须含量的增加向低频移动的更快,频宽更宽。 相似文献
3.
使用产量与性能稳定的工业化生产的黑色二氧化钛制备成QDSSCs的光阳极,通过性能表征与理论计算研究,与常见的Anatase TiO2,Rutile TiO2展开了全面对比。结果表明,由于氧空位的引入导致Magonelli Ti8O15的导带底下降,带隙收缩,吸收光谱范围由紫外光扩展至可见光与近红外,而且吸光度也极大提高。其阻抗也随之减小,明显低于Anatase TiO2,Rutile TiO2。这导致其组装的QDSSCs的性能获得极大提升,尤其是FF与Jsc表现最为显著,最终获得了PCE 5.3%优异成绩。这项工作进一步丰富了黑色二氧化钛的研究,在工业化生产黑色二氧化钛组装太阳能电池领域取得了阶段性成果,为太阳能电池的生产提供了新的可能。 相似文献
4.
以Ti,Al和TiC为原材料,用无压煅烧合成法制备三元化合物Ti3AlC2。详细讨论了煅烧温度和铝含量对多晶Ti3AlC2纯度的影响。利用X射线衍射仪、场发射扫描电镜和场发射透射电镜研究了粉末材料的组织结构、晶粒大小、层板厚度和选区电子衍射花样。结果表明1300℃是合成Ti3AlC2粉末的最佳煅烧温度,1:1.2:2是Ti/Al/TiC原材料的最佳摩尔比。用热压法制备了不同烧结温度下的Ti3AlC2块体试样,在1300℃热压制备的Ti3AlC2块体的相对密度可达99.9%,其维氏硬度和三点抗弯强度分别为5.7 GPa和630 MPa。通过场发射扫面电镜观察材料的断口形貌,进一步分析了Ti3AlC2块体材料的强化机理。 相似文献
5.
采用高温固相法合成了Cr3+掺杂的LiNi0.5Mn1.5O4正极材料,研究了掺杂量对材料物理性能和电化学性能的影响。利用XRD、SEM对材料的结构和形貌进行了表征,结果显示样品具有棱边清晰的尖晶石形貌。讨论了不同Cr3+掺杂量对LiCrxNi0.5-0.5xMn1.5-0.5xO4(x=0,0.05,0.1,0.15,0.2)正极材料性能的影响。充放电测试、循环伏安和交流阻抗测试结果表明:当Cr3+的掺杂量为x=0.1时(LiCr0.1Ni0.45Mn1.45O4)正极材料的性能最好,0.1C、0.5C、1C、2C及5C的首次放电比容量依次为131.54mAh g-1、126.84mAh g-1、121.28mAh g-1、116.49mAh g-1和96.82mAh g-1,1C倍率下循环50次,容量保持率仍为96.5%。 相似文献
6.
Al含量为0.50%(质量分数)的Cu-Al合金薄板在900℃下内氧化25 h制备Cu-Al_2O_3薄板复合材料,并用富集萃取法提取Cu-Al_2O_3复合材料中的Al_2O_3相。利用TEM分析了Cu-Al_2O_3薄板中的Al_2O_3相的种类、分布、与Cu基体的界面关系,用X射线衍射和TEM研究了萃取粉末的组成。结果表明,Cu-Al薄板内氧化法所得的Cu-Al_2O_3复合材料的析出相主要为γ-Al_2O_3,有少量的α-Al_2O_3和θ-Al_2O_3相存在。析出相Al_2O_3颗粒弥散分布在Cu基体上,且析出相γ-Al_2O_3与Cu基体完全共格;Cu-Al_2O_3薄板复合材料从表层至深约0.5 mm处,Al_2O_3颗粒粒径逐渐减小,从14 nm减小到5 nm,颗粒间距逐渐增大,从10 nm增加到15 nm。 相似文献
7.
基于密度泛函第一性原理平面波赝势方法对Lu_2O_3六方、单斜和立方3种结构进行计算。结合能结果表明C型Ia3立方结构最稳定。立方Lu_2O_3的力学、热力学、电子结构以及光学性质计算揭示:Lu_2O_3有良好的韧性和弹性各向异性特征;热力学稳定性较好;Lu_2O_3为直接带隙,位于导带底的电子有效质量小,非局域程度高;价带顶到导带底跃迁主要源于Lu 4f和O 2p电子。Lu原子5d轨道和O原子2p轨道的强烈杂化形成Lu–O共价键;Lu_2O_3最大光反射率为0.36,在3~10 eV能量范围内其光吸收能力较强,近红外线和可见光范围内有优异透光性能,是良好光绝缘性材料。 相似文献
8.
程功金 周新磊 高明磊 常富增 滕艾均 邢振兴 宋翰林 高子先 汤卫东 赵备备 王金龙 赵丹 刘超 李兰杰 杨合 陈东辉 薛向欣 白瑞国 张卫军 《稀有金属材料与工程》2021,50(6):1990-1998
为了确定高钛型钒钛磁铁矿烧结过程中铁酸钙的生成是受TiO2还是TiO2和CaO形成的CaTiO3影响,首先利用Fe2O3和CaO的纯试剂合成了铁酸钙,并研究了TiO2和CaTiO3对钛铁酸钙 (FCT) 形成的影响。在Factsage 7.0软件进行热力学计算的基础上,通过在空气气氛下进行烧结,获得了在1023~1423 K温度范围内、不同烧结时间的不同样品。通过X射线衍射和扫描电镜-能谱分析等表征手段,对烧结样品的物相转变和微观结构变化进行了表征。发现FCT的形成过程主要分为2个阶段:前一阶段为1023~1223 K温度范围内Fe2O3与CaO之间的反应,合成产物为Ca2Fe2O5,反应方程式为“Fe2O3(s)+ 2CaO(s)= Ca2Fe2O5(s)”;后一阶段为1223~1423 K温度范围内Ca2Fe2O5和Fe2O3的反应,主要产物为CaFe2O4,反应为“Ca2Fe2O5(s)+ Fe2O3(s)= 2CaFe2O4(s)”,该阶段尤其是温度为1423 K时,反应速率显著加快,随温度的升高CaTiO3显著增加。然而,Ti元素在铁酸钙中的固溶很难实现,TiO2与铁酸钙之间的反应不是形成FCT的有效途径。随着保温时间的延长,CaTiO3和FCT相界中Fe元素含量增加。FCT主要是通过Fe组分在CaTiO3中固溶形成的,主要反应是“Fe2O3+CaTiO3(s)=FCT(s)”。 相似文献
9.
采用高温固相反应制备了CaO-Bi_2O_3-MoO_3-XNb_2O_5(X=0.000%~0.075%,质量分数,步长:0.015%)复合掺杂的高磁导率Mn-Zn铁氧体材料,利用XRD、SEM、四探针电阻测试仪、阻抗分析仪、和软磁测试仪等分析测试手段对材料结构和性能进行表征,研究了复合掺杂剂中Nb_2O_5掺杂量对高磁导率Mn-Zn铁氧体材料的结构和电磁性能的影响。结果表明:当Nb_2O_5少量掺杂时,Nb_2O_5可以改善材料的微观结构,提高其密度、频率稳定性和品质因数,提高其电阻率,降低其体积功耗;当Nb_2O_5过量掺杂时,Nb_2O_5将恶化材料的微观结构,导致材料的电磁性能变差。当Nb2O5掺杂量为0.030%时材料的综合电磁性能最佳。 相似文献
10.
通过2TiC-Ti-1.2Al体系的原位热压反应制备了Ti3AlC2陶瓷,然后以59.2Ti-30.8Al-10Ti3AlC2(wt%)为反应体系,采用放电等离子烧结技术制备出Ti2AlC/TiAl基复合材料。借助XRD、SEM分析了产物的相组成和微观结构,并测量了其室温力学性能。结果表明:原位热压烧结产物由Ti3AlC2和TiC相组成,Ti3AlC2呈典型的层状结构,TiC颗粒分布在其间。SPS法制备的Ti2AlC/TiAl基复合材料主要由TiAl、Ti3Al和Ti2AlC相组成,Ti2AlC增强相主要分布于基体晶界处,表现为晶界/晶内强化作用。力学性能测试表明:Ti2AlC/TiAl基复合材料的密度、维氏硬度、断裂韧性和抗弯强度分别为3.85 g/cm3、5.37 GPa、7.17 MPa?m1/2和494.85 MPa。 相似文献
11.
Zhihang Peng Qiang ChenJiagang Wu Xiaohong ZhuDingquan Xiao Jianguo Zhu 《Journal of Alloys and Compounds》2011,509(33):8483-8486
Sb5+-doped (NaBi)0.38(LiCe)0.05[]0.14Bi2Nb2O9 (represented as NBNLCS-x, where [] represents A-site vacancies) ceramics were prepared by the conventional solid-state route. The ceramics well sintered to approach ∼98.5% theoretical density and the tetragonality of crystal structure increased with Sb5+ additions. However, the Curie temperature (TC) and the piezoelectric coefficient (d33) of Sb5+-modified ceramics gradually decreased. The 3 mol% Sb5+-doped samples exhibited optimum properties with a d33 value of ∼22 pC/N planar electromechanical coupling factor (kp) of ∼11.2% and relatively high TC of ∼765 °C. These results indicate that NBNLCS-x material is a promising candidate for high-temperature piezoelectric applications. 相似文献
12.
采用粉末层叠和整体热压烧结的方法,制备了Y2Ti2O7/316L不锈钢功能梯度复合材料。经金相显微镜、X射线衍射仪和电子探针分析确定,该材料在金属和氧化物界面处实现了成分和微观组织的梯度过渡。对不同梯度含量复合材料的力学性能测试表明,界面处的力学性能存在相应的梯度变化,即随各层金属相含量的逐渐增加,过渡区材料的致密度、抗弯强度不断提升,而硬度则不断下降。 相似文献
13.
Prasit Thongbai Bundit PutasaengTeerapon Yamwong Santi Maensiri 《Journal of Alloys and Compounds》2011,509(27):7416-7420
Non-ohmic and dielectric properties of Ca2Cu2Ti4O12 (CaCu3Ti4O12/CaTiO3 composite) ceramics prepared by a polymer pyrolysis method (PP-ceramic samples) are investigated. The PP-ceramics show a highly dense structure and improved non-ohmic and dielectric properties compared to the ceramics obtained by a solid state reaction method (SSR-ceramic samples). ?′ (tan δ) of the PP-ceramic samples is found to be higher (lower) than that of the SSR-ceramic samples. Interestingly, the PP-ceramic sintered at 1050 °C for 10 h exhibits the high ?′ of 2530 with weak frequency dependence below 1 MHz, the low tan δ less than 0.05 in the frequency range of 160 Hz-177 kHz, and the little temperature coefficient, i.e., |Δ?′| ≤ 15 % in the temperature range from −55 to 85 °C. These results indicate that the CaCu3Ti4O12/CaTiO3 composite system prepared by PP method is a promising high-?′ material for practical capacitor application. 相似文献
14.
J.J. ShenS.N. Zhang S.H. YangZ.Z. Yin T.J. ZhuX.B. Zhao 《Journal of Alloys and Compounds》2011,509(1):161-164
The polycrystalline pseudo-binary Bi0.5Sb1.5Te3 alloys have been prepared by hot pressing. X-ray diffraction analysis indicated that there is no noticeable preferred orientation in all the samples. Thermoelectric properties were measured and a relatively high ZT value of ∼0.9 was obtained at room temperature. Thermal mechanical properties were characterized by dilatometer and dynamic-mechanical thermal analyzer. The thermodynamic stability of these alloys could be kept from room temperature to 500 K. It is suggested that Bi0.5Sb1.5Te3 alloys are suitable for the applications below 500 K. 相似文献
15.
Xiaohua ZhangWei Ren Peng ShiM. Saeed Khan Xiaofeng ChenXiaoqing Wu Xi Yao 《Journal of Alloys and Compounds》2011,509(38):9302-9306
Bi2Zn2/3Nb4/3O7 thin films were deposited on Pt/TiO2/SiO2/Si(1 0 0) substrates at a room temperature under the oxygen pressure of 1-10 Pa by pulsed laser deposition. Bi2Zn2/3Nb4/3O7 thin films were then post-annealed below 200 °C in a rapid thermal process furnace in air for 20 min. The dielectric and leakage current properties of Bi2Zn2/3Nb4/3O7 thin films are strongly influenced by the oxygen pressure during deposition and the post-annealing temperature. Bi2Zn2/3Nb4/3O7 thin films deposited under 1 Pa oxygen pressure and then post-annealed at a temperature of 150 °C show uniform surface morphologies. Dielectric constant and loss tangent are 57 and 0.005 at 10 kHz, respectively. The high resolution TEM image and the electron diffraction pattern show that nano crystallites exist in the amorphous thin film, which may be the origin of high dielectric constant in the Bi2Zn2/3Nb4/3O7 thin films deposited at low temperatures. Moreover, Bi2Zn2/3Nb4/3O7 thin film exhibits the excellent leakage current characteristics with a high breakdown strength and the leakage current density is approximately 1 × 10−7 A/cm2 at an applied bias field of 300 kV/cm. Bi2Zn2/3Nb4/3O7 thin films are potential materials for embedded capacitor applications. 相似文献
16.
YVO4:Bi3+ phosphors have been prepared by a convenient high-temperature solid-state method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) technologies are used to study the luminescence properties of YVO4:Bi3+ phosphors. The emission and excitation spectra of Bi3+ in the YVO4 lattice have been investigated at room temperature. The excitation band peaks at 330 nm in a region among 250-400 nm, and the emission spectrum exhibits an intense yellowish-white broad emission centered at about 543 nm covering from 400 nm to 800 nm. The full width at half maximum (FWHM) is about 144 nm. The color coordinates of the as-synthesized YVO4:Bi3+ phosphors are in a range of x = 0.358-0.374, y = 0.482-0.496. The dependence of the luminescence intensity on Bi3+ concentrations and heat treatment condition has also been discussed. In addition, we found that a little amount of flux NH4Cl could enhance the Bi3+ luminescence intensity. 相似文献
17.
Nanoparticles of ZnFe2O4 with grain size of 30 nm have been synthesized via sol-gel auto combustion method and characterized using DSC (differential scanning calorimetry), XRD (X-ray diffraction), SEM (scanning electron microscopy), EDAX (energy dispersive X-ray analysis), FTIR (Fourier transform infrared spectroscopy), VSM (vibrating sample magnetometer) and Ac-electrical conductivity measurement setup. Structural analysis using XRD and FTIR show the formation of spinel structure in nano ZnFe2O4 particles. The cation distribution in the sample has been estimated theoretically and the results show that as-prepared nanoparticles of ZnFe2O4 have partially inverted ionic distribution in comparison with that of bulk zinc ferrite. Results from EDAX indicate the ratio of Fe:Zn as close to 2:1. The presence of a weak ferrimagnetic phase for nano ZnFe2O4 at room temperature has been established from its hysteresis behavior. Redistribution of cations occurring at nano-regime and surface spin canting of nanoparticles of ZnFe2O4 are expected to be responsible for the presence of magnetic ordering in nano ZnFe2O4. The Curie temperature of nano ZnFe2O4 determined from magnetization versus temperature measurement is equal to 375 °C. The electrical conductivity of the present ZnFe2O4 at a frequency of 100 kHz at room temperature is observed to be 2.11 × 10−8 Ω−1 cm−1 which is four orders lesser in magnitude than the value of bulk ZnFe2O4. Overall conductivity response with respect to temperature and frequency confirm that ZnFe2O4 tends to become more dielectric in the nano-regime. 相似文献
18.
The phases, microstructure and microwave dielectric properties of ZnTiNb2O8-xTiO2 composite ceramics with different weight percentages of BaCu(B2O5) additive prepared by solid-state reaction method have been investigated using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results showed that the microwave dielectric properties were strongly dependent on densification, grain sizes and crystalline phases. The sintering temperature of ZnTiNb2O8 ceramics was reduced from 1250 °C to 950 °C by doping BaCu(B2O5) additive and the temperature coefficient of resonant frequency (τf) was adjusted from negative value of −52 ppm/°C to 0 ppm/°C by incorporating TiO2. Addition of 2 wt% BaCu(B2O5) in ZnTiNb2O8-xTiO2 (x = 0.8) ceramics sintered at 950 °C showed excellent dielectric properties of ?r = 38.89, Q × f = 14,500 GHz (f = 4.715 GHz) and τf = 0 ppm/°C, which represented very promising candidates as LTCC dielectrics for LTCC applications. 相似文献
19.
Seung-Yong SHIN Ji-Hyun LEE Hai-Woong PARK 《中国有色金属学会会刊》2009,19(4):961-964
The electrical properties of solder contact layers between Cu-Ni shunt metal and tube type Bi2212 superconductor that is applied in superconducting fault current limiter were studied. The contact properties of the solders are improved not only by Ag precoating layers, but also by the pre-sprayed Ag layer and subsequent Ag precoating layers. The annealed Ag sprayed layers onto Bi2212 superconductor prior to Ag electroplating work as protecting layers for the superconductor from plating solutions. The contact angle of the electroplated Ag layer is 42.91° and decreases to 15.25° and 5.88° with Ag sprayed layer and additional Ag electroplated layers. The Ag sprayed layer with suitable annealing prior to Ag electroplating improves contact strength of the Ag electroplated layer by about 12% due to denser microstructure of the Ag electroplated layers. 相似文献