榍石固溶体的稳定性

以H_2SiO_3、CaCO_3、TiO_2、Nd_2O_3和Al_2O_3为原料,通过固相法合成的榍石固溶体,对合成榍石固溶体进行PCT粉末浸泡实验和~(60)Co源辐照试验,借助X射线衍射(XRD)、扫描电镜(SEM)、能谱(EDS)、原子吸收光谱(AAS)、荧光光谱(FS)、激光拉曼光谱(LRS)分析等手段,研究榍石固溶体的化学稳定性和抗γ射线辐照的稳定性.结果表明,在pH值为5～9的水溶液中掺钕榍石固溶体具有良好的化学稳定性;辐照累计剂量为5.76×10~5 Cy的~(60)Co源辐照没有造成榍石固溶体晶格的的辐射损伤,榍石固溶体具有良好的抗γ射线辐照稳定性;在90℃、pH值为7的浸泡条件下,榍石固溶体的Ca~(2+)、Ti~4和Nd~(3+)的42 d归一化浸出率分别为6.32×10~(-3)、3.9×10~(-5)、5.38×10~(-3)g/(m~2·d).     

榍石基人造岩石固化模拟四价铀的研究

以分析纯CaCO3、TiO2、SiO2和CeO2为原料,铈作为铀的模拟元素,采用高温固相反应,合成了包容铈的榍石基人造岩石固化体。通过XRD、SEM、EDX等手段对固化体物相组成及微区成分进行了分析,参照国家标准放射性废物固化体长期浸出试验(GB 7023—86)及美国PCT(Product Consistency Test)法对固化体进行了抗浸出性能试验。结果表明,在1 300℃下保温2 h可以制备出以榍石为主要晶相的人造岩石固化体,在不引入任何电价补偿离子时,Ce4+在榍石晶体内Ca2+位置的固溶度小于0.05个结构单位。榍石对Ce具有良好的固溶效果,当固化体中Ce的荷载量高达13.47%时,MCC-1静态浸出法测得Ce的90 d浸出率和累积浸出分数低至0.15×10-8cm/d和0.90×10-6cm,PCT粉末浸泡法测得Ce的7 d归一化浸出率仅为3.11×10-7g/(m2.d)。这一结果为榍石基人造岩石应用于固化放射性核素铀提供了理论依据。     

钙钛矿人造岩石固化模拟铀的浸出性能研究

通过高温固相反应,以铈作为铀的模拟元素,在1 300℃下保温2h合成了钙钛矿基人造岩石固化体。采用XRD对固化体进行物相分析,同时采用MCC-1静态浸泡法及美国PCT粉末浸泡法对不同铈核素包容量的固化体进行浸出性能研究。结果表明,Ce在钙钛矿人造岩石固化体中的包容量低于质量分数18.94%,约为0.15～0.2个结构单位。Ce元素的掺入起到了促进烧结和稳定钙钛矿晶格的作用,当固化体中Ce的荷载量高达35.04%时,Ca元素的90d浸出浓度已超出检测限而未测得,累积浸出分数低至1.87×10-5 cm;Ce元素的90d浸出率和累积浸出分数低至0.27×10-8cm.d-1和6.55×10-7 cm,比玻璃固化体浸出率低了2～3个数量级,说明钙钛矿固化体具有良好的化学稳定性,且当铈核素掺量接近钙钛矿最大包容量时固化体结构最稳定,抗浸出性能最好。     

硅酸镥单晶体生长方法研究

结合掺铈硅酸镥(Ce:Lu2SiO5)粉体的组成与性能特点、提拉法和焰熔法晶体生长工艺异同,讨论了目前使用提拉法生长掺铈硅酸镥单晶体存在的坩埚溶蚀、组分挥发、杂质浸入、闪烁性能不稳定等问题和原因,提出使用焰熔法生长Ce:Lu2SiO5单晶体可以有效解决这些问题,给Ce:Lu2SiO5单晶体的生长提供了一个新的研究方向。     

微波场中催化剂对甲苯废气的氧化分解研究

为减少挥发性有机化合物所造成的污染,改善大气环境质量,探究微波催化氧化甲苯废气技术的实际应用,采用传统浸渍法,制备具有尖晶石结构的铜锰铈负载型催化剂,利用X射线衍射、扫描电子显微镜和氮气吸附法等检测方法对该催化剂进行表征.利用本课题组自行研制的微波净化设备,研究在微波场-催化剂协同催化的作用下,负载型催化剂对氧化分解甲苯的催化性能,探究各种不同工艺参数条件下的催化效果.表征表明,该铜锰铈催化剂表面的尖晶石相CuMn_2O_4对挥发性有机物(volatile organic compounds,VOCs)有较高的催化氧化活性.催化实验结果表明,600℃条件下焙烧制成的铜锰铈催化剂具有明显的低温催化氧化特性,在微波功率为400 W、反应温度为280～350℃、空间速度(单位时间、单位体积催化剂上通过的标准状态下反应器气体的体积)为1 400～5 600 h~(-1)、甲苯的质量浓度为7. 5～30. 0g/m3的条件下,对甲苯的去除率可超过90%.且对于甲苯的去除具有较强的抗冲击能力;在100 h的稳定性实验过程中,催化效率均保持在90%以上,稳定性很好,具有良好的应用前景.     

铈在钙钛锆石固溶体中的固溶量

以CaCO3、TiO2、ZrO2和CeO2粉体为原料,通过高温固相反应合成钙钛锆石固溶体,借助X射线衍射(XRD)、背散射二次电子像(BSE)和能谱(EDS)分析手段,研究铈在钙钛锆石固溶体中的固溶情况。研究结果表明,Ce4+取代Zr4+时,Ce4+固溶在CaZr1-xCexTi2O7固溶体中,其最大固溶量为10.84%;Ce4+取代Ca2+时,Ce4+固溶在Ca1-2 xCexZrTi2O7固溶体中,其最大固溶量为8.87%;掺Ce钙钛锆石固溶体的较佳合成温度为1 300℃。     

负载型LaCoO_3的催化性能与EPR研究

用柠檬酸法制备了Ce0.6Zr0.4O2(简称CZ)和Ce0.6Zr0.35Y0.05O2(简称CZY)固溶体,分别在Ce0.6Zr0.4O2和Ce0.6Zr0.35Y0.05O2固溶体上负载不同质量的LaCoO3。用热重法测试了催化剂对碳烟的催化活性。采用程序升温还原法(H2-TPR)、比表面(BET)、X-射线衍射仪(XRD)和电子顺磁共振仪(EPR)对催化剂进行了测试。结果表明:随着钙钛矿组分La、Co在铈锆固溶体或铈锆钇固溶体表面负载量的增加,催化剂催化燃烧碳烟的起燃温度下降,催化活性增强;TPR结果显示,CZ或CZY为载体的催化剂体系,随着表面La、Co组分含量的增加,可还原氧总量也相应增加,催化活性也对应增加,表明催化剂对碳烟的催化活性与催化剂表面的氧化还原性密切相关;EPR结果也显示由于钇的掺杂增加了铈锆固溶体表面缺陷,提高了O-离子的浓度,有利于催化活性提高。     

混合稀土铁石榴石(HoYbBi)_3Fe_5O_12单晶磁光性能的研究

为了改善用于光隔离器中的掺铋稀土铁石榴石的法拉第旋转温度稳定性 ,采用高温溶液法 ,以Bi2 O3 /B2 O3 为助熔剂生长掺铋混合稀土铁石榴石 ( Ho Yb Bi) 3 Fe5O1 2 (简称 :Ho Yb Bi IG)单晶 .在近红外波段测量了晶体的法拉第旋转谱和光吸收损耗谱 .当 λ=1 .5 5 μm时 ,Ho Yb Bi IG单晶的比法拉第旋转角θF 和磁光优值分别为 :- 767.0 deg/cm和 4 5 deg/d B;在 1 0～ 1 1 0℃温度范围内测得 Ho Yb Bi IG单晶的法拉第旋转温度系数 ( FTC)为 1 .8%,在目前所知磁光晶体中属最小 .研究结果还表明 ,将两种法拉第旋转温度系数符号相反的石榴石型材料进行复合 ,是一种行之有效的改善晶体材料法拉第旋转温度稳定性的方法     

La2(Ce0.3Zr0.7)2O7-NiCr2O4材料高温红外发射率研究

固相法合成了La₂(Ce_0.3Zr_0.7)₂O₇-nNiCr₂O₄(n=0%,5%,10%,15%)陶瓷材料,利用X射线衍射仪、扫描电镜以及傅里叶变换红外光谱仪对其物相结构、显微形貌、高温红外发射率以及红外吸收光谱进行表征.结果表明：合成的La₂(Ce_0.3Zr_0.7)₂O₇-nNiCr₂O₄陶瓷材料均为以烧绿石晶体为主相的立方结构,显微结构致密,晶粒尺寸均匀且随NiCr₂O₄含量的增加而增大.随NiCr₂O₄(n=0%,5%,10%,15%)质量分数的增加,陶瓷材料1 100℃红外发射率(3～5μm)不断升高,n=15%时,高温红外发射率最高可达0.76.红外吸收光谱分析结果显示,NiCr     

CCTO掺杂对BaTiO3-Nb2O5-Co3O4陶瓷系统介电性能的影响

以BaTiO3-Nb2O5-Co3O4(BTNC)系统陶瓷为研究对象,研究了掺杂CaCu3Ti4O12(CCTO)对该系统陶瓷介电性能的影响.结果表明,在20～85℃温度范围内,BT系统中CC-TO掺杂量为3.0%时,体系平均介电常数>2 600,温度稳定性△C/C≤4.7%;在20～125℃温度范围内,BTNC系统中CCTO掺杂量为2.0%时,体系的平均介电常数>2 700,温度稳定性△C/C≤10%;CCTO掺杂量为4.0%时,平均介电常数>2 200,温度稳定性△C/C≤4.7%.     

Ba3La2Ti2Ta2O15: A new microwave dielectric of A5B4O15-type cation-deficient perovskites

The synthesis, structure and properties of a new A5B4O15-type cation-deficient perovskite Ba3La2Ti2Ta2O15 were discribed. The compound was prepared by the conventional solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）. The results reveal that the compound is successfully synthesized. The compound crystallizes in the trigonal system with unit cell parameter a=5.6730（2） A, c=11.6511（2） A, V=324.93（1） A^3 and Z=1. The microwave dielectric properties of the ceramic are studied using a network analyzer, and it shows a high dielectric constant of 45.1, a high quality factors with Q×fof21 029 GHz, and a positive τf of 5.3 ppm℃^-1.     

Electrical conductivity of （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts

The effects of contents of AlF3 and Al2O3, and temperature on electrical conductivity of （Na3AlF6-40%K3AlF6）- AlF3-Al2O3 were studied by continuously varying cell censtant （CVCC） technique. The results show that the conductivities of melts increase with the increase of temperature, but by different extents. Every increasing 10 ℃ results in an increase of 1.85 × 10^-2, 1.86× 10^-2, 1.89 × 10^-2 and 2.20 × 10^-2 S/cm in conductivity for the （Na3AlF6-40%K3AlF6）-AlF3 melts containing 0%, 20%, 24%, and 30% AlF3, respectively. An increase of every 10 ℃ in temperature results an increase about 1.89× 10^-2, 1.94 × 10^-2, 1.95 × 10^-2, 1.99× 10^-2 and 2.10× 10^-2 S/cm for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts containing 0%, 1%, 2%, 3% and 4% Al2O3, respectively. The activation energy of conductance was calculated based on Arrhenius equation. Every increasing 1% of AlF3 results in a decrease of 0.019 and 0.020 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3 melts at 900 and 1 000 ℃, respectively. Every increase of 1% Al2O3 results in a decrease of 0.07 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts. The activation energy of conductance increases with the increase in content of AlF3 and Al2O3.     

一种基于 MXene 的Fe2O3/Nb2O5/Nb4C3Tx 高灵敏丙酮传感器

MXene 具有较大比表面积和优异的导电性, 当与金属氧化物半导体结合时可以抑制片层团聚, 还可以大大提高载流子转移速率, 提高气敏性能。通过简单的水热和煅烧两步法成功合成了Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 三元复合材料。通过表征, Fe₂O₃ 微米球分布在 MXene 纳米片层之间。气敏测试结果表明, 与原始Fe₂O₃相 比, Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器对丙酮的响应能力有明显的提高。传感器灵敏度高, 选择性较好, 对环境中 浓度为 5 ×10^?6 的丙酮响应高 (R_a /R_g = 7.81, 30% RH), 响应和恢复速度快, 具有出色的重复性和长期稳定性。Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器具有良好的气敏性能, 主要因为三元复合材料提供了较大比表面积和丰富的氧空位, 增强了活性位点, 使得气体易于在传感器表面扩散, 为开发丙酮敏感复合材料提供了参考。     

低介Ba(Al0.98Co0.02)2Si2O8-Ba5Si8O21基LTCC微波介质陶瓷的研究

采用传统固相反应法,按摩尔比合成0.7Ba(Al_0.98Co_0.02)₂Si₂O₈?0.3Ba₅Si₈O₂₁(BACS-BS)基陶瓷,分析Li₂O-B₂O₃(1wt%)(L-B)烧结助剂对其烧结特性、相组成和微波介电性能的影响,探讨0.7BACS-0.3BS+1wt%(L-B)陶瓷理论与实验介电常数(ε_r)的差异。结果表明:添加1wt%(L-B)烧结助剂能有效降低0.7BACS-0.3BS基陶瓷的烧结温度(950 ℃),但严重影响其微波介电性能;在950℃烧结的0.7Ba(Al_0.98Co_0.02)₂Si₂O₈-0.3Ba₅Si₈O₂₁+1wt%(Li₂O-B₂O₃)陶瓷具有较好的微波介电性能,其ε_r=7.56, Q×f=13 976 GHz, τ_f=?6.32 ppm/℃;0.7BACS-0.3BS+1wt%(L-B)复合陶瓷与Ag电极有很好的化学相容性,这为其在LTCC技术的应用奠定了良好的基础。     

Synthesis and characterization of Mg3(PO4)2-coated Li1.05Ni1/3Mn1/3Co1/3O2 cathode material for Li-ion battery

Mg₃(PO₄)₂-coated Li_1.05Ni_1/3Mn_1/3Co_1/3O₂ cathode materials were synthesized via co-precipitation method. The morphology, structure, electrochemical performance and thermal stability were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), charge/discharge cycling and differential scanning calorimeter (DSC). SEM analysis shows that Mg₃(PO₄)₂-coating changes the morphologies of their particles and increases the grains size. XRD and CV results show that Mg₃(PO₄)₂-coating powder is homogeneous and has better layered structure than the bare one. Mg₃(PO₄)₂-coating improved high rate discharge capacity and cycle-life performance. The reason why the cycling performance of Mg₃(PO₄)₂-coated sample at 55 °C was better than that of room temperature was the increasing of lithium-ion diffusion rate and charge transfer rate with temperature rising. Mg₃(PO₄)₂-coating improved the cathode thermal stability, and the result was consistent with thermal abuse tests using Li-ion cells: the Mg₃(PO₄)₂ coated Li_1.05Ni_1/3Mn_1/3Co_1/3O₂ cathode did not exhibit thermal runaway with smoke and explosion, in contrast to the cells containing the bare Li_1.05Ni_1/3Mn_1/3Co_1/3O₂. Funded by the National Natural Science Foundation of China (No. 20273047)     

Modification of LiCo1/3Ni1/3Mn1/3O2 cathode material by CeO2-coating

LiCo_1/3Ni_1/3Mn_1/3O₂ was coated by a layer of 1.0 wt% CeO₂ via sol-gel method. The bared and coated LiMn_1/3Co_1/3Ni_1/3O₂ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammogram (CV) and galvanotactic charge-discharge test. The results show that the coating layer has no effect on the crystal structure, only coating on the surface; the 1.0 wt% CeO₂-coated LiCo_1/3Ni_1/3Mn_1/3O₂ exhibits better discharge capacity and cycling performance than the bared LiCo_1/3Ni_1/3Mn_1/3O₂. The discharge capacity of 1.0 wt% CeO₂-coated cathode is 182.5 mAh·g⁻¹ at a current density of 20 mA·g⁻¹, in contrast to 165.8 mAh·g⁻¹of the bared sample. The discharge capacity retention of 1.0 wt% CeO₂-coated sample after 12 cycles reaches 93.2%, in comparison with 86.6% of the bared sample. CV results show that the CeO₂ coating could suppress phase transitions and prevent the surface of cathode material from direct contact with the electrolyte, thus enhance the electrochemical performance of the coated material.     

Electrolysis expansion performance of semigraphitic cathode in [K3AlF6/Na3AlF6]-AlF3-Al2O3 bath system

The electrolysis expansion of semigraphitic cathode in [K₃AlF₆/Na₃AlF₆]-AlF₃-Al₂O₃ bath system was tested by self-made modified Rapoport apparatus. A mathematical model was introduced to discuss the effects of α _CR (cryolite ratio) and β _KR (elpasolite content divided by the total amount of elpasolite and sodium cryolite) on performance of cathode electrolysis expansion. The results show that K and Na (potassium and sodium) penetrate into the cathode together and have an obvious influence on the performance of cathode electrolysis expansion. The electrolysis expansion and K/Na penetration rate increase with the increase of α _CR. When α _CR=1.9 and β _KR=0.5, the electrolysis expansion is the highest, which is 3.95%; and when α _CR=1.4 and β _KR=0.1, the electrolysis expansion is the lowest, which is 1.28%. But the effect of β _KR is correlative with α _CR. When α _CR=1.6 and 1.9, with the increase of β _KR, the electrolysis expansion and K/Na penetration rate increase. However, when α _CR=1.4, the electrolysis expansion and K/Na penetration rate firstly increase and then decrease with the increase of β _KR. Foundation item: Project (2005CB623703) supported by the Major State Basic Research and Development Program of China; Project (2008AA030502) supported by the National High-Tech Research and Development Program of China     

Preparation and electrical-magnetic properties of Co0.6Cu0.16Ni0.24Fe2O4/MWCNTs composites

Co0.6Cu0.16Ni0.24Fe2O4/multi-walled carbon nanotube nanocomposites (CCNF/MWCNTs) were synthesized by solution filling method.The phase structure,thermal stability,morphology and electrical-magnetic properties of the samples were characterized by means of modern testing technology.The effect of iron concentration,filling time,sintering temperature on their electrical and magnetic performance was discussed.The results indicated that conductivity was related to the content of MWCNTs,while the magnetism correlated with the volume fraction of the filled CCNF in the composites.When the optimal condition satisfied the filling time of 18 h,ferric concentration of 0.25 mol L-1 and sintering temperature of 350°C,the prepared composite had the best magnetic loss performance,and its minimum reflection loss reached-22.47 dB on 9.76 GHz,the available bandwidth was beyond 2.0 GHz.Hence,the obtained composite can be used as advancing absorption and shielding material due to its favorable microwave absorbing property.     

Characteristics of LiCoO2, LiMn2O4 and LiNi0.45Co0.1Mn0.45O2 as cathodes of lithium ion batteries

LiNi_0.45Co_0.10Mn_0.45O₂ was synthesized from Li₂CO₃ and a triple oxide of nickel, cobalt and manganese at 950 °C in air. The structures and characteristics of LiNi_0.45Co_0.10Mn_0.45O₂, LiCoO₂ and LiMn₂O₄ were investigated by XRD, SEM and electrochemical measurements. The results show that LiNi_0.45Co_0.10Mn_0.45O₂ has a layered structure with hexagonal lattice. The commercial LiCoO₂ has sphere-like appearance and smooth surfaces, while the LiMn₂O₄ and LiNi_0.45Co_0.10Mn_0.45O₂ consist of cornered and uneven particles. LiNi_0.45Co_0.10Mn_0.45O₂ has a large discharge capacity of 140.9 mA · h/g in practical lithium ion battery, which is 33.4% and 2.8% above that of LiMn₂O₄ and LiCoO₂, respectively. LiCoO₂ and LiMn₂O₄ have higher discharge voltage and better rate-capability than LiNi_0.45Co_0.10Mn_0.45O₂. All the three cathodes have excellent cycling performance with capacity retention of above 89.3% at the 250th cycle. Batteries with LiMn₂O₄ or LiNi_0.45Co_0.10Mn_0.45O₂ cathodes show better safety performance under abusive conditions than those with LiCoO₂ cathodes. Foundation item: Project(50302016) supported by the National Natural Science Foundation of China; Project(2005037698) supported by the Postdoctoral Science Foundation of China     

Molar heat capacities of La2Mo2O9 and La1.9Sr0.1MO209-δ

The molar heat capacities of La2Mo209 and La1.9Sr0.1MO209-δ were obtained using the differential scanning calorimetry （DSC） technique in a temperature range from 298 to 1473 K. The DSC curve of La2Mo209 showed an endothermal peak around 834 K corresponding to a first-order monoclinic-cubic phase transition, and the enthalpy change accompanying this phase transition is 5.99 kJ/mol. No evident endothermal peak existed in the DSC curve of La1.9Sr0.1MO209-δ, but a broad thermal anomaly existed in its heat capacity curve at around 832 K. In addition, the heat capacity values of La2Mo209 and La1.9Sr0.1MO209-δ began to decrease at 1196 and 1330 K, respectively. The non-transitional heat capacity values of La2Mo209 and La1.9Sr0.1MO209-δ were formulated using multiple regression analysis in two temperature ranges.