Nd掺杂Gd2Zr2O7烧绿石的高温高压制备及其物相结构表征

为探索Gd2Zr2O7烧绿石在高温高压合成条件下的相选择、相转变及其对三价锕系核素模拟物Nd固溶度的影响,本实验采用高温高压固相反应法在合成压力为3～4GPa、合成温度为1573～1673K范围内合成了系列样品,并利用X射线衍射仪、扫描电镜对样品进行了分析。XRD结果表明:所有样品均获得了烧绿石(Gd,Nd)2Zr2O7与萤石Zr2(Gd,Nd)2O7共存相,未生成单一的立方烧绿石相,其原因可能是合成时间过短和压力诱导相变所致;模拟核素Nd在极短合成时间内全部固溶进入烧绿石和萤石相中,说明采用高温高压法可加快锕系核素在陶瓷基材中的固溶;Nd掺杂导致所有样品中P和F相的晶格常数均发生不同程度膨胀,且其值随合成温度的升高而增大,随合成压力的增加而减小;SEM结果显示在高温高压合成条件下,样品微观组织较一般烧绿石合成方法晶粒更加细小,分布更均匀且致密性好。     

Nd2（C7H4NO4）2(SiW12O40)·18H2O的合成及其光电性能的研究

以硅钨酸和2,3-吡啶二羧酸为配体合成了一种新型的配合物Nd2(C7H4NO4)2(SiW12O40)·18H2O,并对其进行了元素分析、红外光谱、紫外光谱、荧光光谱、热重分析和电化学分析等一系列表征。结果表明:配合物在261nm处具有较强的紫外吸收;在361nm处进行荧光激发,分别在431nm和480nm处得到两个强度不同的荧光发射峰;具有较好的热稳定性;在-0.3~0.3V的电势范围具有电化学活性。     

La2O3的添加方式对Al2O3热稳定性的影响

采用3种不同添加方式制备La₂O₃改性的Al₂O₃材料La-Al₂O₃。La-Al₂O₃分别经500 ℃、1 000 ℃和1 200 ℃焙烧,采用物理吸附、X射线衍射和荧光光谱等对高温处理的La-Al₂O₃进行比表面积和结构表征。结果表明,La₂O₃的添加能有效抑制Al₂O₃在高温条件下向热力学稳定态α-Al₂O₃转变,同时提高高温处理后La-Al₂O₃比表面积,使Al₂O₃热稳定性得到明显提高。在3种La₂O₃添加方式中,La(NO₃)₃浸渍法效果最为显著,制得的La-Al₂O₃(N)材料经1 200 ℃焙烧4 h的比表面积为30 m²·g^－1,是未经改性的Al₂O₃样品经同等温度焙烧比表面积的2.2倍。     

锶掺杂的La2Ce2O7烧绿石催化甲烷氧化偶联性能研究

基于烧绿石类材料热稳定性高、晶格氧流动性可调控的特点,通过溶胶-凝胶法制备了La₂Ce₂O₇催化剂,向其中掺杂碱土金属Sr,研究了其在甲烷氧化偶联（OCM）反应中的催化性能。通过一系列表征确认了La₂Ce₂O₇样品的缺陷立方萤石结构;锶掺杂不仅显著提高了晶格氧的活动性,还提升了催化剂表面强碱位点的比例;与OCM反应活性关联发现,晶格氧流动性增强以及表面强碱位点的增加是提高OCM反应活性的关键因素;在优化的La_1.5Sr_0.5Ce₂O₇催化剂上,800℃下可以获得57%的C₂选择性和14%以上的C₂收率,连续反应30 h性能保持稳定。     

沉淀剂浓度对喷雾共沉淀法合成Tb2O3纳米粉体的影响

采用喷雾共沉淀法结合还原气氛处理制备了Tb₂O₃超细纳米粉体,探究了碳酸氢铵沉淀剂浓度对前驱体物相、粉体微观形貌和烧结性能的影响。研究表明,沉淀剂浓度会显著影响纳米粉体的微观形态、均匀性和烧结活性。沉淀剂浓度过低会导致沉淀物晶粒过度生长,造成粉体粒径增大和不均匀性;沉淀剂浓度过高会造成不良的软团聚。最佳沉淀剂浓度为1.5 mol/L,该条件下可获得平均粒径约为52.45 nm的超细Tb₂O₃均匀粉体,粒径分布范围为30～80 nm。粉体经1 400℃的保护气氛烧结和热等静压处理后制得的Tb₂O₃透明陶瓷在1 064 nm波长下Tb₂O₃透明陶瓷线性透过率为76.11%。     

Ce0.75Cu0.25-xO2固溶体催化剂用于PVOCs催化燃烧

通过柠檬酸络合法制得Ce_0.75Cu0._25-xO₂固溶体催化剂,采用X射线衍射、X射线光电子能谱和H2-程序升温还原对催化剂性能进行研究,考察催化剂对苯基挥发性有机物的催化燃烧活性。结果表明,催化剂中大量CuO溶入CeO2晶格中形成Ce_0.75Cu0._25-xO₂固溶体,固溶体的形成削弱了催化剂中的Cu-O和Ce-O键,提高了相应氧化物的低温可还原性,也提高了催化剂表面活性氧物种含量,从而提高了催化剂上苯基挥发性有机物的催化燃烧活性。在反应温度250 ℃和275 ℃时,Ce_0.75Cu0._25-xO₂固溶体催化剂上甲苯和二甲苯的催化燃烧转化率分别为97.6%和95.0%。Ce_0.75Cu0._25-xO₂催化剂上苯在280 ℃时催化燃烧转化率仅为61.0%,这可归因于苯分子稳定的芳香环结构不易被破坏。     

AgBr/Zn3(OH)2V2O7·2H2O可见光催化降解亚甲基蓝溶液

采用水热和沉淀两步合成法制备AgBr/Zn₃(OH)₂V₂O₇·2H₂O催化剂,研究其在可见光下降解亚甲基蓝溶液的性能,并考察催化剂用量、亚甲基蓝溶液初始浓度、pH值以及盐浓度对光催化性能的影响,评价AgBr/Zn₃(OH)₂V₂O₇·2H₂O催化剂的重复使用性能。结果表明,在前驱液pH为10、120 ℃水热10 h、Ag与Br物质的量比为0.20条件下制备的复合催化剂在可见光下反应120 min后,1.0 g·L^-1的催化剂对10 mg·L^-1的亚甲基蓝溶液脱色率达到85.2%。NaCl对亚甲基蓝的降解起抑制作用,Na₂SO₄对亚甲基蓝的降解起促进作用。催化剂重复使用4次后,光照120 min后的亚甲基蓝溶液脱色率可达66.4%。催化剂对不同初始浓度亚甲基蓝溶液的光催化降解符合一级动力学模型。     

Li(NixCoyMnz)O2正极材料对溶胶-凝胶法制备KAlSi2O6的侵蚀研究

将不加和添加CaF₂的KAlSi₂O₆(KAS₄)溶胶于800～1 300℃煅烧得到的KAS₄以及原料CaF₂粉,分别与Li(Ni_xCo_yMn_z)O₂(LNCM)按照质量比70∶30混合均匀,然后在1 100℃保温6 h进行侵蚀试验。对比分析了不加和添加CaF₂的KAS₄的物相组成以及侵蚀试验后几种材料的物相组成和显微结构。结果表明：1)添加1.88%(w)CaF₂可以使KAS₄纯相的生成温度下降约100℃;2)不加CaF₂的KAS₄比添加CaF₂的具有更好的抗LNCM侵蚀性能;3)CaF₂与LNCM在高温下容易发生反应。     

炭吸附La2O3/TiO2复合粉体的制备及其光催化性能研究

采用炭吸附共沉淀法制备了La₂O₃/Ti O₂催化剂,利用TG-DTG、XRD、TEM、UV-Vis等对催化剂进行表征,并考察了不同条件制备的La₂O₃/Ti O₂对可见光催化甲基橙降解效果的影响。结果表明,炭黑的加入可有效阻止粉体在制备、干燥及焙烧过程中的团聚和烧结;在600℃煅烧后得到的粉体结晶度高、颗粒分散均匀、颗粒粒径小。在可见光照射1 h后,炭吸附沉淀法制备的La2O3/Ti O₂对甲基橙的降解率高达92.25%,是普通沉淀法制得的La₂O₃/Ti O₂的3倍,光催化活性显著提高。     

Nd（C2H5CO2）3·H2O热分解性质的研究

用热重分析(TG),差热分析(DTA),傅里叶红外光谱分析(FTIR)和X射线衍射(XRD)等方法研究了Nd(C2H5CO2)3.H2O的热分解性质。在流动的Ar气中加热到1200℃,水合丙酸钕的分解可以分成6个步骤。在经过脱水反应之后,Nd(C2H5CO2)3首先在250℃和292℃之间生成Nd2(C2H5CO2)4.CO3并释放出二乙基甲酮。当温度升高到315℃,伴随着CO2气体的放出,Nd(C2H5CO2)3立即分解成Nd2O(C2H5CO2)4。在424℃之前,伴随着二乙基甲酮和CO2气体产生,Nd2O(C2H5CO2)4首先分解成中间相Nd2O(CO3)2,并立即转化成分解产物Nd2O2CO3。随着温度升高到770℃,含Nd化合物完全转化成Nd2O3。研究表明,Nd(C2H5CO2)3.H2O在空气中的TG曲线和其在Ar气中的没有任何改变。但是,分解产物二乙基甲酮气体在空气中的燃烧会产生很强的放热效应。与其它稀土金属丙酸盐的热分解的研究结果比较而言,Nd(C2H5CO2)3.H2O的分解性质表现出一些有趣的特点。特别是,在其它丙酸盐中没有发现类似中间相Nd2(C2H5CO2)4.CO3的生成的情况。     

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A₂B₂O₇, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La₂Zr₂O₇ (LZO) and La₂Hf₂O₇ (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu³⁺ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O²⁻→Zr⁴⁺/Hf⁴⁺ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu³⁺-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu³⁺ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays.     

表面活性剂对Sm2Zr2O7纳米热障涂层材料烧结性能的影响

采用水热合成法制备Sm2Zr2O,纳米晶体,研究了聚乙二醇(PEG)、十六烷基三甲基溴化铵(CTAB)、十二烷基苯磺酸钠(SDBS)三种不同类型的表面活性剂对材料相结构、分散性能以及烧结性能的影响.实验结果表明:材料的物化性能与表面活性剂的类型密切相关,阳离子表面活性剂的添加抑制了材料由萤石结构向烧绿石结构的转变,样品比表面积为174.67 m2·g-1,经过高温烧结后块材的体积收缩和相对密度分别为24.5％和81.2％.相比之下,阳离子表面活性剂CTAB对于提高材料的抗烧结性能方面要明显好于非离子表面活性剂PEG和阴离子表面活性剂SDBS.     

(Ti0.25Zr0.25Nb0.25Ta0.25)C高熵陶瓷的制备、力学性能及氧化行为研究

本文通过对碳化物粉末进行放电等离子烧结(SPS),成功制备了(Ti_0.25Zr_0.25Nb_0.25Ta_0.25)C高熵陶瓷(HECs),系统研究了HECs的微观结构演变、力学性能和氧化行为。结果表明,单相HECs的形成温度为1 800 ℃,低于已报道的HECs烧结温度。1 900 ℃烧结的陶瓷晶粒细小,平均晶粒尺寸约7.5 μm,元素分布均匀,相对密度高达99.2%。1 800 ℃和1 900 ℃烧结的HECs的室温显微硬度值分别为30.9 GPa和33.2 GPa,断裂韧性值分别为(4.6±0.24) MPa·m^1/2和(4.5±0.31) MPa·m^1/2,高于大多数已报道的HECs。原位高温纳米压痕试验结果表明,HECs的硬度随温度的升高而降低,当温度达到500 ℃时,1 800 ℃和1 900 ℃烧结的陶瓷硬度分别下降到21.9 GPa和22.2 GPa,具有突出的高温稳定性。此外,HECs在温度低于500 ℃时无明显氧化,当温度超过650 ℃时会发生明显氧化,氧化速率随温度升高而增加。     

A novel porous La2Zr2O7 ceramic aerogels with ultralow thermal conductivity and photocatalytic property

Porous La₂Zr₂O₇ ceramic aerogels (CAs) were prepared by sol-gel template method and thermal treated process. The microstructure and crystallisation behavior of the samples were systematically characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The results indicated that the as-prepared porous La₂Zr₂O₇ CAs had a single-phase pyrochlore structure with typical three-dimensional (3-D) porous structure. Meanwhile, the formation mechanisms of the as-prepared porous La₂Zr₂O₇ CAs were investigated. At the same time, the as-prepared porous La₂Zr₂O₇ CAs presented an ultralow room-temperature thermal conductivity of 0.07 W/(m K), high specific surface areas of 325.17 m²/g, and a relatively high compressive strength of 11.95 MPa. What's more, the as-prepared porous La₂Zr₂O₇ CAs possessed ideal photocatalytic activities due to its high crystallinity, large surface area as well as unique 3-D porous structure. Therefore, the present work is proposing some new insight to prepare rare-earth zirconates CAs with porous structures for thermal insulation and dye degradation applications.     

The toughening of pyrochlore La2Zr2O7 by a ferroelastic NdAlO3 second phase for potential thermal barrier coating applications

The poor fracture toughness of La₂Zr₂O₇ severely limits its application as a high temperature thermal barrier coating topcoat material. To toughen it, a ferroelastic second phase, NdAlO₃, with a Curie temperature of 1367°C has been introduced to form x NdAlO₃/(1-x) La₂Zr₂O₇ composite ceramics by a spark plasma sintering technique, where x = 10, 20, 30, 40, and 50 mol%. The fracture toughness of sintered composite ceramic compacts is measured at both room temperature and 1200°C, respectively, by a single-edge-notch beam test method. The results show that, at room temperature, the residual compressive stress in the La₂Zr₂O₇ matrix plays an important role in the toughening of composite ceramics. By eliminating this factor, the remaining toughening effects agree with the measured fracture toughness at 1200°C, suggesting that the other toughening is probably ferroelastic domain switching toughening and that it is still valid at high temperature. Furthermore, the toughening effect arising from ferroelastic domain switching is governed by the overall domain switching zone, which is determined by both individual domain switching zone width and the “concentration” of ferroelastic phases. A relatively high coercive stress of NdAlO₃ and relatively low residual tensile stress in NdAlO₃ second phases contribute to negligible influence of residual tensile stress on domain switching zone width, leading to the continuous increase of fracture toughness of composite ceramics with more NdAlO₃ added at room temperature.     

Immobilization of simulated waste into pure Gd2Zr2O7 pyrochlore without space occupancy design

In this study, different molar ratios of Nd:Ce were directly mixed with prepared pure Gd₂Zr₂O₇ powders without space occupancy design. Samples were obtained by performing sparking plasma sintering (SPS) at 1750°C for 5 minutes. X-ray diffraction (XRD) results show that maximum solid solubility of simulated radionuclides can reach 50 mol%. In addition, all samples with the maximum solid solubility have high compactness, and all elements are evenly distributed on the surface of the samples. The samples show a better crystallization effect as the molar ratio of Nd:Ce increases. The maximum solid solubility increases from 42 mol% to 50 mol% when the amount of Nd₂O₃ reaches 66 mol%.     

Effect of CaO doping on densification and microstructure control of highly transparent La0.4Gd1.6Zr2O7 ceramics

Calcium oxide (CaO) as sintering additive was first used to fabricate La_0.4Gd_1.6Zr₂O₇ transparent ceramics by a simple solid-state reaction and one-step vacuum sintering method. The effects of CaO dopant amount on the densification, as well as sintering behaviors and microstructure evolution of the as-fabricated La_0.4Gd_1.6Zr₂O₇ ceramics, were systematically investigated. Under the different sintering temperatures, the relationships during the sintering process between grain growth and zpore elimination were analyzed as well. It was found that 0.1 wt% CaO doping can effectively control the rate of grain growth and promote densification dominated by surface diffusion. Furthermore, Ca²⁺ entered the lattice of La_0.4Gd_1.6Zr₂O₇ ceramics to accelerate ion diffusion and suppress grain boundary migration. With the introduction of 0.1 wt% CaO doping, the highly transparent La_0.4Gd_1.6Zr₂O₇ ceramics (T = 80.4% at 1100 nm) were successfully fabricated at the traditional sintering temperature (1850°C).     

Effect of Li2O excess in Li6.4Ga0.2La3Zr2O12 electrolyte for all-solid-state Li-ion batteries

Li₇La₃Zr₂O₁₂ is a promising material used as solid electrolyte in all-solid-state lithium batteries. However, the lithium ionic conductivity of LLZO is limited, and the cycling stability of lithium symmetric battery based on LLZO is not good. In this research, different Ga-doped LLZO samples were prepared by adding different excess amounts of Li₂O, and the effect of excess amount of Li₂O on the structure and performance of LLZO have been researched. The results show that with the rise of the amount of Li₂O, the lithium ionic concentration increases gradually, and the lithium ionic conductivity and the ratio of grain resistance to total resistance rise first and then drop. When the excess amount of Li₂O is 10 wt.%, the sample exhibits the highest lithium ionic conductivity of 1.36 mS/cm, and the lithium symmetric battery exhibits the most stable operation.     

固态无机电解质Li7La3Zr2O12的改性研究进展

作为一种固态无机电解质材料,石榴石型立方相Li₇La₃Zr₂O₁₂具有较高的室温锂离子电导率、较宽的电化学窗口和优良的热稳定性等特点,是高安全性、高能量密度固态锂离子电池实现商业化应用的关键。阐述了Li₇La₃Zr₂O₁₂的晶体结构与锂传导机理,综述了元素掺杂、聚合物电解质复合、烧结助剂引入、表面包覆或修饰等方式对Li₇La₃Zr₂O₁₂的物相结构稳定性、界面阻抗与相容性、烧结活性、离子电导率等进行改性的最新研究进展。最后,针对Li₇La₃Zr₂O₁₂在产业化应用中所面临的障碍与挑战,提出了制备新工艺的开发、离子电导率的多重改性以及柔性复合电解质膜的结构设计与优化等应对策略,为推动高性能固态锂离子电池的发展提供依据。     

Ta、Ba共掺杂石榴石型Li7La3Zr2O12电解质的制备及性能研究

传统锂离子电池采用有机电解液体系,能量密度难以进一步提升,同时存在一定的安全隐患。采用无机固体电解质构建全固态锂电池,在提高电池能量密度同时可兼顾安全性问题。在众多无机固体电解质中,Li₇La₃Zr₂O₁₂(LLZO)石榴石电解质具有离子电导率高、与金属锂接触稳定等优势,成为受人关注的材料。为了进一步提高该材料的导电性,采用固相法合成Ta、Ba共掺杂LLZO(Li_7-x+yLa_3-yBa_yZr_2-xTa_xO₁₂)电解质,采用X射线衍射、扫描电子显微镜和电化学阻抗法分析样品的物相结构、微观形貌及离子电导率。结果表明,Ta⁵⁺掺杂能够稳定立方相结构,Ba²⁺作为掺杂剂和烧结剂,促进晶粒生长和陶瓷致密化,从而降低总电阻。其中,Li_6.45La_2.95Ba_0.05Zr_1.4Ta_0.6O₁₂样品在室温下的总电导率为1.07×10^-3 S·cm^-1,活化能为0.378 eV。Ta⁵⁺/Ba²⁺共掺杂有利于制备高致密度和高电导率的石榴石型电解质材料。