La2O3添加对MgAl2O4-CaAl4O7-CaAl12O19复合材料烧结行为的影响

为适应材料轻量化的发展需要,在1 400~1 600℃温度下开发了MgAl₂O₄-CaAl₄O₇-CaAl₁₂O₁₉（MA-CA₂-CA₆）复合材料,并考察了La₂O₃添加对该复合材料烧结行为、显微结构和力学性能的影响。结果表明,La₂O₃添加剂优先固溶到MA-CA₂-CA₆复合材料组成晶相CA₆中,促使CA₆相发生晶格畸变,有效抑制了CA₆晶粒沿基面的异常长大,其形貌由片状向等轴状趋势转变,促使MA-CA₂-CA₆复合材料制备过程中由于CA₆晶粒异常长大而导致的多孔网状显微结构得以有效消除,因此也极大地改善了Mg²⁺的扩散条件,在一定程度上间接促进了MA晶粒的发育,有效促进了MA-CA₂-CA₆复合材料的烧结。经1 200℃预烧、1 600℃保温2 h烧成后,当La₂O₃的添加量为4wt%时,MA-CA₂-CA₆复合材料试样的显气孔率由19.2%下降至6.1%,体积密度由2.78 g/cm³上升至3.18 g/cm³,制得了MA、CA₂、CA₆晶相呈现交织分布、显微结构致密、有利于其力学性能改善的La₂O₃/MA-CA₂-CA₆复合材料,经1 200℃预烧、-1 600℃保温2 h烧成后的4wt% La₂O₃添加试样,其冷态抗压强度由317 MPa增加到了501 MPa。     

A simple and novel effective strategy using mechanical treatment to improve the oxygen uptake/release rate of YBaCo4O7+δ for thermochemical cycles

In recent years,oxygen storage materials(OSMs)have been widely used in many fields.It would be particularly important for researchers to design high-oxygen-uptake/release-rate materials.In this study,various synthesis processes were used to successfully synthesize YBaCo₄O_7+δand comprehensively investigate their potential applications.Compa red with traditional solid-state reaction method and co-precipitation method,the results demonstrated that the utilization of mechanical ball milling treatment on co-precipitated precursors could lead to samples with reversible oxygen uptake/release under an oxidative atmosphere at low temperatures.The resultant materials exhibited fast oxygen absorption/desorption rate that could uptake/release oxygen directly to the equilibrium state within 9 min and20 min,respectively.The mechanochemically ball-milled sample possessed outstanding oxygen sto rage performance,which could be attributed to their small particle size,the active outer surface of particles,large specific surface area,and relatively low activation energy.Moreover,the ball-milled sample also exhibited excellent cycling stability during relatively short time spacing.TG results also demonstrated that the ball-milled samples could reversibly uptake/release 2.90 wt.%of excess oxygen(while only 0.70 wt.%for solid-state samples)by adjusting the ambient temperature under pure O₂ atmosphere,which would make them promising candidates in various applications.This research demonstrated that mechanical treatment could be an effective strategy to tune the properties and oxygen storage capacity(OSC)performances of YBaCo₄O_7+δ.     

稀土Sm掺杂的YbBaCo4O7+δ纳米粉体制备及其氧吸附性能的研究

采用溶胶凝胶制备了不同浓度Sm掺杂的YbBaCo₄O_7+δ氧吸附材料,并利用XRD分析、SEM和差热分析仪等仪器对其进行了结构、形貌、氧吸附/脱附性能分析,研究了不同浓度Sm掺杂对YbBaCo₄O_7+δ氧吸附/脱附性能的影响,测试结果表明：在较低掺杂浓度下,稀土元素Sm完全进入了Yb_1-xSm_xBaCo₄O_7+δ纳米粉体的晶格,Yb_1-xSm_xBaCo₄O_7+δ纳米粉体仍是单一的114相结构;稀土元素Sm掺杂对Yb_1-xSm_xBaCo₄O_7+δ纳米粉体的形貌影响较小。氧吸附/脱附性能测试结果表明：一定量的稀土元素Sm掺杂可以明显提高的YbBaCo₄O_7+δ纳米粉体的氧吸附性能,YbBaCo     

Ce元素掺杂对YBaCo_4O_(7+δ)氧吸附/脱附性能的影响

本研究采用固态反应法制备了Ce掺杂的YBaCo_4O_(7+δ)氧吸附材料,对其进行了X射线衍射(XRD)分析和热重分析测试,研究了Ce掺杂对其氧吸附/脱附性能的影响。XRD分析结果表明:在x=0.10,0.15,0.20掺杂比例范围内,Ce很好地进入了YBaCo_4O_(7+δ)的晶格,具有单一的YBaCo_4O_(7+δ)的晶体结构,没有出现第二相。热重分析结果表明:从室温到1000℃,所有样品都经历了两次氧吸附过程,Ce掺杂的YBaCo_4O_(7+δ)样品最大氧吸附量明显高于YBaCo_4O_(7+δ)的最大氧吸附量。     

Tb掺杂DyBaCo4O7+δ纳米粉体的制备及其氧吸附/脱附性能的研究

利用溶胶凝胶工艺合成了稀土元素Tb掺杂DyBaCo₄O_7+δ纳米粉体,采用XRD、SEM、差热分析仪等设备研究了不同浓度Tb掺杂对DyBaCo₄O_7+δ纳米粉体形貌、晶体结构及氧吸附-脱附性能的影响,测试结果表明：在较低掺杂浓度下,Tb很好地进入了Dy_1-xTb_xBaCo₄O_7+δ的晶格,稀土Tb掺杂的DyBaCo₄O_7+δ纳米粉体仍是六方密排晶体结构;Tb元素掺杂对DyBaCo₄O_7+δ粉体的形貌影响不大。从室温到1000℃,DyBaCo₄O_7+δ纳米粉体与Tb掺杂的DyBaCo₄O_7+δ纳米粉体均表现出两次氧吸附和脱附现象,与未掺杂的DyBaCo₄O_7+δ纳米粉体氧吸附性能相比,Tb掺杂的Dy...     

混合导电体Y1-xLaxBa2Cu3O7-δ透氧膜的透氧性能研究

用稳态法研究了具有类钙钛矿结构的Y1-xLaxBa2Cu3O7-δ(x=0.1、0.3、0.5、0.8和1.0)致密透氧膜在750～1000℃之间的透氧量.实验发现,透氧速率随着La替代Y的比例x的增加而增加;在大约875℃,氧空位的有序-无序转变导致透氧率有一个突然增加.透氧膜的两侧分别为He气氛和空气,当La完全替代Y时,厚1.0mm的LaBa2Cu3O7-δ膜的透氧量达到1.22μmol/s.cm2(1.64 mL/min.cm2).     

Cr掺杂Ba0.5Sr0.5Co0.8Fe0.1Cr0.1O3-δ钙钛矿型膜的透氧性能研究

采用固相反应法合成了钙钛矿型Ba0.5Sr0.5Co0.8Fe0.2-xCrxO3-δ(x=0.00,0.10)透氧膜粉体。利用XRD和SEM研究了Ba0.5Sr0.5Co0.8Fe0.2-xCrxO3-δ(x=0.00,0.10)的晶体结构和烧结性能,考察了在700~850℃范围内Ba0.5Sr0.5Co0.8Fe0.2-xCrxO3-δ(x=0.00,0.10)膜片的氧渗透性能。结果表明,它们均显示出优良的透氧性能,850℃时的透氧量分别为1.05mL/(min.cm2)、0.85mL/(min.cm2)。透氧稳定性的研究表明,Cr掺杂Ba0.5Sr0.5-Co0.8Fe0.1Cr0.1O3-δ在800℃时显示出较高的稳定性,证实用Cr离子部分取代Ba0.5Sr0.5Co0.8Fe0.2O3-δ的Fe离子能明显提高钙钛矿的结构稳定性。     

铝酸钙基稀土荧光粉CaAl4O7∶Eu3+的制备及热稳定性研究

在目前商用白光LED的实际应用中,存在发光色温高、显色指数低及热稳定性差等问题。为了改进白光LED存在的不足,使其更适用于人类生活的需求,本文通过共沉淀法合成了一系列CaAl₄O₇∶Eu^{3+高温红光荧光粉,采用扫描电子显微镜、X射线衍射仪、能谱仪分别对样品的形态、结构、组成元素及分布进行表征,并通过荧光光谱仪对CaAl₄O₇∶Eu3+的荧光特性及热稳定性进行了研究。实验结果表明,最佳样品为CaAl₄O₇∶0.02Eu3+}。其激发光谱中,在 393及464 nm处有两个强光激发峰,分别属于⁷F₀→⁵L₆及⁷F₀→⁵D₂跃迁;在发射光谱中,最强发射峰位于612 nm,为⁵D₀→⁷F₂跃迁的窄带红光发射;最佳样品的发光具有负的热猝灭效应,其在90 ℃时发射光强度最大,此时积分荧光发射强度为30 ℃时初始值的114.5%。当测试温度升高至150 ℃时,积分荧光发射强度仍为初始值的108%;在CaAl₄O₇∶0.02Eu^{3+的原型红光LED的电致发光测试中,发射红光比随着驱动电流的增大而增大。CaAl₄O₇∶0.02Eu3+}荧光粉具有优异的高温荧光特性,满足LED对荧光粉的发光热稳定性的要求,表明其在WLEDs领域具有潜在的应用前景。     

负热膨胀材料ZrV2O7与金属Al的复合行为及特性

利用湿化学法制备先驱体-煅烧合成制备钒酸锆-ZrV₂O₇的新技术,采用粉末冶金方法,研究了ZrV₂O₇与金属Al两类不同材料的复合行为及其热膨胀特性。X射线衍射结果表明:利用上述技术合成的ZrV₂O₇纯度高,杂质含量极少。采用合成的ZrV₂O₇粉体与金属Al粉末混合,按不同成形-烧结工艺制备ZrV₂O₇与金属Al的复合材料试样,经扫描电子显微组织分析、微区电子探针能谱成分分析及X射线衍射分析发现,在一定烧结温度范围内,ZrV₂O₇与金属Al ( 无论是固态还是熔融态 ) 均表现出了良好的烧结性与浸渍性,但在烧结温度下在ZrV₂O₇与金属Al之间存在Al对Zr的置换反应,且随温度升高而加剧。用热膨胀仪分别对合成的ZrV₂O₇及其与金属Al烧结而成的复合材料进行热膨胀特性测试,结果表明:ZrV₂O₇在400~680K的温度区间具有很强的负膨胀特性;其与金属Al的复合材料虽然仍具有正的热膨胀特性,但其膨胀率较金属Al低得多。      

新型超级电容器电极材料NaxCo2O4的制备及电性能研究

采用溶胶-凝胶法制备得到Na x Co2O4(x=1.0、1.2、1.4、1.6、1.8和2.0)样品,并首次将其应用于超级电容器电极材料;经XRD、SEM和电性能研究得出,制备出的Na x Co2O4晶体均为层状结构,x=1.6时样品电容性能最好,在6mol/L NaOH电解液中,0.25~0.7V电压范围内,以50mA/g的电流密度进行恒流充放电,比电容高达413F/g。     

YBaCo4O7-x的透氧性研究

采用固相反应合成了YBaCo4O7-x致密透氧膜材料,并对其进行了XRD分析和热重-差式扫描量热分析.用稳态法测量了在400℃以下的透氧率,在得到YBaCo4O7-x的透氧率随厚度变化的曲线后发现,在实验的膜厚范围内,透氧率受体相扩散所控制.最后测量了它在较高温度下的透氧率,结果表明在900℃时远远高于400℃左右的透氧率,接近于它们的5～8倍.     

尖晶石型LiMn_2O_4阴极材料电化学性能研究

利用柠檬酸络合法制备锂离子电池正极材料尖晶石型LiMn2 O4,利用X射线衍射、循环伏安、充放电测试、交流阻抗等手段对它进行了研究。发现活性物质在不同的电位下具有不同的电化学特征 ,电位处在平台区时与处在非平台区时相比 ,交流阻抗谱明显不同。电位处于非充放电平台区时 ,高频表现为锂离子电极材料中的固态扩散 ,在充放电平台区时 ,高频表现为电子到达活性物质的通道的阻抗。     

Metal Atom-Doped Co3O4 Hierarchical Nanoplates for Electrocatalytic Oxygen Evolution

Electrocatalysts based on hierarchically structured and heteroatom-doped non-noble metal oxide materials are of great importance for efficient and low-cost electrochemical water splitting systems. Herein, the synthesis of a series of hierarchical hollow nanoplates (NPs) composed of ultrathin Co₃O₄ nanosheets doped with 13 different metal atoms is reported. The synthesis involves a cooperative etching−coordination−reorganization approach starting from zeolitic imidazolate framework-67 (ZIF-67) NPs. First, metal atom decorated ZIF-67 NPs with unique cross-channels are formed through a Lewis acid etching and metal species coordination process. Afterward, the composite NPs are converted to hollow Co₃O₄ hierarchical NPs composed of ultrathin nanosheets through a solvothermal reaction, during which the guest metal species is doped into the octahedral sites of Co₃O₄. Density functional theory calculations suggest that doping of small amount of Fe atoms near the surface of Co₃O₄ can greatly enhance the electrocatalytic activity toward the oxygen evolution reaction (OER). Benefiting from the structural and compositional advantages, the obtained Fe-doped Co₃O₄ hierarchical NPs manifest superior electrocatalytic performance for OER with an overpotential of 262 mV at 10 mA cm⁻², a Tafel slope of 43 mV dec⁻¹, and excellent stability even at a high current density of 100 mA cm⁻² for 50 h.     

锂离子电池正极材料LiMn2O4的研究进展

具有尖晶石相的LiMn₂O₄因价格低、无毒、无环境污染、制备简单、研究较成熟,因此有着很好的应用前景,被看作最有可能成为新一代商用锂离子二次电池正极材料.由于LiMn₂O₄电化学循环稳定性能不好,表现在可逆容量衰减较大,尤其在高温下(>55℃)使用衰减更严重,从而限制了它的商业化应用.经过近十几年的研究,人们对其衰减机理有了比较清晰的了解,提出了造成容量衰减的几种可能原因如Jahn-Teller畸变效应、Mn²⁺在电解质中的溶解、出现稳定性较差的四方相以及电解质的分解等.通过掺杂、表面包覆、制备工艺的改进,人们已能制得循环稳定性能较好的尖晶相材料.本文结合我们研究小组的最新研究成果对锂离子二次电池正极材料LiMn₂O₄的最新研究进展进行综述和评论.     

Li2B4O7:Eu3+荧光体的合成及表征

利用Li₂B₄O₇作为基质,掺杂稀土元素Eu³⁺,在空气中合成了Li₂B₄O₇:Eu³⁺荧 光体.探讨了体系的烧结条件,分析了晶体结构,并研究了该体系的荧光性质.结果表明,体 系中同时存在着[BO₄]和[BO₃]结构;稀土离子Eu3+的发光以电偶极跃迁⁵D₀-⁷F₂为主,处 于非中心对称的格位上,并且可以很好地存在于基质中.     

锂离子电池负极材料Ge4+掺杂Li4Ti5O12的制备及其电化学性能研究

以Ti(OC₄H₉)₄、CH₃COOLi·2H₂O和GeO₂为原料, 采用溶胶-凝胶法合成了尖晶石型Li₄Ti_5-xGe_xO₁₂(x=0、0.05、0.1、0.15)电极材料。通过X射线衍射(XRD)、扫描电镜(SEM)、充放电测试、循环伏安(CV)以及交流阻抗对材料进行结构、形貌及电化学性能表征。研究结果表明, 适量Ge⁴⁺掺杂不会改变Li₄Ti₅O₁₂的尖晶石结构, 但对其颗粒尺寸和形貌均产生影响。由于掺Ge⁴⁺后样品的颗粒尺寸减小, 使得Ge⁴⁺掺杂Li₄Ti₅O₁₂倍率性得到不同程度的提高。其中Li₄Ti_4.9Ge_0.1O₁₂显示出较好的倍率性和循环稳定性, 0.2C下的首次放电容量为172.43 mAh/g, 5C下循环100次后比容量为140.62 mAh/g, 容量保持率为97.3%。     

水热法制备八面体Fe3O4亚微米晶及其影响因素

利用水热法在80～90℃制备了八面体Fe3O4,并对样品进行了X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和磁学性能表征.制备的八面体亚微米晶形貌规整,物相纯净,结晶性好,颗粒尺寸为200～320nm,饱和磁化强度Ms=85.2emu/g,矫顽力Hc=114.20e.探索了NaOH和KNO3溶液的滴加速率、pH值、反应温度和时间及聚乙二醇(PEG)等因素对产物纯度、形貌及颗粒尺寸的影响.     

Self‐Assembled Nanostructured CuCo2O4 for Electrochemical Energy Storage and the Oxygen Evolution Reaction via Morphology Engineering

CuCo₂O₄ films with different morphologies of either mesoporous nanosheets, cubic, compact‐granular, or agglomerated embossing structures are fabricated via a hydrothermal growth technique using various solvents, and their bifunctional activities, electrochemical energy storage and oxygen evolution reaction (OER) for water splitting catalysis in strong alkaline KOH media, are investigated. It is observed that the solvents play an important role in setting the surface morphology and size of the crystallites by controlling nucleation and growth rate. An optimized mesoporous CuCo₂O₄ nanosheet electrode shows a high specific capacitance of 1658 F g⁻¹ at 1 A g⁻¹ with excellent restoring capability of ≈99% at 2 A g⁻¹ and superior energy density of 132.64 Wh kg⁻¹ at a power density of 0.72 kW kg⁻¹. The CuCo₂O₄ electrode also exhibits excellent endurance performance with capacity retention of 90% and coulombic efficiency of ≈99% after 5000 charge/discharge cycles. The best OER activity is obtained from the CuCo₂O₄ nanosheet sample with the lowest overpotential of ≈290 mV at 20 mA cm⁻² and a Tafel slope of 117 mV dec⁻¹. The superior bifunctional electrochemical activity of the mesoporous CuCo₂O₄ nanosheet is a result of electrochemically favorable 2D morphology, which leads to the formation of a very large electrochemically active surface area.     

Light‐Switchable Oxygen Vacancies in Ultrafine Bi5O7Br Nanotubes for Boosting Solar‐Driven Nitrogen Fixation in Pure Water

Solar‐driven reduction of dinitrogen (N₂) to ammonia (NH₃) is severely hampered by the kinetically complex and energetically challenging multielectron reaction. Oxygen vacancies (OVs) with abundant localized electrons on the surface of bismuth oxybromide‐based semiconductors are demonstrated to have the ability to capture and activate N₂, providing an alternative pathway to overcome such limitations. However, bismuth oxybromide materials are susceptible to photocorrosion, and the surface OVs are easily oxidized and therefore lose their activities. For realistic photocatalytic N₂ fixation, fabricating and enhancing the stability of sustainable OVs on semiconductors is indispensable. This study shows the first synthesis of self‐assembled 5 nm diameter Bi₅O₇Br nanotubes with strong nanotube structure, suitable absorption edge, and many exposed surface sites, which are favorable for furnishing sufficient visible light‐induced OVs to realize excellent and stable photoreduction of atmospheric N₂ into NH₃ in pure water. The NH₃ generation rate is as high as 1.38 mmol h^?1 g^?1, accompanied by an apparent quantum efficiency over 2.3% at 420 nm. The results presented herein provide new insights into rational design and engineering for the creation of highly active catalysts with light‐switchable OVs toward efficient, stable, and sustainable visible light N₂ fixation in mild conditions.     

Coupling of Oxygen Vacancies and Heterostructure on Fe3O4 via an Anion Doping Strategy to Boost Catalytic Activity for Lithium-Sulfur Batteries

The sluggish reaction kinetics and severe shutting behaviors of sulfur cathodes are the major roadblocks to realizing the practical application of lithium−sulfur (Li−S) batteries and need to be solved through designing/constructing rational sulfur hosts. Herein, an effective alternative material of Fe₃O_4−x/FeP in-situ embedded in N-doped carbon-tube (Fe₃O_4−x/FeP/NCT) is proposed. In this fabricated heterostructure, NCT skeleton works as a sulfur host provides physical barrier for lithium polysulfides (LiPSs), while Fe₃O_4−x/FeP heterostructure with abundant oxygen vacancies provides double active centers to simultaneously accelerate e⁻/Li⁺ diffusion/transport kinetics and catalysis for LiPSs. Through the respective advantages, Fe₃O_4−x/FeP/NCT exhibits synergy enhancement effect for restraining sulfur dissolution and enhancing its conversion kinetics. Furthermore, the promoted ion diffusion kinetics, enhanced electrical conductivity, and increased active sites of Fe₃O_4−x/FeP/NCT are enabled by oxygen vacancies as well as the heterogeneous interfacial contact, which is clearly confirmed by experimental and first-principles calculations. By virtue of these superiorities, the constructed cathode shows excellent long-term cycling stability and a high-rate capability up to 10 C. Specially, a high areal capacity of 7.2 mAh cm⁻² is also achieved, holding great promise for utilization in advanced Li−S batteries in the future.