Al_2O_3-SiO_2系耐火材料高温力学性能

对Al_2O_3-SiO_2系高铝区域两个系列烧结材料在不同温度的机械性能(应力—应变关系、强度和蠕变试验等)的研究表明:(1)烧结矾土材料,Al_2O_3含量越接近70%,高温力学性能越好;(2)刚玉-莫来石材料,恰当比例的两晶相材料的高温力学性能优于单晶相材料;在单晶相材料中,莫来石优于刚玉。高铝耐火材料的高温力学行为主要取决于玻璃效应(玻璃基质的数量和粘度)和结晶效应(晶体间接触或结合的程度和方式)。     

近紫外白光LED用Ba_3Y_(1-x-y)B_3O_9∶xEu~(3+),yBi~(3+)高效红色荧光粉的制备与发光性能

采用传统高温固相法在较低温度下制备Eu~(3+)/Bi~(3+)共掺杂Ba_3YB_3O_9红色荧光粉,利用XRD仪和荧光光谱仪对样品Ba_3Y_(1-x-y)B_3O_9∶xEu~(3+),yBi~(3+)的晶体结构和发光性质进行了表征。XRD结果表明,Ba_3Y_(1-x-y)B_3O_9∶xEu~(3+),yBi~(3+)为纯相晶体。激发和发射光谱表明,样品可以被近紫外350～420 nm波段激发,最强激发峰位于393 nm,发射光谱呈现出Eu~(3+)的特征峰,谱带峰值位置在593 nm、613 nm,分别对应~5D_0-~7F_1、~5D_0-~7F_2特征跃迁。最强发射对应的掺杂浓度是0.12 mol。Ba_3Y_(0.87)B_3O_9∶0.12Eu~(3+),0.01Bi~(3+)的CIE坐标为(0.643,0.356)时最接近标准红色坐标,获得极佳的演色性。样品Ba_3Y_(1-x-y)B_3O_9∶xEu~(3+),yBi~(3+)可以用作近紫外激发三基色白光LED的红色荧光粉。     

Y_2O_3和Gd_2O_3掺杂对硼硅酸盐玻璃耐海水性能的影响

本文通过高温熔融法制备了Y_2O_3和Gd_2O_3掺杂的硼硅酸盐玻璃,借助SEM、ICPAES、XRD和pH计等分析手段,探究了稀土掺杂对该玻璃耐蚀性能的影响及其在海水中的腐蚀机理。结果表明:单独掺杂不同量的稀土氧化物对玻璃耐海水性能的影响不同,理想的单独掺杂量分别为1.00mol%的Y_2O_3(ZBY4)和0.25mol%的Gd_2O_3(ZBG1);混合掺杂的试样在耐海水性能上均得到提高,其中最佳掺杂量为0.5mol%Y_2O_3+0.5mol%Gd_2O_3;基础试样腐蚀后表面析出Mg_4Al_2(OH)_(12)(CO_3)·_3H_2O晶体,ZBY4、ZBG1试样及所有混合掺杂试样表面均没有晶体产生。此外,玻璃在海水中的腐蚀与玻璃在去离子水中的腐蚀过程存在较大差别。     

磁控溅射制备Er~(3+)掺杂Al_2O_3薄膜的上转换发光特性

Al_2O_3作为太阳能电池的钝化层,如果掺入稀土元素Er~(3+)通过吸收红外光并将其上转换为可见光被硅吸收,则可以提高太阳能的利用率。本文采用磁控溅射法制备得到厚度为500 nm左右的不同浓度Er~(3+)掺杂Al_2O_3薄膜。X射线衍射测试表明薄膜由θ-(Al,Er)_2O_3、Al_(10)Er_6O_(24)和ErAlO_3相构成。通过波长980nm的激光器激发产生光频上转换,获得了490 nm的绿光和670nm的红光发光,分别对应于Er~(3+)的~4F_(7/2)→~4I_(15/2)和~4F_(9/2)→~4I_(15/2)的能级跃迁。当Er~(3+)掺杂浓度为0.6%(摩尔比)时,上转换发光强度最强。上转换发光强度受到Al_(10)Er_6O_(24)和ErAlO_3晶体的生成以及Er~(3+)掺杂浓度的影响,并且对红光的影响要大于绿光。Er~(3+)掺杂Al_2O_3薄膜相比粉体材料具有较低的声子态密度,从而抑制了Er~(3+)无辐射跃迁,得到了不同于粉体材料的490nm绿光的发光。     

纳米Al_2O_3掺杂对AM60B镁合金表面微弧氧化膜层结构和耐蚀性的影响

为促进大面积镁合金表面耐蚀性能优良的微弧氧化膜层的工业化生产,在硅酸盐水溶液中掺杂纳米Al_2O_3颗粒对AM60B镁合金进行微弧氧化;采用扫描电镜、X射线衍射仪及盐雾试验分析了掺杂纳米Al_2O_3颗粒对氧化膜层的形成过程、形貌、成分以及耐蚀性的影响。结果表明:掺杂纳米Al_2O_3微弧氧化膜物相组成主要有MgO、MgAl_2O_4、Mg_2Si_2O_4、Al_2O_3,纳米Al_2O_3的掺杂能提高氧化膜的密度,促进薄膜生长,使表面孔隙分布更均匀,尺寸更小;掺杂纳米Al_2O_3氧化膜的耐蚀性较未掺杂氧化膜的大幅提高。     

Ta_2O_5掺杂对0.48BCT-0.52BZT陶瓷结构及压电性能的影响

采用固相烧结法制备锆钛酸钡钙(BCZT)无铅压电陶瓷,研究不同Ta_2O_5掺杂浓度对陶瓷结构和压电、铁电、介电性能的影响。实验结果表明,不同掺杂量的钽烧结的BCZT无铅压电陶瓷均为典型的钙钛矿结构,陶瓷晶粒生长均匀,钽的掺杂对晶粒的生长有较大的影响;0.48(Ba_(0.7)Ca_(0.3))TiO_3-0.52Ba(Zr_(0.2)Ti_(0.8))O_3的压电系数、逆压电系数、剩余极化强度都在掺杂量0.3%(摩尔分数)Ta_2O_5最优,综合性能为d_(33)为489 pC/N,2 kV/mm下逆压电系数高达657 pm/V,1 kV/mm下P_r为9.61μC/cm~2,E_c为0.237 kV/mm。     

Eu_2O_3掺杂量及烧结温度对氧化铝基微波陶瓷性能的影响

选用MgO-CuO-TiO_2-Eu_2O_3添加剂作为氧化铝陶瓷的烧结助剂,在空气气氛下经过常压烧结制备Al_2O_3陶瓷。采用XRD,SEM及EDS等方法研究Eu_2O_3掺杂量以及烧结温度对Al_2O_3基微波陶瓷样品物相组成,微观结构和介电性能的影响。结果表明:添加Eu_2O_3的Al_2O_3陶瓷中,均存在Al2Eu2O9次晶相,且随着Eu_2O_3含量的增加,Al2Eu2O9相增加;随着Eu_2O_3添加量的增加,Al_2O_3陶瓷试样致密度先增加后降低;随着烧结温度的增加,Al_2O_3陶瓷的介电常数和品质因数Q·f值先增加后降低。烧结温度为1450℃,Eu_2O_3添加量为0.25%(质量分数)时,烧结体的相对密度达到最大值98.21%,且Al_2O_3陶瓷的介电性能较好:介电常数为10.05,品质因数Q·f为37984GHz。     

熔盐法制备片状CaBi_4Ti_4O_(15)晶粒的研究

以TiO_2、CaCO_3和Bi_2O_3为原料,加入NaCl和KCl(物质的量比为1:1)为熔盐,采用熔盐法制备Ca-Bi_4 Ti_4 O_(15)片状晶体.研究了熔盐含量、合成温度以及保温时间对制备CaBi_4 Ti_4 O_(15)片状晶体的影响,并对其反应机理进行了初步的探讨.结果表明,当熔盐质量分数为30%时开始生成CaBi_4 Ti_4 O_(15),当熔盐质量分数增加到40%左右时可获得较纯的CaBi_4 Ti_4 O_(15)相.熔盐含量对钛酸铋钙晶体的形貌有一定的影响,随着熔盐含量的增加,CaBi_4 Ti_4 O_(15)片状晶体逐渐长大,各向异性程度增大.合成温度的升高和保温时间的延长有利于CaBi_4 Ti_4 O_(15)片状形貌的形成.制备完整片状形貌的CaBi_4 Ti_4 O_(15)晶体的最佳熔盐含量为40%,合成温度为1150℃,保温时间为4h.     

MgH_2-K_2Ti_6O_(13)-Ni球磨复合体系的微观结构与解氢性能

采用机械球磨法制备了K_2Ti_6O_(13)晶须单独掺杂、以及K_2Ti_6O_(13)晶须与Ni粉复合掺杂的MgH2储氢复合体系,并通过XRD,SEM,DSC等检测手段对其微观结构与解氢性能进行表征。结果表明:当K_2Ti_6O_(13)晶须单独掺杂于MgH2时,K_2Ti_6O_(13)晶须起到助磨细化MgH2晶粒的作用,同时还抑制了MgH2颗粒的团聚,有效降低了MgH2基体的解氢温度,且当K_2Ti_6O_(13)与MgH2质量配比为3∶7时,MgH2解氢性能的改善效果尤为明显,其解氢温度较纯MgH2球磨体系降低了近75℃;此外,当K_2Ti_6O_(13)晶须和Ni粉末复合掺杂于MgH2时,得益于K_2Ti_6O_(13)晶须的助磨细化MgH2晶粒以及Ni固溶于MgH2晶格致使其结构稳定性降低的双重作用,从而使得MgH2基体的解氢温度较K_2Ti_6O_(13)晶须单独掺杂时进一步降低,相对于纯MgH2球磨体系降低了近87℃。     

Al_6Si_2O_(13)晶须和TiC颗粒复合强化多孔Al_2TiO_5基复合材料

以γ-AlOOH和TiO_2为原料,添加不同质量分数SiC晶须(SiCw),采用无压反应烧结法制备多孔(Al_6Si_2O_(13)+TiC)/Al_2TiO_5复合材料,分析了SiCw质量分数对(Al_6Si_2O_(13)+TiC)/Al_2TiO_5复合材料孔隙率和抗压强度的影响,讨论了SiCw的强化机制。结果表明:不添加SiCw时,产物主要为Al_2TiO_5和少量Al_2O_3,还有少量未反应的TiO_2;加入SiCw之后,还形成了Al_6Si_2O_(13)和TiC相,TiC和Al_6Si_2O_(13)分别以规则颗粒状和晶须形态存在于Al_2TiO_5基体中。TiC颗粒与Al_6Si_2O_(13)晶须通过细化显微组织、裂纹偏转和晶须桥连机制,起到协同强化作用。SiCw的添加使孔隙率和抗压强度同时大幅度提高,随着SiCw质量分数的增加,(Al_6Si_2O_(13)+TiC)/Al_2TiO_5复合材料孔隙率降低,抗压强度提高的速率减小,当SiCw的质量分数为7.2%时,抗压强度最高,达到301.81 MPa。     

Effects of High Temperature Oxidation on Mechanical Properties of Ti_3AlC_2

The oxidation tests of Ti_3AlC_2 were conducted at 1100 and 1200?C in air for 48 and 360 h, respectively,and the effects of high temperature oxidation on the flexural strength and hardness of Ti_3AlC_2 were investigated. The microstructure, grain size and phase compositions of Ti_3AlC_2 substrate didn't change after oxidation, hence the oxide removed Ti_3AlC_2 substrate maintained its initial flexural strength and hardness. However, the flexural strength of oxide retained Ti_3AlC_2 decreased by about 5%. Acoustic emission monitoring indicated that during the process of three-point bending test, the formed Al_2O_3 scale on Ti_3AlC_2 surface fractured firstly in a cleavage manner, then the substrate/oxide interface cracked,and finally the Ti_3AlC_2 substrate fractured. The mechanical degradation was caused by the preferential formation of cracks in brittle Al_2O_3 scale as well as at defective and lacunose grain boundaries of the substrate where stress concentration generated. The mechanical degradation was insensitive to oxidation temperature and time in the present conditions. In addition, the surface hardness increased significantly after oxidation due to the formed hard Al_2O_3 scale on the surface of Ti_3AlC_2 substrate.     

高频头用微波介质陶瓷的研究进展

目前,高频头用微波介质陶瓷主要有以下几类:BaTi4O9、Ba2Ti9O20、(Zr,Sn)TiO4、CaTiO3-NdAlO3.详细综述了其研究进展,并对其发展趋势进行了讨论和展望.     

Role of late transition metals on pitting resistance of Zr-Ti-(Cu,Ni,Co)-Al bulk metallic glasses in 0.6 M NaCl aqueous solution

Four quanternary Zr-based bulk metallic glasses(BMGs)were selected,including the Zr_(46)Ti_2Cu_(45)Al_7,Zr_(61)Ti_2Cu_(25)Al_(12),Zr_(55)Ti_4Ni_(22)Al_(19)and Zr_(55)Ti_2Co_(28)Al_(15),due to their robust glass-forming ability and containing a single species of late transition metal(LTM)in compositions.Their pitting resistances in 0.6 M Na Cl aqueous solution were investigated to examine the role of LTM elements in the alloys,with electrochemical measurements,surface morphology observation and x-ray photoelectron spectrometry analysis.It is shown that in comparision with two Cu-bearing BMGs,Zr_(55)Ti_4Ni_(22)Al_(19)and Zr_(55)Ti_2Co_(28)Al_(15)BMGs exhibited significantly superior resistance to pitting.Zr_(61)Ti_2Cu_(25)Al_(12),Zr_(55)Ti_4Ni_(22)Al_(19)and Zr_(55)Ti_2Co_(28)Al_(15)BMGs manifested distinct passivation behaviour,because of the formation of surface passive film mainly comprising of Zr O_2,Ti O_2and Al_2O_3.However,no significant differences in the electrochemical resistive properties and thicknesses of passive films were found between Zr_(61)Ti_2Cu_(25)Al_(12)and Zr_(55)Ti_4Ni_(22)Al_(19)BMGs.Nevertheless,at the passive film/metal interface,copper enrichment took place in Zr_(61)Ti_2Cu_(25)Al_(12),whereas the nickel was slightly deficient at the interface in Zr_(55)Ti_4Ni_(22)Al_(19).During pitting propagation,selective dissolution of the zirconium,titanium and aluminum over the copper took place in Zr_(61)Ti_2Cu_(25)Al_(12),but it was not the case in Zr_(55)Ti_4Ni_(22)Al_(19).For the two Cu-bearing BMGs,reduction of passive base metal elements in composition resulted in local selective dissolution,even absence of the passivation.     

YBa2Cu3O7—x超导材料的水解性质

以 Y_2O_3-BaO-CuO 三元系制备的 YBa_2Cu_3O_(7-x)超导材料对水和水蒸汽很敏感。超导相 YBa_2Cu_3O_((?)-x)与水的作用随温度升高而迅速增强,通常的水解产物为 Ba(OH)_2、Y(OH)_3和 CuO。这种性质起因于晶体结构的不稳定性,因为在这类钙钛矿型的超点阵结构中存在很多氧空位。室温下,YBa_2Cu_3O_(7-x)相与水的作用较弱,而杂质相 Ba_4Y_2O_7和 BaCuO_7等可与水迅速产生反应并释放热量,从而导致 YBa_(?)Cu_3O_(7-x)脱氧、水解。     

聚丙烯/四钛酸钾晶须复合材料研究

以PP-g-GMA为增容剂,利用熔融共混法制备了PP/PP-g-GMA/K_2Ti_4O_9晶须复合材料,借助于SEM、DSC和其他测试手段对复合材料的结构和性能进行了考查.SEM观察发现,K_2Ti_4O_9晶须含量较低时,分散较均匀,与树脂界面结合较好,含量较高时,粒子有团聚现象.力学性能测试结果表明,K_2Ti_4O_9晶须的加入提高了基体树脂的缺口冲击强度,对材料的拉伸强度影响不大.DSC测试结果表明,K_2Ti_4O_9晶须对PP的结晶有异相成核作用,出现双熔融峰和双结晶峰现象,使PP的结晶度提高,同时使PP的结晶温度大幅提高.     

原位自生Al_2O_3-TiC_p/Al基复合材料的热力学分析

采用熔铸法制备了原位自生Al2O3-TiCp/Al基复合材料。借助差示扫描量热仪(DSC)、扫描电子显微镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)等测试技术,对Al-TiO2-C体系的热力学进行了详尽的分析,讨论了过量铝对Al-TiO2-C体系反应的影响。结果表明,通过控制反应温度等工艺参数完全可以获得原位自生Al2O3-TiCp/Al基复合材料,避免副产物Al3Ti和Al4C3的产生。Al-TiO2-C体系原位合成Al2O3-TiCp/Al基复合材料存在着复杂的化学反应。首先在无过量铝的情况下,Al与TiO2发生置换反应,生成了Al2O3和游离态[Ti],而后游离态[Ti]与C结合生成TiC;而存在过量铝的情况下,首先发生铝热反应生成Al3Ti,进而Al3Ti与C结合生成TiC。最终完全获得Al2O3-TiCp/Al复合材料。随着过量Al含量由0增加至70%,Al与TiO2反应生成Al2O3的反应起始温度不断降低。     

First-Principles Study on the Stability and Electronic Properties of Bi-Doped Sr3Ti2O7

The electronic and crystal structural properties of Bi-doped Sr_3Ti_2O_7are studied using the first principles density functional theory(DFT)based on pseudopotentials basis and plane-wave method.Our results show that the formation energy of Bi doping in Site-1 and Site-2 of Sr_3Ti_2O_7increases with increasing doping concentration.And at the same doping concentration,the formation energy of Bi doping in Site-2 is lower than that in Site-1.The undoped Sr_3Ti_2O_7is found to be an insulator and its Fermi level stays at the top of the valence band.While the Fermi level of the Bi-doped Sr_3Ti_2O_7moves into the bottom of conduction band,the system undergoes an insulator-to-metal phase transition.Furthermore,our calculation results demonstrated that the Fermi level of the Bi-doped Sr_3Ti_2O_7goes deeper into the bottom of conduction band with increasing doping concentration.     

HIGH TEMPERATURE MECHANICAL PROPERTIES OF Al_2O_3-SiO_2 SYSTEM REFRACTORIES

对Al_2O_3-SiO_2系高铝区域两个系列烧结材料在不同温度的机械性能(应力—应变关系、强度和蠕变试验等)的研究表明:(1)烧结矾土材料,Al_2O_3含量越接近70%,高温力学性能越好;(2)刚玉-莫来石材料,恰当比例的两晶相材料的高温力学性能优于单晶相材料;在单晶相材料中,莫来石优于刚玉。高铝耐火材料的高温力学行为主要取决于玻璃效应(玻璃基质的数量和粘度)和结晶效应(晶体间接触或结合的程度和方式)。     

氧化锆氧化铝复合材料的显微结构

本文研究了在 ZrO_2量为17～78mol%(15～75vol%)的 ZrO_2/Al_2O_3复合材料中 ZrO_2颗粒的分布、晶型以及 Al_2O_3与嵌在 Al_2O_3晶粒内呈球状的 ZrO_2晶界处所形成的反相畴界,并且研究了在该复合材料中形成裂纹时,裂纹两侧和顶端的 ZrO_2颗粒相变后沿相界形成微裂纹的情况。     

Construction of novel TiO_2/Bi_4Ti_3O_(12)/MoS_2 core/shell nanofibers for enhanced visible light photocatalysis

TiO2/Bi4 Ti3 O12 hybrids have been widely prepared as promising photocatalysts for decomposing organic contaminations.However,the insufficient visible light absorption and low charge separation efficiency lead to their poor photocatalytic activity.Herein,a robust methodology to construct novel TiO2/Bi4 Ti3 O12/MoS2 core/shell structures as visible light photocatalysts is presented.Homogeneous bismuth oxyiodide(BiOI) nanoplates were immobilized on electrospun TiO2 nanofiber surface by successive ionic layer adsorption and reaction(SILAR) method.TiO2/Bi4 Ti3 O12 core/shell nanofibers were conveniently prepared by partial conversion of TiO2 to high crystallized Bi4 Ti3 O12 shells through a solid-state reaction with BiOI nanoplates,which is accompanied with certain transition of TiO2 from anatase to rutile phase.Afterwards,MoS2 nanosheets with several layers thick were uniform decorated on the TiO2/Bi4 TiO3 O12 fiber surface resulting in TiO2/Bi4 Ti3 O12/MoS2 structures.Significant enhancement of visible light absorption and photo-generated charge separation of TiO2/Bi4 Ti3 O12 were achieved by introduction of MoS2.As a result,the optimized TiO2/Bi4 Ti3 O12/MoS2-2 presents 60% improvement for photodegrading RhB after 120 min irradiation under visible light and 3 times higher of apparent reaction rate constant in compared with the TiO2/Bi4 Ti3 O12.This synthetic method can also be used to establish other photocatalysts simply at low cost,therefore,is suitable for practical applications.