Laser scattering,transmittance and low thermal expansion behaviors in Y_(2-x)(ZnLi)_xMo_3O_(12) by forming regular grains

Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y_2Mo_3O_(12) ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y_2Mo_3O_(12) could form regular grains, reduce cracking and porosity.With increasing the content of ZnLi, the grain shapes self-assembly gradually and then the laser scattering and transmittance improve.The laser scattering property and transmittance of diverging rays become the best in ceramics Y_(2-x)(ZnLi)_xMo_3O_(12)(x = 1.0 and 1.2) with regular grains and low thermal expansion.The formation mechanism of regular grains is ascribed to the substitutions of Zn~(2+)and Li+for Y~(3+) in Y_2Mo_3O_(12) resulting in the preferential growth.The investigation in laser scattering, transmittance and low thermal expansion behaviors of Y_(2-x)(ZnLi)_xMo_3O_(12) could pave a way to weaken the strong-laser attack from the high-power laser weapon and the other.     

Low thermal expansion and broad band photoluminescence of Zr0.1Al1.9Mo2.9V0.1O12

A new material of Zr0.1Al1.9Mo2.9V0.1O12 is synthesized by the traditional solid state synthesis method.The phase transition,coefficient of thermal expansion,and luminescence properties of Zr0.1Al1.9Mo2.9V0.1O12 are explored with Raman spectrometer,dilatometer,and x-ray diffraction(XRD)diffractometer.The results show that the Zr0.1Al1.9Mo2.9V0.1O12 possesses the strong broad-band luminescence characteristics almost in the whole visible region.The sample is crystallized in a monoclinic structure group of P21/a(No.14)crystallized at room temperature(RT).The crystal is changed from monoclinic to orthorhombic structure when the temperature increases to 463 K.The material has very low thermal expansion performance in a wide temperature range.Its excellent low thermal expansion and strong pale green light properties in a wide temperature range suggest its potential applications in light-emitting diode(LED)and other optoelectronic devices.     

Fe2-xYxMo3O12系列材料的相变及负膨胀性研究

本文对Fe2-xYx(MoO4)3(x=0.0,0.2,0.4,0.5,0.6,0.8,1.0,1.2,1.4,1.6,1.8,2.0)系列材料的相变及负膨胀性能进行了研究.通过对Fe2-xYx( MoO4)3系列材料的XRD和拉曼谱的分析发现,当x≤0.4时Fe2-xYxMo3O12在常温下是单斜结构;当x≥0.5时...     

Thermal expansion properties of Lu2-xFexMo3O12

The structures and thermal expansion properties of Lu2-xFexMo3O12 have been investigated by X-ray diffraction(XRD).XRD patterns at room temperature indicate that compounds Lu2-xFexMo3O12 with x≤1.3 exhibit an orthorhombic structure with space group Pnca;compounds with x=1.5 and 1.7 have a monoclinic structure with space group P21/a.Studies on thermal expansion properties show that the linear thermal expansion coefficients of orthorhombic phase vary from negative to positive with increasing Fe content.Attempts to make zero thermal expansion materials indicate that zero thermal expansion can be observed in Lu1.3Fe0.7Mo3O12 in the temperature range of 200-400℃.     

Near-zero thermal expansion of In_(2(1-x))(HfMg)_xMo_3O_(12) with tailored phase transition

Solid solutions of In_(2(1-x)(HfMg)_xMo_3O_(12) are synthesized by solid state reaction with the aim to reduce the phase transition temperature of In_2Mo_3O_(12) and improve its thermal expansion property.The effects of(HfMg)~(6+) incorporation on the phase transition and thermal expansion are investigated.It is shown that the monoclinic-to-orthorhombic phase transition temperature obviously decreases and the coefficient of thermal expansion(CTE) of the orthorhombic becomes less negative and approaches to zero with increasing the content of(HfMg)~(6+).A near zero thermal expansion covering the case at room temperature(RT) is achieved for the solid solutions with x ≥ 0.85,implying potential applications of this material in many fields.     

Sc2－xGaxW3O12体系负热膨胀性能研究

通过固相反应法,在1100 ℃下成功制备出了系列Ga掺杂Sc_2-xGa_xW₃O₁₂（x=0, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8）固溶体.X射线粉末衍射结构精修表明,Ga以替代Sc的形式成功进入Sc_2-xGa_xW₃O₁₂晶格,但不能获得端元组分Ga₂W₃关键词： 负热膨胀 热膨胀系数 Rietveld结构精修     

硅基板和铜基板垂直结构GaN基LED变温变电流发光性能的研究

本文将硅(Si)衬底上外延生长的氮化镓(GaN)基发光二极管(LED)薄膜剥离转移到新的硅基板和紫铜基板上,并获得了垂直结构的LED芯片,对其变温变电流电致发光(EL)特性进行了研究. 结果表明:当环境温度不变时,在13 K低温状态下铜基板芯片的EL波长始终大于硅基板芯片约6 nm,在300 K 状态下随着驱动电流的加大铜基板芯片的EL波长会由大于硅基板芯片3 nm左右而逐渐变为与硅基板芯片重合;当驱动电流不变时,环境温度由13 K升高到320 K,两种基板芯片的EL波长随温度升高呈现S形变化并且波谱逐渐趋于重合;在100 K以下温度时铜基板芯片的Droop效应比硅基板芯片明显,在100 K 以上温度时硅基板芯片的Droop效应比铜基板芯片明显. 可能是由于两种芯片的基板具有不同的热膨胀系数和热导率导致了其变温变电流的EL特性不同. 关键词： GaN 热膨胀系数 内量子效率 热导率     

Al-Cu-Ge合金的热物理性质与快速凝固规律研究

Al-Cu-Ge合金是典型的三元共晶体系,在工业上有重要的应用价值,对其进行研究有助于了解该合金的热物理性质和提高该合金的结构性能.本文选择了Al55Cu10Ge35,Al70Cu10Ge20和Al80Cu10Ge10三种成分合金作为研究对象,对合金的固态比热和热膨胀系数进行了测量,并对比分析了合金在近平衡凝固和落管快速凝固条件下的组织特征和凝固路径.研究发现,合金比热随Al含量的增大和Ge含量的减少而增大.这三种成分合金的软化温度均为666 K,物理热膨胀系数α在370—650 K温度范围内基本一致,约为1.5×10-5K-1.近平衡凝固条件下合金凝固过程中最后一步反应生成的均为(Al)+(Ge)二相共晶而不是三元共晶,这表明(Al)、(Ge)和CuAl2相在这三种成分的Al-Cu-Ge合金中难以同时形核并协同生长.然而,在快速凝固条件下,初生相的形核和生成受到抑制,合金中更易于形成二相共晶和三元共晶组织.     

Zero and controllable thermal expansion in HfMgMo_(3-x)W_xO_(12)

HfMgMo_(3-x)W_xO_(12) with x = 0.5, 1.0, 1.5, 2.0, and 2.5 are developed with a simple solid state method. With increasing the content of W, solid solutions of Hf Mg Mo3-xWx O12 crystallize in an orthorhombic structure for x≤2.0 and a monoclinic structure for x2.0. A near-zero thermal expansion(ZTE) is realized for HfMgMo_(2.5)W_(0.5)O_(12) and negative coefficients of thermal expansion(NCTE) are achieved for other compositions with different values. The ZTE and variation of NCTE are attributed to the difference in electronegativity between W and Mo and incorporation of a different amount of W, which cause variable distortion of the octahedra and softening of the MoO_4 tetrahedra, and hence an enhanced NCTE in the a- and c-axis and reduced CTE in the b-axis as revealed by Raman spectroscopy and x-ray diffraction.     

The phase transition,hygroscopicity, and thermal expansion properties of Yb_2-xAl_xMo₃O₁₂

Materials with the formula Yb 2-xAlxMo3O12(x =0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8) were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffrac- tion, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3O12 solid solutions crystallize in a single monoclinic phase for 1.7 ≤ x ≤ 2.0 and in a single orthorhombic phase for 0.0 ≤ x ≤ 0.4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhombic phase transition temperature of Al2Mo3O12 can be reduced by partial substitution of Al 3+ by Yb3+, and the Yb2-x AlxMo3O12 (0.0 < x ≤ 2.0) materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of Al3+ for Yb3+ in Yb2Mo3O12 decreases its hygroscopicity, and the linear thermal expansion co- efficients after complete removal of water species are measured to be 9.1×10 6 /K, 5.5×10 6 /K, 5.74×10 6 /K, and 9.5 × 10 6 /K for Yb1.8 Al0.2 (MoO4)3 , Yb1.6Al0.4 (MoO4 )3, Yb0.4 Al1.6 (MoO4)3 , and Yb 0.2Al1.8 (MoO4)3 , respectively.     

氧化物纳米材料Y2O3:(Yb3+,Er3+)上转换发光性质的研究

以Y2O3,Yb2O3,Er2O3为原料,利用燃烧法分别制备了Y2O3:Er3 和Y2O3:(Yb3 ,Er3 )两种纳米材料和相应的体材料Y2O3:(Yb3 ,Er3 ).用发射波长为978 nm的半导体激光器和日立F-4500荧光分析仪测量了它们的上转换发光,得到纳米材料Y2O3:Er3 的上转换发光主要为绿色上转换发射而纳米材料Y2O3:(Yb3 ,Er3 )主要为红色上转换发射,而后者与激活离子掺杂浓度相同的体材料Y2O3:(Yb3 ,Er3 )的上转换发射相比较,体材料以绿色上转换发射为主、红色上转换发射很弱.     

K7[P2Mo4W13M(H2O)O61]及其有机复合材料的合成及光谱研究

用降解法制得了Dawson结构铬、铁取代的磷钼钨酸钾,并将其与溴化(E)-N-丁基-4-(2-(4-二甲氨基苯基)乙烯基)吡啶反应制备了有机复合材料.通过元素分析和TG-DTA确定了配合物的组成分别为K7[P2Mo4W13M(H2O)O61](M=Cr(1),Fe(2))和(C19H25N2)6K3[P2Mo4W13MO62](M=Cr(3),Fe(4)).利用红外光谱、紫外-可见光谱、固体漫反射紫外-可见-近红外光谱、X射线光电子能谱以及荧光光谱对上述化合物进行了表征,并研究了复合材料中无机与有机组分间的相互作用及其荧光性质.     

聚(2-甲氧基-5-辛氧基)对苯乙炔/Y_2O_3:Eu~(3+)纳米复合材料的光致电子转移效应

采用原位脱氯化氢缩合聚合法制备了聚(2-甲氧基-5-辛氧基)对苯乙炔/Y_2O_3:E~(3+)(PMOCOPV/Y_2 O_3:Eu~(3+))纳米复合材料。红外光谱证实了在Y_2O_3:Eu~(3+)表面的包覆层为PMOCOPV。紫外-可见吸收光谱表明与PMOCOPV相比,PMOCOPV/Y_2O_3:Eu~(3+)的最大吸收峰发生红移且强度提高。荧光光谱研究表明PMOCOPV/Y_2O_3:Eu~(3+)的最大发射波长发生红移且强度提高,荧光寿命得到增强,Y_2O_3:Eu~(3+)与PMOCOPV之间形成了光致电子转移体系,使得π电子离域程度增加,并且导致荧光量子效率提高。根据E_g与入射光子能量hv的关系,拟合了PMOCOPV/Y_2O_3:Eu~(3+)薄膜的光学禁带宽度,发现E_g减小。采用简并四波混频方法测试它们的三阶非线性极化率x~((3)),结果发现与PMOCOPV相比,PMOCOPV/Y_2O_3:Eu~(3+)纳米复合体的非线性光学响应逐渐增强,进一步说明PMOCOPV与Y_2O_3:Eu~(3+)之间形成了分子间光致电子转移体系,产生了复杂的分子间离域π电子非线性运动。     

Thermal expansion property of anomalous magnetic alloy Fe70Al30

D0₃-type Fe₇₀Al₃₀ shows a transition from ferromagnetism to spin glass with anomalous slow spin dynamics below 170 K. Furthermore, it shows a structural transition from D0₃ to body-centered cubic (BCC) at 823 K. In this article, the relationship between the magnetic properties, thermal expansion coefficient (TEC), and crystal structure transition of D0₃-type Fe₇₀Al₃₀ is discussed. Below 170 K, TEC decreases with temperature, accompanied by a decrease in the Fe moments. In the ferromagnetic state between 170 K and the Curie temperature (T_C), TEC increases gradually with temperature. Above T_C, TEC increases rapidly. These temperature variations of TEC could be connected to the high-spin/low-spin transition and thermal spin fluctuations. During transition from D0₃ to disordered BCC at 823 K, TEC shows discontinuous behavior, similar to a first-order transformation. With further increase in temperature, TEC becomes constant. This implies that the phase transition from D0₃ to disordered BCC is accompanied by a change in spin fluctuation.     

室温下金属中电子格林艾森常数的测量

在室温条件下用自己研制的超快电子衍射实验设备精确测量了金属铝的电子格林艾森常数(γ_e).当飞秒脉冲激光瞬间加热铝膜时,电子和晶格对固体热膨胀的作用在时间域上是不同步的,借助于超快电子衍射实验设备的高时间分辨能力,可以摆脱以往测量非磁性金属材料时低温的限制,在室温条件下,实验通过直接观测瞬间加热的铝膜中电子和晶格对热膨胀的不同贡献得到电子的格林艾森常数. 关键词： 格林艾森常数 超快电子衍射 晶格热运动 电子热运动     

Effects of W~(6+) occupying Sc~(3+) on the structure,vibration, and thermal expansion properties of scandium tungstate

We experimentally investigate effects of W~(6+)occupying the sites of Sc~(3+)in the unit cell of Sc_2 W_3 O_(12)(Sc_8 W_(12) O_(48))on the structure, vibration and thermal expansion. The composition and structure of the doped sample(Sc_6 W_2)W_(12) O_(48±δ)(with two W~(6+)occupying two sites of Sc~(3+)in the unit cell of Sc_8 W_(12) O_(48)) are analyzed and identified by combining the x-ray photoelectron spectroscopy and the synchronous x-ray diffraction with first-principles calculations based on density functional theory. Results show that the crystal with even W~(6+)occupying even Sc~(3+)in the unit cell is stable and maintains the orthorhombic structure at room temperature. The structure of the doped sample is similar to that of Sc_2 W_3 O_(12), and with even W occupying even positions of Sc in the unit cell and constituting the WO_6 octahedra. Raman analyses show that the doped sample possesses stronger W–O bonds and wider Raman linewidths than those of Sc_2 W_3 O_(12). The sample doped with W also exhibits intrinsic negative thermal expansion in the measured range of 150 K–650 K.     

掺钇二氧化锆薄膜制备及其特性测量

采用电子束蒸发法在室温下制备出掺钇二氧化锆薄膜.借助紫外分光光度计、原子力显微镜(AFM)、X射线衍射(XRD)方法研究了薄膜的透射率、表面结构.同时研究了不同退火温度下对薄膜光学性质的影响.研究的结果表明:退火温度的增加,使得二氧化锆薄膜的漏电流增大,从而导致其热稳定性变差.不同浓度三氧化二钇的掺杂对其透射率影响很小.     

偶氮染料掺杂的聚甲基丙烯酸甲酯薄膜的热光性质研究

本文演示了用阿贝折射仪测定染料掺杂聚合物薄膜热光系数的方法;通过改变掺杂体含量的方法,方便地实现了聚合物体系的折射率控制;通过热光系数的测量,计算了聚合物薄膜的热膨胀系数,并用以解释了聚合物薄膜的热光系数随掺杂体含量增加先增大后减小的实验观察.     

Y0.5Gd0.5Ba2Cu3O7-δ体系中通氧时间对超导转变温度的影响

研究了高温氧化物超导体Y0.5Gd0.5Ba2Cu3O7-δ体系中通氧时间对超导转变温度及超导转变温区的影响。Y0.5Gd0.5Ba2Cu3O7-δ样品是按相等摩尔数的Gd与Y元素配比,采用传统的固相反应法烧结而成的多晶块材。实验结果显示:Y0.5Gd0.5Ba2Cu3O7-δ烧结样品与YBa2Cu3O7-δ烧结样品均具有很好的单相性,在一定的通氧条件下其超导临界转变温度TC与超导初始转变温度TCO值相对YBa2Cu3O7-δ烧结样品有提高。文中对此结果进行了讨论。     

Influences of Carbon Nanotube Networking on the Conductive,Crystallization, and Thermal Expansion Behaviors of PA610-Based Nanocomposites

The electrical, crystallization and thermal expansion behaviors of polyamide 610 (PA610)/multi-walled carbon nanotube (CNT) nanocomposites prepared by melt mixing were investigated. Electron microscopy (Scanning Electron Microscopy and Transmission Electron Microscopy) revealed that a good dispersion of CNT and CNT network was obtained in the PA610 matrix. Addition of CNT to PA610 matrix led to polymer nanocomposites exhibiting higher electrical conductivity and lower thermal expansion. The network of CNT in the PA610 matrix, which can be tuned by the loading of CNT and the melt isothermal treatment, was found to play an important role in reducing thermal expansion and achieving higher conductivity. Furthermore, it was shown that significant reduction in thermal expansion in PA610/CNT nanocomposites was due to both thermally insensitive CNT and formation of CNT network.