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。

Synthesis of Y_2O_3 Nano-Powder from Yttrium Oxalate under Ambient Temperature

High purity Y_2O_3 nano-powders was synthesized directly from solution ofindustrial YCl_3 by method of oxalate precipitation through super-micro-reactors made by complexnon-ionic surfactant. The purity and diameter of Y_2O_3 particles were controlled by such processingparameters as concentration of YCl_3 and oxalic acid and complex non-ionic surfactant etc. TEMphotomicrographs show that Y_2O_3 particles are spherical in shape, with an average diameter of lessthan 30 nm. Test results certify that the purity and particle diameter as well as the dispersion ofY_2O_3 nano-powder depend on the concentrations of YCl_3, oxalic acid and complex non-ionicsurfactant. The optimum ranges of the concentrations for YCl_3 and complex non-ionic surfactant whenthe diameter of Y_2O_3 particles is smaller than 100 nm are 0.43 ～1.4 mol ? L^(-1) and0.031～0.112 mol·L^(-1) respectively, while the mass fraction range of oxalic acid is 10% ～18% .The purity of Y_2O_3 nano-powder tested by ICP-AES analysis is 99.99% .

Site Selective Spectroscopy of Surfactant-Assembled Y_2O_3∶Eu Nanotubes

Y_2O_3∶Eu nanotubes were synthesized by a surfactant assembly mechanism. Under ultraviolet-light excitation, the nanotubes present luminescence properties different from that of Y_2O_3∶Eu nanoparticles. The peak position of the charge transfer band in excitation spectra varies with the monitoring emission peaks, while the emission spectra are dependent on the excitation wavelength. Laser selective spectroscopy was performed to distinguish the local symmetries of the Eu^(3+) ions in the nanotubes. The results of laser-selective excitation indicate that the emission centers near the surface of nanotube walls exhibit inhomogeneously broadened spectra without spectral structures while the two sites (site B and site C) inside the nanotube walls present resolved spectral structures. It is concluded by the number and peak positions of the spectral lines that the sites B and C possess different site symmetries.

Agglomeration Control of Ultrafine Y_2O_3-ZrO_2 and (MgO, Y_2O_3)-ZrO_2 Powders Synthesized by Coprecipitation Process

Chemical coprecipitation was used to produce ultrafine and easily sinterable Y2O3-stabilized and （Y2O3,MgO）-stabilized ZrO2 powders. Six precipitation processes for preparation of ZrO2-based ultrafine powders were designed separately, meanwhile different techniques used to control the agglomeration formation were proposed. By means of TEM, SEM, Raman spectroscopy and IR spectroscopy, the mechanisms of agglomeration control in the precipitation processes and post-precipitation and drying process were investigated. The experimental results show that adding appropriate anion surface active agents （such as PAA1460） or polymer （PEG1540 matching with PEG200） in aqueous solution systems during precipitation processes could reinforce charge effect and location effect for gel particles interface. Adding wetting agents to wet gels washing with distilled water during drying process could change interface structure of gel particles and decrease surface tension between gel particles. The agglomeration control in the precipitation, post-precipitation and drying processes had remarkable influence on the characteristics of powders. By adding various macromolecules in the processes, the agglomeration state could be controlled efficiently, and the characteristics of powders were improved.

Investigation of Y_2O_3 Particle Doped on Superalloy by Laser Irradiation

Possibility to dope Y_2O_3 particles into the sur- face of superalloy sample by means of laser irradiation and the relationship between homogeneity and laser irradiation parameters have been investigated.The results show that homoge- neous distribution of Y_2O_3 particles in melt-doped region can be obtained on a macro scale and the content of Y_2O_3 in the region can reach 2 wt-% when precoating powder quantity is 0.05g/cm^2, laser power density is selected as 1.76× 10~4W/cm^2 and scanning speed 0.36m/min.

Mechanical Properties of Al_2O_3/Cr_3C_2/(W,Ti)C Ceramic Composites with Y_2O_3 Addition

Ceramic composites Al_2O_3/(W, Ti)C/Cr_3C_2 with different contents of Cr_3C_2 and (W, Ti)C particles, and with the additive Y_2O_3, were fabricated with hot-pressing technique at 1700 ℃ under 28 MPa pressure for 30 min in N_2 atmosphere. The mechanical properties were tested, and the microstructure was investigated by environment scanning electron microscope (ESEM), transmission electron microscope (TEM), energy dispersive analysis using X-ray (EDAX) and optical microscope (OM). Results indicate that the incorporation of Cr_3C_2 and (W,Ti)C particles can suppress the grain growth of the others, and the toughening and strengthening effects mainly originate from nano-particles, dispersion toughening and solidification strengthening. The multiphase composite ceramic material Al_2O_3/10%Cr_3C_2/20%(W,Ti)C shows good mechanical properties, especially the fracture toughness increases from 4.0 MPa·m 1/2 (Monolithic Al_2O_3 ceramic) to 8.92 MPa·m 1/2, the flexural strength from 260～340 MPa (Monolithic Al_2O_3 ceramic) to 496 MPa, due to incorporation of the suitable contents of Cr_3C_2 and (W,Ti)C particles.

Effect of Y_2O_3 and Total Oxide Addition on Mechanical Properties of Pressureless Sintered β-SiC

The effect of Y203 and the total oxide volume fraction (Y203+AI203) on density and mechanical properties of low temperature (1770-1940℃) pressureless sintered β-SiC ceramics were presented. The optimum temperature for pressureless sintering of β-SiC was found to be -1850℃ and the optimum content of Y203 in the oxides was found to be between 40 and 57 wt pct. The highest sintered density was achieved by adding oxides at 14 vol. pct. Both of the highest strength and fracture toughness were achieved at -14 vol. pct oxide addition and yttria concentrations between 40 and 57 wt pct in the oxides. Hardness, on the other hand, was found to be the highest for samples with 14 vol. pct oxide addition and -64 wt pct Y2O3 in oxides.

Influence of Y_2O_3 on the Oxidation Behaviour of a β-NiAl Coating

A new-type of β-NiAl coating containing Y_2O_3 particles was obtained by electrolytic co-deposition and pack aluminizing techniques,and the influences of the nature of Y_2O_3 and its content on the oxidation behaviour of the coating at 1100℃ were studied.The test results indicate that the oxidation rates of the composite coatings are reduced and the scale adhesion is also improved remarkably.The content of Y_2O_3 has little influence on the oxidation rates of the composite coatings,but does obviously on the scale adhesion by modifying the configura- tion of the oxides at the scale-coating interface.The needle-like oxides penetrating into the coating show an obvious keying effect.A part of the dispersed Y_2O_3 in the as-deposited coating accumulates and forms a Y_2O_3-rich layer at the coating-substrate interface immediately after aluminizing.The layer is beneficial to reduce the degradation of the composite coating.

Microstructure of Nano-Y_2O_3/Cobalt Based Alloy Composite Coating by Laser Cladding

Composite coatings made of nano-Y_2O_3/cobalt-based alloy and produced by crosscurrent CO_2 laser on Ni-based superalloy are introduced. Cross-section or surface of the coatings was examined to reveal their microstructure using optical microscope, SEM, including EDS microanalysis, TEM and XRD. The results show that some equilibrium or non-equilibrium phases, such as γ-Co, Cr_(23)C_6, Y_2O_3 and ε-Co exist in the coatings. Fine and short dendritic microstructure and columnar to equiaxed transition (CET) occurred by adding nano-Y_2O_3 particles. With the increasing amount of nano-Y_2O_3 (1%, mass fraction), fully equiaxed crystallization appeared. These are caused by nano-Y_2O_3 particles acting as new nucleation site and rapid solidification of the melt. The results also show that inhomogeneous dispersion of nano-Y_2O_3 results in the formation of ε-Co phase in the coatings. The sub-microstructure of the clad is stacking fault. The mechanism of the formation of equiaxed grains is also analyzed.

High Temperature Protection Ability of Oxide Scale Formed on Fe_3Al Enhanced by Surface-applied Y_2O_3 Thin Film

The Y_2O_3 thin film was applied on Fe-3Al intermetallic compound by electrodeposition and thermal decomposition. The cyclic oxidation of the Fe-3Al specimens with and without surfaceapplied Y_2O_3 thin film was carried out at 900 ℃ in air. The results show that the selective oxidation of Al in Fe-3Al was promoted, and both of the plasticity and the adhesion of the oxide scale formed on Fe3Al were improved and the high temperature oxidation resistance of Fe3Al was enhanced markedly.

Influence of Adding Y_2O_3 on the Structure of the Cu-Containing Cermet

The enriching of metals to the center of sample was found and investigated during the sinter process of the cermet.The enrichment is caused by addition with Y_2O_3.The enriching of copper is greatly in- fluenced by sinter temperature and time.The enriching of metal can significantly enhance the electrical con- ductivity of the cermet.

Manufacture Process of 8Y_2O_3 Stabilized ZrO_2 from Nano Powders

The manufacture process of 8mol% Y-2O-3 stabilized ZrO-2(YSZ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increases lineally with the forming press,and the sintering linear shrinkage of YSZ to the forming press compiles to the parabola trend. When the forming press exceeding 500MPa, the samples with lower shrinkage and high density were obtained. The sintering temperature of YSZ decreases greatly because of the small size and high active surface of YSZ powders. As a result, the beginning sintering temperature of YSZ made in the experiment is as low as 825℃, and the end sintering temperature is 1300-1350℃. The relative density of YSZ ceramic by solid sintering at 1300-1350℃ is more than 97%, with little and small pores in the uniform microstructure.

Influence of Y_2O_3 Adding Method on Microstructure and Properties of Al_2O_3 Strengthened Y-TZP

The effects of Y_2O_3 adding methods (i.e.,co-precipitated and mixed) on the microstructure and properties of alumina-strengthened ytrria-stabilized tetragonal zirconia polycrystal (ASZ) were investigated. CYASZ and MYASZ were made by different adding method of Y_2O_3,co-precipitated and mixed,respectively. The results show that CYASZ is of uniform microstructure with fine grain size,however,MYASZ is of inhomogeneous microstructure due to the inhomogeneous distribution of ytrria. Comparing with CYASZ,the density and the strength of MYASZ are decreased,but the toughness is changed only a little. Under sliding wear test,the wear resistance of CYASZ is better than that of MYASZ.

Determination of CeO_2 , Dy_2O_3, CuO and PbO in Yttrium Oxide Reference Material by Isotope Dilution Spark Source Mass Spectrometry

This paper describes the quantitative determination of rare-earth elements cerium, dysprosium and non-rare-earth element copper, lead and the homogeneity examination of these four elements in yttrium oxide reference material by isotope dilution spark source mass spectrometry (ID-SSMS). The sensitivity of the meth- od is l0^(-5)～10^(-7%). The precision is better than 6%. The accuracy is better than 5%. The interferences of the spectra and the optimum amount of the spike added to the sample are discussed. The choice of the conducting material for the sample electrodes is studied.

Determination of Trace Amount of Vanadium in High Purity Y_2O_3 by Electrothermal Vaporization－ICP－AES With Bi（PDC）_3 Coprecipitation

A new method for the determination of vanadium in high purity Y2O3 by fluorination assisted electrothermal vaporization-ICP-AES is presented in this paper. After the sample dissolved,the vanadium in the sample solution was coprecipitated with Bi(PDC)_3 at pH 3. 7. The precipitates were made into a slurry with the fluorinating agent PTFE and directly introduced into the graphite furnace for determination. The analytical results were obtained by aqueous calibration curve method. The detection limit of the method is 1. 1 ng/mL, the RSD is 2. 8% (n=10,1 5 ng/mL vanadium solution), and the recovery of vanadium added to real sample is more than 96%.

Corrosion resistance of plasma sprayed NiCrAl+(ZrO_2+Y_2O_3) thermal barrier coating on 18-8 steel surface

The corrosion resistance of NiCrAl+（ZrO2+Y2O3）thermal barrier coating, formed with the plasma spraying technique, on the 18[CD*2]8 steel surface was investigated. The phase structure and morphology of the coating were analyzed by means of X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The electrochemical corrosion behavior of the coating in 1.0mol/L H2SO4 solution was studied by using electrochemical measurement methods. The results show that the gradient plasma spraying coating is composed of the NiCrAlY primer coating and the （ZrO2+Y2O3 ） top coating, and the coating thickness is 360μm. The microhardness of coating reaches 1100HV. The corrosion resistance of the plasma sprayed coating of the 18[CD*2]8 steel surface is about 5 times as great as that of the original pattern. The corrosion resistance of the coating is enhanced notably.

THE EFFECT OF SUBZERO TREATMENT ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Y_2O_3-ZrO_2 CERAMIC

The effect of subzero treatment on the microstructure and mechanical properites of Y_2O_3- ZrO_2 ceramic have been investigated by TEM,X-ray diffraction and test of mechanical properties.It was shown that the microstructre of 3Y-PSZ after subzero treatment by liquid nitrogen exhibits very long and parallel laths of m-phase and some microcracks around the larger and finer lath of m-phase may be discovered.Suitable subzero treatment can improve the strength and toughness of Y-PSZ efficiently because of decreasing the stability of t-phase and incresing the amount of t-m transformation when exerting a stress.However,when the time of subzero treatment exceeds,the over aging effect may arise.which can decrease the strength and toughness of the material.

A new sol-gel process for preparing Ba(Mg_(1/3)Nb_(2/3))O_3 nanopowders

Commercially available niobium (V) oxide [Nb_2O_5], with barium acetate[Ba(CH_3COO)_2] and magnesium acetate [Mg(CH_3COO)_2·4H_2O] was used as the starting material inthe sol-gel process for preparing Ba(Mg_(1/3)Nb_(2/3))O_3 (BMN) nanopowders. At first, Nb_2O_5reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassysubstance after cooling was dispersed and washed several times in distilled water to remove the Na^+ions. The as-prepared colloidal Nb_2O_5·nH_2O was subsequently mixed with acetic solution ofbarium acetate and magnesium acetate according to the required molar proportions and followed bygelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃ for 1h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwaveQ-factor, of 10397 at 1,45GHz.

Li_(2)O/Na_(2)O对YAS微晶玻璃结构、析晶与力学性能的影响

透明微晶玻璃由于优异的力学性能被广泛应用于电子领域。本文采用熔融法制备了不同质量分数Li_(2)O和Na_(2)O的Y_(2)O_(3)-Al_(2)O_(3)-SiO_(2)(YAS)微晶玻璃,通过Raman、DSC、XRD、FESEM、UV-VIS-NIR等测试方法研究了其结构特征、析晶与力学性能。结果表明:当碱金属氧化物R_(2)O(R=Li,Na)总量保持不变,随着Li_(2)O取代Na_(2)O含量的增加,YAS微晶玻璃的转变温度、软化温度和结晶峰温度逐渐降低,Q^(4)基团对应的含量逐渐减少,说明Li_(2)O作为网络外体使YAS微晶玻璃结构逐步解聚,玻璃的析晶能力逐渐增强。在同一热处理制度下,随着Li_(2)O取代量的增加,YAS微晶玻璃维氏硬度显著提升,而透过率明显下降。在680℃/10 h+750℃/1 h热处理制度下,可以制备出晶体大小一致且分布均匀的以钇稳定氧化锆为主晶相的透明YAS微晶玻璃,此时2%(质量分数,下同)Na_(2)O+4%Li_(2)O YAS微晶玻璃具有良好的综合性能,如维氏硬度为646 HV,断裂韧性为1.07 MPa·m^(1/2),透过率为85.7%,在诸多领域具有巨大的应用潜力。

时效处理对Cu-Y_(2)O_(3)-Ti复合材料组织及性能的影响

以Cu、Y、Ti和CuO粉末为原料,采用机械合金化(MA)和热还原的方法制备了Cu-Y_(2)O_(3)-Ti复合粉末。然后经放电等离子烧结(SPS)技术制备了Cu-Y_(2)O_(3)-Ti复合材料,并对材料进行了900℃固溶1 h和不同温度时效2 h的处理。采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)、能谱仪(EDS)、拉伸试验和导电率测量仪等研究了不同温度时效处理对Cu-Y_(2)O_(3)-Ti复合材料组织及性能的影响。结果表明:随着时效温度的升高,Cu-Y_(2)O_(3)-Ti复合材料的晶粒和第二相尺寸增大,导电率降低,最大应变和抗拉强度先增大后减小。Cu-Y_(2)O_(3)-Ti复合材料经900℃固溶1 h+400℃时效2 h后,综合性能最优,其具有良好塑性的同时,抗拉强度和导电率分别达到326.4 MPa和73.0%IACS。