ZnO–B2O3掺杂BaAl2Si2O8陶瓷的结构及微波介电性能

采用固相反应法制备BaAl_2Si_2O_8–x%ZnO–B_2O_3(x=0,1,2,3,4,质量分数)陶瓷。探究了不同含量的ZnO–B_2O_3(ZB)烧结助剂对BaAl_2Si_2O_8(BAS)陶瓷的烧结温度、结构及微波介电性能的影响。结果表明:ZB烧结助剂可降低BAS陶瓷的烧结温度。并且能够促进BAS晶体结构由六方相转变为单斜相,当x=1时,六方相BAS全部转变为单斜相BAS,并且ZB烧结助剂添加量在4%以内,无第二相生成。添加1%的ZB烧结助剂可促进样品晶粒长大,密度、介电常数和品质因数增大,谐振频率温度系数的绝对值减小。在x=1,烧结温度为1 350℃时,能够获得品质因数较高的单斜相BAS,其介电性能为:ε_r=6.45,Q×f=40 608 GHz,τf=–22.46×10~(–6) K~(–1)。     

Bi_2O_3-B_2O_3掺杂对BaAl_2Si_2O_8陶瓷结构及微波介电性能的影响

采用固相反应法制备BaAl_2Si_2O_8-x wt%Bi_2O_3-B_2O_3(x=0,1,2,3,4)陶瓷。探究了添加不同量的Bi_2O_3-B_2O_3(BiB)烧结助剂对BaAl_2Si_2O_8(BAS)陶瓷的烧结温度、结构及微波介电性能的影响。结果表明:添加1 wt%的BiB烧结助剂可促进BAS晶体结构由六方相全部转变为单斜相,并且BiB烧结助剂添加量在1～4 wt%范围内,均为单一单斜相。添加3 wt%的Bi B烧结助剂可使BAS陶瓷烧结密度增加到最大值,并能将烧结温度由1400℃降低至1250℃。在x=3,烧结温度为1250℃时,BAS陶瓷的介电常数和品质因数均达到最大值,并且谐振频率温度系数的绝对值也显著减小,其介电性能为:ε_r=6.2,Q·f=21 972 GHz,τ_f=-17.06×10~(-6)℃~(-1)。     

Ba~(1–x)Sr_xAl_2Si_2O_8系陶瓷晶体结构及微波介电性能

采用固相反应法制备Ba~(1–x)Sr_xAl_2Si_2O_8 (x=0,0.050,0.075,0.100,0.150)介质陶瓷。通过热分析、密度、X射线衍射和扫描电子显微镜等研究Sr~(2+)对Ba~(1–x)Sr_xAl_2Si_2O_8陶瓷的晶体结构及微波介电性能的影响。结果表明:Sr~(2+)可以有效促进六方相钡长石转变为单斜相钡长石,且当x≥0.075时,转变率达到100%。在x=0.050时,六方相与单斜相共存,样品密度ρ和介电常数ε_r最小。在0.050≤x≤0.100范围内,随着Sr~(2+)含量的增加,样品密度、介电常数和品质因数Q×f均增大。在0.050≤x≤0.150范围内,随着x值的增大,具有单斜钡长石相样品的谐振频率温度系数向负的方向呈线性发展。Ba_(0.9)Sr_(0.1)Al_2Si_2O_8在1 425℃烧结时微波介电性能最佳:ε_r=5.95,Q×f=26 619 GHz,τ_f=–25.1×10~(–6) K~(–1)。     

MgSn0.05Ti0.95O3-SrTiO3复相陶瓷的显微结构与微波介电性能

采用传统固相法制备了不同摩尔配比的(1-x)MgSn0.05Ti0.95O3-xSrTiO3微波介质复相陶瓷材料,研究了复相陶瓷的烧结特性、显微结构和微波介电性能.结果表明:MgSn0.05Ti0.95O3和SrTiO3两相共存,无固溶现象.随着SrTiO3含量的增多,(1-x) MgSn0.05Ti0.95O3-xSrTiO3的相对介电常数(εr)线性增大,品质因数(Q×f)下降,谐振频率温度系数(τf)从负值变为正值.通过调节x值,可以获得近零的τf值.陶瓷的τf变化符合Lichtenecker混合法则.0.98MgSn0.05Ti0.95O3-0.02SrTiO3复相陶瓷在1330℃烧结4h,获得最佳的微波介电性能:εr=19.32,Q×f=193.527 THz,τf=-2×10-6/℃.     

掺Li2O-B2O3-SiO2玻璃低温烧结MgTiO3-CaTiO3陶瓷及其微波介电性能

研究了Li2O-B2O3-SiO2玻璃(LBS)对MgTiO3-CaTiO3(MCT)介质陶瓷烧结特性、相组成和介电性能的影响,分析了MCT陶瓷与银电极的共烧行为.结果表明:通过液相烧结,LBS能有效降低MCT烧结温度至890℃.X射线衍射结果显示有Li2MgTi3O8、硼钛镁石以及Li2TiSiO5等新相生成.随着LBS添加量的增大,陶瓷致密化温度和饱和体积密度降低,介电常数εr品质因数与谐振频率乘积Q×f也呈现下降趋势,频率温度系数δf向负值方向移动.添加质量分数为20%的LBS的0.97MgTiO3-0.03CaTiO3陶瓷在890℃烧结4h,获得最佳性能:εr=16.4,Q×f=11 640GHz,τf=-1.5×10-6/℃.陶瓷与银电极共烧界面结合状况良好,无明显扩散.该材料可用于制造片式多层微波器件.     

ZnO-B2O3-SiO2玻璃对Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ陶瓷微波介电性能的影响

研究了ZnO-B2O3-SiO2(ZBS)玻璃对陶瓷的烧结性能及微波介电特性的影响.研究表明ZBS的掺入能有效降低Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ陶瓷体系的烧结温度150-200℃,谐振频率温度系数随ZBs掺入量增加及烧结温度的提高,由负值向正值方向移动.在1000℃,掺入质量分数7wt%的ZBN,陶瓷微波介电性能最佳:εr=31.1,Qf=9530GHz,τf=8.9ppm/℃.在960℃烧结4小时,可获得介电性能为:εг=28.6,Qf=6410GHz,τf=-9.8ppm/℃陶瓷样品.     

B2O3掺杂对α-CaSiO3/Al2O3陶瓷低温烧结及微波介电性能的影响

通过传统固相法制备了α-CaSiO3/Al2O3-B2O3微波介质陶瓷,研究了不同B2 O3添加量对α-CaSiO3/Al2O3陶瓷烧结特性、相组成及微波介电性能的影响,通过XRD、SEM和网络分析仪对其相结构、微观形貌和微波介电性能进行了表征.结果表明:B2 O3的添加使陶瓷的烧结温度从1375℃降低到了1100℃,并使主晶相由α-CaSiO3相变为β-CaSiO3相;当B2 O3的添加量为3wt%时,在1100℃烧结2 h可获得最佳微波介电性能:εr=6.21,Q×f=30471 GHz,τf=-34.58 ppm/℃.     

(1-x)Li1.0125MgPO4-xBa3(VO4)2复相陶瓷的制备及其微波介电性能

采用固相烧结法制备(1–x)Li_(1.0125)Mg PO_4–x Ba_3(VO_4)_2复相陶瓷,研究了Ba_3(VO_4)_2掺杂对复相陶瓷相组成、烧结特性、显微组织和微波介电性能的影响。结果表明:(1–x)Li_(1.0125)Mg PO_4–x Ba_3(VO_4)_2陶瓷中仅存在Li_(1.0125)Mg PO_4和Ba_3(VO_4)_2相。Ba_3(VO_4)_2的添加能明显降低Li_(1.0125)MgPO_4陶瓷的烧结温度。随着Ba_3(VO_4)_2含量的增加,复相陶瓷的相对介电常数ε_r逐渐增大,品质因子Q×f逐渐减小,谐振频率温度系数τ_f由负值逐渐变为正值。通过调节x值,可获得近零的τ_f值。0.5Li_(1.0125)MgPO_4–0.5Ba_3(VO_4)_2复相陶瓷经875℃烧结2 h后具有最佳微波介电性能,即ε_r=9.72,Q×f=57 347 GHz,τ_f=-1.9×10~(-6)/℃,是一种极具潜力的低温共烧介质材料。     

TiO_2添加量对Zn_(0.8)Mg_(0.2)ZrNb_2O_8微波介质陶瓷结构和性能的影响

采用传统固相合成工艺制备(1–x)Zn0.8Mg0.2Zr Nb2O8-x TiO_2(ZMZNT,x=0.00,0.20,0.40,0.50,0.60,0.65,0.70,0.80)微波介质陶瓷,研究了TiO_2添加量对Zn0.8Mg0.2Zr Nb2O8陶瓷烧结行为、相结构、微观结构以及微波介电性能的影响。结果表明:随着TiO_2添加量增加,ZMZNT陶瓷的烧结温度逐步下降。当x=0~0.5时,形成了Zn0.8Mg0.2(Zr,Ti)Nb2O8固溶体;而当x=0.6~0.8时,陶瓷体系发生了复杂物相变化,微观形貌也呈现对应的变化规律。随着TiO_2添加量的增加,ZMZNT陶瓷相对介电常数εr逐渐增大,品质因数Q×f呈下降趋势,谐振频率温度系数τf呈上升趋势。当x=0.65时,0.35Zn0.8Mg0.2Zr Nb2O8-0.65 TiO_2陶瓷在1 170℃烧结4 h,可以获得较佳的微波介电性能:εr=36.7,Q×f=37 432 GHz,τf=7.12×10–6/℃。     

Zn2+掺杂SrAl2Si2O8陶瓷的结构及微波介电性能

采用传统固相反应法制备(Sr_(1-x)Zn_x)Al_2Si_2O_8(x=0,0.005,0.010,0.030,0.060)微波介电陶瓷,探讨不同Zn~(2+)取代量对SrAl_2Si_2O_8(SAS)陶瓷晶体结构和微波介电性能的影响。将第一性原理引入到锶长石系微波介电陶瓷分析方法中,以确定取代元素(Zn~(2+))可能占据的位置(Sr~(2+),Al~(3+))。结果表明:Zn~(2+)取代可促进SAS品质因数的提高(Q×f 37 502～48 252 GHz),同时也改善了 SAS陶瓷样品的密度和谐振频率温度系数(τ_f)。当x=0.010、烧结温度为1 500℃时,(Sr_(0.99)Zn_(0.01))Al_2Si_2O_8陶瓷获得最佳的介电性能:ε_r=7.0,Q×f=48252 GHz,τ_f=-36.35×10~(-6)/℃。     

Na2O-Al2O3-Fe2O3系烧结过程中铝、铁的反应行为

以Al2O3, Fe2O3和Na2CO3为原料,对Na2O-Al2O3-Fe2O3系烧结过程中的反应行为进行了详细研究. 基于溶出率与时间、温度的关系,证明Na2O×Al2O3和Na2O×Fe2O3的生成反应动力学都服从Zhuralev-Lesokin-Tempelman模型,表观活化能分别为186.59和80.92 kJ/mol,表明Na2O×Fe2O3比Na2O×Al2O3在动力学上更易形成;Al2O3易与Na2O×Fe2O3反应形成Na2O×Al2O3和Fe2O3,在1273 K烧结30 min,所得熟料Al2O3溶出率达98.51%;Fe2O3对Na2O×Al2O3的形成有双重作用,在1273 K下可加速Na2O×Al2O3的形成,超过1323 K,促使Na2O×Al2O3分解成Na2O和b-Al2O3,且随着温度升高或时间延长,分解程度增高,从而导致熟料中Al2O3溶出率显著降低.     

钕-铝系稀土色料的研制

通过钕-铝系列色料合成实验,分析不同配比及不同矿化剂等对色料呈色效果的影响,确定最佳工艺方法。对实验结果进行XRD及色度分析,确定其主晶相为钕酸铝,试样的明度均在70以上,色彩鲜艳亮丽。     

Phase equilibrium in binary La2O3-Dy2O3 and ternary CeO2-La2O3-Dy2O3 systems

Cerium oxide doped with oxides of rare earth elements is a multifunctional material, a wide range of uses which is associated with its unique physicochemical properties. Phase diagrams of multicomponent systems are the physicochemical basis for the creation of new materials with improved characteristics.In this work, phase equilibria in ternary CeO₂–La₂O₃–Dy₂O₃ and binary La₂O₃–Dy₂O₃ systems in the whole concentration range were studied. No new phases have been identified in these systems. An isothermal section of the phase diagram of the CeO₂–La₂O₃–Dy₂O₃ system at a temperature of 1500 °С is constructed. No new phases have been detected in the system. It was found that in the studied ternary system solid solutions are formed on the basis of (F) modification of CeO₂ with structure of fluorite type, monoclinic (B), cubic (C) and hexagonal (A) modifications of Ln₂O₃.In the La₂O₃–Dy₂O₃ binary system (1500–1100 °С) three types of solid solutions are formed: based on hexagonal modification A-La₂O₃, monoclinic modification B-Dy₂O₃ and cubic modification C-Dy₂O₃ separated by two-phase fields (A+B) and (B+C), respectively. The boundaries of the regions of homogeneity of solid solutions based on A-La₂O₃ are determined by compositions containing 35–40, 20–25, 15–20 mol% Dy₂O₃ at 1500, 1250, 1100 °C, respectively. From the obtained data it follows that the solubility of Dy₂O₃ in the hexagonal modification of lanthanum oxide is 39 mol% at 1500 °C, 23 mol. % at 1250 °C and 16 mol% at 1100 °C. The limits of existence of solid solutions based on monoclinic B-modification are determined by compositions containing 30–35, 65–60 (1250 °С), 35–40, 55–60 (1100 °С) 40–45, 70–75 (1500 °C) mol% Dy₂O₃.In the studied system, with a decrease in temperature from 1500° to 1100°C, there is a decrease in the solubility of La₂O₃ in the crystal lattice of cubic solid solutions of C-type from 16 to 10 mol%.     

Polycrystalline In2O3 and In2O3/Y2O3 photoanodes

Single crystal In₂O₃ shows promise as a photoanode for the decomposition of water. Because of various difficulties in the preparation of the single crystal material, two simple techniques were developed for the preparation of polycrystalline In₂O₃ anodes. One method involves the thermal decomposition of the nitrate while the other utilizes the chemical vapour deposition technique. Voltammograms and photoresponse spectra of these anodes are compared to the single crystal material. Among other observations, it is noted that the quantum efficiencies of the thermally decomposed films are comparable to the single crystal material. It is also shown that the on-set potential can be shifted to more negative values by forming the mixed oxide In₂O₃/Y₂O₃.     

UV-Enhanced Exchange of O2with H2O Adsorbed on TiO2

Ultraviolet light dramatically increases the rate of isotope exchange between gas-phase O₂and water adsorbed on TiO₂at room temperature, but it does not affect the rate of CO₂–water exchange. Both ethanol and acetaldehyde, when coadsorbed with H₂¹⁸O, dramatically decrease the rate of O₂exchange, but not CO₂exchange, with adsorbed H₂¹⁸O. This decrease is attributed to a combination of competition for adsorbed oxygen between exchange and photocatalytic oxidation of the adsorbed organic and blocking of the oxygen adsorption sites by the organic. The same oxygen species participate in O₂-H₂¹⁸O exchange and photocatalytic oxidation.     

Properties of RO-Y2O3-Al2O3-SiO2 glasses

The coefficient of linear expansion, glass-transition temperature, temperature at the orset of deformation (strain point), density. Young modulus, microhardness, crystallizability, and contact angle are studied as a function of the composition in RO–Y₂O₃–Al₂O₃–SiO₂ (R=Ca and/or Mg) glass systems. The composition ranges for glasses (with strain point >900°C and coefficient of linear expansion of (32–45)×10^–7°C^–1) that can be used for soldering silicon-nitride ceramics were established.Translated from Steklo i Keramika, No. 12, pp. 5–7, December, 1996     

Fe2O3-MnO-Cr2O3-La2O3系统紫色颜料的制备及表征

采用溶胶均匀共沉淀法于低温下合成了含少量稀土氧化物La2O3的紫色颜料，并采用颜色测定、SEM、XRD等手段对颜料的颜色、检度及结晶构造等进行了表征。     

TNT的O3/H2O2降解规律

利用自制装置,采用连续投加O3、H2O2的方式,研究了O。／H：O：对废水中TNT的降解规律。结果表明,与Oa作用相比,O3／H2O2工艺可显著提高TNT的降解率,还可避免中间产物的形成与积累;在试验研究条件下,H2O2：O3的最优摩尔比为1,最佳初始pH值在11左右,利用缓冲溶液可维持反应体系pH值的稳定,但不利于O3／H2O2功效的发挥,反应适合在常温下进行,尽量避开40℃左右;动力学特征分析表明,O／H2O2降解TNT偏离伪一级反应动力学规律。