煅烧工艺对氧化锌铝(AZO)粉体光学性能的影响

采用聚丙烯酰胺凝胶法制备高浓度Al掺杂ZnO(AZO)前驱体(x(Al)=5.5mol%、6.5mol%), 研究煅烧工艺对AZO粉体光学性能的影响. 结果表明: 随着煅烧温度升高, Al在ZnO中的固溶度降低。当煅烧温度为750℃时, 生成ZnAl₂O₄相。提高煅烧温度, 粉体的紫外吸收峰从366 nm红移至373 nm; 延长煅烧时间, 紫外吸收峰发生蓝移, 吸收强度明显增大。室温下AZO粉体光致发光(PL)光谱主要由354 nm的紫外发射峰、406 nm的近边紫外发射峰和430 nm的蓝光发射峰组成。     

Sol-gel法制备Pb(Zr0.53Ti0.47)O3铁电薄膜

利用Sol-gel工艺在Pt/Ti/SiO2/Si衬底上制备了Pb(Zr0.53Ti0.47)O3(PZT)薄膜,研究了退火温度、保温时间和薄膜厚度对其晶相、微观结构和铁电性能的影响.在500℃退火处理的PZT薄膜开始形成钙钛矿相;在550℃退火处理的PZT薄膜基本形成钙钛矿相结构;升高退火温度(500～850℃)、延长保温时间(30～150min)、增加薄膜厚度(120～630nm)都有利于PZT晶粒的长大.在650～750℃退火的PZT薄膜具有较好的铁电性能,保温时间对PZT薄膜的铁电性能影响不大,PZT薄膜的厚度为200～300nm时可以得到比较好的铁电性能.在退火温度750℃、保温时间30min条件下退火处理厚310nm的PZT薄膜,其剩余极化值(2Pr)和矫顽电场(2Ec)分别是72μC/cm2、158kV/cm.     

纳米TiO2粉体的制备及其表征

采用溶胶-凝胶技术制备了纳米TiO2粉体,并对其热性能、相结构、颗粒大小和分布进行了表征,结果表明,TiO2干凝胶粉经300℃煅烧后已有锐钛矿相出现,经550℃煅烧后有金红石相出现,完全相转变的温度约为600℃,纳米TiO2粉体的颗粒尺寸随煅烧温度的升高而增大,采用溶胶,凝胶技术制备的干凝胶粉经400℃煅烧后可获得团聚轻、颗粒大小分布比较均匀、颗粒尺寸约为15nm的球状TiO2粉体,     

致密PZT95/5铁电陶瓷低温相结构与电性能研究

采用固相法制备了致密PZT95/5铁电陶瓷, 研究了低温下致密PZT95/5铁电陶瓷相结构和电性能的变化规律。变温X射线衍射(XRD)研究表明, 低温(-60℃)下极化和未极化致密PZT95/5铁电陶瓷相结构保持不变。电性能研究表明随着温度从30℃下降至-60℃, 致密PZT95/5铁电陶瓷的相对介电常数从278显著下降至173, 而电阻率和剩余极化强度基本保持不变。结合冲击波载荷下动态放电模拟分析, 发现相对介电常数的降低将引起动态电场增大至常温下的1.5倍, 这可能是导致致密PZT95/5铁电陶瓷低温下击穿概率显著增大的关键因素。     

溶胶-凝胶法合成CaCu3Ti4O12粉体及IR和Raman谱研究

以金属醇盐和无机盐为原料，用溶胶-凝胶法合成了CaCu3Ti4O12干凝胶，进一步将干凝胶磨粉后在不同的温度煅烧不同的时间，得到相应的粉体样品．X射线衍射结果显示，75O℃煅烧2h后的样品呈明显的CaCu3Ti4O12（CCTO）类钙钛矿晶相，表明样品经历非晶相向类钙钛矿晶相转化过程．红外和拉曼谱分析进一步证实了X射线衍射结果．热分析研究结果也表明，在不到300℃，有机物燃烧完毕，随着温度的继续升高，到750℃样品开始向类钙钛矿相转化，直到1000℃完全生成了类钙钛矿晶相，经750、850、1000℃煅烧的样品其Raman光谱大致相同。     

低温固相反应法合成片状六铝酸镧

以九水合硝酸铝、六水合硝酸镧为原料,柠檬酸为络合剂,采用低温固相反应法制备出六铝酸镧前驱体,再通过煅烧的方式合成了六铝酸镧粉体。利用FTIR和TG-DSC分析了前驱体的组成和热分解过程,采用XRD、SEM和TEM分析了合成粉体的物相组成和形貌。结果表明:经1 300℃煅烧后,六铝酸镧开始形成;随着煅烧温度的升高,六铝酸镧晶体形貌逐渐发育成规则的六方片状;经1 500℃煅烧后可获得纯相的六铝酸镧粉体;在1 600℃时合成的六铝酸镧粉体粒径呈双峰分布,平均粒径为7.25μm。     

高能球磨Al-Y2O3粉体固相反应制备YAG陶瓷的研究

用高纯Al粉体和Y₂O₃粉体(Al-Y₂O₃粉体)为原料采用固相反应法制备了YAG陶瓷. Al-Y₂O₃粉体高能经过球磨, 煅烧生成YAG粉体, 再真空烧结制备高致密YAG陶瓷. 采用DTA-TG对球磨Al-Y₂O₃粉体进行分析, 采用XRD、SEM对球磨的Al-Y₂O₃粉体、YAG粉体及YAG陶瓷进行了表征. 实验表明: Al-Y₂O₃粉体在～569℃时, Al粉强烈氧化, 并与Y₂O₃粉反应, 600℃煅烧出现YAM相, 随煅烧温度升高出现YAP相, 1200℃煅烧生成YAG粉体. 成型YAG素坯在1750℃保温2h真空烧结出YAG相陶瓷, YAG陶瓷相对密度可达98.6%, 晶粒生长均匀, 晶粒尺寸为810μm.     

溶胶-凝胶法制备Sr_2SiO_4∶Dy~(3+)荧光粉及其发光性能研究

采用溶胶-凝胶法在不同的煅烧温度下制备了Sr_2SiO_4∶Dy~(3+)荧光粉,并采用热重、X射线衍射、扫描电子显微镜和荧光光谱系统研究了其结构与发光性能。在不同煅烧温度下,粉体中均存在正交α′-Sr_2SiO_4和单斜β-Sr_2SiO_4相,并且随着温度的升高,粉体的形貌由颗粒状逐渐转变为纤维状。Sr_2SiO_4∶Dy~(3+)荧光粉在391nm激发下,发射481nm、496nm的双峰蓝光和583nm的黄光,黄蓝比(Y/B)为0.827,黄光与蓝光发射强度相近。不同温度下的发射峰强度与相应的相组成和表面形貌有关,800℃煅烧得到的粉体具有最高的发光强度。     

湿声化学法制备PZT（52／48）压电陶瓷粉体

将湿化学法中的sol-gel技术与声化学中的超声雾化技术相结合,提出一种新的陶瓷粉体合成方法-湿声化学法,并制备了PZT(52/48)粉体.结果表明,用湿声化学法制备PZT(52/48)粉体,在400℃开始形成PZT钙钛矿相,比其它制备方法的温度(500-900℃)低,在700℃保温2h即可得到具有纯PZT结构相的粉体.用湿声化学法制备的粉体颗粒呈圆形,粒径小于1μm.湿声化学法使用不溶性盐ZrO2而不是Sol-gel方法中必须使用的可溶性盐,从而降低了成本.     

锆钛酸铅95/5纳米粉体Sol-Gel法制备与改进

以醋酸铅、硝酸锆、钛酸丁酯为原料,改进溶胶-凝胶法,制备得到锆钛酸铅95/5纳米粉体.改进溶胶-凝胶法省去溶胶加水、凝胶干燥、干凝胶研磨等步骤,采用加热蒸馏溶胶制备凝胶,蒸馏回收溶剂并干燥凝胶,凝胶分段加热处理等方法,简化了加工工艺,大大缩短了合成周期,降低了成本.XRD和TEM分析表明,用改进sol-gel法制备得到的PZT粉体煅烧温度低、晶粒细小、均匀,直径约10nm.     

Fe86Zr5.5 Nb5.5 B3非晶合金的超高压烧结成型

为了获得致密的块状Fe86Zr55Nb55B3纳米晶合金,研究了高压快速烧结工艺参数对样品致密度和α-Fe相晶粒尺寸的影响.结果表明:快淬球磨破碎非晶粉末在5.5 GPa/3min烧结条件下,当Pw=1150 W后,可获得相对密度为98.3%、单相α-Fe纳米晶(16.3 nm)块体合金,且随着Pw和t的增加,样品相对密度和α-Fe相晶粒尺寸均略有增加,样品典型的比饱和磁化强度σs和矫顽力Hc分别为119.6 emu/g,63.8 Oe.     

Thermodynamic properties of Pt5La,Pt5Ce,Pt5Pr,Pt5Tb and Pt5 Tm intermetallics

The Gibbs’ energies of formation of Pt₅La, Pt₅Ce, Pt₅Pr, Pt₅Tb and Pt₅ Tm intermetallic compounds have been determined in the temperature range 870–1100 K using the solid state cell: $$Ta,M + MF_3 /CaF_2 /Pt_5 M + Pt + MF_3 ,Ta$$ . The reversible emf of the cell is directly related to the Gibbs’ energy of formation of the Pt₅M compound. The results can be summarized by the equations: $$\begin{gathered} \Delta G_f^ \circ \left\langle {Pt_5 La} \right\rangle = - 373,150 + 6 \cdot 60 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Ce} \right\rangle = - 367,070 + 5 \cdot 79 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Pr} \right\rangle = - 370,540 + 4 \cdot 69 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Tb} \right\rangle = - 372,280 + 4 \cdot 11 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Tm} \right\rangle = - 368,230 + 4 \cdot 89 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \end{gathered} $$ relative to the low temperature allotropic form of the lanthanide element and solid platinum as standard states The enthalpies of formation of all the Pt₅M intermetallic compounds obtained in this study are in good agreement with Miedema’s model. The experimental values are more negative than those calculated using the model. The variation of the thermodynamic properties of Pt₅M compounds with atomic number of the lanthanide element is discussed in relation to valence state and molar volume.     

GAMS5

The construction of the double-crystal γ-spectrometer GAMS5 was finished recently and the instrument is now operational. Measurements with double flat crystals were carried out and we will report here on the progress concerning the characteristics of the spectrometer.     

Synthesis of tritium-labeled 5-fluorouracil and 5-fluorocytosine

The effect of various catalysts and temperature on the solid-phase isotope exchange of 5-fluorouracil and 5-fluorocytosine with tritium was studied. The isotope exchange yielding the desired compounds is accompanied by dehalogenation and hydrogenation of the 5,6-double bond of the pyrimidine ring. Performing the reaction at a temperature below 160°C allowed the process to be carried out selectively, i.e., with the preservation of the functional groups and double bond in the starting compound. The yields of various products formed in the reactions of tritium with the above compounds were estimated. Synthesis conditions were found, and tritium-labeled 5-fluorouracil and 5-fluorocytosine were prepared with the molar radioactivity of 0.45 Ci mmol⁻¹ (16.7 TBq mol⁻¹) and 4.4 Ci mmol⁻¹ (0.16 PBq mol⁻¹), respectively, and with the purity exceeding 98%.     

Thermoluminescence solid-state nanodosimetry--the peak 5A/5 dosemeter

The shape of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100) following (90)Sr/(90)Y beta irradiation, previously demonstrated to be dependent on the cooling rate used in the 400°C pre-irradiation anneal, is shown to be dependent on ionisation density in both naturally cooled and slow-cooled samples. Following heavy-charged particle high-ionisation density (HID) irradiation, the temperature of composite peak 5 decreases by ～5°C and the peak becomes broader. This behaviour is attributed to an increase in the relative intensity of peak 5a (a low-temperature satellite of peak 5). The relative intensity of peak 5a is estimated using a computerised glow curve deconvolution code based on first-order kinetics. The analysis uses kinetic parameters for peaks 4 and 5 determined from ancillary measurements resulting in nearly 'single-glow peak' curves for both the peaks. In the slow-cooled samples, owing to the increased relative intensity of peak 5a compared with the naturally cooled samples, the precision of the measurement of the 5a/5 intensity ratio is found to be ～15% (1 SD) compared with ～25% for the naturally cooled samples. The ratio of peak 5a/5 in the slow-cooled samples is found to increase systematically and gradually through a variety of radiation fields from a minimum value of 0.13±0.02 for (90)Sr/(90)Y low-ionisation density irradiations to a maximum value of ～0.8 for 20 MeV Cu and I ion HID irradiations. Irradiation by low-energy electrons of energy 0.1-1.5 keV results in values between 1.27 and 0.95, respectively. The increasing values of the ratio of peak 5a/5 with increasing ionisation density demonstrate the viability of the concept of the peak 5a/5 nanodosemeter and its potential in the measurement of average ionisation density in a 'nanoscopic' mass containing the trapping centre/luminescent centre spatially correlated molecule giving rise to composite peak 5.     

Characterization of coprecipitated ferroelectric Bi2 VO5·5

Fine powders of orthorhombic bismuth vanadate (Bi₂ VO_5·5) have been synthesized by coprecipitation method. Powder X-ray diffraction and electron microscopic techniques have been used to characterize these samples. The formation of the monophasic Bi₂ VO_5·5 was confirmed. The compacted powders sintered at 1070K have been characterized for their dielectric properties as a function of both temperature (300–900 K) and frequency (100 Hz–10 MHz) and found to be superior to those obtained by the conventional solid-state reaction route.     

DFT方法对LaNi5及LaNi5H0.5晶体结构的预测

根据密度泛函理论,以扩展平面波函数为基集,采用超软赝势技术,对LaNi5 储氢合金及其吸氢后的晶胞模型进行了优化,从理论上给出了其结构参数及性质。计算结果表明该方法能较好地符合 LaNi5 及其氢化物结构的实验值,为该类合金的结构预测提供了一个理论估算途径。此外,根据模型的结构参数分析了LaNi5 中不同间隙位的吸氢稳定性,解释了影响间隙位稳定性的因素。     

Fe_(72.5)Cu_1Nb_(1.5)Mo_(1.5)V_1Si_(13.5)B_9合金的磁性和晶化过程

本文研究了Ｆｅ７２．５Ｃｕ１Ｎｂ１．５Ｍｏ１．５Ｖ１Ｓｉ１３．５Ｂ９合金在不同热处理温度下磁性能的变化及其晶化过程。在ＦｅＣｕＮｂＳｉＢ合金中用Ｍｏ,Ｖ部分替代Ｎｂ仍能获得软磁性能良好的纳米微晶。其最合适的热处理退火条件为５３５℃,保温１小时。与用机械合金法合成纳米晶相比较,佐证了非晶晶化法形成纳米微晶,其优异的磁性能是由于微晶中同时存在晶粒和晶界两种磁相,晶粒与晶界之间有交换相互作用。     

Evolution of the structure of Ti-5Al-5Mo-5V alloy deformed by high pressure

Specific features of straining of the Ti-5Al-5Mo-5V (VT22) alloy deformed by high pressure (cold and hot screw extrusion) are studied depending on its phase composition by the methods of X-ray diffraction analysis, optical microscopy, and electron microscopy. It is shown that the application of high pressure and complex schemes of deformation in combination with the action of temperature enables one to attain high levels of strains in the material without fracture. Under these conditions, new structures (containing nanosized particles responsible for the new properties) are formed. The mechanisms of deformation on the mesolevel are specified. It is shown that, in the process of cold hydroextrusion, the alloy in the one-phase β-state is deformed according to the mechanism of rotation via the formation of strain-induced martensite, whereas the alloy in the two-phase state is deformed according to the mechanism of bending. It is also shown that the mechanisms of deformation strongly depend on the initial phase composition of the alloy. The procedure of hot screw extrusion is characterized by the action of several mechanisms of deformation. Knowing these mechanisms, it is possible to choose the required modes of treatment and obtain structures guaranteeing the optimal combination of strength and plasticity. __________ Translated From Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 3, Pp. 57–64, May–June, 2006.