【作者】 朱振峰；

【导师】 马建中；

【作者基本信息】 陕西科技大学 ， 材料学， 2007， 博士

【摘要】 随着科学技术的发展,陶瓷颜料的种类与制备工艺有了新的突破,Ce1-xPrxO2是红色陶瓷颜料的新品种,与传统的红色颜料相比,其具有耐高温、低毒性、呈色范围广的特点,是有毒红色陶瓷颜料的良好替代产品。低温燃烧合成(Low-Temperature Combustion Synthesis,简称LCS)、水热合成(Hydrothermal Synthesis)、微乳液合成(Microemulsion Synthesis)及化学共沉淀合成(Chemical Co-precipitation Synthesis)等技术是陶瓷颜料合成的新工艺。利用这些新工艺所合成的Ce1-xPrxO2红色陶瓷颜料具有纳米晶微粒。此项技术为陶瓷制品计算机非接触式装饰(喷墨打印装饰)的核心材料即纳米陶瓷颜料的制备提供了理论依据。本研究以Ce(NO3)3·6H2O和Pr6O11为主要原料,加入燃烧剂,采用LCS技术,在250°C左右点火反应,制备出了Ce1-xPrxO2纳米晶红色颜料粉体。研究了燃烧反应中燃烧剂的种类、燃烧剂与反应物的配比、Pr的掺杂量、Pr的引入形式、矿化剂等对产物的晶体结构、形貌及呈色性能的影响;并对燃烧合成的样品进行了后续热处理及水热处理,研究了后处理工艺及其对粉体结构与性能的影响。同时,采用反相微乳液法和共沉淀-水热合成法制备了Ce1-xPrxO2纳米晶粉体,并研究了后续热处理温度对其结构与性能的影响。采用DSC,XRD,SEM,TEM,XPS,EDS,激光Raman光谱,CIE色度仪等现代测试方法对样品中Ce和Pr的价态及Ce1-xPrxO2的呈色机理进行了研究,并进一步探讨了水热条件下Ce1-xPrxO2粉体的晶粒生长机理。研究结果表明:对于CO(NH2)2、(COOH)2·2H2O、CH3COONH4、C6H8O7、C6H12O6、CH3COOC2H5以及NH4NO3等多种燃烧剂来说,适用于LCS合成Ce1-xPrxO2纳米晶红色颜料粉体的燃烧剂为CH3COONH4和C6H8O7;对柠檬酸(C6H8O7)和乙酸铵(CH3COONH4)而言,CH3COONH4作为燃烧剂所制备的燃烧产物的结晶程度更完善、Pr离子更容易进入CeO2晶格、呈色更好。在CH3COONH4作为燃烧剂的燃烧反应中,燃烧剂与氧化剂的配比以2:1为宜;在C6H8O7作为燃烧剂的燃烧反应中,燃烧剂与氧化剂的配比以3:1为宜。采用两种燃烧剂制备的燃烧产物颗粒尺寸都在200nm~300nm之间。通过改变Pr的掺杂量,用LCS技术合成出了一系列从粉红到红色直至棕红的Ce1-xPrxO2(x=0~0.5)纳米晶粉体。在一定范围内(x<0.3),随着Pr掺杂量的增加,该粉体的晶粒尺寸逐渐减小;当0.3<x<0.5时,Pr掺杂量对晶粒尺寸影响已经不明显。随着x的增加,红度值(a*)先增加,在x=0.05时呈现极大值,随后a*值随x的增加而减小;当0.35<x<0.50时,a*值基本不变化,说明在此范围Pr掺杂量对a*值影响已经不明显。本研究所制备的粉体的晶粒尺寸在9nm~41nm之间变化。Pr的掺杂量对点火温度影响不明显,影响点火温度的主要因素是燃烧反应中氧化剂的分解温度。以Pr6O11和Pr(NO3)4两种形式引入Pr,结果显示:用Pr(NO3)4引入Pr所制得的粉体的晶粒发育更完善、呈色性能更好,Pr离子进入固溶体的量更接近于实际掺杂量。用Na2CO3、CaF2、NaF、H3BO3、LiF、NaClO3作为矿化剂,研究不同矿化剂对Ce1-xPrxO2纳米晶粉体呈色性能的影响。结果发现:加入矿化剂后粉体的a*值有较大的增加,即颜色有较大的改善。在加入的6种矿化剂中使a*值提高的顺序为: NaClO3>LiF> H3BO3>NaF>CaF2>Na2CO3,所以NaClO3是较为合适的矿化剂。对LCS合成出的Ce1-xPrxO2纳米晶粉体进行后续热处理,结果发现:在1200°C保温时间为2h,样品的a*值可提高到26.95。对LCS合成的Ce1-xPrxO2样品进行水热处理,结果发现水热处理后样品的结晶程度以及呈色性能都有明显的改善。在碱性条件下,填充比为60%时,延长水热处理时间,粉体晶粒的均匀性增加,团聚现象减少。由于水热处理后样品的晶粒发育更好、粒度分布更加均匀,因而大大提高了粉体的呈色性能。对采用OP-乳化剂/水/环己烷/正戊醇反相微乳液体系制备的Ce1-xPrxO2纳米晶粉体进行后续热处理,结果表明:后续热处理温度对晶体结构和颗粒的形貌几乎没有影响,但对粉体的颜色和颗粒尺寸影响较大。随着温度的升高,a*值明显提高、颗粒的团聚加强且颗粒尺寸增大,而且随着温度的增加,Pr离子在固溶体中的含量也同时增加,更接近于实际添加量。以Ce(NO3)3·6H2O和Pr(NO3)4为原料,对Ce1-xPrxO2纳米晶粉体的共沉淀-水热合成进行了系统的研究,结果表明:样品的平均晶粒尺寸为12nm,平均颗粒尺寸为18nm,颜色呈现淡红色,具有片状方形形貌,且分散性能良好。随着水热反应温度的升高,Pr在CeO2晶格中的溶解度增大,但均只有部分Pr固溶。随水热时间的延长,样品的a*值呈现先增加后减小的趋势。水热体系中的Ce离子和Pr离子是动态的溶解-沉淀过程,其离子浓度随温度、时间及pH值的变化而变化。在本实验条件下,pH在9~10之间,水热反应时间为20h时粉体的颜色较好。对水热制备的样品在800°C煅烧2h,样品的呈色性能明显提高,呈现红褐色,同时晶体的发育更加完善,呈现多面体形貌。对Ce1-xPrxO2样品中Ce和Pr的价态及Ce1-xPrxO2红色颜料的呈色机理的研究表明:在本实验条件下,所有样品均形成单一的萤石型固溶体结构,且晶粒尺寸在41nm范围以内。随着Pr含量的增加,固溶体的氧空位浓度也随之增大。固溶体中Ce的价态为+4价,Pr的价态为+3价;样品的红度(a*)、色饱和度(C*)随Pr含量的增加呈现先增加后减小趋势;当x=0.05时,样品有较好的呈色性能。这是因为当Pr离子掺杂时,Pr3+置换了CeO2晶体中的Ce4+,形成固溶体;同时产生了氧离子空位,使晶格发生畸变,自由电子陷落在氧离子空位上而形成缺陷,即形成氧离子空位的F-色心缺陷。缺陷的存在导致粉体吸收波长小于600nm左右的可见光,从而呈现出红色色调。对Ce1-xPrxO2纳米晶粉体的水热合成机理的研究结果表明:Ce1-xPrxO2晶粒生长机理为:随温度升高,分散在液相中的颗粒在毛细管力作用下堆积更紧密,较小的颗粒在颗粒接触点处溶解,通过液相传质,在较大的颗粒或颗粒的自由表面上沉积而使晶体长大,即是一个“溶解-沉淀”的过程。结晶质点从溶液扩散到晶体表面做横向移动,形成一个吸附层,吸附层上产生二维晶核,从液相中扩散来的质点沉积在二维晶核提供的台阶的边缘形成层状结构。晶体进一步长大时产生新的二维晶核,同时产生刃型位错,位错处存在永久的台阶,台阶将缠绕位错线长大,所以晶体长大可以连续不断的进行。更多还原

【Abstract】 With the development of the modern science and technology, many progresses have been made on the preparation technology and new kind of ceramic pigments. Compared with the traditional red pigments, Ce1-xPrxO2 nano-crystallite red ceramic pigment has higher temperature resistance, lower toxicity and wider coloration range. It is a good candidate for the replacement of traditional toxic pigments. Low-temperature combustion synthesis (LCS), hydrothermal method and microemulsion process are all new technologies for powder preparation. The new technology provides new processing for the preparation of nano-crystallites pigments for the key materials of ink-jet printers controlled by computer.Ce1-xPrxO2 nano-crystallites red pigments were prepared by low-temperature combustion synthesis at the ignited temperature of about 250°C with a later hydrothermal treatment, using Ce(NO3)3·6H2O and Pr6O11 as raw materials. The influence of fuel categories, the mole ratio of fuel/cerium nitric, the content and the state of doped Pr ions and the mineralizer categories on the the crystallites structure and properties of prepared pigments were investigated. The later hydrothermal treatment and the heat process of the prepared powders were also studied.The Ce1-xPrxO2 nano-size ceramic pigments powders were also prepared by a W/O microemulsion system and a co-precipitation-hydrothermal method using Ce(NO3)3·6H2O, Pr6O11 as raw materials and ammonia as the precipitation agent. The influence of the annealing conditions on the preparation of Ce1-xPrxO2 powders was also investigated.DSC, XRD, SEM, TEM, XPS, Laser Raman spectra and CIE color measurements were used to analyze the valence of praseodymium and cerium in Ce1-xPrxO2 crystal structure. The mechanism of the color and the grain growth of Ce1-xPrxO2 red pigments were also discussed.The results show, for many fuels, such as CO(NH2)2, (COOH)2·2H2O, CH3COONH4, C6H8O7, C6H12O6, CH3COOC2H5 and NH4NO3 et al, CH3COONH4 and C6H8O7 are suitable for the preparation of Ce1-xPrxO2 nano-size red pigments by LCS process. Compared with citric acid, the as-prepared powders have better crystallites and color performance by using acetic ammonium as fuel; and the more Pr ions entered into CeO2 crystal lattice. The optimal mole ratio of fuel/cerium nitric is 2/1 with acetic ammonium as fuel and 3/1 with citric acid as fuel by LCS process. The particle size of the resulted powders is about 200nm ~ 300nm.The LCS resulted Ce1-xPrxO2 (x=0~0.5) nano-crystallite powders have the color range from pink to red-brown, with diffrent doping amount of Pr ions. In a certain area (x<0.3), the crystallite size of the powders decreasees with the increases of the content of Pr, when x is in the range of 0.3~0.5, the content of Pr has not notable effect on the crystallite size. The parameter a* increase firstly with the increase of x and reaches maximum when x=0.05; and then decrease when x is in the range of 0.3~0.5. This infers that the content of Pr has not notable effect on parameter a* in this range. In the research condition, the crystallites size of powders are in the range of 9~41nm. The content of Pr has little effect on ignited temperature; but decomposition temperature of oxidant in the combustion reaction has important influence on ignited temperature.Pr ions were doped in CeO2 crystal latice for the preparation of Ce1-xPrxO2 crystallites by using Pr6O11 and Pr(NO3)4 respectively. Results show that the crystallites of sample prepared from Pr(NO3)4 grow up more perfectly; and the chromatic performance is greatly improved. Content of Pr ions doped in solid solution is close to doping amount of the experiment. Na2CO3, CaF2, NaF, H3BO3, LiF and NaClO3 were used as mineralizer respectively. The influence of these mineralizers on the structure and performance of the Ce1-xPrxO2 nano-crystallites was investigated. It is found that the value a*of the powders is notablely improved by using mineralizers. The red value improvment of these six mineralizers conform to the order of NaClO3>LiF> H3BO3>NaF>CaF2>Na2CO3. Therefore, NaClO3 is the best one for preparation of Ce1-xPrxO2.A later heat treatment and a later hydrothermal process of Ce1-xPrxO2 nano-crystallite powders prepared by LCS were done. Result show that, the parameter a* is up to 26.95 by the treatment of the powders at 1200oC for 2 hours. The crystallization and the color performance of the samples after hydrothermal treatment are improved obviously. The particle distributions of the powders are more uniform at alkaline condition with filling ratio is 60%. Keeping a long hydrothermal treatment time is useful for the uniformity of the crystallites, which avoids the particle aggregation and improves the color performance of samples.A W/O microemulsion system composed of OP-emolsifier / water / cyclohexane / 1-Pentanol was adopted to prepare ultrafine Ce1-xPrxO2 powders. The influence of the annealing conditions on the preparation of Ce1-xPrxO2 powders was investigated. The results show that preparation temperature has not notable effect on the crystal structure and morphology of the as-prepared powders; but has an effect on the size of the particles. With the increase of temperature, the particles aggregation becomes stronger and the particle size increases. A fluorite structure of Ce1-xPrxO2 was found when the temperature is above 600°C. With the increase of temperature, content of Pr ions doped in solid solution is close to the doping amount.Ce1-xPrxO2 nano-size powders were prepared by a co-precipitation-hydrothermal method using Ce(NO3)3·6H2O, Pr6O11 as raw materials and ammonia as the precipitation agent. Results show that the average crystallite size of Ce1-xPrxO2 powders is 12 nm; the average particle size is 18 nm. The powders exhibit light-red color and quadrate morphologies and no particle aggregation is exhibited. With the increase of hydrothermal treatment temperature, the solubility of praseodymium in the crystal lattice of CeO2 increases; but not all of praseodymium is dissolved into the crystal lattice of CeO2. With the increase of hydrothermal treatment time, the red value of Ce1-xPrxO2 powders firstly increase and then decrease. The growth process of Ce1-xPrxO2 powder is a dynamic dissolution-deposition process of cerium and praseodymium ions. In research condition, with the increase of hydrothermal treatment temperature, the solubility of praseodymium in the crystal lattice of CeO2 is more close to the doping content. The optimal condition of the hydrothermal time is 20 hours which the solution pH of 9~10. After calcining at 800oC for 4 hours, the color of the Ce1-xPrxO2 powders change from light red to red brown; and the powders show faceted polyhedral morphologies with improved crystallization. The valences of Ce and Pr and chromatic mechanism of the Ce1-xPrxO2 red pigments were investigated. The results show that all samples have a fluorite structure monophse in our research, and the crystallite size is smaller than 41 nm. With the increase of Pr content, the concentration of oxygen vacancies increase. There are trivalent Pr and tetravalent Ce in Ce1-xPrxO2 crystal lattice. The red value a* and the color saturation value C* is firstly increase and then decrease with the increase of the content of Pr. The chromatic performance of Ce1-xPrxO2 red pigments samples reache optimum while x is 0.05. The substitution of Ce4+ by Pr3+ will form oxygen vacancies, which cause the distortions and the defections of CeO2 crystal lattice. Therefore, the pigments can absorb the light with wavelength of less then approximate 600nm and present the red tonality.The mechanism of hydrothermal synthesis of Ce1-xPrxO2 powders was investigated. The results show that the growth process of Ce1-xPrxO2 Crystallites is a dissolution-deposition process of cerium and praseodymium ions. Crystallites particles make an orientation movement from solution to the surface of crystallites, resulting in the formations of planar crystallites nucleuses in the boundary layer. Molecules will diffuse from the solution to the nucleus surface and deposit at the edge of the step offered by the planar crystallite,forming a layer structure. The continue growth of crystallites will need new planar crystallite nucleus, which is provided by the edge distortions appeared at the never-disappeared steps. The steps will grow along the edge distortion, resulting in the growth of continuous crystallites.更多还原