共查询到20条相似文献,搜索用时 156 毫秒
1.
利用多重射流氢氧焰燃烧反应器,通过控制进料方式,以TiCl4和SiCl4为原料合成了具有典型核壳结构的纳米TiO2/SiO2复合颗粒,并分析了氢氧焰燃烧合成过程中核壳结构的形成机理.在纳米TiO2/SiO2复合颗粒中,无定形的SiO2均匀地包覆在晶态TiO2颗粒表面形成核壳结构,引入SiO2不但有效抑制TiO2晶粒的生长,而且抑制了锐钛相向金红石相的转变.在TiCl4和SiCl4次序进料时,TiCl4优先反应并通过成核生长生成TiO2纳米颗粒,SiCl4反应生成的SiO2通过在TiO2颗粒表面非均相成核生长,形成核壳结构的纳米复合颗粒. 相似文献
2.
3.
4.
纳米TiO2粉体的制备及其表征 总被引:5,自引:2,他引:5
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, 相似文献
5.
二氧化钛复合纳米晶耐温性能的研究 总被引:2,自引:0,他引:2
以Al2O3为异质相,采用液相共沉淀法制备了系列TiO2纳米复合晶,考察了反应方式、反应产物脱水方式、以及异质相复合量对耐温性能的影响。同时,对其光吸收特性及结构形态进行了表征和研究。结果表明:TiO2纳米晶经异质复合后,耐温性能得到显著改善,表现为:900℃完全是锐钛矿结构,950~1050℃为良好的混晶结构;950℃晶粒呈球形,分散均匀,无团聚现象,粒径20~30nm,UV—vis吸收特性优于700℃纳米TiO2混晶。无定形Al2O3的表面均匀包覆和键和约束机制,抑制了纳米TiO2的晶型转化和颗粒生长。 相似文献
6.
7.
8.
从液相制备陶瓷超细粉料的原理和方法 总被引:1,自引:0,他引:1
液相法合成陶瓷粉科有利于成分的精确控制和均匀混合,可制备颗粒微小、尺寸均一的粉料。但是从液相中制粉容易引起因粉料团聚而使粉料丧失超细粉料的优点。本文分析了固相颗粒在液相中的生长过程,讨论了均一尺才颗粒的生长条件,论述了液相法合成陶瓷粉科中形成团聚的3个过程,以及各种控制团聚的工艺方法和避免团聚的工艺措施。 相似文献
9.
以四氯化钛和六水三氯化铝为原料,采用电化学方法制备了TiO2/Al2O3复合粉体。以XRD对粉体进行表征发现,以电解TiCl4和AlCl3的混合溶液得到的粉体中,氧化铝主要分布在颗粒的表面。分别电解TiCl4与AlCl3的水溶液,待成胶后再混合而得到的粉体中,两种成分布比较均匀。对复合粉体进行高温处理,在500℃可以得到R—TiO2/γ-Al2O3的复合粉体,而在95O℃可以得到R—TiO2/Oα-Al2O3的复合粉体,在1200℃可以得到Al2TiO5复合陶瓷粉。 相似文献
10.
以120目四川三台膨润土为载体,TiCl4为钛源,通过水解法制备了TiO2/蒙脱石复合材料,样品分别在500℃恒温1h、2h、3h和4h,以及在不同温度(300、500℃和700℃)下煅烧1h。利用X射线衍射(XRD)表征了其结构,紫外可见分光光度法(UV-Vis)表征了其光催化性能。通过光降解甲基橙(MO)得到最佳的煅烧温度和恒温时间,并用光催化效果最好的样品和试剂级TiO2作了比较,最后在理论上阐明了通过TiCl4水解法制备的复合材料的光催化性能不如TiO2的原因是TiO2的颗粒过小。 相似文献
11.
12.
以硅烷偶联剂KH-560对纳米TiO2进行表面处理,应用亲油化度值测试和分散稳定性测试方法得到表面改性的最佳实验条件为:KH-560的添加量(占纳米TiO2的质量百分比)8%,温度70~78℃,时间5h。采用适当的乳液聚合工艺,制备了纳米TiO2/聚苯乙烯-丙烯酸酯复合乳液,对表面处理后的纳米TiO2及复合乳液进行表征后证实,硅烷偶联剂以化学键的形式键合在纳米TiO2的表面,TEM照片有力地证明了在复合乳液中纳米TiO2均匀地分散在苯丙乳胶粒中。 相似文献
13.
14.
15.
16.
1. IntroductionThe paint suffering from long-term irradiation ofthe sunlight will degrade due to the photochemical effect. The addition of the conventional organic ultraviolet light absorber into the surface paint is usuallyused to prevent long term degradation of the paint.However, the organic ultraviolet light absorber possesses some shortcomings, such as short life and toxicetc. The nano--TiOZ powder is a strong ultravioletlight absorberll] and can overcome the above mentioned shortcoming… 相似文献
17.
Dicalcium phosphate dihydrate (DCPD) was hydrolysed in water and in 1 M Na2HPO4 solution at temperatures from 25–60°C. Hydrolysis was incomplete in water. At 25 °C, DCPD partially hydrolysed to hydroxyapatite (HAp). Formation of HAp is indicative of incongruent DCPD dissolution. At the higher temperatures, hydrolysis to HAp was more extensive and was accompanied by the formation of anhydrous dicalcium phosphate (DCP). Both of these processes are endothermic. When hydrolysis was carried out in 1 M Na2HPO4 solution, heat absorption was greater at any given temperature than for hydrolysis in water. Complete hydrolysis to HAp occurred in this solution. The hydrolysis of DCPD to HAp in sodium phosphate solution was also endothermic. The complete conversion of DCPD to HAp in sodium phosphate solution would not be expected if the only effect of this solution was to cause DCPD dissolution to become congruent. Because of the buffering capacity of a dibasic sodium phosphate solution, DCPD hydrolysed completely to HAp. Complete conversion to HAp was accompanied by the conversion of dibasic sodium phosphate to monobasic sodium phosphate. The formation of DCP was not observed indicating that the sodium phosphate solution precluded the DCPD-to-DCP dehydration reaction. In addition to affecting the extent of hydrolysis, reaction in the sodium phosphate solution also caused a morphological change in the HAp which formed. HAp formed by hydrolysis in water was needle-like to globular while that formed in the sodium phosphate solution exhibited a florette-like morphology. © 1998 Chapman & Hall 相似文献
18.
19.
Preparation of optically transparent dispersions of TiO2 nanoparticles which are free of the anatase polymorph is a challenging process which has been difficult to control to date. Here, we report and discuss the reproducible formation of such dispersions by hydrolysis of TiCl4. Clouding times of the dispersions and the finally resulting crystal modification of TiO2 was found to depend on a number of synthesis parameters, such as the temperature profile during the reaction, the ratio between the starting substances and the rate of TiCl4 addition. A low pH value and moderate reaction temperatures were required to yield rutile particles, which were established to be formed by transformation of initially amorphous particles just prior to clouding occurred. The latter phenomenon was found to be caused by agglomeration, and not by growth of primary nanosized particles. 相似文献
20.
以硝酸铝、硝酸锌和柠檬酸为原料,以炭黑和酚醛树脂为碳源,采用溶胶-凝胶法制备了纳米锌铝尖晶石粉体,研究了高温还原气氛下不同碳源对纳米锌铝尖晶石合成及颗粒粒径的影响,并以高温氧化气氛热处理、无碳引入的试样作对比。研究表明:在还原气氛下,引入碳源的试样在600℃热处理后,锌铝尖晶石峰不明显,主要是因为碳起空间位阻作用,阻碍了离子传质;800℃热处理后可合成锌铝尖晶石,且纳米颗粒尺寸较小(20~30nm);热处理温度升高至1 000℃时,纳米锌铝尖晶石颗粒尺寸变化不大,碳的空间位阻作用抑制了颗粒长大和烧结。与炭黑相比,酚醛树脂抑制锌铝尖晶石颗粒长大的效果更好,可能因为树脂碳化后呈玻璃态,空间阻隔作用更强。但热处理温度不低于1 200℃时,纳米锌铝尖晶石易被CO或C还原,锌以Zn(g)的形式逸出,只有α-Al2O3相。然而,在空气气氛下,600℃热处理后即可合成纳米锌铝尖晶石,但热处理温度从600℃升至800℃时,锌铝尖晶石颗粒长大较明显,颗粒尺寸从27.5nm增至54.6nm,并呈烧结状。 相似文献