不同工业氧化铝粉在加热过程中物相和形貌的变化

发布时间：2018-04-23 05:32

本文选题：工业氧化铝粉 + 物相转变　；参考：《河南工业大学》2017年硕士论文

【摘要】：氧化铝因具有高强度、抗磨损、耐腐蚀等优异的特性,在耐火材料领域有广泛的应用。随着国内越来越多的生产厂家采用工业氧化铝粉来生产煅烧氧化铝微粉及烧结板状刚玉,工业氧化铝粉在温度升高过程中的物相转变和形貌演变不论是对氧化铝微粉的生产还是对烧结板状刚玉的生产都是有重要的理论及实际意义的。因此,本文采用X射线衍射和扫描电子显微镜这两种检测手段,对不同工业氧化铝粉(澳粉、山东中铝粉、山东荏平粉和广西信发粉)在不同温度煅烧后的物相转变和形貌演变进行了研究,同时也对不同添加剂存在时不同工业氧化铝粉在不同温度煅烧后的物相转变和形貌演变进行了研究,主要研究结果如下:(1)澳粉、山东中铝粉、山东荏平粉和广西信发粉在加热过程中物相转化过程和显微形貌的演变基本一致。经700°C、800°C和900°C煅烧后,物相没有变化,显微形貌也变化不大。在1000°C煅烧后,物相发生明显变化,γ-Al_2O_3和δ-Al_2O_3转变为θ-Al_2O_3和α-Al_2O_3,工业氧化铝粉的显微形貌开始发生了明显的变化,颗粒表面开始出现不规则形状的小晶粒,小晶粒之间的晶界很明显。经1100°C煅烧后,大部分θ-Al_2O_3转化为α-Al_2O_3,小晶粒彼此分离形成缝隙。煅烧温度达到1200°C后,所有氧化铝过渡相全部转化为α-Al_2O_3,小晶粒因为长大,有些彼此又连在了一起。由此可见,工业氧化铝粉在700~1200°C煅烧后,显微形貌演变与物相转变相关。随着煅烧温度从1200°C增加到1600°C,四种工业氧化铝粉中的小晶粒彼此分离,小晶粒之间的缝隙逐渐增大,小晶粒逐渐长大。当煅烧温度达到1400°C时,晶粒逐渐生长成小球状或椭球状,晶粒进一步长大。当煅烧温度继续升高,直至1600℃,球状和椭球状小晶粒继续长大,直到晶粒彼此又粘结在一起。(2)由澳粉、山东中铝粉和广西信发粉三种工业氧化铝粉压制成的圆饼状的块样在1700°C和1800°C煅烧后,观察其显微形貌貌可以发现,这三种工业氧化铝粉样品都是由大量的球状、椭球状和板片状晶粒堆积而成的,晶粒与晶粒之间存在大量的孔隙,并没有烧结致密化。与各自在1600°C煅烧后样品的显微形貌相比,晶粒大小没有变化。说明当煅烧温度进一步升高至1700°C和1800°C,这三种工业氧化铝粉中的晶粒并没有继续长大。(3)NH_4F对澳粉和广西信发粉的物相转变都有一定的促进作用,但两者不同的是,2.0%含量的NH_4F可使澳粉中氧化铝过渡相全部转化为α-Al_2O_3相的温度从1200°C降低到900°C,而1.6%含量的NH_4F可使广西信发粉中氧化铝过渡相全部转化为α-Al_2O_3相的温度从1200°C降低到1000°C。NH_4F对澳粉和广西信发粉的显微形貌也有一定的影响,NH_4F可以改变澳粉和广西信发粉的结晶习性,形成板片状结构。但两者不同的是,在1200°C煅烧后,2.0%NH_4F含量的澳粉颗粒中的α-Al_2O_3晶粒为圆的板片状,而2.0%NH_4F含量的广西信发粉颗粒中的α-Al_2O_3晶粒为规则的六方板片状。随着煅烧温度继续升高,澳粉和广西信发粉中的板片状α-Al_2O_3晶粒逐渐开始消失,当煅烧温度达到1400°C时,2.0%NH_4F含量的澳粉颗粒主要由大量的颗粒状α-Al_2O_3晶粒和少部分的板片状α-Al_2O_3晶粒堆积而成,而2.0%NH_4F含量的广西信发粉颗粒主要由大量颗粒状α-Al_2O_3晶粒堆积而成,板片状的α-Al_2O_3晶粒已完全消失。(4)含有H_3BO_3的澳粉和广西信发粉在1200°C煅烧后所有的氧化铝过渡相才完全转化为α-Al_2O_3。H_3BO_3在900°C对澳粉和广西信发粉的物相转变有微弱的促进作用,在1000°C和1100°C却抑制了澳粉和广西信发粉中氧化铝过渡相向α-Al_2O_3的转变。H_3BO_3对澳粉和广西信发粉的显微形貌也有一定的影响。2.0%H_3BO_3含量的澳粉和广西信发粉在完全转化为α-Al_2O_3后,主要形成了蠕虫状的显微结构。而0.8%H_3BO_3含量的澳粉在1200°C煅烧后,澳粉主要由大量的球状α-Al_2O_3晶粒堆积而成,且α-Al_2O_3晶粒分布相对分散,随着煅烧温度升高至1300°C和1400°C,球状α-Al_2O_3晶粒彼此相连形成蠕虫状结构。而0.8%H_3BO_3含量的广西信发粉在1300°C煅烧后,才形成球状α-Al_2O_3晶粒,且α-Al_2O_3晶粒分布相对分散,当煅烧温度为1400°C时,球状α-Al_2O_3晶粒长大彼此相连也形成了蠕虫状结构。
[Abstract]:Alumina has a wide range of applications in the field of refractories because of its excellent properties such as high strength, abrasion resistance and corrosion resistance. With more and more manufacturers in China, the industrial alumina powder is used to produce alumina micro powder and sintered plate like corundum. The phase transformation and morphology evolution of industrial aluminum oxide powder in the process of temperature rise are not matter It is of great theoretical and practical significance to the production of alumina micropowder or to the production of sintered plate corundum. Therefore, this paper uses two kinds of testing methods, X ray diffraction and scanning electron microscope, to calcined the different industrial aluminum oxide powder (Australia powder, Shandong medium aluminum powder, Shandong's Ping powder and Guangxi powder) at different temperatures. Phase transformation and morphology evolution were studied. The phase transformation and morphology evolution of different industrial aluminum oxide powders at different temperatures were also studied. The main results were as follows: (1) the phase transformation process and display of the Australian powder, Shandong medium aluminum powder, Shandong's Ping powder and Guangxi powder in the heating process. The evolution of Micromorphology is basically the same. After calcining of 700 C, 800 C and 900 degree C, the phase change is not changed, and the micromorphology changes little. After calcining at 1000 C, the phase changes obviously, the gamma -Al_2O_3 and delta -Al_2O_3 change to theta -Al_2O_3 and alpha -Al_2O_3. The microstructure of the industrial aluminum oxide powder begins to change obviously, and the surface of the particle begins to come out. The grain boundary between small grains and small grains is obvious. After calcination at 1100 degree C, most of theta -Al_2O_3 is converted to alpha -Al_2O_3, and the small grains separate from each other to form a gap. After the calcination temperature reaches 1200 C, all the alumina transition phases are converted to alpha -Al_2O_3, and the small grains are connected together because of the growth. The microstructure evolution is related to phase transformation after the calcination of industrial aluminum oxide powder at 700~1200 C. As the calcining temperature increases from 1200 to 1600 C, the small grains in the four kinds of industrial aluminum oxide powder are separated from each other, the gap between the small grains increases gradually and the small grain grows gradually. When the calcining temperature reaches 1400 C, the grain grows gradually into small size. Spheroid or ellipsoid, the grain is further grown. When the calcining temperature continues to rise, the spheroidal and ellipsoid small grains continue to grow until 1600 degrees centigrade, until the grain is bonded together. (2) the round cake shaped samples made of Australian powder, Shandong medium aluminum powder and three kinds of industrial alumina powder in Guangxi powder are calcined at 1700 [C] and 1800 degree C. The microstructure appearance can be found that the three kinds of industrial aluminum oxide powder samples are made up of a large number of spheroid, ellipsoid and plate like grains. There is a large number of pores between grain and grain, and no densification is sintered. Compared with the micromorphology of the samples calcined at 1600 C, the size of grain does not change. Further increase to 1700 C and 1800 degree C, the three kinds of industrial aluminum oxide powders do not continue to grow. (3) NH_4F has a certain promotion effect on the phase transition of Australian powder and Guangxi powder, but the difference is that the 2% content of NH_4F can make the transition phase of Al2O3 into alpha -Al_2O_3 phase from 1200 degrees to C. Low to 900 C, and 1.6% content of NH_4F can make the transition of alumina transition phase to alpha -Al_2O_3 phase from 1200 degree C to 1000 degree C.NH_4F to the microstructure of Australian powder and Guangxi powder, and NH_4F can change the crystallization habit of Australian powder and Guangxi powder and form plate like structure. The difference is that after the calcination at 1200 C, the alpha -Al_2O_3 grain in the 2.0%NH_4F content of the Macau particles is round plate, while the alpha -Al_2O_3 grain in the 2.0%NH_4F content of Guangxi powder particles is a regular six square plate. As the calcination temperature continues to rise, the plate like alpha -Al_2O_3 grain in the Macau powder and the Guangxi powder powder gradually begins to disappear. When the calcining temperature reaches 1400 C, the 2.0%NH_4F content of Australia powder particles is mainly composed of a large number of granular alpha -Al_2O_3 grains and a small portion of the plate like alpha -Al_2O_3 grain. The 2.0%NH_4F content of Guangxi powder particles is mainly composed of a large number of granular alpha -Al_2O_3 grains, and the plate like alpha -Al_2O_3 grains have been completely eliminated. (4) all the Al2O3 transition phase in the calcined of Australian powder and Guangxi powder containing H_3BO_3 after 1200 C is completely converted to alpha -Al_2O_3.H_3BO_3 at 900 [C], which has a weak promoting effect on the phase transition of Australian powder and Guangxi's powder, but at 1000 and 1100 degrees, the transition of alumina to alpha -Al_2O_3 in Australian powder and Guangxi's powder is inhibited. The transformation of.H_3BO_3 to Macau powder and the micromorphology of Guangxi powder also has a certain influence on the.2.0%H_3BO_3 content of Macau and Guangxi powder, which mainly formed a vermicular microstructure after converting to alpha -Al_2O_3, and the Macau powder of 0.8%H_3BO_3 content is mainly accumulated by a large number of spheroidal alpha -Al_2O_3 grains after the calcining of 1200 degree C. In addition, the grain distribution of alpha -Al_2O_3 is relatively dispersed. With the calcining temperature rising to 1300 C and 1400 degree C, the spheroidal alpha -Al_2O_3 grains are connected to each other to form a wormlike structure. The 0.8%H_3BO_3 content of Guangxi powder is calcined at 1300 [C], and the spheroidal alpha -Al_2O_3 grain is formed, and the grain distribution of alpha -Al_2O_3 is relatively dispersed, when the calcining temperature is 1400 degrees C. The spherical -Al_2O_3 grains grow together and form worm like structures.

【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ133.1

【参考文献】