Highly concentrated ceramic bonding suspensions and the influence of the concentration factor

Abstract

Previously [I] the author examined some properties of the starting materials and methods of obtaining highly concentrated ceramic bonding suspensions (VKVS). For the first time a classification was worked out for these materials based the chemical nature of their solid phase. It was thus shown that for the materials most thoroughly studied, that is, those classified as acid and acid-amphoteric, the best method of obtaining them is single-stage wet milling in ceramic ballmills. To obtain the optimum characteristics of VKVS, produced by this method, it is necessary to observe a number of technical principles, the main one of which is the principle of high concentration* directly in the process of wet milling. The latter is the most specific in the VKVS technology.In the present article# on the basis of a summary of known works, and also some new, previously unpublished experimental data, we have formulated and typified the stated technological principle.Principle of High Concentration. Originally in studying the conditions for obtaining suspensions of quartz glass [2, 3], and then quartz sand [4], the VKVS of other materials in siliceous, aluminosilicate and other compositions [I, 5-10] it was established that the final properties of the suspension and the casting (bond) to a considerable degree depend on the volume concentration C v of VKVS during wet milling. With an increase in C v of the suspension during milling it becomes possible to sharply increase the bonding properties of VKS.The nature of the relationship between the properties of VKVS and C v during their wet grinding is shown in Figs. i and 2. These data refer to the case of obtaining VKVS in approximately identical ballmills (capacity I00-180 liters), whose drums in addition have comparable thermal conductivities. The latter in obtaining VKVS plays a significant role. As follows from Fig. I, with increase in C v of the suspension there is a reduction in the effective density of the grinding bodies Ap~ based on quartz sand or quartz glass. Despite the fact that the factor Ap~ during milling of the suspension of quartz sand is much higher, the grinding times to obtain a comparable fineness in the region of high C v are greater, which is due to the greater hardness of the crystalline silica.We noted close porosity and strength values for castings from suspensions of these two types with equal values of C v. With increase in C v during grinding Pcast sharply increased, with a simultaneous reduction in strength. Previously [3, p. 130] it was shown that when the stabilized suspensions with the high original values of C v are diluted to lower C v levels *Other principles of VKVS technology (increased temperature, optimum fineness, grain distribution, deflocculation and solution of the solid phase, additional stabilization, rheoand technological correspondence) will be examined in subsequent articles in the present series. tThe present article is the second in a series of work on VKVS.All-Union Institute of Refractories. September, 1987.