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One of the most important components of refractory glass-fiber heat insulation products which determine the main working properties is the binder, which links the separate glass fibers and gives the strength of the finished articles.Moreover, the binder has a significant effect on the density and thermal conductivity of the heat-insulation products and also on their shrinkage during service.In addition, the effect of the type of binder on the properties of thermal-insulation glass-fiber refractory articles has received inadequate coverage in the literature.Thus, in [i] it was shown that the nature of the binder has a significant effect on the adsorption capacity of the fiber, on its structural features at high service temperatures, and also on the temperature interval in which a change occurs in the mass and volume of the materials. According to the data in [2], inorganic binders do not affect the crystallization of the refractory glass fiber, which is barely possible, particularly at high temperatures when an interaction is observed in most cases between the glass fiber and the binder.The present paper gives some results from a study of the effect of the binder on the main properties of glass-fiber refractory products.We used water glass, silica sol, chromium--aluminophosphate binder (CAPB), and an alumina binder of the bentonite type as the inorganic binders for the production of articles based on aluminosilicate fibers; for the organic binders we used a polyvinyl acetate dispersion (PVAD)We used the refractory glass-fiber ~ and 46-48% Si02 developed for the first of an aluminosilicate composition with 51-53% AI=Os time in the USSR at the All-Union Scientific-Research Institute of Glass Laminates and Fibers and produced at the Bogdanovich Refractory Plant [3][4][5].Because of the different natures of the binders and, consequently, of their adhesive quality, experimental amounts of binder were different and varied from 4-16 to 50-65% (dry material).The main criterion was the use of a minimum amount of binder that would ensure the ultimate bend strength of ~ 0.5 MPa after drying at least.All the specimens with the various binders were made up as a slurry and subsequently evacuated and pressed in equipment which included a mill and vacuum press. The specimens were dried in a hot chamber at 120-150~ for 16-18 h and then fired at various temperatures between 400 and 1300~ with a dwell of 2 h at each temperature.We then studied the temperature dependence of the main properties of the articles and the interaction process between the binder and the glass fiber.The linear shrinkage (or growth) of the heat-insulation products was calculated by measuring the linear dimensions of the specimens to an accuracy of 0.I mm; the ultimate bend strength was determined on an MR-0.5-1 device using a three-point bend method; the specimen was loaded at the center and the distance between the supports was 40 mm. The thermal conductivity of the specimens was determined in a device specially developed at the Ukrainian Institute of Refra...

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The phase diagrams of the ZrO2HfO2--MgO [i] and the ZrO2--HfO2--CaO systems have many common features. These are eutectoid-type diagrams. In both systems, there is a narrow (up to 1%* MgO or CaO) region of monoclinic solid solutions at room temperature and a wide range of solid solutions having a fluorite-type structure; solid solutions based on MgO and CaO have not been established [2].The presence of chemical compounds is of great significance when plotting the phase diagrams of the aforementioned systems. Increasing basicity in the zr+Hi and Mg+Ca series (order) and the difference in the ionic radii of the indicated cations lead to the appearance of one compound each in the ZrO2--MgO and the HfOH--MgO systems: Mg2Zr~012 and Mg2HfsOl~, respectively [3, 4], and in the ZrO2--HfO2--MgO system, there is an unlimited (continuous) series of solid solutions based on these compounds that form fluorite-type rhombic crystals having lattice distortion in the [IIi] direction and belonging to the R3 space group; on the other hand, in the analogous Ca-containing system, there are four compounds, viz., CaHfO~ (CaZrOa) [5], CaHf~09 (CaZr~Og) [6], Ca2Hf?O16 (Ca2ZrT016), CasHfl~044 (Ca6Zr19044) [7]. Among these compounds, calcium tetrazirconate and tetrahafnate and calciumzirconate and hafnate are the most important ones. The latter compounds of the series (Ca2HfT016 and Ca6HflgO44) are metastable [7] and are present only partially in the investigated region of the phase diagram.An analysis of the published literature showed that the structure of the phases present in the ternary systems based on ZrO= has not been studied in detail. This paper deals with a study of the structure of the phases existing in the ZrO~--HfO2--MgO(CaO) systems using the methods of x-ray phase analysis, high-temperature diffraction, and electron microscopy. The obtained results and the new (modified) form of the phase diagram of the ZrO~--HfO2--CaO system are presented.The monoclinic solid solutions of the ZrO2--HfO2--MgO(CaO) systems were studied in order to understand the effect of the additives on the temperature and the nature of the polymorphic transformation. X-ray studies estaSlished that the addition of MgO and CaO leads to a decrease in the temperatures of the monoclinic--tetragonal transformation and that an increase in the concentration of HfO 2 shifts this transformation towards the region of higher temperatures [2].As concerns zirconium and hafnium dioxides, the ~ ~ ~ modification is a martensitetype diffusionless reversible transformation. In this case, the linearity of the temperature dependence of the interplanar distances (lattice parameters) of the aforementioned oxides is retained up to and in the region of the transformation temperatures [8]. Heating the specimens of the ternary systems containing 1% MgO or Ca0 in the furnace of the diffractometer showed that the linear nature of this relation is retained right up to the beginning of the + 8 transformation.In the region of transformation, we observes significant deviations from the ...