Recovery of Polymer Waste in the Production of Ceramics Veneer with a Self-glazing Effect

The results of studies on the development of the composition of the charge based on low-plasticity clay using waste products from the consumption of products made of unplasticized polyvinyl chloride are presented. In addition, boric acid as a flux and titanium dioxide as a source of the vitreous phase are introduced into the composition of the charge to obtain the effects of vitrification of the surface of ceramic particles and self-glazing of the surface of the samples. The dependences of the main properties of ceramics veneer on the ratio between the amounts of polymer waste and titanium dioxide with the introduction of 5% by weight of boric acid have been established. The quantities of charge components that ensure the energy efficiency of the developed ceramics while ensuring strength, water absorption and frost resistance at a level corresponding to the requirements for products for brick cladding of buildings and structures have been determined. The use of this composition expands the range and raw material base for the production of ceramics veneer, allow you to dispose of polymer waste at any degree of purity and destruction in sufficiently large quantities.

Influence of ZnO addition on microstructure and proton electrical conductivity of BaZr0.8Y0.2O3-δ ceramics

Sintering aids are widely used to promote densification and grain growth for electrolytes based on yttriumdoped barium zirconate. However, there are some discrepancies in the literature about the influence of these sintering aids on the microstructure development. Some authors consider that ZnO remains on grain boundaries, forming an amorphous phase that promotes sintering, and others proposed that ZnO forms a solid solution with barium zirconate. Even considering different mechanisms, it was proposed that ZnO addition compromised protonic conductivity. In this work BaZr0.8Y0.2O3-? (BZY20) was prepared by conventional oxide mixture (solid state sintering), adding ZnO as sintering aid. We proposed a mechanism for the ZnO actuation on the microstructure development, by the formation of a liquid phase during sintering and formation of a vitreous phase throughout grain boundaries during cooling. This could be the reason for poor protonic conductivity in comparison to the undoped BZY20 electrolytes. The proposed mechanism was established through the scanning electron microscopy analyses and electrical conductivity measurements under several different atmospheres by impedance spectroscopy. High density samples were obtained by using ZnO, but with compromised electrical conductivity compared to the undoped samples.

Novel Alumina Compounds with Niobia, Silica and Magnesia for Ballistic Armor

Compounds of alumina APC-2011 SG with niobia, silica and magnesia were sintered at 1400°C/3h, in order to evaluate their ballistic performance. The content of niobia (Nb2O5) was 4.0 to 8.0 wt.%; silica (SiO2) was 0.8 wt.%; and magnesia (MgO) at 0.15 wt.%. Sintered samples were characterized by hardness, densification and energy absorption at impact. Ballistic tests were performed by ceramic discs firmly glued to steel plates and then subjecting the target to impact using 7.62 mm projectile shot from a rifle with a throw distance of 5 m. The energy absorbed by the disintegration of the ceramic discs was estimated by the residual velocity. The fracture surfaces of the samples were observed by scanning electron microscopy. It was verified for the first that the addition of high amounts of Nb2O5 to the alumina with the presence of SiO2 and MgO increases the presence of vitreous phase in the contours of alumina grains and improved the properties of the material for use in ballistic protection.

Correlation of Quality Assessment Methods of Class F Fly as for Synthesis of Geopolymers

The demand of highly effective aluminosilicates such as class F fly ash for use in geopolymer synthesis initiated a strong scientific interest for a design of the quality assessment methods. At the same time, the existing assessment methods apparently differ in key parameters which determine the quality of aluminosilicate. This research was focused on determination of relationship between the key parameters of different assessment methods for different types of low-calcium fly ash with high portion of vitreous phase. The insoluble aluminosilicate portion in fly ash that remained after treatment in aggressive acidic media followed by high-temperature treatment at 1000 °C (or the parameter α) was measured in this study. The experimental data showed a very low correlation (R2=0.34) between parameter α and compressive strength of the fly-ash based geopolymer paste. The correlation factors between such genetic parameters of fly ash as portion of vitreous phase (C), SiO2-bonding degree in vitreous phase (fSi) and parameter α demonstrated dramatically different values: R2 (С-α)=0.01; R2(fSi-α)=0.71; R2 (С-fSi)=0.0, respectively.

Estimating the reduction of the firing temperature produced by the addition of energetic fluxes in porcelain tiles through the Fluegel’s model

Reducing the firing temperature and accelerating the densification process bring economic and environmental benefits. This study used Fluegel’s viscosity model, developed for glasses, to estimate the decrease of the firing temperature produced by the introduction of energetic fluxes in a porcelain body. The experimental results confirmed the prediction of the model, a 30 ºC reduction in the temperature, for the addition of wollastonite. However, for the addition of spodumene, the reduction was slightly higher than the predicted. These results suggested that Fluegel’s model may be used to estimate the effects of the introduction of energetic fluxes in porcelain tile compositions. However, the predictions should be seen as a general orientation. Among the limitations of the model were the extrapolation of limit values established by the model for the composition and, above all, the initial hypothesis that the chemical composition of the vitreous phase in porcelain tiles is constant.

Synthesis and Stability of the Strontium Cobaltite Thermally Treated in Air

This paper reports, the studies on chemical transformations at thermal treatment of a mixture of SrCO3 and Co3O4 corresponding to stoichiometric ratio of SrCoO3 compound. The mixture of raw materials was prepared by mechanical activation. Thermal analysis, X-ray diffraction and scanning electron microscopy were used for these studies. It was found that SrCoO3 forms at 930oC but is not stable and turn immediately into Sr2Co2O5 by eliminating of oxygen. This compound, Sr2Co2O5, is unstable and by increasing of the temperature decomposes in Sr3Co2O6 and cobalt oxide. At temperatures above the 1250oC, the samples melt and Sr3Co2O6 crystallizes from vitreous phase by cooling.

High-Temperature Mineral Phases Generated in Natural Clinkers by Spontaneous Combustion of Coal

The aim of this study is to analyze natural clinkers (= calcined clays by coal combustion) from a lower Cretaceous coal outcrop in Ariño (Teruel, NE Spain) in order to describe mineral and textural transformations produced during the spontaneous combustion of coal. To achieve this aim, samples were analyzed using X-ray diffraction and optical and electron microscopy. Spontaneous combustion resulted in the melting of the surrounding clays, with the generation of an Al–Si-rich vitreous phase. Subsequently, high-temperature phases crystallized from this vitreous phase. These new minerals are interesting due to their similarity with those formed during ceramic processes, used in the manufacture of stoneware and ceramic tiles, as well as in refractory ceramics, and with natural events such as metamorphic and igneous processes. The studied natural clinkers are composed of vitreous phase mullite, hematite, hercynite, cristobalite, quartz, pyroxenes, cordierite, gypsum, pyrite, and calcium oxides. A trend from hematite to hercynite composition indicates compositional variations at sample scale, which evidence d-spacing differences in hercynite and may be related to the Al and Fe content in hercynite depending on its texture. The mullite shows higher Si/Al ratio (1.21) than the theoretical composition (0.35), indicating that this mullite is more Si-rich. Three pyroxene-type compositions (diopside-type, ferrosilite-type, and a Ca–Al-rich pyroxene) were found. Both the mullite and the pyroxenes are nonstoichiometric.

Receiving of Ceramic Veneer with the Use of Unsorted Container Glass Breakage

The results of studies on the production of ceramic material, which can be used for face veneer and pedestals are presented. This material was obtained on the basis of stiff clay with the addition of 30 % by weight of unsorted container glass breakage as a flux-hardening additive, which forms a vitreous phase during baking, and 2.5 % by weight of a fluxing agent that increases the amount of the vitreous phase and lowers the temperature of the liquid-phase sintering material. In turn, the vitreous phase acts as a binder in the bulk of the material due to the vitrification of the surface of the ceramic particles and their connection into a strong frame and creates the effect of self-glazing products. Studies have been conducted showing that the highest compressive strength and the lowest water absorption of the material being developed were obtained using boric acid as a fluxing agent and baking at a maximum burning temperature of 1050 °C.

Production of facing ceramic material using cullet

The research presents experimental results concerning the charge composition development for ceramics, used for cladding facades and basements of buildings and structures. The given composition is suggested to be based on the low plasticity clay as a basic component, which cannot be used to produce crackless, durable and frost resistant ceramics without introducing functional additives. The following functional additives were applied in the conducted experiments: boric acid, used as a fuse for the reduction of liquid phase sintering temperature and the increase of vitreous phase amount; various empties cullet, used as a fluxing and strengthening additive, which is the source of vitreous phase, forming the rigid frame of interconnected ceramic particles through a layer of vitreous phase. The research experiments stated that the highest compressive strength and frost resistance and the least water absorption can be achieved when 30 wt. % of colorless empties cullet and 2,5 wt.% of boric acid are introduced into the charge. Besides the research demonstrates the results of determining the dependence of bending strength, density, thermal conductivity, open and total porosity. The developed charge composition on the one hand stipulates the solution environmental and technical-economic problems of natural resources rational use and waste management, and on the other hand allows producing high quality facing ceramic products at a reduced cost and using low demand resources.