Experimental Study of Pt Solubility in the CO-CO2 Fluid at Low fO2 and Subsolidus Conditions of the Ultramafic-Mafic Intrusions

The solubility of Pt in CO-CO2 fluid was studied experimentally at P = 50–200 MPa and T = 950 °C. A mixture of MgC2O4 and MgCO3 was used as a source of the fluid. Upon the reaction of the Pt capsule walls and the fluid, a carbonyl of platinum is formed. The use of the high-temperature quartz ceramics as a fluid trap avoids the effect of mechanical contamination with Pt from the eroded capsule walls. The total content of platinum in the porous fluid traps was measured by the Electrothermal Atomic Absorption (ET-AAS) method. In some experiments, the local analysis of traps was carried out by the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) method. The composition of fluid in bubbles captured in an albite glass trap was studied by micro-Raman spectroscopy. On the capsule walls and MgO, Pt “whiskers” of submicron diameter were observed, which were formed as a product of carbonyl decomposition during quenching. About 5–15% of carbonyl withstands quenching resulting in 1.5 to 2 ppm Pt soluble in acetone (runs at P = 200 MPa) in a quartz glass trap. The amount of Pt soluble in acetone from the capsule walls corresponds to a concentration of up to 8 ppm in the fluid. A high content of soluble Pt of 2000–3000 ppm was determined in a carbon coated MgO matrix. Our study demonstrated that the solubility of Pt in the CO-CO2 fluid is 15–150 ppm, presumably in the form of Pt3(CO)62− under conditions corresponding to the conditions of the subsolidus stage of layered ultramafic-mafic and ultramafic-alkaline intrusions formation. Our preliminary data showed that this solubility will increase with the addition of water at low fO2.

Determination of the influence of aluminum phosphate on the properties of quartz ceramics

One of the significant disadvantages of quartz glass-based materials is their tendency to crystallize cristobalite during firing and, as a consequence, a significant deterioration in performance. In order to prevent crystallization of quartz ceramics during sintering, a number of additives are used. However, all known options some disadvantages, namely, relatively low strength values and increased coefficient of linear thermal expansion of products.In this regard, a promising area of research is to study the effect of aluminum phosphate additives on the properties of quartz ceramics. According to the totality of properties, the addition of AlPO4 in an amount of 20 wt % has the most positive effect on the characteristics of quartz ceramics. According to differential thermal analysis, it is noted that up to a temperature of 1,200 °C, no noticeable phase and modification transformations occur in the base mixtures. In the course of the work, it was found that the most appropriate firing mode is as follows: oxidizing medium; the products are immersed in a hot furnace, after being held at the maximum temperature, they are removed from the hot furnace, cooling occurs slowly in the air. The materials obtained in this way are characterized by the following properties: α=31.6·10-7 deg-1; σcomp=153 MPa; P=2.7 %; tgδ and ε (frequency 1010 Hz, temperature 20 °C) 0.001 and 10, respectively. It is noted that the main crystal phase prevailing in the samples is aluminum phosphate. The microstructure of the material is characterized by the presence of a small number of residual pores and a densely sintered shard.The proposed solution will significantly reduce power consumption, improve production performance and increase the basic properties of polyfunctional quartz ceramic products

Sol - gel method for producing of glass binding in the Li2O - Al2O3 - SiO2 system for ceramic materials

The results of glass binding obtaining in the Li2O — Al2O3 — SiO2 system for ceramic materials are presented in the article. The lithium aluminum silicate system was chosen taking into account the low temperature expansion coefficients of crystalline phases that form in it. This will allow controlling the thermal expansion of materials into which the glass binding will be introduced. A sol - gel method based on ethyl silicate and soluble salts of the corresponding oxides is proposed as a method for producing of glass binding. This method is more rational in comparison with the traditional method of glass melting due to low energy costs. Also, the method allows to obtain a more uniform and active product. The effect of glass binding on the properties of ceramic materials for various purposes has been investigated. As such materials, low-temperature electrotechnical porcelain, quartz ceramics, and engobe coatings were chosen. The glass binding was introduced into the raw material charge of these materials in an amount of 5 wt. %. Further, the properties of calcined product without additives and with additives under the same conditions were compared. The intense fluxing effect of glass binding during the formation of electrical porcelain has been established. The glass binding reinforces the effect of natural fluxes (pegmatites) that are present in the basic composition of the mass. This contributes to the material compaction during firing. The formation of eucryptite and spodumene helps to reduce the thermal expansion of material. The introduction of glass binding into the engobe led to a less intense compaction of its structure. This was observed due to an insufficient amount of the added glass binding for this type of material. In the composition of quartz ceramics, glass binding contributed to the material sintering, but the thermal properties were deteriorated. Thus, the sintering results of ceramic material with the introduction of glass binding in the charge composition are positive. However, sintering significantly depends on the material type. The glass binding stimulates the formation of a melt in which solid finely dispersed components of the ceramic mass dissolve. This contributes to the formation of a dense durable ceramic.