Procedure for setting up the drying regime that is consistent with the nature and properties of the clay raw material

Over the past three decades, traditional ceramic facilities, such as chamber and tunnel dryers, are improved. Better thermotechnical equipment, operational strategies, and reliable scale-up methodologies have lead to higher quality of the dried clay roofing tiles. Although there has been a progress, up to this study, there is no universally or even widely applicable criterion, which could be used to precisely define the change of drying air parameters (humidity, temperature, and velocity) during the drying process. The objective of this study was to specify the variable air parameters that should be used during the drying process to approach as much as possible to the theoretically defined optimal drying process.     

Thermal analysis and microscopic characterization of the piston alloy AlSi13Cu4Ni2Mg

In this research paper, the phases identified by thermal and microscopic analysis of the piston alloy AlSi13Cu4Ni2Mg, which was solidified under different conditions, are presented and compared with different piston alloys. Piston alloys are a group of casting Al–Si alloys, well-known as wear resistant materials, which are widely used as the piston materials for internal combustion engines because of their low thermal expansion coefficient and high wear resistance when alloyed with other elements such as copper, magnesium and nickel. Depending on the combination of alloying elements and other impacting factors, pistons alloys with different mechanical and physical properties are obtained.     

The effect of T4 heat treatment on the microstructure and corrosion behaviour of Zn27Al1.5Cu0.02Mg alloy

The effect of heat treatment on the microstructure and corrosion behaviour of Zn27Al1.5Cu0.02Mg alloy was examined. The alloy was prepared by melting and casting route and then thermally processed (T4 regime). Corrosion behaviour of the as-cast and heat treated alloy was studied in 3.5 wt.% NaCl solution using immersion method and electrochemical polarization measurements. The applied heat treatment affected the alloy microstructure and resulted in increased ductility and higher corrosion resistance of the heat treated alloy. Electrochemical measurements of the corrosion rate at the free corrosion potential are in agreement with the results obtained using the weight loss method.     

Refractory coating based on cordierite for application in new evaporate pattern casting process

Standard raw materials, kaolin, talc, MgO, alumina, feldspar and sepiolite, were used in synthesis of four different cordierite type ceramics. Sintered cordierite was used as refractory filler in the ceramic coating for evaporative polystyrene patterns in the EPC process. The cordierite samples were tested by the following methods: roentgen diffraction analysis, diffraction thermal analysis and polarized microscope. The shape and grain size were analyzed by the program package OZARIA 2.5. In order to evaluate the possible application of cordierite as the refractory filler, four different coating processes were investigated.     

Novel Utilization of Fly Ash for High‐Temperature Mortars: Phase Composition,Microstructure and Performances Correlation

In this study, the feasibility of using fly ash to manufacture high‐temperature mortars was investigated. The investigation was set to define preliminary characteristics of new types of mortars based on ordinary and/or refractory cement with fly ash addition, and to establish mutual correlation between thermally induced changes of mineral phases, microstructure, and final performances of the mortars. New mortars, made up of 21% cement (PC‐CEM I 42.5R/HAC‐Secar 70/71), 70% river sand, and 9% fly ash, were chemically, physically, and mechanically characterized to determine possibilities of fly ash re‐utilization for high‐temperature purposes. The fly ash samples, which originated from four different power plants, were mechanically activated. Mortars were heat‐treated up to 1300°C in a laboratory tunnel furnace with retention time 2 h. Thermal stability of crystalline phases were studied by differential thermal analysis (DTA); thermally induced changes in mineral phase composition were analyzed by XRD; and microstructure were investigated by scanning electron microscopy. Correlated results of DTA, XRD, and SEM analyses indicated initiation of sintering processes at approximately 1300°C and formation of thermally stable minerals (rankinite, gehlenite, anorthite, cristobalite). The investigation highlights a sustainable approach of using fly ash in developing ecofriendly mortars for high‐temperature application.     

Corrosion behaviour of thixoformed and heat-treated ZA27 alloys in NaCl solution

The influence of corrosion on the microstructure of thixoformed and heat-treated ZA27 alloys was investigated. The microstructure of ZA27 alloy was affected by heat treatment. The process of electrochemical corrosion occurs in both ZA27 alloys through the area of η phase. According to the results of immersion test and electrochemical measurements, the corrosion rate of the thixoformed ZA27 alloy is at least 50% lower than that of the thixoformed and thermally processed alloy. This indicates the unfavourable influence of applied heat treatment (T4 regime) on the corrosion resistance of the thixoformed ZA27 alloy.     

The effect of different drinking water treatment processes on the rate of chloroform formation in the reactions of natural organic matter with hypochlorite

This study is concerned with the changes in the rate of chloroform formation during the reactions of groundwater natural organic matter (NOM) and sodium hypochlorite caused by different drinking water treatments schemes: coagulation with FeCl₃, Al₂(SO₄)₃ and polyaluminum chloride (PACl), filtration of the raw water through granular activated carbon (GAC) and filtration through the columns filled with strong base macroporous ion-exchange resins (Purolite A501P and A500P) with and without pretreatment by coagulation process. It was found that the change of the concentration of chloroform, within 2 h and c(Cl₂)=100 mg l⁻¹, can be described by a kinetic equation of the form [CHCl₃]=a+bt^c. On the basis of this equation rates of the reaction were calculated. All processes applied decreased the rate of chloroform formation (process of coagulation moderately decreased the rate of reactions, while GAC adsorption caused dramatically drop of the rate). Also, it was found that the resins have had a higher affinity towards slow-reacting chloroform precursors.

The value of the chloroform formation potential was conventionally determined after a 7-day reaction at pH 7. In addition, the same parameter was estimated with a satisfactory deviation for raw water and for treated water on the basis of the kinetic constant (k) or by determining the chloroform concentration after 2 h (ChFP₂) under rigourous chlorination conditions at pH 8.4.     

What to expect from heavy clay?

The need of testing the quality of brickclay arises in all brick factories, with the opening of new deposits. The analyses are both time and economically consuming, so the aim of this study was to shorten the procedure using the already known data. This study was focused on determining the usability of heavy clays, when only the raw material major elements chemical composition is determined. The effects of chemical composition, firing temperature, and several shape formats of laboratory samples on the final properties were investigated. Chemical composition of major elements was determined on the basis of classical silicate analysis. Firing was conducted in an oxidizing atmosphere, while maintaining all other experimental conditions constant, except the final temperature. Principal component analysis (PCA) was used to determinate groups of samples according to similarity of chemical composition. Prediction of compressive strength (CS) and water absorption (WA) was done by developing five artificial neural networks (ANN). The average regression coefficients r² were used to explore the confidence level of the models. Developed models were able to predict CS and WA in a wide range of chemical composition and temperature treatment data, and the highest average r² of 0.923 for CS was obtained, while r² for WA was 0.958. The wide range of processing variables was considered in the model formulation, and its easy implementation in a spreadsheet using a set of equations makes it very useful and practical for CS and WA prediction. As it is known from literature, all the parameters entered this analysis are dependent on each other, but their mutual relationship was not quantified yet. Most importantly—the developed neural networks can be used on a global scale.     

Modification of piston surfaces by compressed plasma flow

Surface of the casted pieces made of aluminium piston alloys was treated by a plasma jet produced by the magnetoplasma compressor, with an aim to improve their exploitation properties. Fast piston surface heating and melting, physical and chemical changes within the surface layer and the melted layer recrystallization in the fast cooling conditions are the basic characteristics of the interaction between the plasma from the magnetoplasma compressor and piston alloys. The major changes are conducted in the surface layer inducing hardness increment and piston resistance. Micro hardness of plasma treated surface is 750 to 883 HV_0.2, in comparison with 90 to 130 HV_0.2 in initial stage. The X-ray structure analysis of samples in cast state before and after plasma treatment shows existence of modified zones in hardened layer with phase transformations. In plasma flow treated surface at least two new phases are registered, with redistribution of already existing phases. These intermetallic phases contributed to treated surface hardness increasing. These observations show that quasi-stationary compressed plasma flow treatment of sample surface influences remarkably modification and improvement of surface properties.