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From an industrial point of view, porous ceramics represent an important material, however, economically and technologically acceptable solutions are still being sought for its preparation. Porosity control is a key step in achieving the desired properties for a specific application. In order to obtain multiporous ceramics, in this work, kaolin clay and polystyrene beads were used as organic sacrificial phase. After mixing, the samples were sintered at 1050 oC for 1 h. Characterization included Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction analysis (XRPD), elemental CHNS analysis and compressive strength investigations. The analysis of the obtained results showed that hierarchically ordered, multiporous ceramics, with appropriate mechanical properties can be prepared in the presence of an organic component whose burnout during sintering leaves behind pores of different dimensions.

The aim of this study was to investigate a possibility of synthesis of porous ceramics with controlled open porosity, which could be used as sorbents and catalyst supports. Two organic additives were used to obtain open porosity: polystyrene beads and cellulose fibers, which are mixed with kaolin clay powder and the appropriate water content. Samples were sintered at 1050°C for 1 h. Characterization of the obtained products included X-ray powder diffraction analysis (XRPD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and elemental CHNS analysis. In addition, porosity was examined by quantification of visual information. The specific surface areas were determined by the Brunauer–Emmett–Teller (BET) method. Also, density and compressive strength of the obtained samples were assessed. It was determined that by sintering, the organic component completely leaves the system. For samples prepared with polystyrene beads and with cellulose fibers, satisfactory mechanical properties were obtained: compressive strengths were 1.42 and 1.56 MPa, respectively. It was noted that significantly higher open porosity was obtained by using polystyrene beads as a sacrificial template (porosity of ~56 %) instead of cellulose fibers (porosity of ~6 %).

The aim of this research was to study the effect of graphite addition in the process of synthesis of tribological materials based on tin sulphides. The tin sulphides powders were synthesized from selected precursors by pyrometallurgical method in rotary tilting tube furnace. The thermodynamic parameters of the synthesis were determined using HSC Chemistry software modelling package. In addition, the synthesis process was also characterized by the thermal analysis method: simultaneous differential scanning calorimetry and thermogravimetry (DCS-TGA). The characterization of the synthesized tin sulphides powders included analysis of chemical composition by optical emission spectroscopy, phase composition identification by X-ray diffraction (XRD) and examination of morphology, as well as elemental composition by scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The hexagonal SnS2 and orthorhombic Sn2S3 phases were formed after the thermal treatment of starting powders in nitrogen atmosphere. The obtained results indicate the positive effects of the graphite addition which enables the synthesis of tin sulphide powders with appropriate content of sulphide phases with minimal loss of sulphur. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 34033]

The aim of this study was comparative analysis of catalysts with 5 and 20 wt. % Ni loading, with and without Pd additive, and it included: determination of reduction degrees, investigation on microstructure by scanning electron microscopy and chemical analysis by energy-dispersive spectroscopy. Ni/Al2O3 and Ni-Pd/Al2O3 catalysts supported on α-Al2O3-based foams were synthesized by aerosol assisted impregnation. Impregnation of the foams by ultrasonically aerosolized chlorides was followed by drying at 473 K and hydrogen reduction at 533 and 633 K. Lower Ni loading resulted in higher reduction degrees. Ni loading of 20 wt. % enabled relatively uniform coverage of the foam with a metallic coating. With activity modifier (Pd), nearly complete reduction was achieved at both temperatures. Reduction degrees reached 99.4 and 98.2 wt. % at 533 K for 5 and 20 wt. % of Ni, respectively. [Projekat Ministarstva nauke Republike Srbije, br. 34033: Innovative synergy of by-products, waste minimization and clean technologies in metallurgy]

The possibility of using the waste plastic as reducing agent in blast furnace for obtaining pig iron is in focus for the past couple year. The simulation of blast furnace process in BFC software has been performed in order to analyze the coke and coals saving, CO2 emission and determining the economic benefits. Three different batches were made for comparative analysis, depending on the batch composition and input of batch components into the blast furnace: case 1 (C1), case 2 (C2) and case 3 (C3). The base case, C1 contains sinter (bulk material) which is needed for obtaining 1 tone of pig iron, quartz which provides slag alkalinity and coke as reducing and energy agent. C2 has the same components as C1, but contains pulverized coal instead one part of coke and C3 contains granulated waste plastic instead coke in an approximately the same amount as pulverized coal. The substitution of coke with pulverized coal and waste plastic is 18.6 % and 25.2 %, respectively. The economic, productivity and ecologic aspects have been analyzed. The consumption of each tone of waste plastic in blast furnace saves 360 $, which is 18 times more than its price, bearing in mind that the market price of coke is 380 $/t % and waste plastic 20 $/t. Regarding the specific productivity, it decreases from 2.13 for C1 to 1.87 for C3. From an environmental aspect there are two main benefits: reduction of CO2 emission and impossibility of dioxin formation. The CO2 emission was 20.18, 19.46 and 17.21 for C1, C2 and C3, respectively.

This paper presents the synthesis of nano-composite Cu-Al2O3 powder by a thermochemical method and sintering, with a comparative analysis of the mechanical and electrical properties of the obtained solid samples. Nano-crystalline Cu-Al2O3 powders were produced by a thermochemical method through the following stages: spray-drying, oxidation of the precursor powder, reduction by hydrogen and homogenization. Characterization of powders included analytical electron microscopy (AEM) coupled with energy dispersive spectroscopy (EDS), differential thermal and thermogravimetric (DTA-TGA) analysis and X-ray diffraction (XRD) analysis. The size of the produced powders was 20-50 nm, with a noticeable presence of agglomerates. The composite powders were characterized by a homogenous distribution of Al2O3 in a copper matrix. The powders were cold pressed at a pressure of 500 MPa and sintered in a hydrogen atmosphere under isothermal conditions in the temperature range from 800 to 900 °C for up to 120 min. Characterization of the Cu-Al2O3 sintered system included determination of the density, relative volume change, electrical and mechanical properties, examination of the microstructure by SEM and focused ion beam (FIB) analysis, as well as by EDS. The obtained nano-composite, the structure of which was, with certain changes, preserved in the final structure, provided a sintered material with a homogeneous distribution of dispersoid in a copper matrix, with exceptional effects of reinforcement and an excellent combination of mechanical and electrical properties.

The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623–923 K) and time intervals (1–5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K. [ABSTRACT FROM AUTHOR]

This paper presents thermochemical synthesis of copper/alumina nanocomposites in a Cu-Al2O3 system with 1–2.5 wt.% of alumina and their characterization, which included: transmission electron microscopy: focused ion beam (FIB), analytical electron microscopy (AEM) and high resolution transmission electron microscopy (HRTEM). Thermodynamic analysis was used to study the formation mechanism of desirable products during drying, thermal decomposition and reduction processes. Upon synthesis of powders, samples were cold pressed (2 GPa) in tools dimension 8 × 32 × 2 mm and sintered at temperatures within the range 800–1000 °C for 15 to 120 min in a hydrogen atmosphere. Results of characterization showed that dispersion-strengthened compacts could be produced by sintering of thermo-chemically prepared Cu-Al2O3 powders with properties suitable for material application, such as a contact material exhibiting high strength and high electrical conductivity at the same time. Additional research was carried out in order to analyze the application of the obtained nanocomposite powders for the synthesis of copper/alumina nanocomposites by a new method, which is a combination of a thermochemical procedure and mechanical alloying. The measured values of an electric conductivity and hardness were compared with ones in literature, confirming an advantage of the proposed combined strategy. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of tungsten disulfide (WS2) powder by the sulfurization of tungsten trioxide (WO3) particles in the presence of additive potassium carbonate (K2CO3) in nitrogen (N2) atmosphere, first at lower temperature (200 °C) and followed by reduction at higher temperature (900 °C). In addition, the ultrasonic spray pyrolysis of ammonium meta-tungstate hydrate (AMT) was used for the production of WO3 particles at 650 °C in air. The HSC Chemistry® software package 9.0 was used for the analysis of chemistry and thermodynamic parameters of the processes for WS2 powder synthesis. The crystalline structure and phase composition of all synthesized powders were analyzed by X-ray diffraction (XRD) measurements. The morphology and chemical composition of these samples were examined by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX). [ABSTRACT FROM AUTHOR]