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Sintering of Cordierite in the Presence of MoO3 and Crystallization Analysis
No full textCordierite (MAS) is difficult to sinter because of the very narrow sintering temperature range (1300-1400 degrees C). Because a low temperature process is desirable, it is necessary to find functional ads which can allow easier sintering process at lower temperature. The influence of MoO3 on the preparation process of cordierite ceramics was investigated. 2MgO-2Al(2)O(3)-5SiO(2) was researched by sintering followed binary systems: MgO/MoO3, Al2O3/MoO3 and SiO2/MoO3 (all sintered at 850 degrees C and 1100 degrees C, sintering time 2h). Composition of these systems was 80 mass% of oxide and 20 mass% MoO3. The effects of sintering, the composition and morphology were followed by X-ray diffraction and SEM microscopy. It has been found that MoO3, beside liquid phase, forms intermediary unstable compounds with MgO and Al2O3, which is the significance information for further research. MAS ceramics were sintered with 20 mass% MoO3 at 1100 degrees C, 1200 degrees C and 1300 degrees C, during 2h
Utilization of Phosphate Rock from Lisina for Direct Application: Release of Plant Nutrients in the Exchange-Fertilizer Mixtures
No full textThis study examined the possibility of direct application of phosphate rock (PR) from Lisina deposit, in a mixture with natural clinoptilolite (Cp) and clinoptilolite partially saturated with ammonium ions (NH4Cp). Solution P concentrations of the NH4Cp/PR mixtures were sufficient for plant growth and ranged from 0.36 to 0.82 mg L-1. The median NH4Cp/PR ratio and the longest proposed mixing time had the most positive impact on the P concentration. Solution Ca concentrations of the NH4Cp/PR mixtures were between 112.5 and 700.5 mg L-1, indicating that use of the proposed NH4Cp/PR mixtures solves the potential lack of Ca2+ in the solution, which is typical for substrates of similar composition. Selected artificial neural networks (ANNs) were able to predict experimental variables for a broad range of the process parameters all through assay. Manifold effects of small changes in composition of the mixtures and time on the observed concentrations of nutrients were shown using the sensitivity analysis
Influences of synthesis methods and modifier addition on the properties of Ni-based catalysts supported on reticulated ceramic foams
No full textA method of synthesizing Ni-based catalysts supported on alpha-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al2O3 catalysts, the chloride reduction route enabled the formation of a Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness (533 and 633 K) were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method
Thermal, structural and electrical properties of some bi-cu-ni alloys
No full textThe Bi-Cu-Ni ternary system belongs to the group of potential Cu-Ni-based advanced lead-free solder materials for high temperature application. In this study microstructure investigation of the slow-cooled Bi-Cu-Ni samples was done using SEM-EDS analysis. The samples compositions were chosen along three cross-sections with molar ratio Cu:Ni=1:3, 1:1 and 3:1. The experimentally obtained phase structure was compared with the results of thermodynamic calculation according to CALPHAD method. Also, new results regarding thermal and electrical properties investigations of these alloys are presented in this paper, based on DSC and electroconductivity measurements
Optimization of the recycling processes for magnesium from a highly contaminated waste
No full textWith the recently increased use of magnesium alloys, especially in the automotive industry, a large quantity of generated waste, based on magnesium alloys, is expected. Such a waste often contains many impurities such as oil, paint, moisture, non-metallic fractions, oxides, Cu, Fe, etc. In this paper, two different methods for extracting magnesium from a highly contaminated waste are presented: the recycling of magnesium with flux and with the vacuum-distillation process. In addition, we present the process of pre-treating the contaminated magnesium waste that has proved to be a very important step in the recycling process for both economic and environmental reasons. The processing of post-consumer and contaminated magnesium scrap is described with a diagram, providing a sustainable and environmentally friendly procedure for the treatment of such wastes
Properties improvement of the al 7075 alloy castings
No full textU radu je prikazana mogućnost dobijanja homogenije mikrostrukture i ravnomernije raspodele legirajućih elemenata Zn i Mg u aluminijumskoj leguri EN AW 7075, prilikom livenja u prisustvu elektromagnetnog polja. Ispitana su i mehanička svojstva uzoraka koji su odliveni bez i sa elektromagnetnin poljem. Rezultati pokazuju da se livenjem u elektromagnetnom polju postižu prednosti u odnosu na klasičan postupak livenja aluminijumskih legura.The microstructure and the mechanical properties of the samples obtained by conventional vertical continuous casting and electromagnetic casting of 7075 aluminum as-cast alloy were investigated. The better surface quality, more homogeneous alloying elements distribution and hence the microstructure and better mechanical properties were obtained in samples casted with electromagnetic field (EMF) compared with samples casted without EMF. The microstructure was analyzed by optical microscope and the variation of alloying elements, Zn and Mg, through the sample cross section was examined by chemical analysis. The mechanical properties of samples casted with and without electromagnetic field were determined using computerized materials testing machine Zwick/Roel Z 100
Modeling the mill operation according to density of mill batch and specific capacity
No full textU radu je prikazana nova metoda modelovanja tehnoloških parametara rada mlina za nove uslove mehano-hemijskog tretmana mineralne sirovine na bazi hipoteze Buckinghama. Specifični kapacitet projektovanog mlina menja se ukoliko dolazi do promene gustine šarže mlina, a zavisnost te promene određuje se upotrebom kriterijumskih jednačina. Uvidom u većinu poznatih dimenzionih kriterijuma uočeno je da bi Damkohler-ov kriterijum mogao kvantitativno da modeluje specifični kapacitet i gustinu šarže mlina.This paper presents a new method of modeling the technological parameters of mill for the new conditions of mechanochemical treatment of mineral resources based on the Buckingham hypothesis. The specific volume of designed mill is changed if there is a change in the charge density of the mill, and dependence of the change is determined using a criterion equation. After examining the most wellknown dimensional criteria, it was observed that Damkohler's criterion would quantitatively model the specific volume and density of the mill batch
Quality of Zeolite in the Function of Size Class
No full textTesting of the quality of zeolite from the Igros and Donje Jesenje deposits was carried out by size classes. The objective of the testing was to point out the importance of the selection of the preparation procedure in determining the quality of individual size classes provide the required quality of zeolite product range. The results indicate that the Igros and Donje Jesenje zeolite deposits differ by the quality of some size classes. While the Igros sample has better quality of fine size classes, in the case of the Donje Jesenje deposit, the sample size class -2.4 +0.4 mm indicates better quality. Specifically, the cation exchange capacity (CEC) of the Igros zeolite is the highest at 161.25 meq/100g in the case of size class -5 +2.4 mm, while the highest CEC of zeolite from the Donje Jesenje deposits, 163.97 meq/100g, was found for the class -0.4 +0.063 mm. The results of XRD analyses showed that the mineral content was distributed differently in the Igros sample relative to the Donje Jesenje sample. The XRPD results showed a higher content of zeolite minerals in coarse size classes of the Igros sample, while in the Donje Jasenje zeolite, the size class of -0.063 +0 mm, and the presence of feldspar and lower content of clinoptilotite were observed. These results indicate that it is necessary to use the methods for obtaining finer size classes and classification in order to achieve the required quality of zeolite product range
Investigation of efficiency of different sorption materials for Cu(II) removal from aquous solutions
No full textU ovom radu je ispitivana efikasnost (bio)sorpcije više materijala u uklanjanju bakarnih jona iz vodenog rastvora. Koncentracija bakarnih jona u rastvoru je bila 2mmol/l, M/V odnos 10 g/l, a pH rastvora je bio podešen na 5. Karakterizacija korišćenih materijala je izvršena uz pomoć skenirajuće elektronske mikroskopije. SEM-EDX analize materijala ukazuju na to da se vezivanje bakra dešava uglavnom preko jonske izmene.Uklanjnjanje jona bakra je ispitivano na sledećim materijalima: M.spicatum, koštica breskve, koštica kajsije, oklasak kukuruza, bentonit, zeolit, apatit, apatit i modifikovani NH4 zeolit i modifikovani NH4 zeolit. Najbolji rezultati dobijeni su sa bentonitom i biomasom M.spicatum. Stoga, bi trebalo ispitati mogućnost primene kombinovanih adsorbenata. Takođe, ovaj rad ima za cilj da promoviše biosorpciju i adsorpciju kao alternativne tehnologije za prečišćavanje otpadnih voda zasnovanih na upotrebi ekonomski prihvatljivih bioloških otpadnih materija i mineralnih sirovina koje karakterišu niske cene i visoka efikasnost.In the present study the (bio)sorption efficiency of different materials for the removal of copper ions from aqueous solution has been investigated. Concentration of cooper ions in solutions was 2mmol/l, M/V ration 10 g/l and pH of the solutions were adjusted at 5. Used materials were characterized by scanning electron microscopy. SEM-EDX analyses of some materials indicate that copper binding occurs mainly through ion exchange mechanism, between Cu(II) and exchangeable cations. Removal of copper ions was investigated in the following materials: M. spicatum, peach pits, apricot pits, corn cobs, bentonite, zeolite, apatite, apatite and NH4 modified zeolite and modified zeolite NH4. Best results in copper ions removal showed bentonite and M.spicatum. Therefore, it should examine the possibility of using combined adsorbents. The work is aimed to promote biosorption and adsorption as alternative technologies for wastewater treatment based on the use of economically acceptable biological waste materials and mineral raw materials which are characterized by low cost and high efficiency
Processes at the inetrface molten metal-sand mold
No full textThe processes that take place at the liquid metal-sand mold interface during the casting and crystallization of metal were studied in this paper. The mold was made using the CO2 - Method, with the addition of active components, such as: MgO, TiO2, AIK(SO4)(2) and Na2SO4. At the liquid steel pouring temperature, these active components undergo decomposition in the mold, caused by heat release during pouring, Crystallization and cooling of castings. Silicates, which have an important influence on casting surface quality, are formed as a result of the interaction between the mould material and liquid steel