Miodrag Zdujić

Serbian Academy of Sciences and Arts · Institute of Technical Sciences

Synthesis of biodiesel from various plant oils is realized by the transesterification of triglycerides with methanol or by a reaction usually defined as methanolysis. The usage of low-quality oils, such as waste cooking oil (WCO), is followed by undesirable side reactions as a result of the increased content of free fatty acids (FFA), and water. Th...

Deep eutectic solvents (DESs) are called 'designer solvents' due to various structural variations and the benefit of tailoring their physicochemical properties. For industrial applications of DESs it is crucial to know their physical and thermodynamic properties such as density, viscosity, and refractive index. These properties were measured for th...

Hazelnut shell ash was investigated as a new base catalyst for the transesterification of used cooking sunflower oil to biodiesel. To understand its catalytic properties, the prepared ash was characterized by EDX, XRD, TGA/DTA, Hg porosimetry, N2 physisorption, FE-SEM, and basic strength measurements. The effects of the catalyst loading in the rang...

M. V. Zdujić et al On the synthesis of 3-cyano-6-hydroxy-4-methyl-2-pyridone at room temperature ZASTITA MATERIJALA 60 (2019) broj 3 229 ABSTRACT Milling of cyanoacetamide and acetoacetic ester as reactants, in the presence of KOH as the catalyst and ethanol as a viscous control agent (VCA) was performed in a planetary ball mill with the goal of in...

The powder mixtures of calcium oxide (CaO) and silica gel (SiO 2 ) in molar ratios of 1:1, 1.5:1, 2:1 and 3:1 were mechanochemically treated with the addition of water, and were subsequently calcined with a goal of synthesizing CaSiO 3, Ca 3 Si 2 O 7 , Ca 2 SiO 4 compounds and CaO/Ca 2 SiO 4 two-phase mixture. The prepared materials were characteri...

Ten organic solvents (triethanolamine, diethanolamine, ethylene glycol, methyl ethyl ketone, n-hexane, triethylamine, ethylene glycol dimethyl ether, glycerol, tetrahydrofuran and dioxane) were applied as cosolvents in the CaO-catalyzed ethanolysis of sunflower oil performed in a batch stirred reactor under the following reaction conditions: temper...

Triethanolamine was applied as an efficient „green“ cosolvent for biodiesel production by CaO-catalyzed ethanolysis of sunflower oil. The reaction was conducted in a batch stirred reactor and optimized with respect to the reaction temperature (61.6-78.4°C), the ethanol-to-oil molar ratio (7:1-17:1) and the cosolvent loading (3-36 % of the oil weigh...

This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validi...

Molybdenum powders were produced by the rotating electrode process in helium atmosphere. The electrode diameter was 0.01 m and the angular velocity was 524 and 2094 rad/s, respectively. The increase of the angular velocity was followed by the decrease of mean particle size, which was 690 and 193 µm for the indicated angular velocities, respectively...

The fabrication of metal powders the thermophysical properties of which differ considerably, can be performed by the rotating electrode process. The properties of molybdenum, titanium and aluminium powders were discussed. Some results of theoretical calculations concerning both droplets motion and solidification in helium and argon were given.

The continuous biodiesel production from soybean oil was carried out under the subcritical condition of methanol with MnCO3/Na-silicate as a heterogeneous catalyst. The transesterification rate was first investigated in a set of experiments performed in a batch autoclave at 448 K using methanol-to-oil molar ratio of 18:1 and various catalyst loadin...

Choline chloride (ChCl)-based deep eutectic solvents (DESs) with different amides or polyols as hydrogen bond donors were tested as cosolvents in the ethanolysis of expired sunflower oil catalyzed by either calcined or non-calcined CaO. These cosolvents promoted the ethanolysis by a successful activation of non-calcined CaO, which was ascribed to t...

The effects of two different mechanically activated kaolins, AKV (61% kaolinite, 14% quartz and 16% mica) and AKG (51.6% kaolinite and 40.6% quartz) on the compressive strength of cement composites and microstructure of pastes were investigated. Composite mixtures, in which 10, 20, 30, 40 and 50% of ordinary Portland cement (OPC) was replaced by AK...

Тhe MnCO3/Na silicate (Mn/Na/Si mole ratio of 4.65:1:1.65) catalyst in the form of solid particles with diameter of 0.99–1.99 mm was used as a catalyst for transesterification of soybean oil in batch autoclave at different conditions: 388–468 K, methanol-to-oil mole ratio 12:1–30:1, catalyst amount based on the mass of oil 0–12.5 %. The complete tr...

The effects of thermally (MK) or mechanically activated kaolin (AK) on the compressive strength of mortars and microstructure of pastes were investigated. Mortar mixtures, in which 10%, 20% and 30% of ordinary Portland cement (OPC) was replaced by either MK or AK, were prepared (w/b of 0.5) and ordinary (age 2, 28 or 90 days) and autoclave cured. H...

Increased environmental concern and awareness of limited reserves of fossil fuels gave a great importance to alternative and renewable energy sources over the past couple decades. An excellent substitute for mineral diesel fuels is biodiesel, a mixture of fatty acid methyl esters (FAME), made by alcoholysis of different triacylglycerols (TAG) from...

Vegetable oils are mainly esters of fatty acids and glycerol, which can be converted to fatty acid methyl esters (FAME), also known as biodiesel, by the transesterification reaction with methanol. In order to attain environmental benignity, a large attention has been focused in the last decades on utilizing heterogeneous catalysts for biodiesel pro...

Limited reserves of fossil fuels as well as the growing concern for the environment, has led to a worldwide search for renewable energy sources, among which biodiesel, a mixture of fatty acid methyl esters (FAME), is one of the most perspective alternative fuels since it is a non-toxic and can be produced from different renewable sources through si...

In the present work, calcium diglyceroxide (CaDG) was synthesized by mechanochemical treatment of CaO dispersed in glycerol, and characterized by X-ray diffraction (XRD), thermal analysis (TGA/DTA), infrared spectroscopy (FTIR), and Hammett indicator method for base strength determination. The obtained CaDG was tested as a catalyst in the methanoly...

The kinetics of heterogeneous methanolysis of sunflower oil was studied at 60 degrees C using mechanochemically synthesized CaO center dot ZnO as catalyst. The influence of agitation speed, catalyst amount, and methanol-to-oil molar ratio on the rate of reaction was analyzed. The rate of the process depends on the two resistances - mass transfer of...

The goal of this study was to prepare CaO.ZnO catalyst which contain small amount of K2CO3 and analyze its activity for biodiesel synthesis. Catalyst was prepared using the following procedure: CaO and ZnO (molar ratio of 1:2), water and K2CO3 (in various amounts) were mechanochemically treated and after milling heated at 700 oC in air atmosphere f...

The kinetics of heterogeneous methanolysis of sunflower oil and used vegetable oil were studied at different temperatures, ranging from 60 to 96 degrees C using CaO center dot ZnO as catalyst (2 wt% on the basis of oil) and methanol to oil molar ratio of 10:1. Heterogeneous CaO center dot ZnO catalyst was synthesized by mechanochemical treatment of...

Mechanochemical treatment of Serbian kaolin clay was performed in a planetary ball mill using two different milling media, hardened steel or zirconia vials and balls. The samples obtained after various milling times were characterized by particle size laser diffraction (PSLD), X-ray diffraction (XRD), differential scanning calorimetry/thermogravime...

The transesterification of triglycerides (vegetable oil) with methanol using CaO·ZnO mixed oxides catalyst were conducted to produce FAME (Fatty Acid Methyl Esters, i.e. biodiesel). Catalyst was synthesized by ball milling of CaO and ZnO powder mixture (using molar ratio of Ca and Zn of 1:2 and 1:4) with the addition of water, as well as solely by...

In this study, the synthesis of biodiesel or fatty acid methyl esters (FAME) from sunflower oil and methanol using CaO·ZnO catalyst was investigated. Catalyst was synthesized by ball milling of Ca(OH)2 and ZnO powder mixture with the addition of water (BMH), as well as solely by ball milling of mentioned powders (BM) and subsequent calcination at 7...

Nanosized perovskite YTiO 3 with mean crystallite size of 18 nm was synthesized for the first time by mechanochemical treatment. The mechanochemical solid state reaction between commercial Y 2O 3 powder and mechanochemically synthesized TiO powder in molar ratio 0.5:1 was performed over 3 h in a high-energy planetary ball mill in argon atmosphere....

Nano-sized titanium monoxide (TiO) powder was prepared by mechanochemical synthesis. A mixture of commercial Ti and TiO2 (rutile) powders with the molar ratio of 1:1 was milled in a planetary ball mill for 5, 10, 20, 30 and 60 min under argon atmosphere. The final single-phase titanium monoxide sample was characterized by X-ray diffraction (XRD), m...

Powder mixtures of alpha-Bi2O3 containing 2, 5 and 10 mol % of TiO2, ZrO2 or HfO2 were homogenized, heated at 820 degrees C for 24 h and quenched in air. The X-ray powder diffraction technique was used to characterize the prepared samples. In all cases, metastable Bi2O3 polymorphs, gamma-Bi2O3 or beta-Bi2O3, were found as single or major phases. Th...

Extra phase-pure Li4Ti5O12 spinel with particle sizes less than 500 nm was synthesized by solid state reaction of mechanochemicaly activated mixture of nano anatase and Li2CO3 for a very short annealing time, 4 h at 800 °C. Structural and microstructural properties, the mechanism of solid state reaction between anatase and Li2CO3 as well as thermal...

Several samples of oxygen deficient titanium oxides (TiO, Ti4O7, Ti5O9, Ti6O11) or their mixtures were prepared using mechanochemical procedure followed, in some cases, by thermal treatment. The prepared oxides, mixtures identical or similar to Ebonex powder, and original Ebonex powder have proceeded into plastic–bonded foil electrodes using a lo...

The effect of thermal treatment atmosphere (argon, air or oxygen) on the electret behavior of bismuth titanate (Bi4Ti3O12) ceramics was investigated. Polycrystalline ferroelectric ceramics were prepared by reactive liquid phase sintering. Sintered samples were polarized applying an electric field, Ep = 1 MV m−1 at 100 °C for 60 min. Effective surfa...

Concurrent milling of Bi4Ti3O12 was carried out in a planetary ball mill with hardened-steel 13 or 6mm diameter balls with a goal to investigate how the system responds to the constrains imposed by milling. Milling intensity for various milling parameters was derived from the electrical power measurement. The reverse amorphous ↔ crystalline phase t...

A powder mixture of a-Bi2O3 and HfO2, in the molar ratio 2:3, was mechanochemically treated in a planetary ball mill under air, using zirconium oxide vials and balls as the milling medium. After 50 h of milling, the mechanochemical reaction led to the formation of a nanocrystalline a-Bi2O3 phase (fluorite-type solid solution Bi0.87Hf0.59Zr0.63O3.61...

Mechanochemistry represents an alternative route in synthesis of nanomaterials. Mechanochemical routes are attractive because of their simplicity, flexibility, and ability to prepare materials by solid state reactions at room temperature. The aim of this work is the mechanochemical synthesis of nanostructured titanium oxides of different compositio...

The Auger and XPS technique has been used for investigation in the surface of bismuth titanate (Bi4Ti3O12) (BIT) ceramics obtained by reactive sintering from Bi2O3 and TiO2 oxides. All peaks characteristic for bismuth, titanium and oxygen are clearly visible in the spectrum. Oxygen vacancies are preferentially sited in the vicinity of bismuth ions...

Concurrent milling of Bi4Ti3O12 was carried out in a planetary ball mill with hardened-steel 13 or 6 mm diameter balls with a goal to investigate how the system responds to the constrains imposed by milling. Milling intensity for various milling parameters was derived from the electrical power measurement. The reverse amorphous - crystalline phase...

Mechanochemistry represents an alternative route in synthesis of nanomaterials. Mechanochemical routes are attractive because of their simplicity, flexibility, and ability to prepare materials by solid state reactions at room temperature. First part of this work is review of nanomaterials prepared by mechanochemical treathment. The aim of the work...

Nanocrystalline cubic titanium monoxide, TiOx (0.92 < x < 1.19), with mean crystallite size of ≈ 6 nm, was synthesized by mechanochemical treatment of Ti and TiO2 (rutile) powder mixtures with molar ratios of 1:1, 1.10:1 and 1.25:1. The mechanochemical solid state reaction in a high-energy planetary ball mill was completed for 2 h in either air or...

Powder mixtures of α-Bi2O3 (bismite) and monoclinic m-ZrO2 (baddeleyite) in the molar ratio 2:3 were mechanochemically and thermally treated with the goal to examine the phases, which may appear during such procedures. The prepared samples were characterized by X-ray powder diffraction, differential scanning calorimetry (DSC), electrical measuremen...

Two new series of perovskite-type oxides LaMO3 (M=Mg, Ti, Fe) with different ratio Mg/Fe (MF) and Ti/Fe (TF) in the B cation site were prepared by annealing the precursor, obtained by the mechanochemical activation (MCA) of constituent metal oxides, at 1000°C in air. In addition, two closely related perovskites LaFeO3 (LF) and LaTi0.5Mg0.5O3 (TM (5...

The ZnO and ZrO2 powders were prepared by mechanochemical processing and subsequent heat treatment of the starting powder of precursors mixture of ZnCl2 and Ca(OH)2, and ZrOCl 2·8H2O and NaOH, respectively. Inert salt matrix, ether CaCl2 or NaCl, which prevents particle agglomeration was formed during mechanochemical solid state reaction. After mec...

The ZnO and ZrO 2 powders were prepared by mechanochemical processing and subsequent heat treatment of the starting powder of precursors mixture of ZnCl 2 and Ca(OH) 2 , and ZrOCl 2 ·8H 2 O and NaOH, respectively. Inert salt matrix, ether CaCl 2 or NaCl, which prevents particle agglomeration was formed during mechanochemical solid state reaction. A...

Titanium monoxide belongs to the class of highly nonstoichiometric interstitial phases and exists in a wide composition range, from TiO0.80 to TiO1.25. Even among highly nonstoichiometric compounds TiOy is unique in the sense that it contains a large amount of both, metal and non-metal vacancies. To adequately describe the defect structure of titan...

Concurrent mechanochemical treatment of either a stoichiometric 2Bi(2)O(3)(.)3TiO(2) powder mixture or (pulverized) Bi4Ti3O12 compound was performed in a planetary ball mill. Relevant structural parameters: crystallite size, amount of amorphous phase and the transformed fraction (as a result of chemical reaction between Bi2O3 and TiO2) of the powde...

Concurrent mechanochemical treatment of either a stoichiometric 2Bi2O3·3TiO2 powder mixture or (pulverized) Bi4Ti3O12 compound was performed in a planetary ball mill. Relevant structural parameters: crystallite size, amount of amorphous phase and the transformed fraction (as a result of chemical reaction between Bi2O3 and TiO2) of the powders mille...

This review attempts to give a short account of the main aspects of mechanochemical treatment such as: (a) mechanical alloying; (b) commonly used milling units, herewith the influence of milling parameters on the rate and products of mechanochemical treatment; (c) structural changes; (d)mechanochemical reactions; (e) subsequent heat treatment; and...

Mg2Ni-type alloys, i.e., Mg2Ni, Mg2Ni0.75Cu0.25, Mg2Ni0.6Cu0.4 and Mg2Ni0.75V0.25 were synthesized by mechanical alloying and subsequent thermal treatment starting from a corresponding elemental powder mixture. The kinetics of hydrogen absorption and desorption of annealed materials were measured using a manually controlled Sieverts apparatus. The...

The mixed perovskite type oxides with nominal formula LaTi0.5Mg0.5−xPdxO3, (0 ≤ x ≤ 0.10) were prepared by anneling the ethanol solution of precursor in nitrogen flow at 1200 °C. X-ray powder diffraction (XRPD) analysis shows that the orthorhombic perovskite structure was found in all investigated samples. However, at least a part of palladium is n...

Milling is an important step in the processing of metallic and ceramic powders. Its primary usage has been for particle size reduction/growth and change of particle shape as well as for homogenization of mixture of two or more powders which will be subsequently compacted, for example, by pressing and sintering. However, milling may lead (and leads)...

A powder mixture of α-Bi2O3 and ZrO2, both monoclinic, in the molar ratio 2 : 3, was mechanochemically treated in a planetary ball mill in an air atmosphere for up to 20 h, using steel vial and hardened-steel balls as the milling medium. Mechanochemical reaction leads to the gradual formation of an amorphous phase. After 5 h of milling the starting...

A series of γ-Bi2O3 phases doped with Zn, Si, Pb and Fe was prepared by mechanochemical treatment of corresponding oxide mixtures with a nominal composition 6Bi2O3·MOx (MOx=ZnO, SiO2, PbO) and 12Bi2O3·Fe2O3 using high-energy ball mill. The products are characterized by X-ray powder diffraction technique. Influence of milling conditions: milling tim...

Perovskite-type oxide of LaTi0.5Mg0.5O3 composition was synthesized from constituent oxide precursors by mechanochemical activation method in a high power planetary ball-mill, followed by thermal treatment of the product in air. The phase composition after mechanochemical activation of the binary and ternary mixtures was studied by XRPD, while the...

One of the distinguishing features of mechanochemical treatment is crystallite size reduction. The crystallite size of the powder subjected to milling decreases to some minimal value characteristic for the given material. Two processes occur concurrently during milling: reduction of the crystallite size and grain growth, whereby the steady-state cr...

The electrochemical characteristics of the La0.8Ce0.2Ni2.5Co1.8Mn0.4Al0.3 compound, produced by mechanical alloying, are investigated for hydrogen storage in nickel-metal hydride (NiMH) batteries by discharging tests at constant current and by calculating equilibrium pressure of hydrogen from the equilibrium potentials. It is shown that the alloy p...

The mechanochemical treatment of α-Fe2O3 powder was done concurrently in air and oxygen atmospheres using a conventional planetary ball mill. The influence of the duration of milling and of the balls-to-powder mass ratio on the transformation of α-Fe2O3 was investigated. Under appropriate milling conditions, α-Fe2O3 completely transforms to Fe3O4,...

Powder of α-Fe2O3 was mechanochemically treated in a planetary ball mill in an air atmosphere. Structural changes were followed by X-ray diffraction analysis, magnetization measurements and differential scanning calorimetry after various milling times. It was found that complete transformation of α-Fe2O3 to Fe3O4 is possible during milling in an ai...

The kinetics and mechanism of hydrogen evolution at Ti-Ni alloy electrodes prepared by arc-melting and mechanical alloying methods has been studied by means of AC impedance spectrum measurements. The electrode, prepared by mechanical alloying (porous electrode), after activation in a 10% HF solution, is very active despite its large Tafel slope. Th...

A comparative study of the microstructure, mechanical properties and fractography of Ni3Al macro- and microalloyed intermetallics produced by powder metallurgy (PM) and standard vacuum melting and casting processes has been carried out. Non-porous PM compacts were obtained by vacuum hot pressing of powders produced either by gas atomization or by a...

Intermetallic compounds have long been recognized as potentially useful structural materials. Ni3Al aluminides possess excellent oxidation resistance at high temperatures as well as good high-temperature strength. This paper reviews the progress which has been made during the last few years in the research and development of Ni3Al aluminides. Compa...

A mixture of crystalline NiO and α-Fe2O3 powders in equimolar ratio was mechanochemically treated in a planetary ball mill up to 50 h of milling. The mechanochemical reaction leading to the formation of the NiFe2O4 spinel phase was followed by X-ray diffraction and magnetization measurements. The spinel phase was first observed after 10 h of millin...

The effect of oxidation and reduction atmospheres on the ferroelectric behavior of bismuth titanate was investigated. The effective surface density σ_eff of free charges in samples polarized by applying an electric field E_p=1 MV m^-1 at a temperature of 100°C for 90 min was determined by compensation voltage measureme...

Rapidly solidified powder of Ni3Al intermetallic compound modified with Fe, Ti and B was produced by a rotating electrode process (REP). The obtained powder has a mean particle size of 400 urn, spherical shape and very narrow size distribution. The powder was compacted by hot pressing to non-porous, homogeneous compacts with an average grain size o...

The thermal behaviour of Al-xat.%Mo (sx=, 10, 17, 20, 27, 50 and 75 powders mechanically alloyed in a conventional ball mill was investigated by differential scanning calorimetry, differential thermal analysis and X-ray diffraction. The temperature and heat of the solid state reactions leading to the formation of intermetallic phases markedly varie...

Rapidly solidified powder of Ni3Al intermetallic compound modified with Fe, Ti and B was produced by a rotating electrode process (REP). The obtained powder has a mean particle size of 400 micrometers, spherical shape and very narrow size distribution. The powder was compacted by hot pressing to non-porous, homogeneous compacts with an average grai...

The thermal behaviour of powders obtained by mechanically alloying elemental crystalline nickel and molybdenum powders for various times was investigated using differential scanning calorimetry (DSC) and linked to structural data obtained by X-ray diffraction. The two observed exothermic heat effects were correlated with the milling time. The heat...

Mechanochemical treatment of ZnO-Al2O3 powder mixtures of nominal compositions 0, 10, 50 and 100 mol% Al2O3 was carried out in a planetary ball mill up to 10 h of milling. Structural changes as a consequence of milling were followed by X-ray diffraction. Two possibilities of intensive ball milling were demonstrated: one is the synthesis of the ZnAl...

An amorphous Ni-50 at.% Mo alloy powder was prepared by mechanical alloying a mixture of elemental crystalline nickel and molybdenum powders in a conventional ball mill. The amorphous nature and the thermal stability of the powders obtained at various milling times were investigated by X-ray diffraction, transmission electron microscopy and differe...

Mechanical alloying of elemental aluminium and molybdenum powders was performed by conventional low-energy ball milling. Seven compositions (Al-3, 10, 17, 20, 27, 50 and 75 at% Mo), as well as elemental aluminium and molybdenum powders, were milled up to 1000 h. The structural changes during milling were followed by X-ray diffraction. In all cases...

Mechanical alloying of elemental aluminium and molybdenum powders was performed by conventional low-energy ball milling. Seven compositions (Al-3, 10, 17, 20, 27, 50 and 75 at% Mo), as well as elemental aluminium and molybdenum powders, were milled up to 1000 h. The structural changes during milling were followed by X-ray diffraction. In all cases...

Mechanical alloying of elemental powders of aluminum and molybdenum (Al-3 at.% Mo) has been carried out in a conventional horizontal ball mill up to 1000 h of milling time. Mechanically alloyed powders were investigated by scanning electron microscopy, X-ray diffraction analysis and differential scanning calorimetry. After prolonged milling time, m...

Crystallization kinetics of partially crystallized Ti-5 Al alloy powders obtained by the rotating electrode processes have been studied by differential thermal and X-ray diffraction analyses. It is shown that only powders not exceeding a particle size of 90 μm are characterized by a sharp irreversible exothermal peak in the DTA curve which can be a...

Molybdenum powders were produced by the rotating electrode process in helium atmosphere. The electrode diameter was 0.01 m and the angular velocity was 524 and 2094 rad/s, respectively. The increase of the angular velocity was followed by the decrease of mean particle size, which was 690 and 193 μm for the indicated angular velocities, respectively...

Cooling of powders of thirty metals which can be atomized by the rotating electrode process was theoretically considered assuming that heat extraction from spherical droplets occurs during their flight through the helium inert atmosphere. Cooling times and solidification path lengths as well as the cooling rates were numerically calculated for the...

Properties and cooling rates of steel powders produced by rotating electrode process (REP) in argon and helium were studied. The mean particle size and particle size distribution can be precisely controlled changing the angular velocity and the melting rate of rotating electrode. It enables the fabrication of powders with a very narrow particle siz...