Modern industrial requirements include not only the usage of constructive materials with good mec... more Modern industrial requirements include not only the usage of constructive materials with good mechanical properties but also materials obtained through environmentally friendly and low-cost processing procedures. Basalt, as a low-cost raw material, is regarded as a good candidate for industrial constructive parts production. In the present study, andesite basalt originated from the deposit site "Donje Jarinje", Serbia, was examined as a potential raw material for high-density ceramics production. The production of high-density ceramics included dry milling, homogenization, cold isostatic pressing, and sintering in the air. To determine the optimal processing parameters the sintering was conducted at 1040, 1050, 1060, 1070, and 1080 °C, and afterward the sintering duration was varied from 30 to 240 min at the optimal sintering temperature of 1060 °C. Characterization of the starting and sintered materials included the estimation of particle size distribution, density, hardn...
ABSTRACT Intention of this work was to obtain porous silicon dioxide ceramics by using boric acid... more ABSTRACT Intention of this work was to obtain porous silicon dioxide ceramics by using boric acid as an inexpensive additive at low forming pressure and low sintering temperature. Starting raw material, smectite clay from surface coal mine Kolubara, Serbia, was purified from organic and inorganic impurities by using heat and chemical treatment. Boric acid was used as binding and sintering aid in amount of 0.5, 1 and 2 wt%. Powder was compacted by using different pressures: 40, 60 and 80 MPa. Pressed samples were sintered at 850, 1000, 1150, and 1300 degrees C for 4 h in air. A relatively high porosity of nearly 40% is obtained for the samples pressed at 40, 60 and 80 MPa and sintered at 1000 degrees C. Median pore size diameters are in the range of macroporous up to 0.2 mu m and 10 mu m in the samples sintered at 1150 and 1300 degrees C, respectively. X-ray diffraction (XRD), scaning electron microscopy (SEM), and porosimetry measurements were employed to characterize the phases and microstructure of the obtained ceramics. The relations between mechanical characteristics of samples (Young modulus and Poisson ratio) and content of boric acid were studied.
The effect of multiple recasting of commercial Co-Cr base dental alloy (Dentalit-C) on its struct... more The effect of multiple recasting of commercial Co-Cr base dental alloy (Dentalit-C) on its structural characteristics and ion release rates in artificial saliva has been investigated. The number of recasting was once, four and eight times. The as-cast microstructure became more uniform as the number of recasting was increased whereby macro and microhardness and electrical conductivity of the castings decreased. Metallic ion release in artificial saliva was monitored in vitro over the period of 22 weeks at the temperature of 37 0C and pH 2.3. Only Co and Fe were evidenced in artificial saliva and their release rates are measured. The ion release rates increases with time. The ion release rate of Fe was larger than Co. The ion release rates increases substantially by increasing the number of recasting.
Novel three-dimensional cobalt powder structures were successfully prepared by electrodeposition.... more Novel three-dimensional cobalt powder structures were successfully prepared by electrodeposition. Electrodeposited cobalt powder was characterized by scanning electron microscopy (SEM) and light microscopy. It was possible to control the morphology and structure of cobalt particles by adjusting process parameters of electrodeposition such as current density and type of working electrode. The morphology and structure of cobalt powders were investigated and the formation mechanism of agglomerate was also discussed.
One of the important tasks of evaluating the integrity of mechanical process elements and structu... more One of the important tasks of evaluating the integrity of mechanical process elements and structures is to determine the local mechanical properties. In this paper, experimental and numerical analyses of the mechanical behavior of an output inter-heater tube, made of 12H1MF heat-resistant steel, was performed after 200,000 h of exploitation. During exploitation, the tube was exposed to various mechanisms of damage including gas corrosion. The tube was cut from a pipe system during reparations of a thermal power plant, and then cold-deformed by bending to obtain a U-bend tube, which was then used in the experiment. For this purpose, a specimen holder made of structural steel S235 was specifically designed to test such a sample. The U-bend tube was then exposed to the external compressive load during the experiment. Experimental research was based on the application of the 3D digital image correlation (DIC), while a finite element method (FEM) was applied in numerical simulation perfo...
Parts of industrial machines and structures are often exposed to the action of aggressive environ... more Parts of industrial machines and structures are often exposed to the action of aggressive environments, which in a short period of time can provoke the loss of their integrity. It is well known that for extending the service life against erosion and corrosion, protection of the exposed structure zone by coating is frequently used. Various application methods of protective coatings are applied, and the most common are welding and thermal spraying processes. The aim of this study was characterization of coatings made of stainless steel 316L, widely used in chemical and petrochemical industries. The coating was applied on a structural steel S235JR by plasma transferred arc using powder as a filler material. Due to a number of advantages, the plasma transferred arc (PTA) surfacing process has found significant usages in the field of surface protection. This paper presents results of hardness measurements in characteristic zones of the coating and the base material, as well as microstruc...
Introduction. Increases in market prices of gold over the last 20 years have led to expansion of ... more Introduction. Increases in market prices of gold over the last 20 years have led to expansion of basic dental alloys, which, primarily due to their good mechanical properties and acceptable prices, have found their place in everyday dental practice. However, within the procedure of making dental prosthetic restorations, the alloys are melted and cast, which leads to changes in their physical, mechanical and biological properties. Objective. The objective of the study was to test biocompatibility of a Ni-Cr dental alloy (WIRON 99) depending on the number of melting and casting processes. Methods. The working method included the testing of cytotoxicity of the alloy obtained by casting after one, after four, and after eight successive processes of melting. Cytotoxicity of samples was tested by means of a 24-hour and a three-day cytotoxicity test, done on L929 fibroblasts. Results. A repeatedly melted and cast alloy shows a reduced biocompatibility and causes specific responses of the t...
Cobalt 3D powder particles were successfully prepared by the galvanostatic electrodeposition. Ele... more Cobalt 3D powder particles were successfully prepared by the galvanostatic electrodeposition. Electrodeposited cobalt powder were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS) analysis and SQUID magnetometry. It has been shown that morphology, structure and magnetic properties of cobalt particles are closely associated and can be easily controlled by adjusting process parameters of electrodeposition. Morphology of cobalt powder particles is strongly affected by hydrogen evolution reaction as a parallel reaction to cobalt electrodeposition. Depending on the applied current density, the two types of powder particles were formed: dendrites at lower and spongy-like particles at higher current densities. Morphologies and structures of powder particles are correlated with their magnetic properties, and compared with those of the bulk cobalt. In comparison with the properties of bulk cobalt, the obtained 3D structures exh...
Modern industrial requirements include not only the usage of constructive materials with good mec... more Modern industrial requirements include not only the usage of constructive materials with good mechanical properties but also materials obtained through environmentally friendly and low-cost processing procedures. Basalt, as a low-cost raw material, is regarded as a good candidate for industrial constructive parts production. In the present study, andesite basalt originated from the deposit site "Donje Jarinje", Serbia, was examined as a potential raw material for high-density ceramics production. The production of high-density ceramics included dry milling, homogenization, cold isostatic pressing, and sintering in the air. To determine the optimal processing parameters the sintering was conducted at 1040, 1050, 1060, 1070, and 1080 °C, and afterward the sintering duration was varied from 30 to 240 min at the optimal sintering temperature of 1060 °C. Characterization of the starting and sintered materials included the estimation of particle size distribution, density, hardn...
ABSTRACT Intention of this work was to obtain porous silicon dioxide ceramics by using boric acid... more ABSTRACT Intention of this work was to obtain porous silicon dioxide ceramics by using boric acid as an inexpensive additive at low forming pressure and low sintering temperature. Starting raw material, smectite clay from surface coal mine Kolubara, Serbia, was purified from organic and inorganic impurities by using heat and chemical treatment. Boric acid was used as binding and sintering aid in amount of 0.5, 1 and 2 wt%. Powder was compacted by using different pressures: 40, 60 and 80 MPa. Pressed samples were sintered at 850, 1000, 1150, and 1300 degrees C for 4 h in air. A relatively high porosity of nearly 40% is obtained for the samples pressed at 40, 60 and 80 MPa and sintered at 1000 degrees C. Median pore size diameters are in the range of macroporous up to 0.2 mu m and 10 mu m in the samples sintered at 1150 and 1300 degrees C, respectively. X-ray diffraction (XRD), scaning electron microscopy (SEM), and porosimetry measurements were employed to characterize the phases and microstructure of the obtained ceramics. The relations between mechanical characteristics of samples (Young modulus and Poisson ratio) and content of boric acid were studied.
The effect of multiple recasting of commercial Co-Cr base dental alloy (Dentalit-C) on its struct... more The effect of multiple recasting of commercial Co-Cr base dental alloy (Dentalit-C) on its structural characteristics and ion release rates in artificial saliva has been investigated. The number of recasting was once, four and eight times. The as-cast microstructure became more uniform as the number of recasting was increased whereby macro and microhardness and electrical conductivity of the castings decreased. Metallic ion release in artificial saliva was monitored in vitro over the period of 22 weeks at the temperature of 37 0C and pH 2.3. Only Co and Fe were evidenced in artificial saliva and their release rates are measured. The ion release rates increases with time. The ion release rate of Fe was larger than Co. The ion release rates increases substantially by increasing the number of recasting.
Novel three-dimensional cobalt powder structures were successfully prepared by electrodeposition.... more Novel three-dimensional cobalt powder structures were successfully prepared by electrodeposition. Electrodeposited cobalt powder was characterized by scanning electron microscopy (SEM) and light microscopy. It was possible to control the morphology and structure of cobalt particles by adjusting process parameters of electrodeposition such as current density and type of working electrode. The morphology and structure of cobalt powders were investigated and the formation mechanism of agglomerate was also discussed.
One of the important tasks of evaluating the integrity of mechanical process elements and structu... more One of the important tasks of evaluating the integrity of mechanical process elements and structures is to determine the local mechanical properties. In this paper, experimental and numerical analyses of the mechanical behavior of an output inter-heater tube, made of 12H1MF heat-resistant steel, was performed after 200,000 h of exploitation. During exploitation, the tube was exposed to various mechanisms of damage including gas corrosion. The tube was cut from a pipe system during reparations of a thermal power plant, and then cold-deformed by bending to obtain a U-bend tube, which was then used in the experiment. For this purpose, a specimen holder made of structural steel S235 was specifically designed to test such a sample. The U-bend tube was then exposed to the external compressive load during the experiment. Experimental research was based on the application of the 3D digital image correlation (DIC), while a finite element method (FEM) was applied in numerical simulation perfo...
Parts of industrial machines and structures are often exposed to the action of aggressive environ... more Parts of industrial machines and structures are often exposed to the action of aggressive environments, which in a short period of time can provoke the loss of their integrity. It is well known that for extending the service life against erosion and corrosion, protection of the exposed structure zone by coating is frequently used. Various application methods of protective coatings are applied, and the most common are welding and thermal spraying processes. The aim of this study was characterization of coatings made of stainless steel 316L, widely used in chemical and petrochemical industries. The coating was applied on a structural steel S235JR by plasma transferred arc using powder as a filler material. Due to a number of advantages, the plasma transferred arc (PTA) surfacing process has found significant usages in the field of surface protection. This paper presents results of hardness measurements in characteristic zones of the coating and the base material, as well as microstruc...
Introduction. Increases in market prices of gold over the last 20 years have led to expansion of ... more Introduction. Increases in market prices of gold over the last 20 years have led to expansion of basic dental alloys, which, primarily due to their good mechanical properties and acceptable prices, have found their place in everyday dental practice. However, within the procedure of making dental prosthetic restorations, the alloys are melted and cast, which leads to changes in their physical, mechanical and biological properties. Objective. The objective of the study was to test biocompatibility of a Ni-Cr dental alloy (WIRON 99) depending on the number of melting and casting processes. Methods. The working method included the testing of cytotoxicity of the alloy obtained by casting after one, after four, and after eight successive processes of melting. Cytotoxicity of samples was tested by means of a 24-hour and a three-day cytotoxicity test, done on L929 fibroblasts. Results. A repeatedly melted and cast alloy shows a reduced biocompatibility and causes specific responses of the t...
Cobalt 3D powder particles were successfully prepared by the galvanostatic electrodeposition. Ele... more Cobalt 3D powder particles were successfully prepared by the galvanostatic electrodeposition. Electrodeposited cobalt powder were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS) analysis and SQUID magnetometry. It has been shown that morphology, structure and magnetic properties of cobalt particles are closely associated and can be easily controlled by adjusting process parameters of electrodeposition. Morphology of cobalt powder particles is strongly affected by hydrogen evolution reaction as a parallel reaction to cobalt electrodeposition. Depending on the applied current density, the two types of powder particles were formed: dendrites at lower and spongy-like particles at higher current densities. Morphologies and structures of powder particles are correlated with their magnetic properties, and compared with those of the bulk cobalt. In comparison with the properties of bulk cobalt, the obtained 3D structures exh...
Uploads