Andrzej Michalski | Warsaw University of Technology (original) (raw)

Papers by Andrzej Michalski

Ceramic Transactions, Volume 243, 2014

Journal of the European Ceramic Society, 2006

Ti/B/Ni powders were sintered in a pulsed plasma with the participation of the SHS reaction. The ... more Ti/B/Ni powders were sintered in a pulsed plasma with the participation of the SHS reaction. The material obtained after 10 min of this combined process was a composite that contained TiB 2 and Ni phases. Microscopic examinations have shown that nickel occurs at the boundaries of the TiB 2 grains, where it forms a thin film, and also appears in the form of small agglomerates. The density of the composites is 99.8%, and their hardness is 2500 HV1.

Solid State Phenomena, Jul 18, 2006

Key Engineering Materials, 2011

Tungsten carbide (WC) and WCCo powders added with 30 vol.% cubic boron nitride (cBN) and 5 and 12... more Tungsten carbide (WC) and WCCo powders added with 30 vol.% cubic boron nitride (cBN) and 5 and 12 wt% of Ti were sintered by the pulse plasma sintering (PPS) technique. The sintering process was conducted under a load of 75 MPa at a pressure of 5.10 -5 mbar and a temperature of 1100-1500°C for 5min. The phase composition, density, hardness and microstructure of the sintered material thus obtained were examined. In the cBN-WCTi5wt% composite with an addition of 6wt% Co, the cBN particles are well bound with the matrix. The transcrystalline fractures of the cBN particles also indicate that the binding forces between these particles and the WCCoTi matrix exceed the matrix cohesion. The interfaces between the cBN grains and the surrounding matrix are almost straight lines, and no reactions between the cBN grains and the matrix were revealed in SEM observations.

International Journal of Refractory Metals and Hard Materials, 2015

ABSTRACT The cBN/WC6Co composite with the relative density of 99.8% and hardness of 2130 HV5 was ... more ABSTRACT The cBN/WC6Co composite with the relative density of 99.8% and hardness of 2130 HV5 was produced by sintering at a temperature of 1150 °C under a pressure of 100 MPa for 5 min. The composite was sintered using electric pulses generated periodically by discharging a capacitor battery. The constituent phases of the composite, as identified by the NBED method, were the cBN, WC, and Co phases. The HR STEM observations have shown that the interfaces between the individual phases are continuous and no pores or precipitates of other phases can be seen there. Thanks to the specific heating realized by electric pulses, the composite is heated during each current pulse to a temperature of 1950 °C at a rate of 105 °C/s. As a result of these quick changes of the temperature, transient thermal compressive stresses of about 3 GPa are induced in the composite, which results in the grains of the WC composite matrix being refined and defected.

The aim of this project is to develop a Fe-Mn alloy with properties comparable with the propertie... more The aim of this project is to develop a Fe-Mn alloy with properties comparable with the properties of cobalt. It will permit to replace in cemented carbides toxic cobalt by alternative non-toxic matrix. Another measurable effect of this project will a cost reduction of cemented carbides, because price of proposed Fe-Mn matrix is considerably (50 times) lower in relation to cobalt matrix. The worked out new matrix will be used to obtain nanocrystalline cemented carbides, which is in agreement with prevailing trend of manufacture of materials with the best mechanical proprieties. INTRODUCTION

2015 22nd International Conference Mixed Design of Integrated Circuits & Systems (MIXDES), 2015

Solid State Phenomena, 2006

Nanocrystalline copper powders, produced by the reduction of the CuO with hydrogen, were consolid... more Nanocrystalline copper powders, produced by the reduction of the CuO with hydrogen, were consolidated using the pulse plasma sintering (PPS) method. The sintering process was carried out at temperatures between 500 and 900 o C under a load of 60 MPa for 5 min. The average crystallite size of the sintered component obtained at 500 o C was about 80nm and at 900 o C 1880 nm. The components produced at 500 o C had a relative density of 90 %, and those sintered at 900 o C 92 %; their hardness was 215 and 140 HV 0.1 , respectively.

One of the main challenges in fabrication of copper/diamond composites, apart from graphitization... more One of the main challenges in fabrication of copper/diamond composites, apart from graphitization at high temperatures, is a lack of wettability of diamond by copper and the absence of chemical reactions, providing the formation of Cu-carbon compounds needed for a good joint between the diamond and the copper. Moreover, the large mismatch in the values of thermal expansion coef􀂿 cients of these antageous to the cohesion of the diamond/copper interface. The thermal stresses promote voids formation, which reduces the thermal conductivity of the composite. In metal-diamond composites, the quality of the interface has a crucial effect on their thermal conductivity and mechanical properties. Strong and “clean” bond of the diamond to the matrix should assure high strength and minimum thermal resistance of the interface. In the present work, an attempt has been made to fabricate the copper matrix composite with 50 vol.% of diamond by using the Pulse Plasma Sintering (PPS) technique in the ...

Solid State Phenomena, 2006

The paper presents the results of examination of the structure and properties of nanocrystalline ... more The paper presents the results of examination of the structure and properties of nanocrystalline Cu-Al 2 O 3 composites with the two different Al 2 O 3 contents: 10 and 20 vol.%. The composites were produced using a mixture of copper and Al 2 O 3 powders with an average crystallite size of about 60nm for Cu and about 40nm for Al 2 O 3 . The powders were consolidated by pulse plasma sintering (PPS) for 5 minutes at a temperature of 650 o C under a load of 60 MPa. Irrespective of the volumetric content of Al 2 O 3 , the relative density of the composites was about 92%, and the average Cu crystallite size was about 80nm. The hardness of the composites varied with the volumetric content of Al 2 O 3 , and was equal to 270 HV0.1 for 20 and to 240 HV0.1 for 10% of Al 2 O 3 . The Cu-20%Al 2 O 3 composite had a resistivity of 0.386 while that with 10% of Al 2 O 3 was 0.149 µΩm.

Materials Characterization, 2015

The interfaces in Pulse Plasma Sintered composites of Cu0.8Cr and diamond have been characterised... more The interfaces in Pulse Plasma Sintered composites of Cu0.8Cr and diamond have been characterised. The interfaces between the diamond and the Cu0.8Cr matrix generally exhibited a strong degree of bonding, but variations related to the orientation of the diamond facets were revealed. Image analysis established that the surfaces of the diamond particles were partially coated with chromium carbide, which averaged 43% for the {111} facets and 31% for the {100} facets. In addition thin and irregular layers of graphite were also observed. The composite with a 50% volume fraction of diamond possessed a thermal diffusivity of 218 mm 2 /s which infers a thermal conductivity of 589 W/(m·K), which is 76% of the maximum theoretical conductivity predicted by the Maxwell model.

The pulse plasma sintering (PPS) method is an attractive method of consolidating powders that are... more The pulse plasma sintering (PPS) method is an attractive method of consolidating powders that are difficult to sinter, such a Ti-B-C ceramics. The products are consolidated and sintered using highcurrent electric pulses lasting several hundreds of microseconds and the electric current amplitude is several dozens of kilo-amperes [1]. There are many advantages associated with this method: the sintering process only needs to last for a short time, the consumed energy is low, and the powder particles are in an activated state. However, a better understanding of the intermediate phases and microstructures occurring at different stages during the sintering process is required for the development of specific ceramic composites formed by PPS.

Advanced Materials Research, 2009

A Pulse Plasma Sintering (PPS) process was employed to manufacture Cu-diamond composites with a 5... more A Pulse Plasma Sintering (PPS) process was employed to manufacture Cu-diamond composites with a 50% volume fraction of each constituent. Pure and Cr (0.8wt.%) alloyed copper matrices were used and commercial diamond powders. The composites were sintered at temperature of 900°C for 20 min and under pressure of 60 MPa. In these sintering conditions diamond becomes thermodynamically unstable. Cu0.8Cr-diamond and Cu-diamond composites with relative densities of 99,7% and 96% respectively were obtained. The thermal conductivity of Cu0.8Cr-diamond composite is equal to 640 W(mK) -1 whereas that of Cu-diamond is 200 W(mK) -1 . The high thermal conductivity and relative density of Cu0.8Cr-diamond composite is due to the formation of a thin chromium carbide layer at the Cu-diamond interface.

Thin Solid Films, 1975

ABSTRACT The N, Ni, Al, C ion treatment of a silicon single crystal under the conditions of a d.c... more ABSTRACT The N, Ni, Al, C ion treatment of a silicon single crystal under the conditions of a d.c. glow discharge has been studied. It has been found that in such circumstances doping and surface thin film formation may occur. The explanation put forward is based on the assumption of a very low energy ion implantation.

Thin Solid Films, 1981

The pulse plasma method was used to deposit thin films of diamond, boraxone, Al,O,, TazO, and oth... more The pulse plasma method was used to deposit thin films of diamond, boraxone, Al,O,, TazO, and other materials. The main advantage of this method is the possibility that films with good adhesion to the substrate can be prepared under low temperatures and at pressures attainable with a rotary pump. Films of diamond, which are very hard, may have applications as hard coatings and in electronic devices. The main disadvantage of this method in its present stage of development is that the purity of the films produced is insuthcient for their application as semiconductors in electronic devices.

Surface and Coatings Technology, 1991

ABSTRACT

physica status solidi (c), 2010

Journal of Thermal Analysis and Calorimetry, 2007

The ultrasonic spray pyrolysis (USP) technique was used for synthesis of alumina-and zirconia-bas... more The ultrasonic spray pyrolysis (USP) technique was used for synthesis of alumina-and zirconia-based powders. The starting agents were aqueous solutions, atomized by the ultrasonic spray generator and pyrolized in the furnace under the open-air conditions. The powders prepared by USP were in the form of solid and hollow aggregates (spheres) consisted of nanosize amorphous grains as determined by the microscopy and the X-ray diffraction techniques. The alumina-based powders were consolidated by the pulse plasma sintering resulting in single-phase materials. Different behavior of solid and hollow particles during the isostatic sintering is found; a higher degree of deformation of spheres is observed in the second case.

Journal of ASTM International, 2011

ABSTRACT

Ceramic Transactions, Volume 243, 2014

Journal of the European Ceramic Society, 2006

Ti/B/Ni powders were sintered in a pulsed plasma with the participation of the SHS reaction. The ... more Ti/B/Ni powders were sintered in a pulsed plasma with the participation of the SHS reaction. The material obtained after 10 min of this combined process was a composite that contained TiB 2 and Ni phases. Microscopic examinations have shown that nickel occurs at the boundaries of the TiB 2 grains, where it forms a thin film, and also appears in the form of small agglomerates. The density of the composites is 99.8%, and their hardness is 2500 HV1.

Solid State Phenomena, Jul 18, 2006

Key Engineering Materials, 2011

Tungsten carbide (WC) and WCCo powders added with 30 vol.% cubic boron nitride (cBN) and 5 and 12... more Tungsten carbide (WC) and WCCo powders added with 30 vol.% cubic boron nitride (cBN) and 5 and 12 wt% of Ti were sintered by the pulse plasma sintering (PPS) technique. The sintering process was conducted under a load of 75 MPa at a pressure of 5.10 -5 mbar and a temperature of 1100-1500°C for 5min. The phase composition, density, hardness and microstructure of the sintered material thus obtained were examined. In the cBN-WCTi5wt% composite with an addition of 6wt% Co, the cBN particles are well bound with the matrix. The transcrystalline fractures of the cBN particles also indicate that the binding forces between these particles and the WCCoTi matrix exceed the matrix cohesion. The interfaces between the cBN grains and the surrounding matrix are almost straight lines, and no reactions between the cBN grains and the matrix were revealed in SEM observations.

International Journal of Refractory Metals and Hard Materials, 2015

ABSTRACT The cBN/WC6Co composite with the relative density of 99.8% and hardness of 2130 HV5 was ... more ABSTRACT The cBN/WC6Co composite with the relative density of 99.8% and hardness of 2130 HV5 was produced by sintering at a temperature of 1150 °C under a pressure of 100 MPa for 5 min. The composite was sintered using electric pulses generated periodically by discharging a capacitor battery. The constituent phases of the composite, as identified by the NBED method, were the cBN, WC, and Co phases. The HR STEM observations have shown that the interfaces between the individual phases are continuous and no pores or precipitates of other phases can be seen there. Thanks to the specific heating realized by electric pulses, the composite is heated during each current pulse to a temperature of 1950 °C at a rate of 105 °C/s. As a result of these quick changes of the temperature, transient thermal compressive stresses of about 3 GPa are induced in the composite, which results in the grains of the WC composite matrix being refined and defected.

The aim of this project is to develop a Fe-Mn alloy with properties comparable with the propertie... more The aim of this project is to develop a Fe-Mn alloy with properties comparable with the properties of cobalt. It will permit to replace in cemented carbides toxic cobalt by alternative non-toxic matrix. Another measurable effect of this project will a cost reduction of cemented carbides, because price of proposed Fe-Mn matrix is considerably (50 times) lower in relation to cobalt matrix. The worked out new matrix will be used to obtain nanocrystalline cemented carbides, which is in agreement with prevailing trend of manufacture of materials with the best mechanical proprieties. INTRODUCTION

2015 22nd International Conference Mixed Design of Integrated Circuits & Systems (MIXDES), 2015

Solid State Phenomena, 2006

Nanocrystalline copper powders, produced by the reduction of the CuO with hydrogen, were consolid... more Nanocrystalline copper powders, produced by the reduction of the CuO with hydrogen, were consolidated using the pulse plasma sintering (PPS) method. The sintering process was carried out at temperatures between 500 and 900 o C under a load of 60 MPa for 5 min. The average crystallite size of the sintered component obtained at 500 o C was about 80nm and at 900 o C 1880 nm. The components produced at 500 o C had a relative density of 90 %, and those sintered at 900 o C 92 %; their hardness was 215 and 140 HV 0.1 , respectively.

One of the main challenges in fabrication of copper/diamond composites, apart from graphitization... more One of the main challenges in fabrication of copper/diamond composites, apart from graphitization at high temperatures, is a lack of wettability of diamond by copper and the absence of chemical reactions, providing the formation of Cu-carbon compounds needed for a good joint between the diamond and the copper. Moreover, the large mismatch in the values of thermal expansion coef􀂿 cients of these antageous to the cohesion of the diamond/copper interface. The thermal stresses promote voids formation, which reduces the thermal conductivity of the composite. In metal-diamond composites, the quality of the interface has a crucial effect on their thermal conductivity and mechanical properties. Strong and “clean” bond of the diamond to the matrix should assure high strength and minimum thermal resistance of the interface. In the present work, an attempt has been made to fabricate the copper matrix composite with 50 vol.% of diamond by using the Pulse Plasma Sintering (PPS) technique in the ...

Solid State Phenomena, 2006

The paper presents the results of examination of the structure and properties of nanocrystalline ... more The paper presents the results of examination of the structure and properties of nanocrystalline Cu-Al 2 O 3 composites with the two different Al 2 O 3 contents: 10 and 20 vol.%. The composites were produced using a mixture of copper and Al 2 O 3 powders with an average crystallite size of about 60nm for Cu and about 40nm for Al 2 O 3 . The powders were consolidated by pulse plasma sintering (PPS) for 5 minutes at a temperature of 650 o C under a load of 60 MPa. Irrespective of the volumetric content of Al 2 O 3 , the relative density of the composites was about 92%, and the average Cu crystallite size was about 80nm. The hardness of the composites varied with the volumetric content of Al 2 O 3 , and was equal to 270 HV0.1 for 20 and to 240 HV0.1 for 10% of Al 2 O 3 . The Cu-20%Al 2 O 3 composite had a resistivity of 0.386 while that with 10% of Al 2 O 3 was 0.149 µΩm.

Materials Characterization, 2015

The interfaces in Pulse Plasma Sintered composites of Cu0.8Cr and diamond have been characterised... more The interfaces in Pulse Plasma Sintered composites of Cu0.8Cr and diamond have been characterised. The interfaces between the diamond and the Cu0.8Cr matrix generally exhibited a strong degree of bonding, but variations related to the orientation of the diamond facets were revealed. Image analysis established that the surfaces of the diamond particles were partially coated with chromium carbide, which averaged 43% for the {111} facets and 31% for the {100} facets. In addition thin and irregular layers of graphite were also observed. The composite with a 50% volume fraction of diamond possessed a thermal diffusivity of 218 mm 2 /s which infers a thermal conductivity of 589 W/(m·K), which is 76% of the maximum theoretical conductivity predicted by the Maxwell model.

The pulse plasma sintering (PPS) method is an attractive method of consolidating powders that are... more The pulse plasma sintering (PPS) method is an attractive method of consolidating powders that are difficult to sinter, such a Ti-B-C ceramics. The products are consolidated and sintered using highcurrent electric pulses lasting several hundreds of microseconds and the electric current amplitude is several dozens of kilo-amperes [1]. There are many advantages associated with this method: the sintering process only needs to last for a short time, the consumed energy is low, and the powder particles are in an activated state. However, a better understanding of the intermediate phases and microstructures occurring at different stages during the sintering process is required for the development of specific ceramic composites formed by PPS.

Advanced Materials Research, 2009

A Pulse Plasma Sintering (PPS) process was employed to manufacture Cu-diamond composites with a 5... more A Pulse Plasma Sintering (PPS) process was employed to manufacture Cu-diamond composites with a 50% volume fraction of each constituent. Pure and Cr (0.8wt.%) alloyed copper matrices were used and commercial diamond powders. The composites were sintered at temperature of 900°C for 20 min and under pressure of 60 MPa. In these sintering conditions diamond becomes thermodynamically unstable. Cu0.8Cr-diamond and Cu-diamond composites with relative densities of 99,7% and 96% respectively were obtained. The thermal conductivity of Cu0.8Cr-diamond composite is equal to 640 W(mK) -1 whereas that of Cu-diamond is 200 W(mK) -1 . The high thermal conductivity and relative density of Cu0.8Cr-diamond composite is due to the formation of a thin chromium carbide layer at the Cu-diamond interface.

Thin Solid Films, 1975

ABSTRACT The N, Ni, Al, C ion treatment of a silicon single crystal under the conditions of a d.c... more ABSTRACT The N, Ni, Al, C ion treatment of a silicon single crystal under the conditions of a d.c. glow discharge has been studied. It has been found that in such circumstances doping and surface thin film formation may occur. The explanation put forward is based on the assumption of a very low energy ion implantation.

Thin Solid Films, 1981

The pulse plasma method was used to deposit thin films of diamond, boraxone, Al,O,, TazO, and oth... more The pulse plasma method was used to deposit thin films of diamond, boraxone, Al,O,, TazO, and other materials. The main advantage of this method is the possibility that films with good adhesion to the substrate can be prepared under low temperatures and at pressures attainable with a rotary pump. Films of diamond, which are very hard, may have applications as hard coatings and in electronic devices. The main disadvantage of this method in its present stage of development is that the purity of the films produced is insuthcient for their application as semiconductors in electronic devices.

Surface and Coatings Technology, 1991

ABSTRACT

physica status solidi (c), 2010

Journal of Thermal Analysis and Calorimetry, 2007

The ultrasonic spray pyrolysis (USP) technique was used for synthesis of alumina-and zirconia-bas... more The ultrasonic spray pyrolysis (USP) technique was used for synthesis of alumina-and zirconia-based powders. The starting agents were aqueous solutions, atomized by the ultrasonic spray generator and pyrolized in the furnace under the open-air conditions. The powders prepared by USP were in the form of solid and hollow aggregates (spheres) consisted of nanosize amorphous grains as determined by the microscopy and the X-ray diffraction techniques. The alumina-based powders were consolidated by the pulse plasma sintering resulting in single-phase materials. Different behavior of solid and hollow particles during the isostatic sintering is found; a higher degree of deformation of spheres is observed in the second case.

Journal of ASTM International, 2011

ABSTRACT