Cristina Teisanu | Universitatea din Craiova (original) (raw)

Papers by Cristina Teisanu

Journal of Science and Arts, 2020

There is considerable interest in the discovery of biomimetic materials that improve cell adhesio... more There is considerable interest in the discovery of biomimetic materials that improve cell adhesion and reduce the time of bone integration of implants. In vitro bone cells biocompatibility was performed for the two types of biocomposites hydroxyapatite-titanium (HApTi) and hydroxyapatite-titanium with added calcium fructoborate (HApTiCaFb). In order to investigate the potential cytotoxicity of biomaterials, cell adhesion, proliferation, and osteogenic differentiation, human mesenchymal stem cells (MSCs) were used. Regarding the in vitro biocompatibility, a slight improvement in the phenotype was observed for the samples to which CaFb was added.

Advanced Engineering Forum, 2018

Porous hydroxyapatite (HAp) based biocomposites used in biomedical applications were developed in... more Porous hydroxyapatite (HAp) based biocomposites used in biomedical applications were developed in this paper as artificial bone substitute for vertebrae grafts. The trabecular or spongy bone tissue is an open-cell porous network having 40-90% porosity. In order to obtain a porous structure calcium carbonate and ammonium bicarbonate were added as foaming agents to the biocomposite matrix. The biocomposite matrix was prepared using submicronic powder particles of HAp and titanium hydride powder, which was added as reinforcement’s precursor as well as foaming agent. The aim of this study is to emphasize the effect of the foaming agent additions on the pores morphology by performing analyses at both macro and micro scale. These analyses consist of linear measurements, surface auto-detection and statistics of the pores and optical images as well. The powders mixture was homogenized in a planetary ball mill, uniaxial cold compacted and then heated in argon atmosphere using the two step si...

Implant infections are the result of bacterial adhesion to the implant surface and subsequent bio... more Implant infections are the result of bacterial adhesion to the implant surface and subsequent biofilm formation at the implant site. A sustained and high antibiotic concentration over minimal inhibitory concentration (MIC) of pathogenic bacteria at the implant site is expected to inhibit bacterial adhesion, colonization, and biofilm formation. In the present study we performed implants based on hydroxyapatite (HAp), HAp reinforced with titanium particles (HAp/Ti) and Hap/Ti with added calcium fructoborate (CaFb) by chemisorption deposition method (HAp/Ti/CaFb). The implants were immersed in ciprofloxacin (CP) solution for 24 hours, then was determined the release profile of antibiotic for 14 days and the antibacterial effect of the three types of composite. The period of antibiotic release may be considered as sufficient to support osteointegration under antibacterial protection.

Journal of Advanced Thermal Science Research, 2017

The two steps sintering process provide economical, technological and innovative advantageous as... more The two steps sintering process provide economical, technological and innovative advantageous aspects to produce biocomposite foams for alloplastic bone grafts applications. The kinetic window mechanism, working during the 2nd TSS step, provides the nanostructured ceramic matrix, respectively improved biocompatibility. Simultaneously, the high porous structure, fitting the trabecular bone tissue, remained an important technical request of such applications up to this research. The porous biocomposite scaffold could be designed using specific foaming agents, like titanium hydride, calcium carbonate and ammonium bicarbonate, by controlling the foaming reactions depending on the foaming agents’ type and content into the chemical composition of the initial biocomposite powder mixture. The new concept of foaming window, working during the 1st TSS step, includes these factors able to provide the specific foam structure fitting the required biocomposite foams porosity. Both windows may wo...

Advanced Materials Research, 2015

This paper presents a comparative analysis of the foaming process developed in hydroxyapatite (HA... more This paper presents a comparative analysis of the foaming process developed in hydroxyapatite (HAp)-based bicomposites as a function of the foaming agent. The matrix of the biocomposite consists of either submicronic or micronic powder particles of HAp. The titanium hydride powder was added as reinforcement’s precursor as well as blowing agent, and in order to increase the biocomposites’ porosity calcium carbonate was added as space holder agent. The powders mixture was homogenized in a planetary ball mill with a single grinding bowl for 1 minute in air. Uniaxial cold compaction at 120-170 MPa was performed in order to obtain cylindrical green parts, which next were heated in argon atmosphere using the two step sintering technique at temperatures of 900 °C for 1 minute and 800°C for 450 - 600 minutes. The porosity of the biocomposite is analysed through calculations and SEM and EDS analysis highlighting the influence of the above mentioned foaming techniques (blowing and space holder).

Advanced Materials Research, 2015

The paper focuses on the mechanical characterization of porous biocomposites based on hydroxyapat... more The paper focuses on the mechanical characterization of porous biocomposites based on hydroxyapatite submicronic powders (< 200 nm), respectively micronic powders particle (30-50 μm) as matrix, reinforced by titanium hybrid powders (15 and 20% mass; 100-150 μm) as foaming agent. Another foaming agent used is calcium bicarbonate powder (5 and 10% mass). The mixture homogenization was made in a Frisch-Pulverisette 6 type planetary mill (n=200 rpm), for 30 minutes. The green compacts were processed by unilateral cold compaction at 150 MPa. The two-step sintering technology (TSS) has been applied to the green parts, on the Nabertherm conventional furnace: at 900°C for few minutes (first step) and at 800°C for 450 minutes, respectively 600 minutes (the second step). The mechanical characteristics (compression modulus G [MPa] and ultimate compression strength σUTS [MPa]), were studied using the universal mechanical testing machine INSTRON 3382 and compared with the mechanical character...

Advanced Engineering Forum, 2015

Using powder metallurgy techniques new porous materials for self-lubricating bearings were develo... more Using powder metallurgy techniques new porous materials for self-lubricating bearings were developed. These materials are characterized by total porosity, which represents their major advantage for tribological applications, acting like their own oil reservoir. Sometimes the presence of pores can be also detrimental to the part performance. Among the causes of the bearings failure is their increased porosity for improving the lubricant retention capacity. Consequently, this can lead to a significant loss in strength. In the present work tensile test specimens based on Fe-Cu/brass-Sn-Pb powders were prepared in order to investigate the morphology of the fracture surfaces and to analyze the effect of pores on the failure process of these materials subjected to tensile loads. Distinct morphologies of the pores area were revealed by SEM images of the fracture surfaces.

Sintering - Methods and Products, 2012

Powder metallurgy technique has become increasingly interesting for engineering parts manufacture... more Powder metallurgy technique has become increasingly interesting for engineering parts manufacturers due to its advantages which include high productivity, minimum consumption of raw materials and energy, high efficient use of the initial metals (95-98%), near net shape character and unique capability of porous material production. This technique results in sintered parts that reach sufficiently high strength properties, for example, similar to cast iron, already at a porosity of 20-15%, and present remarkable physical, chemical and mechanical characteristics, which are determined by their chemical composition and the phase structure as well as the shape and mass distribution of the powder particles. Moreover, by powder metallurgy methods can be obtained materials of virtually any structure, composition and porosity and, thus, any mechanical and service properties. The performance of equipments, machines, devices and mechanisms is strongly related to their subassemblies and component parts performance. These machines and mechanisms withstand various loads and, thus, complex processes during operating times, but friction, lubrication and wear are among the most frequently met processes.

Materials Science Forum, 2011

In this study the formation of the liquid phase during sintering process of Fe-Cu-Sn-Pb system wa... more In this study the formation of the liquid phase during sintering process of Fe-Cu-Sn-Pb system was investigated. In order to reach this purpose a new material based on iron powder was developed using PM technologies. Additions like copper, tin and lead were added to iron powder and the mixture was sintered in dry hydrogen atmosphere at different temperatures and maintaining time. The liquid phase formed during sintering led to a considerable accurate process and swelling of the sintered compact was observed and studied.

Advances in Tribology, 2011

Using PM technologies, new antifriction materials based on iron powder with different addition el... more Using PM technologies, new antifriction materials based on iron powder with different addition elements were developed in order to obtain self-lubricated bearings with improved tribological features. The elemental powder mixtures were blended for 2 hours in a 3D homogenization device, were compacted at a pressure of 500 MPa, and then sintered in dry hydrogen atmosphere at different temperatures for different maintaining times. The effect of technological parameters on physical properties (density and dimensional changes) was presented in this study. The mechanical and tribological properties (tensile strength, hardness, impact energy, friction coefficient, and wear rate) related to addition elements were evaluated. The tribological behaviour of the selected iron-based alloys was analysed by pin on disc tests without lubrication. Also, the wear surface scars and the microstructure of the wear surfaces were investigated.

Journal of Materials Processing Technology, 2003

In this paper are presented the results obtained by the analysis of a guiding bush-drill system w... more In this paper are presented the results obtained by the analysis of a guiding bush-drill system when is processed by cutting. The guiding bush is performed by metallurgy of iron-copper and graphite powder mixtures. For the analysis by finite elements method were determined experimentally the mechanical specific features of samples performed from considered powder mixture. The cutting force and the cutting torque were determined in drilling process of a semi-finished product obtained from 65Mn10 material, using for drill guiding sintering bush. Using the finite elements method, the tensions were obtained, the deformations and the movements in guiding bush-drill system.

Journal of Science and Arts, 2020

There is considerable interest in the discovery of biomimetic materials that improve cell adhesio... more There is considerable interest in the discovery of biomimetic materials that improve cell adhesion and reduce the time of bone integration of implants. In vitro bone cells biocompatibility was performed for the two types of biocomposites hydroxyapatite-titanium (HApTi) and hydroxyapatite-titanium with added calcium fructoborate (HApTiCaFb). In order to investigate the potential cytotoxicity of biomaterials, cell adhesion, proliferation, and osteogenic differentiation, human mesenchymal stem cells (MSCs) were used. Regarding the in vitro biocompatibility, a slight improvement in the phenotype was observed for the samples to which CaFb was added.

Advanced Engineering Forum, 2018

Porous hydroxyapatite (HAp) based biocomposites used in biomedical applications were developed in... more Porous hydroxyapatite (HAp) based biocomposites used in biomedical applications were developed in this paper as artificial bone substitute for vertebrae grafts. The trabecular or spongy bone tissue is an open-cell porous network having 40-90% porosity. In order to obtain a porous structure calcium carbonate and ammonium bicarbonate were added as foaming agents to the biocomposite matrix. The biocomposite matrix was prepared using submicronic powder particles of HAp and titanium hydride powder, which was added as reinforcement’s precursor as well as foaming agent. The aim of this study is to emphasize the effect of the foaming agent additions on the pores morphology by performing analyses at both macro and micro scale. These analyses consist of linear measurements, surface auto-detection and statistics of the pores and optical images as well. The powders mixture was homogenized in a planetary ball mill, uniaxial cold compacted and then heated in argon atmosphere using the two step si...

Implant infections are the result of bacterial adhesion to the implant surface and subsequent bio... more Implant infections are the result of bacterial adhesion to the implant surface and subsequent biofilm formation at the implant site. A sustained and high antibiotic concentration over minimal inhibitory concentration (MIC) of pathogenic bacteria at the implant site is expected to inhibit bacterial adhesion, colonization, and biofilm formation. In the present study we performed implants based on hydroxyapatite (HAp), HAp reinforced with titanium particles (HAp/Ti) and Hap/Ti with added calcium fructoborate (CaFb) by chemisorption deposition method (HAp/Ti/CaFb). The implants were immersed in ciprofloxacin (CP) solution for 24 hours, then was determined the release profile of antibiotic for 14 days and the antibacterial effect of the three types of composite. The period of antibiotic release may be considered as sufficient to support osteointegration under antibacterial protection.

Journal of Advanced Thermal Science Research, 2017

The two steps sintering process provide economical, technological and innovative advantageous as... more The two steps sintering process provide economical, technological and innovative advantageous aspects to produce biocomposite foams for alloplastic bone grafts applications. The kinetic window mechanism, working during the 2nd TSS step, provides the nanostructured ceramic matrix, respectively improved biocompatibility. Simultaneously, the high porous structure, fitting the trabecular bone tissue, remained an important technical request of such applications up to this research. The porous biocomposite scaffold could be designed using specific foaming agents, like titanium hydride, calcium carbonate and ammonium bicarbonate, by controlling the foaming reactions depending on the foaming agents’ type and content into the chemical composition of the initial biocomposite powder mixture. The new concept of foaming window, working during the 1st TSS step, includes these factors able to provide the specific foam structure fitting the required biocomposite foams porosity. Both windows may wo...

Advanced Materials Research, 2015

This paper presents a comparative analysis of the foaming process developed in hydroxyapatite (HA... more This paper presents a comparative analysis of the foaming process developed in hydroxyapatite (HAp)-based bicomposites as a function of the foaming agent. The matrix of the biocomposite consists of either submicronic or micronic powder particles of HAp. The titanium hydride powder was added as reinforcement’s precursor as well as blowing agent, and in order to increase the biocomposites’ porosity calcium carbonate was added as space holder agent. The powders mixture was homogenized in a planetary ball mill with a single grinding bowl for 1 minute in air. Uniaxial cold compaction at 120-170 MPa was performed in order to obtain cylindrical green parts, which next were heated in argon atmosphere using the two step sintering technique at temperatures of 900 °C for 1 minute and 800°C for 450 - 600 minutes. The porosity of the biocomposite is analysed through calculations and SEM and EDS analysis highlighting the influence of the above mentioned foaming techniques (blowing and space holder).

Advanced Materials Research, 2015

The paper focuses on the mechanical characterization of porous biocomposites based on hydroxyapat... more The paper focuses on the mechanical characterization of porous biocomposites based on hydroxyapatite submicronic powders (< 200 nm), respectively micronic powders particle (30-50 μm) as matrix, reinforced by titanium hybrid powders (15 and 20% mass; 100-150 μm) as foaming agent. Another foaming agent used is calcium bicarbonate powder (5 and 10% mass). The mixture homogenization was made in a Frisch-Pulverisette 6 type planetary mill (n=200 rpm), for 30 minutes. The green compacts were processed by unilateral cold compaction at 150 MPa. The two-step sintering technology (TSS) has been applied to the green parts, on the Nabertherm conventional furnace: at 900°C for few minutes (first step) and at 800°C for 450 minutes, respectively 600 minutes (the second step). The mechanical characteristics (compression modulus G [MPa] and ultimate compression strength σUTS [MPa]), were studied using the universal mechanical testing machine INSTRON 3382 and compared with the mechanical character...

Advanced Engineering Forum, 2015

Using powder metallurgy techniques new porous materials for self-lubricating bearings were develo... more Using powder metallurgy techniques new porous materials for self-lubricating bearings were developed. These materials are characterized by total porosity, which represents their major advantage for tribological applications, acting like their own oil reservoir. Sometimes the presence of pores can be also detrimental to the part performance. Among the causes of the bearings failure is their increased porosity for improving the lubricant retention capacity. Consequently, this can lead to a significant loss in strength. In the present work tensile test specimens based on Fe-Cu/brass-Sn-Pb powders were prepared in order to investigate the morphology of the fracture surfaces and to analyze the effect of pores on the failure process of these materials subjected to tensile loads. Distinct morphologies of the pores area were revealed by SEM images of the fracture surfaces.

Sintering - Methods and Products, 2012

Powder metallurgy technique has become increasingly interesting for engineering parts manufacture... more Powder metallurgy technique has become increasingly interesting for engineering parts manufacturers due to its advantages which include high productivity, minimum consumption of raw materials and energy, high efficient use of the initial metals (95-98%), near net shape character and unique capability of porous material production. This technique results in sintered parts that reach sufficiently high strength properties, for example, similar to cast iron, already at a porosity of 20-15%, and present remarkable physical, chemical and mechanical characteristics, which are determined by their chemical composition and the phase structure as well as the shape and mass distribution of the powder particles. Moreover, by powder metallurgy methods can be obtained materials of virtually any structure, composition and porosity and, thus, any mechanical and service properties. The performance of equipments, machines, devices and mechanisms is strongly related to their subassemblies and component parts performance. These machines and mechanisms withstand various loads and, thus, complex processes during operating times, but friction, lubrication and wear are among the most frequently met processes.

Materials Science Forum, 2011

In this study the formation of the liquid phase during sintering process of Fe-Cu-Sn-Pb system wa... more In this study the formation of the liquid phase during sintering process of Fe-Cu-Sn-Pb system was investigated. In order to reach this purpose a new material based on iron powder was developed using PM technologies. Additions like copper, tin and lead were added to iron powder and the mixture was sintered in dry hydrogen atmosphere at different temperatures and maintaining time. The liquid phase formed during sintering led to a considerable accurate process and swelling of the sintered compact was observed and studied.

Advances in Tribology, 2011

Using PM technologies, new antifriction materials based on iron powder with different addition el... more Using PM technologies, new antifriction materials based on iron powder with different addition elements were developed in order to obtain self-lubricated bearings with improved tribological features. The elemental powder mixtures were blended for 2 hours in a 3D homogenization device, were compacted at a pressure of 500 MPa, and then sintered in dry hydrogen atmosphere at different temperatures for different maintaining times. The effect of technological parameters on physical properties (density and dimensional changes) was presented in this study. The mechanical and tribological properties (tensile strength, hardness, impact energy, friction coefficient, and wear rate) related to addition elements were evaluated. The tribological behaviour of the selected iron-based alloys was analysed by pin on disc tests without lubrication. Also, the wear surface scars and the microstructure of the wear surfaces were investigated.

Journal of Materials Processing Technology, 2003

In this paper are presented the results obtained by the analysis of a guiding bush-drill system w... more In this paper are presented the results obtained by the analysis of a guiding bush-drill system when is processed by cutting. The guiding bush is performed by metallurgy of iron-copper and graphite powder mixtures. For the analysis by finite elements method were determined experimentally the mechanical specific features of samples performed from considered powder mixture. The cutting force and the cutting torque were determined in drilling process of a semi-finished product obtained from 65Mn10 material, using for drill guiding sintering bush. Using the finite elements method, the tensions were obtained, the deformations and the movements in guiding bush-drill system.