Edwin Gevorkyan; Sergiy Lavrynenko; Miroslaw Rucki
Abstract
The paper presents the results of investigations on hot pressure sintering under the alternating current. The powders of different grain sizes were used for the sintering to investigate the impact of the powder on the final sintered structure and relative density. The additional experiments were focused ...
Read More
The paper presents the results of investigations on hot pressure sintering under the alternating current. The powders of different grain sizes were used for the sintering to investigate the impact of the powder on the final sintered structure and relative density. The additional experiments were focused on the kinetics of the Al2O3 nanopowders sintering. They confirmed that the time of the process duration is dependent on the temperature and the applied pressure. However, compared to the powders of tungsten monocarbide, it depends on the temperature rise speed in rather small degree. Discussion of the results pointed out that the obtained data, both theoretical and experimental one, confirmed possibility that during the sintering process the dislocations might appear and spread. It seemed reasonable to assume that in the low voltage regime the activated sliding with diffusion accommodation prevails, while in the high voltage regime the dislocation creep does.
Hamzah Fansuri; Muhammad I. Syafi
Abstract
The aims of this research are to study the sintering technique during the production of BaxSr1-xCo0.8Fe0.2O3-δ (BSCF) membranes and to obtain information about the correlation between Ba 2+ substituent with membrane’s density, hardness and thermal expansion coefficient. BSCF with x = 0.5, ...
Read More
The aims of this research are to study the sintering technique during the production of BaxSr1-xCo0.8Fe0.2O3-δ (BSCF) membranes and to obtain information about the correlation between Ba 2+ substituent with membrane’s density, hardness and thermal expansion coefficient. BSCF with x = 0.5, 0.6 and 0.7 (BSCF 5582, 6482 and 7382) were synthesized by the solid state method. X-ray diffraction analysis revealed that the three oxides possessed a cubic structure with high purity and crystallinity. BSCF membranes were made by dry pressing method from their respective powders which passed through 400 mesh sieves at 1050 o C and 1150 o C. Membranes with high density were obtained from phased sintering technique at 1150 °C. SEM analysis results showed that the surface of the membranes is dense, albeit pores can still be found in the cross section of the membranes. The density of the membranes decreased as the amount of Ba 2+ substituent increases indicated by the increase in pore size. A similar pattern was also found in the membrane hardness which decreased as the amount of Ba 2+ content increased. Thermal expansion coefficient of BSCF 5582 was 18.28 ppm which was the highest one followed by BSCF 6482 and BSCF 7382.
Nelson H. A. Camargo; Eliakim E. G. de Borba; Priscila F. Franczak; Enori Gemelli
Abstract
Microporous calcium phosphate biomaterials are known for their physical and biological applications. Among the best known are the stoichiometric hydroxyapatite (HA) and tricalcium phosphate (TCP). This is because these biomaterials exhibit chemical and crystallographic compositions which are similar ...
Read More
Microporous calcium phosphate biomaterials are known for their physical and biological applications. Among the best known are the stoichiometric hydroxyapatite (HA) and tricalcium phosphate (TCP). This is because these biomaterials exhibit chemical and crystallographic compositions which are similar to that found in bones and teeth. The use of nanotechnology enables obtaining calcium phosphate nanostructured powders and calcium phosphate nanocomposite matrix formed by a second nano phase of type SiO2, TiO2, Al2O3-a, ZrO2, Mg. Different methods and techniques for the synthesis and preparation of nanostructured powders and biomaterials are noted in the literature, but it is known that not all lead to the same results. Calcium phosphates nanostructured biomaterials are a new class of biomaterials which provide new physical, morphological, nanostructural and microstructural features with interconnected microporosity which are promising to wettability, capillary action, cell adhesion and proliferation on the surface of grains and micropores. Based on research of these biomaterials, it has been found that they show potential applications in traumatology, orthopedic and dental applications in reconstruction, defects and bone tissue repairing, implants attachment and dental remineralization treatment. This study was aimed at the sintering and characterization of an HA matrix and three nanocomposite biomaterials with 5% by volume of the respective second phases: SiO2, ZrO2 and Al2O3-a in the HA matrix. The HA powder and nanocomposite HA/SiO2 were sintered at 1100 °C/2h. HA/ZrO2 nanocomposite powder followed two sintering conditions: a temperature of 1100 °C/2h and the other, at 1300 ºC/2h. HA/Al2O3-a nanocomposite powder was only sintered at 1300 ºC/2h. The biomaterials were characterized by scanning electron microscopy, X-ray diffraction and open porosity and hydrostatic density were also determined by applying the Arthur method. The results are encouraging and show for HA, HA/SiO2, HA/ZrO2 biomaterials (obtained by sintering at 1100 °C) interconnected microporous microstructures, formed by fine grains which are favorable for the expected wettability and capillarity characteristics.
Akhilesh Pandey; Shankar Dutta; Anand Kumar; R. Raman; Ashok K. Kapoor; R Muralidhran
Abstract
Molybdenum-di-sulfide (MoS2) is being considered as an alternative 2-D material to graphene. Deposition of ultrathin MoS2 layer from bulk MoS2 sample is an important criterion in determining the viability of its application. This paper discusses about growth and characterization of bulk MoS2 pellet ...
Read More
Molybdenum-di-sulfide (MoS2) is being considered as an alternative 2-D material to graphene. Deposition of ultrathin MoS2 layer from bulk MoS2 sample is an important criterion in determining the viability of its application. This paper discusses about growth and characterization of bulk MoS2 pellet from MoS2 powder and exfoliation of MoS2 layer from it. The MoS2 pellets were sintered at different temperatures (500 - 850 ° in nitrogen atmosphere. The sintered samples were found to be polycrystalline in nature with hexagonal flakes of 100 nm – 1.0 µm sizes. In addition to MoS2 phase, surface of the bulk samples also has also some MoO3 phase content, which was found to decrease with the increase in sintering temperature, confirmed by XRD. The optical absorption study showed MoS2 absorptions around 1.82 eV, 2.01 eV due to spin orbit and direct band to band absorption from ?k-k valley. The sintered MoS2 samples were found to have characteristic Raman peaks of A1g and E2g with a separation of 26.5 cm -1 . Ultrathin MoS2 layers, exfoliated from the sintered sample, showed the reduced separation between Raman peaks A1g and E2g of 24.5 cm -1 few layer MoS2.
Aditya Jain; Neelam Maikhuri; Rakesh Saroha; Mukul Pastor; A. K. Jha; A. K. Panwar
Abstract
In this investigation, the microstructural and dielectric properties of pure BaTiO3 and vanadium (V 5+ ) substituted on Ba 2+ site (A-site) and Ti 4+ site (B-site) in BaTiO3 ceramic have been studied. The three compositions of BaTiO3 (BT), Ba0.9V0.1TiO3 (BTA) and BaTi0.9V0.1O3 (BTB) were synthesized ...
Read More
In this investigation, the microstructural and dielectric properties of pure BaTiO3 and vanadium (V 5+ ) substituted on Ba 2+ site (A-site) and Ti 4+ site (B-site) in BaTiO3 ceramic have been studied. The three compositions of BaTiO3 (BT), Ba0.9V0.1TiO3 (BTA) and BaTi0.9V0.1O3 (BTB) were synthesized using solid-state reaction route. The XRD analysis of all three compositions has been carried out at room temperature and proper phase formation for BT, BTA and BTB are confirmed. However, compositions BTA and BTB indicate the presence of secondary phases, and it may be due to higher amount of vanadium substitution at A and B sites. Addition of vanadium inhibited the grain growth of BaTiO3 ceramic. Vanadium substitution on A- and B-site have resulted in decrease of Curie temperature as well as dielectric loss compared to pure BT. A more diffused behavior is observed in vanadium substituted samples as compare to pure BT which shows a sharp transition and lower value of diffuseness parameter. Impedance study shows that substitution of vanadium on A- as well as B-site results in decrease of AC conductivity. These properties of vanadium substituted samples can be utilized to reduce the dielectric loss in capacitors and in radio frequency applications.
Raju Kumar; Rashmi Rani; Seema Sharma
Abstract
Polycrystalline samples of 1- x(Na0.5 K0.5)(Nb0.95 Ta0.05) ) -x(Bi Fe)O3 with x=0, 0.003, 0.005, 0.007) hereby denoted as NKNT-BF were prepared by the mixed oxide method. Preliminary structural studies carried out by X-ray diffraction technique showed the formation of perovskite structure with orthorhombic ...
Read More
Polycrystalline samples of 1- x(Na0.5 K0.5)(Nb0.95 Ta0.05) ) -x(Bi Fe)O3 with x=0, 0.003, 0.005, 0.007) hereby denoted as NKNT-BF were prepared by the mixed oxide method. Preliminary structural studies carried out by X-ray diffraction technique showed the formation of perovskite structure with orthorhombic symmetry. Addition of BF in the NKNT system lowered the sintering temperature by 500C. The nature of the frequency dependence of ac conductivity of NKNT compounds follows Jonscher power law. Complex impedance and modulus spectra confirm the significant contribution of both grain and grain boundary to the electrical response of the materials. Above the ferroelectric–paraelectric phase transition temperature, the electrical conduction is governed by the thermal excitation of charge carriers from oxygen vacancies exhibiting Negative temperature coefficient (NTCR) behaviour. Detailed study on the multiferroic properties (where magnetism and ferroelectricity are strongly coupled together) of the system is under process which is likely to form key components in the development of future technology, for example, in memories and logic devices.
