Effect of conventional and microwave heating on the structural and
physicochemical properties of silver-doped hydroxyapatite nanopowders
Ravinder Pal Singh and Pradeep Kumar
Department of Mechanical Engineering, Sri Guru Granth Sahib World University, Fatehgarh Sahib, India
ABSTRACT
This paper discussed the infl uence of duration and modes of heating on structural and physicochemical properties of silver-doped hydroxyapatite (Ag-HAP) nanopowders (NPs). Conventional electric furnace and microwave (MW) heating modes were employed during the synthesis. MW mode of synthesis was relatively an effi cient method as it prepared monolithic HAP NP in just one minute of heating. With the increase in duration of heating in both modes of heating; lattice parameters, crystal size, lattice strain, Ca/P ratio, and degree of crystallinity of HAP phase increased. The morphology of particles was rod-shaped having
aspect ratio between 2 and 3. EDX confi rmed the presence of Ag and corroborated the formation of apatite. The hydrodynamic diameter of Ag-HAP NPs was signifi cantly bigger than the particle sizes calculated using XRD, FESEM, and TEM. Thus, an overall examination concluded MW as an effi cient mode of synthesis, able to produce Ag-HAP NPs in a possible minimum time.
KEYWORD S
Hydroxyapatite; silver; microwave; conventional electric furnace; duration of heating; Rietveld; nanorods; strain
Effect of conventional and microwave heating on the structural and
physicochemical properties of silver-doped hydroxyapatite nanopowders
Ravinder Pal Singh and Pradeep Kumar
Department of Mechanical Engineering, Sri Guru Granth Sahib World University, Fatehgarh Sahib, India
ABSTRACT
This paper discussed the infl uence of duration and modes of heating on structural and physicochemical properties of silver-doped hydroxyapatite (Ag-HAP) nanopowders (NPs). Conventional electric furnace and microwave (MW) heating modes were employed during the synthesis. MW mode of synthesis was relatively an effi cient method as it prepared monolithic HAP NP in just one minute of heating. With the increase in duration of heating in both modes of heating; lattice parameters, crystal size, lattice strain, Ca/P ratio, and degree of crystallinity of HAP phase increased. The morphology of particles was rod-shaped having
aspect ratio between 2 and 3. EDX confi rmed the presence of Ag and corroborated the formation of apatite. The hydrodynamic diameter of Ag-HAP NPs was signifi cantly bigger than the particle sizes calculated using XRD, FESEM, and TEM. Thus, an overall examination concluded MW as an effi cient mode of synthesis, able to produce Ag-HAP NPs in a possible minimum time.
KEYWORD S
Hydroxyapatite; silver; microwave; conventional electric furnace; duration of heating; Rietveld; nanorods; strain
Effects of heat treatment temperatures on microstructures and mechanical
properties of the chopped carbon fibres SiC composites
Hui Mei, Hui Zhang, Weizhao Huang, Ming Han, Yawei Xu and Laifei Cheng
Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi’ an, People’ s Republic of China
ABSTRACT
A simple wet papermaking technique was used to fabricate chopped carbon fibre paper (Csfpaper) with random fibre orientation and self-supporting network structures in this work. The Csf-papers were laminated layer by layer and further infiltrated with PyC interface and SiC matrix via chemical vapour infiltration (CVI) to obtain Csf/SiC composites. The effects of heat treatment temperatures on microstructures, phase composition, and mechanical properties were investigated. Results showed that the Csf-paper has played a good self-supporting role and its fibres form a completely random fibre orientation in 2D plane. The fibres almost remained undamaged and unbroken during the CVI. Proper heat treatment could improve the mechanical properties. At 1200°C, the maximum values of flexural strength and Young’s modulus reached about 306 MPa and 196.5 GPa, respectively. Meanwhile, compared with tape casting, reaction sintering and spark plasma sintering, composites fabricated by wet papermaking and CVI can improve the mechanical properties.
KEYWORD S
Csf-paper; heat treatment temperatures; microstructures; mechanical properties; wet papermaking
Study of the structural and dielectric properties of ceramic obtained from
residual electrocoagulation
T. S. M. Fernandesa, R. G. M. Oliveira b, D. X. Gouveiac, M. A. S. Silva b, A. S. B. Sombrab and R. F. Nascimentod
aDepartment of Hydraulic and Environmental Engineering, Federal University of Ceará, Fortaleza, Ceará, Brazil; bTelecommunications and Materials Science and Engineering Laboratory (LOCEM) – Physics Department, Federal University of Ceará, Fortaleza, Ceará, Brazil; cIFCE – Instituto Federal do Ceará, Fortaleza, Ceará, Brazil; dDepartment of Analytical Chemistry and Physical Chemistry, Federal University of Ceará, Fortaleza, Ceará, Brazil
ABSTRACT
This work aims to develop an eco-friendly ceramic obtained from the sludge generated in the textile industry treatment by electrocoagulation to demonstrate a possibility of natural raw materials’ extraction decrease. The sludge generated by the electrocoagulation treatment was treated by some sintering processes. The presence of two crystalline phases was confirmed
through the Rietveld refinement: Fe2O3 and NiCr2O4. In the microwave range it is possible to confirm the relative stability of dielectric permittivity over the wide frequency range. The Temperature Coefficient of Capacitance results demonstrate that the samples can be classified as a class 4 ceramic capacitor. The activation energy measurement profile is similar for all samples. The results showed that samples obtained from the sludge present low dielectric permittivity, two thermo-activated processes one to water loss and another to conduction with activation energy of approximately 0.6 eV for all analysed samples. The manufactured samples can be applied as a barrier layer capacitor and dielectric resonator antennas.
KEYWORD S
Eco-friendly ceramic; sludge; textile industry treatment; electrocoagulation; dielectric properties
Surface amorphisation of TiZrN coatings by laser carburisation
Taewoo Kima, Eunpyo Honga, Youngkue Choib, Myunghyun Kimc and Heesoo Leea
aSchool of Materials Science and Engineering, Pusan National University, Busan, Korea; bMaterial & Components Technology Center, Korea Testing Laboratory, Jinju, Korea; cDepartment of Naval Architecture and Ocean Engineering, Pusan National University, Busan, Korea
ABSTRACT
The enhancement of wear resistance by laser carburisation on TiZrN coatings was investigated in terms of bond state. Graphite paste was used to cover the TiZrN coatings and then pulsed laser ablation was used to solidify the carbon. Tribometer test showed that the friction coefficient was reduced from 0.64 to 0.17 after laser carburisation. The doped carbon was analysed as a mixture with sp2C and sp3C bonds using an X-ray photoelectron spectroscopy depth profile. The sp2/sp3 ratio was 2.29 at the surface and increased up to 2.91 in the depth direction. To verify the effect of the hybrid bonds on the atomic order, annealing was carried
out to the carburised specimens. As the ratio increased to 3.28, graphitisation resulting in transition from sp3 to sp2 was confirmed, and variation in the lattice structure was demonstrated by a reduction in the lattice constant (4.45 Å to 4.40 Å) using Rietveld refinement.
KEYWORD S
Amorphous carbon; bond state; graphitisation; lattice constant; friction coefficient
The toughening mechanism and mechanical properties of graphene-reinforced
zirconia ceramics by microwave sintering
Hongrong Zoua, Yaping Zhanga, Liqi Liua, Lei Shia and Wenrong Lib
aResearch Center of Composite Materials, Shanghai University, Shanghai, People’s Republic of China; bInstitute of Sustainable Energy, Shanghai University, Shanghai, People’s Republic of China
ABSTRACT
The graphene/ZrO2 composites were fabricated by impregnating graphene dispersion into the ZrO2 ceramic matrix and sintered by microwave, and the microstructure and mechanical properties were investigated. The results showed that the graphene was well dispersed in the ceramic matrix and refined the grain size. The fracture toughness reached 8.62 MPa m1/2, confirmed by single-edge notched beam, which was 42% higher than that of the pure ZrO2. Also, the toughening mechanisms were investigated by micro-hardness testing and showed that a combination of crack deflection, micro-crack and crack bridging increased the fracture
toughness.
KEYWORD S
Graphene; zirconia; microwave sintering; mechanical properties; composites
Zrc ceramics incorporated with different-sized SiC particles
Jian Zhaoa,b, Jia-Xiang Xuea, Hai-Tao Liua, Xin-Gang Wanga and Guo-Jun Zhanga
aState Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Shanghai, People’s Republic of China; bGraduate University of the Chinese Academy of Sciences, Beijing, People’s Republic of China
ABSTRACT
Three different SiC powders with average particle sizes of 0.45, 3.5 and 10 µm were used to prepare ZrC-20vol.-% SiC ceramics by hot pressing. The effects of SiC particle size on the densification, microstructure, mechanical properties and thermal properties of ZrC–SiC ceramics were studied. Ceramics prepared from SiC with finer particle sizes exert higher bending strength, hardness and lower thermal conductivity. The ZrC–SiC ceramics with a starting SiC particle size of 3.5 µm has relative high fracture toughness than others. Analysis indicates that SiC grain size and the grain boundaries control the thermal conductivity ZrC–
SiC ceramics. Ceramics prepared from SiC with the particle size of 10 µm exhibits the highest thermal conductivity due to the larger grains and less grain boundaries.
KEYWORD S
Zirconium carbide (ZrC); silicon carbide (SiC); densification; microstructure; mechanical properties
