In order to investigate the material properties ofperiodontal ligament （ PDL） in different locations, the nanoindentation method is used to survey the elastic modulus of the PDL at different levels. Cadaveric specim...In order to investigate the material properties ofperiodontal ligament （ PDL） in different locations, the nanoindentation method is used to survey the elastic modulus of the PDL at different levels. Cadaveric specimens of human mandibular canine were obtained from 4 adult donors, 16 transverse specimens were made from the sections of cervical margin, midroot and apex using the slow cutting machine. The prepared specimens were tested in different sections （along the longitudinal direction） and different areas （in the circumferential direction）. According to the Oliver-Phair theory, the mean values of elastic modulus were calculated foreach area and the differences among them were compared. In the midroot section, the average elastic modulus is ranging from 0. 11 to 0. 23 MPa, the changing range of the cervical margin and apex are from 0. 21 to 0. 53 MPa and 0. 44 to0.62 MPa, respectively. Experimental results indicate that the average elastic modulus in the midroot is lower than that in the cervical margin and apex, and relatively small changes occur among them. However, there is a large change to the elastic modulus value in the cicumferential direction for the PDL.展开更多
The two-stage gas boriding in N_(2)−H_(2)−BCl_(3)atmosphere was applied to producing a two-zoned borided layer on Nisil-alloy.The process was carried out at 910℃ for 2 h.The microstructure consisted of two zones diff...The two-stage gas boriding in N_(2)−H_(2)−BCl_(3)atmosphere was applied to producing a two-zoned borided layer on Nisil-alloy.The process was carried out at 910℃ for 2 h.The microstructure consisted of two zones differing in their phase composition.The outer layer contained only a mixture of nickel borides(Ni_(2)B,Ni_(3)B)only.The inner zone contained additionally nickel silicides(Ni_(2)Si,Ni_(3)Si)occurring together with nickel borides.The aim of this study was to determine the presence of nickel silicides on the mechanical properties of the borided layer produced on Ni-based alloy.The hardness and elastic modulus were measured using the nanoindenter with a Berkovich diamond tip under a load of 50 mN.The average values of indentation hardness(HI)and indentation elastic modulus(E_(I))obtained in the outer zone were respectively(16.32±1.03)GPa and(232±16.15)GPa.The presence of nickel silicides in the inner zone reduced the indentation hardness(6.8−12.54 GPa)and elastic modulus(111.79−153.99 GPa).The fracture toughness of the boride layers was investigated using a Vickers microindentation under a load of 0.981 N.It was confirmed that the presence of nickel silicides caused an increase in brittleness(by about 40%)of the gas-borided layer.展开更多
The purposes of this work were to obtain the accurate elastic modulus of the nanocrystalline WC-Co cemented carbides, and to propose the mechanism for the difference of elastic modulus between the nanocrystalline and ...The purposes of this work were to obtain the accurate elastic modulus of the nanocrystalline WC-Co cemented carbides, and to propose the mechanism for the difference of elastic modulus between the nanocrystalline and conventional polycrystalline cemented carbides. The nanocrystalline cemented carbide was prepared by spark plasma sintering（SPS） technique. The conventional polycrystalline cemented carbides were prepared by SPS and sinter-HIP techniques as references, respectively. The sintered cemented carbides were characterized by X-ray diffractometry, scanning electron microscopy and the transmission electron microscopy with precession electron diffraction technology. The elastic modulus was obtained by averaging the values measured with the continuous stiffness measurement method of the nanoindentation technology. The results show that the nanocrystalline cemented carbide has a relatively low modulus, which could be attributed to the more interface area and higher fraction ratio of the hcp cobalt phase caused by the rapid heating and cooling process during SPS.展开更多
Higher order rnultipole potentials and electrostatic screening effects are introduced to incorporate the dan gling bonds on the surface of a metallic nanopaticle and to modify the coulornb like potential energy terms,...Higher order rnultipole potentials and electrostatic screening effects are introduced to incorporate the dan gling bonds on the surface of a metallic nanopaticle and to modify the coulornb like potential energy terms, respectively. The total interaction energy function for any rnetallic nanoparticle is represented in terms of two- and three-body potentials. The two-body part is described by dipole-dipole interaction potential, and in the three-body part, triple-dipole （DDD） and dipole-dipole-quadrupole （DDQ） terrns are included. The size-dependent cohesive energy and bulk modulus are observed to decrease with decreasing sizes, a result which is in good agreement with the experimental values of Mo and W nanoparticles.展开更多
Based on effective field method,the dynamic effective elastic modulus of polymer matrix composites embedded with dense piezoelectric nano-fibers is obtained,and the interacting effect of piezoelectric surfaces/interfa...Based on effective field method,the dynamic effective elastic modulus of polymer matrix composites embedded with dense piezoelectric nano-fibers is obtained,and the interacting effect of piezoelectric surfaces/interfaces around the nano-fibers is considered.The multiple scattering effects of harmonic anti-plane shear waves between the piezoelectric nano-fibers with surface/interface are averaged by effective field method.To analyze the interacting results among the random nano-fibers,the problem of two typical piezoelectric nano-fibers is introduced by employing the addition theorem of Bessel functions.Through numerical calculations,the influence of the distance between the randomly distributed piezoelectric nano-fibers under different surface/interface parameters is analyzed.The effect of piezoelectric property of surface/interface on the effective shear modulus under different volume fractions is also examined.Comparison with the simplified cases is given to validate this dynamic electro-elastic model.展开更多
基金The National Natural Science Foundation of Chin(No.51305208)
文摘In order to investigate the material properties ofperiodontal ligament （ PDL） in different locations, the nanoindentation method is used to survey the elastic modulus of the PDL at different levels. Cadaveric specimens of human mandibular canine were obtained from 4 adult donors, 16 transverse specimens were made from the sections of cervical margin, midroot and apex using the slow cutting machine. The prepared specimens were tested in different sections （along the longitudinal direction） and different areas （in the circumferential direction）. According to the Oliver-Phair theory, the mean values of elastic modulus were calculated foreach area and the differences among them were compared. In the midroot section, the average elastic modulus is ranging from 0. 11 to 0. 23 MPa, the changing range of the cervical margin and apex are from 0. 21 to 0. 53 MPa and 0. 44 to0.62 MPa, respectively. Experimental results indicate that the average elastic modulus in the midroot is lower than that in the cervical margin and apex, and relatively small changes occur among them. However, there is a large change to the elastic modulus value in the cicumferential direction for the PDL.
基金This work has been financially supported by Ministry of Science and Higher Education in Poland as a part of the Project No.0513/SBAD.
文摘The two-stage gas boriding in N_(2)−H_(2)−BCl_(3)atmosphere was applied to producing a two-zoned borided layer on Nisil-alloy.The process was carried out at 910℃ for 2 h.The microstructure consisted of two zones differing in their phase composition.The outer layer contained only a mixture of nickel borides(Ni_(2)B,Ni_(3)B)only.The inner zone contained additionally nickel silicides(Ni_(2)Si,Ni_(3)Si)occurring together with nickel borides.The aim of this study was to determine the presence of nickel silicides on the mechanical properties of the borided layer produced on Ni-based alloy.The hardness and elastic modulus were measured using the nanoindenter with a Berkovich diamond tip under a load of 50 mN.The average values of indentation hardness(HI)and indentation elastic modulus(E_(I))obtained in the outer zone were respectively(16.32±1.03)GPa and(232±16.15)GPa.The presence of nickel silicides in the inner zone reduced the indentation hardness(6.8−12.54 GPa)and elastic modulus(111.79−153.99 GPa).The fracture toughness of the boride layers was investigated using a Vickers microindentation under a load of 0.981 N.It was confirmed that the presence of nickel silicides caused an increase in brittleness(by about 40%)of the gas-borided layer.
基金Projects(51425101,51631002)supported by the National Natural Science Foundation of China
文摘The purposes of this work were to obtain the accurate elastic modulus of the nanocrystalline WC-Co cemented carbides, and to propose the mechanism for the difference of elastic modulus between the nanocrystalline and conventional polycrystalline cemented carbides. The nanocrystalline cemented carbide was prepared by spark plasma sintering（SPS） technique. The conventional polycrystalline cemented carbides were prepared by SPS and sinter-HIP techniques as references, respectively. The sintered cemented carbides were characterized by X-ray diffractometry, scanning electron microscopy and the transmission electron microscopy with precession electron diffraction technology. The elastic modulus was obtained by averaging the values measured with the continuous stiffness measurement method of the nanoindentation technology. The results show that the nanocrystalline cemented carbide has a relatively low modulus, which could be attributed to the more interface area and higher fraction ratio of the hcp cobalt phase caused by the rapid heating and cooling process during SPS.
基金Supported by King Saud University,College of Science-Research Center,Project Number PHYS/2009/19
文摘Higher order rnultipole potentials and electrostatic screening effects are introduced to incorporate the dan gling bonds on the surface of a metallic nanopaticle and to modify the coulornb like potential energy terms, respectively. The total interaction energy function for any rnetallic nanoparticle is represented in terms of two- and three-body potentials. The two-body part is described by dipole-dipole interaction potential, and in the three-body part, triple-dipole （DDD） and dipole-dipole-quadrupole （DDQ） terrns are included. The size-dependent cohesive energy and bulk modulus are observed to decrease with decreasing sizes, a result which is in good agreement with the experimental values of Mo and W nanoparticles.
基金supported by the National Natural Science Foundation of China(Grant Nos.11172185 and 11272222)the Natural Science Foundation for Outstanding Young Researcher in Hebei Province of China(Grant No.A201410015)+1 种基金the National Key Basic Research Program of China(Grant No.2012CB723300)the Training Program for Leading Talent in University Innovative Research Team in Hebei Province(Grant No.LJRC006)
文摘Based on effective field method,the dynamic effective elastic modulus of polymer matrix composites embedded with dense piezoelectric nano-fibers is obtained,and the interacting effect of piezoelectric surfaces/interfaces around the nano-fibers is considered.The multiple scattering effects of harmonic anti-plane shear waves between the piezoelectric nano-fibers with surface/interface are averaged by effective field method.To analyze the interacting results among the random nano-fibers,the problem of two typical piezoelectric nano-fibers is introduced by employing the addition theorem of Bessel functions.Through numerical calculations,the influence of the distance between the randomly distributed piezoelectric nano-fibers under different surface/interface parameters is analyzed.The effect of piezoelectric property of surface/interface on the effective shear modulus under different volume fractions is also examined.Comparison with the simplified cases is given to validate this dynamic electro-elastic model.
