文档类型

Small range 文档类型:"1"

Totally found 556 items.

  • [会议] Properties of Porous Magnesium Using Polymethyl Methacrylate (PMMA) as a Space Holde
    Porous magnesium has been recognized as a promising biodegradation metal for bone substitute application because of its excellent biocompatibility, low density, ability to biodegrade in vivo and excellent mechanical properties. In the present work, porous magnesium was fabricated by powder metallurgy using spherical polymethyl methacrylate (PMMA) as a space holder. To determine the optimum sintering temperature for porous magnesium fabrication, the porous magnesium was fabricated using double step sintering process at various sintering temperature (550℃, 585℃ and 620℃) in first stage of research. The porous magnesium fabricated was then characterized for morphology, porosity, density and compressive strength. Density of porous magnesium increases and the porosity decreases with increasing sintering temperature. The mechanical characterization indicated that porous magnesium sintered at 620℃ exhibited the highest compressive strength and density with optimum range of porosity of 39.37%. For second stage of research, porous magnesium with porosities of 39.38 - 40.82% was produced with different sizes of PMMA particles (38-63 μm, 63-90 μm and 90-125 μm). The compressive yield strength ranges between 19.95 MPa to 23.28 MPa and increases with decreasing PMMA particles size and porosity. These results proven that the PMMA has a potential to be used as space holder in porous magnesium for biomedical application.
    关键词: -
  • [会议] Properties of Porous Magnesium Using Polymethyl Methacrylate (PMMA) as a Space Holde
    Porous magnesium has been recognized as a promising biodegradation metal for bone substitute application because of its excellent biocompatibility, low density, ability to biodegrade in vivo and excellent mechanical properties. In the present work, porous magnesium was fabricated by powder metallurgy using spherical polymethyl methacrylate (PMMA) as a space holder. To determine the optimum sintering temperature for porous magnesium fabrication, the porous magnesium was fabricated using double step sintering process at various sintering temperature (550℃, 585℃ and 620℃) in first stage of research. The porous magnesium fabricated was then characterized for morphology, porosity, density and compressive strength. Density of porous magnesium increases and the porosity decreases with increasing sintering temperature. The mechanical characterization indicated that porous magnesium sintered at 620℃ exhibited the highest compressive strength and density with optimum range of porosity of 39.37%. For second stage of research, porous magnesium with porosities of 39.38 - 40.82% was produced with different sizes of PMMA particles (38-63 μm, 63-90 μm and 90-125 μm). The compressive yield strength ranges between 19.95 MPa to 23.28 MPa and increases with decreasing PMMA particles size and porosity. These results proven that the PMMA has a potential to be used as space holder in porous magnesium for biomedical application.
    关键词: -
  • [会议] Environmental effects in biaxially orientated Polymethyl Methacrylate
    Environmental stress cracking (ESC) is commonly found in polymers when submerged in an environment under applied stress. In such conditions, a crack may initiate and propagate from a material defect until it reaches a critical size and causes catastrophic failure. It is known that materials with a denser molecular structure are less prone to ESC, hence amorphous polymers often suffer greatly from this effect. A fracture mechanics approach was employed to investigate the fracture mechanism and crack growth in both air and environment. Two different grades of PMMA (amorphous and biaxially stretched PMMA) were tested in solvents with similar solubility parameters as this is known to hasten crazing. Time for crack initiation and crack speed were obtained and plotted against their corresponding fracture toughness. Thus, the ESC resistance of each material can be compared and component life expectance can also be predicted. To validate the experimental results, scanning electron microscopy (SEM) was used to examine the fracture mechanism of ESC.
    关键词: Environmental stress cracking;Biaxially orientated PMMA;Fracture mechanics;Crazing
  • [会议] Thermal Shock Behavior and Bonding Strength of MoSi_2-BaO-Al_2O_3-SiO_2 Gradient Porous Coating with Polymethyl Methacrylate Addition for Porous Fibrous Insulations
    In order to improve the thermal shock behavior of high temperature resistant coating on porous fibrous referactory insulations, the MoSi_2-BaO-Al_2O_3-SiO_2 (MoSi_2-BAS) gradient porous coatings were designed by preparing a dense surface layer and a porous bonding layer with the method of brushing and subsequent sintering at 1773 K. The porous bonding layer was obtained by adding polymethyl methacrylate (PMMA) as pore former. As the content of PMMA increases, the MoSi2-BAS coatings changed from a dense structure into a gradient porous structure. The interface bonding strength and thermal shock resistance of the MoSi_2-BAS coatings were investigated. The result shows that the as-prepared coating with gradient porous structure exhibited excellent thermal shock resistance, which remained gradient structure without cracking after thermal cycling 100 times between 1773 K and room temperature. And the interface bonding strength of the gradient porous coating reached 1.5±0.08 Mpa, which was much better than that of the dense coating.
    关键词: polymethyl methacrylate;porous insulation;gradient porous coating;BAS glass
  • [会议] Environmental effects in biaxially orientated Polymethyl Methacrylate
    Environmental stress cracking (ESC) is commonly found in polymers when submerged in an environment under applied stress. In such conditions, a crack may initiate and propagate from a material defect until it reaches a critical size and causes catastrophic failure. It is known that materials with a denser molecular structure are less prone to ESC, hence amorphous polymers often suffer greatly from this effect. A fracture mechanics approach was employed to investigate the fracture mechanism and crack growth in both air and environment. Two different grades of PMMA (amorphous and biaxially stretched PMMA) were tested in solvents with similar solubility parameters as this is known to hasten crazing. Time for crack initiation and crack speed were obtained and plotted against their corresponding fracture toughness. Thus, the ESC resistance of each material can be compared and component life expectance can also be predicted. To validate the experimental results, scanning electron microscopy (SEM) was used to examine the fracture mechanism of ESC.
    关键词: Environmental stress cracking;Biaxially orientated PMMA;Fracture mechanics;Crazing
  • [会议] Structural Changes in Polymethyl Methacrylate during Laser Machining
    The focus of the article is an issue of laser machining of polymethyl methacrylate materials. Specifically, it deals with evaluation of structural changes in polymers as due to the effect of concentrated energy there appears vaporization of the material in the place of cut as well as heat transfer into the material around the place of cut and thus to the heating. As a result of the raised temperature, different structural changes may occur in the material; some high-molecular substances begin to break down into low-molecular substances, and depoly-merization or degradation of the material may occur. All these changes may result in a change of the final properties of the product. For experimental machining and subsequent study using the "Fourier Transform Infrared" vibration spectroscopy, PMMA was chosen as it is one of the most feasible polymeric materials in this technology.
    关键词: Laser Technology; Structural Changes; Polymeric Material; Vibration Spectroscopy
  • [会议] Deep hole drilling of polymethyl methacrylate with small diameters by actively compensating the hole straightness deviation
    Deep hole drilling is very demanding in terms of process control and precision of the used machine tools. In particular for drilling of polymethyl methacrylate (PMMA) with small drill diameters below 1 mm specific aspects have to be considered compared to regular drilling. Instances are the low glass temperature and the poor heat transmission from the material's viewpoint and the hole straightness deviation and the inability of proper process monitoring from the process viewpoint. Furthermore it hast to be evaluated individually if other manufacturing technology are possibly more suitable for the desired application. In this paper the problems are discussed which occur when drilling polymethyl methacrylate with small diameters. On this basis the results of initial drilling tests are discussed and presented whereby the used concept for live condition monitoring of the process is introduced.
    关键词: Micro Manufacturing;Deep Hole Drilling;Polymethyl Methacrylate
  • [会议] Influence of PMMA and h-BN particles sizes on electrical and thermal properties of PMMA/h-BN composite materials produced by electrostatic adsorption method
    The electrostatic adsorption method can fabricate composite materials with an arbitrary structure. Changing a parameter such as the size of an individual component, which alters the composition, can adjust the composite material's characteristics. To develop a thermally conductive and electrically insulating composite material with a high thermal conductivity and an acceptable breakdown strength, a polymethyl methacrylate (PMMA)/hexagonal boron nitride (h-BN) composite material was produced by changing the h-BN filler size or the PMMA particle size using the electrostatic adsorption method. Regardless of the h-BN size, the DC breakdown strength and the thermal conductivity of the composite increased and decreased, respectively, as the PMMA size increased. For composites with the same sized PMMA particles, the breakdown strength of the composite with a larger h-BN particle size was smaller than that of the composite with a smaller h-BN particle size. The thermal conductivity between these composites showed an inverse trend to the DC breakdown strength. These characteristics are attributed to the length of the h-BN, the filler orientation, and the change in the distance between fillers.
    关键词: Thermal conductivity;Electric breakdown;Adsorption;Conductivity;Electrostatics;Composite materials;Market research
  • [会议] Adsorption of methyl orange from aqueous solution onto PMMA nanofiber: Kinetics study
    The potential of polymethyl methacrylate (PMMA) nanofiber prepared by the electrospinning technique for the methyl orange (MO) adsorption from aqueous solution was investigated. In this study, the adsorption experiments were carried out to investigate the effect of temperatures in a batch system. From experiment it can be seen that the MO adsorption using PMMA nanofiber increased with increasing temperature. The kinetic data of MO were analyzed by pseudo-first-order and pseudo-second-order kinetic models. It was found that the amount of MO adsorbed increase with increasing temperature. Kinetics parameters data indicated that the MO adsorption onto PMMA nanofiber was found to follow both pseudo first and second-order rate equations. L. Wang, A. Wang Bioresource Technology. 99 (2008) 10.1016/j.biortech.2007.01.063 S. Chatterjee, M. W. Lee, S. H. Woo Bioresource Technology. 101 (2010) 10.1016/j.biortech.2009.10.051 C. Namasivayam, D. Kavitha Dyes and Pigments. 54 (2002) 10.1016/S0143-7208(02)00025-6 L. Wang, A. Wang Journal of Hazardous Materials. 160 (2008) 10.1016/j.jhazmat.2008.02.104 S. Chatterjee, D. S. Lee, M. W. Lee, S. H. Woo Bioresource Technology. 100 (2009) 10.1016/j.biortech.2008.12.035 M. A. Zulfikar, H. Setiyanto Int. J. ChemTech. Res. 5 (2013) H. S. Rai, M. S. Bhattacharyya, J. Singh, T. K. Bansal, P. Vats, U. C. Banerjee Critical Reviews in Environmental Science and Technology. 35 (2005) 10.1080/10643380590917932 Y. Y. Xu, M. Zhou, H. J. Geng, J. J. Hao, Q. Q. Ou, S. D. Qi, H. L. Chen, X. G. Chen Applications of Surface Science. 258 (2012) 10.1016/j.apsusc.2011.12.054 Y. Haldorai, J. J. Shim Applications of Surface Science. 292 (2014) 10.1016/j.apsusc.2013.11.158 Z. Aksu, I. Aisoglu Process Biochemistry (Barking, London, England). 40 (2005) 10.1016/j.procbio.2005.02.004 Y. Sang, F. Li, Q. Gu, C. Liang, J. Chen Desalination. 223 (2008) 10.1016/j.desal.2007.01.208 Y. Lu, Z. Wu, M. Li, Q. Liu, D. Wang Reactive &Functional Polymers. 82 (2014) 10.1016/j.reactfunctpolym.2014.06.004 D. K. Sharma, F. Li, Y. Wu Colloids and Surfaces. A, Physicochemical and Engineering Aspects. 457 (2014) 10.1016/j.colsurfa.2014.05.038 M. Aliabadi, M. Irani, J. Ismaeili, H. Piri, M. J. Parnian Chemical Engineering Journal. 220 (2013) 10.1016/j.cej.2013.01.021 H. Liu, X. Lei, Y. Zhai, L. Li Adv. Chem. Eng. Sci. 2 (2012) 10.4236/aces.2012.22031 R. Xu, M. Jia, Y. Zhang, F. Li Microporous and Mesoporous Materials. 149 (2012) 10.1016/j.micromeso.2011.08.024 Z. Xu, Q. Gu, H. Hu, F. Li Environmental Technology. 29 (2008) 10.1080/09593330802008412 L. Ai, C. Zhang, L. Meng Journal of Chemical &Engineering Data. 56 (2011) 10.1021/je200743u R. Gong, J. Ye, W. Dai, X. Yan, J. Hu, X. Hu, S. Li, H. Huang Industrial &Engineering Chemistry Research. (2013) 10.1021/ie402138w J. Yi, L. Zhang Bioresource Technology. 99 (2008) 10.1016/j.biortech.2007.05.028 M. B. Amran, M. A. Zulfikar Int. J. Environ. Sci. 67 (2010) H. Hiroyuki, M. Fukudas, A. Okamato, T. Kataoka Chemical Engineering Science. 48 (1994) M. Saker, S. Podar Proc. Ind. Annu. Commun. 31 (1994) M. A. Zulfikar, H. Setiyanto, D. Wahyuningrum, R. R. Mukti International Journal of Environmental of Research. 8 (2014) A. Mohammadi, H. Daemi, M. Barikani International Journal of Biological Macromolecules. 69 (2014) 10.1016/j.ijbiomac.2014.05.042 M. A. Zulfikar, S. Afrita, D. Wahyuningrum, M. Ledyastuti Environ. Nanotechnol. Monitor. Manage. 6 (2016) 10.1016/j.enmm.2016.06.001 M. Salman, B. El-Eswad, F. Khalili Applied Clay Science. 38 (2007) 10.1016/j.clay.2007.02.011
    关键词: adsorption;dyes;electrospinning;nanofabrication;nanofibres;polymer fibres
  • [会议] Novel measurements of shock pressure decay in PMMA using detonator loading
    An empirical model equation for shock-pressure decay in PMMA was determined through a unique set of experiments employing detonator loading. Custom polymethyl methacrylate (PMMA) witness blocks were designed with monolithic architecture to house precise PMMA gaps with thicknesses ranging from 0-10 mm in nominal increments of 1 mm. The PMMA gaps separated detonator working surfaces from windowed photonic Doppler velocimetry (PDV) probes, and were designed to provide undistorted optical access for ultra-high-speed framing and digital-streak cameras. The shock wave image framing technique (SWIFT), and a new laser-backlit digital-streak diagnostic, simultaneously captured the temporal evolution of detonator-induced diverging shock waves within the PMMA gaps. The PDV diagnostic measured critical mass-velocity histories as the shocks exited the variable gap thicknesses. The multi-diagnostic data package was used to characterize the shock-pressure decay in PMMA as a function of shock-propagation time and PMMA thickness.
    关键词: -
意见反馈
返回顶部