The γ-ray radiation technique combined with hydrothermal crystallization was firstly used to prepare ultrafine metallic particles of An,Cu and Au-Cu alloy.Particle size for Au in average is about 10 nm.The morphologi...The γ-ray radiation technique combined with hydrothermal crystallization was firstly used to prepare ultrafine metallic particles of An,Cu and Au-Cu alloy.Particle size for Au in average is about 10 nm.The morphologies were observed by TEM.The nucleation mechanism of metal particles and their stability are discussed.展开更多
Spray-drying was used to produce the high emissivity NiCr2O4 powders with a spinel structure. Preliminary investigations focused on fabricating the high emissivity powders for infrared radiation coatings and finding t...Spray-drying was used to produce the high emissivity NiCr2O4 powders with a spinel structure. Preliminary investigations focused on fabricating the high emissivity powders for infrared radiation coatings and finding the relationship between microstructure and emissivity. The NiCr2O4 powders were characterized for composition, microstructure, and infrared emissivity by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, infrared radiant instrument, and Fourier transform infrared spectra （FT-IR）. Thermogravimetry and differential thermal analysis show that the appropriate baking temperature for NiCr2O4 powder preparation is about 1200？C. The emissivity measurement and FT-IR spectra show that, because of the special spinel structure, the NiCr2O4 powders have a high emissivity about 0.91. Spray-drying is a suitable method to produce the high emissivity ceramic powders.展开更多
In this paper, two types of high loft nonwoven fabrics have been constructed in the laboratory apparatus made by ourselves with different binders (polyamide and polyethylene powder) and varying binder contents (10%, 2...In this paper, two types of high loft nonwoven fabrics have been constructed in the laboratory apparatus made by ourselves with different binders (polyamide and polyethylene powder) and varying binder contents (10%, 20%, 30% and 40%). The tensile and compression properties of these nonwoven fabrics were tested. It was found that one can reduce powder binder content to increase loft and softness of nonwoven fabrics, but it has to sacrifice its tensile strength. Adhesion force between binder and single fibre was also explored. The experiments showed that the adhesion force at the interface between binder and fibre depends on the fibre variety, the fibre surface morphology, heating temperature and heating time etc..展开更多
The effect of gamma ray energies and volume ratio of micro steel fiber(1 and 1.5%) on attenuation properties of reactive powder concrete(70 MPa compressive strength) was investigated. Different characteristics have be...The effect of gamma ray energies and volume ratio of micro steel fiber(1 and 1.5%) on attenuation properties of reactive powder concrete(70 MPa compressive strength) was investigated. Different characteristics have been considered such as linear attenuation coefficient,mass attenuation coefficient, and half-value thickness.Sodium iodide crystal with a gamma ray spectrometer and collimated beam of gamma ray has been implemented to perform the experimental test. Three sources(Cs-137, Co-60, and Bi-207) with energies of(0.662, 1.17 1.33, 0.569,and 1.063) MeV were adopted in the test. The results obtained indicated that mass attenuation coefficient is proportioned inversely with gamma ray energies and directly with a volume ratio of micro steel fiber. The linear attenuation coefficient and half-value thickness of the tested samples have been calculated and discussed. The obtained results showed that increasing the volume ratio of steel fiber has modified the adequacy of the reactive powder concrete as a shielding element since it increases the density and reduces the half-value thickness.展开更多
This paper presents the results of investigations carried out with Pr-based magnetic powders. The magnetically hard powders were produced from homogenised alloys using a high temperature hydrogen pulverization process...This paper presents the results of investigations carried out with Pr-based magnetic powders. The magnetically hard powders were produced from homogenised alloys using a high temperature hydrogen pulverization process. Alloys and powders were investigated by scanning electron microscopy and by energy dispersive X-ray analysis. Mean crystallite size of the pulverized material was estimated using synchrotron powder diffractometry and the Scherrer method. A comparison between these two investigation techniques has been carried out. The effects of copper on the properties of the magnetic powders have been studied. It has been shown that the addition of this alloying element had a marked effect on the microstructure of the powders.展开更多
NANOCRYSTALLINE nickel is very important for its applications in the fields such as catalysis andmagnetic materials.The usual method used for preparing nanocrystalline nickel is inert gas e-vaporation,which requires h...NANOCRYSTALLINE nickel is very important for its applications in the fields such as catalysis andmagnetic materials.The usual method used for preparing nanocrystalline nickel is inert gas e-vaporation,which requires high temperature.However,high temperature easily leads tothe growth or oxidation of nickel particles.Marignier et al.reported the nickel microaggre-gates dispersed in solution produced by γ-irradiating a dilute solution of Ni<sup>2+</sup>展开更多
The radiation effect of powdery HDPE was studied,and was shown to be different behavior from sheet or film HDPE.Some factors affecting radiation grafting in solid state powdery HDPE like dose,dose rate,monomer kinds,w...The radiation effect of powdery HDPE was studied,and was shown to be different behavior from sheet or film HDPE.Some factors affecting radiation grafting in solid state powdery HDPE like dose,dose rate,monomer kinds,were investigated in detail.The characteristics of grafted HDPE such as melting temperature,crystallinity,decomposition temperature and decomposition activation energy were analyzed.Compared to the ungrafted HDPE, the grafted HDPE has better cohesive force and flexibility.The influence of various groups on cohesive force and flexibility was studied.展开更多
文摘The γ-ray radiation technique combined with hydrothermal crystallization was firstly used to prepare ultrafine metallic particles of An,Cu and Au-Cu alloy.Particle size for Au in average is about 10 nm.The morphologies were observed by TEM.The nucleation mechanism of metal particles and their stability are discussed.
文摘Spray-drying was used to produce the high emissivity NiCr2O4 powders with a spinel structure. Preliminary investigations focused on fabricating the high emissivity powders for infrared radiation coatings and finding the relationship between microstructure and emissivity. The NiCr2O4 powders were characterized for composition, microstructure, and infrared emissivity by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, infrared radiant instrument, and Fourier transform infrared spectra （FT-IR）. Thermogravimetry and differential thermal analysis show that the appropriate baking temperature for NiCr2O4 powder preparation is about 1200？C. The emissivity measurement and FT-IR spectra show that, because of the special spinel structure, the NiCr2O4 powders have a high emissivity about 0.91. Spray-drying is a suitable method to produce the high emissivity ceramic powders.
文摘In this paper, two types of high loft nonwoven fabrics have been constructed in the laboratory apparatus made by ourselves with different binders (polyamide and polyethylene powder) and varying binder contents (10%, 20%, 30% and 40%). The tensile and compression properties of these nonwoven fabrics were tested. It was found that one can reduce powder binder content to increase loft and softness of nonwoven fabrics, but it has to sacrifice its tensile strength. Adhesion force between binder and single fibre was also explored. The experiments showed that the adhesion force at the interface between binder and fibre depends on the fibre variety, the fibre surface morphology, heating temperature and heating time etc..
文摘The effect of gamma ray energies and volume ratio of micro steel fiber(1 and 1.5%) on attenuation properties of reactive powder concrete(70 MPa compressive strength) was investigated. Different characteristics have been considered such as linear attenuation coefficient,mass attenuation coefficient, and half-value thickness.Sodium iodide crystal with a gamma ray spectrometer and collimated beam of gamma ray has been implemented to perform the experimental test. Three sources(Cs-137, Co-60, and Bi-207) with energies of(0.662, 1.17 1.33, 0.569,and 1.063) MeV were adopted in the test. The results obtained indicated that mass attenuation coefficient is proportioned inversely with gamma ray energies and directly with a volume ratio of micro steel fiber. The linear attenuation coefficient and half-value thickness of the tested samples have been calculated and discussed. The obtained results showed that increasing the volume ratio of steel fiber has modified the adequacy of the reactive powder concrete as a shielding element since it increases the density and reduces the half-value thickness.
基金The authors wish to thank FAPESP and IPEN-CNEN/SP for the financial support and infrastructure madeavailable to carry out this investigation.
文摘This paper presents the results of investigations carried out with Pr-based magnetic powders. The magnetically hard powders were produced from homogenised alloys using a high temperature hydrogen pulverization process. Alloys and powders were investigated by scanning electron microscopy and by energy dispersive X-ray analysis. Mean crystallite size of the pulverized material was estimated using synchrotron powder diffractometry and the Scherrer method. A comparison between these two investigation techniques has been carried out. The effects of copper on the properties of the magnetic powders have been studied. It has been shown that the addition of this alloying element had a marked effect on the microstructure of the powders.
文摘NANOCRYSTALLINE nickel is very important for its applications in the fields such as catalysis andmagnetic materials.The usual method used for preparing nanocrystalline nickel is inert gas e-vaporation,which requires high temperature.However,high temperature easily leads tothe growth or oxidation of nickel particles.Marignier et al.reported the nickel microaggre-gates dispersed in solution produced by γ-irradiating a dilute solution of Ni<sup>2+</sup>
文摘The radiation effect of powdery HDPE was studied,and was shown to be different behavior from sheet or film HDPE.Some factors affecting radiation grafting in solid state powdery HDPE like dose,dose rate,monomer kinds,were investigated in detail.The characteristics of grafted HDPE such as melting temperature,crystallinity,decomposition temperature and decomposition activation energy were analyzed.Compared to the ungrafted HDPE, the grafted HDPE has better cohesive force and flexibility.The influence of various groups on cohesive force and flexibility was studied.
