Papers by Keyword: γ-Ray

Abstract: The radiation shielding abilities of functional particles (Sm₂O₃, Er₂O₃, WO₃ and Bi₂O₃) were simulated and proved to have a stronger absorption region and a weaker absorption region respectively. Four kinds of functional particles/epoxy radiation shielding composites used for low energy γ/Xray were designed based on the edge absorption and synergistic absorption. By optimizing the proportion of functional particles in epoxy composites, the radiation shielding abilities bad been further improved. According to the results of optimal design, a kind of Sm₂O₃/Er₂O₃/WO₃/Bi₂O₃/Epoxy composite was prepared and proved to be very efficient to shield low energy γ/X radiation.

Abstract: Nondestructive testing technology on prestressed pipe grouting is an important issue in recent years. Some research methods including Radar Method, Ray Method, and Impact Echo Method were contrasted and verified in this paper. The applicable scope and the defect detectable effect of these methods mentioned above was studied exploringly. The achievements obtained this paper were certain to be significant for the detection on pipeling grouting quality and defect inside concrete.

Abstract: A kind of novel protective coating was prepared by using super-hydrophobic PbWO₄ nanocrystals as functional stuffing. The samples were characterized systematically by means of scanning electron microscope (SEM), contact angle analyzer, atomic force microscope (AFM) and Fourier transform infrared spectroscopy(FT-IR). The effects of various amount of nano-PbWO₄ particles on shielding ratio to 59.5 keV γ-ray were also discussed. The results revealed that the average diameter of PbWO₄ nanocrystals were about 32nm. The contact angle between the modified PbWO₄ and water was amounted to 153.08°, which showed that the modified PbWO4 owned super hydrophobic surfaces. The modified PbWO₄ had good dispersion and stability in organic solvents. Chemistry reaction happened between components of coatings and nano-PbWO₄ particles, thus it showed good compatibility with binders. The shielding ratio to γ-ray was up to 32%, and the hardness and levelling property was greatly improved.

Abstract: In this research, the acrylic acid (AAc) was grafted onto polypropylene (PP) fabrics with the gamma-ray (γ-ray) preirradiation. The effect of acrylic acid concentration, grafting time, grafting temperature were conducted to obtain the optimum carboxyl adsorber manufacturing conditions. Furthermore, the effectiveness of carboxyl adsorber for removal heavy metal ions using various operating conditions such as reaction time, pH and metal/carboxyl adsorber molar ratio was also evaluated in this research.

Abstract: P-channel pentacene field effect transistorswith a Si/SiO₂/pentacene/Au structure were fabricated, and were gamma-ray irradiated with a Co⁶⁰ source. The changes of the drain current I_D vs. source/drain voltage V_SD (I_D - V_SD) characteristics were measured after every 200 Gy in silicon (Gy_Si) irradiations up to the total dose of 1200 Gy_Si. The drain current I_D continuously decreased to less than 10 % of that before irradiation after 1200 Gy_Si irradiation. The threshold voltage V_th continuously decreased up to 800 Gy_Si, started to saturate above 800 Gy_Si, and recovered above 1000 Gy_Si. The mobility m continued to decrease up to 1200 Gy_Si. Those behaviors were explained by accumulation of positive trapped charge within the gate insulator SiO₂ near the interface, continuous increase of interface traps near the interface between the SiO₂ and pentacene, and build up of electrons in the channel regions. These behaviors were discussed in comparisons with previously reported results on ultraviolet (UV) light irradiation experiments on similarly structured pentacene-based transistors.

Abstract: The radiation technology has been applied extensively in the field of biological engineering, tissue engineering, medical practices and so on. It also plays an important role in the sterilization and modification of biomaterials. This work reviews recent development of several types of radiation technology which have been applied in the field of medical biomaterials.

Abstract: This work discusses the degradations caused by high-energy neutrons in advanced MOSFETs and compares them with damages created by γ-rays reviewing the original researches performed in our laboratory during last years [1-6]. Fully–depleted (FD) Silicon-on-Insulator (SOI) MOSFETs and Multiple-Gate (MuG) FETs with different geometries (notably gate lengths down to 50 nm) have been considered. The impact of radiation on device behavior has been addressed through the variation of threshold voltage (VT), subthreshold slope (S), transconductance maximum (Gmmax) and drain-induced barrier lowering (DIBL). First, it is shown that degradations caused by high-energy neutrons in FD SOI and MuG MOSFETs are largely similar to that caused by γ-rays with similar doses [1,3]. Second, it is revealed that, contrarily to their generally-believed immunity to irradiation [7, 8], very short-channel MuGFETs with thin gate oxide can become extremely sensitive to the total dose effect [2,3]. The possible reason is proposed. Third, a comparative investigation of high-energy neutrons effects on strained and non-strained devices demonstrates a clear difference in their response to high-energy neutrons exposure [6]. Finally, based on simulations and modeling of partially –depleted (PD) SOI CMOS D Flip-Flop, we show how radiation-induced oxide charge and interface states build-up can affect well-known tolerance of SOI devices to transient effects [4,5].

Abstract: The effect of the fabrication process of n-channel 6H-SiC MOSFETs on their radiation resistance is investigated. MOSFETs that post implantation annealing for source and drain was carried out with carbon coating on the sample surface are compared to MOSFETs that post implantation annealing was carried out without carbon coating. The radiation resistance (gamma-rays) of the carbon-coated MOSFETs is higher than that of non-coated ones. The channel mobility for MOSFETs whose gate oxide was formed using pyrogenic or dry oxidation process dose not change by gamma-ray irradiation below 1x105 Gy. The value of channel mobility slightly increases with increasing dose above 1x105 Gy. No significant increase in irradiation induced interface traps is observed.

Abstract: N-channel MOSFETs are irradiated with gamma-rays (g-rays) up to 3.16 MGy(SiO2) at room temperature. Above 1 MGy, the effective channel mobility increases with increasing absorbed dose. A similar increase is observed for the Hall mobility in the inversion layer. In addition, the Hall-effect measurements indicate a reduction of the interface trap density.

Abstract: The gamma-ray irradiation causes positive charge traps formation in silicon dioxide films and at silicon dioxide - silicon interface of MOS devices, and the threshold voltage shift in MOS transistors. Here, the Monte Carlo model was used to develop an approach for estimating gammaray induced traps spatially distributed in silicon dioxide films. This is combined with the model of energy distributed traps at silicon dioxide - silicon interface. The developed model enables gammaray induced charge and threshold voltage shift determination as a function of gamma-ray doses. The threshold voltage measurements at a single specified current, both of radiation sensitive and radiation hardened MOS transistors irradiated with different doses of gamma-ray are compared with the developed model and good agreement are obtained.