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The application of carbon fiber epoxy resin composite (CFRP) in the aerospace industry is limited by the laser treatment, because of the poor oxidation resistance and anti-laser ablation performance of the composites. The application of a coating on components is an effective method to improve their laser ablation resistance. The nitride coatings, consisting of Si3N4, AlN, BN, and an epoxy resin, were applied onto the CFRP using brush painting. When irradiating at 100 W/cm2 for 5 s, the damage has occurred on the coating with Si3N4 and AlN, and the BN coating remains original morphology at 100 W/cm2 for 20 s. With the power density has increased to 200 W/cm2, the serious ablation damage occurs in the BN coating irradiated for 10 s. Due to the heat absorption of resin pyrolysis and the low thermal conductivity of CFRP, the highest back-surface temperature is only 75 °C. The laser protection performance of CFRP should mainly improved by increasing the reflectivity of the coating. [ABSTRACT FROM AUTHOR]

China Advance Research Reactor (CARR) at China Institute of Atomic Energy (CIAE), with a non-perturbed maximum thermal neutron flux of 1 × 10 cm s at the center of active area, is one of the most powerful research reactors in the world. Three neutron channels have been allocated for conventional neutron activation analysis (NAA), thermal neutron prompt gamma activation analysis (PGAA) and cold neutron PGAA, respectively. Two irradiation tube systems are installed in the conventional NAA channel. One of them is for short irradiation with the rabbit size of diameter (Φ)19 × 40 mm, the other one is for long irradiation with the rabbit size of Φ39 × 70 mm. The medium temperature is about 45 °C and the thermal neutron flux is about 3 × 10 cm s at sample positions. The flux gradient is expected to be very small according to the designed neutron flux distribution. Pneumatic systems are used for samples transfer. The speed of rabbits is designed to be about 20 m/s, and it takes 3 s to travel from irradiation position to detector. Three sets of gamma counting systems and one delayed neutron counting system are being equipped for routine analysis. They are designed for running continuously and automatically. And all the functions can be operated at laboratory or office through remote controlled computer. Software has been made domestically for spectrum peak search, concentration calculation with relative method and k method with interference corrections and some other functions for the convenience of users. [ABSTRACT FROM AUTHOR]

Taking advantages of nuclear analytical techniques (NATs) with non-destruction, multielement capability, small and estimable uncertainties over a wide range of sample sizes, the sampling behavior of multielements for a home-made natural matrix material was studied with sample sizes ranging from several hundred mg down to tenths ng, namely nine orders of magnitude, by a combination of three NATs, neutron activation analysis (NAA), proton induced X-ray emission (PIXE) and synchrotron radiation X-ray flurescence (SR-XRF), in an effort to explore a procedure for the development of certified reference materials (CRMs) suitable for quality control of microanalysis. For accurately weighable sample sizes (>1 mg), sampling uncertainties for 13 elements were found to be less than 1% by INAA. For sample sizes unable to be accurately weighed (<1 mg), PIXE and SR-XRF were used, respectively. Sampling uncertainties were found to be less than 1% at sample sizes of tenth mg level for seven elements, and less than 10% on ng levels for three elements. Considering these three elements have satisfied homogeneity (sampling uncertainty less than 10%) at ng sample size level, any one of them can be served as a 'relative balance' in sampling behavior characterization of multielements on sample size levels larger than ng (e.g., μg level). On this basis, sampling uncertainties for nine elements were found to be less than 10% on μg sample size level by INAA. The results indicate that the matrix is eligible as a candidate of CRMs suitable for quality control of solid sampling microanalysis. [ABSTRACT FROM AUTHOR]

A total of 178 aerosol samples in two size fractions, PM10-2.5 (coarse) and PM2.5 (fine), were collected on nucleopore films using a Gent stacked filter unit sampler at the Graduate School of China Nuclear Industrial Group during May 2007 to November of 2009. Black carbon was determined by a reflectometer. A total of 16 elements, Mg, Al, S, Si, P, Cl, Ca, K, Ti, Mn, Fe, Ni, Cu, Zn, As and Pb, were determined by Particle Induced X-ray Emission. Mg, Al, Ca, K and Mn were also determined by Neutron Activation Analysis. Concentrations of all these elements were used to identify possible pollution sources and directions of the airborne particulate matter by means of softwares PMF and CPF. Some extraordinary events, such as sandstorms, firework and transboundary fire smoke were pinpointed by a combination of time series of multielement, relevant meteorological data and softwares Wind rose, Hysplit, and Google earth. [ABSTRACT FROM AUTHOR]

The half-life of 97Zr, used for the calculation of thermal/epithermal neutron flux ratio in k0-NAA, is re-determined using three measurement systems with different pulse processing principles. The result of 16.755±0.013 hours clarifies the discrepancy between two widely used literature values, 16.744±0.011 and 16.90±0.05 hours. Different dead-time correction methods used on various measurement systems are evaluated. Factors influencing precise measurement of relative peak counting rates are discussed in time-series measurements over a dynamic range of 1000-fold radioactive intensities (10 half-lives). [ABSTRACT FROM AUTHOR]

Radiochemical neutron activation analysis (RNAA) has been used for the determination of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu) in two Chinese certified reference materials (CRM), GBW 08503 (wheat powder) and GBW 09101 (human hair). These determinations are important for possible certification of the above mentioned ultra-trace elements, so far not certified. A simple one-step (REE)F3 precipitation was used. Chemical yields were determined for all relevant elements by means of tracer experiments. The two CRM were also analyzed by inductively coupled plasma–mass spectrometry (ICP–MS) to compare the merits and drawbacks of these two major trace analytical techniques for these particular elements. RNAA was proven to be a reliable technique for ultra-trace analysis, especially in the certification of some ultra-trace elements. [ABSTRACT FROM AUTHOR]

A PC controlled automatic INAA system is briefly introduced. The unique features of the system in software, hardware, and quality control procedures are described. Major performances are given to show the analytical quality and productivity of the system. [ABSTRACT FROM AUTHOR]

Thirty rats were divided randomly into five groups and fed with different feeds. They were killed after 2 mo. Right thighs of these rats were taken as samples. Bone mineral densities of these samples were measured by the double-energy x-ray bone mineral densitometer, and trace elements contents of the samples were analyzed by neutron activation analysis. Results of the experiments showed that some elements were well correlated with others, and there were obvious variances between some elements of the normal group and those of other four groups. [ABSTRACT FROM AUTHOR]

Three kinds of plant leaves, Chinese white aspen, arborvitae, and pine needles, have been sampled from the Yanshan Oil refinery complex, the Capital Iron and Steel Factory, and Badachu, a control area in Beijing, as biomonitors for air-pollution studies. Each sample was divided into two parts, washed, and unwashed. Thirty-one trace elements (As, Au, Br, Ca, Cd, K, La, Lu, Mo, Na, Sb, Sm, U, W, Yb, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Rb, Sc, Se, Sr, Ta, Tb, Th, and Zn) have been determined by using the relative and the K0 methods of instrumental neutron activation analysis (NAA) techniques. The results indicated the following: (1) The concentration of trace elements in unwashed samples are much higher than these in washed samples; (2) the area around Capital Iron and Steel Factory is heavily polluted, and the Yanshan Oil refinery complex area is moderately polluted; (3) Chinese white aspen is a good biomonitor in particular seasons and pine needles are better than arborvitae for yearly monitoring; (4) elements As, Cd, Hg, Co, Rb, Sb, W, and Zn are highly absorbed by Chinese white aspen. Pine needles are sensitive for the absorption the elements Br, Cr, Cd, Fe, Sc, Cs and rare earth elements, but arborvitae is very sensitive for the absorption of Sr. [ABSTRACT FROM AUTHOR]

Thirty two elements were determined in five pieces of presumed cosmic dust samples with the weights of 5 to 25 μg by neutron activation analysis (NAA). All the interferences from fission, threshold reactions and γ-spectra were corrected for and different counting geometries normalized. Enrichment factors with reference to C1-chondrite are about 200 and 100 for lithophile refractory elements (e.g., V, Th, Hf and W) and rare earth elements (REE), respectively. Deficiencies were observed for Co, Cr, Mg and Na, etc. The C1-chondrite normalized REE patterns are close to those of extraterrestrial materials, with no anomaly of Eu, indicating an extraterrestrial origin of the grain samples analyzed. [ABSTRACT FROM AUTHOR]

Mn-nodule is one of the most important deep sea mineral resources to be explored and exploited in the next century. Analytical quality control based on this kind of Certified Reference Materials (CRMs) is therefore necessay. In the present work, nearly 30 elements in two Chinese Mn nodule Reference Materials (RMs), GSPN-2 and GSPN-3, were determined using extended K0-relative comparison NAA technique, developed in our laboratory. The unique features of this work include; (1) high accuracy obtained by the interal validation function of our technique; (2) extensive determinable elements obtained by the hybrid nature of our software and (3) neutron flux self-shielding corrections. [ABSTRACT FROM AUTHOR]

Taking the advantage of the high precision and accuracy of neutron activation analysis (NAA), sampling constants have been determined for multielements in several international and Chinese reference materials. The suggested technique may be used for finding elements in existing CRMs qualified for quality control (QC) of small size samples (several mg or less), and characterizing sampling behaviors of multielements in new CRMs specifically made for QC of microanalysis. [ABSTRACT FROM AUTHOR]