Narrow Results

We report recent results on the cosmic-ray spectrum and the composition obtained by RUNJOB collaboration (RUssia-Nippon JOint Balloon collaboration). We present the preliminary spectra for individual elements from proton to iron as well as the all-particle and the average mass in the energy range 10 to ~ 1000 TeV/particle, using 95% of the total exposure, and compare them with other experimental data, particularly those recently reported by ATIC group.

Amorphous materials of the Si-(B)-C-N system have recently attracted considerable interest because of its hardness, low density, durability at extremely high temperature and easy to be prepared from precursor compounds by polymer route. The materials show a great potential to be used in the field of the Thermal Protective System (TPS) for the aircrafts, while the microstructure and chemical configuration are still not clearly revealed due to its complicated covalent character for this multi-component amorphous material. This paper focused on the characterization of polymer derived Si-(B)-C-N amorphous ceramic, various method were employed in order to obtain accurate information about the microstructure, chemical composition, bonding mode of components, such as TEM, EPMA, NMR and FT-IR. SiC crystalline was found existing in the amorphous glass, which indicates the preparation process was achieved accompanied by crystallization of SiC from polymer precursor. The microstructure of the researched material was analyzed and relative accurate chemical composition was obtained on the basis of characterization result, furthermore the covalent character of the amorphous material was deduced according to the characterization results obtained.

Corrosion behavior of 7N01 Al alloy is sensitive to chemical composition. In this paper, stress corrosion cracking (SCC) and electrochemical behaviors of A7N01S-T5 Al alloys with three different chemical compositions were investigated. The corrosion weight loss and corrosion pits depth statistics showed that Alloy #3 (4.53wt.%Zn, 1.27%Mg, < 0.001%Cu, 0.24%Cr, 0.15%Zr) possesses the best anti-SCC property, while Alloy #1 (4.54%Zn, 1.09%Mg, 0.102%Cu, 0.25%Cr, 0.15%Zr) was the weakest one. The different SCC susceptibility was mainly related to the Cu content as Alloy #3 contains higher Cu than Alloys #1 and #2. Electrochemical test result showed that Alloy #3 has higher corrosion potential and lower corrosion current density than Alloys #1 and #2. It is believed that a trace Cu can significantly improve the SC resistance of Al alloy, mainly because that Cu element can reduce the potential difference between grain inside and grain boundaries.

In this paper, welded joints of four types of A7N01S-T5 aluminum alloy with different chemical compositions were investigated. The welding process was under 70% environmental humidity conditions at 10${}^{\circ }$C with single-pulse GMAW welding technology. The strength and fracture toughness of the four types of samples were tested, and the microstructures were investigated by micro-X-ray fluorescence (SR-LXRF) technology and backscattered electron diffraction (EBSD) technology. The results showed that the #2 alloy that is composed of Zn: 4.59 wt.%, Mg: 1.56 wt.% Mn: 0.22 wt.%, Cr: 0.14 wt.%, Zr: 0.01 wt.% and Ti: 0.027 wt.% had the best combination of tensile strength and elongation, with the values of 302.35 MPa and 3.74%, respectively. The better result for the combination of the strength and elongation was mainly determined by the volume fraction and size. The fine grain size and compositions played important roles to obtain high fracture toughness.

Particle samples were collected in August 2004 both inside and outside Emperor Qin's Terra-Cotta Museum in Xi'an, China. Mass and chemical composition of total suspended particles (TSP, particles with aerodynamic diameter less than ~30 μm), PM_2.5 (particles with aerodynamic diameter <2.5 μm) were determined. The average levels of indoor PM_2.5 and TSP were 108.4 and 172.4 μg·m^-3, respectively, with PM_2.5 constituting 62.9% of the TSP mass. Sulfate ((32.4±6.2)%), organics ((27.7±8.0)%), and geological material ((12.5±3.4)%) dominated indoor PM_2.5, followed by ammonium ((8.9±2.8)%), nitrate ((7.0±2.9)%), and elemental carbon (EC, (3.9±1.5)%). Particle size distribution varied with the number of tourists in the museum. The size of sulfate, organics, EC, nitrate, and ammonium was found to vary in the range of 0.43 to 3.3 μm in fraction. Ion balance indicated that the aerosol was acidic, with insufficient ammonium ions to neutralize the sulfuric and nitric acids. High concentrations of acidic aerosols will erode the Terra-cotta warriors and horses especially in the summer season with high temperature (30℃) and relative humidity (70%) and undesirable solar radiation inside the museum. More attention should be paid to protecting these precious antiques made 2000 years ago.

The sunflower stem core is one kind of natural polymer material. Its structure presents obvious structure gradient from the center to outer part. This article mainly focuses on the relationship between nature of cell walls and the mechanical properties of sunflower stem core. The mechanical properties recorded by the universal testing machine; the cell wall's chemical composition, the cellulose crystallinity and the microfibril angle were measured using the chemical analysis method and X-ray powder diffraction. Research shows that the Young modulus of outer part is nearly 3 times more than that of center part, while the yield strength is 2.5 times more than that of center part. The main components of the sunflower stem core are cellulose, hemicellulose and lignin. The amount of those three components is about 70% of the total dry weight. The contents in the center and outer part are slightly different. The difference of crystallinity and microfibril angle between the center and outer part are quite small, which are 41.39–41.49% and 29.64–27.20%, respectively. Therefore, the results suggested that the nature of cell walls has little influence to the difference of mechanical properties between the center and outer part, and the cell structure is the main reason.

Since the lithium-ion conductor Li${}_{10}$GeP₂S${}_{12}$ (LGPS) with a super high room-temperature conductivity of 12mS/cm was first reported in 2011, sulfide-type solid electrolytes have been paid much attention. It was suggested by Kwon et al. [J. Mater. Chem. A3, 438 (2015)] that some excess lithium ions in LGPS, namely, Li${}_{10+\delta }$Ge${}_{1+\delta }$ P${}_{2-\delta }$S${}_{12}$, could further improve their ionic conductivities, and the highest conductivity of 14.2mS/cm was obtained at $\delta =0.35$ though a larger lattice parameter that occurred at $\delta =0.5$. In this study, we focus on these two different chemical compositions of LGPS with $\delta =0.35$ and $\delta =0.5$, respectively. Both samples were prepared using the same experimental process. Their lattice parameter, microstructure and room-temperature ionic conductivity were compared in detail. The results show that the main phase is the tetragonal LGPS phase but with a nearly identical amount of orthorhombic LGPS phase coexisting in both samples. Bigger lattice parameters, larger grain sizes and higher ionic conductivities are simultaneously achieved in Li${}_{10.5}$Ge${}_{1.5}$P${}_{1.5}$S${}_{12}$ ($\delta =0.5$), exhibiting an ultrahigh room-temperature ionic conductivity of 18.8mS/cm.

Atmospheric ultrafine particles (with diameter less than 0.1 μm) may be responsible for some of the adverse health effects observed due to airpollutant exposure. To date, little is known about the chemical composition of ultrafine particles in the atmosphere of cities. Ultrafine particle samples collected by inertial separation on the lower stages of cascade impactors can be analysed to determine a material balance on the chemical composition of such samples. Measurements of ultrafine particle mass concentration made in seven Southern California cities show that ultrafine particle concentrations in the size range 0.056−0.1 μm aerodynamic diameter average 0.55−1.16 μg m⁻³. The chemical composition of these ultrafine particle samples averages 50% organic compounds, 14% trace metal oxides, 8.7% elemental carbon, 8.2% sulphate, 6.8% nitrate, 3.7% ammonium ion (excluding one outlier), 0.6% sodium and 0.5% chloride. The most abundant catalytic metals measured in the ultrafine particles are Fe, Ti, Cr, Zn, with Ce also present. A source emissions inventory constructed for the South Coast Air Basin that surrounds Los Angeles shows a primary ultrafine particle emissions rate of 13 tonnes per day. Those ultrafine particle primary emissions arise principally from mobile and stationary fuel combustion sources and are estimated to consist of 65% organic compounds, 7% elemental carbon, 7% sulphate, 4% trace elements, with very small quantities of sodium, chloride and nitrate. This information should assist the community of inhalation toxicologists in the design of realistic exposure studies involving ultrafine particles.