Nano-composite silicon powders have been produced at a maximum process throughput of 6 g/min by plasma spraying with metallurgical grade silicon powder as raw material. The obtained powders are found to be fundamentally composed of crystalline silicon particles of 20-40 nm in diameter, and are coated with an $5-nm-thick amorphous carbonous layer when methane gas is additionally introduced during plasma spraying. The performance of half-cell batteries containing the powders as negative electrodes has shown that the capacity decay observed for the raw Si coarse particles is significantly improved by plasma treatment. The carbonous coating potentially contributes to an improvement in capacity retention, although coexisting SiC particles that inevitably form during high-temperature processing reduce the overall capacity. V C 2014 AIP Publishing LLC.

We reported that T cells with anti-CD38-chimeric antigen receptors (CAR) eliminated B-cell lymphoma cells expressing CD38. To employ anti-CD38-CAR against acute myeloid leukemia (AML) blasts not expressing CD38, it is necessary to induce or increase the intensity of CD38 expression. A lactate dehydrogenase (LDH)-releasing assay and flow cytometry showed that anti-CD38-CAR T cells were cytotoxic against AML lines (THP-1 and CMK) expressing high CD38 levels (>99%), in time- and number of effector-dependent manners. In other AML lines (KG1, U937 and HL60) partially expressing CD38, CD38+ AML cells were killed by CD38-specific T cells, but CD38− AML cells remained survived. Intriguingly, 10 nM all-trans retinoic acid (ATRA) augmented CD38 expression in KG1, U937 and HL60 cells and primary leukemic cells from AML patients. Moreover, the withdrawal of ATRA from the medium decreased CD38 expression in AML cells. Killing effects of anti-CD38-CAR T cells against AML lines and AML cells were limited without ATRA, whereas CD38-specific T cells enhanced cytotoxicity on AML cells by ATRA in association with enhanced CD38 expression. These results indicate that anti-CD38-CAR T cells eliminate AML cells through CD38 expression induced by ATRA.

The authors demonstrate that the electric conductivities of cubic and hexagonal boron nitride (c-BN and h-BN) thin films increased markedly by the in situ doping of zinc. The doped films were electrically semiconducting, and conductivities at room temperature increased from 10−8to10−2Ω−1cm−1 with increasing zinc concentration from 400to20000ppm. Activation energies for electric conduction (Ec) of c-BN decreased from 0.3to0.1eV with increasing zinc concentration, suggesting feasible shallow-level doping. On the other hand, h-BN thin films showed approximately 0.1eV higher Ec than those of c-BN’s, due to the formation of defective B–B bonds.

A numerical model was developed to predict the behavior of a particle in a radio-frequency (rf ) plasma. The analysis obtained the heat, mass, and momentum transfer of a single particle injected into an rf plasma. The governing equations for vaporization of a liquid particle were taken from the model which was used to simulate the vaporization process of liquid droplets in a rocket combuster. All the thermodynamical and transport properties were calculated as functions of temperature in order to simulate the actual behavior more precisely. The boundary conditions are a finite temperature at the particle center and a heat balance at the particle surface. Thermodynamical equilibrium at the particle surface was always assumed. ’’Moving-boundary problems’’ in the case of melting or vaporizing processes were solved by the use of a ’’moving grid system’’. Four sizes of iron particles injected into the rf argon plasma have been computed: r0=20, 40, 60, and 80 μ. The iron particles with radii less than 70 μ could be melted under the assumed plasma conditions. It was found that the potentiality as concerns powder processing of an rf plasma was overestimated by previous models.

No abstract

A numerical model has been developed for predicting the two-dimensional flow and temperature fields in a hybrid plasma which is characterized by the superposition of an rf plasma and an arc jet. Calculations have been made for the confirmation of a prominent feature of the hybrid plasma. As might be expected, the derived results suggested that the hybrid plasma has a possibility to offer higher efficiencies for practical processing than other conventional plasmas. Particularly noteworthy is the disappearance of a recirculation eddy found in a usual rf plasma, by the presence of the high velocity and high-temperature channel caused by an arc jet flow. Moreover, the relative insensitive character of the exit gas enthalpy to the rf input power was found. Based on the theoretical investigations, a reactor was designed to confirm the effectiveness of the hybrid plasma for chemical syntheses. Using the reactor, ultrafine amorphous Si3N4 with the nitrogen content of 37±0.5 wt. % and the size of 10–30 nm, which can meet the purity and size requirements of an ideal Si3N4 powder, could be prepared successfully by a reaction of SiCl4 and NH3. These theoretical and experimental investigations confirmed that the hybrid plasma torch is an effective reactor for the preparation of ultrafine refractory compounds by plasma chemical vapor deposition (CVD) processes.

Nanocomposite Si/SiOx powders were produced by plasma spray physical vapor deposition (PS-PVD) at a material throughput of 480 g h−1. The powders are fundamentally an aggregate of primary ∼20 nm particles, which are composed of a crystalline Si core and SiOx shell structure. This is made possible by complete evaporation of raw SiO powders and subsequent rapid condensation of high temperature SiOx vapors, followed by disproportionation reaction of nucleated SiOx nanoparticles. When CH4 was additionally introduced to the PS-PVD, the volume of the core Si increases while reducing potentially the SiOx shell thickness as a result of the enhanced SiO reduction, although an unfavorable SiC phase emerges when the C/Si molar ratio is greater than 1. As a result of the increased amount of Si active material and reduced source for irreversible capacity, half-cell batteries made of PS-PVD powders with C/Si = 0.25 have exhibited improved initial efficiency and maintenance of capacity as high as 1000 mAh g−1 after 100 cycles at the same time.

No abstract