c-BN as a promising material for industrial applications

Abstract

Diamond and c-BN commonly called “super-hard materials” are characterized by exceptional properties.

Such materials are promising for new developments, in particular c-BN due to its ability to be n or p-doped. In such a way we have focused our effort in two aspects:

-new routes for the h-BN → c-BN conversion,

-original fluxes able to favour the elaboration of crystallites free of defects.     

Resonant ionization of atomic hydrogen as a source of polarized protons

The method of obtaining polarized proton beams by means of resonant ionization of the hydrogen atoms is considered. The main physical features of the phenomenon are discussed. The conditions are found in which the degree of proton polarization is equal to 100%. The optimum values are found of the pulse duration and the field strengths of the exciting and ionizing light waves.     

Coulomb-hadronic interference with polarized protons at intermediate energies

The theory of Coulomb-hadronic interference for particles with spin is discussed. At intermediate energies it is favourable to introduce Bethe phases for each of the amplitudes. For proton-proton scattering the values of the Bethe phases as well as the magnitudes of other correction terms are estimated on the basis of amplitudes reconstructed from current phase shifts. Suitable parameterizations for observables are proposed.     

Acceleration of polarized protons to multi-GeV energies and experiments with polarized protons from 2–6 GeV/c

Acceleration of polarized protons. Experiments with polarized protons. Proton-proton total cross-section. Two and three spin proton elastic scattering measurements. Polarization measurements in nucleon-nucleon elastic scattering. Inelastic interactions. Inclusive lambda production. Coherent polarized proton⁴He interactions. Parity tests.Presented at the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975. Work supported by the U.S. Energy Research and Development Administration.I would like to thank the authors of all the experiments I have mentioned for their information, both published and unpublished.     

Distinctive slit-shaped porous carbon encapsulating phosphorus as a promising anode material for lithium batteries

A distinctive structure of carbon materials for Li-ion batteries is proposed for the preparation of red phosphorus-carbon composites. The slit-shaped porous carbon is observed with aggregation of plate-like particles, whose isotherm belongs to the H3 of type IV. The density functional theory (DFT) method reveals the presence of micro-mesopores in the 0.5–5 nm size range. The unique size distribution plays an important role in adsorbing phosphorus and electrochemical performance. The phosphorus-slit-shaped porous carbon composite shows initial capacity of 2588 mAh g^?1, reversible capacity of 1359 mAh g^?1 at a current density of 100 mA g^?1. It shows an excellent coulombic efficiency of ～99 % after 50 cycles.     

Two-dimensional PC_3 as a promising anode material for potassium-ion batteries: First–principles calculations

With the diversified development of the battery industry, potassium-ion batteries(PIBs) have aroused widespread interest due to their safety and high potassium reserves on earth. However, the lack of suitable anode materials limits their development and application to a certain extent. Based on first-principles calculations, we investigate the possibility of using PC_3 monolayer as the anode material for PIBs. PC_3 sheet has excellent electrical properties and meets the prerequisite of anode materials. The storage capacity of potassium is as high as 1200 m Ah·g~(-1), which is better than many other reported potassium-ion anode materials. In addition, the outstanding advantages of PC_3 sheet, such as low diffusion barrier and moderate open-circuit voltage, make it a potential anode candidate for PIBs.     

Breakup of 4He with polarized protons at 65 MeV

For the ⁴He(p, p³H)¹H reaction, large negative analyzing powers are observed in the FSI regions. For the inelastic scattering of protons, the angular dependence of the analyzing power is well reproduced by the single and double scattering terms of the Faddeev breakup theory.     

Photoproduction with polarized photons as a source of polarized gluon jets

We show that, according to QCD, the direct Compton process γq→qg in polarized photoproduction leads to strongly polarized gluon jets. We also show that this process is expected to dominate in the reaction γp→π⁺ + opposite side jet + X. The study of the opposite side jet will give direct evidence for the spin of the gluon.     

Bismuth silicate glass containing heavy metal oxide as a promising radiation shielding material

Optical and FTIR spectroscopic measurements and electron paramagnetic resonance (EPR) properties have been utilized to investigate and characterize the given compositions of binary bismuth silicate glasses. In this work, it is aimed to study the possibility of using the prepared bismuth silicate glasses as a good shielding material for γ-rays in which adding bismuth oxide to silicate glasses causes distinguish increase in its density by an order of magnitude ranging from one to two more than mono divalent oxides. The good thermal stability and high density of the bismuth-based silicate glass encourage many studies to be undertaken to understand its radiation shielding efficiency. For this purpose a glass containing 20% bismuth oxide and 80% SiO₂ was prepared using the melting–annealing technique. In addition the effects of adding some alkali heavy metal oxides to this glass, such as PbO, BaO or SrO, were also studied. EPR measurements show that the prepared glasses have good stability when exposed to γ-irradiation. The changes in the FTIR spectra due to the presence of metal oxides were referred to the different housing positions and physical properties of the respective divalent Sr²⁺, Ba²⁺ and Pb²⁺ ions. Calculations of optical band gap energies were presented for some selected glasses from the UV data to support the probability of using these glasses as a gamma radiation shielding material. The results showed stability of both optical and magnetic spectra of the studied glasses toward gamma irradiation, which validates their irradiation shielding behavior and suitability as the radiation shielding candidate materials.     

Study on the electrochemical behavior of vanadium nitride as a promising supercapacitor material

Vanadium nitride (VN) powder was synthesized by calcining V₂O₅ xerogel in a furnace under an anhydrous NH₃ atmosphere at 400 °C. The structure and surface morphology of the obtained VN powder were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The supercapacitive behavior of VN in 1 M KOH electrolyte was studied by means of cyclic voltammetry (CV), constant current charge-discharge cycling (CD) and electrochemical impedance spectroscopy (EIS). The XRD result indicates that the obtained VN belongs to the cubic crystal system (Fm3m [2 2 5]) with unit-cell parameter 4.15 Å. SEM images show the homogeneous surface of the obtained VN. The CV diagrams illustrate the existence of fast and reversible redox reactions on the surface of VN electrode. The specific capacitance of VN is 161 F g⁻¹ at 30 mV s⁻¹. Furthermore, the specific capacitance remains 70% of the original value when the scan rate increases from 30 to 300 mV s⁻¹. CD experiments show that VN is suitable for CD at high current density, and the slow and irreversible faradic reactions exist during the charge-discharge process of the VN electrode. The experimental results indicate that VN is a promising electrode material for electrochemical supercapacitors.     

Analysis of PNC neutron resonance experiments with polarized targets

The analysis of parity mixing experiments with unpolarized neutrons on polarized targets is described. Expressions for the neutron total cross section are presented for targets withI=1/2, 3/2, 5/2 and 7/2. These results are compared with the corresponding expressions for polarized neutron beams and unpolarized targets.     

Constraints on leptophobic gauge bosons with polarized neutrons and protons at RHIC

We explore the sensitivity and the physical interest of the measurement of parity-violating spin asymmetries in one-jet production in the presence of a new leptophobic neutral gauge boson, , within polarized hadronic collisions at the BNL RHIC. We focus on polarized neutron collisions which could be achieved in a realistic upgrade of the RHIC-spin program. We show that, in the case of a discovery, a compilation of the information coming from both polarized and collisions should constrain the number of Higgs doublets and the presence or absence of trilinear fermion mass terms in the underlying model of new physics. Received: 20 November 2001 / Published online: 5 April 2002     

用20—1020 keV单能质子刻度CR-39固体核径迹探测器

用北京师范大学2×1.7MV串列加速器和400 kV高压倍加器产生的20—1020 keV单能质子束对CR-39固体核径迹探测器进行了刻度.为了保证质子的单能性和固体核径迹探测器上径迹密度不能超过10⁶/cm²的要求,对两台加速器分别采用了不同方法控制质子辐照数量.在串列加速器上采用了狭缝加转盘的方法,在高压倍加器上采用了100 ns单次高压脉冲扫描束流的方法,既保持了质子的单色性,又达到了质子注量小于10⁶/cm²的 关键词： 单能质子 固体核径迹探测器 CR-39     

Novel PdAgCu ternary alloy as promising materials for hydrogen separation membranes: Synthesis and characterization

The use of the sequential electroless plating method allowed us to obtain the PdAgCu ternary alloy on top of dense stainless steel (SS) 316 L disks. The XRD analysis indicated that initially the nucleation of the two phases of the alloy (FCC and BCC) takes place, but the FCC/BCC ratio increases with the annealing time at 500 °C in H₂ stream. After 162 h, the film contained only the FCC phase, which presents promising properties to be applied in the synthesis of hydrogen selective membranes. SEM cross-section results showed that a dense, continuous, defect-free film was deposited on top of the SS support, and the EDS data indicated that no significant gradient was present on the thickness of the film. XPS and LEIS allowed us to determine that Cu and Ag surface segregation takes place after annealing up to 500 °C/5 days. In the top-most surface layer, Ag enrichment takes place as determined by ARXPS experiments which can be the result of the lower surface tension of Ag compared to that of Cu and Pd. Increasing the annealing temperature results in an increase of the Ag surface segregation while the Cu concentration in the top-most surface layer decreases.