Corrosion behavior of low energy,high temperature nitrogen ion-implanted AISI 304 stainless steel

This work presents the results of a low-energy nitrogen ion implantation of AISI 304 type stainless steel (SS) at a moderate temperature of about 500°C. The nitrogen ions are extracted from a Kauffman-type ion source at an energy of 30 keV, and ion current density of 100 μA cm⁻². Nitrogen ion concentration of 6 × 10¹⁷, 8 × 10¹⁷ and 10¹⁸ ions cm⁻², were selected for our study. The X-ray diffraction results show the formation of CrN polycrystalline phase after nitrogen bombardment and a change of crystallinity due to the change in nitrogen ion concentration. The secondary ion mass spectrometry (SIMS) results show the formation of CrN phases too. Corrosion test has shown that corrosion resistance is enhanced by increasing nitrogen ion concentration.      

Dissociative adsorption of N2 on W(1 1 0): Theoretical study of the dependence on the incidence angle

The dissociative adsorption of N₂ on W(1 1 0) is studied using classical dynamics on a six-dimensional potential energy surface obtained from density functional theory calculations. Two distinct channels are identified in the dissociation process: a direct one and an indirect one. It is shown that the direct channel is inhibited for low energy molecules (E_i < 400 meV) and low incidence angles. The indirect channel includes long-lasting dynamic trapping of the molecule at the surface before dissociation. The dependence of the sticking coefficient on the initial incidence angle is analyzed. The theoretical results compare well with values measured using molecular beam techniques.     

p-type ZnO thin films grown by RF plasma beam assisted Pulsed Laser Deposition

The high exciton binding energy and band gap energy of ZnO thin films open the prospect of fabricating semiconductor lasers in the ultraviolet spectral range. A prerequisite for laser diode fabrication is highly p-doped ZnO which was not reproducibly obtained up to now. Without intentional doping ZnO exhibits n-type conduction. ZnO thin films have been obtained by radio-frequency assisted pulsed laser deposition. A metallic Zn target was used for ablation in an oxygen and nitrogen RF discharge. The electrical and morphological properties of the films grown on Si were studied by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), optical absorption and Hall Effect measurements for different ratios between the nitrogen and oxygen content. The AFM images of the as-grown ZnO films reveal high quality surfaces with low values for the surface roughness and a sharp distribution of grains sizes as an effect of the RF discharge. The XRD patterns for all samples exhibit only (002) and (004) peaks indicating that the c-axis is always oriented normal to the substrate surface. The films present p-type conductivity with different carrier concentration and mobility depending on the nitrogen/oxygen ratio.     

N2-broadening coefficients in the ν2 and ν4 bands of PH3 at low temperature

N₂-broadening coefficients have been measured for 41 transitions of PH₃ at −100 °C in the ^QR branch of the ν₂ band and the ^PP, ^RP, and ^SP branches of the ν₄ band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 1 to 13 and K from 0 to 10 are located between 1026 and 1093 cm⁻¹. The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter models provide larger broadening coefficients than the Voigt model. These coefficients have also been calculated on the basis of a semiclassical model of interacting linear molecules by considering an atom-atom Lennard-Jones potential in addition to the electrostatic contributions. By comparing broadening coefficients at room and low temperatures, the temperature dependence of these broadenings has been determined both experimentally and theoretically.     

Synthesis and characterization of hexasubstituted azacryptands

Using an imine condensation strategy, hexaazacryptands were prepared from an aromatic triamine and various dialdehydes. The global shape of these cages can be modified by simple alkylation of the six nitrogen atoms. The cavity is thus elongated and rendered hydrophobic.     

Anomalous Molecular Phase of Nitrogen: Implications to the Phase Diagram

Despite their simplicity, diatomic molecules of first row elements can exhibit very complex phase diagrams. Determination of the phase diagrams can be further complicated by the existence of hysteretic molecular phases that can be observed over large regions of coexistence. Here we present evidence for a previously unreported molecular phase of nitrogen existing at room temperature at least over the range of 33-74 GPa. Our measurements show that sample history may have a significant impact on the thermodynamic states accessed by the molecular nitrogen solid and, by extension, also on the established phase diagram.     

Evaluation of sample treatment procedures for the routine identification and determination at nanogram level of O6-monoacetylmorphine in urine by capillary GC and dual NPD-FID

Three methods were evaluated for the determination of O⁶-monoacetylmorphine (6-MAM), the specific metabolite of heroin in human urine, by GC-NPD-FID. The procedure devised for a hydrophobic cation exchange column showed superior performances over the liquid-liquid extraction technique and solid phase extraction with C₁₈. 6-MAM can be analyzed in random urines at the 2 ng/mL concentration with classical equipment for the differentiation between heroin intake and opiates from various origins. The procedure was also applied to enzymatic and acid hydrolyzates of urines. The simultaneous presence of morphine and codeine are useful in the interpretation of results.     

Nitrogen doping effects on the structure of graphene

Graphene and nitrogen doped graphene have been prepared by modified Hummers’ method and the following ammonia heat-treatment process, respectively. The effects of N-doping on the structure of graphene have been systematically investigated by various characterization techniques. SEM, TEM, BET, Raman and XRD analysis were used to distinguish the difference of the microstructures; and FT-IR, XPS, especially XANES were performed to elucidate the bonding information such as C-N. The effect of nitrogen doping on the structure of graphene has been obtained. More defects are present on nitrogen doped graphene as elucidated by BET, XRD, Raman, and XANES characterizations. XANES analysis also indicates that the N-doping decreases the surface oxygen-containing groups.     

Rotational spectra, nuclear quadrupole hyperfine tensors, and conformational structures of the mustard gas simulent 2-chloroethyl ethyl sulfide

Rotational spectra have been recorded for both the ³⁵Cl and ³⁷Cl isotopic forms of two structural conformations of 2-chloroethyl ethyl sulfide (CEES). The rotational constants of the ³⁵Cl and ³⁷Cl isotopomers were used to identify the conformational isomers. A total of 236 hyperfine transitions have been assigned for 47 rotational transitions of the ³⁵Cl isotope of a GGT conformer, and 146 hyperfine have been assigned for 37 rotational transitions of the ³⁷Cl isotopomer. For the second conformer, a total of 128 (110) hyperfine and 30 (28) rotational transitions have also been assigned to the ³⁵Cl (³⁷Cl) isotopes of a TGT conformation. The extensive hyperfine splitting data, measured to high resolution with a compact Fourier transform microwave spectrometer, were used to determine both the diagonal and off-diagonal elements of the ³⁵Cl and ³⁷Cl nuclear quadrupole coupling tensors in the inertial tensor principal axis system. The experimental rotational constant data, as well as the ³⁵Cl and ³⁷Cl nuclear quadrupole coupling tensors, were compared to the results from 27 optimized ab initio (HF/6-311++G^∗∗ and MP2/6-311++G^∗∗) model structures.     

SiH3与NO2反应机理的理论研究

采用密度泛函B3LYP/6311G和高级电子相关耦合簇CCSD(T)/6311G方法计算研究了SiH3与NO2的反应机理,全参数优化了反应势能面上各驻点的几何构型,用内禀反应坐标(IRC)计算和频率分析方法,对过渡态进行了验证.研究结果表明,SiH3与NO2是一多通道多步骤的反应,经过缔合,氢转移和离解等复杂过程,最终得到5种产物.