Formation and electron properties of the interface between organic (TPD) and inorganic (ZnO) materials

The initial stage of formation of an organic coating of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) on a crystalline (ZnO) surface in the course of thermal deposition in high vacuum has been studied using the low-energy total current spectroscopy technique. A change in the work function and the density of unoccupied electron states in an energy interval of 0–20 eV above the vacuum level was traced as the organic coating thickness increased up to 8 nm. The energy positions of the bands of unoccupied electron states in the TPD film have been determined, including π* band (7–9 eV above the Fermi level), σ₁* band (10–12 eV), σ₂* band (14–16 and 18–20 eV).     

Effect of new poly 2-acryloyl-N,N'-bis (4-nitrophenyl) propandiamide and poly 2-acryloyl-N,N'-bis (4-methylphenyl) propandiamide and their synergistic action on the stability of nitrocellulose

The stability of nitrocellulose can be significantly improved by incorporating two novel polymeric compounds as new stabilizers, each has two p-substituted phenyl rings in its repeating unit. The two prepared polymers were used independently and in three different blend ratios in comparison with the conventional propellant stabilizer, diphenylamine. The efficiency of the prepared stabilizers and their synergistic effect were evaluated using thermo gravimetric analysis (TGA), Bergmann-Junk test and differential scanning calorimetry (DSC). It was found that both polymers and their 50%:50% blend ratio are more efficient nitrocellulose stabilizers than diphenylamine.     

Thermal stability of epitaxial cubic-TiN/(Al,Sc)N metal/semiconductor superlattices

Journal of Materials Science - We report on the thermal stability of epitaxial cubic-TiN/(Al,Sc)N metal/semiconductor superlattices with the rocksalt crystal structure for potential plasmonic,...     

Electronic structure, density of electronic states, and the chemical bonding properties of 2,4-dihydroxyl hydrazone crystals (C13H11N3O4)

Electronic crystal structure, bonding properties, and the electron charge densities of 2,4-dihydroxybenzaldehyde-4-nitrophenylhydrazone (2,4-DHNPH,C₁₃H₁₁N₃O₄) crystal are theoretically investigated. Calculations are performed with local density approximation, generalized gradient approximation, the Engel–Vosko generalized gradient approximation, and modified Becke–Johnson potential. We present the results of the total and partial (C, N, O, H atoms) density of states. Furthermore, the electronic charge density space distribution contours in the (1 1 0) crystallographic plane, which gives better insight picture of chemical bonding were calculated to understand the effect of hydrogen bonding on the crystal structure of 2,4-DHNP.     

Neutron and X-ray powder diffraction studies of the oxynitrides SrW(O,N)3, Ba3W2(O,N)8 and Ba3Mo2(O,N)8

Oxynitrides of composition SrW(O,N)₃, Ba₃W₂(O,N)₈ and Ba₃Mo₂(O,N)₈ have been prepared by the ammonolysis of stoichiometric mixtures of oxides and carbonates. Combined Rietveld refinements of powder neutron and powder X-ray diffraction data have allowed the structure of each to be determined. SrW(O,N)₃ was found to have a cubic Perovskite structure whereas Ba₃W₂(O,N)₈ and Ba₃Mo₂(O,N)₈ have a layered hexagonal structure. In the hexagonal structures the oxygen and nitrogen atoms are distributed almost randomly over two sites in the unit cell producing 4-fold co-ordination to tungsten and molybdenum, a distorted octahedral co-ordination to one barium site and a 10-fold co-ordination to the other.     

Synthesis of Fe3N by mechano-chemical reactions between iron and organic H x (CN)6 ring compounds

Novel mechanically activated solid state synthesis reactions between elemental Fe powder and amine compounds-piperazine (Hi₁₀C₄N₂) and pyrazine (H₄C₄N₂) — have been studied. Powder samples prepared after 144 and 228 h of ball milling in vacuum were examined by X-ray diffraction, scanning electron microscopy and thermal analysis methods. After ball milling for a time brief compared to that required for most solid state-gas reactions formation of a crystalline iron nitride (Fe₃N) a predominant phase with nitrogen concentration up to ca. 9.0 wt% was observed. Thermal analysis experiments showed structural stability of the Fe₃N phase up to ca. 720 K. In the final product a small residual fraction was formed from Fe and carbon dispersed during mechanical processing. The concentration of carbon in this fraction, estimated from thermogravimetric analysis was up to 2.5 wt%, dependent on milling conditions and the organic compound used. Mechanochemical synthesis, reaction effectiveness, product composition and particle morphology depends on the milling time and chemical characteristics of the organic compound used. Fine Fe₃N particles at a submicrometre size range were obtained only by milling with pyrazine. Further, the higher chemical reactivity of pyrazine than piperazine was confirmed through the higher level of nitridation achieved in the same preparation time.     

Crystal structure of a new organic dihydrogenomonophosphate (C6H8N3O)2(H2PO4)2

Chemical preparation, X-ray single-crystal, thermal behavior, and IR spectroscopy investigations are given for a new organic cation dihydrogenomonophosphate (C₆H₈N₃O)₂(H₂PO₄)₂ (denoted IAHP) in the solid state. This compound crystallizes in the orthorhombic space group P2₁2₁2₁. The unit cell dimensions are: a = 7.422(3) Å, b = 12.568(5) Å, c = 20.059(8) Å with V = 1871.1(13) Å³ and Z = 4. The structure has been solved using direct method and refined to a reliability R factor of 0.029. The atomic arrangement can be described as inorganic layers of H₂PO₄⁻ anions between which are located the organic groups (C₆H₈N₃O)⁺ through multiple hydrogen bonds.     

The synthesis and structure of suspended ultra-thin Si(3)N(4) nanosheets

Suspended Si(3)N(4) nanosheets at least 4?μm in width and ranging from 1.5 to 4?nm in thickness were successfully synthesized for the first time. Several of those nanosheets had scrolled edges due to being ultra-thin. According to transmission electron microscopy (TEM) and atomic force microscopy (AFM) observations, the Si(3)N(4) nanosheets exhibit microscopic corrugations in the range of several tens of nanometres. In addition, the directions of the microscopic corrugations were not random, but instead parallel to specific crystal orientations.     

On the relations between ISE and structure in some RE(Mg)SiAlO(N) glasses

Six oxide and oxynitride glasses were synthesized in the Y–Mg–Si–Al–O–N, Nd–Mg–Si–Al–O–N and La–Mg–Si–Al–O–N systems. As already known, nitrogen introduction increases the T _g, packing factor and mechanical properties of the glasses. Cationic substitution also has an influence on the glasses’ behavior, particularly in terms of sensitivity to indentation load/size effect (ISE). The structure of the yttrium-containing glasses was investigated by mean of ²⁷Al and ²⁹Si MAS-NMR. Al is found to occur for 2/3 as a network former and for 1/3 as a modifier. The oxide glass mainly contains Q² and Q³ silicate units and SiO₃N and SiO₂N₂ units are created when nitrogen is introduced into the glass network. The average number of rigid bonds per network former was calculated from the glasses’ composition. A discrepancy between and the Raman spectra of the glasses suggests that parts of the magnesium behaves as a former in the network. seems to be a key parameter governing hardness and sensitivity to ISE and can be linked to normal/abnormal behavior of glasses regarding indentation.     

基于ECR-PEMOCVD生长的稀磁半导体(Ga,Mn)N的特性

利用电子回旋共振-等离子体增强金属有机物化学气相沉积(ECR-PEMOCVD)技术,在蓝宝石(α-Al2O3)衬底上生长出Mn含量约为3%的(Ga,Mn)稀磁半导体薄膜.利用反射高能衍射(RHEED)、原子力显微镜(AFM)和X射线衍射(XRD)表征(Ga,Mn)N薄膜的表面形貌和结构特征.(Ga,Mn)N薄膜具有良好的(0002)择优取向和纤锌矿结构,表面形貌是由许多亚微米量级的晶粒按一致的取向规则堆砌而成.光致发光(PL)测量发现3.27eV附近出现施主-受主对(DAP)发光峰.超导量子干涉仪(SQUID)测量表明薄膜在室温下具有铁磁性,没有发现超顺磁性和自旋玻璃态,居里温度可达400K.     

Crystal structure and molecular packing in a new organic semiconductor penta[bis(ethylenedithio)tetrathiafulvalene]-hexathiocyanatomononitratoyttrium(III)-ethanol

A new radical cation (ET)₅[Y(NCS)₆NO₃]·C₂H₅OH salt was prepared by electrochemical oxidation of ET in a chlorobenzene–ethanol solution. Its crystal structure and conducting properties were examined. The salt has a layered crystal structure with a new type of molecular packing in the radical cation layer, which was called the ω-type. The observed electroconducting properties suggest that this salt is a semiconductor.     

Environmental and health risks of chlorine trifluoride (ClF3), an alternative to potent greenhouse gases in the semiconductor industry

Glycidyl methacrylate/methelenebisacrylamide resin with immobilized tetraethylenepentamine ligand was prepared. This pentamine containing resin was transformed to two anion exchange resins through treatment by glycidyl trimethylammonium chloride to give (RI) or hydrochloric acid giving (RII). The resins were used to adsorb As(V) at different experimental conditions using batch and column methods. Kinetics and thermodynamic properties as well as the mechanism of interaction between As(V) and resin active sites were discussed. The maximum adsorption capacities of As(V) on RI and RII were found to be 1.83 and 1.12 mmol/g, respectively. The regeneration and the durability of the loaded resin towards the successive reuse were also investigated.     

Electronic structures of Mg3Pn2 (Pn=N, P, As, Sb and Bi) and Ca3N2 calculated by a first-principle pseudopotential method

Electronic structure calculations for Mg₃N₂, Mg₃P₂, Mg₃As₂ (low and high temperature modifications), Mg₃Sb₂, Mg₃Bi₂, and Ca₃N₂ have been performed. Mg₃Sb₂ is predicted to be an indirect semiconductor with the gap value of about 0.41 eV. Mg₃As₂ with a high temperature modification is also predicted to be a semiconductor with the gap value of about 1.1 eV, but the valence band maximum and the conduction band minimum of Mg₃Bi₂ contacts at Γ which would make it a semimetal. Mg₃N₂, Mg₃P₂, and Mg₃As₂ (low temperature phase) are semiconductors with the direct band gaps of 1.64 eV, 1.73 eV, and 1.57 eV, respectively. Ca₃N₂ is a semiconductor with a gap of about 1.2 eV.     

The Coulombic traction on the surfaces of an interface crack in dielectric/piezoelectric or metal/piezoelectric bimaterials

This paper deals with the Coulombic traction usually neglected, but inherently acting, on the surfaces of an interface crack in dielectric/piezoelectric or metal/piezoelectric bimaterials. The dielectric material phase is treated as a special kind of piezoelectric material with a little piezoelectricity, whereas the metal phase is treated as another special kind of piezoelectric material with an extremely large permittivity and an extremely small piezoelectricity. The permittivity of the medium inside the crack gap is accounted for either. The normal electric displacement component and the Coulombic traction on the crack surfaces are unknown, and are determined from a cubic equation deduced from the extended Stroh formula. Numerical results for the Coulombic traction in both kinds of bimaterials reveal that in most cases its magnitude is remarkable and cannot be entirely neglected when the applied electric field is higher. It is concluded that in most cases the Coulombic traction yields significant influence on the effective stress intensity factor at the crack tip and may influence the fracture behavior in such kinds of bimaterials. As compared to homogenous piezoelectric materials, the metal phase always decreases the Coulombic traction, whereas the dielectric phase decreases it under the negative electric field and increases it under the positive electric field. In all cases, BaTiO₃ always yields a much larger Coulombic traction than PZT-4.     

Electrophoretic deposition of poly[3-(3-N,N-diethylaminopropoxy)thiophene] and composite films

Poly[3-(3-N,N-diethylaminopropoxy)thiophene] (PDAOT) was prepared by oxidative polymerization and investigated by ultraviolet (UV), Raman and nuclear magnetic resonance (NMR) spectroscopies. Protonated PDAOT was dissolved in water or ethanol/water mixtures and deposited by cathodic electrophoretic deposition (EPD) on conductive substrates. Film thickness was varied in the range of 0–5 μm by controlling the deposition voltage and deposition time. PDAOT was found to form strong supramolecular interactions with single-walled carbon nanotubes (SWNTs), allowing the formation of stable and concentrated nanotube dispersions, which were used for the formation of composite PDAOT–SWNT films by EPD. Furthermore, introduction of ZnO particles to the PDAOT solutions also allowed the formation of PDAOT–ZnO composite films by EPD. The composition of the films was varied by changing the concentration of SWNTs and ZnO in the suspensions. The dispersion of ZnO particles was improved using protonated dopamine (DA) as a dispersant. The deposits were studied by X-ray analysis (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction and scanning electron microscopy (SEM).