B、N原子掺杂超长扶手椅型碳纳米管的GTOs-PBC方法研究

使用密度泛函B3LYP/3-21G*方法,并用周期边界条件模型,计算了B、N掺杂纳米管的结构参数、掺杂能量、能带结构和能隙.研究表明,碳纳米管掺杂B、N原子后,能隙均增大,变为半导体.B原子掺杂的碳纳米管具有直接带隙,而N原子掺杂则具有间接带隙,B掺杂的(6,6)和(9,9)管以及N掺杂的(6,6)和(9,9)管的能隙...     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.     

Density functional study on electronic properties of P-doped spinel silicon carbon nitride

We performed density functional calculations on the electronic properties of P-doped spinel silicon carbon nitride. When Si is replaced by C at the tetrahedral sites of P-doped c-Si₃N₄, the band gap can be adjusted, and an insulator-to-metal transition is predicted to occur at the C-to-Si ratio of 0.27. Finally, some possible examinations and potential applications for the large band-gap reduction are discussed.     

Sol‐Gel‐Process in the Ammono‐System – a Novel Access to Silicon Based Nitrides

Controlled coammonolysis of elementalkylamides in aprotic organic solvents at low temperatures have been shown to result in the formation of polyazanes. The synthetic procedure developed may be addressed as “sol‐gel‐route in the ammono system”. Pyrolysis of these novel polymer precursors gave access to multinary nitrides. For the model systems Si(NHMe)₄/B(NMe₂)₃, Si(NHMe)₄/Ti(NMe₂)₄, and Si(NHMe)₄/Ta(NMe₂)₅ polymeric boro‐, titano and tantalosilazanes were obtained. Pyrolysis in ammonia at 1000 °C yielded amorphous silicon boron nitride, silicon titanium nitride and silicon tantalum nitride powders; further heating of the nitride powders at 1500 °C in nitrogen atmosphere led to the formation of partly crystalline composites of α‐Si₃N₄ and amorphous silicon boron nitride for the Si/B/N system, a composite of finely dispersed TiN and amorphous silicon titanium nitride for the Si/Ti/N system, and crystalline TaN and amorphous silicon nitride for the Si/Ta/N system. Furthermore, the structure and pyrolysis chemistry of the polymeric intermediates, as well as the morphology of the pyrolysis products, were studied by NMR, MAS‐NMR, FT‐IR, DTA‐TG‐MS, XRD, SEM, EDX and elemental analyses.     

Preparation and Characterization of Si3N4-TiN Nanocomposite via in situ Co-deposition in Liquid Ammonia

"A new method of TiN/Si3N4 nanocomposite synthesis was described and tested. TiCl4 and SiCl4 used as the starting materials and sodium as the reduction agent were conducted in liquid ammonia respectively. TiCl4 and SiCl4 were reduced simultaneously and titanium nitride/silicon nitride nanocomposite powderswere obtained by in situ co-deposition at temperatures around ~ 45 oC. X-ray diffraction patterns indicate that the product was amorphous and the by-product was sodium chloride. The product powders were heated up to 1600 oC and crystallization to TiN and fi-Si3N4 happened. Due to presence of TiN, the crystallization of silicon nitride in the mixture was later than that of pure silicon nitride. Transmission electron microscopy images show the average size of powders range from 10 nm to 40 nm and scanning electron microscopy images conformed that Ti and Si elements were dispersed uniformly. A green bulk nitride composite containing 20%TiN with the mean grain size of 100-300 nm and fracture toughness of 10.1§1.1 m1=2MPa , was obtained by spark plasma sintering at 1500-1600 oC. The effect of TiN additiven microstructure and mechanical properties of composite bulk was discussed."     

Room-temperature ferromagnetism in silicon oxide/silicon nitride composite films

Room-temperature ferromagnetism has been observed in silicon oxide/silicon nitride composite films formed on Si substrates at different substrate temperatures, and the ferromagnetic properties of the samples have been found to depend on the silicon nitride content of the films. It is proposed that the ferromagnetism is related to the interface states between the silicon oxide particles and silicon nitride particles. The saturation magnetization (M_S) reached its maximum value in the film produced at a substrate temperature of 400 °C. A further study on the magnetic properties of the film has been carried out using first-principles calculations based on the density functional theory. The calculations suggest that the magnetic moments of the film originate from N 2p and Si 2p states in the vicinity of the hetoro-interface.     

Preparation of SiBN films deposited by MOCVD

SiBN films were prepared by the MOCVD method using triethylsilane and triethylboron as source materials. The SiBN films were a mixture of boron nitride and silicon nitride determined by IR spectra. The relationship between the ratio of mixture and the preparation condition is clarified. The ratio of silicon nitride to boron nitride in the films was proportional to the ratio of triethylsilane to triethylboron under a large excess of ammonia flow condition. The reaction temperature also influenced the ratio of boron nitride and silicon nitride in the films. The deposition rate of the film increased up to 800°C with a maximum at 1000°C, and decreased up to 1300°C with small value. The crystallinity of SiBN films was very poor because the crystal growth was obstructed.     

Preparation and TG—DTA analysis of manganese silicon nitride

Manganese silicon nitride was prepared quantitatively as a precipitated phase by treating a Mn; Si-alloy (Mn: 1.84 w/o, Si: 1.12 w/o) in a mixture of 2% NH₃ and H₂ at 700°C. Nitriding was carried out in situ in a thermobalance and the nitrogen uptake was recorded as a function of time. The nitride phase was isolated and investigated by means of the combined TG-DTG-DTA technique both in an atmosphere of nitrogen at 25–1600°C and in a mixture of Ar+O₂ (p_O2 = 0.20 atm) at 25–1000°C. In the nitrogen atmosphere MnSiN₂ appears to be stable up to 1000°C. Oxidising the nitride in the Ar/O₂ mixture caused three distinct exothermic processes to occur at characteristic temperatures. The final oxidation products as identified by diffractometry and IR-spectroscopy are manganese oxide silicate (braunite) and silicon dioxide.     

Quantitative Auger depth profiling of LPCVD and PECVD silicon nitride films

Summary Thin silicon nitride films (100–210 nm) with refractive indices varying from 1.90 to 2.10 were deposited on silicon substrates by low pressure chemical vapour deposition (LPCVD) and plasma enhanced chemical vapour deposition (PECVD). Rutherford backscattering spectrometry (RBS), ellipsometry, surface profiling measurements and Auger electron spectroscopy (AES) in combination with Ar⁺ sputtering were used to characterize these films. We have found that the use of (p-p)heights of the Si LVV and N KLL Auger transitions in the first derivative of the energy distribution (dN(E)/dE) leads to an accurate determination of the silicon nitride composition in Auger depth profiles over a wide range of atomic Si/N ratios. Moreover, we have shown that the Si KLL Auger transition, generally considered to be a better probe than the low energy Si LVV Auger transition in determining the chemical composition of silicon nitride layers, leads to deviating results.

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Quantitative Auger-Tiefenprofilanalyse von LPCVD- und PECVD-Siliciumnitridfilmen

     

Preparation of a mesoporous silicon boron nitride via a non-aqueous sol-gel route

A silicon boron imide based gel Si3B(NH)x(NH2)y(NMe2)z was prepared via catalytic ammonolysis of tris[tris(dimethylamino)silylamino]boron B[HNSi[N(CH3)2]3]3; pyrolysis of the gel under ammonia at 1,000 degrees C gives a mesoporous silicon boron nitride with high surface area and narrow pore size distribution.     

Silicon Nitride Capacitive Chemical Sensor for Phosphate Ion Detection Based on Copper Phthalocyanine – Acrylate‐polymer

In this work, we report the development of a highly sensitive capacitance chemical sensor based on a copper C,C,C,C‐ tetra‐carboxylic phthalocyanine‐acrylate polymer adduct (Cu(II)TCPc‐PAA) for phosphate ions detection. A capacitance silicon nitride substrate based Al−Cu/Si‐p/SiO₂/Si₃N₄ structure was used as transducer. These materials have provided good stability of electrochemical measurements. The functionalized silicon‐based transducers with a Cu(II)Pc‐PAA membrane were characterized by using Mott‐Schottky technique measurements at different frequency ranges and for different phosphate concentrations. The morphological surface of the Cu(II)Pc‐PAA modified silicon‐nitride based transducer was characterized by contact angle measurements and atomic force microscopy. The pH effect was also investigated by the Mott‐Schottcky technique for different Tris‐HCl buffer solutions. The sensitivity of silicon nitride was studied at different pH of Tris‐HCl buffer solutions. This pH test has provided a sensitivity value of 51 mV/decade. The developed chemical sensor showed a good performance for phosphate ions detection within the range of 10⁻¹⁰ to 10⁻⁵ M with a Nernstian sensitivity of 27.7 mV/decade. The limit of detection of phosphate ions was determined at 1 nM. This chemical sensor was highly specific for phosphate ions when compared to other interfering ions as chloride, sulfate, carbonate and perchlorate. The present capacitive chemical sensor is thus very promising for sensitive and rapid detection of phosphate in environmental applications.     

Formation and Properties of Medium and High Molecular Weight Compounds of Elements of Groups 3, 4, and 5

The differences between compounds of carbon and of silicon are discussed, and the role of silicon as a fundamental structural component in inanimate nature is described. Starting with silicic acid and silicates, the structure and properties of the silicones and of compounds having Si? C? Si skeletons are described. The possibilities for the formation of high molecular-weight compounds between elements of Groups 3 and 5 of the periodic system are considered, with particular reference to boron nitride and to aluminum-phosphorus compounds.