11B and 15N solid state NMR investigation of a boron nitride preceramic polymer prepared by ammonolysis of borazine

A poly(aminoborazine), precursor for hexagonal boron nitride (h-BN) obtained by reaction of borazine B₃N₃H₆ with ammonia, and its pyrolysis derivatives have been extensively characterised by ¹⁵N and ¹¹B MAS NMR. The various B and N sites have been identified according to their first neighbouring atoms, as well as to the second ones in the case of ¹⁵N, and have also been quantified. This study demonstrates that a suitable choice of NMR techniques together with the use of isotopic enrichment can lead to a large improvement in spectral resolution, which allows a better understanding of such complex BN preceramic polymer structures and permits to follow the polymer-to-ceramic transformation.     

Extraction behaviours of titanium and other impurities in the decompositio process of ilmenite by highly concentrated KOH solution

To effectively utilize ilmenite and recycle KOH solution,the extraction behaviours of titanium and other associated impurities in the decomposition process of ilmenite by highly concentrated KOH solution were studied.Experiments on the extraction behaviours of titanium as well as other associated impurities of ilmenite such as iron,silicon,calcium,and aluminiurn were carried out.The effects of various parameters,including reaction temperature,KOH concentration,reaction time,alkali-to-ore mass ratio,and particle size on the extraction rate of titanium and other impurities were examined.When the finely ground ore (58-75 μm) reacted with KOH solution (80wt％) in an alkali-to-ore mass ratio of 7:1 at 260°C for 60 min,almost complete extraction of titanium was achieved,while the extraction rate of aluminium was 78％ and that of other impurities was less than 22％.Moreover,high purity (98.2wt％) TiO2 with the anatase structure could be gained in the purification process.     

Photocurrent and decay time studies of solution-sprayed Cd0.8Zn0.2S films from liquid nitrogen to room temperature

The photocurrent of solution-sprayed Cd_0.8Zn_0.2S films and its dependence on temperature and light intensity were determined and a detailed investigation of the photocurrent decay was carried out. The photocurrent is almost independent of temperature at low temperatures and increases exponentially to a maximum at about 250 K. The decay times are shorter at low temperatures than at room temperature and they also depend on the light intensity.     

27Al and 29Si n.m.r. studies of HZSM-5: Part 2. The effect of coke formation

The formation of coke in zeolite channels during the conversion of methanol to gasoline in HZSM-5 causes changes in the ²⁷Al and ²⁹Si spectra of the zeolite. Displacement of water and oxygen by bulky molecules in the channels increases the electric-field gradient at ²⁷Al, decreases the ²⁹Si relaxation rate, and eventually distorts the channel walls. Cross-polarization ²⁹Si n.m.r. was used to follow the hydrogen content of the coke, whereas water and oxygen contents were related to the amount of coke in the channels and the proportion of methyl groups.     

氧化铁纳米棒的制备及其在光催化降解水溶性活性染料中的应用

采用均相沉淀法制备了半导体纳米材料α-Fe2O3.通过XRD、TEM等手段对该材料进行了分析.研究了烧结温度、光催化剂的用量、光照等因素对催化剂光催化降解活性染料的影响.并用红外和紫外的分析方法验证了光催化降解效果.结果表明,在适当的用量和350℃烧结并在紫外光照射下,α-Fe2O3对活性染料B-RN蓝、活性艳兰K-NR有极强的光催化降解活性.     

掺杂纳米TiO2在难降解废水处理中的研究进展

掺杂可有效改善纳米TiO2的光催化活性及其光利用率,利于光催化技术在工业生产中的应用推广.介绍了掺杂纳米TiO2的光催化机理,总结了常见的掺杂纳米TiO2的制备方法:溶胶-凝胶法、浸渍法等.阐述了TiO2光催化技术在印染废水、农药废水、造纸废水及工业无机废水处理中的应用,并进一步分析了该研究领域所存在的问题,为今后光催化技术的发展方向提出展望:寻求新的掺杂离子、研制掺杂负载型纳米光催化剂和加强降解机理研究等.     

A scanning and data acquisition system for the Lund proton microprobe

A computer system for scanning control and the evaluation of data obtained using a scanning proton microprobe is described. The system consists of a μVax-II host computer and a VME bus data acquisition and beam scanning system. The VME bus computer controls the front-end electronics, such as ADCs, and sends data in blocks to the μVax-II which does the on-line sorting of data and elemental mapping. To facilitate fast and effective analyses, a software package has been developed which gives the user the possibility of manipulating data acquisition, beam scanning etc. during sample analysis.     

微波促进下5-(色酮基-3-亚甲基)麦氏酸的合成

微波辐射下取代-3-甲酰基色酮与麦氏酸进行Knoevenagel缩合反应,较高产率地合成了5-(色酮基-3-亚甲基)麦氏酸,产物结构经IR、1HNMR和元素分析表征.     

己二酰二腙类化合物的微波无溶剂合成

在微波无溶剂的条件下,由自制的己二酰二肼和芳醛反应,合成了12种己二酰二腙类化合物。反应过程中无需用到载体和催化剂,实验证明此方法方便、简单、环境友好,是合成此类化合物的有价值的新方法。     

Synthesis and micellization behavior of chiral amphiphilic diblock copolymers bearing amino acid/dipeptide pendants

Novel chiral amphiphilic diblock copolymers bearing l-phenylalanine or α-l-aspartyl-l-phenylalanine methyl ester pendants were synthesized using a “click” reaction. The structure and composition of copolymers were characterized by gel permeation chromatography, ¹H NMR, elemental analysis and optical rotation measurements, which showed that the synthetic route can produce copolymers with well-defined composition and optical activity. The results from surface tension measurements, dynamic light scattering, transmission electron microscopy and ¹H NMR spectra indicated that these chiral copolymers formed spherical micelles with an optically active hydrophobic core in a NaH₂PO₄ buffer (pH 4.5) system.