用于珠光颜料的片状氧化铝制备

采用熔融盐法制备片状α-Al2O3,研究了硫酸盐、煅烧温度、添加剂(磷酸盐、二氧化钛)对片状α-Al2O3晶体形貌的影响。当氢氧化铝凝胶煅烧温度为900℃时,没加硫酸盐分解所得的氧化铝晶相为κ-Al2O3晶相,而加入硫酸盐的氧化铝晶相为α-Al2O3晶相,熔融盐降低了片状α-Al2O3的形成温度,促进κ-Al2O3向α-Al2O3晶型转变。煅烧温度由900℃上升到1200℃时,片状α-Al2O3的团聚程度降低,颗粒尺寸分布更加均匀。当煅烧温度在1200℃下、磷酸盐添加量为3%、二氧化钛添加量为2%时,所制得片状氧化铝分散均匀,径厚比较大,片状氧化铝平均粒径为5.225μm、厚度约400-500 nm。     

5α-氯-6β-羟基-雄甾-3,17-二酮的合成

以4-雄烯二酮为原料,经羰基保护、双键卤羟化、水解脱保护三步反应合成了5α-氯-6β-羟基-雄甾-3,17-二酮。讨论了保护试剂、催化剂、卤羟化试剂、反应温度等对实验结果的影响,得出了较佳工艺条件,三步总收率达到88%。     

Chain stiffness and chain conformation of poly(α-methylene-γ-butyrolactone) in dilute solutions

The chain stiffness and local chain conformation of atactic poly(α-methylene-γ-butyrolactone) (PMBL), which is a side chain cyclic structural analog of poly(methyl methacrylate) (PMMA), with a weight-average molecular weight (M_w) ranging from 2.8 × 10³ to 2.6 × 10⁶ in N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) were characterized by size exclusion chromatography with a multi-angle light-scattering detector (SEC-MALS) and synchrotron radiation small-angle X-ray scattering (SAXS). Based on the Kratky-Porod worm-like chain model, the scattering functions and the M_w dependence of z-average root-mean-square radius of gyration <S²>_z^1/2 yielded the Kuhn segment lengths λ⁻¹, the diameter of the PMBL chains d, and the excluded-volume strengths in DMF and GBL. The local conformation of atactic PMBL in DMF and GBL were slightly larger than those of atactic PMMA, due to the presence of the conformationally rigid lactone ring structure.     

高熔点聚α-烯烃的合成

利用过渡金属催化剂,包括负载型Ziegler-Natta催化剂和均相茂金属催化剂,进行了系列α-烯烃的聚合,所得聚α-烯烃的熔点基本都高于200℃,个别样品高于300℃。单体结构强烈影响单体聚合转化率,在所选单体中,以烯丙基环己烷(ACH)转化率最高,3-甲基-1-丁烯(3M1B)转化率最低。同时进行了个别单体的共聚,所得聚合物熔点低于均聚物。     

缩醛/酮的无气味硫缩醛/酮化反应

在甲醇介质中,氯化乙酰存在下,易制备和稳定的2-（1,3-二噻）亚甲基-3-氧代丁酸作无气味代硫醇试剂能与缩醛/酮有效进行硫缩醛/酮化反应。该反应条件温和,操作简单,产率高,且反应和后处理过程中,无硫醇的恶臭气味。     

Comparative hot corrosion studies of EB-PVD and plasma sprayed coatings*

The use of directly fired heat engines, i. e. diesel and gas turbine engines, is likely to grow in the future. However, economic requirements will necessitate the development of highly efficient engines that operate at high temperatures and utilize low-grade fuels. An increase of combustion gas temperature and the utilization of low-grade fuels contaminated with, amongst others, sulphur and vanadium, may be accomplished by careful selection of the materials, e.g. by applying corrosion-resistant coatings on heatresistant alloys. The main purpose of the present work has been to test various coatingsubstrate combinations in a highly corrosive environment. The comparison of various coating techniques, e.g. electron beam physical vapour deposition (EB-PVD), air plasma spraying (APS), and low pressure plasma spraying/vacuum plasma spraying (LPPS/VPS), has been emphasized.     

Temperature gradient controlled crystal growth from TIPS pentacene-poly(α-methyl styrene) blends for improving performance of organic thin film transistors

6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) from simple drop casting typically forms crystals with random orientation and poor areal coverage, which leads to device-to-device performance variation of organic thin film transistors (OTFTs). Previously, a temperature gradient technique was developed to address these problems. However, this approach simultaneously introduced thermal cracks due to the thermally induced stress during crystallization. These thermal cracks accounted for a reduction of charge transport, thereby impacting the device performance of TIPS pentacene based OTFTs. In this work, an insulating polymer, poly(α-methyl styrene) (PαMS) was blended with TIPS pentacene to relieve the thermal stress and effectively prevent the generation of thermal cracks. The results demonstrate that the incorporation of PαMS polymer combined with the temperature gradient technique improves both the hole mobility and performance consistency of TIPS pentacene based OTFTs.     

Spray-dried high-amylose sodium carboxymethyl starch: impact of α-amylase on drug-release profile

Spray-dried high-amylose sodium carboxymethyl starch (SD HASCA) is a promising pharmaceutical excipient for sustained-release (SR) matrix tablets produced by direct compression. The presence of α-amylase in the gastrointestinal tract and the variations of the gastric residence time of non-disintegrating dosage forms may affect the presystemic metabolism of this excipient and, consequently, the drug-release profile from formulations produced with SD HASCA. In this study, the influence of α-amylase and the residence time in acidic conditions on the drug-release profile was evaluated for a once-daily acetaminophen formulation (Acetaminophen SR) and a once-daily tramadol hydrochloride formulation (Tramadol SR). Both formulations were based on SD HASCA. α-Amylase concentrations ranging from 0?IU/L to 20000?IU/L did not significantly affect the drug-release profiles of acetaminophen and tramadol hydrochloride from SD HASCA tablets (f_2?>_?50) for all but only one of the studied conditions (f_2?=_?47). Moreover, the drug-release properties from both SD HASCA formulations were not significantly different when the residence time in acidic medium was 1?h or 3?h. An increase in α-amylase concentration led to an increase in the importance of polymer erosion as the main mechanism of drug-release instead of drug diffusion, for both formulations and both residence times, even if release profiles remained comparable. As such, it is expected that α-amylase concentration and residence time in the stomach will not clinically affect the performance of both SD HASCA SR formulations, even if the mechanism of release itself may be affected.     

Sonochemical fabrication and catalytic properties of α-Fe2O3 nanoparticles

In this study, α-Fe₂O₃ (hematite) nanoparticles were synthesised by a sonochemical method. The influence of different factors such as chemical composition of the precursors, atmosphere of the reactions and type of the sonicator on the chemical formula, crystallinity, morphology and size of the obtained products were investigated. Powder X-ray diffraction, scanning electron microscopy and IR spectroscopy, were used to characterise the nanostructures. The catalytic tests were performed in the reaction of methyl phenyl sulphide oxidation. The results exhibit the good catalytic performance of the as-prepared α-Fe₂O₃ nanoparticles.     

Development of α-Tocopherol Acetate Nanoparticles: Influence of Preparative Processes

We studied different methods of preparing α-tocopherol acetate (ATA) nanoparticles, which are to be used in targeting the lungs as aerosols in order to prevent cigarette smoke toxicity. Poly-(lactide) nanoparticles were prepared using nanoprecipitation and solvent evaporation techniques, which produced, respectively, too small and too large nanoparticles to be aerosolized. The emulsification-diffusion method produced 2 months stable nanoparticles with a size between (500–700 nm). Increasing ATA concentration (1–7 mg/mL) induced a decrease in the association rate (97–93%) and in the adsorbed ATA rate (7–4.5%), which was associated with variations of Zeta potentials (?27.5 to ?24.3 mV) and decrease in polymeric wall thickness and density.