1 kW自呼吸PEMFC堆控制因素试验

自呼吸质子交换膜燃料电池(PEMFC)阴极侧湿度和温度耦合严重,且空气流量对湿度和温度影响不同,从而使得对电池输出电压的控制变得复杂.以氢气压力和提供阴极空气流量的风扇转速为影响因素,对相应的工作点集进行了正交试验研究.分析结果表明,风扇转速高于极值电压转速时,空气会带走更多的水分,从而使得质子交换膜逐渐干燥,阻抗增大,电池性能衰减;风扇转速低于极值电压转速时,空气流量带走的热量减少,使得阴极表面温度升高,阴极端相对湿度迅速减低,从而导致质子交换膜迅速干燥,电池性能衰减迅速.因此,每个工作点存在一个使电池电压最高的风扇转速值.     

电解液中Ce(NO_3)_3/Ce_2(SO_4)_3的含量对Ti6Al4V合金微弧氧化膜层特性的影响

在硅酸钠-氢氧化钠电解液中以Na5P3O10作为稳定剂,通过改变Ce(NO3)3/Ce2(SO4)3的含量对Ti6Al4V合金进行微弧氧化,用XRD、SEM、EDS对试样表面所获得的氧化膜进行表征,并研究电解液中不同Ce(NO3)3/Ce2(SO4)3含量对氧化膜表面形貌的影响.结果表明,随着电解液中Ce3+的加入量增加到0.3 g/L,氧化膜表面的致密性减小,在此基础上加入0.5 g/L的Na5P3O10时,氧化膜致密性增加.EDS分析结果显示,膜层含有Ti、Na、Al、Si、P、O及Ce等元素;XRD分析结果表明,氧化膜的相组成为Ti、锐钛矿以及金红石.     

Copolymer synthesis of poly(L-lactide-b-DMS-L-lactide) via the ring opening polymerization of L-lactide in the presence of α,ω-hydroxylpropyl-terminated PDMS macroinitiator

Various amounts of hydroxy terminated PDMS were linked into PLLA chains via in-situ ring opening polymerization at a very low content of SnOt₂. The ¹H and FTIR spectra provided evidence for the incorporation of the PDMS in the PLLA chains. The molecular weights, T_g, T_m, crystallinity and the heats of fusion decreased as the feed mole ratio of PDMS/LLA in the block copolymer increased. The molecular weight distribution broadened as the content of the PDMS increased, due the occurrence of two initiation and propagation mechanisms. Linking PDMS into the PLLA chains improved its thermal stability. © 1996 John Wiley & Sons, Inc.     

Chemical assays of end-groups displayed on the surface of poly(ethylene terephthalate) (PET) films and membranes by radiolabeling

Poly(ethylene terephthalate) (PET) films and track-etched microporous membranes naturally display, on their surfaces, reactive chain-ends, i.e. carboxyl and hydroxyl functions. These were assayed by suitable activation (reaction with carbodiimide and tosyl chloride, respectively), followed by coupling with ³H-lysine and liquid scintillation counting of the sample-associated radioactivity. Values ranging between 5 and 30 pmol/cm² (open surface) of labeled end-groups were obtained, depending on the physico-chemical nature of the samples. Basic hydrolysis enriched the PET films with both types of endings (15–25 pmol/cm²). Reduction of films with the NaBH₄-catechol complex in tetrahydrofuran enriched their surfaces with hydroxyl groups. However, this procedure was not readily applicable to the surface modification of membranes; we observed an erosion effect that was confirmed by scanning electron microscope analyses. In contrast with the reduction process, the oxidation with KMnO₄ in 1.2N H₂SO₄ could be easily applied to the modification of either films or membranes; their surfaces were significantly enriched with carboxyl groups (15–50 pmol/cm²). This surface modification strategy has been used for the covalent coupling of adhesive proteins on PET membranes developed as supports for cell cultivation.     

纳米级晶种预涂层法Silicalite-1型沸石膜合成及其结构分析

在大孔-αA l2O3陶瓷管载体上采用晶种预涂层法在澄清溶液体系中水热合成了S ilica lite-1型沸石膜,用SEM和XRD表征了晶种、晶种涂层后载体和成膜后沸石膜的结构、晶形变化、晶相结构等成膜情况,并初步考查了两种不同温度(130℃和160℃)下生长成膜的结构变化.结果表明:制备的晶种呈椭球形、晶粒小(约100 nm)而均匀、纯度高,适合作晶种涂层成膜;所用载体孔径大而不均匀、表面粗糙而不平整,但经晶种涂层后表面可形成一层厚度均匀、光滑的晶种层,再水热晶化时有利于成膜,所得膜连续、清晰无裂缺,载体、晶种层和沸石膜层之间相互结合紧密;连续晶种层改善了载体表面的性能,有利于连续S ilica lite-1沸石膜的形成;合成温度不同,沸石晶粒在载体表面生长的方向不同,所形成的膜微观结构也不同.该合成方法能适合其他不同类型沸石膜的制备.     

醋酸纤维薄膜电泳法分离测定鸡血清蛋白质

应用醋酸纤维薄膜电泳法分离测定了鸡血清中不同蛋白质。对电流强度、电泳时间和点样量等影响分离效果的条件进行了选择。并用光度计和薄层扫描仪对样品进行了定量测定。     

Alkaline Stable Anion Exchange Membranes Based on Cross-Linked Poly(arylene ether sulfone) Bearing Dual Quaternary Piperidines for Enhanced Anion Conductivity at Low Water Uptake

Alkaline stable anion exchange membranes based on the cross-linked poly(arylene ether sulfone) grafted with dual quaternary piperidine (XPAES-DP) units were synthesized. The chemical structure of the synthesized PAES-DP was validated using ¹H-NMR and FT-IR spectroscopy. The physicochemical, thermal, and mechanical properties of XPAES-DP membranes were compared with those of two linear PAES based membranes grafted with single piperidine (PAES-P) unit and conventional trimethyl amine (PAES-TM). XPAES-DP membrane showed the ionic conductivity of 0.021 S cm⁻¹ at 40 °C which was much higher than that of PAES-P and PAES-TM because of the possession of more quaternary ammonium groups in the cross-linked structure. This cross-linked structure of the XPAES-DP membrane resulted in a higher tensile strength of 18.11 MPa than that of PAES-P, 17.09 MPa. In addition, as the XPAES-DP membrane shows consistency in the ionic conductivity even after 96 h in 3 M KOH solution with a minor change, its chemical stability was assured for the application of anion exchange membrane fuel cell. The single-cell assembled with XPAES-DP membrane displayed a power density of 109 mWcm⁻² at 80 °C under 100% relative humidity.     

丙烯腈/丙烯酰胺/苯乙烯三元共聚超滤膜材料的制备和表征

以偶氮二异丁腈为引发剂,采用溶液聚合法制备了丙烯腈、丙烯酰胺、苯乙烯三元共聚物,并用红外光谱(IR)、示差扫描量热(DSC)、热重分析(TG)等手段对共聚物进行了结构和性能表征。结果表明:苯乙烯的加入使得参加环化反应的氰基和酰胺基的数目减少,保留了更多作为功能基团的酰胺基。用相转化法制备得到超滤平板膜,膜的渗透通量为2.63 mL/(cm2.h),对聚乙二醇20000(PEG 20000)的截留率为96.95%。     

分子印迹中空纤维复合膜对异丙醇/水体系的渗透汽化

以聚砜(PSF)中空纤维超滤为基膜,二苯甲酰-L-酒石酸(L-DBTA)为模板分子,甲基丙烯酸甲酯(MMA)为功能单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,采用表面热聚合方法制备了L-DBTA印迹中空纤维复合膜。该复合膜对异丙醇/水体系具有很好的分离效果,对于w=0.20和0.50的异丙醇/水体系,经过一次浸膜制得的L-DBTA分子印迹复合膜的分离因子分别为2 400和5 690,通量分别为1 440 g/(m2.h)和551 g/(m2.h);对于w=0.95的异丙醇/水体系,浸膜液浓缩一倍,经过两次浸膜制得的L-DBTA分子印迹复合膜分离因子可达82 100,渗透通量可达739 g/(m2.h);对于异丙醇/水体系,通过实验,获得了L-DBTA分子印迹复合膜与一般渗透汽化膜相反的分离规律:料液温度升高,L-DBTA分子印迹复合膜的渗透通量下降;随着料液浓度的升高,分离因子出现最大值时的温度逐渐升高。     

79颗患牙采用bFGF胶原膜盖髓的临床观察

目的:探讨79例采用碱性生长因子(bFGF)的胶原蛋白膜盖髓的临床疗效,为临床寻找更有效的盖髓材料提供参考。方法:应用含有bFGF胶原蛋白膜对36颗因龋病和43颗因牙外伤而穿髓的患牙进行盖髓,分析其术后效果,同时与应用氢氧化钙对17颗因龋病和33颗因牙外伤而穿髓的患牙进行盖髓的疗效进行对比。结果:应用含bFGF胶原蛋白膜治疗外伤穿髓的盖髓效果优于氢氧化钙(P<0.05),应用含bFGF胶原蛋白膜治疗外伤穿髓的效果优于龋病治疗意外穿髓的效果(P<0.05),但含bFGF胶原蛋白膜与氢氧化钙比较,对龋病治疗意外穿髓的盖髓效果无显著性差别(P>0.05)。结论:含碱性生长因子的生物膜可以作为盖髓材料在临床应用。