水热法制备TiO2纳米管及其影响因素的研究

分别以金属钛(Ti)和氧化钛(TiO2)为原料,通过水热法制备TiO2纳米管,研究水热温度、pH、不同钛源和n(TiO2)/n(NaOH)的比值对TiO2纳米管形貌的影响。结果表明,在最佳实验条件(t=150℃,pH=10~12,n(TiO2)/n(NaOH)=6.25×10-4)下,以TiO2作钛源时制备出管壁厚度和外径分别为2 nm和8~10 nm的TiO2纳米管;以金属钛粉作钛源所制备的TiO2纳米管,其壁厚、外径分别约为1~1.5 nm和3~5 nm,明显小于前者。在温度为130℃~170℃、pH=8~12范围内,温度、pH对TiO2纳米管的壁厚和管径基本无影响。     

静电纺丝法制备氮化镓纳米管

用静电纺丝法,研究了制备氮化镓纳米管的影响因素,并利用扫描电镜(SEM),透射电镜(TEM),X射线衍射(XRD)进行表征。结果表明,PVP浓度为14%,纺丝电压为12 kV,固化距离为12 cm时得到外径约600 nm内径约400 nm的纳米管前躯体;通过焙烧得到外径约300 nm内径约200 nm的纳米管氧化物;最后测试了其介电性能。     

硝酸铁为催化剂大量制备离散Mn2O3纳米管/纤维

采用简单的液相催化法实现了完全离散的Mn2O3纳米管/纤维的大规模制备. TEM电镜观察表明,Mn2O3纳米管外径约30~50 nm,长度约0.2~1.0 mm, Mn2O3纳米纤维直径约10~30 nm,长度约0.4~2.0 mm. 通过控制KMnO4和Fe(NO3)3的用量和比例可以分别得到管状、纤维状和颗粒状等不同微观形态的纳米Mn2O3. Fe(NO3)3是制备Mn2O3纳米管/纤维的理想催化剂,以Co(NO3)2和Ni(NO3)2作催化剂只能制得无定形颗粒. XRD分析表明,Mn2O3纳米管具有不同于已知的o-Mn2O3, t-Mn2O3, h-Mn2O3和g-Mn2O3的晶体结构.     

TC4合金表面氧化钛基纳米管阵列的制备和表征

采用电化学阳极氧化法在TC4合金(Ti-6Al-4V)表面制备了TiO2基高度有序纳米管阵列。阳极氧化电解液体系为0.5wt%NH4F+0.1MH3PO4的水溶液,通过对阳极氧化电压和氧化时间的研究,揭示了纳米管阵列的制备规律。纳米管阵列的最优制备电压为20V,时间为1h,所制备纳米管管径约120nm、壁厚约17nm、管长约300nm。能量色散型X射线光谱(EDX)和X射线光电子能谱(XPS)研究结果表明没有实现对纳米结构的晶格掺杂。所制备的高度有序纳米管阵列具有广阔的应用前景。     

水热法合成二氧化钛纳米管的晶型与形貌控制的研究

晶型与形貌的控制对于二氧化钛纳米管的应用具有重要的影响。采用水热法合成了内径约为5~6nm,外径约为9~10 nm,管长为200~300 nm的纳米管。通过XRD、TEM进行表征,研究了TiO_2纳米管在不同焙烧温度的形貌和晶型组成的转化,同时探讨不同粒径和晶相的二氧化钛粉末原料对合成TiO_2纳米管的形貌和晶型的的影响。结果表明:二氧化钛在水热阶段形成无定型结构纳米管,经高温焙烧后结晶度增强,转变成金红石和锐钛矿混合型。当焙烧温度为400℃时,纳米管能维持稳定的管状结构,焙烧温度升高将会导致TiO_2纳米管转变成不同尺寸的纳米棒。不同晶型和粒径的TiO_2合成原料对纳米管形貌和晶型的影响显著,金红石晶型和粒径大的原料有利于纳米管的合成。     

用于软质PVC的纳米氢氧化镁阻燃性研究

研究了氢氧化镁阻燃剂对软质聚氯乙烯(PVC)增塑体系的阻燃效果.通过X射线粉末衍射(XRD)、透射电子显微镜(TEM)、热分析等手段对氢氧化镁阻燃剂进行了表征,并考察了氢氧化镁在软质PVC体系中的分散情况.结果表明,氢氧化镁的粒径约为80 nm,改性氢氧化镁在软质PVC中分散较为均匀,每100份软质PVC仅添加40份氢氧化镁就可使体系达到较好的阻燃效果和力学性能.     

氢氧化镁阻燃剂的制备工艺研究

介绍了氢氧化镁阻燃剂的国内外研究现状和氢氧化镁的制备工艺。以氢氧化镁的粒度作为考察指标,采用液相沉淀法研究了氢氧化镁制备时的反应时间、反应温度、MgCl2的初始浓度和溶剂等对氢氧化镁粒度的影响,得到最优工艺条件:反应时间90 min,反应温度80℃,MgCl2的初始浓度0.5 mol/L,溶剂为V(水)∶V(乙醇)=1∶1,阻燃型氢氧化镁的平均粒度约为100 nm。     

合成工艺对氮化硼纳米管显微结构和性能的影响

采用无定型B粉为原料,在催化剂Fe2O3和CaO辅助作用下,控制反应气氛氨气的流量(150~200 mL/min),在1200℃下于真空管式炉中保温4 h,制备氮化硼纳米管(BNNTs)。采用透射电子显微镜(TEM)、X射线衍射(XRD)和傅里叶转换红外光谱分析(FTIR)等手段对产物的结构和形貌进行了表征,结果表明:所得产物为竹节状氮化硼纳米管(BNNTs),其晶体结构为六方氮化硼,外径约为35~100 nm,长度为数微米至数十微米。     

白云石制备的纳米氢氧化镁的性能及其影响因素

探讨了白云石碳化法制备纳米级氢氧化镁的工艺条件,研究了沉淀剂、反应温度对纳米级氢氧化镁形貌的影响,以及表面活性剂对纳米级氢氧化镁分散性的改善,并对反应机理进行了阐述.结果表明:以氨水为沉淀剂所得的纳米氢氧化镁近似六边形的薄片状,平均粒径为16nm,其结构稳定性优于以氢氧化钠为沉淀剂的产品.当反应温度为30℃时,Mg(OH)_2形成细小晶核,薄片的厚度为5～7nm,晶粒粒径为10～15nm;反应温度为50℃时,晶核开始生长为大晶粒,但排列无规则;反应温度为70℃时,Mg(OH)_2薄片的厚度增至10nm左右,晶粒粒径为10～20nm,具有规则排列的完整晶粒:反应温度为80℃时,Mg(OH)_2晶粒具有不规则排列.加入表面活性剂聚乙二醇或十二烷基硫酸钠可以提高纳米粒子的分散性.当表面活性剂聚乙二醇用量为氢氧化镁的3.0%(以质量计,下同)时,纳米氢氧化镁的分散性最好,片层的厚度约为10 nm,平均粒径为20 nm.当表面活性剂十二烷基硫酸钠用量为氢氧化镁的4.0%时,纳米氢氧化镁具有较好的分散效果,平均粒径为20nm.     

硫酸镁一步法制备氢氧化镁阻燃剂

实验确定了由硫酸镁一步法制备阻燃型氢氧化镁较适宜的条件为：表面处理剂添加量5~10 mL(以制备5 g氢氧化镁为基准),恒温处理时间3~4 h,陈化时间4~6 h. 此工艺条件下,所制得的氢氧化镁样品XRD分析表明,(001)面对应的衍射峰强度明显高于(101)面,样品(101)方位的扭歪值h<3.0′10-3,比表面积SDET<20 m2/g,颗粒形貌为棒状,直径为25~50 nm,长径比为8~10,且分散性好,样品符合阻燃型氢氧化镁的特殊要求. 该工艺具有流程短、设备简单、操作条件温和(常压、低温操作)、成本低等特点.     

Direct preparation of carbon nanotubes and nanobelts from polymer

Carbon nanotubes and carbon nanobelts were obtained via single-needle electrospinning on a basis of water-in-oil (W/O) emulsion technique, respectively. The morphology of electrospun products can be controlled by controlling the temperature of the collector during the electrospinning process. The mechanism of fabricating PAN nanotubes and nanobelts by emulsion electrospinning is discussed in detail. Transmission electron microscopy and scanning electron microscope results show that the carbon nanotubes (the inner diameter of 25-50 nm and the outer diameter of 50-100 nm) have a wall thickness of 10-50 nm, and the width and thickness of the nanobelts range from 100 to 300 nm, and 1 to 5 nm, respectively. A slight difference of bonding configuration of the carbon nanofibers, carbon nanotubes and carbon nanobelts is attributed partly to their different topological structures. The novel method is versatile and could be extended to the fabrication of various types of nanotubes and nanobelts.     

Preparation of Aligned Ultra-long and Diameter-controlled Silicon Oxide Nanotubes by Plasma Enhanced Chemical Vapor Deposition Using Electrospun PVP Nanofiber Template

Well-aligned and suspended polyvinyl pyrrolidone (PVP) nanofibers with 8 mm in length were obtained by electrospinning. Using the aligned suspended PVP nanofibers array as template, aligned ultra-long silicon oxide (SiOx) nanotubes with very high aspect ratios have been prepared by plasma-enhanced chemical vapor deposition (PECVD) process. The inner diameter (20-200 nm) and wall thickness (12-90 nm) of tubes were controlled, respectively, by baking the electrospun nanofibers and by coating time without sacrificing the orientation degree and the length of arrays. The micro-PL spectrum of SiOx nanotubes shows a strong blue-green emission with a peak at about 514 nm accompanied by two shoulders around 415 and 624 nm. The blue-green emission is caused by the defects in the nanotubes.     

表面有丝状吸附物的氮化硼纳米管的制备

采用简单工艺,即：将块体氧化硼（B2O3）在氮气气氛中球磨后,在1200℃、流动的氨气中热处理,成功合成了表面有大量丝状吸附物的BN纳米管。纳米管为六方BN晶体且呈竹节形貌,其直径为80～120nm,长度近1μm。纳米管表面丝状的吸附层也是六方BN晶体,细丝的长度为100nm左右,直径不到10nm。     

碳包铁颗粒和放射状碳纳米管微观结构的研究

以苯和甲苯为碳源，二茂铁为催化剂前驱体，含硫化合物为助催化剂，采用竖式炉流动催化法，通过减小载人的氢气量以改变催化剂颗粒的状态及反应条件，获得了碳包铁颗粒以及放射状碳纳米管，运用TEM和HRTEM对其形貌和结构进行了分析，并初步探讨了其生长机理。结果表明，在碳源、催化剂和炉温分布相同的条件下，氢气量为5400mL／min时形成直线型和弯曲型两种不同形态的碳纳米管，后者管径大于前者。氢气量为2000mL／min时，产物90％以上为碳包铁颗粒，其平均直径约为530nm，其中还有少量放射状碳纳米管，其外径为45—50nm，内径为3—5nm，管径较为均匀。     

乙醇-催化裂解法大量制备离散碳纳米管

碳纳米管的纯化和切短会造成大量碳纳米管损失。该文以乙醇为碳源,直接大规模制备长度为200~600nm,以单根状态存在的离散碳纳米管,产量为15 g/h。当碳源中乙醇和苯的体积比为1∶2,1∶1和2∶1时,只能合成碳纳米管和碳纳米颗粒的混合物。Ram an光谱结果表明,以乙醇为碳源制备的碳纳米管具有很高的结晶度,且为单壁碳纳米管和多壁碳纳米管的混合物。文章提出了离散碳纳米管生长的剪切机理。     

Effect of 4-sulfobenzoic acid monopotassium salt on oligoanilines for inducing polyaniline nanostructures

Polyaniline (PANI) nanotubes were chemically synthesized with the introduction of 4-sulfobenzoic acid monopotassium salt (KSBA) into an aqueous solution. As opposed to PANI microplates synthesized in the absence of KSBA, the PANI polymerized with KSBA exhibited tubular morphology, tens of micrometers long, with a total diameter of 130-240 nm, an inner diameter of 10-100 nm, and a wall thickness of 60-70 nm. The formation yield of PANI nanotubes was as high as about 95%, and the electrical conductivity was 4.8 × 10⁻¹ S cm⁻¹. However, the PANI microplates exhibited about 10 times lower electrical conductivity of 3.1 × 10⁻² S cm⁻¹ than PANI nanotubes. The morphologies of the final PANIs were greatly affected by the morphologies of the oligoanilines produced with or without KSBA in the early polymerization stage. In this study, KSBA was introduced to regulate the reactant pH and to control oligoaniline morphology (with KSBA: 1D long nanosheets, without KSBA: 2D microplates). Synthetic time-resolved morphology dynamics revealed that the oligoanilines play a key role as templates for the PANI nanosheets polymerized by anilinium cations. Finally, the nanosheets transform into long PANI nanotubes through conformational changes induced by the protonation of the PANI chains in a highly acidic medium. Interestingly, the final products are a simple mixture of pure PANI nanotubes and oligoaniline complexes composed of oligoanilines and aniline sulfate salts. Thus, the oligoaniline do not grow into the PANI chains but function only as templates for the 1D PANI formation.     

TiO2纳米管的制备及对O3的催化性能

用水热法制备了高比表面积的TiO₂纳米管,通过TEM、XRD及BET进行物化表征,试验得到外径5～7 nm、壁厚1 nm左右、长200～300 nm、比表面积276 m²·g^-1的锐钛型TiO₂纳米管。试验考察了TiO₂纳米管的吸附性能及对O₃的催化性能和本征反应动力学,结果显示：60 min时O₃/UV/TiO₂纳米管较O₃/UV/P25和O₃/UV对垃圾渗滤液的COD去除率分别提高了20.83%和32.65%;293 K时0.5 g TiO₂纳米管对COD的最大吸附量为P25的1.34倍,对COD去除率贡献为10.14%; 2 h内O₃/UV/TiO₂纳米管工艺的总反应表观速率常数k分别是O₃/UV/P25工艺的1.19倍和O₃/UV工艺的1.80倍;得出两种催化工艺k-T关系方程,反应表观活化能E_a,nanotube比E_a,P25降低了2.925 kJ·mol^-1。     

New continuous gas-phase synthesis of high purity carbon nanotubes by a thermal plasma jet

We have developed a new gas-phase synthesis technique to produce carbon nanotubes (CNTs) with a continuous process and at high temperature, by using a thermal plasma jet. A thermal plasma jet was generated by applying a direct current of 100-300 A, using Ar as the plasma gas with a flow rate of ∼6 ksccm. The temperature of the thermal plasma jet was very high (∼10⁴ K) and the velocity was very fast (∼100 m/s). Fe(CO)₅ and CO were used as a catalyst precursor and carbon source, respectively. The yield of CNTs was dramatically increased by attaching a helical extension reactor at the end of the plasma nozzle. High purity (∼80%) CNTs were produced with a continuous process by using a thermal plasma jet with helical extension reactor equipment. The number of CNT walls produced was critically affected by the hydrogen gas injected as an auxiliary plasma gas. Without hydrogen gas, single-walled carbon nanotubes whose diameter was about 1 nm were mostly produced while with hydrogen gas double-walled carbon nanotubes (about 4 nm in diameter) were predominantly produced, with small amount of 3- and 4-walled carbon nanotubes.     

钴离子置换钛酸盐纳米管的制备和光催化活性

以掺杂钴的金红石相TiO2纳米粉体为前驱体,采用水热法合成了一系列钴离子置换的钛酸盐纳米管,并用扫描电镜（SEM）、透射电镜（TEM）、粉末X射线衍射（XRD）、能谱（EDS）等手段对产物进行表征和分析.研究了钛酸盐纳米管对染料罗丹明B的降解的影响.结果表明：钛酸盐纳米管的管径在35nm左右,管长约在200～800 nm之间,经钴离子置换后,钛酸盐纳米管对罗丹明B的光催化降解有不同程度的提高,钴离子的掺杂量和纳米管在体系中加入量均存在一个最佳值,光催化性能随着罗丹明B溶液初始浓度的提高而下降.