亲油性ZnS纳米微粒的合成

纳米微粒具有小尺寸效应、表面效应、量子效应和宏观量子隧道效应等一系列普通材料所不具备的特性 ,因而引起科技工作者的广泛重视 ,成为材料科学研究的热点 .制备纳米微粒的方法很多 [1～ 7] ,但由于纳米微粒的小尺寸效应及表面效应 ,通常制备的无机纳米微粒极易团聚 ,而且无机纳米微粒的非油溶性使其在摩擦学领域的应用受到很大限制 .本文采用表面修饰 [8～ 11] 方法 ,通过共沉淀的竞争反应 ,制备了表面为有机修饰剂双十六烷基二硫代磷酸 (DDP)修饰的无机 Zn S纳米微粒 ,并用红外光谱、 X射线光电子能谱和透射电子显微镜等分析手段对表…     

AFM电化学阳极氧化制备二氧化钛纳米线

当材料的微观尺度进入纳米量级后，由于量子效应，材料常常会显现出特殊的性能。因此近年来制备量子点、量子线，以及具有量子效应的量子器件受到深入的研究。一些新的纳米尺度加工技术如原子力显微镜(AFM)微细加工技术受到研究者的重视。     

纳米氧化锌的微乳液法制备

纳米ZnO颗粒尺寸较小,比表面积较大,其粉体具有非常高的化学活性,表现出表面与界面效应、小尺寸效应、量子尺寸效应和宏观量子隧道效应.纳米ZnO在电、磁、光、热等方面具有一般ZnO所无法比拟的性能,广泛用于气体敏感材料、涂料和高效催化剂等许多领域.因而,制备高质量的纳米ZnO是非常重要的.     

纳米CaCO_3改性对医用胶乳制品的影响

纳米CaCO3是20世纪80年代发展起来的一种新型超细固体材料。由于纳米CaCO3的超细微化,其晶体结构和表面电子结构发生变化,产生普通碳酸钙所不具有的量子尺寸效应、小尺寸效应、表面效应和宏观量子效应[1]。也由于纳米CaCO3的超细微化,使其自身存在难以克服的缺点———附聚形成二次结构[2]。如果附聚粒子最终不能被碾碎后分散,就会潜伏下来,成为应力集中点,最终导致改性材料性能的下降,欲充分发挥纳米Ca-CO3的纳米效应,有必要研究其填充改性的影响因素,从而确立纳米CaCO3填充改性的最佳参数。实验证明:纳米CaCO3表面状态、含量、表…     

纳米CaCO3改性对医用胶乳制品的影响

纳米CaCO3是20世纪80年代发展起来的一种新型超细固体材料。由于纳米CaCO3的超细微化，其晶体结构和表面电子结构发生变化，产生普通碳酸钙所不具有的量子尺寸效应、小尺寸效应、表面效应和宏观量子效应。也由于纳米CaCO3的超细微化，使其自身存在难以克服的缺点——附聚形成二次结构。如果附聚粒子最终不能被碾碎后分散，就会潜伏下来，成为应力集中点，最终导致改性材料性能的下降，欲充分发挥纳米CaCO3的纳米效应，有必要研究其填充改性的影响因素，从而确立纳米CaCO3填充改性的最佳参数。实验证明：纳米CaCO3表面状态、含量、表面处理剂用量、纳米CaCO3表面活化改性时搅拌时间都对纳米CaCO3填充改性的效果产生影响。     

气-固相还原硫酸盐制备系列硫化物纳米晶

<正>过渡金属硫化物纳米晶因其特异的结构具有量子尺寸效应、小尺寸效应、表面效应等效应,显示出不同于体相材料的光电磁性质,因而成为近年来纳米科学研究的热点[1-3]。几十年来,硫化亚铁(FeS)     

CdS纳米微粒在LB膜层隙聚集形态的AFM观察

用LB技术制备纳米微粒与超薄有机膜的复合膜是近年来值得注意的研究进展＊．利用该方法所制备出的材料既具有纳米粒子所特有的量子尺度效应，又具有LB股的分子层次有序、股厚可控以及易于组装等特点．它可用来制备结构可控的有机无机交替膜．而且，通过改变LB膜成膜材料和制备条件还可改变纳米粒子的光电特性．因此它在微电子学、光电子学、非线性光学及传感器等研究领域有着十分广阔的应用前景问．纳米微粒的聚集形态及LB膜在生成纳米微粒后的结构变化对材料的特性有着很大的影响．但采用一般的电镜技术或光谱分析手段均不能在实空间和…     

介电限域效应对SnO_2纳米微粒光学特性的影响

半导体纳米微粒作为一种新兴材料，在声、光、电、磁、热及催化等方面显示出全新的异于体相材料和分子或原子的特性，在理论和实验上已引起。们极大的兴趣I‘，’］．当纳米微粒的尺寸接近或小于激于玻尔半径时，表现出明显的量子尺寸效应，其表现光学能隙变大，一些半导体粒子如CdS，Cdse等纳米微粒的量予尺寸效应已经被人们利用有效质量近似模型做了定性解释。八但是，由于纳米微粒尺寸小，具有相对大的表面积，因而粒子周围的介质可以强烈地影响它们的光学性质【’，‘1．我们采用胶体化学方法，对SnO。阶电常数为13）半导体纳米微粒…     

富含缺陷的2D/2D异质结促进光催化清洁能源转化

正低维纳米材料因其特有的厚度尺寸和低维结构等特点,使其具有相应块状材料所不具备的独特性能。低维材料的显著特征就是至少有一个维度低于100 nm;零维材料,如零维纳米颗粒、量子点;一维材料,如纳米棒、纳米线和纳米纤维;二维材料如纳米片、纳米盘等。催化材料维度的降低将显著改善其量子限域效应和电子结构,进而改善其催化性能~(1–4)。基于这些思路,研究者们开始致力于研究用于光催化作用的新型二维半导体超薄材料。研究表明,     

二氧化钛的尺寸与光催化活性的关系

采用溶胶－凝胶法控制制备了晶粒尺寸从１０ｎｍ到８０ｎｍ的二氧化钛纳米半导体．用光催化降解苯酚作为模型反应，结合ＸＲＤ，ＤＲＳ，ＦＳ等表征手段，研究了纳米ＴｉＯ２的制备条件与其晶粒尺寸和相结构的关系，探讨了纳米ＴｉＯ２尺寸效应对其光催化活性的影响．发现当晶粒尺寸小于１６ｎｍ时，二氧化钛半导体具有了明显的尺寸量子效应．尺寸量子效应对提高ＴｉＯ２光催化降解苯酚的催化活性起了极为重要的作用．     

SnO2 纳米棒的氧化还原特性

 利用室温固相反应在 NaCl-KCl 熔盐介质中, 通过焙烧含 SnO2 纳米颗粒前驱体合成了 SnO2 纳米棒, 并采用 X 射线衍射、扫描电镜、透射电镜、选区电子衍射和 X 射线光电子能谱对 SnO2 纳米棒进行了表征. 结果表明, SnO2 纳米棒是表面光滑、结晶完整的金红石结构单晶体, 直径为 10~20 nm, 长度为几百纳米到几个微米. 程序升温还原结果表明, SnO2 纳米棒具有较好的氧化还原性能和催化活性. 探讨了 SnO2 纳米棒的氧化还原机理.     

Effect of hydrogen reduction temperature on the microstructure and magnetic properties of Fe–Ni powders

The effect of hydrogen reduction temperature on the properties of Fe–Ni powders was described. The mixed powders of Fe-oxide and NiO were prepared by chemical solution mixing of nitrates powders and calcination at 350 °C for 2 h in air. The calcined powders formed small agglomeration with an average particle size of 100 nm. The microstructure and magnetic properties were investigated by using X-ray diffractometry, thermogravimetry, differential thermal analyzer, and vibrating sample magnetometer. Microstructure and thermal analysis revealed that the Fe-oxide and NiO phase were changed to FeNi₃ phase in the temperature range of 245–310 °C, and by heat-up to 690 °C the FeNi₃ phase was transformed to γ-FeNi phase. The reduced powder at 350 °C showed saturation magnetization of 76.3 emu/g and coercivity of 205.5 Oe, while the reduced powders at 690 °C exhibited saturation magnetization of 84.0 emu/g and coercivity of 14.0 Oe. The change of magnetic properties was discussed by the observed microstructural features.

     

Enhanced Electrochemical Capacitive Properties of Nickel‐Cobalt Oxide Nano‐flakes Materials

Nickel‐cobalt oxide nano‐flakes materials are successfully synthesized by a facile chemical co‐precipitation method followed by a simple calcination process. The studies show that the as‐prepared nickel‐cobalt oxides with different Ni/Co ratio are composed of NiO and Co₃O₄ compounds. The Co_0.56Ni_0.44 oxide material, which exhibits a mesoporous structure with a narrow distribution of pore size from 2 to 7 nm, possesses markedly enhanced charge‐discharge properties at high current density compared with the pure NiO and pure Co₃O₄. The Co_0.56Ni_0.44 oxide electrode shows a specific capacitance value of 1227 F/g at 5 mA/cm², which is nearly three times greater than that of the pure NiO electrode at the same current density.     

Synthesis and Enhanced Photocatalytic Activity of a Hierarchical Porous Flowerlike p–n Junction NiO/TiO2 Photocatalyst

Hierarchical flowerlike β‐Ni(OH)₂ superstructures composed of intermeshed nanoflakes are synthesized by hydrothermal treatment with a mixed solution of C₂H₄(NH₂)₂, NaOH, and Ni(NO₃)₂. The as‐prepared β‐Ni(OH)₂ superstructures could be easily changed into NiO superstructures without great morphology change by calcination at 400 °C for 5 h. Furthermore, the TiO₂ nanoparticles can be homogeneously deposited on the surface of NiO superstructures by dispersing β‐Ni(OH)₂ powders in Ti(OC₄H₉)₄–C₂H₅OH mixed solution and then vaporizing to remove the ethanol at 100 °C, and finally calcination at 400 °C for 5 h. The prepared NiO/TiO₂ p–n junction superstructures show much higher photocatalytic activity for photocatalytic degradation of p‐chlorophenol aqueous solution than conventional TiO₂ powders and NiO superstructures prepared under the same experimental conditions. An obvious enhancement in the photocatalytic activity can be related to several factors, including formation of hierarchical porous structures, dispersion of TiO₂ particles on the surface of NiO superstructures, and production of a p–n junction. Further results show that NiO/TiO₂ composite superstructures can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and re‐used, compared with conventional powder photocatalysts. After many recycling experiments for the photodegradation of p‐chlorophenol, the NiO/TiO₂ composite sample does not exhibit any great activity loss, confirming that NiO/TiO₂ sample is stable and not photocorroded.     

熔盐法合成LiTaO3粉体

LiTaO3由于其突出的电光、压电和热释电效应,以及居里温度高、介电常数低,介电损耗小、老化速率低等特点,已成为广泛应用的功能材料[1,2]。而且,LiTaO3还可以与其他陶瓷材料如(K0.5Na0.5)NbO3等复合制成新型压电陶瓷[3]。另外,与陶瓷材料PZT相比较,该种压电材料不含铅,不会造成环境污染,属环境协调性绿色材料。LiTaO3的熔点很高(1630℃)[4],目前合成这类材料的常规方法有固相法、质子交换法和溶胶-凝胶法等[5￣9]。其中固相法采用Li2O和Ta2O5为原料,高温煅烧(往往高于1000℃),由于Li2O在高温下易挥发,使化学计量比较难控制[6],且在…     

Synthesis of Sr-doped LaCrO3 powders by combustion method

Lanthanum strontium chromite (LSC) powders were synthesized by the combustion method, using five different fuels (urea, glycine, ethylene glycol, ??-alanine, and citric acid). The ignition of the reagent mixture with urea takes a longer time, and more gases are released by combustion. A calcination step is essential for a good crystallization of the perovskite phase. X-ray diffraction patterns showed formation of perovskite phase and a small amount of SrCrO₄ for the sample synthesized with urea after calcination. The crystallite sizes are in the range of 23?C33?nm. Scanning electron microscopy revealed the porosity of the powders and the presence of agglomerates, formed by fine particles of different shapes. Thermogravimetric analysis showed a large mass loss for the sample synthesized with citric acid, probably caused by the absence of ignition, with primary polymerization of the precursor reagents.     

Electrochemical response of various metals to oxygen gas bubbling in molten LiCl–Li2O melt

The electrochemical response of several alloys (stainless steel 316, Hastelloy C276, Inconel 600, and tantalum) was investigated in molten LiCl–Li₂O (1 wt%) at 923 K while bubbling oxygen gas into the molten salt. Tafel and zero resistance ammeter (ZRA) electrochemical methods were used to measure electrochemical effects of oxidation processes at the surface of each alloy. The Tafel method required approximately 15 min and was, thus, applied only in intervals between periods of oxygen bubbling in the salt. ZRA measurements were made in real time, while the O₂ was actively being bubbled into the salt. This method recorded both open circuit potential of the alloy relative to a Ni/NiO reference electrode and current between the alloy and the galvanically coupled platinum plate that served as the counter electrode. Both open circuit potential and galvanic oxidation current started to increase at the initiation of oxygen flow. Based on the observed oxidation current trend, it was inferred that the metals in order of increasing resistance to oxidation in molten LiCl–Li₂O are as follows: tantalum < SS-316 < Inconel 600 < Haynes C276. Scanning electron microscopy images indicated formation of an oxide layer of thickness 560–3370 nm that correlates with the galvanic oxidation current measurements.

     

Thermal Treatment of Sol-Gel Derived Nickel Oxide Xerogels

Very fine nickel hydroxide and oxide xerogel powders were prepared using a new sol-gel synthesis procedure in which nickel ethoxide was produced through the reaction of nickel chloride, as a precursor, with sodium ethoxide in dehydrated ethanol, followed by the hydrolysis of nickel ethoxide with ammonia and drying the resulting hydrogel under subcritical pressures to form the xerogel. The effects of thermal treatment on the surface area, pore volume, crystallinity and particle structure of the resulting xerogels were investigated and found to have significant effects on all of these properties. Overall, the xerogel remained amorphous as Ni(OH)₂ space up to 200°C, with little change in the surface area and pore volume. At 250°C, the Ni(OH)₂ began to decompose and form crystalline NiO with the uniformity of the crystals increasing with an increase in temperature. The surface area and pore volume decreased sharply when increasingthe temperature beyond 250°C; this was the temperature where maximums of about 270 m²/g and 0.33 cm³/g were exhibited by this composite amorphous Ni(OH)₂ and crystalline NiO xerogel powders. At the higher calcination temperatures, very uniform NiO crystals with average crystallite sizes of 1.7 nm and 14.5 nm were obtained at 400 and 600°C, respectively.     

超音速气流粉碎下NiO纳米棒的低温固相制备

采用超音速气流粉碎技术低温固相合成NiO纳米颗粒前驱体,并通过在650～900 ℃下, NaCl熔盐介质中对前驱体进行焙烧,制备得到NiO纳米棒。采用XRD、SEM、TEM测试技术对NiO前驱体、NiO纳米棒的结构和形貌进行了表征。结果表明,前驱体为直径约25 nm球形颗粒,随着焙烧温度升高,逐渐生成直径为300 nm,长度约十几微米的纳米棒。反应过程中熔盐介质是纳米颗粒前驱体生长的关键因素。     

The preparation of nickel oxide based on infinite dilute method and its electrochemical performance

With NaOH as precipitation agent and NiSO₄ · 6H₂O as raw material, Ni(OH)₂ particles were synthesized by infinite dilute method and sintered at 300°C for NiO. The synthesized NiO particles with a structure of cubic crystalline phase are well dispersed and ball-flower like with a diameter of 500 nm. The electrochemical tests show that the NiO particles have relatively high capacitance and excellent capacitive retention. The good structure and excellent performance suggest its promising application in supercapacitors.