四针状氧化锌晶须的生长机理

用"时间标尺"实验法测定了T-ZnO晶须在不同生长时期的生长速率,用扫描电镜观察分析了不同条件下晶须的生长形貌.结果表明:T-ZnO晶须的结晶作用是气-液-固(VLS)方式,晶须生长受螺旋生长机理控制;锌蒸气中产生凝聚生长的锌液滴是制备T-ZnO晶须的关键,锌从液滴内向外扩散在晶须的端面产生生长台阶,随着液滴内的原子向外不断扩散,针体部分就不断地伸长生长,当液滴内的原子全部消耗尽时,晶须便不再发生轴向生长;气-固(VS)方式的作用主要是促进晶须棱面生长而使晶须变粗,对轴向生长几乎没有影响.     

气相氧化法制备氧化锌的结晶形貌

研究了锌蒸气高温气相氧化条件对氧化锌结晶形貌的影响结果.结果表明:气相氧化法制备的氧化锌有无定形、颗粒状、单针状、四针状、多针状等5种典型的结晶形貌;这些结晶形貌与原料锌粉的粒度及表面状态没有直接联系,但都强烈地依赖于锌蒸气氧化时的物理化学环境;在不同的氧分压下,锌蒸气具有不同的氧化行为,由此导致了不同形貌的氧化锌结晶;通过改变制备条件可以有效地调控氧化锌的结晶形貌.     

O2浓度对纳米氧化锌形貌、产量和发光性质的影响

目的研究不同O_2体积浓度下,双管管式炉内不同沉积位置处纳米ZnO形貌、产量和发光性质的变化规律。方法采用化学气相沉积法,在双管管式炉的三个不同沉积位置制备了具有不同形貌、产量和性质的纳米ZnO产物。采用扫描电子显微镜(SEM)、X-射线衍射仪(XRD)和荧光分光光度计(PL)等对产物的形貌、结构和光致发光性能进行表征和测试。结果 SEM表明O_2体积浓度较小时,有利于形成针状的多脚结构。O_2体积浓度较大时,有利于生成棒状的多脚状结构。通过对比沉积产物产量发现,当O_2体积浓度较低时,沉积反应主要发生在内管外。随着O_2体积浓度的增大,沉积产物逐渐向内管内部转移,内管口附近的沉积产物增多。XRD结果表明所有产物均为六方纤锌矿结构,当O_2体积浓度为0.0625%时,产物沿c轴择优生长。随着O_2体积浓度的增加,无明显择优取向。PL结果表明,紫外发射峰与绿光发射峰强度的比值随着O_2体积浓度的增加而增大,说明绿光发射峰主要由氧空位引起,随着O_2体积浓度的增加,氧空位逐渐减少。结论通过调节O_2体积浓度可以制备出不同形貌和发光性质的纳米ZnO,从而应用于不同领域,并且在适当的沉积位置可以获得最大产量。     

纳米级SiC晶须的微波合成

以酚醛树脂、超细炭黑和超细ＳｉＯ２为原料，用微波加热的方法合成了直径在纳米级的ＳｉＣ晶须。用Ｘ射线衍射、分析电镜等手段对ＳｉＣ晶须进行了结构测定。比较并分析了不同的炭源和温度对ＳｉＣ晶须性能的影响．     

用不同气氛和不同温度的氧化法制备氧化锌纳米线的研究

在不同气氛中和低于锌熔点的350～400℃温度下,在锌箔上用直接氧化法制备了氧化锌纳米线。研究表明,在400℃以下的空气中加热会形成低密度的氧化锌纳米线;在400℃空气中加热时,氧化锌纳米线的密度明显增大。当在氧气与氩气的混合气氛中于400℃加热时,氧化锌纳米线的密度也明显增大。混合气体的流量越大,氧化锌纳米线的密度越大,纳米线越直。氧化锌纳米线的晶体结构为六方晶体,直径为20～150 nm,长度为几μm至十几μm。用直接氧化法可在低温无催化剂条件下制备出纳米材料。     

钇、镉共掺杂氧化锌纳米粉体的合成及光学性能

为了研究能隙修改和发光强度之间的关系,通过化学共沉淀法制备钇、镉共掺杂的氧化锌纳米粉体。采用XRD、XPS及PL对样品的晶体结构和光学性能进行研究。通过对钇、镉离子对氧化锌光学性能影响的研究发现,钇的掺入能够有效地增强氧化锌的紫外发光,钇、镉共掺杂在增强发光的同时,还使得氧化锌的带隙窄化,使得紫外发光红移,从而使得样品的室温光致发光图谱呈现出增强的紫光发射。该材料有望应用在制备光电器件方面。     

氧化锌涂覆硼酸镁晶须增强6061铝基复合材料的拉伸性能和热挤压行为（英文）

用挤压铸造法制备不同ZnO包覆量的硼酸镁晶须增强的6061铝基复合材料,并对其进行热挤压处理。对复合材料的显微组织及其力学性能进行研究。结果表明:随着ZnO包覆量的增大,铸态复合材料的弹性模量直线增加。铸态复合材料的极限抗拉强度和屈服强度随ZnO包覆量的增大先增大后减小。然而,铸态复合材料的伸长率基本一致。经挤压后,复合材料的伸长率大幅增加;无涂层复合材料的极限抗拉强度最大,且其弹性模量有所提高。涂覆ZnO涂层的复合材料中晶须发生明显的折断现象。但是,随着ZnO包覆量的增大,晶须的破坏程度有限。     

硫化亚铜/四针状氧化锌晶须异质结的多元醇法制备及光催化性能(英文)

以聚乙烯吡咯烷酮(PVP)为表面活性剂,通过多元醇法制备 Cu2S/T-ZnOw异质结复合材料,利用 XRD、FESEM、EDS、XPS 和 FTIR 测试方法对样品进行表征,通过测定甲基橙溶液的光降解率来评价样品的光催化活性。结果表明,在紫外光照射下,Cu2S/T-ZnOw纳米复合材料的光催化性能优于纯氧化锌晶须的。当 PVP 的浓度为 3.0 g/L 时,样品的光催化活性最高,在紫外光照射 120 min 后,甲基橙的降解率为 97%。经过 4 个周期的光催化实验后,Cu2S/T-ZnOw 催化剂的光催化活性并没有明显下降,说明该样品具有优异的光稳定性。此外,讨论了Cu2S/T-ZnOw 纳米复合材料的光催化机理。     

钾对羟基磷灰石晶须的形貌及热稳定性的影响

通过α-TCP水化法制备了HA晶须,并通过向原料中添加KOH的方法来提高所制备晶须的热稳定性。结果表明:K的引入对HA晶须形貌有较大影响,K添加量过大时会抑制晶须的生长;同时,K的引入可以有效提高所制备晶须的热稳定性,相对于不添加K的HA晶须,添加适量K的晶须在1000℃下热处理2h后依然能较好的保持晶须形貌,X射线衍射和热分析结果发现此时仅有少量HA发生分解生成β-TCP,主晶相仍为HA。     

熔盐介质对合成莫来石晶须的影响

采用硫酸铝和氧化硅为原料,分别以氯化钾、氯化钠、硫酸钾、硫酸钠盐为熔盐介质,在1000℃下保温3 h,进行了合成莫来石晶须的研究.合成产物经X射线衍射分析发现,在氯化钠熔盐中合成的产物中莫来石含量较少,在氯化钾中合成产物中莫来石含量较高,而在硫酸钾、硫酸钠熔盐中可合成出纯度高的莫来石晶须.经扫描电镜分析发现,在不同盐中所合成的莫来石晶须形貌差异较大.根据熔盐的性质,探讨了熔盐介质对莫来石晶须形貌的影响,认为在相同的合成条件下,熔盐的种类是合成莫来石晶须的主要影响因素.     

Synthesis and characterization of multipod zinc oxide whiskers synthesized via a modified self-propagating high-temperature synthesis method

A self-propagating high-temperature synthesis (SHS) method, which features a 2-step heating process carried out in a closed chamber, was developed to prepare multipod ZnO whiskers (mZnOw). A compacted Zn powder was first heated at 370 °C in air to form a refractory layer of ZnO on the surface of Zn particles. Next, the SHS reaction was ignited by rapidly heating to ∼750 °C under different oxygen gauge pressures (PO₂) to obtain a loose white product mainly composed of mZnOw. It was found that the PO₂ strongly affected the reaction conversion and morphological features, along with the Zn-to-O ratio, of the as-synthesized products, which, in turn, might influence their photoluminescence and microwave absorption properties. A possible explanation for the effects of PO₂ on these characteristics was also proposed.     

Hydrothermal synthesis and conductive properties of Al-doped ZnO rod-like whiskers

The Al-doped ZnO rod-like whiskers were synthesized by a simple hydrothermal method. The resistivity of Al-doped ZnO whisker (AZO_w) samples significantly decreased with the increase of Al³⁺ concentration, and showed a minimum when Al³⁺ doping concentration was 2.0%. If Al³⁺ concentration continued to increase, namely more than 2.0%, the resistivity of Al-doped ZnO samples would increase. So, in this study the optimum Al doping concentration was 2.0%, and the lowest electric resistivity (3.959 × 10⁴ Ω cm) was obtained.     

Solvo-thermal synthesis and characterization of nest-like zinc oxide

With Zn(NO3)2·6H2O and NaOH as starting materials, a novel nest-like ZnO nanostructure was successfully synthesized by a solvo-thermal method. The products were characterized by X-ray diffraction, photoluminescence and scanning electron microscopy. The growth mechanism of the nest-like ZnO was discussed. The results show that the as-synthesized samples have a wurtzite structure, with a weak UV emission at about 395 nm, a green emission at around 557 nm and a blue-green emission at 453 nm. SEM investigation reveals that the growth route of the nest-like ZnO can be considered involving three stages: nano-sized ZnO sheet can be firstly achieved, then outspreads quickly and increasingly becomes a long fishbone-like strip with many branch sheets, and finally these sheets curl into a nest-like structure.     

Morphology and optical properties of Co doped ZnO textured thin films

Depending on the ZnO seed-layers, a new kind of cobalt doped zinc oxide (Zn_1−xCo_xO) thin films with controllable morphology were prepared by a facile solvothermal method. A series of ZnO thin films with different Co contents were applied to study the effect of doped Co on morphology, structural and optical properties. It is found that the doped content plays an important role on morphology evolution of Zn_1−xCo_xO films. The results of scanning electron microscope (SEM) indicate that the Zn_1−xCo_xO films are highly uniform and porous. Co has been successfully doped into the ZnO lattice structure and revealed by X-ray diffraction (XRD) and energy dispersive spectrum (EDS). It can be found that Zn_1−xCo_xO thin films possess good crystalline quality through the characterization of transmission electron microscope (TEM) and high-resolution transmission electron microscopy (HRTEM). All of the samples show a stronger violet emission and ultraviolet absorption, and the violet emission peaks shift towards red with increasing of Co content. In addition, the magnetic result demonstrates that the prepared Co-doped ZnO thin films are room-temperature ferromagnetic materials.     

激光原位制备ZnO纳米柱形貌及光学特性

利用NEL-2500A轴向快速流动CO2连续激光辐射金属锌板(纯度为99.99wt%)同轴输送氧气,在金属锌板表面上原位制备氧化锌纳米柱晶体,晶体的底面直径为60～70nm,高度约为150nm。利用场发射扫描电子显微镜(FE-SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、X射线能谱仪(EDX)以及光致发光(PL)等试验对原位制备的ZnO纳米柱的形貌、组成成分、相结构以及光致发光性质进行了表征,并对ZnO纳米柱生长晶体的机理进行了分析。结果表明,利用本文方法能够制备纯度较高ZnO纳米柱晶体,ZnO纳米柱为单晶结构并沿〈0001〉方向生长,其结晶形貌取决于发生反应局部区域氧气的过饱和度。     

Characterization of zinc oxide nanoparticles synthesized by polymer assisted deposition method

Zinc oxide nanoparticles (ZNPs) are synthesized onto glass substrates by employing simple and low cost solution based modified polymer assisted deposition (PAD) method. Trionx100 is used as a capping agent and zinc acetate as the zinc source. TritonX100 concentration is varied from 0.02 to 0.45 M for the synthesis of pure ZnO NPs. TG-DTA analysis was employed to determine the decomposition temperature of TritonX100 and zinc acetate, which lead to the formation of ZnO. The films were further characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HR-TEM), Fourier transforms infrared spectroscopy (FT-IR) and room temperature photoluminescence (PL). The results indicate that the synthesized nanoparticles (NPs) exhibits the room temperature PL with two emission peaks, one corresponding to ZnO band edge emission and the other one to point defect states created due to oxygen deficiency. The first peak undergoes blue-shift due to change in NPs size while there is no shift in the second peak. Nevertheless, with increase in TritonX100 concentration the peak intensity of defect peak decreases, indicating that the highly pure NPs have been successfully synthesized by PAD method.     

Enhanced photocatalytic degradation of methylene blue by ZnO-reduced graphene oxide composite synthesized via microwave-assisted reaction

A quick and facile microwave-assisted reaction is used to synthesize ZnO-reduced graphene oxide (RGO) hybrid composites by reducing graphite oxide dispersion with zinc nitrate using a microwave synthesis system. Their photocatalytic performance in degradation of methylene blue is investigated and the results show that the RGO plays an important role in the enhancement of photocatalytic performance and the ZnO-RGO composite with 1.1 wt. % RGO achieves a maximum degradation efficiency of 88% in a neutral solution under UV light irradiation for 260 min as compared with pure ZnO (68%) due to the increased light absorption, the reduced charge recombination with the introduction of RGO.     

钛酸钾晶须/聚丙烯导热抗静电复合材料的制备与性能

采用热压成型工艺制备了导电钛酸钾晶须(PTWs)/聚丙烯(PP)复合材料,研究了晶须用量对复合材料导热性能、抗静电性能和力学性能的影响。结果表明,随着PTWs用量的增加,PTWs/PP复合材料的热导率提高、体积电阻率和摩擦静电荷下降;材料的拉伸强度、弯曲强度均随PTWs用量的增加呈先增大后减小的趋势;而熔体流动速率则呈增大趋势。当PTWs体积分数达到0.38%时,材料的热导率达到最大值0.5105 W.m-1.K-1,电阻率降低到109Ω.cm以下,满足一般抗静电材料的要求。