锌蒸气高温气相氧化动力学

用热重法测定了锌蒸气在不同温度和气氛下的氧化动力学曲线,用扫描电镜观察分析产物的结晶形貌.结果表明:氧化动力学遵守直线规律时,产物的结晶形貌是无定形、颗粒状和单针状;氧化动力学曲线为抛物线规律时,产物的结晶形貌是四针状和多针状.氧化动力学转变规律的原因是锌蒸气中存在超细锌微粒与气态锌原子的动态平衡.应用动力学理论和上述结果推断了相关条件下的动力学机理函数和动力学常数,研究了锌微粒的氧化过程并求出了锌原子通过氧化膜层的扩散系数.     

反应条件对固相法制备的纳米氧化锌粒径和形貌的影响

分别以Zn(CH3COO)2·2H2O,Zn(NO3)2·6H2O为原料,通过固相法合成了ZnO纳米粒子,考察了反应体系、超声搅拌、焙烧温度、焙烧时间等条件对ZnO粒径和形貌的影响.当焙烧温度为500℃,焙烧时间为3h,并在超声搅拌的情况下得到的产物较为理想.采用X-射线衍射(XRD)和扫描电镜(SEM)对纳米粒子的结构、粒径和形貌进行表征,结果表明产物为六方晶系结构的ZnO.在最佳反应条件下,以醋酸锌和硝酸锌为反应物制备的ZnO的平均粒径分别为33nm和41nm左右,形貌较规整,分散性良好.     

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。     

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。     

耐热铸铁的氧化膜形貌及能谱分析

本文利用扫描电镜和能谱分析仪，观察了ＲＱＴＳｉ５、Ｃｒ２６Ｎｉ、Ｃｒ２３ＴｉＢ，Ｃｒ３１和ＣｒＭｎＮ五种类型耐热铸铁的氧化膜微观形貌、氧化物颗粒大小和致密性，测定了氧化物的化学万分及合金元素在氧化膜中的分布情况，分析研究了合金元素对氧化膜的形成、生长和抗剥落性能的影响。     

灰铸铁中γ枝晶结晶形貌与机械性能的关系

采用控制传热方向和冷却条件的方法，在灰铸铁中获得不同类型结晶形貌的γ枝晶组织，并研究了γ枝晶的不同生长形貌与机械性能之间的对应关系．结果表明，发达的等轴枝晶所形成的网络骨架结构对铸铁强化作用最显著，柱状枝晶各向异性，平行于一次晶轴方向的σｂ远高于其它方向，也比其他类型的树枝晶高，垂直于一次晶轴方向的σｂ相对较低；短粗不发达枝晶对应的σｂ最低．     

氧化铝种分附聚过程结晶形貌分析

通过对种分附聚过程结晶形貌的分析推断附聚的机理,大部分晶体是通过氢氧化铝晶体晶面缺陷或台阶上生长的细晶粒粘合在一起形成稳定的附聚体。附聚体之间粘结的物质除了氢氧化铝之外还有其他杂质晶体存在;附聚过程发生与晶体粒径无关;附聚效率与晶体表面积成正比,而与需要填充的晶面体积成反比。     

平衡气量控制法合成四针状氧化锌晶须的形貌和发光性能

以金属锌为原料不添加任何催化剂,在700°C时通过平衡气量控制法合成四针状氧化锌晶须。研究了成长时间对样品微结构和发光性能的影响。结果表明,制备的样品是由四针状氧化锌组成的;四针状氧化锌针的长度和直径随成长时间的延长而增加;在样品的室温发光谱中,在385~391nm处出现强的紫外光发射,但没有任何深水平发射,且紫外发射的强度随样品成长时间的延长而增强。     

稀土超磁致伸缩合金结晶形貌研究

研究了成分为Ｔｂ０３Ｄｙ０７（Ｆｅ１－ｘＭｘ）１９５（Ｍ＝Ｍｎ，Ａｌ，Ｔｉ，Ｂ，ｘ＝００３）的合金在高温度梯度区熔定向凝固过程中的结晶形貌与晶体生长速度ｖ，温度梯度ＧＬ之间的关系。发现当温度梯度一定时，随结晶速度增加，结晶形貌由平面晶向胞状晶、胞枝状晶和树枝晶转变。合金的结晶速度为一定时，随温度梯度ＧＬ由低向高变化，合金由发达的树枝晶向胞枝状晶和胞状晶转变。当合金具有胞枝状晶形貌时，＜１１２＞沿棒状样品的轴向取向，此时合金可获得优异的磁致伸缩性能。     

Effects of temperature and pressure on morphologies of quasi-one-dimensional ZnO nanostructures fabricated via thermal evaporation

Quasi one-dimensional zinc oxide nanomaterials were synthesized by thermal evaporation. The structure, morphologies and composition of ZnO nanomaterials prepared under different conditions were studied by XRD, TEM, SEM and EDX. The morphologies are strongly sensitive to the temperature and the pressure during growth, including nanowires, nanobelts, nanocombs and pyramidal-like nanomaterials.     

Synthesis of ZnO nanowalls on Al2O3 (0001) by catalyst-free metalorganic chemical vapor deposition

We report the synthesis of epitaxially aligned ZnO nanowalls on Al₂O₃ (0001) by metalorganic chemical vapor deposition without using any metal catalyst. ZnO nanowalls of 60–150 nm thickness are uniformly assembled on the substrate. A small amount of ZnO nanowires additionally grow and are coupled with the ZnO nanowalls. Interestingly, the crystals in the ZnO nanowalls are aligned in both the out-of-and in-plane direction. A strong UV emission at around 380 nm, observed in a room temperature photoluminescence spectrum, indicates excellent optical quality of the ZnO nanowalls.     

Preparation of ZnO crystal by sol-gel method

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Surface morphology and photoluminescence properties of ZnO thin films obtained by PLD

ZnO thin films on Si(111) substrate were deposited by laser ablation of Zn target in oxygen reactive atmosphere, Nd-YAG laser with wavelength of 1 064 nm was used as laser source. XRD and FESEM microscopy were applied to characterize the structure and surface morphology of the deposited ZnO films. The optical properties of the ZnO thin films were characterized by photoluminescence. The UV and deep level (yellow-green) light were observed from the films. The UV light is the intrinsic property and deep level light is attributed to the existence of antisite defects (Ozn). The intensity of UV and deep level light depends strongly on the surface morphology and is explained by the surface roughness of ZnO film. A strongly UV emission can be obtained from ZnO film with surface roughness in nanometer range.     

退火处理对氧化锌纳米棒形貌及气敏性能的影响（英文）

研究水热合成氧化锌纳米棒的高温热稳定性。采用X射线衍射和扫描电镜对氧化锌纳米棒的结构与形貌进行表征。采用热重分析研究氧化锌纳米棒在热处理过程中的失重情况。结果表明:在退火温度低于400°C时,氧化锌纳米棒具有较好的热稳定性。当退火温度超过600°C时,氧化锌纳米棒的长径比明显降低并且纳米棒的团聚趋势加剧。退火处理对氧化锌纳米棒的气敏性能具有显著影响。与未经退火处理的氧化锌纳米棒相比,经历400°C退火处理的氧化锌纳米棒对浓度为25×10-6的H2灵敏度可以从2.22提高至3.56。经历400°C热退火处理的氧化锌纳米棒对H2表现出最优的气敏性能。     

Rapid growth of ZnO hexagonal prism crystals by direct microwave heating

ZnO hexagonal prism crystals were synthesized from ZnO powders by microwave heating in a short time (within 20 min) without any metal catalyst or transport agent.Zinc oxide raw materials were made by evaporating from the high-temperature zone in an enclosure atmosphere and crystals were grown on the self-source substrate.The inherent asymmetry in microwave heating provides the temperature gradient for crystal growth.Substrate and temperature distribution in the oven show significant effects on the growth of the ZnO crystal.The morphologies demonstrate that these samples are pure hexagonal prism crystals with maximum 80 μm in diameter and 600 μm in length,which possess a well faceted end and side surface.X-ray diffraction (XRD) reveals that these samples are pure crystals.The photoluminescence (PL) exhibits strong ultraviolet emission at room temperature,indicating potential applications for short-wave light-emitting photonic devices.     

Relative photoluminescence of ZnO nanorods size-controlled by changing the precursor ratio in metal organic chemical vapor deposition

The photoluminescent (PL) properties of vertically and laterally well-oriented ZnO nanorod arrays (NRAs) synthesized by metalorganic chemical vapor deposition on Al₂O₃ (0001) substrates were investigated. The size of the NRAs was controlled by systematic tuning of the precursor ratio. Regardless of the size of the NRAs, the PL properties were the same when measured at room temperature and at low temperatures. This observation suggests that changing the precursor ratio is a good way of controlling the size of ZnO NRAs while maintaining consistent PL properties.