ZnO和ZnO/Au纳米流体的制备及光热转换性能

太阳能光热利用是太阳能利用的重要方面,其中,纳米流体光学特性对太阳能光热利用效率起着决定性作用。通过水热法制备不同形貌的ZnO纳米颗粒,再利用硼氢化钠还原法将Au成功还原在ZnO纳米颗粒上,制备出ZnO/Au复合纳米材料。通过SEM、XRD表征ZnO和ZnO/Au纳米粒子的形貌结构与成分。经紫外/可见/近红外吸收光谱测试表明ZnO/Au纳米流体显著提高了在可见光波段的吸收。通过光热转换实验表明,花状ZnO纳米流体的光热转换性能优于棒状ZnO纳米流体, ZnO/Au纳米流体由于Au的等离激元效应,光热转换特性增强。当浓度为1.0 mg/mL时,棒状ZnO/10%Au纳米流体光热转换效率为59%,比纯导热油纳米流体提高16%;当浓度为0.5 mg/mL时,花状ZnO/10%Au纳米流体光热转换效率为71%,比纯导热油纳米流体提高28%。     

Ag@TiO_2核壳纳米粒子的制备与红外发射率研究

在TX-100/环己烷/正己醇/水组成的油包水（W/O）体系中,采用微乳液法制得Ag@TiO2核壳纳米粒子.采用透射电镜（TEM）,X线衍射（XRD）,红外光谱（IR）和紫外可见光谱（UV-Vis）等对其形貌和物相进行分析.利用IR-1红外发射率测量仪测定复合粒子在8～14μm波段的红外发射率.结果表明：该核壳纳米粒子粒径约50 nm,内核为面心立方的金属Ag,外壳为无定型的TiO2.被TiO2包覆后Ag核的紫外共振吸收峰与纯胶体Ag相比发生了微弱红移.高反射性能的金属Ag的引入使该核壳结构复合物的红外发射率明显降低,最低可降至0.483.Ag@TiO2核壳纳米粒子的红外发射率随着外层TiO2结晶性能的提高而下降.     

分级结构纳米ZnO的制备及其光催化性能研究

采用水热合成法,以Zn(CH3COO)2.2H2O和NaOH为原料,糊精为形貌控制剂,在120℃条件下合成了纳米ZnO样品.利用粉末X射线衍射、扫描电子显微镜、透射电子显微镜和高分辨透射电子显微镜对所合成的ZnO样品进行了结构和形貌的表征.分析结果表明,所合成的ZnO样品具有六方纤锌矿结构,且样品中含有大量由ZnO纳米片组装而成的"花状"分级结构纳米颗粒,花状分级结构中纳米片的平均厚度约50 nm.光催化降解实验结果表明,所合成的花状分级结构纳米ZnO具有很好的光催化性能.     

一维纳米结构ZnO的制备

采用溶胶-凝胶法,以醋酸锌(Zn(CH3COO)2.2H2O),草酸((COOH)2.2H2O)和无水乙醇为原料,制备得到了粒子直径在30 nm左右、粒度分布均匀、分散性较好的球状纳米ZnO粒子.以上述反应为基础,在反应体系中加入一定量的有机添加剂三乙醇胺,得到了棒状结构的纳米ZnO.利用透射电子显微镜(Transmission Electron Microscopy,TEM)研究了有机添加剂三乙醇胺的加入对产物纳米ZnO形貌的影响.实验结果表明:有机添加剂三乙醇胺在棒状纳米ZnO的形成过程中起决定性作用,并且所形成的棒状纳米ZnO的形貌随添加剂用量的不同而不同,所以调节三乙醇胺的加入量可以有效地控制纳米ZnO的形貌.     

纳米ZnWO4的水热合成及其光致发光性能研究

采用廉价的无机盐为前驱体,在非离子性表面活性剂PEG-20000存在下采用水热法制备出不同纳米结构的ZnWO4：利用XRD和SEM对其组成、形貌和结构进行了表征,详细考察了影响形貌的因素（比如表面活性剂的用量,反应体系的pH值）：随着表面活性剂用量的增加,产物的形貌从棒状逐渐转变成胎状;随着pH值的增加,产物的组成从ZnWO4转变成ZnO。也就是说,pH值对ZnWO4的形成起到非常重要的作用,纳米ZnWO4结构的形成是由于表面活性剂浓度的增加而引起的PEO和Zn^2＋配位状态的改变。同时研究了ZnWO4和ZnO的光致发光性能：不同形貌的ZnWO4都在激发波长为253nm时,在506nm处仅出现一个绿色峰;当激发波长为262nm时,ZnO的峰出现在396nm和510nm处。     

织物用热红外伪装涂料在8～14 μm波段红外发射率的研究

从金属颜料铝粉的含量，粒子形貌和尺寸，粘合剂的选用和改性等4个方面对织物用热红外伪装涂料在8－14μm波段的红外发射率进行了研究，结果表明，当铝粉质量百分数大于20％时，涂层的发射率不再下降；片状粒子和尺寸较大的粒子对发射率降低的作用较强；以三元乙丙橡胶为基料获得的改性粘合剂在3－14μm波段具有较好的红外透明性。     

微波水热法制备花状氧化锌光催化剂的研究

以乙酸锌和氨水为原料,采用微波水热法成功制备出了花状ZnO光催化剂。探讨了溶液Zn~(2+)初始浓度、pH值和微波加热时间对ZnO物相、形貌及光催化性能的影响。XRD表明制备的样品均为纤锌矿结构,晶型完整且部分ZnO样品晶粒沿(002)晶面发生了取向性生长;SEM表明pH值对ZnO形貌有着重要影响,pH值过低(pH<10.0)时,无法形成花状ZnO,pH过高(pH>10.7)时,花状ZnO"花瓣"会变形甚至溶解;UV-Vis表明制备的ZnO样品的吸收带均发生了红移,拓宽了光催化剂的吸收波长范围;反应条件对ZnO光催化性能的影响主次关系为:pH值>Zn~(2+)初始浓度>微波加热时间,较优工艺及工艺参数为:初始反应Zn~(2+)浓度为0.15 mol/L,pH值为10.5,微波加热时间为2.5 h,较优样品在紫外光辐照4 h后对亚甲基蓝溶液的降解率为85.90%。     

LSS法制备TiO2球形晶体及机理研究

文章通过液相（liquid）-固相（solid）-溶液相（solution）合成法制备单分散TiO2球形晶体。考察了LSS体系中各反应组分（NaOH、油酸、水、乙醇）对于反应终产物TiO2球形晶体的形貌的影响,在单组分和两组分实验中,醇系体系主要得到球形产物,强碱体系得到长菱形和棒状结构,油酸作为表面活性剂可减少产物团聚;四组分体系得到形貌较规整的球形。根据不同的产物形态对LSS合成法的反应机理进行了探讨。     

表面活性剂对氧化锌微纳米晶形貌及光致发光性能的影响

以硝酸锌、氢氧化钠为原料,采用水热法制备出氧化锌微纳米晶,并研究了表面活性剂对氧化锌微纳米晶形貌的影响,探讨了不同形貌氧化锌微纳米晶的生长机理。采用X射线衍射(XRD)、扫描电子显微镜(SEM)以及光致发光谱(PL)等测试手段对产物的结构、形貌和光学性能进行了表征。结果表明,借助表面活性剂CTAB、SDBS、PVPK90可分别制得片状、棒状和花状纤锌矿型氧化锌微纳米晶,3种形貌的氧化锌微纳米晶均具有光致发光特性,尤其片状ZnO微纳米晶的光致发光峰最强。     

Cr掺杂量对Zn1-xCrxO稀磁纳米材料的结构及性能影响

利用水热法制备了Zn1-xCrxO稀磁纳米材料,采用XRD、FESEM、EDS、PL和VSM等方法对样品的结构与性能进行了表征与分析,考察了Cr掺杂量对Zn1-xCrxO样品的结构与性能影响。XRD分析表明Zn1-xCrxO样品为ZnO六方纤锌矿结构,随着Cr掺杂量增加样品的结晶性能下降,并且样品的形貌由较好的六角棒状结构逐渐变得杂乱;磁滞回线分析表明Zn1-xCrxO样品具有良好的室温铁磁性,Cr掺杂量不同,样品的磁性不同;PL谱表明适量Cr掺杂对ZnO的发光性能有促进作用。     

Preparation of ZAO powder and investigation on its infrared emissivity

According to the basic infrared stealth mechanism of low infrared emissivity powders,the ZAO powder materials were prepared by liquid coprecipitation method,and the starting materials were Zn( NO3) 6H2O and Al( NO3) 39H2O. The process parameters were obtained,and the relationship between technology parameters and infrared emissivity was investigated. The temperature of thermal treatment,crystal structure and surface micrograph of ZAO powder was analyzed by the help of TG-DTA,XRD and SEM. The infrared stealth performance of ZAO powder was studied by IR-2 emissivity spectroscopy. Results showed that the infrared emissivity was the lowest when pH was 8. 0,calcination temperature was 1100 ℃,calcination time was 2 h,and the Al2O3doping content was 3% ( mass percentage) . The crystal structure of doped ZAO powder was lead-zinc, and there exists distortion of crystal lattice in nanocrystalline ZnO. The average particle size was 10 μm. The lowest infrared emissivity reached to 0. 61 at between 8 μm and 14 μm. It means that the ZAO powders will be excellent infrared stealthy materials.     

Preparation and characterization of three-dimensional chrysanthemun flower-like calcium carbonate

Calcium carbonate with three-dimensional chrysanthemun flower-like structure was successfully prepared from calcium chloride and sodium carbonate ethanol/water mixed solution by a simple precipitation method,using trisodium citrate as crystal modifier.The experimental results show that the three-dimensional structure of chrysanthemun flower-like calcium carbonate is built up with several symmetrical micrometer multi-layer petals arranged around the multi-layer pancake-liked center,and the micrometer center and petals are assemblied by a large number of nanometer spherical particles with size 10-20 nm.It is found that the amount of trisodium citrate,the ethanol volume content has an important influence on the formation of this morphology.A possible mechanism is proposed to explain the formation of three-dimensional chrysanthemun flower-like calcium carbonate according the results.Scanning electron microscopy(SEM),X-ray powder diffraction(XRD),flourier transform infrared spectroscopy(FT-IR),thermogravimety analysis(TG),transmission electron microscopy(TEM) equipped with energy-dispersive X-ray(EDX),and selected area electron diffraction(SAED) were used to characterize the crystals.     

Study on optical constants inversion and infrared transmission characteristics of aerosol particles

Based on the experimental infrared spectral transmittances,an inverse model has been developed to determine the optical constants of the aerosol particles (SiO2 and Al2O3).Combined with the Mie theory and Kramers-Kronig (K-K) relations,the complex refractive indices of the SiO2 and Al2O3 particles are retrieved.The effects of the measurement errors on the inverse results are also investigated.With the optical constants inversed from the experiment,the discrete ordinate method (DOM) is used to calculate the infrared transmission characteristics of the aerosol particle cloud.Considering the multi-scattering and self-emission of the particles,the equivalent transmittance ratio (ETR) is suggested to evaluate the infrared transmission characteristics of the aerosol particles.Particular attention is given to analyze the effects of the volume fraction and diameters on infrared transmission characteristics.When the volume fraction is larger than 0.001,the particle diameter has little effect on the infrared transmission characteristics.For the uniform monodisperse particles in the detection waveband range of 3-5 μm and 8-12 μm,there exists a critical diameter where the ETR reaches the minimum value.In addition,the ETR of 3-5 μm is smaller than that of 8-12 μm with the same volume fraction and particle diameter.     

Design and calculation of low infrared transmittance and low emissivity coatings for heat radiative applications

The infrared transmittance and emissivity of heat-insulating coatings pigmented with various structural particles were studied using Kubelka-Munk theory and Mie theory. The primary design purpose was to obtain the low transmittance and low emissivity coatings to reduce the heat transfer by thermal radiation for high-temperature applications. In the case of silica coating layers constituted with various structural titania particles (solid, hollow, and core-shell spherical), the dependence of transmittance and emissivity of the coating layer on the particle structure and the layer thickness was investigated and optimized. The results indicate that the coating pigmented with core-shell titania particles exhibits a lower infrared transmittance and a lower emissivity value than that with other structural particles and is suitable to radiative heat-insulating applications.     

宽波段发射率对长波净辐射估算影响分析

地表宽波段发射率是估算地表长波净辐射的关键参数。陆面模式计算的是4—100μm的地表长波净辐射,而遥感仅能提供3～14μm范围内的宽波段发射率。评价遥感宽波段发射率用于地表长波净辐射计算的精度,需要光谱范围更宽的地表发射率光谱。借助辐射传输模型模拟的水体、冰／雪和矿物1～200μm发射率光谱,调查了不同光谱范围的宽波段发射率和全波长宽波段发射率的差异。结果表明4～100μm宽波段发射率与全波长宽波段发射率最接近。调查了不同光谱范围内遥感宽波段发射率在计算4—100μm长波净辐射的精度,发现8—13．5μm的宽波段发射率具有最高的精度,偏差小于0．01W／m2,均方根误差小于1W／m2。并给出由ASTER和MODIS窄波段发射率产品计算8—13．5μm宽波段发射率的转换公式。     

焙烧炭砖孔结构和导热系数与硅粒度变化关系

借助于X射线衍射仪、压汞仪、激光导热仪、扫描电子显微镜和能谱分析仪等测试手段,研究了分别含3种不同粒度硅粉（中位径分别为2．3、45．0、115．6μm）焙烧炭砖试样中的孔结构和导热系数的变化。结果表明,含硅粉的炭砖试样经焙烧后内部均生成pSiC、Si2N2O和石英等相,粒度过粗,试样内有单质硅残留;随着硅粉粒度的减小,生成碳化硅晶须的长径比变小。对所选用的3种粒度硅粉,随着硅粉粒度的减小,焙烧后炭砖试样的孔径分布范围逐渐变窄,小于1μm气孔孔容积变大,而平均孔径变小。受炭砖试样组成和孔结构影响,硅粉粒度变小,导热系数下降。细小气孔容积与导热系数呈反比关系,即细小气孔增多,导热系数下降。     

Er~（3＋）/Yb~（3＋）共掺氟磷酸钙纳米微晶玻璃的高效近红外发光性质研究（英文）

本文制备了Er3＋/Yb3＋共掺的透明氟磷酸钙纳米微晶玻璃,并对其近红外发光性质进行了研究。样品经过热处理后,经X射线衍射和透射电镜测试发现：玻璃基质中均匀地析出了20 nm左右的Ca5（PO4）3F晶体,并且稀土离子进入到了析出的纳米晶相中.同热处理之前的样品相比,在808 nm和980 nm激光的激发下,Er3＋/Yb3＋共掺的微晶玻璃在1.54μm处产生很强的近红外发光,其半高宽高达75 nm.另外,我们对微晶玻璃的近红外发光与Er3＋和Yb3＋浓度的关系进行了研究.由于其具有高效的近红外发光,表明Er3＋/Yb3＋共掺的氟磷酸钙纳米微晶玻璃是一种潜在的激光和光放大材料.     

六方相NaYF_4微米棱柱晶体的水热生长

通过温和的水热方法合成了六方相NaYF4微米棱柱.场发射扫描电镜（FE-SEM）和透射电子显微镜（TEM）分析表明：该晶体结晶性较好,尺寸均一,直径约为1μm,长度约为5μm,晶体笔直且边缘清晰.研究发现六方相NaYF4微米棱柱是随着反应时间的延长由微米花状球上脱落而成的.提出了其可能的生长机制.