Photocatalytic Degradation of Rhodamine B Dye with High Purity Anatase Nano-TiO_2 Synthesized by a Hydrothermal Method

High purity anatase nano-TiO2 powders with high photocatalytic activity were prepared by a hydrothermal synthesis method. X-ray diffraction （XRD）, field emission transmission electron microscopy （FETEM）, ultraviolet-visible （UV-Vis） light absorption spectrum and photoluminescence （PL） spectrum were adopted to characterize the catalyst. Effects of temperature, time and sol concentration of hydrothermal synthesis on particle size and phases were investigated. Photocatalytic activities in the degradation of Rhodamine B Dye were studied. The experimental results indicated that photocatalytic activity of the nano-TiO2 powers was much higher than that of P25 （Degussa）.

Highly photoreactive TiO_2 hollow microspheres with super thermal stability for acetone oxidation

TiO2hollow microspheres(TiO2‐HMSs)have attracted much attention because of their high photoreactivity,low density,and good permeability.However,anatase TiO2‐HMSs have poor thermal stability.In this study,surface‐fluorinated TiO2‐HMSs were assembled from hollow nanoparticles by the hydrothermal reaction of the mixed Ti(SO4)2–NH4HF–H2O2solution at180°C.The effect of the calcination temperature on the structure and photoreactivity of the TiO2‐HMSs was systematically investigated,which was evaluated by photocatalytic oxidation of acetone in air under ultraviolet irradiation.We found that after calcination at300°C,the photoreactivity of the TiO2‐HMSs decreases from1.39×10?3min?1(TiO2‐HMS precursor)to0.82×10?3min?1because of removal of surface‐adsorbed fluoride ions.With increasing calcination temperature from300to900°C,the building blocks of the TiO2‐HMSs evolve from truncated bipyramidal shaped hollow nanoparticles to round solid nanoparticles,and the photoreactivity of the TiO2‐HMSs steady increases from0.82×10?3to2.09×10?3min?1because of enhanced crystallization.Further increasing the calcination temperature to1000and1100°C results in a decrease of the photoreactivity,which is ascribed to a sharp decrease of the Brunauer–Emmett–Teller surface area and the beginning of the anatase–rutile phase transformation at1100°C.The effect of surface‐adsorbed fluoride ions on the thermal stability of the TiO2‐HMSs is also discussed.

Synchrotron-Radiation Photoemission Study of Growth and Stability of Au Clusters on Rutile TiO2（110）-1×1

The growth and thermal stability of Au clusters on a partially-reduced rutile TiO2 （110）-1 × 1 surface were investigated by high-resolution photoelectron spectroscopy using synchrotron- radiation-light. The valence-band photoelectron spectroscopy results demonstrate that the Ti^3＋3d feature attenuates quickly with the initial deposition of Au clusters, implying that Au clusters nucleate at the oxygen vacancy sites. The Au4f core-level photoelectron spectroscopy results directly prove the existence of charge transfer from oxygen vacancies to Au clusters. The thermal stability of Au clusters on the partially-reduced and stoichiometric TiO2（110） surfaces was also comparatively investigated by the annealing experiments. With the same film thickness, Au clusters are more thermally stable on the partially-reduced TiO2（110） surface than on the stoichiometric TiO2（110） surface. Meanwhile, large Au nanoparticles are more thermally stable than fine Au nanoparticles.

Grain growth and thermal stability of nanocrystalline Ni-TiO_2 composites

The grain growth and thermal stability of nanocrystalline Ni-TiO2composites were systematically investigated.Thenanocrystalline Ni-TiO2composites with different contents of TiO2were prepared via electroplating method with the variation ofTiO2nano-particles concentration.The effect of TiO2content on the grain size,phase structure and microhardness was investigatedin detail.The corresponding grain growth and diffusion mechanisms during the heating process were also discussed.The optimalmicrohardness of HV50270was achieved for the composite with addition of20g/L TiO2nano-particles after annealing at400°C for90min.The calculation of the activation energy indicated that lattice diffusion dominated at high temperatures for thenanocrystalline Ni-TiO2composites.It was indicated that the increase of TiO2nano-particles content took effect on restricting thegrain growth at high temperatures by increasing the grain growth activation energy.

纳米TiO2改性复合相变微胶囊的制备及热性能研究

采用溶胶-凝胶法制备了纳米TiO2粒子,以正十四烷(Tet)为内核材料,纳米TiO2改性聚苯乙烯(PS)为壳层材料,制备了纳米TiO2改性复合相变微胶囊。采用扫描电镜(SEM)、X射线衍射仪(XRD)、TG-DSC综合热分析仪和热常数分析仪对未改性和纳米TiO2改性的复合相变微胶囊的形貌和热性能进行了研究,并测试了微胶囊乳液的热导率和机械稳定性。结果表明,纳米TiO2粒子大小均匀,平均粒径约为20nm左右,在聚苯乙烯壳中添加TiO2粒子会增加复合相变微胶囊的粒径;纳米TiO2改性后的复合相变微胶囊比未改性的复合相变微胶囊具有更高的热稳定性,其初始结晶和熔融温度分别达到0.42和2.63℃,均高于未改性复合相变微胶囊;纳米TiO2改性复合相变微胶囊的熔融潜热(ΔH m)达到84.53 kJ/kg,具备优异的热传导性能;相比未改性复合相变微胶囊乳液,纳米TiO 2改性复合相变微胶囊乳液的导热系数提高了16.47%,且具备较高的机械稳定性,可以用作蓄冷功能热流体材料。

离子掺杂对提高锐钛型TiO2高热稳定性的影响

归纳分析了离子掺杂对二氧化钛由锐钛矿型向金红石型转化的抑制作用,得出不同掺杂离子对TiO2相转化温度和粒径具有较大影响的结论。以TiCl4为原料,通过添加少量磷酸二氢钠(NaH2PO4),采用强迫水解法制备纯锐钛相纳米TiO2,相变温度提高到了1000℃,有效抑制了TiO2粒径的长大,与其他文献结果一致。指出掺杂TiO2的相变机理尚处于探索阶段,如何选择适当添加剂、实现高热稳定性锐钛矿型纳米TiO2产业化是今后研究的重点。

Effects of crystallinity, {001}/{101} ratio, and Au decoration on the photocatalytic activity of anatase TiO_2 crystals

Anatase TiO2 nanocrystals and sub-microcrystals with truncated octahedral bipyramidal morphologies were prepared by direct calcination of TiOF2 precursors. The as-prepared TiO2 samples were thoroughly characterized by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and UV-visible diffuse spectroscopy. It was found that the crystallinity, grain size, and {001}/{101} ratio of the samples can be increased by raising the calcination temperature from 500 to 800℃. The higher crystallinity and {001}/{101} facet ratio resulted in an increase in both aqueous and gas-phase photocatalytic activities, by inhibiting the recombination and separation of electrons and holes. After selecting two TiO2 samples with high crystallinity and {001}/{101} ratio, Au nanoparticles were decorated on their surfaces, and the photocatalytic activity of the resulting samples under visible light illumination was studied. It was found that the visible light-induced photocatalytic activity increased by 2.6 and 4.8 times, respectively, upon Au decoration of the samples prepared by calcination of TiOF2 at 700 and 800℃.

可见光响应TiO2-CdS纳米复合光催化剂的可控制备及性能

为改善TiO2的光吸收特性,得到性能优异的光催化剂,以氯化镉(CdCl2·2.5H2O)、硫代乙酰胺(TAA)及钛酸四丁酯(TBOT)为原料,以氯化钾(KCl)调控形貌,采用溶剂热法制备TiO2-CdS纳米复合材料,探究了其对亚甲基蓝溶液的光催化性能。系统地考察了原料配比、反应温度、KCl和表面活性剂的加入对光催化性能的影响。利用FTIR、SEM、XRD、BET和UV-vis对TiO2-CdS纳米复合材料的结构、形貌进行了表征,同时研究了其热稳定性能。结果表明:TiO2-CdS纳米复合材料的吸收波长由紫外区扩展到了可见光区域,在可见光光源照射下时,光催化性能优异;TiO2-CdS复合材料的比表面积为34.67m2/g;不同原料配比下,当TAA∶CdCl2∶TBOT的摩尔比为1∶1∶5,反应温度为160℃时,材料的光催化性能较佳;KCl和表面活性剂的加入会有效改善团聚现象,对亚甲基蓝的降解效率达到95%。并且纳米复合材料的热稳定性能良好,耐热温度可达838.25℃。

Composite structure Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG ceramics with high color spatial uniformity for white laser lighting

Composite ceramic phosphor(CCP)is a candidate light-conversion material to obtain the high-quality laser lighting source.Phosphors based on the transmissive configuration model could not simultaneously meet the requirements of angular color uniformity and high thermal stability.In this study,a novel composite structure ceramic was designed,including Al_(2)O_(3)-YAG:Ce/YAG layered ceramic with a size of 1 mm×1 mm for lighting,and Al_(2)O_(3) ceramic(φ=16.0 mm)was used as the wrapping material due to its outstanding thermal stability.The prepared ceramics exhibited excellent thermal performance and no yellow ring phenomenon.Through this design,we achieved the match of the intensity distribution of the blue and yellow lights,resulting in a high angular color uniformity of 0.9 with a view angle of±80°.All ceramics showed no luminous saturation phenomenon,even the laser power density was increased up to 47.51 W/mm^(2).A high-brightness white-light source with a luminous flux of 618 lm,a luminous efficiency of 126 lm/W,a CCT of 6615 K,and a CRI of 69.9 was obtained in the transmissive configuration.In particular,the surface temperature of the ceramic was as low as 74.1℃ under a high laser radiation(47.51 W/mm^(2)).These results indicate that Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG composite structure ceramic is a promising luminescent material in the high-power laser lighting applications.

Simultaneous enhancement of red luminescence and thermal stability of a novel red phosphor:A Li^(+)-Eu^(3+)co-occupied site strategy in BaAl_(2)Ge_(2)O_(8)lattices

The rapid development of phosphor-converted white light emitting diodes(pc-WLEDs)requires new red phosphors with efficient and thermally stable luminescence for high-quality warm-white lighting.However,it is still a challenge to discover red phosphors with facile synthesis,high internal quantum efficiency(IQE),excellent thermal stability and high color purity.Herein,a novel red-emitting Eu^(3+)activated barium dialuminum digermanate(BaAl_(2)Ge_(3)O_(8),EAGO)phosphor showing strong red emission at 610 nm was prepared.The IQE is improved from 32.91%to 78.84%by employing a charge compensation strategy.The lithium-ion co-dop ed BAGO:Eu^(3+)phosphor exhibits a nearly twofold increase in integral photoluminescence(PL)intensity and the high color purity reaches 94.17%.Impressively,the PL intensity of the BAGO:Eu^(3+),Li^(+)phosphor drops by only 2.6%at 150℃of that at room temperature.Finally,the pc-WLED using the red BAGO:Eu^(3+),Li^(+)phosphor exhibits white light with the chromaticity coordinate of(0.3515,0.3495),a high color-rendering index of 92 and a low correlated color temperature of 4746 K.All these results manifest that BAGO:Eu^(3+),Li^(+)phosphor is a suitable red phosphor for nearultraviolet(NUV)chip-based pc-WLEDs.

碱金属离子共掺Sr_(3)Ga_(2)Ge_(4)O_(14)∶Dy^(3+)发光性能研究

本文采用高温固相法制备了一系列新型Sr_(3-x)Ga_(2)Ge_(4)O_(14)∶xDy^(3+)(x=0~0.40)(摩尔分数)及Sr_(2.68)Ga_(2)Ge_(4)O_(14)∶0.16Dy^(3+),0.16M^(+)(M=Li、Na、K)荧光粉。EDS能谱分析证实该荧光粉中存在Sr、Ga、Ge、O、Dy元素。系列Sr_(3-x)Ga_(2)Ge_(4)O_(14)∶xDy^(3+)在350 nm光激发下产生了以568 nm为主波长,对应于^(4)F_(9/2)→^(6)H_(13/2)跃迁的强黄光发射。荧光粉的发射光谱显示,其发射强度随Dy^(3+)浓度的增加而变化,且当x=0.16时达到最强。共掺杂碱金属M(M=Li、Na、K)作为电荷补偿离子,其中Li^(+)对增加Dy^(3+)的发射强度效果最明显,使得荧光粉的发射强度提高到没有电荷补偿离子时的2倍。此外,随着Dy3+掺杂浓度的提高,荧光粉的荧光寿命不断减少。最后探讨了荧光粉Sr_(2.68)Ga_(2)Ge_(4)O_(14)∶0.16Dy^(3+),0.16Li^(+)的CIE色度坐标和热稳定性,其CIE色度坐标为(0.3719,0.4046),位于黄色区域,在453 K的发光强度约为其室温发光强度的95.5%。因此,Dy^(3+),Li^(+)共掺杂Sr_(3-x)Ga_(2)Ge_(4)O_(14)荧光粉是潜在的显示器件和白光LED器件候选材料。

溶胶-凝胶TiO_2的晶相转变温度

本文以DTA -TG和XRD等分析方法研究钛醇盐溶胶中水含量、硝酸含量和硝酸银掺杂对胶凝时间、热效应、失重和锐钛矿 -金红石相变温度的影响。文章还探讨了各参量影响相变温度的机理。

板钛矿基TiO_2纳米晶的结构相变和热稳定性

研究含一定量锐钛矿和金红石的板钛矿基ＴｉＯ２ 纳米晶的热稳定性，发现其ＤＴＡ 曲线上出现两个吸热峰．ＸＲＤ物相、晶粒度和相含量分析表明，出现于３０ ～１６０℃温区的Ａ峰对应于脱附过程；出现于７８０～８４５℃温区的Ｂ峰对应于样品结构从板钛矿经锐钛矿向着金红石的急剧一级相变； 在Ｂ峰出现前，样品中存在板钛矿向锐钛矿的缓慢转变过程； 相变促进了纳米晶粒的生长．

高热稳定的多孔锐钛矿二氧化钛的制备及表征

以十二烷基胺为模板剂,以廉价的无机钛盐为前驱物,采用模板法水热合成了蠕虫状多孔TiO2粉体,并研究了热处理温度对TiO2粉体的晶相、形貌、微结构和比表面积的影响.结果表明:该法制备的锐钛矿TiO2具有较高的相变稳定性,在高达1 000℃煅烧后锐钛矿相仍然为主要晶相,1 100℃煅烧后转变为金红石相,比通常TiO2的晶型转变温度提高了300℃左右.在300℃和500℃煅烧后,样品的比表面积分别为138,51 m2/g.多孔TiO2粉体具有高度晶化的锐钛矿纳米晶和高比面积共存的特性,使其在光催化以及光电化学转换方面具有潜在的应用价值.

TiO_2超细粉热稳定性的研究

本实验以ＴｉＣｌ４为原料，采用超临界流体干燥法制备出ＴｉＯ２气凝胶超细粉，在６２３～９２３Ｋ温度范围内考察了其织构和结构的热稳定性。实验发现，随着焙烧温度的提高，样品的比表面积和孔体积减小，表观堆积密度增大，同时伴随着颗粒烧结长大并连成链状。对ＴｉＯ２气凝胶超细粉的烧结机理研究表明，其烧结为表面扩散控制过程，烧结活化能为２２２．６ｋＪ／ｍｏｌ。

微波热液法制备光催化TiO_2功能材料

采用微波加热法 ,研究了钛配离子热分解水解反应的规律。结果表明 ,水解产物在大气气氛和 3 0 0℃下煅烧 2h ,所得产物为锐钛型TiO2 粉末。在紫外线照射下 ,乙酸经TiO2 光催化反应 12h后 ,残余量小于初始量的 2 0 %。

WS_2微粉的物理性能及热稳定性

采用ＳＥＭ， ＸＲＤ， ＤＴＡ， ＸＰＳ 等手段， 测定了高纯ＷＳ２ 微粉的密度、组成与价态、结构、摩擦磨损性能等物理性质， 研究了高纯ＷＳ２ 微粉分别在空气、氢气和氮气中的热稳定性。实验结果表明： ＷＳ２的平均密度为（７ ．７２ ±０ ．０２） ×１０３ ｋｇ／ｍ３ ；Ｓ／ Ｗ 比值约为２ ．１ ，Ｓ 为－ ２ 价， Ｗ 为＋ ４ 价； ＷＳ２ 微粉晶体为２ Ｈ 结构； ＷＳ２ 在空气中的热稳定性随着制备温度的升高而变好，４５０ ℃下制备的 ＷＳ２ 起始氧化温度为２４６ ℃，１４００ ℃下制备的ＷＳ２ 起始氧化温度为５７０ ℃；１３００ ℃下制备的ＷＳ２ 在氢气中的还原反应起始温度为６６０ ℃；在密闭氮气中的最高热稳定温度为１ ５００ ℃。

纳米锐钛矿型TiO_2的高温Raman光谱研究

采用沉淀 -胶溶 -絮凝法 ,以偏钛酸为反应物 ,制备出纯锐钛矿型纳米 Ti O2 粉末 .用 XRD和 TEM对其进行表征 .采用高温 Ram an光谱仪对所制备的纳米 Ti O2 从室温 2 98K到高温 16 2 3K进行了原位研究 .随着温度升高到72 3K时 ,Ram an谱峰明显下降变宽 ,预示着锐钛矿相的结构发生变化 ;到 12 73K时 ,Ram an特征频率谱峰几乎全部消失 。

高热稳定性的SrAl2Si2O8∶Eu^2+荧光粉的制备与发光性能研究

采用高温固相法制备了SrAl2Si2O8∶Eu^2+(SASO∶Eu^2+)系列荧光粉,详细研究了荧光粉的晶体结构、激发光谱、发射光谱以及热稳定性。结果表明,在337 nm激发下,发射光谱为一个非对称的宽带单峰,峰值波长404 nm,峰的半高宽约为53 nm,Eu^2+的最佳掺杂摩尔浓度为5%,根据Dexter理论,讨论了SASO∶Eu^2+荧光粉浓度猝灭是由于Eu 2+电偶极-电偶极之间的相互作用引起的。当加热到225℃时,SASO∶0.05Eu^2+荧光粉发光强度仍具有在初始室温下发光强度的97.4%,表明其具有优异的热稳定性。

等离子喷涂TiB_(2)-SiC复合涂层及其热稳定性研究

利用喷雾干燥重构微米级TiB_(2)-SiC喷涂团聚粉,借助等离子喷涂成功制备了TiB_(2)-SiC复合涂层。结果表明,包覆结构可减缓SiC高温分解,获得TiB_(2)、SiC主相共存的复合涂层。通过显微硬度测定及Weibull分布发现,当SiC质量分数为5%时,复合涂层的平均显微硬度为1088.8 Hv_(0.2),分散性系数β为9.2,均高于含20 wt%SiC制备的涂层,表明其具有更稳定的性能和结构。通过900℃和1000℃高温热冲击性及抗氧化性能测定发现,TiB_(2)-5 wt%SiC制备的复合涂层具有更为优异的抗热冲击性能和抗高温氧化性能。