重稀土掺杂对硼酸钐相组成及其性能的影响

利用溶胶凝胶燃烧合成法分别制备了八种重稀土掺杂的硼酸钐粉体,采用XRD和SEM对粉体的物相组成和形貌进行了表征。结果表明,重稀土离子的引入并没有改变SmBO3的晶体结构,SmBO3以三斜相为主,并含有少量的六方相,六方相的含量随着掺杂离子半径的减小而增加。重稀土离子掺杂的SmBO3粉体形貌呈现不规则片状,颗粒尺寸差别不大。采用紫外可见分光光度计对粉体进行了反射率测试,八种粉体在1.064μm处的反射率变化不大,但均较未掺杂SmBO3粉体的反射率略有提高,说明六方相的存在明显降低了SmBO3的光学性能。     

共沉淀法制备六方相ITO纳米粉体及其光电性能

以金属In、SnCl_4·5H_2O为原料、尿素为沉淀剂,采用共沉淀法加入(NH_4)_2SO_4,制备出六方相ITO纳米粉体。通过XRD、TEM、四探针电阻仪、荧光光谱仪以及XPS,研究了ITO粉体的晶型、颗粒形貌、电性能以及光性能。结果表明:加入(NH_4)_2SO_4后,ITO粉体形貌由类菱面体和类球形混合体转变为类球形;不加(NH_4)_2SO_4时晶型为立方相结构,当(NH_4)_2SO_4与铟的物质的量之比为1∶3.45和1∶1.73时粉体晶型转变为六方相结构,继续添加(NH_4)_2SO_4晶型又转变为立方相结构。立方相ITO粉体的电阻率较低为0.64Ω·cm,六方相ITO粉体在相同激发波长下,发射光强度相对较高。     

Yb3+掺杂浓度对LaF3晶相及其上转换光谱的影响

LaF3微米晶的晶相(斜方相和六角相)及其上转换发光光谱可以通过精确调节Yb3+的摩尔掺杂浓度来控制。利用简单的水热法合成了Yb3+和Tm3+共掺杂的LaF3,YF3和NaYF4三种不同基质的氟化物纳米晶。XRD分析表明,当Tm3+的掺杂浓度不变,仅Yb3+的摩尔掺杂浓度从10%提高到20%,就可以使基质结构由六角相过渡到斜方相。实验结果表明,具有较大离子半径的稀土离子由于增强的偶极化率,更容易使电子云产生畸变,有利于基质斜方相结构的形成。     

电子辐照对聚反式1,4-丁二烯晶型转变的影响

由于晶体结构对高分子性能有较大影响,因此研究其晶体结构具有重要意义．目前,已发现聚反式１,４－丁二烯（ＰＴＢＤ）存在两种晶型结构［１］,分别为单斜相和六方相,在低温下主要为单斜相,高温下主要为六方相．在一定温度下,单斜相和六方相可发生可逆的相转变［２］．本文以透射电镜为主要手段,在电子射线辐照下,研究单斜相向六方相的转变过程,不仅摄得样品的单斜相和六方相电子衍射谱,而且还拍摄到两相共存的电子衍射谱．１　ＰＴＢＤ的晶型转变Ｆｉｇ．１　ＤＳＣｔｈｅｒｍａｌｇｒａｍｏｆＰＴＢＤＳｃａｎｒａｔｅ：１０℃…     

共沉淀法制备六方相ITO纳米粉体及其光电性能

以金属In、SnCl₄5H₂O为原料、尿素为沉淀剂,采用共沉淀法加入（NH₄）₂SO₄,制备出六方相ITO纳米粉体。通过XRD、TEM、四探针电阻仪、荧光光谱仪以及XPS,研究了ITO粉体的晶型、颗粒形貌、电性能以及光性能。结果表明：加入（NH₄）₂SO₄后,ITO粉体形貌由类菱面体和类球形混合体转变为类球形;不加（NH₄）₂SO₄时晶型为立方相结构,当（NH₄）₂SO₄与铟的物质的量之比为1：3.45和1：1.73时粉体晶型转变为六方相结构,继续添加（NH₄）₂SO₄晶型又转变为立方相结构。立方相ITO粉体的电阻率较低为0.64 Ωcm,六方相ITO粉体在相同激发波长下,发射光强度相对较高。     

尼龙1012的Brill转变

作为一类重要的结晶性聚合物 ,尼龙在加热或冷却过程中的晶型转变 [1,2 ]一直为人们所关注 .其中对尼龙 66的晶型转变研究得最多 [3～ 6 ] .在加热过程中尼龙 66室温下三斜的α晶型转变为高温下的假六方晶型 ,尼龙 66的这一晶型转变称为 Brill转变 [3] .在变温 X射线衍射测试中可明显观察到 Brill转变 :室温下α晶型的两个强的衍射峰随温度升高逐渐靠近 ,并在某一温度下合并为一个峰 ,这一温度称为 Brill转变温度 .近年来研究表明 ,许多脂肪族的尼龙升温时均表现出 Brill转变 ,并且 Brill转变温度随尼龙结晶条件及其结构的不同而不同 [7…     

NdFeB材料微波吸收特性的研究

采用高能球磨和晶化热处理方法制备钕铁硼吸波粉体,研究制备工艺对钕铁硼粉体吸波性能的影响。结果发现:高能球磨和适当晶化热处理可改善NdFeB粉体的组织结构、复介电常数和复磁导率;NdFeB粉体的反射率最小值为-15.5 dB,高能球磨48 h后粉体的反射率最小值降到-23 dB,高能球磨粉体经600℃晶化热处理后反射率最小值为-19 dB;高能球磨和晶化热处理可降低NdFeB粉体的吸收峰频率;高能球磨会使NdFeB粉体的吸波带宽变窄,经600℃晶化热处理后吸波带宽变宽,并且随着晶化热处理的温度升高,吸波带宽变得更宽。     

立方形貌ITO粉体的水热法制备及光电性能

以金属In和SnCl_4·5H_2O为原料,采用水热法在120~140℃得到In(OH)_3前驱体,该前驱体在550℃下煅烧得到立方体形貌的氧化铟锡粉体.研究了水热反应温度和反应时间对粉体形貌和晶型的影响.通过热分析仪(TG-DSC)、X射线衍射仪(XRD)、拉曼光谱仪(Raman)、透射电子显微镜(TEM)、四探针电阻仪、X射线光电子能谱仪(XPS)、紫外-可见-近红外分光光度计以及荧光光谱仪对粉体进行了表征,并对水热反应条件为140℃及12 h下制备的c-ITO的光电性能进行了分析.结果表明,随着水热反应温度的升高,ITO粉体形貌由立方体向不规则形貌转变,粉体晶型出现少量的六方相.在水热反应条件为140℃,12 h,铟离子与尿素的摩尔比为1∶5时,得到平均粒径为230 nm的立方体ITO粉体,其电阻率为1.247Ω·cm,光学能带间隙为3.685 e V,与c-In2O3相比其能带间隙更高,室温下260 nm激发波长下粉体出现光致发光,发射峰位于蓝光区域.     

微波辅助水热法反应参数对NaYF4:Dy3+晶相、形貌、发光性能的影响

采用微波辅助水热法快速制备了可重复性良好的NaYF_4:Dy~(3+)样品,研究了一系列反应参数对NaYF_4:Dy~(3+)晶相、形貌、发光性能的影响。结果表明微波水热反应时间长短并未对产物的晶相、形貌、光谱性能产生明显的影响。Dy~(3+)掺杂浓度的增加并未改变样品晶相、形貌和尺寸,但发光强度发生改变,发光强度的变化趋势为先增大后减小,当Dy~(3+)掺杂浓度(物质的量分数)为1%时发光强度最强。根据具体的理论依据获得的电多极相互作用指数为6,表明Dy~(3+)之间的相互作用为电偶极-电偶极相互作用。研究了表面活性剂的种类与量对NaYF_4:Dy~(3+)晶相的影响。当使用柠檬酸钠和CTAB作为表面活性剂时,可制备得到六方相NaYF_4:Dy~(3+)。增加柠檬酸钠和CTAB的量,样品晶相未发生改变。使用EDTA-2Na作为表面活性剂时,随着EDTA-2Na量的不断增加发生从六方相到立方相晶相的转变。3种表面活性剂使用量不断增加后样品均出现尺寸减小现象。合成的一系列NaYF_4:Dy~(3+)荧光粉均在350nm紫外光激发下,出现Dy~(3+)特征峰。蓝光发射中心为479 nm,对应于Dy~(3+)的4F9/2→6H15/2跃迁;绿光发射中心为572nm,对应于Dy~(3+)的4F9/2→6H13/2跃迁,样品可实现蓝、绿发光。     

反式1,4-聚丁二烯的非等温结晶动力学研究

采用Nd(P5O7),-LiBu-AlEt3和AlEt3-VCI3两种催化剂体系分别合成了两种分子量与反式1,4单元结构含量不同的反式1,4-聚丁二烯样品(TPBD)。用DSC方法不仅研究了两样品六方相晶体的非等温结晶过程,同时还对单斜相结晶的非等温动力学过程进行了研究。Avrami方程分析显示,在低结晶度下TPBD六方相和单斜相的结晶生长过程呈现热成核的三维球晶生长。研究表明：虽然Ozawa方程在较低温度下能描述TPBD的六方相结构的实验数据,但不能完全描述在较高温度下六方相及单斜相非等温结晶过程,而用莫志深等建议的方程则能很好地描述TPBD六方相和单斜相非等温结晶过程。由Kissinger方程得到TPBD六方相和单斜相结晶的平均结晶活化能分别为-165．8kJ／mol和-220.5kJ／mol。     

SAPO-5分子筛的可控合成及晶化过程探索

在非醋酸体系下分别通过动态和静态水热晶化方法合成了SAPO-5分子筛, 并考察了转速、 晶化时间及凝胶体系水硅比对SAPO-5分子筛晶相及形貌的影响, 采用X射线衍射(XRD)和扫描电子显微镜(SEM)技术研究了静态、 动态水热条件下SAPO-5分子筛的晶化过程. 结果表明, 静态水热条件下晶化6 h得到的SAPO-5分子筛为球状、 六边形柱状聚集晶体; 而在20 r/min转速下晶化2和6 h得到的SAPO-5分子筛分别为分散的凹面柱状晶体(凹面直径约6~8 μm)及均一分散的球状晶体(直径为16 μm); 在60 r/min转速下晶化3 h即可得到高度分散的六边形柱状晶体(六边形直径约5~8 μm); 提高转速至100和140 r/min时仅需晶化1 h即可得到六边形柱状晶体. 通过考察体系水硅比(H₂O/Si摩尔比)的影响, 确定最佳的水硅比为70, 此条件下所得晶相为纯相且分子筛的分散度最好. 综上可知, 相较于静态晶化, 动态晶化不仅从形貌上改善了晶体的分散度, 通过缩短晶化时间、 降低晶化转速也提高了SAPO-5分子筛的晶化效率. 本文采用较小的水硅比(H₂O/Si摩尔比为70)、 较低的模板剂用量在非醋酸体系下合成了SAPO-5分子筛, 为SAPO-5分子筛的合成提供了一条更简单、 经济的路线.     

CePO4纳米线的热稳定性及光学性能

以铈盐和磷酸为前驱体, 经水热合成获得了高长径比的具有六方晶型和单斜晶型独居石结构的CePO4纳米线, 采用XRD、HRTEM、SEM和荧光光度计对其晶相组成、形貌及发光性能进行了表征. 结果表明, 六方晶型CePO4纳米线直径约为40 nm, 长度约为3 μm; 单斜晶型独居石结构CePO4纳米线直径约为50 nm, 长度可达10 μm, 产物均为高纯且结晶良好的CePO4晶体. 可通过控制水热反应时间达到控制CePO4纳米线晶型的目的. 随水热反应时间的延长, 磷酸铈纳米线从六方晶型转变为单斜晶型(独居石结构). 随煅烧温度的升高, 磷酸铈纳米线直径增大, 但经1000 ℃煅烧仍具有一维线性结构, 其热稳定性高. 磷酸铈纳米线在紫外光激发下具有可见光区蓝紫发射区, 但随煅烧温度的升高, 磷酸铈纳米线的发光强度明显降低.     

Optical spectroscopy of low-phonon Ho3+ doped BaY2F8 single crystal

The Ho:BaY₂F₈ crystal was grown by Czochralski method. The crystal phase structure and absorption spectra were tested, the absorption peak exists near 899 nm, the absorption cross section was 1.27 × 10^?21 cm². The emission spectra of crystals in the vicinity of 2 and 3.9 μm were measured, the 2 μm near infrared light induced by ⁵I₇ → ⁵I₈ transition of Ho3+ ions was observed, as well as the fluorescence output at 3.9 μm (⁵I₅ → ⁵I₆), emission cross section at 3.9 μm was calculated to be 0.86 × 10^?21 cm². We suppose that the Ho:BaY₂F₈ crystal has a large application prospect for the 2–4 μm wavelength near infrared laser.     

Light‐Driven Crawling of Molecular Crystals by Phase‐Dependent Transient Elastic Lattice Deformation

The light‐driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase‐dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ‐formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min^?1, which is two orders of magnitude faster than the α and β phases.     

Tm:Lu_3Al_5O_(12)晶体的生长与光谱性能研究

采用提拉法生长高质量的纯LuAG晶体和4%(原子分数)Tm:LuAG晶体.对晶体的晶胞参数和光谱性能进行了详细的表征.研究发现:Tm~(3+)的掺入没有改变LuAG基质的晶体结构;吸收光谱中255 nm处的吸收带是由Fe~(3+),Fe~(2+)引起的;晶体在782 nm处的吸收峰,与商用AlGaAs二极管的发射波长匹配良好,吸收截面为5.07×10~(-21) cm~2.Tm:LuAG晶体在2 μm波段的荧光峰对应~3F_4-~3H_6能级之间的跃迁,荧光寿命长达11.9 ms,有利于激光的高能量调Q输出.结果表明,Tm:LuAG晶体是2 μm激光器中很有发展潜力的增益介质,将会替代Tm:YAG晶体应用于激光雷达系统.     

Light-Driven Crawling of Molecular Crystals by Phase-Dependent Transient Elastic Lattice Deformation

The light-driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase-dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ-formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min⁻¹, which is two orders of magnitude faster than the α and β phases.     

Modulation of Crystal Packing via the Tuning of Peripheral Functionality for a Family of Dinuclear Mesocates

A family of four novel pyrazinyl‐hydrazone based ligands have been synthesized with differing functionality at the 5‐position of the central aromatic ring. Previous work has shown such ligands to form dinuclear triple mesocates which pack to form hexagonal channels capable of gas sorption. The effect of the peripheral functionality of the ligand on the crystal packing was investigated by synthesizing complexes 1 to 4 which feature amino, bromo, iodo and methoxy substituents respectively. Complexes 1 to 3 crystallized in the same hexagonal space group P6₃/m and featured 1D channels. However, on closer inspection while the packing of 1 is mediated by hydrogen bonding interactions, the packing of complexes 2 and 3 are not, due to a subtlety different π–π stacking interaction enforced by the halogen substituent. The more bulky nature of the methoxy substituent of 4 results in the complex crystallizing in the triclinic space group P‐1, featuring an entirely different crystal packing.     

基于DFB型半导体激光器的腔增强吸收光谱研究

The Cavity enhanced absorption spectroscopy based on a tunable DFB diode laser (TDL-CEAS) was described. A brief introduction of cavity enhanced absorption spectroscopy development and experimental scheme was given, the effective absorption path of the medium in the optical cavity was interpreted from the way of Fabry Perot cavity. It is pointed out that the main reason why CEAS has high detection sensitivity is that the medium in the cavity can get a long absorption path. A tunable DFB diode laser which center wavelength is 1.573 μm was used as the light source, and an optical cavity which consists of two high reflectivity mirrors (near 1.573 μm, R about 0.994) separated at a distance of 34 cm was used as the absorption cell. Laser radiation was coupled into the optical cavity via accidental coincidences of laser frequency with the cavity mode when scanning the cavity and the laser. An absorption spectrum of carbon dioxide near 1.573 μm was obtained and a detection sensitivity of about 1.66×10-5 cm-1 was achieved. It is experimentally demonstrated that the CEAS is a highly sensitive and high resolution spectrum technology, and it has the advantage of simple experimental setup and easy operation.     

液液界面反应制备C60微米管阵列及其上转换荧光性能研究

采用C60/甲苯溶液和异丙醇作为原料,通过液液界面渗透反应在AAO模板上制备了垂直定向排列的C60微米管阵列.通过SEM、XRD、Raman、荧光光谱(PL)对材料的结构和性能进行测试表征.结果表明C60微米碳管阵列由C60分子聚合而成,为面心立方结构,微米管直径5～10 μm、壁厚1～3 μm.在1064 nm近红外入射光激发下样品在红光区域发生了上转换发光,分析表明这是由多壁碳管丰富的能级所造成.     

Progress of 1.5～1.6 μm Laser Crystals

Eye-safe 1.5～1.6 μm lasers have important applications in optical fiber communication, medicine, laser-range-finding, lidar, etc. Er^3＋ and Yb^3＋ co-doped crystal pumped by diode laser around 976 nm is an attractive method for obtaining 1.5～1.6 μm laser in compact device with high output beam quality. In this paper, the recent research and progress of several important Er^3＋ and Yb^3＋ co-doped laser crystals at 1.5～1.6 μm in authors’ lab are reported.