循环流化床粉煤灰可控制备高纯F型八面沸石研究

利用粉煤灰制备沸石分子筛是其高值化利用的重要方向之一.以循环流化床粉煤灰为原料,采用酸浸预处理-氢氧化钠碱熔活化-水热晶化法制备F型八面沸石,并用于吸附亚甲基蓝.考察酸浸温度、碱熔温度及碱灰质量比对粉煤灰结构的影响及碱熔温度、碱灰质量比、液固比及晶化时间对沸石的结构和形貌的影响.通过XRD和SEM对粉煤灰沸石的晶体结构和形貌进行表征.结果表明,利用循环流化床粉煤灰制备高纯F型八面沸石适宜条件为碱熔温度550℃,碱灰质量比1.5:1,液固比12 mL/g,晶体导向剂用量10;,晶化温度100℃,晶化时间20 h.其比表面积高达357 m2/g,且对亚甲基蓝的饱和吸附量高达178 mg/g.     

ZSM-22、β和丝光沸石介孔改性对比研究

用碱-酸处理法对ZSM-22 (TON)、β(BEA)和丝光(MOR)型沸石进行介孔改性.研究沸石结构与介孔率、脱硅选择性、介孔生成效率的关系,定量阐述了不同沸石的脱硅反应选择性、改性过程的脱硅选择性及脱硅效率.结果表明,改性沸石具有微孔-介孔结构和介孔尺度分布均一化特性.按沸石结构比较,脱硅反应选择性和改性过程脱硅选择性均满足MOR＜ BEA≤TON,且改性过程脱硅选择性均大于90.6;;与比表面相关的脱硅效率:TON＜MOR＜ BEA.沸石的骨架密度和生成焓绝对值越小、微孔可接近性越好,介孔率和脱硅效率越高.BEA型改性沸石的比表面、比孔容和介孔孔径分别为468.2 m2/g、0.66 cm3/g和5.6nm.     

聚乙二醇对合成ZSM-5分子筛形貌影响的研究

为了探索更多具有应用价值的特殊形貌ZSM-5分子筛,本文通过在常规水热合成条件下添加晶形控制剂聚乙二醇(PEG)的方法,制得了不同形貌的ZSM-5沸石分子筛.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和红外光谱(FTIR)等手段对样品进行表征,分析表明:在晶化过程中,PEG对ZSM-5分子筛晶粒起到了晶形控制剂的作用,并且实验中PEG聚合度较小时分子筛的形貌以不规则的椭球形为主,PEG聚合度增大至45时得到的分子筛为较规则的条状结构.相同聚合度的PEG随在体系中加入量的不同对产物的形貌尺寸影响也有较大差异,在PEG量较小时分子筛有较多没有成型的小晶粒,PEG适量时为规则的条状结构.PEG量较大时大量的表面-OH使得离子之间发生空间位阻从而对分子筛晶体形貌控制作用不明显,分子筛主要为短粗的椭球形.     

不同表面活性剂对合成介孔氧化镁晶体性质的影响

采用液相法,以Mg(NO3)2·6H2O为镁源,NH3·H2O为沉淀剂,研究了不同表面活性剂对介孔MgO晶体性质的影响.采用XRD、FT-IR、SEM、BET和CO2-TPD等手段对介孔MgO晶相组成、骨架结构、微观形貌、孔结构及表面化学性质进行了分析表征.研究结果表明,不同表面活性剂对介孔MgO晶体物化性质影响较大.以非离子型PEG-2000为表面活性剂制得产品表面碱强度和碱总量均大于以阴离子型SDS、阳离子型CTAB制得的产品.以非离子型PEG-2000为表面活性剂制备得到的介孔MgO同时具有弱碱、中强碱特征,碱总量为0.192 mmol·g-1,比表面积、孔容和平均孔径分别为145.42 m2·g-1、0.67 cm3·g-1和18.56 nm.     

微波辅助水热合成条件对直接合成纳米HZSM-5晶体性质的影响

利用微波辅助水热合成法直接制备了纳米HZSM-5晶体.采用XRD、FT-IR、SEM、BET和NH3-TPD等手段对合成样品进行了分析表征,研究了晶化温度和时间对合成产物晶体性质的影响.结果表明,晶化温度和时间对微波辅助水热直接合成产物微观形貌、晶粒尺寸和分散度影响明显.较低的晶化温度和较短的晶化时间均难以形成形貌规则的HZSM-5晶体.随着晶化温度的升高,合成样品逐渐变为球形晶粒、晶粒尺寸逐渐增大、分散度逐渐提高,继续提高晶化温度达180 ℃时,晶粒长大使比表面积稍有降低;随着晶化时间的延长,样品的微孔和介孔增多,比表面积和孔容逐渐增大,继续延长晶化时间,晶体内微孔可能的收缩和晶粒的长大使得样品孔容和比表面积减小.160 ℃和1.5 h条件下制备的HZSM-5分子筛晶体形貌呈球形,晶粒尺寸约为60 nm,分散程度较好;其比表面积、孔容和平均孔径分别为398.45 m2·g-1、0.63 cm3·g-1和6.27 nm;晶体表面具有弱酸特征.     

高岭土水热合成4A沸石实验研究

水热法合成4A沸石的实验是在不同的碱度、不同的液固比、不同的晶化温度和不同的晶化时间条件下进行的,并进行了实验结果和各种合成因素的分析及研究.实验结果分析表明在加碱煅烧及合成沸石的过程中,使用NaOH的效果比使用Na2CO3和KOH,加入适量的晶种能缩短晶化反应时间并能提高合成沸石的质量.在碱度为2.5～4.0M、液固比6∶1～8∶1、晶化温度90～103℃以及晶化时间为3～5h的实验条件下,采用苏州高岭土合成了4A沸石.文中还采用X射线衍射仪和扫描电镜对合成的沸石样品进行了表征.     

以粉煤灰为原料采用两步法制备高纯度ZSM-5型沸石的研究

采用经碱熔融-离心提取处理后的粉煤灰为原料,经水热反应研究两步法合成高纯度ZSM-5型沸石的过程,探讨了碱灰比、焙烧温度对硅铝溶出量的影响,研究了碱度、晶化时间、晶化温度与硅铝比对合成ZSM-5型沸石的影响.结果表明:碱灰比为2.3∶1,焙烧温度为680 ℃时可获得最高的硅铝溶出量;当SiO2/Na2O =7(摩尔比),SiO2/Al2O3=45(摩尔比),晶化时间为68 h,晶化温度为180 ℃时可获得高纯度的ZSM-5型沸石.     

固体硅胶制备小粒径NaA分子筛

以固体硅胶为硅源、偏铝酸钠为铝源,通过水热合成法制备小粒径NaA分子筛.实验探究碱度、陈化温度、陈化时间、晶化温度和晶化时间对合成NaA分子筛的影响.采用X射线衍射(XRD)、扫描电镜(SEM)分析手段表征合成样品的物相、结晶度、形貌和粒径大小.实验确定以固体硅胶为硅源水热合成小粒径NaA分子筛的碱度为n(H2O)/n(Na2O)=30,20℃陈化20h,100℃晶化4h,合成的NaA分子筛晶型完整、粒度分布均匀、平均粒径约为600nm.     

水热体系中不同前驱物对合成镁铝水滑石微结构的影响

以不同的镁源、铝源组合为前驱物,利用XRD、SEM及EDS比较研究了水热体系中不同的前驱物组合对合成镁铝水滑石(Mg-Al-LDHs)晶体微结构及晶体生长的影响,同时利用生长基元的配位体理论对其生长机理进行了初步探讨.研究结果表明:当固定体系的pH =12,水热温度120℃、水热时间18h的条件下,不同的前驱物组合均可以合成结晶度较好的镁铝水滑石晶体;但不同的镁源、铝源组合对产物的物相、分散性、结晶规整性、厚径比、纯度、大小及微结构有一定的影响.当镁源固定为MgCl2,铝源分别为Al2O3、Al(NO3)3、AlCl3时,不溶性氧化铝合成的LDHs规整性、分散性及纯度较差,晶体发育不完整;当铝源分别为溶解度较好Al(NO3)3、AlCl3时,合成产物LDHs晶体的结晶度、规整性、分散性及纯度较好,但由于溶解度和相连阴离子极性的不同,造成产物微结构的微小差异;当镁源固定为溶解度较大的Mg(NO3)2时,铝源分别为Al(NO3)3、AlCl3时,同溶解度较小MgCl2相比,更有利于合成结晶度、规整度、尺寸更小的镁铝水滑石晶体.溶解度较大的镁源、铝源前驱物组合合成的镁铝水滑石有更高的结晶度和规整度.EDS分析证实,溶解度较差的Al2O3合成的镁铝水滑石纯度较差.溶解度较好的不同镁源、铝源前驱物组合合成的镁铝水滑石不含有任何其它阴离子杂质,平均镁铝比约为3,非常接近LDHs的理论值.     

金属有机骨架ZIF-67材料的合成及微结构调控研究

以甲醇为溶剂,室温下合成金属有机骨架结构的ZIF-67,利用XRD、SEM等系统的研究了有机溶剂添加量、金属离子与有机配体配比、搅拌速度、时间、钴源以及不同醇溶剂对ZIF-67 晶体的结晶度、形貌、晶体尺寸变化规律的影响,并初步探究了其影响机理.基于不同影响因素的系统分析及机理探究,对可控合成结晶度高,分散性好,形貌规整,尺寸均一的ZIFs材料意义重大.     

Synthesis of zinc oxide crystals with different shapes from zincate aqueous solutions stabilized with triethanolamine

ZnO crystals were synthesized from basic aqueous solutions including zincate ions stabilized with triethanolamine (N(C₂H₄OH)₃, teaH₃) by heating at 60°C. The influence of the basicity of the solutions on the morphology of the ZnO crystals was examined. The aqueous solutions were prepared using ZnSO₄·7H₂O, N(CH₃)₄OH (TMAOH), and teaH₃ as a zinc source, a base, and a stabilizer, respectively, at a zinc concentration of 0.2 M at a teaH₃ / Zn molar ratio of 4. Clear solutions were obtained at a molar ratio of TMAOH / Zn ≥ 3.0. When the clear solutions, in which glass or polyester substrates were placed, were heated at 60°C, agglomerates of ZnO crystals were deposited on the substrates in the TMAOH / Zn range from 3.0 to 3.6. With increasing the TMAOH / Zn ratio, the shape of the resulting ZnO crystals changed from a short asymmetric column with a hexagonal flat edge and a rounded one, through a rocket‐like shape formed by intergrowth, to a hexagonal rod. Although no films of ZnO were formed, ZnO crystals with different shapes were synthesized. When the glass substrates pre‐coated with a ZnO thin film by a sol‐gel method were used, highly oriented, dense ZnO films were formed. The films consisted of rod‐like crystals aligned normal to the substrate surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of CuCl2 on hydrothermal crystallization of calcium sulfate whiskers prepared from FGD gypsum

Using purified flue‐gas desulfurization (FGD) gypsum as raw material, effects of CuCl₂ on crystal morphology, phase structure, aspect ratio and crystallization of hydrothermal products prepared via hydrothermal crystallization in H₂SO₄‐H₂O solutions were investigated. The results show that dosage of CuCl₂ has a significant effect on the morphology, aspect ratio and crystallization of calcium sulfate whiskers (CSWs), but no effect on their phase transformation . At a dosage of 15 g CuCl₂/kg FGD gypsum, the produced calcium sulfate whiskers had diameters ranging from 1 to 3 μm with average aspect ratio greater than 200 . Transmission electron diffraction patterns and highly magnified surface morphology of CSWs were found different from those of self‐assembly crystals. Compared to self‐assembly crystals, the produced CSWs showed a single crystal structure and their surface was very smooth.     

不同硫源对微波水热法制备SnS粉体结构和光学性能的影响

采用微波水热法,以氯化亚锡为锡源,硫化铵、硫脲、硫代乙酰胺、硫代硫酸钠等为硫源,在相同的条件下制备SnS粉体,研究了不同硫源对产物物相、形貌和光学性能的影响.采用XRD、SEM、TEM对样品的物相和形貌进行了分析.结果表明:除硫代硫酸钠外,由其他硫源制备的产物均为正交晶系的SnS粉体;通过不同的硫源可制备类球形、不规则长方体和花簇状SnS微晶.利用紫外-可见吸收光谱分析,产物的光学带隙约为1.48～1.61eV;室温光致发光光谱表明,产物在830 nm处具有近红外发光特性.     

溅射制备不同厚度Pb(Zr0.52Ti0.48)O3薄膜结晶态的研究

研究了射频磁控溅射的Pb(Zr0.52Ti0.48)O3(PZT52/48)薄膜在退火晶化时,厚度对其结晶态及表面形貌的影响.首先利用Materials Studio软件对PZT分子进行了模拟,并模拟了X射线衍射(XRD)得到PZT的特征峰图;实验上,采用退火炉对不同厚度的PZT(52/48)薄膜进行了不同温度及时间的退火;接着采用XRD对各样片薄膜进行了结晶物相分析;采用FIB对部分样片薄膜表面形貌进行了观察.实验结果显示,薄膜的厚度及退火条件在一定程度上对其结晶态的影响是一致的;对于一定厚度的薄膜,合适且相同的退火(650 ℃)条件都可以使其形成单一的PZT(52/48)物相;二次退火对较厚薄膜结晶化有一定的作用,但随着溅射薄膜厚度的增加而累加了内应力,退火后形成有PZT(52/48)物相的较厚薄膜表面出现裂纹越明显.     

柠檬酸钠作用下碳酸钙的制备

选取柠檬酸钠(Na3C6H5O7)为碳酸钙生长的控制剂,通过气体扩散的方法仿生合成了不同形貌的碳酸钙,并考察矿化时间对碳酸钙晶型和形貌的调控作用.采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅立叶变换红外光谱(FT-IR)以及X射线衍射(XRD)对所得产物进行了表征.结果表明,随着矿化时间的改变所得碳酸钙粒子的形貌发生了显著的变化,出现哑铃状、高尔夫球状、球状等形貌.     

弱外磁场辅助氧化共沉淀法合成正八面体Fe_3O_4纳米颗粒

本文在弱外磁场辅助条件下,采用氧化共沉淀方法调控合成了正八面体Fe_3O_4纳米颗粒.采用XRD、SEM、振动磁强计(VSM)来表征产物的晶型、形貌和磁性能.XRD结果表明,产物具有尖晶石结构,且结晶良好、纯度高;SEM观察结果表明Fe_3O_4纳米颗粒均为二次粒子,由更小的粒子成长而来;VSM测定结果说明各种形貌的Fe_3O_4纳米粒子具备良好的磁性能.同时,分析了粒子不同形貌的成核机理.结果表明采用弱外磁场辅助的办法可以获得具有良好晶型、正八面体形貌形貌和良好磁性能的Fe_3O_4纳米颗粒.     

Initial stages of SiC crystal growth by PVT method

Initial stages of SiC crystal growth by Physical Vapor Transport method were investigated. The following features were observed: (a) many nucleation crystallization centres appeared on the seed surface during the initial stage of the growth, (b) at the same places many separate flat faces generated on the crystallization front, (c) the number of facets was dependent on the shape of the crystallization front and decreased during growth, (d) appearance of many facets lead to decrease of structural quality of crystals due to degradation of regions where crystallization steps from independent centres met. The results revealed that the optimal crystallization front should be slightly convex, which permits the growth of crystals with single nucleation centre and evolution of single facet on the crystallization front. The subjects of study were the shape and the morphology of growth interface. Defects in the crystallization fronts and wafers cut from the crystals were studied by optical microscopy, atomic force microscopy (AFM) combined with KOH etching and X‐ray diffraction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystallization and phase-separation of Li2OSiO2 glass

The crystallization and phase-separation phenomena in the Li₂OSiO₂ glass are studied by positron lifetime and annihilation lineshape measurements. Analysis of the kinetic data shows three-dimensional morphology of growing crystals. Phase-separation is seen to increase the density of crystal nuclei and the rate of volume crystallization, but it does not affect the morphology. In addition, surface crystallization is detected in glasses with small degrees of phase-separation. The results are consistent with scanning electron and optical micrographs.     

Preparation and characterization of superfine ammonium perchlorate (AP) crystals through ceramic membrane anti-solvent crystallization

In this paper, a novel ceramic membrane anti-solvent crystallization (CMASC) method was proposed for the safe and rapid preparation ammonium perchlorate (AP) crystals, in which the acetone and ethyl acetate were chosen as solvent and anti-solvent, respectively. Comparing with the conventional liquid anti-solvent crystallization (LASC), CMASC which successfully introduces ceramic membrane with regular pore structure to the LASC as feeding medium, is favorable to control the rate of feeding rate and, therefore, to obtain size and morphology controllable AP. Several kinds of micro-sized AP particles with different morphology were obtained including polyhedral-like, quadrate-like to rod-like. The effect of processing parameters on the crystal size and shape of AP crystals such as volume ratio of anti-solvent to solvent, feeding pressure and crystallization temperature were investigated. It is found that higher volume ratio of anti-solvent to solvent, higher feeding pressure and higher temperature result in smaller particle size. Scaning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the resulting AP crystals. The nucleation and growth kinetic of the resulting AP crystals were also discussed.