Facile synthesis of uniform hollow hematite sub-micro spheres with controllable shell thickness

A simple method was developed to prepare the uniform hematite hollow submicro-spheres with controllable structure and different diameter based on monodisperse poly(styrene-co-acrylic acid) [P(St-co-AA)] particles. The structure and formation mechanism of the hollow spheres were investigated in detail. The control mechanism of shell thickness was also discussed. The results indicated that the shell thickness and coarseness of the synthesized core-shell hematite hollow spheres could be tuned simply by the surface carboxyl content of the P(St-co-AA) particles. This method provided a new approach for the structure control in the preparation of hollow spheres. A Brunauer-Emmett-Teller (BET) test shows that the prepared hollow spheres have large surface areas which were decreased along with the increase of the diameter. The magnetic properties of the as-obtained hematite hollow spheres were investigated. The result showed that the coercivity and saturated magnetization were increased along with the increase of the shell thickness, and the remanent magnetization was increased along with the decrease of the diameter.     

Carbon spheres prepared via solvent-thermal reaction method and their microstructures after high temperature treatment

Carbon spheres with size of 50–300 nm were synthesized via a solvent-thermal reaction with calcium carbide and chloroform as reactants in a sealed autoclave. The morphologies and microstructures of carbon spheres before and after high temperature treatment (HTT) were characterized by X-ray diffractometry (XRD), scanning electronic microscopy (SEM), energy diffraction spectroscopy (EDS), and transmission electron microscopy (TEM). The formation mechanism of carbon spheres was discussed. The results indicate that the carbon spheres convert to hollow polyhedron through HTT. Carbon spheres are composed of entangled and curve graphitic layers with short range order similar to cotton structure, and carbon polyhedron with dimension of 50–250 nm and shell thickness of 15–30 nm. The change of solid spheres to hollow polyhedron with branches gives a new evidence for formation mechanism of hollow carbon spheres.     

Ni(OH)_2和NiO空心球壳的纳米构筑

以苯乙烯-丙烯酸共聚物(PSA)乳胶粒为模板,分别制备了结构新颖的α-Ni(OH)2和Ni O的空心球壳。在适宜的条件下,首先在PSA乳胶粒表面生长一层Ni(OH)2,制得核壳结构的复合微球。用有机溶剂溶去模板得到Ni(OH)2空心球壳;在空气中焙烧除去模板,得到的是Ni O空心球壳。经物相分析表明壳层是α-Ni(OH)2。用TEM、SEM对核壳结构微球和空心微球的形貌和微结构进行分析。结果表明,壳层是由片状的Ni(OH)2纳米晶构筑而成,焙烧后得到的Ni O空心球壳是由片状的Ni O纳米晶构筑而成。     

SiO2/ZnS核壳结构微球的制备和表征

以自制纳米二氧化硅微粒为模板,硫代乙酰胺和醋酸锌分别为硫源和锌源,通过沉淀法成功制备了SiO2/ZnS核壳结构微球,研究了各种反应条件对该微球形貌的影响。经NaOH溶液蚀刻后,SiO2/ZnS核壳结构微球转变成亚微米级的ZnS空心微球。通过XRD、SEM和TEM等手段对SiO2/ZnS核壳结构微球和ZnS空心微球进行了表征。结果表明,在优化条件下制得的微球形貌规整、大小均匀,其壳层由厚度约20 nm的ZnS纳米颗粒组成。     

新型空心球结构的压缩力学性能

提出新型空心球结构,该结构是将球体上穿孔的空心球按照体心立方体进行排列和连接.通过实验研究了3D打印的单胞和胞元组合结构的压缩力学性能,建立单胞结构的三维有限元数值模型,实验结果验证了有限元模型的有效性.通过数值模拟研究穿孔空心球壁厚和孔径对结构弹性模量以及初始屈服应力的影响.结果表明,单胞结构的变形行为包括弹性变形、坍塌变形以及结构的自接触行为;多胞组合结构的变形过程包括弹性阶段、大变形阶段以及致密化阶段,其中大变形是由结构的层层连续坍塌变形所导致的;结构的弹性模量和初始屈服应力随壁厚的增大而增大,随孔径的增大而减小;与壁厚变化相比,结构的力学性能对孔径变化更为敏感.     

Preparation and Photocatalytic Performance of Double-Shelled Hollow W_(18)O_(49)@C_3N_4@Ti_3C_2 Microspheres

C_3N_4,C_3N_4@Ti_3C_2 and W_(18)O_(49)@C_3N_4@Ti_3C_2 hollow spheres were successfully prepared by using SiO_2 template followed by gradual deposition method.The degradation of phenol solution and photolysis ability were tested to characterize its photocatalytic activity.Compared with the single-shelled C_3N_4 and C_3N_4@Ti_3C_2 hollow spheres,double-shelled W_(18)O_(49)@C_3N_4@Ti_3C_2 hollow spheres possessed larger surface area and fast charge separation efficiency,exhibiting about 8.9 times and 4.0 times higher H_(2 )evolution than those of C_3N_4,C_3N_4@Ti_3C_2 hollow spheres,respectively.The photocatalytic mechanism of the W_(18)O_(49)@C_3N_4@Ti_3C_(2 )hollow spheres were carefully investigated according to the results of morphology design and photoelectric performance.A Z scheme mechanism based on the construction of heterojunctions was proposed to explain the improvement of photocatalytic performance.This new charge transfer mechanism appears to greatly inhibit the recombination of electrons/holes during the charge transfer process,while maintaining its strong hydrogen reduction ability,resulting in a higher photocatalytic performance.     

Facile Synthesis of SnO_2 Hollow Microspheres and Their Optical Property

SnO2 hollow microspheres were fabricated via a hydrothermal synthesis method assisting by the complex surfactant system of polyacrylamide and polyethylene glycol.Observation by field emission scanning electron microscopy (FESEM) showed the SnO2 hollow spheres were composed of nanoparticles.The growth mechanism for the formation of hollow spheres was proposed.UV spectroscopy and photoluminescence (PL) were used to investigate the optical properties of the products.The PL result showed that four peaks,contain...     

SiO_2空心球的制备与表征

与实心球和非球形材料相比,中空微球是内部中空的特殊球形材料,具有许多特殊和优异的物理化学性质.本文采用聚合物胶粒模板法制备SiO2空心球,研究不同pH值和正硅酸乙酯用量对SiO2/PS微球包覆效果的影响.利用透射电子显微镜(TEM)表征SiO2空心球形态结构.     

Facile synthesis of SnO<Subscript>2</Subscript> hollow microspheres and their optical property

SnO2 hollow microspheres were fabricated via a hydrothermal synthesis method assisting by the complex surfactant system of polyacrylamide and polyethylene glycol.Observation by field emission scanning electron microscopy (FESEM) showed the SnO2 hollow spheres were composed of nanoparticles.The growth mechanism for the formation of hollow spheres was proposed.UV spectroscopy and photoluminescence (PL) were used to investigate the optical properties of the products.The PL result showed that four peaks,containing the emission from recombination of free excitons,were observed in the photoluminescence spectrum.     

以聚苯乙烯-丙烯酸微球为模板制备CdS空心球壳

以苯乙烯 丙烯酸聚合物微球为模板 ,利用核 /壳法制备了不同粒径的CdS中空球壳。首次采用了酸性萃取剂二 ( 2 乙基己基 )磷酸 (P2 0 4 )的钠盐作为制备苯丙颗粒模板的乳化剂。当乳化剂的质量分数在 1 5 6 %～ 3 5 4 %范围内逐渐增大时 ,乳液粒子颗粒的直径在 30 0～ 1 2 0nm范围内逐渐减小 ,制得的CdS中空球壳粒径也相应在 40 0～ 1 5 0nm范围内减小。所制得的样品采用红外光谱法、X 射线衍射法和透射电镜法进行了表征     

水热法制备氧化锌空心球及其电化学性能的研究

以硝酸锌为原料,六次甲基四胺为沉淀剂,聚乙烯吡络烷酮为表面活性剂,利用水热法制备了氧化锌空心球。研究了不同聚乙烯吡络烷酮用量对空心球形貌的影响。通过X射线衍射、扫描电子显微镜、透射电子显微镜对产物进行了表征,通过循环伏安测试和恒电流充放电测试对产物进行了电化学测试。结果表明,产物粒径均一,为纯六方晶型的空心结构。当聚乙烯吡络烷酮含量0.13 g时,氧化锌空心球形貌最佳。电化学测试结果表明,在5 mV/s的扫描速率下,比容量可达到241.6 F/g;在0.5 A/g的充放电电流密度下,比容量为137.467 F/g。     

Hexagonal hematite platelets synthesized from pyrite cinders by hydrothermal process

Well-crystallized hexagonal hematite (α-Fe2O3) platelets were synthesized by hydrothermal process,using a highly concentrated ferric hydroxide as precursor.The precursor was prepared by adding ammonia to the ferric sulfate solution which was obtained by leaching pyrite cinders with sulfuric acid.Structure and morphology of the synthesized products were investigated by X-ray diffraction,scanning electron microscope,transmission electron microscope and selected area electron diffraction.The results reveal tha...     

调压塔局部温度内力的研究

由于温度变化引起的变形不同，在混凝土圆柱壳截面变化处产生附加弯矩和剪力。根据平面圆环的热弹性理论解和轴对称空心圆柱壳的弯曲理论，本文提出了温度变化在柱壳型混凝土水塔塔壁厚度变化处所引起的局部温度内力的计算方法     

Synthesis and characterization of core-shell hydroxyapatite/chitosan biocomposite nanospheres

Novel core-shell hydroxyapatite/chitosan biocomposite nanospheres were synthesized in a multiple emulsion. The multiple emulsion was a w/o/w emulsion, made of diammonium phosphate solution as an inner aqueous phase, cyclohexane as an oil phase, and calcium nitrate solution and chitosan solution as an outer aqueous. The forming mechanism of core-shell spheres and the influence of temperature on the morphology of the nanospheres were investigated. The diameter of the resulting core-shell nanospheres was 100–200 nm and the thickness of the chitosan shell was about 10 nm. And it concluded that at different reaction temperature the morphologies of the products would be changed. The core-shell nanospheres have potential applications for the development of new biomedical materials.     

碳纤维增强聚合物基复合材料修补空心柱体结构的屈曲分析

采用有限元数值方法和解析方法研究了碳纤维增强聚合物基复合材料(CFRP)加固含损伤空心柱体钢结构在压缩载荷作用下的屈曲问题。通过有限元数值仿真对受轴向压缩载荷的含损伤钢结构进行了纤维增强复合材料的模拟修复,采用八节点复合材料板壳单元模拟复合材料补片结构,考虑理想黏结,通过约束方程建立了CFRP加固含损伤空心柱体钢结构屈曲分析的有限元模型,计算了钢结构的屈曲临界载荷,并与基于能量原理推导的CFRP加固受轴向压缩载荷空心柱体屈曲载荷的理论公式做了比较。参数讨论表明,粘贴CFRP对提高受压结构载荷效果显著;通过改善CFRP层参数可提高结构的临界载荷,增强修补效果;有限元法结果与解析公式计算结果比较吻合。     

One-pot synthesis of hollow octahedral Cu2O nanostructures at room temperature

Homogeneous hollow Cu2O octahedral nanostructures have been fabricated by a facile one-pot reduction reaction at room temperature. The microscope analysis revealed that the edges of as-prepared hollow structures were around 200 nm with a wall thickness of about 20 nm. To investigate the influence factors and formation mechanism of the hollow octahedral structure, samples subjected to different reaction conditions were studies. The results showed that the morphology and structures of Cu2O particles were greatly affected by the concentration of pH value of the reaction environment and the reaction time. Ostwald ripening process is proposed to explain the growth mechanism of the hollow octahedral nanostructures.     

空间网架焊接空心球节点承载力研究

对焊接空心球节点,采用ANSYS9.0程序进行了承载力的模拟分析计算,获得了球节点受拉压时壳面弹塑性应力和变形分布规律,定出了破坏带区域在球壳中的确切位置.根据焊接空心球节点的受拉失效机理,提出了球节点塑性失效破坏的三维应力状态分析模型.进而研究了球体-焊缝-钢管一体复杂应力状态下的极限受力分析.应用极限状态计算理论得到焊接空心球节点抗拉承载力计算公式.基于空心球节点受压破坏机理的探讨和试验数据的统计分析,以若干变参数的线性回归方法,获得球节点受压承载力计算公式.数据结果表明,所得空心球节点承载力公式计算值与试验值拟合精度较好.     

Stepwise synthesis of cuprous oxide nanoparticles with adjustable structures and growth model

By stepwise adding of reducer N2H4·H2O,cuprous oxide(Cu2O)nanoparticles(NPs)with adjustable structures were synthesized.The features of Cu2O NPs were characterized by XRD,TEM and UV-Vis absorption spectra.When the reducer was added into the reactant system at one time,the sizes of the Cu2O NPs are in the range of 120–140 nm.Most Cu2O NPs are solid spheres.As the reducer was divided into two equal parts and stepwisely added,almost all the NPs are hollow spheres with good size(150–170 nm)distribution and dispersity.But when the reducer was divided into three or four equal parts and stepwisely added,the NPs are hollow spheres,core-shell structures or solid spheres,and the sizes distribution of the products is deteriorated.The effect of sodium hydrate(NaOH)was also probed.Addition of NaOH speeded up the nucleation and growth processes of Cu2O NPs.With the alkalinity increase,the shells of the hollow spheres become compact and the thicknesses of the shells increase,but the size distribution of the NPs is deteriorated.The absorption spectra of the Cu2O NPs are tunable.With the shell thicknesses increase,the absorption peaks have red shifts.An inside-outside growth model of Cu2O NPs was proposed to explain the results.The Cu2O single crystalline grains grow not only in the reactant solution,but also inside of the hollow nanospheres.The new Cu2O nanocrystallines can not only aggregate onto the shells of the nano hollow spheres,but also inside and outside of the hollow spheres,which leads to increasing the shell thicknesses of the hollow spheres,forming core-shell structures or small solid spheres of Cu2O NPs,respectively.     

开孔双层球面网壳结构优化设计

以某火力发电厂干煤棚双层球面网壳结构为工程背景,以结构用钢指标为目标函数,利用有限元软件ANSYS对该开孔双层网壳结构进行弹性阶段的整体优化计算,优化后节省钢材约28.4%;进一步应用ANSYS参数化设计语言（APDL）进行编程,分析了网壳矢高、网壳厚度和杆件截面面积三个因素对用钢指标的影响规律：本网壳结构用钢指标对网壳厚度变化最为敏感,杆件截面面积变化的影响次之,矢高变化对结构用钢指标影响最小。计算结果将为此类网壳结构最优设计提供有益参考。     

双层壳结构抗冲击性能仿真研究

对潜艇结构冲击响应(加速度)的分析可以评价结构的抗冲击能力并为提高结构抗冲击性能提供依据.以某潜艇的结构和型线为基础,利用大型有限元计算软件ANSYS/LS DYNA计算了双层壳结构在改变外层壳体(简称外壳)及内层壳体(简称内壳)的厚度时的冲击环境,分析了双层壳结构在不同工况下的冲击响应,讨论了外壳和内壳对双层壳结构冲击环境的影响.通过数据分析表明:在改变外壳及内壳板厚的情况下,外壳及内壳的冲击响应(加速度)近似服从威布尔分布,内部结构的冲击响应近似服从正态分布;在同一冲击因子下,改变外壳板厚和内壳板厚对结构各部分的冲击响应影响不同.这对于潜艇的抗爆炸抗冲击分析及合理的结构形式具有重要意义.