Core-shell-embedded Mesoporous Silica Capsules for Atmospheric Water Harvesting

A one-step ultrasonic mechanical method was used to synthesize a kind of atmospheric water harvesting material with high water harvesting performance in a wide relative humidity(RH)range,especially at low RH(RH<40%),namely,mesoporous silica capsule(MSC)with core-shell structure.Transmission electron microscopy(TEM),nitrogen adsorption and other characterization techniques were used to study the formation process of nano-microspheres.A new mechanism of self-adaptive concentration gradient regulation of silicon migration and recombination core-shell structure was proposed to explain the formation of a cavity in the MSC system.The core-shell design can enhance the specific surface area and pore volume while maintaining the monodispersity and mesoporous size.To study the water harvesting performance of MSC,solid silica nanoparticles(SSN)and mesoporous silica nanoparticles(MSN)were prepared.In a small atmospheric water collection test(25℃,40%RH),the water vapour adsorption and desorption kinetics of MSC,SSN,MSN and a commercial silica gel(CSG)were compared and analyzed.The results show that the MSC with mesoporous channels and core-shell structure can provide about 0.324 gwater/gadsorbent,79%higher than the CSG(0.181 gwater/gadsorbent).It is 25.1%higher than that of 0.259 gwater/gadsorbentof un-hollowed MSN and 980%higher than that of0.03 gwater/gadsorbentof un-hollowed SSN.The material has a large specific surface area and pore volume,simple preparation method and low cost,which provides a feasible idea for realising atmospheric water collection in arid and semi-arid regions.

Packing Density Improvement through Addition of Limestone Fines, Superfine Cement and Condensed Silica Fume

Adoption of a low water/powder (W/P) ratio is the key to improve the strength and durability of concrete, which relies on a high packing density because fresh concrete requires excess water to offer flowability. To obtain a high packing density, powders with different particle sizes, including limestone fines (LSF), superfine cement (SFC), condensed silica fume (CSF), were added to the cement paste and the resulting packing densities were measured directly by a newly-developed wet packing test. Results demonstrated that addition of powders with a finer size would more significantly improve the packing density but the powders should be at least as fine as 1/4 of the OPC to effectively improve the packing density. Packing density and voids ratio relationship showed that a small increase in packing density can significantly decrease the voids ratio, which could allow the W/P ratio to be reduced to improve the strength and durability of the concrete without compromising the flowability.

Effects of Silica Sol on Structure and Properties of Core-Shell Silicon-Acrylic Materials

Silica sol prepared by sol-gel method was introduced into poly (butyl acrylate) (PBA)/poly (butyl acrylate-styrene-methacryloxypropyl trimethoxysilane) (PSBM) core-shell emulsions to prepare a series of paper surface sizing agents. The rheological measurement indicated that PSBM emulsions exhibited shear-thinning behavior, and the phenomena became more pronounced with increasing silica sol concentration. Dynamic mechanical analysis (DMA) demonstrated that the stronger interfacial interaction between silica sol and polymer matrix, but microphase separation took place with excess silica sol. Thereby the tensile strength and thermal stability of emulsion films were increased with desirable silica sol concentration, and when silica sol concentration was greater than 6 wt%, the tensile strength leveled off and the decomposition temperature decreased from 351.19℃ to 331.63℃. The degree of crystallinity increased from 5.12% to 10.98% with 4% silica sol addition, resulting in enhanced rigidity of films. Furthermore, the interaction between polymer and fiber was improved with certain amount of silica sol, resulting in improved sizing degree, ring crush strength, surface strength and folding strength. However, excessive crosslinking will be harmful for the properties of sized paper.

Synthesis of Octylmethoxycinamate-silica Core-shell Nanoparticles with Self-templating Method

t A self-templating method was employed to synthesize core-shell nanoparticles with octylmethoxycinamate（OMC）, a well-known organic UV absorber, as core and nanosilica particles as shell. The characteristic of this method is that the whole process requires neither surface treatment for nanosilica particles nor additional surfactant or stabilizer, and all the reactions could be finished in one-pot, which exempts removing template and reduces reaction steps compared to the conventional process. The morphology, structure, particle size distribution, chemical composition and optical property of OMC-SiO2 nanoparticles were characterized by scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, dynamic light scattering（DLS）, FTIR spectrometry and UV absorption spectrometry, respectively. Experiment results indicate that the resulting OMC-SiO2 nanoparticles were perfectly spherical with smooth particle surfaces, and had clear core-shell structures. The particle size could be tuned by altering reaction conditions. In addition, the mechanism of the self-templating method for forming core-shell nanoparticles was discussed.

Preparation and Characterization of Silica and Clay-Silica Core-Shell Nanoparticles Using Sol-Gel Method

Silica and montmorillonite-supported silica nanoparticles were prepared via an acid one step sol-gel process. The synthesized solids were characterized using XRD, FTIR, TEM and N2 adsorption. The effect of preparing temperatures on the structure and properties of the silica nanoparticles were studied. The results show that the increase of annealing temperature from 25 to 200℃, don’t change amorphous state of silica. While for montmorillonite-supported silica the clay platelets are delaminated during the sol-gel process. TEM results showed that the average particle size of silica is increased by increasing temperature due to the particle sintering and the clay-silica nanoparticles possessed core–shell morphology with diameter of 29 nm. The surface area measurements showed that by increasing annealing temperature the surface area was decreased due to aggregation of particle. The clay-silica sample showed lower average pore width than that of the silica prepared at 200℃ indicating that it has a macropores structure. The adsorption efficiency of the prepared samples was tested by adsorption of protoporphyrin IX. The highest adsorption efficiency was found for SiO2 prepared at 200℃. Temkin model describe the equilibrium of adsorption of protoporphyrin IX on caly-silica nanoparticles under different conditions.

Synthesis of the Core-Shell Structure Materials as the Controlled-Release Drug Carrier

We have developed a controlled-release drug carrier. Smartly controlled-release polymer nanoparticles were firstly synthesized through RAFT polymerization as the controlled-release core. The structural and particle properties of polymer nanoparticles were characterized by nuclear magnetic resonance spectroscopy (1H-NMR), scanning electron microscope (SEM) and X-ray spectroscopy (EDX). Mesoporous materials were selected as the shell materials to encapsulate the smart core as the stable shell. The mesoporous shell was characterized by transmission electron microscopy (TEM) and scanning electron microscope (SEM). All the results showed that a well-defined core-shell structure with mesoporous structure was obtained, and this controllable delivery system will have the great potential in nanomedicine.

纳米纤维融合改性建筑结构胶制备及性能测试

为提高建筑结构胶性能,通过在传统建筑结构胶中加入纳米纤维材料,制备了一种具有较高应用性能的新型建筑用结构胶。新型建筑结构胶通过在微硅粉和纳米二氧化硅中加入纳米碳酸钙和纳米白炭黑,实现了对建筑结构胶环氧树脂结构胶的改性。当掺入的固定剂质量分数为50%,偶联剂4%,稀释剂10%,组合填料掺量为5%时,可获得抗压强度、抗拉强度等力学指标最佳的建筑结构胶。相对于加入传统的纳米二氧化硅,试验加入的组合填料对结构胶的改性更好。

C18键合硅胶微球的制备及色谱分离性能

目的:制备出中位径为12μm的C18-SiO_(2)微球,并应用在色谱柱填料中,研究了影响微球形貌的制备因素及影响其液相分离的条件,获得制备C18-SiO_(2)微球的制备条件及影响其液相分离的条件。方法:以正硅酸乙酯(TEOS)为硅源,盐酸(HCl)为催化剂,十二烷基苯磺酸钠(C_(18)H_(29)NaO_(3)S)为表面活性剂,利用聚合诱导胶体凝聚法(PICA)合成介孔SiO_(2)微球,研究制备工艺(反应温度、pH值及甲醛和尿素的摩尔比N)对SiO_(2)微球大小形貌的影响规律,优化制备条件,制备出中位径为12μm SiO_(2)微球,经十八烷基三甲氧基硅烷(C_(21)H_(46)O_(3)Si)修饰后制备出C18-SiO_(2)微球,并用应用于高效液相色谱(HPLC)柱的填料,研究其对复合氨基酸的分离条件。结果:获得了中位径为12μm的C18-SiO_(2)微球的制备条件及液相分离条件。结论:利用PICA法成功制备了中位径为12μm的C18-SiO_(2)微球,粒径分布窄(D_(90)/D_(10)=1.63),介孔直径为10 nm,比表面积为236.38 m^(2)/g;在适宜的流动相和洗脱强度条件下,C18-SiO_(2)微球能够对复合氨基酸谷丙甘氨酸进行较快地分离,分离度均大于1.5。

高强耐压丁腈橡胶材料的制备与性能研究

丁腈橡胶(NBR)在汽车零部件及密封圈领域应用广泛,为进一步提高丁腈橡胶的力学性能,笔者采用石墨烯纳米片(GNP)作为补强填料,制备环氧树脂(EP)包覆的添加剂GNP/EP,与白炭黑并用后制备得到环氧树脂包覆石墨烯/白炭黑/丁腈橡胶复合材料,以改善丁腈橡胶的拉伸和压缩形变性能.研究中,使用表面扫描电子显微镜(SEM)观察了复合填料和混炼胶的脆断截面形貌;使用橡胶加工分析仪(RPA)测试了复合材料的硫化时长、储能模量;使用万能试验机测试了橡胶材料的力学性能.研究结果表明:环氧包覆石墨烯/白炭黑复合填料在NBR中分散性提高,橡胶交联密度增大,力学性能提升.使用环氧包覆石墨烯与白炭黑并用增强NBR比使用原始石墨烯与白炭黑并用增强NBR可以取得更佳的断裂力学性能和耐压缩永久变形能力.

Sol-Gel Preparation of Zn2 SiO4 :Mn Phosphor Layers on Silica Spheres and Their Luminescent Properties

The synthesis and luminescence properties of Zn2 SiO4: Mn phosphor layers on spherical silica spheres, i.e.,a kind of core-shell complex phosphor, Zn2SiO4: Mn@ SiO2 were described.Firstly, monodisperse silica spheres were obtained via the Stober method by the hydrolysis of tetraethoxysilane(TEOS) Si ( OC2H5 ) 4 under base condition ( using NH4 OH as the catalyst).Secondly, the silica spheres were coated with a Zn2 SiO4: Mn phosphor layer by a Pechini solgel process.X-ray diffraction ( XRD), scanning electron microscope ( SEM), energy-dispersive X-ray spectrum ( EDS )and photoluminescence (PL) were employed to characterize the resulting complex phosphor.The results confirm that1000 ℃ annealed sample consists of crystalline Zn2SiO4: Mn shells and amorphous SiO2 cores.The phosphor show the green emission of Mn2+ at 521 nm corresponding 4T1 (4G) - 6 A1 (6S) transition, and the possible luminescence mechanism is proposed.

Coating Multi-walled Carbon Nanotubes with Uniform Silica Shells:Independent of Surface Chemistry

A facile and general method was described to coat six types of multi-walled carbon nanotubes, functionalized by either noncovalent or covalent way, with smooth silica shells. 3-Aminopropyltriethoxysilane（APTES） and pH value play important roles in the coating process and the thickness of silica shell could be controlled by the added amount of silicon alkoxides. After the removal of multi-walled carbon nanotubes by calcination, the silica nanotubes were successfully prepared.

Synthesis and Characterization of Polystyrene/Nanosilica Organic-Inorganic Hybrid

A polystyrene（PS）/nanosilica organic-inorganic hybrid material was prepared from styrene monomer and commercial aqueous silica sol containing large amounts of Si-OH by means of emulsion polymerization. The nanosilica sol was modified by the addition of the reactive coupling agent methacrylexy propyltrimethoxysilane （ MPS）, and the resulting latex particles were protected by surfactants such as sodium dodecyl sulphonate（ SDS）, hydroxypropyl methyl cellulose （ HMPC）, and poly （vinylpyrrolidone） （PVP）. The effects of the type of surfactant, the amount of surfactant, and the coupling agent on the shape and stability of the resulting latex particles were investigated. The TEM observation indicates that among SDS, HMPC, and PVP, SDS is the best surfactant. When the content of SDS is 0. 5% and the amount of MPS is 7% in the system, the latex with obvious core-shell structure could be obtained. The average diameters of the monodispersed particles range from 182 to 278 nm, and the average number of silica beads for each composite are 1325 and 4409, respectively. The FrIR analysis shows that PS was chemically linked to silica through MPS. The thermal gravimetric analysis shows that when there is a higher silica content, the hybrid composites have a better heat resistance.

One-pot synthesis of thermally stable gold@mesoporous silica core-shell nanospheres with catalytic activity

A facile one-pot method has been developed to synthesize uniform gold@mesoporous silica nanospheres （Au@MSNs）, which have a well-defined core-shell structure with ordered mesoporous silica as a shell. The resulting Au@MSNs have a high surface area （-521 rna/g） and uniform pore size （-2.5 nm） for the mesoporous silica shell. The diameter of the gold core can be regulated by adjusting the amount of HAuC14. The catalytic performance of the Au@MSNs was investigated using the reduction of 4-nitrophenol as a model reaction. The mesopores of the silica shells provide direct access for the reactant molecules to diffuse and subsequently interact with the gold cores. In addition, the Au@MSNs display the great advantage of sintering-resistance to 950 ℃ because the mesoporous silica shells inhibit aggregation or deformation of the gold cores. The high thermal stability enables the Au@MSNs to be employed in high-temperature catalytic reactions.

Preparation and application of mesoporous core-shell nanosilica using leucine derivative as template in effective drug delivery

Core-shell structured mesoporous silica nanoparticles have been firstly synthesized with the new template from L-leucine methyl ester hydrochloride(H-Leu-OMe·HCl).LMSNs were characterized by transmission electron microscopy(TEM),nitrogen adsorption/desorption,and small-angle X-ray diffraction(SAXRD),demonstrating a well-ordered mesostructure.After loading doxorubicin hydrochloride(Dox) into pores,considerable loading capacity of 30.5% and favorable cumulative release amount were obtained.MTT assay suggested that Dox-loaded LMSNs demonstrated great promise to anti-tumor.The use of MSNs with the synthesized template,as a drug delivery carrier,will exte nd the pharmaceutical applications of silica materials.

超重力法制备超细二氧化硅及影响因素的研究

以水玻璃和硫酸为原料,在超重力反应器中采用沉淀法合成了超细二氧化硅粉体.探讨了反应pH值、陈化作用、旋转床转速等因素对二氧化硅性能的影响规律.研究结果表明：超重力环境不仅可以使沉淀反应时间大大缩短,而且有利于生成粒径小、比表面积大的超细二氧化硅产品;确定了最佳制备工艺条件为反应终点pH值2～3、陈化时间60～90min、旋转床转速800～1000 r/min.

纳米二氧化硅水分散体的制备及复配

通过粒子紧密堆积数学模型计算得到不同粒径硅溶胶粒子间的最优配比,在此基础上合成了3种不同单分散粒径的硅溶胶。将不同粒径硅溶胶按数学模型计算的比例加入到钾水玻璃中,复配制备了不同纳米二氧化硅水分散体。与由单一粒径硅溶胶形成的膜相比,由不同粒径硅溶胶复配后形成的膜,呈现出较高的结构致密性和憎水性,与由粒子紧密堆积模型推导结果吻合。

高效液相色谱用硅质填料的进展

对高效液相色谱用硅质填料的进展情况做了全面的评述。介绍了硅质填料的制备及化学修饰 ,评价了硅胶表面的物理表征 ,概括了硅质填料在高效液相色谱中的应用 ,并对我国的硅质填料前景进行了展望。

分子自组装氧化钛包覆硅球色谱柱载体的制备及正相色谱性能研究

采用分子自组装方法在微米硅球表面涂敷多层纳米二氧化钛,得到了比表面积为202.1 m2/g、孔体积0.3628 m3/g、孔径7 nm的复合颗粒。在正相条件下研究了该TiO2/S iO2壳核型复合微粒的色谱性能,并与ZrO2/S iO2复合微粒色谱性能进行了比较。结果表明:氧化钛复合颗粒渗透性好,柱压低,是一种比较理想的高效液相色谱载体,对中性化合物和碱性化合物有较好的分离选择性,峰形对称;但对酚类化合物强烈保留,峰形较差。

白炭黑制备工艺对比表面积和吸油值的影响

利用正交设计安排实验，在超重力旋转床中，采用硫酸沉淀法制备超细白炭黑，研究实验制备工艺条件pH、硅酸钠浓度、温度、电解质和旋转床转数以及不同干燥方式对白炭黑的BET比表面积和DBP吸油值的影响。实验结果表明，反应终止时pH对白炭黑的BET比表面积影响最大，其次是温度、电解质、硅酸钠的浓度和旋转床的转数。干燥方式是影响DBP吸油值的决定性因素，其次是温度、电解质、旋转床的转数、硅酸钠的浓度和反应终止时pH。制得产品的BET比表面积140～351m^2／g，DBP吸油值1．42-4．41mL/g。