Dissertations / Theses on the topic 'Mesoporous silica sphere'
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1
Nyalosaso, Likoko Jeff. "Synthèse et caractérisation de sphères monodisperses de silice à porosité radiale (multi)fonctionnelles et étude de leur performance en catalyse en phase liquide et en vectorisation de principes actifs." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20218.
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Une nouvelle approche de synthèse a été développée pour non seulement contrôler la morphologie, la taille et la texture de particules de silice mais aussi incorporer une ou plusieurs fonctionnalités à la surface interne de leurs pores. La morphologie sphérique, la monodispersité des particules, la porosité radiale, la dispersion et l'accessibilité des fonctionnalités ainsi que leur taux d'incorporation constituent les propriétés et les paramètres physico-chimiques privilégiés dans notre approche qui est basée sur la méthode de Stöber modifiée et la fonctionnalisation in-situ. Deux différentes applications ont été retenues pour étudier la quintessence de cette approche. La première consiste à incorporer des espèces métalliques (Al et Cu par exemple) dans les sphères de silice afin de les rendre fonctionnelles pour des applications catalytiques en phase liquide; et la deuxième consiste à greffer à la surface des particules des nanomachines sensibles permettant de contrôler le relargage des molécules actives pour des applications thérapeutiques. Dans les deux cas d'application, des performances optimales sont attenduesA novel approach of synthesis has been developed in order to control simultaneously the morphology, size and textural parameters of silica particles, as well as to incorporate one or more functional groups in the pore walls. In this approach, based on the modified Stöber method and in-situ functionalization, emphasis is put on the spherical morphology, the particle monodispersity, the radially disposed porous structure, and the appropriate dispersion and accessibility of surface functional groups. Two potential applications have been selected so as to verify the feasibility of the approach. In view of materials use for heterogenous catalysis in the liquid phase, the monodisperses mesoporous silica spheres were derivatized with metallic species (e.g., Al and Cu) by direct incorporation in the synthesis stage. The second type of applications concerned the use of silica spheres as sensitive nanomachines for the controlled drug release and required grafting of appropriate organic molecules onto the silica surface
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Chen, Chau-Nan, and 陳朝楠. "Synthesis of uniform mesoporous silica sphere." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/dgrf8v.
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碩士國立成功大學
化學系碩博士班
92
On the bases of theory of self-assemble chemistry, we proposed new chemical compositions to synthesize the uniform mesoporous silica spheres with different diameters using alkyltrimethylammonium surfactant as structure-directing agent and sodium silicate as silica source in neutral condition (pH=7.0-9.0). In order to simulate opal with photonic crystal structure in nature, our mesoporous silica spheres must have high uniformity (< 10%) and nice order packing. The diameters of the mesoporous silica spheres can be controlled with pH value and the amount of cosolvent, and we can gain opaline flake from suitable centrifugation. However, the color of the opaline flake varies with particle sizes. The bigger particle sizes (160-180 nm) show light blue color, and the smaller ones (< 100 nm) show transparence. Besides, we also confer the effect of size and concentration of inorganic silicate precursor. The vesicle-like mesoporous silica has been synthesized using block copolymer as surfactant and sodium silicate as silica source at pH value around 5.0. The effect of silica concentration on the mesostructure was discussed. Moreover, the vesicle-like mesoporous silica with high porosity was used as a template to prepare mesocarbon of high surface area, and porosity. Based on the concepts of coprecipitation, we successfully incorporate titanium and zirconium oxide into mesoporous silica framework. Finally, we use titanium oxide incorporated mesoporous silica as solar catalyst to convert NO into NO3-, and its conversion is up to 60%.
3
Li-MingChen and 陳立敏. "Using Surface-Activation and Hard-Templating Methods to Prepare CNT@ or Silica Sphere@Mesoporous Silica, Mesoporous Zeolite and Mesoporous Carbon and Metal Oxide Hollow Spheres." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/67671370026638677935.
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碩士國立成功大學
化學系碩博士班
100
Mesoporous silicas and carbons with high surface area, large porosity, high thermal stability, are of the great interest of its extensive applications, such as catalyst, adsorbents, hard templates and electrode materials. In this research, gelatin was used as surface-activation agent and silica sphere (SS) synthesized using Stöber method and carbon nanotubes (CNT) was used as hard-template to prepare silica sphere@ or CNT@mesoporous silica composites. Combining with impregnation or steaming methods, mesoporous carbon and metal oxides hollow spheres were conveniently synthesized using silica sphere@mesoporous silicas as hard template. In the first part of this thesis, we focused on selection of surface activation agent to induce silicate/surfactant assembly and condensation on the surface of silica sphere. After the pre-products was carried out in a PP bottle at 100℃ for 24 h, the well-dispersed SS@MS with core-shell structure was prepared. Using the SS@MS as hard temple, the mono-dispersed hollow carbon sphere can be obtained from impregnation of phenol-formaldehyde resin, high-temperature pyrolysis and silica removal by 5% HF etching. Finally, using the hollow carbon sphere as hard temple again, the metal oxide hollow spheres can also be prepared by impregnating a proper amount of the precursor metal ion, high-temperature calcination. The results show that thermally stable aluminum oxide replicate the hollow sphere, but zirconia oxide with a less thermal stability show the fragments of the hollow spheres. The second part of this thesis will demonstrate the preparation of CNTs@mesoporous silica. Using the similar synthetic procedures and compositions, the CNTs@mesoporous silica was obtained from a simple mixing of the CNT-gelatin solution and a sodium silicate solution at pH of 4.0, hydrothermal treatment, and 450oC-calcination to remove the gelatin. A versatile mesoporous silica shell have been thoroughly coated onto the surface of CNTs. Due to the polar mesoporous silica shell, the CNTs@mesoporous silica can be easily dispersed into an epoxy matrix. The mesopores structure of silica layer provides multi-functions on tuning modulus matching, improving interaction and disperse-ability between epoxy and CNTs. The epoxy/CNTs@SiO2 composites showed a superior effect on thermal conductivity than epoxy/CNTs. In addition, the preparation of CNT mesoporous carbon composites, using the CNT@mesoporous silica as hard temple, and impregnating with a carbon precursor followed by carbonization and the use HF for etching the silica shell. Through CV analysis, CNT@MC composite materials had better capacitive performance than commercial active carbon, and capacitive retention maintain near 80% at high scan rate, In the future, these materials have opportunity to replace conventional capacitors as energy storage device. In order to reduce the diffusion path length of the microporous zeolite, introducing the intracrystal mesopores is practicable. Because of high thermal stability of the CNT, the mesoporous ZSM-5 can be obtained from a steaming and calcination on the CNTs@MS composites. In addition to using CNTs@MS composites, other carbon/silica composites, such as cracked rice husk and PF/silica, can also be used to prepare the mesoporous zeolite. The results show that crystals size of zeolite synthesized with CNT@MS and cracked rice husk are large than that with cracked PF/silica. Mesoporous zeolite of high surface area and porosity would offer the possibility for improving catalytic performance.
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Liou, Jia-Shin, and 柳佳欣. "Effect of Anion on the Formation of Mesoporous Silica and Synthesis of Metal Modified Hollow Silica Sphere." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/74201315505056095785.
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碩士國立臺灣大學
化學研究所
98
Using amphiphilic triblock copolymers [poly (methyl acrylate)-b- (ethylene oxide)-b- (methyl acrylate)] as templates, we have investigated the anion effect toward the porosity of mesoporous silicas. Under high concentration of potassium salts, pore diameters of the obtained silicas increases in the following order: no salt added < KNO3 < KBr < KCl. However, different hysteresis loops of the nitrogen adsorption diagrams were observed when adopting the low concentration of these salts. Different morphology of mesoporous silica with high loading of transition metal ions can be achieved by the co-condensation method. A simple co-condensation of iron(III) acetylacetone, 3-aminopropyltrimethoxysilane, and TEOS in the presence of triblock copolymers provided the mesoporous silicas in hollow spheres (MSHs) with the diameters in the range of 100-400nm, possessing uniform shell with the thickness of 35-40nm. After removal of the surfactants, iron oxide nano-particles (< 5 nm) were well-dispersed on the surface of meso-channels. Even for the higher concentration of metal ions used, the pore channels remain unblocked. The BET surface area was about 378 m2/g and the pore volume was 0.450 cm3/g.
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Shu-NingYang and 楊書寧. "The correlation between the scattering mechanism of mesoporous silica hollow sphere in LCs and temperature." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/qnwq8m.
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碩士國立成功大學
物理學系
104
Mesoporous silica hollow spheres (MPSHSs) doped in liquid crystals (MPSHSs-LCs) exhibits no aggregation and well-dispersed phenomenon, which reveals some new physics among MPSHSs and LCs. There should be different type of anchoring originated from the surface structure of MPSHSs. In order to realize the phenomenon, we perform the scattering measurement of MPSHSs-LCs with varied temperature to study the correlation between scattering domain and environment temperature, and discuss the dependence of the MPSHS concentration. Besides, dielectric measurement also performed to assist the study the phase transition during the temperature variation, especially in the temperature of phase transition. The real part and the image part of dielectrics result reflect the corresponding relaxation frequency of LCs and isotropic state, respectively. Polymer-dispersed in LCs (PDLCs), chiral LCs (CLCs) and solid silica spheres (SSSs) doped in LCs were also adopted in this work for comparison. We also use the mean field theory to explain our experimental results. The assumption of anisotropic anchoring in the mean field theory can well explain the relation between Tni (nematic-isotropic transition temperature) and the size and concentration of MPSHSs. MPSHS with small size has larger curvature and lead anchoring from the pores of MPSHSs to be strong and random. Thus, larger affected area around MPSHSs is formed at the case of small MPSHSs. We also find the similar behavior in DCS experiments by scattering experiment. A dip appears in the scattering experiment with scan temperature. An opaque state exists on the period of nematic-isotropic transition, which is a transparent nematic state in DSC experiment. In the case of MPSHSs, the dip is quite small and is suppressed as the disorder state overcome the transparent nematic state at larger size or higher concentration. By using two series experiments with different kind of LC scattering devices, the correlation with MSPHS and scattering were confirmed.
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Ruo-TongGu and 顧若桐. "The novel behavior of mesoporous silica hollow sphere in nematic liquid crystals and its application." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3tuw3m.
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Hung-RuHuang and 黃弘儒. "The scattering mechanism of Mesoporous silica hollow sphere and the development of new type smart window." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/46516082136930599517.
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碩士國立成功大學
物理學系
103
Over the past several years of research liquid crystals (LCs), the most fascinating field is that the anisotropic characteristic, indicating the perpendicular direction of dielectric constant or refractive index is different from the direction of parallel. Due to the intrinsic anisotropic characteristic, the application of liquid crystal in the display field is attracting researchers and the display industry. However, the behavior of innate anisotropic fluid, such as nanoparticles or colloidal particles is hard to well disperse in LCs. As the restored elastic continuum of LCs and generated topological defects, the doped nanoparticles couldn’t uniformly disperse in LCs and will gradually aggregate with the time or applied voltage. However, Mesoporous silica hollow sphere (MPSHS) is a candidate artificial material to solve particles aggregation in LCs and also make the controllable scattering effect for further application. The subject of this thesis is to study the scattering phenomenon of MPSHSs and make a better performance of scattering devices, such as smart window. MPSHS-LCs exhibit uniform opaque in the naked eye and optical microscope images. Contrary, in the silica solid spheres (SSS) which without mesoporous on the surface of SSS and hollow structure, the opaque is not uniformly distributed in the naked eye and optical microscope images. In addition, with the increasing applied electric field, the dark section would be disappeared likely to the polymer dispersed liquid crystal. Noticing the particular phenomenon, we proposed the mechanism of light scattering and compare to the scattering phenomena of the polymer dispersed liquid crystals (PDLCs) and cholesteric liquid crystals (CLCs). According to the specific electro-optical behavior of MPSHSs, we improve the performance of the smart window and we also propose the mixture of polymer (NOA61) and chiral (S811) to enhance the electro-optical property of MPSHSs. Besides measuring the transmittance, we also measure the response time and hysteresis effect which involve the anchoring of MPSHSs In order to find out more detailed about the light scattering mechanism and the orientation of liquid crystal surrounding to the MPSHSs so we use the azo dye (Methyl Red) which could induce the transient reorientation of liquid crystal by photoisomerization. Based on the dynamics transmittance after the photoisomerzation of azo dye (Methyl Red), we could infer the reorientation of liquid crystal and the light scattering structure. In addition, we compare this phenomenon with PDLCs and CLCs. Moreover, the intensity of excitation laser energy is changed to observe the corresponding response about MPSHSs.
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Chia-ShengChang and 張家勝. "Synthesis of Mesoporous Silica Hollow Sphere by Hard-Templating Technology for Application in Liquid Crystal Displayer." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/43601352950123527215.
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碩士國立成功大學
化學系碩博士班
101
Hard-templating method has been widely used to prepare the material with hollow interior. Herein, we use the PMMA beads as sacrificial hard templates to synthesize the mesoporous silica hollow spheres. To induce silica condensation on the PMMA beads, an appropriate amount of nature polymer gelatin is needed to be added for surface-activation of the PMMA beads. Consequently, the mesoporous silica hollow spheres were obtained from silicification on the gelatin-activated PMMA beads, and calcination for the removal the organic parts. The resulted mesoporous silica hollow spheres possess high surface area and large and tunable pore size. We can control the diameter and thickness of mesoporous silica hollow spheres by using PMMA beads of different sizes and repeating silicification procedures. In addition to the PMMA beads, we can also use other polymer beads as sacrificial hard templates. By adding appropriate amount of surfactant for surface-activation, the mesoporous silica hollow spheres were synthesized as well. Distinct from previous reports including complicated surface activation procedures, we proposed provides a convenient method to prepare mesoporous silica hollow spheres in high yield and reproducibility. Different from the general polymer-based smart windows (e.g. PDLC), we use the mesoporous silica hollow spheres as the additives to form scattering domains. Owing to the mesoporous shell, the hollow interiors of the silica hollow spheres are accessible to the environments. In addition, the pore size of the silica shell is larger than the dimension of the liquid crystal molecules, interiors in the mesoporous silica hollow spheres after hydrophobic silane modification would be fully filled with the liquid crystals. Thus, the hollow porous-silica spheres well disperse in the liquid crystal matrixes to form homogenous HSS-LC slurry. The HSS-LC slurry can be embedded between two transparent conductive glasses to create a HSS-LC displayer. The electro-optical device showed an opaque state with a light transmittance of about 10 %. The application of low effective voltages (= 60 V) resulted in a fast transition into a clear transparent state (T = 80 %) in millisecond range.
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Li-JieLin and 林莉婕. "Realization of Smart Window with Memory Effect by Mixing Hollow Sphere Mesoporous Silica with Nematic Liquid Crystal." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/svyt4t.
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碩士國立成功大學
化學系
105
Existing liquid crystal smart windows require a continuous power supply to maintain a transparent state, and therefore incur a high power consumption. In this study, a practical energy-saving strategy is demonstrated by mixing 5CB nematic liquid crystal with hollow sphere mesoporous silica (HSMS) synthesized using a soft-templating method under pH=5.5–6.0 and then hydrophobically modified by chlorotrimethylsilane. The optical microscopy observations show that the hierarchical sphere structure divides the 5CB molecules into a large number of scattering regions, and therefore produces a dense opaque state. For example, 7.5 wt% HSMS addition results in an opaque state with a transmittance as low as 23%. However, given an applied voltage of 80 V, the 5CB molecules are almost perfectly aligned and a transparent state with a saturated transmittance of 100% is obtained. Notably, the weak anchoring force between the hydrophobically modified HSMS and the liquid crystal material resists the realignment of the 5CB molecules following the removal of the electrical field and results in a residual transmittance of over 90% for more than 2 hours. Overall, the results presented in this study show that the addition of HSMS material to 5CB liquid crystal enhances the memory effect and therefore makes possible the realization of smart windows with a reduced energy consumption.
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Dai-YanLu and 呂岱諺. "The physical phenomena and application of Mesoporous silica hollow sphere in nematic and chiral nematic liquid crystal." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/hx6cnf.
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碩士國立成功大學
物理學系
107
Mesoporous silica hollow spheres (MPSHSs) is a kind of hollow microsphere that have large surface/volume ratio, the pore on the silica hollow spheres let the liquid crystals molecular arrange disorderly. There is a thin and disorder liquid crystals layer around the MPSHSs called that disorder layer (DOL). The order parameter in the DOL is low. The outer liquid crystals layer cannot feel the director axis from the DOL, so the anchoring of the MPSHSs is weak. According the topological defect theorem, topological defect won’t exist when R≪K/W , R is the radius of the sphere, K is the elastic constant of the liquid crystals, W is the surface anchoring of the sphere. MPSHSs will disperse in the nematic liquid crystals. DOL will not distort the surrounding director axis, the liquid crystals go through nothing. Base on the weak anchoring of MPSHSs, when we apply voltage on liquid crystal bulk, the brightness of the MPSSSs is smaller than SSS. When apply 20 V, the brightness of MPSSS is larger than SSS, because the DOL on MPSSS’s surface. On the other hand, we reduce the size of MPSHSs to 100 nm, 150 nm and 300 nm, and mixed MPSHSs with blue phase liquid crystals (BPLC) by different weight percent. The temperature range of BPLC will extend. The most effective one is 300nm MPSHSs, the temperature range increased by a factor of 1.2 in average.
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Hou, Yong-Xuan, and 侯詠軒. "Synthesis, characterization and antibacterial assessment of high surface area mesoporous silica sphere and its metal oxide-decorated nanocomposites." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/5bdqc9.
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碩士國立臺灣科技大學
材料科學與工程系
104
In this research, mesoporous silica spheres with uniform size were successfully prepare by sol-gel method. The system consists of cetyltrimethylammonium bromide (CTAB) surfactant as a main template, tetraethyl orthosilicate (TEOS) as the silicon precursor, and different kinds of polymers as the second/third polymer in aqueous-phase or oil-in-water phase to synthesis mesoporous silica sphere. By using potassium hexacyanoferrate as ethching agent, mesoporous silica spheres were etched to extend the pore size. By simply changing the amount of second/third polymers in the system, mesoporous silica spheres had the diameter of 290 ~ 613 nm, pore size of 1.86 ~ 4.10 nm, total pore volume of 0.572 – 1.02 cm^3/g, and surface area of 865 ~1286 m^2/g. The potassium hexacyanoferrate was used to etch mesoporous silica sphere. After etching, original pore sizes of 1.86 nm and 3.82 nm were extended to 3.08 nm and 4.60 nm, respectively and the silica sphere kept its shape. When reaction temperature was increased from room temperature to 75 ℃, mesoporous silica sphere diameter about 155 ± 22 nm and remained spherical. However, the average pore size extended from 3.82 to 8.62 nm, total pore volume increased from 1.01 to 2.2 cm^3/g, and specific surface area up to 1021 m^2/g. In addition, four kinds of metal oxide semiconductor nanoparticles such as silver(I) oxide、copper(I) oxide、nickel(II) oxide, and cerium(Ⅳ) oxide were uniformly deposited on mesoporous silica spheres with high specific surface area through chemical synthesis method for the purpose of antibacterial application. We used the metal oxide/silica composite spheres to test antibacterial effect. The chosen strains were gram-positive type bacteria - Staphylococcus aureus (S.aureus). The initial bacterial concentration of 1 × 10^8 CFU/mL was prepared for antibacterial test in a dark room and in the 20-watt LED light condition. The data showed that both silver(I) oxide/silica and copper(I) oxide/silica composite spheres had performed the excellent antibacterial activity to completely sterilize bacteria in one hour no matter in the dark or under the 20 W-LED illumination. Owing to their large and accessible pores and high surface area, the mesoporous silica sphere exhibited excellent performance in adsorption of methylene blue dye with a maximum adsorption capacity of 50.25 mg/g.
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ChinChang and 張勤. "Synthesis of Mesoporous Silica and Mesoporous Alumina Hollow Spheres by Using Hard-Templating Method." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/8y35q9.
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碩士國立成功大學
化學系
106
The hard-templating method is widely used to prepare silica hollow spheres, Herein, two facile routes have been reported for the synthesis of mesoporous silica and carbon/silica hollow spheres using PMMA beads as sacrificial hard templates, AEO-L67 as a surface activation reagent, and TEOS as the silica source. In the first method, silica is condensed on the PMMA beads (PMMA@SiO2)and mesoporous silica hollow spheres (MSHS) are then obtained via calcination at 600℃ for 6 h to remove the organic parts. The MSHS are shown to have a high surface area range from 271- 1014 m2/g. Notably, by changing the PMMA bead size MSHS with a different size can be synthesized. The MSHS are further calcined at 950℃ for 2 hrs to increase their crystallization and reduce the adsorbed water content to less than 1 wt.%. In the second method, the PMMA@SiO2 is pyrolysized in Ar to synthesize carbon-silica hollow spheres. The experimental results show that the carbon-silica hollow spheres are capable of reducing the dye concentration in water from 30 ppm to 0 ppm in 24 hrs. The PMMA hard templating and calcination route is applied to synthesis of mesoporous alumina hollow spheres (MAHS) using aluminum sulfate as the alumina source and gelatin as a surface activation reagent. In general, the silica and alumina hollow spheres synthesized in this study have good potential for industrial application as absorbents, catalysts and biomaterials. Compared to existing methods, the proposed methods have several key advantages, including the use of a non-toxic solvent, a one pot reaction and synthesized materials with high specific surface areas.
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Chun-HanPang and 龎鈞翰. "Synthesis and application of mesoporous silica and metal-silicate hollow spheres prepared using hard-templating method." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/39trzy.
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山田, 有理, and Yuri Yamada. "Fabrication and investigation of the colloidal crystals from monodispersed mesoporous silica spheres." Thesis, 2010. http://hdl.handle.net/2237/14812.
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Chao, Kung-Yi, and 趙公義. "Preparation, Characterization and Properties Studies of Electro-active Polyimide Composites Containing Mesoporous Silica Spheres." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/52642794245205717381.
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碩士中原大學
化學研究所
99
In this study, we present the first synthesis and characterization of electroactive polyimide-mesoporous silica spheres with low dielectric constant and thermal conductivity simultaneously. First of all, amino-modified mesoporous silica spheres were synthesized by base-catalyzed sol-gel reactions of TEOS and APTES with fructose as non-surfactant template, followed by characterization by 13C-NMR and 29Si-NMR spectroscopy. Porosity of as-prepared amino-modified mesoporous silica spheres was determined by BET. Subsequently, the suitable amount of as-prepared mesoporous silica spheres was incorporated into the solution containing diamine of amine-capped aniline trimer (ACAT) and dianhydride of BSAA, followed by thermal imidization up to 250℃. Dispersion of silica spheres with/without porosity in polyimide matrix was identified by TEM observations. It should be noted that the as-prepared composite membranes containing mesoporous silica spheres was found to show lower dielectric properties and thermal conductivity than the corresponding pure polyimide. However, the composite membranes containing raw silicon spheres without mesoporous structures was found to reveal higher dielectric properties and thermal conductivity than neat polymer membrane. Dielectric constant and thermal conductivity of as-prepared samples was determined by dielectric constant analyzer and Hot Disk, respectively. Moreover, thermal properties of all composite membranes were found to slightly higher than corresponding neat polymer membrane, as identified by thermal gravimetric analyzer (TGA) and differential scanning analyzer (DSC). Mechanical strength of as-prepared membranes was measured by dynamic mechanical analyzer (DMA).
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Sheng-JhongJi and 紀盛鐘. "Liquid crystal phase around mesoporous silica hollow spheres and its application on smart window." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/vphu39.
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Chi-HsienSu and 蘇繼憲. "A Study on the Mechanism of the Mesoporous Silica Hollow Spheres and the Application of the High-Surface-Area Mesoporous Carbons in Supercapacitor." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/63805167686521667640.
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碩士國立成功大學
化學系碩博士班
98
This thesis is mainly divided into three research topics. The first part is to explore the formation mechanism and applications of the mesoporous silica hollow particles templated with a biopolymer gelatin. The second part is focused on the investigation of the electrochemical behavior of the mesoporous carbons synthesized via a simple basic synthesis method, which have larger surface areas but different pore sizes. In third part, the treatment methods on the rice husks to get mesoporous silicas with larger surface areas and the applications of these mesoporous silicas in PH3 adsorption were studied. Part I. Synthesis of mesoporous silica hollow particles by using gelatin as template and its applications The as-synthesized gelatin-silica hybrid materials prepared by using sodium silicate as silica source and a low toxic and environment-friendly of organic template, gelatin, were hydrothermally treated under different conditions to explore the formation mechanism of the mesoporous silica hollow spheres. At pH values = 5.0 – 9.0, the gelatin-silica solid particles would gradually transform into hollow ones because of the repulsion interactions between the negatively-charged silica surface and partially negatively-charged gelatin. While at pH less than 5.0, the hydrogen-bonding interactions still exist between the silica and gelatin to reduce the morphology transformation. In addition, hydrothermal temperatures, and reaction time can also have effect on the solid to hollow transformation rate. Owing to the lager surface area and pores size, higher thermal stability, and hollow interiors, these mesoporous silica hollow spheres not only can be used as catalyst supporters and as solid template application but also can applied in drug-release systems for tracer agents in the medical science based on their light-emitting characteristics. Part II. Electrochemical application of mesoporous carbons via a basic synthetic procedure To synthesize the mesoporous carbons of high surface area and tunable pore size, we proposed a novel polymer-blending template of carbonizable phenol formaldehyde and gelatin. The mesoporous carbons can be conveniently obtained from fast silicification, hydrothermal treatment, pyrolysis and silica removal of a basic PF-gelatin silicate solution. Due to the large pore size (＞ 10 nm), high surface area, good electronic conductivity, 3D highly open structure, the mesoporous carbons demonstrates the rectangular-like shape of all i-E curves measured from 100 to 3000 mV s?1 in 4 M H2SO4 that reveals the excellent capacitive performances. The mesoporous carbons electrode exhibits only about 30% loss when the scan rate is varied from 100 to 3000 mV s?1 In contrast to the mesoporous silica of smaller pore size (＜ 5.0 nm), the capacitance retention is less than 40% at scanning rate of 3000 mVs-1. These perfect capacitive performances confirm the promising applicability of these novel mesoporous carbons for supercapacitors of ultrahigh power. Part III. Reuse technology of the abundant the rice husk The rice husk belongs to a great agriculture wastes in the Asian. Besides the few parts used as the fertilizer, most parts were directly burned that causes an air-pollution issue. Therefore, this is a potential research field by using organic-silica hybrid composites of the rice husk as a high value raw material for industry based on the environmental protection aspect and the waste reuse. In our work, mesoporous silicas with high large surface areas and pore size were obtained from a treatment on rice husks in acid aqueous solution at room temperature and 100oC. Moreover, the mesoporous silicas grafted with different copper oxide contents can be used as a high-performance absorbent of PH3 toxic gas.
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Gu, Ying-Min, and 古盈敏. "Synthesis of Mesoporous Silica Vesicles and Concentric Spheres by Using Cationic and Anionic Binary Surfactant as Template." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/52183153240684337810.
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碩士國立成功大學
化學系碩博士班
97
In nature many complex biological structures such as skeleton, teeth of organisms and diatoms, shells in the sea are composed of highly joint complexes of organic and inorganic compounds. Applying the concept to synthesizing various forms of nano-materials, this research uses organic compound-based template which enables the condensation of inorganic compounds through molecular self-assembly process and forming of organic-inorganic nano-composite materials, hoping that morphologies similar to natural diatoms could be synthesized and in this way offers a new insight of bionics material. In order to acquire organic-inorganic complex material, this experiment utilize surfactant as organic template and combined it with inorganic species (Sodium silicate solution, Tetraethyl orthosilicate).In a mixture of cationic and anionic surfactants (i.e. catanionic surfactant), various micelle structures, including cylindrical micelle, vesicles micelle, as well as laminar structure can not only be obtained by adjusting the molar ratio between the two composites but also used as a template of silica mesostructure which has spectacular morphologies. Mixtures of anionic and cationic surfactants through the electrostatic association of their oppositely charged polar head groups consist of vesicles which are able to mimic the structure of phospholipids (double-chained amphiphiles)and thus be viewed as model systems for fluid interfaces and biomembranes. This research use proportioned mixture(SDS / Cn TMAB molar ratio,S ) of cationic surfactant (CnTMAX, n=12-18, X=Br or Cl) and anionic surfactant (SDS) as the organic template.Inorganic TEOS is then mixed with the template above for preparing vesicle-like mesoporous silica in the condition of pH3, 40℃) This experiment can be divided into two main parts: 1. the vesicle-like mesoporous silica prepared from C14TMAB cationic surfactant. 2. alteration of carbonic chain length of cationic surfactant, using CnTMAB (n=12,16,18) to synthesize vesicle-like mesoporous silica. This experiment focuses on variables including molar ratio and concentrations of different surfactants, pH values and temperatures of the reactions to discover the most productive reaction condition, following by integrating the results and speculating about probable mechanisms. This research mix contents in proper circumstances and synthesize vesicle-like mesoporous silica which have intact structures, even diameters and high dispersibility by means of uncomplicated stirring. This method is simple and has high reproducibility and therefore has high reference values in developing mechanisms and theories of biomineralization.
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Shen, Bei-Huw, and 沈北湖. "The Preparation of Hollow Silica Spheres with Mesoporous Shell via Polystyrene Emulsion Latex Template and the Investigations of Ascorbic Acid and Potassium Sulfate Release Behaviors." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/45776367874691416995.
Full textAbstract:
博士國立中興大學
化學工程學系所
102
The positively charged polystyrene latexes (PS) were prepared via surfactant-free emulsion polymerization of styrene by using the cationic initiator AIBA (2,2-azobisisobutyramidine dihydrochloride). When the styrene conversion of 70 % was reached, appropriate amounts of divinylbenzene (DVB) and methacryl oxypropyl trimethoxy silane (MPS) were added to the emulsion as a functional comonomer. Emulsion particle surfaces bear silanol (Si-OH) functional groups that facilitate the reaction of the silica layer formation on PS particles with silica precursor solution through hydrolysis and condensation of tetraethoxysilane (TEOS) at the acidic aqueous/ethanol medium. PS/silica hybrid colloids with core-shell morphology were obtained. The negatively charged shell showed an isoelectric point (IEP) at pH= 3.7 that was different from the IEP of 10.4 for the original positively charged PS latex based on the Zeta-potential analysis. Typical optimal parameters to prepare PS/silica colloids have been developed from series of experiments. The fomulations for core-shell PS/SiO2 as follows: styrene 2.0 wt %, AIBA 0.01 M, MPS 0.22 wt %, DVB 0.02 wt % and TEOS/styrene = 3/1 (weight ratio). The diameter of PS and PS/silica is roughly 360 nm and 411 nm in SEM image, repectively. The TEM analysis shows that the diameter reduces from 433 nm to 383 nm with a shell thickness of 9.3 nm after extraction and calcination (PSM0.1D-T3-E-C). The hollow silicon dioxide spheres (PSM0.1D-T3-C) prepared by calcination were analyzed using BET analysis. The adsorption and desoption isotherms of these spheres show that the specific surface area of 508.9 m2/g and the pore volume of 0.95 cm3/g. After the encapsulation of ascorbic acid, the specific surface area reduces to 47.2 m2/g and the pore volume reduces to 0.18 cm3/g. After the encapsulation of potassium sulfate, the specific surface area reduces to 171.2 m2/g and the pore volume reduces to 0.44 cm3/g. It shows that drugs already enter the cavities of the hollow silica succesfully. Finally, ascorbic acid was encapsulated in the hollow silica spheres, as inspected by SEM and carbon element mapping images, to examine their kinetics of controlled release behavior. The cumulative release percentage was analyzed using the Higuchi model, a zero-model, and a first model for kinetic study of release behaviors. Results show that both zero-order and first-order models describe the release kinetics of ascorbic acid equally well. The release rate constants for the zero-order model before and after 3 hours are 25.89 and 2.4, respectively, and for the first-order model are 0.87 and 0.03, respectively. We speculated that during the first 3 hours, the ascorbic acid is released from the sphere surfaces. After 3 hours, the ascorbic acid diffues from the core through the pores of shell layer into the solution. During the release process, the ascorbic acid may encounter steric barriers in various pore channels, which causes a significant resistance for mass transfer and results in the slow release of ascorbic acid. In addition, cumulative release percentages of potassium sulfate were also analyzed by various models. Comparing the regression fitness of these models, the Higuchi model shows the best fit for potassium sulfate release kinetics. The release rate constant for the initial stage and the later stage is 217.14 and 0.9087, respectively.