Preparation and magnetic characteristics of mesoporous nickel oxide–silica composites

Mesoporous NiO–SiO₂ (MCM-41) silica-matrix composites with various nickel oxide concentrations (NiO : SiO₂ = 0.025 : 1 to 0.2 : 1) have been produced by oxide cocondensation under hydrothermal synthesis conditions in the presence of cetyltrimethylammonium bromide as a template and (2-cyanoethyl) triethoxysilane as an organosubstituted trialkoxysilane additive. X-ray diffraction data have been used to evaluate the maximum nickel(II) oxide concentration (NiO : SiO₂ = 0.1 : 1) that allows the ordered mesopore structure of MCM-41 to persist in the silica-matrix composites. We have studied the magnetic properties of this material as functions of temperature and magnetic field. The results demonstrate that the magnetic properties of the nanocomposite with NiO : SiO₂ = 0.1 : 1 at low temperatures (T < 20 K) are determined by incomplete spin compensation in the matrix and on the surface of the NiO nanoparticles.     

Toward the preparation of a nanocomposite material through surface initiated controlled/“living” radical polymerization of styrene inside the channels of MCM-41 silica

A hybrid organic–inorganic material was prepared by surface initiated controlled/“living” radical polymerization (CRP) of styrene in the internal space of a MCM-41 silica. The inorganic precursor was synthesized, via sol–gel, using tetraethoxysilane and cetyltrimethylammonium bromide, in the presence of ammonia and ethanol to induce the formation of submicrometric spherical particles. After characterization by powder X-ray diffraction (XRD), transmission electron micrography (TEM), scanning electron micrography (SEM), N₂ adsorption and titration of the surface silanol groups, the mesoporous silica was functionalized through a 3-step grafting process, in order to link the nitroxide initiator to the inorganic matrix (TEMPO-MCM-41). The anchorage of the TEMPO-based initiator was checked by diffuse reflectance infrared spectroscopy (DRIFT-IR). Experimental data confirmed that the styrene polymerization occurred inside the MCM-41 channels system.     

H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> supported on mesoporous MCM-41 and Al–MCM-41 materials: preparation and characterisation

MCM-41 and Al–MCM-41 has been synthesized using cetyl-trimethylammonium bromide (CTAB) surfactant as template and adding the silica precursor to aqueous solutions containing CTAB. The obtained solids were calcined at 600 °C for 4 h. HPW heteropolyacid supported on the mesoporous were prepared using the incipient wetness method. The characterization of materials was performed by X-ray diffraction, Transmission Electron Microscopy, N₂ adsorption, ²⁹Si Cross Polarization–Magic Angle Spinning and ²⁷Al MAS NMR. Results showed that the hexagonal structure is obtained in both cases. The Aluminium species are located inside an extra-framework. The impregnation reduces the surface area of the mesoporous materials especially of the Al–MCM-41 suggesting a participation of aluminium during the impregnation. HPW is well dispersed in the mesoporous materials and is located inside the pores interacting with the silanol group of the pores wall. ²⁷Al MAS NMR measurements have showed that the impregnation causes the removal of the non-framework aluminium.     

Pt nanoparticles inside the mesopores of TiO<Subscript>2</Subscript>–MCM-48: synthesis,characterization and catalytic activity for CO oxidation

TiO₂ and Pt nanoparticles were deposited in the channels of siliceous MCM-48 via a sequential incipient wetness-impregnation method employing (NH₄)₂PtCl₄ as platinum source. The resulting composite Pt/TiO₂–MCM-48 (1 wt% Pt, ca. 3 wt% Ti) was characterized using XRD, TEM, nitrogen physisorption, hydrogen chemisorption, UV–vis spectroscopy, and XPS; its catalytic activity for CO oxidation was also explored. These data were compared with those of Pt/MCM-48 prepared via an analogous route. The results reveal that the platinum was deposited inside the intact pore system in both cases. It remains inside upon mild reduction but tends to segregate out of the pore system at higher reduction temperatures or during CO oxidation. Both composites were found to be highly active in CO oxidation, with 50% conversion at 460–475 K after activation of the unreduced catalysts in the (net oxidizing) feed. Striking differences in this activation process between Pt/MCM-48 and Pt/TiO₂–MCM-48 suggest that the precursor reduction is influenced by an interaction with the TiO₂ component in the latter.     

Tribological properties of surface modified nano-alumina/epoxy composites

Nano-sized Al₂O₃ particles grafted with polystyrene or polyarcrylamide were employed as fillers for fabricating epoxy based composites. Curing habit, mechanical properties and tribological performance revealed by sliding wear tests of the composites were investigated. The experimental results indicated that the nanoparticles accelerate curing of epoxy, increase composites' impact strength and decrease wear rate and frictional coefficient of the composites. The surface modification by means of grafting polymerization can further enhance the properties improvement of epoxy due to the increased filler/matrix interfacial interaction. Compared to frictional coefficient, wear rate of epoxy can be decreased more remarkably by the addition of nano-alumina when rubbing against steel. The wear mode changes from severe peeling off of unfilled epoxy to mild micro-ploughing in the case of nano-alumina filled composites.     

MCM-41 填加量与偶联修饰对复合材料拉伸性能的影响

通过溶液共混法制备出MCM-41/ 环氧树脂、偶联修饰MCM-41/ 环氧树脂纳米复合材料。研究了填充MCM-41 介孔分子筛颗粒的偶联修饰以及不同的填充颗粒含量对分散性和复合材料拉伸性能的影响。结果表明: 在MCM-41/ 环氧树脂纳米复合材料中, MCM-41 仍保持着长程有序的孔道结构。修饰后的MCM-41 变成亲油性, 有利于增强颗粒与环氧树脂间的界面结合和纳米网络结构的形成, 使MCM-41 颗粒更能均匀分散在聚合物基体中, 提高复合材料的拉伸性能。修饰后的MCM-41 填加量为2.5 %(质量分数) 时, 拉伸强度达到最大值,比基体树脂提高99.2 % , 杨氏模量提高了110 %。      

Simultaneous epoxy grafting on SiO2 nanoparticles during bead milling and their effects on the mechanical properties of epoxy-based composites

Epoxy resin-grafted SiO₂ nanoparticles stabilized in toluene were successfully designed by the simultaneous surface modification of SiO₂ nanoparticles during bead milling which involves the adsorption of polyethyleneimine-oleic acid complex (PEI-OA) and epoxy resin grafting to the free amine groups of PEI-OA (PEI-OA-Epoxy). The effectiveness of epoxy grafting on the properties of the SiO₂/epoxy based nanocomposites were investigated using a bead-milled SiO₂/toluene suspension stabilized with PEI-OA, PEI-OA-Epoxy, and a complex of PEI and an anionic surfactant comprising an epoxy-soluble polyethylene glycol-based chain (PEI-AS). While SiO₂ nanoparticles were pulverized with similar sizes (c.a. 126–171 nm) and stabilized in toluene with any of the three surface modifications, PEI-OA-stabilized SiO₂ nanoparticles aggregated during processing epoxy-based composites. PEI-AS- and PEI-OA-Epoxy-stabilized SiO₂ nanoparticles maintained their dispersion stability, however, the epoxy composites with PEI-OA-Epoxy-stabilized SiO₂ nanoparticles exhibited better material properties, such as increase in the strain at fracture and higher T_g.     

超临界CO2方法制备环氧树脂/纳米介孔MCM-41复合材料

采用超临界方法先将环氧树脂低聚物引入介孔MCM-41的一维孔道内,再与基体溶液共混,制备出环氧树脂／MCM-41纳米复合材料．研究了复合材料的拉伸性能与填充复合颗粒含量的关系．结果表明,超临界的方法确实可将环氧树脂低聚物分子链引入到MCM-41的孔道,并占据孔道的绝大多数空间．环氧基团进入介孔的孔道中并使孔口处的环氧基团与基体环氧产生了较强的界面相互作用,增加了两者的相容性．填充含量较低的复合颗粒就能提高复合材料的拉伸性能．     

Influence of functional silanes on hydrophobicity of MCM-41 synthesized from rice husk

Mesoporous molecular sieve MCM-41 was synthesized from rice husk and rice husk ash, called RH-MCM-41 and RHA-MCM-41. The sol–gel mixtures were prepared with molar composition of 1.0 SiO₂: 1.1 NaOH: 0.13 CTAB: 0.12 H₂O. After calcination, the polarity of MCM-41 still remained on its surface due to the existence of some silanol groups. In this study, both RH-MCM-41 and RHA-MCM-41 were silylated with two different functional silanes trimethylchlorosilane (TMCS) and phenyldimethylchlorosilane (PDMS) in order to reduce the surface polarity. The efficiency of silylation was determined based on the amount of moisture adsorbed using thermogravimetric analysis (TGA). The structure of silylating agents and silica templates were found to be important parameters affecting the hydrophobic property of the MCM-41 surface. The post-grafting silylation with aliphatic silane can decrease the surface polarity better than that with aromatic silane, probably due to less sterric hindrance effect. Thus, the surface hydrophobicity of MCM-41 can be improved by the silylation of small molecular silane on RH-MCM-41.     

Microstructure and mechanical properties of polypropylene/polystyrene blend filled with as-synthesized MCM-41 prepared by melt-compounding

Nano-sized as-synthesized MCM-41 particle, whose pore channels and outer surface full of organic CTAB template, was used as compatibilizers for immiscible polypropylene (PP)/polystyrene (PS) blends. In this paper, the solid structure SiO₂ was selected to compare with as-synthesized MCM-41 in properties of PP/PS blend. The mechanical results showed that tensile strength of the blend was increased by 32% and the impact strength was increased by 41.1% by addition low content of as-synthesized MCM-41 compared to pure PP/PS. The presence of SiO₂ in the blend cannot improve the mechanical properties obviously. SEM indicated that incorporation of as-synthesized MCM-41 into PP/PS blend can act as compatibilizer, which resulted in a decreased particle size of dispersion phase together with morphological evidence of interfacial adhesion. However, with the presence of SiO₂, 1%, 3%, in the blend, the interface did not show clear change compared with the PP/PS blend.     

Compatibilizing effect of mesoporous fillers on the mechanical properties and morphology of polypropylene and polystyrene blend

Polypropylene(PP)/Polystyrene(PS) (PP/PS = 80/20) blend with different types of fillers were prepared by using melt method. Four different types of fillers, namely mesoporous MCM-41 (without template), nano-SiO₂, Polymethylmethacrylate (PMMA)/MCM-41 and PMMA/SiO₂ were considered. For PMMA/MCM-41 filler, the synthesis of the filler consisting of entrapped strand of PMMA within the pores of mesoporous MCM-41 (without template) was described. The mechanical properties of the blend determined as the nano-fillers contents and the different types of blend were found to vary with the different interface between fillers and the matrix. SEM revealed a good interaction between the matrix phases and PMMA/MCM-41 or MCM-41 (without template). The decreased T_g of PS implied that the good adhesion between PP and PS blend was obtained by adding PMMA/MCM-41 nano-filler.     

Glass–ceramic scaffolds containing silica mesophases for bone grafting and drug delivery

Glass–ceramic macroporous scaffolds were prepared using glass powders and polyethylene (PE) particles of two different sizes. The starting glass, named as Fa-GC, belongs to the system SiO₂–P₂O₅–CaO–MgO–Na₂O–K₂O–CaF₂ and was synthesized by a traditional melting-quenching route. The glass was ground and sieved to obtain powders of specific size which were mixed with PE particles and then uniaxially pressed in order to obtain crack-free green samples. The compact of powders underwent a thermal treatment to remove the organic phase and to sinter the Fa-GC powders. Fa-GC scaffolds were characterized by means of X-Ray Diffraction, morphological observations, density measurements, image analysis, mechanical tests and in vitro tests. Composite systems were then prepared combining the drug uptake-delivery properties of MCM-41 silica micro/nanospheres with the Fa-GC scaffold. The system was prepared by soaking the scaffold into the MCM-41 synthesis batch. The composite scaffolds were characterized by means of X-Ray Diffraction, morphological observations, mechanical tests and in vitro tests. Ibuprofen was used as model drug for the uptake and delivery analysis of the composite system. In comparison with the MCM-41-free scaffold, both the adsorption capacity and the drug delivery behaviour were deeply affected by the presence of MCM-41 spheres inside the scaffold.     

ZnO nanoparticles supported on mesoporous MCM-41 and SBA-15: a comparative physicochemical and photocatalytic study

A simple solvothermal impregnation method was used to prepare ZnO nanoparticles supported on MCM-41 and SBA-15. X-ray powder diffraction, N₂ adsorption–desorption, Electron Probe Micro Analysis (EPMA), and UV–vis spectroscopy were used to characterize the prepared materials. The influence of the ZnO loading of different supports on the structural characteristics and the photocatalytic activity toward degradation of methylene blue in water under ultraviolet irradiation were investigated. Wide angle X-ray diffraction and UV–vis Diffuse Reflectance confirmed the existence of ZnO phase. A much smaller influence of impregnation with ethanolic zinc salt solution on the porosity was observed for SBA-15 compared with MCM-41. Finally, the adsorption and photocatalytic activity of the ZnO/mesoporous materials depend on porous characteristics of the support materials.     

Improvement of epoxy resin properties by incorporation of TiO2 nanoparticles surface modified with gallic acid esters

Epoxy resin/titanium dioxide (epoxy/TiO₂) nanocomposites were obtained by incorporation of TiO₂ nanoparticles surface modified with gallic acid esters in epoxy resin. TiO₂ nanoparticles were obtained by acid catalyzed hydrolysis of titanium isopropoxide and their structural characterization was performed by X-ray diffraction and transmission electron microscopy. Three gallic acid esters, having different hydrophobic part, were used for surface modification of the synthesized TiO₂ nanoparticles: propyl, hexyl and lauryl gallate. The gallate chemisorption onto surface of TiO₂ nanoparticles was confirmed by Fourier transform infrared and ultraviolet–visible spectroscopy, while the amount of surface-bonded gallates was determined using thermogravimetric analysis. The influence of the surface modified TiO₂ nanoparticles, as well as the length of hydrophobic part of the gallate used for surface modification of TiO₂ nanoparticles, on glass transition temperature, barrier, dielectric and anticorrosive properties of epoxy resin was investigated by differential scanning calorimetry, water vapor transmission test, dielectric spectroscopy, electrochemical impedance spectroscopy and polarization measurements. Incorporation of surface modified TiO₂ nanoparticles in epoxy resin caused increase of glass transition temperature and decrease of the water vapor permeability of epoxy resin. The water vapor transmission rate of epoxy/TiO₂ nanocomposites was reduced with increasing hydrophobic part chain length of gallate ligand. Dielectric constant of examined nanocomposites was influenced by gallate used for the modification of TiO₂ nanoparticles. The nanocomposites have better anticorrosive properties than pure epoxy resin, because the surface modified TiO₂ nanoparticles react as oxygen scavengers, which inhibit steel corrosion by cathodic mechanism.     

Synthesis and characterization of Co-Fe Prussian blue nanoparticles within MCM-41

A Prussian blue analogue, K_0.84Co_1.08[Fe(CN)₆] is prepared by reaction between [Fe(CN)₆]³⁻ in aqueous solution and ion-exchanged Co²⁺ in the channels of MCM-41. Powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-vis absorption spectroscopy and magnetic measurements were employed to characterize the product. The results show that the Prussian blue analogue is in nanoparticles within the channels and the hexagonal phase of MCM-41 remains intact during the reactions. A particle size effect on optical and magnetic properties of the nanoparticles was observed.     

Effect of acid and TETA modification on mechanical properties of MWCNTs/epoxy composites

Acid treatment and triethylene-tetramine (TETA) modification of multi-walled carbon nanotubes (MWCNTs) purposing to attain better dispersibility and stronger interfacial bonding between MWCNTs and epoxy matrix have been carried out in this paper. The epoxy and MWCNTs/epoxy composites were produced by cast molding method. Stress–strain curves show that TETA-MWCNTs/epoxy hold the greatest toughness of all samples with 0.5 wt.% nanoparticles. The Young’s modulus of TETA-MWCNTs/epoxy has a significant increase about 38% compared to the neat epoxy, while the Young’s modulus of unmodified MWCNTs/epoxy or acid-modified MWCNTs/epoxy has a bit of decrease. Tensile and impact strength tests reflect that TETA-MWCNTs reinforced epoxy composites have an obvious improvement of tensile strength about 30% and an enhancement of impact strength over 34% compared to the pure epoxy composites with only 0.5 wt.% loading of TETA-MWCNTs. Scanning electron microscopy images of fractured surface of MWCNTs/epoxy indicate homogeneous dispersibility of TETA-MWCNTs and strong interfacial adhesion between the TETA-MWCNTs and the epoxy in the MWCNTs/epoxy composite.     

Preparation of SnO2 nanoparticles by hard template method for high selectivity gas sensors

In this paper, SnO2 nanoparticles were synthesized by the impregnation method with SnCl2 x 2H2O as the inorganic precursor and mesoporous silica MCM-41 as the hard template. The physical and chemical properties of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The SnO2 nanoparticles grew into the ordered channels of MCM-41. After removing the silica template, the products exhibited good rutile structure. The gas sensing properties of the SnO2 nanoparticles were also studied. The results indicated that these SnO2 nanoparticle sensors showed high selectivity towards ethanol.     

Functionalization of mesoporous MCM-41 for the delivery of curcumin as an anti-inflammatory therapy

In this study, mesoporous silica nanoparticles (MSNs) composed of MCM-41 were synthesized and modified with amine groups (i.e., NH₂) to form NH_2/MCM-41, which was loaded with curcumin (CUR) to form CUR@NH₂/MCM-41 to create an efficient carriers in drug delivery systems (DDSs). The three samples (i.e., pure MCM-41, NH₂/MCM-41, and CUR@NH₂/MCM-41) were characterized using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transition electron microscopy (TEM), and a thermogravimetric analyzer (TGA). The study investigated the effect of the carrier dose, CUR concentration, pH, and contact time on the drug loading efficiency (DLE%) by adsorption. The best DLE% for MCM-41 and NH₂/MCM-41 was found to be 15.78 and 80%, respectively. This data demonstrated that the Langmuir isotherm had a greater correlation coefficient (R²) of 0.9840 for MCM-41 and 0.9666 for NH₂/MCM-41 than the Freundlich and Temkin isotherm models. A pseudo-second-order kinetic model seems to fit well with R² = 0.9741 for MCM-41 and R² = 0.9977 for NH₂/MCM-41. A phosphate buffer solution (PBS) with a pH of 7.4 was utilized to study CUR release behavior. As a result, the full release after 72 h was found to have a maximum of 74.1% and 29.95% for pure MCM-41 and NH₂/MCM-41, respectively. The first-order, Weibull, Hixson-Crowell, Korsmeyer-Peppas, and Higuchi kinetic release models were applied to releasing CUR from CUR@MCM-41 and CUR@NH₂/MCM-41. The Weibull kinetic model fit well, with R² = 0.944 and 0.96912 for pure MCM-41 and NH₂/MCM-41, respectively.     

Mesoporous Ti-MCM-41 materials as photodegradation catalysts of 2,4,6-trichlorophenol in water

Titanium-modified MCM-41 type mesoporous silica materials were prepared by hydrothermal [Ti-MCM-41(HT)], sol–gel [Ti-MCM-41(SG)] and post-synthesis impregnation [TiO₂/MCM-41] methods. The materials were characterized and tested as photocatalysts in the oxidative degradation reaction of 2,4,6-trichlorophenol (2,4,6-TCP) in water. The catalysts showed high initial activity. The produced acetate and chloride ions were found to inhibit the degradation reaction. The Ti-MCM-41(HT) sample showed higher overall activity than the Ti-MCM-41(SG) catalyst. One of the probable reasons for this is the difference in the distribution of the active sites that determines the rates of electron (e⁻)–hole (h⁺) recombination within the photoactive species. The HT preparation was found to contain silica-bound titania in higher dispersion, while the SG preparation contained also polymerized species with Ti–O–Ti bonds.     

不同偶联剂对介孔分子筛MCM-41的表面修饰及对MCM-41/环氧树脂性能的影响

使用2种硅烷偶联剂(KH550和KH792)对介孔分子筛MCM-41进行表面改性,采取氮气吸附-脱附、FTIR和TGA等进行表征,并采用原位聚合法制备了MCM-41/环氧树脂复合材料,研究了偶联剂种类和MCM-41用量等对复合材料固化过程及性能的影响。结果表明:硅烷偶联剂可与MCM-41表面的硅羟基反应,在分子筛内外表面接枝上功能化基团。经表面修饰的MCM-41比表面积下降为原来的1/5,KH550在MCM-41表面接枝率仅为KH792的一半。KH550与MCM-41外表面反应得更充分,KH792对MCM-41孔道内壁的修饰效果更强。固化动力学结果表明:KH792的功能化基团有伯胺和仲胺,与环氧树脂具有更高的反应活性,但不利于环氧大分子进入孔道,仅以球形粒子的形式添加在环氧树脂中;KH550表面修饰的MCM-41可使环氧大分子进入孔道内形成互穿结构。KH550表面修饰体系更多体现出MCM-41多孔的特征,形成了有机-无机互穿结构的复合体系,大幅度提高了储能模量和玻璃化转变温度。KH792表面修饰体系则呈常规球形纳米粒子的特征,其储能模量和玻璃化转变温度较纯环氧树脂有所提高但幅度不大。