Solution Impregnation Method Research Articles

TPO/TPD study on the activation of silica supported cobalt catalyst

Silica supported cobalt catalysts have been prepared using urea containing cobalt nitrate solution impregnation method, which can give high loading Co3O4 with relatively smaller crystallite size. Compared to the conventional impregnation method, the catalyst prepared with urea added to the cobalt nitrate solution provides higher activity for CO conversion and C5+ selectivity. To optimize the catalyst activation and simulate the industrial activation, TPO–TPR cycle treatment with or without steam has been applied to the prepared catalysts under various conditions. It is shown that reduction of pure hydrogen with high flow rate leads to a sharp temperature rise in the catalyst bed, which results in the sintering of the cobalt particles. A slow temperature rise with dilute hydrogen helps stabilize the cobalt particles, and the cycle treatment of the catalyst using TPO–TPR without steam induction has little effect on the size of cobalt particles. When steam is included in the reduction stream with hydrogen the TPR–TPO cycle treatment can help increase the Co dispersion, which increases the catalyst activity and selectivity to C5+.

Molding of PBO fabric reinforced thermoplastic composite to achieve high fiber volume fraction

In fiber‐reinforced plastic materials, the fiber volume fraction is one of the most important parameters, and it strongly influences the composite properties. However, it is hard to improve impregnation and the fiber volume fraction in fiber‐reinforced thermoplastics because thermoplastic resins have high melt viscosities. This study explored a reformative solution impregnation method for molding fabric‐reinforced thermoplastic composites with a high fiber volume fraction. The fiber volume fraction was significantly increased, to 60%, which is equal to that of fiber‐reinforced thermosetting plastic materials. A comparison indicated that a fiber‐reinforced thermoplastic and a fiber‐reinforced thermosetting plastic with the same reinforcing fiber had similar tensile properties and that the proposed molding method is effective in thermoplastic composite manufacture. POLYM. COMPOS., 34:953–958, 2013. © 2013 Society of Plastics Engineers

Improved reactivity of large coal particles by K2CO3 addition during steam gasification

In this study, the excess solution impregnation method was used to impregnate large coal particles (5 and 10mm) with K2CO3, and the effect of the additive on steam gasification reactivity was investigated. A washed bituminous, medium rank-C Highveld coal, with an ash content of 12.6wt.% (air-dried basis), was used for experimentation. The excess solution method was used to impregnate coal particles with the selected additive, K2CO3, and results from XRF analysis indicated that the potassium loading increased from 0.05wt.% (raw coal) up to 0.83wt.% (impregnated coal), on a coal basis. The potassium-impregnated large coal particles were used for low temperature (800–875°C) steam gasification experiments. Results obtained for the reactivity of the parent coal were compared to that of the impregnated coal, which indicated that the addition of K2CO3 increased the reaction rate of large coal particles by up to 40%. It was also found that the addition of K2CO3 decreased the activation energy, from 191kJ/mol (raw coal) to 179kJ/mol (impregnated coal).

Highly flexible, transparent cellulose composite films used in UV imprint lithography

Highly flexible, optically transparent epoxy resin/cellulose composites were prepared by using the solution impregnation method firstly and then thermal cured. The composite contained 60 wt% resin was still mechanically stable and flexible, and it integrated the merits of cellulose and resin, but the highly hydrophilic behavior of cellulose has been reduced. Contact angle measurements with water demonstrated that the composite films had obvious hydrophobic properties, and a decrease in the water uptake and the permeability towards water vapor gas was also observed. The transmittance of the composite films at 550 nm was about 85–88 %. The thermal and mechanical properties of the composite films were improved. Moreover, the composite films could be used in UV imprint lithography for circuit, and the definition could be compared with that of widely used glass plate.

Highly ordered TiO2nanostructures by sequential vapour infiltration of block copolymer micellar films in an atomic layer deposition reactor

Sequential vapour infiltration operated in an atomic layer deposition (ALD) reactor was used to controllably deliver precursors of TiO2 into the cores of micellar films of the amphiphilic block copolymer, poly(styrene-block-4-vinylpyridine) (PS-b-P4VP). Vaporized precursors diffused through the PS corona and were exclusively enriched into the P4VP cores. Arrays of hexagonally arranged TiO2 nanoparticles were produced by burning off the polymeric components after UV-crosslinking the TiO2-incorporated micellar films. The size of the TiO2 particles was tunable simply by repeating the cycle numbers, and the interparticle distances were dictated by the distances between neighboring micelles of the original micellar films and could be changed by using block copolymers with different molecular weights. Compared to the extensively used solution impregnation method, the sequential vapour infiltration strategy was distinct in terms of the simplicity accompanying the “dry” process and precise control in particle sizes. More importantly, growth of TiO2 particles inside micellar cores was not limited by the available pyridyl groups as TiO2 continued to grow on preformed TiO2 particles after the pyridyl groups were consumed. Consequently, the particle sizes could be tuned in a much broader range compared to the solution impregnation method in which the particle size was limited by the saturation of impregnated precursors bound to the pyridyl groups. Furthermore, we demonstrated the versatility of this sequential vapour infiltration strategy in producing nanostructures with different morphologies and chemical compositions.

CO–PROX reactions on copper cerium oxide catalysts prepared by melt infiltration

A series of copper cerium oxide catalysts was prepared by melt infiltration routes using silica hollow spheres (SHS) as the support material. Their catalytic activity in CO oxidation and preferential oxidation of CO in H2 stream (PROX) strongly depend on the Cu/Ce ratio. Lower ratios resulted in higher activity, indicating that finely dispersed CuO clusters that strongly interact with ceria are the active sites. The highest activity is found for an atomic Cu/Ce ratio of 1/8. The catalysts prepared by melt infiltration are more active than their counterparts prepared by conventional solution impregnation methods. The difference is attributed to the higher proportion of finely dispersed CuO clusters strongly interacting with ceria in the melt infiltrated catalysts.

Entrapment of metal nanoparticles within nanocages of mesoporous silicas aided by co-surfactants

We demonstrated an efficient approach for in situ encapsulation of metal nanoparticles (NPs) into nanocages of mesoporous silicas using a co-surfactant as the transportation medium. By using this approach, colloidal Pt and Au NPs were successfully encapsulated into the nanocages of cagelike mesoporous silicas (CMS) and FDU-12 using co-surfactants butanol and mesitylene (TMB) as the transportation medium, respectively. The prepared Pt/CMS catalysts are active and highly selective in the hydrogenation of chloronitrobenzene (CNB) to the corresponding chloroaniline (CAN). The catalyst prepared by the in situ method is superior to the catalyst prepared by the traditional solution impregnation method. This work provides a new approach for the synthesis of the mesoporous materials with encapsulated metal NPs.

A solid oxide cell yielding high power density below 600 °C

Here we report solid oxide cells with thin strontium- and magnesium-doped lanthanum gallate electrolytes that yield power densities of 1.06 W cm−2 at 550 °C and 0.81 W cm−2 at 500 °C when operated on humidified hydrogen and ambient air. Cost-effective ceramic processing and chemical solution impregnation methods were utilized, yielding a dual micron- and nano-scale architecture that is essential for achieving good low-temperature performance.

Surface Plasmon Enhanced Photoluminescence of Rhodamine B Confined in SBA15

Rhodamine B dye (RB) has been introduced into the mesoporous silica (SBA15) and Ag anchored mesoporous silica by applying solution impregnation method. Surface treatment of SBA15 with 3-aminopropyltrimethoxysilane (APTMS) facilitates selective anchoring of the RB molecules on SBA15. The photoluminescence spectra of RB confined within SBA15 indicates higher emission intensity, than that of the RB solid, particularly in the presence of Ag nanoparticles. The significant enhancement in photoluminescence intensity is attributed to the local enhancement of the optical fields near the molecules by interactions with silver plasmons.

Aligned electrospun cellulose fibers reinforced epoxy resin composite films with high visible light transmittance

Uniaxially oriented cellulose nanofibers were fabricated by electrospinning on a rotating cylinder collector. The fiber angular standard deviation (a parameter of fiber orientation) of the mats was varied from 65.6 to 26.2o by adjusting the rotational speed of the collector. Optically transparent epoxy resin composite films reinforced with the electrospun cellulose nanofibrous mats were then prepared by the solution impregnation method. The fiber content in the composite films was in the range of 5–30 wt%. Scanning electron microscopy studies showed that epoxy resin infiltrated and completely filled the pores in the mats. Indistinct epoxy/fiber interfaces, epoxy beads adhering on the fiber surfaces, and torn fiber remnants were found on the fractured composite film surfaces, indicating that the epoxy resin and cellulose fibers formed good interfacial adherence through hydrogen-bonding interaction. In the visible light range, the light transmittance was 88–92% for composite films with fiber loadings of 16–32 wt%. Compared to the composite films reinforced with 20 wt% randomly oriented fibers, the mechanical strength and Young’s modulus of the composite films reinforced with same amount of aligned fibers increased by 71 and 61%, respectively. Dynamical mechanical analysis showed that the storage moduli of the composite films were greatly reinforced in the temperature above the glass transition temperature of the epoxy resin matrix.

Catalytic Wet Air Oxidation of Oxalic Acid Using Ceria-promoted Pt/Al2O3

Catalytic wet air oxidation of oxalic acid using ceria-promoted Pt/Al2O3 catalyst was studied in a glass reactor operated at atmospheric pressure. The catalyst was prepared by the excess solution impregnation method and the catalyst characterization was performed using scanning electron microscopy, nitrogen adsorption, hydrogen chemisorption and thermogravimetric analysis techniques. The effect of initial concentration of oxalic acid, air flow rate, reaction temperature and ceria loading on oxidation of oxalic acid was investigated. The activation energy was found to be 42 kJ/mol and a rate equation was proposed for the oxidation of oxalic acid. Catalyst deactivation and regeneration were studied. It was noticed that the presence of ceria reduced the deactivation of the Pt/Al2O3 catalyst.

Enhanced electrochemical performance of solution impregnated La 0.8Sr 0.2Co 0.8Ni 0.2O 3− δ cathode for intermediate temperature solid oxide fuel cells

Solution impregnated La 0.8Sr 0.2Co 0.8Ni 0.2O 3 + Gd-doped CeO 2 (LSCN + GDC) cathodes for intermediate temperature solid oxide fuel cells (IT-SOFC) are prepared and their electrochemical properties are evaluated and compared with the conventional LSCN cathodes. The results indicate that the cathode performance can be enhanced by the presence of the nanosized microstructure produced with the solution impregnation method. It is determined that the amount of LSCN loading in the LSCN + GDC composite cathode needs to be higher than 35 wt% in order to achieve a performance superior to that of the conventional LSCN cathode. The optimum amount of LSCN loading is in the range of 45–55 wt% with an activation energy near 1.32 eV for oxygen reduction. At temperatures between 600 and 750 °C, the polarization resistance of the 55 wt% LSCN loaded LSCN + GDC cathode is in the range of 1.07 and 0.08 Ω cm 2, which is only about one half of that for the conventional cathode.

Effects of fiber surface chemistry and size on the structure and properties of poly(vinyl alcohol) composite films reinforced with electrospun fibers

Electrospun cellulose nanofibrous mats (CNM) and cellulose acetate nanofibrous mats (CANM) reinforced poly(vinyl alcohol) (PVA) composites films were fabricated through solution impregnation method. The effect of fiber size and surface structure on the fiber/PVA interfacial adhesion, and consequently on the macroscopic properties such as optical, tensile, and dynamical mechanical properties of composite films were studied. The fractured surface morphology was examined by scanning electron microscopy. It showed that interfacial debonding happened to CANM/PVA composites, whereas good interfacial adhesion was formed for CNM/PVA composites. The visible light transmittance and the mechanical properties of PVA composite films were evaluated. CNM/PVA showed higher optical transparency than CANM/PVA composite films. Additionally, the light transmittance of CNM/PVA was insensitive to temperature. Dynamical mechanical analysis demonstrated that the storage moduli of electrospun fiber/PVA composite films were obviously improved in the glass–rubber transition and rubbery zone, but more significantly in the melting zone.

Effects of fiber surface chemistry and roughness on interfacial structures of electrospun fiber reinforced epoxy composite films

AbstractThis work reported the effect of surface chemistry and roughness of electrospun fibers on fiber/matrix interfacial structures and the resultant macroscopical properties of composite films. Three types of fibrous mats composed of ultrafine fibers, that is, cellulose acetate (CANM), polyurethane (PUNM), and cellulose acetate/polyurethane composite (CAPUNM) were fabricated through electrospinning. CA fiber surfaces were rough with many hydroxyl groups; PU fiber surfaces were smooth, whereas CAPU composite fibers exhibited cocontiuous structure with rough surfaces. The fiber‐reinforced epoxy composite films were prepared by the solution impregnation method. The fractured surfaces of the composites were analyzed by scanning electron microscopy. Severe interfacial debonding and fiber pullouts were observed for PUNM/epoxy composites, while strong interfacial adhesion was formed for CANM/epoxy and CAPUNM/epoxy composites. The interfacial structure played important roles in the visible light transmittance of the composite films. For example, CANM/epoxy films showed the best optical property, whereas PUNM/epoxy films displayed the poorest light transmitting property and were translucent. The interfacial structure also affected the mechanical properties of the composites. The mechanical strength of fibrous mats followed an increasing order of CANM < CAPUNM < PUNM, but the mechanical strength of the composite films was in a reverse order, that is, CANM/epoxy > CAPUNM/epoxy > PUNM/epoxy. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Winding of High Performance Thermoplastic PPESK Composites Using on-Line Solution Impregnation and <i>In Situ</i> Consolidation

A novel filament winding process technology has been realized which allows to combine on-line solution impregnation with in-situ consolidation for a kind of high performance thermoplastic, poly (phthalazinone ether sulfone ketone) (PPESK). This technology solved the common problem of impregnating a large number of slender filaments with a highly viscous polymer melt which usually existed in thermoplastic manufacturing. During the winding process, the high-quality carbon prepreg tapes were firstly obtained on-line by using solution impregnation method, and then an arc electric heater was utilized to ensure the adaptable preheating and processing temperature. With the help of heat and tensile force, the intimate interlaminar contact was achieved.

Electrospun Nylon Nanofibers as Effective Reinforcement to Polyaniline Membranes

This research demonstrates that a nylon nanofiber (NNF) mat can be an effective mechanical reinforcement to polyaniline (PANI) thin films. Nanofibers of ca. 250 nm diameter were produced by electrospinning of a nylon 6 solution in formic acid. Scanning electron microscopy showed that the solution impregnation method utilized was effective to embed the nanofibers into the PANI matrix. The effectiveness of NNFs as a mechanical reinforcement of a PANI thin film was assessed via dynamic mechanical analysis in tension mode. The as-cast PANI films displayed a tensile dynamic modulus, E', of ca. 0.65 GPa at room temperature. Scanning in the temperature showed that the PANI film has a usage temperature of up to about 80 degrees C, with this being limited by its glass transition temperature, and over this temperature range, the elastic modulus was nearly independent of the temperature. On the other hand, the PANI-NNF composite displayed a significantly higher tensile modulus at room temperature (1.1 GPa) and its usage temperature was extended up to just over 200 degrees C, with this being limited by the melting transition of nylon 6 (at 220 degrees C). The results therefore showed that the NNF mat increased the usage temperature of PANI films over 100 degrees C, opening up applications for PANI membranes.

Development of Recycled Polypropylene Matrix Composites Reinforced with Waste Jute Caddies

Introduction of reinforcing fillers in RPP matrix help to enhance the properties of the matrix. In this study, waste jute fibers called jute caddies have been used as the filler material to RPP and their properties have been studied. The composites have been prepared by solution impregnation method. A silane coupling agent has been used in two weights (2 and 6 wt%) to enhance the interaction between the non-polar PP and the polar jute fiber wastes. Treatment with 6% VTMO enhanced the mechanical properties significantly. Thermal stability was also enhanced after treatment with coupling agent. SEM investigations revealed the fiber/matrix bond at the interface.

Mechanical, moisture absorption, and biodegradation behaviours of bacterial cellulose fibre-reinforced starch biocomposites

In this work, bacterial cellulose (BC) nanofibres were used as the biodegradable reinforcement. The BC nanofibres were incorporated in the starch plasticised with glycerol via a solution impregnation method. Tensile properties of the BC/starch biocomposites were tested and compared with those of the unreinforced starch. Moisture absorption of the biocomposites under 75% RH at 25 °C was analysed. The kinetics of sorption–diffusion process was investigated and typical kinetic parameters D, k, and M ∞ were determined. Additionally, the BC/starch biocomposite (15.1 wt.% BC) and starch were submitted to biodegradation by soil burial experiments in perforated boxes. Tensile strength after exposure to moisture and microorganism attacks was measured. It is found that the moisture sorption mechanism in the BC/starch biocomposites follows a Fickan diffusion mode. The presence of BC nanofibres improves the tensile properties and the resistance to moisture and microorganism attacks. The mechanisms behind these phenomena are discussed in this paper.

Adsorption of carbon dioxide using impregnated activated carbon promoted by Zinc

The effect of impregnation of activated carbon with Cr 2O and Fe 2O 3 and promotion by Zn 2+ on its adsorptive properties of carbon dioxide was studied using a volumetric adsorption apparatus at ambient temperature and low pressures. Slurry and solution impregnation methods were used to compare CO 2 capture capacity of the impregnated activated carbon promoted by Zinc. The obtained adsorption isotherms showed that amount of CO 2 adsorbed on the samples impregnated by Cr 2O was increased about 20% in compare to raw activated carbon. The results also showed that Fe 2O 3 was not an effective impregnating species for activated carbon modification. Moreover slurry impregnation method showed higher CO 2 adsorption capacity in comparison with solution impregnation method. Samples prepared by co-impregnation of two metal species showed more adsorption capacity than samples impregnated by just one metal species individually. Washing the impregnated samples by metal oxide resulted in 15% increase in CO 2 adsorption capacities of activated carbons which can be attributed to the metal oxides removal covering the adsorption surface. Decreasing impregnation temperature from 95 to 25 °C in solution method showed a significant increase in CO 2 adsorption capacity. Sips equation was found a suitable model fitting to the adsorption data in the range studied.

Methanol crossover through PtRu/Nafion composite membrane for a direct methanol fuel cell

This study examined methanol crossover through PtRu/Nafion composite membranes for the direct methanol fuel cell. For this purpose, 0.03, 0.05 and 0.10 wt% PtRu/Nafion composite membranes were fabricated using a solution impregnation method. The composite membrane was characterized by inductively coupled plasma-mass spectroscopy and thermo-gravimetric analysis. The methanol permeability and proton conductivity of the composite membranes were measured by gas chromatography and impedance spectroscopy, respectively. In addition, the composite membrane performance was evaluated using a single cell test. The proton conductivity of the composite membrane decreased with increasing number of PtRu particles embedded in the pure Nafion membrane, while the level of methanol permeation was retarded. From the results of the single cell test, the maximum performance of the composite membrane was approximately 27% and 31% higher than that of the pure Nafion membrane at an operating temperature of 30 and 45 °C, respectively. The optimum loading of PtRu was determined to be 0.05 wt% PtRu/Nafion composite membrane.The PtRu particles embedded in the Nafion membrane act as a barrier against methanol crossover by the chemical oxidation of methanol on embedded PtRu particles and by reducing the proton conduction pathway.