Unique Textural Properties Research Articles

Design of mesostructured H3PW12O40-silica materials with controllable ordered and disordered pore geometries and their application for the synthesis of diphenolic acid

A series of mesostructured H3PW12O40-silica materials were developed by using a single step co-condensation technique in the presence of nonionic oligomeric surfactant, C18H37(OCH2CH2)10OH (C18EO10, Brij76). By tuning the composition ratios of the starting precursors (mainly the molar ratios of water to the other materials) and the preparation conditions, the materials exhibited ordered two-dimensional (2D) hexagonal p6mm, three-dimensional (3D) hexagonal P63/mmc, and 3D disordered sponge-like pore geometries, respectively. The materials possessed unique textural properties including very large BET surface area (590–1050 m2 g−1), very high porosity (0.4–1.3 cm3 g−1), and well-distributed pore diameter (3.0–5.4 nm). As a novel type of reusable solid acid catalyst, as-prepared materials were applied for the synthesis of diphenolic acid (DPA) from biomass-derived platform molecule, levulinic acid (LA), under solvent-free condition, and special attention was paid to investigating the influences of the structural orderings, pore geometries, H3PW12O40 loadings, and template removal methods on the reactivity and selectivity of H3PW12O40-silica materials to the target reaction.

Structure–fracture relationships in gas-filled gelatin gels

Food aeration has become one of the fastest growing unit operations practiced in the food industry. Dispersed air (or other gases) provides an additional phase within the gel that may accommodate new textural and functional demands. This paper addresses the relationships between structural characteristics and fracture properties of gas-filled gelatin gels ( GGG), and compare these properties with those of control gelatin gels ( CGG). Three gases were used in the fabrication of GGG: air, nitrogen and helium. Experimental methods to determine density, gas hold-up, bubble sizes and bubble size distributions as well as fracture properties of GGG are presented. Increasing protein concentration produced higher density, lower gas hold-up and decreased polydispersity of bubbles due to its effect on increased solution viscosity. Type of gas affected density and gas hold-up due to the different diffusivities of gases and structures (bubble size, size distribution and number of bubbles per area) formed in GGG. Fracture values increased for both GGG and CGG with increasing protein concentration for the three gases used. GGG were weaker and less ductile than CGG, the decrease in stress and strain at fracture being between 70 and 80%, and 40 and 65%, respectively. A power law relationship ( σ f = 2.73 × 10 −12 ρ G 4.76) was found between the fracture stress and gel density for the three gases studied. This study shows that the presence of bubbles in gel-based food products results in unique textural properties conferred by the additional gaseous phase.

Synthesis and structural characteristics of highly graphitized carbon nanofibers produced from the catalytic decomposition of ethylene: Influence of the active metal (Co, Ni, Fe) and the zeolite type support

In order to study the influence of the metal phase in the carbon yield and structural characteristics of carbon nanofibers (CNFs) synthesized by CVD over supported catalysts, different catalysts were prepared using iron, cobalt and nickel as active metal and zeolites Y and mordenite as support. The results showed that the metal precursor produced a great influence on the catalytic activity, fact that could be explained in according to the different solubility of carbon in the metals or in the differences in the diffusion and segregation of carbon through the metal particles. Characterization data of the solid carbon products revealed unique structures and textural properties as well as crystalline conditions on function of metal used. Additionally, support-metal interaction was evaluated, where experiments with similar nickel load over Y and mordenite zeolites were carried out, finding higher carbon yields and more ordered structures when Y zeolite was used.

Porous synthetic smectic clay for the reinforcement of epoxy polymers

We report the properties of a porous synthetic clay (saponite, denoted SAP) for the reinforcement of rubbery and glassy epoxy polymers. Remarkably, reinforcement properties superior to those of organo-montmorillonite can be achieved without the need for a surface organic modifier, as evidenced by the improvements in tensile strength, modulus and toughness at temperature above and below the glass transition temperature of the polymer. The disordered stacking of clay platelets ∼50 nm in lateral dimension gives rise to aggregated tactoids with a BET surface area of 920 m2/g, an average BJH pore size of 5.0 nm, and a pore volume of 1.98 cm3/g. These unique textural properties facilitate the dispersion of the tactoids into the polymer matrix and allow reinforcement of the polymer matrix in the absence of an organic modifier.

Grey Goo on the Skin? Nanotechnology, Cosmetic and Sunscreen Safety

Many modern cosmetic or sunscreen products contain nano-sized components. Nanoemulsions are transparent and have unique tactile and texture properties; nanocapsule, nanosome, noisome, or liposome formulations contain small vesicles (range: 50 to 5000 nm) consisting of traditional cosmetic materials that protect light-or oxygen-sensitive cosmetic ingredients. Transdermal delivery and cosmetic research suggests that vesicle materials may penetrate the stratum corneum (SC) of the human skin, but not into living skin. Depending on the physical/chemical properties of the ingredient and the formulation, nano-sized formulations may enhance or reduce skin penetration, albeit at a limited rate. Modern sunscreens contain insoluble titanium dioxide (TiO2) or zinc oxide (ZnO) nanoparticles (NP), which are colorless and reflect/scatter ultraviolet (UV) more efficiently than larger particles. Most available theoretical and experimental evidence suggests that insoluble NP do not penetrate into or through normal as well as compromised human skin. Oral and topical toxicity data suggest that TiO2 and ZnO NP have low systemic toxicity and are well tolerated on the skin. In vitro cytotoxicity, genotoxicity, and photogenotoxicity studies on TiO2 or other insoluble NP reporting uptake by cells, oxidative cell damage, or genotoxicity should be interpreted with caution, since such toxicities may be secondary to phagocytosis of mammalian cells exposed to high concentrations of insoluble particles. Caution needs to be exercised concerning topical exposure to other NP that either have characteristics enabling some skin penetration and/or have inherently toxic constituents. Studies on wear debris particles from surgical implants and other toxicity studies on insoluble particles support the traditional toxicology view that the hazard of small particles is mainly defined by the intrinsic toxicity of particles, as distinct from their particle size. There is little evidence supporting the principle that smaller particles have greater effects on the skin or other tissues or produce novel toxicities relative to micro-sized materials. Overall, the current weight of evidence suggests that nano-materials such as nano-sized vesicles or TiO2 and ZnO nanoparticles currently used in cosmetic preparations or sunscreens pose no risk to human skin or human health, although other NP may have properties that warrant safety evaluation on a case-by-case basis before human use.

Controlling the Morphology of Mesostructured Silicas by Pseudomorphic Transformation: a Route Towards Applications

Micelle-templated silicas (MTSs) such as MCM-41 and MCM-48 feature unique textural properties owing to their uniform distribution of mesopores with tunable sizes. MTS synthesis is relevant to unique self-assembly processes between surfactants and inorganic matter. The properties of MTSs have been explored in view of applications in fields as diverse as catalysis, chromatography, sensing, photonics, optics, drug delivery, etc. The aim of this contribution is to review, and to highlight by new results, a synthesis strategy we have developed since 2002 to control the particle morphology of MTSs at the micro- to millimeter scale, a key step for transferring these materials from the status of beautiful artworks to applicable products. It is based on the concept of pseudomorphic synthesis. Pseudomorphism is well known in the mineral world. It allows preparation of a mineral with a morphology that is not related to its crystallographic symmetry group. The resulting mineral assumes the outward crystal habit of a different mineral. This principle occurs at a nonconstant matter content by using a mineralization solution that exchanges anions (or cations) with an existing (preshaped) solid body, and allows the new structure to precipitate while maintaining the existing morphology. The concept of pseudomorphic transformation is now applied to amorphous preshaped silica particles to produce MTSs with the same morphology, using an alkaline solution to dissolve the silica and reprecipitate it around surfactant micelles into the ordered MTS structures. MTSs with hexagonal and cubic symmetry, different pore sizes, and controlled morphology have been synthesized. The new pseudomorphs have been successfully used as supports in chromatography, a very demanding application in terms of particle size and morphology.

Spherical ordered mesoporous silicas and silica monoliths as stationary phases for liquid chromatography

Ordered mesoporous silicas such as micelle-templated silicas (MTS) feature unique textural properties in addition to their high surface area (approximately 1000 m2/g): narrow mesopore size distributions and controlled pore connectivity. These characteristics are highly relevant to chromatographic applications for resistance to mass transfer, which has never been studied in chromatography because of the absence of model materials such as MTS. Their synthesis is based on unique self-assembly processes between surfactants and silica. In order to take advantage of the perfectly adjustable texture of MTS in chromatographic applications, their particle morphology has to be tailored at the micrometer scale. We developed a synthesis strategy to control the particle morphology of MTS using the concept of pseudomorphic transformation. Pseudomorphism was recognized in the mineral world to gain a mineral that presents a morphology not related to its crystallographic symmetry group. Pseudomorphic transformations have been applied to amorphous spherical silica particles usually used in chromatography as stationary phases to produce MTS with the same morphology, using alkaline solution to dissolve progressively and locally silica and reprecipitate it around surfactant micelles into ordered MTS structures. Spherical beads of MTS with hexagonal and cubic symmetries have been synthesized and successfully used in HPLC in fast separation processes. MTS with a highly connected structure (cubic symmetry), uniform pores with a diameter larger than 6 nm in the form of particles of 5 microm could compete with monolithic silica columns. Monolithic columns are receiving strong interest and represent a milestone in the area of fast separation. Their synthesis is a sol-gel process based on phase separation between silica and water, which is assisted by the presence of polymers. The control of the synthesis of monolithic silica has been systematically explored. Because of unresolved yet cladding problems to evaluate the resulting macromonoliths in HPLC, micromonoliths were synthesized into fused-silica capillaries and evaluated by nano-LC and CEC. Only CEC allows to gain high column efficiencies in fast separation processes. Capillary silica monolithic columns represent attractive alternatives for miniaturization processes (lab-on-a chip) using CEC.

Relationship of Instrumental and Sensory Texture Measurements of Fresh and Stored Apples to Cell Number and Size

During storage, many apple (Malus ×domestica Borkh.) genotypes lose their desirable textural qualities, but some like `Honeycrisp', maintain their sensory Crispness and Firmness. To understand this differential response of genotypes to postharvest changes in texture, reliable and quantifiable methods of texture measurement are needed. This study integrated data from a snapping test, confocal laser scanning microscopy (CLSM), and sensory panels to study postharvest textural changes and to predict sensory textural attributes of Firmness, Crispness, Mealiness, and Juiciness. Three separate analyses on fresh, stored, and combined fresh and stored fruit data yielded different predictors for the same sensory attributes. Change in Crispness during storage was successfully predicted by change in Work during storage. Cell number and size were related to fresh fruit texture and its maintenance during storage. Unique textural properties of `Honeycrisp' were found to be inherited by its progeny.

Removal of SO 2 from O 2-containing flue gas by activated carbon fiber (ACF) impregnated with NH 3

Adsorption of SO 2 from the O 2-containing flue gas by granular activated carbons (GACs) and activated carbon fibers (ACFs) impregnated with NH 3 was studied in this technical note. Experimental results showed that the ACFs were high-quality adsorbents due to their unique textural properties. In the presence of moisture, the desulphurization efficiency for the ACFs was improved significantly due to the formation of sulfuric acid. After NH 3 impregnation of ACF samples, nitrogen-containing functional groups (pyridyl C 5H 4N– and pyrrolyl C 4H 4N–) were detected on the sample surface by using an X-ray photoelectron spectrometer. These functional groups accounted for the enhanced SO 2 adsorption via chemisorption and/or catalytic oxidization.

Catalytic applications of composite aerogels

Unitary and composite aerogels with high specific surface areas and pronounced mesoporosity have been prepared by the controlled sol–gel method and subsequent carbon dioxide supercritical drying and heat treatment. The aerogels were characterized by N2 adsorption–desorption, thermal analyses (TGA–DTA), X-ray diffraction (XRD), temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), infrared spectroscopy (IR), transmission electron microscopy (TEM), and reaction tests. The composite aerogels containing extremely small active metal particles showed strong metal-support or metal–metal interactions. The specific catalytic behaviors of aerogel catalysts are explained in terms of their unique textural and chemical properties.

Catalytic filamentous carbon: Structural and textural properties

Catalytic filamentous carbon (CFC) synthesized by the decomposition of methane over iron subgroup metal catalysts (Ni, Co, Fe or their alloys) is a new family of mesoporous carbon materials possessing the unique structural and textural properties. Microstructural properties of CFC (arrangement of the graphite planes in filaments) are shown to depend on the nature of catalyst for methane decomposition. These properties widely vary for different catalysts: the angle between graphite planes and the filament axis can be 0° (Fe–Co–Al 2O 3), 15° (Co–Al 2O 3), 45° (Ni–Al 2O 3), 90° (Ni–Cu–Al 2O 3). The textural properties of CFC depend both on the catalyst nature and the conditions of methane decomposition ( T, °C). The micropore volume in CFC is very low, 0.001–0.022 cm 3 g −1 at the total pore volume of 0.26–0.59 cm 3 g −1. Nevertheless, the BET surface area may reach 318 m 2 g −1. Results of the TEM (HRTEM), XRD, Raman spectroscopic, SEM and adsorption studies of the structural and textural properties of CFC are discussed.

Collagen as the Major Edible Component of Sea Cucumber (Stichopus japonicus)

ABSTRACT:The body wall collagen of an edible sea cucumber, Stichopus japonicus, was studied with respect to its chemical composition and subunit structure. About 70% of the total body wall protein was accounted for by highly insoluble collagen fibers. The disaggregation with β‐mercaptoethanol, 0.1 M NaOH treatment, and limited pepsin digestion of these collagen fibers resulted in complete solubilization. The solubilized collagen was isolated and characterized; it had 2 distinct subunits, αl and α2, which formed (α1)2α2 heterotrimers and was rich in glutamic acid when compared with other fibrillar collagens. The unique textural properties of cooked sea cucumber seem to be due to thermal denaturation of the insoluble collagen fibers.

Textural and ultrastructural changes during processing and storage of lightly preserved salmon (Salmo salar) products

The effect of a controlled lactic fermentation on textural and ultrastructural properties of salmon fillets was evaluated. When compared with a non-inoculated cured sample, fermented salmon had unique textural properties since it exhibited significantly higher force (p < 0.05) and work (p < 0.001) values in a penetration test on two sampling days but a consistently lower hardness (p < 0.05) in a Texture Profile Analysis (TPA) rheological test. Study of the myofibrillar ultrastructure showed that basic structures were drastically damaged during processing and storage of fermented and cured salmon. Nevertheless, Z-lines were better preserved in fermented samples. It is suggested that the slight protective effect of lactic fermentation with the starter L sake may be the consequence of a lower pH, by putatively inhibiting neutral or alkaline proteolytic enzymes. © 2000 Society of Chemical Industry

New Io data spur discussion on ultrabasic lavas

In the late 1960s, the Viljoen brothers identified a new class of igneous rock in the ancient (3.5 Ga) Barberton greenstone belt of South Africa. Called komatiites, after the Komati River that flows nearby, these new rocks were soon recognized in Precambrian terrains around the world as the metamorphosed remnants of ancient ultrabasic lava flows and shallow intrusions, the extrusive equivalent of peridotites. Komatiites, although rare in the geologic record, soon became of interest to a wide variety of geologists because of their unique texture, composition, and physical properties, and their genetic association with massive nickel sulfide ore deposits.With recognition of the inferred high temperature, low viscosity turbulent emplacement, and great thermal erosive potential of these lavas, komatiites became an analog to low‐viscosity extraterrestrial lavas, which formed long, sinuous lava channels and flow fields on the Moon,Venus, Mars, and Io. Now, with indications from the Galileo spacecraft and other instruments that active volcanism on Jupiter's moon, lo,may include ultrabasic eruptions, there is renewed interest in understanding the nature of komatiite lavas and what they can tell us about the thermal‐compositional‐physical dynamics of the early Earth, and perhaps other planets as well.

Textural and ultrastructural changes during processing and storage of lightly preserved salmon (Salmo salar) products

The effect of a controlled lactic fermentation on textural and ultrastructural properties of salmon fillets was evaluated. When compared with a non-inoculated cured sample, fermented salmon had unique textural properties since it exhibited significantly higher force (p < 0.05) and work (p < 0.001) values in a penetration test on two sampling days but a consistently lower hardness (p < 0.05) in a Texture Profile Analysis (TPA) rheological test. Study of the myofibrillar ultrastructure showed that basic structures were drastically damaged during processing and storage of fermented and cured salmon. Nevertheless, Z-lines were better preserved in fermented samples. It is suggested that the slight protective effect of lactic fermentation with the starter L sake may be the consequence of a lower pH, by putatively inhibiting neutral or alkaline proteolytic enzymes. © 2000 Society of Chemical Industry

Evaluation of Alumina−Aluminum Phosphate Catalyst Supports for Hydrodenitrogenation of Pyridine and Coal-Derived Liquids

Several alumina−aluminum phosphate (AAP) catalyst supports were prepared by a coprecipitation method. Effect of variations in Al/P atomic ratios on support textural properties were examined. Finished NiMo/AAP catalysts containing nominally 3 wt % Ni and 13 wt % Mo were prepared by incipient wetness and characterized by several methods including elemental, BET, and XPS surface analysis. Initial hydrodenitrogenation (HDN) activities of the catalysts were examined in both pyridine model compound and coal liquid reactions. The AAP supports showed the opportunity to tailor the catalyst pore size by variation of the Al/P ratio. On a per unit surface area basis, the AAP-supported catalysts had initial HDN activities comparable to those of a commercial P-promoted NiMo/Al2O3 catalyst. Because of their unique textural properties, i.e. variable pore sizes, the AAP catalysts may offer advantages when dealing with macromolecular feedstocks where hindered diffusion may slow reaction rates.

Summary of commercial experience in use of zeolitic catalysts for hydrogenation processes

Now that G-43-107, L-24-200, and LK-6u units are in commercial service, the demand has increased for more effective catalysts in hydrotreating various petroleum fractions. For many years, researchers have directed their efforts toward investigation of the properties of hydrotreating catalysts formulated with an aluminum oxide support, which has unique textural and mechanical properties, and which can be prepared by currently accessible manufacturing techniques. One of the methods for improving the structure of the support and regulating its porosity is the use of the zeolites. However, this approach has not been studied at all thoroughly in application to hydrotreating catalysts. Studies performed at the All-Union Scientific-Research Institute for Petroleum Processing (VNII NP) have shown that zeolite, when added to an alumina-nickel-molybdenum (ANM) composition, increases the quantity of coarse pores (radii 10-20 nm), increases the number and dispersity of the nickel molybdates that are active in the catalyst, reduces the number of inactive spinel compounds, increases the degree of reduction of the nickel and its dipersity, and stabilizes the metallic nickel in a finely divided state. Thus, modification of aluminum hydroxide by Y zeolite opens up new possibilities in regulating the physicochemical properties of ANM compositions, with the aim of hydrogenative processingmore » of petroleum-derived feedstocks.« less