Sponge-like Morphology Research Articles

Preparation and Performance of Metal-Organic-Frameworks-Derived Activated Mesoporous Carbon Polyhedron with Sponge-Like Structure for Lithium–Sulfur Batteries

A novel metal-organic-frameworks-derived activated mesoporous carbon polyhedron/Sulfur composite (AMCP-950/S) is successfully designed and synthesized. The composition analysis and structure characteristics of samples are conducted by thermogravimetric analyses (TGA), X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM). The electrochemical performances of samples are examined by cyclic voltammetric (CV), charge/discharge and electrochemical impedance spectroscopy (EIS) measurements. The effects of the carbonization temperatures on the physicochemical and electrochemical performances of the resultant mesoporous carbon polyhedron are carefully studied. The results show that the activated mesoporous carbon polyhedron (AMCP-950), which is prepared by the MOF-5 (Zn4O(BDC)3) carbonized at the optimized temperature (950°C) and then KOH activation, has uniform sponge-like morphology, abundant mesoporous structure and huge large specific surface areas of 2211.1 m2/g. Besides, AMCP-950/S composite shows the high sulfur content of 79.0 wt%, the excellent electrochemical performance with the high initial capacity of 1274.0 mAh/g (based on the weight of C/S active substance) and over 81.7% capacity retention after 50 cycles at a discharge rate of 0.2 C (1 C = 1675 mAh/g) as well as excellent coulombic efficiency.

Electrodeposition and Characterization of SiOx Films Photoactive in Organic Solution

The photoactive silicon based films were potentiostatically deposited on Au electrodes from 0.5 M SiHCl3 dissolved in 0.1 M solution of tetrabutylammonium bromide (TBAB) in propylene carbonate (PC). The cyclic voltammetry measurements showed that the range of SiHCl3 reduction was between −2.4 and −2.9 V vs. Ag quasi reference electrode (Ag). Dependence of different ratio of silicon oxides (SiOx) and hydrogen terminated silicon (Si:H) on the electrodeposition potential was characterized by Raman and X-ray Photoelectron Spectroscopies (XPS). The spectroscopic studies revealed that the concentration of SiHCl3 and the electrodeposition potential were the most significant parameters of the deposition process. The highest concentration of lowly oxidized SiOx was observed for the films obtained at −2.7 V. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) observations revealed dependence of the layers' morphology on the deposition potential value i.e. the most uniform films were obtained at −2.7 V, whereas at −2.5 and −2.85 V the deposits were of a granular and sponge-like morphology. Deposits obtained at −2.5 and −2.7 V have shown n-type photoactivity in 0.1 M solution of TBAB in PC and the registered photocurrent density was up to 24 μA × cm−2.

High performance thin-film composite membranes with mesh-reinforced hydrophilic sulfonated polyphenylenesulfone (sPPSU) substrates for osmotically driven processes

We have for the first time combined the strength of hydrophilic sulfonated material and thin woven open-mesh via a continuous casting process to fabricate mesh-reinforced ultrafiltration (UF) membrane substrates with desirable structure and morphology for the development of high-performance thin-film composite (TFC) osmosis membranes. A new sulfonated polyphenylenesulfone (sPPSU) polymer with super-hydrophilic nature is used as the substrate material, while a hydrophilic polyester (PET) open-mesh with a small thickness of 45μm and an open area of 44.5% is employed as the reinforcing fabric during membrane casting. The newly developed sPPSU-TFC membranes not only exhibit a fully sponge-like cross-section morphology, but also possess excellent water permeability (A=3.4–3.7Lm−2h−1bar−1) and selectivity toward NaCl (B=0.10–0.23Lm−2h−1). Due to the hydrophilic nature and low membrane thickness of 53–67μm, the PET-woven reinforced sPPSU substrates have remarkably small structural parameters (S) of less than 300μm. The sPPSU-TFC membranes thereby display impressive water fluxes (Jw) of 69.3–76.5Lm−2h−1 and 38.7–47.0Lm−2h−1 against a deionized water feed using 2M NaCl as the draw solution under pressure retarded osmosis (PRO) and forward osmosis (FO) modes, respectively. This performance surpasses the state-of-the-art commercially available FO membranes. The sPPSU-TFC membranes also show exciting performance for synthetic seawater (3.5wt% NaCl) desalination and water reclamation from real municipal wastewater. The newly developed PET-woven sPPSU-TFC membranes may have great potential to become a new generation membrane for osmotically driven processes.

Effect of sulphonated polyethersulfone substrate for thin film composite forward osmosis membrane

Sulphonated polyethersulfone (SPES) has been synthesized for developing high performance thin film composite (TFC) forward osmosis (FO) membranes with enhanced hydrophilic support layer. Sulphonated substrate not only affects the membrane performance but also changes the membrane morphology from finger-like structure to a sponge-like morphology at higher degree of sulphonation thereby affecting the mechanical strength of the FO membrane. Non-sulphonated TFC-FO membrane with 12wt.% polymer concentration shows a faint finger-like structure while sulphonated samples at a similar polymer concentration show a fully sponge-like structure with a much higher performance. For example, a water flux of 35Lm−2h−1 and 0.28gL−1 specific reverse solute flux was achieved with sulphonated TFC-FO membrane sample (50wt.% SPES) under the FO mode using 2M NaCl as the draw solution and deionized water as feed. Substrate sulphonation also considerably decreased the membrane structural parameter from 1096μm without sulphonation to 245μm at 50wt.% sulphonation. This study therefore shows that, besides surface morphology, the water flux of the FO membrane can also be enhanced by improving its substrate hydrophilic property.

Hard template synthesis of porous carbon nitride materials with improved efficiency for photocatalytic CO2 utilization

Abstract Porous carbon nitrides of different morphology were obtained via bulk and hard template (SBA-15 and MCF) pyrolysis of melamine. Matrix method allowed obtaining ordered porous C 3 N 4 with higher bandgap (2.87 eV) in the contrary to the bulk sample (2.45 eV). Obtained carbon nitrides were found to be p-type semiconductors with catalytic activity towards photoreduction of carbon dioxide with water vapour. Carbon nitride obtained in MCF has the higher bandgap, developed surface, sponge-like morphology, spatially ordering and it's characterized by the highest photocatalytic activity.

Scaffold materials from glycosylated and PEGylated bovine serum albumin.

Bovine serum albumin has been PEGylated and glycosylated to create mimetic materials for the extracellular matrix (ECM) with potential tissue engineering applications. Different surfaces for cell adhesion were achieved by crosslinking the initial albumin product and forming either a coating or a sponge-like three-dimensional morphology to mimic the mesh structure of natural ECM. The biocompatibility of the albumin matrix with mammalian cells was evaluated using cell culture assays with NIH 3T3 cells. The results indicated that glycoprotein composition and specific morphology of the assembly can improve the cell growth environment. These ECM mimetic structures might eventually be considered to serve as alternatives for the more expensive collagen and elastin based ECM substances currently in use in tissue engineering.

Biodegradable silk fibroin/chitosan blend microparticles prepared by emulsification-diffusion method

AbstractIn this study, biodegradable microparticles of silk fibroin (SF)/chitosan (CS) blends with SF/CS blend ratios of 1:0, 2:1, 1:1, 1:2 and 0:1 (w/w) were prepared using the water-in-oil emulsification-diffusion method without any surfactants. An aqueous SF/CS blend solution and ethyl acetate were used as the water and oil phases, respectively. The plain SF had an irregular shape, while the CS microparticles were spherical. The blend microparticles were spherical in shape with a rough surface. Average microparticle sizes were in the range of 73–80 μm. The microparticle matrices had a sponge-like morphology. Conformational changes in the SF component, from random coil to the β-sheet form, were observed in the FTIR data. The dissolution of the blend microparticles was lower than those of the plain SF and CS microparticles. Microparticle density steadily increased and porosity slightly decreased as the amount of CS in the blend increased.

Polymerization and Functionalization of Membrane Pores for Water Related Applications.

Poly(vinylidene fluoride) (PVDF) was modified by chemical treatments in order to create active double bonds to obtain covalent grafting of poly(acrylic acid) (PAA) on membrane. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrum confirms the formation of conjugated C=C double bonds with surface dehydrofluorination. The membrane morphology was studied by scanning electron microscopy (SEM). The surface composition was characterized by X-ray photoelectron spectroscopy (XPS). The thermal stability of the dehydrofluorinated membrane (Def-PVDF) and functionalized membranes were investigated by differential scanning calorimetry (DSC) analysis. The influence of covalently attached PAA on Def-PVDF membrane has been investigated to determine its effect on the transport of water and charged solute. Variations in the solution pH show an effect on both permeability and solute retention in a reversible fashion. Metal nanoparticles were also immobilized in the membrane for the degradation of toxic chlorinated organics from water. In addition, PVDF membranes with an asymmetric and sponge-like morphology were developed by immersion-precipitation phase-inversion methods in both lab-scale and large-scale. The new type of spongy PVDF membrane shows high surface area with higher yield of PAA functionalization. The ion-capacity with Ca2+ ions was also investigated.

Synthesis of pure-phase Sr2MgMoO6 nanostructured powder by the combustion method

Abstracts Pure-phase Sr2MgMoO6 (SMMO) nanopowder was obtained by combustion synthesis (CS) from an aqueous solution of metal nitrates, glycine and ammonium nitrate and subsequent treatment in air at 900 °C. The morphological and structural characterization was performed by X-Ray diffraction (XRD), N2 physisorption and scanning electron microscopy (SEM). This nanostructured powder presents average crystallite size of ~150 nm and a sponge-like morphology composed of highly interconnected crystallites and an effective specific area of 5.6 m2/g. EIS measurements indicate ASR values as low as 0.07 Ω cm2 at 800 °C.

Facile synthesis, structure and visible light photocatalytic activity of recyclable ZnFe2O4/TiO2

A kind of sponge-like ZnFe2O4/TiO2 composite was facilely synthesized by a solution combustion method. The physicochemical properties, including the crystalline phase, surface morphology, spectral response, photogenerated charge carriers’ separation and transfer efficiency, were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption/desorption isotherms, X-ray photoelectron spectroscopy, UV–vis absorption spectroscopy and photoluminescence spectroscopy techniques and analyzed to interpret the relationship between the structure and photocatalytic activity. The sponge-like morphology promotes the adsorption of reaction species as well as functions as a good light harvesting structure for the enhancement of spectral utilization. The heterojunction effectively inhibited the recombination of photogenerated charge carriers. With these synergistic effects, the degradation rate of methylene blue on ZnFe2O4/TiO2 was up to 93.2% under visible light irradiation and remained stable even after five consecutive reaction runs. Moreover, owing to the magnetic property, ZnFe2O4/TiO2 can be recycled easily. Additionally, a photocatalytic mechanism of ZnFe2O4/TiO2 was proposed.

Mesh-reinforced thin film composite membranes for forward osmosis applications: The structure–performance relationship

In this study, thin and durable thin film composite (TFC) polyamide membranes were prepared on mesh-reinforced polysulfone (PSF) supports for forward osmosis (FO) applications. To understand the influence of mesh-incorporation on the formation of support structures and the final FO performance, mesh-embedded PSF supports were prepared via the phase inversion process from various PSF casting solutions in 1-methyl-2-pyrrolidinone (NMP) solvent (9–18wt%) by using a polyester (PE) mesh as a mechanical reinforcing material. A crosslinked aromatic polyamide layer was then fabricated on top of each support to form a TFC membrane. For the mesh-embedded PSF supports prepared with relatively low concentration casting solutions (9 and 12wt%), the PE mesh was oriented towards the bottom of the PSF supports, creating additional macroscopic pores around the mesh lines on the backside surface. However, the PE mesh was moved towards the center of PSF supports when higher viscosity solutions (15 and 18wt%) were used for the support preparation, and consequently the macroscopic pores near the mesh lines were isolated within the support layers without exposing to the bottom surface. The PE-mesh also adversely affected the formation of a finger-like morphology for higher concentration casting solutions (≥12wt%), forming a sponge-like morphology in the lower half of the support layers. A desirable support structure with a well-developed finger-like morphology and macroscopic open-pores on the bottom surface was achieved from the mesh-embedded PSF support prepared with 9wt% casting solution (PSF9). The corresponding TFC membrane (TFC/PSF9) thus exhibited the lowest structural parameter (S=314±29µm) among the tested samples and presented outstanding FO performance, almost 2.5 times higher water flux (49LMH) with lower reverse salt flux (7.0GMH) compared to a commercial CTA membrane in PRO mode evaluation.

Amphiphile Meets Amphiphile: Beyond the Polar-Apolar Dualism in Ionic Liquid/Alcohol Mixtures.

The mesoscopic morphology of binary mixtures of ethylammonium nitrate (EAN), the protic ionic liquid par excellence, and methanol is explored using neutron/X-ray diffraction and computational techniques. Both compounds are amphiphilic and characterized by an extended hydrogen bonding network: surprisingly, though macroscopically homogeneous, these mixtures turn out to be mesoscopically highly heterogeneous. Our study reveals that even in methanol-rich mixtures, a wide distribution of clusters exists where EAN preserves its bulk, sponge-like morphology. Accordingly methanol does not succeed in fully dissociating the ionic liquid that keeps on organizing in a bulk-like fashion. This behavior represents the premises to the more dramatic phenomenology observed with longer alcohols that eventually phase separate from EAN. These results challenge the commonly accepted polar and apolar moieties segregation in ionic liquids/molecular liquids mixtures and the current understanding of technologically relevant solvation processes.

Proton Conductivity in Doped Aluminum Phosphonate Sponges

Proton-conducting networks (NETs) were prepared successfully by the insertion of phosphonated nanochannels into organic-inorganic hybrid materials that contain Al(3+) as the connector and hexakis(p-phosphonatophenyl)benzene (HPB) as the linker. Noncomplexed phosphonic acid groups remain in the framework, which depends on the ratio of both compounds, to yield a proton conductivity in the region of 10(-3) S cm(-1). This conductivity can be further improved and values as high as Nafion, a benchmark proton-exchange membrane for fuel cell applications, can be obtained by filling the network pores with intrinsic proton conductors. As a result of their sponge-like morphology, aluminum phosphonates adsorb conductive small molecules such as phosphonic acids, which results in a very high proton conductivity of approximately 5 × 10(-2) S cm(-1) at 120 °C and 50 % relative humidity (RH). Contrary to Nafion, the doped networks show a remarkably low temperature dependence of proton conductivity from external humidification. This effect indicates a transport mechanism that is different to the water vehicle mechanism. Furthermore, the materials exhibit an activation energy of 40 kJ mol(-1) at 15 % RH that starts to diminish to 10 kJ mol(-1) at 80 % RH, which is even smaller than the corresponding values obtained for Nafion 117.

Pervaporation dehydration of acetone using P84 co-polyimide flat sheet membranes modified by vapor phase crosslinking

In this work, a unique vapor crosslinking method is applied for the first time to fabricate polyimide-based pervaporation membranes for the dehydration of acetone. By controlling the temperature and duration of the crosslinking reaction using ethylenediamine (EDA) vapor and using the right dope formulation to cast P84 co-polyimide membranes with balanced macrovoid and sponge-like morphology, we have optimized the crosslinking parameters to obtain a membrane with a separation factor of 53 (i.e., a water permeate concentration of 90%) and a high flux of 1.8kgm−2h−1 for pervaporation dehydration of acetone at 50°C from a feed of 85/15 acetone/water. With the aid of characterizations for surface chemistry and physics of the modified membranes, such as FTIR-ATR, XPS, and XRD, the crosslinking between EDA and P84 is confirmed at the selective layer of the membrane, as well as structure–performance relationship. This new modification method for pervaporation membranes is attractive for creating a new class of membranes for the separation of organic solvents and biofuel.

Layer reduction method for fabricating Pd-coated Ni foams as high-performance ethanol electrode for anion-exchange membrane fuel cells

An ideal electrode architecture that boosts the performance of anion-exchange membrane direct liquid fuel cells needs the electrode design to meet all the requirements of electrochemical kinetics and mass and charge transport characteristics. In this regard, here we propose a facile, well-controlled, and binder-free layer reduction method for preparing a three-dimensional foam electrode, which enables the catalytic particles to be directly reduced on the surface of the metal foam. This innovative layer reduction method not only avoids the formation of large catalytic aggregation, but also promises a thin and porous catalyst film that presents a sponge-like morphology uniformly coated onto the skeleton, thus both improving the electrochemical kinetics and enhancing the mass and charge transport of species. The results demonstrate that the application of the layer-reduced Pd/Ni foam electrode in an anion-exchange membrane direct ethanol fuel cell enables a peak power density and the maximum current density as high as 164 mW cm−2 and 1.34 A cm−2 at 60 °C, respectively, which are 1.03 and 1.16 times higher than those of the conventional design.

Hollow carbon nanostructures obtained from hydrothermal carbonization of lignocellulosic biomass

Here we describe a new method for obtaining carbon nanocages at relatively low temperatures using a low-cost lignocellulosic waste material as carbon precursor. Coconut coir dust has been submitted to hydrothermal carbonization in the presence of clays minerals such as sepiolite, attapulgite, and montmorillonite followed by a demineralization step. Just after hydrothermal treatment, the samples prepared in the absence of the clays presented a sponge-like morphology as typically described for hard-plant tissues submitted to this treatment while the samples heated in the presence of clays were fundamentally heterogeneous. After chemical etching with hydrofluoric acid, the sample free from clays exhibited irregular round-shaped particles with poorly defined cavities. For samples containing clays, on the other hand, the chemical etching lead to well-defined carbon nanocages as long as the particles were successfully etched such as attapulgite and montmorillonite. For sepiolite, however, the presence of residual inorganic particles was observed along with irregularly shaped hollow nanostructures. Finally, Raman measurements revealed the typical features of amorphous carbons.

Microwave Irradiation for Accelerating Synthesis of New Chiral Nanostructured Poly(amide-imide)s Having a Thiazole Pendant Group

Microwave irradiation was used to accelerate the polycondensation of a new thiazole-containing diamine with several chiral diacids. Polymerization reactions were carried out in molten tetrabutylammonium bromide as a green molten salt medium and triphenyl phosphite as the homogenizer. A series of new compounds were characterized by Fourier transform-infrared spectroscopy, nuclear magnetic resonance spectroscopy, and elemental analysis techniques. The polymeric samples showed high thermal stability with decomposition temperature being above 360°C; they were in a nanoscale size and were assembled uniformly and randomly in a sponge-like morphology.

Synthesis and characterisation of sponge-like carbon anode materials for lithium ion batteries

Micro-sized carbon material with a unique sponge-like morphology has been fabricated by hydrothermal method coordinating etching process. When evaluate its electrochemical properties in lithium ion batteries, the sponge-like carbon structure exhibits very high specific capacity (around 1175mAhg−1 after 140th cycle tested at the charge/discharge current density of 200mAg−1) and wonderful cyclability (about 117% retention is available when cycled back from very high current density of 800mAg−1) during the galvanostatic cycling, indicating it may be a promising candidate as anode material for Li-ion batteries.

Microporous polyvinylidene fluoride hollow fiber membrane contactors for CO2 stripping: Effect of PEG-400 in spinning dope

In order to develop the structure of microporous PVDF membranes, PEG-400 was introduced into the polymer dope as a non-solvent additive. The hollow fiber membranes were prepared via a wet phase-inversion process and then used in the membrane contactor modules for CO2 stripping from water. By addition of different amounts of PEG-400, cloud points of the polymer dope were obtained to examine phase-inversion behavior. From FESEM analysis, the membrane structure changed from a finger-like to an approximately sponge-like morphology with the addition of 4wt.% of PEG-400. The prepared membranes presented smaller mean pore size (0.13μm) and significantly higher wetting pressure (550kPa) compared to the plain membrane. From CO2 stripping test, at water velocity of 0.4m/s, the PVDF membranes prepared by 4% PEG-400 demonstrated an approximate CO2 stripping flux of 4.5×10−5(mol/m2s) which is 125% higher than the flux of the plain membrane. It could be concluded that structurally developed hydrophobic PVDF hollow fiber membranes can be prepared by a controlled phase-inversion process to enhance the performance of gas–liquid membrane contactor.

Impact of controlled ice nucleation on process performance and quality attributes of a lyophilized monoclonal antibody

An efficient and potentially scalable technology was evaluated to control the ice nucleation step of the freezing process for a model monoclonal antibody formulation and the effect on process performance and quality attributes of the final lyophilized product was compared with the conventional shelf ramping method of freezing. Controlled ice nucleation resulted in uniform nucleation at temperatures between -2.3 and -3.2 °C while uncontrolled nucleation resulted in random nucleation at temperatures between -10 and -16.4 °C. The sublimation rate (dm/dt) during primary drying was higher in the controlled nucleation cycle (0.13 g/h/vial) than in the uncontrolled nucleation cycle (0.11 g/h/vial). This was due to the formation of larger ice crystals, leading to lower product resistance (Rp) and 19% reduction in the primary drying for the controlled nucleation cycle. Controlled ice nucleation resulted in lyophilized cakes with more acceptable appearance, no visible collapse or shrinkage and decreased reconstitution times compared with uncontrolled nucleation. There were no observed differences in the particle size, concentration (A280 nm) and presence of aggregates (A410 nm) between the two nucleation cycles when the lyophilized cakes were reconstituted. These were confirmed by SEC and protein A-HPLC analyses which showed similar peak shapes and retention times between the two cycles. However, uncontrolled nucleation resulted in cakes with larger specific surface area (0.90 m(2)/g) than controlled nucleation (0.46 m(2)/g). SEM images of the lyophilized cakes from uncontrolled nucleation revealed a sponge-like morphology with smaller pores while cakes from controlled nucleation cycle revealed plate-like structures with more open and larger pores. While controlled nucleation resulted in a final product with a higher residual moisture content (2.1±0.08%) than uncontrolled nucleation (1.62±0.11%), this was resolved by increasing the secondary drying temperature.