Apparent Surface Area Research Articles

Copper benzene-1,3,5-tricarboxylate (HKUST-1) – graphene oxide pellets for methane adsorption

Abstract Copper benzene-1,3,5-tricarboxylate (HKUST-1) is one of the materials holding the greatest potential for clean energy gases among microporous storage materials. Although this material is commercially available as a powder with particle size 10–20 μm, for easier handling adsorbents are preferentially employed as pellets or monoliths. Even under binder free conditions there could be a high price to pay for compacting: loss in crystallinity and in porosity. To determine the protection potential of graphene oxide (GO) a HKUST-1@GO composite was studied. The material of 16% GO was obtained in a single step solvothermal synthesis. The pristine HKUST-1 as well as HKUST1@GO formed consistent, integrated pellets when compressed at 25 and 50 bar without any binder. PowderXRD and N2 adsorption were used to monitor the changes in crystallinity and pore structure. It was found that GO has a protective effect against the 25 or 50 bar applied pressure, as 75% of the pore volume and the apparent surface area is saved in HKUST1@GO (vs. 43% and 47%, respectively, in HKUST-1) after compression. Presumably, the flexible GO sheets with high mechanical stability act as compressible spacers between the crystals thus preventing their amorphisation. Comparison of the adsorption properties of the HKUST-1 and HKUST-1@GO powders and pellets revealed that the performed compression deteriorated the structure of the MOF and thus reduced the CH4 uptake. Further studies are needed to optimize the compression pressure for a more reasonable loss in the gas uptake capacity.

BN-Doped Metal-Organic Frameworks: Tailoring 2D and 3D Porous Architectures through Molecular Editing of Borazines.

Building on the MOF approach to prepare porous materials, herein we report the engineering of porous BN‐doped materials using tricarboxylic hexaarylborazine ligands, which are laterally decorated with functional groups at the full‐carbon ‘inner shell’. Whilst an open porous 3D entangled structure could be obtained from the double interpenetration of two identical metal frameworks derived from the methyl substituted borazine, the chlorine‐functionalised linker undergoes formation of a porous layered 2D honeycomb structure, as shown by single‐crystal X‐ray diffraction analysis. In this architecture, the borazine cores are rotated by 60° in alternating layers, thus generating large rhombohedral channels running perpendicular to the planes of the networks. An analogous unsubstituted full‐carbon metal framework was synthesised for comparison. The resulting MOF revealed a crystalline 3D entangled porous structure, composed by three mutually interpenetrating networks, hence denser than those obtained from the borazine linkers. Their microporosity and CO2 uptake were investigated, with the porous 3D BN‐MOF entangled structure exhibiting a large apparent BET specific surface area (1091 m2 g−1) and significant CO2 reversible adsorption (3.31 mmol g−1) at 1 bar and 273 K.

Extrapolation of pharmacokinetics and pharmacodynamics of sunitinib in children with gastrointestinal stromal tumors

PurposeThe starting dose of sunitinib in children with gastrointestinal stromal tumors (GIST) was extrapolated based on data in adults with GIST or solid tumors and children with solid tumors.MethodsIntegrated population pharmacokinetics (PK), PK/pharmacodynamics (PD), and exposure–response analyses using nonlinear mixed-effects modeling approaches were performed to extrapolate PK and PD of sunitinib in children with GIST at projected dose(s) with plasma drug exposures comparable to 50-mg/day in adults with GIST. The analysis datasets included PK/PD data in adults with GIST and adults and children with solid tumors. The effect of covariates on PK and safety/efficacy endpoints were explored.ResultsTwo-compartment models with lag time were successfully used to describe the PK of sunitinib and its active metabolite SU012662. PK/PD models were successfully built to describe key continuous safety and efficacy endpoints. The effect of age on sunitinib apparent clearance (CL/F) and body surface area on SU012662 CL/F was statistically significant (P ≤ 0.001): children who were younger or of smaller body size had lower CL/F; however, age and body size did not appear to negatively affect safety or efficacy response to plasma drug exposure.ConclusionBased on PK, safety, and efficacy trial simulations, a sunitinib starting dose of ~ 25 mg/m2/day was predicted to provide comparable plasma drug exposures in children with GIST as in adults with GIST treated with 50 mg/day. However, in the absence of a tumor type effect of sunitinib on CL/F in children, the projected equivalent dose for this population would be ~ 20 mg/m2/day.

Glucose–Carbon Hybrids as Pt Catalyst Supports for the Continuous Furfural Hydroconversion in Gas Phase

Glucose–carbon hybrids were synthetized with different carbon materials, namely carbon nanotubes, reduced graphene oxide, carbon black and activated carbon by a hydrothermal treatment. These carbon hybrids were used as Pt-supports (1 wt.%) for the furfural (FUR) hydroconversion in the gas phase at mild operating conditions (i.e., P = 1 atm and T = 200 °C). The physicochemical properties (porosity, surface chemistry, Pt-dispersion, etc.) were analyzed by different techniques. Glucose–carbon hybrids presented apparent surface areas between 470–500 m2 g−1, a neutral character and a good distribution of small Pt-nanoparticles, some large ones with octahedral geometry being also formed. Catalytic results showed two main reaction pathways: (i) FUR hydrogenation to furfuryl alcohol (FOL), and (ii) decarbonylation to furane (FU). The products distribution depended on the reaction temperature, FOL or FU being mainly produced at low (120–140 °C) or high temperatures (170–200 °C), respectively. At intermediate temperatures, tetrahydrofurfuryl alcohol was formed by secondary FOL hydrogenation. FUR hydroconversion is a structure-sensitive reaction, rounded-shape Pt-nanoparticles producing FU, while large octahedral Pt-particles favor the formation of FOL. Pt-catalysts supported on glucose–carbon hybrids presented a better catalytic performance at low temperature than the catalyst prepared on reference material, no catalyst deactivation being identified after several hours on stream.

Histological and Histometrical Features of the Mammary Gland in Immature and Lactating Local Breed Ewes (Ovis aries)

Twelve samples of mammary glands (6 immature and 6 lactating ewes) were used for this study. Specimens of glands were immediately dissected and fixed in 10% formalin sol. The specimens were processed according to paraffin technique, sectioned at 5-6µm and stained by hematoxylin and eosin, Masson's Trichrom stains. In both immature and lactating ewes the mammary glands were covered by skin. In immature ewes the mammary quarter was composed of few mammary lobes that separated by very thick inter lobar adipose tissue. The lactating quarter was composed of huge mammary lobes and lobules without adipose tissue. In immature the lobe was consisted of few small lobules that composed of few of mammary alveoli while the lactating lobes had large sizes lobules and each had large alveoli which lined by tall cuboidal cells and supported by fibrous tissue and myo epithelial cells. In both immature and lactating ewes, the gland and teat cisternae were showed many of mucosal folds which lined by pseudo stratified columnar epithelium and supported by fibrous connective tissue. The teat cisterna of both immature and lactating was composed three layers; mucosal cisterna, fibro muscular layer and skin. The teat canal was lined by pseudo stratified squamous epithelium and the sub epithelial connective tissue showed well developed venous sinus and fibro muscular. Statistical analysis was revealed significant differences between the values of all parameters of immature and lactating ewes. Apparent surface areas of the lobe in immature and lactating were 122143.063±23.21 µm2 & 992541.188±33.81 µm2 respectively. Surface areas of lobule in immature and lactating were 1042.938±21.02 µm2 & 91565.977±25.60 µm2 respectively. Surface areas of alveoli in immature and lactating were 994.238±11.39 µm2 & 4584.270±19.26 µm2 respectively. Epithelial heights of alveoli in immature and lactating were 10.290±1.01 µm & 23.012±2.81 µm respectively. Thickness of inter lobar tissue in immature and lactating ewes 677.393±23.67 µm and 361.401±10.86 µm respectively. Thickness of inter lobular connective tissue in immature and lactating were 112.969±±11.48 µm and 90.281±9.81 µm respectively.

Chars from wood gasification for removing H2S from biogas

Biomass gasification is a mature thermochemical process used to produce a gaseous fuel to run burners, engines, and gas turbines. One of the byproducts of biomass gasification is char, which is a residue with low value and sometimes this material is even considered waste. Therefore, options for using gasification chars are required. On the other hand, there is a necessity of making biogas production and use more attractive by employing cheap materials for the biogas cleaning process. One of the promising options for using gasification chars is for cleaning biogas produced via anaerobic digestion (AD). The objective of this work was to assess the use of residual gasification chars from fast growing wood species (Eucalyptus Grandis-EG and Pinus Patula-PP) to remove hydrogen sulfide (H2S) from biogas produced via AD. Gasification chars were produced employing a laboratory scale downdraft gasifier. EG char (EG-C30) was produced by gasification of EG using a 30 L min−1 airflow, whereas the PP chars (PP–C20 and PP-C40) were produced from PP using 20 and 40 L min−1 airflow. Results show that these three chars offer potential for biogas cleaning, although PP-derived chars produced at higher airflow rates are more effective. The H2S removal capacity of the chars is ascribed to their large apparent surface area (up to 517 m2 g−1) and the presence of minerals and metals (e.g., Ca, K, and Fe) in the chars’ ash.

Activated carbon impregnated with copper to remove l-cysteine in an aqueous medium

In this work, the surface of commercial activated carbon was modified with the copper sulfate salt by impregnation method, aiming at the removal of reduced sulfur compounds from aqueous media. The materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy with energy dispersion spectroscopy, and using nitrogen gas as adsorbent, the apparent specific surface areas were determined. In addition, the semiquantitative analysis to explore the surface area was performed using methylene blue a ‘molecular probe.’ For the adsorption, was used l-cysteine as the model adsorbate. After the impregnation of activated carbon, the presence of copper in the forms of copper oxide and metallic copper was confirmed. The mapping of functional groups demonstrated the carbonaceous characteristic of the material. The photomicrographs showed crystals on the surface of the activated carbon impregnated with copper and revealed a copper atomic content of 16.8% w/w. However, the impregnation caused a reduction in the apparent specific surface, probably due to the clogging of the pores with the impregnation salt. On the other hand, the results of adsorption tests showed an increase in l-cysteine removal with impregnation, ranging from 76 to 93%. The results suggest that the adsorbent impregnated with copper is considered promising for the removal of compounds with reduced sulfur.

Gas sorption porosimetry for the evaluation of hard carbons as anodes for Li- and Na-ion batteries.

Hard carbons are promising candidates for high-capacity anode materials in alkali metal-ion batteries, such as lithium- and sodium-ion batteries. High reversible capacities are often coming along with high irreversible capacity losses during the first cycles, limiting commercial viability. The trade-off to maximize the reversible capacities and simultaneously minimizing irreversible losses can be achieved by tuning the exact architecture of the subnanometric pore system inside the carbon particles. Since the characterization of small pores is nontrivial, we herein employ Kr, N2 and CO2 gas sorption porosimetry, as well as H2O vapor sorption porosimetry, to investigate eight hard carbons. Electrochemical lithium as well as sodium storage tests are compared to the obtained apparent surface areas and pore volumes. H2O, and more importantly CO2, sorption porosimetry turned out to be the preferred methods to evaluate the likelihood for excessive irreversible capacities. The methods are also useful to select the relatively most promising active materials within chemically similar materials. A quantitative relation of porosity descriptors to the obtained capacities remains a scientific challenge.

Assessment of potato peel and agro-forestry biochars supplementation on in vitro ruminal fermentation.

BackgroundThe awareness of environmental and socio-economic impacts caused by greenhouse gas emissions from the livestock sector leverages the adoption of strategies to counteract it. Feed supplements can play an important role in the reduction of the main greenhouse gas produced by ruminants—methane (CH4). In this context, this study aims to assess the effect of two biochar sources and inclusion levels on rumen fermentation parameters in vitro.MethodsTwo sources of biochar (agro-forestry residues, AFB, and potato peel, PPB) were added at two levels (5 and 10%, dry matter (DM) basis) to two basal substrates (haylage and corn silage) and incubated 24-h with rumen inocula to assess the effects on CH4 production and main rumen fermentation parameters in vitro.ResultsAFB and PPB were obtained at different carbonization conditions resulting in different apparent surface areas, ash content, pH at the point of zero charge (pHpzc), and elemental analysis. Relative to control (0% biochar), biochar supplementation kept unaffected total gas production and yield (mL and mL/g DM, p = 0.140 and p = 0.240, respectively) and fermentation pH (p = 0.666), increased CH4production and yield (mL and mL/g DM, respectively, p = 0.001) and ammonia-N (NH3-N, p = 0.040), and decreased total volatile fatty acids (VFA) production (p < 0.001) and H2 generated and consumed (p ≤ 0.001). Biochar sources and inclusion levels had no negative effect on most of the fermentation parameters and efficiency. Acetic:propionic acid ratio (p = 0.048) and H2 consumed (p = 0.019) were lower with AFB inclusion when compared to PPB. Biochar inclusion at 10% reduced H2 consumed (p < 0.001) and tended to reduce total gas production (p = 0.055). Total VFA production (p = 0.019), acetic acid proportion (p = 0.011) and H2 generated (p = 0.048) were the lowest with AFB supplemented at 10%, no differences being observed among the other treatments. The basal substrate affected most fermentation parameters independently of biochar source and level used.DiscussionBiochar supplementation increased NH3-N content, iso-butyric, iso-valeric and valeric acid proportions, and decreased VFA production suggesting a reduced energy supply for microbial growth, higher proteolysis and deamination of substrate N, and a decrease of NH3-N incorporation into microbial protein. No interaction was found between substrate and biochar source or level on any of the parameters measured. Although AFB and PPB had different textural and compositional characteristics, their effects on the rumen fermentation parameters were similar, the only observed effects being due to AFB included at 10%. Biochar supplementation promoted CH4 production regardless of the source and inclusion level, suggesting that there may be other effects beyond biomass and temperature of production of biochar, highlighting the need to consider other characteristics to better identify the mechanism by which biochar may influence CH4 production.

High adsorption capacity of nitrobenzene from aqueous solution using activated carbons prepared from vegetable waste

AbstractThe present study reports the preparation of chemically activated carbons (PAC and ZAC) from apricot stones using phosphoric acid and zinc chloride, respectively. The potential use of the prepared carbons, as adsorbents, and the effect of chemical activation on the surface properties and adsorptive mechanism of nitrobenzene (NB) were investigated. The physicochemical properties of the obtained materials were characterized by Nitrogen adsorption–desorption isotherms, Scanning Electron Microscope, FTIR Spectroscopy, EDX analysis, Boehm titration, and pH of zero charge. The results show that the prepared samples present high apparent surface areas (1,382 and 1,111 m2/g for PAC and ZAC, respectively) and pores volumes with the presence of various functional groups. It was found that pseudo‐second model was the most suitable for the fitting of the experimental kinetic data and the intraparticle diffusion was not the unique rate‐controlling stage. The adsorption isotherms were well described by the Langmuir and the Freundlich models. According to the Langmuir model, the maximum adsorption capacity of PAC and ZAC were about 476.2 and 490.2 mg/g, respectively. The thermodynamic parameters showed the spontaneity, the exothermic nature, and the decrease in the randomness of the adsorption of nitrobenzene. Chemical regeneration showed that the prepared samples could be used for four time desorption–adsorption cycles with good efficiency for NB removal, indicating that the prepared carbons could be used as a low‐cost alternative to commercial activated carbon for the removal of nitrobenzene from wastewater.

Response in carcass yield, organ weights, and gut morphology of broiler chickens to incremental levels of Vachellia tortilis leaf meal

The objective of this study was to assess the carcass yield, organ weights, and gut morphology response to Vachellia tortilis inclusion in broilers. Unsexed 14-d-old Cobb500™ chicks were randomly assigned to six diets containing 0, 30, 60, 90, 120, and 150 g kg−1 dry matter of V. tortilis leaf meal. The slaughter weight (SW), dressed carcass weight (DCW), breast weight, thigh weight (TW), drumstick weight (DW), and internal organs were measured. Villus height (VH), crypt depth (CD), epithelial, submucosa, and muscularis thickness were taken. The apparent villus surface area (AVSA) and villus to crypt ratio were calculated. There was a linear decrease in SW and DCW (P &lt; 0.05) with the increase of V. tortilis leaf meal. The SW and DCW decreased by 0.77 and 5.25 g for each g kg−1 increase in V. tortilis, respectively. The TW and DW showed no relationship with levels of V. tortilis leaf meal. The relative weight of gizzard, intestine, stomach, heart, and kidney increased linearly (P &lt; 0.05) as levels of V. tortilis increased. The relative weight of the liver was not related to V. tortilis inclusion. The VH, AVSA, VH to CD ratio, as well as submucosa, muscularis, and epithelial thicknesses linearly increased as the V. tortilis inclusion level increased. There was no relationship between V. tortilis leaf meal inclusion and CD (P &gt; 0.05). The increased morphological measurements suggest that leaf meal inclusion alters gut physiology and could influence the digestion and absorption of nutrients in broilers.

From bulk to porous structures: Tailoring monoclinic SrAl2Si2O8 ceramic by geopolymer precursor technique

AbstractIn this paper, monoclinic SrAl2Si2O8 ceramics with porous structures were prepared based on ion‐exchanged geopolymer precursor technique. Micron‐level pores with a homogeneous pore‐size distribution were introduced into the inorganic framework using foaming agents. The results demonstrated that the apparent density, pore‐size distribution and specific surface area of porous geopolymer precursors can be well‐engineered via tailoring the category and concentration of the foaming agent. After being treated at 900°C, hexagonal SrAl2Si2O8 first‐crystallized from the amorphous geopolymer matrix and then gradually converted into monoclinic SrAl2Si2O8 between 1100°C and 1200°C. The resulting monoclinic SrAl2Si2O8 ceramics maintained the porous structures during high‐temperature treatments and exhibited high porosity, specific surface area, and compressive strength. The aforementioned strategy not only achieves monoclinic SrAl2Si2O8 ceramics with well‐defined and robust microstructures, but also provides an alternative route to prepare other porous ceramics, with potential applications in fields of high‐temperature filters, adsorbents, and heterogeneous catalysis.

Effect of Co-solution of Carbon Precursor and Activating Agent on the Textural Properties of Highly Porous Activated Carbon Obtained by Chemical Activation of Lignin With H3PO4

This work analyzes the effect of co-solution of carbon precursor and activating agent on the textural and surface chemistry properties of highly nanoporous activated carbons obtained by chemical activation of Alcell lignin with phosphoric acid. The success of this methodology highlights the possibility of directly using the liquors produced in organosolv process (Alcell) to prepare activated carbons by chemical activation with phosphoric acid. Co-solutions of lignin and phosphoric acid were submitted to a two steps thermal treatment, which consisted of a first oxidative treatment in air at 200 oC, followed by a thermal treatment in N2 at 400 oC, where activation of the oxidized lignin with phosphoric acid took place. A lignin-derived activated carbon with very high apparent surface area (2550 m2/g) and pore volume (1.30 cm3/g) was obtained with an initial phosphoric acid to lignin mass ratio of 2. Up to now, this is one of the highest values of apparent surface area reported not only for activated carbons prepared from lignin, but even for porous carbons prepared by chemical activation of other lignocellulosic materials with phosphoric acid. The use of lignin and phosphoric acid co-solution provided larger and more homogeneous effective interactions between the carbon precursor and the activating agent, by the formation of phosphate esters in the lignin matrix, which seems to be a key factor in the subsequent treatments: promoting crosslinking reactions in the carbonaceous matrix during the oxidative treatment in air at 200 oC and enhancing the development of a wide porosity during the following activation thermal treatment.

Pyrroloquinoline quinone attenuates isoproterenol hydrochloride‑induced cardiac hypertrophy in AC16 cells by inhibiting the NF‑κB signaling pathway.

Pyrroloquinoline quinone (PQQ) is a naturally occurring redox co-factor that functions as an essential nutrient and antioxidant, and has been reported to exert potent anti-inflammatory effects. However, the therapeutic potential of PQQ for isoproterenol hydrochloride (Iso)-induced cardiac hypertrophy has not yet been explored, at least to the best of our knowledge. In the present study, the anti-inflammatory effects of PQQ were investigated in Iso-treated AC16 cells, a myocardial injury cellular model characterized by an increase in the apparent surface area of the cells and the activation of intracellular cardiac hypertrophy-associated proteins. The results revealed that pre-treatment with PQQ significantly inhibited the expression of cardiac hypertrophy marker proteins, such as atrial natriuretic peptide, brain natriuretic peptide and β-myosin heavy chain. PQQ also inhibited the activation of the nuclear factor (NF)-κB signaling pathway in Iso-treated AC16 cells, thus inhibiting the nuclear translocation of NF-κB and reducing the phosphorylation levels of p65. On the whole, the findings of this study suggest that PQQ may be a promising therapeutic agent for effectively reversing the progression of cardiac hypertrophy.

A comparative study of the effects of 7β-hydroxycholesterol, 25-hydroxycholesterol, and cholesterol on the structural and thermal phase behavior of multilamellar dipalmitoylphosphatidylcholine bilayer vesicles

The effects of 7β-hydroxycholesterol (7βOH) and 25-hydroxycholesterol (25OH) on the phase behavior and the structural properties of the multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC) bilayers were investigated with comparing to the effects of cholesterol (Chol). Differential scanning calorimetry (DSC) measurements showed these three sterols have slightly but distinctly different effects on the thermal behavior of DPPC bilayers. X-ray diffraction data analysis on DPPC bilayers containing 30 mol% sterols with the aid of molecular volume data estimated by the neutral buoyancy method indicated that the order of apparent occupied surface area per molecule is DPPC/7βOH > DPPC/25OH > DPPC/Chol at both 25 ℃ and 50 ℃, suggesting that the strength of the condensation effect of these sterols follows inversely this order. Based on the findings in this study, we inferred the molecular orientations of Chol, 7βOH, and 25OH in DPPC bilayers.

Effect of supplementation of encapsulated organic acid and essential oil Gallant+® on some physiological parameters of Japanese quails

The current study was conducted to investigate the effects of dietary supplements of organic acid and essential oil Gallant+® on the growth hormone, glutathione, performance of growth, some biochemical parameters and intestinal histomorphology in quails. Japanese quails one-day-old (n=120) were distributed randomly into four groups included 10 / 3 replicates for each group. The G1, was control group that was fed on a basal diet. Quails of G2, G3, and G4 were fed on a supplemented diet Gallant+® 300, 600 and 900g/ton,respectively. Administration of Gallant+® 600 g/ton and 900g/ton to quail led to significant decrease in triglyceride while supplementation with 600 g/ton caused decrease in cholesterol. On the other hand, 300 g/ton caused an increase in final body weight and total weight through the duration of the experiment, as well as a decrease in total feed consumption and the best feed conversion ratio in all supplementation with 300 g/ton caused a significant growth hormone elevation. All feed additives didn't affect the level of glutathione. The addition of Gallant+® additive groups. Interestingly, the addition of different doses of Gallant+® to the diet increased villus length and width, crypt depth, villus / crypt ratio, percentage of goblet cell, apparent surface area, and intestinal epithelium thickness compared to the control group. It was concluded that dietary supplementation with different doses of Gallant+® improved growth hormone, growth performance and intestinal histomorphology in Japanese quails, and dietary supplementation with organic acid and essential oil as alternatives to the growth promoter of antibiotics.

Glycidyl Methacrylate-ethylene Glycol Dimethacrylate Copolymers with Varied Pore Structures Prepared with Different Reaction Parameters

Abstract Copolymers based on glycidyl methacrylate (GMA) are considered attractive as sorbents because the epoxy groups can be easily converted into other groups. Studies involving the influence of the synthesis parameters on the morphological characteristics of these copolymers are scarce. This work investigates the synthesis of copolymers of poly(GMA-co-EGDMA) with different porosity degrees obtained by varying the synthesis parameters. GMA-EGDMA copolymers were synthesized by suspension polymerization employing varied conditions and characterized by measuring apparent density, surface area and pore volume distribution, optical and scanning electron microcopies, FT-IR, thermogravimetry and titration of epoxide rings. The copolymer with highest surface area and pore volume (260.4 m2/g and 0.5 cm3/g) was prepared employing cyclohexane as diluent, 80% EGDMA in monomeric composition and 100% of dilution degree. There was a relation between the epoxide content of the copolymers determined by titration and the residue content formed in the first decomposition stage.

Effect of porosities on brazed martensitic steel tensile properties: 2D and 3D pre-mortem vs post-mortem characterizations

A quantitative investigation of the porosity and its effects on mechanical properties was conducted on brazed materials presenting macroscopically brittle behavior with various defect levels. Three different techniques for evaluating the porosity and the fracture mechanisms were compared: (i) pre-mortem X-ray computed tomography (XCT), (ii) post-mortem laser scanning confocal microscopy (LSCM), and (iii) post-mortem scanning electron microscopy (SEM). The apparent surface area of the pores was evaluated by segmenting the height maps produced by LSCM and the electron backscattered images produced by SEM. The results show good agreement for different porosity levels. The LSCM height maps for opposite fracture faces were virtually stitched together in order to reconstruct three-dimensional (3D) images of the whole brazed joints. These proved to be similar to the XCT 3D segmented images, yet with some discrepancies due to local plastic deformation. Quantitative volume fraction and spatial distribution of pores were assessed as well as the identification of fracture mechanisms. Interestingly, it was noted that two specimens with different ultimate tensile strengths presented the same porosity amount, but different distributions. Two distinctive features were identified in the broken specimens: plastically teared pillars and walls that were separating the pores before fracture, and plateaus of approximately constant height with micro-sized dimples showing interfacial fracture. Although the specimens exhibited a macroscopic brittle behavior, these features are characteristic of ductile fracture. The most probable scenario for fracture was conjectured as follows: (i) Final fracture occurs in the near-surface region of the samples and conversely early damage develops in the volume, (ii) Interfacial fracture within plateaus is responsible of the rupture/strength of the brazed specimen but detrimental effect is induced by the tearing if highly voided regions are present in the joint.

Intrinsically Microporous Polymer Nanosheets for High-Performance Gas Separation Membranes.

Microporous polymer nanosheets with thicknesses in the range 3-5 nm and with high apparent surface area (Brunauer-Emmett-Teller surface area 940 m2 g-1 ) are formed when the effectively bifunctional (tetrafluoro) monomer used in the preparation of the prototypical polymer of intrinsic microporosity PIM-1 is replaced with an effectively tetrafunctional (octafluoro) monomer to give a tightly crosslinked network structure. When employed as a filler in mixed-matrix membranes based on PIM-1, a low loading of 0.5 wt% network-PIM-1 nanosheets gives rise to enhanced CO2 permeability and CO2 /CH4 selectivity, compared to pure PIM-1.

Synthesis of Nano/Microsized MIL-101Cr Through Combination of Microwave Heating and Emulsion Technology for Mixed-Matrix Membranes.

Nano/microsized MIL-101Cr was synthesized by microwave heating of emulsions for the use as a composite with Matrimid mixed-matrix membranes (MMM) to enhance the performance of a mixed-gas-separation. As an example, we chose CO2/CH4 separation. Although the incorporation of MIL-101Cr in MMMs is well-known, the impact of nanosized MIL-101Cr in MMMs is new and shows an improvement compared to microsized MIL-101Cr under the same conditions and mixed-gas permeation. In order to reproducibly obtain nanoMIL-101Cr microwave heating was supplemented by carrying out the reaction of chromium nitrate and 1,4-benzenedicarboxylic acid in heptane-in-water emulsions with the anionic surfactant sodium oleate as emulsifier. The use of this emulsion with the phase inversion temperature (PIT) method offered controlled nucleation and growth of nanoMIL-101 particles to an average size of <100 nm within 70 min offering high apparent BET surface areas (2,900 m2 g−1) and yields of 45%. Concerning the CO2/CH4 separation, the best result was obtained with 24 wt.% of nanoMIL-101Cr@Matrimid, leading to 32 Barrer in CO2 permeability compared to six Barrer for the neat Matrimid polymer membrane and 21 Barrer for the maximum possible 20 wt.% of microMIL-101Cr@Matrimid. The nanosized filler allowed reaching a higher loading where the permeability significantly increased above the predictions from Maxwell and free-fractional-volume modeling. These improvements for MMMs based on nanosized MIL-101Cr are promising for other gas separations.