Level Of Microporosity Research Articles

Porosity effect on the functional properties and energy harvesting performance of Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramics

AbstractIn this study, the effect of porosity on the structural and functional (dielectric, ferroelectric, nonlinear, and piezoelectric) properties in Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramics was investigated. Various levels of microporosity in the range of 3% to 31 vol.% have been produced using poly(methyl methacrylate) microspheres as sacrificial templates. The structural investigation indicates a phase coexistence, as expected for this composition at room temperature. The maximum permittivity decreases with increasing porosity, from around 7000 (ceramic with 3 vol.% porosity) down to 3500 (ceramic with 31 vol.% porosity), and the Curie temperature shifts from 47 to 67°C when increasing porosity, related to the possible porosity‐induced structural and internal stress modifications. An enhanced piezoelectric response was found in the Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramic with intermediate porosity around 18 vol.%, with the highest value of piezoelectric response of 470 pC/N and a figure of merit of 7.3 pm2/N. The optimum piezoelectric properties at the intermediate porosity level are related to the microstructural changes (pore shape and connectivity) and possible field‐induced structural modifications. The piezoelectric energy harvesting measurement results have shown the possibility of using Pb‐free porous ferroelectric materials in devices for energy harvesting applications.

In-plane quasi-static compression deformation of Ti6Al4V double arrow-headed lattice structures fabricated by electron beam powder bed fusion process: Build orientation, scan speed and failure mechanism

The 2D double arrow-headed (DAH) lattice structures, which are promising cellular structures for impact mitigation, remain relatively unexplored in terms of their compression response when manufactured using the powder bed fusion process with Ti6Al4V (Ti64) alloy. This study aims to investigate the effects of build orientation and beam scan speed of Electron Beam Powder Bed Fusion (PBF-EB) process on the energy absorption of 2D Ti64 DAH lattice structures. Additionally, potential microstructural variations due to adjusted process parameters can be linked to different levels of energy absorption. For the compressions, the lattice structures were manufactured at two build orientations (0° and 45°), using three different beam scan speeds: speed function (SF), low speed (LS), high speed (HS). In micro-characterizations, the unit cells of 0deg-LS exhibited the lowest micro-porosity level at 0.12 %. Based on KAM values, thin struts at unit cells had higher residual stresses than thick struts, contributing to the initiation of failure locations. The compressions revealed that the 0deg-LS group absorbed 21.6 % and 24 % more energy than 0deg-SF and 0deg-HS groups, respectively, at compressions of 33 %. 45° samples absorbed approximately 10 % more energy than 0° samples except HS groups. The lowest micro-porosity of 0deg-LS contributed to having the highest energy absorption among 0deg samples. As the residual stresses in KAM values did not differ strongly with varying beam speed, varied energy absorptions were not linked to them. An optimization of the numerical compressions helped obtain designs with higher energy absorption and less relative volume. This study provides valuable insights into Ti64 cellular applications constrained with 2D-type designs.

Mineralogical Characteristics of Hematitic Iron Ore: A Geometallurgical Study on Ore from Eastern India

After being subjected to geometallurgical evaluation, the iron ores from Singhbhum Bonai-Keonjhar region, eastern India, have been designated as dense martite microplaty hematite high-strength ore (dM-mH-hs ore), massive dense martite microplaty hematite high-strength ore (mdM-mH-hs ore), schistose microplaty hematite low-strength ore (smH-ls ore), microplaty hematite powdery ore (mH-p ore), vitreous goethitic ore (vG ore), and ochreous goethitic ore (oG ore) end members, with varied strengths attributed to the microporosity levels. The first four variants form typical high-grade run-of-mines (ROMs) (hard, soft and powdery iron ore variants, e.g., ROM-HIO, ROM-SSIO, and ROM-PBD, respectively) with better amenability to beneficiation. In contrast, oG and vG ore end members form ROM lateritic iron ore (ROM-LIO) with poor amenability to beneficiation, having relatively higher concentrates of alumina (~3–6 wt%) due to the complex mineral chemistry of goethite and altered hematite. Banded hematite jasper (BHJ) is a very low-grade siliceous end member. In a mining operation, the ROMs may have the attributes of several combinations of the above-stated end members and ROM variants. The designated end members present in the ROMs determine their liberation, mineralogical processes, geometallurgical characteristics, amenability to beneficiation, product grade and recovery.

Bimetallic Metal Organic Framework Composites for Carbondioxide Capture

Maintaining breathable air in human space flight missions is a challenge since there will be a gradual increase in the concentration of CO2 due to the exhalation of the spacecraft crew. Modern air revitalization technology for space missions uses temperature swing adsorption with zeolite-based materials as the adsorbent. However, the major drawbacks of zeolites are difficulty in regenerating used adsorbent and low selectivity towards CO2. Besides, frequent replacement of adsorption beds is necessary because of their low adsorption capacity towards CO2. This requires carrying a few spare beds in the spacecraft, which is not preferred because of the low-weight requirements for space missions. Hence, shifting to alternate materials with more selectivity and adsorption capacity toward CO2 becomes essential. Metal-organic frameworks (MOFs) are a class of crystalline materials found to be potential adsorbents for CO2 capture. Due to their ultra-high porosity, tunable pore characteristics, selective capture, and synergistic performance, they could replace the existing zeolite-based adsorbents. Further enhancement in the adsorption capacity could be achieved by introducing a secondary metal into the framework. This will bring heterogeneity in the structure, creation of defects, and open metal sites, thus enhancing the adsorption behavior. Incorporating a secondary metal into the framework and an additional filler material like activated carbon, making a BMOF composite, would lead to an exemplary improvement in the adsorption activity. The addition of filler material will lead to an increase in pore volume, which will enhance the adsorption capacity. In the current work, activated carbon was synthesized from sawdust via chemical activation method using KOH as the activating agent. It was carried out at low temperatures to boost the porous structure formation. Then the composite of Cu-Ni bimetallic MOF with activated carbon was prepared through one-pot solvothermal synthesis. The incorporation of activated carbon created an additional number of pores in the system leading to enhanced adsorption. N2 adsorption-desorption analysis was carried out to find the surface area. The results showed that the surface area of activated carbon and Cu-Ni-Activated carbon BMOF composite was found to be 576 m2/g and 1321 m2/g, respectively. The analysis also revealed the presence of microporous system in the material. Several characterization techniques, such as IR, SEM, XRD etc., were used to study morphology and characteristic features. The SEM shows that the incorporation of nickel and activated carbon have made a profound modification on the octahedral morphology of copper.CO2 adsorption studies were carried out at 1 bar, 25°C. The BMOF composite adsorbent was found to adsorb ~4.52 mmol/g of CO2 whereas the as-synthesized activated carbon and ZSM-5 were found to adsorb ~2.71 mmol/g and ~1.68 mmol/g respectively. To understand the level of microporosity in the supermicropores range, CO2 adsorption analysis at 1 bar and 0°C was carried out since N2 adsorption at -196°C have limitations due to kinetic diffusion related problems at low temperatures. It revealed a micropore volume (<1.066nm) of 0.252 cm3 /g and a pore size range of 4-10 angstroms, which is ideal for selective CO2 adsorption. Also, the BMOF composite was found to adsorb ~8.27 mmol/g at 0°C, which showed that adsorption capacity increases with a decrease in temperature. Hence, the BMOF composites could serve as a promising adsorbent for selective CO2 capture. Figure 1

Highly Aligned Graphene Oxide for Lithium Storage in Lithium‐Ion Battery Through A Novel Microfluidic Process: The Pulse Freezing

AbstractThe modification of carbon‐based lithium‐ion batteries electrodes is required for the growing need of more reliable electric vehicles. Herein, a new method is introduced to fabricate vertically aligned graphene oxide (GO) films as free‐standing carbon lithium hosts for lithium‐ion batteries with enhanced performance. Vertical alignments are induced of GO in a microfluidic channel by controlling flow rates and patterns of GO suspensions. The vertical alignments are preserved and spontaneously form porous microstructures by Pulse Freezing the GO solutions inside the channel. This combined process results in the increase of levels of microstructure porosity and vertical alignment of GO films. The alignment and porous microstructures increase both electron and ion transfer capabilities across the prepared film. The half‐cell performance of aligned GO films shows a specific capacity of 440 mAh g−1 at a current density of 0.5 A g−1 after 150 cycles. This is a 190% specific capacity increase compared to the performance of a half‐cell prepared with GO without the high level of vertical alignment and microporosity. The significant increase in the value and stability of specific capacity and higher rates of charge transfer favor the promising application of carbon‐based lithium‐ion batteries for electric transportation industries.

Microporosity mediated proliferation of preosteoblast cells on 3D printed bone scaffolds

AbstractMicroporous structure plays a significant role in bone tissue engineering, to influence inductive bone formation and elevate bone ingrowth inside microporous scaffolds. We hereby fabricated microporous scaffolds by 3D printing with mixture of porogens and photopolymerizing resin. Our method can tune the microporosity of scaffolds from 0% to 36% by varying the porogen concentration in the inks from zero to 60 vol%. The microporosity and microspore size of scaffolds can affect in vitro expansion of preosteoblast cells. We evaluated the attachment, spreading and proliferation of MC3T3‐E1 mouse preosteoblast cells on the printed porous scaffolds. Our studies revealed that preosteoblast cells’ in vitro adhesion and proliferation were significantly mediated by the printed scaffolds. Cells proliferation on scaffolds with 20%–30% microporosity showed much higher rate than on other scaffolds. In this microporosity range, scaffolds also showed much better cell spreading and morphologies. At a low level of microporosity (&lt; 7%), the cell proliferation rate was even lower than the solid scaffolds, which indicates that the microporous structure is “toxic” for cells at low microporosity range. A higher microporosity (&gt; 35%) led to very poor cell attachment and is unfavorable for the proliferation of MC3T3‐E1 cells. Furthermore, the printed dual macro‐/micro‐porous scaffolds showed higher proliferation rate of MC3T3‐E1 cells as compared to mono‐pore sized scaffolds, either the macro‐porous or microporous structure.

Ultrahigh-CO2 Adsorption Capacity and CO2/N2 Selectivity by Nitrogen-Doped Porous Activated Carbon Monolith

Abstract Among microporous adsorbents, N-doped activated carbon monolith has been developed to achieve functionalized nanoporous carbon via cross-linked polymer precursors, which are used in Friedel-Craft alkylation and pyrolysis. Nitrogen-doping is establish an efficient method for boosting the CO2 adsorption capacity of carbon-based adsorbents, and research in this area is still full of challenges to reach a fit doping level of nitrogen (N) and intrinsic microporosity. Herein is an easy method that enables the preparation of microporous nitrogen-doped porous carbon monolith with proportion of 4.6 wt% N, which employs poly (H-BINAM) as primary material. By virtue of chemical activation, high microporosity is generated and gives a monolithic structured porous nitrogen-doped activated carbon (MPC-700). The resulting material showed a remarkable CO2 adsorption capacity (6.74 mmol g−1 at 273 K and 5.18 mmol g−1 at 298 K under 1 bar), and an excellent CO2 over N2 selectivity (153), which is measured from single-component adsorption isotherms according to Henry’s Law. This value exceeds the CO2 over N2 selectivity of reported carbon-based adsorbents including diverse nitrogen doped examples, the features of which are largely associated with remarkably high N-content and furthermore partial graphitic framework.

The Birgitta Field, Block 22/19a, UK North Sea

Abstract Birgitta Field was discovered by well 22/19-1 which encountered a 230 ft gas–condensate column in Triassic Skagerrak Formation and tested at a combined rate of 38.3 MMscfgd and 3750 bcpd. The tilted-fault block trap forms the crest of a Triassic ‘pod’ or mini-basin formed by salt withdrawal during Triassic extension, further rotated and eroded during Jurassic extension. Field extent is supported by apparent seismic hydrocarbon indications. An early oil charge was likely converted to condensate by Plio-Pleistocene gas influx and rapid burial, whilst an underlying palaeoresidual gas column reflects some trap leakage. Birgitta typifies certain Triassic reservoir characteristics in this part of the Central North Sea. The thick, relatively high net:gross reservoir comprises moderate to poorly sorted, sub-lithic to sub-arkosic sandstones deposited in a dryland braided fluvial system. Pore-lining chlorite overgrowths dominate the pore fabric, reducing pore throat sizes and contributing to appreciable levels of non-effective micro-porosity and hence elevated water saturation. Key petrophysical challenges are the accurate determination of effective porosity and water saturation. Birgitta approaches high pressure–high temperature conditions and illustrates some of the challenges of progressing small, unappraised field tie-backs. These include resource uncertainty, compartmentalization risk, infrastructure access and marginal economics. Evaluated for development several times, Birgitta presently remains undeveloped.

Modelling of oedometer tests on pellet-powder bentonite mixtures to support mock-up test analysis

Bentonite mixtures of MX-80 (80% of high-density pellets and 20% of bentonite powder on a mass basis) have been recently proposed as a candidate material for sealing deep geological disposals of high-level radioactive waste. A loading/unloading oedometer test at constant water content has been performed on this mixture, which has been modelled using the finite element Code_Bright. The constitutive model used to represent the mechanical response is the Barcelona Expansive Model (BExM), since a multi-modal pore size distribution characterises the pore network of the mixture. During compression at constant water content, an increase in the degree of saturation and a consequent reduction of suction is induced. Consequently, two competing effects occur at different pore-size scales: (a) compression due to mean net stress increase; and (b) expansion on induced suction reduction that mainly affects the micro-porosity level inside aggregates. A sensitivity analysis has been performed to explore these effects, in which the elastic compressibility parameter at the micro-porosity scale for changes in mean effective stress plays an important role.

3D characterization of structure and micro-porosity in two cast irons with spheroidal graphite

Formation of low density graphite phase during solidification increases the volume of semi-solid cast iron with spheroidal graphite (SGI) and resulted pressure could help eliminate shrinkage micro-porosity in casting. Therefore, micro-porosity in casting can be linked to 3D graphite nodule structure. Two experimental SGI's with different levels of shrinkage micro-porosity in castings were intentionally produced by variation in inoculation parameters which influenced graphite nodule structure. 3D-morphological characteristics of graphite nodules and micro-porosity level were determined by μCT scanning. The obtained statistical data was discussed with respect to graphite nodule solidification mode and casting soundness. The capabilities of μCT scanning in predicting micro-shrinkage in SGI casting were compared to the other traditionally used techniques.

Formation of Layer WC-(Co,Ni,Al) Structure on the Cutting Plate Surface of WC-7(W,Ti)C-10Co Cemented Carbide in the Contact Area with Ni3Al Melt

It reported that a new type of the structure was found on the cutting plate surface of the WC-7(W,Ti)C-10Co cemented carbide of T5K10 brand after contact with the Ni3Al melt at 1530°C in a vacuum, which includes external WC-(Co,Ni,Al) and intermediate WC-(W,Ti)C-(Co,Ni,Al) layers with varying chemical and phase composition by thickness. The maximum content and dimensions on the Co-based phase are characteristic of the structure on the boundary of the outer and transition layers, which by 1.7 and 2 times, respectively, exceed the similar indicators in the basic structure of this sample. The formation of such a structure occurs by the output of W, C and the Co-based phase from the volume on the surface of the plate and the subsequent absorption of it by N and Al from the Ni3Al melt. It is shown that in the formed layer structure on the plate surface there is a residual microporosity but less than that in the basic structure outside the surface layer, which also decreased in comparison with the level of microporosity in the structure of the initial plate.

Defect Susceptibility of Tensile Properties to Microporosity Variation in High-Pressure Die-Cast Aluminium Alloy Controlled by Gas Bubbling Flotation Treatment

This study aims to investigate the variability in the tensile properties of high-pressure die-cast aluminium alloy controlled by the gas bubbling filtration or flotation (GBF) process in terms of the defect susceptibility of tensile properties to the variation in the overall microporosity level, including bifilm oxide and pre-existing microvoids. Test specimens were fabricated by adopting a high-pressure die-cast process of the cold chamber type at the production scale using A384.0 aluminium alloy. The volumetric porosity of cast specimens gradually decreased with GBF treatment, even though the fractographic porosity tended to decrease only under a specific GBF condition, with a remarkable microstructural refinement. The degassing treatment of 5 min could achieve a remarkable grain refinement, and further, this optimal condition could induce a practical improvement in the defect susceptibility of tensile properties to microporosity variation as well as the nominal level of tensile properties. The main reason for grain refinement in GBF treatment is the dispersion of small-sized pro-eutectic solid particles by fragmentation of abnormally big-sized dendrites, which are preferentially formed by an undercooling effect in a region around the impeller and gas inlet. Additionally, the improvement in melt quality by degassing action for dissolved hydrogen gas is practically nullified through the coarsening of pro-eutectic solid particles as well as the additional inclusion of bifilm oxide by excessive GBF treatment.

Bioceramic scaffolds fabrication: Indirect 3D printing combined with ice-templating vs. robocasting

Ice-templating combined with indirect 3D printing is proposed as a promising method for preparation of scaffolds with multiscale porosity, including a well-defined interconnected macro-channel network. Robocasting was used as a comparative technique to produce scaffolds with comparable porosity at the introduced macroporosity and the inter-grain microporosity levels. Porosity, phase composition and mechanical stability were measured and compared for bio-scaffolds prepared by both techniques. Comparable total porosities could only be achieved in robocasting by choosing a significantly lower sintering temperature (950 °C vs. 1200 °C). The compressive strength of robocast scaffolds was significantly greater (6.5 ± 1.19 MPa vs. 2.3 ± 1.00 MPa, respectively). However, the increased level of interconnected multiscale porosity coupled to a finer grain size of ice-templated samples sintered at 1200 °C (∼ 500 nm vs. 2.5 μm for robocast parts) could prove to be beneficial for the development of highly porous bioactive scaffolds with enhanced biological performance.

Characterization and biological properties of a novel synthesized silicon-substituted hydroxyapatite derived from eggshell.

In the present study, the effect of adding different concentrations of silicon on physical, mechanical and biological properties of a synthesized aqueous precipitated eggshell-derived hydroxyapatite (e-HA) was evaluated. No secondary phases were detected by X-ray diffraction for the specimens e-HA and e-HA containing silicon (Si-e-HAs) before and after heating at 1200°C. A reduction in the crystallite size and a-axis as well as an increase in c-axis was occurred when silicon replacement was happened in the structure of e-HA. The presence of Si-O vibrations and carbonate modes for Si-e-HAs was confirmed by Fourier transform infrared spectroscopy analysis. The range of porosity and density was varied from 25% and 2.4 g cm-3 to 7% and 2.8 g cm-3 for e-HA and Si-e-HAs. The values of Young's modulus ( E) and compressive strength were varied for e-HA and Si-e-HAs. The porous structure of the samples was reduced when they were heated as e-HA kept the porous microstructure containing some dense areas and Si-e-HAs possessed a rough surface including slight levels of microporosity. The acellular in vitro bioactivity represented different apatite morphologies for e-HA and Si-e-HAs. The G-292 osteoblastic cells were stretched well on the surface with polygon-shaped morphology for 0.8Si-e-HA after 7 days of culture. According to MTT assay and alkaline phosphatase test, the maximum cell activity was related to 0.8Si-e-HA. The minimum inhibitory concentration for 0.8Si-e-HA and e-HA was estimated to be about 3.2 and 4.4 mg/mL, respectively. In overall, the sample 0.8Si-e-HA exhibited a higher bacteriostatic effect than e-HA against gram-negative bacterial strain Escherichia coli.

Reducing Shrinkage Porosity in High-Performance Steel Castings: Case of an ASME B16.34 Gate Valve Body: Part 1—Analysis, Techniques and Experimental Approach

X-ray computed tomography (CT), in combination with scanning electron microscopy (SEM), has been successfully used to evaluate shrinkage macro- and microporosity levels in a high-performance steel casting. As a test case, a commercially available gate valve body of a Class 300 gate valve based on the ASME B16.34 standard and made from A216 WCB cast steel was analysed, in accordance with the specifications of the standard. The radiographic inspection process, in accordance with ASTM E2868 for digital radiographs, is presented. Both X-ray CT radiographs and SEM micrographs are presented, showing the presence of shrinkage macro- and microporosity, in addition to gas porosity. This study is a precursor to the development of a systematic approach for reducing shrinkage porosity in castings based on the optimisation of design and process parameters that influence porosity formation during solidification.

Micro- and mesoporous-enriched carbon materials prepared from a mixture of petroleum-derived oily sludge and biomass

An innovative way of producing micro-mesoporous enriched active carbon (AC) materials from mixtures of petroleum industrial waste (oily sludge) and agricultural residue (rice husk) is presented. The quality of the products was evaluated by N2 adsorption–desorption isotherms and methylene blue (MB) adsorption tests. The asphaltene content of the oily sludge significantly affected the AC's specific surface area. The higher asphaltene content led to a higher specific surface area (2575m2/g) than that observed for the mixture with a lower asphaltene content (1849m2/g). Moreover, the ACs derived from mixtures of raw materials exhibited lower microporosity levels than those prepared with only oily sludge or rick husk. This may have been caused by the asphaltenes contained in oily sludge forming a carbon skeleton with the ash from the rice husk wrapped inside, generating more mesopores. The products prepared from the mixture also possessed far more oxygen-containing functional groups than AC produced from oily sludge alone. Meanwhile, the cellulose in the rice husk appeared to increase the amount of oxygen-functional groups in the AC products. The highest MB adsorption capabilities for the two AC samples were 588.24 and 757.58mg/g for AC-S1-3 and AC-S2-3, respectively. The Langmuir model fitted the experimental data better than the Freundlich model, suggesting the process can be described as homogeneous monolayer adsorption. X-ray diffraction and X-ray photoelectron spectroscopy data revealed the amorphous nature of the carbon in the AC products. Overall, mixtures of oily sludge and rice husk offer a promising option for preparing porous AC.

Scaling-up of mesoporous silica films via an eco-efficient UV processing method. Part 1: Photoinduced mesostructuration

Designing sustainable and industrially viable processing methods to synthesize ordered mesoporous films is a necessary condition to tap their full potential of applications. In order to respond to this challenge, well-established photoacid-catalyzed sol-gel photopolymerization has been harnessed to prepare large (>100 cm2) and micrometer-thick porous silica films possessing a 2D hexagonal mesostructure. Our UV irradiation system consists of two inexpensive and low radiant power fluorescent UV tubes (3 mW cm−2, 280–380 nm) enclosed in a hygrometric chamber. Precise conditions to promote copolymer/silica hybrid film mesostructuration have been determined as regards relative humidity, film thickness and templating agent concentration. The mesostructured films have been analyzed using an extensive range of techniques including electron microscopy, grazing-incidence small-angle X-ray scattering (GISAXS), and N2 sorption measurements, and solid-state NMR spectroscopy. Mesoporous silica films with a specific surface area up to 314 m2 g−1 have been achieved with a very low level of microporosity. Coupling of X–ray diffraction (XRD) and FTIR spectroscopy has enabled to shed light into the photoinduced self-assembly mechanism.

Effect of strain rate on the defect susceptibility of tensile properties to porosity variation

The contribution of the strain rate to the dependence of tensile properties on the microporosity variation in A356 casting alloy was investigated in terms of the defect susceptibility of tensile properties to the microporosity variation with variations of the strain rate as well as the relative contribution of microporosity and strain rate to overall tensile properties. The test samples were prepared using a low-pressure die-casting process and subsequent T4 treatment (12-h at 540°C), and the tensile test was carried out at room temperature for strain rates varying in the 1.4×10−4∼1.4×10−1s−1 range. The overall dependence of tensile properties on the strain rate is not described precisely owing to remarkable deviations in the data that mainly arose from the variation of the fractographic porosity; these deviations can be clearly attributed to the variability in the defect susceptibility coefficient of the tensile properties to the microporosity variation. The defect susceptibility coefficient of ultimate tensile strength (UTS) to microporosity variation increases with the strain rate, whereas the defect susceptibility coefficient of elongation decreases. Although the UTS for the sample with a low microporosity level increases with increasing strain rates, the UTS above a certain porosity level is affected adversely and decreases with the increasing strain rates. However, the nominal level of tensile elongation on the variation of the strain rate clearly decreases with the increase of the microporosity. The fractographic porosity practically decreases with the increase of the strain rate, and the overall fracture path between the micro-voids depends practically upon a certain transition of the fracture mode of Si particles accompanying the variation of the strain rate. Additionally, the damage evolution of eutectic Si particles is transited from a mixed mode of cracking and debonding failure to a failure mode which the debonding failure dominates as the strain rate increases.

Modeling of interdendritic porosity defects in an integrated computational materials engineering approach for metal casting

Modelling and simulation of multiphysical phenomena need to be considered in the design and optimisation of mechanical properties of cast components in order to accelerate the introduction of new cast alloys. The data on casting defects, including microstructure features, are crucial for evaluating the final performance-related properties of the component. In this paper, the required models for the prediction of interdendritic casting defects, such as microporosity and hot tears, are reviewed. The data on calculated solidification shrinkage are presented and its effects on microporosity levels discussed. Numerical simulation results for microporosity are presented for A356, 356 and 319 aluminium alloys using ProCAST™ software. The calculated pressure drop of the interdendritic liquid was observed to be quite significant and the regions of high-pressure drop can be used as an indicator on the severity of interdendritic microporosity defects.

From Azo-Linked Polymers to Microporous Heteroatom-Doped Carbons: Tailored Chemical and Textural Properties for Gas Separation.

Heteroatom-doped porous carbons with ultrahigh microporosity were prepared from a nitrogen-rich azo-linked polymer (ALP-6) as a precursor for gas separation applications. Direct carbonization and chemical activation of ALP-6 with ZnCl2 and KOH were successfully applied to obtain three different classes of porous carbons (ALPDCs). Synthetic processes were conducted at relatively mild temperatures (500-800 °C),which resulted in retention of appreciable levels of nitrogen content (4.7-14.3 wt %). Additionally, oxygen functionalities were found to be present in chemically activated samples. The resultant porous carbons feature a diverse range of textural properties with a predominant microporous nature in common. The highest CO2 uptake value of 5.2 mmol g(-1) at 1 bar and 298 K in ALPDCK600 was originated from well-developed porosity and basic heteroatoms (N and O) on the pore walls. The highest heteroatom doping level (12 wt % nitrogen and 20 wt % oxygen) coupled with the high level of microporosity (84%) for ALPDCK500 led to notable CO2/N2 (62) and CO2/CH4 (11) selectivity values and a high CO2 uptake capacity (1.5 mmol g(-1), at 0.15 bar) at 298 K. This study illustrates the effective use of a single-source precursor with robust nitrogen bonds in combination with diverse carbonization methods to tailor the chemical and textural properties of heteroatom-doped porous carbons for CO2 capture and separation applications.