Porous Frame Research Articles

Evaluation of internal fit of press ceramic and porous structured cobalt–chromium crown fabricated by additive manufacturing

The purpose of this in vitro study is to fabricate a novel metal-ceramic prosthesis with a porous structure, to compensate for the disadvantages associated with the design of existing prostheses, and to measure the internal fit of this prosthesis. In this in vitro study, the mandibular first molar was scanned from the dental computer-aided-design to design a 3 mm porous structure frame. The frame was produced using the lamination method and fired in a pressed ceramic. For comparison, pore-free specimens were fabricated by selective laser sintering (SLS) as described above, and porous specimens were fabricated by casting (total n = 30). The internal fit was then measured using a digital microscope (at 100× magnification), and the data were analyzed using one-way ANOVA (α = 0.05). The total mean internal discrepancies for each group were 42.32 ± 22.50 μm for the porous structure SLS group (PS-group), 107.54 ± 38.75 μm for no-porous casting group (group), and 121.36 ± 50.19 μm for the no-porous SLS group (group), with significant differences (P < 0.05) among all groups. The internal discrepancies of porous structure crown fabricated by SLS were smaller than that of no-porous crown fabricated by casting and SLS. Based on these laboratory findings, further studies should be conducted to evaluate the feasibility of the newly designed porous structure and press ceramic prosthesis to determine whether they can be applied in clinical practice.

Effect of metallic coatings on infiltration of AK12 alloy into porous carbon graphite frame under non-autoclave impregnation conditions

The effect of copper and nickel coatings applied on the carbon graphite framework, as well as on the surface of the open pores of carbon graphite before impregnation by AK12 alloy, in order to obtain composite material carbon graphite—aluminum by non-autoclave technology is studied. It is shown that copper and nickel coatings increase filling of open pores by matrix alloy, which is indicated by increase of physical and mechanical properties and density of composite material after impregnation. It is found that the use of nickel electrochemical coating during impregnation resulted in the formation of a transition zone enriched by nickel at the interface, its concentration sharply decreasing from the periphery to the centre of the pore. When using copper coating, the copper concentration decreases away from the interface, but is traceable across the entire filled cross-sectional area of the metal in the pore, which can be explained by the different diffusion rates of copper and nickel into aluminium. It is shown that the compression strength of specimens with copper coating increased by 17, 92 and 1 10 % at impregnation temperatures of 700, 750 and 850 °C, and of specimens with nickel coating by 14, 75 and 98 % relative to uncoated carbon graphite AG-1500, which is caused by an increase in the metal component in the composition of the composite material.

Photocatalytic degradation of methylene blue using a manganese based metal organic framework

Herein, we report the hydrothermal synthesis of a stable and porous 3D-supramolecular frame work of manganese. The ligands used for the fabrication of Mn-MOF are 1,5–naphthalene di sulphonic acid and 4,4′-bipyridine. The applicability of the synthesized MOF as a reusable catalyst in the degradation of methylene blue (MB) under visible light has been investigated. Through the intervention of advanced oxidation process, the Mn-MOF exhibits enhanced photocatalytic activity in the presence of hydrogen peroxide. The active species that facilitates the dye degradation are hydroxyl radicals and holes.

Heterostructured hollow fibers stitched together from nickel sulfides capped S, N-codoped carbon nanotubes as a trifunctional electrode for flexible hybrid Zn batteries

The explorations of highly performance cathodes are the key concerns of hybrid Zn batteries (HZBs) that combine the Zn-ion (ZIBs) and Zn-air (ZABs) batteries. Herein, a freestanding hollow fiber stitched by the heterostructures of S, N-codoped carbon nanotubes (SNCNT) confined nickel sulfides (Ni3S2) nanoparticles are designed as a trifunctional electrode for HZB. The nickel sulfide nanoparticles are encapsulated by in-situ grown S, N-codoped carbon nanotubes, which stitch together to assemble the hollow fibers. Their highly porous and conductive frame gives fast electron/ion pathways and abundant active sites. The interaction between Ni3S2 and SNCNT favors the OER catalytic properties and the S, N-codopant in SNCNT endows ORR activities in the heterostructured unit. Both experimental and theoretical results demonstrate the Ni3S2@SNCNT hollow fiber is a trifunctional and flexible electrode with high OER/ORR electrocatalytic activities and superior electrochemical properties. The hybrid Zn battery based on Ni3S2@SNCNT hollow fiber cathode manifests two-set charge/discharge characteristics, high energy/power densities and good long-term durability. Additionally, the flexible HZB devices based on the Ni3S2@SNCNT flexible cathode achieve the high performance, unique “self-breathing” abilities and high adaptation in multfarious working conditions. More impressively, they exhibit good uninterrupted working ability even in the sudden transitions on working conditions. Therefore, this work not only provides a highly reliable, trifunctional and flexible electrode, but also promotes the development of the high-performance power sources for the electronics in multifarious conditions.

Converting amorphous kraft lignin to hollow carbon shell frameworks as electrode materials for lithium-ion batteries and supercapacitors

Lignin has been widely used as a high-quality carbon source in the preparation of carbon electrodes. Because the skeleton of lignin molecules is an unordered three-dimensional network structure, it is difficult to obtain high-performance porous carbon electrode materials with regular structures by conventional carbonization methods. To improve the electrochemical performance of lignin-based carbon, green, convenient and mass-produced lignin-based porous hollow carbon shell frameworks (HCSFs) were proposed. With the help of electrostatic forces, lignin/silica nanocomposites were generated by an insitu self-assembly and coprecipitation method using quaternary ammonium lignin and sodium silicate as raw materials. After carbonization and activation, HCSFs with hollow porous frame structures rich in nitrogen were obtained. The prepared HCSFs can maintain a reversible specific capacity of 480 mA h g−1 after 200 cycles at 200 mA g−1 as a lithium-ion battery anode, and they can also maintain a specific capacity of 180.4 mF g−1 after 10,000 cycles at 1 A g−1 as a supercapacitor electrode. Their better energy storage performance is mainly attributed to the special hollow shell structure of HCSFs, which can provide channels for rapid ion transport, and the doping of nitrogen atoms can also provide an increase in the number of storage sites. This work provides a theoretical basis for the preparation of carbon shells from biomass and widens the application field for the high value utilization of industrial lignin.

INCREASING THE INFILTRATION ABILITY OF ALUMINUM ALLOY FOR IMPREGNATION IN A NON-AUTOCLAVE METHOD

An increase in the efficiency of gas-free impregnation of a porous carbon-graphite frame to aluminum alloys by applying thin electroplated metal alloying coatings to the surface of the pores of a carbon-graphite sample by electrochemical method is investigated. It is shown that the preliminary deposition of such coatings makes it possible to obtain alloying with highly pure elements, increasing the filling of pores with matrix melt at impregnation temperature (800 ° C).

Direct Ink Writing of Highly Conductive MXene Frames for Tunable Electromagnetic Interference Shielding and Electromagnetic Wave-Induced Thermochromism

Highlights3D printing of MXene frames with tunable electromagnetic interference shielding efficiency is demonstrated.Highly conductive MXene frames are reinforced by cross-linking with aluminum ions.Electromagnetic wave is visualized by electromagnetic-thermochromic MXene patterns.The highly integrated and miniaturized next-generation electronic products call for high-performance electromagnetic interference (EMI) shielding materials to assure the normal operation of their closely assembled components. However, the most current techniques are not adequate for the fabrication of shielding materials with programmable structure and controllable shielding efficiency. Herein, we demonstrate the direct ink writing of robust and highly conductive Ti3C2Tx MXene frames with customizable structures by using MXene/AlOOH inks for tunable EMI shielding and electromagnetic wave-induced thermochromism applications. The as-printed frames are reinforced by immersing in AlCl3/HCl solution to remove the electrically insulating AlOOH nanoparticles, as well as cross-link the MXene sheets and fuse the filament interfaces with aluminum ions. After freeze-drying, the resultant robust and porous MXene frames exhibit tunable EMI shielding efficiencies in the range of 25–80 dB with the highest electrical conductivity of 5323 S m−1. Furthermore, an electromagnetic wave-induced thermochromic MXene pattern is assembled by coating and curing with thermochromic polydimethylsiloxane on a printed MXene pattern, and its color can be changed from blue to red under the high-intensity electromagnetic irradiation. This work demonstrates a direct ink printing of customizable EMI frames and patterns for tuning EMI shielding efficiency and visualizing electromagnetic waves.

Single-atomic Fe anchored on hierarchically porous carbon frame for efficient oxygen reduction performance

Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques in energy storage and conversion. Herein, a hierarchical porous single atomic Fe electrocatalyst (Fe/Z8-E-C) is rationally designed and synthesized via acid etching, calcination, adsorption of Fe precursor and recalcination processes. This unique electrocatalyst Fe/Z8-E-C shows excellent oxygen reduction performance with a half-wave potential of 0.89 V in 0.1 mol/L KOH, 30 mV superior to that of commercial Pt/C (0.86 V), which is also significantly higher than that of typical Fe-doped ZIF-8 derived carbon nanoparticles (Fe/Z8-C) with a half-wave potential of 0.84 V. Furthermore, Fe/Z8-E-C-based Zn-air battery exhibits greatly enhanced peak power density and specific capacity than those of original Fe/Z8-C, verifying the remarkable performance and practicability of this specially designed hierarchical structure due to its efficient utilization of the active sites and rapid mass transfer. This present work proposes a new method to rationally synthesize single atom electrocatalysts loaded on hierarchical porous frame materials for catalysis and energy conversion.

Recent progress in the removal of mercury ions from water based MOFs materials

• We reviewed the application of MOF materials in removal of Hg 2+ ions. • We described the advantages of MOF membrane in removal of Hg 2+ ions. • We propose the current problems faced by Hg 2+ ions treatment and future solutions. Mercury pollution of water has caused serious health problems in humans. Therefore, reducing the mercury content into the drinking water standard is currently a priority measure. As a kind of porous frame materials with adjustable structure and easy to design and synthesize, metal–organic frameworks (MOFs) materials have attracted widespread attention. Their large specific surface area and adjustable pores make MOFs an excellent platform for removing mercury metals from water. In this review, we discussed the mercury removal performance of functionalized MOF powder materials, including sulfur-functionalized MOF, nitrogen-functionalized MOF, nitrogen-sulfur co-functionalized MOF, MOF composites and MOFs-derived materials. Compared to MOF powder materials, MOF membranes can easily recycle and effectively avoid secondary pollution. Therefore, we also reviewed nanofiber MOF membranes and polymer-supported MOF membranes. At the same time, in order to further explore the potential of MOF materials in heavy metal adsorption, we also introduced the current problems and challenges faced by MOF materials in detail, and proposed future research directions and difficulties to be overcome. We will hope that the review may provide more researchers with a more comprehensive, intuitive, clear cognition.

FORECAST EVALUATION OF HEAT PROTECTION AND MECHANICAL PROPERTIES OF INSULATING CONSTRUCTION CERAMIC MATERIALS

An integrated approach to determine the rational design of wall ceramic products based on modeling their behavior under operating conditions is proposed. This approach was used in the development of technology for heat–efficient insulating construction ceramic materials for energy–saving construction. For two models of porous–hollow ceramic products with a porous frame (40 % of voids) and a dense frame (60 % of voids), a predictive assessment of their heat–shielding and mechanical properties was carried out. Calculations of the equivalent coefficient of thermal conductivity of models based on Fourier’s law established that with a decrease in the voidness of products with a porous wall, the coefficient of their thermal conductivity decreases by 12 %, which improves the heat–shielding properties. Based on the results of computer simulation of the behavior of models under the influence of static power loads, it was determined that porosity of the ceramic framework of products leads to degradation of mechanical strength almost proportionally to a decrease in voidness. The stress–strain state of 3D models of ceramic structures with different pore geometry (spherical, globular, ellipsoidal) is analyzed and it is shown that stresses are concentrated in the contact zones of a ceramic matrix with pores. It is shown that the most durable is the structural model with spherical pores. The expediency of organizing such a structure, the need to strengthen the ceramic matrix of materials and zones surrounding the pores, as the most vulnerable structural sites, is shown. The results of predictive calculations have been experimentally confirmed in the development of technology for structural and heat–insulating composite–type ceramic materials based on low–melting loam and ash microspheres, which provide a given structural picture of the ceramic material.

Features of determining the deformed state of a particle material during hot stamping of porous moldings

The paper describes main methods for assessing the deformed state of porous body metal frames developed by different authors based on the analysis of yield conditions and governing equations, using the principle of equivalent strains and stresses, and studying the kinetics of metal strain during pressing. Formulas were derived to determine the components of the powder particle material strain tensor through dyads, as scalar products of the basis vectors of the convected coordinate system at each moment of porous molding strain. The expediency of using the analytical expressions developed to determine the deformed state of the particle material was experimentally substantiated subject to the known displacement vector parameters of representative elements (macrostrains) of porous billets. The applications of well-known analytical expressions were established, and the proposed formulas proved applicable for the deformed state assessment of particle metal during the pressure processing of powder products of different configurations and designing billets with a defined porosity and geometric parameters as a basis for compiling software algorithms for the computer simulation of porous molding hot stamping.

In situ self-assembly assisted synthesis of N-doped mesoporous hierarchical carbon aerogels-wrapped Li2ZnTi3O8 composite for high-rate lithium ion batteries

Reinforcing electronic and ionic conductivity is very important to realize the high-rate Li2ZnTi3O8 (LZTO) anode for Lithium-ion batteries (LIBs). Here, we reported a synthetic strategy toward in situ growth of homodispersed Li2ZnTi3O8 on ultralight 3D carbon aerogels (CAs) via facile heat treatment and activation process taking LiOH as activating agent. Such an optimized composite obtains a specific surface area of 154.427 m2 g−1 and a high pore volume. The strong interaction between the LZTO and N-doped CAs, a highly electrical conductivity and multidimensional ion transport channels of the hybrid result in a high capacity, outstanding high-rate performance and long cycle life. As a result, the NPC-LZTO electrode (NPC-LZTO-B) delivers a commendable reversible capacity at high-rate (e.g. 162.4 mAh g−1 at 5 A g−1 (22 C) and 127.3 mAh g−1 at 10 A g−1) and durable long-term performance (capacity retention of 73% after 4500 cycles at 5 A g−1). Moreover, the kinetic analysis confirms that the feature of pseudocapacitance boosts lithium-ion storage performance at high rate. Porous carbon aerogels frame constructed LZTO nanocomposite electrodes provide a facile way to design high durable LIBs anode.

Novel Porphyrin Zr Metal-Organic Framework (PCN-224)-Based Ultrastable Electrochemiluminescence System for PEDV Sensing.

The sensitive detection of coronavirus is of vital importance for the prevention of its rapid spread. Porcine epidemic diarrhea virus (PEDV) is a highly contagious coronavirus that causes severe diarrhea and death in neonatal piglets. In this work, a novel PCN-224-based electrochemiluminescence (ECL) system was constructed for PEDV detection with high sensitivity. We found that PCN-224 can be employed as an ECL reporter with a strong signal because of its zirconium-based organic porous frame nanomaterial with a large specific surface area and stable structure. TiO2 nanoparticles were used as an accelerator for the first time to promote the reduction of coreactant potassium peroxydisulfate on the cathode; thus, the initial ECL signal of PCN-224 was significantly amplified. In the presence of PEDV, the ECL signal decreased due to the block effect to electron transfer. As a result, the novel "signal off" biosensor achieved a sensitive detection of PEDV ranging from 1 pg/mL to 10 ng/mL, with a detection limit of 0.4 pg/mL (S/N = 3). Importantly, the PCN-224 nanomaterial enriched the ECL system in biological analysis, and the proposed strategy provided a new route for coronavirus detection.

Features of the processes of heat and mass transfer when drying a large thickness layer of wood biomass

The article presents the results of the experimental studies of heat transfer in a layer of moist wood biomass under conditions of its dehydration when heated in a high-temperature gas environment.The basic laws of the formation process of the temperature field of the biomass layer during its dehydration have been established. It is shown that essentially nonuniform temperature fields are formed in the wood biomass layer, the form of which is a consequence of the influence of a complex of heat and mass transfer processes occurring together under conditions of heat conduction, intense phase transformations (evaporation and condensation of water), and water vapor diffusion through the porous frame of the biomass layer.It has also been found that as a result of intense absorption of heat during evaporation of moisture and vapor filtration, local cooling of biomass occurs. A physical model of heat and mass transfer processes in the porous structure of moist wood biomass upon heating has been formulated, which differs from the well-known detailed descriptions of the processes of filtering water vapor into the area of the relatively low temperatures from the zone of intense evaporation, condensation and subsequent secondary evaporation.

ВЛИЯНИЕ ЭЛЕМЕНТНОГО ПОРОШКОВОГО СЫРЬЯ НА ФОРМИРОВАНИЕ ПОРИСТОГО КАРКАСА МАХ-ФАЗЫ Ti3AlC2 ПРИ ПОЛУЧЕНИИ МЕТОДОМ СВС

The ternary carbide compound Ti3AlC2 belongs to the so-called MAX-phases – a new type of ceramic materials with unique properties. A simple energy-saving method of self-propagating high-temperature synthesis (SHS) based on combustion is one of the promising methods for the production of this MAX-phase. The application of the SHS technology is to produce a Ti3AlC2 MAX-phase porous frame with the homogeneous porous structure without such defects as large pores, laminations, and cracks is of great interest. The paper investigates the possibility of producing such a porous frame with the maximum content of the Ti3AlC2 MAX-phase using powders of Ti, Al, and C elements of various grades different in particle sizes and carbon forms (soot or graphite) as initial components. Porous frame samples were produced by the open-air burning of pressed briquettes of charge of the initial powders of the selected grades without applying external pressure. The authors studied the macro- and microstructure of the obtained samples, their density, and phase composition. The study shows that using the finest titanium and carbon powders leads to the excessively active combustion with gas evolution and the synthesis of the defective porous samples with the charge briquette shape distortion, large pores, laminations, and cracks. Besides the titanium carbide by-phase, the highest values for the MAX-phase amount in the SHS-product were obtained using the titanium powder of the largest-size fraction together with the graphite powder, rather than soot. The excess aluminum powder addition to the stoichiometric ratio to the initial charge leads to an increase in the MAX-phase amount in the SHS product, compensating for the loss of aluminum due to evaporation. An increase in the sample volume (scale factor) also leads to an increase in the MAX-phase amount in the SHS product due to the slower cooling of the product after the reaction.

Mathematical Model of the Motion of Gaseous Thermal Decomposition Products of Composites in a Porous Frame under Strong Heat Flows

The paper describes theoretical issues of the motion of gaseous thermal decomposition products of composite materials in a porous frame structure under the effect of intensive heat flows of different nature. The developed model was verified using benchmark filtration problems and its performance was tested for gas motion using the sample with the porosity that varied in coordinates.

Bayesian inference of human bone sample properties using ultrasonic reflected signals.

The non-intrusiveness and low cost of ultrasonic interrogation is motivating the development of new means of detection of osteoporosis and other bone deficiencies. Bone is a porous media saturated with a viscous fluid and could thus be well characterized by the Biot model. The main purpose of this work is to present an in vitro methodology for the identification of the properties and structural parameters of the bone, adopting a statistical Bayesian inference technique using ultrasonic reflected signals at normal incidence. It is, in this respect, a companion paper to a previous work [J. Acoust. Soc. Am. 146, 3 (2019), pp. 1629-1640], where ultrasonic transmitted signals were considered. This approach allows the retrieval of some important parameters that characterize the bone structure and associated uncertainties. The method was applied to seven samples of bone extracted from femoral heads, immersed in water, and exposed to ultrasonic signals with a center frequency of ≈500 kHz. For all seven samples, signals at different sites were acquired to check the method robustness. The porosity, pore mean size and standard deviation, and the porous frame bulk modulus were all successfully identified using only ultrasonic reflected signals.

Pretreatment-free SERS analysis of raw bile juice for identification of gall bladder disease using paper-coupled Au nanodendrite-encaged nickel foam

For pretreatment-free SERS measurement of raw bile juice for the identification of gall bladder (GB) disease, a paper strip bridging Au nanodendrite-encaged nickel foam (PS-AuND@NF) was demonstrated. To build a medium for facile sample diffusion as well as SERS generation, Au nanodendrite (AuND) with a high SERS efficiency was constructed on the porous frame of the NF (AuND@NF). Then, the PS-AuND@NF was built by simply positioning AuND@NF on a paper strip, which functioned as a channel for sample introduction to AuND@NF and a subsequent sample drain. With the continuous elution of raw bile juice, non-specific adsorption of SERS-inactive constituents such as lipids on the Au surface could be minimized. Using the PS-AuND@NF, raw bile juice samples obtained from 6 GB polyp and 21 GB stone patients were measured. Since only a few components in bile juice are expected to be SERS-active such as bilirubin-containing metabolites, the information obtained from the SERS spectra is not descriptive enough for the discrimination of both GB diseases. Therefore, two-trace two-dimensional (2T2D) correlation analysis, which is able to effectively feature out asynchronous (dissimilar) spectral behaviors in the comparison of two spectra, was carried out in parallel. When the principal component (PC) scores obtained from the 2T2D slice spectra were used for the k-nearest neighbor (k-NN), the discrimination accuracy improved to 88.9 % from 81.5 % obtained when using the PC scores of the raw spectra. Overall, the PS-AuND@NF enabled simple pretreatment-free SERS analysis of complex and viscous bile juice without interference from other existing components.

Explicit expression for complex velocity of Rayleigh wave in dissipative poroelastic solid

ABSTRACT This study considers to solve the complex dispersion equation for propagation of Rayleigh waves in a dissipative porous composite. This porous medium is a viscoelastic porous solid frame saturated with a viscous fluid. Seepage of fluid at the boundary is controlled through pore-fluid pressure and its normal gradient. A complex irrational equation governs the propagation, attenuation and dispersion of the Rayleigh waves. A complex analysis technique is used to solve this equation into an explicit expression for complex phase velocity. Effects of porosity and seepage from surface pores are analyzed numerically on the velocity of Rayleigh wave in a saturated poroelastic material.

Selective CO2 capture through microporous Tb(BTC)(H2O).(DMF)1.1 MOF as an additive in novel MMMs fabricated from Matrimid® 5218

Mixed matrix membranes (MMMs) fabricated with porous metal organic frame works have enhanced the separation performance of polymer membranes. In this context microporous 3D Tb(BTC)(H2O).(DMF)1.1 MOF was incorporated into pristine Matrimid® with loadings of 10, 20 and 30 weight percentages. SEM micrographs indicated proper distribution of filler in the Matrimid and no interfacial voids were observed. Gas permeation studies evidenced the CO2 permeability to be 13.2 (82.32%) and 18.34 (153.31%) and 25.86 Barrer for 10, 20 and 30 wt% MMMs respectively. The 257.18% increase in CO2 permeability of 30 wt% MMM than methane was attributed to polar nature of CO2, its smaller kinetic diameter, condensability, and larger solubility within the Matrimid matrix than non – polar and larger CH4 molecules.Addition of filler influenced the pure gas selectivity of all MMMs positively. So, 30 wt% MMM exhibited the highest 58.04% increase in selectivity that was attributed to the molecular sieving property of the filler and the size exclusion phenomena as followed by CH4 and CO2. The high values of mixed and pure gas selectivity were obtained upon increasing filler concentration. The commercial applicability of these MMMs was tested by checking their selectivity under increased feed concentrations of CO2 and checking permeability and selectivities at high temperatures. The study depicted that, competitive sorption of gases, prevalence of size exclusion phenomena and polymer chains relaxation at higher temperature were responsible for low gas selectivity. MMM with 30 wt% of MOF lied close to Robson’s Upper bound 2008 that indicated its good separation potential.