Gas Foaming Research Articles

Investigation of NiCoOx catalysts for anion exchange membrane water electrolysis: Performance, durability, and efficiency analysis

Anion exchange membrane (AEM) water electrolysis is a promising method for hydrogen production using inexpensive metal oxide catalysts. This study investigates the catalytic activity and performance of nickel cobalt oxide (NiCoOx) catalysts in AEM water electrolysis for hydrogen production. The catalysts were synthesized with varying ratios of Ni to Co. The NiCoOx catalysts were coated on nickel foam gas diffusion layer (GDL) at the anode. Scanning electron microscopy (SEM) analysis revealed a distinct flaky structure of the NiCoOx catalyst. X-ray diffraction (XRD) studies confirmed the presence of NiCo2O4 spinel crystal structure in the catalysts. Linear sweep voltammetry (LSV) measurements for Oxygen evolution reaction (OER) in three electrode systems showed that NiCoOx (1:3) exhibited the highest catalytic activity, with a current density of 238 mA cm−2 at 1.8 V. Tafel analysis indicated that NiCoOx (1:3) had the lowest Tafel slope, suggesting faster reaction kinetics and lower overpotential for higher current density. Chronoamperometry tests demonstrated the stability of the catalysts at various current densities, and long-term stability testing of NiCoOx (1:3) for 500 h revealed minimal voltage increase during OER, demonstrating its stability in prolonged operation. NiCoOx (1:3) displayed the highest activity among the catalysts at different temperatures, with current densities reaching 1700 mA cm−2 at 2.2 V and 70 °C for single-cell electrolysis. The Nyquist plots and equivalent circuit analysis reveal that the NiCoOx (1:3) catalyst exhibits lower activation resistance and higher efficiency in oxygen evolution reaction compared to other catalyst compositions. Temperature-dependent measurements demonstrate decreased resistances (ohmic, activation, and membrane) with increasing temperature, indicating improved reaction kinetics and ion conductivity. Long-term durability tests reveal the stable operation of the catalyst, while short-term tests confirm its effectiveness at higher current densities for single-cell electrolyzer operation. These findings highlight the importance of electrochemical Impedance Spectroscopy (EIS) and equivalent circuit fitting in optimizing AEM water electrolysis performance, aiding the development of efficient and durable electrolyzers for hydrogen production.

Silica aerogel nanoparticle-stabilized flue gas foams for simultaneous CO2 sequestration and enhanced heavy oil recovery

With declining conventional reserves, tapping heavy oils generates substantial emissions yet is essential to meet energy demands. This study pioneers an integrated approach using silica aerogels to develop thermally stable flue gas foams for enhanced CO2 sequestration and heavy oil recovery. Microfluidic experiments and molecular dynamics simulations revealed a 5-fold decrease in gas diffusion rates for aerogel-stabilized versus pure surfactant foams at 95 °C due to the ultralow thermal conductivity of the nanoparticle coating layer. The thermally stable nanoengineered foams demonstrated a remarkable 81.23% CO2 trapping efficiency in heterogeneous cores, surpassing conventional flue gas foam. Additionally, three-dimensional simulations in an oil reservoir model showed improved vertical conformance and oil recovery with aerogel-stabilized foam. The exceptional insulating properties redirected heat downward to enhance sweep efficiency. This novel concept transforms flue gas emissions into value-added foams for concurrent environmental and productivity benefits during heavy oil development.

Utilization of synthesized silane-based silica Janus nanoparticles to improve foam stability applicable in oil production: static study

This study investigated the effect of silane-based silica (SiO2) Janus nanoparticles (JNPs) on stabilizing the foam generated by different types of gases. Two types of SiO2 JNPs were synthesized through surface modification using HMDS and APTS silane compounds. Static analyses were conducted to examine the impact of different concentrations of the synthesized nanoparticles in various atmospheres (air, CO2, and CH4) on surface tension, foamability, and foam stability. The results indicated that the synthesized SiO2 JNPs and bare SiO2 nanoparticles exhibited nearly the same ability to reduce surface tension at ambient temperature and pressure. Both of these nanoparticles reduced the surface tension from 71 to 58–59 mN m−1 at 15,000 ppm and 25 °C. While bare SiO2 nanoparticles exhibited no foamability, the synthesis of SiO2 JNPs significantly enhanced their ability to generate and stabilize gas foam. The foamability of HMDS-SiO2 JNPs started at a higher concentration than APTS-SiO2 JNPs (6000 ppm compared to 4000 ppm, respectively). The type of gas atmosphere played a crucial role in the efficiency of the synthesized JNPs. In a CH4 medium, the foamability of synthesized JNPs was superior to that in air and CO2. At a concentration of 1500 ppm in a CH4 medium, HMDS-SiO2 and APTS-SiO2 JNPs could stabilize the generated foam for 36 and 12 min, respectively. Due to the very low dissolution of CO2 gas in water at ambient pressure, the potential of synthesized JNPs decreased in this medium. Finally, it was found that HMDS-SiO2 JNPs exhibited better foamability and foam stability in all gas mediums compared to APTS-SiO2 JNPs for use in oil reservoirs. Also, the optimal performance of these JNPs was observed at a concentration of 15,000 ppm in a methane gas medium.

Versatile, elastomeric and degradable polyHIPEs of poly(glycerol sebacate)-methacrylate and their application in vascular graft tissue-engineering

Polymer scaffolds are an important enabling technology in tissue engineering. A wide range of manufacturing techniques have been developed to produce these scaffolds, including porogen leaching, phase separation, gas foaming, electrospinning and 3D printing. However, all of these techniques have limitations. Delivering suitable scaffold porosity, small feature sizes and macroscopic geometry remain challenging.Here, we present the development of a highly versatile scaffold fabrication method utilising emulsion templating to produce polymerised high internal phase emulsions (polyHIPEs) of the polymer poly(glycerol sebacate) methacrylate (PGS-M). PGS-M is biocompatible, degradable and highly elastic, with tunable mechanical properties. PGS-M was formulated into an emulsion using solvents and surfactants and then photocured into polyHIPE structures. The porosity, degradation behaviour, mechanical properties and biocompatibility of the PGS-M polyHIPEs was investigated.The versatility of the PGS-M polyHIPEs was demonstrated with the production of various complex tubular scaffold shapes, using injection moulding. These shapes were designed for applications in vascular graft tissue engineering and included straight tubes, bends, branches, functioning valves, and a representative aortic arch. The PGS-M polyHIPE scaffolds supported vascular smooth muscle cells (SMCs) in 3D cell culture in a bioreactor.

Current Trend and New Opportunities for Multifunctional Bio-Scaffold Fabrication via High-Pressure Foaming.

Biocompatible and biodegradable foams prepared using the high-pressure foaming technique have been widely investigated in recent decades as porous scaffolds for in vitro and in vivo tissue growth. In fact, the foaming process can operate at low temperatures to load bioactive molecules and cells within the pores of the scaffold, while the density and pore architecture, and, hence, properties of the scaffold, can be finely modulated by the proper selection of materials and processing conditions. Most importantly, the high-pressure foaming of polymers is an ideal choice to limit and/or avoid the use of cytotoxic and tissue-toxic compounds during scaffold preparation. The aim of this review is to provide the reader with the state of the art and current trend in the high-pressure foaming of biomedical polymers and composites towards the design and fabrication of multifunctional scaffolds for tissue engineering. This manuscript describes the application of the gas foaming process for bio-scaffold design and fabrication and highlights some of the most interesting results on: (1) the engineering of porous scaffolds featuring biomimetic porosity to guide cell behavior and to mimic the hierarchical architecture of complex tissues, such as bone; (2) the bioactivation of the scaffolds through the incorporation of inorganic fillers and drugs.

Research and Evaluation of Foam-Drainage Corrosion-Inhibition Hydrate Anti-Aggregation Integrated Agent

In natural gas exploitation, foam drainage, corrosion inhibition and hydrate inhibition of wellbore fluid are conventional operations. However, there is often a problem where multiple chemical agents cannot be effectively used together and can only be used separately, resulting in complex production processes. In this study, the final integrated formulation was determined: 0.1% sodium alpha-olefin sulfonate (AOST) + 0.3% dodecyl dimethyl betaine (BS-12) + 0.3% sodium lignosulfonate + 0.5% hydrazine hydrate. The minimum tension of the integrated agent could be reduced to 23.5 mN/m. The initial foaming height of the integrated agent was 21.5 cm at 65 °C, the liquid-carrying capacity was 143 mL, and the liquid-carrying rate reached 71.5%. The maximum corrosion depth also decreased from 11.52 µm without the addition of hydrazine hydrate, gradually decreasing to 5.24 µm as the concentration of hydrazine hydrate increased. After adding an integrated agent, the growth rate of hydrates was slow and aggregation did not easily occur, and the formation temperature was also more demanding. Therefore, the integrated agent has a inhibitory effect on the formation of hydrates and has a good anti-aggregation effect. From the observation of the microstructure, the emulsion is an oil-in-water type, and the integrated agent adsorbs at the oil–water interface, preventing the dispersed water droplets in the oil phase from coalescing in one place. The oil-in-water type emulsion is more likely to improve the performance of the natural gas hydrate anti-aggregation agent.

Experimental Study on Multi-Dimensional Visualization Simulation of Gas and Gel Foam Flooding in Fractured-Vuggy Reservoirs.

Gas flooding and foam flooding are potential technologies for tertiary oil recovery in fractured-vuggy reservoirs. The development and mechanism research of fractured-vuggy reservoirs is difficult due to the complex structures and the strong heterogeneity of fractured-vuggy reservoirs. Visualization simulation is one of the effective methods to study the flow behavior of fluid in fractured-vuggy reservoirs. In this study, an upscaling method of visualization simulation from one dimension (1D) to three dimensions (3D) was established, and the physical models of fractured-vuggy reservoirs were designed and fabricated. Water flooding, gas flooding, and gel foam flooding were carried out in the models. The experimental results showed that gas flooding has a single flow channel and water flooding has multiple flow channels in fractures and vugs. Gel foam with an excellent capability of mobility control and a high microscopic displacement efficiency swept in all directions at a uniform velocity. The EOR mechanisms of gel foam in fractured-vuggy reservoirs were mainly as follows: reducing interfacial tension, increasing mobility ratio, selectively plugging high permeability channels, and discontinuous flow. In the displacement process of fractured-vuggy reservoirs, water should be injected from the well at the bottom of the reservoir, and gas should be injected from the well located in the vug at the high part of the reservoir. Gel foam with strong stability and high viscosity should be selected and injected in most kinds of injection wells in fractured-vuggy reservoirs. This study provides a complete method of visualization simulation for the study of flow behavior in fractured-vuggy reservoirs and provides theoretical support for the application of gas flooding and gel foam flooding in fractured-vuggy reservoirs.

Vibration and Audio Measurements in the Monitoring of Basic Oxygen Furnace Steelmaking

A basic oxygen furnace (BOF) is the main unit process for refining carbon steel. The aim of this work was to study the use of vibration and audio signal measurements to monitor, predict, and control the BOF process. Vibration and audio data from nearly 300 blows were collected and analyzed together with process variables. We could confirm high correlations between some of the process variables and vibration and audio measurements. Median filtered low-frequency (3–20 Hz) audio as well as X- and Z-direction acceleration root mean square (RMS) time series correlate with the off-gas temperature, although this is much more significant for the audio data. For Y-direction measurements (the upward direction) the correlation is negligible. The low-frequency audio and vibration data are likely related to the rate of decarburization. Median filtered mid-frequency (100–1000 Hz) audio as well as X-, Y-, and Z-direction acceleration RMS time series correlate with the lance height measurement during the interval 20–600 seconds from the beginning of oxygen blow. For the audio data, the correlation was high even without median filtering. We suggest that audio and vibration activity in this frequency range is possibly related to the formation of the metal–slag–gas foam and maybe even to slopping.

Macroporous Hydrogels Prepared By Ice Templating: Developments And Challenges†

Comprehensive SummaryMacroporous hydrogels are water‐swollen polymer networks with porous structures beyond the mesh size. They provide high specific surface areas and hieratical mass transfer channels which are desired for emerging applications including cell culturing, bio‐separation, and drug delivery. A variety of approaches have been developed to fabricate macroporous hydrogels, including gas foaming, porogen templating, phase separation, 3D printing, etc. Alternatively, ice templating utilizes the crystallization of water as the porogenation mechanism which doesn't need the leaching of porogens. The porous structures can be easily manipulated by controlling the morphology of ice (size, orientation, etc.) upon freezing. In addition, mechanical properties of obtained porous hydrogels are commonly better than those of other macroporous hydrogels since the pore walls are made up of concentrated polymers through the freezing step. These three characteristics, that is, the green process, the highly tunable morphology, and the enhanced mechanical strength make the ice templating a superior porogenation method. This review expects to give an overview on macroporous hydrogels prepared by the ice templating, namely, cryogels. Recent progresses on emerging cryo‐porogenation methods are introduced. Fundamental understanding concerning the behavior of the polymer chains during the formation of ice is proposed. Future opportunities on the application of cryogels are prospected.

Gas foaming of polyphenyl sulfone: Effect of the blowing agents and operating parameters

AbstractPolyphenyl sulfone (PPSU) is a highly stable and rigid polymer with good chemical and mechanical resistance used in automotive and aerospace industries in high‐temperature applications during long‐operating cycles. PPSU foams are applied as core materials in lightweight composites ensuring high strength, fire resistance, thermal and acoustic insulation. In this paper, PPSU slabs are foamed using CO2, N2, and He as blowing agents (BAs). An experimental campaign is carried out to estimate the BAs' diffusivity in the polymer. In details, CO2 diffusivity ranges from 8E‐11 to 1E‐09 m2/s at temperatures from 220 to 260°C; diffusivity of N2 ranges from 2E‐10 to 5E‐09 m2/s (220–260°C) and it is 4E‐09 m2/s for He at 220°C. Foaming tests reveal an expansion ratio as high as 400% for CO2, 130% for He, and 150% for N2.Scanning electron microscopy analysis is also performed on produced samples, obtaining a cell number density of 1.3E07, 2.6E05, and 1.8E06 cells/cm3 when saturating, respectively, with CO2 at 220°C and 100 bar, N2 at 220°C and 100 bar, and He at 230°C and 100 bar.

Study on the preparation and properties of colloidal gas foam concrete to prevent spontaneous combustion of coal

Colloidal gas foam concrete (CFC) was successfully prepared by high water retention of colloidal gas aphrons (CGA) and cement slurry. The preparation conditions of colloidal gas foam concrete with optimal performance and the addition ratio between its components were determined based on single-factor experiments and orthogonal tests. Then, the compressive strength, water retention, water content, and ability to inhibit coal spontaneous combustion of colloidal gas foam concrete were systematically studied. CFC's performance test to prevent spontaneous combustion of coal showed that CFC could form a hard protective shell of oxygen barrier on the surface of coal, thus inhibiting spontaneous combustion of coal. In addition, compared with traditional aqueous foam concrete (AFC), the water content of CFC increased from 0.65 to 1.40, and the protective shell formed by CFC could still retain some water after seven days without cracking. The programmed temperature rise experiment showed that CFC inhibited coal spontaneous combustion better than traditional AFC, and the cross-point temperature of coal treated by CFC was higher. This paper provides a high-performance mine fireproof material, which is important for the safe and efficient production of mines.

Decellularized extracellular matrix-based 3D nanofibrous scaffolds functionalized with polydopamine-reduced graphene oxide for neural tissue engineering

One of the exciting prospects of using decellularized extracellular matrices (ECM) lies in their biochemical profile of preserved components, many of which are regeneration-permissive. Herein, a decellularized ECM from adipose tissue (adECM) was explored to design a scaffolding strategy for the challenging repair of the neural tissue. Targeting the recreation of the nano-scaled architecture of native ECM, adECM was first processed into nanofibers by electrospinning to produce bidimensional platforms. These were further shaped into three-dimensional (3D) nanofibrous constructs by gas foaming. The conversion into a 3D microenvironment of nanofibrous walls was assisted by blending the adECM with lactide-caprolactone copolymers, wherein tuning the adECM/copolymer ratio along with the amount of caprolactone in the copolymer led to modulating the mechanical properties towards soft, yet structurally stable, 3D constructs. In view of boosting their performance to guide neural stem cell fate, adECM-based platforms were doped with a bioinspired surface modification relying on polydopamine-functionalized reduced graphene oxide (PDA-rGO). These adECM-based 3D constructs revealed a permissive microenvironment for neural stem cells (NSCs) to adhere, grow, and migrate throughout the microporosity, owing to the synergy between the unique biochemical features of the adECM and the nanofibrous architecture. NSC responded differently depending on the adECM-based architecture–nanofibrous bidimensional, or 3D design. The 3D spatial arrangement of the nanofibers – induced by the gas foaming – exhibited a remarkable effect on NSCs’ phenotype determination and neurite formation, thereby reinforcing the critical importance of engineering scaffolds with multiple length-scale architecture. Furthermore, PDA-rGO promoted the differentiation of NSC towards the neuronal lineage. Specifically in 3D, it significantly increases the levels of Tuj1 and MAP2 a/b isoforms, confirming its effectiveness in boosting neuronal differentiation and neuritogenesis.

Experimental study on gas-assisted cyclic steam stimulation under heavy-oil sandstone reservoir conditions: Effect of N2/CO2 ratio and foaming agent

After several rounds of cyclic steam stimulation (CSS), the formation energy of heavy oil reservoirs is depleted. The water content in the reservoir is increased, which leads to a decrease in production. The injection of N2 and CO2 can effectively improve the recovery efficiency. In this paper, the experiments of mixed gas-assisted CSS with different N2/CO2 injection ratios and mixed gas foam-assisted CSS were performed. The temperature change, liquid production, pressure change and residual oil distribution of the sandpack were tested during the experiment, and the influencing factors of enhanced oil recovery were explored. The results show that the range of recovery variation can be divided into an increasing phase from 1:0 to 2:1 and a decreasing phase from 2:1 to 0:1 based on the different injection ratios of N2/CO2. The viscosity reduction of heavy oil under the effect of CO2 dissolution is the dominant factor in the increasing phase, while the formation energy increase under the effect of N2 expansion is the dominant factor in the decreasing phase. The recovery factor is the best when the ratio of injected N2/CO2 is 2:1. The cumulative recovery factor increases by 6.46% after adding the A-9 foaming agent solution. This shows that the mixed gas foam combines the advantages of the mixed gas and foam. It increases the flow resistance and improve the oil displacement efficiency by plugging the lager pore-throat from a microscopic perspective. Therefore, mixed gas foam-assisted CSS can effectively improve the production of heavy oil reservoirs. The research results provide theoretical guidance for improving the effectiveness of the CSS of heavy oil reservoirs.

Cartilage Lacuna-Inspired Microcarriers Drive Hyaline Neocartilage Regeneration.

Cartilage equivalents from hydrogels containing chondrocytes exhibit excellent potential in hyaline cartilage regeneration, yet current approaches have limited success at reconstituting the architecture to culture nondifferentiated chondrocytes in vitro. In this study, specially designed lacunar hyaluronic acid microcarriers (LHAMCs) with mechanotransductive conditions that rapidly form stable hyaluronic acid (HA) N-hydroxy succinimide ester (NHS-ester) are reported. Specifically, carboxyl-functionalized HA is linked to collagen type I via amide-crosslinking, and gas foaming produced by ammonium bicarbonate forms concave surface of the microcarriers. The temporal 3D culture of chondrocytes on LHAMCs uniquely remodels the extracellular matrix to induce hyaline cartilaginous microtissue regeneration and prevents an anaerobic-to-aerobic metabolism transition in response to the geometric constraints. Furthermore, by inhibiting the canonical Wnt pathway, LHAMCs prevent β-catenin translocation to the nucleus, repressing chondrocyte dedifferentiation. Additionally, the subcutaneous implantation model indicates that LHAMCs display favorable cytocompatibility and drive robust hyaline chondrocyte-derived neocartilage formation. These findings reveal a novel strategy for regulating chondrocyte dedifferentiation. The current study paves the way for a better understanding of geometrical insight clues into mechanotransduction interaction in regulating cell fate, opening new avenues for advancing tissue engineering.

High performance porous poly(ethylene oxide)-based composite solid electrolytes

A single inorganic or organic solid-state electrolyte can’t meet the requirements of commercial solid-state batteries, which motivates the composite solid electrolytes (CSEs). However, the room-temperature ionic conductivity, mechanical strength and interface stability of CSEs are still difficult to support the required cycling performance. Here we propose the design of high performance porous PEO-based CSEs via solvent boiling method, inspired by the gas foaming used in polymer porous scaffold field. Crystallization of the PEO chain segment could be suppressed by the pore structure which could also increase interface stability and reduce density. Therefore, the porous PEO/LLZTO CSEs prepared via solvent boiling exhibit enhanced Li-ion conductivity, mechanical strength, electrochemical and cycling stability. Especially, the porous PEO/SN/LLZTO CSEs prepared via solvent boiling exhibit an excellent Li-ion conductivity (2.26 × 10-4 S cm−1 at 25 ℃) and high cycling stability. In this work, the effects of the porous structure on PEO-based CSEs were systemically studied, providing a novel controllable strategy for designing high performance CSEs.

In-situ gas foaming synthesis of N, S-rich co-doped hierarchically ordered porous carbon as an efficient oxygen reduction reaction catalyst

The design and manufacture of cost-effective and efficient oxygen reduction reaction (ORR) catalysts is critical to the widespread application of multiple energy conversion devices. Herein, a combination of in-situ gas foaming and the hard template method is proposed to construct the N, S-rich co-doped hierarchically ordered porous carbon (NSHOPC) as an effective metal-free electrocatalyst for ORR via carbonizing a mixture of polyallyl thiourea (PATU) and thiourea in silica colloidal crystal template (SiO2-CCT) voids. Benefiting from the hierarchically ordered porous (HOP) architectures and the mass doping of N and S, NSHOPC displays excellent ORR activities (the half-wave potential of 0.889 V in 0.1 M KOH and 0.786 V in 0.5 M H2SO4) and long-term stability, which are all better than those of Pt/C. As the air cathode in a Zn-air battery (ZAB), NSHOPC exhibits a high peak power density of 174.6 mW·cm−2 and long-term discharge stability. The remarkable performance of the as-synthesized NSHOPC signifies broad prospects for actual applications in energy conversion devices.

Room temperature triethylamine gas sensor with excellent performances based on novel porous CuO foam via a simple and facile route

Monitoring of explosive and toxic triethylamine (TEA) is essential for environmental safety and human health. However, high sensitivity detection of TEA remains a huge challenge at low temperature or even room temperature. Here, we developed a CuO porous foam-based gas sensor for TEA detection at room temperature by defect engineering of oxygen vacancies. The CuO porous foam with rich surface oxygen vacancies have been synthesized through a sol-gel autocombustion method, and the formation mechanism of porous foam structure and rich oxygen vacancies of CuO have been investigated by various characterization methods. Moreover, the fabricated CuO foam gas sensor reveals the high response of 140.0 for 50 ppm TEA, a low detection limit of 0.5 ppm, excellent selectivity, good stability and repeatability at room temperature, which are ascribed to porous structure and rich surface oxygen vacancies of CuO foam. Importantly, the surface redox reaction model and density function theoretical calculation have been applied to deeply explore the sensing mechanism. This work can not only realize the ultra-sensitive sensing of TEA at room temperature, but also provide a novel strategy for the design of other ideal performance sensors at low operating temperatures.

Study on Flow Characteristics of Flue Gas and Steam Co-Injection for Heavy Oil Recovery

Flue gas is composed of N2 and CO2, and is often used as an auxiliary agent for oil displacement, with good results and very promising development prospects for co-injection with steam to develop heavy oil. Although research on the oil displacement mechanism of flue gas has been carried out for many years, the flow characteristics of steam under the action of flue gas have rarely been discussed. In this paper, the flow resistance and heat transfer effect of flue gas/flue gas + steam were evaluated by using a one-dimensional sandpack, a flue gas-assisted steam flooding experiment was carried out using a specially customized microscopic visualization model, and the microscopic flow characteristics in the process of the co-injection of flue gas and steam were observed and analyzed. The results showed that flue gas could improve the heat transfer effect of steam whilst accelerating the flow of steam in porous media and reducing the flow resistance of steam. Compared with pure steam, when the volume ratio of flue gas and steam was 1:2, the mobility decreased by 2.8 and the outlet temperature of the sandpack increased by 35 °C. This trend intensified with an increase in the proportion of flue gas. In the microscopic oil displacement experiments, the oil recovery and sweep efficiency of the flue gas and steam co-injection stage increased by 4.7% and 32.9%, respectively, compared with the pure steam injection stage due to the effective utilization of blocky remaining oil and corner remaining oil caused by the expansion of fluid channels, the flow of flue gas foam, and the dissolution and release of flue gas in heavy oil.

A Review of 3D Polymeric Scaffolds for Bone Tissue Engineering: Principles, Fabrication Techniques, Immunomodulatory Roles, and Challenges.

Over the last few years, biopolymers have attracted great interest in tissue engineering and regenerative medicine due to the great diversity of their chemical, mechanical, and physical properties for the fabrication of 3D scaffolds. This review is devoted to recent advances in synthetic and natural polymeric 3D scaffolds for bone tissue engineering (BTE) and regenerative therapies. The review comprehensively discusses the implications of biological macromolecules, structure, and composition of polymeric scaffolds used in BTE. Various approaches to fabricating 3D BTE scaffolds are discussed, including solvent casting and particle leaching, freeze-drying, thermally induced phase separation, gas foaming, electrospinning, and sol-gel techniques. Rapid prototyping technologies such as stereolithography, fused deposition modeling, selective laser sintering, and 3D bioprinting are also covered. The immunomodulatory roles of polymeric scaffolds utilized for BTE applications are discussed. In addition, the features and challenges of 3D polymer scaffolds fabricated using advanced additive manufacturing technologies (rapid prototyping) are addressed and compared to conventional subtractive manufacturing techniques. Finally, the challenges of applying scaffold-based BTE treatments in practice are discussed in-depth.

Effect of recycled fine powder on autoclaved aerated concrete: Gas-foaming, physic-mechanical property and hydration products

The production process for cement and quicklime consumes a large amount of energy, and involves chemical reactions that inevitably release CO2. High calcium solid wastes, recycled fine powder (RFP) and carbide slag, are used to replace the cement and quicklime to prepare autoclaved aerated concretes (AAC) for reducing the carbon emissions and energy consumption. The effects of the content and activation by ball milling of recycled fine powder on the rheological, gas foaming, bulk density and compressive strength of AAC were studied in this study. The influence of activated recycled fine powder on the early hydration degree of cement and the reactivity of siliceous materials (fly ash and quartz) under hydrothermal conditions were further investigated by Isothermal Micro-Calorimetry (IMC) and 29Si NMR. The results show that AAC products with good performance can be prepared by using high content of solid waste. With the increase of RFP content, the bulk density of AAC products increases due to the decrease of foaming rate of AAC slurry, but the decrease of tobermorite content has a negative effect on the mechanical property of AAC products. The increasing fineness of recycled fine powder promotes the foaming rate of slurry and produces more amorphous C–S–H gels to form tobermorite under hydrothermal conditions, so finer recycled fine powder can effectively enhance the strength of AAC products.