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NiV2O6 thin films were grown on glass slides with varying thicknesses using nebulizer spray pyrolysis. The impact of thickness on the thin films' optical, structural, morphological, and electrical characteristics was systematically investigated. X-ray diffraction and micro-Raman analysis confirmed the formation of the triclinic NiV2O6 system. Surface morphology and roughness variations in the as-deposited NiV2O6 films were studied using scanning electron microscopy (SEM) and a profilometer. Optical properties, including optical band gap (Eg), extinction coefficient (k), absorption coefficient (α), and refractive index (n), were determined through optical reflectance and transmittance measurements. The optical energy gap of the as-deposited NiV2O6 films decreased from 2.02 eV to 1.58 eV with increased layer thickness. Furthermore, the photo-detectivity of the films demonstrated an enhancement corresponding to the prolonged spray time. The sensitivity values obtained for visible irradiation were 328, 511, and 433 for samples S1, S2, and S3, respectively. The obtained results can be imputed to the specific porous microstructure. [ABSTRACT FROM AUTHOR]

ABSTRACTTo enhance semiconductor efficiency, it is imperative to develop a die-bonding material possessing exceptional thermal conductivity and stress-shielding capabilities to safeguard semiconductor components from detrimental heat and destructive stress. In this study, we employed a multi-objective topology optimization approach to design a porous microstructure for the die-bonding layer of semiconductors, targeting high thermal conductivity and low shear modulus. The finite element analysis method for a representative volume element (RVE) facilitates computational evaluations of macroscopic mechanical and thermal properties arepsilong from a periodic microstructure. Our investigation commenced with the creation of an RVE generator for obtaining periodic microstructures featuring randomly distributed pores with controlled morphological features. A high-throughput evaluation of numerous generated microstructures explored the impact of volume fraction and pore connectivity on macroscopic shear modulus and thermal conductivity. Despite the high-throughput evaluation indicating that pore connectivity has minimal effect on properties, the multi-objective topology optimization, addressing the conflict between maximizing thermal conductivity and minimizing shear modulus, revealed that connected pores and dispersed distribution in the architected microstructure contribute to improved material performance. In this optimization process, we employed a weighted sum method to find optimal compromised microstructures. Anisotropic and orthotropic microstructures were designed, and the effects of volume constrains and weight factors on microscopic morphology were explored. Despite the high-throughput evaluation suggesting a limited impact of pore connectivity, the results from multi-objective topology optimization underscored the significance of connected pores and dispersed distribution in achieving superior material performance.

Human‐machine interaction(HMI) is extensively employed in various applications such as robotic control and augmented reality/virtual reality. However, HMIs are mainly based on single‐interaction mode, requiring bulky equipment to be worn or sustaining physical contact with the interfaces, resulting in limited interaction efficiency and intelligence. Here, it proposes a novel flexible dual‐mode capacitive sensor using 12 sensing units for touchless and tactile sensing during HMIs, the sensor has a labyrinth‐patterned electrode to improve the performance of proximity sensing and a truncated pyramid‐shaped porous hierarchical dielectric structure to improve the pressure sensing performance. The fabricated dual‐mode sensor is characterized by a high proximity detection range of up to 110 mm, the pressure detection range is from 0 to 200 kPa with a sensitivity of 0.464% kPa−1. Further, the dual‐mode sensor exhibits excellent discrimination between proximity and pressure signals, along with remarkable stability and repeatability. Then, a touchless‐tactile HMI platform is developed for real‐time control of robotics through accurate perception of touchless hand gestures and contact‐pressing interactions. This platform demonstrates the superior dual‐mode sensing performance of the sensor and validates its potential in future intelligent HMI scenarios. [ABSTRACT FROM AUTHOR]

The gas-species dependence of permeation flow in solid oxide fuel cell anodes is experimentally and numerically investigated to clarify the Knudsen effect on the gas transport phenomena in porous media. The effective permeability of porous anodes fabricated with pore former is experimentally measured using various working gases with different mean free paths, and the effect of the working gas species on the permeation phenomena is evaluated. A linear relationship is found between the effective permeability and the mean free path of the gas species. It is clarified that the representative pore size of the porous media fabricated with the pore formers considering the permeation phenomena is larger than that quantified by the microstructural analysis. A numerical model based on the dusty-gas model is developed and three-dimensionally visualizes the flow distribution in porous anodes. The 3D simulation shows that permeation gas mainly flows through the larger pores formed by the pore formers. In addition, the molar flux distribution of the permeation flow for the gases is similar, and its absolute flow rate depends on the physical properties of the permeation gas.

NiV2O6 thin films were grown on glass slides with varying thicknesses using nebulizer spray pyrolysis. The impact of thickness on the thin films’ optical, structural, morphological, and electrical characteristics was systematically investigated. X-ray diffraction and micro-Raman analysis confirmed the formation of the triclinic NiV2O6 system. Surface morphology and roughness variations in the as-deposited NiV2O6 films were studied using scanning electron microscopy (SEM) and a profilometer. Optical properties, including optical band gap (Eg), extinction coefficient (k), absorption coefficient (α), and refractive index (n), were determined through optical reflectance and transmittance measurements. The optical energy gap of the as-deposited NiV2O6 films decreased from 2.02 eV to 1.58 eV with increased layer thickness. Furthermore, the photo-detectivity of the films demonstrated an enhancement corresponding to the prolonged spray time. The sensitivity values obtained for visible irradiation were 328, 511, and 433 for samples S1, S2, and S3, respectively. The obtained results can be imputed to the specific porous microstructure.

Tissue regeneration of large bone defects is still a clinical challenge. Bone tissue engineering employs biomimetic strategies to produce graft composite scaffolds that resemble the bone extracellular matrix to guide and promote osteogenic differentiation of the host precursor cells. Aerogel-based bone scaffold preparation methods have been increasingly improved to overcome the difficulties in balancing the need for an open highly porous and hierarchically organized microstructure with compression resistance to withstand bone physiological loads, especially in wet conditions. Moreover, these improved aerogel scaffolds have been implanted in vivo in critical bone defects, in order to test their bone regeneration potential. This review addresses recently published studies on aerogel composite (organic/inorganic)-based scaffolds, having in mind the various cutting-edge technologies and raw biomaterials used, as well as the improvements that are still a challenge in terms of their relevant properties. Finally, the lack of 3D in vitro models of bone tissue for regeneration studies is emphasized, as well as the need for further developments to overcome and minimize the requirement for studies using in vivo animal models. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Micro/nanostructure is a popular and effective structure for boiling heat transfer enhancement. In this study, ultrasonic cavitation modification is employed firstly to create microstructured aluminum surface for boiling heat transfer. With the impact of ultrasonic cavitation microjet, numerous micro pits and holes are formed on the surface in one step, constituting microstructures on aluminum plate. The saturated and subcooled pool boiling experiments are conducted at atmospheric pressure using ethanol as a working fluid. It is found that boiling hysteresis is apparent on the modified plate (MP) with the porous microstructure layer, which can be eliminated by periodically fluctuating heat flux. Under the stable saturated boiling condition, the maximum heat transfer coefficient is enhanced by 208% and wall superheat is decreased by 17.6 °C compared to the bare aluminum surface. Under subcooled boiling conditions, the boiling hysteresis on MP becomes weaker and the positive effect of microstructures on heat transfer performance is enhanced. The enhanced heat transfer coefficient of MP is mainly attributed to the increase of nucleation site density and further to the facilitation of bubble coalescence and departure, while the increased critical heat flux under subcooled boiling conditions is derived from the delaying occurrence of mushroom-like bubble. • The microstructured aluminum surface was fabricated by ultrasonic cavitation. • Additional nuclear sites can be activated by the second increase of heat flux. • The maximum HTC of the modified plate is enhanced by 208%. • The positive effect of microstructures becomes stronger as subcooling degree increases. [ABSTRACT FROM AUTHOR]

In this study, the electrical conductivity characteristics of SmBaCo 2 O 5+d (SBCO) and SmBa 0.5 Sr 0.5 Co 2 O 5+d (SBSCO) were measured and analyzed by changing the characteristics of the microstructure from dense microstructure to porous microstructure for the cathode application in solid oxide fuel cells. SBCO and SBSCO comprised of the dense microstructure showed metal insulator transition (MIT) and metallic behavior, respectively. In SBCO, when the oxygen partial pressure is reduced, the conductivity value decreases, and the conductivity behavior changes to the behavior of a semiconductor. However, the electrical conductivity behavior of SBSCO did not change even when the oxygen partial pressure was decreased. The electrical conductivities of the porous cathodes were lower than those of the dense cathodes due to the discontinuous electric path, but all porous cathodes showed semiconductor behavior. The conductivity value decreases when the oxygen partial pressure decreases, but the general conductivity behavior of the samples with a porous microstructure does not change under N 2 atmosphere. The porous cathode showed the highest electrical conductivity when Pt lines were led to the top of the cathode. In this case, a relatively high electrical conductivity was measured using the method of measuring multiple conductivities at different temperatures while decreasing the measurement temperature starting from a high temperature rather than the method of measuring while raising the temperature starting from a low temperature. In the dense cathode, higher electrical conductivities were measured when a low current was applied, but in the porous cathode, the same electrical conductivity values were measured regardless of the applied current values. • All porous cathodes were shown to display semiconductor conductivity behavior. • The electrical conductivity of the sample in which the Pt line was printed on the cathode surface was the highest. • Dense cathodes have higher electrical conductivity when a low current is applied. • Porous cathodes have no difference in electrical conductivity with respect to the applied current value. [ABSTRACT FROM AUTHOR]

Three-dimensional printing technology enables the production of open cell porous structures. This has advantages but not only in terms of weight reduction. In implant structures, the process of osseointegration is improved, mechanical integration is better, the open cell porous structures resemble a trabecular structure that mimics bone tissue. In this work, we investigated titanium structures made porous by cutting spheres. Based on the patterns of different types of crystal models we created porosity with different strategies. We have shown that there are significant differences in mechanical properties between the porous structures formed with different strategies. We determined the structure that loses the least load-bearing capacity compared to the solid structure, with the same porosity levels and mechanical stresses. We characterized the possibility location and environment of becoming an open cell structure. We performed the calculations with mechanical simulations, which were validated experimentally. The quality of the three-dimensional printing of samples was checked by computed tomography reconstruction analysis.

Tissue regeneration of large bone defects is still a clinical challenge. Bone tissue engineering employs biomimetic strategies to produce graft composite scaffolds that resemble the bone extracellular matrix to guide and promote osteogenic differentiation of the host precursor cells. Aerogel-based bone scaffold preparation methods have been increasingly improved to overcome the difficulties in balancing the need for an open highly porous and hierarchically organized microstructure with compression resistance to withstand bone physiological loads, especially in wet conditions. Moreover, these improved aerogel scaffolds have been implanted in vivo in critical bone defects, in order to test their bone regeneration potential. This review addresses recently published studies on aerogel composite (organic/inorganic)-based scaffolds, having in mind the various cutting-edge technologies and raw biomaterials used, as well as the improvements that are still a challenge in terms of their relevant properties. Finally, the lack of 3D in vitro models of bone tissue for regeneration studies is emphasized, as well as the need for further developments to overcome and minimize the requirement for studies using in vivo animal models.

This work compared thermally reversible emulsion gels and high internal phase emulsions (HIPEs) based on pea protein for 3D printing at different oil volume fraction (ϕ) ranging from 0.2 to 0.8. Thermally reversible emulsion gels were obtained with ϕ from 0.2 to 0.65, which melt into liquid emulsion as temperature increased, and recovered into emulsion gels upon cooling as reflected by consistent rheological measurements. The Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the transition between intermolecular β-sheet at 1630 cm−1 and intramolecular β-sheet at 1618 cm−1 through reversible H-bonds upon changes in temperature, which was responsible for the repeated thermo-reversibility. With ϕ increased to 0.74–0.8, HIPEs were confirmed by Scanning Electron Microscope (SEM) and Confocal Laser Scanning Microscope (CLSM), yet the thermo-reversibility was not maintained. In addition, the thermally reversible emulsion gels exhibited strong shear-thinning and thixotropic recovery through the untangling and reformation of the H-bonded gel network. Whereas deformation and restructuring of the close packed droplets were responsible for such behaviors in HIPEs. 3D printing test has further demonstrated excellent performance of thermally reversible emulsion-filled gel with ϕ 0.4, comparable to HIPE with ϕ 0.74 b y enabling printed objects with high shape fidelity (printability index (Pr) of 0.95–1.08) and shape stability (prints height maintenance (Hm) of 82.2%–87.8%). This research opens up thermally reversible emulsion gels solely from sustainable protein source for 3D printing, with low oil content and no synthetic ingredients needed. [Display omitted] • Emulsion-filled pea protein gels reversibly melt and recover with temperature change. • The above thermo-reversibility allowed excellent 3D printability comparable to HIPEs. • FTIR revealed that the reversible H-bonds contributed to the thermo-reversibility. • HIPEs lost thermo-reversibility at higher oil volumes yet showed great heat stability. • 3D printable low-fat emulsion-filled gels can be prepared solely by pea protein. [ABSTRACT FROM AUTHOR]

The development of lightweight shape memory materials with exceptional thermal insulation properties is highly important in aerospace applications. Herein, shape memory polyimide (PI) aerogels was fabricated by molecularly designed PI molecular chains through freeze gelation and subsequent thermal imidization. The freezing conditions were controlled to regulate the porous microstructures of the aerogels. The interactions between PI chains formed physically crosslinked netpoints, which could overcome the expansive force and capillary force, thereby creating a stable porous structure. Because shape memory was thermally activated, the shape memory mechanisms associated with the thermal conductivity of the aerogels were comprehensively explored. Upon decreasing the pore size, dense frameworks were formed, contributing to the improved thermo-mechanical and compressive properties. Moreover, the heat transfer efficiency in the aerogel skeleton was enhanced, resulting in a rapid shape recovery response. Benefiting from the physically crosslinked structures, including entangled chains and π-π interactions, the fabricated PI aerogels demonstrated exceptional shape fixation and recovery capabilities. These findings may provide guidelines for designing smart aerogels for aerospace applications. [Display omitted] • Shape memory polyimide aerogels with tunable porous microstructures were fabricated. • The size of the micropores was regulated by controlling the freezing conditions. • The reduction of pore size accelerated the shape recovery process. • The comprehensive exploration of the shape memory mechanisms was conducted. [ABSTRACT FROM AUTHOR]

Fe 3-x Zn x O 4 (x = 0.1, 0.2, and 0.3) powders were synthesized by facile combustion method using metal nitrates as oxidants and glycine as fuel. The structural, microstructural, magnetic, and microwave absorption properties are characterized as a function of Zn2+ substitution. With the increase of Zn2+ contents, some hematite (α-Fe 2 O 3) phases appeared together with the magnetite (Fe 3 O 4) phase. The transmission and scanning electron microscopy observations showed that the particle size was decreased from 120 to 70 nm, while the amount and size of pores increased with adding Zn2+ cations. The as-synthesized Fe 2.9 Zn 0.1 O 4 powders had the highest saturation magnetization of 92 emu/g, which decreased to 72 emu/g for the Fe 2.7 Zn 0.3 O 4 sample. The Fe 2.8 Zn 0.2 O 4 sample exhibited an intense reflection loss of −53 dB in the K u band at the matching thickness of 2 mm. Despite the reduction of reflection loss, the effective bandwidth increased up to 5.5 GHz with the Zn content, which is attributed to the better impedance matching and higher contribution of magnetic and dielectric loss mechanisms. [ABSTRACT FROM AUTHOR]

Porous hydroxyapatite-biochar composites with layered microstructures (SC–HA/C) were prepared by carbonizing sugarcane stem nodes and then soaking them in lime water and (NH4)2HPO4 solutions in rotation. The surface area of SC–HA/C ranges from 8.52 to 28.44 m2/g, and its microstructure inherits various macro-, meso-, and micro-pores in the cell walls of sugarcane and in the pits of the vessel walls. The maximum removal capacities were 11.50, 14.65, and 19.81 mg/g for the Cu (II) immobilization at 25 °C, 35 °C, and 45 °C with the solution Cu (II) concentration of 10~320 mg/L, respectively, which were in accordance with the copper sorption capacities of synthesized nano-hydroxylapatites. The Cu (II)-removal kinetics and isotherm followed the pseudo-second-order equation and the Langmuir equation very well. The formation of the Cu-containing hydroxylapatite solid solutions ((CuxCa1−x)5(PO4)3(OH)) through adsorption, ion exchange (x = 0.01~0.04), and dissolution-coprecipitation (x = 0.13~0.35) was the dominant process for the Cu (II) removal by the SC–HA/C composite. [ABSTRACT FROM AUTHOR]

A deep learning based homogenization framework is proposed to link the microstructures of porous nickel/yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) to their effective macroscopic properties. A variety of microstructures are generated by the discrete element method and the meso‑scale kinetic Monte Carlo method. Then, the finite element method and the homogenization theory are used to calculate the effective elastic modulus (E), Poisson's ratio (υ), shear modulus (G) and coefficient of thermal expansion (CTE) of representative volume elements. In addition, the triple-phase boundary length density (LTPB) is also calculated. The convolutional neural network (CNN) based deep learning model is trained to find the potential relationship between the microstructures and the five effective macroscopic properties. The comparison between the ground truth and the predicted values of the new samples proves that the CNN model has an excellent predictive performance. This indicates that the CNN model could be used as an effective alternative to numerical simulations and homogenization because of its accurate and rapid prediction performance. Hence the deep learning-based homogenization framework could potentially accelerate the continuum modeling of SOFCs for microstructure optimization.

In this work, a deep learning accelerated homogenization framework is developed for prediction of elastic modulus of porous materials directly from their inner microstructures. The finite element method (FEM) and the homogenization theory are used to obtain the macroscopic properties of materials based on their microstructures. Based on a large dataset consisting of various microstructures and corresponding elastic properties via FEM, a deep convolutional neural network (CNN) is trained to capture the nonlinear functional relationship between the microstructure features and their macroscopic elastic properties. The deep learning model is finally well validated against extra new samples with excellent predictive performances. This demonstrates that the CNN deep learning model can be trusted as a surrogate model for the FEM based homogenization method, with the computation time being reduced by several orders of magnitude. The proposed deep learning framework is highly extendable for prediction of various macroscopic properties from microstructures. [Display omitted] • Meso scale finite element model (FEM) is built for calculation of anisotropic elastic properties of a porous SOFC cathode. • Convolutional neural network based deep learning model is built on basis of the large simulation data by FEM. • The deep learning framework is highly extendable for linking more macroscopic material properties to microstructures. [ABSTRACT FROM AUTHOR]

The poor frost resistance of supersulfated cement (SSC) is of great concerns for its application. This research assessed the frost resistance performance of SSC with 1 wt. % and 3 wt. % cement clinker activator (C1 and C3) and explored the effects of nano-SiO 2 (NS) (1 wt. % and 3 wt. %, N1 and N3) on the frost resistance of SSC through macro- and micro-evaluation on loss of the compressive strength/the mass/the relative dynamic elastic modulus and XRD/MIP/SEM. Results showed that the frost resistance of C1 sample was superior than those of C3 sample. The addition of NS enhanced the frost resistance of SSC: the maximum mass loss was reduced by about 92.8% and the maximum relative dynamic elastic modulus loss was decreased by about 34.6%. This could be ascribed to the change of the porous microstructure: the portion of micro-pores smaller than 20 nm increased and the microstructure was densified. Moreover, Moreover, NS changes the long needle-like crystalline phase (AFt) shape to a short rod-like shape, the latter of which was more tightly wrapped by the gel phase, leading to a more compact microstructure, and the detachment of AFt from gel matrix (would be introduced by the difference of their contraction/expansion rate under F-T cycles) could result in the poor performance of SSC, while this could be relieved by the reduction of the AFt-to-gel ratio as seen from the NS-added SSC sample. • Nano-SiO 2 (1%) can improve the frost resistance of supersulfated cement (SSC). • The compaction of the microstructure of SSC by Nano-SiO 2 is the reason for the improvement of frost resistance. • The crystalline AFt peels from the C-S-H gel and forms a fragile structure after freeze-thaw cycles. • The poor frost resistance of SSC is related to the higher crystalline-to-gel ratio. [ABSTRACT FROM AUTHOR]

Porous morphology and mechanical properties determine the applications of cryogels. To understand the influence of the ionic network on the microstructure and mechanical properties of pectin cryogels, we prepared low-methoxyl pectin (LMP) cryogels with different Ca2+ concentrations (measured as R-value, ranging from 0 to 2) through freeze-drying (FD). Results showed that the R-values appeared to be crucial parameters that impact the pore morphology and mechanical characteristics of cryogels. It is achieved by altering the network stability and water state properties of the cryogel precursor. Cryogel precursors with a saturated R-value (R = 1) produced a low pore diameter (0.12 mm) microstructure, obtaining the highest crispness (15.00 ± 1.85) and hardness (maximum positive force and area measuring 2.36 ± 0.31 N and 12.30 ± 1.57 N·s respectively). Hardness showed a negative correlation with Ca2+ concentration when R ≤ 1 (−0.89), and a similar correlation with the porosity of the gel network when R ≥ 1 (−0.80). Given the impacts of crosslinking on the pore structure, it is confirmed that the pore diameter can be designed between 56.24 and 153.58 μm by controlling R-value in the range of 0–2. • Average diameter of ice crystal is minimum at R value = 1. • crosslinked pectin network favours the formation of large ice crystals. • Pore size of cryogels decrease with reducing water freedom of precursor. • Lamellar structure gradually disappears with increasing of gel crosslinks. • The cyrogel prepared at R = 1 obtained the highest crispness. [ABSTRACT FROM AUTHOR]

Porous hydroxyapatite-biochar composites with layered microstructures (SC–HA/C) were prepared by carbonizing sugarcane stem nodes and then soaking them in lime water and (NH4)2HPO4 solutions in rotation. The surface area of SC–HA/C ranges from 8.52 to 28.44 m2/g, and its microstructure inherits various macro-, meso-, and micro-pores in the cell walls of sugarcane and in the pits of the vessel walls. The maximum removal capacities were 11.50, 14.65, and 19.81 mg/g for the Cu (II) immobilization at 25 °C, 35 °C, and 45 °C with the solution Cu (II) concentration of 10~320 mg/L, respectively, which were in accordance with the copper sorption capacities of synthesized nano-hydroxylapatites. The Cu (II)-removal kinetics and isotherm followed the pseudo-second-order equation and the Langmuir equation very well. The formation of the Cu-containing hydroxylapatite solid solutions ((CuxCa1−x)5(PO4)3(OH)) through adsorption, ion exchange (x = 0.01~0.04), and dissolution-coprecipitation (x = 0.13~0.35) was the dominant process for the Cu (II) removal by the SC–HA/C composite.

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Porous CeO 2 powder with different mean pore size and volume fraction was produced. • The structure, microstructure, and BET surface area of the powders were explored. • The formation mechanism of the porous powder was explained. The aim of this study was synthesis of Mg-doped porous cerium oxide powder by self-propagating high-temperature synthesis reaction of Mg- x CeO 2 -O 2 system. Results indicated that doping Mg in the CeO 2 crystal structure increased its lattice parameter slightly, and shifted the Ce-O band in the FTIR spectra from 490 to 574 cm−1. Moreover, the EDS results revealed the distribution of Mg in the CeO 2 microstructure. There were a high volume fraction of interconnected macro-pores in the microstructure of cerium oxide after the synthesis process. Increase in the x -value from 0.05 to 0.25 mol decreased the mean size and volume fraction of pores from 2.4 to 1 µm and 50 to 30 vol%, respectively. In addition, the BET surface area of porous CeO 2 varied between 0.3 and 1.57 m2/g. Finally, it was inferred that the SHS technique can be introduced as a rapid and novel method for synthesis of Mg-doped porous CeO 2 powders. [ABSTRACT FROM AUTHOR]

In the food industry, drying is a crucial unit process for extending product shelf life. Many methods are available for drying of foods but spray drying and freeze drying have been widely adopted for industrial drying of a variety of heat-sensitive foods keeping in mind the drying efficiency as well as retention of nutritive components of foods. More recently a novel cutting-edge technique spray freeze drying (SFD) has started evolving in the food sector to accomplish this highly significant unit operation of drying. The advantages of traditional freeze-drying and spray-drying methods are combined in this process. This article explains various spray freeze-drying methods, both new and old, based on a number of factors, particularly the chilling medium and atomization settings. The method with freeze drying and spray drying is then compared, particularly in terms of the morphology and other significant characteristics of the final product obtained. The article also covers how this technology is used in the food sector to preserve bioactive compounds, which serves as confirmation for the comparison made above in terms of data pertaining to the obtained end goods. A brief description is given for its applications in food industry where it first evolved. The technology's scope and potential difficulties have finally been briefly covered. The review was put together using data from roughly ten years' worth of research and analysis in the area of this unique technology. • Spray freeze drying (SFD) is a novel technology for drying heat-sensitive materials. • SFD preserves the degradation of bioactive compounds during drying. • SFD has different applications in the food and pharmaceutical industry. [ABSTRACT FROM AUTHOR]

Development of the Digital Material Representation (DMR) model, based on 3D reconstruction algorithm and serial sectioning, is the main goal of the present paper. Details on the serial sectioning and image processing algorithms are presented first. Serial sectioning is realized on the basis of light microscopy (LM). Then concept of 3D reconstruction and developed algorithms are presented. Two approaches, based on shape coefficients and the flood fill algorithms, are developed to identify corresponding features on subsequent 2D images. Then, the interpolation algorithm to reconstruct 3D volume between 2D images is presented. Finally, obtained 3D model is an input for finite element mesh generation software for subsequent finite element calculations.

It had been proven that carbon aerogel (CA) can effectively improve the conductivity of sulfur (S) and suppress the shuttle effect of polysulfides in Li-S batteries, due to its outstanding electrical conductivity and micropore-rich structure. However, the microstructure of CA was easy to collapse and shrink during carbonization, resulting in a dramatically drop in specific surface area and porosity. Herein, graphene nanosheets (GNs) were introduced in CA to reinforce the structural stability. As-prepared CA/GNs composites were fabricated from in-situ polymerization of resorcinol (R) and formaldehyde (F) in graphene oxide (GO) solution. It was found that the mass concentration of the GO solution had a significantly positive effect on hierarchical porous structure of the CA/GNs composites, which presented improve the electrochemical performances due to the combination of micro-, meso- and macro-pores. It is worth noting that the CA/GNs0.1 sample, obtained from 10 wt % GO solution, possessed the largest specific surface area of 665.477 m2 g−1 and the largest pore volume of 0.912 cm3 g−1. Especially, after incorporated with moderate amount of S (58.86 wt %), the CA/GNs0.1/S cathode exhibited the best electrochemical performances (initial discharging capacity of 1501 mAh g−1 at 0.1C and reversible capacities of 471 mAh g−1 after 100 cycles and 341 mAh g−1 after 500 cycles at 1C). This was attributed to the tunable hierarchical porous microstructure of the CA/GNs0.1 sample. Unfortunately, when increased the S content to 68.39 wt %, the electrochemical performance deteriorated in all aspects because of their sluggish reaction kinetics. These all results suggested that introducing GNs can feasibly enhance the performance of CA as matrix in Li-S batteries. • Tunable hierarchical porous carbon aerogel/graphene composites were prepared;. • The CA/GNs0.1 material possesses an ultrahigh specific surface area;. • The CA/GNs0.1 material possesses a large total pore volume;. • The electrochemical performance of CA/GNs0.1/S composite was enhanced.. [ABSTRACT FROM AUTHOR]

Abstract Macro-mesoporous structured gamma alumina (γ-Al 2 O 3) has been prepared using a low cost aqueous sol-gel method in the presence of various amounts (0, 2, 4, 6 wt%) of biological gelatin. The primary cationic source was saved via an aqueous solution of the aluminum nitrate and partially hydrolyzed by an ammonia solution. A porous structure was obtained from the agglomeration of alumina nano-particles in the presence of the gelatin chains as a network former. X-ray Diffraction (XRD) shows direct crystallization of gamma alumina from the amorphous precursor without formation of any hydrated or other transition alumina phases. Also, Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM) and Brunauer–Emmett–Teller (BET) analysis demonstrate formation of the macro-mesoporous structure. The specific surface area and particle size varied from 140 to 45.9 m2 g−1 and from 11 to 35 nm, according to gelatin addition (0–6 wt%). [ABSTRACT FROM AUTHOR]

Bio-based aerogels containing cellulose nanofibrils (CNFs) are promising materials due to the inherent physical properties of CNF. The high affinity of cellulose to plant hemicelluloses (xyloglucan, xylan, pectin) is also an opportunity to develop biomaterials with new properties. Here, we prepared aerogels from gelled dispersions of CNFs and xyloglucan (XG) at different ratios by using a freeze-casting procedure in unidirectional (UD) and non-directional (ND) manners. As showed by rheology analysis, CNF and CNF/XG dispersions behave as true gels. We investigated the impact of the freezing procedure and the gel’s composition on the microstructure and the water absorption properties. The introduction of XG greatly affects the microstructure of the aerogel from lamellar to cellular morphology. Bio-based aerogels showed high water absorption capacity with shape recovery after compression. The relation between morphology and aerogel compositions is discussed.

Ruthenium dioxide occurs in two morphologically varied structures: anhydrous and hydrous form; both of them were studied in the scope of this work and applied as mediation layers in ion-selective electrodes. The differences between the electrochemical properties of those two materials underlie their diverse structure and hydration properties, which was demonstrated in the paper. One of the main differences is the occurrence of structural water in RuO2•xH2O, which creates a large inner surface available for ion transport and was shown to be a favorable feature in the context of designing potentiometric sensors. Both materials were examined with SEM microscope, X-ray diffractometer, and contact angle microscope, and the results revealed that the hydrous form can be characterized as a porous structure with a smaller crystallite size and more hydrophobic properties contrary to the anhydrous form. Potentiometric and electrochemical tests carried out on designed GCD/RuO2/K+-ISM and GCD/RuO2•xH2O/K+-ISM electrodes proved that the loose porous microstructure with chemically bounded water, which is characteristic for the hydrous form, ensures the high electrical capacitance of electrodes (up to 1.2 mF) with consequently more stable potential (with the potential drift of 0.0015 mV/h) and a faster response (of a few seconds).

The densification behavior, surface morphology and attendant microstructural characteristics of the selective laser melting (SLM) processed AlSi10Mg alloy affected by the processing parameters were systematically investigated. Increasing the laser scanning speed or hatch spacing will deteriorate the metallurgical bonding between melt pools, resulting in the increase of irregular pores. Scanning speed and hatch spacing affect the liquid metallurgical bonding of melt pools in different ways. By manipulating scanning speed, the shape of the melt pool changes, resulting in different extents of metallurgical bonding. Whereas hatch spacing influences the resultant metallurgical bonding by controlling the overlapping rate between neighboring scan tracks simply. The formations of the hierarchical microstructures which discriminated by the Si phase are elucidated. Coarse zones are formed by the instantaneous existence of extremely high ratio of thermal gradient (G) and solidification rate (R) at the melt pool boundary, where solidification microstructure grows planar. Fine zones are formed by columnar-dendritic growth of microstructure. During the solidification process, the contraction forces that generated by the trapped gas in the pores and gravity are applied to the liquid around irregular pores and, forms the porous microstructures different from that in dense areas eventually. The tensile tests reveal that the tensile properties of SLM-processed samples are significantly affected by the formation of porosity.

Highly sensitive H2 gas sensors were prepared using pure and Pt-loaded SnO2 nanoparticles. Thick film sensors (~35 μm) were fabricated that showed a highly porous interconnected structure made of high density small grained nanoparticles. Using Pt as catalyst improved sensor response and reduced the operating temperature for achieving high sensitivity because of the negative temperature coefficient observed in Pt-loaded SnO2. The highest sensor response to 1000 ppm H2 was 10,500 at room temperature with a response time of 20 s. The morphology of the SnO2 nanoparticles, the surface loading concentration and dispersion of the Pt catalyst and the microstructure of the sensing layer all play a key role in the development of an effective gas sensing device.

Porous 0.8Na 0.5 Bi 0.5 TiO 3 -0.2K 0.5 Bi 0.5 TiO 3 ceramics are fabricated via the pore-forming agent method with polymethyl methacrylate (PMMA) and stearic acid (SA) as pore forming agents, and microstructure observations demonstrate that the porosity, pore shape, and pore sizes can be controlled by the synthesis technology. The dielectric properties of porous ceramics are found not only correlated to the pore-matrix composite model, but also have a significant grain-size effect. Based on the Zener Theory, pining forces exerted by pores on the grain boundary are calculated, to explain the shape effect of pores on grain boundary migration. A phase-field simulation is carried out to investigate pore shape effect on the grain size regulation in porous polycrystalline, and simulation results are in good agreements with experiential results as well as theoretical calculations. Thus, a modified equation is proposed to predict the effective permittivity of the porous piezoelectric ceramics by considering effects of porosity, pore shape and grain size. [ABSTRACT FROM AUTHOR]

In this work, we have investigated theoretically the spectral radiative properties of a monolayer aluminum porous microstructure, including wavelength-selective transmission, reflection, and absorption. The finite-difference time-domain method for electromagnetics has been used to calculate the spectral radiative properties of the monolayer aluminum porous microstructure. It is found that the absorption spectra of the aluminum porous microstructure will generate two peaks within the wavelength ranging from 1.0 to 15.0mm at normal incidence of light. Then the surface plasma polarition resonance could be observed clearly in the obtained results of this work, especially on the top surface near the orifice. Inside the porous structure, magnetic polariton is the crucial mechanism to elucidate for the power absorption enhancement. Furthermore, the absorption capacity of the aluminum porous structure with Si/SiO2 substrate has been analyzed, to explain the influence of base on the monolayer porous material. The findings indicate that the absorptance peak at 3 mm incident wavelength significantly improved with silicon substrate, while that of silica substrate has little difference with aluminum porous plate. The silicon and silica bases disrupted the distribution of the electromagnetic fields of the original aluminum porous structure, and form a new magnetic field within the subbases. Meanwhile the internal microcavity polarition of the porous structure has enhanced obviously near the bases. [ABSTRACT FROM AUTHOR]

In the last decade, different absorber geometries, such as foams and honeycombs, have been tested at laboratory or industrial scale in order to achieve high performance in the conversion of the solar radiation into usable heat, with the current state-of-the-art , the HiTRec-II monolithic honeycomb, characterized by a square-channel section and made out of siliconized silicon carbide (SiSiC). Such geometry has been so far the best compromise for large-scale application thanks to the low production costs, easy manufacturability through extrusion procedure and overall acceptable performance. However, it does present some drawbacks, since the geometry is not able to contain the radiative heat losses, especially from the front surface. An optimized absorber geometry, capable to reduce overall thermal losses, is presented in this work, being able to increase the final thermal efficiency of more than 12% compared to the current state-of-the-art and showing the presence of the so-called volumetric effect, since the outlet fluid temperature is higher than the solid inlet temperature. A test sample has been produced for laboratory-scale experiments, in the form of a 3:1 scaled prototype through additive manufacturing procedure, using a titanium-aluminium alloy (Ti6Al4V) and the experimental results were in good agreement with the numerical calculation, with a deviation of 3%, computed considering a 3:1 Ti6Al4V scaled-up sample. As the manufacturing technology will progress and become cheaper in the near future, it will be possible to improve the overall Solar Power Tower (SPT) plants performance using advanced micro-geometry for open volumetric receivers. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated void growth in von Mises materials which contain realistic porous microstructures. For that purpose, we have performed finite element calculations of cubic unit-cells which are subjected to periodic boundary conditions and include porosity distributions representative of three additively manufactured metals. The initial void volume fraction in the calculations varies between 0.00564% and 1.75%, the number of actual voids between 14 and 5715, and the pores size from 2. 3 μ m to 110 μ m. Several tests with different void sizes and positions have been generated for each of the three porous microstructures considered, and for each test we have performed several realizations with different spatial arrangement of the voids. The simulations have been carried out with random spatial distributions of pores and with clusters of the same size and different void densities. The macroscopic stress state in the unit-cell is controlled by prescribing constant triaxiality and Lode parameter throughout the loading. Calculations performed exchanging the loading directions for a given distribution of void sizes and positions have shown that the porous microstructure makes the macroscopic strain softening of the unit-cell (slightly) anisotropic. Moreover, the results obtained with the realistic porous microstructures have been compared with unit-cell calculations having an equivalent single central pore, and with calculations in which the material behavior is modeled with Gurson plasticity. It has been shown that both initial void volume fraction and spatial and size distribution of voids affect the macroscopic response of the porous aggregate and the void volume fraction evolution. Moreover, the calculations with random spatial distribution of voids have brought out that different tests of the same microstructure carry significant variations to the effective behavior of the porous aggregate, and that the interaction between neighboring pores dictates the volume evolution of individual voids, especially at higher macroscopic triaxiality. The calculations with clusters have shown that pores clustering promotes localization/coalescence due to increased interaction between the voids, which results in an increased growth rate of voids in clusters with large number of pores. Moreover, the results for the evolution of the distribution of plastic strains in the unit-cell have provided quantitative indications of the role of porous microstructure on the development of heterogeneous plastic strain fields which promote macroscopic strain softening. Namely, the accelerated growth rate of the plastic strains near the voids which indicates the onset of localization/coalescence has been shown to occur earlier as the number of voids in the microstructure increases. • Numerical investigation of void growth in materials with realistic porous microstructures. • Simulations with random spatial distributions of voids and with clusters of different sizes. • Effect of void size distribution on the collective behavior of individual pores. • Interaction between neighboring pores affects void volume fraction evolution. • Clustering promotes coalescence localization due to increased voids interaction. [ABSTRACT FROM AUTHOR]

The porous Fe 3 O 4 /Ag composite is successfully fabricated by a handy self-propagating combustion method, and the underlying mechanisms for lightweight and efficient microwave absorption performance are roundly revealed based on magnetic-dielectric composition and porous microstructure. [Display omitted] • The porous Fe 3 O 4 /Ag composites are achieved via a handy self-propagating combustion. • Multiple electromagnetic loss mechanisms are integrated in the Fe 3 O 4 /Ag composites. • The strong reflection loss (−45.01 dB) is achieved at thin thickness and low density. Due to the growing demands for radar stealth and electromagnetic pollution prevention, EM-waves absorbing materials with lightweight, broad bandwidth, thin thickness and strong strength are in high need nowadays. However, the achievement of both lightweight and efficient absorption still remains a challenge. In this work, the porous Fe 3 O 4 /Ag composites are successfully synthesized by a self-propagating combustion method, which has the advantages of simplicity, green and high yield. The magneto-electric synergy components and porous microstructure not only effectively reduces the density of the composites, but also significantly reinforces the absorption of EM waves. The sample with Fe 3 O 4 /Ag molar ratio of 4:1 attains the maximum reflection loss of −45.01 dB at the matching thickness of 1.85 mm and it can realize dramatical reduction of RCS signal by coating on the perfect electric conductor. The findings shed light on the promising application of the porous Fe 3 O 4 /Ag composites in the fields of environmental protection and military stealth. [ABSTRACT FROM AUTHOR]

In this work, we report a novel, simple and reproducible etching technique named Silver-Assisted Chemical Vapor Etching method (Ag-ACVE). It consists to expose Ag-loaded silicon substrates to vapors emanating from HF/H2O2 hot solution. The surface treatment performed with this method aims to enhance both optical and electrical properties of conventional silicon solar cells. SEM images of Ag-ACVE treated samples exhibit the appearance of porous micro-cavity like-structure for short etching duration. For long etching duration, sporadic and curved silicon nanowires (SiNWs) were formed. A kinetic study of the vapor etching reaction revealed a relatively high etching rate. Furthermore, the dimension of the micro-cavities increased as a function of the H2O2 molar ratio. UV-Visible measurement showed a significant decrease of the total reflectivity versus the molar ratio. Whereas, at the same time the minority carrier life time was significantly enhanced and as a result the solar cell performance was improved. [ABSTRACT FROM AUTHOR]

The properties of the porous ceramics are known not only related to the pore-solid composite model, but also have a significant grain-size effect. In this study, a phase field simulation is carried out to study the effect of different micropores on the grain growth kinetics of porous ceramics, and results indicate that the average grain size and distribution are highly influenced by the topological shape of the second-phase. The efficiency of the grain boundary migration is determined by the pinning forces applied in the interaction of the grains and pores. The pining forces are calculated based on Zener Theory, and results indicate that the maximum pinning force is highly dependent on the second-phase shape, and the contacting mode between the grain boundaries and second-phase pores is the determining factor of the grain boundary migration in porous materials. [ABSTRACT FROM AUTHOR]

The relationships between porous microstructures and transport properties are of fundamental importance in various scientific and engineering applications. Due to the intricacy, stochasticity and heterogeneity of porous media, reliable characterization and modeling of transport properties often require a complete dataset of internal microstructure samples. However, it is often an unbearable cost to acquire sufficient 3D digital microstructures by purely using microscopic imaging systems. This paper presents a machine learning-based technique to hierarchically reconstruct 3D well-connected porous microstructures from one isotropic or several anisotropic low-cost 2D exemplar(s). To compactly characterize the large-scale microstructural features, a Gaussian image pyramid is built for each 2D exemplar. Local morphology patterns are collected from the Gaussian image pyramids, and then they serve as the training data to embed the 2D morphological statistics into feed-forward neural networks at multiple length levels. By using a specially-developed morphology integration scheme, the 3D morphological statistics at different levels can be inferred from the statistics-informed neural networks. Gibbs sampling is adopted to hierarchically reconstruct 3D microstructures by using multi-level 3D morphological statistics, where the large-scale, regional and local morphological patterns are statistically generated and successively added to the same 3D random field. The proposed method is tested on a series of porous media with distinct morphologies, and the statistical equivalence between the reconstructed and the real microstructures is systematically evaluated by comparing morphological descriptors and transport properties. The results demonstrate that the proposed 2D-to-3D microstructure reconstruction method is a universal and efficient approach to generating morphologically and physically realistic samples of porous media. [ABSTRACT FROM AUTHOR]

The porous microstructure of hydrates governs the mechanical strength of the hydrate-bearing sediment. To investigate the growth law and microstructure of hydrates in porous media, the growth process of tetrahydrofuran (THF) hydrate under different concentration of THF solution is directly observed using Magnetic Resonance Imaging (MRI). The images show that the THF hydrate grows as different models under different concentration of THF solution (19%, 11.4% and 5.7% by weight) at 1 °C. When the concentration is 19% (stoichiometric molar ratio of THF/H2O = 1:17), the THF hydrate grows as cementing model. However, with the decreasing concentration of THF, the growth model transfers from cementing model to floating model. The results show that the growth of the THF hydrate was influenced by the dissolved quantity of THF in the water. The extension of the observed behavior to methane hydrate could have implications in understanding their role in seafloor and permafrost stability.