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Liquid-metal dealloying generates porous metals or interpenetrating-phase composites. Particularly attractive is the use of the alloy's innate melt for activating dealloying throughout the bulk, even in extended sample geometries, during reverse peritectic melting. We explore if interpenetrating-phase microstructures may be observed more generally during partial melting of solid solutions with an extended temperature interval of solid-melt coexistence. Incomplete wetting of grain boundaries by the melt is then a prerequisite for a bicontinuous structure. For a Cu-In alloy, we show that special grain boundaries remain non-wetted and provide a load-bearing backbone in the partially molten alloy, and that the bicontinuous structure is preserved during quenching to room temperature. Samples with a contiguous porosity can be obtained by leaching the solidified melt. As extended melting intervals are ubiquitous in binary alloys, our observations provide for the innate-melt-enabled preparation of monolithic interpenetrating-phase composites or porous metals in an extended set of alloy systems. [ABSTRACT FROM AUTHOR]

Bicontinuous nanoporous metallic glasses (MG) synergize the outstanding properties of MGs and open-cell nanoporous materials. The low-density and high-specific-surface-area of bicontinuous nanoporous structures have the potential to enhance the applicability of MGs in catalysis, sensors, and lightweight structural designs. Here, we report molecular dynamics simulations of tensile loading deformation and failure of bicontinuous nanoporous Cu 64 Zr 36 MG with 55% porosity and 4.4 nm ligament size. Results indicate an anomalous mechanical behavior featuring delocalized plastic deformation preceding ductile failure. The deformation follows two mechanisms: i) Necking of ligaments aligned with the loading direction and ii) progressive alignment of randomly oriented ligaments. Failure occurs at 0.16 strain, following massive rupture of ligaments. This work indicates that a bicontinuous nanoporous design is able to effectively delocalize strain localization in a MG due to a combination of size effect on the ductility of MGs resulting in nano ligaments necking and progressive asynchronous alignment of ligaments. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A new type of porous carbon/MnO 2 composites, having bicontinuous structures, i.e., continuous channels and carbon skeletons, was prepared using a phase separation method, followed by a carbonization procedure and a subsequent redox reaction. In this work, such composite electrodes show a high specific capacitance of ca. 260 F g −1 at 0.5 A g −1 in 1 M Na 2 SO 4 aqueous solution, a superior cycling stability (~80% retention after 2000 cycles) and a distinctive high-rate performance. Especially, unique bicontinuous structures endow such composites with a great specific capacitance of the constituent MnO 2 (~1100 F g −1 ), very close to the theoretical value. These excellent electrochemical behaviors may render this material a promising candidate as high-performance electrodes in supercapacitors. Therefore, our findings suggest that the strategy for constructing bicontinuous hybrid electrodes represents an exciting direction for designing next-generation supercapacitors. [ABSTRACT FROM AUTHOR]

Titanium-magnesium (Ti-Mg) composites with bicontinuous structure have been successfully fabricated by powder metallurgy and ultrasonic infiltration for biomaterial potential. In the composites, Ti phase is distributed continuously by sintering necks, while Mg phase is also continuous, distributing at the interconnected pores surrounding the Ti phase. The results showed that the fabricated Ti-Mg composites exhibited low modulus and high strength, which are very suitable for load bearing biomedical materials. The composites with 100 µm and 230 µm particle sizes exhibited Young's modulus of 37.6 GPa and 23.4 GPa, 500.7 MPa and 340 MPa of compressive strength and 631.5 MPa and 375.2 MPa of bending strength, respectively. Moreover, both of the modulus and strength of the composites increase with decreasing of Ti particle sizes. In vitro study has been done for the preliminary evaluation of the Ti-Mg composites. [ABSTRACT FROM AUTHOR]

The ECTFE membrane with bicontinuous structure was prepared by a binary diluent via thermally induced phase separation method. The effect of binary diluent composition on membrane structure was investigated systematically. The Flory–Huggins interaction parameters between ECTFE and diluents were investigated to analyze the mechanism of phase separation. Dibutyl sebacate (DBS) was selected as the primary diluent due to the high boiling point and strong interaction with ECTFE, while triphenyl phosphite (TPP) was selected as the secondary diluent because of the good compatibility with DBS. As the weight ratio of DBS to TPP was 3/2, a uniform bicontinuous structure was obtained. A typical upper critical solution temperature behavior was displayed and the monotectic concentration was as high as approximately 50 wt.%. Finally, an ECTFE hollow fiber membrane with a bicontinuous structure was prepared by the binary diluent and revealed high mechanical strength (tensile strength of 2.40 MPa) and filtration performance (water flux of 313 L m−2 h−1at 0.1 MPa). [ABSTRACT FROM PUBLISHER]

Bicontinuous Tin oxide (SnO 2 ) thin films were fabricated by atomic layer deposition (ALD), annealing, and acid washing with nanoporous gold (NPG) structure serving as templates. The resultant SnO 2 films show high sensitivity on NO 2 gas. The detection limit is as low as 170 ppb in dry N 2 flow with a rapid response/recovery time of 40/130 s at the optimized working temperature of 300 °C. The performances dependence of the gas sensor on the working temperatures and the exposure environments reveal that the gas responses strongly rely on the dynamic balance of O 2 , O 2 − , O − , N O 2 − , and N O 3 − . Our study not only shows this bicontinuous SnO 2 films is promising for sensitive gas sensor but also provides insightful understanding on the NO 2 gas sensing mechanism. [ABSTRACT FROM AUTHOR]

While coarsening of spherical particles has been well documented, our understanding of coarsening of complex microstructures is still limited. The first step in developing a theory of coarsening of microstructures with complex morphologies is to study coarsening of microstructures that evolve self-similarly. In this paper, we examine the morphological evolution of a self-similar two-phase bicontinuous structure generated via nonconserved dynamics (i.e., motion by mean curvature) to elucidate the complex dynamics of coarsening. We find that the evolution proceeds with some interfaces evolving toward topological singularities (pinching) while the majority of interfaces flatten. These two processes were also illustrated through the evolution equation for the mean curvature, which has a term that depends solely on the local curvatures, as well as a term that is proportional to the surface Laplacian of the mean curvature. The first term causes an increase in the magnitude of the mean curvature, while the second term causes smoothing of the mean curvature in a manner similar to diffusion of chemical species on a surface. The second term causes a large dispersion in the values of the time derivative of mean curvature at various locations in the structure, characterized neither by the mean curvature nor the Gaussian curvature. [ABSTRACT FROM AUTHOR]

Abstract: The rheology of mixed κ-carrageenan/ι-carrageenan gels was investigated in the presence of 75 or 150 mM K+. The addition of ι-carrageenan to κ-carrageenan led to an initial weak increase of the Young's modulus. A maximum occurred at concentrations ratios close to 1:1, followed by a weak decrease at higher ι-carrageenan concentrations. When κ- and ι-carrageenan were mixed at a constant total polysaccharide concentration, a plateau of the Young's modulus and a clear local minimum in the fracture strain in both compression and extension were identified at ratios between 2:1 and 4:3 (ι:κ). At all other ratios, the expected strong increase of the Young's modulus and decrease of the fracture strain were observed with an increasing κ-carrageenan fraction. A weak maximum of the fracture stress in compression and extension was observed at ratios between 1:1 and 1:2 (ι:κ). The structural and rheological findings support segregative phase-separation of mixed carrageenan gels in the presence of K+. Phase separation could be promoted through curing of the gel network of ι-carrageenan at temperatures above the coil-to-helix transition of κ-carrageenan. [Copyright &y& Elsevier]

• We successfully prepared a Cu 55.4 Zr 35.2 Al 7.5 Y 1.9 bi-continuous nanoporous metallic glass with ligaments size of ∼20 nm. The mechanical properties and plastic deformation of nanoporous and solid metallic glasses have been studied using depth-sensing nanoindentation combined with electron microscopy characterization. • The nanoporous metallic glass has distinct mechanical properties and deformation behavior comparing to solid glass. It fails in transverse fracture under tension but becomes ductile under compression without any noticeable shear banding events. Irreversible plastic deformation has taken place well before the global yield point from partial unload compression. • We discovered a transition of deformation modes at a critical strain near 0.03. The global yielding in this nanoporous metallic glass obeys a universal scaling law of yielding in metallic glasses. The results provide intrinsic relations between classic Gibson-Ashby law and the universal scaling law in metallic glasses. • This nanoporous metallic glass has the highest yield stress comparing to crystalline nanoporous materials and it maintains a high strain hardening index under compression. The mechanical properties and plastic deformation of a Cu 55.4 Zr 35.2 Al 7.5 Y 1.9 nanoporous metallic glass (MG) have been studied using depth-sensing nanoindentation combined with electron microscopy characterization. The nanoporous MG exhibits an initial relative density of 50.9% and a bicontinuous structure with 20.84 ± 1.49 nm-diameter interconnecting ligaments. It is brittle in tension, whereas it has significant homogeneous plasticity under compression. It has a hardness of 0.67 ± 0.06 GPa and Young's modulus of 14.72 ± 0.74 GPa from nanoindentation. While under tensile and compression, it has a yield strength of 0.22 to 0.23 GPa and an effective modulus of 10.37 ± 0.99 GPa. The discrepancy between the moduli is caused by irreversible shear transformation zone (STZ) plasticity that takes place well ahead of the yield point. The deformation in the nanoporous MG begins with both elastic and plastic bending in ligaments and transfers to plastic uniaxial deformation in ligaments at a critical strain near 0.03, at which a significant change in stiffness is observed. The yielding stress follows the universal scaling law predicted by the critical-like behavior in glassy systems. The strength to modulus ratio is well maintained in this nanoporous MG and is higher than the porous crystalline alloys. Our experimental study clarifies the fundamental failure mechanism and deformation behavior in nanoporous MGs. [ABSTRACT FROM AUTHOR]

Abstract: The phase behavior of polydisperse ABA triblock copolymers is studied using dissipative particle dynamics simulations, focusing on the emergence and property of bicontinuous structures. Bicontinuous structures are characterized by two separate, intermeshed nanoscopic domains extending throughout the material. The connectivity of polymeric bicontinuous structures makes them highly desirable for many applications. For conventional monodisperse diblock and triblock copolymers, regular bicontinuous structures (i.e., gyroid and Fddd) can be formed over a narrow composition window of 3%. We demonstrate that the composition window for the formation of bicontinuous structures can be regulated by designed polydispersity distributions of ABA triblock copolymers. In particular, introducing polydispersity in both A and B blocks can lead to a significant enhancement of the composition window of bicontinuous structures with both continuous A and B domains. The mechanism of the bicontinuous structure enhancement is elucidated from the distribution of the long and short blocks. Furthermore, it is shown that the polymeric bicontinuous structures from polydisperse ABA triblock copolymers possess good continuity throughout the sample, making them ideal candidates for advanced applications. [Copyright &y& Elsevier]

Abstract: A mixed diluent composed of γ-butyrolactone (γ-BL) and dioctyl phthalate (DOP) was employed for preparing PVDF microporous membrane via TIPS method. The relation equations expressing the quantitative relationship between interaction parameter and phase separation temperature were deduced based on Flory–Huggins equation and solubility parameter theory. The unknown constants in the relation equations were solved out by fitting the binodal curve with cloud points in phase diagram. The binodal curves of PVDF/mixed diluent systems with different diluent compositions were calculated according to the relation equations. The compositions possible to yield bicontinuous structure inside microporous membrane were predicted in phase diagram. Finally, the hollow fiber membrane with interconnected sponge-like structures was prepared successfully from the predicted system (PVDF 12.74%, DOP 58.44%). The DCMD performances of the fabricated hollow fiber membranes were investigated with 3.5wt% NaCl solution. The permeate flux of the membrane achieved 51.5kg/m2 h with the NaCl rejection of 99.99% at the feed temperature of 90°C. As a result, this prediction method is effective in constructing the polymer/mixed diluent system which is used for preparing MD hollow fiber membrane in TIPS process. [Copyright &y& Elsevier]

Abstract: Rigid methacrylate-based polymer monoliths with well-defined macropores have been synthesized from glycerol 1,3-dimethacrylate (GDMA) and trimethylolpropane trimethacrylate (Trim) by organotellurium-mediated living radical polymerization. In each system, poly(ethylene oxide) induced spinodal decomposition with the progress of polymerization of GDMA or Trim. Well-defined macroporous structure can be tailored by fixing the bicontinuous structure by the sol–gel transition. Both polymer monoliths possessed macropores with narrow size distributions and the macropore size can be controlled simply by varying the amount of poly(ethylene oxide). Starting from GDMA, polymer monoliths with unimodal macropores can be obtained due to the collapse of micro- and mesopores, which were originally embedded in macropore skeletons, by large shrinkage during drying. In contrast, starting from Trim, the obtained polymer monoliths include not only macropores but also micro- and mesopores, which lead to high specific surface area (470 m2 g−1), owing to the higher crosslinking density. [Copyright &y& Elsevier]

Abstract: In this study, a bicontinuous structure of poly(methyl methacrylate) (PMMA) membrane was obtained via wet immersion method by coagulating PMMA/1,4-dioxane casting film into alcohol bath. Freeze-dried method was utilized to investigate the evolution of membrane structure at various coagulation times. The FTIR-microscope, scanning electronic microscope (SEM), ternary phase diagram as well as light transmission were used to investigate the formation and structure evolution mechanism of PMMA membrane. The results show that the bicontinuous structure can be formed on the top surface of PMMA membrane as contacted the PMMA/1,4-dioxane casting film with n-propanol only 2s. Furthermore, it also can be found that as increasing the immersion time in n-propanol bath over than 1.5min, the bicontinuous structure would be broken up to form nodules morphology due to capillarity effect, or led to a matrix/disperse domain morphology by coalescence effect. The analysis of FTIR-microscopy shows that the PMMA polymer concentration in the top layer of nascent membrane was decreased as immersed the casting film into n-propanol bath. The lower PMMA polymer concentration in the top layer could cause the composition path entered into the unstable region, resulting in the formation of bicontinuous structures. [Copyright &y& Elsevier]

The dielectric relaxation spectra of the non-aqueous ionic liquid (IL) microemulsions composed of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ])/p-(1,1,3,3-tetramethylbutyl)phenoxypolyoxyethyleneglycol (TX-100)/toluene were obtained, the measured frequency is between 1 MHz and 3 GHz. A unique dielectric relaxation located at 10–100 MHz was observed. The direct current (dc) conductivity data were obtained from the total dielectric loss. Near the percolation transition, weight fraction dependence of dc conductivity and static dielectric constant, frequency dependence of permittivity and loss angle all suggest that static percolation occurs in this hydrophilic IL microemulsion. Phase boundaries of IL-in-toluene (IL/O), bicontinuous (B.C.) and toluene-in-IL (O/IL) subregions were determined by the inflection points in the dependent curve of relaxation parameters varied with weight fraction. The mechanism of this dielectric relaxation is attributed to the interfacial polarization of droplets by analyzing relaxation time with Maxwell-Wagner theory. The phase parameters, which reflect the interior properties of the spherical dispersed particle, were calculated by Hanai theory. The dependence of phase parameters on the variation of sample composition was properly explained. For O/IL subregion, the continuous phase should be an IL/TX-100 binary solvent rather than the pure IL. For IL/O subregions, a certain amount of toluene was dissolved in the droplets. The dielectric properties of three subregions, namely, IL-in-toluene, bicontinuous and toluene-in-IL for non-aqueous ionic liquid microemulsion [bmim][BF 4 ]/TX-100/toluene. [Display omitted] [ABSTRACT FROM AUTHOR]

The porous solids with bicontinuous structures have received significant attention due to their complex structure with unique physical functionalities. They are often obtained through structural transformation from lamellae or cylindrical precursors. However, the experimental verification of this relationship is challenging due to the short life-living of the structural intermediates and the soft nature of the assembled amphiphilic systems. Herein, we report the observation of the structural change of macroporous bicontinuous diamond-surface structure in the self-assembly of block copolymeric system with inorganic precursors in a mixture solvent of tetrahydrofuran (THF) and HCl aqueous solution. By controlling the addition amount of HCl/H 2 O, both the electrostatic interactions of the organic/inorganic precursor and the hydrolyzation and condensation rate of tetraethyl orthosilicate (TEOS) can be controlled. A structural transformation from bicontinuous diamond-surface to several intermediates between lamellar and bicontinuous structures has been observed with increasing the concentration of HCl. Our results show that the transition centers play an important role in the formation of the bicontinuous structure from the lamellae. Furthermore, we have proved the formation of interlamellar attachments (ILAs) and stalks as the intermediate phase. This study may bring new insights into the formation and the structural relationship of the bicontinuous porous solids and the corresponding relevant biological structures. A structural transformation from macroporous bicontinuous diamond-surface to several intermediates between lamellar and bicontinuous structure has been observed in the self-assembly of block copolymeric system with inorganic precursors in a mixture solvent of tetrahydrofuran and HCl aqueous solution. The stalks or interlamellar attachments play key role in the transition process. This study may bring new insights into the formation and the structural relationship of the bicontinuous porous solids. [Display omitted] • A structural transformation between lamellar and bicontinuous diamond surface has been observed. • By co-assembly of block copolymer and inorganic source, long-living intermediates can be investigated. • The transition center plays an important role in formation of the bicontinuous structure from the lamellae. [ABSTRACT FROM AUTHOR]

Substrate morphology has a significant effect on the CO 2 transport performance of a thin-film composite (TFC) membrane. In this study, a new mixed solvent comprising 2-pyrrolidone (2-PD) and 2-methoxyethanol (2-ME) was used to prepare polyethersulfone (PES) substrates with bicontinuous structure by water vapor-induced phase separation, followed by immersion in water as nonsolvent. Compared with the commonly used solvent, N -methyl-2-pyrrolidone (NMP), the 2-PD/2-ME mixed solvent is more hydrophilic and can decrease the thermodynamic stability of the casting solution significantly. As a result, the phase separation was induced via the spinodal decomposition mechanism. The open morphology bestowed the optimized substrate with a very high CO 2 permeance of 133,226 ± 3870 GPU (1 GPU = 10–6 cm3(STP) s–1 cm–2 cmHg–1 = 3.3464 × 10-9 kg-mol s–1 m–2 Pa–1), which was 5 times more permeable than the baseline substrate synthesized with NMP. By using this new substrate, the prepared TFC membrane containing amines showed an increased CO 2 permeance of 908 ± 8 GPU at 57 °C, which was 48 GPU higher than that with the baseline substrate. Meanwhile, the CO 2 /N 2 selectivity was retained at 162 ± 4 at 57 °C. In addition, the good scalability of the new PES substrate was demonstrated by roll-to-roll fabrication of a 50′ long scale-up PES substrate with a width of 21ʺ. • PES substrate with bicontinuous structure was prepared using a new mixed solvent. • The mixed solvent comprised 2-pyrrolidone and 2-methoxyethanol. • The PES substrate exhibited a very high CO 2 permeance of 133,226 GPU. • The optimized morphology enhanced the CO 2 transport in a composite membrane. • The good scalability of PES substrate with bicontinuous structure was demonstrated. [ABSTRACT FROM AUTHOR]

• A method to generate bicontinuous nanoporous microstructure is proposed. • Method is based on Cahn's ideas combined with Fibonacci spherical grids. • Structures are validated by Mean and Gaussian curvatures and Genus density. • The method provides efficiency in the generation of adjustable nanoporous models. A direct method is proposed for the generation of 3D stochastic bicontinuous microstructures on general periodic parallelepiped cells, providing flexibility in the design of atomistic nanoporous simulation models. The method combines the ideas of Cahn with a modified Fibonacci grid to ensure the generation of a stochastic structure, while strictly enforcing periodicity in a flexibly defined parallelepiped cell. To validate the method, the topology of three parallelepiped cells is evaluated: cubic, rectangular prism, with different edge lengths, and general parallelepiped, with different edge lengths and angles. Results show consistent ligament size distribution among the different microstructures. The Mean and Gaussian curvatures for all systems calculated at different relative densities agree well with their theoretical values. The scaled genus density for relative density ranging from 25% to 55% is in good agreement with experimental values and data from molecular dynamics and phase field methods. The proposed method offers an efficient framework for the generation of 3D stochastic periodic bicontinuous microstructures. The method is particularly convenient in the design of adjustable nanoporous models for atomistic simulations. [ABSTRACT FROM AUTHOR]