Bulk Scales Research Articles

Measuring deformation processes in granular materials from intragranular to bulk scales

Granular materials (assemblies of contacting grains with inter-granular porosity) form a vast family of materials important in both natural and industrial contexts. Under mechanical loads such systems show complex behaviours relating to the inter- and intra-granular stresses, strains and force transmission as well as the individual grain kinematics and interactions leading to multi-scale, heterogeneous behaviour. To understand such systems requires detailed understanding of these different structures and processes at the pertinent scales. This paper provides a brief overview of some new opportunities for enhanced experimental description of structures and mechanisms relating to the deformation of granular materials exploiting the penetrating power of x-rays for both imaging, giving access to granular structures and their evolution, and diffraction-based measurements, giving access to intra-granular grain structure and changes as well as inter- and intra-granular force transmission.

Unravelling the emulsifying properties of unfractionated plant powders: From interface to bulk

Crude plant-based by-product powders can stabilise emulsions. Their chemical composition varies substantially depending on both the source plant and the manufacturing process, resulting in different emulsifying properties. This diversity was assessed by studying the emulsifying properties of three chemically different by-products (apple seed cake: protein-rich, apple pomace: non-protein soluble-rich, and liquorice root: mostly water-insoluble) ground into fine and coarse powders. The properties (droplet size, particle anchoring ratio, rheological properties) of the powder-stabilised emulsions were monitored for one month and linked to powder suspensions properties assessed in the presence and absence of solid particles. The interfacial scale was emphasized as the primary location to study the interactions between mixed emulsifiers. The interfacial properties of the powders, and especially the competition between solid particles and soluble compounds, were successfully linked to emulsions properties. Protein-rich powder-stabilised emulsions contained smaller droplets, whose diameter varied slightly with particle size, confirming soluble macromolecules dominance at interfaces. With the soluble powder, particles and soluble macromolecules acted synergistically at both interfacial and bulk scales, indicating mixed interfaces. Particle size determined the properties of the emulsions stabilised with insoluble powder, suggesting interfaces mostly composed of solid particles. Solid particles ensured the gravitational and thermodynamic stability of all powder-stabilised emulsions.

Droplet freeze desalination high fidelity modeling for sustainable water purification and diverse applications

Freeze desalination (FD) is an environmentally clean water purification technique that holds a great promise for low-energy consumption and with unlimited brine's salinity levels. The brine cooling induces freezing, rendering separation and removing contaminants. A high-fidelity molding using CFD is employed to explain the purification of ice from saline droplets in a sub-cold environment under natural free-convection. Comparisons were made with analytical predictions derived from experimentally acquired data through brine cooling in bulk and droplet scales. The procedural sequence employed facilitated the model's ability to accurately represent the ion diffusion and phase-change phenomena across various temperatures (−15 °C and − 25 °C), concentrations, partition & heat-transfer coefficients, and droplet volumes (3 μL to 9 μL). The salt concentration ranged from seawater (35 g/L) to RO (70 g/L) salinity levels. The model successfully accommodates the experimental temperatures observed during the equilibrium between the solid and liquid phases. The achieved desalination efficiency ranges from 20 % to above 40 %. Lastly, machine learning is implemented to identify the principal experimental parameters influencing desalination efficiency. In the suggested system, dynamic salinity/impurity and temperature profiles enable natural free convection brine cooling research. The current framework can study the purification/concentration efficiency of diverse range of mixtures subjected to freeze crystallization.

Surfactant foam injection for remediation of diesel-contaminated soil: A comprehensive study on the role of co-surfactant in foaming formulation enhancement

Aqueous foam injection is a promising technique for in-situ remediation of soil and aquifers contaminated by petroleum products. However, the application efficiency is strongly hindered by foam's instability upon contact with hydrocarbons. Addressing this, we propose a new binary surfactant mixture of Sodium Dodecyl Sulfate (SDS) and Cocamidopropyl Hydroxysultaine (CAHS). This study investigates CAHS's role as a co-surfactant in enhancing foam stability against antifoaming diesel oil under static and dynamic conditions. Using a dynamic foam analyzer (DFA-100), we assessed static foam's stability by monitoring decay profiles and bubble growth over time. The results revealed that the highest stability can be reached at a CAHS to SDS ratio of 50:50, increasing the half-life of the foam by 7.7 times. Remarkably, our analyses at bulk and bubble scales also elucidated the mechanisms behind the enhanced foam stability of the proposed binary surfactant mixture in the absence and presence of diesel. Additionally, in a 1D sand column, the SDS-CAHS mixture demonstrated more than twofold improvement of the Resistance Factor, attributed to the better survival of the lamellae due to the reduced rate of their destruction. This formulation also yielded a recovery improvement of >10 % compared to SDS foam. The significant improvements in stability and performance of the SDS-CAHS (50:50) mixture were credited to a robust pseudo-emulsion film formation, creating a higher oil entry barrier. This reinforcement and the surfactant molecules' synergistic interactions at the gas-liquid-oil interface significantly contributed to the overall effectiveness.

Understanding poromechanical response of a biogenic coalbed methane reservoir

Biogenic coalbed methane (BCBM) reservoirs aim to produce methane from in situ coal deposits following microbial conversion of coal. Success of BCBM reservoirs requires economic methane production within an acceptable timeframe. The work reported here quantifies the findings of previously published qualitative work, where it was found that bioconversion induces strains in the pore, matrix and bulk scales. Using imaging and dynamic strain monitoring techniques, the bioconversion induced strain is quantified here. To understand the effect of these strains from a reservoir geomechanics perspective, a corresponding poromechanical model is developed. Furthermore, findings of imaging experiments are validated using core-flooding flow experiments. Finally, expected field-scale behavior of the permeability response of a BCBM operation is modeled and analyzed. The results of the study indicated that, for Illinois coals, bioconversion induced strains result in a decrease in fracture porosity, resulting in a detrimental permeability drop in excess of 60% during bioconversion, which festers itself exponentially throughout its producing life. Results indicate that reservoirs with high initial permeability that will support higher Darcian flowrates, would be better suited for coal bioconversion, thereby providing a site-selection criteria for BCBM operations.

Phase-separation facilitated one-step fabrication of multiscale heterogeneous two-aqueous-phase gel

Engineering heterogeneous hydrogels with distinct phases at various lengths, which resemble biological tissues with high complexity, remains challenging by existing fabricating techniques that require complicated procedures and are often only applicable at bulk scales. Here, inspired by ubiquitous phase separation phenomena in biology, we present a one-step fabrication method based on aqueous phase separation to construct two-aqueous-phase gels that comprise multiple phases with distinct physicochemical properties. The gels fabricated by this approach exhibit enhanced interfacial mechanics compared with their counterparts obtained from conventional layer-by-layer methods. Moreover, two-aqueous-phase gels with programmable structures and tunable physicochemical properties can be conveniently constructed by adjusting the polymer constituents, gelation conditions, and combining different fabrication techniques, such as 3D-printing. The versatility of our approach is demonstrated by mimicking the key features of several biological architectures at different lengths: macroscale muscle-tendon connections; mesoscale cell patterning; microscale molecular compartmentalization. The present work advances the fabrication approach for designing heterogeneous multifunctional materials for various technological and biomedical applications.

Investigating the Electromechanical Properties of Carbon Black-Based Conductive Polymer Composites via Stochastic Modeling.

Conductive polymer composites (CPCs) have shown potential for structural health monitoring applications based on repeated findings of irreversible transducer electromechanical property change due to fatigue. In this research, a high-fidelity stochastic modeling framework is explored for predicting the electromechanical properties of spherical element-based CPC materials at bulk scales. CPC dogbone specimens are manufactured via casting and their electromechanical properties are characterized via uniaxial tensile testing. Model parameter tuning, demonstrated in previous works, is deployed for improved simulation fidelity. Modeled predictions are found in agreement with experimental results and compared to predictions from a popular analytical model in the literature.

Severe plastic deformation close to the melting point enables Mg-Fe nanocomposites with exceptional strength

The attractive properties of Mg-bcc nanocomposites have gained increasing interest, but fabrication to bulk scales failed so far as strain immediately localizes within the Mg-phase. Targeting successful processing strategies, we analyze the deformation behavior and resulting microstructures of Mg-Fe composites as a function of applied strain and processing temperature using high-pressure torsion. Counterintuitively, processing at 73% of Mg's melting point accelerated microstructural refinement and improved homogeneity. Suppressing strain localization of the phases, a three-fold hardness increase compared to ambient processing is obtained. Such hardness levels suggest that further optimization likely paves the way towards bulk Mg-based materials beyond a gigapascal strength.

Triple silicon isotope insights into the formation of Precambrian cherts

Cherts are pervasive in the Precambrian and their O and Si isotopic compositions have been used extensively for reconstructing seawater paleo-temperatures. However, these reconstructions are obscured by the fact that cherts exhibit, at a given age, a large isotopic (O and Si) heterogeneity at bulk and micrometer scales. This is understood as reflecting the fact that cherts are an assemblage of silica precursors having different origins, and that diagenesis and metamorphism have modified the isotopic compositions acquired during the last equilibration with seawater. To test the contributions of the different processes that control the Si isotopic composition of cherts, we developed high-precision triple Si isotope measurements by Multicollector-Inductively Coupled-Plasma Mass-Spectrometer (MC-ICP-MS). This approach allows to identify deviations from the equilibrium Si isotopic fractionation at the level of a few ppm. Triple Si isotope data combined with trace elements and O isotope data in Precambrian cherts demonstrate that three different sources of silica were involved in the formation of cherts, and that both equilibrium and kinetic isotopic fractionation took place for Si. Archean seawater is predicted to have a triple Si isotopic composition kinetically fractionated relative to bulk silicate Earth. This requires a large kinetic isotopic fractionation during hydrothermalism of the oceanic crust and appears consistent with warm oceans in the Precambrian. However more work is required on the triple isotope systematics of Si inputs and output to seawater by rivers and authigenic clays formation. Triple Si isotope variations can thus be used as a new tool to unravel the origin of cherts and of their O and Si isotopic compositions. The present evidence of kinetic isotopic fractionations for Si isotopes also implies that Si isotopes should be associated to triple O isotope for paleotemperature reconstructions.

A comprehensive study on the processing of Co:ZnO nanostructured ceramics: Defect chemistry engineering and grain growth kinetics

• Co:ZnO samples were prepared from different Co precursor (Co3O4, CoO, and metallic Co) in different sintering atmosphere (oxygen and argon). • First-principles calculations were performed to give support to the defect chemical analysis and insight into the mechanisms of the Co incorporation in the ZnO. • A detailed structural characterization was employed to determine the Co apparent incorporation activation energy and the grain growth kinetic parameters. • The Ar sintering atmosphere promotes an incongruent decomposition of the ZnO, leading to a higher Zn i density and a higher Co solubility. • To achieve high grain growth and densities the Co3O4 demonstrated to be a good additive for the w -ZnO sintering. • In the Ar sintering atmosphere the metallic Co precursor, due to its higher solubility into the w -ZnO, leads to a high Co homogeneous distribution over the w -ZnO grain. • CoO present the lowest solubility into w -ZnO and final grain size, being the best choice for top-down approach in processing of Co-doped w -ZnO nanopowders. In this report, we present a systematic study on the preparation of Co:ZnO ceramics via a standard solid-state route from different Co precursors (Co 3 O 4 , CoO, and metallic Co) and atmospheres (O 2 and Ar). Particular emphasis is given to defect chemistry engineering and the sintering growth kinetics. First-principles calculations based on density functional theory are employed to determine the formation energy of the main point defects in ZnO and Co:ZnO systems. Based on the theoretical results, a set of chemical reactions is proposed. Detailed microstructural characterization is also performed to determine the degree of Co incorporation into the ZnO lattice. The samples prepared in Ar atmosphere and metallic Co present the highest Co solubility limit (lower apparent Co incorporation activation energy) due to the incongruent ZnO decomposition. Determination of the parameters of the sintering growth kinetics reveals that Co 3 O 4 is the best sintering additive to achieve larger grain sizes, and possible higher densities, in both sintering atmospheres, while metallic Co is the best to achieve the smallest grain size with higher Co concentration and homogeneous spatial distribution for a subsequent reduction of dimensionality. The results show that the sintering in O 2 effectively promotes zinc vacancies in the ZnO structure, while the sintering in Ar promotes zinc interstitial defects. Our findings contribute to understanding the preparation of Co-doped ZnO ceramics and the sintering growth kinetics, which may improve the state of the art in processing the material at both bulk and nanometric scales.

Mapping 3D grain and precipitate structure during in situ mechanical testing of open-cell metal foam using micro-computed tomography and high-energy X-ray diffraction microscopy

• 3D grain structure is mapped and tracked during loading of open-cell metal foam. • Challenges included sample size relative to beam size and large ligament motions. • X-ray CT and far-field HEDM measurements collected at incremental displacements. • New scanning and stitching methodology established for far-field HEDM measurements. • Ligament-tracking code used to express crystal orientation in local reference frame. Open-cell metal foams are ultra-low-density cellular metals with complex hierarchical structures that span bulk, cell, ligament, and sub-ligament scales and give rise to desirable properties such as high strength-to-weight ratio and excellent energy absorption. Although literature suggests that intrinsic material structures at sub-ligament length scales (e.g., grains and precipitates) play an important role in mechanical behavior of open-cell metal foams, there are very few experimental measurements of such structures in three dimensions and for meaningful volumes of foam. This study seeks to map and track the three-dimensional (3D) grain and precipitate structures of an intact volume of open-cell aluminum foam by advancing microstructural characterization techniques that leverage X-ray micro-computed tomography ( μ CT ) and far-field high-energy X-ray diffraction microscopy (FF-HEDM). A 6%-relative-density aluminum foam sample was mechanically tested in compression while μ CT and FF-HEDM measurements were collected at interrupted loading states at beamline 1-ID of the Advanced Photon Source. A new scanning strategy and reconstruction algorithm were established to enable characterization of a foam volume with diameter approximately four times wider than the nominal width of the X-ray beam. The result is a set of maps that detail both the 3D grain and precipitate structures throughout the foam volume at successive strain steps. A novel grain tracking procedure was developed to track individual grains within the foam volume by accounting for the large rigid-body motions that individual ligaments can undergo during mechanical loading. The ability to track grains and precipitate structures in three dimensions throughout large bulk deformation of ultra-low-density polycrystalline materials enables new possibilities for validating numerical models and investigating local failure mechanisms. Furthermore, the methods and procedures developed in this study could be applied to other ultra-low-density structures, such as additively manufactured lattices.

Effect of Cu Substitution in P′2- and P2-Type Sodium Manganese-Based Oxides

Layered manganese oxides have been considerably studied toward sustainable sodium-ion battery materials. There has been a focus on the specific roles of Cu as a member of substituents in sodium manganese oxides. Herein, the effects of Cu substitution for Mn in P′2- and P2-type Na0.67[CuxMn1–x]O2 (0 ≤ x ≤ 0.33) are systematically investigated, focusing on the cooperative Jahn–Teller distortion of Mn3+ and Cu2+ ions. P2-type Na0.67[Cu0.2Mn0.8]O2 is selected to gain further insights on oxygen redox along with P2-type Na0.67[Cu0.1Mg0.1Mn0.8]O2 and P2-type Na0.67[Cu0.1Zn0.1Mn0.8]O2. Comparative studies among the three materials reveal that the type of substituent(s) for Mn has no impact on the activation of oxygen redox. In contrast, the nature and the concentration of substituted element(s) influence structural evolution during charge/discharge. P2-type Na0.67[Cu0.2Mn0.8O2] maintains a P2 phase without any secondary phase at the bulk and local scales at the end of charge to 4.5 V, leading to suppressed voltage hysteresis. At the end of discharge to 1.5 V, the presence of higher Cu2+ in P2-type Na0.67[Cu0.2Mn0.8]O2 results in a distorted P′2 phase with a distortion degree of 10.6(1)%. This can induce a large lattice stress related to the lattice mismatch between P2 and P′2, which jeopardizes cyclability.

Marangoni effect and its potential utilization in supporting lunar habitats and other extraterrestrial endeavors

Tears of wine is a phenomenon frequently observed as a ring of wine formed near the top of the glass generates droplets that fall back into the wine. This phenomenon can be explained by the Marangoni effect driven by the surface tension created via gradient on concentration and temperature along the interface between two phases. Besides being observed while drinking wine, the Marangoni effect is crucial for welding metals, manufacturing integrated circuits, and growing crystals. This paper aims to establish that the Marangoni effect has the potential to be also crucial supporting lunar habitats and other extraterrestrial endeavors, as vacuum and reduced gravity are expected to augment the Marangoni effect on extraterrestrial molten soil leading to sustainable extraterrestrial in-situ resources utilization (ISRU). The authors conducted a Marangoni effect assessment on molten lunar regolith via JSC-1A lunar regolith simulant under vacuum yielding a spontaneous upwards migration of a uniform molten thin-film front as well as at bulk scale that climbed the crucible wall covering the entire wall’s surface and reaching the crucible’s top end. This unique formation and self-migration of a thin-film front could enable key ISRU processes such as, thin-film coating, crystal growth, and feedstock generation for additive 3D printing. Further assessment on higher-temperature vacuum-driven decomposition of the uniform thin-film front as it climbed the crucible’s wall revealed a significant decomposition of various simulant’s metal-oxide components into their respective oxygen and metal elements strengthening the feasibility of extraterrestrial generation and fractional separation of oxygen and metals/alloys with none or minimal need for terrestrial precursors. These two-coupled phenomena, spontaneous material transportation at both thin-film and bulk scales via Marangoni effect and vacuum-driven decomposition open novel pathways in extraterrestrial mining and manufacturing. Future extraterrestrial mining will require an operational approach completely different from the terrestrial one that heavily relies on not only mechanical excavation and transportation but also on a stand-alone refinery process to extract the mineral components. In this paper, the authors propose an extraterrestrial all-in-one mining process in which the Marangoni effect would allow non-mechanical transportation of the extraterrestrial mineral to feed an also in-situ pyrolysis-based refinery unit.

Elemental analysis of scale inhibitors' effect on water incompatibility in carbonate reservoirs: Modeling, bulk and core scales studies

Water flooding is one of the common techniques for increasing petroleum reservoirs' pressure and production life. Seawater (SW) is a preferable choice for waterflooding because of its high availability and low cost. However, SW could be incompatible with formation water (FW) and causes to precipitate inorganic minerals and reduce reservoirs' permeability. A method for preventing inorganic scales is using scale inhibitors (SIs) which need more precise studies to find the critical factors for achieving better efficiency. In this study, the effect of Hydroxyethylenediphosphonic Acid (HEDP) and 2-Phosphonobutane −1,2,4-Tricarboxylic Acid (PBTC) on preventing inorganic scales formation were studied in three stages. In the modeling step, mixing FW and SW was simulated by PHREEQC software. In the second step, as static experiments, the inhibitor efficiency (IE) of two SIs were compared. At dynamic experiments, the performance of SIs in carbonate rocks was studied by core flooding tests. ICP analyses were taken on solutions for interpreting results measured in both static and dynamic scenarios. Results indicated that the ionic composition of SW and FW plays a vital role in types of inorganic scales deposition. PHREEQC software could predict type and amount of scales although its prediction is 9% more than experimental results. It was shown that although SIs could mitigate precipitating inorganic minerals, they have different performances in each concentration. While HEDP is more effective in lower concentrations, PBTC's efficiency will improve with rising its concentration. Elemental analysis showed 100 ppm HEDP has %65 IE which is the most efficient SI. The results of dynamic experiments demonstrated that HEDP and PBTC have a pleasing inhibitory effect in carbonate rocks. The presence of SIs in SW could decrease formation damage during flooding into carbonate reservoirs. • Scale inhibitors' effects were studied in modeling, bulk and core flooding steps. • Elemental Analyses were used to study the scale inhibitors' mechanisms. • Scale inhibitors have not the same efficiency in different concentrations. • HEDP at lower and PBTC at higher concentrations are more effective. • PBTC and HEDP have a pleasing performance in carbonate reservoirs.

Tracking mineral and geochemical characteristics of Holocene lake sediments: the case of Hotagen, west-central Sweden

PurposeIntact lake sediments reflect the development of terrestrial ecosystems. This development can be understood by decoding mineral and geochemical information of sedimentary archives. Therefore, we characterized a Holocene lake sediment core and revealed bulk to micro-scale variations via a combination of geochemical techniques and statistical methods.MethodsA 2.3 m sediment core was collected from Hotagen, a lake in west-central Sweden; a sediment sample was collected every 5 cm. A part of each sediment sample was kept untreated (named bulk) and another part was size-fractionated into < 4, 4–16, 16–64, and > 64 µm subsamples. Characterization was then made with respect to grain size distribution (GSD), physico-chemical parameters, geochemical properties, organic composition, and mineralogy. The sediments were investigated at bulk, micro-, and elemental scales using powder X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM–EDX).ResultsThe deepest sediment was identified as glacial till dating back to the Late Pleistocene. The bulk sediments showed a clear distinction between 0–195 cm (unit 1, U1) and 200–225 cm (unit 2, U2) depths. Quartz and feldspar minerals decreased and organic matter and clay minerals increased from the till towards the lower limit of U1. The development in the sedimentary properties marked the transformation of the terrestrial ecosystem from glacier-covered land to vegetated areas. This development was also well reflected by the appearance of X-ray amorphous materials and the formation of distinct organo-mineral aggregates; chlorite was the predominant clay mineral in these aggregates. The geochemical variation between U2 and U1 sediments was further established by resolving the DRIFT spectral components through multivariate curve resolution alternating least square (MCR-ALS). The U1 sediments settled over a period of ~ 7500 years and showed comparable mineral, geochemical, and organic composition. However, the size-fractionated sediments, mainly < 4 µm, showed diverse mineral and geochemical composition. Indeed, these sediments were distinct by containing relatively higher amounts of X-ray amorphous materials and clay minerals, the latter had variable Na, Mg, and K contents.ConclusionThe combined use of geochemical and statistical approaches used in this study followed the mineral and geochemical development of sediments that had settled during the Late Pleistocene and Early Holocene Epochs. Finally, the U2 sediments marked the terrestrial ecosystem development that occurred during the late glaciation, deglaciation, and post-glaciation periods.Graphical abstract

Intrinsic luminescence blinking from plasmonic nanojunctions

Plasmonic nanojunctions, consisting of adjacent metal structures with nanometre gaps, can support localised plasmon resonances that boost light matter interactions and concentrate electromagnetic fields at the nanoscale. In this regime, the optical response of the system is governed by poorly understood dynamical phenomena at the frontier between the bulk, molecular and atomic scales. Here, we report ubiquitous spectral fluctuations in the intrinsic light emission from photo-excited gold nanojunctions, which we attribute to the light-induced formation of domain boundaries and quantum-confined emitters inside the noble metal. Our data suggest that photoexcited carriers and gold adatom - molecule interactions play key roles in triggering luminescence blinking. Surprisingly, this internal restructuring of the metal has no measurable impact on the Raman signal and scattering spectrum of the plasmonic cavity. Our findings demonstrate that metal luminescence offers a valuable proxy to investigate atomic fluctuations in plasmonic cavities, complementary to other optical and electrical techniques.

Carbon-enabled microwave chemistry: From interaction mechanisms to nanomaterial manufacturing

The multiple interaction effects between external microwave fields and carbon materials trigger the thermocatalysis and conversion reactions by constructing the uniformly thermal room or localized heat microenvironment in confined space, providing an alternative and promising technology for functional materials engineering and manufacturing. This review summarizes the state-of-the-art microwave chemistry techniques involved in or enabled by the carbon additives, with a focus on the introduction of the underlying mechanism, influence factors/key parameters, and the technologies of advanced material preparation from nano to bulk scales. Specifically, it is reviewed in detail that the carbon materials are used as microwave heating media and hotspots/arc plasmas generators to drive and boost the thermochemical reactions. The carbon materials as precursors in microwave are also summarized, which can be helpful for producing the advanced materials with tailored properties and multi-functionalities that are not far realized by conventional techniques/methods. Moreover, the expectation for the future of carbon-participated microwave processes and some approaches to optimizing the corresponding reactions in terms of the technical and industrial levels are proposed, which will help to jump out of gap from lab to industrial application and finally inspire many more endeavors for the manufacturing of advanced/innovative nanomaterials in future. This review summed up the state-of-the-art microwave chemistry techniques involved in or enabled by the carbon additives, with a focus on the introduction of the underlying interaction mechanism, influence factors/key parameters, and the technologies of advanced material manufacturing from nano to bulk scales. Moreover, the challenges and perspectives in this field were also presented and commented. • The fundamental interaction mechanism of carbon and microwave was highlighted. • The factors affecting the microwave absorption properties of carbon materials and related key parameters were summarized. • The recent material manufacturing involved in carbon-enabled microwave chemistry was discussed. • The expectation for the future of carbon-participated microwave processes was proposed.

Thermal conduction through individual cellulose nanofibers

Cellulose nanofibers (CNF) are abundant biomaterials that have attracted significant attention in the thermal management field for a wide range of applications including flexible heat dissipation materials and thermal insulators. While thermal transport properties of individual CNFs are significant for the fundamental understanding and design of advanced materials, experimental studies of the thermal transport properties of CNFs are limited to bulk scales and thermal measurement on individual CNFs has not been reported to date. We report here the experimental study on the thermal conductivity (κ) of individual CNFs using the well-established thermal bridge method. The κ of individual CNFs is found to be approximately 2.2 (±1.2) W/m K at 300 K, and the temperature dependent data from 40 to 320 K indicate that the phonon transport of CNFs is dominated by boundary scattering. Theoretical simulation results on κ of individual CNFs and cellulose bulk crystal support the experimental results and suggest that intermolecular interaction also impedes the thermal transport.

Self-assembly of superstructures at all scales

Summary Controllable assembly of molecular and nanoscale building blocks into uniform superstructures up to bulk dimensions remains a key challenge in the next phase of nanotechnology development. Here, we report the self-assembly of superstructures at all scales by taking advantage of the partial miscibility of water and 1-butanol to generate transient aqueous emulsion droplets that can encapsulate the target materials and introduce them into template holes. Further diffusion of water into 1-butanol depletes the emulsion droplets, assembling the building blocks into one well-defined superstructure in each hole. Superstructuring of various types and shapes of nanoparticles, biomolecules, and inorganic compounds could be achieved without the need for surfactants and chemical modifications. The versatility, scalability, low-cost, and accurate positioning are crucial advantages for the future development of advanced precision manufacturing.

Progress towards nanoengineered energetic materials

Given the constraints on typical bond energies and the commonality of final products produced from combustion of CHNO based energetic materials, the possibilities for further increases in stored potential energy and thermodynamic performance from these classes of materials are limited. Thus, modulating the energy release to achieve efficiency and effectiveness for desired applications is of great value. Investigation of nanomaterials as energetic materials began more than twenty years ago with much of the interest to increase reaction rates and reduce sensitivity. During this period, research on energetic nanoparticles was devoted to reducing the loss of energy density with metallic materials due to the naturally occurring oxide passivating layer, managing their high surface area preventing high loadings in solids, minimizing particle-particle interactions making dispersion in the gas-phase difficult, and understanding combustion mechanisms. As an outcome, novel synthesis methods of producing nanocomposites, and new fields of applications, such as micro-pyrotechnics, have developed. Yet, the research community is only beginning to understand how to manipulate and build energetic materials at the nanoscale, and what designs are optimal for desired functions. Furthermore, recognizing the difficulties for increased energy density and reduced sensitivity, the development of multifunctional and smart nanoenergetic materials is currently being researched to enable control of energy release rates and material sensitivity on demand. This research is being advanced by assembly of nanoengineered energetic materials to bulk scales by additive manufacturing, the development and application of combustion diagnostics that resolve nanometer and micron scales, and ab initio quantum chemistry and molecular dynamics calculations. The challenges that have been confronted and the directions of continuing research on nanoenergetics are presented and discussed.