Thin Outer Shell Research Articles

Perforated cenospheres used to enhance the engineering performance of high-performance cement-slag-limestone ternary binder

Slag-limestone-cement ternary mixed binder is a new type of cementitious material. There are 1137 published literatures on this new type of cementitious material in the Scopus database, but so far, no papers have been published on the research of reactive internal curing of this new type of cementitious material. One kind of fly ash is called a cenosphere with a very thin outer shell and a hollow center. Cenospheres generate pores through chemical etching, thereby achieving the effect of self-curing. This article conducted multiple experimental studies to ascertain the impact of perforated cenospheres regarding the execution of cement-slag-limestone binder. The mixture samples with different dosage of perforated cenospheres and cenospheres are numbered C0 (control group), P3.3 (content of perforated cenospheres in the binder is 3.3 %), P6.6 (content of perforated cenospheres in the binder is 6.6 %), and C6.6 (content of perforated cenospheres in the binder is 6.6 %). Based on the results of autogenous shrinkage and compressive strength, perforated cenospheres as an internal curing agent not only reduces the autogenous shrinkage of cement-slag-limestone concrete, but also avoids a significant decrease in strength of cement-slag-limestone concrete. In fact, because of volcanic ash reactivity of advanced cenospheres and the internal curing effect, the compressive strength of P3.3 mixed mortar increased by 0.7 and 4 MPa compared to C0 mixed mortar at 7 and 28 days of age, achieving a dual effect of reducing shrinkage and improving strength. Secondly, the experimental results of Fourier transform infrared spectroscopy and X-ray diffraction showed that perforated cenospheres can undergo volcanic ash reaction with calcium hydroxide. The scanning electron microscope images indicate that the P3.3 and P6.6 mixed paste with added perforated cenospheres exhibit better and denser bonding between the perforated cenospheres and the matrix. In summary, the microscopic reactions of perforated cenospheres can enhance concrete's macroscopic qualities, which can be utilized as reactive internal curing materials.

A triple emulsion droplet in an extensional flow

In this theoretical report we analytically explore the deformation and breakup of an initially spherical triple emulsion drop undergoing an axisymmetric extensional creeping flow. The triple emulsion, suspended in an external fluid (fluid 1), is originally made from an inner spherical drop (fluid 4), engulfed by a spherical shell (fluid 3), which is subsequently engulfed by another spherical shell (fluid 2). The problem is described by eight dimensionless parameters: the external capillary number (Ca), three viscosity ratios (λ21, λ32, λ43), two radii ratios (K, k), and two surface tensions ratios (M, m). When the triple emulsion is subjected to an external uniaxial extensional flow (Ca > 0), the outer interface (21) and the inner drop interface (43) deform into prolate spheroids, while the interface between them (32) deforms into an oblate spheroid. The reverse occurs for an external biaxial flow (Ca < 0), the outer interface (21) and the inner drop interface (43) deform into oblate spheroids and the middle interface (32) becomes a prolate spheroid. Three types of breakup mechanisms are to be expected: when the outer and the middle interfaces are in contact, when the middle and the inner interfaces are in contact, and when the inner drop breaks while the two shell phases remain continuous. Finally, an analytical expression for the effective viscosity of a dilute emulsion containing spherical triple emulsion droplets is suggested. For a triple emulsion which behaves like a solid: a very viscous or a very thin outer shell (λ21→∞ or K→ 1), the effective viscosity reduces to Einstein’s formula, and when the triple emulsion behaves like a single drop: a very thick outer shell such that the inner shell and the inner drop disappear (K→ 0), Taylor’s expression is recovered.

Pearl‐Like Sheen in Soft Capsules: An Unusual Optical Effect that is Reversibly Induced by Temperature

AbstractA pearl‐like sheen (i.e., pearlescence) is seen in many natural materials like nacre and in some commercial paints and cosmetics. This phenomenon is attributed to the interaction of light with plate‐like particles in the material. Here, for the first time, pearlescence is demonstrated in soft millimeter‐scale capsules that contain no plate‐like particles. The capsules have a thin (~500 µm) outer shell of N‐isopropylacrylamide (NIPA) hydrogel, which has a lower critical solution temperature (LCST) of 32 °C. When a transparent NIPA‐shelled capsule is heated above this LCST, it turns pearlescent. The effect is reversible, with the transparent state being recovered upon cooling. This is the first example of reversible pearlescence in any solid. Specular reflectance measurements show that the pearlescence of the capsules is comparable to that of natural pearls. Pearlescence is not observed in NIPA hydrogels; it arises only in NIPA‐shelled capsules, and that too only when the shell is thin. Above its LCST, the NIPA shell shrinks and gets stretched, and nanoscale NIPA‐rich domains arise within this shell, which induce the pearlescence. This study sheds fresh insight into the nature of pearlescence, on how it can be tuned, and on how this property can be introduced into various soft materials.

Mesoporous N-rich Carbon with Single-Ni Atoms as a Multifunctional Sulfur Host for Li-S Batteries.

Physicochemical confinement and catalytic conversion of lithium polysulfides (LiPSs) are crucial to suppress the shuttle effect and enhance the redox kinetics of lithium-sulfur (Li-S) batteries. In this study, a NH4 Cl-assisted pyrolysis strategy is developed to fabricate highly mesoporous N-rich carbon (designed as NC(p)) featuring thin outer shells and porous inner networks, on which single-Ni atoms are anchored to form an excellent sulfur host (designed as Ni-NC(p)) for Li-S batteries. During pyrolysis, the pyrolytic HCl from confined NH4 Cl within ZIF-8 will in situ etch ZIF-8 to produce rich mesoporous in the carbonized product NC(p). The mesoporous Ni-NC(p) enables favorable electron/ion transfer, high sulfur loading, and effective confinement of LiPSs, while the catalytic effect of single-Ni species enhances the redox kinetics of LiPSs. As a result, the sulfur cathode based on the Ni-NC(p) host delivers obviously improved Li-S battery performance with high specific capacity, good rate capability, and cycling stability.

Mesoporous N‐rich Carbon with Single‐Ni Atoms as a Multifunctional Sulfur Host for Li‐S Batteries

AbstractPhysicochemical confinement and catalytic conversion of lithium polysulfides (LiPSs) are crucial to suppress the shuttle effect and enhance the redox kinetics of lithium‐sulfur (Li‐S) batteries. In this study, a NH4Cl‐assisted pyrolysis strategy is developed to fabricate highly mesoporous N‐rich carbon (designed as NC(p)) featuring thin outer shells and porous inner networks, on which single‐Ni atoms are anchored to form an excellent sulfur host (designed as Ni‐NC(p)) for Li‐S batteries. During pyrolysis, the pyrolytic HCl from confined NH4Cl within ZIF‐8 will in situ etch ZIF‐8 to produce rich mesoporous in the carbonized product NC(p). The mesoporous Ni‐NC(p) enables favorable electron/ion transfer, high sulfur loading, and effective confinement of LiPSs, while the catalytic effect of single‐Ni species enhances the redox kinetics of LiPSs. As a result, the sulfur cathode based on the Ni‐NC(p) host delivers obviously improved Li‐S battery performance with high specific capacity, good rate capability, and cycling stability.

The Influence of Hollow Carbon Sphere in Heterogeneous Catalysis

Hollow carbon spheres (HCSs) are hollow structured carbon particles of sizes ranging between micron and nanometre sizes with thin outer shells. They are of importance for their unique properties such as encapsulation ability, controllable permeability, surface functionality, high surface-to-volume ratios, and excellent chemical and thermal stabilities. In this communication, a precise description is presented of the synthesis, characterization, and applications of HCSs. Synthesis of HCSs is normally carried out in two ways, namely, hard-templating and soft-templating methods. These materials are characterized by modern techniques to investigate their structural and textural properties to get an insight into the material. Finally, the recent progress made in the applications of HCSs has been reported in the area of catalysis as a support material and energy storage device.

Mo2 C/C Hierarchical Double-Shelled Hollow Spheres as Sulfur Host for Advanced Li-S Batteries.

One of the major challenges regarding the sulfur cathode of Li-S batteries is to achieve high sulfur loading, fast Li ions transfer, and the suppression of lithium polysulfides (LiPSs) shuttling. This issue can be solved by the development of molybdenum carbide decorated N-doped carbon hierarchical double-shelled hollow spheres (Mo2 C/C HDS-HSs). The mesoporous thick inner shell and the central void of the HDS-HSs achieve high sulfur loading, facilitate the ion/electrolyte penetration, and accelerate charge transfer. The microporous thin outer shell suppresses LiPSs shuttling and reduces the charge/mass diffusion distance. The double-shelled hollow structure accommodates the volume expansion during lithiation. Furthermore, Mo2 C/C composition renders the HDS-HSs cathode with improved conductivity, enhanced affinity to LiPSs, and accelerated kinetics of LiPSs conversion. The structural and compositional advantages render the Mo2 C/C/S HDS-HSs electrode with high specific capacity, excellent rate capability, and ultra-long cycling stability in the composed Li-S batteries.

Mo2C/C Hierarchical Double‐Shelled Hollow Spheres as Sulfur Host for Advanced Li‐S Batteries

AbstractOne of the major challenges regarding the sulfur cathode of Li‐S batteries is to achieve high sulfur loading, fast Li ions transfer, and the suppression of lithium polysulfides (LiPSs) shuttling. This issue can be solved by the development of molybdenum carbide decorated N‐doped carbon hierarchical double‐shelled hollow spheres (Mo2C/C HDS‐HSs). The mesoporous thick inner shell and the central void of the HDS‐HSs achieve high sulfur loading, facilitate the ion/electrolyte penetration, and accelerate charge transfer. The microporous thin outer shell suppresses LiPSs shuttling and reduces the charge/mass diffusion distance. The double‐shelled hollow structure accommodates the volume expansion during lithiation. Furthermore, Mo2C/C composition renders the HDS‐HSs cathode with improved conductivity, enhanced affinity to LiPSs, and accelerated kinetics of LiPSs conversion. The structural and compositional advantages render the Mo2C/C/S HDS‐HSs electrode with high specific capacity, excellent rate capability, and ultra‐long cycling stability in the composed Li‐S batteries.

Boosting the Energy Migration Upconversion through Inter-Shell Energy Transfer in Tb 3+ -Doped Sandwich Structured Nanocrystals

Boosting the Energy Migration Upconversion through Inter-Shell Energy Transfer in Tb ³⁺ -Doped Sandwich Structured Nanocrystals

To improve the performance of green light-emitting devices by enhancing hole injection efficiency

For the quantum dots (QDs) based light-emitting diodes (QLEDs), the performance is determined mostly by the carrier injection. Unfortunately, the large band offset between QDs and the hole transport materials makes hole injection efficiency lagging far behind electron injection efficiency. Therefore, it is critical for the QLEDs to improve hole injection efficiency. While, the materials with high valence band maximum (VBM), such as ZnSe, are apt to be oxidated. Therefore, if the QDs could combine the merits of high hole injection efficiency of materials with high VBM and the stability of the materials with large band gap, the QLEDs are expected to be with better performance and more efficient. In this article, the QDs with high VBM intermediate shell and thin ZnS outer shell were employed as the emitting layer to fabricate QLEDs. The highest luminance and maximum external quantum efficiency of 550,000 cd/m2 and 20.06% are achieved, respectively. The fun part is that the highest efficiency of QLEDs can be achieved at high luminance (50,000 cd/m2). More importantly, the device exhibits long half lifetime of over 214,000 h at 100 cd/m2. All these excellent characteristics (high efficiency, luminance and stability) are quite beneficial for the devices aiming at lighting devices.

Insight into the structure of polystyrene-poly(methyl methacrylate) core-shell particles synthesized by seeded suspension polymerization

Core-shell particles were synthesized employing seeded suspension polymerization. Suspension polystyrene (PS) particles were used as seeds, and poly(methyl methacrylate) (PMMA) was synthesized in the presence of polystyrene seeds. A combination of solvent extraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy techniques were employed to study the structure and morphology of synthesized particles. The results suggested a core-inner shell-outer shell structure for the synthesized particles in which the PS core was covered by a PMMA-rich inner shell and a very thin PS-rich outer shell. The size and concentration of PMMA domains decreased from the outer shell toward the core of the particle, and particle morphology was mainly controlled by the limitations to the diffusion of MMA through the polymer particle.

A novel negative regulatory mechanism of Smurf2 in BMP/Smad signaling in bone

Transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) play important roles in bone metabolism. Smad ubiquitination regulatory factors (Smurfs) regulate TGF-β/BMP signaling via ubiquitination, resulting in degradation of signaling molecules to prevent excessive activation of TGF-β/BMP signaling. Though Smurf2 has been shown to negatively regulate TGF-β/Smad signaling, its involvement in BMP/Smad signaling in bone metabolism has not been thoroughly investigated. In the present study, we sought to evaluate the role of Smurf2 in BMP/Smad signaling in bone metabolism. Absorbable collagen sponges containing 3 μg of recombinant human BMP2 (rhBMP2) were implanted in the dorsal muscle pouches of wild type (WT) and Smurf2−/− mice. The rhBMP2-induced ectopic bone in Smurf2−/− mice showed greater bone mass, higher mineral apposition and bone formation rates, and greater osteoblast numbers than the ectopic bone in WT mice. In WT mice, the ectopic bone consisted of a thin discontinuous outer cortical shell and scant inner trabecular bone. In contrast, in Smurf2−/− mice, the induced bone consisted of a thick, continuous outer cortical shell and abundant inner trabecular bone. Additionally, rhBMP2-stimulated bone marrow stromal cells (BMSCs) from Smurf2−/− mice showed increased osteogenic differentiation. Smurf2 induced the ubiquitination of Smad1/5. BMP/Smad signaling was enhanced in Smurf2−/− BMSCs stimulated with rhBMP2, and the inhibition of BMP/Smad signaling suppressed osteogenic differentiation of these BMSCs. These findings demonstrate that Smurf2 negatively regulates BMP/Smad signaling, thereby identifying a new regulatory mechanism in bone metabolism.

Formation of micro-spherulitic barite in association with organic matter within sulfidized stromatolites of the 3.48 billion-year-old Dresser Formation, Pilbara Craton.

The shallow marine and subaerial sedimentary and hydrothermal rocks of the ~3.48 billion-year-old Dresser Formation are host to some of Earth's oldest stromatolites and microbial remains. This study reports on texturally distinctive, spherulitic barite micro-mineralization that occur in association with primary, autochthonous organic matter within exceptionally preserved, strongly sulfidized stromatolite samples obtained from drill cores. Spherulitic barite micro-mineralization within the sulfidized stromatolites generally forms submicron-scale aggregates that show gradations from hollow to densely crystallized, irregular to partially radiating crystalline interiors. Several barite micro-spherulites show thin outer shells. Within stromatolites, barite micro-spherulites are intimately associated with petrographically earliest dolomite and nano-porous pyrite enriched in organic matter, the latter of which is a possible biosignature assemblage that hosts microbial remains. Barite spherulites are also observed within layered barite in proximity to stromatolite layers, where they are overgrown by compositionally distinct (Sr-rich), coarsely crystalline barite that may have been sourced from hydrothermal veins at depth. Micro-spherulitic barite, such as reported here, is not known from hydrothermal systems that exceed the upper temperature limit for life. Rather, barite with near-identical morphology and micro-texture is known from zones of high bio-productivity under low-temperature conditions in the modern oceans, where microbial activity and/or organic matter of degrading biomass controls the formation of spherulitic aggregates. Hence, the presence of micro-spherulitic barite in the organic matter-bearing Dresser Formation sulfidized stromatolites lend further support for a biogenic origin of these unusual, exceptionally well-preserved, and very ancient microbialites.

Conceptual Design of the Cryostat for a Highly Radiation Transparent 2 T Superconducting Detector Solenoid for FCC-ee+

The Future Circular Collider electron-positron version (FCC-ee+) may be the next step towards a next generation of particle colliders. It may include an Experiment for probing ee+ collisions using the IDEA (International Detector for Electron-positron Accelerator), or a similar detector, requiring a solenoid enclosing the inner tracking detector. An innovative 2 T superconducting solenoid with 4 m bore and 6 m long has been accepted as baseline. Positioning the solenoid in between tracker and calorimeter requires an ultra-thin and highly radiation transparent cold mass. Likewise, a thin and radiation transparent cryostat is needed. The set value for the solenoid's maximum radiation length is 1 × X0. The cryostat is designed as a sandwich of thin Aluminum alloy inner and outer shells, eventually locally reinforced, for achieving vacuum tightness, and layers of innovative insulation material providing lowest thermal conductivity and sufficient mechanical resistance. Cryogel Z, a composite blanket of silica aerogel and reinforcing fibers, has a density of 160 kg/m3 and would allow a 250 mm cryostat thickness. As an alternative, glass spheres (e.g., K1 type, manufactured by 3M, with a $\text{65}\,\mu \text{m}$ diameter and a 125 kg/m3 density), or similar material, can be dispersed between the vacuum vessel thin-walls providing structural support. Besides the cryostat conceptual design, we outline the setup developed at CERN to represent the real-case cryostat and to measure the heat load transferred through the above-mentioned materials and we present the test results for Cryogel Z.

Cadmium-free quantum dot LEDs

Coming soon to a television near you: next generation, quantum dot light-emitting diodes (QD-LEDs) that will illuminate displays without using cadmium, a toxic metal. Researchers led by Eunjoo Jang of Samsung Electronics report QD-LEDs made with quantum dots that feature an indium phosphide core surrounded by a thick inner shell of zinc selenide and a thin outer shell of zinc sulfide. The core’s size determines what color light it emits. This InP/ZnSe/ZnS structure has been reported for quantum dots before, but defects in those materials resulted in decreased performance. Jang and colleagues developed a method for making this type of quantum dot that improves its properties (Nature 2019, DOI: 10.1038/s41586-019-1771-5). Their key innovation was to use hydrofluoric acid to etch away the oxidized surface of the InP core as the ZnSe shell grew. After completing the growth of the ZnSe shell at 340 °C, the team found that the resulting

The Equation of State of MH-III: A Possible Deep CH4 Reservoir in Titan, Super-Titan Exoplanets, and Moons

Abstract We investigate the thermal equation of state, bulk modulus, thermal expansion coefficient, and heat capacity of MH-III (CH4 filled-ice Ih), needed for the study of CH4 transport and outgassing for the case of Titan and super-Titans. We employ density functional theory and ab initio molecular dynamics simulations in the generalized-gradient approximation with a van der Waals functional. We examine the temperature range 300–500 K and pressures between 2 and 7 GPa. We find that in this P-T range MH-III is less dense than liquid water. There is uncertainty in the normalized moment of inertia (MOI) of Titan; it is estimated to be in the range of 0.33–0.34. If Titan’s MOI is 0.34, MH-III is not stable at present in Titan’s interior, yielding an easier path for the outgassing of CH4. However, for an MOI of 0.33, MH-III is thermodynamically stable at the bottom of an ice-rock internal layer capable of storing CH4. For rock mass fractions upwelling melt is likely hot enough to dissociate MH-III along its path. For super-Titans considering a mixture of MH-III and ice VII, melt is always positively buoyant if the H2O:CH4 mole fraction is &gt;5.5. Our thermal evolution model shows that MH-III may be present today in Titan’s core, confined to a thin (≈10 km) outer shell. We find that the heat capacity of MH-III is higher than measured values for pure water ice, larger than heat capacity often adopted for ice-rock mixtures with implications for internal heating.

Modulating Guest Uptake in Core-Shell MOFs with Visible Light.

A two-component core-shell UiO-68 type metal-organic framework (MOF) with a nonfunctionalized interior for efficient guest uptake and storage and a thin light-responsive outer shell was prepared by initial solvothermal MOF synthesis followed by solvent-assisted linker exchange. The bulky shell linker features two tetra-ortho-fluorinated azobenzene moieties to exploit their advantageous photoisomerization properties. The obtained perfect octahedral MOF single crystals can be switched repeatedly and with an unprecedented efficiency between E- and Z-rich states using visible light only. Due to the high photoswitch density per pore of the shell layer, its steric demand and thus molecular uptake (and release) can be conveniently modulated upon green and blue light irradiation. Therefore, the "smart" shell acts as a light-controlled kinetic barrier or "gate" for the diffusion of cargo molecules in and out of the MOF crystals.

ZomeFab: Cost‐Effective Hybrid Fabrication with Zometools

AbstractIn recent years, personalized fabrication has received considerable attention because of the widespread use of consumer‐level three‐dimensional (3D) printers. However, such 3D printers have drawbacks, such as long production time and limited output size, which hinder large‐scale rapid‐prototyping. In this paper, for the time‐ and cost‐effective fabrication of large‐scale objects, we propose a hybrid 3D fabrication method that combines 3D printing and the Zometool construction set, which is a compact, sturdy and reusable structure for infill fabrication. The proposed method significantly reduces fabrication cost and time by printing only thin 3D outer shells. In addition, we design an optimization framework to generate both a Zometol structure and printed surface partitions by optimizing several criteria, including printability, material cost and Zometool structure complexity. Moreover, we demonstrate the effectiveness of the proposed method by fabricating various large‐scale 3D models.

Development of light and highly radiation transparent cryostats for FCC detector magnets: first analyses of insulation materials

For both versions of the Future Circular Collider, the electron-positron FCC ee+, requiring a 2 T/4 m bore solenoid for particles spectrometry, and the hadron-hadron FCC hh, CERN is developing an innovative design for the detector solenoids, to enable their positioning inside the calorimeters directly surrounding the inner tracker. For this to happen, the cryostat design has to be optimized to achieve minimum radiation length. The novel design consists of a sandwich of thin inner and outer metallic shells for vacuum tightness, supported by an insulating material with sufficient mechanical resistance paired with lowest thermal conductivity, like Cryogel, a flexible aerogel structure (density 0.16 g/cm2), or glass spheres (e.g. type K1 manufactured by 3M, with 65 μm diameter and density of 0.125 g/cm3). These materials would allow constructing a 4 m bore, 6 m long cryostat with a 250 mm total thickness, a heat load less than 400 W on the cold mass and 10 kW on the thermal shield. In this paper, design options are discussed and methods for qualifying the materials presented.

Numerical modeling of the 1840s major eruption of η Carinae as an explosion

In this paper, new two-dimensional hydrodynamical simulations of η Car’s nebulae are performed. In the 1840s, the massive star η Car suffered a major eruption that resulted in the formation of a bipolar structure, which is commonly known as the large Homunculus. During this event, η Car expelled into the circumstellar material a total mass of ~10 M⊙ and released a total energy of Ek ~ 1050 erg over a very short time (≤5 yr). These kinds of explosive events are frequently called supernova impostors due to their resemblance to a type II supernova, but the stars survive the explosion. In the case of η Car, a brief explosion scenario provides a potential explanation for the behavior of the historical light curve of η Car a few years (~10 yr) after the nineteenth century outburst. Here, such an alternative scenario of an explosion is assumed (instead of a super-Eddington wind) in order to investigate whether an explosive event is also able to explain the shape and kinematics of the large Homunculus. I show that the numerical simulations presented here indeed resemble some of the observed features of the nebula, such as the present-day double-shell structure of the Homunculus, with a thin outer dense shell and a thicker inner layer, as well as thermal instabilities (Rayleigh-Taylor and Kelvin-Helmholtz) along the dense shell that may lead to the current mottled appearance of the large Homunculus. Nonetheless, the explosion model for the 1840s major eruption of η Car is not able to account for the estimated age of the large Homunculus.