Application of a new Structural Joint Inversion Approach to Teleseismic and Gravity Data from Mt.Vesuvius, Italy

A 3-D joint inversion of seismic and gravimetric data is performed to re-investigate the subsurface structure of Mt. Vesuvius (Italy) utilizing an improved joint inversion method. The aim is to derive models of the 3D distribution of velocity and density perturbations that are consistent with both data sets and with local velocity models. Mt. Vesuvius is a strato volcano located within a graben (Campania Plain) formed in Plio-Pleistocene. Campania Plain is bordered by mostly Mesozoic carbonaceous rocks. Mt. Vesuvius is the southernmost and the youngest of a group of Pleistocene volcanoes, three of which (Ischia, Campi Flegrei and Mt. Vesuvius) have erupted in historical times. The most recent eruption of Mt. Vesuvius occurred in 1944 and since then the volcanic activity has been characterized by moderate low magnitude seismicity and low temperature fumaroles at the summit crater. We modified the coupling mechanism between velocity and density models in the JI-3D optimized joint inversion method (Jordan and Achauer, 1999). This method was designed to provide stable and high resolution results and involves iterative optimized parameterization, 3D ray tracing, and the incorporation of a priori information. The coupling of the velocity and density models, vital to the joint inversion, is based on a cross-gradient approach (e.g. Gallardo and Meju, 2004), which has been proven to work very well in a variety of cases involving seismic, magnetic, CSEM, MT and gravity data sets. We implemented the cross-gradient coupling for our 3-D irregular adaptive grid parameterization. In contrast to conventional joint inversion methods this approach encourages structural similarities in the models and does not rely on predefined relationships between velocity and density parameters. As a consequence, the resulting velocity-density relations are not contaminated by a priori assumptions and can be utilized to derive rock physical parameters. We apply this method to data from the TomoVes project (Gasparini et al. 1998), combining seismics and Bouguer gravity and local high resolution velocity models as a priori information. The starting models for the joint inversion are derived by separate inversions of the individual data sets. We show 3D distributions of velocity perturbations and density variations from the joint inversion of teleseismic relative traveltimes and Bouguer anomaly data with the aim of extracting further information about the physical status of the volcano- tectonic system

Silicene Flowers: A Dual Stabilized Silicon Building Block for High-Performance Lithium Battery Anodes

Nanostructuring is a transformative way to improve the structure stability of high capacity silicon for lithium batteries. Yet, the interface instability issue remains and even propagates in the existing nanostructured silicon building blocks. Here we demonstrate an intrinsically dual stabilized silicon building block, namely silicene flowers, to simultaneously address the structure and interface stability issues. These original Si building blocks as lithium battery anodes exhibit extraordinary combined performance including high gravimetric capacity (2000 mAh g^–1 at 800 mA g^–1), high volumetric capacity (1799 mAh cm^–3), remarkable rate capability (950 mAh g^–1 at 8 A g^–1), and excellent cycling stability (1100 mA h g^–1 at 2000 mA g^–1 over 600 cycles). Paired with a conventional cathode, the fabricated full cells deliver extraordinarily high specific energy and energy density (543 Wh kg_ca^–1 and 1257 Wh L_ca^–1, respectively) based on the cathode and anode, which are 152% and 239% of their commercial counterparts using graphite anodes. Coupled with a simple, cost-effective, scalable synthesis approach, this silicon building block offers a horizon for the development of high-performance batteries

Intertwined Network of Si/C Nanocables and Carbon Nanotubes as Lithium-Ion Battery Anodes

We demonstrate a new kind of Si-based anode architectures consisting of silicon nanowire/overlapped graphene sheet core–sheath nanocables (SiNW@G) intertwined with carbon nanotubes (CNTs). In such a hybrid structure, the CNTs, mechanically binding SiNW@G nanocables together, act as a buffer matrix to accommodate the volume change of SiNW@G, and overlapped graphene sheets (that is, G sheaths) effectively prevent the direct contact of silicon with the electrolyte during cycling, both of which enable the structural integrity and interfacial stabilization of such hybrid electrodes. Furthermore, the one-dimensional nature of both components affords the creation of a three-dimensional interpenetrating network of lithium ion and electron pathways in the resultant hybrids, thereby enabling efficient transport of both electrons and lithium ions upon charging/discharging. As a result, the hybrids exhibit much-improved lithium storage performance

High-Performance Silicon Battery Anodes Enabled by Engineering Graphene Assemblies

We propose a novel material/electrode design formula and develop an engineered self-supporting electrode configuration, namely, silicon nanoparticle impregnated assemblies of templated carbon-bridged oriented graphene. We have demonstrated their use as binder-free lithium-ion battery anodes with exceptional lithium storage performances, simultaneously attaining high gravimetric capacity (1390 mAh g^–1 at 2 A g^–1 with respect to the total electrode weight), high volumetric capacity (1807 mAh cm^–3 that is more than three times that of graphite anodes), remarkable rate capability (900 mAh g^–1 at 8 A g^–1), excellent cyclic stability (0.025% decay per cycle over 200 cycles), and competing areal capacity (as high as 4 and 6 mAh cm^–2 at 15 and 3 mA cm^–2, respectively). Such combined level of performance is attributed to the templated carbon bridged oriented graphene assemblies involved. This engineered graphene bulk assemblies not only create a robust bicontinuous network for rapid transport of both electrons and lithium ions throughout the electrode even at high material mass loading but also allow achieving a substantially high material tap density (1.3 g cm^–3). Coupled with a simple and flexible fabrication protocol as well as practically scalable raw materials (e.g., silicon nanoparticles and graphene oxide), the material/electrode design developed would propagate new and viable battery material/electrode design principles and opportunities for energy storage systems with high-energy and high-power characteristics

High Volumetric Capacity Silicon-Based Lithium Battery Anodes by Nanoscale System Engineering

The nanostructuring of silicon (Si) has recently received great attention, as it holds potential to deal with the dramatic volume change of Si and thus improve lithium storage performance. Unfortunately, such transformative materials design principle has generally been plagued by the relatively low tap density of Si and hence mediocre volumetric capacity (and also volumetric energy density) of the battery. Here, we propose and demonstrate an electrode consisting of a textured silicon@graphitic carbon nanowire array. Such a unique electrode structure is designed based on a nanoscale system engineering strategy. The resultant electrode prototype exhibits unprecedented lithium storage performance, especially in terms of volumetric capacity, without the expense of compromising other components of the battery. The fabrication method is simple and scalable, providing new avenues for the rational engineering of Si-based electrodes simultaneously at the individual materials unit scale and the materials ensemble scale

Adaptable Silicon–Carbon Nanocables Sandwiched between Reduced Graphene Oxide Sheets as Lithium Ion Battery Anodes

Silicon has been touted as one of the most promising anode materials for next generation lithium ion batteries. Yet, how to build energetic silicon-based electrode architectures by addressing the structural and interfacial stability issues facing silicon anodes still remains a big challenge. Here, we develop a novel kind of self-supporting binder-free silicon-based anodes <i>via</i> the encapsulation of silicon nanowires (SiNWs) with dual adaptable apparels (overlapped graphene (G) sheaths and reduced graphene oxide (RGO) overcoats). In the resulted architecture (namely, SiNW@G@RGO), the overlapped graphene sheets, as adaptable but sealed sheaths, prevent the direct exposure of encapsulated silicon to the electrolyte and enable the structural and interfacial stabilization of silicon nanowires. Meanwhile, the flexible and conductive RGO overcoats accommodate the volume change of embedded SiNW@G nanocables and thus maintain the structural and electrical integrity of the SiNW@G@RGO. As a result, the SiNW@G@RGO electrodes exhibit high reversible specific capacity of 1600 mAh g^–1 at 2.1 A g^–1, 80% capacity retention after 100 cycles, and superior rate capability (500 mAh g^–1 at 8.4 A g^–1) on the basis of the total electrode weight

High Oxygen Reduction Reaction Performances of Cathode Materials Combining Polyoxometalates, Coordination Complexes, and Carboneous Supports

A series of carbonaceous-supported precious-metal-free polyoxometalate (POM)-based composites which can be easily synthesized on a large scale was shown to act as efficient cathode materials for the oxygen reduction reaction (ORR) in neutral or basic media via a four-electron mechanism with high durability. Moreover, exploiting the versatility of the considered system, its activity was optimized by the judicious choice of the 3d metals incorporated in the {(PW₉)₂M₇} (M = Co, Ni) POM core, the POM counterions and the support (thermalized triazine-based frameworks (TTFs), fluorine-doped TTF (TTF-F), reduced graphene oxide, or carbon Vulcan XC-72. In particular, for {(PW₉)₂Ni₇}/{Cu­(ethylenediamine)₂}/TTF-F, the overpotential required to drive the ORR compared well with those of Pt/C. This outstanding ORR electrocatalytic activity is linked with two synergistic effects due to the binary combination of the Cu and Ni centers and the strong interaction between the POM molecules and the porous and highly conducting TTF-F framework. To our knowledge, {(PW₉)₂Ni₇}/{Cu­(ethylenediamine)₂}/TTF-F represents the first example of POM-based noble-metal-free ORR electrocatalyst possessing both comparable ORR electrocatalytic activity and much higher stability than that of Pt/C in neutral medium

Direct Chemical-Vapor-Deposition-Fabricated, Large-Scale Graphene Glass with High Carrier Mobility and Uniformity for Touch Panel Applications

In this work, we report the transfer-free measurement of carrier dynamics and transport of direct chemical vapor deposition (CVD) grown graphene on glass with the aid of ultrafast transient absorption microscopy (TAM) and demonstrate the use of such graphene glass for high-performance touch panel applications. The 4.5 in.-sized graphene glass was produced by an optimized CVD procedure, which can readily serve as transparent conducting electrode (TCE) without further treatment. The graphene glass exhibited an intriguing optical transmittance and electrical conductance concurrently, presenting a sheet resistance of 370–510 Ω·sq^–1 at a transmittance of 82%, much improved from our previous achievements. Moreover, direct measurement of graphene carrier dynamics and transport by TAM revealed the similar biexponential decay behavior to that of CVD graphene grown on Cu, along with a carrier mobility as high as 4820 cm²·V^–1·s^–1. Such large-area, highly uniform, transparent conducting graphene glass was assembled to integrate resistive touch panels that demonstrated a high device performance. Briefly, this work aims to present the great feasibility of good quality graphene glass toward scalable and practical TCE applications

Direct Chemical-Vapor-Deposition-Fabricated, Large-Scale Graphene Glass with High Carrier Mobility and Uniformity for Touch Panel Applications

In this work, we report the transfer-free measurement of carrier dynamics and transport of direct chemical vapor deposition (CVD) grown graphene on glass with the aid of ultrafast transient absorption microscopy (TAM) and demonstrate the use of such graphene glass for high-performance touch panel applications. The 4.5 in.-sized graphene glass was produced by an optimized CVD procedure, which can readily serve as transparent conducting electrode (TCE) without further treatment. The graphene glass exhibited an intriguing optical transmittance and electrical conductance concurrently, presenting a sheet resistance of 370–510 Ω·sq^–1 at a transmittance of 82%, much improved from our previous achievements. Moreover, direct measurement of graphene carrier dynamics and transport by TAM revealed the similar biexponential decay behavior to that of CVD graphene grown on Cu, along with a carrier mobility as high as 4820 cm²·V^–1·s^–1. Such large-area, highly uniform, transparent conducting graphene glass was assembled to integrate resistive touch panels that demonstrated a high device performance. Briefly, this work aims to present the great feasibility of good quality graphene glass toward scalable and practical TCE applications