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Register a new userHigh-speed ionic synaptic memory based on two-dimensional titanium carbide MXene
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Synaptic devices with linear high-speed switching can accelerate learning in artificial neural networks (ANNs) embodied in hardware. Conventional resistive memories however suffer from high write noise and asymmetric conductance tuning, preventing parallel programming of ANN arrays as needed to surpass conventional computing efficiency. Electrochemical random-access memories (ECRAMs), where resistive switching occurs by ion insertion into a redox-active channel address these challenges due to their linear switching and low noise. ECRAMs using two-dimensional (2D) materials and metal oxides suffer from slow ion kinetics, whereas organic ECRAMs enable high-speed operation but face significant challenges towards on-chip integration due to poor temperature stability of polymers. Here, we demonstrate ECRAMs using 2D titanium carbide (Ti3C2Tx) MXene that combines the high speed of organics and the integration compatibility of inorganic materials in a single high-performance device. Our ECRAMs combine the speed, linearity, write noise, switching energy and endurance metrics essential for parallel acceleration of ANNs, and importantly, they are stable after heat treatment needed for back-end-of-line integration with Si electronics. The high speed and performance of these ECRAMs introduces MXenes, a large family of 2D carbides and nitrides with more than 30 compositions synthesized to date, as very promising candidates for devices operating at the nexus of electrochemistry and electronics.
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Photothermal therapy (PTT) has shown significant potential in cancer treatment. However, developing nanomaterial-based photothermal agents with good biocompatibility and high photothermal conversion efficiency (PTCE) remains a key challenge. Titanium has been widely employed as biomedical materials based on their excellent biocompatibility. In this work, the titanium based plasmonic photothermal therapy (Ti-PPTT) is demonstrated. Using the liquid-phase exfoliation (LPE), the metallic Ti can be fabricated into the two-dimensional (2D) nanosheets (NSs), similar to exfoliating other layered 2D materials. The 2D Ti NSs exhibited good biocompatibility, high extinction coefficient of 20.8 Lg-1cm1 and high PTCE of 73.4%, owing to localized surface plasmon resonances (LSPR); which is significantly higher than other photothermal agents, including Au (21%), MoS2 (24.4%), BP (28.4%) and Ti3C2 MXene (30.6%). Consequently, 2D Ti-PPTT exhibited a notable therapeutic effect in a human hepatocellular carcinoma model without side effects. Our study could pave a new avenue for PTT using metal Ti and arouse a wide interest in the potential efficient PTT for other elemental transition metals owing to their LSPR. Furthermore, the efficient photothermal effect and environmental friendliness of Ti NSs make them deserve more research toward other application, such as solar energy harvesting and sea water desalination.
The successful application of titanium oxide-graphene hybrids in the fields of photocatalysis, photovoltaics and photodetection strongly depends on the interfacial contact between both materials. The need to provide a good coupling between the enabling conductor and the photoactive phase prompted us to directly grow conducting graphenic structures on TiO2 crystals. We here report on the direct synthesis of tailored graphenic structures by using Plasma Assisted Chemical Vapour Deposition that present a clean junction with the prototypical titanium oxide (110) surface. Chemical analysis of the interface indicates chemical bonding between both materials. Photocurrent measurements under UV light illumination manifest that the charge transfer across the interface is efficient. Moreover, the influence of the synthesis atmosphere, gas precursor (C2H2) and diluents (Ar, O2), on the interface and on the structure of the as-grown graphenic material is assessed. The inclusion of O2 promotes vertical growth of partially oxidized carbon nanodots/rods with controllable height and density. The deposition with Ar results in continuous graphenic films with low resistivity (6.8x10-6 ohm x m). The synthesis protocols developed here are suitable to produce tailored carbon-semiconductor structures on a variety of practical substrates as thin films, pillars or nanoparticles.
The titanium fire as produced during high pressure and friction is the major failure scenario for aero-engines. To alleviate this issue, Ti-V-Cr and Ti-Cu-Al series burn resistant titanium alloys have been developed. However, which burn resistant alloy exhibit better property with reasonable cost needs to be evaluated. This work unveils the burning mechanisms of these alloys and discusses whether burn resistance of Cr and V can be replaced by Cu, on which thorough exploration is lacking. Two representative burn resistant alloys are considered, including Ti14(Ti-13Cu-1Al-0.2Si) and Ti40(Ti-25V-15Cr-0.2Si)alloys. Compared with the commercial non-burn resistant titanium alloy, i.e., TC4(Ti-6Al-4V)alloy, it has been found that both Ti14 and Ti40 alloys form protective shields during the burning process. Specifically, for Ti14 alloy, a clear Cu-rich layer is formed at the interface between burning product zone and heat affected zone, which consumes oxygen by producing Cu-O compounds and impedes the reaction with Ti-matrix. This work has established a fundamental understanding of burning resistant mechanisms for titanium alloys. Importantly, it is found that Cu could endow titanium alloys with similar burn resistant capability as that of V or Cr, which opens a cost-effective avenue to design burn resistant titanium alloys.
Titanium diboride (TiB2) is a low-density refractory material belonging to the family of ultra-high temperature ceramics (UHTCs). This paper reports on the production and microstructural and optical characterization of nearly fully dense TiB2, with particular interest to its potential utilization as novel thermal solar absorber. Monolithic bulk samples are produced starting from elemental reactants by a two-step method consisting of the Self-propagating High-temperature Synthesis (SHS) followed by the Spark Plasma Sintering (SPS) of the resulting powders. The surface of obtained samples has-been characterized from the microstructural and topological points of view. The hemispherical reflectance spectrum has been measured from 0.3 to 15 um wavelength, to evaluate the potential of this material as solar absorber for future concentrating solar plants.
Two-dimensional (2D) materials have been shown to be efficient in energy harvesting. Here, we report utilization of waste heat to generate electricity via combined piezoelectric and triboelectric property of 2D Cobalt Telluride (CoTe2). The piezo-triboelectric nanogenerator (PTNG) produced an open-circuit voltage of ~5V under 1N force and the effect of temperature in the 305-363 K range shows a four-fold energy conversion efficiency improvement. The 2D piezo-tribogenerator shows excellent characteristics with a maximum voltage of ~10V, fast response time and high responsivity. Density functional theory was used to gain further insights and validation of the experimental results. Our results could lead to energy harvesting approaches using 2D materials from various thermal sources and dissipated waste heat from electronic devices.
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