Optimal Microstructure of Silicon Monoxide as the Anode for Lithium-Ion Batteries.

Because of its metastable nature, silicon monoxide (SiO) consists of Si nanodomains in an amorphous matrix of SiO2. The microstructure of SiO, including SiO2, Si domains, and interphase (SiOx) between domains, was modified via an annealing treatment in argon gas and thoroughly characterized by in-situ and ex-situ X-ray diffraction, pair distribution function, and electron energy loss spectroscopy. Two microstructure transformation routes were observed during the annealing process: (1) at a temperature of <800 °C, the annealing treatment was found to affect mainly the structural conformation of the amorphous SiO2 matrix and the interphase, while (2) an annealing temperature of >800 °C led to significant Si nanodomain growth. We found that the microstructure has a great impact on the electrochemical performance of SiO. The optimized microstructure of SiO appears to be achieved through annealing treatment at 800 °C or less, which results in interphase (SiOx) reduction without causing significant Si domain growth. This work provides a deep insight into the domain and interphase transformation of SiO upon heat treatment. The improved understanding of the relationship between SiO microstructure and its electrochemical behavior will enable proper design and development of high-energy SiO for lithium-ion batteries.

Catalytically Active Oil-Based Lubricant Additives Enabled by Calcining Ni-Al Layered Double Hydroxides.

Layered double hydroxides (LDHs) have lately been hailed as robust lubricant additives for improving tribological properties and as ideal catalysts for synthesizing carbon-based nanomaterials. In this paper, in situ analytical tools are used to track the evolution of the crystal structure and chemical composition of LDHs during calcination. Nickel oxide and elemental nickel can be produced by calcining NiAl-LDH in air (LDH-C-Air) and argon (LDH-C-Ar), respectively. For the base oil with 1 wt % LDH-C-Air, negligible wear can be detected even after a 2 h friction test under a severe contact pressure (∼637 MPa). A relatively thick tribofilm (∼60 nm) with a better mechanical property is formed, which protects the solid surface from severe wear. In addition, the possible formed carbon debris may also prevent the direct collision of asperities and effectively improve the wear resistance. This work provides a unique vision for the application of calcined LDHs with the combination of catalysis and tribology.

Stabilizing the Interface between Sodium Metal Anode and Sulfide-Based Solid-State Electrolyte with an Electron-Blocking Interlayer.

Sulfide-based Na-ion conductors are promising electrolytes for all-solid-state sodium batteries (ASSSBs) because of high ionic conductivity and favorable formability. However, no effective strategy has been reported for long-duration Na cycling with sulfide-based electrolytes because of interfacial challenges. Here we demonstrate that a cellulose-poly(ethylene oxide) (CPEO) interlayer can stabilize the interface between sulfide electrolyte (Na3SbS4) and Na by shutting off the electron pathway of the electrolyte decomposition reaction. As a result, we achieved stable Na plating/stripping for 800 cycles at 0.1 mA cm-2 in all-solid-state devices at 60 °C.

BCC-Phased PdCu Alloy as a Highly Active Electrocatalyst for Hydrogen Oxidation in Alkaline Electrolytes.

Anion-exchange membrane fuel cells hold promise to greatly reduce cost by employing nonprecious metal cathode catalysts. More efficient anode catalysts are needed, however, to improve the sluggish hydrogen oxidation reaction in alkaline electrolytes. We report that BCC-phased PdCu alloy nanoparticles, synthesized via a wet-chemistry method with a critical thermal treatment, exhibit up to 20-fold HOR improvement in both mass and specific activities, compared with the FCC-phased PdCu counterparts. HOR activity of the BCC-phased PdCu is 4 times or 2 times that of Pd/C or Pt/C, respectively, in the same alkaline electrolyte. In situ HE-XRD measurements reveal that the transformation of PdCu crystalline structure favors, at low annealing temperature (<300 °C), the formation of FCC structure. At higher annealing temperatures (300-500 °C), a BCC structure dominates the PdCu NPs. Density functional theory (DFT) computations unravel a similar H binding strength and a much stronger OH binding of the PdCu BCC surface (cf. FCC surface), both of which are simultaneously close to those of Pt surfaces. The synergistic optimization of both H and OH binding strengths is responsible for the enhancement of HOR activity on BCC-phased PdCu, which could serve as an efficient anode catalyst for anion-exchange membrane fuel cells. This work might open a new route to develop efficient HOR catalysts from the perspective of crystalline structure transformation.

Localized Symmetry Breaking for Tuning Thermal Expansion in ScF3 Nanoscale Frameworks.

The local symmetry, beyond the averaged crystallographic structure, tends to bring unusual performances. Negative thermal expansion is a peculiar physical property of solids. Here, we report the delicate design of the localized symmetry breaking to achieve controllable thermal expansion in ScF3 nanoscale frameworks. Intriguingly, an isotropic zero thermal expansion is concurrently engineered by localized symmetry breaking, with a remarkably low coefficient of thermal expansion of about +4.0 × 10-8/K up to 675 K. This mechanism is investigated by the joint analysis of atomic pair distribution function of synchrotron X-ray total scattering and extended X-ray absorption fine structure spectra. A localized rhombohedral distortion presumably plays a critical role in stiffening ScF3 nanoscale frameworks and concomitantly suppressing transverse thermal vibrations of fluorine atoms. This physical scenario is also theoretically corroborated by the extinction of phonon modes with negative Grüneisen parameters in rhombohedral ScF3. The present work opens an untraditional chemical modification route to achieve controllable thermal expansion by breaking local symmetries in materials.

Colossal Volume Contraction in Strong Polar Perovskites of Pb(Ti,V)O3.

The unique physical property of negative thermal expansion (NTE) is not only interesting for scientific research but also important for practical applications. Chemical modification generally tends to weaken NTE. It remains a challenge to obtain enhanced NTE from currently available materials. Herein, we successfully achieve enhanced NTE in Pb(Ti1-xVx)O3 by improving its ferroelectricity. With the chemical substitution of vanadium, lattice tetragonality (c/a) is highly promoted, which is attributed to strong spontaneous polarization, evidenced by the enhanced covalent interaction in the V/Ti-O and Pb-O2 bonds from first-principles calculations. As a consequence, Pb(Ti0.9V0.1)O3 exhibits a nonlinear and much stronger NTE over a wide temperature range with a volumetric coefficient of thermal expansion αV = -3.76 × 10-5/°C (25-550 °C). Interestingly, an intrinsic giant volume contraction (∼3.7%) was obtained at the composition of Pb(Ti0.7V0.3)O3 during the ferroelectric-to-paraelectric phase transition, which represents the highest value ever reported. Such volume contraction is well correlated to the effect of spontaneous volume ferroelectrostriction. The present study extends the scope of the NTE family and provides an effective approach to explore new materials with large NTE, such as through adjusting the NTE-related ferroelectric property in the family of ferroelectrics.

Versatile NiO/mesoporous carbon nanodisks: controlled synthesis from hexagon shaped heterobimetallic metal-organic frameworks.

Hexagonal NiO/mesoporous carbon nanodisks (NiO/MCN) are facilely and controllably synthesized via constructing nickel-zinc trimesic acid heterobimetallic metal-organic framework (HMOF) disks before pyrolysis at 910 °C. Tailoring the Ni/(Zn + Ni) feed ratio and the reaction time during the HMOF synthesis creates a well-defined hexagonal carbon nanodisk with properly populated NiO nanocrystals while maintaining high porosity and conductivity. Such an elaborately fabricated NiO/MCN is highly stable, and exhibits the largest specific capacitance of 261 F g-1 and the highest specific activity factor of 1.93 s-1 g-1 of any composite nanodisk during the capacitive test and 4-nitrophenol reduction, respectively.

Red Blood Cell Count Automation Using Microscopic Hyperspectral Imaging Technology.

Red blood cell counts have been proven to be one of the most frequently performed blood tests and are valuable for early diagnosis of some diseases. This paper describes an automated red blood cell counting method based on microscopic hyperspectral imaging technology. Unlike the light microscopy-based red blood count methods, a combined spatial and spectral algorithm is proposed to identify red blood cells by integrating active contour models and automated two-dimensional k-means with spectral angle mapper algorithm. Experimental results show that the proposed algorithm has better performance than spatial based algorithm because the new algorithm can jointly use the spatial and spectral information of blood cells.

Coexpression of CdSe and CdSe/CdS quantum dots in live cells using molecular hyperspectral imaging technology.

A direct spatial and spectral observation of CdSe and CdSe/CdS quantum dots (QDs) as probes in live cells is performed by using a custom molecular hyperspectral imaging (MHI) system. Water-soluble CdSe and CdSe/CdS QDs are synthesized in aqueous solution under the assistance of high-intensity ultrasonic irradiation and incubated with colon cancer cells for bioimaging. Unlike the traditional fluorescence microscopy methods, MHI technology can identify QD probes according to their spectral signatures and generate coexpression and stain titer maps by a clustering method. The experimental results show that the MHI method has potential to unmix biomarkers by their spectral information, which opens up a pathway of optical multiplexing with many different QD probes.

Achieving large linear elasticity and high strength in bulk nanocompsite via synergistic effect.

Elastic strain in bulk metallic materials is usually limited to only a fraction of 1%. Developing bulk metallic materials showing large linear elasticity and high strength has proven to be difficult. Here, based on the synergistic effect between nanowires and orientated martensite NiTi shape memory alloy, we developed an in-situ Nb nanowires -orientated martensitic NiTi matrix composite showing an ultra-large linear elastic strain of 4% and an ultrahigh yield strength of 1.8 GPa. This material also has a high mechanical energy storage efficiency of 96% and a high energy storage density of 36 J/cm(3) that is almost one order of larger than that of spring steel. It is demonstrated that the synergistic effect allows the exceptional mechanical properties of nanowires to be harvested at macro scale and the mechanical properties of matrix to be greatly improved, resulting in these superior properties. This study provides new avenues for developing advanced composites with superior properties by using effective synergistic effect between components.

A novel multifunctional NiTi/Ag hierarchical composite.

Creating multifunctional materials is an eternal goal of mankind. As the properties of monolithic materials are necessary limited, one route to extending them is to create a composite by combining contrasting materials. The potential of this approach is neatly illustrated by the formation of nature materials where contrasting components are combined in sophisticated hierarchical designs. In this study, inspired by the hierarchical structure of the tendon, we fabricated a novel composite by subtly combining two contrasting components: NiTi shape-memory alloy and Ag. The composite exhibits simultaneously exceptional mechanical properties of high strength, good superelasticity and high mechanical damping, and remarkable functional properties of high electric conductivity, high visibility under fluoroscopy and excellent thermal-driven ability. All of these result from the effective-synergy between the NiTi and Ag components, and place the composite in a unique position in the properties chart of all known structural-functional materials providing new opportunities for innovative electrical, mechanical and biomedical applications. Furthermore, this work may open new avenues for designing and fabricating advanced multifunctional materials by subtly combining contrasting multi-components.

Leukocyte cells identification and quantitative morphometry based on molecular hyperspectral imaging technology.

Leukocyte cells identification is one of the most frequently performed blood tests and plays an important role in the diagnosis of diseases. The quantitative observation of leukocyte cells is often complemented by morphological analysis in both research and clinical condition. Different from the traditional leukocyte cells morphometry methods, a molecular hyperspectral imaging system based on acousto-optic tunable filter (AOTF) was developed and used to observe the blood smears. A combined spatial and spectral algorithm is proposed to identify the cytoplasm and the nucleus of leukocyte cells by integrating the fuzzy C-means (FCM) with the spatial K-means algorithm. Then the morphological parameters such as the cytoplasm area, the nuclear area, the perimeter, the nuclear ratio, the form factor, and the solidity were calculated and evaluated. Experimental results show that the proposed algorithm has better performance than the spectral based algorithm as the new algorithm can jointly use the spatial and spectral information of leukocyte cells.

Review of spectral imaging technology in biomedical engineering: achievements and challenges.

Spectral imaging is a technology that integrates conventional imaging and spectroscopy to get both spatial and spectral information from an object. Although this technology was originally developed for remote sensing, it has been extended to the biomedical engineering field as a powerful analytical tool for biological and biomedical research. This review introduces the basics of spectral imaging, imaging methods, current equipment, and recent advances in biomedical applications. The performance and analytical capabilities of spectral imaging systems for biological and biomedical imaging are discussed. In particular, the current achievements and limitations of this technology in biomedical engineering are presented. The benefits and development trends of biomedical spectral imaging are highlighted to provide the reader with an insight into the current technological advances and its potential for biomedical research.

AOTF based molecular hyperspectral imaging system and its applications on nerve morphometry.

The neuroanatomical morphology of nerve fibers is an important description for understanding the pathological aspects of nerves. Different from the traditional automatic nerve morphometry methods, a molecular hyperspectral imaging system based on an acousto-optic tunable filter (AOTF) was developed and used to identify unstained nerve histological sections. The hardware, software, and system performance of the imaging system are presented and discussed. The gray correction coefficient was used to calibrate the system's spectral response and to remove the effects of noises and artifacts. A spatial-spectral kernel-based approach through the support vector machine formulation was proposed to identify nerve fibers. This algorithm can jointly use both the spatial and spectral information of molecular hyperspectral images for segmentation. Then, the morphological parameters such as fiber diameter, axon diameter, myelin sheath thickness, fiber area, and g-ratio were calculated and evaluated. Experimental results show that the hyperspectral-based method has the potential to recognize and measure the nerve fiber more accurately than traditional methods.

The device performance of Cu(In, Ga)Se2 solar cells influenced by the type-inverted layer.

The type-inversion to n-type at the surface of p-type Culn(1-x)Ga(x)Se2 absorber layer is taken as an important factor for the high efficiency of Culn(1-x)Ga(x)Se2 (CIGS) with low Ga content, however, the further increase of Ga content makes the n-type doping difficult and the type-inverted layer vanish, which may have a negative effect on the device performance. Previous first-principles calculation had shown that the donor density becomes lower and level deeper when Ga content increases, while it's not clear how significantly the changes in the type-inverted layer influence the device performance. Through device simulation, we show that the efficiency decreases obviously as the donor density becomes lower and the level deeper in the inversion layer, thus they are important factors responsible for the limitation of the efficiency of CIGS solar cell, i.e., the efficiency decreases as Ga content exceeds 30%. Our work gives a good example in how to combine the electronic structure calculation of materials and device simulation to explain the experimental observation.