Transition metal perovskite chalcogenides, a class of materials with rich tunability in functionalities, are gaining increased attention as candidate materials for renewable energy applications. Perovskite oxides are considered excellent n-type thermoelectric materials. Compared to oxide counterparts, we expect the chalcogenides to possess more favorable thermoelectric properties such as lower lattice thermal conductivity and smaller band gap, making them promising material candidates for high temperature thermoelectrics. Thus, it is necessary to study the thermal properties of these materials in detail, especially thermal stability, to evaluate their potential. In this work, we report the synthesis and thermal stability study of five compounds, α-SrZrS3, β-SrZrS3, BaZrS3, Ba2ZrS4, and Ba3Zr2S7. These materials cover several structural types including distorted perovskite, needle-like, and Ruddlesden–Popper phases. Differential scanning calorimeter and thermogravimetric analysis measurements were performed up to 1200 °C in air. Structural and chemical characterizations such as X-ray diffraction, Raman spectroscopy, and energy dispersive analytical X-ray spectroscopy were performed on all the samples before and after the heat treatment to understand the oxidation process. Our studies show that perovskite chalcogenides possess excellent thermal stability in air at least up to 550 °C.

Formamidinium–tin–strontium halides (CH(NH2)2Sn1−ySryX3 (FASnX3), X = I, Br and 0.0 ≤ y ≤ 0.1) were investigated. X-ray diffraction analysis revealed orthorhombic FASnI3 (space group Amm2) and SnI2 for X = I as well as cubic FASnBr3 (space group $Pm\bar{3}m$) and SnBr2 for X = Br, respectively. For X = I, the optical spectra displayed a decrease of the absorption edges with increasing Sr content (1055 nm, y = 0.0; 950–960 nm, y > 0.0) and a direct semiconducting behavior with narrow band energy gaps (1.31–1.34 eV). For X = Br, on increasing the absorption edges (492 nm, y = 0.0; 975 nm, y = 0.075), a direct semiconducting behavior with band energy gaps between 2.65 eV (y = 0.0) and 1.38 eV (y = 0.075) were observed and the emission photoluminescence (PL) spectra (excitation wavelength λexc = 380 nm) showed an increase of the luminescence response after the thermal treatment.

High-index ferroelectric thin films show excellent dielectricity, piezoelectricity and switching behaviors. Understanding the misfit strain relaxation behavior may prove beneficial to gaining insights into the high-quality growth of high-index ferroelectric films. In this study, ferroelectric PbTiO3 thin films were deposited on the (101)-oriented (La, Sr)(Al, Ta)O3 substrate by pulsed laser deposition and were investigated using (scanning) transmission electron microscopy. Two types of misfit dislocations with line directions of 〈111〉 and [010] were found at the interface. The 〈111〉 dislocation exhibited Burgers vectors of a[011] or $a\left[ {0\bar{1}1} \right]$, while the [010] dislocation featured Burgers vectors of $a\left[ {\bar{1}01} \right]$. The former might be generated by gliding, and the latter by climbing. We propose that the misfit strain relaxation in this film system basically results from the formation of dislocations and the residual misfit strain is relaxed via the formation of 90° ac domains.

Thin films of insulating Ti1−xNixO2 (x = 0.00, 0.05, 0.10, and 0.15) are synthesized by the spray pyrolysis technique. All the films are seen to crystallize into polycrystalline anatase phase of TiO2. However, weak signature of the NiTiO3 phase is also observed for the films having higher Ni ion concentration. Optical absorption analysis suggests nonmonotonous band gap decrease from 3.67 to 3.59 eV with respect to added concentration of Ni ions unto ‘x’ = 0.10 in the TiO2 matrix. The presence of ferromagnetic ordering at room temperature in Ni incorporated TiO2 films is revealed by M–H measurements. Calculated values of saturation magnetization indicate that the observed ferromagnetism is not due to the presence of Ni clusters or segregation of other ferromagnetic phase. Electrically insulating nature of the films suggests that the observed FM ordering is most probably due to the ferromagnetic interaction between bound magnetic polarons which formed due to the creation of oxygen vacancies or defects.

Black nano-TiO2 samples with core–shell nanostructure were successfully prepared by sol–gel method combined with Mg reduction using butyl titanate as titanium source and calcining at 500°C in air atmosphere and at 400–600°C in nitrogen atmosphere. The prepared black TiO2 samples were characterized by X-ray diffraction, high resolution transmission electron microscopy, Raman spectra, photoluminescence emission spectra, N2 adsorption–desorption, and ultraviolet–visible spectroscopy. The results show that the black TiO2 exhibits a crystalline core–disordered shell structure composed of disordered surface and oxygen vacancies, and the thickness of the disordered layer is about 2–3 nm. The optical absorption properties of black nano-TiO2 samples have been remarkably enhanced in visible light region. Compared with the white TiO2, the reduced black TiO2 samples exhibit enhanced photocatalytic hydrogen production under the full solar wavelength range of light, and the sample prepared with the Mg and TiO2 ratio of 9:1 calcined at 500 °C has the maximum hydrogen production rate.

Li[Lix/3Mn2x/3M1−x]O2 (M = Ni, Mn, Co) (HE-NMC) materials, which can be expressed as a combination of trigonal LiTMO2 (TM = transition metal) and monoclinic Li2MnO3 phases, are of great interest as high capacity cathodes for lithium-ion batteries. However, structural stability prevents their commercial adoption. To address this, Si doping was applied, resulting in improved stability. Raman and differential capacity analyses suggest that silicon doping improves the structural stability during electrochemical cycling. Furthermore, the doped material exhibits a 10% higher capacity relative to the control. The superior capacity likely results from the increased lattice parameters as determined by X-ray diffraction (XRD) and the lower resistance during the first cycle found by impedance and direct current resistance (DCR) measurements. Density functional theory (DFT) predictions suggest that the observed lattice expansion is an indication of increased oxygen vacancy concentration and may be due to the Si doping.

SnO2 aerogels were successfully synthesized by using SnCl4, ammonium hydroxide (AH), formamide, propylene oxide, and tetraethoxysilane as tin source, reaction promoter, drying control chemical additive (DCCA), gel accelerator, and surface modifier, respectively, via the sol–gel method, combined with subsequent ambient pressure drying of sol–gel. The results of Fourier transform infrared spectroscopy proved that the CH3CH2OSi-bond was transferred to SnO2 gel. A contact angle measuring instrument was utilized for the study of hydrophicity and hydrophobicity of SnO2 aerogels, and the complete porous skeleton structure of SnO2 aerogels was confirmed by field emission scanning electron microscopy (FESEM) and nitrogen adsorption–desorption analyzer, denoting AH allowed SnO2 aerogels to shape more macropores. Based on the thermal resistance tester, it showed that the SnO2 aerogels had low thermal conductivity. The biggest specific surface area and lowest thermal conductivity of SnO2 aerogels were 447.26 m2/g and 0.0717 K/(m•K), respectively.

In this work, the negatively charged [NbMoO6]− nanosheets (NSs) were combined with positively charged [5,10,15,20-tetrakis (N-methylpyridinium-4-yl) porphyrinato cobalt] (CoTMPyP) to fabricate a sandwich-like CoTMPyP/[NbMoO6]− NSs intercalated material by a direct self-assembling process. The results confirmed that CoTMPyP cations formed an inclined monolayer between [NbMoO6]− NSs and the inclined angle was about 68°. The electrochemical properties of CoTMPyP/[NbMoO6]− NSs composite were also investigated by cyclic voltammetry and liner sweep voltammetry, which showed the enhanced electron transferred ability. The CoTMPyP/[NbMoO6]− NSs modified electrode displayed excellent electrocatalytic activity towards oxygen reduction with the reduction peak potential shifting from −0.681 to −0.235 V. And oxygen could be reduced to generate hydrogen peroxide with a two-electron process in neutral electrolytes. Moreover, the reduction peak current was linear relationship with the square root of scan rates, implying that the catalytic reaction depended on oxygen diffusion.

Transient transmission oscillations in X-cut and Z-cut congruent, iron-doped, and magnesium-doped lithium niobate samples were measured using 50 fs, 800 nm, 0.5 nJ pulses from a self-mode-locked Ti:sapphire laser in an optical pump–probe system. Several Raman-active oscillation modes excited by these pulses were observed as changes in the transmitted probe intensity versus time delay between the pump and probe pulses. The samples were rotated to determine how the incident polarization of the pump pulses affects the mode excitations. The observed Raman-active oscillations correspond to previously reported symmetry modes measured with traditional, continuous-wave, Raman spectroscopy using the same scattering geometry. In addition, a polariton mode and other, previously unreported, lower-frequency modes were observed in each of the samples. The transmission intensity data for each sample were fit successfully to a superposition of sinusoidal functions with exponentially decaying amplitudes.

The layer-by-layer self-assembly technology was adopted to prepare a new generation of supercapacitor electrode material, GOQDs@NiAl-LDH, between Ni–Al layered double hydroxide (LDH) and graphene oxide quantum dots (GOQDs). First, Ni–Al LDH was prepared by coprecipitation of nickel nitrate and aluminum nitrate and then delaminated by ultrasonication. Second, NiAl-LDH was combined with GOQDs that were prepared by a ball milling reaction using hexachlorobenzene as raw material. The electrochemical data indicate that the composite (OGL9) exhibits highest specific capacitance, large current charge and discharge characteristics, and excellent cycle stability when the content of GOQDs is 10%. And the specific capacitance of composite reaches to 869 F/g at the current density of 1 A/g. Moreover, the capacitance retention at 1 A/g discharge current condition is 69.6% after 2000 cycles. And the results indicate that the OGL9 can be a promising electrode material for supercapacitor applications.

Manganese sulfides (MnS) with a diversity of well-defined morphologies and phases have been successfully synthesized by the solvothermal approach. The phase structure and morphology of MnS could readily be tuned by adjusting the sulfur sources and solvents. Hollow γ-MnS spheres were obtained by treating L-cysteine and manganese source in ethylene glycol (EG) at 200 °C for 2 h, whereas a replacement of the mixture solvent by EG and deionized water yields the hierarchical flower-like γ-MnS. γ-MnS tubes were also produced under the same condition by using diethylene glycol and deionized water as solvents. When thioacetamide used as the sulfur source and oleylamine used as the solvent, monodisperse α-MnS nanoparticles with the mean diameter of 17 nm could be synthesized successfully. The phase structures, sizes, and morphologies of samples were investigated in detail by powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The UV-vis absorption peak and the width of band gap with different morphologies of the as-prepared MnS were measured. The samples described in this paper are promising to be utilized in solar cells, biomedicine, short wavelength electronic devices, photocatalysis, and other fields.

In this study, we have successfully grown hBN/graphene heterostructures on copper thin films using chemical vapor deposition in a single process. The first and most surprising result is that graphene grows underneath hBN and adjacent to the Cu film even though it is deposited second. This was determined from cross-sectional TEM analysis and XPS depth profiling, which chemically identified the relative positions of hBN and graphene. The effect of various growth conditions on graphene/hBN heterostructures was also studied. It was found that a pressure of 200 torr and a hydrogen flow rate of 200 sccm (∼1 H2/N2) yielded the highest quality of graphene, with full surface coverage occurring after a growth time of 120 min. The resulting graphene films were found to be approximately 6–8 layers thick. The grain size of the nanocrystalline graphene was found to be 15–50 nm varying based on growth conditions.

Atomic layer deposition (ALD) of air stable cobalt and nickel complexes based on tridentate enaminones N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylethyldiamine (Htfb-dmeda) and N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylpropyldiamine (Htfb-dmpda) successfully produced metallic cobalt and nickel thin films. Detailed X-ray photoelectron spectroscopy (XPS) studies on the binding interaction of the first precursor monolayer with the surface functional groups elucidated the chemisorption behavior of the new precursor systems. A reactive remote hydrogen plasma was used as the co-reactant to activate the precursor decomposition yielding metal hydroxide intermediates. Subsequent hydrogen plasma etching of as-deposited films resulted in phase-pure metallic films through a recrystallization process, verified by surface and sub-surface XPS. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed pinhole-free films, with low surface roughness (0.2 ± 0.06 nm root mean square, RMS) for both, cobalt and nickel thin films. Herein, the competitive role of hydrogen as etchant and reactant was demonstrated as prolonged plasma exposure time periods resulted in the formation of metal hydrides. This is mostly due to the catalytic dissociation of molecular hydrogen on transition metal surfaces, which already occurs upon low energy input.

Carbon nanotubes (CNTs) were added to carbon nanofibers (CNFs) as additives to improve their electrochemical properties. In the present work, CNFs were prepared by using pressurized gyration with polyacrylonitrile as the precursor. The microstructure and electrochemical properties of samples were investigated by scanning electron microscopy and electrochemical workstation, respectively. The results showed that the network structure formed in the fiber, and the fiber diameter decreased with the increase of working pressure. The integral area of cyclic voltammetry curve reached the maximum and the charge/discharge time of constant current charge/discharge curve reached the longest in the case of the CNT concentration is 0.50 wt% and working pressure is 0.2 MPa. At the same time, it exhibited the best electrochemical performance with a specific capacitance of 79 F/g at a current density of 100 mA/g. Compared with the specific capacitance of pure CNFs, the specific capacitance of CNFs with the concentration of CNTs 0.50 wt% increased by about 40%.

Magnesium alloy (AZ31) reinforced with carbon nanotubes (CNTs) and grapheme nanoplatelets (GNPs) were fabricated with the method of hot-pressing sintering and hot extrusion processes. GNPs and CNTs were predispersed with Al and Zn powders by ball milling used as precursor for sintering, which effectively guaranteed the integrity and dispersion of them. The microstructure and mechanical properties of the composites (denoted as Mg–3 wt% Al–1 wt% Zn–1 wt% (xCNTs + yGNPs)(x:y = 1:1, 1:2, 1:3) were investigated. The results show that the CNTs and GNPs are uniformly distributed in the matrix and closely combined with the matrix in nanoscale. Among the tested composites, Mg–3 wt% Al–1 wt% Zn–1 wt% (xCNTs + yGNPs)(x:y = 1:2) exhibits the most favorable mechanical properties, and the yield strength, tensile and compressed strength, and elongation of composites are substantially improved by the addition of 0.33 wt% CNTs and 0.67 wt% GNPs. Novel strengthening mechanisms such as three-dimensional reinforced structure formed by CNTs and GNPs are found for the remarkable improvement in mechanical properties.

The immobilization of cytochrome c (cyt c) on tea polyphenol functionalized and reduced graphene oxide (TPG) was carried out by a simple adsorption process. Intriguingly, TPG with large surface area exhibited excellent adsorption behaviors and good biocompatibility. The adsorbed materials were characterized by various methods including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). And the effects of adsorption behavior of cyt c were discussed in detail. The results showed the adsorption behavior was dependent on the pH value and showed a high adsorption capacity as high as 1.414 × 104 mg/g and was friendly to normal cells (mouse fibroblast cell line, L929). In conclusion, we proposed the introduction of TPG as novel material and used the adsorption method to immobilize cyt c, which would provide a novel material and simple method for the enrichment of protein.

The aim of this study was to investigate the in vivo degradation mechanism and the mechanical properties of poly(lactide-co-glycolide)/beta-tricalcium phosphate (PLGA/β-TCP) composite anchors. Anchors composed of PLGA and β-TCP were implanted in the dorsal subcutaneous tissue of beagle dogs for 6, 12, 16, and 26 weeks. The degradation of the materials was evaluated by measuring the changes in thermal behavior, crystallinity, and mechanical properties. Scanning electron microscope (SEM) was used to observe the surface and longitudinal section of the material. The evaluation of mechanical strength retention and degradation properties suggest that the addition of β-TCP particles efficiently enhances their mechanical properties and thermal characteristics and delays their degradation rate. By analyzing the results of SEM, X-ray diffraction, and differential scanning calorimetry, we can infer that after 12 weeks, the connection between β-TCP and PLGA becomes less compact, which accelerates the decline of mechanical strength.

In this study, the bioactivity and cytocompatibility of electrospun polyamide 6 (PA6)/hydroxyapatite (HA) coating on zirconia-toughened alumina (ZTA) were investigated. Adjusting the PA6/HA ratio to 1.15 (w/w) had a significant role in achieving an appropriate fibrous coating with an average diameter of 120 ± 10 nm and surface porosity of 64.3%. The surface of bare and coated samples was hydrophilic, which promoted bone regeneration. The adhesion test of the PA6/HA mat demonstrated that a cohesive coating was formed on the ZTA via electrospinning. The in vitro bioactivity test of the PA6/HA coating in simulated body fluid (SBF) corroborated the formation of a nanostructured bonelike apatite phase. Cytocompatibility of the samples was evaluated through in vitro osteosarcoma-like cell (MG63) culture assays. The cytotoxicity study showed that the electrospun PA6/HA coating significantly improved cell attachment and spreading. The development of such bioactive, biomedical coatings opens new avenues for bone tissue engineering applications.

The design and the processing of a new class of titanium boride (TiB)-based bulk cermets containing a metallic phase (β-Ti phase) for toughening is presented. The general approach is rapid reaction and densification, using starting powders of Ti, TiB2, Fe, and Mo, by electric-field-activated sintering. The cermets consist of two-phase microstructures in which the boride phase formed as a networked structure of TiB whiskers that were created in situ upon the reaction between the powders. Hardness, flexural strength, and fracture toughness measurements of these materials revealed that they possess an interesting set of properties up to: hardness values of 1090 kg/mm2, flexural strength values of 953 MPa, and fracture toughness values of 18 MPa m1/2. A remarkable finding is that although the metallic phase fractured by microscopic cleavage, the cermets showed good fracture toughness values. The present study not only illustrates the process details and microstructure leading to these properties but also provides a broad powder metallurgical approach to design and synthesize cermets that may yield further improved properties.

In the present work, the TiB2-reinforced AA6061 composites were successfully in situ synthesized by laser surface alloying using a mixture of Ti and AlB2 powders. The microstructure evolution and properties of the composites were systematically studied. The results showed that TiB2 particles displayed a homogeneous distribution in the aluminum matrix with controllable contents and morphologies. By adjusting the molar ratio of alloying powders, phase constitution of the composites was varied. Thermodynamic calculation was used to analyze the phase selection during the solidification. It was found that the morphology of TiB2 particles was converted from hexagonal plate into rod-like structure with an increase of Ti contents. Transmission electron microscopy results illustrated that the in situ synthesized TiB2 particles exhibited a well-bonded interface with the Al matrix. Properties characterization revealed a significant enhancement in microhardness and abrasion resistance compared with the aluminum substrate attributed to the presence of the TiB2 reinforcements. The strengthening and wear mechanism were also discussed.