Hydrogenation Properties of TiFe Doped with Zirconium.
Ontology highlight
ABSTRACT: The goal of this study was to optimize the activation behaviour of hydrogen storage alloy TiFe. We found that the addition of a small amount of Zr in TiFe alloy greatly reduces the hydrogenation activation time. Two different procedural synthesis methods were applied: co-melt, where the TiFe was melted and afterward re-melted with the addition of Zr, and single-melt, where Ti, Fe and Zr were melted together in one single operation. The co-melted sample absorbed hydrogen at its maximum capacity in less than three hours without any pre-treatment. The single-melted alloy absorbed its maximum capacity in less than seven hours, also without pre-treatment. The reason for discrepancies between co-melt and single-melt alloys was found to be the different microstructure. The effect of air exposure was also investigated. We found that the air-exposed samples had the same maximum capacity as the argon protected samples but with a slightly longer incubation time, which is probably due to the presence of a dense surface oxide layer. Scanning electron microscopy revealed the presence of a rich Zr intergranular phase in the TiFe matrix, which is responsible for the enhanced hydrogenation properties of these Zr-doped TiFe alloys.
Project description:Zirconium-lithium-phosphate glasses were elaborated through the melting-quenching technique. The primary objective of this research is to investigate how the replacement of lithium oxide with zirconium oxide impacts the physical, thermal, mechanical, and electrical properties of the fabricated glasses. The result showed that the vitreous materials were obtained with a ZrO2 content lower than 1 mol%. Furthermore, it is found that incorporating ZrO2 in the glassy phosphate framework affects mal compatibility and increases the durability of the glassy samples. Analyzing the mechanical performance reveals that the incorporation of ZrO2 leads to enhancements in the elastic constants of the glasses, including the longitudinal modulus, shear modulus, Young's modulus, bulk modulus, and Poisson coefficient. The bond strengths are used to calculate and explain the glasses' Vickers hardness values. On the other hand, the infrared (IR) spectroscopy results reveal that replacing Li2O with ZrO2 oxide in the glassy matrix causes significant structural changes. Finally, the dielectric features of the prepared glasses versus frequency and temperature are analyzed. The significance lies in the fact that the replacement of lithium with zirconium leads to a reduction in the ionic conductivity of the glasses.
Project description:Tantalum (Ta) metal is well known for its ideal corrosion resistance and biological effects as endosseous implants. However, the metal has a elastic modulus as high as 186GPa which is not comparable to the natural bone (10-40GPa), and it also has a relative high cost. Here, to fully exploit the advantages of Ta as endosseous implants, a small amount of Ta (as low as 3 at.%) was successfully added into a zirconium-based metallic glass (MG) to generate an advanced functional endosseous implant, Zr58Cu25Al14Ta3 MG, with superior comprehensive properties. Upon carefully dissecting the surface chemistry and atomic structure, the results show that amorphization of Ta enable the uniform distribution in material surface, leading to a significantly improved chemical stability and extensive material-cell contact regulation. Systematical analyses on the immunological, angiogenesis and osteogenesis capability of the material is carried out by utilizing the next-generation sequencing, revealing that Zr58Cu25Al14Ta3 MG can regulate angiogenesis through VEFG signaling pathway and osteogenesis via BMP signaling pathway. Animal experiment further confirms a sound osseointegration of Zr58Cu25Al14Ta3 MG in achieving better bone-implant-contact and inducing faster peri-implant bone formation.
Project description:Tantalum (Ta) metal is well known for its ideal corrosion resistance and biological effects as endosseous implants. However, the metal has a elastic modulus as high as 186GPa which is not comparable to the natural bone (10-40GPa), and it also has a relative high cost. Here, to fully exploit the advantages of Ta as endosseous implants, a small amount of Ta (as low as 3 at.%) was successfully added into a zirconium-based metallic glass (MG) to generate an advanced functional endosseous implant, Zr58Cu25Al14Ta3 MG, with superior comprehensive properties. Upon carefully dissecting the surface chemistry and atomic structure, the results show that amorphization of Ta enable the uniform distribution in material surface, leading to a significantly improved chemical stability and extensive material-cell contact regulation. Systematical analyses on the immunological, angiogenesis and osteogenesis capability of the material is carried out by utilizing the next-generation sequencing, revealing that Zr58Cu25Al14Ta3 MG can regulate angiogenesis through VEFG signaling pathway and osteogenesis via BMP signaling pathway. Animal experiment further confirms a sound osseointegration of Zr58Cu25Al14Ta3 MG in achieving better bone-implant-contact and inducing faster peri-implant bone formation.
Project description:Tantalum (Ta) metal is well known for its ideal corrosion resistance and biological effects as endosseous implants. However, the metal has a elastic modulus as high as 186GPa which is not comparable to the natural bone (10-40GPa), and it also has a relative high cost. Here, to fully exploit the advantages of Ta as endosseous implants, a small amount of Ta (as low as 3 at.%) was successfully added into a zirconium-based metallic glass (MG) to generate an advanced functional endosseous implant, Zr58Cu25Al14Ta3 MG, with superior comprehensive properties. Upon carefully dissecting the surface chemistry and atomic structure, the results show that amorphization of Ta enable the uniform distribution in material surface, leading to a significantly improved chemical stability and extensive material-cell contact regulation. Systematical analyses on the immunological, angiogenesis and osteogenesis capability of the material is carried out by utilizing the next-generation sequencing, revealing that Zr58Cu25Al14Ta3 MG can regulate angiogenesis through VEFG signaling pathway and osteogenesis via BMP signaling pathway. Animal experiment further confirms a sound osseointegration of Zr58Cu25Al14Ta3 MG in achieving better bone-implant-contact and inducing faster peri-implant bone formation.
Project description:The activation of molecule hydrogen (H2) by metal-free catalysts is always a challenge in the field of catalysis. Herein, a series of N, P dual-doped carbon catalysts were constructed by the pyrolysis of chitosan and phytic acid and utilized as metal-free catalysts for the hydrogenation of nitrobenzene. The characterization indicated that the doping of phosphorus atoms not only formed the species with catalytic activity for hydrogenation reaction but also promoted the doping of N. The experimental results indicated that their catalytic performance could be improved by the regulation of pyrolysis temperature and heating rate. CP-900-1 (pyrolysis at 900 °C with a heating rate of 1 °C/min) exhibited a promising catalytic activity with >99% nitrobenzene conversion. N, P codoping was the key factor to its catalytic performance. All results indicated that the excellent catalytic activity of CP-900-1 was attributed to the synergistic interaction among pyridinic N, P-C species, and graphitic N. This work provides an effective route for the rational design and construction of highly efficient metal-free catalysts for hydrogenation.
Project description:Ferroelectric tunneling junctions (FTJs) with tunable tunneling electroresistance (TER) are promising for many emerging applications, including non-volatile memories and neurosynaptic computing. One of the key challenges in FTJs is the balance between the polarization value and the tunneling current. In order to achieve a sizable on-current, the thickness of the ferroelectric layer needs to be scaled down below 5 nm. However, the polarization in these ultra-thin ferroelectric layers is very small, which leads to a low tunneling electroresistance (TER) ratio. In this paper, we propose and demonstrate a new type of FTJ based on metal/Al2O3/Zr-doped HfO2/Si structure. The interfacial Al2O3 layer and silicon substrate enable sizable TERs even when the thickness of Zr-doped HfO2 (HZO) is above 10 nm. We found that F-N tunneling dominates at read voltages and that the polarization switching in HZO can alter the effective tunneling barrier height and tune the tunneling resistance. The FTJ synapses based on Al2O3/HZO stacks show symmetric potentiation/depression characteristics and widely tunable conductance. We also show that spike-timing-dependent plasticity (STDP) can be harnessed from HZO based FTJs. These novel FTJs will have high potential in non-volatile memories and neural network applications.
Project description:Due to radiation resistance and the immunosuppressive microenvironment of metastatic osteosarcoma, novel radiosensitizers that can sensitize radiotherapy (RT) and antitumor immunity synchronously urgently needed. Here, the authors developed a nanoscale metal-organic framework (MOF, named TZM) by co-doping high-atomic elements Ta and Zr as metal nodes and porphyrinic molecules (tetrakis(4-carboxyphenyl)porphyrin (TCPP)) as a photosensitizing ligand. Given the 3D arrays of ultra-small heavy metals, porous TZM serves as an efficient attenuator absorbing X-ray energy and sensitizing hydroxyl radical generation for RT. Ta-Zr co-doping narrowed the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap and exhibited close energy levels between the singlet and triplet photoexcited states, facilitating TZM transfer energy to the photosensitizer TCPP to sensitize singlet oxygen (1 O2 ) generation for radiodynamic therapy (RDT). The sensitized RT-RDT effects of TZM elicit a robust antitumor immune response by inducing immunogenic cell death, promoting dendritic cell maturation, and upregulating programmed cell death protein 1 (PD-L1) expression via the cGAS-STING pathway. Furthermore, a combination of TZM, X-ray, and anti-PD-L1 treatments amplify antitumor immunotherapy and efficiently arrest osteosarcoma growth and metastasis. These results indicate that TZM is a promising radiosensitizer for the synergistic RT and immunotherapy of metastatic osteosarcoma.
Project description:Optoelectronic devices based on lead halide perovskites are processed in facile ways, yet are remarkably efficient. There are extensive research efforts investigating lead-free perovskite and perovskite-related compounds, yet there are challenges to synthesize these materials in forms that can be directly integrated into thin film devices rather than as bulk powders. Here, we report on the colloidal synthesis and characterization of lead-free, antifluorite Cs2ZrX6 (X = Cl, Br) nanocrystals that are readily processed into thin films. We use transmission electron microscopy and powder X-ray diffraction measurements to determine their size and structural properties, and solid-state nuclear magnetic resonance measurements reveal the presence of oleate ligand, together with a disordered distribution of Cs surface sites. Density functional theory calculations reveal the band structure and fundamental band gaps of 5.06 and 3.91 eV for Cs2ZrCl6 and Cs2ZrBr6, respectively, consistent with experimental values. Finally, we demonstrate that the Cs2ZrCl6 and Cs2ZrBr6 nanocrystal thin films exhibit tunable, broad white photoluminescence with quantum yields of 45% for the latter, with respective peaks in the blue and green spectral regions and mixed systems exhibiting properties between them. Our work represents a critical step toward the application of lead-free Cs2ZrX6 nanocrystal thin films into next-generation light-emitting applications.
Project description:The development of high-activity and low-price cathodic catalysts to facilitate the electrochemically sluggish O2 reduction reaction (ORR) is very important to achieve the commercial application of fuel cells. Here, we have investigated the electrocatalytic activity of the two-dimensional single-layer Nb-doped zirconium diselenide (2D Nb-ZrSe2) toward ORR by employing the dispersion corrected density functional theory (DFT-D) method. Through our study, we computed structural properties, electronic properties, and energetics of the 2D Nb-ZrSe2 and ORR intermediates to analyze the electrocatalytic performance of 2D Nb-ZrSe2. The electronic property calculations depict that the 2D monolayer ZrSe2 has a large band gap of 1.48 eV, which is not favorable for the ORR mechanism. After the doping of Nb, the electronic band gap vanishes, and 2D Nb-ZrSe2 acts as a conductor. We studied both the dissociative and the associative pathways through which the ORR can proceed to reduce the oxygen molecule (O2). Our results show that the more favorable path for O2 reduction on the surface of the 2D Nb-ZrSe2 is the 4e- associative path. The detailed ORR mechanisms (both associated and dissociative) have been explored by computing the changes in Gibbs free energy (ΔG). All of the ORR reaction intermediate steps are thermodynamically stable and energetically favorable. The free energy profile for the associative path shows the downhill behavior of the free energy vs the reaction steps, suggesting that all ORR intermediate structures are catalytically active for the 4e- associative path and a high 4e- reduction pathway selectivity. Therefore, 2D Nb-ZrSe2 is a promising catalyst for the ORR, which can be used as an alternative ORR catalyst compared to expensive platinum (Pt).