Theoretical study of electronic properties and chemical stability of cubic phase zirconia nanowires

Zirconia bulk is one of the most studied materials around the world due to different properties such as a high melting temperature, biocompatibility, and high thermal expansion, among many others. However, there is little experimental research about Zirconia nanowires and until now there are few theoretical papers on the subject. In this work, DFT calculations on bare ZrO2 nanowires with diameter variation were performed. In order to get the more accurate parameters for calculation on nanowires, we employed the Murnaghan equation of state in a cubic phase of ZrO2 and we compared the results obtained with some experimental data as well as the lattice parameter and the bulk modulus. The nanowires were grown along with the [1 1 1] direction with five different diameters. All calculations were carried out by Density Functional Theory (DFT) implemented in SIESTA code. According to our results, GGA-PBE is the more accurate functional for describing the Exc on ZrO2. The calculation of formation and surface energies shows that these nanowires are highly stable chemically. Furthermore, nanowires larger than 8.78 ˚A present a direct bandgap. These results indicate the possibility of applying ZrO2 nanowires in the optoelectronic field.

Low-temperature synthesis and growth model of thin Mo2C crystals on indium

Chemical vapor deposition is a promising technique to produce Mo2C crystals with large area, controlled thickness, and reduced defect density. Typically, liquid Cu is used as a catalyst substrate; however, its high melting temperature (1085 °C) prompted research groups to search for alternatives. In this study, we report the synthesis of large-area thin Mo2C crystals at lower temperatures using liquid In, which is also advantageous with respect to the transfer process due to its facile etching. SEM, EDS, Raman spectroscopy, XPS, and XRD studies show that hexagonal Mo2C crystals, which are orthorhombic, grow along the [100] direction together with an amorphous carbon thin film on In. The growth mechanism is examined and discussed in detail, and a model is proposed. AFM studies agree well with the proposed model, showing that the vertical thickness of the Mo2C crystals decreases inversely with the thickness of In for a given reaction time.

Melting Curve Analysis of Aptachains: Adenosine Detection with Internal Calibration

Small molecules are ubiquitous in nature and their detection is relevant in various domains. However, due to their size, sensitive and selective probes are difficult to select and the detection methods are generally indirect. In this study, we introduced the use of melting curve analysis of aptachains based on split-aptamers for the detection of adenosine. Aptamers, short oligonucleotides, are known to be particularly efficient probes compared to antibodies thanks to their advantageous probe/target size ratio. Aptachains are formed from dimers with dangling ends followed by the split-aptamer binding triggered by the presence of the target. The high melting temperature of the dimers served as a calibration for the detection/quantification of the target based on the height and/or temperature shift of the aptachain melting peak.

Performance Characteristics of Custom Thermocouples for Specialized Applications

This work reports the performance characteristics of custom thermocouples developed for use in elevated temperatures such as metal casting operations. The scope of this research is limited to thermocouples designed using pyrolytic graphite (PG) as the primary thermoelement in connection with aluminum, copper, steel, and tungsten. The Seebeck coefficients of the sensors were determined from experimental data after heating to ~500 °C. Cooling from ~500 °C to room temperature enabled us to compare the characteristic behaviors of the sensors from the obtained near-linear responses in the voltage-temperature plots. Tungsten being a refractory metal produced the highest sensitivity of the sensors. The sensitivity of the PG-tungsten thermocouple upon heating measured up to 26 μV/°C and a slightly lower value of 24.2 μV/°C was obtained upon cooling. Conversely, the PG-steel thermocouple rather produced the lowest Seebeck coefficients of 13.8 μV/°C during heating and 14.0 μV/°C for the cooling experiments though steel has a high melting temperature than most of the other thermoelements.

Theoretical prediction of high melting temperature for a Mo–Ru–Ta–W HCP multiprincipal element alloy

While rhenium is an ideal material for rapid thermal cycling applications under high temperatures, such as rocket engine nozzles, its high cost limits its widespread use and prompts an exploration of viable cost-effective substitutes. In prior work, we identified a promising pool of candidate substitute alloys consisting of Mo, Ru, Ta, and W. In this work we demonstrate, based on density functional theory melting temperature calculations, that one of the candidates, Mo0.292Ru0.555Ta0.031W0.122, exhibits a high melting temperature (around 2626 K), thus supporting its use in high-temperature applications.

New insights into the digestion and bioavailability of a high-melting-temperature solid triacylglycerol fraction in bovine milk fat

Clarifying the health risks associated with the consumption of high-melting-temperature solid triacylglycerol (TAG) from milk fat has profound significance for the nutritional evaluation and development of new dairy products. Our...

Low Temperature Synthesis and Growth Model of Thin Mo2C Crystals on Indium

CVD method is a promising technique to produce Mo2C crystals with large-area, controlled thickness, and reduced defect density. Typically, liquid Cu is used as a catalyst substrate; however, its high melting temperature (1085 C) prompted a research for alternatives. In this study, we report the synthesis of large-area thin Mo2C crystals on liquid In surface at 1000 C for the first time. SEM, EDS, Raman Spectroscopy, XPS and XRD studies show that the hexagonal shaped Mo2C crystals, that are orthorhombic, grow along the [100] direction together with amorphous carbon thin film on In. The growth mechanism is examined and discussed in detail and a model is proposed. The AFM studies agree well with the proposed model showing that the vertical thicknesses of the Mo2C crystals decrease inversely with the thickness of the In for the given reaction time.

Controlling the Tube Diameter of SWCNTs Using High Melting Point Promotors

A particular control of the diameter of Single Walled-Carbon Nanotube (SWCNT) using Chemical vapor Deposition (CVD) system will enable many promising applications in different fields. Here we demonstrate the growth of SWCNT with good control of diameter (1.5 nm ± 0.7) using a high melting temperature metal (Ru) as a catalyst promotor with the main catalyst Co at 850˚C via CVD. We hypothesis that using high melting temperature metal as a promotor, like Ru can limit the mobility/change in the shape of the formed metal nanoparticles and eventually decrease the effects of Ostwald ripening (OR). FTS-GP is used as a carbon precursor. The results have been verified by high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM) and multi-excitation Raman.