Electrochemical investigation of chromium nanocarbide coated Ti–6Al–4V and Co–Cr–Mo alloy substrates

This study investigated the electrochemical behavior of chromium nano-carbide cermet coating applied on Ti–6Al–4V and Co–Cr–Mo alloys for potential application as wear and corrosion resistant bearing surfaces. The cermet coating consisted of a highly heterogeneous combination of carbides embedded in a metal matrix. The main factors studied were the effect of substrate (Ti–6Al–4V vs. Co–Cr–Mo), solution conditions (physiological vs. 1 M H₂O₂ of pH 2), time of immersion (1 vs. 24 h) and post coating treatments (passivation and gamma sterilization). The coatings were produced with high velocity oxygen fuel (HVOF) thermal spray technique at atmospheric conditions to a thickness of 250 μm then ground and polished to a finished thickness of 100 μm and gamma sterilized. Native Ti–6Al–4V and Co–Cr–Mo alloys were used as controls. The corrosion behavior was evaluated using potentiodynamic polarization, mechanical abrasion and electrochemical impedance spectroscopy under physiologically representative test solution conditions (phosphate buffered saline, pH 7.4, 37 °C) as well as harsh corrosion environments (pH ～ 2, 1 M H₂O₂, T = 65 °C). Severe environmental conditions were used to assess how susceptible coatings are to conditions that derive from possible crevice-like environments, and the presence of inflammatory species like H₂O₂. SEM analysis was performed on the coating surface and cross-section. The results show that the corrosion current values of the coatings (0.4–4 μA/cm²) were in a range similar to Co–Cr–Mo alloy. The heterogeneous microstructure of the coating influenced the corrosion performance. It was observed that the coating impedances for all groups decreased significantly in aggressive environments compared with neutral and also dropped over exposure time. The low frequency impedances of coatings were lower than controls. Among the coated samples, passivated nanocarbide coating on Co–Cr–Mo alloy displayed the least corrosion resistance. However, all the coated materials demonstrated higher corrosion resistance to mechanical abrasion compared to the native alloys.     

Optical,electrical, mechanical,and thermal properties and non-isothermal decomposition behavior of poly(vinyl alcohol)–ZnO nanocomposites

Iranian Polymer Journal - Poly(vinyl alcohol) (PVA) nanocomposites incorporated with ZnO nanofiller were prepared and examined to study the influence of nanofiller on their properties. All the...     

Single-phase and binary phase nanogranular ferrites for magnetic hyperthermia application

The study demonstrates the performance of heating efficiency in single-phase and binary phase spinel ferrite nanosystems. Ferrimagnetic cobalt ferrite (CoFe₂O₄) (CFO) and superparamagnetic copper ferrite/copper oxide (CuFe₂O₄/CuO) (CuF) nanosystems of different particle sizes were synthesized through a microwave-assisted coprecipitation method. The heating behavior was observed in range of both field amplitudes (8-24 kA/m at 516 kHz) and frequencies (325-973 kHz at 12 kA/m). The heating efficiency was analyzed and compared by means of particle size, magnetization, effective anisotropy constant, and Néel relaxation mechanism. Indeed, the heating rate was maximized in larger ferrite particles with low effective anisotropy constant. Moreover, though the magnetization and effective anisotropy constant of single-phase CoFe₂O₄ nanoparticles were higher, the binary phase CuFe₂O₄/CuO nanosystems of similar crystallite size (28 nm) exhibited superior heating efficiency (4.21°C/s). For a field amplitude and frequency of 24 kA/m and 516 kHz, the heating rate of CuF and CFO ferrites with different crystallite sizes decreased in the order of 4.21 > 2.14 > 0.58 > 0.52°C/s for 29 nm > 25 nm > 12 nm > 15 nm, respectively. The results emphasize that binary phase ferrite nanoparticles are better thermoseeds than the single-phase ferrites for the magnetic hyperthermia application.     

Formation of Zinc–Antimony-Based Spinel Phases

Formation of spinel phases in ZnO–Sb₂O₃and ZnO–Sb₂O₃–Bi₂O₃systems is studied by the use of X-ray diffraction. The formation of nonstoichiometric Zn_2.33Sb_0.67O₄phase is observed in both the systems at ∼900°C. However, in these systems, at higher temperatures ( T ≥ 1100°C), formation of the inverse spinel phase Zn₇Sb₂O₁₂is observed. The study has been extended to understand the effect of CrO₃doping on the stability of the different spinel phases in the previously mentioned systems. Interestingly, in both the systems, samples doped with CrO₃, displayed the presence of Zn_2.33Sb_0.67O₄phase <1200°C, indicating the stabilization of the spinel phase by CrO₃.     

n-Hexadecane hydroisomerization over Pt/ZSM-12: role of Si/Al ratio on product distribution

The crystallization of pure ZSM-12 phase was accomplished at Si/Al ratios ranging from 45 to 120 using tetraethylammonium bromide as the structure directing agent. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy, temperature programmed desorption of ammonia, and nitrogen adsorption–desorption measurements at 77 K, respectively. The well characterized samples were used to prepare Pt (0.5 wt%)/ZSM-12 hydroisomerization catalysts which were employed to perform n-hexadecane isomerization reaction. The catalysts were compared in terms of their activity, selectivity and product distribution at different conversion levels obtained through variation in temperature and residence times. Thus, obtained trend for product distribution over Pt/ZSM-12 system has been discussed in terms of framework Si/Al ratio to understand its role in determining the product selectivity. ZSM-12 with Si/Al ratio of 120 depicted the highest overall selectivity and favored mono-branching while those having Si/Al ratio of 45, 60 and 90 were found to favor mutlti-branching.     

A Rapid Synthesis of Oriented Palladium Nanoparticles by UV Irradiation

Palladium nanoparticles of average size around 8 nm have been synthesized rapidly by UV irradiation of mixture of palladium chloride and potassium oxalate solutions. A rod-shaped palladium oxalate complex has been observed as an intermediate. In the absence of potassium oxalate, no Pd nanoparticles have been observed. The synthesized Pd nanoparticles have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selective area electron diffraction and energy dispersive analysis by X-rays (EDAX) analyses. XRD analysis indicates the preferential orientation of catalytically active {111} planes in Pd nanoparticles. A plausible mechanism has been proposed for the formation of anisotropic Pd nanoparticles.     

Fabrication of Worm-Like Nanorods and Ultrafine Nanospheres of Silver Via Solid-State Photochemical Decomposition

Worm-like nanorods and nanospheres of silver have been synthesized by photochemical decomposition of silver oxalate in water by UV irradiation in the presence of CTAB and PVP, respectively. No external seeds have been employed for the synthesis of Ag nanorods. The synthesized Ag colloids have been characterized by UV-visible spectra, powder XRD, HRTEM, and selected area electron diffraction (SAED). Ag nanospheres of average size around 2 nm have been obtained in the presence of PVP. XRD and TEM analyses revealed that top and basal planes of nanorods are bound with {111} facets. Williamson–Hall plot has revealed the presence of defects in the Ag nanospheres and nanorods. Formation of defective Ag nanocrystals is attributed to the heating effect of UV-visible irradiation.     

Fabrication and Tunable Dielectric Properties of (Ba0.7Sr0.3)TiO3-Glass-Based Thick-Film Capacitors

Ferroelectric glass–ceramics of composition 0.90 (Ba_0.7Sr_0.3) TiO₃–0.10(B₂O₃:SiO₂) (0.90 BST:0.10 BS) synthesized by sol–gel method have been used for the preparation of dielectric thick-film inks. The particle dispersion of the glass–ceramic powders in the thick-film ink formulations have been studied through rheological measurements for fabricating thick-film capacitors by screen printing technique. The thick films derived from such glass–ceramics are found to sinter at considerably lower temperatures than the pure ceramic, and exhibit good dielectric characteristics with a tunability of 32% at 1 MHz under a dc bias field of 35 kV/cm.     

Lipid and Phospholipid Profiling of Biological Samples Using MALDI Fourier Transform Mass Spectrometry

Here we describe a study of the feasibility of lipid and phospholipid (PL) profiling using matrix assisted laser desorption/ionization (MALDI) Fourier transform mass spectrometry (FTMS) for two different applications. In this work PL profiles of different mammalian tissues as well as those of whole cell organisms were examined. In particular, comparative analysis of lipid and PL profiles of tissues from mice fed different diets was done and, in another application, MALDI FTMS was used to analyze PL profiles of genetically modified Saccharomyces cerevisiae. Computational sorting of the observed ions was done in order to group the lipid and PL ions from complex MALDI spectra. The PL profiles of liver tissues from mice fed different diets showed a cross correlation coefficient of 0.2580, indicating significant dissimilarity, and revealed more than 30 significantly different peaks at the 99.9% confidence level. Histogram plots derived from the spectra of wild type and genetically modified yeast resulted in a cross correlation coefficient 0.8941 showing greater similarity, but still revealing a number of significantly different peaks. Based on these results, it appears possible to use MALDI FTMS to identify PLs as potential biomarkers for metabolic processes in whole cells and tissues.     

Amyloidogenic Properties of Peptides Derived from the VHL Tumor Suppressor Protein

The von Hippel-Lindau tumor suppressor protein (pVHL) is involved in maintaining cellular oxygen homeostasis through the regulated degradation of HIF-α. The intrinsically disordered nature of pVHL makes it prone to aggregation that impairs its function, and this is further aggravated in mutant versions of the protein, thus promoting tumor development. By using in silico analysis, we predicted six peptide fragments from pVHL to be amyloidogenic. This was verified for two of the peptides by biophysical approaches, which demonstrated self-assembly and formation of β-sheet-rich aggregates, which, under transmission electron microscopy, atomic force microscopy, and X-ray diffraction, displayed typical fibrillar amyloid characteristics. These motifs may serve as proxies for exploring the nature of pVHL aggregation.