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High entropy carbides (HECs) are a promising new class of ultra-high temperature ceramics that could provide novel material solutions for leading edges of hypersonic vehicles, which can reach temperatures > 3,500 �C and experience extreme thermal gradients. Although the mechanical and thermal properties of HECs have been studied extensively at room temperature, few works have examined HEC properties at high temperatures or considered these materials� responses to thermal shock. In this work, we measure the thermal conductivity of a five-cation HEC up to 1200 �C. We find that thermal conductivity increases with temperature, consistent with trends demonstrated in single-metal carbides. We also measure thermal conductivity of an HEC deposited with varying CH4 flow rate, and find that although thermal conductivity is reduced when carbon content surpasses stoichiometric concentrations, the films all exhibited the same temperature dependent trends regardless of carbon content. To compare the thermal shock resistance of HECs with a refractory carbide, we conduct pulsed laser ablation measurements to determine the fluence threshold the HECs can withstand before damaging. We find that this metric for the average bond strength trends with the theoretical hardness of the HECs as expected.

Raising awareness about Toxoplasma gondii infection among cat owners in Bangladesh is indispensable to formulate persuasive management tactics to avoid zoonotic infections from pet cats. However, to the authors' best knowledge, no studies have been performed in Bangladesh to determine knowledge and practices of toxoplasmosis in cat owners. Therefore, the objectives of the current study were to cover this research gap. We carried out a cross-sectional study in Bangladesh from June 2020 through December 2021. A structured online questionnaire was distributed to cat owners, which were voluntarily completed by them. The questionnaire included socio-demographic data, aetiology, transmissions, clinical signs, and preventive practices towards toxoplasmosis. Overall, 1,019 cat owners participated voluntarily in the cross-sectional survey. Among them, 793 (77.82%) participants showed poor knowledge regarding toxoplasmosis. Under specific knowledge sections, 62.51% of the participants revealed incorrect knowledge that toxoplasmosis was a zoonotic disease. In the same way, (72.03-85.77) % of the cat owners were unaware that the disease could be transmitted from improperly washed vegetables, raw or undercooked meat and fish, and contaminated water and milk with cat faeces. Respondents' age, education, occupation, residence type, and marital status were significantly (p .05) associated with their knowledge level. Besides, 94.11% of cat owners had a good practice level. They followed good practices in different issues; however, they practiced those activities without knowing their impacts on disease control. Cat owners' age, education, occupation, and residence type had a significant (p .05) association with the practice level against toxoplasmosis. This is the first study highlighting the low level of knowledge among cat owners about toxoplasmosis in Bangladesh. These knowledge gaps could increase the risk and transmission of Toxoplasma gondii infection among them and their families. The survey recommends the arrangement of educational training and programmes to increase the awareness of toxoplasmosis among cat owners.

A study was conducted to know the fertility status of coastal soils of Bangladesh for agricultural planning. Thirty composite soil samples were collected from different locations of Kalapara upazila under Patuakhali coastal district in Bangladesh with Geographic Positioning System (GPS) positions. The soil samples were analyzed for physical properties (moisture, texture, bulk density, particle density and porosity) and chemical properties (pH, electrical conductivity, total nitrogen, organic carbon, exchangeable sodium, exchangeable potassium, available sulphur and available phosphorus). The range of moisture contents of collected soils was 24 to 29% and the textural class was silty clay. The bulk density ranged from 1.30 to 1.47 gcm-3. The particle density ranged from 2.31 to 2.49 gcm-3. The porosity of soil samples ranging from 40.96 to 46.06%. The pH ranged from 5.85 to 6.45. The EC value of collected soils ranged from 3.10 to 5.12 dSm-1. The total nitrogen and organic carbon content was low to medium. The exchangeable sodium and potassium content of soils ranged from 9.22 to 18.47 meq 100g-1 and 0.16 to 0.27 meq 100g-1, respectively. The available sulphur and phosphorus content of soils ranged from 17.21 to 33.21 mg kg-1 and 17.12 to 33.09 mg kg-1, respectively. The results revealed that the soils of the study area were slightly to moderately saline and thus the nutrients present in the soils were low to medium level. Hence, salinity problem of soils should be considered before agricultural planning in the study area.

We have developed a novel set of (Mn3O4 and/or MnxNi1-xO)/NiO heterostructured nanocrystals (HNCs) that show promise for multifunctionality. A two-step procedure was used to synthesize our HNC samples. Thermal decomposition was used first to synthesize NiO core nanoparticles, while hydrothermal synthesis under varying pH conditions was then used to produce overgrowth of a MnxNi1-xO shell and/or Mn3O4 islands on the NiO core. In this work, we report on the investigation of the defects and surface/interface chemistry of our HNC samples using x-ray photoelectron spectroscopy (XPS). The results from a detailed analysis of the Mn 2p XPS spectra show that the Mn3+:Mn2+ ratio increases with the increasing pH value used in synthesis of the samples. This is consistent with a trend toward a predominance of Mn3O4 islands at higher pH values, a predominance of MnxNi1-xO shell at the lowest pH values, and a mixture of both for intermediate pH values. A reduction of the satellite features of the Ni 2p XPS with increasing pH of the synthesis medium is attributed predominantly to surface/interface defects of the HNCs. Fitting of the O 1 s XPS spectra shows that Ni-OH and Mn-OH are likely the dominant contributions to the lateral peak, whereas defects such as oxygen in an oxygen-deficient environment and/or oxygen vacancies comprise a smaller contribution. Analysis of both the Ni 2p and O 1 s XPS measured from our samples only shows evidence for a Ni2+ chemical environment (i.e., negligible Ni3+) in octahedral coordination, consistent with a rocksalt structure and well-ordered NiO or MnxNi1-xO nanomaterial. The presence of point defects and the nature of the surface/interface chemistry as determined using XPS suggests that our HNC samples may also be suitable for heterogeneous catalysis applications.

Background and Aim: Toxoplasma gondii is a protozoan parasite that is responsible for the major cause of congenital diseases, abortion, and stillbirth in humans and farm animals. Primary infection in pregnant goats due to T. gondii leads to abortion and significant economic losses in the livestock industry. Moreover, very few studies have been performed for the identification of T. gondii from aborted fetuses of goats. The study was conducted for the molecular identification of Toxoplasma gondii from aborted fetuses of goats in Chattogram, Bangladesh. Materials and Methods: Twenty aborted fetuses of goats were collected from 52 farms in the study area. A nested polymerase chain reaction (PCR) assay targeting the B1 gene was performed, and a positive sample yield of 197 bp amplified DNA products consistent with T. gondii. Results: The overall prevalence of toxoplasmosis in the aborted fetus of goats was 35.0%. Heart muscle, liver, brain, and placenta showed positive PCR results. The risk factors related to the does age, presence of cats in farms, and aborted fetus age were found to be statistically significant (p

A series of bimagnetic heterostructured nanocrystals having an antiferromagnetic NiO core and a ferrimagnetic MnxNi1–xO and/or FiM Mn3O4 island nanophase overgrowth has been synthesized under varying aqueous solution pH conditions. The two-step self-assembly process employs a thermal decomposition method to synthesize NiO nanoparticles, followed by growth of the MnxNi1–xO and/or Mn3O4 nanophase over the NiO core using hydrothermal synthesis at pH values ranging from 2.4–7.0. The environmentally benign hydrothermal process involves pH control of the protonation vs hydroxylation reactions occurring at the nanoparticle surface. TEM analysis and Rietveld refinement of XRD data show that three distinct types of heterostructured nanocrystals occur: NiO/MnxNi1–xO core–shell-like heterostructures at the pH of 2.4, mixed NiO/MnxNi1–xO and/or/Mn3O4 core-overgrowth structures for 2.4 < pH < 4.5, and predominantly NiO/Mn3O4 core-island structures for pH > 4.5. The magnetic coercivity and exchange bias of the heterostructured nanocrystals vary systematically with the pH of the aqueous solution used to synthesize the samples. The temperature-dependent magnetization and hysteresis loop data are consistent with the nature of overlayer coverage of the NiO core. Our DFT based calculations show that the MnxNi1–xO phase has ferrimagnetic properties with a stable spin orientation along the ⟨111⟩ orientation. Furthermore, the calculations show that the magnetic anisotropy constant (K1) of the Mn3O4 phase is considerably larger than that of the MnxNi1–xO phase, which is confirmed by our experimental results. The coercivity and exchange bias field are the largest for the NiO/Mn3O4 core-island nanocrystals, synthesized at a pH value of 5.0, with robust values of nearly 6 kOe and 3 kOe, respectively. This work demonstrates the tunability of hydrothermal deposition, and concomitant magnetic coercivity and exchange bias properties, of MnxNi1–xO and/or Mn3O4 nanophase overgrowth over a NiO core with pH, that makes these heterostructured nanocrystals potentially useful for magnetic device, biomedical, and other applications.

Due to their diverse bonding character and corresponding property repertoire, carbides are an important class of materials regularly used in modern technologies, including aerospace applications and extreme environments, catalysis, fuel cells, power electronics, and solar cells. The recent push for novel materials has increased interest in high entropy carbides (HECs) for such applications. The extreme level of tunability alone makes HECs a significant materials platform for a variety of fundamental studies and functional applications. We investigate the thermal conductivity of high entropy carbide thin films as carbon stoichiometry is varied. The thermal conductivity of the HEC decreases with an increase in carbon stoichiometry, while the respective phonon contribution scales with elastic modulus as the excess carbon content increases. Based on the carbon content, the HECs transition from an electrically conducting metal-like material with primarily metallic bonding to a primarily covalently-bonded crystal with thermal conductivities largely dominated by the phononic sub-system. When the carbon stoichiometry is increased above this critical transition threshold dictating bonding character, the electronic contribution to thermal conductivity is minimized, and a combination of changes in microstructure, defect concentration and secondary phase formation, and stiffness influence the phononic contribution to thermal conductivity. Our results demonstrate the ability to tune the thermal functionality of high entropy materials through stoichiometries that dictate the type of bonding environment.

Heavy metals (HMs) are natural environmental constituents, but their geochemical processes and biochemical equilibrium have been altered by indiscriminate use for human purposes. Due to their toxicity, persistence in the environment and bioaccumulative nature; HMs are well-known environmental contaminants. As result, there is excess release into natural resources such as soil and marine habitats of heavy metals such as cadmium, chromium, arsenic, mercury, lead, nickel, copper, zinc, etc. Their natural sources include the weathering of metal-bearing rocks and volcanic eruptions, while mining and other industrial and agricultural practices include anthropogenic sources. Prolonged exposure and increased accumulation of such heavy metals may have detrimental effects on human life and aquatic biota in terms of health. Finally, the environmental issue of public health concern is the pollution of marine and terrestrial environments with toxic heavy metals. Therefore, because of the rising degree of waste disposal from factories day by day, it is a great concern. Pollution of HMs is therefore a problem and the danger of this environment needs to be recognized.

High-entropy ceramics are attracting significant interest due to their exceptional chemical stability and physical properties. While configurational entropy descriptors have been successfully implemented to predict their formation and even to discover new materials, the contribution of vibrations to their stability has been contentious. This work unravels the issue by computationally integrating disorder parameterization, phonon modeling, and thermodynamic characterization. Three recently synthesized carbides are used as a testbed: (HfNbTaTiV)C, (HfNbTaTiW)C, and (HfNbTaTiZr)C. It is found that vibrational contributions should not be neglected when precursors or decomposition products have different nearest-neighbor environments from the high-entropy carbide., The contribution of vibrations to the stability of high-entropy ceramics is still controversial. Here the authors computationally integrate disorder parameterization, phonon modelling, and thermodynamic characterization to investigate the role of vibrations to the stability of high-entropy carbides.

The entropy landscape of high-entropy carbides can be used to understand and predict their structure, properties, and stability. Using first principles calculations, the individual and temperature-dependent contributions of vibrational, electronic, and configurational entropies are analyzed, and compare them qualitatively to the enthalpies of mixing. As an experimental complement, high-entropy carbide thin films are synthesized with high power impulse magnetron sputtering to assess structure and properties. All compositions can be stabilized in the single-phase state despite finite positive, and in some cases substantial, enthalpies of mixing. Density functional theory calculations reveal that configurational entropy dominates the free energy landscape and compensates for the enthalpic penalty, whereas the vibrational and electronic entropies offer negligible contributions. The calculations predict that in many compositions, the single-phase state becomes stable at extremely high temperatures (>3000 K). Consequently, rapid quenching rates are needed to preserve solubility at room temperature and facilitate physical characterization. Physical vapor deposition provides this experimental validation opportunity. The computation/experimental data set generated in this work identifies "valence electron concentration" as an effective descriptor to predict structural and thermodynamic properties of multicomponent carbides and educate new formulation selections.

Mastitis is a significant disease affecting dairy cattle farms in Egypt. The current study aimed to investigate the prevalence and major bacterial pathogens causing subclinical mastitis (SCM) in three bovine dairy herds, with a history of SCM, at three Governorates in North Upper Egypt. The antimicrobial resistance profiles and specific virulence-associated genes causing bovine SCM were investigated. One thousand sixty-quarter milk samples (QMS) were collected aseptically from 270 apparently healthy cows in three farms and examined. The total prevalence of SCM was 46% and 44.8% based on California Mastitis Test (CMT) and Somatic Cell Count (SCC), respectively. Bacteriological examination of CMT positive quarters revealed that the prevalence of bacterial isolation in subclinically mastitic quarters was 90.4% (26 and 64.3% had single and mixed isolates, respectively). The most frequent bacterial isolates were E. coli (49.8%), Staphylococcus aureus (44.9%), streptococci (44.1%) and non-aureus staphylococci (NAS) (37.1%). Antimicrobial susceptibility testing of isolates revealed a high degree of resistance to the most commonly used antimicrobial compound in human and veterinary medicine. Implementation of PCR revealed the presence of mecA and blaZ genes in 60% and 46.7% of S. aureus isolates and in 26.7% and 53.3% of NAS, respectively. Meanwhile 73.3% of streptococci isolates harbored aph(3’)-IIIa gene conferring resistance to aminoglycosides and cfb gene. All E. coli isolates harbored tetA gene conferring resistance to tetracycline and sul1 gene conferring resistance to sulfonamides. The fimH and tsh genes were found in 80% and 60%, respectively. A significant association between the phenotypes and genotypes of AMR in different bacteria was recorded. The presence of a high prevalence of SCM in dairy animals impacts milk production and milk quality. The coexistence of pathogenic bacteria in milk is alarming, threatens human health and has a public health significance. Herd health improvement interventions are required to protect human health and society.

This manuscript demonstrates ferroelectricity in B-substituted AlN thin films and a complementary set of first-principles calculations to understand their structure-property relationships. ${\mathrm{Al}}_{1--x}{\mathrm{B}}_{x}\mathrm{N}$ films are grown by dual-cathode reactive magnetron sputtering on $(110)\mathrm{W}/(001){\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ substrates at 300\ifmmode^\circ\else\textdegree\fi{}C at compositions spanning $x=0$ to $x=0.20$. X-ray diffraction studies indicate a decrease in both the $c$ and $a$ lattice parameters with increasing B concentration, resulting in a decrease in unit cell volume and a constant $c$/$a$ axial ratio of 1.60 over this composition range. Films with $0.02\ensuremath{\le}x\ensuremath{\le}0.15$ display ferroelectric switching with remanent polarizations exceeding $125\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{C}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{--2}$ while maintaining band gap energies of $g5.2\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$. The large band gap allows low frequency hysteresis measurement (200 Hz) with modest leakage contributions. At B concentrations of $xg0.15$, $c$-axis orientation deteriorates and ferroelectric behavior is degraded. Density-functional theory calculations corroborate the structural observations and provide predictions for the wurtzite $u$ parameter, polarization reversal magnitudes, and composition-dependent coercive fields.

The use of antibiotics in animals for both therapeutic and non-therapeutic purposes is a major driver of the emergence and spread of antimicrobial resistance (AMR). While several studies have investigated prescription and consumption patterns in humans, little attention has been paid to the veterinary sector. A cross-sectional study was conducted in 3002 veterinary students (VS) and non-medical students (NMS) from 12 universities in Bangladesh to explore their knowledge, attitudes and practices (KAP) about antibiotics and AMR using a self-administered questionnaire, and assess the influence of the veterinary curriculum. KAP regarding antibiotic use and AMR was significantly higher in veterinary than non-medical students, and in first-year than final-year students. However, gaps in knowledge and practices were highlighted, suggesting deficiencies in training. Moreover, final-year veterinary students were found to be more likely than first-year students to use antibiotics without instructions, which could indicate deficiencies in their curriculum. Although the study suggested a positive impact of the veterinary curriculum on KAP about antibiotics and AMR in Bangladesh, critical gaps remain that are likely to contribute to inadequate use in their future practice. Therefore, there is scope for improving educational programs on AMR in professional curricula.

Room-temperature ferrimagnetic and superparamagnetic properties, and the magnetic interactions between the core and shell, of our iron-incorporated chromia-based core shell nanoparticles (CSNs) have been investigated using a combination of experimental measurement and density functional theory (DFT) based calculations. We have synthesized CSNs having an epitaxial shell and well-ordered interface properties by utilizing our hydrothermal nanophase epitaxy (HNE) technique. The ferrimagnetic and superparamagnetic properties of the CSNs are manifested beyond room temperature and magnetic measurements reveal that the exchange bias interaction between the antiferromagnetic (AFM) core and ferrimagnetic (FiM) shell persists close to ambient temperature. The DFT calculations confirm the FiM ordering of the Fe-chromia shell. Our calculations show that the FiM ordering is associated with a band gap reduction, Fe–O d–p orbital hybridization, and AFM type Fe–Cr σ type superexchange interaction in the α-Fe0.40Cr1.60O2.92 shell of the CSNs. The novel magnetic core–shell nanoparticles possess a shell comprised of a metastable Fe(II)-chromia phase, resulting in unique magnetic properties that make them ideal for magnetic device and medicinal applications.

The search for new materials via compositional exploration has recently led to the discovery of entropy stabilized and high entropy ceramics. The chemical diversity in the cation sublattice of high entropy ceramics has led to many enhanced properties and applications such as reversible energy storage, low temperature water splitting, amorphous-like thermal transport in crystalline solids and enhanced mechanical properties. This work describes the synthesis and mechanical properties of high entropy (HfNbTaTiZr)Cx thin films as a function of carbon content. The nature of the bonding and microstructure evolves as the material transforms from metallic to ceramic to nanocomposite with variations in the quantity and types of carbon, yielding large variations in the film hardness. Through multiple characterization techniques and first principles investigations, we separate the roles of microstructure and bonding characteristics in the mechanical property development of (HfNbTaTiZr)Cx thin films. This study presents a strategy to establish the bonding, structure, and property relationships in chemically disordered high entropy ceramics, largely based on the relative populations of filled or empty antibonding states for which there are new abilities to do so in high configurational entropy systems that exhibit high solubility of diverse cations while retaining rocksalt structure.

Due to their diverse bonding character and corresponding property repertoire, carbides are an important class of materials regularly used in modern technologies, including aerospace applications and extreme environments, catalysis, fuel cells, power electronics, and solar cells. The recent push for novel materials has increased interest in high entropy carbides (HECs) for such applications. The extreme level of tunability alone makes HECs a significant materials platform for a variety of fundamental studies and functional applications. We investigate the thermal conductivity of high entropy carbide thin films as carbon stoichiometry is varied. The thermal conductivity of the HEC decreases with an increase in carbon stoichiometry, while the respective phonon contribution scales with elastic modulus changes as the excess carbon content increases. Based on the carbon content, the HECs transition from an electrically conducting metal-like material with primarily metallic bonding to a primarily covalently bonded crystal with thermal conductivities largely dominated by the phononic sub-system. When the carbon stoichiometry is increased above this critical transition threshold dictating bonding character, the electronic contribution to thermal conductivity is minimized and remains at a constant, and a combination of changes in film morphology and phase precipitation systematically lower the phononic contribution to thermal conductivity. This trend in thermal conductivity with carbon content in the HECs is opposite to those observed in binary metal carbide systems. Our results demonstrate the ability to tune the thermal functionality of high entropy materials through stoichiometries that dictate the type of bonding environment.

This manuscript reports the temperature dependence of ferroelectric switching in Al0.84Sc0.16N, Al0.93B0.07N, and AlN thin films. Polarization reversal is demonstrated in all compositions and is strongly temperature dependent. Between room temperature and 300 °C, the coercive field drops by almost 50% in all samples, while there was very small temperature dependence of the remanent polarization value. Over this same temperature range, the relative permittivity increased between 5% and 10%. Polarization reversal was confirmed by piezoelectric coefficient analysis and chemical etching. Applying intrinsic/homogeneous switching models produces nonphysical fits, while models based on thermal activation suggest that switching is regulated by a distribution of pinning sites or nucleation barriers with an average activation energy near 28 meV.

The search for new materials via compositional exploration has recently led to the discovery of entropy stabilized and high entropy ceramics. The chemical diversity in the cation sublattice of high entropy ceramics has led to many enhanced properties and applications such as reversible energy storage, low temperature water splitting, amorphous-like thermal transport in crystalline solids and enhanced mechanical properties. This work describes the synthesis and mechanical properties of high entropy (HfNbTaTiZr)Cx thin films as a function of carbon content. The nature of the bonding and microstructure evolves as the material transforms from metallic to ceramic to nanocomposite with variations in the quantity and types of carbon, yielding large variations in the film hardness. Through multiple characterization techniques and first principles investigations, we separate the roles of microstructure and bonding characteristics in the mechanical property development of (HfNbTaTiZr)Cx thin films. This study presents a strategy to establish the bonding, structure, and property relationships in chemically disordered high entropy ceramics, largely based on the relative populations of filled or empty antibonding states for which there are new abilities to do so in high configurational entropy systems that exhibit high solubility of diverse cations while retaining rocksalt structure.

Magnetic core shell nanoparticles (NPs) have potential for applications in magnetic random access memory, spintronic devices, and drug delivery systems. Our investigations are focused on the synthesis of inverted core shell nanoparticles and characterization of their structural and magnetic properties. By using our hydrothermal nanophase epitaxy technique, we are able to synthesize well-ordered α-Cr2O3@α-MxCr2-xO3 (M = Co, Ni, Mn, Fe) inverted core-shell nanoparticles. This typically results in the formation of novel phases of MxCr2-xO3 shells having ferromagnetic/ferrimagnetic (FM/FiM) spin ordering and an antiferromagnetic (AFM) Cr2O3 core structure. The combined results from XRD and high-resolution TEM (HRTEM) provide evidence of the presence of corundum phase both in the shell and in the core regions. HRTEM results also show a sharp interface exhibiting epitaxial atomic registry of shell atoms over highly ordered core atoms whereas TEM-EDX analyses show that the M atoms reside predominantly in the shell regions. The XPS analyses of the NPs indicate the M transition metals incorporated in the shell are in the +2 oxidation state. Magnetic measurements show well developed hysteresis loops: The field cooled hysteresis loops reveal horizontal shifts in the applied field axis and vertical shifts in the magnetization axis, relative to the zero-field cooled hysteresis loops. This provides direct evidence for the exchange bias effect between the AFM α-Cr2O3 core and the FM/FiM α-MxCr2-xO3 shell. The XPS data are consistent with oxygen vacancy formation in order to maintain charge neutrality upon substitution of the M2+ ion for the Cr3+ ion in the α-MxCr2-xO3 shell. The FM/FiM ordering in the shell may at least partially result from the F-center exchange coupling between the oxygen-vacancy induced bound magnetic polaron and nearby cations.

We have synthesized bimagnetic core–shell nanoparticles containing a first-of-its-kind Ni(II)-chromia nanophase shell and a well-defined, epitaxial core–shell interface. Magnetic measurements reveal a substantial coercivity of the nanoparticles and a significant exchange bias effect between the antiferromagnetic chromia core and the ferromagnetic Ni(II)-chromia shell at low temperatures. The ferromagnetism and a weak exchange bias effect are found to persist to room temperature in the core–shell nanoparticles of ∼57 nm average size. Our first principles Density Functional Theory (DFT) calculations confirm that the novel corundum-structured Ni(II)-chromia phase has an equilibrium cluster-localized ferromagnetic spin configuration. In addition, the DFT-based calculations show that the Ni(II)-chromia phase is a Mott–Hubbard insulator, with a narrowed energy band gap and increased covalent bonding due to strong hybridization between Ni 3d and O 2p levels in the upper portion of the valence band and within the band gap region. The antiferromagnetic, ferromagnetic and magnetoelectric properties of our core–shell nanoparticles make these well suited for patterned recording media and biomedical applications.

The influence of Mg addition on the corrosion behaviour of as-cast and heat treated Al–4.5Cu–3.4Fe in-situ composite was investigated. The composite was produced by solidification processing whereby Al3Fe intermetallic formed in-situ in Al–Cu matrix. Magnesium additions were made to the composite to modify the microstructure of the in-situ composite. Specimens were then heat treated at 580 °C for homogenization. The as-cast and heat treated in-situ composites were subjected to corrosive media comprising of NaCl + H2O2 solution and the corrosion rate was evaluated by gravimetric weight loss method. Both the as-cast and heat treated in-situ composite were found to be susceptible to intergranular corrosion (IGC), the heat treated specimens being less prone to attack. Optical and scanning electron micrographic observation of the corroded surface revealed highly corroded network in the as-cast in-situ composite. On the contrary, the heat treated composite revealed minimal corrosion network. The rate of corrosion and the IGC network for both the as-cast and heat treated in-situ composite decreases as Mg additions are increased.

Core–shell nanoparticles have potential for a wide range of applications due to the tunability of their magnetic, catalytic, electronic, optical, and other physicochemical properties. A frequent drawback in the design of core–shell nanoparticles and nanocrystals is the lack of control over an extensive, disordered, and compositionally distinct interface that occurs due to the dissimilarity of structural and compositional phases of the core and shell. In this work, we demonstrate a new hydrothermal nanophase epitaxy (HNE) technique to synthesize highly structurally ordered α-Cr2O3@α-Co0.38Cr1.62O2.92 inverted core–shell nanoparticles (CSNs) with evidence for the nanoscale growth of corundum structure beginning from the core and extending completely into the shell of the CSNs with minimal defects at the interface. The high-resolution TEM results show a sharp interface exhibiting epitaxial atomic registry of shell atoms over highly ordered core atoms. The XPS and Co K-edge XANES analyses indicate the +2 oxidation state of cobalt is incorporated in the shell of the CSNs. Our XPS and EXAFS results are consistent with oxygen vacancy formation in order to maintain charge neutrality upon substitution of the Co2+ ion for the Cr3+ ion in the α-Co0.38Cr1.62O2.92 shell. Furthermore, the CSNs exhibit the magnetic exchange bias effect, which is attributed to the exchange anisotropy at the interface made possible by the nanophase epitaxial growth of the α-Co0.38Cr1.62O2.92 shell on the α-Cr2O3 core of the nanoparticles. The combination of a well-structured, sharp interface and novel nanophase characteristics is highly desirable for nanostructures having enhanced magnetic properties.

Normal 0 MicrosoftInternetExplorer4 Viscous dissipation and Joule heating effects on steady MHD combined heat and mass transfer flow through a porous medium along a semi-infinite vertical porous plate in a rotating system has been studied numerically. The boundary layer equations have been transformed into dimensionless coupled nonlinear ordinary differential equations by appropriate transformations. The similarity solutions of the transformed dimensionless equations for the flow field and heat and mass transfer characteristics are obtained by shooting iteration technique. Numerical results are presented in the form of primary and secondary velocities, temperature and concentration distributions within the boundary layer for different parameters entering into the analysis. Finally, the effects of the pertinent parameters on the Skin-friction coefficients, Nusselt number and Sherwood number are also examined. Keywords: MHD; Joule heating; porous medium; rotating system simulation. doi: http://dx.doi.org/10.3329/jname.v8i2.5055 Journal of Naval Architecture and Marine Engineering 8(2011) 105-120

New dinuclear Ru complexes of bis-tridentate 2,6-bis(benzimidazol-2-yl)pyridine derivatives, [Ru2(terpy)2(H4Ln)]4+ (terpy = 2,2′:6′,2″-terpyridine, n = 0∼2), have been synthesized. The Ru complexes act as tetrabasic acids, in which N–H protons on benzimidazole moieties are responsible for a deprotonation site. Both the absorption spectra and oxidation potentials are strongly dependent on the solution pH, which leads to the basis of a proton-induced molecular switch. The dinuclear Ru complexes bridged by bis-tridentate bis{2,6-bis(benzimidazol-2-yl)pyridine} show a lower Ru(II/III) oxidation potential but almost similar MLCT absorption maxima, compared to the corresponding dinuclear Ru complexes with “back-to-back” bis-2,2′:6′,2″-terpyridine bridging ligands. These results indicate that the bis-tridentate bis{2,6-bis(benzimidazol-2-yl)pyridine} ligand has a stronger σ/π donor property and a weaker π-acceptor property than the bis-2,2′:6′,2″-terpyridine bridging ligand. The solubility of Ru complexes in solution is progressively decreased with increasing number of phenyl group in the bridging ligand, and therefore it becomes difficult to study the change of chemical properties for external stimuli such as pH change. Immobilization of complexes on a solid surface is one of the approaches to overcome their low solubility. The [Ru2(bpbbip)2(H4L0)]4+ complex with phosphonate groups (bpbbip = 2,6-bis(1-(4-diphosphonyl)butylbenzimidazol-2-yl)pyridine) was successfully immobilized on an ITO electrode and characterized by means of XPS, and cyclic voltammetry. The Ru complex monolayers exhibit a reversible Ru(II/III) oxidation at +0.80 V vs. Ag/AgCl in 0.1 M aqueous HClO4. The immobilized Ru complex monolayer is stable over the pH range 1 < pH < 10. The oxidation potential, E½, vs. pH plot reveals several lines, indicating that the proton-coupled oxidative reactions occur on the ITO surface. The phosphonate-immobilized Ru dinuclear complex monolayers exhibited a stable electrochromic response on an ITO electrode.

A novel amphiphilic Ru(II) complex, Ru(L18)(tpy-PO3H)PF6, where L18 = 2,6-bis(N-octadecylbenzimidazol-2-yl)pyridine and tpy-PO3H = 2,2‘;6‘,2‘ ‘-terpyridine-4‘-phosphonic acid, was synthesized. The ...

A series of mono- and dinuclear Ru complexes containing a bridging ligand, L-diimide-L (L = 2-(2-pyridyl)benzimidazole; diimide = benzene-1,2:4,5-bis(dicarboximide) (bdi; pyromellitimide) or naphthalene-1,8:4,5-bis(dicarboximide) (ndi), with either propane or xylene group as linkers, have been prepared. The mono- and dinuclear Ru complexes containing the bdi or ndi ligand, exhibit characteristic metal-to-ligand charge transfer (MLCT) transition at 458 nm. The mono- and dinuclear Ru/Os complexes exhibit a rich redox chemistry arising from both M(II) to M(III) oxidation and ligand-based consecutive reduction of diimide and 2,2'-bipyridine (bpy) ligands. The emission decays fit well with double- or triple-exponential decay models. The non-exponential decay curve reveals the existence of several conformers in solution due to the flexible propane or p-xylene linker. The much shorter emission lifetimes of the [M(bpy)2(L-diimide-L)] complexes compared with the parent [M(bpy)2L] indicates the intramolecular electron-transfer from the excited M(bpy)2 moiety to the diimide. The fastest rates of electron transfer (3 · 1010 s-1) are attributable to the folded conformers suitable for the electron donor/acceptor through-space interaction. A time-resolved absorption spectroscopic study of the dinuclear bdi and ndi complexes revealed appearance of the electron-transfer products, M(III) and the diimide radical anion, and their rapid disappearance. The effect of the linkers of the ligand L-diimide-L on the rates of electron transfer and the back electron transfer is also discussed.

A novel dinuclear ruthenium complex, [(tpy)Ru(tmbimbpyH 4 )Ru(tpy)](ClO 4 ) 4 , has been synthesized to introduce a new proton-induced molecular switching system, where tpy=2,2′:6′,2″-terpyridine and tmbimbpyH 4 =2,6,2′,6′-tetra(4,5-dimethylbenzimidazol-2-yl)-4,4′-bipyridine. Both fully protonated and deprotonated forms of the dinuclear Ru complex were isolated and the forms were interchangeable by the addition of acid or base. A longer wavelength shift and a negative oxidation potential shift were observed when the protonated Ru complex was fully deprotonated.

We have examined the applicability of ‘metal complex as a ligand’ strategy at the interface by using the Ru complexes acting as a ligand. New amphiphilic ruthenium complexes containing 2,6-bis(1-octadecylbenzimidazolyl)-pyridine (L18), [Ru(L18)(X)]2+ were synthesized, where X=2,3,5,6-tetrakis(2′pyridyl)pyrazine (tppz) and 1,4-bis(2,2′ : 6′, 2″-terpyridine-4′-yl)benzene (bteb), in which the bis-tridentate ligand (tppz or bteb) of [Ru(L18)(X)]2+ can act not only as a hydrophilic head group but also as a coordination site to a metal ion from the subphase at the air–water interface. These amphiphilic Ru complexes lead to a stable Langmuir–Blodgett (LB) film formation. The incorporation of metal ion from subphase at the air–water interface was proved by the measurements of π–A isotherms, UV spectra and angular dependent XPS spectra.

The charge separated(CS) state was efficiently formed as a result of stepwise electron transfer reactions in a novel Ru(II)(bpy)2-diimide-Os(III)(bpy)2 triad system (efficiency > 0.7); the rate of electron transfer and the charge separation yield were determined from picosecond time-resolved absorption spectra.