Phase Synthesis Research Articles

Ceramic Immobilization Options for Technetium

ABSTRACTLong half-life biologically active fission products, such as technetium-99, present particular problems for the disposal of spent nuclear fuel (SNF). Technetium is present in relatively high concentrations in fuel (approx. 1kg tonne-1 SNF) and has very high mobility in oxidizing environments. Technetium is therefore generally removed from SNF either by solvent extraction and reduction, during the PUREX process, or by sorption via ion exchange processes. Historically technetium has been disposed of via dilution and dispersion in the sea but stringent regulations now mean that the preferred long term option is immobilization in a highly stable and durable matrix. In this contribution we have looked at the synthesis of fluorite derivative crystalline host phases based on the zirconolite structure. Samples have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), thermo-gravimetric analysis (TG), and mass spectroscopy (MS). We have used Mo as an inactive surrogate for Tc.

Mechanical activation-assisted electro-thermal explosion synthesis of the Ti2AlC phase

ABSTRACTThis study deals with the synthesis of the Ti2AlC phase using the Electro-Thermal Explosion under Pressure with Confinement (ETEPC) technique. The effects of the ETEPC technique and the milling process parameters on the TiCx phase content and the formation mechanism of the Ti2AlC phase were investigated. The latter is mainly affected by the morphology of the powder mixture and aluminum melted amount. The optimization of the above parameters allowed the achievement of the desired reaction, leading to the formation of the Ti2AlC phase with a purity of about 97 wt%. The results clearly demonstrate that the ETEPC process enables one to control both time and material synthesis temperature.

A non-revisiting artificial bee colony algorithm for phased array synthesis

An effective non-revisiting artificial bee colony (NrABC) algorithm based on the paradigm of artificial bee colony (ABC) is developed in this paper. NrABC is applied to tackle the synthesis of phased linear arrays. Pros and cons of NrABC is provided along with a comparison to standard ABC. Binary space partitioning tree structure is used to record history evolutionary information. Non-revisiting scheme assures NrABC keeping good diversity of population. Moreover, scout bee stage is discarded in NrABC which also removes an algorithmic parameter of standard ABC. Three phased array synthesis examples are employed to study the performance of NrABC. It turns out that under the same experimental configuration, NrABC outperforms standard ABC in terms of both solution quality and reliability in repeated runs.

Conversion of protonic magadiite to PLS-1 zeolite: thermal stability and acidity

AbstractA synthetic protonic magadiite was used as a silica source to prepare zeolitic material (PLS-1) in the presence of tetramethylammonium hydroxide and water. The conversion of the protonic magadiite to the PLS-1 phase was achieved at 150°C after 5 days, or at 170°C after 3 days for SiO2: TMAOH:H2O molar ratios of 2.54:1:4.4. The synthesis of the pure PLS-1 phase depended also on the amounts of tetramethylammonium hydroxide and water used. Analysis by 29Si magic angle spinning nuclear magnetic resonance spectroscopy confirmed the layered character of the PLS-1 phase with a resonance at −93 ppm, and its dehydroxylation-condensation process. The chemical formula of (TMA)2Si18O33(OH)6 for PLS-1 was refined with the Rietveld method and the tetrahedron-splitting model. The later model has been proposed to describe the presence of silanol defects in the layered structure of PLS-1. Upon calcinations of the PLS-1 phase at temperatures >400°C, the removal of TMA cations and dehydroxlyation of PLS-1 layers resulted in a three-dimensional structure phase identified as the CDS-1 phase, with a chemical formula of Si18O36. The CDS-1 phase exhibited a large specific surface area of 288 m2/g and microporous character, as indicated by the nitrogen adsorption isotherms. The temperature-programmed desorption profile of ammonia indicated that CDS-1 exhibited one weak type of acid sites, confirmed, by pyridine desorption studies, as weak Lewis acid sites.

Synthesis and photoluminescence of the solid phases of the binary system of mixed-ligand Eu(III) and Tb(III) dithiophosphinate complexes

Solid phases of the [Eu(Phen)(i-Bu2PS2)2(NO3)]–[Tb(Phen)(i-Bu2PS2)2(NO3)] binary system are synthesized. The results of X-ray diffraction phase analysis and photoluminescence measurements allow the synthesized isostructural phases to be classed with substitutional solid solutions. The photoluminescence measurements revealed Tb(III)→Eu(III) energy transfer which induces Eu3+ luminescence.

Aroma volatile analyses and 2AP characterization at various developmental stages in Basmati and Non-Basmati scented rice (Oryza sativa L.) cultivars.

BackgroundRice plant growth is comprised of distinct phases, such as vegetative, reproductive, grain filling and maturity phases. In these phases synthesis and availability of primary and secondary metabolites including volatile organic compounds (VOC’s) is highly variable. In scented rice, aroma volatiles are synthesized in aerial plant parts and deposited in mature grains. There are more than 100 VOCs reported to be responsible for flavor in basmati rice. It will be interesting to keep track of aroma volatiles across the developmental stages in scented rice. Therefore, the aroma volatiles contributing in aroma with special reference to the major compound 2 acetyl-1-pyrroline (2AP) were screened at seven developmental stages in scented rice cultivars Basmati-370 and Ambemohar-157 along with non-scented rice cultivar IR-64 as a control following HS-SPME-GC-MS method. In addition, the expression levels of key genes and precursor levels involved in 2AP biosynthesis were studied.ResultsThe study indicated that volatilome of scented rice cultivars is more complex than non-scented rice cultivar. N-heterocyclic class was the major distinguishing class between scented from non-scented rice. A total of 14 compounds including, 2AP were detected specifically in scented rice cultivars. Maximum number of compounds were synthesized at seedling stage and decreased gradually at reproductive and maturity. The seedling stage is an active phase of development where maximum number green leaf volatiles were synthesized which are known to act as defense molecules for protection of young plant parts. Among the 14 odor active compounds (OACs), 10 OACs were accumulated at higher concentrations significantly in scented rice cultivars and contribute in the aroma. 2AP content was highest in mature grains followed by at booting stage. Gene expression analysis revealed that reduced expression of betaine aldehyde dehydrogenase 2 (badh2) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and elevated level of triose phosphate isomerase (TPI) and Δ1-Pyrolline-5-carboxylic acid synthetase (P5CS) transcript enhances 2AP accumulation.ConclusionsMost diverse compounds were synthesized at seedling stage and OACs were accumulated more at flowering followed by seedling stage. Distinct accumulation pattern exists for 2AP and other aroma volatiles at various developmental stages. The study revealed the mechanism of 2AP accumulation such that 2AP in mature grains might be transported from leaves and stem sheath and accumulation takes place in grains.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0113-6) contains supplementary material, which is available to authorized users.

Pharmacological Inhibition of Myostatin Protects Against Atrophy and Weakness after ACL Tear

Objectives:Many patients who suffer ACL tears have persistent atrophy and weakness even after rehabilitation. Myostatin is a cytokine that directly induces muscle atrophy, and previous studies using rodent models and patients have demonstrated an up regulation of myostatin after ACL tear. Using a preclinical rat model, our objective was to determine if the use of a bioneutralizing antibody against myostatin could prevent muscle atrophy and weakness after ACL tear.Methods:This study was approved by our IACUC. The left ACL and was transected in 3mo-old male F344 rats. At the time of surgery rats received a single IP injection of either a bioneutralizing antibody against myostatin (10B3, GlaxoSmithKline) or a sham IgG (E1-82.15, GlaxoSmithKline) at a dose of 10mg/kg. Rats (N=8 per group) were sacrificed and tissue was harvested 7 days or 21 days after tear. Contractile force measurements of the extensor digitorum longus (EDL) were performed. The size of muscle fibers in histological sections from the EDL and distal vastus lateralis were also measured. RNA was isolated from the distal rectus femoris and gene expression analysis was performed with RT-qPCR. The expression of each gene was normalized to b actin, and further normalized to the expression of muscles from control, uninjured rats. A two-way ANOVA (alpha=0.05) followed by Holm Sidak post hoc sorting was used to evaluate the effect of time and treatment on measured parameters.Results:Inhibition of myostatin resulted in an increase in muscle fiber size at the 21D time point compared to all other groups (Table 1). While both the sham antibody and myostatin antibody groups increased maximum isometric force production from 7D to 21D, the myostatin antibody group at 21D had a further increase in force compared to the 21D sham group. The muscle E3 ubiquitin ligases atrogin-1 and muscle ring finger 1 (MuRF-1) are the major rate limiting enzymes in muscle protein degradation, and inhibition of myostatin resulted in decreases in the expression of these genes at 7D (Figure 1A). Additionally, IGF-1Ea and IGF-1Eb which are important growth factors that induce muscle protein synthesis, were elevated in the myostatin antibody groups at the 21D time point. For genes related to fibrosis (Figure 1B), although there was no significant difference in MMP-2, there was a significant decrease of MMP-8 expression in the 21D MSTN group when compared to the 21D sham. There were also increases in the expression of TIMP-1 and 2 in the 21D MSTN group.Conclusion:In a preclinical rat model, the targeted inhibition of myostatin protected leg muscles from muscle atrophy and improved force production after ACL tear. While the mechanism of action is not entirely clear, it is possible that the inhibition of myostatin preserves strength by limiting the expression of proteolytic enzymes in the post-acute atrophy phase and increasing protein synthesis in later phases.

Design and Simulation of a Reflectarray Antenna using New Cell for Different Beam Angles

In this paper a new cell is proposed for reflectarray antenna and is used to design the antenna to obtain to maximum gain and efficiency using phase synthesis in a frequency band of 11 GHz up to 11.7 GHz for different beam angles. The proposed cell is a double ring of hexagon which introduces multiple resonances which can provide more than 360 degrees phase variation by changing the loop size. Design method is based on phase-only algorithm where amplitude of the field on the reflectarray surface is forced by the feed. A 1.2 m reflectarray is designed for different beam directions. The results show maximum directivity of 42 dB and maximum efficiency of 73% for the required bandwidth. Focal length is 1.5 m which is set for maximum efficiency.

Synthesis and study of mesoporous xerogels and nanopowders of a metastable solid solution 97ZrO2–3Y2O3 for the fabrication of catalyst substrates

The—technology of the liquid-phase synthesis of metastable phases in the ZrO2–Y2O3 system has been developed. Mesoporous xerogels with the specific surface area of ~350 m2/g and monophase nanopowders (5–10 nm) of the tetragonal solid solution (ZrO2)0.97(Y2O3)0.03 have been obtained and their structural peculiarities have been revealed. The efficiency of the suggested technology and good prospects of the synthesized ZrO2-based precursors in creating catalysts’ substrates have been demonstrated.

Synthesis of a stationary phase based on silica modified with branched octadecyl groups by Michael addition and photoinduced thiol-yne click chemistry for the separation of basic compounds.

A novel silica-based stationary phase with branched octadecyl groups was prepared by the sequential employment of the Michael addition reaction and photoinduced thiol-yne click chemistry with 3-aminopropyl-functionalized silica microspheres as the initial material. The resulting stationary phase denoted as SiO2 -N(C18)4 was characterized by elemental analysis, FTIR spectroscopy and Raman spectroscopy, demonstrating the existence of branched octadecyl groups in silica microspheres. The separations of benzene homologous compounds, acid compounds and amine analogues were conducted, demonstrating mixed-mode separation mechanism on SiO2 -N(C18)4 . Baseline separation of basic drugs mixture was acquired with the mobile phase of acetonitrile/H2 O (5%, v/v). SiO2 -N(C18)4 was further applied to separate Corydalis yanhusuo Wang water extracts, and more baseline separation peaks were obtained for SiO2 -N(C18)4 than those on Atlantis dC18 column. It can be expected that this new silica-based stationary phase will exhibit great potential in the analysis of basic compounds.

Synthesis of a decagonal phase in the Al–Cu–Fe–Cr system by mechanical alloying

Quasicrystalline Al–Cu–Fe–Cr alloys have been prepared by mechanical activation. The morphology of powder particles has been investigated after thermomechanical processing under various conditions. We have identified the sequence of phase transformations in the quaternary alloys in the stability region of quasicrystalline phases and optimized conditions for obtaining a maximum fraction of a decagonal state in powder materials.

Particle-loaded monolithic materials for separations via planar electrochromatography

The synthesis and characterization of novel stationary phases for analytical applications as well as for planar electrochromatography are presented. The stationary phases are C8-functionalized silica-based monoliths, which are supported by silica particles in order to avoid shrinkage and to increase mechanical stability. After optimizing the separation conditions in capillaries for capillary electrochromatography (CEC), the novel materials were implemented in a planar test cell and tested for the electrochromatochraphic separation of polyaromatic hydrocarbons (PAHs). Although the change of geometries implied a scale-up of the filling procedure, high separation performances with theoretical plate numbers of up to 30,000 m−1 and throughputs of 50 mL h−1 could be achieved.

Synthesis of quasi-crystalline phases in the Al–Cu–Fe–Cr system

Phase equilibria in the Al–Cu–Fe system alloyed with 5% Cr were studied. Based on the data of X-ray powder diffraction analysis, electron microscopy, and differential thermal analysis, the effect of temperature on i ⇔ d phase transitions in alloys Al65Cu25Fe5Cr5 and Al70Cu20Fe5Cr5. In the Al–Cu–Fe–Cr system, multiphase structures were detected; these structures are mixtures of quasi-crystalline and approximant phases, the contents and morphologies of which depend on the composition of the initial mixture and the crystallization rate.

The synthesis and characterization of novel brush-type chiral stationary phase based on terpenoid selector for resolution of chiral drugs

In the light of the chiral resolution mechanism and structures of brush-type CSP, a new chiral selector 4′-carboxyl-1′-ursolic methyl ester-3β-yl-benzoate has been prepared. Then the terpenoid chiral selector was covalently linked to 3-aminopropyl silica gel. Its structure identification data are provided by 1H NMR, MS and elementary analysis. The enantiodiscriminating capability of the brush-type CSP was evaluated by static adsorption experiment with methyl mandelate, aniline derivative of mandelic acid, benzoin and ibuprofen. Experimental results demonstrated that the chiral selector has selectivity, and the enantiomers of methyl mandelate and ibuprofen could be separated on the CSP, which indicated that the novel brush-type CSP possess a bright prospects for chiral separation potentially.

Plasmadynamic synthesis of dispersed crystalline phases in supersonic jet of boron carbon electrodischarged plasma

The possibility for the direct plasmadynamic synthesis of dispersed crystalline boron carbide in a supersonic jet of boron carbon electrodischarged plasma flowing into a chamber filled with argon at ambient pressure and temperature is shown. Phase composition is determined using X-ray diffraction. Particle morphology is shown using electron microscopy.

Physicochemical properties of low-hydrated zirconium and hafnium hydroxides and their thermolysis products

We have studied the physicochemical properties of low-hydrated zirconium and hafnium hydroxides with the general formula M(OH)3–1O0.5–1.5 · mH2O (M = Zr, Hf) as precursors for the synthesis of zirconiumand hafnium-based oxide phases.

Effect of Mg/B2O3 molar ratio and furnace temperature on the phase evaluation and morphology of SiC–B4C nanocomposite prepared by MASHS method

In this study, SiC–B4C nanocomposite has been synthesized in situ successfully by Mechanical activated combustion synthesis method (MASHS). Initially Si, C, B2O3 and Mg powders as raw materials were weighed according to different molar ratio of Mg to B2O3. In next step theses materials were milled in a planetary mill under Ar atmosphere. The synthesis step was performed in a tube furnace equipped with controlled atmosphere system. The different furnace temperature was investigated on the phase synthesis and morphology of the products. The specimens in the various steps were studied by XRD analysis for evaluation of the phase compositions and calculation of the average crystallite size of them. The morphology of synthesized products was investigated by scanning and transmission electron microscopes (SEM&TEM). The final product contains main phases MgO, B4C and SiC. Also, In this sample byproducts were characterized such as Mg3B2O6, Mg2B2O5 and remaining carbon. XRD pattern of synthesized sample showed the considerable effect of increasing Mg to B2O3 molar ratio on reducing the amount of Mg3B2O6, Mg2B2O5 and remaining carbon. SiC–B4C composite was synthesized with more homogenous morphology by reducing the furnace temperature from 1000 to 900 °C, but reduction of temperature up to 800 °C give rise to uncompleted reaction whereas some unreacted Si remains. Average crystallite sizes of optimal sample were calculated 10.5 and 8 nm for SiC and B4C respectively. These values are consisted of the TEM results somehow while grain size was less than 70 nm. Also SEM observation showed fine grains with sizes falling in the nanometer range.

MANAGEMENT OF THE MICROSTRUCTURE AND PROPERTIES OF FERRITE BY MEANS OF TWO–PHASIC SYNTHESIS

Two−phase influence on microstructure and property of ferrite of different purpose was investigated. It is shown that fine dispersed component doped at the second step (milling) effectively brakes growth of grains, promoting reception of dense, homogeneous, fine−grained ferrite materials. Thus such properties as initial magnetic permeability, mechanical strength essentially raise and magnetic losses decrease. Change of modes of baking allows to receive coarse−grained homogeneous materials.Influence of two−phase synthesis on a microstructure and property nickel−zinc, manganese−zinc, lithium−titanic ferrite spinels is more below considered discussed.

Singularities in cylindrical vector beams

Cylindrical vector beams with azimuthal and radial polarization distributions are studied for singularities. It is shown experimentally that these beams have screw dislocation as well as edge dislocation at the same time. The relation between phase and polarization of light beam is the key to understand this fact. We envisage that this has potential application in phase synthesis using polarization engineering. Further, the polarization singularities in these inhomogeneously polarized beams are examined by measuring Stokes parameters across the cross-section of these beams.

Laser in situ synthesis of gradient aluminides in metal matrix composite during DMD process

The suitability of direct metal deposition process of exothermic powders (Ni-Al, Ti-Al, Fe-Al systems), traditionally used in the self-propagating high-temperature synthesis technology, is described. Owing to the synthesis of new intermetallic phases, the overlapping of laser in situ synthesis and layerwise deposition processes makes it possible both to obtain more durable parts of complex shape, and to enlarge the functional resource of these functional-graded structures. Besides, relationships between the main laser deposition parameters and the intermetallic phase structures of the built-up objects were studied. In our research we applied optical microscopy, X-ray analysis, microhardness measurement and SEM with EDX analysis of the laser-fabricated intermetallics.