High-purity Samples Research Articles

^{7}Be(n,p)^{7}Li Reaction and the Cosmological Lithium Problem: Measurement of the Cross Section in a Wide Energy Range at n_TOF at CERN.

We report on the measurement of the ^{7}Be(n,p)^{7}Li cross section from thermal to approximately 325keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the big bang nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and they showed a large discrepancy between each other. The measurement was performed with a Si telescope and a high-purity sample produced by implantation of a ^{7}Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low energy, relative to current evaluations, in the region of BBN interest, the present results are consistent with the values inferred from the time-reversal ^{7}Li(p,n)^{7}Be reaction, thus yielding only a relatively minor improvement on the so-called cosmological lithium problem. The relevance of these results on the near-threshold neutron production in the p+^{7}Li reaction is also discussed.

Utilization of Water Utility Lime Sludge for Flue Gas Desulfurization in Coal-Fired Power Plants: Part II. Lime Sludge Characterization and Mercury Reemission.

The feasibility of utilizing lime sludge in the flue gas desulfurization process of coal-fired power plants was evaluated through laboratory-scale studies. Eight lime sludge samples, collected from various water treatment plants, and a high-purity limestone sample were extensively characterized and tested for their ability to capture SO2 from a simulated flue gas, while investigating the mercury reemission profiles during the scrubbing process. The reactivity of lime sludge samples for acid neutralization was significantly higher than the reactivity of the tested limestone sample. At doses less than that of the limestone sample, the lime sludge materials reduced the SO2 concentration from 2,000 to <0.5 ppm. The residual lime, higher surface area, and more accessible pores in lime sludge samples were the major factors contributing to their higher reactivity. Concentrations of several elements including B, Mg, Mn, Fe, Cu, Zn, As, Sr, and Ba in some of the tested lime sludge samples were considerably higher than those elements in the limestone. However, no significant leaching of these elements into the scrubber solutions was observed. To investigate mercury reemission during the scrubbing process, ionic mercury was introduced into the simulated slurry and mercury reemission was monitored continuously. Results showed that compared with the limestone sample, the lime sludge samples tested had lower or similar cumulative mercury reemissions. However, different lime sludge samples showed different emission profiles. No conclusive correlation between the composition or trace element content of lime sludge samples and their mercury reemission could be identified. This result was likely due to the oxidative condition of the scrubbing process, which prohibited the reducing species from transforming the ionic mercury into elemental mercury.

Screened moments and extrinsic in-gap states in samarium hexaboride

Samarium hexaboride (SmB6) is a Kondo insulator, with a narrow gap due to hybridization between localized and conduction electrons. Despite being an insulator, many samples show metal-like properties. Rare-earth purification is exceedingly difficult, and nominally pure samples may contain 2% or more of impurities. Here to determine the effects of rare-earth doping on SmB6, we synthesized and probed a series of gadolinium-doped samples. We found a relationship between specific heat and impurity moment screening which scales systematically. Consistent with this finding, our neutron scattering experiments of a high purity sample of doubly isotopic 154Sm11B6 show no intrinsic excitations below the well-established 13 meV spin-exciton. The result of introducing impurities into a Kondo insulator is incompletely understood, but it is clear from our measurements that there is a systematic relationship between rare-earth impurities and metal-like properties in SmB6.

Nucleation study for an undercooled melt of intermetallic NiZr.

Electrostatic levitation is applied in order to undercool liquid glass forming NiZr significantly below its melting temperature. For NiZr large undercoolings are found to be highly reproducible with this experimental method. One single NiZr sample of high purity is undercooled 200 consecutive times which leads to a distribution function of undercooling temperatures. Within a statistical approach of classical nucleation theory, the undercooling distribution is analyzed yielding parameters, e.g., a pre-exponential factor of KV ≈ 1035 m-3 s-1, which indicates homogeneous nucleation. This result is consistent with the crystallization behavior of NiZr at high undercooling and with the corresponding microstructural analysis. Since NiZr is a representative of the very common CrB structure type, with 132 isostructural phases existing, understanding its nucleation behavior adds important knowledge to the nucleation of binary alloys in general.

Synthesis and characterization of argyrodite solid electrolytes for all-solid-state Li-ion batteries

Li6PS5X (X = Cl, Br, I) argyrodites possess high ionic conductivity but with rather scattered values due to various processing conditions. In this work, Li6PS5X solid electrolytes were prepared by solid-state sintering or mechanical alloying and optimized with or without excess Li2S. Solid-state sintering prefers excess Li2S, whereas mechanical alloying prefers stoichiometric Li2S to synthesize high-purity samples with high ionic conductivity. Solid-state sintering is also more suitable than mechanical milling for high ionic conductivity. Li6PS5Cl with the highest ionic conductivity among Li6PS5X was comprehensively characterized for electrochemical performance and air stability. MoS2/Li6PS5Cl all-solid-state batteries assembled with Li6PS5Cl-coated MoS2 as cathode and with Li6PS5Cl as solid electrolyte demonstrate high capacity and good cycling stability.

Preparation of long linear carbon chain inside multi-walled carbon nanotubes by cooling enhanced hydrogen arc discharge method.

Long linear carbon chains with sp hybridization inside multi-walled carbon nanotubes (LLCC@MWCNTs) can be prepared in the cathode deposits obtained by hydrogen arc discharge. In this work, a cooling system was introduced into the hydrogen arc discharge method to improve the growth yield of LLCC@MWCNTs samples, as indicated by the corresponding stronger Raman peaks between 1780 cm-1 and 1880 cm-1, compared with conventional systems. Moreover, the cooling largely expanded the narrow scope of suitable conditions for the preparation of LLCC@MWCNTs, and high purity samples were easily produced. Qualitative analysis of arc discharge process helped conclude that cooling helps to increase the temperature of arc plasma, which is beneficial to improve both the growth yield of LLCC@MWCNTs and the purity of MWCNTs. This work provides a new approach to improve the growth yield of LLCC@MWCNTs and will benefit further studies and future applications of this new one-dimensional allotrope.

Direct determination of fluorine in high-purity water samples using vacuum sample chamber total reflection X-ray fluorescence spectrometry

Trace levels of F in high-purity water samples were determined using vacuum chamber total reflection X-ray fluorescence spectrometry.

Magnetic properties of the natural and isotope-modified diamond and silicon carbide

The magnetic properties of single crystals of synthetic diamond and crystals of silicon carbide were studied. High-purity samples of diamonds synthesized with HPHT and CVD technologies were used. The crystals of silicon carbide were grown by sublimation and industrial technology. Along with samples with a natural isotopic composition, monoisotopic crystals of diamond (99.96% 12C and 99.96% 13C) and silicon carbide (99.993% of 28Si) were studied. On the basis of the data obtained, the diamagnetic susceptibility was determined and the concentration of paramagnetic centers and the content of the ferromagnetic component were evaluated. The results are discussed.

Fiber sensor on the basis of Ge26As17Se25Te32 glass for FEWS analysis

The high-purity Ge26As17Se25Te32 glass sample was prepared by chemical distillation purification method. This glass is characterized by high value of glass transition temperature (263°С), high optical transparency in the spectral range of 2–10 μm, and low content of residual impurities. The Ge26As17Se25Te32 glass rods were drawn into single-index fibers using the ”rod” method and the single crucible technique. The optical losses in the 400 μm diameter fiber, fabricated by the ”rod” method, were within 0.3–1 dB/m in the spectral range 5.2–9.3 μm. The minimum optical losses in the 320 μm diameter fiber, fabricated by the ”crucible” technique, were 1.6–1.7 dB/m in the spectral range 6–8.5 μm. Using these Ge26As17Se25Te32 glass fibers as a sensor, the aqueous solutions of acetone (0–20 mol.%) and ethanol (0–90 mol.%) were analyzed by fiber evanescent wave spectroscopy. Peculiarities in the change of the integrated intensity and spectral position of absorption bands of these organic substances in dependence on the analyte composition and the length of the sensitive zone were established.

Novel applications of magnetic materials and technologies for medicine

We analyze the applications of the magnetocaloric effect (MCE) achieved with advanced magnetic materials and technologies. New results such as the use of MCE-based composite material for ‘smart’ coating of implants, which allows for a controlled release of drugs over time. The material is comprised of two layers: the one manifesting a large MCE and the other made of a temperature-responsive polymer containing the drug. The latter is released by the polymer if the temperature induced by magnetic field (due to MCE) is changed. The polymer undergoes sharp phase transition in response to the slight temperature drop of ∼1–3 °C (down to 34–36 °C in the body). Local cooling is achieved with FeRh alloy, one of the most perspective MCE materials with the first order phase transition. It is critically important to take into account several peculiarities of phase transition and MCE behavior in these series of alloys. Recent studies on high-purity samples showed an ‘irreversible’ effect of MCE indicating that the temperature of FeRh does not return to its initial value after the full cycle of the magnetic field during dynamic MCE measurements. A theoretical explanation based on ab initio calculations has been provided. Magnetic hyperthermia in oncology is rapidly developing therapeutic modality. Recent experiments have shown that Mn-Zn ferrite emerges as a cost-effective material for this method compared with currently used magnetite nanoparticles. We present our achievements on magnetically guided capsule endoscopy. The advances in magnetically guided capsule endoscopy are also discussed. We provide the experimental setup for the computer-controlled system of magnetic field sources that create necessary forces to control the position of the capsule in five degrees of freedom in a given area. The system has the feedback on the position and is designed to monitor the endoscopic capsule during gastrointestinal tract examination.

A magneto-optical study on magnetic flux expulsion and pinning in high-purity niobium

The magnetic flux trapped inside high-purity niobium samples after field cooling was investigated by indirect magneto-optical imaging using an indicator film. The detected magnetic field was compared with the field present during the phase transition, and the distribution of trapped flux was investigated. The measurements were performed on an untreated sample cut from an ingot and a sample that was heated at 1400 °C for 4 h. For untreated niobium, the trapped flux was found to be homogeneously distributed and almost all applied field during phase transition was trapped. In contrast, the heat treated niobium showed significantly reduced trapping. Neither did the grain boundaries play a major role as pinning centers nor did the crystal orientation influence the amount of trapped flux significantly, which is contrary to recent assumptions. However, niobium hydrides, which formed during the cool-down-stage to cryogenic temperatures, were found to enhance trapping considerably.

Effect of aluminum addition on the densification behavior and mechanical properties of synthesized high-purity nano-laminated Ti3SiC2 through spark plasma sintering

To reveal the effect of Al content on the purity and mechanical properties of Ti3SiC2, the powder mixture of 1Ti/1.2Si/2TiC/xAl (x = 0–0.4) were sintered to synthesize Ti3SiC2 through spark plasma sintering (SPS). The sintering process was conducted at 1150 °C for 8 min under a pressure of 40 MPa. To evaluate the phase constituents and morphology of the sintered samples, X-ray diffraction and field emission scanning electron microscopy were used. It was found that addition of Al from 0.2 to 0.4 mol in the starting powder mixture led to synthesis of high-purity Ti3SiC2. Besides, with increasing the Al content in the starting powder mixture, the densification behavior of sintered samples was promoted. The results showed that the Vickers microhardness of high-purity samples became almost same at higher loads and moreover the measured Young's modulus (E) of the high-purity Ti3SiC2 samples were near to each other and increased with promoting the densification.

Shock and Microstructural Characterization of the $$\alpha$$ α – $$\omega$$ ω Phase Transition in Titanium Crystals

A multicrystal comprised of a small number of large crystals of high-purity titanium and a $$[0001]$$ oriented high-purity single crystal titanium sample were shock loaded using gas gun plate impact experiments. Tests were performed at stresses above the $$\alpha {-}\omega$$ phase transition stress (for high-purity polycrystalline specimens) to observe the behavior of oriented crystals under similar conditions. Post-mortem characterization of the shocked microstructure was conducted on the single crystal sample to measure textures, and quantify phases and twinning. The apparent activation of plastic and transformation mechanisms was dependent upon crystal orientation. Specifically, the $$[0001]$$ crystal showed a higher Hugoniot elastic limit than the $$[10\bar{1}0]$$ or $$[3\bar{1}\bar{4}4]$$ orientations. The slope of velocity as a function of time was lower in the $$[0001]$$ orientation than the other orientations during plastic deformation, indicating sluggish transformation kinetics for the $$\alpha$$ to $$\omega$$ phase transition for the $$[0001]$$ oriented crystal. Microtexture measurements of a recovered $$[0001]$$ oriented single crystal revealed the presence of retained $$\omega$$ phase after unloading, with orientations of the constituent phase fractions indicative of the forward $$\alpha \rightarrow \omega$$ transition, rather than the reverse $$\omega \rightarrow \alpha$$ transition, suggesting that the material never achieved a state of 100% $$\omega$$ phase.

Corrosion Behavior of Ion-Implanted Metalloid-Magnesium Surfaces

Ion implantation was used to modify the surface chemistry of magnesium in order to improve the corrosion resistance. Metalloids which have recently been shown to reduce the cathodic reaction kinetics in magnesium alloys, were implanted into high purity polycrystalline magnesium at varying doses and the composition gradient, microstructure, and electrochemical behavior were characterized. The primary chemical reactions at a magnesium alloy surface during corrosion are water reduction, wherein water is split to evolve hydrogen, and oxidation of Mg to Mg2+. Recently, germanium and arsenic have been reported to have a significant impact on the kinetics of the cathodic water reduction reaction by inhibiting the recombination of hydrogen atoms and subsequent evolution of H2 gas from the Mg surface.(1, 2) Density functional theory (DFT) has provided support for these observations indicating unfavorable enthalpy changes for adsorbed hydrogen atom diffusion toward several metals and metalloids alloyed on a magnesium surface.(3) The DFT results also showed that the reaction enthalpy of diatomic hydrogen evolution was unfavorable on a dilute Mg-metalloid surface. Ion implantation into the surface of metals has been known to improve wear and corrosion resistance, alter conductivity and optical properties, and improve thermal oxidation resistance. For example, the corrosion resistance of 1070 and 52100 steels has been improved by implanting Ta or Ti. Although lesser studied than some substrates, implantation into Mg and Mg alloys has been examined for corrosion and wear in implantable medical devices.(4-6) Implantation of Y into Mg and of Al into AZ31 is known to increase open circuit potential (OCP) and co-implantation of Cr and O is known to form a protective oxide film. This study examines the role of ion implantation in forming protective, corrosion resistant magnesium surface alloys. Germanium and arsenic ions were implanted at 1532 keV into high-purity Mg samples using a National Electrostatics 5SDH-2 positive ion accelerator at doses sufficient to achieve 1-micrometer thick doped layers with peak concentrations of 0.01-0.3 atomic percent at approximately 1.5 micrometers beneath the surface. The depth of implantation and concentration were verified using Rutherford backscattering spectrometry, and were consistent with what had been expected from the ion implantation simulation program SRIM. Energy dispersive spectroscopy, and x-ray photoelectron spectroscopy were used to characterize surface chemistry. Surface morphology was characterized using scanning electron microscopy, tunneling electron microscopy, and atomic force microscopy. Higher concentrations of Ge and As were both observed to roughen the alloy surface, generating a thick MgO surface film, whereas low doses had a minimal effect. The corrosion behavior was evaluated using potentiodynamic polarization and immersion in quiescent NaCl. In order to de-convolute the effect of surface oxide thickness from the chemical effect of the alloying addition, Mg was also implanted into the Mg substrate as a reference. 1. R. Liu, M. Hurley, A. Kvryan, G. Williams, J. Scully and N. Birbilis, Scientific Reports, 6(2016). 2. N. Birbilis, G. Williams, K. Gusieva, A. Samaniego, M. A. Gibson and H. N. McMurray, Electrochemistry Communications, 34, 295 (2013). 3. K. R. Limmer, K. S. Williams, J. P. Labukas and J. W. Andzelm, CORROSION, 73, 506 (2017). 4. C. Liu, Y. Xin, X. Tian, J. Zhao and P. K. Chu, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 25, 334 (2007). 5. Y. Z. Wan, G. Y. Xiong, H. L. Luo, F. He, Y. Huang and Y. L. Wang, Applied Surface Science, 254, 5514 (2008). 6. R. Xu, G. Wu, X. Yang, T. Hu, Q. Lu and P. K. Chu, Materials Letters, 65, 2171 (2011).

Nanometric P2-Na2/3Fe1/3Mn2/3O2 with controlled morphology as cathode for sodium-ion batteries

P2-Na2/3Fe1/3Mn2/3O2 was synthesized by an emulsion-based method. This preparative route provides a crystalline and high-purity sample with homogeneous distribution of the elements. The polycrystalline material contains nanometric particles and the morphology is controlled by the surfactant content. The effect of the nanometric texture on the performance in sodium test batteries was clearly evidenced by better coulombic efficiencies and lower cell polarization of nanometric P2-Na2/3Fe1/3Mn2/3O2 as compared to a sample of the same composition with micron-size particles. The kinetic improvement was related to low internal cell impedances and higher sodium diffusion coefficient. The superior performance found for the nanorod-like layered oxide assembled in a full Na-ion test cell allows envisaging this material as a potential candidate for the positive electrode of future Na-ion batteries.

Active Crystal Growth Techniques for Quantum Materials

We review recent advances in crystal growth techniques, focusing on the development of novel quantum materials. Recent progress in instrumentation design, opening new avenues in bulk crystal growth of oxide and intermetallic compounds, is highlighted. Specifically, we illustrate leading techniques that allow for the active control of crystal nucleation/growth and provide platforms for the realization of single crystals with ultrahigh purity and minimized defects. Advances in the postgrowth manipulation of crystals, as well as the impact of purification techniques on the stabilization of delicate quantum phases, are also discussed. Throughout, we highlight new scientific avenues opened by access to high-purity single-crystal samples.

Synthesis and physicochemical properties of NaK, K, Na, and Li forms of LSX zeolite

Powder LSX zeolite samples of high phase purity and near 100% crystallinity have been synthesized in NaK, K, Na, and Li forms. The effect of the chemical nature and content of the exchange cation and air calcination temperature on the degree of crystallinity and the porous structure characteristics and adsorption properties of the mentioned LSX zeolite forms were established by X-ray diffraction and adsorption methods.

Optimized method for isolation of immature intracytoplasmic retroviral particles from mammalian cells

To biochemically and structurally characterize viral intracytoplasmic particles (ICAPs), a sample of high purity and homogeneity is usually required. Production of ICAPs in the system closely related to their natural host cells is crucial for the analysis of host-cell binding proteins involved in ICAPs assembly, transport and budding. However, this approach is often hampered by problems with low yield of the ICAPs due to either low expression or fast release from the host cell. Another obstacle may be a low stability or fragility of the intracellular particles. The published methods for ICAPs isolation often involved several time-consuming centrifugation steps yielding damaged particles. Other papers describe the ICAPs production in non-natural host cells. Here, we optimized the method for purification of unstable Mason-Pfizer monkey virus (M-PMV) ICAPs from non-human primate derived cells, commonly used to study MPMV replication i.e. African green monkey kidney fibroblast cell line (COS-1). Our simple and rapid procedure involved separation of the intracytoplasmic particles from the cell debris and organelles by differential, low-speed centrifugation, their purification using sucrose velocity gradient and final concentrating by low-speed centrifugation. Importantly, the method was established for unstable and fragile M-PMV intracytoplasmic particles. Therefore, it may be suitable for isolation of ICAPs of other viruses.

The Structure and Properties of Rapid Cooled Iron Based Alloy

In this paper we studied the structure of rapidly cooled alloy which composition was based on iron. Samples were prepared using arc melting under protective atmosphere of argon and then casted in the process of rapid cooling into water cooled copper mold. Samples of the same composition were also made using the liquid melt casting method on a spinning copper roll. The high purity samples in the form of rods and ribbons were obtained. As expected, the obtained samples were characterized by an amorphous structure as confirmed by Mössbauer spectroscopy and X-ray diffraction studies.

Development and screening of epoxy-spacer-phage cryogels for affinity chromatography: Enhancing the binding capacity.

Macroporous epoxy cryogels can be used as an alternative for classical matrices in affinity chromatography. Due to the structural properties of cryogels, with pores of up to 100μm, crude samples can be processed at high speed without previous manipulations such as clarification or centrifugation. Also, we previously used a peptide-expressing M13 bacteriophage as an affinity ligand. These ligands show high specificity toward the target to be purified. Combination of both, leads to a relative cost-effective one-step chromatographic set-up delivering a high purity sample (>95%), however, so far with limited capacity. To increase the binding capacity of the affinity columns, we now inserted spacers between the chromatographic matrix and the phage ligand. Both linear spacers, di-amino-alkanes (C2 -C10 ), and branched polyethyleneimine spacers with different molecular weights (800Da-10kDa) were analyzed. Two types of peptide expressing phage ligands, a linear 15-mer and a cyclic 6-mer, were used for screening. Up to a tenfold increase in binding capacity was observed depending on the combination of phage ligand and spacer type.