Ultra-high Purity Research Articles

A novel auto-gaping magnetic pole system for inner surface finishing of non-circular pipes using magnetic abrasive finishing process

This study explored the design of a novel auto-gaping magnetic pole system for finishing the inner surface of non-circular pipes using a magnetic abrasive finishing (MAF) process. Non-circular pipes are widely used for the transportation of ultra-high purity substances, including gases and fluids in many industries for semiconductor, medical, and aerospace applications. MAF process typically utilizes non-movable magnetic poles. However, due to the noncircular cross-section of the pipe, the magnetic flux density, produced by non-movable magnetic poles, across the polishing surface will exhibit huge variations, resulting in uneven and poor finish at some areas. The proposed auto-gaping magnetic pole system allows the magnetic poles to move so that they can track the workpiece surface to keep the gap between the magnetic pole and workpiece’s external surface constant. As a result, the magnetic densities can be maintained at desired values to achieve even and effective finishing by MAF process. Elliptical pipes were used as the non-circular pipes for experimental validation under different MAF process parameters. The results showed that this novel technique for inner surface finishing of a non-circular pipe is capable of improving the surface roughness, reducing the Ra values from over 0.20 μm to 0.05 μm or lower, across the entire inner surface of the elliptical pipe. In addition, superior material removal efficiency was achieved. The results demonstrate that the MAF process combined with a novel auto-gaping magnetic pole system is feasible to produce the ultra-smooth inner surface of non-circular pipe.

Growing clean crystals from dirty precursors: Solid-source metal-organic molecular beam epitaxy growth of superconducting Sr2RuO4 films

Ultra-high purity elemental sources have long been considered a prerequisite for obtaining low impurity concentrations in compound semiconductors in the world of molecular beam epitaxy (MBE) since its inception in 1968. However, we demonstrate that a “dirty” solid precursor, ruthenium(III) acetylacetonate [also known as Ru(acac)3], can yield single-phase, epitaxial, and superconducting Sr2RuO4 films with the same ease and control as III–V MBE. A superconducting transition was observed at ∼0.9 K, suggesting a low defect density and a high degree of crystallinity in these films. In contrast to the conventional MBE, which employs the ultra-pure Ru metal evaporated at ∼2000 °C as a Ru source, along with reactive ozone to obtain Ru → Ru4+ oxidation, the use of the Ru(acac)3 precursor significantly simplifies the MBE process by lowering the temperature for Ru sublimation (less than 200 °C) and by eliminating the need for ozone. Combining these results with the recent developments in hybrid MBE, we argue that leveraging the precursor chemistry will be necessary to realize next-generation breakthroughs in the synthesis of atomically precise quantum materials.

Separation and purification of Yb2O3 by ion exchange chromatography and preparation of ultra-high purity Yb2O3

Separation and purification of Yb2O3 by ion exchange chromatography and preparation of ultra-high purity Yb2O3

Blue-Hazard-Free Organic Light-Emitting Diode with a Lifetime Greater than 200,000 h

Blue-hazard-free lighting is in urgent need in order to protect human eyes and physiology. A candlelight-style organic light emitting diode (OLED) is so far the safest measure for its blue-hazard-free, low-color-temperature illumination. However, lifetime is still the most critical reliability issue in OLEDs, especially in lighting applications that are closely associated with high current density operation. Here, we present a novel approach to develop blue-hazard-free OLEDs with a lifetime exceeding 200,000 h at 1000 cd/m2 by employing a tandem structure with ultra-high purity emitter. The resultant device shows a current efficacy of 37.4 cd/A, an external quantum efficiency (EQE) of 22.7%, an 80 CRI, and a 78 SRI with a 223,500 h lifetime (t50). Additionally, the resultant device also exhibits a long retina exposure duration of 12,300 s (3.42 h) and suppresses very less melatonin generation (1.7%), demonstrating that the fabricated OLED device is a highly prospective general lighting source to safeguard human health.

Length-Dependent Enantioselectivity of Carbon Nanotubes by Gel Chromatography

High-purity enantiomer separation of chiral single-wall carbon nanotubes (SWCNTs) remains a challenge compared with electrical type and chirality separations due to the limited selectivities for both chirality and handedness, which is important for an exploration of their properties and practical applications. Here, we performed length fractionation for enantiomer-purified SWCNTs and found a phenomenon in which the enantioselectivities were higher for longer nanotubes than for shorter nanotubes due to length-dependent interactions with the gel medium, which provided an effective strategy of controlling nanotube length for high-purity enantiomer separation. Furthermore, we employed a gentler pulsed ultrasonication instead of traditional vigorous ultrasonication for preparation of a low-defect long SWCNT dispersion and achieved the enantiomer separation of single-chirality (6,5) SWCNTs with an ultrahigh enantiomeric purity of up to 98%, which was determined by using the linear relationship between the normalized circular dichroism intensity and the enantiomeric purity. Compared with all results reported previously, the present enantiomeric purity was significantly higher and reached the highest level reported to date. Due to the ultrahigh selectivity in both chirality and handedness, the two obtained enantiomers exhibited perfect symmetry in their circular dichroism spectra, which offers standardization for characterizations and evaluations of SWCNT enantiomers.

Aggregation-induced emission phenanthroline derivatives for ultrahigh color purity deep blue OLEDs with CIEx≤0.15 and CIEy≤0.08 and low efficiency roll-off

Due to the limited molecular design strategy, the development of ultrahigh color purity deep blue aggregation-induced emission (AIE) emitters with excellent photophysical and electroluminescence performances is still facing challenges at present. In this study, an effective design strategy for deep blue emitters is proposed, which can improve the performances of non-doped organic light-emitting diodes (OLEDs) by adjusting the link mode of the phenyl bridge and utilizing the steric hindrance effect of the rigid plane. Two new emitters, 3BCzPT and 4BCzPT, were obtained with phenanthroline acceptor and carbazole donor for deep blue emitting OLEDs. Particularly, 3BCzPT has been proven to have AIE characteristics through photophysical properties. Non-doped OLEDs with 3BCzPT demonstrate prominent electroluminescence (EL) performances reaching a maximum current efficiency (CEmax) of 6.3 cd A−1 and maximum external quantum efficiency (EQEmax) of 3.81%, well as ultrahigh color purity with Commission Internationale de L'Eclairage (CIE) coordinates of (0.151, 0.053). While the parameters of non-doped OLED based 4BCzPT are 4.2 cd A−1, 1.96% and (0.147, 0.082). Both emitters exhibit narrow EL spectra with the full-width at half maximum (FWHM) of 56 and 52 nm.

Experimental determination of interaction between the radiation fields of Dragonfly's MMRTG and Titan's environment II: Gamma induced atmospheric conductivity

The apparatus described in part I of this investigation was filled with various blends of ultra high purity nitrogen and a mixture of 95% nitrogen/5% methane, simulating Titan's atmosphere with up to 50% relative methane humidity, as well as an Earth atmosphere for comparison, with a source of gamma rays suspended therein. Readings were taken from a plate immersed in the atmosphere at the top of the chamber connected to a conductivity probe, with the source at various distances from the plate. Gamma-induced conductivity was not found to be significant at a distance from the source equivalent to that on the surface of the hull segment on Dragonfly containing the radioisotope generator when gamma ray energies and field geometry were corrected for, however ion buildup in the experiment chamber indicated the possibility of similar buildup within the hull segment itself. The effect of methane in the atmosphere was statistically indeterminate, reflecting earlier simulation results, however molecular ions were shown more likely to be the predominant carriers of charge than the free electrons measured in the simulation.

Dispersive Liquid - Liquid Micro extraction Technique Coupled with High Performance Liquid Chromatography Diode Array Detector for the Determination of Sulfonamides in Water Samples

A dispersive liquid-liquid microextraction combined with high-performance liquid chromatography with diode array detection (DLLME-HPLC-DAD) has been developed for the determination of 15 sulfonamides in water samples. The effects of experimental parameters on the performance of the method such as the type and volume of extraction and disperser solvents, pH of the solution, effect of salt, and centrifugation time were evaluated, and optimum conditions were established. Under these optimum conditions, linearity was found in the range of 2 - 1 000 μg L-1 with regression coefficients better than 0.9990. The limit of detection (LOD) and limit of quantification (LOQ) values were in the range of 0.6 - 7.8 μg L-1 and 1.5 - 8.3 µg L-1, respectively. Intra-day and inter-day precision ranged from 1.5 - 9.7% and from 3.1 - 9.9%, respectively. The accuracy of the method were also evaluated in samples from three different sources of water (river water, groundwater, and tap water) were found to range from 70.5 to 103.9% with %RSD values ranging from 0.5 to 9.8%, with the exception of sulfaguanidine in river water and groundwater where the percentage recovery ranged from 54.3 - 84.9% at the two higher concentration levels (100 and 400 µg L-1).Furthermore, the effect of sample matrix on the extraction of target compounds was evaluated using the relative recovery (%RR) of the samples from three different water sources relative to the ultrahigh purity (UHP) water sample spiked with target analytes, and found in the range of 70.3 - 106.1%.The proposed method was successfully applied to wastewater treatment plant samples and Sulfisoxazole (SSO) was detected in the influent samples in the range of 14.8 - 17.8 µg L-1 with corresponding %RSD, (n = 5) value of 1.6% to 1.9%.The results indicated that the proposed method is effective for the extraction and determination of the sulfonamides in water samples.

Development of Large‐Diameter and Very High Purity Ge Crystal Growth Technology for Devices

AbstractHigh‐purity germanium (HPGe) single crystals find their applications as radiation detectors especially for spectroscopy of high‐energy photons and particles in nuclear physics. Growing “detector‐grade” HPGe single crystals, with tailored structural defects and controlled impurity content, uniform throughout the crystal is a challenging task in this type of crystalline semiconductor material. All different process steps for HPGe, namely, i) reducing germanium dioxide powder into Ge metal; ii) zone refining of intrinsic source material (6 N) up to an ultrahigh purity (13 N); iii) Czochralski growth of high‐purity single crystals, are developed in house. A specific preparatory coating process for zone refining is entrenched as part of this work. Gallium, a dominant impurity usually found in HPGe, can be avoided. Using these advanced process know‐hows, a technology to grow volume Ge single crystals of large diameter (3 in.) with very high purity (net carrier concentration ≈ 5 × 1010 cm−3 or equivalent to 1 part per trillion level) is successfully developed. The zone‐refined Ge bars and the crystals show p‐type conductivity. Some crystals exhibit n‐type conductivity, and n–p or p–n transition is encountered in a single growth experiment. Besides the first results of encompassing very high‐purity crystals with uniform diameter, a controlled dislocation density (≈104 cm−2) can be realized.

The high corrosion-resistance of ultra-high purity Mg–Ge alloy and its discharge performance as anode for Mg–air battery

This study reports cast ultra-high-purity (UHP) Mg–Ge alloys that exhibited remarkably high corrosion resistance and good discharge performance as anodes for Mg-air batteries. The UHP Mg-0.5Ge had a corrosion rate of 0.15 mm y−1, which is twice better than Mg's intrinsic corrosion rate of 0.3 mm y−1. The outstanding corrosion resistance is attributed to the low impurity content, the restricted HER, and the presence of a protective surface film. The energy density of Mg-0.5Ge is 37% higher than UHP Mg at 10 mA cm−2. The better discharge properties are ascribed to the more negative corrosion potential and suppressed NDE.

Effects of a small amount of H2O on negative ion mobility and ion‐molecule reactions in O2 at atmospheric pressure

AbstractIn this study, we have measured the negative ion mobility in O2 at high pressures with a little amount of H2O concentration between 15 and 17,000 ppb. After that, we carried out a Monte Carlo simulation using mobility of electrons, that of the ions obtained in the measurements, and rate coefficients of ion‐molecule reactions. As a result, the mobility value 2.39 cm2/V·s of O4¯ is obtained in ultrahigh purity O2 of which the H2O concentration is between 15 and 100 ppb. Moreover, the mobility decreases with the H2O concentrations at which the ion species are considered to be O2¯·(H2O)n (n = 1, 2, 3). Then, we compared the experimental result with that of the simulation and estimated the ion mobility and rate coefficients of ion molecule reactions. Simulation results using estimated values of the ion mobility and rate coefficients agree well with measurement results.

Chemical Potential-Modulated Ultrahigh-Phase-Purity Growth of Ultrathin Transition-Metal Boride Single Crystals.

Two-dimensional (2D) transition-metal borides (TMBs) are especially expected to exhibit excellent performance in various fields among electricity, superconductivity, magnetism, mechanics, biotechnology, battery, and catalysis. However, the synthesis of ultrathin TMB single crystals with ultrahigh phase purity was deemed extremely challenging and has not been realized till date. That is because TMBs have the most kinds of crystal structures among inorganic compounds, which possess generous phase structures with similar formation energies compared with other transition-metal compounds, attributing to the metalloid and electron-deficient characteristics of boron. Herein, for the first time, we demonstrate a chemical potential-modulated strategy to realize the precise synthesis of various ultrahigh-phase-purity (approximately 100%) ultrathin TMB single crystals, and the precision in the phase formation energy can reach as low as 0.01 eV per atom. The ultrathin MoB2 single crystals exhibit an ultrahigh Young's modulus of 517 GPa compared to other 2D materials. Our work establishes a chemical potential-modulated strategy to synthesize ultrathin single crystals with ultrahigh phase purity, especially those with similar formation energies, and undoubtedly provides excellent platforms for their extensive research and applications.

Nitrogen carrier gas for the separation of trace explosives on CI-GC/MS.

Fluctuations in ultra high purity (UHP) helium supply has the potential to negatively impact critical research efforts. Disruptions have increased significantly with suppliers prioritizing delivery to medical facilities. Due to the greater demand for helium, supply issues are likely to continue through the coming years. Many gas chromatography (GC)-based analytical methods rely on the supply of UHP helium, including those developed for the quantification of trace explosives. Vapor validation is critical in establishing sensor performance, limits of detection, and instrument performance. An alternate carrier gas must be established to maintain these critical functionalities. To circumvent the UHP helium disruptions, UHP nitrogen was explored as a replacement carrier gas in negative mode chemical ionization-gas chromatography/mass spectrometry (CI-GC/MS). Although, hydrogen is considered an acceptable alternative to helium in most GC-based separations, its' use as a replacement was omitted due to reactivity resulting in degradation of the CI-MS detector and incompatibility with the programmable temperature vaporization inlet on the GC used in this work. Herein discusses the method development of nitrogen carrier gas in the separation of an explosives mixture. Adjustments in flow rate, initial oven temperature, and ramp rate were made to achieve comparable analysis to that of helium. By lowering the flow rate and initial oven temperature peak resolution and sensitivity increased when using nitrogen carrier gas. Development of this method allows for continual laboratory output in times of helium scarcity.

Ultra-high spectral purity laser derived from weak external distributed perturbation

Ultra-high spectral purity lasers are of considerable research interests in numerous fields such as coherent optical communication, microwave photonics, distributed optical fiber sensing, gravitational wave detection, optical clock, and so on. Herein, to deeply purify laser spectrum with compact size under normal condition, we propose a novel and practical idea to effectively suppress the spontaneous radiation of the laser cavity through weak external distributed perturbation. Subsequently, a laser configuration consisting of a main lasing cavity and an external distributed feedback cavity is proposed. The feedback signal with continuous spatio-temporal phase transition controlled by a distributed feedback structure is injected into the main cavity, which can deeply suppress the coupling rate from the spontaneous radiation to the stimulated emission and extremely purify the laser spectrum. Eventually, an ultra-narrow linewidth on-chip laser system with a side mode suppression ratio greater than 80 dB, an output linewidth of 10 Hz, and a relative intensity noise less than -150 dB/Hz is successfully obtained under normal conditions. The proposed concept in this work provides a new perspective for extreme regulation of laser parameters by using weak external distributed perturbation, which can be valid for various gain-type lasers with wide wavelength bands.

Cyanide Molecular Laser-Induced Plasma Spectroscopy

This work communicates recent measurements of CN in laser-induced plasma. The main goals and objectives comprise (a) exploring CN measurement using optical emission spectroscopy in optical breakdown plasma; (b) determining the effects of laser-induced shockwave for time delays of the order of 1 μs; (c) evaluating the spatial distribution of CN signals; (d) inferring CN temperature distribution; and (e) associating recorded shadowgraphs with laser-spectroscopy results. Q-switched, 150 mJ, 6 ns pulsed Nd:YAG laser radiation at the fundamental wavelength of 1064 nm is used to generate micro-plasma in a gas mixture with ultra-high purity nitrogen and research grade carbon dioxide. The CO2 to N2 molar ratio is 1 to 1 for the gaseous mixture near atmospheric pressure flowing through the chamber. Optical emissions are dispersed by a 0.64-m Czerny-Turner spectrometer and an intensified charge-coupled device records the data along the wavelength and slit dimensions. The analysis utilizes Abel integral inversion techniques for determination of spatiotemporal profiles.

Comb-assisted cavity ring-down spectroscopy for ultra-sensitive traceable measurements of water vapour in ultra-high purity gases

We report on the development of a comb-assisted cavity ring-down spectrometer for trace water mole fraction determinations in high purity gases. By tuning the laser light in coincidence with a H2O absorption line at 1.3946 µm, we were able to determine sub-ppm relative concentrations of water vapour in N2 with a sub-percent statistical uncertainty. The sensitivity of the spectrometer was carefully assessed, yielding a detection limit of about 2 nmol/mol.

Enhancing photoluminescence of manganese chloride perovskite-analogues through phase transformations induced by Sn incorporation

Herein, we develop a facile strategy to synthesize one-dimensional Sn-incorporated CsMnCl3 microcrystals (MCs) via an acid dissolution method under high humidity. The prepared CsMnCl3(H2O)α:0.50%Sn (α = 0 or 2, noted as CMCH:0.50%Sn) MCs exhibit an intense red emission assigned to 4T1g→6A1g transition of Mn2+ with a photoluminescence (PL) quantum yield (QY) of 15.77%, which is four times than that of pristine CsMnCl3(H2O)2 MCs, with an activation energy of 160 meV determined from a temperature-dependent PL Boltzmann analysis. Sn2+ ions incorporation can promote the formation of anhydrous CsMnCl3 and are likely bonded to Cl ions. A red LED device based on CMCH:0.50%Sn MCs shows ultra-high color purity at a drive current of 300 mA and good stability. This work successfully addresses the issue of typically low PL QY of lead-free manganese halide perovskite-analogues (MHPAs) and provides insight into the fundamental optical properties and phase transformation mechanisms of all-inorganic MHPAs.

The Effectiveness of Cooled-Finger and Vacuum Distillation Processes in View of the Removal of Fe, Si and Zn from Aluminium

The increasing demand for ultra-high purity aluminum for technological applications has led to the improvement of refining methods in recent decades. To achieve ultra-purity levels (>5N), the common industrial way is to firstly purify aluminum from 2N8 up to 4N8 via three-layer electrolysis, followed by fractional crystallization (usually zone melting). Since both of these methods are very cost- and time-intensive, this paper aims at providing other alternatives of purification. For this purpose, here, the purification of some selected impurities through cooled-finger fractional crystallization method and vacuum distillation have been the focus of this investigation. Both processes are more environmentally friendly than three-layer electrolysis and require less time than zone melting. In this paper, both methods were explored for the aluminum purification. Moreover, the effect of process parameters on the purification efficiency of iron, zinc, and silicon has been investigated. At the end, the effectiveness of the two processes was compared and advantages and disadvantages were summarized. The results showed that the cooling finger process effectively removed iron and silicon impurities, but the removal efficiency of zinc was low. The vacuum distillation process successfully removes zinc in the first stage of distillation. Iron and silicon removal requires additional distillation stages to achieve lower impurity levels.

Evidence for nitrogen binding to surface defects for topological insulator Bi2Se3

Using scanning tunneling spectroscopy and theoretical simulations we have studied the effects of nitrogen gas exposure on the electronic density of states of Bi2Se3, a well-studied topological insulator. In carefully controlled measurements, Bi2Se3 crystals were initially cleaved in a helium gas environment and then exposed to a 22 SCFH flow of ultra-high purity N2 gas. We observe a resulting change in the spectral curves, with the exposure effect saturating after approximately 50 min, ultimately bringing the Dirac point about 50 meV closer to the Fermi level. These results are compared to density functional theory calculations, which support a picture of N2 molecules physisorbing near Se vacancies. Furthermore, ab initio molecular dynamics simulations aided by a Blue Moon ensemble method reveal the dissociative adsorption of N2 molecules which then bind strongly to Se vacancies at the surface. In this scenario, the binding of the N atom to a Se vacancy site removes the surface defect state created by the vacancy and changes the position of the Fermi energy with respect to the Dirac point.

All-Dielectric Nanostructured Metasurfaces with Ultrahigh Color Purity and Selectivity for Refractive Index Sensing Applications

In this study, two kinds of nanostructured metasurfaces are presented and compared to exhibit ultrahigh color purity and selectivity in the visible wavelength range. The proposed nanostructured metasurfaces are composed of all-dielectric materials, which are Si3N4 fabricated on quartz substrates to form one-dimensional (1D) and two-dimensional (2D) nanogratings (NGs). These nanostructured metasurfaces exhibit over 98 % reflection intensity with ultra-narrow bandwidths less than 20 nm to perform vivid red, green, and blue colors, implying the potentials in high-saturation display. Among nanostructured metasurfaces, 2D-NGs allow a wider range of incident angle than 1D-NGs and show polarization-independent characteristic owing to the symmetric arrangement in nanoscale in the incident plane. Furthermore, the numerical simulation results prove that 1D-NGs and 2D-NGs exhibit single- and dual-resonance when exposed on the ambient environment with different refractive indexes. Such excellent optical performances verify their potentials not only in high-resolution display but also in chemical sensing applications.