Silica Tube Research Articles

Quantitative and qualitative analysis of polycyclic aromatic hydrocarbons in urine samples using a non-separative method based on mass spectrometry

In this work, a method for the quantitative and qualitative analysis of 11 polycyclic aromatic hydrocarbons (PAHs) in urine samples is reported. The method is based on the coupling of a programmed temperature vaporizer (PTV) with a quadrupole mass spectrometer (qMS), via a deactivated fused silica tubing. Before the PTV-qMS analysis, the samples were subjected to a liquid-liquid extraction (LLE).The method was rapid since no chromatographic separation was performed. The samples were introduced directly into the PTV, and the analytes were trapped in the Tenax-TA® packed liner while the solvent was purged. After that, all the compounds reached the mass spectrometer, obtaining the fingerprint of the analysed samples.Urine samples free of PAHs and the same samples spiked with the compounds were analysed. The resulting profile signals were used to quantify the analytes using multivariate calibration, and to classify the samples according to the presence or absence of the PAHs. In the latter task, non-supervised and supervised pattern recognition techniques were employed. The calibration models worked satisfactorily and errors lower or equal to 15% were obtained, in most cases, when an external validation set was analysed. Regarding the classification of the samples, most of the supervised pattern recognition techniques provided excellent results (100% success), where all of the samples were classified correctly.

Experimental and theoretical studies on the NLO properties of two quaternary non-centrosymmetric chalcogenides: BaAg2GeS4 and BaAg2SnS4.

New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg2GeS4 (1) and BaAg2SnS4 (2), were synthesized from a high-temperature solid-state reaction using BaCl2 flux in evacuated closed silica tubes. Although 1 and 2 show identical stoichiometry, they crystallize in different NCS space groups, tetragonal I4[combining macron]2m (no. 121) and orthorhombic I222 (no. 23), respectively, based on the results of crystal structure solution. In their structures, highly distorted AgS4 tetrahedra interconnect together via corner-sharing to form two-dimensional (2D) layers, which are further bridged with isolated GeS4 or SnS4 units to produce a three-dimensional (3D) framework structure with Ba cations lying in the tunnels. Remarkably, they not only possess phase-matchable (PM) abilities but also exhibit a good balance between strong SHG responses (1.7× and 0.4× AgGaS2) and high LIDTs (3.2× and 1.5× AgGaS2). Moreover, theoretical calculations based on density functional theory (DFT) methods have aided the understanding of energy bands, electronic structures, and linear and NLO properties.

Synthesis of Hybrid Silica-Carbon Tubular Structures by Chemical Vapor Deposition with Methane or Ethene

Silica microtube and carbon nanotube hybrid structures have been synthesized by catalytic chemical vapor deposition using either methane or ethene as the carbon source, and cobalt-grafted or impregnated silica tubes (200–800 nm) as catalyst. The cobalt-grafted catalyst shows a high resistance to reduction (>1000 °C) and selectivity to single-wall carbon nanotubes (SWCNT). While ethene deposition produces more carbonaceous material, methane experiments show higher selectivity for SWCNT. After removing the silica with an excess of HF, the carbon nanostructure endured, resulting in a coaxial carbon nanostructure. The novel hybrid nanostructures obtained consist of a submicron-sized tube, with walls that are formed by a succession of carbon/silica/carbon layers to which multiwall (20–25 nm) and/or single-wall (0.6–2.0 nm) carbon nanotubes are attached. This synthesis approach combines the mechanical properties of carbon nanotubes and the thermal properties of silica tubes into a synergetic nanostructured material, opening further possibilities for polymer reinforcement and potential applications in catalysis.

Anti-Resonant Reflecting Guidance in Silica Tube for High Temperature Sensing

A high temperature fiber sensor based on silica tube is proposed and experimentally demonstrated. The sensor consists of a short section of silica tube spliced between singlemode fibers. Due to the anti-resonant reflecting effect in the silica tube, the transmission spectrum of the structure exhibits periodic notches. When the sensor is exposed in increasing temperatures, the transmission notches shift toward longer wavelength. A temperature sensitivity of 20.31 pm/°C is obtained between room temperature and 1000 °C. The sensor structure is simple, compact with good spectrum repeatability, which can find applications in harsh environments.

Long Period Fiber Grating Inscribed in Hollow-Core Photonic Bandgap Fiber for Gas Pressure Sensing

In this paper, we have proposed and experimentally prepared an improved gas pressure sensing device. It is mainly constructed by a short hollow silica tube segment and a CO2-laser-induced long period grating in hollow-core photonic bandgap fiber (HC-PBF). To effectively enhance the interaction between light in the air-core of HC-PBF and external surroundings, thus to achieve the best possible gas pressure sensitivity, a microchannel is introduced in the middle of the hollow silica tube segment with the femtosecond laser processing technique. The corresponding gas pressure experiments demonstrate that the resonant wavelength of the LPFG shows a blue shift up to −1.3 nm/MPa. Moreover, the temperature response sensitivity of this sensor is as low as 5.3 pm/°C and enable it possible as a temperature-insensitive gas pressure measure apparatus.

Structure and magnetic properties of Sm2Rh3Sn5 – an intergrowth of TiNiSi- and NdRh2Sn4-related slabs

Abstract The stannide Sm2Rh3Sn5 was obtained by arc-melting of the elements and subsequent annealing at 1070 K in a silica tube. Sm2Rh3Sn5 crystallizes with the orthorhombic Y2Rh3Sn5 type structure, space group Cmc21, Z=4: a=444.46(8), b=2636.2(4), c=718.3(1) pm, wR=0.0711, 1761 F 2 values and 61 variables. The three crystallographically independent rhodium atoms show tricapped trigonal prismatic coordination by samarium and tin atoms. Sm2Rh3Sn5 can be considered as a simple 1:1 intergrowth structure of TiNiSi- and NdRh2Sn4-related slabs of compositions SmRhSn and SmRh2Sn4 . Temperature dependent magnetic susceptibility data revealed van Vleck type behavior caused by the proximity of the exited 6H7/2 state to the 6H5/2 ground state of Sm3+, and an antiferromagnetic ordering occurs at T N=3.5(5) K.

High-sensitivity pressure sensor based on fiber Mach–Zehnder interferometer

In this paper we propose and experimentally demonstrate an optical fiber structure sensor based on a Mach–Zehnder interferometer for pressure measurement. The fiber sensor is composed of a single-mode-no-core-single-mode structure, a section of capillary pure silica tube and refractive index matching fluid (RIMF). As the pressure decreases, the sealed air in the tube expands and the liquid level of the RIMF increases, which causes a wavelength shift of the interferometer. The measurement of the pressure variation can thus be achieved by monitoring the wavelength shift. The experimental results agree well with the numerical simulation, and a maximum pressure sensitivity of 266.6 nm is achieved experimentally. Furthermore, the proposed fiber sensor has the potential to obtain higher sensitivity by enlarging the length of the air cavity.

Te-As-Se glass destabilization using high energy milling

The Te20As30Se50 (TAS) glass has been studied under the extreme conditions of high energy milling. Starting from the raw materials, an amorphization process occurs progressively reaching an unstable intermediate state and the final stable state then. Despite its high resistance against crystallization when made using silica tubes, an intermediate state is reached when mechanically alloyed into powder. The evolution of the glass structure has been investigated using Raman spectroscopy and MAS NMR of 77Se according to the milling time. Optimized parameters and conditions to compact milled powders by Spark Plasma Sintering show the possibility to design infrared windows transparent from 2 to 20μm. A correlation to the thermo-mechanical properties of densified powder using hot pressing has been made.

Synthesis and characterization of two lead-containing metal chalcogenides: Ba5Pb2Sn3S13 and Ba6PbSn3Se13

Two new metal chalcogenides, Ba5Pb2Sn3S13 (BPSS) and Ba6PbSn3Se13 (BPSSe), were successfully synthesized in vacuum–sealed silica tubes for the first time. Both of them are isostructural and crystallize in the Pnma space group of orthorhombic system. Their three-dimensional (3D) framework structures are composed of 2D layers formed by the interconnection of [(Pb/Ba)Qn] (n = 6 and 7) polyhedra and isolated SnQ4 tetrahedra and charge–balanced Ba atoms filled into the interlayers. Note that the Q8 atoms are only surrounded by two Pb/Ba and four Ba atoms to form the distorted octahedra without the covalent Sn-Q bonds in their structures. Measured results of diffuse reflection and Raman spectra show that title compounds possess the wide transmission ranges from 0.5 to 20µm. Electronic structures and linear optical properties were also systematically investigated by the first–principle calculation, and calculated results indicate that title compounds possess the large birefringences about 0.123 and 0.135 for BPSS and BPSSe at 1µm, respectively, which indicate that they may be expected as potential IR birefringent materials.

The high-temperature modification of ScRuSi – Structure, 29Si and 45Sc solid state NMR spectroscopy

A polycrystalline sample of the TiNiSi type low-temperature (LT) modification of ScRuSi was synthesized by arc-melting. Longer annealing in a sealed silica tube (6 weeks at 1270 K) followed by quenching led to the high-temperature (HT) phase. HT-ScRuSi adopts the ZrNiAl structure type: P6¯2m, a = 688.27(9), c = 336.72(5) pm, wR2 = 0.0861, 260 F2 values, 14 variables. The striking structural building units are regular, tricapped trigonal prisms Si1@Ru3Sc6 and Si2@Ru6Sc3. Both polymorphs have been characterized by 29Si and 45Sc MAS-NMR spectroscopy. The local scandium environments in the two polymorphs are easily distinguished by their electric field gradient tensor values, in agreement with theoretically calculated values.

Poisoning of Hydrogen Recombination on Silica Due to Water Adsorption

The role of water adsorption in poisoning hydrogen recombination on silica is studied using a two-layer Langmuir isotherm model. In the model, hydrogen atoms adsorb directly on the silica surface, while water molecules physisorb above the surface, blocking gas atoms from reaching or reacting on the surface. Model parameters such as heat of adsorption and activation energy are informed using experimental values and data from atomic-scale simulations. Using this model for a gas-phase radical concentration of 1016 cm–3 (representative of a room-temperature gas at 1 Torr), the addition of water vapor is predicted to lower the room-temperature recombination coefficient of hydrogen (γH) from 3 × 10–3 to 2 × 10–4, consistent with experimental data. In general, surface reaction rates are reduced significantly for temperatures below 400 K. An analytical model is used to estimate the effect of reactive walls on radical concentration in a silica tube used in hydrogen plasma experiments. In the model, radical concent...

Excitation of Whispering Gallery Modes in Silica Capillary Using SMF-MMF Joint With Lateral Offset

Whispering gallery modes (WGMs) have been effectively excited in a silica tube by employing a single-mode-fiber/multimode-fiber (SMF/MMF) joint with the lateral offset to enhance the evanescent field over the tapered MMF region. Experimental results indicate that thanks to the lateral offset at the SMF-MMF joint, the taper diameter is about one order of magnitude larger than that of a standard fiber taper coupler. The WGMs in the silica capillary have been theoretically analyzed by using the eigen equation to deal with WGMs in cylindrical microresonators. Our proposed WGM excitation scheme is more robust than the conventional WGM systems based on fiber tapers of a few micrometers in diameter, which is anticipated to serve as micro-fluidic-channel for biological and chemical sensing applications.

Model-based optimization of the heat flux distribution of IR-heaters for high heat flux testing

For the testing of helium cooled plasma facing components a homogeneous surface heat flux distribution has to be generated with up to 500kW/m2 in the case of the ITER Test Blanket Module. One option is to use infrared radiation heaters which consist of several quartz glass (fused silica) tubes with tungsten filaments inside to generate the required heat flux. This paper introduces the numerical model of the heater which has been investigated in the SIRHEX (“Surface Infrared Radiation Heating Experiment”) facility at KIT. The model uses a transient simulation to assess the heat flux distribution on the surface of the test mock-up. To validate the model, the numerical results are compared with the latest results from SIRHEX. Using the now qualified model, the heater set-up is optimized to generate a homogeneous distribution for a future test of a blanket first wall.

A simple method for preparing superconducting FeSe pellets without sealing in evacuated silica tubes

Abstract Superconducting tetragonal FeSe pellets were made by reacting mixtures of elemental Fe and Se powders in argon atmosphere without sealing in evacuated silica tubes. A simple tube furnace has been used. Although the tube's material consisted of quartz, an alumina tube could be used as well. X-ray pure samples with onset of superconducting transition between 8.0 K and 8.5 K were obtained under specific heat treatment conditions. Residual, unreacted Fe particles could be virtually eliminated through prolonged annealing. A key factor for the synthesis of good samples consists in using processing parameters that minimize Se losses.

The behavior of Pt, Pd, Cu and Ni in the Se-sulfide system between 1050 and 700 °C and the role of Se in platinum-group elements fractionation in sulfide melts

The behavior of Pt, Pd, Ni and Cu in Se-sulfide system and the role of Se in platinum-group elements (PGE) fractionation have been experimentally investigated at temperatures between 1050 and 700°C in evacuated silica tubes. At 1050°C, Se partially partitions into a vapor phase. At 980°C, monosulfide solid solution (mss) and sulfide melt are the only stable phases. No Pt or Pd-bearing discrete selenide phases form down to 700°C. Instead cooperite (PtS) forms at 900°C. Both mss and sulfide melt can accommodate wt.% levels of Se over the whole temperature range covered by the experiments. The addition of Se in the sulfide system leads to an increase in the activity coefficients of Ni and Pd in sulfide melt. This is reflected by an increase in the partition coefficients of Ni and Pd between mss and sulfide melt. The Pt-Se activity coefficient in sulfide melt is lower than that of Pt-S. Owing to selenium’s high solubility in sulfides, there never become oversaturated in Se to the extent that discrete selenides form. As such, base metal sulfides are expected to control the geochemical behavior of Se in natural systems. Interestingly, partition coefficients for the platinum-group elements (Os, Ir, Ru, Pt, Rh, Pd) between mss and sulfide melt are undistinguishable regardless of whether Se is present or not. These results imply that Se plays little role in the fractionation of PGE as sulfide melt cools down and crystallize. Furthermore, our experimental results provide evidence that Se is volatile at magmatic temperature and is likely to be degassed like sulfur.

Influence of Dissolved Ions on the Water Purification Performance of TiO2-Impregnated Porous Silica Tubes

TiO2-coated porous silica glass tubes containing macropores were fabricated and evaluated for their water-purification capacity using aqueous solutions of methylene blue. From the results of photocatalytic degradation tests at different initial methylene blue concentrations, the equilibrium adsorption constant (K) was determined to be 4.6 × 10−2 L µmol−1, and the Langmuir-Hinshelwood rate constant (kLH) was calculated as 2.6 µM min−1. To determine the influence of ions on the efficiency of methylene blue degradation, we examined both Milli-Q water (soft water) and Contrex water (hard water) as solvents, and confirmed the reduced purification for the Contrex solution. It was, therefore, considered that the presence of inorganic salts decreased the photocatalytic efficiency. Furthermore, variations in the methylene blue decomposition ability were observed between anion-free and cation-free Contrex. Finally, we concluded that the efficiency of photocatalytic decomposition of TiO2 was influenced by multiple parameters, including the presence of anions and cations, as well as the solution pH.

Synthesis, crystal structure, and optical properties of the noncentrosymmetric sulfide Ce8Sb2S15

The new noncentrosymmetric sulfide Ce8Sb2S15 has been prepared at 1223K in an evacuated silica tube. It crystallizes in the RE8Sb2S15 (RE=La, Pr, Nd) structure type with a=15.7871(6)Å, c=19.7992(16)Å, V=4934.6(5)Å3. The structure contains the discrete [SbS3]3– trigonal pyramids, which are packed in a noncentrosymmetric pseudolayer motif perpendicular to the c direction and lead to a polar structure. The Ce3+ cations and S2– anions located between them. It exhibits a weak SHG response in the IR region. UV/Vis diffuse reflectance spectroscopy study indicates that the optical gap of Ce8Sb2S15 is about 1.99eV, showing a red shift with respect to the corresponding ternary sulfides: La8Sb2S15, which was attributed to the allowed electronic transfer from the narrow Ce 4f level to the conduction band, mainly built from the empty Ce 5d orbitals.

Synthesis, Luminescence and Nonlinear Optical Properties of Homoleptic Tetracyanamidogermanates ARE[Ge(CN2)4] (A = K, Cs, and RE = La, Ce, Pr, Nd, Sm, Eu, Gd)

Two new series of tetracyanamidogermanates were prepared by solid‐state reaction of appropriate amounts of REF3 (RE = rare earth), A2[GeF6] (A = alkaline), and Li2(CN2) in evacuated silica tubes. Powder X‐ray diffraction patterns of crystalline samples of KRE[Ge(CN2)4] and CsRE[Ge(CN2)4] were indexed isotypically to KRE[Si(CN2)4] and RbRE[Ge(CN2)4], respectively. Luminescence properties of Ce3+, Eu3+, and Tb3+ doped compounds and non‐linear optical properties (NLO) of KRE[Ge(CN2)4] are reported.

The New Semiconductor Cs4Cu3Bi9S17

New quaternary chalcogenide Cs4Cu3Bi9S17 has been synthesized by solid state reaction in a vacuum-sealed silica tube. Cs4Cu3Bi9S17 adopts monoclinic space group P21/m, with the following dimensions: a = 20.006(4) A, b = 4.0556(8) A, c = 22.279(5) A, and β = 96.921°. The crystal structure of Cs4Cu3Bi9S17 features a unique three-dimensional framework consisting of interconnected Bi2Te3- and CdI2-type fragments forming three different-sized tunnels running parallel to the b-axis. The tunnels are filled with different numbers (1, 2, or 4) of Cs atoms. Cs4Cu3Bi9S17 is stable in air at room temperature, and differential thermal analysis showed that it decomposes at elevated temperatures. Cs4Cu3Bi9S17 is a semiconductor with a direct optical band gap of 0.9 eV, which is in agreement with density functional theory calculations. Electrical conductivity and Seebeck coefficient measurements show n-type semiconductor behavior. The electrical conductivity is 10–4 S/cm at 300 K and increases to 0.9 S/cm at 773 K. Cs4Cu...

Innovative Technology for Preparation of Seamless Nitinol Tubes Using SHS Without Forming

This paper presents innovative technology for the production of seamless Ni-Ti tubes using self-propagating high-temperature synthesis (SHS). The proposed production technology is a unique method which removes the need of forming operations, reduces machining processes, and at the same time it eliminates the negatives of production Ni-Ti alloys by conventional melting methods. The proposed process consists in SHS reaction in evacuated silica tube with the use of extremely high heating rate (over 300 K min−1).