Silica Tube Research Articles

Li9Yb2[PS4]5 and Li6Yb3[PS4]5: two lithium-containing ytterbium(III) thiophosphates(V) revisited

Abstract The lithium ytterbium ortho-thiophosphates Li9Yb2[PS4]5 and Li6Yb3[PS4]5 were prepared through the reaction of stoichiometric amounts of ytterbium metal, elemental sulfur, red phosphorus and lithium hemisulfide at elevated temperatures in sealed silica tubes. The compounds occur as dark red single crystals which crystallize monoclinically in space group C2/c with the lattice parameters a = 1487.98(9), b = 978.63(6), c = 2046.75(12) pm and β = 96.142(3)° for Li9Yb2[PS4]5 (Z = 4) and a = 2814.83(16), b = 997.34(6), c = 3338.52(19) pm and β = 113.685(3)° for Li6Yb3[PS4]5 (Z = 12). Li9Yb2[PS4]5 can be assigned to the structure type of Li9Nd2[PS4]5, whereas the structure of Li6Yb3[PS4]5 the structure is similar to that of the prototypic Li6Gd3[PS4]5. Both structures feature discrete [PS4]3– tetrahedra (d(P–S) = 202–207 pm) and strands of [YbS8]13− polyhedra (d(Yb–S) = 271–319 pm) propagating along [010]. When attributed to the general formula (Li3[PS4]) x (Yb[PS4]) y , ideas of the dimensionality of both structures can be derived. Whilst the lithium-richer Li9Yb2[PS4]5 (x/y = 1.5) develops planes with the composition ∞ 2 { [ Y b [ P S 4 ] 3 ] 6 − } ${}_{\infty }^{2}\left\{{\left[\mathrm{Y}\mathrm{b}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{3}\right]}^{6-}\right\}$ , Li6Yb3[PS4]5 (x/y = 0.667) exhibits a rather complex three-dimensional network of ytterbium-centered polyhedra connected via [PS4]3– tetrahedra with lithium cations in the framework structure ∞ 3 { [ Y b 3 [ P S 4 ] 5 ] 6 − } ${}_{\infty }^{3}\left\{{\left[\mathrm{Y}{\mathrm{b}}_{\mathrm{3}}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{5}\right]}^{6-}\right\}$ . These Li+ cations are hard to locate in both compounds, but reside in four- to sixfold sulfur coordination (d(Li–S) = 235–304 pm). Some Li+ positions are underoccupied and some Li+ cations share sites with Yb3+ cations in Li6Yb3[PS4]5, and even in Li9Yb2[PS4]5 their high displacement values suggest Li+ cation mobility. According to the empirical formulae, three Li+ cations have to be replaced with one Yb3+ cation to reach the lithium-poorer compound and structure (Li6Yb3[PS4]5) starting from the lithium-richer one (Li9Yb2[PS4]5).

Temperature-independent ultra-sensitive refractive index sensor based on hollow-core silica tubes and tapers.

We demonstrate a simple and ultra-sensitive refractive index (RI) sensor using a hollow-core silica tube (HCST) sandwiched between an up-taper and a down-taper in single mode fibers (SMF). According to our theoretical analysis, the interference spectrum comes from a combination of a three-beam multi-mode interference and anti-resonance effects. RI sensing will affect the mode interference. By demodulating the fringe contrast of the interference spectra, an ultrahigh sensitivity of -120.18 dB/RIU is achieved, implying a RI resolution of ∼ 8×10-6 in the RI range from 1.35 to 1.43. What's more, the sensor has great temperature insensitivity of -0.0085 dB/°C, indicating an extremely low cross sensitivity of 7×10-5 RIU/°C, which further benefits its practical application. The proposed configuration does not require special fiber or fabrication technique. In addition, the sensor's other merits such as simple and compact structure and ease offabrication offer the potential in biochemical sensing applications.

Effects on the seebeck co-efficient and electrical properties of Tl10-x ATe6 (A= Pb & Sn) in chalcogenide system

The different elements are doping in the tellurium telluride to determine the different properties like electrical and thermal properties of nanoparticles. The chalcogenide nanoparticles can be characteristics by the doping of the different metals which are like the holes. We present the effects of Pb and Sn doping on the electrical and thermoelectric properties of Tellurium Telluride Tl10-xPbxTe6 and Tl10-xSnxTe6(x=1.00, 1.25, 1.50, 1.75, 2.00) respectively, which were prepared by solid state reactions in an evacuated sealed silica tubes. Structurally, all these compounds were found to be phase pure as confirmed by the x-rays diffractometery (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis. The thermo-power or Seebeck co-efficient (S) was measured for all these compounds which show that S increases with increasing temperature from 295 to 550 K. The Seebeck coefficient is positive for the whole temperature range, showing p-type semiconductor characteristics. Similarly, the electrical conductivity (σ) and the power factors have also complex behavior with Pb and Sn concentrations. The power factor (PF=S 2 σ) observed for Tl10-xPbxTe6 and Tl10-xSnxTe6 compounds are increases with increase in the whole temperature range (290 K-550 K) studied here. Telluride’s are narrow band-gap semiconductors, with all elements in common oxidation states, according to (Tl + ) 9 (Pb 3+ )(Te 2- )6 and (Tl + )9(Sn 3+ )(Te 2- )6. Phases range were investigated and determined with different concentration of Pb and Sn with consequents effects on electrical and thermal properties.

Stability of aqueous Fe(III) chloride complexes and the solubility of hematite between 150 and 300 °C

Three sets of experiments were performed to test the stability and geologic importance of ferric (FeIII) chloride complexes in acidic, Cl-rich solutions at 150–300 °C, p = psat. Experiment Set A used the change in solubility of AgCl(s) in the presence of FeCl3 or FeCl2 to determine the stoichiometry of Fe(III) and Fe(II) chloride complexes at ΣCl = 0.1–3.0 molal. Results show that FeCl4− and FeCl2(aq) are the dominant Fe(III) and Fe(II) species, respectively, at T > 200 °C and ΣCl ≥ 1 m. Set B experiments used the solubility of elemental gold as a redox sensor to determine the aO2 of the FeCl4−/FeCl2(aq) boundary and log K values of +6.56 and +7.19 for the following reaction at 250 and 300 °C, respectively: FeCl2(aq) + ¼O2(g) + 2Cl− + H+ = FeCl4− + ½H2O(l). Ferric chloride complexes are stable under conditions of aCl−, aO2, and pH where gold is soluble as AuCl2−. Set C experiments measured the solubility of hematite in NaCl-HCl solutions at 200–300 °C by preparing a series of silica tubes with identical matrix chemistry (0.9 m NaCl + 0.1 m HCl) and increasing concentration of FeCl3. Hematite saturation was constrained by the tube with the lowest FeCl3 concentration that precipitated hematite at high temperature. Set C results were used to compute log K values of +3.6, +5.2, and + 7.4 for the following reaction at 200, 250 and 300 °C, respectively: 0.5Fe2O3(s) + 4Cl− + 3H+ = FeCl4− + 1.5H2O.Hematite solubility as FeCl4− is independent of redox state, and increases quickly with an increase in temperature, increase in Cl− concentration (power of 4), and decrease in pH (power of 3). Concentrations in excess of 100 mg/L ΣFe are attainable under geologically realistic conditions. Once formed, FeCl4− is an extremely effective oxidizing agent, capable of destabilizing any sulfide mineral and dissolving Fe, Au, and other metals (e.g., Cu, Pt, Pd) as chloride complexes. In deep hydrothermal systems, FeCl4− is a more viable oxidant than dissolved O2 gas, although its presence requires a source area with abundant hematite and a lack of reductants such as organic carbon, sulfides, or silicate minerals containing ferrous iron. Dissolved ferric chloride could be an important and previously overlooked reactant in the formation of certain types of hematite-rich hydrothermal mineral deposits, including iron oxide-copper–gold (IOCG) deposits.

Phase equilibrium in the system Y-Ni-In at 870 K

Interaction of the components in Y ‑ Ni ‑ In system was investigated by X-ray powder methods and isothermal section of phase diagram was constructed at 870 K in full concentration range. The samples were synthesized in an arc-furnace on a water-cooled Cu-plate under an argon atmosphere and annealed in silica tubes at 870 K for one month. The phase analysis was performed by X-ray powder diffraction method. Twelve ternary compounds, namely YNi 9 In 2 (YNi 9 In 2 -type structure), Y 1-1 . 40 Ni 4 In 1-0 . 60 (MgCu 4 Sn-type structure), YNiIn 2 (MgCuAl 2 -type structure), Y 4 Ni 11 In 20 (U 4 Ni 11 Ga 20 -type structure), YNi 1 . 00-0 . 50 In 1 . 00-1 . 50 (ZrNiAl-type structure), Y 2 Ni 2 In (Mn 2 AlB 2 -type structure), Y 2 Ni 1 . 78 In (Mo 2 FeB 2 -type structure), Y 5 Ni 2 In 4 (Lu 5 Ni 2 In 4 -type structure), Y 11 Ni 4 In 9 (Nd 11 Pd 4 In 9 -type structure), Y 12 Ni 6 In (Sm 12 Ni 6 In-type structure), Y 13.84 Ni 3.19 In 2.97 (Lu 14 Co 3 In 3 -type structure), ~Y 3 Ni 0.05 In 0.95 (AuCu 3 -type structure) exist in the Y ‑ Ni ‑ In system at the temperature of annealing. Compound Y 3 Ni 2.26 In 3.74 exists at higher temperature. The substitution of Ni for In was observed for YNi 1.00-0.50 In 1.00-1.50 and In for Y in the case of Y 1-1,40 Ni 4 In 1-0,60 compound. Besides, yttrium can enter the structure of NiIn (CoSn-type) leading to formation of including-subtraction type solid solution, which is stable for 0 ‑ 8 at. % Y. The composition of this solid solution can be described by the formula Y 0-0 . 16 NiIn 1-0 . 93 . The inclusion of yttrium and indium atoms in position (2 e ) with the simultaneous exclusion of a small amount of indium atoms from position (1 a ) takes place in the homogeneity range of this solid solution. The character of component interaction in the ternary Y ‑ Ni ‑ In system is similar to other related ternary system R ‑ T ‑ In ( R – rare earth of the yttrium subgroup). The common feature of all these systems is the existence of large number isotypical ternary compounds, the formation of homogeneity range for compounds with ZrNiAl and including-subtraction type solid solutions based on the binary compound NiIn. Keywords: yttrium, indium, nickel, phase equilibria, ternary compound, crystal structure.

Crystal structure of the new ternary aluminide ErAg0.77Al2.23

Сrystal structure of the ternary erbium and silver aluminide ErAg 0 . 77 Al 2 . 23 has been studied using powder X-ray diffraction data: space group R-3m , Pearson symbol h R36 , lattice parameters a = 0.55049(1) nm, c = 2.61415(6) nm, final residual values are R I = 0,0450; R P = 0,0314; wR P = 0,0430. Samples were prepared by an arc melting under purified argon atmosphere with nonconsumable tungsten electrode and water-cooled copper hearth of the elemental components with certified purities of 99.999 wt.% Er, 99.95 wt.% Ag and 99.99 wt.% Al. All samples were re-melted twice to ensure homogeneity, and then heat treated in evacuated silica tubes at 600 o C during 700 hours. Annealed alloys were quenched in cold water without breaking the tubes. Phase analysis of the prepared samples and crystal structure determination of new compound were carried out using X-ray powder diffraction patterns recorded on a automatic powder diffractometer Huber Imaging Plate Guinier Camera G670 (Cu K α1 -radiation, l = 0.154056 nm; 3.503 ≤ 2 θ ≤ 99.99°; step 0,01° of 2 θ , scan time is 250 sec per step). Refinement of the atomic positional and displacement parameters in the crystal structure of the compounds was carried out by the full profile Rietveld method in the range 2 θ =3.50­–99.99 o (Cu K α1 -radiation) using the WinCSD program package. Existence of the new ternary aluminide ErAg 0 . 77 Al 2 . 23 with the rhombohedral structure of the PuNi 3 -type was found in the two three-component samples of the starting compositions Er 0 . 25 Ag 0 . 20 Al 0 . 55 and Er 0 . 25 Ag 0 . 17 Al 0 . 58 . In both samples new aluminide was in thermodynamic equilibrium with the small admixtures of the earlier known ternary phases ErAg 2 . 5 Al 2 . 5 (DyAg 2 . 4 Al 2 . 6 -type structure) and Er 8 Ag 17 Al 49 (Yb 8 Cu 17 Al 49 -type structure). Partially ordered distribution of the smaller atoms Ag and Al was observed in the crystal structure of new intermetallide, in particular Wyckoff site 6 с is fully occupied by Ag atoms, whereas Wyckoff sites 3 b and 18 h are occupied by the statistical mixtures of Ag and Al atoms with a predominant content of aluminum atoms leading to the next formulas ErAg 0 . 77(1) Al 2 . 23(1) or Er(Ag 0 . 26 Al 0 . 74 ) 3 . Interatomic distances in the ErAg 0 . 77 Al 2 . 23 crystal structure are in good correlation with the respective sums of the atomic radii of the components indicating predominance of the metallic bonding. Structure type PuNi 3 (or NbBe 3 ) can be considered as formed from the structural units of the CaCu 5 and MgZn 2 structure types. Keywords: crystal structure, X-ray powder diffraction, aluminide, erbium, silver.

Electrochemical delithiation of the binary LiAl, Li3Al2, Li9Al4 and boron–doped phases

The process of electrochemical delithiation of LiAl (structure type (ST) NaTl, space group (SG) Fd m ), Li 3 Al 2 (own ST, SG R m ), Li 9 Al 4 (own ST, SG C 2/ m ) intermetallic compounds and doped by boron LiAl 1- y B y , Li 3 Al 2- y B y , Li 9 Al 4- y B y phases was investigated by X-ray powder diffraction and scanning electron microscopy. The samples were synthesized by arc melting of pressed pellets of pure components under an argon atmosphere and further annealing of the alloys at 200 ºC for 1 month in sealed evacuated silica tubes without quenching. Electrochemical delithiation of the phases, which were used as anode materials, was carried out in the two-electrode prototype of the battery “Swagelok-cell”. LiCoO 2 (ST NaFeO 2 ) was used as cathode material. The anode and cathode materials were separated by pressed cellulose to avoid contact between them. An electrolyte for batteries consisted of 1 M Li[PF 6 ] solution and a mixture of aprotic solvents ethylene carbonate and dimethyl carbonate (1:1 vol. ratio). X-ray phase analysis was carried out on powder data obtained on automatic diffractometer DRON-2.0M (Fe K α -radiation). Investigated alloys contained the expected phases and small amount of other phases. Solid solutions of the substitution had homogeneity ranges about 5 at. % of boron and were characterized by reduced unit cell parameters. All observed binary and ternary phases demonstrated electrochemical ability. The unit cell parameters of the binary and ternary phases reduced after the delithiation. The lithium mobility of the electrodes on the basis of the LiAl, Li 3 Al 2 , and Li 9 Al 4 alloys was 0.16 Li/f.u., 0.52 Li/f.u., and 1.6 Li/f.u., respectively. The better results were obtained for the electrodes based on the B-doped alloys: 0.18 Li/f.u. for the LiAl 1- y B y , 0.61 Li/f.u. for the Li 3 Al 2- y B y , and 1.8 Li/f.u. for the Li 9 Al 4- y B y phase. In all cases the surface morphology of the electrodes after 50 cycles of delithiation was changed and became more porous. The small particles (80‒500 nm) aggregation increased as a result of material amorphization and interaction of the electrode surface with electrolyte. Keywords: synthesis, solid solution of the substitution, electrochemical delithiation, Li-ion batteries.

Experimental investigation and modeling of boundary layer flashback for non-swirling premixed hydrogen/ammonia/air flames

Carbon free fuels such as hydrogen/ammonia blends show a promising potential to become sustainable and renewable fuels for gas turbines and other combustion systems. One interesting aspect about these blends is the possibility to adjust different combustion properties like the laminar burning velocity or ignition delay time by changing the ratio between H2 and NH3. Such fuel blends can be produced via partial catalytic decomposition of NH3. However, such mixtures can lead to flame instabilities such as flashback, especially if the hydrogen content is high. In the present study, the boundary layer flashback of premixed hydrogen/ammonia/air mixtures is investigated experimentally for non-swirling flows at normal temperature (293 K) and normal pressure (101 kPa). A new experimental setup for boundary layer flashback investigation with a fully automated measurement procedure is introduced. With preliminary studies, the influence of various measurement procedures on the flashback limits is firstly investigated. For a broad flashback study, the data of 351 flashback experiments are collected. The ammonia content in H2/NH3 fuel mixtures is varied from 0 vol% to 50 vol% in 10 vol% steps. The fuel–air equivalence ratio is ranging from 0.38 to 1.17. As the ammonia content is increasing, the mean flow velocities at flashback are exponentially decreasing. Additionally, theoretical modeling is performed. A model is derived based on the concept of the critical velocity gradient which is able to predict the measured data with high accuracy. For two exemplary cases with H2/air and 80% H2/20% NH3/air mixtures, the process of boundary layer flashback is investigated in detail with low and high speed direct imaging and image post-processing. During the flashback onset of H2/NH3/air flames a separate reaction of H2 followed by the reaction of NH3 can be observed. Also, a flame-oscillation between fused silica tube and burner head with approximately 10 Hz was observed. Furthermore, indications for an adverse pressure gradient based on the flame propagation speed is seen. Details about the flame structure during the flashback process of H2/NH3/air flames are shown. During the upstream flame propagation of H2/NH3/air flames, high frequency oscillations with about 830 Hz of the leading flame tip are observed, which are assumed to be related to thermoacoustic instabilities.

DIPG-42. TOWARD MULTIMODALITY THERAPY FOR DIPG/DMG: DEVELOPMENT AND INVESTIGATION OF CRANIOSPINAL IRRADIATION AND CONVECTION-ENHANCED DELIVERY PDX MODELS

BACKGROUNDDiffuse intrinsic pontine glioma (DIPG) and diffuse midline glioma (DMG) are metastatic diseases, as demonstrated by early convection-enhanced delivery (CED) clinical trials in which prolonged local tumor control can sometimes be achieved, but fatal disseminated disease then develops. We hypothesize that improvements in treatment of both focal disease and the entire neuraxis are necessary for long-term survival, and patient-derived xenograft (PDX) models can help advance these efforts.METHODSWe used a BT245 murine orthotopic DIPG PDX model for this work. We developed a protocol and specialized platform to deliver craniospinal irradiation (CSI) with a pontine boost. We separately compared intratumoral drug concentration by CED and intraperitoneal delivery. In our CED model, mice receive gemcitabine 60 ug x1 in 15 ul at 0.5 ul/minute through a stepped catheter design with silica tubing extending 2mm beyond a 27G needle.RESULTSMice receiving CSI (4 Gy x2d) plus boost (4 Gy x2d) showed minimal spinal and brain leptomeningeal metastatic disease by bioluminescence, MRI, and pathology compared to mice receiving radiation to the pons only (4 Gy x4d) or no radiation. CED achieved an intratumoral gemcitabine concentration 50-fold greater than intraperitoneal dosing when controlled for dose.CONCLUSIONSIn a DIPG PDX model, CSI+boost minimizes tumor dissemination compared to focal radiation, and CED achieves clinically significant improvements in intratumoral chemotherapy concentration compared to systemic delivery. Adding these modalities to current treatment could improve both focal and metastatic tumor control, leading to meaningful improvements in survival.

Ba3[LiSbS2(S2)2Cl2]: The first zero-dimensional (0D) lithium metal thioantimonate featuring molecular anions of [LiSbS2(S2)2Cl2]6–

The first lithium metal thioantimonate featuring 0D structure, namely Ba3[LiSbS2(S2)2Cl2], has been prepared from a mixture of BaCl2, LiCl, Ba, Sb, and S in an evacuated graphite crucible coated silica tube. The Ba3[LiSbS2(S2)2Cl2] crystallizes in space group C2/m (No. 12) with a ​= ​13.308(9) Å, b ​= ​12.116(7) Å, c ​= ​9.408(6) Å, V ​= ​1425.4(16) Å3 and Z ​= ​4. It adopts a new 0D structure type with unusual discrete clusters of [LiSbS2(S2)2Cl2]6– arranged in a pseudolayer motif extending in ab plane. The Ba2+ cations are located in the interspaces. The molecular anions of [LiSbS2(S2)2Cl2]6– can be best regarded as eight-membered rings built of two LiS2(S2)2 tetrahedra and two disordered SbS2Cl2 teeter-totter polyhedra via corner-sharing. Another notable structural feature is the occurrence of the LiS2(S2)2 tetrahedra which are derived from the LiS4 tetrahedra by substituting two terminal S2− anions with two disulfide [S2]2– units. Disordered SbS2Cl2 teeter-totter polyhedra are derived from the fusing of the two trigonal-pyramidal SbS2Cl units. Moreover, presence of chloride anions in terminal vertexes of SbS2Cl trigonal pyramids as well as Ba-rich ratio may be responsible for ceasing the propagation of Li/Sb/S networks, resulting in the unusual 0D structure in the titled compound. In addion, the density functional theory (DFT) study reveals a direct bandgap of 2.6 ​eV, which can be ascribed to the electronic transitions from the top of valence band dominated by the 3p states of disulfide [S2]2– to the 5d states of Ba atoms and 3p states of disulfide [S2]2–.

Development of Highly Sulfur-Loadable Microporous Activated Carbon from Azulmic Acid for Lithium-Sulfur Battery

IntroductionThe lithium-Sulfur battery shows ca. 10 times higher energy density than that of the lithium ion battery. However, a major problem is the behavior of lithium polysulfide intermediates, which may dissolve into an electrolyte. We have investigated microporous activated carbon as matrix stabilizing S and realized stable cycling performance.1,2 However, the activated carbon with only micropores has a relatively low sulfur loading (ca.30 wt.%) and needs to be improved. We previously reported azulmic carbon (AZC), which has many micropores that suppress the dissolution of lithium polysulfides and is capable of high sulfur loading (ca.60 wt.%).3 In this study, we have successfully produced AZC capable of further high sulfur loading by improving a typical activated carbon production method. The sulfur cathode using this improved AZC and sulfur composite showed a better charge-discharge capacity than the previous AZC.MethodAZC was carbonized from azulmic acid (AZA) at 800°C for 1h under N2 atmosphere (the obtained product is denoted by AZA-800 hereafter). AZA-800 and KOH or K2CO3 were mixed by a ratio of 1:2. Those mixtures were heated at a predetermined temperature of 800 to 900 ℃ for 1h under Ar atmosphere in a silica tube for alkaline activation of AZA-800. The AZC-S composite was prepared by mixing various AZC with S, and then applying heat treatment: 155°C for 5 h, then 300°C for 2 h. The AZC-S composite cathode was prepared by mixing the AZC-S composite, acetylene black, carboxymethyl cellulose, and styrene-butadiene rubber at a respective weight ratio of 89:5:3:3. The electrolyte was prepared by mixing lithium bis(trifluoromethylsulfonyl)imide with tetraglyme and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether at a ratio of 10:8:40 (by mol). All the cell components were installed into a demountable cell with a lithium anode. A typical charge-discharge cycling test was carried out at 167.2 mA g-1 (0.1 C) with cutoff voltages of 3.0 and 1.0 V at 25°C.Major results and conclusionFigure 1 shows the pore size distribution of AZC-KOH and AZC-K2CO3. It was confirmed that the pore volume of AZC-K2CO3 increased as the activation temperature increased. When K2CO3 was used as an activator, the proportion of micropores tended to be higher than that with KOH. AZC-K2CO3 can confine up to 70 wt.% sulfur, which is ca.10 wt.% higher than the previous AZC-KOH. Figure 2 shows the results of constant current charge and discharge tests of the cathode prepared using AZC-KOH and AZC-K2CO3 with sulfur composites. AZC-K2CO3 has a lower capacity decay rate with charge / discharge cycles than AZC-KOH, which may be due to a large proportion of micropores that suppresses the elution of lithium polysulfides. The activation procedure using K2CO3 provides activated carbon with a lot of micropores and hence high sulfur loading. It was suggested that AZC-K2CO3 is a promising activator for achieving high energy density in positive electrodes of lithium-sulfur batteries.This work was supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING)” from Japan Science and Technology Agency (JST); Grant#: JPMJAL1301.References T. Takahashi et al., Prog. Nat. Sci.: Mater. Int., 25, 612 (2015).S. Okabe et al., Electrochemistry, 85, 671 (2017).S. Usuki et al., Electrochemistry, 85, 650 (2017). Figure 1

Full‐Inorganic Micro‐Fiber Probe for Real‐Time Radiation Monitoring

AbstractScintillators convert high‐energy radiation into visible luminescence and have been widely applied in various significant fields such as nuclear fusion monitoring, high‐energy particle physics, medical imaging, and geological exploration. The scalable fabrication of scintillating fiber with the desirable combination of uniform size, superior radiation blocking ability, and excellent thermal/radiation stability is a major challenge. Here, a template solidification strategy for fabrication of full‐inorganic and efficient scintillating fiber is presented. The strategy involves the direct solidification of high‐density scintillator melt in a softened silica tube, allowing for the continuous production of small and uniform scintillating fiber. The fabricated scintillating fiber can effectively attenuate radiation up to ≈118 times higher than what conventional silica fiber can. In addition, it exhibits good compatibility with commercial fiber. Using this scintillating fiber, a radiation fiber detector is constructed and its application for online radiation monitoring is demonstrated.

Hollow-Core Negative Curvature Fiber with High Birefringence for Low Refractive Index Sensing Based on Surface Plasmon Resonance Effect.

In this paper, a hollow-core negative curvature fiber (HC-NCF) with high birefringence is proposed for low refractive index (RI) sensing based on surface plasmon resonance effect. In the design, the cladding region of the HC-NCF is composed of only one ring of eight silica tubes, and two of them are selectively filled with the gold wires. The influences of the gold wires-filled HC-NCF structure parameters on the propagation characteristic are investigated by the finite element method. Moreover, the sensing performances in the low RI range of 1.20–1.34 are evaluated by the traditional confinement loss method and novel birefringence analysis method, respectively. The simulation results show that for the confinement loss method, the obtained maximum sensitivity, resolution, and figure of merit of the gold wires-filled HC-NCF-based sensor are −5700 nm/RIU, 2.63 × 10−5 RIU, and 317 RIU−1, respectively. For the birefringence analysis method, the obtained maximum sensitivity, resolution, and birefringence of the gold wires-filled HC-NCF-based sensor are −6100 nm/RIU, 2.56 × 10−5 RIU, and 1.72 × 10−3, respectively. It is believed that the proposed gold wires-filled HC-NCF-based low RI sensor has important applications in the fields of biochemistry and medicine.

Fabry-Perot vector curvature sensor based on cavity length demodulation

Abstract We have demonstrated a high-sensitivity Fabry-Perot curvature sensor. The main components of its sensing fiber are hollow silica tube and single-mode fiber (SMF). When the sensor is bent, the length of the FPI changes with curvature. Hereby, we can achieve vector curvature measurement through cavity length demodulation. The convex and concave bending sensitivities are 151.30 nm/m−1 and −333.89 nm/m−1, respectively. Besides, the curvature sensitivity is optimized with the increase of air cavity length. The packaging of the sensing fiber increases its robustness while increasing its sensitivity from 151.30 nm/m−1 to 251.54 nm/m−1. Meanwhile, the structure is insensitive to axial stress and refractive index (RI). This sensor has potential applications in engineering health detection and small-scale structural deformation detection.

Cascaded Fabry-Perot interferometer-regenerated fiber Bragg grating structure for temperature-strain measurement under extreme temperature conditions.

We demonstrated an optical fiber sensor based on a cascaded fiber Fabry-Perot interferometer (FPI)-regenerated fiber Bragg grating (RFBG) for simultaneous measurement of temperature and strain under high temperature environments. The FPI is manufactured from a ∼74 µm long hollow core silica tube (HCST) sandwiched between two single mode fibers (SMFs). The RFBG is inscribed in one of the SMF arms which is embedded inside an alundum tube, making it insensitive to the applied strain on the entire fiber sensor, just in case the temperature and strain recovery process are described using the strain-free RFBG instead of a characteristic due-parameter matrix. This feature is intended for thermal compensation for the FPI structure that is sensitive to both temperature and strain. In the characterization tests, the proposed device has exhibited a temperature sensitivity ∼ 18.01 pm/°C in the range of 100 °C - 1000 °C and excellent linear response to strain in the range of 300 °C - 1000 °C. The measured strain sensitivity is as high as ∼ 2.17 pm/µɛ for a detection range from 0 µɛ to 450 µɛ at 800 °C, which is ∼ 1.5 times that of a FPI-RFBG without the alundum tube.

Ultrasensitive Fabry–Perot Strain Sensor Based on Vernier Effect and Tapered FBG-in-Hollow Silica Tube

A dual Fabry-Perot interferometers (FPIs) sensor is demonstrated theoretically and experimentally for ultrasensitive strain sensing by using the Vernier effect and the tapered FBG-in-hollow silica tube (HST) structure. The proposed sensor consists of two parallel structured FPIs connected by a 3dB coupler to generate the Vernier effect, and the tapered FBG-in-HST structure has long active length to achieve strain sensitivity enhancement and plays the role as the sensing interferometer. Moreover, utilizing the characteristic of FBG not affected by strain, the temperature compensation has been achieved by means of a demodulating matrix. The fabricated strain sensor achieves an ultra-high strain sensitivity of 1.307 nm/με, which is the highest strain sensitivity of the FPI-based sensors reported so far. It is low-cost, robust, easy-fabrication, and expected to have great application prospects in several fields where large strain sensitivity is really required.

Time-Resolved In Situ Neutron Diffraction Study of Cu22Fe8Ge4S32 Germanite: A Guide for the Synthesis of Complex Chalcogenides

Solid-state synthesis in a sealed silica tube is one of the most popular methods for the production of inorganic materials. Nevertheless, the determination of the best synthesis conditions is a trial-and-error process that generally requires many experiments, varying temperature and duration time. In the present work, the synthesis of a polycrystalline sulfide by solid-liquid-gas reaction in a sealed silica tube is, for the first time, monitored in situ by time-resolved neutron powder diffraction (NPD). All successive crystallization/decomposition sequences and intermediate products were analyzed in detail. These results were combined with ex situ X-ray powder diffraction and thermal analyses on crystallized samples. Our results revealed that sealed tube synthesis is highly dynamic, with reaction times shorter than expected. Importantly, the experiments revealed the primordial role of the cooling conditions on the secondary phase formation and stability. Beyond new data on the complex crystal chemistry of germanite Cu22Fe8Ge4S32, our study demonstrates the compelling benefits of time-resolved in situ NPD in the optimization of the synthesis process for a wide range of complex chalcogenide materials.

Advanced distributed feedback lasers based on composite fiber heavily doped with erbium ions

Specially designed composite heavily Er3+-doped fiber in combination with unique point-by-point inscription technology by femtosecond pulses at 1,026 nm enables formation of distributed-feedback (DFB) laser with ultra-short cavity length of 5.3 mm whose parameters are comparable and even better than those for conventional Er3+-doped fiber DFB lasers having much longer cavity. The composite fiber was fabricated by melting rare-earth doped phosphate glass in silica tube. The ultra-short DFB laser generates single-polarization single-frequency radiation at 1,550 nm with narrow linewidth (3.5 kHz) and 0.5 mW output power at 600 mW 980-nm pumping. The same fiber with conventional CW UV (244 nm) inscription technology using phase mask enables fabrication of 40-mm long DFB laser with > 18 mW output power at 3.3% pump conversion, which is a record efficiency for Er3+-doped fiber DFB lasers. The developed technologies form an advanced platform for Er3+-doped fiber DFB lasers operating around 1.55 µm with excellent output characteristics and unique practical features, in particular, the ultra-short DFB lasers are attractive for sensing applications.

Exceeding 50% slope efficiency DBR fiber laser based on a Yb-doped crystal-derived silica fiber with high gain per unit length.

We fabricated a Yb-doped yttrium aluminium garnet (Yb:YAG) crystal-derived silica fiber (YCDSF) using an assembly consisting of a YAG crystal rod and silica tube on a CO2 laser-heated drawing tower. The fiber has a Yb concentration of 5.66 wt%, and absorption coefficient of 32 dB/cm at 980 nm. The figure of merit of the unsaturated absorption and gain per unit length of the YCDSF are 93% and 4.4 dB/cm, respectively. Based on the results of the numerical simulation, an all-fiber distributed Bragg reflector (DBR) laser using only a 1.5-cm-long YCDSF is experimentally demonstrated to have a maximum output power of 360 mW with a pump threshold power of 21 mW. The fiber laser also achieved an optical signal-to-noise ratio of 80 dB, a beam quality factor of 1.022 in two orthogonal directions and a slope efficiency of up to 50.5%. These results indicate that the all-fiber DBR laser has potential applications in high-quality seed sources and coherent optical communications.

The Influence of the MCVD Process Parameters on the Optical Properties of Bismuth-Doped Phosphosilicate Fibers

In this article, we describe the technology for manufacturing of the phosphosilicate bismuth-doped optical fibers providing optical amplification near 1.32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m. The effect of preforming sintering process and fiber drawing on the optical properties of the fabricated fibers were studied. We showed that an increase in the vitrification temperature of the P-doped silica glass soot layers deposed on the inner surface of a fused silica tube from 1850 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf {\sim \text{2000}}$</tex-math></inline-formula> °C (while keeping other parameters unchanged) provides a noticeable reduction of the unsaturable losses. We also found that the fiber drawing speed significantly affects the optical properties of bismuth-doped fibers. In particular, an increase in the drawing speed from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 1 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 80 m/min led to a decrease of both active absorption and unsaturable losses, while the ratio of active absorption to unsaturable losses became greater. As a result, the laser efficiency of the bismuth-doped fibers grew two-fold from 19.5% to 37%.