Ti Fiber Research Articles

New Electrocatalyst with the Content of Ir

Introduction Proton exchange membrane (PEM) water electrolysis (WE) is a promising technology for hydrogen production. However, the local environment of the anode in PEMWE is highly acidic and high potential due to the oxygen evolution reaction (OER; 2H2O → O2 + 4H+ + 4e-), and the available anode materials are limited to precious metal elements such as Pt, Ru and Ir. In the current technology, Ir-based materials are the mainstream anode catalysts, and Ir loading of 1-2 mg/cm2 is necessary to achieve both activity and durability. On the other hand, the annual production of Ir is said to be only 5-7 tons. The demand for hydrogen is expected to increase to the GW scale in the future. For example, if water electrolysis is operated at 2 A/cm2 and 2 V with Ir loading of 2 mg/cm2 (0.5 mgIr/W), it is difficult to meet the demand with the existing Ir resources. Tosoh have been engaged in the electrolytic manganese dioxide (EMD) business. EMD is synthesized thorough anodic oxidation of Mn2+ ion (Mn2+ + 2H2O → MnO2 + 4H+ + 2e-) under acidic conditions, therefore it is potentially suitable for the anode environment of PEMWE. In this study, a very small amount of Ir (<0.1 mg/cm2) was successfully composited with EMD. The resulting composite consisting of Ir and EMD showed more active than commercial Ir oxide with the same Ir content, and operated stably for at least 1000 h. Experiment EMD thin film was electrodeposited anodically on Pt-coated Ti fibers (Pt/Ti) thorough electrolyzing a mixed solution of MnSO4 and H2SO4. The obtained EMD-coated Pt/Ti were immersed in an Ir-containing solution, and then annealed to obtain Ir-containing EMD (hereinafter referred to as "Ir-EMD"). The Pt-coated Ti fibers are used as a porous transport layer (PTL) in PEMWE cells, and our developed material serves as both an OER catalyst and a PTL. OER property was evaluated using a PEMWE cell at 80°C in a two-electrode system. Pt-supported carbon was used as the cathode catalyst and Nafion®-115 as the PEM. See Fig. 1 for PEMWE cell construction flow. Result and discussion The Ir content in Ir-EMD was determined to be 0.1 mg/cm2 by ICP-AES. This Ir content is 10-20 times lower than that used in current PEMWE electrolyzers. The OER activity of Ir-EMD was evaluated by linear sweep voltammetry (LSV) (Fig. 2). For comparison, EMD (with no Ir) and Ir oxide (commercial product) with an Ir content of 0.1 mg/cm2 were evaluated in the same way. The slow OER property of EMD was improved dramatically by introducing Ir into EMD. Also, at the same amount of Ir, Ir-EMD exhibited higher OER activity than that of Ir oxide. The inset in Fig. 2 shows Tafel plots corresponding to LSVs, and the slope of the linear region (Tafel slope) can be used to predict which elementary reaction is the rate-limiting step in the OER. The Tafel slope of Ir-EMD is 58 mV/dec., which is close to the Tafel slope of Ir oxide, 50 mV/dec. This suggests that OER on Ir-EMD proceeds by the same mechanism as Ir oxide. The durability of Ir-EMD and Ir oxide was tested at a current density of 2 A/cm2 (Fig. 3). Ir oxide was deactivated within only 8 days, and it is confirmed that Ir have disappeared after electrolysis. On the other hand, Ir-EMD has operated stably for more than 42 days (≈1000 h), with a degradation rate of only 13 μV/h. In other words, Ir-EMD has practical durability while reducing the amount of Ir by more than 10 times compared to current technology.Acknowledgements : This presentation is based on results obtained from a project, JPNP20003, subsidized by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1

Strengthening of continuous Ti fibre with CrFeCoNiCu high entropic alloy coating by magnetron sputtering

The CrFeCoNiCu high entropic alloy (HEA) was coated on the surface of continuous Ti fibres by magnetron sputtering. The coatings' morphology, structure, and strength were then analyzed. The results showed that the CrFeCoNiCu HEA coating inherited the FCC structure of the bulk HEA, and the coating crystallinity decreased with introduced N2. The CrFeCoNiCu and (CrFeCoNiCu)N coatings covered fibres uniformly. The tensile strength of fibres was enhanced greatly with coating CrFeCoNiCu and (CrFeCoNiCu)N by 24.10% and 32.23%, respectively.

Unidirectional titanium fiber-reinforced porous titanium with mechanical properties suitable for load-bearing biomaterials

Biomaterials for load-bearing implants are expected to exhibit mechanical biocompatibility of low stiffness and high strength for avoiding stress shielding and failure of the implants in vivo, respectively. This study aimed to develop porous titanium (Ti) reinforced with long Ti fibers so that the porous Ti exhibited low Young's modulus and high tensile strength. The unidirectional Ti fiber-reinforced porous Ti with porosities (p) of 40%–58% and volume percentages of Ti fiber (Vf) of 3%–33% has been successfully fabricated via the space holder technique. Mechanical testing revealed that its strength was improved, compared with uniform porous Ti because Ti fibers prevent microscopic damage progress. The porous Ti with p = 40% and Vf = 33% exhibited the strength of 233 MPa and Young's modulus of 26 GPa, which were higher than and comparable to those of natural bones, respectively. Hence, the Ti fiber-reinforced porous Ti exhibited ideal mechanical properties for implant applications.

Corrosion-resistant cobalt phosphide electrocatalysts for salinity tolerance hydrogen evolution

Seawater electrolysis is a viable method for producing hydrogen on a large scale and low-cost. However, the catalyst activity during the seawater splitting process will dramatically degrade as salt concentrations increasing. Herein, CoP is discovered that could reject chloride ions far from catalyst in electrolyte based on molecular dynamic simulation. Thus, a binder-free electrode is designed and constructed by in-situ growth of homogeneous CoP on rGO nanosheets wrapped around the surface of Ti fiber felt for seawater splitting. As expected, the as-obtained CoP/rGO@Ti electrode exhibits good catalytic activity and stability in alkaline electrolyte. Especially, benefitting from the highly effective repulsive Cl− intrinsic characteristic of CoP, the catalyst maintains good catalytic performance with saturated salt concentration, and the overpotential increasing is less than 28 mV at 10 mA cm−2 from 0 M to saturated NaCl in electrolyte. Furthermore, the catalyst for seawater splitting performs superior corrosion-resistance with a low solubility of 0.04%. This work sheds fresh light into the development of efficient HER catalysts for salinity tolerance hydrogen evolution.

Enhancing H2 production rate in PGM-free photoelectrochemical cells by glycerol photo-oxidation

The photo-oxidation of glycerol was carried out by using TiO2 NTs photoanodes and Ni foam as the cathode for the Hydrogen Evolution Reaction. The photoanodes were prepared by anodizing Ti foils and titanium felt and then annealed under air exposure. They were tested in acidic aqueous solution without and with the addition of glycerol. When glycerol was present, the hydrogen production rate increased and allowed the simultaneous production of high value added partial oxidation compounds, i.e. 1,3-dihydroxyacetone (DHA), and glyceraldehyde (GA). The highest H2 evolution and partial oxidation compounds production rates were obtained by using home prepared TiO2 nanotubes (TiO2 NTs) synthesized on Ti fiber felt as the photoanode with an irradiated area of 90 cm2. These photoanodes were found to be highly stable both from a mechanical and a chemical point of view, so they can be reused after a simple cleaning step.

Study on the Microstructure and Wear Behavior of In-Situ Al3Ti/Al Composites Under Induction Heating

In the study, Ti fiber (200 μm, 99.8 wt.%) and pure aluminum (99.6 wt.%) were respectively used as the reaction source and matrix to prepare Al-based composites by in-situ synthesis methods. During the stage of preparing the preform, Ti fibers were fixed in the matrix at equal intervals to pre-control the initial position of the product. The preform was heated in an induction heating device finally, at the same time, parameter combinations of different frequencies and currents were applied to promote the in-situ reaction between Al-Ti, thereby the Al matrix composites reinforced by Al3Ti were obtained. The phase composition, microstructure and wear resistance of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and wear testers. The results show that when the frequency and current are 5 kHz and 15 A respectively, the Ti fiber is completely reacted, and the product is the isometric Al3Ti with a size of 1 – 2 μm and a particle spacing of about 5 μm, reaching the optimal microstructure under all parameters. Under the condition of a load of 9.8 N, the wear rate of the composites at 5 kHz and 15 A is 2.325 mg/mm2, indicating the best values in this experiment.

Metallic Gas Diffusion Layers for Polymer Electrolyte Fuel Cells

1. Introduction Various carbon materials are currently used in PEFCs.1,2 In particular, relatively expensive porous carbon materials such as carbon fiber cloth and carbon paper with a thickness of around 0.2 mm are commonly used as the gas diffusion layers (GDLs), which ensure gas flow, electron transport, and water management in fuel cells.3,4 However, electrical conductivity of these carbon materials could be lower than that of metallic materials. Another technical issue is the reduction of GDL thickness to achieve higher power density per cell stack volume, which could however lead to a decrease in mechanical strength of GDLs.5 Here in this study, we evaluate and compare several types of metallic materials to apply as GDLs. Using such alternative metallic GDLs, current-voltage (I-V) characteristics were measured and overvoltages were separated. The purpose of this study is to examine possibilities of using metallic GDLs for PEFCs, by varying materials, thickness, porosity, and preparation conditions. 2. Experimental Ti fiber sheets and stainless steel mesh sheets were used as GDL substrates, and Sn coating was made on the sheets. Then, current-voltage characteristics of the cells using these GDLs were evaluated. Five types of porous metallic sheets were used as GDLs: (i) Ti fiber sheet with a porosity of 70% and thickness of 100 μm, (ii) Ti fiber sheet with Sn plating layer (Sn/Ti sheet), (iii) Ti fiber sheet with Pt nanoparticles and Sn plating layer (Sn/Pt/Ti sheet), (iv) SUS316 mesh with a porosity of 60% and thickness of 32 μm, and (v) SUS316 mesh with porous Sn layer. For all the evaluations, the electrocatalyst layers were prepared by dispersing Pt/C (Pt 46.5%, TEC10E50E, Tanaka Kikinzoku Kogyo Corp., Japan), 99.5% ethanol, pure water, and 5% Nafion solution using an ultrasonic homogenizer. The dispersions were printed on the electrolyte membrane (Nafion 212) using a spray printer (C-3 J, Nordson). The electrode area was 1.0 cm2 (1.0 cm × 1.0 cm), and the Pt loading on both electrodes was 0.3 mg-Pt cm-2. The metallic GDL was used for the cathode, and a carbon paper (EC-TPI-060T) was used as the standard GDL for the anode. In the electrochemical characterization of this study, electrochemical impedance spectroscopy (EIS, 1255WB, Solatron) was applied to measure the current-voltage characteristics and to separate overvoltages. 3. Results and discussion I-V characteristics of the cells with the MEAs (i) to (v) are shown in Figure 1. Decrease in cell performance was mainly caused by an increase in ohmic losses. Comparing the MEA (i) and the MEA (iv), Ti fiber sheet showed higher electrical conductivity than stainless steel mesh sheet. Comparing the MEA (i) and the MEA (ii), it was confirmed that the Sn plating on the Ti fiber contributed to a reduction of ohmic loss and concentration overvoltage. Furthermore, the current-voltage curve of the MEA (iii) indicates higher conductivity than that of the MEA (ii), suggesting that the Pt coating promoted the Sn plating or acted as catalysts on the electrocatalyst layer side during the operation of the cell. When the SUS316 mesh sheet was used for the MEA (iv), the concentration overvoltage tended to fluctuate in each measurement. For the MEA (v), a decrease in cell performance was observed. These could be caused by, e.g., degradation of stainless steel due to strong acidity, and contact resistance between the Sn porous layer and the mesh sheet. Further study is in progress to improve I-V characteristics of MEAs by optimizing materials and structure of metallic GDLs. Acknowledgement Financial support from New Energy and Industrial Technology Development Organization (NEDO) is gratefully acknowledged (Contract No. 20001214-0). References Takahashi, T. Ikeda, K. Murata, O. Hotaka, S. Hasegawa, Y. Tachikawa, M. Nishihara, J. Matsuda, T. Kitahara, S. M. Lyth, A. Hayashi, and K. Sasaki, J. Electrochem. Soc., 169, 044523 (2022).Larminie, and A. Dicks, Fuel Cell Systems Explained, John Wiley & Sons, (2006).Kitahara, T. Konomi, H. Nakajima, and J. Shiraishi, kikaib, 76(761), 101 (2010).A. Reiser, L. Bregoli, T. W. Patterson, J. S. Yi, D. Yang, M. L. Perry, and T. D. Jarvi, Electrochem. Solid-State Lett., 8, A273 (2005).N. Hussain, E. V. Steen, S. Tanaka, and P. Levecque, J. Power Sources, 337, 18 (2017).

One-step preparation of gel-electrolyte-friendly fiber-shaped aerogel current collector for solid-state fiber-shaped supercapacitors with large capacity

Fiber-shaped aerogel conductive structures are a promising template for preparing fiber-shaped supercapacitors with high length-specific capacitance used in flexible and wearable electronics. The challenge lies in how to easily infiltrate enough active mass and gel electrolyte into micropores and achieve intimate contact so that the active mass can be fully utilized for large capacitance and small contact resistance to be obtained for fast rate response. Here, one-step preparation of gel electrolyte friendly, fiber-shaped conductive and hydrophilic aerogel is reported, which was produced from electrospinning poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PP) and poly(ethylene oxide) (PEO) on a centering Ti metal wire. Thanks to the high conductivity of PP, high hydrophilicity of PEO, high porosity of the aerogel structure and high mass loading of PP, the as-prepared PP-PEO/Ti showed a fiber-length-specific capacitance of 68.4 mF cm−1 and excellent rate performance due to well infiltration of gel electrolytes. More interestingly, PP-PEO/Ti was used as a template to load polyaniline (PANI). The as-prepared PANI@PP-PEO/Ti fibers were studied as electrodes in solid-state supercapacitors. A fiber-length-specific capacitance is as large as 136.7 mF cm−1 was measured. These results suggest our PP-PEO/Ti is a promising 3D fiber-shaped aerogel structure for high-performance fiber energy storage devices.

PEFCs Using Metallic Ti and Sn Gas Diffusion Layers

Introduction Many types of carbon materials are used in PEFCs. Especially, gas diffusion layer (GDL), with a thickness of ca. 0.2 mm are made of relatively expensive carbon fibers. In general, metallic materials can be more electronically conductive than carbon black based materials, and thinner GDLs could be prepared using metals. Here in this study, we evaluate and compare several types of metallic materials to apply as GDLs. Using such alternative metallic GDLs, current-voltage (I-V) characteristics were measured and overvoltages were separated. The purpose of this study is to examine possibilities of metallic GDLs for PEFCs, by varying materials, thickness, porosity, and preparation conditions. Experimental We measured I-V characteristics of PEFCs using metallic GDLs. Four types of porous metallic sheets were used as GDLs, shown in Figures 1 to 3: (i) Ti fiber-based sheet (porosity: 70%; thickness: 200μm; Nikko Techno Ltd.), (ii) Ti fiber-based sheet with porous Sn layer, (iii) Ti punching metal sheet (sheet thickness: 12μm; hole diameter: 300μm; Fukuda Metal Foil & Powder Co., Ltd.), and (iv) Sn punching metal sheet (sheet thickness: 100μm; hole diameter: 300μm, Fukuda Metal Foil & Powder Co., Ltd.). Except for cathode-side GDLs, standard materials were used such as Pt/C electrocatalyst (Tanaka Kikinzoku Kogyo, TEC10E50E). Electrochemical impedance spectroscopy (EIS, Solartron 1255WB) was used to separate overvoltages in the electrochemical characterization. Results and discussion I-V characteristics of the cells with the cathode GDLs (i) to (iv) are shown in Figure 4. Decrease in cell performance was mainly caused by an increase in ohmic losses. Comparing these GDLs, Sn-based materials are generally more conductive than Ti-based materials to decrease ohmic losses, but concentration overvoltage can also be high when the GDLs (ii) and (iv) were used. Both contact and internal resistance were reduced when using the porous Ti punching metal sheet instead of the Ti fiber sheet. Further study is in progress to increase I-V characteristics of MEAs by optimizing materials selection and structure. Acknowledgement Financial support from New Energy and Industrial Technology Development Organization (NEDO) is gratefully acknowledged (Contract No. 20001214-0). References Larminie，A. Dicks，Fuel Cell Systems Explained, 2nd Edition, John Wiley & Sons, West Sussex, England, 2003.T．Kitahara，T．Konomi，H．Nakajima, and J．Shiraishi， Japan Soc. Mech. Engineers, B76 (761) 101 (2010), in Japanese.S．Matsumoto，M．Nagamine，Z．Noda，J．Matsuda，S．M．Lyth，A．Hayashi，and K．Sasaki，J ． Electrochem ．，165 (14)，1165 (2018).C．A．Reiser，L．Bregoli，T．W．Patterson，J．S．Yi，J．D．yang，M．L．Perry，and T．D．Jarvi，Electrochem . Solid-State Lett.，8 (6)，A273 (2005). Figure 1

Rapid and Highly Efficient Solid-Phase Microextraction Based on in Situ Derivation of Robust Carbonaceous Nanostrips on Anodized Titanium Fiber for Sensitive Determination of Polycyclic Aromatic Hydrocarbons in Environmental Water

With titanium wire as a titanium source and a fiber substrate, titania nanostrips (TiO2NSs) were in situ grown on the fiber surface by electrochemical anodization and used as supporting templates for subsequent uniform deposition of polar glucose via hydrothermal reaction. After annealing, controllable in situ derivation of TiO2NSs-templated carbonaceous coating (TiO2@CNSs) was achieved on the Ti fiber substrate. Coupled to high-performance liquid chromatography with UV detection, the extraction performance was investigated using representative aromatic compounds as model analytes and compared with those of commercially available fibers. The results demonstrated that the Ti@TiO2@CNSs fiber exhibited good extraction selectivity for PAHs, especially for high-molecular-weight PAHs. For this purpose, the key parameters affecting extraction efficiency of PAHs were optimized. Under optimized conditions, linearity was shown in the ranges of 0.02–200 μg·L−1 with the correlation coefficients of greater than 0.999. Limits of detection were 0.005–0.056 μg·L−1. The intra-day and inter-day repeatability of the proposed method with the single fiber varied from 2.06% to 3.99% and from 2.85% to 5.17%, respectively. The fiber-to-fiber reproducibility ranged from 2.86% to 5.21%. The proposed method was successfully applied to selective preconcentration and sensitive determination of target PAHs in real water samples. Moreover, this fiber has a long service time.

Temperature and time-controlled hydrothermal growth and sorption selectivity of titania nanowires on titanium fiber for highly efficient solid-phase microextraction

Two kinds of TiO2 nanowires (TiO2NWs) with different orientation were in-situ grown on Ti substrates by controlling temperature and time during the hydrothermal process. The adsorption performance was evaluated by using typical aromatic compounds as model analytes coupled to HPLC with UV detection. The results demonstrated that the TiO2NWs coating grown at higher temperature within longer time had better affinity towards PAHs. For this purpose, the key experimental factors affecting the adsorption performance of the TiO2NWs coating fabricated at 200 °C for 10 h were further investigated and optimized for the extraction of PAHs. Under the optimized conditions, the proposed method presented linear responses in the concentration ranges of 0.05 to 200 μg·L−1 PAHs with correlation coefficients more than 0.998. LODs (S/N=3) were 0.008 to 0.034 μg·L−1. Moreover, RSDs for the single fiber repeatability of the intra-day and the inter-day analyses were less than 5.6% (n=5) and 5.8%, respectively. RSDs for the fiber-to-fiber reproducibility were between 5.1% and 6.5%. Finally, the proposed method was successfully applied to the selective preconcentration and determination of trace PAHs in environmental water samples. In addition, The fabricated Ti fiber can be used at least 200 times due to its high mechanical and chemical stability.

Li dendrites inhibition realized by lithiophilic and ion/electron conductive 3D skeleton for Li metal anodes

• The Si layer is sputtered on the surface of Ti fibers by magnetron sputtering. • The STM electrodes exhibit good lithiophilicity and ion/electron conductivity. • Dendrite-free and smooth Li deposition is obtained on STM electrodes. • The STM@Li anodes deliver stable cycling in both symmetric and full cells. Li metal anode holds the key for further high-energy-density batteries. Inhibition of Li dendrites and superior electrochemical performance are critical for its practical application. Herein, a low-cost Si membrane with dual effects on 3D Ti mesh (STM) is designed through magnetron sputtering. The in situ formed Li-Si alloy layer presents highly lithiophilic and ion conductive, endowing lower nucleation barrier and homogeneous Li-ion flux, while the high electron conductive of 3D host with capacious voids immensely facilitates kinetics and relieves volume expansion. Consequently, a smooth Li layer looked like a “quilt” is uniformly formed instead of generating fair share of 1D Li whiskers. The constructed Li ‖ STM@Li symmetric cell keeps operating for 800 h at 2 mA cm −2 and 2 mAh cm −2 with a low overpotential of 25 mV. Even under carbonate-based electrolyte, the full cells using Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 (LNCM) as cathode can deliver a high initial capacity (245 mAh g −1 ) and capacity retention (81.2%) after 100 cycles at 1 C.

Macroscale amphiphilic aerogel fibers made from nonwoven nanofibers for large active mass loading

Fiber-shaped templates that can be easily loaded with a large amount of hydrophilic and/or lipophilic active materials in a facile process like dip coating, will find many applications including for wearable electronics. Here, macroscale amphiphilic aerogel-like fiber, made from electrospun glycerol-functionalized polyacrylonitrile (PAN) nanofibers (GPN) on a centering metal wire, is reported. With its high porosity, large void space, and both hydrophilic and lipophilic characteristics, this unique GPN aerogel fiber can absorb a large amount of aqueous and oil solutions dispersed with different active materials. In particular, poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PP) represented water-soluble active material is selected to prepare PP-loaded fiber, which is further coated with polyaniline (PANI). The PP@GPN/Ti and PANI@PP@GPN/Ti fibers are studied as electrodes for flexible yarn-shaped solid-sate supercapacitors. A fiber-length-specific capacitance as large as 243 mF cm−1 is measured at 0.1 mA cm−1, one of the best capacitances ever reported for fiber supercapacitors. Colza oil is also tested as a representative oily solvent to investigate the load capacity of GPN aerogel fiber and a mass loading of 124 μl cm−1 is achieved. These results suggest that our unique amphiphilic aerogel fiber could act as a carrier loading a large amount of active masses for many novel applications.

Alternately Dipping Method to Prepare Graphene Fiber Electrodes for Ultra-high-Capacitance Fiber Supercapacitors.

SummaryFlexible fiber supercapacitors are promising candidate for power supply of wearable electronics. Fabrication of high-performance fibers is in progress yet challenging. The currently available graphene fibers made from wet-spinning or electro-deposition technologies are far away from practical applications due to their unsatisfactory capacitance. Here we report a facile alternately dipping (AD) method to coat graphene on wire-like substrates. The excellent mechanical properties of the substrate with greatly diverse choices can be carried over to the fiber supercapacitors. Under such guideline, the graphene fiber with a titanium core made by our AD method (AD:Ti@RGO) shows an ultra-high specific capacitance of up to 1,722.1 mF cm−2, which is ∼1,000 times that of wet-spinning- and electro-deposition-fabricated neat graphene fibers and presents the highest specific capacitance to date. With excellent mechanical properties and striking electrochemical performances, the AD:Ti@RGO-based supercapacitors light the path to the next-generation technologies for wearable devices.

Robust Fabrication of Novel Silica Nanosheets on Titanium Fibers for the Selective and Sensitive Determination of Ultraviolet Filters in Environmental Waters by Solid-Phase Microextraction

A novel silica nanosheet coating was fabricated on a titanium (Ti) fiber substrate by electrophoretic deposition followed by annealing. Prior to the electrophoretic deposition, titania nanowire arrays were grown in-situ on the titanium wires by a hydrothermal process in alkaline solution and used as the active support for the subsequent deposition of the silica coatings. After annealing at 550 °C, the homogeneous silica nanosheets were formed on the titania nanowires coated titanium fiber. The fabricated fiber has controllable preparation reproducibility and long recycling stability. The extraction performance of the resulting coating was investigated using typical aromatic compounds as model analytes coupled to high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. Excellent extraction selectivity and capability were demonstrated for the ultraviolet filters. Under the optimized extraction conditions for the analytes, good linearity was achieved across the concentration range from 0.02 to 400 μg·L−1 with correlation coefficients above 0.999 and limits of detection from 0.004 to 0.059 μg·L−1. Relative standard deviations below 7.3% were obtained for the determination of ultraviolet filters with the single fiber. The developed method was applied to the selective enrichment and sensitive determination of the target ultraviolet filters in real water samples with relative recoveries from 83.6% to 104%.

Preparation of Ti, Ti/TiC or Ti/TiN based hollow fibres with extremely low electrical resistivity.

Porous Ti based hollow fibres with extremely low electrical resistivity (4.1–9.6 μΩ m), orders of magnitude smaller than reported for Ti-fibres in the literature, were produced by dry-wet spinning of a mixture of Ti-particles, polyethersulfone (PES), and N-methylpyrrolidone (NMP). Utilizing a two-step thermal decomposition of PES, consisting of treatment in air at 475 °C, followed by treatment in argon at 800 °C, hollow fibres of entirely metallic Ti are obtained, as confirmed by XRD, SEM-EDS, and TGA-MS analyses. Only a thin oxide layer is formed due to ambient surface oxidation, as identified by XPS analysis. Carbonization of the polymer under an inert atmosphere can be used to produce a Ti/TiC-composite. To obtain a Ti/TiN composite, the porous Ti-tubes can be treated in nitrogen atmosphere at 800 °C. The porosity, pore size distribution, and bending-strength of the fibres were determined for a low (800 °C) and high (1100 °C) degree of sintering, and it was found that these are largely independent of the chemical surface composition. The presence of TiC or TiN, likely in an outer, but crystalline shell (based on XRD and XPS data), results in lower resistivity than of the pure Ti fibres, which can be attributed to the insulating layer of TiC or TiN preventing capacitive effects at the Ti/air interface. The developed preparation methodology results in porous metallic and composite Ti based fibres, which are very suitable for electrochemical applications.

Understanding Interfaces of PEM Electrolyzers with Operando Synchrotron X-Ray Computed Tomography and Radiography

Polymer electrolyte membrane (PEM) electrolyzers are electrochemical energy-conversion devices that convert electricity into hydrogen fuel at high efficiencies. The state-of-the-art systems use high IrOx loading (~2-3 mg/cm2), largely due to a lack of stable electrocatalyst supports that can effectively disperse the catalyst particles. Currently, the catalyst layers are made of IrOx and ionomer without an additional support. Without micro-porous layers (MPLs), the rough contact between the porous transport layer (PTL) and catalyst layer presents a challenge. In this study we use operando x-ray computed tomography (CT) and x-ray radiography to visualize operation of PEM electrolyzer under two current densities: 500 and 800 mA/cm2. First, we compare performance of electrolyzer with catalyst-coated membrane (CCM) and that with porous transport electrode (PTE) and correlate polarization curves to morphology of the interfaces observed with x-ray CT. At 1 A/cm2, the micro-CT CCM electrolyzer showed 200 mV improvement in potential primarily due to better contact between the electrocatalyst, membrane, and PTL. From the nano-CT imaging we discovered non-homogeneous distribution of IrOx electrocatalsyt and from the images it is also not clear whether the larger IrOx agglomerates are electrically connected via a percolating conductive network of nanoparticles. The modeling study shows that the primary reason for performance loss in PTE configuration is low connectivity of catalyst particles with membrane. This causes bottlenecks in proton transport and results in high potential losses in anode. We also compared the polarization behavior and morphology of cells with CCMs but two types of PTLs. One was made with sintered Ti and the other with Ti fiber. The Ti fiber PTL showed higher porosity and lower tortuosities, both in-plane and thru-plane. However these better morphological properties did not necessarily translate into lower potentials, as 1 A/cm2 was not a high enough current density to resolve differences attributable to improved two phase flow. This was also confirmed by radiography study, where oxygen residence fraction in the channels showed similar fractions for both types of the PTLs.

Polymer Electrolyte Water Electrolysis: Correlating Porous Transport Layer Structural Properties and Performance: Part I. Tomographic Analysis of Morphology and Topology

In the first paper of this series, the bulk, surface and transport properties of porous transport layer materials (PTL) for polymer electrolyte water electrolysis cells (PEWE) are characterized. A systematic PTL matrix of Ti fiber materials with 3 fiber diameters and 2 nominal porosities as well as a state of the art sintered powder material are investigated to get a better understanding of the governing parameters in electrolysis cells. X-ray tomographic microscopy analysis of ex situ PTL structures and post operando membrane electrode assemblies is performed. On the tomographic structures, bulk (porosity, pore/solid size distributions, fiber orientation), mass transport (diffusivity, permeability, conductivities) and surface parameters (roughness, membrane deformation, PTL surface area and interfacial contact area) are determined. The second paper of this series will correlate the structural parameters with in-depth electrochemical analysis. The new insights into the effect of PTL properties on PEWE performance allow to isolate governing key parameters. From know-how obtained on the fiber based materials fundamental design guidelines for optimization of PTL structures are deduced.

Electrochemical filtration process for simultaneous removal of refractory organic and particulate contaminants from wastewater effluents

Versatile electrochemical reactions are effective for removing a wide range of water contaminants. This study focuses on the development and testing of bifunctional electrocatalytic filter anodes as reactive and separating media for the simultaneous removal of refractory dissolved organic and particulate contaminants from real wastewater effluents. The results show that the TiO2 particle interlayers formed between the Ti fiber support and the top composite metal oxide catalyst layers assist in reducing filter pores to an effective size range that enables removal of most particulates within the wastewater. The double-sheet design, which is a sandwich-structured module with an internal void space for permeate, prevents filter fouling, and transmembrane pressure can be maintained at a very low level of <5 kPa during batch and continuous flow reactor operations. Substantive and simultaneous removal of dissolved organics (e.g., chromophores, fluorophores, 1,4-dioxane, chemical oxygen demand, and total organic carbon) and particulate matter (i.e., turbidity) are achieved, although removal rates and efficacies differ depending on the electric current density applied. Decolorization and particulate rejection occur swiftly and immediately, but 1,4-dioxane degradation is relatively slow and quite time-dependent. Possible 1,4-dioxane degradation pathways during electrocatalysis are also proposed. Electrochemical filtration technology shows considerable promise for use in the next generation of advanced wastewater treatment solutions.

Preliminary analysis of underwater detonation performance of titanium fiber explosive

In this study we examined the changing tendency of the shock wave energy, bubble energy, total energy per unit mass and the total energy per unit volume by analysis of the pressure-time curves, and analyzed the chemical reaction process of the Ti fiber explosive through the total energy per unit mass. The results show that the peak pressure and the shock wave energy of the Ti fiber explosive per unit decreases as the Ti fiber content increases, the bubble energy per unit mass increases with the increase of the Ti fiber content, the total energy per unit mass and its energy density increase with the increase of the Ti fiber content. With the increase of the distance between the sensor and explosive, the rate of the Ti fiber explosive's peak pressure decay is slower than that of RDX, while the tendency of the shock wave energy and the bubble energy per unit mass with different contents of the Ti fiber explosive is basically in keeping with the increase of the distance. The chemical reaction process of the Ti fiber explosive was also obtained through the total energy per unit mass.