Mixed Ethylene Research Articles

Study of Na Deposition Formation in Mixed Ethylene: Propylene Carbonate Electrolytes by Inert/Cryoelectron Microscopy.

The sodium anode-free combines low-cost and high energy density, demonstrating a promising alternative to the Li battery counterpart. Nevertheless, the uptake of a sodium anode-free battery is greatly impeded by the uncontrollable dendrite proliferation upon the chemically active metallic Na. An insightful mechanistic understanding of Na deposition nucleation and growth behavior in ethylene carbonate and propylene carbonate (EC/PC, 1:1) is revealed via various inert and/or cryo-electron microscopy characterization techniques. The deposit morphology, size, and distribution were studied with different current densities and areal capacity. The Na deposit distribution changes from nonparametric distribution to normal distribution which can be attributed to the effect of interparticle diffusion coupling (IDP). The atomic information on the Na deposit was revealed via cryogenic transmission electron microscopy.

Incipient sooting tendency of oxygenated fuels doped in ethylene counterflow diffusion flames

The incipient sooting tendencies of oxygenated fuels in counterflow diffusion flames were systematically assessed by doping selected oxygenate fuels into the baseline fuel of ethylene with various mixing ratios. Laser light scattering and planar laser-induced fluorescence (PLIF) techniques were adopted. The critical oxygen mole fractions at different mixing ratios were identified with the use of laser scattering. It is found that the critical oxygen mole fraction varies with oxygenates, suggesting that the effect of mixing ethylene with oxygenates is highly sensitive to the types of oxygenate. While the doping of acetone moderately promoted the incipient sooting tendency, the doping of methanol, acetic acid, formic acid, and diethyl carbonate suppressed the formation of incipient soot. On the other hand, the doping of ethanol, dimethyl carbonate, diethyl ether, and dimethoxymethane had weak influences on the incipient sooting tendency. The production of polycyclic aromatic hydrocarbons (PAHs) of different sizes were measured by PLIF. The results show there was a strong correlation between the incipient sooting tendency and the production of large PAHs. One important finding is that, at their sooting limits, the total oxygen-to-carbon ratio of a stoichiometric fuel/oxygen mixture is linearly correlated with the mixing ratio of the ethylene-oxygenate mixture. This slope of these two quantities can be defined as an incipient sooting index (ISI) of oxygenated fuels for ranking their tendency of incipient sooting formation. Having the slopes correlated well with the oxygenates’ hydrogen/oxygen ratio, a reasonably accurate prediction of critical oxygen mole fractions from the molecule information of oxygenated fuels can be achieved.

Synergistic Effect of Mixing Ethylene with Propane on the Morphology and Nanostructure of Soot in Laminar Coflow Diffusion Flames

AbstractThe synergistic effect of mixing ethylene with propane on the nanostructure and morphology evolution of soot in laminar coflow diffusion flames was investigated via combining thermophoresis...

SYNTHESIS AND APPLICATION OF MIXED ETHYLENE GLYCOL DIESTERS BASED ON PETROLEUM ACIDS CHEMISTRY AND CHEMICAL TECHNOLOGY

In order to increase the range of plasticizers and antioxidants using the ZnO catalyst, mixed ethylene glycol diesters based on petroleum and fatty acids were synthesized by a waste-free method. To determine the optimal conditions for obtaining the target products, the effect of temperature, the amount of catalyst, the molar ratio of the components involved in the reaction for the maximum yield were studied and the optimal condition was established with a yield of 90-93. The properties of mixed diesters of petroleum acids have been studied, the physicochemical parameters have been determined by analytical and spectral methods. The degree of compatibility of ethers with polyvinyl chloride and the ability to prolong the life of diesel fuel have been determined. It was found that ethers can be recommended as effective plasticizers for polyvinyl chloride and antioxidants for diesel fuel. Taking into account the wide practical application of mixed esters, including esters of petroleum acids, and their high demand, the main goal of the article is to obtain mixed ethylene glycol esters based on natural, synthetic and fatty acids with a high yield without waste method, as well as to study their properties and applications. In this article, to solve the problem posed, natural petroleum acids of the fraction 90-230ºC / 6.65 × 10-4 MPa were used in the studies, taken from the "Meriken" unit of the H. Aliyev`s New Baku Oil Refinery, as well as synthetic petroleum acids synthesized by liquid-phase oxidation with atmospheric oxygen at a temperature of 135-140°С. In the following studies, asymmetric ethylene glycol diesters were synthesized based on natural, synthetic and fatty acids of the C6-C8 series at temperatures of 80-140oC, with a catalyst amount of 0.6-1.6% by weight (with respect to acid), molar ratio of components 2:1.1-1.6, the optimal conditions were determined (T,°C = 110-120, acid: alcohol - 2:1.3-1.5 mol, ZnO - 0.8-1.5% by weight ( in relation to acid)), the properties of the synthesized mixed diesters have been studied, their indicators have been determined by modern analytical and spectral methods, and the material balance of these ethers has been compiled. Other representatives of ethylene glycol based on oil and fatty acids in a similar way were synthesized and the physicochemical parameters were determined. The synthesized products are light yellow, transparent, odorless, insoluble in water, readily soluble in organic solvents. The compatibility of mixed diesters with polyvinyl chloride (PVC), as well as the effect of diesel fuel on thermal-oxidative stability in laboratory conditions has been studied. The research results are presented below: • mixed diesters of petroleum acids have been synthesized in the presence of a ZnO catalyst by one-stage method, which makes it possible to reduce intermedi; • the influence of various amounts of catalyst, the molar ratio of the components involved in the reaction, the temperature range the course of the reaction in order to select the optimal synthesis conditions were studied, mixed esters in high yield were synthesized and their physicochemical parameters by analytical and spectral methods were determined; • the degree of compatibility of mixed diesters synthesized on the basis of petroleum and fatty acids with PVC has been studied and tested as a new component to improve the thermal stability of diesel fuel. These esters can be recommended as effective plasticizers and antioxidants. Keywords: natural petroleum acids, synthetic petroleum acids, ethylene glycol, mixed diester, plasticizer, antioxidant

A Molecular Dynamics Study of Na Ion Transport and Storage inside Nanoporous Carbon Electrode for Na-Ion Batteries

Hard carbon has emerged as an attractive anode material for sodium ion batteries (NIBs) because of its low cost, high initial coulombic efficiency, high specific capacity, and steady cycling performance. Based on combined molecular dynamics (MD) simulation and density functional theory (DFT) calculations, we present an atomistic description of the electrolyte-electrode interaction of sodium hexafluorophosphate (NaPF6) in mixed ethylene (EC) and dimethyl carbonate (DMC) electrolyte inside nanoporous carbon electrode. We investigate the microstructure of electrolyte in carbon nanopores with an average pore size of 8.9 Å and a specific surface area of 1794 m2g-1 at 0 V and 2 V to gain molecular insight into electrolyte behavior such as solvent packing, preferential adsorption sites, and solvation structure. Our simulation suggests good accessibility of carbon nanopores by electrolyte molecules upon charging. At 2 V, Na+ is desolvated and intercalates into highly confined carbon structures as a result of the strong interaction between Na+ and charged carbon atoms while PF6 - occupies weakly confined carbon nanostructures by forming ion pairs with Na+. Also, we examined the various levels of confinement of electrolyte components using a degree of confinement (DoC) analysis, and present the effects of confinement on electrolyte properties. Our calculations show a 29 % reduction in Na+ adsorption distance for a nanoporous structure compared to a planar structure of carbon, and the preferential adsorption of Na+ at a hydrogen-terminated edge of porous carbon with an adsorption energy of -0.27 eV compared to a basal site with a higher adsorption energy of 0.02 eV. Finally, an investigation of the solvation sheath structure as a function of DoC shows decreased solvation shell, shortened adsorption distances, and increased counter-charge with increasing DoC.

Controllable alkylation of benzene with mixed olefins for producing C8-C15 aromatics in jet fuel

C8-C15 aromatics are used widely as key components of jet fuel, whereas effectively producing these aromatic components remains a big challenge. We reported the oriented synthesis of C8-C15 aromatic components in jet fuel by alkylation of benzene with mixed ethylene and propylene in vapor-phase over nanosize ZSM-5 (N-ZSM-5) catalyst. The selectivity and yield of aromatics, mainly of carbon number ranging from 8 to 15, could be enhanced by decreasing the particle size of ZSM-5, owing to the faster mass transfer and shorter intraparticle diffusion route for reactants and target products during the reaction process, as well as by increasing the acid strength via decreasing the Si/Al molar ratio, thus improving the alkylation performance conspicuously. In addition, mesopore volume of N-ZSM-5 zeolite showed an increase tendency with decreased particle size, contributing to the carbon chain growth and diffusion of target products. The resultant N-ZSM-5 catalyst showed superior benzene conversion of 40.3%, ethylene and propylene conversion of 99.5% and 99.2%, with aromatic C8-C15 selectivity and yield of 94.8% and 54.9%, respectively, under the optimized reaction conditions.

Investigation of Solvent Type and Salt Addition in High Transference Number Nonaqueous Polyelectrolyte Solutions for Lithium Ion Batteries

High Li+ transference number electrolytes have attracted recent interest as a means to improve the energy density and rate capabilities of current lithium ion batteries. Here the viscosity and transport properties of a sulfonated polysulfone/poly(ethylene glycol) copolymer that displays both high transference number and high conductivity when dissolved in dimethyl sulfoxide (DMSO) are investigated for the first time in a battery-relevant solvent of nearly equivalent dielectric constant: mixed ethylene carbonate (EC)/dimethyl carbonate (DMC). The addition of a binary salt to each solution is investigated as a means to improve conductivity, and the diffusion coefficient of each species is tracked by pulse field gradient nuclear magnetic resonance (PFG-NMR). Through the 7Li NMR peak width and quantum chemistry calculations of the dissociation constant, it is shown that although the two solvent systems have nearly equivalent dielectric constants, the conductivity and transference number of the EC/DMC solution...

Dye diazonium-modified multiwalled carbon nanotubes: Light harvesters for elastomeric optothermal actuators

Novel elastomer/modified carbon nanotube nanocomposites were prepared by melt mixing ethylene vinyl acetate (EVA) matrix with dye-grafted multiwalled carbon nanotubes (MWCNTs, CNTs in short). The latter were prepared by spontaneous reactions of diazotized Azure A (AA-N2+), Neutral Red (NR-N2+) and Congo Red (CR-N2+) dyes with CNTs in water at RT. The dispersion of the dye-modified CNTs was facilitated with cholesteryl 1-pyrenecarboxylate (PyChol) surfactant. The EVA/modified CNT nanocomposites were employed as optothermal actuators. The photo-actuation measurements were performed on the un-stretched as well as the stretched strips of pristine EVA and EVA/CNT-dye nanocomposites using a dynamic mechanical analyzer (DMA) equipped with a red light emitting diode (red LED) at a wavelength of 627 nm illuminated either 10 s or 30 s. The concentration of modified dyes, the use of PyChol surfactant and the applied pre-strain were the parameters investigated in this work.To sum up, the nanocomposites prepared so far could be regarded as promising optothermal actuators used for touch displays visually impaired people.

Performance of mixture of ethylene glycol and glycine in inhibiting methane hydrate formation

This study investigates synergistic hydrate inhibition performance of conventional thermodynamic hydrate inhibitors (THIs) combined with amino acids. For this purpose, hydrate-liquid-vapor equilibrium (HLVE) data for methane were measured in the presence of mixed ethylene glycol and glycine using 1:1 mixtures at concentrations of 1 wt% (0.5 wt% ethylene glycol +0.5 wt% glycine), 5 wt% (2.5 wt% ethylene glycol +2.5 wt% glycine), 10 wt% (5 wt% ethylene glycol +5 wt% glycine), 20 wt% (10 wt% ethylene glycol +10 wt% glycine), and 30 wt% (15 wt% ethylene glycol +15 wt% glycine) by the isochoric pressure search method. Thermodynamic inhibition efficiency has been investigated by observing the shifts in the hydrate equilibrium curves and trends of the calculated hydrate suppression temperatures at various concentrations and pressures. The results were also obtained for ethylene glycol, glycine and ionic liquids for comparison. An improving inhibition performance by mixing ethylene glycol and glycine was observed, indicating the potential of amino acids as inhibition synergists in hydrate exploitation, oil/gas transportation and flow assurance. Molar hydrate dissociation enthalpies were calculated by using the Clausius-Clapeyron equation and showed that the interaction of ethylene glycol and glycine has no impact on the hydrate structure.

Effects of additives and post‐treatment on the thermoelectric performance of vapor‐phase polymerized PEDOT films

ABSTRACTVapor‐phase polymerization (VPP) is an important method for the fabrication of high‐quality conducting polymers, especially poly(3,4‐ethylenedioxythiophene) (PEDOT). In this work, the effects of additives and post‐treatment solvents on the thermoelectric (TE) performance of VPP‐PEDOT films were systematically investigated. The use of 1‐butyl‐3‐menthylinidazolium tetrafluoroborate ([BMIm][BF4], an ionic liquid) was shown to significantly enhance the electrical conductivity of VPP‐PEDOT films compared with other additives. The VPP‐PEDOT film post‐treated with mixed ethylene glycol (EG)/[BMIm][BF4] solvent displayed the high power factor of 45.3 μW m−1 K−2 which is 122% higher than that prepared without any additive or post‐treatment solvent, along with enhanced electrical conductivity and Seebeck coefficient. This work highlighted the superior effect of the [BMIm][BF4] additive and the EG/[BMIm][BF4] solvent post‐treatment on the TE performance of the VPP‐PEDOT film. These results should help with developing the VPP method to fabricate high‐performance PEDOT films. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1738–1744

Exploring the Energetics of the Lithium Ion-Organic Carbonate Interaction: A Temperature-Dependent FTIR Study

Lithium ion batteries are now essential to the portable energy storage industry. However, this technology still faces many problems associated with safety and energy storage density. While the energy storage density is related to all components of the battery, its safety concerns are mostly associated with the lithium ion electrolyte. Typical lithium ion electrolytes are composed of a lithium salt in a mixture of organic carbonate solvents of both linear and cyclic structure. Specifically, the industry standard, referred to as the generation 2 lithium ion battery electrolyte, is composed of ~1M lithium hexafluorophosphate salt in a mixed ethylene carbonate/ethyl methyl carbonate solvent at a volume ratio of 3:7 and has the highest conductivity reported for a carbonate-based electrolyte so far. However, the underlying reasons for realizing higher conductivity and better electrochemical cycling in specific carbonate mixtures are unknown. By further characterizing the interactions between the lithium ion and the organic carbonates, a more complete understanding of these electrolytes and how they function within the battery can be obtained. In this study, we have characterized the energetics of the lithium ion-carbonate interaction for several carbonates, both linear and cyclic in structure using temperature-dependent infrared spectroscopy. Our studies show new insights into the interplay between the energetics of lithium solvation.

Preparation of the Sm3+-Doped Magnetic Nanoparticles via Microwave-Assisted Polyol Synthesis

Sm3+-doped magnetic nanoparticles (NPs) were prepared via microwave-assisted polyol synthesis in ethylene glycol, poly(ethylene glycol) and mixed ethylene glycol—poly(ethylene glycol) solutions. In present work, the effects of organic solvent composition on particle size, particle size distribution, extent of agglomeration, and samarium content in prepared NPs were studied. The synthesized NPs were characterized by several techniques as follows: X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry (TGA) and X-Ray fluorescence (XRF) analysis. XRD and TEM results showed formation of ~6.0–17.9 nm NPs having different microstructure characteristics (average particle size, particle size distribution, and agglomeration). The TGA analysis indicated the presence of organic components on the surface of NPs. Cytotoxic activity of the prepared magnetic NPs towards HeLa cells was evaluated by using standard live/dead assay in comparison to a control solution. It was shown that prepared magnetic NPs are characterized by low toxicity that makes possible their use for biomedical applications.

Preparation and Characterization of UV Cured Optical Films Containing a Fluorene Compound

In this study, the high refractive coating films applicable for optical materials were produced. the conversion and the photo curing behaviors were examined through FTIR-ATR and photo-DSC, and thermal and mechanical properties of cured films were examined by using DMA and UTM, and pencil hardness, refractive index and optical transmittance of film were measured. Urethane metacrylate oligomer was synthesized by mixing bisphenoxyethanolfluorene (BPEF), polycaprolactone diol (PCL), and polytetramethylene ether glycol (PTMeG) in varying ratios. Also, as the results of mixing ethylene glycol phenyl ether acrylate (PHEA) and trimethylolpropanetriacrylate (TMPTA) in varying ratios, the more time UV irradiated, the higher conversion and the heat of enthalpy (ΔH) and the initial curing rate increased with increasing TMPTA content up to 70%. Also, as the trifunctional monomer increased, the storage modulus and Tg increased, and the stress increased while the strain decreased to reach its maximum value. Also, as the BPEF ratio increased, the maximum value of stress increased while the strain decreased, the refractive index and pencil hardness increased, and light transmittance was all over 80%.

Facile preparation of thermoplastic elastomer with high service temperature from dry selective curing of compatibilized EPDM/polyamide-12 blends

A facile preparation of thermoplastic elastomer (TPE) from simple polymer blends, elastically reinforced through a dry curing process, is introduced in this study. A TPE with a high service temperature of up to ∼180°C is prepared by melt mixing ethylene–propylene–diene rubber (EPDM) with polyamide-12 in the presence of maleated EPDM as a compatibilizer. A dry curing process employing electron beam (e-beam) irradiation is then applied for the selective cross-linking of the EPDM components, which is confirmed by the gel content and differential scanning calorimetry measurements. The mechanical and elastic properties of the TPE are improved by the e-beam irradiation, as evidenced by the measurements of tensile strength, elongation at break, Young’s modulus and tension set, affording a tough TPE. Repeated thermal recycling of the TPE demonstrates an excellent reprocessing capability, affording environmentally friendly TPEs using commercially available resources.

Solvothermal syntheses and characterizations of the first example of lanthanide selenidostannates prepared in mixed ethylene polyamines

Samarium selenidostannates [Hen][Sm(dien)3]Sn2Se6 (1), [Sm(trien)(tren)(Cl)]2Sn2Se6·0.5en (2), and [{Sm(en)(trien)}2(μ-OH)2]Sn2Se6 (3) (en=ethylenediamine, dien=diethylenetriamine, trien=triethylenetetramine, tren=tris(2-aminoethyl)amine) were prepared by solvothermal methods in mixed solvents of en/dien and en/trien, respectively. Compounds 1 and 2 consist of [Sn2Se6]4− anion and mononuclear Sm(III)-complex cations, and/or a protonated en and half a free en molecule. Compound 3 is composed of a [Sn2Se6]4− anion and a binuclear [{Sm(en)(trien)}2(μ-OH)2]4+ complex cation. As far as we know, 1–3 are the first examples of the lanthanide selenidostannates prepared in mixed ethylene polyamines. In the crystal structures of 1–3, the cations and anions are connected into three-dimensional supramolecular networks by N–H⋯Se and/or N–H⋯N, N–H⋯Cl and O–H⋯Se hydrogen bonds. Compounds 1–3 exhibit bandgaps in the range of 2.18–2.41eV, and a distinct blue-shift of the bandgap from 2 to 1 and 3 is observed.

Characterization tests for plug-in hybrid electric vehicle application of graphite/LiNi0.4Mn1.6O4 cells with two different separators and electrolytes

The paper reports and discusses the results of electrochemical tests carried out according to the DOE Battery Test Manual for plug-in Hybrid Electric Vehicles (PHEVs) on laboratory high-voltage graphite/LiNi0.4Mn1.6O4 cells with electrode formulation and mass-loading suitable for scale-up, and mixed ethylene carbonate–dimethyl carbonate with two diverse lithium salts, lithium tris(pentafluoroethyl)trifluorophosphate and LiPF6, as electrolytes. The cells, assembled with two different separators, a polypropylene monolayer separator (Celgard®2400) and a reinforced polyvinylidene fluoride macroporous membrane (PVdF-NCC), were also tested by deep charge/discharge cycles. The results show the strong impact of the separator on high-rate cell functioning in PHEVs.

In-situ synthesizing superior high-rate LiFePO4/C nanorods embedded in graphene matrix

To overcome the detrimental effects of LiFePO4 on the tap density and volumetric energy density accompanied by conventional carbon-based additives, C-LiFePO4/graphene was successfully prepared via hydrothermal synthesis, followed by heat treatment, and by substitution of superior conductive graphene nanosheets for some conventional carbon. The reduction of graphite oxide and the synthesis of LiFePO4 were carried out simultaneously in mixed ethylene glycol/water medium, facilitating desirable compatibility and architecture of LiFePO4 particles and graphene nanosheets. Due to the synergism of thin carbon coating and graphene matrix with low fraction on the basis of complementary advantages, C-LiFePO4/graphene exhibits superior high-rate performance and favorable energy density, which with a unique structural and geometrical feature that LiFePO4/C nanorods embedded in a matrix built of interweaved graphene nanosheets. The dual coatings exert a significantly energetic impact on the electronic conductivity and lithium ion transport, thus novel composite presented excellent electrochemical properties, which was achieved with reversible capacities of 100 mAh/g at 20C and 80 mAh/g at 50C, while preserving a high tap density of 1.76g/cm3.

The effect of in-process ethylene incorporation on the evolution of particle morphology and molecular characteristics of commercial heterophasic ethylene propylene copolymers (HEPCs)

The development of particle morphology, composition, crystallinity and microstructure were investigated for commercial heterophasic (high impact) propylene–ethylene copolymers (HEPCs). Samples from gas phase polymerization processes were collected at set intervals after the introduction of ethylene into the second reactor. TREF profiles show pronounced differences between these samples where the amount of the lower crystallinity fractions (30–80°C), increased with increasing ethylene content, with a corresponding decrease in the relative amount of SEM analysis of the external surfaces of all the samples has indicated very little porosity, whereas the internal porosity has been maintained (as indicated by FE-SEM). FE-SEM images have also shown the presence of thin threads of copolymer between polypropylene globules for the lowest ethylene content sample and this detail seemingly disappears with higher ethylene contents as larger parts of the surface are covered through copolymer pooling effects. Solution 13C NMR has shown a disproportionate microstructural development where continuous ethylene (E) sequences seem to increase at a higher rate than random-like mixed ethylene (E) and propylene (P) sequences. The overall length of continuous E sequences is however limited by the total ethylene content. Solid state NMR has shown that the sample with the highest ethylene content has at least some ethylene monomers incorporated in rigid amorphous areas within the polymer. From GPC analysis, it was observed that molecular weight and -distribution increased with ethylene content. SEC–FTIR results for bulk samples have shown that both ethylene content and crystallinity is prevalent in the high molecular weight area of the curves, whereas the same properties for propylene were found in the lower molecular weight portion.

Solvothermal Syntheses and Characterization of Three Lanthanide Thioantimonates(V) with Mixed Ethylene Polyamines

Three new lanthanide thioantimonates(V) [Ln(en)(teta)(SbS4)] {Ln=Sm (1), Eu (2), Gd (3); en=ethylenediamine; teta=triethylenetetramine} have been solvothermally synthesized and structurally characterized. Compounds 1 - 3 are isostructural. The [SbS4]3- anion acting as bichelating ligand is bound to the [Ln(en)(teta)]3+ ion, resulting in a neutral complex [Ln(en)(teta)(SbS4)]. The central Ln3+ ion lies within an eight-coordinate environment forming a distorted bicapped trigonal prism LnN6S2. Although a few lanthanide thioantimonates have been reported to date, they only contain one type of ethylene polyamine. Compounds 1 - 3 are rare examples of lanthanide thioantimonates with mixed ethylene polyamine ligands. The absorption edges of 1:75 eV for 1 and 2:27 eV for 3 have been derived from optical absorption spectra.

ITOナノ粒子のソルボサーマル合成と透明導電膜への応用

Indium tin oxide (ITO) nanoparticles have been synthesized from the mixed ethylene glycol solution of indium (III) chloride, tin (II) chloride and sodium hydroxide by the solvothermal process with the addition of oleylamine or oleic acid as a protective reagent. The x-ray diffraction patterns of particles synthesized at 250°C show that the ITO begins to be produced after the reaction duration of 6 h when oleylamine is added to the reaction solution, indicating a promoting effect on the ITO formation, whereas only indium oxyhydroxide is formed when oleic acid is used. The transmission electron microscopic observation has revealed that ITO nanoparticles obtained by the addition of oleylamine are monodisperse and their size increases from 4-5 nm to 50-60 nm with elongating reaction duration from 6 to 96 h. ITO thin films are prepared by the multiple deposition of a collodion membrane incorporating synthesized ITO nanoparticles on the glass substrate followed by sintering at 400-500°C. They exhibit a good transparency in the visible region and a specific resistivity as low as 1.0 Ω·cm.