Dyeing bacterial cellulose pellicles for energetic heteroatom doped carbon nanofiber aerogels

The energy crisis and environmental pollution are serious challenges that humanity will face for the long-term. Despite tremendous efforts, the development of environmentally friendly methods to fabricate new energy materials is still challenging. Here we report, for the first time, a new strategy to fabricate various doped carbon nanofiber （CNF） aerogels by pyrolysis of bacterial cellulose （BC） pellicles which had adsorbed or were dyed with different toxic organic dyes. The proposed strategy makes it possible to remove the toxic dyes from waste-water and then synthesize doped CNF aerogels using the dyed BC pellicles as precursors. Compared with other reported processes for preparing heteroatom doped carbon （HDC） nanomaterials, the present synthetic method has some significant advantages, such as being green, general, low-cost and easily scalable. Moreover, the as-prepared doped CNF aerogels exhibit great potential as electrocatalysts for the oxygen reduction reaction （ORR） and as electrode materials for supercapacitors.     

Controlled synthesis of core-mesoporous shell from biomass sustainable N-doped hollow carbonaceous nanospheres

Encompassing ecological and economic concerns, the utilization of biomass to produce carbonaceous materials has attracted intensive research and industrial interest. Using nitrogen containing precursors could realize an in situ and homogeneous incorporation of nitrogen into the carbonaceous materials with a controlled process. Herein, N-doped hollow core-disordered mesoporous shell carbonaceous nanospheres （HCDMSs） were synthesized from glucosamine hydrochloride （GAH）, an applicable carbohydrate-based derivative. The obtained HCDMSs possessed controlled size （-450-50 nm） and shell thickness （-70-10 nm）, suitable nitrogen contents （-6.7-4.4 wt.%）, and Brunauer-Emmett-Teller （BET） surface areas up to 770 m^2.g^-1. These materials show excellent electrocatalytic activity as a metal-free catalyst for the oxygen reduction reaction （ORR） in both alkaline and acidic media. Specifically, the prepared HCDMS-1 exhibits a high diffusion-limited current, and superior durability and better immunity towards methanol crossover and CO poisoning for ORR in alkaline solution than a commercial 20 wt.% Pt/C catalyst.     

Active catalysts based on cobalt oxide@cobalt/N-C nanocomposites for oxygen reduction reaction in alkaline solutions

Over the past few years, electrocatalysis for the oxygen reduction reaction in alkaline solutions has undergone tremendous advances, and non-precious metal catalysts are of prime interest. In this study, we present a highly promising CoO@Co/N-C （where N-C represents a N-doped carbon material） catalyst, achieving an onset potential of 0.99 V （versus the reversible hydrogen electrode （RHE）） and a limiting current density of 7.07 mA-cm-2 （at 0.3 V versus RHE） at a rotation rate of 2,500 rpm in an O2-saturated 0.1 M KOH solution, comparable to a commercial Pt/C catalyst. The H2--O2 alkaline fuel cell test of CoO@Co/N-C as the cathode reveals a maximum power density of 237 mW.cm 2. Detailed investigation clarifies that a synergistic effect, induced by C-N, Co-N-C, and CoO/Co moieties, is responsible for the bulk of the gain in catalytic activity.     

High-temperature reaction networks in graphite furnaces

The intensity of gas-phase species present in a graphite furnace/dilatometer from room temperature to 1400°C were recorded by a mass spectrometer in real time. Based on the relative intensities and fragmentation factors, the species could be assigned to carbon dioxide, carbon monoxide, oxygen, water, and cyanogen. At low temperature, carbon dioxide was the main species observed whereas at high temperature, carbon monoxide was the predominant compound. The appearance of these species at low and high temperature was consistent with the results of equilibrium calculations for the coupled reactions of C + O₂ = CO₂ and CO₂ + C = 2CO. The intensity data from the mass spectrometer indicate that trace oxygen reacts with the graphite to form the carbon dioxide and carbon monoxide.     

Europium niobium bronzes

The structural and the electrical properties of the europium niobium bronzes with various europium and oxygen compositions (Eu_xNbO_y) have been investigated. A niobium bronze with a stoichiometric oxygen content, namely y = 3, is tetragonal for x = 0.5 ? 0.65 and cubic for x = 0.65 ? 1.00. A niobium bronze with full oxygen vacancies, Eu_xNbO_2+x, where all europium and niobium ions are in bivalent and tetravalent states respectively, crystallizes in the cubic form in the single-phase region (0.5 < x < 1.0). The cubic niobium bronzes of any composition between y = 3 and 2+x exhibit metallic conduction, and the tetragonal bronzes are semiconductors. The thermal coefficients of the electrical resistivity for the cubic bronzes are very small; they are minimal at x = 1.0 for the oxygen-stoichiometric bronzes (y = 3) and at x = 0.6 for the bronze having “full oxygen vacancies” (y = 2+x). Thermoelectric-power measurements have shown that the charge carriers of each bronze are electrons. The effective electron mass for the cubic bronzes does not depend on x, but on y. The mass for the oxygen-stoichiometric bronzes (y = 3) is a constant (2m_o), but the mass for the bronzes having full oxygen vacancies increases from 2m_o to 5m_o with decreasing y.     

Observation of Room Temperature Ferromagnetism in Conducting and Insulating Cu doped ZnO Thin Films

With pulsed laser deposition, the Cu_0.04Zn_0.96O thin films are grown at 600 °C under three different oxygen pressures, namely PO₂ = 0.00, 0.02, and 1.00 Pa. X-ray diffraction shows single-phase material for the samples grown under PO₂ = 0.00 and 1.00 Pa and CuO secondary phase for the PO₂ = 0.02 Pa grown sample. The observation of satellite structures in the Cu 2p core level X-ray photoelectron spectroscopy (XPS) spectra suggest the presence of Cu²⁺ and CuO secondary phases in the samples grown at PO₂ = 0.02 and 1.00 Pa. The sample grown under vacuum (PO₂ = 0.00 Pa) shows mixed Cu oxidation state of 1 + or 2 + . The sample grown without oxygen is n-type and those grown with oxygen are highly insulating. The insulating sample grown at PO₂ = 0.02 Pa shows highest magnetization due to possible collective behavior of Cu²⁺ – O _v – Cu²⁺ network in the form of bound magnetic polaron (BMP) and ferromagnetic superexchange interaction coming from uncompensated surface spins of the Cu ions in the CuO secondary phase. Both delocalized electrons (～3.32 × 10¹⁸) due to oxygen deficient defects and reduced amount of effective Cu²⁺ ions discredit the BMP model for this vacuum grown sample, and magnetism is suggested due to O _v and presence of possible CuO secondary phase.     

RBaCo2O5+δ陶瓷的氧阻性能研究（英文）

用固相反应法制备了RBaCo2O5+δ(R=Y、Dy、Gd、Pr、Nd、Sm和Eu)系列陶瓷.用标准四探针法测量了它们从室温到600℃之间的电阻率变化.在温度较低时,它们的电阻率都随着温度的升高而减小,显示为半导体特征.当电阻率在某一温度达到最大值后,电阻率开始随着温度升高而缓慢增加,显示为半金属特征.进一步研究了RBaCo2O5+δ系列陶瓷在高温恒温时的电阻率随着环境气氛的变化情况.结果表明RBaCo2O5+δ陶瓷是一类潜在的氧阻传感器材料,并且它们的响应速率从快到慢顺序是YBaCo2O5+δ>DyBaCo2O5+δ>GdBaCo2O5+δ>PrBaCo2O5+δ>NdBaCo2O5+δ>SmBaCo2O5+δ>EuBaCo2O5+δ.以YBaCo2O5+δ陶瓷为例,在700℃恒温时,当从氧气氛切换到氮气氛时,由于晶格中氧的脱附导致电阻率先是快速上升,然后缓慢上升,并在90 s内达到最大平衡值.反之,当从氮气氛切换为氧气氛时,由于氧的吸附,电阻率迅速降低,约30 s内达到最小平衡值.     

Solid-state NMR and TGA studies of silver reduction in chabazite

Silver-exchanged molecular sieves have shown great promise in applications ranging from antimicrobial materials to the adsorption of xenon and iodide, two key contaminants emitted from nuclear reactors. In this work, solid-state 27Al and 29Si MAS NMR and TGA were used to study silver reduction in silver-exchanged chabazite under various thermal conditions. The solid-state NMR results for both 27Al and 29Si show that there are no major changes in the chabazite during silver reduction in an argon stream; however a progressive structural change does take place in the hydrogen stream. The structural change likely involves breaking the silicon oxygen bond of the Si-O-AI fragment of chabazite, leading to the formation of extra-framework aluminum oxide. The TGA results at temperatures up to 600 degrees C indicate that silver reduction is less complete in an argon stream than in a hydrogen stream. In this paper we propose that silver reduction occurs via the following reactions: 2(Ag + ZO-)+H2O --> 1/2O2+2Ag0 + 2ZOH and nAg + mAg = Ag(m+n)n+ (in an argon stream); and Ag(+) + ZO(-) + 1/2H2 = Ag0 + ZOH and 2ZOH = ZO(-) + Z(+) + H2O (in a hydrogen stream).     

On the formation of radiation-induced defects in fluoroaluminate glasses

The spectra of electron paramagnetic resonance (EPR) of fluoroaluminate glass (FAG-36) based on mineral usovite Ba₂CaMgAlF₁₄ were studied. The paramagnetic centers responsible for EPR signals were induced by ion bombardment of the substrates prepared from this glass. The N⁺, O⁺, Ar⁺ and Pb + ions with energy E = 150 keV were used. The integrated dose D was 2 × 10¹⁶ ions/cm². It is shown by means of isochronal anneal experiments and computer simulation of the EPR spectra that they contain four components: broad Gaussian line (GL) with g = 2.016 and σ oscillating in the range 30–40; two anisotropic spectra with g_z = 2.016, g_y = 2.009; g_x = 2.001 (FA₁) and g_z = 2.045; g_y = 2.010; g_x = 1.98 (FA₂) as well as narrow isotropic line of Lorentzian shape with g = 2.0025 and ΔH = 0.6 mT. The comparison of obtained results with literature data for γ-irradiated fluoride glasses and ion-implanted oxide glasses of different compositions permitted to conclude that GL is due to hole defects typical of fluoride glasses and localized on several anions (fluorines and oxygen(s)); anisotropic FA₁- and FA₂-spectra are attributed to molecular 0₂⁻-ions, and narrow isotropic signal is supposedly assigned to big molecular ions (O₂O⁻, 0₄⁻ , CO⁺, CO⁻) located in voids of damaged implantation layer.     

Ce元素掺杂对YBaCo_4O_(7+δ)氧吸附/脱附性能的影响

本研究采用固态反应法制备了Ce掺杂的YBaCo_4O_(7+δ)氧吸附材料,对其进行了X射线衍射(XRD)分析和热重分析测试,研究了Ce掺杂对其氧吸附/脱附性能的影响。XRD分析结果表明:在x=0.10,0.15,0.20掺杂比例范围内,Ce很好地进入了YBaCo_4O_(7+δ)的晶格,具有单一的YBaCo_4O_(7+δ)的晶体结构,没有出现第二相。热重分析结果表明:从室温到1000℃,所有样品都经历了两次氧吸附过程,Ce掺杂的YBaCo_4O_(7+δ)样品最大氧吸附量明显高于YBaCo_4O_(7+δ)的最大氧吸附量。     

Anomalous elastic properties of RF-sputtered amorphous TeO2+x thin film for temperature-stable SAW device applications

The anomalous elastic properties of TeO_2+x thin films deposited by rf diode sputtering on substrates at room temperature have been studied. The deposited films are amorphous, and IR spectroscopy reveals the formation of Te-O bond. X-ray photoelectron spectroscopy confirms the variation in the stoichiometry of TeO_2+x film from x = 0 to 1 with an increase in the oxygen percentage in processing gas composition. The elastic parameters of the films in comparison to the reported values for TeO_2+x single crystal are found to be low. However, the temperature coefficients of elastic parameters of all deposited films exhibit anomalous behavior showing positive values for TC(C₁₁) in the range (32.0 to 600.0) x 10^-40 C^-1 and TC(C¹¹) = (35.0 to 645.5) x 10^-4degC^-1 against the negative values TC(Cn) = -2.7 x 10^-4degC^-1 and TC(C₁₁) = -0.73 x 10^-4degC^-1 reported for TeO₂ single crystal. The variation in the elastic parameters and their temperature coefficients is correlated with the change in the three-dimensional network of Te-O bonding. The anomalous elastic properties of the TeO_2+x films grown in 100% O₂ are useful for potential application in the design of temperature stable surface acoustic wave devices.     

La2Ni1-xFexO4＋δ复合氧化物的合成及表征

以EDTA为配位体,采用溶胶-凝胶法合成了La2Ni1-xFexO4＋δ系复合氧化物,XRD结果表明,所有样品都具有K2NiF4型结构。通过碘量法测定结果表明Ni／Fe的平均化合价和样品的非化学计量氧含量,均随x的增加而增大;当x=0．2时,非化学计量氧含量最高为0．2462。通过FT—IR发现Fe的引入导致Ni-O键的振动加强,这有利于间隙氧离子的活动。交流阻抗法测定样品的离子电导率随x的增加而逐渐增大,同一样品离子电导率在低温段随温度的升高而增大,表现出小极化子占主要的电导作用。     

Sintering Caβ″/β/α-Al_2O_3 High Temperature Oxygen Sensor

An extended-life and ultra-low oxygen sensor has been fabricated by using polycrystalline Caβ″/β/α-Al2O3 as a solid electrolyte. Five reference electrodes CaO+O2, Caβ″/β/α-Al2O3 (powder)+O2,Cr+Cr2O3, Nb+NbO and Mo+MoO2 were tested in order to select a better reference electrode for this sensor. The limit of determining oxygen activity and the extended-life of the sensor were also tested in this study.     

铌钽酸钠钾锂-铟酸铋铁电压电性能的研究

采用传统固相合成法制备了(1-x)(0.97Na_0.5K_0.5NbO₃+0.03LiTaO₃)+xBiInO₃[(1-x)(KNN+LT)+xBI]无铅压电陶瓷, 研究了该体系的晶体结构、压电、铁电与介电性能。结果表明: (1-x)(KNN+LT)+xBI陶瓷的晶体结构在室温下为正交相和四方相两相共存, 随着BI含量的增加, 四方相含量逐渐增多, 居里温度T_c降低, 但是正交四方相转变温度T_o-t呈现升高趋势, 晶格参数逐渐增大。随着BI含量的继续增加, Bi在高温下的挥发导致氧空位的增多, 从而使材料性能下降。在x=0.0015时得到组分的最佳性能, 其居里温度T_c、相转变温度T_o-t、压电常数d₃₃、剩余极化P_r、矫顽场E_c分别达到400℃、126℃、160 pC/N、19.26 μC/cm2和7.75 kV/cm。     

Nonlinear Electrical Properties of SnO_2-Li_2O-Nb_2O_5 Varistor System

The electrical properties of (Nb, Li)-doped SnO2 ceramics as a new varistor material were investigated. The sample 97.95%SnO2·0.50%Li2O·0.05%Nb2O5 (mol fraction) sintered at 1450= possess the highest density (ρ=6.77 g/cm3) and nonlinear electrical coefficient (α=11.6). The substitution of Sn4+ with Li+ increases the concentration of oxygen vacancies, together with the formation of solid solution, which will increase the sintering rate greatly and decrease the optimized sintering temperature. The substitution of Sn4+ with Li+ and the variation of temperature play very important effects on the densities, dielectric constant, nonlinear electrical properties and other characteristics of the samples. The properties of the grain boundary barrier and the microstructural characteristics were investigated to ensure the effect of the dopants and the temperature. A grain boundary defect barrier model was used to illustrate the grain boundary barriers formation in SnO2-Li2O-Nb2O5 varistors.     

NASICON solid electrolytes part I: The Na-diffusion path and its relation to the structure

NASICON is a solid solution system which is given by the formula Na_1+x+4yZr_2-ySi_xP_3-xO₁₂, 0x3, 0y1. Using single crystal X-ray data collected at high temperatures on three different NASICON compositions (x=0; x=1.4, y=0.2; x=3) the diffusion paths and the effective one particle potentials of the Na ions were studied. These structure investigations show how the Na diffusion is influenced by the NASICON framework. A simple model is presented describing the opening mechanism of the diffusion path as a function of composition and temperature. The NASICON framework of the composition x=1.4, y=0.2 exhibits a Na interstitial site which is not involved in the diffusion process, but is correlated with oxygen split positions. Taking into account also other static disorder effects found in the composition x=0 (see the following paper), the picture of a rigid NASICON framework cannot longer be maintained.     

Nonlinear Electrical Properties of SnO2—LiO—Nb2O5 Varistor System

The electrical properties of (Nb,Li)-doped SnO2 ceramics as a new varistor material were investigated.The sample 97.95% SnO20.50%Li2O0.05%Nb2O5( mol fraction)sintered at 1450℃ possess the highest density(p=6.77g/cm^3) and nonlinear electrical coefficient(α=11.6).The substitution of Sn^4 with Li^ increases the concentration of oxygen vacancies,together with the formation of solid solution ,which will increase the sintering rate greatly and decrease the optimized sintering temperature.The substitution of Sn^4 with Li^ and the variation of temperature play very important effects on the densities,dielectric constant,nonlinear electrical properties and other characteristics of the samples.The properties of the grain boundary barrier and the microstructural characteristics were investigated to ensure the effect of the dopants and the temperature.A grain boundary defect barrier model was used to illustrate the grain boundary barriers formation in SnO2-Li2O-Nb2O5 varistors.     

第一原理研究LuPO4中氧空位的性质

磷酸结构的晶体在掺杂二价阳离子后容易形成产生焦磷酸结构(P₂O₇) ^4-, 这种含有焦磷酸结构的氧化物材料十分适合做质子导体、燃料电池、气体传感器以及陶瓷膜等。本文利用第一性原理研究了LuPO₄晶体中氧空位的结构性质, 结果显示当氧空位带二价正电时, 会引发氧空位周围原子奇特的畸变, 形成焦磷酸结构。为了解释这种结构畸变的机理, 本文利用过渡态搜索计算了结构变化过程中势能面的变化情况, 正一价氧空位形成焦磷酸 结构需要越过2.4 eV的势垒, 而正二价氧空位形成焦磷酸结构则不需要越过任何势垒, 因此很容易形成焦磷酸 结构。最后给出氧空位不同带电态的晶格结构、电子态密度以及电荷密度分布等基本物理性质, 氧空位处于正二价态结构下, 氧空位附近的P原子与O原子成键, 又由于O原子有较强的电负性, P的s轨道电子向O的p轨道转 移。P的s、p轨道在禁带中出现了与总态密度对应的缺陷能级, 结果表明带正二价氧空位的晶体性质发生了明显变化。     

Instrumentation for the breath-by-breath determination of oxygen and carbon dioxide based on nondispersive absorption measurements.

This paper describes the development and evaluation of instrumentation for the breath-by-breath determination of oxygen and carbon dioxide in respiratory gases. The method is based on nondispersive absorption and uses the 145-nm absorption band for detection of oxygen and the 4.3-micron band for detection of carbon dioxide. A xenon discharge lamp with a sharp band at 147 nm was chosen as the source for the determination of oxygen, and a carbon dioxide discharge lamp with a sharp band at 4.3 micron was chosen for determination of carbon dioxide. A vacuum photodiode was used as the detector for oxygen, and a photoconductive cell with a built-in interference filter was used for detection of carbon dioxide. Plots of absorbance (A) vs concentration (C, %) were linear for oxygen and were nonlinear for carbon dioxide. Typical least-squares calibration equations were A = 0.020C + 0.02 for oxygen (0-100%) and A = 0.0012C2 + 0.050C + 0.008 for carbon dioxide (0-8%). Comparisons of computed (y) vs prepared (x) values for the concentrations given above were linear for both gases, yielding y = (1.00 +/- 0.01)x - 0.13 +/- 0.73 for oxygen and y = (1.07 +/- 0.02)x - 0.04 +/- 0.06 for carbon dioxide. The standard deviations were 1.2% at 50% oxygen and 1.5% at 4% carbon dioxide. Records are presented to illustrate breath-by-breath monitoring of these gases in a healthy subject.     

High temperature oxidation of C2Cl4/CH4 mixtures

Experiments on high temperature oxidation of multi-chlorinated hydrocarbons, tetrachloroethylene (C2Cl4), with hydrocarbon fuels, CH4, were performed in a 15 mm i.d. tubular flow reactor. Temperatures ranged from 700 to 850 degrees C, with the average residence time in the range from 0.3 to 1.5s. Three equivalence ratios, phi=0.87 (fuel-lean (FL)), phi=1 (stoichiometry (S)), and phi=1.3 (fuel-rich (FR)), were studied. The global Arrhenius equations for the decomposition of C(2)Cl(4) for each reactant set ratio are: k(lean)=5.77 x 10(15) exp(-30447/RT), k(stoi)=5.15 x 10(15) exp(-30421/RT), and k(rich)=6.32 x 10(14) exp(-28879/RT). The important reactions for destruction of parent C2Cl4 include: C2Cl4 --> C2Cl3 + Cl, C2Cl4 + H--> C2Cl3 + HCl and C2Cl4 + H --> C2HCl3 + Cl. The resulting reactant loss, and intermediate and final product profiles were determined. C2HCl3, C2Cl2, CO, CO2 and HCl are the major products for the reaction of C2Cl4/CH4/O2 mixtures for these three reaction systems. Minor intermediates include C2H3Cl, C2HCl, COCl2, CH3CHCl2, C2H4, C2H6, CCl2CHCH3 , trans-CHClCHCl, cis-CHClCHCl, trans-ClHC=CClCH(3), C6H6, and Cl2. The experimental data showed that as the oxygen concentration increased, the temperature needed to detect the resulting products decreased.