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Sample records for alkali carbonate reactions

  1. Lithological influence of aggregate in the alkali-carbonate reaction

    International Nuclear Information System (INIS)

    The reactivity of carbonate rock with the alkali content of cement, commonly called alkali-carbonate reaction (ACR), has been investigated. Alkali-silica reaction (ASR) can also contribute in the alkali-aggregate reaction (AAR) in carbonate rock, mainly due to micro- and crypto-crystalline quartz or clay content in carbonate aggregate. Both ACR and ASR can occur in the same system, as has been also evidenced on this paper. Carbonate aggregate samples were selected using lithological reactivity criteria, taking into account the presence of dedolomitization, partial dolomitization, micro- and crypto-crystalline quartz. Selected rocks include calcitic dolostone with chert (CDX), calcitic dolostone with dedolomitization (CDD), limestone with chert (LX), marly calcitic dolostone with partial dolomitization (CD), high-porosity ferric dolostone with clays (FD). To evaluate the reactivity, aggregates were studied using expansion tests following RILEM AAR-2, AAR-5, a modification using LiOH AAR-5Li was also tested. A complementary study was done using petrographic monitoring with polarised light microscopy on aggregates immersed in NaOH and LiOH solutions after different ages. SEM-EDAX has been used to identify the presence of brucite as a product of dedolomitization. An ACR reaction showed shrinkage of the mortar bars in alkaline solutions explained by induced dedolomitization, while an ASR process typically displayed expansion. Neither shrinkage nor expansion was observed when mortar bars were immersed in solutions of lithium hydroxide. Carbonate aggregate classification with AAR pathology risk has been elaborated based on mechanical behaviours by expansion and shrinkage. It is proposed to be used as a petrographic method for AAR diagnosis to complement the RILEM AAR1 specifically for carbonate aggregate. Aggregate materials can be classified as I (non-reactive), II (potentially reactive), and III (probably reactive), considering induced dedolomitization ACR

  2. Alkali-metal intercalation in carbon nanotubes

    Science.gov (United States)

    Béguin, F.; Duclaux, L.; Méténier, K.; Frackowiak, E.; Salvetat, J. P.; Conard, J.; Bonnamy, S.; Lauginie, P.

    1999-09-01

    We report on successful intercalation of multiwall (MWNT) and single wall (SWNT) carbon nanotubes with alkali metals by electrochemical and vapor phase reactions. A LiC10 compound was produced by full electrochemical reduction of MWNT. KC8 and CsC8-MWNT first stage derivatives were synthesized in conditions of alkali vapor saturation. Their identity periods and the 2×2 R 0° alkali superlattice are comparable to their parent graphite compounds. The dysonian shape of KC8 EPR line and the temperature-independent Pauli susceptibility are both characteristic of a metallic behavior, which was confirmed by 13C NMR anisotropic shifts. Exposure of SWNT bundles to alkali vapor led to an increase of the pristine triangular lattice from 1.67 nm to 1.85 nm and 1.87 nm for potassium and rubidium, respectively.

  3. Alkali Aggregate Reaction in Alkali Slag Cement Mortars

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By means of "Mortar Bar Method",the ratio of cement to aggregate was kept as a constant 1∶2.25,the water-cement ratio of the mixture was 0.40,and six prism specimens were prepared for each batch of mixing proportions with dimensions of 10×10×60mm3 at 38±2℃ and RH≥95%, the influences of content and particle size of active aggregate, sort and content of alkali component and type of slag on the expansion ratios of alkali-activated slag cement(ASC) mortars due to alkali aggregate reaction(AAR) were studied. According to atomic absorption spectrometry,the amount of free alkali was measured in ASC mortars at 90d.The results show above factors affect AAR remarkably,but no dangerous AAR will occur in ASC system when the amount of active aggregate is below 15% and the mass fraction of alkali is not more than 5% (Na2O).Alkali participated in reaction as an independent component, and some hydrates containing alkali cations were produced, free alkalis in ASC system can be reduced enormously.Moreover,slag is an effective inhibitor, the possibility of generating dangerous AAR in ASC system is much lower at same conditions than that in ordinary Portland cement system.

  4. Effect of Mineral Admixtures on Alkali-Silica Reaction

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chengzhi; WANG Aiqin

    2008-01-01

    The influence of silica fume,slag and fly ash on alkali-silica reaction under the condition of 70℃ is studied.The results show that silica,slag and fly ash may inhibit alkali-silica reaction only under suitable content.When the content is less than 10%,silica fume does not markedly influence the expansion of alkali-silica reaction.When the content is 15%-20%,silica fume only may delay the expansion of alkali-silica reaction.When the content is 30%-70%,slag may only delay the expansion of alkali-silica reaction,but cannot inhibit the expansion of alkali-silica reaction.When the content is 10%,fly ash does not markedly influence the expansion of alkali-silica reaction.When the content is 20%-30%,fly ash may only delay the expansion of alkali-silica reaction,but cannot inhibit the expansion of alkali-silica reaction.When the content is over 50%,it is possible that fly ash can inhibit effectively alkali-silica reaction.

  5. Effect of Pozzolanic Reaction Products on Alkali-silica Reaction

    Institute of Scientific and Technical Information of China (English)

    WEI Fengyan; LAN Xianghui; LV Yinong; XU Zhongzi

    2006-01-01

    The effect of fly ash on controlling alkali-silica reaction (ASR) in simulated alkali solution was studied. The expansion of mortar bars and the content of Ca(OH)2 in cement paste cured at 80 ℃ for 91 d were measured. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were employed to study the microstructure of C-S-H. TEM/energy dispersive spectroscopy (EDS) was then used to determine the composition of C-S-H. The pore structure of the paste was analyzed by mercury intrusion porosimetry (MIP). The results show that the contents of fly ash of 30% and 45% can well inhibit ASR. And the content of Ca(OH)2 decreases with the increase of fly ash. That fly ash reacted with Ca(OH)2 to produce C-S-H with a low Ca/Si molar ratio could bind more Na+ and K+ ions, and produce a reduction in the amount of soluble alkali available for ASR. At the same time, the C-S-H produced by pozzolanic reaction converted large pores to smaller ones (gel pores smaller than 10 nm) to densify the pore structure. Perhaps that could inhibit alkali transport to aggregate for ASR.

  6. CONTRIBUTION TO THE STUDY OF HYDROXYMETYLATION REACTION OF ALKALI LIGNIN

    OpenAIRE

    Teodor Malutan; Raluca Nicu; Valentin I. Popa

    2008-01-01

    The hydroxymethylation of alkali lignin with formaldehyde in alkaline solution was studied. The influence of reaction conditions of the hydroxymethylation of alkali lignin was followed by modifying the temperature, time, and the ratios of NaOH to lignin and CH2O to lignin. Three different types of alkali lignin were utilized. The reaction was followed by total consumption of formaldehyde, and the resulting products were characterized through FTIR-spectra, thermogravimetry analysis, ash and mo...

  7. Concrete alkali-silica reaction and nuclear radiation damage

    International Nuclear Information System (INIS)

    The deterioration of concrete by alkali-silica reaction of aggregates (ASR) and the effect of nuclear radiations on the ASR have been reviewed based on our studies on the mechanism of ASR and the effect of nuclear radiations on the resistivity of minerals to alkaline solution. It has been found that the ASR is initiated by the attack of alkaline solution in concrete to silicious aggregates to convert them into hydrated alkali silicate. The consumption of alkali hydroxide by the aggregates induces the dissolution of Ca2+ ions into the solution. The alkali silicate surrounding the aggregates then reacts with Ca2+ ions to convert to insoluble tight and rigid reaction rims. The reaction rim allows the penetration of alkaline solution but prevents the leakage of viscous alkali silicate, so that alkali silicate generated afterward is accumulated in the aggregate to give an expansive pressure enough for cracking the aggregate and the surrounding concrete. The effect of nuclear radiation on the reactivity of quartz and plagioclase, a part of major minerals composing volcanic rocks as popular aggregates, to alkaline solution has been examined for clarifying whether nuclear radiations accelerates the ASR. It has been found that the irradiation of these minerals converts them into alkali-reactive amorphous ones. The radiation dose for plagioclase is as low as 108 Gy, which suggests that the ASR of concrete surrounding nuclear reactors is possible to be accelerated by nuclear radiation. (author)

  8. Cold Reactions of Alkali and Water Clusters inside Helium Nanodroplets

    CERN Document Server

    Müller, S; Koslowski, Th; Mudrich, M; Stienkemeier, F

    2008-01-01

    The reaction of alkali (Na, Cs) clusters with water clusters embedded in helium nanodroplets is studied using femtosecond photo-ionization as well as electron impact ionization. Unlike Na clusters, Cs clusters are found to completely react with water in spite of the ultracold helium droplet environment. Mass spectra of the Cs$_n$+(H$_2$O)$_m$ reaction products are interpreted in terms of stability with respect to fragmentation using high-level molecular structure calculations.

  9. Coprecipitation of alkali metal ions with calcium carbonate

    International Nuclear Information System (INIS)

    The coprecipitation of alkali metal ions Li+, Na+, K+ and Rb+ with calcium carbonate has been studied experimentally and the following results have been obtained: (1) Alkali metal ions are more easily coprecipitated with aragonite than with calcite. (2) The relationship between the amounts of alkali metal ions coprecipitated with aragonite and their ionic radii shows a parabolic curve with a peak located at Na+ which has approximately the same ionic radius as Ca2+. (3) However, the amounts of alkali metal ions coprecipitated with calcite decrease with increasing ionic radius of alkali metals. (4) Our results support the hypothesis that (a) alkali metals are in interstitial positions in the crystal structure of calcite and do not substitute for Ca2+ in the lattice, but (b) in aragonite, alkali metals substitute for Ca2+ in the crystal structure. (5) Magnesium ions in the parent solution increase the amounts of alkali metal ions (Li+, Na+, K+ and Rb+) coprecipitated with calcite but decrease those with aragonite. (6) Sodium-bearing aragonite decreases the incorporation of other alkali metal ions (Li+, K+ and Rb+) into the aragonite. (author)

  10. Alkali-aggregate reactions, strengthening or total collaps?

    DEFF Research Database (Denmark)

    Nielsen, Anders

    2000-01-01

    Alkali-aggregate reactions (AAR) can have many different effects, ranging from nothing happening to total cracking of the structure. The reason for this is related to the fact that chemistry and mechanics interfere with each other in the reactions. So, factors such as the concrete composition, the...... be analysed. In the present paper a proposal for the time development is given. The time development of the harmful reactions consists of an initiation period, a propagation period, and a rest period. - For a given concrete in a given environment, the length of the initiation period depends upon the...

  11. The reaction dynamics of alkali dimer molecules and electronically excited alkali atoms with simple molecules

    Energy Technology Data Exchange (ETDEWEB)

    Hou, H [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-12-01

    This dissertation presents the results from the crossed molecular beam studies on the dynamics of bimolecular collisions in the gas phase. The primary subjects include the interactions of alkali dimer molecules with simple molecules, and the inelastic scattering of electronically excited alkali atoms with O2. The reaction of the sodium dimers with oxygen molecules is described in Chapter 2. Two reaction pathways were observed for this four-center molecule-molecule reaction, i.e. the formations of NaO2 + Na and NaO + NaO. NaO2 products exhibit a very anisotropic angular distribution, indicating a direct spectator stripping mechanism for this reaction channel. The NaO formation follows the bond breaking of O2, which is likely a result of a charge transfer from Na2 to the excited state orbital of O2-. The scattering of sodium dimers from ammonium and methanol produced novel molecules, NaNH3 and Na(CH3OH), respectively. These experimental observations, as well as the discussions on the reaction dynamics and the chemical bonding within these molecules, will be presented in Chapter 3. The lower limits for the bond dissociation energies of these molecules are also obtained. Finally, Chapter 4 describes the energy transfer between oxygen molecules and electronically excited sodium atoms.

  12. Effect of Anti-freezing Admixtures on Alkali-silica Reaction in Mortars

    Institute of Scientific and Technical Information of China (English)

    LIU Junzhe; LI Yushun; LV Lihua

    2005-01-01

    The influence of anti-freezing admixture on the alkali aggregate reaction in mortar was analyzed with accelerated methods. It is confirmed that the addition of sodium salt ingredients of anti-freezing admixture accelerates the alkali silica reaction to some extent, whereas calcium salt ingredient of anti-freezing admixture reduces the expansion of alkali silica reaction caused by high alkali cement. It is found that the addition of the fly ash considerably suppresses the expansion of alkali silica reaction induced by the anti-freezing admixtures.

  13. Chemical reactions of ultracold alkali dimers in the lowest-energy $^3\\Sigma$ state

    CERN Document Server

    Tomza, Michał; Moszynski, Robert; Krems, Roman V

    2013-01-01

    We show that the interaction of polar alkali dimers in the quintet spin state leads to the formation of a deeply bound reaction complex. The reaction complex can decompose adiabatically into homonuclear alkali dimers (for all molecules except KRb) and into alkali trimers (for all molecules). We show that there are no barriers for these chemical reactions. This means that all alkali dimers in the $a^3\\Sigma^+$ state are chemically unstable at ultracold temperature, and the use of an optical lattice to segregate the molecules and suppress losses may be necessary. In addition, we calculate the minimum energy path for the chemical reactions of alkali hydrides. We find that the reaction of two molecules is accelerated by a strong attraction between the alkali atoms, leading to a barrierless process that produces hydrogen atoms with large kinetic energy. We discuss the unique features of the chemical reactions of ultracold alkali dimers in the $a^3\\Sigma^+$ electronic state.

  14. Alkali-silica reaction resistant concrete using pumice blended cement

    Science.gov (United States)

    Ramasamy, Uma

    Durability of structures is a major challenge for the building industry. One of the many types of concrete deterioration that can affect durability is alkali-silica reaction (ASR). ASR has been found in most types of concrete structures, including dams, bridges, pavements, and other structures that are 20 to 50 years old. The degradation mechanism of ASR produces a gel that significantly expands in the presence of water as supplied from the surrounding environment. This expansion gel product can create high stresses and cracking of the concrete, which can lead to other forms of degradation and expensive structural replacement costs. The four essential factors that produce an expansive ASR gel in concrete are the presence of alkalis, siliceous aggregate, moisture, and free calcium hydroxide (CH). If concrete is starved of any one of these essential components, the expansion can be prevented. Reducing CH through the use of a supplementary cementitious material (SCM) such as natural pozzolan pumice is the focus of this research. By using a pozzolan, the amount of CH is reduced with time based on the effectiveness of the pozzolan. Many pozzolans exist, but one such naturally occurring pozzolanic material is pumice. This research focuses on determining the effect of a finely ground pumice as a SCM in terms of its resistance to ASR expansion, as well as improving resistance to other potential concrete durability mechanisms. In spite of having high alkali contents in the pumice, mixtures containing the SCM pumice more effectively mitigated the ASR expansion reaction than other degradation mechanisms. Depending on the reactivity of the aggregates and fineness of the pumice, 10-15% replacement of cement with the pumice was found to reduce the ASR expansion to the acceptable limits. The amount of CH remaining in the concrete was compared to the ASR expansion in order to improve understanding of the role of CH in the ASR reaction. Thermo-gravimetric analysis (TGA) and X

  15. How to identify carbonate rock reactions in concrete

    International Nuclear Information System (INIS)

    This paper summarizes the modern petrographic techniques used to diagnose carbonate rock reactions in concrete. Concrete microbar specimens of the prototype RILEM AAR-5 test, provided by the Austrian Cement Research Institute, and typical Canadian concrete that had undergone alkali-carbonate reaction (ACR) were examined. Scanning electron microscopy, element mapping and quantitative analysis using electron-probe microanalyzer with energy-dispersive spectrometry (EPMA/EDS: around x 2000, <0.1 nA) were made of polished thin sections after completing polarizing microscopy. Dedolomitization produced a myrmekitic texture, composed of spotted brucite (<3 μm) and calcite within the reaction rim, along with a carbonate halo of calcite in the surrounding cement paste. However, no evidence was detected that dedolomitization had produced the expansion cracks in the cement paste, while the classical definition of alkali-carbonate reaction postulates their development. It was found that the alkali-silica reaction (ASR) due to cryptocrystalline quartz hidden in the matrix, always associated with dedolomitization in all the carbonate aggregates tested, was responsible for the expansion of both the laboratory and field concretes, even with the Canadian dolomitic limestone from Kingston, the reference material for alkali-carbonate reaction. It is suggested that the term alkali-carbonate reaction is misleading

  16. In situ alkali-silica reaction observed by x-ray microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kurtis, K.E.; Monteiro, P.J.M. [Univ. of California, Berkeley, CA (United States); Brown, J.T.; Meyer-Ilse, W. [Ernest Orlando Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    In concrete, alkali metal ions and hydroxyl ions contributed by the cement and reactive silicates present in aggregate can participate in a destructive alkali-silica reaction (ASR). This reaction of the alkalis with the silicates produces a gel that tends to imbibe water found in the concrete pores, leading to swelling of the gel and eventual cracking of the affected concrete member. Over 104 cases of alkali-aggregate reaction in dams and spillways have been reported around the world. At present, no method exists to arrest the expansive chemical reaction which generates significant distress in the affected structures. Most existing techniques available for the examination of concrete microstructure, including ASR products, demand that samples be dried and exposed to high pressure during the observation period. These sample preparation requirements present a major disadvantage for the study of alkali-silica reaction. Given the nature of the reaction and the affect of water on its products, it is likely that the removal of water will affect the morphology, creating artifacts in the sample. The purpose of this research is to observe and characterize the alkali-silica reaction, including each of the specific reactions identified previously, in situ without introducing sample artifacts. For observation of unconditioned samples, x-ray microscopy offers an opportunity for such an examination of the alkali-silica reaction. Currently, this investigation is focusing on the effect of calcium ions on the alkali-silica reaction.

  17. Alkali-Silica Reaction Inhibited by LiOH and Its Mechanism

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A high alkali reactive aggregate-zeolitization perlite was used to test the long-term effectiveness of LiOH in inhibiting alkali-silica reaction.In this paper,the rigorous conditions were designed that the mortar bars had been cured at 80℃ for 3 years after autoclaved 24 hours at 150℃.Under this condition,LiOH was able to inhibit the alkali-silica reaction long-term effectiveness.Not only the relationship between the molar ratio of n(Li)/(Na) and the alkali contents in systems was established, but also the governing mechanism of such effects was also studied by SEM.

  18. Mechanical effects of alkali silica reaction in concrete studied by SEM-image analysis

    OpenAIRE

    Ben Haha, Mohsen

    2006-01-01

    The occurrence of alkali-silica and alkali-silicate reactions causes damage in concrete. Even though the reaction has been known for some time, the progress of reaction in affected structures is difficult to predict. This research programme aims to study the relationship between the progress of the reaction and the mechanical properties of the concrete in order to support better prognosis of the effect of ASR on affected structure. The basic principal of the research programme is to character...

  19. Mechanical effects of alkali silica reaction in concrete studied by SEM-image analysis

    OpenAIRE

    Ben Haha, Mohsen; Scrivener, Karen

    2007-01-01

    The occurrence of alkali-silica and alkali-silicate reactions causes damage in concrete. Even though the reaction has been known for some time, the progress of reaction in affected structures is difficult to predict. This research programme aims to study the relationship between the progress of the reaction and the mechanical properties of the concrete in order to support better prognosis of the effect of ASR on affected structure. The basic principal of the research programme is to character...

  20. Ion-exchange behavior of alkali metals on treated carbons

    International Nuclear Information System (INIS)

    The ion-exchange behavior of trace quantities of the alkali-metal ions sodium and cesium, on activated carbon impregnated with zirconium phosphate (referred to here as ZrP), was studied. Impregnated carbon had twice as much ion-exchange activity as unimpregnated, oxidized carbon, and 10 times as much as commercial activated carbons. The distribution coefficient of sodium increased with increasing pH; the distribution coefficient of cesium decreased with increasing pH. Sodium and cesium were separated with an electrolytic solution of 0.1 M HCl. Preliminary studies indicated that 0.2 M potassium and cesium can also be separated. Distribution coefficients of the supported ZrP were determined by the elution technique and agreed within 20% of the values for pure ZrP calculated from the literature

  1. Experimental and modelling study of the alkali-silica-reaction in concrete

    OpenAIRE

    Dunant, Cyrille

    2009-01-01

    The alkali-silica reaction (ASR) is a durability issue of concrete. The amorphous silica of aggregates reacts with the alkalies present in the cement paste pore solution to form a hydrophilic gel which swells in the presence of moisture. Many mass concrete structures are affected and understanding of the reaction and its development is crucial, notably for dam owners and managers. Although some parameters affecting the reaction are well understood, such as temperature, others which depend on ...

  2. Investigation on the expansion value of turbine generator foundation affected by Alkali-Silica reaction

    International Nuclear Information System (INIS)

    It is well known that expansion of concrete is occurred in the concrete structure affected by Alkali-silica reaction in addition to crack propagation. However it is difficult to measure expansion value after the alkali silica reaction occurrence in a structure. The turbine generator foundation which is the core discussion item of this paper has been monitored for expansion values and reinforcement bar strains, upon which the expansion of the structure due to affect of the alkali silica reaction is found out. The total expansion values of the turbine generator foundation due to the affect of Alkali-silica reaction were estimated according to those measurement results in order to be utilized for a turbine generator foundation analysis. (authors)

  3. Investigation on lithium migration for treating alkali-silica reaction affected concrete

    OpenAIRE

    Silva De Souza, L.M.; Polder, R.B.; Copuroglu,O.

    2014-01-01

    Alkali-silica reaction (ASR) is one of the major deterioration mechanisms that affect numerous concrete structures worldwide. During the reaction, hydroxyl and alkali (sodium and potassium ) ions react with certain siliceous compounds in the aggregate, forming a hygroscopic gel. The gel absorbs water from the cement paste and swells, possibly leading to deleterious expansion and cracking of the structure. Once ASR is detected in existing structures, there are no treatments to stop it and prol...

  4. Assessment of concrete bridge decks with alkali silica reactions

    DEFF Research Database (Denmark)

    Eriksen, Kirsten; Jansson, Jacob; Geiker, Mette Rica

    , Bagsværd, Denmark to provide information on the damage condition as well as the residual reactivity of the concrete. The Danish Road Directory’s guidelines for inspection and assessment of alkali silica damaged bridges will be briefly presented, and proposed modifications will be describe...

  5. Alkali-Doped Lithium Orthosilicate Sorbents for Carbon Dioxide Capture.

    Science.gov (United States)

    Yang, Xinwei; Liu, Wenqiang; Sun, Jian; Hu, Yingchao; Wang, Wenyu; Chen, Hongqiang; Zhang, Yang; Li, Xian; Xu, Minghou

    2016-09-01

    New alkali-doped (Na2 CO3 and K2 CO3 ) Li4 SiO4 sorbents with excellent performance at low CO2 concentrations were synthesized. We speculate that alkali doping breaks the orderly arrangement of the Li4 SiO4 crystals, hence increasing its specific surface area and the number of pores. It was shown that 10 wt % Na2 CO3 and 5 wt % K2 CO3 are the optimal additive ratios for doped sorbents to attain the highest conversions. Moreover, under 15 vol % CO2 , the doped sorbents present clearly faster absorption rates and exhibit stable cyclic durability with impressive conversions of about 90 %, at least 20 % higher than that of non-doped Li4 SiO4 . The attained conversions are also 10 % higher than the reported highest conversion of 80 % on doped Li4 SiO4 . The performance of Li4 SiO4 is believed to be enhanced by the eutectic melt, and it is the first time that the existence of eutectic Li/Na or Li/K carbonate on doped sorbents when absorbing CO2 at high temperature is confirmed; this was done using systematical analysis combining differential scanning calorimetry with in situ powder X-ray diffraction. PMID:27531239

  6. Alkali silica reaction in concrete induced by mortar adhered to recycled aggregate

    OpenAIRE

    Etxeberria, M.; Vázquez, E.

    2010-01-01

    The durability of recycled concrete must be determined before this material can be used in construction. In this paper the alkali-silica reaction in recycled concrete is analyzed. The recycled concrete is made with recycled aggregates, composed by original limestone aggregates and adhered mortar with reactive silica sand, and high alkali content cement. Due to the manufacturing process used for concrete production and the high water absorption capacity of recycled aggregates, cement accumulat...

  7. Detection of alkali-silica reaction swelling in concrete by staining

    Science.gov (United States)

    Guthrie, Jr., George D.; Carey, J. William

    1998-01-01

    A method using concentrated aqueous solutions of sodium cobaltinitrite and rhodamine B is described which can be used to identify concrete that contains gels formed by the alkali-silica reaction (ASR). These solutions present little health or environmental risk, are readily applied, and rapidly discriminate between two chemically distinct gels; K-rich, Na--K--Ca--Si gels are identified by yellow staining, and alkali-poor, Ca--Si gels are identified by pink staining.

  8. Recovery of alkali and alumina from Bayer red mud by the calcification-carbonation method

    Science.gov (United States)

    Zhu, Xiao-feng; Zhang, Ting-an; Wang, Yan-xiu; Lü, Guo-zhi; Zhang, Wei-guang

    2016-03-01

    Red mud produced in the Bayer process is a hazardous solid waste because of its high alkalinity; however, it is rich in valuable components such as titanium, iron, and aluminum. In this study, a novel calcification-carbonation method was developed to recover alkali and alumina from Bayer red mud under mild reaction conditions. Batch experiments were performed to evaluate the potential effects of important parameters such as temperature, amount of CaO added, and CO2 partial pressure on the recovery of alkali and alumina. The results showed that 95.2% alkali and 75.0% alumina were recovered from red mud with decreases in the mass ratios of Na2O to Fe2O3 and of Al2O3 to Fe2O3 from 0.42 and 0.89 to 0.02 and 0.22, respectively. The processed red mud with less than 0.5wt% Na2O can potentially be used as a construction material.

  9. Relation of expansion due to alkali silica reaction to the degree of reaction measured by SEM image analysis

    International Nuclear Information System (INIS)

    Scanning Electron Microscopy Image Analysis (SEM-IA) was used to quantify the degree of alkali silica reaction in affected microbars, mortar and concrete prisms. It was found that the degree of reaction gave a unique correlation with the macroscopic expansion for three different aggregates, stored at three temperatures and with two levels of alkali. The relationships found for the concretes and the mortars overlap when normalised by the aggregate content. This relationship seems to be linear up to a critical reaction degree which coincides with crack initiation within the reactive aggregates

  10. Intra-zoned luminescence in alkali earth metal carbonates

    International Nuclear Information System (INIS)

    Full text: The fundamental plasma luminescence of wide band alkali halide crystals has been found out by Vaisburd et al. This broadband luminescence with very short duration of attenuation (∼10-12 s) arises at an irradiations of crystals with electronic beam powerful pulses of nanosecond duration. It is related to radiating 'hot' electrons and holes in a conductivity zone and in a valent zone, accordingly and in later time began to refer to as an intra-zoned luminescence. The data set on revealing features of display of an intra-zoned luminescence in different classes of crystals now proceeds. We investigated a fast luminescence at excitation with pulse electrons (3 nanoseconds) in crystals CaCO3, SrCO3, BaCO3 and MgCO3. In spectra all investigated carbonates it is possible to allocate two areas: area concerning high intensity of a fast luminescence (from 2 eV down 3 eV) and area of low intensity (is higher 4 eV) with slow recession at increase in photon energy. Thus it is typical, that in area concerning high intensity at rise in temperature from 80 up to 300 K a sample intensity of luminescence falls down, whereas in area is higher 5 eV with rise in temperature of a sample increase of intensity is observed. This broadband fast (is shorter than the time sanction of the equipment) should be connected a luminescence poorly dependent on temperature and a modular status of a sample with intra zoned transitions This luminescence reaches from 2 eV down to 7 eV but as for carbonates while is absent the reliable data on structure of a valent zone, division of an intra-zoned luminescence into electronic and hole components is not obviously possible on the basis of spectra of a fast luminescence. The nature of other luminescence processes arising at excitation with pulse electrons is discussed

  11. Experimental Investigation of CFRP Confined Columns Damaged by Alkali Aggregate Reaction

    Directory of Open Access Journals (Sweden)

    Siti Radziah Abdullah

    2012-10-01

    Full Text Available Fiber reinforced polymer is the most effective repair material in use to enhance the strength and ductility of deteriorated reinforced concrete columns. Often, fiber reinforced polymer (FRP provides passive confinement to columns until the dilation and cracking of concrete occurs. In the case of concrete suspected of Alkali Aggregate Reaction (AAR where concrete undergoes expansion, FRP wrap provides active confinement to the expanded concrete. In this study, the performance of carbon fiber reinforced polymer (CFRP wrapped columns damaged by AAR is evaluated based on the number of FRP layers and the time of the polymer application which provides two types of confinement: active or passive. The columns were tested under axial compression to evaluate the residual strength of the columns in comparison with unwrapped columns. The results reveal that the strength of the wrapped columns is enhanced with an increase in the number of CFRP layers. The strength of the columns under passive confinement is higher than the columns under active confinement. Under active confinement, early CFRP wrapping leads to improvement in the strength of the columns.

  12. Reactions between cold methyl halide molecules and alkali-metal atoms

    CERN Document Server

    Lutz, Jesse J

    2013-01-01

    We investigate the potential energy surfaces and activation energies for reactions between methyl halide molecules CH$_{3}X$ ($X$ = F, Cl, Br, I) and alkali-metal atoms $A$ ($A$ = Li, Na, K, Rb) using high-level {\\it ab initio} calculations. We examine the anisotropy of each intermolecular potential energy surface (PES) and the mechanism and energetics of the only available exothermic reaction pathway, ${\\rm CH}_{3}X+A\\rightarrow{\\rm CH}_{3}+AX$. The region of the transition state is explored using two-dimensional PES cuts and estimates of the activation energies are inferred. Nearly all combinations of methyl halide and alkali-metal atom have positive barrier heights, indicating that reactions at low temperatures will be slow.

  13. Reactions between cold methyl halide molecules and alkali-metal atoms

    International Nuclear Information System (INIS)

    We investigate the potential energy surfaces and activation energies for reactions between methyl halide molecules CH3X (X = F, Cl, Br, I) and alkali-metal atoms A (A = Li, Na, K, Rb) using high-level ab initio calculations. We examine the anisotropy of each intermolecular potential energy surface (PES) and the mechanism and energetics of the only available exothermic reaction pathway, CH3X + A → CH3 + AX. The region of the transition state is explored using two-dimensional PES cuts and estimates of the activation energies are inferred. Nearly all combinations of methyl halide and alkali-metal atom have positive barrier heights, indicating that reactions at low temperatures will be slow

  14. Influence of granitic aggregates from Northeast Brazil on the alkali-aggregate reaction

    Energy Technology Data Exchange (ETDEWEB)

    Gomes Neto, David de Paiva; Santana, Rodrigo Soares de; Barreto, Ledjane Silva, E-mail: pvgomes@uol.com.br [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Dept. de Ciencias dos Materiais e Engenharia; Conceicao, Herbert; Lisboa, Vinicios Anselmo Carvalho [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Dept. de Geologia

    2014-08-15

    The alkali-aggregate reaction (AAR) in concrete structures is a problem that has concerned engineers and researchers for decades. This reaction occurs when silicates in the aggregates react with the alkalis, forming an expanded gel that can cause cracks in the concrete and reduce its lifespan. The aim of this study was to characterize three coarse granitic aggregates employed in concrete production in northeastern Brazil, correlating petrographic analysis with the kinetics of silica dissolution and the evolution of expansions in mortar bars, assisted by SEM/EDS, XRD, and EDX. The presence of grains showing recrystallization into individual microcrystalline quartz subgrains was associated with faster dissolution of silica and greater expansion in mortar bars. Aggregates showing substantial deformation, such as stretched grains of quartz with strong undulatory extinction, experienced slower dissolution, with reaction and expansion occurring over longer periods that could not be detected using accelerated tests with mortar bars. (author)

  15. Alkali metal carbon dioxide electrochemical system for energy storage and/or conversion of carbon dioxide to oxygen

    Science.gov (United States)

    Hagedorn, Norman H. (Inventor)

    1993-01-01

    An alkali metal, such as lithium, is the anodic reactant; carbon dioxide or a mixture of carbon dioxide and carbon monoxide is the cathodic reactant; and carbonate of the alkali metal is the electrolyte in an electrochemical cell for the storage and delivery of electrical energy. Additionally, alkali metal-carbon dioxide battery systems include a plurality of such electrochemical cells. Gold is a preferred catalyst for reducing the carbon dioxide at the cathode. The fuel cell of the invention produces electrochemical energy through the use of an anodic reactant which is extremely energetic and light, and a cathodic reactant which can be extracted from its environment and therefore exacts no transportation penalty. The invention is, therefore, especially useful in extraterrestrial environments.

  16. Effect of Rice Straw Extract and Alkali Lignin on the Corrosion Inhibition of Carbon Steel

    International Nuclear Information System (INIS)

    A paddy residue based corrosion inhibitor was prepared by treating finely powdered rice straw with aqueous ethanol under acid catalyst (0.01 M H2SO4). Commercial alkali lignin was obtained from Sigma-Aldrich. Prior to the corrosion test, the extraction yield and alkali lignin was characterized via FTIR to determine the functional group. The effect of paddy residue extract and commercial alkali lignin on the corrosion inhibition of carbon steel in 1 M HCl was investigated through the weight loss method, potentiodynamic polarization technique and scanning electron microscopy (SEM). The corrosion inhibition efficiency of the extract and alkali lignin at different immersion times (3 h, 24 h and 42 h) was evaluated. The results show that the paddy waste extract exhibited lesser weight loss of carbon steel in the acidic medium in comparison to the commercial alkali lignin, suggesting that the paddy residue extract is more effective than the commercial alkali lignin in terms of its corrosion inhibition properties. The results obtained proves that the extract from paddy residue could serve as an effective inhibitor for carbon steel in acidic mediums. (author)

  17. Influence of water on alkali-silica reaction: Experimental study and numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Poyet, Stephane [CEA Saclay, DEN/DANS/DPC/SCCME/LECBA, B158, 91191 Gif sur Yvette (France); Sellier, Alain [LMDC, INSA PS, 135 Avenue de Rangueil, 31077 Toulouse Cedex 4 (France); Capra, Bruno [Oxand SA, 36bis Avenue Franklin Roosevelt, 77210 Avon (France); Thevenin-Foray, Genevieve [Universite Lyon 1 2MS ETRA GC, 82 Boulevard Niels BOHR, Domaine Scientifique de la DOUA, 69622 Villeurbanne Cedex (France); Torrenti, Jean-Michel [IRSN, BP17, 92262 Fontenay aux Roses Cedex (France); Tournier-Cognon, Helene [DER DF, Les Renardieres, Route de Sens, Ecuelles, 77818 Moret sur Loing (France); Bourdarot, Eric [Direction de l' Equipement, CIH, Savoie Technolac, 73373 Le Bourget du Lac (France)

    2006-07-01

    Alkali-silica reaction (ASR) is a concrete pathology due to chemical reactions involving reactive silica from reactive aggregates and the inner solution of concrete. Main effects are swelling, cracking, and reduction in the mechanical properties of affected concretes. Water is very important for ASR; the more available water, the more expansion and degradation. This article presents new laws for modeling of the influence of water upon ASR. They are based on experimental results and then used to simulate results taken out of the scientific literature. (authors)

  18. Influence of water on alkali-silica reaction: Experimental study and numerical simulations

    International Nuclear Information System (INIS)

    Alkali-silica reaction (ASR) is a concrete pathology due to chemical reactions involving reactive silica from reactive aggregates and the inner solution of concrete. Main effects are swelling, cracking, and reduction in the mechanical properties of affected concretes. Water is very important for ASR; the more available water, the more expansion and degradation. This article presents new laws for modeling of the influence of water upon ASR. They are based on experimental results and then used to simulate results taken out of the scientific literature. (authors)

  19. Self-Sensing Properties of Alkali Activated Blast Furnace Slag (BFS Composites Reinforced with Carbon Fibers

    Directory of Open Access Journals (Sweden)

    Pedro Garcés

    2013-10-01

    Full Text Available In recent years, several researchers have shown the good performance of alkali activated slag cement and concretes. Besides their good mechanical properties and durability, this type of cement is a good alternative to Portland cements if sustainability is considered. Moreover, multifunctional cement composites have been developed in the last decades for their functional applications (self-sensing, EMI shielding, self-heating, etc.. In this study, the strain and damage sensing possible application of carbon fiber reinforced alkali activated slag pastes has been evaluated. Cement pastes with 0, 0.29 and 0.58 vol % carbon fiber addition were prepared. Both carbon fiber dosages showed sensing properties. For strain sensing, function gage factors of up to 661 were calculated for compressive cycles. Furthermore, all composites with carbon fibers suffered a sudden increase in their resistivity when internal damages began, prior to any external signal of damage. Hence, this material may be suitable as strain or damage sensor.

  20. Gel nanostructure in alkali-activated binders based on slag and fly ash, and effects of accelerated carbonation

    International Nuclear Information System (INIS)

    Binders formed through alkali-activation of slags and fly ashes, including ‘fly ash geopolymers’, provide appealing properties as binders for low-emissions concrete production. However, the changes in pH and pore solution chemistry induced during accelerated carbonation testing provide unrealistically low predictions of in-service carbonation resistance. The aluminosilicate gel remaining in an alkali-activated slag system after accelerated carbonation is highly polymerised, consistent with a decalcification mechanism, while fly ash-based binders mainly carbonate through precipitation of alkali salts (bicarbonates at elevated CO2 concentrations, or carbonates under natural exposure) from the pore solution, with little change in the binder gel identifiable by nuclear magnetic resonance spectroscopy. In activated fly ash/slag blends, two distinct gels (C–A–S–H and N–A–S–H) are formed; under accelerated carbonation, the N–A–S–H gel behaves comparably to fly ash-based systems, while the C–A–S–H gel is decalcified similarly to alkali-activated slag. This provides new scope for durability optimisation, and for developing appropriate testing methodologies. -- Highlights: •C-A-S-H gel in alkali-activated slag decalcifies during accelerated carbonation. •Alkali-activated fly ash gel changes much less under CO2 exposure. •Blended slag-fly ash binder contains two coexisting gel types. •These two gels respond differently to carbonation. •Understanding of carbonation mechanisms is essential in developing test methods

  1. Significance of Alkali-Silica reaction in nuclear safety-related concrete structures

    International Nuclear Information System (INIS)

    Nuclear Power Plant license renewal up to 60 years and possible life extension beyond has established a renewed focus on long-term aging of nuclear generating stations materials, and particularly, on concrete. Large irreplaceable sections of most nuclear generating stations include concrete components. The Expanded Materials Degradation Analysis, jointly performed by the Department of Energy, the U.S. Nuclear Regulatory Commission, the Academia and the Power Generation Industry, identified the need to develop a consistent knowledge base of alkali-silica reaction (ASR) within concrete as an urgent priority (Graves et al., 2014). ASR results in an expansion of Concrete produced by the reaction between alkali (generally from cement), reactive aggregate (like amorphous silica) and water absorption. ASR causes expansion, cracking and loss of mechanical properties. Considering that US commercial reactors in operation enter the age when ASR distress can be potentially observed and that numerous non-nuclear infrastructures (transportation, energy production) in a majority of the States have already experienced ASR-related concrete degradation, the susceptibility and significance of ASR for nuclear concrete structures must be addressed. This paper outlines an on-going research program including the investigation of the possibility of ASR in nuclear power plants, and the assessment of the residual shear bearing capacity of ASR-subjected nuclear structures. (authors)

  2. Low-temperature oxidation of alkali overlayers: Ionic species and reaction kinetics

    International Nuclear Information System (INIS)

    Clean and oxidized alkali metal films have been studied using X-ray photoelectron spectroscopy (XPS). Thin films, typically 10 nm thick, of lithium, sodium, potassium, rubidium and cesium have been deposited on silicon substrates and oxidized at 120 K. Plasmon losses were found to dress the primary photo emission structures of the metals’ core lines which confirms the metallic, bulk like nature of the films. The emission from the O 1s core levels was used to determine the chemical composition and the reaction kinetics during the exposure to molecular oxygen at low pressures. Molecular oxide ions O2− and O22− as well as atomic oxygen ions O2− were detected in varying amounts depending on the alkali metal used. Diffusive transport of material in the film is shown to greatly determine the composition of the oxides. Especially, the growth of potassium superoxide is explained by the diffusion of potassium atoms to the surface and growth at the surface in a Deal–Grove like model.

  3. Theoretical study on the adsorption of carbon dioxide on individual and alkali-metal doped MOF-5s

    Science.gov (United States)

    Ha, Nguyen Thi Thu; Lefedova, O. V.; Ha, Nguyen Ngoc

    2016-01-01

    Density functional theory (DFT) calculations were performed to investigate the adsorption of carbon dioxide (CO2) on metal-organic framework (MOF-5) and alkali-metal (Li, K, Na) doped MOF-5s. The adsorption energy calculation showed that metal atom adsorption is exothermic in MOF-5 system. Moreover, alkali-metal doping can significantly improve the adsorption ability of carbon dioxide on MOF-5. The best influence is observed for Li-doping.

  4. Carbon nitride nanotube as a sensor for alkali and alkaline earth cations

    International Nuclear Information System (INIS)

    Highlights: ► Adsorption of alkali and alkaline earth cations on a CN nanotube studied by DFT. ► The alkaline cation adsorption may raise potential barrier of the electron emission. ► The tube may act as a sensor in the presence of alkali and alkaline cations. - Abstract: Adsorption of several alkali (Li+, Na+, and K+) and alkaline earth (Be2+, Mg2+, and Ca2+) cations on the surface of a zigzag (9, 0) carbon nitride nanotube has been investigated using density functional theory. It has been found that almost all of the cations prefer to be strongly chemisorbed at the center of porous site of the tube surface. The adsorption of alkaline cations much more influences the electronic properties of the tube, in comparison with the alkali ones, so that it is transformed from an intrinsic semiconductor with HOMO/LUMO energy gap of 4.02 eV to extrinsic p-type one with the gap of 0.54–1.94 eV. The alkaline cation adsorption may significantly raise potential barrier of the electron emission from the tube surface, hence impeding the field emission. It has been also concluded that the electrical sensitivity of the tube toward the cations may be in the order: Be2+ ≫ Mg2+ ≫ Ca2+ ≫ Li+ ∼ Na+ ∼ K+.

  5. Influence of mesostasis in volcanic rocks on the alkali-aggregate reaction

    KAUST Repository

    Tiecher, Francieli

    2012-11-01

    Mesostasis material present in the interstices of volcanic rocks is the main cause of the alkali-aggregate reaction (AAR) in concretes made with these rock aggregates. Mesostasis often is referred to as volcanic glass, because it has amorphous features when analyzed by optical microscopy. However, this study demonstrates that mesostasis in the interstitials of volcanic rocks most often consists of micro to cryptocrystalline mineral phases of quartz, feldspars, and clays. Mesostasis has been identified as having different characteristics, and, thus, this new characterization calls for a re-evaluation of their influence on the reactivity of the volcanic rocks. The main purpose of this study is to correlate the characteristics of mesostasis with the AAR in mortar bars containing basalts and rhyolites. © 2012 Elsevier Ltd. All rights reserved.

  6. Carbon fibre-reinforced, alkali-activated slag mortars

    Directory of Open Access Journals (Sweden)

    Garcés, P.

    2007-12-01

    Full Text Available The paper describes the effect of carbon fibre on alkaliactivated slag mortar (AAS mechanical strength, volume stability and reinforcing steel corrosion, compared to its effect on the same properties in Portland cement (PC properties. Mechanical strength and volume stability tests were performed as set out in the respective Spanish UNE standards. The corrosion rate of steel embedded in the specimens studied was determined from polarization resistance analysis. One of the findings of the study performed was that carbon fibre failed to improve AAS or CP mortar strength. As far as volume stability is concerned, the inclusion of carbon fibres in AAS with a liquid/solid ratio of 0.5 reduced drying shrinkage by about 50%. The effect of carbon fibre on PC mortars differed from its effect on AAS mortars. Studies showed that in the presence of carbonation, steel corrosion reached higher levels in carbon-fibre reinforced AAS mortars; the inclusion of 1% carbon fibre improved corrosion resistance perceptibly in these same mortars, however, when exposed to chloride attack.Se ha estudiado el efecto de la incorporación de fibras de carbón en el comportamiento mecánico, estabilidad de volumen y nivel de corrosión de la armadura en morteros de escorias activadas alcalinamente (AAS. Se evalúa la influencia de las fibras de carbón en el comportamiento de morteros alcalinos en comparación con el efecto que producen en morteros de Portland (CP. Los ensayos mecánicos y de estabilidad de volumen se han realizado según lo establecido en la norma UNE que los regula. Se ha utilizado la técnica de la Resistencia a la Polarización para determinar la velocidad de corrosión del acero embebido en las muestras estudiadas. Como consecuencia del estudio realizado, se ha podido concluir que la adición de fibras de carbón a morteros de AAS y CP no mejora las características resistentes de los mismos. En relación con la estabilidad de volumen, la incorporación de

  7. Carbonation Characteristics of Alkali-Activated Blast-Furnace Slag Mortar

    Directory of Open Access Journals (Sweden)

    Keum-Il Song

    2014-01-01

    Full Text Available Alkali-activated ground granulated blast-slag (AAS is the most obvious alternative material for ordinary Portland cement (OPC. However, to use it as a structural material requires the assessment and verification of its durability. The most important factor for a durability evaluation is the degree of carbonation resistance, and AAS is known to show lower performance than OPC. A series of experiments was conducted with a view to investigate the carbonation characteristics of AAS binder. As a consequence, it was found that the major hydration product of AAS was calcium silicate hydrate (CSH, with almost no portlandite, unlike the products of OPC. After carbonation, the CSH of AAS turned into amorphous silica gel which was most likely why the compressive strength of AAS became weaker after carbonation. An increase of the activator dosage leads AAS to react more quickly and produce more CSH, increasing the compaction, compressive strength, and carbonation resistance of the microstructure.

  8. Interactions of alkali metals and electrolyte with cathode carbons

    Energy Technology Data Exchange (ETDEWEB)

    Naas, Tyke

    1997-12-31

    The Hall-Heroult process for electrolytic reduction of alumina has been the only commercial process for production of primary aluminium. The process runs at high temperature and it is important to minimize the energy consumption. To save energy it is desirable to reduce the operating temperature. This can be achieved by adding suitable additives such as LiF or KF to the cryolitic electrolyte. This may conflict with the objective of extending the lifetime of the cathode linings of the cell as much as possible. The thesis investigates this possibility and the nature of the interactions involved. It supports the hypothesis that LiF-additions to the Hall-Heroult cell electrolyte is beneficial to the carbon cathode performance because the diminished sodium activity reduces the sodium induced stresses during the initial period of electrolysis. The use of KF as an additive is more dangerous, but the results indicate that additions up to 5% KF may be tolerated in acidic melts with semigraphitic or graphitic cathodes with little risk of cathode problems. 153 refs., 94 figs., 30 tabs.

  9. Measurement of alkali-silica reaction progression by ultrasonic waves attenuation

    International Nuclear Information System (INIS)

    Development of non-destructive methods, developed specifically for assessing the damage induced by alkali-silica reaction (ASR) in concrete structures, is needed in order to carry out a systematic evaluation of the concrete condition. The aim of this study is to monitor the evolution of the ASR-damage in laboratory with concrete samples with ultrasonic pulse velocity and attenuation of ultrasonic waves methods. For this study, results of both methods were compared with expansion and mass variation. One reactive concrete mixture was made with reactive aggregate, and one other mixture, incorporating non-reactive aggregate, was made as a control. Specimens were kept at 38 deg. C in a 1 mol l-1 NaOH solution to accelerate the reaction. Attenuation of transmitted ultrasonic waves appeared to be more appropriate for the evaluation of ASR-damage compared with pulse velocity. The attenuation of accelerated reactive concrete cylinders increased by 90% after 1 year while it increased by 40% for the non-reactive concrete used as a control. Major part of the attenuation increase in the non-reactive concrete is due to liquid absorption. This work suggests that in-situ non-destructive techniques based on ultrasonic wave attenuation, like ultrasonic attenuation tomography, should be developed in order to evaluate the development of ASR in concrete structures. Petrographic examination confirmed that damage to concrete is associated with ASR

  10. Monitoring, Modeling, and Diagnosis of Alkali-Silica Reaction in Small Concrete Samples

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cai, Guowei [Idaho National Lab. (INL), Idaho Falls, ID (United States); Gribok, Andrei V. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-01

    Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This report describes alkali-silica reaction (ASR) degradation mechanisms and factors influencing the ASR. A fully coupled thermo-hydro-mechanical-chemical model developed by Saouma and Perotti by taking into consideration the effects of stress on the reaction kinetics and anisotropic volumetric expansion is presented in this report. This model is implemented in the GRIZZLY code based on the Multiphysics Object Oriented Simulation Environment. The implemented model in the GRIZZLY code is randomly used to initiate ASR in a 2D and 3D lattice to study the percolation aspects of concrete. The percolation aspects help determine the transport properties of the material and therefore the durability and service life of concrete. This report summarizes the effort to develop small-size concrete samples with embedded glass to mimic ASR. The concrete samples were treated in water and sodium hydroxide solution at elevated temperature to study how ingress of sodium ions and hydroxide ions at elevated temperature impacts concrete samples embedded with glass. Thermal camera was used to monitor the changes in the concrete sample and results are summarized.

  11. Reaction efficiency of organic alkalis with various classes of lipids during thermally assisted hydrolysis and methylation.

    Science.gov (United States)

    Ishida, Yasuyuki; Katagiri, Mizuho; Ohtani, Hajime

    2009-04-10

    Reaction efficiencies of two organic alkalis, tetramethylammonium hydroxide (TMAH) and trimethylsulfonium hydroxide (TMSH), with lipids during thermally assisted hydrolysis and methylation (THM) were examined focusing on (1) the types of lipids and (2) degree of unsaturation of fatty acid moieties. Different types of lipids such as triglycerides, phospholipids, free fatty acids and cholesteryl esters containing saturated, monounsaturated or polyunsaturated fatty acid (PUFA) residues were subjected to THM-gas chromatography (GC) in the presence of TMAH or TMSH. The obtained results revealed that the THM reaction using TMAH allowed almost quantitative methylation of saturated and monounsaturated fatty acid components independently of the classes of lipids. However, strong alkalinity of TMAH brought about isomerization and/or degradation of PUFA components. In contrast, the use of TMSH was effective to highly sensitive detection of PUFA as well as saturated and monounsaturated fatty acid components contained in triglycerides, phospholipids (phosphatidylcholines) and free fatty acids. On the other hand, TMSH was proved to react hardly with any kind of fatty acid residues in cholesteryl esters due to their steric hindrance. PMID:19223033

  12. Simultaneous Synthesis of Dimethyl Carbonate and Poly(ethylene terephthalate) Using Alkali Metals as Catalysts%碱金属化合物催化同时合成碳酸二甲酯和聚对苯二甲酸乙二醇酯

    Institute of Scientific and Technical Information of China (English)

    张丹; 王庆印; 姚洁; 王越; 曾毅; 王公应

    2007-01-01

    Dimethyl carbonate (DMC) and poly(ethylene terephthalate) was simultaneously synthesized by the transesterification of ethylene carbonate (EC) with dimethyl terephthalate (DMT) in this paper. This reaction is an excellent green chemical process without poisonous substance. Various alkali metals were used as the catalysts. The results showed alkali metals had catalytic activity in a certain extent. The effect of reaction condition was also studied. When the reaction was carried out under the following conditions: the reaction temperature 250℃, molar ratio of EC to DMT 3: 1, reaction time 3h, and catalyst amount 0.004 (molar ratio to DMT), the yield of DMC was 68.9%.

  13. Carbon nitride nanotube as a sensor for alkali and alkaline earth cations

    Energy Technology Data Exchange (ETDEWEB)

    Beheshtian, Javad [Department of Chemistry, Shahid Rajaee Teacher Training University, P.O. Box: 16875-163, Tehran (Iran, Islamic Republic of); Baei, Mohammad T. [Department of Chemistry, Azadshahr Branch, Islamic Azad University, Azadshahr, Golestan (Iran, Islamic Republic of); Bagheri, Zargham [Physics Group, Science Department, Islamic Azad University, Islamshahr Branch, P.O. Box: 33135-369, Islamshahr, Tehran (Iran, Islamic Republic of); Peyghan, Ali Ahmadi, E-mail: ahmadi.iau@gmail.com [Young Researchers Club, Islamic Azad University, Islamshahr Branch, Tehran (Iran, Islamic Republic of)

    2013-01-01

    Highlights: Black-Right-Pointing-Pointer Adsorption of alkali and alkaline earth cations on a CN nanotube studied by DFT. Black-Right-Pointing-Pointer The alkaline cation adsorption may raise potential barrier of the electron emission. Black-Right-Pointing-Pointer The tube may act as a sensor in the presence of alkali and alkaline cations. - Abstract: Adsorption of several alkali (Li{sup +}, Na{sup +}, and K{sup +}) and alkaline earth (Be{sup 2+}, Mg{sup 2+}, and Ca{sup 2+}) cations on the surface of a zigzag (9, 0) carbon nitride nanotube has been investigated using density functional theory. It has been found that almost all of the cations prefer to be strongly chemisorbed at the center of porous site of the tube surface. The adsorption of alkaline cations much more influences the electronic properties of the tube, in comparison with the alkali ones, so that it is transformed from an intrinsic semiconductor with HOMO/LUMO energy gap of 4.02 eV to extrinsic p-type one with the gap of 0.54-1.94 eV. The alkaline cation adsorption may significantly raise potential barrier of the electron emission from the tube surface, hence impeding the field emission. It has been also concluded that the electrical sensitivity of the tube toward the cations may be in the order: Be{sup 2+} Much-Greater-Than Mg{sup 2+} Much-Greater-Than Ca{sup 2+} Much-Greater-Than Li{sup +} {approx} Na{sup +} {approx} K{sup +}.

  14. Cascade enzymatic reactions for efficient carbon sequestration.

    Science.gov (United States)

    Xia, Shunxiang; Zhao, Xueyan; Frigo-Vaz, Benjamin; Zheng, Wenyun; Kim, Jungbae; Wang, Ping

    2015-04-01

    Thermochemical processes developed for carbon capture and storage (CCS) offer high carbon capture capacities, but are generally hampered by low energy efficiency. Reversible cascade enzyme reactions are examined in this work for energy-efficient carbon sequestration. By integrating the reactions of two key enzymes of RTCA cycle, isocitrate dehydrogenase and aconitase, we demonstrate that intensified carbon capture can be realized through such cascade enzymatic reactions. Experiments show that enhanced thermodynamic driving force for carbon conversion can be attained via pH control under ambient conditions, and that the cascade reactions have the potential to capture 0.5 mol carbon at pH 6 for each mole of substrate applied. Overall it manifests that the carbon capture capacity of biocatalytic reactions, in addition to be energy efficient, can also be ultimately intensified to approach those realized with chemical absorbents such as MEA. PMID:25708541

  15. A computational linear elastic fracture mechanics-based model for alkali-silica reaction

    International Nuclear Information System (INIS)

    This article presents a fracture mechanics model for Alkali-Silica Reaction (ASR). The model deals with the case of a concrete made up of dense aggregates submitted to chemical attack. The chemistry and diffusion (of ions and gel) are not modelled. The focus is put on the mechanical consequences of the progressive replacement of the outer layer of the aggregate by a less dense gel. A schematic cracking pattern is assumed: a ring-shaped crack appears in the cement paste surrounding the spherical aggregate depending on the pressure build-up. The onset of cracking is determined using an incremental energy criterion. The stored elastic energy and deformation of a given configuration are determined assuming that each aggregate behaves as if it was embedded in an infinite cement paste matrix. The calculations are performed by Finite Element Analysis. We note a very different behaviour of aggregates of different sizes. Adding the contributions of different aggregate sizes leads to an estimation of the global free expansion of a concrete of given aggregate size distribution. A rate of attack is identified that leads to recover the usual sigmoid ASR expansion curve. (authors)

  16. A solid state MAS NMR study of the thermal reactions in alkali-leached aluminosilicates

    International Nuclear Information System (INIS)

    The thermal transformations of aluminosilicate minerals such as kaolinite (Al2Si2O5(OH)4) are of importance for the production of both clay-based ceramics and high-technology ceramics such as sialons. Solid-state MAS NMR can provide information about the intermediate stages in the formation of mullite (Al6Si2O13). These intermediates, which are only poorly crystalline and less amenable to XRD study, may include poorly crystalline mullite, a cubic spinel similar to γ-Al2O3 but which has been suggested to contain Si, and other amorphous aluminosilicate phases of variable composition. Since the 29Si and 27Al MAS NMR spectra of all these phases are expected to contain resonances broadly in the same spectral area, unambiguous differentiation of these phases has not so far proved possible by this technique. The work reported here was suggested by the possibility of selective alkali extraction of some of the more silica-rich phases using techniques developed by Chakravorty and Ghosh, which was hoped to reveal the MAS NMR features of the less-leachable phases. NMR study of the leached products after subsequent thermal treatment also provided useful information about the leaching reactions themselves. Copyright (1999) Australasian Ceramic Society

  17. Microscopy and Cathodoluminescence Spectroscopy Characterization of Quartz Exhibiting Different Alkali-Silica Reaction Potential.

    Science.gov (United States)

    Kuchařová, Aneta; Götze, Jens; Šachlová, Šárka; Pertold, Zdeněk; Přikryl, Richard

    2016-02-01

    Different quartz types from several localities in the Czech Republic and Sweden were examined by polarizing microscopy combined with cathodoluminescence (CL) microscopy, spectroscopy, and petrographic image analysis, and tested by use of an accelerated mortar bar test (following ASTM C1260). The highest alkali-silica reaction potential was indicated by very fine-grained chert, containing significant amounts of fine-grained to cryptocrystalline matrix. The chert exhibited a dark red CL emission band at ~640 nm with a low intensity. Fine-grained orthoquartzites, as well as fine-grained metamorphic vein quartz, separated from phyllite exhibited medium expansion values. The orthoquartzites showed various CL of quartz grains, from blue through violet, red, and brown. Two CL spectral bands at ~450 and ~630 nm, with various intensities, were detected. The quartz from phyllite displayed an inhomogeneous dark red CL with two CL spectral bands of low intensities at ~460 and ~640 nm. The massive coarse-grained pegmatite quartz from pegmatite was assessed to be nonreactive and displayed a typical short-lived blue CL (~480 nm). The higher reactivity of the fine-grained hydrothermal quartz may be connected with high concentrations of defect centers, and probably with amorphized micro-regions in the quartz, respectively; indicated by a yellow CL emission (~570 nm). PMID:26790877

  18. Classification of alkali-silica reaction and corrosion distress using acoustic emission

    Science.gov (United States)

    Abdelrahman, Marwa; ElBatanouny, Mohamed; Serrato, Michael; Dixon, Kenneth; Larosche, Carl; Ziehl, Paul

    2016-02-01

    The Nuclear Regulatory Commission regulates approximately 100 commercial nuclear power reactor facilities that contribute about 20% of the total electric energy produced in the United States. Half of these reactor facilities are over 30 years old and are approaching their original design service life. Due to economic and durability considerations, significant portions of many of the facilities were constructed with reinforced concrete, including the containment facilities, cooling towers, and foundations. While most of these concrete facilities have performed exceptionally well throughout their initial expected service life, some are beginning to exhibit different forms of concrete deterioration. In this study, acoustic emission (AE) is used to monitor two main concrete deterioration mechanisms; alkali-silica reaction (ASR) distress and corrosion of reinforcing steel. An accelerated ASR test was conducted where specimens were continuously monitored with AE. The results show that AE can detect and classify damage due to ASR distress in the specimens. AE was also used to remotely monitor active corrosion regions in a reactor facility. AE monitoring of accelerated corrosion testing was also conducted on a concrete block specimen cut from a similar reactor building. Electrochemical measurements were conducted to correlate AE activity to quantifiable corrosion measurements and to enhance capabilities for service life prediction.

  19. An alkali treating strategy for the colloidization of graphitic carbon nitride and its excellent photocatalytic performance.

    Science.gov (United States)

    Cheng, Fuxing; Yan, Jing; Zhou, Chenjuan; Chen, Binhe; Li, Peiran; Chen, Zhi; Dong, Xiaoping

    2016-04-15

    The colloid of graphitic carbon nitride (g-C3N4) was of great importance for practical application. Herein we introduced an alkali treatment route to efficiently colloidize g-C3N4 under mild conditions by destroying the hydrogen bonds between linearly polymeric melon chains and hydrolyzing partial C−NH−C bonds linked two tri-s-triazine units. The obtained colloidal suspension was extremely stable due to its negative charges on surface, and the particle size of several hundred nanometers and the nanobelt-like morphology were revealed by electron microscopy and dynamic light scattering technologies. The structural, optical and functional group analysis demonstrated that the structure of CN heterocycles was preserved after the alkali treatment, and the produced colloidal g-C3N4 can be re-assembled by an electrostatic interaction. Moreover, contributing to the reduced electron-hole recombination, the photocatalytic performance of restacked carbon nitride colloids had more enhanced photocatalytic performance than bulk g-C3N4. PMID:26835580

  20. Alkali – activated binders: a review part 1. Historical background, terminology, reaction mechanisms and hydration products

    OpenAIRE

    Torgal, Fernando Pacheco; Gomes, J. P. Castro; Jalali, Said

    2008-01-01

    The disintegration of concrete structures made of ordinary Portland cement (OPC) is a worrying topic of increasing significance. The development of new binders with longer durability is therefore needed. Alkali-activated binders have emerged as an alternative to OPC binders, which seems to have superior durability and environmental impact. This paper reviews current knowledge about alkali-activated binders. The subjects of Part 1 in this paper are historical background, terminology a...

  1. Methane coupling reaction in an oxy-steam stream through an OH radical pathway by using supported alkali metal catalysts

    KAUST Repository

    Liang, Yin

    2014-03-24

    A universal reaction mechanism involved in the oxidative coupling of methane (OCM) is demonstrated under oxy-steam conditions using alkali-metal-based catalysts. Rigorous kinetic measurements indicated a reaction mechanism that is consistent with OH radical formation from a H 2O-O2 reaction followed by C-H activation in CH 4 with an OH radical. Thus, the presence of water enhances both the CH4 conversion rate and the C2 selectivity. This OH radical pathway that is selective for the OCM was observed for the catalyst without Mn, which suggests clearly that Mn is not the essential component in a selective OCM catalyst. The experiments with different catalyst compositions revealed that the OH.-mediated pathway proceeded in the presence of catalysts with different alkali metals (Na, K) and different oxo anions (W, Mo). This difference in catalytic activity for OH radical generation accounts for the different OCM selectivities. As a result, a high C2 yield is achievable by using Na2WO4/SiO2, which catalyzes the OH.-mediated pathway selectively. Make it methane: A universal reaction mechanism involved in the oxidative coupling of methane is demonstrated under oxy-stream conditions by using alkali-metal-based catalysts. Rigorous kinetic measurements indicated a reaction mechanism that is consistent with OH radical formation from an H2O-O2 reaction, followed by C-H activation in CH4 with an OH radical. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. C3 coefficients for the alkali atoms interacting with a graphene layer and carbon nanotube

    International Nuclear Information System (INIS)

    We evaluate separation dependent van der Waals dispersion (C3) coefficients for the interactions of the Li, Na, K and Rb atoms with a graphene layer and with a single walled carbon nanotube (CNT) using the hydrodynamic and Dirac models. The results from both the models are evaluated using accurate values of the dynamic polarizabilities of the above alkali atoms. Accountability of accurate dynamic polarizabilities of the alkali atoms to determine the C3 coefficients are accentuated by comparing the obtained coefficients using the precise values of the dynamic dipole polarizabilities against the values estimated from the single oscillator approximation that are generally used in the earlier calculations. For a practical description of the atom–surface interaction potentials, the C3 coefficients are given for a wide range of separation distances between the considered ground states of the atoms and the wall surfaces and also for different nanotube radii. The coefficients for the graphene layer are fitted to a logistic function of the separation distance. For CNT, we find a paraboloid kind of fit dependence both on the separation distances and radii of the CNT. (paper)

  3. Comparative study of the alkali-silica reaction (ASR in granitic aggregates

    Directory of Open Access Journals (Sweden)

    Velasco-Torres, A.

    2010-06-01

    Full Text Available The reaction between certain reactive components of aggregates (like opal and metaestable silica and concrete pore solution is well documented. Nevertheless, in this study it has been shown that some aggregates, like granite, could develop a rapid or slow alkali-silica reaction (ASR depending on the deleterious component involved. Mortar bars were cast with two granitic aggregates extracted from concrete cores drilled in two Spanish Dams affected by ASR, being classified as granitic rocks. The main difference between them is the reactive component: microcrystalline quartz in one case and strained and microcracked quartz in the other case. A petrographic examination was carried out in the mortar bars. Thin sections were cut and the alkalisilica gel was stained for an easier detection. Then, the thin sections were examinated with a stereomicroscope comparing the differences in the progress of the ASR for both aggregates. It can be concluded that the main mechanism of formation and storage of gel is associated to the micro-cracks instead of the subgrain boundaries.

    La reacción entre los componentes de la fase intersticial del hormigón y áridos con minerales como el ópalo o la sílice metaestable, se encuentra bien documentada. Sin embargo, en este estudio, se ha detectado que dentro de un mismo tipo de roca, como es el granito, puede haber diferencias en el tipo de reacción (lenta o rápida dependiendo del componente reactivo que aparezca en la misma. Se han fabricado barras de mortero con los áridos extraídos de dos presas españolas afectadas por la reacción álcali-sílice. Estos áridos son rocas graníticas y la diferencia entre ambos reside en que una de las muestras contiene cuarzo microcristalino como componente reactivo y, la otra, cuarzo deformado. Mediante el estudio petrográfico de barras de mortero y el teñido del gel álcali-sílice se ha podido observar la evolución y progreso de la reacción para cada

  4. Effect of Glass Powder on Chloride Ion Transport and Alkali-aggregate Reaction Expansion of Lightweight Aggregate Concrete

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi; SHI Caijun; SONG Jianming

    2009-01-01

    The effects of glass powder on the strength development, chloride permeability and potential alkali-aggregate reaction expansion of lightweight aggregate concrete were investigated.Ground blast furnace slag, coal fly ash and silica fume were used as reference materials. The re-placement of cement with 25% glass powder slightly decreases the strengthes at 7 and 28 d, but shows no effect on 90 d's. Silica fume is very effective in improving both the strength and chloride penetra-tion resistance, while ground glass powder is much more effective than blast furnace slag and fly ash in improving chloride penetration resistance of the concrete. When expanded shale or clay is used as coarse aggregate, the concrete containing glass powder does not exhibit deleterious expansion even if alkali-reactive sand is used as fine aggregate of the concrete.

  5. Investigation of safety margin for turbine generator foundation affected by Alkali Silica reaction based on non-linear structure analysis

    International Nuclear Information System (INIS)

    A turbine generator foundation is a reinforced concrete structure having a table deck and columns to support equipments. After operation of the plant, the expansion of the table deck in turbine longitudinal axis has been observed. By investigation of concrete material properties, it was found that the expansion has been caused by alkali-silica reaction. This study has been performed to evaluate the safety allowance of strength capacity of the turbine generator foundation by nonlinear analysis using beam element model with elongation, rebar strain and material properties data which have been measured for almost 30 years in actual foundation. (authors)

  6. Modelling The Effects of Aggregate Size on Alkali Aggregate Reaction Expansion

    Directory of Open Access Journals (Sweden)

    N. Z. Sekrane

    2014-06-01

    Full Text Available This work aims at developing models to predict the potential expansion of concrete containing alkali-reactive aggregates. The paper gives measurements in order to provide experimental data concerning the effect of particle size of an alkali-reactive siliceous limestone on mortar expansion. Results show that no expansion was measured on the mortars using small particles (0.5-1.0 mm while the particles (1.0–2.0 mm gave the largest expansions (0.217%. Two models are proposed, the first one studies the correlations between the measured expansions and the size of aggregates, the second one calculates the thickness of the porous zone necessary to take again all the volume of the gel created.

  7. Reactions on carbon anodes in aluminium electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Eidet, Trygve

    1997-12-31

    The consumption of carbon anodes and energy in aluminium electrolysis is higher than what is required theoretically. This thesis studies the most important of the reactions that consume anode materials. These reactions are the electrochemical anode reaction and the airburn and carboxy reactions. The first part of the thesis deals with the kinetics and mechanism of the electrochemical anode reaction using electrochemical impedance spectroscopy. The second part deals with air and carboxy reactivity of carbon anodes and studies the effects of inorganic impurities on the reactivity of carbon anodes in the aluminium industry. Special attention is given to sulphur since its effect on the carbon gasification is not well understood. Sulphur is always present in anodes, and it is expected that the sulphur content of available anode cokes will increase in the future. It has also been suggested that sulphur poisons catalyzing impurities in the anodes. Other impurities that were investigated are iron, nickel and vanadium, which are common impurities in anodes which have been reported to catalyze carbon gasification. 88 refs., 92 figs., 24 tabs.

  8. Corrosion by the Alkali Metals

    International Nuclear Information System (INIS)

    This is a review of the state of the art of corrosion testing of materials by the alkali metals, the models proposed to explain the observed corrosion results, and the status of materials selection for application in alkali metal-cooled systems. Corrosion of structural and fuel cladding materials by liquid Na and NaK has been studied intensively, but intermittently for the last 18 years. These studies and the liquid-metal-cooled reactors in operation demonstrate that stainless steels can be considered for structural and cladding applications below 650°C. Above this temperature increased corrosion and radiation-induced embrittlement make them unsatisfactory. Corrosion models are reviewed and their inability to explain all the experimental observations discussed. An alternate model is proposed which qualitatively is in agreement with experimental observations. In this model, the rate-controlling step is either the surface reaction of Fe with ''available oxygen'' (dissolved Na2O) to form an Fe-O-Na complex or the rate at which ''available oxygen'' can reach the surface to form the complex; which process is rate controlling depends on the temperature, Na velocity and oxygen concentration in the Na. The solution chemistry of oxygen, carbon and alkali metal-oxygen-transition metal complexes dissolved in the alkali metals is reviewed. ''Molecular'' complexes appear unlikely to exist in solution in the alkali metals, although the thermodynamic tendencies for them to form suggest that stable bonds exist in solution between oxygen, the transition and the alkali metals. The insolubility of carbon in ''oxygen-free'' sodium indicates that carbon transfer may be associated with oxygen in sodium down to very low oxygen levels, although experimental data do not generally confirm this postulate. Corrosion of refractory metals by boiling alkali metals at temperatures above 1000°C is markedly affected by impurities in either the liquid or refractory metal; the addition of Ti, Zr or

  9. Nyerereite from carbonatite rocks at Vulture volcano: implications for mantle metasomatism and petrogenesis of alkali carbonate melts Research Article

    Science.gov (United States)

    Stoppa, Francesco; Jones, Adrian; Sharygin, Victor

    2009-06-01

    Vulture volcano displays a wide range of mafic to alkaline, carbonate-, and/or CaO-rich volcanic rocks, with subvolcanic and plutonic rocks together with mantle xenoliths in pyroclastic ejecta. The roles of magmatic volatiles such as CO2, S, and Cl have been determined from compositions and trapping temperatures of inclusions in phenocrysts, which include the Na-K-Ca-carbonate nyerereite within melilite. We surmise that this alkali carbonate crystallised from an appropriate carbonatitic melt at relatively high temperature. Carbonatitic metasomatic features are traceable throughout many of the mantle xenoliths, and various carbonatitic components are found in the late stage extrusive suite. There is no evidence that alkali carbonatite developed as a separate magma, but it may have been an important evolutionary stage. We compare the rare occurrence of nyerereite at Vulture with other carbonatites and with an unaltered kimberlite from the Udachnaya pipe. We review the evidence at Vulture for associated carbonatitic metasomatism in the mantle, and we suggest that low viscosity alkali carbonatitic melts may have a primary and much deeper origin than previously considered.

  10. Cathodoluminescence microscopy and petrographic image analysis of aggregates in concrete pavements affected by alkali-silica reaction

    Energy Technology Data Exchange (ETDEWEB)

    Stastna, A., E-mail: astastna@gmail.com [Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Praha 2 (Czech Republic); Sachlova, S.; Pertold, Z.; Prikryl, R. [Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Praha 2 (Czech Republic); Leichmann, J. [Department of Geological Sciences, Faculty of Science, Masaryk University in Brno, Kotlarska 267/2, 611 37 Brno (Czech Republic)

    2012-03-15

    Various microscopic techniques (cathodoluminescence, polarizing and electron microscopy) were combined with image analysis with the aim to determine a) the modal composition and degradation features within concrete, and b) the petrographic characteristics and the geological types (rocks, and their provenance) of the aggregates. Concrete samples were taken from five different portions of Highway Nos. D1, D11, and D5 (the Czech Republic). Coarse and fine aggregates were found to be primarily composed of volcanic, plutonic, metamorphic and sedimentary rocks, as well as of quartz and feldspar aggregates of variable origins. The alkali-silica reaction was observed to be the main degradation mechanism, based upon the presence of microcracks and alkali-silica gels in the concrete. Use of cathodoluminescence enabled the identification of the source materials of the quartz aggregates, based upon their CL characteristics (i.e., color, intensity, microfractures, deformation, and zoning), which is difficult to distinguish only employing polarizing and electron microscopy. - Highlights: Black-Right-Pointing-Pointer ASR in concrete pavements on the Highways Nos. D1, D5 and D11 (Czech Republic). Black-Right-Pointing-Pointer Cathodoluminescence was combined with various microscopic techniques and image analysis. Black-Right-Pointing-Pointer ASR was attributed to aggregates. Black-Right-Pointing-Pointer Source materials of aggregates were identified based on cathodoluminescence characteristics. Black-Right-Pointing-Pointer Quartz comes from different volcanic, plutonic and metamorphic parent rocks.

  11. Field emission properties of capped carbon nanotubes doped by alkali metals:a theoretical investigation

    Institute of Scientific and Technical Information of China (English)

    Jin Lei; Fu Hong-Gang; Xie Ying; Yu Hai-Tao

    2012-01-01

    The electronic structures and field emission properties of capped CNT55 systems with or without alkali metal atom adsorption were systematically investigated by density functional theory calculation.The results indicate that the adsorption of alkali metal on the center site of a CNT tip is energetically favorable.In addition,the adsorption energies increase with the introduction of the electric field.The excessive negative charges on CNT tips make electron emittance much easier and result in a decrease in work function.Furthermore,the inducing effect by positively charged alkali metal atoms can be reasonably considered as the dominant reason for the improvement in field emission properties.

  12. Tuning indium tin oxide work function with solution-processed alkali carbonate interfacial layers for high-efficiency inverted organic photovoltaic cells

    International Nuclear Information System (INIS)

    Selective electron collection by an interfacial layer modified indium tin oxide cathode is critically important for achieving high-efficiency inverted structure organic photovoltaic (OPV) cells. Here, we demonstrate that solution-processed alkali carbonates, such as Li2CO3, Na2CO3, K2CO3, Rb2CO3, Cs2CO3, are good interfacial layer materials. Both carbonate concentration and annealing conditions can affect cathode work function and surface roughness. By proper optimization, different alkali carbonates can be almost equally effective as the cathode interfacial layer. Furthermore, good device performance can be achieved at a low annealing temperature (<50 ° C), which allows for potential applications in solution-processed inverted OPV cells on plastic substrates. This work indicates that alkali carbonates, not just cesium carbonate, are valid choices as the cathode interlayer in inverted OPV devices. (paper)

  13. Exchange reactions in the systems of alkali metal, silver and thallium, sulfates, niobates and tantalates

    International Nuclear Information System (INIS)

    Investigated are exchange interactions in diagonal cross sections of twenty triple mutual systems with A and A' cations and SO4 and MO3 anions where A and A'-Li, Na, K, Ag, Tl, M-Nb, Ta using the methods of X-ray phase, chemical and differential thermal analyses. Exchange reaction between crystal complex oxide and melted salt are effective synthesis method. These reactions in particular permitted to obtain pure AgNbO3, AgTaO3 and their solid solutions at temperatures hundreds degrees lower than in displacement reactions. Equilibrium samples of AMO3-A'MO3 systems, continuous or discontinuous solid solutions, compounds (except NaMO3-KMO3, and also LiTaO3-KTaO3) are formed in exchange reactions when there is sulfate shortage. Thus, exchange reactions can be applied for solid solution synthesis, and also for phase diagram study

  14. The use of fly ash and metakaolin for the prevention of alkali-silica reaction and delayed ettringite formation in concrete

    OpenAIRE

    Silva, A. Santos; Ribeiro, A. Bettencourt; Jalali, Said; Divet, Loic

    2006-01-01

    One of the most popular preventive measures to minimize the occurrence of chemical expansive reactions, namely the alkali-silica reaction (ASR) and delayed ettringite formation (DEF) in hardened concrete is the use of supplementary cementing materials (SCMs). Several studies have been performed along the last few years related with the use of fly ashes in the suppression of expansion due to ASR. However, relatively little attention are been focused in its effectiveness to control the DEF in c...

  15. The use of fly ashes and metakaolin for the prevention of alkali-silica reaction and delayed ettringite formation in concrete

    OpenAIRE

    Santos Silva, A.; BETTENCOURT RIBEIRO, A; Jalali, S; DIVET, L

    2006-01-01

    One of the most popular preventive measures to minimize the occurrence of chemical expansive reactions, namely the alkali-silica reaction (ASR) and delayed ettringite formation (DEF) in hardened concrete is the use of supplementary cementing materials (SCMs). Several studies are been performed along the last years related the use of fly ashes in the suppression of expansion due to ASR. However, relatively little attention are been focused in its effectiveness to control the DEF in concrete, a...

  16. Activation of pozzolanic and latent-hydraulic reactions by Alkalis in order to repair concrete cracks

    OpenAIRE

    Gruyaert, Elke; Van Tittelboom, Kim; Rahier, Hubert; De Belie, Nele

    2015-01-01

    The low degree of hydration of fly ash (FA) and slag (BFS) particles in high-volume FA and BFS concrete offers the possibility to activate the unreacted particles upon crack formation to close the crack. In this paper, a preliminary study is performed to evaluate the use of alkaline activators to stimulate the formation of reaction products in the crack. First, the reaction rates of crushed pastes mixed with alkaline solutions or water were monitored by calorimetry. These tests showed that al...

  17. Alkali-silica reaction of aggregates for concrete pavements in Chihuahua’s State, Mexico

    Directory of Open Access Journals (Sweden)

    Olague, C.

    2002-12-01

    Full Text Available The concrete of pavements must resist the climatic conditions, heavy traffic, chemical agents or any other type of aggressive agent. A methodology for characterizing materials that would influence concrete durability was developed considering chemical and physical factors. This methodology allows the consideration of several factors like physiography, geology, and climate, among others that would be of great importance to prevent future durability problems of pavements. This methodology takes into account several tests and this paper presents the results of potential reactivity aggregates of the State of Chihuahua. The tests for evaluating the reactive siliceous aggregate and the potential alkali-silica reactivity were performed according to the: petrographic examination (ASTM C 295 and standard quick chemical test (ASTM C 289. 38% of the tested sites resulted innocuous, 48% potentially reactive and 13% reactive. It is discussed the benefit of applying a conscious methodology in order to obtain the best results with a representative quantity of tests.

    El hormigón de los pavimentos debe ser resistente a las condiciones climáticas, tránsito pesado, agentes químicos o cualquier otro tipo de agente agresivo. Se desarrolló una metodología para caracterización de materiales considerando factores físicos y químicos que influyen en la durabilidad del hormigón. Esta metodología se basa en la consideración de varios factores como: fisiografía, geología y clima, entre otros, que podrían ser de gran importancia para prevenir futuros problemas de durabilidad en pavimentos de hormigón. La metodología en cuestión considera varias pruebas, en este artículo se presentan los resultados de la reactividad potencial de los áridos del Estado de Chihuahua. Las pruebas para evaluar la reactividad de áridos silíceos y la reactividad potencial álcali-sílice fueron ejecutadas de acuerdo a: examen petrográfico (ASTM C 295 y la prueba qu

  18. Reaction of carbon with lanthanide silicides. III

    International Nuclear Information System (INIS)

    The reaction of carbon with Gd5Si3 and Ho5Si3 was studied by arc melting the alloys with carbon and comparing the resultant phases with those identified previously in the Er5Si3 system. Ordering in the structure detected at x = 0.5 and x = 0.95 in Ln5Si3Csub(x) in both these systems is identical with that detected in the erbium system. Lower metal volatility in the gadolinium preparations produces single-phase systems more readily, but above x = 0.5 the carbide Gd15C19 is present in small amounts up to x = 0.95. Results for harndess, hydrolysis product distribution and X-ray and metallographic examination are presented. (Auth.)

  19. Polymorphs calcium carbonate on temperature reaction

    International Nuclear Information System (INIS)

    Calcium carbonate (CaCO3) has three different crystal polymorphs, which are calcite, aragonite and vaterite. In this study, effect of reaction temperature on polymorphs and crystallite structure of CaCO3 was investigated. X-ray powder diffraction (XRD), fourier transform infrared (FTIR), and variable pressure scanning electron microscope (VPSEM) were used to characterize the obtained CaCO3 particles. The obtained results showed that CaCO3 with different crystal and particle structures can be formed by controlling the temperature during the synthesis process

  20. Thermal stability and oxidizing properties of mixed alkaline earth-alkali molten carbonates: A focus on the lithium-sodium carbonate eutectic system with magnesium additions

    International Nuclear Information System (INIS)

    Highlights: • TG/DSC analysis was conducted on magnesium-containing eutectic Li/Na eutectic carbonates. • Magnesium influence on the oxygen solubility properties of carbonate was also experimentally determined at 600 °C and 650 °C. • A reproducible partial decarbonation process in premelting region caused formation of magnesium oxycarbonate-like phases. • The acidobase buffering action of magnesium oxycarbonate species could explain the high basic/oxidizing properties of such carbonate melts. • A general correlation between thermal instability in premelting region and basic/oxidizing melt properties was established. - Abstract: A comparative study on thermal behavior and oxygen solubility properties of eutectic 52/48 lithium/sodium carbonate salt containing minor additions of magnesium up to 10 mol% has been made in order to determine whether a general correlation between these two properties can be found or not. Consecutive TG/DSC heating/cooling thermal cycles carried out under alternating CO2 and N2 gas flows allowed to assign thermal events observed in the premelting region to a partial decarbonation process of the magnesium-alkali mixed carbonates. The observed decarbonation process at 460 °C is believed to come from initial stage of thermal decomposition of magnesium carbonate resulting in the metastable formation of magnesium oxycarbonate-like phases MgO·2MgCO3, in a similar manner as previously reported for lanthanum. Reversible formation and decomposition of the magnesium carbonate phase has been observed under a CO2 gas atmosphere. The intensity of the decomposition process shows a maximum for a 3 mol% MgO addition that gives also the highest oxygen solubility, suggesting therefore that instability thermal analysis in the premelting region can be considered as providing an effective measure of the basicity/oxidizing properties of alkali carbonate melts with magnesium or, in more general terms, with cations that are strong modifiers of the

  1. Vibrational spectra of monouranates and uranium hydroxides as reaction products of alkali with uranyl nitrate

    International Nuclear Information System (INIS)

    Vibrational (IR absorption and Raman scattering) spectra for the reaction products of uranyl nitrate hexahydrate with NaOH and KOH have been studied. As a result of exchange reactions, the uranyl-ion coordinated nitrate groups are completely replaced by hydroxyl ions and various uranium and uranyl oxides or hydrates are formed. An analysis of the vibrations has been performed in terms of the frequencies of a free or coordinated nitrate group; comparison with the vibrations of the well-known uranium oxides and of the uranyl group UO22+ has been carried out. Vibrational spectra of a free nitrate group are characterized by four vibrational frequencies 1050, 724, 850, and 1380 cm-1, among which the frequencies at 724 and 1380 cm-1 are doubly degenerate and attributed to E’ symmetry of the point group D3h. When this group is uranium coordinated, its symmetry level is lowered to C2v, all vibrations of this group being active both in Raman and IR spectra. The doubly degenerate vibrations are exhibited as two bands and a frequency of the out-of-plane vibration is lowered to 815 cm-1. (authors)

  2. Self-Sensing Properties of Alkali Activated Blast Furnace Slag (BFS) Composites Reinforced with Carbon Fibers

    OpenAIRE

    Pedro Garcés; Emilio Zornoza; Oscar Galao; Josep Lluís Vilaplana; Francisco Javier Baeza

    2013-01-01

    In recent years, several researchers have shown the good performance of alkali activated slag cement and concretes. Besides their good mechanical properties and durability, this type of cement is a good alternative to Portland cements if sustainability is considered. Moreover, multifunctional cement composites have been developed in the last decades for their functional applications (self-sensing, EMI shielding, self-heating, etc.). In this study, the strain and damage sensing possible applic...

  3. Alkali- or acid-induced changes in structure, moisture absorption ability and deacetylating reaction of β-chitin extracted from jumbo squid (Dosidicus gigas) pens.

    Science.gov (United States)

    Jung, Jooyeoun; Zhao, Yanyun

    2014-01-01

    Alkali- or acid-induced structural modifications in β-chitin from squid (Dosidicus gigas, d'Orbigny, 1835) pens and their moisture absorption ability (MAA) and deacetylating reaction were investigated and compared with α-chitin from shrimp shells. β-Chitin was converted into the α-form after 3h in 40% NaOH or 1-3 h in 40% HCl solution, and α-chitin obtained from NaOH treatment had higher MAA than had native α-chitin, due to polymorphic destructions. In contrast, induced α-chitin from acid treatment of β-chitin had few polymorphic modifications, showing no significant change (P>0.05) in MAA. β-Chitin was more susceptible to alkali deacetylation than was α-chitin, and required a lower concentration of NaOH and shorter reaction time. These results demonstrate that alkali- or acid-treated β-chitin retained high susceptibility toward solvents, which in turn resulted in good biological activity of β-chitosan for use as a natural antioxidant and antimicrobial substance or application as edible coatings and films for various food applications. PMID:24444948

  4. Reaction from Dimethyl Carbonate to Diphenyl Carbonate. 1. Experimental Determination of the Chemical Equilibria

    NARCIS (Netherlands)

    Haubrock, J.; Raspe, M.; Versteeg, G.F.; Kooijman, H.A.; Taylor, R.; Hogendoorn, J.A.

    2008-01-01

    New experimental equilibrium data of the reaction of dimethyl carbonate (DMC) and phenol to methyl phenyl carbonate (MPC) and the subsequent disproportion and transesterification reaction of MPC to diphenyl carbonate (DPC) are presented and interpreted in terms of the reaction equilibrium coefficien

  5. Thermal stability and oxidizing properties of mixed alkaline earth-alkali molten carbonates: A focus on the lithium-sodium carbonate eutectic system with magnesium additions

    Energy Technology Data Exchange (ETDEWEB)

    Frangini, Stefano, E-mail: stefano.frangini@enea.it [Hydrogen and Fuel Cell Laboratory (UTRINN-IFC), ENEA CR Casaccia, Via Anguillarese 301, I-00123 Rome (Italy); Scaccia, Silvera [Sustainable Combustion Laboratory (UTTEI-COMSO), ENEA CR Casaccia, Via Anguillarese 301, I-00123 Rome (Italy)

    2013-12-20

    Highlights: • TG/DSC analysis was conducted on magnesium-containing eutectic Li/Na eutectic carbonates. • Magnesium influence on the oxygen solubility properties of carbonate was also experimentally determined at 600 °C and 650 °C. • A reproducible partial decarbonation process in premelting region caused formation of magnesium oxycarbonate-like phases. • The acidobase buffering action of magnesium oxycarbonate species could explain the high basic/oxidizing properties of such carbonate melts. • A general correlation between thermal instability in premelting region and basic/oxidizing melt properties was established. - Abstract: A comparative study on thermal behavior and oxygen solubility properties of eutectic 52/48 lithium/sodium carbonate salt containing minor additions of magnesium up to 10 mol% has been made in order to determine whether a general correlation between these two properties can be found or not. Consecutive TG/DSC heating/cooling thermal cycles carried out under alternating CO{sub 2} and N{sub 2} gas flows allowed to assign thermal events observed in the premelting region to a partial decarbonation process of the magnesium-alkali mixed carbonates. The observed decarbonation process at 460 °C is believed to come from initial stage of thermal decomposition of magnesium carbonate resulting in the metastable formation of magnesium oxycarbonate-like phases MgO·2MgCO{sub 3}, in a similar manner as previously reported for lanthanum. Reversible formation and decomposition of the magnesium carbonate phase has been observed under a CO{sub 2} gas atmosphere. The intensity of the decomposition process shows a maximum for a 3 mol% MgO addition that gives also the highest oxygen solubility, suggesting therefore that instability thermal analysis in the premelting region can be considered as providing an effective measure of the basicity/oxidizing properties of alkali carbonate melts with magnesium or, in more general terms, with cations that are

  6. Carbon compounds in the atmosphere and their chemical reactions

    OpenAIRE

    Martišová, Petra

    2013-01-01

    The essay dissert on compounds of carbon in the atmosphere and its reaction. The most important are carbon dioxide, carbon monoxide and methane. Included among important compounds of carbon are volatile organic substances, polycyclic aromatic hydrocarbon and dioxin. Carbon dioxide and methane representing greenhouse gases have also indispensable meaning. As they, together with water vapour, nitrogen monoxide and other gases are causing the major part of greenhouse effect. Primarily because of...

  7. Carbon dioxide as a carbon source in organic transformation: carbon-carbon bond forming reactions by transition-metal catalysts.

    OpenAIRE

    Tsuji, Yasushi; Fujihara, Tetsuaki

    2012-01-01

    Recent carbon-carbon bond forming reactions of carbon dioxide with alkenes, alkynes, dienes, aryl zinc compounds, aryl boronic esters, aryl halides, and arenes having acidic C-H bonds are reviewed in which transition-metal catalysts play an important role.

  8. Reaction from Dimethyl Carbonate (DMC) to Diphenyl Carbonate (DPC). 2. Kinetics of the Reactions from DMC via Methyl Phenyl Carbonate to DPC

    NARCIS (Netherlands)

    Haubrock, J.; Wermink, W.; Versteeg, G.F.; Kooijman, H.A.; Taylor, R.; Sint Annaland, M. van; Hogendoorn, J.A.

    2008-01-01

    The kinetics of the reaction of dimethyl carbonate (DMC) and phenol to methyl phenyl carbonate (MPC) and the subsequent disproportion and transesterification reaction of methyl phenyl carbonate (MPC) to diphenyl carbonate (DPC) have been studied. Experiments were carried out in a closed batch reacto

  9. The effect of activating solution on the mechanical strength, reaction rate, mineralogy, and microstructure of alkali-activated fly ash

    NARCIS (Netherlands)

    Ma, Y.; Hu. J.; Ye, G.

    2012-01-01

    Alkali-activated fly ash (AAF) is a promising material that exhibits comparable material properties as cement-based materials but with much less CO2 emission. In the present work, the effect of activating solution (SiO2 and Na2O content) on the performance of AAF was studied by means of isothermal c

  10. Alkali metal cation doping of metal-organic framework for enhancing carbon dioxide adsorption capacity

    Institute of Scientific and Technical Information of China (English)

    Yan Cao; Yunxia Zhao; Fujiao Song; Qin Zhong

    2014-01-01

    Metal-organic frameworks (MOFs) have attracted much attention as adsorbents for the separation of CO2 from flue gas or natural gas. Here, a typical metal-organic framework HKUST-1(also named Cu-BTC or MOF-199) was chemically reduced by doping it with alkali metals (Li, Na and K) and they were further used to investigate their CO2 adsorption capacities. The structural information, surface chemistry and thermal behavior of the prepared adsorbent samples were characterized by X-ray powder diffraction (XRD), thermo-gravimetric analysis (TGA) and nitrogen adsorption-desorption isotherm analysis. The results showed that the CO2 storage capacity of HKUST-1 doped with moderate quantities of Li+, Na+ and K+, individually, was greater than that of unmodified HKUST-1. The highest CO2 adsorption uptake of 8.64 mmol/g was obtained with 1K-HKUST-1, and it was ca. 11%increase in adsorption capacity at 298 K and 18 bar as compared with HKUST-1. Moreover, adsorption tests showed that HKUST-1 and 1K-HKUST-1 displayed much higher adsorption capacities of CO2 than those of N2. Finally, the adsorption/desorption cycle experiment revealed that the adsorption performance of 1K-HKUST-1 was fairly stable, without obvious deterioration in the adsorption capacity of CO2 after 10 cycles.

  11. Properties of solvated electrons, alkali anions and other species in metal solutions and kinetics of cation and electron exchange reactions. Final report

    International Nuclear Information System (INIS)

    The properties of solutions of alkali metals in amine solvents were studied by optical, ETR, NMR and electrochemical methods. Complexation of the alkali cations by crown ethers and cryptands permitted the preparation of concentrated solutions of alkali metals in amine and ether solvents. Extensive alkali metal NMR studies of the exchange of M+ with crown-ethers and cryptands and of the alkali metal anion, M-, were made. The first crystalline salt of an alkali metal anion, Na+ Cryptand [2.2.2]Na- was synthesized and characterized and led to the preparation of other alkali metal anion salts. This research provided the foundation for continuing studies of crystalline alkalide salts

  12. The Influence of Calcined Clay Pozzolan, Low-Cao Steel Slag and Granite Dust On the Alkali-Silica Reaction in Concrete

    Directory of Open Access Journals (Sweden)

    James Sarfo-Ansah

    2015-08-01

    Full Text Available The influence of low CaO steel slag, calcined clay and granite dust on the alkali-silica reaction was investigated over a period of 35 days under accelerated curing conditions. The mineral admixtures were used to replace varying portions of high alkali Portland limestone cement up to an admixture content of 25% in order to study their effect on the alkali-silica reaction (ASR. Portland limestone cement used for the study had a total Na2Oeq of 4.32. XRD analysis of hydrated mortar bar samples confirmed the formation of an expansive sodium silica gel in the reference Portland cement mortar bar as the agent responsible for ASR. Stable calcium silicates were formed in the mortar bars containing calcined clay in increasing quantities whilst the presence of the sodium silicate gel decreased.The occurrence of these stable silicates in hydrated samples containing steel slag and granite dust was however minimal, compared to calcined clay cement mortars. The highest expansion was recorded for granite dust mortar bars, reaching a maximum of 25.98% at 35 days. Mortar-bar expansion decreased as calcined clay content in the cement increased;mortar bars with 25% calcined clay were the least expansive recording expansion less than 0.1% at all test ages. Whilst the expansion was reduced by between 42.5% and 107.8% at 14 days with increasing calcined clay content, expansion rather increased between 36.8% and 169.5% at 14 days with increasing granite dust content.Steel slag mortar bars experienced reduction in 14 days expansion between 14.3% - 46.2%.The study confirms that steel slag and calcined clay pozzolan have greater influence on ASR in mortar bars than granite dust and shows that calcined clay and low CaO steel slag could be considered as remedial admixtures for ASR at replacement levels of 25% and 15% respectively.

  13. Complex formation during dissolution of metal oxides in molten alkali carbonates

    DEFF Research Database (Denmark)

    Li, Qingfeng; Borup, Flemming; Petrushina, Irina;

    1999-01-01

    as the partial pressure of carbon dioxide varies. By combination of solubility and electromotive force measurements, a model is constructed assuming the dissolution involves complex formation. The possible species for lead are proposed to be [Pb(CO3)(2)](-2) and/or [Pb(CO3)(3)](-4). A similar complex......Dissolution of metal oxides in molten carbonates relates directly to the stability of materials for electrodes and construction of molten carbonate fuel cells. In the present work the solubilities of PbO, NiO, Fe2O3,and Bi2O3 in molten Li/K carbonates have been measured at 650 degrees C under...... carbon dioxide atmosphere. It is found that the solubilities of NiO and PbO decrease while those of Fe2O3 and Bi2O3 remain approximately constant as the lithium mole fraction increases from 0.43 to 0.62 in the melt. At a fixed composition of the melt, NiO and PbO display both acidic and basic dissolution...

  14. Demixing and effective volatility of molten alkali carbonate melts in MCFCs

    Energy Technology Data Exchange (ETDEWEB)

    Brenscheidt, T.; Wendt, H. [Institut fuer Chemische Technologie, Darmstadt (Germany)

    1996-12-31

    Since the early investigation of A. Klemm, the demixing of the cations of molten binary salt mixtures with a common anion due to the different mobilities of two different cations had been investigated in numerous experiments and the respective results interpreted in terms of structural features of the melts. 1-1 electrolytes had been preferentially investigated. Okada also reported investigations on lithium carbonate/potassium carbonate mixtures in the temperature range from 980 to 1070 K. From this investigation it is known that the heavier potassium cation is faster than lithium in mixtures which are more concentrated in potassium than x{sub K2CO3} = 0,32 (Chemla effect) whereas below this isotachic concentration lithium is faster. This paper investigates demixing in molten carbonate fuel cells.

  15. Study of carbon-isotope exchange reactions between potassium cyanide and some carbonates, and their use for obtaining C14-labelled potassium cyanide

    International Nuclear Information System (INIS)

    The authors examine the results of a study on the isotope exchange of potassium cyanide with compounds differing greatly from it both in composition and structure, such as carbonates of alkaline and alkali-earth metals. The carbon-isotope exchange reaction in the KC12N-BaC14O3 system was studied at 600-800oC. The ratio between the components of this system and those given below agreed with the equimolecular ratio. The authors show that at high temperatures complete exchange between these compounds can be secured. The exchange reaction begins when the cyanide melt is formed; later it occurs between the liquid and the solid phases, and its speed increases with temperature; at 800oC it is completed in 2 h. With carbonates of alkali metals the exchange reaction occurs in the melt and is completed at lower temperatures. The authors obtained cyanide-labelled potassium by the following method : (1) The isotope exchange reaction KC12N-BaC14O3 is produced at 800oC in 2 h. (2) The mixture KCN+BaCO3 is separated by extracting the KCN with liquid ammonia in a circulating extractor. By exchanging the equimolecular quantities KCN and BaCO3, potassium cyanide is obtained with a chemical yield of more than 90% and a basic-substance content of 96-97%. By using BaCO3 with a high specific activity (60-70 mc/g), a KCN specific activity of over 80 mc/g may be obtained. The barium carbonate depleted of isotope C14 regenerates after the ammonia extraction without appreciable loss. (author)

  16. Efficient destruction of CF4 through in situ generation of alkali metals from heated alkali halide reducing mixtures.

    Science.gov (United States)

    Lee, Myung Churl; Choi, Wonyong

    2002-03-15

    Perfluorocarbons (PFCs) are the most potent green house gases that are very recalcitrant at destruction. An effective way of converting PFCs using hot solid reagents into safe products has been recently introduced. By investigating the thermal reductive destruction of tetrafluoromethane (CF4) we provided new insight and more physicochemical consideration on this novel process. The complete destruction of CF4was successfully achieved by flowing the gas through a heated reagent bed (400-950 degrees C) that contained powder mixtures of alkali halides, CaO, and Si. The silicon acted as a reducing agent of alkali halides for the in-situ production of alkali metals, and the calcium oxide played the role of a halide ion acceptor. The absence of any single component in this ternary mixture drastically reduced the destruction efficiency of CF4. The CF4 destruction efficiencies with the solid reagent containing the alkali halide, MX, increased in the order of Li approximately Na < K < Cs for alkali cations and I < Br < Cl < F for halide anions. This trend agreed with the endothermicity of the alkali metal generation reaction: the higher the endothermicity, the lower the destruction efficiency. Alkali metal generation was indirectly detected by monitoring H2 production from its reaction with water. The production of alkali metals increased with NaF, KF, and CsF in this order. The CsF/CaO/Si system exhibited the complete destruction of CF4 at as low as 600 degrees C. The solid product analysis by X-ray diffraction (XRD) showed the formation of CaF2 and the depletion of Si with black carbon particles formed in the solid reagent residue. No CO/CO2 and toxic HF and SiF4 formation were detected in the exhaust gas. PMID:11944694

  17. Study of the reaction of carbon with atomic oxygen

    International Nuclear Information System (INIS)

    This research thesis reports the study of reactions of carbon when in contact with atomic oxygen in order to have a better understanding of the combustion mechanism. It appears that, at room temperature, oxygen atoms impacting the carbon surface do not all react with this surface (the reaction shock efficiency is very low). At temperatures higher than 200 C, all atoms which reach the surface react with it and the efficiency is much higher. The study of the reaction rate with respect to temperature allows three domains of reaction conditions to be distinguished according to the stability of formed surface oxides. The initial degassing of carbon results in a temporary excitation of the reaction rate, even with atomic oxygen. Whatever is the temperature, reaction is localised at the vicinity of the sample outer surface (this means that the regime is constantly diffusion). The BET surface of carbons does not vary with the reaction. As texture, the structure of the different carbons does not seem to have an influence on the reaction with atomic oxygen. Even though results are obtained in very different temperature ranges (600 C with O2, less than 200 C with atomic oxygen), there is an analogy between some phenomena noticed with atomic oxygen and molecular oxygen: surface oxides play a prevailing role

  18. Aminolysis Reaction of Glycerol Carbonate in Organic and Hydroorganic Medium

    OpenAIRE

    Nohra, Bassam; Candy, Laure; Blanco, Jean-François; Raoul, Yann; Mouloungui, Zephirin

    2012-01-01

    Aminolysis reaction of glycerol carbonate with primary amine in organic and hydroorganic media leads to the formation of two hydroxyurethane isomers and a partial decomposition of glycerol carbonate into glycerol. Aminolysis with a secondary amine promotes the condensation reaction and limits the formation of glycerol. The ratio of α versus β was determined by zgig 13C NMR. This technique permits computing the yield of α and β products in the medium. The quantity of glycerol was determined by...

  19. The effect of activating solution on the mechanical strength, reaction rate, mineralogy, and microstructure of alkali-activated fly ash

    OpenAIRE

    Ma, Y.; Hu J.; Ye, G.

    2012-01-01

    Alkali-activated fly ash (AAF) is a promising material that exhibits comparable material properties as cement-based materials but with much less CO2 emission. In the present work, the effect of activating solution (SiO2 and Na2O content) on the performance of AAF was studied by means of isothermal calorimetry and X-ray diffraction analysis. Meanwhile, the pore structure of AAF was examined by mercury intrusion porosimetry combined with environmental scanning electron microscope. The results i...

  20. Effect of Carbon Containing Materials on Pure Carbon Reaction-bonded SiC

    Institute of Scientific and Technical Information of China (English)

    JI Xiaoli; WEI Lei; SUN Feng

    2008-01-01

    Petroleum coke, graphite, gas carbon and lower sulfur carbon black were used to prepare reaction-bonded silicon carbide. The influences of different carbon containing materials on properties of carbonaceous precursors, sintering process, and microstructure of the prepared SiC were researched. The results show that:(1)With the density of carbon containing materials increasing, the porosity of carbonaceous precursors decreases and the infiltrating process of liquid silicon is more difficult.(2)The reaction between carbon containing materials and liquid silicon, the volume effect is more obvious with the density of carbon containing materials increasing.(3)As the carbon containing materials density decreasing, residual carbon in reaction bonded SiC also decreases.

  1. Reactions of carbon cluster ions stored in an RF trap

    International Nuclear Information System (INIS)

    Reactions of carbon cluster ions with O2 were studied by using an RF ion trap in which cluster ions of specific size produced by laser ablation could be stored selectively. Reaction rate constants for positive and negative carbon cluster ions were estimated. In the case of the positive cluster ions, these were consistent with the previous experimental results using FTMS. Negative carbon cluster ions C-n (n=4-8) were much less reactive than positive cluster ions. The CnO- products were seen only in n=4 and 6. (orig.)

  2. Modeling Corrosion Reactions of Steel in a Dilute Carbonate Solution

    Science.gov (United States)

    Eliyan, Faysal Fayez; Alfantazi, Akram

    2016-02-01

    This research models the corrosion reactions of a high-strength steel in an aerated, dilute, carbonate solution during a single-cycle voltammetry. Based on a previous study (Eliyan et al. in J Mater Eng Perform 24(6):1-8, 2015) and a literature survey, the corrosion reactions of the cathodic reduction, anodic dissolution, and passivation, as well as the interfacial interactions and the chemistry of the corrosion products are illustrated in schematics. The paper provides a visual guide on the corrosion reactions for steel in carbonate solutions based on the available mechanistic details that were reported and are still being investigated in literature.

  3. Carbon induced reactions at low incident energies

    International Nuclear Information System (INIS)

    Accurate knowledge of the reactions which occur when two heavy ions interact is of importance in many trans-disciplinary fields, particularly in cancer therapy and space radiation protection. In these cases one needs to know what happens in a natural process to which all possible reaction mechanisms contribute and thus a theoretical calculation, to be really usable, must indeed be able to reproduce large sets of data in wide energy and mass ranges. We show here the results of an analysis of the spectra of intermediate mass fragments produced in the C + Al interaction at 13 MeV/n, both in direct and inverse kinematics, which supplies a very reasonable reproduction of a great number of data providing useful information on the leading reaction mechanisms

  4. Reactions over catalysts confined in carbon nanotubes.

    Science.gov (United States)

    Pan, Xiulian; Bao, Xinhe

    2008-12-21

    We review a new concept for modifying the redox properties of transition metals via confinement within the channels of carbon nanotubes (CNTs), and thus tuning their catalytic performance. Attention is also devoted to novel techniques for homogeneous dispersion of metal nanoparticles inside CNTs since these are essential for optimization of the catalytic activity. PMID:19048128

  5. A new alkali-resistant Ni/Al2O3-MSU-1 core-shell catalyst for methane steam reforming in a direct internal reforming molten carbonate fuel cell

    Science.gov (United States)

    Zhang, Jian; Zhang, Xiongfu; Liu, Weifeng; Liu, Haiou; Qiu, Jieshan; Yeung, King Lun

    2014-01-01

    An alkali-resistant catalyst for direct internal reforming molten carbonate fuel cell (DIR-MCFC) is prepared by growing a thin shell of mesoporous MSU-1 membrane on Ni/Al2O3 catalyst beads. The MSU-1 shell is obtained by first depositing a monolayer of colloidal silicalite-1 (Sil-1) on the catalyst bead as linkers and then using NaF stored in the beads to catalyze the growth of the MSU-1 layer. The resulting core-shell catalysts display excellent alkali-resistance and deliver stable methane conversion and hydrogen yield in an out-of-cell test simulating the operating conditions of an operating DIR-MCFC. Higher conversion and yield (i.e., up to over 70%) are obtained from the new core-shell catalyst with MSU-1 shell compared to the catalyst with microporous Sil-1 shell. A mathematical model of the reaction and poisoning of the core-shell catalyst is used to predict the optimum shell thickness for its reliable use in a DIR-MCFC.

  6. A stochastic optimization method based technique for finding out reaction paths in noble gas clusters perturbed by alkali metal ions

    International Nuclear Information System (INIS)

    Graphical abstract: The structure of a minimum in Ar19K+ cluster. Abstract: In this paper we explore the possibility of using stochastic optimizers, namely simulated annealing (SA) in locating critical points (global minima, local minima and first order saddle points) in Argon noble gas clusters perturbed by alkali metal ions namely sodium and potassium. The atomic interaction potential is the Lennard Jones potential. We also try to see if a continuous transformation in geometry during the search process can lead to a realization of a kind of minimum energy path (MEP) for transformation from one minimum geometry to another through a transition state (first order saddle point). We try our recipe for three sizes of clusters, namely (Ar)16M+, (Ar)19M+ and (Ar)24M+, where M+ is Na+ and K+.

  7. Kinetics of the reaction between carbon dioxide and tertiary amines

    Energy Technology Data Exchange (ETDEWEB)

    Crooks, J.E.; Donnellan, J.P. (King' s Coll., London (England))

    1990-02-16

    The reaction between carbon dioxide and amines is of great technical importance and has been the subject of many investigations. The authors have shown that the reaction for secondary amines in anhydrous ethanol and in aqueous solution is exclusively second-order in amine and that the zwitterion intermediate postulated by Danckwerts is probably of negligible significance in the mechanism. The reaction with tertiary amines has also been studied, but the data are less controversial. In order to complete their studies of the reactions of carbon dioxide with amines, using their conductimetric stopped-flow apparatus, they have studied this reaction for MDEA (methyldiethanolamine, IUPAC name N-methyl-2,2{prime}-iminodiethanol) and TEA (triethanolamine, IUPAC name 2,2{prime},2{double prime}-nitrilotris(ethanol)).

  8. Carbon-Carbon Cross Coupling Reactions in Ionic Liquids Catalysed by Palladium Metal Nanoparticles

    OpenAIRE

    Martin H. G. Prechtl; Scholten, Jackson D.; Jairton Dupont

    2010-01-01

    A brief summary of selected pioneering and mechanistic contributions in the field of carbon-carbon cross-coupling reactions with palladium nanoparticles (Pd-NPs) in ionic liquids (ILs) is presented. Five exemplary model systems using the Pd-NPs/ILs approach are presented: Heck, Suzuki, Stille, Sonogashira and Ullmann reactions which all have in common the use of ionic liquids as reaction media and the use of palladium nanoparticles as reservoir for the catalytically active palladium species.

  9. Study on material properties in order to apply for structural analysis of turbine generator foundation affected by Alkali-Silica reaction

    International Nuclear Information System (INIS)

    It is well known that material properties (compressive strength, elastic modulus) of a concrete core specimen taken from a structure, which has been affected by alkali-silica reaction (ASR), are reduced significantly in comparison to those of sound concrete. On the other hand, in-situ tests of reinforcement concrete structures also affected by ASR are reported to show only insignificant reduction of rigidity and strength capacities of the structures. The difference of the affect of ASR on a core and a structure is understood to be occurred due to pre-stress effect caused by ASR on the concrete. However, there are only a few reports which show a quantitative evaluation of this effect. Material properties of concrete structure affected by ASR are studied quantitatively by literature review, in-situ tests of actual foundation and model tests. (authors)

  10. Upgrading platform using alkali metals

    Science.gov (United States)

    Gordon, John Howard

    2014-09-09

    A process for removing sulfur, nitrogen or metals from an oil feedstock (such as heavy oil, bitumen, shale oil, etc.) The method involves reacting the oil feedstock with an alkali metal and a radical capping substance. The alkali metal reacts with the metal, sulfur or nitrogen content to form one or more inorganic products and the radical capping substance reacts with the carbon and hydrogen content to form a hydrocarbon phase. The inorganic products may then be separated out from the hydrocarbon phase.

  11. How does the carbon fusion reaction happen in stars?

    International Nuclear Information System (INIS)

    The 12C + 12C fusion reaction is one of the most important reactions in the stellar evolution. Due to its complicated reaction mechanism, there is great uncertainty in the reaction rate which limits our understanding of various stellar objects, such as massive stellar evolution, explosions on neutron stars, and supernovae from accreting white dwarf stars. In this paper, I will review the challenges in the study of carbon burning. I will also report recent results from our studies: 1) an upper limit for the 12C + 12C fusion cross sections, 2) measurement of the 12C + 12C at deep sub-barrier energies, and 3) a new measurement of the 12C(12C, n) reaction. The outlook for the studies of the astrophysical heavy-ion fusion reactions will also be presented

  12. Oxidation reaction of pyrolytic carbon coating

    International Nuclear Information System (INIS)

    The behaviour of pyrolytic carbon coatings on commercial grade graphite substrate in oxidizing environment is described. Specimens were examined under sputtering in plasma of oxygen and argon, or in an oxidizing solution of K2CrO7+H3PO4. Specimens of commercial grade graphite (ATJ) were quickly eroded under these conditions, compared to coated specimens. The erosion rate of the coating is dependent on its thickness and on the mean monticules diameter. The coatings disintegrated in the oxidizing environment in three steps: etching of monticules' boundaries; widening of the boundaries or cracking of the coating; falling off the coating. The degree of erosion decreased with increasing mean monticules diameter and increased where the diameter was non-homogeneous. The resistance of the coating to wear- under these oxidizing conditions- can be enhanced by homogenization of the coating and by its deposition in layered films. (author)

  13. Reactions of carbon atoms in pulsed molecular beams

    Energy Technology Data Exchange (ETDEWEB)

    Reisler, H. [Univ. of Southern California, Los Angeles (United States)

    1993-12-01

    This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

  14. Pattern Formation and Reaction Textures during Dunite Carbonation

    Science.gov (United States)

    Lisabeth, H. P.; Zhu, W.

    2015-12-01

    Alteration of olivine-bearing rocks by fluids is one of the most pervasive geochemical processes on the surface of the Earth. Serpentinized and/or carbonated ultramafic rocks often exhibit characteristic textures on many scales, from polygonal mesh textures on the grain-scale to onion-skin or kernel patterns on the outcrop scale. Strong disequilibrium between pristine ultramafic rocks and common geological fluids such as water and carbon dioxide leads to rapid reactions and coupled mechanical and chemical feedbacks that manifest as characteristic textures. Textural evolution during metasomatic reactions can control effective reaction rates by modulating dynamic porosity and therefore reactant supply and reactive surface area. We run hydrostatic experiments on thermally cracked dunites saturated with carbon dioxide bearing brine at 15 MPa confining pressure and 150°C to explore the evolution of physical properties and reaction textures as carbon mineralization takes place in the sample. Compaction and permeability reduction are observed throughout experiments. Rates of porosity and permeability changes are sensitive to pore fluid chemistry. After reaction, samples are imaged in 3-dimension (3D) using a dual-beam FIB-SEM. Analysis of the high resolution 3D microstructure shows that permeable, highly porous domains are created by olivine dissolution at a characteristic distance from pre-existing crack surfaces while precipitation of secondary minerals such as serpentine and magnesite is limited largely to the primary void space. The porous dissolution channels provide an avenue for fluid ingress, allow reactions to continue and could lead to progressive hierarchical fracturing. Initial modeling of the system indicates that this texture is the result of coupling between dissolution-precipitation reactions and the local stress state of the sample.

  15. Adverse reactions in treatment with lithium carbonate and haloperidol.

    Science.gov (United States)

    Baastrup, P C; Hollnagel, P; Sorensen, R; Schou, M

    1976-12-01

    Hospital records of 425 patients who had been treated simultaneously with lithium carbonate and haloperidol were examined. Adverse reactions in these patients were the same as in patients given lithium alone or haloperidol alone. None of the patients developed a syndrome resembling that described by others in patients treated with a lithium and haloperidol combination. PMID:1036539

  16. Effects of hydrolysis and carbonization reactions on hydrochar production.

    Science.gov (United States)

    Fakkaew, K; Koottatep, T; Polprasert, C

    2015-09-01

    Hydrothermal carbonization (HTC) is a thermal conversion process which converts wet biomass into hydrochar. In this study, a low-energy HTC process named "Two-stage HTC" comprising of hydrolysis and carbonization stages using faecal sludge as feedstock was developed and optimized. The experimental results indicated the optimum conditions of the two-stage HTC to be; hydrolysis temperature of 170 °C, hydrolysis reaction time of 155 min, carbonization temperature of 215 °C, and carbonization reaction time of 100 min. The hydrolysis reaction time and carbonization temperature had a statistically significant effect on energy content of the produced hydrochar. Energy input of the two-stage HTC was about 25% less than conventional HTC. Energy efficiency of the two-stage HTC for treating faecal sludge was higher than that of conventional HTC and other thermal conversion processes such as pyrolysis and gasification. The two-stage HTC could be considered as a potential technology for treating FS and producing hydrochar. PMID:26051497

  17. Milk-alkali syndrome in a middle-aged woman after ingesting large doses of calcium carbonate: a case report

    OpenAIRE

    Grubb, Mandy; Gaurav, Kumar; Panda, Mukta

    2009-01-01

    Introduction Most cases of hypercalcaemia are secondary to malignancy or primary hyperparathyroidism. Here we report a case of hypercalcaemia that we have attributed to milk-alkali syndrome. Case presentation A 51-year-old Caucasian woman with a past history of thyroidectomy and parathyroidectomy secondary to thyroid cancer developed an altered mental state and had an extremely high calcium concentration of 22.8 mg/dl (5.7 mmol/l). Investigations included work up for malignancy and hyperparat...

  18. Investigation of ozonide ion reaction with neptunium (6) ions in alkali aqueous solutions by the method of pulse radiolysis

    International Nuclear Information System (INIS)

    By pulse radiolysis method with spectrophotometric recording of short-living particles kinetics of O3-radical-ion reaction with Np5+ and Np6+ in alkaline solutions is investigated. Rate constant of the first reaction equals to (2.0±0.3)x106, of the second -(2.1±0.2)x105 l/(mol·c) in 0.2-2.0 mol/l of LiOH. Peculiarities of Np6+ γ-radiolysis in alkaline solutions saturated with N2O and in aerated solutions containing K2S2O8 are explained. Np7+ yield is determined by O3-behaviour which depends on Np6+ and OH- concentration

  19. Reaction rate approach to dipolar relaxation in alkali halides: Adiabaticity versus classical, activated-tunneling, and quantal dipoles

    OpenAIRE

    Medrano, C; Georgiev, M.

    2007-01-01

    This paper is aimed at presenting a simple vibronic model for describing the dipolar reorientation in crystals by means of reaction rate theory. The Hamiltonian of an isolated dipole is simplified so as to render the problem solvable. Depending on the crossover splitting the dipoles may reorientate adiabatically with a high electron-transfer expectancy or exhibit low reorientation rates due to low expectancy. An important quantity to distinguish between adiabatic dipoles behaving classically ...

  20. Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    Han Wang; Wenlai Huang; Yongsheng Han

    2013-01-01

    Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering.If we look at crystallization at the atomic level,crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice.Diffusion can be a rate determining step for the growth of crystals.In this paper,we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced.The diffusion effect is studied in a specially designed three-cell reactor.Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concentration gradient in the reaction cell,thus promoting the formation of cubic calcite particles.The reaction rate is regulated by temperature.Increase of reaction rate favors the formation of needle-like aragonite particles.When diffusion and reaction play joint roles in the reaction system,their compromise dominates the formation of products,leading to a mixture of cubic and needle-like particles with a controllable ratio.Since diffusion and reaction are universal factors in the preparation of materials,the finding of this paper could be helpful in the controlled synthesis of other materials.

  1. GRIZZLY Model of Multi-Reactive Species Diffusion, Moisture/Heat Transfer and Alkali-Silica Reaction for Simulating Concrete Aging and Degradation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Hai [Idaho National Lab. (INL), Idaho Falls, ID (United States); Spencer, Benjamin W. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cai, Guowei [Vanderbilt Univ., Nashville, TN (United States)

    2015-09-01

    Concrete is widely used in the construction of nuclear facilities because of its structural strength and its ability to shield radiation. The use of concrete in nuclear power plants for containment and shielding of radiation and radioactive materials has made its performance crucial for the safe operation of the facility. As such, when life extension is considered for nuclear power plants, it is critical to have accurate and reliable predictive tools to address concerns related to various aging processes of concrete structures and the capacity of structures subjected to age-related degradation. The goal of this report is to document the progress of the development and implementation of a fully coupled thermo-hydro-mechanical-chemical model in GRIZZLY code with the ultimate goal to reliably simulate and predict long-term performance and response of aged NPP concrete structures subjected to a number of aging mechanisms including external chemical attacks and volume-changing chemical reactions within concrete structures induced by alkali-silica reactions and long-term exposure to irradiation. Based on a number of survey reports of concrete aging mechanisms relevant to nuclear power plants and recommendations from researchers in concrete community, we’ve implemented three modules during FY15 in GRIZZLY code, (1) multi-species reactive diffusion model within cement materials; (2) coupled moisture and heat transfer model in concrete; and (3) anisotropic, stress-dependent, alkali-silica reaction induced swelling model. The multi-species reactive diffusion model was implemented with the objective to model aging of concrete structures subjected to aggressive external chemical attacks (e.g., chloride attack, sulfate attack, etc.). It considers multiple processes relevant to external chemical attacks such as diffusion of ions in aqueous phase within pore spaces, equilibrium chemical speciation reactions and kinetic mineral dissolution/precipitation. The moisture

  2. GRIZZLY Model of Multi-Reactive Species Diffusion, Moisture/Heat Transfer and Alkali-Silica Reaction for Simulating Concrete Aging and Degradation

    International Nuclear Information System (INIS)

    Concrete is widely used in the construction of nuclear facilities because of its structural strength and its ability to shield radiation. The use of concrete in nuclear power plants for containment and shielding of radiation and radioactive materials has made its performance crucial for the safe operation of the facility. As such, when life extension is considered for nuclear power plants, it is critical to have accurate and reliable predictive tools to address concerns related to various aging processes of concrete structures and the capacity of structures subjected to age-related degradation. The goal of this report is to document the progress of the development and implementation of a fully coupled thermo-hydro-mechanical-chemical model in GRIZZLY code with the ultimate goal to reliably simulate and predict long-term performance and response of aged NPP concrete structures subjected to a number of aging mechanisms including external chemical attacks and volume-changing chemical reactions within concrete structures induced by alkali-silica reactions and long-term exposure to irradiation. Based on a number of survey reports of concrete aging mechanisms relevant to nuclear power plants and recommendations from researchers in concrete community, we've implemented three modules during FY15 in GRIZZLY code, (1) multi-species reactive diffusion model within cement materials; (2) coupled moisture and heat transfer model in concrete; and (3) anisotropic, stress-dependent, alkali-silica reaction induced swelling model. The multi-species reactive diffusion model was implemented with the objective to model aging of concrete structures subjected to aggressive external chemical attacks (e.g., chloride attack, sulfate attack, etc.). It considers multiple processes relevant to external chemical attacks such as diffusion of ions in aqueous phase within pore spaces, equilibrium chemical speciation reactions and kinetic mineral dissolution/precipitation. The moisture

  3. Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Jung, Hun Bok; Martin, Paul F.; McGrail, B. Peter

    2011-11-01

    Portland cement, a common sealing material for wellbores for geological carbon sequestration was reacted with CO{sub 2} in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate cement-CO{sub 2} reaction along the wellbore from carbon injection depth to the near-surface. Hydrated Portland cement columns (14 mm diameter x 90 mm length; water-to-cement ratio = 0.33) including additives such as steel coupons and Wallula basalt fragments were reacted with CO{sub 2} in the wet supercritical (the top half) and dissolved (the bottom half) phases under carbon sequestration condition with high pressure (10 MPa) and temperature (50 C) for 5 months, while small-sized hydrated Portland cement columns (7 mm diameter x 20 mm length; water-to-cement ratio = 0.38) were reacted with CO{sub 2} in dissolved phase at high pressure (10 MPa) and temperature (50 C) for 1 month or with wet CO{sub 2} in gaseous phase at low pressure (0.2 MPa) and temperature (20 C) for 3 months. XMT images reveal that the cement reacted with CO{sub 2} saturated groundwater had degradation depth of {approx}1 mm for 1 month and {approx}3.5 mm for 5 month, whereas the degradation was minor with cement exposure to supercritical CO{sub 2}. SEM-EDS analysis showed that the carbonated cement was comprised of three distinct zones; the innermost less degraded zone with Ca atom % > C atom %, the inner degraded zone with Ca atom % {approx} C atom % due to precipitation of calcite, the outer degraded zone with C atom % > Ca atom % due to dissolution of calcite and C-S-H, as well as adsorption of carbon to cement matrix. The outer degraded zone of carbonated cement was porous and fractured because of dissolution-dominated reaction by carbonic acid exposure, which resulted in the increase in BJH pore volume and BET surface area. In contrast, cement-wet CO{sub 2}(g) reaction at low P (0.2 MPa)-T (20 C) conditions for 1 to 3 months was dominated by precipitation of micron

  4. RILEM recommendations for the prevention of damage by alkali-aggregate reactions in new concrete structures state-of-the-art report of the RILEM technical committee 219-ACS

    CERN Document Server

    Sims, Ian

    2016-01-01

    This book contains the full set of RILEM Recommendations which have been produced to enable engineers, specifiers and testing houses to design and produce concrete which will not suffer damage arising from alkali reactions in the concrete. There are five recommended test methods for aggregates (designated AAR-1 to AAR-5), and an overall recommendation which describes how these should be used to enable a comprehensive aggregate assessment (AAR-0). Additionally, there are two Recommended International Specifications for concrete (AAR-7.1 & 7.2) and a Preliminary International Specification for dams and other hydro structures (AAR-7.3), which describe how the aggregate assessment can be combined with other measures in the design of the concrete to produce a concrete with a minimised risk of developing damage from alkali-aggregate reactions.

  5. Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

    Energy Technology Data Exchange (ETDEWEB)

    Cochain, B; Neuville, D R; Roux, J; Strukelj, E; Richet, P [Physique des Mineraux et Magmas, Geochimie-Cosmochimie, CNRS-IPGP, 4 place Jussieu, 75005 Paris (France); Ligny, D de [Universite Claude Bernard Lyon 1, LPCML, F-69622 Villeurbanne (France); Baudelet, F, E-mail: cochain@ipgp.jussieu.f [Synchrotron SOLEIL, L' Orme des Merisiers, Saint Aubin (France)

    2009-11-15

    In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe{sup 2+} and Fe{sup 3+}, but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

  6. Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

    International Nuclear Information System (INIS)

    In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe2+ and Fe3+, but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

  7. Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

    Science.gov (United States)

    Cochain, B.; Neuville, D. R.; de Ligny, D.; Roux, J.; Baudelet, F.; Strukelj, E.; Richet, P.

    2009-11-01

    In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe2+ and Fe3+, but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

  8. Chemical Reactions in the Processing of Mosi2 + Carbon Compacts

    Science.gov (United States)

    Jacobson, Nathan S.; Lee, Kang N.; Maloy, Stuart A.; Heuer, Arthur H.

    1993-01-01

    Hot-pressing of MoSi2 powders with carbon at high temperatures reduces the siliceous grain boundary phase in the resultant compact. The chemical reactions in this process were examined using the Knudsen cell technique. A 2.3 wt pct oxygen MoSi2 powder and a 0.59 wt pct oxygen MoSi2 powder, both with additions of 2 wt pct carbon, were examined. The reduction of the siliceous grain boundary phase was examined at 1350 K and the resultant P(SiO)/P(CO) ratios interpreted in terms of the SiO(g) and CO(g) isobars on the Si-C-O predominance diagram. The MoSi2 + carbon mixtures were then heated at the hot-pressing temperature of 2100 K. Large weight losses were observed and could be correlated with the formation of a low-melting eutectic and the formation and vaporization of SiC.

  9. Carbon encapsulated magnetic nanoparticles produced by hydrothermal reaction

    Institute of Scientific and Technical Information of China (English)

    Nong Yue He; Ya Fei Guo; Yan Deng; Zhi Fei Wang; Song Li; Hong Na Liu

    2007-01-01

    Carbon encapsulated magnetic nanoparticles (CEMNs) were synthesized by heating an aqueous glucose solution containing FeAu (Au coated Fe nanoparticles) nanoparticles at 160-180 ℃ for 2 h. This novel hydrothermal approach is not only simple but also provides the surface of CEMNs with functional groups like-OH. The formation of carbon encapsulated magnetic nanoparticles was not favored when using pure Fe nanoparticles as cores because of the oxidation of Fe nanoparticles by H2O during the reaction and,therefore, the surfaces of the naked Fe nanoparticles had to be coated by Au shell in advance. TEM, XRD, XPS and VSM measurments characterized that they were uniform carbon spheres containing some embedded Fe-Au nanoparticles, with a saturation of 14.6 emu/g and the size of the typical product is ~350 nm.

  10. Method for producing bio-fuel that integrates heat from carbon-carbon bond-forming reactions to drive biomass gasification reactions

    Science.gov (United States)

    Cortright, Randy D.; Dumesic, James A.

    2011-01-18

    A low-temperature catalytic process for converting biomass (preferably glycerol recovered from the fabrication of bio-diesel) to synthesis gas (i.e., H.sub.2/CO gas mixture) in an endothermic gasification reaction is described. The synthesis gas is used in exothermic carbon-carbon bond-forming reactions, such as Fischer-Tropsch, methanol, or dimethylether syntheses. The heat from the exothermic carbon-carbon bond-forming reaction is integrated with the endothermic gasification reaction, thus providing an energy-efficient route for producing fuels and chemicals from renewable biomass resources.

  11. Effect of partial carbonation on the cyclic CaO carbonation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Grasa, G.; Abanades, J.C.; Anthony, E.J. [CSIC, Zaragoza (Spain)

    2009-10-15

    CaO particles from the calcination of natural limestones can be used as regenerable solid sorbents in some CO{sub 2} capture systems. Their decay curves in terms of CO{sub 2} capture capacity have been extensively studied in the literature, always in experiments allowing particles to reach their maximum carbonation conversion for a given cycle. However, at the expected operating conditions in a CO{sub 2} capture system using the carbonation reaction, a relevant fraction of the CaO particles will not have time to fully convert in the carbonator reactor. This work investigates if there is any effect on the decay curves when CaO is only partially converted in each cycle. Experiments have been conducted in a thermobalance arranged to interrupt the carbonation reaction in each cycle before the end of the fast reaction period typical in the CaO-CO{sub 2} reaction. It is shown that, after the necessary normalization of results, the effective capacity of the sorbent to absorb CO{sub 2} during particle lifetime in the capture system slightly increases and CaO particles partially converted behave 'younger' than particles fully converted after every calcination. This has beneficial implications for the design of carbonation/calcination loops.

  12. Application of micro X-ray diffraction to investigate the reaction products formed by the alkali silica reaction in concrete structures

    Energy Technology Data Exchange (ETDEWEB)

    Dähn, R.; Arakcheeva, A.; Schaub, Ph.; Pattison, P.; Chapuis, G.; Grolimund, D.; Wieland, E.; Leemann, A. (Ecole); (PSI); (Phase Solutions); (ESRF)

    2015-12-21

    Alkali–silica reaction (ASR) is one of the most important deterioration mechanisms in concrete leading to substantial damages of structures worldwide. Synchrotron-based micro-X-ray diffraction (micro-XRD) was employed to characterize the mineral phases formed in micro-cracks of concrete aggregates as a consequence of ASR. This particular high spatial resolution technique enables to directly gain structural information on ASR products formed in a 40-year old motorway bridge damaged due to ASR. Micro-X-ray-fluorescence was applied on thin sections to locate the reaction products formed in veins within concrete aggregates. Micro-XRD pattern were collected at selected points of interest along a vein by rotating the sample. Rietveld refinement determined the structure of the ASR product consisting of a new layered framework similar to mountainite and rhodesite. Furthermore, it is conceivable that understanding the structure of the ASR product may help developing new technical treatments inhibiting ASR.

  13. The Reactions of Hot Fluorine-18 with Gaseous Carbon Tetrafluoride

    International Nuclear Information System (INIS)

    Studies on the reactions of hot Fie atoms with carbon tetrafluoride are reported. Gaseous samples were exposed to the 40-60 MeV (maximum) bremsstrahlung beam of the Yale University Electron Accelerator. The F19 (γ, n) F18 process produces F18 with a kinetic energy of the order of 105-106 eV. These species lose energy by collision and are expected to reach the ''chemical'' energy range (18 atoms. Analysis of products was made using standard radio-gas chromatography techniques. The system was found to be quite sensitive to extraneous radiation damage effects and appropriate precautions were taken. Hot displacement reactions, similar to those observed for hot hydrogen, but much less efficient, were found: F18 + CF4 --> CF3F18 + F, F18 +CF4 --> CF2F18 + (F + F), It was impossible to study the abstraction reaction F18 + CF4 --> CF3 + FF18 directly. However, indirect evidence suggests that it also has a low efficiency. Detailed studies of the effect of moderator on the F18 + CF4 system have been made. The data obtained were analysed by means of the kinetic theory of hot reactions. The system was found to be in accord with this formalism, providing quantitative confirmation of the present interpretation of the results. The carbon tetrafluoride and methane systems provide a basis for some tentative conclusions on the mechanisms of hot fluorine atom reactions. At present it appears that with certain important, but natural, modifications the model first developed for hot hydrogen atoms is applicable

  14. Systematic analysis of reaction cross sections of carbon isotopes

    CERN Document Server

    Horiuchi, W; Kohama, A; Suzuki, Y

    2006-01-01

    We systematically analyze total reaction cross sections of carbon isotopes with N=6--16 on a $^{12}$C target for wide range of incident energy. The intrinsic structure of the carbon isotope is described by a Slater determinant generated from a phenomenological mean-field potential, which reasonably well reproduces the ground state properties for most of the even $N$ isotopes. We need separate studies not only for odd nuclei but also for $^{16}$C and $^{22}$C. The density of the carbon isotope is constructed by eliminating the effect of the center of mass motion. For the calculations of the cross sections, we take two schemes: one is the Glauber approximation, and the other is the eikonal model using a global optical potential. We find that both of the schemes successfully reproduce low and high incident energy data on the cross sections of $^{12}$C, $^{13}$C and $^{16}$C on $^{12}$C. The calculated reaction cross sections of $^{15}$C are found to be considerably smaller than the empirical values observed at l...

  15. Carbon Nanowalls for oxygen reduction reaction in Bio Fuel Cells

    International Nuclear Information System (INIS)

    We report on the usage of Carbon Nanowalls (CNW) synthesized by a PECVD process as electrode material for oxygen reduction reaction (ORR). In order to substitute the platinum based catalysts in fuel cells, graphene is a promising candidate. Carbon Nanowalls are a graphene modification with good accessibility and a controllable morphology. By controlling height and pore size, they can be optimized for different applications. A ID/IG ratio around 2.5 and the SEM images indicate vertical nanocrystallin graphene sheets. Tests with ferrocene as electroactive compound verify CNW suitability as electrode material. Cyclic voltammetry measurements in oxygen saturated PBS prove the catalytic activity of CNW towards ORR. The results support the feasibility of CNW as cathode in Bio Fuel Cells

  16. Study of redox reactions to split water and carbon dioxide

    Science.gov (United States)

    Arifin, Darwin

    The development of carbon-neutral, environmentally-sustainable energy carrier is a technological imperative necessary to mitigate the impact of anthropogenic carbon dioxide on earth's climate. One compelling approach rapidly gaining international attention is the conversion of solar energy into renewable fuels, such as H2 or CO, via a two-step thermochemical cycle driven by concentrated solar power. In accordance with the increased interest in this process, there is a need to better understand the gas splitting chemistry on the metal oxide intermediates encountered in such solar-driven processes. Here we measured the H2 and CO production rates during oxidation by H2O and CO2 in a stagnation flow reactor. Redox cycles were performed over various metal oxide chemistries such as hercynite and ceria based materials that are thermally reduced by laser irradiation. In addition to cycle capacity evaluation, reaction kinetics intrinsic to the materials were extracted using a model-based analytical approach to account for the effects of mixing and dispersion in the reactor. Investigation of the "hercynite chemistry" with raman spectroscopy verifies that, at the surface, the cycle proceeds by stabilizing the reduced and oxidized moieties in two different compounds, which allows the thermal reduction reaction to occur to a greater extent at a temperature 150 °C lower than a similarly prepared CoFe2O4-coated m-ZrO2. Investigation of the ceria cycle shows that the water splitting reaction, in the range of 750 - 950 °C and 20 - 40 vol.% H2O, can best be described by a first-order kinetic model with low apparent activation energy (29 kJ/mol). The carbon dioxide splitting reaction, in the range of 650 - 875 °C and 10 - 40 vol.% CO2, is a more complex surface-mediated phenomena that is controlled by a temperature-dependent surface site blocking mechanism involving adsorbed carbon. Moreover, we find that lattice substitution of ceria with zirconium can increase H2 production by

  17. Sarcoidosis patient: an unexpected reaction to carbonic anhydrase enzyme inhibitor

    OpenAIRE

    Khedr, Yahya A H; Khedr, Abdulla H

    2013-01-01

    Ocular diseases are very common in many of the systemic diseases such as sarcoidosis, and may sometimes be the presenting symptom of the disease. In this case report, we present an unusual reaction of the sarcoid granuloma to carbonic anhydrase enzyme inhibitors (CAIs), which was encountered in a patient with ocular sarcoidosis. This observation was taken after a 2-week interval between a CT scan orbits and an MRI orbits which showed a decrease in size from 4×3×4 cm to 2.5×2.5×2 cm, respectiv...

  18. Functionalized multi-walled carbon nanotubes in an aldol reaction

    Science.gov (United States)

    Chronopoulos, D. D.; Kokotos, C. G.; Karousis, N.; Kokotos, G.; Tagmatarchis, N.

    2015-01-01

    The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction between acetone and 4-nitrobenzaldehyde was evaluated for the first time, showing to proceed almost quantitatively in aqueous media. Furthermore, several amino-modified MWCNTs were prepared and examined in the particular aldol reaction. These new hybrid materials exhibited an enhanced catalytic activity in water, contrasting with the pristine MWCNTs as well as the parent organic molecule, which failed to catalyze the reaction efficiently. Furthermore, the modified MWCNTs proved to catalyze the aldol reaction even after three repetitive cycles. Overall, a green approach for the aldol reaction is presented, where water can be employed as the solvent and modified MWCNTs can be used as catalysts, which can be successfully recovered and reused, while their catalytic activity is retained.The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction

  19. Recovery of alkali metal constituents from catalytic coal conversion residues

    Science.gov (United States)

    Soung, W.Y.

    In a coal gasification operation (32) or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by contacting them with water or an aqueous solution to remove water-soluble alkali metal constituents and produce an aqueous solution enriched in said constituents. The aqueous solution thus produced is then contacted with carbon dioxide to precipitate silicon constituents, the pH of the resultant solution is increased, preferably to a value in the range between about 12.5 and about 15.0, and the solution of increased pH is evaporated to increase the alkali metal concentration. The concentrated aqueous solution is then recycled to the conversion process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst.

  20. Reaction between molybdenum and carbon, and several carbides

    International Nuclear Information System (INIS)

    Diffusion couples of molybdenum with carbon and several carbides, i.e. B4C, SiC, TiC, and TaC, respectively, were heated for up to 3.6 x 105 s at various temperatures ranging from 1373 to 2223 K. The couples were then examined for composition, growth rate, structure, and hardness of reaction layers. Main results obtained are as follows: (1) In the Mo-C system, only Mo2C layer was formed at below 1873 K, while two sub- layers consisted of Mo2C and eta (MoC sub(1-x)), respectively, were found at above 1873 K. The activation energy for growth of total layer was 374 kJ/mol. (2) In the Mo-B4C system, two sub-layers consisted of Mo2B and MoB, respectively, with dispersed carbon particles were formed. (3) In the Mo-SiC system, Mo2C layer, including eta (MoC sub(1-x)) phase at high temperature, mixture of Mo2C and Mo3Si2 phases, and Mo3Si2 phase in order from the Mo side were formed. The activation energy for growth of total layer was 477 kJ/mol. (4) In the Mo-TiC system, two kinds of TiC in point of view of free carbon content were used; one is with 0.2% free carbon and the other is with 0.01%. In the Mo-TiC with 0.2% free carbon system, two sub-layers, i.e. relatively thick Mo2C layer and thin (Ti, Mo)C layer, were formed, while in the Mo-TiC with 0.01% free carbon system two thin sub-layers, Mo2C and (Ti, Mo)C, were formed; the Mo2C layer in the latter case was very thin and was not found after short time heating at low temperature. The activation energy for growth of Mo2C layer in the former system was 393 kJ/mol. (5) In the Mo-TaC with 0.02% free carbon system, two thin sub-layers, (Mo, Ta)2C and (Ta, Mo)C, were observed. (6) TEM studies on the interface between Mo (bcc) and Mo2C (hcp) showed that there was the following orientation relation, called as the Burgers relation, between these two phases; (110)sub(Mo)//(0001)sub(Mo2C), sub(Mo)//-0>sub(Mo2C). (author)

  1. Efficiency enhancement of organic light-emitting diodes with an oxygen-plasma-treated ITO substrate and an electron-injection layer of alkali-metal carbonates

    International Nuclear Information System (INIS)

    The efficiency enhancement of organic light-emitting diodes with an oxygen-plasma-treated substrate and an electron-injection layer of alkali-metal carbonates (Li2CO3 and Cs2CO3) was studied. The Li2CO3 and the Cs2CO3 carbonates were thermally evaporated to a thickness of 1 nm. For the device with a Li2CO3 layer, the luminance at 9.25 V of the device with the plasma-treated ITO substrate was found to be improved by approximately 10% compared to that of the device with the plasma-untreated ITO substrate, and the maximum luminance driving voltage was lowered by 1.0 V. For the device with a Cs2CO3 layer, the luminance at 11.25 V of the device with the oxygen plasma-treated ITO substrate was found to be improved by approximately 42.3% compared to that of the device with plasma-untreated ITO substrate, and the maximum luminance driving voltage was lowered by 1.25 V. Especially, the luminous efficiencies of the devices with the Li2CO3 and the Cs2CO3 layers were confirmed to have been increased by 50.0% and 78.1%, respectively, when the oxygen-plasma-treated ITO substrate was used.

  2. Methods for synthesizing diethyl carbonate from ethanol and supercritical carbon dioxide by one-pot or two-step reactions in the presence of potassium carbonate

    OpenAIRE

    Gasc, Fabien; Thiebaud-Roux, Sophie; Mouloungui, Zephirin

    2009-01-01

    Carbon dioxide sequestration was studied by synthesizing diethyl carbonate (DEC) from ethanol and CO2 under supercritical conditions in the presence of potassium carbonate as a base. The co-reagent was ethyl iodide or a concentrated strong acid. This sequestration reaction occurs in two steps, which were studied separately and in a one-pot reaction. An organic-inorganic carbonate hybrid, potassium ethyl carbonate (PEC) is generated at the end of the first step. This intermediate was character...

  3. Milk-alkali syndrome

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/000332.htm Milk-alkali syndrome To use the sharing features on this page, please enable JavaScript. Milk-alkali syndrome is a condition in which there ...

  4. Carbon and oxygen isotope separation by plasma chemical reactions in carbon monoxide glow discharge

    International Nuclear Information System (INIS)

    The separation of carbon and oxygen isotopes in CO glow discharge has been studied. The isotope enrichment in the products was measured by quadru-pole mass spectrometer. The reaction yield and empirical formula of solid phase products were determined by the gas-volumetric analysis. The stable products obtained in our experiment are CO2 and solid polymers formed on the discharge wall. The polymer consists of both carbon and oxygen and the oxygen/carbon mole ratio in the polymer is 0.35±0.05. Thi isotope enrichment coefficients show a strong negative dependence on discharge current though the relative reaction yields have an opposite tendency. Consequently, the maximum isotope enrichment coefficients for 13C in wall deposit of 2.31 and for 18O in CO2 of 1.37 are obtained when the discharge current and the reaction yields are minimum in our experimental range. The experimental results of isotope enrichment have been compared with theoretical values estimated by an analytical model of literature. The dilution mechanism of the isotope enrichment of stable products is inferred from the isotopic distributions of 13C and 18O in products and theoretical predictions for isotope enrichment. (author)

  5. High effective silica fume alkali activator

    Indian Academy of Sciences (India)

    Vladimír Živica

    2004-04-01

    Growing demands on the engineering properties of cement based materials and the urgency to decrease unsuitable ecologic impact of Portland cement manufacturing represent significant motivation for the development of new cement corresponding to these aspects. One category represents prospective alkali activated cements. A significant factor influencing their properties is alkali activator used. In this paper we present a new high effective alkali activator prepared from silica fume and its effectiveness. According to the results obtained this activator seems to be more effective than currently used activators like natrium hydroxide, natrium carbonate, and water glass.

  6. Carbon-coated magnetic palladium: applications in partial oxidation of alcohols and coupling reactions.

    Science.gov (United States)

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; catalyst can be used for oxidation of alcohols, amination reaction and arylation of aryl halides (cross coupli...

  7. Radiation induced chemical reaction of carbon monoxide and hydrogen mixture

    International Nuclear Information System (INIS)

    Previous studies of radiation induced chemical reactions of CO-H2 mixture have revealed that the yields of oxygen containing products were larger than those of hydrocarbons. In the present study, methane was added to CO-H2 mixture in order to increase further the yields of the oxygen containing products. The yields of most products except a few products such as formaldehyde increased with the addition of small amount of methane. Especially, the yields of trioxane and tetraoxane gave the maximum values when CO-H2 mixture containing 1 mol% methane was irradiated. When large amounts of methane were added to the mixture, the yields of aldehydes and carboxylic acids having more than two carbon atoms increased, whereas those of trioxane and tetraoxane decreased. From the study at reaction temperature over the range of 200 to 473 K, it was found that the yields of aldehydes and carboxylic acids showed maxima at 323 K. The studies on the effects of addition of cationic scavenger (NH3) and radical scavenger (O2) on the products yields were also carried out on the CO-H2-CH4 mixture. (author)

  8. Complete reaction mechanisms of mercury oxidation on halogenated activated carbon.

    Science.gov (United States)

    Rungnim, Chompoonut; Promarak, Vinich; Hannongbua, Supa; Kungwan, Nawee; Namuangruk, Supawadee

    2016-06-01

    The reaction mechanisms of mercury (Hg) adsorption and oxidation on halogenated activated carbon (AC) have been completely studied for the first time using density functional theory (DFT) method. Two different halogenated AC models, namely X-AC and X-AC-X (X=Cl, Br, I), were adopted. The results revealed that HgX is found to be stable-state on the AC edge since its further desorption from the AC as HgX, or further oxidation to HgX2, are energetically unfavorable. Remarkably, the halide type does not significantly affect the Hg adsorption energy but it strongly affects the activation energy barrier of HgX formation, which obviously increases in the order HgIelimination significantly decreases as I-AC>Br-AC>Cl-AC. Thus, the study of the complete reaction mechanism is essential because the adsorption energy can not be used as a guideline for the rational material design in the halide impregnated AC systems. The activation energy is an important descriptor for the predictions of sorbent reactivity to the Hg oxidation process. PMID:26943019

  9. Synthesis of beta carbon nitride nanosized crystal through mechanochemical reaction

    CERN Document Server

    Yin Long Wei; Liu Yu Xian; Sui Jin Ling; Wang Jing Min

    2003-01-01

    Nanosized beta carbon nitride (beta-C sub 3 N sub 4), of grain size several tens of nanometres, has been synthesized by mechanochemical reaction processing. The low-cost synthetic method developed facilitates the novel and effective synthesis of nanosized crystalline beta-C sub 3 N sub 4 (a = 6.36 A, c = 4.648 A) powders. The graphite powders were first milled to a nanoscale state, then the nanosized graphite powders were milled in an atmosphere of NH sub 3 gas. It was found that nanosized beta-C sub 3 N sub 4 was formed after high-energy ball milling under an NH sub 3 atmosphere. After thermal annealing, the shape of the beta-C sub 3 N sub 4 changes from flake-like to sphere-like. The nanosized beta-C sub 3 N sub 4 formed was characterized by x-ray diffraction, Fourier transformation infrared spectroscopy, and transmission electron microscopy. A solid-gas reaction mechanism was proposed for the formation of nanosized beta-C sub 3 N sub 4 at room temperature induced by mechanochemical activation.

  10. Behavior of shungite carbon in reactions simulating thermal transformations of coal

    Energy Technology Data Exchange (ETDEWEB)

    Grigor' eva, E.N.; Rozhkova, N.N. [Russian Academy of Science, Moscow (Russian Federation)

    2000-07-01

    The catalytic activity of shungite carbon in reactions of model compounds (tetralin and benzyl phenyl ether) simulating thermolysis of coal was studied. The orders, rate constants, and activation energies of reactions were determined.

  11. "Homeopathic" palladium nanoparticle catalysis of cross carbon-carbon coupling reactions.

    Science.gov (United States)

    Deraedt, Christophe; Astruc, Didier

    2014-02-18

    Catalysis by palladium derivatives is now one of the most important tools in organic synthesis. Whether researchers design palladium nanoparticles (NPs) or nanoparticles occur as palladium complexes decompose, these structures can serve as central precatalysts in common carbon-carbon bond formation. Palladium NPs are also valuable alternatives to molecular catalysts because they do not require costly and toxic ligands. In this Account, we review the role of "homeopathic" palladium catalysts in carbon-carbon coupling reactions. Seminal studies from the groups of Beletskaya, Reetz, and de Vries showed that palladium NPs can catalyze Heck and Suzuki-Miyaura reactions with aryl iodides and, in some cases, aryl bromides at part per million levels. As a result, researchers coined the term "homeopathic" palladium catalysis. Industry has developed large-scale applications of these transformations. In addition, chemists have used Crooks' concept of dendrimer encapsulation to set up efficient nanofilters for Suzuki-Miyaura and selective Heck catalysis, although these transformations required high PdNP loading. With arene-centered, ferrocenyl-terminated dendrimers containing triazolyl ligands in the tethers, we designed several generations of dendrimers to compare their catalytic efficiencies, varied the numbers of Pd atoms in the PdNPs, and examined encapsulation vs stabilization. The catalytic efficiencies achieved "homeopathic" (TON = 540 000) behavior no matter the PdNP size and stabilization type. The TON increased with decreasing the Pd/substrate ratio, which suggested a leaching mechanism. Recently, we showed that water-soluble arene-centered dendrimers with tri(ethylene glycol) (TEG) tethers stabilized PdNPs involving supramolecular dendritic assemblies because of the interpenetration of the TEG branches. Such PdNPs are stable and retain their "homeopathic" catalytic activities for Suzuki-Miyaura reactions for months. (TONs can reach 2.7 × 10(6) at 80 °C for aryl

  12. Reaction of ISSR Molecular Marker Primers Screening for Saline-alkali Tolerant Flax%亚麻耐盐碱ISSR标记引物筛选的研究

    Institute of Scientific and Technical Information of China (English)

    赵东升

    2013-01-01

      为选育耐盐碱亚麻品种,探讨亚麻耐盐碱分子辅助育种手段,以亚麻耐盐碱材料7000 ha-1和不耐盐碱材料原05-10为材料,对100条ISSR引物进行了筛选。结果表明:筛选出25条在两个品种间有特异性的引物,为进一步ISSR标记应用于亚麻群体分析奠定基础。%In order to breed saline-alkali tolerant flax varieties for saline-alkali tolerant molecular assisted breed-ing means of flax .Taking two saline-alkali tolerant flax varieties 7 000 ha-1 and 05-10 as materials ,100 pairs of ISSR primers were screened .The results showed that 25 pairs of primers had specific between two varieties and that would be a foundation for analyzing groups of flax .

  13. Alkali metal ion storage properties of sulphur and phosphorous molecules encapsulated in nanometer size carbon cylindrical pores

    Directory of Open Access Journals (Sweden)

    Yosuke Ishii

    2016-03-01

    Full Text Available We investigated the physical and chemical stabilities of sulfur and phosphorus molecules encapsulated in a mesoporous carbon (MPC and two kinds of single-walled carbon nanotubes (SWCNTs having different cylindrical pore diameters. The sublimation temperatures of sulfur molecules encapsulated in MPC and the two kinds of SWCNTs were measured by thermo-gravimetric measurements. It was found that the sublimation temperature of sulfur molecules encapsulated in SWCNTs having mean tube diameter of 1.5 nm is much higher than any other molecules encapsulated in larger pores. It was also found that the capacity fading of lithium-sulfur battery can be diminished by encapsulation of sulfur molecules in SWCNTs. We also investigated the electrochemical properties of phosphorus molecules encapsulated in SWCNTs (P@SWCNTs. It was shown that P@SWCNT can adsorb and desorb both Li and Na ions reversibly.

  14. Alkali metal ion storage properties of sulphur and phosphorous molecules encapsulated in nanometer size carbon cylindrical pores

    Science.gov (United States)

    Ishii, Yosuke; Sakamoto, Yuki; Song, Hayong; Tashiro, Kosuke; Nishiwaki, Yoshiki; Al-zubaidi, Ayar; Kawasaki, Shinji

    2016-03-01

    We investigated the physical and chemical stabilities of sulfur and phosphorus molecules encapsulated in a mesoporous carbon (MPC) and two kinds of single-walled carbon nanotubes (SWCNTs) having different cylindrical pore diameters. The sublimation temperatures of sulfur molecules encapsulated in MPC and the two kinds of SWCNTs were measured by thermo-gravimetric measurements. It was found that the sublimation temperature of sulfur molecules encapsulated in SWCNTs having mean tube diameter of 1.5 nm is much higher than any other molecules encapsulated in larger pores. It was also found that the capacity fading of lithium-sulfur battery can be diminished by encapsulation of sulfur molecules in SWCNTs. We also investigated the electrochemical properties of phosphorus molecules encapsulated in SWCNTs (P@SWCNTs). It was shown that P@SWCNT can adsorb and desorb both Li and Na ions reversibly.

  15. Corrosion-electrochemical behavior of nickel in an alkali metal carbonate melt under a chlorine-containing atmosphere

    OpenAIRE

    Nikitina, E. V.; Kudyakov, V. Y.; Malkov, V. B.; Plaksin, S. V.

    2013-01-01

    The corrosion-electrochemical behavior of a nickel electrode is studied in the melt of lithium, sodium, and potassium (40: 30: 30 mol %) carbonates in the temperature range 500-600°C under an oxidizing atmosphere CO2 + 0.5O2 (2: 1), which is partly replaced by gaseous chlorine (30, 50, 70%) in some experiments. In other experiments, up to 5 wt % chloride of sodium peroxide is introduced in a salt melt. A change in the gas-phase composition is shown to affect the mechanism of nickel corrosion....

  16. Carbonates in leaching reactions in context of 14C dating

    Science.gov (United States)

    Michalska, Danuta; Czernik, Justyna

    2015-10-01

    Lime mortars as a mixture of binder and aggregate may contain carbon of various origins. If the mortars are made of totally burnt lime, radiocarbon dating of binder yields the real age of building construction. The presence of carbonaceous aggregate has a significant influence on the 14C measurements results and depending on the type of aggregate and fraction they may cause overaging. Another problem, especially in case of hydraulic mortars that continue to be chemically active for a very long time, is the recrystallization usually connected with rejuvenation of the results but also, depending on local geological structures, with so called reservoir effect yielding apparent ages. An attempt in separating the binder from other carbonaceous components successfully was made for samples from Israel by Nawrocka-Michalska et al. (2007). The same preparation procedure, after taking into account the petrographic composition, was used for samples coming from Poland, Nawrocka et al. (2009). To verify the procedure used previously for non-hydraulic samples determination an experimental tests on carbonaceous mortars with crushed bricks from Novae in Bulgaria were made. Additionally, to identify different carbonaceous structures and their morphology, a cathodoluminescence and scanning electron microscope with electron dispersive spectrometer were applied. The crushed bricks and brick dust used in mortars production process have been interpreted as an alternative use to other pozzolanic materials. The reaction between lime and pozzolanic additives take place easily and affects the rate and course of carbonates decomposition in orthophosphric acid, during the samples pretreatment for dating. The composition of the Bulgarian samples together with influence of climate conditions on mortar carbonates do not allow for making straightforward conclusions in chronology context, but gives some new guidelines in terms of hydraulic mortars application for dating. This work has mainly

  17. Metal doped carbon nanoneedles and effect of carbon organization with activity for hydrogen evolution reaction (HER).

    Science.gov (United States)

    Araujo, Rafael A; Rubira, Adley F; Asefa, Tewodros; Silva, Rafael

    2016-02-10

    Cellulose nanowhiskers (CNW) from cotton, was prepared by acid hydrolysis and purified using a size selection process to obtain homogeneous samples with average particle size of 270 nm and 85.5% crystallinity. Purified CNW was used as precursor to carbon nanoneedles (CNN) synthesis. The synthesis of CNN loaded with different metals dopants were carried out by a nanoreactor method and the obtained CNNs applied as electrocatalysts for hydrogen evolution reaction (HER). In the carbon nanoneedles synthesis, Ni, Cu, or Fe worked as graphitization catalyst and the metal were found present as dopants in the final material. The used metal appeared to have direct influence on the degree of organization of the particles and also in the surface density of polar groups. It was evaluated the influence of the graphitic organization on the general properties and nickel was found as the more appropriate metal since it leads to a more organized material and also to a high activity toward HER. PMID:26686184

  18. Corrosion testing of zirconia, beryllia and magnesia ceramics in molten alkali metal carbonates at 900 °C

    Science.gov (United States)

    Kaplan, Valery; Bendikov, Tatyana; Feldman, Yishay; Gartsman, Konstantin; Wachtel, Ellen; Lubomirsky, Igor

    2016-01-01

    An electrochemical cell containing molten Li2CO3-Li2O at 900 °C has been proposed for the conversion of the greenhouse gas CO2 to CO for chemical energy storage. In the current work, we have examined the corrosion resistance of zirconia, beryllia and magnesia ceramics at 900 °C in the Li2CO3-Li2O and Li-Na-K carbonate eutectic mixtures to identify suitable electrically insulating materials. Conclusions regarding material stability were based on elemental analysis of the melt, primarily via X-ray photoelectron spectroscopy, a particularly sensitive technique. It was found that magnesia is completely stable for at least 33 h in a Li2CO3-Li2O melt, while a combined lithium titanate/lithium zirconate layer forms on the zirconia ceramic as detected by XRD. Under the same melt conditions, beryllia shows considerable leaching into solution. In a Li-Na-K carbonate eutectic mixture containing 10.2 mol% oxide at 900 °C under standard atmospheric conditions, magnesia showed no signs of degradation. Stabilization of the zirconia content of the eutectic mixture at 0.01-0.02 at% after 2 h is explained by the formation of a lithium zirconate coating on the ceramic. On the basis of these results, we conclude that only magnesia can be satisfactorily used as an insulating material in electrolysis cells containing Li2CO3-Li2O melts.

  19. Reaction in plasma generated in supercritical carbon dioxide

    International Nuclear Information System (INIS)

    The generation of non-thermal plasmas was studied under supercritical conditions. This is interesting in view of both the basic phenomena involved and of potential industrial applications. When supercritical fluids are combined with discharge plasma they develop unique characteristics, including an enhanced chemical reactivity. This is the motivation for investigating the generation of discharge plasma in supercritical CO2. In this study, breakdown voltages were measured in CO2 in order to generate electric discharges in supercritical CO2. The experimental data show that the breakdown voltage increased smoothly up to the intersection points, but beyond these points the rates of increase of the breakdown voltage are different. This phenomenon can be explained with the help of pressure-density curves of carbon dioxide at a constant temperature. In addition, the generated plasma in supercritical CO2 was applied to several chemical reactions. The alpha conversion of tocopherols and transesterification of soybean oil with methanol were investigated. In addition, we explored the possibility of replacing catalysts with plasma in supercritical CO2

  20. Reaction in plasma generated in supercritical carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Goto, M; Sasaki, M; Kiyan, T; Fang, T; Roy, B C; Namihira, T; Akiyama, H; Hara, M [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan)], E-mail: mgoto@kumamoto-u.ac.jp

    2008-07-15

    The generation of non-thermal plasmas was studied under supercritical conditions. This is interesting in view of both the basic phenomena involved and of potential industrial applications. When supercritical fluids are combined with discharge plasma they develop unique characteristics, including an enhanced chemical reactivity. This is the motivation for investigating the generation of discharge plasma in supercritical CO{sub 2}. In this study, breakdown voltages were measured in CO{sub 2} in order to generate electric discharges in supercritical CO{sub 2}. The experimental data show that the breakdown voltage increased smoothly up to the intersection points, but beyond these points the rates of increase of the breakdown voltage are different. This phenomenon can be explained with the help of pressure-density curves of carbon dioxide at a constant temperature. In addition, the generated plasma in supercritical CO{sub 2} was applied to several chemical reactions. The alpha conversion of tocopherols and transesterification of soybean oil with methanol were investigated. In addition, we explored the possibility of replacing catalysts with plasma in supercritical CO{sub 2}.

  1. A Study on Reactions of Carbon-Carbonate Mixture at Elevated Temperature : As an Anode Media of SO-DCFC

    International Nuclear Information System (INIS)

    A direct carbon fuel cell (DCFC) generates electricity directly by converting the chemical energy in coal. In particular, a DCFC system with a solid oxide electrolyte and molten carbonate anode media has been proposed by SRI. In this system, however, there are conflicting effects of temperature, which enhances the ion conductivity of the solid electrolyte and reactivity at the electrodes while causing a stability problem for the anode media. In this study, the effect of temperature on the stability of a carbon-carbonate mixture was investigated experimentally. TGA analysis was conducted under either nitrogen or carbon dioxide ambient for Li2 CO3, K2 CO3, and their mixtures with carbon black. The composition of the exit gas was also monitored during temperature elevation. A simplified reaction model was suggested by considering the decomposition of carbonates and the catalyzed Boudouard reactions. The suggested model could well explain both the measured weight loss of the mixture and the gas formation from it

  2. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

    KAUST Repository

    Stoltz, Brian

    2010-06-14

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

  3. Carbon dioxide sequestration via olivine carbonation: Examining the formation of reaction products

    Science.gov (United States)

    King, H. E.; Plümper, O.; Putnis, A.

    2009-04-01

    Due to its abundance and natural ability to sequester CO2, olivine has been proposed as one mineral that could be used in the control of CO2 emissions into the atmosphere (Metz, 2005). Large scale peridotite deposits found in locations such as the Western Gneiss Region in Norway could provide in-situ sites for sequestration or the raw materials for ex-situ mineral carbonation. Determining the conditions under which magnesite (MgCO3) forms most efficiently is crucial to conduct a cost effective process. Understanding the development of secondary minerals is particularly important for in-situ methods as these phases can form passivating layers and affect the host rock porosity. The final solution of flow-through experiments conducted at alkaline pH have been shown to be supersaturated with respect to talc and chrysotile (Giammer et al., 2005), although these phases were not found to have precipitated the formation of a passivating, amorphous silica layer has been observed on reacted olivine surfaces (Bearat et al., 2006). By studying magnesite and other products produced during the carbonation of olivine within Teflon lined steel autoclaves we have begun to form a more comprehensive understanding of how these reactions would proceed during sequestration processes. We have performed batch experiments using carbonated saline solutions in the presence of air or gaseous CO2 from 80 to 200 ˚ C. X-ray powder diffraction was used to identify magnesite within the reaction products. Crystals of magnesite up to 20 m in diameter can be observed on olivine grain surfaces with scanning electron microscopy. Secondary reaction products formed a platy layer on olivine surfaces in reactions above 160 ˚ C and below pH 12. Energy dispersive X-ray analysis of the platy layer revealed an increase in Fe concentration. The macroscopically observable red colouration of the reaction products and Raman spectroscopy indicate that hematite is present in these layers. For experiments with

  4. Alkaline direct ethanol fuel cell performance using alkali-impregnated polyvinyl alcohol/functionalized carbon nano-tube solid electrolytes

    Science.gov (United States)

    Huang, Chien-Yi; Lin, Jia-Shiun; Pan, Wen-Han; Shih, Chao-Ming; Liu, Ying-Ling; Lue, Shingjiang Jessie

    2016-01-01

    This study investigates the application of a polyvinyl alcohol (PVA)/functionalized carbon nano-tubes (m-CNTs) composite in alkaline direct ethanol fuel cells (ADEFC). The m-CNTs are functionalized with PVA using the ozone mediation method, and the PVA composite containing the modified CNTs is prepared. Adding m-CNT into the PVA matrix enhances the alkaline uptake and the ionic conductivity of the KOH-doped electrolyte. Meanwhile, the m-CNT-containing membrane exhibited a lower swelling ratio and suppressed ethanol permeability compared to the pristine PVA film. The optimal condition for the ADEFC is determined to be under operation at an anode feed of 3 M ethanol in a 5 M KOH solution (at a flow rate of 5 cm3 min-1) with a cathode feed of moisturized oxygen (with a flow rate of 100 cm3 min-1) and the KOH-doped PVA/m-CNT electrolyte. We achieved a peak power density value of 65 mW cm-2 at 60 °C, which is the highest among the ADEFC literature data and several times higher than the proton-exchange direct ethanol fuel cells using sulfonated membrane electrolytes. Therefore, the KOH-doped PVA/m-CNT electrolyte is a suitable solid electrolyte for ADEFCs and has potential for commercialization in alkaline fuel cell applications.

  5. Kinetic study of the reaction of uranium with various carbon-containing gases; Etude cinetique de la reaction sur l'uranium de differents gaz carbones

    Energy Technology Data Exchange (ETDEWEB)

    Feron, G. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1963-09-15

    The kinetic study of the reaction U + CO{sub 2} and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C The reaction with carbon monoxide leads to a mixture of dioxide UO{sub 2}, dicarbide UC{sub 2} and free carbon. The main reaction can be written. U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO{sub 2} and UC{sub 2} can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO{sub 2} and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [French] L'etude cinetique des reactions U sol + CO{sub 2} gaz et U sol + CO gaz a ete effectuee par thermogravirnetrie sur une poudre d'uranium a grains spheriques, les domaines de temperature etudies s'etendant respectivement de 460 a 690 deg. C et de 570 a 850 deg. C. L'action du dioxyde de carbone conduit au dioxyde d'uranium UO{sub 2}; il se produit en meme temps un depot de carbone. La reaction globale resulte des deux reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C Le mono-oxyde de carbone conduit a un melange de dioxyde UO{sub 2}, de dicarbure UC{sub 2} et de carbone libre. La reaction principale s'ecrit: U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} Le carbone libre provient de la dismutation du mono-oxyde de carbone. On observe une separation remarquable des deux phases UO{sub 2} et UC{sub 2}; un mecanisme

  6. Steam gasification of carbon: Catalyst properties

    Energy Technology Data Exchange (ETDEWEB)

    Falconer, J.L.

    1991-09-16

    This research uses several techniques to measure the concentration of catalyst sites and determine their stoichiometry for the catalyzed gasification of carbon. Both alkali and alkaline earth oxides are effective catalysts for accelerating the gasification rate of coal chars, but only a fraction of the catalyst appears to be in a form that is effective for gasification, and the composition of that catalyst is not established. Transient techniques, with {sup 13}C labeling, are being used to study the surface processes, to measure the concentration of active sites, and to determine the specific reaction rates. We have used secondary ion mass spectroscopy (SIMS) for both high surface area samples of carbon/alkali carbonate mixtures and for model carbon surfaces with deposited alkali atoms. SIMS provides a direct measure of surface combination of these results can provide knowledge of catalyst dispersion and composition, and thus indicate the way to optimally utilize carbon gasification catalysts.

  7. Carbon catalysis of reactions in the lithium SOCl2 and SO2 systems

    Science.gov (United States)

    Kilroy, W. P.

    1981-01-01

    Certain hazards associated with lithium batteries have delayed widespread acceptance of these power sources. The reactivity of ground lithium carbon mixtures was examined. The effect of carbon types on this reactivity was determined. The basic reaction involved mixtures of lithium and carbon with battery electrolyte. The various parameters that influenced this reactivity included: the nature and freshness of the carbon; the freshness, the purity, and the conductive salt of the electrolyte; and the effect of Teflon or moisture.

  8. Kinetic study of the reaction of uranium with various carbon-containing gases

    International Nuclear Information System (INIS)

    The kinetic study of the reaction U + CO2 and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO2 → UO2 + 2 CO U + CO2 → UO2 + C The reaction with carbon monoxide leads to a mixture of dioxide UO2, dicarbide UC2 and free carbon. The main reaction can be written. U + CO → 1/2 UO2 + 1/2 UC2 The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO2 and UC2 can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO2 and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author)

  9. Impacts of carbon nanotubes on biochemical reactions: insight into interaction between carbon nanotubes and DNA polymerase enzyme

    OpenAIRE

    Uysal, Ebru; Meral, Yüce; Meral, Yuce; Hasan KURT

    2014-01-01

    Recently, the Polymerase Chain Reaction technique has begun to benefit from nanotechnology. In this paper, effects of carbon nanotubes in the Polymerase Chain Reaction were investigated by Electrophoresis, Circular Dichroism Spectrometry and Dynamic Light Scattering Techniques. The unique ability to amplify low copy number DNA within minutes has made in vitro Polymerase Chain Reaction (PCR) one of the most essential techniques in modern biology. In order to harness this technique to its full ...

  10. Inhibition of the maillard reaction in the process of making rice bran protein by alkali method%碱法制取米糠蛋白过程中美拉德反应的抑制

    Institute of Scientific and Technical Information of China (English)

    王雪; 于鹏; 周雪松; 张智; 于殿宇

    2013-01-01

    应用葡萄糖氧化酶(GOD)对米糠中的葡萄糖进行氧化抑制,通过单因素实验,考察了酶解过程中反应温度、pH、反应时间、GOD添加量对蛋白色素抑制率的影响,并在单因素水平的基础上进行响应面优化实验,确定了反应的最佳条件:反应温度45℃,pH5.5,反应时间25min,GOD添加量0.035%,在优化出的最佳条件下进行反应,得到的蛋白色素抑制率为62.73%,说明向米糠中添加GOD可有效改善碱提酸沉法提取米糠蛋白后的色泽,提高蛋白的色素抑制率.%The purpose of the present study was to optimize the process of making rice bran protein by alkali method using single-factor tests and response surface methodology,glucose oxidase was used to inhibit the oxidation of glucose in the rice bran.The effect of reaction temperature,pH,reaction time,the GOD addition amount on the protein pigment inhibition rate in the enzymatic process was investigated,and on the basis of the single-factor test,the optimum conditions of reaction was determined by response surface methodology.The reaction temperature was 45℃,the reaction pH was 5.5,the reaction time was 25min,the addition amount of GOD was 0.035%.The pigment inhibition rate reached to 62.73% on the optimum conditions.Results indicated that this method could improve the color after extraction of rice bran protein by alkali extraction and acid precipitation,and increase protein pigment inhibition rate effectually.

  11. Hybrid direct carbon fuel cells and their reaction mechanisms - a review

    DEFF Research Database (Denmark)

    Deleebeeck, Lisa; Kammer Hansen, Kent

    2014-01-01

    with carbon capture and storage (CCS) due to the high purity of CO2 emitted in the exhaust gas. Direct carbon (or coal) fuel cells (DCFCs) are directly fed with solid carbon to the anode chamber. The fuel cell converts the carbon at the anode and the oxygen at the cathode into electricity, heat and...... efforts is discussed on the fuel cell stack and system levels. The range of DCFC types can be roughly broken down into four fuel cell types: aqueous hydroxide, molten hydroxide, molten carbonate and solid oxide fuel cells. Emphasis is placed on the electrochemical reactions occurring at the anode and the...... proposed mechanism(s) of these reactions for molten carbonate, solid oxide and hybrid direct carbon fuel cells. Additionally, the criteria of choosing the ‘best’ DCFC technology is explored, including system design (continuous supply of solid fuel), performance (power density, efficiency), environmental...

  12. Studies of reductive elimination reactions to form carbon-oxygen bonds from Pt(IV) complexes.

    Science.gov (United States)

    Williams, B S; Goldberg, K I

    2001-03-21

    The platinum(IV) complexes fac-L(2)PtMe(3)(OR) (L(2) = bis(diphenylphosphino)ethane, o-bis(diphenylphosphino)benzene, R = carboxyl, aryl; L = PMe(3), R = aryl) undergo reductive elimination reactions to form carbon-oxygen bonds and/or carbon-carbon bonds. The carbon-oxygen reductive elimination reaction produces either methyl esters or methyl aryl ethers (anisoles) and L(2)PtMe(2), while the carbon-carbon reductive elimination reaction affords ethane and L(2)PtMe(OR). Choice of reaction conditions allows the selection of either type of coupling over the other. A detailed mechanistic study of the reductive elimination reactions supports dissociation of the OR(-) ligand as the initial step for the C-O bond formation reaction. This is followed by a nucleophilic attack of OR(-) upon a methyl group bound to the Pt(IV) cation to produce the products MeOR and L(2)PtMe(2). C-C reductive elimination proceeds from L(2)PtMe(3)(OR) by initial L (L = PMe(3)) or OR(-) (L(2) = dppe, dppbz) dissociation, followed by C-C coupling from the resulting five-coordinate intermediate. Our studies demonstrate that both C-C and C-O reductive elimination reactions from Pt(IV) are more facile in polar solvents, in the presence of Lewis acids, and for OR(-) groups that contain electron withdrawing substituents. PMID:11456927

  13. Calcium silicate hydrate: Crystallisation and alkali sorption

    International Nuclear Information System (INIS)

    Homogeneous single C-S-H gels has been prepared for the investigation of alkali binding potential and crystallisation. A distribution coefficient, Rd, was introduced to express the partition of alkali between solid and aqueous phases at 25 deg. C. Rd is independent of alkali hydroxide concentration and depends only on Ca:Si ratio over wide ranges of alkali concentration. The trend of numerical values of Rd indicates that alkali bonding into the solid improves as its Ca:Si ratio decreases. Reversibility is demonstrated, indicating a possibility of constant Rd value of the material. Al has been introduced to form C-A-S-H gels and their alkali sorption properties also determined. Al substituted into C-S-H markedly increases Rd, indicating enhancement of alkali binding. However, the dependence of Rd on alkali concentration is non-ideal with composition. A two-site model for bonding is presented. Crystallisation both under saturated steam and 1 bar vapour pressure has been investigated. It has been shown that heat treatment by saturated steam causes crystallisation of gels. The principal minerals obtained were (i) C-S-H gel and Ca(OH)2 at -55 deg. C, (ii) 1.1 nm tobermorite, jennite and afwillite at 85 -130 deg. C, and (iii) xonotlite, foshagite and hillebrandite at 150-180 deg. C. Properties of crystalline C-S-H were also reported for reversible phase transformation, pH conditioning ability, seeding effect and solubility. At 1 bar pressure, crystallisation is slower than in saturated steam due to lower water activity. Tobermorite-like nanodomains develop during reaction at low Ca/Si ratios. In some Ca-rich compositions, Ca(OH)2 is exsolved and occurs as nano-sized crystallites. (author)

  14. The Path of Carbon in Photosynthesis IX. Photosynthesis, Photoreduction, and the Hydrogen-Oxygen-Carbon Dioxide Dark Reaction

    Science.gov (United States)

    Badin, E. J.; Calvin, M.

    1950-02-01

    A comparison of the rates of fixation of Carbon 14 dioxide in algae for the processes of photosynthesis, photoreduction and the hydrogen-oxygen-carbon dioxide dark reaction has been made. For the same series of experiments, rates of incorporation of tracer carbon into the separate soluble components using the radiogram method have been determined. The mechanism of carbon dioxide uptake has been shown to occur via two distinct paths. In all cases studied, essentially the same compounds appear radioactive. The distribution with time, however, differs markedly.

  15. Dilepton spectroscopy at intermediate energies; the carbon - carbon reaction at 1 GeV/A

    International Nuclear Information System (INIS)

    The Physics context of this work is heavy ion collisions at relativistic energies where di-electron provide informations on the produced hot and dense nuclear matter. The experiment is performed by the DiLepton Spectrometer (DLS) Collaboration at the Lawrence Berkeley's Bevalac. After a description of the apparatus, we review the whole program and the main results so far obtained: first evidence of a significant di-electron signal at energies above 1 GeV/A; improvement of the understanding of di-electron production (electromagnetic decays of hadrons, π+π- annihilation and hadronic Bremsstrahlung). The results of p-p, p-d reactions from 1 to 4.9 GeV/A show that hadronic Bremsstrahlung (pp, pn) should be reformulated. Our analysis, optimized on the reaction Carbon-Carbon at 1 GeV/A, has been applied to α-Ca and d-Ca. We have developed two main aspects: improvement of the time resolution (500 ps) in order to eliminate all of the protons. Improvement of the space resolution (300 μ) for better mass resolution, in particular in the ρ region. We obtain the cross section of di-electron production as a function of mass, transverse momentum and rapidity from the C-C, α-Ca and d-Ca reactions at 1 GeV/A. We also compare the cross section for all of the measured systems at 1 GeV/A, including Ca-Ca, and we show a (ApAt)α dependence with α ≅ 1.1. A study of the associated multiplicity has also been performed. Nevertheless, the limited acceptance of the DLS and its poor mass resolution to identify the ρ, ω vector mesons, do not allow to conclude on hadron behaviour in nuclear matter. This point is one of the main goal of the HADES project at GSI (Darmstadt), which we give a brief description of the main features. (authors). 60 refs

  16. Insights into the importance of oxygen functional groups in carbon reactions with oxygen containing gases

    International Nuclear Information System (INIS)

    The role of pore structure of carbon in carbon-related adsorptions and reactions has been extensively investigated. However the studies on the role of surface chemistry of carbon are limited. In this paper, we present the importance of oxygen functional groups in carbon reactions with oxygen-containing gases. It is found that there is a good correlation between the electronic structures and reactivities of carbon edge sites. Zigzag sites are more active in oxygen adsorption because of the unpaired electrons and armchair sites are less active in oxygen adsorption due to the triple character. However, the desorption of semi-quinone oxygen from zigzag sites needs a bond energy ca. 30% higher than that of o-quinone oxygen from armchair edge sites. CO2 and H2O adsorb on carbon surface much less favorably than O2. H2O is first physically adsorbed on the virgin graphite surface followed by chemisorption through oxygen atom approaching the carbon edge site and the movements of two hydrogen atoms to produce H2. The adsorption mechanism of H2O is different from that for CO2, but the final result is quite similar, i.e. producing only semi-quinone oxygen. Based upon the above studies, a new generalized mechanism, as shown in Fig. 1, is developed and can account for all the important kinetic phenomena of carbon-gas reactions. The key point is that in CO2/H2O-carbon reaction only semi-quinone formed; while, in O2-carbon reaction, semi-quinone, o-quinone (at lower pressure), and off-plane epoxy oxygen (at relatively higher pressure) can be formed. This is the main reason for the different reaction kinetics of O2 -carbon reaction and CO2/H2O-carbon reactions as observed experimentally. The oxygen functional groups of carbon can be characterized by XPS, PZC (point of zero charge), IEP (isoelectric point) and TPD (temperature-programmed desorption), which were used in our previous studies. We treated the carbon surface with different acids, finding that HNO3 treatment can

  17. Enhanced interfacial properties of carbon fiber composites via aryl diazonium reaction “on water”

    International Nuclear Information System (INIS)

    Highlights: • Carbon fibers are grafted with phenyl amine group via aryl diazonium reaction. • Interfacial shear strength of the carbon fibers increases by 73%. • Tensile strength of the carbon fibers does not decrease distinctly. • Using water as the reaction medium can avoid pollution from organic solvents. • Grafting via aryl diazonium reaction in one step can improve modification efficiency. - Abstract: Polyacrylonitrile-based carbon fibers were functionalized with phenyl amine group via aryl diazonium reaction “on water” to improve their interfacial bonding with resin matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize ordered degree, functional groups, chemical states and morphology of carbon fiber surface, respectively. The results showed that phenyl amine groups were grafted on the fiber surface successfully. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 73%, while the tensile strength was down very slightly. Hence aryl diazonium reaction “on water” could be a facile green platform to functionalize carbon fibers for many interesting applications

  18. Carbon reaction with levitated silicon - Experimental and thermodynamic approaches

    Energy Technology Data Exchange (ETDEWEB)

    Beaudhuin, M., E-mail: mickael.beaudhuin@univ-montp2.fr [SIMAP EPM, UMR-CNRS 5266, 1340 rue de la piscine, F-38402 Saint Martin d' Heres Cedex (France); ICGM C2M, UMR-CNRS 5253, Place Eugene Bataillon, Bat 15 CC1504, F-34095 Montpellier Cedex (France); Chichignoud, G.; Bertho, P.; Duffar, T. [SIMAP EPM, UMR-CNRS 5266, 1340 rue de la piscine, F-38402 Saint Martin d' Heres Cedex (France); Lemiti, M. [Universite de Lyon, INL, UMR-CNRS 5270, INSA de Lyon, Bat. 502, 20 Av. Albert Einstein, F-69621 Villeurbanne Cedex (France); Zaidat, K. [SIMAP EPM, UMR-CNRS 5266, 1340 rue de la piscine, F-38402 Saint Martin d' Heres Cedex (France)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Interaction of methane with levitated silicon at high temperature. Black-Right-Pointing-Pointer Silicon nucleation undercooling decreases when the carbon concentration increases. Black-Right-Pointing-Pointer Experimental and thermodynamical calculation shows remarkable similar behavior. - Abstract: Metallurgical grade silicon (MG-Si) has become a new source of raw material for the photovoltaic industry. The use of this material as an alternative feed stock has however introduced phenomena that are detrimental to both the yield of the manufacturing process and the performance of the photovoltaic cells produced. This is mainly related to the presence of carbon, which precipitates to silicon carbide (SiC) in the ingot. This article focuses on the effect of carbon on silicon nucleation. Statistical experimental results of silicon nucleation are obtained as a function of carbon concentration and are presented and compared to thermodynamic calculations.

  19. Carbon reaction with levitated silicon – Experimental and thermodynamic approaches

    International Nuclear Information System (INIS)

    Highlights: ► Interaction of methane with levitated silicon at high temperature. ► Silicon nucleation undercooling decreases when the carbon concentration increases. ► Experimental and thermodynamical calculation shows remarkable similar behavior. - Abstract: Metallurgical grade silicon (MG-Si) has become a new source of raw material for the photovoltaic industry. The use of this material as an alternative feed stock has however introduced phenomena that are detrimental to both the yield of the manufacturing process and the performance of the photovoltaic cells produced. This is mainly related to the presence of carbon, which precipitates to silicon carbide (SiC) in the ingot. This article focuses on the effect of carbon on silicon nucleation. Statistical experimental results of silicon nucleation are obtained as a function of carbon concentration and are presented and compared to thermodynamic calculations.

  20. Oxidation of rhodium (3) by periodate in alkali medium and chemiluminescent catalytic reaction of luminol with periodate in the presence of rhodium (3)

    International Nuclear Information System (INIS)

    A new reaction of oxidation of Rh (3) chloride by a periodate to Rh (5) has been found to take place in an alkaline medium. Oxidation of luminol by the compound Rh (5) is chemiluminescent. These reactions proceed at a considerable rate. Catalytic action of Rh (3) in the chemiluminescent reaction of luminol with the periodate includes the above reactions with the redox cycle Rh (3) reversible Rh (5). The reaction of oxidation of Rh (3) by the periodate can be used for photometric determination of 20-100 μkg of rhodium in 5 ml of a finite volume as a violent colour compound Rh (5) with the absorption maximum at lambda 600 nm. Time of full colour development is 8-10 min without heating the solutions; colour stability is 16 hrs

  1. New Condensation Reaction of β-keto-δ-valerolactones, Carbon Disulfide and Alkyl Halides

    Institute of Scientific and Technical Information of China (English)

    You Ming WANG; Yu Xin LI; Su Hua WANG; Zheng Ming LI

    2004-01-01

    β-Keto-δ-valerolactones, which were obtained by reaction of acetoacetate with aldehydes or ketones, reacted with carbon disulfide, alkyl halides and a new condensation reaction was developed. The structures of the products 3 were confirmed by 1HNMR spectra and elemental analysis.

  2. Analytical evaluation of the solid rocket motor nozzle surface recession by the alumina-carbon reaction

    OpenAIRE

    Matsukawa, Yutaka; Sato, Yutaka; 松川 豊; 佐藤 裕

    2008-01-01

    A theoretical model describing the chemical ablation of a solid rocket motor nozzle ablator by the alumina-carbon reaction is presented. An application of it to a typical solid rocket motor with a graphite nozzle ablator indicates a large influence of the reaction on the nozzle surface recession.

  3. Preparation of hollow carbon nanospheres at low temperature via new reaction route

    International Nuclear Information System (INIS)

    Hollow carbon nanospheres were obtained at 200oC via a new reaction route, by using magnesium, hexachloroethane and aluminum trichloride as starting materials and benzene as solvent. The products were characterized with X-ray diffraction pattern, transmission electron microscope, high-resolution transmission electron microscope images and Raman spectrum. The reaction conditions are easy to be maintained and controlled. They may provide a new method to produce other carbonaceous materials. A possible mechanism of reaction was proposed

  4. Initial reaction between CaO and SO2 under carbonating and non-carbonating conditions

    DEFF Research Database (Denmark)

    Rasmussen, Martin Hagsted; Wedel, Stig; Pedersen, Kim H.;

    2015-01-01

    The initial kinetics of the CaO/SO2 reaction have been investigated for reaction times shorter than 1s and in the temperature interval between 450 and 600°C under both carbonating and non-carbonating conditions (0-20 vol% CO2) to clarify how recirculating CaO influences the emission of SO2 from a...... showed that the CaO conversion with respect to SO2 declined when the CO2 concentration was increased. Under all conditions, larger specific surface areas of CaO gave higher reaction rates with SO2. Higher temperatures had a positive effect on the reaction between SO2 and CaO under non...

  5. A Small-Scale Capsule Test for Investigating the Sodium-Carbon Dioxide Reaction

    International Nuclear Information System (INIS)

    The utilization of modular sodium-to-supercritical CO2 heat exchangers may yield significant improvements for an overall plant energy utilization. The consequences of a failure of the sodium CO2 heat exchanger boundary, however, would involve the blowdown and intermixing of high-pressure CO2 in a sodium pool, causing a pressurization which may threaten the structural integrity of the heat exchanger. Available data seems to indicate that the chemical reaction between sodium and CO2 would likely produce sodium oxides, sodium carbonate, carbon and carbon monoxide. Information on the kinetics of the sodium-CO2 reaction is virtually non-existent

  6. Measurement and calculation of 238U fission reaction rates induced by neutrons reflected by carbon material

    International Nuclear Information System (INIS)

    To check the data of carbon material reflecting neutrons, the distribution of 238U fission reaction rates induced by D-T fusion neutrons reflected by carbon material was measured by using the small depleted uranium fission chamber and the capturing detector. For comparison, 238U fission rates without carbon material was measured too. The combined standard uncertainty of 238U fission reaction rate is 5.1%-6.4%. The measured results are consistent with the calculated ones with MCNP/4A code and ENDF/B-IV library data in the range of the error

  7. A kinetic study of the reaction of water vapor and carbon dioxide on uranium

    International Nuclear Information System (INIS)

    The kinetic study of the reaction of water vapour and carbon dioxide with uranium has been performed by thermogravimetric methods at temperatures between 160 and 410 deg G in the first case, 350 and 1050 deg C in the second: Three sorts of uranium specimens were used: uranium powder, thin evaporated films, and small spheres obtained from a plasma furnace. The experimental results led in the case of water vapour, to a linear rate of reaction controlled by diffusion at the lower temperatures, and by a surface reaction at the upper ones. In the case of carbon dioxide, a parabolic law has been found, controlled by diffusional processes. (author)

  8. REACTION MECHANISMS OF MAGNESIUM SILICATES WITH CARBON DIOXIDE IN MICROWAVE FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    William B. White; Michael R. Silsbee; B. Joe Kearns

    2004-02-18

    The objective of the investigation was to determine whether microwave fields would enhance the reactions of CO{sub 2} with silicates that are relevant to the sequestration of carbon dioxide. Three sets of experiments were conducted. (1) Serpentine and CO{sub 2} were reacted directly at one atmosphere pressure in a microwave furnace. Little reaction was observed. (2) Serpentine was dehydroxylated in a microwave furnace. The reaction was rapid, reaching completion in less than 30 minutes. A detailed investigation of this reaction produced an S-shaped kinetics curve, similar to the kinetics from dehydroxylating serpentine in a resistance furnace, but offset to 100 C lower temperature. This set of experiments clearly demonstrates the effect of microwaves for enhancing reaction kinetics. (3) Reactions of serpentine with alkaline carbonates and in acid solution were carried out in a microwave hydrothermal apparatus. There was a greatly enhanced decomposition of the serpentine in acid solution but, at the temperature and pressure of the reaction chamber (15 bars; 200 C) the carbonates did not react. Overall, microwave fields, as expected, enhance silicate reaction kinetics, but higher CO{sub 2} pressures are needed to accomplish the desired sequestration reactions.

  9. Alkali metal ionization detector

    Science.gov (United States)

    Bauerle, James E.; Reed, William H.; Berkey, Edgar

    1978-01-01

    Variations in the conventional filament and collector electrodes of an alkali metal ionization detector, including the substitution of helical electrode configurations for either the conventional wire filament or flat plate collector; or, the substitution of a plurality of discrete filament electrodes providing an in situ capability for transferring from an operationally defective filament electrode to a previously unused filament electrode without removing the alkali metal ionization detector from the monitored environment. In particular, the helical collector arrangement which is coaxially disposed about the filament electrode, i.e. the thermal ionizer, provides an improved collection of positive ions developed by the filament electrode. The helical filament design, on the other hand, provides the advantage of an increased surface area for ionization of alkali metal-bearing species in a monitored gas environment as well as providing a relatively strong electric field for collecting the ions at the collector electrode about which the helical filament electrode is coaxially positioned. Alternatively, both the filament and collector electrodes can be helical. Furthermore, the operation of the conventional alkali metal ionization detector as a leak detector can be simplified as to cost and complexity, by operating the detector at a reduced collector potential while maintaining the sensitivity of the alkali metal ionization detector adequate for the relatively low concentration of alkali vapor and aerosol typically encountered in leak detection applications.

  10. Film forming kinetics and reaction mechanism of γ-glycidoxypropyltrimethoxysilane on low carbon steel surfaces

    International Nuclear Information System (INIS)

    The film forming kinetics and reaction mechanism of γ-GPS on low carbon steel surfaces was investigated by FTIR-ATR, AFM, NSS and theoretical calculation method. The results from experimental section indicated that the reaction of γ-GPS on low carbon steel surfaces followed the conventional reaction mechanism, which can be described as reaction (I) (Me (Metal)-OH + HO-Si → Me-O-Si + H2O) and reaction (II) (Si-OH + Si-OH → Si-O-Si + H2O). During film forming process, the formation of Si-O-Fe bond (reaction (I)) exhibited oscillatory phenomenon, the condensation degree of silanol monomers (reaction (II)) increased continuously. The metal hydroxyl density had significant influence on the growth mechanisms and corrosion resisting property of γ-GPS films. The results from theoretical calculation section indicated that the patterns of reaction (I) and reaction (II) were similar, involving a nucleophilic attack on the silicon center. The formation of Si-O-Fe bond (reaction (I)) was kinetically and thermodynamically preferred, which had catalytic effect on its condensation with neighboring silanol monomers (reaction (II)). Our DFT calculations were good consistent with the experimental measurements.

  11. Heterogeneously Catalysed Chemical Reactions in Carbon Dioxide Medium

    DEFF Research Database (Denmark)

    Musko, Nikolai E.

    determination of phase equilibria is very time consuming, expensive, and very often reveals very little information. However, these problems can be overcome when thermodynamic modelling is applied. The Cubic-Plus-Association Equation of State (CPA) was used throughout this study; therefore this model is...... studied. Furthermore, the “one-pot” synthesis with 2-butenal was performed using bifunctional and mixed catalysts. The reactions were studied in different reactor types and reaction conditions were optimised using CPA calculations. Extensive catalyst characterisation was carried out in order to understand...... equilibria of the reaction mixture can make the process economically more feasible. Many different thermodynamic models of different capability and applicability have been applied for this task. The CPA model is an advanced model that accounts for complex interactions between associating molecules like water...

  12. Durability of Concrete Subjected to the Combined Action of Alkali-silica Reaction and Sulfate Attack%碱-硅酸反应和硫酸盐侵蚀复合作用下的混凝土耐久性

    Institute of Scientific and Technical Information of China (English)

    沈佳燕; 施韬; 杨杨

    2012-01-01

    碱-硅酸反应(ASR)和硫酸盐侵蚀是影响混凝土耐久性的两个重要因素.目前,对于单一因素作用下混凝土劣化过程的研究已有诸多报道,但关于混凝土在碱-硅酸反应和硫酸盐侵蚀复合作用下的损伤失效过程及机理研究却很少.本文介绍了近年来国内外在碱-硅酸反应和硫酸盐侵蚀方面的研究现状,主要阐述了它们各自的膨胀机理和抑制措施.在对Grattan等人试验中得到的膨胀数据、X射线衍射图和扫描电子显微镜图进行分析的基础上,讨论了混凝土在这两种因素复合作用下可能出现的膨胀值变化和强度变化,并提出有效的抑制措施.%Alkali-silica reaction (ASR) and sulfate attack are two of the most important problems on concrete durability. The deterioration of concrete under single destructive action have been broadly investigated, but the damage process and the corresponding mechanisms subjected to combined action of ASR and sulfate attack have rarely studied yet. This paper introduces the recent research progress in alkali-silica reaction and sulfate attack achieved home and abroad,and mainly describes the expanding mechanisms and inhibitive measures of each reaction. The probable changes of expansion and strength of concrete subjected to combined action of ASR and sulfate attack are discussed on the base of analyzing experimental results of expansion, X-Ray diffractogram and SEM micrograph by Grattan el al, and the effective inhibitive measures are also been proposed.

  13. Ultra-Low-Temperature Reactions of Carbon Atoms with Hydrogen Molecules

    CERN Document Server

    Krasnokutski, S A; Renzler, M; Jäger, C; Henning, Th; Scheier, P

    2016-01-01

    The reactions of carbon atoms with dihydrogen have been investigated in liquid helium droplets at $T$ = 0.37 K. A calorimetric technique was applied to monitor the energy released in the reaction. The barrierless reaction between a single carbon atom and a single dihydrogen molecule was detected. Reactions between dihydrogen clusters and carbon atoms have been studied by high-resolution mass spectrometry. The formation of hydrocarbon cations of the type C$_m$H$_n^+$, with $m$ = 1-4 and $n$ = 1-15 was observed. With enhanced concentration of dihydrogen, the mass spectra demonstrated the main "magic" peak assigned to the CH$_5^+$ cation. A simple formation pathway and the high stability of this cation suggest its high abundance in the interstellar medium.

  14. Carbon Isotopic Fractionation in Fischer-Tropsch Type Reactions and Relevance to Meteorite Organics

    Science.gov (United States)

    Johnson, Natasha M; Elsila, Jamie E.; Kopstein, Mickey; Nuth, Joseph A., III

    2012-01-01

    Fischer-Tropsch-Type (FTT) reactions have been hypothesized to contribute to the formation of organic compounds in the early solar system, but it has been difficult to identify a signature of such reactions in meteoritic organics. The work reported here examined whether temperature-dependent carbon isotopic fractionation of FTT reactions might provide such a signature. Analyses of bulk organic deposits resulting from FTT experiments show a slight trend towards lighter carbon isotopic ratios with increasing temperature. It is unlikely, however, that these carbon isotopic signatures could provide definitive provenance for organic compounds in solar system materials produced through FTT reactions, because of the small scale of the observed fractionations and the possibility that signatures from many different temperatures may be present in any specific grain.

  15. Alkali promotion of N-2 dissociation over Ru(0001)

    DEFF Research Database (Denmark)

    Mortensen, Jens Jørgen; Hammer, Bjørk; Nørskov, Jens Kehlet

    1998-01-01

    Using self-consistent density functional calculations, we show that adsorbed Na and Cs lower the barrier for dissociation of N2 on Ru(0001). Since N2 dissociation is a crucial step in the ammonia synthesis reaction, we explain in this way the experimental observation that alkali metals promote th...... the ammonia synthesis reaction over Ru catalysts. We also show that the origin of this effect is predominantly a direct electrostatic attraction between the adsorbed alkali atoms and the dissociating molecule....

  16. Investigations on organogermanium compounds XII. Reactions of trialkylgermylalkalimetal compounds in hexamethylphosphoric triamide (HMPT) with some inorganic and organic compounds

    NARCIS (Netherlands)

    Bulten, E.J.; Noltes, J.G.

    1971-01-01

    Trialkylgermyl alkali metal compounds in HMPT have been found to be highly reactive nucleophiles. Reactions with some inorganic and organic compounds, such as oxygen, carbon dioxide, inorganic and orgaanic halides, aldehydes, ketones, epoxides and lactones are described. Several new carbon-functiona

  17. Nuclear fusion in dense matter: Reaction rate and carbon burning

    CERN Document Server

    Gasques, L R; Aguilera, E F; Beard, M; Chamon, L C; Ring, P; Wiescher, M; Yakovlev, D G

    2005-01-01

    In this paper we analyze the nuclear fusion rate between equal nuclei for all five different nuclear burning regimes in dense matter (two thermonuclear regimes, two pycnonuclear ones, and the intermediate regime). The rate is determined by Coulomb barrier penetration in dense environments and by the astrophysical S-factor at low energies. We evaluate previous studies of the Coulomb barrier problem and propose a simple phenomenological formula for the reaction rate which covers all cases. The parameters of this formula can be varied, taking into account current theoretical uncertainties in the reaction rate. The results are illustrated for the example of the ^{12}C+^{12}C fusion reaction. This reaction is very important for the understanding of nuclear burning in evolved stars, in exploding white dwarfs producing type Ia supernovae, and in accreting neutron stars. The S-factor at stellar energies depends on a reliable fit and extrapolation of the experimental data. We calculate the energy dependence of the S-f...

  18. Application of Moessbauer Spectroscopy to the Carbon Oxides Hydrogenation Reactions

    International Nuclear Information System (INIS)

    Iron-based catalysts have favorable activity and selectivity properties for the CO and CO2 hydrogenation reactions. Several Fe phases (oxides and carbides) can be present in these catalysts. The interaction of Fe with the other components of the catalyst (support, promoters) can affect the ease of reduction and also its transformation during the reactions. In this work, the relationship between catalytic behavior in the CO and CO2 hydrogenation reactions and the Fe phase composition of fresh and reacted catalysts was studied. Two types of catalysts were tested: a laterite and the other one made of iron supported on alumina, both unpromoted and promoted with K and Mn. Only those Fe species which can be reduced-carburized, by means of a pretreatment or by an in situ transformation under the reaction, seem to be able to perform the CO or CO2 hydrogenation. The reoxidation of the Fe carbide to magnetite was not associated to deactivation. The selectivity seems to be more affected by Fe species difficult to reduce than by magnetite produced by reoxidation

  19. Carbon Isotopic Fractionation During Formation of Macromolecular Organic Grain Coatings via FTT Reactions

    Science.gov (United States)

    Nuth, J. A.; Johnson, N. M.; Elsila-Cook, J.; Kopstein, M.

    2011-01-01

    Observations of carbon isotopic fractionation of various organic compounds found in meteorites may provide useful diagnostic information concerning the environments and mechanisms that were responsible for their formation. Unfortunately, carbon has only two stable isotopes, making interpretation of such observations quite problematic. Chemical reactions can increase or decrease the C-13/C-12 ratio by various amounts, but the final ratio will depend on the total reaction pathway followed from the source carbon to the final product, a path not readily discernable after 4.5 billion years. In 1970 Libby showed that the C-13/C-12 ratios of terrestrial and meteoritic carbon were similar by comparing carbon from the Murchison meteorite to that of terrestrial sediments. More recent studies have shown that the C-13/C-12 ratio of the Earth and meteorites may be considerably enriched in C-13 compared to the ratio observed in the solar wind [2], possibly suggesting that carbon produced via ion-molecule reactions in cold dark clouds could be an important source of terrestrial and meteoritic carbon. However, meteoritic carbon has been subjected to parent body processing that could have resulted in significant changes to the C-13/C-12 ratio originally present while significant variation has been observed in the C-13/C-12 ratio of the same molecule extracted from different terrestrial sources. Again we must conclude that understanding the ratio found in meteorites may be difficult.

  20. Research of Hydrogen Preparation with Catalytic Steam-Carbon Reaction Driven by Photo-Thermochemistry Process

    Directory of Open Access Journals (Sweden)

    Xiaoqing Zhang

    2013-01-01

    Full Text Available An experiment of hydrogen preparation from steam-carbon reaction catalyzed by K2CO3 was carried out at 700°C, which was driven by the solar reaction system simulated with Xenon lamp. It can be found that the rate of reaction with catalyst is 10 times more than that without catalyst. However, for the catalytic reaction, there is no obvious change for the rate of hydrogen generation with catalyst content range from 10% to 20%. Besides, the conversion efficiency of solar energy to chemical energy is more than 13.1% over that by photovoltaic-electrolysis route. An analysis to the mechanism of catalytic steam-carbon reaction with K2CO3 is given, and an explanation to the nonbalanced [H2]/[CO + 2CO2] is presented, which is a phenomenon usually observed in experiment.

  1. Quantum Chemical and FTIR Spectroscopic Studies on the Linkage Isomerism of Carbon Monoxide in Alkali-Metal-Exchanged Zeolites: A Review of Current Research

    Directory of Open Access Journals (Sweden)

    E. Garrone

    2002-07-01

    Full Text Available Abstract: When adsorbed (at a low temperature on alkali-metal-exchanged zeolites, CO forms both M(CO+ and M(OC+ carbonyl species with the extra-framework alkali-metal cation of the zeolite. Both quantum chemical and experimental results show that C-bondend adducts are characterized by a C−O stretching IR band at a frequency higher than that of 2143 cm-1 for free CO, while for O-bonded adducts this IR band appears below 2143 cm-1. The cation-CO interaction energy is higher for M(CO+ than for M(OC+ carbonyls, although the corresponding difference decreases substantially when going from Li+ to Cs+. By means of variable-temperature FTIR spectroscopy, this energy difference was determined for several alkali-metal cations, and the existence of a thermal equilibrium between M(CO+ and M(OC+ species was established. The current state of research in this field is reviewed here, with a view to gain more insight into the thermal isomerization process.

  2. XPS study on the surface reaction of uranium metal with carbon monoxide at 200 degree C

    International Nuclear Information System (INIS)

    The surface reaction of uranium metal with carbon monoxide at 200 degree C has been studied by X-ray photoelectron spectroscopy (XPS). The carbon monoxide adsorption on the surface oxide layer resulted in U4f peak shifting to the lower binding energy and the content of oxygen in the oxide is decreased. O/U radio decreases with increasing the exposure of carbon monoxide to the surface layer. The investigation indicated the surface layer of uranium metal was further reduced in the atmosphere of carbon monoxide at high temperature. (3 refs., 5 figs.)

  3. Residual carbon detection in barium titanate ceramics by nuclear reaction technique

    International Nuclear Information System (INIS)

    Residual carbon content in BaTiO3 ceramics synthesized by the citric resin route has been evaluated by the 12C(d,p)13C nuclear reaction technique. The C content inside ceramics sintered at 1400oC is about 50 ppm in weight. The surface layer (0.4 μm) exhibits a concentration of several hundreds or thousands ppm with two origins for the detected carbon: atmospheric contamination carbon adsorbed at the surface, which has been roughly evaluated, and material intrinsic carbon: its concentration depends mainly on the sintering conditions, shape of ceramic pieces and sintering temperature. (author)

  4. Reactions between sodium and various carbon bearing compounds

    International Nuclear Information System (INIS)

    The presence of carbon bearing materials in liquid sodium is undesirable because of their ability to carburise stainless steel components. It has been demonstrated for example that carbon taken up by stainless steels can affect their mechanical properties and that thinner sectioned material such as fuel cladding and the tubing of intermediate heat exchanger may be more sensitive to such effects. Generally speaking, there are a number of potential carbon sources in reactor systems. Some of the sources such as the graphite in neutron shield rods, boron carbide in control rods and carbide fuels are part of the reactor designs while others such as oil in mechanical pumps arid 'coupling-fluids' used to inspect plant components are associated with the respective operation arid inspection of the plant. In this paper it is intended to discuss in general terms the way these various compounds behave in liquid sodium and to assess what effect their presence will have on the materials of construction in fast reactor systems. The paper also reviews the chemistry of the environment in relation to the types of carburizing species which may exist in sodium systems

  5. Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

    Institute of Scientific and Technical Information of China (English)

    Fandong Meng; Genhui Xu; Zhenhua Li; Pa Du

    2002-01-01

    The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.

  6. Application of the random pore model to the carbonation cyclic reaction

    Energy Technology Data Exchange (ETDEWEB)

    Grasa, G.; Murillo, R.; Alonso, M.; Abanades, J.C. [Institute of Carboquimica, Zaragoza (Spain). Environment & Energy Department

    2009-05-15

    Calcium oxide has been proved to be a suitable sorbent for high temperature CO{sub 2} capture processes based on the cyclic carbonation-calcination reaction. It is important to have reaction rate models that are able to describe the behavior of CaO particles with respect to the carbonation reaction. Fresh calcined lime is known to be a reactive solid toward carbonation, but the average sorbent particle in a CaO-based CO{sub 2} capture system experiences many carbonation-calcination cycles and the reactivity changes with the number of cycles. This study applies the random pore model (RPM) to estimate the intrinsic rate parameters for the carbonation reaction and develops a simple model to calculate particle conversion with time as a function of the number of cycles, partial pressure of CO{sub 2}, and temperature. This version of the RPM model integrates knowledge obtained in earlier works on intrinsic carbonation rates, critical product layer thickness, and pore structure evolution in highly cycled particles.

  7. Effect of temperature on kinetic parameters of decomposition reaction of calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    CHEN Hongwei; CHEN Jiangtao; WEI Riguang; SUO Xinliang

    2013-01-01

    In order to investigate the influence of temperature on behavior of calcium carbonate decomposition,especially on kinetic parameters of the decomposition reaction,the analytically pure calcium carbonate was calcined on a self-built large dose thermogravimetric analyzer.The results indicated that,with an increase in the reaction temperature,the reactivity index of calcium carbonate decomposition increased at stage state while the kinetic parameters decreased at stage state.Moreover,both the reaction indices and the kinetic parameters can be divided into three stages and the temperature turning points in different stages were the same.The phase boundary reaction (cylindrical symmetry) theory was more suitable for calcium carbonate calcination under N2 atmosphere.The change trend of the logarithm of reaction activation with temperature was similar as that of the pre-exponential factor.There existed good liner relationship and kinetic compensation effect between them.The isokinetic temperature of the CaCO3 calcination was 842 ℃ and the reaction rate constant was 0.104 9 min-1 derived by the compensation coefficients.

  8. Reactions of carbon radicals generated by 1,5-transposition of reactive centers

    Directory of Open Access Journals (Sweden)

    ZIVORAD CEKOVIC

    2005-03-01

    Full Text Available Radical intermediates can undergo specific reactions, such as intramolecular rearrangements, i.e., the transpositions of radical centers, which are not known in classical ionic organic reactions. 1,5-Transposition of a radical center to a non-activated carbon atom are of great synthetic importance. It can be successfully applied for the introduction of different functional groups (oxygen, nitrogen, sulfur, halogens onto a carbon atom remote from the present functional group. In addition to functionalization of a remote non-activated carbon atom, the formation of new C-C bonds on the d-carbon atom have also been achieved. 1,5-Transposition of the radical centers takes place from alkoxyl, aminyl and carbon radicals to a remote carbon atom. Relocation of the radical centers preferentially involves 1,5-transfer of a hydrogen atom, although migrations of some other groups are known. The reactions of the carbon radical generated by 1,5-relocation of the radical center are presented and their synthetic applications are reviewed.

  9. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  10. Characterization of the major reactions during conversion of lignin to carbon fiber

    Directory of Open Access Journals (Sweden)

    Hendrik Mainka

    2015-10-01

    Full Text Available Lightweight design is an essential part of the overall Volkswagen strategy for reducing the CO2 emissions. The use of carbon fiber offers an enormous lightweight potential. In comparison to steel enabling a mass reduction of up to 70% in automotive parts without a degradation of the functionalities is possible. Today, the use of carbon fiber is limited in mass series applications of the automotive industry by the cost of the conventional C-fiber precursor polyacrylonitrile (PAN. 50% of the cost of a conventional carbon fiber already belongs to the cost of the PAN precursor. Lignin as a precursor for carbon fiber production can realize enormous savings in cost. For qualifying lignin-based carbon fiber for automotive mass production a detailed characterization of this new material is necessary. Therefore, nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy are used. Using the results of these experiments, the major reactions during conversion of lignin to carbon fiber are proposed.

  11. The reaction of carbon with rare earth silicides. I

    International Nuclear Information System (INIS)

    The solubility of carbon and its effect on the D88 structure of Er5Si3 were investigated by X-ray examination, metallography and hardness measurements. Corrosion products arising from attack by water vapour and dilute nitric acid on the carbides were analysed. The addition of carbon to Er5Si3Csub(x) in the range from x=0 to x=2.0 produced complex changes. Solutions with x up to 0.2 expanded the lattice, but between x=0.2 and x=0.8 the expansion was accompanied by the appearance of a superlattice unit cell. At x=0.8 the superstructure became disordered prior to changing to a new superstructure at x=1.0. Two new orthorhombic phases in which there appeared to be some C2sup(n-) dipoles were identified at Er5Si3Csub(1.8) and Er5Si3Csub(2.0). (Auth.)

  12. Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

    DEFF Research Database (Denmark)

    Musko, Nikolai; Grunwaldt, Jan-Dierk

    2011-01-01

    preliminary study under the entitled reaction conditions. Small and linear aldehydes, such as propanal, butanal, pentanal and hexanal, react more efficiently than the branched 3-methylbutanal, which is converted much slower. Whereas Amberlyst-15 showed the highest conversion based on the catalyst mass...

  13. Effects of alkali treatments on Ag nanowire transparent conductive films

    Science.gov (United States)

    Kim, Sunho; Kang, Jun-gu; Eom, Tae-yil; Moon, Bongjin; Lee, Hoo-Jeong

    2016-06-01

    In this study, we employ various alkali materials (alkali metals with different base strengths, and ammonia gas and solution) to improve the conductivity of silver nanowire (Ag NW)-networked films. The alkali treatment appears to remove the surface oxide and improve the conductivity. When applied with TiO2 nanoparticles, the treatment appears more effective as the alkalis gather around wire junctions and help them weld to each other via heat emitted from the reduction reaction. The ammonia solution treatment is found to be quick and aggressive, damaging the wires severely in the case of excessive treatment. On the other hand, the ammonia gas treatment seems much less aggressive and does not damage the wires even after a long exposure. The results of this study highlight the effectiveness of the alkali treatment in improving of the conductivity of Ag NW-networked transparent conductive films.

  14. Carbon content influence on the peritectic reaction path in stainless steels

    Directory of Open Access Journals (Sweden)

    J. Głownia

    2013-01-01

    Full Text Available An important role for the peritectic reaction path in castings of stainless steel play small changes in a carbon content (e.g. from 0,02 to 0,06 % C, at maintaining constant chromium and nickel values. An influence of the carbon content on the peritectic reaction stages constitutes the subject of studies. The calculations of the steel solidification pathways in the four-component system, of a constant chromium and nickel content of 18 % and 9 % – respectively and of various carbon content from 0,01 to 0,06 %, were performed. It was proved by means of the PANDAT program that the carbon concentration increases the Cr segregation and thereby changes the solidification path under actual conditions.

  15. Surprisingly Different Reaction Behavior of Alkali and Alkaline Earth Metal Bis(trimethylsilyl)amides toward Bulky N-(2-Pyridylethyl)-N'-(2,6-diisopropylphenyl)pivalamidine.

    Science.gov (United States)

    Kalden, Diana; Oberheide, Ansgar; Loh, Claas; Görls, Helmar; Krieck, Sven; Westerhausen, Matthias

    2016-07-25

    N-(2,6-Diisopropylphenyl)-N'-(2-pyridylethyl)pivalamidine (Dipp-N=C(tBu)-N(H)-C2 H4 -Py) (1), reacts with metalation reagents of lithium, magnesium, calcium, and strontium to give the corresponding pivalamidinates [(tmeda)Li{Dipp-N=C(tBu)-N-C2 H4 -Py}] (6), [Mg{Dipp-N=C(tBu)-N-C2 H4 -Py}2 ] (3), and heteroleptic [{(Me3 Si)2 N}Ae{Dipp-N=C(tBu)-N-C2 H4 -Py}], with Ae being Ca (2 a) and Sr (2 b). In contrast to this straightforward deprotonation of the amidine units, the reaction of 1 with the bis(trimethylsilyl)amides of sodium or potassium unexpectedly leads to a β-metalation and an immediate deamidation reaction yielding [(thf)2 Na{Dipp-N=C(tBu)-N(H)}] (4 a) or [(thf)2 K{Dipp-N=C(tBu)-N(H)}] (4 b), respectively, as well as 2-vinylpyridine in both cases. The lithium derivative shows a similar reaction behavior to the alkaline earth metal congeners, underlining the diagonal relationship in the periodic table. Protonation of 4 a or the metathesis reaction of 4 b with CaI2 in tetrahydrofuran yields N-(2,6-diisopropylphenyl)pivalamidine (Dipp-N=C(tBu)-NH2 ) (5), or [(thf)4 Ca{Dipp-N=C(tBu)-N(H)}2 ] (7), respectively. The reaction of AN(SiMe3 )2 (A=Na, K) with less bulky formamidine Dipp-N=C(H)-N(H)-C2 H4 -Py (8) leads to deprotonation of the amidine functionality, and [(thf)Na{Dipp-N=C(H)-N-C2 H4 -Py}]2 (9 a) or [(thf)K{Dipp-N=C(H)-N-C2 H4 -Py}]2 (9 b), respectively, are isolated as dinuclear complexes. From these experiments it is obvious, that β-metalation/deamidation of N-(2-pyridylethyl)amidines requires bases with soft metal ions and also steric pressure. The isomeric forms of all compounds are verified by single-crystal X-ray structure analysis and are maintained in solution. PMID:27355970

  16. Synthesis and processing of beta silicon carbide powder by silicon - carbon reaction

    International Nuclear Information System (INIS)

    SiC is an important structural ceramic and finds applications in nuclear industry. Processing of SiC ceramic components for such applications require sinter-active beta silicon carbide powders. Various novel methods have been reported for the synthesis of beta SiC powder based on silica - carbon and silicon - carbon reactions. In this research, beta-silicon carbide (β-SiC) was synthesized from the reaction of Si and C. In this research, beta-silicon carbide (β-SiC) was synthesized from the reaction of Si and C. Stoichiometric amount of silicon and petroleum coke having agglomerate size ∼ 5-8μ were planetarily wet mixed, dried, granulated and compacted to reaction specimens

  17. Alkalis and Skin.

    Science.gov (United States)

    Greenwood, John E; Tan, Jin Lin; Ming, Justin Choong Tzen; Abell, Andrew D

    2016-01-01

    The aim of this editorial is to provide an overview of the chemical interactions occurring in the skin of our patients on contact with alkaline agents. Strongly basic alkali is highly aggressive and will readily hydrolyze (or cleave) key biological molecules such as lipids and proteins. This phenomenon is known as saponification in the case of lipids and liquefactive denaturation for peptides and proteins. A short section on current first-aid concepts is included. A better understanding of the basic science behind alkali burns will make us better teachers and provide an insight into the urgency needed in treating these common and dangerous chemical injuries. PMID:26182072

  18. Mechanism of carbon monoxide reactions under high pressure catalyzed by acids and bases

    Energy Technology Data Exchange (ETDEWEB)

    Takezaki, Y.

    1978-05-01

    A review, based mainly on work done at Kyoto University, covers the mechanisms and kinetics of acid-catalyzed carbonylations, including the hydrogen fluoride-catalyzed addition of carbon monoxide to methallyl chloride, the sulfuric acid-catalyzed synthesis of succinic acid from acrylic acid, and the conversion of toluene to p-tolualdehyde in hydrogen fluoride/boron trifluoride by the Gattermann-Koch reaction; and of base-catalyzed reactions, including the production of methyl formate from methanol with 1,8-diazabicyclo (5,4,0)undec-7-ene catalyst and of malonic acid from potassium acetate and potassium carbonate. Graphs, tables, and 34 references.

  19. β-Sialon Produced by Carbon Thermal Nitriding Reaction of Bauxite

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    β-Sialon was produced by carbon thermal nitriding reaction in N2 gas atmosphere when the mixtures of bauxite and anthracite were put into vertical furnace. According to the mass loss of raw materials and the result of X-ray diffration (XRD) of products, the influences of the process parameters on the compositions and relative contents of products, such as the fixed carbon content, the flow of N2, the soaking time and the temperature, were researched.

  20. Activated carbon becomes active for oxygen reduction and hydrogen evolution reactions.

    Science.gov (United States)

    Yan, Xuecheng; Jia, Yi; Odedairo, Taiwo; Zhao, Xiaojun; Jin, Zhao; Zhu, Zhonghua; Yao, Xiangdong

    2016-06-21

    We utilized a facile method for creating unique defects in the activated carbon (AC), which makes it highly active for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The ORR activity of the defective AC (D-AC) is comparable to the commercial Pt/C in alkaline medium, and the D-AC also exhibits excellent HER activity in acidic solution. PMID:27277286

  1. Computational Investigations of Organic Reactions on Graphene, Fullerenes, and Carbon Nanotubes

    OpenAIRE

    Cao, Yang

    2014-01-01

    This dissertation involves explorations of on surfaces and on carbon-based nanomaterials, especially graphene, using quantum chemical calculations. The work evaluates energetics of cycloaddition reactions on different sites of graphene, improving the understanding of graphene chemistry and guiding experiments.Chapter 1 to 3 describes theoretical investigations of 1,3-dipolar cycloadditions, Diels- Alder reactions, (2+2) cycloadditions, (4+4) cycloadditions and non-covalent interactions to gra...

  2. Chemical Reaction Equilibrium in Nanoporous Materials: NO Dimerization Reaction in Carbon Slit Nanopores

    Czech Academy of Sciences Publication Activity Database

    Lísal, Martin; Brennan, J.K.; Smith, W.R.

    2006-01-01

    Roč. 124, č. 6 (2006), s. 64712.1-64712.14. ISSN 0021-9606 R&D Projects: GA ČR(CZ) GA203/05/0725; GA AV ČR(CZ) 1ET400720507; GA AV ČR(CZ) 1ET400720409 Institutional research plan: CEZ:AV0Z40720504 Keywords : nanopore * NO dimerization * reaction Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.166, year: 2006

  3. Methods of recovering alkali metals

    Science.gov (United States)

    Krumhansl, James L; Rigali, Mark J

    2014-03-04

    Approaches for alkali metal extraction, sequestration and recovery are described. For example, a method of recovering alkali metals includes providing a CST or CST-like (e.g., small pore zeolite) material. The alkali metal species is scavenged from the liquid mixture by the CST or CST-like material. The alkali metal species is extracted from the CST or CST-like material.

  4. Structural evaluation of a prestressed concrete bridge under an alkali-silica reaction; Evaluacion estructural de un puente de hormigon pretensado afectado por una reaccion alcali-silice

    Energy Technology Data Exchange (ETDEWEB)

    Carpintero Garcia, I.; Bermudez Adriozola, B.

    2010-07-01

    The Central Laboratory of Structures and Materials (CEDEX) was commissioned by the National Department of Highways to evaluate the safety conditions of one bridge built on 1997, which is part of the net of the Spanish National Highways. Even at the first inspection many cracks were detected in the concrete deck, associated with expansion concrete processes. This examination revealed that concrete deterioration was not associated with any reinforcement corrosion process; in fact, there were no symptoms of this pathology all along the bridge. for that reason the internal chemical reactions were considered as the most probable cause for the expansion of concrete, as no symptoms of deterioration due to external attack were found. In order to check the origin of concrete expansion, some tests were carried out on concrete samples drilled on the decks. Results of these tests show that there had been internal reactions in concrete mass which explains its expansion and the appearance of those cracks observed. Further more, some other activities were also carried out on site to estimate the importance of the structural damages, as topographic levelling and dynamic testing of the decks. Also the mechanical properties of concrete probes were tested at laboratory. This article shows the main results obtained on the study carried on to determine the cause and significance of the structural damages of the bridge. (Author) 3 refs.

  5. Inlfuence of the Alkali Treatment of HZSM-5 Zeolite on Catalytic Performance of PtSn-Based Catalyst for Propane Dehydrogenation

    Institute of Scientific and Technical Information of China (English)

    Huang Li; Zhou Shijian; Zhou Yuming; Zhang Yiwei; Xu Jun; Wang Li

    2013-01-01

    The porous material ATZ with micro-mesopore hierarchical porosity was prepared by alkali treatment of parent HZSM-5 zeolite and applied for propane dehydrogenation. The zeolite samples were characterized by XRD, N2-physisorption, and NH3-TPD analysis. The results showed that the alkali treatment can modify the physicochemical prop-erties of HZSM-5 zeolite. In this case, the porous material ATZ showed larger external surface area with less acid sites as compared to the HZSM-5 zeolite. It was found out that the alkali treatment of HZSM-5 zeolite could promote the catalytic performance of PtSn/ATZ catalyst. The possible reason was ascribed to the low acidity of ATZ. Furthermore, the presence of mesopores could reduce the carbon deposits on the metallic surface, which was also favorable for the dehydrogenation reaction.

  6. Modeling reaction-driven cracking during mineral carbonation in peridotite for CO2 sequestration

    Science.gov (United States)

    Paukert, A. N.; Sonnenthal, E. L.; Matter, J.; Kelemen, P. B.

    2013-12-01

    In situ mineral carbonation in mantle peridotite has been proposed as a mechanism for long-term, environmentally benign CO2 sequestration1,2. This process converts peridotite and CO2 to carbonate minerals, like magnesite, in the subsurface, providing permanent and safe storage of the CO2. The volume that can be sequestered in this manner is an open question as peridotite carbonation involves a positive volume change and peridotite aquifers have limited porosity and permeability to accommodate the addition of solid volume. Conversion of peridotite to magnesite results in a volume increase of ~44%, which will fill the existing pore space and could limit the extent of carbonation by reducing porosity and permeability, clogging fluid flow paths, and armoring the reactive surface area. Alternatively, the force of crystallization and changes in fluid pressure from carbonation could act as driving forces for mechanical deformation and fracture propagation within the peridotite, creating new porosity, permeability, and reactive surface area, allowing carbonation to continue3. Natural examples of peridotite that have been entirely converted to magnesite suggest that reactive cracking from mineral carbonation is possible given the right conditions, such as elevated temperature and pCO2 2. Results will be presented from a reactive transport model that has been developed for peridotite carbonation using TOUGHREACT v.24. This model evaluates water and CO2 flow through peridotite fractured at different scales using a multiple continuum mesh. The effect of fluid flow, chemical reactions, and porosity and permeability feedbacks on carbonation rate and extent are explored, as is the effect of temperature. Peridotite carbonation is exothermic, so the release of heat of reaction could be balanced with the fluid injection temperature to maintain the 185oC conditions that facilitate the fastest carbonation rate2. The effect of fluid temperature and flow rate on the rate of carbonation

  7. Kinetics of reactions of oxidation of carbon by carbon dioxide and water steam at high temperatures and low pressures

    International Nuclear Information System (INIS)

    The first objective of this research thesis was to obtain new and reliable experimental results about the reaction kinetics of the oxidation of carbon by carbon dioxide and water steam, and to avoid some disturbing phenomena, for example and more particularly the appearance of electric discharges beyond 1900 K initiated by the filament thermoelectric emission. The author tried to identify the mechanism of the accelerating effect. It appears that previous experiments had been performed only in these disturbed conditions. At the lowest temperatures, the author highlighted the existence of a surface contamination by the desorption products from the apparatus

  8. Solid-state reactions of hydrogen-containing carbon films with metal substrates

    International Nuclear Information System (INIS)

    Hydrogen-containing carbon films were prepared on tungsten, molybdenum and beryllium as model systems to simulate changes in physiochemical properties of carbon depositing on the inner wall of tokamak, in which carbon tiles are used in combination with two or more plasma facing materials. The properties of the co-existing layers and their solid-state reactions at elevated temperatures were studied by means of infrared, Raman, X-ray photoelectron (XPS), X-ray diffraction (XRD) and thermal desorption (TDS) spectroscopies

  9. Method of carbon chain extension using novel aldol reaction

    Energy Technology Data Exchange (ETDEWEB)

    Silks, Louis A; Gordon, John C; Wu, Ruilan; Hangson, Susan Kloek

    2013-08-13

    Method of producing C.sub.8-C.sub.15 hydrocarbons comprising providing a ketone starting material; providing an aldol starting material comprising hydroxymethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro).sub.2, Yb(Pro).sub.2, and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are: ##STR00001## where R.sub.1 is a C.sub.1-C.sub.6 alkyl moiety, X=(OH) and n=2. ##STR00002## In (III), X may be CH.sub.2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R.sub.1 and R.sub.2 each independently may be a methyl, ethyl, phenyl moiety.

  10. Spectra of alkali atoms

    International Nuclear Information System (INIS)

    Emission spectra of alkali atoms has been determined by using spectrometer at the ultraviolet to infra red waves range. The spectra emission can be obtained by absorption spectrophotometric analysis. Comparative evaluations between experimental data and data handbook obtained by spark method were also presented. (author tr.)

  11. The process of dimethyl carbonate to diphenyl carbonate: thermodynamics, reaction kinetics and conceptual process design

    NARCIS (Netherlands)

    Haubrock, Jens

    2007-01-01

    Diphenyl carbonate (DPC) is a precursor in the production of Polycarbonate (PC), a widely employed engineering plastic. To overcome the drawbacks of the traditional PC process - e.g. phosgene as a reactant and methylene chloride as solvent- a new process route starting from Dimethyl carbonate (DMC)

  12. Estudo das reações alcalis-sílica associadas ao uso da lama vermelha em argamassas colantes e de revestimento Study of alkali-silica reactions associated with the use of red mud in plastering mortars

    Directory of Open Access Journals (Sweden)

    D. V. Ribeiro

    2012-03-01

    Full Text Available A incorporação de resíduos industriais em matrizes cimentícias, com o objetivo de inertização, é uma alternativa de reutilização que tem sido bastante estudada nos últimos anos. No presente trabalho, estudou-se a lama vermelha, resíduo sólido gerado no processo de beneficiamento da bauxita e que, devido a seu elevado pH, é considerado "perigoso". Apesar do uso deste resíduo ter sido reportada em trabalhos anteriores, algumas patologias podem estar associadas à sua utilização, devido à elevada concentração de íons alcalinos (principalmente o sódio, favorecendo as reações álcalis-sílica (RAS e às dificuldades de moldagem (reologia devido à elevada finura deste resíduo. Apesar destes prováveis problemas provenientes do uso indiscriminado da lama vermelha como adição às argamassas e concretos, ainda são poucas as pesquisas que os contemplam, sendo este o foco do presente trabalho. Foram verificadas as propriedades reológicas das argamassas, utilizando um reômetro e a avaliação da RAS, de acordo com as normas ASTM C 1260-07 e NBR 11582. Os resultados obtidos foram bastante satisfatórios quanto ao comportamento das argamassas frente à RAS, apesar da elevada concentração de álcalis na lama vermelha, com grande influência reológica.The incorporation of industrial wastes in cementitious matrices, with the goal of inertization, is an alternative of reuse that has been extensively studied in recent years. In this paper, the red mud, the main waste generated in aluminum and alumina production by the Bayer process from bauxite ore and considered "hazardous" due to the high pH, was studied. Despite the use of this waste have been reported in previous studies, some pathologies may be associated with its use, due to high concentration of alkali ions (mainly sodium, favoring the alkali-silica reactions (ASR and the difficulties of molding (rheology because of high fineness of this waste. Despite these potential

  13. 恢复干扰技术对盐碱化草地植被与土壤碳排放的影响%Effect of Restoration Interference Techniques on Vegetation and Soil carbon Discharge of Saline-alkali Grassland

    Institute of Scientific and Technical Information of China (English)

    焉志远; 赵欣悦; 杨帆; 曾昭文; 刘赢男; 刘峰

    2014-01-01

    针对松嫩平原盐碱化草地生态退化现状,研究运用不同干扰程度的围栏封育、震动深松、浅翻轻耙、施肥(沼气化废弃物)和人工草地等草地植被恢复技术进行生态恢复,通过监测结果表明各种恢复技术对盐碱化草地植被恢复具有明显促进作用,植被盖度、高度和生产力大幅度提高。同时,人为扰动改善了土壤结构,植被凋落物增加,导致土壤呼吸作用加强,CO2排放通量增加,但由于植被碳固定的增加率远高于土壤CO2排放通量增加率,因此,生态恢复技术的实施增强了盐碱化草地碳“汇”功能,并且随着生态恢复技术中人为干扰强度的增加,这种增加趋势更加明显。%In this paper, aiming at current saline-alkali grassland degeneration situation in Songnen plain, the application of different interference level of grassland vegetation restoration techniques such as fencing, deep loosening, shallow -plowing, fertilizing (biogas chemical waste)and artificial grass in ecological restora-tion were studied, the monitoring results showed that, various restoration techniques had pronounced promoter actions on saline-alkali grassland vegetation restoration, and greatly improved the coverage, height, and productivity of vegetation. At the same time, human disturbance had improved soil structure, and increased vegetation litter, leading to the enhancement of soil respiration and increase in CO2 discharge flux. However, due to the increment rate of vegetation carbon fixation amount was much higher than the increment rate of soil CO2 discharge flux, the implementation of ecological restoration techniques enhanced carbon “sink”function of saline-alkali grassland, and with the increasing inten-sity of human disturbance in ecological restoration techniques, this increasing trend was even more evident.

  14. Heterogeneous reactions of gaseous methanesulfonic acid with calcium carbonate and kaolinite particles

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Heterogeneous reactions of gaseous methanesulfonic acid (MSA) with calcium carbonate (CaCO3) and kaolinite particles at room temperature were investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC).Methanesulfonate (MS-) was identified as the product in the condensed phase,in accordance with the product of the reaction of gaseous MSA with NaCl and sea salt particles.When the concentration of gaseous MSA was 1.34 × 10-13 molecules cm-3,the uptake coefficient was (1.21 ± 0.06) × 10-8 (1) for the reaction of gaseous MSA with CaCO3 and (4.10 ± 0.65) × 10 10 (1) for the reaction with kaolinite.Both uptake coefficients were significantly smaller than those of the reactions of gaseous MSA with NaCl and sea salt particles.

  15. Carboxylic Group Embedded Carbon Balls as a New Supported Catalyst for Hydrogen Economic Reactions.

    Science.gov (United States)

    Bordoloi, Ankur

    2016-03-01

    Carboxylic group functionalized carbon balls have been successfully synthesized by using a facile synthesis method and well characterized with different characterization techniques such as XPS, MAS NMR, SEM, ICP and N2 physi-sorption analysis. The synthesized material has been effectively utilized as novel support to immobilized ruthenium catalyst for hydrogen economic reactions. PMID:27455763

  16. Mechanisms of oxygen reduction reactions for carbon alloy catalysts via first principles molecular dynamics

    International Nuclear Information System (INIS)

    Carbon alloy catalysts (CACs) are one of promising candidates for platinum-substitute cathode catalysts for polymer electrolyte fuel cells. We have investigated possible mechanisms of oxygen reduction reactions (ORRs) for CACs via first-principles-based molecular dynamics simulations. In this contribution, we review possible ORRs at likely catalytic sites of CACs suggested from our simulations. (author)

  17. Photochemical reactions of Am(V) in bicarbonate-carbonate solutions

    International Nuclear Information System (INIS)

    The effect of ultraviolet (UV) radiation on Am(V) in sodium carbonate and bicarbonate solutions of pH 9.00 - 11.40 was studied by spectrophotometry. An Am(IV) + Am(VI) mixture was formed at pH 9 to 10; however, the conversion of Am(V) did not exceed 60 - 70%. The reaction rate order with respect to Am(V) was about 1. A quantum yield for the reaction on photolysis with light of λ = 337 nm was estimated at 0.003. The reaction rate and the conversion of Am(V) were decreased with increasing pH. The reaction started with the absorption of a UV quantum by a carbonate complex of Am(V). Its first step was presumably the electron transfer either from a water molecule to Am(V) in the coordination sphere of the excited carbonate complex of Am(V) or between two Am(V) ions in an excimer involving an excited and an unexcited carbonate complex of Am(V)

  18. Modeling of the peritectic reaction and macro-segregation in casting of low carbon steel

    Science.gov (United States)

    El-Bealy, M.; Fredriksson, H.

    1996-12-01

    Macro-microscopic models have been developed to describe the macrosegregation behavior associated with the peritectic reaction of low carbon steel. The macrosegregation model has been established on the basis of previously published work and experimental data. A microscopic model of a three-phase reaction L+ δ→ γ has been modeled by using Fredriksson’s approach. Four horizontal and unidirectional solidified experimental groups simulating continuous casting have been performed with a low carbon steel containing 0.13 wt pct carbon. The extent of macrosegregation of carbon was determined by wet chemical analysis of millings. It is confirmed, by comparing calculated results with experimental results, that this model successfully predicts the occurrence of macrosegregation. The results indicate that a peritectic reaction which is associated with a high cooling rate generates high thermal contraction and a high tensile strain rate at the peritectic temperature. Therefore, the macrosegregation, particularly at the ingot surface, is very sensitive to the cooling rate, where extremely high positive segregation was observed in the case of a high cooling rate. However, in the case of slow cooling rate, negative segregation was noted. The mechanism of macrosegregation with peritectic reaction is discussed in detail.

  19. Tests of carbon targets for 12C+12C reactions at astrophysical energies

    International Nuclear Information System (INIS)

    As a preliminary step towards measurements of the 12C +12 C reactions at astrophysical energies, we investigate the behaviour of targets under beam bombardment, specifically the quantitative relation between hydrogen and deuterium content of different carbon targets and target temperature. Experiments have taken place at the CIRCE accelerator in Caserta, Italy and preliminary results are presented here

  20. Oxalyl chloride as a practical carbon monoxide source for carbonylation reactions

    DEFF Research Database (Denmark)

    Hansen, Steffen V F; Ulven, Trond

    2015-01-01

    A method for generation of high-quality carbon monoxide by decomposition of oxalyl chloride in an aqueous hydroxide solution is described. The usefulness of the method is demonstrated in the synthesis of heterocycles and for hydroxy-, alkoxy-, amino-, and reductive carbonylation reactions, in sev...

  1. Carbophilic versus thiophilic attack in the reaction of metallated aromates and heteroaromates with carbon disulfide

    NARCIS (Netherlands)

    Verkruijsse, H.D.; Brandsma, L.

    1987-01-01

    Copper(I) halides catalyse the formation of carbodithioates RCSSLi in the reaction of aryl- or heteroaryl-lithium reagents with carbon disulfide. Subsequent addition of methyl iodide gives the dithioesters RCSSCH3 in high yields. Appreciable amounts of the methyl sulfides RSCH3 and tars are obtained

  2. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    International Nuclear Information System (INIS)

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice

  3. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Ya-Wen [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, De-Kun, E-mail: dkma@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Wang, Wei; Chen, Jing-Jing; Zhou, Lin; Zheng, Yi-Zhou [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Yu, Kang, E-mail: yukang62@126.com [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Huang, Shao-Ming, E-mail: smhuang@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2015-07-01

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice.

  4. Basalt catalyzed carbonate precipitation reactions using carbon dioxide at low temperatures and low pressures

    Science.gov (United States)

    Petrik-Huff, C.; Finkelstein, D. B.; Mabee, S. B.

    2011-12-01

    Increased attention is being paid to basalts as host formations for the geologic sequestration of anthropogenically produced CO2. Here, we present preliminary results of batch experiments conducted on basalts from the Hartford Basin, the Deerfield and the Holyoke Basalt, to better constrain the optimum conditions to maximize carbon sequestration through the precipitation of carbonate. The purpose of this work is to explore options for CO2 sequestration in a locality where there is a lack of large geologic reservoirs appropriate for storage. In these experiments, 10 grams of 400 micron Deerfield and Holyoke basalt was reacted with deionized water for three hours both at and below supercritical conditions. These experiments showed carbonate precipitation of 15% was consistent at low pressures of CO2 (800 psi) both at high (100 Celsius) and low (20 Celsius) temperatures. These ranges of carbonate precipitation were greatest (15%) when CO2 was at low pressures. Experiments conducted at supercritical conditions precipitated a maximum of 4.7% carbonate. This information is valuable when considering alternative sequestration mechanisms that could be operated adjacent to power generation facilities or more industrial pure sources of CO2. The possibility of low pressure/temperature sequestration reactors to be operated in areas where transport to regional or national sequestration facilities may be cost prohibitive is a parallel course of action that should also be considered. Additionally, it is important to consider how a small ex-situ carbon sequestration project can help increase public acceptance of carbon capture and sequestration.

  5. Mineral carbonation: energy costs of pretreatment options and insights gained from flow loop reaction studies

    International Nuclear Information System (INIS)

    Sequestration of carbon as a stable mineral carbonate has been proposed to mitigate environmental concerns that carbon dioxide may with time escape from its sequestered matrix using alternative sequestration technologies. A method has been developed to prepare stable carbonate products by reacting CO2 with magnesium silicate minerals in aqueous bicarbonate/chloride media at high temperature and pressure. Because this approach is inherently expensive due to slow reaction rates and high capital costs, studies were conducted to improve the reaction rates through mineral pretreatment steps and to cut expenses through improved reactor technology. An overview is given for the estimated cost of the process including sensitivity to grinding and heating as pretreatment options for several mineral feedstocks. The energy costs are evaluated for each pretreatment in terms of net carbon avoided. New studies with a high-temperature, high-pressure flow-loop reactor have yielded information on overcoming kinetic barriers experienced with processing in stirred autoclave reactors. Repeated tests with the flow-loop reactor have yielded insights on wear and failure of system components, on challenges to maintain and measure flow, and for better understanding of the reaction mechanism

  6. Mineral sequestration of carbon dioxide in San Carlos olivine: An atomic level reaction study

    Science.gov (United States)

    Nunez, Ryan

    Since the late 19th century, atmospheric carbon dioxide (CO2) levels have been steadily on the rise. Approximately one third of all human emissions come from fossil fuel power plants. As countries become more dependent on electrical energy and bring on line new power plants, these atmospheric CO2 levels will continue to rise, generating strong environmental concern. Potential avenues to address this problem convert the CO2 from the gaseous phase to a liquid, supercritical fluid, or solid state and store it. Oceans, subsurface reservoirs such as depleted oil fields, and terrestrial carbon pools have all been suggested. The essential problem with all of these possible solutions is the issue of permanency. Mineral sequestration of CO2 is a candidate technology for reducing the amount of anthropogenic CO2 that is being released into the atmosphere. Olivine (e.g. forsterite, Mg2SiO4) is a widely available mineral that reacts with CO2 to form magnesite (MgCO3) and silica (SiO2). Magnesite is capable of immobilizing CO2 over geological time periods. Thus the issue of permanency has been addressed. The most promising mineral sequestration process developed to date is aqueous solution mineral carbonation. The solid/aqueous solution reaction interface provides insight to the mechanisms that govern the carbonation reactivity of olivine. Study of these mechanisms at the atomic level is critically important to facilitate engineering new processes that will enhance the reactivity of olivine with CO2 bearing media and to lower process costs. The study of the olivine carbonation reaction herein can be divided into three separate areas of research. The first area is a comprehensive study of olivine under conditions of electron irradiation. Analyzing radiation damage is critical to the verification and reliability of data collected from the samples using electron beam techniques. The next area of research is the analysis of the reaction layer composition and structure using High

  7. Carbon nanohybrids used as catalysts and emulsifiers for reactions in biphasic aqueous/organic systems

    Institute of Scientific and Technical Information of China (English)

    Daniel E. Resasco

    2014-01-01

    This mini-review summarizes some novel aspects of reactions conducted in aqueous/organic emul-sions stabilized by carbon nanohybrids functionalized with catalytic species. Carbon nanohybrids represent a family of solid catalysts that not only can stabilize water-oil emulsions in the same fash-ion as Pickering emulsions, but also catalyze reactions at the liquid/liquid interface. Several exam-ples are discussed in this mini-review. They include (a) aldol condensation-hydrodeoxygenation tandem reactions catalyzed by basic (MgO) and metal (Pd) catalysts, respectively; (b) Fischer-Tropsch synthesis catalyzed by carbon-nanotube-supported Ru;and (c) emulsion polymerization of styrene for the production of conductive polymer composites. Conducting these reactions in emul-sion generates important advantages, such as increased liquid/liquid interfacial area that conse-quently means faster mass transfer rates of molecules between the two phases, effective separation of products from the reaction mixture by differences in the water-oil solubility, and significant changes in product selectivity that can be adjusted by modifying the emulsion characteristics.

  8. Reactions of the Carbon Anode in Alternative Battery and Fuel Cell Configurations

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, J F; Krueger, R

    2003-10-01

    A model is formulated by combining carbonate dissociation with pre-existing anode mechanisms involving heterogeneous reaction kinetics. The proposed model accounts for both the observed preponderance of CO{sub 2} evolution and dependence of rate on carbon anode microstructure. Implications of the model for the design of carbon batteries and fuel cells are discussed, and the laboratory cells used in earlier research are described. High coulombic efficiencies for the net reaction C + O{sub 2} = CO{sub 2} require severely limiting the thickness of paste anodes in powder-fed fuel cells while the unreacting surfaces of solid prismatic anodes must be isolated from the CO{sub 2} product atmosphere to prevent Boudouard corrosion, according to C + CO{sub 2} = 2CO.

  9. Carbon fiber/reaction-bonded carbide matrix for composite materials - Manufacture and characterization

    International Nuclear Information System (INIS)

    The processing of self-healing ceramic matrix composites by a short time and low cost process was studied. This process is based on the deposition of fiber dual inter-phases by chemical vapor infiltration and on the densification of the matrix by reactive melt infiltration of silicon. To prevent fibers (ex-PAN carbon fibers) from oxidation in service, a self-healing matrix made of reaction bonded silicon carbide and reaction bonded boron carbide was used. Boron carbide is introduced inside the fiber preform from ceramic suspension whereas silicon carbide is formed by the reaction of liquid silicon with a porous carbon xerogel in the preform. The ceramic matrix composites obtained are near net shape, have a bending stress at failure at room temperature around 300 MPa and have shown their ability to self-healing in oxidizing conditions. (authors)

  10. Hydrothermal alkali metal recovery process

    Science.gov (United States)

    Wolfs, Denise Y.; Clavenna, Le Roy R.; Eakman, James M.; Kalina, Theodore

    1980-01-01

    In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by treating them with a calcium or magnesium-containing compound in the presence of water at a temperature between about 250.degree. F. and about 700.degree. F. and in the presence of an added base to establish a pH during the treatment step that is higher than would otherwise be possible without the addition of the base. During the treating process the relatively high pH facilitates the conversion of water-insoluble alkali metal compounds in the alkali metal residues into water-soluble alkali metal constituents. The resultant aqueous solution containing water-soluble alkali metal constituents is then separated from the residue solids, which consist of the treated particles and any insoluble materials formed during the treatment step, and recycled to the gasification process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. Preferably, the base that is added during the treatment step is an alkali metal hydroxide obtained by water washing the residue solids produced during the treatment step.

  11. A facile route to synthesize endurable mesopore containing ZSM-5 catalyst for methanol to propylene reaction.

    Science.gov (United States)

    Sun, Chao; Du, Junming; Liu, Jian; Yang, Yisu; Ren, Nan; Shen, Wei; Xu, Hualong; Tang, Yi

    2010-04-21

    A novel route is proposed for the preparation of mesopore containing zeolite ZSM-5 via in situ hydrothermal treatment of a solution containing alkali-dissolved SBA-15 containing carbonized surfactant P123 in the mesopores; it exhibited prominent stability enhancement for methanol to propylene reaction. PMID:20461876

  12. High-temperature and pressure aluminum reactions in carbon dioxide rich post-detonation environments

    International Nuclear Information System (INIS)

    Powdered aluminum is a common additive to energetic materials, but little is understood regarding its reaction rate at very high temperatures and pressures in specific oxidizing gases such as carbon dioxide. Aluminum reaction kinetics in carbon dioxide have been studied in various reaction conditions, but difficulties arise in the more specific study of Al oxidation at the high pressures and temperatures in detonation reactions. To study these reactions, small particle size Al or the inert surrogate, LiF, was added to the energetic material benzotrifuroxan (BTF). BTF is a hydrogen-free material that selectively forms CO2 as the major oxidizing species for post-detonation Al oxidation. High-fidelity PDV measurements were utilized for early wall velocity expansion measurements in 12.7 mm copper cylinders. The JWL equation of state was solved to determine temperature, pressure and energies at specific time periods. A genetic algorithm was used in conjunction with a numerical simulation hydrocode, ALE3D, which enables the elucidation of aluminum reaction extent. By comparison of the Al oxidation with LiF, data indicate that Al oxidation occurs on an extremely fast time scale, beginning and completing between 1 and 25 microseconds. Unconfined, 6.4 mm diameter rate-sticks were also utilized to determine the effect of Al compared to LiF on detonation velocity.

  13. High-temperature and pressure aluminum reactions in carbon dioxide rich post-detonation environments

    Science.gov (United States)

    Tappan, B. C.; Hill, L. G.; Manner, V. W.; Pemberton, S. J.; Lieber, M. A.; Johnson, C. E.; Sanders, V. E.

    2014-05-01

    Powdered aluminum is a common additive to energetic materials, but little is understood regarding its reaction rate at very high temperatures and pressures in specific oxidizing gases such as carbon dioxide. Aluminum reaction kinetics in carbon dioxide have been studied in various reaction conditions, but difficulties arise in the more specific study of Al oxidation at the high pressures and temperatures in detonation reactions. To study these reactions, small particle size Al or the inert surrogate, LiF, was added to the energetic material benzotrifuroxan (BTF). BTF is a hydrogen-free material that selectively forms CO2 as the major oxidizing species for post-detonation Al oxidation. High-fidelity PDV measurements were utilized for early wall velocity expansion measurements in 12.7 mm copper cylinders. The JWL equation of state was solved to determine temperature, pressure and energies at specific time periods. A genetic algorithm was used in conjunction with a numerical simulation hydrocode, ALE3D, which enables the elucidation of aluminum reaction extent. By comparison of the Al oxidation with LiF, data indicate that Al oxidation occurs on an extremely fast time scale, beginning and completing between 1 and 25 microseconds. Unconfined, 6.4 mm diameter rate-sticks were also utilized to determine the effect of Al compared to LiF on detonation velocity.

  14. Modeling of Sheath Ion-Molecule Reactions in Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes

    Science.gov (United States)

    Hash, David B.; Govindan, T. R.; Meyyappan, M.

    2004-01-01

    In many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.

  15. Shrinkage Cracking: A mechanism for self-sustaining carbon mineralization reactions in olivine rocks

    Science.gov (United States)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xing, T.; Xiao, X.; De Andrade, V. J. D.; Karato, S. I.

    2015-12-01

    The hydration and carbonation of olivine results in an up to ~44% increase in solid molar volume, which may choke off of fluid supply and passivate reactive surfaces, thus preventing further carbonation reactions. The carbonation of olivine has ben studied extensively in the laboratory. To date, observations from these experimental studies indicate that carbonation reaction rates generally decrease with time and the extent of carbonation is limited in olivine rocks. Field studies, however, show that 100% hydration and carbonation occur naturally in ultramafic rocks. The disagreement between the laboratory results under controlled conditions and the field observations underlines the lack of understanding of the mechanisms responsible for the self-sustaining carbonation interaction in nature. We developed a state-of-the-art pressurized hydrothermal cell that is transparent to X-rays to characterize the real-time evolution of pore geometry during fluid-rock interaction using in-situ synchrotron-based X-ray microtomography. Through a time series of high-resolution 3-dimensional images, we document the microstructural evolution of a porous olivine aggregate reacting with a sodium bicarbonate solution at elevated pressure and temperature conditions. We observed porosity increases, near constant rate of crystal growth, and pervasive reaction-induced fractures. Based on the nanometer scale tomography data, we propose that shrinkage cracking is the mechanism responsible for producing new reactive surface and keep the carbonation reaction self-sustaining in our experiment. Shrinkage cracks are commonly observed in drying mud ponds, cooling lava flows and ice wedge fields. Stretching of a contracting surface bonded to a substrate of nearly constant dimensions leads to a stress buildup in the surface layer. When the stress exceeds the tensile strength, polygonal cracks develop in the surface layer. In our experiments, the stretching mismatch between the surface and interior of

  16. Effect of Fiber Surface Structure on Interfacial Reaction between Carbon Fiber and Aluminium

    Science.gov (United States)

    Chang, Kuang-Chih; Matsugi, Kazuhiro; Sasaki, Gen; Yanagisawa, Osamu

    Surface structure of carbon fiber and interfacial reaction between fiber and aluminium in carbon fiber reinforced aluminium composites were investigated by high-resolution transmission electron microscopy. Low and high graphitized carbon fiber reinforced pure aluminium composites were prepared by ultrasonic liquid infiltration. Vapor grown carbon nano fiber (VGCF) reinforced pure aluminium composites were prepared by hot-pressing. Heteroatoms, which existed abundantly in the surface of low graphitized carbon fiber, caused carbon lamellar structure in the fiber surface pronounced curvature. VGCF surface structure appeared regular and linear graphitic lamellae. Low graphitized fiber reinforced pure aluminium composites revealed serious interfacial reaction produced crystalline aluminium carbides (Al4C3), compared to composites reinforced by high graphitized fiber. On the other hand, Al4C3 crystalline reactants were not found at the interface of VGCF reinforced pure aluminium composites, but formation of interlayer was observed. In order to promote Al4C3 growth, carbon fiber reinforced composites were heat-treated at 573K and 873K for 1.8ks. Al4C3 interfacial phases in low and high graphitized fiber reinforced aluminium composites grew with the rise in the temperature. The heat-treatment resulted in the formation of non-crystalline Al4C3 interlayer by energy dispersive X-ray spectroscopy analysis of electron microscopy. At high temperature, Al4C3 was not grew and increased merely at the interface between carbon fiber and pure aluminium matrix, and moreover, the formation of new Al4C3 crystal occurred in this interlayer.

  17. Concurrent Formation of Carbon-Carbon Bonds and Functionalized Graphene by Oxidative Carbon-Hydrogen Coupling Reaction.

    Science.gov (United States)

    Morioku, Kumika; Morimoto, Naoki; Takeuchi, Yasuo; Nishina, Yuta

    2016-01-01

    Oxidative C-H coupling reactions were conducted using graphene oxide (GO) as an oxidant. GO showed high selectivity compared with commonly used oxidants such as (diacetoxyiodo) benzene and 2,3-dichloro-5,6-dicyano-p-benzoquinone. A mechanistic study revealed that radical species contributed to the reaction. After the oxidative coupling reaction, GO was reduced to form a material that shows electron conductivity and high specific capacitance. Therefore, this system could concurrently achieve two important reactions: C-C bond formation via C-H transformation and production of functionalized graphene. PMID:27181191

  18. Changes in a coke structure due to reaction with carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Pusz, S.; Majewska, J.; Pilawa, B. [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, PL-41819 Zabrze (Poland); Krzesinska, M. [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, PL-41819 Zabrze (Poland); Silesian Technical University, Department of Electron Technology, Institute of Physics, Krzywoustego 2, PL-44100 Gliwice (Poland); Smedowski, L. [Silesian Technical University, Department of Electron Technology, Institute of Physics, Krzywoustego 2, PL-44100 Gliwice (Poland); Kwiecinska, B. [AGH-University of Science and Technology, Aleja Mickiewicza 30, PL-30059 Krakow (Poland)

    2010-04-01

    Technological properties of a coke directly depend on a coke structure, i.e., on carbon matrix (a solid phase in a porous medium) and on pore system. Coke structure is deeply transformed during blast furnace operation and one of the most important factors responsible for that is the CO{sub 2} gasification. The objective of this work was to investigate changes of the physical structure of a coke upon the reaction with carbon dioxide to evaluate the effects of structural transformations on technological properties of a coke. Selected physical parameters of cokes produced in a laboratory scale were carried out prior to and after the reaction with CO{sub 2}. The following physical methods were used for the study: helium gas densitometry, physical adsorption of N{sub 2}, optical microscopy, transmission electron microscopy (TEM), ultrasonic measurements and electron paramagnetic resonance spectroscopy (EPR). The results showed that the reaction with CO{sub 2} distinctly affects the physical structure of coke. Coke solid matrix becomes better ordered, with greater structural units, while development of pore structure consists in the enlargement and coalescence of pores and the increase of specific surface area. Great increase of coke porosity after the reaction with CO{sub 2} seems to be more affecting the final strength and reactivity of coke than the transformation of carbon matrix. (author)

  19. Solid-state reaction between tungsten and hydrogen-containing carbon film at elevated temperature

    International Nuclear Information System (INIS)

    The solid-state reaction between hydrogen-containing carbon and tungsten was studied by means of infrared, Raman, X-ray photoelectron (XPS) and thermal desorption (TDS) spectroscopies. Infrared and Raman spectroscopies revealed that as-prepared hydrogen-containing films were composed of carbon atoms with sp2 and sp3 hybridized orbitals, where hydrogen was bound to carbon as -CH3 and >CH2. Vacuum heating of the carbon films deposited on tungsten caused thermal desorption peaks of hydrogen at about 723 and 1173 K in TDS. The former was accompanied by other desorption of CO, CO2 and hydrocarbons, whereas the latter was evolved with only a minor amount of CO. It was observed by XPS that the W4f peak began to appear at about 773 K, with an increasing surface composition corresponding to tungsten carbide at 1273 K. These observations indicate that a solid-state reaction between the carbon film and tungsten took place extensively above 973 K to yield an intermetallic compound of W2C at 1273 K

  20. Fabrication and characterization of reaction bonded silicon carbide/carbon nanotube composites

    International Nuclear Information System (INIS)

    Carbon nanotubes have generated considerable excitement in the scientific and engineering communities because of their exceptional mechanical and physical properties observed at the nanoscale. Carbon nanotubes possess exceptionally high stiffness and strength combined with high electrical and thermal conductivities. These novel material properties have stimulated considerable research in the development of nanotube-reinforced composites (Thostenson et al 2001 Compos. Sci. Technol. 61 1899, Thostenson et al 2005 Compos. Sci. Technol. 65 491). In this research, novel reaction bonded silicon carbide nanocomposites were fabricated using melt infiltration of silicon. A series of multi-walled carbon nanotube-reinforced ceramic matrix composites (NT-CMCs) were fabricated and the structure and properties were characterized. Here we show that carbon nanotubes are present in the as-fabricated NT-CMCs after reaction bonding at temperatures above 1400 deg. C. Characterization results reveal that a very small volume content of carbon nanotubes, as low as 0.3 volume %, results in a 75% reduction in electrical resistivity of the ceramic composites. A 96% decrease in electrical resistivity was observed for the ceramics with the highest nanotube volume fraction of 2.1%

  1. Role of Carbon-Addition and Hydrogen-Migration Reactions in Soot Surface Growth.

    Science.gov (United States)

    Zhang, Hong-Bo; Hou, Dingyu; Law, Chung K; You, Xiaoqing

    2016-02-11

    Using density functional theory and master equation modeling, we have studied the kinetics of small unsaturated aliphatic molecules reacting with polycyclic aromatic hydrocarbon (PAH) molecules having a diradical character. We have found that these reactions follow the mechanism of carbon addition and hydrogen migration (CAHM) on both spin-triplet and open-shell singlet potential energy surfaces at a rate that is about ten times those of the hydrogen-abstraction-carbon-addition (HACA) reactions at 1500 K in the fuel-rich postflame region. The results also show that the most active reaction sites are in the center of the zigzag edges of the PAHs. Furthermore, the reaction products are more likely to form straight rather than branched aliphatic side chains in the case of reacting with diacetylene. The computed rate constants are also found to be independent of pressure at conditions of interest in soot formation, and the activation barriers of the CAHM reactions are linearly correlated with the diradical characters. PMID:26799641

  2. Synthesis of propylene carbonate from urea and propylene glycol over zinc oxide: A homogeneous reaction

    OpenAIRE

    Dengfeng Wang; Xuelan Zhang; Tingting Cheng; Jing Wu; Qijun Xue

    2014-01-01

    In this work, several metal oxides and zinc salts were used to catalyze propylene carbonate (PC) synthesis from urea and propylene glycol (PG). According to the results of catalytic test and characterization, the catalytic pattern of ZnO was different from that of other metal oxides such as CaO, MgO and La2O3, but similar to that of zinc salts. In fact, the leaching of Zn species took place during reaction for ZnO. And ZnO was found to be the precursor of homogenous catalyst for reaction of u...

  3. tert-Butanesulfinamides as Nitrogen Nucleophiles in Carbon-Nitrogen Bond Forming Reactions.

    Science.gov (United States)

    Ramirez Hernandez, Johana; Chemla, Fabrice; Ferreira, Franck; Jackowski, Olivier; Oble, Julie; Perez-Luna, Alejandro; Poli, Giovanni

    2016-01-01

    The use of tert-butanesulfinamides as nitrogen nucleophiles in carbon-nitrogen bond forming reactions is reviewed. This field has grown in the shadow of the general interest in N-tert-butanesulfinyl imines for asymmetric synthesis and occupies now an important place in its own right in the chemistry of the chiral amine reagent tert-butanesulfinamide. This article provides an overview of the area and emphasizes recent contributions wherein the tert-butanesulfinamides act as chiral auxiliaries or perform as nitrogen donors in metal-catalyzed amination reactions. PMID:26931222

  4. Reactions of the inner surface of carbon nanotubes and nanoprotrusion processes imaged at the atomic scale

    Science.gov (United States)

    Chamberlain, Thomas W.; Meyer, Jannik C.; Biskupek, Johannes; Leschner, Jens; Santana, Adriano; Besley, Nicholas A.; Bichoutskaia, Elena; Kaiser, Ute; Khlobystov, Andrei N.

    2011-09-01

    Although the outer surface of single-walled carbon nanotubes (atomically thin cylinders of carbon) can be involved in a wide range of chemical reactions, it is generally thought that the interior surface of nanotubes is unreactive. In this study, we show that in the presence of catalytically active atoms of rhenium inserted into nanotubes, the nanotube sidewall can be engaged in chemical reactions from the inside. Aberration-corrected high-resolution transmission electron microscopy operated at 80 keV allows visualization of the formation of nanometre-sized hollow protrusions on the nanotube sidewall at the atomic level in real time at ambient temperature. Our direct observations and theoretical modelling demonstrate that the nanoprotrusions are formed in three stages: (i) metal-assisted deformation and rupture of the nanotube sidewall, (ii) the fast formation of a metastable asymmetric nanoprotrusion with an open edge and (iii) a slow symmetrization process that leads to a stable closed nanoprotrusion.

  5. Sustainable Ways of Combining Reactions and Separations Using Ionic Liquids and Carbon Dioxide

    OpenAIRE

    Kazemi, S.

    2013-01-01

    Traditional chemical processes show shortcomings caused by using volatile organic compounds as solvents during reactions and separations. Therefore, it is necessary to address this issue by moving toward more environmentally friendly processes. This is possible by using less toxic and hazardous solvents, such as ionic liquids and supercritical carbon dioxide (scCO2). Ionic liquids have attracted a lot of attention as potential “green” solvents to replace conventional organic solvents due to t...

  6. Reaction mechanisms in the reduction of Winterveld chrome spinel with graphite and carbon

    International Nuclear Information System (INIS)

    The reduction of mixtures of various sizes of gangue-free Winterveld chrome spinel and graphite under an argon atmosphere at 1300 degrees Celsius was studied by use of a recording thermobalance. The partially reduced material was examined by scanning electron microscopy, and the observations were analysed in terms of reaction mechanism. A four-stage sequence was deduced, as follows. In the first stage, the ferric iron is reduced to ferrous iron with no metallization. This stage is inherently variable and is controlled by the random packing of particles of reducing agent round the chromite. The second stage starts with a burst of metal nucleation, which is also inherently variable. This is followed by the reaction of carbon monoxide with the relatively highly reducible oxide at the perimeters of the metal nuclei, and is controlled by the regeneration of carbon monoxide by the Boudouard reaction. The second stage merges into the third, with no change in the form of the product until the removal of iron decreases the reducibility of the remaining oxide to such an extent that the activity of the carbon monoxide is not sufficient for reduction to proceed. Reduction is then accomplished by the carbon dissolved in the reduced metallic product, the rate of reduction being limited by the rate of carburization of the metal. The fourth stage is reached at a reduction of about 50 per cent. In that stage the rate is controlled by the diffusion of chromium ions in the oxide, and the reduced product becomes saturated with carbon as the mixed (Fe,Cr)7C3 carbide

  7. Electrochemical characteristics of vanadium redox reactions on porous carbon electrodes for microfluidic fuel cell applications

    International Nuclear Information System (INIS)

    Microfluidic vanadium redox fuel cells are membraneless and catalyst-free fuel cells comprising a microfluidic channel network with two porous carbon electrodes. The anolyte and catholyte for fuel cell operation are V(II) and V(V) in sulfuric acid based aqueous solution. In the present work, the electrochemical characteristics of the vanadium redox reactions are investigated on commonly used porous carbon paper electrodes and compared to a standard solid graphite electrode as baseline. Half-cell electrochemical impedance spectroscopy is applied to measure the overall ohmic resistance and resistivity of the electrodes. Kinetic parameters for both V(II) and V(V) discharging reactions are extracted from Tafel plots and compared for the different electrodes. Cyclic voltammetry techniques reveal that the redox reactions are irreversible and that the magnitudes of peak current density vary significantly for each electrode. The obtained kinetic parameters for the carbon paper are implemented into a numerical simulation and the results show a good agreement with measured polarization curves from operation of a microfluidic vanadium redox fuel cell employing the same material as flow-through porous electrodes. Recommendations for microfluidic fuel cell design and operation are provided based on the measured trends.

  8. Reservoir-Condition Pore-Scale Imaging of Reaction in Carbonates using Synchrotron Fast Tomography

    Science.gov (United States)

    Menke, H. P.; Andrew, M. G.; Bijeljic, B.; Blunt, M. J.

    2015-12-01

    Carbon capture and storage in carbonate reservoirs is essential for mitigating climate change. Supercritical CO2 mixed with host brine is acidic and can dissolve the surrounding pore structure and change flow dynamics. However, the type, speed, and magnitude of the dissolution are dependent on both the reactive transport properties of the pore-fluid and the intrinsic properties of the rock. Understanding how changes in the pore structure, chemistry, and flow properties affect dissolution is vital for successful predictive modelling both on the pore-scale and for up-scaled reservoir simulations. Reaction in carbonates has been studied at the pore-scale but has never been imaged dynamically in situ. We present an experimental method whereby both lab-based benchtop instruments and 'Pink Beam' synchrotron radiation are used in X-ray microtomography to investigate pore structure changes during supercritical CO2 injection at reservoir conditions. Three types of pure limestone rock with broadly varying rock topology were imaged under the same reservoir conditions. Flow-rate and brine acidity was varied in successive experiments by half an order of magnitude to gain insight into the impact of flow, transport, and physical heterogeneity. The images were binarized and the magnitude of dissolution was identified on a voxel-by-voxel basis to extract pore-by-pore dissolution data. The impact of dissolution on flow characteristics was studied by computing the evolution of the pore-scale velocity fields with a flow solver. We found that increasing rock heterogeneity increased channelized flow [Figure 1] through preferential pathways and that higher flow rate increased total dissolution. Additionally, decreasing reaction rate lowered overall reaction rate and made axial flow less uniform. Experimentally measured reaction rates in real rocks are at least an order of magnitude lower when compared to batch experiments. We provide evidence that this can be due to transport limitations

  9. Nitrogen-Doped Carbon Nanotube and Graphene Materials for Oxygen Reduction Reactions

    Directory of Open Access Journals (Sweden)

    Qiliang Wei

    2015-09-01

    Full Text Available Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs and nitrogen-doped graphene (NG, have attracted increasing attention for oxygen reduction reaction (ORR in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e− transfer and superb mechanical properties. Here, the recent progress of NCNTs- and NG-based catalysts for ORR is reviewed. Firstly, the general preparation routes of these two N-doped carbon-allotropes are introduced briefly, and then a special emphasis is placed on the developments of both NCNTs and NG as promising metal-free catalysts and/or catalyst support materials for ORR. All these efficient ORR electrocatalysts feature a low cost, high durability and excellent performance, and are thus the key factors in accelerating the widespread commercialization of metal-air battery and fuel cell technologies.

  10. Reactive scattering of electronically excited alkali atoms with molecules

    International Nuclear Information System (INIS)

    Representative families of excited alkali atom reactions have been studied using a crossed beam apparatus. For those alkali-molecule systems in which reactions are also known for ground state alkali and involve an early electron transfer step, no large differences are observed in the reactivity as Na is excited. More interesting are the reactions with hydrogen halides (HCl): it was found that adding electronic energy into Na changes the reaction mechanism. Early electron transfer is responsible of Na(5S, 4D) reactions, but not of Na(3P) reactions. Moreover, the NaCl product scattering is dominated by the HCl- repulsion in Na(5S, 4D) reactions, and by the NaCl-H repulsion in the case of Na(3P). The reaction of Na with O2 is of particular interest since it was found to be state specific. Only Na(4D) reacts, and the reaction requires restrictive constraints on the impact parameter and the reactants' relative orientation. The reaction with NO2 is even more complex since Na(4D) leads to the formation of NaO by two different pathways. It must be mentioned however, that the identification of NaO as product in these reactions has yet to be confirmed

  11. The neighboring effect of isosorbide and its epimers in their reactions with dimethyl carbonate

    Directory of Open Access Journals (Sweden)

    Fabio Aricò

    2014-10-01

    Full Text Available The reactions of isosorbide and its epimers, isomannide and isoidide, with dimethyl carbonate have been herein investigated as easy access to bio-based products by a free-halogen chemistry approach. Isosorbide and its epimers show a different reactivity in bimolecular nucleophilic substitution with dimethyl carbonate (DMC. Carboxymethylation reaction was carried out in the presence of DMC and a weak base resulting in the high-yielding synthesis of dicarboxymethyl derivatives. Isomannide was the most reactive anydro sugar due to the less sterically hindered exo position of the OH groups. On the other hand, methylation of isosorbide and its epimers, conducted in the presence of a strong base and DMC, showed the higher reactivity of the endo hydroxyl group, isoidide being the most reactive epimer. This result has been ascribed to the neighboring effect due to the combination of the oxygen in β-position and the intramolecular hydrogen bond within the anhydro sugar structure. Methylation reactions were also conducted in autoclave at high temperature with the amphoteric catalyst hydrotalcite using DMC as reagent and solvent. In this case, the reactivity of the epimers resulted quite differently with isosorbide being the most reactive reagent possibly as a result of the structure of hydrotalcite comprising of both acidic and basic sites. The neighboring effect was observed with good evidence in these methylation reactions.

  12. Synthesis of propylene carbonate from urea and propylene glycol over zinc oxide: A homogeneous reaction

    Directory of Open Access Journals (Sweden)

    Dengfeng Wang

    2014-11-01

    Full Text Available In this work, several metal oxides and zinc salts were used to catalyze propylene carbonate (PC synthesis from urea and propylene glycol (PG. According to the results of catalytic test and characterization, the catalytic pattern of ZnO was different from that of other metal oxides such as CaO, MgO and La2O3, but similar to that of zinc salts. In fact, the leaching of Zn species took place during reaction for ZnO. And ZnO was found to be the precursor of homogenous catalyst for reaction of urea and PG. Thus, the relationship between the amount of dissolved zinc species and the catalytic performance of employed ZnO was revealed. In addition, a possible reaction mechanism over ZnO was discussed based on the catalytic runs and the characterization of XRD, FTIR, and element analysis.

  13. Effect of carbon on the Ni catalyzed methane cracking reaction: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jingde; Croiset, Eric; Ricardez–Sandoval, Luis, E-mail: laricard@uwaterloo.ca

    2014-08-30

    Highlights: • Effect of carbon deposition on kinetic properties of methane dissociation is studied. • Existence of surface and subsurface C atoms destabilized CH{sub x} species adsorption. • CH{sub x} activation is hindered with the deposition of C on and in the Ni (1 1 1) surface. - Abstract: To understand the effects of carbon atoms on the Ni catalyzed methane cracking reactions, methane dissociation on clean, surface-carbon-covered, and subsurface-carbon-accumulated Ni(1 1 1) surfaces were investigated using density functional theory (DFT). The results show that the existence of surface and subsurface C atoms destabilized the adsorption of the surface hydrocarbon species when compared to the clean Ni(1 1 1) surface. The projected density state (PDOS) analysis shows that the deposition of C atoms on and into the Ni surface modified the electronic structure of the Ni surface, and thus reduced the catalytic activity of the bonded Ni atoms. Moreover, it was found that the presence carbon atoms increase the CH{sub x} (x = 4–1) species activation barriers especially on the surface carbon covered (1/4 ML) Ni(1 1 1) surface, where CH{sub x} (x = 4–1) species encounter highest energy barrier for dissociation due to the electronic deactivation induced by C-Ni bonding and the strong repulsive carbon -CH{sub x} interaction. The calculations also show that CH{sub x} dissociation barriers are not affected by its neighboring C atom at low surface carbon coverage (1/9 ML). This work can be used to estimate more realistic kinetic parameters for this system.

  14. Effect of carbon on the Ni catalyzed methane cracking reaction: A DFT study

    International Nuclear Information System (INIS)

    Highlights: • Effect of carbon deposition on kinetic properties of methane dissociation is studied. • Existence of surface and subsurface C atoms destabilized CHx species adsorption. • CHx activation is hindered with the deposition of C on and in the Ni (1 1 1) surface. - Abstract: To understand the effects of carbon atoms on the Ni catalyzed methane cracking reactions, methane dissociation on clean, surface-carbon-covered, and subsurface-carbon-accumulated Ni(1 1 1) surfaces were investigated using density functional theory (DFT). The results show that the existence of surface and subsurface C atoms destabilized the adsorption of the surface hydrocarbon species when compared to the clean Ni(1 1 1) surface. The projected density state (PDOS) analysis shows that the deposition of C atoms on and into the Ni surface modified the electronic structure of the Ni surface, and thus reduced the catalytic activity of the bonded Ni atoms. Moreover, it was found that the presence carbon atoms increase the CHx (x = 4–1) species activation barriers especially on the surface carbon covered (1/4 ML) Ni(1 1 1) surface, where CHx (x = 4–1) species encounter highest energy barrier for dissociation due to the electronic deactivation induced by C-Ni bonding and the strong repulsive carbon -CHx interaction. The calculations also show that CHx dissociation barriers are not affected by its neighboring C atom at low surface carbon coverage (1/9 ML). This work can be used to estimate more realistic kinetic parameters for this system

  15. Correlation between carbon-carbon bond length and the ease of retro Diels-Alder reaction

    Indian Academy of Sciences (India)

    Sambasivarao Kotha; Shaibal Banerjee; Mobin Shaikh

    2014-09-01

    The bond length between C8-C9 in (1′R,4′S,4a′R,8a′S)-6′,7′-dimethyl-1′,4′,4a′,8a′-tetrahydrospiro [cyclopropane-1,9′-[1,4]methanonaphthalene]-5′,8′-dione is 1.571 (2) Å and between C7-C12 is 1.567 (2) Å which are longer than the corresponding bond length for saturated bicyclic systems (1.531-1.535Å). This paper reports the correlation between bond length and the ease of retro Diels−Alder reaction.

  16. Thermodynamic Data for Geochemical Modeling of Carbonate Reactions Associated with CO2 Sequestration – Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, Kenneth M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cantrell, Kirk J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McGrail, B. Peter [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2010-09-01

    Permanent storage of anthropogenic CO2 in deep geologic formations is being considered as a means to reduce the concentration of atmospheric CO2 and thus its contribution to global climate change. To ensure safe and effective geologic sequestration, numerous studies have been completed of the extent to which the CO2 migrates within geologic formations and what physical and geochemical changes occur in these formations when CO2 is injected. Sophisticated, computerized reservoir simulations are used as part of field site and laboratory CO2 sequestration studies. These simulations use coupled multiphase flow-reactive chemical transport models and/or standalone (i.e., no coupled fluid transport) geochemical models to calculate gas solubility, aqueous complexation, reduction/oxidation (redox), and/or mineral solubility reactions related to CO2 injection and sequestration. Thermodynamic data are critical inputs to modeling geochemical processes. The adequacy of thermodynamic data for carbonate compounds has been identified as an important data requirement for the successful application of these geochemical reaction models to CO2 sequestration. A review of thermodynamic data for CO2 gas and carbonate aqueous species and minerals present in published data compilations and databases used in geochemical reaction models was therefore completed. Published studies that describe mineralogical analyses from CO2 sequestration field and natural analogue sites and laboratory studies were also reviewed to identify specific carbonate minerals that are important to CO2 sequestration reactions and therefore require thermodynamic data. The results of the literature review indicated that an extensive thermodynamic database exists for CO2 and CH4 gases, carbonate aqueous species, and carbonate minerals. Values of ΔfG298° and/or log Kr,298° are available for essentially all of these compounds. However, log Kr,T° or heat capacity values at temperatures above 298 K exist for less than

  17. Natural Alkali Shifts to the Methanol Business

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Inner Mongolia Yuanxing Natural Alkali Co., Ltd. (Natural Alkali SZ: 000683) established in 1997 is a large chemical enterprise with new energy as its leading business and natural gas chemicals and natural alkali chemicals as the supplement business.

  18. Functionalized Carbon Nanomaterial Supported Palladium Nano-Catalysts for Electrocatalytic Glucose Oxidation Reaction

    International Nuclear Information System (INIS)

    Highlights: • Glucose oxidation reaction (GOR) catalyzed by Pd on carbon nano-supports. • Polyol reduction used for nano-size Pd catalyst synthesis. • Effect of carbon support’s functionality on nano-Pd GOR catalysis disclosed. • Carboxylated MWCNT found to be the best carbon nano-support. • Peak current density of 5.5 mA cm−2 attained for alkaline GOR. - Abstract: Palladium nanoparticles (nPd) are grown on six carbon nanomaterials with different functionalities by one-pot, high-pH polyol reduction of PdCl2. The nanomaterials include pristine multi-walled carbon nanotubes (pMWCNT), carboxylated MWCNT (cMWCNT), amine-modified MWCNT (nMWCNT), hydroxyl-modified MWCNT (oMWCNT), XC72 carbon black (XC72), and carboxylated graphene (cGraphene). The effects of the carbon functionality on Pd-catalyzed glucose oxidation reaction (GOR) in an alkaline medium are studied. From the experimental data of X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM), it reveals that nPds with a particle size ranging from 4.5 nm to 7.4 nm are grown on carbon nanomaterials with a weight loading percentage from 11.1% to 18.6%. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), Tafel analysis, and chronoamperomtry (CA) are used to compare the electrochemical active surface area (ECSA), GOR onset potential, GOR peak current density, Tafel slope, poisoning rate, and cycling stability between the six nPd/C electrocatalysts for GOR. It is found that nPd grown on a functionalized carbon nano-support had better GOR performance than that grown on pMWCNT. Compared to nPd/pMWCNT, nPd/cMWCNT shows a 6.2-fold higher peak current density (5.6 mA cm−2) and a 100 mV lower over-potential (-0.55 V vs. Hg/HgO) for GOR. Besides, the data are among the best for nPd-catalyzed GOR reported to date

  19. Distribution of hydrogen peroxide-dependent reaction in a gelatin sample irradiated by carbon ion beam

    International Nuclear Information System (INIS)

    We investigated the amount and distribution of hydrogen peroxide (H2O2) generated in a solid gelatin sample irradiated by heavy ion (carbon) beam. We irradiated the gelatin sample, which contained a nitroxyl radical (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, TEMPOL), with a 290-MeV/nucleon carbon beam (-128 Gy). To verify the distribution of H2O2 generation in the irradiated sample, we employed both electron paramagnetic resonance (EPR) spectroscopic and magnetic resonance (MR) imaging methods based on H2O2-dependent paramagnetic loss of TEMPOL. We obtained a distribution profile of the H2O2-dependent reaction in the gelatin sample when we irradiated gelatin samples with carbon beams with several different linear energy transfer (LET) values. Because the profiles of oxygen consumption in the gelatin sample measured by L-band EPR oxymetry and of the H2O2-dependent reaction have almost the same shape, the profile of the H2O2-dependent reaction can be used as an estimation of the profile of the generation of H2O2. The H2O2 profile in one intact gelatin sample scanned by 7-tesla MR imaging showed a similar shape as a result of the EPR experiment. We obtained several hundreds of micromolars of H2O2 generated in a gelatin sample irradiated by carbon beam when 200 Gy was given at the surface of the sample. H2O2 distribution was almost flat, with only a slight peak just before the end of the beam. (author)

  20. Sintering uranium oxide in the reaction product of hydrogen-carbon dioxide mixtures

    International Nuclear Information System (INIS)

    Compacted pellets of uranium oxide alone or containing one or more additives such as plutonium dioxide, gadolinium oxide, titanium dioxide, silica, and alumina are heated to 900 to 15990C in the presence of a mixture of hydrogen and carbon dioxide, either alone or with an inert carrier gas and held at the desired temperature in this atmosphere to sinter the pellets. The sintered pellets are then cooled in an atmosphere having an oxygen partial pressure of 10-4 to 10-18 atm of oxygen such as dry hydrogen, wet hydrogen, dry carbon monoxide, wet carbon monoxide, inert gases such as nitrogen, argon, helium, and neon and mixtures of ayny of the foregoing including a mixture of hydrogen and carbon dioxide. The ratio of hydrogen to carbon dioxide in the gas mixture fed to the furnace is controlled to give a ratio of oxygen to uranium atoms in the sintered particles within the range of 1.98:1 to about 2.10:1. The water vapor present in the reaction products in the furnace atmosphere acts as a hydrolysis agent to aid removal of fluoride should such impurity be present in the uranium oxide. (U.S.)

  1. Sulfur-doped carbon nanotubes as catalysts for the oxygen reduction reaction in alkaline medium

    International Nuclear Information System (INIS)

    Based on the unique electronic properties and high surface area of carbon nanotubes as well as the similar electronegativity of sulfur and carbon, a novel electrocatalyst for the oxygen reduction reaction (ORR) was fabricated by directly annealing oxidized carbon nanotubes and p-benzenedithiol in nitrogen. The structural and chemical properties of the resulting sulfur-doped carbon nanotubes (pSCNTs) were investigated using transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The catalytic activity of the pSCNTs towards ORR in alkaline medium was evaluated using rotating ring disk electrode voltammetry. The as-synthesized pSCNT-900 (annealed at 900 °C) exhibits excellent electrochemical performance towards ORR with an onset potential of –0.082 V (vs Ag/AgCl), a high kinetic current density of 34.6 mA cm−2 at –0.35 V), a dominant four-electron transfer mechanism (n = 3.71 at –0.35 V), as well as excellent methanol tolerance and durability. The results obtained are significant for the development of S-doped carbon-based catalysts for alkaline fuel cells

  2. Polyaniline-Derived Ordered Mesoporous Carbon as an Efficient Electrocatalyst for Oxygen Reduction Reaction

    Directory of Open Access Journals (Sweden)

    Kai Wan

    2015-06-01

    Full Text Available Nitrogen-doped ordered mesoporous carbon was synthesized by using polyaniline as the carbon source and SBA-15 as the template. The microstructure, composition and electrochemical behavior were extensively investigated by the nitrogen sorption isotherm, X-ray photoelectron spectroscopy, cyclic voltammetry and rotating ring-disk electrode. It is found that the pyrolysis temperature yielded a considerable effect on the pore structure, elemental composition and chemical configuration. The pyrolysis temperature from 800 to 1100 °C yielded a volcano-shape relationship with both the specific surface area and the content of the nitrogen-activated carbon. Electrochemical tests showed that the electrocatalytic activity followed a similar volcano-shape relationship, and the carbon catalyst synthesized at 1000 °C yielded the best performance. The post-treatment in NH3 was found to further increase the specific surface area and to enhance the nitrogen doping, especially the edge-type nitrogen, which favored the oxygen reduction reaction in both acid and alkaline media. The above findings shed light on electrocatalysis and offer more strategies for the controllable synthesis of the doped carbon catalyst.

  3. Evaluating reaction pathways of hydrothermal abiotic organic synthesis at elevated temperatures and pressures using carbon isotopes

    Science.gov (United States)

    Fu, Qi; Socki, Richard A.; Niles, Paul B.

    2015-04-01

    Experiments were performed to better understand the role of environmental factors on reaction pathways and corresponding carbon isotope fractionations during abiotic hydrothermal synthesis of organic compounds using piston cylinder apparatus at 750 °C and 5.5 kbars. Chemical compositions of experimental products and corresponding carbon isotopic values were obtained by a Pyrolysis-GC-MS-IRMS system. Alkanes (methane and ethane), straight-chain saturated alcohols (ethanol and n-butanol) and monocarboxylic acids (formic and acetic acids) were generated with ethanol being the only organic compound with higher δ13C than CO2. CO was not detected in experimental products owing to the favorable water-gas shift reaction under high water pressure conditions. The pattern of δ13C values of CO2, carboxylic acids and alkanes are consistent with their equilibrium isotope relationships: CO2 > carboxylic acids > alkanes, but the magnitude of the fractionation among them is higher than predicted isotope equilibrium values. In particular, the isotopic fractionation between CO2 and CH4 remained constant at ∼31‰, indicating a kinetic effect during CO2 reduction processes. No "isotope reversal" of δ13C values for alkanes or carboxylic acids was observed, which indicates a different reaction pathway than what is typically observed during Fischer-Tropsch synthesis under gas phase conditions. Under constraints imposed in experiments, the anomalous 13C isotope enrichment in ethanol suggests that hydroxymethylene is the organic intermediate, and that the generation of other organic compounds enriched in 12C were facilitated by subsequent Rayleigh fractionation of hydroxymethylene reacting with H2 and/or H2O. Carbon isotope fractionation data obtained in this study are instrumental in assessing the controlling factors on abiotic formation of organic compounds in hydrothermal systems. Knowledge on how environmental conditions affect reaction pathways of abiotic synthesis of organic

  4. Electrocatalytic Activity of Carbonized Nanostructured Polyanilines for Oxidation Reactions: Sensing of Nitrite Ions and Ascorbic Acid

    International Nuclear Information System (INIS)

    Highlights: • Carbonized PANIs prepared from various nanostructured PANI precursors • Electroanalytical performances of carbonized PANIs evaluated using voltammetry • Study of carbonized PANIs physico-chemical properties related to electroactivity • The lowest over-potential for NO2− oxidation at c-PANI (+0.87 V vs. SCE) • The lowest over-potential for ascorbic acid oxidation at both c-PANI and c-PANI-SSA - Abstract: A comparative study of the electrocatalytic activity of nitrogen-containing carbon nanomaterials, prepared by the carbonization of nanostructured polyaniline (PANI) salts, for the electrooxidation reactions is presented. Nanostructured PANI salts were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous solution in the presence of 5-sulfosalicylic acid (PANI-SSA), 3,5-dinitrosalicylic acid (PANI-DNSA) as well as without added acid (PANI), and subsequently carbonized to c-PANI-SSA, c-PANI-DNSA and c-PANI, respectively. Glassy carbon tip was modified with nanostructured c-PANIs and used for the investigation of sensing of nitrite and ascorbic acid in aqueous solutions as model analytes by linear sweep voltammetry. All three types of the investigated c-PANIs gave excellent response to the nitrite ions and ascorbic acid electrooxidation. The lowest peak potential for nitrite ion oxidation exhibited c-PANI (+0.87 V vs. SCE), and for ascorbic acid oxidation both c-PANI and c-PANI-SSA (ca. + 0.13 V vs. SCE). Electrochemical data were correlated with structural and textural data obtained by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental and nitrogen sorption analysis

  5. The influence of carbon surface chemistry on supported palladium nanoparticles in heterogeneous reactions.

    Science.gov (United States)

    Ding, Yuxiao; Zhang, Liyun; Wu, Kuang-Hsu; Feng, Zhenbao; Shi, Wen; Gao, Qiang; Zhang, Bingsen; Su, Dang Sheng

    2016-10-15

    The surface chemistry of nanocarbon support can tailor chemical properties of precious metal nanoparticle/nanocarbon hybrid catalyst in heterogeneous reactions. We report on modified reduced graphene oxide (rGO) support with ionic liquid-derived carbonaceous surface for palladium nanoparticle (Pd NPs) decoration and their actions in different heterogeneous reactions. The surface chemistry of support materials was characterized in detail, and the influence of which on the formation and distribution of metal particles was further investigated. Three different types of reactions including Suzuki-Miyaura coupling reaction, CO oxidation and phenol reduction were examined in terms of reactivity and selectivity. The roles of substituted nitrogen in graphitic lattice and grafted groups on the carbon surface were exploited. Nitrogen-doping can give rise to changes in electronic properties of supported metals, and the Lewis basicity of the doped nitrogen atoms can favor the adsorption of acidic reactants in phenol reduction. The grafted groups derived a negative impact to the Suzuki-Miyaura coupling reaction, due to the involvement of larger reactant molecules, despite that they could prevent significant sintering of Pd NPs in the CO oxidation. PMID:27442144

  6. Unique Sandwiched Carbon Sheets@Ni-Mn Nanoparticles for Enhanced Oxygen Evolution Reaction.

    Science.gov (United States)

    Zhang, Yan; Zhang, Huijuan; Yang, Jiao; Bai, Yuanjuan; Qiu, Huajun; Wang, Yu

    2016-05-11

    A unique sandwich-like architecture, where Ni-Mn nanoparticles are enveloped in coupled carbon sheets (CS@Ni-Mn), has been successfully fabricated. In the synthesis process, a great quantity of uniform NiMnO3 nanosheets generated by a universal hydrothermal method acts as precursors and templates and the cheap, environmentally friendly and recyclable glucose functions as a green carbon source. Via subsequent hydrothermal reaction and thermal annealing, sandwiched nanocomposites with Ni-Mn nanoparticles embedded inside and carbon sheets encapsulating outside can be massively prepared. The novel sandwich-like CS@Ni-Mn possesses numerous advantages, such as an intrinsic porous feature, large specific surface area, and enhanced electronic conductivity. Moreover, as a promising NiMn-based oxygen evolution reaction (OER) catalyst, the special sandwiched nanostructure demonstrates improved electrochemical properties in 1 M KOH, including a low overpotential of about 250 mV, a modest Tafel slope of 40 mV dec(-1), excellent stability over 2000 cycles, and durability for 40 h. PMID:27101350

  7. Alkali metal and alkali earth metal gadolinium halide scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  8. Mass Transfer and Reaction Kinetics in the Carbonization of Magnesium Oxide from Light Calcined Magnesia with Mechanical Force Enhancement

    Institute of Scientific and Technical Information of China (English)

    张焕军; 朱国才

    2004-01-01

    The carbonization of magnesium oxide particles by CO2 was investigated using a stirring mill reactor.The effects of the system temperature, stirring rotation speed, influx rate of CO2 and initial diameter of the magnesium oxide particles on the carbonization process were determined. The results show that the system temperature and the stirring rotation speed are the most significant influencing factors on the carbonization rate. The determination of critical decomposition temperature (CDT) gives the maximum carbonization rate with other conditions fixed. A theoretical model involving mass transfer and reaction kinetics was presented for the carbonization process.The apparent activation energy was calculated to be 32.8kJ·mo1-1. The carbonization process is co-controlled by diffusive mass transfer and chemical reaction. The model fits well with the experimental results.

  9. Spot-free catalysis using gold carbon nanotube & gold graphene composites for hydrogen evolution reaction

    Science.gov (United States)

    Sai Siddhardha, R. S.; Lakshminarayanan, V.; Ramamurthy, Sai Sathish

    2015-08-01

    Hydrogen has been proposed as the green fuel of the future in the wake of depleting fossil fuels. Recently, carbon paste electrodes (CPE) modified with nanomaterials as electrocatalysts have drawn wide attention for hydrogen evolution reaction (HER) in acid medium. The CPEs are advantageous owing to their chemical stability and ease of fabrication. Their applications for HER without any modification, however, are hampered on account of large hydrogen overpotential associated with carbon surface. In the present study, CPE has been modified with novel gold composites as electro-catalysts for HER in acid medium. The nanocomposites have shown ∼100 fold increased current density than unmodified CPE at -0.3 V. Most strikingly for the first time, this study has quantitatively brought out the difference in catalysis between surfactant capped and pristine gold nanoparticles in terms of their application as spot-free catalysts towards hydrogen gas production by electrochemical route.

  10. Rapid Access to Spirocyclized Indolenines via Palladium-Catalyzed Cascade Reactions of Tryptamine Derivatives and Propargyl Carbonate

    OpenAIRE

    Montgomery, Thomas D.; Nibbs, Antoinette E.; Zhu, Ye; Rawal, Viresh H.

    2014-01-01

    We report the intermolecular palladium-catalyzed reaction of tert-butyl propargyl carbonate with tryptamine derivatives or other indole-containing bis-nucleophiles. The reaction proceeds under mild conditions and with low catalyst loadings to afford novel spiroindolenine products in good to high yields.

  11. Palladium on Carbon-Catalyzed Suzuki-Miyaura Coupling Reaction Using an Efficient and Continuous Flow System

    Directory of Open Access Journals (Sweden)

    Tomohiro Hattori

    2015-01-01

    Full Text Available The continuous flow Suzuki-Miyaura reaction between various haloarenes and arylboronic acids was successfully achieved within only ca. 20 s during the single-pass through a cartridge filled with palladium on carbon (Pd/C. No palladium leaching was observed in the collected reaction solution by atomic absorption spectrometry (detection limit: 1 ppm.

  12. Stepwise Quenching of Exciton Fluorescence in Carbon Nanotubes by Single Molecule Reactions

    CERN Document Server

    Cognet, Laurent; Rocha, John-David R; Doyle, Condell D; Tour, James M; Weisman, R Bruce

    2007-01-01

    Single-molecule chemical reactions with individual single-walled carbon nanotubes were observed through near-infrared photoluminescence microscopy. The emission intensity within distinct submicrometer segments of single nanotubes changes in discrete steps after exposure to acid, base, or diazonium reactants. The steps are uncorrelated in space and time, and reflect the quenching of mobile excitons at localized sites of reversible or irreversible chemical attack. Analysis of step amplitudes reveals an exciton diffusional range of about 90 nanometers, independent of nanotube structure. Each exciton visits approximately 104 atomic sites during its lifetime, providing highly efficient sensing of local chemical and physical perturbations.

  13. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    International Nuclear Information System (INIS)

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min−1. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell

  14. Carbon-14 immobilization via the CO2-Ba(OH)2 hydrate gas-solid reaction

    International Nuclear Information System (INIS)

    Although no restrictions have been placed on the release of carbon-14, it has been identified as a potential health hazard due to the ease in which it may be assimilated into the biosphere. The intent of the Carbon-14 Immobilization Program, funded through the Airborne Waste Program Management Office, is to develop and demonstrate a novel process for restricting off-gas releases of carbon-14 from various nuclear facilities. The process utilizes the CO2-Ba(OH)2 hydrate gas-solid reaction to directly remove and immobilize carbon-14. The reaction product, BaCO3, possesses both the thermal and chemical stability desired for long-term waste disposal. The process is capable of providing decontamination factors in excess of 1000 and reactant utilization of greater than 99% in the treatment of high volumetric, airlike (330 ppM CO2) gas streams. For the treatment of an air-based off-gas stream, the use of packed beds of Ba(OH)2.8H2O flakes to remove CO2 has been demonstrated. However, the operating conditions must be maintained between certain upper and lower limits with respect to the partial pressure of water. If the water vapor pressure in the gas is less than the dissociation vapor pressure of Ba(OH)2.8H2O, the bed will deactivate. If the vapor pressure is considerably greater, pressure drop problems will increase with increasing humidity as the particles curl and degrade. Results have indicated that when operated in the proper regime, the bulk of the increase in pressure drop results from the conversion of Ba(OH)2.8H2O to BaCO3 and not from the hydration of the commercial Ba(OH)2.8H2O (i.e. Ba(OH)2.7.50H2O) to Ba(OH)2.8H2O

  15. Benzyl alcohol oxidation in supercritical carbon dioxide: spectroscopic insight into phase behaviour and reaction mechanism.

    Science.gov (United States)

    Caravati, Matteo; Grunwaldt, Jan-Dierk; Baiker, Alfons

    2005-01-21

    Selective oxidation of benzyl alcohol to benzaldehyde with molecular oxygen over an alumina-supported palladium catalyst was performed with high rate at about 95% selectivity in supercritical carbon dioxide. The experiments in a continuous flow fixed-bed reactor showed that the pressure has a strong influence on the reaction rate. A marked increase of the rate (turnover frequency) from 900 h(-1) to 1800 h(-1) was observed when increasing the pressure from 140 to 150 bar. Video monitoring of the bulk fluid phase behavior and the simultaneous investigation by transmission and attenuated total reflection (ATR) infrared spectroscopy at two positions of the view cell showed that the sharp increase in activity is correlated to a transition from a biphasic to a monophasic reaction mixture. In the single phase region, both oxygen and benzyl alcohol are dissolved in the supercritical CO2 phase, which leads to a reduction of the mass transport resistances (both in the external fluid film and in the catalyst pores) and thus to the high reaction rate measured in the catalytic experiments. The phase transition could be effectively and easily monitored by transmission and ATR-IR spectroscopy despite the small concentration of the dense liquid like phase. Deposition of the Pd/Al2O3 catalyst on the ATR-crystal at the bottom of the view cell allowed to gain insight into the chemical changes and mass transfer processes occurring in the solid/liquid interface region during reaction. Analyzing the shift of the upsilon2 bending mode of CO2 gave information on the fluid composition in and outside the catalyst pores. Moreover, the catalytic reaction could be investigated in situ in this spectroscopic batch reactor cell by monitoring simultaneously the reaction progress, the phase behaviour and the catalytic interface. PMID:19785149

  16. Carbon-13 and deuterium isotope effects on the catalytic reactions of biotin carboxylase

    International Nuclear Information System (INIS)

    13C and 2H kinetic isotope effects have been used to investigate the mechanism of enzymic biotin carboxylation. /sup D/(V/K) is 0.50 in 80% D2O at pD 8.0 for the forward reaction and 0.57 at pD 8.5 for the phosphorylation of ADP by carbamoyl phosphate. These values approach the theoretical maximum limit for a reaction in which a proton is transferred from a sulfhydryl to a nitrogen or oxygen base. Therefore, it appears that this portion of the reaction is at or near equilibrium. 13(V/K) at pH 8 is 1.007; the small magnitude of this number suggests that the reaction is almost fully committed by the time the carbon-sensitive steps are reached. There does not appear to be a reverse commitment to the reaction under the conditions in which 13(V/K) was determined. A large forward commitment is consistent with the failure to observe positional isotope exchange from the βγ-bridge position to the β-nonbridge position in [18O4]ATP or washout of 18O from the γ-nonbridge positions. Transfer of 18O from bicarbonate to inorganic phosphate in the forward reaction was clearly observed, however. These observations suggest that biotin carboxylase exists in two distinct forms which differ in the protonation states of the two active-site bases, one of which is a sulfhydryl. Only when the sulfhydryl is ionized and the second base protonated can catalysis take place. Carboxylation of biotin is postulated to occur via a pathway in which carboxyphosphate is formed by nucleophilic attack of bicarbonate on ATP. Decarboxylation of carboxyphosphate in the active site generates CO2, which serves to carboxylate the isourea tautomer of biotin that is generated by the removal of the proton on N1' by the ionized sulfhydryl

  17. Theoretical and Experimental Study on Reaction Coupling: Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Dehydrogenation of ethylbenzene (EB) to styrene (ST) in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift (RWGS), was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process.The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3.Coke deposition and deep reduction of active components are the major causes of catalyst deactivation.CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.

  18. Evaluating the Catalytic Effects of Carbon Materials on the Photocatalytic Reduction and Oxidation Reactions of TiO2

    International Nuclear Information System (INIS)

    TiO2 composites with seven different carbon materials (activated carbons, graphite, carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene oxides, and reduced graphene oxides) that are virgin or treated with nitric acid are prepared through an evaporation method. The photocatalytic activities of the as-prepared samples are evaluated in terms of H2 production from aqueous methanol solution (photo-catalytic reduction: PCR) and degradation of aqueous pollutants (phenol, methylene blue, and rhodamine B) (photocatalytic oxidation: PCO) under AM 1.5-light irradiation. Despite varying effects depending on the kinds of carbon materials and their surface treatment, composites typically show enhanced PCR activity with maximum 50 times higher H2 production as compared to bare TiO2. Conversely, the carbon-induced synergy effects on PCO activities are insignificant for all three substrates. Colorimetric quantification of hydroxyl radicals supports the absence of carbon effects. However, platinum deposition on the binary composites displays the enhanced effect on both PCR and PCO reactions. These differing effects of carbon materials on PCR and PCO reactions of TiO2 are discussed in terms of physicochemical properties of carbon materials, coupling states of TiO2/carbon composites, interfacial charge transfers. Various surface characterizations of composites (UV-Vis diffuse reflectance, SEM, FTIR, surface area, electrical conductivity, and photoluminescence) are performed to gain insight on their photocatalytic redox behaviors

  19. The reaction of carbon disulphide with -haloketones and primary amines in the presence of potassium iodide as catalyst

    Indian Academy of Sciences (India)

    Javad Safaei-Ghomi; Fariba Salimi; Ali Ramazani

    2013-09-01

    A simple, mild and convenient method has been developed for the synthesis of 3,4,5-trialkyl-1,3-thiazole-2(3)-thione derivatives through one pot three-component reaction between a primary amine, carbon disulphide, and -haloketone in the presence of potassium iodide at room temperature conditions. The products were obtained with excellent yield and appropriate reaction times. This reaction represents a rapid and unprecedented route to the described molecules that have biological specifications.

  20. Study of 16O(12C,α20Ne)α for the investigation of carbon-carbon fusion reaction via the Trojan Horse Method

    Science.gov (United States)

    Rapisarda, G. G.; Spitaleri, C.; Bordeanu, C.; Hons, Z.; Kiss, G. G.; La Cognata, M.; Mrazek, J.; Nita, C.; Pantelica, D.; Petrascu, H.; Pizzone, R. G.; Romano, S.; Szücs, T.; Trache, L.; Tumino, A.; Velisa, G.

    2016-04-01

    Carbon-carbon fusion reaction represents a nuclear process of great interest in astrophysics, since the carbon burning is connected with the third phase of massive stars (M > 8 M⊙) evolution. In spite of several experimental works, carbon-carbon cross section has been measured at energy still above the Gamow window moreover data at low energy present big uncertainty. In this paper we report the results about the study of the 16O(12C,α 20Ne)α reaction as a possible three-body process to investigate 12C(12C,α)20Ne at astrophysical energy via Trojan Horse Method (THM). This study represents the first step of a program of experiments aimed to measure the 12C+12C cross section at astrophysical energy using the THM.

  1. Isotope separation of carbon-13 by counter-current column with exchange reaction between carbon dioxide and carbamic acid

    International Nuclear Information System (INIS)

    The isotope separation performance of carbon-13 with exchange reaction between CO2 and carbamic acid was studied and some factors for the counter-current column were studied for improving the overall performance. The working fluid for the experiments was a solution of DNBA, (C4H9)2NH, and n-octane mixture. The rate-controlling step of 13C transfer at temperatures higher than 10 deg C was the exchange reaction between carbamic acid and CO2 dissolved by physical absorption. The capacity coefficient of 13C transfer between gas and liquid in the counter-current column was successfully related to the product of three factors: the concentration of carbamic acid, the concentration of CO2 dissolved by physical absorption and the liquid holdup of the column. The liquid holdup was also an important factor. As the holdup increased, the isotope exchange rate and the overall separation factor of the column increased. However, the transient time to equilibrium was much longer. (author)

  2. Performance of a biogas upgrading process based on alkali absorption with regeneration using air pollution control residues.

    Science.gov (United States)

    Baciocchi, Renato; Carnevale, Ennio; Costa, Giulia; Gavasci, Renato; Lombardi, Lidia; Olivieri, Tommaso; Zanchi, Laura; Zingaretti, Daniela

    2013-12-01

    This work analyzes the performance of an innovative biogas upgrading method, Alkali absorption with Regeneration (AwR) that employs industrial residues and allows to permanently store the separated CO2. This process consists in a first stage in which CO2 is removed from the biogas by means of chemical absorption with KOH or NaOH solutions followed by a second stage in which the spent absorption solution is contacted with waste incineration Air Pollution Control (APC) residues. The latter reaction leads to the regeneration of the alkali reagent in the solution and to the precipitation of calcium carbonate and hence allows to reuse the regenerated solution in the absorption process and to permanently store the separated CO2 in solid form. In addition, the final solid product is characterized by an improved environmental behavior compared to the untreated residues. In this paper the results obtained by AwR tests carried out in purposely designed demonstrative units installed in a landfill site are presented and discussed with the aim of verifying the feasibility of this process at pilot-scale and of identifying the conditions that allow to achieve all of the goals targeted by the proposed treatment. Specifically, the CO2 removal efficiency achieved in the absorption stage, the yield of alkali regeneration and CO2 uptake resulting for the regeneration stage, as well as the leaching behavior of the solid product are analyzed as a function of the type and concentration of the alkali reagent employed for the absorption reaction. PMID:24045173

  3. Effect of denitrifying bacteria on the electrochemical reaction of activated carbon fiber in electrochemical biofilm system

    Institute of Scientific and Technical Information of China (English)

    YING Diwen; JIA Jinping; ZHANG Lehua

    2007-01-01

    An electrochemical-activated denitrifying biofilm system consisting of activated carbon fiber electrodes immobilized with denitrifying bacteria film as cathode was studied.A revised model for an electrochemical-activated denitrifying biofilm was developed and validated by electrochemical analysis of cathodal polarization curves and nitrate consumption rate.The cathodal polarization curve and nitrate consumption rate were introduced to verify the rate of electrochemical reaction and the activity of denitrifying bacteria,respectively.It was shown that the denitrification process effectively strengthened the electrochemical reaction while the electron also intensified denitrification activity.Electron was transferred between electrochemical process and biological process not only by hydrogen molecule but also by new produced active hydrogen atom.Additionally,a parameter of apparent exchange current density was deprived from the cathodal polarization curve with high overpotential,and a new bio-effect current density was defined through statistical analysis,which was linearly dependent to the activity of denitrification bacteria.Activated carbon fiber (ACF) electrode was also found to be more suitable to the electrochemical denitrifying system compared with graphite and platinum.

  4. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN; ANNUAL

    International Nuclear Information System (INIS)

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO(sub 2) emissions can be overcome. Permanent and safe methods for CO(sub 2) capture and disposal/storage need to be developed. Mineralization of stationary-source CO(sub 2) emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation before and/or during carbonation may provide an important parameter for enhancing carbonation reaction processes. Mg(OH)(sub 2) was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (i) its structural and chemical simplicity, (ii) interest in Mg(OH)(sub 2) gas-solid carbonation as a potentially cost-effective CO(sub 2) mineral sequestration process component, and (iii) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO(sub 2) sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for cost optimization of any lamellar-hydroxide-based mineral carbonation sequestration process

  5. Heating Treated Carbon Nanotubes As Highly Active Electrocatalysts for Oxygen Reduction Reaction

    International Nuclear Information System (INIS)

    Graphical abstract: Heating treatment for multi-walled carbon nanotubes in the air introduces abundant structure defects which improve catalytic performances for oxygen reduction reaction (ORR). There is a positive correlation between the defect levels and ORR activities. The product shows better methanol tolerance and long-term durability than commercial Pt/C which makes it applicable in fuel cells. - Abstract: Carbon nanotubes (CNTs) have been widely developed for electrochemical energy conversion and storage devices for replacement of high-cost Pt-based catalysts. In this paper, a simple and convenient method is developed for improving the catalytic activity of CNTs in a controlled way. By simple heating treatment in the air, the multi-walled carbon nanotubes (MWCNTs) change with special morphologies, compositions and abundant defects (denoted as h-CNT). Those defects significantly improve the electrocatalytic performances for oxygen reduction reaction (ORR) which proceeds in a nearly four-electron pathway. The heating conditions have important effects on the structures and defect properties of h-CNTs which show a positive correlation between the defect levels and ORR performances. The small amounts of iron residues originated from nanotube growth and nitrogen doping during heating treatment also contribute to some catalytic activity. The inner walls of h-CNT remain intact during heating treatment and provide sufficient conductivity which facilitates charge transport during ORR. The h-CNT electrocatalyst shows better methanol tolerance and long-term durability than commercial Pt/C in alkaline media which makes it an alternative cathode catalyst in fuel cells

  6. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells

    Science.gov (United States)

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-01-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells. PMID:26601132

  7. Effect of different chemical modification of carbon nanotubes for the oxygen reduction reaction in alkaline media

    International Nuclear Information System (INIS)

    The electrochemical reduction of oxygen on chemically modified multi-walled carbon nanotubes (CNTs) electrodes in 1 M KOH solution has been studied using the rotating ring disc electrode (RDE). The surface modification of CNTs has been estimated by XPS and Raman spectroscopy. The effect of different oxygen functionalities on the surface of carbon nanotube for the oxygen reduction reaction (ORR) is considered in terms of the number of electrons (n) involved. Electrochemical studies indicate that in the case of the modification of CNTs with citric acid and diazonium salts the n values were close to two in the measured potential range, and the electrochemical reduction is limited to the production of peroxide as the final product. In the case of the modification of carbon nanotubes with peroxymonosulphuric acid, in the measured potential range, the n value is close to 4 indicating the four-electron pathway for the ORR. By correlating ORR measurements with the XPS analysis, we propose that the increase in electrocatalytic activity towards the ORR, for CNT can be attributed to the increase in C-O groups on the surface of CNTs after modification with peroxymonosulphuric acid

  8. Revealing Brown Carbon Chromophores Produced in Reactions of Methylglyoxal with Ammonium Sulfate

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Peng; Laskin, Julia; Nizkorodov, Sergey A.; Laskin, Alexander

    2015-12-15

    Atmospheric brown carbon (BrC) is an important contributor to light absorption and climate forcing by aerosols. Reactions between small water-soluble carbonyls and ammonia or amines have been identified as one of the potential pathways of BrC formation. However, detailed chemical characterization of BrC chromophores has been challenging and their formation mechanisms are still poorly understood. Understanding BrC formation is impeded by the lack of suitable methods which can unravel the variability and complexity of BrC mixtures. This study applies high performance liquid chromatography (HPLC) coupled to photodiode array (PDA) detector and high resolution mass spectrometry (HRMS) to investigate optical properties and chemical composition of individual BrC components produced through reactions of methylglyoxal (MG) and ammonium sulfate (AS), both of which are abundant in the atmospheric environment. A direct relationship between optical properties and chemical composition of 30 major BrC chromophores was established. Nearly all of these chromophores are nitrogen-containing compounds that account for >70% of the overall light absorption by the MG+AS system in the 300-500 nm range. These results suggest that reduced-nitrogen organic compounds formed in reactions between atmospheric carbonyls and ammonia/amines are important BrC chromophores. It is also demonstrated that improved separation of BrC chromophores by HPLC will significantly advance understanding of BrC chemistry.

  9. Carbon-sulfur bond-forming reaction catalysed by the radical SAM enzyme HydE.

    Science.gov (United States)

    Rohac, Roman; Amara, Patricia; Benjdia, Alhosna; Martin, Lydie; Ruffié, Pauline; Favier, Adrien; Berteau, Olivier; Mouesca, Jean-Marie; Fontecilla-Camps, Juan C; Nicolet, Yvain

    2016-05-01

    Carbon-sulfur bond formation at aliphatic positions is a challenging reaction that is performed efficiently by radical S-adenosyl-L-methionine (SAM) enzymes. Here we report that 1,3-thiazolidines can act as ligands and substrates for the radical SAM enzyme HydE, which is involved in the assembly of the active site of [FeFe]-hydrogenase. Using X-ray crystallography, in vitro assays and NMR spectroscopy we identified a radical-based reaction mechanism that is best described as the formation of a C-centred radical that concomitantly attacks the sulfur atom of a thioether. To the best of our knowledge, this is the first example of a radical SAM enzyme that reacts directly on a sulfur atom instead of abstracting a hydrogen atom. Using theoretical calculations based on our high-resolution structures we followed the evolution of the electronic structure from SAM through to the formation of S-adenosyl-L-cysteine. Our results suggest that, at least in this case, the widely proposed and highly reactive 5'-deoxyadenosyl radical species that triggers the reaction in radical SAM enzymes is not an isolable intermediate. PMID:27102684

  10. Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

    Directory of Open Access Journals (Sweden)

    Matthieu Jouffroy

    2014-10-01

    Full Text Available The capacity of two cavity-shaped ligands, HUGPHOS-1 and HUGPHOS-2, to generate exclusively singly phosphorus-ligated complexes, in which the cyclodextrin cavity tightly wraps around the metal centre, was explored with a number of late transition metal cations. Both cyclodextrin-derived ligands were assessed in palladium-catalysed Mizoroki–Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. The inability of both chiral ligands to form standard bis(phosphine complexes under catalytic conditions was established by high-pressure NMR studies and shown to have a deep impact on the two carbon–carbon bond forming reactions both in terms of activity and selectivity. For example, when used as ligands in the rhodium-catalysed hydroformylation of styrene, they lead to both high isoselectivity and high enantioselectivity. In the study dealing with the Mizoroki–Heck reactions, comparative tests were carried out with WIDEPHOS, a diphosphine analogue of HUGPHOS-2.

  11. Effect of Reaction Temperature on Carbon Yield and Morphology of CNTs on Copper Loaded Nickel Nanoparticles

    Directory of Open Access Journals (Sweden)

    Hu Ming

    2016-01-01

    Full Text Available This investigation was attempted to introduce carbon nanotubes (CNTs onto surface of copper powders in order to improve heat transfer performance of copper matrix for engineering application of electrical packaging materials. The Ni/MgO catalyst was formed on the copper powders surface by means of codeposition method. CVD technique was executed to fabricate uniform CNTs on copper powders and effect of reaction temperature on the morphology of CNTs was surveyed. The results showed that CNTs products on the copper powder surface were distributed uniformly even if reaction temperature was different. The diameter dimension of CNTs was within the scope of 30~60 nm. Growth behaviors of CNTs by CVD method were considered to be “tip-growth” mechanism. Raman spectra of CNTs proved that intensity ratio of D-band to G-band (ID/IG increased as deposition reaction temperature increased, which implied that order degree of graphitic structure in synthesized CNTs improved.

  12. Pathways of birnessite formation in alkali medium

    Institute of Scientific and Technical Information of China (English)

    FENG Xionghan; TAN Wenfeng; LIU Fan; HUANG Qiaoyun; LIU Xiangwen

    2005-01-01

    Birnessite is a common weathering and oxidation product of manganese-bearing rocks. An O2 oxidation procedure of Mn(OH)2 in the alkali medium has been used to synthesize birnessite. Fast and powder X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), energy dispersed X-ray analysis (EDAX), infrared spectroscopy (IR) techniques and chemical composition analysis, Eh-pH equilibrium diagram approaches were employed to investigate the reaction process and pathways of birnessite formation. Results showed that the process of the birnessite formation could be divided into four stages: (1) formation stage for hausmannite and feitknechtite, (2) stage of transformation of hausmannite and feitknechtite to buserite, (3) buserite crystal growing stage, and (4) stage of conversion of buserite into birnessite. Mn(OH)2 was mainly present as amorphous state only for a short initial time of oxidation reaction. In the oxidation process, buserite formed following two pathways by recrystallization after dissolution of the intermediates, and the transformations of the minerals depended on the Eh determined by the dissolved O2 concentration on their surfaces. The results are fundamental in further exploration on the mechanism of birnessite formation in the alkali medium. A great practical significance would also be expected with respect to the areas of material sciences.

  13. Final Report: The Impact of Carbonate on Surface Protonation, Electron Transfer and Crystallization Reactions in Iron Oxide Nanoparticles and Colloids

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David Adams [The University of Alabama

    2013-07-02

    This project addresses key issues of importance in the geochemical behavior of iron oxides and in the geochemical cycling of carbon and iron. For Fe, we are specifically studying the influence of carbonate on electron transfer reactions, solid phase transformations, and the binding of carbonate to reactive sites on the edges of particles. The emphasis on carbonate arises because it is widely present in the natural environment, is known to bind strongly to oxide surfaces, is reactive on the time scales of interest, and has a speciation driven by acid-base reactions. The geochemical behavior of carbonate strongly influences global climate change and CO{sub 2} sequestration technologies. Our goal is to answer key questions with regards to specific site binding, electron transfer reactions, and crystallization reactions of iron oxides that impact both the geochemical cycling of iron and CO{sub 2} species. Our work is focused on the molecular level description of carbonate chemistry in solution including the prediction of isotope fractionation factors. We have also done work on critical atmospheric species.

  14. Localized surface grafting reactions on carbon nanofibers induced by gamma and e-beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Evora, M.C., E-mail: cecilia@ieav.cta.br [Institute for Advanced Studies-IEAV/DCTA, Av. Cel Jose Alberto Albano do Amarante, 1-Putim, 12228-001 São Jose dos Campos, SP (Brazil); Araujo, J.R., E-mail: jraraujo@inmetro.gov.br [Instituto Nacional de Metrologia, Qualidade e Tecnologia, Av. Nossa Sra. das Graças, 50, 25250-020 Duque de Caxias, RJ (Brazil); Ferreira, E.H.M. [Instituto Nacional de Metrologia, Qualidade e Tecnologia, Av. Nossa Sra. das Graças, 50, 25250-020 Duque de Caxias, RJ (Brazil); Strohmeier, B.R. [Thermo Fisher Scientific, 5225 Verona Road, Madison, WI 53711 (United States); Silva, L.G.A., E-mail: lgasilva@ipen.br [Institute for Nuclear and Energy Research- IPEN, Av. Prof lineu Prestes, 2242- Cidade Universitaria, 05508-000 SP (Brazil); Achete, C.A. [Instituto Nacional de Metrologia, Qualidade e Tecnologia, Av. Nossa Sra. das Graças, 50, 25250-020 Duque de Caxias, RJ (Brazil)

    2015-04-30

    Graphical abstract: - Highlights: • Methodology for the functionalization of carbon nanofibers was investigated. • Two radiation sources were used to promote grafting reactions: gamma and electron beam. • We report the optimum inhibitor concentration to achieve the functionalization. • Surface of carbon nanofibers showed an increase of oxygen content after irradiation. • The radiation-induced graphitization did not damage the overall sp{sup 2} structure. - Abstract: Electron beam and gamma-ray irradiation have potential application to modify the carbon fiber nanostructures in order to produce useful defects in the graphitic structure and create reactive sites. In this study, the methodology to functionalize carbon nanofiber (CNF), via a radiation process and using acrylic acid as a source of oxygen functional groups, was investigated. The samples were submitted to a direct grafting radiation process with electron beam and gamma-ray source. Several parameters were changed such as: acrylic acid concentration, radiation dose and percentage of inhibitor necessary to achieve functionalization, with higher percentage of oxygen functional groups on CNF surface, and better dispersion. The better results achieved were when mixing CNF in a solution of acrylic acid with 6% of inhibitor (FeSO{sub 4}·7H{sub 2}O) and irradiated at 100 kGy. The samples were characterized by X-ray photoelectron spectroscopy and the surface composition (atomic%) showed a significant increase of oxygen content for the samples after irradiation. Also, the dispersion of the functionalized CNF in water was stable during months which may be a good indication that the functionalization process of CNF via ionizing radiation was successful.

  15. Assesment of Alkali Resistance of Basalt Used as Concrete Aggregates

    Directory of Open Access Journals (Sweden)

    al-Swaidani Aref M.

    2015-11-01

    Full Text Available The objective of this paper is to report a part of an ongoing research on the influence of using crushed basalt as aggregates on one of durability-related properties of concrete (i.e. alkali-silica reaction which is the most common form of Alkali-Aggregate Reaction. Alkali resistance has been assessed through several methods specified in the American Standards. Results of petrographic examination, chemical test (ASTM C289 and accelerated mortar bar test (ASTM C1260 have particularly been reported. In addition, the weight change and compressive strength of 28 days cured concrete containing basaltic aggregates were also reported after 90 days of exposure to 10% NaOH solution. Dolomite aggregate were used in the latter test for comparison. The experimental results revealed that basaltic rocks quarried from As-Swaida’a region were suitable for production of aggregates for concrete. According to the test results, the studied basalt aggregates can be classified as innocuous with regard to alkali-silica reaction. Further, the 10% sodium hydroxide attack did not affect the compressive strength of concrete.

  16. Assesment of Alkali Resistance of Basalt Used as Concrete Aggregates

    Science.gov (United States)

    al-Swaidani, Aref M.; Baddoura, Mohammad K.; Aliyan, Samira D.; Choeb, Walid

    2015-11-01

    The objective of this paper is to report a part of an ongoing research on the influence of using crushed basalt as aggregates on one of durability-related properties of concrete (i.e. alkali-silica reaction which is the most common form of Alkali-Aggregate Reaction). Alkali resistance has been assessed through several methods specified in the American Standards. Results of petrographic examination, chemical test (ASTM C289) and accelerated mortar bar test (ASTM C1260) have particularly been reported. In addition, the weight change and compressive strength of 28 days cured concrete containing basaltic aggregates were also reported after 90 days of exposure to 10% NaOH solution. Dolomite aggregate were used in the latter test for comparison. The experimental results revealed that basaltic rocks quarried from As-Swaida'a region were suitable for production of aggregates for concrete. According to the test results, the studied basalt aggregates can be classified as innocuous with regard to alkali-silica reaction. Further, the 10% sodium hydroxide attack did not affect the compressive strength of concrete.

  17. Reactions of Hot Cl38 Atoms in Mixtures of Carbon Tetrachloride with Aliphatic Alcohols

    International Nuclear Information System (INIS)

    Investigations of the chemical effects of nuclear reactions in binary systems are expected to yield much useful information. Study of the recoil processes of the halogen derivatives when the second component is suitably chosen and its concentration varied in a wide range might permit inferences to be made on the role and mechanism of the various stabilizing processes. Considering the results obtained with CCl4-Cl2, CCl4-SiCl4, CCl4-C6H6 and CCl4-c-hexane mixtures as well as the energy scavenger property of alcohol, it seemed of interest to study the contribution of the alcohols to the stabilization of hot Cl38. Chemical processes induced by hot Cl38 from the nuclear reaction Cl97 (n, γ)Cl38 were investigated in mixtures of CCl4-ROH (where R = CH3-, C2H5-, C3H7- and (CH3)2CH-). The irradiations were performed in the thermal column of the 2 MW VVRS reactor using rather short exposure times to keep the radiation chemical effects at negligible level. The organic fractions were separated from the inorganic ones by extraction and the former were analysed by gas chromatographic method. Total retention and the yield of the complete set of organic chlorine compounds were determined in terms of alcohol concentration. Some interesting results are that the yield of reaction products in which the OH radical of aliphatic alcohol has been replaced by Cl38 increases with increasing alcohol concentration with a simultaneous decrease in the labelled CCI4 yield and that, in addition to the monochlorine derivates with less carbon atoms than the alcohol molecule, a considerable amount of chloroform is formed with maximum yield at a given alcohol concentration. The relative contributions of the hot and the epithermal stabilization processes of energetic Cl38 and the mechanism of the various reactions are discussed. (author)

  18. Utilization of Mineral Wools as Alkali-Activated Material Precursor

    Directory of Open Access Journals (Sweden)

    Juho Yliniemi

    2016-04-01

    Full Text Available Mineral wools are the most common insulation materials in buildings worldwide. However, mineral wool waste is often considered unrecyclable because of its fibrous nature and low density. In this paper, rock wool (RW and glass wool (GW were studied as alkali-activated material precursors without any additional co-binders. Both mineral wools were pulverized by a vibratory disc mill in order to remove the fibrous nature of the material. The pulverized mineral wools were then alkali-activated with a sodium aluminate solution. Compressive strengths of up to 30.0 MPa and 48.7 MPa were measured for RW and GW, respectively, with high flexural strengths measured for both (20.1 MPa for RW and 13.2 MPa for GW. The resulting alkali-activated matrix was a composite-type in which partly-dissolved fibers were dispersed. In addition to the amorphous material, sodium aluminate silicate hydroxide hydrate and magnesium aluminum hydroxide carbonate phases were identified in the alkali-activated RW samples. The only crystalline phase in the GW samples was sodium aluminum silicate. The results of this study show that mineral wool is a very promising raw material for alkali activation.

  19. Thermodynamic modelling of alkali-activated slag cements

    International Nuclear Information System (INIS)

    Highlights: • A thermodynamic modelling analysis of alkali-activated slag cements is presented. • Thermodynamic database describes zeolites, alkali carbonates, C–(N–)A–S–H gel. • Updated thermodynamic model for Mg–Al layered double hydroxides. • Description of phase assemblages in Na2SiO3- and Na2CO3-activated slag cements. • Phase diagrams for NaOH-activated and Na2SiO3-activated slag cements are simulated. - Abstract: This paper presents a thermodynamic modelling analysis of alkali-activated slag-based cements, which are high performance and potentially low-CO2 binders relative to Portland cement. The thermodynamic database used here contains a calcium (alkali) aluminosilicate hydrate ideal solid solution model (CNASH-ss), alkali carbonate and zeolite phases, and an ideal solid solution model for a hydrotalcite-like Mg–Al layered double hydroxide phase. Simulated phase diagrams for NaOH- and Na2SiO3-activated slag-based cements demonstrate the high stability of zeolites and other solid phases in these materials. Thermodynamic modelling provides a good description of the chemical compositions and types of phases formed in Na2SiO3-activated slag cements over the most relevant bulk chemical composition range for these cements, and the simulated volumetric properties of the cement paste are consistent with previously measured and estimated values. Experimentally determined and simulated solid phase assemblages for Na2CO3-activated slag cements were also found to be in good agreement. These results can be used to design the chemistry of alkali-activated slag-based cements, to further promote the uptake of this technology and valorisation of metallurgical slags

  20. Up-Scaling Geochemical Reaction Rates for Carbon Dioxide (CO2) in Deep Saline Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Catherine A

    2013-02-28

    Geochemical reactions in deep subsurface environments are complicated by the consolidated nature and mineralogical complexity of sedimentary rocks. Understanding the kinetics of these reactions is critical to our ability to make long-term predictions about subsurface processes such as pH buffering, alteration in rock structure, permeability changes, and formation of secondary precipitates. In this project, we used a combination of experiments and numerical simulation to bridge the gap between our knowledge of these reactions at the lab scale and rates that are meaningful for modeling reactive transport at core scales. The focus is on acid-driven mineral dissolution, which is specifically relevant in the context of CO2-water-rock interactions in geological sequestration of carbon dioxide. The project led to major findings in three areas. First, we modeled reactive transport in pore-network systems to investigate scaling effects in geochemical reaction rates. We found significant scaling effects when CO2 concentrations are high and reaction rates are fast. These findings indicate that the increased acidity associated with geological sequestration can generate conditions for which proper scaling tools are yet to be developed. Second, we used mathematical modeling to investigate the extent to which SO2, if co-injected with CO2, would acidify formation brines. We found that there exist realistic conditions in which the impact on brine acidity will be limited due to diffusion rate-limited SO2 dissolution from the CO2 phase, and the subsequent pH shift may also be limited by the lack of availability of oxidants to produce sulfuric acid. Third, for three Viking sandstones (Alberta sedimentary basin, Canada), we employed backscattered electron microscopy and energy dispersive X-ray spectroscopy to statistically characterize mineral contact with pore space. We determined that for reactive minerals in sedimentary consolidated rocks, abundance alone is not a good predictor of

  1. Mistletoe alkali inhibits peroxidation in rat liver and kidney

    Institute of Scientific and Technical Information of China (English)

    Zheng-Ming Shi; Ping Feng; Dong-Qiao Jiang; Xue-Jiang Wang

    2006-01-01

    AIM: To explore the antioxidant and free radical scavenger properties of mistletoe alkali (MA).METHODS: The antioxidant effect of mistletoe alkali on the oxidative stress induced by carbon tetrachloride (CCl4) in rats was investigated. The rats were divided into four groups (n = 8): CCl4-treated group (1 mL/kg body weight), MA -treated group (90 mg/kg), CCl4+MA-treated group and normal control group. After 4 wk of treatment,the level of malondialdehyde (MDA), a lipid peroxidation product (LPO) was measured in serum and homogenates of liver and kidney. Also, the level of glutathione (GSH),and activities of glutathione reductase (GR), glutathione peroxidase (GSPx), superoxide dismutase (SOD), and glutathione-S-transferase (GST) in liver and kidney were determined. Scavenging effects on hydroxyl free radicals produced in vitro by Fenton reaction were studied by ESR methods using 5,5-dimethyl-1-pyrroline-N-oxidesource. Urinary 8-hydroxydeoxyguanosine (8-OHdG) was determined by competitive ELISA.RESULTS: In CCl4-treated group, the level of LPO in serum of liver and kidney was significantly increased compared to controls. The levels of GSH and enzyme activities of SOD, GSPx and GR in liver and kidney were significantly decreased in comparison with controls. In CCl4+MA-treated group, the changes in the levels of LPO in serum of liver and kidney were not statistically significant compared to controls. The levels of SOD, GSPx and GR in liver and kidney were significantly increased in comparison with controls. There was a significant difference in urinary excretion of 8-OHdG between the CCl4-treated and MA-treated groups.CONCLUSION: Oxidative stress may be a major mechanism for the toxicity of CCl4. MA has a protective www.wjgnet.comeffect against CCl4 toxicity by inhibiting the oxidative damage and stimulating GST activities. Thus, clinical application of MA should be considered in cases with carbon tetrachloride-induced injury.

  2. Electrical and morphological characterization of multiwalled carbon nanotubes functionalized via the Bingel reaction

    Science.gov (United States)

    Brković, Danijela V.; Ivić, Milka L. Avramov; Rakić, Vesna M.; Valentini, Luca; Uskoković, Petar S.; Marinković, Aleksandar D.

    2015-08-01

    Covalent sidewall functionalization of multiwalled carbon nanotubes (MWCNTs) has been performed using two approaches, direct and indirect cycloaddition through diethyl malonate, based on the Bingel reaction. The results revealed that functionalized MWCNTs demonstrated enhanced electrical properties and significantly lower sheet resistance, especially after electric field thermal assisted annealing at 80 °C was performed. The presence of 1,3-dicarbonyl compounds caused the surface of MWCNTs to be more hydrophilic, approachable for the electrolyte and improved the capacitance performance of Au/MWCNTs electrodes. The modified MWCNTs have been incorporated into nanocomposites by using solution mixing method with polyaniline and drop-casting resulting mixture on the paper substrate. The reduction in the sheet resistance with increasing the content of MWCNTs in the prepared nanocomposite films has been achieved.

  3. Ultraviolet optical absorption of alkali cyanides and alkali halide cyanides

    International Nuclear Information System (INIS)

    The ultraviolet absorption spectra of alkali cyanide and mixed alkali halide cyanide crystals were measured at temperatures ranging from 300K down to 4.2K. A set of small absorption peaks was observed at energies near 6 eV and assigned to parity forbidden X1Σ+→a'3Σ+ transitions of the CN- molecular ions. It was observed that the peak position depends on the alkali atom while the absorption cross section strongly depends on the halogen and on the CN- concentration of the mixed crystals. These effects are explained in terms of an interaction between the triplet molecular excitons and charge transfer excitons. The experimental data were fit with a coupling energy of a few meV. The coupling mechanism is discussed and it is found to be due to the overlap between the wave functions of the two excitations. (Author)

  4. Metal-Organic Framework Derived Hierarchically Porous Nitrogen-Doped Carbon Nanostructures as Novel Electrocatalyst for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Shaofang; Zhu, Chengzhou; Zhou, Yazhou; Yang, Guohai; Jeon, Ju Won; Lemmon, John P.; Du, Dan; Nune, Satish K.; Lin, Yuehe

    2015-10-01

    The hierarchically porous nitrogen-doped carbon materials, derived from nitrogen-containing isoreticular metal-organic framework-3 (IRMOF-3) through direct carbonization, exhibited excellent electrocatalytic activity in alkaline solution for oxygen reduction reaction (ORR). This high activity is attributed to the 10 presence of high percentage of quaternary and pyridinic nitrogen, the high surface area as well as good conductivity. When IRMOF-3 was carbonized at 950 °C (CIRMOF-3-950), it showed four-electron reduction pathway for ORR and exhibited better stability (about 78.5% current density was maintained) than platinum/carbon (Pt/C) in the current durability test. In addition, CIRMOF-3-950 presented high selectivity to cathode reactions compared to commercial Pt/C.

  5. Si-rich layer formation on olivine surfaces during reaction with water and supercritical carbon dioxide under conditions relevant for geologic carbon storage

    Science.gov (United States)

    Johnson, N. C.; Jackson, A.; Maher, K.; Bird, D. K.; Brown, G. E.

    2013-12-01

    The reaction of Mg-silicate minerals (i.e. olivine) with carbon dioxide (CO2) is a promising method for secure, long-term, geologic carbon storage. Several technical challenges must be overcome before implementing mineral carbonation technology on a large scale, one of which is slow reaction kinetics. This study probes surface reaction limitations of olivine carbonation, specifically the formation of a passivating, Si-rich layer on olivine surfaces upon exposure to water and CO2 under sequestration conditions (elevated temperature and pressure). A series of batch reactions were performed at 60°C and 100 bar CO2 pressure in Dickson-style rocker bombs, varying the length of reaction and the amount of mixing (rocking). The initial aqueous phase was spiked with 29Si. Fluid samples were taken periodically and analyzed for cation content, alkalinity, and dissolved inorganic carbon. At the end of each experiment, the solid products were analyzed with a Sensitive High Resolution Ion Microprobe Reverse Geometry (SHRIMP-RG) in order to measure the amount of 29Si incorporated into the Si-rich layer on reacted olivine grains. We also cut cross sections of reacted grains from each experiment using a Focused Ion Beam (FIB) which were thinned to leaching process. SHRIMP-RG data also imply the presence of a precipitated Si-rich layer on top of a leached Si-rich layer, as the 29Si penetration depth is only 25-65% of the total Si-rich layer thickness. The combination of SHRIMP-RG and FIB/TEM analysis leads us to hypothesize that a Si-rich layer forms quickly on olivine surfaces due to preferential Mg removal from the surface (the traditional 'leached' layer), and as the reaction proceeds, amorphous silica reaches saturation in the fluid and precipitates on surfaces inside the reactor (including olivine grains).

  6. Bio-mass derived mesoporous carbon as superior electrode in all vanadium redox flow battery with multicouple reactions

    Science.gov (United States)

    Ulaganathan, Mani; Jain, Akshay; Aravindan, Vanchiappan; Jayaraman, Sundaramurthy; Ling, Wong Chui; Lim, Tuti Mariana; Srinivasan, Madapusi P.; Yan, Qingyu; Madhavi, Srinivasan

    2015-01-01

    We first report the multi-couple reaction in all vanadium redox flow batteries (VRFB) while using bio-mass (coconut shell) derived mesoporous carbon as electrode. The presence of V3+/V4+ redox couple certainly supplies the additional electrons for the electrochemical reaction and subsequently provides improved electrochemical performance of VRFB system. The efficient electro-catalytic activity of such coconut shell derived high surface area mesoporous carbon is believed for the improved cell performance. Extensive power and electrochemical studies are performed for VRFB application point of view and described in detail.

  7. One-pot synthesis of S-alkyl dithiocarbamates via the reaction of N-tosylhydrazones, carbon disulfide and amines.

    Science.gov (United States)

    Sha, Qiang; Wei, Yun-Yang

    2013-09-14

    A new, convenient and efficient transition metal-free synthesis of S-alkyl dithiocarbamates through one-pot reaction of N-tosylhydrazones, carbon disulfide and amines is reported. Tosylhydrazones derived from various aromatic and aliphatic ketones or aldehydes were tested and gave dithiocarbamates in good to excellent yields. The tosylhydrazones can be generated in situ without isolation, which provides a simpler one-pot method to synthesize dithiocarbamates via the reaction of carbonyl compounds, carbon disulfide and amines in the presence of 4-methylbenzenesulfonohydrazide. PMID:23863979

  8. Method for increasing -SiC yield on solid state reaction of coal fly ash and activated carbon powder

    Indian Academy of Sciences (India)

    Sulardjaka; Jamasri; M W Wildan; Kusnanto

    2011-07-01

    A novel process for increasing -SiC yield on solid state reaction of coal fly ash and micro powder activated carbon powder has been proposed. -SiC powder was synthesized at temperature 1300°C for 2 h under vacuum condition with 1 l/min argon flow. Cycling synthesis process has been developed for increasing -SiC yield on solid state reaction of coal fly ash and activated carbon powder. Synthesized products were analyzed by XRD with Cu-K radiation, FTIR spectrometer and SEM fitted with EDAX. The results show that the amount of relative -SiC is increased with the number of cycling synthesis.

  9. A Pt-free Electrocatalyst Based on Pyrolized Vinazene-Carbon Composite for Oxygen Reduction Reaction

    International Nuclear Information System (INIS)

    The 2-vinyl-4, 5-dicyanoimidazole (Vinazene) was used as a nitrogen precursor to synthesize a promising non-precious metal (NPM) catalyst for oxygen reduction reaction (ORR). Vinazene together with an iron source was impregnated into a carbon matrix and pyrolyzed at 900 °C in N2 atmosphere. The structure of the resulting Fe–N–C nanocomposite was analyzed by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. Both rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) experiments showed excellent ORR activity for the obtained catalyst with low H2O2 formation (∼3.0%) in 0.1 M KOH. The catalyst was found to be rich in mesoporous structure along with high percentage of pyrrolic-N function with surface area of about 673 m2 g−1 and pore size of 4.2 nm. In addition to its excellent ORR activity, the catalyst showed remarkable tolerance towards methanol oxidation and demonstrates good stability over 10,000 potential cycles (0.6–1.0 V Vs RHE). We believe that this N-rich Vinazene molecule will be beneficial to further development of nitrogen doped carbon electrocatalysts

  10. Heteropoly Acid/Nitrogen Functionalized Onion-like Carbon Hybrid Catalyst for Ester Hydrolysis Reactions.

    Science.gov (United States)

    Liu, Wei; Qi, Wei; Guo, Xiaoling; Su, Dangsheng

    2016-02-18

    A novel heteropoly acid (HPA)/nitrogen functionalized onion-like carbon (NOLC) hybrid catalyst was synthesized through supramolecular (electrostatic and hydrogen bond) interactions between the two components. The chemical structure and acid strength of the HPA/NOLC hybrid have been fully characterized by thermogravimetric analysis, IR spectroscopy, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption and acid-base titration measurements. The proposed method for the fabrication of the HPA/NOLC hybrid catalyst is a universal strategy for different types of HPAs to meet various requirements of acidic or redox catalysis. The hydrophobic environment of NOLC effectively prevents the deactivation of HPA in an aqueous system, and the combination of uniformly dispersed HPA clusters and the synergistic effect between NOLC and HPA significantly promotes its activity in ester hydrolysis reactions, which is higher than that of bare PWA as homogeneous catalyst. The kinetics of the hydrolysis reactions indicate that the aggregation status of the catalyst particles has great influence on the apparent activity. PMID:26606266

  11. Removal of Cr (VI) with wheat-residue derived black carbon: Reaction mechanism and adsorption performance

    International Nuclear Information System (INIS)

    The removal of Cr (VI) from aqueous solutions using black carbon (BC) isolated from the burning residues of wheat straw was investigated as a function of pH, contact time, reaction temperature, supporting electrolyte concentration and analytical initial Cr (VI) concentration in batch studies. The effect of surface properties on the adsorption behavior of Cr (VI) was investigated with scanning electron microscope (SEM) equipped with the energy dispersive X-ray spectroscope (EDS) and Fourier transform-infrared (FTIR) spectroscopy. The removal mechanism of Cr (VI) onto the BC was investigated and the result showed that the adsorption reaction consumed a large amount of protons along the reduction of Cr (VI) to Cr (III). The oxidation of the BC took place concurrently to the chromium reduction and led to the formation of hydroxyl and carboxyl functions. An initial solution pH of 1.0 was most favorable for Cr (VI) removal. The adsorption process followed the pseudo-second order equation and Freundlich isotherm very well. The Cr (VI) adsorption was temperature-dependent and almost independent on the sodium chloride concentrations. The maximum adsorption capacity for Cr (VI) was found at 21.34 mg/g in an acidic medium, which is comparable to other low-cost adsorbents.

  12. ALKALI-ACTIVATION KINETICS OF PHOSPHORUS SLAG CEMENT USING COMPRESSIVE STRENGTH DATA

    Directory of Open Access Journals (Sweden)

    Hojjatollah Maghsoodloorad

    2015-09-01

    Full Text Available In this research, through compressive strength data, the order and kinetics of alkali-activation of phosphorus slag activated with two compound activators of NaOH + Na2CO3 and Na2CO3 + Ca(OH2, has been evaluated. The kinetics and order of alkali activation is a key factor to forecasting the mechanical behavior of alkali activated cement at different curing time and temperatures without carrying out experimental tests. The apparent activation energy was obtained as 35.6 kJ.mol-1 and 60.7 kJ.mol-1 for the two activators, respectively. Investigations proved that the alkali-activation kinetics of phosphorus slag resembles chemical reactions of second order. Moreover, the order of alkali-activation of phosphorus slag does not depend on the type of activator.

  13. A kinetic study of the reaction of water vapor and carbon dioxide on uranium; Cinetique de la reaction de la vapeur d'eau et du dioxyde de carbone sur l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Santon, J.P. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1964-09-15

    The kinetic study of the reaction of water vapour and carbon dioxide with uranium has been performed by thermogravimetric methods at temperatures between 160 and 410 deg G in the first case, 350 and 1050 deg C in the second: Three sorts of uranium specimens were used: uranium powder, thin evaporated films, and small spheres obtained from a plasma furnace. The experimental results led in the case of water vapour, to a linear rate of reaction controlled by diffusion at the lower temperatures, and by a surface reaction at the upper ones. In the case of carbon dioxide, a parabolic law has been found, controlled by diffusional processes. (author) [French] L'etude cinetique de la reaction de la vapeur d'eau et du dioxyde de carbone sur l'uranium a ete entreprise au moyen de methodes thermogravimetriques, dans te premier cas entre 160 et 410 deg C et dans le second entre 350 et 1050 deg C. Le materiau utilise se presentait sous trois formes: poudres, couches minces evaporees et billes obtenues par fusion en chalumeau a plasma. Les resultats experimentaux ont permis de mettre en evidence, dans le cas de la vapeur d'eau, une cinetique lineaire controlee par la diffusion a basse temperature et d'interface a haute temperature. Dans le cas du dioxyde de carbone par contre, on trouve une cinetique parabolique controlee par la diffusion. (auteur)

  14. Influence of alkali catalyst on product yield and properties via hydrothermal liquefaction of barley straw

    International Nuclear Information System (INIS)

    Barley straw was successfully converted to bio-crude by hydrothermal liquefaction at temperature of 280–400 °C using an alkali catalyst (K2CO3) in our previous work, and the maximum bio-crude yield was obtained at 300 °C. This paper extends previous work on studying liquefaction behavior of barley straw without and with K2CO3 at 300 °C. The effect of alkali catalyst on product distribution was investigated, and a detailed analysis of characteristic properties of bio-crude and solid residue has been performed by an elemental analyzer, FTIR (Fourier Transform infrared spectroscopy), TGA (thermogravimetric analysis) and GC-MS. The addition of K2CO3 increased the bio-crude yield to 34.85 wt%, and inhibited solid residue formation. Moreover, the bio-crude produced in the presence of a catalyst had better properties, in terms of higher heating value and lower O/C. GC-MS analysis showed that the major compounds identified in bio-crude were carboxylic acids, phenolic compounds and ketones, irrespective of whether the catalyst was used. However, the distribution and relative content of these compounds were different. More phenolic compounds and less carboxylic acids were observed in the catalytic run. In addition, the carbon and energy recovery with the addition of K2CO3 were twice as high as that without catalyst, indicating an improvement in energy efficiency. - Highlights: • The effect of an alkali catalyst (K2CO3) on HTL (hydrothermal liquefaction) of barley straw was studied. • High bio-crude yield (34.85 wt%) and energy recovery were achieved with K2CO3. • Comprehensive analysis of bio-crude and solid have been performed. • Bio-crude contained more phenolic compounds and less carboxylic acids with K2CO3. • Deoxygenation reactions were enhanced with K2CO3

  15. Reproducibly creating hierarchical 3D carbon to study the effect of Si surface functionalization on the oxygen reduction reaction

    Science.gov (United States)

    Zeng, Yuze; Flores, Jose F.; Shao, Yu-Cheng; Guo, Jinghua; Chuang, Yi-De; Lu, Jennifer Q.

    2016-06-01

    We report a new method to reproducibly fabricate functional 3D carbon structures directly on a current collector, e.g. stainless steel. The 3D carbon platform is formed by direct growth of upright arrays of carbon nanofiber bundles on a roughened surface of stainless steel via the seed-assisted approach. Each bundle consists of about 30 individual carbon nanofibers with a diameter of 18 nm on average. We have found that this new platform offers adequate structural integrity. As a result, no reduction of the surface area during downstream chemical functionalization was observed. With a fixed and reproducible 3D structure, the effect of the chemistry of the grafted species on the oxygen reduction reaction has been systematically investigated. This investigation reveals for the first time that non-conductive Si with an appropriate electronic structure distorts the carbon electronic structure and consequently enhances ORR electrocatalysis. The strong interface provides excellent electron connectivity according to electrochemical analysis. This highly reproducible and stable 3D platform can serve as a stepping-stone for the investigation of the effect of carbon surface functionalization on electrochemical reactions in general.We report a new method to reproducibly fabricate functional 3D carbon structures directly on a current collector, e.g. stainless steel. The 3D carbon platform is formed by direct growth of upright arrays of carbon nanofiber bundles on a roughened surface of stainless steel via the seed-assisted approach. Each bundle consists of about 30 individual carbon nanofibers with a diameter of 18 nm on average. We have found that this new platform offers adequate structural integrity. As a result, no reduction of the surface area during downstream chemical functionalization was observed. With a fixed and reproducible 3D structure, the effect of the chemistry of the grafted species on the oxygen reduction reaction has been systematically investigated. This

  16. The kinetics of the O2/CO2 reaction in molten carbonate - Reaction orders for O2 and CO2 on NiO. [in fuel cells

    Science.gov (United States)

    Winnick, J.; Ross, P. N.

    1980-01-01

    The kinetics of the O2/CO2 reaction in molten carbonate is investigated using paste electrolytes and nickel sinter electrodes. A two-step approach to the determination of reaction orders is employed. First, exchange currents at various P(CO2) and P(O2) were measured using the low polarization method. Second, alpha(+) and alpha(-) values were obtained from the slope of the Allen-Hickling plot for current densities low enough so that concentration polarization within the electrode can be neglected. The reaction orders are + 1/4 in CO2 and + 5/8 in O2 in the cathodic direction, and - 3/4 in CO2 and + 1/8 in O2 in the anodic direction.

  17. Role of alkalis of aggregate origin in the deterioration of CAC concrete

    International Nuclear Information System (INIS)

    Both hexagonal and cubic calcium aluminate cement (CAC) hydrates react with atmospheric CO2, bringing about mineralogical changes in concrete, which may, on occasion, lead to loss of mechanical strength. Alkaline hydrolysis or carbonation in the presence of alkalis is a highly destructive process. The purpose of the study was to determine what caused CAC concrete deterioration in a prestressed beam that had suffered intense external damage and showed signs of alkaline hydrolysis or a reaction between the aggregate and the cement. Samples of the internal (sound) and external (damaged) parts of the concrete were studied using XRF, XRD, FTIR, OM, SEM/EDX, and BSE techniques, and mechanical strength was measured on microspecimens extracted from both zones. The conclusion drawn from these analyses was that alkaline hydrolysis took place on or near the surface of the concrete. The white deposits observed around the alkali-containing aggregate were found to consist primarily of bayerite whose very loose consistency undermined the aggregate-matrix bond, greatly weakening the material

  18. A novel method to produce potassium chromate from carbon ferrochrome

    Institute of Scientific and Technical Information of China (English)

    胡国荣; 王家良; 彭忠东; 杜柯

    2015-01-01

    The oxidizing roasting of carbon ferrochrome in the presence of potassium carbonate and air was investigated. The effects of reaction temperature, reaction time, ratio of alkali-to-ore were studied, together with a discussion of the thermodynamics and macro kinetics. It is observed that the reaction temperature and reaction time have significant influence on the roasting reaction. The reaction mechanism changes greatly as the temperature varies. A two-stage roasting process is favorable for the roasting reaction, and a recovery ratio of 96.51%is obtained through this two-stage roasting method. The chromium residue yielded from this method is quite little, only one third of the product. Moreover, the component of Fe in the residue is as high as 54.28%. Therefore, it can be easily recovered to produce sponge iron, realizing zero-emission of chromium residue.

  19. Nitrogen-doped ordered mesoporous carbons synthesized from honey as metal-free catalyst for oxygen reduction reaction

    International Nuclear Information System (INIS)

    Highlights: • Nitrogen-doped ordered mesoporous carbons (N-OMCs) were synthesized from honey. • High electrocatalytic activity toward oxygen reduction at N-OMCs modified electrode. • Metal-free, CH3OH tolerable and long term stable catalyst in fuel cell application. • Honey being nitrogen and carbon sources for other metal-free carbon materials. -- Abstract: In this work, nitrogen-doped ordered mesoporous carbons (N-OMCs) were synthesized by a low cost and simple nanocasting method using SBA-15 as a template and honey as a nitrogen and carbon sources. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption-desorption, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that nitrogen was successfully doped into the framework of ordered mesoporous carbon rods. The N-OMCs with high surface area and ordered structure were used as a metal-free catalyst for oxygen reduction reaction (ORR), which exhibited much better electrocatalytic activity, long-term operation stability and high CH3OH tolerance compared to commercial Pt/C catalysts for ORR in alkaline fuel cell. Moreover, the influence of different amounts of nitrogen formed at different carbonization temperatures in N-OMCs on the ORR activity was researched. Honey as a nitrogen and carbon sources may be applied to various carbon materials for the development of other metal-free efficient materials for applications beyond fuel cells

  20. Platinum Nanoparticles Supported on Nitrobenzene-Functionalized Multiwalled Carbon Nanotube as Efficient Electrocatalysts for Methanol Oxidation Reaction

    International Nuclear Information System (INIS)

    Graphical abstract: Multiwalled carbon nanotube was functionalized with nitrobenzene as a promising support material for Pt-based electrocatalysts (Pt-NB-MWCNT) for methanol oxidation. The as-prepared catalysts have higher electrocatalytic activity in terms of both mass and specific activities, and improved durability for methanol oxidation reaction than as compared to the undoped materials. - Highlights: • Multiwalled carbon nanotube was functionalized with nitrobenzene as a support material for Pt-based electrocatalysts for methanol oxidation. • The electronic properties of carbon nanotubes were modified by the nitrobenzene functionalization. • Nitrobenzene-functionalized electrocatalysts revealing the improved electrocatalytic performance of Pt-NB-MWCNT catalyst for the methanol oxidation reaction. - Abstract: A novel method of molecular covalently functionalized multiwalled carbon nanotube using nitrobenzene group is prepared and used as a promising support material of Pt-based electrocatalysts (denoted as Pt-NB-MWCNT) for methanol oxidation reaction. The physical and chemical characteristics are performed by X-ray powder diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric and X-ray photoelectron spectroscopy. The electrocatalytic are evaluated by cyclic voltammetry and chronoamperometry techniques. Compared with the un-functionalized Pt-MWCNT catalyst, Pt-NB-MWCNTs show more uniform particle dispersion, smaller particle size, improved activity and durability for methanol oxidation reaction. The nitrobenzene group is demonstrated to promote the electrocatalytic activity of Pt-MWCNT for methanol oxidation significantly. The results represent a novel approach to functionalize MWCNT in a simple and economic way to prepare efficient electrocatalysts for methanol oxidation

  1. An evaluation of the neutron-induced reaction cross sections on carbon from 10 to 20 MeV

    International Nuclear Information System (INIS)

    Available data on the neutron-induced reactions on carbon are reviewed for the energy range from 10 to 20 MeV. Evaluated cross sections obtained at Bruyeres-le-Chatel are discussed. Comparisons with coupled-channel calculations are presented for the total, elastic and inelastic (to the 2+ level) cross sections of 12C

  2. Microcalorimetric Adsorption of Alumina Oxide Catalysts for Combination of Ethylbenzene dehydrogenation and carbon Dioxide Shift-reaction

    Institute of Scientific and Technical Information of China (English)

    GE Xin; SHEN Jian-yi

    2004-01-01

    Styrene (STY) is now produced industrially in fairly large quantities by the dehydrogenation of ethylbenzene (EB) using promoted iron oxide catalyst with superheated steam.In this case, small amount of carbon dioxide formed as a by-product was known to inhibit the catalytic activity of commercial catalyst. Recently, there have been some reports which carbon dioxide showed positive effects to promote catalytic activities on the reaction over several catalysts.In this study, we attempted to combine the dehydrogenation of EB to STY with the carbon dioxide shift-reaction. The combine reaction (EB + CO2 → STY + H2O + CO) can be considered as one of the ways of using CO2 resources and can yield simultaneously STY and Carbon oxide.Alumina oxide catalysts such as Al2O3, Na2O/Al2O3 and K2O/Al2O3 were prepared by the usual impregnation method with an aqueous solution of NaNO3 and KNO3, and then calcined at 650℃ for 5 h in a stream of air. The reaction condition is 600℃, flow of CO2 38ml/mon and space velocity (EB) 1.28h-1.

  3. Cobalt-Embedded Nitrogen-Rich Carbon Nanotubes Efficiently Catalyze Hydrogen Evolution Reaction at All pH Values

    Czech Academy of Sciences Publication Activity Database

    Zou, X.; Huang, X.; Goswami, A.; Silva, R.; Sathe, B. R.; Mikmeková, Eliška; Asefa, T.

    2014-01-01

    Roč. 53, č. 17 (2014), s. 4372-4376. ISSN 1433-7851 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : carbon nanotubes * cobalt nanoparticles * electrocatalysis * hydrogen evolution reaction * water splitting Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 11.261, year: 2014

  4. Microstructure and Engineering Properties of Alkali Activated Fly Ash -as an environment friendly alternative to Portland cement

    NARCIS (Netherlands)

    Ma, Y.

    2013-01-01

    Alkali activated fly ash (AAFA), also named “geopolymer”, has emerged as a novel engineering material in the construction industry. This material is normally formed by the reaction between fly ash and aqueous hydroxide or alkali silicate solution. With proper mix design, AAFA can present comparable

  5. Synthesis of high purity single-walled carbon nanotubes from ethanol by catalytic gas flow CVD reactions

    International Nuclear Information System (INIS)

    Highly pure single-walled carbon nanotubes (SWNTs) with their contents >96% of the total products were achieved by chemical vapour deposition gas flow reactions using ethanol as the carbon source. The high purity SWNTs were formed under critically controlled synthesis conditions and by applying a high hydrogen flow, under which the non-catalytic condensation of carbon was completely suppressed. Purification of the products in acid at ambient conditions readily yielded over 99% pure SWNT products, as the only impurities left in the products were iron particles of clean surface. Therefore, the present study demonstrates the full potential of the CVD gas flow reactions in continuous production of high quality SWNTs. Comparable syntheses were conducted using other alcohols in place of ethanol and it was found that high alkyl alcohols like isopropanol and hexanol produced more amorphous carbon while methanol produced no carbon. The high yield growth of SWNTs was attributed greatly to the reaction chemistry of ethanol and the 'right' amount of hydrogen in the system, as discussed

  6. Pengaruh Konsentrasi Total Titratable Alkali Terhadap Persen Causticizing Efficiency Dan Persen Sulfidity Di Dalam Whiteliquor Storage Pada Proses Recausticizing Di PT. Toba Pulp Lestari, Tbk

    OpenAIRE

    Parhusip, Arrye Genap

    2014-01-01

    White liquor is a liquor obtained from the reaction of green liquor with calcium oxide (CaO), through a process that occurs in causticizer recausticizing. The content is primarily Sodium hydroxide (NaOH), Sodium sulphide (Na2S), and Sodium Carbonate (Na2CO3) bit, where the total of the amount of the compound represented by the Total Titratable Alkali. White liquor is to be used as the main ingredient in the cooking wood in digester unit. Before the white liquor, should be used to control the ...

  7. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite for methanol synthesis

    Science.gov (United States)

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1993-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  8. Radial deformation of single-walled carbon nanotubes on quartz substrates and the resultant anomalous diameter-dependent reaction selectivity

    Institute of Scientific and Technical Information of China (English)

    Juan Yang; Yu Liu; Daqi Zhang; Xiao Wang; Ruoming Li; Yan Li

    2015-01-01

    Owing to the unique conjugated structure, the chemical-reaction selectivity of single-walled carbon nanotubes (SWNTs) has attracted great attention. By utilizing the radial deformation of SWNTs caused by the strong interactions with the quartz lattice, we achieve an anomalous diameter-dependent reaction selectivity of quartz lattice-oriented SWNTs in treatment with iodine vapor; this is distinctly different from the widely reported and well accepted higher reaction activity in small-diameter tubes compared to large-diameter tubes. The radial deformation of SWNTs on quartz substrate is verified by detailed Raman spectroscopy and mappings in both G-band and radial breathing mode. Due to the strong interaction between SWNTs and the quartz lattice, large-diameter tubes present a larger degree of radial deformation and more delocalized partial electrons are distributed at certain sidewall sites with high local curvature. It is thus easier for the carbon--carbon bonds at these high-curvature sites on large-diameter tubes to break down during reaction. This anomalous reaction activity offers a novel approach for selective removal of small-band~aD large-diameter tubes.

  9. Construction of thermionic alkali-ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Ul Haq, F.

    1986-04-01

    A simple technique is described by which singly charged alkali ions of K, Na, Li, Rb and Cs are produced by heating ultra-pure chemical salts of different alkali metals on tungsten filaments without employing a temperature measuring device. The character of alkali-ion currents at different heating powers and the remarkably constant ion emission current for prolonged periods are discussed.

  10. Improvement of enzymatic saccharification of sugarcane bagasse by dilute-alkali-catalyzed hydrothermal treatment and subsequent disk milling.

    Science.gov (United States)

    Miura, Toyokazu; Lee, Seung-Hwan; Inoue, Seiichi; Endo, Takashi

    2012-02-01

    Dilute-alkali-catalyzed hydrothermal treatment (HT) was conducted to improve the enzymatic degradability of sugarcane bagasse. Wet-disk milling (DM) was also performed after HT. Sodium carbonate with 0-6% concentration on dry weight basis of bagasse was used as the alkali catalyst. A content of more than 4% of the alkali catalyst was necessary for producing a higher amount of glucose than that produced after HT without an alkali catalyst. HT with 6% of the alkali catalyst, which decreased the pH to the neutral region, retained more xylan and less lignin than HT without an alkali. Subsequent DM improved the enzymatic degradability further and increased the specific surface area. For a substrate concentration of 10%, the amounts of glucose and xylose produced were 344 and 188 mg/g-bagasse, respectively. These values corresponded to yields of 77% and 67% on the basis of the glucan and xylan contents in raw bagasse, respectively. PMID:22196074

  11. Electrolytic method to make alkali alcoholates using ion conducting alkali electrolyte/separator

    Science.gov (United States)

    Joshi, Ashok V.; Balagopal, Shekar; Pendelton, Justin

    2011-12-13

    Alkali alcoholates, also called alkali alkoxides, are produced from alkali metal salt solutions and alcohol using a three-compartment electrolytic cell. The electrolytic cell includes an anolyte compartment configured with an anode, a buffer compartment, and a catholyte compartment configured with a cathode. An alkali ion conducting solid electrolyte configured to selectively transport alkali ions is positioned between the anolyte compartment and the buffer compartment. An alkali ion permeable separator is positioned between the buffer compartment and the catholyte compartment. The catholyte solution may include an alkali alcoholate and alcohol. The anolyte solution may include at least one alkali salt. The buffer compartment solution may include a soluble alkali salt and an alkali alcoholate in alcohol.

  12. Simulation Experiments on the Reaction of CH4-CaSO4 and Its Carbon Kinetic Isotope Fractionation

    Institute of Scientific and Technical Information of China (English)

    YueChangtao; LiShuyuan; DingKangle; ZhongNingning

    2005-01-01

    Thermochemical sulfate reduction (TSR) in geological deposits can account for the accumulation of H,S in deep sour gas reservoirs. In this paper, thermal simulation experiments on the reaction of CH4-CaSO4 were carried out using an autoclave at high temperatures and high pressures. The products were characterized with analytical methods including carbon isotope analysis. It is found that the reaction can proceed to produce H2S, H2O and CaCO3 as the main products. Based on the experimental results, the carbon kinetic isotope fractionation was investigated, and the value of Ki(kinetic isotope effect) was calculated. The results obtained in this paper can provide useful information to explain the occurrence of H2S in deep carbonate gas reservoirs.

  13. Energy- and carbon-efficient synthesis of functionalized small molecules in bacteria using non-decarboxylative Claisen condensation reactions.

    Science.gov (United States)

    Cheong, Seokjung; Clomburg, James M; Gonzalez, Ramon

    2016-05-01

    Anabolic metabolism can produce an array of small molecules, but yields and productivities are low owing to carbon and energy inefficiencies and slow kinetics. Catabolic and fermentative pathways, on the other hand, are carbon and energy efficient but support only a limited product range. We used carbon- and energy-efficient non-decarboxylative Claisen condensation reactions and subsequent β-reduction reactions, which can accept a variety of functionalized primers and functionalized extender units and operate in an iterative manner, to synthesize functionalized small molecules. Using different ω- and ω-1-functionalized primers and α-functionalized extender units in combination with various termination pathways, we demonstrate the synthesis of 18 products from 10 classes, including ω-phenylalkanoic, α,ω-dicarboxylic, ω-hydroxy, ω-1-oxo, ω-1-methyl, 2-methyl, 2-methyl-2-enolic and 2,3-dihydroxy acids, β-hydroxy-ω-lactones, and ω-1-methyl alcohols. PMID:27088721

  14. Amorphous Molybdenum Sulfide on Graphene-Carbon Nanotube Hybrids as Highly Active Hydrogen Evolution Reaction Catalysts.

    Science.gov (United States)

    Pham, Kien-Cuong; Chang, Yung-Huang; McPhail, David S; Mattevi, Cecilia; Wee, Andrew T S; Chua, Daniel H C

    2016-03-01

    In this study, we report on the deposition of amorphous molybdenum sulfide (MoSx, with x ≈ 3) on a high specific surface area conductive support of Graphene-Carbon Nanotube hybrids (GCNT) as the Hydrogen Evolution Reaction (HER) catalysts. We found that the high surface area GCNT electrode could support the deposition of MoSx at much higher loadings compared with simple porous carbon paper or flat graphite paper. The morphological study showed that MoSx was successfully deposited on and was in good contact with the GCNT support. Other physical characterization techniques suggested the amorphous nature of the deposited MoSx. With a typical catalyst loading of 3 mg cm(-2), an overpotential of 141 mV was required to obtain a current density of 10 mA cm(-2). A Tafel slope of 41 mV decade(-1) was demonstrated. Both measures placed the MoSx-deposited GCNT electrode among the best performing molybdenum sulfide-based HER catalysts reported to date. The electrode showed a good stability with only a 25 mV increase in overpotential required for a current density of 10 mA cm(-2), after undergoing 500 potential sweeps with vigorous bubbling present. The current density obtained at -0.5 V vs SHE (Standard Hydrogen Electrode potential) decreased less than 10% after the stability test. The deposition of MoSx on high specific surface area conductive electrodes demonstrated to be an efficient method to maximize the catalytic performance toward HER. PMID:26864503

  15. Highly vibrationally excited CO generated in a low-temperature chemical reaction between carbon vapor and molecular oxygen

    Science.gov (United States)

    Jans, E.; Frederickson, K.; Yurkovich, M.; Musci, B.; Rich, J. W.; Adamovich, I. V.

    2016-08-01

    A chemical flow reactor is used to study the vibrational population distribution of CO produced by a reaction between carbon vapor generated in an arc discharge and molecular oxygen. The results demonstrate formation of highly vibrationally excited CO, up to vibrational level v = 14, at low temperatures, T = 400-450 K, with population inversion at v = 4-7, in a collision-dominated environment, 15-20 Torr. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of reaction enthalpy. The results show feasibility of development of a new CO chemical laser using carbon vapor and oxygen as reactants.

  16. Alkali and transition metal phospholides

    International Nuclear Information System (INIS)

    Major tendencies in modern chemistry of alkali and transition metal phospholides (phosphacyclopentadienides) are systematized, analyzed and generalized. Basic methods of synthesis of these compounds are presented. Their chemical properties are considered with a special focus on their complexing ability. Potential applications of phospholides and their derivatives are discussed. The bibliography includes 184 references

  17. Renal tubular acidosis due to the milk-alkali syndrome.

    Science.gov (United States)

    Rochman, J; Better, O S; Winaver, J; Chaimowitz, C; Barzilai, A; Jacobs, R

    1977-06-01

    A 60-year-old man with a history of excessive ingestion of calcium carbonate presented with azotemia, hypercalcemia and hyperphosphatemia. His acid-base status was initially normal. Following the cessation of calcium carbonate treatment, the hypercalcemia and azotemia disappeared, and the patient was found to be in metabolic acidosis with blunted acid excretion and a urine pH of 6.1. Kidney biopsy showed focal tubular calcification; the tubular damage was apparently caused by hypercalcemia and had resulted in renal tubular acidosis. During the three months of observation since that time there has been a tendecy for spontaneous remission of the renal tubular acidosis. Impaired renal hydrogen ion excretion prevented the development of metabolic alkalosis despite ingestion of alkali initially, and was later responsible for the metabolic acidosis. Renal tubular acidosis occurring as a sequel to the milk-alkali syndrome may aggravate the danger of nephrocalcinosis in this syndrome. PMID:885714

  18. Alkali Metal Complexes: Mixed Ligand Complexes of Some Alkali Metal Salts of Some Organic Acids with Isonitroso-PMethylace to phenone

    Directory of Open Access Journals (Sweden)

    O.P. Gupta

    2016-02-01

    Full Text Available A number of mixed ligand complexes of alkali metal salts of o-nitrophenol,2,4-dinitrophenol, 2,4,6,- trinitrophenol, 1-nitroso-2- naphthol and 8- hydroxyquinoline with Insoniroso–p methylacetopheone have been synthesized in absolute ethanol & characterized by elemental analysis and I .B. spectral data. Their I.R spectral data indicate the presence of hydrogen bonding in them, which many be one of the dominant factors of their stability. Further appreciable shift in 1650 cm-1 band (possibly vC=O and 1600 cm-1 band (possibly vC=NSuggests their coordination behavior in these mixed ligand complexes The reactions that take place in natural systems are highly specific and selective. Alkali metal ions actively participate in most of the reaction occurring in the biological systems, which are dominated by mixed ligand complexes. Studies of such mixed ligand complexes of alkali metals can threw light in understanding the role and mechanism of selective absorption of alkali metals ions by plants Coordinating ability of alkali metal with isonitrosoacetophenone1-2 and transition metals with isonitrosoacetophenone3 and isonitroso-p-methylacetophenone4 have been reported earlier. In the present paper we report the mixed ligand complexes of alkali metal salts having the general formula ML.HL, ‘ where M=Li, Na & K and L=deprotonated o- nitrophenol, 2,4 dinitrophenol, 2, 4, 6- trinitrophenol, 1-nitroso-2-naphthol or 8- hydroxquinoline; HL’= p -MeHINAP (isonitroso-p-methylacetophenone.

  19. Science Letters: Nitrogen doping of activated carbon loading Fe2O3 and activity in carbon-nitric oxide reaction

    Institute of Scientific and Technical Information of China (English)

    WAN Xian-kai; ZOU Xue-quan; SHI Hui-xiang; WANG Da-hui

    2007-01-01

    Nitrogen doping of activated carbon loading Fe2O3 was performed by annealing in ammonia, and the activity of the modified carbon for NO reduction was studied in the presence of oxygen. Results show that Fe2O3 enhances the amount of surface oxygen complexes and facilitates nitrogen incorporation in the carbon, especially in the form of pyridinic nitrogen. The modified carbon shows excellent activity for NO reduction in the low temperature regime (<500 ℃) because of the cooperative effect of Fe2O3 and the surface nitrogen species.

  20. In situ observation of the reaction of scandium and carbon by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Juarez-Arellano, Erick A., E-mail: eajuarez@unpa.edu.m [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Universidad del Papaloapan, Circuito Central 200, Parque Industrial, Tuxtepec 68301 (Mexico); Winkler, Bjorn [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Vogel, Sven C. [Los Alamos National Laboratory, Lujan Center. Mail Stop H805, Los Alamos, NM 87545 (United States); Senyshyn, Anatoliy [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universitaet Muenchen, Lichtenbergstr. 1, D-85747 Garching (Germany); Materialwissenschaft, TU Darmstadt, Petersensstr. 23, D-64287 Darmstadt (Germany); Kammler, Daniel R. [Sandia National Laboratories, Albuquerque, NM 87185 (United States); Avalos-Borja, Miguel [CNyN, UNAM, A. Postal 2681, Ensenada, B.C. (Mexico)

    2011-01-05

    Research highlights: {yields} Exist two ScC cubic phases with B1-structure type differing in site occupancy of C. {yields} A new orthorhombic scandium carbide phase is formed at 1473(50) K. {yields} The recrystallization of alpha-Sc occurs between 1000 and 1223 K. - Abstract: The formation of scandium carbides by reaction of the elements has been investigated by in situ neutron diffraction up to 1823 K. On heating, the recrystallization of {alpha}-Sc occurs between 1000 and 1223 K. The formation of Sc{sub 2}C and ScC (NaCl-B1 type structure) phases has been detected at 1323 and 1373 K, respectively. The formation of a new orthorhombic scandium carbide phase was observed at 1473(50) K. Once the scandium carbides are formed they are stable upon heating or cooling. No other phases were detected in the present study, in which the system was always carbon saturated. The thermal expansion coefficients of all phases have been determined, they are constant throughout the temperature interval studied.

  1. Competitive surface complexation reactions of sulfate and natural organic carbon on soil

    International Nuclear Information System (INIS)

    The ecological implications of subsurface SO42- loading on nutrient cation leaching, acidification, and the destruction of concrete containers used to store low-level radioactive waste, has been thoroughly addressed. Processes favoring SO42- adsorption by the subsurface matrix tend to alleviate these adverse ecological conditions and this has been investigated to a lesser extent. In this study, the adsorption of SO42 onto several soil types with indigenous SO42- and organic carbon removed, was measured as a function of pH in the presence and absence of added natural organic matter (NOM). Sulfate adsorption was strongly pH dependent and the presence of >2 mg L-1 NOM resulted in a consistent decrease in sulfate adsorption over the pH range 4.5 to 8. The tendency of these soils to adsorb SO42- was related to their large quantity of Fe-oxides and the presence of kaolinite in the 42- was related to their large quantity of Fe-oxides and the presence of kaolinite in the 42- onto positive or neutral surface sites (XOH + H+ + SO42- = XSO4- + H2O) as a inner-sphere complex proved successful in describing the adsorption of sulfate under the experimental conditions. The estimated value of the intrinsic equilibrium constant (K) for the above reaction was of the order 1010 suggesting strong sulfate adsorption. Estimated K values were found to be unaffected by the presence of added NOM. 57 refs., 3 figs., 3 tabs

  2. One-step synthesis of nitrogen-iron coordinated carbon nanotube catalysts for oxygen reduction reaction

    Science.gov (United States)

    Choi, Woongchul; Yang, Gang; Kim, Suk Lae; Liu, Peng; Sue, Hung-Jue; Yu, Choongho

    2016-05-01

    Prohibitively expensive precious metal catalysts for oxygen reduction reaction (ORR) have been one of the major hurdles in a wide use of electrochemical cells. Recent significant efforts to develop precious metal free catalysts have resulted in excellent catalytic activities. However, complicated and time-consuming synthesis processes have negated the cost benefit. Moreover, detailed analysis about catalytically active sites and the role of each element in these high-performance catalysts containing nanomaterials for large surface areas are often lacking. Here we report a facile one-step synthesis method of nitrogen-iron coordinated carbon nanotube (CNT) catalysts without precious metals. Our catalysts show excellent long-term stability and onset ORR potential comparable to those of other precious metal free catalysts, and the maximum limiting current density from our catalysts is larger than that of the Pt-based catalysts. We carry out a series of synthesis and characterization experiments with/without iron and nitrogen in CNT, and identify that the coordination of nitrogen and iron in CNT plays a key role in achieving the excellent catalytic performances. We anticipate our one-step process could be used for mass production of precious metal free electrocatalysts for a wide range of electrochemical cells including fuel cells and metal-air batteries.

  3. Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide: A facile method for the synthesis of tetrasubstituted olefins

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the catalyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of dibromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.

  4. Nitrogen-doped carbon black as methanol tolerant electrocatalyst for oxygen reduction reaction in direct methanol fuel cells

    International Nuclear Information System (INIS)

    Nitrogen-doped metal free carbon catalysts were prepared via pyrolysis of polyaniline-coated carbon in different ratios with varying nitrogen content. The surface states and surface composition were investigated using XPS (X-ray photoelectron spectroscopy). XPS analysis confirms the presence of pyridinic and pyrollic nitrogen in the carbon network that is responsible for the oxygen reduction activity. The shift in onset potential of oxygen reduction on C:N (1:1) is ∼0.3 V more positive compared to Vulcan carbon, shows improved activity toward oxygen reduction reaction in acidic electrolyte. Hydrodynamic voltammetric studies confirm that the reduction of oxygen follows the 4e− pathway which leads to the formation of water.

  5. The effect of the alkali metal cation on the electrocatalytic oxidation of formate on platinum

    OpenAIRE

    Previdello, B.; E. Machado; Varela, H.

    2014-01-01

    Non-covalent interactions between hydrated alkali metal cations and adsorbed oxygenated species on platinum might considerably inhibit some electrocatalytic reactions. We report in this communication the effect exerted by electrolyte alkali metal cations on the electro-oxidation of formate ions on platinum. The system was investigated by means of cyclic voltammetry and chronoamperometry in the presence of an electrolyte containing Li+, Na+, or K+. As already observed for other systems, the ge...

  6. Behaviour of gaseous alkali compounds in coal gasification; Kaasumaisten alkaliyhdisteiden kaeyttaeytyminen kivihiilien kaasutuksessa

    Energy Technology Data Exchange (ETDEWEB)

    Nykaenen, J. [Imatran Voima Oy, Vantaa (Finland)

    1997-10-01

    In this project the behaviour of alkali compounds emitting from CO{sub 2}/O{sub 2}- and airblown gasification are studied. This research project is closely connected to an EU-project coordinated by the Delft University of Technology (DUT). In that project alkali emissions from a 1.6 MW pilot plant will be measured. The results from those measurements will be compared with the calculations performed in this LIEKKI 2 project. The equilibrium calculations show that the major gaseous alkali compounds emitting from combustion and gasification are chlorides and hydroxides. This applies both to air- and CO{sub 2}/O{sub 2}-blown processes. In all the cases studied the concentration of gaseous alkali compounds is determined mainly by the amount of chlorides. The key parameters, with respect to alkali behaviour, are the temperature of the process and chlorine content of the coal. By cooling the gases down to 600 deg C prior to a ceramic filter the alkali concentration can be kept about at 100 ppbv. In combustion, the addition of calcium carbonate increases the amount of gaseous alkali compounds by decreasing the amount of alkali sulphates. In the case of gasification the importance of limestone is negligible. The difference between air- and CO{sub 2}/O{sub 2}-blown processes, in terms of gaseous alkali emissions, is small. This is because CO{sub 2} concentration of the gas does not have a strong impact on alkali chlorides. Furthermore, the effect of CO{sub 2}/O{sub 2}-ratio of the recirculation process is negligible. (orig.)

  7. Structural models for alkali-metal complexes of polyacetylene

    Science.gov (United States)

    Murthy, N. S.; Shacklette, L. W.; Baughman, R. H.

    1990-02-01

    Structural models for a stage-2 complex are proposed for polyacetylene doped with less than about 0.1 potassium or rubidium atoms per carbon. These structures utilize as a basic motif an alkali-metal column surrounded by four planar-zig-zag polyacetylene chains, a structure found at the highest dopant levels. In the new stage-2 structures, each polyacetylene chain neighbors only one alkali-metal column, so the phase contains four polymer chains per alkali-metal column. Basic structural aspects for stage-1 and stage-2 structures are now established for both potassium- and rubidium-doped polyacetylene. X-ray-diffraction and electrochemical data show that undoped and doped phases coexist at low dopant concentrations (<0.06 K atom per C). X-ray-diffraction data, down to a Bragg spacing of 1.3 Å, for polyacetylene heavily doped with potassium (0.125-0.167 K atom per C) is fully consistent with our previously proposed stage-1 tetragonal unit cell containing two polyacetylene chains per alkali-metal column. There is no evidence for our samples requiring a distortion to a monoclinic unit cell as reported by others for heavily doped samples. The nature of structural transformations and the relationship between structure and electronic properties are discussed for potassium-doped polyacetylene.

  8. Effect of Nonleaving Group on the Reaction Rate and Mechanism: Aminolyses of 4-Nitrophenyl Acetate, Benzoate and Phenyl Carbonate

    International Nuclear Information System (INIS)

    Second-order rate constants have been determined spectrophotometrically for the reaction of phenyl 4- nitrophenyl carbonate with a series of primary amines in H2O containing 20 mol % DMSO at 25.0 .deg. C. The Brφnsted-type plot is linear with a βnuc 0.69 ± 0.04, which is slightly smaller than the βnuc values for the reactions of 4-nitrophenyl acetate (βnuc = 0.82 ± 0.03) and benzoate (βnuc = 0.76 ± 0.01), indicating that the reaction proceeds through a tetrahedral zwitterionic intermediate T±. The carbonate is more reactive than the corresponding acetate and benzoate. The changing Me (or Ph) to PhO has resulted in a decrease in the βnuc value without changing the reaction mechanism but an increase in the reactivity. The electronic effect of the substituent in the nonleaving group appears to be responsible for the enhanced reactivity of the carbonate compared with the corresponding acetate and benzoate

  9. Molecular-level Simulations of Chemical Reaction Equilibrium for Nitric Oxide Dimerization Reaction in Disordered Nanoporous Carbons

    Czech Academy of Sciences Publication Activity Database

    Lísal, Martin; Cosoli, P.; Smith, W. R.; Jain, S.K.; Gubbins, K.E.

    2008-01-01

    Roč. 272, 1-2 (2008), s. 18-31. ISSN 0378-3812 R&D Projects: GA ČR GA203/08/0094; GA AV ČR 1ET400720409; GA AV ČR 1ET400720507; GA AV ČR KAN400720701; GA AV ČR IAA400720710 Institutional research plan: CEZ:AV0Z40720504 Keywords : nanoporous carbon * adsorption model * remc Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.699, year: 2008

  10. Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics.

    Science.gov (United States)

    Chang, E-E; Pan, Shu-Yuan; Yang, Liuhanzi; Chen, Yi-Hung; Kim, Hyunook; Chiang, Pen-Chi

    2015-09-01

    Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewater (CRW) was investigated for carbon dioxide (CO2) fixation under different operating conditions, i.e., reaction time, CO2 concentration, liquid-to-solid ratio, particle size, and CO2 flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO2 fixation capacity of 102g perkg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO2 reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO2 fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion. PMID:26025583

  11. Experimental study of carbon sequestration reactions controlled by the percolation of CO2-rich brine through peridotites.

    Science.gov (United States)

    Andreani, M; Luquot, L; Gouze, P; Godard, M; Hoisé, E; Gibert, B

    2009-02-15

    Carbonation of ultramafic rocks in geological reservoirs is, in theory, the most efficient way to trap CO2 irreversibly; however, possible feedback effects between carbonation reactions and changes in the reservoir permeability must be considered to realistically assess the efficiency and sustainability of this process. We investigated changes in the hydrodynamic properties of sintered dunite samples by means of percolation experiments, under conditions analogous to that of in situ carbonation. Our results show that carbonation efficiency is controlled by the local renewal of the reactants and the heterogeneity of the pore structure. Preferential flow zones are characterized by the formation of magnetite and of a silica-rich layer at the olivine surfaces, which eventually inhibits olivine dissolution. Conversely, sustainable olivine dissolution together with coprecipitation of magnesite, siderite, and minor Mg-TOT-phyllosilicates, occur in reduced-flow zones. Thus carbonate precipitation only decreases porosity in zones where diffusion-controlled transport is dominant. Consequently, while high flow rates will decrease the carbonation efficiency of the reservoir and low flow rates may reduce the permeability irreversibly close to the injection point, moderate injection rates will ensure a partial carbonation of the rock and maintain the reservoir permeability. PMID:19320184

  12. Graphitic cage transformation by electron-beam-induced catalysis with alkali-halide nanocrystals

    Science.gov (United States)

    Fujita, Jun-ichi; Tachi, Masashi; Ito, Naoto; Murakami, Katsuhisa; Takeguchi, Masaki

    2016-05-01

    We found that alkali-halide nanocrystals, such as KCl and NaCl, have strong catalytic capability to form graphitic carbon cages from amorphous carbon shells under electron beam irradiation. In addition to the electron beam irradiation strongly inducing the decomposition of alkali-halide nanocrystals, graphene fragments were formed and linked together to form the final product of thin graphitic carbon cages after the evaporation of alkali-halide nanocrystals. The required electron dose was approximately 1 to 20 C/cm2 at 120 keV at room temperature, which was about two orders of magnitude smaller than that required for conventional beam-induced graphitization. The “knock-on” effect of primary electrons strongly induced the decomposition of the alkali-halide crystal inside the amorphous carbon shell. However, the strong ionic cohesion quickly reformed the crystal into thin layers inside the amorphous shell. The bond excitation induced by the electron beam irradiation seemed to enhance strongly the graphitization at the interface between the outer amorphous carbon shell and the inner alkali-halide crystal.

  13. Effect of Na3PO4 on the Hydration Process of Alkali-Activated Blast Furnace Slag

    Directory of Open Access Journals (Sweden)

    Lukáš Kalina

    2016-05-01

    Full Text Available In recent years, the utilization of different non-traditional cements and composites has been increasing. Alkali-activated cementitious materials, especially those based on the alkali activation of blast furnace slag, have considerable potential for utilization in the building industry. However, alkali-slag cements exhibit very rapid setting times, which are too short in some circumstances, and these materials cannot be used for some applications. Therefore, it is necessary to find a suitable retarding admixture. It was shown that the sodium phosphate additive has a strong effect on the heat evolution during alkali activation and effectively retards the hydration reaction of alkali-activated blast furnace slag. The aim of the work is the suggestion of a reaction mechanism of retardation mainly based on Raman and X‑ray photoelectron spectroscopy.

  14. Formation of brown carbon via reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic precursors

    Science.gov (United States)

    Updyke, Katelyn M.; Nguyen, Tran B.; Nizkorodov, Sergey A.

    2012-12-01

    Filter samples of secondary organic aerosols (SOA) generated from the ozone (O3)- and hydroxyl radical (OH)-initiated oxidation of various biogenic (isoprene, α-pinene, limonene, α-cedrene, α-humulene, farnesene, pine leaf essential oils, cedar leaf essential oils) and anthropogenic (tetradecane, 1,3,5-trimethylbenzene, naphthalene) precursors were exposed to humid air containing approximately 100 ppb of gaseous ammonia (NH3). Reactions of SOA compounds with NH3 resulted in production of light-absorbing "brown carbon" compounds, with the extent of browning ranging from no observable change (isoprene SOA) to visible change in color (limonene SOA). The aqueous phase reactions with dissolved ammonium (NH4+) salts, such as ammonium sulfate, were equally efficient in producing brown carbon. Wavelength-dependent mass absorption coefficients (MAC) of the aged SOA were quantified by extracting known amounts of SOA material in methanol and recording its UV/Vis absorption spectra. For a given precursor, the OH-generated SOA had systematically lower MAC compared to the O3-generated SOA. The highest MAC values, for brown carbon from SOA resulting from O3 oxidation of limonene and sesquiterpenes, were comparable to MAC values for biomass burning particles but considerably smaller than MAC values for black carbon aerosols. The NH3/NH4+ + SOA brown carbon aerosol may contribute to aerosol optical density in regions with elevated concentrations of NH3 or ammonium sulfate and high photochemical activity.

  15. In situ formation of silicon carbide from the kaolin and carbon reaction: quantification using X-ray diffraction

    International Nuclear Information System (INIS)

    In situ formation of silicon carbide by the reaction between kaolin, as a Si O2 natural mineral precursor, and black carbon was analyzed by X-ray diffraction studies in a temperature range from 1400 to 1700 deg C in an argon atmosphere. X-ray patterns showed that needle like SiC (aspect ratio: 20 to 100) begins to form above 1500 deg C. Samples with stoichiometry carbon contents with respect to silica were synthesized. The quantitative influence of temperature on the SiC-formation was determined. (author)

  16. Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

    Science.gov (United States)

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

  17. Applications of the water--gas shift reaction. II. Catalytic exchange of deuterium for hydrogen at saturated carbon

    International Nuclear Information System (INIS)

    Previous studies on the homogeneous catalysis of the water-gas shift reaction by metal complexes of groups 6 and 8 had been carried out using aqueous alcoholic solutions of group 8 metal carbonyl complexes made basic with KOH. Substitution of triethylamine (Et3N) for KOH as base and alcohol for solvent led to the discovery that Et3N in the presence of D2O, CO, and Rh6(CO)16 at 1500C undergoes an unusual catalytic exchange of deuterium for hydrogen. A suggested mechanism for this reaction is given and includes activation of hydrogen at a saturated carbon

  18. On-line alkali monitoring - Part 1

    International Nuclear Information System (INIS)

    As a consequence of the increased knowledge of the environmental impact of combustion based heat and power generation, the use of renewable biofuels will be increased. An obstacle associated to biofuel combustion compared to other fuels is the large release of alkali. Alkali compounds in flue gases are known to cause severe operational problems. Three of the major problems are; fouling of superheating tubes (causing reduced heat transfer and possibly corrosion), agglomeration of the bed material in fluidized beds, and poisoning of SCR catalysts. Yet another alkali related problem arises when, in order to increase the electric efficiency of combustion power plants, combined-cycle technology is used. Alkali vapour present in the fuel gas for the gas turbine is condensed to particles which increase corrosion and erosion of the turbine blades. The research on ash related operational problems has to be extended in order to ensure future use of biofuels in heat and power generation. In all successful research, adequate tools are necessary. To investigate ash related problems the key issue is to be able to perform continuous alkali measurements. This pilot study has investigated the need of continuous alkali measurements, which alkali species are harmful in the different applications and also available instrumentation capable of measuring the specific alkali species. The report gives a short summary presenting alkali related operational problems. In addition a schematic overview is given, showing the alkali species that possibly can exist in various parts of the power plant. 48 refs, 13 figs, 4 tabs

  19. Alkali metal sources for OLED devices

    Science.gov (United States)

    Cattaneo, Lorena; Longoni, Giorgio; Bonucci, Antonio; Tominetti, Stefano

    2005-07-01

    In OLED organic layers electron injection is improved by using alkali metals as cathodes, to lower work function or, as dopants of organic layer at cathode interface. The creation of an alkali metal layer can be accomplished through conventional physical vapor deposition from a heated dispenser. However alkali metals are very reactive and must be handled in inert atmosphere all through the entire process. If a contamination takes place, it reduces the lithium deposition rate and also the lithium total yield in a not controlled way. An innovative alkali metal dispensing technology has been developed to overcome these problems and ensure OLED alkali metal cathode reliability. The alkali Metal dispenser, called Alkamax, will be able to release up to a few grams of alkali metals (in particular Li and Cs) throughout the adoption of a very stable form of the alkali metal. Lithium, for example, can be evaporated "on demand": the evaporation could be stopped and re-activated without losing alkali metal yield because the metal not yet consumed remains in its stable form. A full characterization of dispensing material, dispenser configuration and dispensing process has been carried out in order to optimize the evaporation and deposition dynamics of alkali metals layers. The study has been performed applying also inside developed simulations tools.

  20. Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics

    International Nuclear Information System (INIS)

    Highlights: • Carbonation was performed using CO2, wastewater and bottom ash in a slurry reactor. • A maximum capture capacity of 102 g CO2 per kg BA was achieved at mild conditions. • A maximum carbonation conversion of MSWI-BA was predicted to be 95% by RSM. • The CO2 emission from Bali incinerator could be expected to reduce by 6480 ton/y. • The process energy consumption per ton CO2 captured was estimated to be 180 kW h. - Abstract: Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewater (CRW) was investigated for carbon dioxide (CO2) fixation under different operating conditions, i.e., reaction time, CO2 concentration, liquid-to-solid ratio, particle size, and CO2 flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO2 fixation capacity of 102 g per kg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO2 reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO2 fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion

  1. Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Chang, E-E [Department of Biochemistry, Taipei Medical University, 250 Wu-Hsing Street, Taipei City, Taiwan 110, Taiwan, ROC (China); Pan, Shu-Yuan [Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd., Taipei City, Taiwan 10673, Taiwan, ROC (China); Yang, Liuhanzi [School of Environment, Tsinghua University, Haidin District, Beijing 100084 (China); Chen, Yi-Hung [Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, 1, Sec. 3, Zhongxiao E. Rd., Taipei City, Taiwan 10608, Taiwan, ROC (China); Kim, Hyunook [Department of Energy and Environmental System Engineering, University of Seoul (Korea, Republic of); Chiang, Pen-Chi, E-mail: pcchiang@ntu.edu.tw [Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd., Taipei City, Taiwan 10673, Taiwan, ROC (China)

    2015-09-15

    Highlights: • Carbonation was performed using CO{sub 2}, wastewater and bottom ash in a slurry reactor. • A maximum capture capacity of 102 g CO{sub 2} per kg BA was achieved at mild conditions. • A maximum carbonation conversion of MSWI-BA was predicted to be 95% by RSM. • The CO{sub 2} emission from Bali incinerator could be expected to reduce by 6480 ton/y. • The process energy consumption per ton CO{sub 2} captured was estimated to be 180 kW h. - Abstract: Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewater (CRW) was investigated for carbon dioxide (CO{sub 2}) fixation under different operating conditions, i.e., reaction time, CO{sub 2} concentration, liquid-to-solid ratio, particle size, and CO{sub 2} flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO{sub 2} fixation capacity of 102 g per kg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO{sub 2} reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO{sub 2} fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion.

  2. Carboxyl functionalization of carbon fibers via aryl diazonium reaction in molten urea to enhance interfacial shear strength

    Science.gov (United States)

    Wang, Yuwei; Meng, Linghui; Fan, Liquan; Wu, Guangshun; Ma, Lichun; Zhao, Min; Huang, Yudong

    2016-01-01

    Using molten urea as the solvent, carbon fibers were functionalized with carboxylic acid groups via aryl diazonium reaction in 15 min to improve their interfacial bonding with epoxy resin. The surface functionalization was quantified by X-ray photoelectron spectroscopy, which showed that the relative surface coverage of carboxylic acid groups increased from an initial percentage of 3.17-10.41%. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 66%. Meanwhile, the technique did not adopt any pre-oxidation step to produce functional groups prior to grafting and was shown to maintain the tensile strength of the fibers. This methodology provided a rapid, facile and economically viable route to produce covalently functionalized carbon fibers in large quantities with an eco-friendly method.

  3. Boron Doped Multi-walled Carbon Nanotubes as Catalysts for Oxygen Reduction Reaction and Oxygen Evolution Reactionin in Alkaline Media

    International Nuclear Information System (INIS)

    The boron doped multi-walled carbon nanotubes (B-MWCNTs) were synthesized by thermal annealing multi-walled carbon nanotubes (MWCNTs) in the presence of boric acid. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) results revealed that the structure of MWCNTs does not be destroyed during the doping process, and X-ray photoelectron spectroscopy (XPS) analysis demonstrated the boron atoms were successfully doped in the structure of MWCNTs. The electrocatalytic properties of B-MWCNTs are characterized by rotating disk electrode (RDE) methods. The results demonstrated that the B-MWCNTs catalyzed oxygen reduction reaction (ORR) in alkaline media by a 2 + 2 electron pathway and it showed good catalytic activity for oxygen evolution reaction (OER) as well

  4. Biodegradation of Leonardite by an alkali-producing bacterial community and characterization of the degraded products.

    Science.gov (United States)

    Gao, Tong-Guo; Jiang, Feng; Yang, Jin-Shui; Li, Bao-Zhen; Yuan, Hong-Li

    2012-03-01

    In this study, three bacterial communities were obtained from 12 Leonardite samples with the aim of identifying a clean, effective, and economic technique for the dissolution of Leonardite, a type of low-grade coal, in the production of humic acid (HA). The biodegradation ability and characteristics of the degraded products of the most effective bacterial community (MCSL-2), which degraded 50% of the Leonardite within 21 days, were further investigated. Analyses of elemental composition, (13)C NMR, and Fourier transform infrared revealed that the contents of C, O, and aliphatic carbon were similar in biodegraded humic acid (bHA) and chemically (alkali) extracted humic acid (cHA). However, the N and carboxyl carbon contents of bHA was higher than that of cHA. Furthermore, a positive correlation was identified between the degradation efficiency and the increasing pH of the culture medium, while increases of manganese peroxidase and esterase activities were also observed. These data demonstrated that both alkali production and enzyme reactions were involved in Leonardite solubilization by MCSL-2, although the former mechanism predominated. No fungus was observed by microscopy. Only four bacterial phylotypes were recognized, and Bacillus licheniformis-related bacteria were identified as the main group in MCSL-2 by analysis of amplified 16S rRNA genes, thus demonstrating that Leonardite degradation ability has a limited distribution in bacteria. Hormone-like bioactivities of bHA were also detected. In this study, a bacterial community capable of Leonardite degradation was identified and the products characterized. These data implicate the use of such bacteria for the exploitation of Leonardite as a biofertilizer. PMID:22075634

  5. CO 2 fluid and silicate glass as monitors of alkali basalt/peridotite interaction in the mantle wedge beneath Gobernador Gregores, Southern Patagonia

    Science.gov (United States)

    Scambelluri, M.; Vannucci, R.; De Stefano, A.; Preite-Martinez, M.; Rivalenti, G.

    2009-01-01

    A suite of mantle-wedge amphibole + phlogopite-bearing spinel peridotite xenoliths in Plio-Pleistocene alkali basalts from Southern Patagonia (Gobernador Gregores, Santa Cruz Province, Argentina) contains carbonic fluid inclusions, glass and carbonate in several textural domains. Here we present a microstructural and fluid inclusion study showing that fluid (corresponding to pure CO 2) and glass post-date the hydrous mantle assemblage and formed soon before and/or during xenolith entrainement in the host alkali basalt. The high densities preserved by a number of CO 2 inclusions indicate that fluid infiltration took place at mantle depths. The low densities pertaining to the majority of analyzed fluid inclusions derive from inclusion re-equilibration during xenolith ascent. Glass occurs in reaction haloes around clinopyroxene, amphibole and phlogopite, where it hosts microlites of new pyroxene, olivine and locally carbonate. Glass veins cut the mantle minerals and locally contain primary carbonate. Glasses vary widely in composition depending on the textural domains and attain Si- and alkali-rich compositions (SiO 2 = 47.0-68.3 wt.%; Na 2O + K 2O = 5.8-12.2 wt.%). Incompatible trace element patterns of glasses in anhydrous xenoliths are closely similar to those of the host alkali basalts, whereas the compositions of interstitial and vein glasses in the hydrous xenoliths indicate that a compositional control has been exerted by the local mineral assemblage (mainly amphibole). The δ18O values of carbonate from the glass pockets and veins in the xenoliths, as well as of carbonate globules and amygdales in the host basalts are in the range 19.62 to 21.04‰. Corresponding δ13C values are - 9.25 to - 10.12‰ and - 7.59 to - 9.32‰, respectively. These values are very different from those of primary carbonatites and the δ18O values clearly exceed those expected for minerals and glasses from mantle assemblages. The similarity of isotopic ratios of carbonates from both

  6. Synthesis of graphitic carbon nitride by reaction of melamine and uric acid

    International Nuclear Information System (INIS)

    Highlights: → Graphitic carbon nitrides by CVD of melamine and uric acid on alumina. → The building blocks of carbon nitrides are heptazine nuclei. → Composite particles with alumina core and carbon nitride coating. - Abstract: Graphitic carbon nitrides were synthesized starting from melamine and uric acid. Uric acid was chosen because it thermally decomposes, and reacts with melamine by condensation at temperatures in the range of 400-600 deg. C. The reagents were mixed with alumina and subsequently the samples were treated in an oven under nitrogen flux. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Infrared (IR) spectra, as well as X-ray diffraction (XRD) patterns, are in accordance with the formation of a graphitic carbon nitride with a structure based on heptazine blocks. These carbon nitrides exhibit poor crystallinity and a nanometric texture, as shown by transmission electron microscopy (TEM) analysis. The thermal degradation of the graphitic carbon nitride occurs through cyano group formation, and involves the bridging tertiary nitrogen and the bonded carbon, which belongs to the heptazine ring, causing the ring opening and the consequent network destruction as inferred by connecting the IR and X-ray photoelectron spectroscopy (XPS) results. This seems to be an easy and promising route to synthesize graphitic carbon nitrides. Our final material is a composite made of an alumina core covered by carbon nitride layers.

  7. First-principles study of ternary graphite compounds cointercalated with alkali atoms (Li, Na, and K) and alkylamines towards alkali ion battery applications

    Science.gov (United States)

    Ri, Gum-Chol; Yu, Chol-Jun; Kim, Jin-Song; Hong, Song-Nam; Jong, Un-Gi; Ri, Mun-Hyok

    2016-08-01

    First-principles calculations were carried out to investigate the structural, energetic, and electronic properties of ternary graphite compounds cointercalated with alkali atoms (AM = Li, Na, and K) and normal alkylamine molecules (nCx; x = 1, 2, 3, 4), denoted as AM-nCx-GICs. From the optimization of the orthorhombic unit cells for the crystalline compounds, it was found that, with the increase in the atomic number of alkali atoms, the layer separations decrease in contrast to AM-GICs, while the bond lengths between alkali atoms and graphene layer, and nitrogen atom of alkylamine increase. The calculated formation energies and interlayer binding energies of AM-nC3-GICs indicate that the compounds is increasingly stabilized from Li to K, and the energy barriers for migration of alkali atoms suggest that alkali cation with larger ionic radius diffuses more smoothly in graphite, being similar to AM-GICs. Through the analysis of electronic properties, it was established that more extent of electronic charge is transferred from more electropositive alkali atom to the carbon ring of graphene layer, and the hybridization of valence electron orbitals between alkylamine molecules and graphene layer is occurred.

  8. Protective effect of application of carbon nanoparticles in thyroid cancer surgery and evaluation of inflammatory stress reaction degree

    Institute of Scientific and Technical Information of China (English)

    Qing-Sheng Zheng; Jun-Zheng Li; Wei-Xiong Hong; Jiao-Yuan Xu; Si-Yi Zhang

    2015-01-01

    Objective:To study the protective effect of application of carbon nanoparticles in thyroid cancer surgery and its influence on inflammatory stress reaction degree.Methods:Patients who received thyroid cancer surgery in our hospital from June 2013 to June 2014 were chosen for study and randomly divided into conventional group and nano-carbon group. Then contents of thyroid cancer related malignant molecules, pro-inflammation cytokines and inflammation inhibiting factors in serum were detected.Results:(1) Malignant molecules: compared with conventional group, mRNA levels of Wip1, gal-3, SATB1, LSD1, GDF-15 and TBX2 in serum of nano-carbon group were lower; (2) Inflammation inhibiting factors: compared with conventional group, serum MFG-E8 and Omentin-1 levels of nano-carbon group were higher; (3) Pro-inflammation cytokines: compared with conventional group, serum MIP-1, SGK-1 and β-EP levels of nano-carbon group were lower.Conclusion: Application of carbon nanoparticles in thyroid cancer surgery is helpful to reduce operative damage to thyroid tissue, prevent release of malignant biological molecules into bloodstream and relieve inflammatory response; it’s an ideal surgical method for thyroid cancer.

  9. Hydrogen generation using silicon nanoparticles and their mixtures with alkali metal hydrides

    Science.gov (United States)

    Patki, Gauri Dilip

    Hydrogen is a promising energy carrier, for use in fuel cells, engines, and turbines for transportation or mobile applications. Hydrogen is desirable as an energy carrier, because its oxidation by air releases substantial energy (thermally or electrochemically) and produces only water as a product. In contrast, hydrocarbon energy carriers inevitably produce CO2, contributing to global warming. While CO2 capture may prove feasible in large stationary applications, implementing it in transportation and mobile applications is a daunting challenge. Thus a zero-emission energy carrier like hydrogen is especially needed in these cases. Use of H2 as an energy carrier also brings new challenges such as safe handling of compressed hydrogen and implementation of new transport, storage, and delivery processes and infrastructure. With current storage technologies, hydrogen's energy per volume is very low compared to other automobile fuels. High density storage of compressed hydrogen requires combinations of high pressure and/or low temperature that are not very practical. An alternative for storage is use of solid light weight hydrogenous material systems which have long durability, good adsorption properties and high activity. Substantial research has been conducted on carbon materials like activated carbon, carbon nanofibers, and carbon nanotubes due to their high theoretical hydrogen capacities. However, the theoretical values have not been achieved, and hydrogen uptake capacities in these materials are below 10 wt. %. In this thesis we investigated the use of silicon for hydrogen generation. Hydrogen generation via water oxidation of silicon had been ignored due to slow reaction kinetics. We hypothesized that the hydrogen generation rate could be improved by using high surface area silicon nanoparticles. Our laser-pyrolysis-produced nanoparticles showed surprisingly rapid hydrogen generation and high hydrogen yield, exceeding the theoretical maximum of two moles of H2 per

  10. The Durability and Performance of Short Fibers for a Newly Developed Alkali-Activated Binder

    Directory of Open Access Journals (Sweden)

    Henrik Funke

    2016-03-01

    Full Text Available This study reports the development of a fiber-reinforced alkali-activated binder (FRAAB with an emphasis on the performance and the durability of the fibers in the alkaline alkali-activated binder (AAB-matrix. For the development of the matrix, the reactive components granulated slag and coal fly ash were used, which were alkali-activated with a mixture of sodium hydroxide (2–10 mol/L and an aqueous sodium silicate solution (SiO2/Na2O molar ratio: 2.1 at ambient temperature. For the reinforcement of the matrix integral fibers of alkali-resistant glass (AR-glass, E-glass, basalt, and carbon with a fiber volume content of 0.5% were used. By the integration of these short fibers, the three-point bending tensile strength of the AAB increased strikingly from 4.6 MPa (no fibers up to 5.7 MPa (carbon after one day. As a result of the investigations of the alkali resistance, the AR-glass and the carbon fibers showed the highest durability of all fibers in the FRAAB-matrix. In contrast to that, the weight loss of E-glass and basalt fibers was significant under the alkaline condition. According to these results, only the AR-glass and the carbon fibers reveal sufficient durability in the alkaline AAB-matrix.

  11. Electrocatalytic oxygen evolution reaction at a FeNi composite on a carbon nanofiber matrix in alkaline media

    Institute of Scientific and Technical Information of China (English)

    Xianghua An; Dongyoon Shin; Joey D. Ocon; Jae Kwang Lee; Young-il Son; Jaeyoung Lee

    2014-01-01

    Non-noble metals such as Fe and Ni have comparable electrocatalytic activity and stability to that of Ir and Ru in an oxygen evolution reaction (OER). In this study, we synthesized carbon nanofibers with embedded FeNi composites (FeNi-CNFs) as OER electrocatalysts by a facile route comprising electrospinning and the pyrolysis of a mixture of metal precursors and a polymer solution. FeNi-CNFs demonstrated catalytic activity and stability that were better than that of 20 wt%Ir on Vulcan carbon black in oxidizing water to produce oxygen in an alkaline media. Physicochemical and electrochemical characterization revealed that Fe and Ni had synergistic roles that enhanced OER activity by the uniform formation and widening of pores in the carbon structure, while the CNF matrix also contributed to the increased stability of the catalyst.

  12. Platinum and platinum-ruthenium nanoparticles supported on ordered mesoporous carbon and their electrocatalytic performance for fuel cell reactions

    Energy Technology Data Exchange (ETDEWEB)

    Ding Jie [Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong SAR, Hong Kong (China); Chan, K.-Y. [Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong SAR, Hong Kong (China)]. E-mail: hrsccky@hku.hk; Ren, Jiawen [Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong SAR, Hong Kong (China); Xiao Fengshou [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry and College of Chemistry, Jilin University, Changchun 130023 (China)

    2005-05-20

    Highly ordered meso-porous carbon, denoted CMK-3 was synthesized by using mesoporous silicates, SBA-15 as the starting templating materials. The ordered mesoporous carbon was loaded with platinum and platinum-ruthenium nanoparticles using alternative synthesis techniques. The metal loaded ordered mesoporous carbon powders were characterized by transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, and nitrogen adsorption isotherm experiments. Micrometer-scale and centimeter-scale electrodes containing the mesocarbon/nanometal electrocatalysts were tested for some typical fuel cell reactions. While the nanometal/mesocarbon catalysts have well-defined and uniform properties in the nanometer scale, they have mixed electrocatalytic performance. A synthesized Pt/mesocarbon electrocatalyst outperformed a commercial electrocatalyst for oxygen reduction on a gas-diffusion electrode. The Pt-Ru/mesocarbon electrocatalyst synthesized, however, was not as effective for methanol oxidation.

  13. Platinum and platinum-ruthenium nanoparticles supported on ordered mesoporous carbon and their electrocatalytic performance for fuel cell reactions

    Energy Technology Data Exchange (ETDEWEB)

    Jie Ding; Kwong Yu Chan; Jiawen Ren [Hong Kong Univ. (China). Dept. of Chemistry; Feng Shou Xiao [Jilin Univ., Changchun (China). State Key Lab. of Inorganic Synthesis and Preparative Chemistry

    2005-05-20

    Highly ordered meso-porous carbon, denoted CMK-3 was synthesized by using mesoporous silicates, SBA-15 as the starting templating materials. The ordered mesoporous carbon was loaded with platinum and platinum-ruthenium nanoparticles using alternative synthesis techniques. The metal loaded ordered mesoporous carbon powders were characterized by transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, and nitrogen adsorption isotherm experiments. Micrometer-scale and centimeter-scale electrodes containing the mesocarbon/nanometal electrocatalysts were tested for some typical fuel cell reactions. While the nanometal/mesocarbon catalysts have well-defined and uniform properties in the nanometer scale, they have mixed electrocatalytic performance. A synthesized Pt/mesocarbon electrocatalyst outperformed a commercial electrocatalyst for oxygen reduction on a gas-diffusion electrode. The Pt-Ru/mesocarbon electrocatalyst synthesized, however, was not as effective for methanol oxidation. (Author)

  14. Platinum and platinum-ruthenium nanoparticles supported on ordered mesoporous carbon and their electrocatalytic performance for fuel cell reactions

    International Nuclear Information System (INIS)

    Highly ordered meso-porous carbon, denoted CMK-3 was synthesized by using mesoporous silicates, SBA-15 as the starting templating materials. The ordered mesoporous carbon was loaded with platinum and platinum-ruthenium nanoparticles using alternative synthesis techniques. The metal loaded ordered mesoporous carbon powders were characterized by transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, and nitrogen adsorption isotherm experiments. Micrometer-scale and centimeter-scale electrodes containing the mesocarbon/nanometal electrocatalysts were tested for some typical fuel cell reactions. While the nanometal/mesocarbon catalysts have well-defined and uniform properties in the nanometer scale, they have mixed electrocatalytic performance. A synthesized Pt/mesocarbon electrocatalyst outperformed a commercial electrocatalyst for oxygen reduction on a gas-diffusion electrode. The Pt-Ru/mesocarbon electrocatalyst synthesized, however, was not as effective for methanol oxidation

  15. Oxygen reduction reactions of the thermostable bilirubin oxidase from Bacillus pumilus on mesoporous carbon-cryogel electrodes

    International Nuclear Information System (INIS)

    This study demonstrates the bioelectrocatalytic reactions of a new bilirubin oxidase (BOD) from Bacillus pumilus on a mesoporous carbon cryogel (CCG) electrode, in the presence and absence of a mediator. BOD, physically adsorbed on the mesoporous matrix of a CCG electrode, allowed a direct electron transfer (DET) from the carbon electrode to the type I copper site of the enzyme. The current from the dioxygen reduction reaction (ORR), catalyzed by BOD, depended on the temperature and pH of the electrolyte. The mediated ORR catalyzed by BOD on CCG electrode was also investigated using osmium based redox polymers. The catalytic current on the CCG electrode modified with 0.2 mg cm−2 of hydrogel consisting of an enzyme, a redox polymer and a cross linker, was 1.8 mA cm−2, which was almost five times higher than that on a flat glassy carbon electrode for the same hydrogel composition and loading. The catalytic current linearly increased with the total amount of hydrogel on the porous carbon electrode while the catalytic current on the flat electrode was indifferent to the loading

  16. A new mechanism for radiation damage processes in alkali halides

    Science.gov (United States)

    Dubinko, V. I.; Turkin, A. A.; Vainshtein, D. I.; den Hartog, H. W.

    1999-12-01

    We present a theory of radiation damage formation in alkali halides based on a new mechanism of dislocation climb, which involves the production of VF centers (self-trapped hole neighboring a cation vacancy) as a result of the absorption of H centers of dislocation lines. We consider the evolution of all experimentally observed extended defects: metal colloids, gas bubbles, and vacancy voids. Voids are shown to arise and grow large due to the reaction between F and VF centers at the surface of halogen bubbles. Voids can ignite a back reaction between the radiolytic products resulting in decomposition of the irradiated material.

  17. 气相中碱金属离子与丝氨酸、亮氨酸和赖氨酸五肽复合物的裂解反应%Fragmentation Reactions of Complexes of Alkali Metal Ions with Pentaserine, Pentaleucine and Pentalysine in Gas Phase

    Institute of Scientific and Technical Information of China (English)

    魏王慧; 王青; 储艳秋; 汪日志; 丁传凡

    2014-01-01

    为了探索金属离子对含有不同侧链的多肽气相解离的影响,采用质谱法研究了碱金属离子Li+, Na+, K+, Rb+和Cs+分别与丝氨酸、亮氨酸和赖氨酸五肽(分别简写为S5, L5和K5)形成的复合物的裂解反应.质谱定性结果表明,5种碱金属离子均可以在气相中与丝氨酸、亮氨酸和赖氨酸五肽形成配合比为1:1和2:1的非共价复合物;竞争反应结果表明,随着碱金属离子半径的增加,它们与3种五肽的结合能力逐渐减弱.质谱定量结果表明, K+与丝氨酸、亮氨酸和赖氨酸五肽复合物的结合常数分别为8.94×104,2.83×104和2.50×103 L/mol,表明K+与五肽复合物的结合强度按照丝氨酸、亮氨酸和赖氨酸的顺序依次减小.含不同侧链碱金属离子-五肽复合物的碰撞诱导解离结果表明,复合物的碎裂主要发生在骨架上,丝氨酸五肽复合物最易碎裂,亮氨酸五肽复合物其次,赖氨酸五肽复合物则较难碎裂,且3种复合物的侧链断裂情况也呈现明显差异.此外,研究了Na+与亮氨酸五肽复合物所产生的碎片离子,分析了不同离子之间的来源关系,并以Dunbar的复合物理论模型为依据,推测在碎裂过程中,碱金属离子可能向五肽的碳端或氮端偏移.质谱碎片分析结果表明,在2:1的非共价复合物中,第一个碱金属离子与五肽上4个酰胺键的羰基结合,第二个碱金属离子与五肽的羧基氧原子结合.%For exploring the effects of alkali metal ions on the dissociations of peptides with different side chains in the gas phase, the complexes of Li+, Na+, K+, Rb+ and Cs+ with pentapeptides, Ser-Ser-Ser-Ser-Ser( S5 ) , Leu-Leu-Leu-Leu-Leu ( L5 ) and Lys-Lys-Lys-Lys-Lys ( K5 ) , were chosen to investigate the frag-mentation reaction pathways by mass spectrometry. The experimental results indicated that alkali metal ions and S5, L5, K5 can form 1:1 and 2:1 non-covalent complexes in the gas phase, and the binding

  18. Nitrogen-containing mesoporous carbon cathode for lithium-oxygen batteries: The influence of Nitrogen on oxygen reduction reaction

    International Nuclear Information System (INIS)

    Graphical abstract: The direct effect of nitrogen content and various nitrogen species on oxygen reduction reaction (ORR) activities in nonaqueous Li-O2 batteries are systematically investigated. Mesoporous carbon (MC) with various nitrogen species is prepared through heat treatment of N-containing precursor under different temperature. The effect of the heat treatment temperature on the performance of carbon materials in Li-O2 battery is investigated. The bonding state of nitrogen atoms is found to have a significant effect on the ORR activity. The ORR activity in Li-O2 battery is proved to be dependent on the quaternary N content while the total N content in the carbon material does not play a crucial role in the ORR process. - Highlights: • The role of various N in ORR for Li-O2 battery was investigated. • The total N content does not play an important role in the ORR process. • The ORR activity in Li-O2 battery is dependent on the quaternary N content. - Abstract: The direct effect of nitrogen content and various nitrogen species on oxygen reduction reaction (ORR) activities in non-aqueous lithium-oxygen (Li-O2) batteries are systematically investigated. Mesoporous carbon (MC) with various nitrogen species is prepared through heat treatment of N-containing precursor under different temperature. The effect of the heat treatment temperature on the performance of carbon materials in Li-O2 battery is investigated. The bonding state of nitrogen atoms is found to have a significant effect on the ORR activity. The ORR activity in Li-O2 battery is proved to be dependent on the quaternary N content while the total N content in the carbon material does not play a crucial role in the ORR process

  19. Competition of sulphation and carbonation reactions during looping cycles for CO2 capture by CaO-based sorbents.

    Science.gov (United States)

    Manovic, Vasilije; Anthony, Edward J

    2010-03-25

    Two types of sorbents are investigated here (natural limestone and highly reactive calcium aluminate pellets) to elucidate their reactivity in terms of sulphation and carbonation and determine the resulting effect on looping cycles for CO(2) capture. The sorbents are tested in a thermogravimetric analyzer (TGA) apparatus using typical synthetic flue gas mixtures containing 15% CO(2) and various concentrations of SO(2). The sulphation and carbonation conversions were determined during sulphation/carbonation/calcination cycles. The sorbent morphology and its changes were determined by means of a scanning electron microscope (SEM). The results showed that sulphation, that is, the formation of CaSO(4) at the sorbent surface, is a cumulative process with increasing numbers of reaction cycles, which hinders sorbent ability to capture CO(2). In the case of high sorbent reactivity, as determined by its morphology, the unfavorable effect of sulphation is more pronounced. Unfortunately, any increase in the temperature in the carbonation stage accelerates sulphation more than carbonation as a result of higher activation energy for the sulphation reaction. The SEM analyses showed that although sulphation and carbonation occur during cycles involving calcination, an unreacted core/partially sulphated shell sorbent particle pattern is formed. The main outcomes of this research indicate that special attention should be paid to the sulphation when more reactive and more expensive, synthetic CaO-based sorbents are used for CO(2) capture looping cycles. Desulphurization of flue gas before CO(2) capture appears to be essential because CO(2) looping cycles are so strongly affected by the presence of SO(2). PMID:20050624

  20. Method and composition for testing for the presence of an alkali metal

    International Nuclear Information System (INIS)

    A method and composition for detecting the presence of an alkali metal on the surface of a body such as a metal plate, tank, pipe or the like is provided. The method comprises contacting the surface with a thin film of a liquid composition comprising a light-colored pigment, an acid-base indicator, and a nonionic wetting agent dispersed in a liquid carrier comprising a minor amount of water and a major amount of an organic solvent selected from the group consisting of the lower aliphatic alcohols, ketones and ethers. Any alkali metal present on the surface in elemental form or as an alkali metal hydroxide or alkali metal carbonate will react with the acid-base indicator to produce a contrasting color change in the thin film, which is readily discernible by visual observation or automatic techniques

  1. Performance characterization of rigid polyurethane foam with refined alkali lignin and modified alkali lignin

    Institute of Scientific and Technical Information of China (English)

    LIU Zhi-ming; YU Fei; FANG Gui-zhen; YANG Hui-jun

    2009-01-01

    The two kinds of rigid polyurethane (PU) foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight. The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams. The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples. The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently. Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples. The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.

  2. Alkali- and Sulfur-Resistant Tungsten-Based Catalysts for NOx Emissions Control.

    Science.gov (United States)

    Huang, Zhiwei; Li, Hao; Gao, Jiayi; Gu, Xiao; Zheng, Li; Hu, Pingping; Xin, Ying; Chen, Junxiao; Chen, Yaxin; Zhang, Zhaoliang; Chen, Jianmin; Tang, Xingfu

    2015-12-15

    The development of catalysts with simultaneous resistance to alkalis and sulfur poisoning is of great importance for efficiently controlling NOx emissions using the selective catalytic reduction of NOx with NH3 (SCR), because the conventional V2O5/WO3-TiO2 catalysts often suffer severe deactivation by alkalis. Here, we support V2O5 on a hexagonal WO3 (HWO) to develop a V2O5/HWO catalyst, which has exceptional resistance to alkali and sulfur poisoning in the SCR reactions. A 350 μmol g(-1) K(+) loading and the presence of 1,300 mg m(-3) SO2 do not almost influence the SCR activity of the V2O5/HWO catalyst, and under the same conditions, the conventional V2O5/WO3-TiO2 catalysts completely lost the SCR activity within 4 h. The strong resistance to alkali and sulfur poisoning of the V2O5/HWO catalysts mainly originates from the hexagonal structure of the HWO. The HWO allows the V2O5 to be highly dispersed on the external surfaces for catalyzing the SCR reactions and has the relatively smooth surfaces and the size-suitable tunnels specifically for alkalis' diffusion and trapping. This work provides a useful strategy to develop SCR catalysts with exceptional resistance to alkali and sulfur poisoning for controlling NOx emissions from the stationary source and the mobile source. PMID:26587749

  3. Alkali-activated blast furnace slag-zeolite cements and concretes

    International Nuclear Information System (INIS)

    The aim of this work has been the study of alkali-activated slag-zeolite cements and concretes based on them. Various compositions have been tested and some characteristics such as the compressive strength have been measured versus zeolite additions. A table lists the specific surface area and particle size distributions of different cements. The conclusions of the study are the following. First, alkali-activated slag cements and concretes based on them are effective for immobilization of radioactive wastes and the production of building structures, designed for high radiation load. Secondly, zeolite-containing mineral additions are able to increase the immobilization capacity and radiation resistance of alkali-activated blast furnace slag cements and concretes. Thirdly, the efficiency of different zeolite-containing additions - 10% to increase alkali-activated blast furnace slag-zeolite cement strength was established. It is with alkaline components of water-glass, sodium carbonate, sodium sulphate. Fourth, the effective way of introducing zeolite additions in alkali-activated blast furnace slag-zeolite cement is inter-grinding of the slag and addition. Increase in strength of alkali-activated blast furnace slag-zeolite cement stone is 40% higher than that of the stone of a mixture of separately milled components. Fifth, Alkali-activated blast furnace slag-zeolite cements with zeolite-containing additions with a compressive strength of 10.1 to 140 MPa; alkali-activated blast furnace slag-zeolite cements mortars with compressive strength from 35.2 to 97.7 MPa; alkali-activated blast furnace slag-zeolite cements concretes with compressive strength up to 84.5 MPa and frost resistant up to 800 cycles were obtained

  4. 酸碱腐蚀对聚酰亚胺/碳纤维复合材料摩擦磨损性能的影响%Effects of Friction and Wear Properties of Acid and Alkali Corrosion on the Polyimide/Carbon Fiber Composites

    Institute of Scientific and Technical Information of China (English)

    穆丽柏; 俞娟; 王晓东; 黄培

    2012-01-01

    Abstract :Tribological performances and the infrared spectra of thermoplastic polyimide/carbon fiber composites which were treated at different times with 10% (mass fraction)hydrochloric acid and sodium hydroxide solution were investigated by Fourier transform infrared spectroscopy( ATR) environmental scanning electron microscopy ( SEM ) , friction and wear tester. The results show that the resistance to acid of the composites is better than that to alkaline. The group structure of material surface is changed correspondingly after treated by acid or alkali. The influence of different environments of HC1 solution and NaOH solution on the friction coefficient of material is almost the same, the friction coefficient of the composites is lowered after treated by acid or alkali. The acid treatment has little influence on the wear rate of the composites, while alkali treatment has a greater impact on the wear rate. The corrosive environment accelerates strongly crack growth of the composites. After acid and alkali treatment, the wear mechanism is the synthetic action of abrasive wear and fatigue fracture.%通过傅里叶红外光谱仪(ATR)、环境扫描电镜(SEM)、摩擦磨损试验机,对聚酰亚胺/碳纤维复合材料在质量分数为10%的HCl和NaOH溶液中腐蚀不同时间后的红外光谱及摩擦磨损性能进行实验研究.结果表明:材料的耐酸性明显优于耐碱性;酸碱处理后材料表面的基团结构发生了相应变化;HCl溶液和NaOH溶液腐蚀环境对材料摩擦因数的影响程度基本相同,处理后摩擦因数都降低,酸蚀环境对材料磨损率的影响不大,而碱蚀环境影响较大;腐蚀环境对材料的裂纹扩展有较明显的加速作用,酸碱处理后材料的磨损机制主要是磨粒磨损和疲劳磨损的综合作用.

  5. Mechanistic and kinetic analysis of the oxidative dehydrogenation of ethane via novel supported alkali chloride catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gaertner, C.; Veen, A.C. van; Lercher, J.A. [Technische Universitaet Muenchen (Germany). Catalysis Research Center

    2013-11-01

    The oxidative dehydrogenation of ethane over advanced catalysts is promising to selectively produce ethylene, an essential building block for the chemical industry. In this way, ethane from shale gas can be efficiently valorized. Supported alkali chloride catalysts are investigated in this work. Essential feature of those materials is the presence of a solid core (magnesium oxide in part doped with Dy{sub 2}O{sub 3}) covered under reaction conditions with a molten alkali chloride shell. It is shown that especially the lowered melting point of eutectic mixtures of LiCl with other alkali/alkaline earth metals is the key to taylor highly efficient materials. Elucidating the ODH reaction mechanism is essential to understand the reactivity of this novel catalyst class and provides the basis for improving performances. Information about elementary steps and the rate determining step were extracted from kinetic measurements, both in steady state and in transient configuration. Furthermore, isotopic labelling studies were performed, i.e. SSITKA studies and temperature programmed isotopic exchange experiments. Step experiments showed a significant oxygen uptake by the catalysts. Retained oxygen reacted quantitatively with ethane at nearly 100% selectivity to ethylene and conversion rates were comparable with rates observed during steady state operation. Thus, chemically bound oxygen in the melt is the active and selective intermediate in the ODH. Therefore, it is required to consider an intermediate and the activation is concluded to relate to the oxygen dissociation. The total concentration of stored oxygen can be correlated to the steady-state activity, while the viscosity of the melts mainly influences the selectivity towards ethene. Properties of the solid core impact on the catalyst efficiency suggesting that the oxygen species forms at the interface between support and overlayer. The quantity of retained oxygen additionally depends on the properties of the chloride

  6. Modeling intermediates in carbon monoxide coupling reactions using cyclooctatetraene thorium derivatives

    International Nuclear Information System (INIS)

    The interaction of carbon monoxide with organo-actinides has recently been shown experimentally, particularly by Cloke and co-workers, to result in coupling to give the oligomeric anions CnOn2- (n = 2, 3, 4). In order to model possible intermediates in reactions of this type, we have used density functional theory to explore the systems (C8H8)Th(CO)n (n = 1 to 5) and (C8H8)2Th2(CO)n (n = 2 to 7) related to the known 'thorocene', (η8 -C8H8)2Th. Thorium was chosen as the actinide for this work since its chemistry almost entirely involves the single diamagnetic +4 oxidation state. All of the binuclear (C8H8)2Th2(CO)n structures found in this work have long Th-Th distances ranging from 4.4 to 5.0 Angstroms suggesting the absence of direct Th-Th bonds. Two (C8H8)2Th2(CO)2 isomers of similar energies in which the two CO groups have coupled to form trans and cis isomers of a bridging η4 -μ-C2O2 ligand are low energy structures. These bridging η4-μ-C2O2 ligands exhibit ultralow ν(CO) frequencies around 1000 cm-1 indicating strong back donation of thorium d and f electrons into C-O antibonding orbitals. Most of the carbonyl richer (C8H8)2Th2(CO)n (n = 3 to 7) structures are derived from one of these basic (C8H8)2Th2(CO)2 structures by addition of terminal CO groups. An exception is the lowest energy (C8H8)2Th2(CO)4 structure which has C4v symmetry with four equivalent separate ν2 -μ-CO groups bridging the thorium atoms. The thermochemistry of these systems suggest (C8H8)Th(CO)4 and (C8H8)2Th2(CO)n (n = 2, 4) to be the most promising synthetic objectives, which are potentially obtainable by reductive carbonylation of the known (C8H8)ThCl2. (authors)

  7. Synthesis and Structural Characterization of Alkali Metal Guanidinates

    Institute of Scientific and Technical Information of China (English)

    LUO,Yun-Jie; YAO,Ying-Ming; ZHANG,Yong; SHEN,Qi

    2007-01-01

    Reactions of 1,3-diisopropylcarbodiimide with alkali metal amides,MN(SiMe3)2(M=Li or Na)in hexane or THF produced the alkali metal guanidinates{(j-PrN)2C[N(SiMe3)2]Li}2(1)and{(i-PrN)2C[N(SiMe3)2]Na(THF)}2(2)in nearly quantitative yields.Both complexes 1 and 2 were well characterized by elemental analysis,IR spectra,1H and 13C NMR spectra,and X-ray diffraction.It was found that the guanidinates adopt different coordination modes in these complexes.

  8. Irrelevance of Carbon Monoxide Poisoning in the Methanol Oxidation Reaction on a PtRu Electrocatalyst.

    Science.gov (United States)

    Chen, De-Jun; Tong, YuYe J

    2015-08-01

    Based on detailed in situ attenuated total-reflection-surface-enhanced IR reflection absorption spectroscopy (ATR-SEIRAS) studies of the methanol oxidation reaction (MOR) on Ru/Pt thin film and commercial Johnson-Matthey PtRu/C, a revised MOR enhancement mechanism is proposed in which CO on Pt sites is irrelevant but instead Pt-Ru boundary sites catalyze the oxygen insertion reaction that leads to the formation of formate and enhances the direct reaction pathway. PMID:26148459

  9. Effect of carbon on wettability and interface reaction between melt superalloy and ceramic material

    OpenAIRE

    Chen Xiaoyan; Zhou Yizhou; Jin Tao; Sun Xiaofeng

    2014-01-01

    Effect of C on wettability and interface reaction between a nickel based superalloy and ceramic material was investigated by using a sessile drop method. It was found that the content of C in the alloy is able to influence the wettability and interface reaction. Alloys with C content lower than 0.1wt.% are stable on ceramic material and no interface reaction generates at the alloy-ceramic interface. However, when C content is higher than 0.1wt.%, the interface reaction occurs and the wetting ...

  10. The chemistry of subcritical water reactions of a hardwood derived lignin and lignin model compounds with nitrogen, hydrogen, carbon monoxide and carbon dioxide

    Science.gov (United States)

    Hill Bembenic, Meredith A.

    collected solids from the CO reactions appeared to be the most reacted (i.e., the most changed from the unreacted lignin) according to solid state 13C-NMR analysis, and the widest variety of products (methoxy-substituted phenolic compounds) were obtained when using CO according to GC/MS analysis. Therefore, reactions with CO were completed that varied the initial reaction pressure (300, 500 and 800 psi) in order to elucidate the effects of CO pressure. Similar conversion (≈54--58%) and DCM-soluble liquid product yields (≈53--62%) were obtained for the different pressure reactions, but the reactions with an initial pressure of 500 psi had the greatest change in aromaticity from the unreacted lignin. Additional reactions between Organosolv lignin and H2O with CO (initial pressure of 500 psi) were conducted where the reaction time was varied (15, 30 and 60 min.) to determine the effect of reaction time. Longer reaction time (60 min.) appeared to inhibit conversion to low molecular weight compounds (i.e., conversion and DCM-soluble yields were lower at ≈53% and ≈28%, respectively). Solid state 13C-NMR of collected residues also showed that there are losses in carbons representative of both guaiacyl and syringyl components as reaction time increases, which may indicate that methoxy groups are being cleaved or the products are reacting with each other (i.e., repolymerization) to form high molecular weight compounds as reaction time is increased. The role of H2O and the gases during the baseline reactions and the expanded CO reactions is not intuitive based on the results, so reactions with lignin model compounds (i.e., aromatic aldehydes represented by vanillin and syringaldehyde, aromatic ketones represented by acetovanillone and acetosyringone, and aromatic ethers represented by dibenzyl ether and 2-phenethyl phenyl ether) were completed to study this. From these results, the suggested reaction pathway of Organosolv lignin reactions in subcritical H2O with and without

  11. Highly efficient nonprecious metal catalysts towards oxygen reduction reaction based on three-dimensional porous carbon nanostructures.

    Science.gov (United States)

    Zhu, Chengzhou; Li, He; Fu, Shaofang; Du, Dan; Lin, Yuehe

    2016-02-01

    Developing a low cost, highly active, durable cathode towards an oxygen reduction reaction (ORR) is one of the high-priority research directions for commercialization of low-temperature polymer electrolyte membrane fuel cells (PEMFCs). However, the electrochemical performance of PEMFCs is still hindered by the high cost and insufficient durability of the traditional Pt-based cathode catalysts. Under these circumstances, the search for efficient alternatives to replace Pt for constructing highly efficient nonprecious metal catalysts (NPMCs) has been growing intensively and has received great interest. Combining with the compositional effects, the accurate design of NPMCs with 3D porous nanostructures plays a significant role in further enhancing ORR performance. These 3D porous architectures are able to provide higher specific surface areas and larger pore volumes, not only maximizing the availability of electron transfer within the nanosized electrocatalyst surface area but also providing better mass transport of reactants to the electrocatalyst. In this Tutorial Review, we focus on the rational design and synthesis of different 3D porous carbon-based nanomaterials, such as heteroatom-doped carbon, metal-nitrogen-carbon nanostructures and a series of carbon/nonprecious metal-based hybrids. More importantly, their enhanced ORR performances are also demonstrated by virtue of their favorably porous morphologies and compositional effects. Finally, the future trends and perspectives for the highly efficient porous NPMCs regarding the material design are discussed, with an emphasis on substantial development of advanced carbon-based NPMCs for ORR in the near future. PMID:26658546

  12. Alkali Metal Coolants. Proceedings of the Symposium on Alkali Metal Coolants - Corrosion Studies and System Operating Experience

    International Nuclear Information System (INIS)

    Proceedings of a Symposium organized by the IAEA and held in Vienna, 28 November - 2 December 1966. The meeting was attended by 107 participants from 16 countries and two international organizations. Contents: Review papers (2 papers); Corrosion of steels and metal alloys (6 papers); Mass transfer in alkali metal systems, behaviour of carbon (5 papers); Effects of sodium environment on mechanical properties of materials (3 papers); Effect of water leakage into sodium systems (2 papers); Design-and operation of testing apparatus (6 papers); Control, measurements and removal of impurities (13 papers); Corrosion by other alkali metals: NaK, K, Li, Cs (6 papers); Behaviour of fission products (3 papers). Each paper is in its original language (32 English, 6 French and 8 Russian) and is preceded by an abstract in English and one in the original language if this is not English. Discussions are in English. (author)

  13. Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

    Science.gov (United States)

    Su, Yunhe; Zhu, Yihua; Jiang, Hongliang; Shen, Jianhua; Yang, Xiaoling; Zou, Wenjian; Chen, Jianding; Li, Chunzhong

    2014-11-01

    Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, the Co/N-C composite also shows better bifunctional catalytic activity than its oxidative counterparts, which could be attributed to the high specific surface area and the efficient charge transfer ability of the composite, as well as the good synergistic effect between N-doped carbon and the Co nanoparticles in the Co/N-C composite.Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those

  14. Carbon reaction and diffusion on Ni(111), Ni(100), and Fe(110): Kinetic parameters from x-ray photoelectron spectroscopy and density functional theory analysis

    International Nuclear Information System (INIS)

    This paper investigates the reactivity of elemental carbon films deposited from the vapor phase with Fe and Ni substrates at room temperature. X-ray photoelectron spectroscopy (XPS) measurements are presented as a method for evaluating kinetic reaction data. Carbon films are deposited on different surface orientations representing geometries from a dense atom packing as in fcc (111) to an open surface structure as in fcc (100). During annealing experiments several reactions are observed (carbon subsurface diffusion, carbide formation, carbide decomposition, and graphite ordering). These reactions and the respective kinetic parameters are analyzed and quantified by XPS measurements performed while annealing at elevated temperatures (620-820 K). The resulting activation barriers for carbon subsurface diffusion are compared with calculated values using the density functional theory. The determined kinetic parameters are used to reproduce the thermal behavior of carbon films on nickel surfaces

  15. Flow characteristics and reaction properties of carbon dioxide in microtubules and porous media

    Institute of Scientific and Technical Information of China (English)

    ZHAO RenBao; YUE XiangAn; WU Ya Hong; XU ShaoLiang; WANG Fei; HOU YongLi

    2008-01-01

    Carbon dioxide reacts with porous media while flowing through them enhancing their permeability. Its flow behavior as well as the permeability enhancement effects were studied in synthetic cores, natural cores and microtubes with an inner diameter of 5 μm. The results show that the permeability of H2O-saturated cores (containing carbonate ingredients) was enhanced by increasing the injection volume of a CO2-H2O solution. This enhancement is attributable to carbon dioxide's corrosion, which is justified by SEM scanning. The same phenomenon occurs with a CO2-H2O solution in microtubes, but for a different reason. The gas flow velocity of carbon dioxide in microtubes was approximately 100% aster than that of nitrogen because of the scale and the squeezing effects. Carbon dioxide molecules dissolved in water accelerate the diffusion rate of water molecules within the boundary layer, which in turn diminishes the thickness of the water film and enlarges the effective pore size. This flow behavior facilitates the injection of carbon dioxide into low-permeability reservoirs for oil-displacement and formation energy buildup purposes. This behavior also increases the potential for carbon dioxide channeling or release from the formation.

  16. Transition metal/nitrogen dual-doped mesoporous graphene-like carbon nanosheets for the oxygen reduction and evolution reactions.

    Science.gov (United States)

    Liu, Xiaobo; Amiinu, Ibrahim Saana; Liu, Shaojun; Cheng, Kun; Mu, Shichun

    2016-07-21

    The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been considered as a key step in energy conversion processes. Here, a novel and simple Mg(OH)2 nanocasting method is adopted to fabricate Co and N co-doped porous graphene-like carbon nanosheets (Co@N-PGCS) by using chitosan as both carbon and N sources. The as-obtained Co@N-PGCS shows a mesopore-dominated structure as well as a high specific surface area (1716 cm(2) g(-1)). As a bifunctional electrocatalyst towards both the ORR and OER, it shows favorable ORR performance compared with the commercial Pt/C catalyst with an onset potential of -0.075 V and a half-wave potential of -0.151 V in 0.1 M KOH solutions. Furthermore, it also displays considerable OER properties compared with commercial IrO2. The effective catalytic activity could originate from the introduction of transition metal species and few-layer mesoporous carbon structures. PMID:27341409

  17. Synthesis and infrared spectra of alkaline earth metal carbonates formed by the reaction of metal salts with urea at high temperature

    Indian Academy of Sciences (India)

    S M Teleb; D El-Sayed Nassr; E M Nour

    2004-12-01

    The metal carbonate, MCO3 (M = Ca, Sr and Ba), was synthesized by a novel method of reacting aqueous solution of each of Ca2+, Sr2+ and Ba2+ salts with urea at high temperature, ∼ 80°C. The reaction products were characterized through elemental analysis and infrared spectra. The infrared spectra of the products are the same as those of the corresponding commercially obtained carbonates. A general reaction describing the formation of MCO3 is proposed.

  18. Chemical behaviour of Pu and Am: Hydrolysis reaction in brine solutions, carbonate complexation, α-radiolysis, humate complexation and speciation

    International Nuclear Information System (INIS)

    The chemical behaviour of transuranic elements (Pu and Am) has been investigated in saline solution of different NaCl concentrations in the near neutral pH range. Important reactions considered are hydrolysis, carbonate complexation, redox reaction, alpha-radiolysis, colloid generation and humate complexation. Hydrolysis reactions are studied for Pu(VI) in 3.6 M NaCl and for Am(III) in 0.1 M and 0.6 M NaCl solution, whereas carbonate complexation of Pu(IV) and Am(III) is investigated in HCO3-/CO32- solution of varying pH. Consequences of alpha-radiolysis in NaCl solution are thoroughly analysed as for the Eh change due to Cl- oxidation and the oxidation of Pu(IV) and Am(III). In groundwaters colloid generation of Am(III), particularly pseudocolloids, is characterized and correlated with the concentration of humic substances. Humate complexation under discussion deals mainly with the stabilization of Am(III) in a given groundwater through its colloid generation. (orig.)

  19. Efficient Cycloaddition Reaction of Carbon Dioxide with Epoxide by Rhodamine Based Catalyst Under 1 atm Pressure

    International Nuclear Information System (INIS)

    Rhodamine B (RhB) and rhodamine 6G (Rh6G) were employed as catalysts for the synthesis of cyclic carbonate from carbon dioxide and epoxide. It turned out that the catalytic activity of Rh6G was nearly 29 times higher than that of RhB at 1 atm pressure, 90 .deg. C. Furthermore, the catalytic efficiency of RhB and Rh6G was greatly enhanced with triethylamine as co-catalyst. Under the optimized conditions, the best isolated yield (93%) of cyclic carbonate was achieved without organic solvent and metal component

  20. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution II: Solvent Coordinate-Dependent Reaction Path.

    Science.gov (United States)

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    The protonation of methylamine base CH3NH2 by carbonic acid H2CO3 within a hydrogen (H)-bonded complex in aqueous solution was studied via Car-Parrinello dynamics in the preceding paper (Daschakraborty, S.; Kiefer, P. M.; Miller, Y.; Motro, Y.; Pines, D.; Pines, E.; Hynes, J. T. J. Phys. Chem. B 2016, DOI: 10.1021/acs.jpcb.5b12742 ). Here some important further details of the reaction path are presented, with specific emphasis on the water solvent's role. The overall reaction is barrierless and very rapid, on an ∼100 fs time scale, with the proton transfer (PT) event itself being very sudden (ion pair, stabilizing it by establishment of equilibrium solvation. The solvent water's short time scale ∼120 fs response to the incipient ion pair formation is primarily associated with librational modes and H-bond compression of water molecules around the carboxylate anion and the protonated base. This is consistent with this stabilization involving significant increase in H-bonding of hydration shell waters to the negatively charged carboxylate group oxygens' (especially the former H2CO3 donor oxygen) and the nitrogen of the positively charged protonated base's NH3(+). PMID:26876428

  1. The role of additives in Fischer-Tropsch reactions

    OpenAIRE

    Perdjon-Abel, Michal

    2011-01-01

    The Fischer-Tropsch Synthesis (FTS) is an alternative route to produce liquid fuels from a variety of carbon feedstocks including coal and biomass. Typically iron and cobalt based catalysts have been used for the FTS reaction, in which a mixture of CO and H2 (syn-gas) reacts to form hydrocarbons. Enhanced performance has been reported for iron-based systems doped with alkali metals and chalcogenides. Sulfides are considered a poison for most catalytic processes, but sulfur in the form of sulf...

  2. Velocity Map Imaging Study of Ion-Radical Chemistry: Charge Transfer and Carbon-Carbon Bond Formation in the Reactions of Allyl Radicals with C(.).

    Science.gov (United States)

    Pei, Linsen; Farrar, James M

    2016-08-11

    We present an experimental and computational study of the dynamics of collisions of ground state carbon cations with allyl radicals, C3H5, at a collision energy of 2.2 eV. Charge transfer to produce the allyl cation, C3H5(+), is exoergic by 3.08 eV and proceeds via energy resonance such that the electron transfer occurs without a significant change in nuclear velocities. The products have sufficient energy to undergo the dissociation process C3H5(+) → C3H4(+) + H. Approximately 80% of the reaction products are ascribed to charge transfer, with ∼40% of those products decaying via loss of a hydrogen atom. We also observe products arising from the formation of new carbon-carbon bonds. The experimental velocity space flux distributions for the four-carbon products are symmetric about the centroid of the reactants, providing direct evidence that the products are mediated by formation of a C4H5(+) complex living at least a few rotational periods. The primary four-carbon reaction products are formed by elimination of molecular hydrogen from the C4H5(+) complex. More than 75% of the nascent C4H3(+) products decay by C-H bond cleavage to yield a C4H2(+) species. Quantum chemical calculations at the MP2/6-311+g(d,p) level of theory support the formation of a nonplanar cyclic C4H5(+) adduct that is produced when the p-orbital containing the unpaired electron on C(+) overlaps with the unpaired spin density on the terminal carbon atoms in allyl. Product formation then occurs by 1,2-elimination of molecular hydrogen from the cyclic intermediate to form a planar cyclic C4H3(+) product. The large rearrangement in geometry as the C4H3(+) products are formed is consistent with high vibrational excitation in that product and supports the observation that the majority of those products decay to form the C4H2(+) species. PMID:27434380

  3. Ion exchange reactions in interaction of basic zirconium sulfate with sodium carbonate solution

    International Nuclear Information System (INIS)

    Basic zirconium sulfates, extracted from basic zirconium chloride solution and zirconium disulfate solution, as well as products of their interaction with sodium carbonate solution, which was exposed and not exposed to hydrolysis, were investigated by chemical and NMR spectroscopy methods. It has been established that the process of interaction of the basic zirconium sulfate with sodium carbonate solutions sulfatocarbonatozicrconates and carbonatozirconates of sodium are sequentially formed. In this case carbonate groups, due to different strenght of addition of hydroxogroups in initial basic sulfates, substitute either SOsub(h)sup(2)-)- groups and H2O or SO42--and OH--groups, and sodium ions substitute H3O+-groups. Carbonate groups, if they have substituted sulfato- or hydroxogroup, during hydrolysis of carbonatozirconates are splitted out to a less degree

  4. On the water promoted reaction of titanium isopropoxide with carbon dioxide

    OpenAIRE

    Ghosh, Rajshekhar; Nethaji, Munirathinam; Samuelson, Ashoka G

    2003-01-01

    Insertion of carbon dioxide into titanium isopropoxide takes place only in the presence of trace quantities of water to give an isopropyl carbonato cluster which has been crystallographically characterised.

  5. Transition Metal Catalyzed Reactions for Forming Carbon–Oxygen and Carbon–Carbon Bonds

    DEFF Research Database (Denmark)

    Sølvhøj, Amanda Birgitte

    Dehydrogenative ester formation with a ruthenium NHC complex A new atom-economical methodology for synthesizing esters by the dehydrogenative coupling of primary alcohols was developed. The reaction is catalyzed by the ruthenium N-heterocyclic carbene complex RuCl2(IiPr)(p-cymene). By screening the...... alcohols could be used as substrates, but the yields were generally poor due to decarbonylation of the substrate as a considerable side reaction. Some preliminary mechanistic investigations were performed. The results of these confirmed that the reaction is indeed dehydrogenative with the liberation of two...

  6. Preparation of tantalum carbide films by reaction of electrolytic carbon coating with the tantalum substrate

    OpenAIRE

    Massot, Laurent; Chamelot, Pierre; Taxil, Pierre

    2006-01-01

    This article demonstrates that coatings of tantalum carbide can be obtained by electrodeposition of carbon in molten fluorides on a tantalum substrate as an alternative to the CVD process. The structural characteristics of the carbon deposited by the electrolytic route lead to a high reactivity of this element towards a tantalum cathode to produce tantalum carbide. Mutual reactivity was shown to be enhanced if tantalum plate is replaced by an electrodeposited layer of tantalum, where th...

  7. In vivo MRI biocompatibility evaluation of functionalized carbon fibers in reaction with soft tissues

    OpenAIRE

    Prokić B.B.; Bačić G.; Prokić B.; Kalijadis Ana; Todorović Vera; Puškaš Nela; Vidojević D.; Laušević Mila; Laušević Z.

    2012-01-01

    In modern medicine implants are very important and so is their design and choice of materials. Almost equally important is the choice of imaging technique used to in vivo monitor their fate and biocompatibility. The aim of this study was to evaluate the ability of magnetic resonance imaging (MRI) in monitoring the biocompatibility of two newly designed carbon fibers. We have analyzed the interaction of surface functionalized carbon fibers (basic and acidic)...

  8. Study on the Reaction Mechanism for Carbon Dioxide Reforming of Methane over supported Nickel Catalyst

    Institute of Scientific and Technical Information of China (English)

    Ling QIAN; Zi Feng YAN

    2003-01-01

    The adsorption and dissociation of methane and carbon dioxide for reforming on nickelcatalyst were extensively investigated by TPSR and TPD experiments. It showed that thedecomposition of methane results in the formation of at least three kinds of surface carbon specieson supported nickel catalyst, while CO2 adsorbed on the catalyst weakly and only existed in onekind of adsorption state. Then the mechanism of interaction between the species dissociatedfrom CH4 and CO2 during reforming was proposed.

  9. Characterization of the major reactions during conversion of lignin to carbon fiber

    OpenAIRE

    Hendrik Mainka; Liane Hilfert; Sabine Busse; Frank Edelmann; Edgar Haak; Axel S. Herrmann

    2015-01-01

    Lightweight design is an essential part of the overall Volkswagen strategy for reducing the CO2 emissions. The use of carbon fiber offers an enormous lightweight potential. In comparison to steel enabling a mass reduction of up to 70% in automotive parts without a degradation of the functionalities is possible. Today, the use of carbon fiber is limited in mass series applications of the automotive industry by the cost of the conventional C-fiber precursor polyacrylonitrile (PAN). 50% of the c...

  10. Co/CoO nanoparticles immobilized on Co-N-doped carbon as trifunctional electrocatalysts for oxygen reduction, oxygen evolution and hydrogen evolution reactions.

    Science.gov (United States)

    Zhang, Xian; Liu, Rongrong; Zang, Yipeng; Liu, Guoqiang; Wang, Guozhong; Zhang, Yunxia; Zhang, Haimin; Zhao, Huijun

    2016-05-21

    Co/CoO nanoparticles immobilized on Co-N-doped carbon were successfully developed using shrimp-shell derived N-doped carbon nanodots as precursors by a combined approach of polymerization and pyrolysis, as electrocatalysts exhibiting trifunctional catalytic activities toward oxygen reduction, oxygen evolution and hydrogen evolution reactions and high performance in rechargeable zinc-air batteries. PMID:27056374

  11. Light-particle emission in reactions induced with carbon and oxygen ions

    International Nuclear Information System (INIS)

    Preliminary results are presented from three different experiments in which light particles emitted during the course of heavy-ion-induced reactions have been studied. The common primary motivation for undertaking these studies was to determine the nature and extent of nonequilibrium particle emission. The three experiments involved measurements of energies, angular correlations, and multiplicities of neutrons or alpha particles emitted in coincidence with deeply inelastic products or with evaporation residues produced as follows: neutrons from reactions of 16O with 93Nb at 12.9 MeV/u; alphas produced in the same system; and neutrons produced in 12C reactions with 158Gd and in 13C reactions with 157Gd at about 12.4 MeV/u. 3 figures

  12. A study of the reactions of C+ and O+ with carbon dioxide

    International Nuclear Information System (INIS)

    Crossed ion neutral beam techniques have been employed to investigate the reactions C++CO2→CO++CO, O++CO2→O+CO+2, and O++CO2→ O+2+CO. Cross sections for the first reaction have been obtained in the ion energy range from 0.5--25 eV, while for the second process the range of measurement was 0.5--500 eV. Signals attributed to the third reaction could only be detected at ion energies less than 0.5 eV. Both ion--molecule reactions exhibit an energy dependence which falls off with increasing interaction energy faster than the 1/v dependence often found for such processes. The charge transfer process, which is endothermic by approximately 0.15 eV, is observed to have a finite cross section at the lowest ion energy employed

  13. Evaluation of carbon-supported Pt and Pd nanoparticles for the hydrogen evolution reaction in PEM water electrolysers

    Science.gov (United States)

    Grigoriev, S. A.; Millet, P.; Fateev, V. N.

    Carbon-supported Pt and Pd nanoparticles (CSNs) were synthesized and electrochemically characterized in view of potential application in proton exchange membrane (PEM) water electrolysers. Electroactive metallic nanoparticles were obtained by chemical reduction of precursor salts adsorbed to the surface of Vulcan XC-72 carbon carrier, using ethylene glycol as initial reductant and with final addition of formaldehyde. CSNs were then coated over the surface of electron-conducting working electrodes using an alcoholic solution of perfluorinated polymer. Their electrocatalytic activities with regard to the hydrogen evolution reaction (HER) were measured in sulfuric acid solution using cyclic voltammetry, and in a PEM cell during water electrolysis. Results obtained show that palladium can be advantageously used as an alternative electrocatalyst to platinum for the HER in PEM water electrolysers. Developed electrocatalysts could also be used in PEM fuel cells.

  14. Carbon-coated MoS2 nanosheets as highly efficient electrocatalysts for the hydrogen evolution reaction

    Science.gov (United States)

    Dou, Shuo; Wu, Jianghong; Tao, Li; Shen, Anli; Huo, Jia; Wang, Shuangyin

    2016-01-01

    As a green and highly efficient energy resource, hydrogen (H2) has attracted much attention in recent years. Electrochemical water splitting is an economic process to generate H2. MoS2 is a promising candidate to replace traditional Pt-based electrocatalysts for the hydrogen evolution reaction (HER) under acidic conditions. But low electrical conductivity is one of bottlenecks for the large-scale application of MoS2. In this work, a carbon-coated MoS2 hybrid electrocatalyst was prepared with a chemical vapour deposition (CVD) approach to improve the electrical conductivity of MoS2. In addition to the surface-coating carbon, a small graphene-like layer could also be inserted into the interlayers of MoS2 during the CVD process which resulted in more active sites being exposed in MoS2. Enhanced electrical conductivity and more exposed active sites lead to excellent HER activity.

  15. Nitrogen-modified carbon-based catalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Subramanian, Nalini P.; Li, Xuguang; Nallathambi, Vijayadurda; Kumaraguru, Swaminatha P.; Colon-Mercado, Hector; Wu, Gang; Lee, Jong-Won; Popov, Branko N. [Center for Electrochemical Engineering, Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2009-03-01

    Nitrogen-modified carbon-based catalysts for oxygen reduction were synthesized by modifying carbon black with nitrogen-containing organic precursors. The electrocatalytic properties of catalysts were studied as a function of surface pre-treatments, nitrogen and oxygen concentrations, and heat-treatment temperatures. On the optimum catalyst, the onset potential for oxygen reduction is approximately 0.76 V (NHE) and the amount of hydrogen peroxide produced at 0.5 V (NHE) is approximately 3% under our experimental conditions. The characterization studies indicated that pyridinic and graphitic (quaternary) nitrogens may act as active sites of catalysts for oxygen reduction reaction. In particular, pyridinic nitrogen, which possesses one lone pair of electrons in addition to the one electron donated to the conjugated {pi} bond, facilitates the reductive oxygen adsorption. (author)

  16. In situ catalyzed Boudouard reaction of coal char for solid oxide-based carbon fuel cells with improved performance

    International Nuclear Information System (INIS)

    Highlights: • Industrial coal char was used as a fuel for solid oxide-based carbon fuel cells. • The Boudouard reactivity of coal char is higher than that of a commercial activated carbon. • The mineral matter in coal char has a catalytic effect on the Boudouard reaction. • Added catalysts and the inherent catalysts synergetically improved cell output. - Abstract: The use of industrial coal char as a fuel source for an anode-supported solid oxide-based carbon fuel cell (SO-CFC) with a yttrium-stabilized zirconia electrolyte and La0.8Sr0.2MnO3 cathode was investigated. Both the Boudouard reactivity and electrochemical performance of the coal char samples are higher than those of activated carbon samples under the same conditions. The inherent catalytic activity of the metal species (FemOn, CaO, etc.) in the coal char mineral matter leads to good cell performance, even in the absence of an external catalyst. For example, the peak power density of a cell fueled with pure coal char is 100 mW cm−2 at 850 °C, and that of a cell fueled with coal char impregnated with an FemOn-alkaline metal oxide catalyst is 204 mW cm−2. These results suggest that using coal char as the fuel in SO-CFCs might be an attractive way to utilize abundant coal resources cleanly and efficiently, providing an alternative for future power generation

  17. Reaction Mechanism and Kinetics of Aqueous Solutions of Primary and Secondary Alkanolamines and Carbon Dioxide

    OpenAIRE

    BAVBEK, Olgac; ALPER, Erdoğan

    1999-01-01

    The mechanism and kinetics of the reaction between aqueous solutions of CO2 and the alkanolamines 1-amino-2-propanol, 3-amino-1-propanol,2-methyl aminoethanol and 2-ethyl aminoethanol were investigated using a stopped flow technique. It was found that the reaction orders according to power law kinetics were between 1.1 and 2.0, depending on the alkanolamine and the concentration ranges investigated. This fractional order was therefore considered to be further evidence that carbamate ...

  18. Morphology-Controllable Synthesis of Cobalt Telluride Branched Nanostructures on Carbon Fiber Paper as Electrocatalysts for Hydrogen Evolution Reaction.

    Science.gov (United States)

    Wang, Ke; Ye, Zhiguo; Liu, Chenqi; Xi, Dan; Zhou, Chongjian; Shi, Zhongqi; Xia, Hongyan; Liu, Guiwu; Qiao, Guanjun

    2016-02-10

    Cobalt telluride branched nanostructures on carbon fiber paper (CFP) with two different morphologies were synthesized via solution-based conversion reaction. Both the CoTe2 with nanodendrite and CoTe with nanosheet morphologies on the CoTe2 nanotube (CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs) supported by CFP exhibit high activities toward hydrogen evolution reaction (HER). Particularly, the CoTe NSs/CoTe2 NTs only require an overpotential of 230.0 mV to deliver the current density of 100 mA cm(-2) in acid solution. After cycling for 5000 cycles or 20 h continual electrolysis, only a small performance loss is observed. PMID:26809181

  19. Synthesis of Al4SiC4 powders from kaolin grog, aluminum and carbon black by carbothermal reaction

    International Nuclear Information System (INIS)

    In this paper, the synthesis of Al4SiC4 used as natural oxide materials by carbothermal reduction was investigated in order to explore the synthesis route with low costs. The samples were calcined by using kaolin grog, aluminum and carbon black as raw materials with the selected proportion at the temperature from 1500 to 1800 ° C for 2 hours under flow argon atmosphere. The phase composition of reaction products were determined by X-ray diffraction. The microstructure and elemental composition of different phases were observed and identified by scanning electron microscopy and energy dispersive spectroscopy. The mechanism of reaction processing was discussed. The results show that Al4SiC4 powders composed of hexagonal plate-like particulates with various sizes and the thickness of less than 20 μm are obtained when the temperature reaches 1800 °C

  20. Up-Scaling Geochemical Reaction Rates for Carbon Dioxide (CO2) in Deep Saline Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Lindquist, W Brent

    2009-03-03

    The overall goal of the project was to bridge the gap between our knowledge of small-scale geochemical reaction rates and reaction rates meaningful for modeling transport at core scales. The working hypothesis was that reaction rates, determined from laboratory measurements based upon reactions typically conducted in well mixed batch reactors using pulverized reactive media may be significantly changed in in situ porous media flow due to rock microstructure heterogeneity. Specifically we hypothesized that, generally, reactive mineral surfaces are not uniformly accessible to reactive fluids due to the random deposition of mineral grains and to the variation in flow rates within a pore network. Expected bulk reaction rates would therefore have to be correctly up-scaled to reflect such heterogeneity. The specific objective was to develop a computational tool that integrates existing measurement capabilities with pore-scale network models of fluid flow and reactive transport. The existing measurement capabilities to be integrated consisted of (a) pore space morphology, (b) rock mineralogy, and (c) geochemical reaction rates. The objective was accomplished by: (1) characterizing sedimentary sandstone rock morphology using X-ray computed microtomography, (2) mapping rock mineralogy using back-scattered electron microscopy (BSE), X-ray dispersive spectroscopy (EDX) and CMT, (3) characterizing pore-accessible reactive mineral surface area, and (4) creating network models to model acidic CO{sub 2} saturated brine injection into the sandstone rock samples.

  1. The structure of metallic complexes of polyacetylene with alkali metals

    Science.gov (United States)

    Baughman, R. H.; Murthy, N. S.; Miller, G. G.

    1983-07-01

    The crystal structures of sodium, potassium, rubidium, and cesium doped polyacetylene have been determined using crystal packing and x-ray diffraction analyses. Each of these metallic complexes is tetragonal, with the polyacetylene chains forming a host lattice in which the alkali metal ions are present in channels. Lithium appears to be too small to stabilize the channel structure and an amorphous structure is observed. Predicted unit cell parameters and x-ray diffraction intensities are in agreement with observed values. Similarities with the alkali metal doped graphite suggest that hybridization between carbon pz orbitals and metal s orbitals occurs. Such hybridization is expected to result in a high conductivity component normal to the chain direction. On the other hand, direct overlap between polymer chains appears small, since alkali metal columns separate polymer chains. Compositions calculated for the channel structures (from meridional diffraction spacings, the intensity of equatorial diffraction lines, measured volume expansion, and distances in model complexes) all range from y=0.12 to 0.18 for (CHMy)x, where M is sodium, potassium, rubidium, or cesium.

  2. CARBON DIOXIDE CAPTURE FROM FLUE GAS USING DRY REGENERABLE SORBENTS

    Energy Technology Data Exchange (ETDEWEB)

    David A. Green; Brian S. Turk; Raghubir P. Gupta; William J. McMichael; Douglas P. Harrison; Ya Liang

    2002-04-01

    The objective of this project is to develop a simple, inexpensive process to separate CO{sub 2} as an essentially pure stream from a fossil fuel combustion system using a regenerable, sodium-based sorbent. The sorbents being investigated in this project are primarily alkali carbonates, and particularly sodium carbonate and potassium carbonate, which are converted to bicarbonates, through reaction with carbon dioxide and water vapor. Bicarbonates are regenerated to carbonates when heated, producing a nearly pure CO{sub 2} stream after condensation of water vapor. This quarter, electrobalance tests conducted at LSU indicated that exposure of sorbent to water vapor prior to contact with carbonation gas does not significantly increase the reaction rate. Calcined fine mesh trona has a greater initial carbonation rate than calcined sodium bicarbonate, but appears to be more susceptible to loss of reactivity under severe calcination conditions. The Davison attrition indices for Grade 5 sodium bicarbonate, commercial grade sodium carbonate and extra fine granular potassium carbonate were, as tested, outside of the range suitable for entrained bed reactor testing. Fluidized bed testing at RTI indicated that in the initial stages of reaction potassium carbonate removed 35% of the carbon dioxide in simulated flue gas, and is reactive at higher temperatures than sodium carbonate. Removals declined to 6% when 54% of the capacity of the sorbent was exhausted. Carbonation data from electrobalance testing was correlated using a shrinking core reaction model. The activation energy of the reaction of sodium carbonate with carbon dioxide and water vapor was determined from nonisothermal thermogravimetry.

  3. A prediction model for concrete carbonation based on coupled CO²-H²O-ions transfers and chemical reactions

    OpenAIRE

    Thiery, M.; DANGLA, P; Villain, G.; Platret, G.

    2005-01-01

    It is a recognized fact that steel corrosion reduces the serviceability and safety performance of reinforced concrete. Usually high alkaline conditions in concrete lead to the formation of a passive layer at the steel surface. However the natural diffusion of the atmospheric carbon dioxide (CO²) into the concrete induces a decrease of the pore water pH value after reactions with hydrates such as portlandite Ca(OH)² and calcium silicate hydrates C-S-H. Under low-pH conditions, the passive laye...

  4. A DFT study on the mechanism of palladium-catalyzed divergent reactions of 1,6-enyne carbonates

    Indian Academy of Sciences (India)

    Xing Hui Zhang; Zhi Yuan Geng; Teng Niu; Ke Tai Wang

    2015-03-01

    The reaction mechanisms of palladium-catalyzed divergent reactions of 1,6-enyne carbonates have been investigated using DFT calculations at the B3LYP/6-31G(d,p) (LanL2DZ for Pd) level. Solvent effects on these reactions have been considered by the polarizable continuum model (PCM) for the solvent (DMF). The formation of vinylidenepyridines and vinylidenepyrrolidines were generated through 5-exo-dig cyclization or 6-endo-dig cyclization. Our calculation results suggested the following: (i) The first step of the whole cycle is the rate-determining step, which causes allenic palladium intermediate through two plausible pathways. This intermediate provides the corresponding products and releases the palladium catalyst by a subsequent hydrogen transfer and elimination process. (ii) For the catalyst CH3OPdH, the reaction could occur through two possible pathways, but 5-exo-dig cyclization is favoured over 6-endo-dig cyclization. However, when the hydrogen atom is substituted with a phenyl group, the energy barriers for 5-exo-dig cyclization or 6-endo-dig cyclization become relatively high, 18.0–28.5 kcal/mol. The computational results provide good explanation for the experimental observations.

  5. Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

    OpenAIRE

    Weili Wei; Can Xu; Li Wu; Jiasi Wang; Jinsong Ren; Xiaogang Qu

    2014-01-01

    The non-enzymatic browning, namely Maillard reaction is commonly invoked to account for abiotic chemical transformations of organic matter. Here we report a new reaction pathway via the Maillard reaction to systematically synthesize a series of nitrogen-doped carbon dots (C-dots) with superhigh quantum yield (QY) and tunable multicolor luminescent displayment. The starting materials are glucose and the serial amino acid analogues which allow systemically controlling luminescent and physicoche...

  6. Chemical behaviour of plutonium in natural, aquatic systems: Hydrolysis, carbonate complexation and redox reactions

    International Nuclear Information System (INIS)

    In order to clear up the geochemical behaviour of plutonium and its migration mechanisms in groundwater, hydrolysis, redox behaviour, compound formation in carbonate solutions and colloid formation were examined in groundwater conditions, i.e. at pH values between 5 and 8 and at redox potentials of between -300 and +700 mV. Solubility measurements, spectroscopic processes (UV, VIS, IR spectroscopy and laser induced photoacoustic spectroscopy) and electrochemical processes (cyclic voltammetry, differential pulse polarography) are used as methods of investigation. The hydrolysis constants of Pu IV and Pu VI and the solubility product of Pu (OH)4 were determined and hydrolysis products of divalent and trivalent type are described. From solubility experiments, the stability constants for Pu (IV) carbonate compounds and the solubility product for the carbonate system of stable bodies of Pu (OH)2 CO3 were calculated. Using absorption spectroscopy, the disproportionate kinetics of Pu (V) in carbonate was determined at various pH values. A slow, but continuous, reduction in Pu (VI) was found in carbonate solution, which was derived from radiolytic effects. The speed of this auto-reduction was determined, depending on various experimental parameters. (orig./RB)

  7. The first chiral diene-based metal-organic frameworks for highly enantioselective carbon-carbon bond formation reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sawano, Takahiro; Ji, Pengfei; McIsaac, Alexandra R.; Lin, Zekai; Abney, Carter W.; Lin, Wenbin [UC

    2016-02-01

    We have designed the first chiral diene-based metal–organic framework (MOF), E₂-MOF, and postsynthetically metalated E₂-MOF with Rh(I) complexes to afford highly active and enantioselective single-site solid catalysts for C–C bond formation reactions. Treatment of E₂-MOF with [RhCl(C₂H₄)₂]₂ led to a highly enantioselective catalyst for 1,4-additions of arylboronic acids to α,β-unsaturated ketones, whereas treatment of E₂-MOF with Rh(acac)(C₂H₄)₂ afforded a highly efficient catalyst for the asymmetric 1,2-additions of arylboronic acids to aldimines. Interestingly, E₂-MOF·Rh(acac) showed higher activity and enantioselectivity than the homogeneous control catalyst, likely due to the formation of a true single-site catalyst in the MOF. E₂-MOF·Rh(acac) was also successfully recycled and reused at least seven times without loss of yield and enantioselectivity.

  8. Electrochemical activity and durability of platinum nanoparticles supported on ordered mesoporous carbons for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shou-Heng [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617 (China); Chiang, Chien-Chang; Wu, Min-Tsung; Liu, Shang-Bin [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617 (China); Department of Chemistry, National Taiwan Normal University, Taipei 11677 (China)

    2010-08-15

    A facile procedure for synthesizing platinum nanoparticles (NPs) studded in ordered mesoporous carbons (Pt-OMCs) based on the organic-organic self-assembly (one-pot) approach is reported. These Pt-OMCs, which can be easily fabricated with controllable Pt loading, were found to possess high surface areas, highly accessible and stable active sites and superior electrocatalytic properties pertinent as cathode catalysts for hydrogen-oxygen fuel cells. The enhanced catalytic activity and durability observed for the Pt-OMC electrocatalysts are attributed to the strengthened interactions between the Pt catalyst and the mesoporous carbon that effectively precludes migration and/or agglomeration of Pt NPs on the carbon support. (author)

  9. Laser induced and controlled chemical reaction of carbon monoxide and hydrogen

    Science.gov (United States)

    du Plessis, Anton; Strydom, Christien A.; Uys, Hermann; Botha, Lourens R.

    2011-11-01

    Bimolecular chemical reaction control of gaseous CO and H2 at room temperature and atmospheric pressure, without any catalyst, using shaped femtosecond laser pulses is presented. High intensity laser radiation applied to a reaction cell facilitates non-resonant bond breakage and the formation of a range of ions, which can then react to form new products. Stable reaction products are measured after irradiation of a reaction cell, using time of flight mass spectroscopy. Bond formation of C-O, C-C, and C-H bonds is demonstrated as CO2+, C2H2+, CH+, and CH3+ were observed in the time of flight mass spectrum of the product gas, analyzed after irradiation. The formation of CO2 is shown to be dependent on laser intensity, irradiation time, and on the presence of H2 in the reaction cell. Using negatively chirped laser pulses more C-O bond formation takes place as compared to more C-C bond formation for unchirped pulses.

  10. Effect of carbon on wettability and interface reaction between melt superalloy and ceramic material

    Directory of Open Access Journals (Sweden)

    Chen Xiaoyan

    2014-01-01

    Full Text Available Effect of C on wettability and interface reaction between a nickel based superalloy and ceramic material was investigated by using a sessile drop method. It was found that the content of C in the alloy is able to influence the wettability and interface reaction. Alloys with C content lower than 0.1wt.% are stable on ceramic material and no interface reaction generates at the alloy-ceramic interface. However, when C content is higher than 0.1wt.%, the interface reaction occurs and the wetting angle decreases quickly. The product of interface reaction is discontinuous and composed of 9Al2O3 ⋅Cr2O3. Such result indicates that Cr in the alloy is impossible to react with the ceramic material and form Cr2O3 without the assistance of C. It is suggested that C in the alloy deoxidizes SiO2 in the ceramic material and produces SiO and CO. SiO is unstable and it can release active O atom at the interface. Cr at the interface combines with free O atom and forms Cr2O3. Al2O3 in the ceramic material and Cr2O3 finally forms 9Al2O3 ⋅Cr2O3.

  11. Kinetic isotope effects in the reactions of hydrogen exchange of CH aromatic bonds of benzene, fluorobenzene, and nitrogen-containing heterocycles with alkali metal amide solution in liquid ammonia

    International Nuclear Information System (INIS)

    Kinetic isotope effects during deutero- and tritium exchange of benzene, fluorobenzene, pyridine, N-oxide of pyridine and quinoline with solution of potassium or sodium amide in liquid ammonia were determined experimentally. The character of rate constant change of tritium exchange in benzene, when passing from light-weight to deutero-substituted ammonia, was ascertained. Reasons for reduction in the secondary isotope effect of the solvent in reference to theoretic maximum equal to 2.4, as well as the change in the primary kinetic isotope effect resulting from hydrogen isotopic exchange in CH aromatic bonds, depending on substrates CH-acidity, are discussed. The conclusion on applicability of the Eigen theory for explaining the mechanism of hydrogen isotopic exchange reactions in CH aromatic binds was confirmed

  12. Ab initio molecular dynamics simulation study of successive hydrogenation reactions of carbon monoxide producing methanol

    Science.gov (United States)

    Pham, Thi Nu; Ono, Shota; Ohno, Kaoru

    2016-04-01

    Doing ab initio molecular dynamics simulations, we demonstrate a possibility of hydrogenation of carbon monoxide producing methanol step by step. At first, the hydrogen atom reacts with the carbon monoxide molecule at the excited state forming the formyl radical. Formaldehyde was formed after adding one more hydrogen atom to the system. Finally, absorption of two hydrogen atoms to formaldehyde produces methanol molecule. This study is performed by using the all-electron mixed basis approach based on the time dependent density functional theory within the adiabatic local density approximation for an electronic ground-state configuration and the one-shot GW approximation for an electronic excited state configuration.

  13. Chemical compatibility of structural materials in alkali metals

    International Nuclear Information System (INIS)

    The objectives of this task are to (a) evaluate the chemical compatibility of structural alloys such as V-5 wt.%Cr-5 wt.%Ti alloy and Type 316 stainless steel for application in liquid alkali metals such as lithium and sodium-78 wt.% potassium (NaK) at temperatures in the range that are of interest for International Thermonuclear Experimental Reactor (ITER); (b) evaluate the transfer of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen between structural materials and liquid metals; and (c) evaluate the effects of such transfers on the mechanical and microstructural characteristics of the materials for long-term service in liquid-metal-environments

  14. Chemical compatibility of structural materials in alkali metals

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.; Rink, D.L.; Haglund, R. [Argonne National Lab., Chicago, IL (United States)] [and others

    1995-04-01

    The objectives of this task are to (a) evaluate the chemical compatibility of structural alloys such as V-5 wt.%Cr-5 wt.%Ti alloy and Type 316 stainless steel for application in liquid alkali metals such as lithium and sodium-78 wt.% potassium (NaK) at temperatures in the range that are of interest for International Thermonuclear Experimental Reactor (ITER); (b) evaluate the transfer of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen between structural materials and liquid metals; and (c) evaluate the effects of such transfers on the mechanical and microstructural characteristics of the materials for long-term service in liquid-metal-environments.

  15. RECYCLING PHOSPHORUS SLAG AS A PRECURSOR FOR ALKALI-ACTIVATED BINDER; IMPACT OF TYPE AND DOSAGE OF ACTIVATOR

    OpenAIRE

    Hojjatollah Maghsoodloorad; Hamidreza Khalili Amiri; Allahverdi Ali; Lachemi Mohamed; Hossain Khandaker M. Anwar

    2014-01-01

    The objectives of this study were to investigate the suitability of phosphorus slag as a precursor for alkali-activated binder by studying the effects of type and dosage of alkaline activators on compressive strength and efflorescence formation of the material. Different alkaline activators including; potassium hydroxide, sodium hydroxide, sodium carbonate, calcium hydroxide, and their combinations with liquid sodium silicate were used. Different levels of total alkali content (1, 3,...

  16. Synthesis of Polyaniline (PANI) in Nano-Reaction Field of Cellulose Nanofiber (CNF), and Carbonization

    OpenAIRE

    Yuki Kaitsuka; Noriko Hayashi; Tomoko Shimokawa; Eiji Togawa; Hiromasa Goto

    2016-01-01

    Polymerization of aniline in the presence of cellulose nano-fiber (CNF) is carried out. We used dried CNF, CNF suspension, and CNF treated by enzyme and ultra-sonification to obtain polyaniline (PANI)/CNF as a synthetic polymer/natural nano-polymer composite. The polymerization proceeds on the surface of CNF as a nano-reaction field. Resultant composites show extended effective π-conjugation length because CNF as a reaction field in molecular level produced polymer with expanded coil structur...

  17. Supercritical carbon dioxide as an innovative reaction medium for selective oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Loeker, F.; Leitner, W. [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

    1998-12-31

    Although the catalytic efficiency of all catalytic oxidation processes studied in scCO{sub 2} up to now is far from being satisfactory, the principle possibility to carry out such reactions in this medium is clearly evident. Future research in our group will be directed towards the development of homogeneous and heterogeneous catalysts that are adopted to the special requirements of both the oxidation process and the supercritical reaction medium. Preliminary results from these studies regarding the epoxidation of olefins with molecular oxygen as oxidant will be presented on the conference poster. (orig.)

  18. Nitrogen and Sulfur Co-doped Mesoporous Carbon Materials as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction

    International Nuclear Information System (INIS)

    Nitrogen and sulfur co-doped mesoporous carbon materials are synthesized by pyrolyzing FeSO4 + poly(ethyleneimine) + template SiO2 mixture at a high temperature without additional dopant precursors. For post-treatment, acid leaching is used to remove the metal, and the heat-treatment is tailored to optimize the catalytic activity of the catalysts toward the oxygen reduction reaction (ORR) in acidic solution. Scanning electron microscopy, X-ray diffraction, low-temperature N2 adsorption, X-ray photoelectron spectroscopy and inductively coupled plasma are used to characterize the catalysts' morphologies, structures, and compositions. Rotating disk electrode and rotating ring-disk electrode techniques are employed to quantitatively obtain the ORR kinetic constants and determine the reaction mechanisms. The ORR activity is highly improved by reheating the catalyst after H2SO4 leaching with improved half-wave potential of 0.68 V vs. RHE, and ORR electron number larger than 3.76. Moreover, increasing the catalyst loading of 800 μg cm−2 exhibits only ∼36 mV deviation from Pt/C. It is believed that the synergetic effect between the Fe-, N- and S-containing active sites and the modified carbon matrix structure due to H2SO4 leaching and reheating should make contribution to the high ORR activity

  19. Recent Advances in Carbon Supported Metal Nanoparticles Preparation for Oxygen Reduction Reaction in Low Temperature Fuel Cells

    Directory of Open Access Journals (Sweden)

    Yaovi Holade

    2015-03-01

    Full Text Available The oxygen reduction reaction (ORR is the oldest studied and most challenging of the electrochemical reactions. Due to its sluggish kinetics, ORR became the major contemporary technological hurdle for electrochemists, as it hampers the commercialization of fuel cell (FC technologies. Downsizing the metal particles to nanoscale introduces unexpected fundamental modifications compared to the corresponding bulk state. To address these fundamental issues, various synthetic routes have been developed in order to provide more versatile carbon-supported low platinum catalysts. Consequently, the approach of using nanocatalysts may overcome the drawbacks encountered in massive materials for energy conversion. This review paper aims at summarizing the recent important advances in carbon-supported metal nanoparticles preparation from colloidal methods (microemulsion, polyol, impregnation, Bromide Anion Exchange… as cathode material in low temperature FCs. Special attention is devoted to the correlation of the structure of the nanoparticles and their catalytic properties. The influence of the synthesis method on the electrochemical properties of the resulting catalysts is also discussed. Emphasis on analyzing data from theoretical models to address the intrinsic and specific electrocatalytic properties, depending on the synthetic method, is incorporated throughout. The synthesis process-nanomaterials structure-catalytic activity relationships highlighted herein, provide ample new rational, convenient and straightforward strategies and guidelines toward more effective nanomaterials design for energy conversion.

  20. Surface-oxidized carbon black as a catalyst for the water oxidation and alcohol oxidation reactions.

    Science.gov (United States)

    Suryanto, Bryan H R; Zhao, Chuan

    2016-05-11

    Carbon black (CB) is popularly used as a catalyst support for metal/metal oxide nanoparticles due to its large surface area, excellent conductivity and stability. Herein, we show that surface oxidized CB itself, after acidic treatment and electrochemical oxidation, exhibits significant catalytic activity for the electrochemical oxidation of water and alcohols. PMID:27097802

  1. Influence of surface passivation and water content on mineral reactions in unsaturated porous media: Implications for brucite carbonation and CO2 sequestration

    Science.gov (United States)

    Harrison, Anna L.; Dipple, Gregory M.; Power, Ian M.; Mayer, K. Ulrich

    2015-01-01

    The evolution of mineral reactive surface area is an important control on the progress of carbon mineralization reactions that sequester anthropogenic CO2. Dry conditions in unsaturated porous media and the passivation of reactive surface area by secondary phase precipitation complicate predictions of reactive surface during carbon mineralization reactions. Unsaturated brucite [Mg(OH)2] bearing column experiments were used to evaluate the effects of water saturation and hydrous Mg-carbonate precipitation on reaction of brucite with 10% CO2 gas streams at ambient conditions. We demonstrate that a lack of available water severely limits reaction progress largely due to the requirement of water as a reactant to form hydrated Mg-carbonates. The precipitation of a poorly crystalline carbonate phase in the early stages of the reaction does not significantly hinder brucite dissolution, as the carbonate coating remains sufficiently permeable. It is postulated that the conversion of this phase to substantially less porous, crystalline nesquehonite [MgCO3·3H2O] results in passivation of the brucite surface. Although a mechanistic model describing the passivating effect of nesquehonite remains elusive, reactive transport modeling using MIN3P-DUSTY confirms that conventional geometric surface area update models do not adequately reproduce observed reaction progress during brucite carbonation, while an empirically based model accounting for surface passivation is able to capture the transient evolution of CO2 uptake. Both water limits and surface passivation effects may limit the efficiency of CO2 sequestration efforts that rely on the conversion of mafic and ultramafic rock to carbonate minerals.

  2. A new mechanism for radiation damage processes in alkali halides

    OpenAIRE

    Dubinko, V. I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den

    1999-01-01

    We present a theory of radiation damage formation in alkali halides based on a new mechanism of dislocation climb, which involves the production of VF centers (self-trapped hole neighboring a cation vacancy) as a result of the absorption of H centers of dislocation lines. We consider the evolution of all experimentally observed extended defects: metal colloids, gas bubbles, and vacancy voids. Voids are shown to arise and grow large due to the reaction between F and VF centers at the surface o...

  3. The Development and Application of Two-Chamber Reactors and Carbon Monoxide Precursors for Safe Carbonylation Reactions.

    Science.gov (United States)

    Friis, Stig D; Lindhardt, Anders T; Skrydstrup, Troels

    2016-04-19

    Low molecular weight gases (e.g., carbon monoxide, hydrogen, and ethylene) represent vital building blocks for the construction of a wide array of organic molecules. Whereas experimental organic chemists routinely handle solid and liquid reagents, the same is not the case for gaseous reagents. Synthetic transformations employing such reagents are commonly conducted under pressure in autoclaves or under atmospheric pressure with a balloon setup, which necessitates either specialized equipment or potentially hazardous and nonrecommended installations. Other safety concerns associated with gaseous reagents may include their toxicity and flammability and, with certain gases, their inability to be detected by human senses. Despite these significant drawbacks, industrial processes apply gaseous building blocks regularly due to their low cost and ready availability but nevertheless under a strictly controlled manner. Carbon monoxide (CO) fits with all the parameters for being a gas of immense industrial importance but with severe handling restrictions due to its inherent toxicity and flammability. In academia, as well as research and development laboratories, CO is often avoided because of these safety issues, which is a limitation for the development of new carbonylation reactions. With our desire to address the handling of CO in a laboratory setting, we designed and developed a two-chamber reactor (COware) for the controlled delivery and utilization of stoichiometric amounts of CO for Pd-catalyzed carbonylation reactions. In addition to COware, two stable and solid CO-releasing molecules (COgen and SilaCOgen) were developed, both of which release CO upon activation by either Pd catalysis or fluoride addition, respectively. The unique combination of COware with either COgen or SilaCOgen provides a simple reactor setup enabling synthetic chemists to easily perform safe carbonylation chemistry without the need for directly handling the gaseous reagent. With this technology

  4. Investigation of the red mud catalytic activity in carbon monoxide reaction decomposition

    OpenAIRE

    Кириченко, Алексей Геннадьевич; Колесник, Дмитрий Николаевич

    2011-01-01

    The process of iron carburization using СО-contaning gas as a catalyst red mud is investigated. Determined the catalytic activity of red mud in the decomposition reaction of CO. The effect of red mud addition to iron ore materials to improve their recoverability and carburization

  5. Reaction dynamics of {sup 34-38}Mg projectile with carbon target using Glauber model

    Energy Technology Data Exchange (ETDEWEB)

    Shama, Mahesh K., E-mail: maheshphy82@gmail.com [School of Physics and Material Sciences, Thapar University Patiala-147004 (India); Department of Applied Sciences, Chandigarh Engineering College, Landran Mohali-140307 (India); Panda, R. N. [Department of Physics, ITER, Shiksha O Anusandhan University, Bhubaneswar-751030 (India); Sharma, Manoj K. [School of Physics and Material Sciences, Thapar University Patiala-147004 (India); Patra, S. K. [Institute of Physics, Sachivalaya marg Bhubneswar-751005 (India)

    2015-08-28

    We have studied nuclear reaction cross-sections for {sup 34-38}Mg isotopes as projectile with {sup 12}C target at projectile energy 240AMeV using Glauber model with the conjunction of densities from relativistic mean filed formalism. We found good agreement with the available experimental data. The halo status of {sup 37}Mg is also investigated.

  6. Modular, Catalytic Enantioselective Construction of Quaternary Carbon Stereocenters by Sequential Cross-Coupling Reactions.

    Science.gov (United States)

    Potter, Bowman; Edelstein, Emma K; Morken, James P

    2016-07-01

    The catalytic Suzuki-Miyaura cross-coupling with chiral γ,γ-disubstituted allylboronates in the presence of RuPhos ligand occurs with high regioselectivity and enantiospecificity, furnishing nonracemic compounds with quaternary centers. Mechanistic experiments suggest that the reaction occurs by transmetalation with allyl migration, followed by rapid reductive elimination. PMID:27310927

  7. Sustainable Ways of Combining Reactions and Separations Using Ionic Liquids and Carbon Dioxide

    NARCIS (Netherlands)

    Kazemi, S.

    2013-01-01

    Traditional chemical processes show shortcomings caused by using volatile organic compounds as solvents during reactions and separations. Therefore, it is necessary to address this issue by moving toward more environmentally friendly processes. This is possible by using less toxic and hazardous solv

  8. Reaction dynamics of 34-38Mg projectile with carbon target using Glauber model

    International Nuclear Information System (INIS)

    We have studied nuclear reaction cross-sections for 34-38Mg isotopes as projectile with 12C target at projectile energy 240AMeV using Glauber model with the conjunction of densities from relativistic mean filed formalism. We found good agreement with the available experimental data. The halo status of 37Mg is also investigated

  9. Microstructure and Engineering Properties of Alkali Activated Fly Ash -as an environment friendly alternative to Portland cement

    OpenAIRE

    Ma, Y.

    2013-01-01

    Alkali activated fly ash (AAFA), also named “geopolymer”, has emerged as a novel engineering material in the construction industry. This material is normally formed by the reaction between fly ash and aqueous hydroxide or alkali silicate solution. With proper mix design, AAFA can present comparable or superior engineering properties to Portland cement. Moreover, this material shows great potential for sustainable development since its production has a significantly lower CO2 emission than the...

  10. Advancements in flowing diode pumped alkali lasers

    Science.gov (United States)

    Pitz, Greg A.; Stalnaker, Donald M.; Guild, Eric M.; Oliker, Benjamin Q.; Moran, Paul J.; Townsend, Steven W.; Hostutler, David A.

    2016-03-01

    Multiple variants of the Diode Pumped Alkali Laser (DPAL) have recently been demonstrated at the Air Force Research Laboratory (AFRL). Highlights of this ongoing research effort include: a) a 571W rubidium (Rb) based Master Oscillator Power Amplifier (MOPA) with a gain (2α) of 0.48 cm-1, b) a rubidium-cesium (Cs) Multi-Alkali Multi-Line (MAML) laser that simultaneously lases at both 795 nm and 895 nm, and c) a 1.5 kW resonantly pumped potassium (K) DPAL with a slope efficiency of 50%. The common factor among these experiments is the use of a flowing alkali test bed.

  11. Synthesis of a highly active carbon-supported Ir-V/C catalyst for the hydrogen oxidation reaction in PEMFC

    Energy Technology Data Exchange (ETDEWEB)

    Li, B.; Qiao, J.; Yang, D.; Lv, H.; Zheng, J.; Ma, J. [Tongji Univ., Shanghai (China). School of Automotive Studies, Clean Energy Automotive Engineering Center; Zhang, J.; Wang, H. [National Research Council, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2009-07-01

    Non-platinum catalysts are interesting candidates for use in fuel cell systems, particularly for long-term consideration. Iridium-based catalysts such as IrSn, IrOx and IrCo have very good corrosion resistance, electrical conductivity, and resistance to carbon monoxide poisoning. They also have platinum-like behaviour for the chemisorptions of hydrogen and oxygen. The Ir-based catalysts are also less expensive than platinum. In this study, carbon-supported Ir and Ir-V nanoclusters were synthesized via an ethylene glycol (EG) method using IrCl3 and NH4 VO3 as the Ir and V precursors. The nanoparticle catalysts were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscope (TEM). These carbon-supported catalysts had better characteristic for hydrogen oxidation reaction. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were used to characterize the electrochemical properties of fuel cells by applying Ir/C and Ir-V/C as anode catalysts. According to the discharge characteristics of the fuel cell, the Ir/C and Ir-V/C catalysts affected the performance of electrocatalysts considerably. In this experiment, the catalyst Ir-V/C at 40 wt per cent exhibited the best catalytic activity to hydrogen oxidation reaction. A cell performance of 20 wt per cent higher than that for commercially available Pt/C catalysts was achieved. In addition, there was no significant deterioration in performance of the fuel cell following a 100 hour fuel cell life test at a constant current density of 1000 mA/cm{sup 2} in H{sub 2}/O{sub 2} conditions. 3 refs., 2 figs.

  12. Active Sites Implanted Carbon Cages in Core-Shell Architecture: Highly Active and Durable Electrocatalyst for Hydrogen Evolution Reaction.

    Science.gov (United States)

    Zhang, Huabin; Ma, Zuju; Duan, Jingjing; Liu, Huimin; Liu, Guigao; Wang, Tao; Chang, Kun; Li, Mu; Shi, Li; Meng, Xianguang; Wu, Kechen; Ye, Jinhua

    2016-01-26

    Low efficiency and poor stability are two major challenges we encounter in the exploration of non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) in both acidic and alkaline environment. Herein, the hybrid of cobalt encapsulated by N, B codoped ultrathin carbon cages (Co@BCN) is first introduced as a highly active and durable nonprecious metal electrocatalysts for HER, which is constructed by a bottom-up approach using metal organic frameworks (MOFs) as precursor and self-sacrificing template. The optimized catalyst exhibited remarkable electrocatalytic performance for hydrogen production from both both acidic and alkaline media. Stability investigation reveals the overcoating of carbon cages can effectively avoid the corrosion and oxidation of the catalyst under extreme acidic and alkaline environment. Electrochemical active surface area (EASA) evaluation and density functional theory (DFT) calculations revealed that the synergetic effect between the encapsulated cobalt nanoparticle and the N, B codoped carbon shell played the fundamental role in the superior HER catalytic performance. PMID:26649629

  13. Light charged-particle production in 96 MeV neutron-induced reactions on carbon and oxygen

    International Nuclear Information System (INIS)

    In recent years, an increasing number of applications involving fast neutrons have been developed or are under consideration, e.g. radiation treatment of cancer, neutron dosimetry at commercial aircraft altitudes, soft-error effects in computer memories, accelerator-driven transmutation of nuclear waste and energy production and determination of the response of neutron detectors. Data on light-ion production in light nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron beams, and for dosimetry of high-energy neutrons produced by high-energy cosmic radiation interacting with nuclei (nitrogen and oxygen) in the atmosphere. When studying neutron dose effects, it is especially important to consider carbon and oxygen, since they are, by weight, the most abundant elements in human tissue. Preliminary experimental double-differential cross sections of inclusive light-ion (p, d, t, 3He and α) production in carbon induced by 96-MeV neutrons have been presented. Energy spectra were measured at eight laboratory angles: 20, 40, 60, 80, 100, 120, 140 and 160 deg.. Measurements were performed at The Svedberg Laboratory (TSL), Uppsala, using the dedicated MEDLEY experimental setup. The authors have earlier reported experimental double-differential cross sections of inclusive light-ion production in oxygen. In this paper, the deduced kerma coefficients for oxygen has been presented and compared with reaction model calculations. (authors)

  14. Enhanced catalysis of the electrochemical hydrogen evolution reaction using composites of molybdenum-based compounds, gold nanoparticles and carbon.

    Science.gov (United States)

    Joshi, Ubisha; Lee, Jing; Giordano, Cristina; Malkhandi, Souradip; Yeo, Boon Siang

    2016-08-21

    Molybdenum nitride has been recently reported to interact synergistically with gold to show an enhanced activity for the electrochemical hydrogen evolution reaction (2H(+) + 2e(-)→ H2, HER). In this work, we elucidated the roles of nitrogen, carbon, molybdenum and gold on this observed phenomenon. Composites of Mo-based compounds, carbon black (black pearl 2000) and/or Au nanoparticles (AuNP) were prepared, and their activities for the HER in a 0.5 M H2SO4 electrolyte were measured using linear sweep voltammetry. We show and discuss here for the first time that, while the presence of carbon is necessary for the synergy phenomenon, the nitrogen atoms present in the compounds play no apparent role in this synergy. In fact, all the compounds containing Mo, namely Mo2N, MoB and metallic Mo(0), exhibited extensive synergy with Au for the HER. A hypothesis for the enhanced catalysis of H2 evolution by the mixed metal composites is proposed and discussed. PMID:27424516

  15. Effect of reaction environments on the reactivity of PCB (2-chlorobiphenyl) over activated carbon impregnated with palladized iron

    International Nuclear Information System (INIS)

    Reactive activated carbon (RAC) impregnated with palladized iron nanoparticles has been developed to treat polychlorinated biphenyls (PCBs). In this study, we evaluated the effects of various reaction environments on the adsorption-mediated dechlorination of 2-chlorobiphenyl (2-ClBP) in the RAC system. The results were discussed in close connection to the implementation issue of the RAC system for the remediation of contaminated sites with PCBs. Adsorption event of 2-ClBP onto RAC limited the overall performance under condition with a 2-ClBP/RAC mass ratio of less than 1.0 x 10-4 above which dechlorination of 2-ClBP adsorbed to RAC was the reaction rate-determining step. Acidic and basic conditions were harmful to 2-ClBP adsorption and iron stability while neutral pH showed the highest adsorption-promoted dechlorination of 2-ClBP and negligible metal leaching. Coexisting natural organic matter (NOM) slightly inhibited 2-ClBP adsorption onto RAC due to the partial partitioning of 2-ClBP into NOM in the liquid phase while the 2-ClBP absorbed into NOM, which also tended to adsorb onto RAC, was less available for the dechlorination reaction. Common anions slowed down 2-ClBP adsorption but adsorbed 2-ClBP was almost simultaneously dechlorinated. Some exceptions included strong inhibitory effect of carbonate species on 2-ClBP adsorption and severe detrimental effect of sulfite on 2-ClBP dechlorination. Results on treatment of 2-ClBP spiked to actual sediment supernatants implied site-specific reactivity of RAC.

  16. Preparation of carbon nitride fine powder by laser induced gas-phase reactions

    Science.gov (United States)

    Alexandrescu, R.; Huisken, F.; Pugna, G.; Crunteanu, A.; Petcu, S.; Cojocaru, S.; Cireasa, R.; Morjan, I.

    We present the possibility of carbon nitride fine powder synthesis by sensitized laser pyrolysis of acethylene/nitrous oxide/ammonia mixtures. The powders were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and IR transmission measurements. It was found that nitrogen was incorporated in powders and that in the carbon-nitrogen phases formed, the presence of the triple bonded C≡N was not detected. The majority of X-ray diffraction data suggests the presence of a mixture of the predicted α- and β-C3N4 structure, with an α-C3N4-like form being prevalent. The powders were found to be slightly contaminated by SF6 sensitizer products. Our results suggest that by improving the experimental parameters this contamination might be reduced and that the laser pyrolysis method offers possibilities for production of CxNy materials, with controlled composition.

  17. Reinforcement Effect of Alkali Hydrolyzed Wheat Gluten and Starch in Carboxylated Styrene-Butadiene Composites

    Science.gov (United States)

    Wheat gluten (WG) and wheat starch (WS) are the protein and carbohydrate obtained from wheat flours. Wheat gluten is not water soluble or dispersible due to its hydrophobic nature. To prepare wheat gluten dispersions, an alkali hydrolysis reaction was carried out to produce a stable aqueous disper...

  18. The role of residual cracks on alkali silica reactivity of recycled glass aggregates

    DEFF Research Database (Denmark)

    Maraghechi, Hamed; Shafaatian, Seyed-Mohammad-Hadi; Fischer, Gregor;

    2012-01-01

    Despite its environmental and economical advantages, crushed recycled glass has limited application as concrete aggregates due to its deleterious alkali-silica reaction. To offer feasible mitigation strategies, the mechanism of ASR should be well understood. Recent research showed that unlike some...... percentages of reactive microcracks which may explain why ASR expansions are lowered by reducing the size of glass aggregates....

  19. Porous Carbon-Supported Gold Nanoparticles for Oxygen Reduction Reaction: Effects of Nanoparticle Size.

    Science.gov (United States)

    Wang, Likai; Tang, Zhenghua; Yan, Wei; Yang, Hongyu; Wang, Qiannan; Chen, Shaowei

    2016-08-17

    Porous carbon-supported gold nanoparticles of varied sizes were prepared using thiolate-capped molecular Au25, Au38, and Au144 nanoclusters as precursors. The organic capping ligands were removed by pyrolysis at controlled temperatures, resulting in good dispersion of gold nanoparticles within the porous carbons, although the nanoparticle sizes were somewhat larger than those of the respective nanocluster precursors. The resulting nanocomposites displayed apparent activity in the electroreduction of oxygen in alkaline solutions, which increased with decreasing nanoparticle dimensions. Among the series of samples tested, the nanocomposite prepared with Au25 nanoclusters displayed the best activity, as manifested by the positive onset potential at +0.95 V vs RHE, remarkable sustainable stability, and high numbers of electron transfer at (3.60-3.92) at potentials from +0.50 to +0.80 V. The performance is comparable to that of commercial 20 wt % Pt/C. The results demonstrated the unique feasibility of porous carbon-supported gold nanoparticles as high-efficiency ORR catalysts. PMID:27454707

  20. Backward emitted high-energy neutrons in hard reactions of p and pi^+ on carbon

    OpenAIRE

    Malki, A.; Alster, J.; Asryan, G.; Barton, D; Baturin, V.; Buchkojarova, N.; Carroll, A.; Chtchetkovski, A.; Heppelmann, S.; Kawabata, T.; Leksanov, A.; Makdisi, Y.; Minina, E.; Navon, I.; Nicholson, H.

    2000-01-01

    Beams of protons and pions of 5.9 GeV/c were incident on a C target. Neutrons emitted into the back hemisphere, in the laboratory system, were detected in (triple) coincidence with two emerging $p_t>$0.6 GeV/c particles. We present the momentum spectra of the backward going neutrons, which have the same universal shape observed in earlier (inclusive) reactions induced by hadrons, $\\gamma$, $\

  1. Irradiation effect on the reaction of mixture of carbon monoxide and hydrogen, (3)

    International Nuclear Information System (INIS)

    A series of our studies on radiation chemical reaction of CO and H2 mixture indicated that several organic compounds were produced by electron beam irradiation and the amounts of the products increased with increasing pressure and also increased when the irradiation was carried out under circulation. The present study was carried out in an attempt to investigate whether the amounts of the products increase when the mixture is irradiated under circulation at elevated pressure. For this purpose, a reaction apparatus, which can irradiated the mixture up to 10,000 Torr under circulation, was built and the experiments were carried out on the amounts of products as functions of pressure, irradiation time, gas composition, temperature and dose rate. G values of most compounds were found to increased with increasing pressure under circulation. Among the products, the reaction conditions giving high yield of acetaldehyde were studied in detail, since this compound is considered to be one of the most important intermediate compounds in C1 chemistry. The maximum G value of acetaldehyde was 2.9 which was obtained at 8,000 Torr, 55 CO mol%, 2 x 1019 eV.g-1.sec-1, 1.3 x 1020 eV.g-1 and 22 0C. The selectivity favored this compounds in all organic compounds was 57 mol% at the conversion rate of 0.8 %. In order to elucidate the reaction paths of formation and disappearance of acetaldehyde, the amounts of products were determined for the mixture with or without the presence of small amounts of acetadehyde. The results indicate that acetaldehyde formed by irradiation from

  2. Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

    OpenAIRE

    Matthieu Jouffroy; Rafael Gramage-Doria; David Sémeril; Dominique Armspach; Dominique Matt; Werner Oberhauser; Loïc Toupet

    2014-01-01

    The capacity of two cavity-shaped ligands, HUGPHOS-1 and HUGPHOS-2, to generate exclusively singly phosphorus-ligated complexes, in which the cyclodextrin cavity tightly wraps around the metal centre, was explored with a number of late transition metal cations. Both cyclodextrin-derived ligands were assessed in palladium-catalysed Mizoroki–Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. ...

  3. Improving the durability of methanol oxidation reaction electro-catalysts through the modification of carbon architectures

    Science.gov (United States)

    Wood, Kevin N.

    Carbon materials represent one of the largest areas of studied research today, having integrated applications stretching from energy production and storage to medical use and far beyond. One of these many intriguing applications is fuel cells, which offers the promise of clean electricity through a direct electrochemical energy conversion process. Unfortunately, at the present time the cost per watt-hour produced by fuel cells is more expensive than conventional methods of energy production/storage (i.e. combustion engines, batteries, etc.). Under the umbrella of fuel cell systems, methanol is a promising fuel source because of its high energy density and convenience of direct liquid fuel operation. In this field, recent advancements are bringing direct methanol fuel cells (DMFCs) closer to commercial viability. However, just as in other fuel cell systems, further improvements are greatly needed, particularly in the area of catalyst durability. This need for improved durability has led to increased research activity focused on improving catalyst stability and utilization. This thesis explores one of the most promising areas of enhancing catalyst-support interactions; namely, modification of carbon support architectures. Through the use of heteroatom modifiers, such as nitrogen, fuel cell support systems can be enhanced in such a way as to improve metal nucleation and growth, catalyst durability and catalytic activity. To this end, this thesis employs advanced characterization techniques to study the changes in catalyst particle morphology before and after nitrogen modification of the support structure. These results clearly show the beneficial effects of nitrogen moieties on carbon structures and help elucidate the effects of nitrogen on the stability of supported catalytic nanoparticles systems. Similarly, the novel concept of post-modifying commercially available supported catalysts with nitrogen ion implantation gives further insight into the behavior of

  4. Density of mixed alkali borate glasses: A structural analysis

    International Nuclear Information System (INIS)

    Density of mixed alkali borate glasses has been correlated with the glass structure. It is assumed that in such glasses each alkali oxide associates with a proportional quantity of B2O3. The number of BO3 and BO4 units related to each type of alkali oxide depends on the total concentration of alkali oxide. It is concluded that in mixed alkali borate glasses the volumes of structural units related to an alkali ion are the same as in the corresponding binary alkali borate glass. This reveals that each type of alkali oxide forms its own borate matrix and behaves as if not affected with the presence of the other alkali oxide. Similar conclusions are valid for borate glasses with three types of alkali oxide

  5. Density of mixed alkali borate glasses: A structural analysis

    Energy Technology Data Exchange (ETDEWEB)

    Doweidar, H. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt)]. E-mail: hdoweidar@mans.edu.eg; El-Damrawi, G.M. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt); Moustafa, Y.M. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt); Ramadan, R.M. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt)

    2005-05-15

    Density of mixed alkali borate glasses has been correlated with the glass structure. It is assumed that in such glasses each alkali oxide associates with a proportional quantity of B{sub 2}O{sub 3}. The number of BO{sub 3} and BO{sub 4} units related to each type of alkali oxide depends on the total concentration of alkali oxide. It is concluded that in mixed alkali borate glasses the volumes of structural units related to an alkali ion are the same as in the corresponding binary alkali borate glass. This reveals that each type of alkali oxide forms its own borate matrix and behaves as if not affected with the presence of the other alkali oxide. Similar conclusions are valid for borate glasses with three types of alkali oxide.

  6. Assessment of the apparent activation energies for gas/solid reactions-carbonate decomposition

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The guidelines for assessing the apparent activation energies of gas/solid reactions have been proposed based on the ex-perimental results from literatures. In CO2 free inlet gas flow, CaCO3 decomposition between 950 and 1250 K with thin sample layercould be controlled by the interfacial chemical reaction with apparent activation energy E = (215+10) kJ/mol and E = (200±10)kJ/mol at T = 813 to 1020 K, respectively. With relatively thick sample layer between 793 and 1273 K, the CaCO3 decompositioncould be controlled by one or more steps involving self-cooling, nucleation, intrinsic diffusion and heat transfer of gases, and E couldvary between 147 andl90 kJ/mol. In CO2 containing inlet gas flow (5%-100% of CO2), E was determined to be varied from 949 to2897 kJ/mol. For SrCO3 and BaCO3 decompositions controlled by the interfacial chemical reaction, E was (213+15) kJ/mol (1000-1350 K) and (305+15) kJ/mol (1260-1400 K), respectively.

  7. Synergistic capture mechanisms for alkali and sulfur species from combustion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, T.W.; Shadman, F.; Wendt, J.O.L.; Mwabe, P.O.

    1994-02-01

    Experimental work was carried out on a 17 kW, 600 cm long, gas laboratory combustor, to investigate the post flame reactive capture of alkali species by kaolinite. Emphasis was on alkali/sorbent interactions occurring in flue gas at temperatures above the alkali dewpoint and on the formation of water insoluble reaction products. Time-temperature studies were carried out by injecting kaolinite at different axial points along the combustor. The effect of chlorine and sulfur on alkali capture was investigated by doping the flame with SO{sub 2} and Cl{sub 2} gases to simulate coal flame environments. Particle time and temperature history was kept as close as possible to that which would ordinarily be found in a practical boiler. Experiments designed to extract apparent initial reaction rates were carried using a narrow range, 1-2 {mu}m modal size sorbent, while, a coarse, multi size sorbent was used to investigate the governing transport mechanisms. The capture reaction has been proposed to be between alkali hydroxide and activated kaolinite, and remains so in the presence of sulfur and chlorine. The presence of sulfur reduces sodium capture by under 10% at 1300{degree}C. Larger reductions at lower temperatures are attributed to the elevated dewpoint of sodium ({approximately}850{degree}C) with subsequent reduction in sorbent residence time in the alkali gas phase domain. Chlorine reduces sodium capture by 30% across the temperature range covered by the present experiments. This result has been linked to thermodynamic equilibria between sodium hydroxide, sodium chloride and water.

  8. Thermophysical properties and reaction kinetics of γ-irradiated poly allyl diglycol carbonates nuclear track detector

    Science.gov (United States)

    Elmaghraby, Elsayed K.; Seddik, Usama

    2015-07-01

    Kinetic thermogravimetric technique was used to study the effect of gamma irradiation on the poly allyl diglycol carbonates (PADC) within the dose range from 50 to ? Gy. The approach of Coats-Redfern was used to analyze the data. Results showed that low doses around 50 Gy make the polymer slightly more resistive to heat treatment. Higher radiation doses cause severe effects in the samples accompanied by the formation of lower molecular mass species and consequent crosslinking. Results support the domination of re-polymerization and crosslinking for the γ radiation interaction PADC at dose below about ? Gy, while the situation is inverted above ? Gy in which chain secession dominates.

  9. The reaction of lithium metal vapor with single walled carbon nanotubes of large diameters

    Czech Academy of Sciences Publication Activity Database

    Kalbáč, Martin; Kavan, Ladislav; Dunsch, L.

    2009-01-01

    Roč. 246, 11-12 (2009), s. 2428-2431. ISSN 0370-1972 R&D Projects: GA AV ČR IAA400400911; GA AV ČR KAN200100801; GA AV ČR IAA400400804; GA ČR GC203/07/J067; GA MŠk LC510 Institutional research plan: CEZ:AV0Z40400503 Keywords : lithium * single walled carbon nanotubes * Raman spectroscopy Subject RIV: CG - Electrochemistry Impact factor: 1.150, year: 2009

  10. Biological neutralization of chlor-alkali industry wastewater.

    Science.gov (United States)

    Jain, Rakeshkumar M; Mody, Kalpana H; Keshri, Jitendra; Jha, Bhavanath

    2011-11-01

    The present work reports biological neutralization of chlor-alkali industrial effluent by an alkaliphilic bacterium, isolated from the Gujarat coast, which was identified as Enterococcus faecium strain R-5 on the basis of morphological, biochemical and partial 16S rRNA gene sequencing. The isolate was capable of bringing down the pH of waste water from 12.0 to 7.0 within 3 h in the presence of carbon and nitrogen sources, with simultaneous reduction in total dissolved solutes (TDS) up to 19-22%. This bacterium produced carboxylic acid, as revealed by FT-IR analysis, which facilitated neutralization of alkaline effluent. The presence of unconventional raw materials viz. Madhuca indica flowers or sugar cane bagasse as carbon and nitrogen sources could effectively neutralize alkaline effluent and thus making the bioremediation process economically viable. The time required for neutralization varied with size of inoculum. To the best of our knowledge, this is the first report on biological neutralization of a chlor-alkali industrial effluent. PMID:21944194

  11. Thermochemistry of complex oxides of uranium(6), arsenic and alkali metals

    International Nuclear Information System (INIS)

    Standard reaction enthalpies for stoichiometric mixtures of mono-potassium orthoarsenate, uranium(6) and alkali metal nitrate oxides as well as mixtures of complex oxides of the M1AsUO6 (M1 = Li, Na, K, Rb, Cs) general formulas and potassium nitrate with hydrofluoric acid are determined in adiabatic calorimeter at the temperature of 298.15 K. Standard enthalpies for formation of complex oxides of uranium(6), arsenic and alkali metals at the temperature of 298.15 K are calculated by the obtained results. 8 refs., 1 tab

  12. Intermediate- and high-energy reactions of uranium with neon and carbon

    International Nuclear Information System (INIS)

    Target fragment production from the interactions of 1.0, 3.0, 4.8, and 12 GeV 12C and 5.0, 8.0, 20, and 42 GeV 20Ne with uranium has been measured using off-line gamma-ray spectroscopic techniques. The experimental charge and mass yield distributions are generally consistent with the concepts of limiting fragmentation and factorization at energies of 3.0 GeV and above. The total projectile kinetic energy was found to be the relevant scaling parameter for the comparison of reactions induced by projectiles of different sizes. Light fragments with mass number less than 60 were found to violate limiting fragmentation, and had excitation functions that were strongly increasing with projectile energy until 8.0 to 12.0 GeV. With the 1.0 GeV 12C beam the pattern of mass yields was quite different from that of all the other reactions, with the normal peak in the fission mass region (80 < A < 145), but with much lower yields below mass number 60 and between mass numbers 145 and 210, indicating that these fragments are formed primarily in very energetic reactions in which large excitation energies are transferred to and significant amounts of mass are removed from the target nucleus. Theoretical predictions of the intra-nuclear cascade, nuclear fireball, and nuclear firestreak models are compared with the experimental results. The intra-nuclear cascade and nuclear firestreak models are both able to predict the general shapes of the experimental distributions, with the exception of the yields for the lightest fragments

  13. Nitrogen, carbon, and sulfur isotopic change during heterotrophic (Pseudomonas aureofaciens) and autotrophic (Thiobacillus denitrificans) denitrification reactions.

    Science.gov (United States)

    Hosono, Takahiro; Alvarez, Kelly; Lin, In-Tian; Shimada, Jun

    2015-12-01

    In batch culture experiments, we examined the isotopic change of nitrogen in nitrate (δ(15)NNO3), carbon in dissolved inorganic carbon (δ(13)CDIC), and sulfur in sulfate (δ(34)SSO4) during heterotrophic and autotrophic denitrification of two bacterial strains (Pseudomonas aureofaciens and Thiobacillus denitrificans). Heterotrophic denitrification (HD) experiments were conducted with trisodium citrate as electron donor, and autotrophic denitrification (AD) experiments were carried out with iron disulfide (FeS2) as electron donor. For heterotrophic denitrification experiments, a complete nitrate reduction was accomplished, however bacterial denitrification with T. denitrificans is a slow process in which, after seventy days nitrate was reduced to 40% of the initial concentration by denitrification. In the HD experiment, systematic change of δ(13)CDIC (from -7.7‰ to -12.2‰) with increase of DIC was observed during denitrification (enrichment factor εN was -4.7‰), suggesting the contribution of C of trisodium citrate (δ(13)C=-12.4‰). No SO4(2-) and δ(34)SSO4 changes were observed. In the AD experiment, clear fractionation of δ(13)CDIC during DIC consumption (εC=-7.8‰) and δ(34)SSO4 during sulfur use of FeS2-S (around 2‰), were confirmed through denitrification (εN=-12.5‰). Different pattern in isotopic change between HD and AD obtained on laboratory-scale are useful to recognize the type of denitrification occurring in the field. PMID:26529303

  14. TiO2-sludge carbon enhanced catalytic oxidative reaction in environmental wastewaters applications.

    Science.gov (United States)

    Athalathil, Sunil; Erjavec, Boštjan; Kaplan, Renata; Stüber, Frank; Bengoa, Christophe; Font, Josep; Fortuny, Agusti; Pintar, Albin; Fabregat, Azael

    2015-12-30

    The enhanced oxidative potential of sludge carbon/TiO2 nano composites (SNCs), applied as heterogeneous catalysts in advanced oxidation processes (AOPs), was studied. Fabrification of efficient SNCs using different methods and successful evaluation of their catalytic oxidative activity is reported for the first time. Surface modification processes of hydrothermal deposition, chemical treatment and sol-gel solution resulted in improved catalytic activity and good surface chemistry of the SNCs. The solids obtained after chemical treatment and hydrothermal deposition processes exhibit excellent crystallinity and photocatalytic activity. The highest photocatalytic rate was obtained for the material prepared using hydrothermal deposition technique, compared to other nanocomposites. Further, improved removal of bisphenol A (BPA) from aqueous phase by means of catalytic ozonation and catalytic wet air oxidation processes is achieved over the solid synthesized using chemical treatment method. The present results demonstrate that the addition of TiO2 on the surface of sludge carbon (SC) increases catalytic oxidative activity of SNCs. The latter produced from harmful sludge materials can be therefore used as cost-effective and efficient sludge derived catalysts for the removal of hazardous pollutants. PMID:26223014

  15. Nitrogen, carbon, and sulfur isotopic change during heterotrophic (Pseudomonas aureofaciens) and autotrophic (Thiobacillus denitrificans) denitrification reactions

    Science.gov (United States)

    Hosono, Takahiro; Alvarez, Kelly; Lin, In-Tian; Shimada, Jun

    2015-12-01

    In batch culture experiments, we examined the isotopic change of nitrogen in nitrate (δ15NNO3), carbon in dissolved inorganic carbon (δ13CDIC), and sulfur in sulfate (δ34SSO4) during heterotrophic and autotrophic denitrification of two bacterial strains (Pseudomonas aureofaciens and Thiobacillus denitrificans). Heterotrophic denitrification (HD) experiments were conducted with trisodium citrate as electron donor, and autotrophic denitrification (AD) experiments were carried out with iron disulfide (FeS2) as electron donor. For heterotrophic denitrification experiments, a complete nitrate reduction was accomplished, however bacterial denitrification with T. denitrificans is a slow process in which, after seventy days nitrate was reduced to 40% of the initial concentration by denitrification. In the HD experiment, systematic change of δ13CDIC (from - 7.7‰ to - 12.2‰) with increase of DIC was observed during denitrification (enrichment factor εN was - 4.7‰), suggesting the contribution of C of trisodium citrate (δ13C = - 12.4‰). No SO42 - and δ34SSO4 changes were observed. In the AD experiment, clear fractionation of δ13CDIC during DIC consumption (εC = - 7.8‰) and δ34SSO4 during sulfur use of FeS2-S (around 2‰), were confirmed through denitrification (εN = - 12.5‰). Different pattern in isotopic change between HD and AD obtained on laboratory-scale are useful to recognize the type of denitrification occurring in the field.

  16. An electrochemical immunosensor based on covalent immobilization of okadaic acid onto screen printed carbon electrode via diazotization-coupling reaction.

    Science.gov (United States)

    Hayat, Akhtar; Barthelmebs, Lise; Sassolas, Audrey; Marty, Jean-Louis

    2011-07-15

    In this work, an electrochemical method based on the diazonium-coupling reaction mechanism for the immobilization of okadaic acid (OA) on screen printed carbon electrode was developed. At first, 4-carboxyphenyl film was grafted by electrochemical reduction of 4-carboxyphenyl diazonium salt, followed by terminal carboxylic group activation by N-hydroxysuccinimide (NHS), N-(3-dimethylaminopropyle)-N'-ethyle-carbodiimide hydrochloride (EDC). Hexamethyldiamine was then covalently bound by one of its terminal amine group to the activated carboxylic group. The carboxyl group of okadaic acid was activated by EDC/NHS and then conjugated to the second terminal amine group on other side of the hexamethyldiamine through amide bond formation. After immobilization of OA, an indirect competitive immunoassay format was employed to detect OA. The immunosensor obtained using this novel approach allowed detection limit of 1.44 ng/L of OA, and was also validated with certified reference mussel samples. PMID:21645734

  17. STUDIES ON THE CATALYTIC REACTION OF NITROGEN OXIDE ON METAL MODIFIED ACTIVATED CARBON FIBERS

    Institute of Scientific and Technical Information of China (English)

    FU Ruowen; DU Xiuying; LIN Yuansheng; XU Hao; HU Yiongjun

    2003-01-01

    The catalytic reaction of NO with CO and decomposition of NO over metal modified ACFs were investigated and compared with other carriers supported catalysts. It is demonstrated that Pd/ACF and Pd/Cu/ACF have high catalytic activity for the reaction of NO/CO, while Pt/ACF.Pt/Cu/ACF and Co/Cu/ACF have very Iow catalytic activity in similar circumstance. Pd-modified ACF possesses high catalytic decomposition of NO at 300 ℃. Pd/CB and Pd/GAC present good catalytic decomposition ability for NO only at low flowrate. Pd/G, Pd/ZMS and Pd/A however, do not show any catalytic activity for NO decomposition even at 400 ℃. Catalytic temperature, NO flowrate and loading of metal components affect the decomposition rate of NO. The coexistence of Cu with Pd on Cu/Pd/ACF leads to crystalline of palladium to more unperfected so as to that increase the catalytic activity.

  18. Carbonation of metal silicates for long-term CO2 sequestration

    Science.gov (United States)

    Blencoe, James G; Palmer, Donald A; Anovitz, Lawrence M; Beard, James S

    2014-03-18

    In a preferred embodiment, the invention relates to a process of sequestering carbon dioxide. The process comprises the steps of: (a) reacting a metal silicate with a caustic alkali-metal hydroxide to produce a hydroxide of the metal formerly contained in the silicate; (b) reacting carbon dioxide with at least one of a caustic alkali-metal hydroxide and an alkali-metal silicate to produce at least one of an alkali-metal carbonate and an alkali-metal bicarbonate; and (c) reacting the metal hydroxide product of step (a) with at least one of the alkali-metal carbonate and the alkali-metal bicarbonate produced in step (b) to produce a carbonate of the metal formerly contained in the metal silicate of step (a).

  19. Poisoning by carbon monoxide of the D2-H2O(v) exchange reaction over a platinum catalyst deposited on a hydrophobic support

    International Nuclear Information System (INIS)

    The adsorption of carbon monoxide and its poisoning effect for the D2-H2O(v) exchange reaction over Pt(0.25%)/Porapak Q (copolymer of styrene and divinylbenzene) were studied. It was found that poisoning curves at 263 K, 273 K, and 297 K were similar in shape, which suggested that the activation energy for the D2-H2O(v) exchange over Pt/Porapak Q was not changed by carbon monoxide poisoning. The adsorption of hydrogen and water on the platinum surface on which carbon monoxide was pre-adsorbed to various extents was studied and demonstrated that the pre-adsorption of carbon monoxide does not cause any appreciable decrease in the amount of adsorption of hydrogen and water, and also the rate of hydrogen adsorption, although it is an effective poison for the exchange reaction. (orig.)

  20. Remote Sensing of CO2 Absorption by Saline-Alkali Soils: Potentials and Constraints

    Directory of Open Access Journals (Sweden)

    Wenfeng Wang

    2014-01-01

    Full Text Available CO2 absorption by saline-alkali soils was recently demonstrated in the measurements of soil respiration fluxes in arid and semiarid ecosystems and hypothetically contributed to the long-thought “missing carbon sink.” This paper is aimed to develop the preliminary theory and methodology for the quantitative analysis of CO2 absorption by saline-alkali soils on regional and global scales. Both the technological progress of multispectral remote sensing over the past decades and the conjectures of mechanisms and controls of CO2 absorption by saline-alkali soils are advantageous for remote sensing of such absorption. At the end of this paper, the scheme for remote sensing is presented and some unresolved issues related to the scheme are also proposed for further investigations.