Processing-Moisture Resistance and Thermal Analysis of Macro-Defect-Free Materials

The system of sulfoaluminate ferrite belite (SAFB) clinkers premixed with Portland cement (PC) in mass ratio 85:15 in combination with hydroxypropylmethyl cellulose (HPMC) or polyphosphates(poly-P) was used for the syntheses of Macro-Defect-Free (MDF) materials. The subsequent moisture treatment and thermal stability of these MDF materials were investigated. The effect of individual humidity upon the evolution of mass is more intensive than the effects of composition of MDF materials or duration of the original MDF material synthesis. Detailed values of mass changes at 100% relative humidity (RH) and under ambient conditions are strongly affected by the nature of polymer used. A significant improvement of moisture resistance of MDF materials is achieved when the materials are dried after 24 h of finishing the pressure application. In the inter-phase section of MDF material samples, the content ofC-(A,F)-S hydraulic phases, mainly tetracalcium aluminate ferrite monosulphatehydrate (AFm) decomposing by 250°C and CaCO₃ decomposing at 600–700°C increase after the moisture attack, while cross-links in AFm-like section with typical thermoanalytical traces in temperature region 250–550°C remain intact. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dimerization and Coordination Properties of Zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine in Relation to DABCO in <Emphasis Type="Italic">o</Emphasis>-Xylene and Chloroform

For the first time the interactions between zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine (Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc) and 1,4-diazabicyclo[2.2.2]octane (DABCO) in o-xylene and chloroform have been studied by calorimetric titration and NMR and electron absorption spectroscopic methods. It has been found that in o-xylene at concentrations of Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc higher than 6×10⁻⁴ mol⋅L⁻¹ π–π dimers species are formed (λ _max= 685 nm). Additions of DABCO to the solution up to mole ratio 1 : 8 (Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc : DABCO) lead to a shift of the aggregation equilibrium towards monomer species due to formation of monoligand axial complexes. Further increasing the DABCO concentration results in formation of Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc—DABCO—Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc sandwich dimers (λ _max= 675 nm).     

MDF cements

The applicability of MDF synthesis procedure, the coincidence of the interfacial cross-linking and the moisture resistance of MDF-related mixes based on two industrial Portland cements (CEM I, CEM II) and poly-P are reported. The knowledge of the moisture resistance of synthesized material is of paramount importance; two independent experimental methods confirmed that the moisture resistance of MDF cements based on CEM I (or CEM II) with 5% of poly-P achieves sufficient levels at 50% RH and at ambient values of RH. The results of thermal analysis are directly related to the former knowledge on the appearance and role of cross-links in the interfacial zone of MDF cements. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis,moisture resistance,thermal, chemical and SEM analysis of macro-defect-free (MDF) cements

The results, presented here discusses the Macro-Defect-Free (MDF) cements prepared from the blends of sulfoaluminate ferrite belite (SAFB) clinkers, ordinary Portland cement (OPC), Al₂O₃ and poly(butyl acrylate) (PBA), styrene/acrylonitrile co-polymer (SACP) or sodium polyphosphate (poly-P). Though MDF cements have several attractive properties, their utilization has been limited due to the insufficient moisture resistance. It is a very challenging task for scientists and technologist to improve the moisture resistance of MDF cements. Therefore, the new MDF cements were subjected to various moist atmospheres to investigate their moisture resistance. The most significance of this work is the improvement of moisture resistance of the studied MDF cements. The aim of this work was to understand the effects of polymers, Al₂O₃, OPC and SAFB clinkers in the raw mix and delayed drying on MDF cements and also on their subsequent moisture resistance and thermal stability as well as to discover the new properties of these materials. Their chemical, thermal and scanning electron microscopic (SEM) analysis was also carried out before and after exposure to moisture. PBA was found to be the most suitable polymer for MDF cement synthesis, since the samples containing PBA showed the highest resistance to moisture. There are three main temperature regions on TG curves of both series of MDF cement samples. The significant differences in SEM of MDF cements before and after moisture attack and with different polymers were observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cross-linking of atoms and thermal stability of new MDF compositions

We have summarized Al, Fe, C and P atoms incorporations within cross-linking interaction and location of those after MDF procedure of sulphobelitic clinker — hydroxypropylmethyl cellulose (hpmc) — sodium salt of polyphosphates (poly-P) compositions. Design of Al/Fe-O-C/P cross links is given and discussed. Thermoanalytical patterns (i) give the evidence of the presence of polymers in the reaction products and (ii) confirm the linkages of solidified polymers throughX=C or P of Al/Fe-O-X cross links in interphase regions with decomposition temperature interval higher than this in classical hydraulic materials. Designed local structure of interphase regions gives atomic level explanation of the densification of a bulk, its microstructure and exceptional technological properties. Similar phenomenon has been reported for the high aluminium — polyvinylalcohol/acetate MDF compositions. Moreover, variant clinker as well as polymers employed in syntheses represent one of the proposals aimed to the increase of the moisture resistence; our results are in the power of the above alternative for phases of sulphobelitic clinker.This study was funded under Project 85/92 granted by the Slovak Grant Agency for Science and represents the output of joint research agreed by the Institute of Inorganic Chemistry SAS (Bratislava, Slovak Republic) and the Chemistry Department of University Exeter (Exeter, U.K.). We thank Chemische Fabrik R.A. Oetker (Budenheim, F.R.G.) for provision of sodium polyphosphate glass samples. This study also forms part of EC contracted Copernicus Project (ERB CIPA-CT 94-0105).     

Identification of peroxo groups in supramolecular layered structures as probed by Raman spectroscopy

Peroxide-containing supramolecular structures prepared by reacting lithium aluminum layered double hydroxides (Li-Al LDHs) with concentrated hydrogen peroxide solutions were characterized by Raman spectroscopy. These compounds were formulated as [LiAl₂(OH)₆](OH) · H₂O₂ · H₂O(I) and [LiAl₂(OH)₆](OOH) · H₂O₂ · H₂O(II). The frequencies 830 and 849 cm⁻¹ in the spectra of compounds I and II were assigned to O—C stretching vibrations in two nonequivalent peroxo groups. The band at 866 cm⁻¹ in compound II was assigned to O—O vibrations in the hydroperoxo group (OOH)⁻. Proceeding from calculated strength factors, we inferred that the O—O bond in the hydroperoxo group of compound II is stronger than in the H₂O₂ solvating group. Original Russian Text ? T.A. Tripol’skaya, I.V. Pokhabova, P.V. Prikhodchenko, G.P. Pilipenko, E.A. Legurova, N.A. Chumaevskii, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 513–515.     

Amorphous sol-gel titania modified with heteropolyacids

Samples of amorphous sol-gel titania were prepared at 50%wt with tungstophosphoric or molybdophosphoric acid. The resulting gels were dried and annealed at 100, 150 and 200°C and studied by FT-IR, UV-Vis, EPR, TGA and Raman spectroscopy. By FT-IR the evolution of the stretching vibration of the OH groups (3450–3700 cm⁻¹) was followed. The intensity of this band decreased as the annealing temperature increased. With UV-Vis spectroscopy the band gap was determined for each sample, and the Eg was found between 2.72 and 3.38 eV. Raman spectroscopy revealed the formation of Mo—O—Ti and W—O—Ti—O bonds. An intense EPR signal at g = 1.998 was observed during annealing of the samples. Amorphous solids with a significant number of vacancies and promising photocatalytic properties were obtained.     

Intermolecular interactions in 2,4-dinitrophenylhydrazine hydrochloride hydrate: X-ray structural and quantum mechanical study

2,4-dinitrophenylhydrazine hydrochloride hydrate (I) was determined by X-ray crystallography, and the intermolecular interaction energies were calculated in terms of Natural Bond Orbital analysis. The asymmetric unit of (I) consists of a dinitrophenylhydrazinium cation, a chloride anion and a water molecule. The interatomic distances and angles in (I) show no unusual values. In the structure there are intermolecular N—H⊎⊎⊎O, N—H⊎⊎⊎Cl, O—H⊎⊎⊎Cl, C—H⊎⊎⊎O hydrogen bonds with bonding energy ranging form 16.03 to 0.76 kcal mol⁻¹. These hydrogen bonds create the following N1 motifs: 6D, S(5), S(6), C(6), C(9). N₁D motifs become infinite at the third level and are 2C₃²(6), C₃²(7).      

Standardization on stanag test methods for ease of compatibility and thermal studies

MDF cements using the blends of sulfoaluminate ferrite belite (SAFB) clinkers and ordinary Portland cement (OPC) in mass ratio 85:15 with Al₂O₃, and starch, polyphosphate (poly-P) or butylacrylate/acrylonitrile were subjected to moist atmospheres (ambient, 52 and 100% relative humidity (RH)) to investigate their moisture resistance. Their chemical, thermal, electron microscopic and magnetic properties were also studied before and after moisture attack. Butylacrylate/acrylonitrile (BA/AN) copolymer was found to be the most suitable for MDF cement synthesis since the sample containing BA/AN showed the best moisture resistant. There are significant differences in scanning electron microscopy (SEM) of MDF cements before and after moisture attack and with different polymers. New data on the paramagnetic nonhysteresis magnetization curves for all the samples are observed. The MDF cements synthesized from SAFB clinker with dissolved poly-P give the best signal/noise (S/N) ratio. Three main temperature regions on TG curves of both series of MDF cements are observed. In the inter-phase section of MDF cements, the content of classical cement hydrates decomposing by 250°C is increased. Combustion of organic material took place by 550°C. In the temperature range 550-800°C, the decomposition of CaCO₃ occurs.     

Chemical bonding in silicophosphate gels: Contribution of dipolar and J-derived solid state NMR techniques

A representative silicophosphate gel was synthesized, starting from orthophosphate groups and pyrophosphate species. At 136°C, a complex mixture of crystalline phases and amorphous components was obtained. A new panel of solid state NMR techniques was implemented, including dipolar based experiments (CP MAS), as well as J-derived techniques, in both homonuclear (³¹P INADEQUATE-MAS) and heteronuclear (³¹P/²⁹Si HMQC-MAS) versions. These experiments are suitable for the fine characterization of P–O–P, P–O–Si, P–OH…linkages in silicophosphate gels and materials.     

7-Ethyl-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (echinochrome A): A DFT study of the antioxidant mechanism. 1. Interaction of echinochrome A with hydroperoxyl radical

The molecular geometry and electronic structure of hydroxy-substituted naphthazarin (NZ)-7-ethyl-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (echinochrome A, (Et)NZ(β-OH)₃, 1) were calculated by the B3LYP/6-311G(d) method. The influence of the (i) character of the β-OH groups dissociation and (ii) conformational mobility of molecule 1 and the anions, radicals, and radical anions derived from 1 on the energy of their reactions with hydroperoxyl radical was studied by the (U)B3LYP/6-31G and (U)B3LYP/6-311G(d) methods. The enol-enolic tautomerism due to the transfer of hydrogen atoms of α-OH groups and rotational isomerism of the β-OH groups at the C(2) and C(3) atoms and of the α-OH groups at the C(5) and C(8) atoms were studied. The equilibrium in the gas-phase reaction 1 + ^•OOH ⇄ (Et)(HO-β)₂NZ(β-O^•) + HOOH (1) (quenching of hydroperoxyl radical) is shifted to the separated reagents. Heterolysis of the O—H bond in one of the three β-hydroxy groups considerably reduces the energy of subsequent O—H bond homolysis in either of the two remaining β-hydroxy groups. As a consequence, the reaction (Et)(HO-β)₂NZ(β-O⁻) + ^•OOH ⇄ (Et)(HO-β,⁻O-β)NZ(β-O^•) + HOOH (2) (quenching of hydroperoxyl radical) becomes exothermic and the equilibrium is shifted to the formation of hydrogen peroxide. The Gibbs energy gain in reaction (2) varies from −6.4 to −10.9 kcal mol⁻¹ depending on which β-hydroxy group is involved in the O—H bond homolysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 400–415, March, 2007.     

Mechanism of ethylene hydroformylation on platinum complexes with hydrophosphoryl ligands: a DFT study

The mechanism of ethylene hydroformylation on model organoplatinum hydrides [(R₂PO)₂H]Pt(PR₃)(H)] (R = H, Me, CF₃) was studied within the framework of the density functional theory with the PBE gradient-corrected functional and the TZ2p basis set. The presence of a free coordination site in these square-planar 16-electron platinum complexes provides the possibility of alkene coordination in the first step without energetically unfavorable dissociation of one of the metal-ligand bonds. High strength of the —PR₂O—H....O—R₂ hydrogen bond results in the formation of a bidentate ligand in the coordination sphere of the metal atom. This ligand makes the geometry of the catalytic center rigid, thus enhancing the regioselectivity of the process. The proton can reversibly migrate with ease within the —PR₂O—H... O—R₂ hydrogen bond, thus providing fine adjustment of the electron density in the catalytic center in each reaction step and acting as a molecular switch. The rate-limiting step in the hydroformylation is the CO insertion into the Pt-Et σ-bond. Electron-donating Me groups at the phosphorous atoms hamper, while electron-withdrawing CF₃ groups facilitate, the process.     

New cage-like metallasiloxane containing Fe<Superscript>III</Superscript> ions in different coordination spheres

The first cage-like ferrophenyl siloxane containing Fe^III ions in different coordination spheres (four iron ions have a trigonal-bipyramidal coordination and two iron ions have a distorted octahedral coordination) was synthesized by the exchange reaction of sodium phenylsilanolate with Fe^III chloride. An exotic lantern-like structure is formed with the involvement of two metal oxide fragments Fe—O—Fe. The structure of this compound was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 522–524, March, 2007.     

Generation of fullerenyl radicals and chemiluminescence in the (C<Subscript>60</Subscript>—R<Subscript>3</Subscript>Al)—O<Subscript>2</Subscript> system

Fullerenyl radicals (FR) RC₆₀ ^· and chemiluminescence (CL) are generated in the presence of O₂ in C₆₀—R₃Al (R = Et, Buⁱ) solutions in toluene (T = 298 K). The FR are formed due to the addition of the R^· radical, which is an intermediate of R₃Al autooxidation, to C₆₀. Mass spectroscopy and HPLC were used to identify Et_nC₆₀H_m (n, m = 1–6), Et_pC₆₀ (p = 2–6), and dimer EtC₆₀C₆₀Et as stable products of FR transformations. As found by ESR, the EtC₆₀ ^· radical (g = 2.0037) is also generated by photolysis of solutions obtained after interaction in the (C₆₀— R₃Al)—O₂ system. In the presence of dioxygen, the FR is not oxidized but yields complexes with O₂, which appear as broadening of the ESR signals. Chemiluminescence arising in the (C₆₀—R₃Al)—O₂ system is much brighter (I _max = 1.86·10⁸ photon s⁻¹ mL⁻¹) than the known background CL (I _max = 6.0·10⁶ photon s⁻¹ mL⁻¹) for the autooxidation of R₃Al and is localized in a longer-wavelength spectral region (λ_max = 617 and 664 nm). This CL is generated as a result of energy transfer from the primary emitter ³CH₃CHO* to the products of FR transformation: R_nC₆₀H_m, R_pC₆₀, and EtC₆₀C₆₀Et. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 205–213, February, 2007.     

One-step direct synthesis of mesoporous aluminosilicates Al-SBA-15 with cage-like macropores by using micrometer-sized aluminum balls

Ordered mesoporous aluminosilicate Al-SBA-15 materials with cage-like macropores have been synthesized by using micrometer-sized aluminum balls as an Al source, tetraethyl orthosilicate (TEOS) as a silica source, and triblock copolymer Pluronic P123 as a template. The resulting materials were fully characterized by XRD, N₂ adsorption, SEM, TEM, ICP-AES, and ²⁷Al MAS-NMR. The products (Al-SBA-15) have ordered two-dimensional (2-D) hexagonal mesostructures (space group p6mm). The calcined Al-SBA-15 materials exhibit disordered macropores with diameters of about 70–80 nm and ordered mesopores with a diameter of ∼5 nm, a BET surface area of about 500 m²/g, Si/Al ratio of 40–80, and a ratio of tetrahedral Al to octahedral Al sites of about 2:1. This combination of properties gives these materials potential applications in areas such as adsorption, catalysis and separation. Supported by the National Natural Science Foundation of China (Grant Nos. 20890123 & 20721063), Shanghai Science & Technology Committee (08DZ2270500), and Shanghai Leading Academic Discipline Project (No.B108)     

Supramolecular systems of amphiphilic derivatives of calix[4]resorcinarenes and surfactants in chloroform

Aggregation of amphiphilic calix[4]resorcinarenes (CRA) modified by carboxymethyl (1), 2-hydroxyethyl (2), methylamino acetal (3), and aminomethyl (4) fragments and their interaction with some synthetic (5, 6) and natural (7, 8) surfactants in the low-polarity solvent (chloroform) were studied by permittivity measurements and FT-IR spectroscopy. Compounds 1–4 and surfactants form aggregates at critical micelle concentrations (CMC) of 2.0·10⁻⁵–7.5·10⁻⁵ and 1.7·10⁻⁵–2.0·10⁻³ mol L⁻¹, respectively. The CMC values of CRA—surfactant mixed aggregates depend on the surfactant structure and the structure and concentration of CRA. Analysis of the IR spectra of solutions of a series of amphiphilic CRA (2–4, 9, 10) and their mixtures with the cationic surfactant N-cetyl-N,N-dimethyl-N-(2-hydroxyethyl)ammonium bromide (5) showed that an increase in the concentration of the solutions in individual and mixed systems is accompanied by a decrease in the molar integral intensities and intensities in the maxima of the absorption bands of the O—H and C—H bonds down to the CMC point, after which these values change slightly. The discovered effect, which is differently pronounced for all systems studied, indicates that both the polar “head” groups and nonpolar fragments of CRA and surfactant are involved in the formation of supramolecules of the reverse micelle type in all cases. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 459–466, March, 2007.     

Method for determination of silicon in plant materials by neutron activation analysis

Silicon has been found to be an essential element for the growth and development of many ecomomically important plants such as sugarcane, rice, oats, and wheat. A method is described for the quantitative determination of silicon in plant samples. Measurements were made with two Ge(Li) detectors matched with a multiplexing unit to provide a single amplified signal to a computerized analyzer system. For those materials containing greater than 0.5 weight percent silicon, the reaction²⁹Si(n, p)²⁹Al (1273 keV) provides a direct measurement of the quantity of silicon provided the irradiation is done in a special boron nitride capsule to reduce interferences from thermal neutron reactions and a correction is made for the single escape line from²⁸Al (1268 keV). For lesser quantities of silicon, a technique which utilizes the fast neutron reaction²⁸Si(n, p)²⁸Al is preferred. Corrections for the interference produced by the presence of phosphorus³¹P(n, α)²⁸Al are made by determining the phosphorus content following the instrumental analysis using a unique application of neutron activation analysis, i. e., measurement of tungsten in tungstomolybdophosphoric acid produced when molybdate and tungstate ions are added to dissolved samples of the plant material containing phosphorus. Aluminum, which may also produce an interference by thermal neutron reaction²⁷Al(n, γ)²⁸Al, is determined directly from the original activation data after subtracting out the effect of the phosphorus. Thus, three irradiations in the pneumatic sample irradiator are necessary; one short irradiation (1 min) without thermal neutron shielding, a longer irradiation (6 min) in the boron capsule, and a final irradiation of the tungstomolybdophosphoric acid provide all data required to accurately determine silicon in plant materials. A computer program has been developed that provides rapid reduction of the data in final report format. Elements such as sodium, chlorine, calcium, manganese, potassium, and magnesium extrinsic to the analysis for silicon are also determined by this method. The method has been tested on a large number of samples and reliable results are obtained with less than 0.2 g of sample. This work was supported by Grant 533 from the Michigan Memorial—Phoenix Project.     

Methods of production,structure, and physicochemical characteristics of phosphorylated carbon adsorbents

The paper presents a review of methods for the production of phosphorylated carbon adsorbents, their structure, and their physicochemical characteristics. It was shown that the phosphorylated carbons contain phosphoric acid residues (condensed phosphates) attached to the carbon matrix mainly by a C—O—P bond and, to a lesser degree, by a C—P bond. The presence of the condensed phosphates in the structure of the carbon determines the hydrophilicity and the acidic characteristics and also the ability to absorb cations. The acidic characteristics of the surface of the phosphorylated carbons gives rise to their high catalytic activity in acid catalysis. The presence of the phosphates/polyphosphates improves the electrochemical characteristics of carbon materials for use as electrodes in supercapacitors. Potential fields for the practical application of phosphorylated carbons are the purification of water from heavy metal ions, the acceleration of reactions of the acid–base type, and the accumulation and storage of energy in double-layer capacitors.     

Simultaneous speciation of arsenic (As(III), MMA, DMA, and As(V)) and selenium (Se(IV), Se(VI), and SeCN−) in petroleum refinery aqueous streams

High-performance liquid chromatography (HPLC) coupled to an ICP-MS with an octapole reaction system (ORS) has been used to carry out quantitative speciation of selenium (Se) and arsenic (As) in the stream waters of a refining process. The argon dimers interfering with the ⁷⁸Se and ⁸⁰Se isotopes were suppressed by pressurizing the octapole chamber with 3.1 mL min⁻¹ H₂ and 0.5 mL min⁻¹ He. Four arsenic species arsenite—As(III), arsenate (As(V)), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA)—and three inorganic Se species—selenite Se(IV), selenate Se(VI), and selenocyanate (SeCN⁻)—were separated in a single run by ion chromatography (IC) using gradient elution with 100 mmol L⁻¹ NH₄NO₃, pH 8.5, adjusted by addition of NH₃, as eluent. Repeatabilities of peak position and of peak area evaluation were better than 1% and about 3%, respectively. Detection limits (as 3σ of the baseline noise) were 81, 56, and 75 ng L⁻¹ for Se(IV), Se(VI), and SeCN⁻, respectively, and 22, 19, 25, and 16 ng L⁻¹ for As(III), As(V), MMA, and DMA, respectively. Calibration curve R ² values ranged between 0.996 and 0.999 for the arsenic and selenium species. Column recovery for ion chromatography was calculated to be 97 ± 6% for combined arsenic species and 98 ± 3% for combined selenium species. Because certified reference materials for As and Se speciation studies are still not commercially available, in order to check accuracy and precision the method was applied to certified reference materials, BCR 714, BCR 1714, and BCR 715 and to two different refinery samples—inlet and outlet wastewater. The method was successfully used to study the quantitative speciation of selenium and arsenic in petroleum refinery wastewaters.