共查询到20条相似文献,搜索用时 31 毫秒
1.
Polypropylene fabrics samples were surface functionalized under Ar and O2 RF plasma conditions. Survey and high resolution photoelectron spectroscopy and attenuated total reflectance FTIR comparative
evaluation of virgin and plasma treated substrat surfaces, and their pentafluorophenyl hydrazine-derivatized correspondents,
indicate that both Ar and O2-discharge treated PP surfaces undergo intense oxidation. C=O, O−C=O, and C−O linkages were identified on both inert and reactive
gas plasma exposed surfaces. It was found that the relative surface atomic concentrations and the relative ratios of newly
created functionalities are controlled by the external plasma parameters (RF power and treatment time). The oxidation of Ar-plasma
treated surfaces has been related toex situ post plasma mechanisms. Dynamic contact angle measurements from unmodified and plasma exposed substrates demonstrated the
presence of increased surface polarity, and its dependence on plasma parameters. AFM evaluations of plasma treated samples
indicate the presence of rough surface morphologies.
Paper based on the results presented during the workshop of the Engineering Research Center for Plasma-Aided Manufacturing
held in Madison, Wisconsin, in Spring 1996. 相似文献
2.
Hasan Marai Ewa Kita Emilia Kiersikowska Sylwia Kuchta Anna Bajek Tomasz Drewa 《Transition Metal Chemistry》2012,37(4):337-344
Three chromium(III) complexes with asparagine (Asn) and histidine (His) of the [Cr(ox)2(Aa)]2− type, where Aa = N,O–Asn, N,O–His or N,N′–His, were obtained and characterized in solution. The complexes with N,O–Aa undergo acid-catalysed aquation to give a free amino acid and cis-[Cr(ox)2(H2O)2]−, whereas the complex with N,N′–His undergoes parallel reaction paths: (1) isomerization to the N,O–His complex and (2) liberation of an oxalate ligand. Kinetics of the N,O–Aa complexes in HClO4 media were studied spectrophotometrically under pseudo-first-order conditions. The absorbance changes were attributed to
the chelate ring opening at the Cr–N bond. The linear dependence of rate constants on [H+] was established, and a mechanism for the chelate ring cleavage was postulated. The existence of a metastable intermediate
with O-monodentate Aa ligand was proved experimentally. Effect of [Cr(ox)2(Aa)]2− on 3T3 fibroblasts proliferation was studied. The tests revealed low cytotoxicity of the complexes. Complexes with Ala, His
and Cys are good candidates for biochromium sources. 相似文献
3.
M. I. B. Bernardi E. Antonelli A. B. Lourenço C. A. C. Feitosa L. J. Q. Maia A. C. Hernandes 《Journal of Thermal Analysis and Calorimetry》2007,87(3):725-730
The results reported here based on a study
of BaTi1–xZrxO3
(x=0, 0.2 and 1) nanometric powders prepared
by the modified Pechini method. The powder samples annealed from 600 to 1000°C/2
h were characterized by thermogravimetric analysis (TG), differential scanning
calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy
(SEM) techniques. The decomposition reactions of resins were studied using
thermal analysis measurements. The barium titanate zirconate system presented
just one orthorhombic phase. Furthermore, this study produced BaTiO3
powders with a tetragonal structure using shorter heat treatments and less
expensive precursor materials than those required by the traditional methods. 相似文献
4.
Magdalena Wencka Kinga Wichlacz Henryk Kasprzyk Stefan Lijewski Stanislaw K. Hoffmann 《Cellulose (London, England)》2007,14(3):183-194
By use of 9.7 GHz and 94 GHz ESR spectra and electron spin echo (ESE)-detected spectra the six radical centres produced by
γ-irradiation of cellobiose were identified. The radicals are localized on different carbon atoms. Use of high-frequency ESR
spectra with computer resolution enhancement methods enabled unique radical identification and determination of g-factors and proton hyperfine splitting, A, with high accuracy. For radiation doses below 20 kGy three radicals dominate: on C1 with isotropic doublet A = 1.8 mT; on C2, C3 and C4 with triplet A = 2.9 mT; and localized on CH2 with anisotropic triplet. For doses above 100 kGy the radical on C1 dominates, because of cleavage of the glycosidic bonds. Electron spin–lattice relaxation shows that radiation damage of the
cellulose structure around the radical centres is significant and radical molecules do not participate in phonon dynamics
of the host lattice. The relaxation is because of tunnelling motions of the ring or OH-groups, with tunnelling splitting 2.4 cm−1. Electron spin echo dephasing results identify cellobiose ring torsions with activation energy 117 cm−1. 相似文献
5.
V. A. Rafeev Yu. I. Rubtsov T. V. Sorokina N. V. Chukanov 《Russian Chemical Bulletin》1999,48(1):66-70
The equilibrium of nitration of cellulose was studied at 13.1 and 20 °C in aqueous solutions of HNO3 (77.3–80.5 wt.%) forming quasi-homogeneous solutions with cellulose. At 20 °C under quasi-homogeneous conditions, the rates
of cellulose nitration are comparable to those of homogeneous nitration of alcohols. The effective nitration constants differ
substantially for heterogeneous and homogeneous reactions. Using IR spectra, the partial conversions in the nitration to the
2, 3 and 6 positions of the glucopyranose cycle and the effective equilibrium constants of formation of different isomeric
nitrates were estimated.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 66–70, January, 1999. 相似文献
6.
Yu. M. Shul’ga V. M. Martynenko A. F. Shestakov S. A. Baskakov S. V. Kulikov V. N. Vasilets T. L. Makarova Yu. G. Morozov 《Russian Chemical Bulletin》2006,55(4):687-696
Two methods are described for doping of fullerite C60 with molecular oxygen at a pressure of ∼104 Pa and at temperature 20–30 °C. It was found by mass spectrometry using oxygen
18O as dopant that a portion of molecular oxygen absorbed by the pre-decontaminated fullerite (first method) is removed as CO
and CO2 at the heating temperature ≤200 °C. Doping during fullerite precipitation from the liquid phase (second method) makes it
possible to prepare samples with the oxygen content ≥1.2 at.%. The fullerite doped with oxygen to this level is diamagnetic.
The paramagnetic properties of an O2 molecule disappear when O2 is incorporated into the fullerene lattice. This is interpreted on the basis of quantum chemical calculations as a sequence
of equilibrium formation of the adduct C60O2. Calculations showed that the subsequent chemical transformation of C60O2 resulting in the O-O bond cleavage is energetically favorable, enabling prerequisites for the formation of products of incomplete
(CO) and deep (CO2) oxidation of fullerene under mild conditions.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 662–671, April, 2006 相似文献
7.
A simple, general, and high yielding method has been developed for the synthesis of S-aryl/alkyl-O-aryl/alkyl thiolcarbonates from various chloroformates and disulfides by reductive cleavage of the S–S bond with a Zn/AlCl3 system in dry acetonitrile at 80°C. 相似文献
8.
B. Zapata J. Balmaseda E. Fregoso-Israel E. Torres-García 《Journal of Thermal Analysis and Calorimetry》2009,98(1):309-315
Thermal degradation of orange peel was studied in dynamic air atmosphere by means of simultaneous TG-DSC and TG-FTIR analysis.
According to the obtained thermal profiles, the orange peel degradation occurred in at least three steps associated with its
three main components (hemicellulose, cellulose and lignin). The volatiles compounds evolved out at 150–400 °C and the gas
products were mainly CO2, CO, and CH4. A mixture of acids, aldehydes or ketones C=O, alkanes C–C, ethers C–O–C and H2O was also detected. The E
α on α dependence reveled the existence of different and simultaneous processes suggesting that the combustion reaction is
controlled by oxygen accessibility, motivated by the high evolution low-molecular-mass gases and volatile organic compounds.
These results could explain the non-autocatalytic character of the reactions during the decomposition process. 相似文献
9.
D. N. Bazhin T. I. Gorbunova A. Ya. Zapevalov V. I. Saloutin 《Russian Chemical Bulletin》2007,56(8):1534-1536
Addition of polyfluoroalkyl iodides to the double bond of allyl glycidyl ether occurred under mild conditions (20–25 °C, MeCN/H2O, Na2S2O4, NaHCO3) with retention of the oxirane ring.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1476–1478, August, 2007. 相似文献
10.
Summary. A simple, general, and high yielding method has been developed for the synthesis of S-aryl/alkyl-O-aryl/alkyl thiolcarbonates from various chloroformates and disulfides by reductive cleavage of the S–S bond with a Zn/AlCl3 system in dry acetonitrile at 80°C. 相似文献
11.
Abstract
C-2-unsubstituted imidazoline-3-oxides were reduced with NaBH4 in THF to give the corresponding trans-3,5-diarylimidazolidin-1-ols, while under the same conditions C-2-substituted derivatives gave the corresponding ring–chain–ring tautomers. Treatment of the crude reaction mixture from the reduction of C-2-unsubstituted imidazoline-3-oxides with a MeOH–H2O mixture provided reductive C–N bond cleavage to give hydroxylamines, while under the same conditions ring–chain–ring tautomers remained unchanged. 相似文献12.
Alexander Konkin Frank Wendler Frank Meister Hans-Klaus Roth Albert Aganov Oliver Ambacher 《Cellulose (London, England)》2007,14(5):457-468
Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC)
and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser
flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature,
radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide
type radicals ∼CH2–NO•–CH2∼ and/or ∼CH2–NO•–CH3∼ at the first and methyl •CH3 and formyl •CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination
rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g.,
Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol
and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained
by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO. 相似文献
13.
E. A. Bernardelli T. Belmonte D. Duday G. Frache F. Poncin-Epaillard C. Noël P. Choquet H.-N. Migeon A. Maliska 《Plasma Chemistry and Plasma Processing》2011,31(1):189-203
We study the interaction of thick films (~4 mm) of stearic acid (SA), a C18 alkane skeleton with an acid function, with late Ar–O2 post-discharge. Contrary to what is observed with thin films of SA (~2–3 μm) which are efficiently etched (part I), only functionalization is observed over the first 2 h of treatment with a plasma source operated in the continuous mode,
whatever the temperature. The heat released by surface reactions affects non-linearly the temperature of the substrate. Pulsing
the source at a frequency ranging from 0.1 to 1 kHz slows down the functionalization process but does not allow any etching
of the material. On the contrary, the SA can be etched as thick films by pulsing the oxygen flow rate at a frequency below
50 mHz. By pulsing the reactive gas, the time averaged value of the [O]/[O2] ratio is decreased, limiting the functionalization processes due to oxygen atoms, and the mean temperature is lowered, decreasing
the diffusion length of O2 (and/or possibly O2*) species in the SA which are responsible for the scission of C–C bonds of radicals. 相似文献
14.
A new class of reactions of molecular oxygen O2 + ZH3I → O2ZH3 + I (Z = C, Si) proceeding by the mechanism of “inversion substitution” was investigated by quantum chemistry methods and
the transition state theory (TST). The profiles of the potential energy surfaces (PES) along the reaction coordinate and the
characteristics of transition states were calculated using the DFT approach with the B3LYP hybrid functional and the DZVP
basis set. The characteristics of the transition states were then used for TST calculations of the rate constants for the
direct and reverse “inversion substitution” reactions and their temperature dependences in the temperature interval 273–2000
K. The activation barriers to the substitution reactions under study were found to be substantially lower than the barriers
to the abstraction reactions O2 + ZH3I → ZH2I + HO2 (by 16.3 kcal mol−1 for Z = C and by 7.2 kcal mol−1 for Z = Si). The results obtained show that the “inversion substitution” reactions dominate over the abstraction reactions
in the interaction of molecular oxygen with carbon- and silicon-centered iodides as well as (probably) many other substrates.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1803–1807, September, 2008. 相似文献
15.
M. Kamal I. K. Battisha M. A. Salem A. M. S. El Nahrawy 《Journal of Sol-Gel Science and Technology》2011,58(2):507-517
A sol–gel process for producing monolithic silica–phosphate (SiO2–P2O5) system different concentrations of P2O5, starting with tetra-ethoxysilane TEOS, and triethyl-phosphate as sources of SiO2 and P2O5 was performed. The gels were heat-treated at temperatures ranging from 100 up to 900 °C. The structural and chemical analyses
of the samples were determined by using X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). It was
found from the XRD that the existence of phosphorus enhances the crystallization of silica gel, while the FTIR indicated the
main functional groups of silica–phosphate. It is important to study the effect of hydroxyl in silica–phosphate glass. The
results obtained are promising to use the prepared samples in a variety of applications, ranging from traditional application
such as lighting products) to the modern application (such as optical fibers. Optical studies were measured by using the spectrophotometer
in wavelength range 0.2–2.5 μm. The refractive index (n) was calculated for the prepared samples, it was found to be strongly affected by structural rearrangement resulting from
the elimination of the solvent and the Si–OH, Si–O–Si and Si–O–OH bonding by phosphate and aluminum and it increases by increasing
phosphate concentrations. The weight losses have investigated for prepared samples. 相似文献
16.
Yang Wang Dr. Fei Zhao Yi Zhou Yue Chi Dr. Zitao Wang Prof. Dr. Wen‐Xiong Zhang Prof. Dr. Zhenfeng Xi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(32):10643-10654
This study sheds light on the cleavage and reorganization of C(sp3)? H and C?N bonds of carbodiimides in a three‐component reaction of terminal alkynes, sulfur, and carbodiimides by a combination of methods including 1) isolation and X‐ray analysis of six‐membered‐ring lithium species 2‐S , 2) trapping of the oxygen‐analogues ( B‐O and D‐O ) of both four‐membered‐ring intermediate B‐S and ring‐opening intermediate D‐S , 3) deuterium labeling studies, and 4) theoretical studies. These results show that 1) the reaction rate‐determining step is [2+2] cycloaddition, 2) the C?N bond cleavage takes place before C(sp3)? H bond cleavage, 3) the hydrogen attached to C6 in 2‐S originates from the carbodiimide, and 4) three types of new aza‐heterocycles, such as 1,2‐dihydrothiopyrimidines, N‐acyl 2,3‐dihydropyrimidinthiones, and 1,2‐dihydropyrimidinamino acids are constructed efficiently based on 2‐S . All results strongly support the idea that the reaction proceeds through [2+2] cycloaddition/4π electrocyclic ring‐opening/1,5‐H shift/6π electrocyclic ring‐closing as key steps. The research strategy on the synthesis, isolation, and reactivity investigation of important intermediates in metal‐mediated reactions not only helps achieve an in‐depth understanding of reaction mechanisms but also leads to the discovery of new synthetically useful reactions based on the important intermediates. 相似文献
17.
Michael Santiago Cintrón Glenn P. Johnson Alfred D. French 《Cellulose (London, England)》2011,18(3):505-516
Quantum mechanics (QM) and molecular mechanics (MM) calculations were performed to elucidate Young’s moduli for a series of
cellulose Iβ models. Computations using the second generation empirical force field MM3 with a disaccharide cellulose model, 1,4′-O-dimethyl-β-cellobioside (DMCB), and an analogue, 2,3,6,2′,3′,6′-hexadeoxy-1,4′-O-dimethyl-β-cellobioside (DODMCB), that cannot make hydrogen bonds reveal a considerable contribution of intramolecular hydrogen
bonding to the molecular stiffness of cellulose Iβ; the moduli for DMCB and DODMCB being 85.2 and 37.6 GPa, respectively. QM calculations confirm this contribution with modulus
values of 99.7 GPa for DMCB and 33.0 GPa for DODMCB. However, modulus values for DMCB were considerably lower than values
previously reported for cellulose Iβ. MM calculations with extended cellulose chains (10–40 glucose units) resulted in modulus values, 126.0–147.5 GPa, more akin
to the values reported for cellulose Iβ. Comparison of the cellodecaose model, 1,4′-O-dimethyl-β-cellodecaoside (DMCD), modulus with that of its hydrogen bonding-deficient analogue, 2,3,6,2′,3′,6′-hexadeoxy-1,4′-O-dimethyl-β-cellodecaoside (DODMCD), corroborates the observed stiffness conferred by intramolecular hydrogen bonds; the moduli
for DMCD and DODMCD being 126.0 and 63.3 GPa, respectively. Additional MM3 determinations revealed that modulus values were
not strongly affected by intermolecular hydrogen bonding, with multiple strand models providing values similar to the single
strand models; 87.5 GPa for a 7-strand DMCB model and 129.5 GPa for a 7 strand DMCD model. 相似文献
18.
S. M. Ramsh A. G. Ivanenko V. A. Shpilevyi N. L. Medvedskiy P. M. Kushakova 《Chemistry of Heterocyclic Compounds》2005,41(7):921-928
Alkaline hydrolysis of 3-tert-butyl-7,7-bis(hydroxymethyl)-3,4-dihydro-2H-thiazolo[3,2-a][1,3,5]-triazin-6(7H)-one can occur in three directions: with cleavage of the tetrahydrotriazine ring, with cleavage of the
thiazolidine ring, and also with opening of both rings. Depending on the process conditions, either the hydrolysis product
corresponding to the first direction or the hydrolytic decomposition products corresponding to the second and third directions
can be obtained in preparative quantities. Hydrolysis of 3,3′-di-tert-butyl-3′,4′-dihydro-2′ H-spiro[(perhydro-1,3-oxazine)-5,7′-thiazolo[3,2-a][1,3,5]triazin]-6′-one in (NH4)2CO3 solution occurs in two steps: in the first step, cleavage of the tetrahydrotriazine ring occurs; and in the second step,
opening of the perhydrooxazine ring occurs.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1089–1097, July, 2005. 相似文献
19.
One-step conversion of cellobiose to C6-alcohols using a ruthenium nanocluster catalyst 总被引:1,自引:0,他引:1
Yan N Zhao C Luo C Dyson PJ Liu H Kou Y 《Journal of the American Chemical Society》2006,128(27):8714-8715
The one-step conversion of cellulose to C6-alcohols via green and energy efficient approaches has, as far as we are aware, not been reported. Such a process presents a considerable challenge, the two key problems being (1) finding a suitable solvent that dissolves the cellulose, and (2) the development of advanced catalytic chemistry for selective cleavage of the C-O-C bonds (glycosidic bonds) connecting glucose residues. The dissolution of cellulose has been recently realized by using ionic liquids as green solvents; there is still no efficient method, such as selective hydrogenation, for the precise C-O-C cleavage under mild conditions, however. Cellobiose is a glucose dimer connected by a glycosidic bond and represents the simplest model molecule for cellulose. We disclose in this communication that the one-step conversion of cellobiose to C6-alcohols can be realized by selectively breaking the C-O-C bonds via selective hydrogenation using a water-soluble ruthenium nanocluster catalyst under 40 bar H2 pressure. 相似文献
20.
D. A. Medvedev T. A. Zhuravleva A. A. Murashkina V. S. Sergeeva B. D. Antonov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(9):1623-1627
The phase composition, linear thermal expansion coefficient, electroconductivity (in the temperature interval 600–900°C and
partial pressures of oxygen 10−5–0.21 atm) of solid-oxide materials based on gadolinium-barium cobaltite doped with 3d-elements BaGdCo2 − x
Me
x
O5 + δ, Me = Cu, Fe; x = 0.0, 0.2, …, 2.0 were investigated. The homogeneity regions of samples were established by means of X-ray phase analysis.
It was shown that the linear thermal expansion coefficient of cobaltite decreases with an increase in the copper or iron concentration.
It was established that the electroconductivity of BaGdCo2 − x
Me
x
O5 + δ decreases with an increase in x. We concluded that upon a decrease in p(O2), the electroconductivity of samples first decreases and then reaches a horizontal plateau. 相似文献