Effect of hydroxyl content on the physical properties of calcium metaphosphate glasses

The hydroxyl (OH) content of calcium metaphosphate glasses has been controlled in the range 50–800 ppm by melting calcium dihydrogen phosphate in air, under vacuum and with fluoride addition. Density, refractive index and glass transition temperature of the glasses increase with decrease in OH content while the coefficient of thermal expansion remains almost unchanged. With gradual decrease in OH, the UV cutoff initially shifts towards shorter and finally towards longer wavelengths. IR spectroscopic study shows that the OH groups exist exclusively in the hydrogen bonded states. Correlations of the glass properties with OH content have been explained in terms of structural rearrangement leading to the change in P-O bond length and O-P-O/P-O-P bond angles of the PO₄ tetrahedral units of (PO ₃ ⁻ ) _n chains. These changes are caused due to conversion of non-bridging oxygens (NBOs) of the H-bonded OH groups into bridging oxygens (BOs) during progress of dehydroxylation.     

高羟基含量苯丙乳液聚合工艺稳定性研究

鉴于某种特殊功能涂料的应用,采用预乳化工艺和半连续种子乳液聚合技术,以过硫酸铵为引发剂,合成了羟基含量在48%左右的St-MMA-BA-AA-HEMA五元共聚苯丙乳液,重点考察了乳化剂的种类和用量、种子单体用量、单体滴加工艺、预乳化单体滴加速率和搅拌速率对乳液聚合工艺稳定性的影响.     

Type,stability, and acidity of hydroxyl groups of HNaK-erionites

The concentration and acid strength of the hydroxyl groups of a series of HNaK erionites have been investigated by means of temperature programmed activation (t.p.a.), temperature programmed desorption (t.p.d.) of ammonia, and transmission absorption i.r. spectroscopy. With an increasing degree of NH₄⁺ exchange, primarily Na⁺, at first, and, subsequently, K⁺ cations are replaced. During activation of these materials, NH₃ desorbs in a temperature interval from 540 to 900 K, leading to hydroxyl groups. However, it is impossible to decompose NH₄⁺ quantitatively without dealumination, if the degree of NH₄⁺ exchange is higher than 85%. Five types of hydroxyl groups are present, characterized by i.r. bands at approximately 3741, 3691, 3660, 3618-3608, and 3566 cm⁻¹. The assignment of these bands is discussed. Only the OH groups represented by the bands at 3660, 3618–3608, and 3566 cm⁻¹ adsorb ammonia under the conditions employed. The concentration and strength of the bridging hydroxyls (3618-3608 cm⁻¹), associated with framework Al³⁺, increase with increasing degree of ion exchange.     

Quantification of hydroxyl content in ceramic oxides: a prompt gamma activation analysis study of BaTiO3

Thermogravimetric analysis (TGA) and Fourier transform-infrared spectroscopy (FT-IR) techniques for water content determination were compared with a neutron characterization technique, prompt gamma activation analysis (PGAA). Residual H content in the samples, heat treated at various temperatures, was measured with PGAA and compared with the results obtained from TGA. Two major difficulties in TGA were overlapping of mass loss regimes due to removal of different species and residual water that could not be removed, even though the samples were heated above 900 degrees C. After 3 h of heat treatment at 900 degrees C, 0.007% mass fraction H remained in the sample. FT-IR spectra confirmed the presence of H semiquantitatively. It is concluded that residual H remains even after high-temperature treatments.     

The water vapour sorption behaviour of acetylated birch wood: how acetylation affects the sorption isotherm and accessible hydroxyl content

The water vapour sorption isotherms and sorption kinetics of birch (Betula pendula L) acetylated to different levels have been determined using a dynamic vapour sorption (DVS) apparatus. A DVS instrument was also used to determine the accessible hydroxyl content in the wood samples using deuterium exchange. The results are reported in terms of the reduced equilibrium moisture content (EMC_R), in which the moisture content per unit mass of wood substance is used for the calculation. As the level of acetylation of the wood samples increased there was a corresponding reduction in EMC_R of the wood samples, which was accompanied by a decrease in hysteresis in the same order. The sorption kinetics were also determined using the DVS and analysed using the parallel exponential kinetics model, in which the sorption kinetics curve is composed of two processes (labelled fast and slow). Using this analysis, it is possible to calculate two pseudo-isotherms associated with the two processes. The sorption isotherm is a composite of the sorption isotherms associated with the fast process water and the slow process water and there are significant differences in behaviour between the two. It is suggested in this paper that the fast process is related to diffusion limited kinetics, whereas the slow process is a relaxation-limited phenomenon. The reduction in accessible OH content due to acetylation was well correlated with the weight gain due to acetylation, although the relationship did not exactly correspond with that theoretically determined.     

Equilibria of hydroxyl defects in MgO

Isochronal annealing studies were carried out on slow-cooled MgO single crystals. The annealing behaviour of the hydroxyl defects is consistent with a defect model in which brucite precipitates dissolve in MgO forming OH-V-OH defects with a heat of solution equal to 0.45 eV. These OH-V-OH defects further dissociate into V _OH ^– defects and hydroxyl ions with a dissociation energy of 0.82 eV.     

Pycnogenol inhibits macrophage oxidative burst, lipoprotein oxidation, and hydroxyl radical-induced DNA damage

Pycnogenol (procyanidins extracted from Pinus maritima) has been reputed as a potent free-radical scavenger and an antioxidant phytochemical. We previously reported that pycnogenol prevents vascular endothelial cells from injury induced by an organic oxidant t-butyl hydroperoxide. In this study, we determined the effects of pycnogenol on (a) oxidative burst of macrophages, (b) oxidation of plasma low density lipoprotein (LDL), and (c) hydroxyl radical-induced breakage of plasmid DNA. Pycnogenol was incubated with J774 murine macrophages at 37 degrees C and 5% CO2 and oxidative burst was triggered by zymosan. The intensity of fluorescence was measured. Pycnogenol exhibited a concentration-dependent inhibition of oxidative burst. CuSO4 was used to oxidize human plasma LDL and the formation of thiobarbituric acid reactive substances (TBARS) was determined. Co-incubation with pycnogenol resulted in a concentration-dependent inhibition of LDL oxidation. Exposure of pBR322 plasmid DNA to iron/ascorbic acid system resulted in cleavage/damage of DNA by hydroxyl radical, measured by agarose gel electrophoresis. Pycnogenol significantly minimized this cleavage. The results indicate that pycnogenol exhibits an extensive antioxidant effect in all three in vitro systems.     

羰基、羧基和羟基表面官能团对碳纳米管电容量的影响

分别采用混酸、空气、硝酸和高锰酸钾对碳纳米管进行氧化处理,以在其表面引入官能团,进而研究了表面官能团对碳纳米管电化学性能的影响.X-射线光电子谱分析表明:混酸氧化处理引入的官能团主要为羰基和羧基;空气氧化使碳纳米管表面链接较多的羟基,但羰基和羧基的含量最少;而硝酸处理和高锰酸钾处理引入了中等数量的羰基和羧基.经四种处理方法所得碳纳米管具有相近的比表面积和孔结构.通过比较它们的比电容发现:羰基和羧基贡献了最多的准电容,尤其羰基含量与碳纳米管的电容量呈正比关系;而羟基主要增强了双层电容,并未引入明显的准法拉第容量.由于羰基和羧基比羟基具有更低的电荷传递电阻,有利于快速的法拉第反应,从而引入准电容.     

Effects of hydroxyl group distribution on the reactivity, stability and optical properties of fullerenols

We investigate the impact of hydroxyl groups on the properties of C(60)(OH)(n) systems, with n = 1, 2, 3, 4, 8, 10, 16, 18, 24, 32 and 36 by means of first-principles density functional theory calculations. A detailed analysis from the local density of states has shown that adsorbed OH groups can induce dangling bonds in specific carbon atoms around the adsorption site. This increases the tendency to form polyhydroxylated fullerenes (fullerenols). The structural stability is analyzed in terms of the calculated formation enthalpy of each species. Also, a careful examination of the electron density of states for different fullerenols shows the possibility of synthesizing single molecules with tunable optical properties.     

Low-temperature behavior of alkali halides doped with hydroxyl

The low-temperature dielectric dispersions of LiF, NaCl, KCl, and KBr have been measured for different concentrations of OH^?. With decreasing tunnel splitting of the OH^? levels, and with increasing dipolar interaction, a behavior is observed below ～1 K similar to that found in amorphous materials and attributed to two-level states (TLS). Differences between OH^? and TLS are noted, the main difference being that the broad spectrum of energy levels associated with the OH^? in alkali halides arises from dipolar interactions rather than an atomically disordered environment. It is argued that an electric dipole analog of the magnetic spin-glass state does not occur in the OH^? systems.     

Langmuir-Blodgett films of ethylenedithiotetrathiafulvalene derivative containing hydroxyl groups

Langmuir-Blodgett (LB) films of an ethylenedithiotetrathiafulvalene (EDT-TTF) derivative containing hydroxyl groups, 4, 5-bis(11-hydroxyundecylthio)-4′, 5′-ethylenedithiotetrathiafulvalene were deposited without using stabilizer molecules. Doping of the film with iodine leads to oxidation of EDT-TTF moiety as evidenced by UV-vis and IR spectroscopy. X-ray diffraction studies reveal the presence of layered arrangement of the EDT-TTF derivative molecules in the LB film. Cyclic voltammetry studies indicate that the electrochemical oxidation of the EDT-TTF derivative in its LB film is irreversible. Due to the insulating nature of the alkyl chains, only the first layer of the LB film was found to be redox-active. The electrical conductivity of the 25 layer LB film was found to increase by two orders of magnitude on doping with iodine. On equilibrating the doped film in air, the conductivity gradually reduced with time and finally reached the conductivity of undoped film. This reversibility could be because of the steric hindrance induced by the two long alkyl groups. The alkyl chains help in rendering the EDT-TTF molecule amiable to LB film formation but are found to reduce the electrical conductivity of the films and also cause instability of the doped state. The hydroxyl groups at the end of the alky chain impart amphiphilic nature to the molecules and help in stabilizing the film at the air-water interface.     

羟基封端的有机硅低聚物的合成

采用甲基三乙氧基硅烷,二甲基二乙氧基硅烷,苯基三乙氧基硅烷为原料,通过水解-缩合反应合成一种羟基封端的有机硅低聚物,并初步研究了有机硅低聚物的合成条件。实验表明:反应温度为70℃,时间为4h,pH为3,可合成羟基封端的有机硅低聚物。红外光谱表明,合成的有机硅低聚物在Si-OC2H5及Si-O-Si处都出现吸收峰,其结构与理论基本相符。     

Magnetism in oxidized graphenes with hydroxyl groups

The magnetic properties of three oxidized graphene structures with hydroxyl groups (cases A, B and C) have been investigated through spin-polarized density functional theory. The results reveal that in a graphene hexagonal ring structure, chemical bond formation by two non-neighbored hydroxyl-bonded carbon atoms with one carbon atom between (case B) can cause unpaired spins to produce a magnetic moment of 1.2 μ(B), while chemical bond formation by two neighbored hydroxyl-bonded carbon atoms (case A) or non-neighbored hydroxyl-bonded carbon atoms with two carbon atoms between (case C) cannot generate unpaired spins for nonmagnetic states. These magnetic oxidized graphenes have great promise for new spintronics. This work provides fundamentals to controllably synthesize or/and oxidized graphene with hydroxyl groups at specific carbon positions for magnetic properties.     

Quantitative technique for imaging mixture fraction, temperature, and the hydroxyl radical in turbulent diffusion flames

A technique for obtaining simultaneous quantitative images of the hydroxyl radical, OH, temperature, mixture fraction, and scalar dissipation rates in turbulent diffusion flames is described. Mixture fraction is obtained from images of Rayleigh and fuel Raman scattering. We quantified the OH laser-induced fluorescence (LIF) images using detailed calibration and a correction for quenching and population distribution effects based on the simultaneous mixture fraction and temperature images. This correction was derived from calculations of laminar counterflow diffusion flames for identical fuel mixtures. These laminar flame computations are further used to estimate the errors in the measured OH concentrations. The technique is applied to piloted, nonpremixed flames over a range of jet velocities. The measured mixture fraction, temperature, and OH concentrations are in good agreement with those obtained earlier in similar flames using the single-point Raman/Rayleigh/LIF technique.     

Effect of martensite content,its dispersion,and epitaxial ferrite content on Bauschinger behaviour of dual phase steel

Abstract

Dual phase microstructures were produced in a low carbon steel, in which the martensite volume fraction was kept constant at two levels, of 18 and 25%, while the epitaxial ferrite content was varied independently. The microstructures were produced with two dispersions of martensite, a relatively coarse dispersion by intercritical annealing of a ferrite/pearlite starting microstructure and a finer dispersion from an initial martensitic microstructure. Bauschinger tests were conducted using prestrains in both tension and compression of 0.4, 1, and 2.2%. Prestrain direction had no measurable effect on plastic flow behaviour after strain reversal. Mean back stresses increased with increasing strain and martensite content, and were higher for the finer martensite dispersion. They decreased significantly with increasing epitaxial ferrite content in the case of the finer dispersion, but less significantly in the coarser dispersion. These effects of microstructure are discussed in terms of stress transfer to martensite, work hardening, and tensile properties. It is concluded that about half of the mean back stress developed during early plastic deformation was generated by stress transfer to the martensite, the remainder arising from strain hardening of the matrix. A small permanent softening in the Bauschinger test resulted from a reduction of effective stress in the ferrite matrix when the strain path was reversed.     

Influence of sand grading,fines content and clay content on properties of sand-gypsum mortar

The paper summarizes a series of tests carried out on gypsumsand mixes—made of crushed dolomitic stone sand and retarded hemihydrate—seeking answers to the following questions:

1. Does the sand grading affect mortar properties?
2. How do the fines (fraction passing No. 100 sieve) affect mortar properties?
3. How does the clay content influence the properties of mortars?

Evaluation criteria for the hardened mortars were: flexural and compressive strength, hardness and linear change.     

羟基硅油改性聚丙烯酸酯粘合剂的制备与表征

采用种子乳液聚合法制备了一种新型羟基硅油改性丙烯酸酯粘合剂,并讨论了有机硅用量对乳胶膜的耐水性和耐溶剂性的影响;比较了羟基硅油改性前后粘合剂的力学性能,通过红外光谱和透射电镜分析了改性后的粘合剂的结构和形貌.结果表明,羟基硅油改性后粘合剂的耐水性、耐溶剂性和力学性能得到改善.红外光谱分析表明,羟基硅油与丙烯酸酯以Si-O-C键结合;透射电镜分析表明,其有明显核壳结构.     

可溶性含羟基聚酰亚胺的制备及其性能研究

合成了含羟基的二胺单体4,4′-二氨基-4″-羟基三苯甲烷(DHTM),并将该单体分别同六氟异叉丙基二苯四羧酸二酐(6FDA),3,3′,4,4′-二苯醚四羧酸二酐(ODPA)和4,4′,-二(4,4′,-异丙叉二苯氧基)四羧酸二酐(BPADA)反应制备了3种结构的聚酰亚胺。溶解性实验表明,这3种聚合物在非质子极性溶剂中均显示出良好的溶解性。此外,还对聚酰亚胺薄膜进行了拉伸和动态机械热性能测试。