利用粉煤灰研制高贝利特硫铝酸盐水泥

0前言无水硫铝酸钙(C4A3S)具有早强、高强的特性,而贝利特(β-C2S)具有形成温度低、后期性能好的特点,所以将C4A3S与β-C2S结合研制高贝利特硫铝酸盐水泥必将赋予水泥优异的性能,得到了越来越多的关注[1～3]。本研究用工业废弃料粉煤灰全部取代矾土进行配料,烧制出以β-C2S为主     

Protease stabilization by carboxylic acid salts: Relative efficiencies and mechanisms

Kinetic studies are presented on the inhibition of proteolysis by carboxylic acid salts on the synthetic substrate succinyl ala-ala-pro-phe-para nitroanilide. The inhibition of proteolysis/autodigestion is shown to be the major factor in the stabilization of a detergent protease [i.e., Maxatase (subtilisin Carlsberg)] in an unbuilt, liquid, heavy duty laundry formulation. The inhibition of autodigestion by a carboxylic acid salt as a function of pH parallels the protease stability increase during accelerated aging. Relative inhibition of proteolysis and protease stabilization by various carboxylic acid salts are compared.     

On the determination of belite in clinker by X-ray method

The results of β-C₂S analysis in clinker can be essentially distorted due to the overlap of potassium sulfate lines on analytical line 120. In case of significant quantities of K₂SO₄ in clinker β-C₂S determinations are suggested to be performed either on a sample washed by water or on the coarse fraction of clinker powder obtained by its separation on the sieve.     

感光材料稳定剂的作用机理

本文对几种稳定剂作用机理作了研究和讨论。一些化合物的稳定作用与 (AgAu)S感 光中心的吸附有关 ,而另一些化合物的稳定作用则与 AgX晶体表面的吸附有关,第三类化合物的稳定作用是由于氧化感光材料储存期间所生成的银颗粒 (灰雾中心 )。把不同性能的稳定剂组合使用能有效地改善感光材料的稳定性。     

感光材料稳定剂的作用机理

本文对几种稳定剂作用机理作了研究和讨论.一些化合物的稳定作用与(AgAu)S感光中心的吸附有关,而另一些化合物的稳定作用则与AgX晶体表面的吸附有关,第三类化合物的稳定作用是由于氧化感光材料储存期间所生成的银颗粒(灰雾中心).把不同性能的稳定剂组合使用能有效地改善感光材料的稳定性.     

PVC stabilization mechanisms in the light of practical results

Based on the mechanism of reaction, the function of PVC stabilizers and co-stabilizers is described. In particular, the differing light stabilization abilities of recognized heat stabilizers are demonstrated. Reasons for the differences observed are put forth with chemical explanations.     

An investigation of mechanisms of synergistic interactions in PVC stabilization

Synergism in poly(vinyl chloride) stabilization has been studied by measuring rates of hydrogen chloride evolution from samples of polymer in the presence of stabilizers in di-(2-ethylhexyl) phthalate solution in an inert atmosphere. Barium, cadmium, calcium, and zinc laurates, when used alone, allow escape of hydrogen chloride well before stoichiometric uptake is achieved, whereas synergistic mixtures of calcium–zinc and barium–cadmium laurates absorb almost the theoretical quantity of hydrogen chloride. Cadmium and zinc laurates replace labile chlorine atoms in the polymer backbone by ester groups, reducing formation of long polyene sequences: barium and calcium laurates delay the formation of cadmium and zinc chlorides, apparently by reconverting them into their respective laurates. Polyols function by forming complexes with the prodegradant cadmium and zinc chlorides, but contrary to popular belief phosphites possess little activity in this respect. Instead, they slow down the rate of polymer degradation by removal of labile chlorine atoms, by reaction with hydrogen chloride, and by peroxide decomposition.     

Transformation products of antioxidants: The role in stabilization mechanisms

Antioxidants acting in polymers by chain-breaking and hydroperoxide decomposing mechanisms are chemically transformed during the stabilization process as a consequence of trapping radicals R^?, RO^? or RO and/or reactivity with hydroperoxides. New chemical compounds with typical structures characteristic of the starting stabilizer are formed stepwise in the polymer mass. Most of these transformation products participate actively in consecutive steps of polymer degradation. Finally observed phenomena depend on the concentration of individual transformation products. Generally, autocooperative effects with starting stabilizers take place. Important data regarding properties of transformation products have been summarized.     

非水相体系泡沫的形成及其稳定性机理研究进展

阐述了非水相体系泡沫的形成及其稳定性机理理论研究进展,介绍和评述了表面活性剂、多相体系、改性纳米颗粒和沥青质等在非水相体系中的起泡机理。从不溶膜、体相粘度、Marangoni效应和泡沫破裂机制等四个方面阐述了非水相泡沫的稳定性机理,并指出了今后的研究方向。     

Uptake of Reactive Black 5 by pumice and walnut activated carbon: Chemistry and adsorption mechanisms

The potential of using pumice and walnut wood activated carbon as low-cost adsorbents for the removal of the diazo dye Reactive Black 5 (RB5) from aqueous solutions was investigated. The Langmuir isotherm fit to the data specified the presence of two different natures of adsorption sites with different binding energies on the AC-W surface. Kinetic modelling showed that the adsorption behaviour and mechanism of RB5 for both adsorbents is believed to happen via surface adsorption followed by diffusion into the pores of the AC-W and pumice. The main adsorption mechanisms are hydrogen bonding, electrostatic bonding and n–π interactions.     

Studies of reaction mechanisms during stabilization of electrospun polyacrylonitrile carbon nanofibers

Various reaction mechanisms such as cyclization, oxidation, dehydrogenation, and crosslinking are studied during stabilization of electrospun polyacrylonitrile nanofibers using different in situ techniques such as differential scanning calorimetry (DSC), shrinkage measurement, and dynamic mechanical analysis (DMA). DSC results show that oxidation preferentially occurs in cyclized structure. It is also found that the cyclization reaction has the highest activation energy followed by oxidation/dehydrogenation and crosslinking reactions. In situ shrinkage measurement and DMA data are used to study the extent of cyclization and cross‐linking reactions, respectively, in air. Comparing the in situ shrinkage measurement with DSC data, it is found that cyclization reaction in air progresses in two different mechanisms such as radical cyclization, which depends only on the temperature and ionic cyclization, which is limited by the rate of oxygen diffusion. It is found that complete cyclization time occurs at about 189 min for isothermal heat treatment at 260°C with 5°C/min ramp, while cross‐linking reaction becomes dominant at 132 min. POLYM. ENG. SCI., 58:1315–1321, 2018. © 2017 Society of Plastics Engineers     

Phase development in conventional and active belite cement pastes by Rietveld analysis and chemical constraints

High belite cements may be an alternative to reduce CO₂ emissions. Although CO₂ emissions may be depleted up to 10%, unfortunately, the hydration reactivity of belite phases is slow which leads to low mechanical strengths at early ages. In order to enhance their hydraulic reactivity, the activation of these cements by doping with alkaline oxides has been proposed. Here, we have synthesised a laboratory belite clinker without activation (47 wt.% of β-C₂S and 19 wt.% of α_H′-C₂S) and two alkaline oxide activated clinkers (one with 13 wt.% of β-C₂S, 24 wt.% of α_H′-C₂S and 19 wt.% of α-C₂S; and the second with 12 wt.% of β-C₂S, 42 wt.% of α_H′-C₂S and 5 wt.% of α-C₂S). We have also developed a methodology to analyse quantitatively the phase evolution of cement pastes and we have applied it to these high belite cements. Rietveld quantitative phase analysis of synchrotron X-ray powder diffraction data, together with chemical constraints, is used to determine the phase development up to 1 year of hydration in the belite cement pastes. β-C₂S almost does not react during the first 3 months, meanwhile α_H′-C₂S reacts on average more than 50% in the same period. Moreover, the degree of reaction of α-C₂S is slightly larger (on average about 70% after three months) than that of α_H′-C₂S. Full phase analyses are reported and discussed including the time evolution of amorphous phases and free water.     

A review of alkali-silica reaction and expansion mechanisms 2. Reactive aggregates

Recent literature on the properties of aggregates that take part in alkali-silica or alkali-silicate reactions is reviewed, with special emphasis on those features which are thought to influence the mechanisms and kinetics of the alkali attack.     

Determination of the quantitative phase composition of alite and belite in portland cement clinker by microphotometry

In the light of the growing technical interest in the phase constitution of alite and belite in portland cement clinker, an optical method for determining the quantitative phase composition has been proposed. The change in birefringence upon transition between the relevant phases (M₁ to M₃ for alite and α to α′ for belite) is utilized for this purpose. In the present method the birefringence change with temperature has been recorded by microphotometry as the corresponding change in the integrated light intensity from a large number of grains in the field of view.     

Effect of doping polyacrylic acid with some dopants as studied by different techniques

The molecular weight of polyacrylic acid (PAA) was determined by a viscometric method using NaNO₃ as solvent at 30°C. The specific electric conductivities (σ) of PAA as well as PAA doped with carbon black (CB), chromium oxide (Cr₂O₃), and cupferron with different concentrations (from 0.25 to 1 wt %) were measured at a temperature range 360–400 K. IR spectra of some polymers were determined and it was shown that when PAA was doped with 0.5 wt % CB, a C? O? C band appeared at 775–875 cm^?1. The positron annihilation lifetime (PAL) spectra in PAA doped with the above‐mentioned dopants were measured as a function of their concentrations. It was observed that the short lifetime intensity I₁ decreased, whereas the intermediate lifetime intensity I₂, which is related to the conductivity of the material, increased with increasing the wt % of Cr₂O₃ and cupferron as well as at low concentrations of CB. These results are discussed in terms of the conducting island model. It was found that there were distinct positive relationships between σ and I₂. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 877–883, 2002; DOI 10.1002/app.10381     

Electrical properties and ageing characteristics of BaTiO3 ceramics doped by single dopants

BaTiO₃ ceramics doped by single dopants of Sm₂O₃, Ho₂O₃, Bi₂O₃, La₂O₃, CeO₂ and Ta₂O₅, respectively, were prepared and aged in air. The room-temperature resistivity was measured and the relationship between resistivity change versus ageing time was determined. The electrical resistivity of Bi- and Ta-doped samples decreases at the early ageing stage, and then increases with the ageing time; the other doped ceramics display a monotonous increase of the resistivity with ageing time. The electrical properties and ageing characteristics are analyzed by considering interior oxidation and reduction reactions and the electronegativity of the doping elements.     

Methyl methacrylate stabilization by sodium borohydride

Sodium borohydride was examined as a polymerization inhibitor for methyl methacrylate and found to be more effective than hydroquinone-type inhibitors in preventing polymerization during monomer storage under nitrogen at elevated temperature. NaBH₄ appears to function by reducing peroxide and hydroperoxide impurities that form during monomer storage. Unlike conventional free radical inhibitors, NaBH₄ does not interfere with azo initiator systems. In peroxide-initiated systems, the inhibitory effect of NaBH₄ can be overcome by simple acidification.     

稀土复合稳定剂在PVC加工中的应用及稳定机理探讨

研究了以氯化钕为代表的稀土稳定剂在PVC加工中的应用情况 ,提出了稀土稳定机理 ,并介绍了应用稀土稳定剂生产出合格的UPVC饮用水管。     

Effect of dopants on the properties of metal-doped zirconia prepared by the glycothermal method

The effects of dopants on zirconia prepared via the glycothermal method were investigated by XRD to determine the crystal structure and crystallite size. Morphologies of products were observed by SEM. The basic sites of zirconia were studied by CO₂-temperature programmed desorption (CO₂-TPD). The functional group in the samples was determined using IR. The intensity of Zr³⁺, characterized by ESR, could be described as the oxygen coordinatively unsaturated Zr sites. The results suggest that doping elements can modify the surface chemistry of ZrO₂ to form hydroxyl groups and surface energies depending on the structure (cubic, tetragonal) in different dense phase. ESR peaks of Pb- and Bi-doped zirconia are different from the others, which showed high intensity of Zr³⁺.