ON THE MECHANISM OF CO2 ABSORPTION AND DESORPTION

Recent work by Thomas et al. (1982) showed a significant difference in mass transfer rates between absorption and desorption for a CO₂-water system in a film flow, and attributed the phenomena to density-driven convection. Our experiment with a flat-surface stirred cell shows no enhancement of oxygen absorption in simultaneous absorption with CO₂ under a turbulent flow condition. Also, a comparison of liquid velocities measured extremely close to the gas-liquid interface with a laser doppler anemometer reveals negligible difference between absorption of air and that of CO₂. These results indicate that there is practically no detectable density-driven convection in CO₂ absorption.     

POROSITY: V. RECOMMENDED PROCEDURES FOR DETERMINING POROSITY BY METHODS OF ABSORPTION

Detailed Procedure. —For shaped test pieces details of the procedure are given under the headings. “Preparation of Test Piece.”“Determination of Dry Weight,”“The Absorption Apparatus,”“Preparation of Standard Vaseline,”“Saturation Procedure,”“Calculation,” and “True Density.” A Pycnometer Method. —A new and accurate method, which is applicable equally to shaped test pieces or to granular material, is described. Among other advantages it gives the operator control over the max. size opening which he desires to class as part of the pore space. It also can be made to indicate directly the necessary soaking period.     

POROSITY IV: THE USE OF PETROLEUM PRODUCTS AS ABSORPTION LIQUIDS

Advantages of petroleum products .—-Avoidance of: slaking, chemical reaction, adsorption, and solvent action; but longer soaking time is required. Paraffine and vaseline .—-Materials having high fluidity when hot, and comparatively low fluidity when cold, permit surface of saturated test piece to be brought to definite and reproducible condition with all surface pores full. Paraffine may be used but vaseline is preferable because it undergoes no change of phase on cooling. Procedure and results .—-A saturation procedure is described and comparative results given. Density and penetrativity of vaseline .—-Sp. gr.23°/4° 0.8730, 32°/4° 0.8684, 42°/4° 0.8624. Penetrativity between 100° and 200°C = 0.063 (t— 30)² cms./sec. A penetratimeter for determining the penetrativity of liquids is described     

A THEORETICAL INVESTIGATION OF THE EFFECTS OF VARIABLE POROSITY AND DIFFUSIVITY ON THE MANUFACTURE OF REACTION-BONDED SILICON NITRIDE

Transient behaviour of the exothermic, irreversible silicon-nitrogen reaction has been simulated using a particle-pellet model which incorporates a sharp 'cut-of T reaction into the moving reaction zone in the heat mass transfer Held. Variations of certain physical parameters connected with the micro-structural changes during reaction, with respect to temperature and/or solid concentration are taken into account. The solution procedures to the resulting system or equations are based on an explicit finite difference scheme. Effects of the Thiele modulus and Biot number for heat transfer on the solid conversion and fluid concentration are examined, together with the effect of a zero heat of reaction on the temperature profiles in the compact. The results are graphically presented and interpreted.     

POROSITY: VII. THE DETERMINATION OF THE POROSITY OF HIGHLY VITRIFIED BODIES43

Design and Accuracy .—The accuracy limitations of the general laboratory research type of porosimeter are discussed and the principles of design indicated. McLeod-Gauge Type of Porosimeter .—A new type of porosimeter is described with which the pore volume of any test piece may be directly determined within 0.01–0.02 cc. Results with Electrical Porcelain .—Tests of eight pieces of electrical porcelain indicated a porosity of 0±0.01 per cent. This result was confirmed by dye penetration tests. An Apparatus for Measuring the Porosity of Full Size Brick .—A simple and rapid apparatus for measuring the porosity of full size brick by the “General Method”(Jour. Amer. Ceram. Soc., 5, 113–16 (1922)) is figured and described.     

POROSITY: III. WATER AS AN ABSORPTION LIQUID

Classes of absorption method .—The ordinary immersion method has been shown by previous investigators to be unreliable. Simple immersion in low vacuo without boiling is also shown theoretically to be unreliable. An analysis of the results of previous investigators indicates the presence of unsuspected sources of error. Effect of adsorbed gases upon dry weights of test pieces .—Dry air is shown to be without appreciable influence. Depending upon the humidity of the atmosphere, adsorbed water vapor may cause errors up to 2 per cent in the porosity value. Perfectly dry fired clay will remove water from conc. H₂SO₄, and from fused CaCl₂. Saturation by boiling at atmospheric pressure .—A one hour's (and in one instance a 5 hours') boiling failed to saturate completely. On continued boiling the saturated weight increases linearly with the time and this in spite of the fact that appreciable quantities of dissolved materials are removed from the test piece by the hot water. This result is shown to be due to a gradual and continuous rehydration of the clay by the hot water. The error from this factor may amount to as much as 3% and the error from dissolved materials to as much as 2%, during a 3 hours' boiling. The nature of the dissolved material was determined. Method of cooling the test piece .—It is recommended that the test piece be kept in a closed vessel over 95% sulphuric acid for several hours before its dry weight is taken. Saturation procedure .—A vacuum method is described in which water may be employed as the saturation liquid under conditions where the above sources of error are reduced to a minimum. The method is not however recommended as a primary standard. Necessity of a soaking period .—It is shown from theoretical considerations that a soaking period is necessary and methods are given for calculating and for measuring the minimum soaking period required for a given test piece and a given liquid of known penetrativity.     

POROSITY: VI. DETERMINATION OF POROSITY BY THE METHOD OF GAS EXPANSION*

Theory of the method. —The pore volume is measured by allowing the gas which fills the pores to expand into a measured volume and measuring the accompanying fall in pressure. Applicability. —The method is in general applicable to pieces of any size and shape and to all classes of porous bodies or materials. A new porosimeter. —For rapid work with shaped test pieces a new porosimeter is described. The new instrument measures accurately both pore volume and bulk volume. A complete porosity determination can be made in 5 minutes. No weighing is required. The results on ceramic bodies arc reproducible to one unit in the first decimal place of the per cent porosity. Considerably higher accuracy than this can be secured if desired. Results. —The results obtained with the new method are in all cases higher, in a number of cases very much higher, than those obtained by the methods of liquid absorption in current use. For fired bodies the same results are obtained with dry air, hydrogen or helium as the pore filling gas. The results show conclusively that complete filling of all the pores in a reasonable time can not be secured by any of the current methods using a liquid as the pore filling agent.     

活性碳纤维氧化还原机理初探

在系统研究了活性碳纤维(ACF)氧化还原功能特征的基础上,进一步利用 X 射线衍射、红外、核磁及化学分析等技术,研究了 ACF 在惰性气氛中,非水介质中的氧化还原特性以及ACF 比表面积、表面官能团、水等对氧化还原性能的影响,从面对 ACF 的氧化还原反应机理提出了一些新的见解。实验结果表明,ACF 的氧化还原功能与空气(氧等)的吸附无关,主要是由于 ACF 表面的官能团所引起,其官能团不仅仅是≥C—OH,在有水存在时,≥C—H、甚至>C=O 也参与氧化还原反应,并且还是主要的反应.水对氧化还原容量影响甚大.ACF 的氧化还原容量随比表面积变化不大。     

统计力学在探讨缓蚀机理中的应用——Ⅰ.Temkin吸附等温式的统计力学推导

本文分析了吸附等温式的统计力学推导在探讨缓蚀机理中的作用,在此基础上提出了吸附分子间互作用模型,并根据这个模型,利用统计力学中的系综理论,推导出Temkin吸附等温式θ=RT/αln(AP)。最后从吸附热与复盖分数之间的关系,论证了推导得到的理论公式的正确性。     

双通道放电等离子体对酸性嫩黄的脱色规律及机理研究

以偶氮染料酸性嫩黄水溶液为例,采用低温等离子体技术,在自行设计的双通道放电等离子体装置中考察双通道放电低温等离子体降解染料废水的影响因素及反应机理.结果表明,相同放电时间下随电极距液面间距减少,废水脱色率增高;随着液层厚度的增大,初始质量浓度的增大,在相同放电时间下脱色率会降低,但随着时间的延长,脱色率都可达到90%以上;pH对脱色率的影响不大.研究表明自行设计的双通道放电等离子体装置对模拟酸性嫩黄染料废水的脱色率高,同时具有处理时间短、对废水的操作条件较宽、不受pH限制等优势.此外进一步验证了等离子体技术对染料废水脱色的主要因素是羟基自由基.     

NiNb2O6半导体电极的能级结构和腐蚀机理研究

本文通过测量伏安特性和光谱响应了被还原的ｎ型ｎ型ＮｉＮｂ２Ｏ６半导体晶电极的光电化学物质及其能级结果。观察到两个吸收带，强者在３．２４ｅＶ，对应于氧－铌跃廷；弱者在１．７５ｅＶ，在可见光区，对应于镍－铌跃迁，探讨了阳极暗腐蚀、光腐蚀和水的光电解机理，缓出了ＮｉＮｂ２Ｏ６的电子能级和主主要的裂解能级。     

Permit法研究氯离子渗透性及其与混凝土孔隙率的关系

应用渗透法(permeation migration,Permit)及快速氯离子迁移法(rapid chloride migration,RCM)研究了水胶比及粉煤灰掺量对混凝土抗氯离子渗透性的影响。通过对比试验,分析了Permit方法与RCM方法试验结果之间的相关性。采用可蒸发水含量法测试了混凝土相应的孔隙率,分析了Permit试验结果与混凝土孔隙率的关系。结果表明:Permit试验测定的混凝土氯离子渗透性指标与RCM试验结果及粗毛细孔孔隙率均具有良好的对应关系。由于是无损检测方法,用于现场测试Permit方法比RCM法更具优越性。     

THE DETERMINATION OF POROSITY OF CHINA BY THE WATER SOAKING METHOD1

Comparative tests show that prolonged soaking is more effective than boiling in attaining saturation of nearly vitrified ware, and a period of 4 days' immersion in cold water is recommended.     

陶瓷防护树脂基复合材料的磨损性能及机理研究

为了提高树脂基复合材料的耐磨损性能,采用Al2O3陶瓷贴片制备了陶瓷防护复合材料,通过往复式摩擦磨损试验机对陶瓷片材和复合材料进行了磨损性能试验,得到了防护复合材料在不同加载参数下的磨损形貌,进一步采用三维白光干涉表面形貌仪测试了磨损试样的表面形貌、磨痕深度与宽度,并据此建立了磨损性能数据分析与评价模型,分析了防护复合材料的耐磨损机理。结果表明:复合材料采用陶瓷贴片进行防护可大大提高其耐磨损性能,经陶瓷防护后,复合材料的可承受加载载荷从40 N提高至100 N;随着载荷的进一步增加,陶瓷防护复合材料的磨痕深度大大增加,而钢球的磨损程度迅速下降,其磨损机制发生了变化。分析了造成复合材料磨损性能发生变化的原因。     

THE MECHANISM OF SPALLING1

A study has been made of the stresses and fractures developed in a solid when rapidly heated or cooled. The stresses were measured in bakelite specimens by the photoelastic method. High stresses in all cases were found to occur near the surface of the solids, but no high tension stresses were present when the specimens were being heated. A number of vitreous clay spheres and bricks were heated and cooled rapidly and the nature of the cracks was noted. In practically every case the fractures occurred as predicted from the measured stresses. Torque-deflection curves were obtained for a number of fire brick in torsion at different temperatures. The temperature at which plastic flow occurs for every material tested was approximately the same as the temperature of the initial deflection under compressive loads in a standard load test.     

自蔓延高温合成Ni-Zn铁氧体反应机制的研究

采用“气窒法”实现燃烧波的“淬熄”，获得了自蔓延高温合成Ni-Zn铁氧体中不同阶段的燃烧产物，对燃烧产物进行XRD分析，并结合热力学和TG－DTA分析，探讨了自蔓延高温合成Ni-Zn铁氧体的反应机制，研究结果表明，Fe粉在高压氧气下被氧化生成Fe2O3并放出大量的热，使自蔓延反应进行，同时Fe2O3与ZnO,NiO接触，以溶解析出和扩散机制形成Ni-Zn铁氧体。     

脂环族环氧化物的合成与应用(1)──脂环族环氧树脂性能及其固化机理

本文论述了（ERL－4221,Unox201,Unox269,Unox206和Unox207等）脂环族环氧树脂的性能、固化机理及应用。与双酚A型和酚醛型环氧对比可以看出,脂环族环氧树脂具有粘度低、耐热性好、电气优良等特点,其可用作稀释剂、粘接剂,并在灌封浇铸料、玻璃钢层压制品,缠绕制品和涂料中广泛应用。     

高强度低气孔率耐酸砖的研制与生产

本文详细叙述了高强度低气孔率耐酸砖的研制过程,指出合适的原料是生产该砖的关键所在。研制的耐酸砖主要性能指标为:耐压强度≥70MPa,显气孔率5～8％,耐酸度≥98％。为国内大型烟囱的内衬砌筑提供了优良的建筑材料。     

THE DIELECTRIC STRENGTH OF PORCELAIN: THE INFLUENCE OF POROSITY*

This work utilized the samples used by Monack, Shardlow, and Warnsley in previous experiments.¹ Between cones 7 and 10, the dielectric strength was found to be inversely proportional to the per cent apparent porosity. Between cones 10 and 15 the dielectric strength increased gradually while the apparent porosity remained essentially zero. No relation existed between dielectric strength and total porosity (open and closed pores). Overfiring does not seem to decrease the dielectric strength unless a definite vesicular structure is developed.