Effects of submicrometer particulate silica addenda on the adhesion of micrometer-size particles to a polyester-composite substrate

The force needed to detach five sets of different size particles, having number-averaged diameters between 3.6 and 8.5 µm, from a composite substrate was measured using an ultracentrifuge. In addition to size variations, the asperity concentration for each size particle was adjusted by varying the silica concentration, adjusted so that the surface area concentration at each level was kept constant for the five sizes of particles. Due to the changing silica concentration and particle size, the charge per particle also varied. It was found that the detachment force appeared to be virtually independent of charge, with any correlation actually appearing slightly negative, if anything. However, the detachment force increased monotonically with increasing particle diameter and decreased monotonically with increasing silica concentration. Moreover, upon normalizing the detachment force to the particle diameter and the silica concentration to the surface area concentration of silica, it was found that the detachment force clustered into groups in which the force needed to separate the particle from the substrate depended only on the silica concentration. These results suggest that van der Waals interaction, rather than electrostatic forces, are the dominant mechanism controlling toner adhesion in this instance.     

EXPERIMENTS ON CONTACT OF A LOOP WITH A SUBSTRATE TO MEASURE WORK OF ADHESION

A technique for characterizing surface energies of solid materials is investigated experimentally and numerically. A narrow strip is bent into a loop, pushed into contact with a flat substrate, and then pulled off the substrate. Provided the loop is sufficiently flexible, the size of the contact zone during this process was expected to depend on the interfacial interactions. Larger adhesion forces should tend to increase the contact size, in a manner analogous to the JKR technique. The experiments involve a poly (dimethyl siloxane) (PDMS) loop and glass substrates with various coatings. Anticlastic bending of the loop affects the contact zone. Hysteresis is observed between the loading and unloading data. A three-dimensional finite element analysis is conducted in which adhesion forces are not included, and results from a two-dimensional elastica model of the loop are utilized for comparison purposes. The contact zone appears to be insensitive to the adhesive interactions between the loop and the substrate for the systems studied.     

A NEW CORRELATION FOR THE PARAMETERS IN A VAN DER WAALS-TYPE EQUATION OF STATE FOR SIMPLE LIQUIDS

We present a new method based on a corresponding-states approach to evaluate the equation-of-state parameters of a van der Waals-type equation of state which is valid for simple, non-polar molecules, both spherical and non-spherical, and their mixtures. The proposed method, which has been tried on fourteen liquids, predicts well pure component liquid molar volumes over a large temperature range. The method's predictive capability of the excess thermodynamic functions (G^E, H^E, and V^E) has also been tested on fourteen liquid mixtures and the results compare favorably with those of other more sophisticated treatments.     

ADHESION FORCES OF SPHERICAL ALUMINA PARTICLES ON CERAMIC SUBSTRATES

Adhesion forces of spherical alumina particles on ceramic substrates were studied. Results of direct force measurements using an atomic force microscope (AFM) were compared with theoretical results of a new rod model and with molecular dynamic computer simulation. Spherical alumina particles were produced by a flame process. The particles were glued to cantilevers, and interaction forces were measured by the AFM. A significant reduction of adhesion forces due to adsorbed layers was observed. The interaction volumes were determined by AFM scanning using a soft cantilever. The measured interaction forces were compared with calculated forces using the Hamaker concept including an adsorbed surface layer and the determined interaction volume (rod model). It turned out that calculated adhesion forces, neglecting deformation, are smaller than measured ones. This problem can be overcome if deformation according to Hertz is included in the rod model. Even for such a hard material as alumina, deformation occurs in the contact zone, which was also observed in a molecular dynamic computer simulation.     

硅胶载体制备过程中粘合剂的作用研究

在催化剂载体的制造过程中通常都要用粘合剂，但是由于受保密的限制，极少有资料介绍粘合剂与催化剂载体性能之间的关系。本文以硅胶细粉为原粉，以水，乙醇，聚乙烯醇水溶液及５％，１０％，１５％，２５％４种浓度的硅溶胶为粘合剂，研究了原粉的粒径，粘合剂的种类，粘合剂的浓度用压片法制得的载体的结构，吸附性能的影响，同时讨论了载体的制备条件对载体结构的影响，还初步探讨了载体的制备条件与载体结构及性能的三者之间的部     

EFFECT OF CURE RATE OF RUBBER COMPOUND ON THE ADHESION TO COPPER-PLATED STEEL CORD

Copper-plated steel cord was prepared and its adhesion properties to rubber compounds, which have different loading amounts of both sulfur and accelerator, were examined in comparison with brass-plated steel cord. The lower pullout force of copper-plated steel cord to the rubber compounds was shown compared with brass-plated steel cord. The copper-plated steel cord showed higher adhesion retention to rubber compounds than brass-plated steel cord against various hostile environments. The stability against both humidity aging and thermal aging, and the cause for the high adhesion retention of the copper-plated steel cord to rubber compounds, were discussed compared with those of the brass-plated steel cord. The pullout force of copper-plated steel cord to rubber compound is inversely correlated with cure rate after various aging treatments.     

COMMENTS CONCERNING A SIMPLE EQUATION OF STATE OF THE VAN DER WAALS FORM

When the Carnahan-Starling equation of state for hard spheres is combined with a simple attractive term, the molecular size parameter b for argon (as obtained from critical data) is much closer to the “correct” value than that obtained from the empirical Redlich-Kwong equation

For the critical isotherm for argon, the best simple form of the attractive term lies between the two common forms, proposed by van der Waals and by Redlich. At constant temperature, the attractive contribution to the compressibility factor is proportional to (v + 0.2b)^-1 where v is the molar volume. This proportionality is in agreement with results for a square-well fluid recently reported by Sandier.     

EFFECT OF SURFACE ROUGHNESS ON THE ADHESION OF ELECTROLESSLY PLATED PLATINUM TO POLY(ETHYLENE TEREPHTHALATE) FILMS

Poly(ethylene terephthalate) films were treated with aqueous sodium hydroxide solutions of different concentrations for various times. The rate of weight loss increased with the addition of a swelling agent (methylene chloride) or a cationic surfactant. The surface roughness of the treated films was determined from atomic force microscopy (AFM) and pore diameter was obtained from scanning electron microscopy (SEM). In general, surface roughness was found to increase with increasing weight loss for the treated films. A maximum roughness was obtained for samples with a weight loss of approximately 15-20%, beyond which the roughness of the samples decreased. The addition of methylene chloride and surfactant resulted in an almost two-fold increase in the roughness for all treatment times investigated. The adhesion of electrolessly plated platinum film was dependent on the contact area produced by chemical treatment. Treatments producing smaller diameter pores of greater depth gave better adhesion.     

COMMENTS CONCERNING A SIMPLE EQUATION OF STATE OF THE VAN DER WAALS FORM

When the Carnahan-Starling equation of state for hard spheres is combined with a simple attractive term, the molecular size parameter b for argon (as obtained from critical data) is much closer to the “correct” value than that obtained from the empirical Redlich-Kwong equation

For the critical isotherm for argon, the best simple form of the attractive term lies between the two common forms, proposed by van der Waals and by Redlich. At constant temperature, the attractive contribution to the compressibility factor is proportional to (v + 0.2b)^?1 where v is the molar volume. This proportionality is in agreement with results for a square-well fluid recently reported by Sandier.     

硅溶胶对刚玉莫来石复相陶瓷的性能影响

采用溶胶-凝胶法在刚玉-莫来石质材料中引入活性硅溶胶(SiO2),分析了硅溶胶对刚玉-莫来石复相陶瓷性能的影响机制。研究结果表明,SiO2在主体材料中形成纳米包裹薄膜,SiO2的分布可控、掺入均匀,从而提高了复相陶瓷的抗热震性、高温强度及蠕变性。加入SiO2溶胶产生的莫来石反应化和微裂纹增韧是刚玉-莫来石质材料热震稳定性提高的主要原因。     

以微硅粉为原料制备吸收CO_2材料硅酸锂的研究

硅酸锂(Li_4SiO_4)材料可在高温500～750℃下直接吸收温室气体CO_2。通过高温固相法,采用工业固体废弃物微硅粉和Li_2CO_3为主要反应原料,于不同温度下合成了Li_4SiO_4材料。本研究采用X衍射仪(XRD)和差热分析(TG)分别表征了合成材料的结构特征以及硅酸锂材料对CO_2的吸收性能。实验结果表明,在740℃下煅烧4h可合成出的硅酸锂材料对CO_2吸收性能良好,通过热重分析在CO_2气氛下,于700℃保持15 min即可达到吸收平衡,其吸收量可达30%(wt)以上。与已有文献报道进行对比,改善了材料的合成条件,较大地提高了CO_2的吸收容量,同时还为烟气回收矿物微硅粉的应用寻找到一个变废为宝的新途径。     

THE TEMPERATURE OF BURNING CARBON PARTICLES IN A FAST FLUIDIZED BED OF FINE PARTICLES

The temperature of coarse (6–8 mm) carbon particles burning in a fast fluidized bed was measured. The burning carbon particle was found to be 50–70^°C hotter than the bed solids. The convective heat transfer coefficient on the particle was also measured in a separate experiment to help predict the temperature of the carbon particle using a mathematical model which considered both combustion kinetics and heat transfer on the particle. A good agreement between the predicted and measured values of temperature was found.     

气相二氧化硅对环氧填料体系流变性的影响

采用AR500流变仪,测量了气相法制备的二氧化硅的环氧填料体系的剪切弹性模量G′、剪切粘性模量G″及其随角频率ω的变化曲线。发现当气相二氧化硅质量分数较小时,IgG′,IgG″-lgω相互关系基本上呈直线,在高频部位IgG′,IgG″始微微向下偏离直线形态;随着气相二氧化硅质量分数的增加,直线整体向上平移的同时斜率降低。从分子物理学观点分析认为,气相二氧化硅的增稠性和触变性可以归因于气相二氧化硅原始颗粒表面氢键的相互作用以及与环氧分子之间的作用,引入氢键效应建立理论模型,推得的数学公式拟合了实验曲线。     

QUANTITATIVE EVALUATION OF ADHESION STRENGTH OF INK DEPOSITED ON PLASTIC FILMS WITH A NANO INDENTER AND A SCANNING PROBE MICROSCOPE

As our lifestyles change, the convenience food industry booms. Many convenience food products use flexible, boilable, and microwavable plastic packaging. Almost every package is printed with ink, promoting what is inside the package, listing ingredients and nutrition data, giving preparation instructions, etc. The adhesion of ink on plastic films merits increasing attention to ensure quality packaging. However, this property has not been systematically studied and lacks a scientific method to measure the adhesion strength quantitatively. We are developing a technique of using a Nano-Indenter and a Scanning Probe Microscope to evaluate the adhesion strength of ink deposited on plastic films. It shows promise, and the measurement will be helpful in better understanding the adhesion mechanism, thus giving direction as to how to improve the adhesion.     

QUANTITATIVE EVALUATION OF ADHESION STRENGTH OF INK DEPOSITED ON PLASTIC FILMS WITH A NANO INDENTER AND A SCANNING PROBE MICROSCOPE

As our lifestyles change, the convenience food industry booms. Many convenience food products use flexible, boilable, and microwavable plastic packaging. Almost every package is printed with ink, promoting what is inside the package, listing ingredients and nutrition data, giving preparation instructions, etc. The adhesion of ink on plastic films merits increasing attention to ensure quality packaging. However, this property has not been systematically studied and lacks a scientific method to measure the adhesion strength quantitatively. We are developing a technique of using a Nano-Indenter and a Scanning Probe Microscope to evaluate the adhesion strength of ink deposited on plastic films. It shows promise, and the measurement will be helpful in better understanding the adhesion mechanism, thus giving direction as to how to improve the adhesion.     

铝改性硅溶胶胶粒组成与结构关系研究

用ＦＴ－ＩＲ，＾２７Ａｌ－ＮＭＲ和＾２９Ｓｉ－ＮＭＲ研究了不同Ａｌ／Ｓｉ摩尔比的铝改性硅溶胶胶粒结构。结果表明：在Ａｌ／Ｓｉ比为０．２￣０．５的范围内，铝改性硅溶胶胶粒中Ａｌ主要是以在第二配位圈上与［ＳｉＯ４］四面体相连接的［ＡｌＯ４］四面体的形式存在；Ａｌ／Ｓｉ比的不同，其中铝硅酸阴离子结构也各异，根据＾２９Ｓｉ－ＮＭＲ测定结果能较好地定量计算出各种结构的铝硅酸阴离子的分布；ＩＲ谱的８４０￣１３     

THERMAL RADIATION EFFECTS ON THE COMBUSTION BEHAVIOR OF POROUS CHAR PARTICLES

The effects of thermal radiation on the pseudosteady state and transient behavior of porous char particles exposed to an oxygen containing environment are investigated. The numerical simulation results show that particles that do not interchange radiant energy with their environment are characterized by wider ambient temperature regions where multiple steady states exist, higher combustion rates, and lower burning times     

DEPOSITION OF AEROSOL PARTICLES ON A SURFACE COMPOSED OF DIFFERENT TYPES OF MATERIALS

Experimental and theoretical studies have been conducted on the deposition of aerosol particles on a surface composed of different types of materials (copper-polyethylene and copper-nickel). Deposition of charged particles is affected by localized electrostatic fields created by the contact potential difference between the different types of materials. The particles charged with positive polarity deposit mainly on the polyethylene or the nickel surfaces, which are negatively charged. The deposition profile has been also controlled by varying the thickness of gold layers deposited on nickel surface.     

EFFECTS OF PARTICLE CHARACTERISTICS ON THE PERFORMANCE OF A FAST FLUIDIZED BED REACTOR

A heterogeneous model for the fast fluidized bed reactor which carries out a gas-solid non catalytic reaction is presented. The hydrodynamics of the fast fluidized bed is characterized by the model of Kwauk et al. (1985) which assumes the existence of two phases; a dense phase and a dilute pneumatic transport phase. For a given solid flowrate, the length of the reactor occupied by each phase depends on gas velocity, particle diameter and density and average voidage within the reactor. The gas-solid reaction is assumed to follow the shrinking core model. The solids are assumed to be completely backmixed in the dense phase and move in plug How in the dilute pneumatic transport phase. The gas phase is assumed to be in plug flow in both phases

For given gas and solid flowrates, the transition from the dense phase flow to the fast fluidized bed (containing two regions) as functions of particle size and density is determined using the model of Kwauk et al. (1985). The numerical solution of the governing mass balance equations show that for given solid and gas flowrates, (and average voidage) the gas phase conversion shows an unusual behavior with respect to particle diameter and density. Such behavior is resulted from the effects of particle diameter and density on the reactor volume occupied by each phase and the effect of particle diameter on the apparent reaction rate. The numerical results show that a fast fluidized bed gives the best conversion at large particle density and for the particle diameter which results the fast fluidized bed to be operated near the pure dense phase flow.