Effects of Deformation on the Properties of Emulsion Grains

Emulsion grains have been deformed by bending an emulsion layer coated on film, and the effects of deformation on the dispersity ol photolytic silver and on the number and distribution of development centres have been studied. The observations show thai a major effect of such treatment is to increase the number of sues within a grain at which silver specks can be nucleated.

The usual sensitomelric effect of such changes is to increase sensitivity on internal-image development at the expense of sensitivity on surface-image or conventional development. However, it is shown that surface desensitizalion may be accompanied sometimes by internal desensitization rather than sensitization. The internal desensitization can be attributed to competition between the increased number of internal sensitivity centres. Support for this view was obtained from the fact that changes in the effect of deformation on storage prior to exposure (decrease of surface desensitization. decrease of internal sensitization or desensitization I were associated with a reduction in the number of centres ,il which internal silver could be nucleated.

A further effect of deformation noted with coatings of lodohromide emulsions (but probably general with respect to halide) is to decrease the luminescence intensity at low temperatures, particularly at low intensities of excitation, and to increase the time required for luminescence to reach maximum intensity. These observations show that deformation introduces new recombination centres and electron traps into emulsion grains The connection between the effects of deformation on sensitomelric properties and luminescence properties have been studied as a function of grain size and chemical sensitization in a series of animoniacal emulsions. The findings confirmed that damage to the grains is responsible for the loss of sensitivity on conventional development, and that chemical sensitization, though reducing desensitization hv deformation, has no influence on the grain disorder introduced by this latter treatment. 11 is thought unlikely that the new recombination centres play any significant part in the desensitization by deformation of emulsions chemically sensitized so as lo be al or near optimal speed, but some contribution would appear feasible in the case of emulsions at a low level of sensitization.     

The Relationship between Surface and Internal Sensitivity of Individual Grains

By use of sensitometric and processing techniques it is shown that for typical commercial emulsions the grains which do not form surface image readily are the more sensitive ones for internal-image formation. From residual grain size data it is shown that this relationship between surface and internal sensitivities exists within individual size classes. Arguments are presented in favour of the view that the reciprocal relationship between surface and internal sensitivity is due in part to inherent differences among grains. The observations emphasize that the surface/internal sensitivity ratio for grains of high surface sensitivity can exceed considerably the corresponding ratio for the emulsion layer as a whole for production of small or moderate densities.     

The Chemical Sensitization of Silver-Iodide Emulsions*

The sensitivity of silver-iodide emulsions is shown to be dependent upon the silver-complexes present at the surface of the grains. It is suggested that these complexes increase the useful absorption of light as well as increasing halogen acceptance in the system. No internal image could be found in these emulsions; nor was it possible to sensitize them by a sulphur-digestion although the rate of printing-out was increased.     

Exclusively Internal Latent Image

The presence of emulsion grains bearing only internal latent image (“exclusively” internal image) can be fairly definitely established by firstly developing fully, in a surface developer, and then either bleaching and developing internally, or observing if there is a further density increase on transferring the surface-developed samples to an internal developer, both methods gave similar results, which indicated that digested emulsions at normal exposure levels form internal image only in grains also bearing a surface image. An undigested emulsion formed much exclusively internal image. Solarization has often been thought to proceed by the destruction of surface image on grains in which build-up of internal silver is continuing. In agreement with this concept, good equivalence was found between solarization density losses as shown by surface development, and density gains shown by development for the exclusively internal image.     

Factors Influencing the Response of Silver Iodide Emulsions

Contrary to the conclusions of previous authors, it is shown that silver iodide emulsions may be sulphur sensitized. Additional large increases of speed for exposures at moderate and low intensity may be achieved by bathing in water, solutions of halogen acceptors, or silver nitrate before exposure, or by coating at low pAg. In agreement with the observations of some authors, a silver iodide emulsion can form an internal image. In conformity with this capacity to form an internal image. the emulsion exhibits solarization.     

Influence of internal phase properties on zeta-potential and dielectric constant of o/w emulsion

Dielectric constant (DEC) of internal phase influenced the zeta potential (ZP) of o/w emulsion prepared with or without emulgent. In both systems ZP and DEC of internal phase exhibited an approximately linear relationship. Using homologous aliphatic hydrocarbons as internal phases, emulsions were prepared with polysorbate-80. Increase in carbon chain length brought about increase in interracial area and decrease in ZPs of emulsions. A fair inverse correlation between ZP and DEC of internal phase was revealed in this series. Increase in phase volume ratio from 0.05 to 0.3 brought about limited changes in ZPs whereas by further increasing phase volume ratio, ZP decreased steadily. Studies pertaining to the effect of phase volume ratio on DEC of o/w emulsions are in accordance with earlier observations. Increase in phase volume ratio causes a steady decrease in DEC of emulsion. Of the five equations employed, the Bruggeman equation appears to predict the observed values more accurately.     

The Relationship between Speed and Grain Size

On the assumption that the average size of latent-image speck required for developability, and the average number of absorbed quanta required to form a developable speck, are independent of grain size, it follows that speed should increase indefinitely with grain size.

Speed/grain-size relationships for experimental series of emulsions have been derived and compared with theoretical trends. These comparisons show that the number of quanta per grain required for developability steadily increases with size within the normal size range. In one series this led to an optimum and then a decrease of speed despite increasing grain size.

On exposure of emulsions to X-rays of such energy as to render one grain developable for each quantum absorbed, speed increases up to the largest grain size. In this case the number of electrons released by an X-ray quantum is such that large inefficiencies in formation of a developable latent-image speck can be tolerated. Excellent agreement between theoretical and experimental speed/grain-size relationships for direct X-rays provides justification for the assumptions made in calculating speed/grain-size relationships for light exposures.

On the basis of experimental evidence several explanations for the decrease of quantum sensitivity at large grain-sizes are rejected. The only feasible type of explanation is one in which the latent-image silver is dispersed over a number of sites at the grain surface. Such an effect may arise in part because the grain size becomes large compared with the average diffusion distance of an electron from its point of release.     

Features of water microdrop dispersion flow in microchannels

A remarkable property of inverse water-hydrocarbon emulsions, which is manifested during their flow in microchannels, has been discovered and called dynamic blocking. According to this phenomenon, the flow of emulsion through a microchannel ceases with the time despite the presence of a continuously applied pressure gradient. Experiments show that this effect can be observed for the flow of emulsions with different compositions and rheological properties. The effect is manifested at rather significant pressure gradients, although it is accompanied by a partial degradation of dispersions. A physical mechanism is proposed to explain the dynamic blocking of water-hydrocarbon emulsions in microchannels, which is based on the notion of an interaction between nanodimensional surface shells consisting of surfactant molecules that surround water microdrops.     

Investigation of AGFA-8E56HD photographic emulsion and relief hologram structures by atomic force microscopy

Relief holograms are obtained on Agfa 8E56HD holographic emulsions by a Russian chemical-processing technique that is developed for their PE-2 holographic emulsion. We have shown that the three-dimensional surface profiles can easily be visualized by applying atomic force microscopy to measurement of the relief depth and relief spacing on holographic emulsions. The relief depth and thus diffraction efficiency decreases with increasing exposure time.     

Simple and straightforward determination of the enclosed water volume fraction of W/O/W double emulsions by analytical photocentrifugation

ABSTRACT

During the preparation of W/O/W-type double emulsions, a part of the internal water phase is often released to the external water phase. Thus, it is important that the enclosed water volume fraction can be determined in a simple and straightforward manner after preparation. In this work, a method is developed to determine the enclosed water volume fraction of W/O/W-type double emulsions using analytical photocentrifugation after which the results are compared to the enclosed water volume fraction as determined using pulsed field gradient Nuclear Magnetic Resonance (NMR). From the results, it can be concluded that analytical photocentrifugation is indeed a simple and straightforward method to determine the enclosed water volume fraction of double emulsions.     

“Vitamin E” fortified parenteral lipid emulsions: Plackett–Burman screening of primary process and composition parameters

The objective of this study was to screen the effect of eight formulations and process parameters on the physical attributes and stability of “Vitamin E”-rich parenteral lipid emulsions. Screening was performed using a 12-run, 8-factor, 2-level Plackett–Burman design. This design was employed to construct polynomial equations that identified the magnitude and direction of the linear effect of homogenization pressure, number of homogenization cycles, primary and secondary emulsifiers, pre-homogenization temperature, oil loading, and ratio of vitamin E to medium-chain triglycerides (MCT) in the oil phase on particle size, polydispersity index, short-term stability, and outlet temperature of manufactured emulsions. The viscosity of vitamin E was reduced from 3700 (100%) to 64 mPa.s (30%) by MCT addition. As viscosity is critical for efficient emulsification, vitamin/MCT ratio was the most significant contributor for the stability of emulsions. Particle size increased from 236 to 388 nm, and percentage vitamin remaining emulsified after 48 h dropped from 100 to 73% with increase in vitamin/MCT ratio from 30/70 to 70/30. Significant decrease in particle size and PI, and an increase in outlet temperature were also observed with increase in homogenization pressure and number of homogenization cycles. Emulsifiers and oil loading, however, had insignificant effect on the responses. Overall, stable submicron emulsions at vitamin/MCT ratio of 30/70 could be prepared at 25,000 psi and 25 cycles in ambient conditions. The identification of these parameters by a well-constructed design demonstrated the utility of screening studies in the “Quality by Design” approach to pharmaceutical product development.     

Preparation of spherical SnO2 particles by W/O type emulsion method

An attempt to prepare spherical particles was made using a W/O type emulsion as a reaction field. The effects of surfactant content, W/O ratio and stirring conditions for the preparation of emulsions, which determined the size of water drops in the emulsions, were investigated on the size and morphology of the obtained SnO₂ particles. The size and morphology of the obtained particles were largely influenced by a water/surfactant molar ratio (R-value) for the preparation of the emulsions. Particles having relatively high sphericity were obtained at an R-value below 1500. In order to obtain mono-sized SnO₂ particles with narrow distributions, R-value should be adjusted to the narrow range from 250 to 500. Spherical SnO₂ particles showing narrow particle size distributions were obtained at W/O ratio of 1/1 and surfactant content of 11.2 × 10^–2 mol/l or 22.4 × 10^–2 mol/l. Furthermore, the particle size and morphology of SnO₂ depended on the revolution rate of an emulsifier for emulsification. Mono-dispersed spherical particles having narrow size distributions formed at revolution rates of 3000 and 4000 rpm. At extremely low and high revolution rate of the emulsifier, particles showing high sphericity were not obtained, but agglomerates of un-spherical fine particles. The interfacial reaction time determined the internal structures of spherical particles. The reaction for short time yielded hollow spherical SnO₂ particles, and the internal structure of the particles became denser with increasing reaction time.     

Dynamics of spreading of industrial oil-in-water emulsions on steel surfaces

The spreading of industrial oils, pure and emulsified in water, has been investigated on rough steel surfaces. Oils wet the surface regularly, the spreading remains circular and the contact area can be empirically correlated to timet by a power law similar to those of pure homogeneous liquids. Similar laws can also be found for oil-in-water emulsions, but in this case the spreading behaviour is quite different: first it is not circular, irregularities appear depending on the industrial oil; then retractions can occur and eventually, with some emulsions thinning of the central zone may occur after a certain time. All these effects might be due to the actual composition of these oils which are essentially esters of fatty acids dissolved in mineral oils with various added surfactants. This kind of experiment might be a very simple test to aid the choice of an appropriate rolling-oil.     

基于转静干涉效应的压气机叶片气动载荷分析

转静叶排的相互作用会使压气机内部流场存在复杂的非定常性。为深入研究压气机叶片的气动载荷特性,以某型航空发动机压气机为研究对象,考虑叶排间的转静干涉效应,利用滑移网格技术对整个叶盘的三维流场展开模拟,求解干涉周期T_b内压气机转子内部的流动规律。同时对叶片气动载荷的非定常特性进行进一步分析,讨论了不同压比、转速对压气机叶片气动载荷的影响。结果表明叶片压力面和吸力面气动载荷波动峰值的主导频率皆为转静干涉频率f₀的倍频,其中一倍频（1×f₀）分量占主导地位。在干涉周期T_b内,叶片表面压力涡发生周期性的迁移与耗散,压力面和吸力面气动载荷的变化呈相反趋势。随着压比的增加,压气机叶片气动载荷逐渐增大,但其脉动幅值和频谱峰值基本不变。转速的升高使得转静干涉的频率增大,增强了压气机叶片气动载荷的非定常特性。研究结果能够应用于叶盘结构的气动优化设计,可为高性能航空发动机压气机的研制提供支持和参考。     

An investigation on process of seeded granulation in a continuous drum granulator using DEM

Numerical simulation of wet granulation in a continuous granulator is carried out using Discrete Element Method (DEM) to discover the possibility of formation of seeded granules in a continuous process with the aim of reducing number of experimental trials and means of process control. Simple and scooped drum granulators are utilized to attain homogenous seeded granules in which the effects of drum rotational speed, particles surface energy, and particles size ratio are investigated. To reduce the simulation time a scale-up scheme is designed in which a dimensionless number (Cohesion number) is defined based on the work of cohesion and gravitational potential energy of the particles. Also a mathematical/numerical method along with a MATLAB code is developed by which the percentage of surface coverage of each granule is predicted precisely. The results show that use of continuous granulator for seeded granulation is promising provided that a high level of shear is considered in the granulator design, i.e. using baffles inside drum granulators is essential for producing seeded granules. It is observed that the optimum surface energy for seeded granulation in scooped granulator (used in this study) with rotational speed of 50 rpm is 3 J/m², which is close to the value predicted by the concept of Cohesion number. It is also shown that increasing the seed/fine size ratio enhances the seeded granulation both quantitatively (60% increase in seeds surface coverage) and qualitatively (more homogeneous granules).     

An Electron Spin Resonance Study of Internally Sensitive Emulsions

Abstract

The election spin resonance spectra of two kinds of internally sensitive core–shell emulsions, with chemical structure imperfections and with physical lattice imperfections respectively, were studied in this paper. It was found thai both the internal sensitivity and the intensity of the rlecl rou spin resonance (ESR) signal increased with an increase of the chemical sensitization time to a maximum and then decreased. the ESR signal intensity decreased with a decrease of the core–shell ratio and an increase of the prefogging level. Different desensitizing dyes hud different effects on the internal photographic property and the intensity of the ESR signal because of their desensitizing mechanisms. The results tun be explained on the basis of the behaviour of the positive hole within the silver halide crystal.     

Synthesis of nanocrystalline SiC at ambient temperature through high energy reaction milling

This study investigated the in-situ synthesis of nanosized crystalline SiC powders at room temperature through high energy ball milling of elemental silicon and carbon mixtures. Milling conditions including the mill design, the milling speed, the milling time and the ball-to-powder weight ratio (i.e. the charge ratio) necessary for the in-situ synthesis were studied. It was found that uniform formation of nanosized crystalline SiC powders within the powder charge could be achieved with a correctly designed attritor and the contamination could be minimized with proper selections of milling conditions. The crystalline β-SiC powders synthesized were themselves in nanosize scale, quite different from many previous studies which have shown that it is the internal grain structure of milled powders that is the “nanocrystalline” component of the powders (typically 5–20 nm), while the powders are themselves typically 0.1 μm to > 1 μm in size. Furthermore, it was found that the product structures generated by high energy reaction milling depended strongly on the milling speed, the charge ratio and the milling time.     

旋转速度与焊接速度对铝铜异种材料搅拌摩擦焊接头成形的影响

目的为了获得较好的铝铜异种材料搅拌摩擦焊焊缝,研究旋转速度与焊接速度对焊缝成形的影响规律。方法采用对接的方式对4mm厚的纯铝和紫铜进行搅拌摩擦焊,对比了不同旋转速度和焊接速度对铝铜异种金属焊缝表面的影响,并对焊缝内部成形变化进行了分析。结果旋转速度和焊接速度对焊缝的成形影响较大,当旋转速度为1200 r/min,焊接速度为10 mm/min时,焊缝表面成形美观,焊缝表面相对较为光滑,焊缝内部存在相互交叠的片层结构和漩涡状结构,焊缝内部未见明显缺陷;与旋转速度1200 r/min,焊接速度10mm/min相比,在焊接旋转速度减小或者焊接速度变大时,由于焊接热输入减小,造成焊缝表面出现沟槽、孔洞等焊接缺陷,同时搅拌针的旋转搅拌作用影响焊缝成形和焊缝内部缺陷的产生。结论选择合适的旋转速度和焊接速度能够获得宏观成形较好和内部缺陷较少的焊缝。     

高固含量丙烯酸酯共聚物乳液的单体组成与流变行为

合成了一系列固体含量为70%的丙烯酸丁酯/甲基丙烯酸甲酯/α-甲基丙烯酸(BA/MMA/MAA)共聚物乳液,研究了软(BA)、硬(MMA)段单体用量比对乳液体系流变行为的影响,并对其乳胶粒的粒径分布和微观形态进行了表征。结果表明,所合成乳液乳胶粒的粒径在50nm~650nm范围内,呈宽分散分布状态。当BA/MMA<60/40时,乳液可保持低黏度;而当BA/MMA>60/40时,乳液的黏度急剧增加。随着乳液中软、硬段单体比的不同,乳液的乳胶粒分布状态和凝聚形态均有显著变化。     

Cooperative sensitization by reduction and chemical sensitization in AgX core–shell emulsions

Abstract

Cubic core–shell AgBr and AgBrI emulsions prepared by the twice emulsified method were used to observe the cooperative sensitization of reduction sensitization in the core and sulfur-plus-gold sensitization on the surface of core–shell grains through a space separation of different sensitizing centres by a AgBr shelled layer. The results showed: (1) that core–shell emulsions doped by Ag₂ centres in cores reduced by DMAB exhibited a remarkable increase in sensitivity relative to the corresponding undoped emulsions; (2) that I^? ions in AgBrI grains did not affect the sensitization of internal Ag₂ centres, but were beneficial to the inhibition of fog density; (3) cooperative sensitization by the internal reduced Ag₂ and the surface S+Au sensitizations was considered to result from two different mechanisms, i.e. trapping holes by the former and concentrating electrons by the latter, both of which were beneficial to the efficiency of latent image formation.