Importance of the density gradient effects in modelling electro deposition process at a rotating cylinder electrode

The rotating cylinder electrode configuration is one of the most used electrochemical configurations for electrochemical processes study. It is often used with turbulent flow regime for industrial application such as intensive corrosion or electro deposition processes. It can also be used for laminar regimes but in this case it can appear superposition between forced convection and natural free convection. This natural free convection is generally due to density gradient from electrode to bulk, due to electro deposition or to evolving bubbles. The hydrodynamic regime is then said mixed.There is few knowledge concerning the mixed hydrodynamic and the main goal of the present work is to show the qualitative and quantitative effects and differences between purely forced convective flow and purely free natural flow.     

Effect of biomass particle size and air superficial velocity on the gasification process in a downdraft fixed bed gasifier. An experimental and modelling study

A one-dimensional stationary model of biomass gasification in a fixed bed downdraft gasifier is presented in this paper. The model is based on the mass and energy conservation equations and includes the energy exchange between solid and gaseous phases, and the heat transfer by radiation from the solid particles. Different gasification sub-processes are incorporated: biomass drying, pyrolysis, oxidation of char and volatile matter, chemical reduction of H₂, CO₂ and H₂O by char, and hydrocarbon reforming. The model was validated experimentally in a small-scale gasifier by comparing the experimental temperature fields, biomass burning rates and fuel/air equivalence ratios with predicted results. A good agreement between experimental and estimated results was achieved. The model can be used as a tool to study the influence of process parameters, such as biomass particle mean diameter, air flow velocity, gasifier geometry, composition and inlet temperature of the gasifying agent and biomass type, on the process propagation velocity (flame front velocity) and its efficiency. The maximum efficiency was obtained with the smaller particle size and lower air velocity. It was a consequence of the higher fuel/air ratio in the gasifier and so the production of a gas with a higher calorific value.     

A model of the coagulation process with solid particles and flocs in a turbulent flow

A mathematical model was developed on the basis of population balances to predict the floc size distribution in a coagulating suspension. The coagulation process is performed in a stirred tank reactor with a turbulent flow field. In the population model the influence of the different local energy charges inside the reactor is taken into account. Moreover two sorts of particles are distinguished, i.e. the originally present and completely dispersed primary particles and the flocs. Contrary to the primary particles the flocs can be disrupted due to pressure and shear forces as they are mechanically not very stable. This different behaviour requires separate population balances for the two sorts of particles. The model parameters that are necessary are adapted to one single experiment.For the steady state the results represent different floc size distributions dependent on the solid concentration and the energy charge. Moreover it is shown that the assumption of an ideally mixed reactor that is often used cannot be maintained to be always true for the prediction of the resulting floc size distribution. The calculation results achieved are validated by image processing measurements of coagulating quartz particles in an aqueous suspension.     

Modelling the post treatment process of model implants prepared by in situ polymerized poly(ε-caprolactone) using a BF3-glycerol catalyst system

The post treatment process of a poly(ε-caprolactone) (PCL) model implant prepared using a boron trifluoride (BF₃) catalyst and glycerol initiator by in situ polymerisation process for craniofacial and maxillofacial treatment is modelled using a ‘moving-boundary’ diffusion model. A numerical method was used to solve a system of diffusion equations of the model. The variable diffusion coefficient (D) was correlated with crystallinity (x_c) of the polymer which is a function of its molecular weight (M_w) and its degradation rate constant (k_d), D=f(x_c(M_w,k_d)). The post treatment time and the molecular weight retained after post treatment can be obtained using this model. The modelling results show that the process is potentially suitable for manufacturing thin model implants of complex shape.     

Dynamics and control of thin film surface microstructure in a complex deposition process

In this work, a complex deposition process, which includes two types of macromolecules whose growth behaviors are very different, is investigated. This deposition process is influenced by both short- and long-range interactions. The study of this process is motivated by recent experimental results on the growth of high-κ dielectric thin films using plasma-enhanced chemical vapor deposition. A multi-component kinetic Monte-Carlo (kMC) model is developed for the deposition. Both single- and multi-component cases are simulated and the dependence of the surface microstructure of the thin film, such as island size and surface roughness, on substrate temperature and gas phase composition is studied. The surface morphology is found to be strongly influenced by these two factors and growth regimes governed by short- and long-range interactions are observed. Furthermore, two kMC model-based feedback control schemes which use the substrate temperature to control the final surface roughness of the thin film are proposed. The closed-loop simulation results demonstrate that robust deposition with controlled thin film surface roughness can be achieved under a kMC estimator-based proportional integral (PI) feedback controller in the short-range interaction dominated growth regime, while a kMC model-predictive controller is needed to control the surface roughness in the long-range interaction dominated growth regime.     

Development of a new process in high functioning ceramic core without shape deformation

A new process was developed to prepare a ceramic core with reasonable strength, and without shrinkage and shape deformation. In this work, a mixture of inorganic precursor composed of silicate and metal alkoxide was used to increase the strength of the core during the wax injection under about 50 °C and the casting processes under about 1300–1350 °C. In the case of the core prepared through the new process, the nominal fracture strength is 12 MPa because of the glass phase synthesized by the inorganic precursor. However, in the conventional process, the core shows the strength of about 6 MPa, as manifested by the sintering effect between starting particles occurring during heat treatment. In addition, the core sample prepared using the inorganic precursor is completely eluted in a sodium hydroxide solution, indicating that the new core process is reasonable for the fabrication of a ceramic core having high strength and crushability.     

废弃混凝土中基质胶凝组分作原料煅烧水泥熟料的研究

每年拆除建筑物所产生的废弃混凝土数量巨大,因此废弃混凝土中基质胶凝组分作原料煅烧水泥熟料的再利用研究具有重要的意义。采用热处理和加入表面活性剂与机械粉碎相结合的方法将废弃混凝土中的骨料与基质胶凝组分进行了分离。将分离出的基质胶凝组分按不同配合比制备生料,分别在1400℃,1450℃下进行了熟料煅烧试验,并进行了结构和力学性能测定。试验结果表明,水泥净浆试体的抗压强度随基质胶凝组分配合比的增大而降低,但适当掺入(小于25%)时降低幅度不大;XRD和SEM分析结果表明,1450℃煅烧的熟料矿物结构与常规原料煅烧的熟料基本相同。根据晶种理论和水化物脱水相的反应活性分析了熟料烧成机理。     

An arrangement of ideal zones with shifting boundaries as a way to model mixing processes in unsteady stirring conditions in agitated vessels

This paper investigates the way modelling mixing phenomena occur in unsteady stirring conditions in agitated vessels. In particular, a new model of torus reactor including a well-mixed zone and a transport zone is proposed. The originality of the arrangement of ideal reactors developed here lies in the time-dependent location of the boundaries between the two zones. This concept is applied to model the positive influence of unsteady stirring conditions on homogenization process: the model avoids a mass balance discontinuity when the transition from steady to unsteady stirring conditions is performed.To ascertain the reliability of the model proposed, experimental runs with highly viscous fluids have been carried out in an agitated tank. The impeller used was a non-standard helical ribbon impeller, fitted with an anchor at the bottom. The degree of homogeneity in the tank was observed using a conductivity method after a tracer injection.It is shown that for a given agitated fluid and mixing system, model parameters are easy to estimate and that modelling results are in close agreement with experimental ones. Moreover, it would appear that this model allows the easy derivation of a control law, which is a great advantage when optimizing the dynamics of a mixing process.     

Among the trends for a modern chemical engineering,the third paradigm: The time and length multiscale approach as an efficient tool for process intensification and product design and engineering

To respond to the changing needs of the chemical and related industries in order both to meet today's economy demands and to remain competitive in global trade, a modern chemical engineering is vital to satisfy both the market requirements for specific nano and microscale end-use properties of products, and the social and environmental constraints of industrial meso and macroscale processes. Thus an integrated system approach of complex multidisciplinary, non-linear, non-equilibrium processes and phenomena occurring on different length and time scales of the supply chain is required. That is, a good understanding of how phenomena at a smaller length-scale relates to properties and behaviour at a longer length-scale is necessary (from the molecular-scale to the production-scales). This has been defined as the triplet “molecular Processes-Product-Process (3PE)” integrated multiscale approach of chemical engineering. Indeed a modern chemical engineering can be summarized by four main objectives: (1) Increase productivity and selectivity through intensification of intelligent operations and a multiscale approach to processes control: nano and micro-tailoring of materials with controlled structure. (2) Design novel equipment based on scientific principles and new production methods: process intensification using multifunctional reactors and micro-engineering for micro structured equipment. (3) Manufacturing end-use properties to synthesize structured products, combining several functions required by the customer with a special emphasis on complex fluids and solid technology, necessating molecular modeling, polymorph prediction and sensor development. (4) Implement multiscale application of computational chemical engineering modeling and simulation to real-life situations from the molecular-scale to the production-scale, e.g., in order to understand how phenomena at a smaller length-scale relate to properties and behaviour at a longer length-scale. The presentation will emphasize the 3PE multiscale approach of chemical engineering for investigations in the previous objectives and on its success due to the today's considerable progress in the use of scientific instrumentation, in modeling, simulation and computer-aided tools, and in the systematic design methods.     

Expanded graphite applied in the catalytic process as a catalyst support

An amorphous NiB supported on expanded graphite (EG) catalyst was prepared as an example to show the superior characteristics of EG as a novel carbon support material. EG and the prepared catalysts were characterized by mercury porosimetry, inductively coupled plasma spectrometer (ICP), scanning electronic microscopy (SEM), transmission electron microscope (TEM) and selected area electron diffraction (SAED). The catalytic activities of prepared catalysts were investigated by the hydrogenation of sulfolene to sulfalone and the selective hydrogenation of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CA). We showed that the prepared Ni-B/EG catalyst exhibited very high catalytic activity.     

A simple viscoelastic model for fatigue crack propagation in polymers as a function of molecular weight

A simple theory is presented to explain the strong influence of molecular weight (M) on rates of fatigue crack propagation (FCP) in amorphous polymers. It is proposed that the equation describing FCP rates may be expressed as the product of two functions, one involving the stress intensity factor (ΔK), and the other characterizing the relaxation process occurring in the plastic zone. To provide a physical network in the plastic zone that can sustain fatigue loading, it is proposed that one needs a sufficient fraction of molecular fibrils per unit area ($\text{W1}$) whose lengths are greater than M_c, the critical value of M required for entanglement. This effect can be summarized as a generalized rate process (confined at the plastic zone) expressed by A exp (Bσ) where σ is a stress and A and B are constants (B including the volume of activation). It is deduced that M influences the activation volume through the values of $\text{W1}$ and W, the weight fraction of molecules whose M>M_c. Using the equation developed it was possible to correlate FCP data of PVC and PMMA as a function of M with a high degree of confidence. Also, the value of activation volumes obtained compared favourably with those in the literature for static tests. The complementary value of $\text{W1}$ for these polymers was also seen to approximate closely to the void fraction in a craze. Extension to other cases such as semi-crystalline materials also seems possible.     

The electrochemical quartz crystal microbalance as a sensor in the gold thiosulfate leaching process

A technique was developed for measuring the thiosulfate concentration in gold thiosulfate leaching solutions containing copper and ammonia. The method, which is based on the relationship between thiosulfate concentration and the oxidation rate of silver, was firstly studied using the rotating electrochemical quartz crystal microbalance (REQCM). It was found that the measured silver oxidation rate is directly related to the thiosulfate concentration. The silver oxidation rate was also shown to be unaffected by the presence of other species likely to be found in gold leach solutions. The technique was then evaluated for use as a method of flow injection analysis, utilizing a flow through electrochemical quartz crystal microbalance (EQCM) cell.     

Environmental footprint as a criterion in the ZTA composites forming process via centrifugal slip casting

The main goal of this study was to optimize the technological process of forming and sintering Zirconia Toughened Alumina (ZTA) composites in terms of reducing energy demand. Based on the results of Life Cycle Assessment carried out according to ISO 14044 and EN 15805 standards, the elimination of preliminary homogenization of ceramic suspension in the planetary mill, allowed to reduce energy consumption by over 25%. The method of forming ZTA materials by CSC method, allowed to obtain finished tube-shaped products, which did not require any mechanical treatment after sintering. Such an approach may be an alternative solution for production of ZTA pipes that can be used in transport of aggressive substances, even in extreme corrosive or temperatures conditions.     

实验教学中培养研究生的从师能力和科研素质

参与实验课教学是培养硕士研究生教学能力的一种有效形式。在教学过程中,正确处理研究生助教与主讲教师的关系和研究生教学与科研的关系、注重研究生与主讲教师以及研究生与本科生的交流和沟通、以及实施岗前培训和课后总结等措施是确保本科教学质量和研究生培养质量的有效途径。通过教学实践研究生不仅培养了从师素质,而且提高了实验能力和科研素质,为科研工作和未来的职业发展打下了坚实的基础。     

Major component in male sex pheromone of cereal pestEurygaster integriceps puton (Heteroptera: Scutelleridae) identified as a homosesquiterpenoid

A homosesquiterpenoid, (4Z,4E)-4-(1,5-dimethyl-4-heptenylidene)-1-methylcyclohexene, has been identified as a major component of the scent emitted by calling males ofEurygaster integriceps. Minor components of the scent included vanillin. TheE. integriceps male homosesquiterpenoid is an addition to the list of sesquiterpenoids identified as components of male attractant sex pheromones in pentatomoid Heteroptera.     

Labeling the oily core of nanocapsules and lipid-core nanocapsules with a triglyceride conjugated to a fluorescent dye as a strategy to particle tracking in biological studies

The synthesis of novel fluorescent materials represents a very important step to obtain labeled nanoformulations in order to evaluate their biological behavior. The strategy of conjugating a fluorescent dye with triacylglycerol allows that either particles differing regarding supramolecular structure, i.e., nanoemulsions, nanocapsules, lipid-core nanocapsules, or surface charge, i.e., cationic nanocapsules and anionic nanocapsules, can be tracked using the same labeled material. In this way, a rhodamine B-conjugated triglyceride was obtained to prepare fluorescent polymeric nanocapsules. Different formulations were obtained, nanocapsules (NC) or lipid-core nanocapsules (LNC), using the labeled oil and Eudragit RS100, Eudragit S100, or poly(caprolactone) (PCL), respectively. The rhodamine B was coupled with the ricinolein by activating the carboxylic function using a carbodiimide derivative. Thin layer chromatography, proton nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), UV-vis, and fluorescence spectroscopy were used to identify the new product. Fluorescent nanocapsule aqueous suspensions were prepared by the solvent displacement method. Their pH values were 4.6 (NC-RS100), 3.5 (NC-S100), and 5.0 (LNC-PCL). The volume-weighted mean diameter (D_4.3) and polydispersity values were 150 nm and 1.05 (NC-RS100), 350 nm and 2.28 (NC-S100), and 270 nm and 1.67 (LNC-PCL). The mean diameters determined by photon correlation spectroscopy (PCS) (z-average) were around 200 nm. The zeta potential values were +5.85 mV (NC-RS100), -21.12 mV (NC-S100), and -19.25 mV (LNC-PCL). The wavelengths of maximum fluorescence emission were 567 nm (NC-RS100 and LNC-PCL) and 574 nm (NC-S100). Fluorescence microscopy was used to evaluate the cell uptake (human macrophage cell line) of the fluorescent nanocapsules in order to show the applicability of the approach. When the cells were treated with the fluorescent nanocapsules, red emission was detected around the cell nucleus. We demonstrated that the rhodamine B-conjugated triglyceride is a promising new material to obtain versatile dye-labeled nanocarriers presenting different chemical nature in their surfaces.     

A selective reaction of polyhydroxy fullerene with cycloaliphatic epoxy resin in designing ether connected epoxy star utilizing fullerene as a molecular core

A novel ether connected epoxy star like polymer was synthesized by selective reaction of water soluble polyhydroxy fullerene (fullerenol) with a commercial grade cycloaliphatic epoxy resin (CY-230, Ciba Geigy) in heterogeneous medium at ambient alkaline condition using tetrabutylammonium hydroxide as phase transfer catalyst. The reaction went well in such conditions and the hydroxy groups of fullerenol underwent selective nucleophilic addition reaction with polar carbonyl groups of the epoxy resin with the formation of a hemiketal. The progress of the reaction was monitored by FTIR analysis of the product formed. The disappearance of characteristic FTIR bands of fullerenol (at 1593.2, 1381.2, and 1068 cm⁻¹) and the typical carbonyl peak (at 1725 cm⁻¹) of parent epoxy resin and also changes of broad hydroxy peak (at 3431 cm⁻¹) of fullerenol into a sharp peak (at 3396.6 cm⁻¹, indicating reduced hydrophilicity) in the reaction product clearly demonstrated the chemical attachment of the epoxy units to the fullerene core. Multiple epoxy units (about 8-10) were attached to fullerene core. Non-reactivity of fullerenol towards DGEBA epoxy resin (LY 556 Ciba Geigy) in similar conditions further supports our result. The thermal properties of the product were influenced by the presence of fullerenol and exhibits higher thermal stability compared to parent epoxy. A probable reaction mechanism for the reaction has also been discussed.     

Accident simulation as a tool for assessing and controlling environmental risks in chemical process industries: A case study

Accidents involving toxic releases, explosions, and fires in chemical process industries take a heavy toll of property, human lives, and environment quality. If one could forecast the accidents likely to occur and the damage they were likely to cause, one could devise appropriate strategies to prevent the accidents and contain the damage that did occur. Using this concept, we have developed a computer-automated tool for accident simulation. In this paper the applicability of the concept and the tool is described on the basis of a case study of a typical petrochemical industry. The study reveals that out of eight credible accident scenarios, four would be ’stand-alone’ events, whereas four others would also cause secondary or higher order accidents (domino effects). Of the accidents in the former category, the one as per scenario 8 is the worst as it would adversely impact (within the set limit of 50 % probability of causing lethality) larger areas than the other three such accidents. Among the second category, scenario 1 would be the most undesirable because it would simultaneously cause heat radiation, shock waves, and missile effects over a larger area.