Using a surface complexation model to predict the nature and stability of nanoparticles

Nanoparticles are discrete nanometer-scale assemblies of atoms and have dimensions between those characteristic of ions and those of macroscopic materials. These minerals commonly possess extremely large specific surface areas and surface adsorption capacities for foreign ions. Due to the large specific surface area and large fraction of surface atoms, the natures of nanoparticles are expected to be modified by the adsorption (surface complexation) process. In this paper,we discuss theoretically the stability of nanoparticles that make the surface complex with foreign ions. The principal theoretical assumption is that the surface complexation occurs at the bulk of the nanoparticles, as in a solid solution. The surface complexation affects two aspects of the intrinsic stability of the nanoparticles simultaneously: one is the composition of the nanoparticles; the other is the free energy of formation of nanoparticles. The solubility of hydrous ferric oxide (HFO) was estimated by using surface complexation modeling coupled with published data of the free energy of formation of the relevant components. The solubility modeling of surface-charged (H+ or OH- sorbed) HFO mechanistically and quantitatively explained the observed nonintegral behavior of the solubility of HFO. Moreover, solubility modeling of anion (SO4(2-), PO4(3-), and As(V)) sorption by HFO showed that the sorption process strongly influences the stability of the nanoparticles. This result implies that geochemical modeling leads to the erroneous prediction of a natural system if the effect of the sorption process is not taken into account.     

柔和气力输送-布勒对米厂提升技术的革新

现今在日本,当稻米加工企业要建米厂时,布勒大米设备已成为他们的首选。日本千叶县食粮株式会社(Shokuryo公司)采用布勒新近提供的一条碾米生产线,被认为是日本最先进的一个米厂。今天,日本市场日益增加的米制产品的生产都在与布勒的专业技术相结合。日本消费者对大米的质量要求非常高,在购买大米产品时,所作决定都是依据蒸煮特性和风味作为主要质量的评判。另外,日本消费者对产品的新鲜程度要求也日益增长。仅有新加工的大米具有完美的质量特点,才符合消费者的要求。所有在大型新建米厂中应仔细考虑的设计要求都得到了满足。Shokuryo公司…     

Elimination of unnecessary contact states in contact state graphs for robotic assembly tasks

It needs much computation to develop a contact state graph and find an assembly sequence because polyhedral objects consist of a lot of vertices, edges, and faces. In this paper, we propose a new method to eliminate unnecessary contact states in the contact state graph corresponding to a robotic assembly task. In our method, the faces of polyhedral objects are triangulated, and the adjacency of each vertex, edge, and triangle between an initial contact state and a target contact state is defined. Then, this adjacency is used to create contact state graphs at different priorities. When a contact state graph is finished at a higher priority, a lot of unnecessary contact states can be eliminated because the contact state graph already includes at least one realizable assembly sequence. Our priority-based method is compared with a face-based method through statistically analyzing the contact state graphs obtained from different assembly tasks. Finally, our method results in a significant improvement in the final performance.     

Preparation and cure behavior of organoclay‐modified allyl‐functional benzoxazine resin and the properties of their nanocomposites

A new type of polybenzoxazine‐clay nanocomposites were prepared by the in‐situ polymerization of allyl‐functional benzoxazine monomer, bis(3‐allyl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (B‐ala), in the presence of two different types of organoclay, allyldimethylstearylammonium‐montmorillonite and propyldimethylstearylammonium‐montmorillonite. The organoclays were mixed with molten B‐ala, followed by pouring into glass mold and then gradual curing up to 250°C. DSC and IR were used to follow the cure behavior of B‐ala in the presence of organoclay, indicating that organoclays catalyzed the ring opening of cyclic benzoxazine structure. The XRD of the nanocomposites showed featureless patterns, suggesting the exfoliation of the organoclay into the matrix. The viscoelastic properties of the hybrids showed that the glass transition temperatures (T_g) of the nanocomposites shifted to lower temperature in the presence of small amount of organoclay, but T_g started to increase with the increase of the organoclay content. This result suggests that, in the presence of organoclay, the curing reaction of ally and benzoxazine occurred in a different way, resulting in a different network structure. However, the presence of dispersed layered silicates into the matrix enhanced the thermal stability over the neat thermoset resin. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

The numerical analysis of particle-size distribution of clusters in shear flow at one-dimensional closed system and three-dimensional open system

Aimed at optimizing the resin-molding process, a method for numerically analyzing aggregation and dispersion behavior of the filler in resin composite was proposed. The flow of a resin composite during molding was calculated by using computational fluid dynamics (CFD), and particle-size distribution (PSD) of the cluster in each computational domain of the CFD model was estimated by solving the population balance equation (PBE). The proposed numerical-analysis method is based on the thixotropy model of Usui et al. In the thixotropy model, PSD is calculated by taking into account the aggregation and dispersion rate of the cluster by Brownian coagulation, shear coagulation, and shear breakage. Shear-breakage rate of the cluster is evaluated by solving the energy balance of bonding energy of the primary particles cut at the breakage and the drag applied to the cluster by the flow of the fluid. The composite viscosity was calculated using Krieger and Dougherty’s model based on apparent-solid-volume fraction estimated from the calculated PSD. To solve the PBE at low calculation cost, it was discretized using the fixed-pivot technique of Kumar and Ramkrishna. The proposed method was incorporated into the general-purpose CFD software FLOW-3D®, and its accuracy was proved.