Progress in Research on Structural Ceramic Materials Toughened by Graphene

Graphene has excellent mechanical properties and unique physical/chemical properties,which make it have a good strengthening and toughening effect on structural ceramic materials.In recent years,it has received widespread attention and research.This article reviews the mixing and sintering processes in the preparation of graphene/ceramic com-posites,as well as the toughening mechanism of graphene on ceramic materials.It also looks forward to how to further enhance the toughening effect of graphene.

Impact of the spindle number on the material transport and mixing during planetary roller melt granulation Author links open overlay panel

In comparison to the established twin-screw machines,the application of a planetary roller granulator for continuous operation of melt granulation is a promising alternative based on the unique process concept.An initial study focused on the material transport during processing as a key driver for the overall performance.Hereby,the impact of direct process parameters on the residence time distribution was the main objective.These investigations are complemented in this study by considering the free processing volume,which is defined by the number of planetary spindles applied within a module.The impact on the processing conditions is evaluated with respect to the process setting in terms of feed rate and rotation speed.The results highlight the potential of altering the underlying transport function in planetary roller melt granulation(PRMG)via the investigated direct process and equipment parameters.The impact of the feed rate is lower in comparison,while a higher rotation speed as well as a higher free processing volume promote material mixing.Moreover,a normalization of the determined residence time distribution(RTD)model data was feasible with respect to the process settings and the number of applied planetary spindles in the processing zone.This demonstrates the key role of the free processing volume in the fundamental mechanisms of material transport and mixing during PRMG.

Improvement of corrosion resistance of PEO coated dissimilar Ti/Mg0.6Ca couple

With the growing demand for weight reduction,the application of joint lightweight structural materials is increasing.Magnesium alloys feature low density,high specific strength and good formability,offering significant advantages for fuel efficiency and load capacity.Combined with Ti,a dissimilar Ti/Mg composite material provides great flexibility combining the properties of each material.However,because of the great differences in chemical and electrochemical properties between Mg and Ti,it is imperative to address the galvanic corrosion problem of such dissimilar Ti/Mg components.This work presents an investigation of the PEO processing of sintered Ti/Mg0.6Ca couples,aiming to improve the corrosion resistance of such dissimilar alloy combinations using a phosphate-aluminate electrolyte.The results show that uniform and continuous coatings can be formed on the dissimilar Ti/Mg0.6Ca couple.The coating mainly contains MgO and MgAl_(2)O_(4)on the Mg0.6Ca side,and Al_(2)TiO_(5)is the dominant phase on the Ti side.The work also took advantage of synchrotron X-ray computed tomography(CT)scanning to achieve 3D reconstruction of the coating morphology,which can be a fast method to assess the porosity and compactness of the coating and further predict the coating corrosion resistance.The coating effectively improved the corrosion resistance of the dissimilar Ti/Mg0.6Ca couple.

USE OF INDUSTRIAL WASTE OF PERLITE IN BUILDING MATERIALS INDUSTRY

We have observed the components, structure and properties of perlite ore. Through a series of ex- periments, it has been proved that the perlite has higher pozzolanic activity and maybe used as addi- tion of cement in manufacturing pozzolanic cement. The paper also proposes the way to increase the early strength of this kind of cement and utilize it to make many kinds of silicate concrete products.

Properties and interfacial microstructure of cement-based materials with composite micro-grains

Silica fume, fly ash and nano-fiber mineral materials (NR powder) are employed to incorporate into cement-based materials. According to the grain grading mathematical model of cement-based materials, two packing systems, namely, spherical grading system and nano-fiber reinforced system were designed. Properties and interfacial microstructure of the two systems were studied according to secondary interface theory. It was shown that nano-fiber mineral materials can improve the grain grading of the admixture, increase the density of the system, improve the microstructure of the interface and the hardened paste, and enhance the uniformity of cement-based materials mixed with composite micro-grains and greatly increase their wearable rigidity and flexure strength. In this paper, two kinds of interface models, including spherical grain model and nano-fiber reinforced interface model of the cement-based materials mixed with composite micro-grains, were brought forward.

Design and test of a multi-edge toothed cutting device for membraneimpurity mixed material

As the existing residual film crushing device in Xinjiang cannot directly crush membrane-impurity mixed material,by analyzing the compressive and cutting force characteristics of residual film material layer and cotton stalk,the cutting conditions of mixed materials were obtained,and the method of cutting was determined.A multi-edge toothed cutters was created,and a cutting device was built.It was preliminarily determined that the number of teeth in the cutters was 8,the clearance between the teeth and between the tooth and fixed blade was 3 mm,the speed of the high-speed cutter was 800 r/min,and the speed difference between the high-and low-speed cutters was-300 r/min.Test results show that the ratio of residual film to total residual film sampling mass was(2.22±0.30)%,(19.19±2.02)%,(58.94±3.19)% and(20.65±2.05)%,respectively,when the maximum outer profile size in the range of[0,20)mm,[20,100)mm,[100,500)mm and[500,~)mm.The mass of cotton stalks with lengths of[0,50)mm,[50,100)mm and[100,~)mm accounted for(32.57±1.5)%,(27.77±1.3)%and(39.66±1.75)%,respectively,and the cutting power consumption was(85.41±15.63)kJ.The test results can provide a basis for the subsequent membrane-impurity mixed material cutting technology,as well as some guidance for the separation of it.

COMPUTER ANALOG OF GRAPHITE GRINDING

With the assistance of grinding dynamic model, this paper studied she dynamic parameters of single size ball grinding of single grade size material and mixed materials as well as multi-size ball grinding of single-grade material, and analog-calculated the product size distribution of multi-size ball grinding of mixed materials. The study showed: in a certain grinding timet the analog-calculation achieved the same result as the experiment.

Numerical Simulation of Flow Field and Flow State Division in Thin-Film Evaporators

The flow field and flow state of thin-film evaporators are complex,and it is significant to effectively divide and quantify the flow field and flow state,as well as to study the internal flow field distribution and material mixing characteristics to improve the efficiency of thin-film evaporators.By using computational fluid dynamics(CFD)numerical simulation,the distribution pattern of the high-viscosity fluid flow field in the thin-film evaporators was obtained.It was found that the staggered interrupted blades could greatly promote material mixing and transportation,and impact the film formation of high-viscosity materials on the evaporator wall.Furthermore,a flow field state recognition method based on radial volume fraction statistics was proposed,and could quantitatively describe the internal flow field of thin-film evaporators.The method divides the high-viscosity materials in the thin-film evaporators into three flow states,the liquid film state,the exchange state and the liquid mass state.The three states of materials could be quantitatively described.The results show that the materials in the exchange state can connect the liquid film and the liquid mass,complete the material mixing and exchange,renew the liquid film,and maintain continuous and efficient liquid film evaporation.

Mixing of particles and powders:Where next?

Industrial mixers for powders and granular materials operate with no effective control of mixture quality and lack scientific design. The last twenty years have seen growth in understanding of mixing and mixers. However, research falls far short of what is needed for on-line characterisation of mixture quality. Secondly, although theoretical descriptions of a few mixer types have been reported, these fall far short of what is needed for equipment design. Two thrusts could revolutionise this situation. One is a scientific characterisation of mixer structure applicable to industrial scale as well as laboratory scale equipment; this is now within our grasp using digital imaging. The other is the development of ideas to overcome the restricted number of particles that can be used in the Distinct Element Method （DEM） for mixers. The goal should be to take the designer through a sequence of steps to the most appropriate mixer size, configuration and operating conditions for a given process duty.

Numerical analysis of enhanced mixing in a Gallay tote blender

The mixing performance of a multi-bladed baffle inserted into a traditional Gallay tote blender is explored by graphic processing unit-based discrete element method software. The mixing patterns and rates are investigated for a binary mixture, represented by two different colors, under several loading profiles. The baffle effectively enhances the convective mixing both in the axial and radial directions, because of the disturbance it causes to the initial flowing layer and solid-body zone, compared with a blender without a baffle. The axial mixing rate is affected by the gap between the baffle and the wall on the left and right sides, and an optimal blade length corresponds to the maximum mixing rate. However, the radial mixing rate increases with the blade length almost monotonically.