On the Effect of the Rotating Chamber Reverse Speed on the Mixing of SiC Ceramic Particles in a Dry Granulation Process

In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In particular,an Euler-Euler two-phase flow model is used to analyze the dynamics of both SiC particles and air.The numerical results show that by setting a certain reverse rotating speed of the rotating chamber,the accumulation of SiC particles on the wall can be improved,i.e.,their direction of motion in proximity to the wall can be changed and particles can be forced to re-join the granulation process.Experimental tests conducted to verify the reliability of the numerical findings,demonstrate that when the reverse rotating speed of the rotating chamber is 4 r/min,the sphericity of SiC particles in the rotating chamber is the highest and the fluidity is the best possible one.

Influence of Nozzle Orifice Shape on the Atomization Process of Si3N4 in a Dry Granulation Process

In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-phase flow is analyzed using a VOF(Volume of Fraction)method together with the modified realizable k-εturbulence model.The influence of nozzle orifice shape on velocity distribution,pressure distribution is studied.The results show that the pressure difference in a convergent conical nozzle is the largest with a hollow air core being formed in the nozzle.The corresponding velocity of atomized liquid at nozzle orifice is the largest.Using a self-designed atomization experiment platform,the velocity and pressure of atomized liquid and the spray cone angle are measured for three nozzles with different orifice shapes.The micro-morphology of Si3N4 particles is also determined.These data confirm the correctness of numerical simulation.Considering atomization performance of the nozzle,the contraction conical nozzle is more suitable for the atomization of Si3N4 in practical production based on the dry granulation approach.

Intermediate phase assisted sequential deposition of reverse-graded quasi-2D alternating cation perovskites for MA-free perovskite solar cells

One-step deposition approaches have been widely applied and developed in the fabrication of quasi-2D perovskites.However,the regulation of quantum wells(QWs)and crystalline orientation is difficult and complicated when using this methodology.Sequential deposition is another widespread synthetic approach for preparing perovskite films and perovskite dimension engineering.In this article,δ-CsPbI_(3)intermediate phase assisted sequential(IPAS)deposition is successfully carried out to fabricate MA-free quasi-2D ACI perovskites.The amount of theδ-CsPbI_(3)intermediate phase in the PbI2 layer and the concentration of GAI molecule in the IPA solution both play important roles in the production of MA-free quasi-2D ACI perovskite films.The n value of the MA-free quasi-2D ACI perovskites can be adjusted,which affects the photovoltaic performance and device stability.Compared with one-step deposition,the MA-free quasi-2D ACI perovskites prepared via IPAS deposition have opposite reverse-graded QW distribution and improved vertical orientation,leading to a remarkable PEC of up to 18.86%and allowing the preparation of unpackaged devices with prominent working stability(80%,400 h).The underlying mechanism and crystallization pathway of IPAS deposition confirm that sequential deposition has unique superiority in regulating the QW distribution and crystalline orientation of quasi-2D perovskites.

Effect of geometric parameters at open turbine combined structure on flow field distribution of dry granulation for Si_(3)N_(4) powder

To improve the uniformity of the flow field and the poor axial velocity in the chamber of Si3N4 dry granulation, the influence of geometric parameters at open turbinecombined structure on the flow field distribution is studied. The Euler–Euler gas-solidtwo-phase flow model is established and the physical model of dry granulation chamberunder the combined structure is simplified. Under the same radial structure, the volumedistribution and velocity field of Si3N4 particles in the granulation chamber with a different number and angle of the axial structure at the open turbine are analyzed by theCFD method. The influence of the axial structure at the open turbine on the flow fielddistribution of Si3N4 particles under different geometric parameters is compared. Theresults show that the axial structure of the open turbine in the granulation chamber isthe most uniform when the number of blades is 6 and the inclination angle is 45◦, andthe circulating flow of the upper and lower parts of Si3N4 powder is strong.

Partially stabilized tetragonal ZrO_(2) whiskers with preferred [001] direction derived from CaF_(2)

The simultaneous control of crystal phase stability and one-dimensional growth has always been the major challenge for the preparation of tetragonal zirconia whiskers.In this study,we report a facile molten salt processing that utilizes CaF_(2) as a stabilizer and adsorbent to meet the phase and morphology requirements.The processes of stabilization,phase transition,ion adsorption and formation of special morphology involved in zirconia growth were investigated by XRD,IR,SEM,DTA-TG and TEM.By controlling the amount of CaF_(2)(15 wt%)added in the reaction precursor,tetragonal zirconia whiskers with a desired aspect ratio(>16)can be synthesized,which show single crystalline nature and[001]preferred direction.Ca ions doped at low temperature inhibit the occurrence of phase transition,which allows the tetragonal structure to be retained to room temperature.The inducement and pattern of whisker growth are supposed to be F-adsorption and screw dislocation elongation,respectively.The specific selectivity of surface adsorbed ions to certain zirconia crystal planes reduces or even inhibits the epitaxial growth rate in this direction,offering a viable avenue for the morphology modulation of inorganic nanomaterials.