Driving Spray Drying towards Better Yield: Tackling a Problem That Sticks Around

Powder deposition and accumulation on walls of spray drying chamber has been known to impact spray drying processes, resulting in lower yield, frequent shutdowns, and downtimes. Critical factors that impact the extent and rate of wall deposition have been studied extensively in the chemical and food industry. In this paper, we present an atypical process yield issue wherein acceptable yield is obtained during the first batch of spray drying but undergoes significant yield loss in consecutive batches. Through understanding the interplay of the process, material properties, and equipment, we identify key mechanisms that are playing a role in causing the process yield issue. These mechanisms include surface roughness of the inner wall of the spray dryer, variation in gas flow due to the introduction of process analytical technology, start-up and shutdown operating parameters that expose the wall deposited powder from the prior batch to temperatures close to the onset of glass transition temperature and cause depression of its glass transition temperature. These factors result in more wall accumulation and impact the yield in subsequent batches. By correcting for most of these factors, the yield reduction issue was mitigated, and processing efficiency was improved

Process Optimization for Pulse Reverse Electrodeposition of Graphene-Reinforced Copper Nanocomposites

<p>In the present study, processing of graphene-reinforced copper nanocomposite foils with homogenous dispersion of graphene throughout the matrix, exhibiting good mechanical properties by a simple, cost-effective, and scalable pulse reverse electrodeposition technique (PRED) with special focus on the influence of graphene content in the electrolyte to tailor the properties. A systematic approach has been adopted for enhancing the properties. Distribution of graphene nanosheets in the copper metal matrix and the microstructural properties have been studied by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Interesting observations have been made from nanoindentation studies, where hardness (∼2.7 GPa) enhanced mainly with increase in graphene content (0–0.75 g/L), while maximum elastic modulus (∼139 GPa) is achieved for a graphene content of 0.5 g/L in the electrolyte. Four-point probe testing has been adopted to evaluate the electrical features. The major contribution in enhancement of properties is found to be the presence of graphene and its uniform individual dispersion and distribution as nanosheets in the copper matrix.</p

Controllable Crystallographic Texture in Copper Foils Exhibiting Enhanced Mechanical and Electrical Properties by Pulse Reverse Electrodeposition

The texture evolution in copper foils prepared by a rapid pulse reverse electrodeposition (PRED) technique using an “additive-free” electrolyte and the subsequent correlation with the mechanical and electrical properties is investigated in this study. Control over (111), (100), and (101) crystallographic textures in copper foils has been achieved by optimization of the pulse parameters and current density. A hardness as high as 2.0–2.7 GPa, while the electrical conductivity was maintained in the same range as that of bulk copper, was exhibited by these foils. A complete study of controlling the (111), (100), and (101) textures, CSL Σ3 coherent twin boundaries, grain refinement, and their effect on the mechanical and electrical properties is performed in detail by characterizing the foils with electron backscatter diffraction, X-ray diffraction, nanoindentation, and electrical resistivity measurements. The PRED technique with short and high-energy pulses allowed the (111) texture with increase in forward off-time, while the optimized current density resulted in the formation of (100) and (101) textures. The reverse/anodic pulse applied after every forward pulse aided the minimization of residual stresses with no additives in the electrolyte, the stability of texture in the foils, grain refinement, and formation of growth twins. Among the three highly textured copper foils, those with dominant (111) texture exhibited a lower electrical resistivity of ∼1.65 × 10^–6 Ω cm and better mechanical strength compared to those with (100) and (101) textures