Synthesis and Sintering of ZnO Nanopowders

Abstract

Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders' nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv 50~6 0 nm, easily redispersable) by using a continuous Segmented Flow Tubular Reactor (SFTR), which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a "scale-out" concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 • C and 1100 • C, and Spark Plasma Sintering (SPS) at 900 • C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 • C, while also limiting the grain growth, thus leading to a nanostructured material.

Thermoelectric properties of ZnO ceramics densified through spark plasma sintering

“…The difference could have been caused by the differ ence in powder surface area; C500 had higher surface area of reaction as compared to C700. Similar results were reported by Aimable et al [47] on comparative study of sintering synthesized and commercial powder. The relative density of C600 ceramics did not change much when the temperature was increased.…”

“…Further in crease in the temperature to 700°C caused a decrease in the grains from 6, to 5.4 and 4.2 μm for C500, C600 and C700 ceramics, respectively. The sample C500 showed bigger grains as compared to C600 and C700, probably because of the high surface area of reaction which results in surrounding grain boundaries easily diffuse with each other as ex plained earlier [28,47].…”

The Role of Thin-Film Vacuum-Plasma Coatings and Their Influence on the Efficiency of Ceramic Cutting Inserts

“…All the inserts used in the present studies were from one batch, and were manufactured serially according to a process excluding the influence of additional factors on the experimental results, related to the technology of sintering ceramic inserts [36][37][38][39] and their diamond sharpening. Because ceramics have low electrical conductivity, the application of traditional technological principles to them and the supply of negative voltage to them are less effective than with conductive materials (e.g., high-speed steels and hard alloys).…”

Spark Plasma Sintering of Ceramics: From Modeling to Practice

“…Since its introduction, spark plasma sintering (SPS) has gained significant interest in the ceramic community due to its ability to produce ceramics and ceramic-based composites with short sintering cycles and reduced dwell temperatures [1][2][3][4][5][6][7][8]. A longstanding debate about the origins for the improved densification observed during SPS [9][10][11][12][13][14] arose, given the reported similar apparent activation energies for sintering in SPS compared to other sintering techniques (depending on the sintering stage) [14][15][16].…”