The fast expanding field of wearable technology requires light-weight, low-cost, scalable, flexible and efficient energy harvesters as a source of uninterrupted green power. This work reports fabrication of sub-micron graphite platelet/PVDF composite film-based flexible piezoelectric energy harvester (PGEH) for scavenging the wasted mechanical energy associated with human body motion. The addition of graphite platelet leads to the enhancement of electroactive β phase in PVDF; consequently, the piezoelectric and dielectric properties of the composite are enhanced. 0.5 wt% filler-loaded composite has 96% β phase fraction and dielectric constant 32 at 100 Hz (tanδ = 0.18).The PGEH produces open circuit voltage of 40 V and instantaneous power density of 3.35 mW cm− 3 with energy conversion efficiency of 22.5% under periodic finger tapping. It can generate fair electrical output under gentle heel (0.8 V) and toe movements (1.2 V). A PGEH is directly employed for powering 50 commercial LEDs and quick charging of a 2.2-μF capacitor upto 19.2 V. The device is also employed as self-powered dynamic pressure sensor which shows high sensitivity (0.9 VkPa− 1) with fast response time (1 ms). Therefore, this durable, flexible, efficient PGEH can have promising applications in wearable electronics as a green power source cum self-powered mechanosensor.

During sintering of Ni-electrode multi-layer ceramic capacitors (MLCCs), the Ni electrode often becomes discontinuous because of its lower sintering temperature relative to that of BaTiO3. In an attempt to retard the sintering of Ni, we introduced passivation of the Ni powder. To find the optimal passivation conditions, a thermogravimetric analysis (TGA) was conducted in air. After passivation at 250oC for 11 h in air, a nickel oxide shell with a thickness of 4- 5 nm was formed on nickel nanoparticles of 180 nm size. As anticipated, densification of the compacts of the passivated Ni/NiO core-shell powder was retarded: the starting temperature of densification increased from ~400oC to ~600oC in a 97N2-3H2 (vol %) atmosphere. Grain growth was also retarded during sintering at temperatures of 750 and 1000oC. When the sintering atmosphere was changed from wet 99.93N2-0.07H2 to wet 99.98N2-0.02H2, the average grain size decreased at the same sintering temperature. The conductivity of the passivated powder sample sintered at 1150oC for 8 h in wet 99.93N2-0.07H2 was measured to be 3.9 × 104 S/cm, which is comparable with that, 4.6 × 104 S/ cm, of the Ni powder compact without passivation. These results demonstrate that passivation of Ni is a viable means of retarding sintering of a Ni electrode and hence improving its continuity in the fabrication of BaTiO3-based multi-layer ceramic capacitors.

By means of magnetic pulsed compaction and sintering of weakly aggregated alumina based nanopowders the jet forming nozzle samples for the hydroabrasive cutting were fabricated. The ceramics was obtained from pure alumina, as well as from alumina, doped by , MgO and AlMg. It was shown that the samples sintered from AlMg doped powder have the best mechanical properties and structural characteristics: relative density , channel microhardness. - 18-20 GPa, channel surface roughness , average crystallite size .

전통적으로 초경합금은 무라까미 용액에서 에칭하거나 묽은 염산에 넣고 끓이는 방법에 의해 그 밋구조를 관찰하였다. 그러나 carbide 입자가 suvmicron 크기인 초경합금에서는 전통적인 에칭 방법으 에칭 후에도 입자/기지상, 입자/입자 입계를 동시에 구분시킬 수 있는 SEM 사진을 얻을 수 없다. 본 연구에서는 submicron 크기 초경합금의 고배율 SEM 사진을 얻을 수있는 90H2O2 - 10HNO3 (vol%)의 새로운 에칭 용액을 개발하였다

The microstructures and mechanical properties of submicron WC-Co cemented carbides were investigated in relation to cobalt content. To inhibit the WC grain growth during sintering, VC was added as a inhibitor in each alloy with 3 mass% to the cobalt content. The WC-(5, 8, 10, 15, 20) mass% Co compacts were sintered at for 30 min in vacuum. Some of WC-(5, 8, 10) mass% Co sintered compacts were HIPed with 120 atm at 130 for 1 hr. The shrinkages of all HIPed alloys were increased without depending on the cobalt contents and the sintered densities of them. The relative densities of the alloys were increased with the cobalt content and HIPing. The less the cobalt content, the larger the WC grain. Many contiguities of WC grains were found in WC-5 mass% Co alloy. The sizes and numbers of pores in the alloys were decreased by HIPing. And also the strength and the hardness of each alloy were increased. The maximum hardness was about 18.95 GPa in the WC-5 mass% Co alloy HIPed and the maximum transverse-rupture strength (T.R.S.) 3.2 GPa in the WC-20 mass% Co alloy sintered.

The effects of added VC, CrC and TaC on the microstructures and properties of submicron WC-10%Co cemented carbides. The relative sintered density of compact was increased by addition of CrC but decreased oppositely by addition of VC or TaC. The growth of WC grains was significantly suppressed by addition of these carbides. The hardness of these alloys was increased by addition of other carbides and showed a maximum value by simultaneously added VC and CrC. The transverse rupture strength(T.R.S.) was in- creased by addition of CrC, while it was decreased by addition of VC or TaC. The relative sintered density and T.R.S. of these alloys were improved by HIP-treatment. The maximum T.R.S. was 328kg/mm in the Wc-10%Co cemented carbide with addition of 0.5%VC.