The solid waste of Rapana thomasiana seashells both from domestic activities and natural waste on seashore can be used to obtain viable products for medical applications. However, conventional technologies applied for sintering the materials require massive energy consumption due to the resistance heating. Microwave heating represents an advanced technology for sintering, but the stability of the process, in terms of thermal runaway and microwave plasma arc discharge, jeopardizes the quality of the sintered products. This paper aims to present the results of research focused on viable heating technology and the mechanical properties of the final products. A comparative analysis, in terms of energy efficiency vs. mechanical properties, has been performed for three different heating technologies: direct microwave heating, hybrid microwave heating and resistance heating. The results obtained concluded that the hybrid microwave heating led to final products from Rapana thomasiana solid waste with similar mechanical properties compared with resistance heating. In terms of energy efficiency, the hybrid microwave heating was 20 times better than resistance heating.

The paper presents the results of experimental researches on the formation of barium hexaferrite type M (BHFM) by microwave heating. The microwave heating process takes only a few minutes to obtain calcined barium ferrite powders. Micronic and nanometric powders of BaCO3 and α-Fe2O3 were used as raw materials. In order to obtain BHFM, the microwave heating process was used with following mixtures: stoichiometric homogeneous mixture of BaCO3 and α-Fe2O3 powders, mechanically alloyed mixtures of BaCO3 and α-Fe2O3 powders for 5 and 20 hours in wet medium using a high energy ball mill Pulverisette 4. Using high energy ball milling, the powder size was turned into nanoscale. After using the microwave heating process it was observed a significant reduction of temperature-time parameters to BHFM formation for mechanically alloyed mixtures compared to homogeneous mixture.

This paper presents a study about the influence of some alloying elements like Ni and Co on the elaboration of W-Cu electrical contacts. For the experimental work four types of mixture were prepared using mechanical alloying (MA) technique for six hours. All the samples had the same Ni and Co content (2%) varying the W content as following: 88W-10Cu-Ni, 78W-20Cu-Ni, 68W-30Cu-Ni, 88W-10Cu-Co, 78W-20Cu-Co and 68W-30Cu-Co. The mixtures were pressed in a cylindrical die with 10 mm diameter at two pressures: 400MPa and 600 MPa. The sintering process was carried out in an electrical furnace at the 1180 OC and maintained at this temperature for three hours. For all the samples the electrical properties: resistivity, conductivity, resistance were measured and were made correlation between electrical contacts with Ni and the other with Co. It is observed that, the compaction pressure influence the electrical properties and better properties are obtained for the samples compacted at 600 MPa.

Soldering processes are applied in the fabrication of electronic circuits used in most modern domestic and industrial technologies. This article aims to introduce a new soldering technology based on the microwave joining of copper materials used in electronic applications. The study was focused on microwave technology used as the thermal source for soldering. A simulation model of temperature distributions in copper plates with overall dimensions of 50 × 10 × 0.8 mm was developed in order to determine the necessary microwave power for soldering. For 270 °C simulated on the surface of copper plates, the microwave-injected power was determined to be 598.89 W. An experimental program for 600, 650, 700, and 750 W was set in order to achieve soldering of copper plates in less than 1 min. Soldered copper plates were subject to electrical resistance measurements being obtained with variations up to ±1.5% of the initial electrical resistance of the base materials. The quality of joints has also been analyzed through microscopy after the soldering process. In addition, mechanical properties were determined using a universal testing machine. The results have shown similar behavior of the samples layered with SAC on the one-side and double-side but also a significantly lower force before breaking for one-side-layered samples. An economic analysis was performed and the results obtained have shown that in terms of energy efficiency and total costs for microwave soldering compared with manual soldering, microwave soldering is cost-effective for industrial processing.

Thermal runaway in microwave hybrid heating of ceramics is an unwanted phenomenon which damages the sintered products. The aim of the present study is to establish to what extent the pressing forces of 100, 200 and 300 MPa used in the compaction process and the optimization of the microwave heating mechanism can reduce the occurrence of thermal runaway. Modeling and simulation of temperature distributions alongside defects created by the compaction process are performed in order to evaluate their influence on the stability of MHH. Based on CT scanning, defects with dimensions from 110 to 515 μm are studied in terms of local overheating and how the thermal runaway can lead to internal arc discharge. The results show that samples compacted at 100 MPa and exposed at 600 W injected power reach temperatures peaks around 1010 °C and are affected by major cracks and large melted areas. The samples compacted at 200 and 300 MPa present similar behavior, without arc discharge, but are also affected by cracks. Based on these findings, the MHH process can be applied to sintering processes but with a reduced injected power below 300 W for samples compacted with pressing forces higher than 300 MPa.

Over 60% of reported failures for reactive power compensation systems are given for damage to electrical circuit breaker contacts. This paper presents a study on the development of microwave technology for sintering of W–Cu–Cr alloys at 1012 °C for 65 min using 623.38 W microwave power, as well as microwave joining at 231 °C of the W–Cu–Cr composite material on body contact using 475 W microwave power for 55 s. The joined components were subjected to mechanical and electrical tests in accordance with ICE standards to validate the applied technology. Tests of connection–disconnection of the electrical contacts were carried out in accordance with the maximum number of disconnections allowed by the manufacturer (2 cycles/min): 25 s rest time and 5 s operating time under load. The components of the electrical contact after 111237 switches were analyzed under a microscope revealing a reduction of the damaged area by 27% compared with the original contact.