Manufacturing of Hybrid Al-Cu-Heatsinks by Combining Powder Pressing with Thixoforming

Hybrid material structures allow different material properties to be combined in one single component and thus to meet high functional requirements. When manufacturing such hybrid components, particular attention must be paid to the transition zones between metallic composite partners. These transition zones need to show largely homogeneous and materially bonded structures in order to ensure ideal transmission of the material properties and to prevent component failure due to material defects. In this respect, this paper focuses on a newly developed process in which a powder metallurgical route is combined with semi-solid forming technology. Here, porous copper green bodies are inserted into a forming die and subsequently forged together with a semi-solid aluminium alloy. In this way, it was tried to combine both metal materials into a material locking or at least into a form locking manner in order to achieve ideal material properties in the final hybrid component. The aim of this paper is to find suitable process parameters to infiltrate the porous copper inlay with the semi-solid aluminium alloy during thixoforming. Therefore, different process parameters such as varying liquid fraction of the aluminium alloy and different densities of the green bodies were examined during the production of simply shaped hybrid Al-Cu-components. Afterwards the infiltration depth and produced microstructure of the components was analysed. In the future, this process allows for producing aluminium-copper hybrid heat sinks with improved heat transfer properties compared to conventional produced heat sinks.

Comparison of Three Manufacturing Techniques for Sustainable Porous Clay Ceramics

This study proposes different manufacturing techniques (manual pelletization, powder pressing, and “shell scaffold”) to obtain lightweight clay ceramics containing recovery raw materials. The sintering in an electrical furnace (1000 °C, 1 h processing time) was conducted by traditional firing from room temperature, for pressed and shell-scaffold samples, while the flash heating (i.e., samples directly put at 1000 °C) was used only for the pellets. The porous materials (porosity 40–80%), functionalized with nutrients (K and P) in amounts to confer the fertilizer capability, gave suitable results in terms of pH (6.7–8.15) and electrical conductivity (0.29–1.33 mS/cm). Thus, such materials can be considered as feasible lightweight clay ceramics, with a positive effect on the soil. These findings permit us to hypothesize a potential use in green roofs or in agronomic applications.

ANALYSIS OF EXISTING METHODS FOR URANIUM-PLUTONIUM MIXED NITRIDE FUEL FAB-RICATION IN RUSSIA AND ABROAD

This paper presents a review and a brief analysis of existing methods for producing mixed uranium nitride and plutonium, developed by both Russian and foreign scientists. The main parameters of the processes are considered, and their advantages and disadvantages are studied. Currently, the main areas of nitride fuel production are the metal hydride method and carbothermic reduction from the starting oxides. The methods are traditional ceramic technology. The starting products for the manufacture of nitride fuel powder can be either oxides (uranium dioxide and plutonium dioxide) or metals (uranium, plutonium and their alloys). To date, the technology for the manufacture of nitride fuel powder has not been finally selected. When considering existing methods, significant emphasis was placed on industrial applications and the simplicity of the hardware design processes. The laboratory methods are reflected in the work, which make it possible to simplify the process and reduce the costs of obtaining powders of mixed uranium and plutonium nitrides. However, they have significant difficulties in the technological implementation and low productivity of the processes. Of special interest among laboratory methods for producing mixed uranium and plutonium nitrides is the method of high-voltage electric pulse consolidation. This method allows sintering of tablets at the stage of powder pressing from mixed uranium and plutonium nitrides by passing a short high-voltage discharge with a power of several kW directly through the powder.

Scattering Mechanisms in pressed PbTe

The results of studies of structural and thermoelectric properties obtained by the powder pressing method of PbTe samples are presented. In order to interpret the obtained results, a theoretical calculation of the specific conductivity and the Seebeck coefficient was performed on the basis of a model that takes into account two types of free charge carriers. Conclusions have been made about the mechanisms of carrier scattering.

Stages of technological process of high anisotropy formation of magnetic properties under «dry» pressing of powder products

The article proposes the description of technological production process of anisotropic products from powders of high materials which provides powders preparation and products made of them. It has been shown that the main drawback of «wet» pressing technology is low accuracy at dosing wet charge. To eliminate warping and cracking of briquettes obtained by «wet» pressing during the sintering, they are subjected to air drying at room temperature within 48-72 hours. However, the percentage of product failure due to mechanical and magnetic characteristics remains high. Practically all the drawbacks of «wet» pressing can be eliminated by reverse to dry powder pressing, which allows to obtain low mass magnets without additional final finishing machining, to avoid warping and cracking of the product, and to reduce sintering time. Nevertheless, under the dry powder pressing the magnetic characteristics of products are significantly lower than under the wet pressing. When working with disperse materials, a promising direction is to converse them into fluidized state. To obtain the fluidized state of powder materials, vibrational technologies are used, involving the transfer of a wide range of energy to the powder material, i.e. mechanical, acoustic, electric and magnetic energy.

Thermal Conductivity Mechanisms in Compressed Thermoelectric Materials Based on A4B6 Compounds

The factors influencing the value of the thermal conductivity coefficient of thermoelectric materials based onlead telluride obtained by powder pressing method have been analyzed. The model is presented and itsparameters are defined, which explains qualitatively and quantitatively the temperature dependences of thethermal conductivity coefficient of PbTe and PbSnAgTe.