Microstructure of metal matrix composites reinforced by ceramic microballoons

Metal matrix composites reinforced by ceramic hollow microspheres were produced as special porous metals, called metal matrix syntactic foams (MMSFs). In this paper the microstructure of the ceramic hollow microspheres as reinforcing element was investigated in connection with the production of MMSFs by pressure infiltration. SL150 and SL300 type ceramic microspheres from Envirospheres Ltd. (Australia) were investigated. They contained various oxide ceramics, mainly Al2O3 and SiO2. The chemical composition and the microstructure of the microspheres had strong effect on their infiltration characteristics; therefore in the view of MMSF production it was very important to know microstructural details about the microspheres. Due to this energy dispersive X-ray spectroscopy maps were recorded from the cross sections of the microspheres’ wall. The results showed that the Al2O3 and SiO2 distribution was not equal; the Al2O3 phase was embedded in the surrounding mullite and SiO2 phase in the form of needles. Line energy dispersive X-ray spectroscopy measurements were performed in order to investigate the possible reaction between the different aluminium alloy matrices and the ceramic microspheres. The results showed that, due to the uneven distribution of Al2O3 rich particles, the molten aluminium could reduce the SiO2 rich parts of the microspheres and the wall of the hollow microspheres became damaged and degraded. This chemical reaction between the microspheres and the walls could make the infiltration easier, but the resulting mechanical properties will be lower due to the damaged microsphere walls

The Timing of National Greenhouse Gas Emission Reductions in the Presence of Other Environmental Policies

This paper shows in an empirical context that substantial cost reductions can be achieved in the implementation of Dutch national climate policy by (i) targeting the policy at the stock of greenhouse gases, thus allowing polluters flexibility in their timing of emission reductions; and (ii) integrating climate policy with other policies, thereby optimising the restructuring of the economy needed to achieve environmental policy targets. A dynamic applied general equilibrium model with bottom-up information on abatement techniques is used to show that the optimal timing of GHG emission reductions tends to follow the timing for the other environmental themes with an additional emphasis on emission reductions in the later periods. The optimal mix of technical measures and economic restructuring as source of emission reductions is affected by the strictness of environmental policy targets for all themes and hence can only be derived from an integrated analysis of these policies.Economic growth, Applied general equilibrium model, Climate change, Environmental policy

Compressive behaviour of metal matrix syntactic foams

The compressive behaviour of three different metal matrix syntactic foams (MMSFs) were investigated. The results showed that the engineering factors as the size of the used hollow spheres, the aspect ratio (height / diameter ratio) of the specimens and the temperature of the compression tests have significant effects on the compressive strength and properties. The smaller microballoons with thinner wall ensured higher compressive strength due to their more flawless microstructure and better mechanical stability. The higher aspect ratio of the specimens resulted in worse compressive characteristics (lower strength, lower specific energy consuming capacity). The elevated temperature tests revealed ~30% drop in the compressive strength. However, the strength remained high enough for structural applications; therefore MMSFs are good choices for light structural parts working at elevated or room temperature. The proper size selection of the reinforcing hollow spheres ensures potential for tailoring the compressive characteristics of MMSFs

Compressive characteristics of metal matrix syntactic foams

The compressive behaviour of eight different metal matrix syntactic foams (MMSFs) are investigated and presented. The results showed that the engineering factors as chemical compositions of the matrix material, the size of the microballoons, the previously applied heat treatment and the temperature of the compression tests have significant effects on the compressive properties. The smaller microballoons with thinner wall ensured higher compressive strength due to their more flawless microstructure and better mechanical stability. According to the heat treatments, the T6 treatments were less effective than expected; the parameters of the treatment should be further optimized. The elevated temperature tests revealed ~30% drop in the compressive strength. However, the strength remained high enough for structural applications; therefore MMSFs are good choices for light structural parts working at elevated or room temperature. The chemical composition – microballoon type – heat treatment combinations give good potential for tailoring the compressive characteristics of MMSFs

Impact of the Sector and of Internal Factors on Profitability of the Companies Listed on the Warsaw Stock Exchange

The aim of the article is to assess the impact of the sector environment and of selected internal factors on the profitability level of the companies listed on the Warsaw Stock Exchange in 1998-2016. An increase in the financial leverage, financial liquidity, non-debt tax shield and enterprise size cause a drop in the ROA. An increase in the ratio of fixed assets to the total assets results in an increase in the ROA. Similar results were obtained for the models estimated for the ROE. It means, that profitability of the examined companies results from the decisions made by the managers and from the impact of the sector environment

Big words, little results : the Chinese investments in Poland from the political perspective

In 2017 statistics showed that Chinese Foreign Direct Investments (FDI) in Poland for 2016 amounted to a more than half of all Chinese FDI in Poland for the 2000–2016. Yet the overall amount of Chinese FDI remains modest in comparison with Western Europe or even with Hungary. Despite much proclaimed Sino-Polish rapprochement in 2015–2016 and high hopes for OBOR/BRI initiative in Poland, cooperation with China has not been a breakthrough for Poland in terms of economic results. There have not been ground-breaking Sino-Polish projects and Polish government’s desire to strengthen ties with China loosened in late 2016/early 2017 (though it may revive now).There are several reasons for that, from the perception of Poland as non-attractive for majority Chinese investments, via lack of overall Polish strategy of attracting these investors to discrepancies of economic interests between Poland and China