TY - CONF A1 - Woydt, Mathias T1 - Tailoring the functional properties of niobium carbide N2 - Several phases, like Nb₄C₃, Nb₆C₅ and other short and long range ordered phases occur in the region of homogeneity of NbCₓ (0,75≤ x ≤1.0) in the binary phase diagram. Properties, like micro-hardness, hot hardness, sliding wear resistance, elastic modulus and toughness can be tailored by the C/Nb ratio, the addition of secondary carbides and the type of binder. Supporting results from different grades with varying C/Nb ratio or binder types were illuminated. Thus, the NbC system offers to producers a wider process window, than WC. The impact of These tailored properties on sliding wear and cutting performance was illuminated by tribological and machining results. Niobium is today largely available. NbC can be synthesized by carbothermal conversion of Nb₂O₅ or be metallurgically grown and leached out, provides comparably low friction in many relevant tribo-contacts and displays low wear. NbC and Nb₂O₅ have so far no REACH classification related to human toxicology and are not listed as substances of very high concern contrary to WO₃ and Co₃O₄. T2 - 40th International Conference and Exposition on Advanced Ceramics and Composites CY - Daytona Beach, FL, USA DA - 24.01.2016 KW - Niobium carbide KW - Hard metal KW - Wear KW - Friction KW - Machining KW - Cutting KW - Metal matrix composite PY - 2016 SP - Paper: 2347292, 1 EP - 13 AN - OPUS4-35640 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Priebe, Nsesheye Susan T1 - Obtaining optimum workability using RHA in a modified cementitious system N2 - In order to reduce CO2 emission in concrete and minimize the environmental impact, majority of research focuses on using supplementary cementitious materials (SCMs) such as Fly Ash (FA), blast furnace slag (GGBS) and Silica Fume (SF) or Microsilica as a replacement for ordinary Portland cement in concrete. However, in terms of sustainability, it is not economically feasible to use the above mentioned SCMs in countries where these materials are not readily available. In addition, when dealing with the carbon footprint of concrete, despite their positive influence in concrete, such SCMs cannot be said to be eco-friendly materials due to their high energy production process. In many developing countries in sub-Saharan Africa (SSA), agriculture is the leading economic sector. Generally, agricultural by-products are eco-friendly in terms of low energy in production, and they often have no further use for the environment. These by-products (baggase, cassava peels and rice husks) are mainly not the materials of discussion in this current day and age and especially in the northern hemisphere, where the majority of concrete technology originates. Hence, it is inevitable to consider other more sustainable resources in concrete for SSA. Nevertheless, optimization of these resources in concrete can only function with a clear understanding of the reactivity of the materials and its interaction and mechanism to adopt similar and workable properties as a normal performance cementitious system. This paper addresses rice husk ash (RHA) as a main SCM in various cementitious systems with added limestone filler (LSF) and observes its performance in mortar. Superplasticizers such as polycarboxylate-ethers (PCEs) and lignosulphonates (LS) are incorporated in the cementitious systems to improve workability. The interaction of RHA with the superplasticizers was investigated by means of zeta potential (ZP). According to the results presented, it is shown that RHA powder has a positive compatibility with the chosen superplasticizers and its performance in mortar with LSF also shows increase in strength and workability. T2 - International Concrete Sustainability Conference CY - Washington DC, USA DA - 15.05.2016 KW - Superplaticizers KW - Supplementary cementitious materials; KW - Sub-Saharan Africa KW - Rice husk ash KW - Cement KW - Concrete PY - 2016 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-41033 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Priebe, Nsesheye Susan T1 - Effect of rheological parameters on rice husk ash blended pastes with various superplasticizers N2 - Rice husk ash (RHA) is a low-energy efficient material with high pozzolanic characteristics compared to other supplementary cementitious materials (SCMs). The replacement of cement with RHA has extensive improvement on the mechanical properties of concrete. However due to the porous nature of the RHA particles, it requires a higher water demand when replaced with Portland cement. Therefore, superplasticizers (SPs) are essential to reduce the water demand and improve the workability of the mixes. There is very little information about the effect of RHA with added SPs in its fresh state. Hence, this paper investigates the interaction of RHA pastes with three types of SPs, i.e. one polycarboxylate-based SP and two different types of lignosulphonates. This paper presents results of the investigation related to the flow behaviour of blended mixes with increasing percentage of RHA. The yield stress for the pastes with and without the addition of SPs is investigated over time as well as the plastic viscosity. T2 - 1st International Conference on Construction Materials for Sustainable Future CY - Zadar, Croatia DA - 19.04.2017 KW - Yield stress KW - Cement KW - Workability KW - Superplasticizers KW - Rice husk ash KW - Plastic viscosity PY - 2017 UR - http://www.grad.hr/coms/ocs/public/coms2017/Proceedings_of_the_CoMS_2017.pdf N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-41035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -