Effect of Al2O3 and SiO2 Inert-Fillers on the Microstructural Evolution and High Temperature Oxidation Resistance of B Modified Silicides Coatings Prepared by Pack Cementation Technology

In this study, B modified silicide coatings were prepared on Nb-Si based alloy with Al2O3 or SiO2 inert-filler by pack cementation technology. Both coatings primarily consisted of a (Nb,X)Si2 with a (Nb,X)B2 + (Nb,X)Si2 outer layer. After oxidation at 1250 °C for 100 h, the coatings showed good oxidation resistance due to the formation of a dense silica. The oxidation products of the coating prepared with Al2O3 inert-filler consisted of SiO2, TiO2 and Cr2O3, while that of the coating prepared with SiO2 inert-filler consisted of SiO2, TiO2, Cr2O3, and HfO2. The different oxidation products may be due to the different oxidation process of these two sample at initial oxidation stage.

Use of powder silicon as a photocurable resin filler for laser stereolithography and prospects for transforming stereolithographic parts with silicon from polymeric to ceramic ones.

The article deals with the peculiarities of using silicon micropowder as a chemically inert filler when creating photocurable resins (PCR) for laser stereolithography. The authors provide the results of their experiments on making three-dimensional parts from such resins and discuss the feasibility of transforming the parts from polymeric, containing a filler, into ceramic ones through annealing. The use of silicon allows for a two-fold increase in the mass of the ceramic component due to the interaction of silicon with air oxygen and with products resulting from the thermal decomposition of the photopolymer's polymer base.

Effect of Admixtures on the Thermo-Physical Properties of Non Autoclaved Light Weight Block Using Marble Dust

In the present study, use of marble dust an inert filler produced by the marble cutting industries in the development of light weight block (LWB) of density 800 kg/m3 by non-auto clave method has been studied. Various mechanical and thermo-physical properties have been evaluated. It has been possible to replace cement by up to 20% when no additive is used. With the use of activator and super plasticizer at 50% replacement of cement by marble dust, compressive strength and water absorption are well within the Indian standard code 2185. With the use of accelerator and super plasticizer it is possible to reduce the de moulding time from 48 hrs to 6 hrs. Thermal conductivity of blocks varies from 1.16 to 2.30 [W/mK]. The variation in thermal conductivity depends upon its density which varies from 800 kg/m3 to 2400 kg/m3.

Effect of Macro-, Micro- and Nano-Calcium Carbonate on Properties of Cementitious Composites—A Review

Calcium carbonate is wildly used in cementitious composites at different scales and can affect the properties of cementitious composites through physical effects (such as the filler effect, dilution effect and nucleation effect) and chemical effects. The effects of macro (>1 mm)-, micro (1 μm–1 mm)- and nano (<1 μm)-sizes of calcium carbonate on the hydration process, workability, mechanical properties and durability are reviewed. Macro-calcium carbonate mainly acts as an inert filler and can be involved in building the skeletons of hardened cementitious composites to provide part of the strength. Micro-calcium carbonate not only fills the voids between cement grains, but also accelerates the hydration process and affects the workability, mechanical properties and durability through the dilution, nucleation and even chemical effects. Nano-calcium carbonate also has both physical and chemical effects on the properties of cementitious composites, and these effects behave even more effectively than those of micro-calcium carbonate. However, agglomeration of nano-calcium carbonate reduces its enhancement effects remarkably.

The Preparation of Cf/ SiC-ZrC Composite Material by Adding SiC and ZrC Powders in Organic Precursors

In this paper, we added inert filler SiC and ZrC powders in an organic precursor solution to prepare Cf/SiC-ZrC composites. The experiments of three different contents of slurry in the process of impregnation and pyrolysis for Cf/SiC-ZrC composites were studied. The microstructure and composition of Cf/SiC-ZrC composites were analyzed by scanning electron microscope (SEM) equipped with EDS. This study shows that the addition of inorganic powders in an organic precursor solution can shorten the period of preparation of the composite material and improve its strength. When the mass fraction of the inert filler is 15% in an organic precursor solution, the density of the composite material can be increased to 1.9 g·cm-3 rapidly in 8 periods of preparation. Meanwhile, the internal structure of the prepared composite material becomes more compact, and its mechanical properties are excellent.

Influence of Various Carbonates on the Hydration of Portalnd Cement

Over the last 20 years, the effects of using limestone in Portland cement (PC) have been well studied. The benefits of limestone as a partial replacement for PC are well established. Its economic and environmental advantages of reducing CO2 emissions are well known. For a long time, the limestone has been considered as an inert filler. Recently it has been concluded that limestone serves both as an inert filler and also reacts to a limited extend. The reactivity depends on its fineness (specific surface)[1] and content [2,3]. The question arose, whether a) it is the availability of excess carbonate ion in the hydration system, which determines the degree of influence on the hydration process or b) does the system have its internal capacity to include carbonate ions and the increased availability (more carbonate ions in the solution, embedding the hydrating particles) would not have a significant effect. So the question was if the more soluble carbonates would have more pronounced effect on the hydration of the Portland cement than the limestone, which is only slightly soluble. The influence of slightly soluble (CaCO3, MgCO3, dolomite), medium soluble (Li2CO3) and highly soluble (K2CO3 and KHCO3) carbonates on the hydration of Portland cement was studied using Rietveld analysis. The results indicated that the amount of reacted carbonate in cement hydration at a 15% addition of slightly or medium soluble carbonates does not exceed 5% and is not affected by their solubility; at a 15% addition of the highly soluble carbonate K2CO3 the amount of reacted carbonate is around 6% leading to the conclusion that the system behaves according to the option b). The fugure presents the quantitative analysis of cement hydration at 3, 7, 28 and 90 days of hydration and temperatures of 25 and 400C.