Nanomechanical system (NMS) based on amorphous carbon nanowhiskers localized on the top of tungsten tip were fabricated and investigated. The whiskers were grown in the scanning electron microscope (SEM) chamber using focused electron beam technique. The manipulation of SiO2 and TiO2 nanospheres was provided in SEM by means of dielectrophoretic force. Oscillation trajectories and amplitude-frequency characteristic of the oscillator were visualized at low pressure using a scanning electron microscope. The estimation of mass sensitivity of NMS was conducted.

Highlights • The behavior of belite-cement in presence of PNS and PC types is highlighted. • Flow curves of 2 cements, 2 HRWR, and various w/c are determined and analyzed. • Factors affecting rheology of high-performance cement paste are discussed. • Factors affecting cement–HRWR compatibility are identified and discussed. Abstract The rheological properties of concrete determine its flow performance and thus they are of great importance in placement and consolidation. A full understanding of the behavior of fresh concrete can be achieved through a good understanding of the rheology of paste. Cement pastes exhibit complex rheological behavior affected by several physical and chemical factors, including water-to-cement ratio (w/c), type and dosage of high-range water-reducer (HRWR), and cement characteristics. An experimental investigation was carried out to investigate the rheological properties of belite cement (BC) mixtures made with various w/c ranging between 0.30 and 0.36 and two different types of HRWR. A polynaphthalene sulfonate (PNS) and a polycarboxylate-(PC) based HRWR were evaluated. Test results indicated that the use of BC in low w/c mixtures resulted in shear-thickening behavior when PC is employed and shear-thinning response for higher w/c. Compared to ordinary Portland cement (OC), the use of BC resulted in lower shear-thickening response, regardless of the w/c and HRWR type. The use of PC HRWR promoted the shear-thickening responses of mixtures for both types of cement. On the other hand, the use of PNS in combination with BC resulted in high yield stress values.

Nanomechanical system (NMS) based on amorphous carbon nanowhiskers localized on the top of tungsten tip were fabricated and investigated. The whiskers were grown in the scanning electron microscope (SEM) chamber using focused electron beam technique. The manipulation of SiO2 and TiO2 nanospheres was provided in SEM by means of dielectrophoretic force. Oscillation trajectories and amplitude-frequency characteristic of the oscillator were visualized at low pressure using a scanning electron microscope. The estimation of mass sensitivity of NMS was conducted.

Large (W,V)C cubic carbides in WC-VC-Co cemented carbides are undesirable as their presence is one of the causes for poor properties in the material. Earlier attempts to reduce the (W,V)C cubic carbide grain sizes in the WC-VC-Co cemented carbide have been published before. The present investigation strives to reduce the cubic carbide grain size by using a pre-alloyed (W,V)C powder in the place of VC, to reduce the driving force for the formation of (W,V)C during sintering. This should in turn reduce the possibility of forming large (W,V)C grains. WC-VC-Co was prepared using WC, (W,V)C, and Co powders. The compositions were 8.1 wt% V and 12 wt% Co, with the balance comprising W and C. XRD diffraction patterns confirmed that the bulk of WC-(W,V)C-Co contains WC grains, cubic (W,V)C grains, and a Co-rich binder phase. SEM-EDS measurements yielded an average composition of (W 0.31V 0.69)C x. TEM-EDS of the cubic carbide was in good agreement with the SEM-EDS measurement, yielding the average composition of (W 0.30V 0.70)C x. The average grain size of the cubic carbide of WC-(W,V)C-Co material after sintering had grown to only the same size as that of the starting powder, 1.4 mum. [All rights reserved Elsevier].

The rheological properties of concrete determine its flow performance and thus they are of great importance in placement and consolidation. A full understanding of the behavior of fresh concrete can be achieved through a good understanding of the rheology of paste. Cement pastes exhibit complex rheological behavior affected by several physical and chemical factors, including water-to-cement ratio (w/c), type and dosage of high-range water-reducer (HRWR), and cement characteristics. An experimental investigation was carried out to investigate the rheological properties of belite cement (BC) mixtures made with various w/c ranging between 0.30 and 0.36 and two different types of HRWR. A polynaphthalene sulfonate (PNS) and a polycarboxylate-(PC) based HRWR were evaluated. Test results indicated that the use of BC in low w/c mixtures resulted in shear-thickening behavior when PC is employed and shear-thinning response for higher w/c. Compared to ordinary Portland cement (OC), the use of BC resulted in lower shear-thickening response, regardless of the w/c and HRWR type. The use of PC HRWR promoted the shear-thickening responses of mixtures for both types of cement. On the other hand, the use of PNS in combination with BC resulted in high yield stress values. (C) 2015 Elsevier Ltd. All rights reserved.

Milling was carried out in flowing argon but was interrupted at regular time intervals to take samples for X-ray diffraction (XRD). Because of exposure to air during the interruptions the powder was partly oxidized. The oxides formed did not appear in XRD patterns because they were of extremely fine grain size. As a result of the loss of V and W through oxidation, free carbon was also found in the final powder. The lattice parameter of the (V,W)C powder increased with milling time up to a maximum, then it decreased, which suggests that the amount of W in (V,W)C increased with milling time up to a maximum and then decreased. The crystallite size of the (V,W)C powder was calculated from the X-ray data and was found to be in the nm range (down to approximately 8 nm). Subsequent uninterrupted milling produced a powder which was freer from oxides and free carbon. [All rights reserved Elsevier].