Search

Delafossite CuCrO2was prepared with Cr(NO3)3and Cu(NO3)2by the semi-wet method via two different routes. The samples were characterized with thermogravimetry-differential scanning calorimetry, X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy techniques. It was shown that addition of Cr(OH)3precipitated with aqueous ammonia solution into aqueous Cu(NO3)2solution is a suitable route to synthesize CuCrO2. In the calcination process, the precursor transformed into CuCrO2in the sequence: Cr(OH)3→ CuCrO4→ CuCr2O4→ CuCrO2, as verified by the TG-DSC and XRD results. The composites of CuCrO2-WO3and CuCrO2-ZnO prepared by the grinding method show higher activity than CuCrO2in the photocatalytic splitting of water into hydrogen under the irradiation of a high-pressure mercury lamp or a xenon lamp.

The pure γ-Ca2SiO4(γ-C2S) phase was prepared at 1623 K of calcining temperature, 10 h of holding time and furnace cooling. The β-C2S phase was obtained through γ-C2S conversion with the following calcination system which was adopted at 1473 K of calcining temperature, 1 h of holding time and then water-cooling. The conversion rate of γ-C2S was studied by the Rietveld quantitative laboratory X-ray powder diffraction supported by synchrotron X-ray diffraction images. The refinement results show that the final conversion rate of γ-C2S is higher than 92%. The absolute error of the γ-C2S conversion rate between two Rietveld refinements (sample with or without α-Al2O3) is 3.6%, which shows that the Rietveld quantitative X-ray diffraction analysis is an appropriate and accurate method to quantify the γ-C2S conversion rate.

This paper deals with the hydration of a blend of Portland cement and activated coal gangue in order to determine the relationship between the degree of hydration and compressive strength development. The hydration process was investigated by various means: isothermal calorimetry, thermal analysis, non-evaporable water measurement, and X-ray diffraction analysis. The results show that the activated coal gangue is a pozzolanic material that contributes to the hydration of the cement blend. The pozzolanic reaction occurs over a period of between 7 and 90 d, consuming portlandite and forming both crystal hydrates and ill-crystallized calcium silicate hydrates. These hydrates are similar to those found in pure Portland cement. The results show that if activated coal gangue is substituted for cement at up to 30% (w/w), it does not significantly affect the final compressive strength of the blend. A long-term compressive strength improvement can in fact be achieved by using activated coal gangue as a supplementary cementing material. The relationship between compressive strength and degree of hydration for both pure Portland cement and blended cement can be described with the same equation. However, the parameters are different since blended cement produces fewer calcium silicate hydrates than pure Portland cement at the same degree of hydration.

Tailor welded blanks (TWBs) get popular used in the automobile for the light-weighting, and the assessments for TWBs formability are more and more important owing to the TWBs with different thicknesses. In this paper, based on the tensile test and low carbon high strength steel (ZStE220P), the influences of seam location and the length of sample on the elongation are studied, and the results shows that the location of seam has greater effect on the formability of TWBs and elongation is getting decreased with the seam shifting to the thinner part.

This paper describes the results of an investigation into the effect of the variation of curing temperatures between 0 and 60 °C on the hydration process, pore structure variation, and compressive strength development of activated coal gangue-cement blend (ACGC). Hardened ACGC pastes cured for hydration periods from 1 to 360 d were examined using the non-evaporable water method, thermal analysis, mercury intrusion porosimetry, and mechanical testing. To evaluate the specific effect of activated coal gangue (ACG) as a supplementary cementing material (SCM), a fly ash-cement blend (FAC) was used as a control. Results show that raising the curing temperature accelerates pozzolanic reactions involving the SCMs, increasing the degree of hydration of the cement blends, and hence increasing the rate of improvement in strength. The effect of curing temperature on FAC is greater than that on ACGC. The pore structure of the hardened cement paste is improved by increasing the curing temperature up to 40 °C, but when the curing temperature reaches 60 °C, the changing nature of the pore structure leads to a decrease in strength. The correlation between compressive strength and the degree of hydration and porosity is linear in nature.

The forming of tailor-welded blank is an important technology to body light weighting. While it is difficult to predict the forming limits of tailor welded blanks with different base materials or thickness. For the expanding experiments, an analytical method to predict forming limit height of tailor-welded blanks is established based on the deformation characteristic and plastic theory, and verified by simulation results. This method is not only provided a path to predict forming limit of tailor welded blanks but also provided references to the design of tailor weld parts.

Scanning thermal microscopy (SThM) and infrared thermography are widely used for surface thermal characterization. However, the SThM technique is limited by measurement of the non-electrical conductive surfaces and the infrared thermography has insufficient spatial resolution for submicron localized thermal measurement. The “hot tip” Tribological Probe Microscope (TPM) has been designed to achieve better localized thermal analysis function in this paper. The schemes of system design are presented and the principle of the ‘hot-tip’ technique is explained by relating the signals to established thermal properties. After calibrating the lumped thermal resistances (LTR) of the probe and the ambient environment, the LTRs of 5 metal surfaces were measured and compared. In addition, the paper numerically studied the LTR of the indentation interfaces with defined thermal conductivity (TC) by Finite Element Method (FEM). Numerical linearity was observed and fitted between LTR and TC. Based on the measured LTR and the linearity, the deduced TCs of the 5 metal surfaces are agreed well with the reference values.