Advanced Materials Research Vol. 804

Abstract: Cubic ZnTiO₃ thin films have been prepared by radio frequency magnetron sputtering on n-type (100) Si substrate at different temperatures. The morphological and optical properties of ZnTiO₃ films in relation to substrate temperatures are investigated by spectroscopic ellipsometry (SE) and AFM as well as SEM in detail. X-ray diffraction (XRD) measurement shows that all the films have a cubic phase structure and the optimum substrate temperature to form crystalline ZnTiO₃ thin film is 250 °C. Through SEM and AFM, the particle size in thin films and film surface roughness increase with increasing the substrate temperature. Based on a parameterized TaucLorentz dispersion model, the optical constants and surface roughness of ZnTiO₃ films related to the substrate temperature are systematically extracted by SE measurement. The surface roughness of the film measured from AFM agrees well with result extracted from SE, which proved that the established SE model is reasonable. With increasing substrate temperature, the refractive index decreases and the main factor in determining the refractive index was deduced to be the surface roughness related to the film packing density. The extinction coefficient of the samples is close to zero, but increases slightly with the increase of the substrate temperature, which is due to the enhancement of scattering effect in the crystalline ZnTiO₃ film.

Abstract: As a kind of high performance cement based construction materials, because of good mechanical performance and durability, PVA fiber reinforced cement based materials have been paid more and more attention in the field of civil structure engineering. To grasp the characteristics of PVA fiber reinforced cement based composite materials and promote a better application of PVA fiber reinforced cement based composite in practical engineering, a series of research works on the mechanical properties and durability of PVA fiber reinforced cement based composite were introduced systematically.

Abstract: The effect of superplasticizer on the mechanical property and chloride permeability of concrete containing GGBFS is investigated in this paper. Compressive and rapid chloride-ion diffusion tests were conducted to determine the axial compressive and chloride-ion diffusion coefficients of GGBFS modified concrete. The tests result indicated that the compressive strength of GGBFS modified concrete with the addition of 2wt. % superplasticizer are further improved at 14 and 28 days. Superplasticizer can significantly enhance the resistance to chloride ion penetration of concrete containing GGBFS with a reasonable additive content at long-term age. The optimum content of superplasticizer is suggested to be 1wt. % to 2wt. % of the cementitous materials.

Abstract: Ultra-hard AlMgB₁₄ (30-50 GPa) thin films were deposited on silicon substrate for a nominal thickness of 100 nm using a pulsed excimer laser and then subjected to direct micromachining using a 532 nm, 30 picosecond pulsed Nd:YAG laser. The application is targeted towards synthesizing an artificial nacre material composed of hexagonal bricks and particle bridges of superhard AlMgB₁₄ thin film and mortars of Ti thin film that biomimic the hierarchical architecture of natural nacre. The effects of pulse energy (0.1 to 1 μJ) and laser scanning speed (0.5 to 1.5 m/sec) on ablation depth and quality of scribed channels were evaluated. The morphology of the channels was characterized using confocal microscope and optical profilometer. Results indicated a clean material removal process characterized by absence of heat affected zone, high-speed scribing and small feature size. The energy fluence for the removal of 100 nm thin film without affecting the silicon substrate was 0.3 J/cm². An interesting observation is that particulate matter present in the thin film was not ablated suggesting a size effect. Analysis of thermal transport reveals that the material removal has occurred via spallation and phase explosion mechanisms. The picosecond laser thus offers a high-speed energy source for precisely ablating ultra-hard thin films that in turn will allow the potential for fabrication of novel artificial nacre with exceptional strength and toughness.

Abstract: This paper attempted the feasibility to determine component concentrations in multicomponent mixtures with terahertz time-domain spectroscopy (THz-TDS) combined with different partial least-squares regression (PLS) algorithms. First, THz absorbance spectra for 75 ternary mixtures of anhydrous theophylline, lactose monohydrate and magnesium stearate were investigated using THz-TDS in the frequency range from 0.1 to 3.0 THz, then four different PLS methods, including interval PLS (iPLS), backward interval PLS (biPLS), synergy interval PLS (siPLS) and moving window PLS (mwPLS), were employed to perform quantitative analysis of anhydrous theophylline concentrations in ternary mixtures. The performance of mwPLS model is the best in contrast to other PLS models and full spectrum PLS. The optimal model was achieved with higher correlation coefficient for calibration (R_C) of 0.9842, higher correlation coefficient for prediction (R_P) of 0.9851, lower root mean square error of cross-validation (RMSECV) of 3.8241, and lower root mean square error of prediction (RMSEP) of 4.1540. Experimental results demonstrate that THz spectroscopy combined with PLS algorithms could be successfully applied as an effective nondestructive tool for the quantitative analysis of component concentrations in multicomponent mixtures, and mwPLS is an ideal method for reducing the complexity and improving the performance of the model.

Abstract: Dimethyl Methyl Phosphonate (DMMP) was synthesized via the MichaelisArbuzov rearrangement in the normal pressure and N₂ atmosphere using a novel and can be used repeatedly catalyst. The preparation conditions of DMMP, such as the reaction time, reaction temperature and catalyst dosage were investigated. The FTIR (Fourier transform infrared spectroscopy), NMR (Nuclear magnetic resonance) , and TG-DSC(Thermogravimetric-Dynamic stability control system) results show that the obtained product is DMMP. When the reaction temperature is higher than 180°C, catalyst dosage is 12 wt%, and the reaction time is about 13 h, the highest yield (78 wt%) of DMMP can be obtained. Then DMMP was added to a FRP (Fiber Reinforced Plastics) matrix. The flame retardancy and mechanical properties of the DMMP/ FRP were tested for Limiting Oxygen Index (LOI), breaking elongation, impact toughness, tensile, and flexural strengths. A significant improvement of flame retardancy of the system was observed (increase of LOI up to 30.4) with an addition of 10 wt% DMMP to FRP. But when the DMMP content in the DMMP/ FRP composites is more than 10 wt%, the comprehensive mechanical properties of FRP will appear to decline and the LOI value has not changed, so we conclude that DMMP content in the DMMP/ FRP composites is 10wt%.

Abstract: Er³⁺ doped CaMoO₄(CaMoO₄:Er³⁺) and Er³⁺/Yb³⁺ co-doped CaMoO₄ (CaMoO₄:Er³⁺/Yb³⁺) particles was successfully synthesized by a cyclic microwave-assisted metathetic (MAM) method, followed by heat-treatment. Well-crystallized UC CaMoO₄:Er³⁺/Yb³⁺ particles formed after heat-treatment at 600°C for 3 h showed a fine and homogeneous morphology with particle sizes of 1-3 μm. At excitation at 980 nm, CaMoO₄:Er³⁺/Yb³⁺ particles exhibited a strong 525-nm emission band and a weak 550-nm emission band in the green region, and a weak 655-nm emission band in the red region. The UC intensities of CaMoO₄:Er³⁺/Yb³⁺ particles were much higher than that of the CaMoO₄:Er³⁺ particles. The Raman spectra of CaMoO₄:Er³⁺ and CaMoO₄:Er³⁺/Yb³⁺ particles indicated the appearance of additional strong peaks in comparision with that of pure CaMoO₄.

Abstract: ZrB₂ has some excellent physical performance and chemical stability, it has been widely applied in a lot of fields. In order to improve disadvantages of ZrB₂ that the sintering densification of ZrB₂ is too difficult, and it is easy oxidized at high temperature, in this paper, the sintering character of coated A1₂O₃-Y₂O₃/ZrB₂ composite powder materials via spark plasma sintering were investigated. Al₂O₃-Y₂O₃/ZrB₂ composite powders were prepared by a co-precipitation methods. When the pH is 9, the encapsulted structure of A1(OH)₃-Y(OH)₃/ZrB₂ composite powders is the best. By analyzing the ZrB₂ surface status with TEM, the A1₂O₃-Y₂O₃/ZrB₂ composite powders were prepared under the calcining conditions of 600°C¡æ in argon. The high density ZrB₂-YAG multi-phase ceramics are prepared via spark splama sintering, which indicate the raw materials adding A1₂O₃-Y₂O₃ help for the densification of ZrB₂ ceramics.

Abstract: In order to lay raw materials foundation for increasing the performance of insulating brick with the low grade quartz sand along the Yangtze River, the effect of ball milling methods on the properties of quartz sand powder was researched via the ball milling method in this paper. The results show the mean grain size of quartz powders are 11.25μm via a roller ball milling, the mean grain size of quartz powders are 7.37μm via a planetary ball milling, and the particle size distribution of quartz powders milled via a roller ball milling is wider than that of quartz powders milled via a planetary ball milling. The ball milling strength of planetary ball milling is higher than that of roller ball milling. The planetary ball milling use more electronic energy than the roller ball milling in the same time. The output of powder using the roller ball milling is more than that of powder using the planetary ball milling. when the raw materials of quartz building materials is low particle size remand, and the output is more, the roller ball milling methods is suitable to prepare the raw materials of quartz building materials.