Effects of Small Amounts of Phosphoric Acid as Additive in the Preparation of Microporous Activated Carbons

The activated carbons with well-developed microporosity were prepared from fir wood (Cunninghamia lanceolata) impregnated with small amounts of phosphoric acid (impregnation ratios, 1.5 – 4.5 wt.%). For comparison purpose, a parallel study of fir wood without impregnation was carried out in the same conditions. The results showed that the addition of small amounts of H3PO4 could lower the thermal decomposition temperature of fir wood and significantly promote the adsorption capacity and the yield of activated carbon. The yield without phosphoric acid impregnation was 6.55 wt.%, which rose to 19.82 wt.% in the case of 3.0 wt.% H3PO4 impregnation. Using small amounts of phosphoric acid as additive was beneficial to improve specific surface area (SBET) and micropore volume (Vmic), and could produce activated carbons with well-developed microporous structure. With 3.0 wt.% H3PO4 impregnation, SBET and Vmic of the activated carbon reached as high as 1281.6 m2/g and 0.535 mL/g, the ratio of Vmic/Vtot (total pore volume) was higher than 80 %. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.18999</p

High Temperature Oxidation and Oxyacetylene Ablation Properties of ZrB₂-ZrC-SiC Ultra-High Temperature Composite Ceramic Coatings Deposited on C/C Composites by Laser Cladding

In order to improve the high temperature oxidation and ablation resistance of C/C composites, ZrB2-ZrC-SiC ultra-high temperature composite ceramic coatings were prepared on C/C composites by laser cladding using Zr, B4C, and Si as raw materials. The microstructure of the coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Air isothermal oxidation (1600 °C, 80 min) and oxyacetylene flame ablation (2400 kW/m2, 300 s) were used to evaluate the high-temperature oxidation and ablation properties of the coating, respectively. The results show that the microstructure of laser cladding coating is a totem of black and white. The white part is mainly the first solidified high melting point ZrB2 phase, and the black part is the latter solidified eutectic structure, which is mainly composed of ZrB2(ZrB12)-ZrC or ZrB2(ZrB12)-SiC two phases. After oxidation at 1600 °C and 80 min, the coating is mainly composed of ZrO2 and ZrSiO4 phases, and ZrSiO4 is basically distributed among ZrO2 particles. The high temperature oxidation and ablation properties of the coating are better than the C/C composite matrix, and the mass ablation rate of the coating is about 1/4 of the latter

Effect of Specimen Size on Laser Scribing Width and Depth of Al

To obtain high precision and quality of laser ceramic scribing , people should consider the laser scribing parameters and the geometries of specimen size. In this paper, the effect of specimen size on laser scribing width and depth of Al2O3 ceramics was simulated and verified by using ANSYS software and Diode Pumped Solid State (DPSS) laser scribing, respectively. The calculated results and the experimental results all proved that the specimen size had important effect on laser scribing width and depth due to the heat accumulation effect during laser scribing

Sens. Mater.

SnO2 flat-type coplanar gas sensor arrays were fabricated by a screen-printing technique based on SnO2 nanopowders prepared by a sol-gel method. The SnO2 flat-type coplanar gas sensor arrays had good acetone gas-sensing characteristics such as a fast response, short recovery time, and an almost linear response to acetone concentration of 1-100 ppm. The response could reach 2.11 for acetone concentration as low as 1 ppm, and the response and recovery times for 1 ppm acetone were 8.9 and 10 s, respectively. The surface reactions were investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at different temperatures, and a possible sensing mechanism was proposed. Formate, acetate, carbonate ions, CH3O(ads), CO2, H2O, and adsorbed acetone were detected when the SnO, flims were exposed to 100 ppm acetone at different temperatures.SnO2 flat-type coplanar gas sensor arrays were fabricated by a screen-printing technique based on SnO2 nanopowders prepared by a sol-gel method. The SnO2 flat-type coplanar gas sensor arrays had good acetone gas-sensing characteristics such as a fast response, short recovery time, and an almost linear response to acetone concentration of 1-100 ppm. The response could reach 2.11 for acetone concentration as low as 1 ppm, and the response and recovery times for 1 ppm acetone were 8.9 and 10 s, respectively. The surface reactions were investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at different temperatures, and a possible sensing mechanism was proposed. Formate, acetate, carbonate ions, CH3O(ads), CO2, H2O, and adsorbed acetone were detected when the SnO, flims were exposed to 100 ppm acetone at different temperatures

Mater. Sci.

Nano-SnO2 flat-type coplanar 2-Methyl-2,4-pentanediol (MPD) gas sensor arrays were fabricated by a screen-printing technique based on nano-SnO2 powders prepared by a hydrothermal method. The results show that the fabricated gas sensor arrays have good MPD gas sensing characteristics, such as good selectivity and response-recovery characteristics. Especially, they can be used for detecting the concentration of MPD gas as low as 1 ppm which is much lower than the legal concentration of 20 ppm or 25 ppm. The good sensing properties indicate that the SnO2 gas sensor arrays have great potential for on-line or portable monitoring of MPD gas in practical environments.Nano-SnO2 flat-type coplanar 2-Methyl-2,4-pentanediol (MPD) gas sensor arrays were fabricated by a screen-printing technique based on nano-SnO2 powders prepared by a hydrothermal method. The results show that the fabricated gas sensor arrays have good MPD gas sensing characteristics, such as good selectivity and response-recovery characteristics. Especially, they can be used for detecting the concentration of MPD gas as low as 1 ppm which is much lower than the legal concentration of 20 ppm or 25 ppm. The good sensing properties indicate that the SnO2 gas sensor arrays have great potential for on-line or portable monitoring of MPD gas in practical environments

Appl. Surf. Sci.

The detection of trichloroethylene has attracted much attention because it has an important effect on human health. The sensitivity of the SnO2 flat-type coplanar gas sensor arrays to 100 ppm trichloroethylene in air was investigated. The adsorption and surface reactions of trichloroethylene were investigated at 100-200 degrees C by in-situ diffuse reflection Fourier transform infrared spectroscopy (DIRFTS) on SnO2 films. Molecularly adsorbed trichloroethylene, dichloroacetyl chloride (DCAC), phosgene, HCl, CO, H2O, CHCl3, Cl-2 and CO2 surface species are formed during trichloroethylene adsorption at 100-200 degrees C. A possible mechanism of the reaction process is discussed. (C) 2014 Elsevier B.V. All rights reserved.The detection of trichloroethylene has attracted much attention because it has an important effect on human health. The sensitivity of the SnO2 flat-type coplanar gas sensor arrays to 100 ppm trichloroethylene in air was investigated. The adsorption and surface reactions of trichloroethylene were investigated at 100-200 degrees C by in-situ diffuse reflection Fourier transform infrared spectroscopy (DIRFTS) on SnO2 films. Molecularly adsorbed trichloroethylene, dichloroacetyl chloride (DCAC), phosgene, HCl, CO, H2O, CHCl3, Cl-2 and CO2 surface species are formed during trichloroethylene adsorption at 100-200 degrees C. A possible mechanism of the reaction process is discussed. (C) 2014 Elsevier B.V. All rights reserved

Nanoscale SnO2 Flat-Type Coplanar Hexanal Gas Sensor Arrays at ppb Level

Hexanal is one of the most important aroma compounds which play a crucial role in the odor of cereal, meat, fruit, plant oils and wood. The detection technique of hexanal has attracted more attention. In this paper, the nano-SnO2 flat-type coplanar hexanal gas sensor arrays were fabricated by screen-printing technique based on nano-SnO2 powders prepared by hydrothermal method. The test results show that the nano-SnO2 flat-type coplanar gas sensor arrays have good hexanal gas-sensing characteristics, such as low detection limit and high sensitivity. Especially, the gas sensitivity of the nano-SnO2 gas sensor arrays to 100 ppb hexanal can reach 2.8 at 350 degrees C. The nanometer size effect of nano-SnO2 and nature property of hexanal caused the ppb-level hexanal gas sensing characteristics

In situ diffuse reflectance infrared Fourier transform spectroscopy study of formaldehyde adsorption and reactions on nano gamma-Fe2O3 films

The nano gamma-Fe2O3 films gas sensor was fabricated by the screen printing technology. The phase structures and morphologies of nano gamma-Fe2O3 films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), respectively. The gas sensitivity of the films to 100 ppm formaldehyde was investigated. The surface adsorption and reaction process between nano gamma-Fe2O3 films and formaldehyde was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) method at different temperatures. DRIFTS results showed that dioxymethylene, formate ions, polyoxymethylene and molecularly formaldehyde surface species were detected when the nano gamma-Fe2O3 films exposed to 100 ppm formaldehyde at different temperatures. A possible mechanism of the reaction process was discussed. (c) 2013 Elsevier B.V. All rights reserved

In Situ Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) Study of Formaldehyde Adsorption and Reactions on Pd-Doped Nano-gamma-Fe2O3 Films

Palladium-doped nano-gamma-Fe2O3 films were printed on Al2O3 substrates by screen printing injecting hybrid technology. X-ray diffraction and scanning electron microscopy techniques were used to characterize the phase structures and morphologies of the films, respectively. The sensitivity of the films to 100 ppm formaldehyde in air was investigated. The surface adsorption and reaction process between Pd-doped nano-gamma-Fe2O3 films and formaldehyde was studied by in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) at different temperatures. Dioxymethylene, formate ions, polyoxymethylene, and adsorbed formaldehyde were detected when the Pd-doped nano-gamma-Fe2O3 films were exposed to 100 ppm formaldehyde at different temperatures. A possible mechanism of the reaction process is discussed

J. Mater. Res.

Formaldehyde (HCHO) is widely used in construction, wood processing, furniture, textile, and carpeting industries. However, it is highly toxic. It strongly irritates human eyes and nose, and is a carcinogen. In this paper, the effects of gas concentration and operating temperature on the sensing properties of the nano-SnO2 flat-type coplanar gas sensor arrays to formaldehyde were studied. The results revealed that the nano-SnO2 flat-type coplanar gas sensor arrays exhibited good sensitivity such as a fast response, short recovery time, and low detection limit. In addition, the adsorption and surface reactions of formaldehyde on SnO2 films were also studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at 200-300 degrees C. Molecularly adsorbed formaldehyde, formate, dioxymethylene, polyoxymethylene, H2O, and CO2 surface species were formed during formaldehyde adsorption at 200-300 degrees C. Moreover, a possible mechanism of the reaction process was given.Formaldehyde (HCHO) is widely used in construction, wood processing, furniture, textile, and carpeting industries. However, it is highly toxic. It strongly irritates human eyes and nose, and is a carcinogen. In this paper, the effects of gas concentration and operating temperature on the sensing properties of the nano-SnO2 flat-type coplanar gas sensor arrays to formaldehyde were studied. The results revealed that the nano-SnO2 flat-type coplanar gas sensor arrays exhibited good sensitivity such as a fast response, short recovery time, and low detection limit. In addition, the adsorption and surface reactions of formaldehyde on SnO2 films were also studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at 200-300 degrees C. Molecularly adsorbed formaldehyde, formate, dioxymethylene, polyoxymethylene, H2O, and CO2 surface species were formed during formaldehyde adsorption at 200-300 degrees C. Moreover, a possible mechanism of the reaction process was given