A Study of Cordierite Ceramics Synthesis From domestic kaolin

This work aims to study the effect of chlorine ion on the formation of the cordierite phase (2MgO.2Al2O3.5SiO2) from domestic kaolin at various calcined temperatures.. The cordierite phase was synthesized by a solid-state reaction technique from the mixture of kaolin, aluminum nitrate nonahydrate (Al(NO3)3.9H2O), and magnesium chloride hexahydrate (MgCl2.6H2O) which was designed to the stoichiometric composition of cordierite in the absence and presence of chlorine ion (NH4Cl). The structure and formation of cordierite phase were characterized by X-ray diffraction (XRD) and thermogravimetric - differential thermal analysis (TG-DSC). Phase composition of samples calcined at various temperatures was calculated by using Match! (Version 3.7.0) software. It is noteworthy that the presence of chlorine ion in the mixture declined the formation temperature of cordierite by 50 °C. The cordierite phase was calculated to be 61.3 wt.% and 5.5 wt.% at 1150 °C for the present and absent chlorine ion, respectively. The presence of chlorine ion affected the cordierite formation rate and suppressed the temperature of formation. Cordierite phase could be obtained up to 89.6 wt.% at 1250 °C and 30 wt.% NH4Cl. This investigation found that cordierite ceramic could be synthesized from domestic kaolin at lower temperature by using NH4Cl additive.

Preparation of Co/Ti electrode by electro-deposition for aqueous nitrate reduction

A Co/Ti electrode for nitrate reduction was prepared by electrode-deposition. In the single-compartment electrolysis cell, nitrate (100 mg/L) removal reached nearly 100% after 3 h electrolysis under the current density of 20 mA cm–2 by using the Co/Ti electrode as cathode, and the main reduction products were ammonium nitrogen (66.5%) and nitrogen gas (33.5%). This performance on nitrate removal was comparable to a Co3O4/Ti electrode, and the electroactivity of the Co/Ti electrode towards nitrite reduction was higher than that of a Co3O4/Ti electrode. The Co/Ti electrode exhibited an improved stability with 18.7% of mass loss and 25.5% of Co dissolution compared with the Co3O4/Ti electrode after ultrasonic interference. The presence of chlorine ion (1,000 mg/L) could promote the total nitrogen (TN) removal to approximately 100% after 3 h electrolysis because of the ammonium oxidation by the free chlorine produced from the anode. In the presence of calcium (50 mg/L) and phosphate (0.5 mg/L), the nitrate removal decreased from 85.4 ± 1.5 to 57.7 ± 3.5% after ten reuse cycles. This result suggests that Ca and P should be pre-removed before the electro-reduction of nitrate.

Mechanical and Durability Properties of Latex-Modified Hybrid Fiber-Reinforced Roller-Compacted Rapid-Set Cement Concrete for Pavement Repair

This study evaluated the mechanical properties and durability performance of latex-modified hybrid fiber-reinforced roller-compacted rapid-set cement concrete (LMHFRCRSC) for emergency repair of concrete pavement. Experimental parameters included the blend ratio of the hybrid fiber, which comprised natural jute fiber (0–0.2 vol.%) and structural synthetic fiber (0–2 vol.%). The mechanical performance of LMHFRCRSC of various blend ratios was evaluated in terms of compressive, flexural, and splitting tensile strength. Durability assessment included chlorine ion penetration and abrasion resistance measurements. Compressive and flexural strength values of 21 and 3.5 MPa, respectively, were the set targets after 4 h of curing; a compressive strength of 35 MPa, a flexural strength of 4.5 MPa, a splitting tensile strength of 4.2 MPa, and chloride ion penetration of 2000 C or less were required after 28 days of curing. Our test results confirmed that all mix proportions satisfied the target values, regardless of the blend ratio of the hybrid fiber. Specifically, the mechanical performance of the concrete improved as the blend ratio of the structural synthetic fiber increased. With regard to durability, a greater amount of jute fiber, a hydrophilic fiber, enhanced the concrete’s durability. Additionally, incorporating jute fiber of 0.6 kg/m3 provided excellent chlorine ion penetration resistance. The optimal blend ratio for the hybrid fiber was natural jute fiber at 0.6 kg/m3 and structural synthetic fiber at 13.65 kg/m3 (mix: J0.6 + P13.65); with this mix proportion, a chloride ion penetration amount of 1000 C or less and maximum mechanical performance were achieved.

The study of diffusion characteristics of soil bentonite to control contaminant transport

Purpose The purpose of this paper is to assess sand-bentonite liners (SBL) which could be used as hydraulic barriers with a controllable quality, relatively low cost and easy operation in solid waste landfills. Design/methodology/approach These barriers have been used successfully in various applications and have attracted much attention in a short period of time. The only precautionary use of SBLs is related to the change of their hydraulic properties in high alkaline chemical environments. The main reason for this phenomenon is the presence of high ion exchange minerals in bentonite. By exposure to these environments, it is also laid open to degradation of the montmorillonite microstructure leads to change in hydraulic behavior. Three different compounds were used for laboratory-scale SBL, and diffusion was considered as the dominant mechanism of contamination transmission in these liners. Chlorine ion has been used as pollutant, and its diffusion coefficient was determined in the tested SBLs. Findings The sample’s diffusion coefficient for the first experiment containing 3% bentonite and 97% Semnan sand were 2.5 × 10^(−9) (m^2/s) and 2.44 × 10 ^(−9) (m^2/s), respectively. Similarly, for two samples with 6% bentonite and 94% Semnan sand, this parameter was equal to 2.17 × 10 ^(−9) (m^2/s) and 2.22 × 10 ^(−9) (m^2/s) and for two samples with 3% agglacial clay, 12% bentonite and 85% Semnan sand was 5.55 × 10 ^(−10) (m^2/s) and 6.11 × 10 ^(−10) (m^2/s). These values correspond to the range reported in previous studies. Also, it was observed that with comparing the diffusion coefficients of test, it was concluded that with increasing bentonite, the molecular diffusion decreases significantly. Originality/value In this study, three laboratory samples with different percentages of bentonite, clay and sand were considered and the results obtained from the laboratory were compared with the results obtained from numerical modeling.

Negative photoconductance in 150 GHz transients from irradiated p-type Cz-Silicon

Boron doped (p-type) silicon wafers of the same type are irradiated with gamma, proton and chlorine ion beams. This causes radiation damage in the form of migration of vacancies, traps to photoelectrons. We use time-resolved millimeter wave pump-probe spectroscopy (150 GHz CW probe signal) and 532 nm ultrafast laser as pump source with variable fluence. Upon studying the transient response of the detector probe voltage as function of the pump-probe delay period we note a good positive (absorption) photoconductance peak and soon after recombination of photocarriers there occurs a negative photoconductance (NPC) transient. We consistently find that the NPC lasts for about 36 microseconds and this study points out that the positive to NPC peaks for each laser fluence varies with the type of radiation damaged samples.2 MeV proton beam damage create damage that trap carriers very effectively, and enhances the resistivity of the silicon wafer from 15 Ohms to 150 Ohms. The Chlorine ion damaged silicon responds consistently to the 150 GHz probe beam and correlates strongly with the laser fluence.

Negative photoconductance in 150 GHz transients from irradiated p-type Cz-Silicon

Boron doped (p-type) silicon wafers of the same type are irradiated with gamma, proton and chlorine ion beams. This causes radiation damage in the form of migration of vacancies, traps to photoelectrons. We use time-resolved millimeter wave pump-probe spectroscopy (150 GHz CW probe signal) and 532 nm ultrafast laser as pump source with variable fluence. Upon studying the transient response of the detector probe voltage as function of the pump-probe delay period we note a good positive (absorption) photoconductance peak and soon after recombination of photocarriers there occurs a negative photoconductance (NPC) transient. We consistently find that the NPC lasts for about 36 microseconds and this study points out that the positive to NPC peaks for each laser fluence varies with the type of radiation damaged samples.2 MeV proton beam damage create damage that trap carriers very effectively, and enhances the resistivity of the silicon wafer from 15 Ohms to 150 Ohms. The Chlorine ion damaged silicon responds consistently to the 150 GHz probe beam and correlates strongly with the laser fluence.