Preparation, Characterization and Catalytic Activity of CrSBA-15 for 2-Propanol Decomposition
M. Sánchez-Cruz,
R. Hernández-Huesca,
M. A. Pérez-Cruz,
N. R. Silva-González
Issue:
Volume 9, Issue 3, September 2020
Pages:
42-49
Received:
11 August 2020
Accepted:
26 August 2020
Published:
8 September 2020
Abstract: The chromium mesoporous materials have been used in many catalytic reactions. Some studies have been devoted to determining the nature of chromium species and to characterizing the chemical structure. The different chromium species depend on synthetic methods and the support used. In this work we prepared mesoporous SBA-15 supported chromium materials referred to in this document as xCrSBA-15, was prepared by the incipient wetness impregnation method. The materials were characterized by X-ray diffraction (XRD), nitrogen (N2) adsorption–desorption isotherms, hydrogen temperature-programmed reduction (H2-TPR), scanning electron microscopic (SEM), energy dispersive X-ray spectroscopy (EDS), diffuse reflectance ultraviolet-visible (UV–vis) and Fourier transform IR (FT-IR). Chromium in SBA-15 forms different types of chromates and Cr2O3, causing morphological and textural changes and generating different catalytic centers. The catalytic conversion of 2-propanol to xCrSBA-15 materials were carried out by in a quartz reactor with a loading of 30 mg of the material at 300°C. Before the catalytic test, the material was activated in two ways: with N2 and reduced at a H2/Ar flow (MxCrSBA-15). The catalytic conversion of 2-propanol to xCrSBA-15 did not increase with reduction (MxCrSBA-15) but decreased deactivation. All the materials had an acidic behavior, which is related to the chromate species in the materials. These results suggest that the more acidic materials favor the formation of coke during the deactivation process, and coke reduces the Cr3+ to Cr2+ species, thus decreasing the acidity of the materials.
Abstract: The chromium mesoporous materials have been used in many catalytic reactions. Some studies have been devoted to determining the nature of chromium species and to characterizing the chemical structure. The different chromium species depend on synthetic methods and the support used. In this work we prepared mesoporous SBA-15 supported chromium materi...
Show More
Investigation on Kinetic Glass Transition and Relaxation of Vit1 Bulk Metallic Glass by Calorimetric Method
Wei Zhang,
Qingchun Xiang,
Yinglei Ren,
Keqiang Qiu
Issue:
Volume 9, Issue 3, September 2020
Pages:
50-54
Received:
13 September 2020
Accepted:
23 September 2020
Published:
29 September 2020
Abstract: The kinetic glass transition of the Vit1 (Zr41.2Ti13.8Cu12.5Ni10.0Be22.5) bulk metallic glass (BMG) was calorimetrically studied by using the differential scanning calorimetry (DSC). A wide range of heating rate, q=0.5~100 K min-1, was adopted in the calorimetric experiments. The apparent values of the glass transition temperatures were determined from the DSC curves. Then the kinetic glass transition was analyzed by adopting the function in the form of the Vogel-Tammann-Fucher (VTF) type. In addition, by considering the glass transition of the BMG from non-equilibrium to kinetic equilibrium during the process of heating experiments, a new model which can be used to calculate the relaxation time near the glass transition temperature region was established. The relaxation time of the Vit1 BMG near the glass transition temperature region calculated by the new model was used to compare with the glass transition time (ttrans), as well as the relaxation time calculated by the viscosity and diffusion methods. The result shows that the relaxation time calculated based on the model can reflect the relaxation event reasonably near the glass transition temperature region. This work may provide some new perspectives or ideas for the study of the glass transition and relaxation of metallic glass.
Abstract: The kinetic glass transition of the Vit1 (Zr41.2Ti13.8Cu12.5Ni10.0Be22.5) bulk metallic glass (BMG) was calorimetrically studied by using the differential scanning calorimetry (DSC). A wide range of heating rate, q=0.5~100 K min-1, was adopted in the calorimetric experiments. The apparent values of the glass transition temperatures were determined ...
Show More
A Composite Joint Based on Two Kinds of Connection Mechanisms for TA2/T2 Bimetallic Sheets by Laser-TIG Hybrid Weldings
Yan Zhang,
Yidi Gao,
Jianping Zhou,
Daqian Sun,
Hongmei Li
Issue:
Volume 9, Issue 3, September 2020
Pages:
55-58
Received:
1 September 2020
Accepted:
14 September 2020
Published:
20 October 2020
Abstract: The possibility of two pass welding for TA2/T2 bimetallic sheets joint with laser-TIG hybrid weldings was studied. Laser-gas tungsten arc welding (TIG) hybrid welding of TA2/T2 bimetallic sheets has been applied using BCuP-2 wire as filler metal. A new welding process for TA2/T2 butt joint was introduced on the basis of the controlling the formation of Ti-Cu intermetallics in the joint. One process was two pass welding involving creation of a joint with one laser weld and one TIG weld separated by remaining unmelted TA2/T2 interface. When laser beam on the TA2 side junction surface, T2 would not be completely melted in joint. When TIG welding in groove, the filler metal melted occurred at the TA2 and T2 interfaces. Through two pass welding, the the formation of Ti-Cu intermetallics can be completely avoided during welding. In the paper, microstructure and mechanical characterization of Ti/Cu clad plates laser and arc welded joints were carried out. The unmelted part of TA2/T2 explosive interface acted as a diffusion barrier between Ti and Cu. The unmelted TA2/T2 explosive interface was beneficial to relieve and accommodate the thermal stress. The joint fractured mainly at the brazed weld with the maximum tensile strength of 610 MPa.
Abstract: The possibility of two pass welding for TA2/T2 bimetallic sheets joint with laser-TIG hybrid weldings was studied. Laser-gas tungsten arc welding (TIG) hybrid welding of TA2/T2 bimetallic sheets has been applied using BCuP-2 wire as filler metal. A new welding process for TA2/T2 butt joint was introduced on the basis of the controlling the formatio...
Show More
