Papers by Author: Wen Bin Hu

Abstract: The preparation, mechanism and electromagnetic absorbing properties of Hollow Ceramic Micro-spheres (HCMs) were studied in the present investigation. HCMs were produced by traditional flame spraying technology as well as equipments. Al-TiO₂ was chosen as a main reactive system. The self-reactive agglomerate powders were produced by spraying process by adopting a temperature-controlled media to get the high cooling rate to solidify and crystallize rapidly. HCMs with characteristic of hollow structure and in-situ synthesis were obtained. Electromagnetic parameter of HCMs has been tested and the reflectivity was analyzed. The results showed that HCMs possess the microwave absorbing properties. The relationship between intrinsic parameters of HCMs and microwave absorbing properties has been also investigated.

Abstract: Numerical simulation the temperature and stress of the SHS reactive flame spray coatings which were cooled in air and sand from a high temperature to room temperature (25°C). The distribution of temperature and stress of the coatings were discussed. The results show that the cooling velocity of air-cooled product is fast than that of sand-cooled product; temperature distribution of sand-cooled product is more uniform than that of air-cooled product in the process of cooling; the stress state of air-cooled coating is tensile stress state, while the stress state of sand-cooled coating is compressive stress state; the stress distribution and strain situation are close relative to temperature distribution, heat emission speed and geometric shape of products in process of cooling; the smooth geometric shape of the product, uniform temperature distribution and heat emission speed are beneficial to improve the state of residual thermal stress; the stress and strain state of sand-cooled coating is better than that of air-cooled coating.

Abstract: Based on the Ti-B4C-sucrose(precursor of carbon) -5wt.% Al sprayed system, the self-reactive spray formed multi-phased structural ceramic preforms tests were done. And the organization, structure and performances of the products were studied. The results show that the products are composed of continuous matrix phase TiC0.3N0.7, dispersed micro/nanometric rodlike grains TiB2, some of Al2O3, pores and intermetallic phase Ti3Al which is hard to identify by SEM. Aluminum is benefit to improve organization, structure and performances of the products. The average density of the products is 97.7%, the Vickers hardness is 20.6GPa, and the flexural strength is 425MPa. There are crack deflection and grain bridging toughening mechanisms owing to the rodlike grains of TiB2 in the products, which makes their fracture toughness is as high as 7.3MPa•m1/2.

Abstract: With Ti-B4C-C as self-reactive spray forming system, the flying combustion process of the sprayed particles was studied by means of water-quenching experiments and numerical simulation. It was found that after the particles have been heated in the oxyacetylene flame for a short time, Ti in the particles melts first and then infiltrates B4C and C. The SHS reaction of the sprayed particles takes place subsequently. Then the liquid ceramic beads appear and crystallize into ceramic grains finally. By the ANSYS finite element analysis, it can be known that the SHS reaction of the sprayed particles starts after they have left the muzzle for about 9.5×10-4s and lasts about 1.45×10-3s before the ceramic beads solidify. The calculated optimal melting distance for the spray particles is about 116mm, which is consistent with the experimental results on the whole.