Narrow Results

A 12-mm caliber gas gun was used to launch a high-strength steel cylindrical projectile to impact a polyurea-coated B₄C ceramic target plate to investigate the effects of the polyurea coating position and the thickness of the polyurea coating on the protective ability of the ceramic composite target plate, reveal the penetration resistance mechanism of the polyurea-coated B₄C ceramic plate and protection mechanism of polyurea coating. The result showed that the ceramic cone top diameter of the composite target plate coated with polyurea on the front side was 52.4–60.5% lower than that of the uncoated ceramic target plate, and the ceramic cone bottom diameter was 0.2–4% lower than that of the uncoated ceramic target plate. For the same area density, the ceramic target plate coated with polyurea on both sides had the largest percentage of mass remaining and the smallest mass of dislodged ceramic fragments. In addition, composite target plates coated with polyurea on the back side and both sides significantly reduced the head velocity of the post-target debris cloud. The polyurea coating on the front of the target plate utilizes the strain rate effect to dissipate the kinetic energy of the projectile and inhibit the spallation of ceramic fragments toward the front of the target plate. The polyurea coating on the back of the target plate utilizes bulge deformation to dissipate the kinetic energy of the projectile and intercepts the scattering of the post-target debris cloud. The polyurea coating effectively reduces ceramic target plate damage and improves composite target plate integrity level and resistance penetration.

The drilling of film cooling holes on gas turbine blades made out of ceramic-coated superalloy improves the efficiency of the gas turbine and prolongs the life of the turbine blade. The purpose of this study was to investigate the effects of different stand-off distances (SODs) on abrasive water jet (AWJ)-pierced holes, in which the machining time, entry and exit hole diameters, overcut, hole taper, and surface morphology were studied. In this study, the water jet pressure (WJP) of 275MPa, piercing angle of $90^{\circ }$, dwell time of 0.2s, and abrasive flow rates (AFRs) of 350g/min and 400g/min were considered for the AWJ piercing operations. The entry and exit hole diameters and overcut linearly increased with an increase of SOD with different abrasive flow rates. And hole taper was observed at the coating and substrate sections in which it decreased with an increase of SOD up to 2mm, and a further increase of SOD increased the hole taper. Besides, the drilled holes were found to have an absence of delamination, cracks, and thermal defects. It was also noted that there is a transformation from a brittle to a ductile mode of erosion that may occur in the high-erosion kinetic energy impact region in the YSZ material section. Based on the experimental results, it is confirmed that SOD of 2mm became an influencing factor in AWJ for piercing quality holes in the YSZ-coated superalloy.

Ceramic has a great broad application in high-temperature environment due to its favorable mechanical, antioxidant and corrosion resistance properties. However, it tends to exhibit severe crack or fail under thermal shock resulting from its inherent brittleness. Microstructure property is a vital factor and plays a critical role in influencing thermal shock property of ceramic. The present study experimentally tested and characterized thermal-shock crack and residual strength of ceramic under different quench temperature, while two kinds of alumina ceramics with different grain size are employed. A two-dimensional (2D) numerical model based on statistical mesoscopic damage mechanics is introduced to depict the micro-crack propagation of ceramic sheet under water quenching. The effects of grain size on critical thermal shock temperature, crack characteristics and residual strength are studied. And the microscopic mechanism of the influence of grain size on thermal shock resistance of ceramic is discussed based on the crack propagation path obtained from experimental and simulation results. The qualitative effect and evolution change of grain size on thermal shock property of alumina ceramic will be summarized.

In order to know the impact behavior of turbine blade-grade monolithic silicon nitride ceramic, particle impact tests have been carried out at room and elevated temperatures with and without tensile load, which simulates the centrifugal force of blade rotation. In the experiments, a 1 mm diameter samarium-cobalt particle is impacted at velocities up to 900 ms^-1. The main results are : 1) Degradation of impact strength was clearly observed at elevated temperature and under tensile stress. 2) The critical stresses for the ring cracking were evaluated from both dynamic and static loading tests and were compared with each other. For a candidate material the reasonable stress value was supposed to be 14 GPa or less. 3) Moreover, X-ray inspection revealed that the radial cracks were prevailing in impacts at elevated temperatures.

Novel processes for fabricating micro/nano sized oxide devices employing self-assembled monolayers (SAM) were developed. SAM of PTCS (phenyltrichlorosilane) was modified to have a phenyl / hydroxyl-group pattern by UV irradiation using a photomask and was used as a template to arrange inorganic fine particles. Surface modification of micro/nano sized inorganic particles and chemical reactions between those particles and SAM were studied. Two-dimensional arrangement of functional particles on a SAM in a controlled manner through the formation of strong chemical bonds, such as amide or ester bonds, can be applied to the future microelectronics and photonics.

The promising role of structural ceramics in many useful devices and structures has in turn led to realization of the importance of developing ceramic joining techniques, which is perhaps one of the most important areas in the ceramic field for research and development. The increasing demand for joining ceramics arises from: a) fabrication of ceramic components of complicated shape or large size in one piece can be very expensive and in some cases impractical, and b) in many cases, because of the limitation of ceramics resulting from poor impact properties and lack of tensile ductility they have to be attached to metals, which must withstand stresses or temperature gradients too great for ceramics. This paper covers methods and problems of joining of ceramics with emphasis on brazing technique. This also includes examples of joining silicon nitride ceramic to itself and to molybdenum.

Clay brick with continuous development of limitations, this paper mainly studies under the different design strength grade of lightweight ceramsite concrete hollow brick density and compressive performance of experimental result analysis, analyzes the development of various new building materials in China can adjust measures to local conditions to use a lot of industrial waste residue, waste and agricultural residues, etc., through processing and manufacturing ceramsite concrete hollow brick used in wall, for profit, thus victims of freshwater.

The heating system plays an important role in press quenching. Hydrogen embrittled parts under stress can fail suddenly without any warning, due to the introduction and subsequent diffusion of hydrogen into the metals. As temperatures increase, these individual hydrogen atoms within the metal gradually recombine to form hydrogen molecules, creating pressure from within the metal that weaken the ductility, toughness, and tensile strength, up to the point where cracks might develop (hydrogen-induced cracking or HIC). Hence, AHSS, hydrogen-induced cracking (HIC) is a crucial issue that we will be investigating in this paper.

In here, we explain the problems and provide solutions using an advanced ceramics CE-Pure, which is a fused silica matrix composite that could offer good thermal and energetic advantages for heating the blanks without hydrogen nor oxygen. The CE-Pure ceramic makes furnace design with good thermal and energetic advantages against traditional ones: it has dust-free chamber with three layers of CE-Pure lining; the heating element is mounted in the groove of the CE-Pure ceramic board; CONE-DUCT gas distribution system made of CE-Pure ceramic; shielding gas is injected into the furnace through well-designed small holes on the hollow CE-PURE roller; and over-lap sealing with CE-Pure tile. Results show that CE-Pure has good thermal shock resistance capability. When the blank enters the furnace, the temperature of the blank is about 25°C while the hearth has a maximum temperature of 1050°C. If the roller or support for the blanks has high thermal expansion coefficient, the roll or support will deform, or even break.