Narrow Results

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.

Ceramic bearing surfaces have been used over the last 25 years as a clinical solution to the polyethylene wear debris which has been attributed as the major cause of aseptic loosening in total hip arthroplasties. Research has continued over the last 15 years to transpose the technology from the hip to the knee. Monolithic ceramic knee devices have been implanted, mainly in Japan, but the problem of the femoral fixation has remained. The improvement in the polyethylene materials, coupled with the more congruent knee designs, has focused the major issue to wear particle generation as opposed to fatigue or delamination.

The focus of the Brite EuRam project “Advanced Metal to Ceramic Joining Techniques To Optimise low-friction knee prostheses” was to address the issue of fixation in conjunction with the optimum ceramic bearing surface. This was achieved by the development of a biocompatible active alloy braze for joining medical grade Y-TZP zirconia to titanium alloy. Through optimised chemistry and processing conditions a high strength active alloy braze joint was obtained that satisfied all biological and mechanical requirements.

Extensive Finite Element analysis, mechanical, fatigue, wear and compression strength testing were performed to validate the new concept.

‘Burst’ fracture of alumina and zirconia femoral component in hip is a phenomenon, which has been assumed to occur due to the tensile hoop stresses within the femoral head. The aim of this study was to determine the effect of material properties and taper design on the stresses developed in the ceramic femoral head using finite element analysis [FEA]. An axisymmetric 3D finite element model of a 22mm diameter femoral head and taper was generated in PATRAN and analysed using ABAQUS. The common 8/10 (10mm) and a Zimmer 6° (11.5mm) tapers were modelled. To represent manufacturing tolerances the taper contact was varied by introducing angular mismatch of ±4 minutes. The 3^rd Principal stresses (hoop) were marginally higher with a CoCrMo taper compared to a Ti6A14V taper. Taper mismatch had a significant impact on the femoral head stresses. A smaller taper (10mm) with an acuter angle almost doubled the 3^rd principal stresses. Material properties and geometry is found to effect the hoop stresses generated in the femoral head. Increased rigidity led to higher stress at the taper interface. Although the stresses calculated were below the failure criteria of the materials, in mismatched tapers the induced stresses under certain geometric conditions can possibly reach to relatively critical levels.