Effect of Environment on Fatigue Crack Wake Dislocation Structure in Al-Cu-Mg

Fatigue-induced dislocation structure was imaged at the crack surface using transmission electron microscopy (TEM) of focused ion beam (FIB)-prepared cross sections of naturally aged Al-4Cu-1.4Mg stressed at a constant stress intensity range (7?MPa??m) concurrent with either ultralow (~10^?8?Pa?s) or high-purity (50?Pa?s) water vapor exposure at 296?K (23?°C). A 200-to-600-nm-thick recovered-dislocation cell structure formed adjacent to the crack surface from planar slip bands in the plastic zone with the thickness of the cell structure and slip bands decreasing with increasing water vapor exposure. This result suggested lowered plastic strain accumulation in the moist environment relative to the vacuum. The previously reported fatigue crack surface crystallography is explained by the underlying dislocation substructure. For a vacuum, $ \left\{ { 1 1 1} \right\} $ facets dominate the crack path from localized slip band cracking without resolvable dislocation cells, but cell formation causes some off- $ \left\{ { 1 1 1} \right\} $ features. With water vapor present, the high level of hydrogen trapped within the developed dislocation structure could promote decohesion manifest as either low-index $ \left\{ { 100} \right\} $ or $ \left\{ { 1 10} \right\} $ facets, as well as high-index cracking through the fatigue-formed subgrain structure. These features and damage scenario provide a physical basis for modeling discontinuous environmental fatigue crack growth governed by both cyclic strain range and maximum tensile stress.     

Manufacturing of High-efficiency Air Filter Paper Using Ultra-fine Fibers

In this paper, the manufacturing of high-efficiency air filter paper is reported. The air filter paper was produced using ultra-fine fibers and wateroat fibers mercerized by alkali, using an electrospinning apparatus with multiple rings. The high efficiency air filter paper has an antibacterial effect after adding a chitosan-copper complex which is harmless to humans. As a result of the measurement, the filtering efficiency of the air filter paper is approximately 99.998% and its antibacterial efficiency is approximately 99.5%.     

Catalytic combustion in a domestic natural gas burner

Gastec and Vaillant developed a boiler in which the combustion is catalytically stabilised as well as a completely catalytic boiler. The catalytically stabilised boiler emitted about 5 ppm NO_x and 0 ppm CO. In this boiler the burner is replaced by a metal honeycomb. The honeycomb is partly coated with a catalyst washcoat. The coated part is at the flame side of the honeycomb. The coated length of the channels is an important parameter. A too long coating results in CO emissions, a too short coating in higher NO_x emissions.

The catalytic boiler emitted 0 ppm NO_x, 0 ppm CO and 0 ppm CH₄. The gas is combusted catalytically in two metal honeycombs. Most gas is converted in the first few millimetres from the entrance of the monolith. The heat that is produced is radiated to a heat exchanger. The remaining honeycomb and the secondary honeycomb convert the rest of the methane.

Comparing these boilers, the completely catalytic boiler shows lower emissions and a lower sensitivity to the gas quality. The partly catalytic burner is more reliable and can use a conventional security system. Production and development costs are thus smaller.     

Effect of NH3 plasma treatment on the device performance of ZnO based thin film transistors

We fabricated an enhancement-mode thin film transistor (TFT) using ZnO as an active channel layer deposited by radio frequency (rf) magnetron sputtering. The NH₃ plasma passivation was performed in order to improve the electrical properties of the ZnO TFTs. We observed that the NH₃ plasma treated ZnO TFTs revealed improved device performances, which include the field effect mobility of 34 cm²/Vs, threshold voltage of 14 V, subthreshold swing of 0.44 V/dec, off-current of 10⁻¹¹ A and on to off ratio higher than 10⁵. These results demonstrate that NH₃ plasma treatment could effectively enhance the performance of the ZnO based TFT device.     

Polyethylene wear particles induce TLR 2 upregulation in the synovial layer of mice

A cellular and receptor mediated response to ultra-high-molecular-weight-polyethylene (UHMWPE) wear particles results in a release of proinflammatory cytokines and induces an inflammatory reaction causing osteolysis in total joint replacement. This investigation offers insight into the toll-like receptor (TLR) mediated activation by polyethylene wear particles in the synovial layer of mice. We hypothesized that, similar to recent in vitro results, UHMWPE particles lead to an upregulation of TLR 1 and 2 and TLR 4 in vivo in the synovial tissue of mice as well. Therefore, UHMWPE particles were generated in a common knee simulator according to the ISO standard, separated by acid digestion and determined by scanning electron microscopy. Endotoxin was removed using a method based on ultracentrifugation. A particle suspension (50 μl; 0.1 vol./vol.%) was injected into the left knee joint of female Balb/c mice (n = 8). In a control group, phosphate-buffered saline was injected into the left knee of Balb/c mice (n = 8). The mice were sacrificed after 7 days. Immunohistochemical staining was performed with TLR 1, 2 and 4 polyclonal antibodies for Balb/c mice and evaluated by light microscopy. The particle-stimulated group showed a thickened synovial layer, an increased cellular infiltration and a TLR 2-upregulation in the synovial layer compared to the control group. An increased expression of TLR 1 and TLR 4 could not be demonstrated. These results indicate a mainly TLR 2-induced inflammation to polyethylene wear debris in the synovial layer of mice.