The effects of the addition of Er2O3 on the grain growth and sinterability of c-ZrO2 were investigated using 8 mol.% yttria-stabilized cubic zirconia (c-ZrO2) and various amounts of Er2O3. For these purposes, the content of 0–15 wt.% Er2O3 and c-ZrO2 powders were doped using a colloidal process. Undoped and Er2O3-doped c-ZrO2 specimens were annealed for grain growth at different temperatures and holding times. An increase in annealing temperature and holding time caused grain growth in all specimens. Activation energy of the undoped c-ZrO2 obtained was 358 kJ mol−1 and the activation energies of 1, 5, 10 and 15 wt.% Er2O3-doped specimens obtained were 388, 403, 432 and 476 kJ mol−1, respectively. While excessive grain coarsening in the undoped c-ZrO2 was observed, a lesser level of grain growth occurred in the Er2O3-doped specimens, due to the segregation of Er2O3 at the grain boundaries and the restriction in the grain boundaries mobility of c-ZrO2.
Particleboard can be defined as a wood-based panel produced under pressure and heat with the inclusion of wood particles or other lignocellulosic materials and an adhesive. The need for alternative resources to replace wood raw material has emerged. Poppy husk biomass might have a value-added opportunity, and it is possible to produce particleboards from poppy husk and other softwood species. In this study, moment capacities of L-type corner joints fabricated from poppy husk-based particleboards, which are expected to be an alternative material for case furniture, were investigated. For this purpose, particleboards with five different ratios of poppy husk (P1, P2, P3, P4, P5) were produced, and then L-type corner joints were prepared. Corner joints were connected to each other with two different joint techniques (screwed, minifixed). Specimens were tested under static tension and compression loads, which are the loads commonly experienced by joints during service. According to the results, joints constructed from P5 and connected with screws had the highest moment capacity, whereas joints constructed from P1 and connected with minifix had the lowest moment capacity. In conclusion, from a technical point of view, poppy husk-based particleboards could be utilized in case furniture manufacturing for applications that are not overstressed.
This study aimed to determine the effect of accelerated weathering on gloss, surface hardness and colour changes of Scots pine (Pinus sylvestris L.). Test samples were impregnated with Adolit KD‐5, Wolmanit CX‐8 and Celcure AC‐500 covered with cellulosic and polyurethane varnishes. The results showed that the values of surface hardness and gloss increased after accelerated weathering. While the surface hardness of Scots pine was increased for impregnated and polyurethane‐coated varnish, it decreased for impregnated and cellulosic varnish‐coated Scots pine after 1000 hours of accelerated weathering exposure. Copper‐based chemical impregnation and varnish coating developed the gloss of Scots pine specimens relative to the surface characteristics observed in single‐coated Scots pine specimens. While the most appropriate chemical was Celcure AC‐500 for surface hardness, it was Adolit KD‐5 for the gloss of Scots pine after 1000 hours of accelerated weathering exposure. Wood specimens impregnated prior to the application of varnish were more effective in stabilising the colour of Scots pine than Scots pine only coated with varnish. Polyurethane varnish‐treated Scots pine showed better colour stability for each partial and total accelerated weathering exposure period. The total colour changes were lowest for polyurethane varnish‐coated Scots pine impregnated with Celcure AC‐500 after 1000 hours of accelerated weathering exposure.
Weathering performance of impregnated and coated wood products is an important issue that influences their appearance as well as their service life after outdoor or indoor exposure. A novel procedure to improve the weathering performance of Scots pine wood (Pinus sylvestris L.) is proposed in this study. Wood samples were impregnated with ammonium tetrafluoroborate (ATFB), ammonium pentaborate (APB) and boric acid (BA), and afterward coated with a layer of liquid glass (LG). Surface hardness, color changes, and surface roughness of wood samples were investigated after 250 h and 500 h of exposure to artificial weathering. The results revealed that, except for untreated (control), all other treatment groups caused an increase in surface hardness of Scots pine after weathering. A decrease in the CIE L* value corresponds to the darkening of samples after weathering. Borates-impregnated and LG-coated Scots pine samples possessed the highest color stability. However, all treatment combinations resulted in reddish and yellowish tones after weathering. Exposure to weathering increased surface roughness of wood samples. The surface roughness of the untreated (control) group was higher than that of impregnated and coated samples.
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