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1.
无电解电镀法制备具有电磁屏蔽功能的木材-金属复合材料 总被引：4，自引：0，他引：4
利用无电解电镀的方法制备了导电且具有电磁屏蔽功能的木材-金属复合材料.探讨了镀液用量、施镀时间和施镀温度对复合材料的表面电阻率和电磁屏蔽效能的影响,同时利用能谱分析(EDS)、X射线衍射分析(XRD)和扫描电镜分析(SEM)方法分别测定了不同施镀温度下得到的各镀层的磷含量、微结构和表面形貌.实验结果表明,在镀液使用量为500mL,施镀时间为30min和施镀温度为62℃的最优条件下,所得镀层的导电性和电磁屏蔽效果最佳.而且发现,随着施镀温度的提高,镀层中磷含量缓慢增加.XRD分析表明不同温度所得各镀层的结构均为多晶结构,通过SEM分析,镀层均匀、连续且具有金属光泽,说明在pH值一定的条件下,施镀温度对镀层结构和表面相貌的影响很小.图7表3参11. 相似文献
2.
利用化学镀方法在水曲柳单板表面沉积Ni-Cu-P三元合金,考察镀液pH值和施镀温度对镀后单板电磁屏蔽效能的影响,利用X-射线衍射(XRD)和能谱(EDS)分析各镀层的组织结构和成分含量,采用扫描电镜(SEM)观察镀后单板的表面形貌.结果表明:镀液的pH值在8.5～9.5范围内,所得各镀层均为微晶态,但Cu和P的含量有所差异.镀液的pH值为9.25时,镀后单板的电磁屏蔽效能在9 kHz～1.5 GHz频段达50 dB,镀层中Cu和P的含量分别为9.73%和1.70%;镀液的pH值恒定,施镀温度由60 ℃升高至72 ℃,所得镀层均为微晶镀层,其中63 ℃施镀单板的电磁屏蔽效能最高.扫描电镜观察发现,木材表面完全被均匀、致密、连续的镀层覆盖,具有显著的金属光泽. 相似文献
3.
利用超声波辅助化学镀法在桦木单板表面沉积Ni-P合金镀层.以镀后单板的电磁屏蔽效能为指标,研究100 W超声波辅助下施镀温度和施镀时间的影响,对比0、100和250 W超声波辅助的影响.同时,利用X-射线衍射、扫描电镜和能量分散色谱分析超声波功率与镀层的组织结构、表面形貌和P含量的关系.利用直拉法测定0和100 W超声波辅助化学镀所沉积镀层的结合强度.结果表明:施镀温度较低时,超声波的辅助作用更加明显;100 W超声波辅助,施镀温度62 ℃,施镀时间20 min,镀后桦木单板在9 kHz～1.5 GHz频段,电磁屏蔽效能达到60 dB;较无超声波辅助降低了温度,缩短了时间;超声波辅助使镀层中的P含量随功率的增加而增加,均匀性变差,但晶态结构未改变;无论有无超声波辅助,桦木表面所沉积的镀层均具有很高的结合强度;过高功率的超声波辅助对化学镀过程是不利的, 综合分析认为100 W最为适宜. 相似文献
4.
化学镀镍桦木单板的镀层成分分析及性能研究 总被引：3，自引：2，他引：3
通过对桦木单板表面化学镀镍,可以得到连续、均匀的镀层,从而制得具有良好导电性和电磁屏蔽功能的木材-金属复合材料。扫描电子显微镜(SEM)观察表明:看似光滑的桦木单板表面是很粗糙的,经化学镀后桦木表面金属感极强,但基本构造没有明显改变。利用能谱(EDS)和X射线光电子能谱(XPS)分析表明:镀层中主要成分为镍,磷含量很低。X射线衍射仪分析表明镀层为多晶结构。此木材-金属复合材料的电磁屏蔽效能在9kHz~1.5GHz的频率范围内可达到60dB,导电性和导热性能较素材有显著提高。 相似文献
5.
层状木材陶瓷的制备及表征 总被引：1，自引：0，他引：1
用山毛榉薄木/酚醛树脂(PF)复合材料在常压下密闭隔氧烧结制备具有层状结构的木材陶瓷.用扫描电子显微镜(SEM)和X-射线衍射仪(XRD)对试件的结构和物相进行研究.SEM分析显示:木材陶瓷具有清晰的层状结构,保留了木材作为生物模板的天然特征.XRD的研究结果表明:提高烧结温度在改善木材陶瓷可石墨化程度的同时还能提高其纯度.烧结温度和树脂含量对层状木材陶瓷的力学性能和孔隙结构具有双重作用:抗弯强度在800℃之前迅速增加,在1 200℃附近出现转折点;表观密度呈现出与此基本相同的现象;真密度随着烧结温度和树脂含量的增加而增加.层状木材陶瓷的断裂韧性为0.8～1.2 MPa·m1/2,是采用常规方法制备的木材陶瓷的2倍多,且层状结构能够提高裂纹的扩展容限,避免破坏过程中的灾难性断裂. 相似文献
6.
用点滴加入镀液的方法进行了木材化学镀镍试验,分析施镀温度、镀液pH值和施镀时间等对镍金属沉积速率的影响,得出比较理想的镀镍工艺条件. 相似文献
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为了赋予木基复合材料电磁屏蔽功能,在脲醛树脂胶中加入不锈钢纤维(SF)和黄铜纤维(CF)导电单元,制备三层结构的落叶松复合胶合板,研究不同长度的导电单元以及涂胶量对木基复合材料电磁屏蔽性能(SE)和胶合强度(ST)的影响。结果表明,胶合强度均达到或超过国家标准。涂胶量增大对电磁屏蔽效能有不利影响。在施加不锈钢纤维的条件下,胶合板的电磁屏蔽效能为13．40～21．37dB,电磁屏蔽模型和胶合强度模型均显著。在施加不锈钢纤维的条件下,电磁屏蔽效能为15．61～35．01dB,电磁屏蔽模型均显著,胶合强度模型不显著。金属纤维长度的增加可以使胶层中不锈钢纤维的搭接率增加,有利于电磁屏蔽效能的增加。 相似文献
9.
为了赋予木基复合材料电磁屏蔽功能,在脲醛树脂胶中加入黄铜纤维和不锈钢纤维作为导电单元,制备三层结构的落叶松复合胶合板,研究金属纤维不同施加量以及涂胶量对木基复合材料电磁屏蔽性能(SE)和胶合强度(ST)的影响.结果表明,除SF25-80外,胶合强度均达到或超过国家标准,涂胶量增大对电磁屏蔽效能有不利影响.在施加黄铜纤维条件下,电磁屏蔽效能为6.34～28.76dB,电磁屏蔽和胶合强度模型均不显著;在施加不锈钢纤维条件下,胶合板的电磁屏蔽效能为13.63～21.14dB,电磁屏蔽模型显著,胶合强度模型不显著.金属纤维的加入一方面有利于导电网链的形成,但另一方面对胶合强度有不利影响,进而不利于胶合板的导电性,电磁屏蔽性能是这两个方面综合作用的结果. 相似文献
10.
为研究天然石墨和合成石墨在不同竹炭质量分数条件下复合材料的电磁屏蔽效果,制备屏蔽效能优异的竹炭/石墨/环氧树脂电磁屏蔽复合材料,在两种石墨中分别加入不同质量分数的竹炭,通过模压固化成型制成竹炭/石墨电磁屏蔽复合材料,并对其进行力学性能、动态热机械性能、电阻率性能和电磁屏蔽效能测试及扫描电子显微镜分析。结果表明:随着竹炭质量分数的增加,逐步形成竹炭-石墨网状结构,两种复合材料的玻璃化转变温度均上升;电阻率均降低;30~1 500 MHz频率下电磁屏蔽效能均增大,竹炭质量分数为40%时,合成石墨复合材料电磁屏蔽效能最大,约为30 d B;但由于填料的团聚作用,两种复合材料的弯曲模量下降。扫描电子显微镜分析表明,合成石墨复合材料的界面结合力更好。综合分析可知,当竹炭质量分数为30%时,合成石墨复合材料的力学性能较好;竹炭质量分数增加,石墨复合材料的电磁屏蔽效能增大。 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
13.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
15.
本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(5):472-479
Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken. 相似文献
18.
Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic
or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts
(stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea
(Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content
as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest
N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized
to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea,
largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for
N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant
components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N
released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures
were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality
components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in
the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols.
Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest
age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its
components are mixed. 相似文献
19.
A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste
disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization,
(2) milk sewage sludge at 40 kg N ha−1 target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two
pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha−1. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1); (2) Lolium perenne L. var. Tove (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea
(Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m2, with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect
on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage
sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but
affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
20.
《Scandinavian Journal of Forest Research》2012,27(2):166-178
This study investigated the forest history, structural characteristics, the presence of fungal species suggested to indicate ecological continuity in old-growth forest, and the species composition of saproxylic beetles in 30 old forest ''woodland key habitats'' (WKHs), and compared them with production forest in the same age-class in south-eastern Norway. No statistically significant differences in forest characteristics, community of saproxylic beetles or number of red-listed beetles were found between the WKHs and the production forest, probably owing to a combination of profound long-term logging and a lack of will to delineate sufficiently large WKHs in the one area with significantly less forestry impact. The study indicates the advantage of including forest history information in WKH selection where such data exist, and the importance of restoring habitats in heavily exploited forest landscapes. 相似文献