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1.
以林业废弃物杉木树皮作原料,通过低温炭化和KOH高温活化两步法制备了具有高表面积和孔隙率的杉木树皮基活性炭并应用于超级电容器电极材料。以碱炭比和活化温度为试验因素,以电流密度0.5 A/g下的质量比电容为响应值,进行中心复合设计(CCD)和响应面分析。研究结果表明：杉木树皮基活性炭的比表面积最高可达1 522 m2/g,最大孔容可达0.84 cm3/g,此时平均孔径为1.12 nm,且同时存在大量的中孔和微孔。碱炭比和活化温度的交互作用对比电容的影响显著,响应面法优化得到杉木树皮基活性炭最佳制备工艺为：碱炭比值为3,活化温度605℃,此条件下炭材料的比电容为185.7 F/g。对优化条件下制备的活性炭进行电化学性能测试发现：在0.5 A/g条件下的最大比电容为188 F/g,且具有良好的倍率性能(85.1%)。  相似文献   

2.
炭化温度对竹基活性炭孔结构及电化学性能的影响   总被引：1，自引：0，他引：1  
以毛竹为炭前驱体,KOH作活化剂,通过调节炭化温度在相同活化条件下制备了具有不同孔隙结构的竹基活性炭材料,通过SEM、XRD、BET、直流充放电、交流阻抗和循环伏安等结构与电化学性能分析方法,考察了炭化温度对竹基活性炭材料结构和性能的影响。研究结果表明:随着炭化温度升高,活性炭材料的比表面积与总孔容、中孔孔容均不断减小,微孔比表面积和微孔孔容先增大后减小。其中炭化温度为500℃的样品BAC500比表面积为3447m~2/g,总孔容为1.96cm~3/g,在有机电解液中以1mA/cm~2的电流密度充放电时,比电容高达178.8 F/g,电流密度增大50倍容量保持率为74.6%,显示出良好的功率特性。活性炭材料中存在一定比例的中孔不仅可以改善电极材料的功率特性,而且可以提高微孔的利用率。  相似文献   

3.
以桉木木质纤维素作原料，六对羧基苯氧基环三磷腈(HCPCP)作为氮磷掺杂剂，NaOH作为共活化剂，采用先炭化后活化制备了木质纤维素基氮磷掺杂介孔炭(NPC)材料，采用SEM、XRD、XPS和拉曼光谱等方法对介孔炭材料进行表征。研究结果表明：活化温度650℃下得到的样品(NPC-650)具有丰富的蜂窝状孔隙结构，平均孔径为5.18 nm,介孔体积比89%。用介孔炭NPC-650作为阴极材料组装成锌离子混合电容器，在0.2 A/g电流密度下比电容为194 F/g,能量密度为87.3(W·h)/kg,功率密度为179.5 W/kg,在10 A/g电流密度下充/放电5 000次，电容保持率98.9%。  相似文献   

4.
我国竹材资源丰富,以竹废料为原料,制备可用于超级电容器电极材料的竹活性炭,有助于推动竹产业发展,助力国家“双碳”目标实现。在本研究中,分别采用KOH共热和水热处理对竹粉进行活化,并对制备的竹活性炭进行电化学性能、比表面积、表面微观形貌等测试。实验结果表明,KOH共热活化法的最佳条件为炭化温度350℃,活化温度900℃,升温速率2℃/min,碱炭质量比4∶1;制备的活性炭比表面积为3 299 m2/g, 0.5 A/g电流密度下的比电容为287.8 F/g, 5 000次充放电测试后,电容保持率为95%～105%。水热活化法的最佳条件为KOH质量分数20%,反应温度150℃,反应时间12 h,制备的活性炭比表面积为192.91 m2/g, 0.5 A/g电流密度下的比电容为170.4 F/g,电容保持率为88.89%。2种方法制备的活性炭孔径结构都是以微孔为主,中孔混合分布,含有少量大孔;2种活性炭均含有双层或多层石墨烯结构,但水热活化法制备的活性炭石墨化程度更高,制备条件更温和。研究结果既可为超级电容器用活性炭的研究提供了理论思路,也有效地扩...  相似文献   

5.
以工业滤纸为炭基材料,聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段聚醚(普朗尼克F127)为软模板,1,3,5-三甲苯为扩孔剂,在添加3-氨基苯酚(氮源)和六次甲基四胺的条件下进行水热合成反应制得纸基复合材料,并经炭化制得氮掺杂介孔炭化复合材料(NMC-700),进一步KOH活化后制得活化氮掺杂介孔炭化复合材料(ANMC-700),同时以工业滤纸直接炭化制得的炭化滤纸(C-700)样品为对照,采用SEM、TEM、XRD、XPS等方法对3种炭材料进行了表征。研究结果表明:ANMC-700表面形成了粒径0.6～7μm的炭微球,孔结构由随机分布、蠕虫状的孔组成,比表面积高达1 559 m~2/g,孔容为0.80 cm~3/g,且氮原子已经成功掺杂到炭骨架中,含氮量为3.60%,含氧量为13.65%。电化学性能测试结果表明:以6 mol/L KOH为电解质溶液,在1 A/g的电流密度下,ANMC-700的比电容可达284 F/g,在20 A/g的电流密度下其比电容仍能保持在173 F/g,并在此电流密度下经过10 000次循环充放电,其电容保持率在98.6%,表现出良好的电化学稳定性。  相似文献   

6.
以竹炭为前驱体、三聚氰胺为氮源、碳酸钾为预活化剂,采用两次活化工艺成功制备了氮掺杂竹活性炭超级电容器电极材料。利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、拉曼光谱(Raman)、比表面积及孔隙分析(BET)和X射线光电子能谱(XPS)等测试方法对制备的电极材料的形貌、结构、化学成分进行表征。通过控制活化过程中的炭碱比(质量比)优化样品的电化学性能,结果表明:炭碱比为1∶1时制备的NC-1样品比表面积高达1 984.4 m2/g,平均孔径为1.26 nm,样品具有清晰的介孔以及内部蠕虫状的微孔。炭材料中氮元素和氧元素含量(质量分数)分别为2.20%和4.65%,有利于增加活性炭表面的亲水性和赝电容,从而提高其比电容量。经电化学性能测试,NC-1样品循环伏安曲线(CV曲线)具有良好的对称性,呈近似矩形;其中在低电势窗口出现明显的宽峰,表明充放电过程中材料表面的含氮官能团与电解液之间发生氧化还原反应,贡献赝电容。恒流充放电显示在1 A/g电流密度下质量比电容高达224 F/g,与未采用该活化工艺的样品比较提高了86.7%。在50 A/g电流密度下其质量比电容高达144 F/g,且在10 A/g下经5 000次循环充放电后仍可达到93%的初始电容保持率,显示了氮掺杂竹活性炭超级电容器电极材料较优异的电化学性能和稳定的循环性能。  相似文献   

7.
以工业废弃物木质素磺酸钠为碳源,高含氮量的三聚氰胺为氮源,通过共混物直接热解制得高氮氧含量的木质素基炭材料(NSL-x),当三聚氰胺与木质素磺酸钠的质量比值为2、4和6时,分别标记为NSL-2、NSL-4和NSL-6;采用SEM、XRD和XPS等方法对其形貌和结构进行了表征。结果表明:NSL-x整体是由尺寸为几百纳米到几微米的无规则炭块堆积而成;氮氧掺杂并没有改变其形貌和结晶结构,炭化产物以无定形碳为主。炭材料NSL-4含氮量可达2.41%,含氧量达到20.12%,同时NSL-4中所含的羰基最高(10.27%)。样品的电化学性能测试结果表明:以6 mol/L KOH为电解液,在0.1 A/g的电流密度下,NSL-4的比电容达到229 F/g,在20 A/g的高电流密度下,比电容仍维持在137 F/g。在10 A/g的电流密度下,经过10 000次的充放电循环测试,NSL-4的库伦效率仍然保持在100%左右,比电容仅下降了1%,表现出良好的倍率性能和极佳的电化学稳定性。  相似文献   

8.
以椰壳为原料,水蒸气活化法制备了椰壳活性炭(AC),并以乙醇和水作为溶剂,采用水热法将AC与石墨烯(GR)按质量比90∶0、90∶5、90∶54、90∶90和54∶90复合,将制得的复合材料(GAC1~GAC5)作为电极应用于超级电容器。通过氮气吸脱附、X射线衍射(XRD)、扫描电镜(SEM)方法表征了活性炭的孔结构和表面形貌;采用循环伏安(CV)、恒电流充放电(GCD)方法分析比较不同复合比例下超级电容器电极材料的性能。实验结果表明:在炭化温度800℃,活化温度900℃及活化时间1.5 h的条件下制备的椰壳活性炭比表面积为2482 m^2/g,其孔径主要分布在2~4 nm,孔容可达1.33 cm^3/g,在6 mol/L KOH电解液中比电容为85 F/g,石墨烯改性的复合材料GAC-5作为电极材料具有优异的电化学性能,在电流密度1 A/g时比电容可达186 F/g。  相似文献   

9.
随着经济的发展和社会的进步,人们对具有长的循环寿命、高的功率密度和绿色廉价的能源设备的需求逐渐增加,基于生物质活性炭的超级电容器近年来备受关注。然而,生物质基活性炭的电化学性能仍然缺少竞争力,此外,对其微观结构的控制也是较大难题。笔者以糠醛渣为原料,KOH为活化剂,在氩气氛围下通过两步炭化的方法制备三维多孔炭材料,并将制备的多孔炭用做超级电容的电极材料。通过SEM、TEM、Raman、XPS、XRD等手段系统分析表征了所获多孔炭材料的形貌、结构、组成,并探讨活化剂的比例对糠醛渣多孔炭结构性能的影响。研究结果表明:当KOH和糠醛渣的质量比为3∶1时,所制备的多孔炭材料比表面积为2 164.3 m~2/g,具有良好的电容性能(当电流密度1 A/g时,比电容为235.6 F/g)、倍率性能和循环稳定性(当循环充放电10 000次后,比电容仍能保留96%以上)。本研究从生物精炼废弃物中制备了性能优异的超级电容器用活性炭,为降低高性能超级电容器成本,实现生物质的高值化应用提供新思路。  相似文献   

10.
以竹炭、鳞片石墨为原料,基于机械力效应,通过高能球磨的剥离和粉碎,然后高温炭化,制备出具有优良电化学性能的纳米石墨片/竹炭(GN/BC)复合材料;同时在相同条件下,以不添加鳞片石墨制备的高温多孔竹炭(PBC)为对照样品。利用X射线衍射(XRD)、拉曼光谱(Raman)、扫描电子显微镜(SEM)、比表面积与孔隙分布分析仪表征了材料的表面形貌和结构,并利用三电极体系测试了其电化学性能。研究结果表明：较高结晶度鳞片石墨的加入可以提高复合材料的结晶度,高能球磨可以使石墨片破碎成纳米尺寸,并嵌入竹炭内部;制备的GN/BC复合材料的比表面积为863.47 m2/g,总孔容为0.56 cm3/g、微孔孔容为0.26 cm3/g,平均孔径为2.58 nm;在1 A/g的电流密度下,该复合材料具有280.97 F/g的高质量比电容,同时还具有良好的倍率性能。  相似文献   

11.
The transverse shrinkage variation within trees was examined for five sugi cultivars. The within-tree trends of tangential shrinkage (α T) were different by cultivar, whereas radial shrinkage (α R) increased from pith to bark in most cultivars. The tangential/radial shrinkage ratio (α T/α R) decreased from pith to bark in most cultivars, because the radial variation of α R was larger than that of α T. The cultivars showed significant differences among cultivars in α T, α R, and α T/α R, but the difference among cultivars for α T/α R was smaller. The relationships between transverse shrinkage and microfi bril angle (MFA), basic density (BD), tree ring parameters, and modulus of elasticity were examined. The α T and α R showed positive relationships with BD, latewood percentage, latewood density, and modulus of elasticity, and negative relationships with MFA and ring width. The relationships with earlywood density were weak. Sugi exhibited variation in transverse shrinkage within stem and among cultivars, with the variation affected by MFA, density, and tree ring parameters. Part of this article was presented at the 56th Annual Meeting of the Japan Wood Research Society, Akita, Japan, August 2006, and the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, Japan, August 2007  相似文献   

12.
Jiang XH  Yang JQ  Li N  Wang H  Zhou QX 《Fitoterapia》2011,82(6):878-882
A simple HPLC method was developed to quantify rabbit plasma tetrandrine (Tet) with propranolol (Pro) as internal standard. Based on the established method Tet and Pro were eluted at 7.1 and 12.0 min, respectively. It was shown that the concentration-time data of Tet fit the classical two-compartment model, no matter the drug was administered intravenously or orally to rabbits. The values of AUC0 → ∞, clearance (Cl0 → ∞), volume of distribution (Vd), and elimination half-life (t1/2β) of Tet were 59861.149 ± 26962.196 μg/L ? min, 0.503 ± 0.173 L/min/kg, 179 ± 76.185 L/kg, and 283.808 ± 162.937 min for intravenous injection of 5 mg/kg, or 18986.217 ± 7462.308 μg/L ? min, 0.805 ± 0.267 L/min/kg, 110.284 ± 94.176 L/kg, and 732.919 ± 847.32 min for gavage administration of 10 mg/kg , respectively. The results indicate that Tet displays a limited absorption in intestinal tract, even though it has a favorable pharmacokinetic profile after oral or intravenous administration.  相似文献   

13.
We quantified the effect of water and nutrient availability on aboveground biomass and nitrogen accumulation and partitioning in four species from the southeastern United States, loblolly pine (Pinus taeda), slash pine (Pinus elliottii), sweetgum (Liquidambar styraciflua), and sycamore (Platanus occidentalis). The 6-year-old stands received five levels of resource input (control, irrigation with 3.05 cm water week−1, irrigation + 57 kg N ha−1 year−1, irrigation + 85 kg N ha−1 year−1, and irrigation + 114 kg N ha−1 year−1). Irrigation significantly increased foliage, stem, and branch biomass for sweetgum and sycamore, culminating in 103% and 238% increases in total aboveground biomass. Fertilization significantly increased aboveground components for all species resulting in 49, 58, 281, and 132% increases in total aboveground biomass for loblolly pine, slash pine, sweetgum, and sycamore, respectively. Standing total aboveground biomass of the fertilized treatments reached 79, 59, 48, and 54 Mg ha−1 for loblolly pine, slash pine, sweetgum, and sycamore, respectively. Fertilization increased foliar nitrogen concentration for loblolly pine, sweetgum, and sycamore foliage. Irrigation increased total stand nitrogen content by 6, 14, 93, and 161% for loblolly pine, slash pine, sweetgum, and sycamore, respectively. Fertilization increased total nitrogen content by 62, 53, 172, and 69% with maximum nitrogen contents of 267, 212, 237, and 203 kg ha−1 for loblolly pine, slash pine, sweetgum, and sycamore, respectively. Growth efficiency (stem growth per unit of leaf biomass) and nitrogen use efficiency (stem growth per unit of foliar nitrogen content) increased for the sycamore and sweetgum, but not the loblolly or slash pine.  相似文献   

14.
Seeking an alternative to Sesbania spp. tree fallows, a Tephrosia species and provenance trial was conducted at Msekera Research Station, Chipata (Zambia) to evaluate eleven Tephrosia vogelii and three Tephrosia candida provenances. They were tested for biomass production, quality of biomass, resistance to root-knot nematodes, nitrogen release, and for their effects on soil nitrogen dynamics. At the end of 1.5 years, the T. candida provenances 02970, 02971 and 02972 from Madagascar produced two times greater amount of aboveground biomass than the T. vogelii provenances. There was little variability among the T. vogelii provenances in terms of litter and biomass production. Weed growth was significantly greater under T. vogelii than T. candida provenances. While Tephrosia vogelii provenance 98/02 from Zambia and T. candida 02972 were highly tolerant to the Meloidogyne incognita nematodes, T. vogelii provenances 02977, 98/03, 02973 from Kenya, Zambia and Malawi, respectively, were highly susceptible to the nematodes. The Tephrosia species and provenances showed a wide variability in terms of N, lignin and polyphenol concentration in their foliage. Mineralization of N in the foliage of T. candida provenances 02970 and 02971 and T. vogelii provenances 98/04 and 02974 from Malawi occurred rapidly within 14 weeks of incubation. At the end of the 2-year growth period, there was significantly greater total inorganic N under T. candida provenance 02972 (12.5 mg kg−1) than T. vogelii (5 mg kg−1) provenance Mungwi 98/02. Maize (Zea mays L.) yields after T. candida provenances were greater than those after T. vogelii provenances. Further testing of the most promising provenances is needed for their effects on subsequent maize yields under a range of farm conditions. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

15.
This study was conducted to determine carbon (C) dynamics following forest tending works (FTW) which are one of the most important forest management activities conducted by Korean forest police and managers. We measured organic C storage (above- and below-ground biomass C, forest floor C, and soil C at 50 cm depth), soil environmental factors (soil CO2 efflux, soil temperature, soil water content, soil pH, and soil organic C concentration), and organic C input and output (litterfall and litter decomposition rates) for one year in FTW and non-FTW (control) stands of approximately 40-year-old red pine (Pinus densiflora S. et Z.) forests in the Hwangmaesan Soopkakkugi model forest in Sancheonggun, Gyeongsangnam-do, Korea. This forest was thinned in 2005 as a representative FTW practice. The total C stored in tree biomass was significantly lower (P < 0.05) in the FTW stand (40.17 Mg C ha−1) than in the control stand (64.52 Mg C ha−1). However, C storage of forest floor and soil layers measured at four different depths was not changed by FTW, except for that at the surface soil depth (0–10 cm). The organic C input due to litterfall and output due to needle litter decomposition were both significantly lower in the FTW stand than in the control stand (2.02 Mg C ha−1 year−1 vs. 2.80 Mg C ha−1 year−1 and 308 g C kg−1 year−1 vs. 364 g C kg−1 year−1, respectively, both P < 0.05). Soil environmental factors were significantly affected (P < 0.05) by FTW, except for soil CO2 efflux rates and organic C concentration at soil depth of 0–20 cm. The mean annual soil CO2 efflux rates were the same in the FTW (0.24 g CO2 m−2 h−1) and control (0.24 g CO2 m−2 h−1) stands despite monthly variations of soil CO2 efflux over the one-year study period. The mean soil organic C concentration at a soil depth of 0–20 cm was lower in the FTW stand (81.3 g kg−1) than in the control stand (86.4 g kg−1) but the difference was not significant (P > 0.05). In contrast, the mean soil temperature was significantly higher, the mean soil water content was significantly lower, and the soil pH was significantly higher in the FTW stand than in the control stand (10.34 °C vs. 8.98 °C, 48.2% vs. 56.4%, and pH 4.83 vs. pH 4.60, respectively, all P < 0.05). These results indicated that FTW can influence tree biomass C dynamics, organic C input and output, and soil environmental factors such as soil temperature, soil water content and soil pH, while soil C dynamics such as soil CO2 efflux rates and soil organic C concentration were little affected by FTW in a red pine stand.  相似文献   

16.
A typhoon event catastrophically destroyed a 45-year-old Japanese larch plantation in southern Hokkaido, northern Japan in September 2004, and about 90% of trees were blown down. Vegetation was measured to investigate its regeneration process and CO2 flux, or net ecosystem production (NEP), was measured in 2006–2008 using an automated chamber system to investigate the effects of typhoon disturbance on the ecosystem carbon balance. Annual maximum aboveground biomass (AGB) increased from 2.7 Mg ha−1 in 2006 to 4.0 Mg ha−1 in 2007, whereas no change occurred in annual maximum leaf area index (LAI), which was 3.7 m2 m−2 in 2006 and 3.9 m2 m−2 in 2007. Red raspberry (Rubus idaeus) had become dominant within 2 years after the typhoon disturbance, and came to account for about 60% and 50% of AGB and LAI, respectively. In comparison with CO2 fluxes measured by the eddy covariance technique in 2001–2003, for 4.5 months during the growing season, the sum of gross primary production (GPP) decreased on average by 739 gC m−2 (64%) after the disturbance, whereas ecosystem respiration (RE) decreased by 501 gC m−2 (51%). As a result, NEP decreased from 159 ± 57 gC m−2 to −80 ± 30 gC m−2, which shows that the ecosystem shifted from a carbon sink to a source. Seasonal variation in RE was strongly correlated to soil temperature. The interannual variation in the seasonal trend of RE was small. Light-saturated GPP (Pmax) decreased from 30–45 μmol m−2 s−1 to 8–12 μmol m−2 s−1 during the summer season through the disturbance because of large reduction in LAI.  相似文献   

17.
In 2004 and 2005, the yield, leaf area, dry weight and dry weight partitions of soybeans were determined at the Agroforestry Research Site (ARS) (est. 1987, Ontario, Canada). Soybean was intercropped with poplar (Populus deltoides x nigra DN-177 L., 556 m3crown tree−1), silver maple (Acer saccharinum L., 308 m3), black walnut (Juglans nigra L., 148 m3) and pecan (Carya illinoensis Wangenh., 114 m3), or grown alone (monoculture). Yield of soybean was not different in either year between the monoculture and the black walnut or pecan intercrops. In the poplar and silver maple treatments, yield was 66 and 85% (2004 and 2005) lower than in the monoculture. Despite the fact that different tree species were used, there was a significant negative linear regression between yield and tree crown volume (R 2 = 0.76, P = 0.0049 and R 2 = 0.93, P < 0.0001 in 2004 and 2005, respectively). With increasing tree crown volume, soybean tended to partition more dry matter to the photosynthetic and reproductive parts and less to structural tissue and petiole. This demonstrates the phenotypic flexibility of the crop component in agroforestry systems. Contrary to theoretical predictions, soybean leaves were thicker as shade increased (increase by 6.2 × 10−4–1.2 × 10−3 mg cm−2, per unit of crown volume), pointing to competitive interactions specific to tree-based intercrops.  相似文献   

18.
After a wildfire, the management of burnt wood may determine microclimatic conditions and microbiological activity with the potential to affect soil respiration. To experimentally analyze the effect on soil respiration, we manipulated a recently burned pine forest in a Mediterranean mountain (Sierra Nevada National and Natural Park, SE Spain). Three representative treatments of post-fire burnt wood management were established at two elevations: (1) “salvage logging” (SL), where all trees were cut, trunks removed, and branches chipped; (2) “non-intervention” (NI), leaving all burnt trees standing; and (3) “cut plus lopping” (CL), a treatment where burnt trees were felled, with the main branches lopped off, but left in situ partially covering the ground surface. Seasonal measurements were carried out over the course of two years. In addition, we performed continuous diurnal campaigns and an irrigation experiment to ascertain the roles of soil temperature and moisture in determining CO2 fluxes across treatments. Soil CO2 fluxes were highest in CL (average of 3.34 ± 0.19 μmol m−2 s−1) and the lowest in SL (2.21 ± 0.11 μmol m−2 s−1). Across seasons, basal values were registered during summer (average of 1.46 ± 0.04 μmol m−2 s−1), but increased during the humid seasons (up to 10.07 ± 1.08 μmol m−2 s−1 in spring in CL). Seasonal and treatment patterns were consistent at the two elevations (1477 and 2317 m a.s.l.), although respiration was half as high at the higher altitude.Respiration was mainly controlled by soil moisture. Watering during the summer drought boosted CO2 effluxes (up to 37 ± 6 μmol m−2 s−1 just after water addition), which then decreased to basal values as the soil dried. About 64% of CO2 emissions during the first 24 h could be attributed to the degasification of soil pores, with the rest likely related to biological processes. The patterns of CO2 effluxes under experimental watering were similar to the seasonal tendencies, with the highest pulse in CL. Temperature, however, had a weak effect on soil respiration, with Q10 values of ca. 1 across seasons and soil moisture conditions. These results represent a first step towards illustrating the effects of post-fire burnt wood management on soil respiration, and eventually carbon sequestration.  相似文献   

19.
The effect of seed water content (WC) (2–3, 5–6 and 22–25%, on a fresh weight basis), storage temperature (+4, −20, −80 and −196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2–3% and 5–6% WC declined after 48 months of storage at −80 and −196°C, with a further decline at 60 months at −20, −80, −196°C. Germination remained high when control white spruce seeds and seeds with 2–3, 5–6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2–3% and 5–6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22–25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, −20 and −80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at −20 and −196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22–25% WC, where MGT increased for white spruce seed stored 48 months at −80 and −196°C, and for black spruce seed stored 24 months at +4 and −80°C and 60 months at −196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, −20, −80, and −196°C for black spruce and lodgepole pine, and 2–6% water content is optimal for all 3 species at these temperatures.  相似文献   

20.
 The reaction behavior and kinetics of lignin model compounds were studied in supercritical methanol with a batch-type supercritical biomass conversion system. Guaiacol, veratrole, 2,6-dimethoxyphenol, and 1,2,3-trimethoxybenzene were used as model compounds for aromatic rings in lignin. In addition, 5-5, β-1, β-O-4, and α-O-4 types of dimeric lignin model compounds were used as representatives of linkages in lignin. As a result, aromatic rings and 5-5 (biphenyl)-type structures were stable in supercritical methanol, and the β-1 linkage was not cleaved in the β-1-type structure but converted rapidly to stilbene. On the other hand, β-ether and α-ether linkages of β-O-4 and α-O-4 lignin model compounds were cleaved rapidly, and these compounds decomposed to some monomeric compounds. Phenolic compounds were found to be more reactive than nonphenolic compounds. These results indicate that cleavages of ether linkages mainly contribute to the depolymerization of lignin, whereas condensed linkages such as the 5-5 and β-1 types are not cleaved in supercritical methanol. Therefore, it is suggested that the supercritical methanol treatment effectively depolymerizes lignin into the lower-molecular-weight products as a methanol-soluble portion mainly by cleavage of the β-ether structure, which is the dominant linkage in lignin. Received: December 19, 2001 / Accepted: April 30, 2002 Acknowledgments This research has been done under the research program for the development of technologies for establishing an ecosystem based on recycling in rural villages for the twenty-first century from the Ministry of Agriculture, Forestry and Fisheries, Japan; by a Grant-in-Aid for Scientific Research (B)(2) (no.12460144, 2001.4–2003.3) from the Ministry of Education, Culture, Sports, Science and Technology, Japan; and under the research program from Kansai Research Foundation for Technology Promotion, Japan. The authors thank them for their financial support. This study was presented in part at the 45th Lignin Symposium, Ehime, Japan, October 2000 and the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, Japan, April 2002 Correspondence to:S. Saka  相似文献   

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