热处理温度对有机硅树脂结合不烧铝碳滑板性能的影响

以板状刚玉、石墨、Al粉、Si粉和B4C为主要原料,有机硅树脂作结合剂制备了不烧铝碳滑板试样。研究了在空气中先经240℃24h预处理,然后分别于400℃、600℃、800℃、1000℃、1350℃和1450℃保温3h处理后试样的烧结性能、物相组成和显微结构等变化规律。结果表明:热处理温度对有机硅树脂结合不烧铝碳滑板的性能、物相变化和显微结构影响显著。热处理温度为240~600℃时,有机硅树脂裂解产生质量损失,使试样内部结构松散,显气孔率显著增大,常温耐压强度较低;800~1000℃时,试样边缘部分B4C、Al、Si优先氧化,生成须状Al2O3和针状硼酸铝,有利于边缘骨料与基质结构紧密结合,同时,试样内部局部有柱状氮化物生成,相应的体积密度明显增加,显气孔率急剧下降,常温耐压强度达到最高值;温度>1000℃,试样中石墨大量氧化而留下很多气孔,同时Al、Si等氧化反应加剧,试样质量增加和体积膨胀明显,体积密度下降,显气孔率上升,常温耐压强度有下降趋势。     

纳米颗粒改性酚醛树脂用于镁碳砖结合剂的研究

利用纳米粒子对镁碳砖生产用酚醛树脂粘合剂进行了改性。改性树脂常规指标符合镁碳砖结合剂的要求。FE-SEM照片可以看到球形和近球形的纳米颗粒,分散均匀且基本无团聚。制砖实验结果表明,以改性树脂为结合剂能有效地减小显气孔率,增大体积密度且明显提高砖的压缩强度。特别是以TEOS(正硅酸乙酯)和纳米炭黑改性酚醛树脂为结合剂的镁碳砖,经200℃/12h热处理后的常温压缩强度分别提高了38.5%和30.4%,达到了43.94MPa和41.35MPa。砖坯的理化性能检测表明,随处理温度的升高,压缩强度和体积密度越来越小,显气孔率越来越大,200~1100℃各指标变化显著,1100~1550℃各指标没有显著变化,但呈变差趋势。     

酚醛树脂-CarboresP结合镁碳材料的性能与应用

研究了环境友好型含碳材料CarboresP在镁碳砖中的应用。采用MT14A镁碳砖生产工艺,改变CarboresP的加入量,对试样180℃处理后的体积密度、高温抗折强度(1400℃),以及1000℃埋炭处理后的显气孔率、耐压强度等指标进行了研究和对比,确定镁碳砖中合适的CarboresP添加量为1%,并且可适量降低金属防氧化剂的加入量;分析了酚醛树脂-CarboresP结合炭的显微结构,表明其为均质炭和非均质石墨化炭的混合结构,这将有助于改善炭化结构的抗氧化性能;采用尖劈试验绘制镁碳砖试样的应力-应变曲线,表明添加CarboresP的镁碳砖的特征长度LCH值得到明显提高,说明它具有很好的韧性和吸收应力的能力;与传统工艺生产的MT14A镁碳砖相比较,采用酚醛树脂-CarboresP“软性结合”工艺生产的MT14A镁碳砖,成型性能及热处理后各项性能指标均得到改善,在国内某40tLF-VD精炼钢包渣线上进行现场使用证明,平均使用寿命比现用渣线镁碳砖提高18.4%。     

基于高岭土制备轻量微孔莫来石骨料结构与性能研究

以高岭土细粉和α-Al2O3微粉为主要原料,采用原位分解法制备轻量微孔莫来石骨料,研究了铝硅摩尔比及热处理温度对轻量微孔莫来石骨料结构与性能的影响.结果表明:经过1400～1600℃热处理后,富铝莫来石试样中除主要物相莫来石相外,还残余一定量刚玉相,接近理论莫来石组成试样及富硅试样均仅检测到莫来石相;所制备的轻量骨料孔径分布主要集中于0.1 ～4 μm范围,均具有微孔结构;随着热处理温度的升高,骨料的体积密度上升,显气孔率下降,耐压强度上升;经1500℃热处理后,富铝试样体积密度为2.49 g/cm3、显气孔率为25.6％、耐压强度为146 MPa;接近理论莫来石组成试样及富硅试样体积密度均小于1.95 g/cm3、显气孔率大于38.0％,1000℃时导热系数均小于0.77 W/(m·K).     

利用滑板磨制粉制备转炉挡渣Al_2O_3-C外水口砖

为了合理利用滑板磨制粉,节约资源,并降低转炉挡渣外水口砖的生产成本,以白刚玉颗粒和细粉、片状石墨、SiC细粉、α-Al_2O_3微粉、镁铝合金复合抗氧化剂为原料,加入质量分数分别为0、5%、10%、15%的滑板磨制再生粉(粒度≤0. 045 mm),并以液体热固性酚醛树脂和固体树脂粉为结合剂,对比研究了经200℃固化和1 300℃埋焦炭热处理后试样的体积密度、显气孔率、常温抗折强度、常温耐压强度和抗热震性能。结果表明:引入滑板磨制再生粉后,试样经1 300℃热处理后的体积密度和显气孔率有所下降,常温耐压强度、抗折强度小幅下降,抗热震性变化不大。生产的转炉外水口砖在江苏某钢厂的100 t转炉使用15～17炉,平均每炉扩孔0. 8～1. 3 mm,满足了钢厂冶炼要求。     

成型方向对MgO-C质耐火材料性能的影响

为研究不同成型方向对镁碳质耐火材料性能的影响,选取97级电熔镁砂和-195鳞片状石墨为主要原料,以热固性酚醛树脂为结合剂,在1 300 t摩擦压砖机上分别以平打平砌法(成型方向为砌筑层高方向)和侧打平砌法(成型方向垂直于砌筑层高方向)生产指定尺寸的楔形镁碳砖.按规定取样规则制样,分别检测其显气孔率、体积密度、常温耐压强度和1 400℃×0.5h高温抗折强度.结果 表明,当成型方向为砌筑层高方向时,楔形镁碳砖从小头到大头的各项性能均稳定;当成型方向垂直于砌筑层高方向时,楔形镁碳砖从小头到大头的显气孔率不断升高,体积密度、常温耐压强度和高温抗折强度不断降低并随其稍度增大而愈加明显.采用平打平砌法能获得性能稳定的楔形镁碳砖,可为生产制度的制定提供合理依据.     

煅烧温度对菱镁矿尾矿制备MgO-MgAl2O4-Mg2SiO4复相多孔材料性能的影响

以菱镁矿尾矿和二次铝灰为原料，按m(菱镁矿尾矿)∶m(二次铝灰)=7∶3配料，混料、成型后分别经1 200、1 300、1 400和1 500℃煅烧，制备了MgO-MgAl₂O₄-Mg₂SiO₄试样，并研究了煅烧温度对其性能的影响。结果表明：随着煅烧温度的升高，试样的体积密度和线收缩率随之增大，常温耐压强度基本呈增大的趋势，而显气孔率相应减小；当煅烧温度从1 300℃升高到1 400℃时，显气孔率变化尤为明显，分析认为这与镁铝尖晶石的形成有关。在满足显气孔率超过40%的条件下，试样经1 300℃煅烧后的常温耐压强度较高。因此，最佳煅烧温度为1 300℃。     

纳米氧化锆添加量对氧化锆制品性能的影响

在电熔单斜氧化锆原料中添加不同数量的CaO稳定剂,制备部分稳定氧化锆,研究CaO加入量和稳定相数量的关系.在制备的CaO部分稳定氧化锆中添加纳米氧化锆粉体,经过造粒、200 MPa压力成型、干燥、1650 ℃×2 h烧成制得试样.测试试样的物理性能、分析矿物相组成、观察显微结构,研究纳米氧化锆粉体添加量对试样性能的影响.研究结果表明:2Ca-PSZ、3Ca-PSZ、4Ca-PSZ试样中,4Ca-PSZ试样稳定化程度最高;3Ca-PSZ试样显气孔率小,体积密度较大,耐压强度高.在3Ca-PSZ试样中加入纳米氧化锆粉体,随着加入量的增加,试样的显气孔率下降、烧成收缩率增加、耐压强度提高.其中纳米氧化锆粉体添加比例为8wt%时,试样气孔率为9.4%,体积密度为5.08 g/cm3,抗压强度达到381 MPa.与3Ca-PSZ试样相比,气孔率下降40%,体积密度提高5%,耐压强度提高70%.     

添加Ti-Si-Fe合金粉对埋碳反应烧结法制备Si_3N_4结合SiC材料性能的影响

以碳化硅颗粒、碳化硅细粉、硅粉、炭黑和Ti-Si-Fe合金粉为主要原料,以热固性酚醛树脂作为结合剂,在埋碳气氛下采用反应烧结法制备Si_3N_4结合Si C材料,研究了Ti-Si-Fe合金粉加入量对材料体积密度、显气孔率、常温耐压强度、烧后线变化率、物相组成和显微结构等的影响。结果表明:1)随着Ti-Si-Fe合金粉添加量从0增加至9%(w),烧后试样的显气孔率逐渐降低,体积密度和常温耐压强度逐渐增大,烧后线变化率从-0. 10%逐渐增大至0. 12%。2)各试样的SiC含量均比配料高;但随着Ti-Si-Fe合金粉添加量的增加,烧后试样的Si C含量逐渐减少,氮化产物含量逐渐增多,表明Ti-Si-Fe合金粉的加入促进了氮化物结合相的形成。3)因Ti-Si-Fe合金粉中的TiSi_2、Ti_5Si_3在氮化过程中的体积膨胀比Si粉的大,以Ti-Si-Fe合金粉部分取代Si粉促进了试样的致密化,提高了试样的力学性能。     

蓝晶石粒度对刚玉-莫来石材料性能的影响

以粒度为2～1mm和1～0.5mm的M60莫来石为骨料,以电熔白刚玉粉以及粒度分别为0.8～0.355mm、0.355～0.088mm和<0.088mm的蓝晶石为基质料,以少量二氧化硅微粉和苏州土为结合剂,制成36mm×36mm的试样,在110℃干燥24h后,分别在1200℃、1300℃、1400℃和1500℃保温3h煅烧,然后测定烧后试样的线变化率、显气孔率、体积密度和耐压强度。结果表明:(1)对于在各温度下煅烧后的试样,添加粒度<0.088mm蓝晶石的试样烧后线变化率和显气孔率较添加粒度>0.088mm蓝晶石的小,体积密度和耐压强度较添加粒度>0.088mm蓝晶石的大;(2)当添加粒度<0.088mm的蓝晶石时,随着煅烧温度的升高,试样的烧后线变化率、显气孔率、体积密度和耐压强度变化较小;当添加粒度>0.088mm的蓝晶石时,随着煅烧温度的升高,试样的烧后线变化率和显气孔率迅速增大,体积密度和耐压强度迅速减小。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.