CN1064777C - 金属、合金或金属碳化物的纳米颗粒及其制备方法 - Google Patents
金属、合金或金属碳化物的纳米颗粒及其制备方法 Download PDFInfo
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Abstract
本发明提供一种有碳层覆盖并在室温下呈现滋滞现象的金属或合金的纳米颗粒。这些纳米颗粒的直径在0.5至50nm范围内并且可以是结晶的或无定形的。这种金属、合金或金属碳化物的纳米颗粒的制备方法是先用磁性金属、合金、或金属或合金的氧化物填充石墨棒,然后填充石墨棒经碳弧放电产生含有金属、合金或金属碳化物的纳米颗粒以及非磁性物质的灰分。再用磁场梯度分离灰分,将金属、合金或金属碳化物的纳米颗粒与非磁性物质分开。
Description
本发明涉及的领域包括金属、合金或金属碳化物的化合物和有碳层覆盖的磁性金属合金或金属碳化物的化合物。具体而言,本发明涉及有碳层覆盖的金属、合金或金属碳化物的纳米颗粒(Nanoparticles)以及它们的制造方法。纳米颗粒包括直径为0.5至50纳米的晶体颗粒和无定形颗粒,以及直径为0.5至50纳米,长度不超过一厘米的纳米管(Nanotube)。
微小的磁性颗粒有很多的用途。它们可以作为有机调色剂在静电复印中使用、可以作为造影剂在核磁共振成像中使用、还可以在铁磁流体真空密封和数据磁性存储中使用。这些颗粒的粒径填充是微米级的或者更大。这样大的颗粒尺寸使它们在某些专业化应用中不能尽如人意。
如果这些磁性颗粒更细,就可以通过减少操作步骤降低静电复印的成本。在磁体流体的应用方面,由于由这些更细的颗粒提供碳层可以提高溶解性并带来好处。在数据磁性存储方面,使用更细小的颗粒,可以提高存储密度。此外,在磁性墨水的应用方面,碳层以及纳米颗粒在水溶液中的分散能力均可为润湿和涂敷带来好处。因此,对亚微米级的金属、合金或金属碳化物的颗粒以及用高效工艺大批量生产这种颗粒的方法存在潜在的需求。为了改善在数据磁性存储中的处理,要求磁性颗粒呈现磁滞现象。更为理想的是在室温下呈现磁滞现象。
近来,关于Kratschmer-Huffman碳弧法制造富勒烯(Fullerenes)(即微小的空心碳团)的研究工作日益增加。这些富勒烯(Fullerenes)的粒径通常为1纳米左右。最近,又发现可以用金属离子填充这些空心碳团。这可以用下述方法完成:即在石墨棒上钻孔,再以金属氧化物粉末和石墨胶泥的混合物填充,然后借助碳弧产生灰分。Rodney S.Ruoff、Donald C.Lorents、BryanChan、Ripudaman Malhotra和Shekhar Subramoney讨论了用这种方法生产直径在20至40纳米范围内的有碳层覆盖的碳化镧纳米晶(见Science,Vo1.259,p.346(1993))。Masato Tomita,YahachiSaito和Takayoshi Hayashi在J.Appl.PhysVo1.32,p.280(1993)上报告了类似的结果。
上述的制备碳化镧纳米晶的碳弧法除了生成碳化镧纳米晶之外还生成富勒烯(Fullerenes)和石墨灰分。为了使这种方法有用,分离纳米晶的方法是极为重要的。迄今为止,尚未发现一种化学方法能成功地将宏观量的纳米颗粒从石墨灰分和富勒烯中分离出来。在纳米颗粒得率大约只占灰分的百分之十或更低时提供这种分离方法是极为重要的。因此,需要将金属、合金或金属碳化物的纳米颗粒从石墨灰分中分离出来的方法。
采用改良的Kratschmer-Huffman碳弧法,可以制备直径在约0.5至50nm范围内的有碳层覆盖的纳米颗粒。如果将磁性稀土金属、合金、金属氧化物或合金的氧化物填充到石墨棒中,然后经受碳弧放电,于是将形成包含金属、合金或金属碳化物的纳米颗粒和非磁性物质的灰份。然后,这种金属、合金或金属碳化物的纳米颗粒可以通过磁场梯度处理从灰份中分离出来。
在这个磁分离步骤中,包含纳米颗粒的灰份被碾磨成细粉末,然后向下落入一个电接地的金属管,穿过由一对强磁体建立的磁场梯度。非磁性物质通过该金属管,而磁性成分在磁场力超过重力时则悬浮着。当该设备移离磁体时,磁性材料就被释放到其收集容器中。这种方法可以将顺磁或铁磁成分与用碳弧放电法生产的灰份中的非磁性成分分开。
单畴磁性颗粒理论预言,截止温度(blocking temperature),即在该温度以上亚稳磁滞行为即将消失的温度,该温度(K)取决于颗粒体积与该物质的磁晶各向异性常数的乘积。锰铝碳化物(Mn3AlC)、τ-相锰铝(MnAl)以及几种钐钴相的钐钴(SmCox)等合金在颗粒形态都是铁磁性的并具有很大的各相异性常数。不同合金纳米颗粒的磁化强度是外加磁场和温度的函数,这表明这些合金的单畴磁性颗粒呈现室温磁滞现象。
图1是依据本发明形成的有碳层覆盖的碳化钆纳米晶的透射电子显微镜照片。
图2是依据本发明形成的碳化钆纳米晶的电子衍射图。
图3是按照本发明分离的10mg纳米晶碳化钆样品的M(H,T)的SQUID磁通计测量结果。
图4是按照本发明形成的30mg纳米晶锰铝碳化物样品的M(H,T)的SQUID磁通计测量结果。
图5是图1所用样品的实测矫顽磁力作为T1/2的函数的曲线图。
图6是按照本发明形成的钐钴粉末样品的M(H,T)的SQUID磁通计测量结果。
图7是图3所用样品的实测矫顽磁力作为T1/2的函数的曲线图。
一种基于Kratschmer-Huffnan碳弧法制备富勒烯的方法可用于生产有碳层覆盖的金属、合金或金属碳化物的纳米颗粒。在与磁场梯度分离技术相结合时,可以将大量的这种纳米颗粒分离出来。
如果石墨棒在用磁性稀土金属、合金、金属氧化物或合金氧化物填充后经受碳弧放电,那么,借助Kratschmer-Huffman碳弧法生产的灰份包含金属、合金或金属碳化物的纳米颗粒和非磁性物质。将石墨阴极挖空后用金属、合金、金属氧化物或合金氧化物与石墨胶泥的混合物填充。在碳弧下,形成含金属的微团。该微团的化学计量取决于金属原子、碳和氧之间的化学关系。这些微团在表面(高温阳极或反应器的室温壁)上沉积之前将发生扩散。所产生的纳米晶相取决于由其扩散路径和缓冲氦气的数量决定的微团的表面温度和冷却速率。因此,这种方法在制备亚稳相时是有用的。当颗粒冷却时形成碳层。因为石墨的熔点比金属和金属碳化物的熔点为高,所以在冷却纳米颗粒时发生相分离,形成石墨壳。在某些情况下该碳层阻止对空气和水敏感的化合物降解,但对于重要的磁性材料(Nd2Fe14B)则遇到了问题。
磁场梯度可以将金属、合金或金属碳化物的纳米颗粒与灰分中包括的非磁性物质分开。优选的是在施加磁场梯度之前将由碳弧放电法生产的灰分进一步碾磨成细粉末。如果磁场梯度力大于重力,磁性纳米颗粒将借助磁体悬浮在分离管中,而非磁性物质则通过该分离管。这种磁场梯度分离技术能够将碳弧放电法的非磁性副产品去除并提高离析出来的物质的磁谐振。这种分离方法可将所有的顺磁和铁磁成分与剩余的灰分分开。
图1是按照本发明形成的碳化钆纳米晶的透射电子显微镜照片,其中纳米晶被几层弯曲的石墨层包裹着。为了形成图l所示的碳化钆纳米晶,在直径为1/4英寸的石墨棒上钻孔并且用金属氧化物粉末(在这种情况下是Gd2O3)与石墨粉和石墨胶泥组合物的混合物填充。所用的Gd2O3与石墨粉的体积比为1∶1,并且用最少量的石墨胶泥将两者粘接起来。这些石墨棒在300℃温度下烘烤过夜以驱除水蒸汽。然后,这些石墨棒在交流碳弧的上电极位置上使用。电弧条件是100A、25V,氦气压力为125托。用填充石墨棒作正电极在相同条件下直流碳弧也得到这种纳米晶。
上述碳弧放电法生产的是一种包括石墨颗粒、有碳层覆盖的碳化钆纳米颗粒和Fullerenes混合物的灰分。这种原始的灰分首先用研钵和研杵将它研磨成微米级的细粉再进行磁性分离。然后,让这种经过研磨的灰分通过磁场梯度,以便使磁性物质与非磁性物质分开。在此例中,分离器由一个漏斗、一个两侧各带一块1英寸×1英寸×1/2英寸的钕铁硼磁体的电接地铝管和一对收集烧瓶组成。金属管接地可以防止粉末携带静电荷。在该分离管中,顺磁性颗粒除了受到重力作用之外还经受与磁场梯度、场强
H和磁化率x成比例的磁力,该磁力由下式给出: 在分离管中,磁距为
M的铁磁性颗粒受到磁力由下式给出: 为了获得最大的磁力
该铝管在磁体之间适当地定位。当少量粉末倒入该设备时,磁性物质借助磁体悬浮着,而非磁性部分则通过。然后,更换收集瓶,并将该管移离磁体以便释放磁性粉末。对于钆的情况,在这第一次通过之后,发现大约占原体积1/8的物质是磁性物质。对于钴,在第一次通过后,发现所产生的灰分的95%是磁性物质。让这种粉末反复通过,以便提高磁性物质的丰度。最后获得的磁性“滤液”包括镶嵌在碳质中的磁性纳米晶的混合物以及少量的。这些富勒烯将借助在二硫化碳中萃取而被除去。在纯炭黑与含钆混合物之间没有观察到肉眼可见的差别。因此,不采用磁分离技术,分离含钆化合物如果不是不可能就是非常困难。
磁性粉末的结构特性是借助电子显微术进行研究的。能量分散光谱指明钆均匀地分布在磁性灰分中。用JEOL4000型400KeV的高分辩透射电子显微镜对微团做更进一步的观察。样品的制备方法是在超声波辅助下将粉末分散在甲醇中,然后将一滴溶液滴到被无定形碳覆盖的铜栅极上并干燥之。图1所示的包埋在弯曲石墨壳中的碳化钆纳米晶与被无定形碳包埋的更细小的晶体一起被观察到。在某些直径约为50nm的较大的纳米晶中,看到有多达30个石墨层,而且有些颗粒是多面的。
用Rigaku衍射仪对纳米晶进行X-射线衍射分析揭示出若干陡峰表明存在单一的Gd2C3相,以及石墨峰和表明富勒烯的小角度特征的宽峰。与表列的晶体结构比较的结果表明最丰富的相是顺磁体心立方Gd2C3。这一结构确认是根据X-射线衍射峰和按图2所示{110}方向取向的晶体电子衍射。没有观察到有α-Gd2C、Gd2C或Gd2O3诸相以及Gd晶体存在的证据。这不同于掺镧的情况,对于那种情况观察到有α-LaC2纳米晶存在。
该粉末在9.104GHz进行的室温电子顺磁共振谱显示一个中心在3130G的单一的宽衍生,相应的G值为2.08。这一结果与对Gd+3离子的J=S=7/2基态预测的G值一致。
采用Quantum Design SQUID磁力计获取粉末样品的磁化数据。在螺线管磁场介于±5T之间、温度范围从4K至300K的条件下确定M(H.T)。图3表示以H/T的函数标度的不同温度的磁化数据。数据落在顺磁共振曲线上。在几个温度下的数据的吻合允许确定J=7/2基态与EPR结果一致。在相似的钴纳米晶中观察到铁磁行为。
这种包埋方法与磁分离技术相结合已经用于制备包含铁、钴、镍和锰铋的过渡金属铁磁配合物以及包含钆和钬的稀土金属顺磁配合物。所产生的相似乎是针对所用金属特定的。但是,这种生产和分离方法可应用于所有的磁性物质。
在改进本方法时,业已发现提高分离器的分离磁场将能区分各种不同的磁性纳米颗粒。通过改变磁场可以将单位体积磁矩不同的磁性纳米颗粒分开。这种方法可以用于进一步分离磁性纳米颗粒,以获得具有所需性质的成分。
业已发现,如果在碳弧放电过程中提高氦气压力,则形成纳米管形状的有碳层覆盖的磁性颗粒而不是纳米晶。在复合材料中应用这种纳米管可以提供某些优势。在本发明的另一个改进方案中,业已发现用适宜的两种氧化物粉末的混合物填充石墨棒可以形成无定形的磁性纳米颗粒。
如果颗粒是由铁磁材料形成的,其尺寸则会小到只能支持单一磁畴。这些颗粒被认为是超顺磁的,而且所有原子的自旋一致,从而得到大颗粒的磁矩。旋转这种颗粒的磁矩不是通过磁畴壁的运动而是借助所有原子的自旋一起旋转来完成的。超顺磁学的理论表明:对于具有单一磁畴的球形颗粒,其矫顽磁力Hc的温度依赖性由下式给出:
Hc=Hci[1-(T/TB)1/2] (1)
其中Hci是在0°K的矫顽磁力,TB是截止温度。当温度高于截止温度时,颗粒的磁矩可能悄悄地改变,这是由于在测量整体磁化所花费的以小时计的时段内发生温度波动所致。在这个温度之上,这些颗粒是超顺磁的并且在测量时段内没有观察到磁滞现象。在截止温度以下,颗粒没有足够的热能,不能在这个时段内自发地改变其磁矩,并且用式1给出的温度依从关系可以预计该非零矫顽磁力。单畴球形磁性颗粒的能量E如下式所示: 其中V是颗粒的体积,K是磁晶各相异性,H是外加磁场,M是颗粒的磁矩,θ是颗粒磁矩与其最近的易磁化轴方向之间的角度,φ是外加磁场与颗粒磁矩之间的角度。在没有外加磁场时,颗粒的磁矩将顺着易磁化轴从而使能量最小;然而,在外加的强磁场中,磁矩方向将与H方向一致。为了将磁矩旋转到与磁场方向一致,颗粒必须克服能量壁垒,该壁垒在KV的数量级上。当温度高于截止温度时,颗粒的磁矩可以由于温度变化自发地改变方向。截止温度可能与测量磁化的反比时限ω、越过壁垒的尝试速率ω0(它与磁矩的旋进频率在同一数量级上)和壁垒高度KV有关,依照下面的关系:ω=ω0exp[-KV/kTB] (3)
不超过临界温度细颗粒磁体就象大块儿磁体可以有磁滞。但是,造成磁滞现象的物理原因却截然不同。就单畴颗粒而言,热能与各向异性能之间的比较是重要的,而就大块儿铁磁体而言,在热能与交换能之间的比较决定磁行为。
结合下述实施例可以更容易理解本发明,在这些实施例中研究磁晶各相异性显著的合金。实施例1
在先期制备单质纳米晶体和碳化物纳米晶体时,为了控制所制备的特定相,调整反应器的条件。为了在碳弧中获得微观的化学均匀性,首先制备Mn-Al-O尖晶石相的原料。将Mn2O3和Al2O3按化学计量的量混合,在尖晶石相的温度下烧结,然后冷却硬化,以便保留尖晶石相,借助X-射线衍射和TEM分析描述该相的特征。易变组合物的尖晶石相利用Vegard定律进行鉴定,该定律描述的是在两种最终组合物之间晶格常数与Mn∶Al比率的关系。将2∶1配量的Mn-Al-O填充于石墨棒内以在碳弧下产生Mn-Al-C纳米颗粒。
根据Mn-Al-C的相图,只有1-2%的碳溶解到合金中,我们预计模拟MnAl的τ-相的亚稳定相也是铁磁性的。Mn-Al-C中唯一的其它铁磁相是Mn3AlC,其居里温度是15℃。由于τ-相是室温下Mn-Al-C的唯一已知的铁磁相,所以来自反应器不同部位的原始灰分都用Nd2Fe14B磁体进行试验,以便迅速优化这种铁磁相的生产。业已发现最佳碳弧条件是100A和40V,且间距为1mm。这种条件曾经导致在阳极上形成的薄饼状沉积物区域中含有丰富的铁磁性物质。根据在碳弧中制作的纳米晶体的成长模型,在合金微团沉积前它的表面温度和冷却速率决定生成的纳纳米晶体的晶相。据信,在薄饼状沉积区中的阳极温度比在中心沉淀物中略微低一些,但主要的因素还是微团冷却速率的差异。让ε相的熔体以105-108℃/sec。的冷却速率冷却,然后再退火,借此已经生产了大量的τ-MnAl。
借助几种方法确定存在于样品中的各相。借助X-射线衍射(XRD)获得的结构特征表明存在Mn3AlC、γ-Mn和石墨,但没有显示与τ-相对应的峰。X-射线仪的标定结果表明在不能检测τ-相的情况下,其最大丰度大约在4wt%的数量级上。用能量分散光谱仪(EDS)来确定Mn∶Al的相对丰度。在这种情况下,电子束大到足以在若干纳米晶体中同时激发转变。比率大面积地分布在3∶1至4∶1之间这一事实与借助XRD观察到的主导物种是一致的。根据室温下对磁体的响应,在我们的样品中至少有一些τ-MnAl-C存在。然而,为了获取有大量的Mn3AlC存在的证据,将一个样品放入温度低于该相的居里温度的冷冻柜中。我们发现充分冷却增大磁共振。
高分辩率的TEM显示出颗粒的形状、大小和粒度分布。我们发现所有的颗粒都有碳层覆盖而且被包裹的纳米颗粒都是晶体。一个不寻常的特征是存在细长颗粒以及球形颗粒,而且对应不同形状的相不确定。就细长颗粒而言,典型的长径比大约为3∶1。如果这些颗粒是铁磁性的,那么形状各向异性和磁晶各向异性将对磁行为产生影响。粒度(平均粒径大约为20nm)和粒度分布类似于在用碳弧法制作的金属材料及金属碳化物材料中所见到那样。
磁化作用作为外加磁场和温度的函数是借助SQUID磁强仪确定的。在进行SQUID测量时,将来自Mn-Al-C样品的大约30mg片晶固定,以使纳米颗粒在外加磁场中不移动。磁化曲线是在5°K至200°K之间和0至±5T之间进行测定的。在此范围内的每个温度下都观察到磁滞现象。图4中的磁滞回线的形状表明可能有两种具有不同矫顽力的铁磁成分,很可能是Mn3AlC和τ-MnAl。在图5中,将实测的矫顽力作为T1/2的函数作图,清楚地表明偏离了式1预测的特性。据信这种差别是由于存在多种成分的缘故。在这种情况下,饱和磁化强度Msat将等于两部分之和,并且就相对丰度规范化。实测的矫顽力将介于两种成分的矫顽力之间,确切的数值将取决于磁滞回线的形状。依据截止温度不可能解释任何与图5所示数据吻合的斜率。但是,数据的外推结果意味着室温下将出现磁滞现象,这是单畴磁性颗粒的一种新现象。实施例2
钐钴具有多重稳定的铁磁相。在用碳弧制备钐钴合金的纳米晶体时,采用的是金属性的Sm2Co7粉末,而不是氧化物材料。采用Nd2Fe14B磁体,在自反应器内各部位的物质中都观察到强烈的磁共振。数据取自薄饼形阳极沉积区,研究Mn-Al-C的同一区域。
XRD揭示的结构特征表明有SmCo5相、Sm5Co2相、fcc Co相和石墨相存在,但不存在Sm2Co7相,Sm2Co17相或碳化钐相。EDS表明样品中钐钴比(Sm∶Co)大约为1∶2。这个比值与原料的那个比值之间的差异可能归因于Sm的蒸气压比较高。TEM表明大多数颗粒大体上是球形的,平均粒径大约为20nm。
一般而言,居里温度随着钴的比例增大而升高。虽然钴的居里温度在测定范围之上,但是,我们预计即使由于添加碳造成小幅度温升Sm2Co7(420℃)和SmCo5(710℃)仍将是可观测的。然而,TMA的结果表明在25℃至875℃之间没有转变。此外,业已表明在Sm2Co17钴磁体中添加碳将居里温度升高260℃之上,在SmCo5中也发生类似的效应。
对固定在环氧树脂中的粉末样品进行SQUID磁化测量。图6给出的磁滞回线展示一种比Mn-Al-C更有特色的形状,并且在室温以上有非零矫顽力得到证明。如图7所示,使矫顽力的温度依从关系与式1吻合,从而得出截止温度大约为3800°K,远远超过任何钐钴合金的居里温度。
用于理解截止温度以上的磁滞损失的理论模型在Tc以上就不适用了,在这种场合温度波动破坏了在相临原子上自旋之间的交换耦合,颗粒就不再有大磁矩。在Tc以上,无论算出的截止温度如何,磁滞现象都不复存在。
在室温或高于室温时单畴铁磁体的非零矫顽力现象是真实的,并对颗粒记忆介质有潜在意义。小的铁磁性颗粒通常在记录磁带中使用,但是这种颗粒一般比本文所讨论的颗粒大得多。为了获得抗温度波动和外加磁场微小变化的稳定性,以往曾经采用较大的粒度。稳定的合金磁体的纳米晶(如用碳弧制备的SmCox[C]颗粒)满足稳定性要求并且粒度较小,所以可能用于更高密度的数据存储媒体。
在上述说明书中已经给出本发明的某些优选实施方案和实践,但是应该理解本发明还可在权利要求的范围内有其它的实施办法。
Claims (9)
1.一种带有主要由元素碳组成的碳涂布层的金属、金属合金或金属碳化物的纳米颗粒(nanoparticle),该纳米颗粒是顺磁材料或铁磁材料,这些材料带有在原子自旋之间相互作用的铁磁体或铁淦氧磁物,所述的铁磁材料选自铁,钴,镍和锰铋,所述的顺磁材料选自除镧、镥和钷之外的稀土金属,所述纳米颗粒的直径在约5至60nm范围。
2.根据权利要求1所述的纳米颗粒,是直径在约5至60nm范围内的晶体,直径在约5至60nm范围内的无定形颗粒,或长度小于1cm且直径在约5至60nm范围内的纳米管(nanotube)。
3.一种制备磁金属或磁性金属碳化物纳米颗粒的方法,包括以下步骤:
a)制备石墨棒,并在其内填充顺磁或铁磁金属氧化物中的一种,其中所述的铁磁化合物选自铁,钴,镍和锰铋,所述的顺磁材料选自除镧、镥和钷之外的稀土金属;
b)对该填充过的石墨棒施以碳弧放电,产生含有顺磁或铁磁性金属,或顺磁或铁磁性金属碳化物的纳米颗粒以及非磁性物质的灰分;以及
c)对所述灰分施以磁场梯度,将所述顺磁或铁磁性金属,或顺磁或铁磁性金属碳化物的纳米颗粒与所述的非磁性物质分离开。
4.根据权利要求3所述方法,其中还包括依据单位体积磁矩来改变施于灰分的磁场梯度,将所述磁性金属或金属碳化物的纳米颗粒分开。
5.根据权利要求3所述的方法,其中所述的纳米颗粒在室温下表现出磁滞现象。
6.根据权利要求5所述的方法,其中所述的金属合金是钐钴。
7.根据权利要求6所述的方法,其中所述的钐钴是形式为SmCo5,Sm2Co7和Sm2Co17中的至少一种。
8.根据权利要求5所述的方法,其中所述的金属合金是锰一铝化合物。
9.根据权利要求8所述的方法,其中所述的锰-铝化合物是锰-铝-碳化物。
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/085,298 US5456986A (en) | 1993-06-30 | 1993-06-30 | Magnetic metal or metal carbide nanoparticles and a process for forming same |
US08/085,298 | 1993-06-30 | ||
US08/265,008 US5549973A (en) | 1993-06-30 | 1994-06-24 | Metal, alloy, or metal carbide nanoparticles and a process for forming same |
US08/265,008 | 1994-06-24 |
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CN1129044A CN1129044A (zh) | 1996-08-14 |
CN1064777C true CN1064777C (zh) | 2001-04-18 |
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EP (1) | EP0706709A1 (zh) |
CN (1) | CN1064777C (zh) |
WO (1) | WO1995001643A1 (zh) |
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DE19815698A1 (de) * | 1998-04-08 | 1999-10-14 | Karlsruhe Forschzent | Beschichtete Partikel, Verfahren zu deren Herstellung und deren Verwendung |
EP2000803A1 (en) * | 1998-11-30 | 2008-12-10 | Nanosphere, Inc. | Nanoparticles with Polymer Shells |
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US6479028B1 (en) | 2000-04-03 | 2002-11-12 | The Regents Of The University Of California | Rapid synthesis of carbon nanotubes and carbon encapsulated metal nanoparticles by a displacement reaction |
US6697548B2 (en) | 2000-12-18 | 2004-02-24 | Evident Technologies | Fabry-perot opitcal switch having a saturable absorber |
US6740224B1 (en) | 2001-06-11 | 2004-05-25 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Method of manufacturing carbon nanotubes |
JP2005511761A (ja) | 2001-07-10 | 2005-04-28 | ノース・キャロライナ・ステイト・ユニヴァーシティ | ナノ粒子送達ビヒクル |
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US7008605B1 (en) * | 2001-11-08 | 2006-03-07 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Method for manufacturing high quality carbon nanotubes |
US6689192B1 (en) | 2001-12-13 | 2004-02-10 | The Regents Of The University Of California | Method for producing metallic nanoparticles |
TWI251580B (en) * | 2002-08-02 | 2006-03-21 | Ind Tech Res Inst | Preparation of magnetic metal filled carbon nanocapsules |
US6974493B2 (en) * | 2002-11-26 | 2005-12-13 | Honda Motor Co., Ltd. | Method for synthesis of metal nanoparticles |
US6974492B2 (en) * | 2002-11-26 | 2005-12-13 | Honda Motor Co., Ltd. | Method for synthesis of metal nanoparticles |
US7214361B2 (en) * | 2002-11-26 | 2007-05-08 | Honda Giken Kogyo Kabushiki Kaisha | Method for synthesis of carbon nanotubes |
US7004993B2 (en) * | 2003-06-13 | 2006-02-28 | Philip Morris Usa Inc. | Nanoscale particles of iron aluminide and iron aluminum carbide by the reduction of iron salts |
US6927136B2 (en) * | 2003-08-25 | 2005-08-09 | Macronix International Co., Ltd. | Non-volatile memory cell having metal nano-particles for trapping charges and fabrication thereof |
WO2005060610A2 (en) * | 2003-12-11 | 2005-07-07 | The Trustees Of Columbia University In The City Ofnew York | Nano-sized particles, processes of making, compositions and uses thereof |
US7405002B2 (en) * | 2004-08-04 | 2008-07-29 | Agency For Science, Technology And Research | Coated water-soluble nanoparticles comprising semiconductor core and silica coating |
US7534489B2 (en) * | 2004-09-24 | 2009-05-19 | Agency For Science, Technology And Research | Coated composites of magnetic material and quantum dots |
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CN100434210C (zh) * | 2005-01-17 | 2008-11-19 | 武汉科技大学 | 一种碳包覆金属纳米粒子及其制备方法 |
CN101330969B (zh) | 2005-10-14 | 2011-06-29 | 维乌纳米股份有限公司 | 复合纳米颗粒、纳米颗粒和制备它们的方法 |
WO2008016390A2 (en) * | 2006-01-30 | 2008-02-07 | Honda Motor Co., Ltd. | Catalyst for the growth of carbon single-walled nanotubes |
US20090297626A1 (en) * | 2006-11-03 | 2009-12-03 | The Trustees Of Columbia University In The City Of New York | Methods for preparing metal oxides |
WO2008136853A2 (en) * | 2006-11-07 | 2008-11-13 | William Marsh Rice University | Methods for separating magnetic nanoparticles |
US20090317719A1 (en) * | 2008-06-20 | 2009-12-24 | Toyota Motor Engineering & Manufacturing North America, Inc. | Material With Core-Shell Structure |
US8623470B2 (en) * | 2008-06-20 | 2014-01-07 | Toyota Motor Engineering & Manufacturing North America, Inc. | Process to make core-shell structured nanoparticles |
CN101552058B (zh) * | 2008-12-11 | 2012-07-04 | 复旦大学 | 一种磁饱和强度可控的超顺磁性复合微球及其制备方法 |
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CN101740192B (zh) * | 2009-12-24 | 2012-07-18 | 上海交通大学 | 热塑性磁流变弹性体复合材料及其制备方法 |
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- 1994-06-29 EP EP94921485A patent/EP0706709A1/en not_active Withdrawn
- 1994-06-29 CN CN94192652A patent/CN1064777C/zh not_active Expired - Fee Related
- 1994-06-29 WO PCT/US1994/007601 patent/WO1995001643A1/en not_active Application Discontinuation
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1996
- 1996-06-05 US US08/658,788 patent/US5783263A/en not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
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WO1995001643A1 (en) | 1995-01-12 |
CN1129044A (zh) | 1996-08-14 |
EP0706709A1 (en) | 1996-04-17 |
US5783263A (en) | 1998-07-21 |
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