CN103339063A - 在交变磁场和电磁场中的加热速率改善的铁硅氧化物颗粒 - Google Patents
在交变磁场和电磁场中的加热速率改善的铁硅氧化物颗粒 Download PDFInfo
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Abstract
本发明提供一种铁硅氧化物颗粒,其包含核心和外壳,其中所述核心包含铁氧化物的变体磁赤铁矿、磁铁矿和赤铁矿,并且所述外壳主要由或只由无定形二氧化硅组成,并且a)B0.20nm/B0.25nm≤0.2,其中B0.20nm=包含磁赤铁矿和磁铁矿时,以0.20+/-0.02nm的晶格平面间隔,通过电子衍射测定的德拜-谢勒衍射环的亮度,及B0.25nm=包含磁赤铁矿、磁铁矿和赤铁矿时,以0.25+/-0.02nm的晶格平面间隔,通过电子衍射测定的德拜-谢勒衍射环的亮度,以及b)通过X射线衍射测定的赤铁矿的微晶直径大于120nm。所述铁硅氧化物颗粒通过以下方法制备:在第1区中,将包含以下组分的混合物点燃并使其反应:硅化合物,其含量占硅化合物总量的0-30%,铁化合物,燃料气,和一或多种含氧气体,以及在第2区中,将硅化合物加入所述反应混合物中,硅化合物的加入量占硅化合物的总量的70-100%,以及在第3区中,从混合物中将固体与气体或蒸气形式的材料分离。本发明还提供包含铁硅氧化物颗粒的硅橡胶。
Description
技术领域
本发明涉及在磁场中具有改良加热速率的铁硅氧化物颗粒、其制备及其用途。
背景技术
WO2010/063557公开了可用于交变磁场或电磁场中的感应加热材料的铁硅氧化物颗粒。颗粒具有核心-壳结构,其含有铁氧化物相赤铁矿、磁铁矿和磁赤铁矿作为核心、二氧化硅的无定形壳和存在于壳与核心之间的元素硅、铁和氧的一种或多种化合物。该文献还公开了所述核心可包含1-10重量%的具有20-120nm微晶尺寸的赤铁矿、20-50重量%的具有20-60nm微晶尺寸的磁铁矿和40-75重量%的具有15-50nm微晶尺寸的磁赤铁矿。所述颗粒是通过使硅化合物(其中之一为甲硅烷)和铁化合物的混合物在氢/氧火焰中反应而制得。
已发现在交变磁场或电磁场中进行感应加热时,同时存在三种铁氧化物的变体对于实现可接受的加热速率是必要的。不过,似乎希望进一步改善可达到的加热速率。然而,WO2010/063557中公开的方法不允许制备可完成此任务的铁硅氧化物颗粒。
发明内容
因此,本发明的技术目的是提供进一步改善可达到的加热速率的铁硅氧化物颗粒。另一目的是提供制备这些颗粒的方法。
本发明提供一种铁硅氧化物颗粒,其包含核心和外壳,其中所述核心包含铁氧化物的变体磁赤铁矿、磁铁矿和赤铁矿,并且所述外壳主要由或只由无定形二氧化硅组成,其特征在于
a)B0.20nm/B0.25nm≤0.2,优选0.05-0.20,更优选0.10-0.18,更优选0.12-0.16,其中
B0.20nm=包含磁赤铁矿和磁铁矿时,以0.20+/-0.02nm的晶格平面间隔,通过电子衍射测定的德拜-谢勒衍射环的亮度,以及
B0.25nm=包含磁赤铁矿、磁铁矿和赤铁矿时,以0.25+/-0.02nm的晶格平面间隔,通过电子衍射测定的德拜-谢勒衍射环的亮度,以及
b)通过X射线衍射测定的赤铁矿的微晶直径大于120nm。
附图说明
图1显示本发明颗粒的高结晶性。
图2示意显示本发明方法的具体实施方式。
本发明颗粒的外壳为无定形。为了本发明的目的,术语无定形(amorphous)是指其中没有可通过传统的X射线衍射方法测量的衍射信号的材料。外壳为一种不可渗透的壳。为了本发明的目的,不可渗透表示在特定反应条件下颗粒与盐酸接触时,可检测到小于50ppm的铁。在此,使0.33克的颗粒与20毫升1N盐酸溶液在室温下接触15分钟。然后以适当分析技术例如ICP(电感耦合等离子体光谱法)分析一部分溶液中的铁。外壳的厚度优选为1-40nm,更优选5-20nm。
从德拜-谢勒衍射环(Debye-Scherrer diffraction rings)的亮度获得B0.20nm和B0.25nm值。使用来自SIS的iTEM软件进行测定。为此目的,放置一个矩形的评价区域。选择矩形的高度以便其中存在所要测量的环的最内层和最外层。选择矩形的宽度和位置以便评估衍射环的大致水平线的分量。矩形各条线的相关灰值(grey value)的算术平均值通过软件测定。灰值曲线的相对最大值包含在各自位置的环和背景的亮度。因为背景的亮度随半径增加而减小,所以这必须在环的位置测定。这是通过在衍射环之上和之下的背景灰值的线性内插法实现的。峰的灰值和相关背景值之间的差异为在各个位置的衍射环的实际亮度值。图1显示根据本发明的颗粒的典型电子衍射环。晶格平面间隔0.20nm和0.29nm对应于磁赤铁矿和磁铁矿,而晶格平面间隔0.25nm对应于磁赤铁矿、磁铁矿和赤铁矿。由于在电子衍射图的中心的干扰亮度,B0.20nm/B0.25nm比最适合于定量测定。此外,本领域技术人员从图1可看见本发明颗粒的高结晶性。
B0.20nm/B0.25nm比的测定使得可以相对简单地测定包含赤铁矿、磁铁矿和磁赤铁矿的混合物的相对组成,而不用知道此混合物的精确组成,因为根据本发明的技术目的,混合物的相对组成确保铁硅氧化物颗粒的高加热速率。
如果所述绝对组成是待测定的,则此测定可以使用X射线衍射通过在10-100°的2Θ角度范围内的Co-Kα辐射进行。在此,磁赤铁矿可以通过前角范围的反射(110)和(211)清楚检测。因为反射是独立的,所以赤铁矿可明确地检测。定量相分析是通过Rietveld法进行,具有约10%的相对误差。本发明铁硅氧化物颗粒的核心优选具有20-60重量%,更优选20-40重量%的赤铁矿的比例,25-<50重量%,更优选30-45重量%的磁铁矿的比例,及>30-60重量%,更优选35-50重量%的磁赤铁矿的比例,其中这些比例共计100%。也可存在少量无定形铁氧化物。
此外,已发现对加热速率有利的是:赤铁矿的微晶直径优选为125-300nm和更优选150-250nm。
在本发明颗粒的另外优选的具体实施方式中,赤铁矿和磁铁矿的微晶直径彼此独立地大于120nm,并且磁赤铁矿的微晶直径不大于70nm。这些值在此是通过德拜-谢勒法获得的。在本发明的更优选的具体实施方式中,以此方式测定的赤铁矿的微晶直径为125-300nm,更优选150-250nm,磁铁矿的微晶直径为150-350nm,极更优选200-300nm,及磁赤铁矿的微晶直径为20-50nm,更优选35-45nm。
此外,已发现在核心与外壳之间部分或完全形成的另外的内壳对升温速率具有正面影响,所述内壳包含元素铁、硅和氧,在HR-TEM中具有0.31+/-0.02nm的晶格平面间隔,并且厚度通常小于2nm。
内壳表示无定形二氧化硅壳和结晶铁氧化物核心之间的过渡区,其导致核心和外壳之间的适应性极好。目前假设:利用此紧密结合,改善了从核心到外壳的声子(phonon)传输并因而改善了热传导,当使用本发明的颗粒时,其可导致实质上较高的加热速率。
优选地,本发明的铁硅氧化物颗粒的铁氧化物的含量换算成Fe2O3为60-95重量%,优选75-90重量%。二氧化硅的含量优选为5-40重量%,优选为10-25重量%。此外,本发明的铁硅氧化物颗粒另外可含有小比例的源自起始材料和/或相关方法的杂质。杂质的比例一般不大于1.5重量%,优选小于1.0重量%和更优选小于0.5重量%。
颗粒的BET表面积通常为5-50m2/g。优选10-30m2/g和更优选15-20m2/g。
本发明的铁硅氧化物颗粒一般以聚集体的形式存在。形成聚集体的初级颗粒可经由核心和/或外壳而生长在一起。就加热速率而言,有利的是聚集体的平均支化度(the average degree of branching)为至少7,优选为8-20和更优选10-15。此外,聚集体的平均分支长度(the average length of thebranches)为至少500nm,优选为700-2500nm和更优选1000-1500nm。支化度和分支长度的测定是通过以下方法进行的:使用来自Olympus SoftImaging Solutions GmbH的iTEM软件,根据ASTM-3849,通过数字图像分析,以50000:1的放大率评估约700个聚集体的透射电子显微照片。
此外,本发明的颗粒在其表面上具有羟基。这些羟基可与无机和有机表面改性剂反应从而形成范德华相互作用或离子键或共价键,从而对本发明的铁硅氧化物颗粒的表面改性。合适的表面改性剂例如烷氧基硅烷类、羧酸类、核酸类或多醣类。
本发明进一步提供一种制备本发明的铁硅氧化物颗粒的方法,其中
a)在直流式反应器的第一区(第1区)中,将包含以下组分的混合物点燃并使其反应:
a1)一或多种可水解和/或可氧化的硅化合物,所述硅化合物优选为气体,其含量占可水解和/或可氧化的硅化合物的总量的0-30%,
a2)一或多种可氧化和/或可水解的铁化合物,其优选以气体形式或以通过雾化一或多种溶液获得的气溶胶的形式存在,
a3)一或多种含氢的燃料气,和
a4)一或多种含氧气体,
b)在所述直流式反应器的第二区(第2区)中,将一或多种可水解和/或可氧化的硅化合物加入所述反应混合物中,所述硅化合物优选为气体,所述硅化合物的加入量占可水解和/或可氧化的硅化合物的总量的70-100%,
c)在所述直流式反应器的第3区中,然后任选地冷却所述反应混合物,优选通过加入水来实现冷却,然后将固体与气体或蒸气形式的材料分离,以及然后任选地用表面改性剂处理所述固体。
为了本发明目的,所述总量为第1区和第2区中使用的硅化合物的总和。
本发明的方法的特征在于在第1区中使用不超过总量的30%的硅化合物。已发现:将主要量或全部量的硅化合物加入第2区中首先带来不可渗透的二氧化硅外壳,其次,影响核心组分的比例和尺寸。以此方式显然可能创造其中磁铁矿和磁赤铁矿可确保能量的电磁注入并且赤铁矿可确保导热性的最佳条件。
当选择反应条件使得除了外壳之外还形成内壳时,可进一步改善导热性。
优选选择反应条件以便在第1区中的平均停留时间为10ms-1s,更优选300-600ms,以及第1区中的温度优选为900-1300℃,更优选950-1250℃,在每种情况下在点燃点以下50cm处测量。
此外,优选选择反应条件以便在第2区中的平均停留时间为0.1-10s,更优选1.5-3.0s,以及第2区中的温度优选为400-900℃,在每种情况下于第2区中最高引入点之上15cm处测得,更优选700-850℃。
在本发明的优选具体实施方式中,只在第2区中添加硅化合物。若在第1区和第2区中添加硅化合物,则这些硅化合物在第1区和第2区可相同或不同。硅化合物优选选自由SiCl4、CH3SiCl3、(CH3)2SiCl2、(CH3)3SiCl、HSiCl3、(CH3)2HSiCl和CH3C2H5SiCl2、H4Si、Si(OC2H5)4及Si(OCH3)4组成的组。更优选使用SiCl4和/或Si(OC2H5)4。
优选引入铁化合物作为气溶胶。一般使用雾化气体诸如空气或氮气和双流或多流喷嘴由水溶液形成气溶胶。平均小滴直径优选为小于100微米,更优选小于50微米。优选使用氯化铁(II)作为铁化合物。
在本发明的更优选的具体实施方式中,可在第2区中另外加入水或水蒸汽。在此,分开加入水或水蒸汽与硅化合物,优选在紧靠硅化合物的进料点之前或在硅化合物的进料点的高度加入水或水蒸汽。优选使用摩尔过量的水或水蒸汽。可更优选10-100的水/硅化合物的摩尔比。
作为燃料气,优选使用氢、甲烷、乙烷和/或丙烷。更优选氢。空气或富氧空气主要用作含氧气体。一般使用比氢过量的氧。λ,燃油量与氧量的比值,优选为1.05-1.50。
图2示意性显示本发明方法的具体实施方式。在此:
A=由铁化合物的溶液和空气或氮气组成的气溶胶
B=硅化合物和空气或氮气
C=燃料气
D=含氧气体
E=硅化合物和空气或氮气
F=水蒸汽
G=冷却和沉淀
1、2、3=第1区、第2区、第3区
本发明进一步提供一种包含本发明铁硅氧化物颗粒的硅橡胶。这些颗粒的比例优选为0.5-15重量%和更优选3-6重量%。
本发明进一步提供本发明的铁硅氧化物颗粒作为以下物质的组分:橡胶混合物、聚合物制品、粘合剂组合物、或通过熔融得到的模制聚合物复合材料,在交变电磁场中的用途,以及用于制备分散体。
实施例
分析方法
通过在NaOH中浸渍、溶解在稀H2SO4中和然后进行碘量法,来测定铁氧化物的含量。
根据DIN66131测定BET表面积。
如上所述测定B0.20nm和B0.25nm值。
通过X射线衍射定量测定核心成分。(反射,θ/θ-衍射计,Co-Kα,U=40kV,I=35mA;闪烁计数器,下游石墨单色器;角度范围(2Θ)/步长/测量时间:10-100°/0.04°/6s(4h))。
因为反射是独立的,可明确地识别赤铁矿。通过前角范围的反射(110)和(211)可以清楚检测磁赤铁矿。以Rietveld方法(相对误差:约10%)进行定量相分析。借助于来自ICDD数据库PDF4+(2010)的Set60进行定量相分析。使用Rietveld程序第3.0版(2005)进行定量相分析和微晶尺寸测定。
通过高分辨率透射电子显微镜(HR-TEM)测定包含的铁氧化物相和二氧化硅壳的细微结构。此外,通过HR-TEM中的电子衍射分析测定结晶性和相组成。在200kV的加速电压下,在Jeol2010F仪器上记录HR-TEM和电子衍射图。
通过透射电子显微镜(TEM)测定外壳的厚度。通过高分辨率透射电子显微镜(HR-TEM)测定内壳的晶格平面间隔。通过来自纳米点分析(nanospot analyses)的侧向EDX谱测定局部元素组成(侧向分辨率约3-4nm)。
通过对来自透射电子显微镜的约700个聚集体的图像分析,来测定支化度和分支长度。通过来自Olympus Soft Imaging Solutions GmbH的iTEM软件评估支化度和分支长度。为此目的,通过形态滤波器(morphologicalfilter)记录端点而测定骨架化(skeletization)。骨架化产生聚集体的支化度(每一聚集体的端点数目)。端点的测定使聚集体的长度测定成为可能。
在硅组合物中测定加热至100℃的温度的加热时间。通过利用SpeedMixer,将33克E50(来自Momentive PerformanceMaterials)、13克硅油级M1000(来自Momentive Performance Materials)、4克150(来自Evonik Degussa)及2.5克(相当于4.76重量%)来自实施例1的产物于3000rpm混合2×30秒和2×45秒,获得硅组合物。然后将硅组合物以约1mm的厚度涂覆于玻璃显微镜载玻片上。在40kHz频率和1.9kW的电功率的交变磁场中,通过感应引入能源。
实施例1(根据本发明):
第1区:使以下物质的混合物在第一区(第1区)中反应:0.10kg/h的气体SiCl4、在室温(23℃)下利用双流喷嘴雾化25重量%浓度的氯化铁(II)水溶液,对应于0.88kg/h,及3标准m3/h的氮作为雾化剂获得的气溶胶,8标准m3/h的氢和20.2标准m3/h的空气。反应混合物在第1区中的平均停留时间为约545ms。燃烧器口之下50cm的温度为1028℃。
第2区:将0.26kg/h的气体SiCl4与3标准m3/h的氮的混合物,及与该混合物分开的1kg/h的氢在SiCl4和氮的混合物进的料点高度进料至来自第1区的具有约830℃的温度的反应混合物流。反应混合物在第2区中的平均停留时间为1.9s。
第3区:然后将反应混合物冷却且将所得固体在过滤器上与气体材料分开。
固体具有82重量%的换算成Fe2O3的铁氧化物含量。其BET表面积为19m2/g。
德拜-谢勒评估得到B0.20nm=586和B0.25nm=4024,及因此B0.20nm/B0.25nm比为0.15。
利用X射线衍射的核心取代基的定量测定显示35重量%的赤铁矿、19重量%的磁铁矿和46重量%的磁赤铁矿。
核心组分的微晶尺寸的测定得到赤铁矿的微晶尺寸225nm、磁铁矿的微晶尺寸168nm和磁赤铁矿的微晶尺寸40nm。
此外,发现壳的厚度为约6nm。通过图像分析,平均支化度测定为13和平均分支长度测定为1400nm。加热时间为4.7s。
以类似于实施例1的方式进行根据本发明的实施例2-5。以类似于实施例1的方式进行比较例6和7,但在实施例6中,在第1区中引入硅化合物的总量,及在实施例7中,在第1区中引入硅化合物的总量的80%。表1显示所有实施例的起始材料和反应条件。表2显示从这些实施例获得的粉末的物理化学数据。
与来自比较例6和7的颗粒相比,来自实施例1-5的根据本发明的铁硅氧化物颗粒显示显著缩短的加热时间。
实施例1-5的颗粒在核心和外壳之间具有过渡区。HR-TEM显示在此过渡区中的晶格平面间隔为0.31nm,其与0.29nm的核心组分的晶格平面间隔显著不同。来自比较例6和7的颗粒不显示此过渡区。
表1:起始材料和反应条件
表2:粉末的物理化学数据
Claims (16)
1.铁硅氧化物颗粒,其包含核心和外壳,其中所述核心包含铁氧化物的变体磁赤铁矿、磁铁矿和赤铁矿,并且所述外壳主要由或只由无定形二氧化硅组成,其特征在于
a)B0.20nm/B0.25nm≤0.2,其中
B0.20nm=包含磁赤铁矿和磁铁矿时,以0.20+/-0.02nm的晶格平面间隔,通过电子衍射测定的德拜-谢勒衍射环的亮度,以及
B0.25nm=包含磁赤铁矿、磁铁矿和赤铁矿时,以0.25+/-0.02nm的晶格平面间隔,通过电子衍射测定的德拜-谢勒衍射环的亮度,以及
b)通过X射线衍射测定的赤铁矿的微晶直径大于120nm。
2.根据权利要求1的铁硅氧化物颗粒,其特征在于赤铁矿和磁铁矿的微晶直径彼此独立地大于120nm,并且磁赤铁矿的微晶直径不大于70nm。
3.根据权利要求1或2的铁硅氧化物颗粒,其特征在于在核心与外壳之间部分或完全形成有另外的内壳,所述内壳包含元素铁、硅和氧,在HR-TEM中具有0.31+/-0.02nm的晶格平面间隔,并且厚度小于2nm。
4.根据权利要求1-3中任一项的铁硅氧化物颗粒,其特征在于所述铁硅氧化物颗粒的铁氧化物含量换算成Fe2O3为60-95重量%。
5.根据权利要求1-4中任一项的铁硅氧化物颗粒,其特征在于所述铁硅氧化物颗粒的BET表面积为5-50m2/g。
6.根据权利要求1-5中任一项的铁硅氧化物颗粒,其特征在于聚集体的平均支化度为至少7。
7.根据权利要求6的铁硅氧化物颗粒,其特征在于聚集体的平均分支长度为至少500nm。
8.根据权利要求1-7中任一项的铁硅氧化物颗粒,其特征在于已通过吸附有机和无机试剂、在所述颗粒表面上与有机和无机试剂反应或与有机和无机试剂复合,来对所述颗粒改性。
9.制备根据权利要求1-8中任一项的具有核心-外壳结构的铁硅氧化物颗粒的方法,其特征在于
a)在直流式反应器的第1区中,将包含以下组分的混合物点燃并使其反应:
a1)一或多种可水解和/或可氧化的硅化合物,其含量占可水解和/或可氧化的硅化合物的总量的0-30%,
a2)一或多种可氧化和/或可水解的铁化合物,
a3)一或多种含氢的燃料气,和
a4)一或多种含氧气体,
b)在所述直流式反应器的第2区中,将一或多种可水解和/或可氧化的硅化合物加入所述反应混合物中,所述硅化合物的加入量占可水解和/或可氧化的硅化合物的总量的70-100%,
c)在所述直流式反应器的第3区中,然后任选地冷却所述反应混合物,然后将固体与气体或蒸气形式的材料分离,以及然后任选地用表面改性剂处理所述固体。
10.根据权利要求9的方法,其特征在于在第1区中的平均停留时间为10ms-1s,并且第1区中的温度为800-1300℃。
11.根据权利要求9或10的方法,其特征在于在第2区中的平均停留时间为0.1-10s,并且第2区中的温度为400-800℃。
12.根据权利要求9-11中任一项的方法,其特征在于只在第2区中添加所述硅化合物。
13.根据权利要求9-12中任一项的方法,其特征在于所述硅化合物选自由SiCl4、CH3SiCl3、(CH3)2SiCl2、(CH3)3SiCl、HSiCl3、(CH3)2HSiCl和CH3C2H5SiCl2、H4Si、Si(OC2H5)4及Si(OCH3)4组成的组。
14.根据权利要求9-13中任一项的方法,其特征在于在第2区中另外加入水或水蒸汽。
15.硅橡胶,其包含根据权利要求1-8中任一项的铁硅氧化物颗粒。
16.根据权利要求1-8中任一项的铁硅氧化物颗粒用作以下物质的组分:橡胶混合物、聚合物制品、粘合剂组合物、或通过熔融得到的模制聚合物复合材料,在交变电磁场中的用途,以及用于制备分散体。
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US20130303658A1 (en) | 2013-11-14 |
EP2484637A1 (de) | 2012-08-08 |
TWI461369B (zh) | 2014-11-21 |
PL2484637T3 (pl) | 2013-09-30 |
MX348105B (es) | 2017-05-29 |
MX2013008898A (es) | 2013-08-21 |
US8906983B2 (en) | 2014-12-09 |
TW201247547A (en) | 2012-12-01 |
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CN103339063B (zh) | 2015-05-20 |
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