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1.
硅酸盐熔体微结构单元的探讨 总被引：4，自引：0，他引：4
为了深入了解熔融硅酸盐的各种性质，综合前人的资料并结合自己的实验结果，对硅酸盐熔体中的微结构单元进行了探讨。熔体中包含5种不同的硅氧四面体(以Qn表示，n为四面体中的桥氧数目)，不同的硅氧键中的电荷分布以及Qn在Raman谱图中的特征位移区有区别，熔态谱和玻璃态谱之间也存在差别，同组成熔体和淬冷玻璃中，同一Qn具有不同的摩尔分数、自由能和无序度，并且熔体中Q4的振动是非Raman活性的。 相似文献
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《矿物学报》2017,(6)
综合多种测试方法,考察了研磨对茂名高岭石粒径、形貌与微结构等理化性质的影响。重点采用~(29)Si、~(27)Al MAS NMR光谱考察了研磨过程中结构脱羟、Si、Al配位环境变化、新活性位点形成等微结构演变等。结果表明:研磨初期,高岭石六方片层遭到破碎,颗粒粒径逐渐减小,比表面积在研磨1 h达到最大(43.8 m~2/g);此后,颗粒发生团聚,比表面积减小,样品脱羟量和表面吸附水含量均逐渐增加。核磁Si谱和Al谱分别在化学位移-100.5和14.8处出现新的信号,归属于四面体Si与八面体Al相连顶氧质子化作用而产生的Q~3 Si-OH~+-Al结构。研磨导致高岭石脱羟,Al配位状态从AlⅥ经由AlⅤ逐渐向AlⅣ转变。 相似文献
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采用提纯后的蒙脱石在不同浓度硫酸铬溶液中进行交换吸附制备了含铬蒙脱石,并利用包括粉末X射线衍射术
（XRD）、电子自旋共振谱术（ESR） 和傅里叶变换红外吸收光谱术（FTIR） 等分析测试手段对铬在蒙脱石中的吸附位置进
行了探索研究。研究结果显示铬离子不仅置换了层间域中的Ca2+,K+和Na+等,而且置换了位于八面体位的Mn2+ 和少量
Al3+,并较大量的进入硅氧四面体的六边形孔洞、甚至有可能置换极少量的四面体位的Al3+和Fe3+等。此外,根据X射线衍
射分析可知,在0.2 mol/L硫酸铬溶液中充分交换吸附后的蒙脱石存在两层水型和单层水型两种含铬蒙脱石,其水合阳离子
分别为[Cr(H2O)6]3+和[Cr(H2O)3O3]3+,当吸附量增大至一定程度后水合铬离子借助TOT结构片的硅氧四面体的底氧形成配位多
面体。 相似文献
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用广角度X射线散射 (WAXS)和由它得到的径向分布函数 (RDF)研究了偏岭石的结构。偏岭石是一种以非晶组份为主的部分有序的中间序性物质。构成偏岭石的结构单元是四面体 [MO4 ](M =Si,Al)和八面体 [AlO6](O =O,OH)。偏岭石结构中近邻四面体与四面体共顶连接构成M-O层,八面体与八面体共棱或共面连接构成Al-O层;而四面体与八面体通过不规则的共顶连接构成近程层状结构。它的近程结构将不随序性或结晶性变化。它的微结构及其随热处理温度的变化主要决定于结构基元之间的关系和序性。偏岭石是结构不同于变高岭石的一种粘土. 相似文献
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不同亚类硅酸盐矿物的中红外光谱学特征 总被引：1，自引：0，他引：1
利用热红外发射光谱研究了不同亚类硅酸盐矿物镁橄榄石、透闪石、蛇纹石和钠长石的红外发射光谱特征。在120oC时,通过对400～1650 cm-1的红外波段进行积分计算,发现硅酸盐矿物中镁橄榄石的发射率最高,可达到0.988,钠长石最低为0.947。硅酸盐矿物在850～1300cm-1区间均产生宽的低发射带,该发射带与硅氧四面体层中(Si,Al)-O的伸缩振动相关;在470 cm-1左右则形成相对尖锐的低发射带,与硅氧四面体层中(Si, Al)-O的弯曲振动相关。从岛状、链状、层状到架状硅酸盐矿物由于Si O2聚合程度依次增加,最强发射谷的位置依次向高频方向偏移,说明硅氧四面体中Si-O伸缩振动带的位置受到了n(Si)/n(O)比值的制约。此外,在辐射能量谱里,镁橄榄石、透闪石、蛇纹石和钠长石的最强辐射谷范围趋于变宽,依次为115、162、225和247 cm-1,反映了吸收的辐射能增加。综上可推测,硅酸盐矿物强的发射率可能与硅氧四面体中Si-O的振动模式、Si O2的聚合度、辐射能量谱中最强辐射谷的波长范围有关。 相似文献
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叶蜡石为一种含铝硅酸盐矿物。晶体结构属2:1型最简单的二八面体端员矿物,其结构单元由上下两层 Si—O 四面体层组成。每个四面体层顶端的氧都指向结构单元层的中央,并与八面体所共有。层间结合是靠弱的范德华键连结,因此层内结合很强,层间结合很弱,容易解离成薄片。该矿物不像其它粘土矿物具备离子交换性能。它层内离子极少置换,因其层单胞电荷数近于零,且层内无吸引的阳离子,以区别其它粘土矿物。溧阳叶蜡石岩具多组分,主要成分以叶蜡石为主,其物化性能如下所述:一、漂阳叶蜡石岩化学性质叶蜡石的化学式:Al_2O_3·4SiO_2·H_2O。化学组成:Al_2O_3:28.3%;SiO_2:66.7%;H_2O;5%。溧阳叶蜡石岩按矿石类型划分,其化学组成(表1)。 相似文献
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Zhitao Zhang 《中国地球化学学报》1984,3(3):295-308
This paper deals with compositional variations in fault zones from a dynamic point of view. In the fault zonen consisting of silicates, relative accumulation of Si and Fe is noticed in response to the leaching-out of K, Na, and to a lesser extent, Mg, Ca and Al. The ordee of petrogenetic elements from stable to mobile is tentatively suggested as follows: Si→Fe→Mg→ Ca→Al→K→Na. The difference in ionic radius for these chemical elements is thought to be the major factor controlling dynamic differentiation. In the fault zones arc silicates on one side and carbonates on the other, and new minerals are recognized in tectonites. On the silicate side Ca and Mg increase but Si and Al decrease; and the opposite is true on the carbonate side. This phenomenon indicates that migration of elements in the fault zones is accelerated by dyna mic effect. 相似文献
12.
Sequential non-destructive neutron activation analysis was used to determine the bulk abundance of Fe, Al, Na, Mn, Or, Sc, Co and Ir in approximately 300 individual chondrules from 16 chondrites representing the H (3–5), L4 and LL(3–6) compositional and petrologic classes. For some of the chondrules, Si, Ni, Ca and V were also determined. The histograms indicate that the most probable abundances for lithophilic elements, except Cr, are enriched in the chondrules, while the siderophilic elements are depleted in the chondrules compared to the whole chondrite. Some of the abundance populations, such as Al and Fe, appear to be multimodal. Systematic variations in the composition of the chondrules with increasing petrologic type were observed; most consistent are an increasing Na-Al and Cr-Al correlation, a decreasing Na-Mn correlation, increasing Na abundance and decreasing Na and Mn dispersions among chondrules. The systematic compositional variations with increasing petrologic type are consistent with an increasing approach to equilibrium between chondrules and matrix.Observed elemental correlations are generally consistent with mineralogical controls expected on the basis of geochemical affinities suggested by the mineral assemblages present in the chondrules. However, a prevalent Al-Ir correlation was observed, and is most pronounced for a group of chondrules belonging to a population high in Al. A Sc-Ir correlation was observed. Also, an anti-correlation between chondrule masses and Al (and Ir for some chondrules) content of the chondrules was observed. These correlations are attributed to a fractionation during condensation or chondrule formation and cannot be attributed to classical geochemical similarities i.e. these correlations result from a cosmochemical fractionation. From the compositional evidence, it is suggested that there may be two mechanisms for chondrule production. Some high Al chondrules which exhibit the Al-Ir correlation are believed to be remelted primitive high-temperature aggregates. The elemental composition of the chondrules from the lower Al abundance population is consistent with a preferential remelting of pre-existing silicates. 相似文献
13.
29Si and 27Al magic-angle-spinning NMR studies of the thermal transformation of kaolinite 总被引：1，自引：0，他引：1
Thermal transformations of kaolinite of different degree of crystallinity have been monitored by 27Al and 29Si high-resolution NMR with magic-angle spinning (MAS NMR), X-ray diffraction, Fourier transform infrared, atomic absorption spectrophotometry and thermogravimetric analysis. NMR shows differences in the dehydroxylation process of kaolinites with different degree of crystallinity and reveals the presence of short-range order in metakaolinite. 29Si NMR spectra acquired with a 30 s recycle delay of poorly and highly crystalline samples heated at 480 and 500° C, respectively, contain three distinct signals; we discuss their assignment in the light of experiments involving leaching of the samples with aqueous KOH. Ca. 40% of Si sites retain their original Q 3 symmetry just above the onset of dehydroxylation and the Q 4 environment is present showing that a small amount of amorphous silica has already segregated. The spectrum of samples treated at 1000° C contains a signal at -110ppm (from Q 4 silicons) and a faint resonance, from mullite, at ca. -87 ppm. 29Si NMR also shows that cristobalite germs are already present at 950–1000° C. The 27Al MAS NMR spectra of metakaolinite reveal the presence of 4-, 5-and 6-coordinated Al. Changes in the three Al populations as a function of temperature have been monitored quantitatively. Below 800° C, 4-and 5-coordinated Al appears at the expense of 6-coordinated Al, but above 800° C the amount of 6-coordinated Al increases again. We suggest a dehydroxylation scheme which accounts for the presence of 4-and 5 coordinated Al. Above 900–950° C the latter signal is no longer present in the 27Al NMR spectra and new 4-and 6-coordinated Al species (mullite and γ-alumina) appear. We propose new ideas for the structure of metakaolinite. 相似文献
14.
B.H.W.S. de Jong Charles M. Schramm Victor E. Parziale 《Geochimica et cosmochimica acta》1983,47(7):1223-1236
The coordination of aluminum with oxygen in crystalline and amorphous alumina, aluminates, and aluminosilicates has been determined with magic angle spinning 27Al nuclear magnetic resonance. The 27Al NMR spectra of crystalline materials show that VIAl and IVAl can readily be distinguished. The same is not the case for amorphous aluminosilicates due to the superposition of a narrow peak, characteristic of IVAl, on a broad band. Our spectroscopic results indicate that Al coordination is not the determining factor in explaining differences in devitrification behavior of albite and anorthite glasses. The coordination of Al in aqueous solutions seems to prevent precipitation of the three common Al(OH)3 polymorphs (VIAl) at pH above 10. There is clear evidence to suggest that, in solutions containing Si as well as Al, aluminum coordination is related to the type of precipitate formed in acid (clays, VIAl, IVAl), and basic (zeolites, IVAl) environments. Zeolites can be precipitated in near neutral pH environments at higher temperatures, reflecting an increase in IVAl under these conditions. The Al avoidance principle for aluminosilicates does not seem to be a hard principle. It is likely that the validity of this principle depends on the type of modifying cation present in the aluminosilicate framework. 相似文献
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This paper presents the results of a comprehensive investigation of the interaction of layered silicates with Ca(OH)2 in hydrothermal conditions. The study is intended to evaluate the stability of the clay buffer in radioactive waste repositories, at the intermediate stages of concrete leaching, when the pH is controlled by the dissolution of portlandite. The influence of layer nature, octahedral occupation, presence of tetrahedral Al and degree of crystallinity will be assessed by analysing the behaviour of a set of well-selected phyllosilicates and using the combined capabilities of 29Si and 27Al MAS-NMR spectroscopy, powder X-ray diffraction and SEM/EDX. The results show that the main factor affecting the stability of the clay is the octahedral occupation, so that trioctahedral phyllosilicates are much more stable than dioctahedral ones. The nature and expandability of the layer does not seem to much influence the stability of the clay, so that a 2:1 expandable phyllosilicate shows the same stability as a chemically analogous 1:1 non-expandable phyllosilicate. However other factors like the poor crystallinity of the starting material or the presence of Al in the tetrahedral sheet of trioctahedral phyllosilicates weaken the clay structure in alkaline conditions and favour the transformation towards other phases. 相似文献
16.
Victor C. Farmer Anthony R. Fraser J.Mervyn Tait 《Geochimica et cosmochimica acta》1979,43(9):1417-1420
Infrared spectra in the 300–1400 cm?1 region indicate that the non-crystalline products of interaction between hydroxyaluminium species and orthosilicic acid in dilute aqueous solutions of pH < 5 differ markedly in structure from those formed in near-neutral and alkaline solutions of pH > 6. The compound formed in acid solution has an infrared spectrum similar to imogolite, and is termed proto-imogolite; like imogolite, it contains orthosilicate groups and 6-coordinated aluminium, and has an ideal Si:Al ratio of around 0.5, but it can incorporate some excess alumina or silica and it does not have the regular tubular structure of imogolite. Compounds formed in alkaline solutions that are not too dilute have infrared spectra resembling the feldspathoid group of minerals and are termed hydrous feldspathoids. They incorporate a condensed tetrahedral framework with an Si:Al ratio greater than one, but can also contain 6-coordinated aluminium.Natural allophanes of the proto-imogolite and hydrous feldspathoid types exist. The allophane of weathered pumice, however, contains a condensed silicate anion that incorporates little tetrahedral aluminium. Proto-imogolite forms stable sols at pH < 5 and must play an important role in the transport of aluminium in acidic natural waters containing dissolved silica. 相似文献
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Abstract An analytical electron microscope study of almandine garnet from a metamorphosed Al–Fe‐rich rock revealed detailed composition profiles and defect microstructures of resorption zoning along fluid‐infiltrated veins and even into the garnet/ilmenite (inclusion) interface. This indicates a limited volume diffusion for the cations in substitution (mainly Ca and Fe) and an interface‐controlled partition for the extension of a composition‐invariant margin. A corrugated interface between the Ca‐rich margin/zone and the almandine garnet core is characterized by dislocation arrays and recovery texture further suggesting a resorption process facilitated by diffusion‐induced recrystallization, diffusion‐induced dislocation migration and diffusion–induced grain boundary migration. Integrated microstructural and chemical studies are essential for understanding the underlying mechanisms of processes such as garnet zoning and its modification. Without this understanding, it will not be possible to reliably use garnet compositions for thermobarometry and other applications that rely on garnet chemical information. 相似文献
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From their birth as condensates in the outflows of oxygen-rich evolved stars, processing in interstellar space, and incorporation into disks around new stars, amorphous silicates predominate in most astrophysical environments. Amorphous silicates were a major building block of our Solar System and are prominent in infrared spectra of comets. Anhydrous interplanetary dust particles (IDPs) thought to derive from comets contain abundant amorphous silicates known as GEMS (glass with embedded metal and sulfides) grains. GEMS grains have been proposed to be isotopically and chemically homogenized interstellar amorphous silicate dust. We evaluated this hypothesis through coordinated chemical and isotopic analyses of GEMS grains in a suite of IDPs to constrain their origins. GEMS grains show order of magnitude variations in Mg, Fe, Ca, and S abundances. GEMS grains do not match the average element abundances inferred for ISM dust containing on average, too little Mg, Fe, and Ca, and too much S. GEMS grains have complementary compositions to the crystalline components in IDPs suggesting that they formed from the same reservoir. We did not observe any unequivocal microstructural or chemical evidence that GEMS grains experienced prolonged exposure to radiation.We identified four GEMS grains having O isotopic compositions that point to origins in red giant branch or asymptotic giant branch stars and supernovae. Based on their O isotopic compositions, we estimate that 1-6% of GEMS grains are surviving circumstellar grains. The remaining 94-99% of GEMS grains have O isotopic compositions that are indistinguishable from terrestrial materials and carbonaceous chondrites. These isotopically solar GEMS grains either formed in the Solar System or were completely homogenized in the interstellar medium (ISM). However, the chemical compositions of GEMS grains are extremely heterogeneous and seem to rule out this possibility. Based on their solar isotopic compositions and their non-solar elemental compositions we propose that most GEMS grains formed in the nebula as late-stage non-equilibrium condensates. 相似文献
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微波消解-原子吸收光谱法测定岩芯中的8种金属元素 总被引：1，自引：1，他引：0
岩芯分析是油气田开采前期必须开展的必要研究工作。岩芯样品常见金属元素钾(12.30 mg/g)、钠(15.04 mg/g)、铝(28.83 mg/g)、铁(11.13 mg/g)含量较高,且含有大量有机物,文章首次提出以微波消解方式,用浓硝酸和过氧化氢分解有机物,盐酸和氢氟酸处理二氧化硅等无机物,分解稠油油藏岩芯样品效果明显,原子吸收光谱法测定样品中钾、钠、钙、镁、铝、铁、锰、钡8种金属元素的含量。分析结果表明,方法线性相关系数良好(相关系数为0.9949～0.9998),回收率在92.2%～101.6%。建立的微波消解技术无样品损失,操作简单,消解过程节省试剂,减少了环境污染,测定方法准确、可靠,检出限低。 相似文献
20.
Jer me Viers Bernard Dupr Mireille Polv Jacques Schott Jean-Louis Dandurand Jean-Jacques Braun 《Chemical Geology》1997,140(3-4):181-206
This study deals with the weathering processes operating at the scale of a small catchment (Nsimi-Zoetele, Cameroon) and is focused on the role of organic colloids on mineral weathering and transport of elements in natural waters. Samples of river, spring and groundwaters from Nsimi-Zoetele were filtered through membranes of decreasing pore size (0.22 μm, 0.025 μm, or: 300,000 Da, 5000 Da) to separate colloidal fractions from the truly dissolved one. Major and trace elements and dissolved organic carbon (DOC) were analysed in each fraction. Two kinds of waters can be distinguished in the catchment: clear and coloured waters. Clear waters exhibit low concentrations of major and trace elements and DOC. Elements are carried in these solutions in a true dissolved form except Al and rare earth elements (REEs). By contrast, the higher abundances of Al, Fe and trace elements in coloured waters are controlled by the colloidal fraction. Thermodynamic equilibrium calculations show that clear waters are in equilibrium with kaolinite and iron oxi-hydroxide which are major minerals in the weathered soil. For coloured waters, the aqueous speciation of Ca, Mg, Cu, Fe, Al, La and Th was calculated taking into account the complexes with humic acids. Speciation calculations for Cu, Fe, Al, La, Th show a strong complexation with humic acids, in good agreement with the results of the filtration experiments. By contrast, although filtration experiments show a strong control of major cations by organic matter (for example 75% for Ca), speciation calculations reveal that their complexes with humic ligands do not exceed a few percent of total dissolved elements. This discrepancy is explained as an artefact induced by the organic colloids and occurring during the filtration procedure. Finally, both filtration experiments and speciation calculations show that organic matter plays an important role in natural DOC-rich waters. Organic acids increase significantly the dissolution rates of silicates and oxi-hydroxides and thus the amounts of solutes and of complexed elements leaving the catchment. 相似文献