Antiferromagnetism in Pressure-Amorphized Fe2SiO4

Amorphous Fe(2)SiO(4) synthesized at elevated pressures exhibits a Néel transition at a temperature identical to that observed in the crystalline form, T(N) = 65 (+/-2) kelvin at zero pressure. This behavior contrasts sharply with observations on other disordered systems, such as spin glasses, which characteristically exhibit strong "frustration" of the spins and consequent marked suppression of the Néel transition.     

水田亚铁毒害的治理方法研究

亚铁毒害是在辽中县大黑乡进行水稻"红苗病"治理过程中发现的,其症状为插秧后返青至孕穗阶段秧苗分蘖缓慢,打绺,矮缩,叶片上出现大量锈斑,远看一片红,群众称之为"红苗病".过去对它的研究着重于土壤中各种养分的绝对含量,认为土壤瘠薄所至.本项研究着重了土壤中各种养分的相对含量关系,并提出亚铁含量过多是破坏土壤中养分平衡,而导致"红苗病"大面积发生的重要因素之一.     

Comparative Compressibilities of Silicate Spinels: Anomalous Behavior of (Mg,Fe)2SiO4

Compressibilities of five silicate spinels, including gamma-Mg(2)SiO(4), gamma-Fe(2)SiO(4), Ni(2)SiO(4) and two ferromagnesian compositions, were determined on crystals positioned in the same high-pressure mount. Subjection of all crystals simultaneously to the same pressure revealed differences in compressibility that resulted from compositional differences. Ferromagnesian silicate spinels showed an anomalous 13 percent increase in bulk modulus with increasing iron content, from Mg(2)SiO(4) (184 gigapascals) to Fe(2)SiO(4) (207 gigapascals). This result suggests that ferrous iron and magnesium, which behave similarly under crustal conditions, are chemically more distinct at high pressures characteristic of the transition zone and lower mantle.     

High-Temperature Phase Transition and Dissociation of (Mg, Fe)SiO3 Perovskite at Lower Mantle Pressures

To study the crystallography of Earth's lower mantle, techniques for measuring synchrotron x-ray diffraction from a laser-heated diamond anvil cell have been developed. Experiments on samples of (Mg, Fe)SiO(3) show that silicate perovskite maintains its orthorhombic symmetry at 38 gigapascals and 1850 kelvin. Measurements at 65 and 70 gigapascals provide evidence for a temperature-induced orthorhombic-to-cubic phase transition and dissociation to an assemblage of perovskite and mixed oxides. If these phase transitions occur in Earth, they will require a significant change in mineralogical models of the lower mantle.     

Melting of (Mg,Fe)2SiO4 at the Core-Mantle Boundary of the Earth

The lower mantle of the Earth is believed to be largely composed of (Mg,Fe)O (magnesiowustite) and (Mg,Fe)SiO3 (perovskite). Radiative temperatures of single-crystal olivine [(Mg0.9,Fe0.1)2SiO4] decreased abruptly from 7040 +/- 315 to 4300 +/- 270 kelvin upon shock compression above 80 gigapascals. The data indicate that an upper bound to the solidus of the magnesiowustite and perovskite assemblage at 4300 +/- 270 kelvin is 130 +/- 3 gigapascals. These conditions correspond to those for partial melting at the base of the mantle, as has been suggested occurs within the ultralow-velocity zone beneath the central Pacific.     

Effect of a Coordination Change on the Strength of Amorphous SiO2

Measurements of the yield strength of SiO(2) glass to pressures as high as 81 gigapascals at room temperature show that the strength of amorphous silica decreases significantly as it is compressed to denser strctures with higher coordination. Above 27 gigapascals, as the silicon in amorphous SiO(2) is continuously transformed from fourfold to sixfold coordination, the strength of the glass decrases by more than an order of magnitude. These data confirm theoretical predictions that the mechanical properties of polymerized amorphous silicates are sensitive to pressure-induced structural transformations and suggest that the viscosity of silica-rich liquids decreases significantly at high pressures. Such a change in melt rheology could enhance the processes of chemical differentiation with depth in the Earth's mantle.     

Phase Transitions Between beta and ggr (Mg, Fe)2SiO4 in the Earth's Mantle: Mechanisms and Rheological Implications

The mechanisms of the phase transformations between the spinel (gamma) and modified spinel (beta) polymorphs of Mg(2)SiO(4) have been studied experimentally between 15 and 20 gigapascals and 800 degrees to 950 degrees C. The gamma to beta transformation occurs by a shear mechanism, whereas the beta to gamma transformation involves grain-boundary nucleation and interface-controlled growth. These contrasting mechanisms are a consequence of the number of independent slip systems that are available in the respective crystal structures. This result leads to the prediction that in subduction zones and perhaps also rising plumes in the Earth's mantle, the gamma to beta transformation should be accompanied by a transient reduction in strength.     

Fe3 O4／TiO2复合物的制备

[目的]以钛铁矿为原料,制备包覆性Fe_3O_4/TiO_2磁性光催化剂。[方法]研究不同温度、反应时间、钛铁矿颗粒大小、是否冷凝回流等条件下钛铁矿的溶解情况以及TiO_2、Fe_3O_4/TiO_2的产率和催化效果,并采用X射线粉末衍射仪(XRD)、红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)等对催化剂产物进行表征,且验证催化剂的磁性能。[结果]该方法可以制备出磁性良好、包覆效果好、较纯净的Fe_3O_4/TiO_2包覆性光催化材料。[结论]制备出的Fe_3O_4/TiO_2复合物保持了Fe_3O_4的磁性,是一种性能优良的包覆性光催化材料。     

不同时期施铁对水稻根表铁胶膜中铁镉含量及根系含镉量的影响

采用镉污染土壤-河砂-营养液联合培养的方法,研究了不同时期施铁对水稻根表铁胶膜中铁、镉含量的影响。选择水稻的分蘖、拔节、孕穗和灌浆4个时期,进行分期和各生育时期都施加铁的处理,在每个处理时期,设4个亚铁(Fe2 )水平分别为0、30、50和70mg·L-1,研究根表施铁浓度与水稻根表铁胶膜数量和吸附镉量之间的关系。结果表明,生长过程中取样测定的水稻根表铁胶膜铁含量,除个别处理外,都表现为施加铁的根表铁胶膜铁含量高于未施加铁的根表铁胶膜铁含量,尤其是孕穗期,随着施铁量的增加根表铁胶膜铁含量增加。成熟时测定,灌浆期处理的水稻根表铁胶膜铁的含量变化比较大,分蘖期和拔节期变化比较小。各生育时期都处理的根表铁胶膜铁含量以施加Fe2 50mg·L-1最高。水稻根系的含镉量,生长期间测定的结果是前期处理高于后期处理,而收获时测定的结果是前期和后期处理的根系含镉量趋于一致。各生育期都处理的根系含镉量以施加Fe2 50mg·L-1最高,与根表铁胶膜中含铁量相符。     

Pyroxferroite: Stability and X-ray Crystallography of Synthetic Ca0.15Fe0.85SiO3 Pyroxenoid

Synthetic Ca(0.15)Fe(0.85)SiO(3) pyroxenoid has the same (pyroxmangite) structure and very nearly the same composition as pyroxferroite, a new mineral found in Apollo 11 lunar samples. The synthetic material is not stable below pressures of approximately 10 kilobars. It appears likely that the lunar pyroxferroite has persisted in a metastable state for some billions of years.     

Phonon Density of States and Specific Heat of Forsterite, Mg2SiO4

The phonon density of states of the geophysically important mineral forsterite has been calculated with a rigid-ion model, which gives good agreement with an experimental measurement by inelastic neutron scattering. The density of states has been used to calculate the specific heat as a function of temperature, the results of which are in excellent agreement with calorimetrically measured values. The rigid-ion model takes account of the interatomic interactions and normal modes of vibration on a detailed microscopic basis, and is therefore more realistic than the Debye and other empirical models used previously.     

量子点增强铁(III)催化鲁米诺-过氧化氢化学发光体系测定铁

[目的]建立利用量子点增强鲁米诺一过氧化氢一铁（Ⅲ）化学发光体系测定铁的新方法。[方法]利用CdTe量子点和鲁米诺一过氧化氢一铁（Ⅲ）化学发光体系对样品溶液中的铁含量进行了测定。[结果]单因素试验表明,量子点强烈地增强了化学发光信号,从而增加了反应体系的灵敏度;当鲁米诺浓度为1．0×10^-4mol／L,量子点浓度为7％,过氧化氢浓度为0．5％时,化学发光信号最强。在10～700ng／ml的浓度范围内,铁的浓度与化学发先强度呈良好的线性关系,其线性回归方程为△I=2．569C＋212．7．检出限为2．25ng／ml,RSD为2．6％。利用该法测得的血清1、2和水样1、2的铁含量分别为143．97、406．05、18．67、16．08ng／ml。[结论]该法可用于测定人血清和自来水中的铁含量。     

Bi_2Fe_4O_9/TiO_2复合光催化剂的制备及光催化性能

[目的]制备复合光催化剂Bi2Fe4O9/TiO2并研究其光催化性能。[方法]采用高能球磨法制备复合光催化剂Bi2Fe4O9/TiO2,通过XRD、SEM和UV-Vis对其进行了表征,并探讨Bi2Fe4O9掺杂量及球磨时间对其光催化活性的影响。[结果]当Bi2Fe4O9掺杂量为5.0%,球磨时间为12 h时,复合光催化剂对亚甲基蓝的光催化降解率达到56%。[结论]复合光催化剂光活性的提高可能是由于催化剂中复合半导体结构的光生电子-空穴对的有效分离造成的。     

磷钨酸/SiO2 光催化降解甲基橙研究

[目的]将杂多酸固栽在载体上制得固载化催化剂。[方法]以溶胶-凝胶法合成的SiO2作载体,固栽磷钨酸制得固载化光催化剂,并对甲基橙溶液进行催化降解、矿化处理。[结果]在催化剂浓度为4．2g/L的条件下,光照1．5h,4mg／kg甲基橙溶液的脱色率达到98．8％,但矿化率仅有47．6％;而光照6．0h后,矿化率可达92．7％。这意味着甲基橙的光催化降解是先发生脱色过程,然后再进一步矿化成CO2,且所制备的光催化剂在没有进行任何处理的条件下,重复使用10次,脱色率依然保持在65％以上。[结论]成功制备了固栽化光催化剂,该固栽化磷钨酸光催化剂对甲基橙的光催化降解反应具有较好的催化活性,且对甲基橙溶液的脱色和矿化并不同步。     

蜜蜂体内磁铁矿(Fe3O4)来源问题的研究

以蜂蜜和花粉为实验材料 ,应用X射线衍射仪来检测花粉和蜂蜜中的Fe3 O4。结果表明 :在花粉和蜂蜜中没有检测出Fe3 O4,由此我们推断蜜蜂可以合成Fe3 O4。     

Fe2+的测定及其在CO2腐蚀研究中的局限性

介绍了Ｆｅ＾２＋的分光光度测定法及其在高温高压ＣＯ２腐蚀试验中的应用。该方法与传统的失重腐蚀速率测定法进行了对比，结果表明，分光光度测定法所得到的腐蚀速率明显偏低，并且随着平均腐蚀速率的增大，这种趋势更加明显。分析认为，Ｆｅ＾２＋分光光度法在研究ＣＯ２的腐蚀时产生的这种偏差，主要来源于ＣＯ２腐蚀本身的特殊性。     

Fe/C共掺的TiO_2光催化剂的合成及对环境激素辛基酚的降解

[目的]研究Fe/C共掺的TiO2光催化剂的合成及对环境激素辛基酚的降解。[方法]采用溶胶凝胶法和溶剂热合成法制备出铁碳掺杂的二氧化钛光催化剂,以4-叔辛基酚为测试分子研究该类催化剂的光催化性能,探讨了Fe掺杂量、催化剂用量、pH、光照等对反应的影响,并对干扰离子存在情况下的催化剂性能进行了研究。[结果]Fe/C掺杂量为0.6%时,在25℃、pH=9.0、300 W汞灯照射、催化剂用量为1.0 g/L的条件下,经过100 min的降解可以使初始浓度为1.00 mg/L的辛基酚水溶液浓度降至0.02 mg/L;反应体系pH的升高和光强的增加可以提高催化剂的效率,污水中常见的K+、Na+和Ca2+等对催化剂的催化效果无影响。[结论]Fe/C共掺的TiO2光催化剂在处理含有环境激素的废水时具有良好的效果。     

Pressure Dependence of Elastic Wave Velocity for beta-Mg2SiO4 and the Composition of the Earth's Mantle

The pressure dependence of the elastic wave velocities for hot-pressed, elastically isotropic polycrystals of the beta (modified spinel) phase of magnesium orthosilicate (Mg(2)SiO(4)) has been determined at room temperature to 3 gigapascals (GPa) by ultrasonic pulse interferometry. Pressure derivatives of the bulk (dK/dP = 4.8) and shear (dG/dP = 1.7) moduli derived from the travel times of the compressional (P) and shear (S) waves clearly demonstrate that the velocity contrast between the olivine and beta phases of Mg(2)SiO(4) decreases with increasing pressure. When combined with plausible values for the (as yet unmeasured) temperature derivatives, these new data can be used to calculate the contrast in P and S wave velocities across an olivine-beta phase transformation occuaring at pressure-temperature conditions corresponding to about 400 kilometers depth in the earth. The seismologically observed contrasts DeltaV in both P and S wave velocities constrain the percentage of orthosilicate in a model mantle of uniform chemical composition for appropriate relative magnitudes of the temperature (T) derivatives of the bulk and shear moduli for the beta phase. Allowed combinations of orthosilicate content (percent), dK/dT, and dG/dT (both in gigapascals per Kelvin) for a pair of recent seismological models with DeltaV(p) = DeltaV(s) 4.6% include (65, -0.018, -0.020), (55, -0.015, -0.018), and (45, -0.012, -0.016).     

Fe3+-N改性二氧化钛光催化剂的研制

利用微波等离子体沉膜技术和溶胶-凝胶法在载玻片上制备同时掺Fe3 和N的TiO2膜,经500℃焙烧后所得光催化剂性能较好.分别以紫外和可见光为光源,光催化降解茜素红,结果发现:掺铁量均为0.1%的Fe-N/TiO2较Fe/TiO2的光催化活性好,而且可见光的利用率明显增强;UV-Vis扫描显示掺铁0.1%的Fe-N/TiO2紫外吸收峰较其他TiO2光催化剂强且明显红移.XRD谱图结果表明,分别在500℃和550℃焙烧后的0.1?-N/TiO2,均为锐钛矿型,晶体粒度分别为15.3 nm和20.6 nm,XPS谱图显示Fe-N/TiO2有N1s谱峰.     

纳米Fe3O4/PANI复合体系的微波电磁特性研究

用原位化学反应生成法制备了纳米Fe3O4/PANI复合材料,研究了样品在2~18 GHz范围的微波电磁特性与吸收性能以及复合材料组分对电导率、密度的影响.结果表明,Fe3O4颗粒尺寸约12.7 nm,Fe3O4在复合体系中的质量分数为35%左右时,电导率最大,密度相对较低,微波吸收率最高,吸收峰值为-21 dB,-10 dB频宽大于4 GHz,样品同时具有电损耗和磁损耗.可见,通过优化设计,纳米Fe3O4/PANI复合体系可以成为一种性能优良的微波吸收材料.