Boron in sillimanite

Sillimanite in six granulite-facies, kornerupine-bearing rocks contains 0.035 to 0.43 percent B(2)O(3) and 0.02 to 0.23 percent MgO (by weight). Substitution of boron for silicon and magnesium for aluminum is coupled such that the ratio of magnesium to boron is about 0.5. Sillimanite incorporates more than 0.1 percent B(2)O(3) only at high temperatures in a boron-rich environment at very low partial pressures of water. In the amphibolite facies, the sillimanite boron contents are too low to appreciably affect the stability relations of sillimanite with kyanite and andalusite.     

硼对果胶铝吸附解吸特性的影响

【目的】探讨硼对植物铝胁迫的缓解机理,研究果胶对铝的吸附解吸特征及硼的影响。【方法】利用等温吸附法,研究pH 3.5,25℃时,不同浓度硼处理后的果胶对铝的吸附解吸特性,并利用相关模型计算果胶对铝的吸附参数。【结果】随果胶浓度的上升,其对铝的吸附总量和解吸总量均显著上升,但单位果胶的吸附量和解吸量显著下降;随铝浓度的增加,果胶对铝的吸附量和解吸量也显著上升;硼处理果胶后,影响果胶对铝的吸附解吸特性,＜25 µmol•L-1的低浓度硼处理后,果胶对铝的吸附量和解吸量随硼浓度的增加会显著减少,而当硼浓度＞25 µmol•L-1时,随硼浓度的增加,果胶对铝的吸附量反而会增加,硼浓度为100 µmol•L-1时,果胶对铝的吸附量甚至显著大于硼浓度为0的对照,再增加硼浓度至200 µmol•L-1,果胶对铝的吸附量又开始减少,果胶对铝的吸附或许已经达到饱和。利用Langmuir、Freundlich方程较好地拟合了无硼和加硼条件下果胶对铝的吸附过程,由Langmuir模型计算的最大吸附量分别是5.757 mg•g-1和0.160 mg•g-1,Freundlich方程拟合所得参数n分别为1.4702和 - 0.1758,说明硼与果胶RG-Ⅱ的交联作用强烈影响果胶对Al3+ 的吸附。【结论】pH 3.5,25℃时,低浓度的硼（＜25 µmol•L-1）可有效抑制果胶对铝的吸附,而高浓度的硼（＞25 µmol•L-1）则促进果胶对铝的吸附。     

The core structure of basal dislocations in deformed sapphire (alpha-Al₂O₃)

The atomic structure of dislocation cores is decisive for the understanding of plasticity in crystalline solids. The core structure of dislocations in sapphire introduced by high-temperature plastic deformation has been investigated with the use of the negative spherical-aberration imaging technique. The ability of this technique to discriminate oxygen columns from aluminum (Al) columns, combined with reproduction of subtle contrast features by image simulation, leads to a markedly detailed atomic model of the dislocation cores. The partial dislocations are Al-terminated, with electrical neutrality being achieved because half of the Al columns are missing. These partials also undergo core spreading, which results in random occupancy of both tetrahedrally and octahedrally coordinated sites, though Al in tetrahedral coordination never occurs in a perfect crystal. Unusual dislocation core structures may be present in other technologically important nonmetallic solids.     

Aluminum-rich apatite

More than 25 atomic percent of aluminum can susbtitute for other cations in the structure of apatite [A(10)(XO(4)) (6)Z(2)]. Such a synthetic product was obtained by expelling volatile constituents (H(2)O and F) from morinite during thermal treatment. Infrared absorption spectra, chemical analysis, and x-ray powder diffraction demonstrate that the aluminum has two coordination numbers, and more than twice as much aluminum substitutes for calcium (A position) as for phosphorus (X position).     

Formation of Hardening Coatings for Working Elements of Agricultural Machines When Combining the High-Frequency Heating and High-Temperature Synthesis of the Materials

A method of surfacing of a wide range of cast, hard, wear-resistant materials on a steel base was created based on the performed investigations. The surfacing was carried out in the conditions of heating with high-frequency currents (HFCs). The exothermic thermite mixtures were used, including the mixtures of metal oxides, aluminum, or silicon. In the course of synthesis, the coatings with the weld pad of 100–900 μm were obtained. The surfacing process was carried out in two main synthesis modes—high and low-temperature using the exothermic thermite mixtures—and allowed extending significantly the raw material base of the surfacing materials, including refusing the use of the traditional surfacing eutectic alloys and charge mixtures with the boron carbide for deep borating. It is shown that the synthesis of the coating of the exothermic thermite mixture FeO/B₂O₃/Si is identical to the diffusion saturation of the surface layer with the classical mode of borating during the HFC-heating.     

Dislocations in complex materials

Deformation of metals and alloys by dislocations gliding between well-separated slip planes is a well-understood process, but most crystal structures do not possess such simple geometric arrangements. Examples are the Laves phases, the most common class of intermetallic compounds and exist with ordered cubic, hexagonal, and rhombohedral structures. These compounds are usually brittle at low temperatures, and transformation from one structure to another is slow. On the basis of geometric and energetic considerations, a dislocation-based mechanism consisting of two shears in different directions on adjacent atomic planes has been used to explain both deformation and phase transformations in this class of materials. We report direct observations made by Z-contrast atomic resolution microscopy of stacking faults and dislocation cores in the Laves phase Cr2Hf. These results show that this complex dislocation scheme does indeed operate in this material. Knowledge gained of the dislocation core structure will enable improved understanding of deformation mechanisms and phase transformation kinetics in this and other complex structures.     

X-ray diffraction study of the ultrathin Al2O3 layer on NiAl110

Ultrathin Al2O3 layers on alloys are used as templates for model catalysts, tunneling barriers in electronic devices, or corrosion-resistant layers. The complex atomic structure of well-ordered alumina overlayers on NiAl110 was solved by surface x-ray diffraction. The oxide layer is composed of a double layer of strongly distorted hexagonal oxygen ions that hosts aluminum ions on both octahedral and tetrahedral sites with equal probability. The alumina overlayer exhibits a domain structure that can be related to characteristic growth defects and is generated during the growth of a hexagonally ordered overlayer (Al2O3) on a body-centered cubic (110) substrate (NiAl).     

黄河鲤对水体铜的积累效应

为了研究黄河鲤对水体Cu的积累效应,通过饲养试验,采用原子吸收光谱法测定组织中Cu的含量,结果表明,Cu浓度为0.1 mg/L时,黄河鲤鳃、肌肉、肝胰脏、肾组织内Cu的蓄积量随毒性试验时间的增加而增大,第13天均达到平衡,此时Cu的蓄积量为:肝胰脏(72.864 mg/kg干重)>肌肉(22.497 mg/kg干重)>肾脏(21.683 mg/kg干重)>鳃(8.914 mg/kg干重);染毒的黄河鲤放入清洁自来水中后,随着排放时间的增加,鳃、肌肉、肝胰脏、肾组织中的Cu含量逐渐下降,第13天达到排放平衡,此时Cu的排出率为:鳃(90.98%)>肝胰脏(66.31%)>肌肉(55.99%)>肾脏(42.93%)。随着Cu浓度增加,黄河鲤鳃、肌肉、肝胰脏、肾组织中铜蓄积量均明显上升,铜富集系数均逐渐降低;Cu浓度为1.00 mg/L时,富集系数最低,其鳃、肌肉、肝胰脏、肾组织铜富集系数分别为26.8、36.6、139.6和30.1。     

Synthesis and properties of metallic glasses that contain aluminum

The synthesis and properties of a class of metallic glasses containing up to 90 atomic percent aluminum are reported. The unusual formability of the glasses and their structural features are pointed out. Mechanical properties including tensile fracture strength and Young's modulus are reported along with crystallization temperatures. The unusually high strengths of the aluminum glasses can be of significant importance in obtaining high-strength low-density materials.     

Creep-resistant, Al2O3-forming austenitic stainless steels

A family of inexpensive, Al2O3-forming, high-creep strength austenitic stainless steels has been developed. The alloys are based on Fe-20Ni-14Cr-2.5Al weight percent, with strengthening achieved through nanodispersions of NbC. These alloys offer the potential to substantially increase the operating temperatures of structural components and can be used under the aggressive oxidizing conditions encountered in energy-conversion systems. Protective Al2O3 scale formation was achieved with smaller amounts of aluminum in austenitic alloys than previously used, provided that the titanium and vanadium alloying additions frequently used for strengthening were eliminated. The smaller amounts of aluminum permitted stabilization of the austenitic matrix structure and made it possible to obtain excellent creep resistance. Creep-rupture lifetime exceeding 2000 hours at 750 degrees C and 100 megapascals in air, and resistance to oxidation in air with 10% water vapor at 650 degrees and 800 degrees C, were demonstrated.     

生物炭对铝富集酸性土壤的毒性缓解效应及潜在机制

【目的】红壤铝毒是土壤改良持续关注的问题之一。生物炭因其自身的理化和生物学特性,为探索解决该难题提供了新的思路和途径。论文通过在红壤中添加外源铝并种植作物,研究生物炭对铝富集土壤铝毒的缓解效应及潜在机制。【方法】选用酸性红壤做盆栽试验,种植小白菜,添加花生壳生物炭和外源铝,设置CK(0C+0Al)、C(2%C)、Al(1 mmol·L~(~(-1))Al)、C+Al(2%C+1 mmol·L~(~(-1))Al)4个处理,分析生物炭对铝富集红壤不同活性铝及作物生长的影响。【结果】铝毒会显著抑制小白菜的出苗,且加重红壤小白菜生长受抑制的情况,降低小白菜的生物量,同时,铝毒会显著提高小白菜铝含量。而施用生物炭能缓解铝毒对小白菜的抑制影响,显著改善小白菜的生长状况,降低小白菜铝含量,C+Al处理小白菜铝含量较Al处理降低89.4%。铝毒会显著降低红壤的pH,Al处理红壤pH较CK处理降低了0.36个单位,而施用生物炭能显著提高土壤pH,C+Al处理土壤pH较Al处理上升0.62个单位。Al处理较CK处理土壤活性铝含量上升276.4μg·g~(-1),远大于添加量(27μg·g~(-1)),而施用生物炭能显著降低土壤活性铝含量,C+Al处理较Al处理下降14.9%。此外,Al处理交换性Al~(3+)含量较CK处理上升23.1%,施用生物炭后,C+Al处理交换性Al~(3+)含量较Al处理下降46.5%。CK与Al处理土壤活性铝形态主要以具有生物毒害性的交换性Al~(3+)为主,C与C+Al处理土壤活性铝形态主要以单聚体羟基铝离子、胶体Al(OH)30为主。【结论】添加外源铝降低了土壤pH,加重铝的毒害,抑制作物的生长发育。此外,外源铝的添加对红壤中活性铝有较强的激发效应,使得交换性Al~(3+)含量显著升高。然而,生物炭能显著提高酸性土壤pH,且改变不同活性铝的含量,但其对4种不同形态活性铝的效应有较大差异,其主要通过降低具有生物毒性的Al~(3+)含量来缓解铝毒,从而改善作物生长状况。     

野生竹红菌中微量元素的测定

[目的]为了测定野生竹红菌中微量元素的含量。[方法]通过干灰化法制备了从云南山区采集的野生竹红菌样品,用原子吸收光谱法测定了其中Mn、Cd、Cr、Zn、Cu等9种元素的含量。[结果]竹红菌对各金属元素的集累(富集)能力存在差异,对Fe、Se和Hg的集累(富集)能力相对要强,对Cd、Cr、Pb等几种主要的重金属的集累(富集)能力相对较弱,测定的微量元素含量顺序是Fe>Se>Hg>Mn>Zn>Pb>Cu>Cr>Cd。原子吸收的回收率为98.7%~116.4%,RSD值为0.07%~1.67%,都在实验要求的范围内。[结论]竹红菌中的硒元素含量较高,具有一定的开发价值。原子吸收光谱法测定竹红菌中微量元素是可行的。     

某市工业区两种植物重金属质量分数与土壤污染的关系

以某市工业区为研究地点,用原子吸收分光光度法,测定了该地区土壤及早熟禾(Poa annua L.)和鹅观草(Roegneria kamoji)中镉、铬、铜、镍4种重金属的质量分数,并对富集系数进行了分析,结果发现,植物对镉的富集效果最好,其次是铬和镍,最差是铜.而且工业区内的几个化工厂均属于土壤重污染.     

硼对铝胁迫下杉木生长、生理和光合特性的影响

为了研究硼对铝胁迫下杉木生长、生理和光合特性的影响,揭示硼介导的杉木耐铝调控机制,为进一步利用养分管理手段减轻杉木铝毒害提供参考,以3月龄幼苗为材料,共设置4个处理,对照(CK)、缺硼(-B)、缺硼加铝(-B+Al)和加硼加铝(+B+Al),分析不同处理间杉木生长、叶片光合和抗性生理指标的差异。结果表明：(1)与CK相比,胁迫处理均能显著抑制苗高生长,苗高降幅介于31.83%～55.56%之间,而且铝胁迫下,加硼(+B+Al)能显著缓解缺硼(-B+Al)引起的苗高生长、叶片丙二醛(MDA)、过氧化氢(H₂O₂)和光合色素含量下降;与-B+Al处理相比,+B+Al处理的苗高、MDA、H₂O₂、叶绿素和类胡萝卜素含量分别增加48.02%、24.18%、16.39%、17.16%和17.78%。(2)与CK相比,不同胁迫处理显著提高叶片超氧化物歧化酶、过氧化物酶、过氧化氢酶和抗坏血酸过氧化物酶活性,其活性大小均表现为：+B+Al>-B+Al>-B>CK,增幅分别介于17.10%～128....     

铝胁迫对葡萄苗铝吸收分配及抗氧化系统的影响

为了探明葡萄苗在不同浓度铝胁迫下树体的铝积累特征和生理响应,研究以‘水晶’葡萄为试材,在无土栽培条件下,用1.0~8.0 mmol·L~(-1) KAl(SO4)2处理60 d后测定树体铝含量及相关生理指标。结果表明,过量的铝在葡萄苗中的分配为细根粗根老叶树皮嫩叶木质部新枝,2.0 mmol·L~(-1)铝处理后植株生长旺盛,生物量最大,单株铝积累总量最高,5.0 mmol·L~(-1)铝处理后植株生长较弱,生物量较小,单株铝含量最低;铝浓度超过3.0 mmol·L~(-1)时显著降低葡萄苗叶绿素a、叶绿素b、叶绿素a+b的含量,铝浓度超过4.0 mmol·L~(-1)显著降低葡萄苗类胡萝卜素含量;随着铝浓度的增大,葡萄叶片和根系的脯氨酸含量逐渐升高且显著高于CK;铝浓度达到3.0mmol·L~(-1)时,各处理叶片和根系的丙二醛含量均显著高于CK;铝处理提高了葡萄叶片和根系中的氧自由基产生速率和过氧化氢含量;铝胁迫下,葡萄苗叶片和根系的POD活性高于CK;铝浓度低于4.0 mmol·L~(-1)时,SOD活性高于CK,而浓度达到4.0 mmol·L~(-1)时则显著低于CK。可见,低于3.0 mmol·L~(-1)铝对葡萄苗的伤害较小,甚至还能促进其生长,但超过3.0 mmol·L~(-1)铝将对葡萄苗造成不同程度的伤害。     

Nonstoichiometric dislocation cores in alpha-alumina

Little is known about dislocation core structures in oxides, despite their central importance in controlling electrical, optical, and mechanical properties. It has often been assumed, on the basis of charge considerations, that a nonstoichiometric core structure could not exist. We report atomic-resolution images that directly resolve the cation and anion sublattices in alumina (alpha-Al2O3). A dissociated basal edge dislocation is seen to consist of two cores; an aluminum column terminates one partial, and an oxygen column terminates the second partial. Each partial core is locally nonstoichiometric due to the excess of aluminum or oxygen at the core. The implication for mechanical properties is that the mobile high-temperature dislocation core structure consists of two closely spaced partial dislocations. For basal slip to occur, synchronized motion of the partials on adjacent planes is required.     

Visualization of dislocation dynamics in colloidal crystals

The dominant mechanism for creating large irreversible strain in atomic crystals is the motion of dislocations, a class of line defects in the crystalline lattice. Here we show that the motion of dislocations can also be observed in strained colloidal crystals, allowing detailed investigation of their topology and propagation. We describe a laser diffraction microscopy setup used to study the growth and structure of misfit dislocations in colloidal crystalline films. Complementary microscopic information at the single-particle level is obtained with a laser scanning confocal microscope. The combination of these two techniques enables us to study dislocations over a range of length scales, allowing us to determine important parameters of misfit dislocations such as critical film thickness, dislocation density, Burgers vector, and lattice resistance to dislocation motion. We identify the observed dislocations as Shockley partials that bound stacking faults of vanishing energy. Remarkably, we find that even on the scale of a few lattice vectors, the dislocation behavior is well described by the continuum approach commonly used to describe dislocations in atomic crystals.     

硼和氯化钠复合胁迫对小麦幼苗的影响

以盆栽小麦幼苗为供试植物,设定培养基质硼浓度分别为0、50、100 mg·kg^-1,氯化钠浓度分别为0、1、2 g·kg^-1,研究了硼和盐复合胁迫对植物生长的影响。结果表明,硼和氯化钠的单独胁迫均能显著抑制小麦生长;硼浓度为50 mg·kg^-1时,氯化钠加重了硼对小麦生长的抑制;硼浓度为100 mg·kg^-1时,氯化钠缓解了硼对小麦生长的抑制。硼和氯化钠的复合胁迫以及高硼胁迫使根冠比显著增大,氯化钠抑制了小麦对硼的吸收。综合来看,当硼胁迫较严重时,盐胁迫可以促进小麦增大根冠比和减少硼吸收来抵御硼毒害。     

Anomalous spiral motion of steps near dislocations on silicon surfaces

We have used low-energy electron microscopy to measure step motion on Si(111) and Si(001) near dislocations during growth and sublimation. Steps on Si(111) exhibit the classic rotating Archimedean spiral motion, as predicted by Burton, Cabrera, and Frank. Steps on Si(001), however, move in a strikingly different manner. The strain-relieving anomalous behavior can be understood in detail by considering how the local step velocity is affected by the nonuniform strain field arising from the dislocation. We show how the dynamic step-flow pattern is related to the dislocation slip system.     

X-ray Photoelectron Spectroscopic Studies of Interactions in Multicomponent Metal and Metal Oxide Thin Films

Changes in chemical oxidation states in alloys and at solid-solid interfaces were monitored by using x-ray photoelectron spectroscopy. For an oxidized Nichrome surface, the chromium component was selectively converted to chromic oxide while nickel remained in the metallic state. When this surface was overlaid with a 20-angstrom-thick aluminum film, the chromic oxide was reduced to chromium and the aluminum was oxidized to aluminum oxide in a reaction zone consisting of no more than 10 angstroms of the interface. This scheme appeared general for solid-solid contacts and was predicted, to a first approximation, by bulk thermodynamic free energies.