Defect Chemistry and Electrical Properties of Thallium Oxide Single Crystals

Ehdectrical resistivity and Hall voltage were measured between 4.2 and 300 K on T1₂O₃ crystals annealehd at 550°C for 24 h under oxygen pressures of 2×10⁴ to 10⁷ Pa. The carrier concentration varied from 7.97×10²⁰ to 5.08×10²⁰ cm⁻³, the low-temperature Hall mobility from 131 to 189 cm²/V.s, and the Fermi level from 7.1×10⁴ to 5.05×10⁴ J/mol above the bottom of the conduction band as P ₀₂ was increased from 2×10⁴ to 10⁷ Pa. The dependence of Fermi level on carrier concentration and P _0l was consistent with a parabolic density-of-states function describing the conduction band. Over the entire region of oxygen pressure investigated, Fermi-Dirac statistics were required to describe the dependence of carrier concentration on P ₀₂.     

Defect Structure of TiTa2O7 at Elevated Temperatures

The electrical conductivity of polycrystalline TiTa₂O₇ was measured at 1000° and 1050°C as a function of oxygen partial pressure from 10⁻¹ to 10⁻²¹ MPa. In the apparent n-type region, the value of m in σ_n∝PO₂^−1/m was found to be ∼6 in the region >10⁻¹⁷ MPa and ∼4from 10⁻¹⁶ to 10⁻⁹ MPa. The conductivity appeared to be p-type for P₀₂<10⁻⁵ MPa. The measured data are explained on the basis of the presence of small amounts of acceptor impurities in the undoped sample.     

Annealing of Irradiation-Induced Thermal Conductivity Changes in ThO2-1.3 wt% UO2

The thermal conductivities of sintered pellets of ThO₂-1.3 wt% U0₂ were measured at 60°C before and after irradiation. The irradiation temperature was below 156°C, and the exposures varied from 3.1 × 10¹⁴ to 4.7 × lo^L7 fissions/cm³. Each fission fragment damaged a region of 2.2 × 10^-16 cm³ with the reduction in conductivity saturating by about 10¹⁷ fissions/cm³. Samples having exposures from 10¹⁵ to 10¹⁶ fissions/cm³ were annealed isothermally at 651 °C or isochronally from 300° to 1200° C to study the annealing of damage. Most of the annealing occurred between 500° and 900°C. The width of this interval plus the slow isothermal annealing suggest that the damage is annealed by a number of single order processes with a spectrum of activation energies from 1.8 to 3.9 eV or, less probably, by a high order process with an activation energy of 3.55 ± 0.4 eV.     

Deviation from Stoichiometry in Cr2O3 at High Oxygen Partial Pressures

The deviation from stoichiometry, δ, in Cr₂−δO₃ was measured by a tensivolumetric method in the high pO₂ range of ≊10⁴ to 10⁴ Pa at 1100°C. The value of δ, or chromium vacancy concentration, was≊9×10⁻⁵ mol/mol Cr₂O₃ in air for Cr₂O₃ with 99.999% purity. The chemical diffusion coefficient, DT, determined from equilibration data was ≊4.6× cm²·s⁻¹ at 1100°C for pO₂= 2.2 ×10¹ Pa. The self-diffusion coefficient of Cr ions was calculated from and δ and found to be≊1.6×10-17 cm²-s⁻¹, in good agreement with recently measured values.     

微弧氧化表面的溶胶-凝胶涂料封孔及其耐腐蚀性研究

使用紫外光辅助溶胶 -凝胶的光化学工艺,在微弧氧化的铝合金纤维表面涂敷一层封孔层,封孔层能够有效地将多孔的微弧氧化膜封闭,显著提高铝合金纤维的耐腐蚀性能。对微弧氧化后和封孔后的铝合金纤维进行电化学分析,结果显示,封孔后铝合金纤维的腐蚀电位从 -0.651 V正移至 -0.368V。腐蚀电流密度 Icorr从 6.02×10^-6 A/cm²降低到 9.58×10^-10 A/cm²,极化电阻 R_p从 5.4×10³ Ω·cm²增加到 4.5× 10⁴Ω·cm²,紫外光处理过的封孔膜层的腐蚀速率显著降低,铝合金纤维的耐腐蚀性能显著提高。     

Electrical Conductivity of Coal Slag

The electrical conductivity of natural and synthetic slags (containing 14 to 36 wt% Fe) was measured from 1200 to 1700 K at O₂ pressures from 1 to 2×10⁻⁶ atm. The conductivity is relatively high (∼10⁻²Ω⁻¹ cm⁻¹ at 1700 K) and stems from the transfer of electrons between Fe²⁺ and Fe³⁺ ions. Anomalies in the conductivity around 1600 K are the result of devitrification of the glass samples.     

MUCT工艺处理生活污水短程脱氮的实现及硝化菌群动态变化

采用连续流MUCT工艺处理实际生活污水,研究短程生物脱氮的实现,并采用实时荧光定量PCR方法(quantitative real time PCR,QPCR)分析全程脱氮向短程脱氮转变过程中氨氧化细菌(ammonia-oxidizing bacteria,AOB)和亚硝酸盐氧化菌(nitrite-oxidizing bacteria,NOB)的动态变化。通过降低溶解氧浓度为0.5mg·L^-1和缩短水力停留时间为6h,实现短程硝化,亚硝酸盐积累率达到90%。在短程硝化稳定运行阶段总氮去除率高达90%以上,远远大于全程阶段的74%。QPCR结果表明全程脱氮阶段水力停留时间的缩短使AOB细胞数呈现下降的趋势,NOB细胞总数稳定维持在10⁸cells·(g dried sludge)^-1。短程脱氮阶段,AOB细胞数小幅度上升,由3.17×10⁶cells·(g dried sludge)^-1增长到1.32×10⁷cells·(g dried sludge)^-1,同时AOB占全菌的比例也小幅度增长。NOB的细胞数在5.9×10⁷~1.78×10⁸cells·(g dried sludge)^-1之间波动。NOB占全菌的比例由1.44%下降到0.47%。因此,MUCT工艺处理实际生活污水的系统中NOB丰度降低及活性抑制是实现并维持短程生物脱氮的重要原因。短程脱氮运行期间由于控制低溶解氧浓度和短的水力停留时间,AOB丰度及相对含量没有显著增加,甚至下降,但不会影响氨氮和总氮的去除。     

Thermal Expansion of the Hexagonal (6H) Polytype of Silicon Carbide

The thermal expansion of the hexagonal (6H) polytype of α-SiC was measured from 20° to 1000°C by the X-ray diffraction technique. The principal axial coefficients of thermal expansion were determined and can be expressed for that temperature range by second-order polynomials: α¹¹= 3.27 × 10^–6+ 3.25 × 10^–9T – 1.36 × 10^–12 T ² (1/°C), and ş₃₃= 3.18 × 10^–6+ 2.48 × 10^–9 T – 8.51 × 10^–13 T ² (1/°C). The σ₁₁ is larger than α₃₃ over the entire temperature range while the thermal expansion anisotropy, the δş value, increases continuously with increasing temperature from about 0.1 × 10^–6/°C at room temperature to 0.4 × 10^–6/°C at 1000°C. The thermal expansion and thermal expansion anisotropy are compared with previously published results for the (6H) polytype and are discussed relative to the structure.     

Hot Deformation of YBa2Cu3O7-δ and Composite YBa2Cu3O7-δ/Ag

The response of ceramic superconductors and ceramic composites to compressive stresses at high temperatures has been examined. Monolithic YBa₂Cu₃O_7-δ and composite YBa₂Cu₃O₇-δ₆/Ag were tested at constant true strain rates from 10^-6 to 10^-3 s^-1 at temperatures from 800° to 950°C. Fine-grained monolithic YBa₂Cu₃O_7-δ appears to have a regime of superplastic deformation between temperatures of 850° and 950°C at strain rates from 10^-6 to 10^-4 S^-1. The addition of 20 vol% Ag to a coarser-grained material enhances the ductility of the ceramic and lowers the flow stress by a factor of 3 to 10. However, there is no evidence of superplasticity in the composite material in the range of temperature and strain rate where it was tested.     

湍动流化床内固体颗粒扩散系数

将高速摄影及基于互相关原理的图像处理技术与颗粒扩散规律的研究进行结合,对湍动流化床中甲醇制烯烃催化剂SAPO-34颗粒的扩散系数进行了实验研究。实验表明,对于Geldart A类的SAPO-34颗粒,颗粒纵向扩散系数在10^-2～10^-1 m²·s^-1量级之间,横向扩散系数在10^-3～10^-2 m²·s^-1量级之间,两者均随流化风速的上升而增大。另外,在相同的流化风速下,粒径较小的颗粒具有更大的扩散系数。该结果对湍动床颗粒运动规律的研究有一定意义。     

高压静电场对纤维素Iβ中甲醛扩散的影响

采用分子动力学的方法,进行了在不同高压电场作用下,甲醛分子在纤维素Iβ中扩散运动的模拟。结果表明：当电场强度从0增大到10⁹ V·m^-1时,扩散系数由5.64×10^-10 m²·s^-1增大到7.768×10^-10 m²·s^-1,增大了约38%,说明高压静电场加强了甲醛分子在纤维素Iβ中的扩散运动,提高了扩散系数;电场强度能有限增强纤维素链的整体移动,并不会破坏纤维素的稳定性;高压静电场的施加,改变了甲醛分子与纤维素Iβ相互作用,提高了静电作用、范德华作用和总相互作用。     

Oxidation Behavior of Si-C-O Fibers (Nicalon) under Oxygen Partial Pressures from 102 to 105 Pa at 1773 k

Polycarbosilane-derived SiC fibers (Nicalon) were oxidized at 1773 K under oxygen partial pressures from 10² to 10⁵ Pa. The effect of oxygen partial pressure on the oxidation behavior of the Nicalon fibers was investigated by examining mass change, surface composition, crystal phase, morphology, and tensile strength. The Nicalon fibers were passively oxidized under oxygen partial pressures of >2.5 ×10² Pa and actively oxidized under an oxygen partial pressure of 10² Pa. Under oxygen partial pressures from 2.5 × 10² to 10³ Pa, active oxidation occurred at the earliest stage of oxidation, resulting in the formation of both a silica film and a carbon intermediate layer. Although the unoxidized core retained considerable levels of strength under the passive-oxidation condition, fiber strength was lost under the active-oxidation condition.     

On the Decomposition of Synthetic Gibbsite Studied by Neutron Thermodiffractometry

The thermal decomposition mechanism of synthetic Al(OH)₃ (gibbsite) was studied in situ by neutron thermodiffractometry in an ambient atmosphere from room temperature to 600°C with 50°C steps. Gibbsite decomposed to yield AlO·(OH) (boehmite) and then poorly crystallized χ-Al₂O₃. Rietveld analysis was used to refine the cell parameters' variation of gibbsite and its thermal expansion coefficients were obtained: for the a -axis: 15±1 × 10⁻⁶ K⁻¹, for b : 10±2 × 10⁻⁶ K⁻¹, and for c : 17±2 × 10⁻⁶ K⁻¹.     

Diffusion of Deuterium in Amorphous Cordierite

Diffusion of deuterons from D₂O vapor into cordierite was performed at elevated temperatures. The presence of deuterons is monitored with infrared absorption of OD⁻ ions at 2630 cm⁻¹. The diffusion coefficient D at 1273 K is about 2 × 10⁻¹¹ m²/s. The activation energy E in the Arrhenius equation is 3 × 10⁵ J/mol. Out-diffusion of D⁺ ions can be enhanced by application of an electric field.     

Characterization of diamond-like carbon films before and after heavy energetic ion implantations

Hydrogenated diamond-like carbon films were implanted by 110 keV Fe⁺ at doses ranging from 1 × 10¹³ to 5 × 10¹⁶ ions cm⁻². The film resistivities and the infra-red transmittances of the specimens were determined as functions of the implanted doses. Raman spectra and the infra-red transmittances of the film layers were used to characterize the structural changes of the implanted films. It was found that, when the implantation dose was higher than about 5 × 10¹⁴ or 1 × 10¹⁵ ions cm⁻², the film resistivity and the total infra-red transmittance of the specimens decreased significantly. However, when the dose was smaller than this value, the resistivity decreased firstly and then increased with dose and the measured values were higher than those of corresponding as-grown ones. The infra-red transmittance of the specimens was also improved to some extent under the lower dose range. By using structural characterization results, especially the infra-red transmittances of the film layers, we conclude that the electrical and optical property changes at doses higher than about 5 × 10¹⁴ or 1 × 10¹⁵ ions cm⁻² were due to the following changes, i.e., the decrease in the population of both sp² C-H and sp³ C-H bonds (compared with that of sp³ C-H bonds, the decrease in speed of sp² C-H bonds is smaller), the decrease of bond-angle disorder and the increased population of sp² C-C bonds. However, at doses between 1 × 10¹⁴ and 5 × 10¹⁴ or 1 × 10¹⁵ ions cm⁻², the implantation induced increase of C-H bonds was responsible for the observed property changes. Compared with the previous reports, the novelty of the present work is: the IR transmittance curves of the single film layers give us direct evidence for the changes of different C-H bonds with increasing ion dose and thus proved the transformation mechanism proposed previously.     

Diamond growth by carbon ion implantation of diamond

Medium energy (5–25 keV) ¹³C⁺ ion implantation into diamond (100) to a fluence ranging from 10¹⁶ cm⁻² to 10¹⁸ cm⁻² was performed for the study of diamond growth via the approach of ion beam implantation. The samples were characterized with Rutherford backscattering/channelling spectroscopy, Raman spectroscopy, X-ray photoemission spectroscopy and Auger electron spectroscopy. Extended defects are formed in the cascade collision volume during bombardment at high temperatures. Carbon incorporation indeed induces a volume growth but the diamond (100) samples receiving a fluence of 4 × 10¹⁷ to 2 × 10¹⁸ at. cm⁻² (with a dose rate of 5 × 10¹⁵ at. cm⁻² s⁻¹ at 5 to 25 keV and 800 °C) showed no He-ion channelling. Common to these samples is that the top surface layer of a few nanometers has a substantial amount of graphite which can be removed by chemical etching. The rest of the grown layer is polycrystalline diamond with a very high density of extended defects.     

Effects of M3+ Ions on the Conductivity of Glasses and Glass-Ceramics in the System Li2O—M2O3—GeO2—P2O5 (M = Al, Ga, Y, Dy, Gd, and La)

Glasses with compositions Li_1.2M_0.2Ge_1.8(PO₄)₃ (M = Al, Ga, Y, Gd, Dy, and La) were prepared and converted to glass-ceramics by heat treatment. The effects of the M³⁺ ions on the conductivity of the glasses and glass-ceramics were studied. The main phase present in the glass-ceramics was the conductive phase LiGe₂(PO₄)₃. Al³⁺ and Ga³⁺ ions entered the LiGe₂(PO₄)₃ structure by replacing Ge⁴⁺ ions, but lanthanide ions did not. The glass-ceramics exhibited much higher conductivity than the glasses. With increased ionic radius of the M³⁺ ions, the conductivity remained almost unchanged at ∼3 × 10⁻¹² S/cm for the glasses, but it decreased from 1.5 × 10⁻⁵ to 8 × 10⁻⁹ S/cm for the glass-ceramics at room temperature. The higher conductivity for Al³⁺- and Ga³⁺-containing glass-ceramics was suggested to result from the substitutions of Al³⁺ and Ga³⁺ ions for Ge⁴⁺ ions in the LiGe₂(PO₄)₃ structure.     

Separation and enrichment of carbon dioxide by capillary membrane module with permeation of carrier solution

A novel facilitated transport membrane for gas separation using a capillary membrane module is proposed in which a carrier solution is forced to permeate the membrane. Both a feed gas and a carrier solution are supplied to the lumen side (high pressure side, feed side) of the capillary ultrafiltration membrane and flow upward. Most of the carrier solution which contains dissolved solute gas, CO₂ in the present case, permeates the membrane to the permeate side (low pressure side, shell side), where the solution liberates dissolved gas to form a lean solution. The lean solution is circulated to the lumen side. This type of capillary membrane module was applied to the separation of CO₂ from model flue gases consisting of CO₂ and N₂. Monoethanolamine (MEA), diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) were used as carriers or absorbents of CO₂. The feed side pressure was atmospheric and the permeate side was evacuated at about 10 kPa. CO₂ in the feed gas was successfully concentrated from 5–15% to more than 98%. The CO₂ permeance was as high as 2.7×10⁻⁴ mol m⁻² s⁻¹ kPa⁻¹ (8.0×10⁻⁴ cm³ cm⁻² s⁻¹ cmHg⁻¹) when the CO₂ mole fraction in the feed was 0.1 and temperature was 333 K. The selectivity of CO₂ over N₂ was in the range from 430 to 1790. The membrane was very stable over a discontinuous one-month testing period.     

Fe(Ⅱ)活化过硫酸盐氧化破解剩余污泥

采用 Fe(Ⅱ)活化过硫酸盐,产生强氧化性硫酸根自由基(SO₄^-·),以污泥释放的溶解性COD(SCOD)、相对疏水性(RH)和污泥比阻(SRF)为表征,考察了SO₄^-·氧化破解剩余污泥强化脱水的影响因素,并解析了机理。结果表明:当初始pH为4.5,n(S₂O₈^2-)=2.2 mmol·(g VSS)^-1,n(Fe²⁺)=1.32 mmol·(g VSS)^-1,常温下反应3 h后,SCOD由66.5 mg·L^-1增加到472.3 mg·L^-1,RH由26.9%升高到41.1%,SRF由24.9×10⁸ S²·g^-1降低至4.5×10⁸ S²·g^-1;在此基础上利用响应面法,根据Box-Benhnken中心组合试验设计,以SRF为响应指标,优化条件为pH 4.27,n(S₂O₈^2-)=2.6 mmol·(g VSS)^-1,n(Fe²⁺)=1.59 mmol·(g VSS)^-1时,SRF为3.8×10⁸ S²·g^-1,泥饼含水率为72.7%。镜检发现,破解后污泥变为颗粒碎片状;傅里叶红外光谱显示污泥表面官能团对应的特征吸收峰强度有一定程度的减弱;热重分析表明无明显物理吸附水失重区。证实了在SO₄^-·作用下,污泥菌胶团结构破坏,溶胞释放了有机物,使表观疏水性更强,与水结合力明显减弱,脱水性得到了较大提高,有利于污泥减量化应用。     

Cumulative chemical composition of atmospheric cloud condensation nuclei

Condensation nuclei (CN) separated during winter 1982–1983 in Colorado consisted mostly of sulfates and chlorides, with nitrates practically absent. Nitrates were present in all precipitation (rain and snow). CN condensate collected in the presence of haze contained the largest amounts of SO₄²⁻ (1.7 × 10⁻⁷ moles/ml), Cl (> 1.4 × 10⁻⁷), and NO₃⁻(2.1 × 10⁻⁸) recorded; the concentrations of the cations were > 2.2 × 10⁻⁷ moles/ml of Na⁺, > 1.1 × 10⁻⁷ of NH₄⁺, and > 2.6 × 10⁻⁷ of K⁺. Nitrates were present in low concentrations in CN separated in the presence of fogs.

The pH of the separated CN varied from 5.2 to 6.6; the pH of rain samples was between 4.6 and 5.3, and that of the snow samples was between 3.9 and 4.9.

Analysis of single aerosol particles collected since 1979 showed the predominant anion to be sulfate. Nitrate ion-bearing aerosol particles were not detected on some days.