Pb3Mn7O15:合成、相变、转换和分解

以MnO₂和PbO为原料,采用高温固相法合成Pb₃Mn₇O₁₅,采用粉末衍射、SEM和EDS技术,系统研究Pb₃Mn₇O₁₅的合成、相变、转换和分解规律.结果表明:在使用粉末合成法制备Pb₃Mn₇O₁₅时,较为合适的合成温度为850 ℃,PbO过量度为5 %.室温下Pb₃Mn₇O₁₅为正交结构,高温下为六方结构,两者在100~200 ℃之间的相变是可逆的;亚稳相Pb₄Mn₉O₂₀在800~850 ℃不可逆的分解产生Pb₃Mn₇O₁₅;Pb₃Mn₇O₁₅在950~1 000 ℃之间发生分解,分解产物为晶态Mn₃O₄和非晶态PbO.      

Kinetics of reduction of ferric iron in Fe2O3-CaO-SiO2-Al2O3 slags under argon, CO-CO2, or H2-H2O

The rates of reduction of ferric iron in Fe₂O₃-CaO-SiO₂-Al₂O₃ slags containing 3 to 21 wt pct Fe₂O₃ under impinging argon, CO-CO₂, or H₂-H₂O have been studied at 1370 °C under conditions of enhanced mass transfer in the slag using a rotating alumina disc just in contact with the slag surface. For a 6 wt pct Fe slag at a stirring speed of 900 rpm the observed reduction rates by 50 pct H₂-H₂O were a factor of 2 to 3 times higher than those by 50 pct CO-CO₂ and more than one order of magnitude higher than those under pure argon. The observed rates were analyzed to determine the rate-controlling mechanisms for the present conditions. Analysis of the rate data suggests that the rates under 50 pct H₂-H₂O are predominantly controlled by the slag mass transfer. The derived values of the mass-transfer coefficient followed a square-root dependence on the stirring speed for a given slag and, at a given stirring speed, a linear function of the total iron content of the slags. The rates of oxygen evolution during reduction under pure argon were shown to be consistent with a rate-controlling mechanism involving a fast chemical reaction at the interface and relatively slow mass transfer in the gaseous and the slag phases. The rates of reduction by CO-CO₂ (pCO=0.02 to 0.82 atm) were found to be likely of a mixed control by the slag mass transfer and the interfacial reaction. A significant contribution of oxygen evolution to the overall rates was observed for more-oxidized slags and for experiments with relatively low values of pCO. Assuming a parallel reaction mechanism, the estimated net reduction rates due to CO were found to be of the first order in pCO, with the first-order rate constants being approximately a linear function of the ferric concentration. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS. The original symposium appeared in the October 2000 Vol. 31B issue.     

Synthesis, structure and luminescence properties of KEu0.01Gd0.19Yb0.8（WO4）2 powder

The synthesis of co-doped KEu_0.01Gd_0.19Yb_0.8(WO₄)₂ was achieved by a modified Pechini method at 750 °C. The structure of obtained compound was confirmed using X-ray diffraction measurement and Raman spectroscopy. The Scherrer's formula was used to confirm the grain sizes visualized by TEM technique. The grain sizes of about 100 nm of monoclinic KGW were successfully obtained by this methodology. In order to study spectroscopic properties of the prepared system the emission spectra were measured. The effective down- and up-conversion processes in non-resonant system were investigated.     

复合精炼球团中SiO2、CaO、MgO等7组分的测定

试样用混合熔剂熔融,稀盐酸浸取,定容,移取部分试液,通过控制各元素的酸度,分别用光度法测定SiO2和P;EG-TA滴定法测定CaO,EDTA滴定法测定MgO;强碱沉淀分离氟盐置换、EDTA滴定法测定TAl。另称取1份试样用三氯化铁溶解,加入过量的氢氧化钠,滤液在pH值4.5的乙酸—乙酸铵缓冲介质中,加入过量的EDTA标准溶液,在煮沸条件下与MAl络合后,以PAN为指示剂,用铜标准溶液返滴定过量的EDTA;加氟化物取代,铜标准溶液二次返滴定,计算MAl量,再换算为Al2O3量。实验确定三氯化铁浓度为8%、用量50mL及用振荡器或摇动的最佳时间为60min。该方法测定SiO2、CaO、MgO、P、Al2O3及MAl的相对偏差分别小于0.718%、2.819%、1.171%、7.143%、0.178%和1.013%,完全满足快速分析的需要。     

低温燃烧合成法制备粒径相近的MnO、Mn3O4和Mn2O3纳米颗粒

通过控制硝酸盐(硝酸锰) 与有机燃料(尿素) 的摩尔比, 采用低温燃烧合成法制备了粒径相近、形貌不同的单相MnO、Mn₃O₄和Mn₂O₃纳米粒子。扫描电子显微形貌观察结果显示, 三种纳米粒子尺寸约为100 nm, 依据Mn离子价态的不同, 三种纳米粒子的形貌分别为链状、马铃薯状和球状; 热重-差热分析表明, 样品粒径大小主要取决于有机燃料的着火点; 磁性测量结果显示, 低温时MnO和Mn₂O₃粒子表现出弱铁磁性, 这主要归因于纳米颗粒表面存在未补偿的自旋。本文为制备不同价态高纯锰氧化物纳米颗粒提供了一种环境友好、工业稳定的途径。     

Formation of Fe3N, Fe4N and Fe16N2 on the surface of iron

In order to clarify the phenomenon of nitride formation on the surface of iron, highly polished specimens of well refined and coarsened iron grains have nitrided in flowing H2 + NH3 gas. The morphology and the conditions for formation of Fe₃N are clarified; it forms only on the surface of {lll}_α or near {lll}_α grains and grows in {112}_α directions during nitriding treatment at temperatures between 450 and 550°C. Fe₁₆N₂ and Fe₄N are also formed preferentially on the surfaces of {00l}_α and {210}_α grains, respectively. It is suggested that these iron surfaces are those satisfying the coherency relationships between nitrides and iron matrices. The morphologies and the formation temperature regions of Fe₁₆N₂ and Fe₄N on the surface of iron are quite different to those observed in iron. In particular, Fe₁₆N₂, which has been generally accepted as metastable in bulk iron below 200°C, can exist even at temperatures from 450 to 500°C when it is formed on the surface of iron.     

Effect of electron traps on long afterglow behavior of Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+

The long persistent phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02) were prepared by a high temperature solid state reaction. All samples showed a broad band emission peaking at ~510 nm, which could be ascribed to Eu2+ transition between 4f65d1 and 4f7 electron configurations. With the increase of substitution of Ho3+ ions for the Dy3+ ions in the as-prepared phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02), the initial intensity of the afterglow obviously decreased. From the thermoluminescence (TL) curves of the samples, we concluded that codoped Ho3+ ions led to a decline of the trap depth and redistribution of the trap. This may be responsible for the change of afterglow of Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02).     

燃烧法合成稀土纳米长余辉发光材料SrO·xAl2O3:Eu2+,Dy3+

应用燃烧法在空气中较低的温度(＜900℃)下成功地合成了SrO·xAl2O3∶Eu2+,Dy3+稀土纳米长余辉发光材料,并研究了炉温、反应物中铝锶比、助溶剂和可燃物等对发光材料性能的影响.研究结果表明,反应物置于温度为600℃的高温炉中时燃烧得到的产物性能最好,发光粉的粒径在70nm左右,发射光谱的最大波长在520nm左右.与其它合成方法相比,该方法具有合成温度低、反应时间短,获得的产物疏松、硬度小、粒度小等优点.     

Ln2O3／ZrO2催化合成DOP、DOM和DOA

采用共沉淀－焙烧法制成的Ln2O3/ZrO2(Ln=Nd、Sm、Er)担载型催化剂，由于比表面增大，分散性好，在催化合成DOP、DOM和DOA中效果明显，且Ln2O3的用量比用纯Ln2O3催化剂下降60％左右。     

Visible luminescence of lanthanide ions in Ca3Sc2Si3O12 and Ca3Y2Si3O12

The crystalline materials Ca₃Sc₂Si₃O₁₂ and Ca₃Y₂Si₃O₁₂ were characterized by different crystal structures, as the former is a cubic garnet, while the latter is an orthorhombic compound. We investigated the optical spectroscopy of these materials doped with several trivalent lanthanide ions and compared the results for the two hosts. Polycrystalline samples were prepared by solid state reaction, both undoped and doped with the trivalent lanthanide ions Eu³⁺, Tb³⁺ and Sm³⁺. Emission, excitation and Raman spectra of these materials were measured at temperatures ranging from 300 to 10 K. The optical spectra were assigned and discussed, and the effects of the crystal structure of the host on the spectroscopic behaviour were addressed. The technological potential of these compounds in the field of optical materials and devices was discussed.     

CaO-La2O3-B2O3-Eu2O3转光玻璃的合成及荧光性质

X射线衍射研究表明CaO-La2O3-B2O3-Eu2O3体系的玻璃化温度在1025℃附近.荧光光谱和ESR谱研究表明,在CaO-La2O3-B2O3-Eu2O3玻璃体系中存在着Eu2+和Eu3+两种价态离子. 316, 360, 379, 394, 413, 462和532nm锐线激发峰和592,616和650红区发射峰分别对应Eu3+的f-f激发跃迁和5D0-7FJ (J=1,2,3)跃迁发射;351nm和427nm宽带激发峰和蓝区发射分别对应Eu2+的5d-4f激发跃迁和发射.     

CaO—SiO2—Na2O—CaF2—Al2O3—MgO保护渣系的Al2O3吸收速率和粘度

采用CaO-SiO2-Na2O-CaF2-Al2O3-MgO渣系,通过测定熔渣的粘度和Al2O3吸收速率,研究连铸保护渣的Al2O3吸收速率与粘度及化学成分之间的关系。在一定条件下,当CaO/SiO2为1.2左右时,粘度达到最小值,Al2O3吸收速率达到最大值,分别为0.10?Pa*s、8.403×10-4?kg*m-2*s-1。随着渣中Na2CO3含量、CaF2含量和MgO含量的增加,粘度减小,Al2O3吸收速率增大。随着渣中Al2O3含量的增加,粘度增大,Al2O3吸收速率减小。粘度为Al2O3吸收速率的主要控制因素。随着熔渣粘度的增加,连铸保护渣的Al2O3吸收速率逐渐减小。     

Perceived attributes of the terms client, patient, and typical person..

Helping professionals most commonly refer to seekers of counseling services as clients or as patients. However, little has been known of the implied meanings of each of those labels. 74 undergraduates compared, "client," "patient," and "typical person" using semantic differential-type scales and the Personal Attribute Inventory. Although "client" and "patient" were each evaluated more negatively than was "typical person," no significant differences were found between "client" and "patient." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative Study on Thermodynamical and Electrochemical Behavior of Al（88）Ni6La6 and Al（86）Ni6La6Cu2 Amorphous Alloys

Two amorphous ribbons with the compositions of Al88Ni6La6 and Al86Ni6La6Cu2 were made using the melt-spun method,and their thermal response and electrochemical behavior were studied comparatively.Differential scanning calorimetry（DSC）and electrochemical polarization measurements indicated that Al86Ni6La6Cu2 exhibited slightly higher crystallization temperature（Tx）,lower melting point（Tl）and better corrosion resistance in 0.01 mol·L-1 NaCl alkaline solution.These results demonstrated that Cu（2%）addition could slightly promote the glass forming ability,but it could greatly improve the corrosion resistance of Al88Ni6La6 alloy in 0.01 mol·L-1 NaCl alkaline solution.     

Preparation and Characterization of Red Luminescent Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ Nanophosphor

Nanophosphor with the nominal composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ （CZTOPN） was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti（OC4H9）4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis （TG-DSC）, powder X-ray diffraction （XRD）, and scan election microscopy （SEM）. Results of TG-DSC and XRD reveal that the composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.     

Preparation and Upconversion Luminescence of Y3Al5O12 ： Yb^3＋ , Er^3＋ Trapsparent Ceramics

YAG： 1% （atom fraction） Yb^3＋ , 0.5% （atom fraction） Er3＋ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of ^2H11/2→^4I15/2, ^4S3/2→^4I15/2, and ^4F9/2→^4I15/2 of Er^3＋ ions, respectively.     

Fracture Behavior in Cu46.5Zr46.5Al7 and Cu46.5Zr41.5Al7Y5 Bulk Metallic Glasses

The interplay between chemical composition, plastic behavior, and fracture modes of Cu_46.5Zr_46.5Al₇ and Cu_46.5Zr_41.5Al₇Y₅ bulk metallic glasses (BMGs) was investigated by compression tests and fracture surfaces analyses. The aim was to explore the possibility of coupling physical, chemical, and hardness properties, with adequate macroscopic compressive plasticity. Cylindrical test samples, having a height-to-diameter ratio equal to 2, were machined and ground from as-cast bars and were tested in compression between lubricated plates, the displacement being measured by a clip-gage inserted between the plates. Y free BMG engineering stress-strain curves show a plastic behavior consisting of successive sudden stress drops and linear reloading segments. A detailed analysis of these features was performed to yield a correlation between the plastic deformation steps and the released elastic energy associated with each serration.     

Luminescence properties of a single-host phosphor Bal.8-wSrwLi0.4SiO4： cea＋,Eu2＋,Mn2＋ for WLED

In order to obtain a single-host-white-light phosphor,a series of Ba1.8-w-x-y-zSrwLi0.4-xCexEuyMnzSiO4(BSLS:Ce3+,Eu2+,Mn2+)powder samples were synthesized via high temperature solid-state reaction.The structure and photoluminescence properties were investigated.Under ultraviolet excitation,the emission spectra contained three bands:the 370-470 nm blue band,the 470-570 nm green band and the 570-700 nm red band,which arose from the 5d→4f transitions of Ce3+ and Eu2+,and the 4T1→6A1 transition of Mn2+,respectively.The excitation spectra of the emissions of Ce3+ and Mn2+ ions showed the energy transfer from Ce3+ to Mn2+.White light emission was obtained from the tri-doped samples of appropriate doping concentration under 310-360 nm excitation.     

原位自生 (Cr,Fe)7C3/Fe3Al复合材料组织结构及物相组成的研究

本文通过真空雾化方法制备原位自生(Cr,Fe)_7C_3/Fe_3Al粉末,采用显微硬度,SEM,TEM,XRD等分析方法对制品的成分,表面形貌,物相组成,及硬度等进行初步分析。研究结果表明,(Cr,Fe)_7C_3/Fe_3Al粉末硬度较Fe3Al粉末有明显提高,同时急速冷却状态下,Fe_3Al粉末与(Cr,Fe)_7C_3/Fe_3Al粉末中基体相皆由DO_3型有序相Fe_3Al组成,Cr以固溶方式存在于基体中。(Cr,Fe)_7C_3以类珠光体团簇状均匀弥散分布在基体之中,碳化物保持Cr_7C_3点阵类型,Fe原子固溶在其中。     

Magnetic Transition of La0.8Sr0.2Mn1-xCoxO3（x =0, 0.3, 0.5, 1.0）

A series of rare earth compound oxides with the formula of La0.8Sr0.2Mn1-xCoxO3（ were prepared by the method of citric acid. Structures, figures and magnetic properties of the x=0.0, 0.3, 0.5, 1.0） samples were analyzed by means of XRD, SEM and SQUID. Experiment results prove that all the samples are hexagonal, but their figures and magnetic properties are different. La0.8Sr0.2MnO3 is ferromagnetic. La0.8Sr0.2Mn0.7CO0.3O3 and La0.8Sr0.2Mn0.5Co0.5O3 are ferrimagnetic. La0.8Sr0.2CoO3 is antiferromagnetic. SEM results indicate that the structure of the first three are three-dimensional reticulations which are made up of some small ellipsoids which link up at the head and the end. The fourth sample looks like some dispersed small balls.