Fabrication of nano-sized grains by pulsed laser surface melting

In this work, the formation and characterization of nano-sized grains on the modified surfaces of GCr15 and H13 steels have been investigated. The material was processed by pulsed laser surface melting (LSM) under different depths of de-ionized water. The microstructures and phases of the melted zones were examined by x-ray diffraction, environmental field emission scanning electron microscopy and high resolution transmission electron microscopy. The results indicate that LSM under water can successfully fabricate nano-scaled grains on the surfaces of steel, due to the rapid solidification and crystallization by heterogeneous nucleation. The elemental segregation of chromium and activated heterogeneous nucleation mechanism of austenite in liquid metal play a key role in the formation of nano-sized grains at high cooling rates. This one-step technique provides us a new way to prepare uniform nano-scaled grains, and is of great importance for further understanding the growth of nano-materials under extreme conditions.

微生物法沥取重金属污泥中铬的研究

本文研究了两种微生物及其组合沥取、回收用微生物法治理电镀铬废水产生的铬污泥中的铬。铬污泥富含C、N、O，含铬量为13%， 经X-光电子能谱分析铬以三价态(氢氧化铬)存在。二种微生物分别从一酸性矿水和酸性污泥中分离筛选得到，经鉴定为硫杆菌属 (Thiobacillus Beijerinek)的两个不同种，一为氧化亚铁硫杆菌(Thiobacillu ferrooxidans, TF), 另一为氧化硫硫杆菌 (Thiobacillus thiooxidans, TT)。研究并比较了不同微生物对污泥中铬的沥取能力，结果表明，TT菌沥取铬效率最高。振荡、动 态淋滤、静置等沥取方式经过研究表明动态淋滤为最佳，室温条件下(15-20℃)，污泥浓度为20g/L时，总铬沥出率达60%时所需时 间：动态淋滤为48.5h，振荡和静置方式分别为91.22，81.6h。研究了不同温度、不同起始PH、不同污泥浓度及非成熟菌液对微生 物沥取能力的影响：(1) 沥取前期，温度对铬的沥出影响较大；微生物沥取反应基本属一级反应；温度与反应速率的关系基本符合 Arrhenius方程，但沥取后期这一特点并不突出。(2) 沥取液最适起始PH为菌液自然PH；PH值的人为改变将使铬的沥出大大降低。 (3) 污泥浓度与铬的沥出呈正相关，但浓度高于30g/L时，铬的沥出量不再增加。(4) 非成熟菌液沥出铬的能力较差，但沥取液中 微生物生长繁殖较为活跃。总结微生物沥取反应最佳沥取条件为：TT成熟菌液、污泥浓度10g/L、温度25-36℃、动态淋滤方式，此 时铬几乎可100%从污泥中沥出。经扫描电镜分析，沥取开始时，微生物紧密吸附于污泥颗粒表面上，表面紧密吸附为微生物发挥功 能提供了基础。微生物沥取污泥中铬的反应机理推测为：硫细菌代谢产硫酸或氧化Fe2+成Fe3+，利用酸，Fe3+ 及自身氧化酶系统 氧化污泥中Cr3+为Cr6+,Cr6+溶出结晶为CrO3。This paper has studied bioleaching and recovery of Chronium(Cr)from electroplating sludge by two consortum of bacteria and their combination, with sludge produced by microbiological process treating electroplating wastewater containing Cr as material. The share of Cr is 13% and its state is Cr (OH)3 in the sludge. One of the bacteria in the paper was isolated from acid sewage sludge and the other was from acid mineral water. The former was tested and determined as Thiobacillus ferroxidans(TF) and the latter was Thiobacillus thiooxidans(TT). Different microorganisms, responsible for the metal leaching activity, have great influence on the efficiency of leaching. The results showed that TT has biggest power. Experiments were conducted to examined effects of three different ways of leaching(Shaking, Down-leaching, Static-leaching). When temperature was in-door's (15-20℃)and concentration of the sludge was 20g/L, the bioleaching time required to reach 60% of Cr solubilization with the above three ways were 91.2, 48.5, 81.6h respectively. Down-leaching was proved to be the most efficient. The influence of different temperature, initial PH, concentration of the sludge and non-mature inoculum had been studied. The results obtained reveal that: (1) The variation of temperature is important during the time from initial to middle of leaching. The reaction of bioleaching belongs to first-order. The relation between the bioleaching rate constant(In k)and temerature can be expressed by Arrhenius function. (2) The fittest initial PH is the nature PH of mature inoculum. Any alteration with it could cause clearly negative effection. (3) The concentration of the sludge can make strong influence on the bioleaching efficiency. But when the concentration is above 30g/L, the increasing of Cr in the solution is little. (4) If non-mature inoculum acts as the bioleachin microorganism, little quantity of Cr would be gained from the sludge. But the micormass in the solution is very active. The results from electron microscope showed that microorganisms adhered to the surface of the sludge and the adherence was the first stage of the bioleaching. Some salts of Cr can be obtained afer the water of the bioleaching solution being evaporated. By analysing the results of experiment with X-Ray spectroscopy, the salt was identified as CrO3. The recovery rate of Cr is 78.4%.

制革废水生物强化处理及中水回用试验研究

制革行业是轻工行业中仅次于造纸业的高耗水、重污染行业，作为劳动密集型行业，在解决大量人口就业问题的同时，也对所在地区环境造成了严重污染。目前我国制革行业每年排放废水8,000~12,000万吨，废水中含铬约3,500 t，SS为1.2×105 t，COD为1.8×105 t，BOD为7×104 t，对水体污染严重。 本研究在对厌氧酸化工艺进行研究、一级好氧处理段进行工艺比选研究的基础上，获得了匀质调节—SBBR—BAF的生物处理工艺，并依托该工艺进行了生物强化处理的研究，考察了菌剂的强化运行效果及其处理水回用的可行性。 研究表明，在进水COD＞3,000 mg/L，厌氧酸化具有很好的抗冲击作用，保证了好氧工艺出水COD＜200 mg/L；在进水COD＜3,000 mg/L，可只通过好氧处理实现出水COD＜200 mg/L。厌氧酸化停留时间选择不当，会导致厌氧出水硫化物浓度升高，严重影响好氧系统，会使好氧活性污泥因中毒而解絮。 研究表明，当进水COD为2,000~2,500 mg/L，NH4+-N为130~146 mg/L时，COD、NH4+-N去除率SBBR分别为93.8%~96.6%和14.5%~55.9%，SBR分别为88.8%~94.9%和13%~50.7%，表明SBBR优于SBR。同时，研究发现SBBR污泥增长率为0.05 kgVSS/kgCOD，仅为SBR0.57 kgVSS/kgCOD的8.8%。此外，研究发现SBBR在停止运行后经3个运行周期可回复原油能力，而SBR池经9个周期培养也不能恢复，说明SBBR恢复能力明显优于SBR。 研究表明，以匀质调节—SBBR—BAF为主的制革废水处理工艺，出水水质稳定，进水COD 801~2,834 mg/L、NH4+-N 87~203 mg/L，出水COD＜80 mg/L、NH4+-N＜10 mg/L，基本达到中水回用标准；操作简单灵活，没有污泥回流系统，污泥产率低，污泥处理费用低；工艺基本不需要添加化学药剂，既节约成本、又避免了二次污染；两级生物膜使得该工艺具有很强的耐冲击负荷能力，特别适合制革废水水质水量波动大的特点。 研究表明，高效菌对系统的启动具有一定的促进作用，强化系统生物膜6天可以成熟，对照系统生物膜9天可以成熟。同时高效菌能加速COD降解，缩短停留时间，强化系统6~8 h可使COD＜200 mg/L，对照系统8~10 h可使COD＜200 mg/L。长期运行表明，强化系统的SBBR在COD和NH4+-N的去除率都优于对照系统的SBBR。最终出水COD强化系统平均为53 mg/L、对照系统为74 mg/L。在模拟循环过程中，强化系统均有更高的稳定性。可实现8次理论循环，而对照系统只能实现4次理论循环。 研究表明，通过合理的工艺设计，可以实现猪皮制革废水达到《污水综合排放标准GB8976-1996》一级标准，同时满足工厂部分用水要求。通过添加高效微生物，可提高生物处理系统处理能力，使处理水能够满足工厂的多次回用。 As a labour-intensive industry, tanning has created large amount of working opportunities as well as caused severe contamination to environment. And it is one of the highest water-consuming and polluting industry, only second to manufacturing. At present time, Chinese leather industry emits wastewater about 80,000,000~120,000,000 t annually, which contains chromium about 3,500 t, SS 1.2×105 t, COD 1.8×105 t, BOD 7×104 t and ambient riverhead has been polluted greatly. Based on the research of anaerobic acidification and comparison of SBBR and SBR, biotreatment process (Homogenization—SBBR—BAF) had been established to amend the disadvantages of traditional sewage treatment such as too much sludge, high cost of advanced treatment and NH4+-N can not reach the emission standard. Research on the bioaugmentation was also been carried out. Researches showed, when COD of influent was beyond 3,000 mg/L, anaerobic acidification could resist strong impact, thus COD of effluent was less than 200 mg/L; when COD of influent was less than 3,000 mg/L, only throughout aerobic sewage treatment could COD of effluent beless than 200 mg/L. False residence tiome of anaerobic acidification would lead to the higher effluent concentration of sulfide and disintegration of aerobic activated sludge. Researches showed SBBR worked a better than SBR: when influent between 2,000 and 2,500 mg/L, NH4+-N between 130 mg/L and 146 mg/L, COD, NH4+-N removal rate of SBBR was 93.3%~96.6%, 14.5%~55.9% respectively while COD, NH4+-N removal rate of SBR was 88.8%~94.9%, 13%~50.7% respectively. Sludge growth rate of SBBR was 8.8% of that of 0.05 kgVSS/kgCOD. Besides, SBBR could recovered after 3 operating periods while SBR worked no better after 9 operating periods.Therefore, SBBR excelled SBR. Researches showed, effluent quantity of tannery wastewater treatment process (Homogenization—SBBR—BAF) was stable. When COD of influent was between 801 and 2,834 mg/L, NH4+-N was between 87 mg/L and 203 mg/L, COD of effluent was less than 80 mg/L, NH4+-N was less than 10 mg/L, which achieved the standard of reuse. This biotreatment was featured in low cost, easy and flexible management, less sludge, no inverse sludge system. Besides, this technique required no chemical, which could lower the cost and avoid secondary pollution. Great resistant of impact due to two membranes and was suitable for tannery wastewater which was featured by fluctuation of influent quality and quantity. Researches showed effective microorganisms promotes the startup of the process.Biofilm in the bioaugmentation process matured with 6 days while biofilm in normal process matured with 9 days. Effective microorganisms could accelerate the degradation of COD and shorten the residence time. Aggrandizement system could make COD<200 mg/L with 6 to8 hours while cntrolling system could make COD<200 mg/L with 8 to 10 hours. Long-term operating shows that SBBR in the bioaugmentation system worked better than the normal system in the treatment of COD and NH4+-N. The average COC of effluent in bioaugmentation system was 53 mg/L, normal system was 74 mg/L. In the simulative circulation process,aggrandizement process, which could fulfill 8 times theoretical circulation, works more stably than controlling process which could only fulfill 4 times theoretical circulation. Researches showed that reasonable design could make the wastewater meet the first grade of discharging standard of National Integrated Wastewater Discharge Standard (GB8976-1996), and partially meet the demand of water using of the factory. Adding effective microorganisms could enhance the biotreatment and make the effluents reuse many times.

富铬酵母对实验性糖尿病小鼠模型的治疗

目的：三价铬作为葡萄糖耐量因子的有效活性成分，具有改善糖尿病人的糖代谢和脂代谢的作用，因此补充三价铬是糖尿病治疗中的有效的营养措施，富铬酵母是目前向人体提供三价铬的有效途径，并且葡萄糖耐量因子可以提高靶组织对胰岛素的敏感性而不促进胰腺的胰岛素分泌，为治疗糖尿病提供了一种新方法。 方法：（1）取昆明种小鼠，分对照与实验组，适应性喂养后实验组小鼠按40mg/kg体重注射STZ，对照组注射相应体积柠檬酸缓冲液,连续注射5天，3天后测血糖值，取血糖值≥11.1mmol/L为成功模型。成模小鼠分为两组，一组灌胃富铬酵母悬液4周，另一组灌胃蒸馏水4周，测血糖值。（2）取昆明种小鼠，分对照与实验组，适应性喂养后实验组小鼠按200mg/kg体重注射STZ，对照组注射相应体积柠檬酸缓冲液，3d后测血糖，取血糖值≥11.1mmol/L为成功模型。成模小鼠分为两组，一组灌胃富铬酵母悬液4周，另一组灌胃蒸馏水4周，测血糖值。（3）取C57BL/6J断乳小鼠，随机分为正常饲料组和高脂饲料组，分别用相应饲料喂养3 周。高脂饲料组又分为高脂饲料对照组和高脂饲料实验组。第3 周末, 高脂饲料实验组腹腔内按100mg/kg体重一次性腹腔注射STZ；正常饲料组和高脂饲料对照组腹腔注射相应体积的无菌柠檬酸缓冲液。继续喂养4 周。小鼠以第7周末血糖为准，≥11.1mmol/L为成功模型。成模小鼠分为2组，1组每日灌胃富铬酵母悬液，另一组灌服相应体积的去离子水，4周后，测血糖值。 结果：对Ⅰ型糖尿病小鼠，富铬酵母治疗2周后，治疗组血糖明显低于对照组血糖（p<0.05），4周后显著低于(p<0.01)；对Ⅱ型糖尿病小鼠，富铬酵母治疗2周后，治疗组血糖明显低于对照组血糖（p<0.05），3周后显著低于(p<0.01)；对肥胖引起的Ⅱ型糖尿病小鼠，富铬酵母治疗2周后，治疗组血糖显 著低于对照组血糖(p<0.01)，且血清胰岛素浓度之间没有明显差异。 结论：富铬酵母具有明显的降血糖作用，且不刺激胰岛素分泌

The Early Diagenetic Formation of Organic Sulfur in the Sediments of Mangrove Lake, Bermuda

Due to a low mineral content, the sapropelic sediments depositing in Mangrove Lake, Bermuda, provide an excellent opportunity to explore for possible additions of sulfur to organic matter during the early stages of diagenesis. We evaluated early diagenetic organic sulfur transformations by monitoring the concentrations and stable isotopic compositions of a number of inorganic and organic sulfur pools, thereby accounting for all of the sulfur in the sediments. We have identified and quantified the following sulfur pools: porewater sulfate, porewater sulfide, elemental sulfur, pyrite sulfur, hydrolyzable organic sulfur (HYOS), chromium-reducible organic sulfur (CROS), and nonchromium-reducible organic sulfur (Non-CROS). Of the organic sulfur pools, the Non-CROS pool is by far the largest, followed by CROS, and finally HYOS. By 60 cm depth these pools contribute, respectively, to 85, 7.9, and 3.6% of the total solid phase sulfur. The HYOS pool is probably of biological origin and shows no interaction with the sulfur compounds produced during diagenesis. By contrast, CROS is produced, most likely, from the diagenetic addition of polysulfides to functionalized lipids in the upper, H2S-poor, elemental sulfur-rich, region of the sediment. A portion of this sulfur pool is unstable and decomposes on contact with the H2S-rich porewaters. The portion of CROS that remains in the sulfidic waters appears to readily exchange sulfur isotopes with H2S. While some of the Non-CROS pool is of biological origin, some is also formed by the diagenetic addition of sulfur to organic compounds in the upper H2S-poor region of the sediment. By contrast with CROS, Non-CROS is not diagenetically active in the H2S-rich porewaters. Overall, somewhere between 27 and 53 % of the organic sulfur buried in Mangrove Lake sediments is of diagenetic origin, with the remaining organic sulfur derived from biosynthesis. We extrapolate our Mangrove Lake results and calculate that in typical coastal marine sediments between 11 and 29 μmol g−1 of organic sulfur will form during early diagenesis, of which 2–5 μmol g−1 will be chromium reducible.

Automated voltammetric system for shipboard determination of metal speciation in sea water

An automated and semi-intelligent voltammetric system is described for trace metal analysis. The system consists of a voltammeter interfaced with a personal computer, a sample changer, 2 peristaltic pumps, a motor burette and a hanging mercury drop electrode. The system carries out fully automatically approximately 5 metal determinations per hour (including at least 3 repetitive scans and calibration by standard addition) at trace levels encountered in clean sea water. The computer program decides what level of standard addition to use and evaluates the data prior to switching to the next sample. Alternatively, the system can be used to carry out complexing ligand titration with copper whilst recording the labile copper concentration; in this mode up to 8 full titrations are carried out per day. Depth profiles for chromium speciation in the Mediterranean Sea and a profile for copper complexing ligand concentrations in the North Atlantic Ocean measured on board-ship with the system are presented. The chromium speciation was determined using a new method to differentiate between Cr(III) and Cr(VI) utilizing adsorption of Cr(III) on silica particles.

不同土壤对Cr吸附的动力学特征

该文采用振荡平衡法比较了来自中国15个省区16种土壤对Cr(VI)的吸附及其动力学特性,并探讨了土壤pH值、阳离子交换量、黏粒含量和有机质对Cr(VI)吸附及其动力学参数的影响。结果表明:具有较低土壤pH值和较高物理黏粒含量的土壤对Cr(VI)具有较大的表观吸附量,而土壤阳离子交换量和有机质因素对土壤Cr(VI)的表观吸附量影响较小。酸性土壤对Cr(VI)吸附能力较强,可以采用一级动力学方程和抛物线方程描述Cr(VI)在酸性土壤中的动力学行为,且土壤的表观吸附速率和平衡时的吸附量与土壤的pH值呈显著(p<0.05)负相关关系,而与物理黏粒含量呈显著(p<0.01)正相关关系;而碱性土壤对Cr(VI)吸附能力较小,很难用动力学方程描述其吸附动力学特性。可见,土壤pH值不仅影响土壤对Cr(VI)的表观吸附量,并且对Cr(VI)表观吸附动力学特征产生了较大影响。

重金属对小麦根干重和在不同培肥条件下对土壤铵态氮的影响

笔者的研究目的在于了解土壤重金属污染对小麦根部生长发育的影响以及在不同培肥条件下土壤重金属的生物活性的变化情况。通过盆栽试验研究了重金属铬、镉和铅三种重金属对小麦根重的影响,利用室内培养试验研究了氮磷化肥、氮磷化肥+低秸、氮磷化肥+中秸、氮磷化肥+高秸、氮磷肥+厩肥、氮磷肥+低秸(休闲田)以及无肥对照区等7种不同培肥条件下重金属铬、镉和铅对土壤铵态氮含量的影响。研究结果表明,重金属铬对小麦的根重影响较大,这3种重金属的复合污染对小麦根重的影响要比单因素条件下的影响要明显;在不同肥料条件下重金属对土壤环境内的铵态氮的影响作用存在差异,氮磷肥料条件下,重金属对土壤铵态氮的抑制作用明显增强;氮磷+低秸(休闲田)条件下,重金属铬、镉与铅对土壤铵态氮的抑制性显著降低,铵态氮总量基本影响较小。通过研究表明,不同培肥条件能够影响土壤重金属的生物活性,可以通过控制土壤培肥条件达到降低土壤重金属生物活性,减轻对重金属污染土壤的程度。

Synthesis of N-Methylimidazolium Functionalized Strongly Basic Anion Exchange Resins for Adsorption of Cr(VI)

N-Methylimidazolium functionalized strongly basic anion exchange resins in the Cl- form (RCI) and SO46- form (R2SO4) were synthesized and employed for adsorption of Cr(VI) from aqueous solution. FT-IR and elementary analysis proved the structures of anion exchange resins and the content of functional groups. The gel-type strongly basic anion exchange resins had high thermal stability according to TGA and good chemical stability under the experimental conditions. The adsorption behaviors of Cr(VI) on RCI and R2SO4 were studied using the batch technique. It was shown that adsorption equilibrium was reached rapidly within 60 min. The adsorption data for RCI and R2SO4 were consistent with the Langmuir isotherm equation.

Removal of Cr(III, VI) by quaternary ammonium and quaternary phosphonium ionic liquids functionalized silica materials

A series of silica-based organic–inorganic hybrid materials were prepared by the sol–gel process for Cr(III) and Cr(VI) adsorption. These silica materials generally had high surface areas, good physical–chemical stability and high thermal stability. Trialkylmethylammonium bis 2,4,4-trimethylpentylphosphinate ([A336][C272]) and trihexyl(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL 104) were explored as porogens to prepare porous silica and as extractants to extract chromium ions. Cyphos IL 104 and [A336][C272] functionalized silica sorbents (SG-2, SG-5) can be effectively used for the removal of Cr(III) and Cr(VI) from aqueous solutions by adjusting pH values, whereas trialkylmethylammonium chloride (Aliquat 336) and bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) functionalized silica sorbents (SG-3, SG-4) can only be used for the removal of the single chromium species, Cr(VI) or Cr(III).

Combining chemical reduction with an electrochemical technique for the simultaneous detection of Cr(VI), Pb(II) and Cd(II)

This work herein reports the approach for the simultaneous determination of heavy metal ions including cadmium (Cd(II)), lead (Pb(II)), and chromium (Cr(VI)) using a bismuth film electrode (BFE) by anodic stripping voltammertry (ASV). The BFE used was plated in situ. Due to the reduction of Cr(VI) with H2O2 in the acid medium, on one hand, the Cr(III) was produced and Cr(VI) was indirectly detected by monitoring the content of Cr(III) using square-wave ASV. On the other hand, Pb(II) was also released from the complex between Pb(II) and Cr(VI). Furthermore, the coexistence of the Cd(II) was also simultaneously detected with Pb(II) and Cr(VI) in this system as a result of the formation of an alloy with Bi. The detection limits of this method were 1.39 ppb for Cd(II), 2.47 ppb for Pb(II) and 5.27 ppb for Cr(VI) with a preconcentration time of 120 s under optimal conditions (S/N = 3), respectively. Furthermore, the sensitivity of this method can be improved by controlling the deposition time or by using a cation-exchange polymer (such as Nafion) modified electrode.

Synthesis and Stabilization of Novel Aliphatic Polycarbonate from Renewable Resource

A novel aliphatic polycarbonate from renewable resource was prepared by copolymerization of furfuryl glycidyl ether and CO2 using rare earth ternary catalyst; its number-average molecular weight (M-n) reached 13.3 x 10(4) g/mol. The furfuryl glycidyl ether and CO2 copolymer (PFGEC) was easy to become yellowish at ambient atmosphere due to post polymerization cross-linking reaction oil the furan ring; the gel content was 17.2 wt % after 24 h exposure to air at room temperature. PFGEC could be stabilized by addition of antioxidant 1010 (tetrakis[methylene (3.5-di(tert-butyl)-4-hydroxhydrocinnamate)]methane) in 0.5-3 wt % after copolymerization. The Diels-Alder (DA) reaction between N-phenylmaleimide and the pendant furan ring was also effective for the stabilization of PFGEC by reducing the amount of furan ring and introducing bulky groups into PFGEC. The cyclization degree could reach 72.1% when the molar ratio of N-phenylmaleimide to furan ring was 3: 1, and no gel was observed after 24 h exposure to air. The glass transition temperature (T-g) of PFGEC was 6.8 degrees C, and it increased to 40.3 degrees C after DA reaction (molar ratio of N-phenylmaleimide to furan ring was 3: 1).

Direct synthesis of ordered N-methylimidazolium functionalized mesoporous silica as highly efficient anion exchanger of Cr(VI)

Ordered N-methylimidazolium functionalized mesoporous silica (SBA-15) anion exchangers were directly synthesized by co-condensation of tetraethoxysilane with 1-methyl-3(triethoxysilylpropyl)imidazolium chloride. The prepared samples with rod-like morphology showed high surface areas (> 400 m(2) g(-1)), well-ordered pores (> 58 angstrom), and excellent thermal stability up to 387 degrees C. The adsorption behaviors of Cr(VI) from aqueous solution on the anion exchangers were studied using the batch method. The anion exchangers had high adsorption capacity ranging from 50.8 to 90.5 mg g(-1), over a wider pH range (1-8) than amino functionalized mesoporous silica. The adsorption rate was fast, and the maximum adsorption was obtained at pH 4.6. The adsorption data for the anion exchangers were consistent with the Langmuir isotherm equation. Most active sites of the anion exchangers were easily accessible. The mixed solution of 0.1 mol L-1 NH3 center dot H2O and 0.5 mol L-1 NH4Cl was effective desorption solution, and 95% of Cr(VI) could be desorbed.

Magnetic and electronic properties of CaCu3Cr4O12 and CaCu3Cr2Sb2O12 by first-principles density functional calculation

The electronic and magnetic properties of CaCu3Cr4O12 and CaCu3Cr2Sb2O12 are investigated by the use of the full-potential linearized augumented plane wave (FPLAPW) method. The calculated results indicate that CaCu3- Cr4O12 is a ferrimagnetic and half-metallic compound, in good agreement with previous theoretical studies. CaCu3- Cr2Sb2O12 is a ferrimagnetic semiconductor with a small gap of 0.136 eV. In both compounds, because Cr4+ 3d (d(2)) and Cr3+ 3d (d(3)) orbitals are less than half filled, the coupling between Cr-Cu is antiferromagnetic, whereas that between Cu-Cu and Cr-Cr is ferromagnetic. The total net spin moment is 5.0 and 3.0 mu(B) for CaCu3Cr4O12 and CaCu3Cr2Sb2O12, respectively. In CaCu3Cr4O12, the 3d electrons of Cr4+ are delocalized, which strengthens the Cr-Cr ferromagnetic coupling. For CaCu3Cr2Sb2O12, the doping of nonmagnetic ion Sb5+ reduces the Cr-Cr ferromagnetic coupling, and the half-filled Cr3+ t(2g) (t(2g)(3)) makes the chromium 3d electrons localized. In addition, the ordering arrangement of the octahedral chromium and antimony ions also prevents the delocalization of electrons. Hence, CaCu3Cr2Sb2O12 shows insulating behavior, in agreement with the experimental observation.

Synthesis, luminescence and magnetic properties of YGa3-xCrxB4O12

The synthesis temperature of YGa3B4O12 and the effect of the synthesis temperature and chromium doping on the luminescence properties were studied. YGa3-xCrxB4O12 were synthesized and their magnetic properties were described. Results show that the fluorescence intensity increases with the increasing of synthesis temperature. The structure of compounds was stabilized, and their emission spectra were changed when small quantity of chromium was doped in. The magnetic susceptibilities increase with the increasing of Cr3+ concentration.