Anodic Oxidation of Both Particulate and Compact Iron in Chloride-Containing Acetate Buffer Electrolytes

The voltammetric records of Fe powder and compact iron electrode in chloride-free and chloride-containing acetate buffer electrolytes of various pH values were compared in the range 4.0 to 6.0. Owing to the consumption of the powder, the voltammetric current at the powder electrode decreases nearly to zero. Full passivation of the iron surface was observed in the absence of chloride on both electrodes. The differences become clear in chloride-containing electrolytes: with the compact electrode, the dissolution proceeds continuously while with the powder electrode the rate of the process is limited by both the degree of iron conversion and potential applied. Chloride ions not only incorporate into the intermediate species but also form soluble species in the passivation layer, leading to its degradation. The result is an observable anodic dissolution reaction of further Fe powder. The composition of the layer differs in dependence on pH. At lower pH, dissolution proceeds faster and to a larger extent. At higher pH, the thickness of the passive layer is larger and it contains more Fe hydroxides/oxides with higher resistance to the action of chloride. Scanning electron microscopy confirmed deep breakdown of the crystal structure of Fe grains.     

Voltammetric Investigation of the Oxidation of Iron Powder

Voltammetry measurements were performed on iron powder particles of various size fractions immobilized on the surface of a paraffin-impregnated graphite electrode in electrolytes of various pH values. The course of voltammetric curves implies that the start of the dissolution process is shifted negatively with increasing pH value and the anodic dissolution process of iron is inhibited due to adsorption of products of the electrode reaction on iron particle surfaces. The rate of dissolution is changed also with iron particle size: decreasing dissolution rate and appearance of inhibition were encountered with an increase in particle size. A mechanism was suggested taking into account the influence of both pH of the electrolyte and particle size fraction. Electrochemical dissolution of freshly reduced iron from the solution proceeds at a lower potential than the same process of iron powder immobilized on the electrode.     

A Study of Factors Affecting Reduction of 2,4,6-Trinitrophenol by Particulate Iron

A study on the effect of the type and composition of the Britton-Robinson and acetate buffers on the reduction process of 2,4,6-trinitrophenol by iron particles was performed and the data were interpreted in terms of a first-order kinetics model. The experimental results showed a decrease in pH value enhanced the removal of 2,4,6-trinitrophenol in both buffer solutions. The composition of the surface layer formed at the iron surface is pH dependent. In solutions with higher values of pH (towards pH 7) the surface of iron particles is covered by less soluble phosphate or hydroxide and/or oxide complexes forming a thick passive layer which inhibits the reduction process studied. Towards lower pH values the adsorbed layer of complexes weakens and thus enables to proceed the reduction of 2,4,6-trinitrophenol faster.     

乙酸乙酯作潜伏性酸对铁黄表面改性处理的研究

为了改善铁黄颜料的耐热性,运用乙酸乙酯作为潜伏性酸试剂,研究了一种新的铁黄表面均匀包覆二氧化硅的方法,即通过控制乙酸乙酯的水解速率来实现在铁黄表面均匀包覆二氧化硅。对表面均匀包覆二氧化硅后的铁黄颜料的颜色变化、分散稳定性、吸油量进行了表征。结果表明,均匀包覆二氧化硅可有效改善铁黄颜料的综合性能。     

羰基铁粉抗氧化性能研究现状

羰基铁粉具有高磁导率和高磁损耗等优良特性,被认为是薄层吸波涂层吸收剂的理想材料。加之,羰基铁粉的居里温度较高,有望成为薄层耐温吸波涂层的吸收剂。但是,羰基铁粉由于颗粒尺寸较小,颗粒表面积较大,在高温下的抗氧化性较差,近年来有关其抗氧化性能的研究已成为备受关注的热点。本文概述了羰基铁粉吸收电磁波的机制以及提高抗氧化性能的机理,介绍了几种有助于提高其抗氧化性能的制备方法,最后展望了这一领域的研究前景。     

镀银羰基铁粉的制备及其性能的研究

用化学镀法,甲醛为还原剂,制备镀银羰基铁粉.用XRD,SEM和EDX对粉体进行表征.用重法测定粉体的抗氧化性能,并以镀银羰基铁粉制备电磁屏蔽材料,检测其在100kHz～1.5GHz的屏蔽效能.结果表明:用该法制备的镀银羰基铁粉能够实现表面银层包覆完整、致密;羰基铁粉镀银后的抗氧化性能得到明显提高;电磁屏蔽材料在100kHz～1.5GHz频率范围内获得优于-32dB的屏蔽效能.     

铸铁热浸渗铝及其抗高温氧化性能研究

为了研究热浸温度、时间及硅含量对HT200热浸渗铝的影响, 用称重法分析了未镀、浸镀和浸镀加扩散退火处理铸铁的高温抗氧化能力, 用金相显微镜和XRD分析了渗层组织结构.结果表明:镀层厚度随温度升高和时间延长而增大,本试验中浸镀温度740～810 ℃,浸镀时间5～10 min较佳.硅抑制渗层的生长,当镀液硅含量为2%,6%和9%时,镀层厚度分别为384,200 μm和121 μm.渗层结构由外镀层和中间扩散层(以Fe3Al为主)组成,经扩散退火后,渗层主要为Fe2Al5相.浸铝和浸铝且扩散退火处理后的铸铁抗氧化能力提高2～8倍, 耐蚀性显著改善.     

研磨介质对片状羰基铁结构及电磁性能的影响

分别以直径为6、1.5 mm的ZrO2磨球作为搅拌磨研磨介质制备片状羰基铁,对比研究这两种磨球对制备片状羰基铁的结构及电磁性能的影响。结果表明:采用直径为6 mm的ZrO2磨球所制备的羰基铁粉颗粒具有片状结构;而采用直径为1.5 mm的ZrO2磨球制备的羰基铁粉颗粒形状不规则,表面粗糙。研磨24 h时,采用直径为6 mm的ZrO2磨球所制备片状羰基铁粉微波吸收材料在2~18 GHz频段的反射率超过-15 dB的带宽为5 GHz,最大反射率为-30 dB。     

钡镁锰矿合成及在水溶液中电化学性质研究

合成了一种二氧化锰电池正极材料．用改进的碱性条件下合成晶型良好的纳米δ－ＭｎＯ_２,合成出了含 Ｍｇ^２＋的钡镁锰矿（Ｔｏｄｏｒｏｋｉｔｅ）,经 ＸＲＤ、 ＴＥＭ测试表明其为粒度均匀的纳米大隧道（３×３）ＭｎＯ_２,并在碱性和中性电液中对样品进行恒流放电,循环伏安等电化学性能测试,结果表明循环稳定性良好。     

钡镁锰矿合成及在水溶液中电化学性质研究

合成了一种二氧化锰电池正极材料.用改进的碱性条件下合成晶型良好的纳米δ     

球墨铸铁微弧氧化陶瓷层扩散退火前后的组织状态

过去,对铸铁件热浸镀铝再微弧氧化仅有少量的研究,且还存在残留铝影响氧化层性能的问题。为此,对球墨铸铁先热浸镀铝后再微弧氧化形成陶瓷层,采用扫描电镜、能谱分析和X射线衍射分析了陶瓷层的相组成及形貌,并探讨了对陶瓷层进行扩散退火处理的可行性。结果表明:球墨铸铁浸镀铝后微弧氧化获得的陶瓷层主要由α-Al2O3相和γ-Al2O3相组成;600℃扩散退火时,因陶瓷层与纯铝层之间热膨胀系数不匹配会导致界面处产生热应力,造成陶瓷层与纯铝层的界面处出现明显孔洞;球墨铸件微弧氧化形成的陶瓷层不适合扩散退火处理;对微弧氧化后,热浸镀铝层剩下多少为佳及处理的问题,应进一步研究。     

阳极溶出伏安法测定海洋沉积物中的铅和镉

海洋沉积物经硝酸-高氯酸-硝酸消解后,以高氯酸做支持电解质,采用阳极溶出伏安法的标准加入法,连续测定海洋沉积物中的铅和镉时,铅和镉的半波电位稳定,峰形对称。方法的重复性好、准确度高,可以作为一种测定海洋沉积物中铅和镉含量的使用方法。     

琼脂糖醋酸酯纳米粒子的制备及药物缓释性

通过纳米沉淀法制备了一种粒径均一的琼脂糖醋酸酯纳米粒子,并对影响粒径的相关因素进行了研究。结果表明,纳米粒子分别随着二甲基亚砜(DMSO)与水的比率、姜黄素含量及琼脂糖醋酸酯(AA)的浓度的增加而增大,随转速的增加而下降,异丙醇和聚乙烯醇(PVA)浓度也有一定的影响。同时研究了载体对姜黄素的包载情况及缓释行为。结果显示,无异丙醇组中姜黄素载药率和包封率均比异丙醇组中的高。但两组都表明,随着姜黄素的含量增加,载药粒子的载药率不断增加,包封率不断降低。载药粒子大大延长了姜黄素的缓释时间。获得的琼脂糖醋酸酯纳米粒子可望用于姜黄素的控释。     

智能制造系统AGV小车及缓冲区容量仿真优化

具有MHS(material handling system)的智能制造系统AGV(automated guided vehicle)小车及缓冲区最大容量配置优化,属于典型的非线性整数规划问题。由于约束无法用封闭形式表达,因此较难获得问题的精确解。为此,本文提出了仿真优化的方法以获得问题的近似解。首先,对AGV小车及缓冲区最大容量配置优化问题进行了描述;其次,基于Em plant平台建立了具有MHS的智能制造系统仿真模型;然后,基于不同的优化目标,提出了3种仿真优化方法;最后,通过仿真试验对上述3种方法进行了分析与比较。分析表明,本文提出的方法及优化结果,可为企业配置AGV小车及缓冲区最大容量提供决策支持。     

白酒中乙酸乙酯内标法与外标法的比较

用气相色谱法测定清香型白酒中重要特征指标乙酸乙酯的两种定量方法：内标法和外标法,并采用两种方法对白酒样品进行测定。结果表明,内标法和外标法对清香型白酒中乙酸乙酯的测定无显著性差异,因此可以把外标法推广到平常的清香型白酒的检测工作中,简化了操作步骤,满足现代快速分析的需求。     

气相色谱法测定茶多酚中的氯仿和乙酸乙酯残留

以正已烷为萃取剂,对茶多酚(TP)水溶液进行萃取,用气相色谱法分析了TP溶液中的残迹物氯仿和乙酸乙酯。色谱柱为2m×3mmi.d.不锈钢填充柱,固定相为10%的PEG20M,载体为ChromosorbW/WA。氯仿和乙酸乙酯的回收率分别为96.7%～104.3%和98.5%～103.6%;相对标准偏差分别为3.5%和1.7%;最低检测限分别为0.50ug/和0.36ug/g。     

乙酸纤维素稀溶液粘数和粘度比的测定研究

本文研究乙酸纤维素稀溶液粘数和粘度比的测定方法。确定等同采用ＩＳＯ－１１５７：１９９０（Ｅ）作为我国化工行业标准。     

原子层沉积氧化铝包覆羰基铁粉的抗腐蚀性及吸波性能

为了提高羰基铁粉的抗腐蚀能力及改善其电磁性能, 以TMA和H₂O为前驱体, 利用原子层沉积(ALD)方法对羰基铁粉进行表面包覆改性, 在羰基铁粉表面包覆不同厚度的氧化铝。通过扫描电镜(SEM)、透射电镜(TEM)、综合热分析仪(TGA)、红外光谱(FTIR)和矢量网络分析仪等技术手段系统分析了改性前后羰基铁粉性能指标。结果表明, 通过ALD方法可在羰基铁粉表面生长纳米级别具有良好保型的氧化铝薄膜, 形成了极佳的羰基铁/氧化铝壳层结构复合材料。与原样品相比, 包覆改性后的羰基铁粉热稳定性与抗腐蚀性有极大的提高, 且随着包覆厚度的增加, 抗氧化能力增强, 最大抗氧化温度可超过550℃。同时羰基铁粉包覆氧化铝后, 其介电常数明显减小, 磁导率变化相对较小, 改善了原羰基铁粉的电磁参数与吸波性能。     

碳纤维/羰基铁粉复合涂层吸波效果及机理分析

在碳纤维表面化学镀镍,再将其与羰基铁粉混合制备成吸波涂层,对其吸波性能进行了测试.结果表明:在2～18 GHz内,碳纤维/羰基铁粉吸波涂层,最大吸收峰在5.92 GHz,此时反射率为-8.89 dB,反射率小于-5.00 dB的频宽为9.50 GHz;单层羰基铁粉涂层在相同厚度下,最大吸收峰为7.94 GHz,对应的反射率为-10.36 dB,反射率小于-5.00 dB的频宽为6.90 GHz;碳纤维与羰基铁粉混合后,涂层反射率小于-5.00 dB的频宽增大,有利于吸收雷达波.最后,对碳纤维/羰基铁粉吸波涂层的吸波机理进行了初步分析.     

Role of Soil and Foliar-Applied Carbon Dots in Plant Iron Biofortification and Cadmium Mitigation by Triggering Opposite Iron Signaling in Roots

In China, iron (Fe) availability is low in most soils but cadmium (Cd) generally exceeds regulatory soil pollution limits. Thus, biofortification of Fe along with mitigation of Cd in edible plant parts is important for human nutrition and health. Carbon dots (CDs) are considered as potential nanomaterials for agricultural applications. Here, Salvia miltiorrhiza-derived CDs are an efficient modulator of Fe, manganese (Mn), zinc (Zn), and Cd accumulation in plants. CDs irrigation (1 mg mL⁻¹, performed every week starting at the jointing stage for 12 weeks) increased Fe content by 18% but mitigated Cd accumulation by 20% in wheat grains. This finding was associated with the Fe³⁺-mobilizing properties of CDs from the soil and root cell wall, as well as endocytosis-dependent internalization in roots. The resulting excess Fe signaling mitigated Cd uptake via inhibiting TaNRAMP5 expression. Foliar spraying of CDs enhanced Fe (44%), Mn (30%), and Zn (19%) content with an unchanged Cd accumulation in wheat grains. This result is attributed to CDs-enhanced light signaling, which triggered shoot-to-root Fe deficiency response. This study not only reveals the molecular mechanism underlying CDs modulation of Fe signaling in plants but also provides useful strategies for concurrent Fe biofortification and Cd mitigation in plant-based foods.