镍铝水滑石的合成及其剥离表征

通过控制变量如镍铝摩尔比、镍铝与尿素的摩尔比、反应时间、反应温度,利用尿素法合成了一系列镍铝水滑石,旨在找到适合于剥片的水滑石;并且研究了剥离后水滑石的形态和光学特性。借助XRD和SEM分析发现,在n(Ni)∶n(Al)∶n(尿素)=3∶1∶9、反应温度为180℃、反应时间为24 h时,能得到规整度最好、粒径最大的水滑石样品。同时对在该反应条件下得到的样品进行振荡剥离,用AFM表征其剥离厚度为1.5~4.0 nm、粒径约为20 nm;同时,利用UV-Vis测定剥离胶体样品的光学特性,发现胶体质量浓度与吸光度之间符合线性规律。     

硝酸盐溶液浓度对镁铝水滑石结构记忆效应的影响

用共沉淀法制备了镁铝水滑石,并进行XRD、N₂吸附-脱附、TG-DTA和FT-IR等表征。结果表明,制备的镁铝水滑石呈六方晶型,比表面积为121 m²·g^-1。研究了硝酸盐溶液浓度对水滑石结构记忆性的影响,发现400 ℃焙烧5 h的镁铝水滑石在硝酸铜和硝酸铁溶液中浸泡可以恢复水滑石结构,溶液浓度越低越容易恢复,同时NO₃^-插入水滑石的层间可以形成一种新型应用功能材料。     

镁铝水滑石的水热合成及表征

用一步水热法制得的氢氧化镁作为镁源,采用高过饱和共沉淀水热法制备镁铝水滑石。考察了水热温度、水热时间、氢氧化镁合成条件、晶种等条件对合成水滑石的晶体结构、尺寸、形貌及比表面积的影响。结果表明：采用水热温度为150 ℃、水热时间为3 h合成的氢氧化镁作为原料时,在水热温度为190 ℃、水热时间为12 h条件下制得水滑石的比表面积最小,形貌和结构规整;原料氯化镁中三氧化二硼杂质质量分数为0.020%时,会促进水滑石晶粒径向尺寸和厚度的增加;添加晶种会明显减小水滑石的比表面积,最佳添加量为0.5%（质量分数）。在以上最佳条件下,最终制得水滑石的比表面积达到10.33 m ²/g,水合粒径为878 nm。     

新型镍锡铝水滑石的合成及还原性能

通过改变Ni/Sn和(Ni十Sny)/Al的摩尔比,采用共沉淀法成功合成了新型NiSnAl水滑石0ayered double hydroxides,LDHs).当n(Ni)/n(Sn)≥16和n[(Ni+Sn)]/n(Al)=2～5时可制备纯水滑石相材料.当n(Ni)n/(Sn)≤12时,合成样品中除存在水滑石相外,还伴随有SnO杂相.合成的Ni20SnAl7-LDHs样品形貌呈六边形,其尺寸约为80 nm,并且分散性良好.热重-差热分析显示:在Ni3Al-LDHs基础上添加Sn,其热稳定性变差:随着n[(Ni+Sn)]/n(Al)增大,水滑石层板羟基及层间碳酸根的热分解温度降低.H2程序升温还原分析表明:样品还原过程包含2个阶段,低温还原峰对应于Ni/Sn从水滑石层板中直接还原,高温还原峰则为Ni/Sn从氧化物NiSnAl(O)中还原.并且Sn含量越高,Al含量越低,NiSnAl-LDHs样品越容易被还原.     

活性炭复合镁铝水滑石的制备及表征

利用共沉淀法原位制备活性炭复合镁铝水滑石,考察活性炭和水滑石不同比例对电化学性能的影响,并对产物进行了XRD表征。结果表明:XRD表征图谱中,样品有水滑石的特征衍射峰,说明原位合成法得到的样品具有较好的晶型。电化学测试表明,不同比例的样品其电容性能不同,活性炭与水滑石比例为1∶10时,所得样品的电容量相对较高。     

镁铝及镁锌铝水滑石的合成与表征

采用共沉淀法合成镁铝及镁锌铝水滑石,并通过X射线衍射（XRD）、红外光谱（FT-IR）、扫描电镜（SEM）、热分析（TG/DTG）、粒度分析等手段对合成的水滑石进行表征,研究不同镁、铝、锌的投料比例对合成的水滑石结构及热性能等的影响。XRD表征结果表明,合成产物均具有水滑石特征峰。合成的镁铝水滑石随着镁铝比的增加其层板间距增大,层板上原子密度降低;合成的镁锌铝水滑石随着锌含量的提高层板间距减小,层板上原子密度降低。镁铝水滑石热分解过程有两个明显阶段,层间结晶水先脱除,随后是层间阴离子脱除及层板上部分羟基脱水;镁锌铝水滑石热分解过程只有一个明显的阶段,层板间阴离子在层板间结晶水脱除的同时也在脱除。     

镍铬水滑石的制备与表征

以镍、铬的水合硝酸盐及尿素为主要原料,采用水热法合成了具有片层状结构的镍铬水滑石。考察了镍铬摩尔比、尿素摩尔比、溶剂种类、反应时间以及反应温度对材料制备结果的影响,并利用XRD、SEM、FT-IR、TG-DSC等手段对其进行表征。结果表明,当n(Ni2+)∶n(Cr3+)为2∶1、n(NO3-)∶n(Ur)为1∶5、50%乙醇/水作为溶剂并在150℃恒温环境下晶化96 h时,能够得到结晶度较高的片层状镍铬类水滑石。     

磁性纳米镁铝水滑石的合成研究

利用共沉淀法合成出磁性纳米镁铝水滑石，并借助于XRD，TEM，振动样品磁强计等手段研究了铁（Ⅱ）／镁摩尔比对水滑石结构和磁学性能的影响。这为层状材料与磁性基质进行复合制备新型功能材料提供了实验依据。     

锌铝水滑石的控制合成及吸附性能研究

采用简单的水热法和均匀共沉淀法合成了不同形貌的锌铝水滑石（Zn Al-LDHs）,通过XRD、SEM、N2吸附等对合成的试样进行了表征;研究了甲基橙在Zn Al-LDHs上的吸附性能,考察了酸碱度和温度等对其吸附性能的影响。结果表明：采用水热法,添加乙二醇可合成出海胆状Zn Al-LDHs,添加乙醇可合成出花状Zn Al-LDHs;采用均匀共沉淀法可合成出片状Zn Al-LDHs。其中海胆状Zn Al-LDHs的比表面积最高,达147.3 m2/g,对甲基橙具有优异的吸附性能。在25℃,初始p H=3的条件下,0.2 g/L海胆状Zn Al-LDHs对100 mg/L甲基橙的吸附容量和去除率分别达368 mg/g和73.65%,其吸附动力学和吸附等温线分别符合准二级速率方程和Langmuir方程。     

钙铝类水滑石结构与组成研究

钙铝类水滑石是一种典型层状复合金属氢氧化物,被广泛用作PVC材料的热稳定剂、建筑材料、水污染处理等领域。文章通过晶体化学理论建立Ca/Al-LDHs微观结构模型与静电作用模型,运用几何函数与晶格能Kapustinskii方程,对钙铝类水滑石的结构与热稳定性做出参数量化估算。研究结果表明,该组模型可以用于钙铝类水滑石的结构与性能的简单预测与比较,同时也能为研究新型插层Ca/Al-LDHs材料提供较有价值的参考。     

阳离子掺杂水滑石的制备和表征

采用一种全新的方法成功制备了阳离子掺杂的水滑石催化剂,掺杂的阳离子有Zn2+、Cr3+、La3+、Cu2+、Na+.用XRD、SEM等手段对催化剂进行了结构分析.     

尿素分解水热合成Ni-Al类水滑石的研究

采用尿素分解水热合成Ni-Al类水滑石,其中使Ni2 /Al3 /尿素的摩尔比为2:1:10和3:1:10.用XRD、SEM、TG检测,结果表明,合成出的类水滑石结晶度高,具有规整的片状晶体形貌,延长反应时间和提高反应温度有利于提高类水滑石的结晶度和颗粒的分散性.     

碳酸根型镁铝复合氢氧化物的合成和表征及其催化性能

以恒定pH值共沉淀法合成碳酸根型镁铝水滑石,用XRD、IR、TG-DTA和SEM等手段进行表征。XRD衍射表明，Mg与Al物质的量比为1∶1、3∶1、4∶1和6∶1的合成物均有水滑石结构。热重-差热分析(TG-DTA)显示，水滑石有两个吸热峰值:第一吸收峰值在200～250 ℃, 第二吸热峰值在400～450 ℃,最大损失重量在2780%～33.41%。SEM分析可知，样品呈层状、棒状、针状和蜂窝状等结构。并对镁铝复合氢氧化物作为催化剂用于生物柴油制备作了研究。结果表明，Mg与Al物质的量比为3∶1的水滑石可使甲酯收率达到90%左右，且可重复使用。产品达到德国生物柴油质量标准。     

Synthesis and characterization of Cu–Co–Fe hydrotalcites and their calcined products

A series of new Cu–Co–Fe compounds with the general formula Cu _x Co_2−x Fe₁HT (x = 0, 0.5, 1, 1.5 and 2) has been prepared by hydrotalcite coprecipitation method. The presence of hydrotalcite phase is revealed by XRD analysis for x values of 0, 0.5 and 1. When the copper quantity is higher than 1, the malachite phase is preferentially formed. These results are confirmed by TG-DTA, FT-IR and XPS analysis. After calcination at 500 °C in air of all samples, XRD analysis reveals the presence of spinel phases such as Co₃O₄, CoFe₂O₄, CuFe₂O₄, Cu _x Co _y O₄ in the solids, monoclinic CuO phase when the copper content is greater or equal to 1 and haematite phase for the sample where x is equal to 2. The presence of these phases is also confirmed by XPS results. For comparison, a Co₂Fe₁OH sample has been synthesized by classical coprecipitation method and although Co₂Fe₁HT sample and Co₂Fe₁OH form a similar phase after calcination at 500 °C, Co₂Fe₁HT500 presents a higher BET value than Co₂Fe₁OH500 sample.     

Review on the temperature memory effect in shape memory alloys

Shape memory alloys (SMAs) are well known for their unique shape memory effect (SME) and superelasticity (SE) behavior. The SME and SE have been extensively investigated in past decades due to their potential use in many applications, especially for smart materials. The unique effects of the SME and SE originate from martensitic transformation and its reverse transformation. Apart from the SME and SE, SMAs also exhibit a unique property of memorizing the point of interruption of martensite to parent phase transformation. If a reverse transformation of a SMA is arrested at a temperature between reverse transformation start temperature (A _s) and reverse transformation finish temperature (A _f), a kinetic stop will appear in the next complete transformation cycle. The kinetic stop temperature is a ‘memory’ of the previous arrested temperature. This unique phenomenon in SMAs is called temperature memory effect (TME). The TME can be wiped out by heating the SMAs to a temperature higher than A _f. The TME is a specific characteristic of the SMAs, which can be observed in TiNi-based and Cu-based alloys. TME can also occur in the R-phase transformation. However, the TME in the R-phase transformation is much weaker than that in the martensite to parent transformation. The decrease of elastic energy after incomplete cycle on heating procedure and the motion of domain walls have significant contributions to the TME. In this paper, the TME in the TiNi-based and Cu-based alloys including wires, slabs and films is characterized by electronic-resistance, elongation and DSC methods. The mechanism of the TME is discussed.     

Through air drying of paper—the effect of dryer fabric

A custom experimental apparatus is designed to perform through air drying under well-controlled drying conditions such as air temperature and mass-flowrate. Using a novel optical measurement technique, the spatial distribution of moisture content in paper during through air drying is quantified as a function of time. The technique is capable of measuring the moisture content distribution with high spatiotemporal resolution while air flows through a paper mat sitting on a permeable dryer fabric. Four commercially available fabrics with different structural design and properties are used in the investigations. The effect of the fabrics’ structural properties, which are characterized using optical coherence tomography (OCT), is studied under various drying conditions. It is shown that the geometry of the contact spots of the fabrics has a significant impact on the drying time at high drying intensities. However, at low rates of drying (i.e., low air temperature and flowrate), no correlation between drying time and fabric properties is observed. After a cycle of through air drying, the permeability of paper increases irreversibly. This increased permeability is observed to be a function of the fabric structure. It is shown that the increase in permeability is larger for coarse fabric structures although no monotonic correlation with the fabric permeability can be observed. Comparing the spatial maps of moisture content with the paper grammage distribution reveals that there is a correlation between the local grammage and the spatial pattern of drying in a paper sheet.     

超声对织物清洗效果的实验研究

通过实验,探讨了超声波频率、强度、清洗时间、清洗温度及清洗液对清洗效率的影响,得出了当超声清洗时间小于30min、超声频率较低、超声强度为0.25W/cm2,清洗液温度较高时,超声清洗效率较高;清洗液的种类对超声清洗影响较大;超声清洗对不同污渍、不同织物的清洗效果不同,对沾有污泥的纯棉布具有较佳的清洗效果.     

Cu掺杂的Mg-Al类水滑石的制备、表征及其催化性能

采用浸渍法制备了Cu掺杂的镁铝水滑石类化合物Cu/HT,经过400 ℃焙烧得到Cu掺杂的镁铝复合金属氧化物Cu/ Mg-Al LDO,利用X射线衍射（XRD）、扫描电镜（SEM）、热重分析（TG）、N₂吸附-脱附等技术对催化剂的结构进行了表征。研究了其对尿素与1,2-丙二醇合成碳酸丙烯酯的催化性能。考察了Cu掺杂量、镁铝比、不同催化剂载体等催化剂制备条件对催化剂活性的影响,同时考察了催化剂的再生性能。结果表明,当Cu掺杂量为1%、镁铝比摩尔为3∶1时的Cu/Mg-Al LDO（3）对尿素与1,2-丙二醇合成碳酸丙烯酯具有比较好的催化活性,在170 ℃、1,2-丙二醇与尿素的摩尔比为4∶1、催化剂用量为原料总质量的1%、反应3 h时,碳酸丙烯酯的收率达到96.1%,且催化剂经4次再生重复使用,催化活性稳定。     

镁铝水滑石结构记忆性及其应用研究

用共沉淀法合成了镁铝水滑石,对其结构记忆性进行了研究,并将这一特性应用于乙醇-水体系中水的脱除。结果表明,水滑石在400-700℃焙烧形成的复合氧化物LDO能在水中重新恢复原来的层状结构,当焙烧温度升高到800℃时,镁铝水滑石结构记忆性消失。经过2次重复焙烧一水合后,LDO重构时结合水的能力几乎不再发生变化。将镁铝水滑石的结构记忆性应用于乙醇溶液脱水,发现在w（H2O）=12％的乙醇溶液中,焙烧后的LDO能重新恢复层状结构,此时LDO对乙醇溶液的脱水效率为36．1％,比5A分子筛高4．3％。在w（H2O）=7％的乙醇溶液中,LDO没有发生重新水合,此时LDO对乙醇溶液的脱水效果与5A分子筛相当,脱水效率为23．5％。