钾霞石酸解-水热晶化纳米高岭石EI北大核心CSCD

采用水热碱法制得纯相六方钾霞石(KAlSiO_4),在H_2SO_4-H_2O溶液中破坏其晶体结构,K_2O溶出率达99.8%,固相产物Si/Al摩尔比≈1,用作合成高岭石(Al_2[Si_2O_5](OH)_4)的前驱体。采用OLIAnalyzer 9.2软件对Al_2O_3·2SiO_2·nH_2O-HCl-H_2O体系进行化学平衡计算,预测了水热法合成高岭石的初始HCl浓度、水/固质量比和晶化温度范围,以及平衡固相中高岭石的含量(>98%)。在此基础上通过单因素实验,确定了水热合成高岭石的优化条件和晶化历程。典型合成产物接近纯相纳米高岭石(~91.8%),结构高度有序,1Tc多型;晶体形态呈似六方片状,片径400~500 nm,厚度约20 nm。高岭石的晶化反应历程确定为:铝硅前驱体→板状勃姆石→板状勃姆石+片状高岭石→似六方片状高岭石。     

钾霞石酸解-水热晶化纳米高岭石

采用水热碱法制得纯相六方钾霞石(KAlSiO_4),在H_2SO_4-H_2O溶液中破坏其晶体结构,K_2O溶出率达99.8%,固相产物Si/Al摩尔比≈1,用作合成高岭石(Al_2[Si_2O_5](OH)_4)的前驱体。采用OLIAnalyzer 9.2软件对Al_2O_3·2SiO_2·nH_2O-HCl-H_2O体系进行化学平衡计算,预测了水热法合成高岭石的初始HCl浓度、水/固质量比和晶化温度范围,以及平衡固相中高岭石的含量(98%)。在此基础上通过单因素实验,确定了水热合成高岭石的优化条件和晶化历程。典型合成产物接近纯相纳米高岭石(~91.8%),结构高度有序,1Tc多型;晶体形态呈似六方片状,片径400~500 nm,厚度约20 nm。高岭石的晶化反应历程确定为:铝硅前驱体→板状勃姆石→板状勃姆石+片状高岭石→似六方片状高岭石。     

基于Al合金化的β-Mo(Si,Al)_2自蔓延高温合成

为了研究添加Al粉对自蔓延高温合成β-Mo(Si,Al)2的影响,以Si、Mo和Al粉为原料,按照化学式Mo(Si1-xAlx)2(x分别取0、0.1、0.2、0.3、0.4,即Al取代Si物质的量依次为0、10%、20%、30%、40%)配料,采用自蔓延高温合成制备了不同Al含量的β-Mo(Si,Al)2,并利用X射线衍射仪和扫描电镜对合成产物进行了相组成和产物形貌分析。结果表明:Al的加入有利于自蔓延反应进行得更加完全,在自蔓延过程中,Al进入到MoSi2晶格中,发生Al、Si取代,当Al取代Si物质的量达到40%时,仍能实现Al的合金化,生成高温相β-Mo(Si,Al)2,并且随着Al的添加会使自蔓延合成产物的晶格发生严重变形。通过SEM观察发现:加入Al粉的合成产物形貌都呈现出小颗粒的聚集状态,且小颗粒为球形或接近等轴状,颗粒平均粒径为2~5μm,说明自蔓延合成产物的形貌继承了Mo粉的原始形貌,而与Al粉加入量没有明显关系。     

节能新材料——高纯霞石粉

1产品特性 霞石是一种比较稀少的钠和钾双重的铝硅酸盐矿物产品，外观一般为白色、灰色,密度2.56～2.66,硬度5.5～6.0,熔点为1100℃左右,其化学分子式为：Na3Kal4Si4O16或3Na2O·K2O·4Al2O3·8SiO2。虽然霞石与长石有些类似，但其中氧化钾、氧化钠和氧化铝的含量比长石多一些，而二氧化硅含量则比长石少，在陶瓷生产中可用作长石类原料的代用品。2高温性能霞石在1150～1250℃范围内完全熔化。由于霞石与钠长石之间有一个低共熔点，所以霞石烧结温度范围较宽，而且高温下霞石能溶解石英使熔液粘度提高，所以它可代替长石作为助熔剂使用…     

利用多晶硅切割废料燃烧合成SiC基复相材料

利用多晶硅切割废料,采用燃烧合成的方法成功制备了SiC/Si2N2O及SiC/SiAlON复相粉体材料,并以该粉体为辐射基料制备出高温红外发射涂料。研究了原料配比对产物物相组成和微观形貌的影响,讨论了掺入C粉和Al粉的燃烧反应机理。实验结果表明,当反应剂中SiC∶Si∶C=68∶56∶0(质量比)时,合成产物中的Si2N2O含量最大;当反应剂中SiC∶Si∶C∶Al=68∶53∶24∶21时,合成产物中的SiAlON含量最高,配制成的高温红外涂料的红外发射率数值最高,在2.5～23.5μm波段范围内达到了0.92。     

Combution Synthesis of SiC-based Composite Materials from Kerr Loss Silicon

利用多晶硅切割废料,采用燃烧合成的方法成功制备了SiC/Si2N2O及SiC/SiAlON复相粉体材料,并以该粉体为辐射基料制备出高温红外发射涂料.研究了原料配比对产物物相组成和微观形貌的影响,讨论了掺人C粉和Al粉的燃烧反应机理.实验结果表明,当反应剂中SiC∶ Si∶C =68∶ 56∶0(质量比)时,合成产物中的Si2N2O含量最大;当反应剂中SiC∶ Si∶C∶Al =68∶ 53∶ 24∶21时,合成产物中的SiAlON含量最高,配制成的高温红外涂料的红外发射率数值最高,在2.5 ～23.5 μm波段范围内达到了0.92.     

钾长石碱法分解滤渣制W分子筛

文章以钾长石碱法分解提钾后副产的硅铝质滤渣作为基础原料,通过补加KOH、Al(OH)3和H2O,水热合成W分子筛。利用SEM、XRD和FTIR表征手段,确认所合成产品为W分子筛并得到其最佳合成条件。结果表明,在最佳配比K2O/Si O2=1.0,Al2O3/Si O2=0.067,H2O/Si O2=45的条件下,经30℃下老化2 h,150℃下晶化24 h,可合成出形貌均一、结晶良好的W分子筛,其在模拟海水中的钾离子交换容量约为57 mg/g。     

热压合成Ti3Si0.9Al0.3C1.95固溶体材料

以单质的Ti,Si,Al粉和石墨粉为原料,用热压烧结法原位合成了单一相的Ti3Si0.9Al0.3C1.95层间固溶体材料.研究了合成温度和原料配比对合成产物相组成的影响,并对Ti3Si0.9Al0.3C1.95晶粒的超结构现象及其转变进行了讨论.结果表明:合成单一相Ti3Si0.9Al0.3C1.95固溶体的最佳原料摩尔配比为该相理论配比,相应的最佳热压烧结温度为1 600℃.Ti3Si0.9Al0.3C1.95晶粒具有与Ti3SiC2类似的板状晶外形,但各个晶面的X射线衍射(X-raydiffraction,XRD)峰的2θ与Ti3SiC2相比向小角度方向偏移.块体材料中Ti3Si0.9Al0.3C1.95晶粒的Si(Al)原子层存在原子无序排列的超结构现象,其XRD谱中没有或只有微弱的(OOI)晶面的衍射峰存在,但取自于同一块材料的粉末,其晶粒的Si(Al)原子层发生有序化转变,超结构现象消失.     

熔融水热法合成A型沸石及其吸附性能研究

以略阳粉煤灰为原料,在粉煤灰中加入Al（OH）,固体和NaOH固体,研究熔融温度对试样物相的影响,水热时间对合成A型沸石的影响。结果表明在700℃保温1h物相为硅铝酸钠,在800℃保温1h有霞石产生;在80℃,水热2h,合成A型沸石;水热3h后,有方钠石生成;水热9h,产物主要为方钠石。对A型沸石、天然沸石和粉煤灰吸附性能进行了研究,结果表明：合成的A型沸石吸附能力最好,吸附率为99．83％。     

还原氮化法合成O''''-sialon粉

以SiO2,γAl2O3,Si为原料,采用还原氮化合成了O′sialon粉。研究了原料配比、氮化温度等对O′sialon合成的影响。合成产物中O′sialon的相对质量可以超过90%。对合成的O′sialon的显微结构观察结果表明:在1500℃氮化合成的O′sialon基本为1～2μm左右的等轴颗粒,在1450℃氮化合成的O′sialon试样中,则存在大量的长度达50μm的晶须。     

Hydrothermal Synthesis of Kalsilite: A Simple and Economical Method

This study reports a simple method to synthesize pure kalsilite (KAlSiO₄) using readily available precursors, kaolinite and KOH solution, after only 12 h of hydrothermal treatment in mild conditions. A structural refinement has been carried out using the Rietveld method to obtain unit cell parameters, and the ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance spectra have shown the purity and complete Si/Al ordering of the kalsilite structure obtained. Finally, the morphology of the particles has been analyzed by scanning electron microscopy.     

Effect of Si/Al ratio and a secondary hydrothermal treatment on the properties of Al-MSU-SFAU

This work reexamines the preparation condition of Al-MSU-S_FAU, which is prepared with an assembly method from zeolite Y seed colloidal, and reveals the effect of Si/Al ratio and a secondary hydrothermal treatment on the property of the material, e.g. the texture, the hydrothermal stability, the acidity and the catalytic activity. With the specific condition for preparing Al-MSU-S_FAU, the samples with high Si/Al atomic ratios are uniform, but have no crystalline structure and low hydrothermal stability. The samples with Si/Al <5 contain a significant amount of micropores. However, they are also instable and are the mixtures of zeolite Y and mesoporous material. A secondary hydrothermal treatment destroys a part of the mesopores for all the samples irrespective of the Si/Al ratios but reforms the micropores, specifically improves the micropore volume and surface area for the sample with Si/Al = 5. This sample has the long expected micro/meso composite porous structure with higher hydrothermal stability and acidity.     

Effects of Ageing and Seeding on the Formation of Zeolite Y from Coal Fly Ash

Zeolite Y was selectively synthesised by treating Tarong fly ash in a hydrothermal system. The effects of ageing and seeding on the formation of the resultant phases, crystallisation kinetics, and gel chemistry of Si and Al were investigated. Most of the Si and Al components in the Tarong fly ash could be effectively transformed into zeolite Y in the presence of seeds but not the mineral phase, like mullite. The maximum crystallinity of zeolite Y obtained was 72%. The cation-exchange capacity (CEC) of the fly ash was 0.08 mmol/g but increased to 3.2 mmol/g after a proper treatment. Crystallisation of zeolite materials from fly ash is quite different from that of normal zeolite synthesis because the sources of Si and Al are relatively less reactive and other cation ions (e.g., K⁺, Mg²⁺) are present in fly ash. Zeolite P is a competitive phase present in the resulting products that could be eliminated by employing the seeding method. NMR study demonstrated that ageing plays an important role in enhancing the hydrothermal condition during which both Si and Al in fly ash dissolved into a basic solution and reacted to form ring-like structures, and further to zeolite materials. Seeding can selectively induce the formation of zeolite Y and eliminate the processes of induction and nucleation.     

纳米β沸石的改性

采用水热处理和酸处理等方法对纳米β沸石进行改性,考察纳米β沸石的性质变化。结果表明,Na2O含量越低,水热处理后结晶度越高,热稳定性就越好;酸处理在低浓度时以酸洗掉非骨架铝为主,而高浓度酸时不仅脱除非骨架铝,而且还脱除骨架铝;纳米β沸石较难提高硅铝比,达到相同硅铝比时比小晶粒β沸石所需条件要苛刻,其耐酸性能好于小晶粒β沸石。     

Hydrothermal Solidification of Kaolinite–Quartz–Lime Mixtures

The strength development of hydrothermally solidified kaolinite–quartz–lime systems with kaolinite as the aluminum source was studied. The starting materials were mixed so that the Ca/(Si + Al) atomic ratio was in the range 0.23 to 0.25, and the Al/(Si + Al) ratio was between 0 to 0.50. Specimens were formed by uniaxial pressing and hydrothermal treatment under saturated steam pressure at 200°C for 2 to 20 h. For quartz-rich systems with Al/(Si + Al) = 0 and 0.05, strength development by the formation of calcium silicate hydrates, such as C–S–H and tobermorite (Ca₅(Si₆O₁₈H₂)·(4H₂O), was observed. On the other hand, in the case of kaolinite-rich systems with Al/(Si + Al) = 0.24 to 0.50, strength development by the formation of hydrogarnet (Ca₃Al₂(SiO₄)(OH)₈) was recognized, resulting in flexural strengths between 15 to 20 MPa. It is proposed that strength development is related to the formation of mesopores (∼0.04 μm) that accompanied formation of the hydrogarnet.     

LF精炼废渣水热浸出过程中主要矿相的溶解行为

通过水热浸出实验分别研究了精炼废渣及合成的废渣中2种主要单一矿相12CaO?7Al2O3和2CaO?SiO2的溶解行为,并将二者进行对比分析,探究了LF精炼废渣在水热浸出过程中的溶解行为。结果表明,废渣浸出过程中浸出液的pH?12,且随浸出时间增加,电导率和Ca浓度增加,Al浓度急剧下降,Si浓度低于0.1 mg/L且保持不变;12CaO?7Al2O3浸出过程中,随时间增加,浸出液pH值稳定在约11.3,浸出液中Al浓度增加,Ca浓度略微下降。2CaO?SiO2浸出液中主要为Ca2+,Si浓度低于0.6 mg/L;废渣与单一矿相浸出过程的pH值及Al, Si浓度较接近,可以通过单一矿相的溶解行为研究精炼废渣在水热浸出过程中的溶解行为,但废渣浸出液的Al和Si浓度均低于单一矿相,表明废渣中CaO等其它组分溶解抑制了12CaO?7Al2O3和2CaO?SiO2溶解。     

气相低浓度甲苯在超稳Y分子筛的吸附-脱附性能

为提高Y分子筛对可挥发性有机废气的选择性吸附能力,采用高温水热处理技术对NaY分子筛进行骨架脱铝制备超稳Y分子筛(USY),并在固定床反应器中考察了USY在水汽存在下动态吸附低浓度甲苯的性能。结果表明,随着USY分子筛骨架Si/Al比的增加,虽然其微孔孔体积和比表面积发生了下降,但形成了较多的中孔结构。并且骨架硅含量增加后,USY对非极性的甲苯分子选择性吸附能力明显增加,当Si/Al为22左右,在相对湿度50%下,单位面积甲苯吸附量要比水吸附量大5.6倍。热重脱附研究表明,经过改性后,甲苯脱附温度可从NaY的300℃下降到超稳Y分子筛的160℃,具有优良的热再生性能。     

Variation of the Si/Al ratio in nanosized zeolite Beta crystals

Zeolite Beta nanocrystals were prepared from basic aluminosilicate precursor solutions upon hydrothermal treatment at 100 °C. The Si/Al ratio of the initial system was systematically changed from 25 to infinity in order to study the limits in the framework composition of BEA-type crystallites synthesized from clear basic solutions. Furthermore, the effect of the Si/Al ratio on the precursor species, ultimate crystal size, morphology and yield was investigated. The results revealed that the crystallization kinetics of nanosized Beta are dependent on the amount of Al in the precursor solutions, that is, the nucleation and growth processes are faster in Al-rich systems. The crystallization process of zeolite Beta with Si/Al ratios in the initial solutions of 14, 23 and 32 was accomplished within 72 h, whereas longer crystallization times, 140 and 264 h, were necessary to obtain crystalline products with Si/Al ratios of 42 and infinity, respectively. The intermediates and final products were investigated by complementary techniques such as XRD, HRTEM, DLS, IR, NMR spectroscopy and chemical analysis. Low temperature (77 K) CO adsorption infrared spectroscopy was used to study the Brønsted acidity of zeolite Beta samples with different Si/Al ratios. The properties of Beta nanocrystals important for the design of catalysts and selective separation materials are provided based on the results obtained from the detailed characterization.     

钾长石水热碱法制取硫酸钾反应原理与过程评价

针对东秦岭-大别地区富钾正长岩资源的高效清洁利用技术难题,以代表性产地的钾长石粉体为原料,研究了在KOH-H₂O介质中钾长石的水热稳定性、水热碱法制取硫酸钾的反应原理,以及硅铝组分资源化利用关键技术。结果表明,钾长石在KOH碱液作用下极易脱去2/3的SiO₂而转变为钾霞石相,使K₂O富集约1倍;继而以硫酸溶解,可得近于纯净的硫酸钾近饱和溶液;经蒸发结晶或醇析法,即可制成农用硫酸钾优等品。脱硅碱液与石灰乳反应所得水合硅酸钙沉淀,经水热晶化及煅烧,产物为针状硅灰石。剩余铝硅尾渣经纯化处理和煅烧,即制成煅烧高岭土。整个工艺过程简捷高效,K₂O回收率达94.0%以上,可实现资源利用率最大化,一次性资源消耗量最小化,且环境相容性良好。     

MAS NMR studies of ZSM-5 zeolites: Correlation to para selectivity and SEM observations

²⁷Al and²⁹Si MAS NMR studies of various ZSM-5 zeolites of different Si/Al ratio, crystal size synthesized with and without alkali metal salt addition by the hydrothermal technique were carried out. The NMR observations clearly showed that the technique can be employed to differentiate Si/Al ratio, framework tetrahedral content and the crystal size. The last observation has been confirmed by SEM and catalytic activity test for para ethylation of ethylbenzene. A good correlation was found between the catalytic activity and the data from NMR and SEM.