原子力显微镜测定力-距离曲线的原理和应用

介绍了用原子力显微镜测定力－距离曲线的基本原理以及应用于力－距离曲线的接触区和非接触区分析的基本理论，讨论了用AFM力－距离曲线测定范德华力、双电层力及非DLVO力，并对AFM力－距离曲线在不同领域的应用进行了概括和展望。     

草分枝杆菌与赤铁矿和石英间的作用力分析

草分枝杆菌、赤铁矿、石英具有不同的表面电件,因而具有不同的相互作用力。测定了这3种物质的Zeta电位,利用DLVO理论计算和分析了草分枝杆菌与赤铁矿、草分枝杆菌与石英之间的作用力,并绘制了总作用势能、范德华力势能、静电势能与物质间距之间的关系曲线。分析表明：在pH=5条件下,草分枝杆菌与赤铁矿之间的总作用力始终表现为吸引力,且吸引力随着间距的减小而增大,当间距小于250A后,吸引力迅速增大;而草分枝杆菌与石英之间的总作用力表现为排斥力,且排斥力随着间距的减小而增大,当间距小于250A后,排斥力迅速增大。因此,草分枝杆菌可在几乎没有任何斥力的情况下,迅速吸附在赤铁矿表面,而很难吸附在石英表面。利用草分枝杆菌与赤铁矿、石英吸附能力的差异,可将草分枝杆菌作为赤铁矿、石英分离时赤铁矿的絮凝-捕收剂使用。     

金属离子对滑石浮选行为的影响及机理研究

滑石常存在于硫化矿中影响硫化矿浮选精矿的质量。为了解金属离子对滑石浮选行为的影响和作用机制,考察了Ca²⁺、Mg²⁺、Cu²⁺、Fe³⁺对滑石纯矿物浮选、滑石表面ζ电位及滑石与气泡之间诱导时间的影响。结果表明：Ca²⁺、Mg²⁺、Cu²⁺、Fe³⁺均可在滑石表面形成吸附;Ca²⁺对滑石可浮性影响不大;添加Mg²⁺后,当pH＞10时,滑石可浮性降低;添加Cu²⁺后,滑石在pH=4~10范围被抑制,并且在pH值为6左右时Cu²⁺对滑石抑制作用最强;Fe³⁺在pH=3~9的范围内能够抑制滑石,并且在pH值为7左右时对滑石抑制作用最强。溶液化学计算结果表明,溶液中的金属络合离子可以改变滑石的表面电位,而氢氧化物沉淀吸附在滑石表面会降低滑石的可浮性。静电作用能计算结果表明：当pH值低于氢氧化物的零电点时,金属离子形成的氢氧化物沉淀会特定地吸附于滑石表面,产生多相凝聚,导致滑石表面亲水性增强,可浮性降低;当pH值大于氢氧化物的零电点时,凝聚现象减弱,滑石表面疏水性增强,可浮性提高。试验结果对含滑石硫化矿中滑石的抑制和分离有一定的指导作用。     

新型常温捕收剂DX-1对赤铁矿的浮选性能研究

为提高脂肪酸对赤铁矿的捕收性能,在脂肪酸的非极性基上引入新的键合原子对其进行改性,制成新型常温捕收剂DX-1,通过赤铁矿和石英的单矿物和人工混合矿浮选试验,考察DX-1对赤铁矿的浮选性能。单矿物浮选试验表明,DX-1较月桂酸对赤铁矿的捕收能力强,且矿浆pH、矿浆温度对DX-1对赤铁矿的捕收性能影响较小;人工混合矿浮选试验表明,矿浆pH=3.9~7.0,DX-1用量为250 mg/L时,DX-1对赤铁矿的捕收性能较好。Zeta电位检测表明,pH为3.9~7.0时,赤铁矿吸附DX-1后,赤铁矿表面Zeta电位下降幅度大,并改变了赤铁矿表面电位的符号,捕收剂DX-1与赤铁矿表面发生了静电吸附。红外光谱分析表明,DX-1与赤铁矿表面主要发生了静电吸附,此外还存在部分分子间作用力及化学键力。     

非极性表面矿物滑石与辉钼矿浮选分离中的多糖抑制

多糖作为非极性矿物表面抑制剂应用非常普遍,但关于其抑制机理和影响其抑制的因素研究还未完善。将国内外有关采用糊精、羧甲基纤维素（CMC）、木质素磺酸盐及古尔胶抑制滑石和辉钼矿的研究进行了总结,介绍了多糖抑制剂抑制非极性表面的研究进展,并从浮选分离滑石和辉钼矿的角度分析了这4种有机抑制剂对这2种矿物抑制的影响因素和抑制效果。研究表明,多糖的抑制效果不仅与矿浆的pH值、离子强度和离子种类有关,还与多糖分子的特性有关;在2种矿物的浮选分离方面,除了木质素磺酸盐能够高效率地分离滑石和辉钼矿外,十二烷在辉钼矿表面的吸附可有效阻止木质素磺酸盐的吸附,使木质素磺酸盐也可能成为滑石和辉钼矿有效分离的抑制剂;多糖对2种矿物的抑制不能仅从吸附量方面阐释,更重要的是多糖吸附层的特性;关于多糖的吸附机理则存在争议,主要有疏水力论、静电力论、化学力论、氢键和羟基作用论,或它们的综合作用论。     

硅酸钠对细粒萤石和石英的分散作用机理

针对细粒萤石浮选体系中存在的异相凝聚问题,通过沉降试验、光学显微镜镜下观察、Zeta电位测定、DLVO理论计算及相关溶液化学计算研究了硅酸钠对细粒萤石和石英的分散作用及机理。结果表明,在pH值6~12范围内,萤石分散性能随着pH值增加而逐渐降低,石英保持较好分散状态,混合矿异相团聚现象较明显; 添加硅酸钠可通过SiO(OH)₃^-降低萤石和石英表面电位,增强颗粒间静电排斥力,维持石英分散状态,提高萤石和混合矿的分散性能。上述所有分散体系都符合DLVO理论模型。     

蒙脱石分散体系中用Zeta电位修正静电作用能的计算

针对扩展DLVO理论的静电作用能计算中表面电位难以测定,讨论以Zeta电位代替表面电位进行静电作用能计算的可行性。计算了蒙脱石表面电位,运用扩展的DLVO理论分别用Zeta电位和表面电位计算蒙脱石悬浮液的临界硬度,并通过蒙脱石悬浮液的临界硬度试验进行验证。试验结果表明:(1)悬浮液中蒙脱石颗粒表面与滑动面之间的水和电解质离子起到屏蔽表面电位的作用,表面电位计算的静电势能并不能反映颗粒间的静电作用;用Zeta电位代替表面电位计算颗粒间静电作用能,与实验结果更相符;(2)颗粒间滑动层开始接触时,水化作用能开始增大,电解质离子不仅减小了颗粒间的静电斥力,还减小了滑动层厚度,使水化作用距离缩短,颗粒更容易接近从而发生凝聚;(3)随电解质浓度的增加,蒙脱石颗粒Zeta电位和表面电位的绝对值均表现为减小的趋势,且表面电位的变动幅度要远高于Zeta电位的变动;双电层与滑动层厚度均呈指数减小。     

矿物无捕收剂浮选的可行性及条件的理论分析

本文对选矿厂实现硫化矿物无捕收剂浮选的可行性及必要条件进行了理论分析.结果表明,在特定的条件下,无捕收剂浮选工艺不仅可回收具有天然可浮性的矿物,而且可回收不具有天然可浮性的硫化矿物.无捕收剂浮选硫化矿物的最佳pH值可以根据氧化产物的零点电的电位值或硫化物表面质子化-去质子化的pH值来确定;不同硫化矿物的初始氧化电位不同,表明无捕收剂优先浮选原则上是可行的;为了防止可溶盐离子引起硫化物的活化或相互活化,可以在磨矿和浮选过程中保持所需的矿浆电位Eh值和pH值;所需的矿浆电位Eh值的调节和维持可以通过向矿浆中鼓入不同气体、加入还原剂或氧化剂、安装矿物电化学装置等途径来实现.     

硫化矿物无捕收剂浮选工艺因素与工业实践

本文通过单矿物及矿石浮选试验,电化学测试及溶液平衡计算系统地研究了影响硫化矿物无捕收剂浮选的工艺因素。电位调整剂可控制矿浆电位并与硫化矿物表面存在化学作用;pH 调整剂控制矿浆pH 值并影响矿浆电位;不同起泡剂对无捕收剂浮选影响较大,以HLB 值相对较大的起泡剂较好;金属离子、搅拌条件、矿物表面初始状态等都影响硫化矿物无捕收剂浮选的效果。采用无捕收剂浮选工艺可选择性分选铜硫矿石,在工业上是可能实现的。     

低煤阶煤的表面自由能与可浮选性

将煤的表面用非极性溶液不同程度地覆盖，以测定低煤阶煤的Ｚ电位。用Ｚ电位来确定液体的膜压，使其可以用来计算煤表面自由能的非极性列夫赛特－范德华力γｓ＾Ｗ。通过测量水和甘油与煤的接触角可确定表面自由能中的电子供体γｓ＾－和电子受体γｓ＾－和γｓ＾＋与非色散力γｓ＾ｎ进行比较。从表面自由能各组分的数值证实，随煤化程度增加，煤的憎水性增加。通过在哈利蒙德单气泡管中对不同类型煤的自然可浮选性试验进一步证实了     

Understanding interaction mechanisms between pentlandite and gangue minerals by zeta potential and surface force measurements

Understanding the interaction between valuable and gangue minerals is of both fundamental and practical importance in the field of flotation. In this study, we investigated the interactions between valuable (i.e. pentlandite) and gangue minerals (i.e. serpentine, olivine, and magnesite) in an aqueous solution by directly measuring the zeta potential distributions. In addition, interaction force measurements using an atomic force microscope (AFM) were performed between a silicon nitride tip and gangue mineral surfaces, and the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to fit the interaction force between the silicon nitride tip and gangue mineral surfaces. In the case of serpentine and pentlandite mixture system at pH 10.1, only a single zeta potential distribution was obtained, as compared to two distinct distributions for the two individual minerals, indicating an attractive interaction is present between the two minerals. For olivine and pentlandite mixture system, a single distribution with two distinct spikes was obtained in the zeta potential distribution of the mixture, indicating repulsive interaction between the two minerals. Similarly, a single distribution with two distinct spikes was also observed in the zeta potential distribution of magnesite and pentlandite mixture system, indicating repulsive interaction between the two minerals. Repulsive interaction between silicon nitride tip and olivine surface, and slight attractive interaction between silicon nitride tip and magnesite surface, were observed and consistent with the DLVO model. The zeta potential and AFM force measurements show good agreement regarding the surface charge properties and interactions of the minerals, and provide complementary information and new insights into the interaction mechanism of valuable and gangue minerals.     

Dispersion of kaolinite and talc in aqueous solution: nano-morphology and nano-bubble entrapment

Nano-morphological structure of well-crystallised kaolinite, micronised talc and micronised talc ground in a ring mill has been compared using field emission scanning electron microscopy (SEM) and atomic force microscopy (AFM). The kaolinite and ground talc dispersed in water immediately after shaking whereas the majority of the micronised talc remains at the air–water interface. AFM micrographs revealed more three-dimensional details of growth steps and attached colloid particles on basal planes of the crystallites than high resolution SEM micrographs. Two-dimensional ordered surface structure on the molecular level was measured by AFM. There are major differences in nano-morphology and surface structure between these three samples. The compact, blocky kaolinite crystals show large, relatively flat (<1.5 nm) basal planes with distinctive step growth on their surfaces. The irregular, thin, curved platelets of the micronised talc have much less complex surface structure with flat, smooth basal surfaces. Micronised talc platelets have much larger aspect ratios than either kaolinite or the ground talc. For micronised talc, the total edge contribution to the specific surface area is 13% whereas ground talc and kaolinite edges contribute 21% and 30–50%, respectively. The low edge contribution to total surface area in micronised talc contributes to its poor dispersion. Highly porous re-entrants and folds are frequently displayed at the edges and between sheets of the micronised talc. These voids, observed in both SEM and AFM micrographs, are filled by air nano-bubbles causing poor dispersion and high floatability when the talc is mixed with water. After grinding, the micronised talc particles are smaller, have reduced aspect ratios and much reduced porosity at edges and between sheets. Hence, the morphological differences in aspect ratio and air entrapment in the porous structure of talc are possible causes for the poor dispersability of micronised talc in comparison to kaolinite and ground talc samples.     

Al2O3添加量对锆英石合成ZrN-Sialon的影响

借助XRD和SEM手段,研究了以锆英石和工业氧化铝为原料,在不同温度下采用碳热还原氮化工艺合成ZrN-Sialon复相材料时,氧化铝添加量对复相材料中Sialon相z值的影响。结果表明：在1 500和1 550 ℃下,产物形貌以颗粒状的ZrN和长柱状的β-Sialon为主;当Al₂O₃用量为理论量和过量5%时,Sialon相主要为Si₃Al₃O₃N₅（β-Sialon,z=3）;当Al₂O₃用量为过量10%和20%时,Sialon相出现Si₂Al₄O₄N₄（β-Sialon,z=4）。在1 600 ℃下,产物均为ZrN和Sialon相,其中Sialon相转化为具有片状形貌特征的SiAl₄O₂N₄（15R型AlN多型体）;增加Al₂O₃添加量会促进Sialon相的转化。合成ZrN-Sialon复相材料的适宜氧化铝用量为理论量或过量5%,适宜温度为1 550 ℃。     

羧甲基纤维素钠对滑石可浮性及分散性的影响

通过浮选试验、沉降试验、动电位测定、接触角测量和红外光谱分析,研究了羧甲基纤维素钠(CMC)对滑石可浮性及分散性的影响。研究结果表明:CMC可使滑石颗粒层面和端面的润湿性显著增强并趋于一致,从而较好地抑制因表面疏水而上浮的滑石,实现滑石与硫化矿的浮选分离;但CMC不能阻止少量滑石因泡沫夹带而上浮。CMC可增强滑石表面的负电性,使滑石在水中的分散性变好,但这对CMC抑制滑石无益,相反,能够引起滑石颗粒层面面积降低的颗粒间聚集有利于滑石的抑制。CMC通过分子中的羟基和羧基在滑石颗粒各向表面发生作用。     

搅拌摩擦加工制备颗粒增强镁基复合材料

利用摩擦搅拌加工技术, 对AZ31镁合金进行表面组织细化、表面复合化。通过金相显微镜和扫描电镜观察研究搅拌摩擦加工后的加工显微组织及退火显微组织, 并测试加工区的硬度, 发现摩擦搅拌区晶粒明显细化, 晶粒尺寸可降至几微米, 且复合化表面即使高温长时间退火, 组织依然稳定; 摩擦搅拌加工制备复合材料, 分别添加纳米Si₃N₄粒子和SiO₂粒子复合于AZ31镁合金表面, 纳米粒子均匀分布于合金表面, 与未添加任何粒子的样品相比, 晶粒细化效果明显提高, 且由于复合粒子在基体中产生大量新界面, 抑制了晶界迁移, 使搅拌摩擦加工后的组织具有很高的热稳定性。     

Adsorption of tailored carboxymethyl cellulose polymers on talc and chalcopyrite: Correlation between coverage,wettability, and flotation

A carefully chosen selection of CMC polymers was used to probe the depression of talc and chalcopyrite and to highlight the effect of specific alterations of the bulk polymer chemistry on the power and selectivity of the depressants. In situ tapping mode atomic force microscopy (AFM), captive bubble contact angle measurements, and flotation tests were used to study the adsorption of the CMC polymers on chalcopyrite and talc. The degree of substitution and distribution of substitution of carboxymethyl groups on CMC was seen to have a strong influence on the ability of the polymers to adsorb onto the surface of talc and chalcopyrite. High substitution results in low coverage on both minerals whereas low substitution results in higher coverage. The influence of distribution of substitution (random or clustered) was also seen to affect the adsorption, with more random/even substitution giving rise to greater adsorption on talc and chalcopyrite. The contact angle of talc and chalcopyrite is significantly altered in the presence of the three polymers, with increased surface coverage (determined by AFM) correlating with the ability of the polymers to decrease the wettability of talc and chalcopyrite. This trend was also followed in single and mixed mineral talc and chalcopyrite flotation.     

Co-g-C3N4/La-TiO2复合材料光催化降解废水中乙基黄药

为了降解选矿废水中残留的浮选药剂乙基黄药,采用溶胶-凝胶法制备了一种复合型光催化材料Co-g-C3N4/La-TiO2,通过SEM、XRD、UV-Vis、光致发光光谱和XPS等对样品的形貌、晶型结构、光化学性质 和表面化学性质进行表征,研究了催化剂用量、模拟废水pH、乙基黄药初始浓度和时间对光催化效果的影响,并利用活性自由基捕捉试验确定光催化过程中起作用的活性基团。结果表明：Co-g-C3N4/La-TiO2中La和Co 以La3+和Co2+形式存在,其禁带宽度减小,吸收带边红移,光催化效率较高。在催化剂投加量为1 g/L,乙基黄药浓度为60 mg/L,pH为10的条件下,光催化60 min后乙基黄药的降解率达到了99.1%。空穴（h+）、羟基 自由基（·OH）、超氧自由基（·O2-）都在光催化氧化降解乙基黄药的过程中起到了重要作用,对光催化的贡献程度为：·OH＞h+＞·O2-。     

滑石的矿物结构与浮选性能

滑石矿是在国民经济中占有重要地位的矿种之一,为给我国滑石资源的高效利用提供参考,系统研究了滑石的结构及其浮选性能。滑石为层状结构硅酸盐矿物,层间解离极完全,滑石晶体破碎解离后,有2个性质不同的面,基面疏水性较好,端面疏水性略差,滑石矿物具有非常好的天然疏水性。水介质中,碱金属离子Na^+、K^+会破坏滑石表面的水化膜,提高滑石的天然可浮性;多价金属离子存在时,会以金属离子、羟合络离子或氢氧化物沉淀的形式吸附在滑石表面,只有当氢氧化物吸附在滑石表面时,滑石受抑制,pH升高后,吸附在滑石表面的氢氧化物会脱落,滑石的天然可浮性恢复。煤油与起泡剂混合使用可以提高滑石的回收率,但由于煤油分散性差,浮选过程不太稳定,特别是煤油与松油醇共用时;胺类捕收剂在低pH条件下对滑石的浮选效果较好,高碱性下,胺类捕收剂在矿浆中的分散性变差,作用效果也会与煤油相似,严重影响浮选泡沫性能,恶化浮选效果;油酸不太适宜用于滑石的浮选,使用油酸时可考虑用多价金属离子做滑石的活化剂;阴离子型高分子抑制剂分子中的疏水基团会与疏水性的滑石基面通过范德华力产生物理吸附,而亲水性基团朝外,从而使滑石表面亲水而被抑制;多糖类抑制剂只能通过物理吸附在滑石表面;聚丙烯酰胺经N原子改性后,对滑石抑制效果显著。     

Interaction forces between chemically modified hydrophobic surfaces evaluated by AFM—The role of nanoscopic bubbles in the interactions

The interaction forces between a hydrophobic silicon plate and a silica particle in an aqueous solution were investigated with an atomic force microscope (AFM). The surfaces were hydrophobized chemically by a silane coupling agent, and the hydrophobicity (contact angle θ) of the surfaces was varied. The interactions were long-ranged at θ > 90° with a discontinuous step appearing in the approaching and separating force curves respectively. The range and magnitude of the interaction were decreased with decreasing θ. On the other hand, the interactions at θ = 80° was unstable and no long-range attraction was observed. When the gas phase on the surfaces was removed by flushing organic solvents between the surfaces, the interactions became short-ranged at θ > 90°, and the interaction was described DLVO theory at large distances at θ = 80°. A large number of nano-size domain structures were found on the surfaces by tapping-mode AFM. These results imply that the bridging of nanobubbles is the main origin of the long-range force between chemically hydrophobized surfaces and that the size of the bubble has critical effect on the range and magnitude of the attractive force. The short-range interactions without bubbles were found to consist of an electrostatic repulsive force at larger distances and an attractive force, which was sufficiently longer-ranged than the van der Waals force, at smaller distance.