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Van der Waals (vdW) heterostructures, which are produced by the precise assemblies of varieties of two-dimensional (2D) materials, have demonstrated many novel properties and functionalities. Here we report a nano-plasmonic study of vdW heterostructures that were produced by depositing ordered molecular layers of pentacene on top of graphene. We find through nano-infrared (IR) imaging that surface plasmons formed due to the collective oscillations of Dirac fermions in graphene are highly sensitive to the adjacent pentacene layers. In particular, the plasmon wavelength declines systematically but nonlinearly with increasing pentacene thickness. Further analysis and density functional theory (DFT) calculations indicate that the observed peculiar thickness dependence is mainly due to the tunneling-type electron transfer from pentacene to graphene. Our work unveils a new method for tailoring graphene plasmons and deepens our understanding of the intriguing nano-optical phenomena due to interlayer couplings in novel vdW heterostructures., Comment: 21 pages

High purity layered YbB2C2 powder is synthesized by a boro/carbothermic reduction method using YbBO3, B4C and graphite powders as raw materials. Its X-ray diffraction data are presented, and the space group P4/mbm (No. 127) is confirmed. The lattice parameters are a = b = 5.3389 Å and c = 3.5683 Å, and the atom positions are Yb (0.0000, 0.0000, 0.0000), B (0.3621, 0.8621, 0.5000), and C (0.1606, 0.6606, 0.5000). Porous YbB2C2 ceramics have a high porosity in the range of 69.89–58.11% and a high compressive strength in the range of 19.49–63.44 MPa. Furthermore, the as-produced porous YbB2C2 ceramics show unique chemical activity. Porous YbB2C2 ceramic with a porosity of 69.89% emits so much heat that it can burn a piece of paper when this ceramic is wetted by water. The rate of reaction between the porous YbB2C2 ceramic and water can be simply controlled by adjusting the porosity. The solid reaction products are YbB6, C and an unknown amorphous phase.

The sucrose nonfermenting 1 (SNF1)-related protein kinase 2 (SnRK2) genes play central roles in plant stress signal transduction. In this study, 8 SnRK2 genes were identified from the tea plant genome database and named CsSnRK2.1-8. Phylogenetic analysis showed that the CsSnRK2 genes were classifiable into three groups, similar to those of Arabidopsis thaliana, Oryza sativa and maize. The coding sequences (CDSs) of all CsSnRK2s were separated by eight introns, and their exon-intron organizations exhibited high similarity to those of other plants. The fluorescence of GFP fused with CsSnRK2.3 was detected in only the cytoplasm, while the rest of the proteins showed GFP signal in both the nucleus and the cytoplasm. The results of the expression patterns of the CsSnRK2 genes showed that CsSnRK2s were differentially induced by salt, polyethylene glycol (PEG) and abscisic acid (ABA) stress. Interestingly, The expression of CsSnRK2.3 was inhibited by ABA, suggesting the complicated roles of CsSnRK2s in the ABA signal transduction pathway. Some CsSnRK2 gene pairs showed significant expression change correlations under stresses, indicating that CsSnRK2s might exhibit synergistic effects of signal regulation in response to various stresses. In summary, this comprehensive analysis will facilitate further studies of the SnRK2 family of Camellia sinensis and provide useful information for the functional validation of CsSnRK2s.

Tea plant [Camellia sinensis (L.) O. Kuntze] constitutes one of the most important economic crops in many countries. However, in many areas, tea plants are subjected to high salinity, which severely affects the growth and development of these plants. To understand the potential molecular mechanisms of tea plants in response to salt stress, we used RNA-Seq technology to compare the transcriptomes from tea plants treated with and without NaCl and analyzed the differentially expressed genes (DEGs). In total, 470,738 transcripts and 150,257 unigenes were obtained that had average lengths of 1422.09 and 680.40 nt, respectively, and 28,831 of these sequences were annotated in public databases. In addition, 1769 DEGs were identified, including 947 up-regulated and 822 down-regulated ones. Many of these DEGs were involved in Ca2+ signal transduction, the abscisic acid (ABA) pathway, and mitogen-activated protein kinase (MAPK) cascades. Many DEGs were also transcription factors and key functional proteins involved in salt resistance in tea plants; these genes constitute a regulatory network in response to salt stress. qRT-PCR analyses of nine unigenes were performed to confirm the validity of the data, and the results were highly consistent with the RNA-Seq results. Taken together, these findings reveal the underlying molecular mechanism of tea plants in response to salt stress and could provide many candidate genes for additional studies, especially those involving the genetic engineering and breeding of tea plants that are highly resistant to salt stress.

Drought is a major factor limiting crop productivity and quality. Sucrose non-fermenting-1 (SNF1)-related protein kinase 2s (SnRK2s) play critical roles in plant abiotic stress responses, especially in drought stress. However, knowledge regarding the functional roles of SnRK2s in drought stress and their underlying mechanisms is relatively limited in tea plant. In this study, CsSnRK2.5, a PEG 6000- and ABA-induced SnRK2 gene from tea plant, was overexpressed in Arabidopsis to investigate its potential function in drought stress response. The results showed that overexpression of CsSnRK2.5 resulted in enhanced drought tolerance, as indicated by an amelioration of the changes in various physiological indexes, including a decreased rate of water loss and decreased accumulation of ROS and MDA. In addition, CsSnRK2.5 overexpression conferred hypersensitivity to exogenous ABA, and transgenic plants exhibited improved ABA-mediated stomatal closure compared to WT plants. Moreover, the expression of some stress response genes, including AtRAB18 and AtRD29b, was more strongly induced in transgenic plants than in the WT when subjected to ABA and drought treatments. Taken together, our results indicate that CsSnRK2.5 is a positive regulator of ABA-regulated drought stress responses.

A highly selective and efficient LC-MS/MS method was developed to determine the plasma concentration of magnolol, hesperidin, neohesperidin and geniposide following oral administration of Zhi-Zi-Hou-Po decoction in normal and depressed rats. Plasma samples were pretreated by protein precipitation with methanol. Chromatographic separation was performed on an XTerra® MS C18 column using a gradient elution with a mobile phase composed of acetonitrile-0.1% aqueous formic acid. The proposed method was validated to be specific, accurate and precise for the analytes determination in plasma samples. The calibration curves displayed good linearity over definite concentration ranges for the analytes. The intra- and inter-day precision of the proposed method at three different levels were all within

Recently, tremendous research interest was stimulated to obtain advanced function materials with hierarchical structure and tailored chemical composition from metal-organic frameworks (MOFs) based precursors. Herein, Bimetal-organic frameworks of Ni-Co-BTC solid microspheres synthesized through hydrothermal method were acted as template to induce multishelled NiO/NiCo2O4 hollow microspheres by annealing treatment. When evaluated as gas sensing material, the optimal hybrid of NiO/NiCo2O4 (the molar ration of NiCo = 1.5) multishelled hollow microspheres endowed a high sensitivity (17.86) to 100 ppm acetone with rapid response/recovery time (11/13 s) under low working temperature (160 °C) and the low detection limit reached 25 ppb. The enhanced mechanism was originated from the following aspects: the multishelled hollow architecture provided efficient diffusion path for gas molecules and sufficient active site for gas sensing reaction; the nanoscale p-p heterojunction created at NiO and NiCo2O4 nanoparticles interface amplified the resistance variation by tuning the potential barrier; the potent combination of the “chemical catalytic” effect of NiO and the “electrical catalytic” effect of NiCo2O4 improved the selective acetone detection.

In order to combine the advantages of core-shell and concentration-gradient Li[Ni1-xMx]O2 materials, a novel structured Li[Ni0.66Co0.1Mn0.24]O2 (NSLi[Ni0.66Co0.1Mn0.24]O2) cathode material is facilely synthesized from core-shell precursor [(Ni0.8Co0.1Mn0.1)0.6(Ni0.45Co0.1Mn0.45)0.4](OH)2 via ion diffusion during high temperature calcination. NSLi[Ni0.66Co0.1Mn0.24]O2 is constructed by core layer, concentration-gradient layer and shell layer. From the detailed comparative investigations, it is found that NSLi[Ni0.66Co0.1Mn0.24]O2 delivers remarkably improved cycle life and thermal stability compared with normal Li[Ni0.66Co0.1Mn0.24]O2 (NLi[Ni0.66Co0.1Mn0.24]O2).

As a new atomically layered, two-dimensional material, tin (IV) diselenide (SnSe₂) has attracted extensive attention due to its compelling application in electronics and optoelectronics. However, the great challenge of impurities and the preparation of high-quality ultrathin SnSe₂ nanoflakes has hindered far-reaching research and SnSe₂ practical applications so far. Therefore, a facile chemical vapor deposition (CVD) method is employed to synthesize large-scale ultrathin SnSe₂ flakes on mica substrates using SnSe and Se powder as precursors. The structural characteristics and crystalline quality of the product were investigated. Moreover, Raman characterizations indicate that the intensity of A1g peak and Eg peak, and the Raman shift of Eg are associated with the thickness of the SnSe₂ nanoflakes. The ultrathin SnSe₂ nanoflakes show a strong surface-enhanced Raman spectroscopy (SERS) activity for Rhodamine 6G (R6G) molecules. Theoretical explanations for the enhancement principle based on the chemical enhancement mechanism and charge transfer diagram between R6G and SnSe₂ are provided. The results demonstrate that the ultrathin SnSe₂ flakes are high-quality single crystal and can be exploited for microanalysis detection and optoelectronic application.

Carbon nanofibers (CNFs) and nanotubes (CNTs) were successfully synthesized by chemical vapor deposition using a novel catalyst CaCO3. The reaction process of C2H2 on CaCO3 surface could be classified into three stages; stage I: dehydrogenation reaction (88–129 °C), stage II: dehydrogenation and hydrogenation reactions (129–686 °C) and stage III: dehydrogenation reactions (higher than 686 °C). It was found that the molecular weights of the crosslinked C2H2 products increase with the increase of reaction temperature. Nevertheless, the dehydrogenation reaction of C2H2 into CNFs took place only at a temperature higher than about 500 °C and the highest yield of CNFs occurred at about 600 °C.

Most catalysts used in preparing carbon materials by chemical vapor deposition were transitional metals such as Fe, Co, Ni and only a few references were about the synthesis of carbon materials using water-soluble catalysts until now. Compared with metals, water-soluble catalysts can be conveniently removed from products. In our present works, water-soluble salt potassium iodide (KI) was found to be an efficient catalyst to grow carbon fibers and CNF under suitable conditions. Various structures of carbon fibers were synthesized by chemical vapor deposition using KI as the catalyst. And the experimental results showed that the nanostructure evolution of the fibers is strongly dependent on the temperature and history of the catalyst.

The effect of cationic and anionic dispersants on aqueous suspensions of as-received and surface-modified silicon carbide particles has been studied via observation of the rheological behaviour. Only the cationic dispersants were effective for the as-received SiC, with polyethyleneimine being superior to Hyamine 2389 probably as a result of a greater electrosteric interaction. SiC particles modified using Al(NO3)3 behaved like alumina and so could be dispersed using the anionic dispersants ammonium polyacrylate and polymethacrylate. Such dispersions displayed no heteroaggregation when alumina was added, although the order of mixing could significantly affect the rheological behaviour of the suspension. Nevertheless, the suspensions appeared robust to slight fluctuations in pH.

Carbon nanofibers were synthesized by chemical vapor deposition using alkali chloride catalysts at a temperature range from 500 to 700 °C. Depending on the deposition temperature and catalyst used, either helical or straight fibers with a fiber diameter of about 100 nm can be synthesized. The catalysts are water-soluble, and hence they can be removed from the deposited products by simple water-washing instead of using highly concentrated acid to remove metal catalysts.

The optimal calcination temperature was 600 °C and the highest activities were obtained at Al:K molar ratios of 3:1, 1:1 and 1:1 for Al 2 O 3 /KNO 3 , Al(NO 3 ) 3 /KNO 3 and Al 2 O 3 /KOH precursor combinations, respectively. The active compound in the catalyst prepared by Al(NO 3 ) 3 /KNO 3 was KNO 3 exclusively. However, the catalytic activity of the catalysts prepared by Al 2 O 3 /KOH was affected by the formation of K 2 Al 2 O 4 and K 2 CO 3 compounds. The catalysts prepared by all precursor combinations behaved a comparable thermal stability. High temperature aging of the catalysts would result in the loss of surface area and/or active compounds, and hence the deterioration of their catalytic activities.

GeO 2 single crystals with various morphologies were synthesized at room temperature by an acid-induced homogenous liquid phase precipitation technique without using any surfactants as studied previously. With addition of aqueous ammonia, the solubility of hexagonal GeO 2 in water was significantly increased by formation of soluble germanate ions as confirmed by IR spectra analyses. Supersaturated GeO 2 solution could be produced by adding acid into the GeO 2 -ammonia solution through the acid-induced transformation of germinate ions into GeO 2 . GeO 2 spheres were obtained with phosphoric acid addition. Truncated cubic-like and cubic-like GeO 2 single crystals could be produced in the solutions with hydrochloric acid and ascorbic acid (vitamin C) additions, respectively. The morphology developments of the GeO 2 particles induced by various acids were discussed and the growth mechanism conforms to BFDH and HP crystal growth models.

GeO2 thick (>10 μm) ceramic films were fabricated by facile liquid-phase deposition. The solubility of hexagonal GeO2 in water was increased ten times on adding aqueous ammonia at 70°C because of the formation of soluble Ge5O112–. With the addition of sulfuric acid, the alkaline GeO2–aqueous ammonia was neutralized, leading to the transformation of Ge5O112− into GeO2 precipitates. When the H2SO4/NH4OH molar ratio was higher than 11.7, immediate precipitation of GeO2 particles took place in the solution with no GeO2 particles deposited on the substrate. When the H2SO4/NH4OH molar ratio was decreased from 5.85 to 0.29, the precipitation process was retarded, leading to the gradual growth of uniform hexagonal GeO2 thick films on the substrates. The compactness of the film increased with a decrease in the H2SO4/NH4OH molar ratio. The growth of the GeO2 crystal film followed the Bravais–Freidel–Donnay–Harker and Hartman–Perdok models, and the cubic GeO2 particles with a size of about 10 μm were finally formed on the film. No GeO2 precipitate was produced on the substrate when the GeO2–aqueous ammonia had an excessively low H2SO4/NH4OH molar ratio (≤0.15) because the GeO2 solute did not reach the saturation level and the nucleation process could not take place on the substrate. The particles on the film surface deposited from the solution with an H2SO4/NH4OH molar ratio of 0.29 exhibited a nanopore structure. An initial study using this film as a support for KNO3 catalyst was carried out and the result revealed that the catalyst showed good catalytic activity of diesel soot oxidation.

Ln/K oxide catalysts (Ln = La, Sm, Y) supported on the alumina substrate have been prepared and their catalytic activities of diesel soot oxidation were tested by TPR system. The results showed that all La/K, Sm/K and Y/K catalysts showed a similar change of catalytic activity with the variation of K content. Nevertheless, Y/K catalyst was more active for diesel soot oxidation with a soot ignition temperature of about 350 °C at a loose soot/catalyst contact mode. XRD, TG/DSC analyses were employed to investigate the structures and thermal behaviors of catalysts. It was found that the oxides would react with KNO3 to form the solid solution and the K+ saturation level was related to the ionic radii of the Ln3+. The Ln/K catalysts showed a physical CO2 absorption ability that was further enhanced at higher temperature. However, when the temperature was above a critical temperature, the absorption ability was reduced. The CO2 absorption characteristics was believed to be diffusion controlled and was attributable to the lattice defects (oxygen vacancies) caused by the solid solution formation. The dynamic CO2 transportation within the catalyst could play an important role on the catalytic oxidation process.

A soft solution method for synthesizing nanocrystalline CeO2 powders via formation of cerium citrate compounds with subsequent thermal decomposition was studied. Increasing calcinations temperature could result in a larger crystalline size, while increasing the citric acid content resulted in the powders with less agglomeration. Using this method, the CeO2 particles with a crystalline size of about 4 nm could be obtained. Initial study demonstrated that the precursor prepared with polyacrlic acid resulted in the powders with a crystalline size of about 20–30 nm.

The alkali carbonates displayed a good catalytic activity for soot oxidation and their catalytic performances follow the order K 2 CO 3 > Na 2 CO 3 > Li 2 CO 3 with soot ignition onset temperatures (IOTs) of 310 °C, 320 °C and 320 °C respectively. Na/K and Li/Na/K carbonate catalysts produced by combinations of the three alkali carbonates displayed the lowest IOT of about 320 °C that was higher than that of pure K 2 CO 3 . It was found that the variation of Li:Na:K molar ratios has very limited effect on the catalytic activity, but considerable effect on the thermal stability of the catalysts.Thermal treatment at 700 °C caused a limited change of IOT, but the deterioration of catalytic performance. In the Li/Na/K catalyst system, the formation of crystalline phases with low melting temperature was observed.

The catalytic activities of Co3O4, Sr(NO3)2, Co−Sr, and Co−Sr−K catalysts were studied, and the effect of the contact mode on the soot onset ignition temperature and soot oxidation rate was also discussed. All the catalysts were characterized by X-ray diffraction and thermogravimetry/differential scanning calorimetry. The catalytic activities were evaluated by a soot oxidation reaction using the temperature-programmed reaction system. The soot onset ignition temperature is 370 °C for Co−Sr catalysts with molar ratios of 1:1 and 2:1, which is the same as that of pure Co3O4. The Co−Sr catalysts containing KNO3 can greatly lower the soot onset ignition temperature. The catalytic activity of pure Co3O4 and Sr(NO3)2 is affected by catalysts−soot contact intensity, which has nearly no effect on the soot onset ignition temperature and soot oxidation rate for Co−Sr catalysts with appropriate ratios. The cooperation of Co3O4 and Sr(NO3)2 can accelerate the soot oxidation rate and reduce the effect of the soot−cata...

Compact, crack-free alumina film was fabricated using an alumina sol with a high Al 2 O 3 content. With the addition of ethylacetoacetate (CH 3 COCH 2 COOC 2 H 5 , EAcAc), the stable sol could be prepared with a molar ratio of aluminum sec -butoxide (Al(O- sec -Bu) 3 , ASB) to water up to 1:25. It was found that EAcAc could notably decrease the surface tension of the liquid in the gel pores. The EAcAc modification layer on the colloidal particle retarded greatly the densification of the Al 2 O 3 gel film and provided a long-lasting structural relaxation during heating. Therefore, the formation of cracks was effectively prevented in this alumina material. The alumina gel film contained a high Al 2 O 3 content and there was a rather small mass loss during sintering. The critical thickness of Al 2 O 3 sol–gel film was eight times higher than that could be achieved via the general sol–gel route and a film thicker than 0.8 μm was prepared by a single-step dipping operation.

Multilayered alumina film was deposited onto metallic substrate using cycles of dip-coating method. The film thickness was found not always growing linearly with the increase of the number of dipping cycles, and even a zero-growth in thickness was observed after 20 cycles of dip coatings. This phenomenon was found to be attributed to the dissolving behavior of alumina gel material in original sol. A heat treatment at a temperature higher than 230 °C was found to be able to effectively lower the dissolvability of Al2O3 gel material, but an extra high temperature, i.e., 600 °C led to the formation of cracks in the multilayered film due to the increase of interfacial tension force. It was examined by IR and XRD analyses that a heat treatment at 250 °C for 10 min before each coating process could yield an amorphous multilayered film with no crack formed after calcinations at 600 °C. A crack-free Al2O3 film with a thickness up to 2 μm after 22 cycles of dip coating process could be produced and it showed an excellent antioxidation performance for steel substrate.

The morphology of different ratio K/V catalysts supported on porous α‐alumina substrate was investigated by atomic force microscopy (AFM). Changes in the particle size distribution, pore size distribution were analyzed respectively using AFM software. In addition, their catalytic activities and compositions for carbon oxidation were studied by x‐ray diffraction (XRD), differential scanning calorimetry (DSC), and temperature‐programmed reactions (TPR). As a result, with the increase of K concentration, the mean particle size gradually increased and the mean pore size decreased. According to the catalytic activity studies, the catalytic activity of the KVO3 and K3V5O14 phases are more effective than KCl.

The CeO 2 –K catalysts loaded on porous alumina substrate have been produced by a new route. The potassium halides played an important role on the catalytic activity enhancement of CeO 2 catalyst for soot oxidation. This improvement could partially originate from the catalytic production of CO by the potassium halides. Their effects on the catalytic activity promotion followed the order KF ∼ KCl > KBr > KI and their addition into CeO 2 resulted in the CeO 2 –K catalysts with the lowest soot ignition temperatures of about 334, 335, 345 and 362 °C, respectively, at a loose soot/catalyst contact mode. Nevertheless, the CeO 2 with addition of KCl behaved a better catalytic performance. It was also found that the catalysts have a CO 2 absorption capability.

The CO 2 absorption characteristics and catalytic oxidation activities of V/K and V/Ce/K-based catalysts were studied by temperature-programmed reactions. It was found that the V/K and V/Ce/K catalysts displayed a strong CO 2 absorption characteristic that was believed to be attributable to the formation of potassium bicarbonate species and physical CO 2 absorption. The experimental procedure used could precisely identify the soot ignition onset temperature (IOT) of the prepared catalysts. The V/K catalyst prepared at a V:K molar ratio of 1:2 showed the lowest IOT, but behaved a poor catalytic oxidation performance. The addition of CeO 2 into the V/K catalyst with a V:K molar ratio of 1:6 could reduce the IOT from about 320 to 303 °C at a loose soot/catalyst contact mode.

The K−Sm catalysts added with alkaline earth metals supported on an α-porous alumina ceramic substrate have been prepared. XRD and TG-DSC were used to characterize the catalysts, and their catalytic activities were evaluated by a soot oxidation reaction using the TPR system. The TPR study showed that the catalyst with an 8.41 KNO3:Mg ratio had the lowest soot onset ignition temperature at about 318 °C. It is very likely that the formation of liquid phases improves the catalyst/soot contact condition, which increases the catalytic activity of the catalyst. The catalyst containing a higher KNO3 content exhibits CO2 adsorption, whereas a definite-ratio alkaline earth metal can restrain the adsorption of CO2 and the formation of Sm2O2CO3 with a KNO3 content less than a specified quantity.

Crack-free germanosilicate films, 3.6 µm-thick and containing up to 70 mol% germanium dioxide, which are inaccessible through the conventional sol–gel process, were fabricated using tetraethyl orthogermanate (TEOG) and diethylorthosilicate (DEOS) as precursors for germania and silica, respectively. The studies using viscosity, TEM and SEM revealed that DEOS contributed largely to stabilizing the GeO2–SiO2 sol and suppressing crack formation in thick films. XRD study showed that the films remained amorphous after being sintered at 600 °C in air for 60 min and annealed at 550 °C under a flowing H2/N2 atmosphere for 120 min. An intense absorption band at around 241 nm was distinctly observed in the films. The intensity of this absorption band was found to be effectively bleached by UV illumination. Weak photoluminescence emission bands which originated from the neutral oxygen di-vacancy were detected near 375 and 275 nm. Therefore, the 5 eV absorption band observed in this work was mainly caused by the neutral oxygen monovacancy. A saturated absorptivity change of the UV-bleachable band after prolonged illumination was found to be 389 cm−1 for 70GeO2–30SiO2 films.

Tape casting has been used to produce thin, multi-channel alumina ceramic membranes using aqueous-based suspensions with latex as the binder. Three different kinds of latex binders, vinyl/acrylic, vinyl acetate/acrylic and acrylic/styrene latexes, each plasticized with dibutyl- o -phthalate or glycerol, were evaluated in terms of their slurry rheology and green tape mechanical properties. The results showed that the different binder systems had a substantial effect on the rheology of the system as a function of the dispersant concentration; the acrylic/styrene system proving to be the most useful. As a plasticizer, glycerol was not found to be effective; however, dibutyl- o -phthalate was much more successful, particularly in the acrylic/styrene system where it enabled the strain-to-failure of the green tape to be doubled with only a modest decrease in tensile strength. As expected, both binder content and sintering temperature significantly affected the final porosity and fracture strength of the ceramic membranes; 15 wt.% binder and a sintering temperature of 1500 °C were found to yield a membrane with a porosity of ∼40% and strength of ∼95 MPa. Simple multi-channel substrates could be easily assembled by bonding strips of the green tapes together with the ceramic slurry. Adhesion between the tapes was excellent with no interface being observed and on sintering no warping or deformation occurred.

The formation and complexing behaviors of non-soluble polyelectrolyte complexes (nPECs) between ammonium polyacrylate (A40) and poly(diallyldimethylammonium chloride) (PDC) polyelectrolytes at different A40/PDC mass ratios, pHs and KNO3 concentrations were studied using particle size and zeta potential measurement techniques. It was found that the particle size distributions and surface charge behaviors of the formed nPECs were related to the mass ratio of participating polyelectrolytes and KNO3 concentrations. Without addition of KNO3, there was no nPECs formed at a mass ratio of 0.1. Both fine and large nPECs were formed at mass ratios of 0.2 and 0.6 while only fine nPECs formed at a mass ratio of 0.4. Increasing the mass ratio from 0.8 had no significant effect on particle size distribution. The observed complexing behaviors were related to the histories of charge neutralization degree of PDC and the surface zeta potentials of nPECs. The addition of electrolyte would result in bigger nPECs attributable to the shielding effect and weakened electrostatic interaction for polyelectrolytes and nPECs, and hence the linkage of nPEC became possible. The pH changes affected the surface zeta potentials of nPECs due to the variation in ionization of A40 molecules.

The surface chemistry of a hydrophobic-treated and an untreated AlN powder has been studied using XPS, FTIR and zeta potential measurements. Whilst the surface-treatment provided significant hydrophobic behaviour, experiments revealed that the powder could not completely resist hydrolysis without the additional use of ≥1 wt.% of an appropriate surfactant. The latter also improved the water-resistance of the untreated powder, though to a far lesser extent. The active hydrolysis protection mechanism for the treated powder is believed to be the creation of a molecular shell that was formed as a result of the surfactant adsorbing onto the hydrophobically treated surface.

Silicon carbide (SiC) particles were modified in situ, using Al 3+ complexes in aqueous media, via control of Al(NO 3 ) 3 concentration and pH. The Al 3+ formed hydrolyzed complexes that adsorbed onto the charged sites on the SiC particle surfaces. As a result, the surface-modified SiC particles behaved in an alumina-like manner in the approximate pH range 5-8. The modified SiC particles were further treated with two types of polyelectrolytes that were sequentially adsorbed onto the particle surface, to give a maximum surface charge. As a result of this surface-modification process, the SiC could be dispersed with Al 2 O 3 in aqueous media without heteroaggregation.

Silicon nitride bonded silicon carbide foams have been produced by nitridation of the foamed compacts containing silicon carbide and silicon powders. When no nitridation additive was used the ceramic foams nitrided at all temperatures studied contained a significant amount of whisker phase α-Si3N4 formed both inside and outside the cell walls leading to a loose microstructure and a low mechanical strength. When the Al2O3 and Y2O3 were used as nitridation additives, the ceramic foams nitrided at temperatures of 1360 and 1395 °C containing certain amount of Si2N2O and whisker α-Si3N4 phases that are bonded by a glassy phase and behave as reinforcements for the ceramic foams exhibited a much higher mechanical strength. At nitridation temperature of 1430 °C, the ceramic foam showed the locally formed β-Si3N4 as the main nitrided phase that caused no increase in bonding area between the nitrided phase and the silicon carbide particles. Thus, a relatively lower mechanical strength was observed for the ceramic foam.

The hydrophobic treatment of AlN powders is commonly used for depressing their hydrolysis process. A commercially claimed water-resistant AlN powder (hydrophobic treated) was investigated through hydrolysis with pH measurements of the suspensions. For comparison, an untreated AlN powder was studied with similar hydrolysis condition. The water-contacted powders were subsequently analyzed with XRD. Both pH measurements and XRD results indicated that the water-resistant AlN powders were not resistant to hydrolysis without surfactant addition. It was also found that the surfactant was effective in depressing hydrolysis of the hydrophobic treated AlN powders, but slowed down slightly the hydrolysis process for untreated AlN powders. A critical surfactant concentration of 0.7 wt.% was required for successfully depressing the hydrolysis process.

Low cost production of carbon nanofiber and nanotube has been widely studied. Previously, these carbon materials have been synthesized by using chemical vapor deposition. In this letter, the carbon nanomaterials of various morphologies have been produced by using cesium carbonate as a catalyst and acetylene gas (C 2 H 2 ) as a carbon source via chemical vapor deposition. It was found that the deposited products were mainly carbon nanotubes and nanofibers at deposition temperatures of 600 and 700 °C, respectively. Because the catalysts are water-soluble, they can be removed from the deposited products by simple water-washing instead of using highly concentrated acid for metal catalyst removal.