Effect Of Potassium Content Research Articles

Converse piezoelectric properties of K and Na-modified (Na1-xKx) NbO3 lead free ceramics for x = 0.08 and 0.17

The effect of potassium content on the structure and piezoelectric properties of the Na1−xKxNbO3 (x = 0.08 and 0.17) (SPN) ceramics has been systematically studied. The pellets preparation and characterization have been reported earlier. The piezoelectric properties of the Na1−xKxNbO3 (x = 0.08 and 0.17) were observed. The P-E loops, strain%, and the polarization current were observed. The value of d33* increasing with the application of Electric field, the rate of increasing value of d33* for x = 0.08 was faster than compared to x = 0.17. The value of d33* for x = 0.08 and x = 0.17 are 144 (pm/V), 136 (pm/V) respectively at the applied field 44 kV/cm.

Hydrothermal Synthesis of Sodium Potassium Bismuth Titanates

(Bi0.5Na0.5)TiO3 (BNT) is an excellent candidate lead-free piezoelectric material system. This study prepares BNT ceramics using the hydrothermal method at 180°C with an NaOH concentration of 12 M. The effect of potassium content on the crystal structure of the ceramics is studied. A single phase of [Bi0.5(Na1−xKx)0.5]TiO3 ceramics is obtained using the process applied to obtain BNT. The phase structure transformed from rhombohedral to tetragonal at x = 0.3, as evidenced by the disappearance of the cubic phase. The surface morphology of the materials is affected by K substitution.

Impact of potassium content on the structure of molybdenum nanophases in alumina supported catalysts and their performance in carbon monoxide hydrogenation

The paper focuses on the effect of potassium content on the structure of alumina supported molybdenum sulphide catalysts and their performance in carbon monoxide hydrogenation at the conditions favouring olefin production. Molybdenum oxide is a major phase in the unpromoted calcined catalyst. The formation of mixed K–Mo, Mo–Al and K–Mo–Al oxides occurs in the calcined catalysts in the presence of relatively small amounts of potassium. The mixed potassium molybdenum oxides readily convert into mixed molybdenum sulphides after pre-treatment with H2S. The presence of potassium results in a signification increase in the concentration of basic sites in the sulphided catalyst, while their strength is not much affected by the promotion.The catalytic results suggest the presence of two types of sites associated to unpromoted molybdenum sulphide and K–Mo–S species. Higher olefin (and alcohol) production rates were observed on the mixed K–Mo sulphides, while carbon monoxide hydrogenation on upromoted molybdenum sulphide leads to methane. Molybdenum oxysulphide seems not to be relevant to olefin synthesis.

Hydrothermal synthesis of bamboo-shaped nanosheet KNb3O8 with enhanced photocatalytic activity

A new type of bamboo-shaped KNb3O8 nanosheet was synthesized by using a two-step hydrothermal method. In particular, an effect of potassium content on the phase formation of KNb3O8 in the second-step hydrothermal process at pH=5–6 was investigated. Specific surface area, structural properties and optical characteristics of the as-synthesized samples were investigated by using Brunauer–Emmett–Teller measurement, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and UV–visible diffuse reflectance. Furthermore, the photocatalytic degradation performances of the bamboo-shaped KNb3O8 nanosheet and a rod-like KNb3O8 prepared by using molted salt method were also investigated and compared in terms of degradation of Rhodamine B, and the results indicated that the bamboo-shaped KNb3O8 nanosheet had a higher photocatalytic activity.

Interactions between corncob and lignite during temperature-programmed co-pyrolysis

Interactions between feedstocks during pyrolysis of coal–biomass blends, and their impacts on product distribution and conversion behavior during utilization, need to be understood if we are to successfully develop systems for the effective co-utilization of biomass and coal. A novel two-stage fixed-bed reactor containing three quartz tubes was designed and used in this study to investigate these interactions, with particular emphasis on the impact on product distribution and char properties. The results show that interactions exist during co-pyrolysis of corncob and lignite blends, which increase overall tar yields and decrease overall gas yields compared with those obtained from pyrolysis of unblended feedstocks, with the interactions between corncob volatiles and lignite playing a dominant role. It is also shown that interactions between chars and volatiles can impact on the reactivity of chars to O2. Consistent with our expectations, there is a link between potassium content in char and its reactivity; however, it is found that for lignite chars in particular the potential impact of potassium is dominated by the changes of char chemical structure. The effect of potassium content is the opposite to that of char chemical structure, leading to significant complexity in determining the net result of any co-pyrolysis interactions on char reactivity. This highlights the importance of understanding these complex interactions to develop the industrial scale co-gasification systems and adjust the distributions of products.

Effects of potassium content on the electrical and mechanical properties of (Na1-xKx)0.5Bi0.5TiO3 thin films

(Na1-xKx)0.5Bi0.5TiO3 (NBT-KBT-100x) thin films with different potassium contents (x=0.15, 0.18, 0.20, 0.25) were fabricated on LaNiO3/SiO2/Si(100) substrate by metal-organic decomposition, and the effects of potassium content on piezoelectric, dielectric, and mechanical properties of the thin films were investigated by scanning probe microscopy, impedance analyzer, and nanoindenter, respectively. The residual stress was evaluated by the orientation average method to clarify the dependence on potassium content, and it is used to understand the piezoelectric enhancement mechanism. Among the thin films, NBT-KBT-15 thin film is of the largest piezoelectric coefficient of 95pm/V, dielectric constant of 240, elastic modulus of 203.61GPa, and hardness of 12.36GPa while NBT-KBT-25 thin film is of the largest residual compressive stress 270MPa. The enhanced electrical properties are attributed to coexistent phases, fine grain, and lattice mismatch, respectively.

Effect of potassium content on electrostrictive properties of Na0.5Bi0.5TiO3-based relaxor ferroelectric thin films with morphotropic phase boundary

(1−x)Na0.5Bi0.5TiO3–xK0.5Bi0.5TiO3 (NBT–KBT100x) (x=0.13, 0.15, 0.18, 0.20, 0.25) thin films were prepared by metal–organic decomposition, and the crystalline structures, surface morphologies, leakage current densities and dielectric, piezoelectric, and ferroelectric properties were investigated by X-ray diffractometer, scanning electron microscopy, semiconductor characterization system, scanning probe microscopy, and ferroelectric tester, respectively. The electrostrictive equation in phenomenological theory is used to model the piezoelectric and electrostriction behaviors of relaxor ferroelectric thin films, and the electrostriction coefficient couples effective piezoelectric coefficient with the polarization and relative permittivity. The electrostriction strains are larger than the piezoelectric strains for NBT–KBT100x thin films, and the electrostriction coefficients and electrostrictive strains are at the ranges of 0.019–0.025m4/C2 and 0.12%–0.26%, respectively. NBT–KBT15 thin film is of the largest electrostriction coefficient and electrostrictive strain, and it is attributed to the appropriate potassium content near morphotropic phase boundary and the equivalent energy for the phase coexistence. The results indicate that NBT-based thin film with high electrostrictive properties is a promising candidate for the application in electromechanical devices.

Large piezoelectric response of Bi0.5(Na(1 − x)Kx)0.5TiO3 thin films near morphotropic phase boundary identified by multi-peak fitting

Bi0.5(Na(1 − x)Kx)0.5TiO3 (BNKT100x) (x = 0.11, 0.13, 0.15, 0.17, 0.19) thin films were deposited on Pt/Ti/SiO2/Si(1 0 0) substrates by metal-organic decomposition, and the effects of potassium content on the microstructure and ferroelectric/piezoelectric properties were investigated in detail. The coexistence of typical rhombohedral and tetragonal phases can be identified by multi-peak fitting in grazing incidence x-ray diffraction patterns, which indicates that morphotropic phase boundary (MPB) can be obtained for BNKT100x thin films. The results show that all the thin films are of single-phase perovskite structure and there is intimate coexistence of two phases in the potassium content range x = 0.13–0.17. The BNKT17 thin film is of the largest effective piezoelectric coefficient (d33eff = 98 pm V−1), which is attributed to a high degree of alignment of ferroelectric domains in the MPB region and its largest grain size. The BNKT17 thin film exhibits the classical diffuse phase transition of a relaxor ferroelectric, which is discussed by compositional inhomogeneity and polar nanoregions. This study offers useful guidelines to identify MPB of ferroelectric thin films with improved piezoelectric performance.

The dielectric relaxation behavior of (Na0.82K0.18)0.5Bi0.5TiO3 ferroelectric thin film

(Na1-xKx)0.5Bi0.5TiO3 (NBT-KBT-100 x) thin films were deposited on Pt/Ti/SiO2/Si(100) by metal organic decomposition, and the effects of potassium content (x = 0.15, 0.18, 0.20, 0.25) on ferroelectric, piezoelectric, dielectric properties of the thin films, and the temperature dependence of dielectric permittivity of NBT-KBT-18 thin film were investigated in detail. NBT-KBT-18 thin film is of the largest effective piezoelectric coefficient d33eff, remnant polarization 2Pr, spontaneous polarization 2 Ps, dielectric constant ɛr, and the lowest dielectric loss among the thin films. The dielectric constants decrease steeply with the increase of frequency, and there are a series of resonance peaks with Debye-like relaxation. In dielectric temperature spectra, two abnormal peaks corresponding to depolarization temperature and Curie temperature are at the range of 75-90 °C and 295-320 °C, and they are associated with the phase transitions. Based on the dielectric relaxation theory, Debye-like relaxation and diffused phase transition/frequency dispersion are interpreted by space charge polarization and polar nanoregions. Because of the centrosymmetric paraelectric phase, the 2 Ps and ɛr of NBT-KBT-100 x thin film are responsible for the d33eff according to phenomenological equation. The improved d33eff may make NBT-KBT-18 thin film a promising candidate for piezoelectric thin film devices, and the enhanced Curie temperature will offer useful guidelines of safe working temperature for potential application in micro-electro-mechanical system.

Effect of potassium content and dusting of sodium chloride on the pasture preference of dairy cows

The potassium (K) content of New Zealand ryegrass/white clover pastures can exceed the requirements for optimum pasture production (2.5–3.0%) and dairy cow requirements (0.2–0.6%) during late spring. Experiments were carried out at 13 sites in three different dairying regions over 2–3 years on different soil types to determine the effects on the cow's preference for pasture of either increasing pasture K content from applications of 0, 200, 400, and 800 kg of potassium chloride (KCl) ha–1, or the effect of dusting sodium chloride (NaCl) at 0, 5, 10, and 20 kg ha–1 immediately before grazing. Cow preference was assessed by measurements of bite rate, grazing time, pasture dry matter (DM) disappearance, and bite size. In addition, the pasture intake of two groups of cows, one group grazing pasture with K content in the optimum range for pasture production, and one group on pasture above that range, was measured using the alkane technique. In South Taranaki on Allophanic soils, increasing pasture K content significantly decreased mean cow bite rate and grazing time in October 2000 (P=0.006 and 0.001, respectively) and 2001 (P = 0.006 and 0.045, respectively), but not in November 2000 and 2001. Increasing pasture K content also significantly decreased pasture disappearance in October and November 2001, but had no significant effect on bite size. Pasture K content had no significant effect on bite rate or grazing time on brown and podzol soils in Northland in October 2001, but there was a significant positive linear trend (P = 0.011 and 0.039, respectively) in November 2001. There was no significant effect of pasture K content on pasture disappearance and bite size in Northland. Measurement of pasture preference on pumice soils on the Central Plateau in 2002 also showed no significant effect of pasture K content. In South Taranaki, pasture intake was significantly higher (P < 0.05) (18.0 versus 15.3 kg DM cow–1 day—1) for cows grazing pasture with 4.0 versus 3.3% K in October 2002, but there was no significant difference in intake between pastures containing 3.1 and 4.7% K in November 2002. Sodium chloride applied to pasture prior to grazing significantly increased cow bite rate in October and November 2002 (P=0.045 and 0.018, respectively) and grazing time in November 2002 (P = 0.032) on pumice soils. Rate of KCl or NaCl had no effect on pasture nutritive quality with overall organic matter digestibility ranging from 77 to 85%, crude protein from 9 to 26%, neutral detergent fibre from 30 to 51%, and metabolisable energy from 9 to 12 MJ kg DM–1. These results indicate that pasture K had no consistent measurable effect on cow preference, but at some sites in some years there was a trend for cow bite rate and grazing time to be depressed as pasture K content increased above 3.0%. Over a wide range of pasture Na contents (0.03–0.29%), no effect on cow preference was detected from dusting pasture with NaCl just prior to grazing.

Effects of Potassium Content in Heartwood and Soil on Heart-wood Color of Slope Planted Sugi (Cryptorneria japonica D. Don).

Effects of Potassium Content in Heartwood and Soil on Heart-wood Color of Slope Planted Sugi (<I>Cryptorneria japonica</I> D. Don).

00/02087 Are integrated coal gasification combined cycle power plants competitive?

Interactions between feedstocks during pyrolysis of coal–biomass blends, and their impacts on product distribution and conversion behavior during utilization, need to be understood if we are to successfully develop systems for the effective co-utilization of biomass and coal. A novel two-stage fixed-bed reactor containing three quartz tubes was designed and used in this study to investigate these interactions, with particular emphasis on the impact on product distribution and char properties. The results show that interactions exist during co-pyrolysis of corncob and lignite blends, which increase overall tar yields and decrease overall gas yields compared with those obtained from pyrolysis of unblended feedstocks, with the interactions between corncob volatiles and lignite playing a dominant role. It is also shown that interactions between chars and volatiles can impact on the reactivity of chars to O2. Consistent with our expectations, there is a link between potassium content in char and its reactivity; however, it is found that for lignite chars in particular the potential impact of potassium is dominated by the changes of char chemical structure. The effect of potassium content is the opposite to that of char chemical structure, leading to significant complexity in determining the net result of any co-pyrolysis interactions on char reactivity. This highlights the importance of understanding these complex interactions to develop the industrial scale co-gasification systems and adjust the distributions of products.

Improvement of Properties of Catalyst for Industrial Production of Acrolein from Propylene

The catalytic gas-phase oxidation of propylene on a multicomponent Mo-Co-Fe-Bi-K-O catalyst gives up to 85% yield of acrolein and acrylic acid along with undesirable side products formaldehyde and acetaldehyde. Effects of four factors have now been studied with the aim of suppressing of formation of the by-products viz. the effect of potassium content in the catalyst, that of final annealing temperature of the catalyst, and those of addition of other components (tungsten, nickel). It has been found that a change in potassium content in catalyst affects distinctly its activity and also selectivity for products of total oxidation of propylene but does not practically affect the yields of formaldehyde and acetaldehyde. The yields of the said side products decreased with increasing annealing temperature, however, with concomitant considerable decrease in the catalyst activity. Whereas a partial substitution of molybdenum atoms in the catalyst by tungsten atoms is accompanied by an increase in production of formaldehyde and acetaldehyde, some catalysts with nickel gave acrolein as the only aldehyde.

Steam gasification of residual oils with potassium catalysts.

This review paper is concerned primarily with the activity of potassium catalyst and the reaction path of the catalytic gasification with steam. The activity test of various potassium compounds, effect of potassium content on gas yield, X-ray diffraction patterns of β-alumina before and after the reduction of K, and the results of TG analysis of K2SO4 showed that the catalytically active component was not potassium compound, but metallic or cationic potassium. From the experimental results on steam gasification of activated carbon mixed with alumina supported K2CO3, it is deduced that potassium migrates readily to the carbon surface, and forms an unstable potassium-carbon complex which reacts with steam. Catalytic gasification continues until all potassium is consumed.

Effects of potassium content in brain-cortex slices from adult rats.

Effects of potassium concentrations, varied systematically between 5 and 85 mM, on swelling and contents of potassium and sodium have been studied. The rectilinear rise of the potassium content and the chloride-dependent increase in swelling observed by other authors are confirmed. Furthermore it is demonstrated that: 1. the potassium-induced increase in swelling is dependent upon the presence of sodium in the medium; 2. the sodium content decreases significantly when the external potassium concentration is raised from 5–20 mM (a further rise to 50 mM causes a considerable increase which is not dependent on the swelling); 3. under conditions when no swelling occurs, the potassium content in the tissue shows a relative decline when the external potassium concentration is raised from 20–50 mM; an increase from 5–20 mM causes on the other hand, a steeper increase in potassium concentration than can be explained by diffusion; 4. the glutamate-induced swelling occurs in the absence of chloride in the medium, but is sodium-dependent; and 5. the concentrations of potassium required to cause the increase of swelling are identical to those previously observed to lead to a stimulation of oxygen uptake.