Effect of coral sand on the mechanical properties and hydration mechanism of magnesium potassium phosphate cement mortar

Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and waves.To ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS)are mixed to repair damaged structures on coral islands.However,CS is significantly different from land-sourced sand in mineral composition,particle morphology,and strength.This has a substantial impact on the hydration characteristics and macroscopic properties of MKPC mortar.Therefore,in this study we investigated the compressive strength,interfacial mechanical properties,and corrosion resistance of MKPC CS mortar.Changes in the morphology,microstructure,and relative contents of hydration products were revealed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)and X-ray diffraction(XRD).The results indicated that the compressive strength increased linearly with the interfacial micro-hardness,and then stabilized after long-term immersion in pure water and Na2SO4 solution,showing excellent corrosion resistance.Compared with MKPC river sand(RS)mortar,the hydration products of CS mortar were an intermediate product 6KPO2·8H2O with a relative content of 3.9%at 1 h and 4.1%at 12 h.The hydration product MgKPO_(4)·6H_(2)O increased rapidly after 7-d curing,with an increased growth rate of 1100%.Our results showed that CS promoted the nucleation and formation of hydration products of MKPC,resulting in better crystallinity,tighter overlapping,and a denser interfacial transition zone.The results of this study provide technical support for applying MKPC mortar as a rapid repair material for damaged structures on coral islands.

Molecular Dynamics Study on Microstructure of Potassium Dihydrogen Phosphates Solution

Molecular dynamics simulations were carried out to study the internal energy and microstructure of potassium dihydrogen phosphates （KDP） solution at different temperatures. The water molecule was treated as a simple-point-charge model, while a seven-site model for the dihydrogen phosphate ion was adopted. The internal energy functions and the radial distribution functions of the solution were studied in detail. An unusually large local particle number density fluctuation was observed in the system at saturation temperature. It has been found that the specific heat of oversaturated solution is higher than that of unsaturated solution, which indicates the solution experiences a crystallization process below saturation temperature. The radial distribution function between the oxygen atom of water and the hydrogen atom of the dihydrogen phosphate ion shows a very strong hydrogen bond structure. There are strong interactions between potassium cation and oxygen atom of dihydrogen phosphate ion in KDP solution, and much more ion pairs were formed in saturated solution.

Subsurface Damage in Scratch Testing of Potassium Dihydrogen Phosphate Crystal

Potassium dihydrogen phosphate （KDP） is an important electro-optic crystal, often used for frequency conversion and Pockels cells in large aperture laser systems. To investigate the influence of anisotropy to the depth of subsurface damage and the profiles of cracks in subsurface of KDP crystal, an experimental study was made to obtain the form of subsurface damage produced by scratches on KDP crystal in [100], [120] and [110] crystal directions on （001） crystal plane. The results indicated that there were great differences between depth and crack shape in different directions. For many slip planes in KDP, the plastic deformation and cracks generated under pressure in the subsurface were complex. Fluctuations of subsurface damage depth at transition point were attributed to the deformation of the surface which consumed more energy when the surface deformation changed from the mixed region of brittle and plastic to the complete brittle region along the scratch. Also, the process of subsurface damage from shallow to deep, from dislocation to big crack in KDP crystal with the increase of radial force and etch pit on different crystal plane were obtained. Because crystallographic orientation and processing orientation was different, etching pits on （100） crystal plane were quadrilateral while on （110） plane and （120） plane were trapezoidal and triangular, respectively.

Characteristics of Laser-Induced Surface and Bulk Damage of Large-Aperture Deuterated Potassium Dihydrogen Phosphate at 351 nm

Deuterated potassium dihydrogen phosphate damage performance at 351 nm is studied on a large-aperture laser system. Bulk and rear-surface damage are initiated under the 3ω fluences of 6.T J/cm2 and 33/cm2, and show different growth characteristics under multiple laser irradiations with the fluence of 6 J/cm2. The size and number of bulk damage keep unchanged once initiated. However, surface damage size also does not grow, while surface damage number increases linearly with laser shots. Different damage thresholds and growth behaviors suggest different formations of bulk and surface damage precursors. The cause of surface damage is supposed to be near-surface absorbing particles buried under the sol-gel coating.

Potassium dihydrogen phosphate catalyzed one-pot synthesis of 2,4,5-triaryl-1H-imidazoles

A simple and efficient method has been developed;benzil/benzoin undergoes smooth condensation with various substituted aldehyde and ammonium acetate in the presence of potassium dihydrogen phosphate（KH;PO;） under mild reaction conditions to afford the corresponding trisubstituted imidazole in excellent yields.The method for synthesis of product,the reaction mixture was reflux in ethanol for 40-90 min.The present method is simple,efficient,and cost-effective.

Effect of Borax on Hydration and Hardening Properties of Magnesium and Pottassium Phosphate Cement Pastes

Magnesium and potassium phosphate cement （MKPC） sample were prepared by mixing dead burnt MgO powder, potassium phosphate and different dosages of retarder borax to investigate the effect of borax on its hydration and hardening characteristics. The pH value, fluidity, hydration temperature and strength development of MKPC paste were investigated, and the mineralogical composition and microstructural morphology of its hydration products were analyzed. The experimental results indicated that, within a certain dosage, borax caused an endothermal effect for MKPC paste, which decreased the early hydration rate of MKPC paste, increased the fluidity of MKPC paste. Thus, strength and micro-morphology of hardened MKPC are affected. It can be concluded that borax in MKPC paste retards the early hydration rate of MKPC paste by forming a film onto surface of MgO, decreasing the temperature and increasing the pH value of the system. As borax dosage varying, different factors may dorminate the effects.

Arsenic removal from contaminated soil using phosphoric acid and phosphate

Laboratory batch experiments were conducted to study arsenic （As） removal from a naturally contaminated soil using phosphoric acid （H3PO4） and potassium dihydrogen phosphate （KHEPO4）. Both H3PO4 and KHEPO4 proved to reduce toxicity of the soil in terms of soil As content, attaining more than 20% As removal at a concentration of 200 mmol/L. At the same time, acidification of soil and dissolution of soil components （Ca, Mg, and Si） resulted from using these two extractants, especially H3PO4. The effectiveness of these two extractants could be attributed to the replacement of As by phosphate ions （PO4^3-）. The function of H3PO4 as an acid to dissolve soil components had little effects on As removal. KH2PO4 almost removed as much As as H3PO4, but it did not result in serious damage to soils, indicating that it was a more promising extractant. The results of a kinetic study showed that As removal reached equilibrium after incubation for 360 rain, but dissolution of soil components, especially Mg and Ca, was very rapid. Therefore dissolution of soil components would be inevitable if As was further removed. Elovich model best described the kinetic data of As removal among the four models used in the kinetic study.

Stability of K-struvite in High Temperature and Acid-base Environment

K-struvite was prepared by precipitation method,and the stability of K-struvite in high temperature and acid-base environment were investigated by X-ray diffraction(XRD),thermogravimetric analysis(TG/DSC),and infrared spectroscopy(FT-IR).The results show that K-struvite decomposes from 50 to 110℃,and the mass loss begins at 50℃before being completely destroyed at 110℃,then further heating at temperature above 500℃leading to complete loss of the binding water in K-struvite.Moreover,K-struvite is more stable in alkaline environments than acidic environment.

One-pot synthesis of 1,3,4-oxadiazole-5-thioethers in water

An efficient and environmental-friendly one-pot procedure has been developed for the synthesis of 1,3,4-oxadiazole-5- thioethers by the reaction of acylhydrazine with carbon disulfide and organic halides or α, β-unsaturated carbonyl compounds. The reactions were carried out in water in the presence of potassium phosphate within 2-4 h to afford the expected products in excellent yields.

Synthesis of HTLcs modified by K_(3)PO_(4) for side chain alkylation of toluene with methanol

A series of calcined HTLcs catalysts were prepared and modified with potassium phosphate by impregnation method to clarify the influence of catalyst alkalinity on the side chain alkylation of toluene with methanol for synthesis of ethylbenzene and styrene.The catalysts were characterized by X-ray diffraction(XRD),N_(2)physical adsorption-desorption,Fourier-transform infrared spectroscopy(FT-IR),Scanning electron microscopy(SEM),X-ray photoelectron spectrometry(XPS),NH_(3)temperature-programmed desorption(NH_(3)-TPD)and CO_(2)temperature-programmed desorption(CO_(2)-TPD).It was found that the selectivity of styrene was highest(39.25%)when the K_(3)PO_(4)loading was 7.5 wt%.And the total yield of styrene and ethylbenzene could reach 65.08%with 10 wt%K_(3)PO_(4)loading.This might due to the fact that the addition of K_(3)PO_(4)could adjust the acid and basic sites of catalysts.In addition,appropriate strength and amount of basic sites were favorable to producing more styrene.

A Novel Synthesis of Some Hexasubstituted Cyclotriphosphazenes

Some known and new hexaaryloxyphosphazene: N3P3(O-C6H4-R)(1)/(R=H.CH.OCH3. C(CH3)(3). CHO.F.C6H5COOR. etc) were readily obtained with ca. 70% isolated yield in refluxing acetonitriie in the presence of anhydrous potassium phosphate. All compounds were characterized by means of elemental analysis. H-1-NMR.P-31-NMR sprctroscopy.

DIETARY PHOSPHORUS REQUIREMENT OF YOUNG ABALONE, HALIOTIS DISCUS HANNAI INO.

An experiment was performed to determine the dietary phosphorus requirement of the young abalone, Haliotis discus hannai. Five semi-purified diets were formulated to provide a series of graded levels of dietary total phosphorus (0.23%-1.98) from monobasic potassium phosphate (KH2PO4). The brown alga, Laminaria japonica, was used as a control diet. Similar size abalone were distributed in a single-pass, flow-through system using a completely randomized design with six treatments and three replicates each treatment. The abalone were hand-fed to satiation with appropriate diets in excess, once daily at 17:00. The feeding trial was run for 120-d. Survival rate and soft-body to shell ratio (SB/S) were constantly maintained regardless of dietary treatment. However, the weight gain rate (WGR), daily increment in shell length (DISL), muscle RNA to DNA ratio (RNA/DNA), carcass levels of lipid and protein, soft-body alkaline phosphatase (SBAKP), and phosphorus concentrations of whole body (WB) and soft body (SB) were significantly (ANOVA, P<0.05) affected by the dietary phosphorus level. The dietary phosphorus requirements of the abalone were evaluated from the WGR, DISL, and RNA/DNA ratio respectively, by using second-order polynomial regression analysis. Based on these criteria, about 1.0%-1.2% total dietary phosphorus, i.e. 0.9%-1.1% dietary available phosphorus is recommended for the maximum growth of the abalone.

Elastic-plastic-brittle transitions of potassium dihydrogen phosphate crystals:characterization by nanoindentation

Potassium dihydrogen phosphate(KDP)crystals are widely used in laser ignition facilities as optical switching and frequency conversion components.These crystals are soft,brittle,and sensitive to external conditions(e.g.,humidity,temperature,and applied stress).Hence,conventional characterization methods,such as transmission electron microscopy,cannot be used to study the mechanisms of material deformation.Nevertheless,understanding the mechanism of plastic-brittle transition in KDP crystals is important to prevent the fracture damage during the machining process.This study explores the plastic deformation and brittle fracture mechanisms of KDP crystals through nanoindentation experiments and theoretical calculations.The results show that dislocation nucleation and propagation are the main mechanisms of plastic deformation in KDP crystals,and dislocation pileup leads to brittle fracture during nanoindentation.Nanoindentation experiments using various indenters indicate that the external stress fields influence the plastic deformation of KDP crystals,and plastic deformation and brittle fracture are related to the material's anisotropy.However,the E l Ning Hou 13b908074@hit.edu.cn Liang-Chi Zhang liangchi.zhang@unsw.edu.au 1 School of Mechatronics Engineering,Harbin Institute of Technology,Harbin 150001,People's Republic of China 2 School of Mechatronics Engineering,Shenyang Aerospace University,Shenyang 110136.People's Republic of China'Laboratory for Precision and Nano Processing Technologies,School of Mechanical and Manufacturing Engineering,The University of New South Wales,Sydney,NSW 2052,Australia effect of loading rate on the KDP crystal deformation is practically negligible.The results of this research provide important information on reducing machining-induced damage and further improving the optical performance of KDP crystal components.

Understanding the formation mechanism of subsurface damage in potassium dihydrogen phosphate crystals during ultraprecision fly cutting

Potassium dihydrogen phosphate(KDP)crystals play an important role in high-energy laser systems,but the laser damage threshold(LDT)of KDP components is lower than expected.The LDT is significantly influenced by subsurface damage produced in KDP crystals.However,it is very challenging to detect the subsurface damage caused by processing because a KDP is soft,brittle,and sensitive to the external environment(e.g.,humidity,temperature and applied stress).Conventional characterization methods such as transmission electron microscopy are ineffective for this purpose.This paper proposes a nondestructive detection method called grazing incidence X-ray diffraction(GIXD)to investigate the formation of subsurface damage during ultra-precision fly cutting of KDP crystals.Some crystal planes,namely(200),(112),(312),(211),(220),(202),(301),(213),(310)and(303),were detected in the processed subsurface with the aid of GIXD,which provided very different results for KDP crystal bulk.These results mean that single KDP crystals change into a lattice misalignment structure(LMS)due to mechanical stress in the subsurface.These crystal planes match the slip systems of the KDP crystals,implying that dislocations nucleate and propagate along slip systems to result in the formation of the LMS under shear and compression stresses.The discovery of the LMS in the subsurface provides a new insight into the nature of the laser-induced damage of KDP crystals.

Experimental study on high-efficiency polishing for potassium dihydrogen phosphate (KDP) crystal by using two-phase air-water fluid

A high-efficiency polishing approach using two-phase air–water fluid(TAWF)is proposed to avoid surface contamination and solve the inefficiency of previous water-dissolution polishing techniques for potassium dihydrogen phosphate(KDP)crystal.In the proposed method,controllable deliquescence is implemented without any chemical impurity.The product of deliquescence is then removed by a polishing pad to achieve surface planarization.The mechanism underlying TAWF polishing is analyzed,a special device is built to polish the KDP crystal,and the effect of relative humidity(RH)on polishing performance is studied.The relationship between key parameters of polishing and surface planarization is also investigated.Results show that the polishing performance is improved with increasing RH.However,precisely controlling the RH is extremely difficult during TAWF polishing.Controllable deliquescence can easily be disrupted once the RH fluctuates,which therefore needs to be restricted to a low level to avoid its influence on deliquescence rate.The material removal of TAWF polishing is mainly attributed to the synergistic effect of deliquescence and the polishing pad.Excessive polishing pressure and revolution rate remarkably reduce the life of the polishing pad and the surface quality of the KDP crystal.TAWF polishing using IC-1000 and TEC-168S increase the machining efficiency by 150%,and a smooth surface with a root mean square surface roughness of 5.5 nm is obtained.

Linear optical properties of defective KDP with oxygen vacancy: First-principles calculations

The linear optical properties of potassium dihydrogen phosphate（KDP） with oxygen vacancy are investigated with first-principles density functional theory calculations. We use Heyd–Scuseria–Ernzerhof（HSE06） functional to calculate the linear optical properties because of its accuracy in the band gap calculation. Compared with the perfect KDP, we found that due to the defect states located at the band gap, the defective KDP with oxygen vacancy has new optical adsorption within the energy region from 4.8 eV to 7.0 eV（the corresponding wavelength region is from 258 nm to 177 nm）. As a result, the oxygen vacancy can decrease the damage threshold of KDP crystal. It may give a direction to the KDP production for laser system.

Material removal mechanisms and characteristics of potassium dihydrogen phosphate crystals under nanoscratching

Potassium dihydrogen phosphate(KDP)crystals are important materials in high-energy laser systems.However,because these crystals are brittle and soft,machining-induced defects often emerge in KDP components.This study aimed to investigate the material removal mechanisms and characteristics of KDP during nanoscratching using Berkovich,spherical,and conical indenters.We found that KDP surface layers could be removed in a ductile mode at the micro/nanoscale and that dislocation motion was one of the main removal mechanisms.Removal characteristics are related to the stress fields generated by indenter geometries.The spherical indenter achieved a ductile removal mode more easily.The lateral force of nanoscratching increased with an increase in the normal force.The coefficient of friction(COF)followed the same trend as the lateral force when spherical and conical indenters were used.However,the COF was independent of the normal force when using a Berkovich indenter.We found that these COF variations could be accurately described by friction models.

Optical Planar Waveguides in KTiOPO4 Crystals by MeV Oxygen Ion Implantation

We report on the optical planar waveguide formation in KTiOPO4 crystals by single or double oxygen ion implantation at energies of 2.4-3.0 MeV and doses of 1015 ions/cm^2. The dark-line spectroscopy properties are investigated by a prism-coupling method. With an effective refractive index method, the refractive index profiles of the waveguides are reconstructed. The program code TRIM＇98 （transport of ions in matter） is used to simulate the implantation process of oxygen ions into the KTiOPO4 crystal. It is found that an inherent relationship exists between the nuclear damage and the refractive index changes induced by the ion-beam implantation.

Investigation of the trajectory uniformity in water dissolution ultraprecision continuous polishing of large-sized KDP crystal

Large-sized potassium dihydrogen phosphate(KDP)crystals are an irreplaceable nonlinear optical component in an inertial confinement fusion project.Restricted by the size,previous studies have been aimed mainly at the removal principle and surface roughness of small-sized KDP crystals,with less research on flatness.Due to its low surface damage and high machining efficiency,water dissolution ultraprecision continuous polishing(WDUCP)has become a good technique for processing large-sized KDP crystals.In this technique,the trajectory uniformity of water droplets can directly affect the surface quality,such as flatness and roughness.Specifically,uneven trajectory distribution of water droplets on the surface of KDP crystals derived from the mode of motion obviously affects the surface quality.In this study,the material removal mechanism of WDUCP was introduced.A simulation of the trajectory of water droplets on KDP crystals under different eccentricity modes of motion was then performed.Meanwhile,the coefficient of variation(CV)was utilized to evaluate the trajectory uniformity.Furthermore,to verify the reliability of the simulation,some experimental tests were also conducted by employing a large continuous polisher.The results showed that the CV varied from 0.67 to 2.02 under the certain eccentricity mode of motion and varied from 0.48 to 0.65 under the uncertain eccentricity mode of motion.The CV of uncertain eccentricity is always smaller than that of certain eccentricity.Hence,the uniformity of trajectory was better under uncertain eccentricity.Under the mode of motion of uncertain eccentricity,the initial surface texture of the100 mm×100 mm×10 mm KDP crystal did achieve uniform planarization.The surface root mean square roughness was reduced to 2.182 nm,and the flatness was reduced to 22.013μm.Therefore,the feasibility and validity of WDUCP for large-sized KDP crystal were verified.