Hydrothermal transformation of the calcium aluminum oxide hydrates CaAl2O4·10H2O and Ca2Al2O5·8H2O to Ca3Al2(OH)12 investigated by in situ synchrotron X-ray powder diffraction

The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 °C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl₂O₄·10H₂O converted to Ca₃Al₂(OH)₁₂ and amorphous aluminum hydroxide. Ca₂Al₂O₅·8H₂O transformed via the intermediate phase Ca₄Al₂O₇·13H₂O to Ca₃Al₂(OH)₁₂ and gibbsite, Al(OH)₃. The phase Ca₄Al₂O₇·19H₂O reacted via the same intermediate phase to Ca₃Al₂(OH)₁₂ and mainly amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported.     

Porous structures constructed from [SiMo12O40] and [SiW12O40] Keggin units

Three compounds, K₂(H₂O)₄H₂SiMo₁₂O₄₀ · 7H₂O (1), K₂Na₂(H₂O)₄SiW₁₂O₄₀ · 4H₂O (2), and Na₄(H₂O)₈SiMo₁₂O₄₀ · 6H₂O (3) have been synthesized and structurally characterized by single-crystal X-ray analysis, IR, and thermogravimetry. Compounds 1 and 2 both show the high symmetry trigonal space group P3₂21 and a novel 3D network structure. The Keggin anions [SiM₁₂O₄₀]⁴⁻(M = Mo, W) are linked by potassium or sodium cations to generate hexagon-shaped channels along the c-axis, in which water molecules are accommodated. Compound 3 is tetragonal, space group P4/mnc constructed from [SiMo₁₂O₄₀]⁴⁻ anions and Na ions.     

Hydrothermal synthesis of Ba(Ti, Sn)O3 fine powders and dielectric properties of the corresponding ceramics

Fine powders of submicron-sized crystallites of BaTiO₃ were prepared at 85–130°C by the hydrothermal method, starting from TiO₂.ξH₂O gel and Ba(OH)₂ solution. The products obtained below 110°C incorporated considerable amounts of H₂O and OH⁻ in the lattice. As-prepared BaTiO₃ is cubic and converts to the tetragonal phase after heat treatment at 1200°C, accompanied by the loss of residual OH⁻ ions. Hydrothermal reaction of SnO₂.ξH₂O gel with Ba(OH)₂ at 150–260°C gives rise to the hydrated phase, BaSn(OH)₆.3H₂O, due to the amphoteric nature of SnO₂.ξH₂O which stabilises Sn(OH)₆²⁻ anions in basic media. On heating in air or releasing the pressure in situ at 260°C, BaSn(OH)₆.3H₂O converts to BaSnO₃ through an intermediate, BaSnO(OH)₄. Solid solutions of Ba(Ti,Sn)O₃ are directly formed from (TiO₂ + SnO₂)..ξH₂O gel up to 35 mol% SnO₂. At higher Sn contents, the hydrothermal products are mixtures of BaSn(OH)₆.3H₂O and BaTiO₃, which on annealing at 1000°C result in monophasic Ba(Ti,Sn)O₃. The sintering characteristics and the dielectric properties of the ceramics prepared out of these fine powders are presented. The dielectric properties of fine-grained Ba(Ti,Sn)O₃ ceramics are explained on the basis of the prevailing diffuse phase transition behaviour.     

Crystal structure of zeolite X nickel(II) exchanged at pH 4.3 and partially dehydrated, Ni2(NiOH)35(Ni4AlO4)2(H3O)46Si101Al91O384

Complete Ni²⁺ exchange of a single crystal of zeolite X of composition Na₉₂Si₁₀₀Al₉₂O₃₈₄ per unit cell was attempted at 73°C with flowing aqueous 0.05 M NiCl₂ (pH=4.3 at 23°C). After partial dehydration at 23°C and ≈10⁻³ Torr for two days, its structure, now of composition Ni₂(NiOH)₃₅(Ni₄AlO₄)₂(H₃O)₄₆Si₁₀₁Al₉₁O₃₈₄ per unit cell, was determined by X-ray diffraction techniques at 23°C (space group Fd , a₀=24.788(5) Å). It was refined using all intensities; R₁=0.080 for the 236 reflections for which F_o>4σ(F_o), and wR₂=0.187 using all 1138 unique reflections measured. At four crystallographic sites, 45 Ni²⁺ ions were found per unit cell. Thirty of these are at two different site III′ positions. Twenty of those are close to the sides of 12-rings near O–Si–O sequences, where each coordinates octahedrally to two framework oxygens, to three water molecules which hydrogen bond to the zeolite framework, and to an OH⁻ ion. The remaining 10 are near O–Al–O sequences; only three members of a likely octahedral coordination sphere could be found. In addition, two Ni²⁺ ions are at site I, eight are at site I′, and five are at site II. Forty six H₃O⁺ ions per unit cell, 24 at site II′ and 22 at site II, each hydrogen bond triply to six rings of the zeolite framework. Each of the 22 H₃O⁺ ions also hydrogen bonds to a H₂O molecule that coordinates to a site III′ Ni²⁺ ion. Six of the eight sodalite cages each contain four H₃O⁺ ions at site II′; the remaining two each contains a tetrahedral orthoaluminate anion at its center. Each tetrahedral face of each orthoaluminate ion is centered by a site I′ Ni²⁺ ion to give two Ni₄AlO₄ clusters. The five site II Ni²⁺ ions each coordinate to a OH⁻ ion. With 46 H₃O⁺ ions per unit cell, the great tendency of hydrated Ni²⁺ to hydrolyze within zeolite X is demonstrated. With a relatively weak single-crystal diffraction pattern, with dealumination of the zeolite framework, and with an apparent decrease in long-range Si/Al ordering likely due to the formation of antidomains, this crystal like others treated with hydrolyzing cations appears to have been damaged by Ni²⁺ exchange and partial dehydration.     

Structural studies of reaction products between paramolybdate anion and some cationic [metal(II) and (III)-(ethylenediamine)n] complexes utilized as new photocatalysts under UV–VIS light illumination

Five cationic transition metal (ethylenediamine) complexes (M=Cr(III), Co(III), Ni(II), and Cu(II)):paramolybdate anion (Mo₇O₂₄⁶⁻) have been synthesis and characterized via their elemental analysis, magnetic susceptibility (μ_eff), thermal analysis (TG and DTA), FTIR spectra, and X-ray diffraction (XRD). The FTIR study suggests that the compounds prepared be of the ion-pair type ([M(en)_n]_m·Mo₇O₂₄). Thermal study showed that molybdenum in the Cr(III), and Co(III) compounds is reduced from oxidation state (VI) to (V) at high temperature. The stoichiometries of the resulting mixed oxides at elevated temperatures (500–750°C) are: Cr₂O₃·7MoO_2.5, Co₂O₃·7MoO_2.5, 6CoOCl·7MoO_2.5, 3NiO·7MoO₃ and 3CuO·7MoO₃. Above 750°C the molybdenum oxide in the ion-pair compounds start the sublimation process. X-ray diffraction of [Cr(en)₃]·Mo₇O₂₄, [Co(en)₃]·Mo₇O₂₄, and [Cu(en)₂(H₂O)₂]₃·Mo₇O₂₄ shows that these complexes are crystalline solids with a similar structure, while the [Ni(en)(H₂O)₄]₃·Mo₇O₂₄, and [Co(en)(H₂O)₂Cl₂]₆·Mo₇O₂₄ ion-pair compounds display a different structure.

A novel technique based on photocatalysis to eliminate Cr(VI) ions, a toxic pollutant in the environment, was applied. The photoreduction of Cr(VI) to Cr(III) ion in aqueous suspensions using new-mixed oxides as photocatalysts (Cr₂O₃·MoO_2.5, Co₂O₃·MoO_2.5, NiO·MoO₃, and CuO·MoO₃) under air-equilibration and irradiation by a medium pressure mercury lamp (UV–VIS) was investigated.     

Structural phase transition and high temperature phase structure of Friedels salt, 3CaO · Al2O3 · CaCl2 · 10H2O

Friedels salt, the chlorinated compound 3CaO · Al₂O₃ · CaCl₂ · 10H₂O (AFm phase), presents a structural phase transition at about 30°C from a monoclinic to a rhombohedral phase. It has been studied by X-ray powder diffraction and optical microscopy in transmitted light with crossed polarisers on single crystals prepared by hydrothermal synthesis. The high temperature phase was determined at 37°C from X-ray single crystal diffraction data. The compound crystallises in the space group R c with lattice parameters of a = 5.7358(6)Å and c = 46.849(9)Å (Z = 3 and D_x = 2.111 g/cm³). The refinement of 498 independent reflections with I > 2σ(I) led to a residual factor of 7.1%. The Friedels salt can be described as a layered structure with positively charged main layers of composition [Ca₂Al(OH)₆]⁺ and negatively charged layers of composition [Cl⁻,2H₂O]. The chloride anions are surrounded by 10 hydrogen atoms, of which six belong to hydroxyl groups and four to water molecules. The structural phase transition may be related to the size of the chloride anions, which are not adapted to the octahedral cavity formed by bonded water molecules.     

Study of interactions at water-soluble polymer/Ca(OH)2 or gibbsite interfaces by XPS

In an attempt to better understand interactions occuring at hydrated cement/organic polymer interfaces, the reaction mechanism and products formed at the interfaces between poly(acrylic acid), p(AA) or poly(acrylamide), p(AM), and Ca(OH)₂ or gibbsite, Al₂O₃·3H₂O, were explored using x-ray photoelectron spectroscopy (XPS). It was estimated that at p(AA)/Ca(OH)₂ interfaces, a Ca-complexed carboxylate interfacial reaction product was formed by an ionic reaction between the COOH in p(AA) and Ca²⁺ ions from Ca(OH)₂. A similar reaction product was formed at p(AM)/Ca(OH)₂ interfaces as a result of an inter-facial transformation of amide in p(AM) into carboxylic acid, caused by the alkali-catalyzed hydrolysis of the amide. The proton-accepting hydroxyl groups existing at the outermost surface sites of Al₂O₂·3H₂O react favorably with proton-donating COOH groups in p(AA). This acidbase interaction at the p(AA)/Al₂O₃·3H₂O joint formed hydrogen bonds. Whereas, when the p(AM) was applied on Al₂O₃·3H₂O surfaces, interfacial electrostatic bonds were formed through charge-transferring reaction mechanisms in which the charge density was transferred from the Al in Al₂O₃·3H₂O to the C=0 oxygen in p(AM).     

In-situ growth of needlelike LaAl11O18 for reinforcement of alumina composites

In situ growth of needlelike LaAl₁₁O₁₈ grains reinforcing Al₂O₃ composites can be fabricated by a coprecipitation method using La(NO₃)₃√6H₂O and Al(NO₃)₃√9H₂O as starting materials. The new two-step process involved firstly preparing needlelike LaAl₁₁O₁₈ grains distributed homogeneously in Al₂O₃ powder and then pressureless sintering the composite powders. The Al₂O₃/25 vol.%LaAl₁₁O₁₈ samples pressureless sintered at 1550°C for 4 h achieve relative density up to 96.5% and exhibit a bending strength of 420±30 MPa and a fracture toughness of 4.3±0.4 MPa m^1/2.     

AgBr/Zn3(OH)2V2O7·2H2O可见光催化降解亚甲基蓝溶液

采用水热和沉淀两步合成法制备AgBr/Zn₃(OH)₂V₂O₇·2H₂O催化剂,研究其在可见光下降解亚甲基蓝溶液的性能,并考察催化剂用量、亚甲基蓝溶液初始浓度、pH值以及盐浓度对光催化性能的影响,评价AgBr/Zn₃(OH)₂V₂O₇·2H₂O催化剂的重复使用性能。结果表明,在前驱液pH为10、120 ℃水热10 h、Ag与Br物质的量比为0.20条件下制备的复合催化剂在可见光下反应120 min后,1.0 g·L^-1的催化剂对10 mg·L^-1的亚甲基蓝溶液脱色率达到85.2%。NaCl对亚甲基蓝的降解起抑制作用,Na₂SO₄对亚甲基蓝的降解起促进作用。催化剂重复使用4次后,光照120 min后的亚甲基蓝溶液脱色率可达66.4%。催化剂对不同初始浓度亚甲基蓝溶液的光催化降解符合一级动力学模型。     

Effect of sintering and poling conditions on the properties of 0·125Pb (Mg1/3Nb2/3)O3−0.875Pb(Zr0·5Ti0·5)O3 ceramics doped with 4PbO. B2O3

The influence of sintering and poling conditions on dielectric properties and microstructures of the system 0·125Pb(Mg_1/3Nb_2/3)O₃−0·875Pb (Zr_0·5Ti_0·5)O₃ was investigated. Specimens were prepared by the conventional mixed-oxide technique. On account of eliminating the pyrochlore phase and lowering the sintering temperature, the calcined 0·125PZT−0·875PMN ceramic was doped with 4PbO.B₂O₃ glass powder. The 4PbO.B₂O₃ glass frit not only has a low flow temperature, but also a high polarizability. Additions of 4PbO.B₂O₃ to the perovskite 0·125PMN–0·875PZT solid solution will form a liquid phase, which served as a densification aid for the ceramics. With additions of 0·2 wt% glass frit, densities in excess of 98% of theoretical were obtained after sintering at 115°C. By variation of the fabrication processes, the influence of sintering and poling conditions on the properties of the ceramics was studied.     

Superior performance of Ir-substituted hexaaluminate catalysts for N2O decomposition

Novel Ir-substituted hexaaluminate catalysts were developed for the first time and used for catalytic decomposition of high concentration of N₂O. The catalysts were prepared by one-pot precipitation and characterized by X-ray diffraction (XRD), N₂-adsorption, scanning electronic microscopy (SEM) and temperature-programmed reduction (H₂-TPR). The XRD results showed that only a limited amount of iridium was incorporated into the hexaaluminate lattice by substituting Al³⁺ to form BaIr_xFe_1−xAl₁₁O₁₉ after being calcined at 1200 °C, while the other part of iridium existed as IrO₂ phase. The activity tests for high concentration (30%, v/v) of N₂O decomposition demonstrated that the BaIr_xFe_1−xAl₁₁O₁₉ hexaaluminates exhibited much higher activities and stabilities than the Ir/Al₂O₃-1200, and the pre-reduction with H₂ was essential for activating the catalysts. By comparing BaIr_xFe_1−xAl₁₁O₁₉ with BaIr_xAl_12−xO₁₉ (x = 0–0.8), it was found that iridium was the active component in the N₂O decomposition and the framework iridium was more active than the large IrO₂ particles. On the other hand, Fe facilitated the formation of hexaaluminate as well as the incorporation of iridium into the framework.     

Water vapor sensitivity of nanosized La(Co, Mn, Fe)1−x(Cu, Pd)xO3 perovskites during NO reduction by C3H6 in the presence of oxygen

A series of La(Co, Mn, Fe)_1−x(Cu, Pd)_xO₃ perovskites having high specific surface areas and nanosized crystal domains was prepared by reactive grinding. The solids were characterized by N₂ adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (TPD) of O₂, NO + O₂, C₃H₆, in the absence or presence of 5% H₂O, Fourier transform infrared (FTIR) spectroscopy, as well as activity tests towards NO reduction by propene under the conditions of 3000 ppm NO, 3000 ppm C₃H₆, 1% O₂, 0 or 10% H₂O, and 50,000 h⁻¹ space velocity. The objective was to investigate the influence of H₂O addition on catalytic behavior. A good performance (100% NO conversion, 77% N₂ yield, and 90% C₃H₆ conversion) was achieved at 600 °C over LaFe_0.8Cu_0.2O₃ under a dry feed stream. With the exposure of LaFe_0.8Cu_0.2O₃ to a humid atmosphere containing 10% water vapor, the catalytic activity was slightly decreased yielding 91% NO conversion, 51% N₂ yield, and 86% C₃H₆ conversion. A competitive adsorption between H₂O vapor with O₂ and NO molecules at anion vacancies over LaFe_0.8Cu_0.2O₃ was found by means of TPD studies here. A deactivation mechanism was therefore proposed involving the occupation of available active sites by water vapor, resulting in an inhibition of catalytic activity in C₃H₆ + NO + O₂ reaction. This H₂O deactivation was also verified to be strictly reversible by removing steam from the feed.     

Studies of the effects of synthetic procedure on base catalysis using hydroxide-intercalated layer double hydroxides

Layer double hydroxides (LDHs) based on the hydrotalcite structure (Mg₆Al₂(OH)₁₆CO₃·4H₂O) have been synthesized by coprecipitation, sol–gel and urea hydrolysis methods and with Mg:Al ratios of 2:1 and 5:1. Scanning electron microscopy shows the coprecipitated phases present the smallest individual crystallite sizes (ca. 150 nm) with the largest crystallites (2–4 μm) for urea hydrolysis. Sol–gel samples show crystallites (150–450 nm) fused together into much larger particles. The samples have been calcined at 723 K in flowing air to produce metal oxide phases which have then been rehydrated in the presence of hydroxide ions to produce meixnerite-like LDH phases (Mg₆Al₂(OH)₂₀·4H₂O). The base catalytic activity of these rehydrated samples has been measured by GC for the aldol self-condensation of acetone. Activity data has been correlated with sample characteristics to gain insight into the active sites and mode of action of these catalysts.     

Combined effect of H2O and SO2 on V2O5/AC catalysts for NO reduction with ammonia at lower temperatures

Combined effect of H₂O and SO₂ on V₂O₅/AC the activity of catalyst for selective catalytic reduction (SCR) of NO with NH₃ at lower temperatures was studied. In the absence of SO₂, H₂O inhibits the catalytic activity, which may be attributed to competitive adsorption of H₂O and reactants (NO and/or NH₃). Although SO₂ promotes the SCR activity of the V₂O₅/AC catalyst in the absence of H₂O, it speeds the deactivation of the catalyst in the presence of H₂O. The dual effect of SO₂ is attributed to the SO₄²⁻ formed on the catalyst surface, which stays as ammonium-sulfate salts on the catalyst surface. In the absence of H₂O, a small amount of ammonium-sulfate salts deposits on the surface of the catalyst, which promote the SCR activity; in the presence of H₂O, however, the deposition rate of ammonium-sulfate salts is much greater, which results in blocking of the catalyst pores and deactivates the catalyst. Decreasing V₂O₅ loading decreases the deactivation rate of the catalyst. The catalyst can be used stably at a space velocity of 9000 h⁻¹ and temperature of 250 °C.     

Microstructure and phase development in NiMn2O4 spinel ceramics during isothermal sintering

Studies of the sintering behaviour of NiMn₂O₄ semiconducting ceramics at 1100°C under oxygen atmosphere show the advantage of a powder prepared by thermal decomposition of oxalate mixed crystals NiMn₂ (C₂O₄)₃. 6H₂O at 450°C for the formation of dense ceramics with homogeneous microstructure. The microstructure of the semiconductor ceramics was established by image analysis. SEM and EDX indicate a phase separation related to partial oxygen loss as observed by thermogravimetry and redox analytic measurements. Reoxidation to a single-phase homogeneous microstructure by annealing at 800°C is possible only in porous samples. NiMn₂O₄ is not stable in oxygen at 1100°C. The spinel decomposes into NiO and a Mn-rich spinel matrix Ni_x^IIMn_1−x^IIMn₂^IIIO₄. For producing a reproducible semiconducting ceramics it is necessary to stimulate sintering by separation of NiO. A one-phase spinel is obtained by reoxidation of long duration.     

NO decomposition and reduction by CH4 over Sr/La2O3

Both NO decomposition and NO reduction by CH₄ over 4%Sr/La₂O₃ in the absence and presence of O₂ were examined between 773 and 973 K, and N₂O decomposition was also studied. The presence of CH₄ greatly increased the conversion of NO to N₂ and this activity was further enhanced by co-fed O₂. For example, at 773 K and 15 Torr NO the specific activities of NO decomposition, reduction by CH₄ in the absence of O₂, and reduction with 1% O₂ in the feed were 8.3·10⁻⁴, 4.6·10⁻³, and 1.3·10⁻² μmol N₂/s m², respectively. This oxygen-enhanced activity for NO reduction is attributed to the formation of methyl (and/or methylene) species on the oxide surface. NO decomposition on this catalyst occurred with an activation energy of 28 kcal/mol and the reaction order at 923 K with respect to NO was 1.1. The rate of N₂ formation by decomposition was inhibited by O₂ in the feed even though the reaction order in NO remained the same. The rate of NO reduction by CH₄ continuously increased with temperature to 973 K with no bend-over in either the absence or the presence of O₂ with equal activation energies of 26 kcal/mol. The addition of O₂ increased the reaction order in CH₄ at 923 K from 0.19 to 0.87, while it decreased the reaction order in NO from 0.73 to 0.55. The reaction order in O₂ was 0.26 up to 0.5% O₂ during which time the CH₄ concentration was not decreased significantly. N₂O decomposition occurs rapidly on this catalyst with a specific activity of 1.6·10⁻⁴ μmol N₂/s m² at 623 K and 1220 ppm N₂O and an activation energy of 24 kcal/mol. The addition of CH₄ inhibits this decomposition reaction. Finally, the use of either CO or H₂ as the reductant (no O₂) produced specific activities at 773 K that were almost 5 times greater than that with CH₄ and gave activation energies of 21–26 kcal/mol, thus demonstrating the potential of using CO/H₂ to reduce NO to N₂ over these REO catalysts.     

Oxidation behavior of hot-pressed Si3N4 with Re2O3 (Re=Y, Yb, Er, La)

Four different β-Si₃N₄ ceramics with silicon oxynitrides [Y₁₀(SiO₄)₆N₂, Yb₄Si₂N₂O₇, Er₂Si₃N₄O₃, and La₁₀(SiO₄)₆N₂, respectively] as secondary phases have been fabricated by hot-pressing the Si₃N₄–Re₄Si₂N₂O₇ (Re=Y, Yb, Er, and La) compositions at 1820°C for 2 h under a pressure of 25 MPa. The oxidation behavior of the hot-pressed ceramics was characterized and compared with that of the ceramics fabricated from Si₃N₄–Re₂Si₂O₇ compositions. All Si₃N₄ ceramics investigated herein showed a parabolic weight gain with oxidation time at 1400°C and the oxidation products of the ceramics were SiO₂ and Re₂Si₂O₇. The Si₃N₄–Re₄Si₂N₂O₇ compositions showed inferior oxidation resistance to those from Si₃N₄–Re₂Si₂O₇ compositions, owing to the incompatibility of the secondary phases of those ceramics with SiO₂, the oxidation product of Si₃N₄. Si₃N₄ ceramics from a Si₃N₄–Er₄Si ₂N₂O₇ composition showed the best oxidation resistance of 0·198 mg cm⁻² after oxidation at 1400°C for 192 h in air among the compositions investigated herein.     

Preparation of catalyst precursors for selective oxidation of n-butane by exfoliation–reduction of VOPO4·2H2O in primary alcohol

A new method through intercalation and exfoliation of VOPO₄·2H₂O crystallites in primary alcohol (1-propanol or 1-butanol), followed by reduction with the alcohol, have been investigated for the preparation of catalyst precursor. Lamellar compounds, consisting of V⁴⁺, P⁵⁺ and alkyl group with thin film-like morphology, were formed and was characterized by means of XRD, IR, TG/DTA, and elemental analysis. The chemical formula of the precursor obtained by exfoliation–reduction in 1-butanol was shown to be VO{(n-C₄H₉)_0.16H_0.84}PO₄·0.8H₂O. On the other hand, a direct reduction of VOPO₄·2H₂O in the alcohol gave a mixed phase shown by (VOHPO₄·0.5H₂O)_0.3(VO{(n-C₄H₉)_0.3H_0.7}PO₄·3H₂O)_0.7 comprising plate-like microcrystallites. These precursors transformed to (VO)₂P₂O₇ phase during an activation process at 703 K in the presence of a mixture of n-butane 1.5% and O₂ 17% in He balance. The obtained (VO)₂P₂O₇ through the exfoliation–reduction was well crystallized and consisted of thin flaky crystallites. It was found that (VO)₂P₂O₇ thus prepared through the exfoliation–reduction was highly active and selective for oxidation of n-butane.     

Crystal chemistry of calcium silicates: Germinate and chromate analogues of KF·2[Ca6(SO4)(SiO4)2O]

The germanate KF·2[Ca₆(SO₄) (GeO₄)₂O] was synthesized by solid state reactions; comparison of the observed and calculated powder pattern, assuming an isostructural relationship with the silicate phase, gives good agreement. Sulphate groups may also be substituted by CrO₄²⁻ to give the isostructural KF·2[Ca₆(CrO₄)(SiO₄)₂O].     

四元体系（Li+， Mg2+//Cl-， borate-H2O）308.15 K相平衡与相图研究

采用等温溶解平衡法,开展四元体系Li⁺, Mg²⁺//Cl^-, borate–H₂O固液相平衡与相图研究,测定平衡溶液的液相组成、密度、折射率和pH。该四元体系相图中存在的盐类矿物为：LiCl·H₂O、Li₂B₄O₇·3H₂O、 MgCl₂·6H₂O、Mg₂B₆O₁₁·15H₂O和锂光卤石LiCl·MgCl₂·7H₂O,其中锂光卤石LiCl·MgCl₂·7H₂O是异成分复盐,溶液中MgCl₂存在下章氏硼镁石（MgB₄O₇·9H₂O）不稳定,转化为多水硼镁石（Mg₂B₆O₁₁·15H₂O）。多水硼镁石结晶区最大,表明镁硼酸盐易于结晶析出,而锂光卤石结晶区最小。采用Pitzer热力学模型对该四元体系的溶解度进行理论预测,计算相图与实验相图吻合较好。该四元体系的稳定相平衡与相图研究,可为含锂硼盐湖老卤中锂、镁、硼产品开发及其综合利用提供理论依据。