The stannides Ca1.692Pt2Sn3.308, SrPtSn2 and EuAuSn2

Polycrystalline samples of the stannides Ca1.692Pt2Sn3.308, SrPtSn2 and EuAuSn2 were synthesized directly from the elements, using sealed tantalum ampoules as crucible material. The reactions were performed in muffle or induction furnaces. The phase purity of the samples was studied by X-ray powder diffraction (Guinier technique). The structures of Ca1.692Pt2Sn3.308 and SrPtSn2 were refined from single-crystal X-ray diffractometer data: NdRh2Sn4 type, Pnma, a = 1887.22(13), b = 441.22(3), c = 742.89(4) pm, wR = 0.0626, 1325 F 2 values, 45 variables for Ca1.692(8) Pt2Sn3.308(8) and CeNiSi2 type, Cmcm, a = 462.59(5), b = 1932.8(2), c = 458.00(5) pm, wR = 0.0549, 481 F 2 values, 18 variables for SrPtSn2. The calcium compound shows a homogeneity range Ca1+x Pt2Sn4−x with substantial Sn4/Ca2 mixing on one of the 4c Wyckoff positions. The [PtSn2] network is characterized by Pt–Sn (269–281 pm) and Sn–Sn (306–336 pm) bonding interactions. SrPtSn2 contains two different tin substructures: (i) Sn1–Sn1 zig-zag chains (282 pm) and (ii) orthorhombically distorted Sn2 squares (326 pm) with stronger and weaker Sn–Sn bonding. Together, the platinum and tin atoms build up a three-dimensional [PtSn2] network in which the platinum atoms have a distorted square-pyramidal tin coordination with Pt–Sn distances ranging from 261–270 pm. EuAuSn2 also crystallizes with the CeNiSi2-type structure with the lattice parameters a = 453.9(1), b = 2018.9(5) and c = 456.8(1) pm. Temperature dependent magnetic susceptibility studies indicate europium(II) with an experimental magnetic moment of 8.28(2) µB per Eu atom. EuAuSn2 is ordered antiferromagnetically at T N = 14.8(2) K. 151Eu Mössbauer spectra confirm the oxidation state +2 for europium (isomer shift δ = −11.17(2) mm s−1) and the magnetic ordering at low temperature (21.8 T magnetic hyperfine field at 6 K).

Preventing Silica Scale Formation Using Hydroxide Ions Generated by Water Electrolysis

The reaction of silica with various cations in a solution and with hydroxide ions generated by water electrolysis was investigated as a means of preventing the formation of silica scales in geothermal binary power generation. Through batch and continuous experiments, it was found that all silica in the cathode phase of a reaction device could be removed if the necessary amounts of magnesium and calcium were present. This occurs because a silica-magnesium-calcium compound is produced via a polymerization reaction with cations in a solution and with hydroxide ions generated by electrolysis. Analysis by inductively coupled plasma and energy dispersive X-ray spectroscopy shows that this material has the formula 2CaO-5MgO-8SiO2-H2O, and thus is likely generated by the reaction proposed by Sheikholeslami et al. (2019). Increasing the current sent through the reaction solution subsequently produces calcium carbonate. This technique for the separation of silica and calcium from aqueous solutions can be operated continuously without channel clogging, which indicates the possibility of practical applications. However, overly high currents promote the migration of protons from the anode to cathode phases, which inhibits the formation of precipitates due to a neutralization reaction. The proposed method is an effective approach for removing silica from a solution in geothermal binary power generation; although, a means of suppressing the effects of proton generation will be necessary if the process is also to be used to remove calcium ions.

FABRICATION OF POLY(LACTIC-CO-GLYCOLIC ACID)/CALCIUM PHOSPHATE BONE CEMENT COMPOSITE: SYNTHESIZATION OF CALCIUM PHOSPHATE FROM CRAB SHELLS

Crab shells are waste product, rich with calcium compound. Calcium element is often used as a material for bone scaffold due to its bioactive and biodegradation properties. In this study, calcium phosphate (CaP) nanoparticles were synthesized from crab shells through a wet chemical route. The CaP nanoparticles were then sintered and mixed with poly(lactic-co-glycolic acid) (PLGA) to form a bone cement composite. The mixture was casted in a cylinder shape and it was characterized through ATR-FTIR, XRD, FESEM, contact angle and DSC analyses. The CaP pellet and the CaP/PLGA bone cement composite were then subjected to in vitro simulated body fluid (SBF) bioactivity test. The CaP/PLGA bone cement composite was found to have a composition of crystal CaP and PLGA with a tolerable glass transition state, suitable to be used in a physiological environment. The CaP nanoparticles were agglomerated on the 3D interconnected surface of PLGA. The hydrophobicity of the CaP was increased (66.94%) with the addition of PLGA as a binder matrix where this composite has induced the formation of apatite layer. This bioactive property is crucial in fabricating a bone substitute material as it can promotes cell penetration, attachment and proliferation..

Synthesis and Structural Characterization of [BmMeBenz]2Ca(THF)2: Ca•••H–B interactions in a Sulfur-Rich Coordination Environment

The bis(mercaptoimidazolyl)hydroborato calcium compound,[Bm^MeBenz]₂Ca(THF)₂, may be obtained by the reaction of Ca(BH₄)₂•2(THF) with 1-methyl-1,3-dihydro-2<em>H</em>-benzimidazole-2-thione. X-ray diffraction demonstrates that the [Bm^MeBenz] ligands coordinate in a k³–<em>S₂H</em> manner such that the calcium is eight-coordinate with a dodecahedral geometry that features two Ca•••H–B interactions.

Benz-amidinato calcium iodide catalyzed aldehyde and ketone hydroboration with unprecedented functional group tolerance

A benz-amidinato calcium compound, [PhC(NiPr)2CaI] (1) catalyzed hydroboration of a wide range of aldehydes and ketones using pinacolborane (HBpin) at room temperature is reported.