Effect of Compounding of Sodium Tripolyphosphate and Super Plasticizers on the Hydration of α-calcium Sulfate Hemihydrate

The inhibition and its mechanism of sodium tripolyphosphate （STP） composited with super plasticizers （SPs） on hydration of α-calcium sulfate hemihydrate were studied by setting time, strength, hydration heat, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, electronic probe micro analysis （EPMA）, scanning electron microscopy （SEM） and differential scanning calorimeter （DSC） measurements. The experimental results show that compared with STP addition, compositing STP with polycarboxylate （PC） plasticizer, the final setting time is prolonged from 0.5h to 2hs. While formulating STP with naphthalene-based plasticizer （NAP） or sulfonate melamine formaldehyde plasticizer （SMF）, the final setting time is reduced to quarter of an hour. Similar changes can also be found in the rate of exothermic hydration and hydration degree. Formulating STP with suitable addition of PC can enhance the strength, while compositing STP and NAP or SMF weakens the strength. Besides, adding STP or STP and SMF, obvious movement （more than 1ev） of binding energy of Ca2p1/2 and Ca2p3/2 is detected. Compared with STP addition, content of the characteristic element （P） of STP is cut down form 1.1% to 0.49% by compositing STP with SMF. Furthermore, as hydration age increases, hydration inhibition in the presence of admixtures weakens and even disappears within 56 h.

Preparation of High Percentage α-Calcium Sulfate Hemihydrate via a Hydrothermal Method

α-calcium sulfate hemihydrate (α-HH) is known to be suitable for application as bone void filler. High percentage of α-HH is obviously needed for medical applications, especially for implantation. Three commercially available calcium sulfate dihydrates (DH, CaSO4·2H2O) with different sizes and surface morphologies were used as starting materials to synthesize high percentage α-HH via a hydrothermal method. The median particle sizes of the three types of DH were 946.7 μm, 162.4 μm and 62.4 μm, respectively. They were named as DH-L, DH-M and DH-S in this paper. The particle size distribution, morphology and phase composition of the raw materials were evaluated before synthesis. SEM results revealed that DH-L consisted of irregular large particles, while DH-M and DH-S were composed of plate-like particles with some small ones. High percentage HH can be obtained with proper synthesis parameters by hydrothermal method, specifically, 105 °C/90 min for DH-L (achieving 98.8% HH), 105°C/30 min for DH-M (achieving 96.7% HH) and 100°C/45 min for DH-S (achieving 98.4% HH). All the synthesized HH were hexagonal columns, demonstrating that they were α-phase HH. The particle size and morphology of starting material (DH) have significant influences on not only the rate of phase transition but also the morphology of the synthesized α-HH. Calcium sulfate dihydrate cements were prepared by the synthesized α-HH. The highest compressive strength of calcium sulfate dihydrate cement was 17.2 MPa. The results show that the preparation of high percentage α-HH is feasible via a hydrothermal method and the process can be further scaled up to industrial scale production.

Preparation and characterization of hemihydrate calcium sulfate-calcium hydroxide composite bone repair materials

Objective:To prepare a bone repair material with certain mechanical strength and biological activity,this paper used calcium sulfate hemihydrate(CSH)powder compounded with calcium hydroxide(Ca(OH)2)powder to prepare a bone repair scaffold material for physicochemical property characterization and testing.Methods:The physical and chemical properties and characterization of the dried and cured bone repair materials were determined by Fourier infrared spectroscopy(FT-IR),X-ray diffraction(XRD),and scanning electron microscopy;Universal material testing machine to determine the mechanical and mechanical strength of composite materials.Results:XRD showed that the structure of the composite material phase at 5%concentration was calcium sulfate hemihydrate and calcium hydroxide after hydration.The FT-IR and XRD analyses were consistent.Scanning electron microscopy(SEM)results showed that calcium hydroxide was uniformly dispersed in the hemihydrate calcium sulfate material.0%,1%,5%,and 10%specimen groups had compressive strengths of 3.86±3.1,5.27±1.28,8.22±0.96,and 14.4±3.28 MPa.10%addition of calcium hydroxide significantly improved the mechanical strength of the composites,but also reduced the the porosity of the material.Conclusion:With the addition of calcium hydroxide,the CSH-Ca(OH)2 composite was improved in terms of mechanical material and is expected to be a new type of bone repair material.

Studies on hemolysis properties of medicalα-calcium sulfate hemihydrate

Objective:The as-providedα-calcium sulfate hemihydrate bone repair material exhibits superior degradation properties and osteogenic property to the traditional calcium sulfate bone repair materials. Its effects on the blood and the biocompatibility were studied to ensure its safety for the bone implantation application.Method: The hemolytic tests were conducted to evaluate the blood compatibility of theα-calcium sulfate hemihydrate. The extracts ofα-calcium sulfate hemihydrate with different concentration reacted with 2% rabbit red blood cell suspension. The existence and morphology of the red blood were observed through naked eye observation and microscope observation. The hemolytic ratios were calculated through the absorbances using a ultraviolet spectrophotometer.Result:It was observed by naked eye that the red blood accumulated at the bottom of the test tubes and the upper liquids were clear, colorless and transparent in the experimental sample. The microscope observation exhibited that the cells of the experimental samples had the normal morphology, no deformed and broken blood sell existed. The hemolytic ratios of the experimental sample were all less than 5%. The hemolytic ratios were increased with the increase of the concentration of the extracts. Conclusions: The hemolytic ratios of the medical -calcium sulfate hemihydrate accorded with the standard ISO/TR7405-1984(E). It could be concluded the material would not cause acute hemolysis. The osteogenic property exhibited dose dependence.

Characterization and precipitation mechanism of α-calcium sulfate hemihydrate growing out of FGD gypsum in salt solution

Alpha-calcium sulfate hemihydrate (α-HH) has been prepared from flue gas desulfurization (FGD) gypsum with salt solution method under atmospheric pressure. X-ray diffraction (XRD),thermogra-vimetry and differential scanning calorimetry (TG-DSC),optical micrograph,X-ray photoelectron spec-troscopy (XPS),energy dispersive spectrometry (EDS),and scanning electron microscopy (SEM) have been employed to characterize the α-HH crystals,based on which the formation and growth mecha-nisms of the α-HH crystals have been discussed. The results show that FGD gypsum can be success-fully transformed into high purity α-HH in salt solution under mild conditions,and that a dissolu-tion-recrystallization route is most probably adopted by this transition. The growth of α-HH crystals in salt solution demonstrates a preferred direction along [001] and results in a bundle-of-sheets or bun-dle-of-raphide texture. The characteristics revealed in this study can help to understand and control the growth of the α-HH crystal from solution.

柠檬酸对脱硫石膏水热产品形貌的影响机理

本文以脱硫石膏和柠檬酸为主要原料水热制备半水硫酸钙晶体,采用XRD、FTIR等手段对晶体进行表征,研究柠檬酸对半水硫酸钙晶体形貌的影响及其反应机理。结果表明,当柠檬酸用量为0.20%时,溶液中C_(6)H_(6)O_(7)^(2-)和C_(6)H_(7)O_(7)^(-)不仅能够通过化学吸附的形式与半水硫酸钙晶体的(020)晶面、(400)晶面和(204)晶面上的Ca^(2+)生成柠檬酸钙沉淀,还可通过静电吸附的形式吸附在(204)晶面上。此外,C_(6)H_(8)O_(7)与吸附在半水硫酸钙表面的柠檬酸根通过碳链之间的缔合作用和羟基之间的氢键作用相互吸附进而包覆在晶体表面,不利于SO_(4)^(2-)等生长基元在晶体表面的沉淀,使其形貌从纤维状向六棱柱状转变。当柠檬酸用量大于0.20%时,柠檬酸在溶液中主要以C_(6)H_(8)O_(7)的形式存在,C_(6)H_(8)O_(7)与吸附在半水硫酸钙表面的柠檬酸根之间的缔合作用和氢键作用占主导地位,从而不利于半水硫酸钙晶体的(020)晶面和(400)晶面上的生长,使晶体形貌由六棱柱状向板状转变。

不同微观形貌的半水硫酸钙脱水动力学对比

对比α-半水石膏、β-半水石膏、α-半水晶须3种不同形貌的半水硫酸钙晶体的热脱水动力学的差异。利用热重分析数据计算拟合三者脱水过程的动力学参数和机理函数,结果表明:3种半水硫酸钙晶体的脱水活化能分别为105.01、107.02、93.57 kJ/mol。2种短柱状的石膏相半水硫酸钙的脱水机理符合不同级数的Avrami-Erofeev方程,脱水速率受晶核的形成及生长控制。而纤维状的晶须相半水硫酸钙的脱水机理则转变为相边界反应中的收缩圆柱体模型。通过得到的动力学方程预测3种形貌的半水硫酸钙在不同温度下脱水所需时间。

α-半水硫酸钙的制备、晶形调控与应用

半水硫酸钙水化机械强度高、生物相容性强、干燥气密性好,在建筑材料、生物医药、精密铸造、增材制造等领域已有应用。本文从制备方法、晶形调控和实际应用三个方面简要综述了近年来国内外α-半水硫酸钙材料的研究进展。最后,对α-半水硫酸钙当前研究与应用面临的挑战和未来发展前景进行了展望。

阳离子对制备半水硫酸钙晶须影响的研究进展

可溶性离子对半水硫酸钙晶须的形貌和晶体生长的影响非常显著,为了深入理解晶须调控的基础理论,本文总结了脱硫石膏中不同种类和浓度的可溶性阳离子对晶须制备影响的研究进展。低浓度的Na^(+)对半水硫酸钙晶须的影响较小,几乎不影响晶须的形貌和表面光滑程度;K^(+)的含量适宜在3%(质量分数)及以下,较高含量下反而对半水硫酸钙晶须的生长有不利影响;Mg^(2+)使晶须表面更均匀,结晶度更高;微量具有选择性吸附作用的Al^(3+)对晶须长径比几乎没有影响;与K^(+)相类似,Fe^(3+)也具有最佳浓度,适宜低于2 mmol/L;与上述各阳离子不同的是,Cu^(2+)并非来自原料之中,是一种额外引入的离子,掺加适量的Cu^(2+)有利于形成表面光滑均匀的晶须。

常压无氯盐溶液制备α-CaSO_(4)·0.5H_(2)O晶体研究

本文以Na_(2)SO_(4)溶液为反应介质,研究了反应温度、反应时间、液固比、pH值、Na_(2)SO_(4)质量分数对α-CaSO_(4)·0.5H_(2)O生成的影响。结果表明,在Na_(2)SO_(4)质量分数为12.5%,液固比为5∶1,pH值为7,反应温度为97℃,反应时间为4 h的条件下,制备出平均长度46.0μm、平均长径比17.23、形貌均一的α-CaSO_(4)·0.5H_(2)O晶体。常压无氯盐溶液方法克服了氯离子腐蚀工业设备、污染环境等缺点,为高值化利用磷石膏提供重要的技术支持。

Mg^(2+)、Al^(3+)对制备半水硫酸钙晶须形貌和尺寸的影响

以二水硫酸钙为原料,通过水热法制备半水硫酸钙晶须,在探究反应温度、反应时间对晶须形貌和尺寸影响基础上,分别系统考察了Mg^(2+)、Al^(3+)浓度对其形貌和尺寸的影响。实验结果表明:在料浆质量分数为2%、反应温度为160℃、反应时间为6 h条件下制备的产物其平均长度为273.4μm,平均长径比达到30.4,晶须的形貌为针状且较为均一。在低浓度的Mg^(2+)存在下,半水硫酸钙晶须的直径小,长径比高;Al^(3+)对半水硫酸钙晶须沿c轴的生长有较强的抑制作用,得到的晶须呈现棒状或者纺锤体状。

Preparation of α-High Strength Gypsum from Flue Gas Desulfurization Gypsum Pretreated by Hydrothermal-aging Method

The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD)gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtainα-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD gypsum was firstly hydrothermally converted to α-CSH whiskers, and α-CSH whiskers were further hydrated to synthesize CaSO4·2H2O (CSD) by aging under the regulation of N,N'-methylenebisacrylamide (MBA). The effects of aging time, MBA addition, aging temperature, and pH on the morphology of the synthesized CSD were investigated. The synthesized CSD crystals exhibit highly uniform prismatic morphology with the length of ca 100μm and the whiteness of 91.56%. The regulation mechanism of MBA was also illustrated. The synthesized CSD crystals with prismatic morphology were further used as raw materials to synthesize the short columnar α-CSH. The absolute dry compressive strength of paste prepared from the short columnar α-CSH is 40.85 MPa, which reaches α40 strength grade.

Biomimetic,biodegradable and osteoinductive treated dentin matrix/α-calcium sulphate hemihydrate composite material for bone tissue engineering

It is still a huge challenge for bone regenerative biomaterial to balance its mechanical,biological and biodegradable properties.In the present study,a new composite material including treated dentin matrix(TDM)andα-calcium sulphate hemihydrate(α-CSH)was prepared.The optimal composition ratio between TDM andα-CSH was explored.The results indicate that both components were physically mixed and structurally stable.Its compressive strength reaches up to 5.027±0.035 MPa for 50%TDM/α-CSH group,similar to human cancellous bone tissues.Biological experiments results show that TDM/α-CSH composite exhibits excellent biocompatibility and the expression of osteogenic related genes and proteins(ALP,RUNX2,OPN)is significantly increased.In vivo experiments suggest that the addition of TDM for each group(10%,30%,50%)effectively promotes cell proliferation and osteomalacia.In addition,50%of the TDM/α-CSH combination displays optimal osteoconductivity.The novel TDM/α-CSH composite is a good candidate for certain applications in bone tissue engineering.

水热法制备半水硫酸钙晶须的工艺研究

以二水硫酸钙为原料、硫酸为矿化剂,采用水热合成法制备半水硫酸钙晶须,考察了二水硫酸钙用量、硫酸钾加入量、硫酸浓度、反应温度、反应时间和添加剂等因素对硫酸钙晶须形貌的影响,并进行了表征。实验结果表明:在二水硫酸钙用量(浆液中二水硫酸钙的质量分数)5%、硫酸钾加入量(硫酸钾与二水硫酸钙的质量比)3%、硫酸浓度0.1 mol/L、反应温度140℃、反应时间120 min的条件下,所制得的硫酸钙晶须形貌最佳;添加剂对硫酸钙晶须的生长影响显著,添加CaCl_(2)和ZnCl_(2)可以有效改善硫酸钙晶须的形貌,其中以CaCl_(2)效果最好,晶须长度为30~80μm,而添加柠檬酸和十二烷基苯磺酸后,硫酸钙晶须的形貌明显变差。

盐泥制备半水硫酸钙晶须的工艺研究

以盐泥为原料,采用水热法制备半水硫酸钙晶须。通过单因素试验法探究了反应温度、反应时间、反应物浓度、盐泥酸浸液pH值、预热温度等因素对硫酸钙晶须形貌的影响,然后通过正交实验确认了最佳试验条件。结果表明,盐泥水热法制备硫酸钙晶须的最佳条件为:反应温度130℃、反应时间2h、反应物浓度0.4mol/L、盐泥酸浸液pH值0.5、预热温度100℃。由此方法制备的半水硫酸钙晶须形貌均一,表面细致光滑,为细长针状,其长径比为266,平均长度为518.7μm,平均直径为1.95μm。该水热制备方法通过提前将盐泥转化为酸浸液,提高了钙离子的溶解度,无需进行高温搅拌,降低了对反应设备的要求,提高了生产安全性。

半水硫酸钙晶须生产制备的研究现状

简要介绍了半水硫酸钙晶须的生长机理及其制备方法的优缺点。综述了原料技术品质、工艺技术参数和外加剂等因素对半水硫酸钙晶须制备的影响。此外,还探讨了半水硫酸钙晶须的改性方法及其应用领域。最后,分析了当前工业生产与应用中面临的关键问题,并提出了相应的解决方案。

半水硫酸钙晶须稳定化研究

使用多种稳定剂对半水硫酸钙晶须进行稳定化处理,研究了稳定剂用量、稳定化处理温度和时间等对半水硫酸钙晶须稳定性的影响。通过FTIR、SEM、DSC-TG和XRD对稳定化处理后的产物进行了表征,结果表明:在油酸钠用量0.3%,稳定化处理温度100℃,稳定化处理时间20 min的条件下,实现了半水硫酸钙晶须的稳定;油酸钠在晶须表面的吸附既有物理吸附又有化学吸附,并通过化学吸附在晶须表面形成了油酸钙。

半水硫酸钙晶须水化过程

对半水硫酸钙晶须水化产物进行了形貌的实时、非实时观测和XRD分析.结果表明半水硫酸钙晶须水化过程的显著特点在于其晶型和形貌的改变及由此引起的长径比减小;半水硫酸钙晶须的水化过程包括3个阶段:半水硫酸钙晶须水化初始期,二水硫酸钙晶须生成期,二水硫酸钙晶须的粗化溶解及新的二水硫酸钙晶体生成期.半水硫酸钙晶须的水化过程与半水石膏的水化过程略有不同.

常压水热Ca-Na-Cl溶液中用磷石膏制备α-半水石膏

引言常压水热电解质溶液中,二水石膏（calcium sulfate dihydrate,DH）、α-半水石膏（α-calcium sulfate hemihydrate,α-HH）、无水石膏（calcium sulfate anhydrate,AH）三相之间的转化对于无机盐工业、

半水硫酸钙晶须制备稳定一体化

使用优选稳定剂对半水硫酸钙晶须进行制备稳定一体化处理,研究了稳定剂用量对半水硫酸钙晶须形貌及稳定性的影响.通过SEM和XRD等检测手段对晶须产品进行了表征,结果表明:在制备过程中加入稳定剂油酸钠,当用量为0.025%时,半水硫酸钙晶须可保持形状稳定,但制备后静置72h后,晶型已全部转化为二水硫酸钙;采用分段加药的方式,即制备时加入0.025%硬脂酸钠,制备后加入0.15%油酸钠,半水硫酸钙晶须形貌与晶型可保持不变,实现了半水硫酸钙晶须的制备稳定一体化.