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.

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。

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.

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。

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.

鲍鱼壳对半水硫酸钙复合骨水泥的改性

半水硫酸钙复合骨水泥因其良好的可塑性和原位自固化性,在临床上有广泛的应用,但是其降解产物呈酸性不利于后续的骨组织再生。鲍鱼壳的主要成分是碳酸钙,可有效地调控骨水泥降解后微环境的pH。又因为其含有有机质因子和微量元素,大大提高了骨水泥的生物相容性。通过在骨水泥中加入鲍鱼壳,可注射性可提高到97.20%±0.28%,这主要是由于鲍鱼壳粉末的加入,影响了骨水泥的水化过程,延长了凝固时间(可达26.93±0.31 min)。另一方面,鲍鱼壳粉末阻碍半水硫酸钙晶体长大,使得复合骨水泥中半水硫酸钙晶体变小(从1.42±0.77μm到0.90±0.36μm),有效地缓解了复合骨水泥降解过程中pH的下降(从6.08±0.06到6.93±0.02),极大地提高了细胞存活率(从87.00%±1.60%到96.41%±1.44%)。因此,研究表明鲍鱼壳的加入在临床上是一种潜在地提高骨水泥生物相容性的有效手段。

Mg^(2+) 对半水硫酸钙晶须结晶习性的影响

本文以磷石膏为原料蒸压制备半水硫酸钙晶须,采用数字显微镜、X射线衍射(XRD)和X射线光电子能谱(XPS)等微观测试方法对Mg^(2+)作用下的半水硫酸钙晶须微观形貌、组成及晶面发育情况等进行试验研究,运用分子动力学技术模拟计算Mg^(2+)在半水硫酸钙晶体晶面的相互作用能和径向分布函数,两者结合探讨Mg^(2+)对半水硫酸钙晶体不同晶面结晶习性的影响。结果表明,Mg^(2+)和半水硫酸钙晶体不同晶面的相互作用能从小到大顺序为:ΔE_((200))<ΔE_((002))<ΔE_((400))<ΔE_((020))<ΔE_((204))即Mg^(2+)主要吸附在半水硫酸钙晶体的(200)、(002)、(400)晶面上。Mg^(2+)与SO^(2-)_(4)间的作用距离小于Ca^(2+)与SO^(2-)_(4)间的作用距离,Mg与S之间产生了明显的电子效应,且电子效应随硫酸镁掺量的增加而增强,XRD衍射峰位置随硫酸镁掺量的增多向右偏移变得更加明显,说明有少量的Mg^(2+)嵌入半水硫酸钙晶格。在硫酸镁掺量0.15%(质量分数,下同)时,优先促进晶体c轴方向的生长,使半水硫酸钙晶须呈细长针状,平均长度为47.29μm,平均长径比为36.07;在硫酸镁掺量为0.30%时,抑制晶体沿c轴和径向的生长,使半水硫酸钙晶须呈细短针状,平均长度为39.72μm,平均长径比为28.91。

HCSW/iPP复合材料性能及诱导β晶的机理研究

将质量分数20%半水硫酸钙晶须(HCSW)与等规聚丙烯(iPP)熔融挤出后制备了HCSW/iPP复合材料,研究了HCSW/iPP复合材料性能以及HCSW对iPP诱导β晶的机理。结果表明:HCSW对iPPβ晶有良好的成核效果;与iPP相比,HCSW/iPP复合材料的力学性能有不同程度提高;利用“晶格匹配理论”计算得出HCSW与iPP有较好的附生效果。

晶面活性对丁二酸调控α-半水硫酸钙晶体形貌的影响

晶体形貌决定了α-半水硫酸钙(α-HH)的物化性质与应用领域。本文采用第一性原理计算和Wulff构型理论揭示了晶面活性差异对丁二酸调控α-HH晶体形貌的影响。结果表明:α-HH的(204)晶面是晶体形貌调控的关键晶面。(204)晶面上Ca2+连续分布且密度高,导致(204)晶面活性高,有利于媒晶剂作用。丁二酸以O—Ca离子键形式环状吸附在α-HH的(204)晶面。α-HH的高活性晶面优先被媒晶剂吸附并抑制,使晶体形貌沿高活性晶面方向缩短,过量的媒晶剂使晶体各晶面生长均被抑制,实现晶体形貌调控。

湿法磷酸副产α型和β型半水硫酸钙的鉴定及定量分析

半水硫酸钙存在α型和β型两种晶型,根据两种晶型的结构差异,采用X射线衍射仪(XRD)、固体核磁共振(SSNMR)、傅里叶红外光谱仪(FTIR)、差示扫描量热法(DSC)对两种晶型进行了测试表征和定量分析,结果表明,SSNMR、FTIR和DSC均可定性区分两种晶型;采用FTIR定量分析两种晶型在混合样中的含量,通过MATLAB软件拟合得出两种晶型混合物中α型半水硫酸钙含量与吸光度的关系模型为y=0.1275+0.0034x,通过对比分析混合样品的模型计算值和实际值,验证了该模型的准确性。

湿法磷酸脱硫工艺条件研究

由于现有的湿法磷酸净化工艺在磷酸脱硫过程中有大量的硫酸钙晶体产生,且反应条件不同时会生成不同水合结晶形态的硫酸钙,故需优化净化工艺参数。结合现有的湿法磷酸生产技术,试验研究了磷酸脱硫的最佳工艺条件,在此工艺条件下,脱硫效果最佳,脱硫率能达到90%以上,且生成的石膏为半水石膏。